Auger electron spectroscopic study of the surface oxidation of uranium–niobium alloy {U–6 wt.% Nb} in a UHV environment containing primarily H2, H2O and CO

Auger electron spectroscopy has been used to study the surface oxidation of a uranium–niobium alloy, U–6 wt.% Nb, in a UHV environment containing primarily H2, H2O and CO. For comparison, the reaction of the oxidative species with pure uranium and niobium metals has also been investigated. The observed changes of the shape and position of the Auger transition peaks for U, Nb and O following exposures this UHV environment up to 200 L, and under a continuous electron bombardment indicated that oxidation of the alloy leads, first, to the formation of a surface oxide consisting of UO2.0. The formation of this oxide was followed by the development of Nb-oxides (NbO, NbO2 and Nb2O5) at the metal–oxide interface. Pure uranium was found to exhibit faster oxidation kinetics than the alloy, while pure niobium oxidised at a much lower rate than the uranium based materials.