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Volume 27, Issue 1
Displaying 1-7 of 7 articles from this issue
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On the Formation of Cobalt-Ferrite on γ-Fe2O3 ParticlesMikio Kishimoto, Kenji Sumiya, Masahiro Amemiya, Fumitada Hayama1980 Volume 27 Issue 1 Pages 1-5
Published: January 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAcicular a-Fe2O3 and γ-Fe2O3 particles were treated at 70°C in alkali solution containing CO+2 and Fe2+ With CO2+/Fe2+ ratio of 0.5. The variation of particle shape and magnetic properties with progress of reaction was examined.
In the use of a-Fe2O3 particles for starting material, the quantity of hydroxides decreased with the progress of reaction, and then cobalt-ferrite particles precipitated. The shape of cobalt-ferrite was cubic, and this cobalt-ferrite did not crystallize on a-Fe2O3 particles. The results of magnetic measurements of the particles precipitated in progress of reaction were explained by considering the growth of cobalt-ferrite particles from single-domain size to multi-domain size.
In the use of γ-Fe2O3 particles for starting material, the quantity of hydroxides decreased with the progress of reaction, and the hydroxides finally disappeared. The resultant particles were acicular, and cubic particles were not observed. The results of magnetic measurements of the particles suggested that the, e cobalt-ferrite crystallized on the surface of γ-Fe2O3 particles. The origin of high coercivity of the resultant particles was discussed.View full abstractDownload PDF (2895K) -
Hideki Taguchi, Yuzuru Takahashi, Chujo Matsumoto1980 Volume 27 Issue 1 Pages 6-10
Published: January 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA gas sensor was prepared by calcining rhodium nitrate supported on aluminium nitride at various temperatures in a N2 stream. The sensitivity of the gas sensor increased linearly with CO gas concentration below 3000 ppm at 180°C and 220°C, while addition of rhodium nitrate over 3 wt% was not effective. The sensor calcined at 1000°C was twice as sensitive as that calcined at 600°C. Rhodium nitrate decomposed to RH2O3 at 600°C and to Rh at 1000°C in N2 stream. From these results, Rh was better than RH2O3 as a catalyst. The apparent porosity of the gas sensor was about 50% and this value was kept constant after annealing. It is considered that aluminium nitride is a good material as a support.View full abstractDownload PDF (301K) -
Masaharu Miyano, Hiroshi Inoue, Jiro Shibata1980 Volume 27 Issue 1 Pages 11-16
Published: January 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe induction sintering has been studied using ring shaped Iron-graphite mixed powder compacts heated at 50 and 200 kHz. The compacts were heated rapidly and uniformly by choosing a suitable heating pattern and induction frequency.
The experimental results are summarized as follows:
1) In a case of low sintering temperature (≤1150°C) or low graphite content (≤1.5%), the sintered compacts show low transverse rupture strength because of insufficient contacts between iron particles. Graphite diffuses into the iron particle in short time and the microstructure of such sintered compacts shows pearlite including 5-10% ferrite.
2) However, high transverse rupture strength which often reaches above 60 kg/mm2 is observed at sintering temperatures above 1200°C and above 1.5% graphite content. Since the liquid phase exists and graphite diffuses into iron particle during sintering, the microstructure obtained shows pearlite with free cementite which forms network as increasing sintering temperature.View full abstractDownload PDF (4375K) -
Mikio Fukuhara, Kazuhiko Tsutsumi, Hiroyasu Mitani1980 Volume 27 Issue 1 Pages 17-22
Published: January 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSBy using chemically nickel plated TiNx composite powders, we carried out an examination of sintering characteristics in order to improve the sintering effect, and also investigated some properties of sintered compacts showing maximum sintered density.
The results obtained were as follows:
(1) The shrinkage of Ni-plated TiNx powder compacts was remarkably promoted, whereas the Ni concentration and x in formula TiNx, showing the maximum density ratio and hardness of sintered compacts in the sintering condition at 1400°C for 3 hr., were approximately 23 wt%, x=0.75 and 18 wt%, x=0.75, respectively. Titanium nitride showed its maximum hardness near substoichiometric composition of TiN0.78.
(2) The Corrosion resistance in nitric acid at 25°C of TiN0.75-23.4 wt%Ni sintered alloy was comparable to that of stainless steel, Hastelloy, Inconel and cobalt-based cemented carbide, but in concentrated hydrochloric acid it was inferior to Hastelloy and Inconel.
(3) Oxidation resistance of TiN0.75-23.4 wt%Ni sintered alloy in air at 700-1000°C was superior to that of TiC-Ni alloy.View full abstractDownload PDF (1488K) -
Mikio Fukuhara, Junichi Iwami, Hiroyasu Mitani1980 Volume 27 Issue 1 Pages 23-27
Published: January 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTo expect sintering effect by the prevention against denitrification similar to that obtained in the sintering of TiNx-Ni mixed powder compacts, sintering characteristics of TiN-Ni-Ti ternary mixed powder compacts were studied in connection with phase relationship.
The maximum sintered density in the sintering condition at 1500°C for 1 hr in vacuum, was obtained at the composition ratio of the binder, Ni/Ti=3/2, since a shrinkage was prevented from the liberated nitrogen gas in the Ni rich composition and a small amount of liquid phase in the Ti rich composition.
Sintering of the TiN-18 wt% Ni-12 wt%Ti mixed powder compact was promoted by the liquid phase equilibrated with three phases, i.e., TiNx, TiNi3 and TiNi at 1150°C, where the rate of densification during liquid phase sintering was controlled by phase boundary reaction.View full abstractDownload PDF (1636K) -
Effect of Agitation-GrindingKiyoaki Akechi, Zenshiro Hara1980 Volume 27 Issue 1 Pages 28-31
Published: January 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSEffect of agitation-grinding on the resistance-sintering characteristics of atomized aluminium powder was experimentally studied. The powder pretreated by agitation-grinding in a juice-mixer for 6 min was able to be resistance-sintered. The resistance-sintering behavior of this powder with power input less than 150 kVAC/g was similar to the powder pretreated by drying in low vacuum. But in the powder compacts resistance-sintered with power input higher than 150 kVAC/g, the end region of the specimen was melted down, while the drying-pretreated powder was able to be resistance-sintered as a sound compact with same power input. This difference was considered to be related to the difference of the distribution of oxide film in the powder compacts. Influence of agitation-grinding on the isothermal-sintering behavior of the powder compacts was also studied. Low density compacts of the agitation-ground powder showed larger shrinkage than those of the non-treated powder, while high density compacts of the former showed slower shrinkage than those of the latter. This phenomenon was discussed in connection with the formation of metallic contacts between particles in compressed compacts.View full abstractDownload PDF (2702K) -
Akio Kato, Yasuzo Okabe, Junichi Hojo1980 Volume 27 Issue 1 Pages 32-34
Published: January 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSHighly crystalline and ultrafine SiC powders with particle sizes of -0.02 μ were obtained with a high yield by the vapor phase reaction of CH3SiCl3-H2 system in a simple plasma jet reactor. The formation of SiC powders from CH3SiCl3-N2 system was difficult by the same method.View full abstractDownload PDF (1036K)
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