支链聚醚添加剂对氨配合物体系电沉积锌的界面调控和作用机制研究

Zinc sulfides ores are generally exhausting with the development of zinc metallurgy. The complex zinc oxide ores and secondary zinc resources are become an important sources for zinc metal in China. Treatment of complex zinc oxide ores with ammoniacal ammonium chloride solution is one of an effective method with shorter technological process and higher selectivity. For the existing types of additives in zinc ammonia complexes solution with poor effects and large usage, synergistic using high preferred orientation growth of side-chain polyether and gelatin to prepare smooth and compact zinc deposits is put forward in this project. The main research contents of this subject are as follows: the influences of molecular and groups of additives on the morphology of zinc deposits, growth orientation, electro-crystallization model and interfacial behavior should be illustrated using XRD, SEM, EC-AFM and electrochemical characterization methods to characterize the growth mechanism of zinc crystal after addition of additives in electrolyte. The interactions of additive with cathode and zinc crystal surface will be simulated using molecular dynamics calculation to find out the interaction mechanism of additives molecules and functional groups with electrode. The adsorption behavior and orientation of polyether with side-chain and the group components of additives on the electrode will be investigated using shell isolated nanoparticles enhanced Raman spectra (SHINERS). Consequently, the synergic effects of protein and side-chain polyether should be established. The experimental results should provide a technical prototype and theoretical principle for the optimized additives in ammonia complexes electrolyte of zinc electrodeposition, and also provide theoretical principle to select additives for zinc electrodeposition in other metallic electroplating in different types of electrolytes.

随着国内硫化锌矿逐渐枯竭，复杂氧化锌矿与二次锌资源受到重视。采用氨-氯化铵溶液处理复杂氧化锌矿具有流程短、选择性好的优点。针对锌-氨体系电沉积锌现有的添加剂种类多、用量大、效果差的问题，提出采用高择优取向生长的支链聚醚与骨胶协同作用制备平整、致密的金属锌。本项目主要研究内容：利用XRD、SEM、HRTEM、电化学测试和EC-AFM等表征方法研究添加剂分子和官能团对锌电沉积的形貌演变规律、取向生长、成核模型以及界面行为的影响规律，揭示添加剂对阴极表面锌晶核生长的调控机理；采用分子动力学计算模拟添加剂与电极界面及锌晶面的相互作用，查明添加剂分子和官能团的电极作用机制；在此基础上采用壳层隔绝纳米粒子增强拉曼光谱表征添加剂各组分在电极上的吸附行为和吸附取向，构建复合添加剂的协同作用模型。本项目研究结果不仅为氨配合物体系电沉积添加剂的优化选择提供理论依据，也为其他金属和体系添加剂的选择提供理论指导。

本项目选择具有择优取向的支链聚醚和骨胶作为添加剂，研究其对氨配合物体系锌电沉积过程的影响机制，取得了以下主要结果：.(1) 只添加支链聚醚一种添加剂时，锌电沉积的反应活化能为27.16 kJ·mol-1，反应受扩散控制；支链聚醚的加入不影响锌沉积的形核机理，但会吸附在电极表面，增大阴极极化，1.50 g·L-1的支链聚醚使阴极极化达到最大；支链聚醚对锌电沉积动力学交换电流密度影响显著，对锌的还原动力学过程具有抑制作用。.(2) 支链聚醚和骨胶复配添加剂不改变锌沉积的形核机理，但复配添加剂对锌沉积的极化作用大于单一添加剂，对锌还原动力学的抑制作用增大。1.50 g·L-1支链聚醚和0.10 g·L-1骨胶的极化作用最强。 .(3) 支链聚醚的官能团-HO和C-O在电积过程中吸附在电极表面，抑制锌的沉积，改善阴极锌板的形貌以及力学性能，提高电沉积的阴极效率，降低直流能耗；且支链聚醚对锌晶粒还具有极强的诱导作用，使其在(110)晶面具有高择优取向生长；当加入骨胶后，在两种添加剂的协同作用下，(101)晶面的吸附作用减弱，但阴极锌晶粒进一步细化，且致密度和平整性都得到提高；电流效率和直流能耗进一步优化，1.50 g·L-1的支链聚醚与0.10 g·L-1的骨胶复配时，阴极电流效率最高可达到97.64%，能耗低至2410.31 kW·h·t-1。.(4) 首次采用EC-AFM和表面轮廓分析研究钛电极表面的电流分布和电沉积过程中电极表面轮廓演化，确定了添加剂在电沉积过程中优先吸附在电极表面的划痕、晶界和缺陷区域，提高局部的表面电阻，使表面电流均匀化；在1.4 V偏压下，在随机成核过程中，锌成核后电极表面电流变化幅度为9.3 pA；成核后电极表面的电流密度均匀化，电流变化幅度为1.2 pA。无添加剂随机成核首先发生在电极表面划痕、晶界和缺陷等电流密度大的区域并快速生长，电极表面的粗糙度增大，电锌难以致密成板；添加添加剂后电极表面的粗糙度降低，锌晶体生长速度均匀化，表面粗糙度变化小于0.09 μm，其生长顺序由晶界向晶面扩展。