Well-defined SiO2-coated Fe nanoparticles with various SiO2 thickness from 1.2 to 27.8 nm have been successfully prepared by controlling the amount of tetraethyl orthosilicate and by the subsequent reduction of SiO2-coated Fe3O4 nanoparticles with CaH2. The saturated magnetization of the SiO2-coated Fe nanoparticles increased with decreasing SiO2 thickness. The saturated magnetization of the SiO2-coated Fe nanoparticles with SiO2 thickness of 2.7 nm or more have slightly decreased by 192 hr and did not change above 192 hr throughout atmospheric exposure, whereas that with SiO2 thickness of 1.2 nm steeply decreased in 24 hr and continued to decrease above 24 hr.
2019年度 論文賞
Molecular dynamics simulations were performed to study six grain boundaries of α-alumina (Al2O3) with a glassy phase of anorthite (CaAl2Si2O8) composition. We calculated excess energy, diffusion constant and ratio of excess volume with different thickness of the glassy film. It was found that excess energy for some grain boundaries exhibited a minimum. When the thickness of the glassy film was thick adequately, excess energy corresponded to the energy of alumina-glass interface and they were different for each interface. Diffusion constants depended on the thickness of the glassy film. The diffusion constant of thin film was smaller than that of thick film. Excess volume was the maximum when the thickness of the glassy film was 0.2~0.3 nm. When the atomic arrangement of the crystals didn’t fit each either, the excess volume of the grain boundary with the glassy film was smaller than that of the pure grain boundary. When the glassy film width was nm order, the atomic arrangement of the glassy phase was regular and the atomic diffusion behavior was approached that of a solid (crystalline) phase. We need to consider not only solid-liquid interface but also solid-solid (crystalline) interface for the structure of ceramics made by liquid phase sintering.
2019年度 論文賞
Solid solution strengthening effect by oxygen (O) and nitrogen (N) atoms of α-titanium (Ti) materials was quantitatively evaluated using Labusch model by consideration of the experimental data. When using Labusch model to predict solid solution strengthening improvement, an application of the isotropic strains by solute elements is generally assumed to estimate Fm value, which is the maximum interaction force between the solute atoms and dislocations. It is, however, difficult to exactly calculate Fm value for α-Ti materials with O and N solute atoms because the anisotropic strains are induced in α-Ti crystal with hcp structure by these elements. In this study, Fm value was experimentally derived from the relationship between 0.2% yield stress and solute elements (O and N atoms) content of Ti sintered materials. As a result, the strengthening improvement was proportional to c2/3/Sf (c: soluted atom content, Sf: Schmid factor), and its factor of proportionality of Ti-O and Ti-N materials was 4.17 × 103 and 3.29 × 103, respectively. According to this analysis, it was clarified that Fm value of Ti-O and Ti-N materials was 6.22 × 10−10 and 5.21 × 10−10, respectively, and then the estimated strengthening improvement by using these values was significantly agreed with the experimental results of Ti sintered materials with O and N solution atoms.
平成30年度論文賞
The influence of strain in the Nd-Fe-B was investigated by using the structural phase transition of BaTiO3 in films consisting of a Mo top layer (10 nm), Nd-Fe-B (30 nm), and a Mo bottom layer (20 nm) deposited onto BaTiO3 (001) substrates by sputtering. As a result, it was found that the magnetization along the easy axis jumps up in magnitude by 3% at around 280 K. This significant effect is certainly due to the lattice strain accompanying the structural phase transition of BaTiO3 from orthorhombic to tetragonal. First-principles calculations were applied to simulate the relationship between magnetization, magnetocrystalline anisotropy and the strain in the Nd-Fe-B main phase. It was also found that the magnetization along the easy axis increases as the lattice constant of the a-axis expands, which shows mostly good agreement with the experimental results under some assumptions.
平成30年度論文賞受賞
The WC-Co cemented carbides with the addition of Ti(C,N) base particles with different sizes were fabricated by liquid phase sintering and their microstructures were mainly investigated in detail comparing the microstructure of the alloys with VC and Cr3C2 addition. It was found that the WC grain growth was more strongly inhibited with increasing Ti(C,N) content and with decreasing Ti(C,N) particle size. The degree of inhibition by the addition of Ti(C,N) particle with about 0.1 μm size was lower than that of VC addition and was almost same as that of Cr3C2 addition. Considering the results about the relationship between WC grain size and Ti(C,N) particle size and the analysis of Co phase composition, it was seen that the mechanism of grain growth inhibition by the addition of Ti(C,N) particles was the pinning (Zener) effect by the second phase particle, which was different from the mechanism for the addition of VC and Cr3C2 reported previously. The case that one Ti(C,N) particle contacts plural WC grains was often observed, so that the pinning effect was considered to work by many Ti(C,N) particles neighboring one WC grain. The very important result that the pinning effect by Ti(C,N) addition enable to develop the new type of ultra-fine cemented carbide was obtained in this study.
平成30年度論文賞受賞
粉体の粒度と充填性
公開日: 2009/05/22 | 15 巻 2 号 p. 55-61
荒川 正文
持続型固-液共存状態を利用してSPS成形したAl/SiC複合材料の熱物性
公開日: 2011/06/23 | 58 巻 3 号 p. 160-164
水内 潔, 井上 漢龍, 上利 泰幸, 長岡 亨, 森貞 好昭, 杉岡 正美, 田中 基博, 武内 孝, 谷 淳一, 川原 正和, 巻野 勇喜雄, 井藤 幹夫
金属粉の着火・爆発危険性とその特徴
公開日: 2019/11/15 | 66 巻 11 号 p. 513-524
榎本 兵治
単一加圧焼結鉄の異常脆性
公開日: 2009/05/22 | 20 巻 2 号 p. 49-54
黒木 英憲, 徳永 洋一
硫酸銅水溶液の加熱による生成物について
公開日: 2009/12/04 | 18 巻 4 号 p. 136-144
阿部 照衛, 原 善四郎