Liquid Properties Research Articles

Phase-Field Modelling of Bimodal Dendritic Solidification During Al Alloy Die Casting

Tracking the microstructural evolution during high-pressure die casting of Al-Si alloys is challenging due to the rapid solidification, varying thermal conditions, and severe turbulence. The process involves a transition from slower cooling in the shot sleeve to rapid cooling in the die cavity, resulting in a bimodal dendritic microstructure and nucleation of new finer dendrite arms on fragmented externally solidified crystals. In this study, a two-dimensional phase-field model was employed to investigate the solidification behaviour of a hypoeutectic Al-7% Si alloy during high-pressure die casting. The model is based on thermodynamic formulations that account for temperature changes due to phase transformation heat, thermal boundary conditions, and solute diffusion in both liquid and solid phases. To replicate the observed bimodal microstructure, solid–liquid interface properties such as thickness, energy, and mobility were systematically varied to reflect the transition from the shot sleeve to the die cavity. The results demonstrated the model’s ability to capture the growth of dendrites under shot sleeve conditions and nucleation and development of new dendrite arms under the rapid cooling conditions of the die cavity.

Study of Gas–Liquid Two-Phase Flow Characteristics at the Pore Scale Based on the VOF Model

To study the effects of liquid properties and interface parameters on gas–liquid two-phase flow in porous media. The volume flow model of gas–liquid two-phase flow in porous media was established, and the interface of the two-phase flow was reconstructed by tracing the phase fraction. The microscopic imbibition flow model was established, and the accuracy of the model was verified by comparing the simulation results with the classical capillary imbibition model. The flow characteristics in the fracturing process and backflow process were analyzed. The influence of flow parameters and interface parameters on gas flow was studied using the single-factor variable method. The results show that more than 90% of the flowing channels are invaded by fracturing fluid, and only about 50% of the fluid is displaced in the flowback process. Changes in flow velocity and wetting angle significantly affect Newtonian flow behavior, while variations in surface tension have a pronounced effect on non-Newtonian fluid flow. The relative position of gas breakthrough in porous media is an inherent property of porous media, which does not change with fluid properties and flow parameters.

Structural Origin of Dynamic Heterogeneity in Supercooled Liquids.

As a liquid is supercooled toward the glass transition point, its dynamics slow significantly, provided that crystallization is avoided. With increased supercooling, the particle dynamics become more spatially heterogeneous, a phenomenon known as dynamic heterogeneity. Since its discovery, this characteristic of metastable supercooled liquids has garnered considerable attention in glass science. However, the precise physical origins of dynamic heterogeneity remain elusive and widely debated. In this perspective, we examine the relationship between dynamic heterogeneity and structural order, based on numerical simulations of fragile liquids with isotropic potentials and strong liquids with directional interactions. We demonstrate that angular ordering, arising from many-body steric interactions, plays a crucial role in the slow dynamics and dynamic cooperativity of fragile liquids. Additionally, we explore how the growth of static order correlates with slower dynamics. In fragile liquids exhibiting super-Arrhenius behavior, the spatial extent of regions with high angular order grows upon cooling, and the sequential propagation of particle rearrangements within these ordered regions increases the activation energy for particle motion. In contrast, strong liquids with spatially constrained local ordering display a distinct "two-state" dynamic characteristic, marked by a transition between two Arrhenius-type behaviors. We argue that dynamic heterogeneity, irrespective of a liquid's fragility, arises from underlying structural order, with its spatial extent determined by static ordering. This perspective aims to deepen our understanding of the interplay between structural and dynamic properties in metastable supercooled liquids.

A Comprehensive Review of the Thermophysical Properties of Energetic Ionic Liquids

Energetic ionic liquids (EILs) have various industrial applications because they release chemically stored energy under certain conditions. They can avoid some environmental problems caused by traditionally used toxic fuels. EILs, which are environmentally friendly and safer, are emerging as an alternative source for hypergolic bipropellant fuels. This review focuses on the crucial thermophysical properties of the EILs. The properties of imidazolium and triazolium-based ionic liquids (ILs) are discussed here. The thermophysical properties addressed, such as glass transition temperature, viscosity, and thermal stability, are critical for designing EILs to meet the need for sustainable energy solutions. Imidazolium-based ILs have tunable physical properties making them ideal for use in energy storage while triazolium-based ILs have thermal stability and energetic potential. As a result, it is important to understand and compile thermophysical properties so they can help researchers synthesize tailored compounds with desirable characteristics, advancing their application in energy storage and propulsion technologies.

