Study Of Phase Equilibria Research Articles

Measurements and predictions of phase equilibria in the quaternary system KBr + MgBr2 + SrBr2 + H2O at 273 K and 308 K

The underground brines in Sichuan Basin of China are rich in potassium, magnesium, strontium, bromine. Consequently, the studies of phase equilibria for the underground brines are of great significance. The phase equilibria of the quaternary system KBr + MgBr 2 + SrBr 2 + H 2 O at 273 K and 308 K are determined by the isothermal dissolution equilibrium method in this work. Firstly, the equilibrium liquid phase compositions at two temperatures were measured by chemical analysis. Secondly, the corresponding solid phases were identified by X-ray powder diffraction method. As a result, the corresponding phase diagrams were drawn based on the obtained data. The equilibrium phase diagrams all include four crystallization fields (SrBr 2 ·6H 2 O, MgBr 2 ·6H 2 O, KBr·MgBr 2 ·6H 2 O and KBr), five isothermal solubility curves and two invariant points, which present the same trend at the two temperatures. Furthermore, the mixed ion interaction parameters ( θ Mg , Sr , φ K , Sr , Br , φ Mg , Sr , Br ) of Pitzer model, which have not been reported in the literatures, were obtained by using the solubility data of the ternary system and multiple linear regression. And Pitzer equation and particle swarm optimization algorithm were used to simulate and predict the solubility of salts in the quaternary system. By comparing the calculated phase diagrams at 273 K and 308 K, some obvious deviation in crystalline phase zone of MgBr 2 ·6H 2 O and KBr·MgBr 2 ·6H 2 O at 273 K have been found. And both of them are within the reasonable deviation range. The results show that the fitted parameters and the calculated model of the mixed ion interaction are reliable, and the calculated data agree well with the experimental data.

Thermodynamic optimization and phase equilibria study of the MgO–ZnO, CaO–ZnO, and CaO–MgO–ZnO systems

The binary MgO–ZnO and CaO–ZnO systems and the ternary CaO–MgO–ZnO system were thermodynamically optimized with phase equilibria studies in this study. Bragg-Williams random mixing model was used for solid solutions, while Modified Quasichemical Model was used for liquid solution. The thermodynamic optimization was conducted using Factsage 8.1 thermochemical software. The optimized phase diagrams fit well with phase equilibria experimental results. The phase equilibria studies were performed for the MgO–ZnO systems at 600 °C, 650 °C, 700 °C, and 1000 °C, and for CaO–MgO–ZnO systems at 1500 °C, 1550 °C, and 1600 °C. Quenched samples were analyzed by SEM/EDS to confirm equilibrium phases. Liquid phases were newly observed in the CaO–MgO–ZnO systems at 1550 °C and 1600 °C.

Reference materials for phase equilibrium studies. 2. Solid–liquid equilibria (IUPAC Technical Report)

Abstract This article is the second of three projected IUPAC Technical Reports on reference materials for phase equilibrium studies. The goal of this project was to select reference systems with critically evaluated property values for the verification of instruments and techniques used in phase equilibrium studies of mixtures. This report proposes seven systems for solid–liquid equilibrium studies, covering the four most common categories of binary mixtures: aqueous systems with organic solutes, aqueous systems with inorganic solutes, non-aqueous systems, and systems with low solubility. For each system, the available literature sources, accepted data, smoothing equations, and estimated uncertainties are given.

Study of phase equilibria and thermodynamic properties of liquid mixtures using the integral equation theory: Application to water and alcohol mixtures.

A theoretical method for calculating the thermodynamic properties and phase equilibria of liquid-liquid mixtures using the integral equation theory is proposed. The solvation chemical potentials of the two components are evaluated by the integral equation theory and the isothermal-isobaric variation of the total density with composition is determined to satisfy the Gibbs-Duhem relation. Given the density of a pure component, the method can calculate the densities of the mixture at any composition. Furthermore, it can treat the phase equilibrium without thermodynamic inconsistency with respect to the Gibbs-Duhem relation. This method was combined with the reference interaction-site model integral equation theory and applied to mixtures of water + 1-alcohol by changing the alcohol from methanol to 1-butanol. The destabilization of the mixing Gibbs energy by increasing the hydrophobicity of the alcohol and demixing of the water-butanol mixture were reproduced. However, quantitative agreement with experiments is not satisfactory, and further improvements of the integral equation theory and the molecular models are required.

