Analysis of the variation in mechanical properties of α- and β-SiC under high-temperature Si-ion irradiation

The mechanical properties of silicon carbide (SiC) under high-temperature irradiation have been one of the focal issues for its application in nuclear systems, but the relevant mechanisms remain elusive. In this work, two SiC polytypes inducing α- and β-phase were irradiated by 1.35 MeV Si5+ with a fluence of 1.81×1016 ions/cm2 at 550°C and 750°C, respectively, to investigate the characteristics of irradiation-induced defects and structure and the variation of mechanical properties. Irradiation significantly affected the mechanical properties of both α- and β-SiC. The nanohardness and modulus of α-SiC increased with the increase of irradiation temperature, while for β-SiC they first increased and then decreased significantly. The results of GIXRD and Raman spectra indicated the irradiation-induced defects, lattice deformation, and the changes in the intensity of the Si-C bond region. It was found that the TEM characterization of irradiated SiC samples with numerous point defect clusters, extended defects and a legible defect band. Moreover, the nanohardness and modulus of both SiC types exhibited a critical temperature dependence and were affected by different dominant factors at high temperatures. The potential mechanisms governing the variation in mechanical properties at elevated temperatures of two irradiated SiC polytypes were explored.