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Sample records for additional interfacial force

  1. Additional interfacial force in lattice Boltzmann models for incompressible multiphase flows.

    PubMed

    Li, Q; Luo, K H; Gao, Y J; He, Y L

    2012-02-01

    The existing lattice Boltzmann models for incompressible multiphase flows are mostly constructed with two distribution functions: one is the order parameter distribution function, which is used to track the interface between different phases, and the other is the pressure distribution function for solving the velocity field. In this paper, it is shown that in these models the recovered momentum equation is inconsistent with the target one: an additional force is included in the recovered momentum equation. The additional force has the following features. First, it is proportional to the macroscopic velocity. Second, it is zero in every single-phase region but is nonzero in the interface. Therefore it can be interpreted as an interfacial force. To investigate the effects of the additional interfacial force, numerical simulations are carried out for the problem of Rayleigh-Taylor instability, droplet splashing on a thin liquid film, and the evolution of a falling droplet under gravity. Numerical results demonstrate that, with the increase of the velocity or the Reynolds number, the additional interfacial force will gradually have an important influence on the interface and affect the numerical accuracy. PMID:22463354

  2. Sinusoidal Forcing of Interfacial Films

    NASA Astrophysics Data System (ADS)

    Rasheed, Fayaz; Raghunandan, Aditya; Hirsa, Amir; Lopez, Juan

    2015-11-01

    Fluid transport, in vivo, is accomplished via pumping mechanisms of the heart and lungs, which results in biological fluids being subjected to oscillatory shear. Flow is known to influence biological macromolecules, but predicting the effect of shear is incomplete without also accounting for the influence of complex interfaces ubiquitous throughout the body. Here, we investigated the oscillatory response of the structure of aqueous interfacial films using a cylindrical knife edge viscometer. Vitamin K1 was used as a model monolayer because its behaviour has been thoroughly quantified and it doesn't show any measurable hysteresis. The monolayer was subjected to sinusoidal forcing under varied conditions of surface concentrations, periodic frequencies, and knife edge amplitudes. Particle Image Velocimetry(PIV) data was collected using Brewster Angle Microscopy(BAM), revealing the influence of oscillatory interfacial shear stress on the monolayer. Insights were gained as to how the velocity profile dampens at specific distances from the knife edge contact depending on the amplitude, frequency, and concentration of Vitamin K1. Supported by NNX13AQ22G, National Aeronautics and Space Administration.

  3. Cantilever based optical interfacial force microscope

    NASA Astrophysics Data System (ADS)

    Bonander, Jeremy R.; Kim, Byung I.

    2008-03-01

    We developed a cantilever based optical interfacial force microscopy (COIFM) that employs a microactuated silicon cantilever and optical detection method to establish the measurement of the single molecular interactions using the force feedback technique. Through the direct measurement of the COIFM force-distance curves, we have demonstrated that the COIFM is capable of unveiling structural and mechanical information on interfacial water at the single molecular level over all distances between two hydrophilic surfaces.

  4. Interfacial force sensor with force-feedback control

    SciTech Connect

    Joyce, S.A.; Houston, J.E.; Smith, B.K.

    1990-01-01

    A new interfacial force microscope capable of measuring the forces between two surfaces over the entire range of surface separations, up to contact, has been developed. The design is centered around a differential capacitance displacement sensor where the common capacitor plate is supported by torsion bars. A force-feedback control system balances the interfacial forces at the sensor, maintaining the common capacitor plate at its rest position. This control eliminates the instability which occurs with the conventional cantilever-based force sensors when the attractive force gradient exceeds the mechanical stiffness of the cantilever. The ability to measure interfacial forces at surface separations smaller than this instability point using the feedback control is demonstrated. 11 refs., 3 figs.

  5. Simultaneous measurement of normal and friction forces using a cantilever-based optical interfacial force microscope

    NASA Astrophysics Data System (ADS)

    Kim, Byung I.; Bonander, Jeremy R.; Rasmussen, Jared A.

    2011-05-01

    We measured normal and friction forces simultaneously using a recently developed cantilever-based optical interfacial force microscope technique for studies of interfacial structures and mechanical properties of nanoscale materials. We derived how the forces can be incorporated into the detection signal using the classical Euler equation for beams. A lateral modulation with the amplitude of nanometers was applied to create the friction forces between tip and sample. We demonstrated its capability by measuring normal and friction forces of interfacial water at the molecular scale over all distance ranges.

  6. Simultaneous measurement of normal and friction forces using a cantilever-based optical interfacial force microscope.

    PubMed

    Kim, Byung I; Bonander, Jeremy R; Rasmussen, Jared A

    2011-05-01

    We measured normal and friction forces simultaneously using a recently developed cantilever-based optical interfacial force microscope technique for studies of interfacial structures and mechanical properties of nanoscale materials. We derived how the forces can be incorporated into the detection signal using the classical Euler equation for beams. A lateral modulation with the amplitude of nanometers was applied to create the friction forces between tip and sample. We demonstrated its capability by measuring normal and friction forces of interfacial water at the molecular scale over all distance ranges. PMID:21639511

  7. Investigation of relationship between interfacial electroadhesive force and surface texture

    NASA Astrophysics Data System (ADS)

    Guo, J.; Tailor, M.; Bamber, T.; Chamberlain, M.; Justham, L.; Jackson, M.

    2016-01-01

    A novel investigation into the relationship between the obtainable interfacial electroadhesive forces and different surface textures is presented in this paper. Different surface textures were generated then characterized based on a recognized areal-based non-contact surface texture measurement platform and procedure. An advanced electroadhesive force measurement platform and procedure were then implemented to measure the obtainable electroadhesive forces on those different surface textures. The results show that the obtained interfacial electroadhesive forces increase with decreasing Sq (root mean square height) value of the substrate surface provided that the difference in Sq between the different substrates is over 5 μm. Also, the higher the applied voltage, the larger the relative increase in electroadhesive forces observed. However, when the difference of Sq value between different substrate surfaces is below 2 μm, the obtained interfacial electroadhesive forces do not necessarily increase with decreasing Sq. Furthermore, the obtainable electroadhesive forces are not necessarily the same when the Sq value of two substrate surfaces are the same due to the fact that the direction of the surface texture plays an important role in achieving electroadhesive forces.

  8. Non-contact atomic-level interfacial force microscopy

    SciTech Connect

    Houston, J.E.; Fleming, J.G.

    1997-02-01

    The scanning force microscopies (notably the Atomic Force Microscope--AFM), because of their applicability to nearly all materials, are presently the most widely used of the scanning-probe techniques. However, the AFM uses a deflection sensor to measure sample/probe forces which suffers from an inherent mechanical instability that occurs when the rate of change of the force with respect to the interfacial separation becomes equal to the spring constant of the deflecting member. This instability dramatically limits the breadth of applicability of AFM-type techniques to materials problems. In the course of implementing a DOE sponsored basic research program in interfacial adhesion, a self-balancing force sensor concept has been developed and incorporated into an Interfacial Force Microscopy (IFM) system by Sandia scientists. This sensor eliminates the instability problem and greatly enhances the applicability of the scanning force-probe technique to a broader range of materials and materials parameters. The impact of this Sandia development was recognized in 1993 by a Department of Energy award for potential impact on DOE programs and by an R and D 100 award for one of the most important new products of 1994. However, in its present stage of development, the IFM is strictly a research-level tool and a CRADA was initiated in order to bring this sensor technology into wide-spread availability by making it accessible in the form of a commercial instrument. The present report described the goals, approach and results of this CRADA effort.

  9. Intermolecular and interfacial forces: Elucidating molecular mechanisms using chemical force microscopy

    NASA Astrophysics Data System (ADS)

    Ashby, Paul David

    Investigation into the origin of forces dates to the early Greeks. Yet, only in recent decades have techniques for elucidating the molecular origin of forces been developed. Specifically, Chemical Force Microscopy uses the high precision and nanometer scale probe of Atomic Force Microscopy to measure molecular and interfacial interactions. This thesis presents the development of many novel Chemical Force Microscopy techniques for measuring equilibrium and time-dependant force profiles of molecular interactions, which led to a greater understanding of the origin of interfacial forces in solution. In chapter 2, Magnetic Feedback Chemical Force Microscopy stiffens the cantilever for measuring force profiles between self-assembled monolayer (SAM) surfaces. Hydroxyl and carboxyl terminated SAMs produce long-range interactions that extend one or three nanometers into the solvent, respectively. In chapter 3, an ultra low noise AFM is produced through multiple modifications to the optical deflection detection system and signal processing electronics. In chapter 4, Brownian Force Profile Reconstruction is developed for accurate measurement of steep attractive interactions. Molecular ordering is observed for OMCTS, 1-nonanol, and water near flat surfaces. The molecular ordering of the solvent produces structural or solvation forces, providing insight into the orientation and possible solidification of the confined solvent. Seven molecular layers of OMCTS are observed but the oil remains fluid to the last layer. 1-nonanol strongly orders near the surface and becomes quasi-crystalline with four layers. Water is oriented by the surface and symmetry requires two layers of water (3.7 A) to be removed simultaneously. In chapter 5, electronic control of the cantilever Q (Q-control) is used to obtain the highest imaging sensitivity. In chapter 6, Energy Dissipation Chemical Force Microscopy is developed to investigate the time dependence and dissipative characteristics of SAM

  10. Laser interferometry force-feedback sensor for an interfacial force microscope

    DOEpatents

    Houston, Jack E.; Smith, William L.

    2004-04-13

    A scanning force microscope is provided with a force-feedback sensor to increase sensitivity and stability in determining interfacial forces between a probe and a sample. The sensor utilizes an interferometry technique that uses a collimated light beam directed onto a deflecting member, comprising a common plate suspended above capacitor electrodes situated on a substrate forming an interference cavity with a probe on the side of the common plate opposite the side suspended above capacitor electrodes. The probe interacts with the surface of the sample and the intensity of the reflected beam is measured and used to determine the change in displacement of the probe to the sample and to control the probe distance relative to the surface of the sample.

  11. Observation of Pull-in Instability in Graphene Membranes under Interfacial Forces

    NASA Astrophysics Data System (ADS)

    Liu, Xinghui; Boddeti, Narasimha; Szpunar, Mariah; Wang, Luda; Rodriguez, Miguel; Long, Rong; Xiao, Jianliang; Dunn, Martin; Bunch, Scott; Jianliang Xiao'S Collaboration; Scott Bunch's Team; Martin Dunn's Team

    2014-03-01

    We present a unique experimental configuration that allows us to determine the interfacial forces on nearly parallel plates made from single and few layer graphene membranes. Our approach consists of using a pressure difference across a graphene membrane to bring the membrane to within ~ 10-20 nm above a circular post covered with SiOx or Au until a critical point is reached whereby the membrane snaps into adhesive contact with the post. Continuous measurements of the deforming membrane with an AFM coupled with a theoretical model allow us to deduce the magnitude of the interfacial forces between graphene and SiOx and graphene and Au. The nature of the interfacial forces at ~ 10 - 20 nm separations is consistent with an inverse fourth power distance dependence, implying that the interfacial forces are dominated by van der Waals interactions. Furthermore, the strength of the interactions is found to increase linearly with the number of graphene layers. The experimental approach can be applied to measure the strength of the interfacial forces for other emerging atomically thin two-dimensional materials.

  12. Observation of pull-in instability in graphene membranes under interfacial forces.

    PubMed

    Liu, Xinghui; Boddeti, Narasimha G; Szpunar, Mariah R; Wang, Luda; Rodriguez, Miguel A; Long, Rong; Xiao, Jianliang; Dunn, Martin L; Bunch, J Scott

    2013-05-01

    We present a unique experimental configuration that allows us to determine the interfacial forces on nearly parallel plates made from the thinnest possible mechanical structures, single and few layer graphene membranes. Our approach consists of using a pressure difference across a graphene membrane to bring the membrane to within ~10-20 nm above a circular post covered with SiOx or Au until a critical point is reached whereby the membrane snaps into adhesive contact with the post. Continuous measurements of the deforming membrane with an AFM coupled with a theoretical model allow us to deduce the magnitude of the interfacial forces between graphene and SiOx and graphene and Au. The nature of the interfacial forces at ~10-20 nm separation is consistent with an inverse fourth power distance dependence, implying that the interfacial forces are dominated by van der Waals interactions. Furthermore, the strength of the interactions is found to increase linearly with the number of graphene layers. The experimental approach can be used to measure the strength of the interfacial forces for other atomically thin two-dimensional materials and help guide the development of nanomechanical devices such as switches, resonators, and sensors. PMID:23614533

  13. Interfacial behavior of common food contact polymer additives.

    PubMed

    Heiserman, W M; Can, S Z; Walker, R A; Begley, T H; Limm, W

    2007-07-15

    Irganox 1076 (IN1076) and Irganox 1010 (IN1010), phenol containing species often used as antioxidant additives in food packaging polymers have both hydrophilic and hydrophobic functional groups. Consequently these additives are likely to absorb to surfaces where their free energy is minimized. Experiments described in this work examine the two-dimensional phase behavior and vibrational structure of IN1076 and IN1010 films adsorbed to the air/water interface. Surface pressure isotherms show that repeated compression of these films leads to continued irreversible loss of molecules and that on a per molecule basis, this loss is more pronounced for IN1076 than for IN1010. Differences in the surface properties of these two antioxidant additives are interpreted based on differences in molecular structure. Surface specific vibrational measurements of these organic films show very little conformational order, implying that even when closely packed, both antioxidant species have little affinity for forming highly organized domains. These findings have important ramifications for mechanisms that reduce antioxidant activity in polymers as well as descriptions of antioxidant blooming on polymer surfaces. PMID:17448492

  14. Micromechanical cohesion force measurements to determine cyclopentane hydrate interfacial properties.

    PubMed

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

    2012-06-15

    Hydrate aggregation and deposition are critical factors in determining where and when hydrates may plug a deepwater flowline. We present the first direct measurement of structure II (cyclopentane) hydrate cohesive forces in the water, liquid hydrocarbon and gas bulk phases. For fully annealed hydrate particles, gas phase cohesive forces were approximately twice that obtained in a liquid hydrocarbon phase, and approximately six times that obtained in the water phase. Direct measurements show that hydrate cohesion force in a water-continuous bulk may be only the product of solid-solid cohesion. When excess water was present on the hydrate surface, gas phase cohesive forces increased by a factor of three, suggesting the importance of the liquid or quasi-liquid layer (QLL) in determining cohesive force. Hydrate-steel adhesion force measurements show that, when the steel surface is coated with hydrophobic wax, forces decrease up to 96%. As the micromechanical force technique is uniquely capable of measuring hydrate-surface forces with variable contact time, the present work contains significant implications for hydrate applications in flow assurance. PMID:22484169

  15. Calibration of an interfacial force microscope for MEMS metrology : FY08-09 activities.

    SciTech Connect

    Houston, Jack E.; Baker, Michael Sean; Crowson, Douglas A.; Mitchell, John Anthony; Moore, Nathan W.

    2009-10-01

    Progress in MEMS fabrication has enabled a wide variety of force and displacement sensing devices to be constructed. One device under intense development at Sandia is a passive shock switch, described elsewhere (Mitchell 2008). A goal of all MEMS devices, including the shock switch, is to achieve a high degree of reliability. This, in turn, requires systematic methods for validating device performance during each iteration of design. Once a design is finalized, suitable tools are needed to provide quality assurance for manufactured devices. To ensure device performance, measurements on these devices must be traceable to NIST standards. In addition, accurate metrology of MEMS components is needed to validate mechanical models that are used to design devices to accelerate development and meet emerging needs. Progress towards a NIST-traceable calibration method is described for a next-generation, 2D Interfacial Force Microscope (IFM) for applications in MEMS metrology and qualification. Discussed are the results of screening several suitable calibration methods and the known sources of uncertainty in each method.

  16. Adhesive force measurement between HOPG and zinc oxide as an indicator for interfacial bonding of carbon fiber composites.

    PubMed

    Patterson, Brendan A; Galan, Ulises; Sodano, Henry A

    2015-07-22

    Vertically aligned zinc oxide (ZnO) nanowires have recently been utilized as an interphase to increase the interfacial strength of carbon fiber composites. It was shown that the interaction between the carbon fiber and the ZnO nanowires was a critical parameter in adhesion; however, fiber based testing techniques are dominated by local defects and cannot be used to effectively study the bonding interaction directly. Here, the strength of the interface between ZnO and graphitic carbon is directly measured with atomic force microscopy (AFM) using oxygen plasma treated highly oriented pyrolytic graphite (HOPG) and an AFM tip coated with ZnO nanoparticles. X-ray photoelectron spectroscopy analysis is used to compare the surface chemistry of HOPG and carbon fiber and to quantify the presence of various oxygen functional groups. An indirect measurement of the interfacial strength is then performed through single fiber fragmentation testing (SFF) on functionalized carbon fibers coated with ZnO nanowires to validate the AFM measurements. The SFF and AFM methods showed the same correlation, demonstrating the capacity of the AFM method to study the interfacial properties in composite materials. Additionally, the chemical interactions between oxygen functional groups and the ionic structure of ZnO suggest that intermolecular forces at the interface are responsible for the strong interface. PMID:26107931

  17. Hydrodynamic attraction of immobile particles due to interfacial forces

    NASA Astrophysics Data System (ADS)

    Morthomas, Julien; Würger, Alois

    2010-05-01

    Applying the method of reflections, we derive the flow pattern around a confined colloidal particle with quasislip conditions at its surface, in powers of the ratio a/h of particle radius and wall distance. The lowest order corresponds to a single reflection at the confining wall. Significant corrections occur at higher order: the linear term in a/h modifies the amplitudes of the well-known one-reflection approximation, whereas new features arise in quadratic order. Our results agree with recent experiments where thermo-osmosis drives hydrodynamic attractive forces in confined colloids.

  18. Hydrodynamic attraction of immobile particles due to interfacial forces.

    PubMed

    Morthomas, Julien; Würger, Alois

    2010-05-01

    Applying the method of reflections, we derive the flow pattern around a confined colloidal particle with quasislip conditions at its surface, in powers of the ratio a/h of particle radius and wall distance. The lowest order corresponds to a single reflection at the confining wall. Significant corrections occur at higher order: the linear term in a/h modifies the amplitudes of the well-known one-reflection approximation, whereas new features arise in quadratic order. Our results agree with recent experiments where thermo-osmosis drives hydrodynamic attractive forces in confined colloids. PMID:20866228

  19. 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

  20. Effects of ultrasonic waves on the interfacial forces between oil and water.

    PubMed

    Hamida, Tarek; Babadagli, Tayfun

    2008-04-01

    The effect of ultrasound on flow through a capillary using the pendant drop method was investigated. Water was injected into a 0.1 mm Hastelloy C-276 capillary tube submersed into several mineral oils with different viscosity, and kerosene. The average drop rate per minute was measured at several ultrasonic intensities. We observed that there exists a peak drop rate at a characteristic intensity, which strongly depends on oil viscosity and the interfacial tension between water and the oil. The semi-quantitative results reveal that the remarkable change in the interfacial forces between oil and water could be the explanation to the enhancement of oil recovery when the ultrasonic waves are applied. PMID:17981069

  1. Interfacial water dielectric-permittivity-profile measurements using atomic force microscopy.

    PubMed

    Teschke, O; Ceotto, G; de Souza, E F

    2001-07-01

    The arrangement of water molecules at charged aqueous interfaces is an important question in biology, electrochemistry, and geochemistry. Theoretical studies suggest that the molecules become arranged in several layers adjacent to a solid interface. Using atomic force microscopy we have measured the water dielectric-permittivity profile perpendicular to mica surfaces. The measured variable permittivity profile starting at epsilon approximately 4 at the interface and increasing to epsilon=80 about 10 nm from the surface suggests a reorientation of water molecule dipoles in the presence of the mica interfacial charge. PMID:11461268

  2. Interfacial friction obtained by lateral manipulation of nanoparticles using atomic force microscopy techniques

    NASA Astrophysics Data System (ADS)

    Dietzel, Dirk; Mönninghoff, Tristan; Jansen, Lars; Fuchs, Harald; Ritter, Claudia; Schwarz, Udo D.; Schirmeisen, André

    2007-10-01

    Nanometer scale metallic particles have been manipulated on an atomically flat graphite surface by atomic force microscopy techniques and quantitative information on interfacial friction was extracted from the lateral manipulation of these nanoparticles. Similar to conventional friction force microscopy, the particle-surface interfacial friction was extracted from the torsional signal of the cantilever during the particle pushing process. As a model system, we chose antimony particles with diameters between 50 and 500nm grown on a highly oriented pyrolytic graphite substrate. Three different manipulation strategies have been developed, which either enable the defined manipulation of individual nanoparticles or can be utilized to gather data on a larger number of particles found within a particular scan area, allowing for fast and statistically significant data collection. While the manipulation strategies are demonstrated here for operation under vacuum conditions, extensive testing indicated that the proposed methods are likewise suited for ambient environments. Since these techniques can be applied to a large variety of chemically and structurally different material combinations as well as a large range of particle sizes, our results indicate a viable route to solve many recent issues in the field of nanoscale friction, such as the influence of contact size and interface crystallinity.

  3. All-atom force field for the prediction of vapor-liquid equilibria and interfacial properties of HFA134a.

    PubMed

    Peguin, Robson P S; Kamath, Ganesh; Potoff, Jeffrey J; da Rocha, Sandro R P

    2009-01-01

    A new all-atom force field capable of accurately predicting the bulk and interfacial properties of 1,1,1,2-tetrafluoroethane (HFA134a) is reported. Parameterization of several force fields with different initial charge configurations from ab initio calculations was performed using the histogram reweighting method and Monte Carlo simulations in the grand canonical ensemble. The 12-6 Lennard-Jones well depth and diameter for the different HFA134a models were determined by fitting the simulation results to pure-component vapor-equilibrium data. Initial screening of the force fields was achieved by comparing the calculated and experimental bulk properties. The surface tension of pure HFA134a served as an additional screening property to help discriminate an optimum model. The proposed model reproduces the experimental saturated liquid and vapor densities, and the vapor pressure for HFA134a within average errors of 0.7%, 4.4%, and 3.1%, respectively. Critical density, temperature, vapor pressure, normal boiling point, and heat of vaporization at 298 K are also in good agreement with experimental data with errors of 0.2%, 0.1%, 6.2%, 0%, 2.2%, respectively. The calculated surface tension is found to be within the experimental range of 7.7-8.1 mN.m(-1). The dipole moment of the different models was found to significantly affect the prediction of the vapor pressure and surface tension. The ability of the HFA134a models in predicting the interfacial tension against water is also discussed. The results presented here are relevant in the development of technologies where the more environmentally friendly HFA134a is utilized as a substitute to the ozone depleting chlorofluorocarbon propellants. PMID:19086791

  4. Effects of Ga Addition on Interfacial Reactions Between Sn-Based Solders and Ni

    NASA Astrophysics Data System (ADS)

    Wang, Chao-Hong; Li, Kuan-Ting

    2016-07-01

    The use of Ga as a micro-alloying element in Sn-based solders can change the microstructure of solder joints to improve the mechanical properties, and even suppress the interfacial intermetallic compound (IMC) growth. This research investigated the effects of Ga addition (0.2-1 wt.%Ga) on the IMC formation and morphological evolution in the Sn-based solder joints with Ni substrate. In the soldering reaction at 250°C and with less than 0.2 wt.%Ga addition, the formed phase was Ni3Sn4. When the Ga addition increased to 0.5 wt.%, it changed to a thin Ni2Ga3 layer of ˜1 μm thick, which stably existed at the interface in the initial 1-h reaction. Subsequently, the whole Ni2Ga3 layer detached from the Ni substrate and drifted into the molten solder. The Ni3Sn4 phase became dominant in the later stage. Notably, the Ga addition significantly reduced the grain size of Ni3Sn4, resulting in the massive spalling of Ni3Sn4 grains. With 1 wt.%Ga addition, the Ni2Ga3 layer remained very thin with no significant growth, and it stably existed at the interface for more than 10 h. In addition, the solid-state reactions were examined at temperatures of 160°C to 200°C. With addition of 0.5 wt.%Ga, the Ni3Sn4 phase dominated the whole reaction. By contrast, with increasing to 1 wt.%Ga, only a thin Ni2Ga3 layer was found even after aging at 160°C for more than 1200 h. The 1 wt.%Ga addition in solder can effectively inhibit the Ni3Sn4 formation in soldering and the long-term aging process.

  5. Chemical Force Microscopy: Probing Chemical Origin of Interfacial Forces and Adhesion

    SciTech Connect

    Vezenov, D V; Noy, A; Ashby, P

    2005-03-21

    Experimental methods of measuring intermolecular interactions have had several recent developments which have improved our understanding of chemical forces. First, they allowed direct exploration of the role that different functionalities, solvents and environmental variables play in shaping the strength of intermolecular interactions. Chemical force microscopy approach, in particular, became an extremely effective tool for exploring the contributions of each of these factors. Second, CFM studies clearly debunked the naive notion that intermolecular interaction strength is determined only by the nature of the interacting groups. These studies showed that the interaction strength between two chemical species must always considered in context of the environment surrounding these species. Third, CFM studies highlighted the critical role solvent plays in shaping intermolecular interactions in condensed phases. Emerging kinetic view of the intermolecular interactions introduced a completely new paradigm for understanding these interactions. Kinetic modeling showed that the measured interactions strength depends not only on the energy landscape of the system, but also on the loading history prior to the bond break-up. This new paradigm refocused our attention to the energy landscape as a fundamental characteristic of the interaction. Moreover, dynamic force spectroscopy, derived from kinetic models, allowed direct characterization of the geometry of the potential energy barrier, while some other methods attempt to probe the equilibrium energy landscape directly. Further investigations of the interactions in different systems, especially interactions between biomolecules, will uncover many interesting characteristics of intermolecular potentials. These studies have the potential to reveal, for the first time, a true picture of the energy landscapes of adhesion processes in complex chemical and biological systems.

  6. Erythorbyl laurate as a potential food additive with multi-functionalities: Interfacial characteristics and antioxidant activity.

    PubMed

    Park, Kyung-Min; Lee, Min Joo; Jo, Su-Kyung; Choi, Seung Jun; Lee, JaeHwan; Chang, Pahn-Shick

    2017-01-15

    The interfacial characteristics and antioxidant activities of erythorbyl laurate were investigated to provide information on practical applications as a multi-functional food additive. The critical micelle concentration (CMC) of erythorbyl laurate was 0.101mM and its foam stability was three times (half-life 24.33±0.94h) higher than that of Tween 20 (8.00±1.63h). In free radical scavenging assay, the negligible decrease in EC50 of erythorbyl laurate compared to erythorbic acid manifested that C-5 selective esterification of erythorbic acid with an acyl group (lauric acid) did not reduce the inherent antioxidant activity of the donor (erythorbic acid). Erythorbyl laurate formed lipid peroxides slower (i.e. retarded oxidation) in an emulsion system than did erythorbic acid. The localization of erythorbyl laurate as an emulsifier allowed the antioxidant molecules to be concentrated at the oil-water interface where oxidation is prevalent, which led to more effective retardation of lipid oxidation. PMID:27542455

  7. Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature

    NASA Astrophysics Data System (ADS)

    Moreau-Luchaire, C.; Moutafis, C.; Reyren, N.; Sampaio, J.; Vaz, C. A. F.; van Horne, N.; Bouzehouane, K.; Garcia, K.; Deranlot, C.; Warnicke, P.; Wohlhüter, P.; George, J.-M.; Weigand, M.; Raabe, J.; Cros, V.; Fert, A.

    2016-05-01

    Facing the ever-growing demand for data storage will most probably require a new paradigm. Nanoscale magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films in which the cobalt layer is sandwiched between two heavy metals and so provides additive interfacial Dzyaloshinskii–Moriya interactions (DMIs), which reach a value close to 2 mJ m–2 in the case of the Ir|Co|Pt asymmetric multilayers. Using a magnetization-sensitive scanning X-ray transmission microscopy technique, we imaged small magnetic domains at very low fields in these multilayers. The study of their behaviour in a perpendicular magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the large DMI. This discovery of stable sub-100 nm individual skyrmions at room temperature in a technologically relevant material opens the way for device applications in the near future.

  8. Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature.

    PubMed

    Moreau-Luchaire, C; Mouta S, C; Reyren, N; Sampaio, J; Vaz, C A F; Van Horne, N; Bouzehouane, K; Garcia, K; Deranlot, C; Warnicke, P; Wohlhüter, P; George, J-M; Weigand, M; Raabe, J; Cros, V; Fert, A

    2016-05-01

    Facing the ever-growing demand for data storage will most probably require a new paradigm. Nanoscale magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films in which the cobalt layer is sandwiched between two heavy metals and so provides additive interfacial Dzyaloshinskii-Moriya interactions (DMIs), which reach a value close to 2 mJ m(-2) in the case of the Ir|Co|Pt asymmetric multilayers. Using a magnetization-sensitive scanning X-ray transmission microscopy technique, we imaged small magnetic domains at very low fields in these multilayers. The study of their behaviour in a perpendicular magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the large DMI. This discovery of stable sub-100 nm individual skyrmions at room temperature in a technologically relevant material opens the way for device applications in the near future. PMID:26780660

  9. 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.

  10. Multiple Size Group Modeling of Polydispersed Bubbly Flow in the Mold: An Analysis of Turbulence and Interfacial Force Models

    NASA Astrophysics Data System (ADS)

    Liu, Zhongqiu; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa

    2015-04-01

    An inhomogeneous Multiple Size Group (MUSIG) model based on the Eulerian-Eulerian approach has been developed to describe the polydispersed bubbly flow inside the continuous-casting mold. A laboratory scale mold has been simulated using four different turbulence closure models (modified k - ɛ, RNG k - ɛ, k - ω, and SST) with the purpose of critically comparing their predictions of bubble Sauter mean diameter distribution with previous experimental data. Furthermore, the influences of all the interfacial momentum transfer terms including drag force, lift force, virtual mass force, wall lubrication force, and turbulent dispersion force are investigated. The breakup and coalescence effects of the bubbles are modeled according to the bubble breakup by the impact of turbulent eddies while for bubble coalescence by the random collisions driven by turbulence and wake entrainment. It has been found that the modified k - ɛ model shows better agreement than other models in predicting the bubble Sauter mean diameter profiles. Further, simulations have also been performed to understand the sensitivity of different interfacial forces. The appropriate drag force coefficient, lift force coefficient, virtual mass force coefficient, and turbulent dispersion force coefficient are chosen in accordance with measurements of water model experiments. However, the wall lubrication force does not have much effect on the current polydispersed bubbly flow system. Finally, the MUSIG model is then used to estimate the argon bubble diameter in the molten steel of the mold. The argon bubble Sauter mean diameter generated in molten steel is predicted to be larger than air bubbles in water for the similar conditions.

  11. Additive CHARMM force field for naturally occurring modified ribonucleotides.

    PubMed

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D; Nilsson, Lennart

    2016-04-15

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all-atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. PMID:26841080

  12. Additive CHARMM force field for naturally occurring modified ribonucleotides

    PubMed Central

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D.

    2016-01-01

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all‐atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26841080

  13. Toward improving the graphene-semiconductor composite photoactivity via the addition of metal ions as generic interfacial mediator.

    PubMed

    Zhang, Nan; Yang, Min-Quan; Tang, Zi-Rong; Xu, Yi-Jun

    2014-01-28

    We report a simple and general approach to improve the transfer efficiency of photogenerated charge carriers across the interface between graphene (GR) and semiconductor CdS by introducing a small amount of metal ions (Ca(2+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)) as "mediator" into their interfacial layer matrix, while the intimate interfacial contact between GR and CdS is maintained. This simple strategy can not only significantly improve the visible-light-driven photoactivity of GR-CdS semiconductor composites for targeting selective photoredox reaction, including aerobic oxidation of alcohol and anaerobic reduction of nitro compound, but also drive a balance between the positive effect of GR on retarding the recombination of electron-hole pairs photogenerated from semiconductor and the negative "shielding effect" of GR resulting from the high weight addition of GR. Our current work highlights that the significant issue on improving the photoactivity of GR-semiconductor composites via strengthening interfacial contact is not just a simple issue of tighter connection between GR and the semiconductor, but it is also the optimization of the atomic charge carrier transfer pathway across the interface between GR and the semiconductor. PMID:24304042

  14. Nonlinearly Additive Forces in Multivalent Ligand Binding to a Single Protein Revealed with Force Spectroscopy

    SciTech Connect

    Ratto, T V; Rudd, R E; Langry, K C; Balhorn, R L; McElfresh, M W

    2005-07-15

    We present evidence of multivalent interactions between a single protein molecule and multiple carbohydrates at a pH where the protein can bind four ligands. The evidence is based not only on measurements of the force required to rupture the bonds formed between ConcanavalinA (ConA) and {alpha}-D-mannose, but also on an analysis of the polymer-extension force curves to infer the polymer architecture that binds the protein to the cantilever and the ligands to the substrate. We find that although the rupture forces for multiple carbohydrate connections to a single protein are larger than the rupture force for a single connection, they do not scale additively with increasing number. Specifically, the most common rupture forces are approximately 46, 66, and 85 pN, which we argue corresponds to 1, 2, and 3 ligands being pulled simultaneously from a single protein as corroborated by an analysis of the linkage architecture. As in our previous work polymer tethers allow us to discriminate between specific and non-specific binding. We analyze the binding configuration (i.e. serial versus parallel connections) through fitting the polymer stretching data with modified Worm-Like Chain (WLC) models that predict how the effective stiffness of the tethers is affected by multiple connections. This analysis establishes that the forces we measure are due to single proteins interacting with multiple ligands, the first force spectroscopy study that establishes single-molecule multivalent binding unambiguously.

  15. Interfacial force-driven pattern formation during drying of Aβ (25-35) fibrils.

    PubMed

    Sett, Ayantika; Bag, Sudipta; Dasgupta, Swagata; DasGupta, Sunando

    2015-08-01

    Pattern formation during evaporation of biofluids finds significant applications in the biomedical field for disease identification. Aβ (25-35) is the smallest peptide in the amyloid peptide family that retains the toxicity of a full length peptide responsible for Alzheimer's disease and is chosen here as the model solute. Drying experiments on substrates of varying wettability exhibit unique drying patterns of Aβ (25-35) fibrils visualized through fluorescence microscopy and transmission electron microscopy. The unique pattern formations can be interpreted as manifestations of the changes in the self-pinning mechanism with changes in wettability, which in some cases resembles the well-known coffee ring effect. Additionally, the delicate balance between the drag and capillary forces has been perturbed by initiating controlled rates of evaporation and probing their effects on the fibril patterning. PMID:25964177

  16. Parameterization of an interfacial force field for accurate representation of peptide adsorption free energy on high-density polyethylene

    PubMed Central

    Abramyan, Tigran M.; Snyder, James A.; Yancey, Jeremy A.; Thyparambil, Aby A.; Wei, Yang; Stuart, Steven J.; Latour, Robert A.

    2015-01-01

    Interfacial force field (IFF) parameters for use with the CHARMM force field have been developed for interactions between peptides and high-density polyethylene (HDPE). Parameterization of the IFF was performed to achieve agreement between experimental and calculated adsorption free energies of small TGTG–X–GTGT host–guest peptides (T = threonine, G = glycine, and X = variable amino-acid residue) on HDPE, with ±0.5 kcal/mol agreement. This IFF parameter set consists of tuned nonbonded parameters (i.e., partial charges and Lennard–Jones parameters) for use with an in-house-modified CHARMM molecular dynamic program that enables the use of an independent set of force field parameters to control molecular behavior at a solid–liquid interface. The R correlation coefficient between the simulated and experimental peptide adsorption free energies increased from 0.00 for the standard CHARMM force field parameters to 0.88 for the tuned IFF parameters. Subsequent studies are planned to apply the tuned IFF parameter set for the simulation of protein adsorption behavior on an HDPE surface for comparison with experimental values of adsorbed protein orientation and conformation. PMID:25818122

  17. A finite element technique for accurate determination of interfacial adhesion force in MEMS using electrostatic actuation

    NASA Astrophysics Data System (ADS)

    Shavezipur, M.; Li, G. H.; Laboriante, I.; Gou, W. J.; Carraro, C.; Maboudian, R.

    2011-11-01

    This paper reports on accurate analysis of adhesion force between polysilicon-polysilicon surfaces in micro-/nanoelectromechanical systems (M/NEMS). The measurement is carried out using double-clamped beams. Electrostatic actuation and structural restoring force are exploited to respectively initiate and terminate the contact between the two surfaces under investigation. The adhesion force is obtained by balancing the electrostatic and mechanical forces acting on the beam just before the separation of the two surfaces. Different finite element models are developed to simulate the coupled-field multiphysics problem. The effects of fringing field in the electrostatic domain and geometric nonlinearity and residual stress in the structural domain are taken into consideration. Moreover, the beam stiffness is directly obtained for the case of combined loading (electrostatic and adhesion). Therefore, the overall electrostatic and structural forces used to extract the actual adhesion force from measured data are determined with high accuracy leading to accurate values for the adhesion force. The finite element simulations presented in this paper are not limited to adhesion force measurement and can be used to design or characterize electrostatically actuated devices such as MEM tunable capacitors and micromirrors, RF switches and M/NEM relays.

  18. Acid-Base Interactions at the Molecular Level: Adhesion and Friction Studies with Interfacial Force Microscopy

    SciTech Connect

    Burns, A.R.; Carpick, R.W.; Houston, J.E.; Michalske, T.A.

    1998-12-09

    To examine the forces of acid-base adhesive interactions at the molecular level, we utilize the scanning probe Interracial Force Microscope (IFM). Unlike cantilever-based atomic force microscopes, the EM is a non-compliant, mechanically stable probe that provides a complete adhesive profile without jump-to-contact. In this way, we are able to quantitatively measure the work of adhesion and bond energies at well-defined, nanometer-scale single asperity contacts. In particular, we will discuss the displacement-controlled adhesive forces between self-assembled monolayer of functionalized alkanethiols strongly bound to a gold substrate and a similarly functionalized tip. We also discuss a method utilizing decoupled lateral and normal force sensors to simultaneously observe the onset of both friction and chemical bond formation. Measurements show that friction can be directly attributed to bond formation and rupture well before repulsive contact.

  19. Interfacial structure in thin water layers formed by forced dewetting on self-assembled monolayers of omega-terminated alkanethiols on Ag.

    PubMed

    Tiani, Domenic J; Yoo, Heemin; Mudalige, Anoma; Pemberton, Jeanne E

    2008-12-01

    A method for the spectroscopic characterization of interfacial fluid molecular structure near solid substrates is reported. The thickness and interfacial molecular structure of residual ultrathin D20 films remaining after forced dewetting on alkanethiolate self-assembled monolayers (SAMs) of 11 1-mercaptoundecanoic acid (11-MUA), 11-mercaptoundecanol (11-MUD), and undecanethiol (UDT) on Ag are investigated using ellipsometry and surface Raman spectroscopy. The residual film thickness left after withdrawal is greater on hydrophilic SAMs than on hydrophobic SAMs. This behavior is rationalized on the basis of differing degrees of fluid slip within the interfacial region due to different interfacial molecular structure. The v(O-D) regions of surface Raman spectra clearly indicate unique interfacial molecular properties within these films that differ from bulk D20. Although the residual films are created by shear forces and Marangoni flow at the three-phase line during the forced dewetting process, the nature of the films sampled optically must also be considered from the standpoint of thin film stability after dewetting. Thus, the resulting D20 films exist in vastly different morphologies depending on the nature of the water-SAM interactions. Residual D20 is proposed to exist as small nanodroplets on UDT surfaces due tospontaneous rupture of the film after dewetting. In contrast, on 11-MUD and 11-MUA surfaces, these films exist in a metastable state that retains their conformal nature on the underlying modified surface. Analysis of the peak intensity ratios of the so-called "ice-like" to "liquid-like" v(O-D) modes suggests more ice-like D20 character near 11-MUD surfaces, but more liquid-like character near 11-MUA and UDT surfaces. The creation of residual ultrathin films by forced dewetting is thus demonstrated to be a powerful method for characterizing interfacial molecular structure of fluids near a solid substrate under ambient conditions of temperature and

  20. Sliding/rolling phobic droplets along a fiber: measurement of interfacial forces.

    PubMed

    Mead-Hunter, Ryan; Bergen, Tanja; Becker, Thomas; O'Leary, Rebecca A; Kasper, Gerhard; Mullins, Benjamin J

    2012-02-21

    Phobic droplet-fiber systems possess complex geometries, which have made full characterization of such systems difficult. This work has used atomic force microscopy (AFM) to measure droplet-fiber forces for oil droplets on oleophobic fibers over a range of fiber diameters. The work adapted a previous method and a theoretical model developed by the authors for philic droplet-fiber systems. A Bayesian statistical model was also used to account for the influence of surface roughness on the droplet-fiber force. In general, it has been found that the force required to move a liquid droplet along an oleophobic filter fiber will be less than that required to move a droplet along an oleophilic fiber. However, because of the effects of pinning and/or wetting behavior, this difference may be less than would otherwise be expected. Droplets with a greater contact angle (~110°) were observed to roll along the fiber, whereas droplets with a lesser contact angle (<90°) would slide. PMID:22260243

  1. Interfacial Reactions of Zn-Al Alloys with Na Addition on Cu Substrate During Spreading Test and After Aging Treatments

    NASA Astrophysics Data System (ADS)

    Gancarz, Tomasz; Pstruś, Janusz; Berent, Katarzyna

    2016-04-01

    Spreading tests for Cu substrate with Zn-Al eutectic-based alloys with 0.2, 0.5, and 1.0 wt.% of Na were studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed for 1, 3, 8, 15, 30, and 60 min of contact, at the temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreading area of Zn-Al + Na on Cu was determined in accordance with ISO 9455-10:2013-03. Selected, solidified solder-substrate couples were cross-sectioned and subjected to scanning electron microscopy of the interfacial microstructure. The experiment was designed to demonstrate the effect of Na addition on the kinetics of formation and growth of CuZn, Cu5Zn8, and CuZn4 phases, which were identified using x-ray diffraction and energy-dispersive spectroscopy analysis. The addition of Na to eutectic Zn-Al caused the spreading area to decrease and the thickness of intermetallic compound layers at the interface to reduce. Samples after the spreading test at 500 °C for 1 min were subjected to aging for 1, 10, and 30 days at 120,170, and 250 °C. The greater thicknesses of IMC layers were obtained for a temperature of 250 °C. With increasing Na content in Zn-Al + Na alloys, the thickness reduced, which correlates to the highest value of activation energy for Zn-Al with 1% Na.

  2. Interfacial-Force-Controlled Placing Technique of Microstructures of Sub- to One Hundred Micrometer Size Using Blade Coating

    NASA Astrophysics Data System (ADS)

    Nakagawa, Tohru; Arase, Hidekazu

    2011-01-01

    The surface mounting technology of electronic devices using pick-and-place machines is commonly used to fabricate functional electronic appliances, such as motherboards, flat panel displays, and mobile phones. However, the pick-and-place method begins to encounter difficulties in mounting electronic devices when devices shrink to a few hundreds of micrometers or less. We propose a new blade-coating method of placing microstructures smaller than several hundreds of micrometers on a substrate. The method comprises three steps: (1) preparing a microstructure dispersion consisting of chemically modified microstructures and a water-insoluble organic solvent, (2) continuous blade-coating of water and the dispersion on a chemically patterned substrate on which hydrophilic areas are surrounded by a hydrophobic self-assembled monolayer, and (3) spontaneous placing of the microstructures on the hydrophilic areas by a water/solvent interfacial force that acts on the microstructures. Using this method, we have been able to place microstructures ranging in length from submicrometer to one hundred micrometers, including silicon nanowires and SiO2 microstructures of various sizes. However, our blade-coating method for placing microstructures can be realized with successful combinations of chemical modifiers for the microstructures and water-insoluble solvents. We present a simple method of assessing dispersion using a chemically modified glass test tube filled with water and a solvent for the dispersion.

  3. 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

    2016-06-01

    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. PMID:27276958

  4. 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.

  5. Relationship between interfacial forces measured by colloid-probe atomic force microscopy and protein resistance of poly(ethylene glycol)-grafted poly(L-lysine) adlayers on niobia surfaces.

    PubMed

    Pasche, Stéphanie; Textor, Marcus; Meagher, Laurence; Spencer, Nicholas D; Griesser, Hans J

    2005-07-01

    Adsorbed layers of "comb-type" copolymers consisting of PEG chains grafted onto a poly(l-lysine) (PLL) backbone on niobium oxide substrates were studied by colloid-probe AFM in order to characterize the interfacial forces associated with coatings of varying architectures (PEG/PLL ratios and PEG chain lengths) and their relevance to protein resistance. The steric and electrostatic forces measured varied substantially with the architecture of the PLL-g-PEG copolymers. Varying the ionic strength of the buffer solutions enabled discrimination between electrostatic and steric-entropic contributions to the net interfacial force. For high PEG grafting densities the steric component was most prominent, but at low ionic strengths and high grafting densities, a repulsive electrostatic surface force was also observed; its origin was assigned to the niobia charges beneath the copolymer, as insufficient protonated amine groups in the PLL backbone were available for compensation of the oxide surface charges. For lower grafting densities and lower ionic strengths there was a substantial attractive electrostatic contribution arising from interaction of the electrical double layer arising from the protonated amine groups, with that of the silica probe surface (as under low ionic strength conditions, the electrical double layer was thicker than the PEG layer). For these PLL-g-PEG coatings the net interfacial force can thus be a markedly varying superposition of electrostatic and steric-entropic contributions, depending on various factors. The force curves correlate with protein adsorption data, demonstrating the utility of AFM colloid-probe force measurements for quantitative analysis of surface forces and how they determine interfacial interactions with proteins. Such characterization of the net interfacial forces is essential to elucidate the multiple types of interfacial forces relevant to the interactions between PLL-g-PEG coatings and proteins and to advance interpretation of

  6. Molecular dynamics investigation of the various atomic force contributions to the interfacial tension at the supercritical CO2-water interface.

    PubMed

    Zhao, Lingling; Lin, Shangchao; Mendenhall, Jonathan D; Yuet, Pak K; Blankschtein, Daniel

    2011-05-19

    Sequestration of carbon dioxide (CO(2)) in deep, geological formations involves the injection of supercritical CO(2) into depleted reservoirs containing fluids such as brine or oil. The interfacial tension (IFT) between supercritical CO(2) and the reservoir fluid is an important contribution to the sequestration efficiency. In turn, the IFT is a complex function of the reservoir fluid phase composition, the molecular structure of each reservoir fluid component, and environmental conditions (i.e., temperature and pressure). Molecular dynamics simulations can be used to probe the dependence of the IFT on these factors, since the IFT can be calculated directly from the simulated atomic forces and velocities at system equilibrium using the mechanical definition of the IFT. Here, we examine the contribution of each type of atomic force to the IFT, including bonded and nonbonded forces, as quantified by the anisotropy of the atomic virial tensor. In particular, we first examine a supercritical CO(2)-pure liquid water interface, at typical reservoir conditions (temperature of 343 K and pressure of 20 MPa), as a reference state against which CO(2)-brine systems can be compared. In this system, we note that the interactions between water molecules and between CO(2) molecules ("self" interactions) contribute positively to the IFT, while the interactions between water and CO(2) molecules ("cross" interactions) contribute negatively to the IFT. We find that the magnitude of the water "self" interactions is the dominant contribution. In terms of specific types of forces, we find that nonbonded electrostatic (QQ), bonded angle-bending, and bonded bond-stretching interactions contribute positively to the IFT, while nonbonded Lennard-Jones (LJ) interactions contribute negatively to the IFT. We also find that the balance between the LJ interactions and the bond-stretching interactions, in particular, plays a significant role in determining the magnitude of the IFT. Using

  7. High-resolution imaging of interfacial water by noncontact atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Peng, Jinbo; Guo, Jing; Hapala, Prokop; Cao, Duanyun; Jelínek, Pavel; Xu, Limei; Wang, Enge; Jiang, Ying; Collaborative Innovation Center of Quantum Matter Collaboration

    Resolving the hydrogen-bonding configuration of water on the solid surfaces with atomic-scale precision is crucial in water science yet it remains challenging. Recently we have shown the possibility of attacking this problem by STM based on the submolecular orbital imaging of water. However, STM mainly probes the spatial distribution of the density of states near the Fermi level, thus is not sensitive to the chemical structure of molecules. Here we report the ultrahigh resolution imaging of water molecules on a NaCl film by NC-AFM, which enables us to determine the topology of hydrogen-bonding network in unprecedented details. Comparison with the theoretical simulations reveals that the sharp features in the AFM images result from the relaxation of the tip apex mainly due to the electrostatic force between the tip and the water molecules. Our results shed new light on the underlying mechanism of the ultrahigh imaging with NC-AFM and highlight the importance of electrostatics in the imaging of polar molecules such as water. This work was supported by the National Basic Research Programs of China.

  8. CHARMM additive and polarizable force fields for biophysics and computer-aided drug design

    PubMed Central

    Vanommeslaeghe, K.

    2014-01-01

    Background Molecular Mechanics (MM) is the method of choice for computational studies of biomolecular systems owing to its modest computational cost, which makes it possible to routinely perform molecular dynamics (MD) simulations on chemical systems of biophysical and biomedical relevance. Scope of Review As one of the main factors limiting the accuracy of MD results is the empirical force field used, the present paper offers a review of recent developments in the CHARMM additive force field, one of the most popular bimolecular force fields. Additionally, we present a detailed discussion of the CHARMM Drude polarizable force field, anticipating a growth in the importance and utilization of polarizable force fields in the near future. Throughout the discussion emphasis is placed on the force fields’ parametrization philosophy and methodology. Major Conclusions Recent improvements in the CHARMM additive force field are mostly related to newly found weaknesses in the previous generation of additive force fields. Beyond the additive approximation is the newly available CHARMM Drude polarizable force field, which allows for MD simulations of up to 1 microsecond on proteins, DNA, lipids and carbohydrates. General Significance Addressing the limitations ensures the reliability of the new CHARMM36 additive force field for the types of calculations that are presently coming into routine computational reach while the availability of the Drude polarizable force fields offers a model that is an inherently more accurate model of the underlying physical forces driving macromolecular structures and dynamics. PMID:25149274

  9. Pairwise-additive force fields for selected aqueous monovalent ions from adaptive force matching

    NASA Astrophysics Data System (ADS)

    Li, Jicun; Wang, Feng

    2015-11-01

    Simple non-polarizable potentials were developed for Na+, K+, Cl-, and Br- using the adaptive force matching (AFM) method with ab initio MP2 method as reference. Our MP2-AFM force field predicts the solvation free energies of the four salts formed by the ions with an error of no more than 5%. Other properties such as the ion-water radial distribution functions, first solvation shell water tilt angle distributions, ion diffusion constants, concentration dependent diffusion constant of water, and concentration dependent surface tension of the solutions were calculated with this potential. Very good agreement was achieved for these properties. In particular, the diffusion constants of the ions are within 6% of experimental measurements. The model predicts bromide to be enriched at the interface in the 1.6M KBr solution but predicts the ion to be repelled for the surface at lower concentration.

  10. More About Measuring Interfacial Tension Between Liquids

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser; Balasubramaniam, R.; Del Signore, David M.

    1995-01-01

    Report presents additional discussion of technique for measuring interfacial tension between two immiscible liquids. Technique described in "Measuring Interfacial Tension Between Immiscible Liquids" (LEW-15855).

  11. CHARMM General Force Field (CGenFF): A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields

    PubMed Central

    Vanommeslaeghe, K.; Hatcher, E.; Acharya, C.; Kundu, S.; Zhong, S.; Shim, J.; Darian, E.; Guvench, O.; Lopes, P.; Vorobyov, I.; MacKerell, A. D.

    2010-01-01

    The widely used CHARMM additive all-atom force field includes parameters for proteins, nucleic acids, lipids and carbohydrates. In the present paper an extension of the CHARMM force field to drug-like molecules is presented. The resulting CHARMM General Force Field (CGenFF) covers a wide range of chemical groups present in biomolecules and drug-like molecules, including a large number of heterocyclic scaffolds. The parametrization philosophy behind the force field focuses on quality at the expense of transferability, with the implementation concentrating on an extensible force field. Statistics related to the quality of the parametrization with a focus on experimental validation are presented. Additionally, the parametrization procedure, described fully in the present paper in the context of the model systems, pyrrolidine, and 3-phenoxymethylpyrrolidine will allow users to readily extend the force field to chemical groups that are not explicitly covered in the force field as well as add functional groups to and link together molecules already available in the force field. CGenFF thus makes it possible to perform “all-CHARMM” simulations on drug-target interactions thereby extending the utility of CHARMM force fields to medicinally relevant systems. PMID:19575467

  12. Research Updates: Epitaxial strain relaxation and associated interfacial reconstructions: The driving force for creating new structures with integrated functionality

    NASA Astrophysics Data System (ADS)

    Zhu, Yuanyuan; Chen, Aiping; Zhou, Honghui; Zhang, Wenrui; Narayan, Jagdish; MacManus-Driscoll, Judith L.; Jia, Quanxi; Wang, Haiyan

    2013-11-01

    Here, we report detailed strain mapping analysis at heterointerfaces of a new multiferroic complex oxide Bi3Fe2Mn2Ox(BFMO322) supercell and related layered structures. The state-of-the-art aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) and the modified geometric phase analysis (GPA) have been used to characterize the self-assembled transitional layers, misfit defects, and, in particular, the biaxial lattice strain distributions. We found that not only a sufficient lattice misfit is required through substrate selection and to be preserved in initial coherent epilayer growth, but also an appropriate interfacial reconstruction is crucial for triggering the growth of the new BFMO322 supercell structure. The observation of new transitional interfacial phases behaving like coherent film layers within the critical thickness challenges the conventional understanding in existing epitaxial growth model.

  13. Research Updates: Epitaxial strain relaxation and associated interfacial reconstructions: The driving force for creating new structures with integrated functionality

    SciTech Connect

    Zhu, Yuanyuan; Zhang, Wenrui; Chen, Aiping; Zhou, Honghui; Narayan, Jagdish; MacManus-Driscoll, Judith L.; Jia, Quanxi; Wang, Haiyan

    2013-11-01

    Here, we report detailed strain mapping analysis at heterointerfaces of a new multiferroic complex oxide Bi{sub 3}Fe{sub 2}Mn{sub 2}O{sub x}(BFMO322) supercell and related layered structures. The state-of-the-art aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) and the modified geometric phase analysis (GPA) have been used to characterize the self-assembled transitional layers, misfit defects, and, in particular, the biaxial lattice strain distributions. We found that not only a sufficient lattice misfit is required through substrate selection and to be preserved in initial coherent epilayer growth, but also an appropriate interfacial reconstruction is crucial for triggering the growth of the new BFMO322 supercell structure. The observation of new transitional interfacial phases behaving like coherent film layers within the critical thickness challenges the conventional understanding in existing epitaxial growth model.

  14. Interfacial-tension-force model for the wavy stratified liquid-liquid flow pattern transition: The usage of two different approaches

    NASA Astrophysics Data System (ADS)

    de Castro, Marcelo Souza; Rodriguez, Oscar Mauricio Hernandez

    2016-06-01

    The study of the hydrodynamic stability of flow patterns is important in the design of equipment and pipelines for multiphase flows. The maintenance of a particular flow pattern becomes important in many applications, e.g., stratified flow pattern in heavy oil production avoiding the formation of emulsions because of the separation of phases and annular flow pattern in heat exchangers which increases the heat transfer coefficient. Flow maps are drawn to orientate engineers which flow pattern is present in a pipeline, for example. The ways how these flow maps are drawn have changed from totally experimental work, to phenomenological models, and then to stability analysis theories. In this work an experimental liquid-liquid flow map, with water and viscous oil as work fluids, drawn via subjective approach with high speed camera was used to compare to approaches of the same theory: the interfacial-tension-force model. This theory was used to drawn the wavy stratified flow pattern transition boundary. This paper presents a comparison between the two approaches of the interfacial-tension-force model for transition boundaries of liquid-liquid flow patterns: (i) solving the wave equation for the wave speed and using average values for wave number and wave speed; and (ii) solving the same equation for the wave number and then using a correlation for the wave speed. The results show that the second approach presents better results.

  15. Small Addition of Boron in Palladium Catalyst, Big Improvement in Fuel Cell's Performance: What May Interfacial Spectroelectrochemistry Tell?

    PubMed

    Jiang, Kun; Chang, Jinfa; Wang, Han; Brimaud, Sylvain; Xing, Wei; Behm, R Jürgen; Cai, Wen-Bin

    2016-03-23

    Direct formic acid fuel cell (DFAFC) with Pd-based catalyst anode is a promising energy converter to power portable devices. However, its commercialization is entangled with insufficient activity and poor stability of existing anode catalysts. Here we initially report that a DFAFC using facilely synthesized Pd-B/C with ca. 6 at. % B doping as the anode catalyst yields a maximum output power density of 316 mW cm(-2) at 30 °C, twice that with a same DFAFC using otherwise the state-of-the-art Pd/C. More strikingly, at a constant voltage of 0.3 V, the output power of the former cell is ca. 9 times as high as that of the latter after 4.5 h of continuous operation. In situ attenuated total reflection infrared spectroscopy is applied to probe comparatively the interfacial behaviors at Pd-B/C and Pd/C in conditions mimicking those for the DFAFC anode operation, revealing that the significantly improved cell performance correlates well with a substantially lowered CO accumulation at B-doped Pd surfaces. PMID:26938473

  16. Effect of cerium addition on casting/chill interfacial heat flux and casting surface profile during solidification of Al-14%Si alloy

    NASA Astrophysics Data System (ADS)

    Vijeesh, V.; Prabhu, K. N.

    2016-03-01

    In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast iron chills, to study the effect of Ce melt treatment on casting/chill interfacial heat flux transients and casting surface profile. The heat flux across the casting/chill interface was estimated using inverse modelling technique. On addition of 1.5% Ce, the peak heat flux increased by about 38%, 42% and 43% for copper, brass and cast iron chills respectively. The effect of Ce addition on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of an air gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line (Ra) and arithmetical mean of the absolute departures of the waviness profile from the centre line (Wa) were found to decrease on Ce addition. The interfacial gap width formed for the unmodified and Ce treated casting surfaces at the periphery were found to be about 35µm and 13µm respectively. The enhancement in heat transfer on addition of Ce addition was attributed to the lowering of the surface tension of the liquid melt. The gap width at the interface was used to determine the variation of heat transfer coefficient (HTC) across the chill surface after the formation of stable solid shell. It was found that the HTC decreased along the radial direction for copper and brass chills and increased along radial direction for cast iron chills.

  17. Deciphering the energetic barriers to calcium carbonate nucleation as a continuum of competing interfacial forces between polysaccharide chemistry and ionic strength

    NASA Astrophysics Data System (ADS)

    Giuffre, A. J.; De Yoreo, J. J.; Dove, P. M.

    2013-12-01

    Calcified skeletons are produced within complex assemblages of proteins and polysaccharides whose roles in mineralization are not well understood. Researchers have long-postulated that living organisms utilize organic matrices to actively guide the formation and growth of crystalline structures. The timing and placement of these features are most easily controlled during the nucleation stage. Our recent kinetic study of heterogeneous calcite nucleation found the energy barrier to formation is regulated by a systematic relationship to the competing interfacial energies between the substrate, crystal, and liquid (Giuffre et al., 2013). Chitosan presents a low energy barrier to nucleation because its near-neutral charge favors formation of a substrate-crystal interface, thus reducing substrate interactions with water. Progressively higher barriers are measured for negatively charged alginates and heparin that favor contact with the solution over the formation of new substrate-crystal interfaces. These results showed calcite nucleation is regulated by substrate-crystal interactions but could not quantify the larger continuum of competing forces that must regulate calcite nucleation. To determine these relationships, we estimate the energy barriers to nucleation and crystal-liquid interfacial energies by measuring the kinetics of homogeneous calcite nucleation in NaCl solutions at ionic strengths that extend to seawater salinity (0.6 M). The data show that solutions of greater ionic strength produce faster nucleation rates, smaller crystal-liquid interfacial energies, and lower barriers to nucleation, which concurs with recent theoretical and experimental findings that background electrolytes promote ion desolvation during nucleation. By applying this relationship to heterogeneous nucleation on chitosan and heparin in future work, we will quantify the relative contributions of substrate-crystal-liquid interfacial energies. The findings reiterate a directing role for PS

  18. Non-additivity of molecule-surface van der Waals potentials from force measurements

    NASA Astrophysics Data System (ADS)

    Tautz, Stefan

    2014-03-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Their description as an inherently quantum mechanical phenomenon was developed for single atoms and homogeneous macroscopic bodies by London, Casimir, and Lifshitz. For intermediate-sized objects like organic molecules an atomistic description is required, but explicit first principles calculations are very difficult since correlations between many interacting electrons have to be considered. Hence, semi-empirical correction schemes are often used that simplify the vdW interaction to a sum over atom-pair potentials. A similar gap exists between successful measurements of vdW and Casimir forces for single atoms on the one hand and macroscopic bodies on the other, as comparable experiments for molecules are absent. I will present experiments in which long-range vdW potentials between a series of related molecules and a metal surface have been determined experimentally. The experiments rely on the extremely sensitive force detection of an atomic force microscope in combination with its molecular manipulation capabilities. The results allow us to confirm the asymptotic force law and to quantify the non-additive part of the vdW interaction which is particularly challenging for theory. In the present case, cooperative effects account for 10% of the total interaction. This effect is of general validity in molecules and thus relevant at the intersection of chemistry, physics, biology, and materials science.

  19. Effect of the addition of water-soluble polymers on the interfacial properties of aerosol OT vesicles.

    PubMed

    Valero, Margarita; Velázquez, M Mercedes

    2004-10-15

    The properties of the interface of vesicles of pure sodium bis-(2-ethyl-hexyl) sulfosuccinate (AOT) and binary mixtures composed of AOT with poly(ethylene) glycol (PEG), poly(sodium 4-styrensulfonate) (PSS) and sodium chloride were investigated using absorption and steady-state fluorescence of nabumetone and electrophoretic mobility measurements. Results confirm those obtained in a previous work indicating that the addition of PEG, PSS, and NaCl stabilizes the AOT vesicles. The stabilization mechanism is the screening of the surface charge in the case of binary mixtures of AOT/PSS and AOT/NaCl and the polymer adsorption on the interface for vesicles of AOT/PEG. PMID:15450468

  20. Matching of additive and polarizable force fields for multiscale condensed phase simulations

    PubMed Central

    Baker, Christopher M.; Best, Robert B.

    2013-01-01

    Inclusion of electronic polarization effects is one of the key aspects in which the accuracy of current biomolecular force fields may be improved. The principal drawback of such approaches is the computational cost, which typically ranges from 3 – 10 times that of the equivalent additive model, and may be greater for more sophisticated treatments of polarization or other many-body effects. Here, we present a multiscale approach which may be used to enhance the sampling in simulations with polarizable models, by using the additive model as a tool to explore configuration space. We use a method based on information theory to determine the charges for an additive model that has optimal overlap with the polarizable one, and we demonstrate the feasibility of enhancing sampling via a hybrid replica exchange scheme for several model systems. An additional advantage is that, in the process, we obtain a systematic method for deriving charges for an additive model that will be the natural complement to its polarizable parent. The additive charges are found by an effective coarse-graining of the polarizable force field, rather than by ad hoc procedures. PMID:23997691

  1. Non-additivity of molecule-surface van der Waals potentials from force measurements

    NASA Astrophysics Data System (ADS)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-11-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  2. Non-additivity of molecule-surface van der Waals potentials from force measurements

    PubMed Central

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-01-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction. PMID:25424490

  3. Understanding the effects of a multi-functionalized additive on the cathode-electrolyte interfacial stability of Ni-rich materials

    NASA Astrophysics Data System (ADS)

    Yim, Taeeun; Kang, Kyoung Seok; Mun, Junyoung; Lim, Sang Hoo; Woo, Sang-Gil; Kim, Ki Jae; Park, Min-Sik; Cho, Woosuk; Song, Jun Ho; Han, Young-Kyu; Yu, Ji-Sang; Kim, Young-Jun

    2016-01-01

    Nickel-rich lithium nickel cobalt manganese oxides have received considerable attention as a promising cathode material, however, they have suffered from poor interfacial stability, especially at high temperature. Here, we suggest a bi-functionalized divinyl sulfone that enhances the applicability of a nickel-rich cathode via stabilization of the electrolyte-electrode interface. The divinyl sulfone forms a protective layer on the cathode surface by electrochemical oxidation reactions and this greatly decreases the internal pressure of the cell via stabilization of the Ni-rich cathode-electrolyte interface. The cell controlled with divinyl sulfone shows remarkable cycling performance with 91.9% capacity retention at elevated temperature even after 100 cycles. Additional electrode analyses and first-principles calculations provide critical spectroscopic evidences to demonstrate the combined effects of the sulfone and vinyl functional groups. Once the divinyl sulfone is electrochemically oxidized, the vinyl functional groups readily participate in further stabilizing sulfone-based solid electrolyte interphase intermediates and afford a durable protective layer on the nickel-rich electrode surface.

