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National Institute for Materials Science is an Independent Administrative Institution and one of the largest scientific research centers in Japan. Wikipedia.

Nakao H.,Japan National Institute of Materials Science
Analytical Sciences | Year: 2014

This review highlights work using the author's method for the preparation of highly aligned metallic nanofibers with one-dimensional aggregates of metal nanoparticles (MNPs) and their utilization in surface enhanced Raman scattering (SERS) analysis. The preparation method, which is based on the process of evaporation-induced self-assembly with DNA and a drying front movement, eliminates the need for lithography and an external field; it is also fast, cheap and easy. Dark-field scattering spectroscopy was used to study the strong plasmon coupling of MNPs in metallic nanofibers. Furthermore, Raman spectral imaging of the metallic nanofibers revealed the existence of intense hot spots localized along their axes, which played a significant role in the intensity of SERS signals from DNA bases and rhodamine B in the metallic nanofibers. Our results demonstrate the use of evaporation-induced self-assembly with DNA as a straightforward method to produce the one-dimensional coupling of localized plasmons with a longer scale, and to facilitate the fabrication of optical sensor chips for single-molecule detection via SERS. © 2014 The Japan Society for Analytical Chemistry.

Hosokawa A.,McMaster University | Hosokawa A.,Japan National Institute of Materials Science | Wilkinson D.S.,McMaster University | Kang J.,CANMET Energy | Maire E.,INSA Lyon
Acta Materialia | Year: 2012

Void growth and coalescence/linkage, which play significant roles during ductile fracture processes, are strongly influenced by stress triaxiality in a deforming solid. The stress state can be changed by cutting notches in a tensile sample. In the current paper, void growth and linkage of an artificial void array embedded in a notched model material was studied by X-ray computed tomography, coupled with in situ tensile deformation. The cross-sectional shape of the tensile specimens was square, and a pair of notches was cut along only one direction. Thus, the lateral principal stress does not have an isotropic distribution: the principal stress along the notch direction is considered to be higher. This technique allowed us to explore the entire process of growth and linkage events of a void array embedded in a metal matrix. The notch effect creates a marked acceleration in void growth, leading to a large reduction in the linkage strains, as compared with similarly fabricated unnotched samples. The standard models for coalescence could not provide consistent predictions of the measured notch effect. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Yamada S.,Denki Kagaku Kogyo K K | Emoto H.,Denki Kagaku Kogyo K K | Ibukiyama M.,Denki Kagaku Kogyo K K | Hirosaki N.,Japan National Institute of Materials Science
Journal of the European Ceramic Society | Year: 2012

Three kinds of Eu 2+-doped oxynitride powder phosphors, including green β-SiAlON, yellow Ca-α-SiAlON and newly developed orange Ca-α-SiAlON were prepared by gas pressure sintering, which emit the fluorescent light with emission peak at 540nm, 585nm and 597nm, respectively. Emission intensity more than 90% can be kept in the range of temperature from 30°C to 200°C. Emission characteristics are stable after long-term exposure testing for 6000h at temperature of 85°C and in humidity of 85%. A white LED device composed of a blue LED chip, β-SiAlON and orange Ca-α-SiAlON phosphors exhibits a modest colour rendering index of 72. © 2011 Elsevier Ltd.

Nakanishi J.,Japan National Institute of Materials Science
Chemistry - An Asian Journal | Year: 2014

Cellular activity is highly dependent on the extracellular environment, which is composed of surrounding cells and extracellular matrices. This focus review summarizes recent advances in chemically and physically engineered switchable substrates designed to control such cellular microenvironments by application of an external stimulus. Special attention is given to their molecular design, switching strategies, and representative examples for bioanalytical and biomedical applications. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rosalie J.M.,Japan National Institute of Materials Science | Bourgeois L.,Monash University
Acta Materialia | Year: 2012

θ′ (Al 2Cu) precipitates in Al-Cu-Ag alloys were examined using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The precipitates nucleated on dislocation loops on which assemblies of γ′ (AlAg 2) precipitates were present. These dislocation loops were enriched in silver prior to θ′ precipitation. Coherent, planar interfaces between the aluminium matrix and θ′ precipitates were decorated by a layer of silver two atomic layers in thickness. It is proposed that this layer lowers the chemical component of the Al-θ′ interfacial energy. The lateral growth of the θ′ precipitates was accompanied by the extension of this silver bilayer, resulting in the loss of silver from neighbouring γ′ precipitates and contributing to the deterioration of the γ′ precipitate assemblies. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Takeuchi E.,Japan National Institute of Materials Science
Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A | Year: 2013

The effect of hydrogen on fatigue crack growth properties was investigated for two heats of SCM435 steel used for storage cylinder in hydrogen stations. Fatigue crack growth tests were performed for hydrogen-charged and uncharged specimens at stress ratios R = 0.1, 0.4, 0.7 and under the condition fixing the maximum load. An additional tests in 90 MPa hydrogen gas were also carried out at R = 0.1 and 0.5 at 1 Hz. As the results, the threshold stress intensity range ΔKth of the hydrogen-charged specimens obtained at 50 Hz was almost equal to that of the uncharged specimens. This result meant that hydrogen effect was negligible on ΔKth. The results obtained in the 90 MPa hydrogen gas supported this conclusion. In the middle ΔK region, the fatigue crack growth was accelerated by hydrogen. The acceleration, which depended on frequency, was saturated below 0.2 Hz. Maximum acceleration was about 30 times regardless of the stress ratio and the heat of the materials. Also in the hydrogen gas, the fatigue crack growth was accelerated, while the maximum acceleration was coincident with that of the hydrogen-charged specimens. Moreover, the fitted line of Paris low in the hydrogen gas was parallel to that in air in the high ΔK region. Accordingly, the fatigue crack growth in hydrogen gas could be predicted from the test results of the hydrogen-charged specimens. © 2013 The Japan Society of Mechanical Engineers.

Sathish M.,Tohoku University | Miyazawa K.,Japan National Institute of Materials Science
Molecules | Year: 2012

Fullerene nanowhiskers (FNWs) composed of C 60 fullerene molecules were prepared using the liquid-liquid interfacial precipitation (LLIP) method in the carbon-disulfide (CS 2) and isopropyl alcohol (IPA) system. The electron microscopic images reveal the formation of non-tubular FNWs. The X-ray diffraction (XRD) pattern studies indicate the presence of fcc crystalline structure and unusual triclinic structure in the FNWs. The selected area electron diffraction pattern (SAED) analysis demonstrates the existence of triclinic and electron beam assisted fcc to tetragonal crystalline phase transformation. The formation of triclinic structure might be validated due to the partial polymerization of FNWs at C 60 saturated CS 2-IPA interface. The high solubility of C 60 in CS 2 solvent system results in partial polymerization of FNWs. The polymerization of fullerene molecules in the FNWs has been further confirmed using Raman spectroscopy. © 2012 by the authors.

Teraji T.,Japan National Institute of Materials Science
Journal of Applied Physics | Year: 2015

Defect formation during diamond homoepitaxial growth was sufficiently inhibited by adding oxygen simultaneously in the growth ambient with high concentration of 2%. A 30-μm thick diamond films with surface roughness of <2 nm were homoepitaxially deposited on the (100) diamond single crystal substrates with reasonable growth rate of approximately 3 μm h-1 under the conditions of higher methane concentration of 10%, higher substrate temperature of ∼1000 °C, and higher microwave power density condition of >100 W cm-3. Surface characteristic patterns moved to an identical direction with growth thickness, indicating that lateral growth was dominant growth mode. High chemical purity represented by low nitrogen concentration of less than 1 ppb and the highest 12C isotopic ratio of 99.998% of the obtained homoepitaxial diamond (100) films suggest that the proposed growth condition has high ability of impurity control. © 2015 AIP Publishing LLC.

Wei F.-G.,Nippon Yakin Kogyo Co. | Enomoto M.,Ibaraki University | Tsuzaki K.,Japan National Institute of Materials Science
Computational Materials Science | Year: 2012

The Kissinger's formula has been analyzed theoretically and numerically to be applicable in simulation of not only the detrapping-controlled thermal desorption but also the diffusion-controlled thermal desorption provided that a sufficient pre-exposure before thermal desorption is carried out in the diffusion-controlled desorption. The desorption activation energy or the binding energy can be evaluated by a single thermal desorption spectrum from a single type of trap site. In the case of detrapping-controlled desorption the constant parameter A in the Kissinger's formula approaches the pre-exponential factor of detrap parameter, p0, in the McNabb-Foster model as specimen size becomes smaller. In the case of diffusion-controlled desorption where local equilibrium may be maintained and an effective diffusivity can be expressed, the A value changes according to A = α2D0 where D 0 is the pre-exponential factor of effective diffusivity and α is a geometrical parameter of specimen. © 2011 Elsevier B.V. All rights reserved.

Ishii M.,Japan National Institute of Materials Science | Koizumi A.,Osaka University | Fujiwara Y.,Osaka University
Applied Physics Letters | Year: 2015

A pulse-driven emission-spectroscopy mapping technique is used to investigate the bright emission centers in Eu-doped GaN (GaN:Eu) red light emitting diodes (LED). The LEDs are operated in pulse-driven mode, and the emission spectra are acquired for a range of pulse frequencies. This ensemble of emission spectral data yields a three-dimensional mapping that allows the origin of emission lines to be identified by visual inspection. The identification was achieved even for a weak 5D0→7F3 transition in conventional photoluminescence measurements. A peculiar split is observed in the 5D0→7F3 transition for the bright emission center referred to as OMVPE 8. Despite the unique transition at this emission center, the emission efficiencies for the 5D0→7F3 and 5D0→7F2 transitions were identical. This finding indicates that the excitation of the emission centers, rather than the radiative transitions, is the limiting process that determines the GaN:Eu red LED brightness. © 2015 AIP Publishing LLC.

Nandi M.,Indian Association for The Cultivation of Science | Nandi M.,Integrated Science Education and Research Center | Mondal J.,Indian Association for The Cultivation of Science | Sarkar K.,Indian Association for The Cultivation of Science | And 2 more authors.
Chemical Communications | Year: 2011

Post-synthesis modification of SBA-15 has been carried out to design highly ordered acid functionalized hybrid mesoporous organosilica, AFS-1. This material has been used as an efficient heterogeneous organocatalyst for the syntheses of xanthenes under mild conditions in the absence of any other metal co-catalyst. © 2011 The Royal Society of Chemistry.

Tanaka M.,Japan National Institute of Materials Science
Applied Surface Science | Year: 2014

Ni clusters grown on SrTiO3 (0 0 1) and (1 1 0) substrates were studied with UHV-TEM. Before Ni deposition, both surfaces were cleaned effectively by electron beam annealing and showed atomic level flatness. Both surfaces seemed to have simple 1 × 1 structures. SrTiO3 (1 1 0) substrates are supposed to have O-vacancies on surfaces and inside. Ni clusters grow about 2-5 nm in sizes, and their interfacial structures and morphologies depend on substrate surface orientations. While clusters on SrTiO3 (0 0 1) grow with cube-on-cube epitaxial relationship, those on SrTiO3 (1 1 0) have two kinds of interfaces. In both cases, most of the clusters match the Winterbottom construction. On SrTiO3 (0 0 1) surfaces this appears as truncated pyramids. On SrTiO3 (1 1 0) surfaces they are either huts or hexagons. Those clusters are under the condition of partial wetting. Interface bonding energies are estimated based on their morphologies. © 2014 Elsevier B.V.

Sakoda K.,Japan National Institute of Materials Science | Sakoda K.,University of Tsukuba
Journal of the Optical Society of America B: Optical Physics | Year: 2012

The creation of photonic Dirac cones by accidental degeneracy in the Brillouin-zone center was recently reported for both metamaterials with localized electromagnetic resonant states and dielectric photonic crystals without well-defined resonance. Based on the anticipation that there should be a common physical origin in this phenomenon, we systematically examined the relation between mode symmetries and shapes of dispersion curves for both systems. The result strongly suggests the presence of universality of mode symmetries that enable the creation of photonic Dirac cones irrespective of the details of the sample structure. © 2012 Optical Society of America.

Sakoda K.,Japan National Institute of Materials Science | Sakoda K.,University of Tsukuba
Optics Express | Year: 2012

We formulate a degenerate perturbation theory for the vector electromagnetic field of periodic structures and apply it to the problem of the creation of Dirac cones in the Brillouin-zone center by accidental degeneracy of two modes. We derive a necessary condition by which we can easily select candidates of mode combinations that enable the creation of the Dirac cone. We analyze the structure of a matrix that determines the first-order correction to eigen frequencies by examining its transformation by symmetry operations. Thus, we can obtain the analytical solution of dispersion curves in the vicinity of the zone center and can judge the presence of the Dirac cone. All these findings clearly show that the presence or absence of the Dirac cone in the zone center is solely determined by the spatial symmetry of the two modes. © 2012 Optical Society of America.

Sakoda K.,Japan National Institute of Materials Science | Sakoda K.,University of Tsukuba
Optics Express | Year: 2012

It is shown by analytical calculation based on the tight-binding approximation that the isotropic Dirac cone in the Brillouin zone center can be created in two- and three-dimensional periodic metamaterials by accidental degeneracy of two modes. In the case of two dimensions, the combination of a doubly degenerate E mode and a non-degenerate A1 mode of the square lattice of the C4v symmetry is examined. For three dimensions, the combination of a triply degenerate T1u mode and a non-degenerate A1g mode of the cubic lattice of the Oh symmetry is examined. The secular equation of the electromagnetic field is derived and solved with detailed analysis of electromagnetic transfer integrals by group theory. This is the first theoretical prediction of the presence of the Dirac cone in the three-dimensional periodic structure. © 2012 Optical Society of America.

Takeda H.,Japan National Institute of Materials Science
Optics Express | Year: 2012

I theoretically demonstrate the population inversion of collective two-level atoms using photonic crystals in three-dimensional (3D) systems by self-consistent solution of the semiclassical Maxwell-Bloch equations. In the semiclassical theory, while electrons are quantized to ground and excited states, electromagnetic fields are treated classically. For control of spontaneous emission and steady-state population inversion of two-level atoms driven by an external laser which is generally considered impossible, large contrasts of electromagnetic local densities of states (EM LDOSs) are necessary. When a large number of two-level atoms are coherently excited (Dicke model), the above properties can be recaptured by the Maxwell-Bloch equations based on the first-principle calculation. In this paper, I focus on the realistic 1D PCs with finite structures perpendicular to periodic directions in 3D systems. In such structures, there appear pseudo photonic band gaps (PBGs) in which light leaks into air regions, unlike complete PBGs. Nevertheless, these pseudo PBGs provide large contrasts of EM LDOSs in the vicinity of the upper photonic band edges. I show that the realistic 1D PCs in 3D systems enable the control of spontaneous emission and population inversion of collective two-level atoms driven by an external laser. This finding facilitates experimental fabrication and realization. © 2012 Optical Society of America.

Sakuraba Y.,Japan National Institute of Materials Science
Scripta Materialia | Year: 2015

This article introduces the concept and advantage of thermoelectric power generation (TEG) using anomalous Nernst effect (ANE). The three-dimensionality of ANE can largely simplify a thermopile structure and realize TEG systems using heat sources with a non-flat surface. The improvement of ZT can be expected because of the orthogonal relationship between thermal and electric conductivities. The calculations of an achievable electric power predicted that an improvement of thermopower by one order of magnitude would open up a usage of practical applications. © 2015 Acta Materialia Inc.

Solovyev I.V.,Japan National Institute of Materials Science | Valentyuk M.V.,Ural Federal University | Mazurenko V.V.,Ural Federal University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We discuss the relative roles played by the magnetic inversion symmetry breaking and the ferroelectric (FE) atomic displacements in the multiferroic state of YMnO 3. For these purposes we derive a realistic low-energy model, using results of first-principles electronic structure calculations and experimental parameters of the crystal structure below and above the FE transition. Then, we solve this model in the mean-field Hartree-Fock approximation. We argue that the multiferroic state in YMnO 3 has a magnetic origin, and the centrosymmetric Pbnm structure is formally sufficient for explaining the main details of the noncentrosymmetric magnetic ground state. The relativistic spin-orbit interaction lifts the degeneracy, caused by the frustration of isotropic exchange interactions in the ab plane, and stabilizes a twofold periodic noncollinear magnetic state, which is similar to the E state apart from the spin canting. The noncentrosymmetric atomic displacements in the P2 1nm phase reduce the spin canting, but do not change the symmetry of the magnetic state. The effect of the P2 1nm distortion on the FE polarization ΔP a, parallel to the orthorhombic a axis, is twofold: (i) It gives rise to ionic contributions, associated with the oxygen and yttrium sites; (ii) it affects the electronic polarization, mainly through the change of the spin canting. The relatively small value of ΔP a, observed in the experiment, is caused by a partial cancellation of the electronic and ionic contributions, as well as different contributions in the ionic part, which takes place for the experimental P2 1nm structure. The twofold periodic magnetic state competes with the fourfold periodic one and, even in the displaced P2 1nm phase, these two states continue to coexist in a narrow energy range. Finally, we theoretically optimize the crystal structure. For these purposes we employ the LSDA+U approach and assume the collinear E-type antiferromagnetic alignment. Then, we use the obtained structural information again as the input for the construction and solution of the low-energy model. We have found that the agreement with the experimental data in this case is less satisfactory and |ΔP a| is largely overestimated. Although the magnetic structure can be formally tuned by varying the Coulomb repulsion U as a parameter, apparently LSDA+U fails to reproduce some fine details of the experimental structure, and the cancellation of different contributions in ΔP a does not occur. © 2012 American Physical Society.

Ikeda T.,Japan National Institute of Materials Science
Langmuir | Year: 2015

The oligomers consisting of phenyl-capped bithiophene and tetra(ethylene glycol)s linked by azide-alkyne Huisgen cycloaddition were synthesized. The relationship between the degree of polymerization and self-assembling ability was investigated in o-dichlorobenzene and dimethyl sulfoxide. From the absorption spectrum, it was confirmed that the critical degree of polymerization (CDP) for thiophene unit aggregation was 4. The morphology of the aggregated product was observed by atomic force microscopy. The oligomers 4mer and 5mer could not self-assemble into well-defined structures due to the weak driving force for the self-assembly. In the cases of 6mer and 7mer, aggregates with nonwell-defined and nanosheet structures coexisted. In the cases of 8mer and 9mer, the nanosheet was the main product. The critical point between 7mer and 8mer could be confirmed by different aggregation behaviors in the cooling process of the solution (nonsigmoidal and sigmoidal). In the cases of 8mer and 9mer, polymer folding prior to intermolecular self-assembly, which was supported by sigmoidal aggregation behavior, leads to the nanosheet formation. On the contrary, shorter oligomers than 8mer experience intermolecular aggregation prior to intramolecular polymer folding, which was supported by the nonsigmoidal aggregation behavior. This is the first report to prove the existence of CDP for folded polymer nanosheet formation which requires hierarchical self-assembly, i.e., polymer folding followed by intermolecular self-assembly. © 2014 American Chemical Society.

Tagaya M.,Nagaoka University of Technology | Hanagata N.,Japan National Institute of Materials Science | Kobayashi T.,Nagaoka University of Technology
ACS Applied Materials and Interfaces | Year: 2012

Mesostructured surfactant-silica monolithic films were prepared using a supramolecular templating method. The effect of the templating in the monolithic films on the interfacial interactions was evaluated and elucidated using the atomic force microscope techniques combined with other surface analyses to produce different surface structures and force curves depending on the surfactants. The transparent and flexible surfactant-silica monolithic films were prepared to exhibit the ordered nanostructures. The monolithic films templated by nonionic triblock copolymers (poly(ethylene oxide (EO))-poly(propylene oxide (PO))-poly(ethylene oxide (EO))) of EO 20PO70EO20 (P123) and EO106PO 70EO106 (F127) significantly exhibited flat surfaces and the higher viscoelastic properties which were supported by surface stiffness and adhesive force, whereas the monolithic film by cationic alkylammonium surfactant indicated a rough surface and the plastic deformation property by application of force. This indicated that the higher molecular weight of the EO and PO phases enhanced the phase segregation in the silica surfaces due to the higher solubility differences between both blocks to consolidate the surfactant-silica interfacial interactions. Therefore, the different surface structural and mechanical properties attributed to the interfacial organic-inorganic interaction patterns were successfully clarified. © 2012 American Chemical Society.

Chen B.,Japan National Institute of Advanced Industrial Science and Technology | Matsuhata H.,Japan National Institute of Advanced Industrial Science and Technology | Sekiguchi T.,Japan National Institute of Materials Science | Ichinoseki K.,Japan National Institute of Advanced Industrial Science and Technology | Okumura H.,Japan National Institute of Advanced Industrial Science and Technology
Acta Materialia | Year: 2012

The optical, structural and electrical properties of the killer defects termed down-fall particles and their accompanying imperfections in 4H-SiC homoepitaxial films were studied using electron microscopy techniques. Down-fall particles are polycrystalline 3C-SiC several tens of microns in size. They show unexpected dark contrast at their band edge (525 nm) using cathodoluminescence (CL). Down-fall particles have different effects on epitaxial growth. Most of them (common ones) are accompanied by stacking faults (SFs) which luminesce at 471 nm, while some promote the occurrence of 3C inclusions nearby. Transmission electron microscopy has revealed that the displacement vector of the accompanying SF is in the {0 0 0 1} basal plane, whereas the interface between the 3C inclusion and 4H matrix is composed of Shockley-type and Frank-type partials. The effects of down-fall particles on epitaxial growth as well as their dark contrast in the CL images are discussed. The differences between the common and special particles and the correlation with the electrical properties of the device are also discussed. The detailed structure-property analysis in this study thus provides a fundamental understanding of defect formation and development during the homo- or hetero-epitaxial growth of various materials. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Isago H.,Japan National Institute of Materials Science
Journal of Porphyrins and Phthalocyanines | Year: 2014

Redox properties of the title complex [Ce(pc)2] (where pc denotes phthalocyaninate dianion, C32H16N8 2-) have been investigated in dichloromethane solutions by cyclic- and rotating-diskelectrode voltammetry. Unlike the other rare-earth(III) analogs that show one oxidation and one reduction waves in the potential range of -1 - +1 V vs. the half-wave potential of the redox couple of ferrocene (Fc+/Fc), only the cerium(IV) derivative shows two oxidation and one reduction waves in the same potential range. The frst and second oxidation and the frst reduction waves have been assigned as pc2-pc-•/pc2- pc2-;, pc•-pc•-/pc2-pc•-, and CeIV/III(pc2-)2, respectively, on the basis of spectroelectrochemical works. The ligand-centered electron-transfer processes are fully reversible and diffusion-controlled whereas the frst reduction alone is quasi-reversible. Comparison of absorption and magnetic circular dichroism spectra before and after the metal-centered reduction suggests that structural change upon the electron-transfer is not signifcant in solution apart from the interplanar distance between the two macrocyclic ligands. Copyright © 2014 World Scientific Publishing Company.

Wu R.T.,Japan National Institute of Materials Science | Wang X.,Imperial College London | Atkinson A.,Imperial College London
Acta Materialia | Year: 2010

Thermal barrier coating (TBC) systems based on an electron beam physical vapour deposited, yttria-stabilized zirconia (YSZ) top coat and a substrate material of CMSX-4 superalloy were identically prepared to systematically study the behaviour of different bond coats. The three bond coat systems investigated included two β-structured Pt-Al types and a γ-γ′ type produced by Pt diffusion without aluminizing. Progressive evolution of stress in the thermally grown aluminium oxide (TGO) upon thermal cycling, and its relief by plastic deformation and fracture, were studied using luminescence spectroscopy. The TBCs with the LT Pt-Al bond coat failed by a rumpling mechanism that generated isolated cracks at the interface between the TGO and the YSZ. This reduced adhesion at this interface and the TBC delaminated when it could no longer resist the release of the stored elastic energy of the YSZ, which stiffened with time due to sintering. In contrast, the TBCs with Pt diffusion bond coats did not rumple, and the adhesion of interfaces in the coating did not obviously degrade. It is shown that the different failure mechanisms are strongly associated with differences in the high-temperature mechanical properties of the bond coats. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Goto H.,University of Tsukuba | Nimori S.,Japan National Institute of Materials Science
Journal of Materials Chemistry | Year: 2010

The electrochemical preparation of poly(3,4-ethylenedioxythiophene) (PEDOT) is conducted in liquid crystal (LC) electrolyte solution with nematic (N), cholesteric (Ch*), and smectic A (SmA) phases under a magnetic field. The polymer imprints the molecular arrangement of the LC electrolyte during the polymerisation process. The oriented polymers thus obtained displays optical texture characteristics that resemble those of the LC electrolyte solution. Especially, visualization of SmA domain through PEDOT fibrils is achieved. The magnetic alignment produces linear optical polarisation for the polymers. The PEDOTs thus prepared exhibit good reproducible electroactivity. The present electropolymerisation under magnetic field affords polymer films with linear polarised electrochromism. © 2010 The Royal Society of Chemistry.

Teii K.,Kyushu University | Matsumoto S.,Kyushu University | Matsumoto S.,Japan National Institute of Materials Science
ACS Applied Materials and Interfaces | Year: 2012

Thick cubic boron nitride (cBN) films in micrometer-scale are deposited on tungsten carbide-cobalt (WC-Co) substrates without adhesion interlayers by inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD) using the chemistry of fluorine. The residual film stress is reduced because of very low ion-impact energies (a few eV to ∼25 eV) controlled by the plasma sheath potential. Two types of substrate pretreatment are used successively; the removal of surface Co binder using an acid solution suppresses the catalytic effect of Co and triggers cBN formation, and the surface roughening using mechanical scratching and hydrogen plasma etching increases both the in-depth cBN fraction and deposition rate. The substrate surface condition is evaluated by the wettability of the probe liquids with different polarities and quantified by the apparent surface free energy calculated from the contact angle. The surface roughening enhances the compatibility in energy between the cBN and substrate, which are bridged by the interfacial sp 2-bonded hexagonal BN buffer layer, and then, the cBN overlayer is nucleated and evolved easier. © 2012 American Chemical Society.

