Investigation of NiO reduction dynamics and properties of NiO-Ti powders

Abstract

Abstract A detailed study of the mechanochemical (MC) processing of NiO-Ti [NiO-Ti (x at.%) with x = 20, 35] powders was carried out using a high-energy ball milling technique to investigate the formation of a NiO-based nanocomposite as a function of the milling time. During milling, the reduction of NiO to Ni follows a gradual process with a reduction of 10% and a self-sustaining process with a maximum reduction of 94% for x = 20 and 35 powders, respectively. The types of NiO reduction and the formation of ferromagnetic (FM) Ni from NiO could be accounted for by the change in magnetization to maximum values of 2 emu/g and 24 emu/g for the gradual and self-sustaining reactions, respectively. The relative fractions of Ni and NiO phases play an important role in (i) the formation of FM nanocomposite, (ii) the enhancement of magnetic anisotropy caused by the coexistence of mixed magnetic phases, (iii) temperature-induced structural phase changes and (iv) the gradual decrease in the induced FM phase with the increase in milling time. The process of time-dependent MC reduction and the resulting structural, vibrational and magnetic behavior of the in situ FM nanocomposite were studied in detail. This process may reveal potential applications in metallurgy and ore reduction processes.