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

Hexagonal boron nitride/silicon carbide (h-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 toh-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-likeh-BN was significantly influenced by SiC content inh-BN/SiC ceramics. With the increasing of SiC content, theh-BN flakes gradually became an isotropic distribution from the preferred orientation aligning in a SPS pressure direction. The relative density ofh-BN/SiC ceramics was 97.6 ± 0.9% at a molar ratio of SiC toh-BN of 40/60 mol%. The preferential orientation ofh-BN flakes contributed to a relatively high thermal conductivity along the SPS pressure direction, which was beneficial to increasing the heating rate ofh-BN/SiC ceramics in microwave fields.