Chemical characterization of uniform and localized oxides formed on Zr-2.5 (wt. %) Nb alloy

Uniform and localized oxide morphologies formed on Zr-2.5(wt.%) Nb alloy in water and steam environments have been studied using electron microscopy techniques such as SEM and EPMA. The uniform oxidation was characterized by a compact and thin oxide layer. In contrast, the nodules showed localized thicker oxide growth with cracked and porous morphology. Significant segregation of Nb at the surface of the oxide nodule was observed, leading to destabilization and spallation of the oxide. The chemical states of Zr, Nb, and O in the two types of oxides were analyzed by XPS. The atomic composition of oxides in terms of O and M fractions was evaluated by p-EBS. The study revealed the oxide nodule to be richer in oxygen in comparison to the surrounding uniform oxide. The phase characteristics of these oxides were studied by Raman spectroscopy. The effect of initial surface in-homogeneities on nodule nucleation has been discussed. Polishing made the surface free of initial in-homogeneities and resulted in uniform oxidation on the surface. [Display omitted]