Effects of aggregate/matrix‐phase ratio on the in‐situ synthesis of SiC whiskers and properties of reaction‐bonded SiC

Abstract

AbstractReaction‐bonded silicon carbide (RBSC) materials were synthesized by a carbon‐buried firing method, using α‐SiC powders with different sizes as aggregates, while silicon and graphite powders as matrix‐phase materials for in‐situ synthesis of β‐SiC. The effect of the mass ratio of α‐SiC aggregate to β‐SiC matrix‐phase on the in‐situ synthesis of β‐SiC whiskers was investigated and the optimum mass ratio was determined according to the properties of RBSC materials. The phase compositions, microstructure, and properties of the RBSC materials were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM), respectively. The results showed that the decreasing aggregate/matrix‐phase ratio could increase the yield and aspect ratio of β‐SiC whiskers by improving the amount of pores and SiO2 content. The β‐SiC whiskers with stacking faults grew along [111] direction. The in‐situ formed β‐SiC whiskers and SiO2 in the matrix‐phase enhanced the hot modulus of rupture (HMOR) of the RBSC materials, and the sample with the aggregate/matrix‐phase ratio of 70:30 showed the highest cold modulus of rupture (CMOR) of 53.3 MPa, high HMOR of 43.3 MPa, and medium water absorption of 13.8%.