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.
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 Tg 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 (ΔCp) accompanying the glass transition is the significant measure of degree of changes in the structure of glass preceding crystallization.
Authors:S. Chen, X. Meng, Q. Shuai, B. Jiao, S. Gao, and Q. Shi
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.
enthalpy change of the reaction of formation of the complex in ethanol, ΔrHmθ(l), as –22.2140.081 kJ mol–1,
and the molar heat capacity of the complex, cm,
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, ΔrHmθ(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, ΔcU,
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, ΔcHmθ,
and standard enthalpy of formation, ΔfHmθ,
were calculated to be –16953.379.79 and –1708.2310.69
kJ mol–1, respectively.
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.
Authors:S. Mikheev, V. Sharnin, V. Shormanov, and M. Talanova
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. ΔHsol0
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.
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 (ΔtH0) of the complex former, the ligand and the complex ion from water to binary solvents.
In water—DMSO mixtures, the ΔtH0 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 ΔtH0 for all reagents influence the heat effect equally.
, 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 298.15K . J Therm Anal . 1996 ; 47
Authors:L. Bark, C. Bowmer, L. Kershaw, W. Moreno, and J. Openshaw
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.