Experimental phase equilibria study and thermodynamic modelling of the “CuO0.5”-AlO1.5-SiO2 ternary system in equilibrium with metallic copper

Phase equilibria studies were undertaken on the “CuO0.5”-AlO1.5-SiO2 system in equilibrium with metallic copper using equilibration and quenching technique followed by the electron probe X-ray microanalysis (EPMA). The liquidus of the “CuO0.5”-AlO1.5-SiO2 system, including the two 2-liquid miscibility gaps in the system as well as the cuprite (Cu2O), corundum (Al2O3), delafossite (CuAlO2), tridymite and cristobalite (Si1-x(CuAl)xO2), and mullite (Al6+2xSi2-2xO13-x) primary phase fields has been characterized. New experimental results together with phase equilibria and thermodynamic literature data were used to obtain a self-consistent set of parameters of the thermodynamic model for all phases. The liquidus projection of the “CuO0.5”-AlO1.5-SiO2 system was presented for the first time in the full range of temperatures and compositions. It was found that the simultaneous dissolution of a small amount of alumina and copper oxide (CuAlO2) in SiO2 phases stabilize cristobalite over tridymite at low temperatures.

PHASE FORMATION DURING STEEL REFINING BY ALLOYS WITH ALKALINE EARTH ELEMENTS (Ba, Mg, Sr)

Important factors affecting the quality of steel are both the level of metal contamination with non-metallic inclusions and the properties of these inclusions. Hard-to-remove magnesium-containing compounds have a pronounced negative effect on the performance of metal products. This type of inclusions is distinguished by a high melting point, a characteristic acute-angled shape, and a significant difference in the coefficient of thermal expansion from the matrix material. Despite the fact that the magnesium-containing modifiers are practically not used for out-of-furnace processing of steel and the magnesium-containing inclusions are mostly exogenous, the task of their removal from the metal is extremely important. At present, to improve the quality of metal, especially low-alloyed metal, out-of-furnace steel processing technologies are used using complex alloys, which include barium and strontium. The study of the effect of barium and strontium additives on the processes of liquid steel refining is one of the promising areas of research in the field of metallurgical technologies. This paper presents the results of thermodynamic studies of phase equilibria in the Fe–Mg–Ba–Sr–O and Fe–Mg–Ba–Sr–O–C systems. Based on the literature data and our own research, we have constructed the phase diagram of the BaO–MgO–SrO ternary system for the first time. For the systems under study, the component solubility surfaces (SSS) in liquid iron were constructed for steel treatment temperatures of 1550 and 1600 ºС. According to the calculations, the most probable type of inclusions are solid solutions based on magnesium oxides. As the temperature decreases, the probability of participation of strontium and barium in the steel refining process increases, which creates conditions for the formation of easily removed barium- and strontium-containing non-metallic inclusions. The gas phase formed in the presence of carbon creates additional conditions for efficient refining of the melt.

Effect of source heterogeneity, melt extraction and crystal separation on the composition of a suite of ferroan (A-type) granites from parts of the Chotanagpur Granite Gneissic Complex (CGGC), India

Ferroan granitoids constitute a considerable proportion of the upper continental crust formed during the Proterozoic eon and their origin is usually linked to high-temperature processes (fractionation or anatexis) occurring at shallow crustal depths. However, the relative role of mantle melts vs. crustal rocks as the source of these granitoids has been largely debated. In the Chotanagpur Granite Gneissic Complex (CGGC), located in the East Indian shield, a suite of Mesoproterozoic (ca. 1450–1350 Ma) ferroan granites has intruded the Paleoproterozoic (ca. 1700–1630 Ma) arc granites and currently occurs either as migmatitic gneisses or as biotite gneisses in different parts of the terrane . Previous studies postulated that these Mesoproterozoic extensional granites were sourced from older crustal rocks with limited mantle input. In the current study, the geochemistry of the biotite gneisses is combined with that of the migmatitic gneisses and coeval ferroan granites from northern and western parts of the CGGC to comprehend the wide spatial and compositional variation observed. With the help of phase equilibrium modelling, the current study quantifies the role of the heterogeneity of the crustal source and path-dependent melting in shaping the composition of the ferroan granites. The study demonstrates that the composition of the modelled melt derived from the older (late Paleoproterozoic) granites under low-pressure high-temperature conditions (750-1000 °C; 4–8 kbar) closely resembles the compositions observed in the younger (Mesoproterozoic) ferroan granites. Compositional variation of the melt is further accentuated by high-temperature progressive melting and extraction of melt in small batches during anatexis . Phase equilibrium studies further delineate the significant role of crystal fractionation in shaping the chemical variations observed in the studied granites. • Mesoproterozoic ferroan granites of CGGC formed via anatexis of older arc granites. • Source heterogeneity produces variable composition of the granites. • Melt extraction in small batches produces chemical variation in ferroan granites. • Post-emplacement crystal separation accentuates the compositional variations.

