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 4
April
Displaying 1-12 of 12 articles from this issue
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  • Preparation of MnAl2O4 by Corrosion Synthesis
    Osami SERI, Takuya TSUJI, Daichi SASAKI
    2014 Volume 61 Issue 4 Pages 153-157
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.153
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    Attempts have been made to obtain the manganese spinel (MnAl2O4) by using corrosion of manganese and aluminium chloride as catalysis. Particle diameter range of 10 − 350 micrometers was obtained when the corrosion product was hydrolyzed and calcinated at the temperature of 1573 K or more. The powder was identified as MnAl2O4 spinel by XRD diffraction analysis. Corrosion synthesis as one of the inorganic synthesis is explained from the viewpoint of electrochemical phenomena and considered its merits and demerits in the case of making the spinel of MnAl2O4.
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  • Initial Cycling Performance of LiFePO4/C Composite Particles Prepared by Gas-Solid Phase Reaction
    Chihiro TOMONOBU, Yoshihiro OKA, Tatsuya NAKAMURA
    2014 Volume 61 Issue 4 Pages 158-162
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.158
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    LiFePO4 particles were prepared by the solid state reaction, and coated with conducting carbon layer through the hydrocarbon gas decomposition technique. The uniformity of the carbon layer was examined using the small angle X-ray diffraction with the core shell model. The half cell using these composite particles as cathode exhibited a peculiarity, that is, the capacity increment during the initial cycling process. In this study, the initial cycling process was studied with the AC impedance method. As a result, it was found that the interfacial impedance becomes small on the cycling sequence. It implies that the cathode/electrolyte interface is built on the initial cycling.
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Special Issue: Magnetic Materials with High Performance for Energy and Environmental Applications
Summarization
Memorial Lecture of JSPM Award
  • Sintering Densification of Thermally Degradable Magnetic Powders and Characterization of Their Grain Boundaries
    Kenta TAKAGI, Hiroyuki NAKAYAMA , Kimihiro OZAKI
    2014 Volume 61 Issue 4 Pages 165-170
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.165
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    This paper reviews our study of developing a sintering technique of thermally degradable Sm – Fe – N powders. The Sm – Fe – N coarse powder in the flake form was sintered using a low-thermal-load process of high pressure current sintering. By using cyclic compaction and optimum sintering temperature, this process produced dense isotropic bulk magnets without thermal decomposition that exhibited the high maximum energy product of 17.1 MGOe. Meanwhile, the Sm – Fe – N fine powder was also sintered by the same sintering technique. The coercivity of the sintered compacts considerably decreased regardless of sintering temperatures under the thermal decomposition temperature. TEM and XPS analyses on the grain boundaries led to estimation of the mechanism of coercivity decrease: the oxidation-reduction reaction between the initial iron oxides and the primary Sm – Fe – N phase generated α – Fe phases which might act as reverse magnetic domain nucleation sites.
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Paper
  • Pulsed Electric-current Pressure Sintering of Spinel Type (Fe, Mn)Al2O4 Ferrites and their Physical Property Evaluation
    Masahiro UEDA, Masaki KATO, Ken HIROTA
    2014 Volume 61 Issue 4 Pages 171-178
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.171
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    Single-phase spinel type FeAl2O4 and Mn – doped solid solutions of (Fe1−xMnx)Al2O4 (0 < x ≤ 1.0) powders have been prepared by solid state reaction at 900 ˚C for 6 h in 1.0 % H2 – bal.N2 using reactive fine powders of α – Fe2O3 (particle size of 0.1 µmφ), γ – Al2O3 (about 10 nmφ) and MnO (about 0.15 µmφ). Afrer the powder characterization using XRD, they were densified using pulsed electiric-curuent pressure sintereing (PECPS) at 1050 ˚C for 10 min under 50 MPa in Ar atmossphere. Thus fabricated dense ceramics, having single-phase spinel strucure with the relative desity ≥ 97.0 %, were evaluated by XRD, SEM, and a SQUID magnetometer. They showed antiferromagnetic properties, except for x = 1.0, i.e., MnAl2O4 (paramagnetic), and at the compositions of x: 0.4～0.6, Mn – doped solid solutions ceramics revealed moderate high magnetic susceptibility.
