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 degrees C and 100 degrees 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 beta-sic and carbon. After thermal shock tests, more oxides were generated and more 0 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. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.