Solid-liquid Interfacial Energy Research Articles

The water cavitation line as predicted by the TIP4P/2005 model.

The formation of vapor bubbles in a metastable liquid, cavitation, is an activated process due to the free energy cost of having both phases at contact. Such an energetic penalty enables the existence of the liquid beyond its thermodynamic borders. Establishing the stability limits of a liquid as ubiquitous as water has important practical implications and has thereby attracted a lot of attention. Different experimental strategies and theoretical analyses have been employed to measure and predict the cavitation line, or the pressure-temperature kinetic stability border of liquid water. Understanding the location of the cavitation line requires knowing the cavitation rate dependence on pressure and temperature. Such dependency is difficult to obtain in experiments, and we use molecular simulations with the TIP4P/2005 model to fill this gap. By deeply overstretching liquid water below the saturation pressure, we are able to observe and quantify spontaneous cavitation. To deal with a lower overstretching regime, we resort to the Seeding technique, which consists of analyzing simulations of a liquid containing a vapor bubble under the theoretical framework of Classical Nucleation Theory. Combining spontaneous cavitation with Seeding, we get a wide overview of the cavitation rate. We study two different temperatures (450 and 550K) and complement our perspective with the results previously obtained at 296.4K [Menzl et al., Proc. Natl. Acad. Sci. 113, 13582 (2016)] to establish a broad simulation-experiment comparison. We find a good agreement between simulations and both isobaric heating and isochoric cooling experiments using quartz inclusions. We are, however, unable to reconcile simulations with other experimental techniques. Our results predict a decrease in the solid-liquid interfacial free energy as the liquid becomes increasingly overstretched with a temperature independent Tolman length of 0.1nm. Therefore, the capillarity approximation underestimates the nucleation rate. Nonetheless, it provides a fair indication of the location of the cavitation line given the steep rate vs pressure dependence. Overall, our work provides a comprehensive view of the water cavitation phenomenon and sets an efficient strategy to investigate it with molecular simulations.

Effects of a high magnetic field on single-phase interface evolution, additional interfacial energy and nucleation undercooling in Al-based alloy

The effects of a high magnetic field on the evolution of the single-phase interface and the liquid-solid interface energy in Al-Cu alloy were investigated experimentally. It is found that the application of the magnetic field has a significant promotion effect on the migration of liquid droplets, accelerating the formation of the single-phase interface. This should be attributed to the thermoelectric (TE) magnetic convection in the droplets which has enhanced the diffusion and increased the migration speed of liquid droplets. Further, the effect of the high magnetic field on the solid-liquid interface energy is analyzed by an improved grain boundary groove (GBG) method. The average solid-liquid interface energy of the α-Al/Al-Cu and Al2Cu/Al-Cu systems increases and decreases with the increase of the magnetic field, respectively. The above experiment results are well explained based on the formation and interaction of the magnetic dipole at the solid-liquid interface. Moreover, experimental results reveal that the magnetic-field-induced interface energy increases and decreases the nucleation undercooling of the Al-30wt.%Cu alloy and Al-35wt.%Cu alloy, respectively. By studying the effect of the magnetic-field-induced interface energy on the nucleation undercooling, the understanding of the interface energy-induced nucleation undercooling deepens.

An efficient analytical model for predicting the microstructure characteristic parameters of the as-cast and solid-solution treated Mg-Gd-Y-Zr cast alloys

In this work, an efficient analytical model is proposed to predict the microstructure characteristic parameters (MCP) of Mg-Gd-Y-Zr cast alloys under different solidification and solid solution conditions, in which, as a featured methodology, the solidification and solid solution processes were simulated by simplifying the grain morphology of the alloys based on the anisotropy function of the solid-liquid interface energy of magnesium. The MCP predicted by the model agree with the ones measured in the experiments, including the volume fraction of the β phase and the element distribution inside the grains of the alloys in different solidification and solid solution processes, which demonstrated that the model provided an efficient approach on the basis of the model prediction to optimize the solid solution process of the Mg-Gd-Y-Zr alloys solidified under various cooling conditions.

