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Abstract  

The physico-geometric kinetics for the solid-state reactions by thermoanalytical (TA) measurements were reexamined by focusing some fundamental aspects: (1) the fundamental kinetic equation, (2) the kinetic model function, (3) the fractional reaction α, and (4) the apparent kinetic parameters. It was pointed out that some pitfalls in the practical kinetic study are originated by the disagreement between the kinetic information from the TA measurements and the theory of the physico-geometric kinetics. In order to increase the degree of coordination between the theory and practice, several attempts were made from both the theoretical and experimental points of views. The significance of the apparent kinetic parameters was discussed with a possible orientation for obtaining the reliable kinetic parameters.

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Abstract  

Effects of sample mass on the kinetics of isothermal dehydration of crushed crystals of Li2SO4·H2O were investigated using conventional TG. The process was characterized by a combination of Avrami-Erofeyev and contracting geometry models. Distribution of the fractional reaction, α, in particles within the sample assembly as well as the change in the rate of gross diffusion of the evolved water vapour appear responsible for the sample-mass-dependent kinetic parameters obtained for the system.

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dependent on temperature [ 16 ]. The solid combustion reaction rates are generally expressed as: 2 where the fractional reaction α is defined in the terms of the change in mass of the bio-oil sample: 3 where m 0 , m , and m f are the

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kinetic equation: 7 where α is the fractional reaction; t , is time; A is the pre-exponential factor; E is the activation energy; R is the gas constant; T is temperature in Kelvin, and f (α) is the kinetic function, which takes different forms

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Journal of Thermal Analysis and Calorimetry
Authors: Juliusz Leszczynski, Krzysztof T. Wojciechowski, and Andrzej Leslaw Malecki

divided by k − σ/k , and a sum of squared error SSE between measured and estimated fractional reaction (α exp − α calc ) 2 . Due to a deceleratory type of the oxidation curves, mainly deceleratory kinetic models for the solid-state reactions were

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-isothermal experiments. These experiments usually involve measurements of mass or heat evolved, etc., which can be related directly to the fractional reaction α, at a series of different, usually constant, heating rates ( β = d T /d t ) [ 13 ]. The direct estimation of

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Theory of solid-state thermal decomposition reactions

Scientific stagnation or chemical catastrophe? An alternative approach appraised and advocated

Journal of Thermal Analysis and Calorimetry
Author: Andrew K. Galwey

(fractional reaction) α–time curve, typical of many solid-state decompositions [ 5 – 7 ], is identified as resulting from energy transfer, a characteristic feature of the active reactant–product interface. During the induction period, S int is zero (no

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