Differential Thermal Analysis Methods Research Articles

Different Approach to Thermodynamic Description of Bi-Te Binary System

The aim this work was the reinvestigation of phase equilibria in Bi-Te system. The as-cast and long-time equilibrated alloys of Bi-Te binary system were analysed by scanning electron microscopy, X-ray diffraction (XRD) and differential thermal analysis (DTA) methods. The primary solidified phases were identified for as-cast samples. The existence of the four intermetallic phases: Bi2Te3, BiTe, Bi2Te, Bi7Te3 was confirmed. Three of them melt incongruently in peritectic reactions. The model parameters of all phases in this system were assessed by optimization using available data by Calphad method. The stabilisation of these phases in other ternary systems was discussed taking into consideration its future application in thermodynamic description of Ag-Bi-Te ternary system.

An investigation of AlN nanoparticles by DTA and DTG methods

Differential thermal analysis (DTA) and differential thermal gravimetry (DTG) studies at different heating rates of were considered for AlN nanoparticles. The free Gibbs energy in the temperature range of 300÷1400 K is determined at 5, 10, 15 and 20 K/min heating rates. Experiments were separately carried out in both heating and cooling processes and obtained results were analyzed in detail. The enthalpy and entropy of the system composed of nano AlN particles at different thermal treatment rates were calculated (theoretical calculations were justified by experimental results). The values acquired from the experimental results were compared for all thermophysical parameters at different thermal treatment rates.

PROPERTIES OF GLASSES IN THE Ag2S–GeS2–As(Sb)2S3 SYSTEMS

The characteristic temperatures for individual glass samples of quasi-ternary systems Ag2S–GeS2–As(Sb)2S3 were determined by differential thermal analysis method. Obtained data show that the glass transition temperature of the alloys is in the range typical of chalcogenide glasses. It was established that the glass transition temperature increases with the modifier content in the range of 402-421 K and 373-438 K for the Ag2S–GeS2–As(Sb)2S3 systems, respectively. For the constant Ag2S concentration, the value of the glass transition and crystallization temperatures increases with the content of germanium (IV) sulfide. The reduced glass transition temperature Tgr was calculated from obtained results which lies in the range of 0.62-0.73 and 0.59-0.70 for the glasses of the Ag2S–GeS2–As(Sb)2S3 systems, respectively, which indicates the high capacity of the samples to glass formation. Optical absorption spectra were measured at 297 K. The band gap energy Eg of the glasses of the Ag2S–GeS2–As(Sb)2S3 systems was estimated from the data on the spectral distribution of the absorption coefficient in the region of the absorption edge. It was determined that the absorption edge shifts to longer wavelengths with the increase of the GeS2 content in glasses, while the energy position of the absorption edge increases. Ade crease in the band gap energy is observed for all glass samples when a modifier is introduced into the glass-forming matrix. The characteristic energy of the degree of tailing of the absorption edge is in the range from 0.066 to 0.079 eV for all studied glass samples.
 Keywords: сhalcogenide glasses; quasi-ternary systems; glass-formation; characteristic temperatures; band gap energy.

