Thermal diffusivity and oxidation of 2D and 3D C/SiC composites from 600 °C to 1400 °C

A 2D C/SiC and a 3D C/siC composite were prepared by a low-pressure chemical vapor infiltration method. Thermal diffusivity of the composites was measured in a mixed gas flow of O₂ and Ar that was used to simulate air. The thermal diffusivity change and the weight change with oxidation time at temperatures from 600 °C to 1400 °C were investigated. The thermal diffusivity of 2D C/SiC was higher than that of 3D C/SiC over the entire temperature range. The former was more sensitive to oxidation than the latter. Below 1000 °C, the thermal diffusivity of 2D C/SiC decreased with increasing oxidation time. The lower the temperature, the more rapidly it decreased. There was no clear decrease in the thermal diffusivity of 3D C/SiC with increasing oxidation time in the whole temperature range. At 600 °C, the weight loss of both composites was accelerated in a parabolic relation to oxidation time, but their thermal diffusivity decreased linearly. At 1300 °C, the weight loss of both composites was decelerated in a parabolic relation to oxidation time, but no obvious thermal diffusivity change corresponded to the weight loss. Therefore, oxidation affected much more strongly the weight loss than the thermal diffusivity of C/SiC composites.