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.

Investigation of the Thermal Decomposition of Talc

In this paper, it is demonstrated that the Arrhenius, Harcourt–Esson and Berthelot–Hood temperature functions describe kinetic data equivalently in the temperature range of measurement. The reason for this finding resides in the fact that, in a narrow temperature range, 1/T, ln T and T are linearly related to each other. The equivalence of the temperature functions enables a recalculation of the kinetic parameters from one function to another. The equivalence holds for the incremental and differential isoconversional methods only; the integral isoconversional methods give incorrect results due to their mathematical incorrectness. It is reasoned that the temperature functions are equivalent not only in the case of the isoconversional methods but also for the model-fitting methods.

Equivalence of the Arrhenius and non-Arrhenian temperature functions in the temperature range of measurement

Thermal decomposition kinetics of calcium carbonate was studied by non-isothermal thermogravimetric analysis at different heating rates. The reaction mechanism was found to follow a two-dimensional phase boundary-controlled model by modelfree and model-fitting methods. Two non-Arrhenius equations (Harcourt–Esson equation and Berthelot–Hood equation) were used to interpret the decomposition kinetics and the results were correlated with those by using the Arrhenius equation. The ambiguous operations in kinetic analysis in the literature, including the determination of reaction mechanism by the shape of thermogravimetry/DTG curves and the correlation of the kinetic parameters of non-Arrhenius and Arrhenius equations, were discussed. Some suggestions were proposed when using nonArrhenius equations in interpreting solid decomposition kinetics.

Application of Non-Arrhenius Equations in Interpreting Calcium Carbonate Decomposition Kinetics: Revisited

Critical study on the identification of reaction mechanism by the shape of TG/DTG curves

Two novel algorithms for the thermogravimetric assessment of polymer degradation under non-isothermal conditions

The nonisothermal kinetics of thermal decomposition of SrCO 3 and BaCO 3 was studied by thermo-gravimetry following non-Arrhenius integral approach of Harcourt and Esson. Variation of activation energy of these two carbonates with fraction decomposition was compared and the average activation energy in the decomposition range was computed.

Application of Non-Arrhenius Method for Analyzing the Decomposition Kinetics of SrCO3 and BaCO3

Solid-state reactions take place by different rate-controlling heterogeneous processes. To find the appropriate kinetic model for a particular solid-state reaction, a genetic algorithm-based simulation technique was carried out using DTA data with a fitness function, and a computer program was developed for the same. The process was applied to the decomposition reactions of limestone and magnesite samples. It was observed that both the decomposition reactions mostly followed the Avrami-Erofeev kinetics model.

Jayita Pal

Papers

Application of Non-Arrhenius Method for Analyzing the Decomposition Kinetics of SrCO3 and BaCO3

Use of Genetic Algorithm to Determine the Kinetic Model of Solid‐State Reactions