Eutectic Equilibrium Research Articles

Calculation of liquidus in eutectic alkali halide mixtures using thermodynamic perturbation theory

A statistical-thermodynamic model that makes it possible to describe with good accuracy phase equilibria between melt and crystal in binary alkali halide mixtures with common cations and anions is proposed. This model is based on the thermodynamic perturbation theory, which takes into account the charge-dipole contribution to the interionic interaction of binary molten salts using a multicomponent mixture of charged hard spheres as a reference system. Specific expressions for chemical potentials, taking into account the charge-induced dipole interaction in the molten phase, are presented within the developed approach. Considering binary eutectic mixtures NaF–NaCl, CsF–CsCl, NaF–CsF, and NaCl–CsCl as an example, the liquidus curves obtained in two series of calculations are shown: with the equation of state and without it. The discrepancies between the calculated and experimental data on the position of eutectic equilibrium for most of the considered mixtures do not exceed about 10 percent on the temperature scale and 5 percent on the composition when using only the tabulated values of ionic radii and polarizabilities without any adjustment.

Фазовое поведение и растворимость компонентов двойной системы масляная кислота–полиэтиленгликоль-1500

A critical review of the literature on the methods of concentration and extraction of biobutyric acid from fermentation solutions has been carried out. The best results of these processes are achieved by combining extraction with salting. It is proposed to use polyethylene glycols with different molecular weights as non-flammable and environmentally friendly extractants. The purpose of the study was to identify the phase behavior of mixtures of components, study solubility and construct a phase diagram of the previously unexplored double system butyric acid – PEG-1500 in the range −10.0–50.0°C. The transition temperatures of phase states in mixtures of components of the dual system butyric acid (BA) – polyethylene glycol-1500 (PEG-1500) in the temperature range −10–50°C have been found by the visual-polythermal method. The phase diagram above the eutectic line shows a large crystallization field of PEG-1500, while the crystallization field of BA has very small dimensions. It has been established for the first time that eutectic equilibrium is carried out in the system at −6.6°C, the solid phases of which are crystals of BA and PEG-1500, the composition of the liquid phase of eutectic (3.20 wt.% BA) has been determined. A method for concentrating BA and separating the components of the investigated system based on the crystallization of PEG-1500 during cooling of mixtures is proposed.

An investigation of structural, thermo-physical, and photoelectric properties of glassy As2Se3–Tl2Te3 alloys

Glass formation and the nature of the chemical interaction in the As2Se3–Tl2Te3 system were studied by differential-thermal (DTA), X-ray phase (XRD), microstructural (MSA) analysis. Based on the performed experiments T-x phase diagram is constructed. It is established that the phase diagram of the system is a partially quasi-binary section of the quaternary system Tl,As//Se,Te. Eutectic equilibrium and peritectic transformation process occur in the system. When the ratio of As2Se3 and Tl2Te3 components is 1:1, a new quaternary compound Tl2As2Se3Te3 is formed. It has been established that the Tl2As2Se3Te3 compound melts with an open maximum at 568[Formula: see text]K and crystallizes in a hexagonal symmetry. In the system, under normal cooling, the glass formation area reaches −80[Formula: see text]mol.% Tl2Te3, and in the mode of quenching in liquid nitrogen up to −100[Formula: see text]mol.% T12Te3. The photoelectric properties of glassy alloys (As2Se[Formula: see text](Tl2Te[Formula: see text] ([Formula: see text]; 0.3; 0.05) have been studied. Depending on the Tl2Te3 concentration of the system, the observed changes in the photoelectric properties and calculated parameters are presented.

Modeling of temperature-concentration ranges of phase stability and liquidus surface in the ternary Fe–P–C system and phase composition experimental study

This paper reports thermodynamic properties and phase equilibria in the iron-phosphorus-carbon system for developing a technology for smelting ferrophosphorus as well as for utilizing them in the processes of phosphorus-alloying of metals. According to the results of thermodynamic calculations, we plotted a ternary Fe–P–C phase equilibrium diagram (liquidus surface) in the form of graphical dependences, which indicate the concentration fields of phase coexistence. The results of simulation allowed finding out five nonvariant points, three of which are new: E1 eutectic (teutectic=12170С), U1 peritectic (tperitectic=10950С), and Е3 eutectic (teutectic=3380С). The experimental studies of the phase composition of ferrophosphorus showed that the phosphorus microstructure is represented by Fe3P phosphide, Fe3C carbide, and carbophosphide eutectic. We carried out the thermodynamic calculation of the temperature-concentration ranges of phase stability in the Fe–P–C system that are at equilibrium with the smelts of both the carbon solid solutions and phosphorus ones in - and -iron, FeP, Fe2P, Fe3P phosphides, and graphite. In this study, three previously unknown nonvariant equilibria have been determined: a eutectic equilibrium at 1216.580C; a peritectic one with a transformation point at 1095.190C; and a eutectic one at a temperature of 337.510C. In experiments, we obtained an equilibrium concentration of carbon which decreases in the Fe–P–C system when the content of phosphorus increases. The research findings largely reveal special features of preparation of ferrophosphorus by carbon reduction of phosphorites.

