Investigation on heating behavior during the preparation of SiC crystals by microwave sintering

Abstract β‐SiC powders were synthesized by microwave sintering at 1400‐1850°C for 60 minutes with coal minerals. Raw materials were prepared with a sol‐gel method by coating SiO ₂ on coal mineral particles, and microwave sintering was conducted in a microwave chamber with TE 666 resonant mode. Heating rates were controlled by input microwave power and heating behavior during the microwave sintering was also investigated. XRD , SEM , Raman, TEM techniques were carried out to characterize samples. It was found that different particle size of coal mineral particles gave rise to different heating effect, leading to different growth mechanisms of SiC crystals. This might be the unique features for microwave sintering. Particular SiC crystals dominated for small coal mineral particles, which attributed to microwave plasma effect. While SiC whiskers or fibers dominated for large coal mineral particles, which corresponded to microwave coupling effect. Microwave coupling effect prevailed for low heating rate which was apt to form particular SiC crystals. Whereas, higher heating rate enhanced microwave plasma and primarily resulted in SiC whiskers or fibers.