Determination Of Phase Diagram Research Articles

Determination of phase diagram of polyolefin blend nanocomposites by rheological approach: Influence of rheological method and nanoparticles on shifting the phase transition boundary

AbstractIn this research, by using different rheometric methods, the temperatures of phase transition for upper critical solution temperature phase diagram of polyethylene (PE) and poly(ethylene‐co‐vinyl acetate) (EVA) blends and filled systems with organically‐modified nanoclay (ONC) were measured. Since the PE/EVA‐based mixtures are widely applied in the film and foam industries, the evaluation of the phase behavior of these mixtures is of great importance. Microscopic observations show that ONC nanoparticles have a compatibilization role on the biphasic microstructure of PE/EVA. ONC nanoparticles have a remarkable impact on the viscoelastic properties of the EVA phase, leading to a reduction in the asymmetry of the viscoelastic properties of the two polymeric phases. The findings of this work focused on the isochronal dynamic temperature sweep tests on the well‐mixed and phase‐separated nanofiller‐filled systems with different cooling/heating rates indicated that these series of experiments did not have the necessary efficiency to determine the phase separation boundary and spinodal temperatures in thermodynamically equilibrium conditions. By using Han plot and dynamic temperature sweep tests at the minimum possible heating rate, 0.25 K/min, it was proved that by adding nanoparticles to PE/EVA blends, the area of well‐mixed region of the phase diagram did not show a significant increment. The pinning effects of nanoparticles on the polymeric chains and correspondingly, the reduction of molecular dynamics mainly affect the phase separation phenomenon.

Green Extraction Strategy Using Bio-Based Aqueous Biphasic Systems for Polyphenol Valorization from Grape By-Product.

Polyphenols are natural compounds with enhanced antioxidant properties. They are present in relatively high concentrations in fruit/vegetable by-products. Therefore, there is a need for the development of efficient and cost-effective methods for the separation and purification of these valuable compounds. Traditional extraction with organic solvents needs to be switched to novel methods that are more efficient, with reduced extraction times and low consumption of organic solvents. Aiming at developing sustainable processes for the separation and purification of phenolic compounds, we used three model compounds, namely resveratrol, quercetin, and gallic acid, to investigate ionic liquid-based aqueous biphasic systems (IL-ABSs) formed by cholinium-based IL in combination with polypropylene glycol with a molecular mass of 400 g/mol (PPG400). The ABS composition in the two-phase region was selected according to a previously determined phase diagram. Extraction studies indicated the preferential partition of resveratrol and quercetin toward the hydrophobic PPG-rich phase that is mainly dominated by its hydrophobic nature and the strong salting-out effect of ILs. On the other hand, due to its considerably hydrophilic nature, gallic acid preferentially migrates toward the IL phase. The achieved results from grape stem extract demonstrated high extraction efficiencies of cholinium dihydrogen phosphate (~99% for resveratrol for the PPG phase and 78% for gallic acid for the IL phase), with considerable selectivity, demonstrating promising outcomes for potential applications.

Determination of the Asymmetric Ternary Phase Diagram and Preparation of Theophylline–Isonicotinamide Cocrystals

Determination of the Asymmetric Ternary Phase Diagram and Preparation of Theophylline–Isonicotinamide Cocrystals

Investigation of the Binary System of Proxyphylline Enantiomers: Structural Resolution and Phase Diagram Determination.

