Preparation and Thermal Decomposition of MgSO4·5Mg(OH)2·2H2O

摘要

Magnesium hydroxide sulfate hydrate (MHSH) whisker was prepared using bitter, ammonia and magnesium sulfate heptahydrate as raw materials by hydrothermal synthesis in autoclave. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis- thermal gravity analysis (DTA -TG) were employed to characterize the structural features and composition of the MHSH samples. The thermal decomposition kinetics of the whisker was studied by thermogravimetric(TG) using the non-isothermal approach. The kinetic mechanism of thermal decomposition kinetics of MHSH whisker was studied using Satava method. The proposed models for thermal decomposition of the sample for the three stages are Avrami-Erofeev model function(n=2) of nucleus formation and growth A2 with integral form 2 / 1 )] 1 ln( [ ) (|á |á --=G , branching nuclei model Au with integral form )] 1 /( ln[ ) (|á |á |á -=G and nucleation model P1/2 with integral form 2 / 1 ) (|á |á =G respectively. The values of kinetic parameters, viz., the apparent activation energy (Ea), the pre-exponential factor (A) and the reaction order (n) had been evaluated by using the Kissinger equation to deal with the date of thermal gravimetric analysis.