Phase Equilibria Research Articles

Phase relations in the La2O3-ZrO2-HfO2 system at 1250 °C and 1500 °C

In the present study, the phase equilibria in the ternary system La2O3-ZrO2HfO2 have been studied in the whole concentration range. In the course of the study, isothermal sections of the phase diagram of the system were constructed at temperatures of 1500 and 1250 °C. The obtained results indicate the no new phase formation in the studied system. It was found that in the La2O3-ZrO2HfO2 ternary system at temperatures of 1500 and 1250 °C, solid solutions are formed on the basis of monoclinic (M, space group P21/C) HfO2 and tetragonal (T, space group P42/nmc) modifications of ZrO2, solid solutions based on a hexagonal modification (A, space group P3m1) of La2O3, and an ordered phase with a pyrochlore-type structure of La2Zr2О7 (La2Hf2О7) (Py, space group Fd-3 m). The system studied is characterized by the formation of a continuous series of solid solutions with a pyrоchlore-type structure. A decrease in temperature from 1500 °C to 1250 °C leads to the shift of the three-phase region, containing solid solutions based on a pyrochlore-type structure of Ln2Zr2О7 (Ln2Hf2О7), monoclinic M-HfO2, and tetragonal T-ZrO2, towards the concentration area with higher ZrO2 content and also to an increase in the extent of the solid solution based on the monoclinic modification M-HfO2.

Phase Equilibria in the Na+,K+//Cl–,NO$$_{3}^{ - }$$–H2O System near Boiling Temperatures. I. Modeling of Ternary Systems

Phase Equilibria in the Na+,K+//Cl–,NO$$_{3}^{ - }$$–H2O System near Boiling Temperatures. I. Modeling of Ternary Systems

Phase Equilibrium for Hydrofluorocarbon R134a Hydrate. Hydrate-Based Desalination of NaCl Salt Solution

Phase Equilibrium for Hydrofluorocarbon R134a Hydrate. Hydrate-Based Desalination of NaCl Salt Solution

Binary phase separation in strongly coupled plasma

We investigated the two-dimensional binary phase separation process of plasma species using classical molecular dynamics in the strongly coupled regime. Both the plasma species interact via a pairwise screened Coulomb (Debye–Hückel) potential; however, the screening parameter κ is different for like- and unlike-species and is the cause for phase separation. We characterize the separation process by measuring the domain growth of equilibrium phases as a function of time—generally, the more significant the inhomogeneity in pairwise interaction, the faster the domain growth. Typically, the domain growth follows a power law in time with an exponent β characterizing the underlying coarsening mechanism. We demonstrate that the growth law exponent is β=1/2 for equal-number-density mixtures and 1/3 otherwise. Further, by comparing these with the corresponding growth laws in binary mixtures of viscous fluids, we show that the viscoelastic nature of plasma fluid modifies the coarsening dynamics, which in turn leads to the observed growth law exponents, notably in the unequal-number-density case.

A ~957 Ma Metamorphism in the Mesoarchaean Hindoli Group Supracrustal Rocks from the Jahazpur Shear Zone, East Rajasthan (India): Constraints from Sm-Nd Dating and Phase Equilibria Modeling

ABSTRACT A petrological-chronological investigation of the Hindoli Group of rocks within the Jahazpur Shear Zone in the eastern segment of the Aravalli Delhi Fold Belt (ADFB), NW India, has been conducted. We infer two stages of deformation (D1 and D2) and metamorphism (M1 and M2) for the garnet - muscovite - biotiteschists interleaved with meta dolomite, Banded Iron Formation (BIF) amphibolite, and foliated granite. The D2 deformation corresponds to the northeast-trending Jahazpur shear zone on a regional scale. Garnet porphyroblasts, syntectonic with the D2 deformation, are chemically zoned with spessartine-rich cores. Geothermobarometry and pseudosection analyses yield peak P-T conditions of ~7.5 kbar, 580°C, followed by decompression and cooling along a clockwise P-T path. The Sm-Nd isotope analysis of the whole rock yields a date of ~3.0 Ga from an amphibolite. This data is interpreted as the age of formation of the litho-units of the Hindoli Group. Sm-Nd analyses of garnet grains yield an age of ~957 Ma. This date corresponds with the age of nucleation of the Jahazpur shear zone. A good correlation is established between the Neoproterozoic crustal segments of the Jiangnan Fold Belt of the South China Craton and that of the ADFB during the formation of the Rodinia Supercontinent.

