粉体および粉末冶金

超硬合金の特性改良に関する基礎研究

林宏爾

1984 年 31 巻 2 号 p. 39-44
発行日: 1984/02/25
公開日: 2009/05/22

DOIhttps://doi.org/10.2497/jjspm.31.39

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WC-PTFE系ガス拡散電極の構造と水素酸化特性

北條純一, 中原勝正, 松本昌士, 加藤昭夫

1984 年 31 巻 2 号 p. 45-50
発行日: 1984/02/25
公開日: 2009/05/22

DOIhttps://doi.org/10.2497/jjspm.31.45

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Porous gas-diffusion electrodes containing WC catalyst (particle size: 0.07 or 1.2μ) were prepared by the sintering of WC-PTFE powder mixture, and their hydrogen oxidation activity was investigated at the potential below +300 mV(vs. NHE) in 1N-H₂SO₄ aqueous solution under latm-H2 atmosphere at 25°C with emphasis on the effect of the electrode structure. It was confirmed that there is the most appropriate content of PTFE. It was found that hydrogen oxidation is governed by the electrical conductivity of electrode, i.e., the current-collecting ability. The increase in molding pressure of electrode film accelerated the hydrogen oxidation, which may be due to the coupling of the realization of a moderate hydrophobic action by PTFE and the increase in the electrical conductivity of electrode.

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Ti(C,N)-Mo焼結体の性質

鈴木寿, 松原秀彰

1984 年 31 巻 2 号 p. 51-55
発行日: 1984/02/25
公開日: 2009/12/04

DOIhttps://doi.org/10.2497/jjspm.31.51

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The microstructures, mechanical properties at room temperature of TiC_0.7N_0.3- and TiC_0.5N_0.5-(5-40)vol%Mo alloys vacuum-sintered at 1973K were mainly studied.
It was found that microstructures of TiC_0.7N_0.3- and TiC_0.5N_0.5-Mo alloys consisted of carbonitride and Mo phases, when Mo content exceeded about 20 and 10 vol%, respectively, and the structure became finer with increasing nitrogen and Mo contents in the alloys. In the alloys sintered in nitrogen, Mo₂C phase was apt to form and the amount depended on nitrogen pressures as well as the nitrogen content of alloys. The transverse-rupture strength and hardness of vacuum-sintered alloys were higher in the alloy with lower nitrogen content, and the former increased and the latter decreased with increasing Mo content, respectively.

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WC-Cr₃C₂-15%Co超硬合金の組織と機械的性質

鈴木寿, 徳本啓

1984 年 31 巻 2 号 p. 56-59
発行日: 1984/02/25
公開日: 2009/12/04

DOIhttps://doi.org/10.2497/jjspm.31.56

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Some properties of WC-15%Co alloy were studied as a function of additional amounts of Cr₃C₂, and carbon contents of the alloy.
It was found that solid solubility limits of Cr in binder were about 4 and 11% in high and low carbon alloys, respectively. When the additional amount of Cr₃C₂ was excess beyond the solubility limit of Cr, M₇C₃ type carbides which crystallized were observed in the structure. Total amounts of Co and W dissolved in M₇C₃ increased in high carbon alloy, and the amount of M₇C₃ was in the same way under a fixed amount of Cr₃C₂. The transverse-rupture strength of the alloy was not almost affected by Cr₃C₂ addition, within the additional amount up to the value nearly corresponding to the solubility limit of Cr in binder. The solubility limit of Cr increased by rapid cooling the specimen after sintering.

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High Oxygen Pressure Synthesis and Magnetic and Electrical Properties of Li_xM_1-xCo₂O₄(M=Co, Zn)

Masao Ohashi, Masahiko Shimada, Mitsue Koizumi

1984 年 31 巻 2 号 p. 60-66
発行日: 1984/02/25
公開日: 2009/05/22

DOIhttps://doi.org/10.2497/jjspm.31.60

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The cubic spinel type oxides, Li_xM_1-xCo₂O₄ (M=Co, Zn), were synthesized under high oxygen pressures. From the result of crystallographic and magnetic properties, the cation distributions of the present systems were determined to be (Li⁺_x Co²⁺_1-x) [Co¹⁺_2-x Co⁴⁺_x](0 ?? x ?? 0.4)and (Li⁺ _0.22 Zn²⁺ _0.66 Co²⁺_0.12)[Co¹⁺ _1.78 Co⁴⁺ _0.22]O₄. Electrical resistivity data indicate that the electron transport in these systems occurs owing to a hopping mechanism between Co⁺¹ and Co⁴⁺ ions located at octahedral site.

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RMn₂Si₂(R=Y,Nd,Gd)とYNi₂Si₂の合成と磁性

木戸博康, 星川武, 島田昌彦, 小泉光恵

1984 年 31 巻 2 号 p. 67-69
発行日: 1984/02/25
公開日: 2009/05/22

DOIhttps://doi.org/10.2497/jjspm.31.67

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A series of the RMn₂Si₂ (R=Y, Nd and Gd) were prepared by heating the mixed powder with the stoichiometric composition in an evacuated silica tube, and YNi₂Si₂ was synthesized under high temperature and pressure conditions. The crystal structure of these compounds was closely identified with the bodycentered tetragonal ThCr₂Si₂ type structure. Results of magnetic measurements showed that all RMn₂Si₂ (R=Y, Nd and Gd) compounds were antiferromagnetic with T_N=514K for YMn₂Si₂, 386K for NdMn₂Si₂ and 477K for GdMn₂Si₂. YNi₂Si₂ was Pauli-paramagnetic indicating that the 3d shells of Ni atoms were fully occupied by the electrons transferred from Si atoms.

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