Abstract: The processes of the thermal decomposition and recrystallization of dickite from Fuzhou, Fujian Province have been studied in dynamic air atmosphere by a simultaneous thermal analysis instrument(thermogravimetric  analysis-derivative thermogravimetric analysis-differential scanning calorimetry, TG-DTG-DSC) and X-ray diffraction techniques.  The data of TG and DSC were used to carry out the kinetic triplet of the thermal decomposition and recrystallization,  respectively.  The Friedman method together with the non-linear regression approach was employed to determine the reaction mechanism and the kinetic parameters of the thermal decomposition.  The iterative procedure and minimum deviation were used to determine the reaction mechanism and the kinetic parameters of the recrystallization.  The results show that the thermal decomposition(dehydrate 2 molecules of water) of dickite occurs in the temperature range of 450—750 ℃ and the reaction mechanisms contains two steps continuously.  The process conforms to a random nucleation and nuclei growth model(An) and auto-catalytic model(CnC).  The recrystallization of dickite appears in the temperature range of  975—1050 ℃.  The reaction mechanism is best described by the random nucleation and nuclei growth model(An).

Key words: Dickite; , Thermal decomposition; , Recrystallization; , Non-isothermal kinetics; , Non-linear regression