Authors:D. Patidar, Sonalika Agrawal, and N. S. Saxena
]. This model (Kissinger) is also employed to study the thermal stability of current CdS/PMMA system in terms of activationenergy which is given by the following relation:
where α is the heating rate, C is constant, and E t is the glass
The validity of the Friedman method is assessed for systems of overlapping reactions. By means of mathematical analysis and numerical examples it is shown that, in the case of competitive reactions, the method gives the true value of the instantaneous mean activation energy. However, some error may be incurred if this method is applied to systems of independent reactions. The relative accuracy of the Friedman and Ozawa-Flynn-Wall methods is discussed in respect of complex systems of reactions.
Authors:M. Reading, D. Dollimore, J. Rouquerol, and F. Rouquerol
The uncertainty surrounding the significance of the measured kinetic parameters of solid state decomposition reactions is discussed briefly. Some suggestions are made about what precautions should be taken in order to favour the measurement of undistorted results. Some criteria are proposed for deciding whether a measuredE value can be considered to have its usual meaning. The results of a series of experiments aimed at measuring the activation energy of the decomposition of calcium carbonate using a variety of methods, sample sizes and experimental conditions are presented. These results are compared with results found in the literature and it is concluded that it is possible to measure a reproducible value forE and it is tentatively proposed that this value is meaningful in terms of the energy barrier model of chemical reaction kinetics.
Authors:Mohan T. Hosamani, Narasimha H. Ayachit, and D. K. Deshpande
to calculate thermodynamic parameters such as change in activationenergy for dipole orientation Δ G* , enthalpy Δ H* , entropy of activation Δ S* , and the other temperature dependent parameters such as relaxation time τ , the distribution parameter
Authors:L. Núñez-Regueira, M. Villanueva, and I. Fraga-Rivas
study of the degradation of a polymer is important because it can determine
the upper temperature limit, the mechanism of a solid-state process, and the
life-time for this system. Since the behavior of thermosets is affected by
the selection of the curing cycle, it is important to investigate the changes
which take place during the thermal degradation of these materials when a
change on the sequence of time and temperature is introduced during the curing
this work, the thermal degradation of two epoxy systems diglycidyl ether of
bisphenol A (BADGE n=0)/1, 2 diamine cyclohexane
(DCH) cured through different sequences of time and temperature was studied
by thermogravimetric analysis in order to determine the reaction mechanism
of the degradation processes, and also to check the influence of the curing
cycle on this mechanism. Values obtained using different kinetic methods were
compared to the value obtained by Kissinger’s method (differential method
which do not require a knowledge of the n-order
reaction mechanism), and to that obtained through Flynn–Wall–Ozawa
method in a previous work.
Activation energy was experimentally determined using the curve-fitting, initial-rise and the peak-shape methods involving
pulse annealing experiments in NaCl samples irradiated at 10, 20, 30 and 40 Gy beta-doses and infrared stimulated luminescence
(IRSL) signal at a temperature range of 100-300 °C. It was observed that the activation energy for NaCl decreases as the dose
increased. The results were compared to other studies and discussed.
Activation energies for electrolyte diffusion of Zn(NO3)2, ZnBr2 and ZnI2 in 1% agar gel at different concentrations are determined by the least-squares fitting of the diffusion coefficient data obtained at various temperatures through the Arrhenius plots. Energy of activation is found to decrease with an increase in electrolyte concentration. This trend is explained by considering the changes in the physical properties of the solution with concentration at microscopic level, as envisaged in Wang's model.
The object of this work is the quantitative explanation of linear correlation between activation energy (E), initial decomposition temperature (Ti) and ionic potential (Vi), observed for thermal degradation of some complexes of transitional metals.
The proposed model allowed the evaluation of characteristic parameter proportional to the activation free enthalpy and also
the variation of effective electrical charge (ΔQ*) of ligand, in the formation process of the activated complex.
These results are satisfactory, taking into account that we utilized many simple hypotheses for deduction of Arrhenius equation.
Authors:N. Ionescu, N. Jaeger, P. Plath, and C. Hornoiu
Activation energies of ignition for the thermokinetic oscillations obtained during the heterogeneous catalytic oxidation of
ethanol on Pd/Al2O3 in a dynamic calorimeter were obtained using the minimum values of the temperature oscillations. These activation energies
of ignition are greater than the activation energies of the corresponding oscillations. The obtained results are discussed
by assuming a PdOx redox cycle.
Authors:P Budrugeac, D. Homentcovschi, and E. Segal
An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters,
instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is
demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods,
varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion
degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding
values obtained with the isoconversional integral method.