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Sample records for dynamic interfacial properties

  1. Molecular Dynamics Studies of Interfacial Properties of Complex Liquid Systems

    NASA Astrophysics Data System (ADS)

    Ouyang, Jian

    1995-01-01

    Molecular dynamics simulations have been used to investigate the interfacial properties of linear and branched chain alkane molecule condensed systems. The only notable effect of branching in our studies is the reduction of system ordering and layering since the degree of branching in the systems is very small. It is found that thin alkane films, adsorbed on a solid substrate at a temperature well above its bulk melting temperature, have about up to four well defined layers near the substrate. Within these layers, molecules are parallel to the substrate and exhibit domains of short range ordering. At the liquid-vapor interface, the molecular segment density tail is well fit by an error function indicating that the molecular height distribution obeys the Gaussian law predicted from the capillary wave model. At a temperature around the liquid bulk solidification temperature, a first order phase transition occurs at the liquid-vapor interfacial region of the alkane thin films. Molecules in this region pack hexagonally and align themselves parallel to the interface normal with a small cant angle. Below this crystalline monolayer, there are four sharp layers where molecules lie parallel to the substrate surface with enhanced domains of transverse ordering. It is observed that the contact angle of an alkane nanodroplet on top of a solid surface increases when the solid-liquid interaction strength decreases, or the molecule length increases. Due to the fact that almost all the molecules are in the liquid-vapor interfacial region, a nanodroplet with molecules of a length comparable to the droplet dimension has clear layers from the solid-liquid interface to the top of the droplet. This layering reduces when the size of the droplet increases or the molecule length decreases. Substrates do not create, but enhance the layering. It is also noticed that in the confined thin fluid films, liquid molecules exhibit partially solid-like characteristics behavior with the ability to

  2. Interfacial properties of an ionic liquid by molecular dynamics.

    PubMed

    Heggen, Berit; Zhao, Wei; Leroy, Frédéric; Dammers, Anton J; Müller-Plathe, Florian

    2010-05-27

    We studied the influence of a liquid-vapor interface on dynamic properties like reorientation and diffusion as well as the surface tension of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) by molecular dynamics simulations. In the interfacial region, reorientation of a short molecular axis is slightly faster than that in the central layer, while that of the longer molecular axis is retarded. The molecular reorientation is well-described by a stretched exponential decay modeled by the Kohlrausch-Williams-Watts equation. Analysis of the average translational diffusion coefficient of molecules in a central layer shows consistency with the Vogel-Fulcher-Tamann equation in a temperature range from 300 to 380 K. A first-passage time analysis of the system at 380 K yields a more refined spatial characterization of translational diffusion perpendicular to the liquid-vapor interfaces. In the central region of the slab, the diffusion coefficient of cations is only marginally higher than that of anions, but close to an interface, this difference is much higher, up to 50%. Apparent activation energies for rotational and diffusional dynamics, respectively, were estimated assuming Arrhenius behavior. They indicate that reorientation of the long molecular axis depends on the diffusion ability, whereas for the reorientation of the short axis, no such correlation is observed. The results are in general agreement with the literature, with slightly overestimated absolute values. This applies as well for the surface tension, where, however, a dependence on the treatment of the electrostatics was found. Particle-mesh Ewald (PME) or reaction field (RF) and the treatment of bonds by constraints have an influence. If no bond constraints are applied, the results are consistent for both methods for the description of the electrostatics.

  3. Equilibrium and dynamic interfacial properties of protein/ionic-liquid-type surfactant solutions at the decane/water interface.

    PubMed

    Cao, Chong; Lei, Jinmei; Zhang, Lu; Du, Feng-Pei

    2014-11-25

    The interfacial behavior of β-casein and lysozyme solutions has been investigated in the presence of an ionic liquid-type imidazolium surfactant ([C16mim]Br) at the decane/water interface. The dynamic dilational properties of the protein/surfactant solutions are investigated by the oscillating drop method and interfacial tension relaxation method. The interfacial tension isotherms for the mixed adsorption layers indicate that the increased addition of [C16mim]Br to a pure protein changes the properties of the complex formed at the decane/water interface. Whereas the interfacial tension data of the protein/surfactant mixed layers do not clearly show differences with changing bulk composition, the dilational rheology provides undoubted evidence that the structure and, in particular, the dynamics of the adsorbed layers depend on the bulk surfactant concentration. The experiment data for β-casein/[C16mim]Br solutions indicate that at higher bulk [C16mim]Br concentrations, β-casein in the interfacial layer is subject to conformational changes, where it gives space to [C16mim]Br molecules in the form of coadsorb rather than replacement; in contrast, in lysozyme/[C16mim]Br solutions some lysozyme molecules desorb from the interface due to the competitive adsorption of free [C16mim]Br molecules. Experimental results related to the interfacial dilational properties of the protein/surfactant solutions show that the dilational modulus turns out to be more sensitive to the conformation of protein/surfactant mixture at the liquid interface than the interfacial tension.

  4. 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

  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. 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.

  7. 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

  8. Dynamic interfacial properties of poly(ethylene glycol)-modified ferritin at the solid/liquid interface.

    PubMed

    Kumashiro, Yoshikazu; Ikezoe, Yasuhiro; Tamada, Kaoru; Hara, Masahiko

    2008-07-17

    Poly(ethylene glycol)-modified ferritins (PEG-ferritins) with various molecular weights were synthesized by the grafting method, and their dynamic interfacial properties at the solid/liquid interface were investigated. The number of PEG grafted to ferritins was controlled by the amount of 1,1'-carbonyldiimidazole-modified PEG adding to the reaction solution. The adsorption kinetics and energy dissipation of PEG-ferritins onto bare Si substrate and amino-modified Si substrate were investigated with a quartz crystal microbalance (QCM) in 10 mM bis-Tris/HCl buffer (pH 5.8), while their morphologies were characterized by scanning electron microscopy (SEM). The adsorption dynamics of PEG-ferritins onto amino-modified Si substrate were quite different from those of unmodified ferritin, which can be reasonably interpreted by the desorption capability of PEG-ferritins on the surface attributed to amphiphilicity and the high-chain mobility of PEG chains.

  9. Molecular dynamics analysis on wetting and interfacial properties of water-alcohol mixture droplets on a solid surface

    NASA Astrophysics Data System (ADS)

    Surblys, D.; Yamaguchi, Y.; Kuroda, K.; Kagawa, M.; Nakajima, T.; Fujimura, H.

    2014-01-01

    Molecular dynamics simulations of single water, water-methanol, or water-IPA (isopropyl-alcohol) mixture droplets on a solid surface were performed with various mixture ratios. An increase in alcohol fraction generally gave an increase in droplet wettability. Both methanol and IPA molecules showed a strong preference to gather at various interfaces, with methanol molecules also showing a tendency to diffuse into the droplet bulk. Specific interfacial tensions were investigated using quasi-one-dimensional simulation systems, and liquid-vapor and solid-liquid interfacial tensions were found to decrease greatly due to the presence of interfacial alcohol, while solid-vapor interfacial tensions were proved to have little influence on wettability. Young's relation was found to hold quantitatively well for both water-methanol and water-IPA droplets. The validity of using Bakker's equation on solid-liquid interfaces was also investigated, and it was shown that for tightly spaced crystal surfaces, the introduced uncertainly is small.

  10. Structure, interfacial properties, and dynamics of the sodium alkyl sulfate type surfactant monolayer at the water/trichloroethylene interface: a molecular dynamics simulation study.

    PubMed

    Shi, Wen-Xiong; Guo, Hong-Xia

    2010-05-20

    In this work, we perform a series of molecular dynamics (MD) simulations on the category of sodium alkyl sulfate (SDS-type) surfactant monolayers at the water/trichloroethylene (TCE) interface. Three separate tail-length SDS-type molecules are used. We investigate the conformation of surfactant chain (i.e., packing, orientation, and order), interfacial properties (i.e., interfacial thickness, interfacial tension, area compressibility, and bending modulus), their dependence on the chain length, and the average area per surfactant chain. We also examine the behavior of the surfactant monolayer in the metastable regime of negative surface tension with reference to collapse. The simulation has clearly shown that the very dilute monolayer is well described as a two-dimensional gas. With the increase of interfacial surfactant coverage, the monolayer is in the liquid-expanded (LE) phase. The surfactant tails at the interface become straighter, more ordered, and thicker at higher surfactant coverage. At the same time, interfacial tension of long-tail systems is always lower than that of short-tail systems. In the LE phase, the area compressibility modulus and the bending modulus increase with an increase in tail length. With a further decrease in molecular areas, the monolayer with large negative surface tension becomes unstable. Our simulations show that buckling of the monolayers is of dynamic nature as a response to mechanical instability. The further transformation pathway from buckling to bud can be controlled by the bending modulus, which depends crucially on the tail length and interfacial surfactant coverage. At a given area per molecule, the short tail chain makes the monolayer softer, and the budding process becomes more probable. For the supersaturated softer SDS monolayer, the collapse transition is initiated by the buckling of monolayers, followed primarily by budding and detachment of the nanoscale swollen micelle from the monolayer. Despite a number of

  11. Molecular weight effects on interfacial properties of linear and ring polymer melts: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Meddah, Chahrazed; Milchev, Andrey; Sabeur, Sid Ahmed; Skvortsov, Alexander M.

    2016-11-01

    Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tension, γ , of linear chains and of ring polymers at the hard walls confining both melts into a slit. We examine the dependence of P and γ on the length (i.e., molecular weight) N of the macromolecules. For linear chains, we find that both pressure and surface tension are inversely proportional to the chain length, P (N ) -P (N →∞ ) ∝N-1,γ (N ) -γ (N →∞ ) ∝N-1 , irrespective of whether the confining planes attract or repel the monomers. In contrast, for melts comprised of cyclic (ring) polymers, neither the pressure nor the surface tension is found to depend on molecular weight N for both kinds of wall-monomer interactions. While other structural properties as, e.g., the probability distributions of trains and loops at impenetrable walls appear quantitatively indistinguishable, we observe an amazing dissimilarity in the probability to find a chain end or a tagged monomer of a ring at a given distance from the wall in both kinds of polymeric melts. In particular, we demonstrate that the conformational equivalence of linear chains in a confined melt to a single chain under conditions of critical adsorption to a planar surface, established two decades ago, does also hold for ring polymers in a melt of linear chains. This analogy does not hold, however, for linear and ring chains in a confined melt of ring chains.

