Interfacial Tension in the CaO-Al2O3-SiO2-(MgO) Liquid Slag-Solid Oxide Systems

NASA Astrophysics Data System (ADS)

Abdeyazdan, Hamed; Monaghan, Brian J.; Longbottom, Raymond J.; Rhamdhani, M. Akbar; Dogan, Neslihan; Chapman, Michael W.

2017-08-01

Interfacial phenomenon is critical in metal processing and refining. While it is known to be important, there are little data available for key oxide systems in the literature. In this study, the interfacial tension ( σ LS) of liquid slag on solid oxides (alumina, spinel, and calcium aluminate), for a range of slags in the CaO-Al2O3-SiO2-(MgO) system at 1773 K (1500 °C), has been evaluated. The results show that basic ladle-type slags exhibit lower σ LS with oxide phases examined compared to that of acid tundish-type slags. Also, within the slag types (acid and base), σ LS was observed to decrease with increasing slag basicity. A correlation between σ LS and slag structure was observed, i.e., σ LS was found to decrease linearly with increasing of slag optical basicity (Λ) and decrease logarithmically with decreasing of slag viscosity from acid to base slags. This indicated a higher σ LS as the ions in the slag become larger and more complex. Through a work of adhesion ( W) analysis, it was shown that basic ladle slags with lower σ LS result in a greater W, i.e., form a stronger bond with the solid oxide phases examined. This indicates that all other factors being equal, the efficiency of inclusion removal from steel of inclusions of similar phase to these solid oxides would be greater.

Oxidation-Mediated Fingering in Liquid Metals

NASA Astrophysics Data System (ADS)

Eaker, Collin B.; Hight, David C.; O'Regan, John D.; Dickey, Michael D.; Daniels, Karen E.

2017-10-01

We identify and characterize a new class of fingering instabilities in liquid metals; these instabilities are unexpected due to the large interfacial tension of metals. Electrochemical oxidation lowers the effective interfacial tension of a gallium-based liquid metal alloy to values approaching zero, thereby inducing drastic shape changes, including the formation of fractals. The measured fractal dimension (D =1.3 ±0.05 ) places the instability in a different universality class than other fingering instabilities. By characterizing changes in morphology and dynamics as a function of droplet volume and applied electric potential, we identify the three main forces involved in this process: interfacial tension, gravity, and oxidative stress. Importantly, we find that electrochemical oxidation can generate compressive interfacial forces that oppose the tensile forces at a liquid interface. The surface oxide layer ultimately provides a physical and electrochemical barrier that halts the instabilities at larger positive potentials. Controlling the competition between interfacial tension and oxidative (compressive) stresses at the interface is important for the development of reconfigurable electronic, electromagnetic, and optical devices that take advantage of the metallic properties of liquid metals.

Ginzburg-Landau theory for the solid-liquid interface of bcc elements. II - Application to the classical one-component plasma, the Wigner crystal, and He-4

NASA Technical Reports Server (NTRS)

Zeng, X. C.; Stroud, D.

1989-01-01

The previously developed Ginzburg-Landau theory for calculating the crystal-melt interfacial tension of bcc elements to treat the classical one-component plasma (OCP), the charged fermion system, and the Bose crystal. For the OCP, a direct application of the theory of Shih et al. (1987) yields for the surface tension 0.0012(Z-squared e-squared/a-cubed), where Ze is the ionic charge and a is the radius of the ionic sphere. Bose crystal-melt interface is treated by a quantum extension of the classical density-functional theory, using the Feynman formalism to estimate the relevant correlation functions. The theory is applied to the metastable He-4 solid-superfluid interface at T = 0, with a resulting surface tension of 0.085 erg/sq cm, in reasonable agreement with the value extrapolated from the measured surface tension of the bcc solid in the range 1.46-1.76 K. These results suggest that the density-functional approach is a satisfactory mean-field theory for estimating the equilibrium properties of liquid-solid interfaces, given knowledge of the uniform phases.

Vapour-liquid interfacial properties of square-well chains from density functional theory and Monte Carlo simulation.

PubMed

Martínez-Ruiz, Francisco José; Blas, Felipe J; Moreno-Ventas Bravo, A Ignacio; Míguez, José Manuel; MacDowell, Luis G

2017-05-17

The statistical associating fluid theory for attractive potentials of variable range (SAFT-VR) density functional theory (DFT) developed by [Gloor et al., J. Chem. Phys., 2004, 121, 12740-12759] is used to predict the interfacial behaviour of molecules modelled as fully-flexible square-well chains formed from tangentially-bonded monomers of diameter σ and potential range λ = 1.5σ. Four different model systems, comprising 4, 8, 12, and 16 monomers per molecule, are considered. In addition to that, we also compute a number of interfacial properties of molecular chains from direct simulation of the vapour-liquid interface. The simulations are performed in the canonical ensemble, and the vapour-liquid interfacial tension is evaluated using the wandering interface (WIM) method, a technique based on the thermodynamic definition of surface tension. Apart from surface tension, we also obtain density profiles, coexistence densities, vapour pressures, and critical temperature and density, paying particular attention to the effect of the chain length on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapour-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. The interfacial thickness and surface tension appear to exhibit an asymptotic limiting behaviour for long chains. A similar behaviour is also observed for the coexistence densities and critical properties. Agreement between theory and simulation results indicates that SAFT-VR DFT is only able to predict qualitatively the interfacial properties of the model. Our results are also compared with simulation data taken from the literature, including the vapour-liquid coexistence densities, vapour pressures, and surface tension.

The Measurement of the Surface Energy of Solids by Sessile Drop Accelerometry

NASA Astrophysics Data System (ADS)

Calvimontes, Alfredo

2018-05-01

A new physical method, the sessile drop accelerometry (SDACC) for the study and measurement of the interfacial energies of solid-liquid-gas systems, is tested and discussed in this study. The laboratory instrument and technique—a combination of a drop shape analyzer with high-speed camera and a laboratory drop tower- and the evaluation algorithms, were designed to calculate the interfacial energies as a function of the geometrical changes of a sessile droplet shape due to the effect of "switching off" gravity during the experiment. The method bases on Thermodynamics of Interfaces and differs from the conventional approach of the two hundred-years-old Young's equation in that it assumes a thermodynamic equilibrium between interfaces, rather than a balance of tensions on a point of the solid-liquid-gas contour line. A comparison of the mathematical model that supports the method with the widely accepted Young`s equation is discussed in detail in this study. The method opens new possibilities to develop surface characterization procedures by submitting the solid-liquid-system to artificial generated and uniform force fields.

Interfacial waves generated by contact line motion through electrowetting

NASA Astrophysics Data System (ADS)

Ha, Jonghyun; Park, Jaebum; Kim, Yunhee; Bae, Jungmok; Kim, Ho-Young

2013-11-01

The contact angle of a liquid-fluid interface can be effectively modulated by EWOD (electrowetting on dielectric). Rapid movement of the contact line, which can be achieved by swift change of voltages at the electrodes, can give rise to interfacial waves under the strong influence of surface tension. Many optofluidic devices employing EWOD actuation, such as lenses, three-dimensional displays and laser radar, use two different liquids in a single cell, implying that the motions of the two liquids should be considered simultaneously to solve the dynamics of interfacial waves. Furthermore, the capillary waves excited by moving contact lines, which inherently involve slipping flows at solid boundaries, pose an interesting problem that has not been treated so far. We perform a perturbation analysis for this novel wave system to find the dispersion relation that relates the wavenumber, and the decay length over which the wave is dissipated by viscous effects. We experimentally corroborate our theory.

Interfacial tension measurement of immiscible liq uids using a capillary tube

NASA Technical Reports Server (NTRS)

Rashidnia, N.; Balasubramaniam, R.; Delsignore, D.

1992-01-01

The interfacial tension of immiscible liquids is an important thermophysical property that is useful in the behavior of liquids both in microgravity (Martinez et al. (1987) and Karri and Mathur (1988)) and in enhanced oil recovery processes under normal gravity (Slattery (1974)). Many techniques are available for its measurement, such as the ring method, drop weight method, spinning drop method, and capillary height method (Adamson (1960) and Miller and Neogi (1985)). Karri and Mathur mention that many of the techniques use equations that contain a density difference term and are inappropriate for equal density liquids. They reported a new method that is suitable for both equal and unequal density liquids. In their method, a capillary tube forms one of the legs of a U-tube. The interfacial tension is related to the heights of the liquids in the cups of the U-tube above the interface in the capillary. Our interest in this area arose from a need to measure small interfacial tension (around 1 mN/m) for a vegetable oil/silicon oil system that was used in a thermocapillary drop migration experiment (Rashidnia and Balasubramaniam (1991)). In our attempts to duplicate the method proposed by Karri and Mathur, we found it quite difficult to anchor the interface inside the capillary tube; small differences of the liquid heights in the cups drove the interface out of the capillary. We present an alternative method using a capillary tube to measure the interfacial tensions of liquids of equal or unequal density. The method is based on the combined capillary rises of both liquids in the tube.

Visualizing the shape of soft solid and fluid contacts between two surfaces

NASA Astrophysics Data System (ADS)

Pham, Jonathan; Schellenberger, Frank; Kappl, Michael; Vollmer, Doris; Butt, Hans-Jürgen

The soft contact between two surfaces is fundamentally interesting for soft materials and fluid mechanics and relevant for friction and wear. The deformation of soft solid interfaces has received much interest because it interestingly reveals similarities to fluid wetting. We present an experimental route towards visualizing the three-dimensional contact geometry of either liquid-solid (i.e., oil and glass) or solid-solid (i.e., elastomer and glass) interfaces using a home-built combination of confocal microscopy and atomic force microscopy. We monitor the shape of a fluid capillary bridge and the depth of indentation in 3D while simultaneously measuring the force. In agreement with theoretical predictions, the height of the capillary bridge depends on the interfacial tensions. By using a slowly evaporating solvent, we quantify the temporal evolution of the capillary bridge and visualized the influence of pinning points on its shape. The position dependence of the advancing and receding contact angle along the three-phase contact line, particle-liquid-air, is resolved. Extending our system, we explore the contact deformation of soft solids where elasticity, in addition to surface tension, becomes an important factor.

Measurement of interfacial tension of immiscible liquid pairs in microgravity

NASA Technical Reports Server (NTRS)

Weinberg, Michael C.; Neilson, George F.; Baertlein, Carl; Subramanian, R. Shankar; Trinh, Eugene H.

1994-01-01

A discussion is given of a containerless microgravity experiment aimed at measuring the interfacial tension of immiscible liquid pairs using a compound drop rotation method. The reasons for the failure to execute such experiments in microgravity are described. Also, the results of post-flight analyses used to confirm our arguments are presented.

Electrowetting-Based Variable-Focus Lens for Miniature Systems

NASA Astrophysics Data System (ADS)

Hendriks, B. H. W.; Kuiper, S.; van As, M. A. J.; et al.

The meniscus between two immiscible liquids of different refractive indices can be used as a lens. A change in curvature of this meniscus by electrostatic control of the solid/liquid interfacial tension leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centred variable-focus lens. The optical properties of this lens were investigated experimentally. We designed and constructed a miniature camera module based on this variable lens suitable for mobile applications. Furthermore, the liquid lens was applied in a Blu-ray Disc optical recording system to enable dual layer disc reading/writing.

The Upper Limit of Energy Density of Nanoporous Materials Functionalized Liquid

NASA Astrophysics Data System (ADS)

Han, Aijie; Punyamurtula, Venkata K.; Kim, Taewan; Qiao, Yu

2008-06-01

In this article, we report the experimental result of energy dissipation of a mobil crystalline material (MCM) 41 in mercury. The MCM41 contains a large volume fraction of nanometer-sized pores. As the applied pressure is relatively high, the nanopore surfaces are exposed to mercury. Due to the large nanopore surface area and the large solid-liquid interfacial tension, the energy dissipation effectiveness of this system is ultrahigh, representing the upper limit that can be achieved by the pressure-induced infiltration technique.

Determination of induction period and crystal growth mechanism of dexamethasone sodium phosphate in methanol-acetone system

NASA Astrophysics Data System (ADS)

Hao, Hongxun; Wang, Jingkang; Wang, Yongli

2005-02-01

The induction period of dexamethasone sodium phosphate at different supersaturation was experimentally determined in a methanol-acetone system. The laser monitoring observation technique was used to determine the appearance of the first nucleus in solution. The effect of solution composition on induction period was discussed. Based on classical homogeneous nucleation theory, the solid-liquid interfacial tension and surface entropy factor were calculated from the induction period data. The experimentally determined values of interfacial tension are in agreement with the theoretical values predicted by the Mersmann equation. It was found that the nucleus of dexamethasone sodium phosphate grows continuously in pure methanol and turns from continuous growth to birth and spread growth with increasing acetone content in a methanol-acetone mixture.

Multiphase flow of miscible liquids: jets and drops

NASA Astrophysics Data System (ADS)

Walker, Travis W.; Logia, Alison N.; Fuller, Gerald G.

2015-05-01

Drops and jets of liquids that are miscible with the surrounding bulk liquid are present in many processes from cleaning surfaces with the aid of liquid soaps to the creation of biocompatible implants for drug delivery. Although the interactions of immiscible drops and jets show similarities to miscible systems, the small, transient interfacial tension associated with miscible systems create distinct outcomes such as intricate droplet shapes and breakup resistant jets. Experiments have been conducted to understand several basic multiphase flow problems involving miscible liquids. Using high-speed imaging of the morphological evolution of the flows, we have been able to show that these processes are controlled by interfacial tensions. Further multiphase flows include investigating miscible jets, which allow the creation of fibers from inelastic materials that are otherwise difficult to process due to capillary breakup. This work shows that stabilization from the diminishing interfacial tensions of the miscible jets allows various elongated morphologies to be formed.

Microfluidic ultralow interfacial tensiometry with magnetic particles.

PubMed

Tsai, Scott S H; Wexler, Jason S; Wan, Jiandi; Stone, Howard A

2013-01-07

We describe a technique that measures ultralow interfacial tensions using paramagnetic spheres in a co-flow microfluidic device designed with a magnetic section. Our method involves tuning the distance between the co-flowing interface and the magnet's center, and observing the behavior of the spheres as they approach the liquid-liquid interface-the particles either pass through or are trapped by the interface. Using threshold values of the magnet-to-interface distance, we make estimates of the two-fluid interfacial tension. We demonstrate the effectiveness of this technique for measuring very low interfacial tensions, O(10(-6)-10(-5)) N m(-1), by testing solutions of different surfactant concentrations, and we show that our results are comparable with measurements made using a spinning drop tensiometer.

Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, Gabriel V.; Müller, Erich A.; Jackson, George

2015-03-21

The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derivedmore » for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large system sizes for both the cylindrical and spherical cases. Estimates of the entropic and energetic contributions are also evaluated for the planar and cylindrical geometries and their magnitudes are in line with the expectations of our simple analysis.« less

Surfactant effects on contact line alteration of a liquid drop in a capillary tube

NASA Astrophysics Data System (ADS)

Yulianti, K.; Marwati, R.

2018-05-01

In this paper, the effect of an insoluble surfactant on the moving contact line of an interface between two fluids filling a capillary tube is studied. The governing equations are the incompressible Navier-Stokes equations with the couple of Eulerian fluid variables and Lagrangian interfacial markers. In our model, capillary force plays a role in the fluids motion. Here, we propose that besides lowering the interfacial tension which affects the capillary force, the surfactant also decreases the surface tension between fluids and a solid surface. That condition is applied to the unbalanced Young condition at the contact line. The front-tracking method is used to solve numerically the free boundary motion of the interface. Results show that the surfactant has a significant effect on the motion of the contact line.

Interfacial profiles in fluid/liquid systems: a description based on the storing of elastic energy.

PubMed

Castellanos-Suárez, Aly J; Toro-Mendoza, Jhoan; García-Sucre, Máximo

2011-06-01

An analytical expression for the interfacial energy is found by solving a Poisson equation and assuming a Boltzmann distribution of volume elements forming the fluid/liquid system. Interfacial phenomena are treated as a result of the response of a liquid when it makes contact with other fluid phase, in order to reach thermal and mechanical equilibrium. This model gives a quantitative description of the interface, obtaining values for its molar, force and energy density profiles. Also, our model allows the determination of the proportion of the fluids present in the interfacial zone, the values of interfacial tension and thickness. In the case of water+n-alkanes systems, the tensions are in agreement with the behavior shown by the experimental data. Finally, the values for interfacial thickness predicted from molar density profiles are lower than the range of influence of the elastic energy and elastic field. Copyright © 2011 Elsevier Inc. All rights reserved.

Tribology Experiment in Zero Gravity

NASA Technical Reports Server (NTRS)

Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.; Finckenor, M. M.

2015-01-01

A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates observation of such motions as controlled by interfacial and capillary forces. Two experimental configurations were used. One deals with the liquid on one solid surface, and the other with the liquid between a pair of closed spaced surfaces. Time sequence photographs of fluid motion on a solid surface yielded spreading rate data of several fluid-surface combinations. In general, a slow spreading process as governed by the tertiary junction can be distinguished from a more rapid process which is driven by surface tension controlled internal fluid pressure. Photographs were also taken through the transparent bushings of several experimental journal bearings. Morphology of incomplete fluid films and its fluctuation with time suggest the presence or absence of unsteady phenomena of the bearing-rotor system in various arrangements.

The competition between the liquid-liquid dewetting and the liquid-solid dewetting.

PubMed

Xu, Lin; Shi, Tongfei; An, Lijia

2009-05-14

We investigate the dewetting behavior of the bilayer of air/PS/PMMA/silanized Si wafer and find the two competing dewetting pathways in the dewetting process. The upper layer dewets on the lower layer (dewetting pathway 1, the liquid-liquid dewetting) and the two layers rupture on the solid substrate (dewetting pathway 2, the liquid-solid dewetting). To the two competing dewetting pathways, the process of forming holes and the process of hole growth, influence their competing relation. In the process of forming holes, the time of forming holes is a main factor that influences their competing relation. During the process of hole growth, the dewetting velocity is a main factor that influences their competing relation. The liquid-liquid interfacial tension, the film thickness of the polymer, and the viscosity of the polymer are important factors that influence the time of forming holes and the dewetting velocity. When the liquid-liquid dewetting pathway and the liquid-solid dewetting pathway compete in the dewetting process, the competing relation can be controlled by changing the molecular weight of the polymer, the film thickness, and the annealing temperature. In addition, it is also found that the rim growth on the solid substrate is by a rolling mechanism in the process of hole growth.

A numeric investigation of co-flowing liquid streams using the Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Somogyi, Andy; Tagg, Randall

2007-11-01

We present a numerical investigation of co-flowing immiscible liquid streams using the Lattice Boltzmann Method (LBM) for multi component, dissimilar viscosity, immiscible fluid flow. When a liquid is injected into another immiscible liquid, the flow will eventually transition from jetting to dripping due to interfacial tension. Our implementation of LBM models the interfacial tension through a variety of techniques. Parallelization is also straightforward for both single and multi component models as only near local interaction is required. We compare the results of our numerical investigation using LBM to several recent physical experiments.

Non-equilibrium surface tension of the vapour-liquid interface of active Lennard-Jones particles

NASA Astrophysics Data System (ADS)

Paliwal, Siddharth; Prymidis, Vasileios; Filion, Laura; Dijkstra, Marjolein

2017-08-01

We study a three-dimensional system of self-propelled Brownian particles interacting via the Lennard-Jones potential. Using Brownian dynamics simulations in an elongated simulation box, we investigate the steady states of vapour-liquid phase coexistence of active Lennard-Jones particles with planar interfaces. We measure the normal and tangential components of the pressure tensor along the direction perpendicular to the interface and verify mechanical equilibrium of the two coexisting phases. In addition, we determine the non-equilibrium interfacial tension by integrating the difference of the normal and tangential components of the pressure tensor and show that the surface tension as a function of strength of particle attractions is well fitted by simple power laws. Finally, we measure the interfacial stiffness using capillary wave theory and the equipartition theorem and find a simple linear relation between surface tension and interfacial stiffness with a proportionality constant characterized by an effective temperature.

Quantitative analysis of liquid penetration kinetics and slaking of aggregates as related to solid-liquid interfacial properties

NASA Astrophysics Data System (ADS)

Goebel, Marc-O.; Woche, Susanne K.; Bachmann, Jörg

2012-06-01

SummaryAggregate stability is frequently shown to be enhanced by strong soil water repellency, however, there is limited systematic evidence on this effect for moderately (subcritically) water repellent soils. This study aimed to investigate the specific effects of interfacial properties on the liquid penetration kinetics in relation to the stability of subcritically water repellent aggregates (4-6.3 mm) from various arable and forest soils against breakdown by slaking. In contrast to many other studies, where aggregate stability was determined by wet sieving, we here assessed the stability by immersion of air-dry aggregates in water-ethanol solutions with surface tensions ranging from 30 to 70 mN m-1. This approach allowed a highly sensitive discrimination of different stability levels and the determination of breakdown kinetics also for less stable aggregates. Interfacial properties were characterized in terms of contact angle measured on crushed aggregates, θc, and calculated for intact aggregates, θi, based on infiltration measurements with water and ethanol. Aggregate stability turned out to be higher in forest soils compared to arable soils with topsoil aggregates generally found to be more stable than subsoil aggregates. For water repellent aggregates, characterized by contact angles >40° and low water infiltration rates (<0.2 mm3 s-0.5), the fraction of disrupted aggregates after 30 s of immersion was generally below 10%, whereas in case of the more wettable aggregates, characterized by contact angles <10° and higher infiltration rates (>0.25 mm3 s-0.5) more than 80% of the aggregates were disrupted. In accordance, we found a close relationship between aggregate stability and wettability with differences between θc and θi being generally small. In addition, aggregate stability turned out to be related to organic carbon content. However, correlation analysis revealed that both persistence of aggregate stability and kinetics of aggregate breakdown were more strongly affected by the contact angle, θc (r = 0.90 and r = -0.83, respectively) and θi (r = 0.89 and r = -0.76, respectively) than the organic carbon content (r = 0.62 and -0.52, respectively), suggesting that stability was primarily controlled by aggregate interfacial properties. Calculation of liquid penetrativity as a function of surface tension and contact angle clearly demonstrated the importance of both solid and liquid interfacial properties in determining the stability of subcritically water repellent aggregates against slaking.

Effects of crystal-melt interfacial energy anisotropy on dendritic morphology and growth kinetics

NASA Technical Reports Server (NTRS)

Glicksman, M. E.; Singh, N. B.

1989-01-01

Morphological and kinetic studies of succinonitrile, a BCC crystal with a low (0.5 percent) anisotropy and pivalic acid, and FCC crystal with relatively large (5 percent) anisotropy in solid-liquid interfacial energy, show clearly that anisotropy in the solid-liquid interfacial energy does not affect the tip radius-velocity relationship, but has a profound influence on the tip region and the rate of amplification of branching waves. Anisotropy of the solid-liquid interfacial energy may be one of the key factors by which the microstructural characteristics of cast structures reflect individual material behavior, especially crystal symmetry.

The investigation of contact line effect on nanosized droplet wetting behavior with solid temperature condition

NASA Astrophysics Data System (ADS)

Haegon, Lee; Joonsang, Lee

2017-11-01

In many multi-phase fluidic systems, there are essentially contact interfaces including liquid-vapor, liquid-solid, and solid-vapor phase. There is also a contact line where these three interfaces meet. The existence of these interfaces and contact lines has a considerable impact on the nanoscale droplet wetting behavior. However, recent studies have shown that Young's equation does not accurately represent this behavior at the nanoscale. It also emphasized the importance of the contact line effect.Therefore, We performed molecular dynamics simulation to imitate the behavior of nanoscale droplets with solid temperature condition. And we find the effect of solid temperature on the contact line motion. Furthermore, We figure out the effect of contact line force on the wetting behavior of droplet according to the different solid temperature condition. With solid temperature condition variation, the magnitude of contact line friction decreases significantly. We also divide contact line force by effect of bulk liquid, interfacial tension, and solid surface. This work was also supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2015R1A5A1037668) and BrainKorea21plus.

Intermolecular network analysis of the liquid and vapor interfaces of pentane and water: microsolvation does not trend with interfacial properties.

PubMed

Ghadar, Yasaman; Clark, Aurora E

2014-06-28

Liquid:vapor and liquid:liquid interfaces exhibit complex organizational structure and dynamics at the molecular level. In the case of water and organic solvents, the hydrophobicity of the organic, its conformational flexibility, and compressibility, all influence interfacial properties. This work compares the interfacial tension, width, molecular conformations and orientations at the vapor and aqueous liquid interfaces of two solvents, n-pentane and neopentane, whose varying molecular shapes can lead to significantly different interfacial behavior. Particular emphasis has been dedicated toward understanding how the hydrogen bond network of water responds to the pentane relative to the vapor interface and the sensitivity of the network to the individual pentane isomer and system temperature. Interfacial microsolvation of the immiscible solvents has been examined using graph theoretical methods that quantify the structure and dynamics of microsolvated species (both H2O in C5H12 and C5H12 in H2O). At room temperature, interfacial water at the pentane phase boundary is found to have markedly different organization and dynamics than at the vapor interface (as indicated by the hydrogen bond distributions and hydrogen bond persistence in solution). While the mesoscale interfacial properties (e.g. interfacial tension) are sensitive to the specific pentane isomer, the distribution and persistence of microsolvated species at the interface is nearly identical for both systems, irrespective of temperature (between 273 K and 298 K). This has important implications for understanding how properties defined by the interfacial organization are related to the underlying solvation reactions that drive formation of the phase boundary.

Understanding the liquid-liquid (water-hexane) interface

NASA Astrophysics Data System (ADS)

Murad, Sohail; Puri, Ishwar K.

2017-10-01

Nonequilibrium molecular dynamics simulations are employed to investigate the interfacial thermal resistance of nanoscale hexane-water interfaces subject to an applied heat flux. Our studies show that these liquid-liquid interfaces exhibit behavior significantly dissimilar to that of solid-liquid and solid-vapor interfaces. Notably, the thermal resistance of a hexane-water interface is contingent on the interfacial temperature gradient alone with negligible dependence on the mean interfacial temperature, while the solid-liquid dependent strongly on the interfacial temperature. Application of a heat flux also increases the interface thickness significantly as compared to an equilibrium isothermal interface. Since liquid-liquid interfaces have been proposed for diverse applications, e.g., sensors for wastewater treatment and for extraction of toxic ions from water, they can be designed to be wider by applying a heat flux. This may allow the interface to be used for other applications not possible currently because of the very limited thickness of the interface in isothermal systems.

Thermal Transport at Solid-Liquid Interfaces: High Pressure Facilitates Heat Flow through Nonlocal Liquid Structuring.

PubMed

Han, Haoxue; Mérabia, Samy; Müller-Plathe, Florian

2017-05-04

The integration of three-dimensional microelectronics is hampered by overheating issues inherent to state-of-the-art integrated circuits. Fundamental understanding of heat transfer across soft-solid interfaces is important for developing efficient heat dissipation capabilities. At the microscopic scale, the formation of a dense liquid layer at the solid-liquid interface decreases the interfacial heat resistance. We show through molecular dynamics simulations of n-perfluorohexane on a generic wettable surface that enhancement of the liquid structure beyond a single adsorbed layer drastically enhances interfacial heat conductance. Pressure is used to control the extent of the liquid layer structure. The interfacial thermal conductance increases with pressure values up to 16.2 MPa at room temperature. Furthermore, it is shown that liquid structuring enhances the heat-transfer rate of high-energy lattice waves by broadening the transmission peaks in the heat flux spectrum. Our results show that pressure is an important external parameter that may be used to control interfacial heat conductance at solid-soft interfaces.

Polymer-grafted Lignin: Molecular Design and Interfacial Activities

NASA Astrophysics Data System (ADS)

Gupta, Chetali

The broader technical objective of this work is to develop a strategy for using the biopolymer lignin in a wide variety of surfactant applications through polymer grafting. These applications include emulsion stabilizers, dispersants and foaming agents. The scientific objective of the research performed within this thesis is to understand the effect of molecular architecture and polymer grafting on the interfacial activity at the air-liquid, liquid-liquid and solid-liquid interface. Research has focused on designing of these lignopolymers with controlled architecture using polyethylene glycol, poly(acrylic acid) and polyacrylamide grafts. The interfacial activity for all polymer grafts has been tested at all three interfaces using a broad range of techniques specific to the interface. Results have shown that the hydrophobicity of the lignin core is responsible for enhanced interfacial activity at the air-liquid and liquid-liquid interface. Conversely, improved hydrophilicity and "electrosteric" interactions are required for higher interfacial activity of the lignin at the liquid-solid interface. The high interfacial activity of the polymer-grafted lignin observed in the air-liquid and liquid-liquid interfaces not only resulted in viscosity reduction but also strength enhancement at the liquid-solid interface. The broader implication of this study is to be able to predict what chemical functionalities need to be adjusted to get the desired viscosity reduction.

Solid/liquid interfacial free energies in binary systems

NASA Technical Reports Server (NTRS)

Nason, D.; Tiller, W. A.

1973-01-01

Description of a semiquantitative technique for predicting the segregation characteristics of smooth interfaces between binary solid and liquid solutions in terms of readily available thermodynamic parameters of the bulk solutions. A lattice-liquid interfacial model and a pair-bonded regular solution model are employed in the treatment with an accommodation for liquid interfacial entropy. The method is used to calculate the interfacial segregation and the free energy of segregation for solid-liquid interfaces between binary solutions for the (111) boundary of fcc crystals. The zone of compositional transition across the interface is shown to be on the order of a few atomic layers in width, being moderately narrower for ideal solutions. The free energy of the segregated interface depends primarily upon the solid composition and the heats of fusion of the component atoms, the composition difference of the solutions, and the difference of the heats of mixing of the solutions.

Molecular dynamics analysis of the influence of Coulomb and van der Waals interactions on the work of adhesion at the solid-liquid interface

NASA Astrophysics Data System (ADS)

Surblys, Donatas; Leroy, Frédéric; Yamaguchi, Yasutaka; Müller-Plathe, Florian

2018-04-01

We investigated the solid-liquid work of adhesion of water on a model silica surface by molecular dynamics simulations, where a methodology previously developed to determine the work of adhesion through thermodynamic integration was extended to a system with long-range electrostatic interactions between solid and liquid. In agreement with previous studies, the work of adhesion increased when the magnitude of the surface polarity was increased. On the other hand, we found that when comparing two systems with and without solid-liquid electrostatic interactions, which were set to have approximately the same total solid-liquid interfacial energy, former had a significantly smaller work of adhesion and a broader distribution in the interfacial energies, which has not been previously reported in detail. This was explained by the entropy contribution to the adhesion free energy; i.e., the former with a broader energy distribution had a larger interfacial entropy than the latter. While the entropy contribution to the work of adhesion has already been known, as a work of adhesion itself is free energy, these results indicate that, contrary to common belief, wetting behavior such as the contact angle is not only governed by the interfacial energy but also significantly affected by the interfacial entropy. Finally, a new interpretation of interfacial entropy in the context of solid-liquid energy variance was offered, from which a fast way to qualitatively estimate the work of adhesion was also presented.

In situ measurement of contact angles and surface tensions of interfacial nanobubbles in ethanol aqueous solutions.

PubMed

Zhao, Binyu; Wang, Xingya; Wang, Shuo; Tai, Renzhong; Zhang, Lijuan; Hu, Jun

2016-04-14

The astonishing long lifetime and large contact angles of interfacial nanobubbles are still in hot debate despite numerous experimental and theoretical studies. One hypothesis to reconcile the two abnormalities of interfacial nanobubbles is that they have low surface tensions. However, few studies have been reported to measure the surface tensions of nanobubbles due to the lack of effective measurements. Herein, we investigate the in situ contact angles and surface tensions of individual interfacial nanobubbles immersed in different ethanol aqueous solutions using quantitative nanomechanical atomic force microscopy (AFM). The results showed that the contact angles of nanobubbles in the studied ethanol solutions were also much larger than the corresponding macroscopic counterparts on the same substrate, and they decreased with increasing ethanol concentrations. More significantly, the surface tensions calculated were much lower than those of the gas-liquid interfaces of the solutions at the macroscopic scale but have similar tendencies with increasing ethanol concentrations. Those results are expected to be helpful in further understanding the stability of interfacial nanobubbles in complex solutions.

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces.

PubMed

Manga, Mohamed S; Hunter, Timothy N; Cayre, Olivier J; York, David W; Reichert, Matthew D; Anna, Shelly L; Walker, Lynn M; Williams, Richard A; Biggs, Simon R

2016-05-03

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher than previously reported for nanoparticle and surfactant systems, and similar in magnitude to protein stabilized droplets.

Dynamics of premelted liquid films

NASA Astrophysics Data System (ADS)

Worster, Grae

2005-11-01

On small scales, surface tension forces are enormously powerful. When such forces act on every grain of a fine soil, they can move mountains, quite literally, in a process called frost heave. In fact, it is not surface tension per se but the intermolecular forces that underlie surface tension that also cause frost heave in partially solidified soils. In detail, these forces cause the premelting of solids. For example, at temperatures below 0^oC, water is solid (ice) in bulk but remains liquid in thin films adjacent to surfaces in contact with many other materials, such as silica. The intermolecular forces, such as the van der Waals force, acting between the materials on either side of an interface can cause interfacial premelting and simultaneously produce a strong normal stress across the premelted film. Whether these stresses cause large-scale motions relies significantly on the fluid mechanics of the microscopic films. I shall introduce the fundamental thermodynamic principles of premelting and illustrate its fluid mechanical consequences with simple theoretical models and experimental results. Applications of these ideas include the rejection of particulate matter during solidification, with consequences for the fabrication of composite materials, the freezing of colloidal suspensions, with consequences for the cryopreservation of biological systems, and the evolution of grain boundaries, with consequences for the redistribution of climate proxies sequestered in the Earth's ice sheets.

Suppression of thermally excited capillary waves by shear flow.

PubMed

Derks, Didi; Aarts, Dirk G A L; Bonn, Daniel; Lekkerkerker, Henk N W; Imhof, Arnout

2006-07-21

We investigate the thermal fluctuations of the colloidal gas-liquid interface subjected to a shear flow parallel to the interface. Strikingly, we find that the shear strongly suppresses capillary waves, making the interface smoother. This phenomenon can be described by introducing an effective interfacial tension that increases with the shear rate. The increase of sigma(eff) is a direct consequence of the loss of interfacial entropy caused by the flow, which affects especially the slow fluctuations. This demonstrates that the interfacial tension of fluids results from an intrinsic as well as a fluctuation contribution.

Giant and switchable surface activity of liquid metal via surface oxidation

PubMed Central

Khan, Mohammad Rashed; Eaker, Collin B.; Bowden, Edmond F.; Dickey, Michael D.

2014-01-01

We present a method to control the interfacial tension of a liquid alloy of gallium via electrochemical deposition (or removal) of the oxide layer on its surface. In sharp contrast with conventional surfactants, this method provides unprecedented lowering of surface tension (∼500 mJ/m2 to near zero) using very low voltage, and the change is completely reversible. This dramatic change in the interfacial tension enables a variety of electrohydrodynamic phenomena. The ability to manipulate the interfacial properties of the metal promises rich opportunities in shape-reconfigurable metallic components in electronic, electromagnetic, and microfluidic devices without the use of toxic mercury. This work suggests that the wetting properties of surface oxides—which are ubiquitous on most metals and semiconductors—are intrinsic “surfactants.” The inherent asymmetric nature of the surface coupled with the ability to actively manipulate its energetics is expected to have important applications in electrohydrodynamics, composites, and melt processing of oxide-forming materials. PMID:25228767

A quantitative study of factors influencing lamellar eutectic morphology during solidification

NASA Technical Reports Server (NTRS)

Kaukler, W. F. S.

1981-01-01

The factors that influence the shape of the solid-liquid interface of a lamellar binary eutectic alloy are evaluated. Alloys of carbon tetrabromide and hexachloroethane which serve as a transparent analogue of lamellar metallic eutectics are used. The observed interface shapes are analyzed by computer-aided methods. The solid-liquid interfacial free energies of each of the individual phases comprising the eutectic system are measured as a function of composition using a 'grain boundary groove' technique. The solid-liquid interfacial free energy of the two phases are evaluated directly from the eutectic interface. The phase diagram for the system, the heat of fusion as a function of composition, and the density as a function of composition are measured. The shape of the eutectic interface is controlled mainly by the solid-liquid and solid-solid interfacial free energy relationships at the interface and by the temperature gradient present, rather than by interlamellar diffusion in the liquid at the interface, over the range of growth rates studied.

Microfluidics with fluid walls.

PubMed

Walsh, Edmond J; Feuerborn, Alexander; Wheeler, James H R; Tan, Ann Na; Durham, William M; Foster, Kevin R; Cook, Peter R

2017-10-10

Microfluidics has great potential, but the complexity of fabricating and operating devices has limited its use. Here we describe a method - Freestyle Fluidics - that overcomes many key limitations. In this method, liquids are confined by fluid (not solid) walls. Aqueous circuits with any 2D shape are printed in seconds on plastic or glass Petri dishes; then, interfacial forces pin liquids to substrates, and overlaying an immiscible liquid prevents evaporation. Confining fluid walls are pliant and resilient; they self-heal when liquids are pipetted through them. We drive flow through a wide range of circuits passively by manipulating surface tension and hydrostatic pressure, and actively using external pumps. Finally, we validate the technology with two challenging applications - triggering an inflammatory response in human cells and chemotaxis in bacterial biofilms. This approach provides a powerful and versatile alternative to traditional microfluidics.The complexity of fabricating and operating microfluidic devices limits their use. Walsh et al. describe a method in which circuits are printed as quickly and simply as writing with a pen, and liquids in them are confined by fluid instead of solid walls.

Density, refractive index, interfacial tension, and viscosity of ionic liquids [EMIM][EtSO4], [EMIM][NTf2], [EMIM][N(CN)2], and [OMA][NTf2] in dependence on temperature at atmospheric pressure.

PubMed

Fröba, Andreas P; Kremer, Heiko; Leipertz, Alfred

2008-10-02

The density, refractive index, interfacial tension, and viscosity of ionic liquids (ILs) [EMIM][EtSO 4] (1-ethyl-3-methylimidazolium ethylsulfate), [EMIM][NTf 2] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), [EMIM][N(CN) 2] (1-ethyl-3-methylimidazolium dicyanimide), and [OMA][NTf 2] (trioctylmethylammonium bis(trifluoromethylsulfonyl)imide) were studied in dependence on temperature at atmospheric pressure both by conventional techniques and by surface light scattering (SLS). A vibrating tube densimeter was used for the measurement of density at temperatures from (273.15 to 363.15) K and the results have an expanded uncertainty ( k = 2) of +/-0.02%. Using an Abbe refractometer, the refractive index was measured for temperatures between (283.15 and 313.15) K with an expanded uncertainty ( k = 2) of about +/-0.0005. The interfacial tension was obtained from the pendant drop technique at a temperature of 293.15 K with an expanded uncertainty ( k = 2) of +/-1%. For higher and lower temperatures, the interfacial tension was estimated by an adequate prediction scheme based on the datum at 293.15 K and the temperature dependence of density. For the ILs studied within this work, at a first order approximation, the quantity directly accessible by the SLS technique was the ratio of surface tension to dynamic viscosity. By combining the experimental results of the SLS technique with density and interfacial tension from conventional techniques, the dynamic viscosity could be obtained for temperatures between (273.15 and 333.15) K with an estimated expanded uncertainty ( k = 2) of less than +/-3%. The measured density, refractive index, and viscosity are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with but always smaller than the expanded uncertainties ( k = 2). Besides a comparison with the literature, the influence of structural variations on the thermophysical properties of the ILs is discussed in detail. The viscosities mostly agree with values reported in the literature within the combined estimated expanded uncertainties ( k = 2) of the measurements while our density and interfacial tension data differ by more than +/-1% and +/-5%.

Aerosol Particle Interfacial Thermodynamics and Phase Partitioning Measurements Using Biphasic Microfluidics

NASA Astrophysics Data System (ADS)

Dutcher, Cari; Metcalf, Andrew

2015-03-01

Secondary organic aerosol particles are nearly ubiquitous in the atmosphere and yet there remain large uncertainties in their formation processes and ambient properties. These particles are complex microenvironments, which can contain multiple interfaces due to internal aqueous-organic phase partitioning and to the external liquid-vapor surface. Interfacial properties affect the ambient aerosol morphology, or internal structure of the particle, which in turn can affect the way a particle interacts with an environment of condensable clusters and organic vapors. To improve our ability to accurately predict ambient aerosol morphology, we must improve our knowledge of aerosol interfaces and their interactions with the ambient environment. Unfortunately, many techniques employed to measure interfacial properties do so in bulk solutions or in the presence of a ternary (e.g. solid) phase. In this talk, a novel method using biphasic microscale flows will be introduced for generating, trapping, and perturbing complex interfaces at atmospherically relevant conditions. These microfluidic experiments utilize high-speed imaging to monitor interfacial phenomena at the microscale and are performed with phase contrast and fluorescence microscopy on a temperature-controlled inverted microscope stage. From these experiments, interfacial thermodynamic properties such as surface or interfacial tension, rheological properties such as interfacial moduli, and kinetic properties such as mass transfer coefficients can be measured or inferred.

Interfacial waves generated by electrowetting-driven contact line motion

NASA Astrophysics Data System (ADS)

Ha, Jonghyun; Park, Jaebum; Kim, Yunhee; Shin, Bongsu; Bae, Jungmok; Kim, Ho-Young

2016-10-01

The contact angle of a liquid-fluid interface can be effectively modulated by the electrowetting-on-dielectric (EWOD) technology. Rapid movement of the contact line can be achieved by swift changes of voltage at the electrodes, which can give rise to interfacial waves under the strong influence of surface tension. Here we experimentally demonstrate EWOD-driven interfacial waves of overlapping liquids and compare their wavelength and decay length with the theoretical results obtained by a perturbation analysis. Our theory also allows us to predict the temporal evolution of the interfacial profiles in either rectangular or cylindrical containers, as driven by slipping contact lines. This work builds a theoretical framework to understand and predict the dynamics of capillary waves of a liquid-liquid interface driven by EWOD, which has practical implications on optofluidic devices used to guide light.

Domain Nucleation Rates and Interfacial Line Tensions in Supported Bilayers of Ternary Mixtures Containing Galactosylceramide

PubMed Central

Blanchette, Craig D.; Lin, Wan-Chen; Orme, Christine A.; Ratto, Timothy V.; Longo, Marjorie L.

2008-01-01

Domains within the plane of the plasma membrane, referred to as membrane rafts, have been a topic of considerable interest in the field of membrane biophysics. Although model membrane systems have been used extensively to study lipid phase behavior as it relates to the existence of rafts, very little work has focused on either the initial stage of lipid domain nucleation, or the relevant physical parameters such as temperature and interfacial line tension which control nucleation. In this work, we utilize a method in which the kinetic process of lipid domain nucleation is imaged by atomic force microscopy and modeled using classical theory of nucleation to map interfacial line tension in ternary lipid mixtures. These mixtures consist of a fluid phase lipid component (1,2-dilauroyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, or 1,2-dioleoyl-sn-glycero-3-phosphocholine), a solid phase component (galactosylceramide), and cholesterol. Interfacial line tension measurements of galactosylceramide-rich domains track with our previously measured area/perimeter ratios and height mismatches measured here. Line tension also follows known trends in cholesterol interactions and partitioning, as we observed previously with area/perimeter ratios. Our line tension measurements are discussed in combination with recent line tension measurements to address line tension regulation by cholesterol and the dynamic nature of membrane rafts. PMID:18065459

Keyhole and weld shapes for plasma arc welding under normal and zero gravity

NASA Technical Reports Server (NTRS)

Keanini, R. G.; Rubinsky, B.

1990-01-01

A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

Measurement and modeling on hydrodynamic forces and deformation of an air bubble approaching a solid sphere in liquids.

PubMed

Shahalami, Mansoureh; Wang, Louxiang; Wu, Chu; Masliyah, Jacob H; Xu, Zhenghe; Chan, Derek Y C

2015-03-01

The interaction between bubbles and solid surfaces is central to a broad range of industrial and biological processes. Various experimental techniques have been developed to measure the interactions of bubbles approaching solids in a liquid. A main challenge is to accurately and reliably control the relative motion over a wide range of hydrodynamic conditions and at the same time to determine the interaction forces, bubble-solid separation and bubble deformation. Existing experimental methods are able to focus only on one of the aspects of this problem, mostly for bubbles and particles with characteristic dimensions either below 100 μm or above 1 cm. As a result, either the interfacial deformations are measured directly with the forces being inferred from a model, or the forces are measured directly with the deformations to be deduced from the theory. The recently developed integrated thin film drainage apparatus (ITFDA) filled the gap of intermediate bubble/particle size ranges that are commonly encountered in mineral and oil recovery applications. Equipped with side-view digital cameras along with a bimorph cantilever as force sensor and speaker diaphragm as the driver for bubble to approach a solid sphere, the ITFDA has the capacity to measure simultaneously and independently the forces and interfacial deformations as a bubble approaches a solid sphere in a liquid. Coupled with the thin liquid film drainage modeling, the ITFDA measurement allows the critical role of surface tension, fluid viscosity and bubble approach speed in determining bubble deformation (profile) and hydrodynamic forces to be elucidated. Here we compare the available methods of studying bubble-solid interactions and demonstrate unique features and advantages of the ITFDA for measuring both forces and bubble deformations in systems of Reynolds numbers as high as 10. The consistency and accuracy of such measurement are tested against the well established Stokes-Reynolds-Young-Laplace model. The potential to use the design principles of the ITFDA for fundamental and developmental research is demonstrated. Copyright © 2014. Published by Elsevier B.V.

The two-phase flow IPTT method for measurement of nonwetting-wetting liquid interfacial areas at higher nonwetting saturations in natural porous media

PubMed Central

Zhong, Hua; Ouni, Asma El; Lin, Dan; Wang, Bingguo; Brusseau, Mark L

2017-01-01

Interfacial areas between nonwetting-wetting (NW-W) liquids in natural porous media were measured using a modified version of the interfacial partitioning tracer test (IPTT) method that employed simultaneous two-phase flow conditions, which allowed measurement at NW saturations higher than trapped residual saturation. Measurements were conducted over a range of saturations for a well-sorted quartz sand under three wetting scenarios of primary drainage (PD), secondary imbibition (SI), and secondary drainage (SD). Limited sets of experiments were also conducted for a model glass-bead medium and for a soil. The measured interfacial areas were compared to interfacial areas measured using the standard IPTT method for liquid-liquid systems, which employs residual NW saturations. In addition, the theoretical maximum interfacial areas estimated from the measured data are compared to specific solid surface areas measured with the N2/BET method and estimated based on geometrical calculations for smooth spheres. Interfacial areas increase linearly with decreasing water saturation over the range of saturations employed. The maximum interfacial areas determined for the glass beads, which have no surface roughness, are 32±4 and 36±5 cm−1 for PD and SI cycles, respectively. The values are similar to the geometric specific solid surface area (31±2 cm−1) and the N2/BET solid surface area (28±2 cm−1). The maximum interfacial areas are 274±38, 235±27, and 581±160 cm−1 for the sand for PD, SI, and SD cycles, respectively, and ~7625 cm−1 for the soil for PD and SI. The maximum interfacial areas for the sand and soil are significantly larger than the estimated smooth-sphere specific solid surface areas (107±8 cm−1 and 152±8 cm−1, respectively), but much smaller than the N2/BET solid surface area (1387±92 cm−1 and 55224 cm−1, respectively). The NW-W interfacial areas measured with the two-phase flow method compare well to values measured using the standard IPTT method. PMID:28959079

Calculation of a solid/liquid surface tension: A methodological study

NASA Astrophysics Data System (ADS)

Dreher, T.; Lemarchand, C.; Soulard, L.; Bourasseau, E.; Malfreyt, P.; Pineau, N.

2018-01-01

The surface tension of a model solid/liquid interface constituted of a graphene sheet surrounded by liquid methane has been computed using molecular dynamics in the Kirkwood-Buff formalism. We show that contrary to the fluid/fluid case, the solid/liquid case can lead to different structurations of the first fluid layer, leading to significantly different values of surface tension. Therefore we present a statistical approach that consists in running a series of molecular simulations of similar systems with different initial conditions, leading to a distribution of surface tensions from which an average value and uncertainty can be extracted. Our results suggest that these distributions converge as the system size increases. Besides we show that surface tension is not particularly sensitive to the choice of the potential energy cutoff and that long-range corrections can be neglected contrary to what we observed in the liquid/vapour interfaces. We have not observed the previously reported commensurability effect.

Shape dependence of slip length on patterned hydrophobic surfaces

NASA Astrophysics Data System (ADS)

Gu, Xiaokun; Chen, Min

2011-08-01

The effects of solid-liquid interfacial shape on the boundary velocity slip of patterned hydrophobic surfaces are investigated. The scaling law in literature is extended to demonstrate the role of such shape, indicating a decrease of the effective slip length with increasing interfacial roughness. A patterned surface with horizontally aligned carbon nanotube arrays reaches an effective slip length of 83 nm, by utilizing large intrinsic slippage of carbon nanotube while keeping away from the negative effects of interfacial curvature through the flow direction. The results emphasize the importance of avoiding the solid-liquid interfacial roughness in low-friction patterned surface design and manufacture.

Surface pressure affects B-hordein network formation at the air-water interface in relation to gastric digestibility.

PubMed

Yang, Jingqi; Huang, Jun; Zeng, Hongbo; Chen, Lingyun

2015-11-01

Protein interfacial network formation under mechanical pressure and its influence on degradation was investigated at molecular level using Langmuir-Blodgett B-hordein monolayer as a 2D model. Surface properties, such as surface pressure, dilatational and shear rheology and the surface pressure--area (π-A) isotherm, of B-hordein at air-water interface were analyzed by tensiometer, rheometer and a Langmuir-Blodgett trough respectively. B-Hordein conformation and orientation under different surface pressures were determined by polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). The interfacial network morphology was observed by atomic force microscopy (AFM). B-Hordein could reduce the air-water surface tension rapidly to ∼ 45 mN/m and form a solid-like network with high rheological elasticity and compressibility at interface, which could be a result of interactions developed by intermolecular β-sheets. The results also revealed that B-hordein interfacial network switched from an expanded liquid phase to a solid-like film with increasing compression pressure. The orientation of B-hordein was parallel to the surface when in expended liquid phase, whereas upon compression, the hydrophobic repetitive region tilted away from water phase. When compressed to 30 mN/m, a strong elastic network was formed at the interface, and it was resistant to a harsh gastric-like environment of low pH and pepsin. This work generated fundamental knowledge, which suggested the potential to design B-hordein stabilized emulsions and encapsulations with controllable digestibility for small intestine targeted delivery of bioactive compounds. Copyright © 2015 Elsevier B.V. All rights reserved.

Recent applications of liquid metals featuring nanoscale surface oxides

NASA Astrophysics Data System (ADS)

Neumann, Taylor V.; Dickey, Michael D.

2016-05-01

This proceeding describes recent efforts from our group to control the shape and actuation of liquid metal. The liquid metal is an alloy of gallium and indium which is non-toxic, has negligible vapor pressure, and develops a thin, passivating surface oxide layer. The surface oxide allows the liquid metal to be patterned and shaped into structures that do not minimize interfacial energy. The surface oxide can be selectively removed by changes in pH or by applying a voltage. The surface oxide allows the liquid metal to be 3D printed to form free-standing structures. It also allows for the liquid metal to be injected into microfluidic channels and to maintain its shape within the channels. The selective removal of the oxide results in drastic changes in surface tension that can be used to control the flow behavior of the liquid metal. The metal can also wet thin, solid films of metal that accelerates droplets of the liquid along the metal traces .Here we discuss the properties and applications of liquid metal to make soft, reconfigurable electronics.

Field-Controlled Electrical Switch with Liquid Metal.

PubMed

Wissman, James; Dickey, Michael D; Majidi, Carmel

2017-12-01

When immersed in an electrolyte, droplets of Ga-based liquid metal (LM) alloy can be manipulated in ways not possible with conventional electrocapillarity or electrowetting. This study demonstrates how LM electrochemistry can be exploited to coalesce and separate droplets under moderate voltages of ~1-10 V. This novel approach to droplet interaction can be explained with a theory that accounts for oxidation and reduction as well as fluidic instabilities. Based on simulations and experimental analysis, this study finds that droplet separation is governed by a unique limit-point instability that arises from gradients in bipolar electrochemical reactions that lead to gradients in interfacial tension. The LM coalescence and separation are used to create a field-programmable electrical switch. As with conventional relays or flip-flop latch circuits, the system can transition between bistable (separated or coalesced) states, making it useful for memory storage, logic, and shape-programmable circuitry using entirely liquids instead of solid-state materials.

Nucleation processes of nanobubbles at a solid/water interface

NASA Astrophysics Data System (ADS)

Fang, Chung-Kai; Ko, Hsien-Chen; Yang, Chih-Wen; Lu, Yi-Hsien; Hwang, Ing-Shouh

2016-04-01

Experimental investigations of hydrophobic/water interfaces often return controversial results, possibly due to the unknown role of gas accumulation at the interfaces. Here, during advanced atomic force microscopy of the initial evolution of gas-containing structures at a highly ordered pyrolytic graphite/water interface, a fluid phase first appeared as a circular wetting layer ~0.3 nm in thickness and was later transformed into a cap-shaped nanostructure (an interfacial nanobubble). Two-dimensional ordered domains were nucleated and grew over time outside or at the perimeter of the fluid regions, eventually confining growth of the fluid regions to the vertical direction. We determined that interfacial nanobubbles and fluid layers have very similar mechanical properties, suggesting low interfacial tension with water and a liquid-like nature, explaining their high stability and their roles in boundary slip and bubble nucleation. These ordered domains may be the interfacial hydrophilic gas hydrates and/or the long-sought chemical surface heterogeneities responsible for contact line pinning and contact angle hysteresis. The gradual nucleation and growth of hydrophilic ordered domains renders the original homogeneous hydrophobic/water interface more heterogeneous over time, which would have great consequence for interfacial properties that affect diverse phenomena, including interactions in water, chemical reactions, and the self-assembly and function of biological molecules.

Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air

DOE PAGES

Chong, Leebyn; Lai, Yungchieh; Gray, McMahan; ...

2017-03-15

For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends betweenmore » each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.« less

Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chong, Leebyn; Lai, Yungchieh; Gray, McMahan

For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends betweenmore » each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.« less

Extraction of effective solid-liquid interfacial free energies for full 3D solid crystallites from equilibrium MD simulations

DOE PAGES

Zepeda-Ruiz, L. A.; Sadigh, B.; Chernov, A. A.; ...

2017-11-21

Molecular dynamics simulations of an embedded atom copper system in the NPH ensemble are used to study the e ective solid-liquid interfacial free energy of quasispherical solid crystals within a liquid. This is within the larger context of MD simulations of this system undergoing solidi cation, where single individually-prepared crystallites of di erent sizes grow until they reach a thermodynamically stable nal state. The resulting equilibrium shapes possess the full structural details expected for solids with weakly anisotropic surface free energies (in these cases, ~5 % radial attening and rounded [111] octahedral faces). The simplifying assumption of sphericity and perfectmore » isotropy leads to an e ective interfacial free energy as appearing in the Gibbs-Thomson equation, which we determine to be ~179 erg/cm 2, roughly independent of crystal size for radii in the 50 - 250 A range. This quantity may be used in atomistically-informed models of solidi cation kinetics for this system.« less

Extraction of effective solid-liquid interfacial free energies for full 3D solid crystallites from equilibrium MD simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zepeda-Ruiz, L. A.; Sadigh, B.; Chernov, A. A.

Molecular dynamics simulations of an embedded atom copper system in the NPH ensemble are used to study the e ective solid-liquid interfacial free energy of quasispherical solid crystals within a liquid. This is within the larger context of MD simulations of this system undergoing solidi cation, where single individually-prepared crystallites of di erent sizes grow until they reach a thermodynamically stable nal state. The resulting equilibrium shapes possess the full structural details expected for solids with weakly anisotropic surface free energies (in these cases, ~5 % radial attening and rounded [111] octahedral faces). The simplifying assumption of sphericity and perfectmore » isotropy leads to an e ective interfacial free energy as appearing in the Gibbs-Thomson equation, which we determine to be ~179 erg/cm 2, roughly independent of crystal size for radii in the 50 - 250 A range. This quantity may be used in atomistically-informed models of solidi cation kinetics for this system.« less

Complex Fluids at Interfaces and Interfaces of Complex Fluids

NASA Astrophysics Data System (ADS)

Nouri, Mariam

The present thesis deals with two independent projects and is consequently divided into two parts. The first part details a computational study of the fluid structure of ring-shaped molecules and their positional and orientational molecular organizations in different degrees of confinement, while the second part concerns an experimental study of phase behavior and interfacial phenomena in confined colloid-polymer systems. In the first part, ring-shaped molecules are studied using Monte Carlo simulation techniques in one, two and three dimensions. The model used to describe ring-shaped molecules is composed of hard-spheres linked together to form planar rigid rings. For rings of various sizes and for a wide range of densities, positional and orientational orderings are reported in forms of pair distribution functions of the ring centers and correlation functions of the ring normal orientations. Special emphasis is given to understand structural formation at interfaces, i.e., the structure and orderings of these molecules when they are confined to two dimensions. In a plane but the rings themselves are free to rotate around all axes, nematic ordering is observed at sufficiently high densities. In the second part, phase equilibria of confined aqueous colloid-polymer systems are studied experimentally using fluorescence microscopy. Aqueous mixtures of fluorescent polystyrene spheres and polyacrylamide are confined between a glass slide and a coverslip. The phase diagram is determined as a function of the colloidal and polymer concentrations. Liquid-liquid phase coexistence between a colloid-rich phase and a polymer-rich phase occurs at intermediate polymer concentrations, while liquid-solid phase coexistence between a polymer-rich liquid and a colloid-rich solid is observed at high polymer concentrations. Interfacial thickness and tension of the interface between these coexisting phases are measured using image analysis techniques. It is also observed that the colloid-rich solid and liquid domains coarsen mainly by Ostwald ripening.

Solid-liquid interfacial free energy of ice Ih, ice Ic, and ice 0 within a mono-atomic model of water via the capillary wave method.

PubMed

Ambler, Michael; Vorselaars, Bart; Allen, Michael P; Quigley, David

2017-02-21

We apply the capillary wave method, based on measurements of fluctuations in a ribbon-like interfacial geometry, to determine the solid-liquid interfacial free energy for both polytypes of ice I and the recently proposed ice 0 within a mono-atomic model of water. We discuss various choices for the molecular order parameter, which distinguishes solid from liquid, and demonstrate the influence of this choice on the interfacial stiffness. We quantify the influence of discretisation error when sampling the interfacial profile and the limits on accuracy imposed by the assumption of quasi one-dimensional geometry. The interfacial free energies of the two ice I polytypes are indistinguishable to within achievable statistical error and the small ambiguity which arises from the choice of order parameter. In the case of ice 0, we find that the large surface unit cell for low index interfaces constrains the width of the interfacial ribbon such that the accuracy of results is reduced. Nevertheless, we establish that the interfacial free energy of ice 0 at its melting temperature is similar to that of ice I under the same conditions. The rationality of a core-shell model for the nucleation of ice I within ice 0 is questioned within the context of our results.

Crystallization of hard spheres revisited. II. Thermodynamic modeling, nucleation work, and the surface of tension.

PubMed

Richard, David; Speck, Thomas

2018-06-14

Combining three numerical methods (forward flux sampling, seeding of droplets, and finite-size droplets), we probe the crystallization of hard spheres over the full range from close to coexistence to the spinodal regime. We show that all three methods allow us to sample different regimes and agree perfectly in the ranges where they overlap. By combining the nucleation work calculated from forward flux sampling of small droplets and the nucleation theorem, we show how to compute the nucleation work spanning three orders of magnitude. Using a variation of the nucleation theorem, we show how to extract the pressure difference between the solid droplet and ambient liquid. Moreover, combining the nucleation work with the pressure difference allows us to calculate the interfacial tension of small droplets. Our results demonstrate that employing bulk quantities yields inaccurate results for the nucleation rate.

Effect of MnO content on the interfacial property of mold flux and steel

NASA Astrophysics Data System (ADS)

Wang, Wanlin; Li, Jingwen; Zhou, Lejun; Yang, Jian

2016-07-01

The interfacial property between liquid mold flux and steel has significant impact on the quality of casting slab, and this property is mainly determined by the chemical composition of mold flux and the reaction between the flux and steel. The effect of MnO content on the contact angle and interfacial tension between liquid mold flux and ultra-low carbon steel was investigated by sessile drop method in this article, and the results suggested that both the contact angle and interfacial tension decreased with the increase of MnO content in the mold flux. The increase of Si and Mn and the reduction of Al and Ti in the interaction layer were caused by the chemical reactions occurred in the vicinity of interface between mold flux and steel substrate. Besides, the thickness of the interaction layer increased from 4 μm to 7 μm, then to 9 μm, 11 μm and 15 μm when the MnO content was added from 1 wt% to 3 wt%, then to 5 wt%, 7 wt%, and 9 wt% due to the fact that MnO can simplify the polymerized structure of the melt and improve the penetrability of molten mold flux to make the interfacial reaction easier.

A finite element analysis of the freeze/thaw behavior of external artery heat pipes

NASA Technical Reports Server (NTRS)

Lu, X. J.; Peterson, G. P.

1993-01-01

A two-dimensional finite element model was used to determine the freeze/thaw characteristics of an external artery heat pipe. During startup, the working fluid, which was located in the liquid channel and the circumferential wall grooves, experienced a phase transformation from a solid to a liquid state. The transient heat conduction equations with moving interfacial conditions were solved using the appropriate initial boundary conditions. The modelling results include the cross-sectional temperature distribution and the interfacial or melt front position as a function of time. A fixed grid approach was adopted in the model for the phase-change process during thawing of frozen working fluid. The interfacial position between the liquid and solid regions was found by balancing the latent heat caused by interfacial movement with the heat addition or extraction at the related grid points.

Interfacial tension and vapor-liquid equilibria in the critical region of mixtures

NASA Technical Reports Server (NTRS)

Moldover, Michael R.; Rainwater, James C.

1988-01-01

In the critical region, the concept of two-scale-factor universality can be used to accurately predict the surface tension between near-critical vapor and liquid phases from the singularity in the thermodynamic properties of the bulk fluid. In the present work, this idea is generalized to binary mixtures and is illustrated using the data of Hsu et al. (1985) for CO2 + n-butane. The pressure-temperature-composition-density data for coexisting, near-critical phases of the mixtures are fitted with a thermodynamic potential comprised of a sum of a singular term and nonsingular terms. The nonuniversal amplitudes characterizing the singular term for the mixtures are obtained from the amplitudes for the pure components by interpolation in a space of thermodynamic 'field' variables. The interfacial tensions predicted for the mixtures from the singular term are within 10 percent of the data on three isotherms in the pressure range (Pc - P)/Pc of less than 0.5. This difference is comparable to the combined experimental and model errors.

Membrane rafts stabilized by chiral liquid crystal correction to bare interfacial tension

NASA Astrophysics Data System (ADS)

Kang, Louis; Lubensky, T. C.

Lipid rafts are hypothesized to facilitate protein interaction, tension regulation, and trafficking in biological membranes, but the mechanisms responsible for their formation and maintenance are not clear. Recently, experiments showed that bidisperse mixtures of filamentous viruses can self-assemble into colloidal monolayers with thermodynamically stable rafts that exhibit chiral structure and repulsive interactions. We quantitatively explain these observations by modeling the membrane particles as chiral liquid crystals. Chiral twist promotes the formation of finite-sized rafts by decreasing the effective interfacial tension between rafts and background membrane. It also mediates a repulsion that distributes rafts evenly throughout the membrane. Although this system is composed of filamentous viruses whose aggregation is entropically driven by dextran depletants instead of phospholipids and cholesterol with prominent electrostatic interactions, colloidal and biological membranes share many of the same physical symmetries. Chiral twist can contribute to the behavior of both systems and may account for certain stereospecific effects observed in molecular membranes.

Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

NASA Technical Reports Server (NTRS)

Rashidnia, N.; Balasubramaniam, R.

1991-01-01

An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

NASA Technical Reports Server (NTRS)

Rashidnia, N.; Balasubramaniam, R.

1989-01-01

An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

The effects of surface tension on flooding in counter-current two-phase flow in an inclined tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deendarlianto; Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, D-01314 Dresden; Ousaka, Akiharu

2010-10-15

The purpose of the present study is to investigate the effects of surface tension on flooding phenomena in counter-current two-phase flow in an inclined tube. Previous studies by other researchers have shown that surface tension has a stabilizing effect on the falling liquid film under certain conditions and a destabilizing or unclear trend under other conditions. Experimental results are reported herein for air-water systems in which a surfactant has been added to vary the liquid surface tension without altering other liquid properties. The flooding section is a tube of 16 mm in inner diameter and 1.1 m length, inclined atmore » 30-60 from horizontal. The flooding mechanisms were observed by using two high-speed video cameras and by measuring the time variation of liquid hold-up along the test tube. The results show that effects of surface tension are significant. The gas velocity needed to induce flooding is lower for a lower surface tension. There was no upward motion of the air-water interfacial waves upon flooding occurrence, even for lower a surface tension. Observations on the liquid film behavior after flooding occurred suggest that the entrainment of liquid droplets plays an important role in the upward transport of liquid. Finally, an empirical correlation for flooding velocities is proposed that includes functional dependencies on surface tension and tube inclination. (author)« less

Dynamic Nucleation of Supercooled Melts and Measurement of the Surface Tension and Viscosity

NASA Technical Reports Server (NTRS)

Trinh, E. H.; Ohsaka, K.

1999-01-01

We investigate the phenomenon of acoustic pressure-induced nucleation by using a novel approach involving the large amplitude resonant radial oscillations and collapse of a single bubble intentionally injected into a supercooled liquid. Using a combination of previously developed and proven techniques, the bubble is suspended in a fluid host by an ultrasonic field which supplies both the levitation capability as well as the forcing of the radial oscillations. We observe the effects of an increase in pressure (due to bubble collapse) in a region no larger than 100 microns within the supercooled melt to rigorously probe the hypothesis of pressure-induced nucleation of the solid phase. The use of single bubbles operating in narrow temporal and spatial scales will allow the direct and unambiguous correlation between the origin and location of the generation of the disturbance and the location and timing of the nucleation event. In a companion research effort, we are developing novel techniques for the non-contact measurements of the surface tension and viscosity of highly viscous supercooled liquids. Currently used non-invasive methods of surface tension measurement for the case of undercooled liquids generally rely of the quantitative determination of the resonance frequencies of drop shape oscillations, of the dynamics of surface capillary waves, or of the velocity of streaming flows. These methods become quickly ineffective when the liquid viscosity rises to a significant value. An alternate and accurate method which would be applicable to liquids of significant viscosity is therefore needed. We plan to develop such a capability by measuring the equilibrium shape of levitated undercooled melt droplets as they undergo solid-body rotation. The experimental measurement of the characteristic point of transition (bifurcation point) between axisymmetric and two-lobed shapes will be used to calculate the surface tension of the liquid. Such an approach has already been validated through the experimental verification of numerical modeling results. The experimental approach involves levitation, melting, and solidification of undercooled droplets using a hybrid ultrasonic-electrostatic technique in both a gaseous as well as a vacuum environment. A shape relaxation method will be investigated in order to derive a reliable method to measure the viscosity of undercooled melts. The analysis of the monotonic relaxation to equilibrium shape of a drastically deformed and super-critically damped free drop has been used to derive interfacial tension of immiscible liquid combinations where one of the component has high viscosity. A standard approach uses the initial elongation of a droplet through shear flows, but an equivalent method could involve the initial deformation of a drop levitated in a gas by ultrasonic radiation pressure, electric stresses, or even solid body rotation. The dynamic behavior of the free drop relaxing back to equilibrium shape will be modeled, and its characteristic time dependence should provide a quantitative means to evaluate the liquid viscosity.

Atomistic and Coarse-Grained Modeling of the Adsorption of Graphene Nanoflakes at the Oil-Water Interface.

PubMed

Ardham, Vikram Reddy; Leroy, Frédéric

2018-03-01

The high interfacial tension between two immiscible liquids can provide the necessary driving force for the self-assembly of nanoparticles at the interface. Particularly, the interface between water and oily liquids (hydrocarbon chains) has been exploited to prepare networks of highly interconnected graphene sheets of only a few layers thickness, which are well suited for industrial applications. Studying such complex systems through particle-based simulations could greatly enhance the understanding of the various driving forces in action and could possibly give more control over the self-assembly process. However, the interaction potentials used in particle-based simulations are typically derived by reproducing bulk properties and are therefore not suitable for describing systems dominated by interfaces. To address this issue, we introduce a methodology to derive solid-liquid interaction potentials that yield an accurate representation of the balance between interfacial interactions at atomistic and coarse-grained resolutions. Our approach is validated through its ability to lead to the adsorption of graphene nanoflakes at the interface between water and n-hexane. The development of accurate coarse-grained potentials that our approach enables will allow us to perform large-scale simulations to study the assembly of graphene nanoparticles at the interface between immiscible liquids. Our methodology is illustrated through a simulation of many graphene nanoflakes adsorbing at the interface.

Blowing bubbles in Lennard-Jonesium along the saturation curve.

PubMed

Ashbaugh, Henry S

2009-05-28

Extensive molecular simulations of the Lennard-Jones fluid have been performed to determine its liquid-vapor coexistence properties and solvent contact densities with cavities up to ten times the diameter of the solvent from the triple point to the critical point. These simulations are analyzed using a revised scaled-particle theory [H. S. Ashbaugh and L. R. Pratt, Rev. Mod. Phys. 78, 159 (2006)] to evaluate the thermodynamics of cavity solvation and curvature dependent interfacial properties along the saturation curve. While the thermodynamic signatures of cavity solvation are distinct from those in water, exhibiting a chemical potential dominated by a large temperature independent enthalpy, the solvent dewets cavities of increasing size similar with water near coexistence. The interfacial tension for forming a liquid-wall interface is found to be consistently greater than the liquid-vapor surface tension of the Lennard-Jones fluid by up to 10% and potentially reflects the suppression of high amplitude fluctuations at the cavity surface. The first-order curvature correction for the surface tension is negative and appears to diverge to negative infinity at temperatures approaching the critical point. Our results point to the success of the revised scaled-particle theory at bridging molecular and macroscopic descriptions of cavity solvation.

Solid-liquid surface tensions of critical nuclei and nucleation barriers from a phase-field-crystal study of a model binary alloy using finite system sizes.

