Low Temperature Catalytic Synthesis of β-SiC Powders via Microwave Heating

β-SiC powders were synthesized by a microwave heating method at 1150℃ for 30 min under Ar atomosphere using silicon powders and phenolic resin as raw materials, and nickel nitrate as catalyst precursor. The effects of temperature, catalyst content and holding time on the formation of SiC were investigated. XRD, SEM and TEM were used to characterize the phase and microstructure of the prepared samples. It indicated that β-SiC can be synthesized at 1150℃ for 0.5 h by using 1.0wt% Ni as catalysts. In contrast, for the sample prepared without Ni catalysts, corresponding preparation temperature of β-SiC was as high as 1250℃. Both β-SiC whiskers and particles were formed in the samples prepared with or without catalysts, and the length of formed β-SiC whiskers in the samples prepared with Ni catalysts were larger than those without catalyst. Density functional theory (DFT) calculation shows that the formation of Ni-Si alloy can elongate the length of Si-Si chemical bond, weaken its bond strength, and finally accelerate the carbonization reaction of Si powder at a relative low temperature.