Calorimetry Methods Research Articles

Research on the low-temperature waste heat storage performance of a novel microencapsulated phase change material with a double-shell encapsulation of hexadecylamine

Phase change materials (PCMs) have the advantages of high energy storage density and the temperature can be kept stable when the phase change process occurs, so they can be widely applied to the recovery of industrial waste heat. In this paper, hexadecylamine (HDA) was selected as PCMs, polystyrene (PS) and calcium carbonate (CaCO3) as wall materials, and PS/CaCO3/HDA microencapsulated phase change materials (MEPCMs) were prepared by ultrasonic emulsification. Then the prepared PCMs were characterized and their properties were tested by using transmission electron microscopy, scanning electron microscopy, X-ray diffraction analyzer, X-ray photoelectron spectrometer, Fourier infrared spectrometer, thermogravimetry, differential scanning calorimetry and other characterization methods. The results showed that PS/CaCO3/HDA MEPCMs with microcapsule structure were successfully prepared with a diameter of about 1.5 μm. The thermal conductivity of PS/ CaCO3/HDA MEPCMs was 0.491 W/(m·K), which was 3.41 times of the thermal conductivity of pure HDA. The highest latent heat of PS/CaCO3/HDA MEPCMs was 33.96 kJ/kg, and no leakage problems occurred. The above results indicate that PS/CaCO3/HDA MEPCMs have good stability and high thermal conductivity, and they have good thermal storage performance at low temperatures.

Heat capacity of leucite powder in the temperature range of 300–980 K

An experimental study of the heat capacity of leucite used as the main component in the new generation of composite ceramics was carried out. The heat capacity was measured by the method of differential scanning calorimetry using a DSC 404 F1 setup in the temperature range from 300 to 980 K of the solid state. The estimated error of the obtained results was 2– 3%. The fitting equation and the table of recommended data were developed for scientific and practical application. The heat capacity temperature dependence in the range of about 820–950 K revealed two phase transformations, which were related to the transition from the tetragonal leucite phase to the cubic one upon heating: I41/a(tetragonal) → I41/acd(tetragonal) → Ia3d(cubic).

On the issue of optimizing protein and energy supply for patients with acute cerebrovascular accident

To study the severity of systemic metabolic dysfunction in various types of stroke and determine the parameters of optimal energy and protein supply for this category of patients in the presence of severe neurological deficit (National Institutes of Health Stroke Scale - NIHSS score of 15 points or more) during different periods of the disease. The retrospective study included 512 patients with acute cerebrovascular accident (ACVA) who received nutritional support (NS) for 10 days or more: 367 (71.7%) people with ischemic stroke (IS) and 145 (28.3%) - with hemorrhagic stroke (HS). The course of stroke in all patients included in the study was accompanied by severe and extremely severe neurological disorders (15 points or more on the NIHSS scale). Energy expenditure and the severity of the catabolic reaction of the body were studied by dynamic assessment of indirect calorimetry indicators and actual nitrogen losses. More than 99% of patients received tube feeding. Using the method of indirect calorimetry, the ranges of energy expenditure during stroke were determined: for IS - 1600-2100 kcal/day (24-26 kcal/kg/day), for HS - 1900-2600 kcal/day (26-30 kcal/kg/day) in depending on the period of the disease. The average nitrogen losses at all stages of the disease in patients with IS and HS were comparable. In IS, these amounts were 19 g/day (0.25 g/kg/day), which corresponds to 119 g/day of protein (1.56 g/kg/day of protein), and in HS patients lost an average of 18.9 g/day of nitrogen (0.24 g/kg/day) or 118 g/day of protein (1.5 g/kg/day of protein). The maximum nitrogen losses were observed in the period from 10 to 20 days of illness and amounted to 24.7 g/day in patients with HS (0.31 g/kg/day or 1.93 g/kg/day protein), and in patients with IS - 24.5 g/day (0.29 g/kg/day or 1.81 g/kg/day protein). An identified trend towards a decrease in mortality in patients with acute stroke with energy supply in the amount of 27-28 kcal/kg/day and protein consumption in the amount of 1.3-1.4 g/kg/day compared with patients receiving 20-21 kcal/kg /day and 1-1.2 g/kg/day of protein requires further prospective randomized studies.