  4. Computing the acoustic radiation force exerted on a sphere using the translational addition theorem.

    PubMed

    Silva, Glauber T; Baggio, André L; Lopes, J Henrique; Mitri, Farid G

    2015-03-01

    In this paper, the translational addition theorem for spherical functions is employed to calculate the acoustic radiation force produced by an arbitrary shaped beam on a sphere arbitrarily suspended in an inviscid fluid. The procedure is also based on the partial-wave expansion method, which depends on the beam-shape and scattering coefficients. Given a set of beam-shape coefficients (BSCs) for an acoustic beam relative to a reference frame, the translational addition theorem can be used to obtain the BSCs relative to the sphere positioned anywhere in the medium. The scattering coefficients are obtained from the acoustic boundary conditions across the sphere's surface. The method based on the addition theorem is particularly useful to avoid quadrature schemes to obtain the BSCs. We use it to compute the acoustic radiation force exerted by a spherically focused beam (in the paraxial approximation) on a silicone-oil droplet (compressible fluid sphere). The analysis is carried out in the Rayleigh (i.e., the particle diameter is much smaller than the wavelength) and Mie (i.e., the particle diameter is of the order of the wavelength or larger) scattering regimes. The obtained results show that the paraxial focused beam can only trap particles in the Rayleigh scattering regime. PMID:25768823

  5. Influence of Polarization on Carbohydrate Hydration: A Comparative Study Using Additive and Polarizable Force Fields.

    PubMed

    Pandey, Poonam; Mallajosyula, Sairam S

    2016-07-14

    Carbohydrates are known to closely modulate their surrounding solvent structures and influence solvation dynamics. Spectroscopic investigations studying far-IR regions (below 1000 cm(-1)) have observed spectral shifts in the libration band (around 600 cm(-1)) of water in the presence of monosaccharides and polysaccharides. In this paper, we use molecular dynamics simulations to gain atomistic insight into carbohydrate-water interactions and to specifically highlight the differences between additive (nonpolarizable) and polarizable simulations. A total of six monosaccharide systems, α and β anomers of glucose, galactose, and mannose, were studied using additive and polarizable Chemistry at HARvard Macromolecular Mechanics (CHARMM) carbohydrate force fields. Solvents were modeled using three additive water models TIP3P, TIP4P, and TIP5P in additive simulations and polarizable water model SWM4 in polarizable simulations. The presence of carbohydrate has a significant effect on the microscopic water structure, with the effects being pronounced for proximal water molecules. Notably, disruption of the tetrahedral arrangement of proximal water molecules was observed due to the formation of strong carbohydrate-water hydrogen bonds in both additive and polarizable simulations. However, the inclusion of polarization resulted in significant water-bridge occupancies, improved ordered water structures (tetrahedral order parameter), and longer carbohydrate-water H-bond correlations as compared to those for additive simulations. Additionally, polarizable simulations also allowed the calculation of power spectra from the dipole-dipole autocorrelation function, which corresponds to the IR spectra. From the power spectra, we could identify spectral signatures differentiating the proximal and bulk water structures, which could not be captured from additive simulations. PMID:27266974

  6. Influence of Additional Tensile Force on Springback of Tube Under Rotary Draw Bending

    NASA Astrophysics Data System (ADS)

    E, Daxin; Guan, Zhiping; Chen, Jisheng

    2012-11-01

    According to the characteristics of tube under rotary draw bending, the formulae were derived to calculate the springback angles of tubes subjected to combined bending and additional tension. Especially, as the neutral layer (NL) moves to the inner concave surface of the bend, the analytical values agree very well with the experimental results. The analysis shows that the additional tensile force causes the movement of the NL toward the bending center and makes the deformation behavior under rotary draw bending or numerically controlled (NC) bending different with that under pure bending, and also it could enlarge the springback angle if taking the movement of the NL into consideration. In some range, the springback angle would increase slightly with larger wall thickness/diameter ratio and decrease with wall thinning. The investigation could provide reference for the analysis of rotary draw bending, the design of NC tube bender and the related techniques.

  7. Transferability and additivity of dihedral parameters in polarizable and nonpolarizable empirical force fields.

    PubMed

    Zgarbová, Marie; Rosnik, Andreana M; Luque, F Javier; Curutchet, Carles; Jurečka, Petr

    2015-09-30

    Recent advances in polarizable force fields have revealed that major reparameterization is necessary when the polarization energy is treated explicitly. This study is focused on the torsional parameters, which are crucial for the accurate description of conformational equilibria in biomolecules. In particular, attention is paid to the influence of polarization on the (i) transferability of dihedral terms between molecules, (ii) transferability between different environments, and (iii) additivity of dihedral energies. To this end, three polarizable force fields based on the induced point dipole model designed for use in AMBER are tested, including two recent ff02 reparameterizations. Attention is paid to the contributions due to short range interactions (1-2, 1-3, and 1-4) within the four atoms defining the dihedral angle. The results show that when short range 1-2 and 1-3 polarization interactions are omitted, as for instance in ff02, the 1-4 polarization contribution is rather small and unlikely to improve the description of the torsional energy. Conversely, when screened 1-2 and 1-3 interactions are included, the polarization contribution is sizeable and shows potential to improve the transferability of parameters between different molecules and environments as well as the additivity of dihedral terms. However, to reproduce intramolecular polarization effects accurately, further fine-tuning of the short range damping of polarization is necessary. PMID:26224547

  8. CHARMM Additive All-Atom Force Field for Acyclic Polyalcohols, Acyclic Carbohydrates and Inositol

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    Parametrization of the additive all-atom CHARMM force field for acyclic polyalcohols, acyclic carbohydrates and inositol is conducted. Initial parameters were transferred from the alkanes and hexopyranose carbohydrates, with subsequent development and optimization of parameters unique to the molecules considered in this study. Using the model compounds acetone and acetaldehyde, nonbonded parameters for carbonyls were optimized targeting quantum mechanical interaction data for solute-water pairs and pure solvent thermodynamic data. Bond and angle parameters were adjusted by comparing optimized geometries to small molecule crystal survey data and by performing vibrational analyses on acetone, acetaldehyde and glycerol. C-C-C-C, C-C-C-O, C-C-OH and O-C-C-O torsional parameters for polyol chains were fit to quantum mechanical dihedral potential energy scans comprising over 1500 RIMP2/cc-pVTZ//MP2/6-31G(d) conformations using an automated Monte Carlo simulated annealing procedure. Comparison of computed condensed-phase data, including crystal lattice parameters and densities, NMR proton-proton couplings, densities and diffusion coefficients of aqueous solutions, to experimental data validated the optimized parameters. Parameter development for these compounds proved particularly challenging because of the flexibility of the acyclic sugars and polyalcohols as well as the intramolecular hydrogen bonding between vicinal hydroxyls for all of the compounds. The newly optimized additive CHARMM force field parameters are anticipated to be of utility for atomic level of detail simulations of acyclic polyalcohols, acyclic carbohydrates and inositol in solution. PMID:20160980

  9. Simulation of uphill/downhill running on a level treadmill using additional horizontal force.

    PubMed

    Gimenez, Philippe; Arnal, Pierrick J; Samozino, Pierre; Millet, Guillaume Y; Morin, Jean-Benoit

    2014-07-18

    Tilting treadmills allow a convenient study of biomechanics during uphill/downhill running, but they are not commonly available and there is even fewer tilting force-measuring treadmill. The aim of the present study was to compare uphill/downhill running on a treadmill (inclination of ± 8%) with running on a level treadmill using additional backward or forward pulling forces to simulate the effect of gravity. This comparison specifically focused on the energy cost of running, stride frequency (SF), electromyographic activity (EMG), leg and foot angles at foot strike, and ground impact shock. The main results are that SF, impact shock, and leg and foot angle parameters determined were very similar and significantly correlated between the two methods, the intercept and slope of the linear regression not differing significantly from zero and unity, respectively. The correlation of oxygen uptake (V̇O2) data between both methods was not significant during uphill running (r=0.42; P>0.05). V̇O2 data were correlated during downhill running (r=0.74; P<0.01) but there was a significant difference between the methods (bias=-2.51 ± 1.94 ml min(-1) kg(-1)). Linear regressions for EMG of vastus lateralis, biceps femoris, gastrocnemius lateralis, soleus and tibialis anterior were not different from the identity line but the systematic bias was elevated for this parameter. In conclusion, this method seems appropriate for the study of SF, leg and foot angle, impact shock parameters but is less applicable for physiological variables (EMG and energy cost) during uphill/downhill running when using a tilting force-measuring treadmill is not possible. PMID:24811045

  10. CHARMM Additive All-Atom Force Field for Aldopentofuranoses, Methyl-Aldopentofuranosides and Fructofuranose

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    An additive all-atom empirical force field for aldopentofuranoses, methyl-aldopentofuranosides (Me-aldopentofuranosides) and fructofuranose carbohydrates, compatible with existing CHARMM carbohydrate parameters, is presented. Building on existing parameters transferred from cyclic ethers and hexopyranoses, parameters were further developed using target data for complete furanose carbohydrates as well as O-methyl tetrahydrofuran. The bond and angle equilibrium parameters were adjusted to reproduce target geometries from a survey of furanose crystal structures, and dihedral parameters were fit to over 1700 quantum mechanical (QM) MP2/cc-pVTZ//MP2/6-31G(d) conformational energies. The conformational energies were for a variety of complete furanose monosaccharides, and included two-dimensional ring pucker energy surfaces. Bonded parameter optimization led to the correct description of the ring pucker for a large set of furanose compounds, while furanose-water interaction energies and distances reproduced QM HF/6-31G(d) results for a number of furanose monosaccharides, thereby validating the nonbonded parameters. Crystal lattice unit cell parameters and volumes, aqueous-phase densities, and aqueous NMR ring pucker and exocyclic data were used to validate the parameters in condensed-phase environments. Conformational sampling analysis of the ring pucker and exocyclic group showed excellent agreement with experimental NMR data, demonstrating that the conformational energetics in aqueous solution are accurately described by the optimized force field. Overall, the parameters reproduce available experimental data well and are anticipated to be of utility in future computational studies of carbohydrates, including in the context of proteins, nucleic acids and/or lipids when combined with existing CHARMM biomolecular force fields. PMID:19694450

  11. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  12. CHARMM Additive All-Atom Force Field for Phosphate and Sulfate Linked to Carbohydrates

    PubMed Central

    Mallajosyula, Sairam S.; Guvench, Olgun; Hatcher, Elizabeth; MacKerell, Alexander D.

    2012-01-01

    Presented is an extension of the CHARMM additive all-atom carbohydrate force field to enable the modeling of phosphate and sulfate linked to carbohydrates. The parameters are developed in a hierarchical fashion using model compounds containing the key atoms in the full carbohydrates. Target data for parameter optimization included full two-dimensional energy surfaces defined by the glycosidic dihedral angle pairs in the phosphate/sulfate model compound analogs of hexopyranose monosaccharide phosphates and sulfates, as determined by quantum mechanical (QM) MP2/cc-pVTZ single point energies on MP2/6-31+G(d) optimized structures. In order to achieve balanced, transferable dihedral parameters for the dihedral angles, surfaces for all possible anomeric and conformational states were included during the parametrization process. In addition, to model physiologically relevant systems both the mono- and di-anionic charged states were studied for the phosphates. This resulted in over 7000 MP2/cc-pVTZ//MP2/6-31G+(d) model compound conformational energies which, supplemented with QM geometries, were the main target data for the parametrization. Parameters were validated against crystals of relevant monosaccharide derivatives obtained from the Cambridge Structural Database (CSD) and larger systems, namely inositol-(tri/tetra/penta) phosphates non-covalently bound to the pleckstrin homology (PH) domain and oligomeric chondroitin sulfate in solution and in complex with cathepsin K protein. PMID:22685386

  13. Demonstration of non-additivity and asymmetry in the lateral Casimir force

    NASA Astrophysics Data System (ADS)

    Chiu, Hsiang-Chih

    2009-10-01

    The Casimir effect is a purely quantum mechanical phenomenon which has drawn extensive attention in the last decade. With the rapid development of modern scientific instruments, it has been demonstrated and measured with unprecedented precision. Because of its unique dependence on the separation and geometry, the Casimir force is expected to play an important role in modern nano-electro-mechanical systems. An understanding of the shape dependence of the Casimir force and its control has become a very important research topic for the future nano-technology. Since the demonstration of the lateral Casimir force in 2002 at UC Riverside, this special effect has inspired a lot of theoretical research. The asymmetry of the lateral Casimir has been predicted and exact theories which take into account diffraction-like correlation effect between the scattered zero point photons from the boundaries have been proposed. We improved the experimental setup and experimental conditions (grating period of order of the separation distance) to study these new phenomenon. In this research, we demonstrate the asymmetrical lateral Casimir force for the first time. The experimental results show very good agreement with a recently developed exact theory based on the scattering approach with no tting parameters. The measured force also show the expected deviation from the commonly used proximity force approximation. The results provide a further understanding of the shape dependence of the Casimir force and will enhance the capabilities for its application in nano technology, especially for the frictionless transmission of lateral motion.

  14. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  15. Interfacial solvation thermodynamics.

    PubMed

    Ben-Amotz, Dor

    2016-10-19

    Previous studies have reached conflicting conclusions regarding the interplay of cavity formation, polarizability, desolvation, and surface capillary waves in driving the interfacial adsorptions of ions and molecules at air-water interfaces. Here we revisit these questions by combining exact potential distribution results with linear response theory and other physically motivated approximations. The results highlight both exact and approximate compensation relations pertaining to direct (solute-solvent) and indirect (solvent-solvent) contributions to adsorption thermodynamics, of relevance to solvation at air-water interfaces, as well as a broader class of processes linked to the mean force potential between ions, molecules, nanoparticles, proteins, and biological assemblies. PMID:27545849

  16. Interfacial engineering of microstructured materials

    NASA Astrophysics Data System (ADS)

    Poda, Aimee

    The tribological behavior of octadecyltrichlorosilane self assembled monolayers (OTS-SAMs) has been successfully exploited to reduce energy losses and to produce adequate adhesion barrier properties on many MEMS surfaces. Unfortunately, performance discrepancies are reported in the literature between films produced on smooth surfaces as compared to typical MEMS surfaces maintaining topographical roughness. Rational explanations in terms of reproducibility issues, production considerations, and the scale of measurement technique have been introduced to account for some of the variation. The tribological phenomena at the micro-scale are complicated by the fact that rather than inertial effects, the forces associated with the surface become dominant factors influencing the mechanical behavior of contacting components. In MEMS, real mechanical contacts typically consist of a few nanometer scale asperities. Furthermore, various surface topographies exist for MEMS device fabrication and their corresponding asperity profiles can vary drastically based on the production process. This dissertation presents research focusing on the influence of topographical asperities on OTS film properties of relevance for efficient tribological improvement. A fundamental approach has been taken to carefully examine the factors that contribute to high quality film formation, specifically formation temperature and the role of interfacial water layer associated with the sample surface. As evidenced on smooth surfaces, the characteristics for successful tribological performance of OTS films are strongly dependent on the lateral packing density and molecular orientation of the monolayer. Limited information is available on how monolayers associate on topographical asperities and whether these topographical asperities influence the interfacial reactivity of MEMS surfaces. A silica film produced from a low temperature, vapor-phase hydrolysis of tetrachlorosilane with a tunable topography is

  17. Addition of Electrostatic Forces to EDEM with Applications to Triboelectrically Charged Particles

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Calle, Carlos; Curry, David

    2008-01-01

    Tribocharging of particles is common in many processes including fine powder handling and mixing, printer toner transport and dust extraction. In a lunar environment with its high vacuum and lack of water, electrostatic forces are an important factor to consider when designing and operating equipment. Dust mitigation and management is critical to safe and predictable performance of people and equipment. The extreme nature of lunar conditions makes it difficult and costly to carryout experiments on earth which are necessary to better understand how particles gather and transfer charge between each other and with equipment surfaces. DEM (Discrete Element Modeling) provides an excellent virtual laboratory for studying tribocharging of particles as well as for design of devices for dust mitigation and for other purposes related to handling and processing of lunar regolith. Theoretical and experimental work has been performed pursuant to incorporating screened Coulombic electrostatic forces into EDEM Tm, a commercial DEM software package. The DEM software is used to model the trajectories of large numbers of particles for industrial particulate handling and processing applications and can be coupled with other solvers and numerical models to calculate particle interaction with surrounding media and force fields. In this paper we will present overview of the theoretical calculations and experimental data and their comparison to the results of the DEM simulations. We will also discuss current plans to revise the DEM software with advanced electrodynamic and mechanical algorithms.

  18. Impact of interfacial tension on residual CO2 clusters in porous sandstone

    NASA Astrophysics Data System (ADS)

    Jiang, Fei; Tsuji, Takeshi

    2015-03-01

    We develop a numerical simulation that uses the lattice Boltzmann method to directly calculate the characteristics of residual nonwetting-phase clusters to quantify capillary trapping mechanisms in real sandstone. For this purpose, a digital-rock-pore model reconstructed from micro-CT-scanned images of Berea sandstone is filtered and segmented into a binary file. The residual-cluster distribution is generated following simulation of the drainage and imbibition processes. The characteristics of the residual cluster in terms of size distribution, major length, interfacial area, and sphericity are investigated under conditions of different interfacial tension (IFT). Our results indicate that high interfacial tension increases the residual saturation and leads to a large size distribution of residual clusters. However, low interfacial tension results in a larger interfacial area, which is beneficial for dissolution and reaction processes during geological carbon storage. Analysis of the force balance acting on the residual clusters demonstrates that trapping stability is higher in high interfacial tension case, and the interfacial tension should be a controlling factor for the trapping stability in addition to the pore geometry and connectivity. The proposed numerical method can handle the complex displacement of multicomponent systems in porous media. By using this method, we can obtain residual-cluster distributions under different conditions for optimizing the storage capacity of carbon-storage projects.

  19. Magnetic Force Microscopy Study of Zr2Co11 -Based Nanocrystalline Materials: Effect of Mo Addition

    DOE PAGESBeta

    Yue, Lanping; Jin, Yunlong; Zhang, Wenyong; Sellmyer, David J.

    2015-01-01

    Tmore » he addition of Molybdenum was used to modify the nanostructure and enhance coercivity of rare-earth-free Zr2Co11-based nanocrystalline permanent magnets. he effect of Mo addition on magnetic domain structures of melt spun nanocrystalline Zr16Co84-xMox(x=0, 0.5, 1, 1.5, and 2.0) ribbons has been investigated. It was found that magnetic properties and local domain structures are strongly influenced by Mo doping. he coercivity of the samples increases with the increase in Mo content (x≤1.5). he maximum energy product(BH)maxincreases with increasingxfrom 0.5 MGOe forx=0to a maximum value of 4.2 MGOe forx=1.5. he smallest domain size with a relatively short magnetic correlation length of 128 nm and largest root-mean-square phase shiftΦrmsvalue of 0.66° are observed for thex=1.5. he optimal Mo addition promotes magnetic domain structure refinement and thus leads to a significant increase in coercivity and energy product in this sample.« less

  20. Coriolis Force Mass-Flow Meter Composed of a Straight Pipe and an Additional Resonance-Vibrator

    NASA Astrophysics Data System (ADS)

    Tsutsui, Hirohide; Tomikawa, Yoshiro

    1993-05-01

    This paper deals with a new construction for a mass-flow meter using Coriolis force, and its basic experimental results. Some Coriolis force mass-flow meters, proposed up to now, are of a twin construction of, for example, a U-type pipe or a straight-type pipe, where the mass-flow is determined by measuring the relative displacement between the pipes. Therefore, their structure is too complex. To improve this situation, the authors propose a new mass-flow meter using one straight pipe, together with an additional flexural resonance-vibrator. The experimental results prove that a mass-flow meter can be realized by such a simple construction as dealt with here.

  1. Interfacial tension of complex coacervated mussel adhesive protein according to the Hofmeister series.

    PubMed

    Lim, Seonghye; Moon, Dustin; Kim, Hyo Jeong; Seo, Jeong Hyun; Kang, In Seok; Cha, Hyung Joon

    2014-02-01

    Complex coacervation is a liquid-liquid phase separation in a colloidal system of two oppositely charged polyelectrolytes or colloids. The interfacial tension of the coacervate phase is the key parameter for micelle formation and interactions with the encapsulating material. However, the relationship between interfacial tensions and various salt solutions is poorly understood in complex coacervation. In the present work, the complex coacervate dynamics of recombinant mussel adhesive protein (MAP) with hyaluronic acid (HA) were determined in the presence of Hofmeister series salt ions. Using measurements of absorbance, hydrodynamic diameter, capillary force, and receding contact angle in the bulk phase, the interfacial tensions of complex coacervated MAP/HA were determined to be 0.236, 0.256, and 0.287 mN/m in 250 mM NaHCOO, NaCl, and NaNO3 solutions, respectively. The sequences of interfacial tensions and contact angles of the complex coacervates in the presence of three sodium salts with different anions were found to follow the Hofmeister ordering. The tendency of interfacial tension between the coacervate and dilute phases in the presence of different types of Hofmeister salt ions could provide a better understanding of Hofmeister effects on complex coacervated materials based on the protein-polysaccharide system. This information can also be utilized for microencapsulation and adsorption by controlling intramolecular interactions. In addition, the injection molding dynamics of mussel byssus formation was potentially explained based on the measured interfacial tension of coacervated MAP. PMID:24490867

  2. Lessons Learned at the Idaho National Laboratory for the Entry into Force of the U.S. Additional Protocol

    SciTech Connect

    Jeffrey C. Joe; Shauna A. Hoiland

    2009-07-01

    For a number of years, the Idaho National Laboratory (INL) has been preparing for the entry into force of the U.S. Additional Protocol (AP). These preparations included attending training, participating in tabletop exercises, preparing draft declarations, developing INL-specific guidance documents, preparing for and hosting a mock complementary access visit, and preparing declarations for official submittal. All of these activities, the training materials, and software developed by other U.S. DOE national laboratories (PNNL, ORNL, LANL, and BNL) were very helpful in preparing for the entry into force of the AP. As with any endeavor of this size and complexity, however, there are always instances where even the best preparations and advanced planning do not anticipate every challenge. As the DOE's lead nuclear energy research and development facility, the INL faced many unique challenges. The majority of research conducted at the INL is nuclear fuel cycle related, most of which is not protected by the National Security Exclusion. This paper describes the lessons learned from the INL’s experience of preparing for the entry into force of the AP, specifically how translating and implementing general principles into actual activities proved to be one of many challenges, and provides general suggestions on how to respond effectively and efficiently to routine annual data calls and other AP requests.

  3. SEI Formation and Interfacial Stability of a Si Electrode in a LiTDI-Salt Based Electrolyte with FEC and VC Additives for Li-Ion Batteries.

    PubMed

    Lindgren, Fredrik; Xu, Chao; Niedzicki, Leszek; Marcinek, Marek; Gustafsson, Torbjörn; Björefors, Fredrik; Edström, Kristina; Younesi, Reza

    2016-06-22

    An electrolyte based on the new salt, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), is evaluated in combination with nano-Si composite electrodes for potential use in Li-ion batteries. The additives fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are also added to the electrolyte to enable an efficient SEI formation. By employing hard X-ray photoelectron spectroscopy (HAXPES), the SEI formation and the development of the active material is probed during the first 100 cycles. With this electrolyte formulation, the Si electrode can cycle at 1200 mAh g(-1) for more than 100 cycles at a coulombic efficiency of 99%. With extended cycling, a decrease in Si particle size is observed as well as an increase in silicon oxide amount. As opposed to LiPF6 based electrolytes, this electrolyte or its decomposition products has no side reactions with the active Si material. The present results further acknowledge the positive effects of SEI forming additives. It is suggested that polycarbonates and a high LiF content are favorable components in the SEI over other kinds of carbonates formed by ethylene carbonate (EC) and dimethyl carbonate (DMC) decomposition. This work thus confirms that LiTDI in combination with the investigated additives is a promising salt for Si electrodes in future Li-ion batteries. PMID:27220376

  4. Enzymatically activated emulsions stabilised by interfacial nanofibre networks.

    PubMed

    Moreira, Inês P; Sasselli, Ivan Ramos; Cannon, Daniel A; Hughes, Meghan; Lamprou, Dimitrios A; Tuttle, Tell; Ulijn, Rein V

    2016-03-01

    We report on-demand formation of emulsions stabilised by interfacial nanoscale networks. These are formed through biocatalytic dephosphorylation and self-assembly of Fmoc(9-fluorenylmethoxycarbonyl)dipeptide amphiphiles in aqueous/organic mixtures. This is achieved by using alkaline phosphatase which transforms surfactant-like phosphorylated precursors into self-assembling aromatic peptide amphiphiles (Fmoc-tyrosine-leucine, Fmoc-YL) that form nanofibrous networks. In biphasic organic/aqueous systems, these networks form preferentially at the interface thus providing a means of emulsion stabilisation. We demonstrate on-demand emulsification by enzyme addition, even after storage of the biphasic mixture for several weeks. Experimental (Fluorescence, FTIR spectroscopy, fluorescence microscopy, electron microscopy, atomic force microscopy) and computational techniques (atomistic molecular dynamics) are used to characterise the interfacial self-assembly process. PMID:26905042

  5. Resonance scattering and radiation force calculations for an elastic cylinder using the translational addition theorem for cylindrical wave functions

    SciTech Connect

    Mitri, F. G.

    2015-09-15

    The standard Resonance Scattering Theory (RST) of plane waves is extended for the case of any two-dimensional (2D) arbitrarily-shaped monochromatic beam incident upon an elastic cylinder with arbitrary location using an exact methodology based on Graf’s translational addition theorem for the cylindrical wave functions. The analysis is exact as it does not require numerical integration procedures. The formulation is valid for any cylinder of finite size and material that is immersed in a nonviscous fluid. Partial-wave series expansions (PWSEs) for the incident, internal and scattered linear pressure fields are derived, and the analysis is further extended to obtain generalized expressions for the on-axis and off-axis acoustic radiation force components. The wave-fields are expressed using generalized PWSEs involving the beam-shape coefficients (BSCs) and the scattering coefficients of the cylinder. The off-axial BSCs are expressed analytically in terms of an infinite PWSE with emphasis on the translational offset distance d. Numerical computations are considered for a zeroth-order quasi-Gaussian beam chosen as an example to illustrate the analysis. Acoustic resonance scattering directivity diagrams are calculated by subtracting an appropriate background from the expression of the scattered pressure field. In addition, computations for the radiation force exerted on an elastic cylinder centered on the axis of wave propagation of the beam, and shifted off-axially are analyzed and discussed.

  6. Modeling and characterization of interfacial adhesion and fracture

    NASA Astrophysics Data System (ADS)

    Yao, Qizhou

    2000-09-01

    The loss of interfacial adhesion is mostly seen in the failure of polymer adhesive joints. In addition to the intrinsic physical attraction across the interface, the interfacial adhesion strength is believed to highly depend on a number of factors, such as adhesive chemistry/structure, surface topology, fracture pattern, thermal and elastic mismatch across the interface. The fracture failure of an adhesive joint involves basically three aspects, namely, the intrinsic interfacial strength, the driving force for fracture and other energy dissipation. One may define the intrinsic interfacial strength as the maximum value of the intrinsic interfacial adhesion. The total work done by external forces to the component that contains the interface is partitioned into two parts. The first part is consumed by all other energy dissipation mechanisms (plasticity, heat generation, viscosity, etc.). The second part is used to debond the interface. This amount should equal to the intrinsic adhesion of the interface according to the laws of conservation of energy. It is clear that in order to understand the fundamental physics of adhesive joint failure, one must be able to characterize the intrinsic interfacial adhesion and be able to identify all the major energy dissipation mechanisms involved in the debonding process. In this study, both physical and chemical adhesion mechanisms were investigated for an aluminum-epoxy interface. The physical bonding energy was estimated by computing the Van de Waals forces across the interface. A hydration model was proposed and the associated chemical bonding energy was calculated through molecular simulations. Other energy dissipation mechanisms such as plasticity and thermal residual stresses were also identified and investigated for several four-point bend specimens. In particular, a micromechanics based model was developed to estimate the adhesion enhancement due to surface roughness. It is found that for this Al-epoxy system the major

  7. Interfacial Phenomena in Al/Al, Al/Cu, and Cu/Cu Joints Soldered Using an Al-Zn Alloy with Ag or Cu Additions

    NASA Astrophysics Data System (ADS)

    Pstruś, Janusz; Gancarz, Tomasz

    2014-05-01

    The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

  8. Mechanobiology of interfacial growth

    NASA Astrophysics Data System (ADS)

    Ciarletta, P.; Preziosi, L.; Maugin, G. A.

    2013-03-01

    A multiscale analysis integrating biomechanics and mechanobiology is today required for deciphering the crosstalk between biochemistry, geometry and elasticity in living materials. In this paper we derive a unified thermomechanical theory coupling growth processes with mass transport phenomena across boundaries and/or material interfaces. Inside a living system made by two contiguous bodies with varying volumes, an interfacial growth mechanism is considered to force fast but continuous variations of the physical fields inside a narrow volume across the material interface. Such a phenomenon is modelled deriving homogenized surface fields on a growing non-material discontinuity, possibly including a singular edge line. A number of balance laws is derived for imposing the conservation of the thermomechanical properties of the biological system. From thermodynamical arguments we find that the normal displacement of the non-material interface is governed by the jump of a new form of material mechanical-energy flux, also involving the kinetic energies and the mass fluxes. Furthermore, the configurational balance indicates that the surface Eshelby tensor is the tangential stress measure driving the material inhomogeneities on the non-material interface. Accordingly, stress-dependent evolution laws for bulk and interfacial growth processes are derived for both volume and surface fields. The proposed thermomechanical theory is finally applied to three biological system models. The first two examples are focused on stress-free growth problems, concerning the morphogenesis of animal horns and of seashells. The third application finally deals with the stress-driven surface evolution of avascular tumours with heterogeneous structures. The results demonstrate that the proposed theory can successfully model those biological systems where growth and mass transport phenomena interact at different length-scales. Coupling biological, mechanical and geometrical factors, the proposed

  9. Repeated forced swim stress has additive effects in anxiety behavior and in cathecolamine levels of adult rats exposed to deltamethrin.

    PubMed

    Habr, Soraya F; Macrini, Daclé J; Florio, Jorge C; Bernardi, Maria M

    2014-01-01

    Deltamethrin (DTM) is a type II pyrethroid insecticide that elicits autonomic and neuroendocrine responses that indicate high levels of stress, presumably caused by the neurotoxic effect of the insecticide. This study investigated the effect of DTM exposure (10 mg/kg, p.o.) and an additional stress induced in the forced swim test (FST) in behavioral tasks related to anxiety, serum corticosterone levels, and striatal neurotransmitter levels. Open field behavior and social interaction were evaluated after DTM administration (10 mg kg(-1), p.o). DTM per se reduced rearing frequency in the open field, but no alterations in locomotion frequency or immobility duration were detected. Stress increased immobility duration compared with non-stressed animals. DTM reduced social interaction and increased corticosterone levels, and these effects were enhanced in stressed animals. Mainly stress affected dopaminergic and serotoninergic activity. In anxiety behavior and in both neurotransmitters and metabolites levels it was observed an additive effect of stress in DTM treated rat data. These results indicate that DTM enhanced the anxiogenic responses and stress had an additive effect over the DTM stress. The neurochemical data did not indicate an interaction between stress and DTM exposure. The present results maybe important for implementing pyrethroid insecticide safety standards. PMID:25444720

  10. Examination of humidity effects on measured thickness and interfacial phenomena of exfoliated graphene on silicon dioxide via amplitude modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Jinkins, K.; Camacho, J.; Farina, L.; Wu, Y.

    2015-12-01

    The properties of Few-Layer Graphene (FLG) change with the number of layers and Amplitude Modulation (AM) Atomic Force Microscopy (AFM) is commonly used to determine the thickness of FLG. However, AFM measurements have been shown to be sensitive to environmental conditions such as relative humidity (RH). In the present study, AM-AFM is used to measure the thickness and loss tangent of exfoliated graphene on silicon dioxide (SiO2) as RH is increased from 10% to 80%. We show that the measured thickness of graphene is dependent on RH. The loss tangent values of the graphene and oxide regions are both affected by humidity, with generally higher loss tangent for graphene than SiO2. As RH increases, we observe the loss tangent of both materials approaches the same value. We hypothesize that there is a layer of water trapped between the graphene and SiO2 substrate to explain this observation. Using this interpretation, the loss tangent images also indicate movement and change in this trapped water layer as RH increases, which impacts the measured thickness of graphene using AM-AFM.

  11. Role of the dispersion force in modeling the interfacial properties of molecule-metal interfaces: adsorption of thiophene on copper surfaces

    PubMed Central

    Hu, Zhi-Xin; Lan, Haiping; Ji, Wei

    2014-01-01

    We present density functional theory calculations of the geometry, adsorption energy and electronic structure of thiophene adsorbed on Cu(111), Cu(110) and Cu(100) surfaces. Our calculations employ dispersion corrections and self-consistent van der Waals density functionals (vdW-DFs). In terms of speed and accuracy, we find that the dispersion-energy-corrected Revised Perdue-Burke-Enzerhof (RPBE) functional is the “best balanced” method for predicting structural and energetic properties, while vdW-DF is also highly accurate if a proper exchange functional is used. Discrepancies between theory and experiment in molecular geometry can be solved by considering x-ray generated core-holes. However, the discrepancy concerning the adsorption site for thiophene/Cu(100) remains unresolved and requires both further experiments and deeper theoretical analysis. For all the interfaces, the PBE functional reveals a covalent bonding picture which the inclusion of dispersive contributions does not change to a vdW one. Our results provide a comprehensive understanding of the role of dispersive forces in modelling molecule-metal interfaces. PMID:24849493

  12. Examination of humidity effects on measured thickness and interfacial phenomena of exfoliated graphene on silicon dioxide via amplitude modulation atomic force microscopy

    SciTech Connect

    Jinkins, K.; Farina, L.; Wu, Y.; Camacho, J.

    2015-12-14

    The properties of Few-Layer Graphene (FLG) change with the number of layers and Amplitude Modulation (AM) Atomic Force Microscopy (AFM) is commonly used to determine the thickness of FLG. However, AFM measurements have been shown to be sensitive to environmental conditions such as relative humidity (RH). In the present study, AM-AFM is used to measure the thickness and loss tangent of exfoliated graphene on silicon dioxide (SiO{sub 2}) as RH is increased from 10% to 80%. We show that the measured thickness of graphene is dependent on RH. The loss tangent values of the graphene and oxide regions are both affected by humidity, with generally higher loss tangent for graphene than SiO{sub 2}. As RH increases, we observe the loss tangent of both materials approaches the same value. We hypothesize that there is a layer of water trapped between the graphene and SiO{sub 2} substrate to explain this observation. Using this interpretation, the loss tangent images also indicate movement and change in this trapped water layer as RH increases, which impacts the measured thickness of graphene using AM-AFM.

  13. Interfacial instabilities in vibrated fluids

    NASA Astrophysics Data System (ADS)

    Porter, Jeff; Laverón-Simavilla, Ana; Tinao Perez-Miravete, Ignacio; Fernandez Fraile, Jose Javier

    2016-07-01

    Vibrations induce a range of different interfacial phenomena in fluid systems depending on the frequency and orientation of the forcing. With gravity, (large) interfaces are approximately flat and there is a qualitative difference between vertical and horizontal forcing. Sufficient vertical forcing produces subharmonic standing waves (Faraday waves) that extend over the whole interface. Horizontal forcing can excite both localized and extended interfacial phenomena. The vibrating solid boundaries act as wavemakers to excite traveling waves (or sloshing modes at low frequencies) but they also drive evanescent bulk modes whose oscillatory pressure gradient can parametrically excite subharmonic surface waves like cross-waves. Depending on the magnitude of the damping and the aspect ratio of the container, these locally generated surfaces waves may interact in the interior resulting in temporal modulation and other complex dynamics. In the case where the interface separates two fluids of different density in, for example, a rectangular container, the mass transfer due to vertical motion near the endwalls requires a counterflow in the interior region that can lead to a Kelvin-Helmholtz type instability and a ``frozen wave" pattern. In microgravity, the dominance of surface forces favors non-flat equilibrium configurations and the distinction between vertical and horizontal applied forcing can be lost. Hysteresis and multiplicity of solutions are more common, especially in non-wetting systems where disconnected (partial) volumes of fluid can be established. Furthermore, the vibrational field contributes a dynamic pressure term that competes with surface tension to select the (time averaged) shape of the surface. These new (quasi-static) surface configurations, known as vibroequilibria, can differ substantially from the hydrostatic state. There is a tendency for the interface to orient perpendicular to the vibrational axis and, in some cases, a bulge or cavity is induced

  14. Forced and natural carbonation of lime-based mortars with and without additives: Mineralogical and textural changes

    SciTech Connect

    Cultrone, G.

    2005-12-15

    We have studied the carbonation process in different types of mortars, with and without pozzolana or air-entraining additives, subject to a CO{sub 2}-rich atmosphere and compared the results with those of similar naturally carbonated mortars. We used X-ray diffraction technique to demonstrate that high CO{sub 2} concentrations favour a faster, more complete carbonation process with 8 days being sufficient to convert portlandite into 90 wt.% calcite. Full carbonation, however, is not reached during the life-span of the tests, not even in forced carbonation experiments. This could be due to at least one of the following phenomena: a premature drying of samples during carbonation reaction, the temperature at which the carbonation process was carried out or the reduction of pore volume occupied by newly formed calcite crystals. This last option seems to be the least probable. We observed a more prolific development of calcite crystals in the pores and fissures through which the carbonic anhydride flows. Under natural conditions, carbonation is much slower and similar levels are not reached for 6 months. These differences suggest that the carbonation process is influenced by the amount of CO{sub 2} used. Both the mineralogy and texture of mortars vary depending on the type of additive used but the speed of the portlandite-calcite transformation does not change significantly. Pozzolana produces hydraulic mortars although the quantity of calcium aluminosilicate crystals is low. The air-entraining agent significantly alters the texture of the mortars creating rounded pores and eliminating or reducing the drying cracks.

  15. Smart interfacial bonding alloys

    SciTech Connect

    R. Q. Hwang; J. C. Hamilton; J. E. Houston

    1999-04-01

    The goal of this LDRD was to explore the use of the newly discovered strain-stabilized 2-D interfacial alloys as smart interface bonding alloys (SIBA). These materials will be used as templates for the heteroepitaxial growth of metallic thin films. SIBA are formed by two metallic components which mix at an interface to relieve strain and prevent dislocations from forming in subsequent thin film growth. The composition of the SIBA is determined locally by the amount of strain, and therefore can react smartly to areas of the highest strain to relieve dislocations. In this way, SIBA can be used to tailor the dislocation structure of thin films. This project included growth, characterization and modeling of films grown using SIBA templates. Characterization will include atomic imaging of the dislocations structure, measurement of the mechanical properties of the film using interface force microscopy (IFM) and the nanoindenter, and measurement of the electronic structure of the SIBA with synchrotron photoemission. Resistance of films to sulfidation and oxidation will also be examined. The Paragon parallel processing computer will be used to calculate the structure of the SIBA and thin films in order to develop ability to predict and tailor SIBA and thin film behavior. This work will lead to the possible development of a new class of thin film materials with properties tailored by varying the composition of the SIBA, serving as a buffer layer to relieve the strain between the substrate and the thin film. Such films will have improved mechanical and corrosion resistance allowing application as protective barriers for weapons applications. They will also exhibit enhanced electrical conductivity and reduced electromigration making them particularly suitable for application as interconnects and other electronic needs.

  16. Interfacial Slip in Polymer Blends with Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Jaber, Eihab; Gersappe, Dilip

    2010-03-01

    The interfacial region in polymer blends has been identified as a low viscosity region in which considerable slip can occur when the blend is subjected to shear forces. Here we use Molecular Dynamics simulations to establish the role that added nanoparticle fillers play in modifying the interfacial rheology. By choosing conditions under which the fillers are localized, either in the two phases or at the interface, we can look at the interplay between the strengthening capability of nanoparticles and the change in the interfacial slip behavior. We examine particle size, attraction between the particle and the polymer component, and the amount of filler in the material. Our studies are performed both above and below the point at which the filler particles form a transient network in the blend.

  17. Interfacial Slip in Polymer Blends with Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Jaber, Eihab; Gersappe, Dilip

    2009-03-01

    The interfacial region in polymer blends has been identified as a low viscosity region in which considerable slip can occur when the blend is subjected to shear forces. Here we use Molecular Dynamics simulations to establish the role that added nanoparticle fillers play in modifying the interfacial rheology. By choosing conditions under which the fillers are localized, either in the two phases or at the interface, we can look at the interplay between the strengthening capability of nanoparticles and the change in the interfacial slip behavior. We examine particle size, attraction between the particle and the polymer component, and the amount of filler in the material. Our studies are performed both above and below the point at which the filler particles form a transient network in the blend.

  18. Interfacial slip in polymer blends with nanoparticles

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Jaber, Eihab; Gersappe, Dilip

    2008-03-01

    The interfacial region in polymer blends has been identified as a low viscosity region in which considerable slip can occur when the blend is subjected to shear forces. Here, we use Molecular Dynamics simulations to establish the role that added nanofiller particles play in modifying the interfacial rheology. By choosing conditions under which the fillers are localized either in the two phases, or at the interface we can look at the interplay between the strengthening capability of nanoparticles, and the change in the interfacial slip behavior. We examine particle size, attraction between the particle and the polymer component and the amount of filler in the material. Our studies are performed both above and below the point at which the filler particles form a transient network in the blend.

  19. Bridging the gap between the nanostructural organization and macroscopic interfacial rheology of amyloid fibrils at liquid interfaces.

    PubMed

    Jordens, Sophia; Rühs, Patrick A; Sieber, Christine; Isa, Lucio; Fischer, Peter; Mezzenga, Raffaele

    2014-08-26

    The interfacial behavior of proteins and protein aggregates such as fibrils influences the bulk behavior of multiphase systems in foods, pharmaceuticals, and other technological applications. Additionally, it is an important factor in some biological processes such as the accumulation of amyloid fibrils at biological membranes in neurodegenerative diseases. Here, using β-lactoglobulin fibrils as a model system, we cover a large range of characteristic measuring length scales by combining atomic force microscopy, passive probe particle tracking, tensiometry, interfacial shear, and dilatational rheology in order to correlate the intricate structure of fibril-laden interfaces with their macroscopic adsorption kinetics and viscoelasticity. A subtle change in solution pH provokes pronounced changes in interfacial properties such as alignment, entanglement, multilayer formation, and fibril fracture, which can be resolved and linked across the various length scales involved. PMID:25100189

  20. Effects of Bi-2212 addition on the levitation force properties of bulk MgB2 superconductors

    NASA Astrophysics Data System (ADS)

    Taylan Koparan, E.; Savaskan, B.; Guner, S. B.; Celik, S.

    2016-02-01

    We present a detailed investigation of the effects of Bi2Sr2Ca1Cu2O8+κ (Bi-2212) adding on the levitation force and magnetic properties of bulk MgB2 obtained by hot press method. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 10 wt%) of the total MgB2. Moreover, we present MgB2 bulk samples fabricated by using different production methods including hot pressing method to our knowledge. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano-boron (B) powder and Bi-2212 powder which are produced by hot press method. As a result of hot press process, compact pellet samples were manufactured. The vertical and lateral levitation force measurements were executed at the temperatures of 20, 24 and 28 K under zero-field-cooled (ZFC) and field-cooled (FC) regimes for samples with various adding levels. At 24 K and 28 K under ZFC regime, the 2 wt% Bi-2212 added sample exhibits a higher vertical levitation force than the pure sample. Bi-2212 added MgB2 samples compared to the pure sample have lower attractive force values in FC regime. The magnetic field dependence of the critical current density J c was calculated from the M-H loops for Bi-2212 added MgB2 samples. The 2 wt% Bi-2212 added sample has the best levitation and critical current density performance compared to other samples. The critical temperature ( T c ) has slightly dropped from 37.8 K for the pure MgB2 sample to 36.7 K for the 10 wt% of Bi-2212 added sample. The transition temperature slightly decreases when Bi-2212 adding level is increased.

  1. CHARMM All-Atom Additive Force Field for Sphingomyelin: Elucidation of Hydrogen Bonding and of Positive Curvature

    PubMed Central

    Venable, Richard M.; Sodt, Alexander J.; Rogaski, Brent; Rui, Huan; Hatcher, Elizabeth; MacKerell, Alexander D.; Pastor, Richard W.; Klauda, Jeffery B.

    2014-01-01

    The C36 CHARMM lipid force field has been extended to include sphingolipids, via a combination of high-level quantum mechanical calculations on small molecule fragments, and validation by extensive molecular dynamics simulations on N-palmitoyl and N-stearoyl sphingomyelin. NMR data on these two molecules from several studies in bilayers and micelles played a strong role in the development and testing of the force field parameters. Most previous force fields for sphingomyelins were developed before the availability of the detailed NMR data and relied on x-ray diffraction of bilayers alone for the validation; these are shown to be too dense in the bilayer plane based on published chain order parameter data from simulations and experiments. The present simulations reveal O-H:::O-P intralipid hydrogen bonding occurs 99% of the time, and interlipid N-H:::O=C (26-29%, depending on the lipid) and N-H:::O-H (17–19%). The interlipid hydrogen bonds are long lived, showing decay times of 50 ns, and forming strings of lipids, and leading to reorientational correlation time of nearly 100 ns. The spontaneous radius of curvature for pure N-palmitoyl sphingomyelin bilayers is estimated to be 43–100 Å, depending on the assumptions made in assigning a bending constant; this unusual positive curvature for a two-tailed neutral lipid is likely associated with hydrogen bond networks involving the NH of the sphingosine group. PMID:24988348

  2. Theoretical study of the molecular force field and vibration analysis of the hydrogen cyanide addition compound with boron tribromide.

    PubMed

    Hase, Y

    2010-01-01

    An extensive HF, MP2, B3LYP and CCSD study of the molecular structure, force field and normal vibrations has been carried out for the hydrogen cyanide compound with boron tribromide. Most of the calculations agree that the HCN-BBr(3) molecule belongs to C(3v) point group and has a N-B length of 1.55-1.70 A and a N-B-Br angle of 103-105 degrees. These calculations also have estimated the missing low-wavenumber fundamentals in the 190 (nu(5)), 150 (nu(9)) and 105 cm(-1) (nu(10)) regions, instead of the supposed fundamentals at 207, 188 and 150 cm(-1), respectively, based on the combination bands. The quantum chemical force constants, by the B3LYP/6-31G and CCSD/3-21G calculations, have been adjusted by the scaling factors to reproduce the fundamentals in the literature [3] to include the bands below 200 cm(-1) proposed in this study. Normal coordinate analysis using the scaled force constants has been performed to interpret the molecular vibrations of four isotopic molecules, HCN-(10)BBr(3), HCN-(11)BBr(3), DCN-(10)BBr(3) and DCN-(11)BBr(3). PMID:19955013

  3. Theoretical study of the molecular force field and vibration analysis of the hydrogen cyanide addition compound with boron tribromide

    NASA Astrophysics Data System (ADS)

    Hase, Y.

    2010-01-01

    An extensive HF, MP2, B3LYP and CCSD study of the molecular structure, force field and normal vibrations has been carried out for the hydrogen cyanide compound with boron tribromide. Most of the calculations agree that the HCN-BBr 3 molecule belongs to C3v point group and has a N-B length of 1.55-1.70 Å and a N-B-Br angle of 103-105°. These calculations also have estimated the missing low-wavenumber fundamentals in the 190 ( ν5), 150 ( ν9) and 105 cm -1 ( ν10) regions, instead of the supposed fundamentals at 207, 188 and 150 cm -1, respectively, based on the combination bands. The quantum chemical force constants, by the B3LYP/6-31G and CCSD/3-21G calculations, have been adjusted by the scaling factors to reproduce the fundamentals in the literature [3] to include the bands below 200 cm -1 proposed in this study. Normal coordinate analysis using the scaled force constants has been performed to interpret the molecular vibrations of four isotopic molecules, HCN- 10BBr 3, HCN- 11BBr 3, DCN- 10BBr 3 and DCN- 11BBr 3.

  4. Emulsions for interfacial filtration.

    SciTech Connect

    Grillet, Anne Mary; Bourdon, Christopher Jay; Souza, Caroline Ann; Welk, Margaret Ellen; Hartenberger, Joel David; Brooks, Carlton, F.

    2006-11-01

    We have investigated a novel emulsion interfacial filter that is applicable for a wide range of materials, from nano-particles to cells and bacteria. This technology uses the interface between the two immiscible phases as the active surface area for adsorption of targeted materials. We showed that emulsion interfaces can effectively collect and trap materials from aqueous solution. We tested two aqueous systems, a bovine serum albumin (BSA) solution and coal bed methane produced water (CBMPW). Using a pendant drop technique to monitor the interfacial tension, we demonstrated that materials in both samples were adsorbed to the liquid-liquid interface, and did not readily desorb. A prototype system was built to test the emulsion interfacial filter concept. For the BSA system, a protein assay showed a progressive decrease in the residual BSA concentration as the sample was processed. Based on the initial prototype operation, we propose an improved system design.

  5. Comparison of operation efficiency for the insert task when using stereoscopic images with additional lines, stereoscopic images, and a manipulator with force feedback

    NASA Astrophysics Data System (ADS)

    Matsunaga, Katsuya; Shidoji, Kazunori; Matsubara, Kenjiro

    1999-05-01

    It has been reported that operation efficiency for the teleoperations using stereoscopic video images is lower than when using the naked eye in real environments. Here, the authors tried to improve the human-machine interface of this particular system to achieve higher operation efficiency for stereoscopic video imags by adding other information. An experiment was carried out under the four following conditions: when the insert task was performed by subjects using conventional stereoscopic video imags, when the centering lines of the cylindrical objects and holes were added to the conventional stereoscopic video images, when the force feedback was provided to the system manipulator as one object touched another object, and when both of the additional centering lines and force feedback were provided. The subject's task was to inset a cylindrical object into a round hole. The completion time was measured from the time of the starting signal to the time when the object was inserted into the hole. Completion time, when additional lines were given, was shorter than when the force feedback was provided, and when no additional information was provided. It was concluded that additional visual information contributed more to the recognition of the space rather than providing additional information about surface phenomena.

  6. Interfacial free energy adjustable phase field crystal model for homogeneous nucleation.

    PubMed

    Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Huang, Yunhao

    2016-05-18

    To describe the homogeneous nucleation process, an interfacial free energy adjustable phase-field crystal model (IPFC) was proposed by reconstructing the energy functional of the original phase field crystal (PFC) methodology. Compared with the original PFC model, the additional interface term in the IPFC model effectively can adjust the magnitude of the interfacial free energy, but does not affect the equilibrium phase diagram and the interfacial energy anisotropy. The IPFC model overcame the limitation that the interfacial free energy of the original PFC model is much less than the theoretical results. Using the IPFC model, we investigated some basic issues in homogeneous nucleation. From the viewpoint of simulation, we proceeded with an in situ observation of the process of cluster fluctuation and obtained quite similar snapshots to colloidal crystallization experiments. We also counted the size distribution of crystal-like clusters and the nucleation rate. Our simulations show that the size distribution is independent of the evolution time, and the nucleation rate remains constant after a period of relaxation, which are consistent with experimental observations. The linear relation between logarithmic nucleation rate and reciprocal driving force also conforms to the steady state nucleation theory. PMID:27117814

  7. Hydrophilicity and the viscosity of interfacial water.

    PubMed

    Goertz, Matthew P; Houston, J E; Zhu, X-Y

    2007-05-01

    We measure the viscosity of nanometer-thick water films at the interface with an amorphous silica surface. We obtain viscosity values from three different measurements: friction force in a water meniscus formed between an oxide-terminated W tip and the silica surface under ambient conditions; similar measurements for these interfaces under water; and the repulsive "drainage" force as the two surfaces approach at various speeds in water. In all three cases, we obtain effective viscosities that are approximately 10(6) times greater than that of bulk water for nanometer-scale interfacial separations. This enhanced viscosity is not observed when we degrade the hydrophilicity of the surface by terminating it with -H or -CH3. In view of recent results from other interfaces, we conclude that the criterion for the formation of a viscous interphase is the degree of hydrophilicity of the interfacial pair. PMID:17408290

  8. Oxidation-resistant interfacial coatings for continuous fiber ceramic composites

    SciTech Connect

    Stinton, D.P.; Besmann, T.M.; Bleier, A.; Shanmugham, S.; Liaw, P.K.

    1995-08-01

    Continuous fiber ceramic composites mechanical behavior are influenced by the bonding characteristics between the fiber and the matrix. Finite modeling studies suggest that a low-modulus interfacial coating material will be effective in reducing the residual thermal stresses that are generated upon cooling from processing temperatures. Nicalon{trademark}/SiC composites with carbon, alumina and mullite interfacial coatings were fabricated with the SiC matrix deposited using a forced-flow, thermal gradient chemical vapor infiltration process. Composites with mullite interfacial coatings exhibited considerable fiber pull-out even after oxidation and have potential as a composite system.

  9. Interfacial roughness in ceramic matrix composites

    SciTech Connect

    Jero, P.D.; Parthasarathy, T.A.; Kerans, R.J.

    1992-08-01

    Recent work using push-out and push-back tests has shown that interfacial roughness contributes substantially to the sliding friction in at least some ceramic matrix composites (CMC's). Other work examining frictional heating of CMC's during cyclic fatigue has shown the important role that interfacial friction plays, and further that the interface is degraded upon extended cycling. From this it is apparent that interfacial roughness may play a key role in determining composite behavior. Although the observation of a seating drop during fiber push-back gives some information about the amplitude and spatial extent of the interfacial roughness, actual measurement of the roughness has proven difficult due to its extremely fine scale. In the present work, a laser interferometer has been used to examine the roughness of composite interfaces (both fiber and matrix) as well as virgin fibers. In addition, long range (mm scale) push-out tests have been followed by interferometric characterization to examine the severity and rate of interfacial degradation associated with fiber sliding. 4 refs.

  10. Interfacial bonding stability

    NASA Technical Reports Server (NTRS)

    Boerio, J.

    1984-01-01

    Interfacial bonding stability by in situ ellipsometry was investigated. It is found that: (1) gamma MPS is an effective primer for bonding ethylene vinyl acetate (EVA) to aluminum; (2) ellipsometry is an effective in situ technique for monitoring the stability of polymer/metal interfaces; (3) the aluminized back surface of silicon wafers contain significant amounts of silicon and may have glass like properties.

  11. Effect of interfacial free energy on the formation of polymer microcapsules by emulsification/freeze-drying.

    PubMed

    Yin, Weisi; Yates, M Z

    2008-02-01

    Hollow polymer microparticles with a single opening on the surface were formed by freeze-drying aqueous polymer colloids swollen with solvent. The results show that the particle morphology is due to phase separation in the polymer emulsion droplets upon freezing in liquid nitrogen, and that morphological changes are driven largely by lowering interfacial free energy. The effects of added surfactant, volume fraction of solvent, type of solvent, and processing conditions on the particle morphology were examined and compared to theoretical predictions. The dried hollow particles were resuspended in a dispersing media and exposed to a second swelling solvent to close the surface opening and form microcapsules. The interfacial free energy difference between the inside and outside surfaces is the driving force for closing the hole on the surface. The emulsification/freeze-drying technique can be used to encapsulate hydrophilic additives in the core of the microcapsules, demonstrating the potential of the technique in controlled-release applications. PMID:18173290

  12. Interfacial phenomena and microscale transport processes in evaporating ultrathin menisci

    NASA Astrophysics Data System (ADS)

    Panchamgam, Sashidhar S.

    The study of interfacial phenomena in the three-phase contact line region, where a liquid-vapor interface intersects a solid surface, is of importance to many equilibrium and non-equilibrium processes. However, lack of experimental data on microscale transport processes controlled by interfacial phenomena has restricted progress. This thesis includes a high resolution image analyzing technique, based on reflectivity measurements, that accurately measures the thickness, contact angle and curvature profiles of ultrathin films, drops and curved menisci. In particular, the technique was used to emphasize measurements for thicknesses, delta < 100 nm, while studying delta < 2.5 mum. Using the "reflectivity technique", we studied fluid flow and heat transfer in a wickless, miniature heat pipe, a device which will be a very effective passive heat exchanger in a microgravity environment. The heat pipe is based on the Vertical Constrained Vapor Bubble (VCVB) concept. The broad objective was to increase the efficiency of the miniature heat pipe by enhancing the liquid flow towards the hotter region. This was achieved by understanding and manipulating the wetting and spreading characteristics of the liquid on the solid surface. By using a binary mixture (98% pentane and 2% octane by volume) instead of either pure pentane or octane, we were able to achieve a significant increase in the microscale phase change heat transfer. The experimental work was supported by numerical studies to understand the physics of the system at microscopic scale. In addition, using the reflectivity technique, we enhanced our understanding of interfacial phenomena in the contact line region. Experiments included flow instabilities in HFE-7000 meniscus on quartz (System S1), the spreading of a pentane (System S2 and S3), octane (System S4) and binary mixture menisci (System S5) during evaporation. The main objectives of the work are to present a new experimental technique, new observations, new data

  13. Lessons learned during the training exercise for the entry into force of the U.S. additional protocol in the DOE complex

    SciTech Connect

    Boyer, Brian D

    2009-01-01

    In 2008 in anticipation of the United States bringing into force the Additional Protocol in early 2009 DOE/NNSA planned and executed training exercises in the conduct of Additional Protocol complementary access activities. Brookhaven National Laboratory and Los Alamos National Laboratory together produced the exercises designed to prepare the following types of DOE laboratories for complementary access - weapons laboratories, nuclear engineering laboratories, and science laboratories. This panel provides a forum to discuss and summarize the results and lessons learned from the 2008 exercise.

  14. Interfacial adhesion - Theory and experiment

    NASA Technical Reports Server (NTRS)

    Ferrante, John; Banerjea, Amitava; Bozzolo, Guillermo H.; Finley, Clarence W.

    1988-01-01

    Adhesion, the binding of different materials at an interface, is of general interest to many branches of technology, e.g., microelectronics, tribology, manufacturing, construction, etc. However, there is a lack of fundamental understanding of such diverse interfaces. In addition, experimental techniques generally have practical objectives, such as the achievement of sufficient strength to sustain mechanical or thermal effects and/or have the proper electronic properties. In addition, the theoretical description of binding at interfaces is quite limited, and a proper data base for such theoretical analysis does not exist. This presentation will review both experimental and theoretical aspects of adhesion in nonpolymer materials. The objective will be to delineate the critical parameters needed, governing adhesion testing along with an outline of testing objectives. A distinction will be made between practical and fundamental objectives. Examples are given where interfacial bonding may govern experimental consideration. The present status of theory is presented along with recommendations for future progress and needs.

  15. Interfacial adhesion: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Ferrante, John; Bozzolo, Guillermo H.; Finley, Clarence W.; Banerjea, Amitava

    1988-01-01

    Adhesion, the binding of different materials at an interface, is of general interest to many branches of technology, e.g., microelectronics, tribology, manufacturing, construction, etc. However, there is a lack of fundamental understanding of such diverse interfaces. In addition, experimental techniques generally have practical objectives, such as the achievement of sufficient strength to sustain mechanical or thermal effects and/or have the proper electronic properties. In addition, the theoretical description of binding at interfaces is quite limited, and a proper data base for such theoretical analysis does not exist. This presentation will review both experimental and theoretical aspects of adhesion in nonpolymer materials. The objective will be to delineate the critical parameters needed, governing adhesion testing along with an outline of testing objectives. A distinction will be made between practical and fundamental objectives. Examples are given where interfacial bonding may govern experimental consideration. The present status of theory is presented along wiith recommendations for future progress and needs.

  16. A nanoscale study of charge extraction in organic solar cells: the impact of interfacial molecular configurations

    NASA Astrophysics Data System (ADS)

    Tang, Fu-Ching; Wu, Fu-Chiao; Yen, Chia-Te; Chang, Jay; Chou, Wei-Yang; Gilbert Chang, Shih-Hui; Cheng, Horng-Long

    2014-11-01

    In the optimization of organic solar cells (OSCs), a key problem lies in the maximization of charge carriers from the active layer to the electrodes. Hence, this study focused on the interfacial molecular configurations in efficient OSC charge extraction by theoretical investigations and experiments, including small molecule-based bilayer-heterojunction (sm-BLHJ) and polymer-based bulk-heterojunction (p-BHJ) OSCs. We first examined a well-defined sm-BLHJ model system of OSC composed of p-type pentacene, an n-type perylene derivative, and a nanogroove-structured poly(3,4-ethylenedioxythiophene) (NS-PEDOT) hole extraction layer. The OSC with NS-PEDOT shows a 230% increment in the short circuit current density compared with that of the conventional planar PEDOT layer. Our theoretical calculations indicated that small variations in the microscopic intermolecular interaction among these interfacial configurations could induce significant differences in charge extraction efficiency. Experimentally, different interfacial configurations were generated between the photo-active layer and the nanostructured charge extraction layer with periodic nanogroove structures. In addition to pentacene, poly(3-hexylthiophene), the most commonly used electron-donor material system in p-BHJ OSCs was also explored in terms of its possible use as a photo-active layer. Local conductive atomic force microscopy was used to measure the nanoscale charge extraction efficiency at different locations within the nanogroove, thus highlighting the importance of interfacial molecular configurations in efficient charge extraction. This study enriches understanding regarding the optimization of the photovoltaic properties of several types of OSCs by conducting appropriate interfacial engineering based on organic/polymer molecular orientations. The ultimate power conversion efficiency beyond at least 15% is highly expected when the best state-of-the-art p-BHJ OSCs are combined with present arguments

  17. Protein interfacial structure and nanotoxicology

    NASA Astrophysics Data System (ADS)

    White, John W.; Perriman, Adam W.; McGillivray, Duncan J.; Lin, Jhih-Min

    2009-02-01

    Here we briefly recapitulate the use of X-ray and neutron reflectometry at the air-water interface to find protein structures and thermodynamics at interfaces and test a possibility for understanding those interactions between nanoparticles and proteins which lead to nanoparticle toxicology through entry into living cells. Stable monomolecular protein films have been made at the air-water interface and, with a specially designed vessel, the substrate changed from that which the air-water interfacial film was deposited. This procedure allows interactions, both chemical and physical, between introduced species and the monomolecular film to be studied by reflectometry. The method is briefly illustrated here with some new results on protein-protein interaction between β-casein and κ-casein at the air-water interface using X-rays. These two proteins are an essential component of the structure of milk. In the experiments reported, specific and directional interactions appear to cause different interfacial structures if first, a β-casein monolayer is attacked by a κ-casein solution compared to the reverse. The additional contrast associated with neutrons will be an advantage here. We then show the first results of experiments on the interaction of a β-casein monolayer with a nanoparticle titanium oxide sol, foreshadowing the study of the nanoparticle "corona" thought to be important for nanoparticle-cell wall penetration.

  18. Stochastic level-set variational implicit-solvent approach to solute-solvent interfacial fluctuations.

    PubMed

    Zhou, Shenggao; Sun, Hui; Cheng, Li-Tien; Dzubiella, Joachim; Li, Bo; McCammon, J Andrew

    2016-08-01

    Recent years have seen the initial success of a variational implicit-solvent model (VISM), implemented with a robust level-set method, in capturing efficiently different hydration states and providing quantitatively good estimation of solvation free energies of biomolecules. The level-set minimization of the VISM solvation free-energy functional of all possible solute-solvent interfaces or dielectric boundaries predicts an equilibrium biomolecular conformation that is often close to an initial guess. In this work, we develop a theory in the form of Langevin geometrical flow to incorporate solute-solvent interfacial fluctuations into the VISM. Such fluctuations are crucial to biomolecular conformational changes and binding process. We also develop a stochastic level-set method to numerically implement such a theory. We describe the interfacial fluctuation through the "normal velocity" that is the solute-solvent interfacial force, derive the corresponding stochastic level-set equation in the sense of Stratonovich so that the surface representation is independent of the choice of implicit function, and develop numerical techniques for solving such an equation and processing the numerical data. We apply our computational method to study the dewetting transition in the system of two hydrophobic plates and a hydrophobic cavity of a synthetic host molecule cucurbit[7]uril. Numerical simulations demonstrate that our approach can describe an underlying system jumping out of a local minimum of the free-energy functional and can capture dewetting transitions of hydrophobic systems. In the case of two hydrophobic plates, we find that the wavelength of interfacial fluctuations has a strong influence to the dewetting transition. In addition, we find that the estimated energy barrier of the dewetting transition scales quadratically with the inter-plate distance, agreeing well with existing studies of molecular dynamics simulations. Our work is a first step toward the inclusion of

  19. Stochastic level-set variational implicit-solvent approach to solute-solvent interfacial fluctuations

    NASA Astrophysics Data System (ADS)

    Zhou, Shenggao; Sun, Hui; Cheng, Li-Tien; Dzubiella, Joachim; Li, Bo; McCammon, J. Andrew

    2016-08-01

    Recent years have seen the initial success of a variational implicit-solvent model (VISM), implemented with a robust level-set method, in capturing efficiently different hydration states and providing quantitatively good estimation of solvation free energies of biomolecules. The level-set minimization of the VISM solvation free-energy functional of all possible solute-solvent interfaces or dielectric boundaries predicts an equilibrium biomolecular conformation that is often close to an initial guess. In this work, we develop a theory in the form of Langevin geometrical flow to incorporate solute-solvent interfacial fluctuations into the VISM. Such fluctuations are crucial to biomolecular conformational changes and binding process. We also develop a stochastic level-set method to numerically implement such a theory. We describe the interfacial fluctuation through the "normal velocity" that is the solute-solvent interfacial force, derive the corresponding stochastic level-set equation in the sense of Stratonovich so that the surface representation is independent of the choice of implicit function, and develop numerical techniques for solving such an equation and processing the numerical data. We apply our computational method to study the dewetting transition in the system of two hydrophobic plates and a hydrophobic cavity of a synthetic host molecule cucurbit[7]uril. Numerical simulations demonstrate that our approach can describe an underlying system jumping out of a local minimum of the free-energy functional and can capture dewetting transitions of hydrophobic systems. In the case of two hydrophobic plates, we find that the wavelength of interfacial fluctuations has a strong influence to the dewetting transition. In addition, we find that the estimated energy barrier of the dewetting transition scales quadratically with the inter-plate distance, agreeing well with existing studies of molecular dynamics simulations. Our work is a first step toward the inclusion of

  20. Iridium Interfacial Stack (IRIS)

    NASA Technical Reports Server (NTRS)

    Spry, David James (Inventor)

    2015-01-01

    An iridium interfacial stack ("IrIS") and a method for producing the same are provided. The IrIS may include ordered layers of TaSi.sub.2, platinum, iridium, and platinum, and may be placed on top of a titanium layer and a silicon carbide layer. The IrIS may prevent, reduce, or mitigate against diffusion of elements such as oxygen, platinum, and gold through at least some of its layers.

  1. Interfacial behavior of asphaltenes.

    PubMed

    Langevin, Dominique; Argillier, Jean-François

    2016-07-01

    We review the existing literature on asphaltenes at various types of interfaces: oil-water, air-water, gas-oil and solid-liquid, with more emphasis on the oil-water interfaces. We address the role of asphaltene aggregation, recently clarified for asphaltenes in bulk by the Yen-Mullins model. We discuss the questions of adsorption reversibility and interfacial rheology, especially in connection with emulsion stability. PMID:26498501

  2. Exploring the retention properties of CaF2 nanoparticles as possible additives for dental care application with tapping-mode atomic force microscope in liquid.

