Study On Preparation Of Titanium And Its Alloys By Molten Salt Electrolysis Of High Titanium Slag

Titanium and its alloys own the characteristics of strong corrosion resistance,good heat resistance,high specific strength and compatibility with living organisms,so they may be widely used in chemical,aerospace,biomedical and other fields.Ti as matrix and other metal elements are added to form titanium alloys.The alloys are mainly prepared by self-propagating high temperature synthesis method,metal thermal reduction method and remelting method.But these methods have many problems such as long production process,high raw material cost and low product quality.High titanium slag with high contents of Ca and Mg in our country cannot be directly used as raw material for the production of TiO₂by chlorination process.Because the content of impurity is high.It is primarily used to prepare TiO₂ by sulphate method,unfortunately,waste acid was produced and caused the environment pollution.It is urgently to find a way to utilize high titanium slag with high contents of Ca and Mg reasonably and efficiently.In order to resolve the problems mentioned above,this paper used the high titanium slag as raw material,adopted the FFC process which was environmental protection,short process and easy operation.Ti Fe alloy was directly prepared by electrochemical reduction of high titanium slag cathode in molten CaCl₂.The effects of electrolysis time,1mol%CaO addition in molten salt,electrolysis temperature,and cell voltage on the product were studied.On this basis,low-melting metal zinc and bismuth were added as metal cathodes,the electrolysis of high titanium slag in molten CaCl₂ was performed to prepare titanium alloys.The effects of pre-melting,melt structure,pre-melting and electrolysis time on the product were investigated.The results of this study are as follows:(1)Ti Fe alloy was successfully prepared by the electrolysis of high titanium slag cathode under the conditions of 850?,3.0V,and 10h in molten CaCl₂.The reduction process can be divided into three stages:The early reaction was that high titanium slag immediately became calcium titanate under the action of current;Ca TiO₃electrochemically reduced to generate TiO after a period time of electrolysis;TiO transformed into target product Ti Fe or Ti₂O which was more reduced,that depended on whether TiO was in contact with Fe.(2)Adding 1mol%CaO to CaCl₂ molten salt could promote and change the reaction path in the electrolysis of high titanium slag cathode.The optimal conditions for preparing Ti Fe alloy from the electrolysis of high titanium slag cathode in molten CaCl₂ were 850?,2.8V,and 8h.Under these conditions,Ti Fe alloy was successfully prepared.(3)The electrolysis of TiO₂ powder using metal Zn cathode in molten CaCl₂ was carried out.There was a reduced reaction of titanium oxide during the potential rang from-0.77V to-1.73V(vs.Ag/Ag Cl)showed by cyclic voltammetry.Ti-Zn alloy prepared by three-electrode potentiostatic electrolysis,which proved the feasibility of the method.Thermodynamic analysis,EDS and XPS characterization further confirmed the occurrence of electrochemical reduction reaction.(4)The electrolysis of high titanium slag using metal Zn cathode in molten CaCl₂was carried out.The necessary pre-melting and proper melt structure were prerequisites for effective electrolysis under the conditions of 850?,2.8V.Under the combined action of metal thermal reduction and electrochemical reduction,a small amount of high-titanium slag in the Zn solution was reduced in a short time.Ti diffused in the liquid Zn to form Ti-Zn or Ti-Al-Zn stable component which had the content of titanium 5%or25%,respectively.(5)The electrolysis of high titanium slag using metal Bi cathode in molten CaCl₂was carried out.Ti-Bi alloy consisted of Ti-Bi-Ca ternary composition with 33%Ti in enriched region was successfully prepared.The diffusion of Ti in metal cathode showed the following rules:before the metal was reduced which could form a ternary stable component with Ti and metal cathode,Ti diffused steadily in the metal cathode according to the binary alloy equilibrium state.