EFFECT OF IRRADIATION ON THERMAL EXPANSION OF SiC_f/SiC COMPOSITES

摘要

Silicon carbide (SiC) has long been considered an attractive material for use in a fusion reactor environment because of its excellent high temperature strength and thermal conductivity, dimensional stability during irradiation, and low neutron activation. However, monolithic SiC is not a suitable choice for structural applications due to its brittle nature. In contrast, SiC-fiber-reinforced/SiC-matrix (SiC_f/SiC) composites have recently been shown to exhibit non-catastrophic failure modes analogous to the plastic deformation exhibited by traditional metallic materials [1]. As a result, SiC_f/SiC composites are under consideration as candidate structural materials in several fusion reactor concepts. However, several issues must be addressed before their inclusion in detailed designs: optimization of constituent materials, refinement of fabrication and processing methods, and characterization of the effect of irradiation on material properties. The present study seeks to quantify the effect of irradiation on the linear thermal expansion of several SiC_f/SiC composites fabricated using different constituent materials and processing routes. Six different SiC,/SiC composites were characterized by measuring their thermal expansion in the unirradiated and irradiated conditions over the temperature range 300 to 1000 deg C. The irradiation was conducted in the Experimental Breeder Reactor II (EBR-II), in an inert gas atmosphere, at a nominal temperature of 1000 deg C, to doses of either 33 or 43 dpa-SiC.