SYNTHESIS AND PHYSICO-CHEMICAL INVESTIGATION OF ALLOYS OF THE Sb2S3–Cu2Cr4Te7 SYSTEM

To study the nature of the interaction between Sb2S3 and Cu2Cr4Te7 compounds, alloys were synthesized in a wide range of concentrations and studied using physicochemical analysis (DTA, XRD, MSA, as well as measurements of density and microhardness) and a phase diagram was constructed. The state diagram of the system is partially quasi-binary, with the formation of eutectic equilibrium and peritectic transformation. The regions of homogeneity in the Sb2S3–Cu2Cr4Te7 system were determined from the initial components. In a system based on the Sb2S3 compound, solid solutions reach up to 4 mol % Cu2Cr4Te7, and solid solutions based on Cu2Cr4Te7 – up to 10 mol % Sb2S3 at room temperature. The temperature dependence of electrical conductivity and thermo-emf has been studied. 1, 2 and 4 mol % Cu2Cr4Te7 solid solutions of alloys of the Sb2S3–Cu2Cr4Te7 system in the temperature range of 20–2500C

Ho–Co and Ho-Co-Fe phase diagrams

Phase equilibria in the Ho-Co-Fe ternary and the boundary binary Ho–Co systems are investigated using differential thermal analysis, scanning electron microscopy, electron-probe microanalysis, and X-ray diffraction. Based on the experimental results, the binary Ho–Co phase diagram was revised resulting in confirmation of the general features of the previously published phase diagram, except for the mode of formation of the Ho3Co compound. The temperatures of most invariant reactions were adjusted. The ternary Ho-Co-Fe phase diagram was constructed over the whole concentration range. The liquidus and solidus projections, Scheil reaction scheme and isothermal sections at 1250, 1200 and 1000 °C are presented. The most prominent feature of this system is existence of three continuous solid solutions Ho2(Co,Fe)17, Ho(Co,Fe)3 and Ho(Co,Fe)2, which define the character of the solidus projection. Other binary compounds have significant solubility of third component. Among them Ho6Fe23 has a widest homogeneity range and dissolves up to 28.0 at.% Co at all studied temperatures. All intermetallic phases are linear phases in terms of holmium. Five four-phase invariant reactions are found. One of them is of eutectic type and four ones are of U-type. Four invariant three-phase eutectic equilibria are present in the system.

On the pressure dependence of salty aqueous eutectics

The eutectic is fundamental to multicomponent systems, defining the lowest temperature at which a given liquid phase is stable. Although binary aqueous eutectics have been broadly characterized at atmospheric pressure, eutectic data at high pressure are scarce, leaving critical gaps both in the data available for modeling and in our understanding of how eutectic equilibria may evolve with pressure. In this work, we deploy a simple, high-throughput, isochoric freezing method to measure the pressure dependences of five binary aqueous eutectics, chosen for their importance in compositional modeling of the distant icy planets deemed most likely to harbor life. Our data reveal that the pressure dependence of all the eutectics measured herein can be approximated by the pressure dependence of the ice Ih melting curve, providing a key rule of thumb for future analysis, and we further demonstrate multiple methods by which additional thermophysical properties of these high-pressure eutectics may be extracted from the measured pressure-temperature coordinates. • Characterize high-pressure eutectics for several aqueous binaries • Eutectic pressure dependences approximately follow pressure-melting curve of ice Ih • Develop methods to extract additional eutectic properties from measured P-T curves • Isochoric freezing method enables high-throughput measurement of multiphase equilibria The eutectic defines the threshold of stability for liquid phases, and high-pressure eutectic data are essential to the modeling of icy worlds. Chang et al. acquire measurements of the pressure dependences of five salty aqueous eutectics, providing both reference data and physical insight into the pressure evolution of the eutectic temperature.

