Fabrication of continuous-SiC-fiber-reinforced SiAION-based ceramic composites by reactive melt infiltration

A technique for fabrication of beta ' -SiAlON-based ceramics in three-dimen sional woven fabrics of BN-coated SiC (Nicalon (TM)) fibers was developed b y reactive melt infiltration in a controlled N-2 atmosphere. beta ' -SiAlON was produced in situ by the reaction of beta -Si3N4, AlN, and Y-Al-Si-O mo lten glass. The wettability of the fibers with the molten glass was improve d by infiltration and pyrolysis of perhydropolysilazane, resulting in fully dense matrix composites. The reaction between the fiber and molten glass c ould be depressed by increasing the N2 partial pressure during the melt inf iltration. The inhibition of the interfacial reaction may be related to the formation of carbon and oxynitride on the SiC fiber, in agreement with the rmodynamic calculations as a function of N2 partial pressure. The fabricate d composites had a high ultimate flexure strength and a large work of fract ure at room temperature. Degradation of the mechanical performance of the c omposites was small, even at 1773 K in an argon atmosphere.