  12. A primer on selecting grain boundary sets for comparison of interfacial fracture properties in molecular dynamics simulations

    DOE PAGES

    Dingreville, Remi; Aksoy, Doruk; Spearot, Douglas E.

    2017-08-21

    In this study, all grain boundaries are not equal in their predisposition for fracture due to the complex coupling between lattice geometry, interfacial structure, and mechanical properties. The ability to understand these relationships is crucial to engineer materials resilient to grain boundary fracture. Here, a methodology is presented to isolate the role of grain boundary structure on interfacial fracture properties, such as the tensile strength and work of separation, using atomistic simulations. Instead of constructing sets of grain boundary models within the misorientation/structure space by simply varying the misorientation angle around a fixed misorientation axis, the proposed method creates setsmore » of grain boundary models by means of isocurves associated with important fracture-related properties of the adjoining lattices. Such properties may include anisotropic elastic moduli, the Schmid factor for primary slip, and the propensity for simultaneous slip on multiple slip systems. This approach eliminates the effect of lattice properties from the comparative analysis of interfacial fracture properties and thus enables the identification of structure-property relationships for grain boundaries. As an example, this methodology is implemented to study crack propagation along Ni grain boundaries. Segregated H is used as a means to emphasize differences in the selected grain boundary structures while keeping lattice properties fixed.« less

  13. 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.

  14. Studies of structural, dynamical, and interfacial properties of 1-alkyl-3-methylimidazolium iodide ionic liquids by molecular dynamics simulation.

    PubMed

    Ghatee, Mohammad Hadi; Zolghadr, Amin Reza; Moosavi, Fatemeh; Ansari, Younes

    2012-03-28

    Bulk and surface properties of the ionic liquids 1-alkyl-3-methyl-imidazolium iodides ([C(n)mim]I) were simulated by classical molecular dynamics using all atom non-polarizable force field (n = 4, butyl; 6, hexyl; 8, octyl). The structure of ionic liquids were initially optimized by density functional theory and atomic charges obtained by CHELPG method. Reduction of partial atomic charges (by 20% for simulation of density and surface tension, and by 10% for viscosity) found to improve the accuracy, while a non-polarizable force field was applied. Additionally, the simulation ensembles approach the equilibrium faster when the charge reduction is applied. By these refined force field parameters, simulated surface tensions in the range of 323-393 k are quite in agreement with the experiments. Simulation of temperature dependent surface tension of [C(4)mim]I well beyond room temperature (up to 700 K) permits prediction of the critical temperature in agreement with that predicted from experimental surface tension data. Simulated densities in the range of 298-450 K for the three ionic liquids are within 0.8% of the experimental data. Structural properties for [C(4)mim]I were found to be in agreement with the results of Car-Parrinello molecular dynamics simulation we performed, which indicates a rather well-structured cation-anion interaction and occurs essentially through the imidazolium ring cation. Diffusion coefficient changes with alkyl chain length in the order of [C(8)mim]I > [C(6)mim]I > [C(4)mim]I for the cation and the anion. Formation of a dense domain in subsurface region is quite evident, and progressively becomes denser as the alkyl chain length increases. Bivariate orientational analysis was used to determine the average orientation of molecule in ionic liquids surface, subsurface, and bulk regions. Dynamic bisector-wise and side-wise movement of the imodazolium ring cation in the surface region can be deduced from the bivariate maps. Atom-atom density

  15. 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.

  16. Interfacial properties of semifluorinated alkane diblock copolymers

    NASA Astrophysics Data System (ADS)

    Pierce, Flint; Tsige, Mesfin; Borodin, Oleg; Perahia, Dvora; Grest, Gary S.

    2008-06-01

    The liquid-vapor interfacial properties of semifluorinated linear alkane diblock copolymers of the form F3C(CF2)n-1(CH2)m-1CH3 are studied by fully atomistic molecular dynamics simulations. The chemical composition and the conformation of the molecules at the interface are identified and correlated with the interfacial energies. A modified form of the Optimized Parameter for Liquid Simulation All-Atom (OPLS-AA) force field of Jorgensen and co-workers [J. Am. Chem. Soc. 106, 6638 (1984); 118, 11225 (1996); J. Phys. Chem. A 105, 4118 (2001)], which includes specific dihedral terms for H-F blocks-and corrections to the H-F nonbonded interaction, is used together with a new version of the exp-6 force field developed in this work. Both force fields yield good agreement with the available experimental liquid density and surface tension data as well as each other over significant temperature ranges and for a variety of chain lengths and compositions. The interfacial regions of semifluorinated alkanes are found to be rich in fluorinated groups compared to hydrogenated groups, an effect that decreases with increasing temperature but is independent of the fractional length of the fluorinated segments. The proliferation of fluorine at the surface substantially lowers the surface tension of the diblock copolymers, yielding values near those of perfluorinated alkanes and distinct from those of protonated alkanes of the same chain length. With decreasing temperatures within the liquid state, chains are found to preferentially align perpendicular to the interface, as previously seen.

  17. Structural features and interfacial properties of WH2, β-thymosin domains and other intrinsically disordered domains in the regulation of actin cytoskeleton dynamics.

    PubMed

    Renault, Louis; Deville, Célia; van Heijenoort, Carine

    2013-11-01

    Many actin-binding proteins (ABPs) use complex multidomain architectures to integrate and coordinate multiple signals and interactions with the dynamic remodeling of actin cytoskeleton. In these proteins, small segments that are intrinsically disordered in their unbound native state can be functionally as important as identifiable folded units. These functional intrinsically disordered regions (IDRs) are however difficult to identify and characterize in vitro. Here, we try to summarize the state of the art in understanding the structural features and interfacial properties of IDRs involved in actin self-assembly dynamics. Recent structural and functional insights into the regulation of widespread, multifunctional WH2/β-thymosin domains, and of other IDRs such as those associated with WASP/WAVE, formin or capping proteins are examined. Understanding the functional versatility of IDRs in actin assembly requires apprehending by multiple structural and functional approaches their large conformational plasticity and dynamics in their interactions. In many modular ABPs, IDRs relay labile interactions with multiple partners and act as interaction hubs in interdomain and protein-protein interfaces. They thus control multiple conformational transitions between the inactive and active states or between various active states of multidomain ABPs, and play an important role to coordinate the high turnover of interactions in actin self-assembly dynamics.

  18. 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

  19. 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.

  20. Interfacial gauge methods for incompressible fluid dynamics

    DOE PAGES

    Saye, R.

    2016-06-10

    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,more » 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.« less

  1. Interfacial gauge methods for incompressible fluid dynamics

    SciTech Connect

    Saye, R.

    2016-06-10

    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.

  2. Dynamic interfacial behavior of viscoelastic aqueous hyaluronic acid: effects of molecular weight, concentration and interfacial velocity.

    PubMed

    Vorvolakos, Katherine; Coburn, James C; Saylor, David M

    2014-04-07

    , understood in terms of physical properties, may be broadened to probe interfacial dynamics of other viscoelastic aqueous biopolymers.

  3. Novel Colloidal and Dynamic Interfacial Phenomena in Liquid Crystalline Systems

    DTIC Science & Technology

    2014-09-13

    investigation supported by this grant moved beyond past studies of interfacial and colloidal phenomena involving isotropic liquids to explore and understand a...2010 20-May-2014 Approved for Public Release; Distribution Unlimited Final Report: Novel Colloidal and Dynamic Interfacial Phenomena in Liquid...Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 liquid crystals, interfacial phenomena, colloids , amphiphiles

  4. The effect of chain rigidity on the interfacial layer thickness and dynamics of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Cheng, Shiwang; Carrillo, Jan-Michael Y.; Carroll, Bobby; Sumpter, Bobby G.; Sokolov, Alexei P.

    There are growing experimental evidences showing the existence of an interfacial layer that has a finite thickness with slowing down dynamics in polymer nanocomposites (PNCs). Moreover, it is believed that the interfacial layer plays a significant role on various macroscopic properties of PNCs. A thicker interfacial layer is found to have more pronounced effect on the macroscopic properties such as the mechanical enhancement. However, it is not clear what molecular parameter controls the interfacial layer thickness. Inspired by our recent computer simulations that showed the chain rigidity correlated well with the interfacial layer thickness, we performed systematic experimental studies on different polymer nanocomposites by varying the chain stiffness. Combining small-angle X-ray scattering, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry, we find a good correlation between the polymer Kuhn length and the thickness of the interfacial layer, confirming the earlier computer simulations results. Our findings provide a direct guidance for the design of new PNCs with desired properties.

  5. Dynamics of deeply supercooled interfacial water

    NASA Astrophysics Data System (ADS)

    Swenson, Jan; Cerveny, Silvina

    2015-01-01

    In this review we discuss the relaxation dynamics of glassy and deeply supercooled water in different types of systems. We compare the dynamics of such interfacial water in ordinary aqueous solutions, hard confinements and biological soft materials. In all these types of systems the dielectric relaxation time of the main water process exhibits a dynamic crossover from a high-temperature non-Arrhenius temperature dependence to a low-temperature Arrhenius behavior. Moreover, at large enough water content the low-temperature process is universal and exhibits the same temperature behavior in all types of systems. However, the physical nature of the dynamic crossover is somewhat different for the different types of systems. In ordinary aqueous solutions it is not even a proper dynamic crossover, since the water relaxation decouples from the cooperative α-relaxation of the solution slightly above the glass transition in the same way as all secondary (β) relaxations of glass-forming materials. In hard confinements, the physical origin of the dynamic crossover is not fully clear, but it seems to occur when the cooperative main relaxation of water at high temperatures reaches a temperature where the volume required for its cooperative motion exceeds the size of the geometrically-confined water cluster. Due to this confinement effect the α-like main relaxation of the confined water seems to transform to a more local β-relaxation with decreasing temperature. Since this low-temperature β-relaxation is universal for all systems at high water content it is possible that it can be considered as an intrinsic β-relaxation of supercooled water, including supercooled bulk water. This possibility, together with other findings for deeply supercooled interfacial water, suggests that the most accepted relaxation scenarios for supercooled bulk water have to be altered.

