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 61, Issue 12
December
Displaying 1-10 of 10 articles from this issue
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Paper
Rapid Communication
  • Thermal Properties of cBN Particle Dispersed Al Matrix Composites Fabricated by SPS
    Kiyoshi MIZUUCHI1, Kanryu INOUE, Yasuyuki AGARI, Masami SUGIOKA, Motoh ...
    2014 Volume 61 Issue 12 Pages 549-555
    Published: December 15, 2014
    Released on J-STAGE: February 03, 2015
    DOIhttps://doi.org/10.2497/jjspm.61.549
    JOURNAL OPEN ACCESS
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    cBN-particle-dispersed-aluminum (Al) matrix composites were fabricated in solid-liquid co-existent state by Spark Plasma Sintering (SPS) process from the mixture of cBN powders, Al powders and Al-5 mass% Si powders. The microstructures and thermal conductivities of the composites fabricated were examined. These composites were all well consolidated by heating at a temperature range between 798 K and 876 K for 1.56 ks during SPS process. No reaction at the interface between the cBN particle and the Al matrix was observed by scanning electron microscopy for the composites fabricated under the sintering conditions employed in the present study. The relative packing density of the Al/cBN composite fabricated at a pressure of 300 MPa was higher than 99 % in a volume fraction range of cBN between 35 % and 50 %. Thermal conductivity of the Al/cBN composite increased with increasing the cBN content in the composite in a volume fraction range between 35 and 45 vol%. The highest thermal conductivity was obtained for Al-45 vol% cBN composite and reached 305 W/mK. The coefficients of thermal expansion of the composites were a little higher than the theoretical values estimated by the upper line of Kerner’s model, indicating the bonding between the cBN particle and the Al matrix in the composite is weak a little.
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Paper
Special Issue: Functional Materials Design in Highly-Ordered Assembly Systems
Summarization
Review
  • Influence of Loading Condition on Fabrication of Transparent MgAl2O4 Spinel Ceramics by Spark-Plasma-Sintering (SPS) Technique
    Koji MORITA, Byung-Nam KIM, Hidehiro YOSHIDA, Keijiro HIRAGA, Yoshio S ...
    2014 Volume 61 Issue 12 Pages 565-574
    Published: December 15, 2014
    Released on J-STAGE: February 03, 2015
    DOIhttps://doi.org/10.2497/jjspm.61.565
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    Loading schedule during spark-plasma-sintering (SPS) processing strongly affected the densification and the optical transmission of MgAl2O4 spinel ceramics. By loading at room temperature prior to heating, high density transparent spinel ceramics were attained only at slow heating rates of ≤10 ˚C/min. By loading at high temperatures, however, spinel ceramics attained reasonable high density and resultant optical transmission even at a high heating rate of 100 ˚C/min though the transmission is lower than those attained by the slow heating SPS processing. The loading dependent densification can be ascribed to closed pore formation mechanisms. This suggests that during the SPS processing, the load controlling is one of the important key factors as well as the heating rate and sintering temperature. In order to fully utilize the high heating rate, that is the primary advantage of the SPS processing, the loading schedule should be optimized on the bases of the densification mechanisms. Depending on the loading schedule, discoloration of the SPSed spinel ceramics also changed and was ascribed mainly to carbon contamination. The optical transmission of the SPSed spinel ceramics was restrained by the carbon contamination, and hence, lowered than the highest value reported by the HIP technique.
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Paper
  • Sintering Condition and Microstructure of Translucent Silicon Nitride Ceramics
    Junichi HOJO, Wenwu YANG, Miki INADA, Yumi TANAKA, Naoya ENOMOTO
    2014 Volume 61 Issue 12 Pages 575-581
    Published: December 15, 2014
    Released on J-STAGE: February 03, 2015
    DOIhttps://doi.org/10.2497/jjspm.61.575
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    Translucent Si3N4 ceramics are expected to use for a special optical application in high temperature and corrosive environment owing to its high mechanical strength and thermal and chemical stability. To achieve the translucency of Si3N4 ceramics, fine-grained microstructure with an appropriate sintering aid is important to reduce light scattering. The Si3N4 ceramics were fabricated by spark-plasma sintering (SPS) with AlN – MgO additive. Fine α – Si3N4 powder with high purity was useful to obtain translucent Si3N4 sintered body. When the additive content was large, α – SiAlON formed, whereas β – Si3N4 formed at a small additive content, revealing the high translucency of both phases in visible light region. The AlN/MgO ratio should be on the SiAlON forming line (AlN/MgO = 3/1) in Si3N4 – AlN – MgO phase diagram. The short-time sintering at high temperature (1850 ˚C, 5 min) by SPS was effective to obtain the dense and fine-grained microstructure, and the transmittance of 22～28 % at the wavelength of 900 nm was achieved under the optimal conditions.
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  • Low-Tepmerature Synthesis Process of Lanthanum Germanate Oxyapatite by Citrate Combustion Method
    Yukihito IGARASHI, Shouta KITAJIMA, Kiyoshi KOBAYASHI, Tohru HIGUCHI, ...
    2014 Volume 61 Issue 12 Pages 582-586
    Published: December 15, 2014
    Released on J-STAGE: February 03, 2015
    DOIhttps://doi.org/10.2497/jjspm.61.582
    JOURNAL OPEN ACCESS
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    New synthesis route of the lanthanum germanate oxyapatite was successfully developed by a citrate combustion method from a homogeneous aqueous solution. The homogeneous solution can be prepared by dissolving lanthanum nitrate, germanium dioxide, dilute ammonia, and dilute nitric acid, and citric acid in water. From X-ray diffraction and thermogravimetric-thermal differential analyses, the lanthanum germanate oxyapatite was formed about 1003 K by a precursor prepared from the homogeneous solution. This oxyapatite-synthesis temperature is about 370 K lower than the temperature by conventional solid-state reaction and coprecipitation methods. Furthermore, control of the pH in the homogeneous aqueous solution was found to be important in order to prohibit the impurity formation.
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