Journal of the Society of Powder Technology, Japan

Contamination and Sinterability of Planetary Milled Alumina

Osami ABE

1993 Volume 30 Issue 8 Pages 548-555
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_548

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The contamination of planetary milled alumina powder has been studied and correlated to sinterability. The powder contained Si-and N-contaminations caused by the wear from the grinding media and mill wall made of Si₃N₄. A part of worn-out Si₃N₄ was oxidized into Si(OH)₄ by H₂O contained in CH₃OH used as the grinding liquid. The strong shear stress between the media generated during planetary milling promoted mechanochemical reactions among worn-out Si₃N₄, Si(OH)₄ and Al₂O₃ forming an amorphous reaction layer on the alumina particles. This provided possibilities of planetary milling by applying the surface modification of ceramic powders despite the problem of contamination. The surface layer containing the contaminations resulted in the formation of the mullite phase at the grain boundary during sintering. The low diffusion coefficient of the mullite phase degraded sinterability even at a contamination as low as 400ppm-Si. When the contamination increased to 0.5wt%-Si, irregular grain growth and the formation of closed pores took place, suggesting the degradation of the mechanical properties.

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The Mixing of Toner Composition and its Evaluation

Takashi TESHIMA, Naruo YABE, Keijiro TERASHITA, Kei MIYANAMI

1993 Volume 30 Issue 8 Pages 556-562
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_556

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Thermoplastic resin, carbon black and a charge control agent (materials for toner) were mixed with a stir type mixer at various mixing times. The mixing process was investigated by measuring the load current and temperature of the mixture during the mixing operation, and the state of the mixture were examined by SEM obserbvation, X-ray micronanalysis and so on.
The results showed that the following processes, that is, the crushing of resin, the deagglomeration of carbon black and charge control agent, coating the surface of the resin particles by the finer particles, and the reagglomeration of crushed resin simultaneously progressed during mixing. It was suggested that the states of the mixture obtained by pre-mixing contributed to the dispersion of carbon black and the charge control agent in the following kneading process.

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The Simultaneous Operation of Granulation, Grinding and Separation in a Continuous Tumbling Conical Granulator

On the Shape Evaluation of the Granules and Granulating Conditions

Masunori SUGIMOTO, Naoko YOKOTA, Hiroaki MIYANAGA

1993 Volume 30 Issue 8 Pages 563-569
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_563

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Small and spherical granules were made from CaCO₃-powder by the simultaneous operation of granulation, grinding and separation in a continuous rotating conical vessel. The shape characteristics of the granules were evaluated by a pair of shape indices: φ is a measure of sphericity, and ζ is that of surface roughness. φ, ζ and granule size x were plotted on three-dimensional graphs for various operating conditions of the granulator.
The result was that the increase in rotation speed of the vessel was found to be more effective in obtaining smaller and spherical granules with smooth surface. The increase in ball charge B and feed ratio W made the granules smaller and non-spherical. Longer residence time θ made the granules more spherical with smooth surface remaining x unchanged.

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The Effet of Alcohol Grinding Aids on the Ultrafine Grinding of Feldspar

Masahiro HASEGAWA, Yoshiteru KANDA

1993 Volume 30 Issue 8 Pages 570-575
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_570

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The effect of grinding aids on the ultrafne grinding of feldspar was studied by using a vibrating rod mill with a laboratory-scale. Alcohols with different alkyl groups were mainly used as the grinding aids, and all of the experiments were carried out by dry batch operation. The variations in specific surface areas of the products were investigated with grinding time and amount of grinding aid. The results showed that alcohols were effective grinding aids on the ultrafine grinding of feldspar. However, the effect of grinding aids varied remarkably with the different kinds of alcohols and the amount of alcohol added. The most effective amount of grinding aid was found to increase with the fineness of the feldspar. The effect of alcohol is considered to be caused by the increase in the flowability of feldspar powder due to the alkoxylation of hydroxyl groups on the feldspar surface.

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Evaluation of Agglomeration of Fine Particles Suspended in Water by Aerosolizing Method

Yasuo KOUSAKA, Yoshiyuki ENDO, Takahiro HORIUCHI, Chiho KAJITA

1993 Volume 30 Issue 8 Pages 576-578
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_576

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[title in Japanese]

Satoshi OKUDA

1993 Volume 30 Issue 8 Pages 588-590
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_588

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[title in Japanese]

Masanobu AWANO

1993 Volume 30 Issue 8 Pages 591-592
Published: August 10, 1993
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.30.8_591

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