All issues
Volume 18, Issue 5
Displaying 1-4 of 4 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kenzo Hijikaka1972 Volume 18 Issue 5 Pages 163-174
Published: January 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe isothermal shrinkages of high purity SnO2, ZnO, TiO2 (rutile) and α-Al2O3 powder compacts with varying oxygen partial pressure (total pressure : 1 atm) have been measured by means of a shrinkage-meter with which linear dimentional changes could be continuously observed. Changing oxygen partial pressure in the sintering atmospheres, there was observable effect on shrinkage rates of these oxides. SnO2: The slow shrinkage of SnO2 in a nitrogen atmosphere would appear to be due to a volatility of SnO, rather than an oxygen deficient structure of SnO2 at temperatures ranging from 1200°C to 1350°C. ZnO: The shrinkage of ZnO may be enchenced by increasing interstitial zinc concentration with decreasing oxygen partial pressure at the sintering temperature of 850-1000°C. TiO2 : If a defect structure of n-type rutile involves oxygen vacancies, the shrinkage rate of n-type rutile powders may be accelerated by increased concentration of oxygen vacancies in a nitrogen atmosphere at900-1050°C. α-Al2O3: The shrinkage rate seems to be promoted by oxygen vacancies resulted from oxygen uptake in an argon atmosphere at tem-peratures ranging from 1000-1500°C.View full abstractDownload PDF (927K) -
Tadaaki Aoyama1972 Volume 18 Issue 5 Pages 175-180
Published: January 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn order to determine the final tapping density, we examined the tapping characteristics of samples of tungsten and other metal powders for powder metallurgy by using the tapping apparatus of cam-type.
Results obtained are as follows:
(I) The equation of hyperbolic relation is applicable for the tapping range of more than 10 numbers.
N/V=p+qN
where, N: tapping numbers(max 1000), V: bulk volume, p, q: constant
(2) The gradient of the decrease in porosity a against the increase of tapping numbers N is shown below.
-dε/dN=k1/N2
(3) The infinite bulk volume V∞ having the value V=1/q of the asymptote can be adopted for the final bulk volume.
(4) Concerning the tungsten metal powder
a. The variance in the value of V- is smaller variance than that of V100 and V1000.
b. The good correspondence was observed between T. D.- and mean particle size, and also T. D.100 and apparent density (A. D.).
c. There was founded out the different production method from the T. D.∞/A. D. (Hausner ratio).
d. It has been frequently observed the broken line in the N/V vs. N relation. This reason is considered to be depended upon that the aggregates are broken.View full abstractDownload PDF (1627K) -
Mechanochemistry of the Sintered BodyOsamu Yamaguchi, Masanori Yasumoto, Kiyoshi Takeoka, Kiyoshi Shimizu1972 Volume 18 Issue 5 Pages 181-186
Published: January 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIt is the purpose of this study to obtain the foundamental information of non-stoichiometric PZT powders in the pulverizing process by wet method. The effects of wet pulverizing by ball-milling (for 150 hrs.) on the structural properties of the powders have been studied by thermobalance, X-ray diffraction and some other methods.
The following results were obtained.
(1) The weight of the specimens pulverized for a long time decreased continuously up to 900°C, due to the discharge of the bonding water caused by the mechano-chemical reaction between PZT and water by wet pulverizing.
(2) The crystallite dimension of the powder decreased remarkably for 25-50 hours. The lattice distortion, however, increased gradually with decreasing the crystallite dimension and this was not recovered to the original stage by heating up to 900°C for the specimen pulverized for 150 hours.
(3) The layer of the bonding water penetrated gradually to the inner part of grains from the surface with increasing of the pulverizing time. From this result, it was found that the unfarorable effects on the properties of PZT appeared by such a long pulverizing time.
(4) As a result of calculating the number of OH radical by assuming that the weight loss at 150-900°C is due to the bonding water, the number of OH radical increased with increasing of the pulverizing time, and it attained nearly constant values after 100 hours.
(5) Judging from the above mentioned results, the bonding water seemed to be not only the adsorbed water on the surface of PZT particles but also the water which penetrated into PZT grains, and formed the hydrogen bonding with the parts of oxygen ion.
(6) After the long time pulverizing, the aggregation or agglomeration of the primary particles occurred and resulted in the growth of the secondary particles.View full abstractDownload PDF (1689K) -
Sukeji Kachi, Norihiko Nakanishi, Hiroshi Sugiyama, Akira Kani, Yoshiy ...1972 Volume 18 Issue 5 Pages 187-196
Published: January 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis report is a summary of our past five years experiments on the crystal growth in gels.
A technique for the growing of crystals in silicate gels was attempted. By controlling the softness and pH values of the gel at room temperature, various kinds of organic salt-crystals were grown. Acicular or needle-like crystals of Cu and Ni-oxalates and Ba-tartrate, granular or globular crystals of Fe and Co-tartrates, and single crystals of Ca, Sr, Cu and Mn tartrates were obtained. In particular, by means of the "double-layer technique" using the tube-method (T-method), the authors have attempted to enlarge a seed crystal to a larger single crystal. The growth behaviours in gel which concern the present experiment have been discussed in terms of "nucleation and growth" mechanism.View full abstractDownload PDF (4753K)
- |<
- <
- 1
- >
- >|