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 O-2 and Ar that was used to simulate air. The thermal diffusivity change and the weight change with oxidation time at temperatures from 600degreesC to 1400degreesC 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 1000degreesC, 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 600degreesC, the weight loss of both composites was accelerated in a parabolic relation to oxidation time, but their thermal diffusivity decreased linearly. At 1300degreesC, 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.