Phase equilibrium in the hydrogen energy chain

• A thorough review on the whole hydrogen energy chain to figure out the potential existence of phase transition and application of phase equilibrium studies. • A thermodynamically-consistent flash calculation scheme to calculate phase equilibrium states with physical meanings. • Predictions of phase equilibrium states in practical hydrogen production, storage and transportation applications. • Suggestions to the hydrogen industry for different engineering purposes based on the phase equilibrium calculations. In this paper, a thorough review of the current state of the hydrogen phase equilibrium approaches is presented. Potential applications of phase equilibrium calculations for the accurate simulation of the entire process are then identified. Based on the first and second laws of thermodynamics, an advanced constant (N), volume (V), and temperature (T) (NVT) flash calculation scheme is developed for fluid mixtures containing hydrogen, which can be used to calculate the phase equilibrium for various feed compositions. We produce reasonable predictions of the phase transition under various environmental conditions for a number of engineering scenarios during the hydrogen production and storage processes, thus demonstrating the effectiveness and robustness of the proposed phase equilibrium calculation scheme.

Excluded volume of the system of hard-core spheres revisited: New insights from computer simulations

The role of excluded volume in the equation of state of hard-sphere system is studied by analytical theory and computer simulations. The excluded-volume parameter b(ρ) introduced in the van der Waals equation is examined as a function of density. A number of approximations are considered and tested against Monte Carlo simulations. Parameter b(ρ) is seen to decline by a factor of 2 over the density range in which the system is still in the fluid state. Partial contributions of two- and three-sphere intersections to b(ρ) are analyzed as a function of density. The resulting series is seen to be converging very slowly. An approximation based on Padé approximants is seen to offer best accuracy at the lowest cost. It involves computation of the three lowest virial expansion coefficients B2,B3 and B4. Numerical tests reveal that this approximation is accurate in the case of ellipsoids and a number of hard-core polyhedra, supporting a potential application in phase equilibria studies of molecules with non-spherical shapes, such as cubes, pear-shaped molecules and so on.

Crystal growth of ReCa3Mn3O3(BO3)4 (Re = Gd, Y) gaudefroyite: Phase sequence and equilibrium study in multi-component fluxes

The work is aimed at studying the crystallization of ReCa3Mn3O3(BO3)4 (Re = Gd, Y) borates with the gaudefroyite structure in different flux systems. Gaudefroyites are promising materials in the field of spin ice and magnetocaloric effect. The study has been performed on systems based on the following solvents: Bi2Mo3O12-Na2B4O7-B2O3, Bi2O3-Na2B4O7-B2O3, Bi2O3-BaO-Na2B4O7-B2O3, Li2WO4-Li2O-B2O3. The influence of the solvent components on the sequence of high-temperature crystallizing phases has been studied. The feature of Mo- and W-containing fluxes consisting in the formation of stable chemical bonds of the M2+Mo(W)O4 (M = Ca, Mn) molybdate or tungstate types has been revealed which prevents the formation of gaudefroyite type bonds. An approach has been suggested for changing the sequence of the crystallizing phases which consists in the super saturation of molybdate (tungstate) bonds by Na+ or Li+ cations up to the formation of delafossite-type bonds (Li(Na)-Mn-O phase) with higher manganese valence states Mn3+ and Mn4+. The optimization of the growth conditions of ReCa3(MnO)3(BO3)4 (Re = Gd, Y) gaudefroyite crystals has allowed one to obtain single crystal samples with the size up to 0.8 × 0.8 × 5 mm3. The structural characterization and chemical composition of all the obtained phases are also presented.