PHASE EQUILIBRIUM STATES IN A TWO-COMPONENT DIPHENYL-n-NONADECANE SYSTEM

The melting curves of the diphenyl-n-nonadecane system were calculated using the Schroeder equation and using the UNIFAC and UNIFAC Dortmund methods. The calculation results showed that the diphenyl-n-nonadecane system is eutectic. The compositions experimentally studied by the method of differential thermal analysis and calculated by the indicated methods are not eutectic. Individual substances and 9 compositions within the studied system were experimentally studied using a differential scanning calorimeter. Based on the data obtained, a phase diagram was constructed, including one single-phase field above the liquidus curve and 4 two-phase fields – α-n-C19H40+(Ph)2, β-n-C19H40+(Ph)2, L+n-C19H40, L+(Ph)2. The predominant branch of the liquidus curve belongs to the more refractory component, diphenyl. In the solidus at a temperature of 18.7 °C, a polymorphic transformation α-n-C19H40 ⇆ β-n-C19H40 is noted, which coincides with the literature temperature data. The heating DTA curve of the eutectic alloy showed two endoeffects corresponding to the polymorphic transition of n-nonadecane and the melting of the eutectic. The calculation of the eutectic coordinates by the UNIFAC Dortmund method showed the smallest deviation in the composition of the eutectic alloy from the experimental data. For an alloy of eutectic composition, the specific enthalpy of melting, the molar values of the entropy and enthalpy of melting, the volumetric specific enthalpy of melting, and the density for standard conditions are determined. This two-component system was studied by low-temperature differential thermal analysis. The eutectic melt can be used in industry as a heat carrier. Also, the eutectic composition of the diphenyl-n-nonadecane system under study can be used as a working fluid of a heat accumulator. For citation: Kazakova A.I., Yakovlev I.G., Garkushin I.K. Phase equilibrium states in a two-component diphenyl-n-nonadecane system. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 46-53. DOI: 10.6060/ivkkt.20236606.6733.

About the Possibility of the Hydrate Formation in Subpermafrost Aquifers Saturated with Calcium Chloride-Type of Waters

In this work, we consider the results of studying the natural gas hydrates formation in porous media saturated with fresh water and sodium chloride solutions of 5, 10, and 15 wt%. at a pressure of 8 MPa. The studies were carried out by the method of differential thermal analysis. It was found that the presence of salts in porous media reduces the degree of water conversion into hydrate, as well as the rate of the gas consumption in the process of the hydrate formation

SYNTHESIS OF SUPER-BRANCHED POLYGLYCERIDES OF SACCHARIN-6-CARBOXYLIC ACID

By polycondensation of triglyceride of saccharin-6-carboxylic acid with some aliphatic diamines, the thermal-stable super-branched polyestersulfoimides – polyglycerides of saccharin-6-carboxylic acid have been obtained. The structures of the synthesized compounds have been confirmed by data of the IR spectroscopy. The yield of the purposeful product was 80–83%. It has been found that the synthesized polyglycerides are well dissolved in polar aprotonic solvents. The thermal stability of the obtained compounds was studied by a method of differential-thermal analysis on derivatograph of system ʺPaulik-Paulik-Erdeyʺ. The derivatographic investigations showed that the synthesized polyglycerides have high thermal stability, decreasing with the growth of length of the aliphatic fragment in their composition. For comparative estimation of the thermal and physical-mechanical indices of the synthesized polyglycerides, the corresponding indices of the industrial polyesterimide Zellamid 1000 have been also given. It has been found that the obtained polyglycerides do not concede to industrial polyesterimides on physical-mechanical indices, but exceed them on thermal stability

Solid-state synthesis of ZnMn2O4 spinel: Sequence of phase transformations, thermal stability, localization and charge state of manganese ions in the intermediate and final reaction products

This paper presents data on the solid-state synthesis of spinel ZnMn2O4, one of the leading promising materials for numerous practical applications. The evolution of the phase composition and charge state of manganese ions during the solid-state synthesis of ZnMn2O4 in air from ZnO and Mn2O3 has been studied. Using differential thermal, thermogravimetric, and X-ray diffraction analysis methods it has been established that, at a temperature of about 700 °C, an insignificant amount of ZnMn2O4 is present in the mixture with the initial oxides. During further heat treatment ZnMn2O4 interacts with Mn2O3 to form the solid solution based on ZnMn2O4. In parallel with this process, in the temperature range of 800–850 °C, ZnMn2O4 reacts with ZnO to form the compound ZnMn4+O3. It has been shown that heat treatment at 880–1180 °C leads to the formation of the final single-phase product – ZnMn2O4. Using diffuse reflectance spectroscopy, XPS, and FT-IR methods, the charge state and localization of Mn ions in the intermediate and final synthesis products have been determined. It has been shown that in the Zn1-xMn2+xMn3+2O4 solid solution Mn2+ ions are localized in the tetrahedral positions and Mn3+ ions in the octahedral positions of the structure. In the final single-phase product, ZnMn2O4, the tetrahedral positions are occupied only by zinc ions, and the octahedral positions are occupied only by Mn3+ ions. It has been established that ZnMn2O4 is stable up to 1300°С. Upon reaching this temperature, ZnMn2O4 decomposes into ZnO and Zn1-хMn2+хMn3+2O4.