Prediction of thermodynamic properties of ionic liquids using the PC-SAFT EoS coupled with COSMO-RS model

In this work, a new methodology has been introduced to predict the thermodynamic properties of ionic liquids (ILs) using the PC-SAFT EOS and COSMO-RS models. In this regard, the PC-SAFT EOS model parameters have been predicted using molecular volume obtained by the COSMO-RS model. The density of ILs has been predicted up to high pressures and temperatures using the linear relationship between the molecular volume and PC-SAFT model parameters. Accurate predictions for density were observed across the entire pressure and temperature range. The average relative deviation (ARD%) of the predicted ILs densities from the experimental ones was found to be 1.76%. The model performance has been assessed by prediction of the isentropic compressibility coefficient, isothermal compressibility coefficient, thermal expansion coefficient, speed of sound, isobaric/isochoric heat capacity, and thermal pressure coefficient. The comparison of the model predictions and the experimental data showed that the model predictions are reliable in a broad range of ILs. The new method can be applied for some specific cases in which the experimental data is not available such as pre-design of drugs and desired solvent selection.

Thermodynamics and transport in molten chloride salts and their mixtures.

Molten salts are important in a number of energy applications, but the fundamental mechanisms operating in ionic liquids are poorly understood, particularly at higher temperatures. This is despite their candidacy for deployment in solar cells, next-generation nuclear reactors, and nuclear pyroprocessing. We perform extensive molecular dynamics simulations over a variety of molten chloride salt compositions at varying temperature and pressures to calculate the thermodynamic and transport properties of these liquids. Using recent developments in the theory of liquid thermophysical properties, we interpret our results on the basis of collective atomistic dynamics (phonons). We find that the properties of ionic liquids are well explained by their collective dynamics, as in simple liquids. In particular, we relate the decrease of heat capacity, viscosity, and thermal conductivity to the loss of transverse phonons from the liquid spectrum. We observe the singular dependence of the isochoric heat capacity on the mean free path of phonons, and the obeyance of the Stokes-Einstein equation relating the viscosity to the mass diffusion. The transport properties of mixtures are more complicated compared to simple liquids, however viscosity and thermal conductivity are well guided by fundamental bounds proposed recently. The kinematic viscosity and thermal diffusivity lie very close to one another and obey the theoretical fundamental bounds determined solely by fundamental physical constants. Our results show that recent advances in the theoretical physics of liquids are applicable to molten salts mixtures, and therefore that the evolution and interplay of properties common to all liquids may act as a guide to a deeper understanding of these mixtures.

Study of the extraction properties of choline dicyanamide ionic liquid

Study of the extraction properties of choline dicyanamide ionic liquid

Interaction between newly synthesized surface-active ionic liquids with pharmaceutically active anion and bovine serum albumin

This work describes the synthesis and properties of new surface active (octyl-, and dodecyl-) imidazolium and choline-based ionic liquids with pharmaceutically active 5-fluorouracil anion (SAAPI-IL). The effect of the novel SAAPI-IL on the secondary and tertiary structure of bovine serum albumin (BSA) was studied using circular dichroism (CD) spectroscopy. The binding constants of BSA with SAAPI-IL were estimated from the fluorescence quenching of BSA. The influence of the length of the alkyl chain SAAPI-IL on the binding constant with BSA was analyzed. The localization of ions on BSA was estimated using the molecular docking method. Also, the effect of alkyl substituent length on the aggregation tendency of SAAPI-IL was studied by dynamic light scattering (DLS). Cytotoxicity and selectivity of SAAPI-ILs on cancer and normal cell lines were compared to molecular 5-fluorouracil and API-IL without the alkyl substituents. Surprisingly, increasing the length of the alkyl substituent did not increase the binding of SAAPI-IL to BSA. On the other hand, [C8Ch][FU] showed selectivity against A 549 cell line, which 5-fluorouracil does not possess.

The structural, electronic and thermodynamic properties of the designed p-benzoquinone based dicationic ionic liquids: insight from DFT–GD3 and QTAIM

In this work, physicochemical properties of the dicationic ionic liquids [BTAD][A1–8]2 ([BTAD]2+ = [p-C6O2(N3H2)2]2+ and A1–8 = [CH3CO2]−, [CF3CO2]−, [N(CN)2]−, [CF3SO3]−, [ClO4]−, [BF4]−, [NTf2]− and [PF6]−) were theoretically investigated.

