Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Estimation of the activation energy as a function of the extent of conversion in a thermite system by various isoconversional methods
Submission Author:
Kesiany Máxima de Souza , SP
Co-Authors:
Kesiany Máxima de Souza, Marcelo De Lemos
Presenter: Kesiany Máxima de Souza
doi://10.26678/ABCM.ENCIT2022.CIT22-0581
Abstract
Solid energetic mixtures like thermites usually burn through a heterogeneous reaction where the burning reactants present more than one phase. So, the chemical reaction happens at the interface between reactants, where the particles interact with the neighboring particles. This process is complex and can be affected by the formation of products, crystalline defects, and experimental variables, following, in general, more than one-step mechanisms. Therefore, the estimated activation energy of this kind of reaction is generally an apparent value and can vary throughout the overall process. It is necessary to apply a proper kinetic method to obtain this variation. Isoconversional methods are more suitable for this application because they allow the activation energy estimation at several instants of the reaction. Also, they do not require the fitting of a reaction model. So, in this present study, various isoconversional methods are applied to obtain the activation energy as a function of the extent of conversion in the Al-Ti-Fe2O3 system. The data analyzed was retrieved from literature in the differential thermal analysis of this thermite system at three different heating rates. The differential method of Friedman and the flexible integral methods of Vyazovkin and Popescu, evaluated in small segments, captured substantial variations in activation energy as the extent of reaction varies. On the other hand, the rigid integral methods of Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, and Starink predicted nearly constant activation energies throughout the reaction process. Finally, among all methods analyzed, we indicate the isoconversional method of Popescu for the kinetics analysis of this kind of reaction because of its simplicity of application, accuracy, and proper estimation of the variations in activation energy during the combustion process.
Keywords
thermite, isoconversional method, model-free method, activation energy, heterogeneous reaction
