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Abstract  

Thermochemistry of crystal phase formation in vitrified municipal and hospital waste combustion ash and Ca, Fe pyroxene crystallization mechanism are presented. Pyroxene structure is capable of accumulate heavy metals and toxicants contained in ash. Due to this vitrification and crystallization is one of most effective method of immobilization dangerous contaminant of waste.

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Abstract  

Thermochemistry and structural mechanism of crystallization of MgO-Al2O3-SiO2 glasses with TiO2 as crystallization activator were studied. Thermal and HREM investigation proved that near the T g temperature crystallization is going by rearrangement of glass structure elements and part of its components redistribution like at disorder — order phase transition in solid bodies. Nanocrystals of Mg-titanate and high quartz structure solid solution are formed then. Next enstatite and cordierite are crystallizing. Thermochemical and chemical bonds strength analysis indicate that during multistage crystallization of glasses, kind and order of crystal phase formation, is determined by the glass structure decomposition progress and its particular components release accompanying increase of temperature. It has been proved that molar heat capacity change (ΔC p) accompanying the glass transition is the significant measure of degree of changes in the structure of glass preceding crystallization.

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Abstract  

A solid complex Eu(C5H8NS2)3(C12H8N2) has been obtained from reaction of hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen⋅H2O) in absolute ethanol. IR spectrum of the complex indicated that Eu3+ in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms from the o-phen. TG-DTG investigation provided the evidence that the title complex was decomposed into EuS. The enthalpy change of the reaction of formation of the complex in ethanol, Δr H m θ(l), as –22.2140.081 kJ mol–1, and the molar heat capacity of the complex, c m, as 61.6760.651 J mol–1 K–1, at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy change of the reaction of formation of the complex in solid, Δr H m θ(s), was calculated as 54.5270.314 kJ mol–1 through a thermochemistry cycle. Based on the thermodynamics and kinetics on the reaction of formation of the complex in ethanol at different temperatures, fundamental parameters, including the activation enthalpy (ΔH θ), the activation entropy (ΔS θ), the activation free energy (ΔG θ), the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A) and the reaction order (n), were obtained. The constant-volume combustion energy of the complex, Δc U, was determined as –16937.889.79 kJ mol–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δc H m θ, and standard enthalpy of formation, Δf H m θ, were calculated to be –16953.379.79 and –1708.2310.69 kJ mol–1, respectively.

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Abstract  

The flexibility of the internal structures of solids, both crystalline and amorphous, is a result of the freedom of the displacement of their elements, without disturbance of the continuity of the structure as a whole. This article discusses peculiarities of solids with flexible structures. The effects of flexibility in the thermal reactions of the creation of new compounds in the internal structure of solids, and the phase transitions, are considered. Flexibility is indispensable for random amorphous structure formation. The glass transition effect is a consequence of the high flexibility of the structure of glasses.

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Abstract  

The integral heat effects of CuCl2 dissolution in aqueous DMSO, aqueous ethanol and aqueous acetone solutions at 298. 15 K in the electrolyte concentration range 0.001–0.01M were measured by means of calorimetry. ΔH sol 0 values were obtained by extrapolation to zero electrolyte concentration. Literature data were used to determine the thermodynamic characteristics of Cu2+ transfer from water to aqueous organic solvents.

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Abstract  

The heat effects of the reactions of formation of ethylenediamine-copper(II) complexes were determined calorimetrically in mixtures of water with ethanol, acetone and dimethylsulfoxide. The results were interpreted in terms of the enthalpies of transfer (Δt H 0) of the complex former, the ligand and the complex ion from water to binary solvents. In water—DMSO mixtures, the Δt H 0 values for copper(II) and complex ions were found to change in similar ways, and their contributions to the reaction heat effects compensate each other to a large extent. Thus, the reaction enthalpy change due to solvent composition variation is caused mainly by the changes in ligand solvation enthalpies. In aqueous ethanol and acetone solutions, the changes in Δt H 0 for all reagents influence the heat effect equally.

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, Waliszewski , D . Enthalpic pair interaction coefficients in DMF solution. Part 3. Thermochemistry of NaI solutions in mixtures of N,N -dimethylformamide with urea, formamide, acetamide and N,N -dimethylacetamide at 298.15K . J Therm Anal . 1996 ; 47

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Abstract  

The advantages of using diodes as thermal sensors in solution thermochemistry are discussed and a simple, low-cost circuit for the use of diodes as temperature sensors is reported. In preliminary studies, the titration of TRIS and hydrochloric acid is used to compare the precision of thermistors and diodes in thermometric titrimetry. Several systems are assayed at various temperatures by enthalpimetric methods to illustrate the advantages of diodes as sensors for monitoring thermal methods capable of being used in quality control system.

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. Bel Hadj Yahia , F , Jemal , M . Synthesis, structural analysis and thermochemistry of B-type carbonate apatites . Thermochim Acta . 2010 ; 505 : 22 – 32 . 10.1016/j.tca.2010.03.017 . 21

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