Ion-mixing-induced mitigation of swelling and modulus reduction in irradiated SiC fibers

Abstract

The competition between shrinkage and swelling in irradiated silicon carbide (SiC) with progressive defect recovery was investigated. Both chemical vapor infiltration-prepared SiC (CVI-SiC) and fibers containing excess C showed irradiation-induced swelling, with fibers exhibiting less swelling than the CVI-matrix, suggesting that excess C reduces SiC swelling. Swelling in the SiC fibers was proportional to the degree of ion-mixing. The effect of ion-mixing-induced swelling at the fiber rim was considered dominant, while the shrinkage effect played a leading role in the fiber core. Furthermore, post-irradiation reductions in Young’s modulus were observed, reaching up to 73.6 % in the rim of HNLS and 89.6 % in the core of TSA3. When the damage increased to 100 displacements per atom, the modulus reduction of the fiber core stopped, whereas the modulus increased at the fiber rim, likely because of the competition between swelling and shrinkage. This study qualitatively explains SiC fiber swelling and modulus changes under irradiation, offering insights into addressing composite strength degradation arising from swelling mismatches in SiC components.