Tominaka S.,Waseda University | Tominaka S.,Japan National Institute of Materials Science | Hayashi T.,Waseda University | Nakamura Y.,Waseda University | Osaka T.,Waseda University
Journal of Materials Chemistry | Year: 2010

A mesoporous PdCo sponge-like nanostructure was successfully synthesized by the combination of electrodeposition and dealloying, and was evaluated as a catalyst for the oxygen reduction reaction of fuel cells. The synthesized film had a sponge-like mesoporosity consisting of 5-30 nm thick ligaments with pores of tens of nanometers. Its porosity was estimated to be ca. 62%, suggesting that the oxygen transport in the film was smooth. The resultant composition was Pd93Co7, whose crystalline phase was determined to be a solid solution of Pd92Co8 by X-ray diffractometry. This degree of alloying is known to induce the most desirable lattice contraction into a Pd catalyst for the oxygen reduction reaction. Actually, the mesoporous PdCo catalyst had a higher specific activity than the Pt catalyst in the potential range of <0.85 V vs. SHE, i.e., the potential range of interest for fuel cell operation. This fascinatingly higher catalytic activity was attributable to the preferable reaction mechanism, because the PdCo electrode had a lower Tafel slope (43 mV decade-1) than a typical Pt electrode (71 mV decade-1). © 2010 The Royal Society of Chemistry.

Kameoka S.,Tohoku University | Tsai A.-P.,Tohoku University | Tsai A.-P.,Japan National Institute of Materials Science
Journal of Materials Chemistry | Year: 2010

Nanoporous gold fabricated by the dealloying of binary Au alloys has a three-dimensional network of fine ligaments on the nano-scale, which is a novel unsupported gold catalyst with exceptional catalytic activity for CO oxidation. Here we report a new nanoporous structure - a composite formed by alternately layered Au/Fe3O4/Au with layer spacing ∼200 nm and with porous structure (the pore size is below 20 nm). The Au/Fe 3O4/Au revealed much higher catalytic performance for CO oxidation than the previously reported conventional Au/Fe2O 3 catalyst, where the porous Au and porous Fe3O 4 were responsible for the high activity and high thermal stability, respectively. The porous structure is formed via a self-assembly process by the dealloying of Al in a NaOH aqueous solution for a conventionally melting Al-Au-Fe alloy precursor with an alternately layered Al2Au/Al 2Fe/Al2Au structure. We show here, that a fine composite nanoporous structure could be intentionally designed on the basis of the metallurgically tailored microstructure of the precursor alloy. © 2010 The Royal Society of Chemistry.

Sakuma H.,Japan National Institute of Materials Science | Ichiki M.,Tohoku University
Geofluids | Year: 2016

We report on molecular dynamics (MD) simulations for predicting the density and isothermal compressibility of an H2O-NaCl fluid as a function of temperature (673-2000 K), pressure (0.2-2.0 GPa), and salt concentration (0.0-21.9 wt%). The atomistic behavior was analyzed via the hydration number of ions and number of ion pairs. Hydration numbers of Na+ and Cl- increased with increasing pressure and decreasing temperature. Conversely, the fraction of Na-Cl ion pairs increased with decreasing pressure and increasing temperature. This hydration and association behavior is consistent with the low dielectric constant of H2O under these conditions. The presence of polynuclear clusters of Na-Cl was confirmed at high temperatures, low pressures, and high salt concentrations. We propose a purely empirical equation of state (EoS) for H2O-NaCl fluids under high temperatures and pressures that should be useful for estimating the fluid distribution in Earth's crust and upper mantle in relation to effects on earthquakes and volcanic eruptions. © 2016 John Wiley & Sons Ltd.

Ping D.H.,Japan National Institute of Materials Science | Geng W.T.,University of Science and Technology Beijing
Materials Chemistry and Physics | Year: 2013

Steel remains to be one of the most common structural materials in the world as human civilization advances from the Iron Age to the ongoing Silicon Age. Our knowledge of its microstructure evolution and structure-performance relationship is nevertheless still incomplete. We report the observation and characterization of a long ignored metastable phase formed in steels with body-centered cubic (bcc) structure using both transmission electron microscopy and density functional theory calculations. This ω phase has a hexagonal structure and coherent interface with the matrix: aω = √2 × abcc and cω = √3/2 × a bcc. It is 3.6% smaller in volume and 0.18 eV higher in energy than bcc-Fe, with atoms in alternating close- and loose-packed layers couple anti-ferromagnetically. Carbon plays a crucial role in promoting bcc to ω transformation. At a concentration higher than 4 at.% they tend to segregate from the bcc matrix to the ω-phase; at about 14 at.%, they can induce bcc to ω transformation; and finally at 25 at.%, they stabilize the ω phase as ω-Fe3C. The ω phase in bcc Fe can serve as sinks for vacancies, H, and He atoms, leading to improved resistance of martensitic steels to irradiation damage. © 2013 Elsevier B.V. All rights reserved.

Kato S.,Japan National Institute of Advanced Industrial Science and Technology | Kurimura S.,Japan National Institute of Materials Science | Mio N.,University of Tokyo
Optical Materials Express | Year: 2016

Light-induced heating under high-average-power laser is investigated in LiNbO3-type crystals in green second-harmonic generation. A rate-equation based on the kinetics of polarons is proposed and important parameters of the rate-equation are determined by reproducing experimental results. Light-induced heat and threshold intensity of catastrophic breakdown are evaluated using the rate-equation. The accumulation effect of polarons causes the decrease of threshold intensity of catastrophic breakdown of crystals. © 2016 Optical Society of America.

Ochiai T.,Japan National Institute of Materials Science
Journal of the Physical Society of Japan | Year: 2015

We theoretically demonstrate the realization of photonic topological insulators in photonic crystals made of circular cylinders with the Tellegen-type magnetoelectric coupling as a photospin-orbit interaction. Although the magnetoelectric coupling breaks the conventional (bosonic) time-reversal symmetry for photons, the electromagnetic duality between permittivity and permeability gives rise to a fermionic time-reversal symmetry. This symmetry along with the space-inversion symmetry enables us to imitate the Kane-Mele model of two-dimensional topological insulators in a photonics platform. Even if the space-inversion symmetry is broken, a photonic topological insulator can emerge owing to the photospin-orbit interaction. We present bulk and edge properties of the photonic topological insulators and discuss their possible realization. ©2015 The Physical Society of Japan.

Kotani T.,Tottori University | Kino H.,Japan National Institute of Materials Science | Akai H.,University of Tokyo
Journal of the Physical Society of Japan | Year: 2015

The augmented plane waves and the muffin-tin orbitals method (the PMT method) was proposed by Kotani and van Schilfgaarde in Phys. Rev. B 81, 125117 (2010). It is a mixed basis all-electron full-potential method, which uses two types of augmented waves simultaneously, in addition to the local orbitals. In this paper, this mixed basis method is reformulated on the basis of a new formalism named as the 3-component formalism, which is a mathematically transparent version of the additive augmentation originally proposed by Soler and Williams in Phys. Rev. B 47, 6784 (1993). Atomic forces are easily derived systematically. We discuss some problems in the mixed basis method and ways to manage them. In addition, we compare the method with the PAW method on the same footing. This PMT method is the basis for our new development of the quasiparticle self-consistent GW method in J. Phys. Soc. Jpn. 83, 094711 (2014), available as the ecalj package at github. ©2015 The Physical Society of Japan.

Bay T.V.,University of Amsterdam | Naka T.,Japan National Institute of Materials Science | Huang Y.K.,University of Amsterdam | De Visser A.,University of Amsterdam
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We report a high-pressure single-crystal study of the noncentrosymmetric superconductor YPtBi (T c=0.77 K). Magnetotransport measurements show a weak metallic behavior with a carrier concentration n2.2×1019 cm -3. Resistivity measurements up to p=2.51 GPa reveal superconductivity is promoted by pressure. The reduced upper critical field B c2(T) curves collapse onto a single curve, with values that exceed the model values for spin-singlet superconductivity. The B c2 data point to an odd-parity component in the superconducting order parameter, in accordance with predictions for noncentrosymmetric superconductors. © 2012 American Physical Society.

Nishimura T.,Japan National Institute of Materials Science
Materials Transactions | Year: 2016

Distribution of the corrosion depth around a surface scratch of epoxy-coated High Tensile (HT) Strength steel (0.7Ni-0.6Cr-0.3Mo-Fe) was measured by using a laser microscope after a wet and dry cyclic corrosion test and compared with that of epoxy-coated carbon (SM) steel. The Gumbel distribution analysis was applied to the corrosion depth profile as a function of distance far from the scratch. In the analysis, the mode (λ) and distribution parameter (α) of the coated HT steel displayed much smaller values than those of coated carbon (SM) steel. The smaller values indicate that the coated HT steel has higher corrosion resistance than that of the coated SM steel. The SEM (Scanning Electron Microscope)-EDS (Energy dispersive X-ray spectrometry) analysis showed that Cr and Mo were enriched in the inner rust layer and Ni distributed in all rust layer around the scratched area of the coated HT steel after the corrosion test. The TEM (Transmission Electron Microscope)-EELS (Electron Energy Loss Spectroscopy) analysis confirmed the presence of nanoscale Fe oxides containing Cr, Ni and Mo in the rust of the HT steel, and these nanostructures of the rust was assumed to enhance the corrosion resistance of the coated HT steel. ©2015 The Japan Institute of Metals and Materials.

Nishimura T.,Japan National Institute of Materials Science
Journal of Materials Engineering and Performance | Year: 2016

The effect of microstructure on the corrosion of heat-treated Ti-10 mass% Mn alloys was investigated by electrochemical impedance spectroscopy (EIS) in 10% NaCl solution of pH 0.5 at 97 °C. Sample of solution heat treatment (ST) had a single β phase, and samples subjected to the aging heat treatment at 600 °C had α phase precipitation in β phases. The EIS measurements showed that the corrosion resistance of the aging heat-treated samples showed lower values than ST sample, however, much higher values than pure Ti. Thus, Mn was effective to increase the corrosion resistance of Ti alloys. Laser micrographs of heat-treated samples indicated that α phase was selectively corroded and made the pit after the corrosion test. The transmission electron microscope (TEM)-energy dispersive x-ray spectrometry (EDXS) analyses showed that the Mn content was 9 mass% in the β phase and 0.7 mass% in α phase. Hence, it was understood that less-Mn α phase was selectively corroded in the corrosion test. However, as compared with pure Ti, the aging heat-treated samples showed much higher resistance against the corrosion by the 0.7 mass% Mn in α phase. Finally, it was concluded that it was possible to keep the high corrosion resistance for heat-treated Ti-10 mass% Mn alloy by controlling the microstructure of α phase. © 2015, The Author(s).

Hollamby M.J.,Keele University | Nakanishi T.,Japan National Institute of Materials Science
Journal of Materials Chemistry C | Year: 2013

The power of branched alkyl substituents to alter material properties is known to soft matter chemistry, with examples found in both surfactants and ionic liquids. Here, we highlight their potency in organic molecular/polymeric materials with optoelectronic applications. Attaching branched alkyl chains to the active π-conjugated core modulates core-core interactions and thus softens the material. This can lead to optimised assemblies with improved optoelectronic properties. By increasing the number and volume of the flexible chains, individual cores can be isolated, yielding functional organic liquids with bulk optical properties the same as the intrinsic molecular characteristics obtained for their dilute solutions. These liquid materials can accommodate dopants to offer diverse and tuneable emission colours, and provide an easily applicable flexible and foldable continuous layer for future optoelectronic media. © 2013 The Royal Society of Chemistry.

Nagashima N.,Japan National Institute of Materials Science
Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A | Year: 2013

Micro-hardness distribution was measured by using an ultra-micro hardness test at a crack tip under a plane strain condition for a crack propagation test specimen made of a low-carbon austenite stainless steel JIS-SUS316L. Moreover, crystal orientations were analyzed by EBSD for individual crystal grains in the plastic strained area at the crack tip. The conclusions can be summarized as follows. (1) The mean strain in a 500-μm region around the crack tip was supposed with 3% from the hardness distribution in an ultra-micro hardness test. Therefore, the plasticity strain distribution of the crack tip under a plane strain condition can be visualized based on the ultra-micro hardness and an experience equation of the true strain by measuring the hardness distribution. (2) When the analysis by EB SD increased the step size of the KAM map, the local misorientation increased. On the other hand, the color map of some grain boundary neighborhoods reversed when the step size changed in a GROD map. Therefore, an analysis of KAM is suitable for the local transformation of the crack tip neighborhood. (3) From the results of an EBSD analysis, it became clear that a local heterogeneous transformation occurred in random grain boundaries at the crack tip, and the transformation hardly occurred at the CSL grain boundary of the crack tip. © 2013 The Japan Society of Mechanical Engineers.

Kurahashi M.,Japan National Institute of Materials Science
Progress in Surface Science | Year: 2016

Molecular oxygen (O2) is a paramagnetic linear molecule, yet the effect of its molecular alignment and electron spin on the dynamics of O2 adsorption has remained unclear. Recently, it has been however shown that the use of magnetic hexapolar field allows us to prepare a single spin-rotational state [(J,M) = (2, 2)] selected O2 beam for which both the molecular alignment and the spin state of O2 are well defined. State-resolved studies of O2 sticking on Si(1 0 0), Al(1 1 1), Ni(1 1 1) surfaces conducted with this beam have clarified that the O2 sticking probability depends strongly on the molecular alignment and the spin orientation of O2 relative to the surface. The mechanism of O2 adsorption on Al(1 1 1) has been disputed in the past few decades, but the observed steric effect has provided a reasonable picture for it. The preparation method of the state-selected O2 beam and its application to the alignment- and spin-resolved O2 sticking studies are reviewed. © 2016 Elsevier Ltd.

Nishimura T.,Japan National Institute of Materials Science
ISIJ International | Year: 2015

Wet and dry corrosion tests using a NaCl solution were performed on Cr bearing steels in concrete. The nano-scale structure and electrochemical behavior of the rust were analyzed by TEM (Transmission Electron Microscopy) and EIS (Electrochemical Impedance Spectroscopy). The carbon steel (SM) had large amount of corrosion and produced cracking in the concrete after corrosion test. On the other hand, the Cr bearing steel showed much less corrosion, and had no concrete cracking. After corrosion test, EIS measurements were performed on the samples to determine rust resistance (Rrust) and corrosion resistance (Rt) of the different steel types. The Rrust and Rt of Cr bearing steel were much larger than those of SM after corrosion test. SEM (Scanning Electron Spectroscopy) with EDS (Energy Dispersive Spectroscopy) showed that Cr and Si were enriched in inner rust of the Cr and Si bearing steel. TEM showed that nano-scale complex iron oxides containing Cr and Si were formed in inner rust. It was found that the Cr bearing steel formed nano-scale iron complex oxides containing Cr and Si in inner rust, which increased Rrust and Rt, and suppressed the corrosion by chloride ions in the concrete. © 2015 ISIJ.

Tanaka M.,Japan National Institute of Materials Science
e-Journal of Surface Science and Nanotechnology | Year: 2012

Ni clusters and particles grown on SrTiO 3(001) were investigated with UHV-TEM/STM combined system. Substrate surface was cleaned by chemical etching and subsequent electron beam heating, and confirmed by TEM observation and EELS analysis. Direct observation of Ni clusters deposited on these substrates revealed that they grow epitaxially and coherently. When the cluster size is small, they have almost the same sizes. When they become bigger, their heights and diameters began to show variation. In both cases, their structures were deformed due to lattice strain. Reduction and oxidation process changed their heights and morphology. These results suggest strong interaction at the interface. © 2012 The Surface Science Society of Japan.

Guo S.,Japan National Institute of Materials Science
Journal of the European Ceramic Society | Year: 2016

In this study, hybrid composites comprising SiC(SCS-6)/Ti composite and ZrB2-ZrC ceramics were prepared by sandwiching Ti/SiC(SCS-6)/Ti sheets and Zr+B4C powder layers, followed by reactive hot pressing (RHPing) between 1250°C and 1400°C. The effects of RHPing temperature on the microstructures and the mechanical behaviours of the composites were examined. For the samples prepared at 1250°C and 1300°C, a Ti-rich zone was observed in the matrix and around the fibres. However, for the sample prepared at 1400°C, no Ti-rich zone was observed. In addition, the hybrid composites show noncatastrophic fracture behaviour, irrespective of RHPing temperature. Compared to the sample processed at 1400°C, the samples processed at 1250°C and 1300°C exhibited higher flexural strength and greater damage tolerance. The lower strength and damage tolerance for the composite processed at 1400°C are attributed to stronger interface bonding via significant degradation of the C-rich coating and to strength degradation of the fibres. © 2016 Elsevier Ltd.

Guo S.,Japan National Institute of Materials Science
Journal of the American Ceramic Society | Year: 2016

In this study, hybrid composites comprising SiC(SCS-6)/Ti and ZrB2-ZrC ceramics were prepared by sandwiching Ti/SiC(SCS-6)/Ti sheets and Zr + B4C powder layers, followed by reactive hot pressing at 1300°C. The microstructure of the obtained hybrid composites was characterized by field-emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that after reactive hot pressing, a highly dense matrix was achieved in the hybrid composites. A Ti-rich zone was observed only in the hybrid composite prepared using a 10-μm-thick Ti foil. Interface reaction occurred during sintering and interface reaction layers were formed between the fibers and the matrix, and the phases were identified. In addition, the mechanical behavior of the hybrid composites was evaluated using by testing under four-point bend testing. The results indicate that the hybrid composites exhibited greater flexural strengths and noncatastrophic fracture behavior. The flexural strength ranged from 440 to 620 MPa, depending on the thickness of the Ti foils and the fiber volume amount. © 2016 American Ceramic Society.

Bressler I.,BAM Federal Institute of Materials Research and Testing | Pauw B.R.,Japan National Institute of Materials Science | Thunemann A.F.,BAM Federal Institute of Materials Research and Testing
Journal of Applied Crystallography | Year: 2015

A user-friendly open-source Monte Carlo regression package (McSAS) is presented, which structures the analysis of small-angle scattering (SAS) using uncorrelated shape-similar particles (or scattering contributions). The underdetermined problem is solvable, provided that sufficient external information is available. Based on this, the user picks a scatterer contribution model (or 'shape') from a comprehensive library and defines variation intervals of its model parameters. A multitude of scattering contribution models are included, including prolate and oblate nanoparticles, core-shell objects, several polymer models, and a model for densely packed spheres. Most importantly, the form-free Monte Carlo nature of McSAS means it is not necessary to provide further restrictions on the mathematical form of the parameter distribution; without prior knowledge, McSAS is able to extract complex multimodal or odd-shaped parameter distributions from SAS data. When provided with data on an absolute scale with reasonable uncertainty estimates, the software outputs model parameter distributions in absolute volume fraction, and provides the modes of the distribution (e.g. mean, variance etc.). In addition to facilitating the evaluation of (series of) SAS curves, McSAS also helps in assessing the significance of the results through the addition of uncertainty estimates to the result. The McSAS software can be integrated as part of an automated reduction and analysis procedure in laboratory instruments or at synchrotron beamlines.

Tanaka A.,Japan National Institute of Materials Science
Journal of Physics: Conference Series | Year: 2011

We revisit our framework for studying competing orders in quantum antiferro-magnets (A. Tanaka and X. Hu, Phy. Rev. Lett. 95 (2005) 036402; Phys. Rev. B 74 (2006) 140407(R)), in which we showed that when two or more ordering tendencies are organized into a single composite order parameter, the corresponding effective sigma model action can generally host a new topological term. It has since been argued by several authors that such terms are indicative of novel critical behaviors. Here we reinforce this assertion by searching for nonva-nishing fermionic bilinears (Golstone-Wilczek-type currents) associated with the same models. We arrive at a duality relation among the competing orders (e.g. a direct relation between the topological charge of the antiferromagnetic order sector and a Noether current associated with the rotational symmetry in the valence bond solid order sector), which becomes relevant upon approaching criticality. We also discuss the physical implications of this duality in the context of topological insulators. © 2011 Published under licence by IOP Publishing Ltd.

Dong S.,Stanford University | Watanabe M.,Japan National Institute of Materials Science | Dauskardt R.H.,Stanford University
Advanced Functional Materials | Year: 2014

The successful deposition of conductive transparent TiNx/ TiO2 hybrid films on both polycarbonate and silicon substrates from a titanium ethoxide precursor is demonstrated in air using atmospheric plasma processing equipped with a high-temperature precursor delivery system. The hybrid film chemical composition, deposition rates, optical and electrical properties along with the adhesion energy to the polycarbonate substrate are investigated as a function of plasma power and plasma gas composition. The film is a hybrid of amorphous and crystalline rutile titanium oxide phases and amorphous titanium nitride that depend on the processing conditions. The visible transmittance increases from 71% to 83% with decreasing plasma power and increasing nitrogen content of the plasma gas. The film resistivity is in the range of ∼8.5 × 101 to 2.4 × 105 ohm cm. The adhesion energy to the polycarbonate substrate varies from ∼1.2 to 8.5 J/m2 with increasing plasma power and decreasing plasma gas nitrogen content. Finally, annealing the film or introducing hydrogen to the primary plasma gas significantly affects the composition and decreases thin-film resistivity. The successful deposition of conductive transparent TiN x/TiO2 hybrid films on polycarbonate substrates is demonstrated in air using atmospheric plasma processing. The visible transmittance ranges from 71% to 83% and the film resistivity is in the range ∼6.0 × 10-1 to 2.4 × 105 ohm cm. It provides a new promising way to fabricate transparent conductive films with low cost. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hollamby M.J.,Japan National Institute of Materials Science
Physical Chemistry Chemical Physics | Year: 2013

Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel. Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below. © 2013 the Owner Societies.

Furumi S.,Japan National Institute of Materials Science | Furumi S.,Japan Science and Technology Agency | Furumi S.,University of Tsukuba
Polymer Journal | Year: 2013

This article describes an overview of recent developments in fabrication and uses of self-assembled photonic crystals (PCs) of organic and polymer materials, such as chiral liquid crystals (CLCs) and colloidal crystals (CCs), for laser applications. Both CLCs and CCs have intrinsic capabilities to spontaneously assemble 1D-PC and 3D-PC structures, respectively. When a periodic length in the PC structures of CLCs and CCs corresponds to several hundred nanometers of the light wavelength, the photonic band-gaps (PBGs) can be visualized as Bragg reflection colors. When combining fluorescence dyes in the CLCs and CCs, the stimulated laser action at PBG band edge(s) or within the PBG wavelength can be generated by optical excitation. Moreover, the optically excited laser action is controllable by external stimuli due to the self-organization of CLCs and CCs. This review highlights not only the research backgrounds of CLC and CC structures as PCs, but also the experimental results of their versatile soft and tunable laser applications. We believe that a wide variety of CLC and CC structures will have leading roles in the next generation of optoelectronic devices of organic and polymer materials. © 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved.

Wang P.L.,McMaster University | Kolodiazhnyi T.,Japan National Institute of Materials Science | Yao J.,McMaster University | Mozharivskyj Y.,McMaster University
Journal of the American Chemical Society | Year: 2012

Compromise between the electrical conductivity and Seebeck coefficient limits the efficiency of chemical doping in the thermoelectric research. An alternative strategy, involving the control of a local crystal structure, is demonstrated to improve the thermoelectric performance in the RE 2SbO 2 system. The RE 2SbO 2 phases, adopting a disordered anti-ThCr 2Si 2-type structure (I4/mmm), were prepared for RE = La, Nd, Sm, Gd, Ho, and Er. By traversing the rare earth series, the lattice parameters of the RE 2SbO 2 phases are gradually reduced, thus increasing chemical pressure on the Sb environment. As the Sb displacements are perturbed, different charge carrier activation mechanisms dominate the transport properties of these compounds. As a result, the electrical conductivity and Seebeck coefficient are improved simultaneously, while the number of charge carriers in the series remains constant. © 2012 American Chemical Society.

Hosoda N.,Japan National Institute of Materials Science | Gorb S.N.,University of Kiel
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

For the first time, we report the remarkable ability of the terrestrial leaf beetle Gastrophysa viridula to walk on solid substrates under water. These beetles have adhesive setae on their feet that produce a secretory fluid having a crucial role in adhesion on land. In air, adhesion is produced by capillary forces between the fluid-covered setae and the substrate. In general, capillary forces do not contribute to adhesion under water. However, our observations showed that these beetles may use air bubbles trapped between their adhesive setae to walk on flooded, inclined substrata or even under water. Beetle adhesion to hydrophilic surfaces under water was lower than that in air, whereas adhesion to hydrophobic surfaces under water was comparable to that in air. Oil-covered hairy pads had a pinning effect, retaining the air bubbles on their feet. Bubbles in contact with the hydrophobic substrate de-wetted the substrate and produced capillary adhesion. Additional capillary forces are generated by the pad's liquid bridges between the foot and the substrate. Inspired by this idea, we designed an artificial silicone polymer structure with underwater adhesive properties. © 2012 The Royal Society.

Yamasaki S.,Japan National Institute of Advanced Industrial Science and Technology | Gheeraert E.,CNRS Neel Institute | Koide Y.,Japan National Institute of Materials Science
MRS Bulletin | Year: 2014

Diamond has been attracting the attention of many researchers because of its potential for new applications such as in quantum devices and power electronics. These applications are enabled by the progress made in improving the quality of undoped, boron-doped, and phosphorus-doped diamond films grown by chemical vapor deposition techniques. Recent progress in diamond film growth and heterostructures of diamond and other compound semiconductors to realize these electronics applications are reported. © Materials Research Society 2014.

Hayami W.,Japan National Institute of Materials Science
Journal of Solid State Chemistry | Year: 2014

It is known that elemental boron has five polymorphs: α- and β-rhombohedral, α- and β-tetragonal, and the high-pressure γ phase. β-tetragonal (β-t) boron was first discovered in 1960, but there have been only a few studies since then. We have thoroughly investigated, using first-principles calculations, the atomic and electronic structures of β-t boron, the details of which were not known previously. The difficulty of calculation arises from the fact that β-t boron has a large unit cell that contains between 184 and 196 atoms, with 12 partially-occupied interstitial sites. This makes the number of configurations of interstitial atoms too great to calculate them all. By introducing assumptions based on symmetry and preliminary calculations, the number of configurations to calculate can be greatly reduced. It was eventually found that β-t boron has the lowest total energy, with 192 atoms (8 interstitial atoms) in an orthorhombic lattice. The total energy per atom was between those of α- and β-rhombohedral boron. Another tetragonal structure with 192 atoms was found to have a very close energy. The valence bands were fully filled and the gaps were about 1.16 to 1.54 eV, making it comparable to that of β-rhombohedral boron. © 2014 Elsevier Inc. All rights reserved.

