Influence of Grain Size on Thermal Conductivity of SiC Ceramics

SiC fiber reinforced-SiC ceramic matrix (SiCf/SiC) composites are one of the candidate structural materials for nuclear fusion reactors systems because of their low activation, mechanical property and chemical stability at high temperature. High thermal conductivity of SiCf/SiC composites is required to reduce heat load and to provide high thermal conversion efficiency. The objective of this study is to determine thermal conductivity on grain size dependence of SiC ceramics which is the matrix in composites. β-SiC powder was sintered by hot-press method. Al2O3 and Y2O3 were used as sintering additives. The grains size was grew with increase of holding time at 1900 deg. C. Thermal conductivity of SiC ceramics was gradually increased up to 112 W/mK. Thermal conductivity of SiC ceramics is dependent on growth of grain size due to the scattering of the phonon by the grain boundaries leads to a size-dependence.