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 theⅠstage, diffusion and reaction co-controlled in theⅡandⅢstages.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·mo1~(-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.