Optimisation of PCM passive cooling efficiency on lithium-ion batteries based on coupled CFD and ANN techniques

Ever since the lithium-ion batteries (LIBs) outbreak, there has been an exponential bloom of application over the last decade, especially for electric vehicles, automobiles and other transportation systems. Nonetheless, as the first-generation LIBs eventually aged and became increasingly thermally unstable, the utilisation of thermal management cooling systems is essential to maintain the safe operation of LIB packs in the long term. Compared to active cooling methods, passive cooling often offers a cost-effective, easy-to-install and energy-saving solution without significant changes to the design complexity. This article focuses on the thermal management of prismatic battery packs and proposes a coupling passive cooling method that combines phase change material (PCM) cooling and immersion cooling, which proves to be cost-effective and efficient. Furthermore, the study incorporates an artificial neural network (ANN) model into computational fluid dynamics (CFD) simulations to optimize a specific battery cooling system. This optimization takes into account the PCM package method and the properties of PCM and immersion liquid. The results demonstrate that the immersion liquid exhibits different behaviours under various PCM conditions than natural convection. Overall, this modelling framework presents an innovative approach by utilizing high-fidelity CFD numerical results as inputs for establishing a numerical dataset. Through ANN optimisation, eleven input parameters are considered, and the optimised scenario confirmed that PCM material with a density of 760 kg/m3, thermal conductivity 32 W/(m K), specific heat 1691 (J/kg K), latent heat 80,160 (J/kg), liquidus temperature 302.93 K, solidus temperature 315.15 K and direct liquid density 1.4 (g/ml), thermal conductivity 0.4 (W/m K), specific heat 1220 (J/kg K) with side thickness 5 (mm) and mid thickness 2.5 (mm). With this combination, the optimised performance demonstrated considerable decreases in the maximum temperature and the temperature difference by 4.26 % and 10.8 %, respectively. This approach has the potential to enhance the state-of-the-art thermal management of LIB systems, reducing the risks of thermal runaway and fire outbreaks.

MODELAGEM DE MISTURAS BINÁRIAS PELA APLICAÇÃO DA EQUAÇÃO DE SCHRÖEDER-van LAAR A UM CONJUNTO DE SUBSTÂNCIAS COM DIVERSIDADE ESTRUTURAL

MODELING OF BINARY MIXTURES BY APPLYING THE SCHRÖEDER-van LAAR EQUATION TO A SET OF SUBSTANCES WITH STRUCTURAL DIVERSITY. The Schröeder-van Laar equation to predict the theoretical eutectic melting temperature values was applied to a set of fourteen binary mixtures (UR1 to UR14). The fourteen binary mixtures belong to a structurally diverse group of organic molecules. They are represented by the 5-membered heterocycles containing N-S and N-O rings, flexible methylene chains (RH), semi-rigid semi-fluorinated chains (RF), and hydrogen bonds (HB). A virtual screening totalizing ninety-one possible theoretical combinations was planned. The UR1 to UR14 were prepared by mixing individual components using the calculated mole fractions. The experimental (Te) and theoretical (Tt) temperatures for the eutectic melting points were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) techniques. Heterogeneous mixtures were formed for components with large structural diversity as seen by POM. During the melting of the mixtures, irregular behavior through the segregation of the components was recorded. The study showed that the similarities in structural diversities favor the formation of homogeneous mixtures, with Te values approaching Tt, as predicted by the Schröeder-van Laar equation and by the theory of eutectic mixtures. Liquid crystal properties were affected in homogeneous binary mixtures containing one of the individual liquid crystal components.

Feedback-induced phase separation of hollow condensates to create biomimetic membraneless compartments.

Intracellular macromolecules have the ability to form membraneless compartments, such as vacuoles and hollow condensates, through liquid-liquid phase separation (LLPS) in order to adapt to changes in their environment. The development of artificial non-homogeneous compartments, such as multiphase hollow or multicavity condensates, has gained significant attention due to their potential to uncover the mechanisms underlying the formation of artificial condensates and biomolecular condensates. However, the complexity of design and construction has hindered progress, particularly in creating dynamic non-homogeneous compartments. In this study, we present a dynamic membraneless compartment using peptide-oligonucleotide conjugates derived from short elastin-like polypeptides (sELP-ONs), which undergo pH-mediated phase transition. Below pH 8.8, the microcompartment exists as microdroplets that transform into non-homogeneous hollow condensates above pH 8.8. Notably, these hollow condensates retain liquid properties and high molecular ordering, and effectively sequester guest molecules with a hollow condensed layer. Furthermore, our sELP-ON microcompartments exhibit a feedback-induced phase transition in response to environmental pH fluctuations generated by complex enzymatic reactions mimicking cellular metabolism, providing a novel dynamic model for creating biomimetic membraneless compartments.

