Time filter

Source Type

Rafi-Ud-Din,State Key Laboratory for Advanced Metals and Materials | Rafi-Ud-Din,Pakistan Institute of Nuclear Science and Technology | Xuanhui Q.,State Key Laboratory for Advanced Metals and Materials | Ping L.,State Key Laboratory for Advanced Metals and Materials | And 6 more authors.
Journal of Physical Chemistry C | Year: 2012

Sodium alanate (NaAlH 4) is a promising complex metal hydride due to its reasonable hydrogen storage capacity (7.4 wt %). However, the pristine NaAlH 4 suffers from the inherent limitations of unfavorable thermodynamics (high desorption temperature), slow kinetics, and poor reversibility. In the present work, the efficacy of Nb 2O 5, TiO 2, and Cr 2O 3 nanoparticles in ameliorating hydrogen sorption properties of NaAlH 4 was evaluated. The use of Nb 2O 5 and TiO 2 displayed superior catalytic effects in terms of enhancing dehydriding/rehydriding kinetics and reducing the dehydrogenation temperature of NaAlH 4. Isothermal volumetric measurements at 150 °C revealed that kinetics of hydrogen desorption with Nb 2O 5 and TiO 2 were almost 11-12 times that of pristine NaAlH 4. The apparent activation energy as well as enthalpy of dehydrogenation were considerably lowered by addition of Nb 2O 5 and TiO 2 nanopowders. Moreover, the pronounced enhancement on hydrogen capacity arising upon adding Nb 2O 5 and TiO 2 was observed to persist well in rehydrogenation/ dehydrogenation cycles. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and FESEM-EDS analyses demonstrated that reduction of Nb 2O 5 and TiO 2 during the first desorption was coupled to the migration of reduced titanium oxide species from surface to bulk during cycling. It was suggested that these finely dispersed oxygen-deficient niobium and titanium species might contribute to kinetic improvement by facilitating the hydrogen diffusion during both dehydrogenation/rehydrogenation. © 2012 American Chemical Society.


Rafi-Ud-Din,State Key Laboratory for Advanced Metals and Materials | Rafi-Ud-Din,Pakistan Institute of Nuclear Science and Technology | Xuanhui Q.,State Key Laboratory for Advanced Metals and Materials | Ping L.,State Key Laboratory for Advanced Metals and Materials | And 5 more authors.
RSC Advances | Year: 2012

Nowadays, the technological utilization of reactive hydride composites (RHC) as promising hydrogen storage materials is hampered by their reaction kinetics. In the present work, effects of reactant stoichiometry on ensuing hydrogen sorption properties and pathway of the MgH 2-NaAlH 4 (mole ratios 1:2, 1:1 and 2:1) system, both undoped and doped with Nb 2O 5 nanoparticles, were investigated. It was found that the as-prepared reactant stoichiometry of MgH 2/NaAlH 4 system had a profound impact on its dehydrogenation kinetics and reaction mechanism. Variable temperature dehydrogenation data revealed that undoped binary composites possessed enhanced hydrogen desorption properties compared to that of pristine NaAlH 4 and MgH 2. The use of Nb 2O 5 displayed superior catalytic effects in terms of enhancing dehydriding/rehydriding kinetics and reducing the dehydrogenation temperature of MgH 2-NaAlH 4 system. Isothermal volumetric measurements at 300°C revealed that enhancements arising upon adding Nb 2O 5 were almost double that of undoped MgH 2-NaAlH 4 composites. The apparent activation energies for NaAlH 4, Na 3AlH 6, MgH 2, and NaH relevant decompositions in doped composite were found to be much lower than that for the undoped one. Moreover, Nb 2O 5 doping also markedly enhanced the reversible capacity of MgH 2-NaAlH 4 composites under moderate conditions, persisting well during three de/rehydrogenation cycles. XRD, XPS, and FESEM-EDS analyses demonstrated that reduction of Nb 2O 5 during first desorption was coupled to the migration of reduced niobium oxide species from the bulk to the surface of the material. It was suggested that these finely dispersed oxygen-deficient niobium species might contribute to kinetic improvement by serving as the active sites to facilitate hydrogen diffusion through the diffusion barriers both during dehydrogenation and rehydrogenation. © 2012 The Royal Society of Chemistry.