Research of innovative adsorbents in cottonseed oil refinement technology

Based on the results of a comprehensive research of the nature and colloid-chemical properties of selected local clays before and after their acid activation, it has been established that Shafrikan bentonite (Bukhara region) and Mayskiy clay (Tashkent region) are promising raw materials for obtaining effective adsorbents for the oil and fat industry. The new types of adsorbents in cottonseed oil bleaching technology have been studied. The main sorption properties of local clays as adsorbents have been determined. The dependence of the chromaticity of cottonseed oils on the sorption properties of innovative types of adsorbents has been established. The temperature limits of the first, second and third “effect” for selected samples of local clays has been established by the method of differential thermal analysis. A spectral method has been developed for quantitative evaluation of the selectivity of adsorbents in the bleaching of vegetable oils, in particular cottonseed oils. Mathematical models have been developed for obtaining activated adsorbents from local clays, and based on them the optimal modes of recommended processes have been selected. The intensifying role of vacuum in the production of activated adsorbents from local clays has been established.

Metallurgical aspects in production of nickel high-temperature alloy disk blanks obtained by hot forging

The main metallurgical aspects that must be taken into account in the production of disk blanks with a diameter of up to 300 mm by hot forging are presented using the example of a nickel high-temperature alloy of the VZh179 type. The temperatures of phase transformations in the material under study are determined using the method of differential thermal analysis. On the basis of these data, the temperature-time modes of heat treatment of disk forgings are selected. The computer simulation of the hot forging process is carried out in the QForm 3D software package. The distribution fi elds of temperature and intensity of plastic deformation over the forging volume are determined. The optimal modes of hot forging and heat treatment of a nickel heat-resistant alloy are selected, which ensure high manufacturability and a level of mechanical characteristics that meets the requirements of technical specifications.

Investigation of thermal properties and composition on basalts of the Aydarkul deposit by methods DTA/DTG and X-ray diffraction

To study the applicability of the basalt fiber through various experimental works in thermal and chemical environments, lining heat-insulating materials basis on basalt of Aydarkul deposit were compared and discussed. The identification and study phase pert structures lining heat-insulating materials basis on basalt of Aydarkul deposit used X-ray diffraction analysis. The basalt fiber showed better strength retention than the glass fiber at relatively high temperature. The article studies the endothermic effects of the thermolysis process, which appear at a temperature of 80 ÷240 0C. They show the decomposition of clay impurities or the removal of hygroscopic water contained in rocks. The chemical and mineralogical composition of the basalts of the Aydarkul deposit has been studied by such modern methods as X-ray diffraction and differential thermal analysis methods.

SYNTHESIS OF NEW THERMOSTABLE POLYHYDROXYESTER ON THE BASIS OF 2- HYDROXYPROPYL-1,3-BIS-CARBOXYMETHYLESTEROSULFOIMIDE OF SACCHARIN-6-CARBOXYLIC ACID

By polycondensation of 2-hydroxypropyl-1,3-bis-carboxymethylesterosulfoimide of saccharin-6- carboxylic acid with ethylene glycol, a thermostable polyhydroxyester was obtained. The structure of the synthesized compound was confirmed by data of the infrared spectroscopy and the thermal stability studied by a method of differential-thermal analysis on a derivatograph of “Paulik—Paulik Erdei” system. The derivatographic investigations showed that the synthesized polyhydroxyester had high thermal stability and physical-mechanical properties.

