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Abstract  

For the most common kinetic models used in heterogeneous reactions, the dependencies on x m = E/RT m (E is the activation energy, T m is the temperature corresponding to maximum process rate, R is the gas constant) on the relative errors (e%) in the determination of the activation energy from the slope of the Kissinger straight line ln(β / T m 2) vs. 1/T m (β is the heating rate) are evaluated. It is pointed out that, for x m≥10.7 and all kinetic models, ∣e%∣≤5%. Some possible cases exhibiting high values of ∣e%∣, which can be higher than 10%, are put in evidence and discussed.

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Abstract  

The thermal polymerization kinetics of dimethacrylate monomers was studied by differential calorimetry using non-isothermal experiments. The kinetic analysis compared the following procedures: isoconversional method (model-free method), reduced master curves, the isokinetic relationship (IKR), the invariant kinetic parameters (IKP) method, the Coats-Redfern method and composite integral method I. Although the study focused on the integral methods, we compared them to differential methods. We saw that even relatively complex processes (in which the variations in the kinetic parameters were only slight) can be described reasonably well using a single kinetic model, so long as the mean value of the activation energy is known (E). It is also shown the usefulness of isoconversional kinetic methods, which provide with reliable kinetic information suitable for adequately choosing the kinetic model which best describes the curing process. For the system studied, we obtained the following kinetic triplet: f(α)=α0.6(1−α)2.4, E=120.9 kJ mol−1 and lnA=38.28 min−1.

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Summary  

The paper contains an analysis of the used of Diefallah's composite integral method of kinetic parameters evaluation. It is shown that the application of this method should be preceded by the application of an isoconversional method through which the dependence of the activation energy, E, on the conversion degree,a, should be established. If Edepends ona, Diefallah's composite integral method leads to erroneous results. If Edoes not depend ona, the true kinetic model should be comprised in the pre-established set of kinetic models. These observations were checked for two sets of non-isothermal data, namely: (a) the TG curves corresponding to the dehydration of CaC2O4H2O; (b) the TG curves corresponding to the thermal decomposition of polyvinyl chloride (PVC).

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Heteroleptic cadmium(II) complex, potential precursor for semiconducting CDS layers

Thermal stability and non-isothermal decomposition kinetics

Journal of Thermal Analysis and Calorimetry
Authors: Anna Kropidłowska, A. Rotaru, M. Strankowski, Barbara Becker, and E. Segal

Abstract  

Coordination compounds may be used as efficient precursors for fabrication of semiconducting layers. Thermal stability of such a potential precursor — [Cd{SSi(O-tBu)3}(S2CNEt2)]2 — was investigated (tBu means tert-butyl and Et means ethyl). The kinetic study was performed by means of different multi-heating rate methods: isoconversional (Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Friedmann) methods associated with the criterion of the independence of the activation parameters on the heating rate. The kinetic triplet of the non-isothermal decomposition of this Cd(II) complex was established.

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Abstract  

A new approximation has been proposed for calculation of the general temperature integral
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\int\limits_0^T {T^m } e^{ - E/RT} dT$$ \end{document}
, which frequently occurs in the nonisothermal kinetic analysis with the dependence of the frequency factor on the temperature (A=A 0 T m). It is in the following form:
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\int\limits_0^T {T^m } e^{ - E/RT} dT = \frac{{RT^{m + 2} }} {E}e^{ - E/RT} \frac{{0.99954E + (0.044967m + 0.58058)RT}} {{E + (0.94057m + 2.5400)RT}}$$ \end{document}
The accuracy of the newly proposed approximation is tested by numerical analyses. Compared with other existed approximations for the general temperature integral, the new approximation is significantly more accurate than other approximations.
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Abstract  

Thermal investigation has allowed us to show the changes undergone by a sort of nitrile-butadiene rubber (NBR) as a consequence ofγ-radiation-induced ageing. The parameters of the processes, which occur at progressive heating of the investigated samples, were determined. It was shown that for γ-irradiated samples the activation parameters corresponding to the thermo-oxidative process leading to solid products are correlated through the relation of compensation effect. Also, it was shown that, by γ-irradiation, NBR undergoes a relatively rapid change of its thermal behaviour which can be due to structural changes.

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Abstract  

The kinetic and thermal behaviour of the following compounds: R-HN-CO-NH-(CH2)n-C6H4-SO2NH2 where R=3,4-dichlorophenyl, phenyl, cyclohexyl; n=0, 1, 2 were studied by TG and DTA techniques. The compounds decompose in many steps; the last one corresponding to the burning of H2N–S–C6H4–C6H4–S–NH2 occurs with comparable reaction rates.

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Abstract  

A new compound cyclohexyl-t-butyldimethylammonium tetraphenylborate, [C6H11N(CH3)2(C(CH3)3)]BPh4 has been prepared, and its decomposition mechanism was studied by TG. The IR spectra of the products of thermal decomposition were examined at every stage. Kinetic analysis for the first stage of thermal decomposition process was obtained by TG and DTG curves, and kinetic parameters were obtained from the analysis of the TG-DTG curves with integral and differential equations. The most probable kinetic function was suggested by comparison of kinetic parameters.

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Abstract  

This paper reports an investigation of the thermal stabilities of the class of coordination compounds containing lanthanide ions Ln(III) (Ln=La, Sm, Eu, Dy, Er), Co(II) ions and oxalate anions C2O 4 2– . The thermal decomposition steps were identified, and in some cases the values of the non-isothermal kinetic parameters were determined.

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