Effect of Ceramic Powders on the Reaction Sintering of Ceramic/Metal Mixed Powders

Abstract

The reaction-sintered alumina and zirconia-alumina ceramics with low firing shrinkage were prepared from Al 2 O 3 /Al and ZrO 2 (C a -PSZ)/Al powder mixture by attrition milling and the effect of the characteristics of used ceramic powders was investigated. Flaky Al powders mixed with coarse alumina powders could be effectively pulverized due to high hardness of alumina powders. On the contrary fused Ca-PSZ/Al powder mixture could not be effectively comminuted due to lower hardness than alumina powders. So by using hard alumina ball media or coarse Al 2 O 3 powders rather than Al, the milling efficiency could be much more increased. After attrition milling the Al 2 O 3 /Al specimens were oxidized at 1200°C for 8 hours and followed by sintering at 1550°C for 3 hours. Because mixed powders of Al with alumina were much more effectively comminuted, more than 97% theoretical density of sintered body could be achieved. In the case of fused Ca-PSZ powder reaction-sintered with Al at 1550°C for 3 hours, the reaction-sintering and densification were a little more difficult than Al 2 O 3 /Al specimens because of the insufficient milling. And the unstabilization of Ca-PSZ body which caused the cracks in the specimens was brought by the diffusion of Ca ion from Ca-PSZ grains to alumina.