Miscible Mixtures Research Articles

Phase segregation of a partially miscible binary mixture subjected to an external force field

Phase segregation of a partially miscible binary mixture subjected to an external force field

Lattice Boltzmann Model for Rarefied Gaseous Mixture Flows in Three-Dimensional Porous Media Including Knudsen Diffusion

Numerical modeling of gas flows in rarefied regimes is crucial in understanding fluid behavior in microscale applications. Rarefied regimes are characterized by a decrease in molecular collisions, and they lead to unusual phenomena such as gas phase separation, which is not acknowledged in hydrodynamic equations. In this work, numerical investigation of miscible gaseous mixtures in the rarefied regime is performed using a modified lattice Boltzmann model. Slip boundary conditions are adapted to arbitrary geometries. A ray-tracing algorithm-based wall function is implemented to model the non-equilibrium effects in the transition flow regime. The molecular free flow defined by the Knudsen diffusion coefficient is integrated through an effective and asymmetrical binary diffusion coefficient. The numerical model is validated with mass flow measurements through microchannels of different cross-section shapes from the near-continuum to the transition regimes, and gas phase separation is studied within a staggered arrangement of spheres. The influence of porosity and mixture composition on the gas separation effect are analyzed. Numerical results highlight the increase in the degree of gas phase separation with the rarefaction rate and the molecular mass ratio. The various simulations also indicate that geometrical features in porous media have a greater impact on gaseous mixtures’ effective permeability at highly rarefied regimes. Finally, a permeability enhancement factor based on the lightest species of the gaseous mixture is derived.

(1-Deoxy)ceramides in bilayers containing sphingomyelin and cholesterol

The discovery of a novel sphingolipid subclass, the (1-deoxy)sphingolipids, which lack the 1-hydroxy group, attracted considerable attention in the last decade, mainly due to their involvement in disease. They differed in their physico-chemical properties from the canonical (or 1-hydroxy) sphingolipids and they were more toxic when accumulated in cells, inducing neurodegeneration and other dysfunctions. (1-Deoxy)ceramides, (1-deoxy)dihydroceramides, and (1- deoxymethyl)dihydroceramides, the latter two containing a saturated sphingoid chain, have been studied in this work using differential scanning calorimetry, confocal fluorescence and atomic force microscopy, to evaluate their behavior in bilayers composed of mixtures of three or four lipids. When compared to canonical ceramides (Cer), a C16:0 (1-deoxy)Cer shows a lower miscibility in mixtures of the kind C16:0 sphingomyelin/cholesterol/XCer, where XCer is any (1-deoxy)ceramide, giving rise to the coexistence of a liquid-ordered phase and a gel phase. The latter resembles, in terms of thermotropic behavior and nanomechanical resistance, the gel phase of the C16:0 sphingomyelin/cholesterol/C16:0 Cer mixture [Busto et al., Biophys. J. 2014, 106, 621–630]. Differences are seen between the various C16:0 XCer under study in terms of nanomechanical resistance, bilayer thickness and bilayer topography. When examined in a more fluid environment (bilayers based on C24:1 SM), segregated gel phases are still present. Probably related to such lateral separation, XCer preserve the capacity for membrane permeation, but their effects are significantly lower than those of canonical ceramides. Moreover, C24:1 XCer show significantly lower membrane permeation capacity than their C16:0 counterparts. The above data may be relevant in the pathogenesis of certain sphingolipid-related diseases, including certain neuropathies, diabetes, and glycogen storage diseases.

Estimation of the Shear Viscosity of Mixed-Polymer Materials for Screw Extrusion-Based Recycling Process Modeling.

The scope of this work is the development of a method to estimate the temperature and shear rate-dependent viscosity of mixtures composed of two polymers. The viscosity curve of polymer mixtures is crucial for the modeling and optimization of extrusion-based recycling, which is the most efficient way to recycle polymeric materials. The modeling and simulation of screw extruders requires detailed knowledge of the properties of the processed material, such as the thermodynamic properties, the density, and the rheological behavior. These properties are widely known for pure materials; however, the incorporation of impurities, like other polymers in recycled materials, alters the properties. In this work, miscible, immiscible, and compatibilized immiscible polymer mixtures are considered. A new method based on shear stress is proposed and compared to the shear rate-based method. Several mixing rules are evaluated for their accuracy in predicting mixture viscosity. The developed methods allow the prediction of the viscosity of a compatibilized immiscible mixture with deviations below 5% and that of miscible polymer mixtures with deviations below 3.5%.

