Effects of deposition temperature on microstructures and ablative properties of SiC coatings prepared by CVD from methylsilane
(1. National Key Laboratory of Science and Technology on High-strength Structural Materials, Central South University, Changsha 410083, China;
2. Hunan Provincial Key Laboratory for Advanced Carbon Materials and Applied Technology, Hunan University, Changsha 410082, China)
2. Hunan Provincial Key Laboratory for Advanced Carbon Materials and Applied Technology, Hunan University, Changsha 410082, China)
Abstract: Using the methylsilane (MS) as a gas precursor, SiC coatings were prepared on the surface of graphite by the chemical vapor deposition (CVD) method at different deposition temperatures. The effects of temperature on the deposition rate, microstructures and ablative properties of SiC coatings were investigated systematically. The results showed that the SiC deposition rate of SiC coating using MS at 1000 °C was 50-120 μm/h, which was much higher than that using methyltrichlorosilane (5-10 μm/h). The SiC coatings deposited at lower temperatures (900-1000 °C) exhibited smooth and spherical compact packing morphology, while the SiC coatings deposited at higher temperatures (1100-1200 °C) appeared to possess an irregular cauliflower morphology with an significantly increased size of SiC particles. Therefore, the SiC coating prepared at deposition temperature of 1000 °C had suitable density, roughness, and uniform size of coating microstructure. Meanwhile, the mass ablation rate and linear ablation rate of the obtained SiC coating were respectively 0.0096 mg/s and 0.3750 μm/s after plasma ablation at 2300 °C for 80 s, exhibiting excellent ablative resistance. This study provided a theoretical and technical foundation for the preparation of SiC coating using the MS as the gas precursor by the CVD method.
Key words: methylsilane; chemical vapor deposition; SiC coating; deposition temperature; microstructure; ablative properties