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

摘要

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 CaCl_2 at 850°C. The electro-reduction behavior of solid alumina in molten CaCl_2 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, ～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°C with current efficiency of ～50%. NiAl alloy with well controlled composition was successfully produced from a mixture of Al_2O_3 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.