碳纤维表面预处理及化学镀Ni-P工艺对镀层性能的影响

Effects of Pretreatment and Plating Condition on Microstructure and Adhesion to Substrate of Electroless Nickel-Phosphorous Coating on Carbon Fiber

过去,对碳纤维表面预处理、化学镀Ni-P工艺条件影响镀层性能影响的综合报道不多。为此,先对碳纤维表面预处理,再化学镀Ni-P。分析了粗化和活化对碳纤维表面形貌的影响,探讨了镀液温度、pH值、次磷酸钠还原剂和柠檬酸钠配位剂浓度,添加糖精、十二烷基硫酸钠对碳纤维表面化学镀Ni-P沉积速率的影响。采用扫描电镜(SEM)和能谱仪(EDS)观测了Ni-P镀层的表面、截面形貌,测试了不同工艺条件对Ni-P镀层与碳纤维的结合力。结果表明:粗化使碳纤维表面积增大,有助于提高其与镀层的结合力,AgNO3活化后碳纤维表面附着了较多的催化晶核;随着镀液温度、pH值和柠檬酸钠浓度的增加,化学镀Ni-P的沉积速率均呈先增大后减小的趋势;随着次磷酸钠浓度的增加,化学镀Ni-P的沉积速率先增大后相对稳定;加入糖精后的Ni-P镀层平整、光滑,完全覆盖碳纤维表面,与碳纤维结合良好。

Carbon fiber was pretreated and coated with electroless Ni-P alloy coating. The effects of coarsening and activation on the morphology of carbon fibers were investigated; and the effects of bath temperature and pH value as well as the concentration of sodium hypophosphite reducing agent and sodium citrate complexing agent on the deposition rate of Ni-P alloy coating were examined. Moreover,the surface and cross-section morphologies and elemental composition of as-prepared Ni-P alloy coating were analyzed with a scanning electron microscope and an energy dispersive spectrometer; and the adhesion to substrate of the Ni-P alloy coating was determined as well. Results indicated that coarsening led to increase of surface area of carbon fibers thereby increasing the adhesion of Ni-P alloy coating to the substrate. Besides,activation by AgNO 3 generated a large amount of catalytic crystal nuclei attached to carbon fiber surface thereby accelerating deposition of electroless Ni-P alloy coating. Moreover,with the increase of bath temperature,pH value and complexing agent concentration, the deposition rate of Ni-P alloy coating rose firstly and then slowed down. With the increase of reducing agent concentration, the deposition rate of Ni-P alloy coating initially rose and then tended to stabilize. Furthermore,the introduction of saccharin in the electroless Ni-P bath helped to improve the smoothness and brightness of the coating; and resultant Ni-P alloy coating on carbon fiber surface was complete and had good adhesion to the substrate.