The microstructure evolution in a SiCf/SiC composite under triple ion beam irradiation

Abstract Simultaneous H, He and Fe ion beam irradiations were conducted on a pyrolytic carbon (PyC) - SiCf/SiC composite at 475 °C with the peak displacement damage level up to 47 dpa and concentrations of He and H up to 38 and 3400 appm, What respectively. Cross-sectional transmission electron microscopy was used to study the evolution of microstructure after the triple beam irradiation. Results show that the interface between SiC fiber and PyC interphase cracked after the triple ion beam irradiation. The PyC interphase could infiltrate into the multilayer SiC coating to cause deformation of the multilayer due to volume expansion. After irradiation, no obvious cavities were observed in multilayer SiC coating and SiC matrix, while He bubbles as large as 15 nm in diameters were observed at the peak displacement damage region in the SiC fiber and SiC coating/PyC interface. Hydrogen promotes nucleation and growth of He bubbles by reducing their surface energy. The formation process of cavities at the interface between PyC interphase and multilayer SiC coating is discussed.