Theoretical Investigation for the Active-to-Passive Transition in the Oxidation of Silicon Carbide
The oxidation of silicon carbide at high temperatures from 673.15 to 2173.15 K is investigated by using thermodynamic equilibrium calculations and a mass transfer model. The dominant reaction of the active-to-passive transition and five other dominant reactions, which are in six different temperature regions, have been determined according to the main equilibrium products. Then, a modified Wagner's model has been developed to determine the active-to-passive transition boundary by combining mass transport and thermodynamic calculations. The present theoretical calculations satisfactorily explained the reported experimental and theoretical data. The influence of flow rate on the active-to-passive transition boundary has been explained using our model. The rate controlling mechanism of the oxidation at the active-to-passive transition point is proposed.
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Document Type: Research Article
National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi'an 710072, China
Laboratory for Thermostructural Composites, UMR 5801, NRS-CEA-Snecma-Universite Bordeaux l, F-33600 Pessac, France
May 1, 2008