Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 56, Issue 2
February
Displaying 1-7 of 7 articles from this issue
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  • Spark Sinterability of WC-Ni(-P) Powders and Wear Characteristics of their Sintered Compacts
    Kazuhiro Matsugi, Hirotoshi Abo, Yong Bum Choi, Gen Sasaki, Hideaki Ku ...
    2009 Volume 56 Issue 2 Pages 51-60
    Published: 2009
    Released on J-STAGE: March 13, 2009
    DOIhttps://doi.org/10.2497/jjspm.56.51
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    The spark sintering technique was utilized to fabricate WC-16 mass%(Ni-P) compacts with different P contents using two starting powders, Ni plated WC particles by elctroless Ni plating solutions with different P contents and their elementally blended ones. The sintering temperature decreased as P content in Ni binders increased, and all compacts had theoretical densities (13.6-13.9 Mg/m3) under the optimum sintering conditions depending on binder-compositions. The sintered compacts consisted of WC, Ni and Ni3P phases. Higher P containing alloy fabricated at lower temperature (1150 K), showed theoretical density, compared with that (1273 K) for lower P containing ones. Both uniform deformation of Ni+P binders and a large amount of Ni3P with low melting point, resulted in excellent sinterability. It was found that noticeable grain growth of WC particles during the spark sintering was not observed and homogeneously sintered structure was obtained, due to pressure application at lower temperature and uniformly Ni plating on WC particles. The compacts produced from the electroless Ni plated WC particles showed higher and no-scatter values on hardness, compared with ones produced by elementally powder blending. The dynamic coefficient of friction showed the same value at initial state, but a little higher value at steady state in higher P containing alloys. Wear loss of alloys increased as Ni3P contents increased in binder phase, because in addition to wear of WC particles, separation of WC particles was also caused from alloy-structure by failure of binder phases consisting of Ni and Ni3P due to their brittleness under the wear conditions.
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  • Thermal Effusivity/Conductivity of Sintered Alumina at Micrometer-scale
    Ikuko Yamada, Shoichi Kume, Koji Watari
    2009 Volume 56 Issue 2 Pages 61-64
    Published: 2009
    Released on J-STAGE: March 13, 2009
    DOIhttps://doi.org/10.2497/jjspm.56.61
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    Thermal properties of sintered alumina at the micrometer-scale were quantitatively measured with a thermal microscope using thermo-reflectance and periodic heating techniques. The average value of thermal conductivity of 28.9 W·m−1K−1 was obtained from a 50 μm×50 μm area, and the average value was also in good agreement with that measured by a laser flash technique.
    The anomalous data were found by the measurement with the thermal microscope in some regions, which were correlated with the surface pores or inside defects of the specimen. The portions with very low thermal conductivities, 5 to 10 W·m−1K−1, were found to correspond to around the pore presents.
    In addition, unshared 10 square areas of 10 μm×10 μm were randomly selected and were scanned by an area scanning mode in order to calculate the average conductivities at the areas. The conductivity values were in the range of 24.9 to 37.7 W·m−1K−1 and the variation in the conductivities was estimated about 13 W·m−1K−1. The area with maximum thermal conductivity was consisted of large grains and the value was considered to be almost equal to that of one grain. On the other hand, the area including several small grains indicated the minimum conductivity. The decrease of the conductivity was due to the influence of the grain boundaries.
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  • Influence of La Substitute on Sintering Behavior, Electronic Properties and Thermal Expansion of Sr1-1.5xLaxTiO3
    Hiroshi Tsukuda, Shigeru Okuma, Kazuo Tomida
    2009 Volume 56 Issue 2 Pages 65-70
    Published: 2009
    Released on J-STAGE: March 13, 2009
    DOIhttps://doi.org/10.2497/jjspm.56.65
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    SrTiO3 is one of candidates for interconnect materials of solid oxide fuel cell (SOFC). Sintering behavior, electronic properties and thermal expansion character of A site deficient Sr1-1.5xLaxTiO3 (0≤x≤0.6) were evaluated. Substituted La in the Sr1-1.5xLaxTiO3 played an important role for the grain growth and densification, which were indicated from the microstructure observation and the iso-thermal shrinkage. The conductivity of Sr0.55La0.3TiO3 was 0.17 S/cm at 1173 K in the air and the temperature dependence of conductivity was metal like manner. However, this value was not enough conductivity as the interconnect material of SOFC. In order to apply to SOFC, the conductivity of this material has to be improved. Single phase samples were observed by the powder X-ray diffraction for Sr1-1.5xLaxTiO3 (0≤x≤0.4)which did not have phase transition between room temperature and SOFC operation temperature. The thermal expansion coefficients of these materials were similar to those of the other materials of SOFC. They will be the useful materials for interconnect of SOFC when the conductivity was improved.
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  • Study on All Solid Lithium Polymer Batteries with the LiFePO4/C Cathode
    Kazuma Hanai, Ryuji Uchiyama, Nobuyuki Imanishi, Atsushi Hirano, Yasuo ...
    2009 Volume 56 Issue 2 Pages 71-75
    Published: 2009
    Released on J-STAGE: March 13, 2009
    DOIhttps://doi.org/10.2497/jjspm.56.71
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    The interfacial resistance between the PEO-Li(CF3SO2)2N electrolyte and the LixFePO4 cathode was examined as a function of the content of Li(CF3SO2)2N in PEO and x in LixFePO4. The interfacial resistances were attributed to two parts; one is the interfacial layer produced between the polymer electrolyte and the cathode, and the other is the charge transfer resistance between the interfacial layer and the electrode. The charge transfer resistance increased with increasing x. No significant dependence of the activation energy for the charge transfer resistance on the salt content in PEO and the molecular weight of PEO were observed.
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