Dense Phase Research Articles

A pH-Dependent Phase Separation Drives Polyamine-Mediated Silicification from Undersaturated Solutions.

Silica polymerization from its soluble monomers is fundamental to many chemical processes. Although industrial methods require harsh conditions and concentrated precursors, biological silica precipitation occurs under ambient conditions from dilute solutions. The hallmark of biosilica is the presence of amine-rich organic macromolecules, but their functional role remains elusive. Here, we show a pH-dependent stimulatory effect of such polyamines on silica polymerization. Notably, this process is decoupled from the saturation degree, allowing the synthesis of polymer-silica hybrid products with controlled network morphologies from undersaturated solutions. The data suggest a two-step phase separation process. First, an associative liquid-liquid phase separation forms a micrometer-size dense phase. Second, silica undergoes a liquid-to-solid transition in the supersaturated condensates to form a bicontinuous silica structure. This study can inspire "soft chemistry" routes to design organic-inorganic nanomaterials with regulatory principles optimized by evolution.

Estimation of uncertainties in the density driven flow in fractured porous media using MLMC

AbstractWe use the Multi Level Monte Carlo method to estimate uncertainties in a Henry-like salt water intrusion problem with a fracture. The flow is induced by the variation of the density of the fluid phase, which depends on the mass fraction of salt. While the fracture’s location is fixed, its aperture is uncertain. In our setting, porosity and permeability vary spatially and recharge is time-dependent. So we introduce three random variables, one controlling both the porosity and permeability fields, one for the fracture width and one for the intensity of recharge. For each realization of these uncertain parameters, the evolution of mass fraction and pressure fields is modeled using a system of non-linear, time-dependent PDEs with a solution discontinuity at the fracture. These uncertainties propagate, affecting the distribution of salt concentration, a key factor in water resource quality. We show that the MLMC method can be successfully applied to this problem. It significantly reduces the computational cost compared to classical Monte Carlo methods by effectively balancing discretisation and statistical errors, and by evaluating multiple scenarios over different spatial and temporal mesh levels. The deterministic PDE solver, using the ug4 library, runs in parallel to compute all stochastic scenarios.

Improving the performance of crumb rubber concrete using waste ultrafine glass powder

Due to its superior toughness and environmental benefits over traditional concrete, crumb rubber (CR) concrete (CRC) gained considerable attention in both research and practical engineering fields. However, the static mechanical characteristics of CRC exhibit a certain level of decline as CR demonstrates a lower elastic modulus and less effective bonding capabilities with mortar when compared to natural aggregates. Consequently, this study explores the potential of substituting cement with ultra-fine waste glass powder (WGP) to enhance the mechanical characteristics and microstructure of CRC. The impact of varying WGP substitution rates on workability, wet packing density (WPD) in the fresh phase is examined. Moreover, analyses on compressive strength, flexural-tensile strength, ductility index, dynamic elastic modulus, damping ratio, and impermeability post-hardening are presented. The use of scanning electron microscopy (SEM), X-ray diffraction (X-RD), and mercury intrusion piezometry (MIP) provided insights into the influence of WGP on the micromorphology, mineral composition, and pore structure characteristics. The results revealed that WGP introduction enhanced the fresh properties of CRC, notably in terms of workability and WPD. The slump and slump-flow increased to 270 mm and 630 mm for WGP dosing increased to 30 %. A gradual enhancement in strength, dynamic elastic modulus, and impermeability was observed with increased WGP content, alongside a significant improvement in toughness. The compressive and flexural strengths of 30 % WGP were mentioned to be about 11 % and 62 %, respectively, and the permeability coefficient was reduced to 0.78 × 10−12 m2/s. The damping ratio initially decreases, then rises to a peak of 1.6 % at a WGP content of 30 %. Integration of WGP resulted in a progressive decrease in interfacial frictional zone width, average pore diameter, and porosity, while the fraction of harmless pores increased, likely aiding the strength and dynamic elastic modulus.