  6. Interfacial properties and emulsification performance of thylakoid membrane fragments.

    PubMed

    Tenorio, A Tamayo; de Jong, E W M; Nikiforidis, C V; Boom, R M; van der Goot, A J

    2017-01-18

    Thylakoids membranes are sophisticated, dynamic structures found in plant leaves, composed of protein complexes in a dynamic lipid matrix. The interfacial absorption dynamics and viscoelasticity of thylakoid membranes fragments were measured to assess the properties of the interfacial layer and to elucidate an emulsifying mechanism that includes the role of thylakoid's composition and 3D structure. Thylakoid membranes were extracted from sugar beet leaves by a series of buffer washing, filtration and centrifugation. The extract containing the intact thylakoid membranes was suspended in water through high-pressure homogenisation, which disrupted the structure into membrane fragments. Thylakoid fragments showed surface and interfacial behaviour similar to soft particles or Pickering stabilizers with slow adsorption kinetics. After adsorption, an elastic and stable thin film was formed, indicating formation of new interactions between adjacent thylakoid fragments. In an emulsion, thylakoid fragments stabilised oil droplets against coalescence, despite droplet aggregation occurring already during emulsification. Droplet aggregation occurred by steric and electrostatic bridging, which in turn forms a 3D network where the oil droplets are immobilised, preventing further droplet coalescence or aggregation. It was concluded that both composition and structure of thylakoid fragments determine their emulsifying properties, conferring potential for encapsulation systems, where the search for natural materials is gaining more attention.

  7. Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions

    NASA Astrophysics Data System (ADS)

    Cheng, Shiwang; Carroll, Bobby; Bocharova, Vera; Carrillo, Jan-Michael; Sumpter, Bobby G.; Sokolov, Alexei P.

    2017-05-01

    In recent years it has become clear that the interfacial layer formed around nanoparticles in polymer nanocomposites (PNCs) is critical for controlling their macroscopic properties. The interfacial layer occupies a significant volume fraction of the polymer matrix in PNCs and creates strong intrinsic heterogeneity in their structure and dynamics. Here, we focus on analysis of the structure and dynamics of the interfacial region in model PNCs with well-dispersed, spherical nanoparticles with attractive interactions. First, we discuss several experimental techniques that provide structural and dynamic information on the interfacial region in PNCs. Then, we discuss the role of various microscopic parameters in controlling structure and dynamics of the interfacial layer. The analysis presented emphasizes the importance of the polymer-nanoparticle interactions for the slowing down dynamics in the interfacial region, while the thickness of the interfacial layer appears to be dependent on chain rigidity, and has been shown to increase with cooling upon approaching the glass transition. Aside from chain rigidity and polymer-nanoparticle interactions, the interfacial layer properties are also affected by the molecular weight of the polymer and the size of the nanoparticles. In the final part of this focus article, we emphasize the important challenges in the field of polymer nanocomposites and a potential analogy with the behavior observed in thin films.

  8. 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.

  9. Interfacial properties of semiconducting transition metal chalcogenides

    NASA Astrophysics Data System (ADS)

    Jaegermann, W.; Tributsch, H.

    This review is aimed at the correlation of structural and electronic properies of semiconducting transition metal chalcogenides with molecular surface processes and mechanisms in photoelectrochemistry, (photo)catalysis, geochemistry and hydrometallurgy. Layer-type, pyrite structured and transition metal cluster containing chalcogenides are selected as model systems to explain the principles involved. Special emphasis is given to the discussion of materials which involve transition metal d- states in the interfacial reaction pathways of holes and electrons. Since they initiate and control heterogeneous coordination chemistry at the surfaces they may provide the possibility of tailoring selective and catalytically demanding reactions. Examples of such mechanisms are presented and discussed in relation to surface properties involved.

  10. Direct, Dynamic Measurement of Interfacial Area within Porous Media

    SciTech Connect

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

    2010-01-01

    Standard models of two-phase flow in porous media have been shown to exhibit several shortcomings that might be partially overcome with a recently developed model based on thermodynamic principles (Hassanizadeh and Gray, 1990). This alternative two-phase flow model contains a set of new and non-standard parameters, including specific interfacial area. By incorporating interfacial area production, destruction, and propagation into functional relationships that describe the capillary pressure and saturation, a more physical model has been developed. Niessner and Hassanizadeh (2008) have examined this model numerically and have shown that the model captures saturation hysteresis with drainage/imbibition cycles. Several static experimental studies have been performed to examine the validity of this new thermodynamically based approach; these allow the determination of static parameters of the model. To date, no experimental studies have obtained information about the dynamic parameters required for the model. A new experimental porous flow cell has been constructed using stereolithography to study two-phase flow phenomena (Crandall et al. 2008). A novel image analysis tool was developed for an examination of the evolution of flow patterns during displacement experiments (Crandall et al. 2009). This analysis tool enables the direct quantification of interfacial area between fluids by matching known geometrical properties of the constructed flow cell with locations identified as interfaces from images of flowing fluids. Numerous images were obtained from two-phase experiments within the flow cell. The dynamic evolution of the fluid distribution and the fluid-fluid interface locations were determined by analyzing these images. In this paper, we give a brief introduction to the thermodynamically based two-phase flow model, review the properties of the stereolithography flow cell, and show how the image analysis procedure has been used to obtain dynamic parameters for the

  11. Interfacial interaction between polypropylene and nanotube: A molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Danhui; Yang, Houbo; Liu, Zhongkui; Liu, Anmin; Li, Yunfang

    2017-09-01

    The interfacial interaction between polypropylene (PE) and single walled carbon nanotube (SWCNT) was studied using molecular dynamics (MD) simulations. The result showed that the PE chain could stabilize the SWCNT and then extended along the direction of SWCNT. The mechanism of interfacial interaction between PE and SWCNT was also discussed. Furthermore, the interfacial interaction between more PE and SWCNT was also investigated and the position also deeply influenced the interaction. This will be beneficial to understanding the interfacial interaction between polymer and CNT in solution, and also guiding the fabrication of high performance polymer/CNT nanocomposites.

  12. Interfacial properties of stanene-metal contacts

    NASA Astrophysics Data System (ADS)

    Guo, Ying; Pan, Feng; Ye, Meng; Wang, Yangyang; Pan, Yuanyuan; Zhang, Xiuying; Li, Jingzhen; Zhang, Han; Lu, Jing

    2016-09-01

    Recently, two-dimensional buckled honeycomb stanene has been manufactured by molecular beam epitaxy growth. Free-standing stanene is predicted to have a sizable opened band gap of 100 meV at the Dirac point due to spin-orbit coupling (SOC), resulting in many fascinating properties such as quantum spin Hall effect, quantum anomalous Hall effect, and quantum valley Hall effect. In the first time, we systematically study the interfacial properties of stanene-metal interfaces (metals = Ag, Au, Cu, Al, Pd, Pt, Ir, and Ni) by using ab initio electronic structure calculations considering the SOC effects. The honeycomb structure of stanene is preserved on the metal supports, but the buckling height is changed. The buckling of stanene on the Au, Al, Ag, and Cu metal supports is higher than that of free-standing stanene. By contrast, a planar graphene-like structure is stabilized for stanene on the Ir, Pd, Pt, and Ni metal supports. The band structure of stanene is destroyed on all the metal supports, accompanied by a metallization of stanene because the covalent bonds between stanene and the metal supports are formed and the structure of stanene is distorted. Besides, no tunneling barrier exists between stanene and the metal supports. Therefore, stanene and the eight metals form a good vertical Ohmic contact.

  13. Tunable interfacial properties of epitaxial graphene on metal substrates

    NASA Astrophysics Data System (ADS)

    Gao, Min; Pan, Yi; Zhang, Chendong; Hu, Hao; Yang, Rong; Lu, Hongliang; Cai, Jinming; Du, Shixuan; Liu, Feng; Gao, H.-J.

    2010-02-01

    We report on tuning interfacial properties of epitaxially-grown graphenes with different kinds of metal substrates based on scanning tunneling microscopy experiments and density functional theory calculations. Three kinds of metal substrates, Ni(111), Pt(111), and Ru(0001), show different interactions with the epitaxially grown graphene at the interfaces. The different interfacial interaction making graphene n-type and p-type doped, leads to the polarity change of the thermoelectric property of the graphene/metal systems. These findings may give further insights to the interfacial interactions in the graphene/metal systems and promote the use of graphene-based heterostructures in devices.

  14. Dynamic characteristics of gas-water interfacial plasma under water

    SciTech Connect

    Zheng, S. J.; Zhang, Y. C.; Ke, B.; Ding, F.; Tang, Z. L.; Yang, K.; Zhu, X. D.

    2012-06-15

    Gas-water interfacial plasmas under water were generated in a compact space in a tube with a sandglass-like structure, where two metal wires were employed as electrodes with an applied 35 kHz ac power source. The dynamic behaviors of voltage/current were investigated for the powered electrode with/without water cover to understand the effect of the gas-water interface. It is found that the discharge exhibits periodic pulsed currents after breakdown as the powered electrode is covered with water, whereas the electrical current reveals a damped oscillation with time with a frequency about 10{sup 6} Hz as the powered electrode is in a vapor bubble. By increasing water conductivity, a discharge current waveform transition from pulse to oscillation presents in the water covering case. These suggest that the gas-water interface has a significant influence on the discharge property.

  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. Surface and interfacial properties of polymer blends

    SciTech Connect

    Rafailovich, M.; Sokolov, J.

    1991-11-01

    This is a summary of the research we have conducted since receiving our DOE grant and research plans for the coming year. As you will notice most of the research objectives of our original proposal were met, especially in regard to measuring surface segregation and interface formation in polymer blends. Our program has therefore expanded into other directions such as the study of the surface visco-elastic properties of polymer liquids and solutions, the conformations of polymer chains grafted onto silica surfaces, and the dynamics of cross linked polymer networks.

