防变色Ag/C纳米复合镀层的制备工艺研究

Process for Preparation of Electroplated Antitarnishing Ag/C Nano- Composite Coating

为了研发具有良好防变色能力的银镀层，采用复合电镀技术，在以酒石酸钾钠为配位剂的无氰复合镀银溶液中制备了Ag／C纳米复合镀层。采用SEM和XRD对Ag／C纳米复合镀层的形貌、结构进行了表征，测试了其电阻及防变色能力。结果表明，Ag／C复合镀层中的碳粉含量随镀液中纳米碳粉浓度的增加而增大，当镀液中纳米碳粉浓度超过10g／L时，镀层中的碳粉含量又开始下降。Ag／C复合镀层中碳粉的复合量随着电流密度的增加先增大后减小，在电流密度为0．6～0．8A／dm^2范围内，镀层中碳粉的复合原子分数接近8％。Ag／C复合镀层中基质金属银的晶粒尺寸在纳米级，其择优取向沿（220）晶面。Ag／C复合镀层的电阻与光亮银镀层的相当，但其抗变色能力较光亮银镀层显著提高。

Ag/C nanocomposite coatings were prepared by electroplating in a solution containing C4H4KNaO6 as the complexing agent, aiming at developing Ag coatings with good antitarnishing capability. The morphology and structure of the coatings were characterized by means of scanning electron microscopy and X-ray diffraction, while their resistance and antitarnishing behavior were also measured. Results showed that the content of C nano-powders in the composite coatings first increased with increasing concentration of C nano-powders in the bath solution and then decreased therewith at a concentration of over 10 g/L of C nano-powders in the bath solution. In the current density range of 0.6～0.8 A/dm2, the content of C nano-powders in the composite plating was about 8%. At the same time, the Ag matrix grains in the composite coatings had nanoscale size and preferential orientation along crystal plane (220), and the Ag/C nanocomposite coatings having almost the same resistance as bright Ag coating showed much better antitarnishing performance.