Polymer drag reduction in dispersed oil–water flow in tubes

Drag reduction by polymers is a critical issue, with several applications first reported more than 70 years ago. The number of related works is vast, but most are restricted to single-phase flow. The few available works treating two-phase flow use drag reducers only in the water phase. One goal of the present work is to study the role of polymer additives in both phases for a range of water fractions. We conduct the main tests by considering the pressure drop in a fully developed turbulent flow in a pipeline and fixing each phase flow rate. In our tests, the pressure drop depends on the water fraction, mixing viscosity, mean phase densities, polymer concentration, and molecular weight. It is worth mentioning that, in small concentrations, the water drops also work as a drag reducer. We conduct the tests to compare the role of polymers in single and two-phase flow, paying particular attention to mechanical polymer degradation. Our main conclusion is that drag reducers are effective only in the external phase. In our tests, the water drag reducer is effective for water fractions larger than 0.5, and the oil drag reducer for water fractions smaller than 0.5. When both phases contain additives, the pressure drops, relatively to the case in the absence of additives, for an entire range of water fractions.

Effect of cumulative plastic deformation on microstructure and strengthening mechanism of extruded Al-Zn-Mg-Cu alloy

Al-Zn-Mg-Cu alloy profiles are widely used as aircraft components because of lightweight and high strength. The section of thin-walled profile is easy to have unavoidable heterogeneous strain. However, the influence mechanism of different cumulative plastic strains (CPS) on the material properties at different cross-section locations needs to be further clarified. This study carried out an extrusion experiment to study the influence of CPS on the microstructure, properties, and strengthening mechanisms by TEM, SEM and XRD. Results show that the strength and micro-hardness are positively correlated with CPS, while the elongation exhibits an inverse correlation. The orientation relationships between different micro- and nano-scale precipitates and the matrix were characterized. The strengthening mechanisms under different CPS were clarified. It was found that the contribution of solid solution strengthening is 22.6 % under the maximum cumulative strain, while Orowan strengthening accounts for 20.3 %. In contrast, these contributions are 30.2 % and 11.9 % under lower cumulative strain, respectively. Specimens at low CPS have the precipitated phase bands parallel to the extrusion direction, while the high CPS induces smaller and dense precipitated phases in the matrix and grain boundaries, resulting in precipitate-free zones with a width of 200–500 nm at the sub-grain boundary, which reduces the strengthening effect at the grain boundary. The research findings can guide for optimizing the heat treatment processes of thin-walled profiles.

Continuity of Short-Time Dynamics Crossing the Liquid-Liquid Phase Separation in Charge-Tuned Protein Solutions.

Liquid-liquid phase separation (LLPS) constitutes a crucial phenomenon in biological self-organization, not only intervening in the formation of membraneless organelles but also triggering pathological protein aggregation, which is a hallmark in neurodegenerative diseases. Employing incoherent quasi-elastic neutron spectroscopy (QENS), we examine the short-time self-diffusion of a model protein undergoing LLPS as a function of phase splitting and temperature to access information on the nanosecond hydrodynamic response to the cluster formation both within and outside the LLPS regime. We investigate the samples as they dissociate into microdroplets of a dense protein phase dispersed in a dilute phase as well as the separated dense and dilute phases obtained from centrifugation. By interpreting the QENS results in terms of the local concentrations in the two phases determined by UV-vis spectroscopy, we hypothesize that the short-time transient protein cluster size distribution is conserved at the transition point while the local volume fractions separate.

Transportation characteristics analysis of the dense-phase gas-solid two-phase flow based on phase space reconstruction

The operational efficiency and safety of the dense phase pneumatic conveying system is deeply influenced by the transportation characteristics of the dense-phase gas-solid two-phase flow in conveying pipelines. This paper presents a framework for analyzing the transport characteristics of the gas-solid two-phase flow based on the phase space reconstruction. The framework explores the transport characteristics by reconstructing the state evolution trajectories of the two-phase flow system in state space. The main goal is to enhance the interpretability of feature analysis. By employing the phase space reconstruction method to process the output signals of an electrostatic sensor, the evolution trajectory of the dynamic state of the gas-solid two-phase flow system was reconstructed in phase space.This provides an effective entry point for extracting the essential dynamic characteristics of the gas-solid two-phase flow system. Furthermore, a series of feature values were proposed, including the average speed of the trajectory, Shannon entropy of the trajectory, and the average distance between state points in phase space, which were used to respectively evaluate important transportation characteristics such as flowability, stability, and particle aggregation degree of the gas-solid two-phase flow. Moreover, through comparative analysis with visualization images that represent actual conveying conditions, the effectiveness of these proposed feature values in evaluating these transportation characteristics was verified.

