34 / 2021-06-28 13:31:56

Liquid-phase deposition of SiO2/SiC submicron coating on carbon fiber improving anti-oxidation and strength

Carbon fiber; SiO2/SiC coating; Liquid phase deposition; Antioxidant; Thermogravimetric kinetics

To improve the oxidation resistance of carbon fiber, this study used liquid phase deposition to deposit a SiO₂/SiC coating on it. The coating was deposited by supersaturated hexafluorosilicic acid (H₂SiF₆) solution at 40°C. The impact of the deposited time for the coating on the microstructure, chemical composition and oxidation resistance was studied, and the deposited rate was also analyzed. The thickness of the coating was 118nm, 182nm, 271nm and 286nm after a deposited time of 2h, 4h, 6h and 8h, respectively. SiO₂/SiC coating had a good adhesion to the carbon fiber as well as good oxidation resistance. Antioxidant performance was improved as the deposited time increased, evidenced by the complete weightlessness for the bare carbon fiber while a weightlessness rate of ~ 39.1 wt.% for the 8-hour-processing fiber at 950°C. A residual amount of ~26.5 wt.% was got for the 8-hour-processing fiber at 1000°C. The breaking load improved from ~19.4% for the 2-hour-processing fiber to ~51.8% for the 8-hour-processing fiber. It was inferred that a nucleation point was first formed on the surface of the carbon fiber. Then the nucleation point continued to grow and accumulated to form a continuous coating. Thermogravimetric kinetics was analyzed by calculating Arrhenius parameters.