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 8
August
Displaying 1-9 of 9 articles from this issue
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  • Preparation of LiFePO4 Cathode with Use of Carbon Wool as Current Collector
    Chihiro TOMONOBU, Yoshihiro OKA, Tatsuya NAKAMURA
    2014 Volume 61 Issue 8 Pages 392-396
    Published: August 15, 2014
    Released on J-STAGE: November 19, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.392
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    The composite cathodes were prepared using carbon wool as a current collector, where carbon-coated LiFePO4 fine particles and acetylene black particles were applied as active material and conducting additive, respectively. The composite electrodes were thick film with sufficiently high active material loading. From the electrochemical redox test, they had almost the same energy density at low current density as the ordinary electrode on Al current collector. Simultaneously, the composite electrodes exhibited larger current density as compared with that of the ordinary electrode. According to the results, it is possible to fabricate the composite electrodes suitable to the battery application combining high-energy and high-power performance.
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  • Effect of Microstructure on the Mechanical Properties of Magnesium Composites Containing Dispersed Alumina Particles by MM/SPS Process
    Hiroshi FUJIWARA, Suguru HAMANAKA, Shigehiro KAWAMORI, Hiroyuki MIYAM ...
    2014 Volume 61 Issue 8 Pages 397-402
    Published: August 15, 2014
    Released on J-STAGE: November 19, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.397
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    Magnesium composites containing 0 − 20 vol% Al2O3 particles were produced via mechanical milling (MM) followed by spark plasma sintering (SPS), and the effect of the microstructure on their mechanical properties was investigated. Microstructural observation of the MM powders and SPS compacts was achieved using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM)/energy dispersive X-ray spectroscopy (EDS). The mechanical properties of the MM powders and SPS compacts were evaluated on the basis of the results of the Vickers hardness test. SEM micrographs indicated that Al2O3 fine particles were dispersed in the Mg composites with 10 vol% and 20 vol% Al2O3. The hardness values for the MM powder and the SPS compact containing 10 vol% Al2O3 were nearly the same owing to their similar microstructures. However, the hardness of the SPS compact was higher than that of the MM powder for the Mg composite with 20 vol% Al2O3. TEM/EDS and XRD analyses revealed that the needle-like Mg17Al12 and equiaxed nano MgO particles formed in the Mg matrix with 20 vol% Al2O3 during the SPS process. The increase in hardness of the SPS compact compared to that of the MM powder is attributed to strengthening resulting from the formation of the Mg17Al12 and MgO phases.
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  • Surface Fluorination of Aluminum-Bronze Powder Using Fluorine Gas and its Sintering Property
    Shigeyuki KIMURA, Sachiko MASUOKA, Yoshiro ARAMI, Fumihiro NISHIMURA, ...
    2014 Volume 61 Issue 8 Pages 403-409
    Published: August 15, 2014
    Released on J-STAGE: November 19, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.403
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    The sintering and mechanical properties of CuAl powder fluorinated with fluorine gas (F2) were investigated. XPS results proved the creation of Al2O3, AlF3, CuF and CuF2 on the surface of samples after surface fluorination. The sintering property of CuAl powders was improved by surface fluorination at below 473 K and 0.1 MPa (F2). As a result, the mechanical strength of sintered compact of sample fluorinated at 373 K was 528 MPa higher than that (119 MPa) of untreated sample. However, the mechanical property of sample fluorinated at 573 K was fade due to the formation of thick fluoride on the surface of samples. To improve the sintering and mechanical properties of CuAl powders, the control of surface fluorination is very important in this study.
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  • Thermal Shock Examination of Cermets by Laser Irradiation and the Analysis
    Tetsushi MATSUDA, Hideaki MATSUBARA
    2014 Volume 61 Issue 8 Pages 410-415
    Published: August 15, 2014
    Released on J-STAGE: November 19, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.410
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    Titanium carbonitride (Ti (C, N))–based cermets have been studied for applying them to cutting tools and wear–resistant tools. Thermal shock resistance is an important property of tool materials used in severer environment. However, evaluation method of thermal shock resistance has not been established for cermets. In order to develop a method to evaluate the thermal shock resistance, irradiation experiments using a high power laser were conducted;laser beam was irradiated on the surface of thin specimens. The experimental results showed that a critical laser power for crack initiation can be used practically to evaluate the thermal shock resistance of cermets. AE signals occurred with crack initiation were monitored, and it indicated that the crack occurred after stopping of the irradiation. Finite element analysis (FEM) was carried out in order to clarify the crack initiation mechanism.
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  • The Development of the Sintered Micro Gear by Die Compacting
    Zenzo ISHIJIMA, Hideshi MIURA
    2014 Volume 61 Issue 8 Pages 416-420
    Published: August 15, 2014
    Released on J-STAGE: November 19, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.416
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    In recent years, demands of miniaturization and thinner component parts have been increased corresponding to the increase of miniaturized and multi-functionalized digital home appliances or advanced medical equipment. It is difficult to manufacture such micro products under conventional methods. Powder metal process with improved compactibility may be applicable and attractive technology to achieve it. The authors attempted sintering of a micro gear with a multi-step axis, which is unable to be sintered by conventional powder metallurgy or machining. Then a cylindrical discharge mechanism has been invented and provided in the die. Forming has been done using a die driven by a servomechanism. Sintered structure and dimensional accuracy of the gear were investigated.
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