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Volume 23, Issue 7
Displaying 1-5 of 5 articles from this issue
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Tetsuo Kato, Katsushi Kusaka1976 Volume 23 Issue 7 Pages 217-223
Published: October 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe objective of the present work was mainly to study the pressing and sintering behavior of water atomized 17/25% Cr stainless steel powders containing Ni less than 20%.
The results were summarized as follows.
(1) Compressibility of powders got higher in proportion to an increase of Ni and a decrease of Cr, almost independently of phase constitution of particles.
(2) Compressibility was not improved by heat-decomposing a metastable (Delta-)ferrite which had been obtained during water-quenching, except the case where the α single-phase powder was annealed below 900°C.
(3) Green strength of compacts tended to be higher in an α-rich duplex phase range, mainly due to the roughness of surface of particles.
(4) Sinterability was appreciably affected by phase constitution of particles and in particular, proved to be higher in the α-rich duplex phase state in the case of Ni-varied 25%Cr steel powders.View full abstractDownload PDF (3081K) -
Hisashi Suzuki, Koji Hayashi, Tsutomu Yamamoto, Wan Jae Lee1976 Volume 23 Issue 7 Pages 224-229
Published: October 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe transverse-rupture strength (σm) and the strength (σ0) of the sound matrix free from structural defects of TiC-(0, 20)%Mo2C-(0-30)%TiN-20%Ni alloys were investigated at room temperature as a function of the amount of additional titanium nitride (TiN).
The results obtained were as follows: (1) The effects of TiN addition on the carbide grain size, σm and σ0, were found to be negligible in TiC-20%Ni alloy, while remarkable in TiC-20%Mo2C-20%Ni alloy. (2) In TiC-Mo2C-TiN-Ni alloys, additional TiN generally formed carbonitride with TiC and Mo2C around TiC particles, and decreased the grain size of carbonitride including TiC core with increasing TiN contents up to about 15%TiN. The σ0 value increased with increasing TiN contents and attained to a maximum at this TiN content. The σm, value, however, decreased with increasing TiN contents, owing to the increased dimension of defects which acted as a fracture source. From the results, it was estimated that σm, for example, of TiC-20%Mo2C-15%TiN-20%Ni alloy would exceed about 290 kg/mm2 (according to JIS) when the dimension of defects is decreased to values of about 5μ in average. Brief consideration was also given as to the results mentioned above.View full abstractDownload PDF (4714K) -
Yasuo Mihashi, Hiroshi Ito, Takenobu Iida, Kunio Iitoyo1976 Volume 23 Issue 7 Pages 230-234
Published: October 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSProcessing method of sintered electrodes for mercury vapour lamps was investigated. The results obtained were as follows:
A mercury vapour lamp with sintered electrode exhibited a lower high frequency interference, a lower required ignition voltage and a longer life compared with that with spiral electrodes previously used.
These effects are caused by the fact that a lower thermal conductivity and much greater amount of emitter materials are obtained in the sintered electrode compared with the characters involved in the spiral electrode.
Because of the application of powder metallurgical method, sintered electrodes with good quality can be readily and economically manufactured.View full abstractDownload PDF (4271K) -
Masaaki Miyamoto, Tetsuo Suzuki, Masumi Kindaichi, Junichi Shinohara, ...1976 Volume 23 Issue 7 Pages 235-241
Published: October 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA series of phenomena have been encounted by implying negative resistance, conductive switching and memory switching effects in the sintered α-Fe2O3 with the conductive path formed by electrical breakdown. In the conductive path, are always seen some cracks perpendicular to the current flow direction which seem to play an important role for the memory switching phenomena. The variation of the phase in the path, however, has not been detected by a direct method. To clarify the role of the path or its cracks, several kinds of samples were subjected to the measurements of their electrical properties accompanied by the successive cycles of heating and cooling. It was recognized that Fe2O4 samples quenched from the temperature over the region of the dissociation of α-Fe2O3 showed the same properties as switching samples'. The formation of conductive path, its construction, and their role have been discussed. In the conductive path some α-Fe2O3 can be partially reduced to Fe2O4 and the origin of the memory switching effects may be due to the reoxidized layer around the contact in the crack.View full abstractDownload PDF (2003K) -
Mikio Matsuura, Michio Matsuoka1976 Volume 23 Issue 7 Pages 242-249
Published: October 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper is concerned with the humidity dependence of resistivity of potassium-modified ferric oxide ceramics which show the bulk-type sensitivity for ambient humidity. The potassium-modified ferric oxide ceramics show remarkable dependence of resistivity on humidity, especially in low humidity range less than 50% relative humidity and at an ambient temperature from 0°to 100°C. The effects of composition, sintering temperature, microstructure, and reaction product on humidity dependence of resistivity are discussed. The sensitivity on humidity is due to ionic conductivity in or on, small. grains of potassium-(β+β") hematite caused by adsorption of diffused moisture through the pore of sintered discs.View full abstractDownload PDF (1566K)
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