Thermal shock properties of 3D-C/SiC composites prepared via polymer infiltration pyrolysis (PIP)

SiC ceramic matrix composites reinforced by three-dimensional braided carbon fibers were prepared via polymer infiltration pyrolysis (PIP). The thermal shock properties of C/SiC composites were investigated in air. 3D-C/SiC specimens were thermally shocked for five cycles between 1500 °C and 100 °C. The thermal shock resistance was characterized by mass variation and residual flexural strength properties. Scanning electron microscope was used to examine the change of the surface morphology and micro-structural evolution of the composites. In addition, the phase evolution of the surfaces was identified by XRD, EDS and XPS. It was found that the strength of 3D-C/SiC composites decreased after thermal shock tests. The phase composition of 3D-C/SiC composites was mainly β-SiC and carbon. After thermal shock tests, more oxides were generated and more O atoms were detected when there was no coating on the surface of 3D-C/SiC. The matrix cracking offered the channels through which oxygen could penetrate into the composites and consume the fibers during thermal shock tests. CVD-SiC coating played an important role in enhancing the resistance to the thermal shock of the composites.