PubMed

Choudhary, Muhammad Ajmal; Kundin, Julia; Emmerich, Heike; Oettel, Martin

2014-08-01

Phase-field-crystal (PFC) modeling has emerged as a computationally efficient tool to address crystal growth phenomena on atomistic length and diffusive time scales. We use a two-dimensional phase-field-crystal model for a binary system based on Elder et al. [Phys. Rev. B 75, 064107 (2007)] to study critical nuclei and their liquid-solid phase boundaries, in particular the nucleus size dependence of the liquid-solid interface tension as well as of the nucleation barrier. Critical nuclei are stabilized in finite systems of various sizes, however, the extracted interface tension as function of the nucleus radius r is independent of system size. We suggest a phenomenological expression to describe the dependence of the extracted interface tension on the nucleus radius r for the liquid-solid system. Moreover, the numerical PFC results show that this dependency can not be fully described by the nonclassical Tolman formula.

Self-healing gold mirrors and filters at liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

Smirnov, Evgeny; Peljo, Pekka; Scanlon, Micheál D.; Gumy, Frederic; Girault, Hubert H.

2016-03-01

The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of ``floating islands'' of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing tetrathiafulvalene with neocuproine as the AuNP capping ligand in the nanofilm. These interfacial nanofilms formed with neocuproine and 38 nm mean diameter AuNPs, at monolayer surface coverages and above, were black due to aggregation and broadband absorbance.The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of ``floating islands'' of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing tetrathiafulvalene with neocuproine as the AuNP capping ligand in the nanofilm. These interfacial nanofilms formed with neocuproine and 38 nm mean diameter AuNPs, at monolayer surface coverages and above, were black due to aggregation and broadband absorbance. Electronic supplementary information (ESI) available: Interfacial tension measurements for various water-organic solvent systems, step-by-step optical microscopy and SEM characterization of the obtained film, optical photographs of all tested solvents and molecules, and influence of the interfacial tension on optical responses of AuNPs assemblies. See DOI: 10.1039/c6nr00371k

Three-Dimensional Visualization of Interfacial Phenomena Using Confocal Microscopy

NASA Astrophysics Data System (ADS)

Shieh, Ian C.

Surfactants play an integral role in numerous functions ranging from stabilizing the emulsion in a favorite salad dressing to organizing the cellular components that make life possible. We are interested in lung surfactant, which is a mixture of lipids and proteins essential for normal respiration because it modulates the surface tension of the air-liquid interface of the thin fluid lining in the lungs. Through this surface tension modulation, lung surfactant ensures effortless lung expansion and prevents lung collapse during exhalation, thereby effecting proper oxygenation of the bloodstream. The function of lung surfactant, as well as numerous interfacial lipid systems, is not solely dictated by the behavior of materials confined to the two-dimensional interface. Rather, the distributions of materials in the liquid subphase also greatly influence the performance of interfacial films of lung surfactant. Therefore, to better understand the behavior of lung surfactant and other interfacial lipid systems, we require a three-dimensional characterization technique. In this dissertation, we have developed a novel confocal microscopy methodology for investigating the interfacial phenomena of surfactants at the air-liquid interface of a Langmuir trough. Confocal microscopy provides the excellent combination of in situ, fast, three-dimensional visualization of multiple components of the lung surfactant system that other characterization techniques lack. We detail the solutions to the numerous challenges encountered when imaging a dynamic air-liquid interface with a high-resolution technique like confocal microscopy. We then use confocal microscopy to elucidate the distinct mechanisms by which a polyelectrolyte (chitosan) and nonadsorbing polymer (polyethylene glycol) restore the function of lung surfactant under inhibitory conditions mimicking the effects of lung trauma. Beyond this physiological model, we also investigate several one- and two-component interfacial films of the various lipid constituents of lung surfactant. Confocal microscopy allows us to use a water-soluble, cationic fluorophore that partitions into the disordered phases of lipid monolayers. By exploiting the properties of this water-soluble fluorophore, we investigate both the phase behavior and electrostatics of the interfacial lipid systems. Overall, we believe the work presented in this dissertation provides the building blocks for establishing confocal microscopy as a ubiquitous characterization technique in the interfacial and surface sciences.

Dynamics of two-phase interfaces and surface tensions: A density-functional theory perspective

NASA Astrophysics Data System (ADS)

Yatsyshin, Petr; Sibley, David N.; Duran-Olivencia, Miguel A.; Kalliadasis, Serafim

2016-11-01

Classical density functional theory (DFT) is a statistical mechanical framework for the description of fluids at the nanoscale, where the inhomogeneity of the fluid structure needs to be carefully accounted for. By expressing the grand free-energy of the fluid as a functional of the one-body density, DFT offers a theoretically consistent and computationally accessible way to obtain two-phase interfaces and respective interfacial tensions in a ternary solid-liquid-gas system. The dynamic version of DFT (DDFT) can be rigorously derived from the Smoluchowsky picture of the dynamics of colloidal particles in a solvent. It is generally agreed that DDFT can capture the diffusion-driven evolution of many soft-matter systems. In this context, we use DDFT to investigate the dynamic behaviour of two-phase interfaces in both equilibrium and dynamic wetting and discuss the possibility of defining a time-dependent surface tension, which still remains in debate. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031 and from the Engineering and Physical Sciences Research Council of the UK via Grants No. EP/L027186 and EP/L020564.

Mechanical properties of dissimilar metal joints composed of DP 980 steel and AA 7075-T6

DOE PAGES

Squires, Lile; Lim, Yong Chae; Miles, Michael; ...

2015-03-18

In this study, a solid state joining process, called friction bit joining, was used to spot weld aluminium alloy 7075-T6 to dual phase 980 steel. Lap shear failure loads for specimens without adhesive averaged ~10kN, while cross-tension specimens averaged 2·8 kN. Addition of adhesive with a thickness up to 500 μm provided a gain of ~50% to lap shear failure loads, while a much thinner layer of adhesive increased cross-tension failure loads by 20%. Microstructures of the welds were martensitic, but the hardness of the joining bit portion was greater than that of the DP 980, owing to its highermore » alloy content. Softening in the heat affected zone of a welded joint appeared to be relatively small, though it was enough to cause nugget pullout failures in some lap shear tension specimens. Finally, other failures in lap shear tension were interfacial, while all of the failures in cross-tension were interfacial.« less

Free energy of formation of a crystal nucleus in incongruent solidification: Implication for modeling the crystallization of aqueous nitric acid droplets in polar stratospheric clouds

NASA Astrophysics Data System (ADS)

Djikaev, Yuri S.; Ruckenstein, Eli

2017-04-01

Using the formalism of classical thermodynamics in the framework of the classical nucleation theory, we derive an expression for the reversible work W* of formation of a binary crystal nucleus in a liquid binary solution of non-stoichiometric composition (incongruent crystallization). Applied to the crystallization of aqueous nitric acid droplets, the new expression more adequately takes account of the effects of nitric acid vapor compared to the conventional expression of MacKenzie, Kulmala, Laaksonen, and Vesala (MKLV) [J. Geophys. Res.: Atmos. 102, 19729 (1997)]. The predictions of both MKLV and modified expressions for the average liquid-solid interfacial tension σls of nitric acid dihydrate (NAD) crystals are compared by using existing experimental data on the incongruent crystallization of aqueous nitric acid droplets of composition relevant to polar stratospheric clouds (PSCs). The predictions for σls based on the MKLV expression are higher by about 5% compared to predictions based on our modified expression. This results in similar differences between the predictions of both expressions for the solid-vapor interfacial tension σsv of NAD crystal nuclei. The latter can be obtained by using the method based on the analysis of experimental data on crystal nucleation rates in aqueous nitric acid droplets; it exploits the dominance of the surface-stimulated mode of crystal nucleation in small droplets and its negligibility in large ones. Applying that method to existing experimental data, our expression for the free energy of formation provides an estimate for σsv of NAD in the range ≈92 dyn/cm to ≈100 dyn/cm, while the MKLV expression predicts it in the range ≈95 dyn/cm to ≈105 dyn/cm. The predictions of both expressions for W* become identical for the case of congruent crystallization; this was also demonstrated by applying our method for determining σsv to the nucleation of nitric acid trihydrate crystals in PSC droplets of stoichiometric composition.

Topology-generating interfacial pattern formation during liquid metal dealloying

DOE PAGES

Geslin, Pierre -Antoine; McCue, Ian; Gaskey, Bernard; ...

2015-11-19

Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growthmore » of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Furthermore, we deduce scaling laws governing microstructural length scales and dealloying kinetics.« less

Topology-generating interfacial pattern formation during liquid metal dealloying.

PubMed

Geslin, Pierre-Antoine; McCue, Ian; Gaskey, Bernard; Erlebacher, Jonah; Karma, Alain

2015-11-19

Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growth of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Moreover, we deduce scaling laws governing microstructural length scales and dealloying kinetics.

Wetting of silicone oil onto a cell-seeded substrate

NASA Astrophysics Data System (ADS)

Lu, Yongjie; Chan, Yau Kei; Chao, Youchuang; Shum, Ho Cheung

2017-11-01

Wetting behavior of solid substrates in three-phase systems containing two immiscible liquids are widely studied. There exist many three-phase systems in biological environments, such as droplet-based microfluidics or tamponade of silicone oil for eye surgery. However, few studies focus on wetting behavior of biological surfaces with cells. Here we investigate wetting of silicone oil onto cell-seeded PMMA sheet immersed in water. Using a simple parallel-plate cell, we show the effect of cell density, viscosity of silicone oil, morphology of silicone oil drops and interfacial tension on the wetting phenomenon. The dynamics of wetting is also observed by squeezing silicone oil drop using two parallel plates. Experimental results are explained based on disjoining pressure which is dependent on the interaction of biological surfaces and liquid used. These findings are useful for explaining emulsification of silicone oil in ophthalmological applications.

Inclusions in freely suspended smectic films

NASA Astrophysics Data System (ADS)

Stannarius, Ralf; Harth, Kirsten

Smectic liquid crystal phases have a unique property: Like soap solutions, they can form stable freely suspended films. Their aspect ratios can be larger than one million to one. Such films can serve as models for two-dimensional (2D) uids, with or without in-plane anisotropy. Solid or liquid inclusions trapped in these films by capillary forces can move in the film plane and interact with other inclusions, with film thickness gradients or the film boundaries, and even with the local orientation field. We describe preparation techniques to incorporate particles or droplets in thin smectic films, and optical observation methods. Several aspects make inclusions in freely suspended films interesting research objects: They provide rich information on capillary forces as well as surface and interfacial tensions, they can serve as platforms for hydrodynamic studies in 2D, and they may help to understand coalescence dynamics at the transition from 2D to 3D...

On the early and developed stages of surface condensation: competition mechanism between interfacial and condensate bulk thermal resistances.

PubMed

Sun, Jie; Wang, Hua Sheng

2016-10-10

We use molecular dynamics simulation to investigate the early and developed stages of surface condensation. We find that the liquid-vapor and solid-liquid interfacial thermal resistances depend on the properties of solid and fluid, which are time-independent, while the condensate bulk thermal resistance depends on the condensate thickness, which is time-dependent. There exists intrinsic competition between the interfacial and condensate bulk thermal resistances in timeline and the resultant total thermal resistance determines the condensation intensity for a given vapor-solid temperature difference. We reveal the competition mechanism that the interfacial thermal resistance dominates at the onset of condensation and holds afterwards while the condensate bulk thermal resistance gradually takes over with condensate thickness growing. The weaker the solid-liquid bonding, the later the takeover occurs. This competition mechanism suggests that only when the condensate bulk thermal resistance is reduced after it takes over the domination can the condensation be effectively intensified. We propose a unified theoretical model for the thermal resistance analysis by making dropwise condensation equivalent to filmwise condensation. We further find that near a critical point (contact angle being ca. 153°) the bulk thermal resistance has the least opportunity to take over the domination while away from it the probability increases.

On the early and developed stages of surface condensation: competition mechanism between interfacial and condensate bulk thermal resistances

PubMed Central

Sun, Jie; Wang, Hua Sheng

2016-01-01

We use molecular dynamics simulation to investigate the early and developed stages of surface condensation. We find that the liquid-vapor and solid-liquid interfacial thermal resistances depend on the properties of solid and fluid, which are time-independent, while the condensate bulk thermal resistance depends on the condensate thickness, which is time-dependent. There exists intrinsic competition between the interfacial and condensate bulk thermal resistances in timeline and the resultant total thermal resistance determines the condensation intensity for a given vapor-solid temperature difference. We reveal the competition mechanism that the interfacial thermal resistance dominates at the onset of condensation and holds afterwards while the condensate bulk thermal resistance gradually takes over with condensate thickness growing. The weaker the solid-liquid bonding, the later the takeover occurs. This competition mechanism suggests that only when the condensate bulk thermal resistance is reduced after it takes over the domination can the condensation be effectively intensified. We propose a unified theoretical model for the thermal resistance analysis by making dropwise condensation equivalent to filmwise condensation. We further find that near a critical point (contact angle being ca. 153°) the bulk thermal resistance has the least opportunity to take over the domination while away from it the probability increases. PMID:27721397

Influence of spray drying and dispersing agent on surface and dissolution properties of griseofulvin micro and nanocrystals.

PubMed

Shah, Dhaval A; Patel, Manan; Murdande, Sharad B; Dave, Rutesh H

2016-11-01

The purpose for the current research is to compare and evaluate physiochemical properties of spray-dried (SD) microcrystals (MCs), nanocrystals (NCs), and nanocrystals with a dispersion agent (NCm) from a poorly soluble compound. The characterization was carried out by performing size and surface analysis, interfacial tension (at particle moisture interface), and in-vitro drug dissolution rate experiments. Nanosuspensions were prepared by media milling and were spray-dried. The SD powders that were obtained were characterized morphologically using scanning electron microscopy (SEM), polarized light microscopy (PLM), and Flowchem. Solid-state characterization was performed using X-ray powder diffraction (XRPD), Fourier transfer infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC) for the identification of the crystalline nature of all the SD powders. The powders were characterized for their redispersion tendency in the water and in pH 1.2. Significant differences in redispersion were noted for both the NCs in both dissolution media. The interfacial tension for particle moisture interface was determined by applying the BET (Braunauer-Emmett-Teller) equation to the vapor sorption data. No significant reduction in the interfacial tension was observed between MCs and NCs; however, a significant reduction in the interfacial tension was observed for NCm at both 25 °C and 35 °C temperatures. The difference in interfacial tension and redispersion behavior can be attributed to a difference in the wetting tendency for all the SD powders. The dissolution studies were carried out under sink and under non-sink conditions. The non-sink dissolution approach was found suitable for quantification of the dissolution rate enhancement, and also for providing the rank order to the SD formulations.

Interfacial layers from the protein HFBII hydrophobin: dynamic surface tension, dilatational elasticity and relaxation times.

PubMed

Alexandrov, Nikola A; Marinova, Krastanka G; Gurkov, Theodor D; Danov, Krassimir D; Kralchevsky, Peter A; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Arnaudov, Luben N; Pelan, Eddie G; Lips, Alex

2012-06-15

The pendant-drop method (with drop-shape analysis) and Langmuir trough are applied to investigate the characteristic relaxation times and elasticity of interfacial layers from the protein HFBII hydrophobin. Such layers undergo a transition from fluid to elastic solid films. The transition is detected as an increase in the error of the fit of the pendant-drop profile by means of the Laplace equation of capillarity. The relaxation of surface tension after interfacial expansion follows an exponential-decay law, which indicates adsorption kinetics under barrier control. The experimental data for the relaxation time suggest that the adsorption rate is determined by the balance of two opposing factors: (i) the barrier to detachment of protein molecules from bulk aggregates and (ii) the attraction of the detached molecules by the adsorption layer due to the hydrophobic surface force. The hydrophobic attraction can explain why a greater surface coverage leads to a faster adsorption. The relaxation of surface tension after interfacial compression follows a different, square-root law. Such behavior can be attributed to surface diffusion of adsorbed protein molecules that are condensing at the periphery of interfacial protein aggregates. The surface dilatational elasticity, E, is determined in experiments on quick expansion or compression of the interfacial protein layers. At lower surface pressures (<11 mN/m) the experiments on expansion, compression and oscillations give close values of E that are increasing with the rise of surface pressure. At higher surface pressures, E exhibits the opposite tendency and the data are scattered. The latter behavior can be explained with a two-dimensional condensation of adsorbed protein molecules at the higher surface pressures. The results could be important for the understanding and control of dynamic processes in foams and emulsions stabilized by hydrophobins, as well as for the modification of solid surfaces by adsorption of such proteins. Copyright © 2012 Elsevier Inc. All rights reserved.

Core Formation: an Experimental Study of Metallic Melt-Silicate Segregation

NASA Astrophysics Data System (ADS)

Herpfer, M. A.; Larimer, J. W.

1993-07-01

To a large extent, the question of how metallic cores form reduces to the problem of understanding the surface tension between metallic melts and silicates [1]. This problem was addressed by performing experiments to determine the surface tensions between metallic melts with variable S contents and the silicate phases (olivine and orthopyroxene) expected in planetary mantles. The experiments were conducted in a piston-cylinder apparatus at P = 1GPa and T = 1250-1450 degrees C. Textural and chemical equilibration was confirmed in several ways: theoretical estimates were checked by conducting a series of experiments at progressively longer times (up to 72 hrs) until phase composition and dihedral angle ceased to change and the distribution of measured "apparent" angles matched the standard cumulative frequency curve. The dihedral "wetting" angles (theta) were measured from high resolution photomicrgraphs using a 10X optical protractor; 100-400 measurements were made for most experiments. The dihedral angle is related to the ratio of interfacial energies: gamma(sub)ss/gamma(sub)sl = 2 cos(theta/2), where gamma(sub)ss and gamma(sub)sl are the interfacial energies between solid-solid and liquid-solid. Since data exist for the pertinent solid-solid energies, the liquid-solid interfacial energies can be computed from measured theta values. However, the important relations are best expressed in terms of theta values. The extent to which a melt is interconnected along grain boundaries, and hence able to flow and segregate depends on the value of theta and the fraction of melt present. When theta < 60 degrees, the liquid can be interconnected at all melt fractions but when theta > 60 degrees, the melt fraction must be at least 1 vol% and increses as theta increases. Actually there is a predicted effect, analogous to a hysteresis effect, where for a given theta value the amount of melt that needs to be added for interconnection is greater than the amount left when the melt disconnects (pinches off). In our experiments, where dense metallic melt drained away, the disconnect theta values match the theoretical predictions. The composition of the metallic melt in the experiments was varied from stoichiometric FeS to Fe/S ratios near the the eutectic and on to more Fe rich compositons. The theta values vary in a systematic manner; for example, for melts in contact with olivine at 1300 degrees C the theta values range from 67 degrees for FeS to 55 degrees at the eutectic and back toward higher values at higher Fe contents. Theoretical considerations indicate that eutectic compositions are expected to have the lowest theta values, just as observed. The theta values indicate that melts with eutectic composition can interconnect and segregate at 1-2 vol% melt fraction at 1300 degrees C. Some previous estimates of the melt fraction required for interconnection are much higher [2,3], but the inferences were drawn from experiments that were not designed to test for textural equilibrium, fraction of melt present, etc. The present experiments clearly show that metallic melts can readily segregate from solid silicates. Simple extrapolations to other phases, compositions and PT conditions provide a rather complete picture of how the "plumbing" worked in the mantles of planetary objects during the initial stages of core segregation. References: [1] Stevenson D. J. (1990) In Origin of the Earth, 231-249. [2] Taylor G. J. (1989) LPSC XX, 1109. [3] Walker D. and Agee C. B. Meteor. 23, 81-91.

Unusual dewetting of thin polymer films in liquid media containing a poor solvent and a nonsolvent.

PubMed

Xu, Lin; Sharma, Ashutosh; Joo, Sang Woo; Liu, Hui; Shi, Tongfei

2014-12-16

We investigate the control of pattern size and kinetics in spontaneous dewetting of thin polymer films (polystyrene) that are stable to thermal annealing by annealing in a poor solvent (acetone)/nonsolvent (ethanol or n-hexane) liquid mixture. Dewetting occurs by the formation and growth of circular holes that coalesce to form droplets. The influence of the nature and the volume fraction of the nonsolvents on the contact angle of polymer droplets, number density of holes, and the kinetics of holes formation and growth is studied. Addition of ethanol greatly increases the hole density and slows down the kinetics substantially, while affecting only a small change in wettability. n-Hexane addition shows an interesting nonmonotonic response in decreasing the hole density and contact angle in the volume fraction range of 0-0.3 but an opposite effect beyond that. Although the two nonsolvents chosen cannot by themselves induce dewetting, their relative affinity for the solid substrate vis-à-vis acetone can strongly influence the observed dewetting scenarios that are not understood by the existing theoretical considerations. n-Hexane, for example, has great affinity for silicon substrate. In addition to the changes in wettability, viscosity, and film interfacial tension engendered by the nonsolvents, the possibility of the formation of adsorbed liquid layers at the substrate-polymer interface, which can modify the interfacial friction and slippage, needs to be considered.

Adsorption and Retardation of PFASs in Soil

NASA Astrophysics Data System (ADS)

Chen, W.; Yan, N.; Fu, X.; Carroll, K. C.; Holguin, F. O. O.; Brusseau, M. L.

2017-12-01

Per- and poly-fluorinated alkyl substances (PFASs) are emerging contaminants of concern that are present in the subsurface at numerous military and industrial facilities. Knowledge of the retention behavior of these compounds in the subsurface environment is critical for effective risk characterization and remediation. The objective of this research is to investigate the role of adsorption at the air-water interface on PFAS retention in vadose-zone systems. Surface tensions were measured for select PFAS to determine interfacial adsorption coefficients. Column experiments were conducted to characterize retardation and transport under saturated and unsaturated flow conditions. The impact of soil properties and groundwater constituents on surface tension, solid-phase adsorption, and interfacial adsorption was investigated.

Exploring parameter space effects on structure-property relationships of surfactants at liquid-liquid interfaces.

PubMed

Emborsky, Christopher P; Cox, Kenneth R; Chapman, Walter G

2011-08-28

The ubiquitous use of surfactants in commercial and industrial applications has led to many experimental, theoretical, and simulation based studies. These efforts seek to provide a molecular level understanding of the effects on structuring behavior and the corresponding impacts on observable properties (e.g., interfacial tension). With such physical detail, targeted system design can be improved over typical techniques of observational trends and phenomenological correlations by taking advantage of predictive system response. This research provides a systematic study of part of the broad parameter space effects on equilibrium microstructure and interfacial properties of amphiphiles at a liquid-liquid interface using the interfacial statistical associating fluid theory density functional theory as a molecular model for the system from the bulk to the interface. Insights into the molecular level physics and thermodynamics governing the system behavior are discussed as they relate to both predictions qualitatively consistent with experimental observations and extensions beyond currently available studies. © 2011 American Institute of Physics

Numerical determination of the interfacial energy and nucleation barrier of curved solid-liquid interfaces in binary systems

NASA Astrophysics Data System (ADS)

Kundin, Julia; Choudhary, Muhammad Ajmal

2016-07-01

The phase-field crystal (PFC) technique is a widely used approach for modeling crystal growth phenomena with atomistic resolution on mesoscopic time scales. We use a two-dimensional PFC model for a binary system based on the work of Elder et al. [Phys. Rev. B 75, 064107 (2007), 10.1103/PhysRevB.75.064107] to study the effect of the curved, diffuse solid-liquid interface on the interfacial energy as well as the nucleation barrier. The calculation of the interfacial energy and the nucleation barrier certainly depends on the proper definition of the solid-liquid dividing surface and the corresponding nucleus size. We define the position of the sharp interface at which the interfacial energy is to be evaluated by using the concept of equimolar dividing surface (re) and the minimization of the interfacial energy (rs). The comparison of the results based on both radii shows that the difference re-rs is always positive and has a limit for large cluster sizes which is comparable to the Tolman length. Furthermore, we found the real nucleation barrier for small cluster sizes, which is defined as a function of the radius rs, and compared it with the classical nucleation theory. The simulation results also show that the extracted interfacial energy as function of both radii is independent of system size, and this dependence can be reasonably described by the nonclassical Tolman formula with a positive Tolman length.

Quantifying the Pathway and Predicting Spontaneous Emulsification during Material Exchange in a Two Phase Liquid System.

PubMed

Spooner, Stephen; Rahnama, Alireza; Warnett, Jason M; Williams, Mark A; Li, Zushu; Sridhar, Seetharaman

2017-10-30

Kinetic restriction of a thermodynamically favourable equilibrium is a common theme in materials processing. The interfacial instability in systems where rate of material exchange is far greater than the mass transfer through respective bulk phases is of specific interest when tracking the transient interfacial area, a parameter integral to short processing times for productivity streamlining in all manufacturing where interfacial reaction occurs. This is even more pertinent in high-temperature systems for energy and cost savings. Here the quantified physical pathway of interfacial area change due to material exchange in liquid metal-molten oxide systems is presented. In addition the predicted growth regime and emulsification behaviour in relation to interfacial tension as modelled using phase-field methodology is shown. The observed in-situ emulsification behaviour links quantitatively the geometry of perturbations as a validation method for the development of simulating the phenomena. Thus a method is presented to both predict and engineer the formation of micro emulsions to a desired specification.

Adhesion force interactions between cyclopentane hydrate and physically and chemically modified surfaces.

PubMed

Aman, Zachary M; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

2014-12-07

Interfacial interactions between liquid-solid and solid-solid phases/surfaces are of fundamental importance to the formation of hydrate deposits in oil and gas pipelines. This work establishes the effect of five categories of physical and chemical modification to steel on clathrate hydrate adhesive force: oleamide, graphite, citric acid ester, nonanedithiol, and Rain-X anti-wetting agent. Hydrate adhesive forces were measured using a micromechanical force apparatus, under both dry and water-wet surface conditions. The results show that the graphite coating reduced hydrate-steel adhesion force by 79%, due to an increase in the water wetting angle from 42 ± 8° to 154 ± 7°. Two chemical surface coatings (nonanedithiol and the citric acid ester) induced rapid hydrate growth in the hydrate particles; nonanedithiol increased hydrate adhesive force by 49% from the baseline, while the citric acid ester coating reduced hydrate adhesion force by 98%. This result suggests that crystal growth may enable a strong adhesive pathway between hydrate and other crystalline structures, however this effect may be negated in cases where water-hydrocarbon interfacial tension is minimised. When a liquid water droplet was placed on the modified steel surfaces, the graphite and citric acid ester became less effective at reducing adhesive force. In pipelines containing a free water phase wetting the steel surface, chemical or physical surface modifications alone may be insufficient to eliminate hydrate deposition risk. In further tests, the citric acid ester reduced hydrate cohesive forces by 50%, suggesting mild activity as a hybrid anti-agglomerant suppressing both hydrate deposition and particle agglomeration. These results demonstrate a new capability to develop polyfunctional surfactants, which simultaneously limit the capability for hydrate particles to aggregate and deposit on the pipeline wall.

Does Marine Surface Tension Have Global Biogeography? Addition for the OCEANFILMS Package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elliott, Scott; Burrows, Susannah; Cameron-Smith, Philip

We apply principles of Gibbs phase plane chemistry across the entire ocean-atmosphere interface to investigate aerosol generation and geophysical transfer issues. Marine surface tension differences comprise a tangential pressure field controlling trace gas fluxes, primary organic inputs, and sea spray salt injections, in addition to heat and momentum fluxes. Mapping follows from the organic microlayer composition, now represented in ocean system models. Organic functional variations drive the microforcing, leading to (1) reduced turbulence and (by extension) laminar gas-energy diffusion; plus (2) altered bubble film mass emission into the boundary layer. Interfacial chemical behaviors are, therefore, closely reviewed as the background.more » We focus on phase transitions among two dimensional "solid, liquid, and gaseous" states serving as elasticity indicators. From the pool of dissolved organic carbon (DOC) only proteins and lipids appear to occupy significant atmospheric interfacial areas. The literature suggests albumin and stearic acid as the best proxies, and we distribute them through ecodynamic simulation. Consensus bulk distributions are obtained to control their adsorptive equilibria. We devise parameterizations for both the planar free energy and equation of state, relating excess coverage to the surface pressure and its modulus. Constant settings for the molecular surrogates are drawn from laboratory study and successfully reproduce surfactant solid-to-gas occurrence in compression experiments. Since DOC functionality measurements are rare, we group them into super-ecological province tables to verify aqueous concentration estimates. Outputs are then fed into a coverage, tension, elasticity code. The resulting two dimensional pressure contours cross a critical range for the regulation of precursor piston velocity, bubble breakage, and primary aerosol sources plus ripple damping. Concepts extend the water-air adsorption theory currently embodied in our OCEANFILMS aerosol emissions package, and the two approaches could be inserted into Earth System Models together. Uncertainties in the logic include kinetic and thermochemical factors operating at multiple scales.« less

Composite electrolytes of polyethylene oxides/garnets interfacially wetted by ionic liquid for room-temperature solid-state lithium battery

NASA Astrophysics Data System (ADS)

Huo, Hanyu; Zhao, Ning; Sun, Jiyang; Du, Fuming; Li, Yiqiu; Guo, Xiangxin

2017-12-01

Paramount attention has been paid on solid polymer electrolytes due to their potential in enhancement of energy density as well as improvement of safety. Herein, the composite electrolytes consisting of Li-salt-free polyethylene oxides and 200 nm-sized Li6.4La3Zr1.4Ta0.6O12 particles interfacially wetted by [BMIM]TF2N of 1.8 μL cm-2 have been prepared. Such wetted ionic liquid remains the solid state of membrane electrolytes and decreases the interface impedance between the electrodes and the electrolytes. There is no release of the liquid phase from the PEO matrix when the pressure of 5.0 × 104 Pa being applied for 24 h. The interfacially wetted membrane electrolytes show the conductivity of 2.2 × 10-4 S cm-1 at 20 °C, which is one order of magnitude greater than that of the membranes without the wetted ionic liquids. The conduction mechanism is related to a large number of lithium ions releasing from Li6.4La3Zr1.4Ta0.6O12 particles and the improved conductive paths along the ion-liquid-wetted interfaces between the polymer matrix and ceramic grains. When the membranes being used in the solid-state LiFePO4/Li and LiFe0.15Mn0.85PO4/Li cells at 25 °C, the excellent rate capability and superior cycle stability has been shown. The results provide a new prospect for solid polymer electrolytes used for room-temperature solid-state lithium batteries.

Characterization methods for liquid interfacial layers

NASA Astrophysics Data System (ADS)

Javadi, A.; Mucic, N.; Karbaschi, M.; Won, J. Y.; Lotfi, M.; Dan, A.; Ulaganathan, V.; Gochev, G.; Makievski, A. V.; Kovalchuk, V. I.; Kovalchuk, N. M.; Krägel, J.; Miller, R.

2013-05-01

Liquid interfaces are met everywhere in our daily life. The corresponding interfacial properties and their modification play an important role in many modern technologies. Most prominent examples are all processes involved in the formation of foams and emulsions, as they are based on a fast creation of new surfaces, often of an immense extension. During the formation of an emulsion, for example, all freshly created and already existing interfaces are permanently subject to all types of deformation. This clearly entails the need of a quantitative knowledge on relevant dynamic interfacial properties and their changes under conditions pertinent to the technological processes. We report on the state of the art of interfacial layer characterization, including the determination of thermodynamic quantities as base line for a further quantitative analysis of the more important dynamic interfacial characteristics. Main focus of the presented work is on the experimental possibilities available at present to gain dynamic interfacial parameters, such as interfacial tensions, adsorbed amounts, interfacial composition, visco-elastic parameters, at shortest available surface ages and fastest possible interfacial perturbations. The experimental opportunities are presented along with examples for selected systems and theoretical models for a best data analysis. We also report on simulation results and concepts of necessary refinements and developments in this important field of interfacial dynamics.

Determination of the mean solid-liquid interface energy of pivalic acid

NASA Technical Reports Server (NTRS)

Singh, N. B.; Gliksman, M. E.

1989-01-01

A high-confidence solid-liquid interfacial energy is determined for an anisotropic material. A coaxial composite having a cylindrical specimen chamber geometry provides a thermal gradient with an axial heating wire. The surface energy is derived from measurements of grain boundary groove shapes. Applying this method to pivalic acid, a surface energy of 2.84 erg/sq cm was determined with a total systematic and random error less than 10 percent. The value of interfacial energy corresponds to 24 percent of the latent heat of fusion per molecule.

Nano scale dynamics of bubble nucleation in confined liquid subjected to rapid cooling: Effect of solid-liquid interfacial wettability

NASA Astrophysics Data System (ADS)

Hasan, Mohammad Nasim; Rabbi, Kazi Fazle; Mukut, K. M.; Tamim, Saiful Islam; Faisal, A. H. M.

2017-06-01

This study focuses on the occurrence of bubble nucleation in a liquid confined in a nano scale confinement and subjected to rapid cooling at one of its wall. Due to the very small size scale of the present problem, we adopt the molecular dynamics (MD) approach. The liquid (Argon) is confined within two solid (Platinum) walls. The temperature of the upper wall of the confinement is maintained at 90 K while the lower wall is being cooled rapidly to 50 K from initial equilibrium temperature of 90 K within 0.1 ns. This results in the nucleation and formation of nanobubbles in the liquid. The pattern of bubble nucleation has been studied for three different conditions of solid-liquid interfacial wettability such as hydrophilic, hydrophobic and neutral. Behavior of bubble nucleation is significantly different in the three case of solid-liquid interfacial wettability. In case of the hydrophobic confinement (weakly adsorbing), the liquid cannot achieve deeper metastability; vapor layers appear immediately on the walls. In case of the neutral confinement (moderately adsorbing), bubble nucleation is promoted by the walls where the nucleation is heterogeneous. In case of the hydrophilic walls (strongly adsorbing) bubbles are developed inside the liquid; that is the nucleation process is homogeneous. The variation in bubble nucleation under different conditions of surface wettability has been studied by the analysis of number density distribution, spatial temperature distribution, spatial number density distribution and heat flux through the upper and lower walls of the confinement. The present study indicates that the variation of heat transfer efficiency due to different surface wettability has significant effect on the size, shape and location of bubble nucleation in case rapid cooling of liquid in nano confinement.

Thermocapillary convection in two immiscible liquid layers with free surface

NASA Technical Reports Server (NTRS)

Doi, Takao; Koster, Jean N.

1993-01-01

Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one liquid/liquid interface, and differential heating applied parallel to the interfaces. An analytical solution is introduced for infinite horizontal layers. The defining parameter for the flow pattern is lambda, the ratio of the temperature coefficient of the interfacial tension to that of the surface tension. Four different flow patterns exist under zero gravity conditions. 'Halt' conditions which halt the fluid motion in the lower encapsulated liquid layer have been found. A numerical experiment is carried out to study effects of vertical end walls on the double layer convection in a 2D cavity. The halt condition obtained from the analytical study is found to be valid in the limit of small Reynolds numbers. The flow in the encapsulated liquid layer can be suppressed substantially.

Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel.

PubMed

Ray, Bahni; Reddy, Puchalapalli Dinesh Sankar; Bandyopadhyay, Dipankar; Joo, Sang W; Sharma, Ashutosh; Qian, Shizhi; Biswas, Gautam

2011-11-01

We consider the stability of a thin liquid film with a free charged surface resting on a solid charged substrate by performing a general Orr-Sommerfeld (O-S) analysis complemented by a long-wave (LW) analysis. An externally applied field generates an electroosmotic flow (EOF) near the solid substrate and an electrophoretic flow (EPF) at the free surface. The EPF retards the EOF when both the surfaces have the same sign of the potential and can even lead to the flow reversal in a part of the film. In conjunction with the hydrodynamic stress, the Maxwell stress is also considered in the problem formulation. The electrokinetic potential at the liquid-air and solid-liquid interfaces is modelled by the Poisson-Boltzmann equation with the Debye-Hückel approximation. The O-S analysis shows a finite-wavenumber shear mode of instability when the inertial forces are strong and an LW interfacial mode of instability in the regime where the viscous force dominates. Interestingly, both the modes are found to form beyond a critical flow rate. The shear (interfacial) mode is found to be dominant when the film is thick (thin), the electric field applied is strong (weak), and the zeta-potentials on the liquid-air and solid-liquid interfaces are high (small). The LW analysis predicts the presence of the interfacial mode, but fails to capture the shear mode. The change in the propagation direction of the interfacial mode with the zeta-potential is predicted by both O-S and LW analyses. The parametric range in which the LW analysis is valid is thus demonstrated. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating buried polymer interfaces using sum frequency generation vibrational spectroscopy

PubMed Central

Chen, Zhan

2010-01-01

This paper reviews recent progress in the studies of buried polymer interfaces using sum frequency generation (SFG) vibrational spectroscopy. Both buried solid/liquid and solid/solid interfaces involving polymeric materials are discussed. SFG studies of polymer/water interfaces show that different polymers exhibit varied surface restructuring behavior in water, indicating the importance of probing polymer/water interfaces in situ. SFG has also been applied to the investigation of interfaces between polymers and other liquids. It has been found that molecular interactions at such polymer/liquid interfaces dictate interfacial polymer structures. The molecular structures of silane molecules, which are widely used as adhesion promoters, have been investigated using SFG at buried polymer/silane and polymer/polymer interfaces, providing molecular-level understanding of polymer adhesion promotion. The molecular structures of polymer/solid interfaces have been examined using SFG with several different experimental geometries. These results have provided molecular-level information about polymer friction, adhesion, interfacial chemical reactions, interfacial electronic properties, and the structure of layer-by-layer deposited polymers. Such research has demonstrated that SFG is a powerful tool to probe buried interfaces involving polymeric materials, which are difficult to study by conventional surface sensitive analytical techniques. PMID:21113334

Temperature-Tuned Faceting and Shape Changes in Liquid Alkane Droplets

DOE PAGES

Guttman, Shani; Sapir, Zvi; Ocko, Benjamin M.; ...

2017-01-09

Recent extensive studies reveal that surfactant-stabilized spherical alkane emulsion droplets spontaneously adopt polyhedral shapes upon cooling below a temperature T d while remaining liquid. Further cooling induces the growth of tails and spontaneous droplet splitting. Two mechanisms were offered to account for these intriguing effects. One assigns the effects to the formation of an intradroplet frame of tubules consisting of crystalline rotator phases with cylindrically curved lattice planes. The second assigns the sphere-to-polyhedron transition to the buckling of defects in a crystalline interfacial monolayer, known to form in these systems at some T s > T d. The buckling reducesmore » the extensional energy of the crystalline monolayer’s defects, unavoidably formed when wrapping a spherical droplet by a hexagonally packed interfacial monolayer. The tail growth, shape changes, and droplet splitting were assigned to the decrease and vanishing of surface tension, γ. Here we present temperature-dependent γ(T), optical microscopy measurements, and interfacial entropy determinations for several alkane/surfactant combinations. We demonstrate the advantages and accuracy of the in situ γ(T) measurements made simultaneously with the microscopy measurements on the same droplet. The in situ and coinciding ex situ Wilhelmy plate γ(T) measurements confirm the low interfacial tension, ≲0.1 mN/m, observed at T d. Here, our results provide strong quantitative support validating the crystalline monolayer buckling mechanism.« less

Molecular simulation of thermodynamic and transport properties for the H{sub 2}O+NaCl system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orozco, Gustavo A.; Jiang, Hao; Panagiotopoulos, Athanassios Z., E-mail: azp@princeton.edu

Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H{sub 2}O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and themore » Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration.« less

Effect of adsorption on the surface tensions of solid-fluid interfaces.

PubMed

Ward, C A; Wu, Jiyu

2007-04-12

A method is proposed for determining the surface tensions of a solid in contact with either a liquid or a vapor. Only an equilibrium adsorption isotherm at the solid-vapor interface needs to be added to Gibbsian thermodynamics to obtain the expressions for the solid-vapor and the solid-liquid surface tensions, gamma[1](SV) and gamma[1](SL), respectively. An equilibrium adsorption isotherm relation is formulated that has the essential property of not predicting an infinite amount adsorbed when the pressure is equal to the saturation-vapor pressure. Five different solid-vapor systems from the literature are examined, and found to be well described by the new isotherm relation. The surface-tension expressions obtained from the isotherm relation are examined by determining the surface tension of the solid in the absence of adsorption, gamma[1](S0), a material property of a solid surface. The value of gamma[1](S0) can be determined by adsorbing different vapors on the same solid, determining the isotherm parameters in each case, and then from the expression for gamma[1](SV) taking the limit of the pressure vanishing to determine gamma[1](S0). From previously reported measurements of benzene and of n-hexane adsorbing on graphitized carbon, the same value of gamma[1](S0) is obtained.

Numerical Study on the Effects of Gravity and Surface Tension on Condensation Process in Square Minichannel

NASA Astrophysics Data System (ADS)

Li, Panpan; Chen, Zhenqian; Shi, Juan

2018-02-01

A volume of fluid (VOF) method is adopted to simulate the condensation of R134a in a horizontal single square minichannel with 1 mm side length. The effect of gravity, surface tension and gas-liquid interfacial shear stress are taken into account. The result denotes that condensation is first appeared at the corner of channel, and then the condensation is stretched at the effect of surface tension until the whole channel boundary covered. The effect of gravity on the distribution of the liquid film depends on the channel length. In short channel, the gravity shows no significant effect, the distribution shape of steam in the cross section of the channel is approximately circular. In long channel, due to the influence of gravity, the liquid converges at the bottom under the effect of gravity, and the thickness of the liquid film at the bottom is obviously higher than that of the upper part of the channel. The effect of surface tension on condensation is also analysed. The surface tension can enhance the condensation heat transfer significantly when the inlet mass flux is low. Whilst, at high mass flux, the enhancement of surface tension on heat transfer is unobvious and can be neglected.

Tribology experiment in zero gravity

NASA Technical Reports Server (NTRS)

Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.

1984-01-01

A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates studies of the motion of liquid lubricants over solid surfaces as controlled by interfacial and capillary forces. Observations were made of phenomena associated with the liquid on one solid surface and also with the liquid between a pair of closely spaced surfaces. Typical photographic records obtained on Spacelab 1 are described.

Comparison of united-atom potentials for the simulation of vapor-liquid equilibria and interfacial properties of long-chain n-alkanes up to n-C100.

PubMed

Müller, Erich A; Mejía, Andrés

2011-11-10

Canonical ensemble molecular dynamics (MD) simulations are reported which compute both the vapor-liquid equilibrium properties (vapor pressure and liquid and vapor densities) and the interfacial properties (density profiles, interfacial tensions, entropy and enthalpy of surface formation) of four long-chained n-alkanes: n-decane (n-C(10)), n-eicosane (n-C(20)), n-hexacontane (n-C(60)), and n-decacontane (n-C(100)). Three of the most commonly employed united-atom (UA) force fields for alkanes (SKS: Smit, B.; Karaborni, S.; Siepmann, J. I. J. Chem. Phys. 1995,102, 2126-2140; J. Chem. Phys. 1998,109, 352; NERD: Nath, S. K.; Escobedo, F. A.; de Pablo, J. J. J. Chem. Phys. 1998, 108, 9905-9911; and TraPPE: Martin M. G.; Siepmann, J. I. J. Phys. Chem. B1998, 102, 2569-2577.) are critically appraised. The computed results have been compared to the available experimental data and those fitted using the square gradient theory (SGT). In the latter approach, the Lennard-Jones chain equation of state (EoS), appropriately parametrized for long hydrocarbons, is used to model the homogeneous bulk phase Helmholtz energy. The MD results for phase equilibria of n-decane and n-eicosane exhibit sensible agreement both to the experimental data and EoS correlation for all potentials tested, with the TraPPE potential showing the lowest deviations. However, as the molecular chain increases to n-hexacontane and n-decacontane, the reliability of the UA potentials decreases, showing notorious subpredictions of both saturated liquid density and vapor pressure. Based on the recommended data and EoS results for the heaviest hydrocarbons, it is possible to attest, that in this extreme, the TraPPE potential shows the lowest liquid density deviations. The low absolute values of the vapor pressure preclude the discrimination among the three UA potentials studied. On the other hand, interfacial properties are very sensitive to the type of UA potential thus allowing a differentiation of the potentials. Comparing the interfacial tension MD results to the available experimental data and SGT results, the TraPPE model exhibits the lowest deviations for all hydrocarbons.

Freezing point and solid-liquid interfacial free energy of Stockmayer dipolar fluids: a molecular dynamics simulation study.

PubMed

Wang, Jun; Apte, Pankaj A; Morris, James R; Zeng, Xiao Cheng

2013-09-21

Stockmayer fluids are a prototype model system for dipolar fluids. We have computed the freezing temperatures of Stockmayer fluids at zero pressure using three different molecular-dynamics simulation methods, namely, the superheating-undercooling method, the constant-pressure and constant-temperature two-phase coexistence method, and the constant-pressure and constant-enthalpy two-phase coexistence method. The best estimate of the freezing temperature (in reduced unit) for the Stockmayer (SM) fluid with the dimensionless dipole moment μ*=1, √2, √3 is 0.656 ± 0.001, 0.726 ± 0.002, and 0.835 ± 0.005, respectively. The freezing temperature increases with the dipolar strength. Moreover, for the first time, the solid-liquid interfacial free energies γ of the fcc (111), (110), and (100) interfaces are computed using two independent methods, namely, the cleaving-wall method and the interfacial fluctuation method. Both methods predict that the interfacial free energy increases with the dipole moment. Although the interfacial fluctuation method suggests a weaker interfacial anisotropy, particularly for strongly dipolar SM fluids, both methods predicted the same trend of interfacial anisotropy, i.e., γ100 > γ110 > γ111.

A surface physicochemical rationale for calculus formation in the oral cavity

NASA Astrophysics Data System (ADS)

Busscher, Henk J.; White, Don J.; Kamminga-Rasker, Hannetta J.; van der Mei, Henny C.

2004-01-01

Surface free energies of dental hard tissues, including salivary conditioning films on enamel, play a crucial role in mineralization, dissolution and adhesion processes at the tooth surface. These mineralization reactions at oral surfaces control the development and progression of various diseases. In this paper, we compare the surface free energies, as derived from measured contact angles with liquids, of salivary conditioning films on enamel after exposure to dentifrices with and without anti-calculus additives, such as hexametaphosphate, pyrophosphate or zinc citrate trihydrate. Measured contact angles were converted to surface free energies using the concept of Lifshitz-Van der Waals and Lewis acid-base components. Nearly all dentifrices yield film properties with a negative interfacial tension against an aqueous phase, which thermodynamically opposes mineralization. Concurrent with negative interfacial tensions, are positive values of the interfacial free energy of adhesion for octacalcium-phosphate (OCP) to the film surfaces, indicating that adhesion of newly mineralized, calcium-phosphate rich phases is thermodynamically unfavorable. Interestingly, two out of the three dentifrices with anti-calculus additives containing hexametaphosphate and pyrophosphate cause most positive interfacial free energies for OCP adhesion of 5.8 and 2.6 mJ/m 2, respectively. In summary, surface thermodynamical analyses indicate that anti-calculus effects of commercial dentifrice formulations are consistent with more negative interfacial tensions of salivary conditioning films on enamel surfaces and thus with more positive values for the interfacial free energy of adhesion toward newly formed mineral phases. A dentifrice containing hexametaphosphate yielded thermodynamic properties of salivary conditioning films most unfavorable for calculus formation.

Molecular dynamics analysis of a equilibrium nanoscale droplet on a solid surface with periodic roughness

NASA Astrophysics Data System (ADS)

Furuta, Yuma; Surblys, Donatas; Yamaguchi, Yastaka

2016-11-01

Molecular dynamics simulations of the equilibrium wetting behavior of hemi-cylindrical argon droplets on solid surfaces with a periodic roughness were carried out. The rough solid surface is located at the bottom of the calculation cell with periodic boundary conditions in surface lateral directions and mirror boundary condition at the top boundary. Similar to on a smooth surface, the change of the cosine of the droplet contact angle was linearly correlated to the potential well depth of the inter-atomic interaction between liquid and solid on a surface with a short roughness period while the correlation was deviated on one with a long roughness period. To further investigate this feature, solid-liquid, solid-vapor interfacial free energies per unit projected area of solid surface were evaluated by using the thermodynamic integration method in independent quasi-one-dimensional simulation systems with a liquid-solid interface or vapor-solid interface on various rough solid surfaces at a constant pressure. The cosine of the apparent contact angles estimated from the density profile of the droplet systems corresponded well with ones calculated from Young's equation using the interfacial energies evaluated in the quasi-one dimensional systems.

Numerical and experimental study of liquid breakup process in solid rocket motor nozzle

NASA Astrophysics Data System (ADS)

Yen, Yi-Hsin

Rocket propulsion is an important travel method for space exploration and national defense, rockets needs to be able to withstand wide range of operation environment and also stable and precise enough to carry sophisticated payload into orbit, those engineering requirement makes rocket becomes one of the state of the art industry. The rocket family have been classified into two major group of liquid and solid rocket based on the fuel phase of liquid or solid state. The solid rocket has the advantages of simple working mechanism, less maintenance and preparing procedure and higher storage safety, those characters of solid rocket make it becomes popular in aerospace industry. Aluminum based propellant is widely used in solid rocket motor (SRM) industry due to its avalibility, combusion performance and economical fuel option, however after aluminum react with oxidant of amonimum perchrate (AP), it will generate liquid phase alumina (Al2O3) as product in high temperature (2,700˜3,000 K) combustion chamber enviornment. The liquid phase alumina particles aggromorate inside combustion chamber into larger particle which becomes major erosion calprit on inner nozzle wall while alumina aggromorates impinge on the nozzle wall surface. The erosion mechanism result nozzle throat material removal, increase the performance optimized throat diameter and reduce nozzle exit to throat area ratio which leads to the reduction of exhaust gas velocity, Mach number and lower the propulsion thrust force. The approach to avoid particle erosion phenomenon taking place in SRM's nozzle is to reduce the alumina particle size inside combustion chamber which could be done by further breakup of the alumina droplet size in SRM's combustion chamber. The study of liquid breakup mechanism is an important means to smaller combustion chamber alumina droplet size and mitigate the erosion tack place on rocket nozzle region. In this study, a straight two phase air-water flow channel experiment is set up for liquid breakup phenomenon observation. The liquid water material in this experiment will play a comparison role as liquid alumina in high temerature enviornment. The method proposed to control the liquid breakup size of liquid droplet is done by the means of changing the liquid properties of surface tension. The surface tenion of liquid plays an inportant role of providing major liquid droplet bounding pressure or Laplace pressure. By reduceing surface tension of liquid leads to lower Laplace pressure of droplet and result in less droplet dynamic stability which could be breakup under external pressure difference. The reduction of surface tension of liquid aluminum could be achieved by adding magnisium and strontium, it is reported that the surface tension reeducation level could reach 10%˜15% when those additive mension above are adding to aluminum. This study of liquid breakup mechanism include two major part, first part is straight two-phase channel experiment and simulation comparison which provide a validation work of CFD simulation performance when compare to experiment. Second part is single droplet breakup experiment, in this experiment the relation of surface tension and liquid breakup behavior is carefully studied. The straight two-phase flow channel experiment setting will enable to us to study the liquid breakup process in macro scale. The quantification method is achieved by analyzing high-speed camera image by MatLab image process code develop in UW-Milwaukee wind tunnel lab which extract data in images and provide information including liquid droplet count and size distribution, wave frequency and time averaging two-phase free boundary. It was found that liquid breakup mechanism proportional to gas-droplet velocity difference square, gas density and liquid droplet size and inverse proportional to liquid surface tension. The single droplet experiment part is provide a close up view of liquid breakup and prove the reduced surface tension will enhance liquid breakup activity. In this study, we could observe the evidence of enhance liquid breakup activity by the reduced surface tension of liquid. Therefor the approach of reducing surface tension of Solid Rocket Motor (SRM) fuel reacting product is a high potential solution to SRM nozzle erosion.

Interfacial binding of cutinase rather than its catalytic activity determines the steady state interfacial tension during oil drop lipid hydrolysis.

PubMed

Flipsen, J A; van Schaick, M A; Dijkman, R; van der Hijden, H T; Verheij, H M; Egmond, M R

1999-02-01

Hydrolysis of triglycerides by cutinase from Fusarium solani pisi causes in oil drop tensiometer experiments a decrease of the interfacial tension. A series of cutinase variants with amino acid substitutions at its molecular surface yielded different values of the steady state interfacial tension. This tension value poorly correlated with the specific activity as such nor with the total activity (defined as the specific activity multiplied by the amount of enzyme bound) of the cutinase variants. Moreover, it appeared that at activity levels above 15% of that of wild type cutinase the contribution of hydrolysis to the decrease of the tension is saturating. A clear positive correlation was found between the interfacial tension plateau value and the interfacial binding of cutinase, as determined with attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR). These results indicate that the interfacial steady state level is not determined by the rate of hydrolysis, but mainly by the interfacial binding of cutinase.

Tuning Interfacial Properties and Processes by Controlling the Rheology and Structure of Poly( N-isopropylacrylamide) Particles at Air/Water Interfaces.

PubMed

Maestro, Armando; Jones, Daniel; Sánchez de Rojas Candela, Carmen; Guzman, Eduardo; Duits, Michel H G; Cicuta, Pietro

2018-06-05

By combining controlled experiments on single interfaces with measurements on solitary bubbles and liquid foams, we show that poly( N-isopropylacrylamide) (PNIPAM) microgels assembled at air/water interfaces exhibit a solid to liquid transition changing the temperature, and that this is associated with the change in the interfacial microstructure of the PNIPAM particles around their volume phase transition temperature. We show that the solid behaves as a soft 2D colloidal glass, and that the existence of this solid/liquid transition offers an ideal platform to tune the permeability of air bubbles covered by PNIPAM and to control macroscopic foam properties such as drainage, stability, and foamability. PNIPAM particles on fluid interfaces allow new tunable materials, for example foam structures with variable mechanical properties upon small temperature changes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martínez-Ruiz, F. J.; Blas, F. J., E-mail: felipe@uhu.es; Moreno-Ventas Bravo, A. I.

We determine the interfacial properties of a symmetrical binary mixture of equal-sized spherical Lennard-Jones molecules, σ{sub 11} = σ{sub 22}, with the same dispersive energy between like species, ϵ{sub 11} = ϵ{sub 22}, but different dispersive energies between unlike species low enough to induce phase separation. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 110, 6264 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] and Martínez-Ruiz et al. [J. Chem. Phys. 141, 184701 (2014)], to deal with the interaction energy and microscopic components ofmore » the pressure tensor. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of the symmetrical mixture with different cut-off distances r{sub c} and in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The liquid-liquid interfacial tension is also evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the test-area methodology. This allows to check the validity of the recent extensions presented to deal with the contributions due to long-range corrections for intermolecular energy and pressure tensor in the case of binary mixtures that exhibit liquid-liquid immiscibility. In addition to the pressure tensor and the surface tension, we also obtain density profiles and coexistence densities and compositions as functions of pressure, at a given temperature. According to our results, the main effect of increasing the cut-off distance r{sub c} is to sharpen the liquid-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative minimum in the total density profiles of the symmetrical mixture. This minimum is related with a desorption of the molecules at the interface, a direct consequence of a combination of the weak dispersive interactions between unlike species of the symmetrical binary mixture, and the presence of an interfacial region separating the two immiscible liquid phases in coexistence.« less

Water ball collision

NASA Technical Reports Server (NTRS)

Fujimoto, K.

1986-01-01

What happens if a stainless steel ball hits a water ball in the weightless space ot the Universe? In other words, it was the objective of our experiments in the Space to observe the surface tension of liquid by means of making a solid collide with a liquid. Place a small volume of water between 2 glass sheets to make a thin water membrane: the 2 glass sheets cannot be separated unless an enormous force is applied. It is obvious from this phenomenom that the surface tension of water is far greater than presumed. On Earth, however, it is impossible in most cases to observe only the surface tension of liquid, because gravity always acts on the surface tension. Water and stainless steel balls were chosen the liquid and solids for the experiments. Because water is the liquid most familiar to us, its properties are well known. And it is also of great interest to compare its properties on the Earth with those in the weightless space.

Recent developments in the kinetic theory of nucleation.

PubMed

Ruckenstein, E; Djikaev, Y S

2005-12-30

A review of recent progress in the kinetics of nucleation is presented. In the conventional approach to the kinetic theory of nucleation, it is necessary to know the free energy of formation of a new-phase particle as a function of its independent variables at least for near-critical particles. Thus the conventional kinetic theory of nucleation is based on the thermodynamics of the process. The thermodynamics of nucleation can be examined by using various approaches, such as the capillarity approximation, density functional theory, and molecular simulation, each of which has its own advantages and drawbacks. Relatively recently a new approach to the kinetics of nucleation was proposed [Ruckenstein E, Nowakowski B. J Colloid Interface Sci 1990;137:583; Nowakowski B, Ruckenstein E. J Chem Phys 1991;94:8487], which is based on molecular interactions and does not employ the traditional thermodynamics, thus avoiding such a controversial notion as the surface tension of tiny clusters involved in nucleation. In the new kinetic theory the rate of emission of molecules by a new-phase particle is determined with the help of a mean first passage time analysis. This time is calculated by solving the single-molecule master equation for the probability distribution function of a surface layer molecule moving in a potential field created by the rest of the cluster. The new theory was developed for both liquid-to-solid and vapor-to-liquid phase transitions. In the former case the single-molecule master equation is the Fokker-Planck equation in the phase space which can be reduced to the Smoluchowski equation owing to the hierarchy of characteristic time scales. In the latter case, the starting master equation is a Fokker-Planck equation for the probability distribution function of a surface layer molecule with respect to both its energy and phase coordinates. Unlike the case of liquid-to-solid nucleation, this Fokker-Planck equation cannot be reduced to the Smoluchowski equation, but the hierarchy of time scales does allow one to reduce it to the Fokker-Plank equation in the energy space. The new theory provides an equation for the critical radius of a new-phase particle which in the limit of large clusters (low supersaturations) yields the Kelvin equation and hence an expression for the macroscopic surface tension. The theory was illustrated with numerical calculations for a molecular pair interaction potential combining the dispersive attraction with the hard-sphere repulsion. The results for the liquid-to-solid nucleation clearly show that at given supersaturation the nucleation rate depends on the cluster structure (for three cluster structures considered-amorphous, fcc, and icosahedral). For both the liquid-to-solid and vapor-to-liquid nucleation, the predictions of the theory are consistent with the results of classical nucleation theory (CNT) in the limit of large critical clusters (low supersaturations). For small critical clusters the new theory provides higher nucleation rates than CNT. This can be accounted for by the fact that CNT uses the macroscopic interfacial tension which presumably overpredicts the surface tension of small clusters, and hence underpredicts nucleation rates.

Improving Attachments of Non-Invasive (Type III) Electronic Data Loggers to Cetaceans

DTIC Science & Technology

2011-09-30

Micro texturing of the suction cup to reduced leakage: Objective: Use microtexturing to create a superhydrophobic barrier between the lip and the...surface area of a solid, thereby amplifying the natural hydrophobicity of a surface. Superhydrophobicity is created by interfacial tension forces that

Solid-liquid work of adhesion of coarse-grained models of n-hexane on graphene layers derived from the conditional reversible work method.

PubMed

Ardham, Vikram Reddy; Deichmann, Gregor; van der Vegt, Nico F A; Leroy, Frédéric

2015-12-28

We address the question of how reducing the number of degrees of freedom modifies the interfacial thermodynamic properties of heterogeneous solid-liquid systems. We consider the example of n-hexane interacting with multi-layer graphene which we model both with fully atomistic and coarse-grained (CG) models. The CG models are obtained by means of the conditional reversible work (CRW) method. The interfacial thermodynamics of these models is characterized by the solid-liquid work of adhesion WSL calculated by means of the dry-surface methodology through molecular dynamics simulations. We find that the CRW potentials lead to values of WSL that are larger than the atomistic ones. Clear understanding of the relationship between the structure of n-hexane in the vicinity of the surface and WSL is elucidated through a detailed study of the energy and entropy components of WSL. We highlight the crucial role played by the solid-liquid energy fluctuations. Our approach suggests that CG potentials should be designed in such a way that they preserve the range of solid-liquid interaction energies, but also their fluctuations in order to preserve the reference atomistic value of WSL. Our study thus opens perspectives into deriving CG interaction potentials that preserve the thermodynamics of solid-liquid contacts and will find application in studies that intend to address materials driven by interfaces.

Analysis of the Effect of Water Activity on Ice Formation Using a New Theory of Nucleation

NASA Technical Reports Server (NTRS)

Barahona, Donifan

2013-01-01

In this work a new theory of nucleation is developed and used to investigate the effect of water activity on the formation of ice within super-cooled droplets. The new theory is based on a novel concept where the interface is assumed to be made of liquid molecules trapped by the solid matrix. Using this concept new expressions are developed for the critical ice germ size and the nucleation work, with explicit dependencies on temperature and water activity. However unlike previous approaches, the new theory does not depend on the interfacial tension between liquid and ice. Comparison against experimental results shows that the new theory is able to reproduce the observed effect of water activity on nucleation rate and freezing temperature. It allows for the first time a theoretical derivation of the constant shift in water activity between melting and nucleation. The new theory offers a consistent thermodynamic view of ice nucleation, simple enough to be applied in atmospheric models of cloud formation.

Fluoroalkylated Silicon-Containing Surfaces - Estimation of Solid Surface Energy

DTIC Science & Technology

2010-10-20

surface tension liquids such as octane (γlv = 21.6 mN/m) and methanol (γlv = 22.7 mN/m), requires an appropriately chosen surface micro/nano-texture in...addition to a low solid surface energy (γsv). 1H,1H,2H,2H- Heptadecafluorodecyl polyhedral oligomeric silsesquioxane (fluorodecyl POSS) offers one of...27.5 mN/m), while Girifalco-Good analysis was performed using a set of polar and non-polar liquids with a wider range of liquid surface tension (15.5

Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.

PubMed

Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando

2015-10-21

The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties.

POISON SPIDER FIELD CHEMICAL FLOOD PROJECT, WYOMING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Douglas Arnell; Malcolm Pitts; Jie Qi

2004-11-01

A reservoir engineering and geologic study concluded that approximate 7,852,000 bbls of target oil exits in Poison Spider. Field pore volume, OOIP, and initial oil saturation are defined. Potential injection water has a total dissolved solids content of 1,275 mg/L with no measurable divalent cations. If the Lakota water consistently has no measurable cations, the injection water does not require softening to dissolve alkali. Produced water total dissolved solids were 2,835 mg/L and less than 20 mg/L hardness as the sum of divalent cations. Produced water requires softening to dissolve chemicals. Softened produced water was used to dissolve chemicals inmore » these evaluations. Crude oil API gravity varies across the field from 19.7 to 22.2 degrees with a dead oil viscosity of 95 to 280 cp at 75 F. Interfacial tension reductions of up to 21,025 fold (0.001 dyne/cm) were developed with fifteen alkaline-surfactant combinations at some alkali concentration. An additional three alkaline-surfactant combinations reduced the interfacial tension greater than 5,000 fold. NaOH generally produced the lowest interfacial tension values. Interfacial tension values of less than 0.021 dyne/cm were maintained when the solutions were diluted with produced water to about 60%. Na{sub 2}CO{sub 3} when mixed with surfactants did not reduce interfacial tension values to levels at which incremental oil can be expected. NaOH without surfactant interfacial tension reduction is at a level where some additional oil might be recovered. Most of the alkaline-surfactant-polymer solutions producing ultra low interfacial tension gave type II- phase behavior. Only two solutions produced type III phase behavior. Produced water dilution resulted in maintenance of phase type for a number of solutions at produced water dilutions exceeding 80% dilution. The average loss of phase type occurred at 80% dilution. Linear corefloods were performed to determine relative permeability end points, chemical-rock compatibility, polymer injectivity, dynamic chemical retention by rock, and recommended injected polymer concentration. Average initial oil saturation was 0.796 Vp. Produced water injection recovered 53% OOIP leaving an average residual oil saturation of 0.375 Vp. Poison Spider rock was strongly water-wet with a mobility ratio for produced water displacing the 280 cp crude oil of 8.6. Core was not sensitive to either alkali or surfactant injection. Injectivity increased 60 to 80% with alkali plus surfactant injection. Low and medium molecular weight polyacrylamide polymers (Flopaam 3330S and Flopaam 3430S) dissolved in either an alkaline-surfactant solution or softened produced water injected and flowed through Poison Spider rock. Recommended injected polyacrylamide concentration is 2,100 mg/L for both polymers for a unit mobility ratio. Radial corefloods were performed to evaluate oil recovery efficiency of different chemical solutions. Waterflood oil recovery averaged 46.4 OOIP and alkaline-surfactant-polymer flood oil recovery averaged an additional 18.1% OIP for a total of 64.6% OOIP. Oil cut change due to injection of a 1.5 wt% Na{sub 2}CO{sub 3} plus 0.05 wt% Petrostep B-100 plus 0.05 wt% Stepantan AS1216 plus 2100 mg/L Flopaam 3430S was from 2% to a peak of 23.5%. Additional study might determine the impact on oil recovery of a lower polymer concentration. An alkaline-surfactant-polymer flood field implementation outline report was written.« less

A phase-field approach to nonequilibrium phase transformations in elastic solids via an intermediate phase (melt) allowing for interface stresses.

PubMed

Momeni, Kasra; Levitas, Valery I

2016-04-28

A phase-field approach for phase transformations (PTs) between three different phases at nonequilibrium temperatures is developed. It includes advanced mechanics, thermodynamically consistent interfacial stresses, and interface interactions. A thermodynamic Landau-Ginzburg potential developed in terms of polar order parameters satisfies the desired instability and equilibrium conditions for homogeneous phases. The interfacial stresses were introduced with some terms from large-strain formulation even though the small-strain assumption was utilized. The developed model is applied to study the PTs between two solid phases via a highly disordered intermediate phase (IP) or an intermediate melt (IM) hundreds of degrees below the melting temperature. In particular, the β ↔ δ PTs in HMX energetic crystals via IM are analyzed. The effects of various parameters (temperature, ratios of widths and energies of solid-solid (SS) to solid-melt (SM) interfaces, elastic energy, and interfacial stresses) on the formation, stability, and structure of the IM within a propagating SS interface are studied. Interfacial and elastic stresses within a SS interphase and their relaxation and redistribution with the appearance of a partial or complete IM are analyzed. The energy and structure of the critical nucleus (CN) of the IM are studied as well. In particular, the interfacial stresses increase the aspect-ratio of the CN. Although including elastic energy can drastically reduce the energy of the CN of the IM, the activation energy of the CN of the IM within the SS interface increases when interfacial tension is taken into account. The developed thermodynamic potential can also be modified to model other multiphase physical phenomena, such as multi-variant martensitic PTs, grain boundary and surface-induced pre-melting and PTs, as well as developing phase diagrams for IPs.

Solid liquid interfacial free energies of benzene

NASA Astrophysics Data System (ADS)

Azreg-Aı¨nou, M.

2007-02-01

In this work we determine for the range of melting temperatures 284.6⩽T⩽306.7 K, corresponding to equilibrium pressures 20.6⩽P⩽102.9 MPa, the benzene solid-liquid interfacial free energy by a cognitive approach including theoretical and experimental physics, mathematics, computer algebra (MATLAB), and some results from molecular dynamics computer simulations. From a theoretical and mathematical points of view, we deal with the elaboration of an analytical expression for the internal energy derived from a unified solid-liquid-vapor equation of state and with the elaboration of an existing statistical model for the entropy drop of the melt near the solid-liquid interface. From an experimental point of view, we will use our results obtained in collaboration with colleagues concerning the supercooled liquid benzene. Of particular interest for this work is the existing center-of-mass radial distribution function of benzene at 298 K obtained by computer simulation. Crystal-orientation-independent and minimum interfacial free energies are calculated and shown to increase slightly with the above temperatures. Both crystal-orientation-independent and minimum free energies agree with existing calculations and with rare existing experimental data. Taking into account the fact that the extent of supercooling is generally admitted as a constant, we determine the limits of supercooling by which we explore the behavior of the critical nucleus radius which is shown to decrease in terms of the above temperatures. The radius of the, and the number of molecules per, critical nucleus are shown to assume the average values of 20.2 A˚ and 175 with standard deviations of 0.16 Å and 4.5, respectively.

Liquid phase stabilization versus bubble formation at a nanoscale curved interface

NASA Astrophysics Data System (ADS)

Schiffbauer, Jarrod; Luo, Tengfei

2018-03-01

We investigate the nature of vapor bubble formation near a nanoscale-curved convex liquid-solid interface using two models: an equilibrium Gibbs model for homogenous nucleation, and a nonequilibrium dynamic van der Waals-diffuse-interface model for phase change in an initially cool liquid. Vapor bubble formation is shown to occur for sufficiently large radius of curvature and is suppressed for smaller radii. Solid-fluid interactions are accounted for and it is shown that liquid-vapor interfacial energy, and hence Laplace pressure, has limited influence over bubble formation. The dominant factor is the energetic cost of creating the solid-vapor interface from the existing solid-liquid interface, as demonstrated via both equilibrium and nonequilibrium arguments.

Specific interface area in a thin layer system of two immiscible liquids with vapour generation at the contact interface

NASA Astrophysics Data System (ADS)

Pimenova, Anastasiya V.; Gazdaliev, Ilias M.; Goldobin, Denis S.

2017-06-01

For well-stirred multiphase fluid systems the mean interface area per unit volume, or “specific interface area” SV, is a significant characteristic of the system state. In particular, it is important for the dynamics of systems of immiscible liquids experiencing interfacial boiling. We estimate the value of parameter SV as a function of the heat influx {\\dot{Q}}V to the system or the average system overheat <Θ> above the interfacial boiling point. The derived results can be reformulated for the case of an endothermic chemical reaction between two liquid reagents with the gaseous form of one of the reaction products. The final results are restricted to the case of thin layers, where the potential gravitational energy of bubbles leaving the contact interface is small compared to their surface tension energy.

How faceted liquid droplets grow tails: from surface topology to active motion

NASA Astrophysics Data System (ADS)

Sloutskin, Eli

Among all possible shapes of a volume V, a sphere has the smallest surface area A. Therefore, liquid droplets are spherical, minimizing their interfacial energy γA for a given interfacial tension γ > 0 . This talk will demonstrate that liquid oil (alkane) droplets in water, stabilized by a common surfactant can be temperature-tuned to adopt icosahedral and other faceted shapes, above the bulk melting temperature of the oil. Although emulsions have been studied for centuries no faceted liquid droplets have ever been reported. The formation of an icosahedral shape is attributed to the interplay between γ and the elastic properties of the interfacial monomolecular layer, which crystallizes here 10-15K above bulk melting, leaving the droplet's bulk liquid. The icosahedral symmetry is dictated by twelve five-fold topological defects, forming within the hexagonally-packed interfacial crystalline monolayer. Moreover, we demonstrate that upon further cooling this `interfacial freezing' effect makes γ transiently switch its sign, leading to a spontaneous splitting of droplets and an active growth of their surface area, reminiscent of the classical spontaneous emulsification, yet driven by completely different physics. The observed phenomena allow deeper insights to be gained into the fundamentals of molecular elasticity and open new vitas for a wide range of novel nanotechnological applications, from self-assembly of complex shapes to new delivery strategies in bio-medicine. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for support of this research and to the Kahn Foundation for the purchase of equipment.