Molecular insights into the interaction between a disordered protein and a folded RNA

Intrinsically disordered protein regions (IDRs) are well established as contributors to intermolecular interactions and the formation of biomolecular condensates. In particular, RNA-binding proteins (RBPs) often harbor IDRs in addition to folded RNA-binding domains that contribute to RBP function. To understand the dynamic interactions of an IDR-RNA complex, we characterized the RNA-binding features of a small (68 residues), positively charged IDR-containing protein, Small ERDK-Rich Factor (SERF). At high concentrations, SERF and RNA undergo charge-driven associative phase separation to form a protein- and RNA-rich dense phase. A key advantage of this model system is that this threshold for demixing is sufficiently high that we could use solution-state biophysical methods to interrogate the stoichiometric complexes of SERF with RNA in the one-phase regime. Herein, we describe our comprehensive characterization of SERF alone and in complex with a small fragment of the HIV-1 Trans-Activation Response (TAR) RNA with complementary biophysical methods and molecular simulations. We find that this binding event is not accompanied by the acquisition of structure by either molecule; however, we see evidence for a modest global compaction of the SERF ensemble when bound to RNA. This behavior likely reflects attenuated charge repulsion within SERF via binding to the polyanionic RNA and provides a rationale for the higher-order assembly of SERF in the context of RNA. We envision that the SERF-RNA system will lower the barrier to accessing the details that support IDR-RNA interactions and likewise deepen our understanding of the role of IDR-RNA contacts in complex formation and liquid-liquid phase separation.

Formation of Multi-Compartment Structures through Aging of Protein-RNA Condensates

Cells can dynamically organize reactions through the formation of biomolecular condensates. These viscoelastic networks exhibit complex material properties and mesoscale architectures, including the ability to form multi-phase assemblies. It was shown previously that condensates with complex architectures may arise at equilibrium in multicomponent systems or in condensates that were driven out-of-equilibrium by changes in external parameters such as temperature. In this study, we demonstrate that the aging of initially homogeneous protein-RNA condensates can spontaneously lead to the formation of kinetically arrested double-emulsion and core-shell structures without changes in external variables such as temperature or solution conditions. By combining time-resolved fluorescence-based experimental techniques with simulations based on the Cahn-Hilliard theory, we show that, as the protein-RNA condensates age, the decrease of the relative strength of protein-RNA interactions induces the release of RNA molecules from the dense phase. In condensates exceeding a critical size, aging combined with slow diffusion of the macromolecules trigger nucleation of dilute phase inside the condensates, which leads to the formation of double-emulsion structures. These findings illustrate a new mechanism of formation of multi-compartment condensates.

Decoding the entropy-stabilized matrix of high-entropy layered double hydroxides: Harnessing strain dynamics for peroxymonosulfate activation and tetracycline degradation

The current understanding of the mechanism of high-entropy layered double hydroxide (LDH) on enhancing the efficiency of activating peroxymonosulfate (PMS) remains limited. This work reveals that a strong strain effect, driven by high entropy, modulates the structure of FeCoNiCuZn-LDH (HE-LDH) as evidenced by geometric phase analysis (GPA) and density functional theory (DFT) calculations. Compared to FeCoNiZn-LDH and FeCoNi-LDH with weaker strain effects, the high entropy-driven strain effect in HE-LDH shortens metal–oxygen-hydrogen (MOH) bond lengths, allows system to be in a constant steady state during catalysis, reduces the leaching of active M−OH sites, and enhances the adsorption capacity of these sites and the excess strain strength of the interfacial stretches the IO-O of the PMS, facilitates reactive oxygen species (·OH, SO4·−, 1O2 and O2·−) generation, and thereby improving the efficiency of PMS in degrading tetracycline (TC). Consequently, HE-LDH demonstrated a 90% TC degradation within 3 min, maintained over 92% TC removal across a wide pH range (3–11), and achieved over 90% degradation performance after 6 cycles. This study reports the first use of high-entropy LDH material as a non-homogeneous catalyst and provides insights into the extremely different catalytic behaviors of high entropy mechanisms for the activation of PMS.