Determination of hydrate phase equilibrium (H-L-V) data for the binary CO2–CH4 gas mixture in the presence of 1,3 dioxolane

Present work details the determination of three phase hydrate equilibrium data (H-L-V) using temperature search method for the binary CO2/CH4 gas mixture (50:50 molar ratio) in presence of 1,3 dioxolane (DIOX). DIOX concentration used for phase equilibrium determination were 1,3 and 5.56 mol% respectively. In the presence of DIOX, it was observed that phase equilibrium curve was shifted right with respect to the curve using same gas mixture with no additive (pure water). This indicates that the presence of DIOX moderates the hydrate formation equilibrium conditions. Also, as DIOX concentration increases from 1 mol% to 5.56 mol%, a decrement in phase equilibrium pressure at same temperatures was observed, confirming the potential of DIOX as an effective thermodynamic promoter. Enthalpy of hydrate dissociation was calculated for CO2/CH4 gas mixture in presence of DIOX using Clausius- Clapeyron plot and it was found to be 90.81±6.55 KJ/mol which confirms the sII structure of CO2-CH4-DIOX mixed hydrate. Besides providing the phase equilibrium data of formed hydrates with CO2/CH4 gas mixture using different concentration of DIOX, the present study will aid in determining suitable experimental conditions for examining kinetics and performing separation studies of CO2/CH4 gas mixture through hydrate formation.

Phase equilibrium and mixing thermodynamics of polystyrene with copolymers of styrene and methyl methacrylate

AbstractData on the solubility of oligomer polystyrene and random copolymers of styrene and methyl methacrylate with different styrene contents have been obtained. Phase diagrams were constructed and the values of critical points were determined. The upper critical solution temperature is localized in the temperature range above 420 K and grows with increasing molecular weight of PS and decreasing styrene content in the copolymer. Based on the compositions of the coexisting phases, paired interaction parameters were calculated and their temperature dependences were plotted. The dependence of the interaction parameter on the copolymer composition and the correlation dependence between its enthalpy and entropy components were constructed. A method for simulation phase equilibrium for copolymers of arbitrary composition and molecular weight is proposed.

Influence of substitution of Cr by Cu on phase equilibria and microstructures in the Fe–Ni–Co–Cr high-entropy alloys

The article describes how substitution of chromium by copper affects phase equilibria in Fe–Ni–Co–Cr high-entropy alloy. The alloys with copper content ranging from 0 to 20 % (at.) of Cu were prepared. The alloys were equilibrated at 900, 800, 700, and 650 °C. The samples were investigated by electron microscopy, EDX spectroscopy, and EBSD method. The face-centred cubic phases have only occurred in equilibrated alloys: austenite matrix, copper-rich FCC(Cu) phase, and regions containing these phases. The compositions of equilibrated samples at annealing temperatures are given. Fine microstructures including a semicoherent FCC phase rich in Cu and an FCC phase including the main magnetic elements (Fe, Co, Ni) were formed. The experimental results were compared with the calculated phase equilibria obtained by the CALPHAD method.

A robust and efficient solution for COSMO-based activity coefficient models

COSMO-based activity coefficient models, such as COSMO-RS and COSMO-SAC, offer a powerful tool that bridges quantum chemical calculations with macroscopic phase equilibrium calculations. These models utilize a group contribution methodology similar to UNIFAC but require an expensive numerical solution of the self-consistency equation for interactions among all surface segments, representing a primary bottleneck in their application to analyses that involve extensive phase equilibrium calculations. This work demonstrates that the self-consistency equation can be derived by minimizing the system energy from all pairwise segment interactions. The derivation leads to an optimization-based second-order solution procedure that ensures convergence and enhances efficiency. We demonstrate the robustness and efficiency of the proposed solution using various examples, including a comparison with the classical successive substitution method, and illustrate that COSMO-based models can be coupled with modern second-order convergent algorithms for phase equilibrium calculations. Furthermore, this work reveals the similarity between COSMO-based models and the SAFT method.