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  • The Relations between Sintering Conditions and Magnetic Properties of SrMg2W – type Ferrites Prepared by Spark Plasma Sintering Method
    Koki YOSHIDA, Takashi NAKAGAWA, Yoshinori KOBAYASHI, Yusuke RYOSHI, S ...
    2014 Volume 61 Issue 4 Pages 179-185
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.179
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    The effects of sintering condition to magnetic properties of the SrMg2W–type ferrite (SrMg2Fe16O27) prepared by the Spark Plasma Sintering (SPS) method were investigated. SrMg2W–type ferrite powders with average particle sizes of 0.43 µm were prepared by iron ball-milling for 10 hours. Some kinds of SrMg2W–type ferrite samples were obtained by sintering SrMg2W–type powders by the SPS method at 1073−1173 K for 0−20 min as holding time. Compared to the SrMg2W–type ferrite prepared at 1523 K by the conventional solid reaction method, all the spark-plasma-sintered samples had larger coercivity. Mass magnetization of the SPS samples were almost the same (51.9～54.3 Am2/kg @1 T) regardless of the sintering condition. In the case of SPS without holding time, the coercivity of the SPS samples increased with increasing the sintering temperature, and reached 191 kA/m at 1173 K. When the samples sintered at 1073 K, the coecivity became the maximum (190 kA/m) at 10 min. From the results of X-ray diffraction, it was found that the coercivity of the samples enhanced as lattice strain of them was small. The influence of the lattice strain on the coercivity was discussed using the Kronmüller equation.
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  • Study of Microscopic Structure of Ga Added Neodymium Magnet Alloy
    Akihiko SAGUCHI , Mitsuharu YONEMURA, Kenji HIGASHI
    2014 Volume 61 Issue 4 Pages 186-192
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.186
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    R–Fe–B type strip-cast (SC) alloys containing trace amounts of Ga were prepared with different cooling rates and their microstructures have been investigated in details using TOF–SIMS, FE–EPMA, HR–TEM and EDS. Ga was confirmed to be distributed in R2Fe14B matrix phase and R–rich boundary phase and had a tendency to segregate as a R–rich boundary phase with Al and Cu. This tendency was enhanced with decreasing SC cooling rate. Ga–rich amorphous-phase containing Al and Cu was observed in the alloy prepared with a slower cooling rate, coexisting with other crystalline phase. Ga distribution in R–rich boundary phase may be controlled by optimizing SC conditions.
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  • Development of Power Generation Device Using Inverse Magnetostriction Effect of Elastomer Material Dispersed with Magnetic Powder
    Fujio TSUMORI, Suguru ECHIKAWA, Yujiro HIRABAYASHI, Tsuyoshi NAKATSUJI ...
    2014 Volume 61 Issue 4 Pages 193-198
    Published: April 15, 2014
    Released on J-STAGE: August 02, 2014
    DOIhttps://doi.org/10.2497/jjspm.61.193
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    Elastomer dispersed with magnetic particles can deform under a magnetic field. It alsochanges its permeability by deformation. These phenomena are similar with magnetostriction and inverse magnetostriction effects, so that the elastomer could be classified as a magnetostriction material in a broad category. Generally, the magnetostriction effect is based on the interaction between atoms, while the effect in the elastomer is caused by interaction between magnetic particles in its body. As the inverse magnetostriction effect is available for power generation, the elastomer with particles would be used as a power generator. In the present work, silicone rubber and some steel powders were prepared as base materials of the magnetic elastomer for power generation. The rubber and powder were mixed and cured to shape cylindrical specimen, and subsequentlyelectric wire was looped around the specimen to make a coil. The specimen was set between permanent magnets and was vibrated. The output voltage was measured from the coil. We prepared some kinds of specimens changing dispersed magnetic powder, vibration frequency, and orientation of particles’ chain. The power generation efficiency was evaluated, and was discussed using some results of magnetic finite element analysis.
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