Molecular dynamics study of cascade damage at SiC/C interface

Continuous silicon carbide (SiC) fiber-reinforced SiC (SiCf/SiC) composites have been considered to be used as structural materials in advanced nuclear reactors for its excellent properties. Their mechanical properties have been greatly improved during the last decade. But the radiation damage at the SiC and pyrolytic carbon interface would degrade the mechanical integrity of the composites, while the mechanism of degradation is remaining unknown at present. In this study, molecular dynamics simulations have been used to model the irradiation cascade of five SiC/C composite systems. According to the angle between the graphite layer and the interface, the models are marked as M0, M28, M56, M77 and M90, in which the number represents the angle. Forty primary knock-on atoms (PKAs) at different positions in each composite system are used to bombard the interface. In each run a collision cascade may be initiated by giving one of the 40 atoms 1.5 keV kinetic energy. The relationships between the distribution of defects and simulation time and PKA position are systematically studied, and compared with those in bulk SiC, which are marked as MW. Results show that the radiation damage resistance of SiC/C interface is significantly lower than bulk SiC, and the interface structure has an impact on the number of defects. Radial distribution function (RDF) is employed to examine the coordination of interfacial atoms. The results show that the higher the density of graphite atoms in the interface, the larger impact the irradiation on the RDF and coordination.