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Toyoda M.,Oita University | Ohuchi Y.,Oita University | Wada T.,High Performance Plastics Company | Kinumoto T.,Oita University | Tsumura T.,Oita University
Journal of Physics and Chemistry of Solids | Year: 2012

The formation of new acceptor-type graphite intercalation compounds (GICs) by traditional methods require a high oxidation potential, rendering the methods unsuitable for a number of compounds. Thus, we have synthesized novel acceptor-type GICs through an electrochemical method. Sodium dimethyldithiocarbamate (NaMDC) and sodium diethyldithiocarbamate (NaEDC) were selected as electrolytes for electrochemical processing in this study. Constant current electrolysis was applied for the synthesis of these acceptor-GICs. An exfoliated graphite sheet was used as the working electrode and a platinum plate in a three electrode cell was used as the counter electrode. Compounds synthesized in this way were identified using X-ray diffraction, enabling crystal structure determination. It appears that the intercalated graphite sheets exhibit a classical stacking in two layers such that there are regularly alternating electropositive and electronegative planes along the c-axis. It is shown that MDC and EDC-GICs were successfully synthesized through this electrochemical method. © 2012 ElsevierLtd.Allrightsreserved.

Wada T.,Oita University | Wada T.,High Performance Plastics Company | Yasutake T.,Oita University | Nakasuga A.,High Performance Plastics Company | And 3 more authors.
Journal of Nanomaterials | Year: 2014

Layered graphene was prepared via the hydroxylation of potassium-graphite intercalation compound (KC8) produced from exfoliated graphite flake powder. When a small amount of water was dropped onto the KC8 in an oxygen-free atmosphere, the stage structure of the intercalation compounds was broken, and agglomerated graphene was obtained. Sonication of this agglomerated graphene in buffered water containing sodium dodecyl sulfate followed by rinsing with hot water yielded gray samples. Using scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy, the gray samples were determined to be composed of a few layers of graphene with an area of 20-100 μm2 and thickness of 1.7 nm. They were thinner than those obtained when starting with natural graphite. © 2014 Takuya Wada et al.

Kyono A.,University of Tsukuba | Hayakawa A.,High Performance Plastics Company | Horiki M.,High Performance Plastics Company
Physics and Chemistry of Minerals | Year: 2015

Composition dependence of the crystal structure between stibnite and antimonselite is investigated by using the single-crystal X-ray diffraction and the ab initio calculation methods to clarify the Se substitution effect on the crystal structure, especially focusing on the stereochemical behavior of Sb 5s2 lone-pair electrons. The single-crystal X-ray diffraction measurements indicate no phase change throughout the solid solution range. The lattice parameters of a, b, c and unit cell volume are linearly increased as Se content increases. The lattice parameter variations normalized show an anisotropic expansion that the largest expansion is observed along the a-axis, followed by the c- and b-axes. The large Se atom exhibits a strong site preference for the X(1) and X(3) sites, while the small S atom prefers to occupy the X(2) site. The intra-ribbon Sb(1)–X and Sb(2)–X distances (X = S, Se) are continuously increased with the Se content. The three Sb(1)–X bond distances in the trigonal pyramids are changed within the similar range between 2.52 and 2.68 Å, while the five Sb(2)–X distances in the tetragonal pyramids vary from 2.45 to 2.59 Å, from 2.68 to 2.80 Å, and from 2.86 to 3.00 Å, respectively. With increasing Se content in the solid solution, the inter-ribbon distances where the Sb 5s2 LPEs are located monotonously increase as well. However, the variations between the ribbons are considerably smaller than those of intra-ribbon distances. The polyhedral volumes of the Sb(1)X7 and Sb(2)X7 in which the Sb 5s2 LPEs are accommodated constantly increase from 35.9 to 40.0 Å3 and from 34.1 to 38.8 Å3, respectively, and these eccentricity parameters decrease from 0.66 to 0.62 and from 0.57 to 0.55. As a result of ab initio calculation, the Sb 5s orbitals on the Sb(1) atoms remain almost unchanged throughout the solid solution. On the other hand, those on the Sb(2) atoms become smaller with the incorporation of Se. The result gives a more reasonable interpretation that the stereochemistry of Sb 5s2 LPEs and the stereochemistry of the coordination polyhedra around the Sb atoms are affected by the Se substitution in the structure. © 2015, Springer-Verlag Berlin Heidelberg.

Sun R.-D.,High Performance Plastics Company | Tsuji T.,The University of Shimane
Applied Surface Science | Year: 2015

In this paper, we report on the synthesis of antimony sulfide (Sb2S3) semiconductor nanoparticles by pulsed laser ablation in liquid without using any surfactants or capping agents. Different results were obtained in water and organic solvents. In the case of water, Sb2S3 nanoparticles with chemical compositions of stoichiometry were successfully prepared when laser irradiation was performed under the condition with the dissolved oxygen removed by argon gas bubbling. It was shown that thus-obtained Sb2S3 nanoparticles exhibit features of not only low-temperature crystallization but also low-temperature melting at a temperature as low as 200 °C. Nanoparticle-coated Sb2S3 thin films were found to show good visible light absorption and satisfying semiconductor properties (i.e., carrier mobility and density), which are essential for photovoltaic application. On the other hand, in the case of organic solvents (e.g., acetone, ethanol), such unexpected byproducts as CS2, CO and CH4 were detected from the reaction system by GC-MS analysis, which suggests that both Sb2S3 and organic solvents were partially decomposed during laser irradiation. The possible mechanism will be discussed. © 2015 Elsevier B.V. All rights reserved.

Wakiya T.,Kumamoto University | Wakiya T.,High Performance Plastics Company | Morisaki T.,Kumamoto University | Ishibashi N.,Kumamoto University | And 6 more authors.
Materials Letters | Year: 2011

This paper introduces a stepwise formation method for micro-sized, multilayered core-shell particles comprising an inorganic core, organic inner shell, and inorganic outer shell. A silica core was coated with a polystyrene seed layer, followed by surface seed polymerization with styrene, to afford the inner shell. These particles were then coated with a silica outer shell by a surface sol-gel reaction with tetraethoxysilane. The versatility of this combined surface seed polymerization and sol-gel method is emphasized by the precise control achieved over particle diameter as well as shell thickness and count. Moreover, the organic inner shell can be readily eliminated to afford a single-core-containing micro-capsular structure. © 2011 Elsevier B.V. All rights reserved.

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