Cavity Swelling and Dislocation Evolution in SiC at Very High Temperatures

The temperature and fluence dependence of cavity swelling and dislocation development in CVD SiC irradiated with fast neutrons at high temperatures (1050-1460 C, up to 9.6 dpa) were evaluated using transmission electron microscopy. The cavity swelling was very limited below 1300 C (<0.01% at 1300 C, 9.3 dpa). Temperature and fluence dependent swelling became visible above ∼1400 C. The maximum value of the cavity swelling was 0.25% at 1460 C, 9.6 dpa, but this appeared to be below the peak swelling temperature. Frank loops were the dominant dislocation structure in this temperature regime, and the number density decreased and the size increased with increasing irradiation temperature. The loop microstructures depended less significantly on both the irradiation temperature and fluence below 1200 C. A significant decrease in the number density and increase in the size were observed at 1300-1460 C