Room Temperature Oxidation Kinetics of a U-Nb Alloy

The reaction of atmospheric gases with metal surfaces plays a crucial role in driving many beneficial and detrimental processes such as heterogeneous catalysis, corrosion, protection from degradation, and environmental dispersal. The chemistry and kinetics of the oxide formed on uranium metal alloyed with 14 at.% Nb was investigated following exposure to dry and ambient air environments. Using a combination of x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS), the evolution of the oxide as a function of time and oxygen partial pressure were determined. Segregation of the solute element was found to occur, resulting in the formation of a niobium rich oxide interfacial layer between the UO₂ surface and bulk metal. The potential role of this segregation on passivating the material against further oxidation will be discussed and comparisons will be made to the oxidation mechanism of unalloyed uranium under similar environments.<br/>This work was prepared by LLNL under Contract DE-AC52-07NA27344. This support does not constitute an express or implied endorsement on the part of the government.