Effect of SiC content on properties of reaction sintered SiC-Si₃N₄ composites

Four groups SiC-Si₃N₄ composites with 10%, 30%, 50% and 70% SiC respectively were prepared by 200 MPa cold isostatic pressing and then in-situ sintering at 1 395°C in nitrogen atmosphere (P_N2=1. 25 MPa) with industrial Si powder (≤0.044 mm) and α-SiC powder as starting materials, while the amount of phenolic resin binder (6.5% of the total powder mixture) was kept constant. The materials were investigated by SEM, XRD and EDS. The results showed that: the bulk density and modulus of rupture of sintered specimen decreased, and apparent porosity increased with increasing of SiC addition. The properties of the specimen with 10% SiC addition are optimum. The residual rates of bending strength of all specimens were more than 90% after 15 air cooling cycles from 800°C to room temperature, showing high thermal shock resistance.