An Investigation on the Electrodeposition Mechanism of Ni-TiO2 Nanocomposite Coatings

Abstract

In this research, a sol-modified composite electrodeposition technique that combines the sol-gel method with the conventional electrodeposition process was utilized to deposit Ni-TiO₂ nanocomposite coatings. Cyclic voltammetry and chronoamperometry techniques were applied to study the influence of the TiO₂ sol concentration on the deposits' electrochemical behavior. The results clearly showed that for higher sol concentrations, the onset potential of the nanocomposite deposition decreased compared to that of the pure Ni. The Scharifker-Hill model was utilized at the initial times of deposition to study the nucleation mechanism. It was demonstrated that the nucleation mechanism of the nanocomposite at low overpotentials followed the progressive system, whereas at higher overpotentials it was found to be instantaneous with the three-dimensional growth mechanism. The weight percentages of the codeposited TiO₂ nanoparticles were measured, and according to the results, the higher sol concentrations in the plating bath led to a higher TiO₂ nanoparticle content. The XRD results confirmed the presence of the anatase phase in the Ni-TiO₂ nanocomposite coatings after 3 hours of heat treatment at 450°C. The surface morphology was studied by the scanning electron microscopy, confirming that the addition of higher sol concentrations refined the microstructure, particularly under higher deposition overpotentials. This was attributed to increased nucleation sites and the slow growth rate of the nuclei.