Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 57, Issue 1
January
Displaying 1-11 of 11 articles from this issue
Paper
Paper
  • Takamitsu Honjo, Tohru Nobuki, Toshiro Kuji
    2010 Volume 57 Issue 1 Pages 3-9
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    Carbon-metal composite materials are expected for application to the catalyst and the electromagnetic wave absorbers. In this study, carbon-metal composite materials synthesized by the ball-milling (BM) process. Elemental powder of the Carbon (purity 99.9 %) was used. In this study the SUS304 γ-austenite stainless steel was used for the container and the balls. The weight ratio of ball to powder was 120:1. BM was carried out for maximum 216 ks at a speed of 11.4 Hz and the BM system was water-cooled by high-power BM apparatus (NEV-MA8, Nissin-Giken, Japan). The samples prepared by BM were removed from the pot in a glove box under argon. Obtained samples were somewhat contaminated from ball or container of stainless steel due to heavy scraping action between ball and container. BM for 216 ks yielded metallic phase (SUS304) to transform to α'-martensite due to heavy strain given to the γ-austenite during ball milling as mentioned above. As the result, fine metallic grains with equivalent composition to SUS304, C70Fe20Cr6Ni3 were distributed in carbon. This composite material was fully magnetized to 10 Am2 kg-1 at the magnetic field of 2.0 MA m-1.
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  • Koji Kondo, Yoshitaro Yazaki, Yoshihiko Shiraishi, Kazuo Tada, Hideshi ...
    2010 Volume 57 Issue 1 Pages 10-16
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    In order to construct the multi layers IVH (Interstitial Via Hole) structure with only one time hot pressing, we have developed the new diffusion bonding technology. In this paper, the sintering process of Ag-Sn mixed powders (Ag/Sn:65/35 mass%) between copper foils in IVH with hot vacuum pressing was investigated, and the effect of temperature on the respective diffusion reactions was discussed. Ag and Sn formed Ag3Sn up to 473 K with the solid diffusion reaction. At 483 K, Ag particles disappeared completely and the mixed compact consisted of Ag3Sn and excess Sn. Cu-Sn diffusion reaction between excess Sn and copper foil commenced at 493 K. Excess Sn was consumed completely below 573 K. The liquid phase of Sn contributed not only to Cu-Sn diffusion bonding but also to Ag3Sn sintering. As a result of hot pressing above 573 K, the mechanical properties were improved without large grain growth of Ag3Sn (about 4 μm).
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Special Issue: Magnetic Materials for Environment, Resource, Recycling and Energy-saving Technologies
Summarization
Memorial Lecture of JSPM Award
  • Haruhiro Komura, Mikio Kitaoka, Teruo Kiyomiya, Yoshio Matsuo
    2010 Volume 57 Issue 1 Pages 19-26
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    Strong magnetization for Nd-Fe-B isotropic bonded magnets is an important technology that contributes to miniaturization of electromagnetic devices and smaller fractional movement. This technology, especially the fine pole-pitch magnetization, is significant in stepper motors installed in portable terminals, etc. However, as Nd-Fe-B magnets have a high coercivity, large amounts of energy are required for magnetization. Miniaturization of devices is associated with insufficient magnetization characteristics due to the limitations of current density. So, we developed a new magnetization method using a heating system. This method involves cooling in the magnetizing field by permanent magnets after rapid heating to temperatures above the Curie point of the Nd-Fe-B magnet. This method, which we called the Ultra High Magnetizing (UHM) Process, achieved greater magnetization characteristics than conventional technology. Therefore, the "UHM process" is a useful technology to achieve further miniaturization of electromagnetic devices. In addition, the microminiature motors which used this technology have already been mass-produced.
