Synthesis of Ni–Y2O3 nanocomposite powders by a very high speed planetary milling process: Microstructural development and refinement behavior

In the present work, Ni–Y2O3 nanocomposite powders were synthesized in-situ using a very high speed planetary ball milling process; their microstructure and refinement behaviors were investigated as functions of milling speed and time. At a very high milling speed of 1000 rpm, the resultant composite powders were extremely blended and homogenized, forming a purely monoclinic Y2O3 with a size of ~ 10 nm; these results were achieved within an hour. Moreover, it was notable that the original coarse cubic Y2O3 particles were predominantly transformed into the monoclinic phase as milling time went by. On the other hand, at a conventional milling speed (~ 400 rpm), the limits of refinement were deemed to have been reached in terms of phase transition and homogenization of the particles, even for a long milling time of up to 240 min.