Fabrication of two-layer SiC nanowire cladding tube with high thermal conductivity

Among the various concepts of SiC-based accident-tolerant fuel cladding, duplex SiC cladding, consisting of an inner composite layer and an outer monolithic SiC layer, is considered an optimal design due to its low load failure probability. In this study, SiC nanowires (SiCnw) were introduced on the substrate graphite rod to decrease the diameter of architectural valley-regions of SiC fiber (SiC_f) tubular preform. By avoiding the architectural valley-voids, a dense two-layer SiCnw tube consisting of an inner SiC fiber-reinforced SiC matrix (SiC_f/SiC) composite layer deposited by chemical vapor infiltration with a smooth inner surface was obtained. The microstructure and thermal properties of as-obtained two-layer SiCnw tubes were studied. Results showed that the thermal conductivity of the whole tube was highly sensitive to variations in thermal conductivity of the inner composite layer. By improving the thermal conductivity of the inner composite layer, the two-layer SiCnw tube exhibited a thermal conductivity of 23.8 W m⁻¹ K⁻¹ at room temperature, which had an improvement of 71 % compared to the two-layer SiC tube (13.9 W m⁻¹ K⁻¹). Moreover, the thermal transport properties of the two-layer SiCnw tube were significantly improved by a reduction in roughness of the inner surface.