【作者】 王威；

【导师】 张永君； 胡会松；

【作者基本信息】 华南理工大学 ， 安全工程（专业学位）， 2023， 硕士

【摘要】 电接触材料是电气和电子设备中的关键材料,各种电器的功能都取决于电接触材料的质量和性能。金属银常用作制备电接触材料,但银的价格昂贵,在生产过程中成本较高。铜具有良好的导电性且储量丰富,与银相比价格低廉,适用于大规模生产。但铜表面易发生氧化反应,生成不导电的氧化物,严重影响材料的导电性能。为了保护铜基电接触材料需进行镀银处理。普通纯银镀层硬度较低,容易发生磨损、剥落导致基底暴露,使电接触材料故障频发,因此需要制备高性能的复合镀层。本文利用复合化学镀技术,在紫铜基材表面制备了银基复合镀层,探究了碳化硅颗粒和石墨烯的共沉积对复合镀层结构和性能的影响。以下是论文的主要工作和实验结果:(1)铜基表面化学镀银工艺优化。首先,考虑到安全、环保、稳定性等方面,选择无氰化学镀银体系。以镀层外观、镀速和电导率作为技术指标,通过单因素实验对化学镀银的配方组分及工艺条件进行优化,确定最佳镀液配方为:硝酸银8 g/L,酒石酸钾钠100 g/L,氨水80 m L/L,最佳工艺条件为:p H值为12.0,施镀温度为20℃,施镀时间为1.5 h。(2)复合镀层工艺优化。选择非离子型OP-10作为表面活性剂,以镀速、孔隙率和显微硬度为技术指标对复合化学镀工艺进行优化,确定表面活性剂最佳添加量为60mg/L,碳化硅颗粒浓度为5 g/L,碳化硅粒径为500 nm,搅拌速率为600 r/min,石墨烯浓度为200 mg/L。(3)复合镀层结构和成分表征。通过SEM对Ag基复合镀层表面及截面微观形貌进行观察,结果显示镀层具有典型的化学镀银沉积结构,且致密均匀,与基材有良好的结合性。通过EDS分析证明了Si C和石墨烯成功地沉积在镀层中。XRD结果显示,Si C颗粒的引入改变银生长的择优取向,择优取向从(111)面转变为(220)面。(4)银基复合镀层性能研究。使用划格法证明了复合镀层与铜基体之间具有良好的结合力。复合镀层的显微硬度明显高于纯银镀层。复合镀层的表面粗糙度略高于纯银镀层。电阻率和接触电阻测量结果表明,Ag基镀层可以减小铜基的电阻率和接触电阻。碳化硅和石墨烯的添加不会对电阻率和接触电阻造成太大的负面影响。使用动电位极化法测量复合镀层在不同腐蚀介质中的耐腐蚀性。在中性介质中,银/碳化硅/石墨烯复合镀层具有最正的腐蚀电位和最小的腐蚀电流密度,惰性颗粒碳化硅和石墨烯的加入能够作为屏障减缓腐蚀介质扩散。在酸性介质中,镀层会发生钝化反应,银/碳化硅/石墨烯复合镀层的钝化区最宽,三种银基镀层的耐蚀性皆优于铜基材。在碱性介质中,银/碳化硅/石墨烯复合镀层的腐蚀热力学敏感性最低,腐蚀电流密度最小。证明碳化硅和石墨烯的共沉积能够有效改善镀层耐腐蚀性。更多还原

【Abstract】 Electrical contact materials play a crucial role in electrical and electronic equipment,as the quality and performance of these materials directly impact the functionality of various appliances.While metallic silver is commonly utilized in the preparation of electrical contact materials,its high cost poses a challenge in the production process.Copper,on the other hand,boasts excellent electrical conductivity,abundant reserves,and affordability,making it an ideal choice for mass production.Nevertheless,copper surfaces are susceptible to oxidation reactions that create non-conductive oxides,significantly impacting the material’s conductivity.To address this issue,copper-based electrical contact materials require silver plating for protection.However,conventional pure silver coating exhibits low hardness,leading to wear,flaking,and substrate exposure.This frequent material failure necessitates the development of high-performance composite plating.In this paper,silver-based composite coatings were prepared on the surface of copper substrates using electroless plating technology,and the effect of co-deposition of Si C and graphene on the structure and properties of the composite coatings was investigated.The following are the main work and experimental results of the paper:（1）Optimization of the electroless silver plating process.In consideration of safety,environmental protection,and stability,a cyanide-free silver coating system was chosen.Single-factor experiments were conducted to optimize the formulation components and process conditions of the electroless silver plating,with the appearance,plating rate,and electrical conductivity as the technical indexes.The optimal process conditions were determined as follows:Ag NO₃ 8 g/L,KNa C₄O₆H₄100 g/L,NH₃·H₂O 80 m L/L,p H 12.0,plating temperature of 20°C,and plating time of 1.5 hours.（2）Optimization of the composite plating process.By absorbance measurement,non-ionic OP-10 was selected as the surfactant based on absorbance measurement,and the optimum amount of surfactant addition was determined to be 60 mg/L,the concentration of silicon carbide particles was 5 g/L,the carbonization particle size was 500 nm,the stirring rate was 600 r/min,and the concentration of graphene was 200 mg/L,using microhardness as the index.（3）Structural characterization of the composite coating.The surface and cross-sectional microscopic morphology of the silver-based composite coating were observed using SEM.The results indicated that the coating exhibited a typical electroless silver deposition structure,characterized by a dense and uniform appearance and strong bonding with the substrate.The successful deposition of Si C and graphene in the coating was confirmed through EDS analysis.Additionally,XRD analysis revealed that the introduction of Si C particles altered the preferential orientation of silver growth from the（111）plane to the（220）plane.（4）Silver-based composite coating performance study.Good bonding between the composite coating and the copper substrate was demonstrated.The microhardness of the composite coating was significantly higher than that of the pure silver coating.The surface roughness of the composite coating was slightly higher than that of the pure silver coating.The resistivity and contact resistance measurements show that the silver-based coating can reduce the resistivity and contact resistance of the copper.The addition of Si C and graphene does not have much negative impact on the resistivity and contact resistance.The corrosion resistance of the composite coatings in different corrosive media was measured using the kinetic potential polarization method.In neutral media,the Ag/Si C/Gr composite coating has the most positive corrosion potential and the lowest corrosion current density,and the addition of inert particles of Si C and graphene acts as a barrier to slow down the diffusion of corrosive media.In acidic media,passivation occurs,and the Ag/Si C/Gr composite coating has the widest passivation zone,and all three silver-based coatings have better corrosion resistance than the copper substrate.In alkaline media,the Ag/Si C/Gr composite coating has the lowest thermodynamic sensitivity to corrosion and the lowest corrosion current density.The co-deposition of silicon carbide and graphene proved to be effective in improving the corrosion resistance of the coating.更多还原