离子液体中三价铬脉冲电沉积功能性纳米晶镀层机理研究

In this project, electrochemical quartz crystal microbalance(EQCM) method is used to study the pulse electrodepositing mechanism for functional nanocrystalline chromium and chromium alloys coatings from imidazolium-based ionic liquid solution(IBILS) containing Cr(III). The primary researches are as follows: studying the discharge mechanism of Cr(III), measuring the kinetic parameters, and developing the mathematical and physical model of the electrodeposition process for the IBILS. The effects of pulse durations and duty cycles on the composition, thickness and microstructure of nanocrystalline chromium and chromium alloys coatings in IBILS should be ascertained. The form of Cr(III) complexes and its effect on the electrodeposition process in IBILS should be discovered. The interfacial microstructure between the coatings and substrates, and the change rule of the composition and microstructure with the thickness of the coatings will also be discussed. Thus, the effect on thickening the nanocrystalline chromium and chromium alloys coatings and increasing the chromium content in the chromium alloys coatings should be identified. Therefore, the key theoretical issues, which are the difficulties in thickening the coatings from the trivalent chromium baths and increasing the chromium content in the chromium alloys coatings, should be solved. Based on this study, the theoretical study for electrodepositing chromium and chromium alloys coatings from ionic liquid solution(ILS) containing Cr(III) can be promoted.

本项目主要采用电化学石英晶体微天平（EQCM）法，研究咪唑类离子液体中三价铬脉冲电沉积功能性纳米晶铬及铬合金镀层的机理。主要包括：研究Cr(III)放电机理，测定电沉积过程动力学有关参数，并建立数理模型；查明咪唑类离子液体中脉冲作用对三价铬电沉积纳米晶铬及铬合金镀层组成、厚度以及微观结构的影响规律；探明咪唑类离子液体中，Cr(III)配合的形态及其对电沉积的影响机制；探讨镀层/基体两固相交界面的结构及镀层的组成和结构随镀层厚度变化之规律，从而确定它们对纳米晶铬及铬合金镀层增厚与铬含量增加的影响机制，以解决三价铬镀层难增厚、合金镀层铬含量难增加等关键理论问题，促进离子液体中三价铬电沉积理论研究的发展。

本项目主要采用电化学石英晶体微天平（EQCM）法，研究了咪唑类离子液体中三价铬脉冲电沉积功能性纳米晶铬及铬合金镀层的机理。主要包括：研究了Cr(III)放电机理，结果表明： Cr3+电沉积历程为：Cr(III) + e- = Cr(II)，Cr(II) + 2 e- = Cr(0)，为不可逆过程，并且受扩散控制；获得不同离子液体体系中铬离子的扩散系数; 采用线性扫描曲线、交流阻抗和恒电流阶跃曲线等技术，进一步证明了三价铬在不同离子液体体系中的电化学还原反应是一个两步反应。利用计时电流法，获得了不同离子液体体系中，三价铬的电结晶机理，研究结果表明，不同的离子液体体系中，其结晶机理有显著差异。查明了咪唑类离子液体中脉冲作用对三价铬电沉积纳米晶铬及铬合金镀层组成、厚度以及微观结构的影响规律；探讨镀层/基体两固相交界面的结构及镀层的组成和结构随镀层厚度变化之规律，从而确定它们对纳米晶铬及铬合金镀层增厚与铬含量增加的影响机制，解决了三价铬镀层难增厚、合金镀层铬含量难增加等关键理论问题，促进了离子液体中三价铬电沉积理论研究的发展。