The Role of Re-Entrant Microstructures in Modulating Droplet Evaporation Modes.

The evaporation dynamics of sessile droplets on re-entrant microstructures are critical for applications in microfluidics, thermal management, and self-cleaning surfaces. Re-entrant structures, such as mushroom-like shapes with overhanging features, trap air beneath droplets to enhance non-wettability. The present study examines the evaporation of a water droplet on silicon carbide (SiC) and silicon dioxide (SiO2) re-entrant structures, focusing on the effects of material composition and solid area fraction on volume reduction, contact angle, and evaporation modes. Using surface free energy (SFE) as an indicator of wettability, we find that the low SFE of SiC promotes quick depinning and contact line retraction, resulting in shorter CCL phases across different structures. For instance, the CCL phase accounts for 55-59% of the evaporation time on SiC surfaces, while on SiO2 it extends to 51-68%, reflecting a 7-23% increase in duration due to stronger pinning effects. Additionally, narrower pillar gaps, which increase the solid area fraction, further stabilize droplets by extending both CCL and constant contact angle (CCA) phases, while wider gaps enable faster depinning and evaporation. These findings illustrate how hydrophobicity (via SFE) and structural geometry (via solid area fraction) influence microscale interactions, offering insights for designing surfaces with optimized liquid management properties.

Solution rheology of poly(ionic liquid)s: current understanding and open questions

AbstractPoly(ionic liquid)s are ion-containing polymers possessing ionic liquid structures on their repeating units. Owing to the unique physicochemical properties of ionic liquids, many existing studies have found that the properties of poly(ionic liquid)s are distinct from those of conventional ion-containing polymers, such as poly(sodium styrene sulfonate). A lot of scientific efforts have been made to understand the relationship between the chemical structure and the material properties of poly(ionic liquid)s, and several good review papers are available in the literature. The aim of this short review is to summarize key results on the viscoelastic properties of poly(ionic liquid)s in solution. We discuss in detail the counterion condensation and the charge screening in poly(ionic liquid) solutions. Graphical Abstract

The Use of Graphite Micropowder in the Finish Turning of the Ti-6Al-4V Titanium Alloy Under Minimum Quantity Lubrication Conditions.

The use of the minimum quantity lubrication (MQL) method during machining leads to the reduced consumption of cooling and lubricating liquids, thus contributing to sustainable machining. To improve the properties of liquids used under MQL conditions, they are enriched with various types of micro- and nanoparticles. The purpose of this study was to investigate the effect of the addition of graphite micropowder (GMP) on tool life, cutting force components, and selected surface roughness parameters during the finish turning of the Ti-6Al-4V titanium alloy under MQL conditions. The addition of 0.6 wt% of GMP to the base liquid in machining under MQL conditions leads to an extension of tool life by 7% and 96% compared to machining with a liquid without the addition of GMP and dry machining, respectively. Mathematical models of the cutting force components and surface roughness parameters were developed, taking into account the change in cutting speed and feed. It was found that the use of a liquid with the addition of GMP extends the range of cutting parameters for which the shape of chips obtained is acceptable in terms of work safety. The novelty of this study lies in the use of a cutting fluid composed of bis(2-ethylhexyl) adipate and diester, enriched with graphite micropowder, which has not been extensively investigated for machining titanium alloys under MQL conditions.

Stabilization of Environmental Conditions when Liquid Density Measuring by Hydrostatic Weighting

When assessing the quality of products, especially oil and oil products, the density value is widely used along with other parameters. Density data are fundamental for studying the properties of liquids, their identification and determining the degree of purity. They are also necessary for indirectly assessing with a certain degree of accuracy some other properties of the liquid, such as specific gravity, thermal expansion or contraction, the mass of a known volume of liquid, etc. In turn, the accuracy of the density determination determines the correctness of the decision made in the technological quality control of the manufactured products. Determining the density of a liquid with high accuracy requires maintaining stable temperature conditions during the measurement process. The purpose of the work was to establish the effect of temperature stability on the reproduction and transmission of the unit of liquid density. To stabilize the temperature, a technical solution is proposed, implemented in the form of a climatic chamber, inside which reference equipment is placed. A study of the temperature conditions in the process chamber was carried out. It was found that due to the technical solutions used, the influence of environmental conditions on the change in the temperature of the liquid under study is a negligible value.

Rheological Properties of Dense Particle Suspensions of Starches: Shear Thickening, Shear Jamming, and Shock Absorption Properties.

