Preparation and mechanical properties of SiC/BN multiphase ceramics via spark plasma sintering

The h-BN-25%SiC multiphase ceramics were prepared via spark plasma sintering (SPS) using h-BN and SiC nanopowders as raw materials and B2O3 as a sintering aid. The phase composition and microstructure were characterized by X-ray diffraction and scanning electronic microscopy. Furthermore, the sintering behavior and the effect of sintering temperature on the densification, microstructure and mechanical properties of h-BN-SiC multiphase ceramics were investigated. The results show that the high density of the ceramics can be reached at a relatively low temperature in the SPS Process. The directional arrangement of h-BN grains promotes, and the density, grain size and mechanical properties (i.e., flexural strength, fracture toughness and elastic modulus) increase with increasing the sintering temperature. The increased fracture toughness is attributed to the intergranular fracture mode and h-BN grains, which cause crack deflection, grain pullout and the pinning effect of fine SiC particles. The flexural strength, fracture toughness and elastic modulus of the sample sintered at 1600℃ are 289.2 MPa, 3.45 MPa·m1/2 and 150.9 GPa, respectively, which are better than those of other samples. © 2016, Editorial Department of Journal of the Chinese Ceramic Society. All right reserved.