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Paper
  • Noriyuki Nozawa, Takeshi Nishiuchi, Satoshi Hirosawa
    2010 Volume 57 Issue 1 Pages 27-32
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    We applied Hydrogenation-Disproportionation-Desorption-Recombination (HDDR) treatment on compacts of fine powder of Nd-Fe-B-based alloys to obtain porous, submicron-grained bulk permanent magnets. The crystallographic orientation of the Nd2Fe14B particles was maintained in the porous magnets, which could be further densified to the full density by hot pressing. Significant improvements over conventional HDDR-processed magnets were observed in the squareness of demagnetization curves for the full-density bulk magnets.
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  • Hiroshi Yamamoto, Hiroaki Nishio, Yuuki Yoshinaga
    2010 Volume 57 Issue 1 Pages 33-40
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    An experiment was carried out to investigate the effect of Nd2O3 substitution, molar ratio n {=Fe3+/(Co2++Ni2++Nd3+)}, concentration of alkali, inflowed time of alkali on the magnetic and physical properties of Co-Ni-Nd system spinel ferrite fine particles prepared by the chemical coprecipitation method without post-annealing. The chemical coprecipitation compositions were chosen according to the formula (CoO)0.5(NiO)0.5-x(Nd2O3)0.5x·n/2(Fe2O3), where x varied between 0 and 0.2 and n varied between 2.00 and 2.75. The typical magnetic properties were saturation magnetization σs=47.0×10-6 Wb·m/kg, residual magnetization σr=23.6×10-6 Wb·m/kg, coercivity HcJ =620.7 kA/m. To remove the superparamagnetic substance, the coprecipitation fine particles were etched with dilute sulfuric acid. As a result, in the (CoO)0.5(NiO)0.45(Nd2O3)0.025·1.25(Fe2O3) composition, when the excess NaOH and inflowed time were 1.1 mol and 1 s respectively, the following magnetic and physical properties were obtained: σs=75.1×10-6 Wb·m/kg, σr=56.7×10-6 Wb·m/kg, HcJ=861.8 kA/m, K1=3.56×105 J/m3, K2=-13.1×105 J/m3, and HA=3.90 MA/m.
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  • Nobuyuki Hosaka, Yoshihisa Yamamoto, Seiji Kano, Jingsha He, Hiroshi I ...
    2010 Volume 57 Issue 1 Pages 41-45
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    Ba2Ni2Fe28O46 (Ni2X) samples were prepared by using a conventional ceramic method. The crystal structure and magnetic properties of the samples were investigated. The X-ray diffraction patterns of the samples sintered at 1250°C and 1300°C were in agreement with the diffraction pattern simulated from the real space coordinates of Ba, Fe and O ions.
    The Curie temperature was found to be 478°C, which was different from the Curie temperatures of M-type and Ni2W-type hexaferrites. The single phase of X-type hexaferrite was obtained at 1250°C, which suggests that the sintering processes should be carefully controlled for the synthesis of the X-type hexaferrite.
    The saturation magnetization of Ni2X-type hexaferrite was higher than that of M-type and W-type hexaferrite at room temperature. Whereas, the coercivity was lower than that of M-type hexaferrite.
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  • Satoshi Sunada, Takuya Tsugawa, Tetsuo Aida, Katsuhiko Nishimura
    2010 Volume 57 Issue 1 Pages 46-53
    Published: 2010
    Released on J-STAGE: February 16, 2010
    JOURNAL OPEN ACCESS
    Zinc-coating and tin-coating have been used for improvement of the corrosion resistance of steels. Magnesium alloys of less noble metal could be also used as the sacrificial anodes. In this study, the extruded compacts composed of magnesium and Sm2Co7 of magnetic alloy were brought into contact with SS400 steel through the magnetic force of Sm2Co7, and the effect of their sacrificial anode was investigated by using the potentiodynamic polarization test, the corrosion test under constant quantity of electricity, the ICP measurement for the dissolved elements and the surface analysis on the specimens by XPS. The sacrificial anodic effect of the magnesium alloy with Sm2Co7 could not be recognized. However, the suppression of corrosion rate by magnesium alloy with Sm2Co7 brought into contact with steels was observed. This result suggests that the magnesium alloy is effective for the improvement of the corrosion resistance of steels.
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