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Journal of Thermal Analysis and Calorimetry
Authors: Xian'e Cia, Daichun Du, Youming Jin, and Yixiang Qian

Abstract  

N(C5F11)3 (Fluorint FC-70) has been chosen as the test material to compare the chemicophysical data obtained by static-sample and DSC methods. The normal boiling point, the molar enthalpy of vaporization, and the constants of the Antoine equation of fluorint FC-70 are reported. DSC can be developed into a simple and rapid routine instrument to determine the enthalpy of vaporization as well as the boiling point of liquid, particularly at relative high temperature.

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Abstract  

A thermobalance for studies of the high-temperature sulfidation of metals and alloys is described. This apparatus permits the determination of mass changes in a sulfidized sample as a function of temperature and sulfur vapour pressure. The main parts of this apparatus are the container with liquid sulfur and the reaction chamber with the quartz space and quartz spiral. All parts of the apparatus are equipped with thermostating furnaces. The temperature within the apparatus is controlled with an accuracy of 0.5 K. The quartz spiral (diameter 0.2 mm), consisting of 50 coils (diameter 30 mm), permits the recording of mass changes in the sample (about 200 mg) with an accuracy of 10-5 g. Besides heterogeneous kinetics measurements, it has been shown that the self- and chemical diffusion coefficients or the deviation from stoichiometry of the metal sulfides can also be studied as functions of temperature and sulfur pressure by means of equilibration measurements.

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Abstract  

The effect of atmospheric water vapor on the kinetic rate behavior of the thermal decomposition of copper(II) carbonate hydroxide, Cu2CO3(OH)2, was investigated by means of TG-DTA coupled with a programmable humidity controller. With increasing water vapor pressure p(H2O) from 0.8 to 10.6 kPa, a systematic reduction of the reaction temperature of the thermal decomposition was observed as the continuous trend from the previous works at the lower p(H2O). Through a comparative kinetic analysis of the reaction at different p(H2O), a catalytic action of the atmospheric water vapor on the nucleation process at the first half of the reaction was identified as the possible origin of the reduction of the reaction temperature.

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The present article describes the synthesis, spectral, coordination and thermal aspects of N,N′-polymethylene bis(1-phenyl-3-methyl-4-trifluoroacetylimino-2-pyrazoline-5-ol)oxovanadium(IV) or copper(II) Schiff base complexes with alkyl backbones ranging from two to four carbons have been characterized on the basis of elemental analysis, magnetic moments, molar conductivity measurements, spectra (FTIR, ESR, UV-Visible, MS), VPO and thermal studies. The vapour pressure osmometry (VPO) and mass spectral studies indicate that the complexes are monomeric. An ESR study of all these complexes of VO(IV) and Cu(II) are consistent with the square pyramidal and square planar geometries of these metal ions, respectively. In addition, the kinetics and thermodynamic parameters for the different thermal decomposition steps of the complexes have been studied employing Horowitz-Metzger and Freemen-Carroll methods.

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Abstract  

Thermal effects in a low-pressure plane plasma discharge were obtained in a novel implementation of triode sputtering method. This plane plasma discharge is formed in a relatively low vapor pressure of 0.03-0.65 Pa. Electron beam temperature and ion beam concentration distribution, as well as their dependence on argon pressure within the plasma, were experimentally studied, using the Langmuir probe technique. The influence of an external magnetic field on the ion beam concentration, and electron beam temperature, were studied too. As a result of these studies, sputtering of various materials was done using the novel plane plasma discharge method. This method enables the deposition of homogeneous thin film coatings. Analysis is done on Cu sputtered layers with plane plasma discharge.

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Abstract  

A differential microcalorimeter (E. Calvet) was used to study the processes of adsorption of five aliphatic alcohols (C1-C5) on α-Al2O3 at 25, 50, 100, 150 and 200°C. In particular, the importance of the thermokinetic study of the chemisorption of such alcohols at different experimental temperatures was demonstrated, with regard to the variations in the thermokinetic parameters (tmax, t1/2 and t0) and the evolution of the alcohol vapor pressure on the adsorbent during the adsorption process. It was concluded that: a)  all the heat emission peaks of alcohol adsorption have the same rounded shape at 25°C; b)  on passing from methanol to 1-pentanol, the area of the adsorption peaks increases as the chain length or molecular weight increases; c)  on passing from 25 to 200°C, the shape of the adsorption peaks becomes more pointed.

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Abstract  

TNAZ (1,3,3-trinitroazetidine) is a relatively new, powerful, steam castable, strained ring explosive. Owing these characteristics it is of considerable interest to the energetic material community. A relatively high vapour pressure, volume contraction and formation of shrinkage cavities in the solidification of its melt may be considered as some of its disadvantages. The kinetics and heats of TNAZ sublimation and evaporation were studied by the non-isothermal and isothermal thermogravimetry method. The activation energy of 94-102 kJ mol-1 was found for TNAZ sublimation, while the activation energy of 60-81 kJ mol-1 was found for TNAZ evaporation. The enthalpy of TNAZ sublimation at the melting temperature was found to be 95 kJ mol-1, and the enthalpy of TNAZ evaporation equals 66 kJ mol-1.

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Abstract  

Elementary thermochemical calculations show that in all cases of formation of solid product in the process of the congruent dissociative vaporization of reactants, the equilibrium partial pressure of the main product greatly exceeds its saturation vapour pressure, and therefore causes the appearance of vapour oversaturation. The oversaturation is responsible for the formation and growth of nuclei, their shape and position, the transfer of condensation energy to the reactant, the existence of induction and acceleration decomposition periods, the reaction localization, the epitaxial/topotaxy effects and the nanocrystal structure of the solid product. Variations in the energy transfer explain an increase of the molar enthalpy with temperature and the decelerating influence of melting on the rate of decomposition.

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Abstract  

Hydroxy benzoic acids were subjected to rising temperature thermogravimetric analysis. After optimizing the procedural variables, the kinetics of decomposition was determined and methyl paraben was taken as the calibration compound to characterize the evaporation patterns for the ortho and meta derivatives. The E act values for ortho, meta and para derivatives were 64.8, 78.2, and 119.1 kJ mol–1, respectively. The Antoine and Langmuir equations were utilized to determine the coefficient of evaporation k, which was 1245250.8, units being in the SI system. The vapor pressure plots were generated for the ortho and meta derivatives; ΔH vap for these two compounds were obtained as 66.7 and 80.4 kJ mol–1, respectively.

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Abstract  

The comprehensive analysis of volatile β-diketonate compound—ruthenium(III) trifruoroacetylacetonate (Ru(tfac)3)—was carried out. By means of flow method in quasi-equilibrium conditions and static method the temperature dependencies of saturated vapor pressure have been measured over solid and liquid cis- and trans-modifications of Ru(tfac)3 and isomer mixture. The thermodynamic characteristics of sublimation, evaporation, melting, and phase conversion have been calculated for structural isomers. Also by differential-scanning calorimetry the temperature meanings and the thermodynamic characteristics of melting have been determined for individual isomers of Ru(tfac)3 and their mixtures. By XRD the structures for cis- and trans-modifications have been determined. Both structures consist of neutral molecules arranged in pseudo layers.

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