Search

When gases evolve during a chemical reaction, a fraction of the reaction heat is lost with them. We have analyzed, both theoretically and experimentally, the deviations that this effect can produce on the determination of the reaction heat by differential scanning calorimetry (DSC). It is shown that, even in the absence of gas overheating, deviations related to variations in the sample heat capacity can be substantial in experiments involving very intense DSC peaks. However, experiments performed on thermal decomposition of metal organic salts and on evaporation of liquids have shown that deviations usually arise from gas overheating 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. 2009SGR185

We have developed a new method to measure the thermal conductivity of powders by differential scanning calorimetry (DSC) that works with masses in amounts as low as tens of mg. The method is based on that used by Camirand to determine the thermal conductivity of materials in the form of thin sheets but introducing a hemispherical pan to contain powders in such a way that the issue of heat transfer is reduced to a one-dimensional problem. The modification of the method was successfully validated on obtaining identical results in determining the thermal conductivity of a commercial silicone with both Camirand"s method and the modified method. We have also tested our method with materials that, in bulk, cover a wide range of thermal conductivities and have performed the experiments with several atmospheres and reference metals. The results are consistent with already published general trends in that they confirm that thermal conductivity of powders is mainly governed by thermal conduction through the surrounding gas 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

A new method is developed to obtain the kinetic parameters of polymer crystallization from measure- ments of the transformation rate usually done at (but not restricted to) constant heating or cooling rates. It can be considered a generalization of the Fiedman's isoconversional method to deal with the Hoffman- Lauritzen temperature dependence. Apart from delivering the U* and Kg parameters as a function of the transformed fraction, this method allows to predict the crystallization course for an arbitrary thermal history. It has been applied to the crystallization of PET and PA6 samples, monitored by differential scanning calorimetry (DSC). This work was funded by the Spanish Programa Nacional de Materiales through project MAT2014-51778-C2-2-R. We also acknowledge financial support from the Generalitat de Catalunya (contract num.SGR948) and from the University of Girona (program MPCUdG2016)

Recrystallization of Cu deformed under compression has been monitored by differential scanning calorimetry (DSC) with experiments carried out at constant heating rate. From these experiments, an isothermal crystallization process has been predicted by the classical Kolmogorov-Johnson-Mehl-Avrami (KJMA) kinetics and by model-free isoconversional analysis. Whereas prediction by KJMA does not match the experimental curve, the isoconversional prediction is successful. The paper also highlights the need to correct the raw DSC curves to obtain the actual sample temperature and to avoid curve distortion due to thermal inertia This work was partially funded by the Spanish Programa Nacional de Materiales through projects MAT2014-51778-C2-2-R