    PubMed

    Wasem, Matthias; Köser, Joachim; Hess, Sylvia; Gnecco, Enrico; Meyer, Ernst

    2014-01-13

    Amplitude-modulation atomic force microscopy (AM-AFM) is used to determine the retention properties of CaF2 nanoparticles adsorbed on mica and on tooth enamel in liquid. From the phase-lag of the forced cantilever oscillation the local energy dissipation at the detachment point of the nanoparticle was determined. This enabled us to compare different as-synthesized CaF2 nanoparticles that vary in shape, size and surface structure. CaF2 nanoparticles are candidates for additives in dental care products as they could serve as fluorine-releasing containers preventing caries during a cariogenic acid attack on the teeth. We show that the adherence of the nanoparticles is increased on the enamel substrate compared to mica, independently of the substrate roughness, morphology and size of the particles. PMID:24455460

  3. Exploring the retention properties of CaF2 nanoparticles as possible additives for dental care application with tapping-mode atomic force microscope in liquid

    PubMed Central

    Köser, Joachim; Hess, Sylvia; Gnecco, Enrico; Meyer, Ernst

    2014-01-01

    Summary Amplitude-modulation atomic force microscopy (AM-AFM) is used to determine the retention properties of CaF2 nanoparticles adsorbed on mica and on tooth enamel in liquid. From the phase-lag of the forced cantilever oscillation the local energy dissipation at the detachment point of the nanoparticle was determined. This enabled us to compare different as-synthesized CaF2 nanoparticles that vary in shape, size and surface structure. CaF2 nanoparticles are candidates for additives in dental care products as they could serve as fluorine-releasing containers preventing caries during a cariogenic acid attack on the teeth. We show that the adherence of the nanoparticles is increased on the enamel substrate compared to mica, independently of the substrate roughness, morphology and size of the particles. PMID:24455460

  4. Interfacial behaviours of smart composites

    NASA Astrophysics Data System (ADS)

    Poon, Chi-Kin

    The success of conventional fiber reinforced composites (FRC) relies on the quality of bonding between fibers and matrix. A review of literatures shows that there is a lack of theoretical models and experimental findings on the interfacial behaviours of the SMA-composites. In the past, the operation limit as well as the ideal actuation condition of SMA inclusions could not be predicted accurately during the design stage and the SMA-composite structures may therefore suffer a potential risk of sudden failure due to overloading or over-actuation. The theoretical models developed in this research provide a study basis for the prediction of internal stresses and interfacial strength of the SMA-composites. Martensite volume fraction is considered as a critical parameter which determines the material properties and shape memory effect (SME) of the SMA inclusions. The proposed model reproduce the SMA behaviour inside a substrate, evolutions of martensite volume fraction and elastic modulus of SMA, and the internal stresses along the embedded length in different loading and actuation scenarios. The concepts of 'constant martensite volume fraction region (CMR)' and 'constant axial stress region (CASR)' are proposed to justify the desired SMA actuation. In addition, substantial improvement of the initial debond stress is predicted with the increase of the actuation temperature. The 'Optimum Actuation Condition (OAC)' that ensures the reinforcement of SMA composite but avoids the failure of composite interface due to over-actuation is also defined to optimize the application of SME in the composite structure within a safety actuation limit. A simplified OAC (SOAC) is also developed to provide an analytical solution of OAC and thus the ideal actuation temperature for achieving such specific actuation condition can be estimated more easily. Single fiber pullout test and finite element analysis (FEA) are employed to evaluate the interfacial behaviours and analyze the stress

  5. Recent Advances in Colloidal and Interfacial Phenomena Involving Liquid Crystals

    PubMed Central

    Bai, Yiqun; Abbott, Nicholas L.

    2011-01-01

    This article describes recent advances in several areas of research involving the interfacial ordering of liquid crystals (LCs). The first advance revolves around the ordering of LCs at bio/chemically functionalized surfaces. Whereas the majority of past studies of surface-induced ordering of LCs have involved surfaces of solids that present a limited diversity of chemical functional groups (surfaces at which van der Waals forces dominate surface-induced ordering), recent studies have moved to investigate the ordering of LCs on chemically complex surfaces. For example, surfaces decorated with biomolecules (e.g. oligopeptides and proteins) and transition metal ions have been investigated, leading to an understanding of the roles that metal-ligand coordination interactions, electrical double-layers, acid-base interactions, and hydrogen bonding can have on the interfacial ordering of LCs. The opportunity to create chemically-responsive LCs capable of undergoing ordering transitions in the presence of targeted molecular events (e.g., ligand exchange around a metal center) has emerged from these fundamental studies. A second advance has focused on investigations of the ordering of LCs at interfaces with immiscible isotropic fluids, particularly water. In contrast to prior studies of surface-induced ordering of LCs on solid surfaces, LC- aqueous interfaces are deformable and molecules at these interfaces exhibit high levels of mobility and thus can reorganize in response to changes in interfacial environment. A range of fundamental investigations involving these LC-aqueous interfaces have revealed that (i) the spatial and temporal characteristics of assemblies formed from biomolecular interactions can be reported by surface-driven ordering transitions in the LCs, (ii) the interfacial phase behaviour of molecules and colloids can be coupled to (and manipulated via) the ordering (and nematic elasticity) of LCs, and (iii) confinement of LCs leads to unanticipated size

  6. Effect of nanoscale patterned interfacial roughness on interfacial toughness.

    SciTech Connect

    Zimmerman, Jonathan A.; Moody, Neville Reid; Mook, William M.; Kennedy, Marian S.; Bahr, David F.; Zhou, Xiao Wang; Reedy, Earl David, Jr.

    2007-09-01

    The performance and the reliability of many devices are controlled by interfaces between thin films. In this study we investigated the use of patterned, nanoscale interfacial roughness as a way to increase the apparent interfacial toughness of brittle, thin-film material systems. The experimental portion of the study measured the interfacial toughness of a number of interfaces with nanoscale roughness. This included a silicon interface with a rectangular-toothed pattern of 60-nm wide by 90-nm deep channels fabricated using nanoimprint lithography techniques. Detailed finite element simulations were used to investigate the nature of interfacial crack growth when the interface is patterned. These simulations examined how geometric and material parameter choices affect the apparent toughness. Atomistic simulations were also performed with the aim of identifying possible modifications to the interfacial separation models currently used in nanoscale, finite element fracture analyses. The fundamental nature of atomistic traction separation for mixed mode loadings was investigated.

  7. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-Lun; Onuki, Akira

    1996-01-01

    The study of the interface in a charge-free, nonpolar, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In zero gravity, the interface is unstable at all long wavelengths in the presence of a field applied across it. It is conjectured that this will cause the binary fluid to break up into domains small enough to be outside the instability condition. The resulting pattern formation, and the effects on the critical properties as the domains approach the correlation length are of acute interest. With direct observation, laser light scattering, and interferometry, the phenomena can be probed to gain further understanding of interfacial instabilities and the pattern formation which results, and dimensional crossover in critical systems as the critical fluctuations in a particular direction are suppressed by external forces.

  8. Interfacial gauge methods for incompressible fluid dynamics.

    PubMed

    Saye, Robert

    2016-06-01

    Designing numerical methods for incompressible fluid flow involving moving interfaces, for example, in the computational modeling of bubble dynamics, swimming organisms, or surface waves, presents challenges due to the coupling of interfacial forces with incompressibility constraints. A class of methods, denoted interfacial gauge methods, is introduced for computing solutions to the corresponding incompressible Navier-Stokes equations. These methods use a type of "gauge freedom" to reduce the numerical coupling between fluid velocity, pressure, and interface position, allowing high-order accurate numerical methods to be developed more easily. Making use of an implicit mesh discontinuous Galerkin framework, developed in tandem with this work, high-order results are demonstrated, including surface tension dynamics in which fluid velocity, pressure, and interface geometry are computed with fourth-order spatial accuracy in the maximum norm. Applications are demonstrated with two-phase fluid flow displaying fine-scaled capillary wave dynamics, rigid body fluid-structure interaction, and a fluid-jet free surface flow problem exhibiting vortex shedding induced by a type of Plateau-Rayleigh instability. The developed methods can be generalized to other types of interfacial flow and facilitate precise computation of complex fluid interface phenomena. PMID:27386567

  9. Interfacial gauge methods for incompressible fluid dynamics

    PubMed Central

    Saye, Robert

    2016-01-01

    Designing numerical methods for incompressible fluid flow involving moving interfaces, for example, in the computational modeling of bubble dynamics, swimming organisms, or surface waves, presents challenges due to the coupling of interfacial forces with incompressibility constraints. A class of methods, denoted interfacial gauge methods, is introduced for computing solutions to the corresponding incompressible Navier-Stokes equations. These methods use a type of “gauge freedom” to reduce the numerical coupling between fluid velocity, pressure, and interface position, allowing high-order accurate numerical methods to be developed more easily. Making use of an implicit mesh discontinuous Galerkin framework, developed in tandem with this work, high-order results are demonstrated, including surface tension dynamics in which fluid velocity, pressure, and interface geometry are computed with fourth-order spatial accuracy in the maximum norm. Applications are demonstrated with two-phase fluid flow displaying fine-scaled capillary wave dynamics, rigid body fluid-structure interaction, and a fluid-jet free surface flow problem exhibiting vortex shedding induced by a type of Plateau-Rayleigh instability. The developed methods can be generalized to other types of interfacial flow and facilitate precise computation of complex fluid interface phenomena. PMID:27386567

  10. Formation of Lenses by Liquid Interfacial Surfaces

    NASA Astrophysics Data System (ADS)

    Zimmerman, Charlotte; Cerjan, Benjamin; Baylor, Martha-Elizabeth

    2013-03-01

    In this study, we examined the geometry of polymer lenses formed by liquid interfacial surfaces. We formed lenses by dropping hydrophobic photo-curable monomer on the surface of various hydrophilic liquid substrates. Due to intermolecular forces between the monomer and the substrate liquid, the interface is pulled into a curved shape. Upon exposure to UV light, the monomer solidifies while maintaining the boundary interface. The result is a plano-convex, optically-smooth polymer lens. The interfacial surface tension is manipulated by altering the amount of thin film present on the surface of the hydrophilic liquid, producing lenses of different curvatures. The lens curvature is further modified by using various salts that change the polarity of the substrate solution. We will present data demonstrating modification of the lens shape due to specific changes made to the physical and chemical properties of the hydrophilic liquid. We believe this liquid interfacial fabrication technique offers an alternative to current molding techniques for forming polymer lenses.

  11. Interfacial insert for electrical connectors

    NASA Technical Reports Server (NTRS)

    Macavay, D.

    1975-01-01

    The development of interfacial inserts for improved electric connectors is discussed. The inserts were manufactured from epoxy resins. The design features of the inserts and the manufacturing equipment are described. The reliability test program is reported. Drawings of the interfacial inserts are provided.

  12. Modulating DNA configuration by interfacial traction: an elastic rod model to characterize DNA folding and unfolding.

    PubMed

    Huang, Zaixing

    2011-01-01

    As a continuum model of DNA, a thin elastic rod subjected to interfacial interactions is used to investigate the equilibrium configuration of DNA in intracellular solution. The interfacial traction between the rod and the solution environment is derived in detail. Kirchhoff's theory of elastic rods is used to analyze the equilibrium configuration of a DNA segment under the action of the interfacial traction. The influences of the interfacial energy factor and bending stiffness on the toroidal spool formation of the DNA segment are discussed. The results show that the equilibrium configuration of DNA is mainly determined by competition between the interfacial energy and elastic strain energy of the DNA itself, and the interfacial traction is one of the forces that drives DNA folding and unfolding. PMID:22210963

  13. Nanoscale interfacial friction and adhesion on supported versus suspended monolayer and multilayer graphene.

    PubMed

    Deng, Zhao; Klimov, Nikolai N; Solares, Santiago D; Li, Teng; Xu, Hua; Cannara, Rachel J

    2013-01-01

    Using atomic force microscopy (AFM), supported by semicontinuum numerical simulations, we determine the effect of tip-subsurface van der Waals interactions on nanoscale friction and adhesion for suspended and silicon dioxide supported graphene of varying thickness. While pull-off force measurements reveal no layer number dependence for supported graphene, suspended graphene exhibits an increase in pull-off force with thickness. Further, at low applied loads, friction increases with increasing number of layers for suspended graphene, in contrast to reported trends for supported graphene. We attribute these results to a competition between local forces that determine the deformation of the surface layer, the profile of the membrane as a whole, and van der Waals forces between the AFM tip and subsurface layers. We find that friction on supported monolayer graphene can be fit using generalized continuum mechanics models, from which we extract the work of adhesion and interfacial shear strength. In addition, we show that tip-sample adhesive forces depend on interactions with subsurface material and increase in the presence of a supporting substrate or additional graphene layers. PMID:23215163

  14. Magnetic microwire probes for the magnetic rod interfacial stress rheometer.

    PubMed

    Tajuelo, J; Pastor, J M; Martínez-Pedrero, F; Vázquez, M; Ortega, F; Rubio, R G; Rubio, M A

    2015-02-01

    The magnetic needle interfacial shear rheometer is a valuable tool for the study of the mechanical properties of thin fluid films or monolayers. However, it is difficult to differentiate the interfacial and subphase contributions to the drag on the needle. In principle, the problem can be addressed by decreasing the needle diameter, which decreases the bulk contribution while the interfacial contribution remains essentially the same. Here we show the results obtained when using a new type of needle, that of magnetic microwires with diameter approximately 10 times thinner than for commercial needles. We show that the lower inertia of the microwires calls for a new calibration procedure. We propose such a new calibration procedure based on the flow field solution around the needle introduced in refs 1 and 2. By measuring thin silicone oil films with well-controlled interfacial viscosities as well as eicosanol (C20) and pentadecanoic acid (PDA, C15) Langmuir monolayers, we show that the new calibration method works well for standard needles as well as for the microwire probes. Moreover, we show that the analysis of the force terms contributing to the force on the needle helps to ascertain whether the measurements obtained are reliable for given surface shear viscosity values. We also show that the microwire probes have at least a 10-fold-lower resolution limit, allowing one to measure interfacial viscosities as low as 10(-7) N·m/s. PMID:25495270

  15. Kirkwood-Buff analysis of aqueous N-methylacetamide and acetamide solutions modeled by the CHARMM additive and Drude polarizable force fields.

    PubMed

    Lin, Bin; Lopes, Pedro E M; Roux, Benoît; MacKerell, Alexander D

    2013-08-28

    Kirkwood-Buff analysis was performed on aqueous solutions of N-methylacetamide and acetamide using the Chemistry at HARvard Molecular Mechanics additive and Drude polarizable all-atom force fields. Comparison of a range of properties with experimental results, including Kirkwood-Buff integrals, excess coordination numbers, solution densities, partial molar values, molar enthalpy of mixing, showed both models to be well behaved at higher solute concentrations with the Drude model showing systematic improvement at lower solution concentrations. However, both models showed difficulties reproducing experimental activity derivatives and the excess Gibbs energy, with the Drude model performing slightly better. At the molecular level, the improved agreement of the Drude model at low solute concentrations is due to increased structure in the solute-solute and solute-solvent interactions. The present results indicate that the explicit inclusion of electronic polarization leads to improved modeling of dilute solutions even when those properties are not included as target data during force field optimization. PMID:24007020

  16. Impact of 2′-hydroxyl sampling on the conformational properties of RNA: Update of the CHARMM all-atom additive force field for RNA

    PubMed Central

    Denning, Elizabeth J.; Priyakumar, U. Deva; Nilsson, Lennart; MacKerell, Alexander D.

    2011-01-01

    Here, we present an update of the CHARMM27 all-atom additive force field for nucleic acids that improves the treatment of RNA molecules. The original CHARMM27 force field parameters exhibit enhanced Watson-Crick (WC) base pair opening which is not consistent with experiment while analysis of MD simulations show the 2′-hydroxyl moiety to almost exclusively sample the O3′ orientation. Quantum mechanical studies of RNA related model compounds indicate the energy minimum associated with the O3′ orientation to be too favorable, consistent with the MD results. Optimization of the dihedral parameters dictating the energy of the 2′-hydroxyl proton targeting the QM data yielded several parameter sets, which sample both the base and O3′ orientations of the 2′-hydroxyl to varying degrees. Selection of the final dihedral parameters was based on reproduction of hydration behavior as related to a survey of crystallographic data and better agreement with experimental NMR J-coupling values. Application of the model, designated CHARMM36, to a collection of canonical and non-canonical RNA molecules reveals overall improved agreement with a range of experimental observables as compared to CHARMM27. The results also indicate the sensitivity of the conformational heterogeneity of RNA to the orientation of the 2′-hydroxyl moiety and support a model whereby the 2′-hydroxyl can enhance the probability of conformational transitions in RNA. PMID:21469161

  17. Transport processes and interfacial phenomena in an evaporating meniscus

    SciTech Connect

    Sujanani, M.; Wayner, P.C. Jr.

    1991-01-01

    When a liquid film wets a solid surface, a contact line region is formed where the vapor, liquid and solid phases are in close proximity. The film thickness in this region varies from about 10 {mu}m (Capillary Meniscus) to less than about 100 nm (Adsorbed film). In addition to being functions of temperature and pressure (as for a bulk phase), the thermodynamic properties (e.g., chemical potential) of these thin films depend on their shape (curvature) and thickness due to surface forces. The coupled transport processes and interfacial phenomena occurring in this microscopic region are also controlled by these surface forces. The objective of this paper is to report experimental data which complement earlier analytical models of this region. The experimental setup consists of a flat silicon plate partially immersed at a small angle, {theta}, in a pool of liquid. The plate is in a closed cell and a spreading liquid (1,1,2-Trichlorotrifluoro ethane), in equilibrium with its own vapor, forms a zero contact angle with the plate. The plate can be electrically heated at the upper end by supplying power to a thin, rectangular platinum heater which is painted on the backside of the silicon wafer. The meniscus thickness profile, which is related to the effective pressure in the liquid, was used as a probe for understanding the sensitivity of the meniscus to the non-equilibrium effects associated with evaporation/condensation mechanisms. 5 refs., 8 figs.

  18. Pore invasion dynamics during fluid front displacement - an interfacial front model

    NASA Astrophysics Data System (ADS)

    Moebius, F.; Or, D.

    2013-12-01

    The dynamics of fluid fronts in porous media shape subsequent phase distribution and the transport properties of the partially saturated region with implications ranging from gaseous transport to plant roots to extraction or injection of fluids to petroleum reservoirs. What macroscopically seems as a smooth and continuous motion of a displacement fluid front, involves numerous rapid pore-scale interfacial jumps often resembling avalanches of invasion events. We present a 2D model for simulating interfacial front displacement that was developed to study details of invasion dynamics at the front and to systematically study effects of boundary conditions on the resulting macroscopic properties after passage of a front. The interfacial front is represented by hydraulically connected sinusoidal capillaries allowing for redistribution and capillary pressure relaxation through exchange with neighboring interfaces. The model focuses on processes at the front and neglects interfacial redistribution left behind the front as well as saturated fluid flow below the front. The description of the dynamics of the rapid non-wetting fluid invasions induced by constant wetting fluid withdrawal includes capillary, viscous and hydrostatic component and inertia. Results show that the additional inertial force (not considered in previous studies) does significantly affect invasion pathways such as the hypothesized 'consecutive jumps'. The menisci jump velocities show a strong relation to geometrical throat dimensions that reflect local capillary gradients. The front model further enables to link boundary conditions (macroscopic Capillary number, throat size distribution) effects on pore invasion sequences and impact on residual wetting phase entrapment and front morphology. A limited comparison of model predictions with experimental results from sintered glass-beads micro-models will be presented.

  19. The effects of a soluble surfactant on the interfacial dynamics of stationary bubbles in inclined tubes

    NASA Astrophysics Data System (ADS)

    Cavanagh, Daniel P.; Eckmann, David M.

    2002-10-01

    We have experimentally examined the effects of a common soluble surfactant on gas bubbles in liquid flows in inclined tubes. Air bubbles of known size ([lambda] = 0.8, 1.0, 1.5) are held stationary under minimum flow conditions in tubes inclined at fixed angles ([omega] = 25°, 45°, 65°, 90°). Sodium dodecyl sulphate (SDS) is infused into the bulk flow at two bulk concentrations (C = 10% or 100% critical micelle concentration (CMC)). In addition to recording pressure and flow waveforms, we capture video images of bubbles before and during exposure to the surfactant. Modification of the interfacial properties by the surfactant results in extremely dynamic bubble behaviour including interfacial deformation, deformation plus axial translation, and bubble detachment from the wall plus translation. We measure the corresponding time-dependent pressure gradient within the tube. The surfactant mediated responses observed are dependent upon the interrelated effects of C, [lambda] and [omega]. A high bulk concentration of surfactant may produce more rapid modification of bubble shape and influence wetting, thus increasing the potential for bubble detachment. The likelihood that detachment will occur increases further as bubble volume in increased. In both vertical tubes in which contact forces are absent and in non-vertical tubes, the infusion of surfactant may result in axial translation either in the direction of, or opposite to, the direction of the bulk flow. Critical to the translation and/or detachment of the bubble is the surfactant-mediated modification of contact line mechanics. Contact line velocities corresponding to rates of shrinkage of dewetted surface area are extracted from experimental data. We also explore the potential effects of surfactants on interfacial remobilization. This investigation demonstrates the potential use of surfactants to be used for dislodging dewetted gas bubbles by the intentional manipulation of interfacial properties.

  20. Competition among Li+, Na+, K+ and Rb+ Monovalent Ions for DNA in Molecular Dynamics Simulations using the Additive CHARMM36 and Drude Polarizable Force Fields

    PubMed Central

    Savelyev, Alexey; MacKerell, Alexander D.

    2015-01-01

    In the present study we report on interactions of and competition between monovalent ions for two DNA sequences in MD simulations. Efforts included the development and validation of parameters for interactions among the first-group monovalent cations, Li+, Na+, K+ and Rb+, and DNA in the Drude polarizable and additive CHARMM36 force fields (FF). The optimization process targeted gas-phase QM interaction energies of various model compounds with ions and osmotic pressures of bulk electrolyte solutions of chemically relevant ions. The optimized ionic parameters are validated against counterion condensation theory and buffer exchange-atomic emission spectroscopy measurements providing quantitative data on the competitive association of different monovalent ions with DNA. Comparison between experimental and MD simulation results demonstrates that, compared to the additive CHARMM36 model, the Drude FF provides an improved description of the general features of the ionic atmosphere around DNA and leads to closer agreement with experiment on the ionic competition within the ion atmosphere. Results indicate the importance of extended simulation systems on the order of 25 Å beyond the DNA surface to obtain proper convergence of ion distributions. PMID:25751286

  1. CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field

    SciTech Connect

    Lee, Jumin; Cheng, Xi; Swails, Jason M.; Yeom, Min Sun; Eastman, Peter K.; Lemkul, Justin A.; Wei, Shuai; Buckner, Joshua; Jeong, Jong Cheol; Qi, Yifei; Jo, Sunhwan; Pande, Vijay S.; Case, David A.; Brooks, Charles L.; MacKerell, Alexander D.; Klauda, Jeffery B.; Im, Wonpil

    2015-11-12

    Here we report that proper treatment of nonbonded interactions is essential for the accuracy of molecular dynamics (MD) simulations, especially in studies of lipid bilayers. The use of the CHARMM36 force field (C36 FF) in different MD simulation programs can result in disagreements with published simulations performed with CHARMM due to differences in the protocols used to treat the long-range and 1-4 nonbonded interactions. In this study, we systematically test the use of the C36 lipid FF in NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM. A wide range of Lennard-Jones (LJ) cutoff schemes and integrator algorithms were tested to find the optimal simulation protocol to best match bilayer properties of six lipids with varying acyl chain saturation and head groups. MD simulations of a 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) bilayer were used to obtain the optimal protocol for each program. MD simulations with all programs were found to reasonably match the DPPC bilayer properties (surface area per lipid, chain order parameters, and area compressibility modulus) obtained using the standard protocol used in CHARMM as well as from experiments. The optimal simulation protocol was then applied to the other five lipid simulations and resulted in excellent agreement between results from most simulation programs as well as with experimental data. AMBER compared least favorably with the expected membrane properties, which appears to be due to its use of the hard-truncation in the LJ potential versus a force-based switching function used to smooth the LJ potential as it approaches the cutoff distance. The optimal simulation protocol for each program has been implemented in CHARMM-GUI. This protocol is expected to be applicable to the remainder of the additive C36 FF including the proteins, nucleic acids, carbohydrates, and small molecules.

  2. CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field

    PubMed Central

    2015-01-01

    Proper treatment of nonbonded interactions is essential for the accuracy of molecular dynamics (MD) simulations, especially in studies of lipid bilayers. The use of the CHARMM36 force field (C36 FF) in different MD simulation programs can result in disagreements with published simulations performed with CHARMM due to differences in the protocols used to treat the long-range and 1-4 nonbonded interactions. In this study, we systematically test the use of the C36 lipid FF in NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM. A wide range of Lennard-Jones (LJ) cutoff schemes and integrator algorithms were tested to find the optimal simulation protocol to best match bilayer properties of six lipids with varying acyl chain saturation and head groups. MD simulations of a 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) bilayer were used to obtain the optimal protocol for each program. MD simulations with all programs were found to reasonably match the DPPC bilayer properties (surface area per lipid, chain order parameters, and area compressibility modulus) obtained using the standard protocol used in CHARMM as well as from experiments. The optimal simulation protocol was then applied to the other five lipid simulations and resulted in excellent agreement between results from most simulation programs as well as with experimental data. AMBER compared least favorably with the expected membrane properties, which appears to be due to its use of the hard-truncation in the LJ potential versus a force-based switching function used to smooth the LJ potential as it approaches the cutoff distance. The optimal simulation protocol for each program has been implemented in CHARMM-GUI. This protocol is expected to be applicable to the remainder of the additive C36 FF including the proteins, nucleic acids, carbohydrates, and small molecules. PMID:26631602

  3. CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field

    DOE PAGESBeta

    Lee, Jumin; Cheng, Xi; Swails, Jason M.; Yeom, Min Sun; Eastman, Peter K.; Lemkul, Justin A.; Wei, Shuai; Buckner, Joshua; Jeong, Jong Cheol; Qi, Yifei; et al

    2015-11-12

    Here we report that proper treatment of nonbonded interactions is essential for the accuracy of molecular dynamics (MD) simulations, especially in studies of lipid bilayers. The use of the CHARMM36 force field (C36 FF) in different MD simulation programs can result in disagreements with published simulations performed with CHARMM due to differences in the protocols used to treat the long-range and 1-4 nonbonded interactions. In this study, we systematically test the use of the C36 lipid FF in NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM. A wide range of Lennard-Jones (LJ) cutoff schemes and integrator algorithms were tested to find themore » optimal simulation protocol to best match bilayer properties of six lipids with varying acyl chain saturation and head groups. MD simulations of a 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) bilayer were used to obtain the optimal protocol for each program. MD simulations with all programs were found to reasonably match the DPPC bilayer properties (surface area per lipid, chain order parameters, and area compressibility modulus) obtained using the standard protocol used in CHARMM as well as from experiments. The optimal simulation protocol was then applied to the other five lipid simulations and resulted in excellent agreement between results from most simulation programs as well as with experimental data. AMBER compared least favorably with the expected membrane properties, which appears to be due to its use of the hard-truncation in the LJ potential versus a force-based switching function used to smooth the LJ potential as it approaches the cutoff distance. The optimal simulation protocol for each program has been implemented in CHARMM-GUI. This protocol is expected to be applicable to the remainder of the additive C36 FF including the proteins, nucleic acids, carbohydrates, and small molecules.« less

  4. The relaxation of intrinsic compressive stress in complementary metal-oxide-semiconductor transistors by additional N ion implantation treatment with atomic force microscope-Raman stress extraction

    NASA Astrophysics Data System (ADS)

    Liao, M.-H.; Chen, C.-H.; Chang, L.-C.; Yang, C.; Kao, S.-C.

    2012-05-01

    Based on the stress extraction and measurement by atomic force microscope-Raman technique with the nanometer level space resolution, the high compressive stress about 550 MPa on the Si active region (OD) is observed for the current complementary metal-oxide-semiconductor (CMOS) transistor. During the thermal budget for the standard manufacture process of the current CMOS transistor, the difference of thermal expansion coefficients between Si and Shallow Trench Isolation (STI) oxide results in this high compressive stress in Si OD and further degrades the electron carrier mobility seriously. In order to relax this intrinsic processed compressive stress in Si OD and try to recover this performance loss, the novel process is proposed in this work in addition to the usage of one-side pad SiN layer. With this novel process of additional N-ion implantation (IMP) treatment in STI oxide, it can be found that the less compressive stress about 438 MPa in Si OD can be achieved by the smaller difference of thermal expansion coefficients between Si and N-doped SiO2 STI oxide. The formation of Si-N bonding in N-doped SiO2 STI region can be monitored by Fourier transform infrared spectroscopy spectra and thermal expansion coefficients for Si, SiO2, and SiN are 2.6 ppm/K, 0.4 ppm/K, and 2.87 ppm/K, respectively. The effective relaxation of intrinsic processed compressive stress in Si OD about 112 MPa (from 550 MPa to 438 MPa) by this proposed additional N IMP treatment contributes ˜14% electron carrier mobility enhancement/recovery. The experimental electrical data agree well with the theoretical piezoelectricity calculation for the strained-Si theory.

  5. Dynamics of interfacial pattern formation

    NASA Technical Reports Server (NTRS)

    Ben-Jacob, E.; Goldenfeld, N.; Langer, J. S.; Schon, G.

    1983-01-01

    A phenomenological model of dendritic solidification incorporating interfacial kinetics, crystalline anisotropy, and a local approximation for the dynamics of the thermal diffusion field is proposed. The preliminary results are in qualitative agreement with natural dendrite-like pattern formation.

  6. Numerical simulation of toughening of alumina particulate glass matrix composite by interfacial precipitation

    SciTech Connect

    Kageyama, K.; Enoki, M.; Kishi, T.

    1994-12-31

    Strengthening and toughening by interfacial precipitation are strongly connected with crack bowing and deflection. In the present study, three dimensional numerical simulation of these events was performed on ceramics particulate glass matrix composites with interfacial precipitation by calculating the equations for a crack bowing and deflection. This numerical simulation revealed that fracture toughness and strength increased with the addition of interfacial precipitation because a crack bowing emerged. These results are in agreement with experimental data for fracture toughness.

  7. Role of the elasticity of pharmaceutical materials on the interfacial mechanical strength of bilayer tablets.

    PubMed

    Busignies, Virginie; Mazel, Vincent; Diarra, Harona; Tchoreloff, Pierre

    2013-11-30

    The effect of the elasticity of various pharmaceutical materials on the interfacial adhesion in bilayer tablets was investigated. The elastic properties of five pharmaceutical products were characterized by their total elastic recovery. To test the interfacial strength of the bilayer tablets a new flexural test was proposed. Thanks to the test configuration, the experimental breaking force is directly correlated with the interfacial layer strength. Depending on the materials, the fracture occurred over the interface or in one of the two layers. In most cases, the highest breaking forces were obtained when the materials had close elastic recovery. On the contrary, for materials with different elastic recovery, the breaking forces were reduced. The observed changes in the interfacial mechanical strength were statistically analyzed. Such an approach has an importance in the growing interest in the Quality by Design (QbD) concept in pharmaceutical industry. PMID:24055440

  8. High temperature interfacial superconductivity

    SciTech Connect

    Bozovic, Ivan; Logvenov, Gennady; Gozar, Adrian Mihai

    2012-06-19

    High-temperature superconductivity confined to nanometer-scale interfaces has been a long standing goal because of potential applications in electronic devices. The spontaneous formation of a superconducting interface in bilayers consisting of an insulator (La.sub.2CuO.sub.4) and a metal (La.sub.1-xSr.sub.xCuO.sub.4), neither of which is superconducting per se, is described. Depending upon the layering sequence of the bilayers, T.sub.c may be either .about.15 K or .about.30 K. This highly robust phenomenon is confined to within 2-3 nm around the interface. After exposing the bilayer to ozone, T.sub.c exceeds 50 K and this enhanced superconductivity is also shown to originate from a 1 to 2 unit cell thick interfacial layer. The results demonstrate that engineering artificial heterostructures provides a novel, unconventional way to fabricate stable, quasi two-dimensional high T.sub.c phases and to significantly enhance superconducting properties in other superconductors. The superconducting interface may be implemented, for example, in SIS tunnel junctions or a SuFET.

  9. Reduced Cardiac Contractile Force Due to Sympathovagal Dysfunction Mediates the Additive Hypotensive Effects of Limited-Access Regimens of Ethanol and Clonidine in Spontaneously Hypertensive Rats

    PubMed Central

    El-Mas, Mahmoud M.

    2010-01-01

    Our previous attempts to investigate the long-term hemodynamic interaction between ethanol and clonidine in telemetered spontaneously hypertensive rats (SHRs) were hampered by the lack of a sustained hypotensive response to continuous clonidine exposure. This limitation was circumvented when we adopted a limited-access clonidine (8:30 AM–4:30 PM) paradigm in a recent study. The latter paradigm was employed here to evaluate the ethanol-clonidine interaction and possible roles of myocardial function and autonomic control in this interaction. Changes in blood pressure (BP), heart rate, maximum rate of rise in BP wave (+dP/dtmax), and spectral cardiovascular autonomic profiles were measured by radiotelemetry in pair-fed SHRs receiving clonidine (150 μg/kg/day), ethanol [2.5% (w/v)], or their combination during the day for 12 weeks. Ethanol or clonidine elicited long-term decreases in BP, and their combination caused additive hypotensive response. Significant reductions in +dP/dtmax were observed upon concurrent treatment with ethanol and clonidine, in contrast to no effect for individual treatment. In addition, the combined treatment increased the high-frequency (HF) spectral band of interbeat interval (IBI-HFnu, 0.75–3 Hz) and decreased low-frequency (IBI-LFnu, 0.2–0.75 Hz) bands and IBILF/HF ratios. Clonidine-evoked reductions in plasma and urine norepinephrine and BP-LF spectral power (measure of vasomotor sympathetic tone) were not affected by ethanol. In conclusion, concurrent treatment with ethanol and clonidine shifts the sympathovagal balance toward parasympathetic dominance and elicits exaggerated hypotension as a result of a reduction in cardiac contractile force. PMID:20864507

  10. Interfacial assembly of Graphene Oxide at oil/water and polymer/polymer interfaces

    NASA Astrophysics Data System (ADS)

    Sun, Zhiwei; Feng, Tao; Russell, Thomas

    2013-03-01

    Amphiphilic structure of graphene oxide makes it a candidate ``surfactant'' to preferentially segregate to the interface between different fluids. The affinity of graphene oxide towards different phases was tuned by grafting with polystyrene (PS-NH2) through hydrogen bonding, and its interfacial behavior, both in toluene/water and polystyrene/poly(methyl methacrylate), was studied. The surface tension of the toluene/water interface decreases in the presence of PS-NH2 grafted graphene oxide, indicating that graphene oxide flakes can be forced to the toluene/water interface when grafted with PS-NH2. Transmission electron microscopy shows that graphene oxide can even be forced into a ``jammed'' state at the water/toluene interface. In addition, polystyrene and poly(methyl methacrylate) were blended with graphene oxide, its morphology changes from island type to co-continuous structure, but the mechanism of this behavior is still not clear. These interfacial sheets may provide a model system to study buckling and crumpling behavior at interfaces.

  11. Interfacial models of nerve fiber cytoskeleton.

    PubMed Central

    Malev, V V; Gromov, D B; Komissarchik YaYu; Brudnaya, M S

    1992-01-01

    A new approach, basing on a resemblance between cytoskeleton structures associated with plasma membranes and interfacial layers of coexisting phases, is proposed. In particular, a lattice model, similar to those of the theory of surface properties of pure liquids and nonelectrolyte solutions (Ono, S., and S. Kondo. 1960. Handbuch der Physik.), has been developed to describe nerve fiber cytoskeleton. The preliminary consideration of the model shows the existence of submembrane cytoskeleton having increased peripheral densities of microtubules (compared with the bulk density) which is in qualitative agreement with the data in literature. Some additional possibilities of the approach proposed are briefly discussed. Images FIGURE 2 FIGURE 3 FIGURE 4 PMID:1420929

  12. A Thermodynamic Study of Dopant Interfacial Segregation Effect on Nanostability and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Wu, Longjia

    Nanoparticles, with great surface area and high surface to volume ratio, have been widely applied in many applications due to their unique size related effects. However, this high surface area character of nanoparticles also brings great excess energy to the whole system, making the system unstable and even causing the failure of nanoparticles, especially at higher temperatures. In order to maintain nanocrystalline structure of the materials, nanostability enhancement is of great significance in nanotechnology. It is well known that the global driving force for particles growth is to eliminate the excess energy brought by surface and grain boundary. Therefore, interfacial energetics has a great influence on the nanostability of the materials. And according to previous studies, dopant interfacial segregation could be a potential way to control the interfacial energetics of the nanoparticles and possibly lead to an improved nanostability. Furthermore, the interfacial energetics even can affect mechanical properties of nano-grain ceramic materials based on recent research. The main goals of the present work were to experimentally measure the interfacial energies of nanoparticles as well as nano-grain ceramics, modify the interfacial energetics through dopant segregation effect and engineer the nanostability and mechanical properties of the nanocrystalline materials through interfacial energetics modification. To achieve this goal, Mn cation has been chosen to introduce Mn interfacial segregation on ceria nanoparticles, and La cation has been added to 12 mol% yttria stabilized zirconia (12YSZ) and magnesium aluminate spinel (MAO) two-phase nano-grain ceramics to cause La interfacial segregation. Both of the dopant segregation phenomena were directly proved by electron energy loss spectroscopy (EELS). To quantify the dopant segregation effect on the interfacial energies, high-temperature oxide melt drop solution calorimetry, water adsorption calorimetry and differential

  13. Liquid-Solid Nanofriction and Interfacial Wetting.

    PubMed

    An, Rong; Huang, Liangliang; Long, Yun; Kalanyan, Berc; Lu, Xiaohua; Gubbins, Keith E

    2016-01-26

    Using atomic force microscopy, the nanofriction coefficient was measured systematically for a series of liquids on planar graphite, silica and mica surfaces. This allows us to explore the quantitative interplay between nanofriction at liquid-solid interfaces and interfacial wetting. A corresponding states theory analysis shows that the nanofriction coefficient, μ = dF(F)/dF(N), where FF is the friction force and FN is the normal force, is a function of three dimensionless parameters that reflect the intermolecular forces involved and the structure of the solid substrate. Of these, we show that one parameter in particular, β = ρ(s)Δ(s)σ(ls)(2), where ρ(s) is the atomic density of the solid, Δ(s) is the spacing between layers of solid atoms, and σ(ls) is the molecular diameter that characterizes the liquid-substrate interaction, is very important in determining the friction coefficient. This parameter β, which we term the structure adhesion parameter, provides a measure of the intermolecular interaction between a liquid molecule and the substrate and also of the surface area of contact of the liquid molecule with the substrate. We find a linear dependence of μ on the structure adhesion parameter for the systems studied. We also find that increasing β leads to an increase in the vertical adhesion forces FA (the attractive force exerted by the solid surface on the liquid film). Our quantitative relationship between the nanofriction coefficient and the key parameter β which governs the vertical adhesive strength, opens up an opportunity for describing liquid flows on solid surfaces at the molecular level, with implications for the development of membrane and nanofluidic devices. PMID:26716469

  14. Oscillatory interfacial instability between miscible fluids

    NASA Astrophysics Data System (ADS)

    Shevtsova, Valentina; Gaponenko, Yuri; Mialdun, Aliaksandr; Torregrosa, Marita; Yasnou, Viktar

    Interfacial instabilities occurring between two fluids are of fundamental interest in fluid dynamics, biological systems and engineering applications such as liquid storage, solvent extraction, oil recovery and mixing. Horizontal vibrations applied to stratified layers of immiscible liquids may generate spatially periodic waving of the interface, stationary in the reference frame of the vibrated cell, referred to as a "frozen wave". We present experimental evidence that frozen wave instability exists between two ordinary miscible liquids of similar densities and viscosities. At the experiments and at the numerical model, two superimposed layers of ordinary liquids, water-alcohol of different concentrations, are placed in a closed cavity in a gravitationally stable configuration. The density and viscosity of these fluids are somewhat similar. Similar to the immiscible fluids this instability has a threshold. When the value of forcing is increased the amplitudes of perturbations grow continuously displaying a saw-tooth structure. The decrease of gravity drastically changes the structure of frozen waves.

  15. Surfactants and interfacial phenomena, 2nd Ed

    SciTech Connect

    Rosen

    1989-01-01

    The second edition of this monograph on surfactants has been updated to reflect recent advances in our knowledge of theory and practices. New applications run the gamut from microelectronics and magnetic recording, to biotechnology and nonconventional energy conversion. There is a new chapter on the interactions between surfactants. New sections have been added, and original sections expanded, on such topics as ultralow liquid-liquid interfacial tension; microemulsions, miniemulsions, and multiple emulsions; liquid crystal formation; hydrotropy; and steric forces in the stabilization of dispersions. There is also new material on lime soap dispersing agents; fabric softeners, adsorption and wetting of solid surfaces, both equilibrium and none-equilibrium; the relationship between adsorption and micellation in aqueous solutions and its effect on surface tension reduction; and factors determining micellar structure and shape.

  16. Compound pendant drop tensiometry for interfacial tension measurement at zero bond number.

    PubMed

    Neeson, Michael J; Chan, Derek Y C; Tabor, Rico F

    2014-12-30

    A widely used method to determine the interfacial tension between fluids is to quantify the pendant drop shape that is determined by gravity and interfacial tension forces. Failure of this method for small drops or small fluid density differences is a critical limitation in microfluidic applications and when only small fluid samples are available. By adding a small spherical particle to the interface to apply an axisymmetric deformation, both the particle density and the interfacial tension can be simultaneously and precisely determined, providing an accurate and elegant solution to a long-standing problem. PMID:25494530

  17. Interfacial thermal degradation in inverted organic solar cells

    SciTech Connect

    Greenbank, William; Hirsch, Lionel; Wantz, Guillaume; Chambon, Sylvain

    2015-12-28

    The efficiency of organic photovoltaic (OPV) solar cells is constantly improving; however, the lifetime of the devices still requires significant improvement if the potential of OPV is to be realised. In this study, several series of inverted OPV were fabricated and thermally aged in the dark in an inert atmosphere. It was demonstrated that all of the devices undergo short circuit current-driven degradation, which is assigned to morphology changes in the active layer. In addition, a previously unreported, open circuit voltage-driven degradation mechanism was observed that is highly material specific and interfacial in origin. This mechanism was specifically observed in devices containing MoO{sub 3} and silver as hole transporting layers and electrode materials, respectively. Devices with this combination were among the worst performing devices with respect to thermal ageing. The physical origins of this mechanism were explored by Rutherford backscattering spectrometry and atomic force microscopy and an increase in roughness with thermal ageing was observed that may be partially responsible for the ageing mechanism.

  18. Interfacial activity in alkaline flooding enhanced oil recovery

    SciTech Connect

    Chan, M.K.

    1981-01-01

    The ionization of long-chained organic acids in the crude oil to form soaps was shown to be primarily responsible for the lowering of oil-water interfacial tension at alkaline pH. These active acids can be concentrated by silica gel chromatography into a minor polar fraction. An equilibrium chemical model was proposed based on 2 competing reactions: the ionization of acids to form active anions, and the formation of undissociated soap between acid anions and sodium ions. It correlates the interfacial activity with the interfacial concentration of active acid anions which is expressed in terms of the concentrations of the chemical species in the system. The model successfully predicts the observed oil-alkaline solution interfacial phenomenon, including its dependence on pH, alkali and salt concentrations, type of acid present and type of soap formed. Flooding at different alkali concentrations to activate different acid species present in the crude was shown to give better recovery than flooding at a single high alkali concentration. Treating the crude oil with a dilute solution of mineral acids liberates additional free active acids and yields better interfacial activity during subsequent alkali contact.

  19. Interfacial Bubble Deformations

    NASA Astrophysics Data System (ADS)

    Seymour, Brian; Shabane, Parvis; Cypull, Olivia; Cheng, Shengfeng; Feitosa, Klebert

    Soap bubbles floating at an air-water experience deformations as a result of surface tension and hydrostatic forces. In this experiment, we investigate the nature of such deformations by taking cross-sectional images of bubbles of different volumes. The results show that as their volume increases, bubbles transition from spherical to hemispherical shape. The deformation of the interface also changes with bubble volume with the capillary rise converging to the capillary length as volume increases. The profile of the top and bottom of the bubble and the capillary rise are completely determined by the volume and pressure differences. James Madison University Department of Physics and Astronomy, 4VA Consortium, Research Corporation for Advancement of Science.

  20. Atomistic simulation of surface functionalization on the interfacial properties of graphene-polymer nanocomposites

    SciTech Connect

    Wang, M. C.; Lai, Z. B.; Galpaya, D.; Yan, C.; Hu, N.; Zhou, L. M.

    2014-03-28

    Graphene has been increasingly used as nano sized fillers to create a broad range of nanocomposites with exceptional properties. The interfaces between fillers and matrix play a critical role in dictating the overall performance of a composite. However, the load transfer mechanism along graphene-polymer interface has not been well understood. In this study, we conducted molecular dynamics simulations to investigate the influence of surface functionalization and layer length on the interfacial load transfer in graphene-polymer nanocomposites. The simulation results show that oxygen-functionalized graphene leads to larger interfacial shear force than hydrogen-functionalized and pristine ones during pull-out process. The increase of oxygen coverage and layer length enhances interfacial shear force. Further increase of oxygen coverage to about 7% leads to a saturated interfacial shear force. A model was also established to demonstrate that the mechanism of interfacial load transfer consists of two contributing parts, including the formation of new surface and relative sliding along the interface. These results are believed to be useful in development of new graphene-based nanocomposites with better interfacial properties.

  1. Probing adhesion forces at the molecular scale

    SciTech Connect

    Thomas, R.C.; Houston, J.E.; Michalske, T.A.

    1996-12-31

    Measurements of adhesion forces at the molecular scale, such as those discussed here, are necessary to understand macroscopic boundary-layer behavior such as adhesion, friction, wear, lubrication, and many other important phenomena. The authors` recent interfacial force microscopy (IFM) studies have provided detailed information about the mechanical response of both self-assembled monolayer (SAM) films and the underlying substrates. In addition, they recently demonstrated that the IFM is useful for studying the chemical nature of such films. In this talk, the authors discuss a new method for studying surface interactions and chemical reactions using the IFM. To quantitatively measure the work of adhesion and bond energies between two organic thin films, they modify both a Au substrate and a Au probe with self-assembling organomercaptan molecules having either the same or different end groups (-CH{sub 3}, -NH{sub 2}, and -COOH), and then analyze the force-versus-displacement curves (force profiles) that result from the approach to contact of the two surfaces. Their results show that the magnitude of the adhesive forces measured between methyl-methyl interactions are in excellent agreement with van der Waals calculations using Lifshitz theory and previous experimentally determined values. Moreover, the measured peak adhesive forces scale as expected for van der Waals, hydrogen-bonding, and acid-base interactions.

  2. Non-additive Empirical Force Fields for Short-Chain Linear Alcohols: Methanol to Butanol. Hydration Free Energetics and Kirkwood-Buff Analysis Using Charge Equilibration Models

    PubMed Central

    Zhong, Yang; Patel, Sandeep

    2010-01-01

    Building upon the nonadditive electrostatic force field for alcohols based on the CHARMM charge equilibration (CHEQ) formalism, we introduce atom-pair specific solute-solvent Lennard-Jones (LJ) parameters for alcohol-water interaction force fields targeting improved agreement with experimental hydration free energies of a series of small molecule linear alcohols as well as ab initio water-alcohol geometries and energetics. We consider short-chain, linear alcohols from methanol to butanol as they are canonical small-molecule organic model compounds to represent the hydroxyl chemical functionality for parameterizing biomolecular force fields for proteins. We discuss molecular dynamics simulations of dilute aqueous solutions of methanol and ethanol in TIP4P-FQ water, with particular discussion of solution densities, structure defined in radial distribution functions, electrostatic properties (dipole moment distributions), hydrogen bonding patterns of water, as well as a Kirkwood-Buff (KB) integral analysis. Calculation of the latter provides an assessment of how well classical force fields parameterized to at least semi-quantitatively match experimental hydration free energies capture the microscopic structures of dilute alcohol solutions; the latter translate into macroscopic thermodynamic properties through the application of KB analysis. We find that the CHEQ alcohol force fields of this work semi-quantitatively match experimental KB integrals for methanol and ethanol mole fractions of 0.1 and 0.2. The force field combination qualitatively captures the concentration dependence of the alcohol-alcohol and water-water KB integrals, but due to inadequacies in the representation of the microscopic structures in such systems (which cannot be parameterized in any systematic fashion), a priori quantitative description of alcohol-water KB integrals remains elusive. PMID:20687517

  3. Interfacial behavior of polymer electrolytes

    SciTech Connect

    Kerr, John; Kerr, John B.; Han, Yong Bong; Liu, Gao; Reeder, Craig; Xie, Jiangbing; Sun, Xiaoguang

    2003-06-03

    Evidence is presented concerning the effect of surfaces on the segmental motion of PEO-based polymer electrolytes in lithium batteries. For dry systems with no moisture the effect of surfaces of nano-particle fillers is to inhibit the segmental motion and to reduce the lithium ion transport. These effects also occur at the surfaces in composite electrodes that contain considerable quantities of carbon black nano-particles for electronic connection. The problem of reduced polymer mobility is compounded by the generation of salt concentration gradients within the composite electrode. Highly concentrated polymer electrolytes have reduced transport properties due to the increased ionic cross-linking. Combined with the interfacial interactions this leads to the generation of low mobility electrolyte layers within the electrode and to loss of capacity and power capability. It is shown that even with planar lithium metal electrodes the concentration gradients can significantly impact the interfacial impedance. The interfacial impedance of lithium/PEO-LiTFSI cells varies depending upon the time elapsed since current was turned off after polarization. The behavior is consistent with relaxation of the salt concentration gradients and indicates that a portion of the interfacial impedance usually attributed to the SEI layer is due to concentrated salt solutions next to the electrode surfaces that are very resistive. These resistive layers may undergo actual phase changes in a non-uniform manner and the possible role of the reduced mobility polymer layers in dendrite initiation and growth is also explored. It is concluded that PEO and ethylene oxide-based polymers are less than ideal with respect to this interfacial behavior.

  4. Liquid metal actuation by electrical control of interfacial tension

    NASA Astrophysics Data System (ADS)

    Eaker, Collin B.; Dickey, Michael D.

    2016-09-01

    By combining metallic electrical conductivity with low viscosity, liquid metals and liquid metal alloys offer new and exciting opportunities to serve as reconfigurable components of electronic, microfluidic, and electromagnetic devices. Here, we review the physics and applications of techniques that utilize voltage to manipulate the interfacial tension of liquid metals; such techniques include electrocapillarity, continuous electrowetting, electrowetting-on-dielectric, and electrochemistry. These techniques lower the interfacial tension between liquid metals and a surrounding electrolyte by driving charged species (or in the case of electrochemistry, chemical species) to the interface. The techniques are useful for manipulating and actuating liquid metals at sub-mm length scales where interfacial forces dominate. We focus on metals and alloys that are liquid near or below room temperature (mercury, gallium, and gallium-based alloys). The review includes discussion of mercury—despite its toxicity—because it has been utilized in numerous applications and it offers a way of introducing several phenomena without the complications associated with the oxide layer that forms on gallium and its alloys. The review focuses on the advantages, applications, opportunities, challenges, and limitations of utilizing voltage to control interfacial tension as a method to manipulate liquid metals.

  5. Measurement of surface and interfacial tension using pendant drop tensiometry.

    PubMed

    Berry, Joseph D; Neeson, Michael J; Dagastine, Raymond R; Chan, Derek Y C; Tabor, Rico F

    2015-09-15

    Pendant drop tensiometry offers a simple and elegant solution to determining surface and interfacial tension - a central parameter in many colloidal systems including emulsions, foams and wetting phenomena. The technique involves the acquisition of a silhouette of an axisymmetric fluid droplet, and iterative fitting of the Young-Laplace equation that balances gravitational deformation of the drop with the restorative interfacial tension. Since the advent of high-quality digital cameras and desktop computers, this process has been automated with high speed and precision. However, despite its beguiling simplicity, there are complications and limitations that accompany pendant drop tensiometry connected with both Bond number (the balance between interfacial tension and gravitational forces) and drop volume. Here, we discuss the process involved with going from a captured experimental image to a fitted interfacial tension value, highlighting pertinent features and limitations along the way. We introduce a new parameter, the Worthington number, Wo, to characterise the measurement precision. A fully functional, open-source acquisition and fitting software is provided to enable the reader to test and develop the technique further. PMID:26037272

  6. Interfacial/free radical polymerization microencapsulation: kinetics of particle formation.

    PubMed

    Mahabadi, H K; Ng, T H; Tan, H S

    1996-01-01

    Microcapsules containing pigment and polymer were prepared by dispersing a viscous mixture of pigment, core monomers, initiators and oil-soluble shell monomer in an aqueous solution of surfactants, forming oil-in-water droplets. Subsequently, a water-soluble shell monomer was added to these droplets, encapsulating them via interfacial (IF) polycondensation. These microcapsules were then heated for free radical (FR) polymerization of the core monomers. Effects of primary variables, such as the shearing time during particle formation, surfactant concentration, organic phase concentration, and mode of water-soluble shell monomer addition, were studied. The results indicated that polyvinylalcohol (PVOH), used as the surfactant/stabilizer, reacted with the oil-soluble shell monomers. The depletion of PVOH, especially when PVOH concentration was low, resulted in rapid growth of particle size and, eventually, suspension failure. The kinetic data revealed a particle formation mechanism which consists of two processes. The first process is the formation of an equilibrium particle size by the equilibrium process of particle breakage due to the mechanical shearing force and coalescence due to collisions among particles and surface tension forces. The second process is the reaction between PVOH and oil-soluble shell monomer which leads to the depletion of PVOH and consequently causes more coalescence of particles and a significant increase in the equilibrium particle size. The net effect of these two processes shows an optimum shearing time where the smallest particle size can be attained, and this optimum time is a function of several primary variables. Methods to prevent the reaction and therefore the depletion of PVOH are proposed. PMID:8864993

  7. Elastic response of DNA molecules under the action of interfacial traction and stretching: An elastic thin rod model

    NASA Astrophysics Data System (ADS)

    Xiao, Ye; Huang, Zaixing; Qiang, Lei; Gao, Jun

    2015-11-01

    In a multivalent salt solution, a segment of DNA is modeled as an elastic rod subjected to the interfacial traction. The shooting method is used to calculate the equilibrium configurations of condensed DNA under the action of the longitudinal end-force and interfacial traction simultaneously. The results show that the shapes of DNA are mainly determined by the competition between the interfacial energy and elastic strain energy of stretching. The change of end-to-end distance with the longitudinal end-force is consistent with the worm-like chain (WLC) model. The higher the concentration is, the stronger the condensation of DNA.

  8. Turbulence and Interfacial Mixing

    SciTech Connect

    Glimm, James; Li, Xiaolin

    2005-03-15

    The authors study mix from analytical and numerical points of view. These investigations are linked. The analytical studies (in addition to laboratory experiments) provide bench marks for the direct simulation of mix. However, direct simulation is too detailed to be useful and to expensive to be practical. They also consider averaged equations. Here the major issue is the validation of the closure assumptions. They appeal to the direct simulation methods for this step. They have collaborated with several NNSA teams; moreover, Stony Brook alumni (former students, faculty and research collaborators) presently hold staff positions in NNSA laboratories.

  9. Elastocapillary-mediated interfacial assembly

    NASA Astrophysics Data System (ADS)

    Evans, Arthur

    2015-11-01

    Particles confined to an interface are present in a large number of industrial applications and ubiquitous in cellular biophysics. Interactions mediated by the interface, such as capillary effects in the presence of surface tension, give rise to rafts and aggregates whose structure is ultimately determined by geometric characteristics of these adsorbed particles. A common strategy for assembling interfacial structures relies on exploiting these interactions by tuning particle anisotropy, either by constructing rigid particles with heterogeneous wetting properties or fabricating particles that have a naturally anisotropic shape. Less explored, however, is the scenario where the interface causes the particles to deform. In this talk I will discuss the implications for interfacial assembly using elastocapillary-mediated interactions. The competition between surface energy and elasticity can wrinkle and buckle adsorbed soft particles, leading to complicated (but programmable) aggregates.

  10. Study of the flow field in the magnetic rod interfacial stress rheometer.

    PubMed

    Verwijlen, Tom; Moldenaers, Paula; Stone, Howard A; Vermant, Jan

    2011-08-01

    Several technological applications, consumer products, and biological systems derive their functioning from the presence of a complex fluid interface with viscoelastic interfacial rheological properties. Measurements of the "excess" rheological properties of such an interface are complicated by the intimate coupling of the bulk and interfacial flows. In the present work, analytical, numerical, and experimental results of the interfacial flow fields in a magnetic rod interfacial stress rheometer (ISR) are presented. Mathematical solutions are required to correct the experimentally determined apparent interfacial shear moduli and phase angles for the drag exerted by the surrounding phases, especially at low Boussinesq numbers. Starting from the Navier-Stokes equations and using the generalized Boussinesq-Scriven equation as a suitable boundary condition, the problem is solved both analytically and numerically. In addition, experimental data of the interfacial flow field are reported, obtained by following the trajectories of tracer particles at the interface with time. Good agreement is found between the three methods, indicating that both the analytical solution and the numerical simulations give an adequate description of the flow field and the resulting local interfacial shear rate at the rod. Based on these results, an algorithm to correct the experimental data of the ISR is proposed and evaluated, which can be extended to different types of interfacial shear rheometers and geometries. An increased accuracy is obtained and the measurement range of the ISR is expanded toward viscosities and elastic moduli of smaller magnitude. PMID:21696160

  11. Evaluation of the interfacial mechanical properties in fiber-reinforced ceramic composites

    SciTech Connect

    Ferber, M.K.; Wereszczak, A.A.; Riester, L.; Lowden, R.A.; Chawla, K.K.

    1993-06-01

    The present study examined the application of a micro-indentation technique to the measurement of interfacial properties in fiber reinforced ceramic composites. Specific fiber/matrix systems included SiC/glass, SiC/macro-defect-free (MDF) cement, SiC/SiC, and mullite/glass. The effect of fiber coatings upon the interfacial properties was also investigated. These properties, which included the debond strength, interfacial shear stress, and residual axial fiber stress, were evaluated by measuring the force-displacement curves generated during load-unload cycles. Estimates of these three stress values were obtained by matching the experimental force-displacement curves with data predicted from an existing model. In general the SiC/glass composites exhibited the lowest values of the interfacial shear and debond stresses. The sliding characteristics of the SiC/MDF cement and SiC/SiC composites were strongly influenced by the residual axial stress and the nature of the fiber coating. In the case of the mullite/glass composite, the high values of the interfacial shear and debond stresses reduced the measurement sensitivity, thereby increasing the uncertainty in the estimates of the interfacial properties. 17 refs, 6 figs, 1 tab.

  12. The balanced-force volume tracking algorithm and global embedded interface formulation for droplet dynamics with mass transfer

    SciTech Connect

    Francois, Marianne M; Carlson, Neil N

    2010-01-01

    Understanding the complex interaction of droplet dynamics with mass transfer and chemical reactions is of fundamental importance in liquid-liquid extraction. High-fidelity numerical simulation of droplet dynamics with interfacial mass transfer is particularly challenging because the position of the interface between the fluids and the interface physics need to be predicted as part of the solution of the flow equations. In addition, the discontinuity in fluid density, viscosity and species concentration at the interface present additional numerical challenges. In this work, we extend our balanced-force volume-tracking algorithm for modeling surface tension force (Francois et al., 2006) and we propose a global embedded interface formulation to model the interfacial conditions of an interface in thermodynamic equilibrium. To validate our formulation, we perform simulations of pure diffusion problems in one- and two-dimensions. Then we present two and three-dimensional simulations of a single droplet dynamics rising by buoyancy with mass transfer.

  13. Stationary patterns in centrifugally driven interfacial elastic fingering.

    PubMed

    Carvalho, Gabriel D; Gadêlha, Hermes; Miranda, José A

    2014-12-01

    A vortex sheet formalism is used to search for equilibrium shapes in the centrifugally driven interfacial elastic fingering problem. We study the development of interfacial instabilities when a viscous fluid surrounded by another of smaller density flows in the confined environment of a rotating Hele-Shaw cell. The peculiarity of the situation is associated to the fact that, due to a chemical reaction, the two-fluid boundary becomes an elastic layer. The interplay between centrifugal and elastic forces leads to the formation of a rich variety of stationary shapes. Visually striking equilibrium morphologies are obtained from the numerical solution of a nonlinear differential equation for the interface curvature (the shape equation), determined by a zero vorticity condition. Classification of the various families of shapes is made via two dimensionless parameters: an effective bending rigidity (ratio of elastic to centrifugal effects) and a geometrical radius of gyration. PMID:25615189

  14. Stationary patterns in centrifugally driven interfacial elastic fingering

    NASA Astrophysics Data System (ADS)

    Carvalho, Gabriel D.; Gadêlha, Hermes; Miranda, José A.

    2014-12-01

    A vortex sheet formalism is used to search for equilibrium shapes in the centrifugally driven interfacial elastic fingering problem. We study the development of interfacial instabilities when a viscous fluid surrounded by another of smaller density flows in the confined environment of a rotating Hele-Shaw cell. The peculiarity of the situation is associated to the fact that, due to a chemical reaction, the two-fluid boundary becomes an elastic layer. The interplay between centrifugal and elastic forces leads to the formation of a rich variety of stationary shapes. Visually striking equilibrium morphologies are obtained from the numerical solution of a nonlinear differential equation for the interface curvature (the shape equation), determined by a zero vorticity condition. Classification of the various families of shapes is made via two dimensionless parameters: an effective bending rigidity (ratio of elastic to centrifugal effects) and a geometrical radius of gyration.

  15. Interfacial Reactivity of Radionuclides: Emerging Paradigms from Molecular Level Observations

    SciTech Connect

    Felmy, Andrew R.; Ilton, Eugene S.; Rosso, Kevin M.; Zachara, John M.

    2011-08-15

    Over the past few decades use of an increasing array of molecular-level analytical probes has provided new detailed insight into mineral and radionuclide interfacial reactivity in subsurface environments. This capability has not only helped change the way mineral surface reactivity is studied but also how field-scale contaminant migration problems are addressed and ultimately resolved. Here we overview examples of relatively new interfacial reactivity paradigms with implications for future research directions. Specific examples include understanding: the role of site-to-site electron conduction at mineral surfaces and through bulk mineral phases, effects of local chemical environment on the stability of intermediate species in oxidation/reduction reactions, and the importance of mechanistic reaction pathway for defining possible reaction products and thermodynamic driving force. The discussion also includes examples of how detailed molecular/microscopic characterization of field samples has changed the way complex contaminant migration problems were conceptualized and modeled.

  16. Interfacial assignment of branched-alkyl benzene sulfonates: A molecular simulation

    NASA Astrophysics Data System (ADS)

    Liu, Zi-Yu; Wei, Ning; Wang, Ce; Zhou, He; Zhang, Lei; Liao, Qi; Zhang, Lu

    2015-11-01

    A molecular dynamics simulation was conducted to analyze orientations of sodium branched-alkyl benzene sulfonates molecules at nonane/water interface, which is helpful to design optimal surfactant structures to achieve ultralow interfacial tension (IFT). Through the two dimensional density profiles, monolayer collapses are found when surfactant concentration continues to increase. Thus the precise scope of monolayer is certain and orientation can be analyzed. Based on the simulated results, we verdict the interfacial assignment of branched-alkyl benzene sulfonates at the oil-water interface, and discuss the effect of hydrophobic tail structure on surfactant assignment. Bigger hydrophobic size can slow the change rate of surfactant occupied area as steric hindrance, and surfactant meta hydrophobic tails have a stronger tendency to stretch to the oil phase below the collapsed concentration. Furthermore, an interfacial model with reference to collapse, increasing steric hindrance and charge repulsive force between interfacial surfactant molecules, responsible for effecting of surfactant concentration and structure has been supposed.

  17. Azo Dyes and Their Interfacial Activity: Implications for Multiphase Flow Experiments

    SciTech Connect

    Tuck, D.M.

    1999-04-21

    Interfacial effects play an important role in governing multiphase fluid behavior in porous media (Neustadter 1984; Tuck et al. 1988). For instance, several dimensionless numbers have been developed to express important force ratios applicable to multiphase flow in porous media (Morrow and Songkran 1981; Chatzis and Morrow 1984; Wardlaw 1988; Pennell et al. 1996; Dawson and Roberts 1997). These force ratios emphasize the importance of interfacial properties. Our objectives are to provide chemical information regarding the dyes commonly used in multiphase flow visualization studies and to show the surface chemistry effects of the most commonly used dye, Sudan IV, in the tetrachloroethylene (PCE)-water-glass system

  18. Numerical investigation of the factors affecting interfacial stresses in an MOD restored tooth by auto-meshed finite element method.

    PubMed

    Lin, C L; Chang, C H; Wang, C H; Ko, C C; Lee, H E

    2001-06-01

    Many researches have addressed the high correlation between the fracture of restored teeth and the prepared cavity geometry. In addition, concerns about bonding versus debonding dental materials from cavity walls and different occlusal force conditions could also alter the mechanical responses in a restored tooth. This study employed an automatic mesh procedure to investigate the mechanical interactions between different interfacial conditions and cavity parameters such as pulpal wall depth under different chewing functions. The results indicated that when occlusal force was applied directly on the tooth, it could increase unfavourable stress dramatically. When interfacial fixation was simulated as the contact condition between the tooth tissue and restorative material, it might increase the fracture potential exponentially compared with the bonded interface. For pulpal wall depth analyses, greater risks of fracture for the remaining tooth were observed in deeper cavity of mesio-occlusal-distal (MOD) restorations and the existence of a pulpal wall is essential even it is only 1 mm above the gingival wall. PMID:11422677

  19. Attempt to control the interfacial strength

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.

    1997-11-01

    Composites consisting of a B2 iron aluminide matrix and 40 vol.% of TiB{sub 2} particles were processed by liquid phase sintering. In order to encourage segregation of B or Ti at the FeAl/TiB{sub 2} interfaces, the iron aluminide matrix was microalloyed with B or Ti, respectively. Additions of Ti degraded the mechanical properties. However, for composites microalloyed with B, room temperature flexure tests show slight increases in the maximum strength (from 1250 to 1380 MPa) and the fracture toughness. Interfacial segregation of B may have contributed to this result. Significantly improved processing of the composites would be required in order to verify the effect of B conclusively. 15 refs., 6 figs., 2 tabs.

