Near-Net Shape beta-Si4Al2O2N6 Parts by Hydrolysis Induced Aqueous Gelcasting Process

In this paper, a new net-shaping process, an hydrolysis-induced aqueous gelcasting (GC) (GCHAS) has been reported for consolidation of beta-Si4Al2O2N6 ceramics from aqueous slurries containing 48-50 vol% alpha-Si3N4, alpha-Al2O3, AlN, and Y2O3 powders mixture. Dense ceramics of same composition were also consolidated by aqueous GC and hydrolysis assisted solidification routes. Among three techniques used, the GCHAS process was found to be superior for fabricating defect-free thin wall beta-Si4Al2O2N6 crucibles and tubes. Before use, the as purchased AlN powder was passivated against hydrolysis. The sintered beta-Si4Al2O2N6 ceramics exhibited comparable properties with those reported for similar materials in the literature.