Preparation of NiO nanoparticles from Ni(OH)₂·NiCO₃·4H₂O precursor by mechanical activation

A mechanical activation process was introduced as a facile method for producing nickel oxide nanopowders. The precursor compound Ni(OH)₂·NiCO₃·4H₂O was synthesized by chemical precipitation. The precursor was milled with NaCl diluent. A high-energy ball milling process led to decomposition of the precursor and subsequent dispersal in NaCl media. Nickel oxide nanocrystalline powders were produced by subsequent heat treatment and water washing. Milling rotation speed, milling time, ball-to-powder ratio (BPR), and nickel chloride-to-precursor ratio were introduced as influential parameters on the wavelength of maximum absorption (λ_max). The effects of these parameters were investigated by the Taguchi method. The optimum conditions for this study were a milling rotation speed of 150 r/min, a milling time of 20 h, a BPR of 15/1, and a NaCl-to-powder weight ratio (NPR) of 6/1. In these conditions, λ_max was predicted to be 292 nm. The structural properties of the samples were determined by field emission scanning electron microscopy, X-ray diffraction, and energy dispersive spectrometry.