ABSTRACT
Metal oxide dissolution reactions are heterogeneous processes; as such, mass transport is involved and may dominate the overall rate. In turn, the chemical processes taking place at the interface may also be sluggish enough to control the rate. This chapter discusses the basic principles governing the kinetic behavior of the dissolution of ionic, semiconducting, and insulating covalent oxides. Atomic displacements are still essential for the occurrence of a change, but these atomic displacements are much more limited in magnitude: in the direction perpendicular to the interface, a jump across a more or less arbitrarily defined plane may be involved (i.e., a displacement of the order of atomic distances). Along the surface, more important movements may be involved: surface mobility of atomic units may result in irreversible changes. Dissolution reaction rates controlled by chemical processes at the interface span several orders of magnitude and it is convenient to sort them out according to the types of chemical processes actually involved.