Density functional theory of gas-liquid phase separation in dilute binary mixtures

NASA Astrophysics Data System (ADS)

Okamoto, Ryuichi; Onuki, Akira

2016-06-01

We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference of the solvation chemical potential between liquid and gas Δ {μ\\text{s}} (the Gibbs energy of transfer) is considerably larger than the thermal energy {{k}\\text{B}}T for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by {{k}\\text{B}}Tn2\\ell\\exp ≤ft(Δ {μ\\text{s}}/{{k}\\text{B}}T\\right) , where n2\\ell is the solute density added in liquid. For \\exp ≤ft(Δ {μ\\text{s}}/{{k}\\text{B}}T\\right)\\gg 1 , phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, even when the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor.

The Dissolution of an Interfween Miscible Liquids

NASA Technical Reports Server (NTRS)

Vlad, D.H.; Maher, J.V.

1999-01-01

The disappearance of the surface tension of the interface of a binary mixture, measured using the dynamic surface light scattering technique, is slower for a binary mixture of higher density contrast. A comparison with a naive diffusion model, expected to provide a lower limit for the speed of dissolution in the absence of gravity shows that the interfacial surface tension disappears much slower than even by diffusion with the effect becoming much more pronounced when density contrast between the liquid phases is increased. Thus, the factor most likely to be responsible for this anomalously slow dissolution is gravity. A mechanism could be based on the competition between diffusive relaxation and sedimentation at the dissolving interface.

Solid-liquid work of adhesion of coarse-grained models of n-hexane on graphene layers derived from the conditional reversible work method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ardham, Vikram Reddy; Leroy, Frédéric, E-mail: vandervegt@csi.tu-darmstadt.de, E-mail: f.leroy@theo.chemie.tu-darmstadt.de; Deichmann, Gregor

We address the question of how reducing the number of degrees of freedom modifies the interfacial thermodynamic properties of heterogeneous solid-liquid systems. We consider the example of n-hexane interacting with multi-layer graphene which we model both with fully atomistic and coarse-grained (CG) models. The CG models are obtained by means of the conditional reversible work (CRW) method. The interfacial thermodynamics of these models is characterized by the solid-liquid work of adhesion W{sub SL} calculated by means of the dry-surface methodology through molecular dynamics simulations. We find that the CRW potentials lead to values of W{sub SL} that are larger thanmore » the atomistic ones. Clear understanding of the relationship between the structure of n-hexane in the vicinity of the surface and W{sub SL} is elucidated through a detailed study of the energy and entropy components of W{sub SL}. We highlight the crucial role played by the solid-liquid energy fluctuations. Our approach suggests that CG potentials should be designed in such a way that they preserve the range of solid-liquid interaction energies, but also their fluctuations in order to preserve the reference atomistic value of W{sub SL}. Our study thus opens perspectives into deriving CG interaction potentials that preserve the thermodynamics of solid-liquid contacts and will find application in studies that intend to address materials driven by interfaces.« less

Pattern formation during healing of fluid-filled cracks: an analog experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

F. Renard; D. K. Dysthe; J. G. Feder

2009-11-01

The formation and subsequent healing of cracks and crack networks may control such diverse phenomena as the strengthening of fault zones between earthquakes, fluid migrations in the Earth's crust, or the transport of radioactive materials in nuclear waste disposal. An intriguing pattern-forming process can develop during healing of fluid-filled cracks, where pockets of fluid remain permanently trapped in the solid as the crack tip is displaced driven by surface energy. Here, we present the results of analog experiments in which a liquid was injected into a colloidal inorganic gel to obtain penny-shaped cracks that were subsequently allowed to close andmore » heal under the driving effect of interfacial tension. Depending on the properties of the gel and the injected liquid, two modes of healing were obtained. In the first mode, the crack healed completely through a continuous process. The second mode of healing was discontinuous and was characterized by a 'zipper-like' closure of a front that moved along the crack perimeter, trapping fluid that may eventually form inclusions trapped in the solid. This instability occurred only when the velocity of the crack tip decreased to zero. Our experiments provide a cheap and simple analog to reveal how aligned arrays of fluid inclusions may be captured along preexisting fracture planes and how small amounts of fluids can be permanently trapped in solids, modifying irreversibly their material properties.« less

Interfacial free energy of the NaCl crystal-melt interface from capillary wave fluctuations.

PubMed

Benet, Jorge; MacDowell, Luis G; Sanz, Eduardo

2015-04-07

In this work we study, by means of molecular dynamics simulations, the solid-liquid interface of NaCl under coexistence conditions. By analysing capillary waves, we obtain the stiffness for different orientations of the solid and calculate the interfacial free energy by expanding the dependency of the interfacial free energy with the solid orientation in terms of cubic harmonics. We obtain an average value for the solid-fluid interfacial free energy of 89 ± 6 mN m(-1) that is consistent with previous results based on the measure of nucleation free energy barriers [Valeriani et al., J. Chem. Phys. 122, 194501 (2005)]. We analyse the influence of the simulation setup on interfacial properties and find that facets prepared as an elongated rectangular stripe give the same results as those prepared as squares for all cases but the 111 face. For some crystal orientations, we observe at small wave-vectors a behaviour not consistent with capillary wave theory and show that this behavior does not depend on the simulation setup.

Bio-dispersive liquid liquid microextraction based on nano rhaminolipid aggregates combined with magnetic solid phase extraction using Fe3O4@PPy magnetic nanoparticles for the determination of methamphetamine in human urine.

PubMed

Haeri, Seyed Ammar; Abbasi, Shahryar; Sajjadifar, Sami

2017-09-15

In the present investigation, extraction and preconcentration of methamphetamine in human urine samples was carried out using a novel bio-dispersive liquid liquid microextraction (Bio-DLLME) technique coupled with magnetic solid phase extraction (MSPE). Bio-DLLME is a kind of microextraction technique based nano-materials which have potential capabilities in many application fields. Bio-DLLME is based on the use of a binary part system consisting of methanol and nano rhaminolipid biosurfactant. Use of this binary mixture is ecologically accepted due to their specificity, biocompatibility and biodegradable nature. The potential of nano rhaminolipid biosurfactant as a biological agent in the extraction of organic compounds has been investigated in recent years. They are able to partition at the oil/water interfaces and reduce the interfacial tension in order to increase solubility of hydrocarbons. The properties of the prepared Fe 3 O 4 @PPy magnetic nanoparticles were characterized using Fourier transform infrared spectroscopy and X-ray diffraction methods The influences of the experimental parameters on the quantitative recovery of analyte were investigated. Under optimized conditions, the enrichment factor was 310, the calibration graph was linear in the methamphetamine concentration range from 1 to 60μgL -1 , with a correlation coefficient of 0.9998. The relative standard deviations for six replicate measurements was 5.2%. Copyright © 2017 Elsevier B.V. All rights reserved.

On interfacial properties of tetrahydrofuran: Atomistic and coarse-grained models from molecular dynamics simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrido, J. M.; Algaba, J.; Blas, F. J., E-mail: felipe@uhu.es

2016-04-14

We have determined the interfacial properties of tetrahydrofuran (THF) from direct simulation of the vapor-liquid interface. The molecules are modeled using six different molecular models, three of them based on the united-atom approach and the other three based on a coarse-grained (CG) approach. In the first case, THF is modeled using the transferable parameters potential functions approach proposed by Chandrasekhar and Jorgensen [J. Chem. Phys. 77, 5073 (1982)] and a new parametrization of the TraPPE force fields for cyclic alkanes and ethers [S. J. Keasler et al., J. Phys. Chem. B 115, 11234 (2012)]. In both cases, dispersive and coulombicmore » intermolecular interactions are explicitly taken into account. In the second case, THF is modeled as a single sphere, a diatomic molecule, and a ring formed from three Mie monomers according to the SAFT-γ Mie top-down approach [V. Papaioannou et al., J. Chem. Phys. 140, 054107 (2014)]. Simulations were performed in the molecular dynamics canonical ensemble and the vapor-liquid surface tension is evaluated from the normal and tangential components of the pressure tensor along the simulation box. In addition to the surface tension, we have also obtained density profiles, coexistence densities, critical temperature, density, and pressure, and interfacial thickness as functions of temperature, paying special attention to the comparison between the estimations obtained from different models and literature experimental data. The simulation results obtained from the three CG models as described by the SAFT-γ Mie approach are able to predict accurately the vapor-liquid phase envelope of THF, in excellent agreement with estimations obtained from TraPPE model and experimental data in the whole range of coexistence. However, Chandrasekhar and Jorgensen model presents significant deviations from experimental results. We also compare the predictions for surface tension as obtained from simulation results for all the models with experimental data. The three CG models predict reasonably well (but only qualitatively) the surface tension of THF, as a function of temperature, from the triple point to the critical temperature. On the other hand, only the TraPPE united-atoms models are able to predict accurately the experimental surface tension of the system in the whole temperature range.« less

Protected Lithium-Metal Anodes in Batteries: From Liquid to Solid.

PubMed

Yang, Chunpeng; Fu, Kun; Zhang, Ying; Hitz, Emily; Hu, Liangbing

2017-09-01

High-energy lithium-metal batteries are among the most promising candidates for next-generation energy storage systems. With a high specific capacity and a low reduction potential, the Li-metal anode has attracted extensive interest for decades. Dendritic Li formation, uncontrolled interfacial reactions, and huge volume effect are major hurdles to the commercial application of Li-metal anodes. Recent studies have shown that the performance and safety of Li-metal anodes can be significantly improved via organic electrolyte modification, Li-metal interface protection, Li-electrode framework design, separator coating, and so on. Superior to the liquid electrolytes, solid-state electrolytes are considered able to inhibit problematic Li dendrites and build safe solid Li-metal batteries. Inspired by the bright prospects of solid Li-metal batteries, increasing efforts have been devoted to overcoming the obstacles of solid Li-metal batteries, such as low ionic conductivity of the electrolyte and Li-electrolyte interfacial problems. Here, the approaches to protect Li-metal anodes from liquid batteries to solid-state batteries are outlined and analyzed in detail. Perspectives regarding the strategies for developing Li-metal anodes are discussed to facilitate the practical application of Li-metal batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Drop impact onto a thin film: Miscibility effect

NASA Astrophysics Data System (ADS)

Chen, Ningli; Chen, H.; Amirfazli, A.

2017-09-01

In this work a systematic experimental study was performed to understand the process of liquid drop impact onto a thin film made of a different liquid from drop. The drop and film liquids can be miscible or immiscible. Three general outcomes of deposition, crown formation without splashing, and splashing, were observed in the advancing phase of the drop impact onto a solid surface covered by either a miscible or an immiscible thin film. However, for a miscible film, a larger Weber number and film thickness are needed for the formation of a crown and splashing comparing with immiscible cases. The advancing phase of drop impact onto a thin immiscible film with a large viscosity is similar to that of drop impact onto a dry surface; for a miscible film viscous film, the behavior is far from that of a dry surface. The behavior of liquid lamella in the receding phase of drop impact onto a thin miscible film is reported for the first time. The results show that immiscibility is not a necessary condition for the existence of a receding phase. The existence of a receding phase is highly dependent on the interfacial tension between the drop and the film. The miscibility can significantly affect the receding morphology as it will cause mixing of the two liquids.

Project Description and Publications List for UAH CMMR

NASA Technical Reports Server (NTRS)

Kaukler, William F.

1999-01-01

This research combines a state of the art X-ray Transmission Microscope, XTM, with a specially designed x-ray transparent horizontal Bridgman furnace to image (with resolutions up to 3 micrometers) the solidification of metal alloys in real-time. The objective is to obtain real-time dynamic data to provide direct measure of the solute profile in the liquid, phase coalescence and growth in the liquid, and the detailed interface morphology (e,g., dendrites and cells) during solidification. We are also enhancing the XTM data with precise solid-liquid interfacial temperature and the thermal gradient measurement techniques, and working on the application of this technology to the study of the fundamentals of solidification in microgravity. Over the last several years we have successfully imaged in real-time: interfacial-morphologies, phase growth, coalescence, incorporation of phases into the growing interface, and the solute boundary layer in the liquid at the solid-liquid interface. We have also measured true local growth rates and can evaluate segregation structures in the solid. Interfacial undercoolings are being measured either with a special Seebeck furnace or with micro-thermocouple arrays we are developing. These later techniques are presently being incorporated with the XTM furnace. This last year emphasized the investigation of the solute layer in the melt during solidification. Methods were developed to quantify the solute concentrations using x-ray absorption and to compare to predictions from simulations. In addition, work is being completed on a brass-board portable XTM that incorporates a vertical Bridgman furnace.

Interfacial layering and capillary roughness in immiscible liquids.

PubMed

Geysermans, P; Pontikis, V

2010-08-21

The capillary roughness and the atomic density profiles of extended interfaces between immiscible liquids are determined as a function of the interface area by using molecular dynamics and Lennard-Jones (12-6) potentials. We found that with increasing area, the interface roughness diverges logarithmically, thus fitting the theoretical mean-field prediction. In systems small enough for the interfacial roughness not to blur the structural details, atomic density profiles across the fluid interface are layered with correlation length in the range of molecular correlations in liquids. On increasing the system size, the amplitude of the thermally excited position fluctuations of the interface increases, thus causing layering to rapidly vanish, if density profiles are computed without special care. In this work, we present and validate a simple method, operating in the direct space, for extracting from molecular dynamics trajectories the "intrinsic" structure of a fluid interface that is the local density profile of the interface cleaned from capillary wave effects. Estimated values of interfacial properties such as the tension, the intrinsic width, and the lower wavelength limit of position fluctuations are in agreement with results collected from the literature.

Contact Angle of Drops Measured on Nontransparent Surfaces and Capillary Flow Visualized

NASA Technical Reports Server (NTRS)

Chao, David F.; Zhang, Nengli

2003-01-01

The spreading of a liquid on a solid surface is important for various practical processes, and contact-angle measurements provide an elegant method to characterize the interfacial properties of the liquid with the solid substrates. The complex physical processes occurring when a liquid contacts a solid play an important role in determining the performance of chemical processes and materials. Applications for these processes are in printing, coating, gluing, textile dyeing, and adhesives and in the pharmaceutical industry, biomedical research, adhesives, flat panel display manufacturing, surfactant chemistry, and thermal engineering.

Predicting CO2-H2O Interfacial Tension Using COSMO-RS.

PubMed

Silvestri, A; Stipp, S L S; Andersson, M P

2017-02-14

Knowledge about the interaction between fluids and solids and the interfacial tension (IFT) that results is important for predicting behavior and properties in industrial systems and in nature, such as in rock formations before, during, and after CO 2 injection for long-term storage. Many authors have studied the effect of the environmental variables on the IFT in the CO 2 -H 2 O system. However, experimental measurements above CO 2 supercritical conditions are scarce and sometimes contradictory. Molecular modeling is a valuable tool for complementing experimental IFT determination, and it can help us interpret results and gain insight under conditions where experiments are difficult or impossible. Here, we report predictions for CO 2 -water interfacial tension performed using density functional theory (DFT) combined with the COSMO-RS implicit solvent model. We predicted the IFT dependence as a function of pressure (0-50 MPa), temperature (273-383 K), and salinity (0-5 M NaCl). The results agree well with literature data, within the estimated uncertainty for experiments and for molecular dynamics (MD) simulations, suggesting that the model can be used as a fast alternative to time-consuming computational approaches for predicting the CO 2 -water IFT over a range of pressures, temperatures, and salinities.

Role of adsorption in liquid lubrication

NASA Technical Reports Server (NTRS)

Groszek, A. J.

1973-01-01

Changes at solid-liquid interfaces caused by adsorption from solution are discussed paying attention to the following aspects: (1) stability of adsorbed films and the structure of metal-additive-film-liquid interface and effect of adsorbate orientation. (2) chemical versus physical adsorption, (3) heat of adsorption, (4) adsorption of additives, (5) activated adsorption, effect of activating adsorbates, (6) displacement phenomena at solid-liquid interfaces, (7) competition of antiwear additives, their solvents, and water, (8) effect of adsorption on the orientation of liquid in the interfacial region, and (9) relation between the chemical nature of solid surfaces and their interaction with liquid lubricants. The relevance of the above adsorption phenomena to lubrication is discussed, referring where possible to specific examples.

Interpreting contact angle results under air, water and oil for the same surfaces

NASA Astrophysics Data System (ADS)

Ozkan, Orkun; Yildirim Erbil, H.

2017-06-01

Under-water and under-oil superhydropobicity and superhydrophilicity have gained significant attention over the last few years. In this study, contact angles on five flat surfaces (polypropylene, poly(methyl methacrylate), polycarbonate, TEFLON-FEP and glass slide) were measured in water drop-in-air, air bubble-under-water, oil drop-in-air, air bubble-under-oil, oil drop-under-water and water drop-under-oil conditions. Heptane, octane, nonane, decane, dodecane, and hexadecane hydrocarbons were used as oils. Immiscible water/oil pairs were previously mutually saturated to provide thermodynamical equilibrium conditions and their surface and interfacial tensions were determined experimentally. These pairs were used in the two-liquid contact angle measurements. Surface free energies of the solid surfaces in air were determined independently by using the van Oss-Good method, using the contact angle results of pure water, ethylene glycol, formamide, methylene iodide and α-bromonaphalene. In addition, Zisman’s ‘critical surface tension’ values were also determined for comparison. In theory, the summation of contact angle results in a complementary case would give a total of 180° for ideal surfaces. However, it was determined that there are large deviations from this rule in practical cases and these deviations depend on surface free energies of solids. Three complementary cases of (water-in-air with air bubble-under-water); (oil-in-air with air bubble-under-oil); and (oil-under-water with water-under-oil) were investigated in particular to determine the deviations from ideality. A novel approach, named ‘complementary hysteresis’ [γ WA(cosθ 1  -  cosθ 2) and γ OW(cosθ 6  -  cosθ 5)] was developed where γ WA and γ OW represent the interfacial tensions of water/air and oil/water, and θ 1, θ 2, θ 5, and θ 6 were the contact angles of water/air, air bubble/water, oil/water and water/oil respectively. It was experimentally determined that complementary hysteresis varies almost linearly with the surface free energy of the flat solid samples. This is the first report showing the relation of the surface free energy of a solid which is determined under-air with the contact angles obtained on the same solid in different three-phase systems.

Corresponding-states behavior of a dipolar model fluid with variable dispersion interactions and its relevance to the anomalies of hydrogen fluoride

NASA Astrophysics Data System (ADS)

Weiss, Volker C.; Leroy, Frédéric

2016-06-01

More than two decades ago, the elusiveness of a liquid-vapor equilibrium and a corresponding critical point in simulations of the supposedly simple model of dipolar hard spheres came as a surprise to many liquid matter theorists. van Leeuwen and Smit [Phys. Rev. Lett. 71, 3991 (1993)] showed that a minimum of attractive dispersion interactions among the dipolar particles may be needed to observe regular fluid behavior. Here, we adopt their approach and use an only slightly modified model, in which the original point dipole is replaced by a dipole moment produced by charges that are separated in space, to study the influence of dispersion interactions of variable strength on the coexistence and interfacial properties of a polar fluid. The thermophysical properties are discussed in terms of Guggenheim's corresponding-states approach. In this way, the coexistence curve, the critical compressibility factor, the surface tension, Guggenheim's ratio, and modifications of Guldberg's and Trouton's rules (related to the vapor pressure and the enthalpy of vaporization) are analyzed. As the importance of dispersion is decreased, a crossover from simple-fluid behavior to that characteristic of strongly dipolar systems takes place; for some properties, this transition is monotonic, but for others it occurs non-monotonically. For strongly dipolar systems, the reduced surface tension is very low, whereas Guggenheim's ratio and Guldberg's ratio are found to be high. The critical compressibility factor is smaller, and the coexistence curve is wider and more skewed than for simple fluids. For very weak dispersion, liquid-vapor equilibrium is still observable, but the interfacial tension is extremely low and may, eventually, vanish marking the end of the existence of a liquid phase. We discuss the implications of our findings for real fluids, in particular, for hydrogen fluoride.

Mobile interfaces: Liquids as a perfect structural material for multifunctional, antifouling surfaces

DOE PAGES

Grinthal, Alison; Aizenberg, Joanna

2013-10-14

Life creates some of its most robust, extreme surface materials not from solids but from liquids: a purely liquid interface, stabilized by underlying nanotexture, makes carnivorous plant leaves ultraslippery, the eye optically perfect and dirt-resistant, our knees lubricated and pressure-tolerant, and insect feet reversibly adhesive and shape-adaptive. Novel liquid surfaces based on this idea have recently been shown to display unprecedented omniphobic, self-healing, anti-ice, antifouling, optical, and adaptive properties. In this Perspective, we present a framework and a path forward for developing and designing such liquid surfaces into sophisticated, versatile multifunctional materials. Drawing on concepts from solid materials design andmore » fluid dynamics, we outline how the continuous dynamics, responsiveness, and multiscale patternability of a liquid surface layer can be harnessed to create a wide range of unique, active interfacial functions-able to operate in harsh, changing environments-not achievable with static solids. We discuss how, in partnership with the underlying substrate, the liquid surface can be programmed to adaptively and reversibly reconfigure from a defect-free, molecularly smooth, transparent interface through a range of finely tuned liquid topographies in response to environmental stimuli. In conclusion, with nearly unlimited design possibilities and unmatched interfacial properties, liquid materials-as long-term stable interfaces yet in their fully liquid state-may potentially transform surface design everywhere from medicine to architecture to energy infrastructure.« less

Adsorption of the natural protein surfactant Rsn-2 onto liquid interfaces.

PubMed

Brandani, Giovanni B; Vance, Steven J; Schor, Marieke; Cooper, Alan; Kennedy, Malcolm W; Smith, Brian O; MacPhee, Cait E; Cheung, David L

2017-03-22

To stabilize foams, droplets and films at liquid interfaces a range of protein biosurfactants have evolved in nature. Compared to synthetic surfactants, these combine surface activity with biocompatibility and low solution aggregation. One recently studied example is Rsn-2, a component of the foam nest of the frog Engystomops pustulosus, which has been predicted to undergo a clamshell-like opening transition at the air-water interface. Using atomistic molecular dynamics simulations and surface tension measurements we study the adsorption of Rsn-2 onto air-water and cyclohexane-water interfaces. The protein adsorbs readily at both interfaces, with adsorption mediated by the hydrophobic N-terminus. At the cyclohexane-water interface the clamshell opens, due to the favourable interaction between hydrophobic residues and cyclohexane molecules and the penetration of cyclohexane molecules into the protein core. Simulations of deletion mutants showed that removal of the N-terminus inhibits interfacial adsorption, which is consistent with the surface tension measurements. Deletion of the hydrophilic C-terminus also affects adsorption, suggesting that this plays a role in orienting the protein at the interface. The characterisation of the interfacial behaviour gives insight into the factors that control the interfacial adsorption of proteins, which may inform new applications of this and similar proteins in areas including drug delivery and food technology and may also be used in the design of synthetic molecules showing similar changes in conformation at interfaces.

Development of DPD coarse-grained models: From bulk to interfacial properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solano Canchaya, José G.; Dequidt, Alain, E-mail: alain.dequidt@univ-bpclermont.fr; Goujon, Florent

2016-08-07

A new Bayesian method was recently introduced for developing coarse-grain (CG) force fields for molecular dynamics. The CG models designed for dissipative particle dynamics (DPD) are optimized based on trajectory matching. Here we extend this method to improve transferability across thermodynamic conditions. We demonstrate the capability of the method by developing a CG model of n-pentane from constant-NPT atomistic simulations of bulk liquid phases and we apply the CG-DPD model to the calculation of the surface tension of the liquid-vapor interface over a large range of temperatures. The coexisting densities, vapor pressures, and surface tensions calculated with different CG andmore » atomistic models are compared to experiments. Depending on the database used for the development of the potentials, it is possible to build a CG model which performs very well in the reproduction of the surface tension on the orthobaric curve.« less

DETERMINING EFFECTIVE INTERFACIAL TENSION AND PREDICTING FINGER SPACING FOR DNAPL PENETRATION INTO WATER-SATURATED POROUS MEDIA. (R826157)

EPA Science Inventory

The difficulty in determining the effective interfacial tension limits the prediction of the wavelength of fingering of immiscible fluids in porous media. A method to estimate the effective interfacial tension using fractal concepts was presented by Chang et al. [Water Resour. Re...

Electrode-Electrolyte Interfaces in Lithium-Sulfur Batteries with Liquid or Inorganic Solid Electrolytes.

PubMed

Yu, Xingwen; Manthiram, Arumugam

2017-11-21

Electrode-electrolyte interfacial properties play a vital role in the cycling performance of lithium-sulfur (Li-S) batteries. The issues at an electrode-electrolyte interface include electrochemical and chemical reactions occurring at the interface, formation mechanism of interfacial layers, compositional/structural characteristics of the interfacial layers, ionic transport across the interface, and thermodynamic and kinetic behaviors at the interface. Understanding the above critical issues is paramount for the development of strategies to enhance the overall performance of Li-S batteries. Liquid electrolytes commonly used in Li-S batteries bear resemblance to those employed in traditional lithium-ion batteries, which are generally composed of a lithium salt dissolved in a solvent matrix. However, due to a series of unique features associated with sulfur or polysulfides, ether-based solvents are generally employed in Li-S batteries rather than simply adopting the carbonate-type solvents that are generally used in the traditional Li + -ion batteries. In addition, the electrolytes of Li-S batteries usually comprise an important additive, LiNO 3 . The unique electrolyte components of Li-S batteries do not allow us to directly take the interfacial theories of the traditional Li + -ion batteries and apply them to Li-S batteries. On the other hand, during charging/discharging a Li-S battery, the dissolved polysulfide species migrate through the battery separator and react with the Li anode, which magnifies the complexity of the interfacial problems of Li-S batteries. However, current Li-S battery development paths have primarily been energized by advances in sulfur cathodes. Insight into the electrode-electrolyte interfacial behaviors has relatively been overshadowed. In this Account, we first examine the state-of-the-art contributions in understanding the solid-electrolyte interphase (SEI) formed on the Li-metal anode and sulfur cathode in conventional liquid-electrolyte Li-S batteries and how the resulting chemical and physical properties of the SEI affect the overall battery performance. A few strategies recently proposed for improving the stability of SEI are briefly summarized. Solid Li + -ion conductive electrolytes have been attempted for the development of Li-S batteries to eliminate the polysulfide shuttle issues. One approach is based on a concept of "all-solid-state Li-S battery," in which all the cell components are in the solid state. Another approach is based on a "hybrid-electrolyte Li-S battery" concept, in which the solid electrolyte plays roles both as a Li + -ion conductor for the electrochemical reaction and as a separator to prevent polysulfide shuttle. However, these endeavors with the solid electrolyte are not able to provide an overall satisfactory cell performance. In addition to the low ionic conductivity of solid-state electrolytes, a critical issue lies in the poor interfacial properties between the electrode and the solid electrolyte. This Account provides a survey of the relevant research progress in understanding and manipulating the interfaces of electrode and solid electrolytes in both the "all-solid-state Li-S batteries" and the "hybrid-electrolyte Li-S batteries". A recently proposed "semi-solid-state Li-S battery" concept is also briefly discussed. Finally, future research and development directions in all the above areas are suggested.

Fundamental Processes of Atomization in Fluid-Fluid Flows

NASA Technical Reports Server (NTRS)

McCready, M. J.; Chang, H.-C.; Leighton, D. T.

2001-01-01

This report outlines the major results of the grant "Fundamental Processes of Atomization in Fluid-Fluid Flows." These include: 1) the demonstration that atomization in liquid/liquid shear flow is driven by a viscous shear instability that triggers the formation of a long thin sheet; 2) discovery of a new mode of interfacial instability for oscillatory two-layer systems whereby a mode that originates within the less viscous liquid phase causes interfacial deformation as the oscillation proceeds; 3) the demonstration that rivulet formation from gravity front occurs because the local front shape specified by gravity and surface tension changes from a nose to a wedge geometry, thus triggering a large increase in viscous resistance; and 4) extension of the studies on nonlinear wave evolution on falling films and in stratified flow, particularly the evolution towards large-amplitude solitary waves that tend to generate drops.

Theory of hydrophobicity: transient cavities in molecular liquids

NASA Technical Reports Server (NTRS)

Pratt, L. R.; Pohorille, A.

1992-01-01

Observation of the size distribution of transient cavities in computer simulations of water, n-hexane, and n-dodecane under benchtop conditions shows that the sizes of cavities are more sharply defined in liquid water but the most-probable-size cavities are about the same size in each of these liquids. The calculated solvent atomic density in contact with these cavities shows that water applies more force per unit area of cavity surface than do the hydrocarbon liquids. This contact density, or "squeezing" force, reaches a maximum near cavity diameters of 2.4 angstroms. The results for liquid water are compared to the predictions of simple theories and, in addition, to results for a reference simple liquid. The numerical data for water at a range of temperatures are analyzed to extract a surface free energy contribution to the work of formation of atomic-size cavities. Comparison with the liquid-vapor interfacial tensions of the model liquids studied here indicates that the surface free energies extracted for atomic-size cavities cannot be accurately identified with the macroscopic surface tensions of the systems.

Theory of hydrophobicity: Transient cavities in molecular liquids

PubMed Central

Pratt, Lawrence R.; Pohorille, Andrew

1992-01-01

Observation of the size distribution of transient cavities in computer simulations of water, n-hexane, and n-dodecane under benchtop conditions shows that the sizes of cavities are more sharply defined in liquid water but the most-probable-size cavities are about the same size in each of these liquids. The calculated solvent atomic density in contact with these cavities shows that water applies more force per unit area of cavity surface than do the hydrocarbon liquids. This contact density, or “squeezing” force, reaches a maximum near cavity diameters of 2.4 Å. The results for liquid water are compared to the predictions of simple theories and, in addition, to results for a reference simple liquid. The numerical data for water at a range of temperatures are analyzed to extract a surface free energy contribution to the work of formation of atomic-size cavities. Comparison with the liquid-vapor interfacial tensions of the model liquids studies here indicates that the surface free energies extracted for atomic-size cavities cannot be accurately identified with the macroscopic surface tensions of the systems. PMID:11537863

Experimental evidence of a liquid-liquid transition in interfacial water

NASA Astrophysics Data System (ADS)

Zanotti, J.-M.; Bellissent-Funel, M.-C.; Chen, S.-H.

2005-07-01

At ambient pressure, bulk liquid water shows an anomalous increase of thermodynamic quantities and apparent divergences of dynamic properties on approaching a temperature Ts of 228 K. At normal pressure, supercooled water spontaneously freezes below the homogeneous nucleation temperature, TH = 235 K. Upon heating, the two forms of Amorphous Solid Water (ASW), LDA (Low Density Amorphous Ice) and HDA (High Density Amorphous Ice), crystallise above TX = 150 K. As a consequence, up to now no experiment has been able to explore the properties of liquid water in this very interesting temperature range between 150 and 235 K. We present nanosecond-time-scale measurements of local rotational and translational dynamics of interfacial, non-crystalline, water from 77 to 280 K. These experimental dynamic results are combined with calorimetric and diffraction data to show that after exhibiting a glass transition at 165 K, interfacial water experiences a first-order liquid-liquid transition at 240 K from a low-density to a high-density liquid. This is the first direct evidence of the existence of a liquid-liquid transition involving water.

Wetting of a partially immersed compliant rod

NASA Astrophysics Data System (ADS)

Hui, Chung-Yuen; Jagota, Anand

2016-11-01

The force on a solid rod partially immersed in a liquid is commonly used to determine the liquid-vapor surface tension by equating the measured force required to remove the rod from the liquid to the vertical component of the liquid-vapor surface tension. Here, we study how this process is affected when the rod is compliant. For equilibrium, we enforce force and configurational energy balance, including contributions from elastic energy. We show that, in general, the contact angle does not equal that given by Young's equation. If surface stresses are tensile, the strain in the immersed part of the rod is found to be compressive and to depend only on the solid-liquid surface stress. The strain in the dry part of the rod can be either tensile or compressive, depending on a combination of parameters that we identify. We also provide results for compliant plates partially immersed in a liquid under plane strain and plane stress. Our results can be used to extract solid surface stresses from such experiments.

Moving contact lines in partial wetting: bridging the gap across the scales

NASA Astrophysics Data System (ADS)

Pahlavan, Amir; Cueto-Felgueroso, Luis; McKinley, Gareth; Juanes, Ruben

2017-11-01

The spreading and dewetting of liquid films on solid substrates is a common phenomenon in nature and industry from a snail secreting a mucosal film to printing and coating processes. A quantitative description of these phenomena, however, requires a detailed understanding of the flow physics at the nanoscale as the intermolecular interactions become important close to the contact line. Classical hydrodynamic theory describes wetting as an interplay between viscous and interfacial forces, neglecting the intermolecular interactions, leading to a paradox known as the moving contact line singularity. By contrast, molecular kinetic theory describes wetting as an activated process, neglecting the bulk hydrodynamics in the spreading viscous fluid film altogether. Here, we show that our recently developed model for thin liquid films in partial wetting, which properly incorporates the role of van der Waals interactions in a thin spreading fluid layer into a height-dependent surface tension, bridges the gap between these two approaches and leads to a unified framework for the description of wetting phenomena. We further use our model to investigate the instability and dewetting of nanometric liquid films, and show that it brings theoretical predictions closer to experimental observations.

Stabilization of Oil-Water Emulsions by Hydrophobic Bacteria

PubMed Central

Dorobantu, Loredana S.; Yeung, Anthony K. C.; Foght, Julia M.; Gray, Murray R.

2004-01-01

Formation of oil-water emulsions during bacterial growth on hydrocarbons is often attributed to biosurfactants. Here we report the ability of certain intact bacterial cells to stabilize oil-in-water and water-in-oil emulsions without changing the interfacial tension, by inhibition of droplet coalescence as observed in emulsion stabilization by solid particles like silica. PMID:15466587

Effect of demulsifiers on interfacial properties governing crude oil demulsification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, S.; Kushnick, A.P.

1987-01-01

The purpose of this paper is to illustrate how various parameters such as interfacial tension, interfacial shear viscosity, dynamic interfacial tension gradient, dilational elasticity and demulsifier clustering affect the demulsification effectiveness. The authors believe such an understanding is needed for developing more effective demulsifiers. At small thicknesses, an interfacial oil film can rupture if a continuous hydrophilic pathway exists between the droplets. Such a pathway can be provided by a demulsifier by forming water swollen reverse micelle-like clusters. They believe the differences in the effectiveness between P1 and P2 at low concentrations may be related to this phenomenon. The authorsmore » found that with both P1 and P2, the crude oil-brine interfacial shear viscosity is less than 0.1 surface poise. The interfacial dilational measurements also do not reveal any significant differences in their dynamic tension properties. But the interfacial tension vs. concentration curves show significant differences. The leveling of interfacial tension implies formation of clusters. The data indicate that the demulsifier P1 will form such clusters in the crude oil at a lower concentration than P2. Thus, other parameters being equal, the demulsifier P1 will be more efficient at a lower concentration than P2 for this crude oil emulsion.« less

ELECTRON TRANSFER MECHANISM AT THE SOLID-LIQUID INTERFACE OF PHYLLOSILICATES

EPA Science Inventory

Interfacial electron transfer processes on clay minerals have significant impact in natural environments and geochemical systems. Nitrobenzene was used as molecular probes to study the electron transfer mechanism at the solid-water interfaces of Fe-containing phyllosicates. For...

Unexpected finite size effects in interfacial systems: Why bigger is not always better—Increase in uncertainty of surface tension with bulk phase width

NASA Astrophysics Data System (ADS)

Longford, Francis G. J.; Essex, Jonathan W.; Skylaris, Chris-Kriton; Frey, Jeremy G.

2018-06-01

We present an unexpected finite size effect affecting interfacial molecular simulations that is proportional to the width-to-surface-area ratio of the bulk phase Ll/A. This finite size effect has a significant impact on the variance of surface tension values calculated using the virial summation method. A theoretical derivation of the origin of the effect is proposed, giving a new insight into the importance of optimising system dimensions in interfacial simulations. We demonstrate the consequences of this finite size effect via a new way to estimate the surface energetic and entropic properties of simulated air-liquid interfaces. Our method is based on macroscopic thermodynamic theory and involves comparing the internal energies of systems with varying dimensions. We present the testing of these methods using simulations of the TIP4P/2005 water forcefield and a Lennard-Jones fluid model of argon. Finally, we provide suggestions of additional situations, in which this finite size effect is expected to be significant, as well as possible ways to avoid its impact.

van der Waals model for the surface tension of liquid 4He near the λ point

NASA Astrophysics Data System (ADS)

Tavan, Paul; Widom, B.

1983-01-01

We develop a phenomenological model of the 4He liquid-vapor interface. With it we calculate the surface tension of liquid helium near the λ point and compare with the experimental measurements by Magerlein and Sanders. The model is a form of the van der Waals surface-tension theory, extended to apply to a phase equilibrium in which the simultaneous variation of two order parameters-here the superfluid order parameter and the total density-is essential. The properties of the model are derived analytically above the λ point and numerically below it. Just below the λ point the superfluid order parameter is found to approach its bulk-superfluid-phase value very slowly with distance on the liquid side of the interface (the characteristic distance being the superfluid coherence length), and to vanish rapidly with distance on the vapor side, while the total density approaches its bulk-phase values rapidly and nearly symmetrically on the two sides. Below the λ point the surface tension has a |ɛ|32 singularity (ɛ~T-Tλ) arising from the temperature dependence of the spatially varying superfluid order parameter. This is the mean-field form of the more general |ɛ|μ singularity predicted by Sobyanin and by Hohenberg, in which μ (which is in reality close to 1.35 at the λ point of helium) is the exponent with which the interfacial tension between two critical phases vanishes. Above the λ point the surface tension in this model is analytic in ɛ. A singular term |ɛ|μ may in reality be present in the surface tension above as well as below the λ point, although there should still be a pronounced asymmetry. The variation with temperature of the model surface tension is overall much like that in experiment.

Multifunctional Poro-Vascular Composites for UAV Performance Enhancement

DTIC Science & Technology

2012-07-31

structural “skin” materials with surface pores and internal vascular channels filled with an ionic- liquid whose height and shape at the pore exits is...2 V t e e q q          Intrinsic contact angle (zero voltage) Applied potential Interfacial tension (IFT) of ionic liquid Lippmann...Characterization flat plates  single (capillary) pore  PV pore arrays FTA 1000 Drop-Shape Characterization • Microscope lens : 0.5 to 12x magnification • Side

Effect of the Thermocouple on Measuring the Temperature Discontinuity at a Liquid-Vapor Interface.

PubMed

Kazemi, Mohammad Amin; Nobes, David S; Elliott, Janet A W

2017-07-18

The coupled heat and mass transfer that occurs in evaporation is of interest in a large number of fields such as evaporative cooling, distillation, drying, coating, printing, crystallization, welding, atmospheric processes, and pool fires. The temperature jump that occurs at an evaporating interface is of central importance to understanding this complex process. Over the past three decades, thermocouples have been widely used to measure the interfacial temperature jumps at a liquid-vapor interface during evaporation. However, the reliability of these measurements has not been investigated so far. In this study, a numerical simulation of a thermocouple when it measures the interfacial temperatures at a liquid-vapor interface is conducted to understand the possible effects of the thermocouple on the measured temperature and features in the temperature profile. The differential equations of heat transfer in the solid and fluids as well as the momentum transfer in the fluids are coupled together and solved numerically subject to appropriate boundary conditions between the solid and fluids. The results of the numerical simulation showed that while thermocouples can measure the interfacial temperatures in the liquid correctly, they fail to read the actual interfacial temperatures in the vapor. As the results of our numerical study suggest, the temperature jumps at a liquid-vapor interface measured experimentally by using a thermocouple are larger than what really exists at the interface. For a typical experimental study of evaporation of water at low pressure, it was found that the temperature jumps measured by a thermocouple are overestimated by almost 50%. However, the revised temperature jumps are still in agreement with the statistical rate theory of interfacial transport. As well as addressing the specific application of the liquid-vapor temperature jump, this paper provides significant insight into the role that heat transfer plays in the operation of thermocouples in general.

Coexistence and interfacial properties of a triangle-well mimicking the Lennard-Jones fluid and a comparison with noble gases.

PubMed

Bárcenas, M; Reyes, Y; Romero-Martínez, A; Odriozola, G; Orea, P

2015-02-21

Coexistence and interfacial properties of a triangle-well (TW) fluid are obtained with the aim of mimicking the Lennard-Jones (LJ) potential and approach the properties of noble gases. For this purpose, the scope of the TW is varied to match vapor-liquid densities and surface tension. Surface tension and coexistence curves of TW systems with different ranges were calculated with replica exchange Monte Carlo and compared to those data previously reported in the literature for truncated and shifted (STS), truncated (ST), and full Lennard-Jones (full-LJ) potentials. We observed that the scope of the TW potential must be increased to approach the STS, ST, and full-LJ properties. In spite of the simplicity of TW expression, a remarkable agreement is found. Furthermore, the variable scope of the TW allows for a good match of the experimental data of argon and xenon.

Spontaneous mode-selection in the self-propelled motion of a solid/liquid composite driven by interfacial instability

NASA Astrophysics Data System (ADS)

Takabatake, Fumi; Magome, Nobuyuki; Ichikawa, Masatoshi; Yoshikawa, Kenichi

2011-03-01

Spontaneous motion of a solid/liquid composite induced by a chemical Marangoni effect, where an oil droplet attached to a solid soap is placed on a water phase, was investigated. The composite exhibits various characteristic motions, such as revolution (orbital motion) and translational motion. The results showed that the mode of this spontaneous motion switches with a change in the size of the solid scrap. The essential features of this mode-switching were reproduced by ordinary differential equations by considering nonlinear friction with proper symmetry.

Direct numerical simulation of turbulent channel flow over a liquid-infused micro-grooved surface

NASA Astrophysics Data System (ADS)

Chang, Jaehee; Jung, Taeyong; Choi, Haecheon; Kim, John

2016-11-01

Recently a superhydrophobic surface has drawn much attention as a passive device to achieve high drag reduction. Despite the high performance promised at ideal conditions, maintaining the interface in real flow conditions is an intractable problem. A non-wetting surface, known as the slippery liquid-infused porous surface (SLIPS) or the lubricant-impregnated surface (LIS), has shown a potential for drag reduction, as the working fluid slips at the interface but cannot penetrate into the lubricant layer. In the present study, we perform direct numerical simulation of turbulent channel flow over a liquid-infused micro-grooved surface to investigate the effects of this surface on the interfacial slip and drag reduction. The flow rate of water is maintained constant corresponding to Reτ 180 in a fully developed turbulent channel flow, and the lubricant layer is shear-driven by the turbulent water flow. The lubricant layer is also simulated with the assumption that the interface is flat (i.e. the surface tension effect is neglected). The solid substrate in which the lubricant is infused is modelled as straight ridges using an immersed boundary method. DNS results show that drag reduction by the liquid-infused surface is highly dependent on the viscosity of the lubricant.

Propelling a water drop with the vapor-mediated Marangoni effect

NASA Astrophysics Data System (ADS)

Kim, Seungho; Kim, Ho-Young

2013-11-01

We show that a water drop on solid surfaces can be propelled just by placing a volatile alcohol drop nearby. It is found to be because the water-air interface near the alcohol drop mixes with alcohol vapor, thereby locally lowering the surface tension. The surface-tension-gradient induces the motion of the water drop, enabling the trajectory control of water drops through the motion of remote alcohol drops. This vapor-mediated Marangoni effect also gives rise to other interesting interfacial flow phenomena, such as nucleation of holes on a water film and ballooning of a water drop hanging from a syringe needle with the approach of an alcohol drop. We visualize such interfacial dynamics with a high-speed camera and rationalize their salient features by scaling analysis. This work was supported by the National Research Foundation of Korea (grant no. 2012-008023).

Thermodiffusion as a means to manipulate liquid film dynamics on chemically patterned surfaces

PubMed Central

Kalpathy, Sreeram K.; Shreyes, Amrita Ravi

2017-01-01

The model problem examined here is the stability of a thin liquid film consisting of two miscible components, resting on a chemically patterned solid substrate and heated from below. In addition to surface tension gradients, the temperature variations also induce gradients in the concentration of the film by virtue of thermodiffusion/Soret effects. We study the stability and dewetting behaviour due to the coupled interplay between thermal gradients, Soret effects, long-range van der Waals forces, and wettability gradient-driven flows. Linear stability analysis is first employed to predict growth rates and the critical Marangoni number for chemically homogeneous surfaces. Then, nonlinear simulations are performed to unravel the interfacial dynamics and possible locations of the film rupture on chemically patterned substrates. Results suggest that appropriate tuning of the Soret parameter and its direction, in conjunction with either heating or cooling, can help manipulate the location and time scales of the film rupture. The Soret effect can either potentially aid or oppose film instability depending on whether the thermal and solutal contributions to flow are cooperative or opposed to each other. PMID:28595391

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guttman, Shani; Sapir, Zvi; Ocko, Benjamin M.

Recent extensive studies reveal that surfactant-stabilized spherical alkane emulsion droplets spontaneously adopt polyhedral shapes upon cooling below a temperature T d while remaining liquid. Further cooling induces the growth of tails and spontaneous droplet splitting. Two mechanisms were offered to account for these intriguing effects. One assigns the effects to the formation of an intradroplet frame of tubules consisting of crystalline rotator phases with cylindrically curved lattice planes. The second assigns the sphere-to-polyhedron transition to the buckling of defects in a crystalline interfacial monolayer, known to form in these systems at some T s > T d. The buckling reducesmore » the extensional energy of the crystalline monolayer’s defects, unavoidably formed when wrapping a spherical droplet by a hexagonally packed interfacial monolayer. The tail growth, shape changes, and droplet splitting were assigned to the decrease and vanishing of surface tension, γ. Here we present temperature-dependent γ(T), optical microscopy measurements, and interfacial entropy determinations for several alkane/surfactant combinations. We demonstrate the advantages and accuracy of the in situ γ(T) measurements made simultaneously with the microscopy measurements on the same droplet. The in situ and coinciding ex situ Wilhelmy plate γ(T) measurements confirm the low interfacial tension, ≲0.1 mN/m, observed at T d. Here, our results provide strong quantitative support validating the crystalline monolayer buckling mechanism.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martínez-Ruiz, F. J.; Blas, F. J., E-mail: felipe@uhu.es; Centro de Investigación de Física Teórica y Matemática, Universidad de Huelva, 21071 Huelva

We propose an extension of the improved version of the inhomogeneous long-range corrections of Janeček [J. Phys. Chem. B 110, 6264–6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, r{sub c} = 2.5, 3, 4, and 5σ. In addition,more » we have also considered cutoff distances r{sub c} = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long-range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases, the width of the tangential microscopic component of the pressure tensor profile increases, and the surface tension increases as the cutoff distance is larger. We have also checked the effect of the impulsive contribution to the pressure due to the discontinuity of the intermolecular interaction potential when it is cut. If this contribution is not accounted for in the calculation of the microscopic components of the pressure tensor, incorrect values of both components as well as a wrong structure along the vapour-liquid interface are obtained.« less

Modeling Evaporation and Particle Assembly in Colloidal Droplets.

PubMed

Zhao, Mingfei; Yong, Xin

2017-06-13

Evaporation-induced assembly of nanoparticles in a drying droplet is of great importance in many engineering applications, including printing, coating, and thin film processing. The investigation of particle dynamics in evaporating droplets can provide fundamental hydrodynamic insight for revealing the processing-structure relationship in the particle self-organization induced by solvent evaporation. We develop a free-energy-based multiphase lattice Boltzmann method coupled with Brownian dynamics to simulate evaporating colloidal droplets on solid substrates with specified wetting properties. The influence of interface-bound nanoparticles on the surface tension and evaporation of a flat liquid-vapor interface is first quantified. The results indicate that the particles at the interface reduce surface tension and enhance evaporation flux. For evaporating particle-covered droplets on substrates with different wetting properties, we characterize the increase of evaporate rate via measuring droplet volume. We find that droplet evaporation is determined by the number density and circumferential distribution of interfacial particles. We further correlate particle dynamics and assembly to the evaporation-induced convection in the bulk and on the surface of droplet. Finally, we observe distinct final deposits from evaporating colloidal droplets with bulk-dispersed and interface-bound particles. In addition, the deposit pattern is also influenced by the equilibrium contact angle of droplet.

Water liquid-vapor interface subjected to various electric fields: A molecular dynamics study.

PubMed

Nikzad, Mohammadreza; Azimian, Ahmad Reza; Rezaei, Majid; Nikzad, Safoora

2017-11-28

Investigation of the effects of E-fields on the liquid-vapor interface is essential for the study of floating water bridge and wetting phenomena. The present study employs the molecular dynamics method to investigate the effects of parallel and perpendicular E-fields on the water liquid-vapor interface. For this purpose, density distribution, number of hydrogen bonds, molecular orientation, and surface tension are examined to gain a better understanding of the interface structure. Results indicate enhancements in parallel E-field decrease the interface width and number of hydrogen bonds, while the opposite holds true in the case of perpendicular E-fields. Moreover, perpendicular fields disturb the water structure at the interface. Given that water molecules tend to be parallel to the interface plane, it is observed that perpendicular E-fields fail to realign water molecules in the field direction while the parallel ones easily do so. It is also shown that surface tension rises with increasing strength of parallel E-fields, while it reduces in the case of perpendicular E-fields. Enhancement of surface tension in the parallel field direction demonstrates how the floating water bridge forms between the beakers. Finally, it is found that application of external E-fields to the liquid-vapor interface does not lead to uniform changes in surface tension and that the liquid-vapor interfacial tension term in Young's equation should be calculated near the triple-line of the droplet. This is attributed to the multi-directional nature of the droplet surface, indicating that no constant value can be assigned to a droplet's surface tension in the presence of large electric fields.

From elasticity to capillarity in soft materials indentation

NASA Astrophysics Data System (ADS)

Pham, Jonathan T.; Schellenberger, Frank; Kappl, Michael; Butt, Hans-Jürgen

2017-06-01

For soft materials with Young's moduli below 100 kPa, quantifying mechanical and interfacial properties by small scale indentation is challenging because in addition to adhesion and elasticity, surface tension plays a critical role. Until now, microscale contact of very soft materials has only been studied by static experiments under zero external loading. Here we introduce a combination of the colloidal probe technique and confocal microscopy to characterize the force-indentation and force-contact radius relationships during microindentation of soft silicones. We confirm that the widespread Johnson-Kendall-Roberts theory must be extended to predict the mechanical contact for soft materials. Typically a liquid component is found within very soft materials. With a simple analytical model, we illustrate that accounting for this liquid surface tension can capture the contact behavior. Our results highlight the importance of considering liquid that is often associated with soft materials during small scale contact.

Double-diffusive boundary layers along vertical free surfaces

NASA Astrophysics Data System (ADS)

Napolitano, L. G.; Viviani, A.; Savino, R.

1992-05-01

This paper deals with double-diffusive (or thermosolutal) combined free convection, i.e., free convection due to buoyant forces (natural convection) and surface tension gradients (Marangoni convection), which are generated by volume differences and surface gradients of temperature and solute concentration. Attention is focused on boundary layers that form along a vertical liquid-gas interface, when the appropriately defined nondimensional characteristic transport numbers are large enough, in problems of thermosolutal natural and Marangoni convection, such as buoyancy and surface tension driven flows in differentially heated open cavities and liquid bridges. Classes of similar solutions are derived for each class of convection on the basis of a rigorous order of magnitude analysis. Velocity, temperature and concentration profiles are reported in the similarity plane; flow and transport properties at the liquid-gas interface (interfacial velocity, heat and mass transfer bulk coefficients) are obtained for a wide range of Prandtl and Schmidt numbers and different values of the similarity parameter.

Interfacial thermodynamics of water and six other liquid solvents.

PubMed

Pascal, Tod A; Goddard, William A

2014-06-05

We examine the thermodynamics of the liquid-vapor interface by direct calculation of the surface entropy, enthalpy, and free energy from extensive molecular dynamics simulations using the two-phase thermodynamics (2PT) method. Results for water, acetonitrile, cyclohexane, dimethyl sulfoxide, hexanol, N-methyl acetamide, and toluene are presented. We validate our approach by predicting the interfacial surface tensions (IFT--excess surface free energy per unit area) in excellent agreement with the mechanical calculations using Kirkwood-Buff theory. Additionally, we evaluate the temperature dependence of the IFT of water as described by the TIP4P/2005, SPC/Ew, TIP3P, and mW classical water models. We find that the TIP4P/2005 and SPC/Ew water models do a reasonable job of describing the interfacial thermodynamics; however, the TIP3P and mW are quite poor. We find that the underprediction of the experimental IFT at 298 K by these water models results from understructured surface molecules whose binding energies are too weak. Finally, we performed depth profiles of the interfacial thermodynamics which revealed long tails that extend far into what would be considered bulk from standard Gibbs theory. In fact, we find a nonmonotonic interfacial free energy profile for water, a unique feature that could have important consequences for the absorption of ions and other small molecules.

Atomistic modelling of evaporation and explosive boiling of thin film liquid argon over internally recessed nanostructured surface

NASA Astrophysics Data System (ADS)

Hasan, Mohammad Nasim; Shavik, Sheikh Mohammad; Rabbi, Kazi Fazle; Haque, Mominul

2016-07-01

Molecular dynamics (MD) simulations have been carried out to investigate evaporation and explosive boiling phenomena of thin film liquid argon on nanostructured solid surface with emphasis on the effect of solid-liquid interfacial wettability. The nanostructured surface considered herein consists of trapezoidal internal recesses of the solid platinum wall. The wetting conditions of the solid surface were assumed such that it covers both the hydrophilic and hydrophobic conditions and hence effect of interfacial wettability on resulting evaporation and boiling phenomena was the main focus of this study. The initial configuration of the simulation domain comprised of a three phase system (solid platinum, liquid argon and vapor argon) on which equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. After equilibrium of the three-phase system was established, the wall was set to different temperatures (130 K and 250 K for the case of evaporation and explosive boiling respectively) to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat flux normal to the solid surface was also calculated to illustrate the effectiveness of heat transfer for hydrophilic and hydrophobic surfaces in cases of both nanostructured surface and flat surface. The results obtained show that both the wetting condition of the surface and the presence of internal recesses have significant effect on normal evaporation and explosive boiling of the thin liquid film. The heat transfer from solid to liquid in cases of surface with recesses are higher compared to flat surface without recesses. Also the surface with higher wettability (hydrophilic) provides more favorable conditions for boiling than the low-wetting surface (hydrophobic) and therefore, liquid argon responds quickly and shifts from liquid to vapor phase faster in case of hydrophilic surface. The heat transfer rate is also much higher in case of hydrophilic surface.

Towards building a robust computational framework to simulate multi-physics problems - a solution technique for three-phase (gas-liquid-solid) interactions

NASA Astrophysics Data System (ADS)

Zhang, Lucy

In this talk, we show a robust numerical framework to model and simulate gas-liquid-solid three-phase flows. The overall algorithm adopts a non-boundary-fitted approach that avoids frequent mesh-updating procedures by defining independent meshes and explicit interfacial points to represent each phase. In this framework, we couple the immersed finite element method (IFEM) and the connectivity-free front tracking (CFFT) method that model fluid-solid and gas-liquid interactions, respectively, for the three-phase models. The CFFT is used here to simulate gas-liquid multi-fluid flows that uses explicit interfacial points to represent the gas-liquid interface and for its easy handling of interface topology changes. Instead of defining different levels simultaneously as used in level sets, an indicator function naturally couples the two methods together to represent and track each of the three phases. Several 2-D and 3-D testing cases are performed to demonstrate the robustness and capability of the coupled numerical framework in dealing with complex three-phase problems, in particular free surfaces interacting with deformable solids. The solution technique offers accuracy and stability, which provides a means to simulate various engineering applications. The author would like to acknowledge the supports from NIH/DHHS R01-2R01DC005642-10A1 and the National Natural Science Foundation of China (NSFC) 11550110185.

High-pressure Experimental Studies on Geo-liquids Using Synchrotron Radiation at the Advanced Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yanbin; Shen, Guoyin

2014-12-23

Here, we review recent progress in studying silicate, carbonate, and metallic liquids of geological and geophysical importance at high pressure and temperature, using the large-volume high-pressure devices at the third-generation synchrotron facility of the Advanced Photon Source, Argonne National Laboratory. These integrated high-pressure facilities now offer a unique combination of experimental techniques that allow researchers to investigate structure, density, elasticity, viscosity, and interfacial tension of geo-liquids under high pressure, in a coordinated and systematic fashion. Moreover, we describe experimental techniques, along with scientific highlights. Future developments are also discussed.

Solidification phenomena of binary organic mixtures

NASA Technical Reports Server (NTRS)

Chang, K.

1982-01-01

The coalescence rates and motion of liquid bubbles in binary organic mixtures were studied. Several factors such as temperature gradient, composition gradient, interfacial tension, and densities of the two phases play important roles in separation of phases of immiscible liquids. An attempt was made to study the effect of initial compositions on separation rates of well-dispersed organic mixtures at different temperatures and, ultimately, on the homogeneity of solidification of the immiscible binary organic liquids. These organic mixtures serve as models for metallic pseudo binary systems under study. Two specific systems were investigated: ethyl salicylate - diethyl glycol and succinonitrile - water.

Chemical demulsification of petroleum emulsions using oil-soluable demulsifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krawczyk, M.A.; Wasan, D.T.; Shetty, C.S.

1991-02-01

This paper investigates the factors affecting the coalescence and interfacial behavior of water- in-crude-oil emulsions in the presence of oil-soluble demulsifiers. The emulsion-breaking characteristics and interfacial properties of East Texas Crude and a model system were compared. The variation of interfacial tension with demulsifier concentration for the model system was ascertained by measuring the interfacial tensions between the oil and water phase. Interfacial activity, adsorption kinetics, and partitioning were shown to be the most important parameters governing demulsifier performance. A conceptual model of drop-drop coalescence process in demulsification was presented which indicates that the interfacial activity of the demulsifier mustmore » be high enough to suppress the interfacial tension gradient. This accelerates the rate of film drainage, thus promoting coalescence.« less

Mixtures of charged colloid and neutral polymer: Influence of electrostatic interactions on demixing and interfacial tension

NASA Astrophysics Data System (ADS)

Denton, Alan R.; Schmidt, Matthias

2005-06-01

The equilibrium phase behavior of a binary mixture of charged colloids and neutral, nonadsorbing polymers is studied within free-volume theory. A model mixture of charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with nonadditive diameters and then onto an effective Asakura-Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter—the ratio of the polymer diameter to the effective colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into colloid-rich (liquid) and colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attraction between electrostatically repelling macroions. Comparison with predictions of density-functional theory reveals a corresponding increase in the liquid-vapor interfacial tension. The predicted trends in phase stability are consistent with observed behavior of protein-polysaccharide mixtures in food colloids.

Overview: Experimental studies of crystal nucleation: Metals and colloids.

PubMed

Herlach, Dieter M; Palberg, Thomas; Klassen, Ina; Klein, Stefan; Kobold, Raphael

2016-12-07

Crystallization is one of the most important phase transformations of first order. In the case of metals and alloys, the liquid phase is the parent phase of materials production. The conditions of the crystallization process control the as-solidified material in its chemical and physical properties. Nucleation initiates the crystallization of a liquid. It selects the crystallographic phase, stable or meta-stable. Its detailed knowledge is therefore mandatory for the design of materials. We present techniques of containerless processing for nucleation studies of metals and alloys. Experimental results demonstrate the power of these methods not only for crystal nucleation of stable solids but in particular also for investigations of crystal nucleation of metastable solids at extreme undercooling. This concerns the physical nature of heterogeneous versus homogeneous nucleation and nucleation of phases nucleated under non-equilibrium conditions. The results are analyzed within classical nucleation theory that defines the activation energy of homogeneous nucleation in terms of the interfacial energy and the difference of Gibbs free energies of solid and liquid. The interfacial energy acts as barrier for the nucleation process. Its experimental determination is difficult in the case of metals. In the second part of this work we therefore explore the potential of colloidal suspensions as model systems for the crystallization process. The nucleation process of colloids is observed in situ by optical observation and ultra-small angle X-ray diffraction using high intensity synchrotron radiation. It allows an unambiguous discrimination of homogeneous and heterogeneous nucleation as well as the determination of the interfacial free energy of the solid-liquid interface. Our results are used to construct Turnbull plots of colloids, which are discussed in relation to Turnbull plots of metals and support the hypothesis that colloids are useful model systems to investigate crystal nucleation.

Simultaneous measurement of surface tension and viscosity using freely decaying oscillations of acoustically levitated droplets.

PubMed

Kremer, J; Kilzer, A; Petermann, M

2018-01-01

Oscillations of small liquid drops around a spherical shape have been of great interest to scientists measuring physical properties such as interfacial tension and viscosity, over the last few decades. A powerful tool for contactless positioning is acoustic levitation, which has been used to simultaneously determine the surface tension and viscosity of liquids at ambient pressure. In order to extend this acoustic levitation measurement method to high pressure systems, the method is first evaluated under ambient pressure. To measure surface tension and viscosity using acoustically levitated oscillating drops, an image analysis method has to be developed and factors which may affect measurement, such as sound field or oscillation amplitude, have to be analyzed. In this paper, we describe the simultaneous measurement of surface tension and viscosity using freely decaying shape oscillations of acoustically levitated droplets of different liquids (silicone oils AK 5 and AK 10, squalane, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol) in air. These liquids vary in viscosity from 2 to about 30 mPa s. An acoustic levitation system, including an optimized standing wave acoustic levitator and a high-speed camera, was used for this study. An image analysis was performed with a self-written Matlab® code. The frequency of oscillation and the damping constant, required for the determination of surface tension and viscosity, respectively, were calculated from the evolution of the equatorial and polar radii. The results and observations are compared to data from the literature in order to analyze the accuracy of surface tension and viscosity determination, as well as the effect of non-spherical drop shape or amplitude of oscillation on measurement.

Simultaneous measurement of surface tension and viscosity using freely decaying oscillations of acoustically levitated droplets

NASA Astrophysics Data System (ADS)

Kremer, J.; Kilzer, A.; Petermann, M.

2018-01-01

Oscillations of small liquid drops around a spherical shape have been of great interest to scientists measuring physical properties such as interfacial tension and viscosity, over the last few decades. A powerful tool for contactless positioning is acoustic levitation, which has been used to simultaneously determine the surface tension and viscosity of liquids at ambient pressure. In order to extend this acoustic levitation measurement method to high pressure systems, the method is first evaluated under ambient pressure. To measure surface tension and viscosity using acoustically levitated oscillating drops, an image analysis method has to be developed and factors which may affect measurement, such as sound field or oscillation amplitude, have to be analyzed. In this paper, we describe the simultaneous measurement of surface tension and viscosity using freely decaying shape oscillations of acoustically levitated droplets of different liquids (silicone oils AK 5 and AK 10, squalane, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol) in air. These liquids vary in viscosity from 2 to about 30 mPa s. An acoustic levitation system, including an optimized standing wave acoustic levitator and a high-speed camera, was used for this study. An image analysis was performed with a self-written Matlab® code. The frequency of oscillation and the damping constant, required for the determination of surface tension and viscosity, respectively, were calculated from the evolution of the equatorial and polar radii. The results and observations are compared to data from the literature in order to analyze the accuracy of surface tension and viscosity determination, as well as the effect of non-spherical drop shape or amplitude of oscillation on measurement.

Hardening of particle/oil/water suspensions due to capillary bridges: Experimental yield stress and theoretical interpretation.

PubMed

Danov, Krassimir D; Georgiev, Mihail T; Kralchevsky, Peter A; Radulova, Gergana M; Gurkov, Theodor D; Stoyanov, Simeon D; Pelan, Eddie G

2018-01-01

Suspensions of colloid particles possess the remarkable property to solidify upon the addition of minimal amount of a second liquid that preferentially wets the particles. The hardening is due to the formation of capillary bridges (pendular rings), which connect the particles. Here, we review works on the mechanical properties of such suspensions and related works on the capillary-bridge force, and present new rheological data for the weakly studied concentration range 30-55 vol% particles. The mechanical strength of the solidified capillary suspensions, characterized by the yield stress Y, is measured at the elastic limit for various volume fractions of the particles and the preferentially wetting liquid. A quantitative theoretical model is developed, which relates Y with the maximum of the capillary-bridge force, projected on the shear plane. A semi-empirical expression for the mean number of capillary bridges per particle is proposed. The model agrees very well with the experimental data and gives a quantitative description of the yield stress, which increases with the rise of interfacial tension and with the volume fractions of particles and capillary bridges, but decreases with the rise of particle radius and contact angle. The quantitative description of capillary force is based on the exact theory and numerical calculation of the capillary bridge profile at various bridge volumes and contact angles. An analytical formula for Y is also derived. The comparison of the theoretical and experimental strain at the elastic limit reveals that the fluidization of the capillary suspension takes place only in a deformation zone of thickness up to several hundred particle diameters, which is adjacent to the rheometer's mobile plate. The reported experimental results refer to water-continuous suspension with hydrophobic particles and oily capillary bridges. The comparison of data for bridges from soybean oil and hexadecane surprisingly indicate that the yield strength is greater for the suspension with soybean oil despite its lower interfacial tension against water. The result can be explained with the different contact angles of the two oils in agreement with the theoretical predictions. The results could contribute for a better understanding, quantitative prediction and control of the mechanical properties of three-phase capillary suspensions solid/liquid/liquid. Copyright © 2017 Elsevier B.V. All rights reserved.

PREFACE: Functionalized Liquid Liquid Interfaces

NASA Astrophysics Data System (ADS)

Girault, Hubert; Kornyshev, Alexei A.; Monroe, Charles W.; Urbakh, Michael

2007-09-01

Most natural processes take place at interfaces. For this reason, surface science has been a focal point of modern research. At solid-liquid interfaces one can induce various species to adsorb or react, and thus may study interactions between the substrate and adsorbates, kinetic processes, optical properties, etc. Liquid-liquid interfaces, formed by immiscible liquids such as water and oil, have a number of distinctive features. Both sides of the interface are amenable to detailed physical and chemical analysis. By chemical or electrochemical means, metal or semiconductor nanoparticles can be formed or localised at the interface. Surfactants can be used to tailor surface properties, and also to place organic molecular or supermolecular constructions at the boundary between the liquids. Electric fields can be used to drive ions from one fluid to another, or even change the shape of the interface itself. In many cases, both liquids are optically transparent, making functionalized liquid-liquid interfaces promising for various optical applications based on the transmission or reflection of light. An advantage common to most of these systems is self-assembly; because a liquid-liquid interface is not mechanically constrained like a solid-liquid interface, it can easily access its most stable state, even after it has been driven far from equilibrium. This special issue focuses on four modes of liquid-liquid interfacial functionalization: the controlled adsorption of molecules or nanoparticles, the formation of adlayers or films, electrowetting, and ion transfer or interface-localized reactions. Interfacial adsorption can be driven electrically, chemically, or mechanically. The liquid-liquid interface can be used to study how anisotropic particles orient at a surface under the influence of a field, how surfactants interact with other adsorbates, and how nanoparticles aggregate; the transparency of the interface also makes the chirality of organic adsorbates amenable to optical study. Film formation goes a step beyond adsorption; some surfactants form monolayers or multilayers at the interface. A polymer microfilm or a polymer-particle matrix can be synthesized at the liquid-liquid boundary. Such films exhibit unique adsorption and ion-intercalation properties of their own. Electrowetting refers broadly to the phenomenon in which an applied voltage modulates the shape of a liquid-liquid interface, essentially by altering the surface tension. Electric fields can be used to induce droplets on solid substrates to change shape, or to affect the structure of liquid-liquid emulsions. Various chemical reactions can be performed at the liquid-liquid boundary. Liquid-liquid microelectrodes allow detailed study of ion-transfer kinetics at the interface. Photochemical processes can also be used to control the conformations of molecules adsorbed at the interface. But how much precise control do we actually have on the state of the interfacial region? Several contributions to this issue address a system which has been studied for decades in electrochemistry, but remains essentially unfamilar to physicists. This is the interface between two immiscible electrolytic solutions (ITIES), a progressing interdisciplinary field in which condensed-matter physics and physical chemistry meet molecular electrochemistry. Why is it so exciting? The reason is simple. The ITIES is chargeable: when positioned between two electrodes it can be polarized, and back- to-back electrical double layers form on both sides of the liquid-liquid interface. Importantly, the term immiscible refers not only to oil and water but also to the electrolytes. Inorganic electrolytes, such as alkali halides, tend to stay in water, whereas organic electrolytes, such as tetrabutylammonium tetraphenylborate, stay in oil. This behaviour arises because energies of the order of 0.2-0.3 eV are needed to drive ions across the interface. As long as these free energies of transfer are not exceeded by the external potential bias, the ITIES works as an 'electrode'; there is no traffic of ions across it. Thus the interface can sustain fields of the order of 106 V/cm, which are localized in a nanoscopic layer near the interface. This gives many new options for building various kinds of electrically tunable self assembled moloecular devices. Through the years, ITIES have been considered by electrochemists as a popular biomimetic model system, or for studies of interfacial reaction kinetics; ITIES were also used in industrial phase-transfer catalysis. Recently, this system has opened up new options for nano-scale engineering of functional assemblies (for dense information storage, efficient energy conversion, light-harvesting, and miniaturized sensors), which justifies its presentation in this issue.

Interfacial tensiometry and dilational surface visco-elasticity of biological liquids in medicine.

PubMed

Fainerman, V B; Trukhin, D V; Zinkovych, Igor I; Miller, R

2018-05-01

Dynamic surface tensions and dilational visco-elasticity are easy accessible parameters of liquids. For human body liquids, such as urine, blood serum, amniotic fluid, gastric juice, saliva and others, these parameters are very characteristic for the health status of people. In case of a disease the composition of certain liquids specifically changes and the measured characteristics of dynamic surface tension of the dilational surface elasticity and viscosity reflect these changes in a clear way. Thus, this kind of physico-chemical measurements represent sensitive tools for evaluating the severity of a disease and can serve as control tool for the efficiency of applied therapies. The overview summarises the results of a successful work over about 25years on this subject and gives specific insight into a number of diseases for which the diagnostics as well as the therapy control have been significantly improved by the application of physico-chemical experimental techniques. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantification of bulk solution limits for liquid and interfacial transport in nanoconfinements.

