Effect of current density and grain refining agents on pulsed electrodeposition of nanocrystalline nickel

Abstract

Nanocrystalline nickel was electrodeposited on copper substrate using a Watt's bath at a temperature of 50°C. The effect of pulsed current density (up to 1·5 A cm⁻²) and role of organic additives (namely saccharin and sodium citrate) in the deposition bath was evaluated for rendering grain refinement. The deposited samples were characterised for current efficiency, colonial morphology, crystallite size, texture, coercivity and nanomechanical properties (such as Young's modulus and hardness). Results were compared with deposition using direct current, and utilising annealed Cu substrate. The smallest crystallite size of 22 nm was obtained, and the lowest coercivity equaled 22 Oe for the sample deposited using pulsed current with the peak current density 1 A cm⁻² and 10 g L⁻¹ saccharin addition. Annealing of the substrate has shown to increase the Young's modulus of electrodeposited Ni by 10·2%, which increases further by 14·4% with saccharin addition when compared to those of deposits without saccharin addition.