Authors:V. Balek, J. Pérez-Rodríguez, L. Pérez-Maqueda, J. Šubrt, and J. Poyato
Thermal behaviour of natural vermiculite (Santa Olalla, Huelva, Spain) was investigated by TG, DTA, emanation thermal analysis
(ETA) and high temperature XRD on heating in the temperature range from 30 to 1100°C before and after vibratory mill grinding.
Microstructure changes of natural and ground vermiculite samples were characterized by using ETA under in situ conditions
of heating. By comparing the ETA and XRD results it was demonstrated that a decrease of radon release rate measured by ETA
characterized the decrease in the interlayer spacing of the vermiculite samples that followed the dehydration.
The thermal behavior of Nafion-117 membranes was investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). TG measurements revealed that the mechanism of thermal degradation of a Nafion membrane in the acid form is different from that of Nafion in the sodium form. The DSC curves for the first heating, for both acid and salt forms, display two endothermic peaks, near 120 and 230°C. The high-temperature peak was assigned to the crystalline domains melting in Nafion, and the low-temperature peak was attributed to a transition into ionic clusters, since this transition exhibits significant changes depending on the nature of the counterion and the degree of hydration.
], photodegradation of 4-nitrophenol [ 7 ], and CHCl 3 oxidation [ 8 ]. The catalytic activities of TiO 2 –Fe 2 O 3 largely depend on preparation methods, iron content, calcination temperature, and phase composition. Therefore, the thermalbehaviors of TiO 2 and Fe
Authors:B. Ambrozini, P. R. Dametto, and M. Ionashiro
thermal decomposition of strontium tartrate crystals [ 8 ] and thermalbehaviour of solid-state tartrate of some trivalent metal ions have also been described [ 9 ].
In this article, solid-state compounds of heavy trivalent lanthanides (Tb to Y
Authors:P. R. Dametto, F. J. Caires, B. Ambrozini, and M. Ionashiro
considered in this work.
The TG-DTA and DSC curves provided information about the thermal stability and thermalbehaviour of these compounds.
The authors thank FAPESP, CNPq and CAPES Foundations (Brazil) for financial support
Thermal behaviour of some minerals (kaolinite, halloysite, two montmorillonites, quartz and calcite) for different sample amounts and heating rates has been investigated using differential thermal analysis. On the basis of the DTA analysis carried out, the PA curves of each mineral have been obtained for different heating rates. These diagrams can be employed in the semiquantitative evaluation of identical substances contained in uncharacterized polymineral samples.
Authors:L. Abate, A. Chisari, R. Maggiore, and G. Siracusa
The thermal behaviour of solid zinc phenoxyacetate was investigated by DSC and TG techniques. The results obtained showed that this compound is a dihydrate and that the water molecules are differently bonded. The compound melts and then decomposes in two steps, with the formation of ZnCO3 and ZnO, respectively. The thermodynamic parameters associated with the thermal processes were evaluated.
The thermal behaviors of [1,1,1-trifluro-3-(2-thenoyl)-acetonato]copper(II) Cu(TTA)2 and its adducts with pyridine Cu(TTA)2(Py)2, 2,2'-bipyridine Cu(TTA)2(Bpy), quinoline Cu(TTA)2(Ql)2, and dimethyl sulfoxide Cu(TTA)2(DMS) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC technique. The
results showed that the evolution of the solvent molecules generally proceeded before the release of TTA in different ways
according to their structures. The Cu(TTA)2(Bpy) exhibited a unique decomposition pattern due to its distinctive structure. The dependences of activation energy on extent
of reaction for all the stage of each compound were determined by using an isoconversional method, Flynn-Wall-Ozawa equation,
which show E values varied with reaction progress, indicating the complexity of these decomposition reactions. In addition,
the values of activation energy E for TTA molecules evolution are generally higher than that for the solvent molecules release.
Authors:G. Mohamed, F. Nour El-Dien, and N. El-Gamel
The present work aims chiefly to study the thermal behaviour of complex compounds with general formula: [M(HL)
yH2O (where HL=C13H11N4O2=6-(2-pyridylazo)-3-acetamidophenol (PAAP), M=Cu(II), Zn(II), Cd(II) and Fe(III) x=1, 3; y=2, 5) while A=CH3COO– (Ac), Cl2. The second formula is [M(H2L)
xH2O]Cl2yH2O, (where H2L=C13H12N4O2 (PAAP), M=Ni(II), Co(II) x=3; y=4, 6). The compounds were identified by elemental analysis, FT-IR spectra and TG/DTG,DTA methods. It was found that during the thermal decomposition of complex compounds water molecules of crystallization are released in the first step. In the next step the pyrolysis of organic ligand takes place. Metal oxide remained as a solid product of the thermal decomposition. Mass spectroscopy has been used for the determination of the thermal decomposition on the intermediate products. It was found that the thermal stability of the studied compounds increases as the ionic radii decreases. The activation energy E, the entropy change
S*, the enthalpy
H* change and Gibbs free energy change
G* were calculated from TG curve.
Authors:Patricia B. da Silva, Paulo H. Terra, Regina C. G. Frem, Adelino V. G. Netto, and Antonio E. Mauro
], and metallomesogens, but also by their beautiful and unusual supramolecular architectures [ 5 – 11 ]. Particularly, we have been interested in the thermalbehavior of metal-based pyrazolyl compounds [ 12 – 15 ] due to the possibility in obtaining