镀银铜粉的制备及其抗氧化和导电性能

Preparation of Silver-Plated Copper Powder and Study of Its Oxidation Resistance and Electrical Conductvity

为了避免铜粉银氨体系镀银过程中生成铜氨配离子,采用乙二胺四乙酸(EDTA)二钠盐与Ag+配位,利用化学置换法对铜粉镀银,分别讨论了反应体系中的主盐硝酸银浓度、主盐与配位剂的摩尔比对镀银铜粉的抗氧化性及导电性能的影响,研究了镀银铜粉的组成及形貌。结果表明:本法避免了使用氨水配位银离子镀银中[Cu(NH3)4]2+的出现,一次镀覆即可制得银镀层较完整、均匀的铜粉;随着硝酸银浓度的提升,镀银铜粉的导电性及抗氧化性均呈现先增强后减弱的趋势,当B液中硝酸银浓度为7.5 g/L时,镀银铜粉的抗氧化性能和导电性最佳,比纯铜粉的有较大幅度提高;主盐硝酸银与配位剂EDTA二钠盐摩尔比为2.0∶1.0时镀银铜粉的导电性能最佳,电阻率为4.95×10-6Ω·m。

Chemical replacement method was adopted to plate silver on Cu powder in the presence of disodium ethylenediamine tetra acetate( EDTA·2Na) as the complexing agent and silver nitrate as Ag+source so as to get rid of [Cu(NH3)4]2+ during silver plating of Cu powder from ammonia bath.The effect of concentration of AgNO3 and molar ratio of AgNO3 to EDTA·2Na on the oxidation resistance and conductivity of silver plated Cu powder was investigated;and the composition and morphology of silver plated Cu powder were analyzed.Results indicated that introducing EDTA·2Na could avoid the formation of [Cu(NH3)4]2+,and resultant silver plated Cu powder contained complete and uniform Ag overcoat.Besides,the electrical conductivity and oxidation resistance of silver plated Cu powder tended to increase initially but declined later with increasing concentration of AgNO3.Parti cularly,Cu powder coated with silver when AgNO 3 concentration was 7.5 g/L possessed the best electrical conductivity and oxidation resistance,which were much better than those of pure Cu powder.Moreover,when the molar ratio of AgNO3 to EDTA·2Na was 2.0 ∶ 1.0,resultant Cu powder coated with silver had the best electrical conductivity,showing an electrical resistivity of 4.95 × 10-6Ω·m.