  17. 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.

  18. 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).

  19. Interfacial and emulsifying properties of designed β-strand peptides.

    PubMed

    Dexter, Annette F

    2010-12-07

    The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely related to known β-sheet formers. Surface activity, interfacial mechanical properties, electronic circular dichroism (ECD), droplet sizing and zeta potential measurements were used to gain an overview of the peptide behavior as the molecular charge varied from ±4 to 0 with pH. ECD data suggest that the peptides form polyproline-type helices in bulk aqueous solution when highly charged, but may fold to β-hairpins rather than β-sheets when uncharged. In the uncharged state, the peptides adsorb readily at a macroscopic fluid interface to form mechanically strong interfacial films, but tend to give large droplet sizes on emulsification, apparently due to flocculation at a low droplet zeta potential. In contrast, highly charged peptide states gave a low interfacial coverage, but retained good emulsifying activity as judged by droplet size. Best emulsification was generally seen for intermediate charged states of the peptides, possibly representing a compromise between droplet zeta potential and interfacial binding affinity. The emulsifying properties of β-strand peptides have not been previously reported. Understanding the interfacial properties of such peptides is important to their potential development as biosurfactants.

  20. Liquid-vapor interfacial properties of vibrating square well chains.

    PubMed

    Chapela, Gustavo A; Alejandre, José

    2011-08-28

    Liquid-vapor interfacial properties of square well chains are calculated. Surface tension, orthobaric densities, and vapor pressures are reported. Spinodal decomposition with a discontinuous molecular dynamics simulation program is used to obtain the results which are compared to previously published data for orthobaric densities and vapor pressures. In order to analyze the effect of the chain stiffness results for near tangent and overlapping linear chains as well as angled chains are obtained. Properties are calculated for linear chains of 2, 4, and 8 spheres for intramolecular distances of 0.97, 0.6, and 0.4 as well as for angled chains of 4 and 8 spheres and intramolecular distances of 0.4. The complete series of fully flexible near tangent square well chains is also studied (chains of 2, 4, 8, 12, and 16 particles with intramolecular distances of 0.97). The corresponding states principle applies to most of the systems considered. Critical properties values are reported as obtained from orthobaric densities, surface tensions, and vapor pressures. For the near tangent chains the critical temperatures increase with chain length but the rate of increment tends to zero for the longest chains considered. When the stiffness of the chain increases (intramolecular distance from 1 , 0.6, and 0.4) this saturation effect is either not present or reverses itself. The surface tension increases with the length of the chain while the width of the interface decreases. © 2011 American Institute of Physics

  1. Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

    DOE PAGES

    Ge, Ting; Robbins, Mark O.; Perahia, Dvora; ...

    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

  2. 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.

  3. 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.

  4. Microfluidic Dynamic Interfacial Tensiometry (μDIT).

    PubMed

    Brosseau, Quentin; Vrignon, Jérémy; Baret, Jean-Christophe

    2014-05-07

    We designed, developed and characterized a microfluidic method for the measurement of surfactant adsorption kinetics via interfacial tensiometry on a microfluidic chip. The principle of the measurement is based on the deformability of droplets as a response to hydrodynamic forcing through a series of microfluidic expansions. We focus our analysis on one perfluoro surfactant molecule of practical interest for droplet-based microfluidic applications. We show that although the adsorption kinetics is much faster than the kinetics of the corresponding pendant drop experiment, our droplet-based microfluidic system has a sufficient time resolution to obtain quantitative measurement at the sub-second time-scale on nanoliter droplet volumes, leading to both a gain by a factor of ∼10 in time resolution and a downscaling of the measurement volumes by a factor of ∼1000 compared to standard techniques. Our approach provides new insight into the adsorption of surfactant molecules at liquid-liquid interfaces in a confined environment, relevant to emulsification, encapsulation and foaming, and the ability to measure adsorption and desorption rate constants.

  5. Thermal and mechanical interfacial properties of the DGEBA/PMR-15 blend system.

    PubMed

    Park, Soo-Jin; Lee, Hwa-Young; Han, Mijeong; Hong, Sung-Kwon

    2004-02-15

    In this work, the blend system of diglycidyl ether of bisphenol A and PMR-15 polyimide is investigated in terms of thermal and dynamic mechanical interfacial properties of the casting specimens. The thermal stabilities are studied by thermogravimetric and thermomechanical analyses, and the dynamic mechanical properties are carried out by dynamic mechanical analysis. The results show that the thermal stabilities based on the initial decomposition temperature, the integral procedural decomposition temperature, and the glass transition temperature are increased with increasing PMR-15 content. The crosslinking density (rho) of the blend system is increased at 10 phr of PMR-15, compared with that of neat epoxy. Mechanical interfacial properties measured in the context of critical stress intensity factor and critical strain energy release rate show similar behaviors with E(a) and rho, probably due to the increase in intermolecular interactions or hydrogen bondings in polymer chains.

  6. 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.

  7. Dynamic film and interfacial tensions in emulsion and foam systems

    SciTech Connect

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

    1997-03-01

    In concentrated fluid dispersions the liquid films are under dynamic conditions during film rupture or drainage. Aqueous foam films stabilized with sodium decylsulfonate and aqueous emulsion films stabilized with the nonionic Brij 58 surfactant were formed at the tip of a capillary and the film tension was measured under static and dynamic conditions. In the stress relaxation experiments the response of the film tension to a sudden film area expansion was studied. These experiments also allowed the direct measurement of the Gibbs film elasticity. In the dynamic film tension experiments, the film area was continuously increased by a constant rate and the dynamic film tension was monitored. The measured film tensions were compared with the interfacial tensions of the respective single air/water and oil/water interfaces, which were measured using the same radius of curvature, relative expansion, and expansion rate as in the film studies. It was found that under dynamic conditions the film tension is higher than twice the single interfacial tension (IFT) and a mechanism was suggested to explain the difference. When the film, initially at equilibrium, is expanded and the interfacial area increases, a substantial surfactant depletion occurs inside the film. As a result, the surfactant can be supplied only from the adjoining meniscus (Plateau border) by surface diffusion, and the film tension is controlled by the diffusion and adsorption of surfactant in the meniscus. The results have important implications for the stability and rheology of foams and emulsions with high dispersed phase ratios (polyhedral structure).

  8. A growing-drop technique for measuring dynamic interfacial tension

    SciTech Connect

    MacLeod, C.A.; Radke, C.J.

    1993-10-01

    A novel, growing-drop technique is described for measuring dynamic interfacial tension due to sorption of surface-active solutes. The proposed method relates the instantaneous pressure and size of expanding liquid drops to interfacial tension and is useful for measuring both liquid/gas and liquid/liquid tensions over a wide range of time scales, currently from 10 ms to several hours. Growing-drop measurements on surfactant-free water/air and water/octanol interfaces yield constant tensions equal to their known literature values. For surfactant-laden, liquid drops, the growing-drop technique captures the actual transient tension evolution of a single interface, rather than interval times as with the classic maximum-drop-pressure and drop.-volume tension measurements. Dynamic tensions measured for 0.25 mM aqueous 1-decanol solution/air and 0.02 kg/m{sup 3} aqueous Triton X-100 solution/dodecane interfaces show nonmonotonic behavior, indicating slow surfactant transport relative to the imposed rates of interfacial dilatation. The dynamic tension of a purified and fresh 6 mM aqueous sodium dodecyl sulfate (SDS) solution/air interface shows only a monotonic decrease, indicating rapid surfactant transport relative to the imposed rates of dilatation. ConverselY, an aged SDS solution, naturally containing trace dodecanol impurities, exhibits dynamic tensions which reflect a superposition of the rapidly equilibrating SDS and the slowly adsorbing dodecanol.

  9. Interfacial Properties of Electron Beam Cured Composites

    SciTech Connect

    Eberle, C.C.

    1999-12-30

    The objectives of the CRADA are to: Confirm that fiber-resin adhesion is responsible for the observed poor shear properties; Determine the mechanism(s) responsible for poor adhesion between carbon fibers and epoxy resins after e-beam curing; Develop and evaluate resin systems and fiber treatments to improve the properties of e-beam cured, carbon-fiber-reinforced composites; and Develop refined methods for processing e-beam cured, carbon-fiber-reinforced composites.

  10. Dynamically reconfigurable complex emulsions via tunable interfacial tensions

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  11. Dynamically reconfigurable complex emulsions via tunable interfacial tensions

    PubMed Central

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

    2015-01-01

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

  12. Dynamics of Pickering Emulsions in the Presence of an Interfacial Reaction: A Simulation Study.

    PubMed

    Zhao, Shuangliang; Zhan, Bicai; Hu, Yaofeng; Fan, Zhaoyu; Pera-Titus, Marc; Liu, Honglai

    2016-12-13

    Pickering emulsions combining surface-active and catalytic properties offer a promising platform for conducting interfacial reactions between immiscible reagents. Despite the significant progress in the design of Pickering interfacial catalysts for a broad panel of reactions, the dynamics of Pickering emulsions under reaction conditions is still poorly understood. Herein, using benzene hydroxylation with aqueous H2O2 as a model system, we explored the dynamics of benzene/water Pickering emulsions during reaction by dissipative particle dynamics. Our study points out that the surface wettability of the silica nanoparticles is affected to a higher extent by the degree of polymer grafting rather than an increase of the chain length of hydrophobic polymer moieties. A remarkable decline of the oil-in-water (O/W) interfacial tension was observed when increasing the yield of the reaction product (phenol), affecting the emulsion stability. However, phenol did not alter to an important extent the distribution of immiscible reagents around the nanoparticles sitting at the benzene/water interface. A synergistic effect between phenol and silica nanoparticles on the O/W interfacial tension of the biphasic system could be ascertained.

  13. Shape Oscillations of Gas Bubbles With Newtonian Interfacial Rheological Properties

    NASA Technical Reports Server (NTRS)

    Nadim, Ali

    1996-01-01

    The oscillation frequency and damping rate for small-amplitude axisymmetric shape modes of a gas bubble in an ideal liquid are obtained, in the limit when the bubble interface possesses Newtonian interfacial rheology with constant surface shear and dilatational viscosities. Such results permit the latter surface properties to be measured by analyzing experimental data on frequency shift and damping rate of specific shape modes of suspended bubbles in the presence of surfactants.

