High thermal conductivity SiC/SiC composites for fusion applications
SiC/SiC composites offer excellent potential for fusion energy as well as numerous commercial applications. High manufacturing cost and very low through-the-thickness (transverse) thermal conductivity (below 15 W/m K) hinders wider applications of SiC/SiC composites. To overcome these obstacles, a low cost chemical vapor reaction (CVR) process was developed to fabricate crystalline, high-purity SiC fibers. Several variations of the CVR process were used to fabricate SiC/SiC composites. An unirradiated, 4-mm thick SiC/SiC composite was completely CVR-converted from a converted SiC fiber preform with a pitch graphite matrix, and exhibited a bulk density of 2.65 g/cc, 10% open porosity, room temperature (RT) and 1000°C thermal conductivity values of 70 and 35 W/m K, respectively, and an RT bend strength of 200 MPa.
Silicon carbide fibers and composites from graphite precursors for fusion energy applications
Abstract A high purity β-SiC is projected to exhibit neutron stability in a fusion reactor environment because of its microstructure and physical dimension stability. A pure β-SiC fiber could therefore be expected to be an excellent candidate as a reinforcement to produce β-SiC/β-SiC composites. Graphite fibers can be converted to pure β-SiC utilizing several different siliconizing reactions, however, fiber cracking and low strengths are typical. A reaction window has been demonstrated that has produced pure β-SiC fiber with strengths in the 1–2 GPa range. Fiber and composite properties are discussed in comparison with other commercially available SiC fibers and composites.
Effects of neutron irradiation on fine structure and strength of sic fibers
Abstract Two types of SiC fibers, amorphous SiC(1000) (heat-treated at 1000°C) and microcrystalline SiC(1300) (heat-treated at 1300°C), were neutron-irradiated at 423 K to 8 × 10 23 and 2 × 10 24 n/m 2 , and at 923 K to 9 × 10 24 n/m 2 in JMTR ( E > 1 MeV ). In the 423 K irradiation, density increased and X-ray radial distribution function (RDF) indicated that the atomic arrangement of SiC(1000) scarcely changed and that of SiC(1300) was disordered. Tensile strength and Young's modulus gradually increased with neutron fluences. In the 923 K irradiation, density increased and RDF indicated that the atomic arrangement of SiC(1300) scarcely changed and that of SiC(1000) was ordered. Young's moduli of SiC(1000) and SiC(1300) greatly increased. There were differences in density, tensile strength and Young's modulus between SiC(1000) and SiC(1300) before the irradiation, but their values became almost the same by the irradiation at 423 K to 2 × 10 24 n/m 2 and 923 K to 9 × 10 24 n/m 2 , respectively.