PubMed

Kelly, Shaina; Balhoff, Matthew T; Torres-Verdín, Carlos

2015-02-24

Liquid imbibition, the capillary-pressure-driven flow of a liquid into a gas, provides a mechanism for studying the effects of solid-liquid and solid-liquid-gas interfaces on nanoscale transport. Deviations from the classic Washburn equation for imbibition are generally observed for nanoscale imbibition, but the identification of the origin of these irregularities in terms of transport variables varies greatly among investigators. We present an experimental method and corresponding image and data analysis scheme that enable the determination of independent effective values of nanoscale capillary pressure, liquid viscosity, and interfacial gas partitioning coefficients, all critical transport variables, from imbibition within nanochannels. Experiments documented herein are performed within two-dimensional siliceous nanochannels of varying size and as small as 30 nm × 60 nm in cross section. The wetting fluid used is the organic solvent isopropanol and the nonwetting fluid is air, but investigations are not limited to these fluids. Optical data of dynamic flow are rare in geometries that are nanoscale in two dimensions due to the limited resolution of optical microscopy. We are able to capture tracer-free liquid imbibition with reflected differential interference contrast microscopy. Results with isopropanol show a significant departure from bulk transport values in the nanochannels: reduced capillary pressures, increased liquid viscosity, and nonconstant interfacial mass-transfer coefficients. The findings equate to the nucleation of structured, quasi-crystalline boundary layers consistently ∼10-25 nm in extent. This length is far thicker than the boundary layer range prescribed by long-range intermolecular force interactions. Slower but linear imbibition in some experimental cases suggests that structured boundary layers may inhibit viscous drag at confinement walls for critical nanochannel dimensions. Probing the effects of nanoconfinement on the definitions of capillary pressure, viscosity, and interfacial mass transfer is critical in determining and improving the functionality and fluid transport efficacy of geological, biological, and synthetic nanoporous media and materials.

Surface tension and phase coexistence properties of the lattice fluid from a virtual site removal Monte Carlo strategy

NASA Astrophysics Data System (ADS)

Provata, Astero; Prassas, Vassilis D.; Theodorou, Doros N.

1997-10-01

A thin liquid film of lattice fluid in equilibrium with its vapor is studied in 2 and 3 dimensions with canonical Monte Carlo simulation (MC) and Self-Consistent Field Theory (SCF) in the temperature range 0.45Tc to Tc, where Tc the liquid-gas critical temperature. Extending the approach of Oates et al. [Philos. Mag. B 61, 337 (1990)] to anisotropic systems, we develop a method for the MC computation of the transverse and normal pressure profiles, hence of the surface tension, based on virtual removals of individual sites or blocks of sites from the system. Results from implementation of this new method, obtained at very modest computational cost, are in reasonable agreement with exact values and other MC estimates of the surface tension of the 2-d and 3-d model systems, respectively. SCF estimates of the interfacial density profiles, the surface tension, the vapor pressure curve and the binodal curve compare well with MC results away from Tc, but show the expected deviations at high temperatures.

Structural ordering at solid-liquid interfaces in Al-Sm system: A molecular-dynamics study

DOE PAGES

Sun, Yang; Zhang, Feng; Ye, Zhuo; ...

2016-07-12

The structural ordering at solid-liquid interfaces far from equilibrium is studied with molecular dynamics simulations for the Al-Sm system. Using the van-Hove self-correlation function as the criterion to identify attachment/detachment events that occur at the interface, we are able to determine the time-dependent interface position, and characterize the detailed interfacial structure ordering surrounding the attached atoms. For the interface between an undercooled Al90Sm10 liquid and a metastable cubic structure, the solid induces the crystalline order of the cubic phase in the liquid layers, promoting the continuous growth of the crystal phase. When the same liquid is put in contact withmore » f.c.c. Al, Sm from the liquid can still attach to the solid interface despite its insolubility in the Al lattice. Non-f.c.c. order is revealed surrounding the attached Sm atoms. Lastly, we show that the local structure ordering at interface is highly correlated to solid packing and liquid ordering.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heverhagen, Jonas; Checco, Antonio; Tasinkevych, Mykola

In our study, the development of highly efficient nanofluidic devices necessitates means for enhancing and controlling fluid transport under confinement. We show experimentally that significant interfacial drag reduction in nanoscale channels can be obtained with hydrophobic arrays of conical textures tapering to a radius of less than 10 nanometer at their tip. Finally, this geometry maximizes interfacial slippage by trapping a highly resilient air layer at the solid/liquid interface.

Interfacial Tension and Surface Pressure of High Density Lipoprotein, Low Density Lipoprotein, and Related Lipid Droplets

PubMed Central

Ollila, O. H. Samuli; Lamberg, Antti; Lehtivaara, Maria; Koivuniemi, Artturi; Vattulainen, Ilpo

2012-01-01

Lipid droplets play a central role in energy storage and metabolism on a cellular scale. Their core is comprised of hydrophobic lipids covered by a surface region consisting of amphiphilic lipids and proteins. For example, high and low density lipoproteins (HDL and LDL, respectively) are essentially lipid droplets surrounded by specific proteins, their main function being to transport cholesterol. Interfacial tension and surface pressure of these particles are of great interest because they are related to the shape and the stability of the droplets and to protein adsorption at the interface. Here we use coarse-grained molecular-dynamics simulations to consider a number of related issues by calculating the interfacial tension in protein-free lipid droplets, and in HDL and LDL particles mimicking physiological conditions. First, our results suggest that the curvature dependence of interfacial tension becomes significant for particles with a radius of ∼5 nm, when the area per molecule in the surface region is <1.4 nm2. Further, interfacial tensions in the used HDL and LDL models are essentially unaffected by single apo-proteins at the surface. Finally, interfacial tensions of lipoproteins are higher than in thermodynamically stable droplets, suggesting that HDL and LDL are kinetically trapped into a metastable state. PMID:22995496

Multifunctional picoliter droplet manipulation platform and its application in single cell analysis.

PubMed

Gu, Shu-Qing; Zhang, Yun-Xia; Zhu, Ying; Du, Wen-Bin; Yao, Bo; Fang, Qun

2011-10-01

We developed an automated and multifunctional microfluidic platform based on DropLab to perform flexible generation and complex manipulations of picoliter-scale droplets. Multiple manipulations including precise droplet generation, sequential reagent merging, and multistep solid-phase extraction for picoliter-scale droplets could be achieved in the present platform. The system precision in generating picoliter-scale droplets was significantly improved by minimizing the thermo-induced fluctuation of flow rate. A novel droplet fusion technique based on the difference of droplet interfacial tensions was developed without the need of special microchannel networks or external devices. It enabled sequential addition of reagents to droplets on demand for multistep reactions. We also developed an effective picoliter-scale droplet splitting technique with magnetic actuation. The difficulty in phase separation of magnetic beads from picoliter-scale droplets due to the high interfacial tension was overcome using ferromagnetic particles to carry the magnetic beads to pass through the phase interface. With this technique, multistep solid-phase extraction was achieved among picoliter-scale droplets. The present platform had the ability to perform complex multistep manipulations to picoliter-scale droplets, which is particularly required for single cell analysis. Its utility and potentials in single cell analysis were preliminarily demonstrated in achieving high-efficiency single-cell encapsulation, enzyme activity assay at the single cell level, and especially, single cell DNA purification based on solid-phase extraction.

Measurement of the Surface Dilatational Viscosity of an Insoluble Surfactant Monolayer at the Air/Water Interface Using a Pendant Drop Apparatus

NASA Technical Reports Server (NTRS)

Lorenzo, Jose; Couzis, Alex; Maldarelli, Charles; Singh, Bhim S. (Technical Monitor)

2000-01-01

When a fluid interface with surfactants is at rest, the interfacial stress is isotropic (as given by the equilibrium interfacial tension), and is described by the equation of state which relates the surface tension to the surfactant surface concentration. When surfactants are subjected to shear and dilatational flows, flow induced interaction of the surfactants; can create interfacial stresses apart from the equilibrium surface tension. The simplest relationship between surface strain rate and surface stress is the Boussinesq-Scriven constitutive equation completely characterized by three coefficients: equilibrium interfacial tension, surface shear viscosity, and surface dilatational viscosity Equilibrium interfacial tension and surface shear viscosity measurements are very well established. On the other hand, surface dilatational viscosity measurements are difficult because a flow which change the surface area also changes the surfactant surface concentration creating changes in the equilibrium interfacial tension that must be also taken into account. Surface dilatational viscosity measurements of existing techniques differ by five orders of magnitude and use spatially damped surface waves and rapidly expanding bubbles. In this presentation we introduce a new technique for measuring the surface dilatational viscosity by contracting an aqueous pendant drop attached to a needle tip and having and insoluble surfactant monolayer at the air-water interface. The isotropic total tension on the surface consists of the equilibrium surface tension and the tension due to the dilation. Compression rates are undertaken slow enough so that bulk hydrodynamic stresses are small compared to the surface tension force. Under these conditions we show that the total tension is uniform along the surface and that the Young-Laplace equation governs the drop shape with the equilibrium surface tension replaced by the constant surface isotropic stress. We illustrate this technique using DPPC as the insoluble surfacant monolayer and measured for it a surface dilatational viscosity in the LE phase that is 20 surface poise.

Calculation of contact angles at triple phase boundary in solid oxide fuel cell anode using the level set method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Xiaojun; Hasegawa, Yosuke; CREST, JST

2014-10-15

A level set method is applied to characterize the three dimensional structures of nickel, yttria stabilized zirconia and pore phases in solid oxide fuel cell anode reconstructed by focused ion beam-scanning electron microscope. A numerical algorithm is developed to evaluate the contact angles at the triple phase boundary based on interfacial normal vectors which can be calculated from the signed distance functions defined for each of the three phases. Furthermore, surface tension force is estimated from the contact angles by assuming the interfacial force balance at the triple phase boundary. The average contact angle values of nickel, yttria stabilized zirconiamore » and pore are found to be 143°–156°, 83°–138° and 82°–123°, respectively. The mean contact angles remained nearly unchanged after 100 hour operation. However, the contact angles just after reduction are different for the cells with different sintering temperatures. In addition, standard deviations of the contact angles are very large especially for yttria stabilized zirconia and pore phases. The calculated surface tension forces from mean contact angles were close to the experimental values found in the literature. Slight increase of surface tensions of nickel/pore and nickel/yttria stabilized zirconia were observed after operation. Present data are expected to be used not only for the understanding of the degradation mechanism, but also for the quantitative prediction of the microstructural temporal evolution of solid oxide fuel cell anode. - Highlights: • A level set method is applied to characterize the 3D structures of SOFC anode. • A numerical algorithm is developed to evaluate the contact angles at the TPB. • Surface tension force is estimated from the contact angles. • The average contact angle values are found to be 143o-156o, 83o-138o and 82o-123o. • Present data are expected to understand degradation and predict evolution of SOFC.« less

Atomistic modelling of evaporation and explosive boiling of thin film liquid argon over internally recessed nanostructured surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasan, Mohammad Nasim, E-mail: nasim@me.buet.ac.bd.com; Shavik, Sheikh Mohammad, E-mail: shavik@me.buet.ac.bd.com; Rabbi, Kazi Fazle, E-mail: rabbi35.me10@gmail.com

2016-07-12

Molecular dynamics (MD) simulations have been carried out to investigate evaporation and explosive boiling phenomena of thin film liquid argon on nanostructured solid surface with emphasis on the effect of solid-liquid interfacial wettability. The nanostructured surface considered herein consists of trapezoidal internal recesses of the solid platinum wall. The wetting conditions of the solid surface were assumed such that it covers both the hydrophilic and hydrophobic conditions and hence effect of interfacial wettability on resulting evaporation and boiling phenomena was the main focus of this study. The initial configuration of the simulation domain comprised of a three phase system (solidmore » platinum, liquid argon and vapor argon) on which equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. After equilibrium of the three-phase system was established, the wall was set to different temperatures (130 K and 250 K for the case of evaporation and explosive boiling respectively) to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat flux normal to the solid surface was also calculated to illustrate the effectiveness of heat transfer for hydrophilic and hydrophobic surfaces in cases of both nanostructured surface and flat surface. The results obtained show that both the wetting condition of the surface and the presence of internal recesses have significant effect on normal evaporation and explosive boiling of the thin liquid film. The heat transfer from solid to liquid in cases of surface with recesses are higher compared to flat surface without recesses. Also the surface with higher wettability (hydrophilic) provides more favorable conditions for boiling than the low-wetting surface (hydrophobic) and therefore, liquid argon responds quickly and shifts from liquid to vapor phase faster in case of hydrophilic surface. The heat transfer rate is also much higher in case of hydrophilic surface.« less

The Diverse Structures and Functions of Surfactant Proteins.

PubMed

Schor, Marieke; Reid, Jack L; MacPhee, Cait E; Stanley-Wall, Nicola R

2016-07-01

Surface tension at liquid-air interfaces is a major barrier that needs to be surmounted by a wide range of organisms; surfactant and interfacially active proteins have evolved for this purpose. Although these proteins are essential for a variety of biological processes, our understanding of how they elicit their function has been limited. However, with the recent determination of high-resolution 3D structures of several examples, we have gained insight into the distinct shapes and mechanisms that have evolved to confer interfacial activity. It is now a matter of harnessing this information, and these systems, for biotechnological purposes. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Anti-Adhesive Behaviors between Solid Hydrate and Liquid Aqueous Phase Induced by Hydrophobic Silica Nanoparticles.

PubMed

Min, Juwon; Baek, Seungjun; Somasundaran, P; Lee, Jae W

2016-09-20

This study introduces an "anti-adhesive force" at the interface of solid hydrate and liquid solution phases. The force was induced by the presence of hydrophobic silica nanoparticles or one of the common anti-agglomerants (AAs), sorbitan monolaurate (Span 20), at the interface. The anti-adhesive force, which is defined as the maximum pushing force that does not induce the formation of a capillary bridge between the cyclopentane (CP) hydrate particle and the aqueous solution, was measured using a microbalance. Both hydrophobic silica nanoparticles and Span 20 can inhibit adhesion between the CP hydrate probe and the aqueous phase because silica nanoparticles have an aggregative property at the interface, and Span 20 enables the hydrate surface to be wetted with oil. Adding water-soluble sodium dodecyl sulfate (SDS) to the nanoparticle system cannot affect the aggregative property or the distribution of silica nanoparticles at the interface and, thus, cannot change the anti-adhesive effect. However, the combined system of Span 20 and SDS dramatically reduces the interfacial tension: emulsion drops were formed at the interface without any energy input and were adsorbed on the CP hydrate surface, which can cause the growth of hydrate particles. Silica nanoparticles have a good anti-adhesive performance with a relatively smaller dosage and are less influenced by the presence of molecular surfactants; consequently, these nanoparticles may have a good potential for hydrate inhibition as AAs.

Interfacial mechanisms for stability of surfactant-laden films

PubMed Central

Chai, Chew; Àlvarez-Valenzuela, Marco A.; Tajuelo, Javier; Fuller, Gerald G.

2017-01-01

Thin liquid films are central to everyday life. They are ubiquitous in modern technology (pharmaceuticals, coatings), consumer products (foams, emulsions) and also serve vital biological functions (tear film of the eye, pulmonary surfactants in the lung). A common feature in all these examples is the presence of surface-active molecules at the air-liquid interface. Though they form only molecular-thin layers, these surfactants produce complex surface stresses on the free surface, which have important consequences for the dynamics and stability of the underlying thin liquid film. Here we conduct simple thinning experiments to explore the fundamental mechanisms that allow the surfactant molecules to slow the gravity-driven drainage of the underlying film. We present a simple model that works for both soluble and insoluble surfactant systems in the limit of negligible adsorption-desorption dynamics. We show that surfactants with finite surface rheology influence bulk flow through viscoelastic interfacial stresses, while surfactants with inviscid surfaces achieve stability through opposing surface-tension induced Marangoni flows. PMID:28520734

Water at surfaces with tunable surface chemistries

NASA Astrophysics Data System (ADS)

Sanders, Stephanie E.; Vanselous, Heather; Petersen, Poul B.

2018-03-01

Aqueous interfaces are ubiquitous in natural environments, spanning atmospheric, geological, oceanographic, and biological systems, as well as in technical applications, such as fuel cells and membrane filtration. Where liquid water terminates at a surface, an interfacial region is formed, which exhibits distinct properties from the bulk aqueous phase. The unique properties of water are governed by the hydrogen-bonded network. The chemical and physical properties of the surface dictate the boundary conditions of the bulk hydrogen-bonded network and thus the interfacial properties of the water and any molecules in that region. Understanding the properties of interfacial water requires systematically characterizing the structure and dynamics of interfacial water as a function of the surface chemistry. In this review, we focus on the use of experimental surface-specific spectroscopic methods to understand the properties of interfacial water as a function of surface chemistry. Investigations of the air-water interface, as well as efforts in tuning the properties of the air-water interface by adding solutes or surfactants, are briefly discussed. Buried aqueous interfaces can be accessed with careful selection of spectroscopic technique and sample configuration, further expanding the range of chemical environments that can be probed, including solid inorganic materials, polymers, and water immiscible liquids. Solid substrates can be finely tuned by functionalization with self-assembled monolayers, polymers, or biomolecules. These variables provide a platform for systematically tuning the chemical nature of the interface and examining the resulting water structure. Finally, time-resolved methods to probe the dynamics of interfacial water are briefly summarized before discussing the current status and future directions in studying the structure and dynamics of interfacial water.

Molecular dynamics of the water liquid-vapor interface

NASA Technical Reports Server (NTRS)

Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

1987-01-01

The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C2 nu molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 +/- 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.

A compressible multiphase framework for simulating supersonic atomization

NASA Astrophysics Data System (ADS)

Regele, Jonathan D.; Garrick, Daniel P.; Hosseinzadeh-Nik, Zahra; Aslani, Mohamad; Owkes, Mark

2016-11-01

The study of atomization in supersonic combustors is critical in designing efficient and high performance scramjets. Numerical methods incorporating surface tension effects have largely focused on the incompressible regime as most atomization applications occur at low Mach numbers. Simulating surface tension effects in high speed compressible flow requires robust numerical methods that can handle discontinuities caused by both material interfaces and shocks. A shock capturing/diffused interface method is developed to simulate high-speed compressible gas-liquid flows with surface tension effects using the five-equation model. This includes developments that account for the interfacial pressure jump that occurs in the presence of surface tension. A simple and efficient method for computing local interface curvature is developed and an acoustic non-dimensional scaling for the surface tension force is proposed. The method successfully captures a variety of droplet breakup modes over a range of Weber numbers and demonstrates the impact of surface tension in countering droplet deformation in both subsonic and supersonic cross flows.

Transport properties at fluids interfaces: a molecular study for a macroscopic modelling

NASA Astrophysics Data System (ADS)

Russo, Antonio; Morciano, Matteo; Sibley, David N.; Nold, Andreas; Goddard, Benjamin D.; Asinari, Pietro; Kalliadasis, Serafim

2017-11-01

Rapid developments in the field of micro- and nano-fluidics require detailed analysis of the properties of matter at the molecular level. But despite numerous works in the literature, appropriate macroscopic relations able to integrate a microscopic description of fluid and soft matter properties at liquid-vapour and multi-fluid interfaces are missing. As a consequence, studies on interfacial phenomena and micro-device designs often rely on oversimplified assumptions, e.g. that the viscosities can be considered constant across interfaces. In our work, we present non-equilibrium MD simulations to scrutinise efficiently and systematically, through the tools of statistical mechanics, the anisotropic properties of fluids, namely density variations, stress tensor, and shear viscosity, at the fluid interfaces between liquid and vapour and between two partially miscible fluids. Our analysis has led to the formulation of a general relation between shear viscosity and density variations validated for a wide spectrum of interfacial fluid problems. In addition, it provides a rational description of other interfacial quantities of interest, including surface tension and its origins, and more generally, it offers valuable insight of molecular transport phenomena at interfaces.

Interfacial strength development in thermoplastic resins and fiber-reinforced thermoplastic composites

NASA Technical Reports Server (NTRS)

Howes, Jeremy C.; Loos, Alfred C.

1987-01-01

An experimental program to develop test methods to be used to characterize interfacial (autohesive) strength development in polysulfone thermoplastic resin and graphite-polysulfone prepreg during processing is reported. Two test methods were used to examine interfacial strength development in neat resin samples. These included an interfacial tension test and a compact tension (CT) fracture toughness test. The interfacial tensile test proved to be very difficult to perform with a considerable amount of data scatter. Thus, the interfacial test was discarded in favor of the fracture toughness test. Interfacial strength development was observed by measuring the refracture toughness of precracked compact tension specimens that were rehealed at a given temperature and contact time. The measured refracture toughness was correlated with temperature and contact time. Interfacial strength development in graphite-polysulfone unidirectional composites was measured using a double cantilever beam (DCB) interlaminar fracture toughness test. The critical strain energy release rate of refractured composite specimens was measured as a function of healing temperature and contact time.

Bubble-Free Containers For Liquids In Microgravity

NASA Technical Reports Server (NTRS)

Kornfeld, Dale M.; Antar, Basil L.

1995-01-01

Reports discuss entrainment of gas bubbles during handling of liquids in microgravity, and one report proposes containers filled with liquids in microgravity without entraining bubbles. Bubbles are troublesome in low-gravity experiments - particularly in biological experiments. Wire-mesh cage retains liquid contents without solid wall, because in microgravity, surface tension of liquid exerts sufficient confining force.

In situ creation of reactive polymer nanoparticles and resulting polymer layers formed at the interfaces of liquid crystals (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kang, Shin-Woong; Kundu, Sudarshan; Park, Heung-Shik; Oh, Keun Chan; Lyu, Jae Jin

2017-02-01

We report the in situ creation of reactive polymer nanoparticles and resulting polymer networks formed at the interfaces of liquid crystals. It is known that polymerization-induced phase separation proceeds in two distinct regimes depending on the concentration of monomer. For a high monomer concentration, phase separation occurs mainly through the spinodal decomposition process, consequently resulting in interpenetrating polymer networks. For a dilute system, however, the phase separation mainly proceeds and completes in the binodal decomposition regime. The system resembles the aggregation process of colloidal particle. In this case, the reaction kinetics is limited by the reaction between in situ created polymer aggregates and hence the network morphologies are greatly influenced by the diffusion of reactive polymer particles. The thin polymer layers localized at the surface of substrate are inevitably observed and can be comprehended by the interfacial adsorption and further cross-linking reaction of reactive polymer aggregates at the interface. This process provides a direct perception on understanding polymer stabilized liquid crystals accomplished by the interfacial polymer layer. The detailed study has been performed for an extremely dilute condition (below 0.5 wt%) by employing systematic experimental approaches. Creation and growth of polymer nanoparticles have been measured by particle size analyzer. The interfacial localization of polymer aggregates and resulting interfacial layer formation with a tens of nanometer scale have been exploited at various interfaces such as liquid-solid, liquid-liquid, and liquid-gas interfaces. The resulting interfacial layers have been characterized by using fuorescent confocal microscope and field emission scanning electron microscope. The detailed processes of the polymer stabilized vertically aligned liquid crystals will be discussed in support of the reported study.

Nonequilibrium Interfacial Tension in Simple and Complex Fluids

NASA Astrophysics Data System (ADS)

Truzzolillo, Domenico; Mora, Serge; Dupas, Christelle; Cipelletti, Luca

2016-10-01

Interfacial tension between immiscible phases is a well-known phenomenon, which manifests itself in everyday life, from the shape of droplets and foam bubbles to the capillary rise of sap in plants or the locomotion of insects on a water surface. More than a century ago, Korteweg generalized this notion by arguing that stresses at the interface between two miscible fluids act transiently as an effective, nonequilibrium interfacial tension, before homogenization is eventually reached. In spite of its relevance in fields as diverse as geosciences, polymer physics, multiphase flows, and fluid removal, experiments and theoretical works on the interfacial tension of miscible systems are still scarce, and mostly restricted to molecular fluids. This leaves crucial questions unanswered, concerning the very existence of the effective interfacial tension, its stabilizing or destabilizing character, and its dependence on the fluid's composition and concentration gradients. We present an extensive set of measurements on miscible complex fluids that demonstrate the existence and the stabilizing character of the effective interfacial tension, unveil new regimes beyond Korteweg's predictions, and quantify its dependence on the nature of the fluids and the composition gradient at the interface. We introduce a simple yet general model that rationalizes nonequilibrium interfacial stresses to arbitrary mixtures, beyond Korteweg's small gradient regime, and show that the model captures remarkably well both our new measurements and literature data on molecular and polymer fluids. Finally, we briefly discuss the relevance of our model to a variety of interface-driven problems, from phase separation to fracture, which are not adequately captured by current approaches based on the assumption of small gradients.

Measurement of interfacial tension by use of pendant drop video techniques

NASA Astrophysics Data System (ADS)

Herd, Melvin D.; Thomas, Charles P.; Bala, Gregory A.; Lassahn, Gordon D.

1993-09-01

This report describes an instrument to measure the interfacial tension (IFT) of aqueous surfactant solutions and crude oil. The method involves injection of a drop of fluid (such as crude oil) into a second immiscible phase to determine the IFT between the two phases. The instrument is composed of an AT-class computer, optical cell, illumination, video camera and lens, video frame digitizer board, monitor, and software. The camera displays an image of the pendant drop on the monitor, which is then processed by the frame digitizer board and non-proprietary software to determine the IFT. Several binary and ternary phase systems were taken from the literature and used to measure the precision and accuracy of the instrument in determining IFT's. A copy of the software program is included in the report. A copy of the program on diskette can be obtained from the Energy Science and Technology Software Center, P.O. Box 1020, Oak Ridge, TN 37831-1020. The accuracy and precision of the technique and apparatus presented is very good for measurement of IFT's in the range from 72 to 10(exp -2) mN/m, which is adequate for many EOR applications. With modifications to the equipment and the numerical techniques, measurements of ultralow IFT's (less than 10(exp -3) mN/m) should be possible as well as measurements at reservoir temperature and pressure conditions. The instrument has been used at the Idaho National Engineering Laboratory to support the research program on microbial enhanced oil recovery. Measurements of IFT's for several bacterial supernatants and unfractionated acid precipitates of microbial cultures containing biosurfactants against medium to heavy crude oils are reported. These experiments demonstrate that the use of automated video imaging of pendant drops is a simple and fast method to reliably determine interfacial tension between two immiscible liquid phases, or between a gas and a liquid phase.

Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or enhanced oil recovery: High performance at low concentration

PubMed Central

Luo, Dan; Wang, Feng; Zhu, Jingyi; Cao, Feng; Liu, Yuan; Li, Xiaogang; Willson, Richard C.; Yang, Zhaozhong; Chu, Ching-Wu; Ren, Zhifeng

2016-01-01

The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil–water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl2), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions. PMID:27354529

Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or enhanced oil recovery: High performance at low concentration.

PubMed

Luo, Dan; Wang, Feng; Zhu, Jingyi; Cao, Feng; Liu, Yuan; Li, Xiaogang; Willson, Richard C; Yang, Zhaozhong; Chu, Ching-Wu; Ren, Zhifeng

2016-07-12

The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil-water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl2), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions.

Adsorption kinetics of alkanethiol-capped gold nanoparticles at the hexane-water interface

NASA Astrophysics Data System (ADS)

Ferdous, Sultana; Ioannidis, Marios A.; Henneke, Dale

2011-12-01

The pendant drop technique was used to characterize the adsorption behavior of n-dodecane-1-thiol and n-hexane-1-thiol-capped gold nanoparticles at the hexane-water interface. The adsorption process was studied by analyzing the dynamic interfacial tension versus nanoparticle concentration, both at early times and at later stages (i.e., immediately after the interface between the fluids is made and once equilibrium has been established). A series of gold colloids were made using nanoparticles ranging in size from 1.60 to 2.85 nm dissolved in hexane for the interfacial tension analysis. Following free diffusion of nanoparticles from the bulk hexane phase, adsorption leads to ordering and rearrangement of the nanoparticles at the interface and formation of a dense monolayer. With increasing interfacial coverage, the diffusion-controlled adsorption for the nanoparticles at the interface was found to change to an interaction-controlled assembly and the presence of an adsorption barrier was experimentally verified. At the same bulk concentration, different sizes of n-dodecane-1-thiol nanoparticles showed different absorption behavior at the interface, in agreement with the findings of Kutuzov et al. (Phys Chem Chem Phys 9:6351-6358, 2007). The experiments additionally demonstrated the important role played by the capping agent. At the same concentration, gold nanoparticles stabilized by n-hexane-1-thiol exhibited greater surface activity than gold nanoparticles of the same size stabilized by n-dodecane-1-thiol. These findings contribute to the design of useful supra-colloidal structures by the self-assembly of alkane-thiol-capped gold nanoparticles at liquid-liquid interfaces.

Thermo-Physical Properties of B2O3-Containing Mold Flux for High Carbon Steels in Thin Slab Continuous Casters: Structure, Viscosity, Crystallization, and Wettability

NASA Astrophysics Data System (ADS)

Park, Jun-Yong; Kim, Gi Hyun; Kim, Jong Bae; Park, Sewoong; Sohn, Il

2016-08-01

The effect of B2O3 on the thermo-physical properties of commercial mold fluxes, including the viscosity, crystallization behavior, and wettability, was investigated. Viscosity was measured using the rotating spindle method, and CCT (continuous cooling transformation) diagrams were obtained to investigate the crystallization behavior at various cooling rates using CLSM (confocal laser scanning microscope). The wettability of the fluxes was determined by measuring the contact angles at 1573 K (1300 °C) using the digital images generated by the sessile drop method and were used to calculate the surface tension, interfacial tension, and work of adhesion for Flux A (existing flux) and B (modified flux). These thermo-physical properties were correlated with the structural analysis obtained using FT-IR (Fourier transform-infrared), Raman and MAS-NMR (magic angle spin-nuclear magnetic resonance) spectroscopy. In addition, DTA (differential thermal analysis) was performed on the samples to measure the liquidus temperatures. Higher B2O3 concentrations resulted in lower liquidus temperatures, consequently decreasing the viscosity, the break temperature, and the crystallization temperature. However, B2O3 addition accelerated crystal growth owing to the higher diffusion kinetics of the cations, which also reduced the size of the liquid/solid co-existing region.

Fabricating small-scale, curved, polymeric structures with convex and concave menisci through interfacial free energy equilibrium.

PubMed

Cheng, Chao-Min; Matsuura, Koji; Wang, I-Jan; Kuroda, Yuka; LeDuc, Philip R; Naruse, Keiji

2009-11-21

Polymeric curved structures are widely used in imaging systems including optical fibers and microfluidic channels. Here, we demonstrate that small-scale, poly(dimethylsiloxane) (PDMS)-based, curved structures can be fabricated through controlling interfacial free energy equilibrium. Resultant structures have a smooth, symmetric, curved surface, and may be convex or concave in form based on surface tension balance. Their curvatures are controlled by surface characteristics (i.e., hydrophobicity and hydrophilicity) of the molds and semi-liquid PDMS. In addition, these structures are shown to be biocompatible for cell culture. Our system provides a simple, efficient and economical method for generating integrateable optical components without costly fabrication facilities.

Interfacial behavior of alkaline protease at the air-water and oil-water interfaces

NASA Astrophysics Data System (ADS)

Zhang, Jian; Li, Yanyan; Wang, Jing; Zhang, Yue

2018-03-01

The interfacial behavior of alkaline protease at the air-water and n-hexane-water interfaces was investigated using interfacial tension, dilatational rheology and dynamic light scattering. Additionally, different adsorption models which are Langmuir, Frumkin, Reorientation-A and Reorientation-R were used to fitting the data of equilibrium interfacial tension for further understanding the interfacial behavior of alkaline protease. Data fitting of the equilibrium interfacial tension was achieved by IsoFit software. The results show that the molecules arrangement of the alkaline protease at the n-hexane-water interface is more tightly than at the air-water interface. The data were further analyzed to indicate that the hydrophobic chains of alkaline protease penetrate into oil phase deeper than the air phase. Also data indicate that the electrostatic interactions and hydrophobic interactions at the n-hexane-water interface are stronger than at the air-water interface within molecules of the alkaline protease. Based on comprehensive analysis of the adsorption kinetics and interfacial rheological properties, interfacial structures mechanism of alkaline protease at n-hexane-water and air-water interfaces was proposed.

Thermodynamic properties of triangle-well fluids in two dimensions: MC and MD simulations.

PubMed

Reyes, Yuri; Bárcenas, Mariana; Odriozola, Gerardo; Orea, Pedro

2016-11-07

With the aim of providing complementary data of the thermodynamics properties of the triangular well potential, the vapor/liquid phase diagrams for such potential with different interaction ranges were calculated in two dimensions by Monte Carlo and molecular dynamics simulations; also, the vapor/liquid interfacial tension was calculated. As reported for other interaction potentials, it was observed that the reduction of the dimensionality makes the phase diagram to shrink. Finally, with the aid of reported data for the same potential in three dimensions, it was observed that this potential does not follow the principle of corresponding states.

Abnormal gas-liquid-solid phase transition behaviour of water observed with in situ environmental SEM.

PubMed

Chen, Xin; Shu, Jiapei; Chen, Qing

2017-04-24

Gas-liquid-solid phase transition behaviour of water is studied with environmental scanning electron microscopy for the first time. Abnormal phenomena are observed. At a fixed pressure of 450 Pa, with the temperature set to -7 °C, direct desublimation happens, and ice grows continuously along the substrate surface. At 550 Pa, although ice is the stable phase according to the phase diagram, metastable liquid droplets first nucleate and grow to ~100-200 μm sizes. Ice crystals nucleate within the large sized droplets, grow up and fill up the droplets. Later, the ice crystals grow continuously through desublimation. At 600 Pa, the metastable liquid grows quickly, with some ice nuclei floating in it, and the liquid-solid coexistence state exists for a long time. By lowering the vapour pressure and/or increasing the substrate temperature, ice sublimates into vapour phase, and especially, the remaining ice forms a porous structure due to preferential sublimation in the concave regions, which can be explained with surface tension effect. Interestingly, although it should be forbidden for ice to transform into liquid phase when the temperature is well below 0 °C, liquid like droplets form during the ice sublimation process, which is attributed to the surface tension effect and the quasiliquid layers.

Interfacial behaviour of biopolymer multilayers: Influence of in vitro digestive conditions.

PubMed

Corstens, Meinou N; Osorio Caltenco, Lilia A; de Vries, Renko; Schroën, Karin; Berton-Carabin, Claire C

2017-05-01

Although multilayered emulsions have been related to reduced lipolysis, the involved interfacial phenomena have never been studied directly. In this work, we systematically built multilayers of whey protein and pectin, which we further subjected to digestive conditions, using two different techniques: droplet volume tensiometry to investigate interfacial rheology, and reflectometry to determine the amount of adsorbed material. Interfacial tension and dilatational rheology were linked to adsorption/desorption kinetics measured under static in vitro conditions. The interfacial tension and rheology of the multilayers was rather similar to those found for single whey protein layers, as well as their resistance to duodenal conditions and lipolytic components, which is explained by the rapid destabilisation of multilayers at neutral pH. Sequential adsorption of bile extract or lipase to pre-adsorbed films rapidly lowered the interfacial tension via co-adsorption and displacement, forming a viscoelastic film with low mechanical strength, and highly dynamic adsorption/desorption. When both were present, bile salts dominated the initial adsorption, followed by lipase co-adsorption and formation of lipolysis products that further lowered the interfacial tension, forming a complex interface (including biopolymers, bile salts, lipase, and lipolysis products), independent of pre-adsorbed biopolymer layers. Our study shows that the combination of drop volume tensiometry and reflectometry can be used to study complex interfacial behaviours under digestive conditions, which can lead to smart design of interfacial structures for controlled lipolysis in food emulsions. Copyright © 2017 Elsevier B.V. All rights reserved.

Interfacial Effects on the Band Edges of Functionalized Si Surfaces in Liquid Water

DOE PAGES

Pham, Tuan Anh; Lee, Donghwa; Schwegler, Eric; ...

2014-11-17

By combining ab initio molecular dynamics simulations and many-body perturbation theory calculations of electronic energy levels, we determined the band edge positions of functionalized Si(111) surfaces in the presence of liquid water, with respect to vacuum and to water redox potentials. We considered surface terminations commonly used for Si photoelectrodes in water splitting experiments. We found that, when exposed to water, the semiconductor band edges were shifted by approximately 0.5 eV in the case of hydrophobic surfaces, irrespective of the termination. The effect of the liquid on band edge positions of hydrophilic surfaces was much more significant and determined bymore » a complex combination of structural and electronic effects. These include structural rearrangements of the semiconductor surfaces in the presence of water, changes in the orientation of interfacial water molecules with respect to the bulk liquid, and charge transfer at the interfaces, between the solid and the liquid. Our results showed that the use of many-body perturbation theory is key to obtain results in agreement with experiments; they also showed that the use of simple computational schemes that neglect the detailed microscopic structure of the solid–liquid interface may lead to substantial errors in predicting the alignment between the solid band edges and water redox potentials.« less

Slip length enhancement in nanofluidic flow using nanotextured superhydrophobic surfaces

DOE PAGES

Heverhagen, Jonas; Checco, Antonio; Tasinkevych, Mykola; ...

2016-06-28

In our study, the development of highly efficient nanofluidic devices necessitates means for enhancing and controlling fluid transport under confinement. We show experimentally that significant interfacial drag reduction in nanoscale channels can be obtained with hydrophobic arrays of conical textures tapering to a radius of less than 10 nanometer at their tip. Finally, this geometry maximizes interfacial slippage by trapping a highly resilient air layer at the solid/liquid interface.

The Marangoni convection induced by acetone desorption from the falling soap film

NASA Astrophysics Data System (ADS)

Sha, Yong; Li, Zhangyun; Wang, Yongyi; Huang, Jiali

2012-05-01

By means of the falling soap film tunnel and the Schlieren optical method, the Marangoni convection were observed directly in the immediate interfacial neighborhood during the desorption process of acetone from the falling soap film. Moreover, the hydraulic characteristics of the falling soap film tunnel, the acetone concentration, the surface tension of the soap liquid and the mass transfer has been investigated in details through the experimental or theoretical method.

Interfacial behaviours between lithium ion conductors and electrode materials in various battery systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Bingbin; Wang, Shanyu; Evans IV, Willie J.

In recent years room temperature Li+ ion conductors have been intensively revisited in order to develop safe lithium ion (Li-ion) batteries and beyond that can be deployed in the electrical vehicles. Through careful modification on materials synthesis, promising solid Li+ conductors with high ionic conductivity, competitve with liquid electrolytes, have been demonstrated. However, the integration of those highly conductive solid electrolytes into the whole system is still very challenging mainly due to the high impedance existing in the different interfaces throughout the entire battery structure. Herein , this review paper focuses on the overview of the interfacial behaviors between Li+more » conductors and cathode/anode materials. The origin, evolution and potential solutions to reuce these interfacial impedances are reviewed for various battery systems spanning from Li-ion, lithium sulfur (Li-S), lithium oxygen (Li-O2) batteries to lithium metal protection. The predicted gravimetric and volumetric energy densities at different scenarios are also discussed along with the prospectives for further development of solid state batteries.« less

Behavior of fluids in a weightless environment

NASA Technical Reports Server (NTRS)

Fester, D. A.; Eberhardt, R. N.; Tegart, J. R.

1977-01-01

Fluid behavior in a low-g environment is controlled primarily by surface tension forces. Certain fluid and system characteristics determine the magnitude of these forces for both a free liquid surface and liquid in contact with a solid. These characteristics, including surface tension, wettability or contact angle, system geometry, and the relationships governing their interaction, are discussed. Various aspects of fluid behavior in a low-g environment are then presented. This includes the formation of static interface shapes, oscillation and rotation of drops, coalescence, the formation of foams, tendency for cavitation, and diffusion in liquids which were observed during the Skylab fluid mechanics science demonstrations. Liquid reorientation and capillary pumping to establish equilibrium configurations for various system geometries, observed during various free-fall (drop-tower) low-g tests, are also presented. Several passive low-g fluid storage and transfer systems are discussed. These systems use surface tension forces to control the liquid/vapor interface and provide gas-free liquid transfer and liquid-free vapor venting.

Effect of surfactant on kinetics of thinning of capillary bridges

NASA Astrophysics Data System (ADS)

Nowak, Emilia; Kovalchuk, Nina; Simmons, Mark

2015-11-01

Kinetics of thinning of capillary bridges is of great scientific and industrial interest being of vital importance for example in various emulsification and microfluidic processes. It is well known that the rate of bridge thinning is proportional to the interfacial tension. Therefore it is expected that the process should slow down by addition of surfactant. The kinetics of capillary bridges in the presence of surfactant was studied by the dripping of liquid from a capillary tip under conditions of nearly zero flow rate (We << 1). The tested liquids were aqueous solutions of sodium lauryl ether sulphate (SLES), which is broadly used in personal care products. The viscosity, surfactant activity and adsorption kinetics have been controlled by addition of glycerol and sodium chloride. The study has shown that the kinetics of capillary bridges are determined by dynamic surface tension rather than by its equilibrium value. In particular, the kinetics of the bridge thinning for the 0.1 g L-1 aqueous SLES solution is practically the same as that of pure water despite twice lower equilibrium surface tension. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

Surfactant effects on interfacial flow and thermal transport processes during phase change in film boiling

NASA Astrophysics Data System (ADS)

Premnath, Kannan N.; Hajabdollahi, Farzaneh; Welch, Samuel W. J.

2018-04-01

The presence of surfactants in two-phase flows results in the transport and adsorption of surfactants to the interface, and the resulting local interfacial concentration significantly influences the surface tension between the liquid and vapor phases in a fluid undergoing phase change. This computational study is aimed at understanding and elucidating the mechanisms of enhanced flows and thermal transport processes in film boiling due to the addition of surfactants. A change in surface tension results in a change in the critical Rayleigh-Taylor wavelength leading to different bubble release patterns and a change in the overall heat transfer rates. Due to the presence of surfactants, an additional transport mechanism of the Marangoni convection arises from the resulting tangential gradients in the surfactant concentration along the phase interface. Our computational approach to study such phenomena consists of representing the interfacial motion by means of the coupled level set-volume-of-fluid method, the fluid motion via the classical marker-and-cell approach, as well as representations for the bulk transport of energy and surfactants, in conjunction with a phase change model and an interfacial surfactant model. Using such an approach, we perform numerical simulations of surfactant-laden single mode as well as multiple mode film boiling and study the effect of surfactants on the transport processes in film boiling, including bubble release patterns, vapor generation rates, and heat transfer rates at different surfactant concentrations. The details of the underlying mechanisms will be investigated and interpreted.

Stability of Shapes Held by Surface Tension and Subjected to Flow

NASA Technical Reports Server (NTRS)

Chen, Yi-Ju; Robinson, Nathaniel D.; Steen, Paul H.

1999-01-01

Results of three problems are summarized in this contribution. Each involves the fundamental capillary instability of an interfacial bridge and is an extension of previous work. The first two problems concern equilibrium shapes of liquid bridges near the stability boundary corresponding to maximum length (Plateau-Rayleigh limit). For the first problem, a previously formulated nonlinear theory to account for imposed gravity and interfacial shear disturbances in an isothermal environment is quantitatively tested in experiment. For the second problem, the liquid bridge is subjected to a shear that models the effect of a thermocapillary flow generated by a ring heater in a liquid encapsulated float-zone configuration. In the absence of gravity, this symmetric perturbation can stabilize the bridge to lengths on the order of 30 percent beyond the Plateau-Rayleigh limit, which is on the order of heretofore unexplained Shuttle observations. The third problem considers the dynamics of collapse and pinchoff of a film bridge (no gravity), which happens in the absence of stabilization. Here, we summarize experimental efforts to measure the self-similar cone-and-crater structure predicted by a previous theory.

Ambient-Pressure X-ray Photoelectron Spectroscopy to Characterize the Solid/Liquid Interface: Probing the Electrochemical Double Layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favaro, Marco; Liu, Zhi; Crumlin, Ethan J.

Ambient-pressure X-ray photoelectron spectroscopy (APXPS) has contributed greatly to a wide range of research fields, including environmental science, catalysis, and electrochemistry, to name a few. The use of this technique at synchrotron facilities primarily focused on probing the solid/gas interface; however, it quickly advanced to the probing of liquid/vapor interfaces and solid/liquid interfaces through an X-ray-transparent window. Most recently, combining APXPS with “Tender” X-rays (~2.5 keV to 8 keV) on beamline 9.3.1 at the Advanced Light Source in Lawrence Berkeley National Laboratory (which can generate photoelectrons with much longer inelastic mean free paths) has enabled us to probe the solid/liquidmore » interface without needing a window. This innovation allows us to probe interfacial chemistries of electrochemically controlled solid/liquid interfaces undergoing charge transfer reactions. Lastly, these advancements have transitioned APXPS from a traditional surface science tool to an essential interface science technique.« less

Ambient-Pressure X-ray Photoelectron Spectroscopy to Characterize the Solid/Liquid Interface: Probing the Electrochemical Double Layer

DOE PAGES

Favaro, Marco; Liu, Zhi; Crumlin, Ethan J.

2017-03-31

Ambient-pressure X-ray photoelectron spectroscopy (APXPS) has contributed greatly to a wide range of research fields, including environmental science, catalysis, and electrochemistry, to name a few. The use of this technique at synchrotron facilities primarily focused on probing the solid/gas interface; however, it quickly advanced to the probing of liquid/vapor interfaces and solid/liquid interfaces through an X-ray-transparent window. Most recently, combining APXPS with “Tender” X-rays (~2.5 keV to 8 keV) on beamline 9.3.1 at the Advanced Light Source in Lawrence Berkeley National Laboratory (which can generate photoelectrons with much longer inelastic mean free paths) has enabled us to probe the solid/liquidmore » interface without needing a window. This innovation allows us to probe interfacial chemistries of electrochemically controlled solid/liquid interfaces undergoing charge transfer reactions. Lastly, these advancements have transitioned APXPS from a traditional surface science tool to an essential interface science technique.« less

Effects of temperature, pH, and ionic strength on the adsorption of nanoparticles at liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

Ferdous, Sultana; Ioannidis, Marios A.; Henneke, Dale E.

2012-05-01

The effects of temperature, pH and sodium chloride (NaCl) concentration on the equilibrium and dynamic interfacial tension (IFT) of 4.4-nm gold nanoparticles capped with n-dodecanethiol at hydrocarbon-water interfaces was studied. The pendant drop technique was used to study the adsorption properties of these nanoparticles at the hexane-water and nonane-water interfaces. The physical size of the gold nanoparticles was determined by TEM image analysis. The interfacial properties of mixtures of these nanoparticles, having different sizes and capping agents, were then studied. The addition of NaCl was found to cause a decrease of the equilibrium and dynamic IFT greater than that which accompanies the adsorption of nanoparticles at the interface in the absence of NaCl. Although IFT values for acidic and neutral conditions were found to be similar, a noticeable decrease in the IFT was found for more basic conditions. Increasing the temperature of the system was found to cause an increase in both dynamic and equilibrium IFT values. These findings have implications for the self-assembly of functionalized gold nanoparticles at liquid-liquid interfaces.

Engineering the biosynthesis of novel rhamnolipids in Escherichia coli for enhanced oil recovery.

PubMed

Han, L; Liu, P; Peng, Y; Lin, J; Wang, Q; Ma, Y

2014-07-01

The interfacial tension of rhamnolipids and their applications in enhanced oil recovery are dependent on their chemical structures and compositions. To improve their performances of interfacial tension and enhanced oil recovery, the engineered strategies were applied to produce novel rhamnolipids with different chemical structures and compositions. By introducing different key genes for rhamnolipid biosynthesis, Escherichia coli was firstly constructed to produce rhamnolipids that showed different performances in interfacial tension from those from Pseudomonas aeruginosa due to the different fatty acyl compositions. Then, the mutant RhlBs were created by directed evolution and subsequent site-directed mutagenesis and resulted in the production of the novel rhamnolipids with the different performances in interfacial tension as well as enhanced oil recovery. Lastly, computational modelling elucidates that the single amino acid mutation at the position 168 in RhlB would change the volume of binding pocket for substrate and thus affect the selectivity of rhamnolipid formation in E. coli. The novel rhamnolipids that showed the improved performances of interfacial tension and the potential different applications in enhanced oil recovery were successfully produced by engineered E. coli. This study proved that the combination of metabolic engineering and protein engineering is an important engineered strategy to produce many novel metabolites in micro-organisms. © 2014 The Society for Applied Microbiology.

Collective Cell Migration in Embryogenesis Follows the Laws of Wetting.

PubMed

Wallmeyer, Bernhard; Trinschek, Sarah; Yigit, Sargon; Thiele, Uwe; Betz, Timo

2018-01-09

Collective cell migration is a fundamental process during embryogenesis and its initial occurrence, called epiboly, is an excellent in vivo model to study the physical processes involved in collective cell movements that are key to understanding organ formation, cancer invasion, and wound healing. In zebrafish, epiboly starts with a cluster of cells at one pole of the spherical embryo. These cells are actively spreading in a continuous movement toward its other pole until they fully cover the yolk. Inspired by the physics of wetting, we determine the contact angle between the cells and the yolk during epiboly. By choosing a wetting approach, the relevant scale for this investigation is the tissue level, which is in contrast to other recent work. Similar to the case of a liquid drop on a surface, one observes three interfaces that carry mechanical tension. Assuming that interfacial force balance holds during the quasi-static spreading process, we employ the physics of wetting to predict the temporal change of the contact angle. Although the experimental values vary dramatically, the model allows us to rescale all measured contact-angle dynamics onto a single master curve explaining the collective cell movement. Thus, we describe the fundamental and complex developmental mechanism at the onset of embryogenesis by only three main parameters: the offset tension strength, α, that gives the strength of interfacial tension compared to other force-generating mechanisms; the tension ratio, δ, between the different interfaces; and the rate of tension variation, λ, which determines the timescale of the whole process. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Surface Tension and Viscosity of SCN and SCN-acetone Alloys at Melting Points and Higher Temperatures Using Surface Light Scattering Spectrometer

NASA Technical Reports Server (NTRS)

Tin, Padetha; deGroh, Henry C., III.

2003-01-01

Succinonitrile has been and is being used extensively in NASA's Microgravity Materials Science and Fluid Physics programs and as well as in several ground-based and microgravity studies including the Isothermal Dendritic Growth Experiment (IDGE). Succinonitrile (SCN) is useful as a model for the study of metal solidification, although it is an organic material, it has a BCC crystal structure and solidifies dendriticly like a metal. It is also transparent and has a low melting point (58.08 C). Previous measurements of succinonitrile (SCN) and alloys of succinonitrile and acetone surface tensions are extremely limited. Using the Surface Light Scattering technique we have determined non invasively, the surface tension and viscosity of SCN and SCN-Acetone Alloys at different temperatures. This relatively new and unique technique has several advantages over the classical methods such as, it is non invasive, has good accuracy and measures the surface tension and viscosity simultaneously. The accuracy of interfacial energy values obtained from this technique is better than 2% and viscosity about 10 %. Succinonitrile and succinonitrile-acetone alloys are well-established model materials with several essential physical properties accurately known - except the liquid/vapor surface tension at different elevated temperatures. We will be presenting the experimentally determined liquid/vapor surface energy and liquid viscosity of succinonitrile and succinonitrile-acetone alloys in the temperature range from their melting point to around 100 C using this non-invasive technique. We will also discuss about the measurement technique and new developments of the Surface Light Scattering Spectrometer.

In-drop capillary spooling of spider capture thread inspires hybrid fibers with mixed solid-liquid mechanical properties.

PubMed

Elettro, Hervé; Neukirch, Sébastien; Vollrath, Fritz; Antkowiak, Arnaud

2016-05-31

An essential element in the web-trap architecture, the capture silk spun by ecribellate orb spiders consists of glue droplets sitting astride a silk filament. Mechanically this thread presents a mixed solid-liquid behavior unknown to date. Under extension, capture silk behaves as a particularly stretchy solid, owing to its molecular nanosprings, but it totally switches behavior in compression to now become liquid-like: It shrinks with no apparent limit while exerting a constant tension. Here, we unravel the physics underpinning the unique behavior of this "liquid wire" and demonstrate that its mechanical response originates in the shape-switching of the silk filament induced by buckling within the droplets. Learning from this natural example of geometry and mechanics, we manufactured programmable liquid wires that present previously unidentified pathways for the design of new hybrid solid-liquid materials.

In-drop capillary spooling of spider capture thread inspires hybrid fibers with mixed solid-liquid mechanical properties

NASA Astrophysics Data System (ADS)

Elettro, Hervé; Neukirch, Sébastien; Vollrath, Fritz; Antkowiak, Arnaud

2016-05-01

An essential element in the web-trap architecture, the capture silk spun by ecribellate orb spiders consists of glue droplets sitting astride a silk filament. Mechanically this thread presents a mixed solid-liquid behavior unknown to date. Under extension, capture silk behaves as a particularly stretchy solid, owing to its molecular nanosprings, but it totally switches behavior in compression to now become liquid-like: It shrinks with no apparent limit while exerting a constant tension. Here, we unravel the physics underpinning the unique behavior of this ”liquid wire” and demonstrate that its mechanical response originates in the shape-switching of the silk filament induced by buckling within the droplets. Learning from this natural example of geometry and mechanics, we manufactured programmable liquid wires that present previously unidentified pathways for the design of new hybrid solid-liquid materials.

Interfacial Surgery Determination of Succinonitrile and Succinonitrile-Acetone Alloy Using Surface Light Scattering Spectrometer

NASA Technical Reports Server (NTRS)

Tin, Padetha; Frate, David T.; deGroh, Henry C., III

2001-01-01

The objectives of this ground based research is to measure the liquid/vapor interfacial surface energies of succinonitrile (SCN) and alloys of succinonitrile and acetone using Surface Light Scattering Spectrometer. Liquid/vapor interfacial energy measurements will be made near and above the melting point and are the primary goal of this proposal. A measurement of viscosity also results from the Surface Light Scattering technique employed. Interfacial free energies between the phases enters into many analysis of phase transformation and flow, including nucleation, dendritic growth, interface stability, Ostwald ripening, and Marangoni flow. Succirionitrile (SCN) is useful as a model for the study of metal solidification, although it is an organic material, it has a BCC crystal structure and solidifies dendriticly like a metal. It is also transparent and has a low melting point (58.08 C). Succinonitrile has been and is being used extensively in NASAs Microgravity Materials Science and Fluid Physics programs and as well as in several ground-based and microgravity studies including the Isothermal Dendritic Growth Experiment (IDGE) due to Glicksman and coworkers and subsequently in several theoretical and numerical studies of dendritic growth. Previous measurements of succinonitrile (SCN) and alloys of succinonitrile and acetone surface tensions are extremely limited. We believe the data sought through this proposal have significant basic physical property data value and thus the work proposed will provide needed data in support of NASAs Microgravity program research.

Surface charge-induced EDL interaction on the contact angle of surface nanobubbles.

PubMed

Jing, Dalei; Li, Dayong; Pan, Yunlu; Bhushan, Bharat

2016-11-01

The contact angle (CA) of surface nanobubbles is believed to affect the stability of nanobubbles and fluid drag in micro/nanofluidic systems. The CA of nanobubbles is dependent on size and is believed to be affected by the surface charge-induced electrical double layer (EDL). However, neither of these of attributes are well understood. In this paper, by introducing an EDL-induced electrostatic wetting tension, a theoretical model is first established to study the effect of EDLs formed near the solid-liquid interface and the liquid-nanobubble interface on the gas phase CA of nanobubbles. The size-dependence of this EDL interaction is studied as well. Next, by using atomic force microscopy (AFM), the effect of the EDL on nanobubbles' gas phase CA is studied with variable electrical potential at the solid-liquid interface, which is adjusted by an applied voltage. Both the theoretical and the experimental results show that the EDLs formed near the solid-liquid interface and the liquid-nanobubble interface lead to a reduction of gas phase CA of the surface nanobubbles because of an electrostatic wetting tension on the nanobubble due to the attractive electrostatic interaction between the liquid and nanobubble within the EDL, which is in the nanobubbles' outward direction. An EDL with a larger zeta potential magnitude leads to a larger gas phase CA reduction. Furthermore, the effect of EDL on the nanobubbles' gas phase CA shows a significant size-dependence considering the size dependence of the electrostatic wetting tension. The gas phase CA reduction due to the EDL decreases with increasing nanobubble height and increases with the nanobubble's increasing curvature radius, indicating that a surface charge-induced EDL could possibly explain the size dependence of the gas phase CA of nanobubbles.

Surface tension dominates insect flight on fluid interfaces.

PubMed

Mukundarajan, Haripriya; Bardon, Thibaut C; Kim, Dong Hyun; Prakash, Manu

2016-03-01

Flight on the 2D air-water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary-gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air-water interface presents a radically modified force landscape for flapping wing flight compared with air. © 2016. Published by The Company of Biologists Ltd.

Surface tension dominates insect flight on fluid interfaces

PubMed Central

Mukundarajan, Haripriya; Bardon, Thibaut C.; Kim, Dong Hyun; Prakash, Manu

2016-01-01

ABSTRACT Flight on the 2D air–water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary–gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air–water interface presents a radically modified force landscape for flapping wing flight compared with air. PMID:26936640

A Theoretical Study of Remobilizing Surfactant Retarded Fluid Particle Interfaces

NASA Technical Reports Server (NTRS)

Wang, Yanping; Papageorgiou, Dimitri; Maldarelli, Charles

1996-01-01

Microgravity processes must rely on mechanisms other than bouyancy to move bubbles or droplets from one region to another in a continuous liquid phase. One suggested method is thermocapillary migration in which a temperature gradient is applied to the continuous phase. When a fluid particle contacts this gradient, one pole of the particle becomes warmer than the opposing pole. The interfacial tension between the drop or bubble phase and the continuous phase usually decreases with temperature. Thus the cooler pole is of higher interfacial tension than the warmer pole, and the interface is tugged in the direction of the cooler end. This thermocapillary or thermally induced Marangoni surface stress causes a fluid streaming in the continuous phase from which develops a viscous shear traction and pressure gradient which together propel the particle in the direction of the warmer fluid. In this paper, we provide a theoretical basis for remobilizing surfactant retarded fluid particle interfaces in an effort to make viable the use of thermocapillary migrations for the management of bubbles and drops in microgravity,

Containerless Measurement of Thermophysical Properties of Ti-Zr-Ni Alloys

NASA Technical Reports Server (NTRS)

Hyers, Robert; Bradshaw, Richard C.; Rogers, Jan C.; Rathz, Thomas J.; Lee, Geun W.; Gangopadhyay, Anup K.; Kelton, Kenneth F.

2004-01-01

The surface tension, viscosity, density, and thermal expansion of Ti-Zr-Ni alloys were measured for a number of compositions by electrostatic levitation methods. Containerless methods greatly reduce heterogeneous nucleation, increasing access to the undercooled liquid regime at finite cooling rates. The density and thermal expansion are measured optically, while the surface tension and viscosity are measured by the oscillating drop method. The measured alloys include compositions which form a metastable quasicrystal phase from the undercooled liquid, and alloys close to the composition of several multi-component bulk metallic glass-forming alloys. Measurements of surface tension show behavior typical of transition metals at high temperature, but a sudden decrease in the deeply undercooled liquid for alloys near the quasicrystal-forming composition range, but not for compositions which form the solid-solution phase first.

Real-time single-molecule observations of proteins at the solid-liquid interface

NASA Astrophysics Data System (ADS)

Langdon, Blake Brianna

Non-specific protein adsorption to solid surfaces is pervasive and observed across a broad spectrum of applications including biomaterials, separations, pharmaceuticals, and biosensing. Despite great interest in and considerable literature dedicated to the phenomena, a mechanistic understanding of this complex phenomena is lacking and remains controversial, partially due to the limits of ensemble-averaging techniques used to study it. Single-molecule tracking (SMT) methods allow us to study distinct protein dynamics (e.g. adsorption, desorption, diffusion, and intermolecular associations) on a molecule-by-molecule basis revealing the protein population and spatial heterogeneity inherent in protein interfacial behavior. By employing single-molecule total internal reflection fluorescence microscopy (SM-TIRFM), we have developed SMT methods to directly observe protein interfacial dynamics at the solid-liquid interface to build a better mechanistic understanding of protein adsorption. First, we examined the effects of surface chemistry (e.g. hydrophobicity, hydrogen-bonding capacity), temperature, and electrostatics on isolated protein desorption and interfacial diffusion for fibrinogen (Fg) and bovine serum albumin (BSA). Next, we directly and indirectly probed the effects of protein-protein interactions on interfacial desorption, diffusion, aggregation, and surface spatial heterogeneity on model and polymeric thin films. These studies provided many useful insights into interfacial protein dynamics including the following observations. First, protein adsorption was reversible, with the majority of proteins desorbing from all surface chemistries within seconds. Isolated protein-surface interactions were relatively weak on both hydrophobic and hydrophilic surfaces (apparent desorption activation energies of only a few kBT). However, proteins could dynamically and reversibly associate at the interface, and these interfacial associations led to proteins remaining on the surface for longer time intervals. Surface chemistry and surface spatial heterogeneity (i.e. surface sites with different binding strengths) were shown to influence adsorption, desorption, and interfacial protein-protein associations. For example, faster protein diffusion on hydrophobic surfaces increased protein-protein associations and, at higher protein surface coverage, led to proteins remaining on hydrophobic surfaces longer than on hydrophilic surfaces. Ultimately these studies suggested that surface properties (chemistry, heterogeneity) influence not only protein-surface interactions but also interfacial mobility and protein-protein associations, implying that surfaces that better control protein adsorption can be designed by accounting for these processes.

Surfactant Effect on Hydrate Crystallization at the Oil-Water Interface.

PubMed

Dann, Kevin; Rosenfeld, Liat

2018-05-29

Gas hydrates pose economic and environmental risks to the oil and gas industry when plug formation occurs in pipelines. A novel approach was applied to understand cyclopentane clathrate hydrate formation in the presence of nonionic surfactant to achieve hydrate inhibition at low percent weight compared to thermodynamic inhibitors. The hydrate-inhibiting performance of low (CMC) concentrations of Span 20, Span 80, Pluronic L31, and Tween 65 at 2 °C on a manually nucleated 2 μL droplet showed a morphological shift in crystallization from planar shell growth to conical growth. Monitoring the internal pressure of the water droplet undergoing hydrate crystallization provides information on the change in interfacial tension during the crystallization process. The results of this study will provide information on the surfactant effect on hydrate crystallization and inhibition. At low surfactant concentrations (below CMC), a planar hydrate crystal was formed. Decreasing interfacial tension was observed, which can be related to the shrinking area of the water-cyclopentane interface. At high surfactant concentration, the crystal morphology was shifted to conical. Interfacial tension measurements reveal oscillations of the interfacial tension during the crystallization process. The oscillations of the interfacial tension result from the fact that once the crystal has reached a critical size a portion of the cone breaks free from the droplet surface, which results in a sudden increase in the available surface for the surfactant molecules. Hence, a temporary increase in the interfacial tension can be observed. The oscillatory behavior of the interfacial tension is a result of the growth and release of the hydrate cones from the surface of the droplet. We have found that the most efficient surfactant in hydrate inhibition would be the one with HLB closest to 10 (equal hydrophilic-hydrophobic parts). In this way, the surfactant molecules will stay at the interface as they observe equal affinities for both the oil and water phases. Surfactant molecules that have the strongest affinity to the interface will be able to inhibit the growth of the crystal as they will force the cones to break and will not allow them to grow.

Absence of molecular slip on ultraclean and SAM-coated surfaces

NASA Astrophysics Data System (ADS)

Pye, Justin; Wood, Clay; Burton, Justin

2016-11-01

The liquid/solid boundary condition is a complex problem that is becoming increasingly important for the development of nanoscale fluidic devices. Many groups have now measured slip near an interface at nanoscale dimensions using a variety of experimental techniques. In simple systems, large slip lengths are generally measured for non-wetting liquid/solid combinations, but many conflicting measurements and interpretations remain. We have developed a novel pseudo-differential technique using a quartz crystal microbalance (QCM) to measure slip lengths on various surfaces. A drop of one liquid is grown on the QCM in the presence of a second, ambient liquid. We have isolated any anomalous boundary effects such as interfacial slip by choosing two liquids which have identical bulk effects on the QCM frequency and dissipation in the presence of no-slip. Slip lengths are -less than 2 nm- for water (relative to undecane) on all surfaces measured, including plasma cleaned gold, SiO2, and two different self assembled monolayers (SAMs), regardless of contact angle. We also find that surface cleanliness is crucial to accurately measure slip lengths. Additionally, clean glass substrates appear to have a significant adsorbed water layer and SAM surfaces show excess dissipation, possibly associated with contact line motion. In addition to investigating other liquid pairs, future work will include extending this technique to surfaces with independently controllable chemistry and roughness, both of which are known to strongly affect interfacial hydrodynamics.

Pore-scale modeling of moving contact line problems in immiscible two-phase flow.

NASA Astrophysics Data System (ADS)

Kucala, A.; Noble, D.; Martinez, M. J.

2016-12-01

Two immiscible fluids in static equilibrium form a common interface along a solid surface, characterized as the static contact (wetting) angle and is a function of surface geometry, intermolecular forces, and interfacial surface energies manifested as interfacial tension. This static configuration may become perturbed due to external force imbalances (mass injection, pressure gradients, buoyancy, etc.) and the contact line location and interface curvature becomes dynamic. Accurate modeling of moving contact line (MCL) problems is imperative in predicting capillary pressure vs. saturation curves, permeability, and preferential flow paths for a variety of applications, including geological carbon storage (GCS) and enhanced oil recovery (EOR). Here, we present a model for the moving contact line using pore-scale computational fluid dynamics (CFD) which solves the full, time-dependent Navier-Stokes equations using the Galerkin finite-element method. The MCL is modeled as a surface traction force proportional to the surface tension, dependent on the static properties of the immiscible fluid/solid system. The moving two-phase interface is tracked using the level set method and discretized with the conformal decomposition finite element method (CDFEM), allowing for surface tension effects to be computed at the exact interface location. We present a variety of verification test cases for simple two- and three-dimensional geometries to validate the current model, including threshold pressure predictions in flows through pore-throats for a variety of wetting angles. Simulations involving more complex geometries are also presented to be used in future simulations for GCS and EOR problems. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000

Wetting and evaporation of salt-water nanodroplets: A molecular dynamics investigation.

PubMed

Zhang, Jun; Borg, Matthew K; Sefiane, Khellil; Reese, Jason M

2015-11-01

We employ molecular dynamics simulations to study the wetting and evaporation of salt-water nanodroplets on platinum surfaces. Our results show that the contact angle of the droplets increases with the salt concentration. To verify this, a second simulation system of a thin salt-water film on a platinum surface is used to calculate the various surface tensions. We find that both the solid-liquid and liquid-vapor surface tensions increase with salt concentration and as a result these cause an increase in the contact angle. However, the evaporation rate of salt-water droplets decreases as the salt concentration increases, due to the hydration of salt ions. When the water molecules have all evaporated from the droplet, two forms of salt crystals are deposited, clump and ringlike, depending on the solid-liquid interaction strength and the evaporation rate. To form salt crystals in a ring, it is crucial that there is a pinned stage in the evaporation process, during which salt ions can move from the center to the rim of the droplets. With a stronger solid-liquid interaction strength, a slower evaporation rate, and a higher salt concentration, a complete salt crystal ring can be deposited on the surface.

Measurement of dielectric constant of organic solvents by indigenously developed dielectric probe

NASA Astrophysics Data System (ADS)

Keshari, Ajay Kumar; Rao, J. Prabhakar; Rao, C. V. S. Brahmmananda; Ramakrishnan, R.; Ramanarayanan, R. R.

2018-04-01

The extraction, separation and purification of actinides (uranium and plutonium) from various matrices are an important step in nuclear fuel cycle. One of the separation process adopted in an industrial scale is the liquid-liquid extraction or solvent extraction. Liquid-liquid extraction uses a specific ligand/extractant in conjunction with suitable diluent. Solvent extraction or liquid-liquid extraction, involves the partitioning of the solute between two immiscible phases. In most cases, one of the phases is aqueous, and the other one is an organic solvent. The solvent used in solvent extraction should be selective for the metal of interest, it should have optimum distribution ratio, and the loaded metal from the organic phase should be easily stripped under suitable experimental conditions. Some of the important physical properties which are important for the solvent are density, viscosity, phase separation time, interfacial surface tension and the polarity of the extractant.

Synthesis of ZnO nanoparticles for oil-water interfacial tension reduction in enhanced oil recovery

NASA Astrophysics Data System (ADS)

Soleimani, Hassan; Baig, Mirza Khurram; Yahya, Noorhana; Khodapanah, Leila; Sabet, Maziyar; Demiral, Birol M. R.; Burda, Marek

2018-02-01

Nanoparticles show potential use in applications associated with upstream oil and gas engineering to increase the performance of numerous methods such as wettability alteration, interfacial tension reduction, thermal conductivity and enhanced oil recovery operations. Surface tension optimization is an important parameter in enhanced oil recovery. Current work focuses on the new economical method of surface tension optimization of ZnO nanofluids for oil-water interfacial tension reduction in enhanced oil recovery. In this paper, zinc oxide (ZnO) nanocrystallites were prepared using the chemical route and explored for enhanced oil recovery (EOR). Adsorption of ZnO nanoparticles (NPs) on calcite (111) surface was investigated using the adsorption locator module of Materials Studio software. It was found that ZnO nanoparticles show maximum adsorption energy of - 253 kcal/mol. The adsorption of ZnO on the rock surface changes the wettability which results in capillary force reduction and consequently increasing EOR. The nanofluids have been prepared by varying the concentration of ZnO nanoparticles to find the optimum value for surface tension. The surface tension (ST) was calculated with different concentration of ZnO nanoparticles using the pendant drop method. The results show a maximum value of ST 35.57 mN/m at 0.3 wt% of ZnO NPs. It was found that the nanofluid with highest surface tension (0.3 wt%) resulted in higher recovery efficiency. The highest recovery factor of 11.82% at 0.3 wt% is due to the oil/water interfacial tension reduction and wettability alteration.

Solid surface vs. liquid surface: nanoarchitectonics, molecular machines, and DNA origami.

PubMed

Ariga, Katsuhiko; Mori, Taizo; Nakanishi, Waka; Hill, Jonathan P

2017-09-13

The investigation of molecules and materials at interfaces is critical for the accumulation of new scientific insights and technological advances in the chemical and physical sciences. Immobilization on solid surfaces permits the investigation of different properties of functional molecules or materials with high sensitivity and high spatial resolution. Liquid surfaces also present important media for physicochemical innovation and insight based on their great flexibility and dynamicity, rapid diffusion of molecular components for mixing and rearrangements, as well as drastic spatial variation in the prevailing dielectric environment. Therefore, a comparative discussion of the relative merits of the properties of materials when positioned at solid or liquid surfaces would be informative regarding present-to-future developments of surface-based technologies. In this perspective article, recent research examples of nanoarchitectonics, molecular machines, DNA nanotechnology, and DNA origami are compared with respect to the type of surface used, i.e. solid surfaces vs. liquid surfaces, for future perspectives of interfacial physics and chemistry.

Structural changes in block copolymer micelles induced by cosolvent mixtures†

PubMed Central

Kelley, Elizabeth G.; Smart, Thomas P.; Jackson, Andrew J.; Sullivan, Millicent O.

2013-01-01

We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (low interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles. PMID:24282441

Structural changes in block copolymer micelles induced by cosolvent mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelley, Elizabeth G.; Smart, Thomas P.; Jackson, Andrew J.