Statistical validity of quantitative assessment of the structure of building composites for sustainable development

This paper proposes the problem of the complexity and consistency of a qualitative description and the reliability of a quantitative assessment of the characteristics of the structure of building composites. The results of an experimental assessment of the statistical error in identifying the structure of building composites (by the example of silicate microconcrete) by the methods of X-ray phase and differential thermal analysis are presented in comparison with the relative error of mechanical tests of the material. It is shown that under the condition of setting technological factors under control, the statistical variability of the composition and structure of the material does not exceed 5-7%, and the physical and mechanical properties are at the level of 10%.

Character of the interaction in the As2Te3-TISe System and Electrophysical Propertes of the Phases Obtained

The character of the interaction in the As2Te3-TlSe system was studied by the methods of Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Microstructure analysis (MCA), and also by measuring the microhardness and determining the density of alloys, and state diagram was constructed. It is established that the As2Te3-TlSe state diagram is a quasibinary section of the triple mutual system As, Tl // Se, Te. Two new compounds, TlAs2Te3Se and Tl3As2Se3Te3, are formed in the As2Te3-TlSe system. Both compounds are obtained in the vitreous state. Solid solutions based on As2Te3 at room temperature reach up to 3 mol.% TlSe, and based on TlSe-2 mol.% As2Te3. The electrical conductivity and thermoelectric power coefficient of the (As2Te3)1-x (TlSe)x solid solutions have been measured as functions of temperature.

Screening of cold hardiness-related indexes and establishment of a comprehensive evaluation method for grapevines (V. vinifera).

The goals of this work were to screen physiological and biochemical indexes to assess a set of V. vinifera germplasm resources, to compare evaluation methods for cold hardiness, and to establish a comprehensive method that can be used for more accurate screening for cold hardiness in V. vinifera. Four single methods were used to evaluate the cold hardiness of 20 germplasms resources and 18 physiological and biochemical indexes related to cold hardiness were determined. The LT50 values determined by electrical conductivity (EL), 2,3,5-triphenyltetrazolium chloride staining (TTC), differential thermal analysis (DTA), and recovery growth (RG) methods showed extremely significant positive correlation. Bound water content (BW), proline content (Pro), total soluble sugar content (TSS), malondialdehyde content (MDA), catalase content (CAT), and ascorbic acid content (ASA) exhibited significant correlation with LT50 values measured by different evaluation methods. The comprehensive cold hardiness index calculated by principal component analysis (PCA) combined with subordinate function (SF) was negatively correlated with LT50 values measured by different evaluation methods. Meili and Ecolly exhibited the highest cold hardiness, indicating their potential for use as parents for cold hardiness breeding. EL, DTA, TTC, and RG methods successfully distinguished cold hardiness among different V. vinifera germplasm lines. Measurements of BW, Pro, TSS, MDA, CAT, and ASA in dormant shoots also can be used as main physiological and biochemical indexes related to cold hardiness of V. vinifera. Comprehensive evaluation by PCA combined with SF can accurately screen cold hardiness in V. vinifera. This study provides a reference and accurate identification method for the selection of cold hardiness parents and the evaluation of cold hardiness of germplasm of V. vinifera.

Powder metallurgical processing of CrMnFeCoMo high entropy alloy: Phase evolution, microstructure, thermal stability and mechanical properties

