Preparation of Titanium Deposit in Chloride Melts
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ODUCTION
TITANIUM has many attractive properties, and the use of titanium and its alloys can be increased greatly if a less expensive process for the production of pure titanium is developed. Electrolysis in molten salts is possibly a low-cost way to produce titanium; therefore, many attempts to develop an electrolysis process have been reported. Examples include the FFC-Cambridge process,[1–4] calciothermic reduction,[5–8] the molten oxide electrolysis process,[9] and the composite anode electrolysis (USTB[10,11] and the MER[12]) process. Large cells and pilot plants have been run, but no commercial electrolysis production has been achieved. The main obstacles for the successful development of an electrochemical route for titanium production have been to fulfill the purity requirements of the titanium product, mainly because of the problems associated with the existence of various valences of dissolved titanium species and the content of oxygen in cathode titanium product. The oxygen content in titanium products is influenced by the deposited titanium morphology. A large grain size deposit will facilitate a lesser oxygen content in the titanium products. In all the electrowinning of Ti processes, including our USTB process, they are all involved in how to control the deposit morphology and XIAOHUI NING and HEFEI REN, Students, and SHUQIANG JIAO and HONGMIN ZHU, Professors, are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Xueyuan Road 30, Beijing 100083, P.R. China. Contact e-mail: [email protected] HENRIK A˚SHEIM, Student, is with the Department of Materials Technology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Manuscript submitted September 16, 2010. Article published online August 25, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS B
how the electrolytic parameters affect the deposit morphology. In previous research, the influence of electrokinetic parameters on anodic dissolution of titanium oxycarbide was investigated in detail.[13,14] The electrochemistry of titanium dichloride in molten salts and the deposition of metallic titanium from titanium chlorides have been the subject of many investigations.[15–25] Therefore, as part of our USTB process, in which titanium ion from the anode dissolution of titanium oxycarbide in molten salts will electrodeposit in the cathode, the electrokinetic parameters of cathodic deposition such as current density, and initial titanium ion concentration could affect the morphology and purity of titanium deposit. However, not much work about the influence of electrokinetic parameters on the morphology of titanium deposits has been reported. This article reports on an investigation of the electrodeposition of titanium in NaCl-KCl-TiCl2 mixture at 1023 K (750 °C). To rationalize the experimental runs, the influence of electrokinetic parameters, including starting current density and titanium ion concentration, on the morphology of titanium deposits were studied. II.
EXPERIMENTAL PROCEDURES
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