2012-11-26

We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (lowmore » interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles.« less

Interfacial tension measurement between CO2 and brines under high temperature and elevated pressure conditions

NASA Astrophysics Data System (ADS)

Li, X.; Boek, E. S.; Maitland, G. C.; Trusler, J. P. M.

2012-04-01

We have investigated the dependence of interfacial tension of (CO2 + brine) on temperature, pressure and salinity (including both salt type and molality) over the range of conditions applicable to CO2 storage in saline aquifers. The study covered a wide range of measurements of the interfacial tensions between carbon dioxide and (NaCl + KCl)(aq), CaCl2(aq), MgCl2(aq), Na2SO4(aq), KHCO3(aq), NaHCO3(aq) and two laboratory constructed brines with molality ranging from (0.3 to 5.0) mol·kg-1. The measurements were made at temperatures between (298 and 448) K at various pressures up to 50 MPa, using the pendant drop method in a high-pressure view cell filled with water-saturated CO2. The drop to be imaged was created by injecting brine from a high-pressure syringe pump into a capillary sealed through the top of the cell. The expanded uncertainties of the experimental state variables at 95 % confidence are +0.05 K in temperature and +70 kPa in pressure. For the interfacial tension, the overall expanded relative uncertainty at 95 % confidence was +1.6%. The experimental results show that interfacial tension for all the systems increases linearly with molality, indicating that relatively few measurements and simple interpolation procedures are adequate for describing this property accurately over wide ranges of conditions.

Line tension effects on the wetting of nanostructures: an energy method

NASA Astrophysics Data System (ADS)

Guo, Hao-Yuan; Li, Bo; Feng, Xi-Qiao

2017-09-01

The superhydrophobicity and self-cleaning property of micro/nano-structured solid surfaces require a stable Cassie-Baxter (CB) wetting state at the liquid-solid interface. We present an energy method to investigate how the three-phase line tension affects the CB wetting state on nanostructured materials. For some nanostructures, the line tension may engender a distinct energy barrier, which restricts the position of the three-phase contact line and affects the stability of the CB wetting state. We ascertain the upper and lower limits of the critical pressure at the CB-Wenzel transition. Our results suggest that superhydrophobicity on nanostructures can be modulated by tailoring the line tension and harnessing the curvature effect. This study also provides new insights into the sinking phenomena observed in the nanoparticle-floating experiment.

Breaking of the Bancroft rule for multiple emulsions stabilized by a single stimulable polymer.

PubMed

Besnard, L; Protat, M; Malloggi, F; Daillant, J; Cousin, F; Pantoustier, N; Guenoun, P; Perrin, P

2014-09-28

We investigated emulsions of water and toluene stabilized by (co)polymers consisting of styrene (S) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) monomer units with different compositions and structures such as a PDMAEMA homopolymer, a P(S-co-DMAEMA) random copolymer and various PS-b-PDMAEMA and PS-b-(S-co-DMAEMA) block copolymers. The model system is used to study the fundamental conditions under which the different kinds of polymer-stabilized emulsions (direct oil in water, inverse water in oil and multiple emulsions) are stabilized or destabilized by pH change (at constant temperature). Polymer properties like chain conformation at the toluene-water interface as probed by SANS and neutron reflectivity at the liquid-liquid interface, the oil-water partitioning of the polymer chains (Bancroft's rule of thumb) as determined by UV spectroscopy and interfacial tensions measured by the rising and spinning drop techniques are determined. Overall, results evidence that the curvature sign, as defined by positive and negative values as the chain segments occupy preferentially the water and toluene sides of the interface respectively, reliably predicts the emulsion kind. In contrast, the Bancroft rule failed at foreseeing the emulsion type. In the region of near zero curvature the crossover from direct to inverse emulsions occurs through the formation of either unstable coexisting direct and inverse emulsions (i) or multiple emulsions (ii). The high compact adsorption of the chains at the interface as shown by low interfacial tension values does not allow to discriminate between both cases. However, the toluene-water partitioning of the polymeric emulsifier is still a key factor driving the formation of (i) or (ii) emulsions. Interestingly, the stabilization of the multiple emulsions can be tuned to a large extent as the toluene-water polymer partitioning can be adjusted using quite a large number of physico-chemical parameters linked to polymer architecture like diblock length ratio or polymer total molar mass, for example. Moreover, we show that monitoring the oil-water partitioning aspect of the emulsion system can also be used to lower the interfacial tension at low pH to values slightly higher than 0.01 mN m(-1), irrespective of the curvature sign.

Rapid Thermal Annealing of Cathode-Garnet Interface toward High-Temperature Solid State Batteries.

PubMed

Liu, Boyang; Fu, Kun; Gong, Yunhui; Yang, Chunpeng; Yao, Yonggang; Wang, Yanbin; Wang, Chengwei; Kuang, Yudi; Pastel, Glenn; Xie, Hua; Wachsman, Eric D; Hu, Liangbing

2017-08-09

High-temperature batteries require the battery components to be thermally stable and function properly at high temperatures. Conventional batteries have high-temperature safety issues such as thermal runaway, which are mainly attributed to the properties of liquid organic electrolytes such as low boiling points and high flammability. In this work, we demonstrate a truly all-solid-state high-temperature battery using a thermally stable garnet solid-state electrolyte, a lithium metal anode, and a V 2 O 5 cathode, which can operate well at 100 °C. To address the high interfacial resistance between the solid electrolyte and cathode, a rapid thermal annealing method was developed to melt the cathode and form a continuous contact. The resulting interfacial resistance of the solid electrolyte and V 2 O 5 cathode was significantly decreased from 2.5 × 10 4 to 71 Ω·cm 2 at room temperature and from 170 to 31 Ω·cm 2 at 100 °C. Additionally, the diffusion resistance in the V 2 O 5 cathode significantly decreased as well. The demonstrated high-temperature solid-state full cell has an interfacial resistance of 45 Ω·cm 2 and 97% Coulombic efficiency cycling at 100 °C. This work provides a strategy to develop high-temperature all-solid-state batteries using garnet solid electrolytes and successfully addresses the high contact resistance between the V 2 O 5 cathode and garnet solid electrolyte without compromising battery safety or performance.

Redox Electrocatalysis of Floating Nanoparticles: Determining Electrocatalytic Properties without the Influence of Solid Supports.

PubMed

Peljo, Pekka; Scanlon, Micheál D; Olaya, Astrid J; Rivier, Lucie; Smirnov, Evgeny; Girault, Hubert H

2017-08-03

Redox electrocatalysis (catalysis of electron-transfer reactions by floating conductive particles) is discussed from the point-of-view of Fermi level equilibration, and an overall theoretical framework is given. Examples of redox electrocatalysis in solution, in bipolar configuration, and at liquid-liquid interfaces are provided, highlighting that bipolar and liquid-liquid interfacial systems allow the study of the electrocatalytic properties of particles without effects from the support, but only liquid-liquid interfaces allow measurement of the electrocatalytic current directly. Additionally, photoinduced redox electrocatalysis will be of interest, for example, to achieve water splitting.

Interfacial rheology of asphaltenes at oil-water interfaces and interpretation of the equation of state.

PubMed

Rane, Jayant P; Pauchard, Vincent; Couzis, Alexander; Banerjee, Sanjoy

2013-04-16

In an earlier study, oil-water interfacial tension was measured by the pendant drop technique for a range of oil-phase asphaltene concentrations and viscosities. The interfacial tension was found to be related to the relative surface coverage during droplet expansion. The relationship was independent of aging time and bulk asphaltenes concentration, suggesting that cross-linking did not occur at the interface and that only asphaltene monomers were adsorbed. The present study extends this work to measurements of interfacial rheology with the same fluids. Dilatation moduli have been measured using the pulsating droplet technique at different frequencies, different concentrations (below and above CNAC), and different aging times. Care was taken to apply the technique in conditions where viscous and inertial effects are small. The elastic modulus increases with frequency and then plateaus to an asymptotic value. The asymptotic or instantaneous elasticity has been plotted against the interfacial tension, indicating the existence of a unique relationship, between them, independent of adsorption conditions. The relationship between interfacial tension and surface coverage is analyzed with a Langmuir equation of state. The equation of state also enabled the prediction of the observed relationship between the instantaneous elasticity and interfacial tension. The fit by a simple Langmuir equation of state (EOS) suggests minimal effects of aging and of nanoaggregates or gel formation at the interface. Only one parameter is involved in the fit, which is the surface excess coverage Γ∞ = 3.2 molecules/nm(2) (31.25 Å(2)/molecule). This value appears to agree with flat-on adsorption of monomeric asphaltene structures consisting of aromatic cores composed of an average of six fused rings and supports the hypothesis that nanoaggregates do not adsorb on the interface. The observed interfacial effects of the adsorbed asphaltenes, correlated by the Langmuir EOS, are consistent with the asphaltene aggregation behavior in the bulk fluid expected from the Yen-Mullins model.

Wetting kinetics of nanodroplets on lyophilic nanopillar-arrayed surfaces: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Zong, Diyuan; Yang, Zhen; Duan, Yuanyuan

2017-10-01

Wetting kinetics of water droplets on substrates with lyophilic nanopillars was investigated using molecular dynamics simulations. Early spreading of the droplet is hindered by the nanopillars because of the penetration of the liquid which induce an extra dissipation in the droplet. Droplet spreading is mainly controlled by liquid viscosity and surface tension and not dependent on solid wettability. Propagation of the fringe film is hindered by the enhanced solid wettability because of the energy barrier introduced by the interaction between water molecules and nanopillars which increase with solid wettability.

Gate-Induced Metal–Insulator Transition in MoS 2 by Solid Superionic Conductor LaF 3

DOE PAGES

Wu, Chun-Lan; Yuan, Hongtao; Li, Yanbin; ...

2018-03-23

Electric-double-layer (EDL) gating with liquid electrolyte has been a powerful tool widely used to explore emerging interfacial electronic phenomena. Due to the large EDL capacitance, a high carrier density up to 10 14 cm –2 can be induced, directly leading to the realization of field-induced insulator to metal (or superconductor) transition. However, the liquid nature of the electrolyte has created technical issues including possible side electrochemical reactions or intercalation, and the potential for huge strain at the interface during cooling. In addition, the liquid coverage of active devices also makes many surface characterizations and in situ measurements challenging. Here, wemore » demonstrate an all solid-state EDL device based on a solid superionic conductor LaF 3, which can be used as both a substrate and a fluorine ionic gate dielectric to achieve a wide tunability of carrier density without the issues of strain or electrochemical reactions and can expose the active device surface for external access. Based on LaF 3 EDL transistors (EDLTs), we observe the metal–insulator transition in MoS 2. Interestingly, the well-defined crystal lattice provides a more uniform potential distribution in the substrate, resulting in less interface electron scattering and therefore a higher mobility in MoS 2 transistors. Finally, this result shows the powerful gating capability of LaF 3 solid electrolyte for new possibilities of novel interfacial electronic phenomena.« less

A New Model for Temperature Jump at a Fluid-Solid Interface

PubMed Central

Shu, Jian-Jun; Teo, Ji Bin Melvin; Chan, Weng Kong

2016-01-01

The problem presented involves the development of a new analytical model for the general fluid-solid temperature jump. To the best of our knowledge, there are no analytical models that provide the accurate predictions of the temperature jump for both gas and liquid systems. In this paper, a unified model for the fluid-solid temperature jump has been developed based on our adsorption model of the interfacial interactions. Results obtained from this model are validated with available results from the literature. PMID:27764230

Self-similarity of solitary waves on inertia-dominated falling liquid films.

PubMed

Denner, Fabian; Pradas, Marc; Charogiannis, Alexandros; Markides, Christos N; van Wachem, Berend G M; Kalliadasis, Serafim

2016-03-01

We propose consistent scaling of solitary waves on inertia-dominated falling liquid films, which accurately accounts for the driving physical mechanisms and leads to a self-similar characterization of solitary waves. Direct numerical simulations of the entire two-phase system are conducted using a state-of-the-art finite volume framework for interfacial flows in an open domain that was previously validated against experimental film-flow data with excellent agreement. We present a detailed analysis of the wave shape and the dispersion of solitary waves on 34 different water films with Reynolds numbers Re=20-120 and surface tension coefficients σ=0.0512-0.072 N m(-1) on substrates with inclination angles β=19°-90°. Following a detailed analysis of these cases we formulate a consistent characterization of the shape and dispersion of solitary waves, based on a newly proposed scaling derived from the Nusselt flat film solution, that unveils a self-similarity as well as the driving mechanism of solitary waves on gravity-driven liquid films. Our results demonstrate that the shape of solitary waves, i.e., height and asymmetry of the wave, is predominantly influenced by the balance of inertia and surface tension. Furthermore, we find that the dispersion of solitary waves on the inertia-dominated falling liquid films considered in this study is governed by nonlinear effects and only driven by inertia, with surface tension and gravity having a negligible influence.

Water-mediated ion-ion interactions are enhanced at the water vapor-liquid interface.

PubMed

Venkateshwaran, Vasudevan; Vembanur, Srivathsan; Garde, Shekhar

2014-06-17

There is overwhelming evidence that ions are present near the vapor-liquid interface of aqueous salt solutions. Charged groups can also be driven to interfaces by attaching them to hydrophobic moieties. Despite their importance in many self-assembly phenomena, how ion-ion interactions are affected by interfaces is not understood. We use molecular simulations to show that the effective forces between small ions change character dramatically near the water vapor-liquid interface. Specifically, the water-mediated attraction between oppositely charged ions is enhanced relative to that in bulk water. Further, the repulsion between like-charged ions is weaker than that expected from a continuum dielectric description and can even become attractive as the ions are drawn to the vapor side. We show that thermodynamics of ion association are governed by a delicate balance of ion hydration, interfacial tension, and restriction of capillary fluctuations at the interface, leading to nonintuitive phenomena, such as water-mediated like charge attraction. "Sticky" electrostatic interactions may have important consequences on biomolecular structure, assembly, and aggregation at soft liquid interfaces. We demonstrate this by studying an interfacially active model peptide that changes its structure from α-helical to a hairpin-turn-like one in response to charging of its ends.

Water-mediated ion–ion interactions are enhanced at the water vapor–liquid interface

PubMed Central

Venkateshwaran, Vasudevan; Vembanur, Srivathsan; Garde, Shekhar

2014-01-01

There is overwhelming evidence that ions are present near the vapor–liquid interface of aqueous salt solutions. Charged groups can also be driven to interfaces by attaching them to hydrophobic moieties. Despite their importance in many self-assembly phenomena, how ion–ion interactions are affected by interfaces is not understood. We use molecular simulations to show that the effective forces between small ions change character dramatically near the water vapor–liquid interface. Specifically, the water-mediated attraction between oppositely charged ions is enhanced relative to that in bulk water. Further, the repulsion between like-charged ions is weaker than that expected from a continuum dielectric description and can even become attractive as the ions are drawn to the vapor side. We show that thermodynamics of ion association are governed by a delicate balance of ion hydration, interfacial tension, and restriction of capillary fluctuations at the interface, leading to nonintuitive phenomena, such as water-mediated like charge attraction. “Sticky” electrostatic interactions may have important consequences on biomolecular structure, assembly, and aggregation at soft liquid interfaces. We demonstrate this by studying an interfacially active model peptide that changes its structure from α-helical to a hairpin-turn–like one in response to charging of its ends. PMID:24889634

Application of α-amylase as a novel biodemulsifier for destabilizing amphiphilic polymer-flooding produced liquid treatment.

PubMed

Jiang, Jiatong; Wu, Hairong; Lu, Yao; Ma, Tao; Li, Zhe; Xu, Derong; Kang, Wanli; Bai, Baojun

2018-07-01

The performance and de-emulsification mechanism of α-amylase, a novel environmental friendly biodemulsifier in petroleum industry, was investigated at room temperature. The effects of α-amylase on the viscosity of amphiphilic polymer solution and de-emulsification rate were studied by changing the concentration of α-amylase, temperature and salinity. Polymer molecular weight, Zeta potential, interfacial film strength and interfacial tension were measured to investigate the de-emulsification mechanism of α-amylase. The results show that α-amylase is an efficient biodemulsifier to increase the de-emulsification rate of amphiphilic polymer emulsions. Hydrolysis of α-amylase to amphiphilic polymers destroys the structure of the amphiphilic polymer, thereby reduces the viscosity and the interfacial film strength of the system. Once de-emulsification is completed, the lower layer, i.e. the emulsified layer, will be clear. Thus, α-amylase can be applied as an effective de-emulsifier for amphiphilic polymer-stabilized O/W emulsion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Colloidal Particle Adsorption at Water-Water Interfaces with Ultralow Interfacial Tension

NASA Astrophysics Data System (ADS)

Keal, Louis; Colosqui, Carlos E.; Tromp, R. Hans; Monteux, Cécile

2018-05-01

Using fluorescence confocal microscopy we study the adsorption of single latex microparticles at a water-water interface between demixing aqueous solutions of polymers, generally known as a water-in-water emulsion. Similar microparticles at the interface between molecular liquids have exhibited an extremely slow relaxation preventing the observation of expected equilibrium states. This phenomenon has been attributed to "long-lived" metastable states caused by significant energy barriers Δ F ˜γ Ad≫kBT induced by high interfacial tension (γ ˜10-2 N /m ) and nanoscale surface defects with characteristic areas Ad≃10 - 30 nm2 . For the studied water-water interface with ultralow surface tension (γ ˜10-4 N /m ) we are able to characterize the entire adsorption process and observe equilibrium states prescribed by a single equilibrium contact angle independent of the particle size. Notably, we observe crossovers from fast initial dynamics to slower kinetic regimes analytically predicted for large surface defects (Ad≃500 nm2). Moreover, particle trajectories reveal a position-independent damping coefficient that is unexpected given the large viscosity contrast between phases. These observations are attributed to the remarkably diffuse nature of the water-water interface and the adsorption and entanglement of polymer chains in the semidilute solutions. This work offers some first insights on the adsorption dynamics or kinetics of microparticles at water-water interfaces in biocolloidal systems.

Elasto-capillary torsion at a liquid interface

NASA Astrophysics Data System (ADS)

Oratis, Alexandros; Farmer, Timothy; Bird, James

2016-11-01

When a liquid drop wets a solid, the droplet typically spreads over the solid. By contrast, for sufficiently compliant solids, the solid can instead spread around the drop. This wrapping phenomenon has been exploited to assemble 3-dimensional structures from 2-dimensional sheets, a process often referred to as capillary origami. Although existing studies of this self-assembly have demonstrated bending and folding, methods of inducing spontaneous twisting by means of capillarity are less clear. Here we demonstrate that spontaneous twist can be initiated in a compliant solid through a combination of surface chemistry and capillarity. Experimentally, we measure the angle of twist on a surface with binary patterns of surface wettability as we vary the solid's geometric and material properties. We develop a scaling law to relate this angle of twist to the elastic and interfacial properties, which compares well with our experimental results.

Real Space Imaging of Nanoparticle Assembly at Liquid-Liquid Interfaces with Nanoscale Resolution.

PubMed

Costa, Luca; Li-Destri, Giovanni; Thomson, Neil H; Konovalov, Oleg; Pontoni, Diego

2016-09-14

Bottom up self-assembly of functional materials at liquid-liquid interfaces has recently emerged as method to design and produce novel two-dimensional (2D) nanostructured membranes and devices with tailored properties. Liquid-liquid interfaces can be seen as a "factory floor" for nanoparticle (NP) self-assembly, because NPs are driven there by a reduction of interfacial energy. Such 2D assembly can be characterized by reciprocal space techniques, namely X-ray and neutron scattering or reflectivity. These techniques have drawbacks, however, as the structural information is averaged over the finite size of the radiation beam and nonperiodic isolated assemblies in 3D or defects may not be easily detected. Real-space in situ imaging methods are more appropriate in this context, but they often suffer from limited resolution and underperform or fail when applied to challenging liquid-liquid interfaces. Here, we study the surfactant-induced assembly of SiO2 nanoparticle monolayers at a water-oil interface using in situ atomic force microscopy (AFM) achieving nanoscale resolved imaging capabilities. Hitherto, AFM imaging has been restricted to solid-liquid interfaces because applications to liquid interfaces have been hindered by their softness and intrinsic dynamics, requiring accurate sample preparation methods and nonconventional AFM operational schemes. Comparing both AFM and grazing incidence X-ray small angle scattering data, we unambiguously demonstrate correlation between real and reciprocal space structure determination showing that the average interfacial NP density is found to vary with surfactant concentration. Additionally, the interaction between the tip and the interface can be exploited to locally determine the acting interfacial interactions. This work opens up the way to studying complex nanostructure formation and phase behavior in a range of liquid-liquid and complex liquid interfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Chun-Lan; Yuan, Hongtao; Li, Yanbin

Electric-double-layer (EDL) gating with liquid electrolyte has been a powerful tool widely used to explore emerging interfacial electronic phenomena. Due to the large EDL capacitance, a high carrier density up to 10 14 cm –2 can be induced, directly leading to the realization of field-induced insulator to metal (or superconductor) transition. However, the liquid nature of the electrolyte has created technical issues including possible side electrochemical reactions or intercalation, and the potential for huge strain at the interface during cooling. In addition, the liquid coverage of active devices also makes many surface characterizations and in situ measurements challenging. Here, wemore » demonstrate an all solid-state EDL device based on a solid superionic conductor LaF 3, which can be used as both a substrate and a fluorine ionic gate dielectric to achieve a wide tunability of carrier density without the issues of strain or electrochemical reactions and can expose the active device surface for external access. Based on LaF 3 EDL transistors (EDLTs), we observe the metal–insulator transition in MoS 2. Interestingly, the well-defined crystal lattice provides a more uniform potential distribution in the substrate, resulting in less interface electron scattering and therefore a higher mobility in MoS 2 transistors. Finally, this result shows the powerful gating capability of LaF 3 solid electrolyte for new possibilities of novel interfacial electronic phenomena.« less

Experimental and Theoretical Study on Supramolecular Ionic Liquid (IL)-Asphaltene Complex Interactions and Their Effects on the Flow Properties of Heavy Crude Oils.

PubMed

Hernández-Bravo, R; Miranda, A D; Martínez-Magadán, J-M; Domínguez, J M

2018-04-19

A combined study for understanding the molecular interactions of asphaltenes with molecular species such as ionic liquids (ILs) comprised experimental measurements and computational numerical simulation calculations, using density-functional theory (DFT) with dispersion corrections, molecular dynamics (MD) calculations, and experimental rheological characterization of the heavy crude oils (HCOs), before and after doping with ILs, respectively. The main results show that ILs influence the asphaltenic dimer association by forming supramolecular complexes that modify the properties of crude oils such as viscosity and interfacial tension. The IL-cation and asphaltene-π ligand molecular interactions seem to dominate the interactions between ionic liquids and asphaltenes, where ILs' high aromaticity index induces a strong interaction with the aromatic hard core of asphaltenes.

Dynamically reconfigurable complex emulsions via tunable interfacial tensions

PubMed Central

Zarzar, Lauren D.; Sresht, Vishnu; Sletten, Ellen M.; Kalow, Julia A.; Blankschtein, Daniel; Swager, Timothy M.

2015-01-01

Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including multiple emulsions and Janus droplets which contain hemispheres of differing material, are of increasing importance1 in pharmaceuticals and medical diagnostics2, in the fabrication of microparticles and capsules3–5 for food6, in chemical separations7, in cosmetics8, and in dynamic optics9. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets’ physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes10, to small-volume but more precise microfluidic methods11,12. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have greatly increased utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials. PMID:25719669

Dynamically reconfigurable complex emulsions via tunable interfacial tensions.

PubMed

Zarzar, Lauren D; Sresht, Vishnu; Sletten, Ellen M; Kalow, Julia A; Blankschtein, Daniel; Swager, Timothy M

2015-02-26

Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials.

Dynamically reconfigurable complex emulsions via tunable interfacial tensions

NASA Astrophysics Data System (ADS)

Zarzar, Lauren D.; Sresht, Vishnu; Sletten, Ellen M.; Kalow, Julia A.; Blankschtein, Daniel; Swager, Timothy M.

2015-02-01

Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials.

Effect of demulsifier partitioning on the destabilization of water-in-oil emulsions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Y.H.; Wasan, D.T.

1996-04-01

The factors affecting the demulsification and interfacial behavior of water-in-oil emulsions in the presence of oil-soluble demulsifiers were investigated. Using both model water-in-oil and water-in-crude oil emulsion systems with demulsifiers with different chemical structures, the effects of demulsifier partitioning on the interfacial and film rheological properties were studied. The experimental results were compared and related with the demulsifier performance. There is a one-to-one correlation between the performance of demulsifier and the interfacial activity of the partitioned demulsifier; the partitioned demulsifier components exhibit an increase in static and dynamic interfacial activity, low dynamic interfacial and film tension, and a low filmmore » dilational modulus with a high adsorption rate - low interfacial tension gradient (Marangoni-Gibbs stabilizing effect) and have excellent demulsification performance.« less

On the Hofmeister effect: fluctuations at the protein-water interface and the surface tension.

PubMed

Bogár, Ferenc; Bartha, Ferenc; Násztor, Zoltán; Fábián, László; Leitgeb, Balázs; Dér, András

2014-07-24

We performed molecular dynamics simulations on the tryptophane-cage miniprotein using a nonpolarizable force field, in order to model the effect of concentrated water solutions of neutral salts on protein conformation, which is a manifestation of Hofmeister effects. From the equilibrium values and the fluctuations of the solvent accessible surface area of the miniprotein, the salt-induced changes of the mean value of protein-water interfacial tension were determined. At 300 K, the chaotropic ClO4(-) and NO3(-) decreased the interfacial tension according to their position in the Hofmeister series (by approximately 5 and 2.7 mN/m, respectively), while the kosmotropic F(-) increased it (by 1 mN/m). These values were compared to those obtained from the Gibbs equation using the excess surface adsorption calculated from the probability distribution of the water molecules and ions around the miniprotein, and the two sets were found to be very close to each other. Our results present a direct evidence for the central role of interfacial tension and fluctuations at the protein-water interface in Hofmeister phenomena, and provide a computational method for the determination of the protein-water interfacial tension, establishing a link between the phenomenological and microscopic description of protein-water interfaces.

The Mechanism of Atomization Accompanying Solid Injection

NASA Technical Reports Server (NTRS)

Castleman, R A , Jr

1933-01-01

A brief historical and descriptive account of solid injection is followed by a detailed review of the available theoretical and experimental data that seem to throw light on the mechanism of this form of atomization. It is concluded that this evidence indicates that (1) the atomization accompanying solid injection occurs at the surface of the liquid after it issues as a solid stream from the orifice; and (2) that such atomization has a mechanism physically identical with the atomization which takes place in an air stream, both being due merely to the formation, at the gas-liquid interface, of fine ligaments under the influence of the relative motion of gas and liquid, and to their collapse, under the influence of surface tension, to form the drops in the spray.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, Sandra Lynn; Bala, Greg Alan

Surfactin, a lipopeptide biosurfactant, produced by Bacillus subtilis is known to reduce the surface tension of water from 72 to 27 mN/m. Potato substrates were evaluated as a carbon source for surfactant production by B. subtilis ATCC 21332. An established potato medium, simulated liquid and solid potato waste media, and a commercially prepared potato starch in a mineral salts medium were evaluated in shake flask experiments to verify growth, surface tension reduction, and carbohydrate reduction capabilities. Total carbohydrate assays and glucose monitoring indicated that B. subtilis was able to degrade potato substrates to produce surfactant. Surface tensions dropped from 71.3±0.1more » to 28.3±0.3 mN/m (simulated solid potato medium) and to 27.5±0.3 mN/m (mineral salts medium). A critical micelle concentration (CMC) of 0.10 g/l was obtained from a methylene chloride extract of the simulated solid potato medium.« less

Tutorial: Determination of thermal boundary resistance by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Liang, Zhi; Hu, Ming

2018-05-01

Due to the high surface-to-volume ratio of nanostructured components in microelectronics and other advanced devices, the thermal resistance at material interfaces can strongly affect the overall thermal behavior in these devices. Therefore, the thermal boundary resistance, R, must be taken into account in the thermal analysis of nanoscale structures and devices. This article is a tutorial on the determination of R and the analysis of interfacial thermal transport via molecular dynamics (MD) simulations. In addition to reviewing the commonly used equilibrium and non-equilibrium MD models for the determination of R, we also discuss several MD simulation methods which can be used to understand interfacial thermal transport behavior. To illustrate how these MD models work for various interfaces, we will show several examples of MD simulation results on thermal transport across solid-solid, solid-liquid, and solid-gas interfaces. The advantages and drawbacks of a few other MD models such as approach-to-equilibrium MD and first-principles MD are also discussed.

Elastocapillarity: When Surface Tension Deforms Elastic Solids

NASA Astrophysics Data System (ADS)

Bico, José; Reyssat, Étienne; Roman, Benoît

2018-01-01

Although negligible at large scales, capillary forces may become dominant for submillimetric objects. Surface tension is usually associated with the spherical shape of small droplets and bubbles, wetting phenomena, imbibition, or the motion of insects at the surface of water. However, beyond liquid interfaces, capillary forces can also deform solid bodies in their bulk, as observed in recent experiments with very soft gels. Capillary interactions, which are responsible for the cohesion of sandcastles, can also bend slender structures and induce the bundling of arrays of fibers. Thin sheets can spontaneously wrap liquid droplets within the limit of the constraints dictated by differential geometry. This review aims to describe the different scaling parameters and characteristic lengths involved in elastocapillarity. We focus on three main configurations, each characterized by a specific dimension: three-dimensional (3D), deformations induced in bulk solids; 1D, bending and bundling of rod-like structures; and 2D, bending and stretching of thin sheets. Although each configuration deserves a detailed review, we hope our broad description provides a general view of elastocapillarity.

Anomalous interfacial tension temperature dependence of condensed phase drops in magnetic fluids

NASA Astrophysics Data System (ADS)

Ivanov, Aleksey S.

2018-05-01

Interfacial tension temperature dependence σ(T) of the condensed phase (drop-like aggregates) in magnetic fluids undergoing field induced phase transition of the "gas-liquid" type was studied experimentally. Numerical analysis of the experimental data has revealed the anomalous (if compared to ordinary one-component fluids) behavior of the σ(T) function for all tested magnetic colloid samples: the condensed phase drops at high T ≈ 75 C exhibit higher σ(T) than the drops condensed at low T ≈ 20 C. The σ(T) behavior is explained by the polydispersity of magnetic colloids: at high T, only the largest colloidal particles are able to take part in the field induced condensation; thus, the increase of T causes the growth of the average particle diameters inside the drop-like aggregates, what in its turn results in the growth of σ(T). The result is confirmed by qualitative theoretical estimations and qualitative experimental observation of the condensed phase "evaporation" process after the applied magnetic field is removed: the drops that are formed due to capillary instability of the drop-like aggregates retract by one order of magnitude faster at high T, and the evaporation of the drops slows down at high T.

PCE solubilization and mobilization by commercial humic acid

NASA Astrophysics Data System (ADS)

Johnson, William P.; John, W. Wynn

1999-01-01

In this paper, comparison is made of terms describing solubilization of hydrophobic organic compounds (HOC) by dissolved humic substances (DHS) and commercial non-ionic surfactants. This paper examines the ability of a commercial humic acid (Aldrich humic acid) to solubilize and mobilize tetrachlorothene (PCE) residual in porous media. The constant for solubilization of PCE by Aldrich humic acid is shown to be a factor of two to thirty times less than that published for dodecyl alcohol ethoxylate surfactants, showing that Aldrich humic acid is less capable than some non-ionic surfactants at solubilizing residual PCE. The depression of PCE-water interfacial tension in the presence of DHS is shown to be significantly less than published values for a non-ionic surfactant, and surfactant mixtures, indicating that the DHS used in this study is less prone to cause mobilization of non-aqueous phase liquids relative to surfactants. Several possible advantages of DHS use in the remediation of subsurface media contaminated with HOC are described, including the ability of DHS to solubilize HOC irrespective of the DHS concentration, and potential lesser tendency of DHS to depress the interfacial tension between non-aqueous phases and water relative to surfactants (an advantage when mobilization is undesired).

Sound-induced Interfacial Dynamics in a Microfluidic Two-phase Flow

NASA Astrophysics Data System (ADS)

Mak, Sze Yi; Shum, Ho Cheung

2014-11-01

Retrieving sound wave by a fluidic means is challenging due to the difficulty in visualizing the very minute sound-induced fluid motion. This work studies the interfacial response of multiphase systems towards fluctuation in the flow. We demonstrate a direct visualization of music in the form of ripples at a microfluidic aqueous-aqueous interface with an ultra-low interfacial tension. The interface shows a passive response to sound of different frequencies with sufficiently precise time resolution, enabling the recording of musical notes and even subsequent reconstruction with high fidelity. This suggests that sensing and transmitting vibrations as tiny as those induced by sound could be realized in low interfacial tension systems. The robust control of the interfacial dynamics could be adopted for droplet and complex-fiber generation.

Formulation and performance test of palm-based foaming agent concentrate for fire extinguisher application

NASA Astrophysics Data System (ADS)

Rivai, M.; Hambali, E.; Suryani, A.; Fitria, R.; Firmansyah, S.; Pramuhadi, G.

2018-03-01

The utilization of foaming agent for fire extinguisher application improves the efficiency of water as a fire extinguishing agent, lowers surface tension, and acts as a foaming agent. The formed foam cools the fire down and covers the burned material to avoid it from further contact with oxygen which may reignite the fire. This study aimed to produce and assess the performance of foaming agent concentrate from palm oil as a fire extinguisher agent. In the performance test, measurements were taken on foam stability, foaming ability, surface tension, interfacial tension, viscosity, contact angle, density, and specific gravity. The formulation was conducted by using the best produced potassium palmitate, potassium methyl ester, and sodium lauric combined with diluents, chelating agent, and other additives at various composition comparisons. The produced foaming agent concentrate was found to be in a rather paste and liquid form with viscosity of 2.34 – 253 cP. It was also found that the resulted foaming agent concentrate dissolved in water at the concentration rate of 1% had a foam stability level of 30-91%, foaming ability of 288 – 503%, surface tension of 19.68 – 25.05 dyne/cm, interfacial tension of 0.54 – 4,20 dyne/cm, viscosity of 1.00 – 1.05 cP, contact angles of 53.75 – 63.79° at 0 minute and 11.84 – 22.42 ° at minute 10, density of 0.99586 – 0.99612 g/cm3, and a specific gravity of 1.00021 – 1.00046. Based on foam stability, foaming ability, and surface tension parameters, it was concluded that NF5 and NF17 were the best formulas.Compared to the other formulas, NF5 formula had the best droplet diameter (minimum 0.14 mm) and droplet density (maximum 3056 droplets/cm2).

Curvature singularity and film-skating during drop impact

NASA Astrophysics Data System (ADS)

Duchemin, Laurent; Josserand, Christophe

2011-09-01

We study the influence of the surrounding gas in the dynamics of drop impact on a smooth surface. We use an axisymmetric model for which both the gas and the liquid are incompressible; lubrication regime applies for the gas film dynamics and the liquid viscosity is neglected. In the absence of surface tension a finite time singularity whose properties are analysed is formed and the liquid touches the solid on a circle. When surface tension is taken into account, a thin jet emerges from the zone of impact, skating above a thin gas layer. The thickness of the air film underneath this jet is always smaller than the mean free path in the gas suggesting that the liquid film eventually wets the surface. We finally suggest an aerodynamical instability mechanism for the splash.

Surface chemistry of carbon dioxide revisited

NASA Astrophysics Data System (ADS)

Taifan, William; Boily, Jean-François; Baltrusaitis, Jonas

2016-12-01

This review discusses modern developments in CO2 surface chemistry by focusing on the work published since the original review by H.J. Freund and M.W. Roberts two decades ago (Surface Science Reports 25 (1996) 225-273). It includes relevant fundamentals pertaining to the topics covered in that earlier review, such as conventional metal and metal oxide surfaces and CO2 interactions thereon. While UHV spectroscopy has routinely been applied for CO2 gas-solid interface analysis, the present work goes further by describing surface-CO2 interactions under elevated CO2 pressure on non-oxide surfaces, such as zeolites, sulfides, carbides and nitrides. Furthermore, it describes additional salient in situ techniques relevant to the resolution of the interfacial chemistry of CO2, notably infrared spectroscopy and state-of-the-art theoretical methods, currently used in the resolution of solid and soluble carbonate species in liquid-water vapor, liquid-solid and liquid-liquid interfaces. These techniques are directly relevant to fundamental, natural and technological settings, such as heterogeneous and environmental catalysis and CO2 sequestration.

Laundry Detergency of Solid Non-Particulate Soil Using Microemulsion-Based Formulation.

PubMed

Chanwattanakit, Jarussri; Chavadej, Sumaeth

2018-02-01

Laundry detergency of solid non-particulate soil on polyester and cotton was investigated using a microemulsion-based formulation, consisting of an anionic extended surfactant (C 12,13 -4PO-SO 4 Na) and sodium mono-and di-methyl naphthalene sulfonate (SMDNS) as the hydrophilic linker, to provide a Winsor Type III microemulsion with an ultralow interfacial tension (IFT). In this work, methyl palmitate (palmitic acid methyl ester) having a melting point around 30°C, was used as a model solid non-particulate (waxy) soil. A total surfactant concentration of 0.35 wt% of the selected formulation (4:0.65 weight ratio of C 12,13 -4PO-SO 4 Na:SMDNS) with 5.3 wt% NaCl was able to form a middle phase microemulsion at a high temperature (40°C),which provided the highest oil removal level with the lowest oil redeposition and the lowest IFT, and was much higher than that with a commercial detergent or de-ionized water. Most of the detached oil, whether in liquid or solid state, was in an unsolubilized form. Hence, the dispersion stability of the detached oil droplets or solidified oil particles that resulted from the surfactant adsorption played an important role in the oil redeposition. For an oily detergency, the lower the system IFT, the higher the oil removal whereas for a waxy (non-particulate) soil detergency, the lower the contact angle, the higher the solidified oil removal. For a liquefied oil, the detergency mechanism was roll up and emulsification with dispersion stability, while that for the waxy soil (solid oil) was the detachment by wettability with dispersion stability.

Atomization and dense-fluid breakup regimes in liquid rocket engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oefelein, Joseph; Dahms, Rainer Norbert Uwe

Until recently, modern theory has lacked a fundamentally based model to predict the operating pressures where classical sprays transition to dense-fluid mixing with diminished surface tension. In this paper, such a model is presented to quantify this transition for liquid-oxygen–hydrogen and n-decane–gaseous-oxygen injection processes. The analysis reveals that respective molecular interfaces break down not necessarily because of vanishing surface tension forces but instead because of the combination of broadened interfaces and a reduction in mean free molecular path. When this occurs, the interfacial structure itself enters the continuum regime, where transport processes rather than intermolecular forces dominate. Using this model,more » regime diagrams for the respective systems are constructed that show the range of operating pressures and temperatures where this transition occurs. The analysis also reveals the conditions where classical spray dynamics persists even at high supercritical pressures. As a result, it demonstrates that, depending on the composition and temperature of the injected fluids, the injection process can exhibit either classical spray atomization, dense-fluid diffusion-dominated mixing, or supercritical mixing phenomena at chamber pressures encountered in state-of-the-art liquid rocket engines.« less

Atomization and dense-fluid breakup regimes in liquid rocket engines

DOE PAGES

Oefelein, Joseph; Dahms, Rainer Norbert Uwe

2015-04-20

Until recently, modern theory has lacked a fundamentally based model to predict the operating pressures where classical sprays transition to dense-fluid mixing with diminished surface tension. In this paper, such a model is presented to quantify this transition for liquid-oxygen–hydrogen and n-decane–gaseous-oxygen injection processes. The analysis reveals that respective molecular interfaces break down not necessarily because of vanishing surface tension forces but instead because of the combination of broadened interfaces and a reduction in mean free molecular path. When this occurs, the interfacial structure itself enters the continuum regime, where transport processes rather than intermolecular forces dominate. Using this model,more » regime diagrams for the respective systems are constructed that show the range of operating pressures and temperatures where this transition occurs. The analysis also reveals the conditions where classical spray dynamics persists even at high supercritical pressures. As a result, it demonstrates that, depending on the composition and temperature of the injected fluids, the injection process can exhibit either classical spray atomization, dense-fluid diffusion-dominated mixing, or supercritical mixing phenomena at chamber pressures encountered in state-of-the-art liquid rocket engines.« less

A perspective on the interfacial properties of nanoscopic liquid drops.

PubMed

Malijevský, Alexandr; Jackson, George

2012-11-21

The structural and interfacial properties of nanoscopic liquid drops are assessed by means of mechanical, thermodynamical, and statistical mechanical approaches that are discussed in detail, including original developments at both the macroscopic level and the microscopic level of density functional theory (DFT). With a novel analysis we show that a purely macroscopic (static) mechanical treatment can lead to a qualitatively reasonable description of the surface tension and the Tolman length of a liquid drop; the latter parameter, which characterizes the curvature dependence of the tension, is found to be negative and has a magnitude of about a half of the molecular dimension. A mechanical slant cannot, however, be considered satisfactory for small finite-size systems where fluctuation effects are significant. From the opposite perspective, a curvature expansion of the macroscopic thermodynamic properties (density and chemical potential) is then used to demonstrate that a purely thermodynamic approach of this type cannot in itself correctly account for the curvature correction of the surface tension of liquid drops. We emphasize that any approach, e.g., classical nucleation theory, which is based on a purely macroscopic viewpoint, does not lead to a reliable representation when the radius of the drop becomes microscopic. The description of the enhanced inhomogeneity exhibited by small drops (particularly in the dense interior) necessitates a treatment at the molecular level to account for finite-size and surface effects correctly. The so-called mechanical route, which corresponds to a molecular-level extension of the macroscopic theory of elasticity and is particularly popular in molecular dynamics simulation, also appears to be unreliable due to the inherent ambiguity in the definition of the microscopic pressure tensor, an observation which has been known for decades but is frequently ignored. The union of the theory of capillarity (developed in the nineteenth century by Gibbs and then promoted by Tolman) with a microscopic DFT treatment allows for a direct and unambiguous description of the interfacial properties of drops of arbitrary size; DFT provides all of the bulk and surface characteristics of the system that are required to uniquely define its thermodynamic properties. In this vein, we propose a non-local mean-field DFT for Lennard-Jones (LJ) fluids to examine drops of varying size. A comparison of the predictions of our DFT with recent simulation data based on a second-order fluctuation analysis (Sampayo et al 2010 J. Chem. Phys. 132 141101) reveals the consistency of the two treatments. This observation highlights the significance of fluctuation effects in small drops, which give rise to additional entropic (thermal non-mechanical) contributions, in contrast to what one observes in the case of planar interfaces which are governed by the laws of mechanical equilibrium. A small negative Tolman length (which is found to be about a tenth of the molecular diameter) and a non-monotonic behaviour of the surface tension with the drop radius are predicted for the LJ fluid. Finally, the limits of the validity of the Tolman approach, the effect of the range of the intermolecular potential, and the behaviour of bubbles are briefly discussed.

Instability and dynamics of volatile thin films

NASA Astrophysics Data System (ADS)

Ji, Hangjie; Witelski, Thomas P.

2018-02-01

Volatile viscous fluids on partially wetting solid substrates can exhibit interesting interfacial instabilities and pattern formation. We study the dynamics of vapor condensation and fluid evaporation governed by a one-sided model in a low-Reynolds-number lubrication approximation incorporating surface tension, intermolecular effects, and evaporative fluxes. Parameter ranges for evaporation-dominated and condensation-dominated regimes and a critical case are identified. Interfacial instabilities driven by the competition between the disjoining pressure and evaporative effects are studied via linear stability analysis. Transient pattern formation in nearly flat evolving films in the critical case is investigated. In the weak evaporation limit unstable modes of finite-amplitude nonuniform steady states lead to rich droplet dynamics, including flattening, symmetry breaking, and droplet merging. Numerical simulations show that long-time behaviors leading to evaporation or condensation are sensitive to transitions between filmwise and dropwise dynamics.

How to Attain an Ultralow Interfacial Tension and a Three-Phase Behavior with a Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 2. Performance Improvement Trends from Winsor's Premise to Currently Proposed Inter- and Intra-Molecular Mixtures.

PubMed

Salager, Jean-Louis; Forgiarini, Ana M; Márquez, Laura; Manchego, Lisbeth; Bullón, Johnny

2013-01-01

The minimum interfacial tension occurrence along a formulation scan at the so-called optimum formulation is discussed to be related to the interfacial curvature. The attained minimum tension is inversely proportional to the domain size of the bicontinuous microemulsion and to the interfacial layer rigidity, but no accurate prediction is available. The data from a very simple ternary system made of pure products accurately follows the correlation for optimum formulation, and exhibit a linear relationship between the performance index as the logarithm of the minimum tension at optimum, and the formulation variables. This relation is probably too simple when the number of variables is increased as in practical cases. The review of published data for more realistic systems proposed for enhanced oil recovery over the past 30 years indicates a general guidelines following Winsor's basic studies concerning the surfactant-oil-water interfacial interactions. It is well known that the major performance benefits are achieved by blending amphiphilic species at the interface as intermolecular or intramolecular mixtures, sometimes in extremely complex formulations. The complexity is such that a good knowledge of the possible trends and an experienced practical know-how to avoid trial and error are important for the practitioner in enhanced oil recovery.

Experimental Investigation of the Self-Propelled Motion of a Sodium Oleate Tablet and Boat at an Oil-Water Interface.

PubMed

Watahiki, Yasuhito; Nomoto, Tomonori; Chiari, Luca; Toyota, Taro; Fujinami, Masanori

2018-05-15

The self-propelled behaviors of macroscopic inanimate objects at surfaces and interfaces are ubiquitous phenomena of fundamental interest in interface science. However, given the existence of a large variety of systems with their own inherent chemical properties, the kinematics of the self-propelled motion and the dynamics of the forces driving these systems often remain largely unknown. Here, we experimentally investigate the spontaneous motion of a sodium oleate tablet at a water-nitrobenzene interface, under nonequilibrium and global isothermal conditions, through measurements of the interfacial tension with the noninvasive, quasi-elastic laser scattering method. The sodium oleate tablet was self-propelled due to an imbalance in the interfacial tension induced by the inhomogeneous adsorption of oleate/oleic acid molecules. The kinetics of the self-propelled motion of a boat-shaped plastic sheet bearing sodium oleate tablets at a sodium oleate aqueous solution-nitrobenzene interface was also studied. The interfacial tension difference between the front and rear of the boat was quantitatively identified as the force pushing the boat forward, although the Marangoni flow due to the uneven distribution of the interfacial tension behind the boat tended to decelerate the motion.

Dropwise Condensation of Low Surface Tension Fluids on Omniphobic Surfaces

PubMed Central

Rykaczewski, Konrad; Paxson, Adam T.; Staymates, Matthew; Walker, Marlon L.; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H.; Chinn, Jeff; Scott, John Henry J.; Varanasi, Kripa K.

2014-01-01

Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient. PMID:24595171

Dropwise condensation of low surface tension fluids on omniphobic surfaces.

PubMed

Rykaczewski, Konrad; Paxson, Adam T; Staymates, Matthew; Walker, Marlon L; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H; Chinn, Jeff; Scott, John Henry J; Varanasi, Kripa K

2014-03-05

Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient.

Interfacial properties of acidified skim milk.

PubMed

Cases, E; Rampini, C; Cayot, Ph

2005-02-01

The purpose of this study is to investigate the tension properties and dilatational viscoelastic modulus of various skim milk proteins (whole milk, EDTA-treated milk, beta-casein, and beta-lactoglobulin) at an oil/water interface at 20 degrees C. Measurements are performed using a dynamic drop tensiometer for 15,000 s. The aqueous bulk phase is a skim milk simulated ultrafiltrate containing 11 x 10(-3) g L(-1) milk protein. At pH 6.7, beta-casein appears as the best to decrease the interfacial tension, whereas beta-lactoglobulin leads to the highest interfacial viscoelastic modulus value. Whole milk was almost as surface-active as individual beta-casein in terms of the final (steady-state) lowering of the interfacial tension, but the rate of tension lowering was smaller. EDTA treatment improved the rate of tension lowering of whole milk. The acidification of milk, from previous measurements, would lead to the enhancement of surface activity. At t=15,000 s, the order of effectiveness is pH 4.3 > pH 5.3 = pH 5.6 > pH 6.7 whole milk, suggesting that pH 4.3 whole milk is the best surface active. As compared to pH 6.7 whole milk, the use of pH 5.3 and pH 5.6 milk as surface active would result in the use of milk containing more free beta-casein born of pH-dissociated casein micelles.

Effect of intermolecular dipole-dipole interactions on interfacial supramolecular structures of C3-symmetric hexa-peri-hexabenzocoronene derivatives.

PubMed

Mu, Zhongcheng; Shao, Qi; Ye, Jun; Zeng, Zebing; Zhao, Yang; Hng, Huey Hoon; Boey, Freddy Yin Chiang; Wu, Jishan; Chen, Xiaodong

2011-02-15

Two-dimensional (2D) supramolecular assemblies of a series of novel C(3)-symmetric hexa-peri-hexabenzocoronene (HBC) derivatives bearing different substituents adsorbed on highly oriented pyrolytic graphite were studied by using scanning tunneling microscopy at a solid-liquid interface. It was found that the intermolecular dipole-dipole interactions play a critical role in controlling the interfacial supramolecular assembly of these C(3)-symmetric HBC derivatives at the solid-liquid interface. The HBC molecule bearing three -CF(3) groups could form 2D honeycomb structures because of antiparallel dipole-dipole interactions, whereas HBC molecules bearing three -CN or -NO(2) groups could form hexagonal superstructures because of a special trimeric arrangement induced by dipole-dipole interactions and weak hydrogen bonding interactions ([C-H···NC-] or [C-H···O(2)N-]). Molecular mechanics and dynamics simulations were performed to reveal the physics behind the 2D structures as well as detailed functional group interactions. This work provides an example of how intermolecular dipole-dipole interactions could enable fine control over the self-assembly of disklike π-conjugated molecules.

Interfacial force field characterization of a constrained vapor bubble thermosyphon using IAI

NASA Technical Reports Server (NTRS)

Dasgupta, Sunando; Plawsky, Joel L.; Wayner, Peter C., Jr.

1994-01-01

The isothermal profiles of the extended meniscus in a quartz cuvette were measured in a gravitational field using IAI (image analyzing interferometer) which is based on computer enhanced video microscopy of the naturally occurring interference fringes. The experimental results for heptane and pentane menisci were analyzed using the extended Young-Laplace Equation. These isothermal results characterized the interfacial force field in-situ at the start of the heat transfer experiments by quantifying the dispersion constant for the specific liquid-solid system. The experimentally obtained values of the disjoining pressures and the dispersion constants are compared to the subsequent non-isothermal experiments because one of the major variables in the heat sink capability of the CVBT is the dispersion constant. In all previous studies of micro heat pipes the value of the dispersion constant has been 'guesstimated'. The major advantages of the current glass cell is the ability to view the extended meniscus at all times. Experimentally, we find that the extended Young-Laplace Equation is an excellent model for for the force field at the solid-liquid vapor interfaces.

Analysis of a static undulation on the surface of a thin dielectric liquid layer formed by dielectrophoresis forces

NASA Astrophysics Data System (ADS)

Brown, Carl V.; McHale, Glen; Mottram, Nigel J.

2011-07-01

A layer of insulating liquid of dielectric constant ɛOil and average thickness h- coats a flat surface at y = 0 at which a one-dimensional sinusoidal potential V(x ,0)=VOcos(πx /p) is applied. Dielectrophoresis forces create a static undulation (or "wrinkle") distortion h(x) of period p at the liquid/air interface. Analytical expressions have been derived for the electrostatic energy and the interfacial energy associated with the surface undulation when h(x)=h--(1/2)Acos(2πx /p) yielding a scaling relationship for A as a function of h-, p, VO, ɛOil and the surface tension. The analysis is valid as A/p → 0, and in this limit convergence with numerical simulation of the system is shown.

Monte Carlo studies on the interfacial properties and interfacial structures of ternary symmetric blends with gradient copolymers.

PubMed

Sun, Dachuan; Guo, Hongxia

2012-08-09

Using Monte Carlo simulation methods, the effects of the comonomer sequence distribution on the interfacial properties (including interfacial tension, interfacial thickness, saturated interfacial area per copolymer, and bending modulus) and interfacial structures (including chain conformations and comonomer distributions of the simulated copolymers at the interfaces) of a ternary symmetric blend containing two immiscible homopolymers and one gradient copolymer are investigated. We find that copolymers with a larger composition gradient width have a broader comonomer distribution along the interface normal, and hence more pronouncedly enlarge the interfacial thickness and reduce the interfacial tension. Furthermore, the counteraction effect, which arises from the tendency of heterogeneous segments in gradient copolymers to phase separate and enter their miscible phases to reduce the local enthalpy, decreases the stretching of copolymers along the interface normal direction. As a result, copolymers with a larger width of gradient composition can occupy a larger interfacial area and form softer monolayers at saturation and are more efficient in facilitating the formation of bicontinuous microemulsions. Additionally, chain length ratio, segregation strength, and interactions between homopolymers and copolymers can alter the interfacial character of gradient copolymers. There exists a strong coupling between the comonomer sequence distribution, chain conformation, and interfacial properties. Especially, bending modulus is mainly determined by the complicated interplay of interfacial copolymer density and interfacial chain conformation.

A review of solid-fluid selection options for optical-based measurements in single-phase liquid, two-phase liquid-liquid and multiphase solid-liquid flows

NASA Astrophysics Data System (ADS)

Wright, Stuart F.; Zadrazil, Ivan; Markides, Christos N.

2017-09-01

Experimental techniques based on optical measurement principles have experienced significant growth in recent decades. They are able to provide detailed information with high-spatiotemporal resolution on important scalar (e.g., temperature, concentration, and phase) and vector (e.g., velocity) fields in single-phase or multiphase flows, as well as interfacial characteristics in the latter, which has been instrumental to step-changes in our fundamental understanding of these flows, and the development and validation of advanced models with ever-improving predictive accuracy and reliability. Relevant techniques rely upon well-established optical methods such as direct photography, laser-induced fluorescence, laser Doppler velocimetry/phase Doppler anemometry, particle image/tracking velocimetry, and variants thereof. The accuracy of the resulting data depends on numerous factors including, importantly, the refractive indices of the solids and liquids used. The best results are obtained when the observational materials have closely matched refractive indices, including test-section walls, liquid phases, and any suspended particles. This paper reviews solid-liquid and solid-liquid-liquid refractive-index-matched systems employed in different fields, e.g., multiphase flows, turbomachinery, bio-fluid flows, with an emphasis on liquid-liquid systems. The refractive indices of various aqueous and organic phases found in the literature span the range 1.330-1.620 and 1.251-1.637, respectively, allowing the identification of appropriate combinations to match selected transparent or translucent plastics/polymers, glasses, or custom materials in single-phase liquid or multiphase liquid-liquid flow systems. In addition, the refractive indices of fluids can be further tuned with the use of additives, which also allows for the matching of important flow similarity parameters such as density and viscosity.

Fixed Packed Bed Reactors in Reduced Gravity

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro; McCready, Mark J.

2004-01-01

We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid and liquid-solid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients kLa and kGa (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

Using “Tender” x-ray ambient pressure x-Ray photoelectron spectroscopy as a direct probe of solid-liquid interface

DOE PAGES

Axnanda, Stephanus; Crumlin, Ethan J.; Mao, Baohua; ...

2015-05-07

We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a “dip & pull” method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, “dip & pull” approach, with a “tender” X-ray synchrotron source (2 keV–7 keV), we are able to access the interface between liquidmore » and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt²⁺ and Pt⁴⁺ interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of “tender” AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.« less

Using “Tender” x-ray ambient pressure x-Ray photoelectron spectroscopy as a direct probe of solid-liquid interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Axnanda, Stephanus; Crumlin, Ethan J.; Mao, Baohua

We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a “dip & pull” method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, “dip & pull” approach, with a “tender” X-ray synchrotron source (2 keV–7 keV), we are able to access the interface between liquidmore » and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt²⁺ and Pt⁴⁺ interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of “tender” AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.« less

3D lithography by rapid curing of the liquid instabilities at nanoscale

PubMed Central

Coppola, Sara; Vespini, Veronica; Merola, Francesco; Finizio, Andrea; Ferraro, Pietro

2011-01-01

In liquids realm, surface tension and capillarity are the key forces driving the formation of the shapes pervading the nature. The steady dew drops appearing on plant leaves and spider webs result from the minimization of the overall surface energy [Zheng Y, et al. (2010) Nature 463:640–643]. Thanks to the surface tension, the interfaces of such spontaneous structures exhibit extremely good spherical shape and consequently worthy optical quality. Also nanofluidic instabilities generate a variety of fascinating liquid silhouettes, but they are however intrinsically short-lived. Here we show that such unsteady liquid structures, shaped in polymeric liquids by an electrohydrodynamic pressure, can be rapidly cured by appropriate thermal treatments. The fabrication of many solid microstructures exploitable in photonics is demonstrated, thus leading to a new concept in 3D lithography. The applicability of specific structures as optical tweezers and as novel remotely excitable quantum dots–embedded microresonators is presented. PMID:21896720

Supra-molecular inclusion complexation of ionic liquid 1-butyl-3-methylimidazolium octylsulphate with α- and β-cyclodextrins

NASA Astrophysics Data System (ADS)

Banjare, Manoj Kumar; Behera, Kamalakanta; Satnami, Manmohan L.; Pandey, Siddharth; Ghosh, Kallol K.

2017-12-01

Host-guest complexation between ionic liquid (IL) 1-butyl-3-methylimidazolium octylsulphate [Bmim][OS] and cyclodextrins (α- and β- CDs) have been studied. Surface tension, conductivity measurements revealed the formation of 1:1 (M) stoichiometry for inclusion complexes (ICs) and further confirmed by UV-Visible and FT-IR results. The nature of the complexes has been established using interfacial and thermodynamic parameters. The aggregation number, Stern-Volmer constants, association constants were obtained from fluorescence quenching and Benesi-Hildebrand methods. The critical micelle concentration (cmc) and association constants of [Bmim][OS] are higher for β-CD as compared to α-CD. FT-IR spectra indicated that CDs and [Bmim][OS] could from ICs with stoichiometry 1:1 (M).

Getting in shape: molten wax drop deformation and solidification at an immiscible liquid interface.

PubMed

Beesabathuni, Shilpa N; Lindberg, Seth E; Caggioni, Marco; Wesner, Chris; Shen, Amy Q

2015-05-01

The controlled production of non-spherical shaped particles is important for many applications such as food processing, consumer goods, adsorbents, drug delivery, and optical sensing. In this paper, we investigated the deformation and simultaneous solidification of millimeter size molten wax drops as they impacted an immiscible liquid interface of higher density. By varying initial temperature and viscoelasticity of the molten drop, drop size, impact velocity, viscosity and temperature of the bath fluid, and the interfacial tension between the molten wax and bath fluid, spherical molten wax drops impinged on a cooling water bath and were arrested into non-spherical solidified particles in the form of ellipsoid, mushroom, disc, and flake-like shapes. We constructed cursory phase diagrams for the various particle shapes generated over a range of Weber, Capillary, Reynolds, and Stefan numbers, governed by the interfacial, inertial, viscous, and thermal effects. We solved a simplified heat transfer problem to estimate the time required to initiate the solidification at the interface of a spherical molten wax droplet and cooling aqueous bath after impact. By correlating this time with the molten wax drop deformation history captured from high speed imaging experiments, we elucidate the delicate balance of interfacial, inertial, viscous, and thermal forces that determine the final morphology of wax particles. Copyright © 2015 Elsevier Inc. All rights reserved.

What Controls Thermo-osmosis? Molecular Simulations Show the Critical Role of Interfacial Hydrodynamics

NASA Astrophysics Data System (ADS)

Fu, Li; Merabia, Samy; Joly, Laurent

2017-11-01

Thermo-osmotic and related thermophoretic phenomena can be found in many situations from biology to colloid science, but the underlying molecular mechanisms remain largely unexplored. Using molecular dynamics simulations, we measure the thermo-osmosis coefficient by both mechanocaloric and thermo-osmotic routes, for different solid-liquid interfacial energies. The simulations reveal, in particular, the crucial role of nanoscale interfacial hydrodynamics. For nonwetting surfaces, thermo-osmotic transport is largely amplified by hydrodynamic slip at the interface. For wetting surfaces, the position of the hydrodynamic shear plane plays a key role in determining the amplitude and sign of the thermo-osmosis coefficient. Finally, we measure a giant thermo-osmotic response of the water-graphene interface, which we relate to the very low interfacial friction displayed by this system. These results open new perspectives for the design of efficient functional interfaces for, e.g., waste-heat harvesting.

What Controls Thermo-osmosis? Molecular Simulations Show the Critical Role of Interfacial Hydrodynamics.

PubMed

Fu, Li; Merabia, Samy; Joly, Laurent

2017-11-24

Thermo-osmotic and related thermophoretic phenomena can be found in many situations from biology to colloid science, but the underlying molecular mechanisms remain largely unexplored. Using molecular dynamics simulations, we measure the thermo-osmosis coefficient by both mechanocaloric and thermo-osmotic routes, for different solid-liquid interfacial energies. The simulations reveal, in particular, the crucial role of nanoscale interfacial hydrodynamics. For nonwetting surfaces, thermo-osmotic transport is largely amplified by hydrodynamic slip at the interface. For wetting surfaces, the position of the hydrodynamic shear plane plays a key role in determining the amplitude and sign of the thermo-osmosis coefficient. Finally, we measure a giant thermo-osmotic response of the water-graphene interface, which we relate to the very low interfacial friction displayed by this system. These results open new perspectives for the design of efficient functional interfaces for, e.g., waste-heat harvesting.

Dynamics of liquid bridges inside microchannels subject to pure oscillatory flows

NASA Astrophysics Data System (ADS)

Ahmadlouydarab, Majid; Azaiez, Jalel; Chen, Zhangxin

2014-11-01

We report on 2D simulations of liquid bridges' dynamics in microchannels of uniform wettability and subject to external oscillatory flows. The flow equations were solved using the Cahn-Hilliard diffuse-interface formulation and the finite element method with unstructured grid. It was found that regardless of the wettability properties of the microchannel walls, there is a critical frequency above which the bridge shows perpetual periodic oscillatory motion. Below that critical frequency, the liquid bridge ruptures when the channel walls are philic and detaches from the surface when they are phobic. This critical frequency depends on the viscosity ratio, oscillation amplitude and geometric aspect ratio of the bridge. It was also found that the flow velocity is out of phase with the footprint/throat lengths and that the latter two show a phase difference. These differences were explained in terms of the motion of the two contact lines on the substrates and the deformation of the fluid-fluid interfaces. To characterize the behavior of the liquid bridge, two quantitative parameters; the liquid bridge-solid interfacial length and the length of the throat of the liquid bridge were used. Variations of the interfacial morphology development of the bridge were analyzed to understand the bridge response.

Charge transfer kinetics at the solid-solid interface in porous electrodes

NASA Astrophysics Data System (ADS)

Bai, Peng; Bazant, Martin Z.

2014-04-01

Interfacial charge transfer is widely assumed to obey the Butler-Volmer kinetics. For certain liquid-solid interfaces, the Marcus-Hush-Chidsey theory is more accurate and predictive, but it has not been applied to porous electrodes. Here we report a simple method to extract the charge transfer rates in carbon-coated LiFePO4 porous electrodes from chronoamperometry experiments, obtaining curved Tafel plots that contradict the Butler-Volmer equation but fit the Marcus-Hush-Chidsey prediction over a range of temperatures. The fitted reorganization energy matches the Born solvation energy for electron transfer from carbon to the iron redox site. The kinetics are thus limited by electron transfer at the solid-solid (carbon-LixFePO4) interface rather than by ion transfer at the liquid-solid interface, as previously assumed. The proposed experimental method generalizes Chidsey’s method for phase-transforming particles and porous electrodes, and the results show the need to incorporate Marcus kinetics in modelling batteries and other electrochemical systems.

Wettability of supercritical carbon dioxide/water/quartz systems: simultaneous measurement of contact angle and interfacial tension at reservoir conditions.

PubMed

Saraji, Soheil; Goual, Lamia; Piri, Mohammad; Plancher, Henry

2013-06-11

Injection of carbon dioxide in deep saline aquifers is considered as a method of carbon sequestration. The efficiency of this process is dependent on the fluid-fluid and rock-fluid interactions inside the porous media. For instance, the final storage capacity and total amount of capillary-trapped CO2 inside an aquifer are affected by the interfacial tension between the fluids and the contact angle between the fluids and the rock mineral surface. A thorough study of these parameters and their variations with temperature and pressure will provide a better understanding of the carbon sequestration process and thus improve predictions of the sequestration efficiency. In this study, the controversial concept of wettability alteration of quartz surfaces in the presence of supercritical carbon dioxide (sc-CO2) was investigated. A novel apparatus for measuring interfacial tension and contact angle at high temperatures and pressures based on Axisymmetric Drop Shape Analysis with no-Apex (ADSA-NA) method was developed and validated with a simple system. Densities, interfacial tensions, and dynamic contact angles of CO2/water/quartz systems were determined for a wide range of pressures and temperatures relevant to geological sequestration of CO2 in the subcritical and supercritical states. Image analysis was performed with ADSA-NA method that allows the determination of both interfacial tensions and contact angles with high accuracy. The results show that supercritical CO2 alters the wettability of quartz surface toward less water-wet conditions compared to subcritical CO2. Also we observed an increase in the water advancing contact angles with increasing temperature indicating less water-wet quartz surfaces at higher temperatures.

Aerodynamic repellency of impacting liquids

NASA Astrophysics Data System (ADS)

Gauthier, Anaïs; Bouillant, Ambre; Clanet, Christophe; Quéré, David

2018-05-01

Impacting liquids can be reflected by moving solid plates, provided the surface is fast enough. We describe and model here the threshold speed of bouncing, in particular as a function of the impact velocity of the incoming liquid. We also demonstrate that the aerodynamic force responsible for the nonwetting behavior induces an oblique rebound, which contributes to the liquid removal. In summary, this situation repels viscous, low surface tension drops of any size, all kinds of cases where repellency is impossible to achieve by other means.

Liquid droplets of cross-linked actin filaments

NASA Astrophysics Data System (ADS)

Weirich, Kimberly; Banerjee, Shiladitya; Dasbiswas, Kinjal; Vaikuntanathan, Suriyanarayan; Gardel, Margaret

Soft materials constructed from biomolecules self-assemble into a myriad of structures that work in concert to support cell physiology. One critical soft material is the actin cytoskeleton, a viscoelastic gel composed of cross-linked actin filaments. Although actin networks are primarily known for their elastic properties, which are crucial to regulating cell mechanics, the viscous behavior has been theorized to enable shape changes and flows. We experimentally demonstrate a fluid phase of cross-linked actin, where cross-linker condenses dilute short actin filaments into spindle-shaped droplets, or tactoids. Tactoids have shape dynamics consistent with a continuum model of liquid crystal droplets. The cross-linker, which acts as a long range attractive interaction, analogous to molecular cohesion, controls the tactoid shape and dynamics, which reports on the liquid's interfacial tension and viscosity. We investigate how the cross-linker properties and filament length influence the liquid properties. These results demonstrate a novel mechanism to control organization of the actin cytoskeleton and provide insight into design principles for complex, macromolecular liquid phases.

Studies on aqueous two phase polymer systems useful for partitioning of biological materials

NASA Technical Reports Server (NTRS)

Brooks, D. E.; Bamberger, S.

1982-01-01

The two phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) (PEG) are mixed above a critical concentration of a few percent provide a useful medium for the separation of biological cell subpopulations via partition between the top, PEG-rich phase and the liquid-liquid phase boundary. Interfacial tensions of such systems have been measured by the rotating drop technique and found to range between 0.1-100 micro-N/m. The tension was found to depend on the length of the tie line describing the system on a phase diagram, via a power law relationship which differed depending on the concentration of Na phosphate buffer present. The electrokinetic properties of drops of one phase suspended in the other were studied for a variety of systems. It was found that the droplet electrophoretic mobility increased monotonically with phosphate concentration and drop diameter but exhibited the opposite sign from that anticipated from phosphate partition measurements. It was possible to take advantage of these electrokinetic properties and dramatically enhance the speed of phase separation through application of relatively small electric fields.

Jumping liquid metal droplet in electrolyte triggered by solid metal particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Jianbo; University of Chinese Academy of Sciences, Beijing 100049; Wang, Junjie

2016-05-30

We report the electron discharge effect due to point contact between liquid metal and solid metal particles in electrolyte. Adding nickel particles induces drastic hydrogen generating and intermittent jumping of a sub-millimeter EGaIn droplet in NaOH solution. Observations from different orientations disclose that such jumping behavior is triggered by pressurized bubbles under the assistance of interfacial interactions. Hydrogen evolution around particles provides clear evidence that such electric instability originates from the varied electric potential and morphology between the two metallic materials. The point-contact-induced charge concentration significantly enhances the near-surface electric field intensity at the particle tips and thus causes electricmore » breakdown of the electrolyte.« less

Probing alpha-helical and beta-sheet structures of peptides at solid/liquid interfaces with SFG.

PubMed

Chen, Xiaoyun; Wang, Jie; Sniadecki, Jason J; Even, Mark A; Chen, Zhan

2005-03-29

We demonstrated that sum frequency generation (SFG) vibrational spectroscopy can distinguish different secondary structures of proteins or peptides adsorbed at solid/liquid interfaces. The SFG spectrum for tachyplesin I at the polystyrene (PS)/solution interface has a fingerprint peak corresponding to the B1/B3 mode of the antiparallel beta-sheet. This peak disappeared upon the addition of dithiothreitol, which can disrupt the beta-sheet structure. The SFG spectrum indicative of the MSI594 alpha-helical structure was observed at the PS/MSI594 solution interface. This research validates SFG as a powerful technique for revealing detailed secondary structures of interfacial proteins and peptides.

Real-Time X-Ray Microscopy of Al-Cu Eutectic Solidification

NASA Technical Reports Server (NTRS)

Kaukler, William F.; Curreri, Peter A.; Sen, Subhayu

1998-01-01

Recent improvements in the resolution of the X-ray Transmission Microscope (XTM) for Solidification Studies provide microstructure feature detectability down to 5 micrometers during solidification. This presentation will show the recent results from observations made in real-time of the solid-liquid interfacial morphologies of the Al-CuAI2 eutectic alloy. Lamellar dimensions and spacings, transitions of morphology caused by growth rate changes, and eutectic grain structures are open to measurements. A unique vantage point viewing the face of the interface isotherm is possible for the first time with the XTM due to its infinite depth of field. A video of the solid-liquid interfaces seen in-situ and in real-time will be shown.

