On the theory of low-temperature oxidation of titanomagnetite grains

Abstract

It is shown that the space-time distribution of vacancies in the process of formation of cation-deficient spinels is determined mainly by the boundary kinetics. At low rates of vacancy appearance in the surface layer (e.g., owing to oxygen deficit), the degree of grain oxidation remains invariant over the entire volume. The rate of oxidation in this case does not depend on the diffusion coefficient, but is determined by the boundary processes. With an excess of oxygen, the process of oxidation occurs inhomogeneously over the grain volume. In this case the rate of oxidation is determined by the diffusion coefficient. Approximate estimates have been made of the physical parameters characterising the two types of oxidation.