Characterization of Ball Milled Ni–Al₂O₃ Nanocomposite Powders

Homogenous Ni–Al₂O₃ nanocomposite powders with uniform distribution of Al₂O₃ nanoparticles were obtained through ball milling of Ni and Al₂O₃ powders for 9 hours. Field emission scanning electron microscopy and X-ray mapping were used to characterize the ball milled powders and Al₂O₃ nanoparticles’ dispersion, respectively. The evolution of crystallite size and lattice strain in the nanostructured Ni powder was followed through X-ray diffraction. It was found that ball milling led not only to the uniform dispersion of the Al₂O₃ nanoparticles, but also to the reduction in crystallite size and increase in the lattice strain of the Ni phase. For the composite containing 5 wt.% Al₂O₃, the increase of milling time from 0 to 9 hours led to a continuous decrease of the crystallite size of the Ni phase from 1120 to 36 nm. For the composite containing 10 wt.% Al₂O₃, the increase of milling time from 0 to 2 hours augmented the lattice strain of the Ni phase and a further increase of milling time to 9 hours led to its decrease.