研究者詳細 - 伊藤　孝至

論文 - 伊藤　孝至

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Effect of Acid Treatment on Removing Sodium Ions from Sodium Cobalt Oxide Thermoelectric Materials

R. Watanabe, T. Itoh, K. Kitagawa

Proc. of International Symposium on EcoTopia Science 2007 頁： CD-ROM 23P01-13 (1100) 2007年11月

記述言語：英語

NaxCo2O4 with a laminar structure is a promising thermoelectric oxide having anisotropic thermoelectric property. An excellent thermoelectric performance equivalent to the single crystal is expected to be attainable in the polycrystalline body of this material by improvement of crystal orientation. It will be effective for controlling the crystal orientation to separate CoO2 nanosheets from the polycrystalline body and to pile them up for making highly orientated layers. This study aims at preparation of the CoO2 nanosheets. First, samples of NaxCo2O4 were synthesized. The interlayer Na+ ions were removed from the CoO2 layers of the synthesized powder by an acid treatment. The interlayer distance of the synthesized and the Na+ ion removed samples was measured by XRD analysis. The removal efficiency of Na+ ions was evaluated from ICP measurement. The morphology of the samples was observed by a SEM. We found that the condition of the acid treatment greatly influences the removal efficiency of Na+ ions in the synthesized NaxCo2O4.

Polyol Process Synthesis of CoSb3 Termoelectric Nanoparticles 査読有り

K. Isogai, T. Itoh

Proc. of International Symposium on EcoTopia Science 2007 頁： CD-ROM 23P01-15 (1122) 2007年11月

記述言語：英語

The cobalt-antimony skutterdite compounds have relatively high power factor at around 380 oC, but they have relatively high thermal conductivity. Nanostructuring is expected to lower the lattice thermal conductivity by phonon scattering on the grain boundary, improving the thermoelectric performance of the materials. In this study, we aim at synthesizing CoSb3 thermoelectric nanoparticles by using polyol process for constructing the nanostructural body of the materials. The polyol process that synthesizes nanoparticles is one of liquid-phase process using polyol as a solvent. The CoSb3 nanoparticles were syn-thesized in mole ratio of Co(OOCH3)·4H2O to SbCl3 of 1:4.5 at reaction temperature of 240 oC in the sol-vent of tetra ethylene glycol. The reaction products were characterized by XRD, EDX, SEM, and TEM. Extremely small particles with about 10 nm in diameter mainly existed in the reaction products. The minimum particle size was 3-5 nm. The nanoparticles were identified as the CoSb3 compounds.

Influence of Fullerene Addition on Thermoelectric Properties of Non-filled/Filled Cobalt-Skutterudite Compounds 査読有り

K. Ishikawa, A. Okada, T. Itoh

Proc. of International Symposium on EcoTopia Science 2007 頁： CD-ROM 23P01-14 (1101) 2007年11月

記述言語：英語

The cobalt-skutterudite compounds are promising thermoelectric materials having relatively good thermoelectric properties with respect to the Seebeck coefficient and the electrical resistivity over the temperature range between 500 and 800K. The high thermal conductivity of the materials, however, prevents from achieving high thermoelectric performance. In this study, we attempted to disperse the fullerene particles uniformly into the cobalt-skutterudite compounds for decreasing the lattice thermal conductivity by phonon scattering. The influence of the fullerene addition on the thermoelectric properties was investigated with respect to both of the n-type non-filled and filled cobalt-skutterudite compounds. The n-type lanthanum-filled cobalt-skutterudite compound was synthesized via the route of mechanical alloying-pulse discharge sintering process. In both of the non-filled and the filled skutterudite samples, the thermal conductivity was decreased with the addition of fullerene. For the non-filled skutterudite, though the electrical resistivity of the samples was increased with the addition of fullerene, the thermoe-lectric performance was improved.

Consolidation and Microstructure Control of Bismuth Telluride Thermoelectric Compounds by Compressive Torsion Forming 査読有り

T. Itoh, T. Kadoi and N. Kanetake

Materials Transactions 48 巻 ( 8 ) 頁： 2056-2061 2007年8月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Bismuth antimony telluride has the best performance among the p-type thermoelectric materials used in the range of temperature between 300K and 500K. This material has a trigonal-hexagonal scalenohedral crystal structure and the cleavage parallel to the basal plane of the crystal can readily occur. Suppression of the electrical resistivity and the thermal conductivity will be effective for further
improvement of the performance of the thermoelectric elements made from this material. The compressive torsion forming is the severe plastic deformation technique, in which the loads of compression and distortion are simultaneously subjected to the materials without change in its shape. In this work, we applied this technique to the powder of bismuth antimony telluride for consolidation and improvement of the thermoelectric performance by refining the grain structure and by controlling the crystal orientation. The samples consolidated under various forming conditions were investigated with respect to density, microstructure, XRD, texture, and thermoelectric properties. It was found out that the compressive torsion forming is effective for the microstructure control, the grain structure less than
10μm can be obtained, and the thermoelectric performance is
obviously improved by the compressive torsion forming.

