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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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Thermal decomposition kinetics of some aromatic azomonoethers

Part III. Non-isothermal study of 4-[(4-chlorobenzyl)oxy]-4′-chloroazobenzene in dynamic air atmosphere

Journal of Thermal Analysis and Calorimetry
Authors: A. Rotaru, Anca Moanţă, P. Rotaru, and E. Segal

Abstract  

Thermal analysis of 4-[(4-chlorobenzyl)oxy]-4′-chloro-azobenzene dye, exhibiting liquid crystalline properties, was performed in dynamic air atmosphere. The compound behavior was investigated using TG, DTG, DTA and DSC techniques, under non-isothermal linear regime. The evolved gases were analyzed by FTIR spectroscopy. Kinetic parameters of the first decomposition step were obtained by means of multi-heating rates methods, such as isoconversioanl methods, IKP method and Perez-Maqueda et al. criterion.

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Computational thermal and kinetic analysis

Software for non-isothermal kinetics by standard procedure

Journal of Thermal Analysis and Calorimetry
Authors: A. Rotaru, M. Goşa, and P. Rotaru

Abstract  

A software package to determine the non-isothermal kinetic parameters of heterogeneous reactions has been developed. The dynamic handle of conversion degree step and ranges, heating rates and kinetic models makes the evaluation of the activation parameters much faster. The standard procedure: ‘model-free’ kineitc, IKP and Perez-Maqueda et al. methods, is applied for the determination of the kinetic triplet corresponding to thermal induced transformations. The software is designed mainly for thermogravimetric, temperature programmed reduction and dilatometry data processing, but may also import already transformed numeric data.

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Thermal decomposition of bismuth laurates

Study of process kinetics

Journal of Thermal Analysis and Calorimetry
Authors: V. Logvinenko, K. Mikhailov, and Yu. Yukhin
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Abstract  

Dehydration processes of series of rhenium cluster compounds were studied (by thermogravimetry, differential scanning calorimetry, dilatometry methods). Cluster anions of compounds are [Re6S8Br6]3−, [Re6S7Br7]3−, [Re6S8(OH)6]4−, [Re6Se8(OH)6]4−. TG- and DSC-data were used for kinetic studies, these data were processed using special computer program with ‘model-free’ approach. Quantitative data on thermodynamic and kinetic stability of compounds are obtained. The role of water molecules in the cluster compounds stability is discussed.

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