Study of wetting promotion mechanism of Pb/Cu interface assisted by ultrasonic vibration from molecular dynamics simulation and experiments

In the paper, the molecular dynamics method was used to study the wetting promotion mechanism of liquid Pb/solid Cu system under ultrasonic vibration, which provided theoretical guidance for the application of ultrasonic wetting. The result showed that both ultrasound and temperature increase could improve the wettability of the system by promoting the dissolution and diffusion of the solid-liquid interface. However, ultrasound had a more obvious promotion effect. At 900K, the contact angle without ultrasound was 22.3°, while the contact angle with ultrasound was reduced to 0°, and the system was completely wetted. In addition, it was found that ultrasonic frequency had a significant effect on wettability. The 250 GHz ultrasonic vibration had an obvious effect on the wetting, but there were a large number of Cu atoms dissolved at the edge of the droplet, which hindered the spreading of the droplet, while the 25 GHz ultrasonic frequency only promoted the spreading of the droplet. In addition, experiment at different temperatures confirmed that ultrasonic vibration improved the wettability of the system. The wetting promotion mechanism of ultrasonic was that ultrasonic vibration caused the system to generate tension and pressure at the solid-liquid interface, which promoted the spreading of droplet and the diffusion of interface atoms, and reduced the solid-liquid interface energy and equilibrium contact angle.

Temperature-dependent slip length for water and electrolyte solution

HypothesisThe temperature dependence of boundary slip at liquid–solid interface is critical both for the fundamental theory and applications of fluid mechanics on micro and nanoscale, such as sustainable cooling of electronic devices. However, there is a controversy on the temperature dependence of boundary slip which lacks experimental evidence, we aim to resolve it by hypothesizing that the temperature dependent slip length depends on the variation in the interfacial energy barrier. ExperimentsHere, we measured ls – T relation of water and NaCl solution on self-assembled FDTS (Perfluorodecyltrichlorosilane) surface using colloidal probe AFM. The transition of ls – T monotonicity is found. For water and 0.1 M NaCl solution, ls is negatively correlated with T, while for 1 M NaCl solution, ls is positively correlated with T. FindingsTogether with molecular dynamics simulations, such observation is quantitatively explained with an analytical model based on rate theory, where the ls – T monotonicity depends on the difference between liquid–solid interfacial energy barrier and liquid internal energy barrier. Our results provide not only solid experimental evidence for the boundary slip being a rate process, but also a basis for the thermal-hydrodynamic design of microfluidic and nanofluidic devices.

Decorating nano Ni on the surface of CNTs and their wettability behaviors analysis with aluminum alloy

CNTs have poor wettability with aluminum resulting in strengthening much less than expected. Nano Ni of 50 to 80 nm are uniformly decorated on the surface of CNTs (CNTs@Ni) to improve interface wettability with aluminum. The results of wettability measurements indicate that CNTs@Ni/2024Al system has contact angles of 81.9° at 1133 K. Gibbs free energy calculations show that interfacial reactions of CNTs@Ni/2024Al system are more active than those of CNTs/2024Al system. The interfacial reaction of producing Al4C3 is inhibited, because solid solubility of C in Al is extremely low. More active interfacial reactions of producing AlNi release significant heat to reduce surface tension and solid–liquid interfacial energy, resulting in molten 2024Al interface breakdown and making CNTs@Ni/2024Al system exhibits wettability.

Unveiling the mechanisms for Si addition on solidification microstructure and properties of Cu-Fe alloy