In-situ scattering and calorimetric studies of crystallization pathway and kinetics in a Cu-Zr-Al bulk metallic glass

The crystallization route and kinetics of a Cu-Zr-Al bulk metallic glass (BMG), based on Cu50Zr50, were investigated using in-situ synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS), in-situ high-energy X-ray diffraction (HEXRD), and differential scanning calorimetry (DSC). The acquisition of kinetic diagrams of SAXS/WAXS enables the direct construction of the overall phase transformation route from room temperature to the onset temperature of solid state phase transformation upon heating. It is revealed that the studied alloy undergoes multiple steps (at least five steps) before reaching the high-temperature thermodynamic equilibrium. This is distinct from the commonly believed simple path of glass → Cu10Zr7 + CuZr2 → B2-CuZr predicted by the Cu-Zr equilibrium phase diagram. In addition to thermodynamics, we emphasize that kinetic factors play a prominent role in the phase transformation process of Cu-Zr-Al BMGs. Furthermore, isothermal crystallization kinetics analyses conducted by in-situ HEXRD and DSC indicate that the formation of the initial crystalline phase, specifically the Cu10Zr7, follows an interface-controlled quasi-polymorphic process with an increasing nucleation rate. The findings of this study may provide novel insights into the crystallization mechanism of glass-forming supercooled liquids from a thermophysical perspective.

Equilibrium phase behavior of gyroid-forming diblock polymer thin films.

Thin-film confinement of self-assembling block polymers results in materials with myriad potential applications-including membranes and optical devices-and provides design parameters for altering phase behavior that are not available in the bulk, namely, film thickness and preferential wetting. However, most research has been limited to lamella- and cylinder-forming polymers; three-dimensional phases, such as double gyroid (DG), have been observed in thin films, but their phase behavior under confinement is not yet well understood. We use self-consistent field theory to predict the equilibrium morphology of bulk-gyroid-forming AB diblock polymers under thin-film confinement. Phase diagrams reveal that the (211) orientation of DG, often observed in experiments, is stable between nonpreferential boundaries at thicknesses as small as 1.2 times the bulk DG lattice parameter. The (001) orientation is stable between modestly B-preferential boundaries, where B is the majority block, while a different (211)-oriented termination plane is stabilized by strongly B-preferential boundaries, neither of which has been observed experimentally. We then describe two particularly important phenomena for explaining the phase behavior of DG thin films at low film thicknesses. The first is "constructive interference," which arises when distortions due to the top and bottom boundaries overlap and is significant for certain DG orientations. The second is a symmetry-dependent, in-plane unit-cell distortion that arises because the distorted morphology near the boundary has a different preferred unit-cell size and shape than the bulk. These results provide a thermodynamic portrait of the phase behavior of DG thin films.

Phase equilibria relations in the V2O5-rich part of the Fe2O3-TiO2-V2O5 system at 1200°C related to converter vanadium-bearing slag

Phase equilibria relations in the V2O5-rich part of the Fe2O3-TiO2-V2O5 system at 1200°C related to converter vanadium-bearing slag

Designing type V deep eutectic solvents with antimalarial pharmaceutical ingredients

This work studies the formation of deep eutectic solvents formed by one active pharmaceutical ingredient (quinine, pyrimethamine, or 2-phenylimidazopyridine) and a second component potentially acting as an excipient (betaine, choline chloride, tetramethylammonium chloride, thymol, menthol, gallic acid, vanillin, acetovanillone, 4-hydroxybenzaldehyde, syringaldehyde, propyl gallate, propylparaben, or butylated hydroxyanisole), aiming to address challenges regarding drug solubility, bioavailability, and permeability. A preliminary screening was carried out using the thermodynamic model COSMO-RS, narrowing down the search to three promising excipients (thymol, propyl gallate, and butylated hydroxyanisole). Nine solid–liquid equilibrium (SLE) phase diagrams were experimentally measured combining the three model drugs with the screened excipients, and using a combination of a visual melting method and differential scanning calorimetry. Negative deviations from thermodynamic ideality were observed in all nine systems. Furthermore, a total of four new cocrystals were found, with powder and single crystal X-ray diffraction techniques being employed to verify their unique diffraction patterns. In the thermodynamic modelling of the SLE diagrams, two COSMO-RS parametrizations (TZVP and TZVPD-FINE) were also applied, though neither consistently delivered a better description over the other.

