Initial Reactions at the Electrodes of the FFC-Cambridge Process in Molten CaCl 2 to Produce Ti
- PDF / 2,974,522 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 61 Downloads / 150 Views
INTRODUCTION
THE FFC-Cambridge (Fray–Farthing–Chen) process[1] offers a new approach compared to the Kroll Process by directly extracting Ti from TiO2 through electrochemical electrolysis in molten CaCl2, which has stimulated significant scientific and industrial interest worldwide. This process is simpler, less resource-consuming, and more environmentally friendly than the Kroll process used to produce titanium metal in industries.[2,3] There are many researches about preparation of metal and its alloys reported since the FFC-Cambridge proposed. Recently, the process has broadened into new field, such as preparation of high entropy alloy, improvement of the electrolytic cell, manufacturing of dysprosium-iron alloys, and so on.[4–7] In the FFC-Cambridge process, graphite is typically used as the anode, molten calcium chloride is the electrolyte, and a mixture of metal oxide and other oxides or chlorides is the cathode. At elevated temperatures, an appropriate voltage is applied between the anode and cathode.
PINGSHENG LAI, MEILONG HU, ZHENGFENG QU, LEIZHANG GAO, CHENGUANG BAI, SHENGFU ZHANG, and GUIBAO QIU are with the School of Materials Science and Engineering, Chongqing University, Chongqing, 400044, China. Contact e-mail: [email protected] TIANXIONG WANG is with the Shanxi Metallurgical & Mining Group Co., Ltd, No. 50, Gaoxing District, Xi’an 710075, China. Manuscript submitted October 4, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
Initially, the electro-deoxidation mechanism of the cathode (TiO2) is ionization of oxygen at a cathodic potential.[1] Oxygen ions are formed from the cathodic metal oxide, dissolved into the electrolyte and subsequently transferred to the anode under the electrolytic field. Finally, these ions discharged at the graphite anode by the generation of CO or CO2. In the OS (Ono–Suzuki) process, Suzuki et al.[8–11] believed that the removal of oxygen via electrochemistry should be attributed to calcium thermal reduction. The TiO2 cathode is directly reduced by Ca, which is produced from the electrolysis of the by-product CaO and dissolved in the molten CaCl2. Before 2002, there were few reports mentioned the intermediate phase of calcium titanate. In 2002, Chen et al.[12] found that the fast discharge of oxygen anions from the oxide phase into the molten salt could cause saturation of CaO, which would subsequently reacted with the partially reduced oxides to form calcium titanates (perovskite phase) during the reduction of TiO2. In 2005, Fray et al.[13] proposed a relatively clear reaction pathway from titanium dioxide to titanium metal and claimed that the calcium-containing intermediate compounds (perovskite phase) were inherent steps in the kinetic pathway in molten CaCl2. Table I shows the sequence of the reactions. During the entire reduction process, the formation and decomposition of the interphases of calcium titanate require a substantial amount of time. Therefore, the generation of CaTiO3 was considered a kinetic barrier[14,15] because of its dense structure during the electrochem
Data Loading...
