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 57, Issue 12
December
Displaying 1-16 of 16 articles from this issue
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Paper
Paper
  • Fabrication and Characteristic Evaluation for Clay Tile Composites Reinforced with Flaky Nickel-Chromium Alloy Particles
    Yoshiharu Waku, Shoki Iwamoto, Masahiro Yoshinobu, Shinji Harui, Keiic ...
    2010 Volume 57 Issue 12 Pages 747-752
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.747
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    The flake-forming behavior of Ni-Cr alloy powders during a wet ball milling process and the effect of volume percent of flaky Ni-Cr alloy particles on three-point flexural strength and fracture toughness of clay tile composites reinforced with flaky Ni-Cr alloy particles have been investigated. The flexural strength and fracture toughness of composites can be simultaneously improved by increasing the volume percent of flaky Ni-Cr alloy particles. The SEM observations indicates that the improvement in fracture toughness may be attributed to plastic deformation of flaky Ni-Cr alloy particles at crack tip. Fabricating composites reinforced with flaky Ni-Cr alloy particles is an effective toughening technique capable of simultaneously improving the strength and toughness of brittle materials by utilizing plastic deformation of ductile phase. The volume resistance of the clay tile/30%flaky Ni-Cr alloy particle composites is 7.5×10-2 Ω·cm, which is larger than that of Ni-Cr (JIS NCH-1) (1.1×10-4 Ω·cm). The resistance temperature coefficient of the composite is almost the same as that of Ni-Cr (JIS NCH-1). The composite is therefore promising candidate as resistance materials.
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Rapid Communication
  • Fabrication of TiN and TiCN Coatings by Microwave Irradiation
    Kohei Miyashita, Yamato Hayashi, Hirotsugu Takizawa
    2010 Volume 57 Issue 12 Pages 753-757
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.753
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    TiN coating was successfully formed by burying a quartz glass substrate into Ti powder and subsequent microwave irradiation in air. The temperature of the powder rapidly rose up to 1100°C by microwave irradiation, and TiN coating was formed on the substrate by vapor phase reaction. Particle size, film thickness, and Vicker's hardness of the coating increased with increasing the irradiation time and microwave power. Similar technique was also applied to form TiCN coating by using mixture of Ti and carbon powder instead of Ti powder. It was revealed that the carbon content, film thickness, and Vicker's hardness of the coating increased with increasing the carbon content in the starting powder.
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Paper
  • Effects of Boron Content and Heat Treatment on Behavior of Complex Boride Forming in Ni-Cr-Mo-B Gas Atomized Powder
    Toshiyuki Sawada, Katsu Yanagimoto
    2010 Volume 57 Issue 12 Pages 758-763
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.758
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    Effects of B content and heat treatment on properties of gas atomized powders with Ni-10mass%Cr-36mass%Mo-Xmass%B compositions (X=1.5∼4) were investigated. Examined powders were produced by gas atomization, followed by sieving under 150 μm. These powders were heat treated at various temperatures to investigate the effect of heat treatment temperature.
    As a result, tetragonal M3B2, tetragonal M5B3 and orthorhombic M3B2 type complex borides were observed in examined powders before and after the heat treatment. Compositions and crystal structures of complex borides varied depending on B contents in examined powders, hereby compositions of Ni-based matrix phases also varied. Vickers hardness after the heat treatment at 1473 K increased with increasing B content.
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  • Preparation and Mechanical Property for WC-25vol%FeAl Using Wet Milling Process
    Akihiro Matsumoto, Kiyotaka Kato, Koji Shimojima, Hiroyuki Hosokawa, M ...
    2010 Volume 57 Issue 12 Pages 764-768
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.764
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    WC-25vol%FeAl compacts have been prepared using wet milling and the subsequent pulse current sintering. Powder mixtures consisting of (1) WC, Fe-40at%Al and (2) WC, Fe, Al powders have been mixed to give the desired composition of WC-25vol%FeAl. They have been milled using a cylindrical ball mill with ethanol. Milled powders have been dried at room temperature and consolidated using pulse current sintering method at 1273 K in vacuum. The compacts thus obtained have had fine and homogeneous structure. Vickers hardness of both compacts has increased with increasing milling time. Transverse rupture strength of the former compact has increased with increasing milling time, but that of the latter one abruptly decreased. This is due to the formation of Fe3W3C and Al-O phase.
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Review
  • Intelligent Nanosintering for Ceramics
    Hiroshi Kimura
    2010 Volume 57 Issue 12 Pages 769-778
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.769
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    This article describes a study of intelligent nanosintering, as the author here use this term, by which one can provide a platform for the bulk nanocrystalline synthesis using multi-variable controled thermo-mechanical processing equipped with pulse electric current and microwave heating. Emphasis is firstly placed on the set-up of the phenomenology of electric field assisted densification during heating of the amorphous ceramic powder by varying manipulating variables of electric current, compact height and millimeter wave radiation power. In the case of amorphous and/or nanocrystalline ZrO2-Al2O3, the rate of densification enhanced under electric field (E) is expressed on the basis of an Arrhenius-type equation of Newtonian viscous flow, ηp = ηp0(E) esp{Q(E)/kT}, having a decreased value of the apparent activation energy (H). Then, within the framework of sintering route map up to full-density, the optimal condition for in process nonequilibrium structure control densification is provided with the reference to constitutive equations for densification during viscous flow and/or superplastic flow and the master sintering curve for densification accompanying grain growth. Moreover, it is evidenced that a variety of nanosintering techniques makes it possible to synthesize fully densified samples of amorphous B4C, nanocrystalline cubic and tetragonal (ZrO2-3mol%Y2O3)80(Al2O3)20 using nanomechanochemically synthesized amorphous powders.