The solid-state landscape of proxyphylline (PXL), a chiral derivative of theophylline crystallizing as a racemic compound, was extensively investigated by means of thermal analyses and diffraction techniques. This study revealed the presence of five distinct polymorphic forms that were characterized: two polymorphs of the racemic mixture and three polymorphs of the pure enantiomer. The nature of each solid phase was confirmed by combining the different analytical techniques, revealing the presence of a thermodynamically stable racemic compound, RI (TFus= 134 °C), in equilibrium with the stable enantiopure crystal form, EI (TFus = 148.3 °C). Additionally, other crystal forms could be evidenced: a polymorph of the racemic compound, RII (TFus= 111.5 °C), as well as two metastable conglomerates, cEI and cEII, and two other polymorphs of the pure enantiomer, EII and EIII. The crystal structures of RI and EI are reported and discussed, highlighting the diversity of molecular conformations that can be adopted by the PXL molecule, which accounts for the versatility of the crystallization behaviors observed in this system. These findings enhance our understanding of the crystallization behavior of chiral pharmaceutical compounds and have implications for optimizing their crystallization processes in the pharmaceutical industry.

Excited-State Phase Diagram of a Ferromagnetic Quantum Gas.

The ground-state phases of a quantum many-body system are characterized by an order parameter, which changes abruptly at quantum phase transitions when an external control parameter is varied. Interestingly, these concepts may be extended to excited states, for which it is possible to define equivalent excited-state quantum phase transitions. However, the experimental mapping of a phase diagram of excited quantum states has not yet been realized. Here we present the experimental determination of the excited-state phase diagram of an atomic ferromagnetic quantum gas, where, crucially, the excitation energy is one of the control parameters. The obtained phase diagram exemplifies how the extensive Hilbert state of quantum many-body systems can be structured by the measurement of well-defined order parameters.

Phase diagram determination at fivefold nuclear compression

In the standard model of particle physics, the strong force is characterized by the theory of quantum chromodynamics (QCD). It is commonly understood from QCD properties that hadrons, at sufficiently high temperatures or densities, melt into their constituent quarks, thereby undergoing a deconfinement transition to a new phase of quarks and gluons, often referred to as quark matter or quark-gluon plasma (QGP) [1,2]. Although QGP has been observed in relativistic heavy-ion collisions [3,4], uncertainties remain about when the onset of deconfinement occurs. After comparing simulations from a reliable hadron and quark relativistic transport model with recent data from the STAR experiment, we determined that the onset of the hadron-quark phase transition occurs at about five times nuclear compression, corresponding to temperature T∼ 112 MeV and baryon chemical potential μB∼ 586 MeV, in the nuclear matter phase diagram. This discovery has significant implications for the studies of both the early and present universe [5], including the fraction of dark matter formed in the early universe [6–8] and the structure and dynamics of neutron stars and their mergers [9].

Thermo-Calc determination of phase diagram and thermodynamic properties of Ni-Al binary system

Ni-Al alloys have good corrosion-resistant properties making them preferable as a material of choice compared to ordinary metals. A good understanding of the phase diagram and thermodynamic properties of the Ni-Al alloy binary system is essential in determining relevant industrial applications of the system. The Ni-Al phase diagram is being reassessed since those found in the literature are based on old experimental studies. The phase diagram and thermodynamic properties of the Ni-Al alloy is determined using the Thermo-Calc 2022b software over a temperature range of 200 K to 2000 K and 1 atm of pressure. A total of nineteen fields (including elemental Al and Ni) comprising five single solid phases, one liquid phase, and twelve double regions were obtained from the equilibrium calculation. The thermodynamic calculation has six invariant reactions containing two eutectic reactions (914.83 ± 0.025 K and 1641.80 ± 0.025 K), three peritectic reactions (1123.55 ± 0.025 K, 1400.72 ± 0.025 K and 1642.65 ± 0.025 K), and one peritectoid reaction (913.96 ± 0.025 K). The solubility of Al in Ni is also determined. The Gibbs free energy, the molar enthalpy and the activities of Al in Ni are all calculated at temperatures 913 K, 1642 K, and 1953 K. The Thermo-Calc temperature – composition of the Ni-Al alloy is compared with the existing experimental studies to identify the physical properties of the different thermodynamic properties of the Ni-Al alloy binary system.

