All issues
Volume 19, Issue 4
Displaying 1-5 of 5 articles from this issue
- |<
- <
- 1
- >
- >|
-
Yoshiharu Ozaki, Sinroku Saito1972 Volume 19 Issue 4 Pages 137-141
Published: September 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe vibratory compacting of alumina powder has been investigated using a mechanical vibrator. In order to form small spherical granules, the almina powder is spray-dried with 6% waxes which induces a plasticity.
The results are as follows:
(1) Compacting pressures could be greatly reduced by applying vibration to both a die assembly and a loading weight.
(2) The maximum effect for the green density was observed in the first few seconds of vibration and after that the density of the vibratory compact increased gradually with vibration time.
(3) After 5 seconds, the vibratory compact reached a sufficient green strength to permit easy handling.
(4) The hardness of the sintered compact increased with the loading weight or the green density of the compact.
(5) In this technique the density variations of the green bodies was not improved, which gives an important problem in the conventional die compacting.
(6) When the vibratory compact was treated with isostatic pressing, the lower the green density, the harder the sintered compact was.
The application of the vibratory compacting to a production of powder pre-forms for the isostatic pressing is also discussed.View full abstractDownload PDF (1486K) -
Kiyoshi Okazaki, Kunihiro Nagata, Hitoshi Saeki1972 Volume 19 Issue 4 Pages 142-147
Published: September 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe transparent piezoelectric ceramics were prepared by hot-pressing the Pb(Zr.Ti)O3 containing small at% of various oxides. As additives, La2O3 and Bi2O3 increased the transmittance, La2O3 and Sb2O3 decreased the coercive field and gave a hysteresis loop with fairly square form, and Sb2O3 and WO3 improved the piezoelectric properties.
The average grain diameter of a composition of s(Pb0.92La0.08) (Zr0.65Ti0.35)O3 was controlled by the hot-pressing conditions such as hot-pressing temperature, pressure, time, and annealing temperature and time. For these specimens, the electrical and optical properties were examined as a function of the average grain diameter. In conclusion, the electrical constants such as dielectric constant, coercive field, remanent polarization were changed linearly against logarithm plot of the grain diameter. On the other hand, the optical constants such as transmittance, reflectivity showed a maximum or minimum at a grain size range of 2.5-3.0μm. The reason why the transparency is decreased at larger grain size region seems to be caused by the enhancement of the impurity concentration on the grain boundaries accompanying the grain growth.View full abstractDownload PDF (323K) -
Properties of Pb2O (OH)2 PowderOsamu Yamaguchi, Kazuharu Miwa, Haruo Suzuki, Kiyoshi Shimizu1972 Volume 19 Issue 4 Pages 148-156
Published: September 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe thermal decomposition process of Pb2O(OH)2 and the phase transformation of the decomposed PbO were studied by using T.G.A., D.T.A. and X-ray diffraction.
The thermogravimetric curves of the samples heated in air, nitrogen and vacuum showed the three stages in the decompostition process and in the oxygen atmosphere the four stages. The temperature of the complete dehydration shifted to higher with increasing the partial pressure of the oxygen. apparent activation energy and the reaction order for the dehydration process in the various atmospheres were determined as follows.
The rate constants for the three dehydration stages in air were represented by K= 107.4 exp (-17000/RT), K = 108.5 exp (-28000/RT) and K = 1016 exp (-45000/RT), respectively.
The phase transformation from litharge to massicot was the second order reaction. The rate determining step of this transformation may be linear growth of the new phase of massicot and the apparent activation energy was about 58 kcal/mol.View full abstractDownload PDF (1615K) -
Hiroyasu Mitani, Kazuhiko Majima1972 Volume 19 Issue 4 Pages 157-163
Published: September 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt has been often observed that the mixed powder compacts of multi-components begin to expand from a definite temperature during heating process, and one of the authors has explained these phenomena mainly due to the phase transformation mechanism. However, we observed that the Cu-Ni binary mixed powder compacts expanded from about 600°C during heating process, where the solid Cu and Ni are soluble each other in all range, while any explanation has not yet been established about the meaning of this temperature. In order to investigate this problem, the authors carried out the present work by means of the dilatometric methods by using the Cu-Ni mixed powder compats with different contents, where the pure Cu and Ni powders, the electroless Ni plated Cu powder, the Cu-Ni prealloyed powder, and the electroplated specimen of Cu and Ni in alternate layers were used. The results obtained are summarized as follows.
(1) The Cu-Ni binary mixed powder compacts expanded from about 600°C independently of the heating rate, the compacting pressure, and the particle size.
(2) The multi-layers specimen made by the alternative electroplate of Cu and Ni expanded gradually from 500°C followed by abrupt expansion from about 600°C.
(3) The specimen consisted of the Cu-Ni prealloyed powders and the carbonyl Ni powders showed a higher temperature expansion with the increase of Ni content in the Cu-Ni prealloyed powder, i.e. 650°C for Cu-5%Ni alloy powder, and 680°C for the Cu-10%Ni alloy powder.
(4) In the model experiment by using the synthetic Cu and Ni wire compacts sintered at 600°C for 48 hours, some pores were found on the Cu side. Judging from the Kuczynski's interpretation, it may be considered that the pore formation originates from the Kirkendall diffusion.View full abstractDownload PDF (3287K) -
Toranosuke Kawaguchi, Hiroshi Yamamoto1972 Volume 19 Issue 4 Pages 164-171
Published: September 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSStudies on magnetic properties of intermetallic compounds of 3d-transition elements and metals of rare-earth (R) have been carried out by many workers. The authors have investigated previously the effect of composition and heat-treatment on magnetic properties of cast (Ce-MM)-Co-Cu alloys and proposed the new process of "High-temperature heat treatment", by which the remarkably improved higher magnetic properties were obtained.
This experiment was carried to produce (Ce-MM)-Co-Cu alloys by means of powder metallurgy. The effects of particle size distribution, pressing pressure, sintering temperature, and sintering time on magnetic and physical properties of the sintered compacts were examined. Some properties of a typical sample are as follows : 4πI15K = 4200 G, 4πIr, = 4180 G, IHC = 4500 Oe, BHC = 3600 Oe, (BH)max = 4.2 MG-Oe, D = 8.0 g/cm3, and Hv = 639. The condition to reach the above properties was such that ball milling time for 5 hr, pressing pressure of 4t/cm2, sintering temperature at 1200°C, sintering time for 2 hr, and sintering atmosphere of Ar gas.View full abstractDownload PDF (2665K)
- |<
- <
- 1
- >
- >|