Electrochemical Formation of Functional Silver Coatings: Nanostructural Peculiarities

Abstract

The microstructure of silver coatings electrodeposited from different types of baths without brightening agents had been studied. The principal formulations of baths were following: cyanide: 0.75M KAg(CN)2+1.5M KCN+0.2M KOH; dicyanoargentate-thiocyanate (DCAT): 0.75M KAg(CN)2+6M KCNS + 1M K2CO3; dicyanoargentate-borate-phosphate-carbonate (BPC): 0.75M KAg(CN)2+0.82M KH2PO4+ 0.41M H3BO3+0.15M K2CO3+0.69M KOH; thiocyanate: 0.75M AgNO3 + 6M KCNS. The values of grain size was evaluated based on the XRD examination and are in the range 60 nm (for coatings electrodeposited from cyanide baths at current densities (15-40 mA cm-2) to 100 nm (for thiocyanate and BPC baths). The values of lattice parameter and interplanar distance obtained for Ag coatings are higher than that obtained for metallurgically prepared silver. Regardless on the type of bath, the obtained coatings were polycrystalline and nanocrystalline. The coatings electrodeposited at low current densities (< 10 mA cm-2) are rather crystalline that evidently was confirmed by SEM examination of surface morphology.