Modelling of the isothermal vapor-liquid equilibrium of alternative refrigerants: Determination of phase diagrams (high-pressure/low-pressure) and optimized binary interaction parameters

In this work, a thermodynamic model for prediction of Vapor-Liquid Equilibrium (VLE) at moderate pressures (up to 19 bar) and different temperatures (288-323 K) is developed by using Soave-Redlich-Kwong (SRK) and Peng-Robenson (PR) equations of state (EoS) in combination with the classical van der Waals (vdW) mixing rules. Four refrigerant binary systems have been considered in this study (R134a+ R1336mzz (E)), (R600a+R1234ze (Z)), (R600a+R1243zf), (R744+R152a). Also, a new method was used to improve binary interaction parameters (kij). A comparison of experimental phase equilibrium data in the literature with the predicted results showed very good representation for some mixing rules.

Redox-responsive microemulsion: Fabrication and application to curcumin encapsulation

HypothesisStimulus-responsive microemulsions have aroused significant attention because of their versatile and reversible switchability between stable and unstable states. However, most stimuli-responsive microemulsions are based on stimuli-responsive surfactants. We posit that the change in the hydrophilicity of a selenium-containing alcohol triggered by a mild redox reaction could also influence the stability of microemulsions and provide a new nanoplatform for the delivery of bioactive substances. ExperimentsA selenium-containing diol (3,3′-selenobis(propan-1-ol), PSeP) was designed and used as a co-surfactant in a microemulsion with ethoxylated hydrogenated castor oil (HCO40), diethylene glycol monohexyl ether (DGME), 2-n-octyl-1-dodecanol (ODD) and water. The redox-induced transition in PSeP was characterized by 1H NMR, 77Se NMR, and MS. The redox-responsiveness of the ODD/HCO40/DGME/PSeP/water microemulsion was investigated through determination of a pseudo-ternary phase diagram, analysis by dynamic light scattering, and electrical conductivity, and its encapsulation performance was evaluated by determination of the solubility, stability, antioxidant activity, and skin penetrability of encapsulated curcumin. FindingsThe redox conversion of PSeP enabled efficient switching of ODD/HCO40/DGME/PSeP/water microemulsions. Addition of oxidant (H2O2), oxidized PSeP into more hydrophilic PSeP-Ox (selenoxide), disrupting the emulsifying capacity of the combination of HCO40/DGME/PSeP, markedly reducing the monophasic microemulsion region in the phase diagram, and inducing phase separation in some formulations. Addition of reductant (N2H4·H2O), reduced PSeP-Ox and restored the emulsifying capacity of the combination of HCO40/DGME/PSeP. In addition, PSeP-based microemulsions can significantly enhance the solubility in oil (by 23 times), stability, antioxidant capacity (DPPH∙ radical scavenging by 91.74 %), and skin penetrability of curcumin, showing clear potential for encapsulation and delivery of curcumin and other bioactive substances.

Investigating the Phase Diagram of SiO<sub>2</sub>–CaO–CrO<i><sub>x</sub></i> System to Evaluate Distribution of Platinum between Slag and Molten Copper

In the hydrometallurgical process used for recycling platinum group metals (PGMs), a residue containing mainly Cr2O3 and a small amount of PGMs is generated. In the present work, a pyrometallurgical process was applied in which PGMs from the residue generated in the hydrometallurgical process are concentrated in a molten copper phase as a collector-metal, and Cr2O3 is separated into a slag phase with SiO2 and CaO as a flux. To reduce the loss of PGMs to the slag, it is necessary to have a homogenous liquid and a lower dissolution of PGMs into the slag. Therefore, the phase diagram of the SiO2–CaO–CrOx system was investigated at 1773 and 1873 K in an oxygen partial pressure pO2 = 10-10 to obtain knowledge of the homogeneous melts. Based on the determined phase diagram, the distribution ratios of Pt as representative PGMs between the liquid SiO2–CaO–Al2O3–CrOx or the liquid SiO2–CaO–CrOx slag and molten copper were measured at 1773 K in pO2 = 10-10. The experimental results showed that CrOx solubility in the slag increased with decreasing slag basicity, B defined as B = (mass%CaO)/(mass%SiO2). Furthermore, the results showed that the distribution of Pt in the slag increased with increasing CrOx concentration in the slag.