Experimental study on creep characteristics of electrolyte-bearing salt rock under long-term triaxial cyclic loading

During the operation of the Salt Cavern Flow Battery (SCFB) system, the rock surrounding a salt cavern is subjected to erosion by the electrolyte. To study the creep characteristics of electrolyte-bearing salt rock under long-term triaxial cyclic loading in SCFB, a triaxial creep experiment with a cycle period of 1 day was conducted. The results indicated that, when not subjected to failure, the axial stress-strain curve of electrolyte-bearing sample undergoes only two phases of “sparse-dense”, entering dense phase approximately 4 cycles earlier than that of sample without electrolyte. Under the same stress conditions, the strain generated in electrolyte-bearing salt rock surpasses that of sample without electrolyte, demonstrating an initial rapid increase followed by a gradual stabilization trend. The stress-strain curve of electrolyte-bearing sample in a single cycle can be divided into six stages. The number of cycles has almost no effect on the axial strain in stages I, IV, V and VI, and the axial strain in stages IV and VI is basically 0. Additionally, the elastic deformation generated in stage I is basically recovered in stage V. The strain in stage II gradually decreases and disappears in the 4th cycle, which is 13 cycles earlier than that of the sample without electrolyte. The creep rate of electrolyte-bearing sample shows a trend of “gradual decrease—basically stabilization” as the number of cycles increases, and the creep experiment contains only the decay creep stage and steady creep stage. Irreversible deformation of electrolyte-bearing sample exhibits a gradual decrease followed by stabilization with increasing number of cycles. The research findings hold significant implications for the stability analysis of SCFB systems.

Data-driven design of novel lightweight refractory high-entropy alloys with superb hardness and corrosion resistance

Lightweight refractory high-entropy alloys (LW-RHEAs) hold significant potential in the fields of aviation, aerospace, and nuclear energy due to their low density, high strength, high hardness, and corrosion resistance. However, the enormous composition space has severely hindered the development of novel LW-RHEAs with excellent comprehensive performance. In this paper, an machine learning (ML)-based alloy design strategy combined with a multi-objective optimization method was proposed and applied for a rational design of Al-Nb-Ti-V-Zr-Cr-Mo-Hf LW-RHEAs. The quantitative relation of “composition-structure-property” was first established by ML modeling. Then, feature analysis reveals that Cr content greater than 12 at.% is a key criterion for alloys with high corrosion resistance. The phase structure, density, melting point, hardness and corrosion resistance of the alloys were screened layer by layer, and finally, three LW-RHEAs with superb hard and corrosion resistance were successfully designed. Key experimental validation indicates that three target alloys have densities around 6.5 g/cm3, and all alloys are disordered bcc_A2 single-phase with the highest hardness of 593 HV and the largest pitting potential of 2.5 VSCE, which far exceeds all the literature reports. The successful demonstration in this paper clearly demonstrates that the present design strategy driven by the ML technique should be generally applicable to other RHEA systems.

Microstructural and mechanical analysis of (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 high-entropy oxide ceramic fabricated in-situ via laser powder bed fusion

High-entropy ceramics (HECs) have gained attention for their exceptional properties, yet their manufacturing techniques face challenges of long cycles and complex processes. Laser powder bed fusion (LPBF) technology has the potential to address these challenges. In this study, the phase composition, microstructure, crystallography, density, and hardness were investigated at various scanning speeds. The findings reveal that (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 (RE3Al5O12) were in-situ synthesized via LPBF. Samples deposited at varying scanning speeds exhibited RE3Al5O12 phase with dendritic morphologies, showing notable enrichment of Al, O, and Eu elements at inter-dendritic and grain boundary. The interior of dendrites has been confirmed to be a garnet-structured high-entropy phase, and it is inferred that the segregation may consist of incompletely reacted Al2O3 and an intermediate phase of (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3AlO3 (REAlO3). Density, pore morphology, and grain size changed with scanning speed, achieving a density of 97.83 % ± 0.55 % at 60 mm/s. Hardness peaked at 15.09 ± 0.68 GPa at 120 mm/s.