Pressure–temperature evolution, protolith characteristics and tectonic setting of granulite facies rocks from Laojinchang area in the Longgang Block, China

The Archean supracrustal rock series in the Laojinchang area of Jilin Province, China provide valuable insights into the Precambrian geological evolution of the North China Craton. This study presents new results on petrography, geochemistry, mineralogy, isotope geochronology and phase equilibrium modeling of the Laojinchang granulite facies metamorphic rocks. The protolith ages of garnet two-pyroxene granulite and amphibolite from Sidaolazihe Formation, and two-pyroxene granulite from Laoniugou Formation are 2565 ± 5.9 Ma, 2512 ± 17 Ma, and 2509.2 ± 8.6 Ma, respectively, with the metamorphic age recorded by amphibolite being 2475.6 ± 9 Ma. New geochemical data indicates that TTGs (tonalite-trondhjemite-granodiorite) weathering in an island arc environment formed the protolith of argillaceous gneiss of Sidaolazihe Formation. Basaltic andesite, formed under an island arc environment, was the protolith of garnet two-pyroxene granulite of Sidaolazihe Formation; while calc-alkaline basalt was the protolith of amphibolite from the same formation and two-pyroxene granulite from Laoniugou Formation. All these Archean supracrustal rocks exposed in the Laojinchang area have recorded nearly isobaric cooling (IBC) anticlockwise P-T paths with distinct prograde, peak and post-peak stages. The peak P-T conditions reached granulite facies, suggesting a heat source from underplated magmas. A tectonic model involving an island-arc setting is proposed for the evolution of these Neoarchean supracrustal rocks in Laojinchang area.

Lawsonite eclogite records subduction rheology and slab detachment, Faro, Yukon-Tanana Terrane, Yukon Territory, Canada

Lawsonite eclogites represent cold subduction in the rock record, and new localities provide rare natural field laboratories to investigate deep deformation processes. We present a new lawsonite eclogite locality near Faro, Yukon Territory, Canada, the first reported lawsonite eclogite locality of the Yukon-Tanana Terrane. The discovery indicates that mid- to Late Permian subduction in the Yukon-Tanana Terrane subducted cold material in an oceanic subduction zone, in contrast to most previous models. We define a pressure-temperature-deformation (P-T-d) pathway for the lawsonite eclogites using a combination of microstructures, mineral compositional mapping, crystal orientation mapping, and phase equilibrium modeling. Metamorphism in the Faro eclogites followed a clockwise pathway through the lawsonite eclogite facies, reaching peak pressures of 22−24 MPa at 525−550 °C. Rocks then exhumed to 14.5−16 MPa during heating to 630−655 °C. Crystallographic preferred orientations (CPOs) in omphacite developed dominantly by dissolution-precipitation creep and oriented grain growth concurrently with CPOs developed in glaucophane by a combination of dislocation- and dissolution-precipitation creep with oriented grain growth. We link this fabric and CPO development in omphacite and amphibole to lawsonite dehydration, slab decoupling, and initiation of exhumation of the eclogites, providing evidence that lawsonite dehydration plays a significant role in changes in subduction zone rheology.

Molecular mechanism of antioxidant activity of mesona chinensis benth extracts based on arginine-citric acid deep eutectic solvent

In the pursuit of sustainable development, the research and development of environmentally friendly green solvents have become increasingly important. Deep eutectic solvents (DES) represent a novel type of green solvent with broad application potential. Although our research group has previously successfully developed various new DES, the separation mechanism of Mesona chinensis Benth (MB) using arginine (Arg)-citric acid (CA) DES and the antioxidant activity of its extracts remain unclear. Therefore, this study aims to extract MB using natural deep eutectic solvents and investigate the antioxidant activity of its extracts. Initially, thermodynamic analysis of Arg-CA DES is conducted using solid-liquid equilibrium phase diagrams. Subsequently, the antioxidant activity of MB is screened through in vitro antioxidant experiments. The composition of MB extracts is analyzed using LC-MS, and their antioxidant mechanisms are explored through network pharmacology and molecular docking. Finally, further validation is carried out through in vitro antioxidant experiments. The cell experiments show that DES extracts could enhance cellular antioxidant capacity by increasing GSH-PX, CAT enzyme activity and reducing MDA levels. PCR studies reveal that MB extracts obtained with DES could regulate the expression of antioxidant-related genes to improve the antioxidant capacity of cells. Overall, this study demonstrates that the MB Arg-CA (4:6) DES extract can serve as a novel antioxidant for functional food and healthcare sectors.

