Thermal diffusivity/conductivity of Tyranno SA fiber- and Hi-Nicalon type S fiber-reinforced 3-D SiC/SiC composites

Yamada, Reiji; Igawa, Naoki   ; Taguchi, Tomitsugu

SiC fiber reinforced SiC composites (SiC/SiC) have a potential for a structural material for a blanket wall of advanced fusion reactors. To reduce thermal stresses in the wall under heavy thermal loads SiC/SiC composites are expected to have high thermal conductivity as possible. Advanced SiC fibers recently developed, such as Tyranno SA and Hi-Nicalon Type S have been employed for weaving 3D textures as well as those 2D unwoven fabrics. The CVI and PIP/CVI fabrication methods were used. The thermal conductivity at RT was 40-50 W/mK and 35-40 W/mK for Tyranno CVI and PIP/CVI composites, respectively, whereas about 25 and about 17 W/mK at 1000 C. 2D unwoven CVI composites had less than 12 W/mK for RT-1000 C. For Hi-Nicalon Type S, 3D CVI composites had about 35 and about 20 for RT and 1000 C, respectively. The reason of these high thermal conductivities was ascribed to higher density as well as better SiC crystallinity. The fiber configuration effects on the thermal conductivity of SiC/SiC composites were dominant in the low temperature region.