Ni/nano-TiO2 composite electrodeposits: Textural and structural modifications

Nanocomposite coatings were obtained by electrochemical codeposition of TiO2 nano-particles (mean diameter 21 nm) with nickel, from an additive-free Watts type bath. The electrodeposition of Ni–TiO2 composites was carried out on a rotating disk electrode (RDE), by applying direct current. Pure Ni deposits were also produced under the same experimental conditions for comparison. The surface morphology, the crystallographic orientation of nickel matrix and the grain size of the deposits were investigated, along with the distribution and the percentage, of the embedded nano-particles in nickel matrix, as a function of pH, current density and concentration of TiO2 nano-particles in the bath. The observed textural modifications of composite coatings are associated with specific structural modifications of Ni crystallites provoked by the adsorption–desorption phenomena occurring on the metal surface, induced by the presence of TiO2 nano-particles. It has been observed that the presence of TiO2 nano-particles favours the [1 0 0] texture of nickel matrix. Moreover, the codeposition of titania nano-particles with nickel was found to be favoured at low pH and low applied current values. As the titania incorporation percentage is increased, a considerable grain refinement in the nanometer region was revealed followed by an improvement of the quality of the nickel preferred orientation.