Aqueous solubilization of hydrophobic compounds by inorganic nano-ions: An unconventional mechanism

HypothesisSolubilization of hydrophobic compounds in water is commonly performed by using organic solubilizers such as hydrotropes, surfactants, co-solvents, and macrocycles to form host–guest complexes. 3,3′-commo-bis[closo-1,2-dicarba-3-cobaltadodecaborane] derivatives (COSANs) are fully inorganic and non-amphiphilic ionic boron clusters with nanometric size (nano-ions) showing superchaotropic properties as they strongly bind to neutral organic molecules. Therefore, we expect COSANs to act as solubilizers of sparingly water-soluble molecules, but with a mechanism different from all other organic solubilizers known so far. ExperimentsThe aqueous solubilization efficiency of COSANs towards butanol was evaluated by determining phase diagrams and comparing them to classical solubilizers. Nanostructuration of the mixture was studied using UV spectroscopy, small-angle X-ray, and neutron scattering with contrast variation. FindingsCOSANs act as efficient aqueous solubilizers of medium-chain alcohols (0.6 < log P < 1.5). Unlike surfactants, COSAN is an efficient solubilizer in its monomeric state, at concentrations well below its critical aggregation concentration. Solubilization by COSAN takes place with a bi-dimensional anisotropic growth of COSAN/butanol co-assemblies, whereas solubilization by surfactant occurs via an isotropic swelling of micelles. Appealingly, COSANs/2-butanol co-assemblies efficiently solubilize more hydrophobic compounds with log P values up to around 6, offering new opportunities in many applied fields.

Phase diagrams-Why they matter and how to predict them.

Understanding the thermodynamic stability and metastability of materials can help us to, for example, gauge whether crystalline polymorphs in pharmaceutical formulations are likely to be durable. It can also help us to design experimental routes to novel phases with potentially interesting properties. In this Perspective, we provide an overview of how thermodynamic phase behavior can be quantified both in computer simulations and machine-learning approaches to determine phase diagrams, as well as combinations of the two. We review the basic workflow of free-energy computations for condensed phases, including some practical implementation advice, ranging from the Frenkel-Ladd approach to thermodynamic integration and to direct-coexistence simulations. We illustrate the applications of such methods on a range of systems from materials chemistry to biological phase separation. Finally, we outline some challenges, questions, and practical applications of phase-diagram determination which we believe are likely to be possible to address in the near future using such state-of-the-art free-energy calculations, which may provide fundamental insight into separation processes using multicomponent solvents.

The Thermal Stability of Asymmetric Separated Configurations inside Alloy Nanoparticles: Atomic-Scale Modeling of Pd-Ir Nanophase Diagrams.

Compared to alloy bulk phase diagrams, the experimental determination of phase diagrams for alloy nanoparticles (NPs), which are useful in various nanotechnological applications, involves significant technical difficulties, making theoretical modeling a feasible alternative. Yet, being quite challenging, modeling of separation nanophase diagrams is scarce in the literature. The task of predicting comprehensive nanophase diagrams for Pd-Ir face-centered cubic-based three cuboctahedra is facilitated in this study by combining the computationally efficient statistical-mechanical Free-energy Concentration Expansion Method, which includes short-range order (SRO) with coordination-dependent bond-energy variations as part of the input and with rotationally symmetric site grouping for extra efficiency. This nanosystem has been chosen mainly because of the very small atomic mismatch that simplifies the modeling, e.g., in the assessment of vibrational entropy contributions based in this work on fitting to the Pd-Ir experimental bulk critical temperature. This entropic effect, together with SRO, leads to significant destabilization of low-T Quasi-Janus (QJ) asymmetric configurations of the NP core, which transform to symmetric partially mixed nanophases. First-order and second-order intracore transitions are predicted for dilute and intermediate-range compositions, respectively. Caloric curves computed for the former case yield the NP-size dependent transition latent heat, and in the latter case critical temperatures exhibit a specific scaling behavior. The computed separation diagrams and intracore solubility diagrams reflect enhanced elemental mixing in smaller QJ nanophases. In addition to these diagrams, the revealed near-surface compositional variations are likely to be pertinent to the utilization of Pd-Ir NPs, e.g., in catalysis.

