Solid-liquid Interfacial Energy Research Articles

Supercooled erythritol for high-performance seasonal thermal energy storage

Seasonal storage of solar thermal energy through supercooled phase change materials (PCM) offers a promising solution for decarbonizing space and water heating in winter. Despite the high energy density and adaptability, natural PCMs often lack the necessary supercooling for stable, long-term storage. Leveraging erythritol, a sustainable mid-temperature PCM with high latent heat, we introduce a straightforward method to stabilize its supercooling by incorporating carrageenan (CG), a bio-derived food thickener. By improving the solid-liquid interfacial energy with the addition of CG the latent heat of erythritol can be effectively locked at a very low temperature. We show that the composite PCM can sustain an ultrastable supercooled state below −30 °C, which guarantees no accidental loss of the latent heat in severe cold regions on Earth. We further demonstrate that the common ultrasonication method can be used as the key to unlocking the latent heat stored in the CG-thickened erythritol, showing its great potential to serve as a high-performance, eco-friendly PCM for long-term seasonal solar energy storage.

Hydrogen-bond linking is crucial for growing ice VII embryos.

We use molecular dynamics simulations to examine the homogeneous nucleation of ice VII from metastable liquid water. An unsupervised machine learning classification identifies two distinct local structures composing Ice VII nuclei. The seeding method, combined with the classical nucleation theory (CNT), predicts the solid-liquid interfacial free energy, consistent with the value from the mold integration method. Meanwhile, the nucleation rates estimated from the CNT framework and brute force spontaneous nucleations are inconsistent, and we discuss the reasons for this discrepancy. Structural and dynamical heterogeneities suggest that the potential birthplace for an ice VII embryo is relatively ordered, although not necessarily relatively immobile. Moreover, we demonstrate that without the formation of hydrogen-bond links, ice VII embryos do not grow.

Capillary Condensation of Water in Graphene Nanocapillaries.

Recent experiments have revealed that the macroscopic Kelvin equation remains surprisingly accurate even for nanoscale capillaries. This phenomenon was so far explained by the oscillatory behavior of the solid-liquid interfacial free energy. We here demonstrate thermodynamic and capillarity inconsistencies with this explanation. After revising the Kelvin equation, we ascribe its validity at nanoscale confinement to the effect of disjoining pressure. To substantiate our hypothesis, we employed molecular dynamics simulations to evaluate interfacial heat transfer and wetting properties. Our assessments unveil a breakdown in a previously established proportionality between the work of adhesion and the Kapitza conductance at capillary heights below 1.3 nm, where the dominance of the work of adhesion shifts primarily from energy to entropy. Alternatively, the peak density of the initial water layer can effectively probe the work of adhesion. Unlike under bulk conditions, high confinement renders the work of adhesion entropically unfavorable.

Electrode microstructure design to improve effective utilization of Fe-N/C catalysts towards oxygen reduction reaction process

Fe-N/C materials have shown intrinsic activities comparable to Pt/C catalysts for oxygen reduction reaction on rotating ring-disk electrodes (RRDE). However, due to the insufficient three-phase interfaces (TPIs) and high oxygen transport resistance (RT), the high intrinsic activity cannot be sufficiently utilized in electrodes, resulting in a gap between the intrinsic catalytic activity on RRDE and the performance in devices. To expand the TPIs and promote oxygen transport, a novel electrode with a transition layer structure is proposed to disperse the active sites. The dispersion degree of active sites is optimized by tuning the solid–liquid interfacial energy between the ink solvent and the substrate. A high electrochemical active area of 1264 cm2 and a low RT of 2.0 s cm−1 are achieved for the electrode prepared by an alcohol-rich ink. The simulation and experimental results demonstrate that the microstructure can benefit the extension of TPIs and facilitate oxygen transport in the air cathode, ultimately achieving efficient utilization of catalytic activities. A maximum power density of 35.4 mW cm−2 is achieved in a membrane-less direct formate fuel cell, surpassing most congeneric devices. Our approach clarifies the relationship between TPI construction, mass transport, and electrode microstructure, which successfully exploits the intrinsic activity on air cathodes and improves the power generation ability.

Influence of Organic Impurities on Fractional Crystallization of NaCl and Na2SO4 from High-Salinity Coal Chemical Wastewater: Thermodynamics and Nucleation Kinetics Analysis.

