Preparation of Silicon Carbide Film by Composite Sintering of Silicon Nitride and Silicon Carbide

Graphite can be protected by coating it with a silicon carbide film. However, studies on the effects of different coating methods and process parameters on the thickness and bond strength of the films are not yet mature. In this paper, silicon nitride (Si3N4) and silicon carbide (SiC) are used as raw materials, and SiC films are successfully prepared on the surface of graphite substrate by composite sintering at high temperatures. The phase and microstructure of SiC films were characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively, and the effect and mechanism of sintering temperature on the formation of SiC films were investigated. The results show that Si3N4 and SiC decompose under high temperatures to generate silicon vapor and carbon-silicon gas molecules, which migrate to the graphite surface to react with C and recrystallize to form a SiC film. The main crystal phase of the SiC film at high temperature is 3C-SiC, the spherical SiC grains with smooth surfaces and small size gradually grow into regular hexagonal grains, and the SiC film is denser and thicker.