The effect of high dose/high temperature irradiation on high purity fibers and their silicon carbide composites

Silicon carbide composites were fabricated by chemical vapor infiltration method using high purity fiber, Hi-Nicalon Type-S and Tyranno SA, and non-high purity fiber Hi-Nicalon. Bare fibers, SiC/SiC composites and CVD SiC were irradiated at 7.7 dpa and 800 °C or 6.0 dpa and 300 °C. The density of fiber and CVD SiC was measured by gradient column technique. Mechanical properties of the composites were evaluated by four-point flexural tests. Fracture surfaces were observed by SEM. Tyranno SA fiber and CVD SiC showed similar swelling behavior following irradiation at 7.7 dpa and 800 °C. Mechanical properties of composites reinforced with Hi-Nicalon Type-S and Tyranno SA fibers were stable even following neutron irradiation at 7.7 dpa and 800 °C. Fracture surfaces of these composites following irradiation were similar to those of non-irradiated composites with relatively short fiber pull-out.