Higuchi M.,Japan National Institute of Materials Science | Higuchi M.,Japan Science and Technology Agency
Journal of Materials Chemistry C | Year: 2014

Metallo-supramolecular polymers, which were synthesized via the 1:1 complexation of metal ions with ditopic organic ligands, showed unique electro- and photo-chemical properties based on the metal-ligand or metal-metal interactions. Fe(ii)-, Ru(ii)- and Cu(ii)-based metallo-supramolecular polymer films exhibited reversible electrochromic behaviour and electrochromic display devices were successfully fabricated. A polymer containing both Fe(ii) and Ru(ii) ions exhibited multi-colour electrochromic properties. Ionic conductivity of a Ni(ii)-based polymer film was significantly enhanced with increasing humidity, and real-time humidity sensing was realized by utilizing the polymer film. A Eu(iii)-based polymer showed vapoluminescence. Reversible switching of emission was achieved in the polymer with Fe(ii) and Eu(iii) ions introduced in an alternating manner. This journal is © the Partner Organisations 2014.

Tsai A.-P.,Tohoku University | Tsai A.-P.,Japan National Institute of Materials Science
Chemical Society Reviews | Year: 2013

The geometrical concept and structural framework of quasicrystals (QCs) were established shortly after the discovery of QCs. Specifically, the static and dynamic properties of the atoms and the electronic structures of quasiperiodic lattices were theoretically developed. Experimental studies lagged behind theoretical progress due to the lack of suitable samples. This situation changed with the discovery of several highly ordered stable QCs. Studies of these new QCs have provided new insights into the structure and properties of QCs. This article chronologically reviews the discoveries of various stable icosahedral QCs and subsequent studies that determined their structures, properties, and stabilization mechanisms. © 2013 The Royal Society of Chemistry.

Ramanathan M.,Oak Ridge National Laboratory | Tseng Y.-C.,Natural Resources Canada | Tseng Y.-C.,McMaster University | Ariga K.,Japan National Institute of Materials Science | And 2 more authors.
Journal of Materials Chemistry C | Year: 2013

Block copolymers with metals confined in one or more blocks are emerging as candidate materials for nanomanufacturing applications due to their unprecedented nanoscale pattern transfer capabilities. In this article we highlight recent developments in metal-containing block copolymers in terms of their novel synthetic methodologies with particular emphasis on sequential infiltration synthesis, their hierarchical self-assembly from nano, meso, and submicron scales, and their applications as an etch mask for high-throughput, high-aspect-ratio nano and meso scale patterning. © 2013 The Royal Society of Chemistry.

Shinohara T.,Japan National Institute of Materials Science
Zairyo to Kankyo/ Corrosion Engineering | Year: 2014

Atmospheric corrosion commonly initiates and develops under thin water films formed by dew or rain drops. A composition of water film depends on the air pollutant deposition rate, and changes with the humidity and temperature conditions of the atmosphere. Many sensors and the measurement techniques have been developed to evaluated corrosivities in atmospheric environments and corrosion behaviors in those environments. In this paper, the present state and visions of atmospheric corrosion researches are discussed based on the roles of water and deposits and environmental factors which are evaluated by those sensors and measurement techniques.

Qin W.,University of Saskatchewan | Qin W.,McGill University | Szpunar J.A.,University of Saskatchewan | Umakoshi Y.,Japan National Institute of Materials Science
Acta Materialia | Year: 2011

Electron or ion irradiation-induced phase change between the amorphous and crystalline state is a long-standing and puzzling problem. In this paper, the energy dissipation based on irradiation-assisted atomic rearrangement was found to be a crucial mechanism for irradiation-induced crystallization. The occurrence of crystallization needs to meet two criteria: (i) that the irradiation enhances the atomic order and (ii) that the crystalline nuclei are structurally stable. This work provides a general answer as to why the external energy deposition into an amorphous system could cause the lowering of free energy and trigger the athermal transformation from the amorphous to the crystalline state. Based on the energy dissipation assumption and the modified Lindemann model, the underlying relationship between irradiation-induced crystallization and amorphization was clarified. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Wang Z.L.,Georgia Institute of Technology | Wang Z.L.,Japan National Institute of Materials Science
Advanced Materials | Year: 2012

Sensor networks are a key technological and economic driver for global industries in the near future, with applications in health care, environmental monitoring, infrastructure monitoring, national security, and more. Developing technologies for self-powered nanosensors is vitally important. This paper gives a brief summary about recent progress in the area, describing nanogenerators that are capable of providing sustainable self-sufficient micro/nanopower sources for future sensor networks. Sensor networks are a key technological and economic driver for global industries in the near future, with applications in health care, environmental monitoring, infrastructure monitoring, national security, and more. This paper introduces a technology that is capable of providing sustainable self-sufficient micro/nano-power sources for future sensor networks. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Naito K.,Japan National Institute of Materials Science | Kagawa Y.,Tokyo University of Science | Kurihara K.,Tokyo University of Science
Composite Structures | Year: 2012

Electromagnetic wave reflections from glass fiber reinforced epoxy matrix composites with 0°/90° and ±45° fiber oriented plain-woven glass fabric (PW-GFRP-0/90, PW-GFRP-±45) at incident angles of 30°, 40° and 50° were measured in the frequency range 50-75. GHz using a free-space reflection measurement system. The complex dielectric constants of both composites were calculated using a simple transmission line theory. The complex dielectric constants of PW-GFRP-0/90 and PW-GFRP-±45 are similar and were measured to be ε'. =. 4.61. ±. 0.01 and ε'. =. 0.16. ±. 0.002, respectively.The damage stored in PW-GFRP-0/90 and PW-GFRP-±45 was also evaluated by dielectric constant changes using the same system at an incident angle of 30°. For both composites, ε' decreased with increasing applied stress and damage parameter. The dielectric constant change is effective for detecting the damage stored in composites and can be used to quantitatively evaluate the damage. © 2011 Elsevier Ltd.

Iliev H.,Sofia University | Buchvarov I.,Sofia University | Kurimura S.,Japan National Institute of Materials Science | Petrov V.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy
Optics Letters | Year: 2010

Periodically poled stoichiometric lithium-tantalate is used for mode locking of a diode-pumped Nd: GdVO4 laser by intracavity second-harmonic generation. Stable and self-starting operation is observed achieving average output powers of up to 5 W at a pulse-repetition rate of 107 MHz. The obtained pulse durations range from 6.5 ps at maximum output power down to 3.2 ps at 1.4 W. © 2010 Optical Society of America.

Calcagnotto M.,Max Planck Institute Fur Eisenforschung | Adachi Y.,Japan National Institute of Materials Science | Ponge D.,Max Planck Institute Fur Eisenforschung | Raabe D.,Max Planck Institute Fur Eisenforschung
Acta Materialia | Year: 2011

Three ferrite/martensite dual-phase steels varying in the ferrite grain size (12.4, 2.4 and 1.2 μm) but with the same martensite content (∼30 vol.%) were produced by large-strain warm deformation at different deformation temperatures, followed by intercritical annealing. Their mechanical properties were compared, and the response of the ultrafine-grained steel (1.2 μm) to aging at 170 °C was investigated. The deformation and fracture mechanisms were studied based on microstructure observations using scanning electron microscopy and electron backscatter diffraction. Grain refinement leads to an increase in both yield strength and tensile strength, whereas uniform elongation and total elongation are less affected. This can be partly explained by the increase in the initial strain-hardening rate. Moreover, the stress/strain partitioning characteristics between ferrite and martensite change due to grain refinement, leading to enhanced martensite plasticity and better interface cohesion. Grain refinement further promotes ductile fracture mechanisms, which is a result of the improved fracture toughness of martensite. The aging treatment leads to a strong increase in yield strength and improves the uniform and total elongation. These effects are attributed to dislocation locking due to the formation of Cottrell atmospheres and relaxation of internal stresses, as well as to the reduction in the interstitial carbon content in ferrite and tempering effects in martensite. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Celardo I.,University of Rome Tor Vergata | Pedersen J.Z.,University of Rome Tor Vergata | Traversa E.,Japan National Institute of Materials Science | Ghibelli L.,University of Rome Tor Vergata
Nanoscale | Year: 2011

Nanotechnology promises a revolution in pharmacology to improve or create ex novo therapies. Cerium oxide nanoparticles (nanoceria), well-known as catalysts, possess an astonishing pharmacological potential due to their antioxidant properties, deriving from a fraction of Ce 3+ ions present in CeO 2. These defects, compensated by oxygen vacancies, are enriched at the surface and therefore in nanosized particles. Reactions involving redox cycles between the Ce 3+ and Ce 4+ oxidation states allow nanoceria to react catalytically with superoxide and hydrogen peroxide, mimicking the behavior of two key antioxidant enzymes, superoxide dismutase and catalase, potentially abating all noxious intracellular reactive oxygen species (ROS) via a self-regenerating mechanism. Hence nanoceria, apparently well tolerated by the organism, might fight chronic inflammation and the pathologies associated with oxidative stress, which include cancer and neurodegeneration. Here we review the biological effects of nanoceria as they emerge from in vitro and in vivo studies, considering biocompatibility and the peculiar antioxidant mechanisms. © 2011 The Royal Society of Chemistry.

El-Safty S.A.,Japan National Institute of Materials Science
Journal of Porous Materials | Year: 2011

The development of the nanoscale structures and their integration into components, systems, and natural architectures (such as monoliths), and large-scale devices, is one of the most promising areas in the emerging field of nanotechnology.We believe that it is time to write a review that focused on the rapid synthesis and the functional properties of HOM mesoporous monoliths. Thus, we here introduce comprehensive and up-to-date reports on the instant synthesis (within minutes) of a range of mesoporous silica monoliths (HOM-type, High-Order-Monolith) by means of a directlating method of lyotropic and microemulsion liquid crystalline phases. A number of nonionic n-alkyl-oligo(ethylene oxide), namely, Brij-type (CxEOy), and Triton- and Tween-type and cationic alkyl trimethylammonium bromide or chloride (CnTMA-B or -C, where n = 12, 14, 16 and 18) surfactants were used as soft templates. A variety of 1D, 2D and 3D mesostructure geometries were successfully fabricated by using this simple, fast and yet reproducible design strategy. This is the first and detailed review of using rapid synthesis to fabricate disordered and ordered silica/surfactant mesophases with supermicro- and meso-pore engineering systems. In this review, we also addressed the prominent factors affected the formation of the large-scale ordered and worm-like structures (HOM): (1) the phase composition of domains, (2) the extent of solubilization of hydrocarbons, and (3) the nature of surfactant molecules (corona/ core features). Significantly, due to large morphological particle sizes, these HOM monolithic structures exhibited considerable structural stability against longer hydrothermal treatment times. Such retention is crucial in industrial applications. © Springer Science+Business Media, LLC 2010.

Timokhina I.B.,Deakin University | Beladi H.,Deakin University | Xiong X.Y.,Monash University | Adachi Y.,Japan National Institute of Materials Science | Hodgson P.D.,Deakin University
Acta Materialia | Year: 2011

A 0.79 C-1.5 Si-1.98 Mn-0.98 Cr-0.24 Mo-1.06 Al-1.58 Co (wt.%) steel was isothermally heat treated at 200 °C for 10 days and 350 °C for 1 day to form a nanoscale bainitic microstructure consisting of nanobainitic ferrite laths with high dislocation density and retained austenite films. The microstructures of the samples were characterized by transmission electron microscopy and atom probe tomography. Despite the formation of nanoscale bainite with a high volume fraction of retained austenite in both steels, the ductility of both steels was surprisingly low. It is believed that this was associated with the formation of carbon-depleted retained austenite after isothermal transformation at 200 °C due to the formation of high number of Fe-C clusters and particles in the bainitic ferrite laths and carbon-enriched austenite after isothermal transformation at 350 °C. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Spevacek J.,Czech Institute of Macromolecular Chemical | Hanykova L.,Charles University | Labuta J.,Japan National Institute of Materials Science
Macromolecules | Year: 2011

The behavior of water during the temperature-induced phase separation in PVME/D2O solutions was investigated by 1H NMR methods and optical microscopy. A fast exchange between water (HDO) bound in mesoglobules and free water was found from 1H NMR spin-spin relaxation measurements at temperature above the LCST transition for semidilute PVME/D 2O solutions where the exchange time is 1.2 ms for c = 6 wt %. In contrast, there is a slow exchange between bound and free water in highly concentrated PVME solutions and the residence time of the bound water 2 s was found for concentrations c = 20-50 wt % using one-dimensional NOE 1H NMR experiment. A 3 order of magnitude slower exchange in highly concentrated PVME/D2O solutions is in accord with our optical microscopy findings that globular-like structures are here approximately 20 times larger than in PVME solution with c = 6 wt %. © 2011 American Chemical Society.

Hu X.,Japan National Institute of Materials Science
Advanced Materials | Year: 2012

Spintronics is expected as the next-generation technology based on the novel notch of spin degree of freedom of electrons. Half-metals, a class of materials which behave as a metal in one spin direction and an insulator in the opposite spin direction, are ideal for spintronic applications. Half-metallic antiferromagnets as a subclass of half-metals are characterized further by totally compensated spin moments in a unit cell, and have the advantage of being able to generate fully spin-polarized current while exhibiting zero macroscopic magnetization. Considerable efforts have been devoted to the search for this novel material, from which we may get useful insights for prospective material exploration. Half-metals are a class of materials that behave as a metal in one spin direction and an insulator in the opposite spin direction. Half-metallic antiferromagnets as a subclass of half-metals are characterized further by totally compensated spin moments in a unit cell. Being able to generate fully spin-polarized current while exhibiting zero macroscopic magnetization, half-metallic antiferromagnets are expected as one of the most ideal materials for spintronic applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ida T.,Nagoya Institute of Technology | Izumi F.,Nagoya Institute of Technology | Izumi F.,Japan National Institute of Materials Science
Journal of Applied Crystallography | Year: 2011

A new methodology is proposed for structure refinement using powder diffraction data, from which models for particle statistics and any other statistical errors can be formally optimized. This method is nothing but a straightforward implementation of the maximum-likelihood method, extended to the error estimation. Structure parameters refined by the method for fluorapatite [Ca5(PO4)3F], anglesite (PbSO4) and barite (BaSO4) become significantly closer to those obtained by single-crystal structure analyses in comparison with the results of the conventional Rietveld method. © 2011 International Union of Crystallography.

Furumi S.,Japan National Institute of Materials Science | Ichimura K.,Toho University
Physical Chemistry Chemical Physics | Year: 2011

Highly sensitive photoalignment of liquid crystals (LCs) can be realized by axis-selective triplet energy transfer. Addition of a triplet photosensitizer (phosphorescent donor) into a photocrosslinkable polymer tethering E-cinnamate side chains ensures dramatic enhancement of photosensitivity to generate the optical anisotropy of polymer film and surface-assisted LC photoalignment. Photoirradiation of triplet photosensitizer-doped polymer films with linearly polarized 365 nm light for the selective excitation of triplet sensitizer gives rise to optical anisotropy of cinnamates as a result of axis-selective triplet energy transfer. By analyzing phosphorescence spectra with theoretical Perrin's formula, we find that triplet energy transfer is efficient within a radius of ∼0.3 nm from the triplet photosensitizer. Such photoaligned polymer films can be used for the surface-assisted orientation photocontrol of not only calamitic LC, but also discotic LC, even for extremely low exposure energies. The present procedure would be greatly advantageous for high-throughput fabrication of optical devices by photoalignment techniques. © the Owner Societies 2011.

Somekawa H.,Massachusetts Institute of Technology | Somekawa H.,Japan National Institute of Materials Science | Schuh C.A.,Massachusetts Institute of Technology
Acta Materialia | Year: 2011

The effect of solid solution alloying elements on the plastic deformation of fine grained Mg alloys was studied in five binary systems: Mg-0.3 at.% X (X = Al, Ca, Li, Y or Zn). All the alloys were produced by extrusion and had an average grain size of ∼2-3 μm. Solid solution strengthening is observed for all of the alloys subjected to hardness tests with a scale much larger than the grain size, and the efficacy of the various solutes is in line with expectations based on recent solution strengthening models. The different alloying elements also have an impact on the rate dependence of deformation, with activation volumes ranging between 20 b 3 and 80 b 3 being consistent with cross-slip as a rate limiting mechanism. For nanoscale indentations the yield point is identified by a pop-in event, and this event is found to have a dramatically different rate dependence and activation volume than does global plasticity. Specifically, the dislocation generation mechanism associated with pop-in has an activation volume of scale ∼0.2-1 b 3, and is far less affected by solute content than is global plasticity. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Solovyev I.V.,Japan National Institute of Materials Science | Pchelkina Z.V.,RAS Institute of Metal Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We present the microscopic theory of improper multiferroicity in BiMnO 3, which can be summarized as follows: (1) the ferroelectric polarization is driven by the hidden antiferromagnetic order in the otherwise centrosymmetric C2/c structure; (2) the relativistic spin-orbit interaction is responsible for the canted spin ferromagnetism. Our analysis is supported by numerical calculations of electronic polarization using the Berry-phase formalism, which was applied to the low-energy model of BiMnO3 derived from the first-principles calculations. We explicitly show how the electric polarization can be controlled by the magnetic field and argue that BiMnO3 is a rare and potentially interesting material where ferroelectricity can indeed coexist and interplay with the ferromagnetism. © 2010 The American Physical Society.

Yamaura K.,Japan National Institute of Materials Science | Yamaura K.,Hokkaido University
Journal of Solid State Chemistry | Year: 2016

High-pressure crystal growth and synthesis of selected solid-state osmium oxides, many of which are perovskite-related types, are briefly reviewed, and their magnetic and electrical properties are introduced. Crystals of the osmium oxides, including NaOsO3, LiOsO3, and Na2OsO4, were successfully grown under high-pressure and high-temperature conditions at 6 GPa in the presence of an appropriate amount of flux in a belt-type apparatus. The unexpected discovery of a magnetic metal-insulator transition in NaOsO3, a ferroelectric-like transition in LiOsO3, and high-temperature ferrimagnetism driven by a local structural distortion in Ca2FeOsO6 may represent unique features of the osmium oxides. The high-pressure and high-temperature synthesis and crystal growth has played a central role in the development of solid-state osmium oxides and the elucidation of their magnetic and electronic properties toward possible use in multifunctional devices. © 2015 Elsevier Inc. All rights reserved.

Kanai T.,Yokohama National University | Yamamoto S.,Yokohama National University | Sawada T.,Japan National Institute of Materials Science
Macromolecules | Year: 2011

A study was conducted to demonstrate the use of hydrophilic ionic liquids as suitable swelling solvents for gel-immobilized colloidal crystals. The optical stop band of the colloidal crystals had the potential to be adjusted over a wide range of wavelengths by varying the mixing ratio of hydrophilic and hydrophobic ionic liquids. It was also demonstrated that the stop-band wavelength was linearly dependent on the mixing ratio, making it more advantageous in practical applications. The system used to conduct the investigations consisted of loosely packed colloidal crystals immobilized in a hydrogel film. It was demonstrated that a gel film shrunk considerably when it was soaked in hydrophobic ionic liquids, such as 1,3-diallylimidazolium bis(trifluoromethanesulfonyl)imide. It was observed that the structure of the colloidal crystal immobilized in the gel was destroyed, the sample turned cloudy, and the Bragg peak in the spectrum disappeared in such a case.

Mandal M.,Indian Institute of Technology Kanpur | Moon A.P.,Indian Institute of Technology Kanpur | Deo G.,Indian Institute of Technology Kanpur | Mendis C.L.,Japan National Institute of Materials Science | Mondal K.,Indian Institute of Technology Kanpur
Corrosion Science | Year: 2014

The corrosion behavior of few cast Mg-Zn alloys, micro-alloyed with Ag and/or Ca (0.1. at.% each), has been investigated in 3.5. wt.% NaCl solution with the help of dynamic polarization, electrochemical impedance spectroscopy, and immersion tests. The effect of microstructures on corrosion behavior has been discussed thoroughly. The corrosion products formed on the immersed samples have been characterized by X-ray diffraction and Fourier transformed infrared spectroscopy. It has been observed that the Ca containing alloys show good corrosion resistance. This is attributed to the particular microstructure and carbonate-based protective film (corrosion products) formed on the surface. © 2013 Elsevier Ltd.

Gong W.,Ibaraki University | Tomota Y.,Ibaraki University | Koo M.S.,POSCO | Adachi Y.,Japan National Institute of Materials Science
Scripta Materialia | Year: 2010

The effect of ausforming on kinetics, morphology and crystallography of nanobainite steel was examined by electron backscattered diffraction and transmission electron microscopy. Ausforming has been found to accelerate bainite transformation at 573 K. A characteristic microstructure consisting of blocky bainitic laths and retained austenite is observed in the ausformed bainite steel, where strong variant selection takes place due to the operated slip systems. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Samitsu S.,Kyoto University | Samitsu S.,Japan National Institute of Materials Science | Takanishi Y.,Kyoto University | Yamamoto J.,Kyoto University
Nature Materials | Year: 2010

Collective long-range interactions between micrometre-sized impurities in liquid crystals result from the elastic distortion of the liquid-crystalline order1-8. For substantially smaller polymeric impurities, what is relevant is not the elastic interaction between them but the coupling between the scalar nematic order parameter S and the polymer concentration ∅. This coupling originates from local molecular interactions, but becomes long ranged because the total polymer concentration is conserved over the whole sample. Here, we propose a new mechanism by which the spatial variation of S generates a force, mediated by the coupling between S and ∅, that transports nanoscale polymeric impurities. We have designed a prototype of a molecular manipulator that moves molecules along spatial variations of the scalar order parameter, modulated in a controlled manner by spot illumination of an azobenzene-doped nematic phase with ultra-violet light. We also demonstrate the use of the manipulator for the measurement of the anisotropic diffusion constant of a polymer in the nematic phase. The manipulator can control the spatial variation of the polymer concentration, thus showing promise for use in the design of hybrid soft materials. © 2010 Macmillan Publishers Limited. All rights reserved.

Guo S.,Japan National Institute of Materials Science
Ceramics International | Year: 2014

In this study, two methods of powder reactions and reactive hot-pressing were used for the reaction of Zr+B4C powder mixtures. The powder reactions were performed at various temperatures, between 600 °C and 1100 °C, to examine the reaction behaviour occurring during the synthesis. To fabricate a cermet composed of platelet-like ZrB2 grains and equiaxed ZrCx grains, with intergranular Zr phase, reactive hot-pressing was conduced within temperature range of 1100-1900 °C. The effects of temperature on the reactions, densification behaviour and microstructure of the samples were assessed. For samples sintered at 900 °C or above, the Zr+B4C mixture was converted into ZrB2 and ZrC x; the conversion was completed at ~1100 °C. Densification resulted from volume contraction due to the conversion of Zr+B4C mixture into ZrB2 and ZrCx, and the shrinkage due to grain boundary diffusion and grain boundary migration. For Zr+B4C mixtures sintered at or above 1400 °C, relative densities exceeding 97% were obtained. When sintered at or below 1400 °C, the resulting ZrB 2-ZrCx-Zr cermet consisted of rod-like ZrB2 grains, equiaxed ZrCx grains and residual Zr. Highly-developed platelet-like ZrB2-ZrCx-Zr cermet was obtained only at sintering temperature of 1600 °C or greater. © 2014 Elsevier Ltd and Techna Group S.r.l.

He D.F.,Japan National Institute of Materials Science
Review of Scientific Instruments | Year: 2011

By improving the compensation circuit, a hand-held high-Tc rf superconducting quantum interference devices (SQUID) system was developed. It could operate well when moving in unshielded environment. To check the operation, it was used to do eddy-current testing by hand moving the SQUID, and the artificial defect under 6 mm aluminum plate could be successfully detected in shielded environment. © 2011 American Institute of Physics.

Hill J.P.,Japan National Institute of Materials Science
Angewandte Chemie - International Edition | Year: 2016

Here comes the sun: By using a combined strategy of molecular engineering and cosensitization, impressively high Jsc and Voc values were achieved for porphyrin dyes, resulting in high photovoltaic efficiencies up to 11.5 %, a record for non-ruthenium dye-sensitized solar cells (DSSCs) with the I-/I3 - electrolyte. The results provide insight into furthering the development of efficient DSSCs through synergistically enhanced photovoltage and photocurrent. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ruiz-Hitzky E.,CSIC - Institute of Materials Science | Darder M.,CSIC - Institute of Materials Science | Aranda P.,CSIC - Institute of Materials Science | Ariga K.,Japan National Institute of Materials Science
Advanced Materials | Year: 2010

The rapid increase of interest in the field of biohybrid and biomimetic materials that exhibit improved structural and functional properties is attracting more and more researchers from life science, materials science, and nanoscience. Concomitant results offer valuable opportunities for applications that involve disciplines dealing with engineering, biotechnology, medicine and pharmacy, agriculture, nanotechnology, and others. In the current contribution we collect recent illustrative examples of assemblies between materials of biological origin and inorganic solids of different characteristics (texture, structure, and particle size). We introduce here a general overview on strategies for the preparation and conformation of biohybrids, the synergistic effects that determine the final properties of these materials, and their diverse applications, which cover areas as different as tissue engineering, drug delivery systems, biosensing devices, biocatalysis, green nanocomposites, etc. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

Xuan T.-T.,East China Normal University | Liu J.-Q.,East China Normal University | Xie R.-J.,Japan National Institute of Materials Science | Li H.-L.,East China Normal University | Sun Z.,East China Normal University
Chemistry of Materials | Year: 2015

High quality CdS/ZnS:Cu quantum dots (QDs) were first synthesized via a green microwave irradiation route. As-prepared core/shell doped QDs presented a strong absorption in the blue light region and highly efficient red to deep red emission with a maximum quantum yield of 40%. The composite formed by dispersing CdS/ZnS:Cu QDs into silicone resin showed an excellent photostability under blue illumination. Finally, high color rendition white light was generated from the CdS/ZnS:Cu QDs-assisted phosphor-converted white light-emitting diode (WLED) in which there was no reabsorption between quantum dots and phosphors. Under operation of 40 mA forward bias current, the fabricated WLED emitted bright natural white light with a high color rendering index of 90, a luminous efficiency of 46.5 lm/W, and the correlated color temperature of 6591 K. Simultaneously, the good color stability was accompanied by the CIE color coordinates of (0.3155, 0.3041) under different forward bias currents. © 2015 American Chemical Society.

Kobayashi T.,Japan National Institute of Materials Science
Chemical Physics Letters | Year: 2013

Intense radiation of light, covering the visible region and extending into the infrared region, has been observed when powder materials are shock compressed in plate-impact experiments. The time duration of the radiation is on the order of 10 ns, and the intensity increases with the shock strength, but intense radiation is still observed in the visible region for very weak shocks. Thermal radiation from the shock-compressed powder cannot explain the observed radiation spectrum. Adiabatic compression of the residual gas in the shock-compressed powder appears to generate high temperatures and intense thermal radiation. © 2013 Elsevier B.V. All rights reserved.

