Microstructures of a carbon-fiber-reinforced silicon-carbide composite produced by precursor pyrolysis and hot pressing

The microstructures of a 1D-Cf/SiC composite, prepared by polymeric precursor pyrolysis and hot pressing, with polycarbosilane (PCS) as precursor and AlN–Y2O3 as sintering additives, were investigated by using XRD, HRTEM, and SEM. During sintering, Y2O3 reacted with the pyrolysis products of the PCS and the oxides on the surfaces of the AlN and SiC grains, forming a liquid-phase which assisted in the densification. Owing to the formation of a carbon-rich fiber/matrix interphase with a certain number of SiC–AlN solid solution grains, a desirable level of fiber/matrix interfacial bonding could be obtained which facilitated the debonding and pull-out of the fibers. The composite therefore exhibited better mechanical properties and the average flexural strength and fracture toughness values were 691.6 MPa and 20.7 MPa m1/2, respectively.