Concentrated suspensions of Brownian and non-Brownian particles display distinctive rheological behavior highly dependent on shear rate and shear stress. Cornstarch suspensions, composed of starch particles from corn plants, served as a model for concentrated non-Brownian suspensions, demonstrating discontinuous shear thickening (DST) and dynamic shear jamming (SJ). However, starch particles from other plant sources have not yet been investigated, despite their different sizes and shapes. This study is focused on the evaluation of the effects of the structural parameters of starch particles by preparing concentrated suspensions of starch particles from 13 different plants at particle fractions of 25-50% and their rheological behavior through steady shear, pull-out, and ball-drop tests. Starch particles can be roughly classified as polygonal and ellipsoidal. The DST and SJ behavior typically reported for concentrated cornstarch suspensions were confirmed for other starch particles in both particle groups. The ball-drop test demonstrated excellent shock absorption properties for 11 concentrated suspensions of starch particles, except for sago palms. In the case of concentrated suspensions of starch particles, the particle fraction and shear applied were the dominant factors that significantly affected the rheological behavior, whereas the particle shape was not a primary contributor. The findings of this study drive further investigation on the effect of liquid and particle surface properties in concentrated particle suspensions on DST and SJ behaviors.

Structural and molecular properties of mumps virus inclusion bodies.

Viral RNA synthesis of mononegaviruses occurs in cytoplasmic membraneless organelles called inclusion bodies (IBs). Here, we report that IBs of mumps virus (MuV), which is the causative agent of mumps and belongs to the family Paramyxoviridae, displayed liquid organelle properties formed by liquid-liquid phase separation. Super-resolution microscopic analysis of MuV IBs demonstrated that nucleocapsid and phospho (P)-proteins formed a cage-like structure and that the viral polymerase adopted a reticular pattern and colocalized with viral RNAs. In addition, we characterized host RNAs localized in MuV IBs by a spatial transcriptome analysis, and found that RNAs containing G-quadruplex motif sequences (G4-RNAs) were concentrated. An in vitro phase separation assay showed that the G4-RNAs interacted with the P protein and enhanced condensation in P droplets. Together, our data show that MuV generates IBs with a characteristic cage-like structure and host G4-RNAs play an important role in forming MuV IBs.

Potential energy landscape formalism for quantum molecular liquids

The potential energy landscape (PEL) formalism is a powerful tool within statistical mechanics to study the thermodynamic properties of classical low-temperature liquids and glasses. Recently, the PEL formalism has been extended to liquids/glasses that obey quantum mechanics, but applications have been limited to atomistic model liquids. In this work, we extend the PEL formalism to liquid/glassy water using path-integral molecular dynamics (PIMD) simulations, where nuclear quantum effects (NQE) are included. Our PIMD simulations, based on the q-TIP4P/F water model, show that the PEL of quantum water is both Gaussian and anharmonic. Importantly, the ring-polymers associated to the O/H atoms in the PIMD simulations, collapse at the local minima of the PEL (inherent structures, IS) for both liquid and glassy states. This allows us to calculate, analytically, the IS vibrational density of states (IS-VDOS) of the ring-polymer system using the IS-VDOS of classical water (obtained from classical MD simulations). The role of NQE on the structural properties of liquid/glassy water at various pressures are discussed in detail. Overall, our results demonstrate that the PEL formalism can effectively describe the behavior of molecular liquids at low temperatures and in the glass states, regardless of whether the liquid/glass obeys classical or quantum mechanics.

Analysis of Liquid Sweat Transport in Underwear Combined with Multilayer Fabric Assemblies for Firefighter Outfits.

A firefighter's outfit consists of several layers with distinct properties and functions. These layers serve as barriers against external hazards but also impede the transport of sweat generated by the human body. As a result, sweat vapor often fails to transfer effectively from the body through the firefighter's protective clothing (FPC) to the environment. This can lead to sweat condensation on the firefighter's skin, causing discomfort. To enhance the physiological comfort of firefighters during firefighting and other rescue operations, it is essential to consider the transport of condensed sweat within the multilayer textile system comprising both the underwear and the FPC. In this study, 16 assembly variants were tested, combining four types of knitted fabrics for underwear with four types of multilayer textile sets designed for FPC. The liquid moisture transport properties of these assemblies were evaluated using the Moisture Management Tester (MMT290), an innovative instrument manufactured by SDL Atlas. The results demonstrated that the knitted fabrics effectively transport liquid sweat, whereas in the case of multilayer textile sets for FPC, liquid sweat transport is primarily confined to the inner layer adjacent to the skin. Furthermore, the findings indicate that by selecting an appropriate combination of knitted fabric for underwear and the inner layer of the FPC, it is possible to optimize liquid moisture transport in a firefighter's outfit.