  14. Corrosion protection properties and interfacial adhesion mechanism of an epoxy/polyamide coating applied on the steel surface decorated with cerium oxide nanofilm: Complementary experimental, molecular dynamics (MD) and first principle quantum mechanics (QM) simulation methods

    NASA Astrophysics Data System (ADS)

    Bahlakeh, Ghasem; Ramezanzadeh, Bahram; Saeb, Mohammad Reza; Terryn, Herman; Ghaffari, Mehdi

    2017-10-01

    The effect of cerium oxide treatment on the corrosion protection properties and interfacial interaction of steel/epoxy was studied by electrochemical impedance spectroscopy, (EIS) classical molecular dynamics (MD) and first principle quantum mechanics (QM) simulation methods X-ray photoelectron spectroscopy (XPS) was used to verify the chemical composition of the Ce film deposited on the steel. To probe the role of the curing agent in epoxy adsorption, computations were compared for an epoxy, aminoamide and aminoamide modified epoxy. Moreover, to study the influence of water on interfacial interactions the MD simulations were executed for poly (aminoamide)-cured epoxy resin in contact with the different crystallographic cerium dioxide (ceria, CeO2) surfaces including (100), (110), and (111) in the presence of water molecules. It was found that aminoamide-cured epoxy material was strongly adhered to all types of CeO2 substrates, so that binding to ceria surfaces followed the decreasing order CeO2 (111) > CeO2 (100) > CeO2 (110) in both dry and wet environments. Calculation of interaction energies noticed an enhanced adhesion to metal surface due to aminoamide curing of epoxy resin; where facets (100) and (111) revealed electrostatic and Lewis acid-base interactions, while an additional hydrogen bonding interaction was identified for CeO2 (110). Overall, MD simulations suggested decrement of adhesion to CeO2 in wet environment compared to dry conditions. Additionally, contact angle, pull-off test, cathodic delamination and salt spray analyses were used to confirm the simulation results. The experimental results in line with modeling results revealed that Ce layer deposited on steel enhanced substrate surface free energy, work of adhesion, and interfacial adhesion strength of the epoxy coating. Furthermore, decrement of adhesion of epoxy to CeO2 in presence of water was affirmed by experimental results. EIS results revealed remarkable enhancement of the corrosion

  15. Lipases at interfaces: unique interfacial properties as globular proteins.

    PubMed

    Reis, P; Miller, R; Krägel, J; Leser, M; Fainerman, V B; Watzke, H; Holmberg, K

    2008-06-01

    The adsorption behavior of two globular proteins, lipase from Rhizomucor miehei and beta-lactoglobulin, at inert oil/water and air/water interfaces was studied by the pendant drop technique. The kinetics and adsorption isotherms were interpreted for both proteins in different environments. It was found that the adopted mathematical models well describe the adsorption behavior of the proteins at the studied interfaces. One of the main findings is that unique interfacial properties were observed for lipase as compared to the reference beta-lactoglobulin. A folded drop with a "skinlike" film was formed for the two proteins after aging followed by compression. This behavior is normally associated with protein unfolding and covalent cross-linking at the interface. Despite this, the lipase activity was not suppressed. By highlighting the unique interfacial properties of lipases, we believe that the presented work contributes to a better understanding of lipase interfacial activation and the mechanisms regulating lipolysis. The results indicate that the understanding of the physical properties of lipases can lead to novel approaches to regulate their activity.

  16. A perspective on the interfacial properties of nanoscopic liquid drops

    NASA Astrophysics Data System (ADS)

    Malijevský, Alexandr; Jackson, George

    2012-11-01

    The structural and interfacial properties of nanoscopic liquid drops are assessed by means of mechanical, thermodynamical, and statistical mechanical approaches that are discussed in detail, including original developments at both the macroscopic level and the microscopic level of density functional theory (DFT). With a novel analysis we show that a purely macroscopic (static) mechanical treatment can lead to a qualitatively reasonable description of the surface tension and the Tolman length of a liquid drop; the latter parameter, which characterizes the curvature dependence of the tension, is found to be negative and has a magnitude of about a half of the molecular dimension. A mechanical slant cannot, however, be considered satisfactory for small finite-size systems where fluctuation effects are significant. From the opposite perspective, a curvature expansion of the macroscopic thermodynamic properties (density and chemical potential) is then used to demonstrate that a purely thermodynamic approach of this type cannot in itself correctly account for the curvature correction of the surface tension of liquid drops. We emphasize that any approach, e.g., classical nucleation theory, which is based on a purely macroscopic viewpoint, does not lead to a reliable representation when the radius of the drop becomes microscopic. The description of the enhanced inhomogeneity exhibited by small drops (particularly in the dense interior) necessitates a treatment at the molecular level to account for finite-size and surface effects correctly. The so-called mechanical route, which corresponds to a molecular-level extension of the macroscopic theory of elasticity and is particularly popular in molecular dynamics simulation, also appears to be unreliable due to the inherent ambiguity in the definition of the microscopic pressure tensor, an observation which has been known for decades but is frequently ignored. The union of the theory of capillarity (developed in the nineteenth

  17. Interfacial Properties of Bilayer and Trilayer Graphene on Metal Substrates

    PubMed Central

    Zheng, Jiaxin; Wang, Yangyang; Wang, Lu; Quhe, Ruge; Ni, Zeyuan; Mei, Wai-Ning; Gao, Zhengxiang; Yu, Dapeng; Shi, Junjie; Lu, Jing

    2013-01-01

    One popular approach to prepare graphene is to grow them on transition metal substrates via chemical vapor deposition. By using the density functional theory with dispersion correction, we systematically investigate for the first time the interfacial properties of bilayer (BLG) and trilayer graphene (TLG) on metal substrates. Three categories of interfacial structures are revealed. The adsorption of B(T)LG on Al, Ag, Cu, Au, and Pt substrates is a weak physisorption, but a band gap can be opened. The adsorption of B(T)LG on Ti, Ni, and Co substrates is a strong chemisorption, and a stacking-insensitive band gap is opened for the two uncontacted layers of TLG. The adsorption of B(T)LG on Pd substrate is a weaker chemisorption, with a band gap opened for the uncontacted layers. This fundamental study also helps for B(T)LG device study due to inevitable graphene/metal contact. PMID:23803738

  18. Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites

    SciTech Connect

    Holt, Adam P.; Bocharova, Vera; Cheng, Shiwang; Kisliuk, Alexander M.; White, B. Tyler; Saito, Tomonori; Uhrig, David; Mahalik, J. P.; Kumar, Rajeev; Imel, Adam E.; Etampawala, Thusitha; Martin, Halie; Sikes, Nicole; Sumpter, Bobby G.; Dadmun, Mark D.; Sokolov, Alexei P.

    2016-06-23

    It is generally believed that the strength of the polymer nanoparticle interaction controls the modification of near-interface segmental mobility in polymer nanocomposites (PNCs). However, little is known about the effect of covalent bonding on the segmental dynamics and glass transition of matrix-free polymer-grafted nanoparticles (PGNs), especially when compared to PNCs. In this article, we directly compare the static and dynamic properties of poly(2-vinylpyridine)/silica-based nanocomposites with polymer chains either physically adsorbed (PNCs) or covalently bonded (PGNs) to identical silica nanoparticles (RNP = 12.5 nm) for three different molecular weight (MW) systems. Interestingly, when the MW of the matrix is as low as 6 kg/mol (RNP/Rg = 5.4) or as high as 140 kg/mol (RNP/Rg= 1.13), both small-angle X-ray scattering and broadband dielectric spectroscopy show similar static and dynamic properties for PNCs and PGNs. However, for the intermediate MW of 18 kg/mol (RNP/Rg = 3.16), the difference between physical adsorption and covalent bonding can be clearly identified in the static and dynamic properties of the interfacial layer. We ascribe the differences in the interfacial properties of PNCs and PGNs to changes in chain stretching, as quantified by self-consistent field theory calculations. These results demonstrate that the dynamic suppression at the interface is affected by the chain stretching; that is, it depends on the anisotropy of the segmental conformations, more so than the strength of the interaction, which suggests that the interfacial dynamics can be effectively tuned by the degree of stretching a parameter accessible from the MW or grafting density.

  19. Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites

    SciTech Connect

    Holt, Adam P.; Bocharova, Vera; Cheng, Shiwang; Kisliuk, Alexander M.; White, B. Tyler; Saito, Tomonori; Uhrig, David; Mahalik, J. P.; Kumar, Rajeev; Imel, Adam E.; Etampawala, Thusitha; Martin, Halie; Sikes, Nicole; Sumpter, Bobby G.; Dadmun, Mark D.; Sokolov, Alexei P.

    2016-06-23

    It is generally believed that the strength of the polymer nanoparticle interaction controls the modification of near-interface segmental mobility in polymer nanocomposites (PNCs). However, little is known about the effect of covalent bonding on the segmental dynamics and glass transition of matrix-free polymer-grafted nanoparticles (PGNs), especially when compared to PNCs. In this article, we directly compare the static and dynamic properties of poly(2-vinylpyridine)/silica-based nanocomposites with polymer chains either physically adsorbed (PNCs) or covalently bonded (PGNs) to identical silica nanoparticles (RNP = 12.5 nm) for three different molecular weight (MW) systems. Interestingly, when the MW of the matrix is as low as 6 kg/mol (RNP/Rg = 5.4) or as high as 140 kg/mol (RNP/Rg= 1.13), both small-angle X-ray scattering and broadband dielectric spectroscopy show similar static and dynamic properties for PNCs and PGNs. However, for the intermediate MW of 18 kg/mol (RNP/Rg = 3.16), the difference between physical adsorption and covalent bonding can be clearly identified in the static and dynamic properties of the interfacial layer. We ascribe the differences in the interfacial properties of PNCs and PGNs to changes in chain stretching, as quantified by self-consistent field theory calculations. These results demonstrate that the dynamic suppression at the interface is affected by the chain stretching; that is, it depends on the anisotropy of the segmental conformations, more so than the strength of the interaction, which suggests that the interfacial dynamics can be effectively tuned by the degree of stretching a parameter accessible from the MW or grafting density.

