The Molten Salt Electrolysis Of Tio <sub> 2 </ Sub> Preparation Of The New Technology Of Titanium Sponge

Titanium is a kind of new metallic material. Although titanium has many desirable properties, its use has been restricted because the current Kroll process has complicated and expensive procedures. New process of direct electrolysis reduction of TiO2 to titanium sponge in molten salt is an interesting and relatively new development and fundamentally different from the other conventional approaches in recent years. Development of this process has important meaning to expand new technique, new process applying in the metallurgy, and to enhance efficiency, to save energy, to achieve non-pollution process.In this paper, the new process of electrolysis reduction of TiO2 to titanium sponge in molten salt has been investigated. The thermodynamical analysis and calculation of molten salt, TiO2 and some of metal has been carried out. Varieties of molten salt have been selected. An experimental apparatus of electrolysis has been designed. According calculated result, the electrolysis voltage of TiO2 is 3.0V in molten calcium chloride at 850℃, 2.0V in molten potassium fluotitanate at 830℃.The research results of TiO2 solubility in molten salt show that the TiO2 solubility is 1.5-2% in the molten CaCl2 at 850 ℃ and 18% in the molten K2TiF6 at 830℃.The process of electrolysis by three different addition means of TiO2 in molten CaCl2 at 850℃ has been investigated. The results of EPMA and X-ray analysis indicate that the content of cathodal products is 94.646%, 80.632% and 99.784% respectively after cathodal products disposed. Additionally, the result of EPMA analysis indicates that the content of cathodal products is 91 . 1 93% in the molten K2TiF6 by the TiO2 powder at 830℃. Investigation on mechanism of graphite anode damaged shows oxygen is emitted on the anode during the process of electrolysis.The reaction mechanism of reduction TiO2 to titanium in molten CaCl2 has studied according to summarizing reported literature, analyzing the results of X-ray analysis on composition in molten calcium chloride after electrolyzing and basing on experimental phenomena. Under normal electrolysis condition, the reaction mechanism is as follows: Ti4+ is directly reduced and O2- discharged on the anode and O2 emitted from the molten salt. The reaction of reduction Ti4+ processed step by step, The reactions are as follows:(1) TiO2 + 2e- - TiO + O2-(2) TiO + 2e - Ti + O2-abnormal electrolysis condition, the reaction mechanism is as follows: a bit of CaCl2 is electrolyzed, Ca2+ reduced, Cl- discharged on the anode and Cl2 emitted from the molten salt; Ti02 is reduced by Ca entirely or partially, CaO, Ti and TixOy obtained, and CaO reacted with remnant TiO2 producing complex metallic oxide of xCaO . yTiO2, which exiting in molten CaCl2.