Влияние структурных характеристик полиэтилентерефталата и вторичных продуктов его производства на технологические параметры получения филамента

The temperatures of phase transitions were analyzed and the ratio of crystalline and amorphous phases was determinedfor polyethylene terephthalate samples involving secondary PET (Vivilen product) and its wastes by methods of differential scanning calorimetry and X-ray structural analysis. The studied polyethylene terephthalate samples were ranked according to their glass transition and melting temperatures, which made it possible to correlate the samples according to the degree of crystallinity.To obtain filament on the basis of dust-like wastes of the solid-phase polycondensation process, the extrusion temperature conditions were justified and filament samples for 3D printing were obtained.

CHEMICAL STABILITY OF CELLULOSE NITRATES: REVIEW

The results of the analysis of literature data on updated methods for determining the chemical stability of cellulose nitrates are presented. The relevance of research is due to the need to control the operation and storage of a widespread component of solid rocket fuels and explosive compositions. The criterion for chemical resistance is the value of the decomposition rate or the time dependence of the degree of decomposition of the sample. It is shown that methods for assessing the chemical resistance of cellulose nitrates are based on determining the rate of its thermal decomposition, which is measured by a specific parameter accompanying decomposition. These parameters include weight loss, amount of gaseous decomposition products released, decomposition temperature or thermal effects. Studies are carried out at elevated temperatures and allow you to control the magnitude or rate of change in the parameter that accompanies thermal decomposition. The possibility of using modern analytical methods for evaluating chemical resistance is shown: differential scanning calorimetry, thermogravimetric analysis, chemiluminescent analysis, infrared spectroscopy, high-performance liquid and thin-layer chromatography, gas chromatography, electron paramagnetic resonance, mass spectrometry, X-ray diffraction analysis. The preference for methods of differential scanning calorimetry or differential thermal analysis is substantiated. The results of studies on improving the chemical resistance of cellulose nitrates and compositions based on it with the use of new stabilizers of the aniline series, stabilizers of natural origin with the advantage of the latter on the examples of curcumin and lignins are presented. Due to the insufficient stability of cellulose nitrates, stabilizers added to the formulation of explosive compositions lengthen the induction period of the decomposition of nitro compounds and do not allow the development of the autocatalytic decomposition stage. Methods for determining the chemical stability of cellulose nitrates obtained from alternative sources of raw materials are presented. For citation: Vdovina N.P., Korchagina А.А., Budaev I.А. Chemical stability of cellulose nitrates: Review. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 5. P. 6-20. DOI: 10.6060/ivkkt.20236605.6725.

Определение температуры самовоспламенения веществ и материалов методом синхронного термического анализа

Introduction. The article presents the results of a study of materials of various chemical nature (pine wood, high-density polyethylene, polyvinyl chloride) by the method of synchronous thermal analysis. The relevance of the application of a high-precision and informative method of synchronous thermal analysis for determining the indicators of fire hazard of solid substances and materials is substantiated. The methodology for determining the self-ignition temperature by thermal analysis methods is considered. Research task. The objective of the study was to improve the methods for determining the fire hazard indicators of substances and materials, in particular, the autoignition temperature. Methods. The following methods were used in the study: thermogravimetric analysis, differential thermogravimetry and the method of differential scanning calorimetry. Results and its discussion. As a result of the research, the regularities of thermal-oxidative degradation of polymeric materials were studied. It has been established that it is expedient to determine the auto-ignition temperature from the temperature of the maximum of the first derivative of the curve of differential scanning calorimetry of the thermal-oxidative destruction (combustion) of the material. The auto-ignition temperature values of the studied polymeric materials (pine wood, high-density polyethylene, polyvinyl chloride) were determined by synchronous thermal analysis method, which showed satisfactory agreement with the data obtained by standard methods presented in the literature. Conclusions. The high accuracy of synchronous thermal analysis method (the error during verification by the sensitivity of the device is below 3 %), as well as the satisfactory convergence of the results of parallel tests, allows us to assert the reliability of the obtained research results. The analysis of research results and their comparison with data from reference and literary sources indicates the possibility of using the method of synchronous thermal analysis to determine the autoignition temperature of solid materials. Keywords: thermal-oxidative degradation; auto-ignition temperature; differential scanning calorimetry.

