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Journal of Thermal Analysis and Calorimetry
Authors: T. Tanaka, J. Magoshi, Y. Magoshi, S. ichi Inoue, M. Kobayashi, H. Tsuda, M. Becker, and Sh. Nakamura

Abstract  

The thermal properties of liquid silk from domestic and wild silkworms are investigated. Liquid silks obtained from the silk gland of the domesticated silkworm, Bombyx mori and four wild silkworms, Samia cynthia ricini, Dictyoploca japonica, Antheraea pernyi and Antheraea yamamai were used. The DSC curves for the liquid silk from the domestic silkworm have weak endothermic peaks corresponding to the breaking of hydrogen bonds in the β-form or to the untangling of physical network. The DSC curves for the wild silkworm silks, however, show clear exothermic peaks corresponding to a phase transition from the α-helix conformation to the β-form. Liquid silk from all the different silkworms undergoes a characteristic irreversible phase transition.

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Abstract  

A solid-state phase transition in cobalt dibromide at 647 K has been revealed by three different alternative current techniques. A small thermal effect of (181±18) J mol−1 corresponding to the enthalpy of the transition has been determined by differential scanning calorimetry. The effect was observed on cooling and on heating as well.

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Abstract  

Both temperatures, T C, (T C —Curie temperature) and heat of the phase transition: ferroelectric-paraelectric, ΔH, in the BaxSr1−xTiO3 materials have been studied by means of the microcalorimetric method. The determined parameters were verified by either temperature dependence of the dielectric permittivity (Curie-Weiss law) or thermodynamic method. The effect of strontium content on T C has been discussed. It was found that microcalorimetry is useful tool studying phase transition phenomena in ferroelectric perovskites.

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Abstract  

Phase transition and thermal decomposition of hexadimethylsulfoxidealuminium chloride were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and simultaneous differential thermal analysis (SDTA). The gaseous products of the decomposition were on-line identified by a quadrupole mass spectrometer (QMS). In the temperature range of 95–300 K, [Al(DMSO)6]Cl3 indicates one phase transition at T c h=244.96 K (on heating) and at T c c=220.87 K (on cooling). Large thermal hysteresis of the phase transition (∼24 K) indicates its first order character. Large value of transition entropy (ΔS≈40 J mol−1 K−1) suggests its configurational character. Thermal decomposition of the title compound proceeds in four main stages. In the first stage, which starts just above ca. 300 K, the compound loses two DMSO molecules per one formula unit and undergoes into [Al(DMSO)4]Cl3. In the second stage, the next three DMSO ligands are released and simultaneously decomposed. The third stage, which continues up to ca. 552 K, is connected with a loss of the last DMSO ligand and the formation of AlCl3. In the fourth stage AlCl3 reacts with carbon monoxide that originates from the decomposition of DMSO, and first aluminium oxychloride and next solid Al2O3 plus carbon are created.

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. Thermodynamics and introduction to thermostatistics 1985 Brokate M., Sprekels J. Hysteresis and phase transitions , Springer

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Abstract  

The phase transition and the crystal structures of CuITe were investigated by differential thermal analysis and X-ray powder diffraction measurements in the temperature range between 300 and 683 K. The new phase transition in CuITe was observed at 592 K. The enthalpy of transition is ΔH=0.125 kJ mol-1. The new phase above 592 K belongs to tetragonal system with the space group I41 /amd.

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Journal of Thermal Analysis and Calorimetry
Authors: George G. G. de Oliveira, Humberto G. Ferraz, Patrícia Severino, and Eliana B. Souto

]. The aim of this article was to analyse the phase transition and dehydration processes of nevirapine using DSC and thermogravimetry differential thermal analysis (TG-DTA). Materials and methods Nevirapine was provided by the

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Abstract  

The heat capacity of PbMO3 (M=Ti, Zr and Hf) at constant pressure was measured using a differential scanning calorimeter (DSC) from room temperature up to 870 K. Large anomalies were found in the heat capacity curves, corresponding to the ferroelectricparaelectric phase transition in PbTiO3 (PT), the antiferroelectric-paraelectric phase transitions in PbZrO3 (PZ) and PbHfO3 (PH). The transition entropies were estimated as 7.3 J K−1 mol−1 (PT), 9.9 J K−1 mol−1 (PZ) and 9.3 J K−1 mol−1 (PH). These values of transition entropies are much larger than that of a typical displacive-type phase transition.

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Abstract  

Phase transition behaviour of neutral galactomannans, i.e., locust bean gum (LBG), tara gum (Tara-G) and guar gum (GG)-water systems is investigated. In this study, water content {Wc=(gram of water)/(gram of dry sample)} of these systems was varied from 0.2 to 3.6 g g-1. In the DSC heating curves, glass transition (Tg), cold crystallization (Tcc) and melting (Tm) were observed in all three samples. In addition, liquid crystal transition (T*) was observed in GG-water systems at a temperature higher than Tm. Using Tg, Tcc, Tm and T*, phase diagrams of each system were established. From the melting enthalpy of ice in the systems, three types of water, non-freezing water (Wnf), freezing bound water (Wfb) and free water were calculated. The maximum amount of Wnf was observed at Wc=0.7 g g-1, where Tg showed the lowest temperature. The amount of Wnf in LBG and GG is higher than that of Tara-G, whereas the highest amount of Wfb is found in GG. T* was only observed in GG-water systems. It is concluded that frequency of the side chains in the repeating unit of the main chains of these three galactomannan affects the frozen structure of the glassy state in the presence of water.

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Abstract  

Yttrium orthoborate crystallizes in the vaterite-type structure and has two polymorphous forms, viz. a low- und a high temperature one. DTA measurements of YBO3 confirmed a reversible phase transition with a large thermal hysteresis. The phase transition has been accurately characterized by the application of different heating and cooling rates (β). Consequently, the extrapolation of the experimental data to zero β yields the transition points at 986.9C for the heating up and at 596.5C for the cooling down cycle. These values correspond to samples just after treatment at 1350C. For samples with a different ‘thermal history’ other phase transition temperatures are observed, (e.g. after having performed several heating and cooling cycles). The linear relationship between the associated DTA signal ΔT=T onsetT offset and the square root of the heating rate β was confirmed, but the relation between T onset and square root of β is not found here. From the empirical data a good linear fitting between T onset and ln(β+1) can be derived. From the kinetic analysis (Kissinger method) of the phase transformation of YBO3 an apparent activation energy of about 1386 kJ mol–1 for heating and of about 568 kJ mol–1 for cooling can be determined

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