Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 18, Issue 1
Displaying 1-6 of 6 articles from this issue
  • Yasutoshi Saito, Yutaka Shinata, Kyoko Yokota, Seiichi Ikawa
    1971 Volume 18 Issue 1 Pages 1-7
    Published: July 25, 1971
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    Thermal decomposition of yttrium oxalate octahydrate, Y2(C2O4)3⋅8H2O, has been studied by thermogravimetry, differential thermal analysis, infra-red absorption spectroscopy, X-ray diffraction analysis and surface area measurement. The results obtained were as follows:
    (1) Yttrium oxalate octahydrate decomposed to the oxide in the order of the following five stages: (i) octahydrate→trihydrate, (ii) tihydrate→dihydrate, (iii) dihydrate→monohydrate, (iv) monohydrate→anhydrate, and anhydrate→intermediary (such as carbonate or oxycarbonate), and (v) anhydrous oxalate or intermediary→oxide.
    (2) The dehydration of the octahydrate to the monohydrate took place below about 200°C, and the monohydrate was nearly stable between about 200°C and 320°C. It was unable to find out the temperature range in which the anhydrate was separately stable. The anhydrate decomposed to the oxide directly, or through the formation of the intermediary above about 350°C.
    (3) Surface area of the thermal decomposition products obtained on heating the octahydrate to the various temperatures at a constant rate increased with increasing temperature below the temperature in which the monohydrate was formed due to the dehydration, being followed by a decrease with increasing temperature.
    (4) Above the temperatures where the monohydrate decomposed, surface area remarkably increased and showed maximum by holding the temperature in which the formation of the intermediary was pronounced.
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  • Wlodzimierz Wolski, Irena Okonska Koztowska
    1971 Volume 18 Issue 1 Pages 8-18
    Published: July 25, 1971
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Wlodzimierz Wolski and Irena Okonska Kozlowska: Dissolution Velocity of Zinc Ferrite in Acids
    The kinetics of the system ZnFe2O4/H+ has been examined in various concentrations of hydrochloric and nitric acids separately and in their mixtures. It was found that in nitric acid independent of its concentration the process is non-stoichiometric one, giving after the same lapse of time more zinc cations to the solution than the stoichiometricity requires. This behaviour can be observed in both dilute and concentrated HNO3.
    In the presence of hydrochloric acid the same ferrite displays quite different way of dissolution ; here according to the analytical data, the amounts of ferric and zinc ions do indicate the molar solubility. Rather surprisingly, however, the best conditions in order to dissolve stoichiometrically this compound in acids under investigation, have been achieved for the mixture of 2N HNO3 and 2N HCl even, when. the proportion of HCl:HNO3 had been as small as 1:20.
    The results of temperature effects examination |20°, 40°, 60°C| upon this reaction showed, as to be expected, much more greater rate of dissolution in higher temperatures. The findings allowed to establish the kinetic equation and calculate the rate constants K and k. The most accurately they fit when put in the following equation : dx/dt=s0k(1-x)3;K=1/t[1/(1-x)2-1];K=2ks0, where s0 is the specific area.
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  • Kohei Kodaira, Fumikazu Kanamaru, Mitsue Koizumi
    1971 Volume 18 Issue 1 Pages 19-22
    Published: July 25, 1971
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Submicron particles of BeO without additives have been subjected to temperatures ranging from 1000 to 1400°C and pressure at 20 kb. Translucent specimens with theoretical density were fabricated in the case when sintering time was longer than 5 minutes. The optical transmissions in the vissible range were determined to be about 60% for the specimen with the thickness of 0.8mm sintered at 1000-1200°C.
    Concerning the grain growth of polycrystalline body, there exsists the following relation between grain size (D) and sintering time (t).
    D=Ktn
    The value of n in the above formula was determined to be 1/2 for this study. The activation energy for grain growth was calculated as 44 Kcal/mol from the slope in the logK/n vs. 1/T plots.
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  • [in Japanese], [in Japanese], [in Japanese]
    1971 Volume 18 Issue 1 Pages 23-27
    Published: July 25, 1971
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    It has been observed that the change in the content of carbon and oxygen occurs when the WC+Co mixed powder or compact is heated in a hydrogen atmosphere. In this paper, the behavior of carbon and oxygen was studied and the mechanism was also considered, by heating WC+5% and 10% Co ball milled powders in the hydrogen atmosphere under various conditions. The changes of carbon and oxygen content after heating were estimated by chemical analysis. The gases generated in the atmosphere were measured by using a gaschromatograph and a dew point meter.
    The results are as follows:
    (1) Decarburization and deoxygen occurred slightly even at low temperatures such as 200°C.
    (2) Below about 600°C, only CH4 gas was generated as the result of decarburization. At higher temperatures CO gas was generated, and with an increase of temperature the amount of CO gas increased while that amount of CH4 gas decreased.
    (3) Below about 600°C, H2O gas was generated as the result of deoxygen.
    (4) Below about 600°C, the H2O content in hydrogen did not affect decarburization but at higher temperatures the moisture in hydrogen increased decarburization greatly.
    (5) These phenomena (1-4) can be explained by thermodynamical treatment.
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  • Takeyuki Suzuki, Sinroku Saito
    1971 Volume 18 Issue 1 Pages 28-32
    Published: July 25, 1971
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    For the purpose of an effective spark sintering, differences of sintering state by the graphite and insulating dies, are investigated with Ni powder. Main results obtained are as follows.
    (1) In the case of graphite dies, almost all the initial electric current goes through this dies and nickel powders are heated by this graphite mold. We may not expect the powder itself as a main heater at the first stage of sintering. Temperature distribution in the specimen is small and sintering time is very short (10-15 see).
    (2) In the case of insulating die, there exists a critical pressure (below which the current path melts but other part keeps its original powder state) and it is impossible to set the primary pressure considerably low. This results in the slow temperature rise and eventually makes the sintering time longer (40-80 see). Temperature distribution in the specimen is larger than in the case of graphite die.
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  • Properties of Hardfaced Layers on WC Skeletons
    Yasuhiko Hashimoto, Shinichirô Omori, Kensuke Hidaka, Takao Tera ...
    1971 Volume 18 Issue 1 Pages 33-39
    Published: July 25, 1971
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    The application of infiltration to the hardfacing was examined by using the skeletons of WC compacts (particle size: 0.5-2μ) and the infiltrants of Ni-B-Si, Co-B-Si, Ni-P, Fe-C, Fe-C-Mo and Fe-C-W alloys having nearly eutectic composition.
    In all cases, the infiltration proceeded successfully and the hardfaced layers which tightly adhered to base metal were obtained.
    Among them, the system WC/Ni-3%B-4.5%Si was particularly excellent in the mechanical properties such as hardness, rupture strength and abrasion resistance.
    Small addition of Cu or Cr into the system improved remarkably the corrosion resistance in 5% boiling H2SO4 or HCl aqueous solution.
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