Liquid-liquid Miscibility Gap Research Articles

Experimental investigation and thermodynamic assessment of the Al–Er system

The phase equilibria of the Al–Er binary system have been investigated through both experiments and CALPHAD assessment. The phase relationship in the compositional range of 0–50 at. % Er was experimentally redetermined using scanning electron microscopy (SEM) with Energy Dispersive Spectroscopy (EDS), electron probe micro analysis (EPMA) with wavelength dispersive spectrometer (WDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results confirmed the existence of the Al3Er phase (Al3Ho-type structure) with limited homogeneity range in the Al–Er system. It was formed through the peritectic reaction L + Al2Er ↔ Al3Er at 1105.3 ± 2.4 °C. While the Al17Er2 phase was proved to be metastable in the present work. A full thermodynamic optimization of the Al–Er binary system has been carried out by utilizing the current experimental data as well as all available results in the previous publications. A set of self-consistent thermodynamic parameters for the Al–Er system was established. The calculated phase diagram and thermodynamic properties agree well with the available data. The artificial inverted liquid-liquid miscibility gap at high temperature in the previous evaluation is removed.

A Metastable Amorphous Intermediate Is Responsible for Laser-Induced Nucleation of Glycine.

Laser-induced crystal nucleation through optical tweezing, and in particular polymorph selection through laser polarization, promises unprecedented control over crystallization. However, in the absence of a nearby liquid-liquid critical point or miscibility gap, the origin of the required mesoscale clusters remains unclear. A number of recent studies of so-called nonclassical nucleation have suggested the presence of large amorphous clusters. Here, we show that supersaturated aqueous glycine solutions form metastable intermediate particles that are off the direct path to crystal nucleation. Laser-induced crystal nucleation only occurs when the laser "activates" one of these particles. In situ low-frequency Raman spectroscopy is used to demonstrate their amorphous or partially ordered character and transformation to various crystal polymorphs. The requirement for solution aging in many previously reported laser-induced crystal nucleation experiments strongly suggests that the presence of amorphous intermediates is a general requirement.

Phase diagram study of the SnO2-SiO2 system and thermodynamic optimization of the SnO-SnO2-SiO2 system

The phase diagram of the SnO2-SiO2 system was investigated using sealed Pt crucibles. A eutectic reaction of L → SiO2 (s) + SnO2 (s) was experimentally determined at about 1670 °C and 1.15 mol % SiO2. No mutual solid solution between SiO2 and SnO2 was found. To explain this eutectic, a large liquid-liquid miscibility gap with a monotectic at about 1821 °C must exist between SnO2 and SiO2. Based on the present phase diagram experimental data of the SnO2-SiO2 system and the available thermodynamic and phase diagram data for the binary SnO-SiO2, SnO-SnO2, and ternary SnO-SnO2-SiO2 systems found in the literature, the thermodynamic optimization of the entire SnO-SnO2-SiO2 system was carried out. The new phase diagram of the entire SnO-SnO2-SiO2 system at 1 atm total pressure was constructed from the optimized Gibbs energy functions of all phases. The optimized database was also applied to simulation of the evaporation and condensation phenomena in float glass making process.

Stable Prenucleation Calcium Carbonate Clusters Define Liquid–Liquid Phase Separation

Liquid–liquid phase separation (LLPS) is an intermediate step during the precipitation of calcium carbonate, and is assumed to play a key role in biomineralization processes. Here, we have developed a model where ion association thermodynamics in homogeneous phases determine the liquid–liquid miscibility gap of the aqueous calcium carbonate system, verified experimentally using potentiometric titrations, and kinetic studies based on stopped‐flow ATR‐FTIR spectroscopy. The proposed mechanism explains the variable solubilities of solid amorphous calcium carbonates, reconciling previously inconsistent literature values. Accounting for liquid–liquid amorphous polymorphism, the model also provides clues to the mechanism of polymorph selection. It is general and should be tested for systems other than calcium carbonate to provide a new perspective on the physical chemistry of LLPS mechanisms based on stable prenucleation clusters rather than un‐/metastable fluctuations in biomineralization, and beyond.

Liquid Metastable Precursors of Ibuprofen as Aqueous Nucleation Intermediates.

The nucleation mechanism of crystals of small organic molecules, postulated based on computer simulations, still lacks experimental evidence. In this study we designed an experimental approach to monitor the early stages of the crystallization of ibuprofen as a model system for small organic molecules. Ibuprofen undergoes liquid–liquid phase separation prior to nucleation. The binodal and spinodal limits of the corresponding liquid–liquid miscibility gap were analyzed and confirmed. An increase in viscosity sustains the kinetic stability of the dense liquid intermediate. Since the distances between ibuprofen molecules within the dense liquid phase are similar to those in the crystal forms, this dense liquid phase is identified as a precursor phase in the nucleation of ibuprofen, in which densification is followed by generation of structural order. This discovery may make it possible to enrich poorly soluble pharmaceuticals beyond classical solubility limitations in aqueous environments.