Investigation of rheological properties of extruded composites based on UHMWPE

The influence of the CO-4 stabilizer on the rheological properties of polymer composite materials based on UHMWPE has been studied. It has been shown that the addition of a CO-4 stabilizer to polymer matrices significantly affects the rheological properties of materials and their extrudability. There is a change in the conformations of macromolecular chains, the absence of dependence of the viscous component on the relaxation process of the dispersed system, an increase in the complex viscosity, which led to a deterioration in the processability of the material. Based on the Han curves, it is shown that the addition of a CO-4 stabilizer leads to a deterioration in the miscibility of mixtures, i.e., the phase separation of the components of the obtained samples increases.

Investigation of mixing miscible liquids with high viscosity contrasts in turbulently stirred vessels using electrical resistance tomography

The time required to attain a sufficient degree of homogeneity i.e., mixing time, is an important parameter in mixing processes. This paper presents results from a study employing an experimental approach to estimate mixing times for a miscible Newtonian liquid mixture system with high viscosity contrasts in a turbulent stirred vessel. An Electrical Resistance Tomography (ERT) based technique has been adopted to monitor dimensionless mixing time across a range of additive viscosities, impeller designs, sizes, and speed. Dimensional analysis has been used to interpret these mixing time results in terms of the magnitude of the bulk inertia forces relative to the initial viscous forces within the added fluid. Critical non-dimensional numbers, uniting the properties of the two liquids, have been proposed as the criterion for avoiding undesirable operating conditions under which the mixing time is much longer than that required for mixing fluids with similar properties. The work proposes novel correlations for mixing time and incorporates a new dimensionless group, thereby enabling a more nuanced and accurate characterisation of mixing behaviours. This research stands to contribute to energy saving and waste minimisation efforts in the industry. It provides insights for process designers and simulation engineers, propelling a leap forward in the design and operation of mixing processes when dealing with liquid systems that have significant viscosity differences.

Binding potential and wetting behavior of binary liquid mixtures on surfaces.

We present a theory for the interfacial wetting phase behavior of binary liquid mixtures on rigid solid substrates, applicable to both miscible and immiscible mixtures. In particular, we calculate the binding potential as a function of the adsorptions, i.e., the excess amounts of each of the two liquids at the substrate. The binding potential fully describes the corresponding interfacial thermodynamics. Our approach is based on classical density functional theory. Binary liquid mixtures can exhibit complex bulk phase behavior, including both liquid-liquid and vapor-liquid phase separation, depending on the nature of the interactions among all the particles of the two different liquids, the temperature, and the chemical potentials. Here we show that the interplay between the bulk phase behavior of the mixture and the properties of the interactions with the substrate gives rise to a wide variety of interfacial phase behaviors, including mixing and demixing situations. We find situations where the final state is a coexistence of up to three different phases. We determine how the liquid density profiles close to the substrate change as the interaction parameters are varied and how these determine the form of the binding potential, which in certain cases can be a multivalued function of the adsorptions. We also present profiles for sessile droplets of both miscible and immiscible binary liquids.

Competitive Mechanochemical Solvate Formation of Theophylline in the Presence of Miscible Liquid Mixtures

Competitive Mechanochemical Solvate Formation of Theophylline in the Presence of Miscible Liquid Mixtures

Heat transfer by transiently superheated fluids: Decay of unstable water-based mixtures

The present study sets out to elucidate the characteristic features of instantaneous heat transfer accompanying transient superheating of partially miscible mixtures having a lower critical solution temperature (LCST) with respect to the liquid–liquid binodal and the diffusion (liquid–liquid) spinodal. The research has employed the method of controlled pulsed heating of a wire probe, which can be used to directly measure heat flux into the medium at a strictly fixed heater temperature Tst. At a characteristic heating time of 100 ms, values of Tst were gradually increased from 100 to 500 °C, while the corresponding pressures varied from 0.1 to 35 MPa. The objects of study were aqueous solutions of PPG-425 and PPG-2000 polypropylene glycols, as well as 2,6-Lutidine, all having LCST in the range convenient for achieving large superheats. The values of the heat transfer coefficient (whose highest values reached 90 kW/m2 K for the solution with 5 wt% PPG-2000 content at the superheat degree of about 390 °C) and the energy absorbed by the solution were calculated on the basis of the primary data. The calculation results related the individual features of the studied systems to the phase diagram and characteristic system relaxation times depending on the concentration and superheat degree with respect to the spinodal. The applicability of such systems as coolants under conditions of high-power heat release for elements with a short response time is demonstrated. Based on the experimental results, we validated the selection of solutions as coolants in the concentration range from the left branch of the spinodal to the critical concentration of the solution.

