电沉积镍包石墨粉体的工艺和成核机理研究

发布时间：2019-03-14 11:52

【摘要】：镍包石墨复合粉体兼具金属镍优良的导磁性、耐磨性和石墨的自润滑性、耐高温等优异性能,可用做导电硅橡胶填料、微波吸收材料以及电磁屏蔽材料。采用粉体电沉积的方法制备镍包石墨复合材料,可以避免传统化学镀镀液不稳定,工艺流程复杂,成本高且污染环境的问题,制备出镀层致密均匀有一定厚度的镍包石墨复合粉体。本文采用微米级的天然鳞片石墨为原材料,利用间歇电镀工艺制备镍包石墨复合材料。优化了前处理工艺,在电镀前增加化学镀预镀步骤以提升电镀效果。对电沉积工艺参数进行了研究,并对电沉积成核机理进行了探究。通过扫描电镜对复合粉体的表面形貌和镀层厚度进行分析,用EDS能谱分析表面元素,获得了以下研究结果。(1)利用SEM电镜观察化学镀预镀后再电镀制备的镍包石墨复合粉体的表面形貌,比较不同活化处理方法对石墨的活化效果。通过石墨沉降实验研究化学镀预镀影响电镀效果的原因。(2)通过电镀效率、复合粉体的镍含量和表面形貌确定电镀制备镍包石墨粉体的电流密度、温度、装载量、占空比、电镀时间等最佳工艺条件。使用沉降—电镀—搅拌的周期循环电镀,有效电镀时间为30 min时,获得的镍包石墨粉体包覆率高、镀层均匀。提高电解液中Ni Cl2含量和阳极与阴极面积比,能有效避免阳极钝化。(3)利用开路电位和阴极极化测试研究石墨在电镀初期对镀液的影响。利用恒电位暂态阶跃实验研究在大电流密度下,镍在石墨上沉积的成核机理。(4)镀液中加入有机添加剂可以增大阴极过电位和电化学反应阻抗,提高镍的电结晶几率,细化晶粒,提升镀层光亮度。
[Abstract]:Nickel-coated graphite composite powder has excellent magnetic conductivity, wear resistance, self-lubricating property of graphite, high temperature resistance and so on. It can be used as conductive silicone rubber filler, microwave absorbing material and electromagnetic shielding material. The preparation of Ni-coated graphite composites by powder electrodeposition can avoid the problems of traditional electroless plating solution instability, complex process flow, high cost and environmental pollution. Nickel-coated graphite composite powder with dense and uniform coating was prepared. In this paper, nickel-coated graphite composites were prepared by batch electroplating using micron-grade natural flake graphite as raw material. The pretreatment process was optimized and the electroless plating pre-plating step was added before plating to improve the plating effect. The technological parameters of electrodeposition and the nucleation mechanism of electrodeposition were studied. The surface morphology and coating thickness of the composite powders were analyzed by scanning electron microscopy (SEM), and the surface elements were analyzed by EDS. The following results were obtained. (1) the surface morphology of Ni-coated graphite composite powder prepared by electroless plating and re-plating was observed by SEM electron microscope, and the activation effects of different activation treatments on graphite were compared. The reason of the influence of electroless plating preplating on plating effect was studied by graphite deposition experiment. (2) the current density, temperature, loading and duty cycle of nickel-coated graphite powder were determined by electroplating efficiency, nickel content of composite powder and surface morphology. Plating time and other optimal technological conditions. When the plating time is 30 min, the coating rate of nickel-coated graphite powder is high and the coating is uniform when sedimentation-plating-stirring cyclic plating is used. The passivation of anode can be effectively avoided by increasing the content of Ni Cl2 and the area ratio of anode to cathode in electrolyte. (3) the effect of graphite on plating bath is studied by open circuit potential and cathodic polarization test. The nucleation mechanism of nickel deposited on graphite under high current density was studied by potentiostatic transient step experiment. (4) the cathodic overpotential and electrochemical impedance could be increased and the electrocrystallization probability of nickel could be increased by adding organic additives into the plating bath. Refine the grain and improve the brightness of the coating.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ153.12;TQ127.11

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