PHASE EQUILIBRIUM IN THE Sb2Te3-HoTe3 SYSTEM

The phase equilibrium of the Sb2Te3-HoTe3 system was studied by means of physical and chemical analysis methods DTA, RFA, MQA, as well as density and microhardness measurements, and its phase diagram was constructed. It has been determined that the Sb2Te3-HoTe3 system is a partial quasi-binary cross section of the ternary Bi-Ho-Te system. The system undergoes a process of eutectic equilibrium and peritectic transformation. In the Sb2Te3-HoTe3 system at room temperature, of the based Sb2Te3 solid solutions extend to 4.5 mol % and of the based HoTe3 solid solutions have practically not been established.

PHASE EQUILIBRIUM IN THE As2Te3-Cu2Cr4Te7 SYSTEM

The alloys of the As2Te3-Cu2Cr4Te7 system were investigated by methods of physicochemical analyzes (DTA, XRD, MSA, as well as density and microhardness measurements) and its phase diagram was constructed. Studies have shown that the As2Te3-Cu2Cr4Te7 system is a partially quasi-binary section of the As2Te3-Cr2Te3-CuTe quasiternary system. In a system at room temperature based on As2Te3, solid solutions reach 3.5 mol %, and based on the Cu2Cr4Te7 solid solutions reach up to 17 mol %. Eutectic equilibrium and peritectic transformation occur during chemical interactions between As2Te3 and Cu2Cr4Te7 compounds in the system.

REFINEMENT OF THE PHASE DIAGRAM OF THE MnTe–In2Te3 SYSTEM

The MnTe–In2Te3 system was re-investigated by DTA and XRD methods, and its phase diagram was constructed somewhat differently from the previously known ones. It was found that the system is characterized by the formation of the MnIn2Te4 compound congruently melting at 1025 K with a wide (49–67 mol% In2Te3) homogeneity region. This phase is in eutectic equilibrium (1015 K) with solid solutions based on lt-MnTe (lt – low temperature) and in peritectic equilibrium with solid solutions based on In2Te3. A comparative analysis of the results obtained with the literature data is carried out

SYNTHESIS AND PHYSICO-CHEMICAL STUDY OF THE Bi2Te3-HoTe3 SYSTEM

The physicochemical study of the Bi2Te3-HoTe3 system was carried out by differential thermal (DTA), X-ray phase (XRD), microstructural (MSA) methods, as well as by measuring the microhardness and determining the density, and a T-x phase diagram was constructed. It was found that the Bi2Te3-HoTe3 system is a partially quasibinary section of the Bi-Ho-Te ternary system. The system is undergoing eutectic equilibrium and peritectic transformation. Solid solutions based on Bi2Te3 at room temperature reach 6 mol % HoTe3, while solid solutions based on HoTe3 have practically not been established.

Фазовая диаграмма двойной системы β-аланин – вода

The phase diagram of the β-alanine–water binary system was studied using the visual polythermal method and the method of time–temperature curves in а temperature range of -20–90°С. There is a eutectic equilibrium at -18.3°С in the system; the solid phases of this equilibrium are ice and individual β-alanine. For the first time, the composition of the liquid phase of the eutectic state was determined.

Construction of Gallium–Tin Nonequilibrium State Diagram and Its Analysis

Overcooling of gallium–tin alloys under normal conditions has been studied by thermal analysis. The following samples have been analyzed: Ga (I); two hypoeutectic alloys: 95% Ga + 5% Sn (II), 90% Ga + 10% Sn (III); eutectic alloy: 96.3% Ga + 13.7% Sn (IV); and five hypereutectic alloys with Sn content of 20% (V), 35% (VI), 50% (VII), 80% (VIII), and pure tin (IX). A nonequilibrium state diagram of this system is constructed. Herewith, the eutectic composition does not vary and the eutectic temperature decreases to 5.5°C, that is, 26°C below that of three-phase eutectic equilibrium. The eutectic temperature does not actually vary upon a variation of cooling rates of eutectic alloy from 0.06 to 60°C/min. It has been detected that a slight decrease in overcooling is expected in the hypoeutectic region, whereas in the hypereutectic region overcooling increases while the alloy composition approaches eutectic. Activities and activity coefficients of components on the lines of equilibrium and nonequilibrium liquidus have been calculated. It is demonstrated that the activities on the lines of both equilibrium and nonequilibrium liquidus decrease in a predictable manner, and the activity coefficients increase while the composition approaches eutectic. Concentration paths of equilibrium and nonequilibrium crystallization are shown in the state diagrams.

