Preparation Of Niobium And Nb-Ti Alloy By Electro-Deoxidation In A Eutectic Melt

Niobium exhibits many good properties such as good ductility, high thermal conductivity and corrosion-resistant. As a valuable metal material in the science and technology, niobium and niobium-based alloys have been used in the extensive fields, such as steel, aerospace, electronic industry and low temperature superconductivity. The existing pyrometallurgical process to prepare metal niobium is complex, expensive, energy intensive and probably polluting. Therefore, it is highly desirable to develop a simple, low-cost and environmentally sound process to prepare niobium and niobium-base alloys.In the paper, the novel method of electro-deoxidization, namely, FFC Cambridge Process method was used to reduce solid Nb₂O₅ directly to niobium metal in a eutectic melt of CaCl₂-NaCl. A graphite rod was employed as the anode and the sintered Nb₂O₅ pellet served as cathode. The applied voltage between the cathode and anode was 3.1 V below the decomposition potentials of the chloride melt and over the decomposition potentials of the oxide of niobium.The influence of sintering temperature, sintering time, electrolyzing temperature, electrolyzing duration, compaction load, diameters of cathode pellet and anode pellet on the electro- deoxidization of solid Nb₂O₅ in a eutectic CaCl₂-NaCl melt are studied. The results show that the sintered cathode pellets exhibit good electrochemical performance and the oxygen content of the product reached the minimum value of 1.09% after electrolyzing for 8 hours when the Nb₂O₅ pellets were formed at 10 MPa and sintered at 1200 ℃ for 12 hours. It can be found that the electrode reaction rate in the electro-deoxidization process is not uniform, which decreases gradually with increasing the electrolyzing time. The oxygen content in the reduction product decreases with increasing the electrolyzing temperature. However, when the electrolyzing temperature exceeds 850 ℃, the electrolyzing temperature has no obvious effect on the oxygen content. The oxygen content is also related to the cathode pellet size, and it reduces with increasing of cathode pellet surface area. But, the current efficiency drops gradually when the cathode pellet surface area increases. The size of the...