以针刺整体炭毡为预制体, 采用CVD+MSI工艺制备了C/SiC复合材料, 借助XRD和SEM研究材料的微观组织, 通过等温氧化失重和非等温热重分析研究材料的氧化反应动力学和反应机理. 结果表明: MSI工艺所制备的C/SiC材料致密度高, 物相组成为类石墨结构的C、反应生成的SiC和残留Si. 其等温氧化反应机理: 第Ⅰ阶段为反应控制, 第Ⅱ和Ⅲ阶段为扩散和反应共同控制; 材料的非等温氧化过程呈现自催化特征, 氧化机理为随机成核, 氧化动力学参数为: lgA=8.752min-1, Ea=169.167kJ·mol-1. 与C/C材料相比, C/SiC材料有较差的低温氧化性能和稳定的高温氧化性能, 这与MSI的工艺特征密切相关.
C/SiC composites were made of the integrity felt which was densified by CVD (chemical vapor deposition) and subsequently MSI (melt silicon infiltration) process. XRD and SEM were used to analyze the microstructure. Isothermal oxidation-weight loss and TG analysis were performed to study the oxidation kinetics and mechanism of the composites. The results show that the prepared composites are of high density, consisting of quasi-graphite C, reaction-formed SiC and free Si. The oxidation process of C/SiC composites in isothermal condition is reaction-controlled in the Ⅰstage·, diffusion and reaction co-controlled in the Ⅱand Ⅲ stages. The non-isothermal oxidation process exhibits self-catalytic characteristics. The oxidation mechanism is random nucleation, and the kinetic parameters are lgA=9.703min-1 and Ea=182.009kJ·mol-1. Compared with C/C composites, C/SiC composites fabricated by MSI process have inferior oxidation resistance at low temperature and higher oxidation resistance at high temperature.
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