Effect of the Phase Composition and the Microstructure on the Microhardness of As-Cast Cu–Ce–La Alloys

The Cu–Ce–La system is of interest for the production of both rare-earth-added bronzes and amorphous alloys. In this work, we investigate the phase composition, the microstructure, and the microhardness of 13 as-cast Cu–Ce–La samples corresponding to the copper angle of the Cu–Ce–La phase diagram. The experimental samples are studied by optical microscopy, scanning electron microscopy, electron microprobe analysis, atomic emission analysis with inductively coupled plasma, X-ray diffraction, and differential thermal analysis. The Vickers microhardnesses of the samples are measured. The microstructure of the samples is characterized by the presence of a eutectic, which is observed at Cu-based solid-solution grain boundaries and, according to electron microprobe analysis data, contains copper, lanthanum, and cerium. The X-ray diffraction analysis data also indicate the presence of the Cu6Ce and Cu6La compounds along with the Cu-based solid solution. The volume fraction of the eutectic component is determined (it is equal to the fraction of the area corresponding to the eutectic in the section of a sample). As the Ce and La contents increase, the fraction of the eutectic component increases. According to thermal analysis data, the ternary eutectic equilibrium takes place along with the binary eutectic equilibria. Significant correlation between the fraction of eutectic component in the microstructure and the hardness of the experimental samples is shown to exist. As the fraction of eutectic in the microstructure increases, microhardness HV also increases. The obtained results are of interest for materials scientists for analyzing the effect of rare-earth metal additions on the phase composition, the microstructure, and the mechanical characteristics of copper alloys.

Phase Equilibria in the MnGa2Tе4-MnIn2Tе4 System, Crystal Structure and Physical Properties of MnGaInTе4

The phase equilibria in the MnGa2T?4-MnIn2T?4 system were experimentally investigated by means of differential thermal analysis and powder X-ray diffraction technique. It was found that this system is quasi-binary and characterized by dystectic and eutectic equilibria and the formation of a wide area of solid solutions based on the starting compounds. The crystal structures of the MnGaInTe4 and MnIn2T?4 were refined by the Rietveld method using powder X-ray diffraction data. It was established, that both phases crystallize in the tetragonal system (Space group I-42m). Electron paramagnetic resonance and Raman spectra, as well as the temperature dependences of the electrical conductivity and the Hall effect for the MnGaInTe4 crystal, were studied.

PHYSICO-CHEMICAL INTERACTION IN THE Tl4PbTe3–Tl9BiTe6–TlBiTe2

Using DTA, XRD and mathematical modelling methods the character of physicochemical interaction in the Tl4PbТe3–Tl9BiTe6–TlBiTe2 quasiternary system was studied, the isothermal section at the temperature of 473 K, projection of the liquidus surface and 3D state phase diagram was investigated. The detailed course of the lines of monovariant equilibria is established by the using of polynomial analysis. Formation of the new compounds in the Tl4PbТe3–Tl9BiTe6–TlBiTe2 system is not found.The main purpose of this scientific work was to establish the possibility of modifying the composition of the initial ternary compounds of thallium (I) Tl4PbTe3, Tl9BiTe6 та TlBiTe2, by experimentally studying of physico-chemical interaction on the basis of their.This quasiternary system is formed by three quasibinary sections, two of which belong to eutectic type Tl4PbТe3–TlBiTe2 (the eutectic е2 – 36 mol.% TlBiТe2, 756 К) and Tl9BiTe6–TlBiTe2 (the eutectic е1 – 52 mol.% Tl9BiTe6, 775 К), and the Tl4PbТe3–Tl9BiTe6 system, which is characterized by the formation of unlimited solid solutions without extreme points on the liquidus and solidus curves.To study the physico-chemical interaction in the Tl4PbТe3–Tl9BiTe6–TlBiTe2 system was synthesed a number of points. The synthesis of binary, ternary compounds and the number of alloys was carried out in evacuated (0.13 Pa) quartz ampoules using a direct one-temperature method. The maximum synthesis temperature on 50-70 K exceeds the melting point of the most initial component. Annealing was performed for 480 hours at a temperature of 473 K. Cooling to room temperature – in the mode of the off oven.On the basis of the obtained results it was established that the fields of primary crystallization intersect along the line of monovariant eutectic equilibrium e1-e2. This monovariant eutectic process L«(Tl4PbTe3)х(Tl9BiTe6)1–х+(TlBiTe2) takes place in the temperature range from 778 K (eutectic e1) to 763 K (eutectic e2). The character of the physico-chemical interaction in the quasiternary system Tl4PbТe3–Tl9BiTe6–TlBiTe2 describes well the plot space phase diagram.