Starving Free Solvents: Toward Immiscible Binary Liquid Electrolytes for Li‐Metal Full Cells

AbstractCurrent state‐of‐the‐art Li batteries use single‐phase electrolytes; however, these electrolytes often encounter difficulty in simultaneously fulfilling the nonidentical electrochemical requirements of cathodes and anodes. Here, a class of immiscible binary liquid electrolyte (BLE) is designed by starving free solvent molecules. Based on their electrochemical stability window, 1,2‐dimethoxyethane (DME) and succinonitrile (SN) are selected as model solvents for Li‐metal anodes and LiNi0.8Co0.1Mn0.1 (NCM811) cathodes, respectively. Li bis(fluorosulfonyl)imide (LiFSI), which promotes Li+ solvation (i.e., reduces free solvents), enables the phase separation of the miscible solvent mixture (SN−DME), and an increase in its concentration strengthens the coordination of Li+−FSI− in the solvation sheath, thus yielding (anion‐derived) fluorine‐rich electrode–electrolyte interphases. The resulting BLE allows 4.4 V Li‐metal full cells to exhibit a stable capacity retention under a constrained cell condition (Li (20 µm, 4.1 mAh cm−2)||NCM811 (3.8 mAh cm−2), N (negative)/P (positive) capacity ratio = 1.08), which exceed those of previously reported binary liquid electrolytes.

Repeated Microphase Separation and Heating-free Distillation-like Behavior of Miscible Binary Liquid Mixtures Using Nanoconfined Grafted Polymer Layers.

Nanoconfinement is known to drive phase separation (often denoted as microphase separation) of two highly miscible liquids by subjecting the two liquids to disparate influences. Here, we propose a paradigm shift to this problem: we introduce the idea of "repeatability" in nanoconfinement-driven microphase separation. A drop consisting of two highly miscible liquids (A and B) is made to pass through a nanochannel grafted with a collapsed layer of polymer that is philic to A but phobic to B. Subsequently, a significant number of molecules of liquid A get imbibed into the polymer layer and the polymer layer partially swells, while the molecules of liquid B mostly remain out of the polymeric layer and are carried away, emerging as a drop on the other side of the polymer bilayer. This passage of drop (of liquids A and B) is continued, and each time liquids A and B get separated with liquid A imbibing into the polymer layer and liquid B being carried away with the drop. This scenario, therefore, points to the repeated occurrence of the microphase separation of miscible binary liquid mixtures, enabling the processing of a much larger volume of liquid, given the fact that the presence of a grafted polymer layer continues to provide a dynamically increasing space where liquid A can get localized after being separated from liquid B. We quantify such repeated microphase separation by noting the extent of separation (of liquid A) and extent of recovery (of liquid B) as functions of nanochannel height and number of passes. Interestingly, we establish that this process also leads to a distillation-like behavior (without any heat addition), where the concentration of liquid B (equivalent to the "less volatile" liquid in a standard distillation process) progressively increases inside the drop after its passage through the nanochannel.

Start-up and heat transfer characteristics of oscillating heat pipe charged with binary partially miscible organic fluid mixtures

The development of highly-efficient, cost-effective and reliable cooling schemes is still a crucial need for prospective applications in energy- and thermal-related areas, and oscillating heat pipes become a promising option due to their simple structures, high performance and versatilities. In this work, an oscillating heat pipe fabricated by a copper flat-plate evaporator and a capillary copper-tube condenser has been developed, and the experimental study was conducted to investigate the start-up and heat transfer characteristics of the heat pipe device using partially miscible HFE7100-ethanol mixtures at mixing ratios in the range of 1:8 to 8:1 due to the advantage of complementary thermo-physical characteristics and the figure of merit with respect to an OHP. Results demonstrate that the oscillating heat pipe performance was mixing ratio dependent, and there existed optimal mixing ratios of 3.5:1 and 3:1 with respect to the start-up temperature/duration and thermal resistance, respectively. At the optimal mixing ratio of 3.5:1, the time and temperature constants related to the startup performance were reduced by 50.5 s and 5.9 °C, respectively, in comparison with that of ethanol. Besides, the thermal resistance of the oscillating heat pipe charged with HFE7100-ethanol mixture was maximally reduced by 35.5% as compared with that of ethanol at an optimal mixing ratio of 3:1. The complementary thermo-physical properties of partially miscible organic fluids as well as the phase transition suppression and easy transition to unidirectional flow circulation account for the performance improvement. Different from single organic mixtures, the binary organic mixtures exhibited distinctive capabilities to improve the oscillating heat pipe performance, and provides a promising candidate for oscillating heat pipe applications.

