Surface characterization of oxidative corrosion of U-Nb alloys

We have studied the relative rates of oxidative corrosion of U-Nb alloys co ntaining 2-8 wt. % Nb, using x-ray photoelectron spectroscopy and depth pro filing by sputtered neutrals mass spectroscopy. The alloys have been charac terized after exposure to dry and humidified air (up to 50% relative humidi ty) at temperatures from 25 to 125 degreesC, and after exposure to electroc hemical solutions. Oxidation of the U-Nb alloys in a tube furnace results i n oxide layers comprised of UO2 and Nb2O5 under all experimental conditions used. The thickness of the oxides increased with treatment time and temper ature, but decreased with increasing Nb alloy content. For example, a 48 h treatment at 75 degreesC and 50% relative humidity results in an oxide laye r on U-2% Nb that is approximately 1.5 times as thick as that on U-8% Nb. E lectrochemical oxidation of U-Nb alloys facilely generated UO3( . nH(2)O) a nd Nb2O5 layers similar to 1000 Angstrom thick, qualitatively similar to th ermal oxidation results. U-Nb alloys electrochemically oxidized at low pH e xhibit oxide layers with near-surface regions (50 Angstrom) enhanced in Nb content, as compared to the bulk material. Surface UO3 (. nH(2)O) was not r eadily reduced upon exposure to molecular D-2; however, D atoms facilely re duced UO3(. nH(2)O) to UO2.