Direct Electrochemical Preparation of Ni-Cr Alloy from Solid Oxides in Molten CaCl2.

Direct electro-reduction of mixed powders of chromium oxide (Cr₂O₃) and nickel oxide (NiO) to the intermetallic compound Cr_1.12Ni_2.88 was successfully demonstrated in CaCl₂ molten salt at 900°C. The reduction mechanism was investigated by cyclic voltammetry using a metallic cavity electrode (MCE) as well as the characterizations of some partially electrolyzed products and Ni-Cr alloy prepared from constant voltage electrolysis by terminating the reduction process after different times, which were characterized by means of XRD and SEM et al. It was found that the reduction starts with the formation of Ni metal, accompanied with the formation of an intermediate product CaCr₂O₄. Then, the intermediate product CaCr₂O₄ is further electro-reduced to Cr, which is directly alloyed with the newly-formed Ni to form the Ni-Cr intermetallic compound. At the same time, pure Cr phase could not be detected by the XRD or EDXA when the Cr content is relatively low in the NiO-Cr₂O₃ mixture. Intermetallic compound with the target stoichiometry containing 6000 ppm oxygen is obtained after 4 h electro-reduction in CaCl₂ molten salt at 900°C. [ABSTRACT FROM AUTHOR]