In situ reaction synthesis of silicon carbide-boron nitride composites

SiC-BN composites were prepared via the proposed in situ reaction, which us ed Si3N4, B4C, and carbon as reactants. Adding SiC powder to the reactants controlled the BN content in the composite. For comparison, SiC-BN composit es with the same phase compositions were produced via conventional processi ng. The in situ process was advantageous for obtaining better composites wi th fine grain size and homogeneous microstructures. The in situ composite t hat had a BN content of 53.71 vol% exhibited considerably high strength (34 2 MPa) and a very low elastic modulus (107 GPa). The SiC-25-vol%-BN in situ composite had a peak strength of 588 MPa, which was 95% of that of monolit hic SiC; however, the elastic modulus was as low as half that of monolithic SiC. These irt situ SiC-BN composites can be expected to have excellent th ermal shock resistance and mechanical strain tolerance.