  20. Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites

    DOE PAGES

    Holt, Adam P.; Bocharova, Vera; Cheng, Shiwang; ...

    2016-06-23

    It is generally believed that the strength of the polymer nanoparticle interaction controls the modification of near-interface segmental mobility in polymer nanocomposites (PNCs). However, little is known about the effect of covalent bonding on the segmental dynamics and glass transition of matrix-free polymer-grafted nanoparticles (PGNs), especially when compared to PNCs. In this article, we directly compare the static and dynamic properties of poly(2-vinylpyridine)/silica-based nanocomposites with polymer chains either physically adsorbed (PNCs) or covalently bonded (PGNs) to identical silica nanoparticles (RNP = 12.5 nm) for three different molecular weight (MW) systems. Interestingly, when the MW of the matrix is as lowmore » as 6 kg/mol (RNP/Rg = 5.4) or as high as 140 kg/mol (RNP/Rg= 1.13), both small-angle X-ray scattering and broadband dielectric spectroscopy show similar static and dynamic properties for PNCs and PGNs. However, for the intermediate MW of 18 kg/mol (RNP/Rg = 3.16), the difference between physical adsorption and covalent bonding can be clearly identified in the static and dynamic properties of the interfacial layer. We ascribe the differences in the interfacial properties of PNCs and PGNs to changes in chain stretching, as quantified by self-consistent field theory calculations. These results demonstrate that the dynamic suppression at the interface is affected by the chain stretching; that is, it depends on the anisotropy of the segmental conformations, more so than the strength of the interaction, which suggests that the interfacial dynamics can be effectively tuned by the degree of stretching a parameter accessible from the MW or grafting density.« less

  1. Interfacial Mechanical Properties of Graphene on Self-Assembled Monolayers: Experiments and Simulations.

    PubMed

    Tu, Qing; Kim, Ho Shin; Oweida, Thomas J; Parlak, Zehra; Yingling, Yaroslava G; Zauscher, Stefan

    2017-03-22

    Self-assembled monolayers (SAMs) have been widely used to engineer the electronic properties of substrate-supported graphene devices. However, little is known about how the surface chemistry of SAMs affects the interfacial mechanical properties of graphene supported on SAMs. Fluctuations and changes in these properties affect the stress transfer between substrate and the supported graphene and thus the performance of graphene-based devices. The changes in interfacial mechanical properties can be characterized by measuring the out-of-plane elastic properties. Combining contact resonance atomic force microcopy experiments with molecular dynamics simulations, we show that the head group chemistry of a SAM, which affects the interfacial interactions, can have a significant effect on the out-of-plane elastic modulus of the graphene-SAM heterostructure. Graphene supported on hydrophobic SAMs leads to heterostructures stiffer than those of graphene supported on hydrophilic SAMs, which is largely due to fewer water molecules present at the graphene-SAM interface. Our results provide an important, and often overlooked, insight into the mechanical properties of substrate-supported graphene electronics.

  2. A Molecular Dynamics Simulation of the Local Interfacial Structure of Nanobubbles

    NASA Astrophysics Data System (ADS)

    Kikugawa, Gota; Takagi, Shu; Matsumoto, Yoichiro

    2003-11-01

    A molecular dynamics simulation of "nanobubbles" in the aquaous surfactant system was performed to investigate the local and instantaneous structure of the liquid-vapor interface. At first, we propose the new definition of the interface which can capture the microscopic and instantaneous interfacial structure, and which can be applied to the curved interface like nanobubbles. As this definition is not thermodynamically defined, we compared the newly defined interface with the so-called Gibbs dividing surface and discussed the validity of the new difinition. By using the new definition of the interface, the static and dynamic properties of the interface were analyzed microscopically. It was shown that the rotational relaxation time of water molecules at the interface adsorbed by surfactants was longer than that of bulk liquids. From this result, we found that the water molecules at the interface was structurized by surfactants. Furethermore, we discussed the relation between the interfacial structuring and the stability of nanobubbles.

  3. Molecular dynamics studies of interfacial crack propagation in heterogeneous media

    SciTech Connect

    Corbett, J.M. |; Selinger, R.L.B.

    1999-08-01

    The authors use molecular dynamics simulation to investigate the evolution of a crack front in interfacial fracture in three dimensions. They find that when a crack passes through a localized region of heterogeneous toughness, crack front waves are initiated and propagate laterally. They also investigate the development of roughness of the crack front when the crack propagates in a region of heterogeneous toughness. They find that in steady state the mean square width W of the front scales with system size L as W {approximately} L{sup 0.35}, in agreement with recent theoretical predictions.

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

    PubMed

    Ghadar, Yasaman; Clark, Aurora E

    2014-06-28

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

  5. Atomistic simulations of bulk, surface and interfacial polymer properties

    NASA Astrophysics Data System (ADS)

    Natarajan, Upendra

    In chapter I, quasi-static molecular mechanics based simulations are used to estimate the activation energy of phenoxy rings flips in the amorphous region of a semicrystalline polyimide. Intra and intermolecular contributions to the flip activation energy, the torsional cooperativity accompanying the flip, and the effect of the flip on the motion in the glassy bulk state, are looked at. Also, comparison of the weighted mean activation energy is made with experimental data from solid state NMR measurements; the simulated value being 17.5 kcal/mol., while the experimental value was observed to be 10.5 kcal/mol. Chapter II deals with construction of random copolymer thin films of styrene-butadiene (SB) and styrene-butadiene-acrylonitrile (SBA). The structure and properties of the free surfaces presented by these thin films are analysed by, the atom mass density profiles, backbone bond orientation function, and the spatial distribution of acrylonitrile groups and styrene rings. The surface energies of SB and SBA are calculated using an atomistic equation and are compared with experimental data in the literature. In chapter III, simulations of polymer-polymer interfaces between like and unlike polymers, specifically cis-polybutadiene (PBD) and atatic polypropylene (PP), are presented. The structure of an incompatible polymer-polymer interface, and the estimation of the thermodynamic work of adhesion and interfacial energy between different incompatible polymers, form the focus here. The work of adhesion is calculated using an atomistic equation and is further used in a macroscopic equation to estimate the interfacial energy. The interfacial energy is compared with typical values for other immiscible systems in the literature. The interfacial energy compared very well with interfacial energy values for a few other immiscible hydrocarbon pairs. In chapter IV, the study proceeds to look at the interactions between nonpolar and polar small molecules with SB and SBA thin

  6. Interfacial and emulsifying properties of lentil protein isolate.

    PubMed

    Joshi, M; Adhikari, B; Aldred, P; Panozzo, J F; Kasapis, S; Barrow, C J

    2012-10-01

    The dynamic interfacial tension (DIFT) at oil-water interface, diffusion coefficients, surface hydrophobicity, zeta potential and emulsifying properties, including emulsion activity index (EAI), emulsion stability index (ESI) and droplet size of lentil protein isolate (LPI), were measured at different pH and LPI concentration, in order to elucidate its emulsifying behaviour. Sodium caseinate (NaCas), whey protein isolate (WPI), bovine serum albumin (BSA) and lysozyme (Lys) were used as benchmark proteins and their emulsifying property was compared with that of LPI. The speed of diffusion-controlled migration of these proteins to the oil/water interface, was in the following order: NaCas>LPI>WPI>BSA>Lys, while their surface hydrophobicity was in the following order: BSA>LPI>NaCas>WPI>Lys. The EAI of emulsions stabilised by the above proteins ranged from 90.3 to 123.3 m(2)/g and it was 93.3 ± 0.2 m(2)/g in LPI-stabilised emulsion. However, the stability of LPI-stabilised emulsions was slightly lower compared to that of WPI and NaCas-stabilised emulsions at the same protein concentration at pH 7.0. The ESI of LPI emulsions improved substantially with decrease in droplet size when protein concentration was increased (20-30 mg/ml). Reduction of disulphide bonds enhanced both the EAI and ESI compared to untreated samples. Heat treatment of LPI dispersions resulted in poor emulsion stability due to molecular aggregation. The stability of LPI-stabilised emulsions was found to decrease in the presence of NaCl. This study showed that LPI can be as effective emulsifiers of oil-in-water emulsions as are WPI and NaCas at ≥20 mg/ml concentrations both at low and neutral pH. The emulsifying property of LPI can be improved by reducing the intra and inter-disulphide bond by using appropriate reducing agents. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. 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

  8. Capillary, wettability and interfacial dynamics in polymer electrolyte fuel cells

    SciTech Connect

    Mukherjee, Partha P

    2009-01-01

    In the present scenario of a global initiative toward a sustainable energy future, the polymer electrolyte fuel cell (PEFC) has emerged as one of the most promising alternative energy conversion devices for different applications. Despite tremendous progress in recent years, a pivotal performance/durability limitation in the PEFC arises from liquid water transport, perceived as the Holy Grail in PEFC operation. The porous catalyst layer (CL), fibrous gas diffusion layer (GDL) and flow channels play a crucial role in the overall PEFC performance due to the transport limitation in the presence of liquid water and flooding phenomena. Although significant research, both theoretical and experimental, has been performed, there is serious paucity of fundamental understanding regarding the underlying structure-transport-performance interplay in the PEFC. The inherent complex morphologies, micro-scale transport physics involving coupled multiphase, multicomponent, electrochemically reactive phenomena and interfacial interactions in the constituent components pose a formidable challenge. In this paper, the impact of capillary transport, wetting characteristics and interfacial dynamics on liquid water transport is presented based on a comprehensive mesoscopic modeling framework with the objective to gain insight into the underlying electrodynamics, two-phase dynamics and the intricate structure-transport-interface interactions in the PEFC.

