The microstructure and oxidation behavior of the N-doped modified layers on uranium surface prepared by pulsed laser irradiating

Abstract

The N-doped modified layer on uranium surface was prepared by pulsed laser irradiating in nitrogen atmosphere. The results of microstructure characterised by XRD, AES and XPS show that it is a composite layer with a gradual transition structure from UO2-xNy and uranium oxy-nitride (UNxOy) to UN and eventually to uranium from surface to interior. Initial oxidation behavior after sputtering for different time illustrates that UNxOy with U 4f7/2 BE at 379.6 eV is inert under oxygen exposure. Further, the thermal stability study shows that the modified layer exhibits excellent ability to prevent the O atoms from diffusing into the interior at 423 K. Moreover, the corrosion protective properties of the N-doped modified layers before and after thermal treatment were evaluated through potentiodynamic polarization tests. The results show that the N-doped modified layer improved the corrosion protective properties of metallic uranium. The self-corrosive potential and self-corrosive current of the N-doped modified layer are −5.75 × 10−2 V vs. SCE and 1.37 × 10−7 A/cm2, while the values of metallic uranium were −5.67 × 10−1 V vs. SCE and 8.08 × 10−7 A/cm2. After thermal treatment, its values are −8.57 × 10−2 V vs. SCE and 4.83 × 10−8 A/cm2, indicating that the corrosion resistance of the N-doped modified layer was further improved.