Electrochemical preparation of the Fe–Ni36 Invar alloy from a mixed oxides precursor in molten carbonates

The Fe–Ni36 alloy was prepared via the one-step electrolysis of a mixed oxides precursor in a molten Na₂CO₃–K₂CO₃ eutectic melt at 750°C, where porous Fe₂O₃–NiO pellets served as the cathode and the Ni10Cu11Fe alloy was an inert anode. During the electrolysis, NiO was preferentially electro-reduced to Ni, then Fe₂O₃ was reduced and simultaneously alloyed with nickel to form the Fe–Ni36 alloy. Different cell voltages were applied to optimize the electrolytic conditions, and a relatively low energy consumption of 2.48 kW·h·kg⁻¹ for production of FeNi36 alloy was achieved under 1.9 V with a high current efficiency of 94.6%. The particle size of the alloy was found to be much smaller than that of the individual metal. This process provides a low-carbon technology for preparing the Fe–Ni36 alloy via molten carbonates electrolysis.