| Aluminium and its alloys show low density,excellent ductility,and high electrical and thermal conductivity,which make them are widely used in construction materials,packaging materials,aerospace and other industries.Aluminum-magnesium alloy has the advantages of aluminum and magnesium,for instance light weight,excellent mechanical properties,and good corrosion resistance.It can be used as a component protective layer and hydrogen storage material.There are many methods for producing aluminum and aluminum-magnesium alloys,such as smelting,mechanically alloying and electrochemical co-deposition,The electrodeposition method is considered to be the simplest preparation method because of its simple operation and easy control.Molten salt electrolysis has high temperature,low energy efficiency,and sophisticated operation;the standard electrode potential of aluminum and magnesium are both more negative than hydrogen,which means that aluminum and magnesium coatings cannot be electrolyzed in aqueous solutions.Therefore,researchers are committed to produce of aluminum and aluminum-magnesium alloy in nonaqueous solution.In this paper,the electrodeposition of aluminum and aluminum-magnesium alloy is studied in a new solvated ionic liquid DMI-AlCl3(1 M)system.First,the Raman spectrometer was used to study the structure of the DMI-AlCl3(1 M)system,and[AlCl4]-and[Al2Cl7]-ions were detected.In addition,the conductivity and viscosity of the electrolyte system were measured by the fixed conductivity cell constant method and the rotation method.It is found that the relationship between its conductivity,viscosity and temperature is in accordance with the Arrehninus formula.The electrolyte can dissolve the inorganic salt MgCl2,and obtain aluminum and aluminum-magnesium alloy by electrodeposition,the electrodeposition mechanism and better preparation conditions of metal aluminum and aluminum-magnesium alloy are studied.Cyclic voltammetry results show that the electrodeposition of metallic aluminum in the DMI-AlCl3(1 M)system is an irreversible process,and the reduction reaction of metallic aluminum on the tungsten wire working electrode is 4Al2Cl7-+3e-=Al+7 AlCl4-.A potentiostatic electrolysis at-2.3 V(vs.Pt)was applied on the high-purity copper substrate for 2 h.And it was found that the aluminum coating obtained by electrodeposition on the Cu substrate is Al2Cu alloy.By investigating the influence of the deposition process on the morphology of the coating,it is concluded that applied potential of-2.3 V at 313 K is the better conditions for room temperature electrodeposition of aluminum.In the DMI-AlCl3(1 M)-MgCl2(0.5 M)system,cyclic voltammetry and chronoamperometry were used to study the reversibility of electrode reactions and the electrochemical nucleation mechanism of magnesium.The electrodeposition of metallic magnesium is an irreversible process.Using the data by the cyclic voltammetry curves at different sweep speeds,it can be calculated that the average mass transfer coefficient of Mg(II)is of 0.0392,and the diffusion coefficient is of 2.32×10-13 cm2/s.The results of chronoamperometry shows that the electrochemical crystallization process of metallic magnesium on the electrode is three-dimensional instantaneous nucleation controlled by diffusion.Electrodeposition was carried out in the DMI-AlCl3(1 M)-MgCl2(0.5 M)electrolyte system by potentiostatic electrolysis,and the structure of the coating was characterized by XPS,which confirmed the existence of metallic aluminum and magnesium in the coating.XRD results shows that magnesium exists in the form of Al3Mg2,AlMg alloy.By investigating the influence of the deposition process on the morphology of the coating,the best conditions for electrodeposition of aluminum-magnesium alloy should be-2.5 V(vs.Pt)at 323 K for 2 h. |
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