In this present study, the Si element was intentionally introduced into Cu-20Fe alloy by tuning composition, thus deliberately tailoring resultant microstructure and properties. Accordingly, the effect of Si addition on solidification microstructure and resultant properties of experimental Cu-20Fe-xSi alloys was systematically investigated and elucidated. Microstructural characterization and quantitative analysis demonstrate that the Si addition brings about considerable morphology change (e.g., from original well-developed dendrite to cellular morphology, and eventually being the coral-like morphology) and significant refinement (e.g., from 77.2 ± 15 µm to 7.3 ± 1.3 µm, and then coarsening to 18.9 ± 3.0 µm.), as well as interior sub-microstructure evolution of Fe-rich phase. It is believed that the enhanced undercooling ahead of the solid-liquid interface and the change in the solid-liquid interfacial energy γsℓ resulted from the Si addition should be responsible for such considerable morphology change and significant refinement of Fe-rich phase, respectively. In addition, the morphology and size of Fe-rich phase have a substantial influence on the magnetic and mechanical properties of experimental alloys. It is confirmed that the Fe-rich phase with cellular morphology contributes greatly to the decrease of coercivity by ∼ 60.5% and the enhancement of fracture elongation by ∼ 34.1%, while the dendritic Fe-rich phase with refined size is remarkably beneficial for both improvement of the saturation magnetization (by ∼ 10.6%) and strength (by ∼ 7.2% in ultimate tensile strength). In addition, the corresponding influencing mechanisms have also been clarified through experimental analysis with incorporation of Finite element analysis (FEA) simulation. This present study demonstrates a highly effective and promising method for tailoring solidification microstructure of Cu-Fe alloy by Si addition, which is beneficial for further manipulation of alloy properties either for as-cast or subsequent deformation-processed application.

Direct Measurement of Solid-Liquid Interfacial Energy Using a Meniscus

Solid-liquid interactions are central to diverse processes. The interaction strength can be described by the solid-liquid interfacial free energy (γ_{SL}), a quantity that is difficult to measure. Here, we present the direct experimental measurement of γ_{SL} for a variety of solid materials, from nonpolar polymers to highly wetting metals. By attaching a thin solid film on top of a liquid meniscus, we create a solid-liquid interface. The interface determines the curvature of the meniscus, analysis of which yields γ_{SL} with an uncertainty of less than 10%. Measurement of classically challenging metal-water interfaces reveals γ_{SL}∼30-60 mJ/m^{2}, demonstrating quantitatively that water-metal adhesion is 80% stronger than the cohesion energy of bulk water, and experimentally verifying previous quantum chemical calculations.

Concentration dependence of the crystal nucleation kinetics in undercooled Cu-Ge melts.

The crystallization temperature of deeply undercooled Cu-Ge alloy melts is repeatedly measured. A statistical analysis is applied on the undercooling distributions obtained from nine different compositions, ranging from the pure semimetal (Ge) to the pure metal (Cu). By considering each undercooling distribution as an inhomogeneous Poisson process, the nucleation rates for every composition are calculated. The Thompson-Spaepen model for homogeneous nucleation in binary alloys is applied, enabling the estimation of nucleation parameters, such as kinetic pre-factors and interfacial energies, as a function of composition. Furthermore, the Turnbull coefficient α, a dimensionless solid-liquid interfacial energy constant, is also calculated as a function of alloy constitution, suggesting a dependence on the liquid composition. The composition-dependent changes of α are of considerable importance, since the α is originally defined for pure systems as a quantity dependent on crystal structure, and is nevertheless used for describing nucleation kinetics of binary and glass forming multi-component alloy systems.

Influence of La addition on Fe-rich intermetallic phases formation and mechanical properties of Al-7Si-4Cu-0.35Mg-0.2Fe alloys prepared by squeeze casting

Brittle β-Al5FeSi (β-Fe) intermetallic phases directly affect the mechanical properties of Al–Si alloys; thus, it is essential to modify these phases. Scanning electron microscope analysis showed that rare earth Lanthanum (La) additions (0, 0.15, 0.30 and 0.50 wt%) had a refining effect on β-Fe phases in Al–7Si–4Cu-0.35Mg-0.2Fe (wt.%) alloys prepared by squeeze casting. The underlying refinement mechanisms of rare earth La on the β-Fe were discussed in terms of experimental observations, nucleation thermodynamics and growth kinetics. For nucleation thermodynamics, La additions could induce the formation of La-rich intermetallic phases Al4Cu2SiLa with orthorhombic structure. Because β-Fe nuclei had a good lattice matching and epitaxial relationship with the Al4Cu2SiLa phases, the Al4Cu2SiLa provided energetically favorable nucleation sites for β-Fe and greatly promoted the nucleation of β-Fe in alloys. Meanwhile, the added La atoms could restrain the diffusion of atoms to the solid/liquid interface front and alter the β-Fe interfacial structure and energy, therefore restricting the β-Fe growth. Furthermore, β-Fe/Al4Cu2SiLa grew into side-by-side and cross-like morphologies, and its growth behaviors were controlled by solute concentration and anisotropy of the solid-liquid interfacial energy in a cooperative eutectic reaction. In addition, different fracture behaviors from brittle fracture to mixed ductile fracture and quasi-cleavage brittle fracture were also illustrated with increasing La addition, and these fracture behaviors were influenced by the characteristics of brittle La-rich and β-Fe intermetallic phases. When the addition of La was increased to 0.3 wt% and 0.5 wt%, it occurred quasi-cleavage brittle fracture, which was caused by the precipitation of coarse plate-like La-rich phases.

