Application Of Imidazolium Phosphate Ionic Liquid In Electrodeposition Of Metals

Electroplating is of great significance for corrosion protection and surface moderification of metasl,however waste from electroplating industry,characterized by high toxicity,high pollution and refractory,is a major source of pollution to environment.Waste water from electroplating industry mainly comes from heavy metals,additives,p H buffer solutions and cleaning agents,which are associate to processes based on aqueous solution.Therefor,the key to solve this problem is to develop environmentally friendly electrolytes.Ionic Liquids,also known as room temperature molten salt,is a type of nonvolatile liquid,which provides an idea to achieve ‘green chemistry’.In this dissertation,the application of 1-butyl-3-methylimidazolium dibutylphosphate([BMIM][DBP])in electrodeposition was investigated,which mainly focused on the chemical and physical property of [BMIM][DBP],the reaction between [BMIM][DBP] and magnesium alloy AZ31 B and electrodeposition of Ni,Znand Co in [BMIM][DBP].Firstly,[BMIM][DBP] was synthesis by heating the mixture of Nmethylimidazolium and tributylphosphate,and the properties of [BMIM][DBP]such as the viscosity,conductivity,p H value,and electrochemical windows were studied.As a result,the electrochemical windows of [BMIM][DBP] is wide,from which it is suitable for most metals to be reduced.As temperature and water in [BMIM][DBP] have significant influence on its physical properities,the properties can be designed by adjusting temperature and water concentration.Secondly,exploring the possibility of Mg AZ31 B as substrate for electrodeposition of metals in [BMIM][DBP].It is found that a layer of conversion film was formed on the surface of Mg AZ31 B when immersing in [BMIM][DBP],and the film promotes the corrosion resistance of Mg AZ31 B.SEM,EDX and XPS were employed to characterize the morphology and composition of the film;electrochemical tests were used to simulate the formation of the film,and corrosion resistance of the films formed at various conditions were evacuated.It is shown that the conversion film comes from the reaction of Mg AZ31 B with [BMIM][DBP] and water.Then,electrodeposition of bright nickel in [BMIM][DBP] were investigated.Nicoating was obtained by directly potentiostatic electrodeposition in [BMIM][DBP].Cyclic voltammetry tests were carried out to determine the diffusion coefficient of Ni2+ in[BMIM][DBP].SEM were employed to observe grainsn the coating,and grain size distribution was obtained by imagej softwere to analysis the nucleation mechanism.SEM was also used to observe the morphology of the coatings obtained under various conditions,as a result,water concentration and voltage has significant influence on the morphology of resultant coatings,in detail,high voltage results in rough surface and high water concentration produce fine and compact grains,while high water concentration also brings about hydrogen evolution.it is also found that the reduction of Ni2+ in[BMIM][DBP] is an irreversible electrochemical process with diffusion process as the rate control step,and the calculated diffusion coefficient is 5.27×10-10 m2s-1at 363 K.The result from XRD indicates that electrodeposition from [BMIM][DBP] has preferential growth orientations and the ESI-MS results shows that parent cations and anions aggregate with each other and nickel ions form complexes with the cluster parent cations and anions in this IL.Furthermore,the electrodeposition of Znwas studied in this IL.In this section,a layer of Znic coating was obtained by potentiostatic electrodeposition.The influence of temperature and concentration of ZnCl2 on conductivity of ZnCl2/[BMIM][DBP] were investigated.It is shown that conductivity increase with the increase of temperature,which is consistent with Vogel–Tamman–Fulcher(VTF)model,and with the increase of ZnCl2 concentration conductivity arise and then fall.SEM observation of the surface of Zncoatings found that compact and dendrite-free Zncoating was obtained.The influence of water and ethylene glycol in IL increased thedeposition rete,and decrease current efficiency at the same time.Similarly,Co coatings were obtained in Co Cl2/[BMIM][DBP] by potentiostatic electrodeposition.The size of Co crystal in the resultant coatings gets bigger as the increase of water concentration in [BMIM][DBP].Finally,Co-Nicodeposited in[BMIM][DBP] with Co Cl2·6H2O and NiCl2·6H2O as solute,and Co and Niare evenly distributed in the Ni-Co alloy coatings.