Kimoto K.,Japan National Institute of Materials Science | Ishizuka K.,INC Research
Ultramicroscopy | Year: 2011

We demonstrate spatially resolved diffractometry in which diffraction patterns are acquired at two-dimensional positions on a specimen using scanning transmission electron microscopy (STEM), resulting in four-dimensional data acquisition. A high spatial resolution of about 0.1. nm is achieved using a stabilized STEM instrument, a spherical aberration corrector and various post-acquisition data processings. We have found a few novel results in the radial and the azimuthal scattering angle dependences of atomic-column contrast in STEM images. Atomic columns are clearly observed in dark field images obtained using the excess Kikuchi band intensity even in small solid-angle detection. We also find that atomic-column contrasts in dark field images are shifted in the order of a few tens of picometers on changing the azimuthal scattering angle. This experimental result is approximately interpretable on the basis of the impact parameter in Rutherford scattering. Spatially resolved diffractometry provides fundamental knowledge related to various STEM techniques, such as annular dark field (ADF) and annular bright field (ABF) imaging, and it is expected to become an analytical platform for advanced STEM imaging. © 2011 Elsevier B.V.

Gercsi Z.,Imperial College London | Hono K.,Japan National Institute of Materials Science | Sandeman K.G.,Imperial College London
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We extend our previous theoretical study of Mn-based orthorhombic metamagnets to those that possess large nearest neighbor Mn-Mn separations (d1≥3.22̊). Based on our calculations, we design and synthesize a series of alloys, CoMnGe1-xPx, to experimentally demonstrate the validity of the model. Unusually, we predict and prepare several metamagnets from two ferromagnetic end-members, thus demonstrating a new example of how to vary crystal structure, within the Pnma symmetry group, to provide highly tunable metamagnetism. © 2011 American Physical Society.

Hiraga T.,University of Tokyo | Miyazaki T.,University of Tokyo | Yoshida H.,Japan National Institute of Materials Science | Zimmerman M.E.,University of Minnesota
Geology | Year: 2013

We conducted compressional, tensile, and torsional creep experiments on fine-grained forsterite plus Ca-bearing pyroxene aggregates. A distinct microstructure with aggregation of the same phase in the direction of compression was formed in our samples after all the experiments. The stress-strain rate relationship, grain-size dependent flow strength, and the achievement of large tensile strain all indicate that samples underwent creep due to grain boundary sliding (GBS). As a result of GBS, grain-switching events allow dispersed phases to contact grains of the same phase and orient in the direction of compression. We identify similar aggregated microstructures in previously reported micrographs of polymineralic graniteorigin ultramylonites. Mineral phase mixing through GBS, which helps to retain fine grain size in rocks due to grain boundary pinning, has been speculated to occur during formation of mylonites. However, our results contradict this hypothesis because mineral aggregation through GBS promotes demixing rather than mixing of the mineral phases. GBS processes alone will not promote a transformation of well-developed monomineralic bands to polymineralic bands during mylonitization. © 2013 Geological Society of America.

Kohno M.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

In strongly correlated electron systems, the emergence of states in the Mott gap in the single-particle spectrum following the doping of the Mott insulator is a remarkable feature that cannot be explained in a conventional rigid-band picture. Here, based on an analysis of the quantum numbers and the overlaps of relevant states, as well as through a demonstration using the ladder and bilayer t-J models, it is shown that in a continuous Mott transition due to hole doping, the magnetically excited states of the Mott insulator generally emerge in the electron-addition spectrum with the dispersion relation shifted by the Fermi momentum in the momentum region where the lower Hubbard band is not completely filled. This implies that the dispersion relation of a free-electron-like mode in the electron-addition spectrum eventually transforms into essentially the momentum-shifted magnetic dispersion relation of the Mott insulator, while its spectral weight gradually disappears toward the Mott transition. This feature reflects the spin-charge separation of the Mott insulator. © 2015 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Kohno M.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

The single-particle spectral properties of the two-dimensional t-J model in the parameter regime relevant to cuprate high-temperature superconductors are investigated using cluster perturbation theory. Various anomalous features observed in cuprate high-temperature superconductors are collectively explained in terms of the dominant modes near the Mott transition in this model. Although the behavior of the dominant modes in the low-energy regime is similar to that in the two-dimensional Hubbard model, significant differences appear near the Mott transition for the high-energy electron removal excitations which can be considered to primarily originate from holon modes in one dimension. The overall spectral features are confirmed to remain almost unchanged as the cluster size is increased from 4×4 to 6×6 sites by using a combined method of the non-Abelian dynamical density-matrix renormalization group method and cluster perturbation theory. © 2015 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Imai Y.,Japan National Institute of Advanced Industrial Science and Technology | Imai M.,Japan National Institute of Materials Science
Journal of Alloys and Compounds | Year: 2011

We have calculated the band structures of Si clathrate, M 8Si38Ga8 (M = Na, K, Rb, and Cs), using the density-functional theory under the generalized gradient corrected local density approximation, where M is the encapsulated guest alkali atom. They are found to be indirect semiconductors with the calculated gaps (Eg) from 0.45 to 0.89 eV, which should be compared to the calculated gap of 0.65 eV of crystalline Si with the diamond structure. The gaps become wider with the promotion to the heavier guest alkali atoms and the reasons of gap widening are discussed using the calculated dependence of Eg on the cell-volume of guest-free silicon clathrate (Si46). Effect of the substitutional elements in the clathrate framework (Al and In in place of Ga) was also discussed. © 2010 Elsevier B.V. All rights reserved.

Ambrosi A.,Japan National Institute of Materials Science | Pumera M.,Nanyang Technological University
Physical Chemistry Chemical Physics | Year: 2010

In this article, we show that stacked graphene nanofibers (SGNFs) demonstrate superior electrochemical performance for oxidation of DNA bases over carbon nanotubes (CNTs). This is due to an exceptionally high number of accessible graphene sheet edges on the surface of the nanofibers when compared to carbon nanotubes, as shown by transmission electron microscopy and Raman spectroscopy. The oxidation signals of adenine, guanine, cytosine, and thymine exhibit two to four times higher currents than on CNT-based electrodes. SGNFs also exhibit higher sensitivity than do edge-plane pyrolytic graphite, glassy carbon, or graphite microparticle-based electrodes. We also demonstrate that influenza A(H1N1)-related strands can be sensitively oxidized on SGNF-based electrodes, which could therefore be applied to label-free DNA analysis. © 2010 the Owner Societies.

Nonomura Y.,Japan National Institute of Materials Science
Journal of the Physical Society of Japan | Year: 2014

Nonequilibrium relaxation behaviors in the Ising model on a square lattice based on the Wolff algorithm are totally different from those based on local-update algorithms. In particular, the critical relaxation is described by the stretchedexponential decay. We propose a novel scaling procedure to connect nonequilibrium and equilibrium behaviors continuously, and find that the stretched-exponential scaling region in the Wolff algorithm is as wide as the power-law scaling region in local-update algorithms. We also find that relaxation to the spontaneous magnetization in the ordered phase is characterized by the exponential decay, not the stretched-exponential decay based on local-update algorithms. Copyright © 2014 The Physical Society of Japan.

Kohashi T.,Hitachi Ltd. | Motai K.,Hitachi Ltd. | Nishiuchi T.,Hitachi Ltd. | Hirosawa S.,Hitachi Ltd. | Hirosawa S.,Japan National Institute of Materials Science
Applied Physics Letters | Year: 2014

The magnetism in the grain-boundary phase of a NdFeB sintered magnet was measured by spin-polarized scanning electron microscopy (spin SEM). A sample magnet was fractured in the ultra-high-vacuum chamber to avoid oxidation, and its magnetizations in the exposed grain-boundary phase on the fracture surface were evaluated through the spin polarization of secondary electrons. Spin-SEM images were taken as the fracture surface was milled gradually by argon ions, and the magnetization in the grain-boundary phase was quantitatively obtained separately from that of the Nd2Fe14B phase. The obtained magnetization shows that the grain-boundary phase of this magnet has substantial magnetization, which was confirmed to be ferromagnetic. © 2014 AIP Publishing LLC.

Kitashima T.,Japan National Institute of Materials Science | Kawamura T.,Mie University
Scripta Materialia | Year: 2016

The oxidation behavior of near-α Ti alloys with added Al, Ga, Sn, Zr, Mo, Nb, Ta, W, Si, and Ge was analyzed using a regression analysis technique. The regression analysis with the data for oxidation tests at 700 °C for unalloyed Ti, 10 binary alloys, and 27 multicomponent alloys showed good correlation with alloy compositions with the squared multiple correlation coefficient, 0.93. The obtained results demonstrate the role of each element in commercial alloys. The effect of microstructure on the oxidation behavior was also discussed. © 2016 Elsevier B.V.

Pratt A.,University of York | Pratt A.,Japan National Institute of Materials Science | Lari L.,University of York | Hovorka O.,University of York | And 6 more authors.
Nature Materials | Year: 2014

Geometry and confinement effects at the nanoscale can result in substantial modifications to a material's properties with significant consequences in terms of chemical reactivity, biocompatibility and toxicity. Although benefiting applications across a diverse array of environmental and technological settings, the long-term effects of these changes, for example in the reaction of metallic nanoparticles under atmospheric conditions, are not well understood. Here, we use the unprecedented resolution attainable with aberration-corrected scanning transmission electron microscopy to study the oxidation of cuboid Fe nanoparticles. Performing strain analysis at the atomic level, we reveal that strain gradients induced in the confined oxide shell by the nanoparticle geometry enhance the transport of diffusing species, ultimately driving oxide domain formation and the shape evolution of the particle. We conjecture that such a strain-gradient-enhanced mass transport mechanism may prove essential for understanding the reaction of nanoparticles with gases in general, and for providing deeper insight into ionic conductivity in strained nanostructures. © 2014 Macmillan Publishers Limited.

Peng X.,Zhejiang University | Ichinose I.,Japan National Institute of Materials Science
Nanotechnology | Year: 2011

Ultrathin MnOOH nanofibers were synthesized on a large scale from diluted Mn(NO3)2 aqueous solution at room temperature. These MnOOH nanofibers were shape-reservedly converted into Mn3O4 and MnO2 nanofibers by post-heat treatment in air at 400 °C and 600 °C for 1 h, respectively. The morphology and crystalline structures of the nanofibers were characterized by electronic microscopes and x-ray diffraction. These nanofibers had good crystalline structures. These nanofibers were in bundles with a diameter of 25 nm composed of 3-5 nm fine crystalline nanofibers. The Mn3O4 nanofibers had a specific surface area of 71 m2 g-1 and demonstrated highly catalytic degradation of the organic pollutant methylene blue with the assistance of H2O 2 at room temperature. © 2011 IOP Publishing Ltd.

Boukhvalov D.W.,Japan National Institute of Materials Science
Nanotechnology | Year: 2011

A new model for graphene epitaxially grown on silicon carbide is proposed. Density functional theory modeling of epitaxial graphene functionalization by hydrogen, fluorine, methyl and phenyl groups has been performed, with hydrogen and fluorine showing a high probability of cluster formation in high adatom concentration. It has also been shown that the clusterization of fluorine adatoms provides midgap states in formation, due to significant flat distortion of graphene. The functionalization of epitaxial graphene using larger species (methyl and phenyl groups) renders cluster formation impossible, due to the steric effect, and results in uniform coverage with the energy gap opening. © 2011 IOP Publishing Ltd Printed in the UK & the USA.

Somekawa H.,Japan National Institute of Materials Science | Mukai T.,Kobe University
Computational Materials Science | Year: 2013

The deformation behavior at the grain boundary was investigated by the molecular dynamics simulation using two models based on different kinds of [1-100] symmetric tilt boundaries (Σ25 with a tilt angle of θ = 23° and Σ10 with θ = 78°) in magnesium. Grain boundary migrations occurred in both models due to the reduction in the internal energy during deformation. The deformation mechanism at the grain boundary was shown to be the twinning induced grain boundary migration. The grain boundary migration was affected by the grain boundary structures, and it was enhanced in the grain boundaries with high energies. On the other hand, the grain boundary migration was suppressed by the addition of solute atoms, i.e., aluminum and silver. The silver atoms were found to be more effective for suppression than the aluminum atoms. These behaviors occurred in both the molecular dynamics simulation and the experiments. © 2013 Elsevier B.V. All rights reserved.

Lipopeptide amphiphiles are an important class of biobased and biomimetic surfactants that are easily prepared from the cheapest organic reagents, such as natural fatty and amino acids, and in many cases, the resulting compounds are able to harden not only common organic solvents but also waxes, water and ionic liquids. Well-tailored, these gelators can be selective for one variety of liquid, which leads to the formation of a robust gel that is able to incorporate various different elements. In this review, we attempted to provide our opinion regarding the molecular design of the lipopeptide gelator candidates. In addition, we summarized each type of element that is necessary for creating potent supramolecular gel templates that are useful for inorganic nano- and micro-material preparation. This review is not only limited to recent papers found in the literature; a portion of our unpublished results are also provided as a supplement to illustrate our point of view regarding this subject. © 2014 Elsevier B.V.

Furuya Y.,Japan National Institute of Materials Science
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2016

Predictions of gigacycle fatigue strength in high-strength steel were derived by using previously proposed method and past fatigue test results. The predictions were proposed for 5 grades of high-strength steel mainly under R= -1. SUP7 then had 2 heat treatment conditions and predictions for SCM440 were not only under R= -1 but also under R= 0. Accuracy of the predictions was mostly good, while the predictions for S40C, SUJ2 and SCM440 under R= -1 showed a little bit inferior accuracy to others. Although the accuracy for S40C was the lowest, this was perhaps attributable to large scattering of the fatigue test results caused by poor hardenability. In these analysis, existence of fatigue limits was suggested in case of the internal fracture. The new fatigue limits could probably be confirmed by conducting 1011 cycles fatigue tests in future. Temporary predictions of the fatigue limits were derived in this report. Predicted S-N curves showed large difference among the steel grades in a short life region, while the difference was small in a gigacycle region. Although the predicted gigacycle fatigue strength were reduced according to increase of the inclusion size, the reduction became gentle for large inclusions. Accordingly, terribly low fatigue strengths were not predicted even for huge inclusions. Mean stress effects showed good agreements with modified Goodman's rule. However, general predictions regardless of the steel grades were difficult to derive in this study, so analogy or additional fatigue tests were necessary to predict the gigacycle fatigue strength of unlisted steels.

Okamoto Y.,NEC Corp | Kubo Y.,Japan National Institute of Materials Science
Journal of Physical Chemistry C | Year: 2013

Ab initio molecular orbital calculations were done to examine C-O bond-breaking reactions in glyme series CH3O(CH2CH 2O)NCH3 (N = 1-4) by the attack of superoxide anion. We focused our study on N = 4 case where the reaction barrier for the bond break becomes the highest among four glymes. Intrinsic reaction coordinate calculations showed that the barrier height measured from the reaction precursor is 1.087 eV. The value is much higher than that of the analogous bond-breaking reaction in propylene carbonate. © 2013 American Chemical Society.

Van Mechelen J.L.M.,University of Geneva | Van Der Marel D.,University of Geneva | Crassee I.,University of Geneva | Kolodiazhnyi T.,Japan National Institute of Materials Science
Physical Review Letters | Year: 2011

We show an example of a purely magnetic spin resonance in EuTiO3 and the resulting new record high Faraday rotation of 590°/mm at 1.6 T for 1 cm wavelengths probed by a novel technique of magneto-optical gigahertz time-domain ellipsometry. From our transmission measurements of linear polarized light, we map out the complex index of refraction n=μ in the gigahertz to terahertz range. We observe a strong resonant absorption by magnetic dipole transitions involving the Zeeman split S=7/2 magnetic energy levels of the Eu2+ ions, which causes a very large dichroism for circular polarized radiation. © 2011 American Physical Society.

Du X.,University of Sydney | Zhou C.,Japan National Institute of Materials Science | Liu H.-Y.,University of Sydney | Mai Y.-W.,University of Sydney | Wang G.,The Clean Tech Center
Journal of Power Sources | Year: 2013

To improve the electrochemical performance of graphene materials, nitrogen-doped graphene sheets (NGS) were simultaneously reduced and functionalized with nitrogen (N) doping from graphene oxide (GO) by a simple process using 1 wt.% ammonia water solution as the reducing agent, nitrogen precursor and solvent. The NGS were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy-energy dispersive spectroscopy microanalysis, and differential scanning calorimetry. The thermal stability of NGS was much higher than that of GO. The N content in NGS was 4.4 at.% and a maximum specific capacitance up to 233.3 F g-1 was obtained at 0.5 A g-1. At 0.02 V s-1, the NGS exhibited a specific capacitance of 140.3 F g-1, which was over 8 times that of GO and nearly 2 times that of graphene without N-doping. These results revealed that N-doping of functional graphene provide remarkable improvements on the electrochemical capacitive performance of graphene materials. The NGS also showed high cycle stability of capacitive performance. © 2013 Elsevier B.V. All rights reserved.

Inoue J.-I.,Japan National Institute of Materials Science
Journal of Luminescence | Year: 2011

We theoretically discuss the influence of driving laser field on the topological nature, one of the manifestation of the electron Berry phase effect, in two-dimensional electronic systems. Adiabatic change of the laser amplitude with circular polarization alters the "order parameter", termed the Chern number, in topological insulator with broken time-reversal symmetry, resulting in photo-induced phase transition. The finding is an optical analog of the integer quantum Hall effect, that is triggered by the laser field instead of magnetic field. This parallelism suggests the similarity of effects to electron dynamics between circularly polarized light and magnetic field. © 2010 Elsevier B.V. All rights reserved.

Kotani T.,Tottori University | Kino H.,Japan National Institute of Materials Science
Journal of the Physical Society of Japan | Year: 2013

We show that we can efficiently calculate the atomization energies of homogeneous diatomic molecules from H2 through Kr2 within the convergence of chemical accuracy (

Ding Y.,East China University of Science and Technology | Xie Y.,East China University of Science and Technology | Li X.,East China University of Science and Technology | Hill J.P.,Japan National Institute of Materials Science | And 2 more authors.
Chemical Communications | Year: 2011

Di- and tripyrrin sensors D1-D4 exhibit CHEF-type fluorescence enhancement by factors up to 72 upon addition of 1 equiv. Zn2+, with tunable emission colours between green (D1) and red (D4). © 2011 The Royal Society of Chemistry.

Delbecq F.,Japan National Institute of Materials Science | Kawai T.,Tokyo University of Science
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

The colorimetric response of a polydiacetylene structure is achieved in various organic solvents.A blue-to-red transition was also observed in basic condition, not in presence of acid. The formation of colloidal DNA-lipoplex was studied by spectroscopy and electronic microscopy. A polydiacetylene (PDA) sensor derived from amine oxide amphiphile monomers displayed high sensitive colorimetric response in aqueous medium in presence of various polar solvents including methanol or dimethylformamide, but also upon exposure to other stimuli such as temperature and pH variation. In solution, at the lower pH, the zwitterionic heads of PDA are protonated and the resulted cationic extremities are able to form water insoluble lipoplex with DNA easily detected by naked eyes. The morphology of the PDA structures in solution was observed by transmission electronic microscopy (TEM) and Fourier transformed infrared (FT-IR). The colorimetric response of each sample was studied using UV-vis absorption. © 2013 Elsevier B.V.

ABE F.,Japan National Institute of Materials Science
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2015

The creep behavior, deformation mechanisms, and the correlation between creep deformation parameters and creep life have been investigated for Mod.9Cr-1Mo steel (Gr.91, 9Cr-1Mo-VNb) by analyzing creep strain data at 723 K to 998 K (450 °C to 725 °C), 40 to 450 MPa, and tr = 11.4 to 68,755 hours in NIMS Creep Data Sheet. The time to rupture tr is reasonably correlated with the minimum creep rate (Formula presented.) and the acceleration of creep rate by strain in the acceleration region dln(Formula presented.)/dε, as tr = 1.5/[(Formula presented.) (dln(Formula presented.)/dε)], where (Formula presented.) and dln(Formula presented.)/dε reflect the creep behavior in the transient and acceleration regions, respectively. The (Formula presented.) is inversely proportional to the time to minimum creep rate tm, while it is proportional to the strain to minimum creep rate εm, as (Formula presented.) = 0.54 (εm/tm). The εm decreases with decreasing stress, suggesting that the creep deformation in the transient region becomes localized in the vicinity of prior austenite grain boundaries with decreasing stress. The duration of acceleration region is proportional to the duration of transient region, while the dln(Formula presented.)/dε is inversely proportional to the εm. The tr is also correlated with the tm, as tr = g tm, where g is a constant. The present creep life equations reasonably predict the degradation in creep rupture strength at long times. The downward deviation takes place in the trvs(Formula presented.) curves (Monkman–Grant plot). At the same (Formula presented.), both the εm and tm change upon the condition of tm ∝ εm. The decrease in εm with decreasing stress, corresponding to decreasing (Formula presented.), causes a decrease in tm, indicating the downward deviation of the trvs(Formula presented.) curves. © 2015 The Minerals, Metals & Materials Society and ASM International

Guo S.,Japan National Institute of Materials Science
Ceramics International | Year: 2013

Short pitch-based carbon fiber-reinforced ZrB2-20 vol% SiC matrix composites, with fiber volume fractions in the range of 0-50%, were manufactured by a hot-press process. Highly dense composite compacts were obtained at 2000 °C and 20 MPa for 60 min in Ar atmosphere. The microstructure of the resulting composites was characterized by scanning electron microscopy. The thermal and electrical properties of the composites were evaluated at room temperature. The effects of fiber volume fraction on these properties were assessed. The thermal and electrical conductivities decreased with increase of fiber volume fraction. The thermal conductivities of the composites were 48.3-104.7 W m-1 K-1. The electrical conductivities of the composites were in the range 0.79×10 4-3.02×104 Ω-1 cm-1. © 2013 Elsevier Ltd and Techna Group S.r.l.

Naito K.,Japan National Institute of Materials Science
Journal of Materials Engineering and Performance | Year: 2016

Recent interest has emerged in techniques that modify the surfaces of carbon fibers, such as carbon nanotube (CNT) grafting or polymer coating. Hybridization of these surface modifications has the potential to generate highly tunable, high-performance materials. In this study, the mechanical properties of surface-modified polyacrylonitrile (PAN)-based and pitch-based carbon fibers were investigated. Single-filament tensile tests were performed for fibers modified by CNT grafting, dipped polyimide coating, high-temperature vapor deposition polymerized polyimide coating, grafting-dipping hybridization, and grafting-vapor deposition hybridization. The Weibull statistical distributions of the tensile strengths of the surface-modified PAN- and pitch-based carbon fibers were examined. All surface modifications, especially hybrid modifications, improved the tensile strengths and Weibull moduli of the carbon fibers. The results exhibited a linear relationship between the Weibull modulus and average tensile strength on a log-log scale for all surface-modified PAN- and pitch-based carbon fibers. © 2016, ASM International.

Solovyev I.V.,Japan National Institute of Materials Science | Solovyev I.V.,Ural Federal University
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

In many cases, the relativistic spin-orbit (SO) interaction can be regarded as a small perturbation to the electronic structure of solids and treated using regular perturbation theory. The major obstacle on this route comes from the fact that the SO interaction can also polarize the electron system and produce some additional contributions to the perturbation theory expansion, which arise from the electron-electron interactions in the same order of the SO coupling. In electronic structure calculations, it may even lead to the necessity of abandoning the perturbation theory and returning to the original self-consistent solution of Kohn-Sham-like equations with the effective potential v̂, incorporating simultaneously the effects of the electron-electron interactions and the SO coupling, even though the latter is small. In this work, we present the theory of self-consistent linear response (SCLR), which allows us to get rid of numerical self-consistency and formulate the last step fully analytically in the first order of the SO coupling. This strategy is applied to the unrestricted Hartree-Fock solution of an effective Hubbard-type model, derived from the first-principles electronic structure calculations in the basis of Wannier functions for the magnetically active states. We show that by using v̂, obtained in SCLR, one can successfully reproduce results of ordinary self-consistent calculations for the orbital magnetization and other properties, which emerge in the first order of the SO coupling. Particularly, SCLR appears to be an extremely useful approach for calculations of antisymmetric Dzyaloshinskii-Moriya (DM) interactions based on the magnetic force theorem, where only by using the total perturbation one can make a reliable estimate for the DM parameters. Furthermore, due to the powerful 2n+1 theorem, the SCLR theory allows us to obtain the total energy change up to the third order of the SO coupling, which can be used in calculations of magnetic anisotropy of compounds with low crystal symmetry. The fruitfulness of this approach for the analysis of complex magnetic structures is illustrated in a number of examples, including the quantitative description of the spin canting in YTiO3 and LaMnO3, formation of the spin-spiral order in BiFeO3, and the magnetic inversion symmetry breaking in BiMnO3, which gives rise to both ferroelectric activity and DM interactions, responsible for the ferromagnetism. In all these cases, the use of SCLR tremendously reduces the computational efforts related to the search for noncollinear magnetic structures in the ground state. © 2014 American Physical Society.

Nikolaev S.A.,Ural Federal University | Solovyev I.V.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Modern theory of the orbital magnetization is applied to the series of prototype insulating perovskite transition metal oxides (orthorhombic YTiO3, LaMnO3, and YVO3, as well as monoclinic YVO3), carrying a net ferromagnetic (FM) moment in the ground state. For these purposes, we use an effective Hubbard-type model, derived from the first-principles electronic structure calculations and describing the behavior of magnetically active states near the Fermi level. The solution of this model in the mean-field Hartree-Fock approximation with the relativistic spin-orbit coupling typically gives us a distribution of the local orbital magnetic moments, which are related to the site-diagonal part of the density matrix Dî by the "classical" expression μ0=-μBTr{LîDî}. These moments are usually well quenched by the crystal field. In this work, we evaluate "itinerant" corrections ΔM to the net FM moment, suggested by the modern theory. We show that these corrections are small and in most cases can be neglected. Nevertheless, the most interesting aspect of our analysis is that, even for these compounds, which are frequently regarded as prototype Mott insulators, the "itinerant" corrections reveal a strong k dependence in the reciprocal space, following the behavior of Chern invariants. Therefore, the small value of ΔM is the result of strong cancellation of relatively large contributions, coming from different parts of the Brillouin zone. We discuss details as well as possible implications of this cancellation, which depends on the crystal structure as well as the type of the magnetic ground state. © 2014 American Physical Society.