It is a valid path to realize the zero discharge of coal chemical wastewater by using the fractional crystallization method to recycle the miscellaneous salt in high-salinity wastewater. In this study, the thermodynamics and nucleation kinetics of sodium chloride (NaCl) and sodium sulfate (Na2SO4) crystallization in coal chemical wastewater were systematically studied. Through analyses of solubility, metastable zone width, and induction period, it was found that the impurity dimethoxymethane would increase the solid-liquid interface energy and critical crystal size during the nucleation of Na2SO4. Ternary phase diagrams of the pseudo-ternary Na2SO4-NaCl-H2O systems in simulated wastewater were plotted in the temperature range of 303.15 to 333.15 K, indicating that a co-ionization effect existed between NaCl and Na2SO4, and NaCl had a strong salting out effect on Na2SO4. Finally, the nucleation rate and growth rate of Na2SO4 crystals under simulated wastewater conditions were determined by the intermittent dynamic method, and the crystallization kinetic models of Na2SO4 were established. The crystallization nucleation of Na2SO4 crystals was found to be secondary nucleation controlled by surface reactions. The basic theoretical research of crystallization in this study is expected to fundamentally promote the application of fractional crystallization to realize the resource utilization of high-salinity wastewater in the coal chemical industry.

Morphological diversity in directionally-solidified microstructures with varying anisotropy of solid-liquid interfacial free energy

Morphological diversity in directionally-solidified microstructures of fcc-based binary alloys was investigated using quantitative phase-field simulation. The growth morphology for each set of anisotropy parameters was identified from the degree of undercooling of the dendrite tip and a morphology map was constructed. We investigated the effects of solidification conditions and alloy systems on growth morphology and found that the pulling speed has a significant effect, while temperature gradient and partition coefficient have only small effects on the morphology selection. Furthermore, we examined the emergence of doublon and triplet dendrites under conditions of weak interfacial anisotropy.

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect.

We examined the effect of deformability of a solid substrate on the kinetics of a surface reaction that occurs between chemical species present in it and a liquid dispensed on it. In particular, we have dispensed aqueous solutions of gold and silver salt as sessile drops or as a liquid pool on a cross-linked film of poly(dimethylsiloxane) (PDMS). The PDMS surface contains organosilane (SiH), which reduces the salt, producing metallic nanoparticles at the solid-liquid interface. These experiments reveal that, for a sufficiently soft solid, the reaction proceeds about three times faster in the drop mode than in the pool mode. The reaction conditions in both cases remain exactly identical except that, for the drop, the vertical component of the liquid surface tension deforms the solid substrate at the three-phase contact line. We have estimated the solid-liquid and solid-air interfacial energy, which along with the surface energy of the liquid gives an estimate of excess free energy. This energy is found to be different for the drop and pool modes. By considering that this excess free energy decreases the activation energy barrier for the reaction, we have shown that the reaction rate constant in the drop mode should indeed exceed that in the pool mode by about three times.

Further Exploration of Heat of Immersion as a Method to Quantify Wettability for Particulates: Effect of Temperature.

A previous paper [Weston et al. Ind. Eng. Chem. Res. 2015, 54, 4274-4284] by our group concluded that to distinguish between the wettability of different particles, heat of immersion is the best method, as opposed to the Washburn or sessile drop method. In this paper, heats of immersion of three different particles with three different wettabilities are measured at different temperatures to examine one critical assumption concerning the temperature dependence of the heat of immersion. In addition, surfactants are added to the water, and the effect of surfactant concentration on the heat of immersion is measured. One particularly noteworthy aspect of the current study is that some measurements were made at temperatures greater than 100 °C and hence pressures higher than atmospheric pressure with no more difficulty than measurements made at atmospheric pressure. The previous paper showed that, for certain particles, the relationship used by us and others between the heat of immersion and contact angle gave impossible values for certain surfaces. In this paper, the derivation of that expression is reexamined, and certain assumptions are highlighted. Because of issues with the assumptions, we agree with the conclusion from our previous paper that using the heat of immersion as a qualitative measure of wetting is appropriate. However, without measurement of the values of the liquid-solid interfacial energy with temperature as well as the gas-solid interfacial energy with temperature, conversion to the contact angle directly is not appropriate. However, for the same surface, using this approach to quantify the contact angle as a function of temperature is likely appropriate if the contact angle is measured using some other method at one temperature, at least over the limited temperature range (up to 150 °C) explored in this study.

