Studies on Preparation of Thorium-Based Intermetallics in CaCl2 Melt by Electrochemical De-Oxidation Process

Abstract

Thorium and its alloys find immense applications in nuclear technology. In the present study, the feasibility of direct electrochemical de-oxidation of mixed ThO2-NiO (7:3 molar ratio) and ThO2-Fe2O3 (7:1.5 molar ratio) to Th7Ni3 and Th7Fe3 intermetallics was investigated for the first time in CaCl2 melt at 900 °C using FFC Cambridge process. Electro-reduction mechanisms of the mixed metal oxides were elucidated by conducting constant voltage electrolysis at 3.1 V cell potential with sintered mixed metal oxides pellet cathode and HD graphite anode in molten CaCl2 for different time intervals. The electrolysed products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis techniques. Reduction of the less stable metal oxide, e.g., NiO or Fe2O3, occurred at the initial phase of electrolysis, and de-oxidation of more stable ThO2 took place in presence of newly formed metallic Ni or Fe in the later stage, leading to the formation of Th7Ni3 or Th7Fe3. Electro-reduction mechanism of ThO2 was evaluated using cyclic voltammetry technique with ThO2 filled Mo cavity electrode, and a single-step reduction of ThO2 to Th was perceived.