Comparative study on the effect of current density on Ni and Ni–Al₂O₃ nanocomposite coatings produced by electrolytic deposition

Nickel was deposited galvanostatically at 0·23, 0·77, 1·55, 3·1 and 5·4 A dm −2 current densities at room temperature. An XRD technique was employed for evaluating the grain size and preferred orientation of the nickel deposit. The cross-sections of the nickel deposits were subjected to microhardness and microstructure analysis. Nanosize alumina was prepared by a solution combustion technique, and the powder was characterised by XRD and particle size analysis. The particle size of Al 2 O 3 powder synthesised by the combustion process was 30 nm. XRD confirmed the presence of pure α-Al 2 O 3 . Combustion synthesised alumina (CSA) powder was codeposited in the nickel matrix at various current densities, as in the case of nickel. Similarly, commercially available 0·05 μm Al 2 O 3 containing a mixture of α and β phases was codeposited in nickel matrix. The Ni–Al 2 O 3 nanocomposite coatings were characterised by XRD, microhardness measurement and image analysis. The results obtained with nickel and Ni–Al 2 O 3 composite coatings are compared.