Calculation and experimental determination of equilibrium composition of liquors in certain instances of the Na2O – К2O – Al2O3 – H2O System

Presently, one can definitely state a rising interest to potassium-bearing aluminium ores, which is due to a gradual depletion of conventional raw materials and the fact that the ores that are mined today are leaner and have a more complex composition. At the same time, soda-potassium products, potassium fertilizers, aluminium hydroxide, alumina and alumina materials are in high demand and sell at high prices. Today, the focus is on new deposits of urtite rock and nepheline ores, as well as those of ultrapotassium rischorrite and synnyrite rock. That’s why it is very important to have a basic understanding of the nature and properties of the technically important system Na2O – К2O – Al2O3 – H2O, which defines the performance of the key processes involved, as well as the output and quality of the final product. In this regard, studying phase equilibria in the above system, the information about which is lacking or inconsistent, can be pointed out as one of the current research priorities. Two methods were tested aimed at reducing the time necessary to reach equilibrium in the Na2O – K2O – Al2O3 – H2O system. One involves hydrolytic decomposition of aluminate liquors with aluminium hydroxide used as seed; the other involves a mathematical description of the curves characterizing the kinetics of gibbsite solubility in alkaline liquors with a given mole fraction of K2O. Similar laboratory equipment and materials were used in the experimental study regardless of the way equilibrium was reached and identified. Through experiments, it was established that the process of approaching equilibrium in predominantly potassium aluminate liquors has complex kinetics and mechanics impeding rapid identification of equilibrium composition of liquors. With regard to the technique that involves gibbsite dissolution in weak sodium-potassium liquors, the authors demonstrate how asymptotic approximation functions can be effectively used to determine maximum solubility of aluminium oxide. The results of experiments aimed at defining the equilibrium compositions of liquors at 60 oC in certain instances of the Na2O – К2O – Al2O3 – H2O system have a good and satisfactory correlation with the modelling data based on the additivity principle, which suggests that the modelling technique can effectively be applied to other temperatures and instances of the 4-component system in view. This research was funded by the Russian Science Foundation under the Agreement No. 18-19-00577-П dated April 28, 2021 on granting funds for basic scientific research and exploratory research.

The system KCl−CaCO3−MgCO3 at 6 GPa: A link between saline and carbonatitic diamond-forming fluids

Alkaline chlorides and carbonates are abundant in melt inclusions in diamonds, mantle xenoliths, and igneous minerals from kimberlites. Despite this, the phase relationships in chloride‑carbonate systems remain poorly constrained. Here we studied phase equilibria in the system KCl–CaCO3–MgCO3 in multianvil experiments at 6 GPa and 1000–1600 °C. It was found that at 1000 °C, subsolidus assemblage consists of KCl, magnesite, and aragonite. At higher temperatures, the stabilization of dolomite splits the system into two partial ternaries: KCl + dolomite + aragonite and KCl + magnesite + dolomite. Both ternaries start to melt near 1200 °C. The melting of the first ternary is controlled by the KCl-dolomite-aragonite eutectic situated at 30 mol% (24 wt%) KCl and Ca# 92, where Ca# = 100∙Ca/(Ca + Mg). The melting of the second ternary is controlled by the peritectic, KCl + dolomite = magnesite + liquid, producing chloride‑carbonate melt with 33 mol% (27 wt%) KCl and Ca# 69.The established melting temperature of the KCl + Ca-Mg carbonate assemblages is 200–500 °C higher than the subduction geotherms. This indicates that chlorides and carbonates can survive subduction to a depth of 200 km. However, the stagnation and warming of slabs to the ambient mantle temperature must result in partial melting of KCl + Ca-Mg carbonate assemblages producing a KCl-rich low-Mg carbonate melt. Percolation of this melt into the subcontinental lithospheric mantle should yield crystallization of KCl and CaMg carbonates. In the presence of water, KCl will form hydrous saline melt or fluid, while Ca and Mg carbonates, which are poorly soluble in water, will remain solid. The obtained results imply that the hydrous saline fluids (brines) found as inclusions in diamonds are a lower temperature derivative of mantle carbonatite melts and do not support the hypothesis of chloride melt generation owing to the chloride‑carbonate liquid immiscibility since no such immiscibility was established.

