Preparation of nanosized zinc oxide by vacuum oxidation and kinetic study of oxidation

Abstract

Nanosized zinc oxide was prepared with a vacuum oxidation method by using hot-dip galvanizing slag as the raw material and air as the oxygen source. The oxidation kinetics curves of zinc vapor at different pressures were plotted by thermogravimetry, and the morphology of ZnO was observed by scanning electron microscopy. The nanosized ZnO products were hexagonal wurtzite crystals with the purity ≥99.98. When parabolic kinetics occurred, the ZnO products were granular, amorphous, tetra-needle-like or single needle-like. In the case of linear kinetics, the products were short tetra-needle-like or needle-like crystals. Zinc oxidation was controlled by the contracting spherical model R₃ initially and the three-dimensional diffusion model D₄ thereafter, with the apparent activation energies of 101.3–122.1 kJ/mol and 111.2–143.4 kJ/mol respectively.