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Volume 15, Issue 4
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[in Japanese]1968 Volume 15 Issue 4 Pages 151-167
Published: June 25, 1968
Released on J-STAGE: May 22, 2009
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Testuo Tokue, Ken Ishino, Motohiko Makino1968 Volume 15 Issue 4 Pages 168-173
Published: June 25, 1968
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of calcination and ball-milling on the sintering and magnetic characteristics of iron-rich Ni.Zn ferrite is investigated. Results are summarized as follows.
It has serious effects on the properties of ferrite powder whether recrystalization is finished or not at the calcination process. When calcined above the recrystalization temperature, the average particle size of ferrite powder is closely related to the tap density, shrinkage and magnetic properties. When calcined below this temperature, however, the deviation from the above mentioned relations were observed. This is explained by the fact that in the latter a particle has more pores.
There are also close interrelations between permeability and porosity calculated from the volume and X-ray density and the characteristics of sintered ferrite itself ; with increasing porosity, μs ' and μs " become smaller but μs" is no so closely related to porosity. The product μs' × Q has a maximum value at 10-15% porosity.View full abstractDownload PDF (1449K) -
Hiroshi Yamamoto, Kazuyoshi Ueki, Noboru Ichiyama1968 Volume 15 Issue 4 Pages 174-183
Published: June 25, 1968
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe preparation and properties of ultrafine powders of tungsten, tungsten 18.7 % rhenium and thoriated tungsten (4.4% ThO2 for W) are described. The preparation consists of two processes, freeze-drying and reduction with hydrogen at relatively low temperature. According to the desired powder composition, the solution of ammonium paratungstate, the mixed solution of ammonium paratungstate and ammonium perrhenate or the solution of thorium nitrate suspending the fine particles of tungstic acid were frozen rapidly and dryed under the reduced pressure through sublimation. The products thus obtained consist of fine particles having a mean diameter of 0.3-3 microns. The more rapidly the solution was frozen, the finer the particles became. Freeze-dryed powders were reduced with hydrogen at 300-800°C. Metal particles of tungsten or tungsten alloy were obtained above 600°C, and the mean diameter was 0.02-0.1 microns. Inter-particle sintering was observed at higher reduction temperatures, resulting in larger particles.View full abstractDownload PDF (5777K) -
Hidenori Kuroki, Hideto Goto, Yoichi Tokunaga1968 Volume 15 Issue 4 Pages 184-190
Published: June 25, 1968
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThis investigation was undertaken to determine whether or not the gases are enclosed in residual pores of sintered iron. The gas analysis was carried out by the vacuum-fusion method and by the solution-distillation method.
Carbonyl iron powder contains about 1600 p.p.m. of oxygen, as oxide films on powder particles. When the powder compact was sintered in hydrogen at 1200°C, the oxide film was mostly reduced within 1 min. to produce water vapour, which desorbed through the pores to the outer surface. It was suggested, therefore, that the air or nitrogen is not enclosed in residual pores. Approximately 10200 p.p.m. oxygen were detected in sintered iron, which had been cooled to room temperature in hydrogen after sintering. These oxygen contents correspond to the variation of surface area including the inner surface of open pores, which may be explained by assuming that the inner surface of open pores was quickly oxidized in air at room temperature. However, small amounts of nitrogen were not removed by sinteririg in hydrogen.
From the above results it maybe suggested that residual pores in sintered iron contained hdyrogen of about 1 atm.View full abstractDownload PDF (517K) -
Hiroyasu Mitani, Hiroshi Sasabe1968 Volume 15 Issue 4 Pages 191-197
Published: June 25, 1968
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn the present paper the authors studied the kinetics of sintering and diffusion in the Cu-Al-Fe-Ni quaternary mixed compacts, where pure aluminium powder was not mixed but alloy powder of Al-Fe or Al-Ni binary system was used in order to prevent the exothermic expansion reported already in the previous papers, and aluminium contents were always kept 10%.
As the present work attaches special importance to examine the diffusivities of nickel contained in different types, i.e., pure nickel, 10AI.3, 7 Ni binary and electroless nickel plated Cu powders, the three different types of Cu-10Al-3, 7 Fe-3, 7 Ni quaternary mixed compacts sintered at 900°C for 1hr were subjected to the X-ray microanalyser, and then we, confirmed that the electroless nickel plated Cu powder showed the best diffusivity of nickel in the sintered compacts, followed by compacts which contained the pure nickel powder. Judging from. the results of X-ray microanalysis and from the dilatometric measurement, it may be proved that the compacts expanded in volume by diffusion of nickel.
When the electroless nickel double-plated Cu powder was used in the quaternary mixed compacts, its chemical composition automatically amounted to Cu-lOAl-6, 9Fe-6, 9Ni, where the rank of Ni-diffusivity reversed the order in Cu-10Al-3, 7 Fe-3, 7 Ni quaternary system above described.View full abstractDownload PDF (3008K) -
Teruhisa Watanabe, Kazumasa Oishi1968 Volume 15 Issue 4 Pages 198-200
Published: June 25, 1968
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (1295K)
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