Influence of surface-active agents on Ni–ZrO₂ nanocomposite coatings

Abstract

For the first time, Ni–ZrO₂ nanocomposite coatings have been successfully co-electrodeposited by varying the concentration of ZrO₂ particles in the bath. For this, to prevent agglomeration of ZrO₂ nanoparticles in the plating bath and enhance the mass fraction of nano-particles in the composite coatings, the effects of surfactants and ZrO₂ content on the Ni–ZrO₂ nanocomposite coatings have been investigated. It was shown that the ZrO₂ fraction and the microhardness of the composite coatings are improved by using less than 20 g L⁻¹ ZrO₂ and adding anionic and cationic surfactants, respectively. A high concentration of nanoparticles can cause agglomeration, which affects the Orowan strengthening effect. The addition of a cationic surfactant increases the charge on the ZrO₂, migrates faster toward the cathode, and aids improvement of the ZrO₂ nanoparticle fraction. In contrast, the anionic surfactant, due to its dispersion and ZrO₂ fraction with a small increase, enhances the Orowan strengthening, which limits the plastic deformation of the coating and increases the improvement in coating hardness. Furthermore, the microhardness of the Ni–ZrO₂ composite coating is further increased after a high-temperature annealing process up to a maximum temperature of 900°C, which results from the oxidation of nickel and the dispersion of ZrO₂ nanoparticles.