Crocin Protects Mice Pancreatic Islets from Oxidative Stress Induced by Methylglyoxal and Increases Insulin Secretion

Aim: Islets of Langerhans are more sensitive to oxidative damage because of their low antioxidant capacity. In diabetes, methylglyoxal (MG) accumulates in the pancreas. The present study examined the effect of crocin on oxidative stress induced by MG in isolated Langerhans islets from male mice.
 Material and Methods: Twenty-four male mice weighing 20 to 25 g were prepared. The isolated Langerhans islets were transferred to the culture medium. Oxidative stress was induced through MG administration for 30 min, and then 10, 20, 30, and 40 μM of crocin was used for 2 h. Samples were divided into seven groups with 2.8, 5.6, and 16.7 mM glucose concentrations: control, MG 300 μM, MG+glibenclamide 10 μM, and MG+crocin in four doses of 10, 20, 30, and 40 μM. At the end, the islet’s insulin, antioxidant levels, and lipid peroxidation were assessed by ELISA and calorimetry methods.
 Results: Increased levels of malondialdehyde (MDA) in MG groups significantly decreased in 2.8 (p=0.008), 5.6 (p=0.004), and 16.7 (p˂0.001) mM glucose concentrations, with administration of 30 and 40 μM crocin. Total antioxidant capacity (TAC) was reduced in MG groups (p˂0.001) and significantly restored in all crocin-treated groups in 2.8, 5.6, and 16.7 mM glucose concentrations. Also, a significant decrease in insulin secretion and content was observed in MG groups of all three glucose concentrations (p˂0.001). Crocin at high doses improved these alterations.
 Conclusion: MG caused oxidative damage and reduced insulin secretion in isolated islets. Crocin improved the antioxidant defense system, diminished MDA, and increased insulin secretion.

Methods and devices for researching the energy value of food products

Rational nutrition is the main factor in ensuring optimal physical and mental health of a person. The balanced diet development requires reliable information about the nutritional and energy value of raw materials, semi-finished products, and ready-made food products and dishes. Determining the energy value of food products is carried out in several ways: chemical, taking into account the caloric content of individual components, the amount of which requires preliminary determination, calculation, and tabulation according to normative and technical averaged parameters, and experimental method of direct calorimetry. This paper shows that experimental studies of the energy value of food products can be carried out using specialized combustion calorimeters designed for measuring the calorific value of solid, liquid, and gaseous fuels. The standard procedure for determining the combustion heat of fuels has been analyzed and the expediency of using it for studies of the caloricity of other organic substances, in particular, food products, has been proven. Two main types of combustion bomb calorimeters used for laboratory research in Ukraine are considered – a liquid enthalpy calorimeter and a more modern aneroid conductive calorimeter, their design features and principle of operation are described, and advantages and disadvantages are analyzed. Approbation of the products energy value measuring technique using a liquid calorimeter is carried out on samples of sausage products developed according to an experimental recipe. The results of the research, processed according to the author's algorithm, showed the adequacy of the obtained caloricity values within 8-10% in comparison with known indicators. It should be noted that the research procedure is quite complicated, and the final results have low accuracy due to significant heat losses and energy dissipation. However, although liquid calorimeters are considered morally and physically obsolete, this device can be recommended for calorimetric studies of products and recipes in educational laboratories. Using an anhydrous conductive calorimeter does not require distilled water preparation and the maintenance of constant normal conditions in the laboratory room, automation of measurement processes and processing of results excludes possible subjective errors of the operator. The results of studies of practically pure carbohydrate-sugar showed convergence with the reference data within the device measurement error ±3%. Direct calorimetric studies on the newest metrologically certified aneroid combustion calorimeter allow us to determine the energy value of innovative food products, developed according to new recipes or with the addition of atypical ingredients, with high accuracy, which is an undeniable advantage and a necessary condition for scientific research.

Molecular mobility and thermal transitions study in renewable PLA-polyols star-like copolymers

The molecular dynamics mapping in poly(lactic acid) (PLA)-based star-like copolymers is performed herein, employing dielectric spectroscopy techniques supplemented by calorimetry and other structure characterization methods. Next to the neat linear PLA, three star-like copolymers, with 3, 4 and 5 branches were synthesized via ring opening polymerization at the presence of, respectively, glycerol, pentaerythritol and sorbitol (initiators). When increasing the branch number, consequently, the overall molar mass drops, from 55 kg/mol (neat PLA) to 17k (PLA@glycerol), 25k (PLA@pentaerythritol), and 14k (PLA@sorbitol) and, thus, the branch length decreases to ∼6k, ∼6k, and ∼3 k g/mol in the stars. The latter leads to faster segmental mobility, documented by the accelerated α relaxation and the drop in the calorimetric and dielectric glass transition temperatures. Simultaneously, the cooperativity (chains’ fragility) drops. Together these results suggest possibly the increase in free volume, a factor that can potentially favour the physical biodegradability. Next to the segmental dynamics, the local beta relaxation is recorded to have a mild dependence on the type of star (mainly decelerates), while the rare case of Normal Mode relaxation is recorded here only in the stars, providing additional support for the quite short branches. The overall data suggest the co-implementation of two antagonistic effects on mobility, i.e., the chain length changes in parallel to the constraints imposed by the star-like structure. Moreover, the in general low crystallizability of linear PLA further drops in the stars in terms of both suppressed crystalline fraction and nucleation, as well as lower quality of crystals. The materials exhibit single thermal transitions, indicating a homogeneous character, whereas a variety of semicrystalline morphologies can be achieved via both the composition and the thermal treatment. This provides a tool for tuning various properties and, consequently, the manipulation of the macroscopic performance.

