Enhanced oxidation resistance of Ce by addition of Ga and nanocrystallization

Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying. Herein, we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.% Ga. Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy. The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga (75 at.%) is reached. After nanocrystallization, uniform distribution of Ga was achieved. After oxidation, a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance. The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.