Advanced technology for fabrication of reaction-bonded SiC with controlled composition and properties

Abstract

An advanced fabrication technology of reaction-bonded SiC is developed, which includes the preparation of a C/SiC preform by repeated cycles of phenolic resin impregnation and pyrolysis, followed by infiltration with silicon melt. The use of different number of impregnation stages provides control of carbon content in the preform and the corresponding SiC content in final ceramics. The effect of the impregnation number on the preform characteristics and ceramics composition, thermal and mechanical properties are investigated comprehensively. With an increase of impregnation number up to four, SiC fraction in the ceramics enlarges to 93 vol%, thermal conductivity and Young’s modulus increase to 186 W/(m∙K) and 427 GPa respectively, which are superior to most reaction-bonded SiC. Flexural strength (225 MPa) and thermal expansion coefficient (2∙10−6 K-1) are not dependent on the impregnation number. The obtained results provide an opportunity to design and fabricate reaction-bonded SiC ceramics with a given set of properties.