Oxidation of metals with highly reactive vapors: Extension of wagner theory

Abstract

In this article, a theoretical analysis of the behavior of metallic materials at high temperature in the presence of gaseous oxygen is presented. A generalized Wagner approach is presented in the limiting scenario of highly reactive vapors, Wagner’s theory being the lower limit for null reactivity. Oxygen transfer from the gas phase to the condensed phase is expressed in terms of oxygen effective pressure, accounting for the contribution of volatile oxides. The theoretical approach allows the prediction of the oxygen partial pressures in the feed gas corresponding to oxidation/deoxidation conditions. Such conditions can be different from those given by thermodynamic equilibrium by several orders of magnitude. Moreover, the actual oxygen partial pressure at the condensed phase interface can be expressed as a function of the feed-gas oxygen content, which is measurable. The theory is applicable for metals and nonmetallic materials, such as semiconductors, both in solid and liquid phase. An application to the molten silicon-oxygen system is presented.