SIC MATRIX COMPOSITES REINFORCED WITH INTERNALLY SYNTHESIZED TIB2

A new process of preparing particulate-reinforced ceramic composites by internal synthesis has been developed. SiC powder mixed with TiN and amorphous boron was hot-pressed above 2000° C in an argon atmosphere. The boron molar content in the mixture was designed to be more than twice that of TiN. In the process of hot-pressing, the following reaction took place between 1100 and 1700° C TiN+2B → TiB2+1/2N2↑ The synthesis of TiB2 was followed by the densification of SiC matrix with the aid of the excess boron. The new process provides SiC matrix composites in which fine TiB2 particulates are dispersed. Compared with hot-pressed monolithic SiC, the composite containing 20 vol % TiB2 exhibits a 80% increase in fracture toughness and about the same flexural strength of 490 MPa at 20° C in air and 750 MPa at 1400° C in a vacuum. © 1990 Chapman and Hall Ltd.