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Volume 26, Issue 1
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[in Japanese]1979 Volume 26 Issue 1 Pages 1-9
Published: February 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (4409K) -
Osamu Yamaguchi, Minoru Yamadera, Tadashi Hikita, Kiyoshi Shimizu1979 Volume 26 Issue 1 Pages 10-15
Published: February 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe present study was performed in order to study the phase transformation of alkoxy-derived PbO, two polymorphic modifications of litharge (tetragonal) and massicot (orthorhombic), caused by heating and grinding. Techniques employed are DTA, X-ray analysis and electron microscopy.
Transformation isotherms of litharge (A) having a tetragonal plate-like form were characterized by sigmoidal shape, and kinetics were best described by the Avrami equation, ln(1-α)=-ktn(n=2), where a, t, k, and n are the fraction of transformation, time, rate constant and proportionality constant, respectively. In the case of litharge (B) obtained by grinding, n in the Avrami equation was 3. The above results are explained by the difference on particle forms. The values of the activation energies calculated from the Arrhenius plots are about 50 kcal/mol and 35kcal/mol, respectively. These activation energies represent those of the nucleation growth of massicot.
The transformation from massicot to litharge was completed by grinding for 10min in vacuum, and the ground product was only litharge through long times. The line profiles of the X-ray powder diffraction patterns of the ground litharge showed the decrease of height and the broadening of breadth with increasing time. The size of crystallites became rapidly small by grinding for 20 h, and it was hardly influenced by the subsequent grinding. On the other hand, the lattice distortion increased gradually with increasing time. When litharge ground for long times was heated in air, PbCO3·PbO and 4PbCO3·3PbO were formed by the reaction with CO2 in the heating process. This results show that PbO has a tendency to absorb CO2.View full abstractDownload PDF (2571K) -
Masaya Miyake, Akio Hara1979 Volume 26 Issue 1 Pages 16-21
Published: February 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe reaction of the carbon reduction of WO3 in a nitrogen atmosphere was studied fundamentally.
The results obtained are as follows:
1) Sublimination of WO3 was observed at high temperatures over 1200°C and its decomposition occurred simultaneously when the atmosphere had a low oxygen potential.
2) The carbon reduction of WO3 is proceeded by the thermal decomposition of WO3 as well as the reaction with carbon at the starting stage of reaction.
3) It was noted in small samples that the carbon reduction was induced after WO3 had been changed to W18O49 of needle-like crystal between 800°C and 1000°C.
4) On an industrial scale, the reaction is more complex due to the effect of the great quantity of product gas and heat supply. For this purpose, a new type of furnace is needed.View full abstractDownload PDF (4140K) -
Effects of a Small Amount of Additional Carbides on High-Temperature Strength of TiC-Mo2C-Ni CermetsHisashi Suzuki, Koji Hayashi, Tsutomu Yamamoto1979 Volume 26 Issue 1 Pages 22-26
Published: February 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of a small amount of additional carbides such as V4C3, Cr3C2, ZrC, NbC, HfC, TaC, and WC on the transverse-rupture strength of TiC-20%Mo2C-20%Ni cermet were studied mainly at 900°C.
It was found that the strength of the cermet was particularly improved by the addition of ZrC or HfC, and the most suitable amount of addition was about 1.5% in ZrC and 2.7-5.3% in HfC. The reason was suggested to be in the fact that the titanium carbide phase in the cermet was most solution-hardened by the addition of those carbides, leading to the strength increase of carbide skeletons or to the low plastic-defor-mability of cermet at elevated temperatures.View full abstractDownload PDF (2876K) -
Tohru Kohno, Kunio Obara1979 Volume 26 Issue 1 Pages 27-33
Published: February 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe relation between the static and dynamic properties and homogenization aspect of added elements (Ni, Mo) in the sinter-forged 95-100% dense steels contained 0.2-0.5%C was investigated.
The results obtained are as follows;
1) Mechanical properties of full dense materials made from the alloyed powder are the most excellent, while in the case of the material made from the admixed powder, mechanical properties are inferior because Mo does not sufficiently diffuse into the matrix, and brittle intermetallic compounds are formed near the interface of the matrix and Mo particles.
2) In the material which contains the ferro-molybdenum powder instead of the metallic molybdenum pow-der, static properties are improved but dynamic ones show no sign of improvement at all owing to brittle intermetallic compounds scattered in the matrix.
3) In the case of the materials with residual pores, however, the difference of the dynamic properties between the materials made from the alloyed and the admixed powder extremely decreases, and at 97% density ratio there is little difference in both static and dynamic properties.View full abstractDownload PDF (3436K) -
Kiyoaki Akechi, Zenshiro Hara1979 Volume 26 Issue 1 Pages 34-37
Published: February 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSBoron fibre reinforced aluminium composite was produced by a resistance sintering process. A mixture of atomized aluminium powder (-150 mesh) and boron fibre (200 μm in diameter, tensile strength 320 kg/mm2) was resistance-sintered for 1.2-1.5 sec. When a composite was produced with appropriate power input so that the aluminium matrix does not fuse excessively, a sound fibre-matrix interface without a reaction layer could be formed and the mechanical properties of the obtained composite was excellent (for example, Al-20 vol%B: 50 kg/mm2).View full abstractDownload PDF (1180K) -
Akio Kato, Shigeki Matsuya1979 Volume 26 Issue 1 Pages 38-40
Published: February 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe vapor phase reactions of FeCl2-NiCl2-O2 system and FeCl2-CoCl2-O2 system at 700-1000°C were found to produce the fine powders of Ni-and Co-ferrites, respectively. The ferrite particles were single-crystalline and finer than 1μ, having the mean sizes of 0.16-0.5μ (Ni-ferrite) and 0.15-0.25μ (Co-ferrite).View full abstractDownload PDF (1422K)
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