Rafi-Ud-Din,State Key Laboratory for Advanced Metals and Materials | Xuanhui Q.,State Key Laboratory for Advanced Metals and Materials | Ping L.,State Key Laboratory for Advanced Metals and Materials | Zhang L.,State Key Laboratory for Advanced Metals and Materials | Ahmad M.,Tsinghua University
Journal of Physical Chemistry C | Year: 2011

The use of LiAlH4 as a promising hydrogen storage material is limited by its high desorption temperature, slow kinetics, and poor reversibility. In the present work, the influence of the catalytic activity of Nb2O5 and Cr2O3 nanoparticles on the hydrogen sorption properties of LiAlH4 was investigated. It was shown that Nb2O5 was superior to Cr2O 3 in improving the dehydriding property. For instance, samples of LiAlH4 doped with 1 and 2 mol % Nb2O5 showed improvement in the onset desorption temperature with little decrease in hydrogen capacity, where approximately 6.9 wt % was released by 193 °C. Isothermal desorption results at 120 °C revealed that enhancements arising upon adding Nb2O5 were almost 6-7 times that of pristine LiAlH 4. Moreover, LiAlH4-2 mol % Nb2O5 displayed a substantially reduced activation energy and enthalpy change for LiAlH4 dehydrogenation. The results of the first rehydrogenation indicated that the amount of restored hydrogen for Nb2O 5-doped samples was lower than that of samples with Cr 2O3. XRD, FESEM-EDS, and XPS examinations suggested that finely dispersed Nb species with a range of valence states might contribute to the kinetic improvement by serving as active sites for nucleation and growth of dehydrogenated product. © 2011 American Chemical Society.


Lin P.,State Key Laboratory for Advanced Metals and Materials | Yan X.,State Key Laboratory for Advanced Metals and Materials | Zhang Z.,State Key Laboratory for Advanced Metals and Materials | Shen Y.,State Key Laboratory for Advanced Metals and Materials | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Developing tailored micro/nanostructure interfaces is an effective way to make novel optoelectronic devices or enhance their performances. Here we report the fabrication of a PEDOT:PSS/ZnO micro/nanowire-based self-powered UV photosensor. The generation of photocurrent at zero bias is attributed to the separation of photogenerated electron-hole pairs within the built-in electric field at the PEDOT:PSS/ZnO interface upon UV light illumination. Furthermore, the piezotronic effect on the UV photoresponsivity under different strains is investigated, which is due to the modification of energy band diagram at the p-n heterojunction by strain-induced piezoelectric polarization. This study demonstrates a prospective approach to engineering the performance of a photodetector through straining and may offer theoretical supporting in future optoelectronic device fabrication and modification. © 2013 American Chemical Society.


Rafi-Ud-Din,State Key Laboratory for Advanced Metals and Materials | Zhang L.,State Key Laboratory for Advanced Metals and Materials | Ping L.,State Key Laboratory for Advanced Metals and Materials | Xuanhui Q.,State Key Laboratory for Advanced Metals and Materials
Journal of Alloys and Compounds | Year: 2010

The catalytic effect of TiC nanopowder addition in varying proportions on the hydrogen storage properties of LiAlH4 has been investigated by pressure-composition-temperature (PCT) experiments, thermogravimetry (TG), and differential scanning calorimetry (DSC). The results indicate that doped samples are able to dehydrogenate at much lower temperatures; for example, the onset of dehydrogenation is 85 °C for LiAlH4-2 mol% TiC, and the majority of hydrogen (∼6.9 wt.%) can be released by 188 °C. About 5 out of 6.9 wt.% of H2 can be released in the range of 85-138 °C (heating rate 4 °C min-1). Isothermal desorption results at 115 °C reveal that doped alanate exhibits dehydriding rate 7-8 times faster than that of pure LiAlH4. DSC measurements indicate that enthalpies of decomposition in LiAlH4 decrease significantly with doping. From Kissinger analysis, the apparent activation energies are estimated to be 59 kJ/mol, 70 kJ/mol and 99 kJ/mol for the decompositions of LiAlH4, Li3AlH6 and LiH, respectively. The results of first rehydrogenation indicate that 5 mol% dopant exhibits the maximum absorption of about 1.9 wt.%. XRD, FESEM, EDS, FTIR, and XPS analyses are utilized to put forward a possible catalytic mechanism of nano-sized TiC in ameliorating the dehydriding/rehydriding characteristics of doped LiAlH4. © 2010 Elsevier B.V. All rights reserved.


