| Titanium and titanium alloy have the advantages of light weight,high strength,corrosion resistance and good oxidation resistance.In recent years,they have been widely used in aviation,automobile,shipping,medical,chemical,construction,sports and daily necessities.Preparation of titanium and its alloys by FFC processhas received wide attention because of its short technological process and low production cost.However,its low efficiency and the long production cycle limit the application of the process.Nano TiO2-Al2O3 composite powders were prepared by LCS to solve the problem.The research on FFC electrolysis process based on the Nano TiO2-Al2O3 composite powders was carried out and the influence of A1 doping on the electronic structure of TiO2 crystal was studied in this paper.The results of quantitative calculation with CASTEP software show that the band gap of anatase TiO2 is about 2.17eV,the valence band is located at 0?-5.leV and the conduction band is located at 2.5?6.9eV.Band gap of the anatase TiO2 after doping Al becomes narrow and the density of states near the Fermi level increases significantly.The changes of number and bond length of crystal population were caused by doping Al.The electron distribution around A1 is anisotropic and conducive to the transport of crystal electrons.Using Ti(SO4)2and Al(NO3)3·9H2O as raw materials,TiO2-Al2O3 powder were prepared by low temperature combustion synthesis.The influences of the amount of fuel,the ignition temperature and the proportion of raw material on preparing the TiO2-Al2O3 powder were studied.The experimental results show that when the amount of urea is 1.5 times of the theoretical dosage,the product is white and has uniform color and better fluffy degree.When the ignition temperature is 600? together with the aluminum content of 10%?50%,the particle of the synthesized powders prepared by low temperature combustion is fine.The particle size is 21?3 5nm.Using cathode,a diameter of 20mm,thickness of 3mm disc,made of composite powder and graphite anode,titanium aluminum alloy was prepared by electro-Deoxidation in CaCl2-NaCl molten salt.The effects of molten salt ratio,temperature,electrolytic voltage,aluminum content in cathode film and electrolysis time on the electrolysis effect were investigated.The results show that the CaCl2 content and electrolytic temperature of molten salt can be improved properly the reaction of electro-Deoxidation.The current density of the electrolytic voltage of 3.2V is higher than that of 2.8V and 3.0V.When the composite powders of different contents of aluminum are used as cathode,the variation of current density gradually decreases with the electrolytic process,and tends to be a smaller and stable value.With the increasing of the aluminum content in the cathode,current density firstly increases and then decreases.It has higher current density at the beginning of electrolysis when the content of aluminium is 10%-20%.The current density dropped from about 0.53A/cm2 at the beginning to about 0.35A/cm2 2 h latter.The decrease of current amplitude changes gently and the trend can be maintained to 8 h.When cathode is made of composite powder with aluminum content of 20%as raw material,electrolytic voltage of 3.2V and electrolytic temperature of 800?,titanium alloy phase appears after electrolytic of 25 h in molten salt in which the ratio of CaCl2 to NaCl is 2:1. |
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