Sakurai H.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

β-CaCr2O4 has a cycloidal magnetic structure and isostructural NaCr2O4 shows unconventional colossal magnetoresistance below a canted antiferromagnetic (AFM) ordering temperature of TN=125 K. In this paper, magnetic and electronic properties of the solid-solution system Ca1-xNaxCr2O4, are investigated. The TN value decreases with decreasing x from x=1 to 23. A spin-glass behavior appears for 0.1≤x≤0.6. Interestingly, the spin-glass character is detected even for 23≤x≤0.95 coexisting with the AFM ordering. Curie constant increases and Weiss temperature decreases with decreasing x. Curie constant is significantly suppressed from theoretical value, suggesting large quantum fluctuations and strong hybridization between Cr and O ions for higher-x values. Substitution of Ca for Na introduces the ligand holes. The decrease in Weiss temperature points out that a single ligand hole mediates ferromagnetic interaction of approximately 400 K by the double-exchange mechanism. Saturation magnetization and magnetic susceptibility at 2 K show unusual x dependencies, which suggests that not only the canting angle but also the periodicity of magnetic ordering depend on x. Electrical resistivity for 0.2≤x≤0.95 follows the variable-range hopping mechanism, suggesting Anderson localization at the x range. © 2014 American Physical Society.

Takada K.,Japan National Institute of Materials Science
Acta Materialia | Year: 2013

The development of lithium-ion batteries has energized studies of solid-state batteries, because the non-flammability of their solid electrolytes offers a fundamental solution to safety concerns. Since poor ionic conduction in solid electrolytes is a major drawback in solid-state batteries, such studies have been focused on the enhancement of ionic conductivity. The studies have identified some high performance solid electrolytes; however, some disadvantages have remained hidden until their use in batteries. This paper reviews the development of solid electrolytes and their application to solid-state lithium batteries. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Iwanaga M.,Japan National Institute of Materials Science
Applied Physics Letters | Year: 2010

It has been experimentally and numerically shown that transmission at near infrared wavelengths is selectively controlled by polarizations in two-dimensional complementary plasmonic crystal slabs (2D c-PlCSs) of stacked unit cell. This feature is naturally derived by taking account of Babinet's principle. Moreover, the slight structural modification of the unit cell has been found to result in a drastic change in linear optical responses of stacked 2D c-PlCSs. These results substantiate the feasibility of 2D c-PlCSs for producing efficient polarizers with subwavelength thickness. © 2010 American Institute of Physics.

Furuya Y.,Japan National Institute of Materials Science
Materials Letters | Year: 2013

Internal small fatigue crack growth caused by gigacycle fatigue of high-strength steel was successfully visualized using beach marks created by a repeated two-step fatigue test. The created beach marks were clear enough to visualize the initial stage of the internal fatigue crack growth. The beach marks indicated that the internal crack shape just after initiation from an inclusion was not a circle but a half-ellipse, suggesting that the early stage of the internal crack growth requires three-dimensional modeling, and therefore, an extremely slow crack propagation rate, smaller than the lattice length, is expected in two-dimensional modeling. Moreover, it was found that the crack propagation life exceeded 1.42×107 cycles. This meant that the minimum crack propagation rate per cycle in two-dimensional modeling was smaller than the lattice length. © 2013 Elsevier B.V. All rights reserved.

Pradel K.C.,Georgia Institute of Technology | Wu W.,Georgia Institute of Technology | Ding Y.,Georgia Institute of Technology | Wang Z.L.,Georgia Institute of Technology | And 2 more authors.
Nano Letters | Year: 2014

Emerging applications in wearable technology, pervasive computing, human-machine interfacing, and implantable biomedical devices demand an appropriate power source that can sustainably operate for extended periods of time with minimal intervention (Wang, Z. L.; et al. Angew. Chem., Int. Ed. 2012, 51, 11700). Self-powered nanosystems, which harvest operating energy from its host (i.e., the human body), may be feasible due to their extremely low power consumption (Tian, B. Z.; et al. Nature 2007, 449, 885. Javey, A.; et al. Nature 2003, 424, 654. Cui, Y.; et al. Science 2001, 291, 851). Here we report materials and designs for wearable-on-skin piezoelectric devices based on ultrathin (2 μm) solution-derived ZnO p-n homojunction films for the first time. The depletion region formed at the p-n homojunction effectively reduces internal screening of strain-induced polarization charges by free carriers in both n-ZnO and Sb-doped p-ZnO, resulting in significantly enhanced piezoelectric output compared to a single layer device. The p-n structure can be further grown on polymeric substrates conformable to a human wrist and used to convert movement of the flexor tendons into distinguishable electrical signals for gesture recognition. The ZnO homojunction piezoelectric devices may have applications in powering nanodevices, bioprobes, and self-powered human-machine interfacing. © 2014 American Chemical Society.

Solovyev I.V.,Japan National Institute of Materials Science | Solovyev I.V.,Ural Federal University | Nikolaev S.A.,Ural Federal University
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We argue that many aspects of improper ferroelectric (FE) activity in orthorhombic manganites can be rationalized by considering the limit of infinite intra-atomic splitting between majority- and minority-spin states (or the double-exchange limit), which reduces the problem to the analysis of a spinless double-exchange (DE) Hamiltonian. We apply this strategy to the low-energy model, derived from the first-principles electronic-structure calculations, and combine it with the Berry-phase theory of electric polarization. We start with the analysis of the simplest two-orbital model, describing the behavior of the eg bands, and apply it to the E-type antiferromagnetic (AFM) phase, which in the DE limit effectively breaks up into one-dimensional zigzag chains. We derive an analytical expression for the electronic polarization (Pel) and explain how it depends on the orbital ordering and the energy splitting Δ between eg states. Then, we evaluate parameters of this model for the series of manganites. For these purposes, we start from a more general five-orbital model for all Mn 3d bands and construct a new downfolded model for the eg bands. From the analysis of these parameters, we conclude that the behavior of Pel in realistic manganites always corresponds to the limit of large Δ. This property holds for all considered compounds even in the local-density approximation, which typically underestimates Δ. We further utilize this property in order to derive an analytical expression for Pel in a general twofold periodic magnetic texture, based on the five-orbital model and the perturbation-theory expansion for the Wannier functions in the first order of 1/Δ. This expression explains the functional dependence of Pel on the relative directions of spins. Furthermore, it suggests that Pel is related to the asymmetry of transfer integrals, which should have simultaneously symmetric and antisymmetric components in the crystal-field representation. The main contribution to this asymmetry comes from the antiferro-orbital ordering in the ab plane. Finally, we explain how the FE polarization can be switched between orthorhombic a and c directions by inverting the zigzag AFM texture in every second ab plane. We argue that this property is generic and can be realized even in the twofold periodic texture. © 2013 American Physical Society.

Ohtake A.,Japan National Institute of Materials Science | Hagiwara A.,University of Electro - Communications | Nakamura J.,University of Electro - Communications
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

A combined experimental and theoretical study on the incorporation of Mn in GaAs has been presented. We have successfully controlled the location of Mn atoms at GaAs(001) surfaces by changing the surface atomic geometry. While Mn atoms prefer to substitute Ga sites at a subsurface layer under the As-rich conditions, the incorporation into interstitial sites becomes more favorable as the surface As coverage is decreased. The present results provide a mechanism for the enhanced incorporation of substitutional Mn atoms in GaMnAs under low-temperature (i.e., As-rich) growth conditions. © 2013 American Physical Society.

Solovyev I.V.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

MnWO4 is regarded as a canonical example of multiferroic materials, where the multiferroic activity is caused by a spin-spiral alignment. We argue that, in reality, MnWO4 has two sources of the spin spirality, which conflict with each other. One source is the Dzyaloshinskii-Moriya (DM) interactions, reflecting the P2/c symmetry of the lattice. The P2/c structure of MnWO4 has an inversion center that connects two Mn sublattices. Therefore, from the viewpoint of DM interactions, different Mn sublattices are expected to have opposite spin chirality. Another source is competing isotropic exchange interactions, which tend to form a spin-spiral texture with the same chirality in both magnetic sublattices. Thus there is a conflict between DM and isotropic exchange interactions, which makes these two sublattices inequivalent and, therefore, breaks the inversion symmetry. Our theoretical analysis is based on the low-energy model, derived from first-principles electronic structure calculations. © 2013 American Physical Society.

Yamase H.,Max Planck Institute for Solid State Research | Yamase H.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We analyze an effective model on a square lattice with two types of forward scattering interactions, which, respectively, drive ferromagnetism (FM) and electronic nematic order via a d-wave Pomeranchuk instability (dPI). The FM and dPI in general compete with each other and they are typically separated by a first-order phase boundary in the plane of the chemical potential and temperature. Nevertheless, there is a parameter region where the dPI occurs inside the FM phase, leading to their coexistence. We also study the effect of a magnetic field by choosing a chemical potential where the ground state is paramagnetic without a field. In this case, instead of FM, the dPI competes with a metamagnetic instability. The latter occurs above a threshold strength of the FM interaction and otherwise the dPI is stabilized with a dome-shaped phase diagram in the plane of a magnetic field and temperature. The FM interaction shifts the center of the dome to a lower field, accompanied by a substantial reduction of the field range where the dPI is stabilized and by an extension of the first-order part of the transition line, although the maximal critical temperature does not change. Our results indicate that proximity to the FM instability can be important to understand the experimental phase diagram observed in the bilayer ruthenate Sr3Ru2O7. © 2013 American Physical Society.

Horvath B.,Japan National Institute of Materials Science | Horvath B.,Budapest University of Technology and Economics
Microelectronics Reliability | Year: 2013

Whisker growth on electroplated bright (grain size < 0.5 μm) tin layers is examined and discussed in terms of the variety of shapes formed. Whiskers may be categorized by three basic morphological types of crystal structure which are usually observed on tin-based finishes (hillocks, nodules and filaments). In this paper, analysis of different whisker shapes and the reason for their development are defined. Constant elevated temperature in ambient humidity (105 °C/15% relative humidity) tests were used to accelerate the growth of very large whiskers (>50 μm nodule/hillock base) through enhanced diffusion, and to minimize the effect of corrosion on the samples. Cross sections from the layers and whiskers were etched and observed using a Focused Ion Beam (FIB). Transmission Electron Microscopy (TEM) was used to analyze the developing whiskers and to provide insight on the development of hillocks, nodules and filaments. Results indicate that fragmentation of a hillock/nodule, and later mass migration and segregation of copper, are critical steps in the evolution of these large whiskers. Copper impurities segregating at the whisker grain boundaries are responsible for the development of various whisker shapes. © 2013 Elsevier Ltd. All rights reserved.

Tsujii N.,Japan National Institute of Materials Science
Journal of Electronic Materials | Year: 2013

We focus on the chalcopyrite CuFeS2 to utilize the interaction between carriers and magnetic moments of Fe as a possible source to achieve high power factor. Polycrystalline samples of Cu1-x Fe1+x S2 were synthesized and their thermoelectric properties are reported. Electrical resistivity decreased by two orders of magnitude with increasing x, while the Seebeck coefficient showed large values of -200 μV/K at room temperature. Thermal conductivity also decreased with the increase of x. As a result, the power factor and the figure of merit, zT, of the carrier-doped samples are about 10 times larger than those of CuFeS2. These observations suggest that magnetic semiconductors can make good thermoelectric materials. © 2013 TMS.

Qiu H.,Japan National Institute of Materials Science
Materials Transactions | Year: 2013

The ductility of ductile metals, evaluated in terms of fracture strain, is strongly affected by temperature, stress state and strain rate. A parameter integrating the three parameters was proposed, which can be used as a single variable representing the fracture strain of ductile metals. © 2013 The Japan Institute of Metals.

Inoue J.-I.,Japan National Institute of Materials Science
European Physical Journal B | Year: 2013

We theoretically investigate a phase transition of Frenkel exciton polaritons in an organic nanofiber. Assuming a phenomenological Hamiltonian, we derive a mean field equation for the condensation after finding an effective action for the phenomenon using the functional integral method and stationary phase analysis. From a solution of the mean field equation, we construct a phase diagram for the condensation and highlight features that distinguish J- and H-aggregates. We also detail a connection with the superradiant phase transition, which has been studied using the Dicke model. © 2013 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Yamamoto A.,Japan National Institute of Materials Science
Acta Crystallographica Section A: Foundations of Crystallography | Year: 2010

A theory for the diffuse scattering intensity owing to short-range order (SRO) in quasicrystals is given. The diffuse scattering intensity can be calculated based on higher-dimensional cluster models of quasicrystals. It is determined by the overlapped area (or volume) of occupation domains separated from each other by distances up to the correlation length and the SRO correlation functions. It is applied to a random atom distribution in phason flip sites in the Penrose pattern. To confirm the validity of the derived formula, analytical and numerical results for this case have been compared. Both results give similar diffuse scattering intensity, suggesting the validity of the theory. © 2010 International Union of Crystallography. Printed in Singapore-all rights reserved.

Yamamoto A.,Japan National Institute of Materials Science
Acta Crystallographica Section A: Foundations of Crystallography | Year: 2010

An analytical expression is derived for the short-range order (SRO) magnetic neutron diffuse scattering intensity in quasicrystals, and it is applied to a fictitious model of spin-orientation disorder in the Penrose pattern. The SRO diffuse scattering intensity depends on the overlapped volume of the occupation domains which are separated from each other by distances less than the correlation length and the SRO correlation functions. Analytical results for four different spin arrangements in the Penrose pattern are compared with numerical ones. The corresponding analytical and numerical results for all the cases are quite similar, suggesting the validity of the analytical expression. © 2010 International Union of Crystallography. Printed in Singapore-all rights reserved.

Boukhvalov D.W.,Japan National Institute of Materials Science
Chemical Physics Letters | Year: 2011

Novel route for the establishing of magnetism in realistic oxidized graphene nanoribbons is proposed. Modelling of the migration of hydroxyl groups from central part to the zig-zag edges of graphene nanoribbons passivated by oxygen are performed with using density functional theory. The presence of hydroxyl groups near the edges leads formation of dangling bonds there instead saturated due to oxidation and repairs of magnetism diminished by edges oxidation. The route of manufacturing and stability of new type of magnetic graphene nanoribbons are also discussed. © 2010 Elsevier B.V. All rights reserved.

Bali S.,Georgia Institute of Technology | Chen T.T.,Georgia Institute of Technology | Chaikittisilp W.,Georgia Institute of Technology | Jones C.W.,Georgia Institute of Technology | Jones C.W.,Japan National Institute of Materials Science
Energy and Fuels | Year: 2013

Amine/oxide hybrid carbon dioxide adsorbents prepared via impregnation of low molecular weight polymeric amines into porous oxide supports are among the most promising solid adsorbents developed for postcombustion CO2 capture or CO2 extraction from ambient air. The oxidative stability of adsorbents prepared by impregnation of poly(ethylenimine) (PEI) or poly(allylamine) (PAA) into mesoporous γ-alumina under humid oxidation conditions is evaluated in this work. The PEI-based adsorbents, which contain primary, secondary, and tertiary amines, are shown to degrade drastically at elevated temperatures (110 C) and in high oxygen concentrations (21%, akin to air), with these effects reduced by both reductions in temperature (70 C) and oxygen concentration (5%, akin to flue gas). The oxidation behavior of PEI-based adsorbents supported on alumina is qualitatively similar to past work on silica-supported PEI adsorbents. In contrast, the alumina-supported PAA adsorbents that contain only primary amines show significantly improved oxidative stability, losing only 10% or less of their original CO2 capacity after prolonged oxidative treatment under a variety of conditions. Analysis of the fresh and thermally treated samples by Fourier transform (FT) IR, FT-Raman, and 13C NMR spectroscopies demonstrates the clear formation of carbonyl functionalities over the oxidized PEI-based adsorbents, whereas no significant changes in the spectra for PAA samples are observed after oxidative treatments. The collected data demonstrate that secondary-amine-free, primary-amine-rich polymers such as PAA may be used to formulate supported amine adsorbents with improved oxidative stability compared to adsorbents based on PEI, which is used ubiquitously in the field today. © 2013 American Chemical Society.

Sugimoto S.,University of Tokyo | Fukuma Y.,RIKEN | Kasai S.,Japan National Institute of Materials Science | Kimura T.,University of Tokyo | And 4 more authors.
Physical Review Letters | Year: 2011

We here experimentally demonstrate that gyration modes of coupled vortices can be resonantly excited primarily by the ac current in a pair of ferromagnetic disks with variable separation. The sole gyration mode clearly splits into higher and lower frequency modes via dipolar interaction, where the main mode splitting is due to a chirality sensitive phase difference in gyrations of the coupled vortices, whereas the magnitude of the splitting is determined by their polarity configuration. These experimental results show that the coupled pair of vortices behaves similar to a diatomic molecule with bonding and antibonding states, implying a possibility for designing the magnonic band structure in a chain or an array of magnetic vortex oscillators. © 2011 American Physical Society.

Makino S.,Shinshu University | Yamauchi Y.,Japan National Institute of Materials Science | Yamauchi Y.,Japan Science and Technology Agency | Sugimoto W.,Shinshu University
Journal of Power Sources | Year: 2013

Synthesis of ordered mesoporous RuOx electrodes was conducted by electro-deposition using a lyotropic liquid crystal template method with Ti substrates and subsequent electro-oxidation. The obtained ordered mesoporous Ru metal was characterized by XRD, TEM and electrochemical measurements in 0.5 M H2SO4. After electro-oxidation by potential cycling, the ordered mesoporous RuOx afforded specific capacitance of ∼400 F (g-Ru)-1. A micro-supercapacitor with ordered mesoporous RuO x was fabricated by controlled electro-deposition of ordered mesoporous RuOx on an inter-digitated array electrode (IDA; 10 μm electrode width, 5 μm gap and 65 × 2 electrodes). This micro-supercapacitor exhibited good capacitive property with maximum specific capacitance of 12.6 mF cm-2 and specific energy of 12.5 Wh (kg-Ru)-1 based on the mass of the deposited material. © 2012 Elsevier B.V. All rights reserved.

Yi Z.G.,Japan International Center for Materials Nanoarchitectonics | Iwai H.,Japan National Institute of Materials Science | Ye J.H.,Japan International Center for Materials Nanoarchitectonics
Applied Physics Letters | Year: 2010

Sr2 TiO4:Cr complexes are found to possess photochromism. After the photochromism, the catalytic performance of the complexes for H2 generation increases markedly. In fact, it was found that the performance increased more than 20 times compared to the original Sr2 TiO4: 10 mol % Cr complex. These results suggest that it is worthwhile searching and optimizing visible-light-sensitive photocatalysts by investigating possible photochromism. © 2010 American Institute of Physics.

Abe F.,Japan National Institute of Materials Science
Procedia Engineering | Year: 2011

The boundary and sub-boundary hardening is shown to be the most important strengthening mechanism in creep of 9Cr steel. The soluble boron reduces the coarsening rate of M23C6 carbides along boundaries near prior austenite grain boundaries during creep, enhancing the boundary and sub-boundary hardening for up to long times. The enhancement of boundary and sub-boundary hardening retards the onset of acceleration creep, which decreases the minimum creep rate and improves the creep life. Excess addition of boron and nitrogen promotes the formation of boron nitrides during normalizing heat treatment, which significantly reduces soluble boron and nitrogen concentrations and offsets the benefit due to boron and nitrogen. © 2011 Published by Elsevier Ltd.

Iwanaga M.,Japan National Institute of Materials Science | Iwanaga M.,Japan Science and Technology Agency
Applied Physics Letters | Year: 2014

Limit of resolution of conventional optical microscopes has never reached below 100 nm under visible light illumination. We show that numerically designed high-transmittance hyperlens array (HLA) is implemented in an optical microscope and works in practice for achieving one-shot-recording optical images of in-situ placed objects with sub 50 nm resolution in lateral direction. Direct resolution test employing well-defined nanopatterns proves that the HLA-implemented imaging is super-resolution optical microscopy, which works even under nW/mm2 visible illumination for objects. The HLA implementation makes the resolution of conventional microscopes one-scale higher, leading to the 1/10 illumination wavelength range, that is, mesoscopic range. © 2014 AIP Publishing LLC.

Sakurai H.,Japan National Institute of Materials Science
Journal of the Physical Society of Japan | Year: 2014

Using pure samples of α-Sr2CrO4, an antiferromagnetic (AF) transition was first detected at TN = 112K by magnetic susceptibility and specific heat measurements. In addition, another transition was observed at TS = 140K with a clear peak in the specific heat and a small enhancement in the magnetic susceptibility. Despite the two-dimensional crystal structure, the magnetic susceptibility at higher temperatures almost obeys the Curie-Weiss law down to TS. These properties are similar to those of α-Sr2VO4. Electrical resistivity clearly indicates the insulating nature with an electronic band gap of Δ=1150 K. © 2014 The Physical Society of Japan.

Cui J.,Xian University of Science and Technology | Ren X.,Xian University of Science and Technology | Ren X.,Japan National Institute of Materials Science
Applied Physics Letters | Year: 2014

Elinvar effect is observed in non-magnetic Co doped TiNi strain glass alloys. The Elinvar effect is explained by the coupling of dynamic size effect and size dependence of elastic modulus. The appearance of Elinvar effect is highly correlated with the nucleation size, so that only for strain glass with high point defect concentration, Elinvar effect can be observed. Due to the generality of size dependence of elastic modulus, Elinvar effect is expected to be observed in many other strain glass materials, which points out a way to find new Elinvar materials. © 2014 AIP Publishing LLC.

Moritomo Y.,University of Tsukuba | Yonezawa K.,University of Tsukuba | Yasuda T.,Japan National Institute of Materials Science
Applied Physics Letters | Year: 2014

The internal quantum efficiency (φIQ) of an organic photovoltaic cell is governed by plural processes. Here, we propose that φIQ can be experimentally decomposed into carrier formation (φCF) and carrier transfer (φCT) efficiencies. By combining femtosecond time-resolved and electrochemical spectroscopy, we clarified the effect of temperature on φCF in a regioregular poly(3-hexylthiophene) (rr-P3HT)/[6,6]-phenyl C61-butyric acid methyl ester blend film. We found that φCF (= 0.55) at 80K is the same as that (=0.55) at 300K. The temperature insensitivity of φCF indicates that the electron-hole pairs at the D/A interface are seldom subjected to coulombic binding energy. © 2014 AIP Publishing LLC.

Mizuno Y.,Tokyo Institute of Technology | Hayashi N.,Tokyo Institute of Technology | Tanaka H.,Tokyo Institute of Technology | Nakamura K.,Tokyo Institute of Technology | Todoroki S.-I.,Japan National Institute of Materials Science
Applied Physics Letters | Year: 2014

Although high-transmission-capacity optical fibers are in demand, the problem of the fiber fuse phenomenon needs to be resolved to prevent the destruction of fibers. As polymer optical fibers become more prevalent, clarifying their fuse properties has become important. Here, we experimentally demonstrate a fuse propagation velocity of 21.9 mm/s, which is 1-2 orders of magnitude slower than that in standard silica fibers. The achieved threshold power density and proportionality constant between the propagation velocity and the power density are 1/180 of and 17 times the values for silica fibers, respectively. An oscillatory continuous curve instead of periodic voids is formed after the passage of the fuse. An easy fuse termination method is also presented. © 2014 Author(s).

Toko K.,University of Tsukuba | Numata R.,University of Tsukuba | Oya N.,University of Tsukuba | Fukata N.,Japan National Institute of Materials Science | And 2 more authors.
Applied Physics Letters | Year: 2014

The Al-induced crystallization (AIC) yields a large-grained (111)-oriented Ge thin film on an insulator at temperatures as low as 180 C. We accelerated the AIC of an amorphous Ge layer (50-nm thickness) by initially doping Ge in Al and by facilitating Ge diffusion into Al. The electron backscatter diffraction measurement demonstrated the simultaneous achievement of large grains over 10 μm and a high (111) orientation fraction of 90% in the polycrystalline Ge layer formed at 180 C. This result opens up the possibility for developing Ge-based electronic and optical devices fabricated on inexpensive flexible substrates. © 2014 AIP Publishing LLC.

Tanuma S.,Japan National Institute of Materials Science | Powell C.J.,U.S. National Institute of Standards and Technology | Penn D.R.,U.S. National Institute of Standards and Technology
Surface and Interface Analysis | Year: 2011

We have calculated inelastic mean free paths (IMFPs) for 41 elemental solids (Li, Be, graphite, diamond, glassy C, Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Ge, Y, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, Pt, Au and Bi) for electron energies from 50 eV to 30 keV. The IMFPs were calculated from experimental optical data using the full Penn algorithm for energies up to 300 eV and the simpler single-pole approximation for higher energies. The calculated IMFPs could be fitted to a modified form of the Bethe equation for inelastic scattering of electrons in matter for energies from 50 eV to 30 keV. The average root-mean-square (RMS) deviation in these fits was 0.48%. The new IMFPs were also compared with IMFPs from the predictive TPP-2M equation; in these comparisons, the average RMS deviation was 12.3% for energies between 50 eV and 30 keV. This RMS deviation is almost the same as that found previously in a similar comparison for the 50 eV-2 keV range. Relatively large RMS deviations were found for diamond, graphite and cesium. If these three elements were excluded in the comparison, the average RMS deviation was 9.2% between 50 eV and 30 keV. We found satisfactory agreement of our calculated IMFPs with IMFPs from recent calculations and from elastic-peak electron-spectroscopy experiments. © 2010 John Wiley & Sons, Ltd.

Tetsui T.,Japan National Institute of Materials Science
Rare Metals | Year: 2011

Based on the experience of the author, an overview of manufacturing technologies for TiAl alloy components in current and future applications is provided. The main current application consists of turbochargers for gasoline engines used in passenger vehicles, while future applications include high temperature turbochargers for passenger vehicle direct injection gasoline engines, mass production turbochargers for passenger vehicle diesel engines, and aerospace structural parts. The paper presented here first reviews the characteristics of the respective products together with the features of the TiAl alloys used or likely to be used. Representative manufacturing technologies are then presented with respect to these products, and desirable new technologies aimed toward future applications are discussed. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2011.

Ahmad S.,Abengoa | Ikeda T.,Japan National Institute of Materials Science
Nanoscience and Nanotechnology Letters | Year: 2013

Electrochromic devices (ECDs) are in the public domain for more than four decades, and they have evolved from inorganic to organic to polymer and now to hybrid (organic/inorganic) materials based devices. With the use of polymer in ECDs all hues of color are now possible by the proper choice of backbone from conjugated polymer family and with fast switching speed. This has also opened a new avenue in plethora of other application as optical shutters and displays. The cost can be drastically reduced but at the expense of device durability and life time. In this perspective article we will summarize the use of conducting polymers as electrochromes with selected research findings. The major obstacles in wide implementation of this technology arise from the uneconomical use of transparent conducting glasses (TCO) both as an anode and cathode and the high energy treatment during materials coating method. It is paramount research to quest for at least one TCO replacement materials as well as batch to batch reproducibility protocol development, by using less energy demanding methods i.e., wet chemistry routes. Copyright © 2013 American Scientific Publishers All rights reserved.

