锌电解沉积物复杂生长形态的研究

【作者】 戎茂华；

【导师】 杨兵初；

【作者基本信息】 中南大学 ， 凝聚态物理， 2005， 硕士

【摘要】 在电化学沉积过程中,随沉积条件（电解池的几何形状、外加电压、电解液浓度、溶液的PH值、重力场、外加磁场等）的不同,会产生很多复杂形态的沉积物。这些沉积物生长形态的形成机制和演化规律的认识,对于理解远离平衡条件下的生长过程和物理本质有重要意义。 本文在近二维的生长条件下,以ZnSO₄水溶液作为电解液电解沉积金属锌,研究了不同电解沉积条件对沉积物生长形态的影响,主要结论如下: （1） 研究了电解液浓度和外加电压对电解沉积物生长形态的影响。实验结果表明,沉积物生长形态随着外加电压和电解液浓度的不同而发生变化,且沉积物生长形貌主要取决于沉积物生长界面离子的浓度分布以及离子的传输方式和速度。 （2） 研究了电解液中不同杂质(预先放置不同形态的锌沉积物小颗粒、阳极溶解的Cu²⁺、锌离子水解产生的H⁺以及另外加入的H⁺等)对沉积物生长形态的影响。实验发现沉积物可以从预先放置于电解液中的锌沉积物杂质小颗粒生长,并且杂质小颗粒的形态不影响从其生长出的沉积物形态;阳极溶解的Cu²⁺和锌离子水解产生的H⁺是得到DLA分形形态沉积物的关键因素;改变溶液中H⁺浓度,得到不同生长形态的沉积物,再一次证明了H⁺浓度的变化对于影响电解沉积物的生长形态是至关重要的。 （3） 研究了外加磁场对电解沉积生长形态的影响。实验结果表明,沉积物分枝在磁场作用下呈螺旋状弯曲生长。分析认为,在薄层电解液中的沉积物分枝弯曲生长主要是因为磁场引起的电解液对流冲击形核生长的小晶粒而形成的,然而在抑制对流情况下得到的沉积物分枝弯曲生长是由霍尔效应形成。更多还原

【Abstract】 With the different conditions of the electrodeposits, such as the geometry of the electrochemical cell, voltage, concentration, the gravity field, magnetic field, electrochemical deposition（ECD） provides a wide range of morphologies. It is a challenge to understand the origin of the formation of these morphologies.Using ZnSO₄ aqueous solution as the electrolyte, Zinc was deposited in the quasi two-dimensional radial electrochemical cell. The dependence of morphologies on the different conditions of the electrodeposits has been studied, and main conclusions are as follows:（1） The dependence of morphologies on voltage and concentration has been studied by the experiments of electrodeposits of Zinc. When the voltage, the numbers of the ramification and the size of the side branch are changed, the clamp of the side branch on dendrite is also altered accordingly;When the concentration of the solution is different, the morphology of the deposition is changed from the dendrite to the dense radial, which mainly depends on the concentration distributing of ions and the transport mode and speed of ions.（2） The dependence of morphologies on impurity has been studied by the experiments of Zinc electrodeposits. The new deposition will grow from not only the cathode but also the original deposition that has been put into the electrochemical cell. The growth pattern of new deposition is not affected by the original deposition and is related with the concentration and thickness of the electrolyte, the potential between the anode and the cathode;The Cu²⁺ ion and H⁺ ion have important effect on the transformation of the growth morphology in the Zinc electrodeposits.（3） The influence of a magnetic field on the microstructure of the Zinc electrodeposits obtained in a 2-dimensional concentric electrode cell is investigated. The growth fractal morphology of metal electrodeposits is dramatically altered when a static magnetic field is applied to the cell. Based on the experimental results , the mechanism of the magnetohydrodynamic（MHD） for the morphological transition is proposed. If the convection is inhibited, the morphological transition isattributed to the Hall Effect.更多还原