Construction and high throughput exploration of phase diagrams of multi-component organic blends

During solvent-based fabrication of organic blends the blend composition changes significantly as solvent is removed from the blend triggering phase transformations and structure formation. The choice of the solvent in conjunction with the processing pathways (i.e. quench profile) affects this process. Using a combination of solvents as well as solvent additives has produced favorable structures for organic electronic applications. However, selecting which solvent, solvent blend, or additive to use becomes a combinatorially complex problem. Successful efforts to pre-screen based on solubility spheres, and in general thermodynamics arguments, suggest that the phase diagram can be a useful design tool for solvent composition selection. Here, we report a workflow for high-throughput construction of a library of phase diagrams, followed by an exploration of the solvent selection space guided by the library. Our analysis pipeline consists of (i) a convex-hull based method to determine phase diagrams of multi-component mixtures; and (ii) high throughput analysis of a large set of phase diagrams using dimensionality reduction coupled with clustering. Using this workflow, we illustrate exploration of solvent and the associated design rules for a model material system used in organic thin films fabrication. We envision this workflow to be useful for rapid exploration and selection of multi-component solvent blends and additive formulations.

Experimental determination of phase diagram involving silicides in the Fe-Si binary system

The phase diagram of the Fe-Si binary system was precisely determined using FE-EPMA/WDS and thermal analysis of DSC. It was confirmed that the concentration ranges of the β-Fe2Si and ζα-FeSi2 phases are slightly narrower and shifted toward higher Fe concentrations compared with the literature, and the other iron-silicide phases have low but certain concentration ranges less than 1 at%. The A2/B2/D03 order-disorder transition and Curie temperatures in the BCC phases exhibited concentration dependences consistent with those temperatures reported by Meco and Napolitano, and the Curie temperatures of the α”-Fe3Si (D03) alloys deviated higher from the extrapolated values of the α-Fe (A2) phase with increasing Si content and bent at the stoichiometric composition of 25 at%Si. Invariant reaction temperatures were mostly coincident with those of the phase diagram in the literature, except for the peritectoid temperature of the η-Fe5Si3 phase, whereas a small discrepancy was revealed in the solidus and liquidus lines.

CALPHAD modeling of uranium nitride (UN) fabrication routes enabled by first-principles calculations

The thermochemical details of fabricating uranium nitride (UN) by ammonolysis of uranium tetraflouride (UF4) were determined using density functional theory (DFT) and CALculation of PHAse Diagrams (CALPHAD) computational methods. The thermochemical data of all binary, ternary, and quaternary U–H–N–F phases were computed using DFT, and the data for the phases that have not been measured experimentally, including UN2 and NH4F(g), were combined with existing experimentally-determined data for CALPHAD modeling. The DFT data were benchmarked using experimental Gibbs energy of reaction and experimental thermochemical data for individual species. Phase diagrams relevant to the ammonolysis reaction are depicted, showing regions of stability for solid U–N, U–F and U–N–F phases. An unidentified phase produced in a previous experiment was identified as UN0.95F1.2 (UNF) by comparing its X-ray diffraction spectrum to the experimental spectrum, and its formation during the fabrication of UN from UF4 is supported by the simulated phase diagram. It is calculated that UN2 can be produced by the ammonolysis of UF4, but requires elevated temperatures, high NH3(g) partial pressure, and large amounts of flowing NH3(g) to avoid solid fluoride impurities in the uranium nitride. Likewise, U2N3 can be produced instead at temperatures greater than 980 K. The use of silane (SiH4) gas was investigated as a potential additive in the ammonolysis fabrication route to speed removal of fluorine. The addition of SiH4(g) offers little advantage to the removal of fluorine, and adds the complication of Si3N4 formation. The use of DFT to fill in missing data to perform CALPHAD calculations demonstrated here allows for the determination of more comprehensive and trustworthy phase diagrams than the use of existing experimental data alone.