The outstanding properties of the high entropy alloys (HEAs) are attributed to various factors like composition, microstructure, phase formation, synthesis route etc. In this regard, the present investigation deals with phase evolution, microstructure, thermal stability and microhardness properties of an equiatomic quinary Cr-Mn-Fe-Co-Mo high entropy alloy synthesized by mechanical alloying followed by pressure-less sintering. The structure and phase evolution with milling time was studied by x-ray diffraction technique. After completion of 40 h of milling, two simple solid solution phases with BCC structure (a = 3.146 ± 0.002 Å and 2.873 ± 0.002 Å) along with a minor amount of undissolved α-Mn were identified. Phase formation, chemical composition, thermal stability etc. were also evaluated using electron microscopy and differential thermal analysis (DTA) methods as well as in-situ high temperature x-ray diffraction technique. In the sintered sample, four phases consisting of two BCC solid solutions, σ (sigma) and μ (mu) type phases are observed to coexist and to be stable up to the melting point. The phase formation was predicted by Thermo-Calc approach and was compared with the experimental observation as well as other calculated results. The sintered samples were tested by instrumented hardness tester for evaluation of mechanical properties and was found to exhibit high hardness (9.3 ± 0.3 GPa) and Young’s modulus (∼245 ± 6 GPa).

Analysis of phase transformations of modified silicate xerogels during heat treatment

The ways of obtaining glass for dental cements with low synthesis temperature were analyzed. The xerogels of the SiO2–CaO–P2O5 systems were synthesized by sol-gel technology from affordable raw materials. The physicochemical processes, temperature regions of phase transformations and intensity of their course, which occur during heat treatment of xerogels of two series of the system at the SiO2 content of 50 wt.% and 60 wt.% were investigated by the method of differential thermal analysis. Analysis of the obtained results allowed us to affirm that all regions of phase transformations in the xerogel powders with 50 wt.% SiO2 content shifted to the lower temperature range. It was established that an increase in the temperature during heat treatment of the xerogel powders with different compositions led to the phase transformations: from a loose powdered state through a sintered state to the formation of a glassy state. It was determined that all samples are X-ray amorphous up to the temperature of 6500C. It was shown that increasing the CaO content in the composition of xerogels up to 30 wt.%, and accordingly increasing the ratio CaO:P2O5 from 1 to 6, leads to the absence of glass phase. The optimal ratio CaO:P2O5 is 2. The influence of Li2O and BaO on a decrease in the glass formation temperature was substantiated and experimentally confirmed by thermal analysis.

Electrical interactions in mixtures of ferroelectric powders

The results of studies of phase transitions in mixtures of C6H16NBr (DIPAB) powders with PbTiO3 and Pb(Zr0.52Ti0.48)O3 (PZT) by the method of differential thermal analysis (DTA) are presented. The measurements were carried out in the heating and cooling mode in the range from 300 to 440 K. It was found that electrical interactions between ferroelectric particles led to the appearance of additional phase transitions for DIPAB in powder mixtures. Interaction effects in mixtures of DIPAB and PbTiO3 as well as DIPAB and PZT powders depend on the magnitude of the dipole moments of the particles.

ТЕРМИЧЕСКИЙ АНАЛИЗ ПРОДУКТОВ ОКИСЛЕНИЯ АКТИВИРОВАННОГО СПЛАВА АЛЮМИНИЯ RAU-85 В РАЗЛИЧНЫХ ОКИСЛИТЕЛЬНЫХ СРЕДАХ

By methods of differential thermal and thermogravimetric analysis, the composition of the thermally active part of the studied multicomponent samples of the products of the interaction of the activated aluminum alloy with various oxidizers was determined, and their thermal behavior was revealed under conditions of dynamic temperature rise. Thermal analysis was carried out in air environment, in the temperature range from 20 to 1000°C. The heating mode of the furnace was linear (dT/dt = 10 grad/min), the reference substance was calcined Al2 O3 . Water, 3% aqueous solution of hydrogen peroxide, 5% aqueous solution of sulfuric acid were used as oxidizing agents. Establishment of the material composition of the active part of powder samples was carried out according to the morphologies of thermal curves and numerical values of the intensities of endo- and exothermic effects using the thermogravimetric readings of TG-lines associated with them. A series of endo- and exothermic effects revealed during the decomposition of the test samples made it possible to follow the order of the stage of their thermal destruction and quantitatively determine the composition of volatile components. A number of features of sample decomposition were established depending on their composition and weight ratios of thermally active sample components. The obtained data on the thermal analysis of the oxidation products of the activated alloy RAU-85 in various oxidizing environments can be successfully applied to develop a technology for cleaning the bottomhole zone of the well from asphalt resin paraffin deposits, based on the thermal gas-chemical interaction of the activated aluminum alloy and formation water, which results in the formation of a large amount of heat and vapor-gas mixture.

