All issues
Volume 30, Issue 1
Displaying 1-6 of 6 articles from this issue
- |<
- <
- 1
- >
- >|
-
Koichi Haneda, Hiroshi Kojima, A.H. Morrish1983 Volume 30 Issue 1 Pages 1-5
Published: January 25, 1983
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSNiFe2O4 small particles (in the few hundred angstrom size range and up) have been prepared by a chemical precipitation method and subsequent heat treatments, and their magnetic properties have been explored in particular reference to their magnetic structure for its smallness of the particle size. The magnetic moment at low temperatures is appreciably lower than the value reported for bulk material. Mossbauer spectra, obtained with a longitudinal high magnetic field applied, unambiguously establish that a non-collinear structure exists that is most pronounced for the smallest particles. The analysis indicates that a surface effect of the crystallites which make up a particle is the origin of this phenomenon.View full abstractDownload PDF (2355K) -
Mamoru Senna, Hiroshi Kuno1983 Volume 30 Issue 1 Pages 6-11
Published: January 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSReactants of NiO-MoO3 binary solid state reaction are preliminary ground either separately or together in air (dry) or in cyclohexane (wet) by a laboratory vibro-mill. Subsequently, the rate of nickel molybdate formation on heating at 600°C in air was determined by applying Dander rate equation. Dry grinding of NiO followed by an intimate mixing with MoO3 and by wet co-grinding brought the highest rate, due to the large amounts of lattice imperfections introduced into NiO. Preliminary grinding of MoO3, on the other hand, was effectiveless, because of high degree of agglomeration which hinders the intimate mixing on subsequent wet vibromilling. Dry co-grinding was also effective, although less amounts of lattice im-perfections are introduced, compared with dry separate grinding, presumably because of originating precursory products at the contact points of foreign reactant particles during grinding.View full abstractDownload PDF (1720K) -
Effects of Sintering Atmosphere on the Magnetic Properties of Sm(Co, Fe, Cu)7 Permanent Magnet AlloyNaoyuki Ishigaki, Kazuhiko Majima1983 Volume 30 Issue 1 Pages 12-20
Published: January 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSm (Co, Fe, Cu)7 powder compacts were sintered in three different kinds of sintering atmospheres; i.e., hydrogen, argon and vacuum of 10-5 Torr.
The remarkable contraction due to the liquid phase sintering occured at a sintering temperature higher than 1220°C, where the amount of shrinkage increased in the order of argon, vacuum and hydrogen atmos-phere.
Higher density specimen were obtained and the alignment ratio of the grains was successfully improved by the sintering in hydrogen atmosphere.
Therefore the use of the hydrogen atmosphere led to enhance the resultant magnetic properties of Sm(Co, Fe, Cu)7 permanent magnet alloys.View full abstractDownload PDF (5800K) -
Hisashi Suzuki, Koji Hayashi, Yoshio Takashima, Naomi Namiki1983 Volume 30 Issue 1 Pages 21-24
Published: January 25, 1983
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe WC-β-Co alloys having several amounts of nitrogen were prepared by using WC-TiC-TiN solid solution (named β(N); nitrogen content, about 4%), and sintering in vacuum or in nitrogen gas of up to 10kPa. Some properties of alloys such as microstructure, lattice parameter of binder phase or β(N) phase, and transverse-rupture strength, etc., were studied. It was noted that the strength of alloys tended to decrease with increasing nitrogen content of β(N) in the alloy; however, the strength after HIP was excellent, when the nitrogen content of β(N) was less than about 3%.View full abstractDownload PDF (1440K) -
Hisashi Suzuki, Koji Hayashi, Naomi Namiki1983 Volume 30 Issue 1 Pages 25-28
Published: January 25, 1983
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTwo sorts of green compacts were made by using β(WC-TiC solid solution) and β(N)(WC-TiC-TiN solid solution containing 4.2%N) starting powders. They were nitrified at 1523 K in N2 (nitrogen atmosphere) of 2.7-20kPa and subsequently sintered at 1673-1873 K in N2. The microstructure, hardness, transverse-rupture strength, etc., of sintered compacts were studied.
Fine WC particles were precipitated from f or β(N) when β or β(N) compact was. nitrified, resulting in the mixture of nitrogen contained i and WC phases. The dense compacts were obtained when the mixture was sintered at temperature above about 1823 K. The compact prepared by using β(N) powder showed in particular a very high hardness and an excellent transverse-rupture strength.View full abstractDownload PDF (2936K) -
Microstructure and Mechanical PropertyKiyoaki Akechi, Kenzo Hanawa, Takeo Nakagawa1983 Volume 30 Issue 1 Pages 29-35
Published: January 25, 1983
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe mechanism of graphite nodularization and how to control graphite morphologies in sintered products of cast iron swarf powder, Fe-Si-C mixed powders, or Ni-C mixed powders have been investigated.
When the powder contains carbon less than the maximum solubility at the given sintering temperature, all carbon atoms dissolve in solid solution (γ-Fe or Ni-phase) during sintering and precipitate as the graphite into the pores during cooling. Consequently, if the pores in the sintered products are spherical by long-time sintering or powder forging processes, spherical frames for the graphite to grow in nodular morphology, can be provided. Then for example, the products (Imass%C) made from mixtures of cast iron swarf powder and reduced iron powder show the high tensile strength of 95 kgf/mm2 by long-time sintering (1150°C⋅20 hr).
On the other hand, when carbon contents are more than the maximum solubility, no nodular graphite can be obtained because of residual undissolved graphite.View full abstractDownload PDF (7133K)
- |<
- <
- 1
- >
- >|