Chowdhury S.,University of Tsukuba | Sumita U.,University of Tsukuba | Islam A.,Japan National Institute of Materials Science | Bedja I.,King Saud University
Energy Policy | Year: 2014

Photovoltaic (PV) has the highest cost reduction potential among all renewable energy sources (RES). To overcome institutional barriers, developing the technology, and creating an initial market, policies are needed. Comparative case studies of Japan and German PV sector from 1990 to 2011 were developed. Japan dominated the PV industry during 1994-2004, PV market increased to 290. MW in 2005. After 2005 Japan's PV market decreased. German PV market increased from 44. MW in 2000 to 7.5. GW in 2011. The reason behind Japanese PV market decline was the unaligned energy policy and termination of incentives. This paper discusses about successful policy implementation and the impact of policy for the diffusion of PV technology. The analysis section of this paper shows how much the PV technology has been diffused during the period of 1990-2011 and finally what will make the transformation process successful. © 2014 Elsevier Ltd.

Hosokawa A.,McMaster University | Hosokawa A.,Japan National Institute of Materials Science | Wilkinson D.S.,McMaster University | Kang J.,CanmetMATERIALS | Maire E.,INSA Lyon
Acta Materialia | Year: 2013

Void growth and coalescence in model materials containing a pre-existing three-dimensional void array were studied by X-ray computed tomography coupled with in situ uniaxial tensile deformation. A newly developed continuous tomography technique was employed to capture the onset of coalescence. Using a picosecond laser machining system and a diffusion bonding technique, model materials with different void geometries were prepared. By implementing continuous tomography, the plastic strain at the onset of void coalescence was measured (instead of simple linkage) for the first time. The plastic strains at the onset of void coalescence were compared with the existing void coalescence models. Finite-element (FE) simulations were performed to study the influences of void shape (sphere, cylinder, tapered-cylinder) on the void growth behavior. This study shows that the coalescence models developed by Thomason and later extended by Pardoen and Hutchinson provide accurate predictions of coalescence strain when the voids are aligned normal to the tensile axis. However, offsets can induce shear effects that lower the coalescence strain in a manner not predicted by the models. Two-dimensional plane-strain FE simulations were also used to explore the influence of shear localization between two misaligned coalescing voids on ductility. These demonstrate the nature of the effect. © 2012 and Elsevier Ltd. Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Xie R.-J.,Japan National Institute of Materials Science | Hintzen H.T.,TU Eindhoven
Journal of the American Ceramic Society | Year: 2013

(Oxy)nitride materials, consisting mainly of transition metal and ionic-covalent (oxy)nitrides, show a vast number of interesting physical and chemical properties due to their substantial structural diversity. The optical properties of these (oxy)nitrides, in combination with their excellent mechanical strength, thermal properties, and chemical stability, enable (oxy)nitrides to be used in a variety of industrial fields, such as photovoltaic, photothermal, photocatalytic, pigment, lighting and display, optoelectronic, and defense industries. The optical properties are extremely related to the electronic band structure of (oxy)nitrides, and can be varied significantly by changing the chemical composition (e.g., the oxygen to nitrogen ratio) and preparation/processing conditions. This article overviews the optical properties (including refractive index, reflectance, absorbance, band gap, photoluminescence, and transmittance) of (oxy)nitride materials that are in the form of thin films, powders, or bulk ceramics, and highlights their applications as antireflection coatings, solar spectral selectivity coatings, visible-light-driven photocatalysts, ecological pigments, phosphors for light-emitting diodes, and transparent window materials. © 2013 The American Ceramic Society.

Mamiya H.,Japan National Institute of Materials Science
Journal of Nanomaterials | Year: 2013

Targeted hyperthermia treatment using magnetic nanoparticles is a promising cancer therapy that enables selective heating of hidden microcancer tissues. In this review, I outline the present status of chemical synthesis of such magnetic nanoparticles. Then, the latest progress in understanding their heat dissipation mechanisms under large magnetic fields is overviewed. This review covers the recently predicted novel phenomena: magnetic hysteresis loops of superparamagnetic states and steady orientations of easy axes at the directions parallel, perpendicular, or oblique to the AC magnetic field. Finally, this review ends with future prospects from the viewpoint of optimal design for efficacy with a low side-effect profile. © 2013 Hiroaki Mamiya.

Dawson J.A.,Kyoto University | Chen H.,Japan National Institute of Materials Science | Tanaka I.,Kyoto University
Physical Chemistry Chemical Physics | Year: 2014

Both classical and quantum mechanical simulation techniques have been applied to investigate the incorporation, migration and potential binding of protonic defects in bulk yttria-stabilised zirconia (YSZ). The calculated redox reaction energies are found to be high, although the reduction energies are lower than those of bulk cubic ZrO2 and are shown to decrease further with increasing Y content. The hydration energies for YSZ are also lower than the values calculated for bulk ZrO2 and are found to be lowest when the oxygen ion is in close proximity to at least one Y ion. Strong binding (proton trapping) energies are observed between the protons and additional acceptor dopants including Sc, Yb and Gd. These energies are found to vary significantly depending on local configuration and again are generally lower than the values for ZrO2. Density functional theory (DFT) calculations are used to determine energy barriers for proton transfers via neighbouring oxygen ions (Grötthuss-type mechanism). Energy barriers of 0.32-0.42 eV are obtained for the pathways with the closest O-O interatomic distances and are found to be very comparable to well-established proton conducting materials. © 2014 the Owner Societies.

Mamiya H.,Japan National Institute of Materials Science | Jeyadevan B.,University of Shiga Prefecture
Journal of Magnetism and Magnetic Materials | Year: 2011

We have numerically simulated the dynamic response of single-domain nanomagnets to alternating magnetic fields and discuss nanometer-sized thermal seeds suitable for selectively targeted magnetic hyperthermia. When we assign priority to the easy delivery and biological safety of these fields, the maximum heating power is obtained by the irradiation of a weak field at a medium frequency (∼1 MHz) on almost spherical magnetite nanomagnets with a diameter of approximately 20 nm. On the other hand, the irradiation of the amplified field at a low frequency (∼100 kHz) is more effective if the neural stimulation is allowable. © 2010 Elsevier B.V. All rights reserved.

Kawabata K.,University of Tsukuba | Nimori S.,Japan National Institute of Materials Science | Goto H.,University of Tsukuba
ACS Macro Letters | Year: 2013

Macroscopically highly oriented polythiophene derivative films are synthesized by electrochemical polymerization in a smectic liquid crystal reaction medium. Control of orientation direction of conjugated main chains is performed by use of magnetic field which is applied parallel, obliquely, and perpendicularly to the substrate electrodes to align the liquid crystal reaction medium. © 2013 American Chemical Society.

Zhao Y.,Beijing Normal University | Li J.-G.,Japan National Institute of Materials Science | Guo M.,Beijing Normal University | Yang X.,Beijing Normal University
Journal of Materials Chemistry C | Year: 2013

Rare-earth phosphors with tunable optical properties are used in display panels and fluorescent lamps and have potential applications in lasers and bioimaging. This work reported the preparation, structure and photoluminescence of the unilamellar nanosheets containing Tb3+/Eu3+ delaminated from layered rare-earth hydroxides (LRHs). Highly crystallized LTbH and LEuH with monolayered dodecyl sulfate ions vertical to the layer were synthesized by a one-step homogeneous precipitation method for the first time, and were shown to be readily delaminated in formamide. The obtained unilamellar nanosheets exhibited a decrease of the coordination number of the lanthanide ions, to probably 8-fold, when compared with the bulky precursor crystals. This change resulted in different photoluminescence emission peak shapes. Colloidal hybrids were constructed using these nanosheets as building blocks, and the emission colors of the hybrids can be facilely and precisely tuned from green to yellow, orange, and finally to red by controlling the relative contents of the two kinds of nanosheets. This method provides a novel and simple route to prepare color-tunable hybrid materials from 2-dimensional crystals. © 2013 The Royal Society of Chemistry.

Tachibana M.,Japan National Institute of Materials Science
Solid State Communications | Year: 2013

Thermal conductivity measurements have been performed from 2 to 330 K on single crystals of pyrochlore R2Ti2O7 (R=Gd, Tb, Dy, Ho, Er, Lu, and Y). The spin-liquid system Tb2Ti 2O7 shows heavily suppressed thermal conductivity below 100 K, which can be attributed to the presence of unusually strong coupling between the phonons and crystal electric field excitations in this compound. For the other R2Ti2O7 compounds, the magnetic moment of the R ion does not appear to play important roles in thermal conductivity for the present temperature region. © 2013 Elsevier Ltd.

Furumi S.,Japan National Institute of Materials Science | Furumi S.,Japan Science and Technology Agency | Furumi S.,University of Tsukuba
Journal of Materials Chemistry C | Year: 2013

This Highlight provides a brief review of recent progress in the field of colloidal crystals (CCs) combined with functional organic materials for active lasers. Colloidal microparticles have the intrinsic capability to form self-organized 3D ordered structures of microparticles, so-called CCs. From a technological perspective, it is of prime importance to fabricate CCs with photonic band gaps (PBGs) in a visible range. When a light-emitting dye is embedded in the CCs, optical excitation causes the laser emission by the PBG effect. Interestingly, such laser emission can be controlled by utilizing the functional controllability of organic materials. This article covers the background of research into CCs as photonic crystals, and highlights intriguing precedents of active organic CC lasers in response to external stimuli. This journal is © 2013 The Royal Society of Chemistry.

Shock pressure and particle velocity measurements have been performed separately on a powdered material under a similar shock loading condition by employing time-resolved luminescence spectroscopy and velocity interferometry (VISAR). Shock pressure measurement adopts the pressure-shift characteristic of ruby crystal that is used as a window material. Exactly the same shock condition could be realized for the particle velocity measurement by using a sapphire crystal as a window. A good agreement between the results of two different measurements has been obtained and they indicate a 7 times or more increase in shock impedance of the powdered material. © 2014 Elsevier B.V. All rights reserved.

Nishimura T.,Japan National Institute of Materials Science
Corrosion Science | Year: 2010

The corrosion resistance of Si- and Al-bearing steel was estimated by atmospheric exposure test, and the structure of the rust was examined by EPMA (electroprobe X-ray microanalysis) and TEM (transmission electron microscopy) analysis. Moreover, the electrochemical behaviour of rust was investigated by EIS (electrochemical impedance spectroscopy). The Si- and Al-bearing steel exhibited excellent corrosion resistance in the exposure test as compared with carbon steel (SM). EPMA and TEM analysis showed that Si and Al mainly existed in nanoscale iron complex oxides in the inner rust formed on this steel. The Al K spectrum of the rust exhibited a peak that was the same as that of Al2O3 in the EPMA and TEM-EELS (electron energy loss spectroscopy) analysis. This result suggests that Al was present in the complex oxides as Al3+. In the same way, Si was identified as being in an intermediate state in the complex oxides of the inner rust. EIS measurement of the exposure test samples revealed much higher rust resistance (Rrust) and corrosion reaction resistance (Rt) of Si- and Al-bearing steel compared to that of SM. Finally, it was found that nanoscale complex iron oxides formed in the inner rust of Si- and Al-bearing steel, resulting in increased Rrust and Rt, and corrosion suppression. © 2010 Elsevier Ltd.

Sang L.,Japan National Institute of Materials Science
Sensors (Basel, Switzerland) | Year: 2013

Ultraviolet (UV) photodetectors have drawn extensive attention owing to their applications in industrial, environmental and even biological fields. Compared to UV-enhanced Si photodetectors, a new generation of wide bandgap semiconductors, such as (Al, In) GaN, diamond, and SiC, have the advantages of high responsivity, high thermal stability, robust radiation hardness and high response speed. On the other hand, one-dimensional (1D) nanostructure semiconductors with a wide bandgap, such as β-Ga2O3, GaN, ZnO, or other metal-oxide nanostructures, also show their potential for high-efficiency UV photodetection. In some cases such as flame detection, high-temperature thermally stable detectors with high performance are required. This article provides a comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only semiconductor thin films, but also 1D nanostructured materials, which are attracting more and more attention in the detection field. A special focus is given on the thermal stability of the developed devices, which is one of the key characteristics for the real applications.

Kobayashi T.,Japan National Institute of Materials Science
Chemical Physics Letters | Year: 2016

Luminescence generated by a plate-impact-induced shock wave has been detected from a Ce-doped phosphor powder, Ce3+:Y3Al5O12. The observed luminescence spectrum shows two strong bands in the visible region: one at ∼410 nm and the other at ∼530 nm. The second band is very similar to the well-known luminescence band of Ce:YAG corresponding to the T2g → 2F transition, but the first band is hardly observed in the photoluminescence spectrum. One possible mechanism for the first band is the radiative transition from the higher energy excited level of Ce3+ to the ground level, namely Eg → 2F. © 2015 Elsevier B.V.

Boukhvalov D.W.,Japan National Institute of Materials Science
Surface Science | Year: 2010

Density functional theory (DFT) modeling of the physisorption of four different types of molecules (toluene, bromine dimmer, water and nitrogen dioxide) over and under graphene ripples has been performed. For all types of molecules changes of charge transfer and binding energies in respect to flat graphene are found. The changes in the electronic structure of corrugated graphene and turn of π-orbitals of carbon atoms in combination with the chemical structure of adsorbed molecules are proposed as the causes of difference with the perfect graphene case and variety of adsorption properties of different types of molecules. The results of calculation suggest that the tops of the ripples are more attractive for large molecules and valley between ripples for small molecules. Stability of molecules on the ripples and energy barriers for migration over flat and corrugated graphene is also discussed. © 2010 Elsevier B.V. All rights reserved.

Boukhvalov D.W.,Japan National Institute of Materials Science
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

Density functional modeling of atomic structure and calculation of electronic structure of one-side one-sublattice functionalized graphene (graphone) are performed for hydrogen and fluorine adatoms. It is shown here that using fluorine for functionalization not only enhances stability of compound but also provides switch of magnetic ground state from ferro- to antiferromagnetic. Half-metallic ferromagnetic state in fluorine-based graphone is also discussed. © 2010 Elsevier B.V.

Guo S.,Japan National Institute of Materials Science
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2016

In this study, laminated composites consisting of ZrB2-SiC (ZS) ceramic and carbon fiber (Cf ) reinforced-ZrB2-SiC matrix composites (Cf/ZrB2-SiC, hereafter denoted by CfZS) were fabricated by hot-pressing. The effects of the layer thickness ratio of ZS to CfZS (ZS/CfZS) and the fiber concentration on the flexural strength were investigated. The flexural strength of the laminated composites was improved compared to that of the single-composites and the improvement was enhanced with increase of the ZS/CfZS ratio. However, the flexural strength decreased with increasing the fiber concentration of CfZS. In addition, the crack propagation behavior of the laminated composites was examined under indent cracking. The results showed that the crack propagation behavior related to the fiber concentration of CfZS, irrespective of the layer thickness. The cracks induced by the indenter rapidly propagated through the CfZS layer when the fiber volume fraction was 10%. However, the cracks were arrested ahead the CfZS layers for the fiber volume fraction equal to or greater than 30%. © 2016 The Ceramic Society of Japan. All rights reserved.

Bandyopadhyay A.,Japan Science and Technology Agency | Higuchi M.,Japan National Institute of Materials Science
European Polymer Journal | Year: 2013

Co(III)- and Fe(III)-based metallosupramolecular polymers with aromatic azo ligands were synthesized via polycondensation of the diamino-substituted metal complexes with aromatic dialdehydes. Three different amino-substituted Co(III)-complexes were prepared through CN fusion reaction of [Co(pap) 3](ClO4)2 with 1,4-phenylenediamine. All Co(III)- and Fe(III)-monomers and the metallosupramolecular polymers and a Co(III)-dimer were characterized by NMR, MS and UV-vis spectroscopy. Both the Co(III)- and Fe(III)-based metallosupramolecular polymers were electrochemically active and exhibited reversible electrochromism. The color of the Co(III)-based metallosupramolecular polymer could be changed upon application of an appropriate potential and regenerated upon reversal of the potential. © 2013 Elsevier B.V. All rights reserved.

Naito K.,Japan National Institute of Materials Science
Journal of Applied Polymer Science | Year: 2013

The tensile properties and fracture behavior of poly-(para-phenylene-2,6- benzobisoxazole), poly-(para-phenylene terephthalamide), co-poly-(para- phenylene-3,4′-oxydiphenylene terephthalamide), polyarylate, polyethylene, and poly(lactic acid) high-performance polymeric fibers have been investigated. The Weibull statistical distributions of the tensile strength were also characterized. The results clearly show that for various types of high-performance polymer fibers, the Weibull modulus decreases with an increase in the tensile modulus, the tensile strength, and inverse of the failure strain. © 2012 Wiley Periodicals, Inc.

Furuya Y.,Japan National Institute of Materials Science
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2013

Synopsis: Ultrasonic fatigue tests up to gigacycle regimes were conducted for double-melted SCM440 low-alloy steel using enlarged and conventional specimens, comparing the results with those of single-melted steel. Although both types of specimens of the double-melted steel showed internal fracture, the difference between the enlarged and conventional specimens was very small in spite of large difference in case of the single-melted steel. The inclusion sizes of an internal fracture origin also showed negligible difference between the two types of the specimens. Namely, size effects were small in case of the double-melted steel, unlike the case of the single-melted steel. These results meant that the double-melted steel showed superior gigacycle fatigue properties to the single-melted steel when the enlarged specimens were used in the fatigue tests, while the superiority was invisible when conventional specimens were used. Moreover, when the inclusion sizes were evaluated by the enlarged specimens, the double-melted steel showed much smaller inclusion sizes than the single-melted. Hence, using the enlarged specimens was highly advisable in evaluating the gigacycle fatigue properties and the inclusion size, particularly in case of high-cleanliness steels.

Grasso S.,Queen Mary, University of London | Sakka Y.,Japan National Institute of Materials Science
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2013

Electrical heating of the graphite die and punch assembly is a unique feature of the spark plasma sintering (SPS) process. The high currents needed to heat the die, despite its low resistance, can produce an electric field across the ceramic specimens that may be enough to induce field assisted sintering. Despite the large number of publications of SPS, the electric field intensity has not been accounted in previous investigations. A FEM model is employed to quantify the magnitude of electric field applied during sintering across zirconia sample. We show that the electric field depends most critically on the ratio of the outer and inner diameter of the die. We also report that the intensity of the electric field across the sintering sample is significantly affected by duty cycle of the pulsed current. © 2013 The Ceramic Society of Japan. All rights reserved.

Delbecq F.,Japan National Institute of Materials Science | Kono F.,Tokyo University of Science | Kawai T.,Tokyo University of Science
European Polymer Journal | Year: 2013

The direct exfoliation of graphite was achieved in water using water-soluble poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA). Prepared wrapped graphene dispersion was employed for the synthesis of chemically cross-linked PVP/PVA/exfoliated graphite (G) composite hydrogels. The swelling behaviour of these hydrogels was studied in aqueous solution of stannous chloride, followed by treatment in a bath of sodium borohydride (NaBH4). The previous PVP/PVA-graphene aqueous dispersion was analyzed by UV-Visible and Raman spectroscopy. The morphology of the composite hydrogels was observed by field-emission scanning electron microscopy (FE-SEM). The successive modifications of the composite hydrogels, in particular the incorporation of tin nanoparticles (SnNPs) were monitored by (FT-IR) Fourier transform-infrared spectroscopy. The size and shape of the incorporated SnNPs were controlled by transmission electron microscopy (TEM). © 2013 Elsevier Ltd. All rights reserved.

Tanaka M.,Japan National Institute of Materials Science
Applied Physics A: Materials Science and Processing | Year: 2013

The fundamental and technological importance of metal clusters and particles on oxide surfaces is growing. Here, room temperature deposited Ni clusters and particles on clean SrTiO3 (001) surfaces were analyzed with a UHV-TEM/STM combined system to investigate reaction, growth, morphology, and crystal structure consistently. STM observation revealed their growth process from isolated clusters almost of the size of the nuclei to bigger particles. From TEM observation, it was found that small clusters have a semi-commensurate epitaxial orientation relationship, but that bigger ones grow into an incommensurate cube-on-cube epitaxial orientation relationship. STS measurement on Ni particles caused field-induced diffusion of Ni atoms, in which piling up of Ni was recognized at the positions of the STM tips. This is assumed to be related with interfacial reaction. © 2013 Springer-Verlag Berlin Heidelberg.

Hiraga T.,University of Tokyo | Tachibana C.,University of Tokyo | Ohashi N.,Japan National Institute of Materials Science | Sano S.,Ube Industries
Earth and Planetary Science Letters | Year: 2010

Grain growth kinetics of forsterite (Fo) and enstatite (En) in fine grain aggregates of Fo ± En are examined as a function of volume fraction of En (fEn = 0.00 to 0.42). Growth rates fit dn∝ k · t (d: mean grain diameter; n: grain growth exponent; k: growth constant; t: time), where n ∼ 5 for both forsterite and enstatite grains in the enstatite-bearing samples. A negative correlation between kFo and fEn can be expressed as kFo ≈ 0.06 exp [30 fEn (fEn - 1.1)], whereas kEn takes almost constant values for different fEn. In addition, the ratio of dFo/dEn is almost constant during grain growth, and its value becomes smaller with increasing fEn, such that dFo/dEn ≈ 0.74/fEn0.59. Our obtained grain growth parameters and the microstructural characteristics in experimental and natural samples all indicate that the rate-controlling process for grain growth in both experiments and in nature is grain boundary diffusion of Si through grain boundaries of olivine. Thus, we are able to propose a semi-empirical relationship of dAve / ddun ≈ {exp [30 fpx {dot operator} (fpx - 1.1)]}frac(1, 5) {dot operator} (1 + 1.35 fpx 1.59 - fpx) (dAve: average grain size in the rock; ddun: average grain size in dunite; fpx: fraction of pyroxenes), which can predict how lithology affects grain size in the upper mantle. Grain size in lherzolite (pyroxenes content of 40%) can be ∼ 4 times smaller than that in dunite (pyroxenes content of 5%). Such grain size reduction through change in lithology can significantly affect viscosity of mantle deformation via grain-size sensitive creep. © 2009 Elsevier B.V. All rights reserved.

Iwanaga M.,Japan National Institute of Materials Science
Optics Express | Year: 2010

Resonant electromagnetic fields in stacked complementary plasmonic crystal slabs (sc-PlCSs) are numerically explored in subwavelength dimensions. It is found that the local plasmon resonances in the sc-PlCSs are composite states of locally enhanced electric and magnetic fields. Two sc-PlCSs are analyzed in this paper and it is shown that each sc-PlCS realizes a resonant electromagnetic state suggested by one of Maxwell equations. It is moreover clarified that the local plasmons open efficient paths of Poynting flux, those result in high-contrast polarized transmission. © 2010 Optical Society of America.

Hu L.,Fudan University | Chen M.,Fudan University | Shan W.,Fudan University | Zhan T.,Fudan University | And 4 more authors.
Advanced Materials | Year: 2012

Innovative bilayer nanofilms composed of semiconducting ZnS and ZnO hollow microspheres are successfully fabricated by an oil-water interfacial self-assembly strategy. The photocurrent of the bilayer film-based photodetectors is dependent on the stacking orders of the building blocks. The optimal optoelectronic properties of the ZnS(up)/ZnO(down) device are much better than those of the monolayer-film based device. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gong Y.-K.,Northwest University, China | Winnik F.M.,University of Montreal | Winnik F.M.,Japan National Institute of Materials Science
Nanoscale | Year: 2012

Engineered nanoparticles (NPs) play an increasingly important role in biomedical sciences and in nanomedicine. Yet, in spite of significant advances, it remains difficult to construct drug-loaded NPs with precisely defined therapeutic effects, in terms of release time and spatial targeting. The body is a highly complex system that imposes multiple physiological and cellular barriers to foreign objects. Upon injection in the blood stream or following oral administation, NPs have to bypass numerous barriers prior to reaching their intended target. A particularly successful design strategy consists in masking the NP to the biological environment by covering it with an outer surface mimicking the composition and functionality of the cell's external membrane. This review describes this biomimetic approach. First, we outline key features of the composition and function of the cell membrane. Then, we present recent developments in the fabrication of molecules that mimic biomolecules present on the cell membrane, such as proteins, peptides, and carbohydrates. We present effective strategies to link such bioactive molecules to the NPs surface and we highlight the power of this approach by presenting some exciting examples of biomimetically engineered NPs useful for multimodal diagnostics and for target-specific drug/gene delivery applications. Finally, critical directions for future research and applications of biomimetic NPs are suggested to the readers. © 2012 The Royal Society of Chemistry.

Naito K.,Japan National Institute of Materials Science | Onta M.,Tokyo University of Science | Kogo Y.,Tokyo University of Science
International Journal of Adhesion and Adhesives | Year: 2012

The effect of adhesive thickness on tensile and shear strength of a polyimide adhesive has been investigated. Tensile and shear tests were carried out using butt and single lap joints. Commercially available polyimide (Skybond 703) was used as adhesive and aluminum alloy (5052-H34) was used as adherends. The tensile strength of the butt joints decreased with increasing adhesive thickness. In contrast, adhesive thickness did not seem to affect the shear strength of single lap joints. The fabricated joints using the polyimide adhesive failed in an interfacial manner regardless of adhesive thickness. The linear elastic stress analysis using a finite element method (FEM) indicates that the normal stress concentrated at the interface between the adherend and the adhesive. The FEM analysis considering the interfacial stress well explains the effect of adhesive thickness on the joint strength. © 2012 Elsevier Ltd.

