Silicon carbide has unique oxidation properties that differ from those of ablative thermal protection materials, forming a stable oxide layer. A general thermodynamic equilibrium approach is presented for analysis of the oxidation and nitridation of silicon carbide, combining mass transport and multi-component equilibrium. Passive-to-active transitions are investigated in diluted oxygen, air, and nitrogen environments, and show good agreement with theory and experiments. Different passive-to-active transition mechanisms are examined for oxidation and nitridation, and oxidation exhibits a bifurcation between passive and active states. The thermodynamics leading to temperature jump are explained in the context of these results, and surface temperatures differ from experimental measurements in the literature to within 8%.
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