Thermal Decomposition Mechanism of MgCl_2·6H_2O

The thermal decomposition mechanism and the intermediate morphology of MgCl2·6H2O before and after calcination by a resistance furnace,were studied using integrated thermal analysis,X-ray diffraction,scanning electron microscope,energy dispersive X-ray spectrum and chemical analysis.The results showed that there were six steps in the thermal decomposition of MgCl2·6H2O,producing MgCl2·4H2O at 69℃,MgCl2·2H2O at 129℃,MgCl2·nH2O(1≤n≤2) and MgOHCl at 167℃,and the MgCl2·nH2O(1≤n≤2) converted to Mg(OH)Cl·0.3H2O with dehydration and hydrolysis simultaneously at 203℃,Mg(OH)Cl·0.3H2O dehydrated to MgOHCl at 235℃,MgOHCl directly converted to MgO at 415℃.The MgOHCl particle was irregular with porous structure,while Mg(OH)Cl·0.3H2O particle had relatively flat surface.