  20. Measuring Interfacial Tension Between Immiscible Liquids

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser; Balasubramaniam, R.; Delsignore, David M.

    1995-01-01

    Glass capillary tube technique measures interfacial tension between two immiscible liquids. Yields useful data over fairly wide range of interfacial tensions, both for pairs of liquids having equal densities and pairs of liquids having unequal densities. Data on interfacial tensions important in diverse industrial chemical applications, including enhanced extraction of oil; printing; processing foods; and manufacture of paper, emulsions, foams, aerosols, detergents, gel encapsulants, coating materials, fertilizers, pesticides, and cosmetics.

  1. Interfacial reactions between titanium and borate glass

    SciTech Connect

    Brow, R.K.; Saha, S.K.; Goldstein, J.I.

    1992-12-31

    Interfacial reactions between melts of several borate glasses and titanium have been investigated by analytical scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). A thin titanium boride interfacial layer is detected by XPS after short (30 minutes) thermal treatments. ASEM analyses after longer thermal treatments (8--120 hours) reveal boron-rich interfacial layers and boride precipitates in the Ti side of the interface.

  2. Parametric evaluation of shear sensitivity in piezoresistive interfacial force sensors

    NASA Astrophysics Data System (ADS)

    Benfield, David; Lou, Edmond; Moussa, Walied A.

    2011-04-01

    A three-axis load detector has been designed and manufactured utilizing four piezoresistive sensors on a flexible silicon membrane. The detector was prototyped using bulk microfabrication techniques on a single-crystal silicon wafer and was designed to detect normal and shear loadings applied to the membrane. Finite element analysis and experimental calibration methods have been used to determine the shear and normal sensitivity values. Device parameters were modified with emphasis on increasing the absolute shear to normal sensitivity ratio of the sensors without reducing their ultimate strength. It was determined that the shear to normal sensitivity ratio greater than 0.5 would allow detection of shear loads considering experimental error present. For devices with square membranes having 1000 µm edge lengths and 65 µm thicknesses, this amount of shear sensitivity was achievable using a mesa with a height of at least 150 µm.

  3. Measurement of Interfacial Area Production and Permeability within Porous Media

    SciTech Connect

    Crandall, Dustin; Ahmadi, Goodarz; Smith, Duane H.

    2010-01-01

    An understanding of the pore-level interactions that affect multi-phase flow in porous media is important in many subsurface engineering applications, including enhanced oil recovery, remediation of dense non-aqueous liquid contaminated sites, and geologic CO2 sequestration. Standard models of two-phase flow in porous media have been shown to have several shortcomings, which might partially be overcome using a recently developed model based on thermodynamic principles that includes interfacial area as an additional parameter. A few static experimental studies have been previously performed, which allowed the determination of static parameters of the model, but no information exists concerning the interfacial area dynamic parameters. A new experimental porous flow cell that was constructed using stereolithography for two-phase gas-liquid flow studies was used in conjunction with an in-house analysis code to provide information on dynamic evolution of both fluid phases and gas-liquid interfaces. In this paper, we give a brief introduction to the new generalized model of two-phase flow model and describe how the stereolithography flow cell experimental setup was used to obtain the dynamic parameters for the interfacial area numerical model. In particular, the methods used to determine the interfacial area permeability and production terms are shown.

  4. Manipulating Ordering Transitions in Interfacially Modified Block Copolymers

    SciTech Connect

    Singh, N.; Tureau, M; Epps, T

    2009-01-01

    We report a synthetic strategy that allows us to manipulate the interfacial region between blocks and control ordering transitions in poly(isoprene-b-styrene) [P(I-S)] block copolymers. This interfacial modification is accomplished by combining a semi-batch feed with anionic polymerization techniques. Using this approach, we are able to control the segmental composition and molecular interactions in our phase-separated block copolymers, independent of molecular weight and block constituents. A library of copolymers is prepared with various interfacial modifications to examine the effect of interfacial composition on copolymer self-assembly. The morphological characteristics of the self-assembled structures are investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). Normal and inverse tapered block copolymers, containing approximately 15-35 vol% tapered material, show a measurable decrease in the order-disorder transition temperature (TODT) relative to the corresponding non-tapered diblock copolymers, with the inverse tapered materials showing the greatest deviation in TODT. Additionally, TODT was inversely related to the volume fraction of the tapered region in both normal and inverse tapered copolymer materials.

  5. Wavebreaking of Interfacial Stokes Flows

    NASA Astrophysics Data System (ADS)

    Maiden, Michelle; Lowman, Nicholas; Anderson, Dalton; Hoefer, Mark

    2015-11-01

    Viscous fluid conduits provide a versatile system for the study of dissipationless, dispersive hydrodynamics. A dense, viscous fluid serves as the background media through which a less dense, less viscous fluid buoyantly rises. If fluid is continuously injected into the exterior fluid, an interface forms that behaves like a deformable pipe. Conservation of mass implies that the interfacial dynamics are conservative, i.e., they behave like a superfluid. Through buoyancy, high viscosity contrast, and a long wave assumption, conduit interfacial dynamics can be modeled by a scalar, nonlinear, dispersive wave equation with no assumption on amplitude. Experiments involving solitons, wavebreaking leading to dispersive shock waves (DSWs), and their interactions will be presented. The results include the refraction and absorption of a soliton by a DSW and the refraction of a DSW by a second DSW, resulting in two-phase behavior. Excellent agreement between nonlinear wave (Whitham) averaging, numerics, and laboratory experiments will be presented. The nonlinear wave dynamics observed in this model system have implications for a broad range of other conservative dispersive hydrodynamic systems. Support provided by NSF CAREER DMS-1255422, NSF GRFP.

  6. Nanotube attachment for prevention of interfacial delamination

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sharmila M.; Karumuri, Anil K.

    2010-09-01

    A new approach to suppressing interfacial delamination in composites has been investigated. It involves growing strongly attached nanotubes on the surface of the core phase prior to matrix infiltration. Unusually durable interfaces between epoxy and graphite have been demonstrated using this technique. Two types of graphitic core materials have been studied: complex cellular foams having open-interconnected porosity and highly oriented pyrolitic graphite (HOPG) providing a model flat interface. When untreated foam is infiltrated with epoxy, the resulting composite is brittle, and shatters before 10% compression. However, when carbon nanotubes (CNTs) are grown on the foam prior to epoxy infiltration, the specimen becomes pliable, and visibly flattens out rather than fracturing. Model studies on a flat graphite-epoxy interface were performed by joining two HOPG specimens with a thin layer of epoxy, and testing the flexural response of the 'seam' using the three-point bend test. The untreated HOPG sandwich fails easily, whereas nanotube-attached HOPG sandwich shows an over three times increase in flexural load-carrying capacity, close to that of seamless monolithic graphite having identical dimensions. Microscopic evaluations of fractured interfaces indicate that, in all geometries, CNT grafting prevents delamination at the graphite-epoxy interface, and forces any crack(s) to propagate through the graphitic phase. This added inter-laminar strength and toughness can be related to the hierarchical morphology of the interface created by CNT attachment, and unprecedented composite structures can be envisioned.

  7. Interfacial interactions between plastic particles in plastics flotation.

    PubMed

    Wang, Chong-qing; Wang, Hui; Gu, Guo-hua; Fu, Jian-gang; Lin, Qing-quan; Liu, You-nian

    2015-12-01

    Plastics flotation used for recycling of plastic wastes receives increasing attention for its industrial application. In order to study the mechanism of plastics flotation, the interfacial interactions between plastic particles in flotation system were investigated through calculation of Lifshitz-van der Waals (LW) function, Lewis acid-base (AB) Gibbs function, and the extended Derjaguin-Landau-Verwey-Overbeek potential energy profiles. The results showed that van der Waals force between plastic particles is attraction force in flotation system. The large hydrophobic attraction, caused by the AB Gibbs function, is the dominant interparticle force. Wetting agents present significant effects on the interfacial interactions between plastic particles. It is found that adsorption of wetting agents promotes dispersion of plastic particles and decreases the floatability. Pneumatic flotation may improve the recovery and purity of separated plastics through selective adsorption of wetting agents on plastic surface. The relationships between hydrophobic attraction and surface properties were also examined. It is revealed that there exists a three-order polynomial relationship between the AB Gibbs function and Lewis base component. Our finding provides some insights into mechanism of plastics flotation. PMID:26337962

  8. Insect flight on fluid interfaces: a chaotic interfacial oscillator

    NASA Astrophysics Data System (ADS)

    Mukundarajan, Haripriya; Prakash, Manu

    2013-11-01

    Flight is critical to the dominance of insect species on our planet, with about 98 percent of insect species having wings. How complex flight control systems developed in insects is unknown, and arboreal or aquatic origins have been hypothesized. We examine the biomechanics of aquatic origins of flight. We recently reported discovery of a novel mode of ``2D flight'' in Galerucella beetles, which skim along an air-water interface using flapping wing flight. This unique flight mode is characterized by a balance between capillary forces from the interface and biomechanical forces exerted by the flapping wings. Complex interactions on the fluid interface form capillary wave trains behind the insect, and produce vertical oscillations at the surface due to non-linear forces arising from deformation of the fluid meniscus. We present both experimental observations of 2D flight kinematics and a dynamic model explaining the observed phenomena. Careful examination of this interaction predicts the chaotic nature of interfacial flight and takeoff from the interface into airborne flight. The role of wingbeat frequency, stroke plane angle and body angle in determining transition between interfacial and fully airborne flight is highlighted, shedding light on the aquatic theory of flight evolution.

  9. Interfacial microstructure and properties of carbon fiber composites modified with graphene oxide.

    PubMed

    Zhang, Xiaoqing; Fan, Xinyu; Yan, Chun; Li, Hongzhou; Zhu, Yingdan; Li, Xiaotuo; Yu, Liping

    2012-03-01

    The performance of carbon fiber-reinforced composites is dependent to a great extent on the properties of fiber-matrix interface. To improve the interfacial properties in carbon fiber/epoxy composites, we directly introduced graphene oxide (GO) sheets dispersed in the fiber sizing onto the surface of individual carbon fibers. The applied graphite oxide, which could be exfoliated to single-layer GO sheets, was verified by atomic force microscope (AFM). The surface topography of modified carbon fibers and the distribution of GO sheets in the interfacial region of carbon fibers were detected by scanning electron microscopy (SEM). The interfacial properties between carbon fiber and matrix were investigated by microbond test and three-point short beam shear test. The tensile properties of unidirectional (UD) composites were investigated in accordance with ASTM standards. The results of the tests reveal an improved interfacial and tensile properties in GO-modified carbon fiber composites. Furthermore, significant enhancement of interfacial shear strength (IFSS), interlaminar shear strength (ILSS), and tensile properties was achieved in the composites when only 5 wt % of GO sheets introduced in the fiber sizing. This means that an alternative method for improving the interfacial and tensile properties of carbon fiber composites by controlling the fiber-matrix interface was developed. Such multiscale reinforced composites show great potential with their improved mechanical performance to be likely applied in the aerospace and automotive industries. PMID:22391332

  10. 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.

  11. Interfacial functionalization and engineering of nanoparticles

    NASA Astrophysics Data System (ADS)

    Song, Yang

    also of the metal elements in the nanoparticle cores, in contrast to the bulk-exchange counterparts where these distributions were homogeneous within the nanoparticles, as manifested in contact angle, UV--vis, XPS, and TEM measurements. More interestingly, the electrocatalytic performance of the Janus nanoparticles was markedly better than the bulk-exchange ones, suggesting that the segregated distribution of the polar ligands from the apolar ones might further facilitate charge transfer from Ag to Au in the nanoparticle cores, leading to additional improvement of the adsorption and reduction of oxygen. This interfacial protocol was then adopted to prepare trimetallic Ag AuPt Neapolitan nanoparticles by two sequential galvanic exchange reactions of 1-hexanethiolate-capped silver nanoparticles with gold(I)-thiomalic acid and platinum(II)-hexanethiolate complexes. As both reactions were confined to an interface, the Au and Pt elements were situated on two opposite poles of the original Ag nanoparticles, which was clearly manifested in elemental mapping of the nanoparticles, and consistent with the damping and red-shift of the nanoparticle surface plasmon resonance. As nanoscale analogs to conventional amphiphilic molecules, the resulting Janus nanoparticles were found to form oil-in-water micelle-like or water-in-oil reverse micelle-like superparticulate structures depending on the solvent media. These unique characteristics were exploited for the effective transfer of diverse guest nanoparticles between organic and water phase. The transfer of hydrophobic nanoparticles from organic to water media or water-soluble nanoparticles to the organic phase was evidenced by TEM, DLS, UV-Vis, and PL measurements. In particular, line scans based on EDS analysis showed that the vesicle-like structures consisted of multiple layers of the Janus nanoparticles, which encapsulated the guest nanoparticles in the cores. The results highlight the unique effectiveness of using Janus

  12. Accelerated Nucleation Due to Trace Additives: A Fluctuating Coverage Model.

    PubMed

    Poon, Geoffrey G; Peters, Baron

    2016-03-01

    We develop a theory to account for variable coverage of trace additives that lower the interfacial free energy for nucleation. The free energy landscape is based on classical nucleation theory and a statistical mechanical model for Langmuir adsorption. Dynamics are modeled by diffusion-controlled attachment and detachment of solutes and adsorbing additives. We compare the mechanism and kinetics from a mean-field model, a projection of the dynamics and free energy surface onto nucleus size, and a full two-dimensional calculation using Kramers-Langer-Berezhkovskii-Szabo theory. The fluctuating coverage model predicts rates more accurately than mean-field models of the same process primarily because it more accurately estimates the potential of mean force along the size coordinate. PMID:26485064

  13. Interfacial tension between immiscible melts in the system K2O - FeO - Fe2O3 - Al2O3 - SiO2

    NASA Astrophysics Data System (ADS)

    Kaehn, J.; Veksler, I. V.; Franz, G.; Dingwell, D. B.

    2009-12-01

    Interfacial tension is a very important parameter of the kinetics of phase nucleation, dissolution and growth. Excess surface energy contributes to the energy barrier for phase nucleation, and works as the main driving force for minimization of phase contact surfaces in heterogeneous systems. Immiscible silicate melts have been found to form in a broad range of basaltic, dacitic and rhyolitic magmas (Philpotts, 1982). However, liquid-liquid interfaces remain poorly studied in comparison with crystal-melt and vapor-melt interfaces. Here we present first experimental measurements of interfacial tension between synthetic Fe-rich and silica-rich immiscible melts composed of Fe oxides, K2O, alumina and silica. According to Naslund (1983), the miscibility gap in the 5-oxide system expands with increasing fO2 and becomes widest in air (fO2 = 0.2). Our goal was to estimate the maximal liquid-liquid interfacial tension for the immiscible liquids composed of silica and Fe oxides. Therefore, we have chosen the most contrasting liquid compositions that coexist in air at and above 1465 °C. Silica-rich and Fe-rich conjugate liquids at these conditions contain 73 and 17 wt. % SiO2, and 14 and 80 wt. % FeOt, respectively. These starting compositions were synthesized by fusion of reagent-grade oxides and K2CO3 at 1600 °C. In addition to interfacial tension, we have measured density and surface tension of individual coexisting liquids. All the measurements were done at 1500, 1527 and 1550 °C. Density was measured by the Archimedean method; surface and interfacial tensions were calculated from the maximal pool on a vertical cylinder (a 3-mm Pt rod attached to a high precision balance). We found interfacial tension between the immiscible liquids to decrease with increasing temperature from 16.4±2 mN/m at 1500 °C to 8.2±0.8 mN/m at 1550 °C. These values are approximately 2 orders of magnitude lower than typical interfacial tensions between silicate melts and crystals (Wanamaker

  14. Control of interfacial chemistry and mechanical properties in metal/ceramic composites. Ph.D. Thesis

    SciTech Connect

    Wang, Hsin-Fu

    1994-12-31

    Evaluation of the mechanical properties of metal/ceramic interfaces (Ti/AI2O3) was accomplished by using four-point bending tests, nanoindentation tests and fiber pushout tests. At first, the interfacial fracture energy of composites with different applied bonding temperatures from 700 C to 1000 C and thickness of the metal interlayers were measured by four-point bending tests. The mixed mode interfacial fracture energy of the Ti/Al2O3 interface was found to increase with increasing bonding temperatures up to 950 C. There is increasing interdiffusion of the constituent atoms across the interfaces with increasing temperature as verified by X-ray mapping. Thus, a stronger chemical bond forms between the Ti and the Al2O3. Above this temperature, the interfacial fracture energy drops due to the formation of a continuous brittle intermetallic compound (Ti3Al) at the Ti/Al2O3 interface. Modification of the interface was achieved with a diffusion barrier consisting of a refractory metal and Y2O3 duplex coating prepared by r.f. sputtering methods. The diffusion barrier significantly reduces the diffusion of the constituent atoms and prevents the formation of a continuous Ti3Al reaction layer, thus maintaining the chemical integrity and stability at the Ti/Al2O3 interface. The interfacial fracture energy can be further reduced by providing thinner Ti interlayers. The contribution of the energy dissipation process to the interfacial fracture energy is due to plastic energy absorption in the Ti interlayer during the fracture process. The interfacial shear strength, interfacial frictional stress and mode II interfacial fracture energy of the fiber composites were obtained by performing the fiber pushout tests. Using the Atomic Force Microscope (AFM), the surface roughness and texture of the three different Al2O3 fibers were evaluated. Incorporation of the experimental data and the theory gives the calculated frictional coefficient to be 0.35.

  15. Interfacial optimization of fiber-reinforced hydrogel composites for soft fibrous tissue applications.

    PubMed

    Holloway, Julianne L; Lowman, Anthony M; VanLandingham, Mark R; Palmese, Giuseppe R

    2014-08-01

    Meniscal tears are the most common orthopedic injuries to the human body, yet the current treatment of choice is a partial meniscectomy, which is known to lead to joint degeneration and osteoarthritis. As a result, there is a significant clinical need to develop materials capable of restoring function to the meniscus following an injury. Fiber-reinforced hydrogel composites are particularly suited for replicating the mechanical function of native fibrous tissues due to their ability to mimic the native anisotropic property distribution present. A critical issue with these materials, however, is the potential for the fiber-matrix interfacial properties to severely limit composite performance. In this work, the interfacial properties of an ultra-high-molecular-weight polyethylene (UHMWPE) fiber-reinforced poly(vinyl alcohol) (PVA) hydrogel are studied. A novel chemical grafting technique, confirmed using X-ray photoelectron spectroscopy, is used to improve UHMWPE-PVA interfacial adhesion. Interfacial shear strength is quantified using fiber pull-out tests. Results indicate significantly improved fiber-hydrogel interfacial adhesion after chemical grafting, where chemically grafted samples have an interfacial shear strength of 256.4±64.3kPa compared to 11.5±2.9kPa for untreated samples. Additionally, scanning electron microscopy of fiber surfaces after fiber pull-out reveal cohesive failure within the hydrogel matrix for treated fiber samples, indicating that the UHMWPE-PVA interface has been successfully optimized. Lastly, inter-fiber spacing is observed to have a significant effect on interfacial adhesion. Fibers spaced further apart have significantly higher interfacial shear strengths, which is critical to consider when optimizing composite design. The results in this study are applicable in developing similar chemical grafting techniques and optimizing fiber-matrix interfacial properties for other hydrogel-based composite systems. PMID:24814880

  16. Interfacial instabilities and Kapitsa pendula

    NASA Astrophysics Data System (ADS)

    Krieger, Madison

    2015-11-01

    Determining the critera for onset and amplitude growth of instabilities is one of the central problems of fluid mechanics. We develop a parallel between the Kapitsa effect, in which a pendulum subject to high-frequency low-amplitude vibrations becomes stable in the inverted position, and interfaces separating fluids of different density. It has long been known that such interfaces can be stabilized by vibrations, even when the denser fluid is on top. We demonstrate that the stability diagram for these fluid interfaces is identical to the stability diagram for an appopriate Kapitsa pendulum. We expand the robust, ``dictionary''-type relationship between Kapitsa pendula and interfacial instabilities by considering the classical Rayleigh-Taylor, Kelvin-Helmholtz and Plateau instabilities, as well as less-canonical examples ranging in scale from the micron to the width of a galaxy.

  17. An analysis of interfacial waves and air ingestion mechanisms

    NASA Astrophysics Data System (ADS)

    Galimov, Azat

    This research was focused on developing analytical methods with which to derive the functional forms of the various interfacial forces in two-fluid models [Galimov et al., 2004], and on the Direct Numerical Simulations (DNS) of traveling breaking waves and plunging liquid jets. Analytical results are presented for a stable stratified wavy two-phase flow and the associated interfacial force densities of a two-fluid model. In particular, the non-drag interfacial force density [Drew & Passman, 1998], the Reynolds stress tensor, and the term ( p˜cli -pcl)∇alphacl, which drives surface waves, were derived, where p˜cli is interfacial average pressure, pcl is the average pressure, and alphacl is the volume fraction of the continuous liquid phase. These functional forms are potentially useful for developing two-fluid model closure relations for computational multiphase fluid dynamics (CMFD) numerical solvers. Moreover, it appears that this approach can be generalized to other flow regimes (e.g., annular flows). A comparison of the analytical and ensemble-averaged DNS results show good agreement, and it appears that this approach can be used to develop phenomenological flow-regime-specific closure laws for two-fluid models [Lahey & Drew, 2004], [Lahey, 2005]. A successful 2-D DNS of breaking traveling waves was performed. These calculations had periodic boundary conditions and the physical parameters for air/water flow at atmospheric pressure, including a liquid/gas density ratio of 1,000 and representative surface tension and viscosities. Detailed 3-D DNS was also made for a plunging liquid jet. The processes of forming the liquid jet, the associated air cavity, capturing an initial large donut-shaped air bubble, and developing and breaking-up this bubble into smaller bubbles due to liquid shear, were shown. These simulations showed that the inertia of the liquid jet initially depressed the pool's surface and the toroidal liquid eddy formed subsequently resulted in air

  18. Interfacial phenomena in foam flooding process for heavy oil recovery

    SciTech Connect

    Sharma, M.K.; Shah, D.O.

    1983-08-01

    The ability of pure and commercial foaming agents to generate in situ foams and their effects on air mobility, breakthrough time, fluid recovery and oil displacement efficiency have been studied. These parameters were correlated with the interfacial properties of foaming agents. A striking decrease in the air mobility was observed with increasing temperature as well as pressure which in turn increased the effectiveness of foams to displace additional fluid. It was observed that the chain length compatibility and molecular packing at the air-liquid interface strikingly influenced the interfacial properties of foaming agents, microscopic characteristics and behavior of foams. From the studies on mixed surfactant systems, a minimum in surface tension, a maximum in surface viscosity, a minimum in bubble size and a maximum in heavy oil displacement efficiency in a porous medium were observed when both the components of the foaming system had equal chain length.

  19. Tunable Interfacial Thermal Conductance by Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Shen, Meng

    We study the mechanism of tunable heat transfer through interfaces between solids using a combination of non-equilibrium molecular dynamics simulation (NEMD), vibrational mode analysis and wave packet simulation. We investigate how heat transfer through interfaces is affected by factors including pressure, interfacial modulus, contact area and interfacial layer thickness, with an overreaching goal of developing fundamental knowledge that will allow one to tailor thermal properties of interfacial materials. The role of pressure and interfacial stiffness is unraveled by our studies on an epitaxial interface between two Lennard-Jones (LJ) crystals. The interfacial stiffness is varied by two different methods: (i) indirectly by applying pressure which due to anharmonic nature of bonding, increases interfacial stiffness, and (ii) directly by changing the interfacial bonding strength by varying the depth of the potential well of the LJ potential. When the interfacial bonding strength is low, quantitatively similar behavior to pressure tuning is observed when the interfacial thermal conductance is increased by directly varying the potential-well depth parameter of the LJ potential. By contrast, when the interfacial bonding strength is high, thermal conductance is almost pressure independent, and even slightly decreases with increasing pressure. This decrease can be explained by the change in overlap between the vibrational densities of states of the two crystalline materials. The role of contact area is studied by modeling structures comprised of Van der Waals junctions between single-walled nanotubes (SWCNT). Interfacial thermal conductance between SWCNTs is obtained from NEMD simulation as a function of crossing angle. In this case the junction conductance per unit area is essentially a constant. By contrast, interfacial thermal conductance between multiwalled carbon nanotubes (MWCNTs) is shown to increase with diameter of the nanotubes by recent experimental studies [1

  20. Tunable Interfacial Thermal Conductance by Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Shen, Meng

    We study the mechanism of tunable heat transfer through interfaces between solids using a combination of non-equilibrium molecular dynamics simulation (NEMD), vibrational mode analysis and wave packet simulation. We investigate how heat transfer through interfaces is affected by factors including pressure, interfacial modulus, contact area and interfacial layer thickness, with an overreaching goal of developing fundamental knowledge that will allow one to tailor thermal properties of interfacial materials. The role of pressure and interfacial stiffness is unraveled by our studies on an epitaxial interface between two Lennard-Jones (LJ) crystals. The interfacial stiffness is varied by two different methods: (i) indirectly by applying pressure which due to anharmonic nature of bonding, increases interfacial stiffness, and (ii) directly by changing the interfacial bonding strength by varying the depth of the potential well of the LJ potential. When the interfacial bonding strength is low, quantitatively similar behavior to pressure tuning is observed when the interfacial thermal conductance is increased by directly varying the potential-well depth parameter of the LJ potential. By contrast, when the interfacial bonding strength is high, thermal conductance is almost pressure independent, and even slightly decreases with increasing pressure. This decrease can be explained by the change in overlap between the vibrational densities of states of the two crystalline materials. The role of contact area is studied by modeling structures comprised of Van der Waals junctions between single-walled nanotubes (SWCNT). Interfacial thermal conductance between SWCNTs is obtained from NEMD simulation as a function of crossing angle. In this case the junction conductance per unit area is essentially a constant. By contrast, interfacial thermal conductance between multiwalled carbon nanotubes (MWCNTs) is shown to increase with diameter of the nanotubes by recent experimental studies [1

  1. Directed disassembly of an interfacial rubisco protein network.

    PubMed

    Onaizi, Sagheer A; Malcolm, Andrew S; He, Lizhong; Middelberg, Anton P J

    2007-05-22

    We present the first study of the directed disassembly of a protein network at the air-water interface by the synergistic action of a surfactant and an enzyme. We seek to understand the fundamentals of protein network disassembly by using rubisco adsorbed at the air-water interface as a model. We propose that rubisco adsorption at the air-water interface results in the formation of a fishnet-like network of interconnected protein molecules, capable of transmitting lateral force. The mechanical properties of the rubisco network during assembly and disassembly at the air-water interface were characterized by direct measurement of laterally transmitted force through the protein network using the Cambridge interfacial tensiometer. We have shown that, when used individually, either 2 ppm of the surfactant, sodium dodecyl benzyl sulfonate (SDOBS), or 2 ppm of the enzyme, subtilisin A (SA), were insufficient to completely disassemble the rubisco network within 1 h of treatment. However, a combination of 2 ppm SDOBS and 2 ppm SA led to almost complete disassembly within 1 h. Increasing the concentration of SA in the mixture from 2 to 10 ppm, while keeping the SDOBS concentration constant, significantly decreased the time required to completely disassemble the rubisco network. Furthermore, the initial rate of network disassembly using formulations containing SDOBS was surprisingly insensitive to this increase in SA concentration. This study gives insight into the role of lateral interactions between protein molecules at interfaces in stabilizing interfacial protein networks and shows that surfactant and enzyme working in combination proves more effective at disrupting and mobilizing the interfacial protein network than the action of either agent alone. PMID:17447802

  2. Effect of the environmental humidity on the bulk, interfacial and nanoconfined properties of an ionic liquid.

    PubMed

    Jurado, L Andres; Kim, Hojun; Rossi, Antonella; Arcifa, Andrea; Schuh, Jonathon K; Spencer, Nicholas D; Leal, Cecilia; Ewoldt, Randy H; Espinosa-Marzal, Rosa M

    2016-08-10

    With reference to our previous surface-force study on 1-hexyl-3-methylimidazolium ethylsulfate ([HMIM] EtSO4) using an extended surface forces apparatus, which showed an ordered structure within the nanoconfined dry ionic liquid (IL) between mica surfaces that extended up to ∼60 nm from the surface, this work focuses on the influence of the environmental humidity on the bulk, interfacial and nanoconfined structure of [HMIM] EtSO4. Infrared spectroscopy and rheometry reflect the changes in chemical and physical properties of the bulk IL due to the uptake of water when exposed to ambient humidity, while wide-angle X-ray scattering shows a mild swelling of the bulk nanostructure, and the AFM sharp tip reveals an additional surface layer at the mica-IL interface. When the water-containing [HMIM] EtSO4 is nanoconfined between two mica surfaces, no long-range order is detected, in contrast to the results obtained for the dry IL, which demonstrates that the presence of water can prevent the liquid-to-solid transformation of this IL. A combination of techniques and the calculated Bjerrum length indicate that water molecules weaken interionic electrostatic and hydrogen-bonding interactions, which lessens ion-ion correlations. Our work shows that the solid-like behavior of the nanoconfined IL strongly depends on the presence of absorbed water and hence, it has implications with regard to the correct interpretation of laboratory studies and their extension to real applications in lubrication. PMID:27430333

  3. Incorporating interfacial phenomena in solidification models

    NASA Technical Reports Server (NTRS)

    Beckermann, Christoph; Wang, Chao Yang

    1994-01-01

    A general methodology is available for the incorporation of microscopic interfacial phenomena in macroscopic solidification models that include diffusion and convection. The method is derived from a formal averaging procedure and a multiphase approach, and relies on the presence of interfacial integrals in the macroscopic transport equations. In a wider engineering context, these techniques are not new, but their application in the analysis and modeling of solidification processes has largely been overlooked. This article describes the techniques and demonstrates their utility in two examples in which microscopic interfacial phenomena are of great importance.

  4. Indirect measurement of interfacial melting from macroscopic ice observations.

    PubMed

    Saruya, Tomotaka; Kurita, Kei; Rempel, Alan W

    2014-06-01

    Premelted water that is adsorbed to particle surfaces and confined to capillary regions remains in the liquid state well below the bulk melting temperature and can supply the segregated growth of ice lenses. Using macroscopic measurements of ice-lens initiation position in step-freezing experiments, we infer how the nanometer-scale thicknesses of premelted films depend on temperature depression below bulk melting. The interfacial interactions between ice, liquid, and soda-lime glass particles exhibit a power-law behavior that suggests premelting in our system is dominated by short-range electrostatic forces. Using our inferred film thicknesses as inputs to a simple force-balance model with no adjustable parameters, we obtain good quantitative agreement between numerical predictions and observed ice-lens thickness. Macroscopic observations of lensing behavior have the potential as probes of premelting behavior in other systems. PMID:25019705

  5. NGSI student activities in open source information analysis in support of the training program of the U.S. DOE laboratories for the entry into force of the additional protocol

    SciTech Connect

    Sandoval, M Analisa; Uribe, Eva C; Sandoval, Marisa N; Boyer, Brian D; Stevens, Rebecca S

    2009-01-01

    In 2008 a joint team from Los Alamos National Laboratory (LANL) and Brookhaven National Laboratory (BNL) consisting of specialists in training of IAEA inspectors in the use of complementary access activities formulated a training program to prepare the U.S. Doe laboratories for the entry into force of the Additional Protocol. As a major part of the support of the activity, LANL summer interns provided open source information analysis to the LANL-BNL mock inspection team. They were a part of the Next Generation Safeguards Initiative's (NGSI) summer intern program aimed at producing the next generation of safeguards specialists. This paper describes how they used open source information to 'backstop' the LANL-BNL team's effort to construct meaningful Additional Protocol Complementary Access training scenarios for each of the three DOE laboratories, Lawrence Livermore National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory.

  6. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    Lonsdale, H.K.; Babcock, W.C.; Friensen, D.T.; Smith, K.L.; Johnson, B.M.; Wamser, C.C.

    1990-08-14

    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclosed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers. 3 figs.

  7. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    Lonsdale, Harold K.; Babcock, Walter C.; Friensen, Dwayne T.; Smith, Kelly L.; Johnson, Bruce M.; Wamser, Carl C.

    1990-01-01

    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclsoed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers.

  8. Influence of compaction properties and interfacial topography on the performance of bilayer tablets.

    PubMed

    Kottala, Niranjan; Abebe, Admassu; Sprockel, Omar; Akseli, Ilgaz; Nikfar, Faranak; Cuitiño, Alberto M

    2012-10-15

    Bilayer tablets are generating great interest recently as they can achieve controlled delivery of different drugs with pre-defined release profiles. However, the production of such tablets has been facing great challenges as the layered tablets are prone to delaminate or fracture in the individual layers due to insufficient bonding strength of layers and adhesion at the interfaces. This paper will provide an insight into the role of interfacial topography on the performance of the bilayer tablets. In this study, two widely used pharmaceutical excipients: microcrystalline cellulose and lactose were investigated. Bilayer tablets were manufactured with a range of first and second layer compression forces. A crack of known dimensions was introduced at the interface to investigate the crack propagation mechanisms upon axially loading the bilayer tablet, and to determine the stress intensity factor (K(I)) of the interface (will be discussed in a separate paper). The results indicated that a strong dependency of the strength of bilayer tablets and mode of crack propagation on the material and compaction properties. The results showed that the strength of bilayer tablets increased with the increase of interfacial roughness, and the first layer and second layer forces determined the magnitude of interfacial roughness for both plastic and brittle materials. Further, the results also indicated that layer sequence and compaction forces played a key role in influencing the strength of the bilayer tablets. For the same (first and second layer) force combination, interfacial strength is higher for the tablets made of brittle material in the first layer. It was observed that interfacial strength decreased with the increase of lubricant concentration. The studies showed that the effect of lubricant (i.e. reduction in compact strength with the increase of lubricant concentration) on the strength of compacts is higher for tablets made of plastic material as compared to the tablets

  9. A Comparative Study of Interfacial Slip in Polymer Blends with Nanoparticles and Diblock Copolymer Compatibilizers

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Gersappe, Dilip

    2012-02-01

    The interfacial region in polymer blends has been identified as a low viscosity region in which considerable slip can occur when the blend is subjected to shear forces. Here we use Molecular Dynamics simulations to establish and compare the roles that added nanoparticle fillers and diblock copolymers play in modifying the interfacial rheology. By choosing conditions under which the fillers and diblocks are localized, either in the two phases or at the interface, we can look at the interplay between their strengthening capabilities and the change in the interfacial slip behavior. We examine particle size, attraction between the particle and the polymer component, and the amount of filler in the material and compared this to systems including diblock copolymers at the same volume fraction. Our studies are performed, for a variety of shear values, both above and below the point at which the filler particles form a transient network in the blend.

  10. Buckling Morphologies and Interfacial Properties of Silicon Nitride Films Deposited on Float Glass Substrates

    NASA Astrophysics Data System (ADS)

    Sun, Ya-Dong; Chen, Qi-Xiang; Feng, Yu-Fei; Chen, Jun; Yu, Sen-Jiang

    2015-04-01

    We report on the buckling morphologies and interfacial properties of silicon nitride films deposited on float glass substrates. The coexistence of straight-sided and telephone cord buckles can be observed in the silicon nitride films after annealing at a high temperature. The straight-sided structure is metastable and can spontaneously evolve into the telephone cord structure accompanied by the increase in the buckle width and height. The geometric parameters of various buckling structures (including the straight blister, telephone cord and their transition state) have been measured by optical microscopy and atomic force microscopy (AFM). The internal stress and interfacial adhesion of the films are evaluated and analyzed based on the continuum elastic theory. It is valid to measure the interfacial properties of thin films by simplifying the telephone cord buckle as a straight-sided structure. This measurement technique is suitable for all the film systems provided that the buckles can form in the film.

  11. Design principles of interfacial thermal conductance

    NASA Astrophysics Data System (ADS)

    Polanco, Carlos; Rastgarkafshgarkolaei, Rouzbeh; Zhang, Jingjie; Le, Nam; Norris, Pamela; Ghosh, Avik

    We explore fundamental principles to design the thermal conductance across solid interfaces by changing the composition and disorder of an intermediate matching layer. In absence of phonon-phonon interactions, the layer addition involves two competing effects that influence the conductance. The layer can act as an impedance matching 'bridge' to increase the mode-averaged phonon transmission. However, it also reduces the relevant modes that conserve their momenta transverse to the interface, so that the net result depends on features such as the overlap of conserving modes and the dispersivity of the transverse subbands. Moving into the interacting anharmonic regime, we find that the added layer aids conductance when the decreased resistances at the contact-layer boundaries compensate for the layer resistance. In fact, we show that the maximum conductance corresponds to an exact matching of the two separate contact-layer resistances. For instance, if we vary just the atomic mass across layers, then maximum conductance happens when the intervening layer mass is the geometric mean of the contact masses. We conjecture that the best interfacial layer is one that is compositionally graded into many geometric means - in other words, an exponential variation in thermal impedance.

  12. Quantitative morphological characterization of bicontinuous Pickering emulsions via interfacial curvatures.

    PubMed

    Reeves, Matthew; Stratford, Kevin; Thijssen, Job H J

    2016-05-14

    Bicontinuous Pickering emulsions (bijels) are a physically interesting class of soft materials with many potential applications including catalysis, microfluidics and tissue engineering. They are created by arresting the spinodal decomposition of a partially-miscible liquid with a (jammed) layer of interfacial colloids. Porosity L (average interfacial separation) of the bijel is controlled by varying the radius (r) and volume fraction (ϕ) of the colloids (L∝r/ϕ). However, to optimize the bijel structure with respect to other parameters, e.g. quench rate, characterizing by L alone is insufficient. Hence, we have used confocal microscopy and X-ray CT to characterize a range of bijels in terms of local and area-averaged interfacial curvatures; we further demonstrate that bijels are bicontinuous using an image-analysis technique known as 'region growing'. In addition, the curvatures of bijels have been monitored as a function of time, which has revealed an intriguing evolution up to 60 minutes after bijel formation, contrary to previous understanding. PMID:27035101

  13. Modeling interfacial fracture in Sierra.

    SciTech Connect

    Brown, Arthur A.; Ohashi, Yuki; Lu, Wei-Yang; Nelson, Stacy A. C.; Foulk, James W.,; Reedy, Earl David,; Austin, Kevin N.; Margolis, Stephen B.

    2013-09-01

    This report summarizes computational efforts to model interfacial fracture using cohesive zone models in the SIERRA/SolidMechanics (SIERRA/SM) finite element code. Cohesive surface elements were used to model crack initiation and propagation along predefined paths. Mesh convergence was observed with SIERRA/SM for numerous geometries. As the funding for this project came from the Advanced Simulation and Computing Verification and Validation (ASC V&V) focus area, considerable effort was spent performing verification and validation. Code verification was performed to compare code predictions to analytical solutions for simple three-element simulations as well as a higher-fidelity simulation of a double-cantilever beam. Parameter identification was conducted with Dakota using experimental results on asymmetric double-cantilever beam (ADCB) and end-notched-flexure (ENF) experiments conducted under Campaign-6 funding. Discretization convergence studies were also performed with respect to mesh size and time step and an optimization study was completed for mode II delamination using the ENF geometry. Throughout this verification process, numerous SIERRA/SM bugs were found and reported, all of which have been fixed, leading to over a 10-fold increase in convergence rates. Finally, mixed-mode flexure experiments were performed for validation. One of the unexplained issues encountered was material property variability for ostensibly the same composite material. Since the variability is not fully understood, it is difficult to accurately assess uncertainty when performing predictions.

  14. Interfacial destabilization and atomization driven by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Qi, Aisha; Yeo, Leslie Y.; Friend, James R.

    2008-07-01

    Surface acoustic wave atomization is a rapid means for generating micron and submicron aerosol droplets. Little, however, is understood about the mechanisms by which these droplets form due to the complex hydrodynamic processes that occur across widely varying length and time scales. Through experiments, scaling theory, and simple numerical modeling, we elucidate the interfacial destabilization mechanisms that lead to droplet formation. Using a millimeter-order fluid drop exposed to surface acoustic waves as it sits atop a single-crystal lithium niobate piezoelectric substrate, large aerosol droplets on the length scale of the parent drop dimension are ejected through a whipping and pinch-off phenomenon, which occurs at the asymmetrically formed crest of the drop due to leakage of acoustic radiation at the Rayleigh angle. Smaller micron order droplets, on the other hand, are formed due to the axisymmetric breakup of cylindrical liquid jets that are ejected as a consequence of interfacial destabilization. The 10μm droplet dimension correlates with the jet radius and the instability wavelength, both determined from a simple scaling argument involving a viscous-capillary dominant force balance. The results are further supported by numerical solution of the evolution equation governing the interfacial profile of a sessile drop along which an acoustic pressure wave is imposed. Viscous and capillary forces dominate in the bulk of the parent drop, but inertia is dominant in the ejected jets and within a thin boundary layer adjacent to the substrate where surface and interfacial accelerations are large. With the specific exception of parent drops that spread into thin films with thicknesses on the order of the boundary layer dimension prior to atomization, the free surface of the drop is always observed to vibrate at the capillary-viscous resonance frequency—even if the exciting frequency of the surface acoustic wave is several orders of magnitude larger—contrary to

  15. Interfacial area transport in bubbly flow

    SciTech Connect

    Ishii, M.; Wu, Q.; Revankar, S.T.

    1997-12-31

    In order to close the two-fluid model for two-phase flow analyses, the interfacial area concentration needs to be modeled as a constitutive relation. In this study, the focus was on the investigation of the interfacial area concentration transport phenomena, both theoretically and experimentally. The interfacial area concentration transport equation for air-water bubbly up-flow in a vertical pipe was developed, and the models for the source and sink terms were provided. The necessary parameters for the experimental studies were identified, including the local time-averaged void fraction, interfacial area concentration, bubble interfacial velocity, liquid velocity and turbulent intensity. Experiments were performed with air-water mixture at atmospheric pressure. Double-sensor conductivity probe and hot-film probe were employed to measure the identified parameters. With these experimental data, the preliminary model evaluation was carried out for the simplest form of the developed interfacial area transport equation, i.e., the one-dimensional transport equation.

  16. International Symposium on Interfacial Joining and Surface Technology (IJST2013)

    NASA Astrophysics Data System (ADS)

    Takahashi, Yasuo

    2014-08-01

    Interfacial joining (bonding) is a widely accepted welding process and one of the environmentally benign technologies used in industrial production. As the bonding temperature is lower than the melting point of the parent materials, melting of the latter is kept to a minimum. The process can be based on diffusion bonding, pressure welding, friction welding, ultrasonic bonding, or brazing-soldering, all of which offer many advantages over fusion welding. In addition, surface technologies such as surface modification, spraying, coating, plating, and thin-film formation are necessary for advanced manufacturing, fabrication, and electronics packaging. Together, interfacial joining and surface technology (IJST) will continue to be used in various industrial fields because IJST is a very significant form of environmentally conscious materials processing. The international symposium of IJST 2013 was held at Icho Kaikan, Osaka University, Japan from 27-29 November, 2013. A total of 138 participants came from around the world to attend 56 oral presentations and 36 posters presented at the symposium, and to discuss the latest research and developments on interfacial joining and surface technologies. This symposium was also held to commemorate the 30th anniversary of the Technical Commission on Interfacial Joining of the Japan Welding Society. On behalf of the chair of the symposium, it is my great pleasure to present this volume of IOP Conference Series: Materials Science and Engineering (MSE). Among the presentations, 43 papers are published here, and I believe all of the papers have provided the welding community with much useful information. I would like to thank the authors for their enthusiastic and excellent contributions. Finally, I would like to thank all members of the committees, secretariats, participants, and everyone who contributed to this symposium through their support and invaluable effort for the success of IJST 2013. Yasuo Takahashi Chair of IJST 2013

  17. Determination of interfacial tension of binary mixtures from perturbative approaches

    NASA Astrophysics Data System (ADS)

    Martínez-Ruiz, F. J.; Blas, F. J.

    2015-05-01

    We determine the interfacial properties of mixtures of spherical Lennard-Jones molecules from direct simulation of the vapour-liquid interface. We consider mixtures with same molecular size but different dispersive energy parameter values. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janeček, presented recently by MacDowell and Blas and Martínez-Ruiz et al., to deal with the interaction energy and microscopic components of the pressure tensor. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of mixtures of Lennard-Jones molecules with a cut-off distance rc = 3σ in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The vapour-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. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, and interfacial thickness as functions of pressure, at a given temperature. According to our results, the main effect of increasing the ratio between the dispersive energy parameters of the mixture, ε22/ε11, is to sharpen the vapour-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative maximum in the density profiles of the less volatile component at the interface. This maximum is related with adsorption or accumulation of these molecules at the interface, a direct consequence of stronger attractive interactions between these molecules in

  18. Polyfluorene Electrolytes Interfacial Layer for Efficient Polymer Solar Cells: Controllably Interfacial Dipoles by Regulation of Polar Groups.

    PubMed

    Liu, Huimin; Hu, Lin; Wu, Feiyan; Chen, Lie; Chen, Yiwang

    2016-04-20

    The polar groups in the conjugated polyelectrolytes (CPEs) can create the favorable dipoles at the electrode/active layer interface, which is critical for the CPEs to minimize the interfacial energy barrier in polymer solar cells (PSCs). Herein, a series of CPEs based on poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-co-2,7-(9,9-dioctylfluorene)] derivates (PFNs) (PFN30, PFN50, PFN70, and PFN100) with different mole ratio of polar groups (-N(C2H5)2) were designed and synthesized to investigate the effect of the numbers of polar groups on the interfacial dipoles. Controllably interfacial dipoles could be readily achieved by only tuning the numbers of -N(C2H5)2 in PFNs, as revealed by the work function of the PFNs modified ITO gradually reduced as the loadings of the -N(C2H5)2 increased. In addition, increasing the numbers of -N(C2H5)2 in PFNs were also favorable for developing the smooth and homogeneous morphology of the active layer. As a result, the content of the polar amine in the PFNs exerted great influence on the performance of polymer solar cells. Increasing the numbers of the pendent -N(C2H5)2 could effectively improve the power conversion efficiency (PCE) of the devices. Among these PFNs, PFN100 with the highest content of -N(C2H5)2 polar groups delivered the device with the best PCE of 3.27%. It indicates tailoring the content of the polar groups in the CPEs interlayer is a facial and promising approach for interfacial engineering to developing high performance PSCs. PMID:27028166

  19. Li-Doped Ionic Liquid Electrolytes: From Bulk Phase to Interfacial Behavior

    NASA Technical Reports Server (NTRS)

    Haskins, Justin B.; Lawson, John W.

    2016-01-01

    Ionic liquids have been proposed as candidate electrolytes for high-energy density, rechargeable batteries. We present an extensive computational analysis supported by experimental comparisons of the bulk and interfacial properties of a representative set of these electrolytes as a function of Li-salt doping. We begin by investigating the bulk electrolyte using quantum chemistry and ab initio molecular dynamics to elucidate the solvation structure of Li(+). MD simulations using the polarizable force field of Borodin and coworkers were then performed, from which we obtain an array of thermodynamic and transport properties. Excellent agreement is found with experiments for diffusion, ionic conductivity, and viscosity. Combining MD simulations with electronic structure computations, we computed the electrochemical window of the electrolytes across a range of Li(+)-doping levels and comment on the role of the liquid environment. Finally, we performed a suite of simulations of these Li-doped electrolytes at ideal electrified interfaces to evaluate the differential capacitance and the equilibrium Li(+) distribution in the double layer. The magnitude of differential capacitance is in good agreement with our experiments and exhibits the characteristic camel-shaped profile. In addition, the simulations reveal Li(+) to be highly localized to the second molecular layer of the double layer, which is supported by additional computations that find this layer to be a free energy minimum with respect to Li(+) translation.

  20. Interfacial phase-change memory.

    PubMed

    Simpson, R E; Fons, P; Kolobov, A V; Fukaya, T; Krbal, M; Yagi, T; Tominaga, J

    2011-08-01

    Phase-change memory technology relies on the electrical and optical properties of certain materials changing substantially when the atomic structure of the material is altered by heating or some other excitation process. For example, switching the composite Ge(2)Sb(2)Te(5) (GST) alloy from its covalently bonded amorphous phase to its resonantly bonded metastable cubic crystalline phase decreases the resistivity by three orders of magnitude, and also increases reflectivity across the visible spectrum. Moreover, phase-change memory based on GST is scalable, and is therefore a candidate to replace Flash memory for non-volatile data storage applications. The energy needed to switch between the two phases depends on the intrinsic properties of the phase-change material and the device architecture; this energy is usually supplied by laser or electrical pulses. The switching energy for GST can be reduced by limiting the movement of the atoms to a single dimension, thus substantially reducing the entropic losses associated with the phase-change process. In particular, aligning the c-axis of a hexagonal Sb(2)Te(3) layer and the 〈111〉 direction of a cubic GeTe layer in a superlattice structure creates a material in which Ge atoms can switch between octahedral sites and lower-coordination sites at the interface of the superlattice layers. Here we demonstrate GeTe/Sb(2)Te(3) interfacial phase-change memory (IPCM) data storage devices with reduced switching energies, improved write-erase cycle lifetimes and faster switching speeds. PMID:21725305

  1. Interfacial Engineering of Molecular Photovoltaics

    NASA Astrophysics Data System (ADS)

    Shelton, Steven Wade

    One of the most worthy pursuits in the field of organic solar cells is that of discovering ways to more effectively harvest charge generated by light absorption. The measure of the efficacy of this process is the external quantum efficiency (EQE). It is determined by the efficiency of incident light absorption, exciton diffusion, exciton splitting and charge transfer, and charge collection. Enhanced EQE can be realized by engineering interfaces between materials in the device to allow for smoother charge transfer throughout the extent of the device, which is usually between 10 and 200 nanometers. Improvements in charge transport are vitally important because the photogenerated excitons in electron donating polymers and small molecules typically only diffuse between 5 and 10 nanometers. These excitons must reach the interface between the electron donor and electron acceptor in order to be split so that the resulting electron and hole can be harvested at the cathode and anode, respectively. The aim of much of this dissertation is to describe a method by which the donor-acceptor interfacial area can be augmented using nanoimprint lithography, first with a single donor and then with multiple donors. Nanoimprint lithography is introduced as a simple embossing technique that can create features in a single component donor with dimensions as small as 20 nm. Solution-processable small molecules are of interest for their ease of synthesis and fabrication. I continue the discussion of nanoimprint lithography by offering candidates for a two-component donor combination. A two-component donor can extend the absorption range across a broader portion of the solar spectrum than just one donor to improve energy harvesting. After considering ways of optimizing the donor-acceptor interface, I describe the use of a charge selective layer for better charge transport and collection. When incorporated into a bilayer solar cell and an inverted solar cell, these two molecules markedly

  2. Interfacial Behavior of Polymer Coated Nanoparticle

    NASA Astrophysics Data System (ADS)

    Qi, Luqing; Shamsijazeyi, Hadi; Mann, Jason; Verduzco, Rafael; Hirasaki, George; Rice University Team

    2015-03-01

    Oxidized carbon black (OCB) nanoparticle is functionalized with different coatings, i.e. alkyl group, polyvinyl alcohol (PVA) and partially sulfonated polyvinyl alcohol (sPVA). In oil and water systems, the functionalized nanoparticle is found to have a versatile dispersion i.e. in lower aqueous phase, in upper oil phase, or in middle phase microemulsion. Oil substitute n-octane and commercial oil IOSPAR have been test as oil phase; series of commercially available surfactant, C12-4,5 orthoxylene sulfonate(OXS), i-C13-(PO)7 -SO4Na (S13B), surfactant blend of anionic Alfoterra with nonionic Tergitol have been test as additive to help with the OCB dispersion. It is found that the OCB with sulfonated polyvinyl alcohol attachment (sPVA-OCB) stays in microemulsion; with the increase of salinity, it follows the microemulsion to go from lower phase, to middle phase, and to upper phase. The dispersion of sPVA and alkyl functionalized OCB (Cn-OCB-sPVA) is the balance of the length of alkyl and sPVA and the degree of sulfonation of PVA, depending on which, it can either disperse into microemulsion or form a separate layer. The sPVA-OCB also indicates a tolerance of high salinity; this is shown by the stable dispersion of it in blend surfactant solution of anionic Alfoterra and nonionic Tergitol at high salinity API brine(8% NaCl and 2% CaCl2). The study of different functionality on OCB dispersion can help design appropriate modified nanoparticle as additive for enhanced oil recovery either to reduce the interfacial tension between oil and water, or to stabilize microemulsion.

  3. Interfacial and near interfacial crack growth phenomena in metal bonded alumina

    SciTech Connect

    Kruzic, Jamie Joseph

    2002-03-01

    Metal/ceramic interfaces can be found in many engineering applications including microelectronic packaging, multi-layered films, coatings, joints, and composite materials. In order to design reliable engineering systems that contain metal/ceramic interfaces, a comprehensive understanding of interfacial and near interfacial failure mechanisms is necessary.

  4. Role of Ag in the formation of interfacial intermetallic phases in Sn-Zn soldering

    NASA Astrophysics Data System (ADS)

    Song, Jenn-Ming; Liu, Pei-Chi; Shih, Chia-Ling; Lin, Kwang-Lung

    2005-09-01

    This study explored the effect of Ag as the substrate or alloying element of solders on the interfacial reaction in Sn-Zn soldering. Results show that instead of Ag-Sn compounds, ζ-AgZn and γ-Ag5Zn8 form at the Sn-Zn/Ag interface. The addition of Ag in Sn-Zn solders leads to the precipitation of ɛ-AgZn3 from the liquid solder on preformed interfacial intermetallics. The morphology of this additional AgZn3 is closely related to the solidification process of Ag-Zn intermetallics and the under intermetallic layer.

  5. Crossflow force transducer. [LMFBR

    SciTech Connect

    Mulcahy, T M

    1982-05-01

    A force transducer for measuring lift and drag coefficients for a circular cylinder in turbulent water flow is presented. In addition to describing the actual design and construction of the strain-gauged force- ring based transducer, requirements for obtained valid fluid force test data are discussed, and pertinent flow test experience is related.

  6. Interfacial strength of novel PMMA/HA/nanoclay bone cement.

    PubMed

    Wang, C X; Tong, J

    2008-01-01

    In the present study, nanoclay was introduced to PMMA bone cement to obtain a new formulation of bioactive PMMA cement (PMMA/HA/nanoclay). To evaluate the interfacial property of the new bioactive cement for use as a fixation agent, Brazilian disk specimens were used to study the interfacial strength of synthetic bone-cement interface. The results show that, for tensile loading, the addition of 17.5 wt% HA into PMMA cement produced a notable decrease in the fracture load, while a further addition of 0.5 wt% nanoclay slightly counteracted the decrease due to the addition of HA. The addition of 1.0 wt% nanoclay brought the fracture load back to the same level as that of pure PMMA cement, although with the further increase of nanoclay (1.5 wt% nanoclay and 2.0 wt% nanoclay), the fracture loads decreased again. The same trend in the calculated strain energy release rates was also observed. For shear loading, however, the same trend was not observed due to the premature fracture and collapsing of the foam. This finding may be useful in the development of novel bioactive bone cements to improve the fixation of joint arthroplasty. PMID:19197113

  7. Interfacial rheometry of polymer at a water-oil interface by intra-pair magnetophoresis.

    PubMed

    Cappelli, Stefano; de Jong, Arthur M; Baudry, Jean; Prins, Menno W J

    2016-07-01

    We describe an interfacial rheometry technique based on pairs of micrometer-sized magnetic particles at a fluid-fluid interface. The particles are repeatedly attracted and repelled by well-controlled magnetic dipole-dipole forces, so-called interfacial rheometry by intra-pair magnetophoresis (IPM). From the forces (∼pN), displacements (∼μm) and velocities (∼μm s(-1)) of the particles we are able to quantify the interfacial drag coefficient of particles within a few seconds and over very long timescales. The use of local dipole-dipole forces makes the system insensitive to fluid flow and suited for simultaneously recording many particles in parallel over a long period of time. We apply IPM to study the time-dependent adsorption of an oil-soluble amino-modified silicone polymer at a water-oil interface using carboxylated magnetic particles. At low polymer concentration the carboxylated particles remain on the water side of the water-oil interface, while at high polymer concentrations the particles transit into the oil phase. Both conditions show a drag coefficient that does not depend on time. However, at intermediate polymer concentrations data show an increase of the interfacial drag coefficient as a function of time, with an increase over more than three orders of magnitude (10(-7) to 10(-4) N s m(-1)), pointing to a strong polymer-polymer interaction at the interface. The time-dependence of the interfacial drag appears to be highly sensitive to the polymer concentration and to the ionic strength of the aqueous phase. We foresee that IPM will be a very convenient technique to study fluid-fluid interfaces for a broad range of materials systems. PMID:27253322

  8. Interfacial area and interfacial transfer in two-phase systems. DOE final report

    SciTech Connect

    Ishii, Mamoru; Hibiki, T.; Revankar, S.T.; Kim, S.; Le Corre, J.M.

    2002-07-01

    In the two-fluid model, the field equations are expressed by the six conservation equations consisting of mass, momentum and energy equations for each phase. The existence of the interfacial transfer terms is one of the most important characteristics of the two-fluid model formulation. The interfacial transfer terms are strongly related to the interfacial area concentration and to the local transfer mechanisms such as the degree of turbulence near interfaces. This study focuses on the development of a closure relation for the interfacial area concentration. A brief summary of several problems of the current closure relation for the interfacial area concentration and a new concept to overcome the problem are given.

  9. Transient Interfacial Phenomena in Miscible Polymer Systems (TIPMPS)

    NASA Technical Reports Server (NTRS)

    Pojman, John A.; Bessonov, Nicholas; Volpert, Vitaly; Wilke, Hermann

    2003-01-01

    the square gradient parameter, k, and our use of the estimates in modeling of the planned TIPMPS experiments. We developed a model consisting of the heat and diffusion equations with convective terms and of the Navier-Stokes equations with an additional volume force written in the form of the Korteweg stresses arising from nonlocal interaction in the fluid. The fluid's viscosity dependence on polymer conversion and temperature was taken from measurements of poly(dodecyl acrylate). Numerical modeling demonstrated that significant flows would arise for conditions corresponding to the planned experiments.

  10. A molecular dynamics study of polymer/graphene interfacial systems

    SciTech Connect

    Rissanou, Anastassia N.; Harmandaris, Vagelis

    2014-05-15

    Graphene based polymer nanocomposites are hybrid materials with a very broad range of technological applications. In this work, we study three hybrid polymer/graphene interfacial systems (polystyrene/graphene, poly(methyl methacrylate)/graphene and polyethylene/graphene) through detailed atomistic molecular dynamics (MD) simulations. Density profiles, structural characteristics and mobility aspects are being examined at the molecular level for all model systems. In addition, we compare the properties of the hybrid systems to the properties of the corresponding bulk ones, as well as to theoretical predictions.

  11. Probing Interfacial Emulsion Stability Controls using Electrorheology

    NASA Astrophysics Data System (ADS)

    Wang, Xiuyu; Brandvik, Amy; Alvarado, Vladimir

    2010-11-01

    The stability of water-in-oil emulsions is controlled by interfacial mechanisms that include oil film rheology of approaching drops and the strength of drop interfaces. Film drainage is mainly a function of the continuous phase rheology. Temperature is used to regulate the viscosity of the continuous phase and hence determine its effect on emulsion stability through film drainage, in contrast with interfacial strength. In this study, one crude oil is used to formulate water-in-oil emulsions. Oil-water interfacial tension is measured to gauge other interfacial changes with temperature. The critical field value, used as proxy of emulsion stability, approaches a plateau value for each crude oil- aqueous solution pair, at sufficiently high temperature (50 ^oC), which is interpreted to reflect the intrinsic drop-coating film resistance to coalescence. Interfacial tension does vary significantly with either aqueous phase composition or temperature. From comparison with previous results, we speculate that drop coating film is composed of a fraction of asphaltic compunds.

  12. Interfacial phenomena in hard-rod fluids

    NASA Astrophysics Data System (ADS)

    Shundyak, K. Y.

    2004-05-01

    the isotropic-nematic (IN) coexistence and may induce (suppress) a demixing of the high-density nematic phase into two nematic phases of different composition (N1 and N2). Studies of their interfaces show an increase of the surface tension with fractionation at the IN interface, and complete wetting of the IN2 interface by the N1 phase upon approach of the triple point coexistence. In all explored cases bulk and interfacial properties of the nonadditive mixtures exhibit a surprising similarity with the properties of additive mixtures of larger diameter ratio. In Chapter VI we consider properties of a monodisperse hard-rod fluid in contact with the single wall (W). Studies of surface properties of a fluid of Onsager hard rods represent significant numerical difficulties, therefore we consider a simpler model fluid of hard rods with a restricted number of allowed orientations. Within this model, known as the Zwanzig model, we explore the thermodynamic properties of a fluid of monodisperse hard rods in contact with a model substrate represented by a hard wall with a short-ranged attractive or repulsive ``tail''. The attraction enhances the orientational ordering near the wall in both isotropic and nematic phases, and shifts the transition from uniaxial (U) to biaxial (B) symmetry in the isotropic surface layer to lower chemical potentials, whereas the wetting properties of the substrate remain similar to those of the pure hard wall. The soft repulsion reduces the density in the surface layer, which leads to the shift (or even suppression) of the UB transition, and strong modification of wetting properties. At the WI interface one always finds the wetting transition at sufficiently large repulsion, whereas a drying transition at the WN interface is observed only for sufficiently long-ranged potentials. In Chapter VII we explore some limitations of models of hard-rod fluids with a finite number of allowed orientations. Within Onsager's second virial theory we construct

  13. Microfluidic ultralow interfacial tensiometry with magnetic particles.

    PubMed

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

    2013-01-01

    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. PMID:23154819

  14. Magneto-ionic control of interfacial magnetism

    NASA Astrophysics Data System (ADS)

    Bauer, Uwe; Yao, Lide; Tan, Aik Jun; Agrawal, Parnika; Emori, Satoru; Tuller, Harry L.; van Dijken, Sebastiaan; Beach, Geoffrey S. D.

    2015-02-01

    In metal/oxide heterostructures, rich chemical, electronic, magnetic and mechanical properties can emerge from interfacial chemistry and structure. The possibility to dynamically control interface characteristics with an electric field paves the way towards voltage control of these properties in solid-state devices. Here, we show that electrical switching of the interfacial oxidation state allows for voltage control of magnetic properties to an extent never before achieved through conventional magneto-electric coupling mechanisms. We directly observe in situ voltage-driven O2- migration in a Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic anisotropy energy by >0.75 erg cm-2 at just 2 V. We exploit the thermally activated nature of ion migration to markedly increase the switching efficiency and to demonstrate reversible patterning of magnetic properties through local activation of ionic migration. These results suggest a path towards voltage-programmable materials based on solid-state switching of interface oxygen chemistry.

  15. Investigating the interfacial dynamics of thin films

    NASA Astrophysics Data System (ADS)

    Rosenbaum, Aaron W.

    This thesis probes the interfacial dynamics and associated phenomena of thin films. Surface specific tools were used to study the self-assembly of alkanethiols, the mono- and bilayer dynamics of SF6, and the surface motion of poly(methyl methacrylate). Non-pertubative helium atom scattering was the principal technique used to investigate these systems. A variety of other complementary tools, including scanning tunneling microscopy, electron diffraction, Auger spectroscopy, atomic force microscopy, and ellipsometry were used in tandem with the neutral atom scattering studies. Controlling the spontaneous assembly of alkanethiols on Au(111) requires a better fundamental understanding of the adsorbate-adsorbate and substrate-adsorbate interactions. Our characterization focused on two key components, the surface structure and adsorbate vibrations. The study indicates that the Au(111) reconstruction plays a larger role than anticipated in the low-density phase of alkanethiol monolayers. A new structure is proposed for the 1-decanethiol monolayer that impacts the low-energy vibrational mode. Varying the alkane chain lengths imparts insight into the assembly process via characterization of a dispersionless phonon mode. Studies of SF6 physisorbed on Au(111) bridge surface research on rare gas adsorbates with complicated dynamical organic thin films. Mono- and bilayer coverages of SF6/Au(111) were studied at cryogenic temperatures. Our experiments probed the surface properties of SF6 yielding insights into substrate and coverage effects. The study discovered a dispersionless Einstein oscillation with multiple harmonic overtones. A second layer of SF6 softened the mode, but did not show any indications of bulk or cooperative interactions. The vibrational properties of SF 6 showed both striking similarities and differences when compared with physisorbed rare gases. Lastly, this thesis will discuss studies of thin film poly(methyl methacrylate) on Si. The non-pertubative and

  16. Mechanisms governing the interfacial delamination of thermal barrier coating system with double ceramic layers

    NASA Astrophysics Data System (ADS)

    Xu, Rong; Fan, Xueling; Wang, T. J.

    2016-05-01

    A systematic study of factors affecting the interfacial delamination of thermal barrier coating system (TBCs) with double ceramic layers (DCL) is presented. Crack driving forces for delaminations at two weak interfaces are examined. The results show that a thicker outermost ceramic layer can induce dramatic increase in crack driving force and make the interface between two ceramic coatings become more prone to delamination. The behavior is shown to be more prominent in TBCs with stiffer outmost coating. The thickness ratio of two ceramic layers is an important parameter for controlling the failure mechanisms and determining the lifetime of DCL TBCs under inservice condition. By accounting for the influences of thickness ratio of two ceramic layers and interfacial fracture toughnesses of two involved interfaces, the fracture mechanism map of DCL TBCs has been constructed, in which different failure mechanisms are identified. The results quanlitatively agree with the aviliable experimental data.

  17. Interfacial friction in cocurrent upward annular flow

    NASA Astrophysics Data System (ADS)

    Hossfeld, L. M.; Bharathan, D.; Wallis, G. B.; Richter, H. J.

    1982-03-01

    Cocurrent upward annular flow is investigated, with an emphasis on correlating and predicting pressure drop. Attention is given to the characteristics of the liquid flow in the film, and the interaction of the core with the film. Alternate approaches are discussed for correlating suitably defined interfacial friction factors. Both approaches are dependent on knowledge of the entrainment in order to make predictions. Dimensional analysis is used to define characteristic parameters of the flow and an effort is made to determine, to the extent possible, the influences of these parameters on the interfacial friction factor.

