Oxidation resistance and wettability of graphite/SiC composite

Abstract

The core-shell structure of graphite@SiC was synthesized at different calcination temperatures using the raw materials of microsilica and carboxy methylated cellulose (CMC). The oxidation resistance and wettability (with water) of graphite@SiC were investigated. The results showed that CMC could react with microsilica to form a SiC shell on the graphite surface at elevated temperature. Consequently, the SiO2 phase was totally converted into the SiC phase at above 1600°C. The microstructure of SiC coating on the graphite became denser with increasing temperature. Thermo-gravimetric curves revealed that the weight loss percent of graphite was about 97.3% while the value decreases to 29.78% when the SiC was formed. Differential scanning calorimetry analysis showed that the existence of SiC coating decreased the enthalpy of carbon oxidation reaction from 12.02 kJ/g to 1.14 kJ/g, confirming excellent oxidation resistance. At the same time, the water contact angle of graphite was about 78.5° while the core-shell structure of graphite@SiC reduced the wetting angle to 43°. The study of the formation mechanism of graphite@SiC showed that SiO2 could be reduced by CMC to SiO(g), which would be deposited on the graphite to form SiC coating.