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Thermal gradients in thermal analysis experiments: Criterions to prevent inaccuracies when determining sample temperature and kinetic parameters

Thermal analysis methods are customarily used to analyze the evolution of solid-state transformations when samples are submitted to a controlled temperature program. Thermal analysis results are generally interpreted under the assumption that no temperature gradients take place inside the sample, so that, under proper calibration the sample temperature can be determined and controlled. Two phenomena may contribute to the formation of temperature gradients within the sample: heat transport through the sample and heat evolved during an exothermic or endothermic transformation. We will provide two analytical relationships that relate the sample mass with the temperature gradient within the sample and that will provide a straightforward criterion for checking the reliability of the sample temperature. We will show that, because of their very low thermal conductivity, significant thermal gradients may occur in those samples in the form of powders. Besides, in the case of exothermic reactions and for typical experimental conditions, the heat released by the reaction significantly affects the determination of the sample temperature. Finally, we analyze how sample overheating affects the observed reaction kinetics

This work was partially funded by the Spanish Programa Nacional de Materiales through projects MAT2011-28874-C02-02 and by the Generalitat de Catalunya contract No. 2009SGR-185

© Thermochimica Acta, 2014, vol. 589, p. 37-46

Elsevier

Author: Sánchez-Rodríguez, Daniel
Eloussifi, Hichem
Farjas Silva, Jordi
Roura Grabulosa, Pere
Dammak, Mohamed Chedly
Date: 2014
Abstract: Thermal analysis methods are customarily used to analyze the evolution of solid-state transformations when samples are submitted to a controlled temperature program. Thermal analysis results are generally interpreted under the assumption that no temperature gradients take place inside the sample, so that, under proper calibration the sample temperature can be determined and controlled. Two phenomena may contribute to the formation of temperature gradients within the sample: heat transport through the sample and heat evolved during an exothermic or endothermic transformation. We will provide two analytical relationships that relate the sample mass with the temperature gradient within the sample and that will provide a straightforward criterion for checking the reliability of the sample temperature. We will show that, because of their very low thermal conductivity, significant thermal gradients may occur in those samples in the form of powders. Besides, in the case of exothermic reactions and for typical experimental conditions, the heat released by the reaction significantly affects the determination of the sample temperature. Finally, we analyze how sample overheating affects the observed reaction kinetics
This work was partially funded by the Spanish Programa Nacional de Materiales through projects MAT2011-28874-C02-02 and by the Generalitat de Catalunya contract No. 2009SGR-185
Format: application/pdf
ISSN: 0040-6031
Document access: http://hdl.handle.net/10256/11385
Language: eng
Publisher: Elsevier
Collection: MICINN/PN 2012-2014/MAT2011-28874-C02-02
AGAUR/2009-2013/2009 SGR-185
Reproducció digital del document publicat a: http://dx.doi.org/10.1016/j.tca.2014.05.001
Articles publicats (D-F)
Is part of: © Thermochimica Acta, 2014, vol. 589, p. 37-46
Rights: Tots els drets reservats
Subject: Anàlisi tèrmica
Thermal analysis
Calor -- Transmissió
Heat -- Transmission
Title: Thermal gradients in thermal analysis experiments: Criterions to prevent inaccuracies when determining sample temperature and kinetic parameters
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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