Direct and indirect salt effects on homotypic phase separation

The low-complexity domain of hnRNPA1 (A1-LCD) phase separates in a salt-dependent manner. Unlike many intrinsically disordered proteins (IDPs) whose phase separation is suppressed by increasing salt concentrations, the phase separation of A1-LCD is promoted by >100 mM NaCl. To investigate the atypical salt effect on A1-LCD phase separation, we carried out all-atom molecular dynamics simulations of systems comprising multiple A1-LCD chains at NaCl concentrations from 50 to 1000 mM NaCl. The ions occupy first shell as well as more distant sites around the IDP chains, with Arg sidechains and backbone carbonyls the favored partners of Cl– and Na+, respectively. They play two direct roles in driving A1-LCD condensation. The first is to neutralize the high net charge of the protein (+9) by an excess of bound Cl– over Na+; the second is to bridge between A1-LCD chains, thereby fortifying the intermolecular interaction networks in the dense phase. At high concentrations, NaCl also indirectly strengthens π–π, cation–π, and amino–π interactions, by drawing water away from the interaction partners. Therefore, at low salt, A1-LCD is prevented from phase separation by net charge repulsion; at intermediate concentrations, NaCl neutralizes enough of the net charge while also bridging IDP chains to drive phase separation. This drive becomes even stronger at high salt due to strengthened π-type interactions. Based on this understanding, four classes of salt dependence of IDP phase separation can be predicted from amino-acid composition.

Direct and indirect salt effects on homotypic phase separation.

The low-complexity domain of hnRNPA1 (A1-LCD) phase separates in a salt-dependent manner. Unlike many intrinsically disordered proteins (IDPs) whose phase separation is suppressed by increasing salt concentrations, the phase separation of A1-LCD is promoted by >100 mM NaCl. To investigate the atypical salt effect on A1-LCD phase separation, we carried out all-atom molecular dynamics simulations of systems comprising multiple A1-LCD chains at NaCl concentrations from 50 to 1000 mM NaCl. The ions occupy first shell as well as more distant sites around the IDP chains, with Arg sidechains and backbone carbonyls the favored partners of Cl- and Na+, respectively. They play two direct roles in driving A1-LCD condensation. The first is to neutralize the high net charge of the protein (+9) by an excess of bound Cl- over Na+; the second is to bridge between A1-LCD chains, thereby fortifying the intermolecular interaction networks in the dense phase. At high concentrations, NaCl also indirectly strengthens π-π, cation-π, and amino-π interactions, by drawing water away from the interaction partners. Therefore, at low salt, A1-LCD is prevented from phase separation by net charge repulsion; at intermediate concentrations, NaCl neutralizes enough of the net charge while also bridging IDP chains to drive phase separation. This drive becomes even stronger at high salt due to strengthened π-type interactions. Based on this understanding, four classes of salt dependence of IDP phase separation can be predicted from amino-acid composition.

Numerical Implementation of Electrostatic Solver Within OpenFOAM for Gas Turbine Intake Filtration

Abstract Gas turbines require filtered air to preserve operability, availability, and efficiency. Fouling, corrosion, and erosion severely affect the performance of the axial compressor and it can be in part prevented by filtering the air intake. For this reason, several stages of filters can be used in series to catch pollutant particles gradually smaller and with a high level of capturing efficiency. Traditionally, the separation is obtained using cartridges of porous material, which provide a high level of filtration but at the same time generate a pressure drop increasing over time. Another common type of filter is the inertial one, whose operating principle is based on the inertial force acting on the solid particles to separate them from the mainstream. The capturing efficiency of the inertial filter is not comparable with the porous one and for this reason, it is used upstream as a pre-filter. In recent years, another technique has been developed to filter air flows thanks to an electrostatic field, that is induced inside the flow. The electrostatic force generated is able to attract and separate metallic particles. In the present work, numerical investigations are carried out to simulate the effect of the electrostatic force for gas turbine filtering systems. The computational fluid dynamics tool used is openfoam, whose official release can simulate inertial and porous filtering media, while for electrostatic one is not possible due to the absence of a library able to simulate the electrostatic force that acts on the discrete phase. A new library was developed in order to calculate the electric field, the electric potential, and the charge density of the continuous phase. Simulation results show how the calculation of these quantities allows us to predict the electrostatic force acting on particle flows in the presence of electrostatic fields.

