Near‐Net Shape β‐Si 4 Al 2 O 2 N 6 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 β‐Si 4 Al 2 O 2 N 6 ceramics from aqueous slurries containing 48–50 vol%α‐Si 3 N 4 , α‐Al 2 O 3 , AlN, and Y 2 O 3 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 β‐Si 4 Al 2 O 2 N 6 crucibles and tubes. Before use, the as purchased AlN powder was passivated against hydrolysis. The sintered β‐Si 4 Al 2 O 2 N 6 ceramics exhibited comparable properties with those reported for similar materials in the literature.