Influence of hydrodynamics and pulse plating parameters on the electrocodeposition of nickel-alumina nanocomposite films

Nickel-alumina nanocomposites were produced by electrocodeposition utilizing two electrode configurations, a parallel plate electrode (PPE) and impinging jet electrode (IJE), and various current modulations, i.e. direct current (DC), pulse plating (PP) and pulse reverse plating (PRP). Particle incorporation increased linearly with the particle loading of the electrolyte for all deposition conditions studied. A maximum incorporation of 12 vol.% of 50 nm γ-Al₂O₃ particles in a nickel matrix was achieved using an unsubmerged IJE system, while PP and PRP resulted in composites with particle contents up to 11 vol.% of 13 nm γ-Al₂O₃ particles. In general, nanocomposites showed higher hardness compared to the pure nickel coatings. The enhanced hardness of the composite films was associated with modifications in the microstructure of the nickel matrix as well as with the nanoparticle incorporation. The pure nickel deposits exhibited a strong (1 0 0) texture. With increasing plating current density and particle incorporation, a variation in the crystallite size and a loss of texture was observed.