Magnetic and electronic properties of alpha-U2N3 and its role in preventing uranium from oxidation: First-principles studies
Abstract
Nitriding treatments have been adopted as an effective way to enhance the anticorrosion properties of uranium metal in ambient conditions but the mechanism remains unclear. We tackle this issue through first principles studies for the geometric, magnetic, electronic and vacancy properties of bulk alpha-U2N3, as well as its reaction with oxygen.
The formation of N (U) single vacancy in alpha-U(2)N(3 )is almost spontaneous under U-rich (O-rich) conditions. The adsorption of oxygen up to 300% of U contents, both on vacancy sites and in interstitial sites, may further gain energy by forming alpha-U2N3Ox and UO3 frameworks.
Energy barriers for oxygen diffusion through alpha-U(2)N(3 )layers are larger than 1.5 eV, and hence the thin U2N3 layer prevents the oxidation in deep uranium layers. The structure of alpha-U2N3O3 is chemically disordered and the final oxidization products are most likely N-2 and UO3.
Our theoretical studies provide useful information to understand the oxidation process of alpha-U2N3, and also give insights in the further development of surface treatment technologies for uranium.