"Bligh and Dyer" and Folch Methods for Solid-Liquid-Liquid Extraction of Lipids from Microorganisms. Comprehension of Solvatation Mechanisms and towards Substitution with Alternative Solvents.

Bligh and Dyer (B & D) or Folch procedures for the extraction and separation of lipids from microorganisms and biological tissues using chloroform/methanol/water have been used tens of thousands of times and are “gold standards” for the analysis of extracted lipids. Based on the Conductor-like Screening MOdel for realistic Solvatation (COSMO-RS), we select ethanol and ethyl acetate as being potentially suitable for the substitution of methanol and chloroform. We confirm this by performing solid–liquid extraction of yeast (Yarrowia lipolytica IFP29) and subsequent liquid–liquid partition—the two steps of routine extraction. For this purpose, we consider similar points in the ternary phase diagrams of water/methanol/chloroform and water/ethanol/ethyl acetate, both in the monophasic mixtures and in the liquid–liquid miscibility gap. Based on high performance thin-layer chromatography (HPTLC) to obtain the distribution of lipids classes, and gas chromatography coupled with a flame ionisation detector (GC/FID) to obtain fatty acid profiles, this greener solvents pair is found to be almost as effective as the classic methanol–chloroform couple in terms of efficiency and selectivity of lipids and non-lipid material. Moreover, using these bio-sourced solvents as an alternative system is shown to be as effective as the classical system in terms of the yield of lipids extracted from microorganism tissues, independently of their apparent hydrophilicity.

Impact of sodium chloride on the expansion of a liquid-liquid miscibility gap in an API/water system. Case study of Brivaracetam

Brivaracetam, or (2S)-2-[(4R)-2-oxo-4-propyl-pyrrolidin-1-yl] butanamide, is an active pharmaceutical ingredient designed for the treatment of epilepsy. During the development of the IV administration mode, a liquid-liquid miscibility gap has been observed with pure water, isotonic and hypertonic solutions (vehicle at 0.9% w/w and 5%w/w NaCl respectively). The study reveals that the NaCl concentration has a direct impact on the extent of the demixing domain; from a sub-micronic demixing in pure water towards a macroscopic miscibility gap in hypertonic aqueous solutions. The thorough exploration of these heterogeneous equilibria led to define experimental parameters for safe IV injections without risk of liquid – liquid miscibility gap at 37°C.

Experimental Investigation and Thermodynamic Assessment of Phase Equilibria in the PLLA/Dioxane/Water Ternary System for Applications in the Biomedical Field.

Fundamental understanding of thermodynamic of phase separation plays a key role in tuning the desired features of biomedical devices. In particular, phase separation of ternary solution is of remarkable interest in processes to obtain biodegradable and biocompatible architectures applied as artificial devices to repair, replace, or support damaged tissues or organs. In these perspectives, thermally induced phase separation (TIPS) is the most widely used technique to obtained porous morphologies and, in addition, among different ternary systems, polylactic acid (PLLA)/dioxane/water has given promising results and has been largely studied. However, to increase the control of TIPS-based processes and architectures, an investigation of the basic energetic phenomena occurring during phase separation is still required. Here we propose an experimental investigation of the selected ternary system by using isothermal titration calorimetric approach at different solvent/antisolvent ratio and a thermodynamic explanation related to the polymer-solvents interactions in terms of energetic contribution to the phase separation process. Furthermore, relevant information about the phase diagrams and interaction parameters of the studied systems are furnished in terms of liquid-liquid miscibility gap. Indeed, polymer-solvents interactions are responsible for the mechanism of the phase separation process and, therefore, of the final features of the morphologies; the knowledge of such data is fundamental to control processes for the production of membranes, scaffolds and several nanostructures. The behavior of the polymer at different solvent/nonsolvent ratios is discussed in terms of solvation mechanism and a preliminary contribution to the understanding of the role of the hydrogen bonding in the interface phenomena is also reported. It is the first time that thermodynamic data of a ternary system are collected by mean of nano-isothermal titration calorimetry (nano-ITC). Supporting Information is available.