Prediction of Metastable Zone Widths: Optimizing the Nucleation Potential Model with Solid–Liquid Interfacial Energy

Prediction of Metastable Zone Widths: Optimizing the Nucleation Potential Model with Solid–Liquid Interfacial Energy

Experimental determination of solid-liquid interface energy for para- and diamagnetic solid solution in equilibrium with eutectic liquid under a high magnetic field

The solid-liquid interface energy (SLIE) of the Al-Cu and Bi-Cd systems under a high magnetic field (HMF) has been experimentally determined by a Bridgeman-type directional solidification furnace. The equilibrated grain boundary groove shapes for the paramagnetic solid α-Al solution and the diamagnetic solid Bi solution in equilibrium with the eutectic liquid under various HMFs were observed in Al-15.3at%Cu alloy and Bi-50at%Cd alloy. It can be found that the profiles of grain boundary grooves changed significantly under the action of the HMF. The Gibbs-Thomson coefficient and the SLIE for the solid α-Al and solid Bi solution in equilibrium with the eutectic liquid under various HMFs were obtained from obtained grain boundary groove shapes. The results show that the SLIE of the Al-Cu and Bi-Cd alloys increase and decrease under an HMF, respectively. The interaction theory of magnetic dipoles induced by an HMF can be responsible for the above experimental phenomena. Additionally, the results of the differential thermal analysis (DTA) and theoretical analysis indicate that the undercooling of the Al-15.3at%Cu and Bi-50at%Cd alloys increase and decrease under the influence of an HMF, respectively, which is ascribed to the existence of HMF-induced interface energy.

Nanoscale insights on the freezing front propagation and ion behaviors during seawater freezing

Seawater freezing holds significant importance in scientific and industrial applications. However, there is a lack of in-depth understanding of the nanoscale mechanism of seawater freezing. In this study, the nanoscale characteristics and mechanisms of seawater freezing are investigated by the molecular dynamics method. Since the solid-liquid interfacial free energy decreases with increasing subcooling or decreasing NaCl solution concentration, the speed of freezing front propagation increases. The formation of nano brine pockets is observed, which is analyzed based on the solid-liquid interfacial free energy. The energy barriers of Na+ and Cl− diffusing from the freezing front into the NaCl solution are smaller than these of diffusing into the hexagonal ice. As a result, most Na+ and Cl− are rejected into the solution, whereas only a few dope into the hexagonal ice. Furthermore, the energy barrier of Cl− diffusion into hexagonal ice is smaller than that of Na+, which makes the amount of Cl− doping into hexagonal ice greater than that of Na+. This study contributes to a deeper understanding of nanoscale characteristics and mechanisms of seawater freezing, which shall promote related technologies such as seawater freeze desalination.

Liquid phase sintering of yttrium oxide: The effect of Al2O3 and SiO2 additives

Solid-state sintering of Y2O3 is difficult and requires high-temperature heat treatment or the use of a sintering additive. In this study, liquid-phase sintering was utilized to produce dense Y2O3 bodies with fine-grained microstructure. Al2O3 and SiO2 were added to a commercial nano-Y2O3 powder using aluminum nitrate and tetraethylorthosilicate (TEOS) as the precursors; the samples were uniaxially pressed at 100 MPa and sintered at 1500 °C and 1650 °C. The addition of the sintering aids increased the relative density of the samples sintered at lower temperatures; also, the sintering aids suppressed grain growth. The dissolution of Y2O3 into the liquid phase changes the solid-liquid interfacial energy resulting in the formation of isolated yttrium-silicate/yttrium-aluminate grains and accounts for the suppression of the growth of yttria grains.

Effect of process impurities on crystallization thermodynamics and nucleation kinetics of taurine

AbstractSolubility and metastable zone width (MSZW) are the basis for purifying products by crystallization. The effects of two process impurities, sodium isethionate (SI) and sodium N‐(β‐ethyl sulfonic acid) aminoethyl sulfonate (SA), on taurine solubility and MSZW in water under different conditions were studied. Solubility and MSZW were measured by laser transmission method. The results show that the process impurities can increase solubility slightly but increase MSZW significantly. The weak solubilization might be due to the antagonism of salting‐out effect and structural similarity between taurine and impurities. Combining the viscosities and parameters calculated by nucleation models, the reason for the different effects of the two impurities on MSZW was studied. The fitting and experiment results show that the solid–liquid interfacial energy γeff was increased by 9.1% and the viscosity by 5.4% at 303.15 K in the presence of SI (0.12 mol per kilo H2O). Meanwhile, γeff was increased by 90.4% and the viscosity by 10.5% with SA added (0.12 mol per kilo H2O). Changes in thermodynamic factors (solubility, γeff) and kinetic factors (viscosity) caused by impurities contribute to the extension of MSZW. This study expands the understanding of the role of process impurities in taurine crystallization.