Long – Time relaxation in liquid eutectics

For binary systems with eutectic equilibrium, the existence of liquid – liquid critical point in the solid – liquid two-phase area is established. The width of corresponding fluctuation region is estimated by Ginsburg-Levanyuk criterion, and it is shown to constitute up to several hundred degrees. Thus, in that wide region, the system should be described in terms of critical dynamics, which implies the critical slowing – down and non-monotonic relaxation.

ФАЗОВАЯ ДИАГРАММА СИСТЕМЫ FeGa2Se4-FeIn2Se4 И КРИСТАЛЛИЧЕСКАЯ СТРУКТУРА FeGaInSe4

Методами дифференциального термического анализа (ДТА) и рентгенофазового анализа (РФА) изучены фазовые равновесия в системе FeGa2Se4-FeIn2Se4. Установлено, что она квазибинарна и характеризуется образованием широких областей твердых растворов со стороны исходных соединений FeGa2Se4 (a-фаза) и FeIn2Se4 (b-фаза). b-фаза состава FeGaInSe4 плавится конгруэнтно при 1222 К и кристаллизуется в тригональной сингонии (Пр. гр. R3m) с параметрами решетки: а = 0.39290(1) нм, с = 3.8542(6) нм. С использованием порошковых дифракционных данных методом Ритвельда определена заселенность кристаллографических позиций в FeGaInSe4 и показано, что она качественно отличается от таковой для FeIn2Se4.
 
 Работа выполнена в рамках научной программы международной лаборатории “Перспективные материалы для спинтроники и квантовых вычислений”, созданной на базе Института катализа и неорганической химии НАНА (Азербайджан) и Международного физического центра Доностиа (Испания).

Phase diagram of the Sn–P system

The T–x diagram of the Sn–P system was studied by differential thermal analysis, X-ray phase analysis and local X-ray spectral microanalysis. An optical tensimetric method was used to evaluate the saturated vapor pressure of phosphorus. The method consists of in situ scanning of electronic absorption spectra of steam at different temperatures in order to obtain quantitative information about the vapor phase. In the concentration range 43–70 mol% P of the system investigated, a single eutectic equilibrium with participation of higher tin phosphides was found: L ↔ Sn4P3 + SnP3. The Sn3P4 intermediate phase is formed only during prolonged annealing of the samples at a temperature of less than 623 K. A P–T–x diagram of the Sn–P system was constructed by a combination of differential thermal analysis and optical tensimetric methods. The coordinates of the four-phase equilibrium points were found: for the synthetics equilibrium Sn4P3 ↔ V + L1 + L2, the vapor pressure is 0.6 atm at 838 ± 2 K; for the eutectic equilibrium L ↔ V + Sn4P3 + SnP3 2.8 atm.

Química mineral e condições de cristalização do Plúton Granítico Barcelona, extremo nordeste da Província Borborema, Nordeste do Brasil

O Plúton Granítico Barcelona (PGB) localiza-se na porção extremo nordeste da Província Borborema, oeste do Domínio São José do Campestre, com idade Ediacarana presumida. O PGB é formado por três fácies petrográficas/texturais distintas, a fácies granito porfirítico dominante no PGB, a partir da análise de micropetrografia associada às análises de química mineral. A fácies granito porfirítico (biotita monzogranito) possui plagioclásio (oligoclásio com An25-20%), K-feldspato (microclina pertítica) e quartzo compondo sempre (> 70 % modal). O anfibólio é a hastingsita com moderadas razões Mg/(Mg+Fe), pressões de cristalização entre 5,0-6,0 kbar e temperatura de 700°C, finalizando com 3,0-5,0 kbar e 500°C no eutético ternário granítico. O conteúdo de AlT do anfibólio, os valores de pistacita Ps = 28 no epídoto e o processo de martitização da magnetita é indicativa de ambiente com ƒO2 moderada a elevada. As biotitas possuem trend com leve tendência para o pólo da annita, denotando reequilíbrio em estágio subsolidus/tardi-magmático. Em diagramas discriminantes de séries magmáticas as biotitas se comportam como às de afinidade geoquímica subalcalina, coerentes com a cálcio-alcalina médio a alto K dos granitos porfiríticos. Zonação em cristais de plagioclásio, K-feldspato e allanita, é indicativo da importância do processo de cristalização fracionada na evolução/cristalização da fácies porfirítica deste plúton. A atuação de fluidos ricos em H2 O e CO2 propicia a transformação tardia de biotita e feldspatos, além de geração de mirmequitas. A presença de agregados de pequenos cristais de plagioclásio mirmequíticos exibindo contatos com ângulos de 120° indica cristalização em equilíbrio eutético.