Oxygen/noble gas binary phase diagrams at 296 K and high pressures

The binary phase diagrams of ${\text{O}}_{2}/\text{rare}$ gas (He, Ne, Ar, and Xe) mixtures have been measured at 296 K up to 20 GPa in a diamond-anvil cell. The boundary lines were determined by visual observation and by the Raman frequency of the ${\text{O}}_{2}$ vibron mode. The ${\text{O}}_{2}\text{-He}$ phase diagram is of eutectic type with a liquid-liquid miscibility gap and complete immiscibility in the solid phase. The ${\text{O}}_{2}\text{-Ne}$ phase diagram is of eutectic type with partial immiscibility in the solid phase. The ${\text{O}}_{2}\text{-Ar}$ phase diagram is of azeotrope type and three different structures of $\text{Ar}/{\text{O}}_{2}$ solid solutions have been identified. The ${\text{O}}_{2}\text{-Xe}$ phase diagram is of peritectic with eutectic type. The stoichiometric compound $\text{Xe}{({\text{O}}_{2})}_{2}$ is observed and characterized as a laves phase with a cubic structure isomorphous to ${\text{MgCu}}_{2}$. A qualitative understanding of these various diagrams is reached by the comparison of the effective hard-sphere diameters of the various species in the 10 GPa range. Some of the usefulness of the knowledge of these binary phase diagrams is highlighted: as a reference data set to test theoretical calculations on mixtures; to grow single crystal of ${\text{O}}_{2}$ in a rare-gas pressure medium; and to synthesize rare-gas oxides at high pressure.

Liquid-Liquid Miscibility Gaps and Hydrate Formation in Drug-Water Binary Systems: Pressure-Temperature Phase Diagram of Lidocaine and Pressure-Temperature-Composition Phase Diagram of the Lidocaine-Water System

The pressure-temperature (P-T) melting curve of lidocaine was determined (dP/dT = 3.56 MPa K(-1)), and the lidocaine-water system was investigated as a function of temperature and pressure. The lidocaine-water system exhibits a monotectic equilibrium at 321 K (ordinary pressure) whose temperature increases as the pressure increases until the two liquids become miscible. A hydrate, unstable at ordinary pressure, was shown to form, on increasing the pressure, from about 70 MPa at low temperatures (200-300 K). The thermodynamic conditions of its stability were inferred from the location of the three-phase equilibria involving the hydrate in the lidocaine-water pressure-temperature-mole fraction (P-T-x) diagram.

Phase equilibria and properties of solid solutions in the Tl5Te3-Tl9BiTe6-Tl5Te2I system

Phase equilibria in the Tl5Te3-Tl9BiTe6-Tl5Te2I system, containing ternary structural analogs of Tl5Te3, have been studied by differential thermal analysis, X-ray diffraction, microhardness tests, and emf measurements using concentration cells with a thallium electrode. A number of T-x sections, the 760- and 800-K sections, and the liquidus and solidus projections of the phase diagram are constructed, and the composition dependences of lattice parameters, microhardness, and emf are obtained. The results demonstrate that, despite the presence of a liquid-liquid miscibility gap, the system contains a continuous series of solid solutions isostructural with Tl5Te3.

Phase relations and magnetic properties of alloys in the Co3Sn2-Bi system

The phase diagram of the Co3Sn2-Bi system has been constructed using physicochemical characterization techniques. The system is pseudobinary, with a limited series of Co3Sn2-based solid solutions (∼7 at % Bi) and a liquid-liquid miscibility gap in the composition range ∼14–88 at % Bi. A Co3Sn2-based solid solution containing about 7 at % Bi has been shown to possess spontaneous magnetization in the temperature range 80–400 K. Its Curie temperature exceeds 400 K.

Phase Relations and Transport Properties of Alloys in the Bi2Te3-TlGaTe2 System

Using physicochemical analysis, the Bi2Te3-TlGaTe2 system is shown to contain Bi2Te3− and TlGaTe2-based restricted solid-solution series and a liquid-liquid miscibility gap in the composition range ≃12–30 mol % TlGaTe2. The power factor α2σ of (Bi2Te3)1−x (TlGaTe2)x solid solutions with 0.01 ≤ x ≤ 0.02 is suitable for thermoelectric applications.

System ZnO ⋅ B2O3-CuO ⋅ B2O3

Differential thermal analysis and x-ray diffraction data indicate that the ZnO ⋅ B2O3-CuO ⋅ B2O3 join of the ternary system CuO-B2O3-ZnO is pseudobinary, with eutectic phase relations and a liquid-liquid miscibility gap in the composition range 25–35 mol % CuO.

Morphology Control of Phase-Separation Texture by Elongation of Two-Liquids Immiscible Melt in Fe3O4-SiO2 System.

The existence of a liquid-liquid miscibility gap in Fe3O4-SiO2 system has been reported. In this study, phaseseparated glasses of 5Fe3O4⋅95SiO2 (mol%) were prepared by melting sintered rods of the same composition at 1800°C (in immiscible region) using an infrared imaging furnace and, subsequently, quenching with elongation of the melts at a constant rate. The glass quenched without elongation exhibited a binodal type phase separation texture consisting of discrete spherical Fe3O4-rich particles. On the contrary, in the sample quenched with elongation, Fe3O4-rich particles were stretched and oriented along the direction of elongation. The length of the stretched particles was proportional to the elongation distance and was not independent of the elongation rate within short elongation distance. However, the stretching of the particles was less pronounced for the long elongation ranges. This suggests that the spherical particles grown by phase separation in the binodal region, were stretched by viscous flow in the early stage of elongation and the stretching in the latter stage was reduced by restoration due to viscoelastic behavior and/or to a steep increase of viscosity. The deformation and orientation of phase separation texture could be achieved in this process, though this deformation proceeded under non-equilibrium conditions. Therefore, the operated elongation process of two-liquid immiscible melts may enable one to fabricate high-functional composite materials owing to morphology control of phase separation texture.