Experimental determination of solid-liquid interfacial free energy anisotropy in Al-Zn via equilibrium droplet method

The increasing Zn content causes dendrite orientation transition during solidification of Al-Zn alloys, which is supposed to be related to the change of solid-liquid interfacial energy anisotropy. In this paper, experimental measurements of the interfacial energy anisotropy were performed in Al-17, 30 and 75wt.%Zn alloys with equilibrium droplet method. Droplets shape in relation to crystal orientation and droplets morphology are obtained by Electron Back-Scatter Diffraction and X-ray Computed Tomography, respectively. The result indicates that anisotropic parameters ε1 and ε2 both decreases with increasing Zn concentration and the directions of maximum interfacial energy transform from 〈100〉 directions in Al-17wt.%Zn and Al-30wt.%Zn to 〈110〉 directions in Al-75wt.%Zn. In addition, the Wulff plot and normalized interfacial stiffness are quantified and compared with the corresponding Al-Zn dendrites orientation selection.

Size dependence of the phase transition temperature of metal nanocrystals

Melting, freezing, and evaporation are common phase transition processes in metallic nanocrystals. Predicting these phase transitions and understanding their underlying mechanisms are crucial for the design, preparation, and application of nanomaterials. In this work, we establish the thermodynamic models to describe the size dependence of cohesive energy Ec, melting temperature Tm, freezing temperature Tf, and evaporation temperature Te. By comparing the predictions with the available experimental results, a good agreement is obtained. In addition, we find that at the same diameter D, the Tm(D)/Tm, Tf(D)/Tf, and Te(D)/Te of nanocrystals increase with the improvement of the ratio of solid-liquid interface energy γsl to interfacial stress f, indicating that γsl/f determines the thermal stability of the surfaces.

Atomistic modeling of Mg-Al-Zn solid–liquid interfacial free energy

In this study anisotropic solid–liquid interfacial energy, γ, of Mg-Al-Zn system is evaluated based on capillary fluctuation method. To investigate effects of temperature and solute compositions on γ, five simulation cases, Cases I-V, are designed and divided into two group, Group I consist of Cases I-III for evaluation on solute compositions, while Group II consist of Cases I, IV and V for evaluation on temperatures. Interfacial energy stiffness of six differently oriented interfaces is evaluated, average interfacial energy, γ0, and anisotropic parameters of the interfaces are obtained. This study determined melting point of Mg as 964 ± 5 K, which matches the standard value of 923 K. Evaluation on γ0, and γ in high symmetric orientations γBasal, γPrismaticIA and γPrismaticIIA suggests, for Cases I-V, lower γ0 values within 15.74–18.19 mJ/m2 compared with elemental Mg could be related with the insufficiency of selected interatomic potential to describe the solid–liquid interface, and relation of γBasal>γPrismaticIIA>γPrismaticIA was identified. Comparisons within Group I indicate the increase of relative average equilibrium composition, c¯i/c¯j, will improve solute adsorption of element i on interface, which causes γ0 , γBasal, γPrismaticIA and γPrismaticIIA to decrease. As for Group II, temperature increase will result in decline of γ0 , γBasal, γPrismaticIA and γPrismaticIIA, similar trend was found in Al-Sm alloy systems. Primary dendrite growth orientations for Cases I-V were determined as [0001], analysis shown increase in either temperature or c¯i/c¯j stabilize this preference further towards [0001].

Machine learning-assisted MD simulation of melting in superheated AlCu validates the Classical Nucleation Theory