Mechanical properties of medium-temperature thermoelectric materials based on tin and lead tellurides

The strength and thermoelectric properties of PbTe and Sn0.9Pb0.1Te medium-temperature polycrystalline specimens with p and n conductivity types, respectively, have been studied. The specimens have been produced using extrusion and spark plasma sintering. The strength parameters of the materials were studied using uniaxial compression at 20 to 500 °C. The structure of the materials was studied using X-ray diffraction and electron microscopy. The electrical conductivity and the Seebeck coefficient were measured simultaneously using the four-probe and differential methods. The temperature conductivity and the specific heat capacity were measured using the laser flash and differential scanning calorimetry methods. The PbTe and Sn0.9Pb0.1Te materials produced using extrusion and spark plasma sintering prove to be single-phase and have homogeneous compositions. For comparable synthesis methods, the dislocation density in the Sn0.9Pb0.1Te specimens is by an order of magnitude lower than in the PbTe ones. Study of the mechanical properties of n and p conductivity type specimens over a wide temperature range from 20 to 500 °C has shown that their deformation is plastic and has no traces of brittle fracture. For these plastic materials, the strength criterion has been accepted to be the arbitrary yield stress corresponding to the stress at a 0.2% deformation. The 20 °C yield stress of PbTe and Sn0.9Pb0.1Te is far higher for the specimens produced by extrusion. For all the test temperatures and synthesis methods the Sn0.9Pb0.1Te specimens have a higher strength than the PbTe ones. The PbTe and Sn0.9Pb0.1Te specimens produced by extrusion have better thermoelectric properties than the spark plasma sintered ones. The heat conductivity of the PbTe and Sn0.9Pb0.1Te specimens is almost the same regardless of compaction method.

Kinetics of isothermal solidification during transient liquid phase bonding of Inconel 718 superalloy by differential scanning calorimetry

In the transient liquid phase bonding of Inconel 718 alloy, the time for isothermal solidification is measured by using the cyclic differential scanning calorimetry method. The enthalpy of solidification of the remnant liquid is used in the current investigation to determine the isothermal solidification rate and time. The differential scanning calorimetry results reveal a reduction in interlayer width during the heating and melting stage of transient liquid phase bonding due to the rapid interdiffusion of elements. The result also reveals that the isothermal solidification time for a eutectic-free joint depends upon the actual width of the interlayer material. The actual width of the interlayer material prior to isothermal solidification is found to be less than the initial width of the interlayer material due to rapid diffusional solidification. The measured isothermal solidification time and rate for transient liquid phase bonding of the Inconel 718 joint are in good agreement with the experimental and theoretical results.

Mesomorphism of (E)-4-[(4-propyloxyphenyl)diazenyl]phenyl alkanoates (3OABOOCm)

Several compounds from the group of (E)-4-[(4-propyloxyphenyl)diazenyl]phenyl alkanoates (3OABOOCm, for m = 1 – 19) were synthesized, with the derivatives for m ≥ 8 being reported for the first time. The phase situation was investigated by polarizing optical microscopy, thermo-optical analysis, and differential scanning calorimetry methods. The enantiotropic nematic mesophase was noted for compounds where m = 2 – 13, whereas the monotropic nematic phase was observed for m = 1, 14, and 15. Multiple crystalline phase were noticed in selected derivatives (for m = 1 – 3, 9, 13, and 14). The X-ray powder diffraction confirmed the polymorphism of the crystalline phase for the 3OABOOC2 compound. The trans-cis photoisomerization process is attributed to the presence of the diazenyl (azo) group. Absorption spectra, collected as a function of UV light exposure time, indicated a first-order reaction comprising two components. The determined values of the kinetic constant k were of the order of 10-2s − 1.

