Ionic Diffusion Oxidation Model of Uranium

Abstract

A theory‐driven model is formulated for the low‐temperature oxidation of uranium exposed to oxygen. The model is based on diffusion of oxygen ions through the oxide film driven by the electrostatic potential generated between the metal and adsorbed oxygen ions. The model fits published experimental data well for temperatures between 20°C and 200°C and for oxide film thicknesses less than 300 nm. The derived reaction rate coefficients for parabolic and inverse logarithmic growth regimes correspond well to the available published values and outperform the existing empirically derived forms. These reaction rate coefficients can be applied to the oxidation of any metal that is driven by the generated electrostatic potential.

Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour

“…If the presence of hydride, whether as an intermediary layer or isolated features, could be conclusively demonstrated it would greatly improve the understanding of the corrosion mechanism of uranium in moist air and water vapour environments. Such mechanistic understanding is needed for the construction of predictive corrosion models, as with the ionic diffusion model used to represent the oxidation of uranium in pure oxygen environments 10 . Unlike the application of empirical models to assess corrosion during long-term storage, such models allow insight beyond the limitations of the data used to generate the model.…”

Low-Temperature Oxidation of Fine UO2 Powders: Thermochemistry and Kinetics

“…At temperatures below the threshold for thermally activated diffusion, oxygen mobility can be driven by an electric-field-assisted mechanism. − Examples of such a field-assisted oxidation are found in the low-temperature oxidation of metallic surfaces, including metallic uranium. − The ionic transport is enabled via a potential difference that is created over a thin (5–10 nm) surface oxide layer (visualized schematically in Figure for the hypothetical case of UO 2 ).…”

“…At more elevated temperatures, due to the increased probability for thermally activated diffusion, growth of the oxide layer may continue. Various metallic surfaces, including metallic uranium, 42,43 follow such an oxidation mechanism when exposed to oxygen. 44−46 A similar mechanism was proposed several decades ago to be involved in the lowtemperature region of UO 2 oxidation.…”

TiN Films Deposited on Uranium by High Power Pulsed Magnetron Sputtering under Low Temperature

“…However, the current density (icorr) of HPPMS TiN (2.6 × 10 −8 A/cm 2 ) was lower by an order of magnitude than that of HP + DC TiN (2.7 × 10 −7 A/cm 2 ) and two orders of magnitude than that of DCMS TiN (5.1 × 10 −7 A/cm 2 ), respectively. As reported, the electrochemical resistance of film is strongly related to the microstructure and surface morphology [ 11 , 27 ]. The relatively lower corrosion resistance of the DCMS TiN film is mainly due to its porous columnar structure so that the solution can easily reach the DU substrate via the pinholes.…”