Hu L.,Fudan University | Yan J.,CAS Hefei Institutes of Physical Science | Liao M.,Japan National Institute of Materials Science | Xiang H.,Fudan University | And 3 more authors.
Advanced Materials | Year: 2012

A novel 1D/1D nanocomposite-based photodetector is successfully fabricated from high-crystalline ZnS/ZnO biaxial nanobelts for the first time. Optimized performance of the ZnS/ZnO nanobelt photodetector is much better than that of pure ZnS or ZnO nanostructures, with a wide-range UV-A light photoresponse, high sensitivity, and very fast response speed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fujiwara M.,Keio University | Tsuya D.,Japan National Institute of Materials Science | Maki H.,Keio University
Applied Physics Letters | Year: 2013

We report electrically driven narrow-linewidth blackbody emission from carbon-nanotube with Fabry-Perot microcavities. We fabricated two types of devices with microcavities consisting of either gold mirrors or distributed Bragg reflectors (DBR). Gold-mirror microcavity devices exhibit blackbody emission with narrowed full-width at half-maximum of ∼50 nm in contrast to the broad normal blackbody emission spectrum. The spectra from these devices can be explained by theoretical calculations accounting for the temperature-dependent intrinsic blackbody spectra and transmittance spectrum of the microcavity. Moreover, the DBR microcavity devices show a narrower resonant peak inside the photonic bandgap, compared with the gold-mirror microcavity device. © 2013 AIP Publishing LLC.

Aikawa S.,Japan International Center for Materials Nanoarchitectonics | Nabatame T.,Japan National Institute of Materials Science | Tsukagoshi K.,Japan International Center for Materials Nanoarchitectonics
Applied Physics Letters | Year: 2013

Amorphous metal oxide thin-film transistors (TFTs) are fabricated using InOx-based semiconductors doped with TiO2, WO3, or SiO2. Even at low-dopant densities, the electrical properties of the film strongly depend on the dopant used. We found that this dependence could be reasonably explained by differences in the bond-dissociation energy of the dopants. By incorporating a dopant with a higher bond-dissociation energy, the film became less sensitive to the partial pressure of oxygen used during sputtering and remained electrically stable upon thermal annealing. Thus, choosing a dopant with an appropriate bond-dissociation energy is important when fabricating stable metal-oxide TFTs for flat-panel displays. © 2013 AIP Publishing LLC.

Sahu S.,Advanced Nano Characterization Center | Ghosh S.,Advanced Nano Characterization Center | Hirata K.,Japan National Institute of Materials Science | Fujita D.,Advanced Nano Characterization Center | Bandyopadhyay A.,Advanced Nano Characterization Center
Applied Physics Letters | Year: 2013

We demonstrate that a single brain-neuron-extracted microtubule is a memory-switching element, whose hysteresis loss is nearly zero. Our study shows how a memory-state forms in the nanowire and how its protein arrangement symmetry is related to the conducting-state written in the device, thus, enabling it to store and process ∼500 distinct bits, with 2 pA resolution between 1 nA and 1 pA. Its random access memory is an analogue of flash memory switch used in a computer chip. Using scanning tunneling microscope imaging, we demonstrate how single proteins behave inside the nanowire when this 3.5 billion years old nanowire processes memory-bits. © 2013 American Institute of Physics.

Wang S.D.,Soochow University of China | Yan Y.,Soochow University of China | Tsukagoshi K.,Japan National Institute of Materials Science
IEEE Electron Device Letters | Year: 2010

We report a simple method for evaluating the contact resistance $(R-{C})$ in organic thin-film transistors, utilizing the measurement of the transition voltage between the linear and saturation regimes in the output characteristics. This method does not need the complex electrode patterning, and thus, it could be useful for the practical RC test. The RC extracted from the transition-voltage method shows a decrease with increasing gate voltage, and the results are similar with those extracted from the transfer-line method, indicating the preciseness of the proposed transition-voltage method. © 2010 IEEE.

Kondo H.,University of Tokyo | Ohno T.,University of Tokyo | Ohno T.,Japan National Institute of Materials Science
Applied Physics Letters | Year: 2013

The spintronic transport properties of a junction system composed of a non-magnetic molecule sandwiched between ferromagnetic metal electrodes are investigated theoretically using a non-equilibrium Green's function method based on density functional theory. It is revealed that in such a system, the molecular magnetic properties induced by hybridization with the magnetic electrodes play a crucial role. Alignment of the induced molecular spin-split levels is strongly related to the spin injection and tunneling magneto-resistance effects. It is found that in the system with weaker molecule-electrode interaction, stronger spintronic effects of the spin injection and tunneling magneto-resistance are observed. © 2013 AIP Publishing LLC.

Nakanishi T.,Japan National Institute of Materials Science | Nakanishi T.,Max Planck Institute of Colloids and Interfaces | Nakanishi T.,Japan Science and Technology Agency
Chemical Communications | Year: 2010

Dimensionally controlled and hierarchically assembled supramolecular architectures in nano/micro/bulk length scales are formed by self-organization of alkyl-conjugated fullerenes. The simple molecular design of covalently attaching hydrophobic long alkyl chains to fullerene (C60) is different from the conventional (hydrophobic-hydrophilic) amphiphilic molecular designs. The two different units of the alkyl-conjugated C60 are incompatible but both are soluble in organic solvents. The van der Waals intermolecular forces among long hydrocarbon chains and the π-π interaction between C60 moieties govern the self-organization of the alkyl-conjugated C60 derivatives. A delicate balance between the π-π and van der Waals forces in the assemblies leads to a wide variety of supramolecular architectures and paves the way for developing supramolecular soft materials possessing various morphologies and functions. For instance, superhydrophobic films, electron-transporting thermotropic liquid crystals and room-temperature liquids have been demonstrated. Furthermore, the unique morphologies of the assemblies can be utilised as a template for the fabrication of nanostructured metallic surfaces in a highly reproducible and sustainable way. The resulting metallic surfaces can serve as excellent active substrates for surface-enhanced Raman scattering (SERS) owing to their plasmon enhancing characteristics. The use of self-assembling supramolecular objects as a structural template to fabricate innovative well-defined metal nanomaterials links soft matter chemistry to hard matter sciences. © 2010 The Royal Society of Chemistry.

Ochiai T.,Japan National Institute of Materials Science
Optics Express | Year: 2010

A novel radiation emission from traveling charged particles in vacuum is theoretically demonstrated. This radiation is conical as in the Cherenkov radiation, but emerges in backward directions of the particle trajectories. The basic mechanism of the radiation is the Smith-Purcell effect via the interaction between the charged particles and a circularsymmetric photonic wire with a one-dimensionally periodic dielectric function. The wire exhibits the photonic band structure characterized with angular momentum. The charged particle can resonantly excite the photonic band modes with particular angular momentum, depending on the particle velocity. A simple kinetics of the Smith-Purcell effect enables us to design the conical radiation emitted in backward directions. Numerical results of the backward radiation are also presented for a metallic wire with aligned air holes. © 2010 Optical Society of America.

Rinaldi A.,University of Rome Tor Vergata | Rinaldi A.,International Research Center for Mathematics and Mechanics of Complex Systems | Licoccia S.,University of Rome Tor Vergata | Traversa E.,Japan National Institute of Materials Science
Nanoscale | Year: 2011

Nanomechanics and structural design of MEMS are intimately tied together. As mechanical properties of hard materials are found to be strongly sample-size dependent, new criteria are in demand for size-dependent structural analysis and design of MEMS components. The paper offers a critical survey of some of the most interesting and challenging advances in nanomechanics of metals from a MEMS design standpoint. The emphasis is not just on sample size effects in intrinsic properties (in plasticity, elasticity and fracture) but also on extrinsic effects arising in material testing of super hard nano-sized samples and crucially affecting MEMS performance if discarded. © 2011 The Royal Society of Chemistry.

El-Safty S.A.,Japan National Institute of Materials Science | El-Safty S.A.,Tanta University | El-Safty S.A.,Waseda University
TrAC - Trends in Analytical Chemistry | Year: 2011

This critical review reports on the up-to-date development designs of mesofilters for molecular sieving of macromolecules. Tight mesoporous silica nanotubes (NTs) provide a promising candidate as a filter for the size-exclusion separation of large quantities of macromolecules within a short period. First, we focus on the formation of the mesoporous structures inside anodic alumina membrane (AAM) using nanolinker approaches. Second, we discuss the systematic design of the robust mesofilters based on densely-engineered mesopores of silica NTs, which are vertically aligned with the open surfaces of top-bottom ends inside the AAM. Third, we present the bench-top filtration method as a powerful tool for the size-exclusion separation of macromolecules. Significantly, the evaluation of the intrinsic properties of mesofilters (e.g., diffusivity, separation efficiency, long-term stability, and reusability) compared them with commercial, mature membranes used for separation of macromolecules. © 2011 Elsevier Ltd.

Guo S.,Japan National Institute of Materials Science
Key Engineering Materials | Year: 2016

In this study, a series of ZrB2-ZrCx-Zr cermets were prepared by reactive hot-pressing of Zr + B4C powder mixtures at different temperatures between 1400°C and 1900°C. The microstructure of the resulting cermets was characterized by field emission scanning electron microscopy. The strength and fracture toughness of the cermets were measured by four-point bending test at room temperature. The results showed that the strength and fracture toughness dependend on the amount of excess Zr and sintering temperature as well. In addition, the crack propagation behavior of the cermets was examined under indent cracking. The cracks induced by indenter directly propagated in the samples with less than 16 vol% Zr. For comparison, the multiple cracking behavior was observed for the samples with equal to or greater than 16% Zr. Furthermore, the effects of compositions and sintering temperatures on the microstructure and the mechanical properties of the cermets were discussed. © 2016 Trans Tech Publications, Switzerland.

Tsukamoto S.,Japan National Institute of Materials Science
Science and Technology of Welding and Joining | Year: 2011

The high speed imaging technique is an attractive tool to elucidate welding phenomena. In this paper, applications of this technique are reviewed in order to understand the power beam welding phenomenon. Monochromatic imaging technique, which can take pictures of plasma with any specific spectrum wavelength, is used to analyse state of the laser induced plasma and distribution of some species, such as ions and atoms of gases and metals. During electron beam welding, intermittent melting process and spiking phenomenon can be clearly recorded by a pinhole X-ray streak camera. The in situ X-ray transmission imaging system is useful to observe the dynamic keyhole and fluid flow behaviour, which cannot be directly observed by any other method. High speed observations of the solidification front clearly show the solidification cracking process. In the present paper, methods to analyse the solidification cracking using high speed imaging are also described. © 2011 Institute of Materials, Minerals and Mining.

Shrestha L.K.,Japan National Institute of Materials Science | Yamamoto M.,Yokohama National University | Arima S.,Mitsubishi Group | Aramaki K.,Yokohama National University
Langmuir | Year: 2011

We report a facile method for the formation of charge-free reverse wormlike micelles in a nonionic surfactant/oil system without addition of water under ambient conditions. This route involves the addition of sucrose dioleate (SDO) to semidilute solutions of sucrose trioleate (STO) in hexadecane. A reverse wormlike micelle was possible to achieve only with ionic surfactants in which water and/or salts are fundamentally required to induce micellar growth so far. In this contribution, we have shown that less lipophilic nonionic surfactant SDO promotes one-dimensional growth to STO reverse micelles and leads to the formation of transient networks of viscoelastic reverse wormlike micelles. The zero-shear viscosity increases by ∼4 orders of magnitude, and it is the mixing fraction of SDO to STO that determines the viscosity growth. The structure and dynamics of the reverse micelles are confirmed by small-angle X-ray scattering (SAXS) and rheometry measurements. © 2011 American Chemical Society.

Irokawa Y.,Japan National Institute of Materials Science
Sensors | Year: 2011

In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C-V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C-V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C-V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I-V) characterization, suggesting that low-frequency C-V method would be effective in detecting very low hydrogen concentrations. © 2011 by the authors.

Inoue J.-I.,Japan National Institute of Materials Science
Optics Express | Year: 2013

As the search for new compounds of a topological insulator (TI) becomes more extensive, it is increasingly important to develop an experimental technique that can identify TIs. In this work, we theoretically propose a simple optical method for distinguishing between topological and conventional insulator thin films. An electromagnetic interference wave consisting of waves transmitted through and reflected by the TI thin film is sensitive to the circular polarization direction of the incident electromagnetic wave. Based on this fact, we can identify a TI by observing the interference wave. This method is straightforward, and thus should propel TI research. © 2013 Optical Society of America.

Seino Y.,Idemitsu Kosan Co. | Ota T.,Idemitsu Kosan Co. | Takada K.,Japan National Institute of Materials Science
Journal of Power Sources | Year: 2011

Rate capability of LiNi 0.8Co 0.15Al 0.05O 2 in solid-state cells was investigated with 70Li 2S-30P 2S 5 glass-ceramics as a sulfide solid electrolyte. It showed higher rate capability than LiCoO 2; discharge capacity observed at a current density of 10 mA cm -2 was ca. 70 mAh g -1. Surface coating with Li 4Ti 5O 12 onto the LiNi 0.8Co 0.15Al 0.05O 2 particles further improved the high-rate performance to give ca. 110 mAh g -1. The rate capability promises to realize all-solid-state lithium secondary batteries with very high performance. © 2011 Elsevier B.V. All rights reserved.

Nagase T.,Osaka University | Yokoyama A.,Osaka University | Umakoshi Y.,Japan National Institute of Materials Science
Scripta Materialia | Year: 2010

The glass-to-liquid transition was evaluated by in situ transmission electron microscope observation of crystalline Cu globule aggregation in Fe-Zr-B amorphous or supercooled liquid matrices in Fe50Zr 10B20Cu20 melt-spun ribbon. Globule aggregation was not observed near the critical glass transition temperature, but was observed near the glass transition temperature evaluated by conventional differential scanning calorimetry measurements. The viscosity of Fe-Zr-B-based metallic glass may decrease during the glass-to-liquid transition, and a polygonal crystalline phase may form by Cu globule aggregation. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Iwanaga M.,Japan National Institute of Materials Science
Optics Letters | Year: 2010

A concrete design for an orthogonal polarization rotator at optical frequencies is presented. The subwave- length rotator is formed from a pair of ultrathin metamaterial plates of transparency and remarkable anisotropy. By traveling through the rotator, the incident light of linear polarization undergoes the azimuthangle rotation by about 90° for a wide range of incident azimuth angles from 0° to 90°. The orthogonal rotator proposed here works with the 1/4 thickness of the incident wavelength and keeps the transmittance as high as 50%, showing a high efficiency as a subwavelength optical element. © 2010 Optical Society of America.

Sakoda K.,Japan National Institute of Materials Science | Sakoda K.,University of Tsukuba
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We show that the propagation direction of the Dirac-cone modes of photonic-crystal slabs can be continuously controlled by the polarization of the incident wave. This property is realized by their isotropic dispersion relation and anisotropic mixture of two dipolar wave functions. To clarify these features, we formulate a Green-function method to describe the excitation process of the Dirac-cone modes and analyze the coupling strength with the incident wave by group theory. This angular dependence of the intensity distribution of the excited wave can be used for experimentally detecting the Dirac cones and distinguishing their mode symmetry. © 2014 American Physical Society.

Tsujii N.,Japan National Institute of Materials Science
Journal of Alloys and Compounds | Year: 2014

Polycrystalline sample of YbCu9Sn4 has been prepared and the physical properties have been investigated. Magnetic susceptibility shows a weak diamagnetism, indicating the Yb ions are in the nonmagnetic Yb 2+ state. Electrical resistivity shows a normal metallic behavior and Seebeck coefficient is as small as the order of 1 μV/K. Specific heat reveals the prominent contribution of Einstein mode at low temperature with the Einstein temperature of 67 K. Lattice thermal conductivity is found to be as small as 2.7 W/Km below room temperature. These results demonstrate that the Yb ions inside the Cu-Sn cage exhibit rattling, which reduces the lattice thermal conductivity of YbCu9Sn4. © 2014 Elsevier B.V. All rights reserved.

Sanchez S.,Japan National Institute of Materials Science | Sanchez S.,Leibniz Institute for Solid State and Materials Research | Solovev A.A.,Leibniz Institute for Solid State and Materials Research | Mei Y.,Leibniz Institute for Solid State and Materials Research | And 3 more authors.
Journal of the American Chemical Society | Year: 2010

We describe the motion of self-propelled hybrid microengines containing catalase enzyme covalently bound to the cavity of rolled-up microtubes. The high efficiency of these hybrid microengines allows them to move at a very low concentration of peroxide fuel. The dynamics of the catalytic engines is mediated by the generation of front-side bubbles, which increase the drag force and make them turn. The specific modification of the inner layer of microtubes with biomolecules can lead to other configurations to generate motion from different chemical fuels. © 2010 American Chemical Society.

Nagase T.,Osaka University | Umakoshi Y.,Japan National Institute of Materials Science
Intermetallics | Year: 2010

MeV electron irradiation can introduce Frenkel pairs, i.e., a vacancy-interstitial pair, in crystals. In metallic glass, density fluctuation, namely, a pair of free volume and anti-free volume, is introduced, resulting in the devitrification of the amorphous phase in some metallic glasses. In this study, we investigated the temperature dependence of MeV-irradiation-induced crystallization of metallic glasses. Phase selection in crystallization shows a significant temperature dependence in various metallic glasses at and under 298 K. The size of the crystalline precipitates changes with irradiation temperature in some metallic glasses. © 2010 Elsevier Ltd. All rights reserved.

Miyamoto N.,Fukuoka Institute of Technology | Iijima H.,Fukuoka Institute of Technology | Ohkubo H.,Fukuoka Institute of Technology | Yamauchi Y.,Japan National Institute of Materials Science
Chemical Communications | Year: 2010

Size-controlled nanosheet colloids of fluorohectorite and fluortetrasilicic mica were prepared in high yield and their transitions to fluid liquid crystal (LC) phases with highly ordered lamellar structures were identified over a wide concentration range, which is a rare case for clay mineral systems. © 2010 The Royal Society of Chemistry.

Yasuda H.Y.,Osaka University | Umakoshi Y.,Japan National Institute of Materials Science
Intermetallics | Year: 2010

Pseudoelasticity which shape memory alloys reveal is generally based on a thermoelastic martensitic transformation. However, Fe-rich Fe3Al single crystals with the D03 structure demonstrate pseudoelasticity regardless of the martensitic transformation. It is strongly suggested that the pseudoelasticity of Fe3Al crystals originates from the peculiar dislocation motion dragging an antiphase boundary (APB). During loading, a 1/4C111D superpartial dislocation moves individually dragging the APB. On the other hand, the APB pulls back the superpartial during unloading due to its tension resulting in the pseudoelasticity of which recoverable strain is as much as 5%. Hence, this phenomenon is called "APB pseudoelasticity". This article summarizes the recent progress in the understanding of the pseudoelastic behaviour of D03-ordered Fe3Al single crystals and the effects of Al concentration, deformation temperature, loading axis and third element addition are discussed. © 2010 Elsevier Ltd. All rights reserved.

Kohno M.,Japan National Institute of Materials Science
Physics Procedia | Year: 2015

By infinitesimal doping of a Mott insulator, states are induced in the Mott gap in the single- particle spectrum. To clarify the nature of these states, their relationships with the magnetically excited states of the Mott insulator are investigated. By using the commutator between the Hamiltonian and an electron creation operator of the t-J model, it is shown that the doping- induced states generally have considerable overlaps with the magnetically excited states of the Mott insulator. In addition, the electron-addition spectral weight of spin-1 states from the spin- 1/2 ground state is shown to be three times as large as that of spin-0 states in the t-J model. These results imply that the doping-induced states in the small-doping limit of a continuous Mott transition can generally be interpreted as essentially the magnetically excited states of the Mott insulator which exhibit the momentum-shifted magnetic dispersion relation primarily outside the free-electron Fermi surface in the electron-addition spectrum following the doping. This picture is supported by numerical results for the one- and two-dimensional t-J models. © 2015 The Authors. Published by Elsevier B.V.

Panaccione G.,CNR Institute of Materials | Kobayashi K.,Hiroshima University | Kobayashi K.,Japan National Institute of Materials Science
Surface Science | Year: 2012

The electronic properties of surfaces and buried interfaces can vary considerably in comparison to the bulk. In turn, analyzing bulk properties, without including those of the surface, is understandably challenging. Hard X-ray photoelectron spectroscopy (HAXPES) allows the well known ability of photoemission to interrogate the electronic structure of material systems with bulk volume sensitivity. This is achieved by tuning the kinetic energy range of the analyzed photoelectrons in the multi-keV regime. This unique ability to probe truly bulk properties strongly compliments normal photoemission, which generally probes surface electronic structure that is different than the bulk selected examples of HAXPES and possible implications towards the study of complex oxide-based interfaces and highly correlated systems are discussed. © 2011 Elsevier B.V. All rights reserved.

Glatzel S.,Max Planck Institute of Colloids and Interfaces | Schnepp Z.,Japan National Institute of Materials Science | Giordano C.,Max Planck Institute of Colloids and Interfaces
Angewandte Chemie - International Edition | Year: 2013

Electrodes from the ink-jet printer: Cellulose sheets can be transformed into mesostructured graphene nanostructures by a simple and general method. Since the iron catalyst can be printed on paper with an ink-jet printer, the products can be prepared with 2D patterns. Subsequent Cu deposition results in further functionalization of the microstructured electrodes (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tanaka H.,Japan National Institute of Materials Science
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2011

Silicon carbide (SiC) was first industrially synthesized in 1894 and has been used as refractories, abrasives and high temperature furnace parts. The basic fabrication and sintering technologies were almost established by about 1970. Recently, sintered SiC has become a key material as it has been widely used in advanced industries of semiconductors and high precision machines. New fabrication methods for modern SiC powders and sintering methods are being developed on the bases of traditional methods. In this review, the original studies and recent developments have been given maximum possible emphasis, and in particular, basic points of view are introduced. © 2011 The Ceramic Society of Japan.

Tachibana M.,Japan National Institute of Materials Science
Solid State Communications | Year: 2015

Thermal conductivity data between 1.8 and 300 K are reported for K1-xLixTaO3 (0≤x≤0.03) and KTa1-xNbxO3 (0≤x≤0.16) single crystals. Whereas lightly Li- and Nb-doped crystals exhibit relaxor-like behavior in dielectric susceptibility, they do not show the glasslike thermal transport found in conventional relaxors such as PbMg1/3Nb2/3O3 and Na1/2Bi1/2TiO3. The lack of glasslike behavior in K1-xLixTaO3 and KTa1-xNbxO3 is confirmed by the absence of temperature-linear contribution in heat capacity. © 2015 Elsevier Ltd. All rights reserved.

Shrestha L.K.,Japan National Institute of Materials Science | Shrestha R.G.,Tokyo University of Science | Aramaki K.,Yokohama National University
Langmuir | Year: 2011

Shape, size, and internal structure of nonionic reverse micelle in styrene depending on surfactant chain length, concentration, temperature, and water addition have been investigated using a small-angle X-ray scattering (SAXS) technique. The generalized indirect Fourier transformation (GIFT) method has been employed to deduce real-space structural information. The consistency of the GIFT method has been tested by the geometrical model fittings, and the micellar aggregation number (Nagg) has been determined. It was found that diglycerol monocaprate (C10G2), diglycerol monolaurate (C12G2), and diglycerol monomyristate (C 14G2), spontaneously self-assemble into reverse micelles in organic solvent styrene under ambient conditions. The micellar size and the Nagg decrease with an increase in surfactant chain length, a scenario that could be understood from the modification of the critical packing parameter (cpp). A clear picture of one-dimensional (1-D) micellar growth was observed with an increase in surfactant weight fraction (Ws) in the C 10G2 system, which eventually formed rodlike micelles at Ws ≥ 15%. On the other hand, micelles shrunk favoring a rod-to-sphere type transition upon heating. Reverse micelles swelled with water, forming a water pool at the micellar core; the size of water-incorporated reverse micelles was much bigger than that of the empty micelles. Model fittings showed that water addition not only increase the micellar size but also increase the Nagg. Zero-shear viscosity was found to decrease with surfactant chain but increase with Ws, supporting the results derived from SAXS. © 2011 American Chemical Society.

Liu K.,Japan International Center for Materials Nanoarchitectonics | Sakurai M.,Japan International Center for Materials Nanoarchitectonics | Liao M.,Japan National Institute of Materials Science | Aono M.,Japan International Center for Materials Nanoarchitectonics
Journal of Physical Chemistry C | Year: 2010

ZnO nanowire photodetectors with and without Au nanoparticles have been fabricated and investigated. The dark current decreases by 2 orders of magnitude and the ratio of photo current to dark current increases after covering with Au nanoparticles. Meanwhile, the decorated Au nanoparticles can drastically improve the response speed of ZnO nanowire photodetectors. A physical model based on band energy theory was developed to illustrate the origin of the improvement of performance for ZnO nanowire photodetector attached with Au. Our work suggests that rational integration of ZnO wire and metal nanoparticles is a viable approach to improving the performance of ZnO nanowire photodetectors, which may help to advance optoelectronic devices.

Jobbagy M.,University of Buenos Aires | Iyi N.,Japan National Institute of Materials Science
Journal of Physical Chemistry C | Year: 2010

The structure of several crystalline Ni(II)-Al(III) and Mg(II)-Al(III) layered double hydroxides (LDHs) intercalated with nitrate anions was studied as a function of the relative humidity. For low charge density LDHs, the electrostatic attraction between the anions and the positive LDH layers prevails over any other interaction, and the anions remain flat, F, with their C 3 axis perpendicular to the xy planes, irrespective of water activity. For LDHs bearing higher charge densities, the incoming water molecules drive an abrupt phase expansion in which the anions tilt their C 3 axis with respect to the interlamellar xy plane, thus resulting in an expanded, T, form. The structural F-T transition is discontinuous, and involves a second staging phase intermediate, with alternated F and T galleries. For intermediate charge density LDHs, the hydration process easily reverts, once the samples are resubmitted to a dry atmosphere. Dehydration of high charge density LDHs is however kinetically hindered; this behavior is explained in terms of the structural features of the involved phases. For all samples, the maximum net gallery expansion is proportional to the layer charge density, irrespective of the nature of the divalent cation. © 2010 American Chemical Society.

Inoue J.-I.,Japan National Institute of Materials Science
Journal of Physics A: Mathematical and Theoretical | Year: 2012

We discuss a possible phase transition in a full Dicke model that allows a local excitation in a two-level system to migrate to the nearest-neighbour sites. This model is found to be singular in the sense that a conventional scheme to handle a Dicke model with a generic interaction is not applicable. We thus begin with devising an appropriate method for the present model, and then evaluate a partition function associated with the model within a framework of imaginary time functional integral method. Through the stationary phase analysis of the partition function, we show that a condensation of a coupling mode of two degrees of freedom that constitute the model, photon and the local excitation, would occur. The result demonstrates contrasting features of the phase, depending on the sign of the migration term. A connection of our findings with an experimental realization, Frenkel exciton polariton condensation in an organic dye aggregate, is pointed out. © 2012 IOP Publishing Ltd.