The influence of mixing time on the structure and thermophysical characteristics of systems based on polyethylene glycol and organomodified montmorillonite

The structure and thermophysical properties of polymer nanocomposite systems based on polyethylene glycol and organomodified montmorillonite were studied using the methods of X-ray structural analysis and differential scanning calorimetry. From the data of X-ray structural analysis, it was found that the optimal degree of delamination of montmorillonite, which corresponds to the maximum interlayer distance, occurs in 3-5 minutes. A further increase in the mixing time has no significant effect on the structural characteristics of the nanocomposite. On the basis of calorimetric studies, it is shown that the melting and glass transition temperatures, as well as the degree of crystallinity, reach critical values at 3 min of treatment, after which they remain unchanged. It was established that the time of extruder mixing is optimal. At the same time, the maximum intercalation takes place, which leads to an impact on the final functional characteristics of the polymer-organoclay system. It was established that extruder mixing during 3 min is optimal.

Assessment of Unfrozen Water Content in Copper Bentonites Using the 1H NMR Technique: Optimization, the Method's Limitation, and Comparative Analysis with DSC.

Studies on changes in unfrozen water content in copper bentonite from Slovakia were conducted using both differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) methods. The aims of this study were to 1. optimize the method for determining changes in unfrozen water content using the 1H NMR technique in model bentonites based on the DSC results; 2. analyze the relationship between unfrozen water content, as determined via DSC and the optimized NMR technique, and the physicochemical parameters of bentonites; and 3. identify the limitations in determining changes in unfrozen water content using the 1H NMR technique in relation to copper-contaminated bentonites. The results obtained using the optimized NMR method applied to the model bentonites correlated well with the DSC results. The unfrozen water content in the Cu-contaminated bentonites was 2-18% lower after NMR compared to the DSC results, likely due to the mobility of copper ions and their paramagnetic properties. Statistically significant differences in unfrozen water content between the DSC and NMR methods were observed, depending on molar concentration, copper ion concentration, and temperature, confirmed via Analysis of Variance (ANOVA). Calorimetric studies are recommended for investigating unfrozen water content changes in contaminated clays. Further NMR research could identify metals influencing free induction decay signals under varying physicochemical conditions.

Compatibility and Thermal Decomposition Kinetics of Hexahydro-1,3,5- trinitro-1,3,5-triazine with Different Polyester-based Polyurethanes

Backround: The compatibility study is an important aspect before pre-formulation of the energetic composites. Any sort of the incompatibility between the ingredients of the energetic composites greatly affects the safety and functionality of the energetic composites. Therefore, to develope safer energetic composites, the compatibility between the different ingredients of the energetic formulations and their thermal decomposition kinetics is important study as it is directly linked with the safety and functionality of the energetic composites. Methods: The compatibility of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) with different polyester-based polyurethanes (PUs) were studied by using vacuum stability tester (VST) and differential scanning calorimetry (DSC) methods as outlined by North Atlantic Treaty Organisation Standardisation Agreement (STANAG 4147). The mixture of RDX with polyester-based PUs was cured with MDI (4,4’-methylene diphenyl diisocyanate), IPDI (isophorone diisocyanate) and TMDI (2,2,4- trimethylhexamethylene diisocyanate) as curatives to get polyester-based PUs. The VST measurements were carried out at isothermal temperature of 100℃ for 40 h. For kinetic study, all the samples were subjected to heat from 25-600℃ at different heating rates under flow rate of nitrogen gas of 40 mL/min Results: The VST results revealed that energetic RDX was compatible with all polyester-based PUs and was chemically stable. The thermal decomposition behaviour was studied by employing thermogravimetric analysis (TGA) and DSC. The DSC results indicated that peak temperature difference (∆Tp) between pure RDX and binary mixture of RDX and polyester-based PUs i.e., RDX/PE/MDI, RDX/PE/IPDI and RDX/PE/TMDI were found to be greater than 4℃, indicating that RDX was not compatible with all types polyester-based PUs. The thermal stability in terms of Tmax values of RDX/PE/MDI, RDX/PE/IPDI and RDX/PE/TMDI was found to be significantly reduced as compared to pure RDX. The activation energy obtained by the Kissinger method for RDX/PE/MDI, RDX/PE/IPDI and RDX/PE/TMDI samples was found to be 220.2, 271.5 and 210.4 kJ/mol, respectively. The experimental results showed that the values are comparable and in good agreement with the values obtained by Ozawa method. Conclusion: This study provides useful information for selecting polyester -based PUs as polymeric binder for the preparation of RDX-based energetic composites.

