Summary Three new complex compounds of general formula Zn[5-ClC6H3-2-(OH)COO]2·L2·nH2O (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2-5), were prepared and characterized by chemical analysis, IR spectroscopy and their thermal properties were studied by TG/DTG, DTA methods. It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition performed up to 800°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.
Authors:J. Rincón, M. Romero, A. Hidalgo, and Ma. Liso
It has been determined the thermal behaviour at high temperatures of an iron aluminum arsenate mineral first described in
the location of La Serena Valley, Extremadura, Spain, which expands until 1173 K contracting later and softening at 1653 K
and full melting at 1773 K. The DTA/TG experiment only detects some rearrangement with an endothermic at 1173 K due to the
mica mixing. The mineral is a scorodite variety mixed with micaceous clay which has been found as aggregates of pyramidal
crystals associated with quartz, wolframite, molibdenite, cassiterite and other secondary minerals in the pegmatite of the
San Nicolas mine. The chemical composition, the physico- chemical characteristics such as density and hardness, as well as
the thermal behaviour has allowed to conclude that this mineral can be an Al-enriched scorodite (mansfieldite): (Fe, Al) AsO42H2O mixed with illite from the scorodite-mansfieldite series.
Authors:Claudia Simonescu, V. Teodorescu, Oana Carp, Luminita Patron, and Camelia Capatina
Thermal behaviour of CuS (covellite) obtained from the Cu(CH3COO)2·H2O and Na2S2O3·5H2O
system, working at different molar ratio (1:6 and 1:4) in presence/absence
of NH4VO3, was studied. It was
established that the presence of vanadium in the system induces a densification
of CuS nodules, but do not change the hexagonal CuS structure. It has an important
influence in thermal behaviour of copper sulfide CuS obtained also. The morphological
characteristics of CuS play an important role in the thermal stability and
the stoichiometry of the thermal decompositions.
Also, the possibility
to obtain copper sulfides with greater cooper content was investigated.
Authors:J. Kristóf, M. Tóth, M. Gábor, P. Szabó, and R. L. Frost
Intercalation complexes of three different Hungarian kaolinites with hydrazine and potassium acetate were investigated by FT-IR (DRIFT) spectrometry, X-ray diffraction, and thermogravimetry combined with mass spectrometry. Differences were found in the thermal behaviour of the complexes as well as in the rehydration — reexpansion patterns of the heated intercalates. An XRD method is proposed for the distinction of kaolinite and 7.2 Å halloysite present in the same mineral.
Authors:M. Luengos, E. Ambrosio, A. Bohé, and D. Pasquevich
The thermal behavior of a purified galena in a chlorine surrounding was determined. The kinetic of the chlorination of galena
and the stoichiometry of this reaction between 723 to 973 K (450 to 700C) were measured by thermogravimetry. The microstructural
characterization of the solid residues were determined by SEM, EDXS and XRD. The ΔHvap of the produced lead chloride volatilization was obtained by the application of Clausius-Clapeyron equation considering the
process in an equilibrium state.
Authors:N. Ananthalakshmi, P. Wadgaonkar, S. Sivaram, and I. Varma
The paper describes the effect of molecular mass and copolymer composition on thermal behaviour of homopolymers and copolymers of glycidyl methacrylate and methyl methacrylate. The polymerisation was done by using group transfer polymerization (GTP) and free radical techniques. A multistep decomposition was observed in polymers prepared by free radical technique indicating the presence of weak linkages in the backbone. Copolymers prepared by GTP had fewer weak sites and degraded in single step by a random chain scission.
Authors:Maria Luisa A. Gonçalves, D. A. Ribeiro, Deusa Angélica P. Da Mota, Ana Maria R. F. Teixeira, and M. A. G. Teixeira
Summary Thermogravimetry (TG) was applied to evaluate the thermal behavior of five refinery atmospheric distillation residues (ATR) obtained from different Brazilian crude oils. The asphaltenes were extracted of each sample and their influence on coke formation was studied. It was observed that they have a great contribution on carbonaceous residues formation during pyrolysis and that the heavier the ATR sample, the higher is the contribution of other heavy components present in ATR samples.
Authors:P. Espeau, B. Nicolaï, R. Céolin, M. Perrin, L. Zaske, J. Giovannini, and F. Leveiller
Investigation into the thermal behavior of orthorhombic Forms I and II of spironolactone, by means of differential scanning
calorimetry and high-resolution X-ray powder diffraction, showed that Form I melts then recrystallizes into Form II at 373–393
K, i.e. in the temperature range within which high resolution X-ray powder diffration showed that Form I transforms into Form II.
Refinements of the lattice parameters of the two forms indicated that Form I is denser than Form II in the range from 298
K up to the temperature at which it melts.
Authors:F. López, A. Mercê, F. Alguacil, and A. López-Delgado
The thermal behaviour of chitosan was studied by means of thermogravimetry, mass spectrometry and infrared spectrometry. Kinetic
parameters were obtained by advanced kinetic evaluation (differential isoconversional analysis) from DSC curves, in non-isothermal
conditions, at several heating rates, between 5 and 30°C min−1. The results showed that the decomposition of chitosan does not follow a single mechanism because both the activation energy
and the pre-exponential factor are not constant during the course of the reaction. A comparison with the results obtained
by applying different conventional calculating methods is also shown.
Authors:Amanda dos Santos, G. Chierice, A. Riga, K. Alexander, and Ellen Matthews
Eugenol is an allyl chain-substituted guaiacol in the biosynthesized phenylpropanoid compound class derived from Syzygium aromaticum L. and widely used in folk medicine. Nonetheless, its pharmacological use is limited by some problems, such as instability
when exposed to light and high temperature. In order to enhance stability, the eugenol molecule was structurally modified,
resulting in eugenyl acetate. The eugenyl acetate’s thermal behavior and crystal structure was then characterized by differential
scanning calorimetry (DSC) and X-ray diffraction (XRD) and compared to a commercial sample.