Preparation of γ-Uranium-Molybdenum Alloys by Electrochemical Reduction of Solid Oxides in LiCl Molten Salt

Uranium-molybdenum (U-Mo) alloys especially the gamma-U-Mo phase, with excellent irradiation performance at high temperatures, have been extensively studied as low-enriched-uranium candidate fuels for strengthening nuclear security and nonproliferation worldwide. Herein, we provide a facile method to successfully prepare the gamma-U-Mo alloys (U-10Mo and U-8Mo) directly from oxide precursors via electro-reduction by constant cell voltage electrolysis in LiCl molten salt at 986 K. The reduction mechanism was elucidated through cyclic voltammetry using the metallic cavity electrode (MCE) combined with XRD, SEM and EDS characterizations toward the electrolysis products under different conditions. It was found that the reduction of mixed MoO3-UO2 oxides may take place in three steps. Firstly, MoO3 was reduced to Li4Mo5O12, and then Li4Mo5O12 was converted into Mo. Finally, the U-Mo alloys were formed due to the underpotential deposition of U on the pre-formed Mo. In addition, the effects of cell voltage, sintering temperature and mixture composition on the electrochemical reduction were investigated. The results found that the reduction rate increased with the augmentation of applied potential and the decrease of sintering temperature. Moreover, the favorable composition of the mixed precursor varied from 24 at% to 21 at%. The reduction conversion rate was determined to be 93.7% by ICP and TGA. (C) 2019 The Electrochemical Society.