Charging and discharging of single colloidal particles at oil/water interfaces

PubMed Central

Gao, Peng; Xing, XiaoChen; Li, Ye; Ngai, To; Jin, Fan

2014-01-01

The physical behavior of solid colloids trapped at a fluid-fluid interface remains in itself an open fundamental issue. Here, we show that the gradients of surface tension can induce particles to jet towards the oil/water interface with velocities as high as ≈ 60 mm/s when particle suspensions come in contact with the interface. We hypothesize that rubbing between the particles and oil lead to the spontaneous accumulation of negative charges on the hemisphere of those interfacial particles that contact the oil phase by means of triboelectrification. The charging process is highly dependent on the sliding distances, and gives rise to long-ranged repulsions that protect interfacial particles from coagulating at the interface by the presence of electrolyte. These triboelectric charges, however, are compensated within several hours, which affect the stability of interfacial particles. Importantly, by charging different kinds of colloidal particles using various spreading solvents and dispersion methods, we have demonstrated that charging and discharging of single colloidal particles at oil/water interfaces impacts a broad range of dynamical behavior. PMID:24786477

A novel coarsening mechanism of droplets in immiscible fluid mixtures

NASA Astrophysics Data System (ADS)

Shimizu, Ryotaro; Tanaka, Hajime

2015-06-01

In our daily lives, after shaking a salad dressing, we see the coarsening of oil droplets suspended in vinegar. Such a demixing process is observed everywhere in nature and also of technological importance. For a case of high droplet density, domain coarsening proceeds with inter-droplet collisions and the resulting coalescence. This phenomenon has been explained primarily by the so-called Brownian-coagulation mechanism: stochastic thermal forces exerted by molecules induce random motion of individual droplets, causing accidental collisions and subsequent interface-tension-driven coalescence. Contrary to this, here we demonstrate that the droplet motion is not random, but hydrodynamically driven by the composition Marangoni force due to an interfacial tension gradient produced in each droplet as a consequence of composition correlation among droplets. This alters our physical understanding of droplet coarsening in immiscible liquid mixtures on a fundamental level.

Application of interface waves for near surface damage detection in hybrid structures

NASA Astrophysics Data System (ADS)

Jahanbin, M.; Santhanam, S.; Ihn, J.-B.; Cox, A.

2017-04-01

Guided waves are acoustic waves that are guided by boundaries. Depending on the structural geometry, guided waves can either propagate between boundaries, known as plate waves, or propagate on the surface of the objects. Many different types of surface waves exist based on the material property of the boundary. For example Rayleigh wave in solid - air, Scholte wave in solid - liquid, Stoneley in solid - solid interface and many other different forms like Love wave on inhomogeneous surfaces, creeping waves, etc. This research work is demonstrating the application of surface and interface waves for detection of interfacial damages in hybrid bonded structures.

On the equilibrium contact angle of sessile liquid drops from molecular dynamics simulations.

PubMed

Ravipati, Srikanth; Aymard, Benjamin; Kalliadasis, Serafim; Galindo, Amparo

2018-04-28

We present a new methodology to estimate the contact angles of sessile drops from molecular simulations by using the Gaussian convolution method of Willard and Chandler [J. Phys. Chem. B 114, 1954-1958 (2010)] to calculate the coarse-grained density from atomic coordinates. The iso-density contour with average coarse-grained density value equal to half of the bulk liquid density is identified as the average liquid-vapor (LV) interface. Angles between the unit normal vectors to the average LV interface and unit normal vector to the solid surface, as a function of the distance normal to the solid surface, are calculated. The cosines of these angles are extrapolated to the three-phase contact line to estimate the sessile drop contact angle. The proposed methodology, which is relatively easy to implement, is systematically applied to three systems: (i) a Lennard-Jones (LJ) drop on a featureless LJ 9-3 surface; (ii) an SPC/E water drop on a featureless LJ 9-3 surface; and (iii) an SPC/E water drop on a graphite surface. The sessile drop contact angles estimated with our methodology for the first two systems are shown to be in good agreement with the angles predicted from Young's equation. The interfacial tensions required for this equation are computed by employing the test-area perturbation method for the corresponding planar interfaces. Our findings suggest that the widely adopted spherical-cap approximation should be used with caution, as it could take a long time for a sessile drop to relax to a spherical shape, of the order of 100 ns, especially for water molecules initiated in a lattice configuration on a solid surface. But even though a water drop can take a long time to reach the spherical shape, we find that the contact angle is well established much faster and the drop evolves toward the spherical shape following a constant-contact-angle relaxation dynamics. Making use of this observation, our methodology allows a good estimation of the sessile drop contact angle values even for moderate system sizes (with, e.g., 4000 molecules), without the need for long simulation times to reach the spherical shape.

On the equilibrium contact angle of sessile liquid drops from molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Ravipati, Srikanth; Aymard, Benjamin; Kalliadasis, Serafim; Galindo, Amparo

2018-04-01

We present a new methodology to estimate the contact angles of sessile drops from molecular simulations by using the Gaussian convolution method of Willard and Chandler [J. Phys. Chem. B 114, 1954-1958 (2010)] to calculate the coarse-grained density from atomic coordinates. The iso-density contour with average coarse-grained density value equal to half of the bulk liquid density is identified as the average liquid-vapor (LV) interface. Angles between the unit normal vectors to the average LV interface and unit normal vector to the solid surface, as a function of the distance normal to the solid surface, are calculated. The cosines of these angles are extrapolated to the three-phase contact line to estimate the sessile drop contact angle. The proposed methodology, which is relatively easy to implement, is systematically applied to three systems: (i) a Lennard-Jones (LJ) drop on a featureless LJ 9-3 surface; (ii) an SPC/E water drop on a featureless LJ 9-3 surface; and (iii) an SPC/E water drop on a graphite surface. The sessile drop contact angles estimated with our methodology for the first two systems are shown to be in good agreement with the angles predicted from Young's equation. The interfacial tensions required for this equation are computed by employing the test-area perturbation method for the corresponding planar interfaces. Our findings suggest that the widely adopted spherical-cap approximation should be used with caution, as it could take a long time for a sessile drop to relax to a spherical shape, of the order of 100 ns, especially for water molecules initiated in a lattice configuration on a solid surface. But even though a water drop can take a long time to reach the spherical shape, we find that the contact angle is well established much faster and the drop evolves toward the spherical shape following a constant-contact-angle relaxation dynamics. Making use of this observation, our methodology allows a good estimation of the sessile drop contact angle values even for moderate system sizes (with, e.g., 4000 molecules), without the need for long simulation times to reach the spherical shape.

Comparison of interfacial properties of electrodeposited single carbon fiber/epoxy composites using tensile and compressive fragmentation tests and acoustic emission.

PubMed

Park, Joung-Man; Kim, Jin-Won; Yoon, Dong-Jin

2002-03-01

Interfacial and microfailure properties of carbon fiber/epoxy composites were evaluated using both tensile fragmentation and compressive Broutman tests with an aid of acoustic emission (AE). A monomeric and two polymeric coupling agents were applied via the electrodeposition (ED) and the dipping applications. A monomeric and a polymeric coupling agent showed significant and comparable improvements in interfacial shear strength (IFSS) compared to the untreated case under both tensile and compressive tests. Typical microfailure modes including cone-shaped fiber break, matrix cracking, and partial interlayer failure were observed under tension, whereas the diagonal slipped failure at both ends of the fractured fiber exhibited under compression. Adsorption and shear displacement mechanisms at the interface were described in terms of electrical attraction and primary and secondary bonding forces. For both the untreated and the treated cases AE distributions were separated well in tension, whereas AE distributions were rather closely overlapped in compression. It might be because of the difference in molecular failure energies and failure mechanisms between tension and compression. The maximum AE voltage for the waveform of either carbon or large-diameter basalt fiber breakages in tension exhibited much larger than that in compression. AE could provide more likely the quantitative information on the interfacial adhesion and microfailure.

Reduced Capillary Length Scale in the Application of Ostwald Ripening Theory to the Coarsening of Charged Colloidal Crystals in Electrolyte Solutions

NASA Astrophysics Data System (ADS)

Rowe, Jeffrey D.; Baird, James K.

2007-06-01

A colloidal crystal suspended in an electrolyte solution will ordinarily exchange ions with the surrounding solution and develop a net surface charge density and a corresponding double layer. The interfacial tension of the charged surface has contributions arising from: (a) background interfacial tension of the uncharged surface, (b) the entropy associated with the adsorption of ions on the surface, and (c) the polarizing effect of the electrostatic field within the double layer. The adsorption and polarization effects make negative contributions to the surface free energy and serve to reduce the interfacial tension below the value to be expected for the uncharged surface. The diminished interfacial tension leads to a reduced capillary length scale. According to the Ostwald ripening theory of particle coarsening, the reduced capillary length will cause the solute supersaturation to decay more rapidly and the colloidal particles to be smaller in size and greater in number than in the absence of the double layer. Although the length scale for coarsening should be little affected in the case of inorganic colloids, such as AgI, it should be greatly reduced in the case of suspensions of protein crystals, such as apoferritin, catalase, and thaumatin.

Hydrodynamic instabilities in miscible fluids

NASA Astrophysics Data System (ADS)

Truzzolillo, Domenico; Cipelletti, Luca

2018-01-01

Hydrodynamic instabilities in miscible fluids are ubiquitous, from natural phenomena up to geological scales, to industrial and technological applications, where they represent the only way to control and promote mixing at low Reynolds numbers, well below the transition from laminar to turbulent flow. As for immiscible fluids, the onset of hydrodynamic instabilities in miscible fluids is directly related to the physics of their interfaces. The focus of this review is therefore on the general mechanisms driving the growth of disturbances at the boundary between miscible fluids, under a variety of forcing conditions. In the absence of a regularizing mechanism, these disturbances would grow indefinitely. For immiscible fluids, interfacial tension provides such a regularizing mechanism, because of the energy cost associated to the creation of new interface by a growing disturbance. For miscible fluids, however, the very existence of interfacial stresses that mimic an effective surface tension is debated. Other mechanisms, however, may also be relevant, such as viscous dissipation. We shall review the stabilizing mechanisms that control the most common hydrodynamic instabilities, highlighting those cases for which the lack of an effective interfacial tension poses deep conceptual problems in the mathematical formulation of a linear stability analysis. Finally, we provide a short overview on the ongoing research on the effective, out of equilibrium interfacial tension between miscible fluids.

Inhomogeneity of block copolymers at the interface of an immiscible polymer blend

NASA Astrophysics Data System (ADS)

Ryu, Ji Ho; Kim, YongJoo; Lee, Won Bo

2018-04-01

We present the effects of structure and stiffness of block copolymers on the interfacial properties of an immiscible homopolymer blend. Diblock and two-arm grafted copolymers with variation in stiffness are modeled using coarse-grained molecular dynamics to compare the compatibilization efficiency, i.e., reduction of interfacial tension. Overall, grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, an increase in the stiffness for one of the blocks of the diblock copolymers causes unusual inhomogeneous interfacial coverage due to bundle formation. However, an increase in the stiffness for one of blocks of the grafted copolymers prevents the bundle formation due to the branched chain. As a result, homogeneous interfacial coverage of homopolymer blends is realized with significant reduction of interfacial tension which makes grafted copolymer a better candidate for the compatibilizer of immiscible homopolymer blend.

Release of surfactant cargo from interfacially-active halloysite clay nanotubes for oil spill remediation.

PubMed

Owoseni, Olasehinde; Nyankson, Emmanuel; Zhang, Yueheng; Adams, Samantha J; He, Jibao; McPherson, Gary L; Bose, Arijit; Gupta, Ram B; John, Vijay T

2014-11-18

Naturally occurring halloysite clay nanotubes are effective in stabilizing oil-in-water emulsions and can serve as interfacially-active vehicles for delivering oil spill treating agents. Halloysite nanotubes adsorb at the oil-water interface and stabilize oil-in-water emulsions that are stable for months. Cryo-scanning electron microscopy (Cryo-SEM) imaging of the oil-in-water emulsions shows that these nanotubes assemble in a side-on orientation at the oil-water interface and form networks on the interface through end-to-end linkages. For application in the treatment of marine oil spills, halloysite nanotubes were successfully loaded with surfactants and utilized as an interfacially-active vehicle for the delivery of surfactant cargo. The adsorption of surfactant molecules at the interface serves to lower the interfacial tension while the adsorption of particles provides a steric barrier to drop coalescence. Pendant drop tensiometry was used to characterize the dynamic reduction in interfacial tension resulting from the release of dioctyl sulfosuccinate sodium salt (DOSS) from halloysite nanotubes. At appropriate surfactant compositions and loadings in halloysite nanotubes, the crude oil-saline water interfacial tension is effectively lowered to levels appropriate for the dispersion of oil. This work indicates a novel concept of integrating particle stabilization of emulsions together with the release of chemical surfactants from the particles for the development of an alternative, cheaper, and environmentally-benign technology for oil spill remediation.

Smooth, All-Solid, Low-Hysteresis, Omniphobic Surfaces with Enhanced Mechanical Durability.

PubMed

Boban, Mathew; Golovin, Kevin; Tobelmann, Brian; Gupte, Omkar; Mabry, Joseph M; Tuteja, Anish

2018-04-11

The utility of omniphobic surfaces stems from their ability to repel a multitude of liquids, possessing a broad range of surface tensions and polarities, by causing them to bead up and either roll or slide off. These surfaces may be self-cleaning, corrosion-resistant, heat-transfer enhancing, stain-resistant or resistant to mineral- or biofouling. The majority of reported omniphobic surfaces use texture, lubricants, and/or grafted monolayers to engender these repellent properties. Unfortunately, these approaches often produce surfaces with deficiencies in long-term stability, durability, scalability, or applicability to a wide range of substrates. To overcome these limitations, we have fabricated an all-solid, substrate-independent, smooth, omniphobic coating composed of a fluorinated polyurethane and fluorodecyl polyhedral oligomeric silsesquioxane. Liquids of varying surface tension, including water, hexadecane, ethanol, and silicone oil, exhibit low-contact-angle hysteresis (<15°) on these surfaces, allowing liquid droplets to slide off, leaving no residue. Moreover, we demonstrate that these robust surfaces retained their repellent properties more effectively than textured or lubricated omniphobic surfaces after being subjected to mechanical abrasion.

Voltage-dependent cluster expansion for electrified solid-liquid interfaces: Application to the electrochemical deposition of transition metals

NASA Astrophysics Data System (ADS)

Weitzner, Stephen E.; Dabo, Ismaila

2017-11-01

The detailed atomistic modeling of electrochemically deposited metal monolayers is challenging due to the complex structure of the metal-solution interface and the critical effects of surface electrification during electrode polarization. Accurate models of interfacial electrochemical equilibria are further challenged by the need to include entropic effects to obtain accurate surface chemical potentials. We present an embedded quantum-continuum model of the interfacial environment that addresses each of these challenges and study the underpotential deposition of silver on the gold (100) surface. We leverage these results to parametrize a cluster expansion of the electrified interface and show through grand canonical Monte Carlo calculations the crucial need to account for variations in the interfacial dipole when modeling electrodeposited metals under finite-temperature electrochemical conditions.

Assembly of acid-functionalized single-walled carbon nanotubes at oil/water interfaces.

PubMed

Feng, Tao; Hoagland, David A; Russell, Thomas P

2014-02-04

The efficient segregation of water-soluble, acid-functionalized, single-walled carbon nanotubes (SWCNTs) at the oil/water interface was induced by dissolving low-molecular-weight amine-terminated polystyrene (PS-NH2) in the oil phase. Salt-bridge interactions between carboxylic acid groups of SWCNTs and amine groups of PS drove the assembly of SWCNTs at the interface, monitored by pendant drop tensiometry and laser scanning confocal microscopy. The impact of PS end-group functionality, PS and SWCNT concentrations, and the degree of SWCNT acid modification on the interfacial activity was assessed, and a sharp drop in interfacial tension was observed above a critical SWCNT concentration. Interfacial tensions were low enough to support stable oil/water emulsions. Further experiments, including potentiometric titrations and the replacement of SWCNTs by other carboxyl-containing species, demonstrated that the interfacial tension drop reflects the loss of SWCNT charge as the pH falls near/below the intrinsic carboxyl dissociation constant; species lacking multivalent carboxylic acid groups are inactive. The trapped SWCNTs appear to be neither ordered nor oriented.

The destabilization of an initially thick liquid sheet edge

NASA Astrophysics Data System (ADS)

Lhuissier, Henri; Villermaux, Emmanuel

2011-09-01

By forcing the sudden dewetting of a free soap film attached on one edge to a straight solid wire, we study the recession and subsequent destabilization of its free edge. The newly formed rim bordering the sheet is initially thicker than the film to which it is attached, because of the Plateau border preexisting on the wire. The initial condition is thus that of an immobile massive toroidal rim connected to a thin liquid film of thickness h. The terminal Taylor-Culick receding velocity V =√2σ/ρh , where σ and ρ are the liquid surface tension and density, respectively, is only reached after a transient acceleration period which promotes the rim destabilization. The selected wavelength and associated growth time coincide with those of an inertial instability driven by surface tension.

Effects of bulk colloidal stability on adsorption layers of poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate at the air-water interface studied by neutron reflectometry.

PubMed

Campbell, Richard A; Yanez Arteta, Marianna; Angus-Smyth, Anna; Nylander, Tommy; Varga, Imre

2011-12-29

We show for the oppositely charged system poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate that the cliff edge peak in its surface tension isotherm results from the comprehensive precipitation of bulk complexes into sediment, leaving a supernatant that is virtually transparent and a depleted adsorption layer at the air/water interface. The aggregation and settling processes take about 3 days to reach completion and occur at bulk compositions around charge neutrality of the complexes which lack long-term colloidal stability. We demonstrate excellent quantitative agreement between the measured surface tension values and a peak calculated from the surface excess of surfactant in the precipitation region measured by neutron reflectometry, using the approximation that there is no polymer left in the liquid phase. The nonequilibrium nature of the system is emphasized by the production of very different interfacial properties from equivalent aged samples that are handled differently. We go on to outline our perspective on the "true equilibrium" state of this intriguing system and conclude with a comment on its practical relevance given that the interfacial properties can be so readily influenced by the handling of kinetically trapped bulk aggregates. © 2011 American Chemical Society

Stochastic kinetics reveal imperative role of anisotropic interfacial tension to determine morphology and evolution of nucleated droplets in nematogenic films

NASA Astrophysics Data System (ADS)

Bhattacharjee, Amit Kumar

2017-01-01

For isotropic fluids, classical nucleation theory predicts the nucleation rate, barrier height and critical droplet size by ac- counting for the competition between bulk energy and interfacial tension. The nucleation process in liquid crystals is less understood. We numerically investigate nucleation in monolayered nematogenic films using a mesoscopic framework, in par- ticular, we study the morphology and kinetic pathway in spontaneous formation and growth of droplets of the stable phase in the metastable background. The parameter κ that quantifies the anisotropic elastic energy plays a central role in determining the geometric structure of the droplets. Noncircular nematic droplets with homogeneous director orientation are nucleated in a background of supercooled isotropic phase for small κ. For large κ, noncircular droplets with integer topological charge, accompanied by a biaxial ring at the outer surface, are nucleated. The isotropic droplet shape in a superheated nematic background is found to depend on κ in a similar way. Identical growth laws are found in the two cases, although an unusual two-stage mechanism is observed in the nucleation of isotropic droplets. Temporal distributions of successive events indi- cate the relevance of long-ranged elasticity-mediated interactions within the isotropic domains. Implications for a theoretical description of nucleation in anisotropic fluids are discussed.

Free energy of steps using atomistic simulations

NASA Astrophysics Data System (ADS)

Freitas, Rodrigo; Frolov, Timofey; Asta, Mark

The properties of solid-liquid interfaces are known to play critical roles in solidification processes. Particularly special importance is given to thermodynamic quantities that describe the equilibrium state of these surfaces. For example, on the solid-liquid-vapor heteroepitaxial growth of semiconductor nanowires the crystal nucleation process on the faceted solid-liquid interface is influenced by the solid-liquid and vapor-solid interfacial free energies, and also by the free energies of associated steps at these faceted interfaces. Crystal-growth theories and mesoscale simulation methods depend on quantitative information about these properties, which are often poorly characterized from experimental measurements. In this work we propose an extension of the capillary fluctuation method for calculation of the free energy of steps on faceted crystal surfaces. From equilibrium atomistic simulations of steps on (111) surfaces of Copper we computed accurately the step free energy for different step orientations. We show that the step free energy remains finite at all temperature up to the melting point and that the results obtained agree with the more well established method of thermodynamic integration if finite size effects are taken into account. The research of RF and MA at UC Berkeley were supported by the US National Science Foundation (Grant No. DMR-1105409). TF acknowledges support through a postdoctoral fellowship from the Miller Institute for Basic Research in Science.

Entropic multiple-relaxation-time multirange pseudopotential lattice Boltzmann model for two-phase flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Feifei; Mazloomi Moqaddam, Ali; Kang, Qinjun

Here, an entropic multiple-relaxation-time lattice Boltzmann approach is coupled to a multirange Shan-Chen pseudopotential model to study the two-phase flow. Compared with previous multiple-relaxation-time multiphase models, this model is stable and accurate for the simulation of a two-phase flow in a much wider range of viscosity and surface tension at a high liquid-vapor density ratio. A stationary droplet surrounded by equilibrium vapor is first simulated to validate this model using the coexistence curve and Laplace’s law. Then, two series of droplet impact behavior, on a liquid film and a flat surface, are simulated in comparison with theoretical or experimental results.more » Droplet impact on a liquid film is simulated for different Reynolds numbers at high Weber numbers. With the increase of the Sommerfeld parameter, onset of splashing is observed and multiple secondary droplets occur. The droplet spreading ratio agrees well with the square root of time law and is found to be independent of Reynolds number. Moreover, shapes of simulated droplets impacting hydrophilic and superhydrophobic flat surfaces show good agreement with experimental observations through the entire dynamic process. The maximum spreading ratio of a droplet impacting the superhydrophobic flat surface is studied for a large range of Weber numbers. Results show that the rescaled maximum spreading ratios are in good agreement with a universal scaling law. This series of simulations demonstrates that the proposed model accurately captures the complex fluid-fluid and fluid-solid interfacial physical processes for a wide range of Reynolds and Weber numbers at high density ratios.« less

Entropic multiple-relaxation-time multirange pseudopotential lattice Boltzmann model for two-phase flow

NASA Astrophysics Data System (ADS)

Qin, Feifei; Mazloomi Moqaddam, Ali; Kang, Qinjun; Derome, Dominique; Carmeliet, Jan

2018-03-01

An entropic multiple-relaxation-time lattice Boltzmann approach is coupled to a multirange Shan-Chen pseudopotential model to study the two-phase flow. Compared with previous multiple-relaxation-time multiphase models, this model is stable and accurate for the simulation of a two-phase flow in a much wider range of viscosity and surface tension at a high liquid-vapor density ratio. A stationary droplet surrounded by equilibrium vapor is first simulated to validate this model using the coexistence curve and Laplace's law. Then, two series of droplet impact behavior, on a liquid film and a flat surface, are simulated in comparison with theoretical or experimental results. Droplet impact on a liquid film is simulated for different Reynolds numbers at high Weber numbers. With the increase of the Sommerfeld parameter, onset of splashing is observed and multiple secondary droplets occur. The droplet spreading ratio agrees well with the square root of time law and is found to be independent of Reynolds number. Moreover, shapes of simulated droplets impacting hydrophilic and superhydrophobic flat surfaces show good agreement with experimental observations through the entire dynamic process. The maximum spreading ratio of a droplet impacting the superhydrophobic flat surface is studied for a large range of Weber numbers. Results show that the rescaled maximum spreading ratios are in good agreement with a universal scaling law. This series of simulations demonstrates that the proposed model accurately captures the complex fluid-fluid and fluid-solid interfacial physical processes for a wide range of Reynolds and Weber numbers at high density ratios.

Entropic multiple-relaxation-time multirange pseudopotential lattice Boltzmann model for two-phase flow

DOE PAGES

Qin, Feifei; Mazloomi Moqaddam, Ali; Kang, Qinjun; ...

2018-03-22

Here, an entropic multiple-relaxation-time lattice Boltzmann approach is coupled to a multirange Shan-Chen pseudopotential model to study the two-phase flow. Compared with previous multiple-relaxation-time multiphase models, this model is stable and accurate for the simulation of a two-phase flow in a much wider range of viscosity and surface tension at a high liquid-vapor density ratio. A stationary droplet surrounded by equilibrium vapor is first simulated to validate this model using the coexistence curve and Laplace’s law. Then, two series of droplet impact behavior, on a liquid film and a flat surface, are simulated in comparison with theoretical or experimental results.more » Droplet impact on a liquid film is simulated for different Reynolds numbers at high Weber numbers. With the increase of the Sommerfeld parameter, onset of splashing is observed and multiple secondary droplets occur. The droplet spreading ratio agrees well with the square root of time law and is found to be independent of Reynolds number. Moreover, shapes of simulated droplets impacting hydrophilic and superhydrophobic flat surfaces show good agreement with experimental observations through the entire dynamic process. The maximum spreading ratio of a droplet impacting the superhydrophobic flat surface is studied for a large range of Weber numbers. Results show that the rescaled maximum spreading ratios are in good agreement with a universal scaling law. This series of simulations demonstrates that the proposed model accurately captures the complex fluid-fluid and fluid-solid interfacial physical processes for a wide range of Reynolds and Weber numbers at high density ratios.« less

Pair correlation functions and the wavevector-dependent surface tension in a simple density functional treatment of the liquid-vapour interface.

PubMed

Parry, A O; Rascón, C; Willis, G; Evans, R

2014-09-03

We study the density-density correlation function G(r, r') in the interfacial region of a fluid (or Ising-like magnet) with short-ranged interactions using square gradient density functional theory. Adopting a simple double parabola approximation for the bulk free-energy density, we first show that the parallel Fourier transform G(z, z'; q) and local structure factor S(z; q) separate into bulk and excess contributions. We attempt to account for both contributions by deriving an interfacial Hamiltonian, characterised by a wavevector dependent surface tension σ(q), and then reconstructing density correlations from correlations in the interface position. We show that the standard crossing criterion identification of the interface, as a surface of fixed density (or magnetization), does not explain the separation of G(z, z'; q) and the form of the excess contribution. We propose an alternative definition of the interface position based on the properties of correlations between points that 'float' with the surface and show that this describes the full q and z dependence of the excess contributions to both G and S. However, neither the 'crossing-criterion' nor the new 'floating interface' definition of σ(q) are quantities directly measurable from the total structure factor S(tot)(q) which contains additional q dependence arising from the non-local relation between fluctuations in the interfacial position and local density. Since it is the total structure factor that is measured experimentally or in simulations, our results have repercussions for earlier attempts to extract and interpret σ(q).

Long-Wavelength Rupturing Instability in Surface-Tension-Driven Benard Convection

NASA Technical Reports Server (NTRS)

Swift, J. B.; Hook, Stephen J. Van; Becerril, Ricardo; McCormick, W. D.; Swinney, H. L.; Schatz, Michael F.

1999-01-01

A liquid layer with a free upper surface and heated from below is subject to thermocapillary-induced convective instabilities. We use very thin liquid layers (0.01 cm) to significantly reduce buoyancy effects and simulate Marangoni convection in microgravity. We observe thermocapillary-driven convection in two qualitatively different modes, short-wavelength Benard hexagonal convection cells and a long-wavelength interfacial rupturing mode. We focus on the long-wavelength mode and present experimental observations and theoretical analyses of the long-wavelength instability. Depending on the depths and thermal conductivities of the liquid and the gas above it, the interface can rupture downwards and form a dry spot or rupture upwards and form a high spot. Linear stability theory gives good agreement to the experimental measurements of onset as long as sidewall effects are taken into account. Nonlinear theory correctly predicts the subcritical nature of the bifurcation and the selection between the dry spot and high spots.

Incorporating contact angles in the surface tension force with the ACES interface curvature scheme

NASA Astrophysics Data System (ADS)

Owkes, Mark

2017-11-01

In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).

Membrane formation in liquids by adding an antagonistic salt

NASA Astrophysics Data System (ADS)

Sadakane, Koichiro; Seto, Hideki

2018-03-01

Antagonistic salts are composed of hydrophilic and hydrophobic ions. In a binary mixture, such as water and organic solvent, these ion pairs preferentially dissolve to those phases, respectively, and there is a coupling between the charge density and the composition. The heterogeneous distribution of ions forms a large electric double layer at the interface between these solvents. This reduces the interfacial tension between water and organic solvent, and stabilizes an ordered structure, such as a membrane. These phenomena have been extensively studied from both theoretical and experimental point of view. In addition, the numerical simulations can reproduce such ordered structures.

Structure and Dynamics of Interfaces: Drops and Films

NASA Technical Reports Server (NTRS)

Mann, J. Adin, Jr.; Mann, Elizabeth K.; Meyer, William V.; Neumann, A. Wilhelm; Tavana, Hossein

2015-01-01

We aim to acquire measurements of the structure and dynamics of certain liquid-fluid interfaces using an ensemble of techniques in collaboration: (1) Total internal reflection (TIR) Surface light scattering spectroscopy (SLSS), (2) Brewster angle microscopy (BAM), and (3) Drop-shape analysis. SLSS and BAM can be done on a shared interfacial footprint. Results using a 50-50 mixture of pentane-isohexane, which extends the range of NASA's Confined Vapor Bubble (CVB) experiment, yield surface tension results that differ from the expected Langmuir Fit. These results were confirmed using both the SLSS and drop-shape analysis approaches.

Creation of Woven Structures Impacting Self-cleaning Superoleophobicity

NASA Astrophysics Data System (ADS)

Lim, Jihye

For protection of human life from harmful or toxic liquids in working areas, solid surface resistance to liquid with low surface tension (e.g. oil) should be achieved in the outermost layer of protective clothing. Based on the literature review, multiscale structures were emphasized because they can increase roughness on a solid surface and create more void spaces of different sizes. The roughness and void spaces contribute to creating a liquid-vapor interface and reducing the liquid contact area to the solid surface. Woven fabric inherently consists of multiscale structures by its construction: microscale in a yarn structure and macroscale in a fabric structure. When the solid surface tension is low relative to oil, creating an appropriate structural geometry will become a critical way to obtain a superoleophobic surface for oil-resistance. Theoretical modeling and experiments with actual fabric samples were utilized to predict and prove the highest performing structural geometry in woven fabric, respectively. The theoretical geometric modeling accounted for the different weave structures, the yarn compression by the yarn flattening factor, e, and the void space by the void space ratio to the fiber or yarn diameter, T, impacting the liquid apparent contact angle on a fabric surface. The Cassie-Baxter equations were developed using Young's contact angle, thetae, thetae and e, or thetae, e, and T, to predict the liquid apparent contact angle for different geometries. In addition, to prevent a liquid's penetration into a solid structure, the ranges of the protuberance height (>> h2) and distance (< 4ℓ 2 cap) were predicted by the definition of the Laplace pressure, the capillary pressure, and the sagging phenomenon. Those predictions were in strong agreement with the results from the empirical experiment using the actual woven fabric samples. This study identified the impact of the geometries in yarn and woven fabric structures on the fabric resistance against oil through theoretical modeling and experiments. The results suggest particular weave structures, the range of the void space (or the protuberance distance) and the protuberance height in the yarn and fabric structures for the highest performing self-cleaning superoleophobic woven fabric surface.

Electrocapillary Phenomena at Edible Oil/Saline Interfaces.

PubMed

Nishimura, Satoshi; Ohzono, Takuya; Shoji, Kohei; Yagihara, Shin; Hayashi, Masafumi; Tanaka, Hisao

2017-03-01

Interfacial tension between edible oil and saline was measured under applied electric fields to understand the electrocapillary phenomena at the edible oil/saline interfaces. The electric responses of saline droplets in edible oil were also observed microscopically to examine the relationship between the electrocapillary phenomena and interfacial polarization. When sodium oleate (SO) was added to edible oil (SO-oil), the interfacial tension between SO-oil and saline decreased. However, no decrease was observed for additive-free oil or oleic acid (OA)-added oil (OA-oil). Microscopic observations suggested that the magnitude of interfacial polarization increased in the order of additive-free oil < OA-oil < SO-oil. The difference in electrocapillary phenomena between OA- and SO-oils was closely related to the polarization magnitude. In the case of SO-oil, the decrease in interfacial tension was remarkably larger for saline (pH 5.4~5.6) than that for phosphate-buffered saline (PBS, pH 7.2~7.4). However, no difference was observed between the electric responses of PBS and saline droplets in SO-oil. The difference in electrocapillary phenomena for PBS and saline could not be simply explained in terms of polarization magnitude. The ratio of ionized and non-ionized OA at the interfaces changed with the saline pH, possibly leading to the above difference.

Droplet impact on deep liquid pools: Rayleigh jet to formation of secondary droplets

NASA Astrophysics Data System (ADS)

Castillo-Orozco, Eduardo; Davanlou, Ashkan; Choudhury, Pretam K.; Kumar, Ranganathan

2015-11-01

The impact of droplets on a deep pool has applications in cleaning up oil spills, spray cooling, painting, inkjet printing, and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension, and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to Rayleigh jet breakup and number of daughter drops formed after its pinch-off. In this article, through systematic experiments we investigate the droplet impact phenomena by varying viscosity and surface tension of liquids as well as impact speeds. Further, using numerical simulations, we show that Rayleigh-Plateau instability is influenced by these parameters, and capillary time scale is the appropriate scale to normalize the breakup time. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested. Interestingly, crown splash is observed to occur at all Ohnesorge numbers; however, at high Oh, a large portion of kinetic energy is dissipated, and thus the Rayleigh jet is suppressed regardless of high impact velocity. The normalized required time for the Rayleigh jet to reach its peak varies linearly with the critical height of the jet.

Motion of deformable drops through granular media and other confined geometries.

PubMed

Davis, Robert H; Zinchenko, Alexander Z

2009-06-15

This article features recent simulation studies of the flow of emulsions containing deformable drops through pores, constrictions, and granular media. The flow is assumed to be at low Reynolds number, so that viscous forces dominate, and boundary-integral methods are used to determine interfacial velocities and, hence, track the drop motion and shapes. A single drop in a flat channel migrates to the channel centerplane due to deformation-induced drift, which increases its steady-state velocity along the channel. A drop moving towards a smaller interparticle constriction squeezes through the constriction if the capillary number (ratio of viscous deforming forces and interfacial tension forces) is large enough, but it becomes trapped when the capillary number is below a critical value. These concepts then influence the flow of an emulsion through a granular medium, for which the drop phase moves faster than the suspending liquid at large capillary numbers but slower than the suspending liquid at smaller capillary numbers. The permeabilities of the granular medium to both phases increase with increasing capillary number, due to the reduced resistance to squeezing of easily deformed drops, though drop breakup must also be considered at large capillary numbers.

Investigations on transparent liquid-miscibility gap systems

NASA Technical Reports Server (NTRS)

Lacy, L. L.; Nishioka, G.; Ross, S.

1979-01-01

Sedimentation and phase separation is a well known occurrence in monotectic or miscibility gap alloys. Previous investigations indicate that it may be possible to prepare such alloys in a low-gravity space environment but recent experiments indicate that there may be nongravity dependent phase separation processes which can hinder the formation of such alloys. Such phase separation processes are studied using transparent liquid systems and holography. By reconstructing holograms into a commercial-particle-analysis system, real time computer analysis can be performed on emulsions with diameters in the range of 5 micrometers or greater. Thus dynamic effects associated with particle migration and coalescence can be studied. Characterization studies on two selected immiscible systems including an accurate determination of phase diagrams, surface and interfacial tension measurements, surface excess and wetting behavior near critical solution temperatures completed.

Wetting of flat gradient surfaces.

PubMed

Bormashenko, Edward

2018-04-01

Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions. The linear approximation of the problem is considered. It is demonstrated that the contact angle hysteresis is inevitable on gradient surfaces. Electrowetting of gradient surfaces is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

Friction at ice-Ih / water interfaces

NASA Astrophysics Data System (ADS)

Louden, Patrick B.; Gezelter, J. Daniel

We present evidence that the prismatic and secondary prism facets of ice-Ih crystals possess structural features that alter the effective hydrophilicity of the ice / water interface. This is shown through molecular dynamics simulations of solid-liquid friction, where the prismatic { 10 1 0 } , secondary prism { 11 2 0 } , basal { 0001 } , and pyramidal { 20 2 1 } facets are drawn through liquid water. We find that the two prismatic facets exhibit differential solid-liquid friction coefficients when compared with the basal and pyramidal facets. These results are complemented by a model solid/liquid interface with tunable hydrophilicity. These simulations provide evidence that the two prismatic faces have a significantly smaller effective surface area in contact with the liquid water. The ice / water interfacial widths for all four crystal facets are similar (using both structural and dynamic measures), and were found to be independent of the shear rate. Additionally, decomposition of orientational time correlation functions show position-dependence for the short- and longer-time decay components close to the interface. Support for this project was provided by the National Science Foundation under Grant CHE-1362211. Computational time was provided by the Center for Research Computing (CRC) at the University of Notre Dame.

Fine Tuning of Tissues' Viscosity and Surface Tension through Contractility Suggests a New Role for α-Catenin

PubMed Central

Stirbat, Tomita Vasilica; Mgharbel, Abbas; Bodennec, Selena; Ferri, Karine; Mertani, Hichem C.; Rieu, Jean-Paul; Delanoë-Ayari, Hélène

2013-01-01

What governs tissue organization and movement? If molecular and genetic approaches are able to give some answers on these issues, more and more works are now giving a real importance to mechanics as a key component eventually triggering further signaling events. We chose embryonic cell aggregates as model systems for tissue organization and movement in order to investigate the origin of some mechanical constraints arising from cells organization. Steinberg et al. proposed a long time ago an analogy between liquids and tissues and showed that indeed tissues possess a measurable tissue surface tension and viscosity. We question here the molecular origin of these parameters and give a quantitative measurement of adhesion versus contractility in the framework of the differential interfacial tension hypothesis. Accompanying surface tension measurements by angle measurements (at vertexes of cell-cell contacts) at the cell/medium interface, we are able to extract the full parameters of this model: cortical tensions and adhesion energy. We show that a tunable surface tension and viscosity can be achieved easily through the control of cell-cell contractility compared to cell-medium one. Moreover we show that -catenin is crucial for this regulation to occur: these molecules appear as a catalyser for the remodeling of the actin cytoskeleton underneath cell-cell contact, enabling a differential contractility between the cell-medium and cell-cell interface to take place. PMID:23390488

A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension

NASA Astrophysics Data System (ADS)

Garrick, Daniel P.; Owkes, Mark; Regele, Jonathan D.

2017-06-01

Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge-Kutta method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten-Lax-van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas-liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.

A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrick, Daniel P.; Owkes, Mark; Regele, Jonathan D., E-mail: jregele@iastate.edu

Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge–Kuttamore » method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten–Lax–van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas–liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.« less

Impact of carbon nanotubes based nanofluid on oil recovery efficiency using core flooding

NASA Astrophysics Data System (ADS)

Soleimani, Hassan; Baig, Mirza Khurram; Yahya, Noorhana; Khodapanah, Leila; Sabet, Maziyar; Demiral, Birol M. R.; Burda, Marek

2018-06-01

This study aims to investigate the influence of carbon nanotubes based nanofluid on interfacial tension and oil recovery efficiency. Practically multi-walled carbon nanotubes were successfully synthesized using chemical vapour deposition technique and characterized using X-ray diffraction and Field Emission Scanning Electron microscope in order to understand its structure, shape, and morphology. Nanofluids are one of the interesting new agents for enhanced oil recovery (EOR) that can change the reservoir rock-fluid properties in terms of interfacial tension and wettability. In this work, different concentration of carbon nanotubes based fluids were prepared and the effect of each concentration on surface tension was determined using pendant drop method. After specifying the optimum concentration of carbon nanotubes based nanofluid, core flooding experiment was conducted by two pore volume of brine and two pore volume of nanofluid and then oil recovery factor was calculated. The results show that carbon nanotubes can bring in additional recovery factor of 18.57% in the glass bead sample. It has been observed that nanofluid with high surface tension value gives higher recovery. It was found that the optimum value of concentration is 0.3 wt% at which maximum surface tension of 33.46 mN/m and oil recovery factor of 18.57% was observed. This improvement in recovery factor can be recognized due to interfacial tension reduction and wettability alteration.

Interfacial Effects in Solid-Liquid Electrolytes for Improved Stability and Performance of Dye-Sensitized Solar Cells.

PubMed

Bella, Federico; Popovic, Jelena; Lamberti, Andrea; Tresso, Elena; Gerbaldi, Claudio; Maier, Joachim

2017-11-01

With the purpose of achieving stable dye-sensitized solar cells (DSSCs) with high efficiency, a new type of soft matter electrolyte is tested in which specific amounts of nanosized silica particles are finely dispersed in short-chained polyethylene glycol dimethylether encompassing an iodide/triiodide redox mediator. This results in a solid-liquid composite having synergistic electrical and favorable mechanical properties. The combination of interfacial effects and particle network formation promotes enhanced ion transport, which directly impacts the short-circuit photocurrent density. Thorough analysis reveals that this newly elaborated class of electrolytes is able to improve, at the same time, the thermal and long-term stability of DSSCs, as well as power conversion efficiency under standard and lower irradiation intensities. Lab-scale devices with champion efficiency exceeding 11% under attenuated sunlight (20 mW cm -2 , with a compact TiO 2 blocking layer) are obtained, along with impressively stable performance under both thermal stress and light soaking in an indoor environment (>96% performance retention after 2500 h of accelerated aging under full sun alternated with thermal ramps), matching the durability criteria applied to silicon solar cells for outdoor applications. The new findings might foster widespread practical application of DSSCs.

The Effect of Water and Confinement on Self-Assembly of Imidazolium Based Ionic Liquids at Mica Interfaces

PubMed Central

Cheng, H.-W.; Dienemann, J.-N.; Stock, P.; Merola, C.; Chen, Y.-J.; Valtiner, M.

2016-01-01

Tuning chemical structure and molecular layering of ionic liquids (IL) at solid interfaces offers leverage to tailor performance of ILs in applications such as super-capacitors, catalysis or lubrication. Recent experimental interpretations suggest that ILs containing cations with long hydrophobic tails form well-ordered bilayers at interfaces. Here we demonstrate that interfacial bilayer formation is not an intrinsic quality of hydrophobic ILs. In contrast, bilayer formation is triggered by boundary conditions including confinement, surface charging and humidity present in the IL. Therefore, we performed force versus distance profiles using atomic force microscopy and the surface forces apparatus. Our results support models of disperse low-density bilayer formation in confined situations, at high surface charging and/or in the presence of water. Conversely, interfacial structuring of long-chain ILs in dry environments and at low surface charging is disordered and dominated by bulk structuring. Our results demonstrate that boundary conditions such as charging, confinement and doping by impurities have decisive influence on structure formation of ILs at interfaces. As such, these results have important implications for understanding the behavior of solid/IL interfaces as they significantly extend previous interpretations. PMID:27452615

The Effect of Water and Confinement on Self-Assembly of Imidazolium Based Ionic Liquids at Mica Interfaces.

PubMed

Cheng, H-W; Dienemann, J-N; Stock, P; Merola, C; Chen, Y-J; Valtiner, M

2016-07-25

Tuning chemical structure and molecular layering of ionic liquids (IL) at solid interfaces offers leverage to tailor performance of ILs in applications such as super-capacitors, catalysis or lubrication. Recent experimental interpretations suggest that ILs containing cations with long hydrophobic tails form well-ordered bilayers at interfaces. Here we demonstrate that interfacial bilayer formation is not an intrinsic quality of hydrophobic ILs. In contrast, bilayer formation is triggered by boundary conditions including confinement, surface charging and humidity present in the IL. Therefore, we performed force versus distance profiles using atomic force microscopy and the surface forces apparatus. Our results support models of disperse low-density bilayer formation in confined situations, at high surface charging and/or in the presence of water. Conversely, interfacial structuring of long-chain ILs in dry environments and at low surface charging is disordered and dominated by bulk structuring. Our results demonstrate that boundary conditions such as charging, confinement and doping by impurities have decisive influence on structure formation of ILs at interfaces. As such, these results have important implications for understanding the behavior of solid/IL interfaces as they significantly extend previous interpretations.

On the interfacial thermodynamics of nanoscale droplets and bubbles

NASA Astrophysics Data System (ADS)

Corti, David S.; Kerr, Karl J.; Torabi, Korosh

2011-07-01

We present a new self-consistent thermodynamic formalism for the interfacial properties of nanoscale embryos whose interiors do not exhibit bulklike behavior and are in complete equilibrium with the surrounding mother phase. In contrast to the standard Gibbsian analysis, whereby a bulk reference pressure based on the same temperature and chemical potentials of the mother phase is introduced, our approach naturally incorporates the normal pressure at the center of the embryo as an appropriate reference pressure. While the interfacial properties of small embryos that follow from the use of these two reference pressures are different, both methods yield by construction the same reversible work of embryo formation as well as consistency between their respective thermodynamic and mechanical routes to the surface tension. Hence, there is no a priori reason to select one method over another. Nevertheless, we argue, and demonstrate via a density-functional theory (with the local density approximation) analysis of embryo formation in the pure component Lennard-Jones fluid, that our new method generates more physically appealing trends. For example, within the new approach the surface tension at all locations of the dividing surface vanishes at the spinodal where the density profile spanning the embryo and mother phase becomes completely uniform (only the surface tension at the Gibbs surface of tension vanishes in the Gibbsian method at this same limit). Also, for bubbles, the location of the surface of tension now diverges at the spinodal, similar to the divergent behavior exhibited by the equimolar dividing surface (in the Gibbsian method, the location of the surface of tension vanishes instead). For droplets, the new method allows for the appearance of negative surface tensions (the Gibbsian method always yields positive tensions) when the normal pressures within the interior of the embryo become less than the bulk pressure of the surrounding vapor phase. Such a prediction, which is allowed by thermodynamics, is consistent with the interpretation that the mother phase's attempted compression of the droplet is counterbalanced by the negative surface tension, or free energy cost to decrease the interfacial area. Furthermore, for these same droplets, the surface of tension can no longer be meaningfully defined (the surface of tension always remains well defined in the Gibbsian method). Within the new method, the dividing surface at which the surface tension equals zero emerges as a new lengthscale, which has various thermodynamic analogs to and similar behavior as the surface of tension.

Modeling, investigation and formulation of hydrophobic coatings for potential self-cleaning applications

NASA Astrophysics Data System (ADS)

Rios, Pablo Fabian

Self-cleaning surfaces have received a great deal of attention, both in research and commercial applications. Transparent and non-transparent self-cleaning surfaces are highly desired. The Lotus flower is a symbol of purity in Asian cultures, even when rising from muddy waters it stays clean and untouched by dirt. The Lotus leaf "self-cleaning" surface is hydrophobic and rough, showing a two-layer morphology. While hydrophobicity produces a high contact angle, surface morphology reduces the adhesion of dirt and water to the surface, thus water drops slide easily across the leaf carrying the dirt particles with them. Nature example in the Lotus-effect and extensive scientific research on related fields have rooted wide acceptance that high hydrophobicity can be obtained only by a proper combination of surface chemistry and roughness. Most researchers relate hydrophobicity to a high contact angle. However, the contact angle is not the only parameter that defines liquid-solid interactions. An additional parameter, the sliding angle, related to the adhesion between the liquid drop and the solid surface is also important in cases where liquid sliding is involved, such as self-cleaning applications. In this work, it is postulated that wetting which is related to the contact angle, and interfacial adhesion, which is related to the sliding angle, are interdependent phenomena and have to be considered simultaneously. A variety of models that relate the sliding angle to forces developed along the contact line between a liquid drop and a solid surface have been proposed in the literature. A new model is proposed here that quantifies the drop sliding phenomenon, based also on the interfacial adhesion across the contact area of the liquid/solid interface. The effects of roughness and chemical composition on the contact and sliding angles of hydrophobic smooth and rough surfaces were studied theoretically and experimentally. The validity of the proposed model was investigated and compared with the existing models. Ultra-hydrophobic non-transparent and transparent coatings for potential self-cleaning applications were produced using hydrophobic chemistry and different configurations of roughening micro and nano-particles, however they present low adhesion and durability. Durability and stability enhancement of such coatings was attempted and improved by different methods.

Electrodeposition of Polymer Nanostructures using Three Diffuse Double Layers: Polymerization beyond the Liquid/Liquid Interfaces

NASA Astrophysics Data System (ADS)

Divya, Velpula; Sangaranarayanan, M. V.

2018-04-01

Nanostructured conducting polymers have received immense attention during the past few decades on account of their phenomenal usefulness in diverse contexts, while the interface between two immiscible liquids is of great interest in chemical and biological applications. Here we propose a novel Electrode(solid)/Electrolyte(aqueous)/Electrolyte(organic) Interfacial assembly for the synthesis of polymeric nanostructures using a novel concept of three diffuse double layers. There exist remarkable differences between the morphologies of the polymers synthesized using the conventional electrode/electrolyte method and that of the new approach. In contrast to the commonly employed electrodeposition at liquid/liquid interfaces, these polymer modified electrodes can be directly employed in diverse applications such as sensors, supercapacitors etc.

Study of glass hydrometer calibration by hydrostatic weighting

NASA Astrophysics Data System (ADS)

Chen, Chaoyun; Wang, Jintao; Li, Zhihao; Zhang, Peiman

2016-01-01

Glass hydrometers are simple but effective instruments for measuring the density of liquids. Glass hydrometers calibration based on the Archimedes law, using silicon ring as a reference standard solid density, n-tridecane with density stability and low surface tension as the standard working liquid, based on hydrostatic weighing method designs a glass hydrometer calibration system. Glass hydrometer calibration system uses CCD image measurement system to align the scale of hydrometer and liquid surface, with positioning accuracy of 0.01 mm. Surface tension of the working liquid is measured by Whihemy plate. According to twice glass hydrometer weighing in the air and liquid can calculate the correction value of the current scale. In order to verify the validity of the principle of the hydrostatic weighing method of glass hydrometer calibration system, for measuring the density range of (770-790) kg/m3, with a resolution of 0.2 kg/m3 of hydrometer. The results of measurement compare with the Physikalisch-Technische Bundesanstalt(PTB) ,verifying the validity of the calibration system.

Infiltration sintering properties of Ni-4B-4Si(wt.%) alloy powders

NASA Astrophysics Data System (ADS)

Yang, Q.; Zhang, X. C.; Wang, F. L.; Zou, J. T.

2018-01-01

The Ni-4B-4Si(wt.%) alloy powders were infiltrated into the nickel skeletons, the effects of sintering temperatures (1050-1150 °C) and skeletons (loose and compact nickel powders) on the microstructures and hardness of the sintered alloys were investigated. The Ni-B-Si alloy sintered at 1100 °C consisted of γ-Ni and Ni3B, and Si mainly solid soluted in the γ-Ni. The loose nickel powders favored to the infiltration of Ni-B-Si liquid alloy into the nickel skeletons, the sintered alloys exhibited dense microstructures and good interfacial bonding with Ni substrates. The interfacial hardness was equal to that of the sintered alloys and Ni substrates. Loose nickel powders ensured the density and interfacial bonding of the sintered alloys, the infiltration sintering process can be simplified and easily applied to practice.

Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

York, Roger L.

2007-01-01

Sum frequency generation (SFG) vibrational spectroscopy has been used to study the interfacial structure of several polypeptides and amino acids adsorbed to hydrophobic and hydrophilic surfaces under a variety of experimental conditions. Peptide sequence, peptide chain length, peptide hydrophobicity, peptide side-chain type, surface hydrophobicity, and solution ionic strength all affect an adsorbed peptide's interfacial structure. Herein, it is demonstrated that with the choice of simple, model peptides and amino acids, surface specific SFG vibrational spectroscopy can be a powerful tool to elucidate the interfacial structure of these adsorbates. Herein, four experiments are described. In one, a series of isosequential amphiphilicmore » peptides are synthesized and studied when adsorbed to both hydrophobic and hydrophilic surfaces. On hydrophobic surfaces of deuterated polystyrene, it was determined that the hydrophobic part of the peptide is ordered at the solid-liquid interface, while the hydrophilic part of the peptide appears to have a random orientation at this interface. On a hydrophilic surface of silica, it was determined that an ordered peptide was only observed if a peptide had stable secondary structure in solution. In another experiment, the interfacial structure of a model amphiphilic peptide was studied as a function of the ionic strength of the solution, a parameter that could change the peptide's secondary structure in solution. It was determined that on a hydrophobic surface, the peptide's interfacial structure was independent of its structure in solution. This was in contrast to the adsorbed structure on a hydrophilic surface, where the peptide's interfacial structure showed a strong dependence on its solution secondary structure. In a third experiment, the SFG spectra of lysine and proline amino acids on both hydrophobic and hydrophilic surfaces were obtained by using a different experimental geometry that increases the SFG signal. Upon comparison of these spectra to the SFG spectra of interfacial polylysine and polyproline it was determined that the interfacial structure of a peptide is strongly dependent on its chain length. Lastly, SFG spectroscopy has been extended to the Amide I vibrational mode of a peptide (which is sensitive to peptide secondary structure) by building a new optical parametric amplifier based on lithium thioindate. Evidence is presented that suggests that the interfacial secondary structure of a peptide can be perturbed by a surface.« less

Governing Influence of Thermodynamic and Chemical Equilibria on the Interfacial Properties in Complex Fluids.

PubMed

Harikrishnan, A R; Dhar, Purbarun; Gedupudi, Sateesh; Das, Sarit K

2018-04-12

We propose a comprehensive analysis and a quasi-analytical mathematical formalism to predict the surface tension and contact angles of complex surfactant-infused nanocolloids. The model rests on the foundations of the interaction potentials for the interfacial adsorption-desorption dynamics in complex multicomponent colloids. Surfactant-infused nanoparticle-laden interface problems are difficult to deal with because of the many-body interactions and interfaces involved at the meso-nanoscales. The model is based on the governing role of thermodynamic and chemical equilibrium parameters in modulating the interfacial energies. The influence of parameters such as the presence of surfactants, nanoparticles, and surfactant-capped nanoparticles on interfacial dynamics is revealed by the analysis. Solely based on the knowledge of interfacial properties of independent surfactant solutions and nanocolloids, the same can be deduced for complex surfactant-based nanocolloids through the proposed approach. The model accurately predicts the equilibrium surface tension and contact angle of complex nanocolloids available in the existing literature and present experimental findings.

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory

NASA Astrophysics Data System (ADS)

Wang, Le; Haghmoradi, Amin; Liu, Jinlu; Xi, Shun; Hirasaki, George J.; Miller, Clarence A.; Chapman, Walter G.

2017-03-01

Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents). To help obtain a better understanding of the dependence of surfactant properties on molecular structure, a classical density functional theory, also known as interfacial statistical associating fluid theory, has been applied to study the effects of surfactant architecture on micelle formation and interfacial properties for model nonionic surfactant/water/oil systems. In this approach, hydrogen bonding is explicitly included. To minimize the free energy, the system minimizes interactions between hydrophobic components and hydrophilic components with water molecules hydrating the surfactant head group. The theory predicts micellar structure, effects of surfactant architecture on critical micelle concentration, aggregation number, and interfacial tension isotherm of surfactant/water systems in qualitative agreement with experimental data. Furthermore, this model is applied to study swollen micelles and reverse swollen micelles that are necessary to understand the formation of a middle-phase microemulsion.

Interfacial material for solid oxide fuel cell

DOEpatents

Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

1999-01-01

Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

Vapor-liquid-solid growth of silicon and silicon germanium nanowires

NASA Astrophysics Data System (ADS)

Nimmatoori, Pramod

2009-12-01

Si and Si1-xGex nanowires are promising materials with potential applications in various disciplines of science and technology. Small diameter nanowires can act as model systems to study interesting phenomena such as tunneling that occur in the nanometer regime. Furthermore, technical challenges in fabricating nanoscale size devices from thin films have resulted in interest and research on nanowires. In this perspective, vertical integrated nanowire field effect transistors (VINFETs) fabricated from Si nanowires are promising devices that offer better control on device properties and push the transistor architecture into the third dimension potentially enabling ultra-high transistor density circuits. Transistors fabricated from Si/Si 1-xGex nanowires have also been proposed that can have high carrier mobility. In addition, the Si and Si1-xGe x nanowires have potential to be used in various applications such as sensing, thermoelectrics and solar cells. Despite having considerable potential, the understanding of the vapor-liquid-solid (VLS) mechanism utilized to fabricate these wires is still rudimentary. Hence, the objective of this thesis is to understand the effects of nanoscale size and the role of catalyst that mediates the wire growth on the growth rate of Si and Si1-xGe x nanowires and interfacial abruptness in Si/Si1-xGe x axial heterostructure nanowires. Initially, the growth and structural properties of Si nanowires with tight diameter distribution grown from 10, 20 and 50 nm Au particles dispersed on a polymer-modified substrate was studied. A nanoparticle application process was developed to disperse Au particles on the substrate surface with negligible agglomeration and sufficient density. The growth temperature and SiH4 partial pressure were varied to optimize the growth conditions amenable to VLS growth with smooth wire morphology and negligible Si thin film deposition on wire sidewalls. The Si nanowire growth rate was studied as a function of growth time, temperature, SiH4 partial pressure and wire diameter and discussed in the context of the literature. The wire growth rate was found to increase with wire diameter in agreement with a size-related effect known as the Gibbs-Thomson effect. Subsequently, the effect of P and Sb doping on the growth rate and structural properties of Si nanowires was investigated. A reduction in wire growth rate was observed upon doping, which was pronounced in case of Sb doping, ascribable to P/Sb segregation at the vapor-liquid interface (catalyst surface) and the liquid-solid interface (growth front) that in turn reduces Si incorporation at these interfaces. The second part of thesis was focused on the Si1-xGe x alloy nanowires. The effect of wire diameter and growth conditions on the interfacial abruptness of Si/Si1-xGex heterostructure nanowires was examined. Abrupt interfaces were obtained at smaller wire diameters. However, the growth temperature wasn't found to have much impact on the interfacial abruptness. These results were explained in terms of catalyst effects on the interfacial abruptness. The remaining part of the study was focused on the effect of growth conditions on the growth rate of Si1-x Gex nanowires. It was found that the Si incorporation mechanism was different between Si and Si1-xGex nanowire growth which was ascribed to changes in the gas phase or catalyst composition that can impact the SiH4 decomposition kinetics at the catalyst surface (vapor-liquid interface) and/or Si incorporation at the growth front (liquid-solid interface).

Effect of sucrose ester concentration on the interfacial characteristics and physical properties of sodium caseinate-stabilized oil-in-water emulsions.

PubMed

Zhao, Qiangzhong; Liu, Daolin; Long, Zhao; Yang, Bao; Fang, Min; Kuang, Wanmei; Zhao, Mouming

2014-05-15

The effect of sucrose ester (SE) concentration on interfacial tension and surface dilatational modulus of SE and sodium caseinate (NaCas)-SE solutions were investigated. The critical micelle concentration (CMC) of SE was presumed to be 0.05% by measuring interfacial tension of SE solution. The interfacial tension of NaCas-SE solution decreased with increased SE concentration. A sharp increase in surface dilatational modulus of NaCas solution was observed when 0.01% SE was added and a decline was occurred at higher SE level. The influence of SE concentration on droplet size and confocal micrograph, surface protein concentration, ζ-potential and rheological properties of oil-in-water (O/W) emulsions prepared with 1% NaCas was also examined. The results showed that addition of SE reduced droplet size and surface protein concentration of the O/W emulsions. The ζ-potential of the O/W emulsions increased initially and decreased afterward with increased SE concentration. All the O/W emulsions exhibited a shear-thinning behaviour and the data were well-fitted into the Herschel-Bulkley model. Copyright © 2013 Elsevier Ltd. All rights reserved.

System for monitoring physical characteristics of fluids

NASA Technical Reports Server (NTRS)

Trinh, E. H.; Wang, T. G. (Inventor)

1983-01-01

An apparatus and method are described for measuring physical characteristics of fluid, by placing a drop of the fluid in a batch of a second fluid and passing acoustic waves through the bath. The applied frequency of the acoustic waves is varied, to determine the precise value of a frequency at which the drop undergoes resonant oscillations. The resonant frequency indicates the interfacial tension of the drop in the bath, and the interfacial tension can indicate physical properties of the fluid in the drop.

Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant.

PubMed

Song, Meirong; Ju, Jie; Luo, Siqi; Han, Yuchun; Dong, Zhichao; Wang, Yilin; Gu, Zhen; Zhang, Lingjuan; Hao, Ruiran; Jiang, Lei

2017-03-01

Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing. For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves. We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT. Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash. Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface. A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface.

Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant

PubMed Central

Song, Meirong; Ju, Jie; Luo, Siqi; Han, Yuchun; Dong, Zhichao; Wang, Yilin; Gu, Zhen; Zhang, Lingjuan; Hao, Ruiran; Jiang, Lei

2017-01-01

Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing. For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves. We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT. Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash. Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface. A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface. PMID:28275735

Liquid drops attract or repel by the inverted Cheerios effect.

PubMed

Karpitschka, Stefan; Pandey, Anupam; Lubbers, Luuk A; Weijs, Joost H; Botto, Lorenzo; Das, Siddhartha; Andreotti, Bruno; Snoeijer, Jacco H

2016-07-05

Solid particles floating at a liquid interface exhibit a long-ranged attraction mediated by surface tension. In the absence of bulk elasticity, this is the dominant lateral interaction of mechanical origin. Here, we show that an analogous long-range interaction occurs between adjacent droplets on solid substrates, which crucially relies on a combination of capillarity and bulk elasticity. We experimentally observe the interaction between droplets on soft gels and provide a theoretical framework that quantitatively predicts the interaction force between the droplets. Remarkably, we find that, although on thick substrates the interaction is purely attractive and leads to drop-drop coalescence, for relatively thin substrates a short-range repulsion occurs, which prevents the two drops from coming into direct contact. This versatile interaction is the liquid-on-solid analog of the "Cheerios effect." The effect will strongly influence the condensation and coarsening of drops on soft polymer films, and has potential implications for colloidal assembly and mechanobiology.

A smoothed particle hydrodynamics framework for modelling multiphase interactions at meso-scale

NASA Astrophysics Data System (ADS)

Li, Ling; Shen, Luming; Nguyen, Giang D.; El-Zein, Abbas; Maggi, Federico

2018-01-01

A smoothed particle hydrodynamics (SPH) framework is developed for modelling multiphase interactions at meso-scale, including the liquid-solid interaction induced deformation of the solid phase. With an inter-particle force formulation that mimics the inter-atomic force in molecular dynamics, the proposed framework includes the long-range attractions between particles, and more importantly, the short-range repulsive forces to avoid particle clustering and instability problems. Three-dimensional numerical studies have been conducted to demonstrate the capabilities of the proposed framework to quantitatively replicate the surface tension of water, to model the interactions between immiscible liquids and solid, and more importantly, to simultaneously model the deformation of solid and liquid induced by the multiphase interaction. By varying inter-particle potential magnitude, the proposed SPH framework has successfully simulated various wetting properties ranging from hydrophobic to hydrophilic surfaces. The simulation results demonstrate the potential of the proposed framework to genuinely study complex multiphase interactions in wet granular media.

Pore-scale Investigation of Surfactant Induced Mobilization for the Remediation of LNAPL

NASA Astrophysics Data System (ADS)

Ghosh, J.; Tick, G. R.

2011-12-01

The presence of nonaqueous phase liquids within the subsurface can significantly limit the effectiveness of groundwater remediation. Specifically, light nonaqueous phase liquids (LNAPLs) present unique challenges as they can become "smeared" within zones above and below the water table. The aim of this research is to understand the interfacial phenomena at the pore scale influencing residual saturation of LNAPL distribution as function of media heterogeneity and remediation processes from various aquifer systems. A series of columns were packed with three types of unconsolidated sand of increasing heterogeneity in grain size distribution and were established with residual saturations of light and heavy crude oil fractions, respectively. These columns were then subjected to flooding with 0.1% anionic surfactant solution in various episodes to initiate mobilization and enhanced recovery of NAPL phase contamination. Synchrotron X-ray microtomography (SXM) imaging technology was used to study three-dimensional (3-D) distributions of crude-oil-blobs before and after sequential surfactant flooding events. Results showed that LNAPL blob distributions became more heterogeneous after each subsequent surfactant flooding episode for all porous-media systems. NAPL recovery was most effective from the homogenous porous medium whereby 100% recovery resulted after 5 pore volumes (PVs) of flushing. LNAPL within the mildly heterogeneous porous medium produced a limited but consistent reduction in saturation after each surfactant flooding episode (23% and 43% recovery for light and heavy after the 5-PV flood). The highly heterogeneous porous medium showed greater NAPL recovery potential (42% and 16% for light and heavy) only after multiple pore volumes of flushing, at which point the NAPL blobs become fragmented into the smaller fragments in response to the reduced interfacial tension. The heterogeneity of the porous media (i.e. grain-size distribution) was a dominant control on the NAPL-blob-size-distribution trapped as residual saturation. The mobility of the NAPL blobs, as a result of surfactant flooding, was primarily controlled by the relative permeability of the medium and the reduction of interfacial tension between the wetting phase (water) and NAPL phase.

A Local Condensation Analysis Representing Two-phase Annular Flow in Condenser/radiator Capillary Tubes

NASA Technical Reports Server (NTRS)

Karimi, Amir

1991-01-01

NASA's effort for the thermal environmental control of the Space Station Freedom is directed towards the design, analysis, and development of an Active Thermal Control System (ATCS). A two phase, flow through condenser/radiator concept was baselined, as a part of the ATCS, for the radiation of space station thermal load into space. The proposed condenser rejects heat through direct condensation of ATCS working fluid (ammonia) in the small diameter radiator tubes. Analysis of the condensation process and design of condenser tubes are based on the available two phase flow models for the prediction of flow regimes, heat transfer, and pressure drops. The prediction formulas use the existing empirical relationships of friction factor at gas-liquid interface. An attempt is made to study the stability of interfacial waves in two phase annular flow. The formulation is presented of a stability problem in cylindrical coordinates. The contribution of fluid viscosity, surface tension, and transverse radius of curvature to the interfacial surface is included. A solution is obtained for Kelvin-Helmholtz instability problem which can be used to determine the critical and most dangerous wavelengths for interfacial waves.

A computational DFT study of structural transitions in textured solid-fluid interfaces

NASA Astrophysics Data System (ADS)

Yatsyshin, Petr; Parry, Andrew O.; Kalliadasis, Serafim

2015-11-01

Fluids adsorbed at walls, in capillary pores and slits, and in more exotic, sculpted geometries such as grooves and wedges can exhibit many new phase transitions, including wetting, pre-wetting, capillary-condensation and filling, compared to their bulk counterparts. As well as being of fundamental interest to the modern statistical mechanical theory of inhomogeneous fluids, these are also relevant to nanofluidics, chemical- and bioengineering. In this talk we will show using a microscopic Density Functional Theory (DFT) for fluids how novel, continuous, interfacial transitions associated with the first-order prewetting line, can occur on steps, in grooves and in wedges, that are sensitive to both the range of the intermolecular forces and interfacial fluctuation effects. These transitions compete with wetting, filling and condensation producing very rich phase diagrams even for relatively simple geometries. We will also discuss practical aspects of DFT calculations, and demonstrate how this statistical-mechanical framework is capable of yielding complex fluid structure, interfacial tensions, and regions of thermodynamic stability of various fluid configurations. As a side note, this demonstrates that DFT is an excellent tool for the investigations of complex multiphase systems. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031.

Water at silica/liquid water interfaces investigated by DFT-MD simulations

NASA Astrophysics Data System (ADS)

Gaigeot, Marie-Pierre

This talk is dedicated to probing the microscopic structural organization of water at silica/liquid water interfaces including electrolytes by first principles DFT-based molecular dynamics simulations (DFT-MD). We will present our very recent DFT-MD simulations of electrolytic (KCl, NaCl, NaI) silica/liquid water interfaces in order to unravel the intertwined structural properties of water and electrolytes at the crystalline quartz/liquid water and amorphous silica/liquid water interfaces. DFT-MD simulations provide direct knowledge of the structural organization of water and the H-Bond network formed between the water molecules within the different water layers above the silica surface. One can furthermore extract vibrational signatures of the water molecules within the interfacial layers from the DFT-MD simulations, especially non-linear SFG (Sum Frequency generation) signatures that are active at solid/liquid interfaces. The strength of the simulated spectra is that a detailed analysis of the signatures in terms of the water/water H-Bond networks formed within the interfacial water layers and in terms of the water/silica or water/electrolytes H-Bond networks can be given. Comparisons of SFG spectra between quartz/water/electrolytes and amorphous silica/water/electrolytes interfaces allow us to definitely conclude on how the structural arrangements of liquid water at these electrolytic interfaces modulate the final spectroscopic signatures. Invited speaker.

Proceedings of the International Workshop on Condensed Matter Theories (8th) Held in San Juan, Puerto Rico on 1-5 June 1992

DTIC Science & Technology

1993-01-15

Canosa, R. Rossignoli and A. Plastino 10. Time-dependent N-Level Systems J. Aliaga , J.L Gruver and A. N. Proto 7 4 Atoms and Molecules 1. Atoms in...Interfacial Phase Transitions Underlying Amphiphile Micellar Self-Assembly A. Robledo and C. Varea 3. Hot-solid Properties From Liquid Structure Within

Theoretical analysis for the optical deformation of emulsion droplets.

PubMed

Tapp, David; Taylor, Jonathan M; Lubansky, Alex S; Bain, Colin D; Chakrabarti, Buddhapriya

2014-02-24

We propose a theoretical framework to predict the three-dimensional shapes of optically deformed micron-sized emulsion droplets with ultra-low interfacial tension. The resulting shape and size of the droplet arises out of a balance between the interfacial tension and optical forces. Using an approximation of the laser field as a Gaussian beam, working within the Rayleigh-Gans regime and assuming isotropic surface energy at the oil-water interface, we numerically solve the resulting shape equations to elucidate the three-dimensional droplet geometry. We obtain a plethora of shapes as a function of the number of optical tweezers, their laser powers and positions, surface tension, initial droplet size and geometry. Experimentally, two-dimensional droplet silhouettes have been imaged from above, but their full side-on view has not been observed and reported for current optical configurations. This experimental limitation points to ambiguity in differentiating between droplets having the same two-dimensional projection but with disparate three-dimensional shapes. Our model elucidates and quantifies this difference for the first time. We also provide a dimensionless number that indicates the shape transformation (ellipsoidal to dumbbell) at a value ≈ 1.0, obtained by balancing interfacial tension and laser forces, substantiated using a data collapse.

