PRODUCTION OF ALUMINUM AND ITS ALLOY AT LOWER TEMPERATURE THROUGH DIRECT ELECTROREDUCTION OF SOLID ALUMINA AND MIXED OXIDES IN CHLORIDE MELT

Different from the conventional way of dissolving alumina into a traditional cryolite melt or mixed fluorides/chlorides melts, here we report a simple way to produce aluminum and its alloy by directly electro-reduction of solid alumina and mixed oxides pellet, respectively in molten CaCl2 at 850 degrees C. The electro-reduction behavior of solid alumina in molten CaCl2 was investigated by cyclic voltammetry using a novel powder modified electrode (PME), it was found that alumina can be reduced at -1.2 V ( vs. Pt pseudo-reference electrode) at Mo electrode, similar to 400mV positive than the onset reduction potential of calcium. Large amount of small metallic aluminum droplets were obtained by constant voltage electrolysis between a solid alumina cathode and a carbon anode at 850 degrees C with current efficiency of similar to 50%. NiAl alloy with well controlled composition was successfully produced from a mixture of Al2O3 and NiO pellet cathode, preferential reduction of nickel oxide provided a conductive nickel matrix which speeding up the reduction of alumina and act as the host of liquid aluminum.