Microstructure and annealing behavior of heavily neutron-irradiated β-SiC

Abstract

TEM studies were carried out on sintered β-SiC specimens which were irradiated in fast breeder reactors up to 1.0 × 10 27 n/m 2 (E > 0.1 MeV) at temperatures around 500°C. In SiC grains irradiated to 10 × 10 25 to 10 × 10 26 n/m 2 , unresolvable small black dots of 2 to 5 nm in size were observed. Change in microstructure occurred in the specimens irradiated to fluerices higher than 4.8 × 10 26 n/m 2 . Clear straight line contrast of dislocations 10 to 30 nm in length was observed, which might be Frank-type interstitial dislocation loops, lying on {111} planes. The size of defects was increased with increasing neutron fluence. Postirradiation annealing of specimens resulted in an increase in size and a decrease in the number density of defects. No void was observed. It is suggested that the dislocation loops observed in this experiment are not the cause of irradiation-induced swelling of SiC.