Influence of Sulphur Impurities on the Interfacial Tension between Aluminium and Cryolite Alumina Melts

NASA Astrophysics Data System (ADS)

Korenko, Michal

2007-06-01

The interfacial tension (IFT) between aluminium and cryolite melts containing different salt additions (AlF3, NaF,Na2SO4) has been measured during electrolysis by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when a capillary, which is moved vertically down through the molten salt layer, passes through the metal/salt interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension is strongly dependent on the n(NaF)/n(AlF3) ratio. The addition of Na2SO4 decreases the IFT of the aluminium/electrolyte interface. We also found the different influence of the conditions of electrolysis on the IFT in systems with and without Na2SO4. In systems without Na2SO4 the IFT decreases with increasing current density, and in systems with Na2SO4 it increases.

Resonant Soft X-ray Scattering as a Powerful Probe of Buried Polymer Interfaces

NASA Astrophysics Data System (ADS)

Chen, Wei; Jiang, Zhang; Tirrell, Matthew

Elucidation of polymer interfacial structures provides insights into interfacial molecular mechanisms for coating protection, adhesion, lubrication, friction, wettability, biocompatibility, and even charge transport properties. Resonant Soft X-ray Scattering (RSoXS) offers a unique element, site and valence specific probe to study spatial modulations of molecular orbital degrees of freedom on the nanoscopic length scale. This unique sensitivity is achieved by merging small angle x-ray scattering and x-ray absorption spectroscopy into a single experiment, where the scattering provides information about spatial modulations and the spectroscopy provides sensitivity to the molecular anisotropy. Here we applied RSoXS to polystyrene (PS) films at solid-solid interfaces and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) brushes at solid-liquid interfaces. It is found that the interfacial width of PS thin film is about one order of magnitude large than those observed by traditional scattering techniques. In addition, although the ion-induced changes of PMPC thickness are not apparent in aqueous solutions, their chain conformations like polyzwitterion distribution and correlation varied, dependent on salt types, ionic strengths and ion valences. Consequently, it is evident that RSoXS is a powerful probe of buried polymer interlaces with both spatial and chemical sensitivities. This work was supported by the U.S. Department of Energy, Office of Science, Program in Basic Energy Sciences, Division of Materials Science and Engineering.

Modeling of zero gravity venting: Studies of two-phase heat transfer under reduced gravity

NASA Technical Reports Server (NTRS)

Merte, H., Jr.

1986-01-01

The objective is to predict the pressure response of a saturated liquid-vapor system when undergoing a venting or depressurization process in zero gravity at low vent rates. An experimental investigation of the venting of cylindrical containers partially filled with initially saturated liquids was previously conducted under zero-gravity conditions and compared with an analytical model which incorporated the effect of interfacial mass transfer on the ullage pressure response during venting. A new model is presented to improve the estimation of the interfacial mass transfer. Duhammel's superposition integral is incorporated to approximate the transient temperature response of the interface, treating the liquid as a semi-infinite solid with conduction heat transfer. Account is also taken of the condensation taking place within the bulk of a saturated vapor as isentropic expansion takes place. Computational results are presented for the venting of R-11 from a given vessel and initial state for five different venting rates over a period of three seconds, and compared to prior NASA experiments. An improvement in the prediction of the final pressure takes place, but is still considerably below the measurements.

Effect of a surface tension gradient on the slip flow along a superhydrophobic air-water interface

NASA Astrophysics Data System (ADS)

Song, Dong; Song, Baowei; Hu, Haibao; Du, Xiaosong; Du, Peng; Choi, Chang-Hwan; Rothstein, Jonathan P.

2018-03-01

Superhydrophobic surfaces have been shown to produce significant drag reduction in both laminar and turbulent flows by introducing an apparent slip velocity along an air-water interface trapped within the surface roughness. In the experiments presented within this study, we demonstrate the existence of a surface tension gradient associated with the resultant Marangoni flow along an air-water interface that causes the slip velocity and slip length to be significantly reduced. In this study, the slip velocity along a millimeter-sized air-water interface was investigated experimentally. This large-scale air-water interface facilitated a detailed investigation of the interfacial velocity profiles as the flow rate, interfacial curvature, and interface geometry were varied. For the air-water interfaces supported above continuous grooves (concentric rings within a torsional shear flow) where no surface tension gradient exists, a slip velocity as high as 30% of the bulk velocity was observed. However, for the air-water interfaces supported above discontinuous grooves (rectangular channels in a Poiseuille flow), the presence of a surface tension gradient reduced the slip velocity and in some cases resulted in an interfacial velocity that was opposite to the main flow direction. The curvature of the air-water interface in the spanwise direction was found to dictate the details of the interfacial flow profile with reverse flow in the center of the interface for concave surfaces and along the outside of the interface for convex surfaces. The deflection of the air-water interface was also found to greatly affect the magnitude of the slip. Numerical simulations imposed with a relatively small surface tension gradient along the air-water interface were able to predict both the reduced slip velocity and back flow along the air-water interface.

Robust Superhydrophobic Carbon Nanotube Film with Lotus Leaf Mimetic Multiscale Hierarchical Structures.

PubMed

Wang, Pengwei; Zhao, Tianyi; Bian, Ruixin; Wang, Guangyan; Liu, Huan

2017-12-26

Superhydrophobic carbon nanotube (CNT) films have demonstrated many fascinating performances in versatile applications, especially for those involving solid/liquid interfacial processes, because of their ability to affect the material/energy transfer at interfaces. Thus, developing superhydrophobic CNTs has attracted extensive research interests in the past decades, and it could be achieved either by surface coating of low-free energy materials or by constructing micro/nanohierarchical structures via various complicated processes. So far, developing a simple approach to fabricate stable superhydrophobic CNTs remains a challenge because the capillary force induced coalescence frequently happens when interacting with liquid. Herein, drawing inspirations from the lotus leaf, we proposed a simple one-step chemical vapor deposition approach with programmable controlled gas flow to directly fabricate a CNT film with rather stable superhydrophobicity, which can effectively prevent even small water droplets from permeating into the film. The robust superhydrophobicity was attributable to typical lotus-leaf-like micro/nanoscale hierarchical surface structures of the CNT film, where many microscale clusters composed of entangled nanotubes randomly protrude out of the under-layer aligned nanotubes. Consequently, dual-scale air pockets were trapped within each microscale CNT cluster and between, which could largely reduce the liquid/solid interface, leading to a Cassie state. Moreover, the superhydrophobicity of the CNT film showed excellent durability after long time exposure to air and even to corrosive liquids with a wide range of pH values. We envision that the approach developed is advantageous for versatile physicochemical interfacial processes, such as drag reduction, electrochemical catalysis, anti-icing, and biosensors.

On-Chip Production of Size-Controllable Liquid Metal Microdroplets Using Acoustic Waves.

PubMed

Tang, Shi-Yang; Ayan, Bugra; Nama, Nitesh; Bian, Yusheng; Lata, James P; Guo, Xiasheng; Huang, Tony Jun

2016-07-01

Micro- to nanosized droplets of liquid metals, such as eutectic gallium indium (EGaIn) and Galinstan, have been used for developing a variety of applications in flexible electronics, sensors, catalysts, and drug delivery systems. Currently used methods for producing micro- to nanosized droplets of such liquid metals possess one or several drawbacks, including the lack in ability to control the size of the produced droplets, mass produce droplets, produce smaller droplet sizes, and miniaturize the system. Here, a novel method is introduced using acoustic wave-induced forces for on-chip production of EGaIn liquid-metal microdroplets with controllable size. The size distribution of liquid metal microdroplets is tuned by controlling the interfacial tension of the metal using either electrochemistry or electrocapillarity in the acoustic field. The developed platform is then used for heavy metal ion detection utilizing the produced liquid metal microdroplets as the working electrode. It is also demonstrated that a significant enhancement of the sensing performance is achieved by introducing acoustic streaming during the electrochemical experiments. The demonstrated technique can be used for developing liquid-metal-based systems for a wide range of applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rheological and interfacial properties at the equilibrium of almond gum tree exudate (Prunus dulcis) in comparison with gum arabic.

PubMed

Mahfoudhi, Nesrine; Sessa, Mariarenata; Ferrari, Giovanna; Hamdi, Salem; Donsi, Francesco

2016-06-01

Almond gum contains an arabinogalactan-type polysaccharide, which plays an important role in defining its interfacial and rheological properties. In this study, rheological and interfacial properties of almond gum and gum arabic aqueous dispersions were comparatively investigated. The interfacial tension of almond gum and gum arabic aqueous dispersions was measured using the pendant drop method in hexadecane. The asymptotic interfacial tension values for almond gum were significantly lower than the corresponding values measured for gum arabic, especially at high concentration. Rheological properties were characterized by steady and oscillatory tests using a coaxial geometry. Almond gum flow curves exhibited a shear thinning non-Newtonian behavior with a tendency to a Newtonian plateau at low shear rate, while gum arabic flow curves exhibited such behavior only at high shear rate. The influence of temperature (5-50  ℃) on the flow curves was studied at 4% (m/m) gum concentration and the Newtonian viscosities at infinite and at zero shear rate, for gum arabic and almond gum, respectively, were accurately fitted by an Arrhenius-type equation. The dynamic properties of the two gum dispersions were also studied. Both gum dispersions exhibited viscoelastic properties, with the viscous component being predominant in a wider range of concentrations for almond gum, while for gum arabic the elastic component being higher than the elastic one especially at higher concentrations.The rheological and interfacial tension properties of almond gum suggest that it may represent a possible substitute of gum arabic in different food applications. © The Author(s) 2015.

Ripplon laser through stimulated emission mediated by water waves

NASA Astrophysics Data System (ADS)

Kaminski, Samuel; Martin, Leopoldo L.; Maayani, Shai; Carmon, Tal

2016-12-01

Lasers rely on stimulated electronic transition, a quantum phenomenon in the form of population inversion. In contrast, phonon masers depend on stimulated Raman scattering and are entirely classical. Here we extend Raman lasers to rely on capillary waves, which are unique to the liquid phase of matter and relate to the attraction between intimate fluid particles. We fabricate resonators that co-host capillary and optical modes, control them to operate at their non-resolved sideband and observe stimulated capillary scattering and the coherent excitation of capillary resonances at kilohertz rates (which can be heard in audio files recorded by us). By exchanging energy between electromagnetic and capillary waves, we bridge the interfacial tension phenomena at the liquid phase boundary to optics. This approach may impact optofluidics by allowing optical control, interrogation and cooling of water waves.

Effects of rotation and magnetic field on the onset of convective instability in a liquid layer due to buoyancy and surface tension

NASA Technical Reports Server (NTRS)

Sarma, G. S. R.

1982-01-01

Thermocapillary stability characteristics of a horizontal liquid layer heated from below rotating about a vertical axis and subjected to a uniform vertical magnetic field are analyzed under a variety of thermal and electromagnetic boundary conditions. Results based on analytical solutions to the pertinent eigenvalue problems are discussed in the light of earlier work on special cases of the more general problem considered here to show in particular the effects of the heat transfer, nonzero curvature and gravity waves at the two-fluid interface. Although the expected stabilizing action of the Coriolis and Lorentz force fields in this configuration are in evidence the optimal choice of an appropriate range for the relevant parameters is shown to be critically dependent on the interfacial effects mentioned above.

Experimental determination of interfacial tension by different dynamical methods under simple shear flow conditions with a novel computer-controlled parallel band apparatus.

PubMed

Megías-Alguacil, David; Fischer, Peter; Windhab, Erich J

2004-06-15

We present experimental investigations on droplet deformation under simple shear flow conditions, using a computer-controlled parallel band apparatus and an optical device which allows us to record the time dependence of the droplet shape. Several methods are applied to determine the interfacial tension from the observed shape and relaxation mechanism. Specific software developed in our laboratory allows the droplet to be fixed in a certain position for extended times, in fact, indefinite. This is an advantage over most other work done in this area, where only limited time is available. In our experiments, the transient deformation of sheared droplets can be observed to reach the steady state. The measured systems were Newtonian, both droplet and fluid phase. Droplet deformation, orientation angle and retraction were studied and compared to several models. The interfacial tension of the different systems was calculated using the theories of Taylor, Rallison, and Hinch and Acrivos. The results obtained from the analysis of the droplet deformation were in very good agreement with drop detachment experiments of Feigl and co-workers. The study of orientation angle shows qualitative agreement to the theory of Hinch and Acrivos but reveals larger quantitative discrepancies for several empirical fitting parameters of the used model. Analysis of the relaxation of sheared drops provided estimates of the interfacial tension that were in very good agreement with the steady-state measurements.

Apparent Interfacial Tension Effects in Protein Stabilized Emulsions Prepared with Microstructured Systems

PubMed Central

Güell, Carme; Ferrando, Montserrat; Trentin, Alexandre; Schroën, Karin

2017-01-01

Proteins are mostly used to stabilize food emulsions; however, production of protein containing emulsions is notoriously difficult to capture in scaling relations due to the complex behavior of proteins in interfaces, in combination with the dynamic nature of the emulsification process. Here, we investigate premix membrane emulsification and use the Ohnesorge number to derive a scaling relation for emulsions prepared with whey protein, bovine serum albumin (BSA), and a standard emulsifier Tween 20, at various concentrations (0.1%, 0.5%, 1.25% and 2%). In the Ohnesorge number, viscous, inertia, and interfacial tension forces are captured, and most of the parameters can be measured with great accuracy, with the exception of the interfacial tension. We used microfluidic Y-junctions to estimate the apparent interfacial tension at throughputs comparable to those in premix emulsification, and found a unifying relation. We next used this relation to plot the Ohnesorge number versus P-ratio defined as the applied pressure over the Laplace pressure of the premix droplet. The measured values all showed a decreasing Ohnesorge number at increasing P-ratio; the differences between regular surfactants and proteins being systematic. The surfactants were more efficient in droplet size reduction, and it is expected that the differences were caused by the complex behavior of proteins in the interface (visco-elastic film formation). The differences between BSA and whey protein were relatively small, and their behavior coincided with that of low Tween concentration (0.1%), which deviated from the behavior at higher concentrations. PMID:28346335

Photopolymerization of complex emulsions with irregular shapes fabricated by multiplex coaxial flow focusing

NASA Astrophysics Data System (ADS)

Wu, Qiang; Yang, Chaoyu; Yang, Jianxin; Huang, Fangsheng; Liu, Guangli; Zhu, Zhiqiang; Si, Ting; Xu, Ronald X.

2018-02-01

We fabricate complex emulsions with irregular shapes in the microscale by a simple but effective multiplex coaxial flow focusing process. A multiphase cone-jet structure is steadily formed, and the compound liquid jet eventually breaks up into Janus microdroplets due to the perturbations propagating along the jet interfaces. The microdroplet shapes can be exclusively controlled by interfacial tensions of adjacent phases. Crescent-moon-shaped microparticles and microcapsules with designated structural characteristics are further produced under ultraviolet light of photopolymerization after removing one hemisphere of the Janus microdroplets. These complex emulsions have potential applications in bioscience, food, functional materials, and controlled drug delivery.

Separation of aqueous two-phase polymer systems in microgravity

NASA Technical Reports Server (NTRS)

Vanalstine, J. M.; Harris, J. M.; Synder, S.; Curreri, P. A.; Bamberger, S. B.; Brooks, D. E.

1984-01-01

Phase separation of polymer systems in microgravity is studied in aircraft flights to prepare shuttle experiments. Short duration (20 sec) experiments demonstrate that phase separation proceeds rapidly in low gravity despite appreciable phase viscosities and low liquid interfacial tensions (i.e., 50 cP, 10 micro N/m). Ostwald ripening does not appear to be a satisfactory model for the phase separation mechanism. Polymer coated surfaces are evaluated as a means to localize phases separated in low gravity. Contact angle measurements demonstrate that covalently coupling dextran or PEG to glass drastically alters the 1-g wall wetting behavior of the phases in dextran-PEG two phase systems.

Optical fingerprints of solid-liquid interfaces: a joint ATR-IR and first principles investigation

NASA Astrophysics Data System (ADS)

Yang, L.; Niu, F.; Tecklenburg, S.; Pander, M.; Nayak, S.; Erbe, A.; Wippermann, S.; Gygi, F.; Galli, G.

Despite the importance of understanding the structural and bonding properties of solid-liquid interfaces for a wide range of (photo-)electrochemical applications, there are presently no experimental techniques available to directly probe the microscopic structure of solid-liquid interfaces. To develop robust strategies to interpret experiments and validate theory, we carried out attenuated total internal reflection (ATR-IR) spectroscopy measurements and ab initio molecular dynamics (AIMD) simulations of the vibrational properties of interfaces between liquid water and well-controlled prototypical semiconductor substrates. We show the Ge(100)/H2O interface to feature a reversible potential-dependent surface phase transition between Ge-H and Ge-OH termination. The Si(100)/H2O interface is proposed as a model system for corrosion and oxidation processes. We performed AIMD calculations under finite electric fields, revealing different pathways for initial oxidation. These pathways are predicted to exhibit unique spectral signatures. A significant increase in surface specificity can be achieved utilizing an angle-dependent ATR-IR experiment, which allows to detect such signatures at the interfacial layer and consequently changes in the hydrogen bond network. Funding from DOE-BES Grant No. DE-SS0008939 and the Deutsche Forschungsgemeinschaft (RESOLV, EXC 1069) are gratefully acknowledged.

Liquid-solid surface phase transformation of fluorinated fullerene on monolayer tungsten diselenide

NASA Astrophysics Data System (ADS)

Song, Zhibo; Wang, Qixing; Li, Ming-Yang; Li, Lain-Jong; Zheng, Yu Jie; Wang, Zhuo; Lin, Tingting; Chi, Dongzhi; Ding, Zijing; Huang, Yu Li; Thye Shen Wee, Andrew

2018-04-01

Hybrid van der Waals heterostructures constructed by the integration of organic molecules and two-dimensional (2D) transition metal dichalcogenide (TMD) materials have useful tunable properties for flexible electronic devices. Due to the chemically inert and atomically smooth nature of the TMD surface, well-defined crystalline organic films form atomically sharp interfaces facilitating optimal device performance. Here, the surface phase transformation of the supramolecular packing structure of fluorinated fullerene (C60F48 ) on single-layer tungsten diselenide (WSe2) is revealed by low-temperature scanning tunneling microscopy, from thermally stable liquid to solid phases as the coverage increases. Statistical analysis of the intermolecular interaction potential reveals that the repulsive dipole-dipole interaction induced by interfacial charge transfer and substrate-mediated interactions play important roles in stabilizing the liquid C60F48 phases. Theoretical calculations further suggest that the dipole moment per C60F48 molecule varies with the surface molecule density, and the liquid-solid transformation could be understood from the perspective of the thermodynamic free energy for open systems. This study offers insights into the growth behavior at 2D organic/TMD hybrid heterointerfaces.

The principle of minimal episteric distortion of the water matrix and its steering role in protein folding

NASA Astrophysics Data System (ADS)

Fernández, Ariel

2013-08-01

A significant episteric ("around a solid") distortion of the hydrogen-bond structure of water is promoted by solutes with nanoscale surface detail and physico-chemical complexity, such as soluble natural proteins. These structural distortions defy analysis because the discrete nature of the solvent at the interface is not upheld by the continuous laws of electrostatics. This work derives and validates an electrostatic equation that governs the episteric distortions of the hydrogen-bond matrix. The equation correlates distortions from bulk-like structural patterns with anomalous polarization components that do not align with the electrostatic field of the solute. The result implies that the interfacial energy stored in the orthogonal polarization correlates with the distortion of the water hydrogen-bond network. The result is validated vis-à-vis experimental data on protein interfacial thermodynamics and is interpreted in terms of the interaction energy between the electrostatic field of the solute and the dipole moment induced by the anomalous polarization of interfacial water. Finally, we consider solutes capable of changing their interface through conformational transitions and introduce a principle of minimal episteric distortion (MED) of the water matrix. We assess the importance of the MED principle in the context of protein folding, concluding that the native fold may be identified topologically with the conformation that minimizes the interfacial tension or disruption of the water matrix.

Static gas-liquid interfacial direct current discharge plasmas using ionic liquid cathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaneko, T.; CREST/JST, Tokyo 102-0075; Baba, K.

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we have succeeded in creating the static and stable gas (plasmas)-liquid (ionic liquids) interfacial field using a direct current discharge under a low gas pressure condition. It is clarified that the ionic liquid works as a nonmetal liquid electrode, and furthermore, a secondary electron emission coefficient of the ionic liquid is larger than that of conventional metal electrodes. The plasma potential structure of the gas-liquid interfacial region, and resultant interactions between the plasma and the ionic liquid are revealed by changingmore » a polarity of the electrode in the ionic liquid. By utilizing the ionic liquid as a cathode electrode, the positive ions in the plasma region are found to be irradiated to the ionic liquid. This ion irradiation causes physical and chemical reactions at the gas-liquid interfacial region without the vaporization of the ionic liquid.« less

NBS: Materials measurements

NASA Technical Reports Server (NTRS)

Manning, J. R.

1981-01-01

Measurement of materials properties and thermophysical properties is described. The topics discussed are: surface tensions and their variations with temperature and impurities; convection during unidirectional solidification: measurement of high temperature thermophysical properties of tungsten liquid and solid; thermodynamic properties of refractory materials at high temperatures; and experimental and theoretical studies in wetting and multilayer adsorption.

3-D Distribution of Retained Colloids in Unsaturated Porous Media

NASA Astrophysics Data System (ADS)

Morales, V. L.; Perez-Reche, F. J.; Holzner, M.; Kinzelbach, W. K.; Otten, W.

2013-12-01

It is well accepted that colloid transport processes in porous media differ substantially between water saturated and unsaturated conditions. Differences are frequently ascribed to colloid immobilization by association with interfaces with the gas, as well as to restrictions of the liquid medium through which colloids are transported. Such factors depend on interfacial conditions provided by the water saturation of the porous medium. Yet, the current understanding of the importance of colloid retention at gas interfaces is based on observations of single pores or two-dimensional pore network representations, leaving open the question of their statistical significance when all pores in the medium are considered. In order to address this question, column experiments were performed using a model porous medium of glass beads through which colloidal silver particles were transported for conditions of varying water content. X-ray microtomography was subsequently employed as a non-destructive imaging technique to obtain pore-scale information of the entire column regarding: i) the presence and distribution of the four main locations where colloids can become retained (interfaces with the liquid-solid, gas-liquid and gas-solid, and the bulk liquid), ii) deposition profiles of colloids along the column classified by the available retention location, iii) morphological characteristics of the deposited colloidal aggregates, and iv) channel widths of 3-dimensional pore-water network representations. The results presented provide, for the first time, a direct statistical evaluation on the significance of colloid retention by attachment to the liquid-solid, gas-liquid, gas-solid interfaces, and by straining in the bulk liquid. Additionally, an effective-pore structure characteristic is proposed to improve predictions of mass removal by straining under various water saturations. A) Unsaturated conditions. B) Saturated conditions. Left: Tomograph slice illustrating with false coloring Regions Of Interest corresponding to retention locations at the gas-liquid (purple), gas-solid (white) and solid-liquid interface (blue), and the bulk liquid (teal). Right: Deposition profiles of silver colloids (Ag) per retention location (T: total, GLI: gas-liquid interface, GSI: gas-solid interface, SLI: solid-liquid interface, L: bulk liquid) (Top). Depth profiles of the volume occupied by each retention location (Middle). Normalized deposition profiles of silver volume retained by its corresponding retention-location volume (Bottom).

Indentation of a rigid sphere into an elastic substrate with surface tension and adhesion

PubMed Central

Hui, Chung-Yuen; Liu, Tianshu; Salez, Thomas; Raphael, Elie; Jagota, Anand

2015-01-01

The surface tension of compliant materials such as gels provides resistance to deformation in addition to and sometimes surpassing that owing to elasticity. This paper studies how surface tension changes the contact mechanics of a small hard sphere indenting a soft elastic substrate. Previous studies have examined the special case where the external load is zero, so contact is driven by adhesion alone. Here, we tackle the much more complicated problem where, in addition to adhesion, deformation is driven by an indentation force. We present an exact solution based on small strain theory. The relation between indentation force (displacement) and contact radius is found to depend on a single dimensionless parameter: ω=σ(μR)−2/3((9π/4)Wad)−1/3, where σ and μ are the surface tension and shear modulus of the substrate, R is the sphere radius and Wad is the interfacial work of adhesion. Our theory reduces to the Johnson–Kendall–Roberts (JKR) theory and Young–Dupre equation in the limits of small and large ω, respectively, and compares well with existing experimental data. Our results show that, although surface tension can significantly affect the indentation force, the magnitude of the pull-off load in the partial wetting liquid-like limit is reduced only by one-third compared with the JKR limit and the pull-off behaviour is completely determined by ω. PMID:25792953

Smoothed dissipative particle dynamics model for mesoscopic multiphase flows in the presence of thermal fluctuations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Huan; Baker, Nathan A.; Wu, Lei

2016-08-05

Thermal fluctuations cause perturbations of fluid-fluid interfaces and highly nonlinear hydrodynamics in multiphase flows. In this work, we develop a novel multiphase smoothed dissipative particle dynamics model. This model accounts for both bulk hydrodynamics and interfacial fluctuations. Interfacial surface tension is modeled by imposing a pairwise force between SDPD particles. We show that the relationship between the model parameters and surface tension, previously derived under the assumption of zero thermal fluctuation, is accurate for fluid systems at low temperature but overestimates the surface tension for intermediate and large thermal fluctuations. To analyze the effect of thermal fluctuations on surface tension,more » we construct a coarse-grained Euler lattice model based on the mean field theory and derive a semi-analytical formula to directly relate the surface tension to model parameters for a wide range of temperatures and model resolutions. We demonstrate that the present method correctly models the dynamic processes, such as bubble coalescence and capillary spectra across the interface.« less

Fluid-fluid interfacial mobility from random walks

NASA Astrophysics Data System (ADS)

Barclay, Paul L.; Lukes, Jennifer R.

2017-12-01

Dual control volume grand canonical molecular dynamics is used to perform the first calculation of fluid-fluid interfacial mobilities. The mobility is calculated from one-dimensional random walks of the interface by relating the diffusion coefficient to the interfacial mobility. Three different calculation methods are employed: one using the interfacial position variance as a function of time, one using the mean-squared interfacial displacement, and one using the time-autocorrelation of the interfacial velocity. The mobility is calculated for two liquid-liquid interfaces and one liquid-vapor interface to examine the robustness of the methods. Excellent agreement between the three calculation methods is shown for all the three interfaces, indicating that any of them could be used to calculate the interfacial mobility.

Nanowire membrane-based nanothermite: towards processable and tunable interfacial diffusion for solid state reactions.

PubMed

Yang, Yong; Wang, Peng-peng; Zhang, Zhi-cheng; Liu, Hui-ling; Zhang, Jingchao; Zhuang, Jing; Wang, Xun

2013-01-01

Interfacial diffusion is of great importance in determining the performance of solid-state reactions. For nanometer sized particles, some solid-state reactions can be triggered accidently by mechanical stress owing to their large surface-to-volume ratio compared with the bulk ones. Therefore, a great challenge is the control of interfacial diffusion for solid state reactions, especially for energetic materials. Here we demonstrate, through the example of nanowire-based thermite membrane, that the thermite solid-state reaction can be easily tuned via the introduction of low-surface-energy coating layer. Moreover, this silicon-coated thermite membrane exhibit controlled wetting behavior ranging from superhydrophilic to superhydrophobic and, simultaneously, to significantly reduce the friction sensitivity of thermite membrane. This effect enables to increase interfacial resistance by increasing the amount of coating material. Indeed, our results described here make it possible to tune the solid-state reactions through the manipulation of interfacial diffusion between the reactants.

Nanowire Membrane-based Nanothermite: towards Processable and Tunable Interfacial Diffusion for Solid State Reactions

NASA Astrophysics Data System (ADS)

Yang, Yong; Wang, Peng-Peng; Zhang, Zhi-Cheng; Liu, Hui-Ling; Zhang, Jingchao; Zhuang, Jing; Wang, Xun

2013-04-01

Interfacial diffusion is of great importance in determining the performance of solid-state reactions. For nanometer sized particles, some solid-state reactions can be triggered accidently by mechanical stress owing to their large surface-to-volume ratio compared with the bulk ones. Therefore, a great challenge is the control of interfacial diffusion for solid state reactions, especially for energetic materials. Here we demonstrate, through the example of nanowire-based thermite membrane, that the thermite solid-state reaction can be easily tuned via the introduction of low-surface-energy coating layer. Moreover, this silicon-coated thermite membrane exhibit controlled wetting behavior ranging from superhydrophilic to superhydrophobic and, simultaneously, to significantly reduce the friction sensitivity of thermite membrane. This effect enables to increase interfacial resistance by increasing the amount of coating material. Indeed, our results described here make it possible to tune the solid-state reactions through the manipulation of interfacial diffusion between the reactants.

Substratum interfacial energetic effects on the attachment of marine bacteria

NASA Astrophysics Data System (ADS)

Ista, Linnea Kathryn

Biofilms represent an ancient, ubiquitous and influential form of life on earth. Biofilm formation is initiated by attachment of bacterial cells from an aqueous suspension onto a suitable attachment substratum. While in certain, well studied cases initial attachment and subsequent biofilm formation is mediated by specific ligand-receptor pairs on the bacteria and attachment substratum, in the open environment, including the ocean, it is assumed to be non-specific and mediated by processes similar to those that drive adsorption of colloids at the water-solid interface. Colloidal principles are studied to determine the molecular and physicochemical interactions involved in the attachment of the model marine bacterium, Cobetia marina to model self-assembled monolayer surfaces. In the simplest application of colloidal principles the wettability of attachment substrata, as measured by the advancing contact angle of water (theta AW) on the surface, is frequently used as an approximation for the surface tension. We demonstrate the applicability of this approach for attachment of C. marina and algal zoospores and extend it to the development of a means to control attachment and release of microorganisms by altering and tuning surface thetaAW. In many cases, however, thetaAW does not capture all the information necessary to model attachment of bacteria to attachment substrata; SAMs with similar thetaAW attach different number of bacteria. More advanced colloidal models of initial bacterial attachment have evolved over the last several decades, with the emergence of the model proposed by van Oss, Chaudhury and Good (VCG) as preeminent. The VCG model enables calculation of interfacial tensions by dividing these into two major interactions thought to be important at biointerfaces: apolar, Lifshitz-van der Waals and polar, Lewis acid-base (including hydrogen bonding) interactions. These interfacial tensions are combined to yield DeltaGadh, the free energy associated with attachment of bacteria to a substratum. We use VCG to model DeltaGadh and interfacial tensions as they relate to model bacterial attachment on SAMs that accumulate cells to different degrees. Even with the more complex interactions measured by VCG, surface energy of the attachment substratum alone was insufficient to predict attachment. VCG was then employed to model attachment of C. marina to a series of SAMs varying systematically in the number of ethylene glycol residues present in the molecule; an identical series has been previously shown to vary dramatically in the number of cells attached as a function of ethylene glycols present. Our results indicate that while VCG adequately models the interfacial tension between water and ethylene glycol SAMs in a manner that predicts bacterial attachment, DeltaGadh as calculated by VCG neither qualitatively nor quantitatively reflects the attachment data. The VCG model, thus, fails to capture specific information regarding the interactions between the attaching bacteria, water, and the SAM. We show that while hydrogen-bond accepting interactions are very well captured by this model, the ability for SAMs and bacteria to donate hydrogen bonds is not adequately described as the VCG model is currently applied. We also describe ways in which VCG fails to capture two specific biological aspects that may be important in bacterial attachment to surfaces:1.) specific interactions between molecules on the surface and bacteria and 2.) bacterial cell surface heterogeneities that may be important in differential attachment to different substrata.

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model

PubMed Central

Bauer, Brad A.; Patel, Sandeep

2009-01-01

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water. Parametrized to reproduce condensed-phase liquid water properties at 298 K, the TIP4P-QDP-LJ model predicts density, enthalpy of vaporization, self-diffusion constant, and the dielectric constant at ambient conditions to about the same accuracy as TIP4P-QDP but shows remarkable improvement in reproducing the liquid-vapor coexistence curve. TIP4P-QDP-LJ predicts critical constants of Tc=623 K, ρc=0.351 g∕cm3, and Pc=250.9 atm, which are in good agreement with experimental values of Tc=647.1 K, ρc=0.322 g∕cm3, and Pc=218 atm, respectively. Applying a scaling factor correction (obtained by fitting the experimental vapor-liquid equilibrium data to the law of rectilinear diameters using a three-term Wegner expansion) the model predicts critical constants (Tc=631 K and ρc=0.308 g∕cm3). Dependence of enthalpy of vaporization, self-diffusion constant, surface tension, and dielectric constant on temperature are shown to reproduce experimental trends. We also explore the interfacial potential drop across the liquid-vapor interface for the temperatures studied. The interfacial potential demonstrates little temperature dependence at lower temperatures (300–450 K) and significantly enhanced (exponential) dependence at elevated temperatures. Terms arising from the decomposition of the interfacial potential into dipole and quadrupole contributions are shown to monotonically approach zero as the temperature approaches the critical temperature. Results of this study suggest that self-consistently treating the coupling of phase-dependent polarizability with dispersion interactions in classical water force fields may be an important effect for the extension of polarizable water force fields to reproduce properties along the liquid-vapor coexistence envelope as well as near critical conditions. More importantly, the present study demonstrates the rather remarkable transferability of a water model parametrized to a single state point to other thermodynamic states. Further studies are recommended. PMID:19725623

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model.

PubMed

Bauer, Brad A; Patel, Sandeep

2009-08-28

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water. Parametrized to reproduce condensed-phase liquid water properties at 298 K, the TIP4P-QDP-LJ model predicts density, enthalpy of vaporization, self-diffusion constant, and the dielectric constant at ambient conditions to about the same accuracy as TIP4P-QDP but shows remarkable improvement in reproducing the liquid-vapor coexistence curve. TIP4P-QDP-LJ predicts critical constants of T(c)=623 K, rho(c)=0.351 g/cm(3), and P(c)=250.9 atm, which are in good agreement with experimental values of T(c)=647.1 K, rho(c)=0.322 g/cm(3), and P(c)=218 atm, respectively. Applying a scaling factor correction (obtained by fitting the experimental vapor-liquid equilibrium data to the law of rectilinear diameters using a three-term Wegner expansion) the model predicts critical constants (T(c)=631 K and rho(c)=0.308 g/cm(3)). Dependence of enthalpy of vaporization, self-diffusion constant, surface tension, and dielectric constant on temperature are shown to reproduce experimental trends. We also explore the interfacial potential drop across the liquid-vapor interface for the temperatures studied. The interfacial potential demonstrates little temperature dependence at lower temperatures (300-450 K) and significantly enhanced (exponential) dependence at elevated temperatures. Terms arising from the decomposition of the interfacial potential into dipole and quadrupole contributions are shown to monotonically approach zero as the temperature approaches the critical temperature. Results of this study suggest that self-consistently treating the coupling of phase-dependent polarizability with dispersion interactions in classical water force fields may be an important effect for the extension of polarizable water force fields to reproduce properties along the liquid-vapor coexistence envelope as well as near critical conditions. More importantly, the present study demonstrates the rather remarkable transferability of a water model parametrized to a single state point to other thermodynamic states. Further studies are recommended.

Mathematical model for self-propelled droplets driven by interfacial tension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagai, Ken H.; Tachibana, Kunihito; Tobe, Yuta

2016-03-21

We propose a model for the spontaneous motion of a droplet induced by inhomogeneity in interfacial tension. The model is derived from a variation of the Lagrangian of the system and we use a time-discretized Morse flow scheme to perform its numerical simulations. Our model can naturally simulate the dynamics of a single droplet, as well as that of multiple droplets, where the volume of each droplet is conserved. We reproduced the ballistic motion and fission of a droplet, and the collision of two droplets was also examined numerically.

Interfacial free energy controlling glass-forming ability of Cu-Zr alloys.

PubMed

Kang, Dong-Hee; Zhang, Hao; Yoo, Hanbyeol; Lee, Hyun Hwi; Lee, Sooheyong; Lee, Geun Woo; Lou, Hongbo; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jianzhong

2014-06-04

Glass is a freezing phase of a deeply supercooled liquid. Despite its simple definition, the origin of glass forming ability (GFA) is still ambiguous, even for binary Cu-Zr alloys. Here, we directly study the stability of the supercooled Cu-Zr liquids where we find that Cu64Zr36 at a supercooled temperature shows deeper undercoolability and longer persistence than other neighbouring compositions with an equivalent driving Gibbs free energy. This observation implies that the GFA of the Cu-Zr alloys is significantly affected by crystal-liquid interfacial free energy. In particular, the crystal-liquid interfacial free energy of Cu64Zr36 in our measurement was higher than that of other neighbouring liquids and, coincidently a molecular dynamics simulation reveals a larger glass-glass interfacial energy value at this composition, which reflects more distinct configuration difference between liquid and crystal phase. The present results demonstrate that the higher crystal-liquid interfacial free energy is a prerequisite of good GFA of the Cu-Zr alloys.

The electrode/ionic liquid interface: electric double layer and metal electrodeposition.

PubMed

Su, Yu-Zhuan; Fu, Yong-Chun; Wei, Yi-Min; Yan, Jia-Wei; Mao, Bing-Wei

2010-09-10

The last decade has witnessed remarkable advances in interfacial electrochemistry in room-temperature ionic liquids. Although the wide electrochemical window of ionic liquids is of primary concern in this new type of solvent for electrochemistry, the unusual bulk and interfacial properties brought about by the intrinsic strong interactions in the ionic liquid system also substantially influence the structure and processes at electrode/ionic liquid interfaces. Theoretical modeling and experimental characterizations have been indispensable in reaching a microscopic understanding of electrode/ionic liquid interfaces and in elucidating the physics behind new phenomena in ionic liquids. This Minireview describes the status of some aspects of interfacial electrochemistry in ionic liquids. Emphasis is placed on high-resolution and molecular-level characterization by scanning tunneling microscopy and vibrational spectroscopies of interfacial structures, and the initial stage of metal electrodeposition with application in surface nanostructuring.

Adhesion of bubbles and drops to solid surfaces, and anisotropic surface tensions studied by capillary meniscus dynamometry.

PubMed

Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Marinova, Krastanka G; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Cox, Andrew R; Pelan, Eddie G

2016-07-01

Here, we review the principle and applications of two recently developed methods: the capillary meniscus dynamometry (CMD) for measuring the surface tension of bubbles/drops, and the capillary bridge dynamometry (CBD) for quantifying the bubble/drop adhesion to solid surfaces. Both methods are based on a new data analysis protocol, which allows one to decouple the two components of non-isotropic surface tension. For an axisymmetric non-fluid interface (e.g. bubble or drop covered by a protein adsorption layer with shear elasticity), the CMD determines the two different components of the anisotropic surface tension, σs and σφ, which are acting along the "meridians" and "parallels", and vary throughout the interface. The method uses data for the instantaneous bubble (drop) profile and capillary pressure, but the procedure for data processing is essentially different from that of the conventional drop shape analysis (DSA) method. In the case of bubble or drop pressed against a substrate, which forms a capillary bridge, the CBD method allows one to determine also the capillary-bridge force for both isotropic (fluid) and anisotropic (solidified) adsorption layers. The experiments on bubble (drop) detachment from the substrate show the existence of a maximal pulling force, Fmax, that can be resisted by an adherent fluid particle. Fmax can be used to quantify the strength of adhesion of bubbles and drops to solid surfaces. Its value is determined by a competition of attractive transversal tension and repulsive disjoining pressure forces. The greatest Fmax values have been measured for bubbles adherent to glass substrates in pea-protein solutions. The bubble/wall adhesion is lower in solutions containing the protein HFBII hydrophobin, which could be explained with the effect of sandwiched protein aggregates. The applicability of the CBD method to emulsion systems is illustrated by experiments with soybean-oil drops adherent to hydrophilic and hydrophobic substrates in egg yolk solutions. The results reveal how the interfacial rigidity, as well as the bubble/wall and drop/wall adhesion forces, can be quantified and controlled in relation to optimizing the properties of foams and emulsions. Copyright © 2015 Elsevier B.V. All rights reserved.

Separating the effects of repulsive and attractive forces on the phase diagram, interfacial, and critical properties of simple fluids

NASA Astrophysics Data System (ADS)

Fuentes-Herrera, M.; Moreno-Razo, J. A.; Guzmán, O.; López-Lemus, J.; Ibarra-Tandi, B.

2016-06-01

Molecular simulations in the canonical and isothermal-isobaric ensembles were performed to study the effect of varying the shape of the intermolecular potential on the phase diagram, critical, and interfacial properties of model fluids. The molecular interactions were modeled by the Approximate Non-Conformal (ANC) theory potentials. Unlike the Lennard-Jones or Morse potentials, the ANC interactions incorporate parameters (called softnesses) that modulate the steepness of the potential in their repulsive and attractive parts independently. This feature allowed us to separate unambiguously the role of each region of the potential on setting the thermophysical properties. In particular, we found positive linear correlation between all critical coordinates and the attractive and repulsive softness, except for the critical density and the attractive softness which are negatively correlated. Moreover, we found that the physical properties related to phase coexistence (such as span of the liquid phase between the critical and triple points, variations in the P-T vaporization curve, interface width, and surface tension) are more sensitive to changes in the attractive softness than to the repulsive one. Understanding the different roles of attractive and repulsive forces on phase coexistence may contribute to developing more accurate models of liquids and their mixtures.

Separating the effects of repulsive and attractive forces on the phase diagram, interfacial, and critical properties of simple fluids.

PubMed

Fuentes-Herrera, M; Moreno-Razo, J A; Guzmán, O; López-Lemus, J; Ibarra-Tandi, B

2016-06-07

Molecular simulations in the canonical and isothermal-isobaric ensembles were performed to study the effect of varying the shape of the intermolecular potential on the phase diagram, critical, and interfacial properties of model fluids. The molecular interactions were modeled by the Approximate Non-Conformal (ANC) theory potentials. Unlike the Lennard-Jones or Morse potentials, the ANC interactions incorporate parameters (called softnesses) that modulate the steepness of the potential in their repulsive and attractive parts independently. This feature allowed us to separate unambiguously the role of each region of the potential on setting the thermophysical properties. In particular, we found positive linear correlation between all critical coordinates and the attractive and repulsive softness, except for the critical density and the attractive softness which are negatively correlated. Moreover, we found that the physical properties related to phase coexistence (such as span of the liquid phase between the critical and triple points, variations in the P-T vaporization curve, interface width, and surface tension) are more sensitive to changes in the attractive softness than to the repulsive one. Understanding the different roles of attractive and repulsive forces on phase coexistence may contribute to developing more accurate models of liquids and their mixtures.

An SFG study of interfacial amino acids at the hydrophilic SiO2 and hydrophobic deuterated polystyrene surfaces.

PubMed

Holinga, George J; York, Roger L; Onorato, Robert M; Thompson, Christopher M; Webb, Nic E; Yoon, Alfred P; Somorjai, Gabor A

2011-04-27

Sum frequency generation (SFG) vibrational spectroscopy was employed to characterize the interfacial structure of eight individual amino acids--L-phenylalanine, L-leucine, glycine, L-lysine, L-arginine, L-cysteine, L-alanine, and L-proline--in aqueous solution adsorbed at model hydrophilic and hydrophobic surfaces. Specifically, SFG vibrational spectra were obtained for the amino acids at the solid-liquid interface between both hydrophobic d(8)-polystyrene (d(8)-PS) and SiO(2) model surfaces and phosphate buffered saline (PBS) at pH 7.4. At the hydrophobic d(8)-PS surface, seven of the amino acids solutions investigated showed clear and identifiable C-H vibrational modes, with the exception being l-alanine. In the SFG spectra obtained at the hydrophilic SiO(2) surface, no C-H vibrational modes were observed from any of the amino acids studied. However, it was confirmed by quartz crystal microbalance that amino acids do adsorb to the SiO(2) interface, and the amino acid solutions were found to have a detectable and widely varying influence on the magnitude of SFG signal from water at the SiO(2)/PBS interface. This study provides the first known SFG spectra of several individual amino acids in aqueous solution at the solid-liquid interface and under physiological conditions.

A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy.

PubMed

Miyazawa, Keisuke; Kobayashi, Naritaka; Watkins, Matthew; Shluger, Alexander L; Amano, Ken-ichi; Fukuma, Takeshi

2016-04-07

Hydration plays important roles in various solid-liquid interfacial phenomena. Very recently, three-dimensional scanning force microscopy (3D-SFM) has been proposed as a tool to visualise solvated surfaces and their hydration structures with lateral and vertical (sub) molecular resolution. However, the relationship between the 3D force map obtained and the equilibrium water density, ρ(r), distribution above the surface remains an open question. Here, we investigate this relationship at an interface of an inorganic mineral, fluorite, and water. The force maps measured in pure water are directly compared to force maps generated using the solvent tip approximation (STA) model and from explicit molecular dynamics simulations. The results show that the simulated STA force map describes the major features of the experimentally obtained force image. The agreement between the STA data and the experiment establishes the correspondence between the water density used as an input to the STA model and the experimental hydration structure and thus provides a tool to bridge the experimental force data and atomistic solvation structures. Further applications of this method should improve the accuracy and reliability of both interpretation of 3D-SFM force maps and atomistic simulations in a wide range of solid-liquid interfacial phenomena.

Interfacial activity of polymeric surfactants at the polystyrene-carbon dioxide interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, K.L.; Rocha, S.R.P. da; Yates, M.Z.

1998-11-24

The reduction of the interfacial tension at the polystyrene (PS, M{sub n} = 1850)-supercritical CO{sub 2} interface is reported for poly(1,1-dihydroperfluorooctyl acrylate)(PFOA) and the block copolymers PS-b-PFOA(3.7K/27K) and PS-b-poly(dimethylsiloxane) (PDMS) (2K/16K, 500/10K) at 45 C. PS-b-PDMS (2K/16K) lowers the interfacial tension to 0.5 dyn/cm at 45 C and 238 bar, more than that of any of the other copolymers. On the basis of the dynamics of the lowering of the interfacial tension, the apparent diffusion coefficient of PS-b-PDMS (2K/16K) is 8 {times} 10{sup {minus}6} cm{sup 2}/s. The critical micelle concentration of PS-b-PFOA (3.7K/27K) is 9 {times} 10{sup {minus}4} wt %.more » Whereas both the PDMS- and PFOA-based copolymers studied adsorb on the PS surface, PS-b-PFOA is much more effective in stabilizing the PS emulsions. The difference in stabilization is discussed in terms of the surfactant adsorption and the interactions of the anchor and buoy blocks with CO{sub 2} and the PS surface.« less

Doping-Driven Wettability of Two-Dimensional Materials: A Multiscale Theory.

PubMed

Tian, Tian; Lin, Shangchao; Li, Siyu; Zhao, Lingling; Santos, Elton J G; Shih, Chih-Jen

2017-11-07

Engineering molecular interactions at two-dimensional (2D) materials interfaces enables new technological opportunities in functional surfaces and molecular epitaxy. Understanding the wettability of 2D materials represents the crucial first step toward quantifying the interplay between the interfacial forces and electric potential of 2D materials interfaces. Here we develop the first theoretical framework to model the wettability of the doped 2D materials by properly bridging the multiscale physical phenomena at the 2D interfaces, including (i) the change of 2D materials surface energy (atomistic scale, several angstroms), (ii) the molecular reorientation of liquid molecules adjacent to the interface (molecular scale, 10 0 -10 1 nm), and (iii) the electrical double layer (EDL) formed in the liquid phase (mesoscopic scales, 10 0 -10 4 nm). The latter two effects are found to be the major mechanisms responsible for the contact angle change upon doping, while the surface energy change of a pure 2D material has no net effect on the wetting property. When the doping level is electrostatically tuned, we demonstrate that 2D materials with high quantum capacitances (e.g., transition metal dichalcogenides, TMDCs) possess a wider range of tunability in the interfacial tension, under the same applied gate voltage. Furthermore, practical considerations such as defects and airborne contamination are also quantitatively discussed. Our analysis implies that the doping level can be another variable to modulate the wettability at 2D materials interfaces, as well as the molecular packing behavior on a 2D material-coated surface, essentially facilitating the interfacial engineering of 2D materials.

The role of Minkowski functionals in the thermodynamics of two-phase systems

NASA Astrophysics Data System (ADS)

Eder, Gerhard

2018-01-01

Within this work quite old concepts from integral geometry are applied to classical equilibrium thermodynamics of two-phase systems. In addition to the area as basic interfacial quantity the full geometric characterization of the interface is used, which includes the two remaining Minkowski functionals, the mean curvature integral and the Euler Poincaré characteristic. The basic energetic characteristic of the interface (i.e. the interfacial tension) is extended by two additional properties: edge force as (up to a factor 4/π) the work necessary to form a right-angled edge of unit length, and item energy as the work to form an additional item in the phase morphology. Both quantities are of increasing importance, when going to micro- and nano-scales. They are subsequently used for interfaces of arbitrary shape to derive a relationship extending the classical Young-Laplace equation. The supplementary contribution is proportional to the Gaussian curvature, with the edge force as proportionality constant. Furthermore, both edge force and item energy are shown to be applicable to the description of crystal nucleation in liquids (extending the classical Becker Döring theory). It turns out, that even above the thermodynamic melting temperature stable nuclei can be present in the liquid phase. They immediately are able to grow when quenched to a temperature below a characteristic temperature. This temperature of spontaneous homogeneous nucleation is simply connected to the edge force, whereas the number of stable clusters per unit volume is dominated by the item energy. Finally, the additional energetic interfacial properties are used in a similar way to characterize the stability of emulsions.

Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

NASA Technical Reports Server (NTRS)

Begg, E.; Faghri, A.; Krustalev, D.

1999-01-01

A physical/mathematical model of annular film condensation at the inlet of a miniature tube has been developed. In the model, the liquid flow is coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and leads to the conclusion that there is complete condensation at a certain distance from the condenser inlet. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads and that this is a special case of a more general condensation regime with two-phase bubbly flow downstream of the initial annular film condensation region. Observations from the flow visualization experiment confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in a small diameter (3.25 mm) circular tube condenser.

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants

DOE PAGES

Huang, Caili; Forth, Joe; Wang, Weiyu; ...

2017-09-25

Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil–water interface. A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use. In this paper, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) thatmore » bind to one another at the oil–water interface. This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m -1. Finally, furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.« less

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Caili; Forth, Joe; Wang, Weiyu

Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil–water interface. A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use. In this paper, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) thatmore » bind to one another at the oil–water interface. This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m -1. Finally, furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.« less

A reconfigurable liquid metal antenna driven by electrochemically controlled capillarity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, M.; Adams, J. J., E-mail: jjadams2@ncsu.edu; Trlica, C.

2015-05-21

We describe a new electrochemical method for reversible, pump-free control of liquid eutectic gallium and indium (EGaIn) in a capillary. Electrochemical deposition (or removal) of a surface oxide on the EGaIn significantly lowers (or increases) its interfacial tension as a means to induce the liquid metal in (or out) of the capillary. A fabricated prototype demonstrates this method in a reconfigurable antenna application in which EGaIn forms the radiating element. By inducing a change in the physical length of the EGaIn, the operating frequency of the antenna tunes over a large bandwidth. This purely electrochemical mechanism uses low, DC voltagesmore » to tune the antenna continuously and reversibly between 0.66 GHz and 3.4 GHz resulting in a 5:1 tuning range. Gain and radiation pattern measurements agree with electromagnetic simulations of the device, and its measured radiation efficiency varies from 41% to 70% over its tuning range.« less

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux

NASA Technical Reports Server (NTRS)

Zhang, Hui; Mudawar, Issam; Hasan, Mohammad M.

2002-01-01

The bubble coalescence and interfacial instabilities that are important to modeling critical heat flux (CHF) in reduced-gravity systems can be sensitive to even minute body forces. Understanding these complex phenomena is vital to the design and safe implementation of two-phase thermal management loops proposed for space and planetary-based thermal systems. While reduced gravity conditions cannot be accurately simulated in 1g ground-based experiments, such experiments can help isolate the effects of the various forces (body force, surface tension force and inertia) which influence flow boiling CHF. In this project, the effects of the component of body force perpendicular to a heated wall were examined by conducting 1g flow boiling experiments at different orientations. FC-72 liquid was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface at conditions approaching CHF. High-speed video imaging was employed to capture dominant CHF mechanisms. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed great sensitivity to orientation for flow velocities below 0.2 m/s, where very small CHF values where measured, especially with downflow and downward-facing heated wall orientations. High flow velocities dampened the effects of orientation considerably. Figure I shows representative images for the different CHF regimes. The Wavy Vapor Layer regime was dominant for all high velocities and most orientations, while all other regimes were encountered at low velocities, in the downflow and/or downward-facing heated wall orientations. The Interfacial Lift-off model was modified to predict the effects of orientation on CHF for the dominant Wavy Vapor Layer regime. The photographic study captured a fairly continuous wavy vapor layer travelling along the heated wall while permitting liquid contact only in wetting fronts, located in the troughs of the interfacial waves. CHF commenced when wetting fronts near the outlet were lifted off the wall. The Interfacial Lift-off model is shown to be an effective tool for predicting the effects of body force on CHF at high velocities.

Solid oxide fuel cell operable over wide temperature range

DOEpatents

Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

2001-01-01

Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

EMIIM Wetting Properties & Their Effect on Electrospray Thruster Design

DTIC Science & Technology

2012-03-01

tension and contact or “wetting" angle formed when a liquid droplet comes in contact with a solid surface. Ideally this angle is a function of the...3 3 Picture of a Taylor cone formed at AFRL, note bubbles present. . . . . . . 3 4 Titanium electrode grids in use at AFRL...cone formed using an internally wetted emitter and the ionic liquid BMI-BG4 is shown in Figure 3.[7] Emitters are precisely aligned with openings

Air Entrapment for Liquid Drops Impacting a Solid Substrate

NASA Astrophysics Data System (ADS)

Liu, Yuan; Tan, Peng; Xu, Lei

2012-11-01

Using high-speed photography coupled with optical interference, we experimentally study the air entrapment during a liquid drop impacting a solid substrate. We observe the formation of a compressed air film before the liquid touches the substrate, with internal pressure considerably higher than the atmospheric value. The degree of compression highly depends on the impact velocity, as explained by balancing the liquid deceleration with the large pressure of compressed air. After contact, the air film expands vertically at the edge, reducing its pressure within a few tens of microseconds and producing a thick rim on the perimeter. This thick-rimmed air film subsequently contracts into an air bubble, governed by the complex interaction between surface tension, inertia and viscous drag. Such a process is universally observed for impacts above a few centimeters high. Hong Kong GRF grant CUHK404211 and direct grant 2060418.

Near-post meniscus-induced migration and assembly of bubbles.

PubMed

Liu, Jianlin; Li, Shanpeng; Hou, Jian

2016-02-21

Although the effect of interfacial tension of liquids is often negligible at the macroscale, it plays an essential role in areas such as superhydrophobicity on rough surfaces, water walking of aquatic creatures and self-assembly of small particles or droplets. In this study, we investigate the migration and assembly of bubbles near the meniscus produced by a slender post with various cross-sections. The results show that the bubble always migrates to the solid wall of the post, although the cross-section shape, material and tilt angle of the post are different. In particular, the final position of the bubble is not located at the singular point of the cross-section, which is beyond what we have imagined. We simulate the morphology of the triple contact line via Surface Evolver, and then address the mechanism of bubble's migration from the viewpoint of force analysis and energy calculation. The factors governing the final position of the bubble are analyzed according to the scaling law. These obtained results cast new light on modulating the assembly of bubbles and small droplets by varying the material, geometric shape and posture of the post in water. These findings also have important implications for oil collection and oil displacement in petroleum engineering, drug delivery, design of microfluidic devices and chemical sensors.

Acoustic Levitation and its Applications in the Study of Liquid Surface Rheology.

NASA Astrophysics Data System (ADS)

Tian, Yuren

Due to its non-contact manipulation and requirement of small amounts of test sample, acoustical levitation has been used to investigate the interfacial dynamics of liquids. In this current work, the surface rheology of liquid drops levitated in air has been studied. The surrounding of a gaseous medium simplifies the theoretical analysis and the interpretation of experimental results. For a ground-based experiment, the effect of gravity and the levitation sound field can change a levitated drop into a nonspherical shape. A theory which involves the multiple interactions between the drop and the sound field, the acoustic scattering by a nonspherical object and the limitation of droplet volume variation is developed. The droplet aspect ratio is determined as a function of the sound pressure, frequency (or wavelength) and the surface tension of liquid under both zero and nonzero gravity environments. The dynamics of a liquid drop of surfactant solution is also theoretically analyzed by including the different surfactant transfer processes at the droplet surface. The approximate solutions of the resonance frequency and damping constant of droplet free quadrupole shape oscillation are derived analytically and verified with the exact numerical solutions. The phase relationship between the driving force and the droplet response is established for the case of forced droplet shape oscillation. The surface viscoelasticity of liquid has shown a strong effect on the droplet dynamics. An acoustic levitation apparatus is constructed and used to levitate a liquid drop in air. By gauging the static shape of the drop versus its spatial location, the equilibrium surface tension of the liquid can be determined. The surface elasticity and viscosity are evaluated from the measurements of the resonance frequency, damping constant and phase relationship of the droplet quadrupole shape oscillation. Different kind of liquids are tested. For surfactant solutions, the experimental results illustrate the existence of surface viscoelasticities.

Plasma-assisted interface engineering of boron nitride nanostructure films.

PubMed

Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

2014-10-28

Today many aspects of science and technology are progressing into the nanoscale realm where surfaces and interfaces are intrinsically important in determining properties and performances of materials and devices. One familiar phenomenon in which interfacial interactions play a major role is the wetting of solids. In this work we use a facile one-step plasma method to control the wettability of boron nitride (BN) nanostructure films via covalent chemical functionalization, while their surface morphology remains intact. By tailoring the concentration of grafted hydroxyl groups, superhydrophilic, hydrophilic, and hydrophobic patterns are created on the initially superhydrophobic BN nanosheet and nanotube films. Moreover, by introducing a gradient of the functional groups, directional liquid spreading toward increasing [OH] content is achieved on the films. The resulting insights are meant to illustrate great potentials of this method to tailor wettability of ceramic films, control liquid flow patterns for engineering applications such as microfluidics and biosensing, and improve the interfacial contact and adhesion in nanocomposite materials.

Adsorption energy as a metric for wettability at the nanoscale

PubMed Central

Giro, Ronaldo; Bryant, Peter W.; Engel, Michael; Neumann, Rodrigo F.; Steiner, Mathias B.

2017-01-01

Wettability is the affinity of a liquid for a solid surface. For energetic reasons, macroscopic drops of liquid form nearly spherical caps. The degree of wettability is then captured by the contact angle where the liquid-vapor interface meets the solid-liquid interface. As droplet volumes shrink to the scale of attoliters, however, surface interactions become significant, and droplets assume distorted shapes. In this regime, the contact angle becomes ambiguous, and a scalable metric for quantifying wettability is needed, especially given the emergence of technologies exploiting liquid-solid interactions at the nanoscale. Here we combine nanoscale experiments with molecular-level simulation to study the breakdown of spherical droplet shapes at small length scales. We demonstrate how measured droplet topographies increasingly reveal non-spherical features as volumes shrink. Ultimately, the nanoscale droplets flatten out to form layer-like molecular assemblies at the solid surface. For the lack of an identifiable contact angle at small scales, we introduce a droplet’s adsorption energy density as a new metric for a liquid’s affinity for a surface. We discover that extrapolating the macroscopic idealization of a drop to the nanoscale, though it does not geometrically resemble a realistic droplet, can nonetheless recover its adsorption energy if line tension is included. PMID:28397869

Exploring the heterogeneous interfaces in organic or ruthenium dye-sensitized liquid- and solid-state solar cells.

PubMed

Kwon, Young Soo; Song, Inwoo; Lim, Jong Chul; Song, In Young; Siva, Ayyanar; Park, Taiho

2012-06-27

The interfacial properties were systematically investigated using an organic sensitizer (3-(5'-{4-[(4-tert-butyl-phenyl)-p-tolyl-amino]-phenyl}-[2,2']bithiophenyl-5-yl)-2-cyano-acrylic acid (D)) and inorganic sensitizer (bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2'-bipyridine-4,4'-dicarboxylato) ruthenium(II) (N719)) in a liquid-state and a solid-state dye-sensitized solar cell (DSC). For liquid-DSCs, the faster charge recombination for the surface of D-sensitized TiO2 resulted in shorter diffusion length (LD) of ∼3.9 μm than that of N719 (∼7.5 μm), limiting the solar cell performance at thicker films used in liquid-DSCs. On the other hand, for solid-DSCs using thin TiO2 films (∼ 2 μm), D-sensitized device outperforms the N719-sensitized device in an identical fabrication condition, mainly due to less perfect wetting ability of solid hole conductor into the porous TiO2 network, inducing the dye monolayer act as an insulation layer, while liquid electrolyte is able to fully wet the surface of TiO2. Such insulation effect was attributed to the fact that the significant increase in recombination resistance (from 865 to 4,400 Ω/cm(2)) but shorter electron lifetime (from 10.8 to 0.8 ms) when compared to liquid-DSCs. Higher recombination resistance for solid-DSCs induced the electron transport-limited situation, showing poor performance of N719-sensitized device which has shorter electron transport time and similar LD (2.9 μm) with D-sensitized device (3.0 μm).

Impact of pressure and temperature on CO2-brine-mica contact angles and CO2-brine interfacial tension: Implications for carbon geo-sequestration.

PubMed

Arif, Muhammad; Al-Yaseri, Ahmed Z; Barifcani, Ahmed; Lebedev, Maxim; Iglauer, Stefan

2016-01-15

Precise characterization of wettability of CO2-brine-rock system and CO2-brine interfacial tension at reservoir conditions is essential as they influence capillary sealing efficiency of caprocks, which in turn, impacts the structural and residual trapping during CO2 geo-sequestration. In this context, we have experimentally measured advancing and receding contact angles for brine-CO2-mica system (surface roughness ∼12nm) at different pressures (0.1MPa, 5MPa, 7MPa, 10MPa, 15MPa, 20MPa), temperatures (308K, 323K, and 343K), and salinities (0wt%, 5wt%, 10wt%, 20wt% and 30wt% NaCl). For the same experimental matrix, CO2-brine interfacial tensions have also been measured using the pendant drop technique. The results indicate that both advancing and receding contact angles increase with pressure and salinity, but decrease with temperature. On the contrary, CO2-brine interfacial tension decrease with pressure and increase with temperature. At 20MPa and 308K, the advancing angle is measured to be ∼110°, indicating CO2-wetting. The results have been compared with various published literature data and probable factors responsible for deviations have been highlighted. Finally we demonstrate the implications of measured data by evaluating CO2 storage heights under various operating conditions. We conclude that for a given storage depth, reservoirs with lower pressures and high temperatures can store larger volumes and thus exhibit better sealing efficiency. Copyright © 2015 Elsevier Inc. All rights reserved.

The Initial Comparison Study of Sodium Lignosulfonate, Sodium Dodecyl Benzene Sulfonate, and Sodium p-Toluene Sulfonate Surfactant for Enhanced Oil Recovery

NASA Astrophysics Data System (ADS)

Khoirul Anas, Argo; Iman Prakoso, Nurcahyo; Sasvita, Dilla

2018-04-01

Surfactant (surface active agent) exhibit numerous interesting properties that enable their use as additional component in mobilising of residual oil from capillary pore after secondary recovery process using gas injection and water flooding. In this study, Sodium Lignosulfonate (SLS) surfactant was successfully synthesized by applying batch method using lignin from oil palm empty fruit bunches as precursor. Furthermore, its performance in reducing interfacial tension of crude oil and formation water colloidal system was compared with commercial available surfactant including Sodium Dodecyl Benzene Sulfonate (SDBS) and Sodium p-Toluene Sulfonate (SpTS). The synthesized SLS surfactant was characterized by using Fourier Transform Infrared (FTIR) spectroscopy. Meanwhile, its performance in reducing interfacial tension of crude oil and formation water colloidal system was analyzed by using compatibility test, phase behaviour analysis, and interfacial tension (IFT) measurement. The compatibility test shows that SLS, SDBS, and SpTS surfactants were compatible with formation water. In addition, the phase behaviour analysis shows that SLS surfactant was better than SpTS surfactant, while SDBS surfactant generates the highest performance proved by the best microemulsion formation resulted by SDBS. Furthermore, the optimum concentration of SLS, SDBS, and SpTS surfactants in reducing the interfacial tension of crude oil and formation water was 1.0%. The IFT measurement indicates that the performance of SLS with the value of 1.67 mN/m was also better than SpTS surfactant with the value of 3.59 mN/m. Meanwhile, SDBS surfactant shows the best performance with the IFT value of 0.47 mN/m.

Pore-scale simulation of wettability and interfacial tension effects on flooding process for enhanced oil recovery.

PubMed

Zhao, Jin; Wen, Dongsheng

2017-08-27

For enhanced oil recovery (EOR) applications, the oil/water flow characteristics during the flooding process was numerically investigated with the volume-of-fluid method at the pore scale. A two-dimensional pore throat-body connecting structure was established, and four scenarios were simulated in this paper. For oil-saturated pores, the wettability effect on the flooding process was studied; for oil-unsaturated pores, three effects were modelled to investigate the oil/water phase flow behaviors, namely the wettability effect, the interfacial tension (IFT) effect, and the combined wettability/IFT effect. The results show that oil saturated pores with the water-wet state can lead to 25-40% more oil recovery than with the oil-wet state, and the remaining oil mainly stays in the near wall region of the pore bodies for oil-wet saturated pores. For oil-unsaturated pores, the wettability effects on the flooding process can help oil to detach from the pore walls. By decreasing the oil/water interfacial tension and altering the wettability from oil-wet to water-wet state, the remaining oil recovery rate can be enhanced successfully. The wettability-IFT combined effect shows better EOR potential compared with decreasing the interfacial tension alone under the oil-wet condition. The simulation results in this work are consistent with previous experimental and molecular dynamics simulation conclusions. The combination effect of the IFT reducation and wettability alteration can become an important recovery mechanism in future studies for nanoparticles, surfactant, and nanoparticle-surfactant hybrid flooding process.

Pore-scale simulation of wettability and interfacial tension effects on flooding process for enhanced oil recovery

PubMed Central

Zhao, Jin

2017-01-01

For enhanced oil recovery (EOR) applications, the oil/water flow characteristics during the flooding process was numerically investigated with the volume-of-fluid method at the pore scale. A two-dimensional pore throat-body connecting structure was established, and four scenarios were simulated in this paper. For oil-saturated pores, the wettability effect on the flooding process was studied; for oil-unsaturated pores, three effects were modelled to investigate the oil/water phase flow behaviors, namely the wettability effect, the interfacial tension (IFT) effect, and the combined wettability/IFT effect. The results show that oil saturated pores with the water-wet state can lead to 25–40% more oil recovery than with the oil-wet state, and the remaining oil mainly stays in the near wall region of the pore bodies for oil-wet saturated pores. For oil-unsaturated pores, the wettability effects on the flooding process can help oil to detach from the pore walls. By decreasing the oil/water interfacial tension and altering the wettability from oil-wet to water-wet state, the remaining oil recovery rate can be enhanced successfully. The wettability-IFT combined effect shows better EOR potential compared with decreasing the interfacial tension alone under the oil-wet condition. The simulation results in this work are consistent with previous experimental and molecular dynamics simulation conclusions. The combination effect of the IFT reducation and wettability alteration can become an important recovery mechanism in future studies for nanoparticles, surfactant, and nanoparticle–surfactant hybrid flooding process. PMID:29308190

Interfacial Properties and Mechanisms Dominating Gas Hydrate Cohesion and Adhesion in Liquid and Vapor Hydrocarbon Phases.

PubMed

Hu, Sijia; Koh, Carolyn A

2017-10-24

The interfacial properties and mechanisms of gas hydrate systems play a major role in controlling their interparticle and surface interactions, which is desirable for nearly all energy applications of clathrate hydrates. In particular, preventing gas hydrate interparticle agglomeration and/or particle-surface deposition is critical to the prevention of gas hydrate blockages during the exploration and transportation of oil and gas subsea flow lines. These agglomeration and deposition processes are dominated by particle-particle cohesive forces and particle-surface adhesive force. In this study, we present the first direct measurements on the cohesive and adhesive forces studies of the CH 4 /C 2 H 6 gas hydrate in a liquid hydrocarbon-dominated system utilizing a high-pressure micromechanical force (HP-MMF) apparatus. A CH 4 /C 2 H 6 gas mixture was used as the gas hydrate former in the model liquid hydrocarbon phase. For the cohesive force baseline test, it was found that the addition of liquid hydrocarbon changed the interfacial tension and contact angle of water in the liquid hydrocarbon compared to water in the gas phase, resulting in a force of 23.5 ± 2.5 mN m -1 at 3.45 MPa and 274 K for a 2 h annealing time period in which hydrate shell growth occurs. It was observed that the cohesive force was inversely proportional to the annealing time, whereas the force increased with increasing contact time. For a longer contact time (>12 h), the force could not be measured because the two hydrate particles adhered permanently to form one large particle. The particle-surface adhesive force in the model liquid hydrocarbon was measured to be 5.3 ± 1.1 mN m -1 under the same experimental condition. Finally, with a 1 h contact time, the hydrate particle and the carbon steel (CS) surface were sintered together and the force was higher than what could be measured by the current apparatus. A possible mechanism is presented in this article to describe the effect of contact time on the particle-particle cohesive force based on the capillary liquid bridge model. A model adapted from the capillary liquid bridge equation has been used to predict the particle-particle cohesive force as a function of contact time, showing close agreement with the experimental data. By comparing the cohesive forces results from gas hydrates for both gas and liquid bulk phases, the surface free energy of a hydrate particle was calculated and found to dominate the changes in the interaction forces with different continuous bulk phases.

Nanowire Membrane-based Nanothermite: towards Processable and Tunable Interfacial Diffusion for Solid State Reactions

PubMed Central

Yang, Yong; Wang, Peng-peng; Zhang, Zhi-cheng; Liu, Hui-ling; Zhang, Jingchao; Zhuang, Jing; Wang, Xun

2013-01-01

Interfacial diffusion is of great importance in determining the performance of solid-state reactions. For nanometer sized particles, some solid-state reactions can be triggered accidently by mechanical stress owing to their large surface-to-volume ratio compared with the bulk ones. Therefore, a great challenge is the control of interfacial diffusion for solid state reactions, especially for energetic materials. Here we demonstrate, through the example of nanowire-based thermite membrane, that the thermite solid-state reaction can be easily tuned via the introduction of low-surface-energy coating layer. Moreover, this silicon-coated thermite membrane exhibit controlled wetting behavior ranging from superhydrophilic to superhydrophobic and, simultaneously, to significantly reduce the friction sensitivity of thermite membrane. This effect enables to increase interfacial resistance by increasing the amount of coating material. Indeed, our results described here make it possible to tune the solid-state reactions through the manipulation of interfacial diffusion between the reactants. PMID:23603809

Fixed Packed Bed Reactors in Reduced Gravity

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro; McCready, Mark J.

2004-01-01

We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients k(L)a and k(G)a (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

Recent Developments of All-Solid-State Lithium Secondary Batteries with Sulfide Inorganic Electrolytes.