Experimental study of the ternary system CdTeZn

The ternary system CdZnTe has been studied by differential thermal analysis, differential scanning calorimetry and X-ray powder diffraction. A solid solution is observed between CdTe and ZnTe. At low temperature this quasi-binary section exhibits a miscibility gap. The liquid-liquid miscibility gap induced by the binary monotectic reaction extends within the ternary system and its boundary has been determined. The only ternary reaction existing in this system is a eutectic reaction at 265 °C and the corresponding composition is located in the very close neighbourhood of the binary eutectic CdZn.

Phase behavior of polylactides in solvent (SINGLEBOND) Nonsolvent mixtures

Isothermal phase diagrams for the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent-nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid-liquid miscibility gap, the solid-liquid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liquid-liquid miscibility gap for the systems with PLLA was located in the same composition range as the corresponding systems with PDLLA. For the systems containing PLLA solid-liquid demixing was thermodynamically preferred over liquid-liquid demixing. Attempts were made to correlate the experimental findings with predictions on the basis of the Flory-Huggins theory for ternary solutions using interaction parameters derived from independent experiments. Qualitative agreement was found between the theoretical predictions and the experimentally obtained liquid-liquid miscibility gap. No good agreement was found for the solid-liquid miscibility gap.

A morphological study of membranes obtained from the systems polylactide-dioxane-methanol, polylactide-dioxane-water and polylactide-N-methyl pyrrolidone-water

The influence of liquid-liquid demixing, solid-liquid demixing, and vitrification on the membrane morphologies obtained from several polylactide-solvent-nonsolvent systems has been investigated. The polymers investigated were the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA). The solvent-nonsolvent systems used were dioxane-water, N-methyl pyrrolidone-water and dioxane-methanol. For each of these systems it was attempted to relate the membrane morphology to the ternary phase diagram at 25°C. It was demonstrated that for the amorphous poly-DL-lactide the intersection of a glass transition and a liquid-liquid miscibility gap in the phase diagram was a prerequisite for the formation of stable membrane structures. For the semicrystalline PLLA a wide variety of morphologies could be obtained ranging from cellular to spherulitical structures. For membrane-forming combinations that show delayed demixing, trends expected on the basis of phase diagrams were in reasonable agreement with the observed membrane morphologies. Only for the rapidly precipitating system PLLA-N-methyl pyrrolidone-water were structures due to liquid-liquid demixing obtained when structures due to solid-liquid demixing were expected. Probably, rapid precipitation conditions promote solid-liquid demixing over liquid-liquid demixing, because the activation energy necessary for liquid-liquid demixing is lower than that for crystallization.

Liquid-Liquid Phase Separation of Melts and Glasses in Ferric Ferrous Oxide-Silica System

ABSTRACTThe existence of liquid-liquid miscibility gap in ferric ferrous oxide-silica system has been reported, however, the phase separation phenomena and the derived morphology of the phase separated glasses are uncertain. In this study, the melt-quenched samples of 5 Fe3O4-95 SiO2 and 15 Fe3O4-85 SiO2 (mol%) were prepared by melting at 2300°C or 2200°C (expected to be above miscibility gap), and subsequently at 1800°C or 1750°C (in immiscible region) by use of infrared image furnace and quenching at the rate of ≈102 K/sec. The glassy materials exhibited phase separation having discrete spherical particles or interconnected structure due to the composition, melting temperature and time. Also, the segregation of Fe component occurred during melting, which was caused by the difference of specific gravity of components in the melt.

Description of the Cu-As-Se ternary system

The phase diagram of the Cu-As-Se ternary system was studied by differential thermal analysis, X-ray diffraction and metallography analysis. Two ternary phases are observed: the Cu3AsSe4 compound, which melts congruently, and the CuAsSe2 compound, which undergoes a peritectic decomposition. The ternary system is subdivided into 12 secondary triangles. The 12 ternary invariants are localized: six eutectics, one of which is degenerated at the selenium apex, and six peritectics. Two ternary liquid-liquid miscibility gaps originating from the Cu-Se binary system are identified. One of these is crossed by a eutectic valley giving a first-class ternary monotectic equilibrium. A large vitreous region, which comes from the As-Se binary glass zone, is identified; it overlaps the liquid-liquid miscibility area, giving phase-separated glasses.