Computing the solid-liquid interfacial free energy and anisotropy of the Al-Mg system using a MEAM potential with atomistic simulations

The solid–liquid interfacial free energy, γ, and its associated anisotropy were computed for the Al-Mg binary alloy system using Molecular Dynamics (MD) simulations in conjunction with the capillary fluctuation method (CFM). Interactions between atoms were modeled based on a second nearest neighbor modified embedded atom method (MEAM) potential, a successor to the established embedded atom method (EAM) potential. The MEAM potential predicts a melting temperature of 938 K ± 17 K for pure Al and the solid–liquid phase equilibria as a function of temperature and composition was found using Monte Carlo technique implemented in Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The average interfacial free energy, γ0, for pure Al was found to be 135.94 ± 3.62 mJ/m2 which agrees well with experimental values and an interfacial free energy relationship of γ100>γ110>γ111 was found across the majority of the temperatures which is consistent with FCC metals. The anisotropy values were found to fall within the 100 growth direction along the orientation selection map suggesting the addition of Mg stabilizes this growth direction. The results from the MEAM potential compares qualitatively well with other EAM potentials, however, experiences larger errors at lower temperatures.

Non-regular dendritic pattern selection induced by interface energy anisotropy in the directional solidification of Al-3 wt% Mg single crystals

• Finding plate-like and hyperbranched seaweed in 3D conditions of metallic alloy. • Constructing a non-regular dendritic pattern selection map. • Well understanding effect of interface energy anisotropy on the dendritic pattern. Dendritic morphology and pattern selection are fundamentally important issues in solidification cycles. Here, a well-designed experiment was employed to investigate the solid–liquid interface energy anisotropy on the directionally solidified microstructures of Al-3 wt% Mg single crystals. Various dendritic morphologies, including regular dendrite, plate-like seaweed and hyperbranched seaweed, were found along the <100>, <110> and <111> orientations, respectively. The primary dendritic arm spacing (PDAS) of the seaweed pattern is closely related to the interface energy anisotropy and deviates from the current PDAS model. A non-regular dendritic pattern selection map is constructed to interpret the different dendrites occurring in alloy solidification.

Wetting of liquid Zinc-aluminum-magnesium alloy on steel substrate during hot-dipping: Understanding the role of the flux

The surface quality of hot-dipping Zn-Al-Mg coatings was significantly influenced by the composition of fluxes. In this study, five different fluxes were chosen and named as F1 (ZnCl2, NH4Cl), F2 (ZnCl2, NaF), F3 (ZnCl2, NH4Cl, KCl), F4 (ZnCl2, NH4Cl, KCl, SnCl2, HCl), and F5 (ZnCl2, NH4Cl, KCl, BiCl3, HCl). Using the sessile drop method, the influence of different fluxes on the wettability between the liquid Zn-Al-Mg alloy and the steel substrate was elucidated. The results showed that: when the flux composition is ZnCl2-NH4Cl-KCl-BiCl3-HCl, a uniform and dense salt film with a protective effect can be formed on the steel substrate, which prevents the oxidation of the steel substrate and removes the harmful reaction products during hot-dipping. By reducing the solid–liquid interface energy, increasing the work of adhesion between the liquid Zn-6Al-3Mg alloy and steel substrate, and shortening the interface reaction time, the strongest wetting effect between the liquid Zn-6Al-3Mg alloy and the steel substrate was achieved. The coating surface quality was the highest after using the F5 flux. Finally, the mechanism of the assistant plating is discussed.