The validity of the Classical Nucleation Theory (CNT), the standard tool for describing and predicting nucleation kinetics in metastable systems, has been under scrutiny for almost a century. While the CNT is commonly employed to describe liquid → crystal and liquid ↔ vapor phase transitions, its application to the crystal → liquid case has been limited because of the experimental challenges in achieving superheating states and detecting homogeneous liquid nucleation. In this study, we performed comprehensive molecular dynamics (MD) simulations of spontaneous melting of a superheated AlCu crystal under atmospheric pressure at five temperatures, covering a superheating range of T/TL = 1.1–1.3, where TL is the liquidus temperature. Two realistic AlCu models were investigated: one described by the modified embedded atom method (MEAM) and the other by an interatomic potential generated by an artificial neural network machine learning (ML) approach, extensively trained on an ab initio dataset of liquid and crystal configurations. Fifty independent melting events were simulated at each temperature. By analyzing the distribution of melting times using the Poisson law, the homogeneous nucleation rate was determined through the mean lifetime method. Additionally, the Zeldovich factor, critical nucleus size, and work of formation were obtained using the mean first-passage time method, utilizing the disorder parameter based on atomic displacements (liquid-like atoms in the superheated crystal) as the reaction coordinate. Also, the effective atomic transport coefficient across the metastable crystal/critical liquid nucleus interface was determined by MD simulations as the interfacial attachment coefficient for nuclei growth rates. Using these simulation-generated data, the theoretical nucleation rates were calculated by the CNT with no fitting parameters. We found excellent agreement between the theoretically and MD-computed liquid nucleation rates for both MEAM and ML crystals. Notably, the effective solid-liquid interfacial free energy value obtained from the MD data aligns with its recent experimental measure. Moreover, the CNT qualitatively and quantitatively described the underlying details of liquid drop nucleation in our ML solid, unprecedentedly and accurately reproducing the kinetic prefactor and the size, formation energy, and growth rate of the critical nuclei. Thus, the melting of the AlCu model created through machine learning-processed quantum calculations, that is, not relying on hand-crafted interatomic potential functions, was successfully described by the CNT phenomenological formalism, without any adjustable parameters. This finding confirms the CNT as a very reliable descriptor of homogeneous nucleation in the superheated AlCu alloy and generalizes this theory as a powerful tool for analyzing and predicting the kinetics of crystal-liquid transitions.

Microstructure evolution in FePt-Cr2O3 granular thin films

Increase in the FePt grain density is necessary to achieve an ultra-high recording density of the heat-assisted magnetic recording. Herein, the highest grain density in FePt-Cr2O3 granular thin films was obtained by utilizing a densified FePt nucleation layer. The reduced magnetic properties were attributed to the grain shape and effect of elemental diffusion at the FePt/Cr2O3 interface. The equilibrium shape of the FePt grains indicated that the solid–liquid interfacial energy in the FePt granular system is a key factor in controlling the microstructures.

Studying kinetics of a surface reaction using elastocapillary effect

HypothesisWhen a liquid is inserted inside a microfluidic channel, embedded within a soft elastomeric layer, e.g. poly(dimethylsiloxane) (PDMS), the thin wall of the channel deforms, due to change in solid–liquid interfacial energy. This phenomenon is known as Elastocapillary effect. The evolution of a new species at this interface too alters the interfacial energy and consequently the extent of deformation. Hence, it should be possible to monitor dynamics of physical and chemical events occurring near to the solid–liquid interface by measuring this deformation by a suitable method, e.g., optical profilometer. ExperimentsAqueous solution of a metal salt inserted into these channels reacts with Silicon-hydride present in PDMS, yielding metallic nanoparticles at the channel surface. The kinetics of this reaction was captured in real time, by measuring the wall deformation. Similarly, physical adsorption of a protein: Bovine Serum Albumin, on PDMS surface too was monitored. FindingThe rate of change in deformation can be related to rate of these processes to extract the respective reaction rate constant. These results show that Elastocapillary effect can be a viable analytical tool for in-situ monitoring of many physical and chemical processes for which, the reaction site is inaccessible to conventional analytical methods.

Insight into the role of ethylene glycol on thermodynamics and nucleation kinetics of dimethyl terephthalate in mixed solvent system

Dissolution and nucleation are two essential processes for industrial crystallization. This paper investigates the effect of ethylene glycol addition on the crystallization behavior of dimethyl terephthalate (DMT) in solution. The DMT solubility in mixed solvent system (methanol-ethylene glycol) was determined by isothermal satiation approach, and the solubility was associated using seven models. The model fitting results were consistent with the experimental values. Based on the results, the metastable zone width (MSZW) of DMT was detected by the polythermal approach; the modified Sangwal's theory was used to investigate the nucleation behavior, which can provide a new way of thought for better analysis of the crystallization behavior. The results demonstrated that MSZW was associated with various elements, such as cooling rate, saturation temperature and mass fraction of ethylene glycol. The addition of ethylene glycol slowed down the nucleation rate as shown by the broadening of MSZW. We derive the solid-liquid interface energy, the nucleation driving force, the critical nucleation size and the critical Gibbs free energy according to the classical nucleation theory. It is demonstrated that the nucleation driving force and the solid-liquid interface energy are dependent and jointly influence the MSZW.