Kinetic–Statistical Approach in a Detailed Study of the Mechanism of Thermal Decomposition of Zinc–Iron-Intermetallic Phase

Abstract

Kinetic–statistical approach was applied to investigate the mechanism of thermal decomposition of Zinc–Iron-intermetallic phase, as by product from neutral leach residues. In present paper, in order to characterize the tested material, the following experimental techniques were used: Rietveld analysis, scanning electron micrograph and tube furnace sample heating procedure. Based on dependence of Avrami constant in function of effective activation energy, it was found that at T > 950 °C, the process of crystal growth takes place in autocatalytic stage, under the conditions, where rate of nucleation rapidly increases. It was established that high nucleation rate can be attributed to formation of both Zn and Fe rich regions which provide a high number of heterogeneous nucleation sites. It has been proposed that emergence of line defects under ZnO branched crystals can serve as pin-points for secondary nucleation to occur. It was confirmed that increase in temperature in Zn vapor did not result in a decrease of existing in Zn constitutional vacancies.