*Effect of Fullerene Addition on Thermoelectric Properties of n-type Skutterudite Compound 査読有り

T. Itoh, K. Ishikawa, and A. Okada

Journal of Materials Research 22 巻 ( 1 ) 頁： 249-253 2007年1月

Prediction of Packing Density of Milled Powder Based on Packing Simulation and Particle Shape Analysis 査読有り

Y. Amano, T. Itoh, H. Terao and N. Kanetake

Materials Science Forum 534-536 巻頁： 1621-1624 2007年1月

Fabrication of the Crystal-Oriented Thermoelectric Material Bi2Te3 by Slip Casting under a High Magnetic Field 査読有り

T. Kuribayashi, M. Sung, T. Itoh, K. Sassa, and S. Asai

Materials Transactions 47 巻 ( 9 ) 頁： 2387-2392 2006年9月

Prediction of Packing Density of Milled Powder Based on Packing Simulation and Particle Shape Analysis 査読有り

Y. Amano, T. Itoh, H. Terao, and N. Kanetake

Extended Abstracts 2006 World Congress on Powder Metallurgy & Particulate Materials, KPMI 頁： 1254-1255 2006年9月

Performance of Segmented Thermoelectric Elements Fabricated by Simultaneous Sintering Method 査読有り

T. Itoh, T. Muto, and K. Kitagawa

Proceedings 25th International Conference on Thermoelectric, IEEE ( CD-ROM ) 頁： PB48 2006年8月

アルミニウムの結晶粒微細化に及ぼす圧縮ねじり複合負荷の効果査読有り

金武直幸，青野圭太郎，伊藤孝至，久米裕二

軽金属 56 巻 ( 1 ) 頁： 34-38 2006年1月

Fabrication of Segmented n-type CoSb3/Bi2Te3 Thermoelectric Module and Its Performance 査読有り

T. Muto, T. Itoh, N. Kanetake and K. Kitagawa

Extended Abstracts International Symposium on EcoTopia Science 2005 頁： 587-588 2005年8月

Syntheses of Fe and La Doped CoSb3 Thermoelectric Compounds by Pulse Discharge Sintering 査読有り

T. Itoh, E. Hattori and K. Kitagawa

Extended Abstracts International Symposium on EcoTopia Science 2005 頁： 219-220 2005年8月

Fabrication of Segmented p-type AgSbTe2/Sb2Te3/Bi0.4Sb1.6Te3 Thermoelectric Module and Its Performance 査読有り

T. Muto, K. Tokuda, T. Itoh and K. Kitagawa

Proceedings 24th International Conference on Thermoelectrics, IEEE 頁： 521-524 2005年6月

Thermoelectric Properties of beta- Zn4Sb3 Synthesized by MA- SPS Method 査読有り

T. Itoh, J. Shan and K. Kitagawa

Proceedings The 2nd International Energy Conversion Engineering Conference (IECEC2004), AIAA 頁： AIAA-2004-5564 2004年8月

MA-SPS法によるCoSb3化合物の合成と熱電特性査読有り

伊藤孝至，山下剛，北川邦行

粉体および粉末冶金 51 巻 ( 6 ) 頁： 441-446 2004年6月

米国粉末冶金界が求める技術情報の変遷と軟磁性に及ぼす焼結組織の影響査読有り

鰐部吉基,草加勝司,横山誠二,伊藤孝至

粉体および粉末冶金 51 巻 ( 6 ) 頁： 458-461 2004年6月

Multi-layer coating of SiC, Al2O3 and glaze on C/C composites for oxidation resistance at high temperature 査読有り

Q. Shen, J. Shan, T. Itoh, K. Kitagawa

Journal of the Japan Society of Powder and Powder Metallurgy 51 巻 ( 4 ) 頁： 237-241 2004年4月

p型AgSbTe2-(Bi,Sb)2Te3熱電モジュールの作製とその評価査読有り

久保雅崇,伊藤孝至,徳田公平,単　佳義,　北川邦行

粉体および粉末冶金 51 巻 ( 1 ) 頁： 10-15 2004年1月

Fabrication of Layered p-type AgSbTe2-(Bi,Sb)2Te3 thermoelectric module and its performance (jointly authored) 査読有り

M. Kobo, T. Itoh, K. Tokuda, J. Shan and K. Kitagawa

Proceedings of 2003 International Conference on Thermoelectrics, International Thermoelectric Society 頁： 429-432 2003年8月

Formation of an Environmental Barrier Coating Using DC-RF Hybrid Plasma 査読有り

A. Otsuka, M. Yamamoto, T. Itoh, K. Kitagawa and S. Hirano

Journal of American Ceramic Society 86 巻 ( 7 ) 頁： 1068-1075 2003年7月

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