Effects of precursor infiltration pyrolysis process on mechanical properties of 2·5D-SiCf/SiC composites

Abstract 2·5D-SiCf/SiC composites were fabricated by hot pressing-precursor infiltration pyrolysis process using SiC fibre preforms which were pretreated by polycarbosilane solution with low concentration. The effects of the infiltration pyrolysis cycles during the pretreatment on the mechanical properties of composites are studied. It is found that the flexural strength of the composites can be improved to a maximum value of 230 MPa when the preform was pretreated by three cycles of infiltration pyrolysis process. This value is about one and half times that of the composites prepared by the fibre preform without pretreatment. This increase of the mechanical properties could be attributed to the SiC coating formed on the pretreated SiC fibre, as revealed by the observation of the fibre surface morphology. This precursor infiltration pyrolysis-SiC coating cannot only decrease the damage to the fibre during the densification process, but also improve the interface between the fibres and the matrix, resulting in an obvious enhancement of the mechanical properties.