Microstructure, nanoindentation, and electrochemical properties of the nanocrystalline nickel film electrodeposited from choline chloride-ethylene glycol

A fully dense nanocrystalline (nc) Ni film on the brass substrate was fabricated by a simple electrodeposition from a choline chloride-based ionic liquid (choline chloride-ethylene glycol) at working voltage (between the two electrodes) of 1.0 V and room temperature. It is found that the nc Ni with an average grain size of about 6 nm has a face-centered cubic crystal structure. At the film/substrate interface, the epitaxial growth of some nc Ni grains on brass grains can be evidenced by the high resolution transmission electron microscope. The 6 nm grain sized Ni exhibits a high strain rate sensitivity (m = 0.051) and enhanced hardness values in the range of 7.6-9.7 GPa. The deformation mechanism of the nc Ni under indentation is also discussed with the theoretical model fitting. The potentiodynamic polarization curve shows that the nc Ni film exhibits a much negative corrosion potential, which provides a sacrificial anode protection for the brass substrate. (C) 2011 Elsevier B.V. All rights reserved.