Thermochimica Acta 

About: Thermochimica Acta is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Thermal decomposition & Differential scanning calorimetry. It has an ISSN identifier of 0040-6031. Over the lifetime, 19176 publications have been published receiving 362692 citations. The journal is also known as: TA.

ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data

Abstract: The present recommendations have been developed by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). The recommendations offer guidance for reliable evaluation of kinetic parameters (the activation energy, the pre-exponential factor, and the reaction model) from the data obtained by means of thermal analysis methods such as thermogravimetry (TGA), differential scanning calorimetry (DSC), and differential thermal analysis (DTA). The recommendations cover the most common kinetic methods, model-free (isoconversional) as well as model-fitting. The focus is on the problems faced by various kinetic methods and on the ways how these problems can be resolved. Recommendations on making reliable kinetic predictions are also provided. The objective of these recommendations is to help a non-expert with efficiently performing analysis and interpreting its results.

The determination of activation energy from linear heating rate experiments: a comparison of the accuracy of isoconversion methods

Abstract: Model-free isoconversion methods are the most reliable methods for the calculation of activation energies of thermally activated reactions. A large number of these isoconversion methods have been proposed in the literature. A classification of these methods is proposed. Type A methods such as Friedman methods make no mathematical approximations, and Type B methods, such as the generalised Kissinger equation, apply a range of approximations for the temperature integral. The accuracy of these methods is investigated, by deriving expressions for the main sources of error which includes the inaccuracy in reaction rate measurement, approximations for the temperature integral and inaccuracies in determination of temperature for equivalent fraction transformed. Both highly inaccurate and highly accurate Type B methods are identified. In cases where some uncertainty over baselines of the thermal analysis data exists or where accuracy of determination of transformation rates is limited, type B methods will often be more accurate than type A methods.

Study of the kinetics of the mechanism of solid-state reactions at increasing temperatures

Abstract: Possible reasons for the misinterpretation of non-isothermal kinetics are discussed. The importance of the correct selection for the assessment of the progress of the reaction and the acquisition of representative experimental data, as well as the effect of non-isothermal conditions and possible change of the equilibrium on the kinetic equation are stressed. Detailed attention is given to the probable mechanisms of individual cases of solid-state reactions as expressed in integral and/or differential forms of kinetic equations. Reactions controlled by the movement of phase boundaries, by simple nucleation. by nucleation followed by nuclei growth and by diffusion are discussed; a combined form of differential equation suggested for the preliminary. appraisal of possible mechanisms is

Model-free and model-fitting approaches to kinetic analysis of isothermal and nonisothermal data

Abstract: The model-free and model-fitting kinetic approaches have been applied to data for nonisothermal and isothermal thermal decompositions of HMX and ammonium dinitramide. The popular model-fitting approach gives excellent fits for both isothermal and nonisothermal data but yields highly uncertain values of the Arrhenius parameters when applied to nonisothermal data. These values cannot be meaningfully compared with the values derived from isothermal measurements, nor they can be used to reasonably predict the isothermal kinetics. On the other hand, the model-free approach represented by the isoconversional method yields similar dependencies of the activation energy on the extent of conversion for isothermal and nonisothermal experiments. The dependence derived from nonisothermal data permits reliable predictions of the isothermal kinetics. The use of the model-free approach is recommended as a trustworthy way of obtaining reliable and consistent kinetic information from both nonisothermal and isothermal data.

Thermal properties of imidazolium ionic liquids

Abstract: We investigated the thermal properties of several imidazolium salts using DSC and TGA/SDTA data. Many of these salts are liquids at sub-ambient temperatures. These ionic liquids form glasses at low temperatures and have minimal vapor pressure up to their thermal decomposition temperature (>400°C). Thermal decomposition is endothermic with the inorganic anions and exothermic with the organic anions investigated. Halide anions drastically reduce the thermal stability of these salts (<300°C). We have observed that aluminium catalyzes the decomposition of the salts containing the inorganic fluoride anions. The imidazolium cations are thermally more stable than the tetraalkyl ammonium cations.