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Model-free kinetics

Staying free of multiplying entities without necessity

Journal of Thermal Analysis and Calorimetry
Author: S Vyazovkin

Abstract  

The paper presents the model-free kinetic approach in the context of the traditional kinetic description based on the kinetic triplet, A, E, and f(α) or g(α). A physical meaning and interpretability of the triplet are considered. It is argued that the experimental values of f(α) or g(α) and A are unlikely to be interpretable in the respective terms of the reaction mechanism and of the vibrational frequency of the activated complex. The traditional kinetic description needs these values for making kinetic predictions. Interpretations are most readily accomplished for the experimental value of E that generally is a function of the activation energies of the individual steps of a condensed phase process. Model-free kinetic analysis produces a dependence of E on α that is sufficient for accomplishing theoretical interpretations and kinetic predictions. Although model-free description does not need the values of A and f(α) or g(α), the methods of their estimating are discussed.

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Journal of Thermal Analysis and Calorimetry
Authors: Maria J. F. Costa, Antonio S. Araujo, Edjane F. B. Silva, Mirna F. Farias, Valter J. Fernandes Jr., Petrus d’Amorim Santa-Cruz, and José G. A. Pacheco

from room temperature up to 900 °C, at a heating rate of 5, 10, and 20 °C min −1 . The model-free kinetics proposed by Vyazovkin and co-workers [ 11 , 12 ] was used to evaluate the kinetic parameters of surfactants decomposition from the optimized

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Abstract  

The evaporation of octanoic (caprylic) acid was investigated by means of thermogravimetric analysis (temperature range: 300–600 K) under a nitrogen dynamic atmosphere (heating rates: 0.16, 0.31, 0.63, 1.25, 2.5, 5 and 10 K min−1). Kinetic plots for a zero-order process were constructed based on the Arrhenius equation. The activation energy for the evaporation process was calculated via both the Arrhenius plot and Vyazovkin’s isoconversional model-free method.

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Journal of Thermal Analysis and Calorimetry
Authors: F. M. Aquino, D. M. A. Melo, R. C. Santiago, M. A. F. Melo, A. E. Martinelli, J. C. O. Freitas, and L. C. B. Araújo

. The objective of this study is to study the thermal degradation of the ligand groups with the metallic ions of the system using the Flynn and Wall and “Model-free kinetics” methods and evaluate the results in order to establish the activation energy as

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Abstract  

Recently, model free kinetic analysis of sinusoidal modulated TG-curves has been presented. In this contribution we compare the activation energies resulting from model free analysis of modulated TG-curves and from Vyazovkin's model free kinetic analysis of non-modulated TG-curves. We used polytetrafluorethylene and manganese oxide as samples. As a result we find, that both methods deliver similar activation energies for polytetrafluorethylene. However, the activation energies of manganese oxide deviate substantially. The main purpose of kinetic analysis is its potential for predictions of the temporal behavior of materials under certain thermal conditions. Analysis of modulated TG-curves allows a model free determination of the temperature dependence of the activation energy. However, in order to make predictions, one still has to rely on kinetic models such as e.g. first order kinetics. This is in contrast to Vyazovkin's approach, which allows a model free description of kinetic processes in terms of a conversion dependent activation energy. This function can then be used to make kinetic predictions without any further assumptions with respect to reaction models. In this paper we further discuss this fundamental difference.

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). Initial mass was defined as the mass at ambient temperature and final mass by the DTG (derived thermogravimetric) curve. This study used model-free kinetics to determine pyrolysis kinetic parameters of the reaction. In this method, the kinetic

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Journal of Thermal Analysis and Calorimetry
Authors: Edjane F. B. Silva, Marcílio P. Ribeiro, Ana C. F. Coriolano, Ana C. R. Melo, Anne G. D. Santos, Valter J. Fernandes Jr., and Antonio S. Araujo

PET and PET/MCM-41 using the model-free kinetics The obtained results of E a for degradation of a Brazilian oil 19°API was close to the sample under this study, were the kinetic parameters calculated by Ozawa

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Journal of Thermal Analysis and Calorimetry
Authors: Edjane F. B. Silva, Marcílio P. Ribeiro, Luzia P. F. C. Galvão, Valter J. Fernandes, and Antonio S. Araujo

. In this case, to obtain reliable and consistent kinetic information about the overall process, the model-free kinetics was applied based on the Vyazovkin theory. This theory is based on an isoconversional computational technique that calculates the

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