基于离子液体的铝电沉积形貌控制过程研究

The electrodeposition of aluminium could be realized through choloroaluminate ionic liquid during which the optimization of structure of ionic liquid and the insight into the structure and property relationship as well as the morphology orientation of regulation of aluminium such as powder,ingot and coating is significant. The functionalization of ionic liquid could lead to unique coordination ability of metal ions in order to improve its electrodeposition behavior. The purpose of this project is to study the electrodeposition of aluminium with amino-functionalized choloroaluminate ionic liquids as electrolytes and the electron withdrawing and donating ability of substitute groups bound to amino as well as the ratio between amino compounds and aluminium chloride would be adjusted so as to synthesize series of amino-based chloroaluminate ionic liquids;Spectra analysis would be applied to investigate the effect of the structure of chemical groups with amino group and the ratio on the characteristic absorption peak of the atom or groups in anions, cations of ionic liquids obtained so as to clarify the mechanism of the micro-interactions between ions and molecules.The physical and chemical properties would be measured systematically and fitted to traditional theoretical equations and molecular simulation;The synergy mechanism of the amino group,ions and the balance of ions on the nucleation and crystal growth of aluminium on electrode would be disclosed; The mechanism of electrochemical reaction of alumnium ions coordinated by amino group would be explored; The influence factors such as temperature, electric current density, voltage and time would be investigated in order to accomplish the morphology orientation of regulation of aluminum deposition.

氯铝酸类离子液体可以用于铝的电沉积制备，优化离子液体结构、洞察构效关系、研究该体系中铝电沉积形貌如铝粉、铝锭、镀层的定向调控具有重大的意义。离子液体的功能化可以赋予其独特的对金属离子的配位能力，并改善其电沉积行为。本项目拟针对以氨基功能化的氯铝酸离子液体为电解质的铝电沉积过程进行研究，通过调节连接氨基基团的吸、斥电子能力及氨基化合物与氯化铝比例，设计合成系列氨基氯铝酸离子液体；采用光谱分析系统研究氨基取代基团的结构及反应物比例对所形成离子液体阴、阳离子结构中原子或基团对应特征峰变化的影响规律，获得微观状态下离子或分子配位及相互作用机理；通过实验系统地研究离子液体的物理化学性质变化并与分子动力学模拟相互印证；研究该类体系中分子和离子结构及反应平衡对铝在阴极表面成核和晶面生长的协同调控机制；研究氨基配位的铝离子在电极的反应机理；研究温度、电流密度、电压及时间等参数以实现电沉积铝形貌的定向调控。

离子液体有望代替高温熔盐电解质，实现常温下铝的电沉积。本项目从几个方面进行了深入研究。1，通过将1-丁基-3-甲基咪唑氯[bmim][Cl]、1-甲基-3-氢咪唑氯[H1mim][Cl]分别与无水氯化铝反应，制备得到了[bmim]x[(AlCl3)yClx]及[H1mim]x[(AlCl3)yClx](x, y 为摩尔分数，x+y=1)系列氯铝酸离子液体。在293.15到343.15K温度区间测定了密度、粘度、电导率，发现随温度升高密度、粘度降低，电导率增加；随y增加，密度增加，粘度下降，[bmim]x[(AlCl3)yClx]电导率呈下降趋势但仍高于[H1mim]x[(AlCl3)yClx]。2，构建了离子液体电解铝反应体系。以玻璃碳为惰性电极，以[bmim][Cl]/ AlCl3（1:1.5到1:2摩尔比）为电解质，在-0.1MPa真空条件下，温度313.2到353.2K，电流密度15~25mA.cm-2进行电解，获得致密光亮的铝电沉积层，电流效率高于98%。3, 发现酰胺基作为功能基团的添加剂分子有助于获得光亮铝沉积层，优化参数分别为：[bmim][Cl]/ AlCl3（40/60 mol%），烟酰胺8 mmol.L-1，电流密度为3.4mA.cm-2；[Emim][Cl]/AlCl3 (33.3/66.7 mol%)，氨基甲酸甲酯45mmol.L-1，电流密度为1.4mA.cm-2。机理是羰基吸附在电极表面阻滞了铝沉积的速度。4，对硅在[N4441][TFSI]中的低温电沉积进行了探索，发现四氯化硅或三氯氢硅在液态镓电极表面形成菱形立方相结构单晶硅膜，表面原子呈现（111）晶面排列。5，计算了四种常用离子液体[Emim][NTf2], [Emmim][NTf2], [Emmim][Cl], [EtAm][NO3]在不同尺寸团簇（2-12个离子对）的摩尔蒸发焓。结果表明，单个离子的蒸发焓数值特别高，甚至超过了700KJ每摩尔。当气相中离子成对存在时，计算数值与实验测试数值接近，说明离子液体蒸发为气态时，离子可以成对在气相中存在。原位红外数据对此进行了验证。