Integrated experimental and thermodynamic modeling study of phase equilibria in the ‘CuO0.5’-MgO-SiO2 system in equilibrium with liquid Cu metal for characterizing refractory-slag interactions

An integrated experimental and thermodynamic modeling study of the phase equilibria in the ‘CuO0.5’-MgO-SiO2 system in equilibrium with liquid Cu metal has been undertaken to better understand the reactions between MgO-based refractories and liquid slag in copper converting and refining processes. New experimental phase equilibria data at 1250–1680 °C were obtained for this system using a high-temperature equilibration of synthetic mixtures with predetermined compositions in silica ampoules or magnesia crucibles, a rapid quenching technique, and electron probe X-ray microanalysis of the equilibrated phase compositions. The system has been shown to contain primary phase fields of cristobalite (SiO2), tridymite (SiO2), pyroxene/protoenstatite (MgSiO3), olivine/forsterite (Mg2SiO4), periclase (MgO), and cuprite (Cu2O). Three regions of 2-liquid immiscibility were found—two in the high-silica range of compositions above the cristobalite primary phase field (close to ‘CuO0.5’-SiO2 and MgO–SiO2 binaries) and one in the low-SiO2, high-‘CuO0.5’ compositional region above the periclase and olivine phase fields. The results obtained in this study indicate that silica in high-copper refining slags likely led to olivine and pyroxene phase formation, increased solubility of MgO in liquid slag, and decline in the performance of MgO-based refractories. New experimental data were used in the development of a thermodynamic database describing this pseudo-ternary system.

Accurate, cost-effective strategy for lean gas condensate sampling, characterization, and phase equilibria study

Accurate recognition of the fluid phase behaviour is the most important and first step for the preservation and hydrocarbon reservoir management. Among the various hydrocarbon fluids, the lean gas condensate fluids show complex and unique behaviour. Due to the nature of these fluids, errors in the laboratory constant volume depletion (CVD) experimental data are inevitable. In this study, the significance of using CVD data in the EoS tuning process is debated using six samples of lean gas condensate. According to the negative composition in the CVD data material balance of all samples, just data of the constant composition expansion (CCE) experiment, saturation pressure, and liquid density in the stock tank are used for tuning the equation of state (EoS) as fundamental experimental data. The results of this study demonstrate that without using any CVD experimental data in the EoS tuning process, this data can be generated accurately using tuned EoS with fundamental data. Therefore, there is no need to do CVD experiments for lean gas condensate fluids characterization, which leads to reduces not only the error in the simulation process but also the laboratory costs. Furthermore, the tuning strategy in this study demonstrates that molecular weight of plus fraction and the volume shift parameter of the heaviest pseudo-component are the effective parameters to adjust the EoS. The objective function has reduced from 0.7360 to 0.1538 (79.10% improvement) just by using these two parameters. A constrained tuning strategy was proposed to keep the critical properties and acentric factor expected trends versus carbon number. The results show uniform and swing trends in the case of constrained and unconstrained tuning strategies, respectively. Therefore, using a constrained tuning strategy is essential to obtain a fluid with an authentic thermodynamic background after the tuning process. The proposed analysis method of CVD experimental data suggests that gas compressibility factor and gas composition as the main sources of error, while the experimental parameters of retrograde liquid and cumulative gas production have ignorable errors.

Phase Equilibrium and Thermodynamics Studies on Dissolving Processes of Energetic Compounds: A Brief Review

Phase Equilibrium and Thermodynamics Studies on Dissolving Processes of Energetic Compounds: A Brief Review

Experimental phase equilibria studies in the “CuO0.5”-CaO-SiO2 ternary system in equilibrium with metallic copper

Phase equilibria studies were undertaken on the “CuO0.5”-CaO-SiO2 system in equilibrium with metallic copper to provide fundamental information on the reactions taking place between slags and refractory materials in metallurgical furnaces. The liquidus isotherms between 1160 and 1706 °C in the tridymite and cristobalite (SiO2), cuprite (Cu2O), pseudowollastonite (CaSiO3), rankinite (Ca3Si2O7) and dicalcium silicate (Ca2SiO4) primary phase fields, and the 2-liquid miscibility gaps in the silica-rich corner and low-silica area of the system, were experimentally determined using the equilibration and quenching technique, followed by the electron probe X-ray microanalysis (EPMA) of phase compositions. The liquidus surface of the “CuO0.5”-CaO-SiO2 system has been constructed. The dissolution of copper oxide in the tridymite and cristobalite (SiO2) was shown to be negligible. The data obtained are used for the optimization of the thermodynamic database for the copper-containing systems.