Mechanism insights into liquid polarity regulation for enhanced dewatering of waste-activated sludge: Specifically focusing on the solid-liquid affinity reduction depending on phase-transfer and conformational features of amphiphilic protein

This study proposed that decreasing liquid polarity could weaken the intermolecular polar force at solid-liquid interface of waste-activated sludge (WAS). Accordingly, a process for enhanced sludge dewatering through liquid polarity regulation was established. The liquid polarity was quantified by dielectric constant and the decrease of liquid dielectric constant below 50 was found to significantly improve the solid-liquid separation performance of WAS in terms of filterability by >70%. The differential scanning calorimeter (DSC) coupled with mass spectrum (MS) identified that 60 °C was the appropriate temperature for liquid amendment (i.e., acetonitrile) recovery from filtered sludge cake, and the corresponding energy consumption was calculated to be at most 799.0 J/g, which was substantially lower than that of water evaporation by sludge drying. The NaCl addition with 75% of saturated concentration could non-thermally recover 91.7 ± 4.9% of acetonitrile amendment from filtrate by salting-out. The great potentials in energy saving and recycle of chemicals make the newly proposed approach act as alternatives for the conventional process (i.e., mechanically dewatering + drying). Regarding the mechanism of liquid polarity regulation for enhanced WAS dewatering, the solid-liquid interfacial free energy was found to be reduced by 39.4% with the liquid dielectric constant decreasing from 78.50 to 41.00. Also, Tandem Mass Tags (TMT) proteomics tracked the phase-transfer of amphiphilic proteins with decreasing liquid polarity, which found that the solubilization of proteins involved in the Gene Ontology (GO) classifications of “membrane protein complex” and “membrane protein complex/outer membrane” could facilitate the enhanced solid-liquid separation of WAS. The conformational analysis on those differential proteins was further conducted to reveal the structure attributes of amphiphilic proteins for the phase-transfer feature. The proteins with more exposed amino acid residues (i.e., average solvent accessibility index over 1.8) tended to dissolve in the liquid phase with lower polarity, which was accompanied with the reduced interfacial free energy of WAS. On the contrary, the proteins with buried amino acid residues (e.g., the central hydrophobic β-sheet is surrounded by the hydrophilic α-helix) precipitated in the solid phase with the decreasing liquid polarity. All these findings are expected to create a novel option for dewatering WAS with recyclable liquid conditioning agents, and provide the improved mechanistic insights into the migration of interfacial compositions controlling the dewaterability of WAS.

Effect of interface anisotropy on tilted growth of eutectics: A phase field study

Interfacial energy anisotropy plays an important role in tilted growth of eutectics. However, previous studies mainly focused on the solid–solid interface energy anisotropy, and whether the solid–liquid interface energy anisotropy can significantly affect the tilted growth of eutectics still remains unclear. In this study, a multi-phase field model is employed to investigate both the effect of solid–liquid interfacial energy anisotropy and the effect of solid–solid interfacial energy anisotropy on tilted growth of eutectics. The findings reveal that both the solid–liquid interfacial energy anisotropy and the solid–solid interfacial energy anisotropy can induce the tilted growth of eutectics. The results also demonstrate that when the rotation angle is within a range of 30°–60°, the growth of tilted eutectics is governed jointly by the solid–solid interfacial energy anisotropy and the solid–liquid interfacial energy anisotropy; otherwise, it is mainly controlled by the solid–solid interfacial energy anisotropy. Further analysis shows that the unequal pinning angle at triple point caused by the adjustment of the force balance results in different solute-diffusion rates on both sides of triple point. This will further induce an asymmetrical concentration distribution along the pulling direction near the solid–liquid interface and the tilted growth of eutectics. Our findings not only shed light on the formation mechanism of tilted eutectics but also provide theoretical guidance for controlling the microstructure evolution during eutectic solidification.

