Papers by Author: Jun Kuwano

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Authors: Katsuya Sakamoto, Hidenobu Shiroishi, Takaaki Shirai, Shunsuke Satou, Morihiro Saito, Jun Kuwano
Abstract: The ternary oxide compositions xZrO2-(0.5–x/2)Al2O3-yP2O5(x=0.8, 0.9, 0.95, 1.0; y=1.0, 1.2, 1.4) and 0.9ZrO2-0.05In2O3-1.4P2O5, xSiO2-(0.5–x/2)Al2O3-1.4P2O5(x=0.9, 1.0) were synthesized by sol-gel methods, and their conductivities were investigated by ac-impedance spectroscopy. The conductivity increased with increasing P2O5 content and with decreasing heat-treatment temperature. The maximum conductivities reached over 10-2 Scm-1 at 150°C for 0.9ZrO2-0.05Al2O3-1.4P2O5 and at 225°C for 0.9SiO2-0.05Al2O3-1.4P2O5.
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Authors: Tomoyasu Eguchi, Soichiro Suda, Takumi Hijii, Seiji Koga, Jun Kuwano, Yasukazu Saito
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Authors: Yasuhiro Harada, Yoshitaka Ishikawa, Jun Kuwano, Yasukazu Saito
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Authors: Naohisa Mori, Yutori Tagoku, Hidenobu Shiroishi, Yoshinobu Saito, Morihiro Saito, Jun Kuwano
Abstract: Photocatalytic proton reduction and water oxidation have been studied in a tris(2,2’-bipyridyl)ruthenium complex-catalyst system. Pyrochlore-type oxides have been used as proton reduction catalysts with a sacrificial electron donor (Na2EDTA) at pH 7 and as water oxidation catalysts with a sacrificial electron acceptor (K2S2O8) at pH 3. Rate constants for the proton reduction were estimated on the basis of photochemical processes. Yb2Ru2O7-δ was found to be the most active catalyst for proton reduction and water oxidation catalyst in this system.
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Authors: Takumi Hijii, Hiroko Amasaki, Tomoyasu Eguchi, Jun Kuwano
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Authors: Masashi Hirakuri, Toyoki Okumura, Morihiro Saito, Jun Kuwano
Abstract: In order to reproduce the observed ionic conductivities and activation energies computationally, the potential parameters (PMs) were optimized for classical molecular dynamic simulations on Li ion conduction in the A-site deficient perovskite solid solution La056Li0.33TiO3 with disordered A-site ion arrangement. By the use of the optimized PMs, the conductivities and the activation energies were improved considerably from 4.1×10-3 Scm-1 to 4.4×10-2 Scm-1 at 800 K and 0.02 eV to 0.2 eV, respectively. The pair correlation functions calculated with the optimized PMs reveal that the Li-ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O2-, and that the simulated Li location is significantly related to the conductivity.
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Authors: Jun Kikuchi, Seiji Koga, Katsuyuki Kishi, Morihiro Saito, Jun Kuwano
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Authors: Toyoki Okumura, Ayumi Dodomi, Morihiro Saito, Jun Kuwano
Abstract: The locations and local environments of the Li ions in La0.56Li0.33TiO3 have been investigated by classical molecular dynamics (MD) simulations and first-principles (FP) calculations. The pair correlation functions of Li-O and Li-Ti indicate that the Li ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O2-. This is consistent well with that suggested from previous neutron diffraction and 6Li-NMR studies. The FP calculations suggest a different location of the Li ion in the vicinity of the midpoint between the centers of two adjcent bottlenecks; however it coincides with one of the locations shown by the trajectories simulated with the MD calculations.
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Authors: Shunsuke Yamashita, Tomoka Kikitsu, Yoshihiro Yamaguchi, Kiyofumi Yamagiwa, Jun Kuwano
Abstract: Highly aligned carbon nanotube arrays (HACNTAs) were synthesized on a stainless steel substrate from a methanol solution of Co(Ⅲ) acetylacetonate by the one-step liquid-phase synthesis, and effects of H2O addition on the HACNTA growth were examined. The growth rate was considerably accelerated, and the lifetime of the catalysts was prolonged by addition of a small amount of H2O. HACNTAs with over 400 m thickness were formed on the side surfaces of the substrate by resistance-heating for one hour. This suggests that the added H2O removes deposited amorphous carbons from the catalyst surfaces and consequently accelerates the growth rate.
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Authors: Itta Komiya, Keisuke Nakao, Kiyofumi Yamagiwa, Jun Kuwano
Abstract: The compositions La0.56Li0.33TiO2.95F0.05•xLiF (x=0-025) were prepared by addition of LiF to the disordered form of the well-known Li ion conductor La0.56Li0.33TiO3. Although the total conductivities improved, there was no change in the bulk conductivity with LiF addition. No reflections due to LiF were observed in their XRD patterns, and the profiles and the chemical shifts of their 19F MAS-NMR resonances were almost the same as those of LiF. The results indicate that no substitution of F takes place, and that the added LiF acts simply as a sintering assistant agent.
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