All issues
Volume 23, Issue 4
Displaying 1-6 of 6 articles from this issue
- |<
- <
- 1
- >
- >|
-
[in Japanese]1976 Volume 23 Issue 4 Pages 125-131
Published: June 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (4597K) -
Hisashi Suzuki, Teruyoshi Tanase, Fumio Nakayama1976 Volume 23 Issue 4 Pages 132-136
Published: June 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSTwo sorts of alloy systems, WC-TiC-16vol%Co and WC-TaC-l6vol%Co alloys having various amounts of TiC or TaC, were vacuum-sintered at 1400°C for 1 hr. The transverse-rupture tests were conducted according to JIS. The effect of addition of carbides on the strength of WC-16vol%Co alloy was studied, assuming that the strength is in close relation to the structural defects in sintered alloys. The method for the strength-analysis was the same as that previously reported by the present authors in WC-Co alloy.
The results obtained were as follows: (1) The strength of the present alloys was also confirmed to be directly controlled by the structural defects, in the same way as in WC-Co alloy. The defects such as pores, carbide-agglomerates and somewhat peculiar defects were generally observed in this case; the latter two sorts of defects were different from those developed in WC-Co alloy. (2) The strength of sound matrix (ao) (having none of defects) in WC-16vol%Co alloy decreased markedly by a small amount of TiC(TaC) addition, however the value of ao was assumed to be nearly the same in both the alloy systems under the same volume percentage of the β (TiC-WC solid solution) and TaC phases. It was also assumed that ao has values of about 300-450 kg/mm2 when the percentage exceeded about 20 vol%.View full abstractDownload PDF (1889K) -
Takajiro Shimohira, Noboru Tomuro1976 Volume 23 Issue 4 Pages 137-142
Published: June 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFrom Si(OC2H5)4-NH3-H2O-C2H5OH system, monodispersed suspensions of spherical silica particles of colloidal size were prepared by means of hydrolysis of tetraethyl silicate.
Several attempts to produce silica spheres under the same experimental condition showed that a very narrow size distribution was always reproduced in each attempt, but it was not easy to obtain a constant median diameter.
In general, larger particles were grown during aging at a lower temperature and at a higher ester concentration, but these factors had no influence on their standard deviations.
An electron microscopic investigation of a series of samples were taken at different times from the same solution indicated that the spherical secondary particles were formed by coalescence of irregular shaped primary particles of a few hundreds Å diameter.
X-ray diffraction pattern showed that the spherical particles were amorphous just like a silica gel, and no crystallization has been observed even if they were heated at 1000°C for 7 hr in air. Although differential thermal analysis curve of the particles was the same as those obtained from silica gel, there was a slight difference in an amount of weight loss during heating, which might be attributed to a different amount of physically absorbed water.View full abstractDownload PDF (2839K) -
Osamu Yamaguchi, Hichiro Omaki, Kiyoshi Takeoka, Kiyoshi Shimizu1976 Volume 23 Issue 4 Pages 143-148
Published: June 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe chemical properties of boemite gel prepared by alkoxy-method were studied by means of differential thermal analysis, thermogravimetric analysis and X-ray diffraction.
1) When boemite gel was heated in air at an atmospheric and reduced pressures, it was converted into a-Al2O3 via the following steps.
boemite gel→amorphous alumina→γ-A12O3→θ-Al2O3→a-A12O3
2) Boemite gel, in the case of sample weight 1 g, was easily converted into amorphous alumina gel by grinding in air, but this amorphous alumina gel did not change in spite of grinding for 250 hrs. On the other hand, the ground amorphous alumina gel was directly converted into α-Al2O3 at 990°C by heating.
3) In the conversion to α-Al2O3 through θ-Al2O3 from γ-Al2O3, the nucleation process may be the rate-determining step. The apparent activation energy for this process was about 115 kcal/mol.
4) Reactions of γ-Al2O3 and α-Al2O3 with ZnO were fitted to Dander's equation. At 850°C, the reaction rate constant of ZnO-γ⋅Al2O3 system was found to be about eighty six times as large as that of ZnO-a⋅Al2O3 system. The activation energies of ZnAl2O4 formation in ZnO-γ⋅Al2O3 system and ZnO-α⋅Al2O3 system were about 51 kcal/mol and 88 kcal/mol, respectively.View full abstractDownload PDF (1519K) -
Junjiro Takekawa, Yoshimichi Masuda1976 Volume 23 Issue 4 Pages 149-153
Published: June 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe radial stress in the cylindrical compact of iron and copper powders of different characteristics during compaction has been evaluated by the indirect method, measuring the elastic strain of the steel die, and the following results have been obtained.
1) In pressing process the slope of the curve for the relation between the average axial and the average radial stress increases with increasing the average axial stress and gradually approaches to the unity.
2) By lubricating the powders with 0.5 wt% of zinc stearate, the sliding motion of the particles in the powder mass is kept up to the higher densification stage and the average radial stress is considerably reduced.
3) In unloading process after compaction, the reduction rate of the average radial stress is larger than that of the average axial stress at the outset of unloading and the curve for the relation between the average axial and the average radial stress does not coincide with that for pressing process.
4) The value of residual radial stress after complete unloading is varied with the class of powder but independent of the lubrication.View full abstractDownload PDF (342K) -
1976 Volume 23 Issue 4 Pages 154-155
Published: June 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (158K)
- |<
- <
- 1
- >
- >|