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Paper
Special Issue: Permanent Magnet Materials and Their Applications
Summarization
Paper
  • Effect of Dy-diffusion Treatment on Coercivity and Magnetic Domain Structure of Nd-Fe-B Sintered Magnets
    Yukio Takada, Keiki Fukumoto, Yuji Kaneko, Akira Manabe, Noritaka Miya ...
    2010 Volume 57 Issue 12 Pages 789-794
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.789
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    Effects of Dy-diffusion treatment to Nd-Fe-B sintered magnets on those microstructure and coercivity were investigated. Coercivity of magnets increases in proportion with raising temperature of Dy-diffusion treatment and keeping longer term. As a result, it is found that changes of coercivity by this treatment can be classified into 2 modes: 1st step shows a rapid increase in coercivity where Dy diffuses into grain boundary and surrounds grains. 2nd step is a gradual increase in coercivity where Dy diffuses into 2-14-1 phases. As an extending study, we have tried to observe the magnetic domains of Nd-Fe-B sintered magnets by using XMCD-PEEM technique. It is found that Dy diffusion treatment suppresses the generation and the growth of magnetic reversed domains as same as Dy-doping into Nd-Fe-B magnets.
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  • Magnetic Properties of Melt-Spun Pr-Fe-Co-Ti-B Ribbons with Low Coercivity
    -Development of the Rotor Materials for the Torque Limiter-
    Hiroshi Yamamoto, Junrou Kajikawa
    2010 Volume 57 Issue 12 Pages 795-800
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.795
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    This research aimed at the development of the rotor material for torque limiter. The coercivity of the rotor material is required to be around 80 kA/m. The melt-spun ribbons of Pr-Fe-Co-Ti-B system alloys were prepared by single roller liquid-quenching method. The effect of composition, wheel velocity and heat treatment on the magnetic properties were investigated. The optimum preparation conditions and some of properties were follows: composition, Pr3.5Fe80.5Co8Ti1B7, wheel velocity, 30.0 m/s; heat treatment condition, 675°C for 5 min in Ar atmosphere; magnetic properties were follows; (BH)max=41.4 kJ/m3, HcJ=85.2 kA/m3, Jr=1.39 T, α(Jr)ave=0.01 %/°C (reversible). The value of (BH)max for the isotropic compression molding Pr3.5Fe80.5Co8Ti1B7 bonded magnet prepared by using the ribbons heated at 675°C for 5 min is 10.1 kJ/m3, HcJ=83.4 kA/m3, Jr=0.535 T, and the density is 5.60 Mg/m3.
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Memorial Lecture of JSPM Award
  • Improvement of Soft Magnetic Properties on Hexagonal Ferrites
    Nobuyuki Hiratsuka
    2010 Volume 57 Issue 12 Pages 801-808
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.801
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    The substitution of elements was carried out to improve the soft magnetic properties in hexagonal ferrites. A series of Ba3Co2RxFe24-xO41 samples (R=La, Nd, Gd, Dy, Ho, Yb) with Z-type structure were made. The initial permeability of Gd3+-substituted sample (x=0.1) was the highest of all samples, because the apparent specific anisotropy field of the sample was the lowest. The substituted sample Ba3Co2Mn0.5xTi0.5xFe24-xO41 with x=0.4 had the maximum μ' of 25.7 and μ' × fr product of 17.6 GHz. The M-T curve showed an anomalous drop below the Curie temperature, which reflected the change from in-plane magnetic anisotropy to vertical one with increasing temperature. BaCoxTixFe12-2xO19 (x=1-3) were prepared. The initial permeability increased to 27 for a sample with x=1.15. The reason for this may be that the coercivity becomes small as a result of the decrease in the anisotropic magnetic field. SrCo2+yMe4+yFe12-2yO19 (Me=Zr, Hf) samples were also fabricated. For SrCoyZryFe12-2yO19 (y=0-1.2), magnetization increased slightly for the sample of y=0.4, and then decreased with increasing y. Coercivity drastically decreased up to y=1.2. Magnetic behavior of the Co-Hf substituted sample was similar to that of the Co-Zr substituted one.
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Paper
  • Preparation and Magnetic Properties of X-type Hexaferrites with Transition Metal Elements
    Nobuyuki Hosaka, Kenji Kamishima, Koichi Kakizaki, Nobuyuki Hiratsuka
    2010 Volume 57 Issue 12 Pages 809-813
    Published: 2010
    Released on J-STAGE: January 19, 2011
    DOIhttps://doi.org/10.2497/jjspm.57.809
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    The conventional synthesis of ferrite compounds consists of two-steps sintering processes. The first process is calcination to produce precursor of a desired ceramic object, and the second is to obtain the desired object.
    However, it was difficult to prepare X-type hexaferrite (Ba2Me2+2Fe28O46: Me2X, Me=Co, Ni, Cu, Zn) samples by this method. Two-steps sintering of these samples resulted in formation of spinel, M and W-type ferrite phases.
    We have found that Me2X can be obtained by a one-step sintering method that skipped the calcination process. When this method is applied, the temperature range of Me2X formation was very narrow and about 1250°C.
    We measured the saturation magnetization at 2 K and room temperature, and examined the Curie temperatures of Me2X samples produced by this method. These magnetic properties for Me2X samples relatively resemble those of MeFe2O4 spinel ferrites, which suggests that Me2+ cations are distributed in spinel blocks in the Me2X crystal structure.
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