Nakamura Y.,Japan National Institute of Materials Science | Ohno T.,Chiyoda Corporation
Materials Chemistry and Physics | Year: 2012

We study the effect of different water models on molecular dynamics simulations of the water structures inside carbon nanotubes, employing not only the commonly used three-and four-site water models, but also the five-site model. The water structures induced by the spontaneous filling of the uncapped carbon nanotubes with the reservoir water are focused on to demonstrate the effect. It is found that for the carbon nanotubes with diameter about 1 nm, there is significant anomalous behavior of water that differs from model to model. The dependence is discussed in terms of model accuracy. © 2011 Elsevier B.V. All rights reserved.

Kawazu T.,Japan National Institute of Materials Science
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

Optical anisotropy in type-II quantum wells (QWs) on high-index substrates is studied theoretically. We analyze GaAs 1-XSb X/GaAs type-II QWs and calculate the degree ρ of polarization. Compared to type-I QWs, the optical anisotropy is enhanced in the type-II QW due to the spatial overlap of holes in the QW and electrons outside. We also evaluate ρ in the QW as a function of the diffusion length to clarify how the optical anisotropy is affected by the interface grading due to the Sb/As interdiffusion. In an initial stage of grading where the diffusion process tends to increase the effective size of the repulsive potential, the electron is more repelled by the QW, leading to an increase in ρ. In later stages, however, the hole confinement and the electron repulsion by the QW both weaken, leading to a decrease in ρ. We also examine the effect of excited carrier concentration on the optical anisotropy in the type-II QW. © 2012 Elsevier B.V.

Somekawa H.,Japan National Institute of Materials Science | Mukai T.,Kobe University
Materials Letters | Year: 2012

The effect of grain boundary structures on the deformation behavior at the grain boundaries in magnesium was examined by the nanoindentation creep test. The results of the nanoindentation creep test showed that the dominant deformation mechanism around the grain boundary was grain boundary sliding; however, the occurrence of grain boundary sliding was closely related to the grain boundary energy. The grain boundary with high energy showed high strain rate sensitivity, which was the same tendency as that of the other metallic materials. Furthermore, the addition of aluminum atoms into magnesium tended to prevent the grain boundary sliding due to the decrease in grain boundary energy. © 2012 Elsevier B.V. All rights reserved.

Solovyev I.V.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

It is well known that, if a crystal structure has no inversion symmetry, it may allow for Dzyaloshinskii-Moriya magnetic interactions, operating between different crystallographic unit cells, which, in turn, should lead to the formation of long-periodic spin-spiral structures. Such a behavior is anticipated for two simple perovskites PbVO 3 and BiCoO 3, crystallizing in the noncentrosymmetric tetragonal P4mm structure. Nevertheless, we argue that, in reality, PbVO 3 and BiCoO 3 should behave very differently. Due to the fundamental Kramers degeneracy for the odd-electron systems, PbVO 3 has no single-ion anisotropy. Therefore, the ground state of PbVO 3 indeed will be the spin spiral with the period of about 100 unit cells. However, the even-electron BiCoO 3 has a large single-ion anisotropy, which locks this system in the collinear easy-axis C-type antiferromagnetic ground state. Our theoretical analysis is based on the low-energy model, derived from the first-principles electronic structure calculations. © 2012 American Physical Society.

Ishida A.,Japan National Institute of Materials Science
Sensors and Actuators, A: Physical | Year: 2015

Polyimide/Ti49Ni33Cu18 composite films were fabricated by the sputtering of an alloy target. The composite films could be used as a simple actuator by cutting an appropriately shaped piece out of an as-sputtered films with scissors and then connecting it to a battery. In order to investigate the design parameters for the composite-film actuators, Ti-Ni-Cu films with various thicknesses (0.8-13 μm) were deposited on two kinds of polyimide films (Kapton EN and H) with various thicknesses (25-175 μm). The force and stroke of the composite-film actuators were found to vary largely with changes in various parameters such as the thickness ratio of Ti-Ni-Cu and polyimide films and the coefficient of thermal expansion of the polyimide films. A simulation tool based on a simple deformation model for a shape memory alloy was developed, and the effects of dimensional parameters (thickness, length, and width) and material parameters (Young's modulus, elastic strain limit, and transformation strain) on the actuation properties (force and stroke) of the composite-film actuators were systematically investigated on the basis of the simulation results. The simulation results revealed that composite-film actuators allow for various combination of force and stroke. Optimized actuators exhibited a long actuation stroke, a high response speed of 3 Hz, and a large force of 0.4 N. © 2014 Published by Elsevier B.V.

Guo S.,Japan National Institute of Materials Science
International Journal of Applied Ceramic Technology | Year: 2015

In this study, ZrB2-ZrCx-Zr cermets with 20 vol% SiC additives were prepared via reactive hot-pressing of Zr + B4C + SiC powder mixtures. Relative density exceeding 95% was obtained for the sintered cermets with 10 vol% excess Zr and without excess Zr. The resulting cermets composed of ZrB2, ZrCx, and SiC primary phases and zirconium silicide secondary phase. The presence of excess Zr improved densification of cermets as well as promoted formation of zirconium silicide. However, excess Zr led to the lowered room temperature flexural strength. The room temperature flexural strength of cermets was in the range of 384.2-409.2 MPa. © 2014 The American Ceramic Society.

Mitani S.,Japan National Institute of Materials Science
Journal of Physics D: Applied Physics | Year: 2011

This paper reviews spin-transfer magnetization switching in ordered alloy-based nanopillar devices. L10-ordered FePt was used for one of the earliest demonstrations of spin-transfer switching in perpendicularly magnetized systems. The behaviour of magnetization switching deviates from the predictions based on a macro-spin model, suggesting incoherent magnetization switching in the system with a large perpendicular magnetic anisotropy. The effect of a 90° spin injector on spin-transfer switching was also examined using L10-ordered FePt. Full-Heusler alloys are in another fascinating material class for spin-transfer switching because of their high-spin polarization of conduction electrons and possible small magnetization damping. A B2-ordered Co2FeAl0.5Si0.5-based device showed a low intrinsic critical current density of 9.3 × 10 6 A cm-2 for spin-transfer switching as well as a relatively large current-perpendicular-to-plane giant-magnetoresistance (CPP-GMR) up to ∼9%. The specific physical properties of ordered alloys may be useful for fundamental studies and applications in spin-transfer switching. © 2011 IOP Publishing Ltd.

Sang L.-C.,Rensselaer Polytechnic Institute | Vinu A.,Japan National Institute of Materials Science | Vinu A.,University of Queensland | Coppens M.-O.,Rensselaer Polytechnic Institute
Langmuir | Year: 2011

A simple but remarkably precise geometric pore-filling model is proposed and experimentally validated for the adsorption of proteins at their iso-electric point (pI) in nanoporous materials. Three different globular proteins-lysozyme, myoglobin, and bovine serum albumin-are used as model proteins to study protein adsorption on two types of ordered mesoporous materials-silica and carbon-which allows us to study the effects of protein and surface structure on the protein adsorption mechanism. The geometric pore-filling model confirms that proteins are closely packed inside the pore channels of mesoporous materials, leading to an exceptionally large protein loading capacity. A relationship for the amount of adsorbed protein as a function of protein size, nanopore volume, and pore diameter is derived. The pore space gradually fills up to complete packing of the available pore space at the highest protein concentration. The high precision of the geometric pore-filling model demonstrates its utility to predict the protein adsorption capacity of ordered nanoporous materials. © 2011 American Chemical Society.

Taguchi T.,Japan National Institute of Materials Science
Science and Technology of Advanced Materials | Year: 2011

The development of materials and technologies for the assembly of cells and/or vesicles is a key for the next generation of tissue engineering. Since the introduction of the tissue engineering concept in 1993, various types of scaffolds have been developed for the regeneration of connective tissues in vitro and in vivo. Cartilage, bone and skin have been successfully regenerated in vitro, and these regenerated tissues have been applied clinically. However, organs such as the liver and pancreas constitute numerous cell types, contain small amounts of extracellular matrix, and are highly vascularized. Therefore, organ engineering will require the assembly of cells and/or vesicles. In particular, adhesion between cells/vesicles will be required for regeneration of organs in vitro. This review introduces and discusses the key technologies and materials for the assembly of cells/vesicles for organ regeneration. © 2011 National Institute for Materials Science.

Pauw B.R.,Japan National Institute of Materials Science
Journal of Physics Condensed Matter | Year: 2013

For obtaining reliable nanostructural details of large amounts of sample - and if it is applicable - small-angle scattering (SAS) is a prime technique to use. It promises to obtain bulk-scale, statistically sound information on the morphological details of the nanostructure, and has thus led to many a researcher investing their time in it over the last eight decades of development. Due to pressure from scientists requesting more details on increasingly complex nanostructures, as well as the ever improving instrumentation leaving less margin for ambiguity, small-angle scattering methodologies have been evolving at a high pace over the past few decades. As the quality of any results can only be as good as the data that go into these methodologies, the improvements in data collection and all imaginable data correction steps are reviewed here. This work is intended to provide a comprehensive overview of all data corrections, to aid the small-angle scatterer to decide which are relevant for their measurement and how these corrections are performed. Clear mathematical descriptions of the corrections are provided where feasible. Furthermore, as no quality data exist without a decent estimate of their precision, the error estimation and propagation through all these steps are provided alongside the corrections. With these data corrections, the collected small-angle scattering pattern can be made of the highest standard, allowing for authoritative nanostructural characterization through its analysis. A brief background of small-angle scattering, the instrumentation developments over the years, and pitfalls that may be encountered upon data interpretation are provided as well. © 2013 IOP Publishing Ltd.

Ochiai T.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We present a photonic realization of the parity anomaly originally found in the (2+1)-dimensional Dirac fermion. We first derive an effective Dirac Hamiltonian around the Brillouin zone corner of triangular-, honeycomb-, and kagome-lattice photonic crystals using group theory. A topological phase transition by broken space-inversion and time-reversal symmetries is derived analytically within the effective theory on the honeycomb lattice. The phase transition is closely related to the Haldane model of the two-dimensional electron system under periodic magnetic flux, which realizes the parity anomaly in a condensed-matter system. We also derive an effective theory around the Brillouin zone center, where quadratic degeneracy in momentum space take places. The effective theory there predicts a similar phenomenon as the parity anomaly. As a result, a topologically nontrivial phase and a chiral edge state are predicted even for staggered configuration of applied magnetic flux. A numerical simulation is also presented to confirm the prediction. © 2012 American Physical Society.

Takeda H.,Nagoya University | Itoh M.,Nagoya University | Sakurai H.,Japan National Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We have made NMR and magnetization measurements on a single crystal to investigate local magnetic properties of an antiferromagnet metal NaV 2O 4 with a frustrated double-chain structure. In the paramagnetic phase, we find there is a double exchange ferromagnetic interaction, which competes with a superexchange antiferromagnetic interaction, yielding a magnetic frustration. In the magnetically ordered state, we propose an incommensurate helical structure with the bc helical plane, which appears due to the competition between the magnetic interactions, as a spin structure. Thus we conclude that the magnetic frustration closely related to a multi-band effect plays an essential role for the magnetic properties of NaV 2O 4. © 2012 American Physical Society.

Ishioka K.,Japan National Institute of Materials Science | Petek H.,University of Pittsburgh
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Ultrafast phonon dynamics in anatase and rutile TiO 2 single crystals are investigated using 400 nm near ultraviolet light pulses, whose wavelength corresponds to the fundamental absorption edges of both polymorphs. Raman-active phonon modes are observed as coherent modulations in THz frequency range of the reflected light intensity. Coherent amplitudes vary as the crystals are rotated with respect to the pump and probe polarizations, depending on the symmetry of the phonon modes. The polarization dependence is quantitatively reproduced by assuming that both the generation and detection are dominated by the Raman scattering process. No evident resonance enhancement is observed in the coherent amplitudes as we vary the excitation light wavelength around the fundamental absorption edges. These results indicate that the creation of coherent bulk phonons by photodoped carriers is negligible compared with the competing Raman process at the fundamental band gap excitation. © 2012 American Physical Society.

Kang Y.,Japan National Institute of Materials Science | Kang S.,Seoul National University
Journal of the European Ceramic Society | Year: 2010

A ceramic microstructure of WC-reinforced (Ti,W)(CN) was designed using thermodynamic instability among the constituent elements and gas species involved in the sintering process. During sintering WC in the shape of platelets formed in (Ti,W)(CN) solid-solution ceramics, which were synthesized from milled mixtures of oxides with carbon. The WC platelets separated from the (Ti,W)(CN) ceramics due to the low chemical affinity of tungsten for nitrogen. The shape of WC varies depending on the composition of the binder phase and the sintering conditions. With increasing binder content, the WC platelet shape became more irregular. This change was attributed not only to surface energy but also to the formation mechanism. The presence of WC platelets toughened (Ti,W)(CN) significantly at excellent hardness value (Hv: 18.5-20.0 GPa, KIC: 6.0-6.8 MPa m1/2) as compared to those of recently reported advanced structural ceramics. © 2009 Elsevier Ltd. All rights reserved.

Hanagata N.,Japan National Institute of Materials Science | Hanagata N.,Hokkaido University
Journal of Bone and Mineral Metabolism | Year: 2015

Interferon-induced transmembrane protein 5 (IFITM5) is an osteoblast-specific membrane protein that has been shown to be a positive regulatory factor for mineralization in vitro. However, Ifitm5 knockout mice do not exhibit serious bone abnormalities, and thus the function of IFITM5 in vivo remains unclear. Recently, a single point mutation (c.-14C>T) in the 5′ untranslated region of IFITM5 was identified in patients with osteogenesis imperfecta type V (OI-V). Furthermore, a single point mutation (c.119C>T) in the coding region of IFITM5 was identified in OI patients with more severe symptoms than patients with OI-V. Although IFITM5 is not directly involved in the formation of bone in vivo, the reason why IFITM5 mutations cause OI remains a major mystery. In this review, the current state of knowledge of OI pathological mechanisms due to IFITM5 mutations will be reviewed. © 2015 The Japanese Society for Bone and Mineral Research and Springer Japan

Watanabe I.,Japan National Institute of Materials Science
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2015

A theoretical framework to describe ductile fracture is reviewed from a multiscale perspective based on continuum solid mechanics. Ductile fracture has a hierarchical multiscale structure from a strain localization of a macroscopic structure to debonding of an atomic debinding. In this article, computational methods founded on continuum approximation are addressed, where discretization methods represented by finite element method are featured. These approaches are recognized as promising tools to understand and visualize the deformation and strengthening mechanisms. Here the concepts of description of fracture mechanics are classified into strong discontinuity models and distributed damage models. Also two types of scale-coupling approaches are illustrated to consider the effect of a microscopic heterogeneity on its coarse scale. © 2015, Iron and Steel Institute of Japan. All rights reserved.

Shigetou A.,Japan National Institute of Materials Science | Suga T.,University of Tokyo
Journal of Electronic Materials | Year: 2012

Homo- and heterogeneous bonding of Cu, SiO2, and polyimide, by using a single vapor-assisted surface activation method at 150 C and atmospheric pressure, is highly feasible and will be of practical use in three-dimensional heterointegration of thin, flat interconnection layers. Since it is necessary to achieve good bondability to diverse materials in a single process in order to maintain bumpless structures, we have to create a compatible bridging layer. Bridging layers, based on Cu hydroxide hydrate and silanol and hydroxyl groups formed from SiO2 and polyimide, respectively, were prepared by introducing water onto the activated surfaces at atmospheric pressure. The growth rate of the bridging layers was tunable via absolute humidity, and exposure of 8 g/m3 was used. Heating at 150 C, after exposure to humidity, caused tight adhesion between the mating surfaces for all combinations of starting materials with voidless amorphous interfacial (bridging) layers. Because of the well-controlled layer thickness, low electrical resistivity of ∼4 × 10-8 Ω m was obtained at the Cu-Cu interface. © 2012 TMS.

Nonomura Y.,Japan National Institute of Materials Science
Journal of Physics: Conference Series | Year: 2012

Motivated by recent experiments on THz wave emission from intrinsic Josephson junctions without or in in-plane magnetic field, effect of surface impedance Z is investigated numerically. Without external field, dynamical phase transitions between the McCumber-like state and various π-phase-kink states occur as the bias current and Z are varied. Emission is optimized for Z ≈ 50 in the n = 1 mode. In this mode dependence of emission intensity on in-plane field shows a crossover behavior around Z = 50: monotonic decrease for Z > 50 and two characteristic peaks for Z < 50, each of which is consistent with a recent experiment. © Published under licence by IOP Publishing Ltd.

Kawabata K.,University of Tsukuba | Takeguchi M.,Japan National Institute of Materials Science | Goto H.,University of Tsukuba
Macromolecules | Year: 2013

We electrochemically polymerized various achiral heteroaromatic monomers in left-handed helical cholesteric liquid crystal (CLC) media. Circular dichroism (CD) spectroscopy revealed that most of the resulting conjugated polymer films exhibited both the first negative and second positive Cotton effects near their absorption maxima. This indicates left-handed helical aggregation of the conjugated main chains, which is consistent with left-handed helical order of the CLC. This result suggests that the left-handed helical CLC environment induced left-handed helical aggregation of the polymers during the electrodeposition. However, CD intensity of the polymers depends on the structure of the parent monomers. Systematic investigation of the relationship between monomer structures and optical activity of the polymers indicates that linearity of the conjugated main chains and excluded volume interaction between the monomers and the CLC are important factors for producing optical activity of the polymers. © 2013 American Chemical Society.

Furumi S.,Japan National Institute of Materials Science | Furumi S.,Japan Science and Technology Agency | Furumi S.,University of Tsukuba
Nanoscale | Year: 2012

Colloids with a size in the nanometres to micrometres range are frequently used in both fundamental research and industrial applications. In this context, colloidal crystals (CCs) - 3D ordered arrays of monodispersed colloidal microparticles with a diameter of several hundred nanometres - have garnered a great deal of attention in the intriguing research realm of photonic crystals (PCs) due to the feasible and high-throughput 3D-PC fabrication with CCs. For optoelectronic applications, it is of prime importance to construct 3D-PCs with photonic band-gaps (PBGs) in the visible wavelength range. With regard to photonic device applications, many reports have been made on a wide variety of optical reflection sensors and displays using CCs that shift the visible PBG wavelength in response to external stimuli. This Minireview describes the research progress in the investigation of CCs and their laser applications. We highlight not only the research background of CCs as 3D-PCs, but also new potential applications of CCs as flexible and widely tunable lasers by low-threshold optical excitation. This journal is © The Royal Society of Chemistry 2012.

Ariga K.,Japan National Institute of Materials Science
Nanoscale | Year: 2010

There is great potential in nanoscale science and technology, and construction of macrosized materials and systems possessing nanoscale structural features is a crucial factor in the everyday application of nanoscience and nanotechnology. Because nanoscale substances are often constructed through self-assembly of unit molecules and nanomaterials, control of the self-assembly process is required. In order to establish general guidelines for the fabrication of materials with nanoscale structural characteristics, i.e., nanoscaled materials, we introduce here examples of recent research in related fields categorised as: (i) self-assembled structures with forms generally determined by intrinsic interactions between molecules and/or unit nanomaterials, (ii) self-assemblies influenced by their surrounding media, especially interfacial environments, (iii) modulation of self-assembly by artificial operation or external stimuli. Examples are not limited to organic molecules, which are often regarded as the archetypal species in self-assembly chemistry, and many examples of inorganic assemblies and hybrid structures are included in this review.

Yan J.,Keio University | Asami T.,Tohoku University | Harada H.,Japan National Institute of Materials Science | Kuriyagawa T.,Tohoku University
CIRP Annals - Manufacturing Technology | Year: 2012

Nanoprecision plunge cutting tests were carried out on single-crystal silicon (0 0 1) samples along various directions at different tool rake angles, and subsurface damage was characterized by cross-sectional transmission electron microscopy and laser micro-Raman spectroscopy. It was found that amorphization, poly-crystallization, dislocation and internal microcracking occurred and these material responses depended strongly on the cutting direction. When cutting in the 11̄0 and 01̄0 directions, deep line defects consisting of microcracks and dislocation groups occurred even when the surface was "ductile"-cut; while for the 1283090 direction, the damage depth was reduced by a factor of five. © 2012 CIRP.

Iwanaga M.,Japan National Institute of Materials Science | Iwanaga M.,Japan Science and Technology Agency
Science and Technology of Advanced Materials | Year: 2012

A decade of research on metamaterials (MMs) has yielded great progress in artificial electromagnetic materials in a wide frequency range from microwave to optical frequencies. This review outlines the achievements in photonic MMs that can efficiently manipulate light waves from near-ultraviolet to near-infrared in subwavelength dimensions. One of the key concepts of MMs is effective refractive index, realizing values that have not been obtained in ordinary solid materials. In addition to the high and low refractive indices, negative refractive indices have been reported in some photonic MMs. In anisotropic photonic MMs of high-contrast refractive indices, the polarization and phase of plane light waves were efficiently transformed in a well-designed manner, enabling remarkable miniaturization of linear optical devices such as polarizers, wave plates and circular dichroic devices. Another feature of photonic MMs is the possibility of unusual light propagation, paving the way for a new subfield of transfer optics. MM lenses having super-resolution and cloaking effects were introduced by exploiting novel light-propagating modes. Here, we present a new approach to describing photonic MMs definitely by resolving the electromagnetic eigenmodes. Two representative photonic MMs are addressed: the so-called fishnet MM slabs, which are known to have effective negative refractive index, and a three-dimensional MM based on a multilayer of a metal and an insulator. In these photonic MMs, we elucidate the underlying eigenmodes that induce unusual light propagations. Based on the progress of photonic MMs, the future potential and direction are discussed. © 2012 National Institute for Materials Science.

El-Safty S.A.,Japan National Institute of Materials Science | Shenashen M.A.,Japan National Institute of Materials Science | El-Safty S.A.,Waseda University
TrAC - Trends in Analytical Chemistry | Year: 2012

The toxicity of mercury (Hg) to humans, including damage to the nervous system, is well known. Hg cannot be degraded into non-toxic compounds or other elements. It is released mainly through mining, industries, and fossil fuel combustion. Anthropogenic and natural activities, such as volcanoes, transform elemental Hg (Hg 0) into its ionic form [Hg(II)], which bioaccumulates in biota and is biomagnified in the food chain, notably in aquatic environments.This critical report aims to control Hg(II)-ion toxicity through risk assessment, recognition, and removal via high-level waste management. We first discuss successful and up-to-date developments in different techniques, designs and studies that are potentially useful in enhancing the effectiveness of control of Hg(II)-ion toxicity.The key to designing optical nanosensors is to construct chromophore and fluorophore receptors as nanoscale platform scavengers with different functional characteristics (e.g., density, accessibility, and intrinsic mobility), which allow for easy, reliable signaling in continuous monitoring modes. We highlight a technique that depends on the use of engineered mesocage materials that have multidirectional cavities and microsized, particle-like monoliths to control the adsorption/detection of toxic metal ions, especially Hg(II) ions.With regard to proximal sensing, we consider controlled assessment processes that involve the evaluation of intrinsic properties (e.g., signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability).This study provides evidence that miniaturized mesosensor strips can revolutionize consumer and industrial markets with the introduction of ion-sensor strips. © 2012 Elsevier Ltd.

Tabuchi M.,Japan National Institute of Materials Science | Takahashi Y.,Japan Central Research Institute of Electric Power Industry
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2012

Creep strength of welded joint for high Cr ferritic heat resisting steels decreases due to Type-IV failure in heat-affected zone (HAZ) during long-term use at high temperatures. In order to review the allowable creep strength of these steels, creep rupture data of base metals and welded joints have been collected, and long-term creep strength has been evaluated in the SHC (strength of high-chromium steel) committee in Japan. In the present paper, the creep rupture data of 370 points for welded joint specimens of modified 9Cr-1Mo steel (ASME Grade 91 steel) offered from seven Japanese companies and institutes were analyzed. These data clearly indicated that the creep strength of welded joints was lower than that of base metal due to Type-IV failure in HAZ at high temperatures. From the activities of this committee, it was concluded that the weld strength reduction factor (WSRF) should be taken into consideration for the design and residual life assessment of boiler components in fossil power plants. The committee recommended the WSRF for 100,000 h creep of Gr.91 steel as 0.85 at 575 °C, 0.75 at 600 °C, 0.74 at 625 °C, and 0.70 at 650 °C. The master curve for residual life assessment of Gr.91 steel welds using Larson-Miller parameter was also proposed. © 2012 American Society of Mechanical Engineers.

Tachibana M.,Japan National Institute of Materials Science
Solid State Communications | Year: 2015

The in-plane thermal conductivity of Bi2WO6, SrBi2Ta2O9, and Bi4Ti3O12 single crystals has been measured from 2 to 320 K. These compounds are representative members of the Aurivillius ferroelectrics having one, two, and three perovskite-like layered blocks in the structure, respectively. In contrast to Bi2WO6 and Bi4Ti3O12, SrBi2Ta2O9 has much lower glasslike thermal conductivity that is attributed to strong cation disorder in the crystal. Unlike glasses, however, SrBi2Ta2O9 does not exhibit a temperature-linear contribution in its heat capacity. © 2015 Elsevier Ltd.

Bay T.V.,University of Amsterdam | Naka T.,Japan National Institute of Materials Science | Huang Y.K.,University of Amsterdam | Luigjes H.,University of Amsterdam | And 2 more authors.
Physical Review Letters | Year: 2012

We report a high-pressure single crystal study of the topological superconductor Cu xBi 2Se 3. Resistivity measurements under pressure show superconductivity is depressed smoothly. At the same time the metallic behavior is gradually lost. The upper-critical field data B c2(T) under pressure collapse onto a universal curve. The absence of Pauli limiting and the comparison of B c2(T) to a polar-state function point to spin-triplet superconductivity, but an anisotropic spin-singlet state cannot be discarded completely. © 2012 American Physical Society.

Kumakura H.,Japan National Institute of Materials Science
Journal of the Physical Society of Japan | Year: 2012

MgB 2 shows no weak coupling of grains, indicating that grain alignment is not essential to obtain large current transfer from one grain to adjacent grain. This is a very big advantage because a simple process, such as powder-intube (PIT) method, can be applied for the fabrication of wires and tapes. Here, we report the recent progress of our MgB 2 tapes and wires. There are two PIT methods. One is an in situ method, in which a powder mixture of Mg and B is used as a starting material. The other is an ex situ method, in which reacted MgB 2 powder is used. Superconducting properties are much sensitive to the quality of the starting powder, the porosity of the MgB 2 core and the heattreatment conditions. Impurity addition to the mixture of starting powder is an effective method to improve J c of MgB 2 tapes and wires. Am