Thermodynamic re-optimisation of the CaO-FeO-Fe2O3 system integrated with experimental phase equilibria studies (Part I)

New experimental measurements of phase equilibria in the CaO-FeO-Fe2O3 system at 1120–1740 °C over a wide range of oxygen partial pressures (pO2 = 1, 10−0.68, 10−2, 10−6, 10−8, 10−10 atm) and in equilibrium with metallic Fe has been obtained. The study was undertaken using equilibration/quenching and electron probe X-ray microanalysis (EPMA) technique enabling the compositions of the liquid and solid phases in equilibrium at temperature to be accurately measured.The data have been used to define the liquidus of hematite (Fe2O3), spinel (Fe,Ca)3O4+x, lime (Ca,Fe)O, wustite (Fe,Ca)O1+x, 2CaO·Fe2O3 (C2F), CaO·Fe2O3 (CF), CaO·2Fe2O3 (CF2), and a solid phase with composition close to (CaO)15(FeO)8(FeO1.5)77, which is believed to belong to the Silico-Ferrite of Calcium and Aluminium (SFCA-I) solid solution. Direct oxygen concentration measurements in the liquid and solid phases using EPMA were also undertaken in the present study to determine the Fe2+/Fe3+ ratio in these phases. The experimental data obtained in the present study will be used for thermodynamic re-optimisation of the CaO-FeO-Fe2O3 system, undertaken as part of the study of the 20-component Pb-Zn-Cu-Fe-Si-Ca-O-S-Al-Mg-Cr-Na-As-Sn-Sb-Bi-Ag-Au-Ni-Co system directly relevant to the applications in the ferrous and non-ferrous metallurgical industries.

Phase equilibrium data for semiclathrate hydrates formed with n-propyl, tri-n-butylammonium bromide and tri-n-butyl, n-pentylammonium bromide under methane, carbon dioxide and nitrogen gas pressure

Semiclathrate hydrates are water-based materials formed from aqueous solutions of ionic substances. To enhance the gas capture performance of these materials, it is necessary to direct focus on the cation, which is a key part of construction of the hydrogen-bonding framework. In this paper, we focus on the partly-asymmetric cations, i.e., the n-propyl, tri-n-butylammonium bromide (N3444Br) and tri-n‑butyl, n-pentylammonium bromide (N4445Br), which are yet to be subjected to gas hydrate formation. The three phase equilibrium (gas–hydrate–liquid) conditions for the systems of (N3444Br or N4445Br) + H2O + (CH4, CO2 or N2) in the range of the pressure and mass fractions of the aqueous solutions between 1 and 11 MPa and 0.10–0.40, respectively, are reported. In all the systems, the semiclathrate hydrates were successfully formed under gas pressure. It was demonstrated that both the N3444Br and N4445Br salts promoted hydrate formation under these gases, while in the case with lean aqueous solutions N3444Br acted as an inhibitor of methane hydrate formation in pure water system. The present data are compared with the literature data, and the effect of the side chain length on the phase behavior of the semiclathrate hydrate phase is discussed.

Fluid Phase Equilibria Carbon Dioxide + Decane + Hexadecane Ternary System

The interest in understanding reservoir fluids' phase behavior is to increase hydrocarbon production without any flow assurance issues. Due to its opacity, the evident complexity of determining phase equilibrium data revolves around the thermodynamic modeling of model systems. The article presents experimental phase equilibrium data and thermodynamic modeling for the CO2 + decane + hexadecane ternary system at 283.15, 298.15, and 323.15 K and pressures up to 20 MPa. The transitions observed during this study were liquid-liquid (LL), vapor-liquid (VL), and vapor-liquid-liquid (VLL). The Peng-Robinson equation of state was used to model this ternary system for various compositions. The temperature-dependent binary interaction parameters (kij) for the CO2 + n-alkane mixtures were adjusted to the experimental data. Additionally, a binary interaction parameter for the n-C16H34/n-C10H22 pair, independent of temperature, was obtained through the critical volume of the components. The results reveal complex behaviors as the mixture's composition of hexadecane progressively increases. Adding this longer-chain linear hydrocarbon influences the phase behavior, leading to the emergence of liquid-liquid transitions and barotropic inversion in the system. This study contributes valuable data on model systems representing crude oil, highlighting complex behaviors in ternary systems with high carbon dioxide content.

Determination of specific surface area of biomass activated carbon vial headspace gas chromatography technique

This paper introduces a method for determining the specific surface area (SSA) of biomass activated carbon (BAC) using a tracer-based headspace gas chromatography (HS-GC) technique. The method relies on the adsorption equilibrium of methanol on BAC samples at elevated temperature. A mathematical model allows for the calculation of SSA from the methanol signal obtained during the headspace analysis. The results demonstrate high precision (relative standard deviation < 2.44%) and strong accuracy (correlation with the conventional BET-N2 adsorption method, R² = 0.986). This method offers several advantages over traditional techniques, including ease of operation, significant time efficiency, and the the ability to perform batch determinations of SSA, as multiple samples can be processed simultaneously during the phase equilibrium step.