Preparation\nand Formation Mechanism of β‑SiC\nCoatings Using a SiCl<sub>4</sub>–CH<sub>4</sub>–H<sub>2</sub>–N<sub>2</sub> System

The mechanism of β-SiC preparation via chemical\nvapor deposition\n(CVD) of the SiCl<sub>4</sub>–CH<sub>4</sub>–H<sub>2</sub>–N<sub>2</sub> system remains unclear. Consequently, the change\nof molar Gibbs free energy of the CVD β-SiC chemical reaction\nin the SiCl<sub>4</sub>–CH<sub>4</sub>–H<sub>2</sub>–N<sub>2</sub> system has been studied by the Helsinki Software\nCorporation (HSC) Chemistry code for the first time. The role of nitrogen\nin the reaction was confirmed. Seven potential reaction pathways of\nCVD β-SiC were presented, and the thermodynamic equilibrium\ncomponents of each reaction were calculated systematically. The most\nviable reaction pathway and corresponding optimal temperature range\nfor CVD β-SiC were determined. In addition, a kinetic study\nof CVD β-SiC was conducted. The microscopic morphology and crystal\nstructure of β-SiC coatings prepared on the graphite surface\nat different temperatures were charactered by scanning electron microscopy\n(SEM), X-ray diffraction (XRD), Raman, etc. Ultimately, through SEM,\nXRD, and Raman observation, uniform and dense β-SiC coatings\nwith fine grains and high crystallinity were successfully obtained.\nFurthermore, large β-SiC-coated graphite trays with diameters\nof 230 and 465 mm were prepared by CVD using the SiCl<sub>4</sub>–CH<sub>4</sub>–H<sub>2</sub>–N<sub>2</sub> system, and the\naverage thickness of β-SiC was about 100.6 μm. This study\nprovides a theoretical basis and technical recommendations for the\nfabrication of SiC-coated graphite trays used in metal–organic\nchemical vapor deposition (MOCVD) equipment.