Contamination and Sinterability of Planetary-milled Alumina [Translated]†
Contamination of planetary milled alumina powder has been studied and correlated to sinterability. Ground powders contain Si and N contaminations derived from the grinding media and mill pot made of Si3N4. Strong shear stress generated during...
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| Format: | Article |
| Language: | English |
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Hosokawa Powder Technology Foundation
2014-05-01
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| Series: | KONA Powder and Particle Journal |
| Online Access: | https://www.jstage.jst.go.jp/article/kona/13/0/13_1995020/_pdf/-char/en |
| Summary: | Contamination of planetary milled alumina powder has been studied and correlated to sinterability. Ground powders contain Si and N contaminations derived from the grinding media and mill pot made of Si3N4. Strong shear stress generated during planetary milling induces a mechanochemical reaction of worn-out Si3N4 with H2O contained in methanol used as a liquid medium forming hydrated SiO2 and provides an amorphous layer consisting of Si3N4, hydrated SiO2 and A12O3 on the surface of alumina particles. This suggests a possibility of applying planetary milling to surface modification of ceramic powders despite the problem of contamination. The surface layer containing the contaminations results in the formation of a mullite phase at the grain boundary during sintering. The low diffusion coefficient of mullite degrades sinterability even at a contamination as low as 400 ppm-Si. When the contamination increases to 0.5 mass%-Si, irregular grain growth and the formation of closed pores take place, suggesting the degradation of mechanical properties.† This report was originally printed in J. Soc. Powder Technology, Japan. 30(8), 548-555 (1993) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan. |
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| ISSN: | 0288-4534 2187-5537 |