基于氯化胆碱的离子液体中电沉积金的工艺与机理研究

发布时间：2018-12-13 13:26

【摘要】：惯性约束聚变（ICF）实验用靶的制备过程中，点火靶以活泼金属铀或其合金作为能量转换材料，在转换层材料表面需沉积一层化学性质稳定的单质金作为支撑层。由于铀基体有较强活性，表面易形成氧化膜，在传统的水溶液体系中电沉积很难获得结合力符合要求的镀层。故开发新型的非水电镀金体系势在必行。 本文分别以基于氯化胆碱的Reline和Ethaline离子液体为溶剂，以氯金酸钠为主盐，二甲基海因（DMH）为配位剂进行了电镀金工艺的探究，分别研究了主盐浓度、配位剂含量等镀液组成及温度、电流密度等工艺条件对镀层性能的影响。 在Reline离子液体中，通过正交试验确定了基本镀液体系，其中Au3+4g/L，DMH45g/L，氯化锂15g/L，沉积电势为-1.4V(vs. Pt)。通过单因素试验，发现电流密度及镀液温度对镀层外观质量影响较大，而氯化锂浓度的影响较小。在基本镀液中，以镍为基体，可以电沉积获得较为均一细致的镀金层，但工作电流密度较小，电流密度区间较窄。尝试了通过提高主盐浓度、镀液温度，加入稀释剂等方法来提高电流密度，结果表明工作电流密度很难提高。 在Ethaline离子液体中，通过大量实验初步确定了基本镀液体系，组成为Au30g/L，DMH156g/L，Na2CO35g/L。在基本镀液中，在电流密度2~10mA/cm2范围内可得到金黄色的镀金层，而电流为6.5mA/cm2时得到的金层的均一性最好。以镍为基体时，阴极片表面容易出现漏镀区，产生黑色区域，，而以金为基体时，则容易得到均一细致的镀金层。提高主盐浓度、镀液温度可大幅提高工作电流密度，而随着温度的升高，镀层外观质量有所改善，最佳镀液温度范围为90~100℃。另外，由于高浓度的Au3+具有强氧化性，阴、阳极过程出现异常现象：新配置镀液中，阴极沉积效率非常低，甚至接近0，而金阳极溶解效率大于100%。 利用XRD对镀层的晶体结构进行了分析，发现两体系中所得金层均为面心立方结构。通过XPS、XRF及EDS对镀层成分进行了分析，并利用SIMS对镀层成分作了深度分析，发现镀金层比较纯净，无有机物夹杂。另外，利用SEM、AFM对镀层的微观形貌进行了表征。 通过循环伏安（CV）方法对体系中金的还原机理以及电极的可逆性进行了研究，发现Au3+的还原是分步，存在Au+中间体，且还原过程为非可逆的；利用LSV方法研究了糖精钠与丁炔二醇对阴极极化的影响，表明糖精钠与丁炔二醇对提高阴极极化的作用效果不大；利用计时电流（CA）方法对玻碳电极上金的成核机理进行了研究，研究表明金在玻碳电极上的成核方式为连续成核。
[Abstract]:During the preparation of inertial confinement fusion (ICF) targets, active metal uranium or its alloys are used as energy conversion materials, and a layer of simple gold with stable chemical properties is deposited as the supporting layer on the surface of the transition layer. Due to the strong activity of uranium substrate and the easy formation of oxide film on the surface, it is difficult to obtain the coating which meets the requirements by electrodeposition in the traditional aqueous solution system. Therefore, it is imperative to develop a new non-hydropower gold plating system. In this paper, Reline and Ethaline ionic liquids based on choline chloride were used as solvents, sodium chloraurate as main salt and dimethylhydantoin (DMH) as coordination agent. The effect of the composition of plating bath, temperature, current density and other process conditions on the properties of the coating. In Reline ionic liquids, the basic bath system was determined by orthogonal test, in which Au3 4g / L, DMH 45g / L, lithium chloride 15g / L, deposition potential -1.4V (vs. Pt). Through single factor test, it is found that the effect of current density and bath temperature on the coating appearance quality is greater than that of lithium chloride concentration. In the basic bath, a uniform and fine gold plating layer can be obtained by electrodeposition with nickel as the substrate, but the working current density is smaller and the current density range is narrow. This paper attempts to increase the current density by increasing the main salt concentration, bath temperature and adding diluent. The results show that the working current density is difficult to increase. In Ethaline ionic liquids, the basic bath system was preliminarily determined by a large number of experiments, and the composition was Au30g/L,DMH156g/L,Na2CO35g/L.. In the basic bath, the gold-plated gold layer can be obtained in the current density 2~10mA/cm2 range, but the gold coating obtained with the current of 6.5mA/cm2 has the best uniformity. When nickel is used as the substrate, the surface of the cathode is prone to a leakage zone, resulting in a black area, while when gold is used as the substrate, a uniform and meticulous gold-plated layer is easy to be obtained. With the increase of the main salt concentration, the working current density can be increased greatly. With the increase of the temperature, the coating appearance quality is improved, and the optimum bath temperature range is 90 ~ 100 鈩

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