Effect Of Preparing Ti By Electrolytic Voltage And Mg Is Added Into TiO₂ For Electrolysis In Molten Salt

Metal titani?m has been known as"aerospace metal"which have high melting point,low density,high temperature resistance,outstanding corrosion resistance and other excellent functional materials.At present,the Kroll method for the mature industrial preparation of titani?m metal has problems such as high production cost,long process cycle,serious pollution and complicated process.FFC method was proposed in2000,the molten salt was used as an electrolyte to electrolyze metal oxide at a high temperature to realize solid phase separation of metal and oxygen,and the metal element was derectly obtained.The process has some primary advantages of low production cost,simple process,short cycle and environmental protection.However,the low electrolysis efficiency in the process restrict its industrial development.Therefore,it is important to study the molten salt electro-deoxidation process of TiO₂ and improve the electrolysis efficiency.Based on the FFC method,the TiO₂ powder was pressed into a cathode to investigate the formation and electrolysis of CaTiO₃ at 3.2 V electrolysis voltage.In addition,different particle voltages were applied and the particle size of CaTiO₃ was changed.Two-stage voltage method was proposed to increase the electrolysis efficiency.The following conclusions were obtained:During the direct electrolysis of TiO₂ at the voltage of 3.2 V,CaTiO₃ is formed rapidly with the particles agglomerate and the size increases.CaTiO₃ is electrolyzed gradually with the electrolysis time increases,the particle size becomes smaller and the smaller size of CaTiO₃ is more easily electrolyzed to form titani?m suboxide.There has exist Ti₂O₃ in the initial stage of electrolysis,in the electrolysis for 1⁴h,the phase composition is CaTiO₃ and Ti₂O₃.The CaTiO₃ bulk structure becomes small and loose particles,and the microscopic morphology and particle size are quite different.Therefore,CaTiO₃ should be directly electrolytically reduced to Ti₂O₃ in the pre-mid phase of the electrolytic reduction process.The higher electrolysis voltage,CaTiO₃ is formed rapidly,it is easier to agglomerate and the larger particle size.A two-stage voltage method is proposed.The surface of the cathode product is densely packed forming a dense layer which hinders the electrochemical reduction of the molten salt and the inside of the cathode sheet resulting in slow internal electrolysis when pressed at 15 MPa.Reduce the tabletting pressure?5 MPa?,the cathode surface particle size is small and there are more pores.The two-stage voltage method is used for electrolysis under the condition of low pressure sheet pressure,the cathode product is Ti₂O₃ which has better crystallized and the efficiency of electric deoxidation of molten salt is improved.Mg was added to the TiO₂ cathode sheet for electrolysis.The effect of Mg-Added cathode sheet on the phase composition and microstructure of the cathode product was investigated.The following conclusions are drawn:There is a certain range of Mg-Added ratio.The cathode sheet is hot-reduced with magnesi?m and it is difficult to form a complete sheet when the Mg-Added ratio is too high.The ratio is too low and the electrolysis effect is not very well.The optim?m mass ratio of Mg is Mg:TiO₂=0.25 which the cathode sheet can be electrically deoxidized faster to obtain titani?m suboxide and improves the electrolysis efficiency.When the temperature rises,the Mg-doped cathode sheet reacts to form geikielite and precursor MgO.The geikielite particles are small and the pores are large.At the initial stage of electrolysis,the geikielite is rapidly electrolyzed to form CaTiO₃ and MgO with smaller particle sizes and the small particles CaTiO₃ are easily electrolyzed to form titani?m suboxide as the electrolysis continues.In addition,MgO is easily soluble in the CaCl₂molten salt which forming better pores in the cathode sheet and promoting electrolytic reduction.Therefore,the Mg-added cathode sheet can promote the entire electrochemical reaction process.