Oxidation kinetics and mechanism of C/SiC composites fabricated by MSI process

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 I stage, diffusion and reaction co-controlled in the II and III stages. The non-isothermal oxidation process exhibits self-catalytic characteristics. The oxidation mechanism is random nucleation, and the kineticparameters are IgA=9.703min(-1) and E-a=182.009kJ center dot 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.