The Effect of SiC Content on Microstructure and Microwave Heating Rate of -BN/SiC Ceramics Fabricated by Spark Plasma Sintering.

Hexagonal boron nitride/silicon carbide (-BN/SiC) ceramics were fabricated by a spark plasma sintering (SPS) method. Phase and microstructure of ceramics were characterized and observed, respectively, using the X-ray diffraction, scanning electron microscope and electron probe microanalysis. The effect of molar ratios of SiC to -BN on the microstructure, relative density, hardness, thermal conductivity, and the heating rate by microwaves on the ceramics were investigated. The results showed that the orientation of flake-like -BN was significantly influenced by SiC content in -BN/SiC ceramics. With the increasing of SiC content, the -BN flakes gradually became an isotropic distribution from the preferred orientation aligning in a SPS pressure direction. The relative density of -BN/SiC ceramics was 97.6 ± 0.9% at a molar ratio of SiC to -BN of 40/60 mol%. The preferential orientation of -BN flakes contributed to a relatively high thermal conductivity along the SPS pressure direction, which was beneficial to increasing the heating rate of -BN/SiC ceramics in microwave fields.