Revalorization of sheep-wool keratin for the preparation of fully biobased printable inks

Sheep wool waste has become a problem affecting the environment, as today the wool of most species has no commercial application and is considered a waste product. Sheep’s wool is mainly composed of keratin which, due to its protein nature and multiple functional groups, has attracted great interest in applications such as support materials in tissue engineering, bioactive materials, and targeted drug delivery. Support materials can be fabricated by 3D printing by syringe extrusion. However, keratin is not suitable for this technique as it does not present proper rheological characteristics. Alginate, a biopolymer derived from brown seaweed, offers a wide range of viscosities at room temperature and offers good performance in 3D printing. Thus, keratin and alginate-based mixtures, due to their properties and ecoefficiency, are interesting candidates to prepare 3D-printed scaffolds. The aim of this work was to develop fully biobased printable inks containing keratin, alginate, salvia extracts, and cellulose nanofibers. In a first stage, keratose, an oxidized form of keratin, was obtained from sheep wool by a clean extraction methodology, and the miscibility and viscosity of keratose-alginate mixtures were assessed. In a second stage, biobased inks were prepared parting from miscible keratose-alginate mixtures. Flow analysis, spectromechanical analysis, and recovery tests were carried out to analyze the effect of the ink formulation over rheological parameters and printability. Mesh and cylinder geometries were 3D printed and their mechanical properties, as well as shape fidelity and self-standing ability, were assessed.

Flash point prediction of binary partially and totally miscible alcohol-water mixtures by various equation of states and experimental validation

In the present article, the experimental flash points (FPs) of partially miscible and non-ideal mixtures including 3-pentanol + water, 2-pentanol + water, and 1-hexanol + water are reported for the first time. The measured FPs were predicted based on the vapor pressure concept and ‎thermodynamic equilibrium. The cubic-plus-association (CPA) equation of state (EoS) along with the CR-1 combining rule and Elliot combining rule (ECR) were used to investigate the non-ideality of investigated systems. In the following, the same method was used with the Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) EoSs to evaluate whether simpler EoSs can accurately predict the FPs of non-ideal mixtures. Therefore, in addition to 3-pentanol + water, 2-pentanol + water, and 1-hexanol + water, numerous totally and partially miscible aqueous-organic systems containing 1-pentanol, isobutanol, 2-butanol, 1-‎butanol, isopropanol, propanol, ethanol, and methanol were studied in terms ‎of FP prediction. The findings indicated that SRK is marginally more effective than PR. Moreover, ‎SRK EoS was almost as effective as the CPA EoS with the CR-1 combining rule. The CPA EoS ‎that used ECR, on the other hand, was far superior to the SRK and PR EoSs. To the best of our knowledge, CPA parameters for 2-pentanol, 3-pentanol, and 1-‎hexanol were calculated and reported for the first time.

Interplay between spin-orbit couplings and residual interatomic interactions in the modulational instability of two-component Bose-Einstein condensates.

The nonlinear dynamics induced by the modulation instability (MI) of a binary mixture in an atomic Bose-Einstein condensate (BEC) is investigated theoretically under the joint effects of higher-order residual nonlinearities and helicoidal spin-orbit (SO) coupling in a regime of unbalanced chemical potential. The analysis relies on a system of modified coupled Gross-Pitaevskii equationson which the linear stability analysis of plane-wave solutions is performed, from which an expression of the MI gain is obtained. A parametric analysis of regions of instability is carried out, where effects originating from the higher-order interactions and the helicoidal spin-orbit coupling are confronted under different combinations of the signs of the intra- and intercomponent interaction strengths. Direct numerical calculations on the generic model support our analytical predictions and show that the higher-order interspecies interaction and the SO coupling can balance each other suitably for stability to take place. Mainly, it is found that the residual nonlinearity preserves and reinforces the stability of miscible pairs of condensates with SO coupling. Additionally, when a miscible binary mixture of condensates with SO coupling is modulationally unstable, the presence of residual nonlinearity may help soften such instability. Our results finally suggest that MI-induced formation of stable solitons in mixtures of BECs with two-body attraction may be preserved by the residual nonlinearity even though the latter enhances the instability.