Glass-Containing Matrices Based on Borosilicate Glasses for the Immobilization of Radioactive Wastes

Glass-containing materials are widely considered among the most reliable materials for the immobilization of radioactive waste materials. The present work considers the synthesis of glass–ceramic and glass crystalline composite materials based on borosilicate glasses. The synthesis of glass–ceramic materials was carried out by a gradual temperature decrease, followed by crystallization for several hours. Sintering of crushed samples with crystalline components was carried out as an alternative procedure. Porous glasses were produced from glass melts by quenching. After impregnating the resulting porous materials with aqueous solutions of cesium nitrate, compaction of the glass was carried out to form glass crystalline composites. The thermochemical characteristics of the parent glasses were determined using the differential scanning calorimetry method. The phase composition and structure of the glass-containing materials were determined using X-ray phase analysis, X-ray spectral microanalysis, and Raman spectroscopy.

Mechanical Properties of High Entropy Alloys Based on Rare Earth Elements with Yttrium and Scandium

Abstract—The high-entropy alloys GdTbDyHoSc and GdTbDyHoY having equiatomic composition are considered as promising materials for magnetic cold generators. The results of the alloys structure and chemical composition investigation are presented in this paper. The solidus and liquidus temperatures of the alloys under investigation were determined by the method of differential scanning calorimetry. Based on these data, an experimental mode of thermocyclic treatment was selected. There were no signs of alloys destruction after five cycles testing for heat resistance in the following regime: 15 min exposition at 1073 K (~0.6 of the melting temperature) and subsequent quenching in room temperature water. It was found that the applied heat treatment led to an increase in the hardness of the alloys by 2–3 times and a decrease in wear resistance by 4–40 times, depending on the composition of the alloys and the number of heat treatment cycles. A significant change in the properties of alloys is associated with the formation of oxides of the REM2O3 type not only on the surface of the alloys, but also in their volume, which is due to the high chemical activity of rare earth metals (REM). The presented data will be useful for the development of modes of thermal and thermomechanical processing of various alloys.

Thermophysical Properties of Lanthanum and Samarium Zirconate—Hafnates

The synthesis and identification of lanthanum and samarium zirconate–hafnates of the pyrochlore structure type have been reported. The heat capacity of the samples in the temperature range 310–1380 K was measured by the differential scanning calorimetry method. The temperature dependences of the cubic lattice parameters were determined, and the thermal expansion coefficients were evaluated in the range 298–1273 K using high-temperature X-ray powder diffraction. The thermal diffusivity of the samples was measured by the laser flash method, and the temperature dependences of the thermal conductivity were calculated considering the porosity of the samples.

Low-temperature behavior of heat capacity and pho-toluminescence of a binuclear pivalate complex [Eu2(bath)2(piv)6

The low-temperature behavior of the heat capacity and photoluminescence of the previously structurally characterized binuclear pivalate complex [Eu2(bath)2(piv)6] (monoclinic, I2/a) (1), where bath = 4,7-diphenyl-1,10-phenanthroline, piv = (CH3)3CCO2-. Using the adiabatic calorimetry method, the temperature dependence of the heat capacity was measured in the temperature range 5.96–302.88 K and the thermodynamic functions Cp0(T), S0(T), Ф0(Т) and Н0(Т) - Н0(0) were calculated. The absence of low-temperature phase transformations of complex 1 was shown. It was established that in the temperature range 98-295 K, complex 1 demonstrates high temperature stability of the integral intensity of photoluminescence of the transitions of the Eu3+ ion 5D0-7Fj (j = 0.6).

Vaporization enthalpy of azeotropes by the solution calorimetry method

This work is devoted to the study of the thermochemistry of solvation of azeotropes. The enthalpies of dissolution of azeotropes (binary systems [organic nonelectrolyte – A], where A is acetonitrile, benzene, cyclohexane or n-hexane) in the medium of cyclohexane or n-heptane have been determined. The impact of the structure of the components of the azeotropes on their properties in solution has been discussed. The approach based on the correlations between the enthalpies of solvation and molar refraction has been first used to determine the vaporization enthalpies of azeotropes. Values were found to be in a fairly good agreement with literature data obtained by direct and calculated methods. The findings of this study allow analyzing the structure–property relationships of the azeotropes obtained.