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研究成果の概要 (和文) : 大気圧近くで発生する熱プラズマは,1万度以上の高い温度を持っている。高温熱源である熱プラズマの利点を活かすと,ナノ粒子の高速合成が可能になる。プラズマ流は尾炎部で超急冷され,非平衡相物質が生成した。また、核生成に引き続く粒子成長プロセスが高温の熱流体中で進行するので、高結晶性で、清浄な表面をもつナノ粒子が生成した。分散性の高いプラズマ合成ナノ粒子を用いて、多機能ナノ粒子構造体への応用が期待される。, 研究成果の概要 (英文) : Synthesis of functional nano-structured powders has been developed through reactive thermal plasma processing. Nano-sized titanium oxide powders has been prepared by the oxidation of solid and liquid precursors. The plasma-synthesized TiO_2 nano-particles showed phase preferences different from those synthesized by conventional wet processes. Nano-sized particles of high crystallinity and non-equilibrium chemical composition were formed by one-step via reactive thermal plasma processing. Also, high dispersion behavior of plasma-synthesized nanopowders was recognized. The ultrasonically irradiated suspensions show aggregate sizes close to the primary particle sizes evaluated by an image analysis. Ultrasonic irradiation was shown to be a powerful way to disperse nanoparticles even in concentrated aqueous suspensions.

Magnetic alignment appears in important devices such as a compass, an electric generator or a memory disc; at present, only effects of spontaneous magnetic moments are used. Here we report that alignment occur for ordinary solid that do not contain spontaneous moment; alignment occurred by anisotropy of magnetic susceptibility Delta(sub chi). Rotational oscillation of a magnetically stable axis with respect to static field was observed for biotite, calcite, forsterite, graphite, muscovite, talc and urea at a low field of 0.11 T produced by a horseshoe magnet. Delta(sub chi) above 4 x 10(exp -8) emu/g are obtained from the period of oscillation tau = 2 pi x (I/(M x Delta(sub chi)))(exp -1/2) x B(exp -1); this was realized because restoration torque of the fiber that suspended the crystal was negligible. Sensitivity for measuring Delta(sub chi) can be improved drastically by realizing the oscillation in microgravity, where the fiber itself is deleted; oscillations were achieved for KDP (Potassium Dihydrogen Phosphate), gypsum, Rochelle salt and urea at B = 1.3 T. Higher sensitivity is necessary to obtain small Delta(sub chi) values; this can be done by increasing tau according to the above equation, and is realized by a parabolic flight or in an orbital laboratory. Characteristics of spontaneous moment have long been conceived to the public by rotational oscillation of a compass caused by terrestrial field, which led to invention of the above mentioned devices. In a same sense, rotational motions of ordinary crystals reported here may induce new types of applications in various fields that are not related to magnetism at present. Magnetically active property may be recognized for almost all the solid materials when sensitivity of Delta(sub chi) reach the level of 10(exp -11) emu/g in an parabolic flight., 資料番号: AA0063349008

The undercoolability of CoPd melts was investigated by using electromagnetic levitation technique. Undercooling limit by classical nucleation theory is utilized to analyze the results of undercooling measurements. It was found that Co81Pd19 melts was kept undercooling state below the Currie temperature of solid state of CoPd alloys. This result was different in previous results of D. Platzek et al. and T. Schenk et al. They reported that the Currie temperature of solid state of CoPd alloys affected undercooling limit of CoPd melts. To clarify the relationship between undercooling limits and magnetic properties of CoPd melts, the new apparatus facilities of electromagnetic levitator under the static magnetic fields of 1.3 T have been developed. Using this new experimental set-up, the temperature of levitated CoPd melts can be precisely measured. Thus, the mechanism of undercooling limits of CoPd melts can be clarified., 資料番号: AA0048095006

High coercive force metastable phase was obtained in a various Nd-Fe binary and Nd70Fe20Al10 ternary samples by using Ar or He gas jet flow type the new electromagnetic levitation process. The high undercooling degree of Nd-Fe binary alloys was shown around Nd50Fe50 composition. On the contrary, the matastable phase formation was increased with increasing Nd concentration. Microstructure of Nd70Fe20Al10 sample was changed remarkably increasing the cooling velocity. But magnetization and coercive force were not change in these samples. High coercive force mechanism in matastable phase was suggested ferromagnetic structure of Fe 3d electron effect on Nd 4f nucleus by XPS (X-ray Photoelectron Spectroscopy) measurements., 資料番号: AA0048095002

Containerless solidification of Nd14Fe79B7 alloys was carried out in a 25 m drop tube. The relationship among the sample size, microstructure, and magnetic properties were investigated. The resultant samples contained a large amount of a metastable phase with a chemical composition near that of the bulk alloy and a trigonal crystal structure similar to that of the Nd2Fe17 phase. The volume fraction of the metastable phase decreased as the sample diameter increased. The metastable phase was partially decomposed into very fine lamellar grains of Nd2Fe14B and some Nd-rich phase by a solid-state reaction in the sample with a diameter of 1,200 micrometer., 資料番号: AA0046917079

2005

The giant magnetostrictive materials (GMM) such as TbFe2, SmFe2 and Terfenol-D have been widely studied because of high magnetostrictions at room temperature. An improvement of the magnetostrictive properties may induce wider application fields of electric-mechanical energy conversion. In this study, magnetic properties of TbFe2 alloys solidified under microgravity (micro G) conditions obtained by drop tube systems were investigated. The magnetic characteristics of TbFe2 giant magnetostrictive alloy were found to be influenced by the solidification rate., 資料番号: AA0046917078

電磁応用機器の特性向上に繋がる基礎的知見を得ることを目的とし，電磁鋼板および鉄心内部の局所的な磁気特性の分布に着目した研究を行った。方向性電磁鋼板については，鋼板内部の局所領域の磁気特性の測定手法を開発し，磁気特性の不均一分布の原因を解明した。無方向性電磁鋼板においては，打抜き，カシメ，応力といった鉄心製造に関わる因子の影響を評価し，鉄心での磁気特性劣化の機構を明らかにした。, Doctor of Philosophy in Engineering, Doshisha University

1 序論||2 高純度Fe-(4, 5, 6) wt% Si 合金の磁気特性||3 高純度Fe-Si 合金における磁区と結晶方位・粒界との関係||4 高純度Fe-4 wt% Si 合金への炭素添加の影響||5 Fe-(4, 5, 6) wt% Si 合金の機械特性及び結晶構造||6 結論, 九州工業大学博士学位論文 学位記番号:生工博甲第257号 学位授与年月日:平成28年3月25日, 平成27年度