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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.
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.
Contamination and Sinterability of Planetary-milled Alumina [Translated]†
Osami Abe (author)
2014
Article (Journal)
Electronic Resource
Unknown
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