  18. Molecular dynamics simulations of the microstructure of the aluminum/alumina interfacial layer

    NASA Astrophysics Data System (ADS)

    Mei, Hai; Liu, Qiwen; Liu, Lisheng; Lai, Xin; She, Wuchang; Zhai, Pengcheng

    2015-01-01

    The atomic structure and charge distribution pattern of the Al/α-Al2O3 interface were studied utilizing molecular dynamics simulations. In order to accurately describe the interactions between the atoms around the interface, the charge transfer ionic and embedded atom method potential was used. Energetically preferable Al/α-Al2O3 interface systems were first determined to study the layer structures of the interface systems. Two energetically preferable Al/α-Al2O3 interface systems with a [ 1 bar 1 0 ](1 1 1) Al ∥ [ 1 0 1 bar 0 ](0 0 0 1) Al2O3 orientation relationship were obtained, corresponding to the atop-O Al-terminated and atop-O O-terminated relaxed models, respectively. Further studies revealed the presence of an interfacial layer, which is consistent with experimental results. The models predict a thickness of the interfacial layer between 12.14 Å and 16.82 Å. It is composed of aluminum suboxide (with an Al to O atomic ratio between 1:1.07 and 1:1.17). In addition, both the combination between the interfacial layer and the metallic Al layer and the interfacial layer and the ceramic α-Al2O3 were perfect. In order to further study the atomic structure of the Al/α-Al2O3 interfacial layer, it was isolated from the system and modeled separately. An analysis of the radial distribution function revealed that the interfacial layer inherits its structure from the α-Al2O3 moiety. The study of the charge distributions in the interface systems indicates that the charge of the Al atoms in the interfacial layer is mainly in the range from +2.1 e to +2.6 e while the charge of the O atoms is at the saturated state of -2e.

  19. Laminar Plunging Jets - Interfacial Rupture and Inception of Entrainment

    NASA Astrophysics Data System (ADS)

    Kishore, Aravind

    number, Cac = η∣Vc/sigma and viscosity ratio, η0/η in postulating an alternate approach involving scaling of the pertinent physics by using liquids as entrained fluids. The scaling approach is tested using a rotating cylinder placed at the interface between two fluids. A mesh-independence study using successively finer meshes predicted critical entrainment velocity values within about 1% of each other. Numerical predictions compared well with experimental data, with less than 1% difference in the case where exact experimental data was available, and a maximum of 6% difference for cases where experimental data was extrapolated to make the comparison. These results lend credibility to our approach. The effect of densities of the two fluids manifests as buoyancy force at the interfacial cusp. Remarkably, contrary to a priori notions, our simulation results showed that as Deltarho increased, the effect of buoyancy decreased relative to other forces at the interfacial cusp. Finally, we proposed an empirical correlation between Cac and η 0/η which allows extrapolation of critical entrainment conditions between the rotating-cylinder configuration (with liquids being entrained) to the plunging-jet configuration (with air being entrained). The primary contribution of this research is the physics-based scaling approach utilized to overcome the simulation challenges posed by the physics of interface rupture and entrainment.

  20. Effect of pendent chains on the interfacial properties of thin polydimethylsiloxane (PDMS) networks.

    PubMed

    Landherr, Lucas J T; Cohen, Claude; Archer, Lynden A

    2011-05-17

    The interfacial properties of end-linked polydimethylsiloxane (PDMS) films on silicon are examined. Thin cross-linked PDMS films (∼10 μm thick) were synthesized over a self-assembled monolayer supported on a silicon wafer. By systematically varying the concentration of monofunctional PDMS in a mixture with telechelic precursor molecules, structures ranging from near-ideal elastic networks to poorly cross-linked networks composed of a preponderance of dangling/pendent chains were synthesized. Lateral force microscopy (LFM) employing bead probes was used to quantify the effect of network structure on the interfacial friction coefficient and residual force. Indentation measurements employing an AFM in force mode were used to characterize the elastic modulus and the pull-off force for the films as a function of pendent chain content. These measurements were complemented with conventional mechanical rheometry measurements on similar thick network films to determine their bulk rheological properties. All networks studied manifested interfacial friction coefficients substantially lower than that of bare silicon. PDMS networks with the lowest pendent chain content displayed friction coefficients close to 1 order of magnitude lower than that of bare silicon, whereas networks with the highest pendent chain content manifested friction coefficients about 3 times lower than that of bare silicon. At intermediate sliding velocities, a crossover in the interfacial friction coefficient was observed, wherein cross-linked PDMS films with the least amount of pendent chains exhibit the highest friction coefficient. These observations are discussed in terms of the structure of the films and relaxation dynamics of elastic strands and dangling chains in tethered network films. PMID:21495649

  1. Micromechanical adhesion force measurements between tetrahydrofuran hydrate particles.

    PubMed

    Taylor, Craig J; Dieker, Laura E; Miller, Kelly T; Koh, Carolyn A; Sloan, E Dendy

    2007-02-15

    Adhesion forces between tetrahydrofuran (THF) hydrate particles in n-decane were measured using an improved micromechanical technique. The experiments were performed at atmospheric pressure over the temperature range 261-275 K. The observed forces and trends were explained by a capillary bridge between the particles. The adhesion force of hydrates was directly proportional to the contact force and contact time. A scoping study examined the effects of temperature, anti-agglomerants, and interfacial energy on the particle adhesion forces. The adhesion force of hydrates was found to be directly proportional to interfacial energy of the surrounding liquid, and to increase with temperature. Both sorbitan monolaurate (Span20) and poly-N-vinyl caprolactam (PVCap) decreased the adhesion force between the hydrate particles. PMID:17126359

  2. The Constrained Vapor Bubble Experiment - Interfacial Flow Region

    NASA Technical Reports Server (NTRS)

    Kundan, Akshay; Wayner, Peter C., Jr.; Plawsky, Joel L.

    2015-01-01

    Internal heat transfer coefficient of the CVB correlated to the presence of the interfacial flow region. Competition between capillary and Marangoni flow caused Flooding and not a Dry-out region. Interfacial flow region growth is arrested at higher power inputs. 1D heat model confirms the presence of interfacial flow region. 1D heat model confirms the arresting phenomena of interfacial flow region Visual observations are essential to understanding.

  3. Highly tunable interfacial adhesion of glass fiber by hybrid multilayers of graphene oxide and aramid nanofiber.

    PubMed

    Park, Byeongho; Lee, Wonoh; Lee, Eunhee; Min, Sa Hoon; Kim, Byeong-Su

    2015-02-11

    The performance of fiber-reinforced composites is governed not only by the nature of each individual component comprising the composite but also by the interfacial properties between the fiber and the matrix. We present a novel layer-by-layer (LbL) assembly for the surface modification of a glass fiber to enhance the interfacial properties between the glass fiber and the epoxy matrix. Solution-processable graphene oxide (GO) and an aramid nanofiber (ANF) were employed as active components for the LbL assembly onto the glass fiber, owing to their abundant functional groups and mechanical properties. We found that the interfacial properties of the glass fibers uniformly coated with GO and ANF multilayers, such as surface free energy and interfacial shear strength, were improved by 23.6% and 39.2%, respectively, compared with those of the bare glass fiber. In addition, the interfacial adhesion interactions between the glass fiber and the epoxy matrix were highly tunable simply by changing the composition and the architecture of layers, taking advantage of the versatility of the LbL assembly. PMID:25599567

  4. Application of nanoindentation testing to study of the interfacial transition zone in steel fiber reinforced mortar

    SciTech Connect

    Wang Xiaohui Jacobsen, Stefan; He Jianying; Zhang Zhiliang; Lee, Siaw Foon; Lein, Hilde Lea

    2009-08-15

    The characteristics of the profiles of elastic modulus and hardness of the steel fiber-matrix and fiber-matrix-aggregate interfacial zones in steel fiber reinforced mortars have been investigated by using nanoindentation and Scanning Electron Microscopy (SEM), where two sets of parameters, i.e. water/binder ratio and content of silica fume were considered. Different interfacial bond conditions in the interfacial transition zones (ITZ) are discussed. For sample without silica fume, efficient interfacial bonds across the steel fiber-matrix and fiber-matrix-aggregate interfaces are shown in low water/binder ratio mortar; while in high water/binder ratio mortar, due to the discontinuous bleeding voids underneath the fiber, the fiber-matrix bond is not very good. On the other hand, for sample with silica fume, the addition of 10% silica fume leads to no distinct presence of weak ITZ in the steel fiber-matrix interface; but the effect of the silica fume on the steel fiber-matrix-aggregate interfacial zone is not obvious due to voids in the vicinity of steel fiber.

  5. The role of spontaneous lipid curvature in the interaction of interfacially active peptides with membranes.

    PubMed

    Koller, Daniel; Lohner, Karl

    2014-09-01

    Research on antimicrobial peptides is in part driven by urgent medical needs such as the steady increase in pathogens being resistant to antibiotics. Despite the wealth of information compelling structure-function relationships are still scarce and thus the interfacial activity model has been proposed to bridge this gap. This model also applies to other interfacially active (membrane active) peptides such as cytolytic, cell penetrating or antitumor peptides. One parameter that is strongly linked to interfacial activity is the spontaneous lipid curvature, which is experimentally directly accessible. We discuss different parameters such as H-bonding, electrostatic repulsion, changes in monolayer surface area and lateral pressure that affect induction of membrane curvature, but also vice versa how membrane curvature triggers peptide response. In addition, the impact of membrane lipid composition on the formation of curved membrane structures and its relevance for diverse mode of action of interfacially active peptides and in turn biological activity are described. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova. PMID:24853655

  6. A novel pyrene-based fluorescing amphiphile with unusual bulk and interfacial properties.

    PubMed

    Salonen, Anniina; Knyazev, Anton; von Bandel, Nicolas; Degrouard, Jéril; Langevin, Dominique; Drenckhan, Wiebke

    2011-01-17

    We have synthesised a new, pyrene-based, low-molecular-mass, amphiphilic molecule that displays a wealth of properties of potential interest for aggregation and interfacial applications. In order to elucidate some of the key properties of this molecule, which consists of a pyrene-containing hydrophobic head and a short PEG-based hydrophilic tail, we investigate herein some aspects of its concentration-dependent behaviour in aqueous solutions. We show that the inclusion of the hydrophobic pyrene group not only provides the molecule with intriguing bulk and interfacial properties down to low concentrations, but also with various means of assessing its aggregation behaviour by means of its well-characterised fluorescence properties. Combining a range of fluorescence techniques with microscopic imaging (optical and Cryo-TEM), interfacial tension measurements and foaming studies, we have been able to identify and characterise three concentration-dependant regimes. At low concentrations, the molecule is dissolved in monomeric form. At intermediate concentrations, labile aggregates are formed, which, at higher concentrations, give way to aggregates containing pre-associated pyrenes. Our measurements strongly imply that the latter aggregates are hexagonally close-packed tubular micelles. In this latter regime we also find a range of micron-sized precipitates. Additionally, the molecule displays strong interfacial activity, yet a surprisingly slow dynamics of interfacial adsorption. Finally, we demonstrate the possibility of using it to visualize interfaces and also create reasonably stable (1 hour) and fluorescing foams. PMID:21226196

  7. Energy dissipation due to interfacial slip in nanocomposites reinforced with aligned carbon nanotubes.

    PubMed

    Gardea, Frank; Glaz, Bryan; Riddick, Jaret; Lagoudas, Dimitris C; Naraghi, Mohammad

    2015-05-13

    Interfacial slip mechanisms of strain energy dissipation and vibration damping of highly aligned carbon nanotube (CNT) reinforced polymer composites were studied through experimentation and complementary micromechanics modeling. Experimentally, we have developed CNT-polystyrene (PS) composites with a high degree of CNT alignment via a combination of twin-screw extrusion and hot-drawing. The aligned nanocomposites enabled a focused study of the interfacial slip mechanics associated with shear stress concentrations along the CNT-PS interface induced by the elastic mismatch between the filler and matrix. The variation of storage and loss modulus suggests the initiation of the interfacial slip occurs at axial strains as low as 0.028%, primarily due to shear stress concentration along the CNT-PS interface. Through micromechanics modeling and by matching the model with the experimental results at the onset of slip, the interfacial shear strength was evaluated. The model was then used to provide additional insight into the experimental observations by showing that the nonlinear variation of damping with dynamic strain can be attributed to slip-stick behavior. The dependence of the interfacial load-transfer reversibility on the dynamic strain history and characteristic time scale was experimentally investigated to demonstrate the relative contribution of van der Waals (vdW) interactions, mechanical interlocking, and covalent bonding to shear interactions. PMID:25905718

  8. Exchange bias mediated by interfacial nanoparticles (invited)

    SciTech Connect

    Berkowitz, A. E.; Sinha, S. K.; Fullerton, E. E.; Smith, D. J.

    2015-05-07

    The objective of this study on the iconic exchange-bias bilayer Permalloy/CoO has been to identify those elements of the interfacial microstructure and accompanying magnetic properties that are responsible for the exchange-bias and hysteretic properties of this bilayer. Both epitaxial and polycrystalline samples were examined. X-ray and neutron reflectometry established that there existed an interfacial region, of width ∼1 nm, whose magnetic properties differed from those of Py or CoO. A model was developed for the interfacial microstructure that predicts all the relevant properties of this system; namely; the temperature and Permalloy thickness dependence of the exchange-bias, H{sub EX}, and coercivity, H{sub C}; the much smaller measured values of H{sub EX} from what was nominally expected; the different behavior of H{sub EX} and H{sub C} in epitaxial and polycrystalline bilayers. A surprising result is that the exchange-bias does not involve direct exchange-coupling between Permalloy and CoO, but rather is mediated by CoFe{sub 2}O{sub 4} nanoparticles in the interfacial region.

  9. Food additives

    MedlinePlus

    Food additives are substances that become part of a food product when they are added during the processing or making of that food. "Direct" food additives are often added during processing to: Add nutrients ...

  10. Direct measurement of anisotropy of interfacial free energy from grain boundary groove morphology in transparent organic metal analong systems

    SciTech Connect

    Rustwick, Bryce A.

    2005-08-01

    Both academia and industry alike have paid close attention to the mechanisms of microstructural selection during the solidification process. The forces that give rise to and the principles which rule the natural selection of particular morphologies are important to understanding and controlling new microstructures. Interfacial properties play a very crucial role to the selection of such microstructure formation. In the solidification of a metallic alloy, the solid-liquid interface is highly mobile and responds to very minute changes in the local conditions. At this interface, the driving force must be large enough to drive solute diffusion, maintain local curvature, and overcome the kinetic barrier to move the interface. Therefore, the anisotropy of interfacial free energy with respect to crystallographic orientation is has a significant influence on the solidification of metallic systems. Although it is generally accepted that the solid-liquid interfacial free energy and its associated anisotropy are highly important to the overall selection of morphology, the confident measurement of these particular quantities remains a challenge, and reported values are scarce. Methods for measurement of the interfacial free energy include nucleation experiments and grain boundary groove experiments. The predominant method used to determine anisotropy of interfacial energy has been equilibrium shape measurement. There have been numerous investigations involving grain boundaries at a solid-liquid interface. These studies indicated the GBG could be used to describe various interfacial energy values, which affect solidification. Early studies allowed for an estimate of interfacial energy with respect to the GBG energy, and finally absolute interfacial energy in a constant thermal gradient. These studies however, did not account for the anisotropic nature of the material at the GBG. Since interfacial energy is normally dependent on orientation of the crystallographic plane of the

  11. Interfacial stress balances in structured continua and free surface flows in ferrofluids

    NASA Astrophysics Data System (ADS)

    Chaves, Arlex; Rinaldi, Carlos

    2014-04-01

    Interfacial linear and internal angular momentum balances are obtained for a structured continuum and for the special case of a ferrofluid, a suspension of magnetic nanoparticles in a Newtonian fluid. The interfacial balance equations account for the effects of surface tension and surface tension gradient, magnetic surface excess forces, antisymmetric stresses, and couple stresses in driving interfacial flows in ferrofluids. Application of the interfacial balance equations is illustrated by obtaining analytical expressions for the translational and spin velocity profiles in a thin film of ferrofluid on an infinite flat plate when a rotating magnetic field is applied with axis of rotation parallel to the ferrofluid/air interface. The cases of zero and non-zero spin viscosity are considered for small applied magnetic field amplitude. Expressions for the maximum translational velocity, slope of the translational velocity profile at the ferrofluid/air interface, and volumetric flow rate are obtained and their use to test the relevance of spin viscosity and couple stresses in the flow situation under consideration is discussed.

  12. Nanoscopic characterization of the water vapor-salt interfacial layer reveals a unique biphasic adsorption process

    PubMed Central

    Yang, Liu; He, Jianfeng; Shen, Yi; Li, Xiaowei; Sun, Jielin; Czajkowsky, Daniel M.; Shao, Zhifeng

    2016-01-01

    Our quantitative understanding of water adsorption onto salt surfaces under ambient conditions is presently quite poor owing to the difficulties in directly characterizing this interfacial layer under these conditions. Here we determine the thickness of the interfacial layer on NaCl at different relative humidities (RH) based on a novel application of atomic force spectroscopy and capillary condensation theory. In particular, we take advantage of the microsecond-timescale of the capillary condensation process to directly resolve the magnitude of its contribution in the tip-sample interaction, from which the interfacial water thickness is determined. Further, to correlate this thickness with salt dissolution, we also measure surface conductance under similar conditions. We find that below 30% RH, there is essentially only the deposition of water molecules onto this surface, typical of conventional adsorption onto solid surfaces. However, above 30% RH, adsorption is simultaneous with the dissolution of ions, unlike conventional adsorption, leading to a rapid increase of surface conductance. Thus, water adsorption on NaCl is an unconventional biphasic process in which the interfacial layer not only exhibits quantitative differences in thickness but also qualitative differences in composition. PMID:27527905

  13. 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. PMID:26954468

  14. Interfacial stress balances in structured continua and free surface flows in ferrofluids

    SciTech Connect

    Chaves, Arlex; Rinaldi, Carlos

    2014-04-15

    Interfacial linear and internal angular momentum balances are obtained for a structured continuum and for the special case of a ferrofluid, a suspension of magnetic nanoparticles in a Newtonian fluid. The interfacial balance equations account for the effects of surface tension and surface tension gradient, magnetic surface excess forces, antisymmetric stresses, and couple stresses in driving interfacial flows in ferrofluids. Application of the interfacial balance equations is illustrated by obtaining analytical expressions for the translational and spin velocity profiles in a thin film of ferrofluid on an infinite flat plate when a rotating magnetic field is applied with axis of rotation parallel to the ferrofluid/air interface. The cases of zero and non-zero spin viscosity are considered for small applied magnetic field amplitude. Expressions for the maximum translational velocity, slope of the translational velocity profile at the ferrofluid/air interface, and volumetric flow rate are obtained and their use to test the relevance of spin viscosity and couple stresses in the flow situation under consideration is discussed.

  15. Nanoscopic characterization of the water vapor-salt interfacial layer reveals a unique biphasic adsorption process.

    PubMed

    Yang, Liu; He, Jianfeng; Shen, Yi; Li, Xiaowei; Sun, Jielin; Czajkowsky, Daniel M; Shao, Zhifeng

    2016-01-01

    Our quantitative understanding of water adsorption onto salt surfaces under ambient conditions is presently quite poor owing to the difficulties in directly characterizing this interfacial layer under these conditions. Here we determine the thickness of the interfacial layer on NaCl at different relative humidities (RH) based on a novel application of atomic force spectroscopy and capillary condensation theory. In particular, we take advantage of the microsecond-timescale of the capillary condensation process to directly resolve the magnitude of its contribution in the tip-sample interaction, from which the interfacial water thickness is determined. Further, to correlate this thickness with salt dissolution, we also measure surface conductance under similar conditions. We find that below 30% RH, there is essentially only the deposition of water molecules onto this surface, typical of conventional adsorption onto solid surfaces. However, above 30% RH, adsorption is simultaneous with the dissolution of ions, unlike conventional adsorption, leading to a rapid increase of surface conductance. Thus, water adsorption on NaCl is an unconventional biphasic process in which the interfacial layer not only exhibits quantitative differences in thickness but also qualitative differences in composition. PMID:27527905

  16. Use of self-assembled monolayers to control interface bonding in a model study of interfacial fracture

    SciTech Connect

    KENT,MICHAEL S.; YIM,HYUN; MATHESON,AARON J.; COGDILL,C.; REEDY JR.,EARL DAVID

    2000-03-02

    The relationship between the nature and spatial distribution of fundamental interfacial interactions and fracture stress/fracture toughness of a glassy adhesive-inorganic solid joint is not understood. This relationship is important from the standpoint of designing interfacial chemistry sufficient to provide the level of mechanical strength required for a particular application. In addition, it is also important for understanding the effects of surface contamination. Different types of contamination, or different levels of contamination, likely impact joint strength in different ways. Furthermore, the relationship is also important from the standpoint of aging. If interfacial chemical bonds scission over time due to the presence of a contaminant such as water, or exposure to UV, etc, the relationship between joint strength/fracture toughness and interface strength is important for predicting reliability with time. A fundamental understanding of the relationship between joint strength and fundamental interfacial interactions will give insight into these issues.

  17. Interfacial activity of acid functionalized single-walled carbon nanotubes (SWCNTs) at the fluid-fluid interface

    NASA Astrophysics Data System (ADS)

    Feng, Tao; Russell, Thomas; Hoagland, David

    2013-03-01

    Interfacial assembly of acid-functionalized single-walled carbon nanotubes at the oil/water interface is achieved by the addition of low molecular weight (MW) amino-terminated polystyrene in the oil phase. The surface activity of carboxylated SWCNTs is strongly influenced by the end-group chemistry and molecular weight of the polystyrene component, the concentrations of this component and the SWCNTs, along with the degree of functionalization of the SWCNTs. The prerequisites for interfacial trapping are amino termini on chains with MW less than 5K and 6 hours or longer incubation of pristine SWCNTs to achieve their carboxylation. Plummets in interfacial tension resembling those for surfactants were observed at critical bulk concentrations of both SWCNTs and PS-NH2. In dried droplets, SWCNTs densely packed with associated PS-NH2 form a bird nest-like interfacial structure, with the SWCNTs preferentially oriented perpendicular to the original interface. Advisor

  18. Interfacial Tension in Binary Polymer Blends and the Effects of Copolymers as Emulsifying Agents

    NASA Astrophysics Data System (ADS)

    Anastasiadis, Spiros H.

    The structure and the thermodynamic state of polymeric interfaces are important features in many materials of technological interest. This is especially true for multiconstituent systems such as blends of immiscible polymers, where the interface structure can affect greatly their morphology and, thus, their mechanical properties. In this article, we first present a review of the experimental and theoretical investigations of the interfacial tension in phase-separated homopolymer blends. We emphasize the effects of temperature and molecular weight on the behavior: interfacial tension γ decreases with increasing temperature (for polymer systems exhibiting upper critical solution temperature behavior) with a temperature coefficient of the order of 10-2 dyn/(cm °C), whereas it increases with increasing molecular weight. The increase follows a γ = γ _infty ( {1 - k_{operatorname{int} } M_{n}}^{ - z} } ) dependence (with z ≈ 1 for high molecular weights), where γ ∞ is the limiting interfacial tension at infinite molecular weight and M n the number average molecular weight. Suitably chosen block or graft copolymers are widely used in blends of immiscible polymers as compatibilizers for controlling the morphology (phase structure) and the interfacial adhesion between the phases. The compatabilitizing effect is due to their interfacial activity, i.e., to their affinity to selectively segregate to the interface between the phase-separated homopolymers, thus reducing the interfacial tension between the two macrophases. The experimental and theoretical works in this area are reviewed herein. The effects of concentration, molecular weight, composition, and macromolecular architecture of the copolymeric additives are discussed. An issue that can influence the efficient utilization of a copolymeric additive as an emulsifier is the possibility of micelle formation within the homopolymer matrices when the additive is mixed with one of the components. These micelles will

  19. Two-phase flow interfacial structures in a rod bundle geometry

    NASA Astrophysics Data System (ADS)

    Paranjape, Sidharth S.

    Interfacial structure of air-water two-phase flow in a scaled nuclear reactor rod bundle geometry was studied in this research. Global and local flow regimes were obtained for the rod bundle geometry. Local two-phase flow parameters were measured at various axial locations in order to understand the transport of interfacial structures. A one-dimensional two-group interfacial area transport model was evaluated using the local parameter database. Air-water two-phase flow experiments were performed in an 8 X 8 rod bundle test section to obtain flow regime maps at various axial locations. Area averaged void fraction was measured using parallel plate type impedance void meters. The cumulative probability distribution functions of the signals from the impedance void meters were used along with a self organizing neural network to identify flow regimes. Local flow regime maps revealed the cross-sectional distribution of flow regimes in the bundle. Local parameters that characterize interfacial structure, that is, void fraction alpha, interfacial area concentration, ai, bubble Sauter mean diameter, DSm and bubble velocity, vg were measured using four sensor conductivity probe technique. The local data revealed the distribution of the interfacial structure in the radial direction, as well as its development in the axial direction. In addition to this, the effect of spacer grid on the flow structure at different gas and liquid velocities was revealed by local parameter measurements across the spacer grids. A two-group interfacial area transport equation (IATE) specific to rod bundle geometry was derived. The derivation of two-group IATE required certain assumption on the bubble shapes in the subchannels and the bubbles spanning more than a subchannel. It was found that the geometrical relationship between the volume and the area of a cap bubble distorted by rods was similar to the one derived for a confined channel under a specific geometrical transformation. The one

  20. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  1. A nano-cheese-cutter to directly measure interfacial adhesion of freestanding nano-fibers

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Najem, Johnny F.; Wong, Shing-Chung; Wan, Kai-tak

    2012-01-01

    A nano-cheese-cutter is fabricated to directly measure the adhesion between two freestanding nano-fibers. A single electrospun fiber is attached to the free end of an atomic force microscope cantilever, while a similar fiber is similarly prepared on a mica substrate in an orthogonal direction. External load is applied to deform the two fibers into complementary V-shapes, and the force measurement allows the elastic modulus to be determined. At a critical tensile load, "pull-off" occurs when the adhering fibers spontaneously detach from each other, yielding the interfacial adhesion energy. Loading-unloading cycles are performed to investigate repeated adhesion-detachment and surface degradation.

  2. Interfacial Reaction Studies Using ONIOM

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.

    2003-01-01

    In this report, we focus on the calculations of the energetics and chemical kinetics of heterogeneous reactions for Organometallic vapor phase epitaxy (OMVPE). The work described in this report builds upon our own previous thermochemical and chemical kinetics studies. The first of these articles refers to the prediction of thermochemical properties, and the latter one deals with the prediction of rate constants for gaseous homolytic dissociation reactions. The calculations of this investigation are at the microscopic level. The systems chosen consisted of a gallium nitride (GaN) substrate, and molecular nitrogen (N2) and ammonia (NH3) as adsorbants. The energetics for the adsorption and the adsorbant dissociation processes were estimated, and reaction rate constants for the dissociation reactions of free and adsorbed molecules were predicted. The energetics for substrate decomposition was also computed. The ONIOM method, implemented in the Gaussian98 program, was used to perform the calculations. This approach has been selected since it allows dividing the system into two layers that can be treated at different levels of accuracy. The atoms of the substrate were modeled using molecular mechanics6 with universal force fields, whereas the adsorbed molecules were approximated using quantum mechanics, based on density functional theory methods with B3LYP functionals and 6-311G(d,p) basis sets. Calculations for the substrate were performed in slabs of several unit cells in each direction. The N2 and NH3 adsorbates were attached to a central location at the Ga-lined surface.

  3. Interfacial undercooling in solidification of colloidal suspensions: analyses with quantitative measurements

    PubMed Central

    You, Jiaxue; Wang, Lilin; Wang, Zhijun; Li, Junjie; Wang, Jincheng; Lin, Xin; Huang, Weidong

    2016-01-01

    Interfacial undercooling in the complex solidification of colloidal suspensions is of significance and remains a puzzling problem. Two types of interfacial undercooling are supposed to be involved in the freezing of colloidal suspensions, i.e., solute constitutional supercooling (SCS) caused by additives in the solvent and particulate constitutional supercooling (PCS) caused by particles. However, quantitative identification of the interfacial undercooling in the solidification of colloidal suspensions, is still absent; thus, the question of which type of undercooling is dominant in this complex system remains unanswered. Here, we quantitatively measured the static and dynamic interface undercoolings of SCS and PCS in ideal and practical colloidal systems. We show that the interfacial undercooling primarily comes from SCS caused by the additives in the solvent, while PCS is minor. This finding implies that the thermodynamic effect of particles from the PCS is not the fundamental physical mechanism for pattern formation of cellular growth and lamellar structure in the solidification of colloidal suspensions, a general case of ice-templating method. Instead, the patterns in the ice-templating method can be controlled effectively by adjusting the additives. PMID:27329394

  4. Interfacial undercooling in solidification of colloidal suspensions: analyses with quantitative measurements.

    PubMed

    You, Jiaxue; Wang, Lilin; Wang, Zhijun; Li, Junjie; Wang, Jincheng; Lin, Xin; Huang, Weidong

    2016-01-01

    Interfacial undercooling in the complex solidification of colloidal suspensions is of significance and remains a puzzling problem. Two types of interfacial undercooling are supposed to be involved in the freezing of colloidal suspensions, i.e., solute constitutional supercooling (SCS) caused by additives in the solvent and particulate constitutional supercooling (PCS) caused by particles. However, quantitative identification of the interfacial undercooling in the solidification of colloidal suspensions, is still absent; thus, the question of which type of undercooling is dominant in this complex system remains unanswered. Here, we quantitatively measured the static and dynamic interface undercoolings of SCS and PCS in ideal and practical colloidal systems. We show that the interfacial undercooling primarily comes from SCS caused by the additives in the solvent, while PCS is minor. This finding implies that the thermodynamic effect of particles from the PCS is not the fundamental physical mechanism for pattern formation of cellular growth and lamellar structure in the solidification of colloidal suspensions, a general case of ice-templating method. Instead, the patterns in the ice-templating method can be controlled effectively by adjusting the additives. PMID:27329394

  5. Molecular Dynamics Simulation and Analysis of Interfacial Water at Selected Sulfide Mineral Surfaces under Anaerobic Conditions

    SciTech Connect

    Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.

    2014-04-10

    In this paper, we report on a molecular dynamics simulation (MDS) study of the behavior of interfacial water at selected sulfide mineral surfaces under anaerobic conditions. The study revealed the interfacial water structure and wetting characteristics of the pyrite (100) surface, galena (100) surface, chalcopyrite (012) surface, sphalerite (110) surface, and molybdenite surfaces (i.e., the face, armchair-edge, and zigzag-edge surfaces), including simulated contact angles, relative number density profiles, water dipole orientations, hydrogen-bonding, and residence times. For force fields of the metal and sulfur atoms in selected sulfide minerals used in the MDS, we used the universal force field (UFF) and another set of force fields optimized by quantum chemical calculations for interactions with interfacial water molecules at selected sulfide mineral surfaces. Simulation results for the structural and dynamic properties of interfacial water molecules indicate the natural hydrophobic character for the selected sulfide mineral surfaces under anaerobic conditions as well as the relatively weak hydrophobicity for the sphalerite (110) surface and two molybdenite edge surfaces. Part of the financial support for this study was provided by the U.S. Department of Energy (DOE) under Basic Science Grant No. DE-FG-03-93ER14315. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the DOE, funded work performed by Liem X. Dang. Battelle operates Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES. The authors are grateful to Professor Tsun-Mei Chang for valuable discussions.

  6. Interfacial Properties of a Hydrophobic Dye in the Tetrachloroethylene-Water-Glass Systems

    SciTech Connect

    Tuck, D.M.

    1999-02-23

    Interfacial effects play an important role in governing multiphase fluid behavior in porous media. Strongly hydrophobic organic dyes, used in many experimental studies to facilitate visual observation of the phase distributions, have generally been implicitly assumed to have no influence on the interfacial properties of the various phases in porous media. Sudan IV is the most commonly used dye for non-aqueous phase liquids (NAPLs) in laboratory experiments. It has also been used in at least one field experiment. The effects of this dye on the tetrachloroethylene (PCE)-water-glass system were investigated to test the assumption that the dye does not effect the interfacial properties and therefore PCE mobility. The results indicate that the dye does indeed change the interfacial relationships.The effect of the dye on the interfacial relationships is a complex function of the dye concentration, the solid phase composition, and the dynamic rate of new interface formation. The dye caused a slight (<10 percent) increase in interfacial tension at low concentrations (<0.1 g/L) and high rates of new interface formation. The dye reduced interfacial tension between PCE and water at low rates of new interface formation for all dye concentrations tested (0.00508 to 5.08 g/L). At the highest dye concentration, the PCE-water interfacial tension was significantly reduced regardless of the rate of new interface formation. The apparent interfacial tension increase at low dye concentrations is suspected to be an artifact of a low measured IFT value for the undyed PCE caused by leaching of rubber o-rings by the PCE prior to testing in the final drop-volume configuration.In addition to reducing interfacial tension, the dye was found to significantly alter the wetting relationship between PCE and water on a glass surface at and above the range of reported dye concentrations cited in the literature (1.1 to 1.7 g/L). The wetting relationship was rendered neutral from a water-wet initial

  7. Nanonet Force Microscopy for Measuring Cell Forces.

    PubMed

    Sheets, Kevin; Wang, Ji; Zhao, Wei; Kapania, Rakesh; Nain, Amrinder S

    2016-07-12

    The influence of physical forces exerted by or felt by cells on cell shape, migration, and cytoskeleton arrangement is now widely acknowledged and hypothesized to occur due to modulation of cellular inside-out forces in response to changes in the external fibrous environment (outside-in). Our previous work using the non-electrospinning Spinneret-based Tunable Engineered Parameters' suspended fibers has revealed that cells are able to sense and respond to changes in fiber curvature and structural stiffness as evidenced by alterations to focal adhesion cluster lengths. Here, we present the development and application of a suspended nanonet platform for measuring C2C12 mouse myoblast forces attached to fibers of three diameters (250, 400, and 800 nm) representing a wide range of structural stiffness (3-50 nN/μm). The nanonet force microscopy platform measures cell adhesion forces in response to symmetric and asymmetric external perturbation in single and cyclic modes. We find that contractility-based, inside-out forces are evenly distributed at the edges of the cell, and that forces are dependent on fiber structural stiffness. Additionally, external perturbation in symmetric and asymmetric modes biases cell-fiber failure location without affecting the outside-in forces of cell-fiber adhesion. We then extend the platform to measure forces of (1) cell-cell junctions, (2) single cells undergoing cyclic perturbation in the presence of drugs, and (3) cancerous single-cells transitioning from a blebbing to a pseudopodial morphology. PMID:27410747

  8. Interfacial action of natural surfactants in oil/water systems

    SciTech Connect

    Ogino, K.; Onishi, M.

    1981-09-01

    This paper concerns the tendency of a few natural surfactants at the oil/water interface to induce spontaneous emulsification. N-paraffin (n-dodecane), liquid triglycerides (oleic safflower oil and corn oil), and liquid fatty acids (oleic acid and linoleic acid) were used as the oil phase and distilled water was used as the water phase. Natural surfactants such as cholesterol, lecithin, and oleic acid were applied to the systems as the oil-soluble additives. Lecithin was the most strongly effective in reducing the interfacial tension of the oil/water systems, and cholesterol was effective at the second strength. The oil/water interface of the systems containing the oil-soluble additives changed in various ways as observed by microscopy and the unaided eye. The most remarkable change was found in the system of glycerides containing cholesterol in contact with water, in which crystals of cholesterol were formed at the interface. 13 references.

  9. Interfacial Microstructure and Enhanced Mechanical Properties of Carbon Fiber Composites Caused by Growing Generation 1-4 Dendritic Poly(amidoamine) on a Fiber Surface.

    PubMed

    Gao, Bo; Zhang, Ruliang; Gao, Fucheng; He, Maoshuai; Wang, Chengguo; Liu, Lei; Zhao, Lifen; Cui, Hongzhi

    2016-08-23

    In an attempt to improve the mechanical properties of carbon fiber composites, propagation of poly(amidoamine) (PAMAM) dendrimers by in situ polymerization on a carbon fiber surface was performed. During polymerization processes, PAMAM was grafted on carbon fiber by repeated Michael addition and amidation reactions. The changes in surface microstructure and the chemical composition of carbon fibers before and after modification were investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. All the results indicated that PAMAM was successfully grown on the carbon fiber surface. Such propagation could significantly increase the surface roughness and introduce sufficient polar groups onto the carbon fiber surface, enhancing the surface wettability of carbon fiber. The fractured surface of carbon fiber-reinforced composites showed a great enhancement of interfacial adhesion. Compared with those of desized fiber composites, the interlaminar shear strength and interfacial shear strength of PAMAM/fiber-reinforced composites showed increases of 55.49 and 110.94%, respectively. PMID:27472250

  10. A Noncontact Picolitor Droplet Handling by Photothermal Control of Interfacial Flow.

    PubMed

    Muto, Masakazu; Yamamoto, Makoto; Motosuke, Masahiro

    2016-01-01

    We present a noncontact handling of droplets in a microfluidic platform by the Marangoni convection, interfacial tension driven flow, generated by a light-induced local temperature gradient in the surrounding liquid of the droplet. Droplets flowing in a microchannel experience a force due to the interfacial tension gradient when approaching the heated area. This method provides noncontact, selective and flexible manipulation for droplets flowing in microchannel network. In this study, an O/W emulsion system with oleic acid for the dispersed phase and a buffer solution for the continuous one was used. Trajectory control and trapping for droplets with 5 - 65 pL in volume was achieved by patterned laser irradiation. Also, we quantitatively evaluated the driving force exerted on droplets by measuring the fluidic temperature distribution around the droplet. From the balance of the drag force and the photo-induced Marangoni force, the driving force was determined using the measured temperature gradient of the droplet. From the results, the applicability of noncontact droplet manipulation using the photothermal Marangoni effect by continuous-phase heating has been demonstrated. PMID:26753705

  11. Intelligent Chiral Sensing Based on Supramolecular and Interfacial Concepts

    PubMed Central

    Ariga, Katsuhiko; Richards, Gary J.; Ishihara, Shinsuke; Izawa, Hironori; Hill, Jonathan P.

    2010-01-01

    Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized. PMID:22163577

  12. Interfacial layers of complex-forming ionic surfactants with gelatin.

    PubMed

    Derkach, Svetlana R

    2015-08-01

    This review is devoted to discussing the results of studies of the influence of low-molecular weight surfactant additions on the composition and properties of gelatin adsorbed layers which are spontaneously created at water/air and water/non-polar-liquid interfaces. The interaction of surfactant with gelatin leads to the formation of complexes of variable content in the bulk of the aqueous phase. The composition content is determined by the component ratio and concentration of the added surfactant. The role of surfactants (anionic, cationic, non-ionic) capable of forming complexes with gelatin due to electrostatic and hydrophobic interactions is considered. Analysis of the interfacial layer properties is based on literature information, as well as the own author's data. These data include the results of measuring thermodynamic properties (interface tension), laws of formation (adsorption kinetics and thickness), and rheological properties of the layers, which are considered to be dependent on gelatin and surfactant concentration, pH, and temperature. The evolution of the interfacial layers' properties (with increasing surfactant concentration) is discussed in connection with the properties and content of gelatin-surfactant complexes appearing in the aqueous phase. Such an approach allows us to explain the main peculiarities of the layers' behavior including their stabilizing activity in relation to bilateral foam and emulsion films. PMID:24970019

  13. Relativistic Linear Restoring Force

    ERIC Educational Resources Information Center

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  14. Azide functional monolayers grafted to a germanium surface: model substrates for ATR-IR studies of interfacial click reactions.

    PubMed

    Zhang, Shuo; Koberstein, Jeffrey T

    2012-01-10

    High-quality azide-functional substrates are prepared by a low temperature reaction of 11-bromoundecyltrichlorosilane with UV-ozone-treated germanium ATR-IR plates followed by nucleophilic substitution of the terminal bromine by addition of sodium azide. The resulting monolayer films are characterized by atomic force microscopy (AFM), contact angle analysis, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR-IR), and ellipsometry. XPS and ellipsometric thickness data correspond well to the results of molecular model calculations confirming the formation of a densely packed azide-functional monolayer. These azide-functional substrates enable interfacial "click" reactions with complementary alkyne-functional molecules to be studied in situ by ATR-IR. To illustrate their potential utility for kinetic studies we show that, in the presence of copper(I) catalyst, the azide-modified surfaces react rapidly and quantitatively with 5-chloro-pentyne to form triazoles via a 1,3-dipolar cycloaddition reaction. Time-resolved ATR-IR measurements indicate that the interfacial click reaction is initially first order in azide concentration as expected from the reaction mechanism, with a rate constant of 0.034 min(-1), and then transitions to apparent second order dependence, with a rate constant of 0.017 min(-1)/(chains/nm(2)), when the surface azide and triazole concentrations become similar, as predicted by Oyama et al. The reaction achieves an ultimate conversion of 50% consistent with the limit expected due to steric hindrance of the 5-chloro-pentyne reactant at the surface. PMID:22081885

  15. Mesoscale Interfacial Dynamics in Magnetoelectric Nanocomposites

    SciTech Connect

    Shashank, Priya

    2009-12-14

    Biphasic composites are the key towards achieving enhanced magnetoelectric response. In order understand the control behavior of the composites and resultant symmetry of the multifunctional product tensors, we need to synthesized model material systems with the following features (i) interface formation through either deposition control or natural decomposition; (ii) a very high interphase-interfacial area, to maximize the ME coupling; and (iii) an equilibrium phase distribution and morphology, resulting in preferred crystallographic orientation relations between phases across the interphase-interfacial boundaries. This thought process guided the experimental evolution in this program. We initiated the research with the co-fired composites approach and then moved on to the thin film laminates deposited through the rf-magnetron sputtering and pulsed laser deposition process

  16. Interfacial geometry dictates cancer cell tumorigenicity

    NASA Astrophysics Data System (ADS)

    Lee, Junmin; Abdeen, Amr A.; Wycislo, Kathryn L.; Fan, Timothy M.; Kilian, Kristopher A.

    2016-08-01

    Within the heterogeneous architecture of tumour tissue there exists an elusive population of stem-like cells that are implicated in both recurrence and metastasis. Here, by using engineered extracellular matrices, we show that geometric features at the perimeter of tumour tissue will prime a population of cells with a stem-cell-like phenotype. These cells show characteristics of cancer stem cells in vitro, as well as enhanced tumorigenicity in murine models of primary tumour growth and pulmonary metastases. We also show that interfacial geometry modulates cell shape, adhesion through integrin α5β1, MAPK and STAT activity, and initiation of pluripotency signalling. Our results for several human cancer cell lines suggest that interfacial geometry triggers a general mechanism for the regulation of cancer-cell state. Similar to how a growing tumour can co-opt normal soluble signalling pathways, our findings demonstrate how cancer can also exploit geometry to orchestrate oncogenesis.

  17. Interfacial geometry dictates cancer cell tumorigenicity.

    PubMed

    Lee, Junmin; Abdeen, Amr A; Wycislo, Kathryn L; Fan, Timothy M; Kilian, Kristopher A

    2016-08-01

    Within the heterogeneous architecture of tumour tissue there exists an elusive population of stem-like cells that are implicated in both recurrence and metastasis. Here, by using engineered extracellular matrices, we show that geometric features at the perimeter of tumour tissue will prime a population of cells with a stem-cell-like phenotype. These cells show characteristics of cancer stem cells in vitro, as well as enhanced tumorigenicity in murine models of primary tumour growth and pulmonary metastases. We also show that interfacial geometry modulates cell shape, adhesion through integrin α5β1, MAPK and STAT activity, and initiation of pluripotency signalling. Our results for several human cancer cell lines suggest that interfacial geometry triggers a general mechanism for the regulation of cancer-cell state. Similar to how a growing tumour can co-opt normal soluble signalling pathways, our findings demonstrate how cancer can also exploit geometry to orchestrate oncogenesis. PMID:27043781

  18. The contact area dependent interfacial thermal conductance

    SciTech Connect

    Liu, Chenhan; Wei, Zhiyong; Bi, Kedong; Yang, Juekuan; Chen, Yunfei; Wang, Jian

    2015-12-15

    The effects of the contact area on the interfacial thermal conductance σ are investigated using the atomic Green’s function method. Different from the prediction of the heat diffusion transport model, we obtain an interesting result that the interfacial thermal conductance per unit area Λ is positively dependent on the contact area as the area varies from a few atoms to several square nanometers. Through calculating the phonon transmission function, it is uncovered that the phonon transmission per unit area increases with the increased contact area. This is attributed to that each atom has more neighboring atoms in the counterpart of the interface with the increased contact area, which provides more channels for phonon transport.

  19. Interfacial thermodynamics of micro heat pipes

    SciTech Connect

    Swanson, L.W. ); Peterson, G.P. )

    1995-02-01

    Successful analysis and modeling of micro heat pipes requires a complete understanding of the vapor-liquid interface. A thermodynamic model of the vapor-liquid interface in micro heat pipes has been formulated that includes axial pressure and temperature differences, changes in local interfacial curvature, Marangoni effects, and the disjoining pressure. Relationships were developed for the interfacial mass flux in an extended meniscus, the heat transfer rate in the intrinsic meniscus, the 'thermocapillary' heat-pipe limitation, as well as the nonevaporating superheated liquid film thickness that exists between adjacent menisci and occurs during liquid dry out in the evaporator. These relationships can be used to define quantitative restrictions and/or requirements necessary for proper operation of micro heat pipes. They also provide fundamental insight into the critical mechanisms required for proper heat pipe operation. 29 refs., 6 figs.

  20. Frontiers of interfacial water research :workshop report.

    SciTech Connect

    Cygan, Randall Timothy; Greathouse, Jeffery A.

    2005-10-01

    Water is the critical natural resource of the new century. Significant improvements in traditional water treatment processes require novel approaches based on a fundamental understanding of nanoscale and atomic interactions at interfaces between aqueous solution and materials. To better understand these critical issues and to promote an open dialog among leading international experts in water-related specialties, Sandia National Laboratories sponsored a workshop on April 24-26, 2005 in Santa Fe, New Mexico. The ''Frontiers of Interfacial Water Research Workshop'' provided attendees with a critical review of water technologies and emphasized the new advances in surface and interfacial microscopy, spectroscopy, diffraction, and computer simulation needed for the development of new materials for water treatment.

  1. Interfacial transport in lithium-ion conductors

    NASA Astrophysics Data System (ADS)

    Shaofei, Wang; Liquan, Chen

    2016-01-01

    Physical models of ion diffusion at different interfaces are reviewed. The use of impedance spectroscopy (IS), nuclear magnetic resonance (NMR), and secondary ion mass spectrometry (SIMS) techniques are also discussed. The diffusion of ions is fundamental to the operation of lithium-ion batteries, taking place not only within the grains but also across different interfaces. Interfacial ion transport usually contributes to the majority of the resistance in lithium-ion batteries. A greater understanding of the interfacial diffusion of ions is crucial to improving battery performance. Project supported by the Beijing S&T Project, China (Grant No. Z13111000340000), the National Natural Science Foundation of China (Grant Nos. 51325206 and 11234013) and the National Basic Research Program of China (Grant No. 2012CB932900).

  2. Molecular Dynamics Simulation of Atomic Force Microscopy at the Water-Muscovite Interface: Hydration Layer Structure and Force Analysis.

    PubMed

    Kobayashi, Kazuya; Liang, Yunfeng; Amano, Ken-Ichi; Murata, Sumihiko; Matsuoka, Toshifumi; Takahashi, Satoru; Nishi, Naoya; Sakka, Tetsuo

    2016-04-19

    With the development of atomic force microscopy (AFM), it is now possible to detect the buried liquid-solid interfacial structure in three dimensions at the atomic scale. One of the model surfaces used for AFM is the muscovite surface because it is atomically flat after cleavage along the basal plane. Although it is considered that force profiles obtained by AFM reflect the interfacial structures (e.g., muscovite surface and water structure), the force profiles are not straightforward because of the lack of a quantitative relationship between the force and the interfacial structure. In the present study, molecular dynamics simulations were performed to investigate the relationship between the muscovite-water interfacial structure and the measured AFM force using a capped carbon nanotube (CNT) AFM tip. We provide divided force profiles, where the force contributions from each water layer at the interface are shown. They reveal that the first hydration layer is dominant in the total force from water even after destruction of the layer. Moreover, the lateral structure of the first hydration layer transcribes the muscovite surface structure. It resembles the experimentally resolved surface structure of muscovite in previous AFM studies. The local density profile of water between the tip and the surface provides further insight into the relationship between the water structure and the detected force structure. The detected force structure reflects the basic features of the atomic structure for the local hydration layers. However, details including the peak-peak distance in the force profile (force-distance curve) differ from those in the density profile (density-distance curve) because of disturbance by the tip. PMID:27018633

  3. Effect of chemical treatment of Kevlar fibers on mechanical interfacial properties of composites.

    PubMed

    Park, Soo-Jin; Seo, Min-Kang; Ma, Tae-Jun; Lee, Douk-Rae

    2002-08-01

    In this work, the effects of chemical treatment on Kevlar 29 fibers have been studied in a composite system. The surface characteristics of Kevlar 29 fibers were characterized by pH, acid-base value, X-ray photoelectron spectroscopy (XPS), and FT-IR. The mechanical interfacial properties of the final composites were studied by interlaminar shear strength (ILSS), critical stress intensity factor (K(IC)), and specific fracture energy (G(IC)). Also, impact properties of the composites were investigated in the context of differentiating between initiation and propagation energies and ductile index (DI) along with maximum force and total energy. As a result, it was found that chemical treatment with phosphoric acid solution significantly affected the degree of adhesion at interfaces between fibers and resin matrix, resulting in improved mechanical interfacial strength in the composites. This was probably due to the presence of chemical polar groups on Kevlar surfaces, leading to an increment of interfacial binding force between fibers and matrix in a composite system. PMID:16290785

  4. Effect of periodic surface cracks on the interfacial fracture of thermal barrier coating system

    NASA Astrophysics Data System (ADS)

    Fan, X. L.; Xu, R.; Zhang, W. X.; Wang, T. J.

    2012-10-01

    Periodic surface cracks and interfacial debonding in thermal barrier coating (TBC) system may be induced during cooling process. The objective of this work is to investigate the effect of periodic surface cracks on the interfacial fracture of TBC system. The finite element method (FEM) incorporating cohesive zone model is used in analysis. It is found that surface crack spacing has significant effect on the initiation and propagation of short interface crack. Three different regions are identified for describing the effect of surface crack spacing. In Region I the interface crack driving force is dramatically reduced due to high surface crack density. In this case, the initiation of interfacial delamination can be delayed. Region II applies as the surface crack spacing is moderate. Analysis of this transition zone brings to the definition of normalized critical surface crack spacing. Region III arises for sufficient large surface crack spacing. In this case, the interface crack driving force reaches a steady state, where the effects of adjacent surface cracks are relatively insignificant and can be ignored. It can be concluded that an appropriately high surface crack density can enhance the durability of TBC system.

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

    NASA Astrophysics Data System (ADS)

    Garrido, J. M.; Algaba, J.; Míguez, J. M.; Mendiboure, B.; Moreno-Ventas Bravo, A. I.; Piñeiro, M. M.; Blas, F. J.

    2016-04-01

    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 coulombic 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

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

    PubMed

    Garrido, J M; Algaba, J; Míguez, J M; Mendiboure, B; Moreno-Ventas Bravo, A I; Piñeiro, M M; Blas, F J

    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 coulombic 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

  7. Interfacial chemistry and structure in ceramic composites

    SciTech Connect

    Jones, R.H.; Saenz, N.T.; Schilling, C.H.

    1990-09-01

    The interfacial chemistry and structure of ceramic matrix composites (CMCs) play a major role in the properties of these materials. Fiber-matrix interfaces chemistries are vitally important in the fracture strength, fracture toughness, and fracture resistance of ceramic composites because they influence fiber loading and fiber pullout. Elevated-temperature properties are also linked to the interfacial characteristics through the chemical stability of the interface in corrosive environments and the creep/pullout behavior of the interface. Physical properties such as electrical and thermal conductivity are also dependent on the interface. Fiber-matrix interfaces containing a 1-{mu}m-thick multilayered interface with amorphous and graphitic C to a 1-nm-thick SiO{sub 2} layer can result from sintering operations for some composite systems. Fibers coated with C, BN, C/BC/BN, and Si are also used to produce controlled interface chemistries and structures. Growth interfaces within the matrix resulting from processing of CMCs can also be crucial to the behavior of these materials. Evaluation of the interfacial chemistry and structure of CMCs requires the use of a variety of analytical tools, including optical microscopy, scanning electron microscopy, Auger electron spectroscopy, and transmission electron microscopy coupled with energy dispersive x-ray analysis. A review of the interfacial chemistry and structure of SiC whisker- and fiber-reinforced Si{sub 3}N{sub 4} and SiC/SiC materials is presented. Where possible, correlations with fracture properties and high-temperature stability are made. 94 refs., 10 figs.

  8. Intrinsic interfacial phenomena in manganite heterostructures

    NASA Astrophysics Data System (ADS)

    Vaz, C. A. F.; Walker, F. J.; Ahn, C. H.; Ismail-Beigi, S.

    2015-04-01

    We review recent advances in our understanding of interfacial phenomena that emerge when dissimilar materials are brought together at atomically sharp and coherent interfaces. In particular, we focus on phenomena that are intrinsic to the interface and review recent work carried out on perovskite manganites interfaces, a class of complex oxides whose rich electronic properties have proven to be a useful playground for the discovery and prediction of novel phenomena.

  9. Microstructural Evolution Based on Fundamental Interfacial Properties

    SciTech Connect

    A. D. Rollett; D. J. Srolovitz; A. Karma

    2003-07-11

    This first CMSN project has been operating since the summer of 1999. The main achievement of the project was to bring together a community of materials scientists, physicists and mathematicians who share a common interest in the properties of interfaces and the impact of those properties on microstructural evolution. Six full workshops were held at Carnegie Mellon (CMU), Northwestern (NWU), Santa Fe, Northeastern University (NEU), National Institute for Standards and Technology (NIST), Ames Laboratory, and at the University of California in San Diego (UCSD) respectively. Substantial scientific results were obtained through the sustained contact between the members of the project. A recent issue of Interface Science (volume 10, issue 2/3, July 2002) was dedicated to the output of the project. The results include: the development of methods for extracting anisotropic boundary energy and mobility from molecular dynamics simulations of solid/liquid interfaces in nickel; the extraction of anisotropic energies and mobilities in aluminum from similar MD simulations; the application of parallel computation to the calculation of interfacial properties; the development of a method to extract interfacial properties from the fluctuations in interface position through consideration of interfacial stiffness; the use of anisotropic interface properties in studies of abnormal grain growth; the discovery of abnormal grain growth from random distributions of orientation in subgrain networks; the direct comparison at the scale of individual grains between experimentally observed grain growth and simulations, which confirmed the importance of including anisotropic interfacial properties in the simulations; the classification of a rich variety of dendritic morphologies based on slight variations in the anisotropy of the solid-liquid interface; development of phase field methods that permit both solidification and grain growth to be simulated within the same framework.

  10. Interfacial tension measurement of Ni-S liquid using high-pressure X-ray micro-tomography

    SciTech Connect

    Terasaki, H.; Urakawa, S.; Funakoshi, K.; Wang, Y.; Shibazaki, Y.; Sanehira, T.; Ueda, Y.; Ohtani, E.

    2008-11-12

    High-pressure, high-temperature X-ray tomography experiments have been carried out using a large volume toroidal cell, which is optimized for interfacial tension measurements. A wide anvil gap, which corresponds to a field of view in the radiography imaging, was successively maintained to high pressures and temperatures using a composite plastic gasket. Obtained interfacial tensions of Ni-S liquid against Na, K-disilicate melt, were 414 and 336 mN/m at 1253 and 1293 K, respectively. Three-dimensional tomography images revealed that the sample had an irregular shape at the early stage of melting, suggesting either non-equilibrium in sample texture and force balance or partial melting of surrounding silicate. This information cannot always be obtained from two-dimensional radiographic imaging techniques. Therefore, a three-dimensional tomography measurement is appropriate for the precise interfacial measurements.

  11. Recent numerical and algorithmic advances within the volume tracking framework for modeling interfacial flows

    SciTech Connect

    François, Marianne M.

    2015-05-28

    A review of recent advances made in numerical methods and algorithms within the volume tracking framework is presented. The volume tracking method, also known as the volume-of-fluid method has become an established numerical approach to model and simulate interfacial flows. Its advantage is its strict mass conservation. However, because the interface is not explicitly tracked but captured via the material volume fraction on a fixed mesh, accurate estimation of the interface position, its geometric properties and modeling of interfacial physics in the volume tracking framework remain difficult. Several improvements have been made over the last decade to address these challenges. In this study, the multimaterial interface reconstruction method via power diagram, curvature estimation via heights and mean values and the balanced-force algorithm for surface tension are highlighted.

  12. Recent numerical and algorithmic advances within the volume tracking framework for modeling interfacial flows

    DOE PAGESBeta

    François, Marianne M.

    2015-05-28

    A review of recent advances made in numerical methods and algorithms within the volume tracking framework is presented. The volume tracking method, also known as the volume-of-fluid method has become an established numerical approach to model and simulate interfacial flows. Its advantage is its strict mass conservation. However, because the interface is not explicitly tracked but captured via the material volume fraction on a fixed mesh, accurate estimation of the interface position, its geometric properties and modeling of interfacial physics in the volume tracking framework remain difficult. Several improvements have been made over the last decade to address these challenges.more » In this study, the multimaterial interface reconstruction method via power diagram, curvature estimation via heights and mean values and the balanced-force algorithm for surface tension are highlighted.« less

  13. Nuclear forces

    SciTech Connect

    Machleidt, R.

    2013-06-10

    These lectures present an introduction into the theory of nuclear forces. We focus mainly on the modern approach, in which the forces between nucleons emerge from low-energy QCD via chiral effective field theory.

  14. Rheology and interfacial tension of biopolymers

    NASA Astrophysics Data System (ADS)

    Kandadai, Madhuvanthi A.

    The rheology and interfacial tension of biomaterials are important factors governing their potential use in biomedical applications. This dissertation presents a study of the rheology and interfacial tension of three very different biomaterials: (1) A hydrophobically modified Hyaluronic acid (HA) with polypeptide side chains, (2) Actin fibers and (3) a highly hydrophobic fluoroalkane, Perfluoropentane, and the effect of various surfactants and their mixtures on lowering its interfacial tension in an aqueous interface. In Chapter 1, we present a description of the properties and applications of these materials and a detailed literature review relevant to our studies to better understand the motivation of our work. In Chapter 2 we describe the techniques used for our studies. In Chapter 3, we present our studies on the hydrophobically modified HA with polyleucine side chains and compare them to unmodified HA of same or similar backbone molecular weights. We found a significantly enhanced viscosity for the modified HA compared to unmodified HA at the same concentration. We also found a viscoelastic behavior that was dependent on the concentration of the solution and grafting ratio of the hydrophobic side chains. The associative thickening properties of modified HA investigated with various rheological experiments and simulation results are presented in this chapter. In Chapter 4, we present our studies on the properties of actin fibers. We used a novel microrheometer VROC(TM) (Viscometer-rheometer-on-a-chip) for studying actin fibers at very high shear rates. We show that at very high shear rats, the actin filaments show irreversible network breakdown. We also studied the surface tension of actin filaments and monomer solutions at the interface with air and report induction times of these materials. In Chapter 5, we study the interfacial tension of a highly hydrophobic fluoroalkane, Perfluoropentane, in the presence of different surfactants and their mixtures. The

  15. Food additives.

    PubMed

    Berglund, F

    1978-01-01

    The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI

  16. Interfacial fracture between highly crosslinked polymer networks and a solid surface: Effect of interfacial bond density

    SciTech Connect

    STEVENS,MARK J.

    2000-03-23

    For highly crosslinked, polymer networks bonded to a solid surface, the effect of interfacial bond density as well as system size on interfacial fracture is studied molecular dynamics simulations. The correspondence between the stress-strain curve and the sequence of molecular deformations is obtained. The failure strain for a fully bonded surface is equal to the strain necessary to make taut the average minimal path through the network from the bottom solid surface to the top surface. At bond coverages less than full, nanometer scale cavities form at the surface yielding an inhomogeneous strain profile. The failure strain and stress are linearly proportional to the number of bonds at the interface unless the number of bonds is so few that van der Waals interactions dominate. The failure is always interfacial due to fewer bonds at the interface than in the bulk.

  17. Labor Force

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2012

    2012-01-01

    The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

  18. The mechanism of deceleration of nucleation and crystal growth by the small addition of transition metals to lithium disilicate glasses

    PubMed Central

    Thieme, Katrin; Avramov, Isak; Rüssel, Christian

    2016-01-01

    The addition of small amounts of niobium or tantalum oxide to lithium disilicate glass provokes a drastic decrease of the steady-state nucleation rates and the crystal growth velocities. The viscosity of the residual glassy matrix is considered as a function of the crystallization degree in the course of a non-isothermal crystallization. For simplification, a homogeneous distribution of the added oxides in the glass matrix is assumed. While the viscosity initially decreases, it significantly increases again for higher crystallization degrees hindering crystal growth. However, it was shown that the additives are enriched at the crystal interface. Several possible reasons for the inhibition of nucleation and growth kinetics such as viscosity, interfacial energy crystal/glassy phase, thermodynamic driving force or impingement rate are discussed. Since the crystallization front is blocked by the additives the impingement rate is decreased with increasing additive concentration. Since small concentrations of Nb2O5 and Ta2O5 have a drastic effect on the nucleation, these components should be enriched at the interface crystal/glass. This will only take place, if it leads to a decrease in the interfacial energy. Since this effect alone should result in an increase of the nucleation rate, it must be overcompensated by kinetic effects. PMID:27150844

  19. The mechanism of deceleration of nucleation and crystal growth by the small addition of transition metals to lithium disilicate glasses.

    PubMed

    Thieme, Katrin; Avramov, Isak; Rüssel, Christian

    2016-01-01

    The addition of small amounts of niobium or tantalum oxide to lithium disilicate glass provokes a drastic decrease of the steady-state nucleation rates and the crystal growth velocities. The viscosity of the residual glassy matrix is considered as a function of the crystallization degree in the course of a non-isothermal crystallization. For simplification, a homogeneous distribution of the added oxides in the glass matrix is assumed. While the viscosity initially decreases, it significantly increases again for higher crystallization degrees hindering crystal growth. However, it was shown that the additives are enriched at the crystal interface. Several possible reasons for the inhibition of nucleation and growth kinetics such as viscosity, interfacial energy crystal/glassy phase, thermodynamic driving force or impingement rate are discussed. Since the crystallization front is blocked by the additives the impingement rate is decreased with increasing additive concentration. Since small concentrations of Nb2O5 and Ta2O5 have a drastic effect on the nucleation, these components should be enriched at the interface crystal/glass. This will only take place, if it leads to a decrease in the interfacial energy. Since this effect alone should result in an increase of the nucleation rate, it must be overcompensated by kinetic effects. PMID:27150844

  20. Weighing graphene with QCM to monitor interfacial mass changes

    NASA Astrophysics Data System (ADS)

    Kakenov, Nurbek; Balci, Osman; Salihoglu, Omer; Hur, Seung Hyun; Balci, Sinan; Kocabas, Coskun

    2016-08-01

    In this Letter, we experimentally determined the mass density of graphene using quartz crystal microbalance (QCM) as a mechanical resonator. We developed a transfer printing technique to integrate large area single-layer graphene on QCM. By monitoring the resonant frequency of an oscillating quartz crystal loaded with graphene, we were able to measure the mass density of graphene as ˜118 ng/cm2, which is significantly larger than the ideal graphene (˜76 ng/cm2) mainly due to the presence of wrinkles and organic/inorganic residues on graphene sheets. High sensitivity of the quartz crystal resonator allowed us to determine the number of graphene layers in a particular sample. Additionally, we extended our technique to probe interfacial mass variation during adsorption of biomolecules on graphene surface and plasma-assisted oxidation of graphene.

  1. Interfacial Shear Strength Evaluation of Jute/Poly(Lactic Acid)

    NASA Astrophysics Data System (ADS)

    Kobayashi, Satoshi; Yamamoto, Tatsuro; Nakai, Asami

    In order to evaluate the interfacial shear strength between fiber bundle and matrix of jute/poly(lactic acid) (PLA), a fiber bundle pull-out test method is proposed. Shear stress distribution was calculated based on the parabolic shear-lag analysis. Fiber bundle pull-out tests were conducted to evaluate the effects of molding condition on the interfacial shear strength. The interfacial shear strength increased with increasing molding temperature up to 185°C. Then gradual decrease in the interfacial shear strength with molding temperature was observed. Similar tendency was also observed in the effect of molding time, whereas the interfacial shear strength decreased with increasing molding pressure. Comparing the result of the tensile tests in the previous study, interfacial shear strength has corelations with tensile strength.

  2. Fully nonlinear interfacial waves in a bounded two-fluid system

    NASA Astrophysics Data System (ADS)

    Barannyk, Lyudmyla Leonidivna

    We study the nonlinear flow which results when two immiscible inviscid incompressible fluids of different densities and separated by an interface which is free to move and which supports surface tension, are caused to flow in a straight infinite channel. Gravity is taken into consideration and the velocities of each phase can be different, thus giving rise to the Kelvin-Helmholtz instability. Our objective is to study the competing effects of the Kelvin-Helmholtz instability coupled with a stably or unstably stratified fluid system (Rayleigh-Taylor instability) when surface tension is present to regularize the dynamics. Our approach involves the derivation of two- and three-dimensional model evolution equations using long-wave asymptotics and the ensuing analysis and computation of these models. In addition, we derive the appropriate Birkhoff-Rott integro-differential equation for two-phase inviscid flows in channels of arbitrary aspect ratios. A long wave asymptotic analysis is undertaken to develop a theory for fully nonlinear interfacial waves allowing amplitudes as large as the channel thickness. The result is a set of evolution equations for the interfacial shape and the velocity jump across the interface. Linear stability analysis reveals that capillary forces stabilize short-wave disturbances in a dispersive manner and we study their effect on the fully nonlinear dynamics described by our models. In the case of two-dimensional interfacial deflections, traveling waves of permanent form are constructed and it is shown that solitary waves are possible for a range of physical parameters. All solitary waves are expressed implicitly in terms of incomplete elliptic integrals of the third kind. When the upper layer has zero density, two explicit solitary-wave solutions have been found whose amplitudes are equal to h/4 or h/9 where 2h is the channel thickness. In the absence of gravity, solitary waves are not possible but periodic ones are. Numerically constructed

  3. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  4. Phosphazene additives

    SciTech Connect

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  5. The influence of interfacial energies and gravitational levels on the directionally solidified structures in hypermonotectic alloys

    NASA Astrophysics Data System (ADS)

    Sandlin, A. C.; Andrews, J. B.; Curreri, P. A.