Marathonite, Pd25Ge9, and palladogermanide, Pd2Ge, two new platinum-group minerals from the Marathon deposit, Coldwell Complex, Ontario, Canada: Descriptions, crystal-chemical considerations, and genetic implications

ABSTRACTMarathonite, Pd25Ge9, and palladogermanide, Pd2Ge, are two new platinum-group minerals discovered in the Marathon deposit, Coldwell Complex, Ontario, Canada. Marathonite is trigonal, space group P3, with a 7.391(1), c 10.477(2) Å, V 495.6(1) Å3, Z = 1. The six strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 2.436(10)(014,104,120,210), 2.374(29)(023,203,121,211), 2.148(100)(114,030), 1.759(10)(025,205,131,311), 1.3605(13)(233,323,036,306), and 1.2395(14)(144,414,330). Associated minerals include: vysotskite, Au-Ag alloy, isoferroplatinum, Ge-bearing keithconnite, majakite, coldwellite, ferhodsite-series minerals (cuprorhodsite-ferhodsite), kotulskite and mertieite-II, the base-metal sulfides, chalcopyrite, bornite, millerite and Rh-bearing pentlandite, oberthürite and torryweiserite, and silicates including a clinoamphibole and a Fe-rich chlorite-group mineral. Rounded, elongated grains of marathonite are up to 33 × 48 μm. Marathonite is white, but pinkish brown compared to palladogermanide and bornite. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 40.8 (470 nm), 44.1 (546 nm), 45.3 (589 nm), and 47.4 (650 nm). The calculated density is 10.933 g/cm3, determined using the empirical formula and the unit-cell parameters from the refined crystal structure. The average result (n = 19) using energy-dispersive spectrometry is: Si 0.11, S 0.39, Cu 2.32, Ge 18.46, Pd 77.83, Pt 1.10, total 100.22 wt.%, corresponding to the empirical formula (based on 34 apfu): (Pd23.82Cu1.19Pt0.18)Σ25.19(Ge8.28S0.40Si0.13)∑8.81 and the simplified formula is Pd25Ge9. The name is for the town of Marathon, Ontario, Canada, after which the Marathon deposit (Coldwell complex) is named.Results from electron backscattered diffraction show that palladogermanide is isostructural with synthetic Pd2Ge. Based on this, palladogermanide is considered to be hexagonal, space group , with a 6.712(1), c 3.408(1) Å, V 133.0(1), Z = 3. The seven strongest lines of the X-ray powder-diffraction pattern calculated for the synthetic analogue [d in Å (I)(hkl)] are: 2.392(100)(111), 2.211(58)(201), 2.197(43)(210), 1.937(34)(300), 1.846(16)(211), 1.7037(16)(002), and 1.2418(18)(321). Associated minerals are the same as for marathonite. Palladogermanide occurs as an angular, anhedral grain measuring 29 × 35 μm. It is white, but grayish-white when compared to marathonite, bornite, and chalcopyrite. Compared to zvyagintsevite, palladogermanide is a dull gray. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths for Ro and Ro' are: 46.8, 53.4 (470 nm), 49.5, 55.4 (546 nm), 50.1, 55.7 (589 nm), and 51.2, 56.5 (650 nm). The calculated density is 10.74 g/cm3, determined using the empirical formula and the unit-cell parameters from synthetic Pd2Ge. The average result (n = 14) using wavelength-dispersive spectrometry is: Si 0.04, Fe 0.14, Cu 0.06, Ge 25.21, Te 0.30, Pd 73.10, Pt 0.95, Pb 0.08, total 99.88 wt.%, corresponding (based on 3 apfu) to: (Pd1.97Pt0.01Fe0.01)Σ1.99(Ge1.00Te0.01)∑1.01 or ideally, Pd2Ge. The name is for its chemistry and relationship to palladosilicide.The crystal structure of marathonite was solved by single-crystal X-ray diffraction methods (R = 7.55, wR2 = 19.96 %). It is based on two basic modules, one ordered and one disordered, that alternate along [001]. The ordered module, ∼7.6 Å in thickness, is based on a simple Pd4Ge3 unit cross-linked by Pd atoms to form a six-membered trigonal ring that in turn gives rise to a layered module containing fully occupied Pd and Ge sites. This alternates along [001] with a highly disordered module, ∼3 Å in thickness, composed of a number of partially occupied Pd and Ge sites. The combination of sites in the ordered and disordered modules give the stoichiometric formula Pd25Ge9.The observed paragenetic sequence is: bornite → marathonite → palladogermanide. Phase equilibria studies in the Pd-Ge system show Pd25Ge9 (marathonite) to be stable over the range of 550–970 °C and that Pd2Ge (palladogermanide) is stable down to 200 °C. Both minerals are observed in an assemblage of clinoamphibole, a Fe-rich, chlorite-group mineral, and fragmented chalcopyrite, suggesting physical or chemical alteration, possibly both. Palladogermanide is also found associated with a magnetite of near end-member composition, potentially indicating a relative increase in fO2. Both minerals are considered to have developed at temperatures of 500–600 °C, under conditions of low fS2 and fO2, given the requirements needed to fractionate, concentrate, and form minerals with Ge-dominant chemistries.