Crystal structure and physical properties of the quaternary phase CuGaxIn5–xS8, 1.4 ≤ x ≤ 2.05, in the Cu2S ​− ​Ga2S3 – In2S3 system

X-ray diffraction and differential-thermal analysis methods were used for investigation of the component interaction in the Cu2S ​− ​Ga2S3 – In2S3 system. The existence of the quaternary phase CuGaxIn5-xS8 where 1.4 ​≤ ​x ​≤ ​2.05 ​at 820 ​K was confirmed. The crystal structure of the quaternary phase was determined by X-ray powder method for the CuGa1.6In3.4S8 composition as the trigonal symmetry, S.G. P-3m, with the cell parameters a ​= ​0.38237(3) nm, c ​= ​3.0870(2) nm. Five vertical sections and the liquidus surface projection of the system were investigated. A single crystal CuGa1.9In3.1S8 was grown by solution-melt method, and its physical parameters such as bandgap energy and photosensitivity range were investigated.

THE DIFFERENTIAL THERMAL ANALYSIS OF COMPLEX CATALYTIC SYSTEM OF 50%Cu3(PO4)2•50%Ni3(PO4)2

The catalytic system of 50% Cu3(PO4)2∙50% Ni3(PO4)2 based on Copper (II) and Nickel (II) orthophosphates was synthesized by the coprecipitation method according to the method developed at the Department of Physical and Colloid Chemistry of Uzhhorod National University. The synthesized system was investigated by the method of differential thermal analysis. The obtained results can be interpreted in favor of the formation of a new phase, which is formed due to the equiatomic interaction of the initial components. Thus, a number of thermal effects different from Cu3(PO4)2∙3H2O and Ni3(PO4)2∙8H2O are observed on the corresponding thermogram. The only endothermic effect at 117 ° C is not recorded on the thermograms of the starting components. In the case of a solid solution or a simple mixture of phases based on starting phosphates, this effect should be observed at intermediate temperatures in the range from 129°C to 268°C. Probably, the newly formed phase, by the number of moles of water of crystallization, differs from the original individual orthophosphates. Information about a more accurate number of molecules of chemically bound water in hydrated forms of the synthesized complex copper-nickel phosphate catalyst will allow to establish the results of additional studies by derivatographic or gravimetric analyzes, which were not performed in this work. After dehydration with a further increase in temperature, no endothermic effect for a complex catalytic system is observed. Instead, four exothermic effects are recorded at once: the first two - at 456ºС and 564ºС (both insignificant in area), and the next two at slightly higher temperatures - 658ºС and 777ºС (larger in area). The effects at 564ºC and 658ºC can be attributed to the crystallization of dehydrated Cu3(PO4)2. The exoeffect at 777°C corresponds to the formation of the structure of dehydrated orthophosphate Nickel Ni3(PO4)2. Thus, the obtained experimental data of differential thermal analysis confirm the effective modifying role of Ni2+ ions on the structure, phase formation and a number of physicochemical properties of copper (II) phosphate in the synthesis of a complex oxide catalyst. This made it possible to obtain a new cheap and active complex acid catalyst with improved catalytic properties of 50 % Cu3(PO4)2∙50 % Ni3(PO4)2, which can be used for the process of converting natural gas components into valuable products of the chemical industry.
 Keywords: differential thermal analysis (DTA); catalysts; сopper (II) orthophosphate; nickel (II) orthophosphate; catalytic 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 system.