    1988-11-01

    Several Cu-Pb-Al alloys were directionally solidified under one-g conditions and alternating high-g/low-g conditions in order to determine the influence of interfacial energies and gravitational levels on the resulting microstructures. The low-g conditions were obtained through use of NASA's KC-135 aircraft. In the Cu-Pb-Al system, changes in the Al content are known to result in variations in the interfacial energy relationships between the phases. Theory predicts that this should lead to a transition from an irregular to a regular, aligned microstructure in monotectic composition alloys. Four different hypermonotectic alloy compositions were used in this study in order to vary systematically the interfacial energies between the phases. Preliminary results indicate microstructural variations between control and flight samples and samples processed at different rates under both one-g and high-g/low-g conditions. In addition, directional solidification of low Al content alloys resulted in samples with coarse, irregular microstructures, as compared to finer, more aligned microstructures in alloys with high Al contents. This was seen in samples processed under both one-g and high-g/low-g conditions. The resulting structures have been related to interfacial energies, growth rates, and gravitational levels.

  6. Electrode dependent interfacial layer variation in metal-oxide-semiconductor capacitor

    NASA Astrophysics Data System (ADS)

    Park, I.-S.; Jung, Y. C.; Lee, M.; Seong, S.; Ahn, J.

    2014-03-01

    The interfacial layer between oxide and semiconductor in metal-oxide-semiconductor (MOS) capacitors depends on the metal electrode material. The metal/HfO2/Si and metal/HfO2/Ge capacitor were made using an atomic layer deposited HfO2 dielectric films and Mo, Ru, and Pt electrodes above Si substrate and Ti, Ru, and Pt electrodes above Ge substrate. The measured saturation capacitance was varied with electrode and evaluated to capacitance equivalent thickness (CET). In Si-based MOS capacitor, the CET value of the capacitor with Pt electrode is larger than those with Mo and Ru electrode. In addition, the CET is 27.4 A, 38.2 A, and 30.8 A for Ti, Ru, and Pt electrode, respectively, for Ge-based MOS capacitors. The CET variation with electrode is attributed the variation of dielectric constant of HfO2 dielectric and the difference of interfacial layer. The CET variation is well in agreement with the interfacial layer thickness taken by a transmission electron microscopy. The thickness variation of interfacial layer results from the oxygen gettering ability of the electrode even though they are apart.

  7. Lattice Boltzmann method for convection-diffusion equations with general interfacial conditions

    NASA Astrophysics Data System (ADS)

    Hu, Zexi; Huang, Juntao; Yong, Wen-An

    2016-04-01

    In this work, we propose an interfacial scheme accompanying the lattice Boltzmann method for convection-diffusion equations with general interfacial conditions, including conjugate conditions with or without jumps in heat and mass transfer, continuity of macroscopic variables and normal fluxes in ion diffusion in porous media with different porosity, and the Kapitza resistance in heat transfer. The construction of this scheme is based on our boundary schemes [Huang and Yong, J. Comput. Phys. 300, 70 (2015), 10.1016/j.jcp.2015.07.045] for Robin boundary conditions on straight or curved boundaries. It gives second-order accuracy for straight interfaces and first-order accuracy for curved ones. In addition, the new scheme inherits the advantage of the boundary schemes in which only the current lattice nodes are involved. Such an interfacial scheme is highly desirable for problems with complex geometries or in porous media. The interfacial scheme is numerically validated with several examples. The results show the utility of the constructed scheme and very well support our theoretical predications.

  8. Alcohol-soluble interfacial fluorenes for inverted polymer solar cells: sequence induced spatial conformation dipole moment.

    PubMed

    Chen, Lie; Liu, Xiangfu; Wei, Yingkai; Wu, Feiyan; Chen, Yiwang

    2016-01-21

    Three fluorene-based alcohol-soluble organic small molecule electrolytes (SMEs) with different conjugated backbones, namely, TFTN-Br, FTFN-Br and FTTFN-Br, were designed as cathode interfacial layers for inverted polymer solar cells (i-PSCs). The insertion of SMEs to the ITO/active layer interfaces effectively lowered the energy barrier for electron transport and improved the inherent compatibility between the hydrophilic ITO and hydrophobic active layers. Due to these advantages, the device based on poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C61 butyric acid methyl ester (PC61BM) with TFTN-Br as the cathode interfacial layer achieved an improved power conversion efficiency (PCE) of 3.8%, which is a 26% improvement when compared to the standard device comprising ZnO cathode interfacial layers (PCE = 3.0%). Devices with FTFN-Br and FTTFN-Br also showed an improved PCE of 3.1% and 3.5%, respectively. The variation in device performance enhancement was found to be primarily correlated with the different conformation of their assembly onto the electrode caused by the joint sequence of the polar group of the SMEs, consequently impacting the dipole moment and interface morphology. In addition, introducing SMEs as the cathode interfacial layer also produced devices with long-term stability. PMID:26694627

  9. The Stokes force on a droplet in an unbounded fluid medium due to capillary effects

    NASA Technical Reports Server (NTRS)

    Subramanian, R. Shankar

    1985-01-01

    The Stokes force on a fluid droplet is obtained when the droplet is placed in an unbounded fluid medium and motion ensues due to an arbitrary interfacial-tension gradient on the droplet surface. The force, derived here for a spherical droplet, is proportional to the integral of the interfacial-tension gradient over the droplet surface. When the interfacial-tension gradients are caused by temperature or concentration variations, the result for the force may be further specialized when convective transport effects are negligible. In this case, it is possible to express the force in terms of the gradient of the undisturbed temperature (or concentration) field evaluated at the location of the droplet center in a form analogous to Faxen's force law.

  10. Interfacial area transport equation for bubbly to cap-bubbly transition flows

    NASA Astrophysics Data System (ADS)

    Worosz, Theodore S.

    To fully realize the benefit of the two-group interfacial area transport equation (IATE) as a constitutive model for the interfacial area concentration in the two-fluid model, it is imperative that models be developed to dynamically transition from one-group to two-group flows. With this in mind, the two-group IATE is derived in detail to establish new expansion source terms that correctly account for the effects of intergroup bubble transport. In addition to this theoretical effort, the state-of-the-art four-sensor conductivity probe is used to establish a reliable experimental database of local two-phase flow parameters to characterize one-group to two-group transition flows and to support model development. The experiments are performed in verticalupward air-water two-phase flow in a 5.08cm pipe. Additionally, the local conductivity probe is improved through systematic studies into: 1) signal "ghosting" electrical interference among probe sensors, 2) sampling frequency sensitivity, 3) measurement duration sensitivity, and 4) probe sensor orientation. Wake-dominated bubble transport characterizes the transition from onegroup to two-group flows. Therefore, the necessary intergroup and intragroup wake entrainment source terms that are required for two-group interfacial area transport in transition flows are developed. Furthermore, an approach is developed to initiate the shearing-off source and reduce the one-group interaction mechanisms as an established two-group flow develops. The new interfacial area transport model for one-group to two-group transition flows is evaluated against the experimental database. The model accurately captures the exchange of void fraction and interfacial area concentration between group-I and group-II in transition flows. Overall, the group-I void fraction and interfacial area concentration are predicted within +/-6% and +/-4%, respectively, of the experimental data. The group-II void fraction and interfacial area concentration are

  11. Direct handling of sharp interfacial energy for microstructural evolution

    DOE PAGESBeta

    Hernández–Rivera, Efraín; Tikare, Veena; Noirot, Laurence; Wang, Lumin

    2014-08-24

    In this study, we introduce a simplification to the previously demonstrated hybrid Potts–phase field (hPPF), which relates interfacial energies to microstructural sharp interfaces. The model defines interfacial energy by a Potts-like discrete interface approach of counting unlike neighbors, which we use to compute local curvature. The model is compared to the hPPF by studying interfacial characteristics and grain growth behavior. The models give virtually identical results, while the new model allows the simulator more direct control of interfacial energy.

  12. Interfacial welding of dynamic covalent network polymers

    NASA Astrophysics Data System (ADS)

    Yu, Kai; Shi, Qian; Li, Hao; Jabour, John; Yang, Hua; Dunn, Martin L.; Wang, Tiejun; Qi, H. Jerry

    2016-09-01

    Dynamic covalent network (or covalent adaptable network) polymers can rearrange their macromolecular chain network by bond exchange reactions (BERs) where an active unit replaces a unit in an existing bond to form a new bond. Such macromolecular events, when they occur in large amounts, can attribute to unusual properties that are not seen in conventional covalent network polymers, such as shape reforming and surface welding; the latter further enables the important attributes of material malleability and powder-based reprocessing. In this paper, a multiscale modeling framework is developed to study the surface welding of thermally induced dynamic covalent network polymers. At the macromolecular network level, a lattice model is developed to describe the chain density evolution across the interface and its connection to bulk stress relaxation due to BERs. The chain density evolution rule is then fed into a continuum level interfacial model that takes into account surface roughness and applied pressure to predict the effective elastic modulus and interfacial fracture energy of welded polymers. The model yields particularly accessible results where the moduli and interfacial strength of the welded samples as a function of temperature and pressure can be predicted with four parameters, three of which can be measured directly. The model identifies the dependency of surface welding efficiency on the applied thermal and mechanical fields: the pressure will affect the real contact area under the consideration of surface roughness of dynamic covalent network polymers; the chain density increment on the real contact area of interface is only dependent on the welding time and temperature. The modeling approach shows good agreement with experiments and can be extended to other types of dynamic covalent network polymers using different stimuli for BERs, such as light and moisture etc.

  13. Interfacial Characterization of Rigid Polymer Coatings

    NASA Astrophysics Data System (ADS)

    DeNolf, Garret C.

    In order to enhance the performance and durability of today's polymer coatings it is pivotal to be able to characterize their mechanical and chemical properties, with emphasized importance on coating-substrate interfaces which are common points of material failure. The purpose of this thesis was to develop and demonstrate novel characterization methods to measure the interfacial and bulk properties of these polymer films and improve the overall understanding of these materials. The first portion of this thesis explores a new peel test technique to measure the adhesion between substrates and coatings. The employed method examines the effect of processing conditions and substrate treatment on the adhesion of polyurethane coatings. This technique successfully quantifies the adhesion of polyurethane coatings to a variety of treated substrates and at multiple curing temperatures. The second thrust of this thesis involves the utilization of a quartz crystal microbalance instrument to characterize the bulk rheological properties of polymer films and coatings in situ. This novel method enables the examination of the effect of temperature and mixing stoichiometry on the rheological properties of curing polyurethane coatings and polymer films. This analysis is extended to measure the curing and aging of paint systems relevant to the art conservation scientific community. The final portion of this thesis focuses on understanding the effect of pH on the interfacial swelling of polymer films in aqueous environments. The quartz crystal microbalance is used to characterize the swelling of interfacial polymer films as water reaches the interface, and the corresponding permeability and osmotic pressure provides insight into the mechanisms of delamination and adhesive failure of coatings attached to metal surfaces. The novel methods and calculations established in this thesis enable precise measurements of coating interfaces and rheological properties and have considerable potential

  14. Effect of the nature of the components of extraction systems used to extract radionuclides on interfacial tension. V. Radiation polymerization products of tri-n-butyl phosphate

    SciTech Connect

    Nikitin, S.D.; Shmidt, V.S.

    1986-01-01

    This paper examines the effect of the polymerization products of tri-n-butylphosphate (TBP) on stratification of normal and inverse emulsions and the interfacial tension in systems of 30% TBP in n-dodecane with water, 5% aqueous solution Na/sub 2/CO/sub 3/, and a solution of 3 moles/liter HNO/sub 3/. It is shown that in these systems there is a direct correlation between the interfacial tension and the phase stratification rate. Small additions of a neutral fraction of the polymerization products do not exert any appreciable effect on the interfacial tension and the phase stratification rate in the investigated systems.

  15. Interfacial Molecular Searching Using Forager Dynamics

    NASA Astrophysics Data System (ADS)

    Monserud, Jon H.; Schwartz, Daniel K.

    2016-03-01

    Many biological and technological systems employ efficient non-Brownian intermittent search strategies where localized searches alternate with long flights. Coincidentally, molecular species exhibit intermittent behavior at the solid-liquid interface, where periods of slow motion are punctuated by fast flights through the liquid phase. Single-molecule tracking was used here to observe the interfacial search process of DNA for complementary DNA. Measured search times were qualitatively consistent with an intermittent-flight model, and ˜10 times faster than equivalent Brownian searches, suggesting that molecular searches for reactive sites benefit from similar efficiencies as biological organisms.

  16. Weak links and interfacial chemistry in coal

    SciTech Connect

    Ross, D.S.; Hirschon, A.S.; Green, T.K.

    1989-12-31

    It has been estimated that the ultrafine mineral component in coal can be up to 15% of the total mineral content (ref 6), and the similarity of our results with coal to those for oil shale suggest that the reactive mineral/organic interfacial volume in coal could be substantial. While the mechanisms for reactions within the interphase are yet to be developed, our results suggest that attention be applied to this feature of coal in considerations of structure effects on both liquefaction and coal pyrolysis.

  17. Weak links and interfacial chemistry in coal

    SciTech Connect

    Ross, D.S.; Hirschon, A.S.; Green, T.K.

    1989-01-01

    It has been estimated that the ultrafine mineral component in coal can be up to 15% of the total mineral content (ref 6), and the similarity of our results with coal to those for oil shale suggest that the reactive mineral/organic interfacial volume in coal could be substantial. While the mechanisms for reactions within the interphase are yet to be developed, our results suggest that attention be applied to this feature of coal in considerations of structure effects on both liquefaction and coal pyrolysis.

  18. Rheology of interfacial protein-polysaccharide composites

    NASA Astrophysics Data System (ADS)

    Fischer, P.

    2013-05-01

    The morphology and mechanical properties of protein adsorption layers can significantly be altered by the presence of surfactants, lipids, particles, other proteins, and polysaccharides. In food emulsions, polysaccharides are primarily considered as bulk thickener but can under appropriate environmental conditions stabilize or destabilize the protein adsorption layer and, thus, the entire emulsion system. Despite their ubiquitous usage as stabilization agent, relatively few investigations focus on the interfacial rheology of composite protein/polysaccharide adsorption layers. The manuscript provides a brief review on both main stabilization mechanisms, thermodynamic phase separation and electrostatic interaction and discusses the rheological response in light of the environmental conditions such as ionic strength and pH.

  19. Viscosity of interfacial water regulates ice nucleation

    SciTech Connect

    Li, Kaiyong; Chen, Jing; Zhang, Qiaolan; Zhang, Yifan; Xu, Shun; Zhou, Xin; Cui, Dapeng; Wang, Jianjun Song, Yanlin

    2014-03-10

    Ice formation on solid surfaces is an important phenomenon in many fields, such as cloud formation and atmospheric icing, and a key factor for applications in preventing freezing. Here, we report temperature-dependent nucleation rates of ice for hydrophilic and hydrophobic surfaces. The results show that hydrophilic surface presents a lower ice nucleation rate. We develop a strategy to extract the thermodynamic parameters, J{sub 0} and Γ, in the context of classical nucleation theory. From the extracted J{sub 0} and Γ, we reveal the dominant role played by interfacial water. The results provide an insight into freezing mechanism on solid surfaces.

  20. Synchrotron X-Ray Microtomography and Interfacial Partitioning Tracer Test Measurements of Napl-Water Interfacial Areas

    NASA Astrophysics Data System (ADS)

    Brusseau, M. L.; Janousek, H.; Murao, A.; Schnaar, G.

    2007-12-01

    Interfacial areas between an immiscible organic liquid (NAPL) and water were measured for two natural porous media using two methods, aqueous-phase interfacial partitioning tracer tests and synchrotron X-ray microtomography. The interfacial areas measured with the tracer tests were similar to previously reported values obtained with the method. The values were, however, significantly larger than those obtained from microtomography. Analysis of microtomography data collected before and after introduction of the interfacial tracer solution indicated that the surfactant tracer had minimal impact on fluid-phase configuration and interfacial areas under conditions associated with typical laboratory application. The disparity between the tracer-test and microtomography values is attributed primarily to the inability of the microtomography method to resolve interfacial area associated with microscopic surface heterogeneity. This hypothesis is consistent with results recently reported for a comparison of microtomographic analysis and interfacial tracer tests conducted for an air-water system. The tracer-test method provides a measure of effective, total (capillary and film) interfacial area, whereas microtomography can be used to determine separately both capillary-associated and film-associated interfacial areas. Both methods appear to provide useful information for given applications. A key to their effective use is recognizing the specific nature of the information provided by each, as well as associated limitations.

  1. Effect of surface modification on interfacial nanobubble morphology and contact line tension.

    PubMed

    Rangharajan, Kaushik K; Kwak, Kwang J; Conlisk, A T; Wu, Yan; Prakash, Shaurya

    2015-07-14

    Past research has confirmed the existence of surface nanobubbles on various hydrophobic substrates (static contact angle >90°) when imaged in air-equilibrated water. Additionally, the use of solvent exchange techniques (based on the difference in saturation levels of air in various solvents) also introduced surface nanobubbles on hydrophilic substrates (static contact angle <90°). In this work, tapping mode atomic force microscopy was used to image interfacial nanobubbles formed on bulk polycarbonate (static contact angle of 81.1°), bromo-terminated silica (BTS; static contact angle of 85.5°), and fluoro-terminated silica (FTS; static contact angle of 105.3°) surfaces when immersed in air-equilibrated water without solvent exchange. Nanobubbles formed on the above three substrates were characterized on the basis of Laplace pressure, bubble density, and contact line tension. Results reported here show that (1) the Laplace pressures of all nanobubbles formed on both BTS and polycarbonate were an order of magnitude higher than those of FTS, (2) the nanobubble number density per unit area decreased with an increase in substrate contact angle, and (3) the contact line tension of the nanobubbles was calculated to be positive for both BTS and polycarbonate (lateral radius, Rs < 50 nm for all nanobubbles), and negative for FTS (Rs > 50 nm for all nanobubbles). The nanobubble morphology and distribution before and after using the solvent exchange method (ethanol-water), on the bulk polycarbonate substrate was also characterized. Analysis for these polycarbonate surface nanobubbles showed that both the Laplace pressure and nanobubble density reduced by ≈98% after ethanol-water exchange, accompanied by a flip in the magnitude of contact line tension from positive (0.19 nN) to negative (-0.11 nN). PMID:26041331

  2. 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.

  3. Molecular level computational studies of polyethylene and polyacrylonitrile composites containing single walled carbon nanotubes: effect of carboxylic acid functionalization on nanotube-polymer interfacial properties

    PubMed Central

    Haghighatpanah, Shayesteh; Bohlén, Martin; Bolton, Kim

    2014-01-01

    Molecular dynamics (MD) and molecular mechanics (MM) methods have been used to investigate additive-polymer interfacial properties in single walled carbon nanotube (SWNT)—polyethylene and SWNT—polyacrylonitrile composites. Properties such as the interfacial shear stress and bonding energy are similar for the two composites. In contrast, functionalizing the SWNT with carboxylic acid groups leads to an increase in these properties, with a larger increase for the polar polyacrylonitrile composite. Increasing the percentage of carbon atoms that were functionalized from 1 to 5% also leads to an increase in the interfacial properties. In addition, the interfacial properties depend on the location of the functional groups on the SWNT wall. PMID:25229056

  4. Consequences of interfacial viscoelasticity on thin film stability.

    PubMed

    Rosenfeld, Liat; Fuller, Gerald G

    2012-10-01

    The phenomenon of dewetting is frequently observed in our everyday life. It is of central importance in many technological applications as well as in a variety of physical and biological systems. The presence of nonsoluble surfactants at an air/liquid interface may affect the dewetting properties of the aqueous layer. An important example is the tear film, which comprises an aqueous layer covered with a ∼100-nm-thick blanket of lipids, known as the meibomian lipids. Interfacial rheological measurements of meibomian lipids reveal that these films are remarkably viscoelastic. Tear film dewetting is of central importance to understanding tear film stability. To better understand the role of surface viscoelasticity in tear film stability, we have developed a methodology to systematically control interfacial rheology of thin aqueous layers at the onset of dewetting events. The apparatus allows control over the surface pressure of the monolayer, which is a key feature since this variable controls the surface viscoelasticity. Three insoluble monolayer materials were used: newtonian arachidyl alcohol (AA), DPPC, a phospholipid that is slightly viscoelastic, and meibum, which produces a strongly viscoelastic monolayer. It is reported that monolayers of viscoelastic surfactants are able to stabilize thin films against spontaneous dewetting. As the surface pressure of these layers is increased, their effectiveness is enhanced. Moreover, these surfactants are able to reduce the critical film thickness for dewetting. Meibum is particularly effective in stabilizing thin films. Our results suggest that the meibomian lipids play a vital role in maintaining tear film stability in addition to suppressing evaporation. PMID:22989061

  5. Interfacial adsorption and aggregation of amphiphilic proteins

    NASA Astrophysics Data System (ADS)

    Cheung, David

    2012-02-01

    The adsorption and aggregation on liquid interfaces of proteins is important in many biological contexts, such as the formation of aerial structures, immune response, and catalysis. Likewise the adsorption of proteins onto interfaces has applications in food technology, drug delivery, and in personal care products. As such there has been much interest in the study of a wide range of biomolecules at liquid interfaces. One class of proteins that has attracted particular attention are hydrophobins, small, fungal proteins with a distinct, amphiphilic surface structure. This makes these proteins highly surface active and they recently attracted much interest. In order to understand their potential applications a microscopic description of their interfacial and self-assembly is necessary and molecular simulation provides a powerful tool for providing this. In this presentation I will describe some recent work using coarse-grained molecular dynamics simulations to study the interfacial and aggregation behaviour of hydrophobins. Specifically this will present the calculation of their adsorption strength at oil-water and air-water interfaces, investigate the stability of hydrophobin aggregates in solution and their interaction with surfactants.

  6. How does interfacial rheology govern soap bubble cluster dynamics?

    NASA Astrophysics Data System (ADS)

    Cohen-Addad, Sylvie; Biance, Anne-Laure; Hohler, Reinhard

    2009-11-01

    Aqueous foams are concentrated dispersions of gas bubbles in a soapy solution. These complex fluids exhibit solid-like or liquid-like mechanical behaviors, depending on the applied shear. When it is increased beyond a yield strain, neighbor switching bubble rearrangements called T1 events are triggered and plastic flow sets in. We study experimentally the dynamics of such strain induced T1s in 3D bubble clusters that we consider as model systems of 3D foams. To determine the hydrodynamics and physico-chemistry that set the duration of T1s, we use foaming solutions of a wide range of well characterized bulk and interfacial rheological properties. At low shear rates, the T1 duration is set by a balance between surface tension and surface viscous forces in qualitative agreement with previous studies of T1s in 2D foams [1] and we present a simple physical model that explains our 3D findings. Moreover, above a characteristic shear rate, rearrangement dynamics are driven by the applied strain. By combining all our results, we link the transition from intermittent to continous flow dynamics in foams to the rheology of the gas-liquid interfaces. [4pt] [1] M. Durand, H. A. Stone, Phys. Rev. Lett. 97, 2226101 (2006).

  7. Interfacial velocities and capillary pressure gradients during Haines jumps.

    PubMed

    Armstrong, Ryan T; Berg, Steffen

    2013-10-01

    Drainage is typically understood as a process where the pore space is invaded by a nonwetting phase pore-by-pore, the controlling parameters of which are represented by capillary number and mobility ratio. However, what is less understood and where experimental data are lacking is direct knowledge of the dynamics of pore drainage and the associated intrinsic time scales since the rate dependencies often observed with displacement processes are potentially dependent on these time scales. Herein, we study pore drainage events with a high speed camera in a micromodel system and analyze the dependency of interfacial velocity on bulk flow rate and spatial fluid configurations. We find that pore drainage events are cooperative, meaning that capillary pressure differences which extend over multiple pores directly affect fluid topology and menisci dynamics. Results suggest that not only viscous forces but also capillarity acts in a nonlocal way. Lastly, the existence of a pore morphological parameter where pore drainage transitions from capillary to inertial and/or viscous dominated is discussed followed by a discussion on capillary dispersion and time scale dependencies. We show that the displacement front is disperse when volumetric flow rate is less than the intrinsic time scale for a pore drainage event and becomes sharp when the flow rate is greater than the intrinsic time scale (i.e., overruns the pore drainage event), which clearly shows how pore-scale parameters influence macroscale flow behavior. PMID:24229279

  8. Effect of transcrystalline morphology on interfacial adhesion in biocomposites

    SciTech Connect

    Karlsson, J.; Hedenberg, P.; Felix, J.

    1995-12-01

    The efficient transfer of load from matrix to fibers is crucial for achieving good mechanical performance in composite materials. Much attention has been paid in recent years to producing strong bonds across fibers and matrix in composite materials. An attractive alternative to surface modification of fibers or the use of compatibilizing agents is creating molecular order at the interphase. In this study, the ability of natural cellulose fibers, such as cotton and wood fibers, to induce transcrystallinity in synthetic polymer such as polypropylene (PP), was utilized to create various interphase morphologies. The effect of trancrystalline layers of different thicknesses at the fiber interface on interfacial shear stress transfer was investigated using the single-fiber fragmentation test. It was found that the trancrystalline morphology at the fiber/matrix interface considerably improved the shear transfer. The fiber surface roughness as measured by Atomic Force Microscopy (AFM) as well as surface crystalline structure is proposed to be responsible for creating a favorable interphase morphology. The interphase morphology of a new generation of biodegradable composites based on celluse fiber-reinforced bacteria-produced polyhydroxybutyrate (PHB) is currently under investigation in our laboratories.

  9. Density-functional study of interfacial properties of colloid-polymer mixtures.

    PubMed

    Moncho-Jordá, A; Dzubiella, J; Hansen, J P; Louis, A A

    2005-04-14

    Interfacial properties of colloid-polymer mixtures are examined within an effective one-component representation, where the polymer degrees of freedom are traced out, leaving a fluid of colloidal particles interacting via polymer-induced depletion forces. Restriction is made to zero-, one-, and two-body effective potentials, and a free energy functional is used that treats colloid excluded volume correlations within Rosenfeld's fundamental measure theory, and depletion-induced attraction within first-order perturbation theory. This functional allows a consistent treatment of both ideal and interacting polymers. The theory is applied to surface properties near a hard wall, to the depletion interaction between two walls, and to the fluid-fluid interface of demixed colloid-polymer mixtures. The results of the present theory compare well with predictions of a fully two-component representation of mixtures of colloids and ideal polymers (the Asakura-Oosawa model) and allow a systematic investigation of the effects of polymer-polymer interactions on interfacial properties. In particular, the wall surface tension is found to be significantly larger for interacting than for ideal polymers, whereas the opposite trend is predicted for the fluid-fluid interfacial tension. PMID:16851746

  10. Interfacial stress affects rat alveolar type II cell signaling and gene expression.

    PubMed

    Hobi, Nina; Ravasio, Andrea; Haller, Thomas

    2012-07-01

    Previous work from our group (Ravasio A, Hobi N, Bertocchi C, Jesacher A, Dietl P, Haller T. Am J Physiol Cell Physiol 300: C1456-C1465, 2011.) showed that contact of alveolar epithelial type II cells with an air-liquid interface (I(AL)) leads to a paradoxical situation. It is a potential threat that can cause cell injury, but also a Ca(2+)-dependent stimulus for surfactant secretion. Both events can be explained by the impact of interfacial tensile forces on cellular structures. Here, the strength of this mechanical stimulus became also apparent in microarray studies by a rapid and significant change on the transcriptional level. Cells challenged with an I(AL) in two different ways showed activation/inactivation of cellular pathways involved in stress response and defense, and a detailed Pubmatrix search identified genes associated with several lung diseases and injuries. Altogether, they suggest a close relationship of interfacial stress sensation with current models in alveolar micromechanics. Further similarities between I(AL) and cell stretch were found with respect to the underlying signaling events. The source of Ca(2+) was extracellular, and the transmembrane Ca(2+) entry pathway suggests the involvement of a mechanosensitive channel. We conclude that alveolar type II cells, due to their location and morphology, are specific sensors of the I(AL), but largely protected from interfacial stress by surfactant release. PMID:22610352

  11. Interfacial stress affects rat alveolar type II cell signaling and gene expression

    PubMed Central

    Hobi, Nina; Ravasio, Andrea

    2012-01-01

    Previous work from our group (Ravasio A, Hobi N, Bertocchi C, Jesacher A, Dietl P, Haller T. Am J Physiol Cell Physiol 300: C1456–C1465, 2011.) showed that contact of alveolar epithelial type II cells with an air-liquid interface (IAL) leads to a paradoxical situation. It is a potential threat that can cause cell injury, but also a Ca2+-dependent stimulus for surfactant secretion. Both events can be explained by the impact of interfacial tensile forces on cellular structures. Here, the strength of this mechanical stimulus became also apparent in microarray studies by a rapid and significant change on the transcriptional level. Cells challenged with an IAL in two different ways showed activation/inactivation of cellular pathways involved in stress response and defense, and a detailed Pubmatrix search identified genes associated with several lung diseases and injuries. Altogether, they suggest a close relationship of interfacial stress sensation with current models in alveolar micromechanics. Further similarities between IAL and cell stretch were found with respect to the underlying signaling events. The source of Ca2+ was extracellular, and the transmembrane Ca2+ entry pathway suggests the involvement of a mechanosensitive channel. We conclude that alveolar type II cells, due to their location and morphology, are specific sensors of the IAL, but largely protected from interfacial stress by surfactant release. PMID:22610352

  12. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    NASA Astrophysics Data System (ADS)

    Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

    2015-02-01

    The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress-strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  13. Interfacial properties of binary mixtures of square-well molecules from Monte Carlo simulation.

    PubMed

    Martínez-Ruiz, F J; Blas, F J

    2016-04-21

    We determine the interfacial properties of mixtures of spherical square-well molecules from direct simulation of the vapor-liquid interface. We consider mixtures with the same molecular size and intermolecular potential range but different dispersive energy parameter values. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of mixtures of square-well molecules. In particular, we determine the pressuretensor using the mechanical (virial) route and the vapor-liquid interfacial tension evaluated using the Irving-Kirkwood method. In addition to the pressuretensor and the surface tension, we also obtain density profiles, coexistence densities, and interfacial thickness as functions of pressure, at a given temperature. This work can be considered as the extension of our previous work [F. J. Martínez-Ruiz and F. J. Blas, Mol. Phys. 113, 1217 (2015)] to deal with mixtures of spherical molecules that interact through a discontinuous intermolecular potential. According to our results, the main effect of increasing the ratio between the dispersive energy parameters of the mixture, ϵ22/ϵ11, is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative maximum in the density profiles of the more volatile component at the interface. This maximum is related with adsorption or accumulation of these molecules at the interface, since there are stronger attractive interactions between these molecules in comparison with the rest of intermolecular interactions. Also, the interfacial thickness decreases and the surface tension increases as ϵ22/ϵ11 is larger, a direct consequence of the increasing of the cohesive energy of the system. PMID:27389232

  14. Interfacial properties of binary mixtures of square-well molecules from Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Martínez-Ruiz, F. J.; Blas, F. J.

    2016-04-01

    We determine the interfacial properties of mixtures of spherical square-well molecules from direct simulation of the vapor-liquid interface. We consider mixtures with the same molecular size and intermolecular potential range but different dispersive energy parameter values. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of mixtures of square-well molecules. In particular, we determine the pressure tensor using the mechanical (virial) route and the vapor-liquid interfacial tension evaluated using the Irving-Kirkwood method. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, and interfacial thickness as functions of pressure, at a given temperature. This work can be considered as the extension of our previous work [F. J. Martínez-Ruiz and F. J. Blas, Mol. Phys. 113, 1217 (2015)] to deal with mixtures of spherical molecules that interact through a discontinuous intermolecular potential. According to our results, the main effect of increasing the ratio between the dispersive energy parameters of the mixture, ɛ22/ɛ11, is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative maximum in the density profiles of the more volatile component at the interface. This maximum is related with adsorption or accumulation of these molecules at the interface, since there are stronger attractive interactions between these molecules in comparison with the rest of intermolecular interactions. Also, the interfacial thickness decreases and the surface tension increases as ɛ22/ɛ11 is larger, a direct consequence of the increasing of the cohesive energy of the system.

  15. Optimization of residual stresses in MMC's through the variation of interfacial layer architectures and processing parameters

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Salzar, Robert S.

    1996-01-01

    The objective of this work was the development of efficient, user-friendly computer codes for optimizing fabrication-induced residual stresses in metal matrix composites through the use of homogeneous and heterogeneous interfacial layer architectures and processing parameter variation. To satisfy this objective, three major computer codes have been developed and delivered to the NASA-Lewis Research Center, namely MCCM, OPTCOMP, and OPTCOMP2. MCCM is a general research-oriented code for investigating the effects of microstructural details, such as layered morphology of SCS-6 SiC fibers and multiple homogeneous interfacial layers, on the inelastic response of unidirectional metal matrix composites under axisymmetric thermomechanical loading. OPTCOMP and OPTCOMP2 combine the major analysis module resident in MCCM with a commercially-available optimization algorithm and are driven by user-friendly interfaces which facilitate input data construction and program execution. OPTCOMP enables the user to identify those dimensions, geometric arrangements and thermoelastoplastic properties of homogeneous interfacial layers that minimize thermal residual stresses for the specified set of constraints. OPTCOMP2 provides additional flexibility in the residual stress optimization through variation of the processing parameters (time, temperature, external pressure and axial load) as well as the microstructure of the interfacial region which is treated as a heterogeneous two-phase composite. Overviews of the capabilities of these codes are provided together with a summary of results that addresses the effects of various microstructural details of the fiber, interfacial layers and matrix region on the optimization of fabrication-induced residual stresses in metal matrix composites.

  16. Instability due to interfacial tension in parallel liquid-liquid flow

    NASA Astrophysics Data System (ADS)

    Rodriguez, Oscar M. H.

    2016-06-01

    The frequent occurrence of multiphase flows in pipes has motivated a great research interest over the last decades. The particular case of liquid-liquid flow is commonly encountered in the petroleum industry, where a number of applications involve oil-water flow such as crude oil production in directional wells. However, it has not received the same attention when compared to gas-liquid flow. In addition, most of the available information has to do with flow in pipes. When it comes to flows in annular ducts the data are scanty. A general transition criterion has been recently proposed in order to obtain the stratified and core-annular flow-pattern transition boundaries in viscous oil-water flow. The proposed criterion was based on an one-dimensional two-fluid model of liquid-liquid two-phase flow. A stability analysis was carried out and interfacial tension is considered. A new destabilizing term arises, which is a function of the cross-section curvature of the interface. It is well accepted that interfacial tension favors the stable condition. However, the analysis of the new interfacial-tension term shows that it can actually destabilize the basic flow pattern, playing an important role in regions of extreme volumetric fractions. Such an interesting effect seems to be more pronounced in flows of viscous fluids and in annular-duct flow. The effect of interfacial tension is explored and the advantages of using a more complete model are discussed and illustrated through comparisons with experimental data from the literature. The evaluation of the effects of fluid viscosity and interfacial tension allows the correction and enhancement of transition models based essentially on data of pipe flow of low viscosity fluids.

  17. Critical-point analysis of the liquid-vapor interfacial surface tension

    NASA Technical Reports Server (NTRS)

    Salvino, R. E.

    1990-01-01

    The interfacial surface tension of the liquid-vapor system is analyzed near the critical point in a manner similar to bulk thermodynamic critical-point analyses. This is accomplished by a critical-point analysis of the single-phase hard-wall surface tension. Both a Landau expansion and a scaling theory equation of state are investigated. Some general exponent relations are derived and, in addition, some thermodynamically defined correlation lengths are discussed.

  18. Study of interfacial crack propagation in flip chip assemblies with nano-filled underfill materials

    NASA Astrophysics Data System (ADS)

    Mahalingam, Sakethraman

    No-flow underfill materials that cure during the solder reflow process is a relatively new technology. Although there are several advantages in terms of cost, time and processing ease, there are several reliability challenges associated with no-flow underfill materials. When mum-sized filler particles are introduced in no-flow underfills to enhance the solder bump reliability, such filler particles could prevent the solder bumps making reliable electrical contacts with the substrate pads during solder reflow, and therefore, the assembly yield would be adversely affected. The use of nano-sized filler particles can potentially improve assembly yield while offering the advantages associated with filled underfill materials. The objective of this thesis is to study the thermo-mechanical reliability of nano-filled epoxy underfills (NFU) through experiments and theoretical modeling. In this work, the thermo-mechanical properties of NFU's with 20-nm filler particles have been measured. An innovative residual stress test method has been developed to measure the interfacial fracture toughness. Using the developed residual stress method and the single-leg bending test, the mode-mixity-dependent fracture toughness for NFU-SiN interface has been determined. In addition to such monotonic interfacial fracture characterization, the interface crack propagation under thermo-mechanical fatigue loading has been experimentally characterized, and a model for fatigue interface crack propagation has been developed. A test vehicle comprising of several flip chips was assembled using the NFU material and the reliability of the flip-chip assemblies was assessed under thermal shock cycles between -40°C and 125°C. The NFU-SiN interfacial delamination propagation and the solder bump reliability were monitored. In parallel, numerical models were developed to study the interfacial delamination propagation in the flip chip assembly using conventional interfacial fracture mechanics as well as

  19. Labor Force

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2010

    2010-01-01

    The labor force is the number of people aged 16 or older who are either working or looking for work. It does not include active-duty military personnel or institutionalized people, such as prison inmates. Quantifying this total supply of labor is a way of determining how big the economy can get. Labor force participation rates vary significantly…

  20. One Force

    NASA Astrophysics Data System (ADS)

    Kotas, Ronald R.

    2002-04-01

    There is only one entity that can extend force and couple through space; and it should be apparent that Electromagnetism is that entity. In the cases of the nuclear strong force and the nuclear weak force, this is the same fundamental Electromagnetism manifesting itself in two different ways in the nucleus. It remains the same basic Electromagnetism. On the other hand, General Relativity fails to produce force at a distance, fails the Cavendish experiment, and does not allow an apple to fall to the ground. The result shows there is only Electromagnetism that functions through physical nature providing gravity, actions in the nucleus, as well as all other physical actions universally, including Gravity and Gravitation. There are many direct proofs of this, the same proofs as in NUCLEAR QUANTUM GRAVITATION. In contrast, General Relativity plainly relies on fallacy abstract and incoherent proofs; proofs which have now been mostly disproved. In the past it was deemed necessary by some to have an "ether" to propagate Electromagnetic waves. The fallacy concept of time space needs "space distortions" in order to cause gravity. However, Electromagnetic gravity does not have this problem. Clearly there is only ONE FORCE that causes Gravity, Electromagnetism, the Nuclear Strong Force, and the Nuclear Weak Force, and that ONE FORCE is Electromagnetism.

  1. Preface: Special Topic on Interfacial and Confined Water

    NASA Astrophysics Data System (ADS)

    Molinero, Valeria; Kay, Bruce D.

    2014-11-01

    This special topic on the chemical physics of interfacial and confined water contains a collection of original research papers that showcase recent theoretical and experimental advances in the field. These papers provide a timely discussion of fundamental aspects of interfacial and confined water that are important in both natural environments and engineered applications.

  2. Preface: Special Topic on Interfacial and Confined Water

    SciTech Connect

    Molinero, Valeria; Kay, Bruce D.

    2014-11-14

    This Special Topic on the Chemical Physics of Interfacial and Confined Water contains a collection of original research papers that showcase recent theoretical and experimental advances in the field. These papers provide a timely discussion of fundamental aspects of interfacial and confined water that are important in both natural environments and engineered applications.

  3. Strong interfacial attrition developed by oleate/layered double hydroxide nanoplatelets dispersed into poly(butylene succinate).

    PubMed

    Zhou, Qian; Verney, Vincent; Commereuc, Sophie; Chin, In-Joo; Leroux, Fabrice

    2010-09-01

    Poly(butylene succinate) (PBS) nanocomposite structure was studied as a function of the filler percentage loading. The resulting state of dispersion was evaluated by XRD and TEM, and the interfacial attrition between PBS chain and lamellar platelets by the melt rheological properties. Hybrid organic inorganic (O/I) layered double hydroxide (LDH) organo-modified by oleate anions was used as filler. It was found that the confinement supplied by the LDH framework forces the interleaved organic molecule to be more distant from each other than in the case of oleate salt, this having as an effect to decrease strongly the homonuclear intermolecular (1)H(1)H dipolar interaction. An additional consequence of this relatively free molecular rotation, affecting the (13)C CPMAS response as well, is to facilitate the delamination of the 2D-stacked layers during extrusion since an quasi-exfoliated PBS:Mg(2)Al/oleate structure is observed for filler loading lower than 5% w/w. This is in association to a non-linear viscoelasticity in the low-omega region and the observed shear-thinning tendency compares better than other PBS:silicate nanocomposite derivatives and is here explained by the presence of a percolated LDH nanoparticle network. Indeed the plastic deformation in the low-omega region is found to be restricted by well-dispersed LDH tactoids in association with a rather strong attrition phenomenon between tethered oleate anions and PBS chains. PMID:20605578

  4. Interfacial separation of a mature biofilm from a glass surface - A combined experimental and cohesive zone modelling approach.

    PubMed

    Safari, Ashkan; Tukovic, Zeljko; Cardiff, Philip; Walter, Maik; Casey, Eoin; Ivankovic, Alojz

    2016-02-01

    A good understanding of the mechanical stability of biofilms is essential for biofouling management, particularly when mechanical forces are used. Previous biofilm studies lack a damage-based theoretical model to describe the biofilm separation from a surface. The purpose of the current study was to investigate the interfacial separation of a mature biofilm from a rigid glass substrate using a combined experimental and numerical modelling approach. In the current work, the biofilm-glass interfacial separation process was investigated under tensile and shear stresses at the macroscale level, known as modes I and II failure mechanisms respectively. The numerical simulations were performed using a Finite Volume (FV)-based simulation package (OpenFOAM®) to predict the separation initiation using the cohesive zone model (CZM). Atomic force microscopy (AFM)-based retraction curve was used to obtain the separation properties between the biofilm and glass colloid at microscale level, where the CZM parameters were estimated using the Johnson-Kendall-Roberts (JKR) model. In this study CZM is introduced as a reliable method for the investigation of interfacial separation between a biofilm and rigid substrate, in which a high local stress at the interface edge acts as an ultimate stress at the crack tip.This study demonstrated that the total interfacial failure energy measured at the macroscale, was significantly higher than the pure interfacial separation energy obtained by AFM at the microscale, indicating a highly ductile deformation behaviour within the bulk biofilm matrix. The results of this study can significantly contribute to the understanding of biofilm detachments. PMID:26474034

  5. A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Miyazawa, Keisuke; Kobayashi, Naritaka; Watkins, Matthew; Shluger, Alexander L.; Amano, Ken-Ichi; Fukuma, Takeshi

    2016-03-01

    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.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

  6. Force sensor

    DOEpatents

    Grahn, Allen R.

    1993-01-01

    A force sensor and related method for determining force components. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

  7. Force sensor

    DOEpatents

    Grahn, A.R.

    1993-05-11

    A force sensor and related method for determining force components is described. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

  8. Scanning probe microscopies for the creation and characterization of interfacial architectures: Studies of alkyl thiolate monolayers at gold

    SciTech Connect

    Green, J.

    1997-01-10

    Scanning probe microscopy (SPM) offers access to the structural and material properties of interfaces, and when combined with macroscopic characterization techniques results in a powerful interfacial development tool. However, the relative infancy of SPM techniques has dictated that initial investigations concentrate on model interfacial systems as benchmarks for testing the control and characterization capabilities of SPM. One such family of model interfacial systems results from the spontaneous adsorption of alkyl thiols to gold. This dissertation examines the application of SPM to the investigation of the interfacial properties of these alkyl thiolate monolayers. Structural investigations result in a proposed explanation for counterintuitive correlations between substrate roughness and heterogeneous electron transfer barrier properties. Frictional measurements are used for characterization of the surface free energy of a series of end-group functionalized monolayers, as well as for the material properties of monolayers composed of varying chain length alkyl thiols. Additional investigations used these characterization techniques to monitor the real-time evolution of chemical and electrochemical surface reactions. The results of these investigations demonstrates the value of SPM technology to the compositional mapping of surfaces, elucidation of interfacial defects, creation of molecularly sized chemically heterogeneous architectures, as well as to the monitoring of surface reactions. However, it is the future which will demonstrate the usefulness of SPM technology to the advancement of science and technology.

  9. Mechanical implications of interfacial defects between femoral hip implants and cement: a finite element analysis of interfacial gaps and interfacial porosity.

    PubMed

    Scheerlinck, T; Broos, J; Janssen, D; Verdonschot, N

    2008-10-01

    Two types of defect between femoral hip implants and cement have been identified. Interfacial porosity arises from cement shrinkage during curing and presents as pores randomly located along the stem. Interfacial gaps are much larger stem-cement separations caused by air introduced during stem insertion. To investigate the mechanical consequences of both types of defect, a finite element analysis model was created on the basis of a computed tomography image of a Charnley-Kerboul stem, and alternating torsional and transverse loads were applied. The propagation of fatigue cracks within the cement and the rotational stability of the stem were assessed in models simulating increasing amounts of interfacial gaps and pores. Anterior gaps covering at least 30 per cent of the implant surface promoted cement cracks and destabilized the stem. Anterolateral gaps were less destabilizing, but had more potential to promote cracks. In both cases, cracks occurred mainly outside gap regions, in areas where the stem contacted the cement during cyclic loading. Although random interfacial pores did not destabilize the implant, they acted as crack initiators even at low fractions (10 per cent). In conclusion, random interfacial pores were more harmful for the cement mantle integrity than were larger regions of interfacial gaps, although gaps were more detrimental for the rotational stability of the stem. PMID:19024152

  10. Measuring Air-Water Interfacial Area via the Interfacial Partitioning Tracer Test Method

    NASA Astrophysics Data System (ADS)

    El Ouni, A.; Zhong, H.; Mainhagu, J.; Araujo, J. B.; Brusseau, M. L.

    2012-12-01

    Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (Aa-w). Two variations of the aqueous IPTT method are compared. One involves the standard approach comprising tracer injection under steady unsaturated-flow conditions with a uniform water-saturation distribution within the column. The other involves tracer injection under steady saturated-flowconditions in the presence of trapped residual air. Sodium dodecylbezenesulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning andnonreactive tracers, respectively. A sandy soil with a median grain diameter of 0.234 mm was used as the porous medium. Initial water saturation, Sw,was approximately 80%. Water saturation was monitored gravimetrically during the experiments. The results of the experiments will be assessed and compared to those of prior studies.

  11. Synergistic behaviour of ZnO nanoparticles and gemini surfactants on the dynamic and equilibrium oil/water interfacial tension.

    PubMed

    Fereidooni Moghadam, Tahereh; Azizian, Saeid; Wettig, Shawn

    2015-03-21

    In this work the effect of ZnO nanoparticles on the interfacial behaviour of gemini surfactants (12-3-12 and 14-3-14) at the oil/water interface was investigated. Equilibrium and dynamic interfacial tension in the absence and presence of ZnO was measured and compared. The results show that the synergistic interactions between the surfactants and nanoparticles decrease the interfacial tension beyond that observed for each component, alone. Modelling of dynamic data with two different models indicates that the mechanism of surfactant migration (with and without ZnO) is mixed diffusion-kinetic-control. The Gibbs free energy of micellization and the Gibbs free energy of adsorption in the absence and presence of ZnO were calculated and compared. Finally the effect of addition of ZnO nanoparticles on emulsion stability was also examined. PMID:25687519

  12. Influences of thermal annealing on P3HT/PCBM interfacial properties and charge dynamics in polymer solar cells

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng-En; Dinelli, Franco; Yu, Chen-Te; Shih, Hwa-Wei; Pei, Zingway; Chang, Chen-Shiung; Shih-Sen Chien, Forest

    2015-12-01

    The effects of thermal annealing on the interfacial properties of poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl C61 butyric acid methyl ester (PCBM) and on the charge dynamics in P3HT:PCBM polymer solar cells (PSCs) are investigated. This study determines that an effective phase separation of the P3HT and PCBM caused by thermal annealing achieves a larger interfacial area for efficient exciton dissociation and a well-defined pn junction with few defect levels at the P3HT/PCBM interface. Additionally, thermal annealing creates a compositional gradient across the P3HT:PCBM films, which enhances the charge transit ability significantly. These improved interfacial properties and efficiency in charge transit ability account for the better power conversion efficiency of P3HT:PCBM PSCs treated with thermal annealing.

  13. Interfacial Widths of Conjugated Polymer Bilayers

    SciTech Connect

    NCSU; UC Berkeley; UCSB; Advanced Light Source; Garcia, Andres; Yan, Hongping; Sohn, Karen E.; Hexemer, Alexander; Nguyen, Thuc-Quyen; Bazan, Guillermo C.; Kramer, Edward J.; Ade, Harald

    2009-08-13

    The interfaces of conjugated polyelectrolyte (CPE)/poly[2-methoxy-5-(2{prime}-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) bilayers cast from differential solvents are shown by resonant soft X-ray reflectivity (RSoXR) to be very smooth and sharp. The chemical interdiffusion due to casting is limited to less than 0.6 nm, and the interface created is thus nearly 'molecularly' sharp. These results demonstrate for the first time and with high precision that the nonpolar MEH-PPV layer is not much disturbed by casting the CPE layer from a polar solvent. A baseline is established for understanding the role of interfacial structure in determining the performance of CPE-based polymer light-emitting diodes. More broadly, we anticipate further applications of RSoXR as an important tool in achieving a deeper understanding of other multilayer organic optoelectronic devices, including multilayer photovoltaic devices.

  14. Orientational anisotropy and interfacial transport in polycrystals

    NASA Astrophysics Data System (ADS)

    Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

    2016-04-01

    Interfacial diffusion is governed to a large degree by geometric parameters that are determined by crystallographic orientation. In this study, we assess the impact of orientational anisotropy on mass transport at internal interfaces, focusing on the role of preferred crystallographic orientation (i.e., texture) on mass diffusion in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion for polycrystals having various grain-orientation distributions. By relating grain misorientation to grain-boundary energies and, via the Borisov relation, to the diffusivity, we link microstructure variability to kinetics. Our aim is to correlate shape features of the orientation distribution, such as the location and shapes of peaks, with the calculated effective diffusivity. Finally, we discuss the role of crystallographic constraints, such as those associated with grain junctions, in determining the effective diffusivity of a polycrystal.

  15. Mapping interfacial excess in atom probe data.

    PubMed

    Felfer, Peter; Scherrer, Barbara; Demeulemeester, Jelle; Vandervorst, Wilfried; Cairney, Julie M

    2015-12-01

    Using modern wide-angle atom probes, it is possible to acquire atomic scale 3D data containing 1000 s of nm(2) of interfaces. It is therefore possible to probe the distribution of segregated species across these interfaces. Here, we present techniques that allow the production of models for interfacial excess (IE) mapping and discuss the underlying considerations and sampling statistics. We also show, how the same principles can be used to achieve thickness mapping of thin films. We demonstrate the effectiveness on example applications, including the analysis of segregation to a phase boundary in stainless steel, segregation to a metal-ceramic interface and the assessment of thickness variations of the gate oxide in a fin-FET. PMID:26346774

  16. Control of interfacial instabilities using flow geometry

    NASA Astrophysics Data System (ADS)

    Al-Housseiny, Talal T.; Tsai, Peichun A.; Stone, Howard A.

    2012-10-01

    The displacement of one fluid by another is one of the most common processes involving interfacial instabilities. It is universally accepted that, in a uniform medium, flow displacement is unstable when a low-viscosity fluid invades a fluid of higher viscosity: the classical viscous fingering instability. Consequently, once fluid properties are specified, opportunities for control become very limited. However, real systems where displacement instabilities occur, such as porous structures, lung airways and printing devices, are rarely uniform. We find that the simplest heterogeneity--a gradient in the flow passage--can lead to fundamentally different displacement behaviours. We use this finding to either inhibit or trigger an instability and, hence, to devise a strategy to manipulate instabilities in fluid-fluid systems. The control setting we identify has a wide spectrum of applications ranging from small-scale technologies such as microfluidics to large-scale operations such as enhanced oil recovery.

  17. Nucleation and interfacial adsorption in ternary systems.

    PubMed

    Philippe, T

    2015-03-01

    Nucleation is studied in incompressible ternary fluids by examining the topology of the overall landscape of the energy surface. Minimum free energy paths for nucleation (MFEPs) of a single nucleus in an infinite matrix are computed with the string method in the framework of the continuum theory of nucleation for the regular solution. Properties of the critical nucleus are compared with the predictions of the classical nucleation theory. MFEPs are found to exhibit complex nucleation pathways with non-monotonic variations of compositions in the interfacial region, specifically adsorption of a component. In the symmetric regular solution, the minority component is found to segregate at the interface during nucleation with a concomitant depletion of the nucleus core, resulting in unpredicted partition of the non-selective component. Despite increasing the gradient energy, such inhomogeneity in composition is shown to lower the nucleation barrier. PMID:25747088

  18. Wear and interfacial transport of material

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1975-01-01

    Bonding across the interface for two solids in contact and the subsequent transfer of material from one surface to another is a direct result of the interfacial bonds being stronger than the cohesive bonds in either of the two solids. Surface tools such as LEED, Auger emission spectroscopy, field ion microscopy, and the atom probe are used to examine adhesive contacts and to determine the direction, nature, quantity of material transfer and properties of the solids which effect transfer and wear. The electronic nature, cohesive binding energies, surface structure, lattice disregistry and distribution of species in surface layers are all found to effect adhesion and transfer or transport for clean surfaces in solid state contact. The influence of adsorbed and reacted surface films from fractions of a monolayer to multilayer reactive films are considered. It is shown that even fractions of a monolayer of surface active species such as oxygen and sulfur can markedly inhibit adhesion and transport.

  19. Liquid-liquid interfacial nanoparticle assemblies

    DOEpatents

    Emrick, Todd S.; Russell, Thomas P.; Dinsmore, Anthony; Skaff, Habib; Lin, Yao

    2008-12-30

    Self-assembly of nanoparticles at the interface between two fluids, and methods to control such self-assembly process, e.g., the surface density of particles assembling at the interface; to utilize the assembled nanoparticles and their ligands in fabrication of capsules, where the elastic properties of the capsules can be varied from soft to tough; to develop capsules with well-defined porosities for ultimate use as delivery systems; and to develop chemistries whereby multiple ligands or ligands with multiple functionalities can be attached to the nanoparticles to promote the interfacial segregation and assembly of the nanoparticles. Certain embodiments use cadmium selenide (CdSe) nanoparticles, since the photoluminescence of the particles provides a convenient means by which the spatial location and organization of the particles can be probed. However, the systems and methodologies presented here are general and can, with suitable modification of the chemistries, be adapted to any type of nanoparticle.

  20. Interfacial tension analysis of oligo(ethylene glycol)-terminated self-assembled monolayers and their resistance to bacterial attachment.

    PubMed

    Ista, Linnea K; López, Gabriel P

    2012-09-01

    The fouling resistance of oligo(ethylene glycol) (OEG)-terminated self-assembled monolayers (SAMs) of alkanethiolates on gold has been well established. Although hydration of the OEG chains seems key to OEG-SAM resistance to macromolecular adsorption and cellular attachment, the details of how hydration prevents biofouling have been inferred largely through computational methods. Because OEG-SAMs of different lengths exhibit differing degrees of fouling resistance, the interactions between water and OEG-SAMs leading to fouling resistance can be deduced by comparing the properties of fouling and nonfouling OEG-SAMs. While all OEG-SAMs had similar water contact angles, contact angles taken with glycerol were able to individuate between different OEG-SAMs and between fouling and nonfouling OEG-SAMs. Subsequent estimation of surface and interfacial tension using a colloidal model showed that nonfouling surfaces are associated with an increased negative interfacial tension between those OEG-SAMs that resisted attachment and water. Further analysis of this interfacial tension experimentally confirmed current mathematical models that cite OEG-water hydrogen-bond formation as a driving force behind short-term fouling resistance. Finally, we found a correlation between solid-water interfacial tension and packing density and molecular density of ethylene glycol. PMID:22891854

  1. Interfacial activity and leaching patterns of Leptospirillum ferrooxidans on pyrite.

    PubMed

    Rojas-Chapana, José A; Tributsch, Helmut

    2004-01-01

    The leaching ability of Leptospirillum ferrooxidans goes beyond the mere oxidation of Fe(2+) to Fe(3+). Addition of these bacteria to pyrite triggers interfacial phenomena that lead to bacterial attachment and local forms of corrosion (surface pitting). As the leaching process proceeds, bacterial cells undergo changes, characterized by the release of extracellular polymeric substances (EPS) and the uptake and storage of electro-dense nanoparticles. The latter are embedded in an exopolymeric capsule, which coats the bacterial surface leading to distinctive biomineralized assemblages. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, quantitative energy-dispersive X-ray measurements and electron diffraction established that the embedded electron-dense nanoparticles comprise pyrite with a well-defined stoichiometry. Addition of Fe(3+) alone did not induce any form of local corrosion on pyrite, which indicates that the reactions taking place between the attached bacteria and the underlying pyrite surface are responsible for the leaching patterns observed in this study. The observed corrosion process resembles that of 'electrochemical machining', because it uses a corrosion promoter, namely the locally concentrated Fe(3+) in the biofilm environment, formed by the attached cells. PMID:19712343

  2. Interfacial electron and phonon scattering processes in high-powered nanoscale applications.

    SciTech Connect

    Hopkins, Patrick E.

    2011-10-01

    The overarching goal of this Truman LDRD project was to explore mechanisms of thermal transport at interfaces of nanomaterials, specifically linking the thermal conductivity and thermal boundary conductance to the structures and geometries of interfaces and boundaries. Deposition, fabrication, and post possessing procedures of nanocomposites and devices can give rise to interatomic mixing around interfaces of materials leading to stresses and imperfections that could affect heat transfer. An understanding of the physics of energy carrier scattering processes and their response to interfacial disorder will elucidate the potentials of applying these novel materials to next-generation high powered nanodevices and energy conversion applications. An additional goal of this project was to use the knowledge gained from linking interfacial structure to thermal transport in order to develop avenues to control, or 'tune' the thermal transport in nanosystems.

  3. Interfacial spin-orbit torque without bulk spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Emori, Satoru; Nan, Tianxiang; Belkessam, Amine M.; Wang, Xinjun; Matyushov, Alexei D.; Babroski, Christopher J.; Gao, Yuan; Lin, Hwaider; Sun, Nian X.

    2016-05-01

    An electric current in the presence of spin-orbit coupling can generate a spin accumulation that exerts torques on a nearby magnetization. We demonstrate that, even in the absence of materials with strong bulk spin-orbit coupling, a torque can arise solely due to interfacial spin-orbit coupling, namely, Rashba-Eldestein effects at metal/insulator interfaces. In magnetically soft NiFe sandwiched between a weak spin-orbit metal (Ti) and insulator (Al2O3 ), this torque appears as an effective field, which is significantly larger than the Oersted field and qualitatively modified by inserting an additional layer between NiFe and Al2O3 . Our findings point to unconventional routes for tuning spin-orbit torques by engineering interfacial electric dipoles.

  4. The Role of Structural Defects and Interfacial Instabilities in the Growth Behaviour of Paracetamol

    NASA Astrophysics Data System (ADS)

    Ristic, R. I.

    The role of structural defects and interfacial instabilities in the growth behaviour of small paracetamol crystals grown from pure aqueous solution and in the presence of p-acetoxy acetanalide (PAA) were investigated. The average growth rates obtained from growth rate distributions were used to predict morphological behaviour of an assembly of small crystals versus supersaturation. It was shown that columnar shape was formed in regions of low supersaturation while a plate like form prevailed at high supersaturations. An addition of PAA led to the development of columnar crystals with an aspect ratio which varied with impurity level. Using modern optical microscopy and X-ray topography it was shown that phenomena such as interfacial instabilities accompanied by formation of inclusions and dislocations in the {110} growth sectors are the key issues for defining particle morphology, size distribution and crystal purity.

  5. Interfacial properties of as-received and coated SiC (SCS-6) fiber reinforced reaction-formed SiC matrix composites

    SciTech Connect

    Gaeta, P.J.; Sisson, R.D. Jr.; Singh, M.; Eldridge, J.I.

    1995-10-01

    The possibility of improving the interfacial shear strength of the SiC fiber reinforced SiC matrix composite system was examined. A ceramic fiber coating was chosen based on availability and chemical stability with the fiber and matrix. Fiber push-out tests conducted on as-received and coated fiber reinforced composite samples allowed characterization of the interfacial shear strength. Average debond shear and frictional sliding stresses were calculated. The effects of sample thickness and second phase addition in the matrix were also evaluated. Tested samples were examined by SEM to determine the location of the interfacial failure and to determine if any interface reactions had occurred. The coating was then evaluated based on the resulting interfacial shear strength, failure location, and integrity of the interface as compared to those properties of samples reinforced with as-received fibers.

  6. Interfacial degradation effects of aqueous solution-processed molybdenum trioxides on the stability of organic solar cells evaluated by a differential method

    SciTech Connect

    Lou, Yan-Hui; Wang, Zhao-Kui E-mail: lsliao@suda.edu.cn; Yuan, Da-Xing; Liao, Liang-Sheng E-mail: lsliao@suda.edu.cn; Okada, Hiroyuki

    2014-09-15

    The authors investigate the influence of two hole interfacial materials poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) and aqueous solution-processed MoO{sub 3} (sMoO{sub 3}) on cell stability. sMoO{sub 3}-based device demonstrated obviously improved stability compared to PEDOT:PSS-based one. Current-voltage characteristics analysis is carried out to investigate the effect of the hole interfacial layers on the cell stability. The formation of additional trap states at the interfaces between the hole interfacial layer and the active layer in degraded devices is verified by a differential method. Improved cell stability is attributed to a relatively stable sMoO{sub 3} interfacial layer compared to PEDOT:PSS by comparing their different trap states distributions.

  7. Interfacial dislocation motion and interactions in single-crystal superalloys

    SciTech Connect

    Liu, B.; Raabe, D.; Roters, F.; Arsenlis, A.

    2014-10-01

    The early stage of high-temperature low-stress creep in single-crystal superalloys is characterized by the rapid development of interfacial dislocation networks. Although interfacial motion and dynamic recovery of these dislocation networks have long been expected to control the subsequent creep behavior, direct observation and hence in-depth understanding of such processes has not been achieved. Incorporating recent developments of discrete dislocation dynamics models, we simulate interfacial dislocation motion in the channel structures of single-crystal superalloys, and investigate how interfacial dislocation motion and dynamic recovery are affected by interfacial dislocation interactions and lattice misfit. Different types of dislocation interactions are considered: self, collinear, coplanar, Lomer junction, glissile junction, and Hirth junction. The simulation results show that strong dynamic recovery occurs due to the short-range reactions of collinear annihilation and Lomer junction formation. The misfit stress is found to induce and accelerate dynamic recovery of interfacial dislocation networks involving self-interaction and Hirth junction formation, but slow down the steady interfacial motion of coplanar and glissile junction forming dislocation networks. The insights gained from these simulations on high-temperature low-stress creep of single-crystal superalloys are also discussed.

  8. Interfacial Aspects of Polymer Based Photovoltaic Structures

    NASA Astrophysics Data System (ADS)

    Russell, Thomas

    2011-03-01

    Controlling thin film morphology is key in optimizing the efficiency of polymer-based photovoltaic (PV) devices. Poly(3- hexylthiophene) and [6,6]-penyl-C61 butyric acid methyl ester (P3HT:PCBM) based solar cell performance is dictated by nanostructure of the active layer, the interfaces between the active layer and the electrodes, and the P3HT chain orientation in the thin film. The above parameters were systematically studied by scanning transmission electron microscopy, scanning force microscopy, optical microscopy, grazing incident angle x- ray diffraction., dynamic secondary ion mass spectroscopy and near edge x-ray absorption fine structure analysis. The influence of thermal annealing on the morphology, interfaces and crystal structure was investigated in films that were either initially confined by two electrodes or confined by only one electrode. While the bulk morphology in these films were identical, significant differences in the concentration of components at the electrode interfaces were found, giving rise to a marked difference in performance. In addition, a model was established, based on the crystallization of the P3HTand the diffusion of the PCBM to describe the origins of the nanoscale morphology found in the active layer. The device performance parameters were quantitatively studied. In collaboration with D. Chen, H. Liu, Y. Gu and F. Lu at UMass Amherst, A. Nakahara at Kuraray Co., D. Wei at Carl Zeiss NTS LLC, D. Nordlund at SSRL and supported by the DOE-supported EFRC at the UMass Amherst (DE-PS02-08ER15944).

  9. Propagating phase interface with intermediate interfacial phase: Phase field approach

    NASA Astrophysics Data System (ADS)

    Momeni, Kasra; Levitas, Valery I.

    2014-05-01

    An advanced three-phase phase field approach (PFA) is suggested for a nonequilibrium phase interface that contains an intermediate phase, in particular, a solid-solid interface with a nanometer-sized intermediate melt (IM). A thermodynamic potential in the polar order parameters is developed that satisfies all thermodynamic equilibrium and stability conditions. The special form of the gradient energy allowed us to include the interaction of two solid-melt interfaces via an intermediate melt and obtain a well-posed problem and mesh-independent solutions. It is proved that for stationary 1D solutions to two Ginzburg-Landau equations for three phases, the local energy at each point is equal to the gradient energy. Simulations are performed for β ↔δ phase transformations (PTs) via IM in an HMX energetic material. The obtained energy IM width dependence is described by generalized force-balance models for short- and long-range interaction forces between interfaces but not far from the melting temperature. A force-balance model is developed that describes phase field results even 100 K below the melting temperature. The effects of the ratios of width and energies of solid-solid and solid-melt interfaces, temperature, and the parameter characterizing interaction of two solid-melt interfaces, on the structure, width, energy of the IM and interface velocity are determined by finite element method. Depending on parameters, the IM may appear by continuous or discontinuous barrierless disordering or via critical nucleus due to thermal fluctuations. The IM may appear during heating and persist during cooling at temperatures well below than it follows from sharp-interface approach. On the other hand, for some parameters when IM is expected, it does not form, producing an IM-free gap. The developed PFA represents a quite general three-phase model and can be extended to other physical phenomena, such as martensitic PTs, surface-induced premelting and PTs, premelting

  10. A polymeric flame retardant additive for rubbers

    SciTech Connect

    Ghosh, S.N.; Maiti, S.