  9. Drop impact on liquid film: dynamics of interfacial gas layer

    NASA Astrophysics Data System (ADS)

    Tang, Xiaoyu; Saha, Abhishek; Law, Chung K.; Sun, Chao

    2016-11-01

    Drop impacting liquid film is commonly observed in many processes including inkjet printing and thermal sprays. Owing to the resistance from the interfacial gas layer trapped between the drop and film surface, impact may not always result in coalescence; and as such investigating the behavior of the interfacial gas layer is important to understand the transition between bouncing and merging outcomes. The gas layer is, however, not easily optically accessible due to its microscopic scale and curved interfaces. We report the measurement of this critical gas layer thickness between two liquid surfaces using high-speed color interferometry capable of measuring micron and submicron thicknesses. The complete gas layer dynamics for the bouncing cases can be divided into two stages: the approaching stage when the drop squeezes the gas layer at the beginning of the impact, and the rebounding stage when the drop retracts and rebounds from the liquid film. The approaching stage is found to be similar across wide range of conditions studied. However, for the rebounding stage, with increase of liquid film thickness, the evolution of gas layer changes dramatically, displaying a non-monotonic behavior. Such dynamics is analyzed in lights of various competing timescales.

  10. 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.

  11. Exploiting interfacial water properties for desalination and purification applications.

    SciTech Connect

    Xu, Hongwu; Varma, Sameer; Nyman, May Devan; Alam, Todd Michael; Thuermer, Konrad; Holland, Gregory P.; Leung, Kevin; Liu, Nanguo; Xomeritakis, George K.; Frankamp, Benjamin L.; Siepmann, J. Ilja; Cygan, Randall Timothy; Hartl, Monika A.; Travesset, Alex; Anderson, Joshua A.; Huber, Dale L.; Kissel, David J.; Bunker, Bruce Conrad; Lorenz, Christian Douglas; Major, Ryan C.; McGrath, Matthew J.; Farrow, Darcie; Cecchi, Joseph L.; van Swol, Frank B.; Singh, Seema; Rempe, Susan B.; Brinker, C. Jeffrey; Clawson, Jacalyn S.; Feibelman, Peter Julian; Houston, Jack E.; Crozier, Paul Stewart; Criscenti, Louise Jacqueline; Chen, Zhu; Zhu, Xiaoyang; Dunphy, Darren Robert; Orendorff, Christopher J.; Pless, Jason D.; Daemen, Luke L.; Gerung, Henry; Ockwig, Nathan W.; Nenoff, Tina Maria; Jiang, Ying-Bing; Stevens, Mark Jackson

    2008-09-01

    A molecular-scale interpretation of interfacial processes is often downplayed in the analysis of traditional water treatment methods. However, such an approach is critical for the development of enhanced performance in traditional desalination and water treatments. Water confined between surfaces, within channels, or in pores is ubiquitous in technology and nature. Its physical and chemical properties in such environments are unpredictably different from bulk water. As a result, advances in water desalination and purification methods may be accomplished through an improved analysis of water behavior in these challenging environments using state-of-the-art microscopy, spectroscopy, experimental, and computational methods.

  12. Single-molecule interfacial electron transfer dynamics in solar energy conversion

    NASA Astrophysics Data System (ADS)

    Dhital, Bharat

    molecule on ITO surface. Finally, the electric field effect on the interface properties has been probed by using surface-enhanced Raman spectroscopy and supported by density functional theory calculations in alizarin-TiO2 system. The perturbation, created by the external potential, has been observed to cause a shift and/or splitting interfacial bond vibrational mode, typical indicator of the coupling energy changes between alizarin and TiO2. Such splitting provides evidence for electric field-dependent electronic coupling changes that have a significant impact on the interfacial electron transfer dynamics.

  13. Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy.

    PubMed

    Okada, Atsushi; He, Shikun; Gu, Bo; Kanai, Shun; Soumyanarayanan, Anjan; Lim, Sze Ter; Tran, Michael; Mori, Michiyasu; Maekawa, Sadamichi; Matsukura, Fumihiro; Ohno, Hideo; Panagopoulos, Christos

    2017-04-11

    Studies of magnetization dynamics have incessantly facilitated the discovery of fundamentally novel physical phenomena, making steady headway in the development of magnetic and spintronics devices. The dynamics can be induced and detected electrically, offering new functionalities in advanced electronics at the nanoscale. However, its scattering mechanism is still disputed. Understanding the mechanism in thin films is especially important, because most spintronics devices are made from stacks of multilayers with nanometer thickness. The stacks are known to possess interfacial magnetic anisotropy, a central property for applications, whose influence on the dynamics remains unknown. Here, we investigate the impact of interfacial anisotropy by adopting CoFeB/MgO as a model system. Through systematic and complementary measurements of ferromagnetic resonance (FMR) on a series of thin films, we identify narrower FMR linewidths at higher temperatures. We explicitly rule out the temperature dependence of intrinsic damping as a possible cause, and it is also not expected from existing extrinsic scattering mechanisms for ferromagnets. We ascribe this observation to motional narrowing, an old concept so far neglected in the analyses of FMR spectra. The effect is confirmed to originate from interfacial anisotropy, impacting the practical technology of spin-based nanodevices up to room temperature.

  14. Molecular Dynamics Studies on the Effects of Water Speciation on Interfacial Structure and Dynamics in Silica-Filled PDMS Composites

    SciTech Connect

    Gee, R H; Maxwell, R S; Dinh, L N; Balazs, B

    2001-11-21

    Significant changes in materials properties of siloxane based polymers can be obtained by the addition of inorganic fillers. In silica-filled polydimethylsiloxane (PDMS) based composites the mechanism of this reinforcing behavior is presumably hydrogen bonding between surface hydroxyls and backbone siloxane species. We have chosen to investigate in detail the effect of chemisorbed and physisorbed water on the interfacial structure and dynamics in silica-filled PDMS based composites. Toward this end, we have combined molecular dynamics simulations and experimental studies employing DMA and Nh4R analysis. Our results suggest that the polymer-silica contact distance and the mobility of interfacial polymer chains significantly decreased as the hydration level at the interface was reduced. The reduced mobility of the PDMS chains in the interfacial domain reduced the overall, bulk, motional properties of the polymer, thus causing an effective ''stiffening'' of the polymer matrix. The role of the long-ranged Coulombic interactions on the structural features and chain dynamics of the polymer were also examined. Both are found to be strongly influenced by the electrostatic interactions as identified by the bond orientation time correlation function and local density distribution functions. These results have important implications for the design of nanocomposite silica-siloxane materials.

  15. Dynamics of various polymer-graphene interfacial systems through atomistic molecular dynamics simulations.

    PubMed

    Rissanou, Anastassia N; Harmandaris, Vagelis

    2014-04-28

    The current work refers to a simulation study on hybrid polymer-graphene interfacial systems. We explore the effect of graphene on the mobility of polymers, by studying three well known and widely used polymers, polyethylene (PE), polystyrene (PS) and poly(methyl-methacrylate) (PMMA). Qualitative and quantitative differences in the dynamical properties of the polymer chains in particular at the polymer-graphene interface are detected. Results concerning both the segmental and the terminal dynamics render PE much faster than the other two polymers; PS follows, while PMMA is the slowest one. Clear spatial dynamic heterogeneity has been observed for all model systems, with different dynamical behavior of the adsorbed polymer segments. The segmental relaxation time of the polymer (τseg) as a function of the distance from graphene shows an abrupt decrease beyond the first adsorption layer for PE, as a result of its well-ordered layered structure close to graphene, though a more gradual decay is observed for PS and PMMA. The distribution of the relaxation times of adsorbed segments was also found to be broader than those of the bulk ones for all three polymer-graphene systems.

  16. 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.

  17. Effect of confinement and molecular architecture on interfacial dynamics

    NASA Astrophysics Data System (ADS)

    Chrissopoulou, K.; Androulaki, K.; Prevosto, D.; Labardi, M.; Anastasiadis, S. H.

    2016-05-01

    The dynamics of polyester polyols in the bulk, under confinement when the polymers are intercalated within the galleries of a hydrophilic clay and close to the inorganic surfaces is investigated utilizing Dielectric Relaxation Spectroscopy (DRS). A series of linear biobased polyesters with hydroxyl end groups were utilized in the bulk and in nanohybrids and the results were compared with the case of hyperbranched polymers of similar chemistry but non-linear architecture. A broad range of temperatures below and above the bulk polymer glass transition temperature, Tg, was investigated covering both the regimes of beta-like local processes and segmental (alpha-process) dynamics. The polymer dynamics observed in all the nanocomposites are quite different compared to the bulk due to the different interactions whereas differences are seen due to the architecture as well. Moreover, non-standard local dielectric spectroscopy has been used to investigate the nanocomposites dynamics at the local scale: polymer relaxation has been investigated in the same material both close and far from the MMT surfaces. The comparison of the results from the two techniques allowed the understanding, in more detail, of the influence of the complex interfacial interactions on the relaxation dynamics.

  18. Glassy Interfacial Dynamics of Ni Nanoparticles: Part I Colored Noise, Dynamic Heterogeneity and Collective Atomic Motion

    PubMed Central

    Zhang, Hao; Douglas, Jack F.

    2014-01-01

    Most condensed materials exhibit a significant fraction of atoms, molecules or particles that are strongly interacting with each other, while being configured geometrically at any instant of time in an ‘amorphous’ state having a relatively uniform density. Recently, both simulations and experiments have revealed that the dynamics of diverse condensed amorphous materials is generally characterized by significant heterogeneity in the local mobility and by progressively increasing collective motion upon cooling that takes the form of string-like collective particle rearrangements. The direct experimental observation of this type of collective motion, which has been directly linked to the growing relaxation times of glass-forming materials, and its quantification under different thermodynamic conditions, has so far been restricted to colloidal and driven granular fluids. The present work addresses the fundamental problem of how to determine the scale of this type of collective motion in materials composed of molecules or atoms. The basic premise of our work is that large scale dynamic particle clustering in amorphous materials must give rise to large fluctuations in particle mobility so that transport properties, especially those related to particle mobility, should naturally exhibit noise related to the cooperative motion scale. In our initial exploratory study seeking a relationship of this kind, we find 1/fα or ‘colored noise’, in both potential energy and particle displacements fluctuations of the atoms within the glassy interfacial layer of Ni nanoparticles (NPs). A direct relation between the particle displacement (mobility) noise exponent α and the average polymerization index of the string-like collective motion L is observed for a range of NP sizes, temperatures and for surface doping of the NPs with other metal atoms (Ag, Au, Pt) to change of fragility of the glassy interfacial layer at the surface of the Ni NPs. We also introduce a successful

  19. Non-equilibrium dynamics and structure of interfacial ice

    NASA Astrophysics Data System (ADS)

    Andreussi, Oliviero; Donadio, Davide; Parrinello, Michele; Zewail, Ahmed H.

