Preparation And Kinetics Study Of Nanograde Zinc Oxide Powders By Solid-state Reaction Under Microwave

As a new type of inorganic multifunctional materials, nanograde ZnO has special performance in the magnetic, optical, electrical and sensitivity. The general zinc oxide is unmatched. So that nanograde ZnO has been gained much attention in the field of ceramic, chemical and biological medicine. In recent years, the preparation of nanograde ZnO has become a hot subject at home and abroad.In this paper, the precursors of nanograde ZnO were synthesized by solid-solid state reaction of Zn(CH3COO)2·2H2O and H2C2O4·2H2O at room temperature. And then the nanograde ZnO powders were prepared in microwave heating and conventional heating. The effect of heating time and heating temperature on ZnO size was investigated. In addition, thermal decomposition process of the precursors and grain growth kinetics of ZnO were studied.the precursors and nanograde ZnO were characterized by XRD, TG-DTA, FT-IR and TEM. The main conclusions were as follows:(1) The precursors of nanograde ZnO have high purity synthesized by solid-solid state reaction of Zn(CH3COO)2·2H2O and H2C2O4·2H2O at room temperature. The results showed that the decomposing temperature of precursors, optimum milling time and optimum material ratio were450℃,2h and1:1. The ZnO size was increasing as heating time and heating temperature rising and the effect of heating temperature on grain growth speed was significant. In the same conditions, the partical size of ZnO prepared by microwave is bigger than that of prepared by the conventional way.(2) Using Ozawa and Coats-Redfern methods, the thermal decomposition mechanism function and activation energy were determined. The decomposition mechanism of precursors was the stochastic coring and subsequent growth and calculated activation energy was119.7kJ/mol. The mechanism function was as follows: G(α)=[-1n(1-α)]1/2f (α)=2(1-α)[-1n(1-α)]1/2(3) In the range of450～600℃, Kinetic index and activation energy of crystallites prepared in two heating ways were as follows:In conventional heating way, the kinetic index and activation energy of crystallites were6.87and74.3kJ/mol. In microwave heating way, the growth kinetic index and activation energy of crystallites were5.58and60.5kJ/mol. In both two ways, the growth kinetic index was declining with the heating temperature.