Fundamental Research On Electrodeposition Of Tantalum And Its Alloys In Solvated Ionic Liquid System

Tantalum has high biocompatibility and corrosion resistance,which is of great significance to the development of biomedical materials.In order to reduce the cost of using tantalum as a medical metal material,a tantalum coating can be deposited on the surface of a traditional medical metal material that is relatively in expensive and easy to process and shape.The current methods for preparing tantalum coatings include vapor deposition,plasma spraying,arc ion plating,magnetron sputtering,and electrodeposition.However,there are still many problems that need to be resolved in terms of economy,scope of application,and technological maturity.In view of this,this paper uses EC-AlCl3-TaCl5 and DMI-ZnCl2-TaCl5 two new solvated ionic liquids as electrolytes to study the electrode reaction mechanism of cathodic electrodeposition of tantalum,and evaluate the performance of the electrodeposited products under different conditions.The main conclusions obtained are as follows:(1)Using tungsten as the working electrode,the electrochemical reduction process of Ta(Ⅴ)in EC-AlCl3-TaCl5 solvated ionic liquid was studied by cyclic voltammetry.And X-ray diffraction(XRD)energy spectrometer(EDS)and X-ray photoelectron spectroscopy(XPS)were used.to characterize electrodeposition products.The results show that the electrochemical reduction process of Ta(Ⅴ)in EC-AlCl3-TaCl5 solvated ionic liquid is Ta(Ⅴ)→Ta(Ⅳ)→Ta(Ⅲ)→Ta,in which Ta(Ⅲ)is reduced to tantalum Metal is an irreversible reaction controlled by diffusion,with a diffusion coefficient of(0.6～9.7)×10-7 cm·2·s-1.With tungsten as the cathode,the products obtained by electrodeposition at-0.8 V(vs Al)for 2 h are tantalum and tantalum oxide.(2)The conductivity(σ),viscosity(η)and density(ρ)of DMI-ZnCl2 solvated ionic liquid at different temperatures were explored.The conductivity of DMI-ZnCl2 at 313～363 K is 0.571～0.932 mS·cm-1,which can be expressed as lnσ=3.095-1129.059/T.The viscosity at 323～373 K is 14.7～22.2 mPa·s,and the density at 313～373 K is 1.163～1.205 g·cm-3,which can be used as Inη=-0.033+1006.014/T andρ=-6.464×10-4T+1.406 means.The results of the cyclic voltammetry curve show that the initial reduction potential of Zn(Ⅱ)is-1.13 V(vs Pt).The XRD and SEM-EDS analysis of the product electrodeposited at 353 K and-2 V(vs Al)for 1 h confirmed that DMI-ZnCl2 can be electrodeposited to obtain a dense and uniform zinc coating.(3)Electrodeposition of zinc-tantalum coatings in DMI-ZnCl2-TaCl5 solvated ionic liquid was carried out to investigate the influence of electrodeposition potential,temperature,time and molar ratio of ZnCl2 to TaCl5 on the microscopic morphology,chemical composition,phase composition and corrosion resistance.The results showed that the optimum experimental conditions were the electrodeposition potential of-1.6 V(vs Ag),the temperature of 353 K,the time of 1 h and the molar ratio of ZnCl2 to TaCl5 of 10:1,under which a dense and homogeneous coating was obtained with a corrosion current density of 1.828×10-4 A·cm-2.The coating was analysed by XRD and XPS,and the results showed that the physical phases of the coating consisted of Zn and Ta2O5,with the mass fractions of Zn,O and Ta being 28.98%,64.81%and 6.21%,respectively,of which tantalum metal accounted for 11.54%of the Ta element.