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Abstract

A series of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of azo-compounds containing hydroxyl quinoline moiety have been synthesized and characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic and ESR spectral studies. The results revealed the formation of 1:1 and 1:2 (L:M) complexes. The molar conductance data reveal that the chelates are nonelectrolyte. IR spectra indicate that the azodyes behave as monobasic bidentate or dibasic tetradentate ligands through phenolate or carboxy oxygen, azo N for 1:1 (L:M) complexes beside phenolate oxygen and quinoline N atoms for 1:2 (L:M) complexes. The thermal analyses (TG and DTA) as well as the solid electrical conductivity measurements are also studied. The molecular parameters of the ligands and their metal complexes have been calculated.

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Abstract

Grewia gum is a naturally occurring polysaccharide which has potential as a pharmaceutical excipient. Differential scanning calorimetry and Fourier transform infrared (FT-IR) spectroscopy techniques were used to examine the thermal and molecular behaviours, respectively, of mixtures of grewia gum with cimetidine, ibuprofen or standard excipients, to assess potential interactions. No disappearance or broadening of the melting endotherm was seen with cimetidine or ibuprofen. Similarly, there was no interaction between grewia gum and the standard excipients tested. The results obtained using thermal analyses were supported by FT-IR analysis of the material mixtures. Grewia gum is an inert natural polymer which can be used alone or in combination with other excipients in the formulation of pharmaceutical dosage forms.

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Abstract

In the present study, thermal decomposition of mono- and di-azocalix[4]arene derivatives (A1A8 and B1B8) was investigated by means of thermogravimetry (TG), differential thermal analysis (DTA) and derivative thermogravimetry (DTG). The exclusion of methanol, hydrolysis of benzoyl ester and methyl ketone groups in lower rim, and decomposition of azo groups in upper rim have occurred during thermal analysis, consecutively. The thermal decomposition degrees amount of volatile pyrolysis products were determined in air atmosphere using TG, DTA and DTG curves. In conclusion, the thermal analyses of azocalix[4]arenes demonstrated that its stability depends on the substituted groups and their positions in the calix[4]arene structure.

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Abstract  

Heat capacities (Cp) of solid benzene, biphenyl,p-terphenyl,p-quaterphenyl, and poly-p-phenylene were analyzed using the ATHAS Scheme of computation. The calculated heat capacities based on approximate vibrational spectra of solid benzene and the series of oligomers containing additional phenylene groups were compared to experimental data newly measured and from the literature to identify possible additional large-amplitude motion. The skeletal heat capacity was fitted to the Tarasov equation to obtain the one- and three-dimensional vibration frequencies Θ1 and Θ3 using a new optimization approach. Their relationship to the number of phenylene groupsn is: Θ1=426.0−150.3/n; and Θ3=55.4+81.8/n. Except for benzene, the quantitative thermal analyses do not show significant contributions from large-amplitude motion below the melting temperatures.

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Abstract  

A free-base tetraphenyl porphyrin (TPP) and its corresponding metalloporphyrins (MTPP) where M = Co, Fe and Sn were synthesized and characterized by UV–visible spectroscopy, FTIR and 1Hnmr spectroscopy. Thermal studies of these porphyrins were carried out in synthetic air from room temperature to 800 °C using thermal analyser. The residues of MTPP after thermal treatment were qualitatively analysed, which showed the presence of corresponding metal oxides. Further, the above MTPP were subjected to thermogravimetry–evolved gas and mass spectrometry (TG–EGA–MS) analysis for the detailed information about evolved gases at their corresponding decomposition temperatures. This information may be used to predict the probable mechanism for ring opening of the macromolecular porphyrins.

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Journal of Thermal Analysis and Calorimetry
Authors: P. S. Epaminondas, K. L. G. V. Araújo, A. Lima de Souza, M. C. D. Silva, N. Queiroz, A. L. Souza, L. E. B. Soledade, I. M. G. Santos, and A. G. Souza

Abstract

Chemical and thermal analyses of golden and brown flaxseeds were carried out for raw and toasted seeds aiming at evaluating their nutritional and thermo-oxidative properties. Moisture, lipids, protein, soluble carbohydrates, and ash contents were quantified. Concerning lipids and proteins, in average, no meaningful differences were observed for the two varieties, being also equivalent to the literature data. The golden variety had a lower amount of fibers and a higher amount of soluble carbohydrates than the brown variety. The techniques of thermogravimetry and differential scanning calorimetry were applied for elucidating the thermal degradation process of the seeds. The toasted gold and brown seeds were more stable to thermal decomposition than the raw seeds, under oxidative conditions. Golden seeds seem to be more susceptible to oxidation than brown seeds, under toasting conditions. Finally, no meaningful advantages were observed for the golden seeds in comparison to the brown ones.

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Abstract  

In this study, aqueous lead magnesium niobate (PMN) slurry formulations were developed for tape casting using a poly(acrylic acid) - poly(ethylene) oxide comb polymer as the dispersant, nonionic acrylic latex as the binder phase and hydroxypropyl methylcellulose as the wetting agent. Concentrated suspensions were cast onto a silicone-coated mylar film, and the effect of acrylic latex on deposition was investigated. Thermal analyses were performed to investigate the mass loss of the green tapes as a function of calcination temperature. Differential scanning calorimetric analyses were made under air and nitrogen atmospheres to investigate the binder distribution through the green tapes. Results showed that it is possible to prepare flexible, crack free PMN thick films using a proper slurry composition in the presence of acrylic latex binder, without using any plasticizer. Additionally, decomposing mechanisms of the acrylic based binder were essentially different in the two atmospheres.

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Abstract  

Heat-treatable aluminium alloys are widely used for structural applications. Their strength is obtained through age hardening phenomena, that are sensitive to microalloying. In the present paper the results of thermal analyses on the ageing behaviour of an Al-Cu-Mg-Si alloy with silver and zirconium additions are presented. Specimens were water quenched after solution heat treatment, then aged at 453 K and a hardness-versus-time plot was drawn. Samples representative of different ageing conditions were subjected to DSC scans. Peaks were identified taking into account θ and Q phases precipitation sequences. Solution treated samples showed GP/θ″/θ′/Q sequence, while in peak aged condition GP and θ″ precipitation peaks disappeared and a reduction of θ′ peak area was observed, witnessing the concurrent presence of θ″ and θ′ phases at peak hardness condition. Experimental data were compared with results from analogous investigations performed on a conventional commercial Al-Cu-Mg-Si alloy.

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Abstract  

In this study, combustion curves of twenty-five Turkish lignites were obtained through use of a differential thermal analyser. 20 mg lignite samples were heated at a constant rate of 10 deg·min−1 in a 40 cc/min flow of air up to 1073 K and held for 10 minutes at this constant temperature. The combustion curves of the samples are compared and discussed.

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Abstract

Four polydentate azomehines and their mono- and binuclear Pt(II), Cu(II), and Ni(II) complexes were synthesized and characterized. The resulting complexes were characterized by FTIR, magnetic measurements, elemental analysis, conductivity measurements, and thermal analysis. Electronic spectra and magnetic susceptibility measurements sustain the proposed distorted square-planar structures for the copper complexes. The electronic spectra display the characteristic pattern of square-planar stereochemistry for the other complexes. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Azomethine complexes have a similar thermal behavior for the selected metal ions. The decomposition processes as water elimination, chloride anion removal as well as degradation of the organic ligands were observed.

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