Emissivity and catalycity measurements on SiC-coated carbon fibre reinforced silicon carbide composite

The emissivity and the catalytic efficiency related to atomic oxygen recombination were experimentally investigated in the range 600–1600 °C for a carbon fibre reinforced silicon carbide composite produced by polymer vapour infiltration and then coated with SiC by chemical vapour deposition. High emissivity (about 0.7 at 1600 °C) and low recombination coefficients (on average 0.07 at 1500 °C) were found for all the samples tested. The experimental data showed a marked effect of the surface finish on the catalytic behaviour only: C/SiC samples belonging to the same production batch but having slightly different surface morphology, while exhibiting the same catalycity trend, are characterized by detectable differences in absolute values of the recombination coefficient. Micro-structural investigations performed on post-test samples have shown the formation of a silica-based glassy layer and have confirmed that the oxidation of C/SiC lies on the boundary line between the active and passive mechanism.