Separation of Azeotropic Mixtures of Ethyl Acetate + Methylcyclohexane: Vapor–Liquid Equilibrium Measurements

It is a challenge to separate ethyl acetate from methylcyclohexane because of the azeotropic phenomenon. To provide a basis for the design of the separation process, the isobaric vapor–liquid equilibria for an ethyl acetate + methylcyclohexane binary system were measured at 101.3 and 20.0 kPa using a modified Othmer-type still. The results show that ethyl acetate and methylcyclohexane form a miscible azeotropic mixture with minimum boiling temperature (349.99 K at 101.3 kPa), of which the composition varies slightly with decreasing pressure (≤101.3 kPa). It implies that ethyl acetate cannot be separated from methylcyclohexane by pressure-swing distillation. The azeotropy of ethyl acetate and methylcyclohexane disappears in the presence of decane (∼0.5 mole fraction), which means that ethyl acetate can be separated from methylcyclohexane by extractive distillation with decane as an entrainer.

Hydrological controls on base metal precipitation and zoning at the porphyry-epithermal transition constrained by numerical modeling

Ore precipitation in porphyry copper systems is generally characterized by metal zoning (Cu–Mo to Zn–Pb–Ag), which is suggested to be variably related to solubility decreases during fluid cooling, fluid-rock interactions, partitioning during fluid phase separation and mixing with external fluids. Here, we present new advances of a numerical process model by considering published constraints on the temperature- and salinity-dependent solubility of Cu, Pb and Zn in the ore fluid. We quantitatively investigate the roles of vapor-brine separation, halite saturation, initial metal contents, fluid mixing and remobilization as first-order controls of the physical hydrology on ore formation. The results show that the magmatic vapor and brine phases ascend with different residence times but as miscible fluid mixtures, with salinity increases generating metal-undersaturated bulk fluids. The release rates of magmatic fluids affect the location of the thermohaline fronts, leading to contrasting mechanisms for ore precipitation: higher rates result in halite saturation without significant metal zoning, lower rates produce zoned ore shells due to mixing with meteoric water. Varying metal contents can affect the order of the final metal precipitation sequence. Redissolution of precipitated metals results in zoned ore shell patterns in more peripheral locations and also decouples halite saturation from ore precipitation.

Catalyzation of supersolidity in binary dipolar condensates

In this work, the authors show realistic conditions for which doping an unmodulated scalar condensate with a second component catalyzes droplet nucleation and supersolidity. In miscible mixtures, droplet nucleation may be induced even by a surprisingly small impurity doping due to the effective modification of the relative dipolar strength. As a result, binary dipolar condensates present different ground-state phases, most intriguingly the possibility of realizing an interacting two-fluid supersolid.

Characteristic Features of Heat Transfer in the Course of Decay of Unstable Binary Mixture

This article is devoted to the study of the phenomenon of superheating of partially miscible mixtures having a lower critical solution temperature and the thermal effect accompanying the relaxation of an unstable mixture, within the framework of the problem of high-density heat flux removal. The study was carried out by using the method of the controlled pulse heating of a platinum wire probe. The characteristic heating time was from 0.2 to 180 ms. The superheating degree of the mixture relative to the diffusion spinodal exceeded 100 K. The heat flux density from the heater surface reached 13.7 MW/m2. The object of research was an aqueous solution of polypropylene glycol-425 (PPG-425). The obtained results clearly indicate that such mixtures can be used as coolants in processes where the possibility of powerful local heat release cannot be excluded. They also form the basis for expanding the phase diagram by involving in the study not-fully-stable and unstable states of the mixture.

Gravitational fingering and droplet formation during the phase separation of a partially miscible binary mixture in a vertical Hele-Shaw cell

In this study, the phase separation process of partially miscible and miscible binary systems in a vertical Hele-Shaw cell is numerically analyzed. The governing equations of a partially miscible binary system for momentum and mass transfer under buoyancy-driven fluid motion are newly implemented by taking into account both the Korteweg force and thermodynamic stability. The thermodynamic instability is reflected in the mass transfer using the modified Cahn-Hilliard equation and the Flory-Huggins Gibbs free energy for mixing. The onset of fingering and drop formation are demonstrated under buoyancy-driven motion depending on the repulsive interaction parameter (χ). When χ is higher than χc, droplet formation in a metastable or unstable region induced by convective mixing ultimately results in enhanced phase separation. Meanwhile, for a hydrodynamic stable system, the diffusional mixing is not strong enough to induce drop formation in stable and metastable regions. The Korteweg force resists the drop formation process induced by convection motion, determining the drop size and wavelength on the long fingers. For a metastable or unstable binary system, high Korteweg force results in the larger size of the droplet. Even in a fully miscible system, i.e., χ<χc, the Korteweg force still affects the system by making it stable, especially with an increase in the gradient interaction parameter (κ). This numerical study provides a deep understanding of phase separation in a thermodynamic binary system under buoyance-driven convection motion.