Effect of Powder Characteristics on Centrifugal Slip Casting of Alumina Powders

Abstract

Two kinds of alumina powders, having different particle size and impurity level, were centrifuged and effects of powder characteristics on the compaction process studied. The powder having a larger particles size and higher impurity level could be dispersed to a higher solid loading (maximum 60% solid loading) with a smaller amount of dispersant addition than the powder having a smaller particle size and lower impurity (maximum 44% solid loading). After centrifugation, a higher packing density was attained for a slip with higher solid loading up to 56%, beyond which the packing density dropped slightly. Mass segregation was negligible in the compact obtained from slips of high solid loadings, namely the 56 vol. % suspension for the coarse powder and the 44 vol.% suspension for the fine powder, respectively. However, a packing density gradient was observed in the green compacts, where the density decreased linearly from bottom to top of the cakes, but the gradient was smaller for the fine powder. The fine powder showed superior sintering and mechanical behaviors as compared to that of the coarse powder.