Phase Diagram Determination and Process Development for Continuous Antisolvent Crystallizations

The development of an antisolvent crystallization process requires the construction of an accurate phase diagram for this ternary system of compound, solvent and antisolvent, preferably as a function of temperature. This study gives an efficient methodology to systematically determine such antisolvent phase diagrams, exemplified with four model compounds: Sodium bromate, DL-Asparagine Monohydrate, Mefenamic acid and Lovastatin. Using clear point temperature measurements, single solvent and mixed solvent-antisolvent solubilities are obtained, showing strongly non-linear solubility dependencies as well as more complex solubility behaviour as a function of antisolvent fraction. A semi-empirical model equation is used to describe the phase diagram of the antisolvent crystallization system as a function of both temperature and antisolvent fraction. The phase diagram model then allows for the identification of condition ranges for optimal productivity, yield, and suspension density in continuous antisolvent crystallization processes.

The study of the dynamics of the order parameter of coupled oscillators in the Ott-Antonsen scheme for generic frequency distributions.

The Ott-Antonsen ansatz shows that, for certain classes of distribution of the natural frequencies in systems of N globally coupled Kuramoto oscillators, the dynamics of the order parameter, in the limit N → ∞, evolves, under suitable initial conditions, in a manifold of low dimension. This is not possible when the frequency distribution, continued in the complex plane, has an essential singularity at infinity; this is the case, for example, of a Gaussian distribution. In this work, we propose a simple approximation scheme that allows one to extend also to this case the representation of the dynamics of the order parameter in a low dimensional manifold. Using the Gaussian frequency distribution as a working example, we compare the dynamical evolution of the order parameter of the system of oscillators, obtained by the numerical integration of the N equations of motion, with the analogous dynamics in the low dimensional manifold obtained with the application of the approximation scheme. The results confirm the validity of the approximation. The method could be employed for general frequency distributions, allowing the determination of the corresponding phase diagram of the oscillator system.

Evaluation of the compressible regular solution model predictions via rheologically determined phase diagram for polyvinylchloride/polycaprolactone blend

Evaluation of the compressible regular solution model predictions via rheologically determined phase diagram for polyvinylchloride/polycaprolactone blend

Co-crystal Phase Diagram Determination by the Solution Addition Method

Multicomponent crystals such as co-crystals, salts, and solid solutions can be used to modify physical properties of active pharmaceutical ingredients. Phase diagrams of such multicomponent crystals are essential for crystallization process development, especially in the case where multiple solid phases may coexist. However, additional components and solid phases make phase diagrams more complex and their determination more time consuming. We propose to accelerate this process by identifying the eutectic points and constructing the rest of the phase diagram using thermodynamic models, informed by further measurements, if necessary. In this work, a novel solution addition method is proposed for determining the eutectic points in a co-crystal system. This method implements gradual compositional changes to traverse various regions of the phase diagram. Phase boundaries are determined by monitoring changes in the liquid phase (UV–vis) and solid phase (Raman), and eutectic points are obtained from intersection of phase boundaries. The results from solution addition are compared to those of an equilibration method, which combines gravimetry, XRPD, and NMR to identify the eutectic solution composition starting from a composition in the three-phase region of a co-crystal phase diagram. Both methods were able to locate all eutectic points, allowing construction of the ternary phase diagrams of benzoic acid and isonicotinamide in ethanol.