In this study, the oxidation processes of SiC coatings with different crystal structures were systematically investigated by experimental and density functional theory (DFT) calculations. The SiC coatings were prepared on carbon/carbon (C/C) composites through pack cementation (PC) and chemical vapor deposition (CVD), respectively. The SiC coating prepared by PC method has superior oxidation resistance to that prepared by CVD. It was ascribed to a strong adhesion of PC-coating and substrate. And, the addition of Al, which improves the strength of Si-O bonding, inhibiting the diffusion of O in the SiO. Additionally, it is found that α-SiC, prepared by PC, has better intrinsic oxidation resistance than β-SiC. The reason is that α-SiC has high adsorption energy of the O atom on the C-terminated surface and low adsorption energy of the O atom on the Si-terminated surface. Moreover, the diffusion of O on the surface of α-SiC at 1773 K was more difficult due to the more stable Si-O bonding. These findings demonstrate that the oxidation resistance of α-SiC is superior to β-SiC and can help guide the structural design of the high-temperature coatings.

中文翻译：

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原子模拟与实验：碳/碳复合材料化学气相沉积和包埋法制备氧化防护SiC涂层

本研究通过实验和密度泛函理论（DFT）计算系统地研究了不同晶体结构的SiC涂层的氧化过程。分别通过包埋（PC）和化学气相沉积（CVD）在碳/碳（C/C）复合材料上制备SiC涂层。PC法制备的SiC涂层比CVD法制备的SiC涂层具有优越的抗氧化性能。这归因于PC涂层与基材的牢固附着力。并且，Al的添加提高了Si-O键的强度，抑制了O在SiO中的扩散。此外，还发现由PC制备的α-SiC比β-SiC具有更好的本征抗氧化性。原因是α-SiC的C端表面O原子的吸附能高，而Si端表面O原子的吸附能低。此外，由于Si-O键更稳定，1773 K时O在α-SiC表面的扩散更加困难。这些发现表明α-SiC的抗氧化性优于β-SiC，有助于指导高温涂层的结构设计。