Size-Dependent Energetics and Thermodynamic Modeling of ZnO Nanoparticles produced by Electrical Wire Explosion Technique

Abstract

Zinc Oxide nanoparticles were produced by the electrical wire explosion technique (EWET) by exploding zinc conductor in oxygen ambience and the transmission electron microscopy confirmed that the particle size distribution followed lognormal distribution with both spherical and non-spherical morphology. The mean particle size of the samples skewed to the lower particle size with the increased energy ratio and decreased pressure. The size dependent thermodynamic model was formulated to predict the optimum process conditions in EWET for the production of uniformly distributed ZnO nanoparticles. High energy ratio and high saturation ratio were identified as ideal process conditions for producing ZnO nanoparticles by WEP. The enthalpy of formation of ZnO nanoparticles was found to be size-dependent and decreased with particle size reduction. The reduction in lattice energy observed was because of the increased number of dangling bonds. The computational results proved that the nucleation rate of ZnO nanoparticles increased with the increasing saturation ratio, which is experimentally justified by the reduction in particle size with increased energy deposition. The model predicts that the activation Gibbs free energy of nucleation of ZnO nanoparticles decreases with the increasing temperature and saturation ratio, which is substantiated by the particle size reduction at higher energy ratios.