Synthesis of MAX-phases, structure and phase composition of modified layers on titanium alloy VT-1 as a result of electron-beam treatment

The article presents the results of research and identification of optimal conditions of formation of MAX-phases during treatment of titanium alloy VT-1 by an electron beam in a vacuum. The study of strength characteristics, thermal properties of composite layers was carried out. Thermodynamic study of phase equilibrium in Ti-Si-C and Ti-B-C systems under high vacuum conditions was carried out in order to optimize conditions of formation of functional layers. A mathematical model of the thermal impact of a powerful fast-moving electron beam on the surface of a titanium alloy has been developed VT-1 under the conditions of electron beam processing in the framework of the theory of thermal conductivity using the COMSOL Multiphysics software complex. The obtained numerical results made it possible to investigate the regularity of the distribution of temperatures and their rates of change depending on the action of the electron beam.

Reference materials for phase equilibrium studies. 1. Liquid–liquid equilibria (IUPAC Technical Report)

Article Reference materials for phase equilibrium studies. 1. Liquid–liquid equilibria (IUPAC Technical Report) was published on October 1, 2021 in the journal Chemistry International (volume 43, issue 4).

Seeing through metamorphic overprints in Archean granulites: Combined high-resolution thermometry and phase equilibrium modeling of the Lewisian Complex, Scotland

Abstract The Lewisian Complex in northwest Scotland presents a record of the transition from the Neo-Archean to the Paleoproterozoic. However, this record is complicated by a long and varied history after peak metamorphism that has erased and/or partially reset much of the early history of the rocks. Such overprinting is a common feature of Archean granulites and poses a substantial problem when trying to understand the tectonic processes that were active prior to the onset of modern plate tectonics. By combining careful petrography with phase diagram modeling and a range of exchange thermometers we obtain the peak and retrograde temperature history of the Lewisian Complex from a single, well-preserved, representative sample of garnet-bearing mafic granulite. We present the application of high-resolution electron probe microanalysis (HR-EPMA) to characterize sub-micrometer orthopyroxene exsolution lamellae in clinopyroxene. We discuss ways to mitigate issues associated with HR-EPMA including surface contamination, beam drift, standards, and the need to correct for secondary fluorescence effects. The resulting compositions from our HR-EPMA analyses provide an independent measure of the retrograde temperature conditions and can also be used to back-calculate the compositions of clinopyroxene in the peak assemblage. We obtain peak metamorphic conditions for the Lewisian of >11 kbar and >1025 °C, and constrain subsequent metamorphic overprints to 850 °C (Grt-Cpx), 590 °C (Opx-Cpx), and 460 °C (Mag-Ilm). These peak and retrograde temperatures span the range of those found in the literature. Whereas recent phase equilibrium studies assume equilibrium among all preserved high-T minerals, this study considers microstructural and mineral-chemical evidence for corona formation that reflects post-peak decompression with partial equilibration at ~850 °C, as recognized in some earlier studies.