An atomistic simulation study of rapid solidification kinetics and crystal defects in dilute Al–Cu alloys

Rapid solidification kinetics of dilute Al–Cu alloys is simulated using a quantum mechanics based bond-order potential (BOP), in free solidification conditions, to determine kinetic and thermodynamic properties of solidification, as well as point defects and chemical ordering of the solidified structures. We measure the anisotropic kinetic coefficient, anisotropic solid–liquid interface energy, as well as solute trapping kinetics in terms of partition coefficient versus velocity and solute drag coefficient. Furthermore, solid–liquid interface free energy and its anisotropy are measured in equilibrium simulations, showing reasonably good agreement with previous studies. We also verified the self-consistency of the MD simulations, by comparing the interfacial temperature vs. velocity to that predicted by the continuous growth model. These solid–liquid interface properties are important for quantitative parametrization of larger scale solidification modeling techniques such as phase field models. We also investigated the point defect content, local chemical ordering, and local crystalline structures in the rapidly solidified samples. We found clustering of solute with vacancies, whereas copper atoms repelled each other in these dilute alloy simulations. In addition to vacancies, a large number of interstitials were found. In solidification velocities approaching the complete solute trapping regime, we found that the vacancies and interstitials formed in conjunction, i.e. as Frenkel pairs. Finally, in addition to FCC, we detected BCC and HCP phases, where the latter two were accompanied by an increase in local copper content. Understanding the formation of point defects and their relationship to chemical ordering is an important step towards controlling the formation of pre-precipitates and precipitates, which are an important strengthening mechanism for aluminum–copper alloys.

Inverse analysis of anisotropy of solid-liquid interfacial free energy based on machine learning

A machine leaning-based approach is proposed for the inverse analysis of the anisotropy parameters of solid–liquid interfacial free energy. The interface shape distribution (ISD) map, which characterizes the details of the dendrite morphology, was selected as the input of a convolutional neural network (CNN). The ISD maps for a free-growing dendrite during the isothermal solidification of a model alloy system were obtained by quantitative phase-field simulations and used as the training and test data for the CNN. Two anisotropy parameters were estimated with errors of less than 5%, which can be further improved by increasing the size of the training dataset.

Modeling the surface stress and solid–liquid interface energy of alkali halide crystals

In this paper, the surface stress f(T) and solid–liquid interface energy γsl(T) of alkali halides are re-examined by introducing a measurable physical quantity bulk evaporation entropy Sb instead of vibration entropy Svib. The predictions show agreement with previous theoretical work and available experimental results. In addition, the temperature effect is considered. We found that both f(T) and γsl(T) functions decrease following the drop of temperature T, and f(T) exhibits a larger reduction than γsl(T). We also found that f is proportional to melting enthalpy Hm and inversely proportional to the atomic diameter h and compressibility κ. All these results will help us to effectively estimate the values of f and γsl and understand the surface phenomenon.

Temperature Dependence of Solid-Liquid Interfacial Energy for Pure Metals by Metadynamics-Based Simulations

Temperature Dependence of Solid-Liquid Interfacial Energy for Pure Metals by Metadynamics-Based Simulations

A temperature-dependent atomistic-informed phase-field model to study dendritic growth

The effects of solid–liquid interface anisotropy and kinetics on crystallization of highly undercooled titanium melts are studied by coupling molecular dynamics and phase-field simulations. Unlike previous models and to consider the actual physics of crystal growth, the phase-field parameters, representing interface mobility, solid–liquid transformation barrier, and interfacial energy gradient, are temperature dependent. The parameters are determined by a combination of molecular dynamics simulations and classical thermodynamic calculations based on the temperature-dependent solid–liquid interface properties and kinetic coefficient. We investigated Ti dendritic growth as a benchmark example to demonstrate that the phase-field model presented in this work is more compatible with the experimental data and theoretical models in comparison to the earlier models with constant model parameters. The capillary fluctuation method is used to determine the solid–liquid interface energy and its anisotropy for undercoolings up to 400 K. Similar to theoretical models, the average solid–liquid interface energy decreases with temperature, and the preferred dendrite growth direction shifts from 〈100〉 to 〈110〉 direction as the undercooling increases. Phase-field simulations also show other favorite growth directions, implying that there is a competition between the interface anisotropy and kinetics of the solid–liquid interface.