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Abstract  

Solid state Ln–L compounds, where Ln stands for light trivalent lanthanides (L–Gd) and L is tartrate, have been synthesized. Thermogravimetry and differential thermal analysis (TG/DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration and thermal decomposition of the isolated compounds.

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Journal of Thermal Analysis and Calorimetry
Authors: Konstantin Gavrichev, Mikhail Ryumin, Alexander Tyurin, Andrey Khoroshilov, Larisa Mezentseva, Alexander Osipov, Valeriy Ugolkov, and Viktor Gusarov

Abstract  

Thermal behavior of LaPO4·nH2O and NdPO4·nH2O nanopowders from room temperature to 973 K was investigated by DSC, TA/DTG, ESM, and X-ray study. Mass loss due to the release of adsorbed and hydrate water was found in the range from 323 to 623 K. Phase transitions from hexagonal structure nanopowders to monoclinic one for bulk specimens were found above 873 K.

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The investigations concerning the thermal behaviour of a series of Ni(II) and Cu(II) complexes of type [MLCln]· mH2O ((1) M:Ni, L:L(1), n=1, m=2; (2) M:Cu, L:L(2), n=1, m=2; (3) M:Ni, L:L(3), n=2, m=0; (4) M:Cu, L:L(3), n=1, m=2) are presented in this paper. The ligands L(1)-L(3) have been synthesised by template condensation of 1,2-diaminoethane with formaldehyde and 2-amino-1,3,4-thiadiazole-5-thiole or 2-acetamino-1,3,4-thiadiazole-5-sulfonamide. The bonding and stereochemistry of the complexes have been characterised by IR, electronic and magnetic studies at room temperature. The thermal behaviour provided confirmation of the complex composition as well as the number and the nature of water molecules and the intervals of thermal stability. The different nature of the ligands and/or the metallic ions generates a different thermal behaviour for complexes. The complexes do not show biological activity against HIV virus.

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Abstract  

In this work the influence of Ag additions on the thermal behavior of the Cu-11 mass% Al alloy was studied using differential scanning calorimetry, in situ X-ray diffractometry and scanning electron microscopy. The results indicated that changes in the heating rate shift the peak attributed to α phase formation to higher temperatures, evidencing the diffusive character of this reaction. The activation energy value for the α phase formation reaction, obtained from a non-isotherm kinetic model, is close to that corresponding to Cu atoms self diffusion, thus confirming that this reaction is dominated by Cu atoms diffusion through the martensite matrix.

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Abstract  

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N2, NH3, CO2, and N2O.

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Abstract  

This paper reports the investigation of the thermal stability of a series of new complexes with mixed ligands of the type M(dipy)(C3H3O2)2(H2O)y ((1) M: Mn, y=1; (2) M: Ni, y=2; (3) M: Cu, y=1; (4) M: Zn, y=2; dipy: 2,2’-dipyridine and C3H3O2 is acrylate anion). The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, oxidative condensation of acrylate and thermolysis processes. The final products of decomposition are the most stable metal oxides.

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Abstract  

The influence of a wide range of concentrations (0.1–40 mass%) of Na(K)I on both the thermal behaviour and melt indexes of polyoxyethylene (POE) in a broad temperature interval was investigated by combined dynamic thermal analysis and with an extrusion plastometer. It was found that addition of 2–5 mass% of alkali salts resulted in the optimum thermal stability of POE and increased the melt index of high molecular POE, regardless of the mode of introduction of the additives into the polymer.

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Abstract  

Poly(2-hydroxyethoxybenzoate), poly(ε-caprolactone), and random poly(2-hydroxyethoxybenzoate/e-caprolactone) copolymers were synthesized and characterized in terms of chemical structure and molecular mass. The thermal behavior was examined by DSC. All the samples appear as semicrystalline materials; the main effect of copolymerization was lowering in the amount of crystallinity and a decrease of melting temperature with respect to homopolymers. Flory's equation described well the T m-composition data. Amorphous samples (in the 20–100%2-hydroxyethoxybenzoate unit concentration range) obtained by quenching showed amonotonic decrease of the glass transition temperature T g as the content of caprolactone units is increased. The Wood's equation described the T g-composition data well.

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Abstract  

Thermal investigation has allowed us to show the changes undergone by a sort of nitrile-butadiene rubber (NBR) as a consequence ofγ-radiation-induced ageing. The parameters of the processes, which occur at progressive heating of the investigated samples, were determined. It was shown that for γ-irradiated samples the activation parameters corresponding to the thermo-oxidative process leading to solid products are correlated through the relation of compensation effect. Also, it was shown that, by γ-irradiation, NBR undergoes a relatively rapid change of its thermal behaviour which can be due to structural changes.

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Abstract  

Using two techniques of thermogravimetry and differential scanning calorimetry under O2 gas atmosphere from 25 to 600°C, the thermal behavior of laboratory-produced compound lead(IV) oxide α-PbO2 was investigated. The identity of products at different stages were confirmed by XRD technique. Both techniques produced similar results supporting the same decomposition stages for the compound. Three distinct energy changes were observed, namely, two endothermic and one exothermic in DSC. The amount of ΔH for each peak is also reported.

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