Neutron irradiation effects on high-crystallinity and near-stoichiometry SiC fibers and their composites

Key characteristics required for the development of fusion-grade SiC/SiC composites are high-crystallinity and near-stoichiometry. To identify the primary mechanisms of degradation caused by neutron irradiation, the radiation behavior of the constituent SiC fibers needs to be examined. In this study, single filament tensile tests were conducted after neutron irradiation on a recently developed highly-crystalline and near-stoichiometric SiC fiber; Hi-Nicalon™ Type-S. Hi-Nicalon™ Type-S fiber exhibited excellent strength retention up to 7.7 dpa independent of irradiation temperature up to 800 °C. The radiation stability of the Hi-Nicalon™ Type-S fiber directly contributed to the excellent radiation performance in composites made with this fiber. The observed 14–20% decrease of elastic modulus due to neutron irradiation of Hi-Nicalon™ Type-S fiber had a minor effect on composite strength.