酰胺类离子液体电沉积铝的基础研究

It is well known that the tradition ionic liquids used for the electrodeposition of aluminum at low temperature have been limited due to their high price and high hygroscopicity. Based on the above mentioned shortcomings of ionic liquids, one kind of novel ionic liquids, AlCl3/amide (urea, acetamide, propionamide, butyramide), have been developed and used for aluminum electrolysis and electrodeposition at room temperature for the first time in this project..To obtain the optimum ionic liquid for aluminum electrodeposition and investigate the effects of temperature and molar ratio (AlCl3/amide) on conductivity and density, the physicochemical properties of AlCl3/amide ionic liquids will be studied at various temperatures and molar ratios, respectively. Meantime, to clarify the aluminum complex species of AlCl3/amide ionic liquids, the effects of temperature and molar ratio on the aluminum complex species, and the reaction mechanism of AlCl3 and amide, the microstructure characteristics of the AlCl3/amide ionic liquids will be studied by Raman spectra technique at various temperatures and molar ratios, respectively. In addition, to reveal the mechanism of the electrode reaction, the mechanism of the aluminum nucleation and growth process, and the effects of temperature and molar ratio on the mechanism of the electrode reaction, the electrodeposition behavior of aluminum will be studied by cyclic voltammetry technique at various temperatures and molar ratios, respectively. Based on the results of above mentioned studies, it can provide a new route for developing ionic liquids, refining aluminum, and electroplating aluminum at low temperature.

针对目前低温电沉积铝普遍采用的离子液体成本相对较高且吸水性强的情况，本项目采用成本相对较低的酰胺类化合物（尿素，乙酰胺等）和氯化铝为原料，通过电沉积法在室温下获得金属铝及铝镀层，并研究铝电沉积过程的基础科学问题。具体研究内容包括：酰胺类离子液体物理化学性质的研究，分析温度和离子液体配比（氯化铝与酰胺类化合物摩尔比）对离子液体电导率和密度的影响规律，探明适合于铝电沉积体系的物理化学性能；酰胺类离子液体微观结构特征的研究，揭示离子液体中金属络合物的存在形态及其随温度和离子液体配比变化的演化规律，阐明氯化铝与酰胺类化合物的反应机理；铝电沉积的电化学行为的研究，揭示温度和离子液体配比对电极反应的影响规律，阐明铝析出的电极反应机理和电结晶机理。为开发新型离子液体和低温电解制备精铝及低温电镀铝奠定理论和技术基础。

针对目前低温电沉积铝普遍采用的离子液体成本相对较高且吸水性强的情况，本项目采用成本相对较低的酰胺类化合物（尿素，乙酰胺等）和氯化铝为原料，通过电沉积法在室温下获得金属铝及铝镀层，开展酰胺类离子液体物理化学性质、酰胺类离子液体微观结构特征及铝电沉积的电化学行为等方面的研究。在313～373K温度范围内，测量了不同摩尔比的AlCl3/酰胺新型离子液体的电导率和密度值，使用回归方程拟合获得了电导率及密度与温度的关系式，AlCl3/酰胺新型离子液体的电导率及密度都随AlCl3与酰胺摩尔比的升高而增大。拉曼光谱研究结果表明，AlCl3与尿素、AlCl3与乙酰胺、丙酰胺、丁酰胺摩尔比分别为1.2、1.0的离子液体中只存在AlCl4−结构的络合物；而AlCl3与尿素、AlCl3与乙酰胺、丙酰胺、丁酰胺摩尔比分别为1.3～1.5、1.1～1.5的离子液体中同时存在AlCl4−和Al2Cl7−两种结构的络合物，且随着摩尔比的增大离子液体中AlCl4−结构的络合物相对含量减少而Al2Cl7−结构的络合物相对含量则会增多。循环伏安结果表明，只有当AlCl3与尿素、AlCl3与乙酰胺、丙酰胺、丁酰胺摩尔比分别为1.3～1.5、1.1～1.5时，Al(III)才能被还原出来，且随着摩尔比的增大Al(III)的起始还原电位向正方向偏移，说明铝更容易被电沉积出来。离子液体中Al(III)在钨电极上的还原反应为：4Al2Cl7−+3e−→Al+7AlCl4−。XRD和EDS检测结果表明，AlCl3/乙酰胺、AlCl3/丙酰胺及AlCl3/丁酰胺离子液体中可获得附着性较好、致密、外表为银白色的高纯铝镀层；而AlCl3/尿素离子液体中获得附着性差、疏松、外表为黑色且含杂质的铝镀层。

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