Morphology and Roughness of Silver Deposit Formed by Cementation at Various Temperatures in Pure Sulfuric Acid

Abstract

The morphology and surface roughness of silver (Ag) deposit formed on metallic copper (Cu) by cementation conducted in a 0.5M H2SO4 solution was investigated at various temperatures above 25°. The influence of the presence or absence of oxygen (O2) on Ag morphology was studied at an initial Ag+ concentration of 20 mg/dm3. An analysis of distribution diagrams of the surface height calculated from scanning-electron-microscope (SEM) top-view images was performed. The cementation reaction results in a non-homogeneous Ag deposit formed on the surface independently of the presence or absence of O2 in solution. The Ag deposit covers Cu mainly with a uniform and compact layer with separated germs of predendrites, but also a huge ‘fern-leaf-shaped’ and ‘lycopodium-twigs-shaped’ dendrites appear occasionally on the surface. The presence of O2 in the system and temperature do not affect significantly the morphology of Ag dendrite as well as a deposit formed on the smooth part of the surface. The roughness of surface with Ag cement varies with temperature only under aerobic conditions where the enhanced Cu corrosion increases the size of anodic sites. The results obtained from the surface-height-distribution diagrams constructed for anaerobic conditions showed that the reaction between Cu+ and Ag+ does not start in the bulk of the solution even at the highest studied temperature.