Zhao J.,University of Science and Technology Beijing | Yan X.,University of Science and Technology Beijing | Yang Y.,University of Science and Technology Beijing | Huang Y.,University of Science and Technology Beijing | And 2 more authors.
Materials Letters | Year: 2010

In-doped ZnO nanostructures with four different morphologies, which are nanotetrapods, nanocombs, nanowires, and nanodisks, have been synthesized on silicon substrates by a simple thermal evaporation method. The XRD patterns show the In-doped ZnO nanostructures are all with the hexagonal wurtzite structure, and a slight difference in lattice parameters had been detected among the samples with various morphologies. The Raman spectra demonstrate that the vibrational mode of 2LA, which is very weak in undoped ZnO, was strongly enhanced with indium ion doping into ZnO structures. The photoluminescence (PL) measurements indicate that the nanodisks have a relative strong ultraviolet (UV) emission than other three kinds of samples. © 2009 Elsevier B.V. All rights reserved.


Lu L.,State Key Laboratory for Advanced Metals and Materials | Lu L.,University of Science and Technology Beijing | Zhang W.,State Key Laboratory for Advanced Metals and Materials | Wang D.,State Key Laboratory for Advanced Metals and Materials | And 3 more authors.
Materials Letters | Year: 2010

Monodisperse Fe@Ag core-shell nanoparticles with relatively uniform Fe cores and Ag shells have been successfully fabricated by a seed mediated method in a two-step reducing process, and then characterized by electron microscopy techniques (HRTEM, EDX), X-ray diffraction (XRD), UV-vis spectroscopy and magnetometry. The results demonstrate unique optical and magnetic properties for Fe@Ag core-shell nanoparticles. The surface plasmon resonance of Fe@Ag core-shell nanoparticles is red shifted as compared with that of pure colloidal nano-silver, while the plasmon band of Fe@Ag core-shell nanoparticles with thinner Ag shells is shifted to a longer wavelength. Fe@Ag core-shell nanoparticles have a narrow plasmon band and therefore sensitive plasmonic properties. The magnetism of Fe@Ag nanoparticles can be tuned from superparamagnetic to ferromagnetic by modifying the proportion between Fe and Ag contents. The multifunctional Fe@Ag core-shell nanoparticles have potential in optoelectronic, spintronic, and biomedicine applications. © 2011 Elsevier Ltd. All rights reserved.


Shi J.X.,State Key Laboratory for Advanced Metals And Materials | Zhu J.,State Key Laboratory for Advanced Metals And Materials
Materials Science Forum | Year: 2015

FeGa/PZT/FeGa magnetoelectric device was prepared and the ME effect examined. FeGa alloys was made by different processing method. The results showed that the domains and texturing of FeGa had a great impact on both magnetic and ME performance. The permeability and d33 (the differential of magnetostrictive coefficient) of FeGa differed with processing. It was found that FeGa rolled sheets had good toughness, d33 could reach 2.7 ppm/Oe, and magnetic permeability reached 180. H/m. The device made of FeGa rolled sheets also had a large output (18. V/cm Oe) and low bias field (~ 96 Oe). © (2015) Trans Tech Publications, Switzerland.


Wang W.,State Key Laboratory for Advanced Metals and Materials | Qi J.,State Key Laboratory for Advanced Metals and Materials | Qin Z.,State Key Laboratory for Advanced Metals and Materials | Wang Q.,State Key Laboratory for Advanced Metals and Materials | And 3 more authors.
Journal of Physical Chemistry C | Year: 2012

The transport properties tuned by gate electron-beam irradiation was investigated for ohmic- and Schotty-contact-type semiconductor optoelectronic devices based on a single zinc oxide (ZnO) nanotetrapod. Measurements of the I-V characteristics and time-dependent current were conducted. The results indicate that, for both ohmic and Schottky contact devices, the electrical transport properties can be readily tuned by electron-beam irradiation at the gate leg of the tetrapod, with favorable repeatability and reversibility. The response for the Schottky-contact-type device was obviously greater than that for the ohmic-contact-type device, and the closer the irradiated position approached the crystal nucleus, the larger the current response became. A probable mechanism is proposed and discussed. The ZnO nanotetrapod could potentially be used as a detector in irradiation environments. © 2012 American Chemical Society.


Hu W.,State Key Laboratory for Advanced Metals and Materials | Zhao H.,State Key Laboratory for Advanced Metals and Materials | Song L.,State Key Laboratory for Advanced Metals and Materials | Yang Z.,State Key Laboratory for Advanced Metals and Materials | And 4 more authors.
Advanced Materials | Year: 2010

Figure Presented A chiral nematic liquid crystal/chiral ionic liquid composite with unique electro-optical characteristics is reported. The composite can be switched electrically between three different light states: transparent, scattering, and mirror reflecting (see images). Moreover, the reflection bandwidth can be controlled accurately and reversibly by adjusting the intensity of the electric field applied. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA,.

Loading State Key Laboratory for Advanced Metals and Materials collaborators
Loading State Key Laboratory for Advanced Metals and Materials collaborators