Comparison of microwave hybrid and conventional heating of preceramic polymers to form silicon carbide and silicon oxycarbide ceramics

Six different preceramic polymers were pyrolyzed via conventional and micro wave hybrid heating; these polymers provide a range of carbon content and l ocal atomic coordination. The products were compared with each other using X-ray diffractometry and transmission electron microscopy. Nanocrystalline beta-SiC was the principal crystal phase detected, and the amount and size of the nanocrystals increased as the processing temperature increased. Diff erences were observed in the amount and size of the beta-SiC nanocrystals a nd the graphitization of residual carbon between the microwave hybrid heati ng and the conventional oven heating of polycarbosilanes. Conventional heat ing of a high-carbon polysiloxane in an oven (in flowing argon) produced a greater amount of beta-SiC from carbothermal reduction at high temperature. Microwave hybrid heating led to better beta-SiC nanocrystal development fo r polyureasilazane.