Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 23, Issue 8
Displaying 1-5 of 5 articles from this issue
  • Tsutomu Iimura
    1976 Volume 23 Issue 8 Pages 253-258
    Published: December 05, 1976
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    The effects of Fe2+ ion content on the initial permeability have been studied in Mn-Zn ferrites of various Mn/Fe ratios. The initial permeability and resistivity depend substantially on the Fe2+ ion content at. the regions containing a small excess of Fe2O3 over the stoichiometric composition.
    While, when additives are used, the relation between initial permeability and resistivity can not be simply compared to none additive ferrites.
    It was found that the values of initial permeability of Mn-Zn ferrite systems containing small amount of Te or MoO3 were strongly dependent on the Fe2+ ion content, but the resistivity values were nearly independent upon the presence of Fe2+ ions. The conduction mechanism of resistivity of the materials containing additives could not be explained on the theory of the electron transfer of Fe2+ ?? Fe3+ ion at the B-site in spinel lattice. Some explanations of these additive effects are presented.
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  • Eiji Ino, Hidetsugu Mori, Tamotsu Yamate
    1976 Volume 23 Issue 8 Pages 259-263
    Published: December 05, 1976
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    The effects of oxide additives on the sintering of LaMnO3 have been discussed on the basis of the isothermal shrinkage, bulk density and grain size at 1300-1450°C for 0.25-70 hr in air. The lattice constants of LaMnO3 with various oxide additives were measured by X-ray diffraction analysis with the internal standard of 99.99% Si.
    The results were summarized as follows; (1) It was shown that sintering was markedly promoted by the addition of ZrO2, ZnO and BaO, while it was not promoted by the addition of Fe2O3 and TiO2 in low temperature range. (2) The results of shrinkage measurement of pure LaMnO3 and modified LaMnO3 with various oxide additives indicated that a constant value of m obtained in the initial stage was about 0.50. (3) The rate of grain growth was found to be followed by the equation Dn-D0n=kt; the values of time exponent n for pure LaMnO3 with TiO2 and CaO additives of 5 mol% were about 2.5, 2.3 and 2.6, and the values of the activation energy were estimated to be 76, 63 and 78 kcal/mol, respectively. (4) LaMnO3 and LaMnO3 with oxide (ZrO2, ZnO and BaO) additives were determined to be perovskite type with orthorhombic unit cell by X-ray diffraction analysis. It was recognized that lattice constants of LaMnO3 were varied by oxide additives up to 10 mol%.
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  • Isao Konda, Hidetsugu Yagi, Yoshikazu Tabata
    1976 Volume 23 Issue 8 Pages 264-268
    Published: December 05, 1976
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    Sintered iron compacts have many pores, which seem to reduce the mechanical properties of them. The pore structure is very complex, and its influences on the mechanical properties are also complicated.
    Then, authors analyzed the pore structure, particularly size, shape, and distribution, quantitatively, and its effects on the mechanical properties were investigated.
    The following conclusions are obtained:
    1) The size of pore becomes large in proportion as the porosity increases, and in a case of the same porosity, the pore size becomes large as the particle size of iron powder is large.
    The shape of pore becomes irregular in proportion as the porosity increases.
    2) Tensile strength decreases with increasing porosity, but in a case of the same porosity, the strength is not much influenced with particle size of iron powder.
    On the other hand, fatigue strength varies not only with the porosity but also the particle size. This is considered to be caused by the characteristics of the mechanism of fatigue fracture.
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  • Hisashi Suzuki, Koji Hayashi, Osamu Terada
    1976 Volume 23 Issue 8 Pages 269-273
    Published: December 05, 1976
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    It has been revealed in previous experiments that the transverse-rupture strength of various cemented carbides is generally dominated by the microstructural defects, so that the strength can be quantitatively expressed, by considering the dimension and location of the defects. In the present study, the same subject was undertaken, using WC-(0-25)%TiC-16vol%Ni and WC-(0.1-20)%TaC-16vol%Ni alloys in order to make clear the influence of addition carbides on the strength of WC-Ni alloy. The results were compared with those in WC-TiC(TaC)-16vol%Co alloys.
    The following results were obtained: It was confirmed that the strength of those alloys was also controlled by the microstructural defects (pores, carbide agglomerates, etc.). The σ0 values (the strength of sound matrix with none of defects) of WC-Ni alloy sharply decreased from about 700kg/mm2 to about 350-400kg/mm2 (according to JIS) by a small addition of TiC(TaC), showing that the sharp decrease in the strength of WC-Ni alloy by addition of TiC(TaC) seems to be substantial. The above results are similar to those in WC-TiC(TaC)-Co alloys. The difference in the ao values between WC-TiC-Ni and WC-TaC-Ni, and between WC-TiC(TaC)-Ni and WC-TiC(TaC)-Co alloys was in detail discussed.
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  • Hisashi Suzuki, Koji Hayashi, Yasuro Taniguchi
    1976 Volume 23 Issue 8 Pages 274-278
    Published: December 05, 1976
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    The transverse-rupture strength of WC-TaC-100%Co alloys containing TaC up to 10% was investigated mainly in the temperature range from 600 to 900°C in relation to the fracture source. The WC-10%Co two-phase alloy (its mean carbide grain size is about 1.4μ) and WC-(1, 5, 10)%TaC-10%Co three-phase alloys (about 1.3μ) were used as specimens. The strength test was carried out according to the Japanese Industrial Standard.
    The results obtained were as follows; (1) The fracture source in the TaC contained alloys was similar to those found in WC-Co alloy; that is, the structural defects were observed as the source below about 600°C and the regions of stable crack propagation were observed above about 600-700°C. (2) The intrinsic strength, i.e., the strength of TaC contained alloys being free from defects sharply decreased at about 600-700°C also in the same way as WC-Co alloy. The difference in the strength between the TaC contained alloy and WC-Co alloy decreased with increasing temperature up to about 800°C, and above this temperature the strength of TaC contained alloys was considered to correspond to that of WC-Co alloy in contrast to the general knowledge, when the carbon contents of the alloy were the same.
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