Effects of Pore on Thermal Diffusivity and Thermal Radiation Properties of C/SiC Composites at High Temperatures

The effects of pore in C/SiC composites on thermal diffusivity and thermal radiation properties were investigated systematically. Pores were introduced into C/SiC by oxidizing carbon phase at 700 °C and damaged the thermal properties of C/SiC composites. Because of little changes in the pore shape and the pore orientation in C/SiC, thermal diffusivity of samples increased linearly with porosity. The pores within C/SiC absorbed and reflected the radiated heat, decreasing spectral emissivity. However, the temperature dependence of spectral emissivity didn’t change by the pore. With measurement temperature increasing, the pores weakened the thermal radiation property of samples gradually. A linear relation was suggested to quantify the negative effect of pores on the total emissivity.