Investigation of the Thermal Decomposition of Talc

Different changes in the structural and thermal properties of various types of talc have been reported in the literature which have made comparison of analytical results difficult. The objective of the present study was to obtain some fundamental insights into the effects of the thermal behavior of talc and to carry out kinetic analyses of the decomposition of talc under high temperature. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry-differential scanning calorimetry (TG-DSC) were used to study the thermal decomposition mechanism. The Coats-Redfern decomposition model was used to determine the decomposition mechanism of talc samples. The results showed that the decomposition of talc commenced at ~800°C, peaking at ~895°C, with the formation of enstatite and amorphous silica. An isothermal treatment at 1000°C caused the complete dehydroxylation of talc. The XRD and FTIR results indicated that the enstatite and amorphous silica phases were transformed into clinoenstatite and paracrystalline opal phases, respectively, after the decomposition stage at 1200°C. Good linearity in the Coats-Redfern model was observed from room temperature to 1300°C and the activation energy was calculated to be 69 kcal/mol.