    1993-12-31

    Synthesis of a polyphosphonate by the interfacial polymerization of bisphenol-A (BPA) and dichloro-phenyl phosphine oxide (DCPO) using cetyltrimethyl ammonium chloride (TMAC) as phase transfer catalyst (PTC) was reported. The polyphosphonate was characterized by elemental analysis, IR, TGA, DSC and 1H-NMR spectroscopy. The flame retardancy of the polymer was done by OI study. The polymer was used as a fire retardant additive to rubbers such as natural rubber (NR), styrene-butadiene rubber(SBR), nitrile rubber (NBR) and chloroprene rubber (CR). The efficiency of the fire retardant property of this additive was determined by LOI measurements of the various rubber samples.

  11. Interfacial Assembly of Graphene Oxide Sheets

    NASA Astrophysics Data System (ADS)

    Cote, Laura J.

    Scientific interest in graphene oxide (GO) sheets, the product of chemical oxidation and exfoliation of graphite powder, has resurged in recent years because GO is considered a promising precursor for the bulk production of graphene-based sheets for a variety of applications. In addition, GO can be viewed as an unconventional type of soft material as it is characterized by two abruptly different length scales. Its thickness is of typical molecular dimensions, measured to be about 1 nm by atomic force microscopy, but its lateral dimensions are that of common colloidal particles, ranging from nanometers to tens of microns. This high anisotropy leads to interesting fundamental colloidal interactions between the soft sheets which have practical implications in the solution processing and assembly of the material. This research therefore aims to use a variety of techniques to control these inter-sheet interactions to gain an understanding of the processing-structure relationships which ultimately determine the overall properties of the bulk GO assembly. GO is identified as a two-dimensional amphiphile with a unique edge-to-center arrangement of hydrophilic and hydrophobic groups, which has led to the demonstration of its pH- and size-dependent surface activity. The water surface is then utilized, as in the Langmuir-Blodgett technique, as an ideal substrate to tile up the GO sheets and study the interactions between them. Sheet-sheet interaction morphologies were successfully altered between wrinkled and overlapped states by pH tuning of sheet charge density, and the resulting structure-property relationships are explored. In addition, a novel flash-reduction and assembly process is described in which a simple photographic camera flash can rapidly and cleanly turn an insulating, well-stacked GO paper to a more open and fluffy conducting film. Lastly, the use of these research results as educational outreach platforms is highlighted. A variety of outlets, such as You

  12. Interfacial tension in immiscible mixtures of alkali halides.

    PubMed

    Lockett, Vera; Rukavishnikova, Irina V; Stepanov, Victor P; Tkachev, Nikolai K

    2010-02-01

    The interfacial tension of the liquid-phase interface in seven immiscible reciprocal ternary mixtures of lithium fluoride with the following alkali halides: CsCl, KBr, RbBr, CsBr, KI, RbI, and CsI was measured using the cylinder weighing method over a wide temperature range. It was shown that for all mixtures the interfacial tension gradually decreases with growing temperature. The interfacial tension of the reciprocal ternary mixtures at a given temperature increases both with the alkali cation radius (K(+) < Rb(+) < Cs(+)) and with the radius of the halogen anion (Cl(-) < Br(-) < I(-)). PMID:20094678

  13. Probing Interfacial Water on Nanodiamonds in Colloidal Dispersion.

    PubMed

    Petit, Tristan; Yuzawa, Hayato; Nagasaka, Masanari; Yamanoi, Ryoko; Osawa, Eiji; Kosugi, Nobuhiro; Aziz, Emad F

    2015-08-01

    The structure of interfacial water layers around nanoparticles dispersed in an aqueous environment may have a significant impact on their reactivity and on their interaction with biological species. Using transmission soft X-ray absorption spectroscopy in liquid, we demonstrate that the unoccupied electronic states of oxygen atoms from water molecules in aqueous colloidal dispersions of nanodiamonds have a different signature than bulk water. X-ray absorption spectroscopy can thus probe interfacial water molecules in colloidal dispersions. The impacts of nanodiamond surface chemistry and concentration on interfacial water electronic signature are discussed. PMID:26267179

  14. Interfacial Micromechanics in Fibrous Composites: Design, Evaluation, and Models

    PubMed Central

    Lei, Zhenkun; Li, Xuan; Qin, Fuyong; Qiu, Wei

    2014-01-01

    Recent advances of interfacial micromechanics in fiber reinforced composites using micro-Raman spectroscopy are given. The faced mechanical problems for interface design in fibrous composites are elaborated from three optimization ways: material, interface, and computation. Some reasons are depicted that the interfacial evaluation methods are difficult to guarantee the integrity, repeatability, and consistency. Micro-Raman study on the fiber interface failure behavior and the main interface mechanical problems in fibrous composites are summarized, including interfacial stress transfer, strength criterion of interface debonding and failure, fiber bridging, frictional slip, slip transition, and friction reloading. The theoretical models of above interface mechanical problems are given. PMID:24977189

  15. Vacuum force

    NASA Astrophysics Data System (ADS)

    Han, Yongquan

    2015-03-01

    To study on vacuum force, we must clear what is vacuum, vacuum is a space do not have any air and also ray. There is not exist an absolute the vacuum of space. The vacuum of space is relative, so that the vacuum force is relative. There is a certain that vacuum vacuum space exists. In fact, the vacuum space is relative, if the two spaces compared to the existence of relative vacuum, there must exist a vacuum force, and the direction of the vacuum force point to the vacuum region. Any object rotates and radiates. Rotate bend radiate- centripetal, gravity produced, relative gravity; non gravity is the vacuum force. Gravity is centripetal, is a trend that the objects who attracted wants to Centripetal, or have been do Centripetal movement. Any object moves, so gravity makes the object curve movement, that is to say, the radiation range curve movement must be in the gravitational objects, gravity must be existed in non vacuum region, and make the object who is in the region of do curve movement (for example: The earth moves around the sun), or final attracted in the form gravitational objects, and keep relatively static with attract object. (for example: objects on the earth moves but can't reach the first cosmic speed).

  16. Interfacial Engineering for Highly Efficient-Conjugated Polymer-Based Bulk Heterojunction Photovoltaic Devices

    SciTech Connect

    Alex Jen; David Ginger; Christine Luscombe; Hong Ma

    2012-04-02

    The aim of our proposal is to apply interface engineering approach to improve charge extraction, guide active layer morphology, improve materials compatibility, and ultimately allow the fabrication of high efficiency tandem cells. Specifically, we aim at developing: i. Interfacial engineering using small molecule self-assembled monolayers ii. Nanostructure engineering in OPVs using polymer brushes iii. Development of efficient light harvesting and high mobility materials for OPVs iv. Physical characterization of the nanostructured systems using electrostatic force microscopy, and conducting atomic force microscopy v. All-solution processed organic-based tandem cells using interfacial engineering to optimize the recombination layer currents vi. Theoretical modeling of charge transport in the active semiconducting layer The material development effort is guided by advanced computer modeling and surface/ interface engineering tools to allow us to obtain better understanding of the effect of electrode modifications on OPV performance for the investigation of more elaborate device structures. The materials and devices developed within this program represent a major conceptual advancement using an integrated approach combining rational molecular design, material, interface, process, and device engineering to achieve solar cells with high efficiency, stability, and the potential to be used for large-area roll-to-roll printing. This may create significant impact in lowering manufacturing cost of polymer solar cells for promoting clean renewable energy use and preventing the side effects from using fossil fuels to impact environment.

  17. Kinetic pathway for interfacial electron transfer from a semiconductor to a molecule.

    PubMed

    Hu, Ke; Blair, Amber D; Piechota, Eric J; Schauer, Phil A; Sampaio, Renato N; Parlane, Fraser G L; Meyer, Gerald J; Berlinguette, Curtis P

    2016-09-01

    Molecular approaches to solar-energy conversion require a kinetic optimization of light-induced electron-transfer reactions. At molecular-semiconductor interfaces, this optimization has previously been accomplished through control of the distance between the semiconductor donor and the molecular acceptor and/or the free energy that accompanies electron transfer. Here we show that a kinetic pathway for electron transfer from a semiconductor to a molecular acceptor also exists and provides an alternative method for the control of interfacial kinetics. The pathway was identified by the rational design of molecules in which the distance and the driving force were held near parity and only the geometric torsion about a xylyl- or phenylthiophene bridge was varied. Electronic coupling through the phenyl bridge was a factor of ten greater than that through the xylyl bridge. Comparative studies revealed a significant bridge dependence for electron transfer that could not be rationalized by a change in distance or driving force. Instead, the data indicate an interfacial electron-transfer pathway that utilizes the aromatic bridge orbitals. PMID:27554412

  18. Interface feature characterization and Schottky interfacial layer confirmation of TiO2 nanotube array film

    NASA Astrophysics Data System (ADS)

    Li, Hongchao; Tang, Ningxin; Yang, Hongzhi; Leng, Xian; Zou, Jianpeng

    2015-11-01

    We report here characterization of the interfacial microstructure and properties of titanium dioxide (TiO2) nanotube array films fabricated by anodization. Field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), nanoindentation, atomic force microscopy (AFM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the interface of the film. With increasing annealing temperature from 200 °C to 800 °C, the interfacial fusion between the film and the Ti substrate increased. The phase transformation of the TiO2 nanotube film from amorphous to anatase to rutile took place gradually; as the phase transformation progressed, the force needed to break the film increased. The growth of TiO2 nanotube arrays occurs in four stages: barrier layer formation, penetrating micropore formation, regular nanotube formation, and nanofiber formation. The TiO2 nanotubes grow from the Schottky interface layer rather than from the Ti substrate. The Schottky interface layer's thickness of 35-45 nm was identified as half the diameter of the corresponding nanotube, which shows good agreement to the Schottky interface layer growth model. The TiO2 nanotube film was amorphous and the Ti substrate was highly crystallized with many dislocation walls.

  19. Causal reasoning with forces

    PubMed Central

    Wolff, Phillip; Barbey, Aron K.

    2015-01-01

    Causal composition allows people to generate new causal relations by combining existing causal knowledge. We introduce a new computational model of such reasoning, the force theory, which holds that people compose causal relations by simulating the processes that join forces in the world, and compare this theory with the mental model theory (Khemlani et al., 2014) and the causal model theory (Sloman et al., 2009), which explain causal composition on the basis of mental models and structural equations, respectively. In one experiment, the force theory was uniquely able to account for people's ability to compose causal relationships from complex animations of real-world events. In three additional experiments, the force theory did as well as or better than the other two theories in explaining the causal compositions people generated from linguistically presented causal relations. Implications for causal learning and the hierarchical structure of causal knowledge are discussed. PMID:25653611

  20. Nano Sized Powder Additives of SiC and Diamond to MgB2 as Artificially Inductor of Pinning Force for the Dense Samples Obtained by High Pressure Technologies

    NASA Astrophysics Data System (ADS)

    Morawski, A.; Pachla, W.; Kuzmenko, D.; Łada, T.; Zaleski, A.; Eibl, O.; Haessler, W.; Kovac, P.

    2006-09-01

    The nano-powder additives of SiC (11nm) and diamond (6 nm) were mixed with Mg and amorphous B powders in the production route of MgB2 bulk and wires samples. Special attention was paid to the precursor powders with the respect to chemical purity, grain morphology and secondary phases. Commercially available MgB2 powders (ex-situ technology) and also mixtures of MgH2 and amorphous B powders (in-situ technology) were applied as the starting precursors. Electron microscopy was used extensively for the characterization of these powders applying both SEM and TEM analysis. Superconducting bulks and wires samples have been produced, by hot pressing, hot isostatic pressing and hydrostatic extrusion processes. High grain refinement and density in the final wire samples have been achieved by the severe plastic deformation (reduction over 99.98%) with the use of the cumulative (multi-step) hydrostatic extrusion. Superconducting properties of these samples were measured, with particular attention paid to the Jc(B) characteristics. Critical currents at lower and higher magnetic fields depended sensitively on the amount of the additives and grain refinement. TEM imaging and electron spectroscopic imaging were used to evaluate the size and distribution of the both of additives within the microstructure. The strain field of the additives resulted from the misfit in thermal expansion coefficient between the additives and the MgB2 matrix was imaged in bright and dark field TEM and is particularly important for the flux-pinning properties of these materials. Influence of such synthesis parameters as pressure, temperature and time on the superconducting properties and the morphology of the products were examined and obtained results were compared. This allowed to choose the optimal conditions for the improvement of the bulk MgB2 characteristics of the wire samples.

  1. Interfacial tension based on-chip extraction of microparticles confined in microfluidic Stokes flows

    NASA Astrophysics Data System (ADS)

    Huang, Haishui; He, Xiaoming

    2014-10-01

    Microfluidics involving two immiscible fluids (oil and water) has been increasingly used to produce hydrogel microparticles with wide applications. However, it is difficult to extract the microparticles out of the microfluidic Stokes flows of oil that have a Reynolds number (the ratio of inertia to viscous force) much less than one, where the dominant viscous force tends to drive the microparticles to move together with the surrounding oil. Here, we present a passive method for extracting hydrogel microparticles in microfluidic Stokes flow from oil into aqueous extracting solution on-chip by utilizing the intrinsic interfacial tension between oil and the microparticles. We further reveal that the thickness of an "extended confining layer" of oil next to the interface between oil and aqueous extracting solution must be smaller than the radius of microparticles for effective extraction. This method uses a simple planar merging microchannel design that can be readily fabricated and further integrated into a fluidic system to extract microparticles for wide applications.

  2. X-Ray Diffraction Studies of Interfacial Roughness in Multilayer Thin Films.

    NASA Astrophysics Data System (ADS)

    Phang, Yew Hoong

    1995-01-01

    Multilayer thin films have many interesting and potentially useful properties. Defects can affect the performance of multilayers. Interfacial roughness is an imperfection that is always present in multilayers. The work investigates multilayer interfacial roughness quantitatively using x-ray diffraction (XRD). Specifically, it focuses on (1) developing new ways of using diffuse-intensity XRD to measure quantitatively interfacial roughness in multilayers and (2) correlating roughness information obtained from XRD with the possible origins of roughness. Interfacial roughness in amorphous W/C multilayers and crystalline Si_{1-x}Ge_{x }/Si multilayers on vicinal Si(001) substrates grown by sputter deposition and molecular beam epitaxy respectively is explored using x-ray scattering. By performing appropriate measurements of scattered x-ray intensity, it is possible to measure, in addition to values of magnitudes of interfacial roughness, magnitude of correlated roughness and its lateral correlation length, the degree of correlation between roughness in different interfaces, and the symmetry of correlated roughness with respect to substrate orientation and substrate miscut. In the W/C multilayers prepared under standard conditions, the correlation of roughness in different interfaces is isotropic but incomplete, and can be described by a simple phenomenological model. Using a cumulative roughness function, we identify the wavelength range in which the roughness predominates in these layers and we show that the long-wavelength roughness replicates better than the short-wavelength roughness. In the Si _{1-x}Ge_{x }/Si multilayers, correlated interfacial roughness is highly anisotropic and is aligned with respect to the substrate miscut direction. The lateral length scale of the anisotropic correlated roughness is many times greater than the average separation of the substrate steps. The existence of the anisotropic correlated roughness depends on the Ge concentration in

  3. Development of a Front Tracking Method for Two-Phase Micromixing of Incompressible Viscous Fluids with Interfacial Tension in Solvent Extraction

    SciTech Connect

    Zhou, Yijie; Lim, Hyun-Kyung; de Almeida, Valmor F; Navamita, Ray; Wang, Shuqiang; Glimm, James G; Li, Xiao-lin; Jiao, Xiangmin

    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 development 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.

  4. Interfacial patterns in magnetorheological fluids: Azimuthal field-induced structures

    NASA Astrophysics Data System (ADS)

    Dias, Eduardo O.; Lira, Sérgio A.; Miranda, José A.

    2015-08-01

    Despite their practical and academic relevance, studies of interfacial pattern formation in confined magnetorheological (MR) fluids have been largely overlooked in the literature. In this work, we present a contribution to this soft matter research topic and investigate the emergence of interfacial instabilities when an inviscid, initially circular bubble of a Newtonian fluid is surrounded by a MR fluid in a Hele-Shaw cell apparatus. An externally applied, in-plane azimuthal magnetic field produced by a current-carrying wire induces interfacial disturbances at the two-fluid interface, and pattern-forming structures arise. Linear stability analysis, weakly nonlinear theory, and a vortex sheet approach are used to access early linear and intermediate nonlinear time regimes, as well as to determine stationary interfacial shapes at fully nonlinear stages.

  5. Interfacial patterns in magnetorheological fluids: Azimuthal field-induced structures.

    PubMed

    Dias, Eduardo O; Lira, Sérgio A; Miranda, José A

    2015-08-01

    Despite their practical and academic relevance, studies of interfacial pattern formation in confined magnetorheological (MR) fluids have been largely overlooked in the literature. In this work, we present a contribution to this soft matter research topic and investigate the emergence of interfacial instabilities when an inviscid, initially circular bubble of a Newtonian fluid is surrounded by a MR fluid in a Hele-Shaw cell apparatus. An externally applied, in-plane azimuthal magnetic field produced by a current-carrying wire induces interfacial disturbances at the two-fluid interface, and pattern-forming structures arise. Linear stability analysis, weakly nonlinear theory, and a vortex sheet approach are used to access early linear and intermediate nonlinear time regimes, as well as to determine stationary interfacial shapes at fully nonlinear stages. PMID:26382499

  6. Exploring the effect of interfacial tension, viscosity, and flow rate on the effectiveness of capillary trapping of CO2

    NASA Astrophysics Data System (ADS)

    Wildenschild, D.; Herring, A. L.; Carey, J. W.; Young, I. M.

    2010-12-01

    Typical geologic carbon sequestration scenarios involve the injection of supercritical CO2 into an aquifer while displacing brine in what is equivalent to a water drainage process. Due to density differences, the CO2 will tend to buoyantly migrate upward until an impermeable barrier is encountered. This buoyant CO2 plume may persist for hundreds to thousands of years posing a challenge to ensuring the long-term integrity of CO2 storage. However, a potentially large fraction of the CO2 may be immobilized by one of several trapping mechanisms. Once injection stops, buoyant forces will continue to propel the supercritical CO2 upwards, while brine reoccupies the pore space in a water imbibition process, resulting in capillary trapping of some of the CO2. In addition, supercritical CO2 is partially miscible in brine and will dissolve in the brine forming a negatively buoyant phase (dissolution trapping), and will subsequently dissolve minerals to form bicarbonate and carbonate ions (ionic trapping) and may ultimately precipitate as mineral carbonates (mineral trapping). In the capillary trapping process, supercritical CO2 is immobilized by the imbibition process where capillary interactions lock isolated CO2 bubbles within unconnected rock pore space. These bubbles have significantly increased surface area with respect to brine and rock compared to bulk storage, and may facilitate enhanced dissolution of gaseous CO2 into the brine as well as chemical reactions. Thus, one approach to demonstrating storage security is the quantification of the rate and extent of these trapping mechanisms. We present experimental results based on computed x-ray microtomography (CMT) for quantifying capillary trapping mechanisms as a function of fluid properties using several pairs of analog fluids to span a range of potential supercritical CO2-brine conditions. Our experiments are conducted in a core-flood apparatus using synthetic porous media and we investigate capillary trapping by

  7. Electronic structures of interfacial states formed at polymeric semiconductor heterojunctions

    NASA Astrophysics Data System (ADS)

    Huang, Ya-Shih; Westenhoff, Sebastian; Avilov, Igor; Sreearunothai, Paiboon; Hodgkiss, Justin M.; Deleener, Caroline; Friend, Richard H.; Beljonne, David

    2008-06-01

    Heterojunctions between organic semiconductors are central to the operation of light-emitting and photovoltaic diodes, providing respectively for electron-hole capture and separation. However, relatively little is known about the character of electronic excitations stable at the heterojunction. We have developed molecular models to study such interfacial excited electronic excitations that form at the heterojunction between model polymer donor and polymer acceptor systems: poly(9,9-dioctylfluorene-co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine) (PFB) with poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), and poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) with F8BT. We find that for stable ground-state geometries the excited state has a strong charge-transfer character. Furthermore, when partly covalent, modelled radiative lifetimes (~10-7s) and off-chain axis polarization (30∘) match observed `exciplex' emission. Additionally for the PFB:F8BT blend, geometries with fully ionic character are also found, thus accounting for the low electroluminescence efficiency of this system.

  8. Interfacial exchange coupling and magnetization reversal in perpendicular [Co/Ni]N/TbCo composite structures

    PubMed Central

    Tang, M. H.; Zhang, Zongzhi; Tian, S. Y.; Wang, J.; Ma, B.; Jin, Q. Y.

    2015-01-01

    Interfacial exchange coupling and magnetization reversal characteristics in the perpendicular heterostructures consisting of an amorphous ferrimagnetic (FI) TbxCo100–x alloy layer exchange-coupled with a ferromagnetic (FM) [Co/Ni]N multilayer have been investigated. As compared with pure TbxCo100–x alloy, the magnetization compensation composition of the heterostructures shift to a higher Tb content, implying Co/Ni also serves to compensate the Tb moment in TbCo layer. The net magnetization switching field Hc⊥ and interlayer interfacial coupling field Hex, are not only sensitive to the magnetization and thickness of the switched TbxCo100–x or [Co/Ni]N layer, but also to the perpendicular magnetic anisotropy strength of the pinning layer. By tuning the layer structure we achieve simultaneously both large Hc⊥ = 1.31 T and Hex = 2.19 T. These results, in addition to the fundamental interest, are important to understanding of the interfacial coupling interaction in the FM/FI heterostructures, which could offer the guiding of potential applications in heat-assisted magnetic recording or all-optical switching recording technique. PMID:26074295

  9. Interfacial exchange coupling and magnetization reversal in perpendicular [Co/Ni]N/TbCo composite structures.

    PubMed

    Tang, M H; Zhang, Zongzhi; Tian, S Y; Wang, J; Ma, B; Jin, Q Y

    2015-01-01

    Interfacial exchange coupling and magnetization reversal characteristics in the perpendicular heterostructures consisting of an amorphous ferrimagnetic (FI) TbxCo(100-x) alloy layer exchange-coupled with a ferromagnetic (FM) [Co/Ni]N multilayer have been investigated. As compared with pure TbxCo(100-x) alloy, the magnetization compensation composition of the heterostructures shift to a higher Tb content, implying Co/Ni also serves to compensate the Tb moment in TbCo layer. The net magnetization switching field Hc⊥ and interlayer interfacial coupling field Hex, are not only sensitive to the magnetization and thickness of the switched TbxCo(100-x) or [Co/Ni]N layer, but also to the perpendicular magnetic anisotropy strength of the pinning layer. By tuning the layer structure we achieve simultaneously both large Hc⊥ = 1.31 T and Hex = 2.19 T. These results, in addition to the fundamental interest, are important to understanding of the interfacial coupling interaction in the FM/FI heterostructures, which could offer the guiding of potential applications in heat-assisted magnetic recording or all-optical switching recording technique. PMID:26074295

  10. Shear Wave Propagation Across Filled Joints with the Effect of Interfacial Shear Strength

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Liu, T. T.; Li, H. B.; Liu, Y. Q.; Liu, B.; Xia, X.

    2015-07-01

    The thin-layer interface model for filled joints is extended to analyze shear wave propagation across filled rock joints when the interfacial shear strength between the filling material and the rocks is taken into account. During the wave propagation process, the two sides of the filled joint are welded with the adjacent rocks first and slide on each other when the shear stress on the joint is greater than the interfacial shear strength. By back analysis, the relation between the shear stress and the relative tangential deformation of the filled joints is obtained from the present approach, which is shown as a cycle parallelogram. Comparison between the present approach and the existing method based on the zero-thickness interface model indicates that the present approach is efficient to analyze shear wave propagation across rock joints with slippery behavior. The calculation results show that the slippery behavior of joints is related to the interfacial failure. In addition, the interaction between the shear stress wave and the two sides of the filling joint influences not only the wave propagation process but also the dynamic response of the filled joint.

  11. Interface investigation of the alcohol-/water-soluble conjugated polymer PFN as cathode interfacial layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Shu; Wang, Rui; Ying Mao, Hong; He, Zhicai; Wu, Hongbin; Chen, Wei; Cao, Yong

    2013-09-01

    In this work, in situ ultraviolet photoelectron spectroscopy measurements were used to investigate the working mechanism of an alcohol-/water-soluble conjugated polymer poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode interfacial layer in organic solar cells from the view of interfacial energy level alignment. Fullerene (C60) was chosen as the model acceptor material in contact with PFN as well as two other cathode interfacial layers ZnO and TiO2 in the configuration of an inverted solar cell structure. Significant charge transfer between PFN modified ITO (indium tin oxide) electrode and C60 is observed due to the low work function of PFN. This results in the Fermi level of the substrate pinned very close to the lowest unoccupied molecular orbital of C60 as well as an additional electric field at the cathode/acceptor interface. Both of them facilitate the electron extraction from the acceptor C60 to the ITO cathode, as confirmed by the electrical measurements of the electron-only devices with PFN modification. The better electron extraction originated from the Fermi level pinning and the additional interface electric field are believed to contribute to the efficiency enhancement of the inverted organic solar cells employing PFN as cathode interfacial layer.

  12. Bulk and interfacial glass transitions of water.

    PubMed

    Bhattacharya, Deepanjan; Payne, Candace N; Sadtchenko, Vlad

    2011-06-16

    Fast scanning calorimetry (FSC) was employed to investigate glass softening dynamics in bulk-like and ultrathin glassy water films. Bulk-like water samples were prepared by vapor-deposition on the surface of a tungsten filament near 140 K where vapor-deposition results in low enthalpy glassy water films. The vapor-deposition approach was also used to grow multiple nanoscale (approximately 50 nm thick) water films alternated with benzene and methanoic films of similar dimensions. When heated from cryogenic temperatures, the ultrathin water films underwent a well manifested glass softening transition at temperatures 20 K below the onset of crystallization. However, no such transition was observed in bulk-like samples prior to their crystallization. These results indicate that thin-film water demonstrates glass softening dynamics that are dramatically distinct from those of the bulk phase. We attribute these differences to water's interfacial glass transition, which occurs at temperatures tens of degrees lower than that in the bulk. Implications of these findings for past studies of glass softening dynamics in various glassy water samples are discussed. PMID:21401034

  13. Nanofiber Scaffold Gradients for Interfacial Tissue Engineering

    PubMed Central

    Ramalingam, Murugan; Young, Marian F.; Thomas, Vinoy; Sun, Limin; Chow, Laurence C.; Tison, Christopher K.; Chatterjee, Kaushik; Miles, William C.; Simon, Carl G.

    2012-01-01

    We have designed a 2-spinnerette device that can directly electrospin nanofiber scaffolds containing a gradient in composition that can be used to engineer interfacial tissues such as ligament and tendon. Two types of nanofibers are simultaneously electrospun in an overlapping pattern to create a nonwoven mat of nanofibers containing a composition gradient. The approach is an advance over previous methods due to its versatility - gradients can be formed from any materials that can be electrospun. A dye was used to characterize the 2-spinnerette approach and applicability to tissue engineering was demonstrated by fabricating nanofibers with gradients in amorphous calcium phosphate nanoparticles (nACP). Adhesion and proliferation of osteogenic cells (MC3T3-E1 murine pre-osteoblasts) on gradients was enhanced on the regions of the gradients that contained higher nACP content yielding a graded osteoblast response. Since increases in soluble calcium and phosphate ions stimulate osteoblast function, we measured their release and observed significant release from nanofibers containing nACP. The nanofiber-nACP gradients fabricated herein can be applied to generate tissues with osteoblast gradients such as ligaments or tendons. In conclusion, these results introduce a versatile approach for fabricating nanofiber gradients that can have application for engineering graded tissues. PMID:22286209

  14. Interfacial phenomena in gas hydrate systems.

    PubMed

    Aman, Zachary M; Koh, Carolyn A

    2016-03-21

    Gas hydrates are crystalline inclusion compounds, where molecular cages of water trap lighter species under specific thermodynamic conditions. Hydrates play an essential role in global energy systems, as both a hinderance when formed in traditional fuel production and a substantial resource when formed by nature. In both traditional and unconventional fuel production, hydrates share interfaces with a tremendous diversity of materials, including hydrocarbons, aqueous solutions, and inorganic solids. This article presents a state-of-the-art understanding of hydrate interfacial thermodynamics and growth kinetics, and the physiochemical controls that may be exerted on both. Specific attention is paid to the molecular structure and interactions of water, guest molecules, and hetero-molecules (e.g., surfactants) near the interface. Gas hydrate nucleation and growth mechanics are also presented, based on studies using a combination of molecular modeling, vibrational spectroscopy, and X-ray and neutron diffraction. The fundamental physical and chemical knowledge and methods presented in this review may be of value in probing parallel systems of crystal growth in solid inclusion compounds, crystal growth modifiers, emulsion stabilization, and reactive particle flow in solid slurries. PMID:26781172

  15. Nucleation of interfacial nanobubbles via solventless exchange

    NASA Astrophysics Data System (ADS)

    Tan, Beng Hau; Arora, Manish; Ohl, Claus-Dieter

    2014-11-01

    Interfacial nanobubbles are flat spherical caps of gas that attach on wetted hydrophobic surfaces. Nanobubbles are typically nucleated by wetting an atomically smooth surface with a water-solvent exchange. The bubbles appear when water is flushed into the system, but dissolve in ethanol. Although there is abundant evidence to suggest the bubbles are gaseous (for instance with infrared spectroscopy, water-solvent exchanges by themselves cannot rule out the possibility that the structures are organic contaminants rather than gaseous bubbles, e.g.. We report an AFM study of nanobubbles on HOPG using an exchange of saturated water and degassed water. Nanobubbles nucleated by our solventless technique are smaller in radius and height than with the standard solvent exchange technique. The nanobubbles disappear on a second exchange with degassed water. Since the exchange is free of organic solvent, we rule out organic contamination. Moreover, since the exchange affects only the dissolved gas in the liquid, the appearance and disappearance of the bubbles by successive exchange can be conclusively linked to the gas.

  16. Interfacial oxygen stabilizes composite silicon anodes.

    PubMed

    Sun, Chuan-Fu; Zhu, Hongli; Okada, Morihiro; Gaskell, Karen; Inoue, Yoku; Hu, Liangbing; Wang, YuHuang

    2015-01-14

    Silicon can store Li(+) at a capacity 10 times that of graphite anodes. However, to harness this remarkable potential for electrical energy storage, one has to address the multifaceted challenge of volume change inherent to high capacity electrode materials. Here, we show that, solely by chemical tailoring of Si-carbon interface with atomic oxygen, the cycle life of Si/carbon matrix-composite electrodes can be substantially improved, by 300%, even at high mass loadings. The interface tailored electrodes simultaneously attain high areal capacity (3.86 mAh/cm(2)), high specific capacity (922 mAh/g based on the mass of the entire electrode), and excellent cyclability (80% retention of capacity after 160 cycles), which are among the highest reported. Even at a high rate of 1C, the areal capacity approaches 1.61 mAh/cm(2) at the 500th cycle. This remarkable electrochemical performance is directly correlated with significantly improved structural and electrical interconnections throughout the entire electrode due to chemical tailoring of the Si-carbon interface with atomic oxygen. Our results demonstrate that interfacial bonding, a new dimension that has yet to be explored, can play an unexpectedly important role in addressing the multifaceted challenge of Si anodes. PMID:25513731

  17. Manipulating interfacial hydrogens at palladium via STM.

    PubMed

    Tremblay, Jean Christophe; Blanco-Rey, María

    2015-06-01

    In this contribution, we provide a detailed dynamical analysis of the interfacial hydrogen migration mediated by scanning tunneling microscopy (STM). Contributions from the STM-current and from the non-adiabatic couplings are taken into account using only first principle models. The slight asymmetry of the tunnelling rates with respect to the potential bias sign inferred from experimental observations is reproduced by weighting the contributions of the metal acceptor-donor states for the propagation of the impinging electrons. The quasi-thermal inelastic collision mechanism is treated perturbatively. The influence of hydrogen pre-coverage is also investigated using new potential energy surfaces obtained from periodic density functional theory calculations. Fully quantum dynamical simulations of the system evolution are performed by solving the Pauli master equation, providing insight into the reaction mechanism of STM manipulation of subsurface hydrogens. It is observed that the hydrogen impurity favors resurfacing over occupation of the bulk and subsurface sites whenever possible. The present simulations give strong indication that the experimentally observed protuberances after STM-excitation are due to hydrogen accumulating in the vicinity of the surface. PMID:25948419

  18. Interfacial Behavior of Polymers: Using Interfaces to Manipulate Polymers

    SciTech Connect

    Russell, Thomas P.

    2015-02-26

    most rapid solvent removal process drives the copolymer film to below its glass transition temperature, freezing in the lateral order. We have quantitatively described the ordering and the parameters influencing the disruption of the ordering in these studies. We have also used e-beam lithography to generate shallow trench patterns on planar surface where the topographic patterning provides an additional constraint on the self-assembly of the block copolymer. The pitches of the trenches were varied while the depth and the trench width of patterns were maintained by constant at 89 and 30nm, respectively. Unidirectional PS-b-PEO line patterns over large area on the shallow trench patterns were obtained by solvent vapor annealing. We extended the solvent annealing process to an in-line coating process using a mini-slot die coater developed in our laboratories. This coater uses minimal materials with operating parameters that can mimic actual industrial processing on a roll-to-roll line. Most important, with this mini-slot die coater, it could also characterize the structure of the film using grazing incidence x-ray scattering. Using the fundamental characterization of the ordering of the block copolymers, we could optimize the coating conditions to enhance lateral ordering of block copolymer in a well-defined manner. The structures produced in this process are directly transferable to flexible electronics where the arrays of block copolymer microdomains can be used for the fabrication of nanostructured components. We have also controlled the orientation of BCP microdomains at the air and substrate interfaces by manipulating the interfacial interactions with selective solvents. This has enabled us to generate nanoporous membranes where the size of the pores is dictated by the size of the bloc copolymer microdomains. We have produced robust nanoporous membranes that can tolerate high pressures and have high throughput using thick films of block copolymers. Exceptional size

  19. Surface and interfacial creases in a bilayer tubular soft tissue

    NASA Astrophysics Data System (ADS)

    Razavi, Mir Jalil; Pidaparti, Ramana; Wang, Xianqiao

    2016-08-01

    Surface and interfacial creases induced by biological growth are common types of instability in soft biological tissues. This study focuses on the criteria for the onset of surface and interfacial creases as well as their morphological evolution in a growing bilayer soft tube within a confined environment. Critical growth ratios for triggering surface and interfacial creases are investigated both analytically and numerically. Analytical interpretations provide preliminary insights into critical stretches and growth ratios for the onset of instability and formation of both surface and interfacial creases. However, the analytical approach cannot predict the evolution pattern of the model after instability; therefore nonlinear finite element simulations are carried out to replicate the poststability morphological patterns of the structure. Analytical and computational simulation results demonstrate that the initial geometry, growth ratio, and shear modulus ratio of the layers are the most influential factors to control surface and interfacial crease formation in this soft tubular bilayer. The competition between the stretch ratios in the free and interfacial surfaces is one of the key driving factors to determine the location of the first crease initiation. These findings may provide some fundamental understanding in the growth modeling of tubular biological tissues such as esophagi and airways as well as offering useful clues into normal and pathological functions of these tissues.

  20. Interfacial Water-Transport Effects in Proton-Exchange Membranes

    SciTech Connect

    Kienitz, Brian; Yamada, Haruhiko; Nonoyama, Nobuaki; Weber, Adam

    2009-11-19

    It is well known that the proton-exchange membrane is perhaps the most critical component of a polymer-electrolyte fuel cell. Typical membranes, such as Nafion(R), require hydration to conduct efficiently and are instrumental in cell water management. Recently, evidence has been shown that these membranes might have different interfacial morphology and transport properties than in the bulk. In this paper, experimental data combined with theoretical simulations will be presented that explore the existence and impact of interfacial resistance on water transport for Nafion(R) 21x membranes. A mass-transfer coefficient for the interfacial resistance is calculated from experimental data using different permeation cells. This coefficient is shown to depend exponentially on relative humidity or water activity. The interfacial resistance does not seem to exist for liquid/membrane or membrane/membrane interfaces. The effect of the interfacial resistance is to flatten the water-content profiles within the membrane during operation. Under typical operating conditions, the resistance is on par with the water-transport resistance of the bulk membrane. Thus, the interfacial resistance can be dominant especially in thin, dry membranes and can affect overall fuel-cell performance.

  1. Interfacial load transfer in polymer/carbon nanotube nanocomposites with a nanohybrid shish kebab modification.

    PubMed

    Nie, Min; Kalyon, Dilhan M; Fisher, Frank T

    2014-09-10

    Interfacial properties are known to have a critical effect on the mechanical properties of a nanocomposite material system. Here, the interfacial load transfer in a carbon nanotube (CNT)/nylon-11 composite was studied with a CNT/nylon-11 nanohybrid shish kebab (NHSK) structure modification using Raman spectroscopy. Characterization of the polymer crystal in the NHSK using differential scanning calorimetry (DSC) for the first time indicates that the NHSK structure formed a more perfect crystal structure than the bulk polymer. On the basis of transmission electron microscopy and DSC results, a new growth model for the NHSK crystal is hypothesized, indicating the formation of an initial uniform crystal layer on the CNT prior to the crystallization of the kebabs. Characterization of the nanocomposites using Raman spectroscopy, with the samples heated to introduce interfacial shear stress caused by thermal expansion mismatch, found that the D* band of the CNT in the NHSK/nylon-11 composite displayed a more pronounced shift with an increase in temperature, which is attributed to the NHSK structure being more effective at transferring load from the nylon matrix to the nanotube inclusions. The NHSK structure was also used to fabricate composites with two amorphous polymers, polycarbonate and poly(methyl methacrylate), to investigate the load transfer mechanism. It was found that when the compatibility between the polymer in the NHSK structure and the bulk polymer matrix at the molecular level is sufficiently high, the ensuing mechanical interlocking effect further enhances the interfacial load transfer for polymer nanocomposites. Additional mechanical characterization of polymer nanocomposites with 0.1 wt % NHSK reinforcement demonstrates how the moduli and ultimate tensile strength of the nanocomposites can be improved via this NHSK structure. PMID:25134606

  2. Establishing a quantitative functional relationship between capillary pressure, saturation and interfacial area. 1997 annual progress report

    SciTech Connect

    Montemagno, C.D.

    1997-01-01

    'There is a fundamental knowledge gap associated with the in situ remediation of non-aqueous phase pollutants. Currently it is not possible to accurately determine the interfacial surface area of non-aqueous contaminants. As a result it is impossible to (1) accurately establish the health and environmental risk associated with the pollution: (2) precisely quantify and evaluate the potential efficacy of various in situ treatment technologies; and (3) conduct reliable performance assessments of the applied remediation technology during and after the clean-up. The global goal of this investigation is to try to remedy these shortcomings through the development of a formalized functional relationship between interfacial area (a), phase saturation (S) and capillary pressure (P). The development of this relationship will allow the direct determination of the fluid-fluid interfacial area from field measurements. Quantitative knowledge of the surface area of the non-aqueous phase pollutant facilitates accurate predictions of both the rate of dissolution and the contact area available for treatment. In addition. if saturation and capillary pressure measurements are made during the remediation process. both the spatial and temporal effectiveness of the remediation technology can be quantified. This information can then be used to optimize the restoration program. The project objective will be achieved through an integrated and focused research program that is comprised of theoretical computational and experimental efforts. These efforts are organized into a framework of four tasks: (1) improve on newly developed laboratory techniques to quantify and directly measure the functional relationship between phase interfacial area (a), saturation (S) and capillary pressure (P). (2) Develop new computational algorithms in conjunction with laboratory measurements to predict P, S and a. (3) Test existing theory and develop new theory to describe the relationship between P, S and a at

  3. Electrochemical tailoring of lamellar-structured ZnO films by interfacial surfactant templating.

    PubMed

    Tan, Yiwei; Steinmiller, Ellen M P; Choi, Kyoung-Shin

    2005-10-11

    Zinc oxide films with ordered lamellar structures can be electrochemically produced by interfacial surfactant templating. This method utilizes amphiphile assemblies at the solid-liquid interface (i.e., the surface of a working electrode) as a template to electrodeposit inorganic nanostructures. To gain the ability to precisely tailor inorganic lamellar structures, the effect of various chemical and electrochemical parameters on the repeat distances, homogeneity, orientation, and quality of the interfacial amphiphilic bilayers were investigated. Surfactants with anionic headgroups (e.g., 1-hexadecanesulfonate sodium salt, dodecylbenzenesulfonate sodium salt, dioctyl sulfosuccinate sodium salt, mono-dodecyl phosphate, and sodium dodecyl sulfate) are critical because they incorporate Zn(2+) ions into their bilayer assemblies as counterions and guide the lamellar growth of ZnO films. Unlike surfactant structures in solution, the interfacial surfactant assemblies are insensitive to the surfactant concentration in solution. The use of organic cosolvents (e.g., ethylene glycol, dimethyl sulfoxide) can increase the homogeneity of bilayer assemblies when multiple repeat distances are possible in a pure aqueous medium. In addition, organic cosolvents can make the interfacial structure responsive to the change in bulk surfactant concentrations. The presence of quaternary alkylammonium salts (e.g., cetyltrimethylammonium bromide) as cationic cosurfactants improves the ordering of anionic bilayers significantly. Consequently, it also affects the orientation of lamellar structures relative to the substrate as well as the surface texture of the films. The quality of lamellar structures incorporated in ZnO films is also dependent on the deposition potentials that determine deposition rates. A higher degree of ordering is achieved when a slower deposition rate (I < 0.15 mA/cm(2)) is used. The results described here will provide a useful foundation to design and optimize synthetic

  4. Coalescence of surfactant covered drops in extensional flows: Effects of the interfacial diffusivity

    NASA Astrophysics Data System (ADS)

    Vannozzi, Carolina

    2012-08-01

    trace amounts of surfactants can be as effective stabilizers as high surfactant concentrations. Moreover, for the polymeric system of interest, the range of Ds in which the drainage time changes from the saturation value to the clean interface value was computed as a function of the surfactant concentration. In the specific, for the PDMS/PBd system of interest the Ds range studied was O(10-12-10-5 cm2 s-1). Additionally, our scaling analysis further validates our simulations, also highlighting the effect on the drainage process of the different parameters, in particular, of the external pushing force, which is increased compared to a clean interface system, as Pes is increased or as the surfactant concentration is increased, because of the reduction in the interfacial mobility of the drop. Finally, our study suggests that matching simulations with four-roll mill drainage time experiments can be an effective method to determine block-copolymer surface diffusivity.

  5. AFM probing of polymer/nanofiller interfacial adhesion and its correlation with bulk mechanical properties in a poly(ethylene terephthalate) nanocomposite.

    PubMed

    Aoyama, Shigeru; Park, Yong Tae; Macosko, Christopher W; Ougizawa, Toshiaki; Haugstad, Greg

    2014-11-01

    The interfacial adhesion between polymer and nanofiller plays an important role in affecting the properties of nanocomposites. The detailed relationship between interfacial adhesion and bulk properties, however, is unclear. In this work, we developed an atomic force microscopy (AFM)-based abrasive scanning methodology, as applied to model laminate systems, to probe the strength of interfacial adhesion relevant to poly(ethylene terephthalate) (PET)/graphene or clay nanocomposites. Graphite and mica substrates covered with ∼2 nm thick PET films were abrasively sheared by an AFM tip as a model measurement of interfacial strength between matrix PET and dispersed graphene and clay, respectively. During several abrasive raster-scan cycles, PET was shear-displaced from the scanned region. At temperatures below the PET glass transition, PET on graphite exhibited abrupt delamination (i.e., full adhesive failure), whereas PET on mica did not; rather, it exhibited a degree of cohesive failure within the shear-displaced layer. Moreover, 100-fold higher force scanning procedures were required to abrade through an ultimate "precursor" layer of PET only ∼0.2-0.5 nm thick, which must be largely disentangled from the matrix polymer. Thus, the adhesive interface of relevance to the strength of clay-filler nanocomposites is between matrix polymer and strongly bound polymer. At 90 °C, above the bulk PET glass transition temperature, the PET film exhibited cohesive failure on both graphite and mica. Our results suggest that there is little difference in the strength of the relevant interfacial adhesion in the two nanocomposites within the rubbery dynamic regime. Further, the bulk mechanical properties of melt mixed PET/graphene and PET/clay nanocomposites were evaluated by dynamic mechanical analysis. The glassy dynamic storage modulus of the PET/clay nanocomposite was higher than that of PET/graphene, correlating with the differences in interfacial adhesion probed by AFM. PMID

  6. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume I. Chapters 1-5)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  7. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume II. Chapters 6-10)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  8. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume III. Chapters 11-14)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  9. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume IV. Chapters 15-19)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  10. Electrostatic patch potentials in Casimir force measurements

    NASA Astrophysics Data System (ADS)

    Garrett, Joseph; Somers, David; Munday, Jeremy

    2015-03-01

    Measurements of the Casimir force require the elimination of the electrostatic force between interacting surfaces. The force can be minimized by applying a potential to one of the two surfaces. However, electrostatic patch potentials remain and contribute an additional force which can obscure the Casimir force signal. We will discuss recent measurements of patch potentials made with Heterodyne Amplitude-Modulated Kelvin Probe Force Microscopy that suggest patches could be responsible for >1% of the signal in some Casimir force measurements, and thus make the distinction between different theoretical models of the Casimir force (e.g. a Drude-model or a plasma-model for the dielectric response) difficult to discern.

  11. Selective modulation of charge-carrier transport of a photoanode in a photoelectrochemical cell by a graphitized fullerene interfacial layer.

    PubMed

    Park, Sun-Young; Lim, Dong Chan; Hong, Eun Mi; Lee, Joo-Yeoul; Heo, Jinhee; Lim, Jae Hong; Lee, Chang-Lyoul; Kim, Young Dok; Mul, Guido

    2015-01-01

    We show that a graphitic carbon interfacial layer, derived from C70 by annealing at 500 °C, results in a significant increase in the attainable photocurrent of a photoelectrochemical cell that contains a WO3 -functionalized fluorine-doped tin oxide (FTO) photoanode. Time-resolved photoluminescence spectroscopy, photoconductive atomic force microscopy, Hall measurements, and electrochemical impedance spectroscopy show that the increase in photocurrent is the result of fast and selective electron transport from optically excited WO3 through the graphitic carbon interfacial layer to the FTO-coated glass electrode. Thus the energy efficiency of perspective solar-to-fuel devices can be improved by modification of the interface of semiconductors and conducting substrate electrodes by using graphitized fullerene derivatives. PMID:25410298

  12. Influence of Water on the Interfacial Nanostructure and Wetting of [Rmim][NTf2] Ionic Liquids at Mica Surfaces.

    PubMed

    Wang, Zhantao; Li, Hua; Atkin, Rob; Priest, Craig

    2016-09-01

    The effect of water concentration on the interfacial nanostructure and wetting behavior of a family of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Rmim][NTf2], at the surface of mica was investigated by contact angle measurement and atomic force microscopy (AFM). AFM reveals that interfacial layers of ILs observed at the surface of mica for "dry" ILs are not present for water-saturated ILs. The interaction of the IL ions of [Rmim][NTf2] with water molecules through hydrogen bonding is suspected to disrupt IL ion layering and precursor film growth on mica. Without the IL precursor film, contact angle relaxation of "wet" ILs on mica is less significant and ambient vapor adsorption becomes more important in determining the macroscopic wetting behavior. PMID:27486675

  13. Formation of periodic interfacial misfit dislocation array at the InSb/GaAs interface via surface anion exchange

    NASA Astrophysics Data System (ADS)

    Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt

    2016-07-01

    The relationship between growth temperature and the formation of periodic interfacial misfit (IMF) dislocations via the anion exchange process in InSb/GaAs heteroepitaxy was systematically investigated. The microstructural and electrical properties of the epitaxial layer were characterized using atomic force microscope, high-resolution x-ray diffraction, transmission electron microscopy, and Hall resistance measurement. The formation of interfacial misfit (IMF) dislocation arrays depended on growth temperature. A uniformly distributed IMF array was found in a sample grown at 310 °C, which also exhibited the lowest threading dislocation density. The analysis suggested that an incomplete As-for-Sb anion exchange process impeded the formation of IMF on sample grown above 310 °C. At growth temperature below 310 °C, island coalescence led to the formation of 60° dislocations and the disruption of periodic IMF array. All samples showed higher electron mobility at 300 K than at 77 K.

  14. Interfacial reaction of silver ultra-thin film deposited on interpenetrating polymer network substrate by liquor-phase reduction

    NASA Astrophysics Data System (ADS)

    Tang, Dongyan; Guo, Yudi; Zhang, Xiaohong; Yin, Yuelong

    2010-08-01

    The interfacial reaction, metal transformations, and nonmetal bond types of silver ultra-thin film deposited on polyurethane (PU) based interpenetrating polymer networks (IPN) substrate by the liquor-phase reduction at room temperatures were studied by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The IPN substrate was prepared by dip-pulling precursors onto a silicon wafer or a glass plate, followed by solidification at room temperature. The interpenetrate structures of IPN with two crosslinked networks restricted the aggregation of silver during the reduction and deposition. The devised -OH terminal group in PU simplified the determination of reactive site in IPN and reinforced the adhesion between IPN and silver through interfacial reaction. The XPS results, which matched well with the ATR-FTIR results, verified the chemical reactive site of PU in IPN with silver in the oxide state.

  15. Nature-Inspired One-Step Green Procedure for Enhancing the Antibacterial and Antioxidant Behavior of a Chitin Film: Controlled Interfacial Assembly of Tannic Acid onto a Chitin Film.

    PubMed

    Wang, Yuntao; Li, Jing; Li, Bin

    2016-07-20

    The final goal of this study was to develop antimicrobial food-contact materials based on a natural phenolic compound (tannic acid) and chitin, which is the second most abundant polysaccharide on earth, using an interfacial assembly approach. Chitin film has poor antibacterial and antioxidant ability, which limits its application in industrial fields such as active packaging. Therefore, in this study, a novel one-step green procedure was applied to introduce antibacterial and antioxidant properties into a chitin film simultaneously by incorporation of tannic acid into the chitin film through interfacial assembly. The antibacterial and antioxidant behavior of chitin film has been greatly enhanced. Hydrogen bonds and hydrophobic interaction were found to be the main driving forces for interfacial assembly. Therefore, controlled interfacial assembly of tannic acid onto a chitin film demonstrated a good way to develop functional materials that can be potentially applied in industry. PMID:27378105

  16. Theoretical modeling of CHF for near-saturated pool boiling and flow boiling from short heaters using the interfacial lift-off criterion

    SciTech Connect

    Mudawar, I.; Galloway, J.E.; Gersey, C.O.

    1995-12-31

    Pool boiling and flow boiling were examined for near-saturated bulk conditions in order to determine the critical heat flux (CHF) trigger mechanism for each. Photographic studies of the wall region revealed features common to both situations. At fluxes below CHF, the vapor coalesces into a wavy layer which permits wetting only in wetting fronts, the portions of the liquid-vapor interface which contact the wall as a result of the interfacial waviness. Close examination of the interfacial features revealed the waves are generated from the lower edge of the heater in pool boiling and the heater`s upstream region in flow boiling. Wavelengths follow predictions based upon the Kelvin-Helmholtz instability criterion. Critical heat flux in both cases occurs when the pressure force exerted upon the interface due to interfacial curvature, which tends to preserve interfacial contact with the wall prior to CHF, is overcome by the momentum of vapor at the site of the first wetting front, causing the interface to lift away from the wall. It is shown this interfacial lift-off criterion facilitates accurate theoretical modeling of CHF in pool boiling and in flow boiling in both straight and curved channels.

  17. Effects of metallic nanoparticle doped flux on the interfacial intermetallic compounds between lead-free solder ball and copper substrate

    SciTech Connect

    Sujan, G.K. Haseeb, A.S.M.A. Afifi, A.B.M.

    2014-11-15

    Lead free solders currently in use are prone to develop thick interfacial intermetallic compound layers with rough morphology which are detrimental to the long term solder joint reliability. A novel method has been developed to control the morphology and growth of intermetallic compound layers between lead-free Sn–3.0Ag–0.5Cu solder ball and copper substrate by doping a water soluble flux with metallic nanoparticles. Four types of metallic nanoparticles (nickel, cobalt, molybdenum and titanium) were used to investigate their effects on the wetting behavior and interfacial microstructural evaluations after reflow. Nanoparticles were dispersed manually with a water soluble flux and the resulting nanoparticle doped flux was placed on copper substrate. Lead-free Sn–3.0Ag–0.5Cu solder balls of diameter 0.45 mm were placed on top of the flux and were reflowed at a peak temperature of 240 °C for 45 s. Angle of contact, wetting area and interfacial microstructure were studied by optical microscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was observed that the angle of contact increased and wetting area decreased with the addition of cobalt, molybdenum and titanium nanoparticles to flux. On the other hand, wettability improved with the addition of nickel nanoparticles. Cross-sectional micrographs revealed that both nickel and cobalt nanoparticle doping transformed the morphology of Cu{sub 6}Sn{sub 5} from a typical scallop type to a planer one and reduced the intermetallic compound thickness under optimum condition. These effects were suggested to be related to in-situ interfacial alloying at the interface during reflow. The minimum amount of nanoparticles required to produce the planer morphology was found to be 0.1 wt.% for both nickel and cobalt. Molybdenum and titanium nanoparticles neither appear to undergo alloying during reflow nor have any influence at the solder/substrate interfacial reaction. Thus, doping

  18. Measuring Non-Wetting/Wetting Interfacial Area: Comparing Synchrotron X-ray Microtomography and Interfacial Partitioning Tracer Methods

    NASA Astrophysics Data System (ADS)

    Narter, M. E.; Brusseau, M. L.

    2008-12-01

    Previous studies have shown that non-wetting/wetting interfacial areas measured with synchrotron X-ray microtomography are significantly smaller than those measured using the interfacial tracer test method for natural porous media. Research was conducted to evaluate the source of the disparity between these methods. It has been hypothesized that the disparity is due primarily to resolution constraints associated with microtomography, wherein the interfacial area associated with microscopic surface roughness is not measured. To test this hypothesis, experiments were conducted with glass beads that were shown to have no measureable surface roughness. Tetrachloroethene (PCE) was used as the model non-wetting fluid and sodium dodecylbenzene sulfonate was used as the interfacial tracer. Tracer tests yielded an average interfacial area of 2.8 +/- 5 1/cm while microtomography results produced an interfacial area of 3.4 +/- 2 1/cm. The values are similar for the two methods, indicating that the disparity observed for natural media is likely due to resolution limitations of microtomography.

  19. The impact of interfacial tension on multiphase flow in the CO2-brine-sandstone system

    NASA Astrophysics Data System (ADS)

    Reynolds, C. A.; Blunt, M. J.; Krevor, S. C.

    2013-12-01

    Two dominant controls on continuum scale multiphase flow properties are interfacial tension (IFT) and wetting. In hydrocarbon-brine systems, relative permeability is known to increase with decreasing IFT, while residual trapping is controlled by the wetting properties of a permeable rock and the hysteresis between drainage and imbibtion (Amaefule & Handy, 1982; Bardon & Longeron, 1980; Juanes et al., 2006). Fluid properties of the CO2-brine system, such as viscosity, density and interfacial tension, are well characterised and have known dependencies on temperature, pressure and brine salinity. Interest in this particular fluid system is motivated by CO2 storage and enhanced oil recovery. Despite increased interest in CO2 storage, the response of the CO2-brine relative permeability to varying IFT has yet to be comprehensively evaluated. Additionally the wide range of thermophysical properties (density, viscosity etc.) that exist across a relatively small range of pressures and temperatures makes it an ideal system with which to investigate the physics of multiphase flow in general. This is the first systematic study to investigate the impact of IFT on drainage and imbibition relative permeability for the CO2-brine-sandstone system. The experimental design has been adapted from a traditional steady state core flood in two ways. First, while conditions may be easily selected to obtain a range of interfacial tensions, isolating the independent impact of interfacial tension on relative permeability is less simple. Thus experimental conditions are selected so as to vary interfacial tension, while minimising the variation in viscosity ratio between CO2 and brine. Second, in order to attribute the impacts of changing conditions, it is necessary to have precise results such that small shifts in observations can be identified. Multiphase flow theory is used to both design the conditions of the test and interpret the observations, leading to a much higher precision in

  20. Endocytic vesicle scission by lipid phase boundary forces

    PubMed Central

    Liu, Jian; Kaksonen, Marko; Drubin, David G.; Oster, George

    2006-01-01

    Endocytosis in budding yeast is thought to occur in several phases. First, the membrane invaginates and then elongates into a tube. A vesicle forms at the end of the tube, eventually pinching off to form a “free” vesicle. Experiments show that actin polymerization is an active participant in the endocytic process, along with a number of membrane-associated proteins. Here we investigate the possible roles of these components in driving vesiculation by constructing a quantitative model of the process beginning at the stage where the membrane invagination has elongated into a tube encased in a sheath of membrane-associated protein. This protein sheath brings about the scission step where the vesicle separates from the tube. When the protein sheath is dynamin, it is commonly assumed that scission is brought about by the constriction of the sheath. Here, we show that an alternative scenario can work as well: The protein sheath acts as a “filter” to effect a phase separation of lipid species. The resulting line tension tends to minimize the interface between the tube region and the vesicle region. Interestingly, large vesicle size can further facilitate the reduction of the interfacial diameter down to a few nanometers, small enough so that thermal fluctuations can fuse the membrane and pinch off the vesicle. To deform the membrane into the tubular vesicle shape, the membrane elastic resistance forces must be balanced by some additional forces that we show can be generated by actin polymerization and/or myosin I. These active forces are shown to be important in successful scission processes as well. PMID:16801551

  1. Theory of plasmon enhanced interfacial electron transfer

    NASA Astrophysics Data System (ADS)

    Wang, Luxia; May, Volkhard

    2015-04-01

    A particular attempt to improve the efficiency of a dye sensitized solar cell is it's decoration with metal nano-particles (MNP). The MNP-plasmon induced enhancement of the local field enlarges the photoexcitation of the dyes and a subsequent improvement of the charge separation efficiency may result. In a recent work (2014 J. Phys. Chem. C 118 2812) we presented a theory of plasmon enhanced interfacial electron transfer for perylene attached to a TiO2 surface and placed in the proximity of a spherical MNP. These earlier studies are generalized here to the coupling of to up to four MNPs and to the use of somewhat altered molecular parameters. If the MNPs are placed close to each other strong hybridization of plasmon excitations appears and a broad resonance to which molecular excitations are coupled is formed. To investigate this situation the whole charge injection dynamics is described in the framework of the density matrix theory. The approach accounts for optical excitation of the dye coupled to the MNPs and considers subsequent electron injection into the rutile TiO2-cluster. Using a tight-binding model for the TiO2-system with about 105 atoms the electron motion in the cluster is described. We again consider short optical excitation which causes an intermediate steady state with a time-independent overall probability to have the electron injected into the cluster. This probability is used to introduce an enhancement factor which rates the influence of the MNP. Values larger than 500 are obtained.

  2. Theory of plasmon enhanced interfacial electron transfer.

    PubMed

    Wang, Luxia; May, Volkhard

    2015-04-10

    A particular attempt to improve the efficiency of a dye sensitized solar cell is it's decoration with metal nano-particles (MNP). The MNP-plasmon induced enhancement of the local field enlarges the photoexcitation of the dyes and a subsequent improvement of the charge separation efficiency may result. In a recent work (2014 J. Phys. Chem. C 118 2812) we presented a theory of plasmon enhanced interfacial electron transfer for perylene attached to a TiO2 surface and placed in the proximity of a spherical MNP. These earlier studies are generalized here to the coupling of to up to four MNPs and to the use of somewhat altered molecular parameters. If the MNPs are placed close to each other strong hybridization of plasmon excitations appears and a broad resonance to which molecular excitations are coupled is formed. To investigate this situation the whole charge injection dynamics is described in the framework of the density matrix theory. The approach accounts for optical excitation of the dye coupled to the MNPs and considers subsequent electron injection into the rutile TiO2-cluster. Using a tight-binding model for the TiO2-system with about 10(5) atoms the electron motion in the cluster is described. We again consider short optical excitation which causes an intermediate steady state with a time-independent overall probability to have the electron injected into the cluster. This probability is used to introduce an enhancement factor which rates the influence of the MNP. Values larger than 500 are obtained. PMID:25764984

  3. Interfacial studies in fiber-reinforced thermoplastic-matrix composites

    SciTech Connect

    Brady, R.L.

    1989-01-01

    The major theme of this dissertation is structure/property relationships in fiber-reinforced thermoplastic-matrix composites. Effort has been focused on the interface: interfacial crystallization and fiber/matrix adhesion. Included are investigations on interfacial nucleation and morphology, measurement of fiber/matrix adhesion, effects of interfacial adsorption and crystallization on fiber/matrix adhesion, and composites reinforced with thermotropic liquid crystal copolyester fibers. Crystallization of a copolyester and polybutylene terephthalate with glass, carbon, or aramid fibers has been studied with regard to interfacial morphology. Techniques employed included hot-stage optical microscopy and differential scanning calorimetry. Nucleation by the fibers was found to be a general phenomenon. Morphology could be varied by changing the cooling rate. In order to better monitor fiber /matrix adhesion, a buckled plate test has been developed. The test measures transverse toughness as the parameter characterizing interfacial adhesion in unidirectional, continuous-fiber composites. The test is simple to perform yet has advantages over other interfacial evaluation techniques. The buckled plate test was found to be a sensitive measure of fiber/matrix adhesion. The buckled plate test has been used along with the transverse tensile test to examine how interfacial adsorption and crystallization affect fiber/matrix adhesion in polycarbonate/carbon fiber composites. Adsorption was found to be of primary importance in developing adhesion, while crystallization is a secondary effect. The toughness data have been fit successfully for annealing time and temperature dependence. The dependence of adsorption and transverse toughness on matrix molecular weight was found to be large, with higher molecular weights adsorbing more effectively.

  4. Experimentally Determined Interfacial Area Between Immiscible Fluids in Porous Media

    SciTech Connect

    Crandall, Dustin; Niessner, J; Hassanizadeh, S.M; Smith, Duane

    2008-01-01

    When multiple fluids flow through a porous medium, the interaction between the fluid interfaces can be of great importance. While this is widely recognized in practical applications, numerical models often disregard interactios between discrete fluid phases due to the computational complexity. And rightly so, for this level of detail is well beyond most extended Darcy Law relationships. A new model of two-phase flow including the interfacial area has been proposed by Hassarizadeh and Gray based upon thermodynamic principles. A version of this general equation set has been implemented by Nessner and Hassarizadeh. Many of the interfacial parameters required by this equation set have never been determined from experiments. The work presented here is a description of how the interfacial area, capillary pressure, interfacial velocity and interfacial permeability from two-phase flow experiments in porous media experiments can be used to determine the required parameters. This work, while on-going, has shown the possibility of digitizing images within translucent porous media and identifying the location and behavior of interfaces under dynamic conditions. Using the described methods experimentally derived interfacial functions to be used in larger scale simulations are currently being developed. In summary, the following conclusions can be drawn: (1) by mapping a pore-throat geometry onto an image of immiscible fluid flow, the saturation of fluids and the individual interfaces between the fluids can be identified; (2) the resulting saturation profiles of the low velocity drainage flows used in this study are well described by an invasion percolation fractal scaling; (3) the interfacial area between fluids has been observed to increase in a linear fashion during the initial invasion of the non-wetting fluid; and (4) the average capillary pressure within the entire cell and representative elemental volumes were observed to plateau after a small portion of the volume was

  5. Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

    SciTech Connect

    Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.

    2014-07-25

    Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface. The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical strength.

  6. Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

    DOE PAGESBeta

    Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.

    2014-07-25

    Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface.more » The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical

  7. Carbohydrate force fields

    PubMed Central

    Foley, B. Lachele; Tessier, Matthew B.; Woods, Robert J.

    2014-01-01

    Carbohydrates present a special set of challenges to the generation of force fields. First, the tertiary structures of monosaccharides are complex merely by virtue of their exceptionally high number of chiral centers. In addition, their electronic characteristics lead to molecular geometries and electrostatic landscapes that can be challenging to predict and model. The monosaccharide units can also interconnect in many ways, resulting in a large number of possible oligosaccharides and polysaccharides, both linear and branched. These larger structures contain a number of rotatable bonds, meaning they potentially sample an enormous conformational space. This article briefly reviews the history of carbohydrate force fields, examining and comparing their challenges, forms, philosophies, and development strategies. Then it presents a survey of recent uses of these force fields, noting trends, strengths, deficiencies, and possible directions for future expansion. PMID:25530813

  8. Improvement of interfacial property between PBO fibers and epoxy resin by surface grafting of polyhedral oligomeric silsesquioxanes (POSS)

    NASA Astrophysics Data System (ADS)

    Song, B.; Meng, L. H.; Huang, Y. D.

    2012-10-01

    PBO fiber as reinforced material has been widely applied in various fields such as aerospace, automobile and sport apparatus due to excellent mechanic property during past two decades. However, poor interfacial adhesion limits the further application of PBO fiber. To solve this problem, plenty of work has been done. In the present study, the surface of PBO fibers was treated through surface grafting of polyhedral oligomeric silsequioxanes (POSS). The effect of POSS grafting on bulk mechanic property and interfacial property of PBO fiber were studied. Surface chemical composition, surface morphologies, surface free energy, single-fiber tensile strength of untreated and treated PBO fiber were characterized. The results show that POSS nanoparticles were grafted on the fiber surface successfully. The surface characteristics of treated PBO fiber were different from that of untreated one. Oxygen-containing polar functional groups, elemental ratio of oxygen to carbon, surface roughness and surface free energy increased significantly. In addition, interfacial shear strength between treated PBO fibers and epoxy resin increased to 54.9 MPa comparative with untreated one. Meanwhile tensile strength of treated PBO fibers only very little decreased. Therefore, POSS surface grafting can be utilized to enhance the interfacial adhesion between PBO fibers and epoxy resin matrix.

