Surface oxidation of uranium metal as studied by X-ray photoelectron spectroscopy

Abstract

X-Ray photoelectron spectroscopy has been used to study the oxidation of uranium metal. The results indicate that even at 1073 K in a residual oxygen partial pressure of less than 1 × 10^–8 N m^–2 the interdiffusion of pure uranium and the surface oxide film is not sufficiently rapid to produce a completely pure uranium surface. Evidence is presented which suggests that under spectrometer conditions the surface layer is composed of a mixture of pure uranium, UO₂ and ‘UO’ stabilised by the presence of uranium carbide. It is shown that values previously reported for the binding energies of uranium are in error and they must have been obtained from an oxidised surface. Accordingly values believed to be representative of pure uranium are presented.