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Volume 16, Issue 7
Displaying 1-5 of 5 articles from this issue
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Physical Structure and Active Center in Supported Nickel CatalystTakayasu Shirasaki, Hitoshi Shimizu, Shigeaki Sakamoto, Akikatsu Kitah ...1970 Volume 16 Issue 7 Pages 291-295
Published: February 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSConfigurational and the physical structures of supported nickel catalysts were observed with electron microscope and the texture of catalytic active center was examined by observing carbon films deposited in catalytic cracking of ethylene. Results obtained are as follows.
1. Supported nickel particles were either (a) chain-like or(b) granular. The chain-like particles (a) consisted of many crystallites, whereas most granular particles (b) consisted of a single crystallite.
2. The nickel particles supported on a clear fused-silica surface had two kinds of catalytic active centers. The one was high-active center formed only on (a), and the other was moderate-active center formed on the border between the nickel particles of (a) or (b) and the silica support.
The former sintered easily but the latter was resistant to heat treatment. It is thus concluded that the catalytic surface of supported nickel particles is heterogeneous, and the active centers correspond to the various kinds of lattice deformation produced in the catalyst crystals.View full abstractDownload PDF (6408K) -
Treated Copper PowderA.S. Reshamwala, G.S. Tendolkar1970 Volume 16 Issue 7 Pages 296-304
Published: February 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThis paper attempts to investigate the mechanism associated with the densification of compacts made from (a) pure copper powder and (b) copper powder treated with aqueous formic acid prior to compaction. Isothermal sintering was carried out in hydrogen atmosphere in the temperature range 775°to 950°C. It has been proposed that densification in compacts made from formic acid treated powders occurs mainly by plastic flow aided by evaporation condensation mechanism. The conclusion is based on kinetic data supported by studies on linear shrinkage, variation in porosity and microstructural changes. For pure (untreated) powder compacts the mechanism associated with densification is confirmed to be volume diffusion.View full abstractDownload PDF (1204K) -
Tatsuo Satoh, Tsukasa Tajima, Naohisa Kohtaki, Teruhisa Watanabe1970 Volume 16 Issue 7 Pages 305-309
Published: February 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSGenerally, the compacting speed of a industrial oil hydraulic press in powder metallurgy lies from 5 to 150 mm/sec.
This report presents the relations between the compacting speed and the green density of compacts made from mill-scale reduced iron powder, as compacted in a single direction under the several maximum compacting pressures of 3.6, 4.6 and 5.6 t/cm2.
Results obtained are as follows :
1) The compacting speed has a close relation to the green density. The green density increased almost linearly with increasing compacting speed. This might be explained as due to the decrease in friction force between the green compact and the die-wall, which resulted from the increase of the compacting speed.
2) The above tendency is associated with the maximum compacting pressure also the effect of compacting pressure is more remarkable for lower compacting pressure. The green density is not influenced by the compacting speed at higher compacting pressure, say, 5.6 ton/cm2.View full abstractDownload PDF (1613K) -
Akio Hara, Takeshi Nishikawa, Tatsuya Nishimoto1970 Volume 16 Issue 7 Pages 310-313
Published: February 25, 1970
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSElectropolishing of multiphase materials, for example, of the WC-Co hard metal, is very difficult. Therefore only a few examples of the transmission electron micrograph of the WC-Co hard metal have been published. In this paper the preparation method of the foil was described and some micrographs are shown. Subgrain boundaries and dislocations were observed in WC phase, and many stacking faults, in Co phase.View full abstractDownload PDF (2603K) -
Takao Kawakita, Sukeaki Kabayama, Kenya Motoyoshi1970 Volume 16 Issue 7 Pages 314-320
Published: February 25, 1970
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIn order to find the best way of adding Cr to sintered ferrous material, the authors investigated the fundamentals of the manufacturing process and the properties of the sintered chromium steel of the system Fe-Cr-C. Three kinds of chromium containing powders, metallic chromium, ferro-chromium and σ (sigma)-phase Fe-Cr powders, were used as a source of chromium for Fe-Cr-C alloys. The mixtures of iron powder, chromium-containing powder and carbon were compacted at 5t/cm2, pre-sintered for lhr at 750°C and sintered for lhr from 1100 to 1320°C. The results obtained are as follows.
(1) Sintered chromium steels made from the σ-phase powder have the best properties of those from three kinds of chromium-containing powders. For example, the Fe-5% Cr-0.5%C alloy from σ-phase powder which was sintered at 1300°C has sintered density of 7.45g/cm3, tensile strength of 95kg/mm2, hardness of 110 HRB and elongation of 1.0%. The metallographical investigation showed that this alloy has a homogenized martensitic microstructure.
(2) The properties of sintered chromium steel made from σ-phase powders, containing 1.5-10.5% chromium and 0-1.0% carbon are as follows: the sintered densities range from 7.36 to 7.50g/cm3, the tensile strength varies from 50 to 110kg/mm2, and the elongation from 0.6 to 120%.
Microstructures of the as-sintered alloys depend on the Cr-content. The martensitic structures are found for more than 5% Cr. This phenomenon can be attributed to the self-hardenability of the Cr element. The properties the above mentioned alloys are in good agreement with those of ordinary cast wrought chromium steel.View full abstractDownload PDF (4066K)
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