Collective dynamics on constrained three-lane exclusion process.

The motivation behind the proposed study stems from multilane traffic systems with finite availability of particles. Our investigation revolves around a totally asymmetric simple exclusion process incorporating a finite reservoir and the occurrence of lane-switching phenomena. The study delves into the system's characteristics, including phase diagrams, density profiles, phase transitions, finite-size effects, and shock positions. These analyses concern the number of particles within the system and various weak-coupling rates. The outcomes obtained from the generalized mean-field theory are cross-validated against the results derived from Monte Carlo simulations. In scrutinizing the system's dynamics, we observe several noteworthy observations. Notably, we identified critical mixed profiles featuring instances of double shocks. The system, intriguingly, demonstrates a transition known as reentrance transition. The study also reports a rare phenomenon, namely, the jumping effect within the shock profile, adding a layer of complexity to the system's behavior and proving the significance of limited resources.

Fabrication of interfacial crystallized oleogel emulsion for quercetin delivery with enhanced environmental stability and bioaccessibility.

Quercetin is a flavonoid compound with numerous bioactivities. However, the low solubility, easy degradation and low bioaccessibility limit its application. In this study, a novel interfacial crystallized oleogel emulsion was fabricated, where beeswax was used as the oleogelator, for quercetin encapsulation with enhanced stability and bioaccessibility. The process of interfacial crystallization was investigated using interfacial rheology and polarized microscopy, with a positive correlation between crystal density and beeswax content in the oil phase. Emulsion stability was directly linked to beeswax concentration in the oil phase, with 100 mg g-1 showing enhanced stability under storage, UVB light exposure and ionic conditions. Beeswax addition significantly increased the quercetin loading capacity of the emulsion; particularly, at a 200 mg g-1 beeswax concentration, the loading capacity was improved by 285.55%, and the environmental stability was enhanced against UV light and Ca2+. Ultimately, in vitro simulated digestion experiment indicated improved bioaccessibility of quercetin. This strategy significantly enriched the formulation of oleogel emulsion and its potential applications in delivering bioactive ingredients with high environmental vulnerability. © 2024 Society of Chemical Industry.

Deformation characteristics of Ti-Ni-Fe based multiphase intermetallic: Experiments and atomistic simulation

This study deals with the development of Ti-Ni-Fe based multi-phase intermetallic having high strength with enhanced ductility and elucidation of their deformation characteristics. The intermetallic exhibited a compressive strain and strength of ⁓ 11 % and ⁓ 2.1± 0.112 GPa at room temperature (RT), respectively. MD simulation at RT showed a higher dislocation density in the DO24 phase, where most of the dislocations were found to be superpartials 13101̅0 and 1311̅00 separated by super intrinsic stacking faults (SISF), which was further corroborated with TEM analysis. It was found that despite its low volume fraction, DO24 phase governed the plastic deformation. Further, hot compression of Ti45Ni50Fe5 exhibited yield strength anomaly (YSA), where yield strength decreased from room temperature to 373 K followed by an increase at 473 K and 573 K. MD simulation of hot compression showed lower dislocation density (⁓300–551×10−6Å−2) for B2 matrix at all temperatures, indicating strength is predominantly governed by it. The dislocation density of B2 matrix was found to increase with temperature up to 373 K followed by a decrease at 473 K and 573 K. This difference in dislocation density has been attributed to the cross-slip of 121̅11 screw partials from {110} plane to {211} plane, resulting in the formation of dislocation lock that led to YSA behavior.

Dual symmetries of dense isotopically and chirally asymmetric QCD

In the present paper, the dual symmetries of dense quark matter phase diagram found in some massless three- and two-color NJL models in the mean field approximation have been shown to exist at a more fundamental level as dual transformations of fields and chemical potentials leaving the Lagrangian invariant. As a result, the corresponding dual symmetries of the full phase diagram can be shown without any approximation. And it has been shown not only in the NJL models, but also in framework of two- and three-color massless QCD itself. This is quite interesting, since one might say that it is not very common to show something completely non-perturbatively in QCD.