Microstructure of the Cf/SiC composites by precursor conversion-hot pressing sintering

The microstructure of the Cf/SiC composites, prepared by precursor conversion-hot pressing sintering with polycarbosilane (PCS) as precursor and binder and AlN-Y2O3 as additives, was investigated using XRD, HRTEM and SEM. The results showed that Y2O3 reacted with the pyrolytic products of the PCS and the oxides on the surface of the AlN and SiC grains, forming the liquid-phase assisting in the densification of the composites, and the fine SiC-AlN solid solution was formed between AlN and the PCS through reaction-dissolution-precipitation at the grain boundaries and the fiber/matrix interface. Due to the presence of the carbon-rich fiber/matrix interphase with a certain of SiC-AlN solid solution, a desirable fiber/matrix interfacial bonding was obtained, which facilitated the debonding and pullout of the fibers. As a result, the composite exhibited excellent mechanical properties.