Oxidation kinetics of nitrided uranium determined by ultraviolet–visible reflectance spectroscopy

Highlights: • The oxidation kinetics of nitrided uranium and DU (50–250 nm) was investigated. • The oxidation process was monitored by a modified reflectance spectroscopy setup. • The oxide thickness of nitrided uranium grew following a parabolic model. • The activation energy of Q_D = 98 kJ/mol was obtained. • The formation of UNO after oxidation may improve the corrosion resistance. The oxidation kinetics of a uranium surface treated by pulsed laser nitriding was studied using reflectance spectroscopy. The growth of the oxide thickness generally followed a parabolic growth model for the nitrided uranium with pure O₂, which agreed with the diffusion barrier model. The activation energy was 98 kJ/mol and was obtained by monitoring the oxide growth in the temperature range 400–460 K. As a comparison, the growth of the oxide thickness of untreated uranium was also monitored, which indicated that the nitriding treatment improved the corrosion resistance of uranium. This may be due to the formation of UNO compounds on the surface of nitrided uranium after oxidation, which can resist the diffusion of oxygen ions into the inner layer.