Pore Size Distribution of Cast, Compressed and Lightly Sintered Alumina with Preliminary Mechanical Treatments

Abstract

Effects of various mechanical pre-treatments and grinding aids on the pore structure of cast green compacts with and without post-compression, and lightly sintered body of alpha alumina were studied. Alumina powders were mechanically activated by a vibration mill, using grinding balls made of polyamide-coated steel (PS) and sintered Si3N4 (SN). Milled products were redispersed by subsequent wet grinding with and without an additive, dextran. PS balls brought about compacts and sintered bodies denser than those treated by SN balls. Wet-grinding and redispersion by a centrifugal ball mill with dextran resulted in by far a better dispersion and hence denser compacts. Dextran lead to the smaller average pore, but broader pore size distribution. The preferential importance of state of dispersion in the green compacts over the mechanical activation was revealed in the present system.