| Aluminum was an important and basic raw material of metal in the national economy. But the current questions had been raised about electrolytic aluminum industry, including production at high temperatures, high energy consumption and emission pollution problems. Ionic liquids(ILS) were labeled as a new low-temperature electrolyte, the field of metal electrodeposition had broad application prospects. But the previous studies found that aluminum product from pure ionic liquid electrodeposition was unable to meet the requirements in both uniformity and smoothness. Electrodepostion in pure ionic liquid often result in the deposits with rough surface or even dentrite products after longtime deposition. pulse electrodeposition as a new method of electrodeposition from ionic liquid has the lack of systematic study. Triethylmethylammonium chloride/Al C l3, 1-ethoxycarbonylmethyl-3-methylimidazolium chloride/Al C l3 ionic liquids as electrolyte has not been reported in detail. In this paper, study on the effect of additives on the morphology of electrodeposition of aluminum from ionic liquid. The maior content of this dissertation is listed as follows:Electrodeposition of Al in ionic liquids for preparation of aluminum products had opened up a new research direction, but the previous studies found that aluminum product from pure ionic liquid electrodeposition was unable to meet the requirements in both uniformity and smoothness. Electrodepostion in pure ionic liquid often results in the deposits with rough surface or even dendritic products after long-time deposition. In this study, five kinds of small organic molecules containing carbonyl as additives were investigated, such as acetone, acetic acid amide, acetic acid, methyl acetate and methyl carbamate. Additives were added to [Emim]C l/Al C l3( 33.3/66.7mol%) with a concentration of 5mmol/L, 15mmol/L, 45mmol/L. Cyclic voltammetry was studied on a glassy carbon electrode at a scan rate of 100 m V/s and temperature of 323 K. The electrode potential was scanned from the open circuit potential to negat ive-potential, then retraced to get cyclic voltammetry curve. Among those organic additives, methyl carbamate was proved to be an excellent additive. The brightness of Al can be improved by adding 45mmol/L methyl carbamate. Smooth, uniform and mirror bright Al deposition would be obtained afterward. Furthermore, the effects of additive for Al deposit on morphology, crystal orientation and Al deposition mechanism by the analysis of galvanostatic deposition, scanning electron microscope(SEM), X-ray diffraction(XRD), ultraviolet–visible spectroscopy(UV-Vis) and nuclear magnetic resonance(NMR) was conjectured.The results showed that: Methyl carbamate as an additive would make grain refinement more apparent and present more strong Al(200) crystal plane orientat ion. As an additive, methyl carbamate did not form new metal complex in the electrolytic liquid and did not affect the structure of active aluminum ion in the electrolyte. The positive center of carbonyl carbon atom in methyl carbamate molecular can be eas ily adsorbed at the cathode surface. This procedure inhibited the process of Al deposition and obtained the smooth and bright effect. Therefore, Al deposition layer of mirror can be obtained, which has an important guiding significance in the selection of ionic liquid additive in electrodeposition system.At the same time, a series of organic molecules containing sulfinyl as additives of ionic liquids electrodeposition of aluminum were investigated. The analysis of different mechanism by comparing with adsorption of additives. The study found: Dimethyl sulfone complexation with Al C l3 form new Al(DMSO2)33+ metal complex ion. This kind of complex ion did not make the surface of Al deposition layer became smooth and bright. On the contrary, the surface of the deposition layer became more rough and easier to form dendrites.Although using the method of pulse electrodeposition of aluminum from ionic liquid had the potential advantage. But there was no literature to be reported the essence of pulse polarization process. There was also the lack of systematic research on the process of aluminum deposition and the change of morphology. Therefore, this paper analysed the aluminum deposition process and morphology under different time, current density, voltage, quantity of electric charge by the method of constant current, constant potential, galvanostatic pulse, constant voltage pulse. Try to found out the rules of deposition morphology and the mechanism of deposition process.Measured and discussed the electrochemical performance of triethylmethylammonium chloride/Al C l3, 1-ethoxycarbonylmethyl-3- methylimidazolium chloride/ Al C l3 ionic liquids as electrolyte. Study on the deposition process of Al in the cathode under different temperature, current density and voltage by CV, SEM, XRD and other methods. At the same time investigated morphology of Al deposition, crystal structure and so on. Screening out the electrodeposition of aluminum optimal experimental parameters and analyse its principle... |