PubMed

Xu, Ruochen; Zhang, Shengzhao; Wang, Xiuli; Xia, Yan; Xia, Xinhui; Wu, Jianbo; Gu, Changdong; Tu, Jiangping

2018-04-20

Due to the increasing demand of security and energy density, all-solid-state lithium ion batteries have become the promising next-generation energy storage devices to replace the traditional liquid batteries with flammable organic electrolytes. In this Minireview, we focus on the recent developments of sulfide inorganic electrolytes for all-solid-state batteries. The challenges of assembling bulk-type all-solid-state batteries for industrialization are discussed, including low ionic conductivity of the present sulfide electrolytes, high interfacial resistance and poor compatibility between electrolytes and electrodes. Many efforts have been focused on the solutions for these issues. Although some progresses have been achieved, it is still far away from practical application. The perspectives for future research on all-solid-state lithium ion batteries are presented. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adhesion Potential of Intestinal Microbes Predicted by Physico-Chemical Characterization Methods

PubMed Central

Niederberger, Tobias; Fischer, Peter; Rühs, Patrick Alberto

2015-01-01

Bacterial adhesion to epithelial surfaces affects retention time in the human gastro-intestinal tract and therefore significantly contributes to interactions between bacteria and their hosts. Bacterial adhesion among other factors is strongly influenced by physico-chemical factors. The accurate quantification of these physico-chemical factors in adhesion is however limited by the available measuring techniques. We evaluated surface charge, interfacial rheology and tensiometry (interfacial tension) as novel approaches to quantify these interactions and evaluated their biological significance via an adhesion assay using intestinal epithelial surface molecules (IESM) for a set of model organisms present in the human gastrointestinal tract. Strain pairs of Lactobacillus plantarum WCFS1 with its sortase knockout mutant Lb. plantarum NZ7114 and Lb. rhamnosus GG with Lb. rhamnosus DSM 20021T were used with Enterococcus faecalis JH2-2 as control organism. Intra-species comparison revealed significantly higher abilities for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T to dynamically increase interfacial elasticity (10−2 vs. 10−3 Pa*m) and reduce interfacial tension (32 vs. 38 mN/m). This further correlated for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T with the decrease of relative hydrophobicity (80–85% vs. 57–63%), Zeta potential (-2.9 to -4.5 mV vs. -8.0 to -13.8 mV) and higher relative adhesion capacity to IESM (3.0–5.0 vs 1.5–2.2). Highest adhesion to the IESM collagen I and fibronectin was found for Lb. plantarum WCFS1 (5.0) and E. faecalis JH2-2 (4.2) whereas Lb. rhamnosus GG showed highest adhesion to type II mucus (3.8). Significantly reduced adhesion (2 fold) to the tested IESM was observed for Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T corresponding with lower relative hydrophobicity, Zeta potential and abilities to modify interfacial elasticity and tension. Conclusively, the use of Zeta potential, interfacial elasticity and interfacial tension are proposed as suitable novel descriptive and predictive parameters to study the interactions of intestinal microbes with their hosts. PMID:26295945

EMIIM Wetting Properties of & Their Effect on Electrospray Thruster Design

DTIC Science & Technology

2012-03-21

materials can be characterized using the surface tension and contact or “wetting" angle formed when a liquid droplet comes in contact with a solid surface...Illustration of the instantaneous dipole formed by electron motion in a hy- drogen atom(left) and how these instantaneous dipoles can attract each other...the extractor grid and of like charge to the emitter. A Taylor cone formed using an internally wetted emitter and the ionic liquid BMI-BG4 is shown in

Dynamique d'étalement

NASA Astrophysics Data System (ADS)

de Gennes, Pierre-Gilles

On analyse la progression d'un coin fiuide sur uo solide (dans le cas ou Tangle de contact thermodynamique θa est nul : regie d'Antonov satisfaite) en tenant compte des interactions Van der Waals a longue portee. On trouve : (a) un angle de contact apparent θa relie a la vitesse d'avancee U par θ^{3}_{a} ˜ U η/γ (η = viscosity, γ tension superficielle du liquide) d'ou une loi rayon/temps d'etalement pour une goutte r(t) 1/10. (b) un film precurseur ζ d'epaisseur ζ(x, f) decroissant asymptotiquement comme x1 ou x est la distance a la ligne triple. L'epaisseur h* d u film au voisinage de la ligne triple est h* a/θa (ou a est une distance atomique). Ceci permet de comprendre le fait (reconnu) que le film precurseur est bien visible seulement si l'angle de contact thermodynamique est nul. We analyse the shape of the liquid-air interface for a droplet spreading on a solid, in a regime where the Antonov rule is satisfied, taking into account the long range Van der Waals interactions between liquid and solid. We find: (a) an apparent contact angle θa related to the velocity U of the triple line by θ^{3}_{a} ˜ U η/γ (η = viscosity, γ surface tension of the liquid). This leads to a law of spreading (radius r/time t) for a droplet r t1/10. (b) a precursor film of thickness ζ, decreasing asymptotically like x-1, where x is the distance from the triple line. The thickness h* of the film at this line is h* a/θa where a is an atomic length: this explains why the precursor films are observed only when the thermodynamic contact angle vanishes.

Similar solutions of double-diffusive dissipative layers along free surfaces

NASA Astrophysics Data System (ADS)

Napolitano, L. G.; Viviani, A.; Savino, R.

1990-10-01

Free convection due to buoyant forces (natural convection) and surface tension gradients (Marangoni convection) generated by temperature and concentration gradients is discussed together with the formation of double-diffusive boundary layers along liquid-gas interfaces. Similarity solutions for each class of free convection are derived and the resulting nonlinear two-point problems are solved numerically using the quasi-linearization method. Velocity, temperature, concentration profiles, interfacial velocity, heat and mass transfer bulk coefficients for various Prandtl and Schmidt numbers, and different values of the similarity parameters are determined. The convective flows are of particular interest because they are considered to influence the processes of crystal growth, both on earth and in a microgravity environment.

Molecular origin of contact line stick-slip motion during droplet evaporation

PubMed Central

Wang, FengChao; Wu, HengAn

2015-01-01

Understanding and controlling the motion of the contact line is of critical importance for surface science studies as well as many industrial engineering applications. In this work, we elucidate the molecular origin of contact line stick-slip motion during the evaporation of liquid droplets on flexible nano-pillared surfaces using molecular dynamics simulations. We demonstrate that the evaporation-induced stick-slip motion of the contact line is a consequence of competition between pinning and depinning forces. Furthermore, the tangential force exerted by the pillared substrate on the contact line was observed to have a sawtooth-like oscillation. Our analysis also establishes that variations in the pinning force are accomplished through the self-adaptation of solid-liquid intermolecular distances, especially for liquid molecules sitting directly on top of the solid pillar. Consistent with our theoretical analysis, molecular dynamics simulations also show that the maximum pinning force is quantitatively related to both solid-liquid adhesion strength and liquid-vapor surface tension. These observations provide a fundamental understanding of contact line stick-slip motion on pillared substrates and also give insight into the microscopic interpretations of contact angle hysteresis, wetting transitions and dynamic spreading. PMID:26628084

Bonding measurement -Strength and fracture mechanics approaches.

PubMed

Anunmana, Chuchai; Wansom, Wiroj

2017-07-26

This study investigated the effect of cross-sectional areas on interfacial fracture toughness and bond strength of bilayered dental ceramics. Zirconia core ceramics were veneered and cut to produce specimens with three different cross-sectional areas. Additionally, monolithic specimens of glass veneer were also prepared. The specimens were tested in tension until fracture at the interface and reported as bond strength. Fracture surfaces were observed, and the apparent interfacial toughness was determined from critical crack size and failure stress. The results showed that cross-sectional area had no effect on the interfacial toughness whereas such factor had a significant effect on interfacial bond strength. The study revealed that cross-sectional area had no effect on the interfacial toughness, but had a significant effect on interfacial bond strength. The interfacial toughness may be a more reliable indicator for interfacial bond quality than interfacial bond strength.

Computational Analyses of Pressurization in Cryogenic Tanks

NASA Technical Reports Server (NTRS)

Ahuja, Vineet; Hosangadi, Ashvin; Mattick, Stephen; Lee, Chun P.; Field, Robert E.; Ryan, Harry

2008-01-01

A) Advanced Gas/Liquid Framework with Real Fluids Property Routines: I. A multi-fluid formulation in the preconditioned CRUNCH CFD(Registered TradeMark) code developed where a mixture of liquid and gases can be specified: a) Various options for Equation of state specification available (from simplified ideal fluid mixtures, to real fluid EOS such as SRK or BWR models). b) Vaporization of liquids driven by pressure value relative to vapor pressure and combustion of vapors allowed. c) Extensive validation has been undertaken. II. Currently working on developing primary break-up models and surface tension effects for more rigorous phase-change modeling and interfacial dynamics B) Framework Applied to Run-time Tanks at Ground Test Facilities C) Framework Used For J-2 Upper Stage Tank Modeling: 1) NASA MSFC tank pressurization: a) Hydrogen and oxygen tank pre-press, repress and draining being modeled at NASA MSFC. 2) NASA AMES tank safety effort a) liquid hydrogen and oxygen are separated by a baffle in the J-2 tank. We are modeling pressure rise and possible combustion if a hole develops in the baffle and liquid hydrogen leaks into the oxygen tank. Tank pressure rise rates simulated and risk of combustion evaluated.

Ethanol effects on binary and ternary supported lipid bilayers with gel/fluid domains and lipid rafts.

PubMed

Marquês, Joaquim T; Viana, Ana S; De Almeida, Rodrigo F M

2011-01-01

Ethanol-lipid bilayer interactions have been a recurrent theme in membrane biophysics, due to their contribution to the understanding of membrane structure and dynamics. The main purpose of this study was to assess the interplay between membrane lateral heterogeneity and ethanol effects. This was achieved by in situ atomic force microscopy, following the changes induced by sequential ethanol additions on supported lipid bilayers formed in the absence of alcohol. Binary phospholipid mixtures with a single gel phase, dipalmitoylphosphatidylcholine (DPPC)/cholesterol, gel/fluid phase coexistence DPPC/dioleoylphosphatidylcholine (DOPC), and ternary lipid mixtures containing cholesterol, mimicking lipid rafts (DOPC/DPPC/cholesterol and DOPC/sphingomyelin/cholesterol), i.e., with liquid ordered/liquid disordered (ld/lo) phase separation, were investigated. For all compositions studied, and in two different solid supports, mica and silicon, domain formation or rearrangement accompanied by lipid bilayer thinning and expansion was observed. In the case of gel/fluid coexistence, low ethanol concentrations lead to a marked thinning of the fluid but not of the gel domains. In the case of ld/lo all the bilayer thins simultaneously by a similar extent. In both cases, only the more disordered phase expanded significantly, indicating that ethanol increases the proportion of disordered domains. Water/bilayer interfacial tension variation and freezing point depression, inducing acyl chain disordering (including opening and looping), tilting, and interdigitation, are probably the main cause for the observed changes. The results presented herein demonstrate that ethanol influences the bilayer properties according to membrane lateral organization. Copyright © 2010 Elsevier B.V. All rights reserved.

Nonlinear vibrational spectroscopy of surfactants at liquid interfaces

NASA Astrophysics Data System (ADS)

Miranda, Paulo Barbeitas

Surfactants are widely used to modify physical and chemical properties of interfaces. They play an important role in many technological problems. Surfactant monolayers are also of great scientific interest because they are two-dimensional systems that may exhibit a very rich phase transition behavior and can also be considered as a model system for biological interfaces. In this Thesis, we use a second-order nonlinear optical technique (Sum-Frequency Generation - SFG) to obtain vibrational spectra of surfactant monolayers at liquid/vapor and solid/liquid interfaces. The technique has several advantages: it is intrinsically surface-specific, can be applied to buried interfaces, has submonolayer sensitivity and is remarkably sensitive to the conformational order of surfactant monolayers. The first part of the Thesis is concerned with surfactant monolayers at the air/water interface (Langmuir films). Surface crystallization of an alcohol Langmuir film and of liquid alkanes are studied and their phase transition behaviors are found to be of different nature, although driven by similar intermolecular interactions. The effect of crystalline order of Langmuir monolayers on the interfacial water structure is also investigated. It is shown that water forms a well-ordered hydrogen-bonded network underneath an alcohol monolayer, in contrast to a fatty acid monolayer which induces a more disordered structure. In the latter case, ionization of the monolayer becomes more significant with increase of the water pH value, leading to an electric-field-induced ordering of interfacial water molecules. We also show that the orientation and conformation of fairly complicated molecules in a Langmuir monolayer can be completely mapped out using a combination of SFG and second harmonic generation (SHG). For a quantitative analysis of molecular orientation at an interface, local-field corrections must be included. The second part is a study of self-assembled surfactant monolayers at the solid/liquid interface. It is shown that the conformation of a monolayer adsorbed onto a solid substrate and immersed in a liquid is highly dependent on the monolayer surface density and on the nature of intermolecular interactions in the liquid. Fully packed monolayers are well ordered in any environment due to strong surfactant-surfactant interactions and limited liquid penetration into the monolayer. In contrast, loosely packed monolayers are very sensitive to the liquid environment. Non-polar liquids cause a mild increase in the surfactant conformational disorder. Polar liquids induce more disorder and hydrogen-bonding liquids produce highly disordered conformations due to the hydrophobic effect. When immersed in alkanes, under certain conditions the surfactant chains may become highly ordered due to their interaction with the liquid molecules (chain-chain interaction). In the case of long-chain alcohols, competition between the hydrophobic effect and chain-chain interaction is observed.

Can we approach the gas-liquid critical point using slab simulations of two coexisting phases?

PubMed

Goujon, Florent; Ghoufi, Aziz; Malfreyt, Patrice; Tildesley, Dominic J

2016-09-28

In this paper, we demonstrate that it is possible to approach the gas-liquid critical point of the Lennard-Jones fluid by performing simulations in a slab geometry using a cut-off potential. In the slab simulation geometry, it is essential to apply an accurate tail correction to the potential energy, applied during the course of the simulation, to study the properties of states close to the critical point. Using the Janeček slab-based method developed for two-phase Monte Carlo simulations [J. Janec̆ek, J. Chem. Phys. 131, 6264 (2006)], the coexisting densities and surface tension in the critical region are reported as a function of the cutoff distance in the intermolecular potential. The results obtained using slab simulations are compared with those obtained using grand canonical Monte Carlo simulations of isotropic systems and the finite-size scaling techniques. There is a good agreement between these two approaches. The two-phase simulations can be used in approaching the critical point for temperatures up to 0.97 T C ∗ (T ∗ = 1.26). The critical-point exponents describing the dependence of the density, surface tension, and interfacial thickness on the temperature are calculated near the critical point.

Transglutaminase-treated conjugation of sodium caseinate and corn fiber gum hydrolysate: Interfacial and dilatational properties

USDA-ARS?s Scientific Manuscript database

The effects of thermochemical hydrolysis of corn fiber gum (CFG) and conjugation of the resulting oligomers with sodium caseinate in presence of transglutaminase was studied. The dynamic interfacial tension at the oil-water interface was studied and the molecular characteristics were determined by h...

Biosurfactant as an Enhancer of Geologic Carbon Storage: Microbial Modification of Interfacial Tension and Contact Angle in Carbon dioxide/Water/Quartz Systems.

PubMed

Park, Taehyung; Joo, Hyun-Woo; Kim, Gyeong-Yeong; Kim, Seunghee; Yoon, Sukhwan; Kwon, Tae-Hyuk

2017-01-01

Injecting and storing of carbon dioxide (CO 2 ) in deep geologic formations is considered as one of the promising approaches for geologic carbon storage. Microbial wettability alteration of injected CO 2 is expected to occur naturally by microorganisms indigenous to the geologic formation or microorganisms intentionally introduced to increase CO 2 storage capacity in the target reservoirs. The question as to the extent of microbial CO 2 wettability alteration under reservoir conditions still warrants further investigation. This study investigated the effect of a lipopeptide biosurfactant-surfactin, on interfacial tension (IFT) reduction and contact angle alteration in CO 2 /water/quartz systems under a laboratory setup simulating in situ reservoir conditions. The temporal shifts in the IFT and the contact angle among CO 2 , brine, and quartz were monitored for different CO 2 phases (3 MPa, 30°C for gaseous CO 2 ; 10 MPa, 28°C for liquid CO 2 ; 10 MPa, 37°C for supercritical CO 2 ) upon cultivation of Bacillus subtilis strain ATCC6633 with induced surfactin secretion activity. Due to the secreted surfactin, the IFT between CO 2 and brine decreased: from 49.5 to 30 mN/m, by ∼39% for gaseous CO 2 ; from 28.5 to 13 mN/m, by 54% for liquid CO 2 ; and from 32.5 to 18.5 mN/m, by ∼43% for supercritical CO 2 , respectively. The contact angle of a CO 2 droplet on a quartz disk in brine increased: from 20.5° to 23.2°, by 1.16 times for gaseous CO 2 ; from 18.4° to 61.8°, by 3.36 times for liquid CO 2 ; and from 35.5° to 47.7°, by 1.34 times for supercritical CO 2 , respectively. With the microbially altered CO 2 wettability, improvement in sweep efficiency of injected and displaced CO 2 was evaluated using 2-D pore network model simulations; again the increment in sweep efficiency was the greatest in liquid CO 2 phase due to the largest reduction in capillary factor. This result provides novel insights as to the role of naturally occurring biosurfactants in CO 2 storage and suggests that biostimulation of biosurfactant production may be a feasible technique for enhancement of CO 2 storage capacity.

Biosurfactant as an Enhancer of Geologic Carbon Storage: Microbial Modification of Interfacial Tension and Contact Angle in Carbon dioxide/Water/Quartz Systems

PubMed Central

Park, Taehyung; Joo, Hyun-Woo; Kim, Gyeong-Yeong; Kim, Seunghee; Yoon, Sukhwan; Kwon, Tae-Hyuk

2017-01-01

Injecting and storing of carbon dioxide (CO2) in deep geologic formations is considered as one of the promising approaches for geologic carbon storage. Microbial wettability alteration of injected CO2 is expected to occur naturally by microorganisms indigenous to the geologic formation or microorganisms intentionally introduced to increase CO2 storage capacity in the target reservoirs. The question as to the extent of microbial CO2 wettability alteration under reservoir conditions still warrants further investigation. This study investigated the effect of a lipopeptide biosurfactant—surfactin, on interfacial tension (IFT) reduction and contact angle alteration in CO2/water/quartz systems under a laboratory setup simulating in situ reservoir conditions. The temporal shifts in the IFT and the contact angle among CO2, brine, and quartz were monitored for different CO2 phases (3 MPa, 30°C for gaseous CO2; 10 MPa, 28°C for liquid CO2; 10 MPa, 37°C for supercritical CO2) upon cultivation of Bacillus subtilis strain ATCC6633 with induced surfactin secretion activity. Due to the secreted surfactin, the IFT between CO2 and brine decreased: from 49.5 to 30 mN/m, by ∼39% for gaseous CO2; from 28.5 to 13 mN/m, by 54% for liquid CO2; and from 32.5 to 18.5 mN/m, by ∼43% for supercritical CO2, respectively. The contact angle of a CO2 droplet on a quartz disk in brine increased: from 20.5° to 23.2°, by 1.16 times for gaseous CO2; from 18.4° to 61.8°, by 3.36 times for liquid CO2; and from 35.5° to 47.7°, by 1.34 times for supercritical CO2, respectively. With the microbially altered CO2 wettability, improvement in sweep efficiency of injected and displaced CO2 was evaluated using 2-D pore network model simulations; again the increment in sweep efficiency was the greatest in liquid CO2 phase due to the largest reduction in capillary factor. This result provides novel insights as to the role of naturally occurring biosurfactants in CO2 storage and suggests that biostimulation of biosurfactant production may be a feasible technique for enhancement of CO2 storage capacity. PMID:28744272

Eddy current sensor concepts for the Bridgman growth of semiconductors

NASA Astrophysics Data System (ADS)

Dharmasena, Kumar P.; Wadley, Haydn N. G.

1997-03-01

Electromagnetic finite element methods have been used to identify eddy current sensor designs for monitoring CdTe vertical Bridgman crystal growth. A model system consisting of pairs of silicon cylinders with electrical conductivities similar to those of solid and liquid CdTe has been used to evaluate the multifrequency response of several sensors designed for locating and characterizing the curvature of liquid-solid interfaces during vertical Bridgman growth. At intermediate frequencies (100-800 kHz), the sensor's imaginary impedance monotonically increases as interfacial curvature changes from concave to convex or the interface location moves upwards through the sensor. The experimental data are in excellent agreement with theoretical predictions. At higher test frequencies (˜ 5 MHz), the test circuit's parasitics contribute to the sensor's response. Even so, the predicted trends with interface location/curvature were found to be still preserved, and the experiments confirm that the sensor's high frequency response depends more on interface location and has only a small sensitivity to curvature. Multifrequency data obtained from these types of sensors have the potential to separately discriminate the location and the shape of liquid-solid interfaces during the vertical Bridgman growth of CdTe and other semiconductor materials of higher electrical conductivity.

Measurement of surface tension and viscosity by open capillary techniques

DOEpatents

Rye,Robert R. , Yost,Frederick G.

1998-01-01

An open-channel capillary is provided, having preferably a v-shaped groove in a flat wettable surface. The groove has timing marks and a source marker in which the specimen to be tested is deposited. The time of passage between the timing marks is recorded, and the ratio of surface tension .gamma. to viscosity .mu. is determined from the equation given below: ##EQU1## where h.sub.0 is the groove depth, .alpha. is the groove angle, .theta. is the liquid/solid contact angle, and t is the flow time. It has been shown by the

Molecular dynamics study of solid-liquid heat transfer and passive liquid flow

NASA Astrophysics Data System (ADS)

Yesudasan Daisy, Sumith

High heat flux removal is a challenging problem in boilers, electronics cooling, concentrated photovoltaic and other power conversion devices. Heat transfer by phase change is one of the most efficient mechanisms for removing heat from a solid surface. Futuristic electronic devices are expected to generate more than 1000 W/cm2 of heat. Despite the advancements in microscale and nanoscale manufacturing, the maximum passive heat flux removal has been 300 W/cm2 in pool boiling. Such limitations can be overcome by developing nanoscale thin-film evaporation based devices, which however require a better understanding of surface interactions and liquid vapor phase change process. Evaporation based passive flow is an inspiration from the transpiration process that happens in trees. If we can mimic this process and develop heat removal devices, then we can develop efficient cooling devices. The existing passive flow based cooling devices still needs improvement to meet the future demands. To improve the efficiency and capacity of these devices, we need to explore and quantify the passive flow happening at nanoscales. Experimental techniques have not advanced enough to study these fundamental phenomena at the nanoscale, an alternative method is to perform theoretical study at nanoscales. Molecular dynamics (MD) simulation is a widely accepted powerful tool for studying a range of fundamental and engineering problems. MD simulations can be utilized to study the passive flow mechanism and heat transfer due to it. To study passive flow using MD, apart from the conventional methods available in MD, we need to have methods to simulate the heat transfer between solid and liquid, local pressure, surface tension, density, temperature calculation methods, realistic boundary conditions, etc. Heat transfer between solid and fluids has been a challenging area in MD simulations, and has only been minimally explored (especially for a practical fluid like water). Conventionally, an equilibrium canonical ensemble (NVT) is simulated using thermostat algorithms. For research in heat transfer involving solid liquid interaction, we need to perform non equilibrium MD (NEMD) simulations. In such NEMD simulations, the methods used for simulating heating from a surface is very important and must capture proper physics and thermodynamic properties. Development of MD simulation techniques to simulate solid-liquid heating and the study of fundamental mechanism of passive flow is the main focus of this thesis. An accurate surface-heating algorithm was developed for water which can now allow the study of a whole new set of fundamental heat transfer problems at the nanoscale like surface heating/cooling of droplets, thin-films, etc. The developed algorithm is implemented in the in-house developed C++ MD code. A direct two dimensional local pressure estimation algorithm is also formulated and implemented in the code. With this algorithm, local pressure of argon and platinum interaction is studied. Also, the surface tension of platinum-argon (solid-liquid) was estimated directly from the MD simulations for the first time. Contact angle estimation studies of water on platinum, and argon on platinum were also performed. A thin film of argon is kept above platinum plate and heated in the middle region, leading to the evaporation and pressure reduction thus creating a strong passive flow in the near surface region. This observed passive liquid flow is characterized by estimating the pressure, density, velocity and surface tension using Eulerian mapping method. Using these simulation, we have demonstrated the fundamental nature and origin of surface-driven passive flow. Heat flux removed from the surface is also estimated from the results, which shows a significant improvement can be achieved in thermal management of electronic devices by taking advantage of surface-driven strong passive liquid flow. Further, the local pressure of water on silicon di-oxide surface is estimated using the LAMMPS atomic to continuum (ATC) package towards the goal of simulating the passive flow in water.

Convergent strand array liquid pumping system

NASA Technical Reports Server (NTRS)

Collins, Earl R., Jr. (Inventor)

1989-01-01

A surface-tension liquid pumping system is provided by one or more arrays of converging solid monofilament fibers or metal wires (strands) spaced apart at an input end to gather liquid, and gathered close together at the opposite end where menisci forms between wetted strands to force liquid in the direction of convergence of the strands. The liquid pumping system is independent of gravity. It is illustrated as being used in a heat pump having a heating box to vaporize the liquid and a condensing chamber. Condensed liquid is returned by the pumping system to the heating box where it is again vaporized. A vapor tube carries the vapor to the condensing chamber. In that way, a closed system pumps heat from the heating box to the evaporating chamber and from there radiated to the atmosphere.

Effects of surface tension and viscosity on gold and silver sputtered onto liquid substrates

NASA Astrophysics Data System (ADS)

De Luna, Mark M.; Gupta, Malancha

2018-05-01

In this paper, we study DC magnetron sputtering of gold and silver onto liquid substrates of varying viscosities and surface tensions. We were able to separate the effects of viscosity from surface tension by depositing the metals onto silicone oils with a range of viscosities. The effects of surface tension were studied by depositing the metals onto squalene, poly(ethylene glycol), and glycerol. It was found that dispersed nanoparticles were formed on liquids with low surface tension and low viscosity whereas dense films were formed on liquids with low surface tension and high viscosity. Nanoparticles were formed on both the liquid surface and within the bulk liquid for high surface tension liquids. Our results can be used to tailor the metal and liquid interaction to fabricate particles and films for various applications in optics, electronics, and catalysis.

The influence of surface-active agents in gas mixture on the intensity of jet condensation

NASA Astrophysics Data System (ADS)

Yezhov, YV; Okhotin, VS

2017-11-01

The report presents: the methodology of calculation of contact condensation of steam from the steam-gas mixture into the stream of water, taking into account: the mass flow of steam through the boundary phase, particularly the change in turbulent transport properties near the interface and their connection to the interface perturbations due to the surface tension of the mixture; the method of calculation of the surface tension at the interface water - a mixture of fluorocarbon vapor and water, based on the previously established analytical methods we calculate the surface tension for simple one - component liquid-vapor systems. The obtained analytical relation to calculate the surface tension of the mixture is a function of temperature and volume concentration of the fluorocarbon gas in the mixture and is true for all sizes of gas molecules. On the newly created experimental stand is made verification of experimental studies to determine the surface tension of pure substances: water, steam, C3F8 pair C3F8, produced the first experimental data on surface tension at the water - a mixture of water vapor and fluorocarbon C3F8. The obtained experimental data allow us to refine the values of the two constants used in the calculated model of the surface tension of the mixture. Experimental study of jet condensation was carried out with the flow in the zone of condensation of different gases. The condensation process was monitored by measurement of consumption of water flowing from the nozzle, and the formed condensate. When submitting C3F8, there was a noticeable, intensification condensation process compared with the condensation of pure water vapor. The calculation results are in satisfactory agreement with the experimental data on surface tension of the mixture and steam condensation from steam-gas mixture. Analysis of calculation results shows that the presence of surfactants in the condensation zone affects the partial vapor pressure on the interfacial surface, and the thermal conductivity of the liquid jet. The first circumstance leads to deterioration of the condensation process, the second to the intensification of this process. There is obviously an optimum value of concentration of the additive surfactants to the vapour when the condensation process is maximum. According to the developed design methodology contact condensation can evaluate these optimum conditions, their practical effect in the field study.

Explicit demonstration of the role of Marangoni effect in the breakup of nanoscale liquid filaments

NASA Astrophysics Data System (ADS)

Seric, Ivana; Mahady, Kyle; Afkhami, Shahriar; Hartnett, Chris; Fowlkes, Jason; Rack, Philip; Kondic, Lou

2016-11-01

We consider a breakup of bi-metal filaments deposited on a solid substrate. These filaments are exposed to laser irradiation and, while in the liquid phase, evolve by a process resembling breakup of a liquid jet governed by the Rayleigh-Plateau instability. The novel element is that the Marangoni effect, resulting from a different surface tension of the two metals from which the filament is built, is crucial in understanding the instability development. In particular, Marangoni effect may lead to the inversion of the breakup process, producing droplets at the locations where according to the Rayleigh-Plateau theory dry spots would be expected. We present experimental results carried out with Cu-Ni filaments, as well as direct numerical simulations based on a novel algorithm that includes variable surface tension in a Volume-of-Fluid based Navier-Stokes solver. These results suggest the possibility of using Marangoni effect for the purpose of self- and directed-assembly on the nanoscale. Supported by the NSF Grant No. CBET-1604351.

Wetting and Interfacial Reactivity of Zn-Coated Steel Products with Cu-Si, Cu-Sn and Al-Si Filler Metals for Laser Brazing Application

NASA Astrophysics Data System (ADS)

Koltsov, Alexey; Cretteur, Laurent

2018-03-01

The laser brazing process is successfully applied in automotive industry for joining of roofs and hatchbacks of vehicles. The bad wetting of the brazing alloy during the process can lead to the formation of random external porosities which are not allowed on visible parts. This paper describes the wettability and reactivity mechanisms at short contact time of Cu and Al matrix brazing alloys with different reactive elements (Si, Sn) on different steel products such as hot-dip galvanized steels, galvannealed steel and bare steel. Wetting experiments were carried out by the dispensed drop technique. The effects of alloying elements and brazing alloy matrix on interfacial reactivity are discussed. It was found that Cu matrix containing 3 wt.% Si is the most favorable for short time liquid/solid adhesion relatively to the other studied brazing alloy compositions. The brazing ability of different steel products is well correlated with the wettability and interfacial reactivity results.

Static and dynamic wetting behaviour of ionic liquids.

PubMed

Delcheva, Iliana; Ralston, John; Beattie, David A; Krasowska, Marta

2015-08-01

Ionic liquids (ILs) are a unique family of molecular liquids ('molten salts') that consist of a combination of bulky organic cations coupled to inorganic or organic anions. The net result of steric hindrance and strong hydrogen bonding between components results in a material that is liquid at room temperature. One can alter the properties of ionic liquids through chemical modification of anion and cation, thus tailoring the IL for a given application. One such property that can be controlled or selected is the wettability of an IL on a particular solid substrate. However, the study of wetting of ionic liquids is complicated by the care required for accurate and reproducible measurement, due to both the susceptibility of the IL properties to water content, as well as to the sensitivity of wettability measurements to the state of the solid surface. This review deals with wetting studies of ILs to date, including both static and dynamic wetting, as well as issues concerning line tension and the formation of precursor and wetting films. Copyright © 2014 Elsevier B.V. All rights reserved.

Superior Blends Solid Polymer Electrolyte with Integrated Hierarchical Architectures for All-Solid-State Lithium-Ion Batteries.

PubMed

Zhang, Dechao; Zhang, Long; Yang, Kun; Wang, Hongqiang; Yu, Chuang; Xu, Di; Xu, Bo; Wang, Li-Min

2017-10-25

Exploration of advanced solid electrolytes with good interfacial stability toward electrodes is a highly relevant research topic for all-solid-state batteries. Here, we report PCL/SN blends integrating with PAN-skeleton as solid polymer electrolyte prepared by a facile method. This polymer electrolyte with hierarchical architectures exhibits high ionic conductivity, large electrochemical windows, high degree flexibility, good flame-retardance ability, and thermal stability (workable at 80 °C). Additionally, it demonstrates superior compatibility and electrochemical stability toward metallic Li as well as LiFePO 4 cathode. The electrolyte/electrode interfaces are very stable even subjected to 4.5 V at charging state for long time. The LiFePO 4 /Li all-solid-state cells based on this electrolyte deliver high capacity, outstanding cycling stability, and superior rate capability better than those based on liquid electrolyte. This solid polymer electrolyte is eligible for next generation high energy density all-solid-state batteries.

In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Lin; Zhao, Ning; Ma, Haitao, E-mail: htma@dlut.edu.cn

2014-05-28

Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu{sub 6}Sn{sub 5} IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end aftermore » solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu{sub 6}Sn{sub 5} IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics.« less

Bead-bead interaction parameters in dissipative particle dynamics: Relation to bead-size, solubility parameter, and surface tension

NASA Astrophysics Data System (ADS)

Maiti, Amitesh; McGrother, Simon

2004-01-01

Dissipative particle dynamics (DPD) is a mesoscale modeling method for simulating equilibrium and dynamical properties of polymers in solution. The basic idea has been around for several decades in the form of bead-spring models. A few years ago, Groot and Warren [J. Chem. Phys. 107, 4423 (1997)] established an important link between DPD and the Flory-Huggins χ-parameter theory for polymer solutions. We revisit the Groot-Warren theory and investigate the DPD interaction parameters as a function of bead size. In particular, we show a consistent scheme of computing the interfacial tension in a segregated binary mixture. Results for three systems chosen for illustration are in excellent agreement with experimental results. This opens the door for determining DPD interactions using interfacial tension as a fitting parameter.

Development of a Front Tracking Method for Two-Phase Micromixing of Incompressible Viscous Fluids with Interfacial Tension in Solvent Extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yijie; Lim, Hyun-Kyung; de Almeida, Valmor F

2012-06-01

This progress report describes the development of a front tracking method for the solution of the governing equations of motion for two-phase micromixing of incompressible, viscous, liquid-liquid solvent extraction processes. The ability to compute the detailed local interfacial structure of the mixture allows characterization of the statistical properties of the two-phase mixture in terms of droplets, filaments, and other structures which emerge as a dispersed phase embedded into a continuous phase. Such a statistical picture provides the information needed for building a consistent coarsened model applicable to the entire mixing device. Coarsening is an undertaking for a future mathematical developmentmore » and is outside the scope of the present work. We present here a method for accurate simulation of the micromixing dynamics of an aqueous and an organic phase exposed to intense centrifugal force and shearing stress. The onset of mixing is the result of the combination of the classical Rayleigh- Taylor and Kelvin-Helmholtz instabilities. A mixing environment that emulates a sector of the annular mixing zone of a centrifugal contactor is used for the mathematical domain. The domain is small enough to allow for resolution of the individual interfacial structures and large enough to allow for an analysis of their statistical distribution of sizes and shapes. A set of accurate algorithms for this application requires an advanced front tracking approach constrained by the incompressibility condition. This research is aimed at designing and implementing these algorithms. We demonstrate verification and convergence results for one-phase and unmixed, two-phase flows. In addition we report on preliminary results for mixed, two-phase flow for realistic operating flow parameters.« less

Synthesis of POSS-based ionic conductors with low glass transition temperatures for efficient solid-state dye-sensitized solar cells.

PubMed

Zhang, Wei; Wang, Zhong-Sheng

2014-07-09

Replacing liquid-state electrolytes with solid-state electrolytes has been proven to be an effective way to improve the durability of dye-sensitized solar cells (DSSCs). We report herein the synthesis of amorphous ionic conductors based on polyhedral oligomeric silsesquioxane (POSS) with low glass transition temperatures for solid-state DSSCs. As the ionic conductor is amorphous and in the elastomeric state at the operating temperature of DSSCs, good pore filling in the TiO2 film and good interfacial contact between the solid-state electrolyte and the TiO2 film can be guaranteed. When the POSS-based ionic conductor containing an allyl group is doped with only iodine as the solid-state electrolyte without any other additives, power conversion efficiency of 6.29% has been achieved with good long-term stability under one-sun soaking for 1000 h.

Interfacial Force Field Characterization in a Constrained Vapor Bubble Thermosyphon

NASA Technical Reports Server (NTRS)

DasGupta, Sunando; Plawsky, Joel L.; Wayner, Peter C., Jr.

1995-01-01

Isothermal profiles of the extended meniscus in a quartz cuvette were measured in the earth's gravitational field using an image-analyzing interferometer that is based on computer-enhanced video microscopy of the naturally occurring interference fringes. These profiles are a function of the stress field. Experimentally, the augmented Young-Laplace equation is an excellent model for the force field at the solid-liquid-vapor interfaces for heptane and pentane menisci on quartz and tetradecane on SFL6. The effects of refractive indices of the solid and liquid on the measurement techniques were demonstrated. Experimentally obtained values of the disjoining pressure and dispersion constants were compared to those predicted from the Dzyaloshinskii - Lifshitz - Pilaevskii theory for an ideal surface and reasonable agreements were obtained. A parameter introduced gives a quantitative measurement of the closeness of the system to equilibrium. The nonequilibrium behavior of this parameter is also presented

Predicting the mixed-mode I/II spatial damage propagation along 3D-printed soft interfacial layer via a hyperelastic softening model

NASA Astrophysics Data System (ADS)

Liu, Lei; Li, Yaning

2018-07-01

A methodology was developed to use a hyperelastic softening model to predict the constitutive behavior and the spatial damage propagation of nonlinear materials with damage-induced softening under mixed-mode loading. A user subroutine (ABAQUS/VUMAT) was developed for numerical implementation of the model. 3D-printed wavy soft rubbery interfacial layer was used as a material system to verify and validate the methodology. The Arruda - Boyce hyperelastic model is incorporated with the softening model to capture the nonlinear pre-and post- damage behavior of the interfacial layer under mixed Mode I/II loads. To characterize model parameters of the 3D-printed rubbery interfacial layer, a series of scarf-joint specimens were designed, which enabled systematic variation of stress triaxiality via a single geometric parameter, the slant angle. It was found that the important model parameter m is exponentially related to the stress triaxiality. Compact tension specimens of the sinusoidal wavy interfacial layer with different waviness were designed and fabricated via multi-material 3D printing. Finite element (FE) simulations were conducted to predict the spatial damage propagation of the material within the wavy interfacial layer. Compact tension experiments were performed to verify the model prediction. The results show that the model developed is able to accurately predict the damage propagation of the 3D-printed rubbery interfacial layer under complicated stress-state without pre-defined failure criteria.

Stable Liquid Jets Bouncing off Soft Gels

NASA Astrophysics Data System (ADS)

Daniel, Dan; Yao, Xi; Aizenberg, Joanna

2018-01-01

A liquid jet can stably bounce off a sufficiently soft gel by following the contour of the dimple created upon impact. This new phenomenon is insensitive to the wetting properties of the gels and was observed for different liquids over a wide range of surface tensions, γ =24 -72 mN /m . In contrast, other jet rebound phenomena are typically sensitive to γ : only a high γ jet rebounds off a hard solid (e.g. superhydrophobic surface) and only a low γ jet bounces off a liquid bath. This is because an air layer must be stabilized between the two interfaces. For a soft gel, no air layer is necessary and the jet rebound remains stable even when there is direct liquid-gel contact.

The Role of Nanofillers in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Xu, Di

Polymer nanocomposites have been widely used in many fields. By introducing nanoparticles as fillers, researchers are able to get reinforced materials and new materials with novel properties, such as stronger mechanics, enhanced optical properties and improved conductivity. Though experimental techniques have rapidly advanced to enable better control of materials at atomic level, there is still a lack of a fundamental understanding of the dynamics and structure-properties relations in polymer nanocomposites. In this thesis, we use computer simulations to study the molecular structure and connections between microstate to macro properties of a variety of nanocomposites. Our goal is to understand the role of nanofillers in complex nanocomposite systems and to assist nanocomposite design. Nanoplatelet fillers, such as clays, have shown superior effects on the properties of polymer gels. We used molecular dynamic simulation to study nanoplatelet-filled composite gel system, in which short-range attraction exists between the polymer and nanoplatelet fillers. We show that the polymers and nanoplatelet fillers formed organic-inorganic networks with nanoplatelets acting as crosslink junctions, and the network eventually percolates the system as fillers reached a critical concentration. Stress auto-correlation and step-strain test were applied to investigate the mechanical properties; the results show the simulated composites changed from fluid-like to solid-like. The mechanical changes were consistent with the percolation transition, and gelation mechanism was therefore believed to be similar to those pure polymer physical gels. It was observed platelets aggregated into a local intercalation structure, which significantly differs from typical spherical fillers. This unique intercalation structure was examined by radial distribution function and ordering parameters. We discussed how intercalation would affect the properties of the platelet composites by comparing them with spherical fillers. Nanofillers have been widely used in polymer blends to improve the interfacial compatibility of otherwise immiscible polymers. In the second system, we investigated the interfacial behavior of binary polymer blends with different types of fillers. The interfacial tension and shear resistance were studied as a function of filler-polymer interaction, filler concentration and species of fillers. We found filler-polymer interaction is the key factor to improve the interfacial compatibility. The results show that nanofillers reduce both interfacial tension and interfacial slip at strong filler-polymer interaction. The effects of nanofillers however differ significantly from each other by their shapes. We analyzed the structure of nanofillers at the interface and their effects on the interfacial behaviors. The self-assembly of polymers into a columnar structure, while subject to a thin film environment, provides an economic route to fabricate polymer solar cell (PSC) with high conversion efficiency. In our work, we showed that two immiscible polymer segregates into to a percolating columnar structure when confined to a thin film. By adding nanofillers, with specific functionality, we can template the segregation of nanofillers to the polymer-polymer interface. We prove this process is surface tension driven and is a result that is particular for thin film geometries, where the thickness is under critical value. The results provide a theoretical basis for the column structure forming in a self-assembled PSC system, and can help to select polymer candidates that optimize PSC efficiency. These studies serve as theoretical guideline for engineering novel nanocomposites, and could lead to the design of materials with new and improved properties.

Effect of Surface Tension Anisotropy and Welding Parameters on Initial Instability Dynamics During Solidification: A Phase-Field Study

NASA Astrophysics Data System (ADS)

Yu, Fengyi; Wei, Yanhong

2018-05-01

The effects of surface tension anisotropy and welding parameters on initial instability dynamics during gas tungsten arc welding of an Al-alloy are investigated by a quantitative phase-field model. The results show that the surface tension anisotropy and welding parameters affect the initial instability dynamics in different ways during welding. The surface tension anisotropy does not influence the solute diffusion process but does affect the stability of the solid/liquid interface during solidification. The welding parameters affect the initial instability dynamics by varying the growth rate and thermal gradient. The incubation time decreases, and the initial wavelength remains stable as the welding speed increases. When welding power increases, the incubation time increases and the initial wavelength slightly increases. Experiments were performed for the same set of welding parameters used in modeling, and the results of the experiments and simulations were in good agreement.

Fingering patterns in magnetic fluids: Perturbative solutions and the stability of exact stationary shapes

NASA Astrophysics Data System (ADS)

Anjos, Pedro H. A.; Lira, Sérgio A.; Miranda, José A.

2018-04-01

We examine the formation of interfacial patterns when a magnetic liquid droplet (ferrofluid, or a magnetorheological fluid), surrounded by a nonmagnetic fluid, is subjected to a radial magnetic field in a Hele-Shaw cell. By using a vortex-sheet formalism, we find exact stationary solutions for the fluid-fluid interface in the form of n -fold polygonal shapes. A weakly nonlinear, mode-coupling method is then utilized to find time-evolving perturbative solutions for the interfacial patterns. The stability of such nonzero surface tension exact solutions is checked and discussed, by trying to systematically approach the exact stationary shapes through perturbative solutions containing an increasingly larger number of participating Fourier modes. Our results indicate that the exact stationary solutions of the problem are stable, and that a good matching between exact and perturbative shape solutions is achieved just by using a few Fourier modes. The stability of such solutions is substantiated by a linearization process close to the stationary shape, where a system of mode-coupling equations is diagonalized, determining the eigenvalues which dictate the stability of a fixed point.

In-Situ Quantification of the Interfacial Rheological Response of Bacterial Biofilms to Environmental Stimuli

PubMed Central

Rühs, Patrick A.; Böni, Lukas; Fuller, Gerald G.; Inglis, R. Fredrik; Fischer, Peter

2013-01-01

Understanding the numerous factors that can affect biofilm formation and stability remain poorly understood. One of the major limitations is the accurate measurement of biofilm stability and cohesiveness in real-time when exposed to changing environmental conditions. Here we present a novel method to measure biofilm strength: interfacial rheology. By culturing a range of bacterial biofilms on an air-liquid interface we were able to measure their viscoelastic growth profile during and after biofilm formation and subsequently alter growth conditions by adding surfactants or changing the nutrient composition of the growth medium. We found that different bacterial species had unique viscoelastic growth profiles, which was also highly dependent on the growth media used. We also found that we could reduce biofilm formation by the addition of surfactants or changing the pH, thereby altering the viscoelastic properties of the biofilm. Using this technique we were able to monitor changes in viscosity, elasticity and surface tension online, under constant and varying environmental conditions, thereby providing a complementary method to better understand the dynamics of both biofilm formation and dispersal. PMID:24244319

Comparison of Surfactants Used to Prepare Aqueous Perfluoropentane Emulsions for Pharmaceutical Applications

PubMed Central

Kandadai, Madhuvanthi A.; Mohan, Praveena; Lin, Genyao; Butterfield, Anthony; Skliar, Mikhail; Magda, Jules J.

2010-01-01

Perfluoropentane (PFP), a highly hydrophobic, non-toxic, non-carcinogenic fluoroalkane, has generated much interest in biomedical applications, including occlusion therapy and controlled drug delivery. For most of these applications, the dispersion within aqueous media of a large quantity of PFP droplets of the proper size is critically important. Surprisingly, the interfacial tension of PFP against water in the presence of surfactants used to stabilize the emulsion has rarely, if ever, been measured. In this study, we report the interfacial tension of PFP in the presence of surfactants used in previous studies to produce emulsions for biomedical applications: polyethylene oxide-co-polylactic acid (PEO-PLA, and polyethylene oxide-co-poly-ε-caprolactone (PEO-PCL). Since both of these surfactants are uncharged diblock copolymers that rely on the mechanism of steric stabilization, we also investigate for comparison’s sake use of the small molecule cationic surfactant cetyl trimethyl ammonium bromide (CTAB), and the much larger protein surfactant bovine serum albumin (BSA). The results presented here complement previous reports of the PFP droplet size distribution, and will be useful for determining to what extent the interfacial tension value can be used to control the mean PFP droplet size. PMID:20218695

A study on the dynamic interfacial tension of acidic crude oil/alkali (alkali-polymer) systems--

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Y.; Yang, P.; Qin, T.

1989-01-01

This paper describes the investigation of dynamic interfacial tension (DIFT) between the acidic Liao-He crude oil and two types of brine: a simple alkali system and a combined alkali-polymer system. It was found that interfacial tension (IFT) changed markedly with time and that the history of DIFT depended upon the concentration of alkali in the brine. The experimental results also showed that the IFT dropped dramatically as soon as the fresh oil contacted brine causing spontaneous emulsification to occur. The steady-state value of DIFT {gamma} st can be lower with the combined alkali-polymer system than with the simple alkali system.more » The results indicate that biopolymer is more effective than partially hydrolyzed polyacrylamide (PHPAM) for lowering {gamma} st and that Na{sub 2}Co{sub 1} causes a lower {gamma} st than NaOH in the combined alkali-polymer system. Optimized formulations containing Na{sub 2}CO{sub 3} added biopolymer can reduce {gamma} st by two orders of magnitude, and PHPAM can reduce {gamma} st by one order of magnitude. The interaction between alkali and polymer in the combined alkali-polymer system is discussed.« less

Microscopic characterization of tension wood cell walls of Japanese beech (Fagus crenata) treated with ionic liquids.

PubMed

Kanbayashi, Toru; Miyafuji, Hisashi

2016-09-01

Tension wood that is an abnormal part formed in angiosperms has been barely used for wood industry. In this study, to utilize the tension wood effectively by means of liquefaction using ionic liquid, we performed morphological and topochemical determination of the changes in tension wood of Japanese beech (Fagus crenata) during ionic liquid treatment at the cellular level using light microscopy, scanning electron microscopy and confocal Raman microscopy. Ionic liquid treatment induced cell wall swelling in tension wood. Changes in the tissue morphology treated with ionic liquids were different between normal wood and tension wood, moreover the types of ionic liquids. The ionic liquid 1-ethyl-3-methylimidazolium chloride liquefied gelatinous layers rapidly, whereas 1-ethylpyridinium bromide liquefied slowly but delignified selectively. These novel insights into the deconstruction behavior of tension wood cell walls during ionic liquid treatment provide better understanding of the liquefaction mechanism. The obtained knowledge will contribute to development of an effective chemical processing of tension wood using ionic liquids and lead to efficient use of wood resources. Copyright © 2016 Elsevier Ltd. All rights reserved.

Laser ultrasonic investigations of vertical Bridgman crystal growth

NASA Astrophysics Data System (ADS)

Queheillalt, Douglas Ted

The many difficulties associated with the growth of premium quality CdTe and (Cd,Zn)Te alloys has stimulated an interest in the development of a non-invasive ultrasonic approach to monitor critical growth parameters such as the solid-liquid interface position and shape during vertical Bridgman growth. This sensor methodology is based upon the recognition that in most materials, the ultrasonic velocity (and the elastic stiffness constants that control it) of the solid and liquid phases are temperature dependent and an abrupt increase of the longitudinal wave velocity occurs upon solidification. The laser ultrasonic approach has also been used to measure the ultrasonic velocity of solid and liquid Cd0.96Zn0.04Te as a function of temperature up to 1140°C. Using longitudinal and shear wave velocity values together with data for the temperature dependent density allowed a complete evaluation of the temperature dependent single crystal elastic stiffness constants for solid and the adiabatic bulk modulus for liquid Cd0.96Zn0.04 Te. It was found that the ultrasonic velocities exhibited a strong monotonically decreasing function of temperature in the solid and liquid phases and the longitudinal wave indicated an abrupt almost 50% decrease upon melting. Because ray propagation in partially solidified bodies is complex and defines the sensing methodology, a ray tracing algorithm has been developed to analyze two-dimensional wave propagation in the diametral plane of cylindrical solid-liquid interfaces. Ray path, wavefront and time-of-flight (TOF) projections for rays that travel from a source to an arbitrarily positioned receiver on the diametral plane have been calculated and compared to experimentally measured data on a model liquid-solid interface. The simulations and the experimental results reveal that the interfacial region can be identified from transmission TOF data and when used in conjunction with a nonlinear least squares reconstruction algorithm, the interface geometry (i.e. axial location and shape) can be precisely recovered and the ultrasonic velocities of both solid and liquid phases obtained. To gain insight into the melting and solidification process, a single zone VB growth furnace was integrated with the laser ultrasonic sensor system and used to monitor the melting-solidification and directional solidification characteristics of Cd0.96Zn 0.04Te.

Understanding the role of ion interactions in soluble salt flotation with alkylammonium and alkylsulfate collectors.

PubMed

Ozdemir, Orhan; Du, Hao; Karakashev, Stoyan I; Nguyen, Anh V; Celik, M S; Miller, Jan D

2011-03-15

There is anecdotal evidence for the significant effects of salt ions on the flotation separation of minerals using process water of high salt content. Examples include flotation of soluble salt minerals such as potash, trona and borax in brine solutions using alkylammonium and alkylsulfate collectors such as dodecylamine hydrochloride and sodium dodecylsulfate. Although some of the effects are expected, some do not seem to be encompassed by classical theories of colloid science. Several experimental and modeling techniques for determining solution viscosity, surface tension, bubble-particle attachment time, contact angle, and molecular dynamics simulation have been used to provide further information on air-solution and solid-solution interfacial phenomena, especially with respect to the interfacial water structure due to the presence of dissolved ions. In addition atomic force microscopy, and sum frequency generation vibrational spectroscopy have been used to provide further information on surface states. These studies indicate that the ion specificity effect is the most significant factor influencing flotation in brine solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

Homogeneous nucleation and droplet growth in nitrogen. M.S. Thesis

NASA Technical Reports Server (NTRS)

Dotson, E. H.

1983-01-01

A one dimensional computer model of the homogeneous nucleation process and growth of condensate for nitrogen flows over airfoils is developed to predict the onset of condensation and thus to be able to take advantage of as much of Reynolds capability of cryogenic tunnels as possible. Homogeneous nucleation data were taken using a DFVLR CAST-10 airfoil in the 0.3-Meter Transonic Cryogenic Tunnel and are used to evaluate the classical liquid droplet theory and several proposed corrections to it. For predicting liquid nitrogen condensation effects, use of the arbitrary Tolman constant of 0.25 x 250 billionth m or the Reiss or Kikuchi correction agrees with the CAST-10 data. Because no solid nitrogen condensation were found experimentally during the CAST-10 experiments, earlier nozzle data are used to evaluate corrections to the classical liquid droplet theory in the lower temperature regime. A theoretical expression for the surface tension of solid nitrogen is developed.

The Gas-Absorption/Chemical-Reaction Method for Measuring Air-Water Interfacial Area in Natural Porous Media

NASA Astrophysics Data System (ADS)

Lyu, Ying; Brusseau, Mark L.; El Ouni, Asma; Araujo, Juliana B.; Su, Xiaosi

2017-11-01

The gas-absorption/chemical-reaction (GACR) method used in chemical engineering to quantify gas-liquid interfacial area in reactor systems is adapted for the first time to measure the effective air-water interfacial area of natural porous media. Experiments were conducted with the GACR method, and two standard methods (X-ray microtomographic imaging and interfacial partitioning tracer tests) for comparison, using model glass beads and a natural sand. The results of a series of experiments conducted under identical conditions demonstrated that the GACR method exhibited excellent repeatability for measurement of interfacial area (Aia). Coefficients of variation for Aia were 3.5% for the glass beads and 11% for the sand. Extrapolated maximum interfacial areas (Am) obtained with the GACR method were statistically identical to independent measures of the specific solid surface areas of the media. For example, the Am for the glass beads is 29 (±1) cm-1, compared to 32 (±3), 30 (±2), and 31 (±2) cm-1 determined from geometric calculation, N2/BET measurement, and microtomographic measurement, respectively. This indicates that the method produced accurate measures of interfacial area. Interfacial areas determined with the GACR method were similar to those obtained with the standard methods. For example, Aias of 47 and 44 cm-1 were measured with the GACR and XMT methods, respectively, for the sand at a water saturation of 0.57. The results of the study indicate that the GACR method is a viable alternative for measuring air-water interfacial areas. The method is relatively quick, inexpensive, and requires no specialized instrumentation compared to the standard methods.

Temperature anisotropy at equilibrium reveals nonlocal entropic contributions to interfacial properties.

PubMed

Wilhelmsen, Øivind; Trinh, Thuat T; Lervik, Anders

2018-01-01

Density gradient theory for fluids has played a key role in the study of interfacial phenomena for a century. In this work, we revisit its fundamentals by examining the vapor-liquid interface of argon, represented by the cut and shifted Lennard-Jones fluid. The starting point has traditionally been a Helmholtz energy functional using mass densities as arguments. By using rather the internal energy as starting point and including the entropy density as an additional argument, following thereby the phenomenological approach from classical thermodynamics, the extended theory suggests that the configurational part of the temperature has different contributions from the parallel and perpendicular directions at the interface, even at equilibrium. We find a similar anisotropy by examining the configurational temperature in molecular dynamics simulations and obtain a qualitative agreement between theory and simulations. The extended theory shows that the temperature anisotropy originates in nonlocal entropic contributions, which are currently missing from the classical theory. The nonlocal entropic contributions discussed in this work are likely to play a role in the description of both equilibrium and nonequilibrium properties of interfaces. At equilibrium, they influence the temperature- and curvature-dependence of the surface tension. Across the vapor-liquid interface of the Lennard Jones fluid, we find that the maximum in the temperature anisotropy coincides precisely with the maximum in the thermal resistivity relative to the equimolar surface, where the integral of the thermal resistivity gives the Kapitza resistance. This links the temperature anisotropy at equilibrium to the Kapitza resistance of the vapor-liquid interface at nonequilibrium.

Temperature anisotropy at equilibrium reveals nonlocal entropic contributions to interfacial properties

NASA Astrophysics Data System (ADS)

Wilhelmsen, Øivind; Trinh, Thuat T.; Lervik, Anders

2018-01-01

Density gradient theory for fluids has played a key role in the study of interfacial phenomena for a century. In this work, we revisit its fundamentals by examining the vapor-liquid interface of argon, represented by the cut and shifted Lennard-Jones fluid. The starting point has traditionally been a Helmholtz energy functional using mass densities as arguments. By using rather the internal energy as starting point and including the entropy density as an additional argument, following thereby the phenomenological approach from classical thermodynamics, the extended theory suggests that the configurational part of the temperature has different contributions from the parallel and perpendicular directions at the interface, even at equilibrium. We find a similar anisotropy by examining the configurational temperature in molecular dynamics simulations and obtain a qualitative agreement between theory and simulations. The extended theory shows that the temperature anisotropy originates in nonlocal entropic contributions, which are currently missing from the classical theory. The nonlocal entropic contributions discussed in this work are likely to play a role in the description of both equilibrium and nonequilibrium properties of interfaces. At equilibrium, they influence the temperature- and curvature-dependence of the surface tension. Across the vapor-liquid interface of the Lennard Jones fluid, we find that the maximum in the temperature anisotropy coincides precisely with the maximum in the thermal resistivity relative to the equimolar surface, where the integral of the thermal resistivity gives the Kapitza resistance. This links the temperature anisotropy at equilibrium to the Kapitza resistance of the vapor-liquid interface at nonequilibrium.

Core-Shell Fe1- xS@Na2.9PS3.95Se0.05 Nanorods for Room Temperature All-Solid-State Sodium Batteries with High Energy Density.

PubMed

Wan, Hongli; Mwizerwa, Jean Pierre; Qi, Xingguo; Liu, Xin; Xu, Xiaoxiong; Li, Hong; Hu, Yong-Sheng; Yao, Xiayin

2018-03-27

High ionic conductivity electrolyte and intimate interfacial contact are crucial factors to realize high-performance all-solid-state sodium batteries. Na 2.9 PS 3.95 Se 0.05 electrolyte with reduced particle size of 500 nm is first synthesized by a simple liquid-phase method and exhibits a high ionic conductivity of 1.21 × 10 -4 S cm -1 , which is comparable with that synthesized with a solid-state reaction. Meanwhile, a general interfacial architecture, that is, Na 2.9 PS 3.95 Se 0.05 electrolyte uniformly anchored on Fe 1- x S nanorods, is designed and successfully prepared by an in situ liquid-phase coating approach, forming core-shell structured Fe 1- x S@Na 2.9 PS 3.95 Se 0.05 nanorods and thus realizing an intimate contact interface. The Fe 1- x S@Na 2.9 PS 3.95 Se 0.05 /Na 2.9 PS 3.95 Se 0.05 /Na all-solid-state sodium battery demonstrates high specific capacity and excellent rate capability at room temperature, showing reversible discharge capacities of 899.2, 795.5, 655.1, 437.9, and 300.4 mAh g -1 at current densities of 20, 50, 100, 150, and 200 mA g -1 , respectively. The obtained all-solid-state sodium batteries show very high energy and power densities up to 910.6 Wh kg -1 and 201.6 W kg -1 based on the mass of Fe 1- x S at current densities of 20 and 200 mA g -1 , respectively. Moreover, the reaction mechanism of Fe 1- x S is confirmed by means of ex situ X-ray diffraction techniques, showing that partially reversible reaction occurs in the Fe 1- x S electrode after the second cycle, which gives the obtained all-solid-state sodium battery an exceptional cycling stability, exhibiting a high capacity of 494.3 mAh g -1 after cycling at 100 mA g -1 for 100 cycles. This contribution provides a strategy for designing high-performance room temperature all-solid-state sodium battery.

A deformable surface model for real-time water drop animation.

PubMed

Zhang, Yizhong; Wang, Huamin; Wang, Shuai; Tong, Yiying; Zhou, Kun

2012-08-01

A water drop behaves differently from a large water body because of its strong viscosity and surface tension under the small scale. Surface tension causes the motion of a water drop to be largely determined by its boundary surface. Meanwhile, viscosity makes the interior of a water drop less relevant to its motion, as the smooth velocity field can be well approximated by an interpolation of the velocity on the boundary. Consequently, we propose a fast deformable surface model to realistically animate water drops and their flowing behaviors on solid surfaces. Our system efficiently simulates water drop motions in a Lagrangian fashion, by reducing 3D fluid dynamics over the whole liquid volume to a deformable surface model. In each time step, the model uses an implicit mean curvature flow operator to produce surface tension effects, a contact angle operator to change droplet shapes on solid surfaces, and a set of mesh connectivity updates to handle topological changes and improve mesh quality over time. Our numerical experiments demonstrate a variety of physically plausible water drop phenomena at a real-time rate, including capillary waves when water drops collide, pinch-off of water jets, and droplets flowing over solid materials. The whole system performs orders-of-magnitude faster than existing simulation approaches that generate comparable water drop effects.

Synthesis and properties evaluation of sulfobetaine surfactant with double hydroxyl

NASA Astrophysics Data System (ADS)

Zhou, Ming; Luo, Gang; Zhang, Ze; Li, Sisi; Wang, Chengwen

2017-09-01

A series of sulfobetaine surfactants {N-[(3-alkoxy-2-hydroxyl)propoxy] ethyl-N,N-dimethyl-N-(2-hydroxyl)propyl sulfonate} ammonium chloride were synthesized with raw materials containing linear saturated alcohol, N,N-dimethylethanolamine, sodium 3-chloro-2-hydroxyl propane sulfonic acid and epichlorohydrin. The molecule structures of sulfobetaine surfactants were characterized by FTIR, 1HNMR and elemental analysis. Surface tension measurements can provide us information about the surface tension at the CMC (γCMC), pC20, Γmax and Amin. The pC20 values of sulfobetaine surfactants increase with the hydrophobic chain length increasing. Amin values of the surfactants decrease with increasing hydrophobic chain length from 10 to 14. The critical micelle concentration (CMC) and surface tension (γCMC) values of the sulfobetaine surfactants decrease with increasing hydrophobic chain length from 10 to 16. The lipophilicity of surfactant was enhanced with the increase of the carbon chain, however, the ability of anti-hard water was weakened. The minimum oil/water interfacial tension of four kinds of sulfobetaine surfactants is 10-2-10-3 mN/m magnitude, which indicates that the synthesized bis-hydroxy sulfobetaine surfactants have a great ability to reduce interfacial tension in the surfactant flooding system. The surface tension (γCMC) values of synthesized surfactants were lower compared with conventional anionic surfactant sodium dodecyl sulfonate.

Methods of Fabricating a Layer of Metallic Glass-Based Material Using Immersion and Pouring Techniques

NASA Technical Reports Server (NTRS)

Hofmann, Douglas (Inventor)

2015-01-01

Systems and methods in accordance with embodiments of the invention implement layers of metallic glass-based materials. In one embodiment, a method of fabricating a layer of metallic glass includes: applying a coating layer of liquid phase metallic glass to an object, the coating layer being applied in a sufficient quantity such that the surface tension of the liquid phase metallic glass causes the coating layer to have a smooth surface; where the metallic glass has a critical cooling rate less than 1000 K/s; and cooling the coating layer of liquid phase metallic glass to form a layer of solid phase metallic glass.

Jamming and liquidity in 3D cancer cell aggregates

NASA Astrophysics Data System (ADS)

Oswald, Linda; Grosser, Steffen; Lippoldt, Jürgen; Pawlizak, Steve; Fritsch, Anatol; KäS, Josef A.

Traditionally, tissues are treated as simple liquids, which holds for example for embryonic tissue. However, recent experiments have shown that this picture is insufficient for other tissue types, suggesting possible transitions to solid-like behavior induced by cellular jamming. The coarse-grained self-propelled Voronoi (SPV) model predicts such a transition depending on cell shape which is thought to arise from an interplay of cell-cell adhesion and cortical tension. We observe non-liquid behavior in 3D breast cancer spheroids of varying metastatic potential and correlate single cell shapes, single cell dynamics and collective dynamic behavior of fusion and segregation experiments via the SPV model.

A Novel Charged Medium Consisting of Gas-Liquid Interfacial Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaneko, Toshiro; Hatakeyama, Rikizo

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we succeed in creating the reactive gas (plasmas)--liquid (ionic liquids) interfacial field under a low gas pressure condition, where the plasma ion behavior can be controlled. The effects of the plasma ion irradiation on the liquid medium are quantitatively revealed for the first time. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the gas-liquid interfacial plasma are investigated by changing a polarity of the electrode in the liquid to evaluate the plasma-liquid interactions. Thesemore » results would contribute to synthesizing the metal nanoparticles with carbon nanotubes as a template in the ionic liquid. It is found that the high density, mono-dispersed, and isolated metal nanoparticles are synthesized between or inside the carbon nanotubes by controlling the gas-liquid interfacial plasmas. Furthermore, we can form novel nano-bio composite materials, such as DNA encapsulated carbon nanotubes using the plasma ion irradiation method in an electrolyte plasma with DNA, and demonstrate modifications of the electrical properties of the carbon nanotubes depending on the kinds of encapsulated DNA for the first time.« less

From Folding to Function: Design of a New Switchable Biosurfactant Protein.

PubMed

Zhao, Chun-Xia; Dwyer, Mirjana Dimitrijev; Yu, Lei; Middelberg, Anton P J

2017-03-03

A new anionic biosurfactant protein (SP16) capable of tuning foaming behaviour by pH or salt has been designed. This biosurfactant exhibits unique foaming behaviour with high sensitivity to pH. A good level of foaming was observed at pH 2 but not at pH 3. A further increase by one pH unit to pH 4 restored good foaming. At pH 5-8, SP16 again showed low foaming propensity, whereas the presence of salt (NaCl) was able to restore foaming again. Interfacial tension and circular dichroism investigations revealed the foaming control mechanism. The high negative charge (-16.6) at pH 6 and above restricted the ability of SP16 to fold into an α-helical conformation and also restricted surface activity. For pH 5 (-13.6), even though SP16 folds in bulk to give α-helical structure, the high charge inhibited adsorption at the air-water interface, resulting in a significant lag time of about 150-200 sec to achieve a decrease in interfacial tension. In contrast to its low foaming behaviour at pH 5-8, the presence of salt (NaCl) was found to effectively screen negative charge, thus leading to its folding and a decrease of interfacial tension. This new design offers a new strategy to control foaming behaviour, and elaborates a clear link between charge, structure and interfacial activity for biosurfactants. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphology Evolution of Polymer Blends under Intense Shear During High Speed Thin-Wall Injection Molding.

PubMed

Zhou, Yi; Yu, Feilong; Deng, Hua; Huang, Yajiang; Li, Guangxian; Fu, Qiang

2017-06-29

The morphology evolution under shear during different processing is indeed an important issue regarding the phase morphology control as well as final physical properties of immiscible polymer blends. High-speed thin wall injection molding (HSTWIM) has recently been demonstrated as an effective method to prepare alternating multilayered structure. To understand the formation mechanism better and explore possible phase morphology for different blends under HSTWIM, the relationship between the morphology evolution of polymer blends based on polypropylene (PP) under HSTWIM and some intrinsic properties of polymer blends, including viscosity ratio, interfacial tension, and melt elasticity, is systematically investigated in this study. Blends based on PP containing polyethylene (PE), ethylene vinyl alcohol copolymer (EVOH), and polylactic acid (PLA) are used as examples. Compatibilizer has also been added into respective blends to alter their interfacial interaction. It is demonstrated that dispersed phase can be deformed into a layered-like structure if interfacial tension, viscosity ratio, and melt elasticity are relatively small. While some of these values are relatively large, these dispersed droplets are not easily deformed under HSTWIM, forming ellipsoidal or fiber-like structure. The addition of a moderate amount of compatibilizer into these blends is shown to be able to reduce interfacial tension and the size of dispersed phase, thus, allowing more deformation on the dispersed phase. Such a study could provide some guidelines on phase morphology control of immiscible polymer blends under shear during various processing methods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Mingyuan; Mead, James; Wu, Yueqin

In this study, a nanoindentation-based microcantilever bending technique was utilized to investigate the interfacial properties of a β-Mg{sub 17}Al{sub 12}/AZ91 Mg alloy film/substrate system under tensile loading conditions. Finite element analysis (FEA) was first undertaken to optimise the design of cantilever structures for inducing high tensile stresses at the interface. Cantilevers consisting of a necked region or notch at the interface were determined to be the most successful designs. Microcantilevers containing the β-Mg{sub 17}Al{sub 12}/AZ91 interface were then made using focused ion beam (FIB) milling technique. Necks were made in the cantilevers to intensify the tension at the interface andmore » notches were used to introduce a stress concentration to the interface. During bending, the cantilevers were deflected to failure. Subsequent analysis of the deformed cantilevers using electron microscopies revealed that plastic deformation, and subsequent ductile rupture, of the AZ91 phase was the dominant failure mechanism. When the β-Mg{sub 17}Al{sub 12}/AZ91 film/substrate system was subjected to tension, the softer AZ91 phase failed prior to interfacial delamination, demonstrating that the strength of the interface exceeded the stresses that caused ductile failure in the substrate material. - Highlights: •Microcantilever bending was used to study the property of film/substrate interface. •FEA was used to optimise cantilever design for achieving high interfacial tension. •The intermetallic coatings on AZ91 substrate have strong interfacial adhesion.« less

Molecular origin of high free energy barriers for alkali metal ion transfer through ionic liquid-graphene electrode interfaces.

PubMed

Ivaništšev, Vladislav; Méndez-Morales, Trinidad; Lynden-Bell, Ruth M; Cabeza, Oscar; Gallego, Luis J; Varela, Luis M; Fedorov, Maxim V

2016-01-14

In this work we study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ion-electrode interactions in ionic liquids. We compare the interfacial behaviour of Li(+) and K(+) at a charged graphene sheet in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, and its mixtures with lithium and potassium tetrafluoroborate salts. Our results show that there are dense interfacial solvation structures in these electrolytes that lead to the formation of high free energy barriers for these alkali metal cations between the bulk and direct contact with the negatively charged surface. We show that the stronger solvation of Li(+) in the ionic liquid leads to the formation of significantly higher interfacial free energy barriers for Li(+) than for K(+). The high free energy barriers observed in our simulations can explain the generally high interfacial resistance in electrochemical storage devices that use ionic liquid-based electrolytes. Overcoming these barriers is the rate-limiting step in the interfacial transport of alkali metal ions and, hence, appears to be a major drawback for a generalised application of ionic liquids in electrochemistry. Some plausible strategies for future theoretical and experimental work for tuning them are suggested.