  9. Investigation of fiber/matrix interfacial mechanical behavior in ceramic matrix composites by cyclic fiber push-in testing

    SciTech Connect

    Eldridge, J.I.; Bhatt, R.T.; Bansal, N.P.; Olmstead, F.A.

    1996-12-31

    Cyclic fiber push-in testing is used to examine the stability of interfacial frictional sliding stresses and fiber debond lengths with continued push-in load/unload cycles. The measured response to applying load cycling to a single fiber reveals the susceptibility of the fiber/matrix interface to degrade under cyclic loading conditions, and thus, helps evaluate the contribution of the interface to the cyclic fatigue behavior of the composite after the occurrence of matrix cracks. From cyclic push-in testing in room temperature air, decreasing interfacial sliding stresses and increasing debond lengths are observed with continued load cycling for SCS-6 SiC fiber reinforced reaction-bonded silicon nitride (SCS-6/RBSN), whereas stable interfacial sliding stresses and no increase in debond lengths are observed with continued load cycling for SCS-6 SiC fiber reinforced strontium aluminosilicate (SCS-6/SAS). These results indicate that fiber-bridged matrix cracks should be stable under cyclic fatigue loading conditions in SCS-6/SAS, but should exhibit increasing crack opening displacements and fiber pull-out with continued cycling in SCS-6/RBSN. In addition, changing the test environment from room air to nitrogen significantly affects the cyclic push-in test results for SCS-6/RBSN, but not for SCS-6/SAS. The different responses to this change in test environment are attributed to different locations of interfacial failure.

  10. Specific effects of Ca(2+) ions and molecular structure of β-lactoglobulin interfacial layers that drive macroscopic foam stability.

    PubMed

    Braunschweig, Björn; Schulze-Zachau, Felix; Nagel, Eva; Engelhardt, Kathrin; Stoyanov, Stefan; Gochev, Georgi; Khristov, Khr; Mileva, Elena; Exerowa, Dotchi; Miller, Reinhard; Peukert, Wolfgang

    2016-07-01

    β-Lactoglobulin (BLG) adsorption layers at air-water interfaces were studied in situ with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry as a function of bulk Ca(2+) concentration. The relation between the interfacial molecular structure of adsorbed BLG and the interactions with the supporting electrolyte is additionally addressed on higher length scales along the foam hierarchy - from the ubiquitous air-water interface through thin foam films to macroscopic foam. For concentrations <1 mM, a strong decrease in SFG intensity from O-H stretching bands and a slight increase in layer thickness and surface pressure are observed. A further increase in Ca(2+) concentrations above 1 mM causes an apparent change in the polarity of aromatic C-H stretching vibrations from interfacial BLG which we associate to a charge reversal at the interface. Foam film measurements show formation of common black films at Ca(2+) concentrations above 1 mM due to considerable decrease of the stabilizing electrostatic disjoining pressure. These observations also correlate with a minimum in macroscopic foam stability. For concentrations >30 mM Ca(2+), micrographs of foam films show clear signatures of aggregates which tend to increase the stability of foam films. Here, the interfacial layers have a higher surface dilatational elasticity. In fact, macroscopic foams formed from BLG dilutions with high Ca(2+) concentrations where aggregates and interfacial layers with higher elasticity are found, showed the highest stability with much smaller bubble sizes. PMID:27337699

  11. Probing the Interfacial Interaction in Layered-Carbon-Stabilized Iron Oxide Nanostructures: A Soft X-ray Spectroscopic Study.

    PubMed

    Zhang, Hui; Liu, Jinyin; Zhao, Guanqi; Gao, Yongjun; Tyliszczak, Tolek; Glans, Per-Anders; Guo, Jinghua; Ma, Ding; Sun, Xu-Hui; Zhong, Jun

    2015-04-22

    We have stabilized the iron oxide nanoparticles (NPs) of various sizes on layered carbon materials (Fe-oxide/C) that show excellent catalytic performance. From the characterization of X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), scanning transmission X-ray microscopy (STXM) and X-ray magnetic circular dichroism spectroscopy (XMCD), a strong interfacial interaction in the Fe-oxide/C hybrids has been observed between the small iron oxide NPs and layered carbon in contrast to the weak interaction in the large iron oxide NPs. The interfacial interaction between the NPs and layered carbon is found to link with the improved catalytic performance. In addition, the Fe L-edge XMCD spectra show that the large iron oxide NPs are mainly γ-Fe2O3 with a strong ferromagnetic property, whereas the small iron oxide NPs with strong interfacial interaction are mainly α-Fe2O3 or amorphous Fe2O3 with a nonmagnetic property. The results strongly suggest that the interfacial interaction plays a key role for the catalytic performance, and the experimental findings may provide guidance toward rational design of high-performance catalysts. PMID:25839786

  12. Optimization of Surfactant Mixtures and Their Interfacial Behavior for Advanced Oil Recovery

    SciTech Connect

    Somasundaran, Prof. P.

    2002-03-04

    The objective of this project was to develop a knowledge base that is helpful for the design of improved processes for mobilizing and producing oil left untapped using conventional techniques. The main goal was to develop and evaluate mixtures of new or modified surfactants for improved oil recovery. In this regard, interfacial properties of novel biodegradable n-alkyl pyrrolidones and sugar-based surfactants have been studied systematically. Emphasis was on designing cost-effective processes compatible with existing conditions and operations in addition to ensuring minimal reagent loss.

  13. Surgical force detection probe

    NASA Technical Reports Server (NTRS)

    Tcheng, Ping; Roberts, Paul; Scott, Charles; Prass, Richard

    1991-01-01

    The development progress of a precision electro-mechanical instrument which allows the detection and documentation of the forces and moment applied to human tissue during surgery (under actual operation room conditions), is reported. The pen-shaped prototype probe which measures 1/2 inch in diameter and 7 inches in length was fabricated using an aerodynamic balance. The aerodynamic balance, a standard wind tunnel force and moment sensing transducer, measures the forces and the moments transmitted through the surgeon's hand to the human tissue during surgery. The prototype probe which was fabricated as a development tool was tested successfully. The final version of the surgical force detection probe will be designed based on additional laboratory tests in order to establish the full scale loads. It is expected that the final product will require a simplified aerodynamic balance with two or three force components and one moment component with lighter full scale loads. A signal conditioner was fabricated to process and display the outputs from the prototype probe. This unit will be interfaced with a PC-based data system to provide automatic data acquisition, data processing, and graphics display. The expected overall accuracy of the probe is better than one percent full scale.

  14. Radiative Forcing by Contrails

    NASA Technical Reports Server (NTRS)

    Meerkoetter, R.; Schumann, U.; Doelling, D. R.; Nakajima, T.; Tsushima, Y.

    1999-01-01

    A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmospheres The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 W/m(exp 2)a daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.

  15. Modeling interfacial area transport in multi-fluid systems

    SciTech Connect

    Yarbro, S.L.

    1996-11-01

    Many typical chemical engineering operations are multi-fluid systems. They are carried out in distillation columns (vapor/liquid), liquid-liquid contactors (liquid/liquid) and other similar devices. An important parameter is interfacial area concentration, which determines the rate of interfluid heat, mass and momentum transfer and ultimately, the overall performance of the equipment. In many cases, the models for determining interfacial area concentration are empirical and can only describe the cases for which there is experimental data. In an effort to understand multiphase reactors and the mixing process better, a multi-fluid model has been developed as part of a research effort to calculate interfacial area transport in several different types of in-line static mixers. For this work, the ensemble-averaged property conservation equations have been derived for each fluid and for the mixture. These equations were then combined to derive a transport equation for the interfacial area concentration. The final, one-dimensional model was compared to interfacial area concentration data from two sizes of Kenics in-line mixer, two sizes of concurrent jet and a Tee mixer. In all cases, the calculated and experimental data compared well with the highest scatter being with the Tee mixer comparison.

  16. Protein adsorption and interfacial rheology interfering in dilatational experiment

    NASA Astrophysics Data System (ADS)

    Rühs, P. A.; Scheuble, N.; Windhab, E. J.; Fischer, P.

    2013-05-01

    The static and dilatational response of β-lactoglobulin fibrils and native β-lactoglobulin (monomers) at water-air and water-oil interfaces (pH 2) was measured using the pendant drop method. The resulting adsorption behavior and viscoelasticity is dependent of concentration and adsorption time. The interfacial pressure of the β-lactoglobulin fibrils obtained in static measurements was 16-18 mN/m (against air) and 7 mN/m (against oil) for all concentrations. With higher concentrations, faster adsorption kinetics and slightly higher interfacial and surface pressure is achieved but did not lead to higher viscoelastic moduli. The transient saturation of the interface is similar for both the fibril solution and the monomers, however the fibril solution forms a strong viscoelastic network. To evaluate the superimposed adsorption behavior and rheological properties, the formed interfacial layer was subjected to dilatational experiments, which were performed by oscillating the surface area of the drop in sinusoidal and sawtooth (diagonal) deformation manner. The sinusoidal oscillations (time depended area deformation rate) result in a complex interfacial tension behavior against air and oil interfaces and show remarkable differences during compression and expansion as emphasized by Lissajous figures. For diagonal (constant area deformation rate) experiments, a slight bending of the interfacial tension response was observed at low frequencies emphasizing the influence of protein adsorption during rheological measurements.

  17. Effect of interfacial coupling on rectification in organic spin rectifiers

    NASA Astrophysics Data System (ADS)

    Hu, Gui-Chao; Zuo, Meng-Ying; Li, Ying; Zhang, Zhao; Ren, Jun-Feng; Wang, Chuan-Kui

    2015-07-01

    The effect of interfacial coupling on rectification in an organic co-oligomer spin diode is investigated theoretically by considering spin-independent and spin-resolved couplings respectively. In the case of spin-independent coupling, an optimal interfacial coupling strength with a significant enhanced rectification ratio is found, whose value depends on the structural asymmetry of the molecule. In the case of spin-resolved coupling, we found that only the variation of the interfacial coupling with specific spin is effective to modulate the rectification, which is due to the spin-filtering property of the central asymmetric magnetic molecule. A transition of the spin-current rectification between parallel spin-current rectification and antiparallel spin-current rectification may be observed with the variation of the spin-resolved interfacial coupling. The interfacial effect on rectification is further analyzed from the spin-dependent transmission spectrum at different biases. Project supported by the National Natural Science Foundation of China (Grant No. 1374195), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AM017), and the Excellent Young Scholars Research Fund of Shandong Normal University, China.

  18. Some Aspects of Interfacial Phenomena in Steelmaking and Refining

    NASA Astrophysics Data System (ADS)

    Wang, L. J.; Viswanathan, N. N.; Muhmood, L.; Kapilashrami, E.; Seetharaman, S.

    2016-03-01

    Unique experiments were designed to study the surface phenomena in steelmaking reactions. The concept of surface sulfide capacities and an understanding of the surface accumulation of surface-active species, based on experimental results, are presented. In order to understand the flow phenomenon at slag/metal interface, experiments were designed to measure the interfacial velocity of S on the surface of an iron drop immersed in an aluminosilicate slag using the X-ray sessile drop method. The oscillation of the iron drop in the slag due to the change in the surface concentration of sulfur at the slag-metal interface was monitored by X-ray imaging. From the observations, the interfacial velocity of sulfur was evaluated. Similar experiments were performed to measure the interfacial velocity of oxygen at the interface as well as the impact of oxygen potential on the interfacial velocity of sulfur. The interfacial shear viscosity and the dilatational modulus were also evaluated. In a study of the wetting of alumina base by iron drop at constant oxygen pressure under isothermal condition, the contact angle was found to be decreased with the progress of the reaction leading to the formation of hercynite as an intermediate layer creating non-wetting conditions. In the case of silica substrate, an intermediate liquid fayalite layer was formed.

  19. Some Aspects of Interfacial Phenomena in Steelmaking and Refining

    NASA Astrophysics Data System (ADS)

    Wang, L. J.; Viswanathan, N. N.; Muhmood, L.; Kapilashrami, E.; Seetharaman, S.

    2016-08-01

    Unique experiments were designed to study the surface phenomena in steelmaking reactions. The concept of surface sulfide capacities and an understanding of the surface accumulation of surface-active species, based on experimental results, are presented. In order to understand the flow phenomenon at slag/metal interface, experiments were designed to measure the interfacial velocity of S on the surface of an iron drop immersed in an aluminosilicate slag using the X-ray sessile drop method. The oscillation of the iron drop in the slag due to the change in the surface concentration of sulfur at the slag-metal interface was monitored by X-ray imaging. From the observations, the interfacial velocity of sulfur was evaluated. Similar experiments were performed to measure the interfacial velocity of oxygen at the interface as well as the impact of oxygen potential on the interfacial velocity of sulfur. The interfacial shear viscosity and the dilatational modulus were also evaluated. In a study of the wetting of alumina base by iron drop at constant oxygen pressure under isothermal condition, the contact angle was found to be decreased with the progress of the reaction leading to the formation of hercynite as an intermediate layer creating non-wetting conditions. In the case of silica substrate, an intermediate liquid fayalite layer was formed.

  20. Fine Adjustment of Interfacial Potential between pH-Responsive Hydrogels and Cell-Sized Particles.

    PubMed

    Monzel, Cornelia; Veschgini, Mariam; Madsen, Jeppe; Lewis, Andrew L; Armes, Steven P; Tanaka, Motomu

    2015-08-11

    We quantitatively determined interfacial potentials between cell-sized particles and stimulus-responsive hydrogels using a microinterferometer. The hydrogel is based on physically interconnected ABA triblock copolymer micelles comprising an inner biocompatible PMPC block and two outer pH-responsive PDPA blocks. The out-of-plane temporal fluctuation in the position of the cell-sized particles was calculated from changes in the interference pattern measured by Reflection Interference Contrast Microscopy (RICM), thus yielding the particle-substrate interaction potential V (Δh). Measurements in pH buffers ranging from 7.0 to 7.8 resulted in a systematic reduction in height of the potential minima ⟨Δh⟩ and a concomitant increase in the potential curvature V″ (Δh). The experimental data were analyzed by applying the modified Ross and Pincus model for polyelectrolytes, while accounting for gravitation, lubrication and van der Waals interactions. Elastic moduli calculated from V″ (Δh) were in good agreement with those measured by Atomic Force Microscopy. The ability to fine-tune both the gel elasticity and the interfacial potential at around physiological pH makes such triblock copolymer hydrogels a promising biocompatible substrate for dynamic switching of cell-material interactions. PMID:26190346

  1. Interfacial growth of controllable morphology of silver patterns on plastic substrates.

    PubMed

    Cui, Guanghui; Qi, Shengli; Wang, Xiaodong; Tian, Guofeng; Sun, Guang; Liu, Wei; Yan, Xiaona; Wu, Dezhen; Wu, Zhanpeng; Zhang, Li

    2012-10-11

    Controllable growth of newly born silver nanoparticles to fractal, cauliflower-like, microscale disks and continuous silver layers with high conductivity and reflectivity on plastic substrates has been developed via solid-liquid interfacial reduction and growing of ion-doped polymeric films. Such approaches involve polyimide (PI) films as substrates, its corresponding silver-ion-doped precursors as solid oxidants, and facile immersion of ion-doped polymeric films in aqueous reducing solution. The solution reducing process belongs to liquid-solid interfacial reduction processes, during which silver ions doped in polymeric matrix transformed to newly born silver nanoparticles which further aggregated and migrated along the liquid-solid interface to form dendrite, cauliflower-like and lamella disk-like architecture and/or severely compact continuous silver nanolayers with highly reflective and conductive properties. Time-dependent morphology evolutions of silver particles were traced by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). This strategy can also extend to synthesis of many other metals on polymeric films while maintaining outstanding metal-polymer adhesion based on incorporation of various metal ions, and may offer an opportunity to fabricate large scale, high-output, cost-effective processes for metal patterns on flexible polymeric substrates. PMID:23016702

  2. Temperature effects on the interfacial properties of semifluorinated diblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Shrestha, Umesh; Clarson, Stephen; Perahia, Dvora

    The interfacial composition and structure of polymer films influence their response to external stimuli and their wetting behavior. Here we probe temperature effects on the interfacial morphology and surface energies of polytrifluoro propyl methyl siloxane- b-polystyrene (SiF-b-PS) films with SiF volume fraction of φ = 0.03 to 0.46 using atomic force microscopy and surface tension measurement. Films were cast from toluene, selective for PS, and annealed at temperatures ranging from 75 to 210°C, below and above Tg of the PS block (~98°C). For φ = 0. 03 a network of small aggregates is formed and hardly changed over the temperature range studied. For φ = 0.16 an asymmetric diblock, spherical aggregates at room temperature transformed to elongated ones at elevated temperatures whereas in the symmetric case, spherical assemblies at room temperature merged into larger structures. Independent of SiF fraction the contact angle increased with temperature which is indicative of migration of fluorine to the interface. Surprisingly, dewetting was not observed even annealing the film at much higher temperature than Tg of PS. NSF DMR 0907390 2009.

  3. Estimation of Liquid Wall and Interfacial Shear Stress in Horizontal Stratified Gas-liquid Pipe Flow

    NASA Astrophysics Data System (ADS)

    Liu, Yiping; Zhang, Hua; Wang, Jing

    2007-06-01

    A modified two-phase shear stress calculation method for pipe flow problems is explored. A force balance has been set up on the control volume of liquid phase to determine the interfacial friction factor by employing both the measured pressure gradient and liquid height. The gradient of height of liquid layer has been taken into account, which is suitable for the case where the interface may be smooth, rippled or wavy. The correlation of model indicates that the careful estimation for liquid-wall shear stress is necessary, and the assumption of a stationary liquid element is not applicable for the case of higher gas flow rates. The interfacial friction factor evaluated indirectly from experimental liquid height and pressure loss measurements, which are obtained in 50mm ID pipeline for air and water in cocurrent stratified flow, is used to achieve its correlation with the combination of characteristic parameters. The evaluation of new correlation has been conducted by the comparison of the predicted pressure drop with the experimental data. The performance of correlation depends on the form of the gas-liquid interface.

  4. High-resolution imaging and spectroscopy of interfacial water at single bond limit

    NASA Astrophysics Data System (ADS)

    Jiang, Ying

    Hydrogen bond is one of the most important weak interactions in nature and plays an essential role in a broad spectrum of physics, chemistry, biology, energy and material sciences. The conventional methods for studying hydrogen-bonding interaction are all based on spectroscopic or diffraction techniques. However, those techniques have poor spatial resolution and only measure the average properties of many hydrogen bonds, which are susceptible to the structural inhomogeneity and local environments, especially when interfacial systems are concerned. The spatial variation and inter-bond coupling of the hydrogen bonds leads to significant spectral broadening, which prohibits the accurate understanding of the experimental data. In this talk, I will present our recent progress on the development of new-generation scanning probe microscopy/spectroscopy (SPM/S) with unprecedentedly high sensitivity and resolution, for addressing weak inter- and intra-molecular interactions, such as hydrogen bonds and van der Waals force. Based on a qPlus sensor, we have succeeded to push the real-space study of a prototypical hydrogen-bonded system, i.e. water, down to single bond limit. Combined with state-of-the-arts quantum simulations, we have discovered exotic nuclear quantum effects (NQEs) in interfacial water and revealed the quantum nature of the hydrogen bond from a completely new perspective

  5. Viscosity and interfacial properties in a mussel-inspired adhesive coacervate†

    PubMed Central

    Srivastava, Aasheesh; Krogstad, Daniel V.; Tirrell, Matthew; Israelachvili, Jacob N.; Waite, J. Herbert

    2011-01-01

    The chemistry of mussel adhesion has commanded the focus of much recent research activity on wet adhesion. By comparison, the equally critical adhesive processing by marine organisms has been little examined. Using a mussel-inspired coacervate formed by mixing a recombinant mussel adhesive protein (fp-151-RGD) with hyaluronic acid (HA), we have examined the nanostructure, viscosity, friction, and interfacial energy of fluid-fluid phase-separated coacervates using the surface forces apparatus and microscopic techniques. At mixing ratios of fp-151-RGD:HA resulting in marginal coacervation, the coacervates showed shear-thickening viscosity and no structure by cryo-transmission electron microscopy (cryo-TEM). However, at the mixing ratio producing maximum coacervation, the coacervate showed shear-thinning viscosity and a transition to a bicontinuous phase by cryo-TEM. The shear-thinning viscosity, high friction coefficient (>1.2), and low interfacial energy (<1 mJ m−2) observed at the optimal mixing ratio for coacervation are promising delivery, spreading and adhesion properties for future wet adhesive and coating technologies. PMID:21544267

  6. Lateral actuation of an organic droplet on conjugated polymer electrodes via imbalanced interfacial tensions.

    PubMed

    Xu, Wei; Xu, Jian; Li, Xin; Tian, Ye; Choi, Chang-Hwan; Yang, Eui-Hyeok

    2016-08-17

    This paper presents a new mechanism for the controlled lateral actuation of organic droplets on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) electrodes at low voltages (∼0.9 V) in an aqueous environment. The droplet actuation is based on the tunable surface wetting properties of the polymer electrodes induced by electrochemical redox reactions. The contact angle of a dichloromethane (DCM) droplet on the PPy(DBS) surface switches between ∼119° upon oxidation (0.6 V) and ∼150° upon reduction (-0.9 V) in 0.1 M NaNO3 solution. The droplet placed across the reduced and oxidized PPy(DBS) electrodes experiences imbalanced interfacial tensions, which prompt the actuation of the droplet from the reduced electrode to the oxidized electrode. The lateral actuation of DCM droplets on two PPy(DBS) electrodes is demonstrated, and the actuation process is studied. The driving force due to the imbalanced interfacial tensions is estimated to be approximately 10(-7) N for a 6 μL droplet. PMID:27426489

  7. Interfacial phenomena on selected cathode materials

    SciTech Connect

    Kostecki, Robert; Matsuo, Yoshiaki; McLarnon, Frank

    2001-06-22

    We have carried out a series of surface studies of selected cathode materials. Instrumental techniques such as Raman microscopy, surface enhanced Raman spectroscopy (SERS), and atomic force microscopy were used to investigate the cathode surfaces. The goal of this study was to identify detrimental processes which occur at the electrode/electrolyte interface and can lead to electrode degradation and failure during cycling and/or storage at elevated temperatures.

  8. Iridium Interfacial Stack - IrIS

    NASA Technical Reports Server (NTRS)

    Spry, David

    2012-01-01

    Iridium Interfacial Stack (IrIS) is the sputter deposition of high-purity tantalum silicide (TaSi2-400 nm)/platinum (Pt-200 nm)/iridium (Ir-200 nm)/platinum (Pt-200 nm) in an ultra-high vacuum system followed by a 600 C anneal in nitrogen for 30 minutes. IrIS simultaneously acts as both a bond metal and a diffusion barrier. This bondable metallization that also acts as a diffusion barrier can prevent oxygen from air and gold from the wire-bond from infiltrating silicon carbide (SiC) monolithically integrated circuits (ICs) operating above 500 C in air for over 1,000 hours. This TaSi2/Pt/Ir/Pt metallization is easily bonded for electrical connection to off-chip circuitry and does not require extra anneals or masking steps. There are two ways that IrIS can be used in SiC ICs for applications above 500 C: it can be put directly on a SiC ohmic contact metal, such as Ti, or be used as a bond metal residing on top of an interconnect metal. For simplicity, only the use as a bond metal is discussed. The layer thickness ratio of TaSi2 to the first Pt layer deposited thereon should be 2:1. This will allow Si from the TaSi2 to react with the Pt to form Pt2Si during the 600 C anneal carried out after all layers have been deposited. The Ir layer does not readily form a silicide at 600 C, and thereby prevents the Si from migrating into the top-most Pt layer during future anneals and high-temperature IC operation. The second (i.e., top-most) deposited Pt layer needs to be about 200 nm to enable easy wire bonding. The thickness of 200 nm for Ir was chosen for initial experiments; further optimization of the Ir layer thickness may be possible via further experimentation. Ir itself is not easily wire-bonded because of its hardness and much higher melting point than Pt. Below the iridium layer, the TaSi2 and Pt react and form desired Pt2Si during the post-deposition anneal while above the iridium layer remains pure Pt as desired to facilitate easy and strong wire-bonding to the Si

  9. Long-ranged solvation forces in a fluid with short-ranged interactions

    NASA Astrophysics Data System (ADS)

    Pertsin, Alexander J.; Grunze, Michael

    2003-05-01

    The grand canonical Monte Carlo technique is used to calculate the solvation force and interfacial tension in a simple Lennard-Jones fluid confined between two solid walls. Emphasis is placed on large wall-to-wall separations, where the oscillations of density and solvation force due to layering effects have decayed. Despite the short range of the fluid-fluid and fluid-wall interaction potentials used, the solvation force shows an unsuspectedly long-ranged behavior, remaining quite perceptible up to a separation of 100 molecular diameters. It is also found that the sign of the solvation force at large separations is not uniquely determined by the sign of the interfacial tension: The walls that are "philic" with respect to the constrained fluid may well exhibit both repulsive and attractive solvation forces.

  10. Interfacial molecular interactions based on the conformation recognition between the insoluble antitumor drug AD-1 and DSPC.

    PubMed

    Yin, Tian; Cao, Xiuxiu; Liu, Xiaolin; Wang, Jian; Shi, Caihong; Su, Jia; Zhang, Yu; Gou, Jingxin; He, Haibing; Guo, Haiyan; Tang, Xing; Zhao, Yuqing

    2016-10-01

    In this study, molecular interactions between the anti-cancer agent 20(R)-25-methoxyl-dammarane-3β, 12β, 20-triol (AD-1) and phospholipid 1,2-Distearoyl-sn-glycero-3-phosphocholine (DSPC) were investigated using the Langmuir film balance technique. The characteristics of binary Langmuir monolayers consisting of DSPC and AD-1 were conducted on the basis of the surface pressure-area per molecule (π-A) isotherms. It was found that the drug was able to become efficiently inserted into preformed DSPC monolayers, indicating a preferential interaction between AD-1 and DSPC. For the examined lateral pressure at 20mN/m, the largest negative values of ΔGex were found for the AD-1/DSPC monolayer, which should be the most stable. Based on the calculated values of ΔGex, we found that the AD-1/DSPC systems exhibited the best mixed characteristics when the molar fraction of the AD-1 was 0.8; at that relative concentration, the AD-1 molecules can mix better and interact with the phospholipid molecules. In addition, the drug-DSPC binary supramolecular structure was also deposited on the mica plates as shown by atomic force microscopy (AFM). Finally, molecular docking calculations explained satisfactorily that, based on the conformations interactions (conformation recognition), even at an AD-1/DSPC molar ratio as high as 8:2, the interfacial stabilization of the AD-1/DSPC system was fairly strong due to hydrophobic interactions. A higher loading capacity of DSPC might be possible, as it is associated with a more flexible geometrical environment, which allows these supramolecular structures to accept larger increases in drug loading upon steric binding. PMID:27469574

  11. Interfacial tensions of liquid Fe-Ni alloys and stainless steels in contact with CaO-SiO2″AI2O3-based slags at 1550 °C

    NASA Astrophysics Data System (ADS)

    Sharan, A.; Cramb, A. W.

    1995-02-01

    In the present work, the interfacial tensions of Fe-Ni alloys in contact with slags of the CaO-Al2O3-SiO2 system were measured at 1550 °C. Nickel additions to the alloy were found to decrease interfacial tension. The effects of alumina and titania additions to the slag on the interfacial tension of the Fe-20 wt pct Ni alloy were determined: alumina was found to increase the interfacial tension by a small amount, while titania was found to decrease it drastically. Using the present interfacial tension data for the CaO-Al2O3-SiO2 system and the ones measured by Jimbo and Cramb, Girifalco and Good’s interaction coefficient (ϕ) was determined as a function of the slag composition using regression analysis and was found to be a useful means of correlating interfacial tension data. The interfacial tension of an Fe-20 wt pct Ni-2.39 wt pct Al alloy in contact with a CaO-Al2O3-SiO2 slag was found to decrease drastically in the first 60 to 75 minutes of the experiment due to the dynamic effects of mass transfer. Slight lowering of interfacial tensions of industrial stainless steels due to sulfur transfer from liquid metal to slag was also observed. The equilibrium interfacial tensions of type 304 stainless steels were found to be more dependent on the slag chemistry than on the nickel and chromium content of the alloy.

  12. Static interfacial properties of Bose-Einstein-condensate mixtures

    NASA Astrophysics Data System (ADS)

    Indekeu, Joseph O.; Lin, Chang-You; Van Thu, Nguyen; Van Schaeybroeck, Bert; Phat, Tran Huu

    2015-03-01

    The interfacial profiles and interfacial tensions of phase-separated binary mixtures of Bose-Einstein condensates are studied theoretically. The two condensates are characterized by their respective healing lengths ξ1 and ξ2 and by the interspecies repulsive interaction K . An exact solution to the Gross-Pitaevskii (GP) equations is obtained for the special case ξ2/ξ1=1 /2 and K =3 /2 . Furthermore, applying a double-parabola approximation (DPA) to the energy density featured in GP theory allows us to define a DPA model, which is much simpler to handle than GP theory but nevertheless still captures the main physics. In particular, a compact analytic expression for the interfacial tension is derived that is useful for all ξ1,ξ2 , and K . An application to wetting phenomena is presented for condensates adsorbed at an optical wall. The wetting phase boundary obtained within the DPA model nearly coincides with the exact one in GP theory.

  13. Preliminary exploration of the interfacial structure of nanocrystalline materials

    SciTech Connect

    Guo, W.Q.; Liu, X.D.; Ding, B.Z.

    1995-12-31

    The present intense interest in exploration on nanostructured materials stems from the studies of interfacial structures of nanocrystalline materials. Up to now, there are two different results of the exploration on interfacial structure of nanocrystalline materials. The first one supposed by Gleiter et al. is a so-called {open_quotes}gas-like{close_quotes} structure. They reported that the interfaces of nanocrystalline materials represent a novel type of solid structure without any long or short range order, corresponding structurally to a {open_quotes}gas-like{close_quotes} solid. This structure can be verified with X-ray diffraction, Mossbauer spectroscopy, positron lifetime spectroscopy and extended X-ray absorption fine structure (EXFAS). The second result obtained by Siegel et al. with high resolution electron microscopy, raman scattering and small angle X-ray and neutron diffraction is that the interfacial structures of nanocrystalline materials are rather similar to those in conventional coarse-grained polycrystals.

  14. Environmental Applications of Interfacial Materials with Special Wettability.

    PubMed

    Wang, Zhangxin; Elimelech, Menachem; Lin, Shihong

    2016-03-01

    Interfacial materials with special wettability have become a burgeoning research area in materials science in the past decade. The unique surface properties of materials and interfaces generated by biomimetic approaches can be leveraged to develop effective solutions to challenging environmental problems. This critical review presents the concept, mechanisms, and fabrication techniques of interfacial materials with special wettability, and assesses the environmental applications of these materials for oil-water separation, membrane-based water purification and desalination, biofouling control, high performance vapor condensation, and atmospheric water collection. We also highlight the most promising properties of interfacial materials with special wettability that enable innovative environmental applications and discuss the practical challenges for large-scale implementation of these novel materials. PMID:26829583

  15. Interfacial electronic effects control the reaction selectivity of platinum catalysts.

    PubMed

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts. PMID:26808458

  16. 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.

  17. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    NASA Astrophysics Data System (ADS)

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  18. Molecular dynamics studies of interfacial water at the alumina surface.

    SciTech Connect

    Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

    2011-01-01

    Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior at distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.

  19. Interfacial properties and mechanical behavior of titanium aluminides

    SciTech Connect

    Yoo, M.H.; Fu, C.L.

    1998-01-01

    The role of various interfaces in deformation and fracture behavior of two phase TiAl-Ti{sub 3}Al alloys is analyzed on the basis of the specific interfacial and surface energies determined from ab initio calculations. The propensity of twinning observed in these alloys is consistent with the low true twin boundary energy. The strong plastic anisotropy reported in TiAl polysynthetically twinned (PST) crystals is attributed partly to the localized slip along lamellar interfaces, thus lowering the yield stress for soft orientations. Interfacial fracture energies are estimated to be the highest for the {alpha}{sub 2}/{gamma} lamellar boundary and the lowest for the 120 {degree} rotational {gamma}/{gamma} boundary. The fracture mode mixity plays an important role in the crack-tip plasticity by ordinary slip and true twinning, leading to translamellar and interfacial fracture.

  20. Graphene as an efficient interfacial layer for electrochromic devices.

    PubMed

    Lin, Feng; Bult, Justin B; Nanayakkara, Sanjini; Dillon, Anne C; Richards, Ryan M; Blackburn, Jeffrey L; Engtrakul, Chaiwat

    2015-06-01

    This study presents an interfacial modification strategy to improve the performance of electrochromic films that were fabricated by a magnetron sputtering technique. High-quality graphene sheets, synthesized by chemical vapor deposition, were used to modify fluorine-doped tin oxide substrates, followed by the deposition of high-performance nanocomposite nickel oxide electrochromic films. Electrochromic cycling results revealed that a near-complete monolayer graphene interfacial layer improves the electrochromic performance in terms of switching kinetics, activation period, coloration efficiency, and bleached-state transparency, while maintaining ∼100% charge reversibility. The present study offers an alternative route for improving the interfacial properties between electrochromic and transparent conducting oxide films without relying on conventional methods such as nanostructuring or thin film composition control. PMID:25950270

  1. Probing model tumor interfacial properties using piezoelectric cantilevers.

    PubMed

    Yegingil, Hakki; Shih, Wan Y; Shih, Wei-Heng

    2010-09-01

    Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G/E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The piezoelectric cantilever used had two lead zirconate titanate layers to facilitate all-electrical elastic (shear) modulus measurements using one single device. We constructed model tissues with tumors by embedding one-dimensional (1D) corrugated inclusions and three-dimensional (3D) spiky-ball inclusions made of modeling clay in gelatin. We showed that for smooth inclusions, G/E was 0.3 regardless of the shear direction. In contrast, for a 1D corrugated rough inclusion G/E was 0.3 only when the shear was parallel to corrugation and G/E increased with an increasing angle between the shear direction and the corrugation. When the shear was perpendicular to corrugation, G/E became >0.7. For 3D isotropic spiky-ball inclusions we showed that the G/E depended on the degree of the roughness. Using the ratio s/r of the spike length (s) to the overall inclusion radius (r) as a roughness parameter, we showed that for inclusions with s/r larger than or equal to 0.28, the G/E ratio over the inclusions was larger than 0.7 whereas for inclusions with s/r less than 0.28, the G/E decreased with decreasing s/r to around 0.3 at s/r=0. In addition, we showed that the depth limit of the G/E measurement is twice the width of the probe area of the piezoelectric cantilever. PMID:20887005

  2. The crystal-fluid interfacial free energy and nucleation rate of NaCl from different simulation methods

    NASA Astrophysics Data System (ADS)

    Espinosa, Jorge R.; Vega, Carlos; Valeriani, Chantal; Sanz, Eduardo

    2015-05-01

    In this work, we calculate the crystal-fluid interfacial free energy, γcf, for the Tosi-Fumi model of NaCl using three different simulation techniques: seeding, umbrella sampling, and mold integration. The three techniques give an orientationaly averaged γcf of about 100 mJ/m2. Moreover, we observe that the shape of crystalline clusters embedded in the supercooled fluid is spherical. Using the mold integration technique, we compute γcf for four different crystal orientations. The obtained interfacial free energies range from 100 to 114 mJ/m2, being (100) and (111) the crystal planes with the lowest and highest γcf, respectively. Within the accuracy of our calculations, the interfacial free energy either does not depend on temperature or changes very smoothly with it. Combining the seeding technique with classical nucleation theory, we also estimate nucleation free energy barriers and nucleation rates for a wide temperature range (800-1040 K). The obtained results compare quite well with brute force calculations and with previous results obtained with umbrella sampling [Valeriani et al., J. Chem. Phys, 122, 194501 (2005)].

  3. Simultaneous Spectroscopic and Topographic Imaging of Single-Molecule Interfacial Electron-Transfer Reactivity and Local Nanoscale Environment.

    PubMed

    He, Yufan; Rao, Vishal Govind; Cao, Jin; Lu, H Peter

    2016-06-16

    The fundamental information related to the energy flow between molecules and substrate surfaces as a function of surface site geometry and molecular structure is critical for understanding interfacial electron-transfer (ET) dynamics. The inhomogeneous nanoscale molecule-surface and molecule-molecule interactions are presumably the origins of the complexity in interfacial ET dynamics; thus, identifying the environment of molecules at nanoscale is crucial. We have developed atomic force microscopy (AFM) correlated single-molecule fluorescence intensity/lifetime imaging microscopy (AFM-SMFLIM) capable of identifying and characterizing individual molecules distributed across the heterogeneous surface at the nanometer length scale. Using the novel AFM-SMFLIM imaging, we are able to obtain nanoscale morphology and interfacial ET dynamics at a single-molecule level. Moreover, the observed blinking behavior and lifetime of each molecule in combination with the topography of the environment at nanoscale provide the location of each molecule on the surface (TiO2 vs cover glass) at nanoscale and the coupling strength of each molecule with TiO2 nanoparticles. PMID:27214587

  4. Surface and Interfacial Properties of Nonaqueous-Phase Liquid Mixtures Released to the Subsurface at the Hanford Site

    SciTech Connect

    Nellis, Scott; Yoon, Hongkyu; Werth, Charlie; Oostrom, Martinus; Valocchi, Albert J.

    2009-05-01

    Surface and interfacial tensions that arise at the interface between different phases are key parameters affecting Nonaqueous Phase Liquid (NAPL) movement and redistribution in the vadose zone after spill events. In this study, the impact of major additive components on surface and interfacial tensions for organic mixtures and wastewater was investigated. Organic mixture and wastewater compositions are based upon carbon tetrachloride (CT) mixtures released at the Hanford site, where CT was discharged simultaneously with dibutyl butyl phosphonate (DBBP), tributyl phosphate (TBP), dibutyl phosphate (DBP), and a machining lard oil (LO). A considerable amount of wastewater consisting primarily of nitrates and metal salts was also discharged. The tension values measured in this study revealed that the addition of these additive components caused a significant lowering of the interfacial tension with water or wastewater and the surface tension of the wastewater phase in equilibrium with the organic mixtures, compared to pure CT, but had minimal effect on the surface tension of the NAPL itself. These results lead to large differences in spreading coefficients for several mixtures, where the additives caused both a higher (more spreading) initial spreading coefficient and a lower (less spreading) equilibrium spreading coefficient. This indicates that if these mixtures migrate into uncontaminated areas, they will tend to spread quickly, but form a higher residual NAPL saturation after equilibrium, as compared to pure CT. Over time, CT likely volatilizes more rapidly than other components in the originally disposed mixtures and the lard oil and phosphates would become more concentrated in the remaining NAPL, resulting in a lower interfacial tension for the mixture. Spreading coefficients are expected to increase and perhaps change the equilibrated organic mixtures from nonspreading to spreading in water-wetting porous media. These results show that the behavior of organic

  5. Analysis of DNA equilibrium configuration under interfacial traction.

    PubMed

    Wang, Y Z; Zhang, Q C; Wang, W; Yang, Y W

    2016-01-01

    Kirchhoff thin elastic rod models are important in the study of the mechanism determining the configurations of flexible structures not only at the macroscopic but also at the microscopic scale. In this study, the energy balance method has been well applied to analyze the configuration of a DNA elastic rod in the presence of interfacial traction. An approximate solution for the shape equations has been obtained, and the relationship between the interfacial factor and the configuration of the DNA segment is derived. The results may provide an explanation for the onset of the formation of kinks in DNA when immersed in a solution. PMID:27323042

  6. Adhesion and interfacial fracture toughness between hard and soft materials

    NASA Astrophysics Data System (ADS)

    Rahbar, Nima; Wolf, Kurt; Orana, Argjenta; Fennimore, Roy; Zong, Zong; Meng, Juan; Papandreou, George; Maryanoff, Cynthia; Soboyejo, Wole

    2008-11-01

    This paper presents the results of a combined experimental and theoretical study of adhesion between hard and soft layers that are relevant to medical devices such as drug-eluting stents and semiconductor applications. Brazil disk specimens were used to measure the interfacial fracture energies between model parylene C and 316L stainless steel over a wide range of mode mixities. The trends in the overall fracture energies are predicted using a combination of adhesion theories and fracture mechanics concepts. The measured interfacial fracture energies are shown to be in good agreement with the predictions.

  7. The ensemble switch method for computing interfacial tensions.

    PubMed

    Schmitz, Fabian; Virnau, Peter

    2015-04-14

    We present a systematic thermodynamic integration approach to compute interfacial tensions for solid-liquid interfaces, which is based on the ensemble switch method. Applying Monte Carlo simulations and finite-size scaling techniques, we obtain results for hard spheres, which are in agreement with previous computations. The case of solid-liquid interfaces in a variant of the effective Asakura-Oosawa model and of liquid-vapor interfaces in the Lennard-Jones model are discussed as well. We demonstrate that a thorough finite-size analysis of the simulation data is required to obtain precise results for the interfacial tension. PMID:25877563

  8. Interfacial Effects in Polymer Membranes for Clean Energy

    NASA Astrophysics Data System (ADS)

    Soles, Christopher

    2013-03-01

    Polymeric membranes are critical components in several emerging clean energy technologies. Examples include proton exchange membranes for hydrogen fuel cells, anion exchange membranes for alkaline fuel cells, flow batteries, and even block copolymer membranes for solid electrolytes/separators in lithium ion and other battery technologies. In all of these examples the function of the membrane is to physically separate two reactive electrodes or reactants, but allow the transport or exchange of specific ions through the membrane between the active electrodes. The flow of the charged ionic species between the electrodes can be used to balance the flow of electrons through an external electrical circuit that connects the electrodes, thereby storing or delivering charge electrochemically. In this presentation I will review the use of polymeric membranes in electrochemical energy storage technologies and discuss the critical issues related to the membranes that hinder these technologies. In particular I will also focus on the role the polymer membrane interface on device performance. At some point the polymer membrane must be interfaced with an active electrode or catalyst and the nature of this interface can significantly impact performance. Simulations of device performance based on bulk membrane transport properties often fail to predict the actual performance and empirical interfacial impedance terms usually added to capture the device performance. In this presentation I will explore the origins of this interfacial impedance in the different types of fuel cell membranes (proton and alkaline) by creating model thin film membranes where all of the membrane can be considered interfacial. We then use these thin films as a surrogate for the interfacial regions of a bulk membrane and then quantify the structure, dynamics, and transport properties of water and ions in the confined interfacial films. Using neutron reflectivity, grazing incidence X-ray diffraction, and

  9. Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion

    NASA Astrophysics Data System (ADS)

    Das, Tanmay; Kulkarni, Prabhanjan D.; Purandare, S. C.; Barshilia, Harish C.; Bhattacharyya, Somnath; Chowdhury, Prasanta

    2014-06-01

    We observed interfacial chemical sharpening due to uphill diffusion in post annealed ultrathin multilayer stack of Co and Pt, which leads to enhanced interfacial perpendicular magnetic anisotropy (PMA). This is surprising as these elements are considered as perfectly miscible. This chemical sharpening was confirmed through quantitative energy dispersive x-ray (EDX) spectroscopy and intensity distribution of images taken on high angle annular dark field (HAADF) detector in Scanning Transmission Electron Microscopic (STEM) mode. This observation demonstrates an evidence of miscibility gap in ultrathin coherent Co/Pt multilayer stacks.

  10. Modelling temperature and concentration dependent solid/liquid interfacial energies

    NASA Astrophysics Data System (ADS)

    Lippmann, Stephanie; Jung, In-Ho; Paliwal, Manas; Rettenmayr, Markus

    2016-01-01

    Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al-FCC with their respective liquids and compared with experimental data.

  11. Estimating interfacial thermal conductivity in metamaterials through heat flux mapping

    SciTech Connect

    Canbazoglu, Fatih M.; Vemuri, Krishna P.; Bandaru, Prabhakar R.

    2015-04-06

    The variability of the thickness as well as the thermal conductivity of interfaces in composites may significantly influence thermal transport characteristics and the notion of a metamaterial as an effective medium. The consequent modulations of the heat flux passage are analytically and experimentally examined through a non-contact methodology using radiative imaging, on a model anisotropic thermal metamaterial. It was indicated that a lower Al layer/silver interfacial epoxy ratio of ∼25 compared to that of a Al layer/alumina interfacial epoxy (of ∼39) contributes to a smaller deviation of the heat flux bending angle.

  12. The ensemble switch method for computing interfacial tensions

    SciTech Connect

    Schmitz, Fabian; Virnau, Peter

    2015-04-14

    We present a systematic thermodynamic integration approach to compute interfacial tensions for solid-liquid interfaces, which is based on the ensemble switch method. Applying Monte Carlo simulations and finite-size scaling techniques, we obtain results for hard spheres, which are in agreement with previous computations. The case of solid-liquid interfaces in a variant of the effective Asakura-Oosawa model and of liquid-vapor interfaces in the Lennard-Jones model are discussed as well. We demonstrate that a thorough finite-size analysis of the simulation data is required to obtain precise results for the interfacial tension.

  13. Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation.

    PubMed

    Amat, Miguel A; Rutledge, Gregory C

    2010-03-21

    A molecular dynamics study is presented to assess the performance of a united-atom model in the prediction of liquid-vapor interfacial properties for short-chain perfluoroalkanes and their alkane counterparts. In particular, the ability of this model to discriminate between the surface-energy values of these two types of compounds was investigated over a wide temperature range corresponding to the liquid-vapor region. Comparisons with available experimental data and surface-tension predictions given by other force-field parameterizations, including those based on the more computationally demanding all-atom method, were performed to gauge the viability of this model. It was found that the model used in this study captures qualitatively the expected behavior of surface energy between alkanes and perfluoroalkanes and yields values that are in excellent agreement with experimental data, especially in the high-temperature limit as the critical temperature is approached. PMID:20331313

  14. Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation

    NASA Astrophysics Data System (ADS)

    Amat, Miguel A.; Rutledge, Gregory C.

    2010-03-01

    A molecular dynamics study is presented to assess the performance of a united-atom model in the prediction of liquid-vapor interfacial properties for short-chain perfluoroalkanes and their alkane counterparts. In particular, the ability of this model to discriminate between the surface-energy values of these two types of compounds was investigated over a wide temperature range corresponding to the liquid-vapor region. Comparisons with available experimental data and surface-tension predictions given by other force-field parameterizations, including those based on the more computationally demanding all-atom method, were performed to gauge the viability of this model. It was found that the model used in this study captures qualitatively the expected behavior of surface energy between alkanes and perfluoroalkanes and yields values that are in excellent agreement with experimental data, especially in the high-temperature limit as the critical temperature is approached.

  15. Interfacial shear stress distribution in model composites. I - A Kevlar 49 fibre in an epoxy matrix

    SciTech Connect

    Jahankhani, H.; Galiotis, C. )

    1991-05-01

    The technique of Laser Raman Spectroscopy has been applied in the study of aramid fibers, such as Kevlar 49, and aramid/epoxy interfaces. A linear relationship has been found between Raman frequencies and strain upon loading a single Kevlar 49 filament in air. Model composites of single Kevlar 49 fibers embedded in epoxy resins have been fabricated and subjected to various degrees of mechanical deformation. The transfer lengths for reinforcement have been measured at various levels of applied tensile load and the dependence of transfer length upon applied matrix strain has been established. Finally, by balancing the tensile and the shear forces acting along the interface, the interfacial shear stress (ISS) distribution along the embedded fiber was obtained. 52 refs.

  16. Interfacial dynamics of a liposome deforming in an axisymmetric extensional flow

    NASA Astrophysics Data System (ADS)

    Gonzalez-Mancera, Andres; Eggleton, Charles D.

    2007-03-01

    Liposomes are self-enclosed structures composed of curved lipid bilayer membranes which entrap part of the solvent in which they freely float. They are predominantly made from amphiphilic molecules, a special class of surface-active molecules. Liposomes have various applications in science and technology including drug delivery systems, medical diagnostics and they can also be used as simple cellular models for basic research. We simulated the deformation of a liposome in an axisymmetric extensional flow using the boundary integral method. The liposome deforms due to hydrodynamic loading on the interface. The dynamics of the system are characterized by the competition between the hydrodynamic and interfacial forces. The lipid bilayer membrane can be modeled as a hyperelastic continuous material or a liquid-liquid interface with a highly packed surfactant layer. We compare the deformation behavior of liposomes with both types of interfaces and identify similarities and differences between the two models.

  17. Multifunctional Paper Strip Based on Self-Assembled Interfacial Plasmonic Nanoparticle Arrays for Sensitive SERS Detection.

    PubMed

    Zhang, Kun; Zhao, Jingjing; Xu, Huiying; Li, Yixin; Ji, Ji; Liu, Baohong

    2015-08-01

    A smart and multifunctional paper-based SERS sensing card is generated through patterning self-assembled interfacial arrays of gold nanoparticles (AuNPs) on the tip of an arrow-shaped paper strip. It is found that the closely packed monolayer of AuNPs is evenly distributed on the paper surface, resulting in a multitude of SERS hot spots over the detection zone. The paper card, with its inherent ability to separate and preconcentrate analytes by the capillary force and polarity difference between sample components, was exploited successfully as an integrated platform, allowing for sub-attomolar (50 × 10(-18) M) detection from microliter-volume (10 μL) samples. Furthermore, the simple preparation (lithography-free process), fast detection (<5 min), and low cost (<3 cents) demonstrate that the paper card is a practical and portable sensing interface for wide application in environmental and food analysis. PMID:26186409

  18. Imaging interfacial micro- and nano-bubbles by scanning transmission soft X-ray microscopy.

    PubMed

    Zhang, Lijuan; Zhao, Binyu; Xue, Lian; Guo, Zhi; Dong, Yaming; Fang, Haiping; Tai, Renzhong; Hu, Jun

    2013-05-01

    Synchrotron-based scanning transmission soft X-ray microscopy (STXM) with nanometer resolution was used to investigate the existence and behavior of interfacial gas nanobubbles confined between two silicon nitride windows. The observed nanobubbles of SF6 and Ne with diameters smaller than 2.5 µm were quite stable. However, larger bubbles became unstable and grew during the soft X-ray imaging, indicating that stable nanobubbles may have a length scale, which is consistent with a previous report using atomic force microscopy [Zhang et al. (2010), Soft Matter, 6, 4515-4519]. Here, it is shown that STXM is a promising technique for studying the aggregation of gases near the solid/water interfaces at the nanometer scale. PMID:23592619

  19. Investigation of optical and interfacial properties of Ag/Ta{sub 2}O{sub 5} metal dielectric multilayer structure

    SciTech Connect

    Sarkar, P. Jena, S.; Tokas, R. B.; Thakur, S.; Sahoo, N. K.; Rao, K. D.; Misal, J. S.; Prathap, C.

    2015-06-24

    One-dimensional periodic metal-dielectric multilayer thin film structures consisting of Ag and Ta{sub 2}O{sub 5} alternating layers are deposited on glass substrate using RF magnetron sputtering technique. The spectral property of the multilayers has been investigated using spectrophotometry technique. The optical parameters such as refractive index, extinction coefficient, band gap etc., along with film thickness as well as the interfacial layer properties which influence these properties have been probed with spectroscopic ellipsometry technique. Atomic force microscopy has been employed to characterize morphological properties of this metal-dielectric multilayer.

  20. CHARGE-BASED FORCES AT THE NAFION-WATER INTERFACE

    PubMed Central

    Das, Ronnie; Pollack, Gerald H.

    2013-01-01

    Interfacial water lying next to hydrophilic surfaces has been shown to be spectroscopically, mechanically, and electrically distinct from bulk water. Interfacial water has also been shown to exclude negatively- and positively-charged microspheres, and has thus become known as the “exclusion zone.” Measurements have demonstrated that exclusion zones exhibit a negative electrical potential on the order of −100 mV relative to bulk water, with a corresponding distribution of positive protons in the bulk water region beyond the exclusion zone. This separation of charge is hypothesized to create an electrostatic force between the exclusion zone and the proton-enriched zone beyond. To test this hypothesis, a hydrophilic Nafion ring was attached to the tip of a deflectable ribbon-like force sensor. The sensor was designed to obstruct the flow of protons from one side of the lever to the other, so that any proton-based force would remain unilateral. pH-sensitive dye measurements confirmed that the protons were largely confined to one side. When the lever assembly was exposed to water, the sensor deflected toward the protons. Over a period of 20 min, deflection amounted to approximately 20 μm, corresponding to a force of approximately 22 μN. Hence, electrostatic forces are confirmed. If exclusion zones exist ubiquitously at hydrophilic surfaces, including biological surfaces, then the resulting electrostatic forces may play significant roles in many biological phenomena including adhesion and protein folding. PMID:23311934

  1. Charge-based forces at the Nafion-water interface.

    PubMed

    Das, Ronnie; Pollack, Gerald H

    2013-02-26

    Interfacial water lying next to hydrophilic surfaces has been shown to be spectroscopically, mechanically, and electrically distinct from bulk water. Interfacial water has also been shown to exclude negatively and positively charged microspheres and has thus become known as the "exclusion zone". Measurements have demonstrated that exclusion zones exhibit a negative electrical potential on the order of -100 mV relative to bulk water, with a corresponding distribution of positive protons in the bulk water region beyond the exclusion zone. This separation of charge is hypothesized to create an electrostatic force between the exclusion zone and the proton-enriched zone beyond. To test this hypothesis, a hydrophilic Nafion ring was attached to the tip of a deflectable ribbonlike force sensor. The sensor was designed to obstruct the flow of protons from one side of the lever to the other, so that any proton-based force would remain unilateral. pH-sensitive dye measurements confirmed that the protons were largely confined to one side. When the lever assembly was exposed to water, the sensor deflected toward the protons. Over a period of 20 min, deflection amounted to approximately 20 μm, corresponding to a force of approximately 22 μN. Hence, electrostatic forces are confirmed. If exclusion zones exist ubiquitously at hydrophilic surfaces, including biological surfaces, then the resulting electrostatic forces may play significant roles in many biological phenomena including adhesion and protein folding. PMID:23311934

  2. The importance of experimental design on measurement of dynamic interfacial tension and interfacial rheology in diffusion-limited surfactant systems

    DOE PAGESBeta

    Reichert, Matthew D.; Alvarez, Nicolas J.; Brooks, Carlton F.; Grillet, Anne M.; Mondy, Lisa A.; Anna, Shelley L.; Walker, Lynn M.

    2014-09-24

    Pendant bubble and drop devices are invaluable tools in understanding surfactant behavior at fluid–fluid interfaces. The simple instrumentation and analysis are used widely to determine adsorption isotherms, transport parameters, and interfacial rheology. However, much of the analysis performed is developed for planar interfaces. Moreover, the application of a planar analysis to drops and bubbles (curved interfaces) can lead to erroneous and unphysical results. We revisit this analysis for a well-studied surfactant system at air–water interfaces over a wide range of curvatures as applied to both expansion/contraction experiments and interfacial elasticity measurements. The impact of curvature and transport on measured propertiesmore » is quantified and compared to other scaling relationships in the literature. Our results provide tools to design interfacial experiments for accurate determination of isotherm, transport and elastic properties.« less

  3. The importance of experimental design on measurement of dynamic interfacial tension and interfacial rheology in diffusion-limited surfactant systems

    SciTech Connect

    Reichert, Matthew D.; Alvarez, Nicolas J.; Brooks, Carlton F.; Grillet, Anne M.; Mondy, Lisa A.; Anna, Shelley L.; Walker, Lynn M.

    2014-09-24

    Pendant bubble and drop devices are invaluable tools in understanding surfactant behavior at fluid–fluid interfaces. The simple instrumentation and analysis are used widely to determine adsorption isotherms, transport parameters, and interfacial rheology. However, much of the analysis performed is developed for planar interfaces. Moreover, the application of a planar analysis to drops and bubbles (curved interfaces) can lead to erroneous and unphysical results. We revisit this analysis for a well-studied surfactant system at air–water interfaces over a wide range of curvatures as applied to both expansion/contraction experiments and interfacial elasticity measurements. The impact of curvature and transport on measured properties is quantified and compared to other scaling relationships in the literature. Our results provide tools to design interfacial experiments for accurate determination of isotherm, transport and elastic properties.

  4. Interfacial Partitioning Tracer Test Measurement of NAPL-Water Interfacial Areas in Porous Media under Two-Phase Flow Condition

    NASA Astrophysics Data System (ADS)

    Zhong, H.; El Ouni, A.; Lin, D.; Wang, B.; Brusseau, M. L.

    2013-12-01

    The NAPL-water interface is of critical importance for the transport, fate, and remediation of organic contaminants in the subsurface due to its influence on contaminant mass transfer, transport, and biotransformation. In this work, the interfacial areas between tetrachloroethene (PCE) liquid (non-wetting phase) and water (wetting phase) in porous media were measured under two-phase flow conditions using the interfacial partitioning tracer test (IPTT) method. Three wetting scenarios of primary drainage, secondary imbibition, and secondary drainage were investigated. Two porous media were used, a well-sorted 45/50 mesh quartz sand and a sandy soil. The theoretical maximum interfacial areas determined from the measured data are compared to the specific solid surface area determined in two ways, based on geometrical calculations for smooth spheres and as measured with the N2/BET method. The results obtained for the NAPL-water system are compared to measurements conducted for comparable air-water systems.

  5. A dual-surfactant approach for the interfacial partitioning tracer test measurement of air-water interfacial area

    NASA Astrophysics Data System (ADS)

    El Ouni, A.; Brusseau, M. L.

    2013-12-01

    Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (A_ia). The method has been shown to provide uncertain measurements that are influenced by surfactant-enhanced drainage. The purpose of this work is to test a revised method that minimizes formation of interfacial-tension gradients in order to prevent surfactant-induced drainage. The method employs a dual-surfactant injection under steady unsaturated-flow conditions. Sodium dodecylbezene sulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning and nonreactive tracers, respectively. Sodium dodecyl sulfate (SDS) was used as the surfactant in the background solution. Three types of porous media were used for the study: a sandy soil, a well-sorted sand, and glass beads. Water saturation was monitored gravimetrically during the experiments. The results obtained with the revised method are compared to those obtained with the standard IPTT method.

  6. A perspective on the interfacial properties of nanoscopic liquid drops

    NASA Astrophysics Data System (ADS)

    Malijevský, Alexandr; Jackson, George

    2012-11-01

    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.

  7. Comparison of interfacial partitioning tracer test and high-resolution microtomography measurements of fluid-fluid interfacial areas for an ideal porous medium

    NASA Astrophysics Data System (ADS)

    Narter, Matt; Brusseau, Mark L.

    2010-08-01

    Fluid-fluid interfacial area for porous media systems can be measured with the aqueous phase interfacial partitioning tracer test (IPTT) method or with high-resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous medium surface roughness on film-associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (±5 cm-1), while microtomography produced an interfacial area of 2.7 (±2 cm-1). Maximum specific interfacial areas, equivalent to areas normalized by nonwetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth sphere assumption and to the specific solid surface area measured using the N2/Brunauer, Emmett, and Teller (BET) method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid-fluid interfacial area and that they are comparable in the absence of the impact of surface roughness.

  8. COMPARISON OF INTERFACIAL PARTITIONING TRACER TEST AND HIGH-RESOLUTION MICROTOMOGRAPHY MEASUREMENTS OF FLUID-FLUID INTERFACIAL AREAS FOR AN IDEAL POROUS MEDIUM.

    PubMed

    Narter, Matt; Brusseau, Mark L

    2010-08-01

    Fluid-fluid interfacial area for porous-media systems can be measured with the aqueous-phase interfacial partitioning tracer test (IPTT) method or with high-resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous-medium surface roughness on film-associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass-beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (± 5 cm(-1)), while microtomography produced an interfacial area of 2.7 (± 2 cm(-1)). Maximum specific interfacial areas, equivalent to areas normalized by non-wetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth-sphere assumption, and to the specific solid surface area measured using the N2/BET method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid-fluid interfacial area, and that they are comparable absent the impact of surface roughness. PMID:24604925

  9. Current Status of Protein Force Fields for Molecular Dynamics

    PubMed Central

    Lopes, Pedro E.M.; Guvench, Olgun

    2015-01-01

    Summary The current status of classical force fields for proteins is reviewed. These include additive force fields as well as the latest developments in the Drude and AMOEBA polarizable force fields. Parametrization strategies developed specifically for the Drude force field are described and compared with the additive CHARMM36 force field. Results from molecular simulations of proteins and small peptides are summarized to illustrate the performance of the Drude and AMOEBA force fields. PMID:25330958

  10. 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.

  11. Time-Dependent Interfacial Properties and DNAPL Mobility

    SciTech Connect

    Tuck, D.M.

    1999-03-10

    Interfacial properties play a major role in governing where and how dense nonaqueous phase liquids (DNAPLs) move in the subsurface. Interfacial tension and contact angle measurements were obtained for a simple, single component DNAPL (tetrachloroethene, PCE), complex laboratory DNAPLs (PCE plus Sudan IV dye), and a field DNAPL from the Savannah River Site (SRS) M-Area DNAPL (PCE, trichloroethene [TCE], and maching oils). Interfacial properties for complex DNAPLs were time-dependent, a phenomenon not observed for PCE alone. Drainage capillary pressure-saturation curves are strongly influenced by interfacial properties. Therefore time-dependence will alter the nature of DNAPL migration and penetration. Results indicate that the time-dependence of PCE with relatively high Sudan IV dye concentrations is comparable to that of the field DNAPL. Previous DNAPL mobility experiments in which the DNAPL was dyed should be reviewed to determine whether time-dependent properties influenced the resutls. Dyes appear to make DNAPL more complex, and therefore a more realistic analog for field DNAPLs than single component DNAPLs.

  12. Summer Research Institute Interfacial and Condensed Phase Chemical Physics

    SciTech Connect

    Barlow, Stephan E.

    2004-10-01

    Pacific Northwest National Laboratory (PNNL) hosted its first annual Summer Research Institute in Interfacial and Condensed Phase Chemical Physics from May through September 2004. During this period, fourteen PNNL scientists hosted sixteen young scientists from eleven different universities. Of the sixteen participants, fourteen were graduate students; one was transitioning to graduate school; and one was a university faculty member.

  13. Photon Upconversion Through Tb(3+) -Mediated Interfacial Energy Transfer.

    PubMed

    Zhou, Bo; Yang, Weifeng; Han, Sanyang; Sun, Qiang; Liu, Xiaogang

    2015-10-28

    A strategy of interfacial energy transfer upconversion is demonstrated through the use of a terbium (Tb(3+) ) dopant as energy donor or energy migrator in core-shell-structured nanocrystals. This mechanistic investigation presents a new pathway for photon upconversion, and, more importantly, contributes to the better control of energy transfer at the nanometer length scale. PMID:26378771

  14. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension

    PubMed Central

    Jackson, Meyer B.

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 oC. PMID:26813712

  15. Meter-long multiblock copolymer microfibers via interfacial bioorthogonal polymerization

    PubMed Central

    Liu, Shuang; Zhang, Han; Remy, Roddel A.; Deng, Fei; Mackay, Michael E.; Fox, Joseph M.; Jia, Xinqiao

    2015-01-01

    High molecular weight multiblock copolymers are synthesized as robust polymer fibers via interfacial bioorthogonal polymerization employing the rapid cycloaddition of s-tetrazines with strained trans-cyclooctenes. When cell-adhesive peptide was incorporated in the tetrazine monomer, the resulting protein-mimetic polymer fibers provide guidance cues for cell attachment and elongation. PMID:25824805

  16. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension.

    PubMed

    Jackson, Meyer B

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 (o)C. PMID:26813712

  17. Undergraduate Laboratory Experiment Modules for Probing Gold Nanoparticle Interfacial Phenomena

    ERIC Educational Resources Information Center

    Karunanayake, Akila G.; Gunatilake, Sameera R.; Ameer, Fathima S.; Gadogbe, Manuel; Smith, Laura; Mlsna, Deb; Zhang, Dongmao

    2015-01-01

    Three gold-nanoparticle (AuNP) undergraduate experiment modules that are focused on nanoparticles interfacial phenomena have been developed. Modules 1 and 2 explore the synthesis and characterization of AuNPs of different sizes but with the same total gold mass. These experiments enable students to determine how particle size affects the AuNP…

  18. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension

    NASA Astrophysics Data System (ADS)

    Jackson, Meyer B.

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 oC.

  19. Interfacial tension measurements using MRI drop shape analysis.

    PubMed

    Hussain, R; Vogt, S J; Honari, A; Hollingsworth, K G; Sederman, A J; Mitchell, J; Johns, M L

    2014-02-18

    Accurate interfacial tension data for fluid systems such as hydrocarbons and water is essential to many applications such as reservoir oil and gas recovery predictions. Conventional interfacial tension measurement techniques typically use optical images to analyze droplet shapes but require that the continuous-phase fluid be optically transparent and that the fluids are not refractive index matched. Magnetic resonance images obtain contrast between fluids using other mechanisms such as magnetic relaxation weighting, so systems that are impossible to measure with optical methods may be analyzed. In this article, we present high-field (9.4 T) MRI images of various droplets analyzed with axisymmetric drop shape analysis. The resultant interfacial tension data show good agreement with literature data. The method is subsequently demonstrated using both opaque continuous phases and refractive-index-matched fluids. We conclude with a brief consideration of the potential to extrapolate the methodology to lower magnetic fields (0.3 T), featuring more accessible hardware; although droplet imaging is possible, resolution and stability do not currently permit accurate interfacial tension measurements. PMID:24471906

  20. Recent progress in interfacial tissue engineering approaches for osteochondral defects.

    PubMed

    Castro, Nathan J; Hacking, S Adam; Zhang, Lijie Grace

    2012-08-01

    This review provides a brief synopsis of the anatomy and physiology of the osteochondral interface, scaffold-based and non-scaffold based approaches for engineering both tissues independently as well as recent developments in the manufacture of gradient constructs. Novel manufacturing techniques and nanotechnology will be discussed with potential application in osteochondral interfacial tissue engineering. PMID:22677924