    2006-07-01

    Stimulated by recent experiments [C.-Y. Ruan et al. Science 304, (2004) 81], we have performed molecular dynamics and ab initio structural studies of the laser-induced heating and restructuring processes of nanometer-scale ice on a substrate of chlorine terminated Si(1 1 1). Starting from proton disordered cubic ice configurations the thin film behavior has been characterized at several temperatures up to the melting point. The surface induces order with crystallization in the Ic lattice, but with void amorphous regions. The structure changes on the ultrashort time scale and restructures by heat dissipation depending on the relaxation time and final temperature. Our results show the general behavior observed experimentally, thus providing the nature of forces in the atomic-scale description of interfacial ice.

  20. Interfacial colloidal rod dynamics: Coefficients, simulations, and analysis

    NASA Astrophysics Data System (ADS)

    Yang, Yuguang; Bevan, Michael A.

    2017-08-01

    Colloidal rod diffusion near a wall is modeled and simulated based on a constrained Stokesian dynamic model of chains-of-spheres. By modeling colloidal rods as chains-of-spheres, complete diffusion tensors are computed for colloidal rods in bulk media and near interfaces, including hydrodynamic interactions, translation-rotation coupling, and all diffusion modes in the particle and lab frames. Simulated trajectories based on the chain-of-spheres diffusion tensor are quantified in terms of typical experimental quantities such as mean squared positional and angular displacements as well as autocorrelation functions. Theoretical expressions are reported to predict measured average diffusivities as well as the crossover from short-time anisotropic translational diffusion along the rod's major axis to isotropic diffusion. Diffusion modes are quantified in terms of closed form empirical fits to model results to aid their use in interpretation and prediction of experiments involving colloidal rod diffusion in interfacial and confined systems.

  1. Interfacial properties of asphaltenes at toluene-water interfaces.

    PubMed

    Zarkar, Sharli; Pauchard, Vincent; Farooq, Umer; Couzis, Alexander; Banerjee, Sanjoy

    2015-05-05

    Asphaltenes are "n-alkane insoluble" species in crude oil that stabilize water-in-oil emulsions. To understand asphaltene adsorption mechanisms at oil-water interfaces and coalescence blockage, we first studied the behavior in aliphatic oil-water systems in which asphaltenes are almost insoluble. They adsorbed as monomers, giving a unique master curve relating interfacial tension (IFT) to interfacial coverage through a Langmuir equation of state (EoS). The long-time surface coverage was independent of asphaltene bulk concentration and asymptotically approached the 2-D packing limit for polydisperse disks. On coalescence, the surface coverage exceeded the 2-D limit and the asphaltene film appeared to become solidlike, apparently undergoing a transition to a soft glassy material and blocking further coalescence. However, real systems consist of mixtures of aliphatic and aromatic components in which asphaltenes may be quite soluble. To understand solubility effects, we focus here on how the increased bulk solubility of asphaltenes affects their interfacial properties in comparison to aliphatic oil-water systems. Unlike the "almost irreversible" adsorption of asphaltenes where the asymptotic interfacial coverage was independent of the bulk concentration, an equilibrium surface pressure, dependent on bulk concentration, was obtained for toluene-water systems because of adsorption being balanced by desorption. The equilibrium surface coverage could be obtained from the short- and long-term Ward-Tordai approximations. The behavior of the equilibrium surface pressure with the equilibrium surface coverage was then derived. These data for various asphaltene concentrations were used to determine the EoS, which for toluene-water could also be fitted by the Langmuir EoS with Γ∞ = 3.3 molecule/nm(2), the same value as that found for these asphaltenes in aliphatic media. Asphaltene solubility in the bulk phase only appears to affect the adsorption isotherm but not the Eo

  2. Grafted Peptides for the Control of Interfacial Properties

    NASA Astrophysics Data System (ADS)

    Ducker, William; Mosse, Wade; Gras, Sally

    2010-03-01

    Peptide or protein polymers that are used to control interfacial properties are usually prepared by solid-state synthesis and then adsorbed to an interface. Such a method results in a low yield and places restrictions on polymer structure, because the peptide must be designed to adsorb, as well as to provide the interfacial control. The method of grafting peptides from surfaces is an alternate method that is potentially very useful because the peptide is covalently linked, and the sequence limitations related to adsorption are removed. To demonstrate this technique, we have used solid-phase peptide synthesis to graft a 15-residue peptide, EKEKEKEKEKEKEGG, containing a zwitterionic sequence of alternating lysine and glutamic acid residues from the surface of an aminosilanized silicon wafer by placing the silicon wafer within a commercial microwave peptide synthesizer. We confirmed the presence of this peptide layer on the surface by X-ray photoelectron spectroscopy (XPS) and ellipsometry. Atomic force microscopy (AFM) was then used to study the forces between the peptide-modified surface and a borosilicate glass sphere as a function of solution pH. We will also discuss the use of grafted peptides to control the stability of colloidal suspensions.

  3. The importance of experimental design on measurement of dynamic interfacial tension and interfacial rheology in diffusion-limited surfactant systems

    DOE PAGES

    Reichert, Matthew D.; Alvarez, Nicolas J.; Brooks, Carlton F.; ...

    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

  4. 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.

  5. Interfacial ionic 'liquids': connecting static and dynamic structures

    DOE PAGES

    Uysal, Ahmet; Zhou, Hua; Feng, Guang; ...

    2014-12-05

    It is well known that room temperature ionic liquids (RTILs) often adopt a charge-separated layered structure, i.e. with alternating cation- and anion-rich layers, at electrified interfaces. However, the dynamic response of the layered structure to temporal variations in applied potential is not well understood. For this research, we used in situ, real-time x-ray reflectivity to study the potential-dependent electric double layer (EDL) structure of an imidazolium-based RTIL on charged epitaxial graphene during potential cycling as a function of temperature. The results suggest that the graphene–RTIL interfacial structure is bistable in which the EDL structure at any intermediate potential can bemore » described by the combination of two extreme-potential structures whose proportions vary depending on the polarity and magnitude of the applied potential. This picture is supported by the EDL structures obtained by fully atomistic molecular dynamics simulations at various static potentials. Lastly, the potential-driven transition between the two structures is characterized by an increasing width but with an approximately fixed hysteresis magnitude as a function of temperature. The results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (~0.15 eV).« less

  6. Particle laden fluid interfaces: dynamics and interfacial rheology.

    PubMed

    Mendoza, Alma J; Guzmán, Eduardo; Martínez-Pedrero, Fernando; Ritacco, Hernán; Rubio, Ramón G; Ortega, Francisco; Starov, Victor M; Miller, Reinhard

    2014-04-01

    We review the dynamics of particle laden interfaces, both particle monolayers and particle+surfactant monolayers. We also discuss the use of the Brownian motion of microparticles trapped at fluid interfaces for measuring the shear rheology of surfactant and polymer monolayers. We describe the basic concepts of interfacial rheology and the different experimental methods for measuring both dilational and shear surface complex moduli over a broad range of frequencies, with emphasis in the micro-rheology methods. In the case of particles trapped at interfaces the calculation of the diffusion coefficient from the Brownian trajectories of the particles is calculated as a function of particle surface concentration. We describe in detail the calculation in the case of subdiffusive particle dynamics. A comprehensive review of dilational and shear rheology of particle monolayers and particle+surfactant monolayers is presented. Finally the advantages and current open problems of the use of the Brownian motion of microparticles for calculating the shear complex modulus of monolayers are described in detail.

  7. Interfacial ionic 'liquids': connecting static and dynamic structures

    SciTech Connect

    Uysal, Ahmet; Zhou, Hua; Feng, Guang; Lee, Sang Soo; Li, Song; Cummings, Peter T.; Fulvio, Pasquale F.; Dai, Sheng; McDonough, John K.; Gogotsi, Yury G.; Fenter, Paul

    2014-12-05

    It is well known that room temperature ionic liquids (RTILs) often adopt a charge-separated layered structure, i.e. with alternating cation- and anion-rich layers, at electrified interfaces. However, the dynamic response of the layered structure to temporal variations in applied potential is not well understood. For this research, we used in situ, real-time x-ray reflectivity to study the potential-dependent electric double layer (EDL) structure of an imidazolium-based RTIL on charged epitaxial graphene during potential cycling as a function of temperature. The results suggest that the graphene–RTIL interfacial structure is bistable in which the EDL structure at any intermediate potential can be described by the combination of two extreme-potential structures whose proportions vary depending on the polarity and magnitude of the applied potential. This picture is supported by the EDL structures obtained by fully atomistic molecular dynamics simulations at various static potentials. Lastly, the potential-driven transition between the two structures is characterized by an increasing width but with an approximately fixed hysteresis magnitude as a function of temperature. The results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (~0.15 eV).

  8. Calorimetric study of surface and interfacial properties of fine coal

    SciTech Connect

    Melkus, T.G.A.

    1986-01-01

    In order to study the surface/interfacial properties of fine coal, heat flux calorimeter was used to make heat of immersion (..delta..H/sub imm/) measurements. These heats have been shown to be a valuable means of investigating the chemistry and surface properties of solids as they interact with adsorbate molecules. In addition, heats of immersion can be used to characterize a solid in terms of hydrophobicity/hydrophilicity and estimate its relative wetting tendency. The first phase of experiments that were performed served as a basis for comparison of coal components/characteristics immersed in deionized, distilled water. The results of these experiments were found to correlate well with reported flotation trends. In the second phase of experiments, the solids that were previously investigated were immersed in various wetting media. The solids were characterized in terms of hydrophobicity/hydrophilicity and their relative wetting tendency was also established. Heat of immersion measurements using surfactant solutions demonstrated that preferential adsorption of the surfactant molecule occurs on the coal surface, thereby altering its surface properties. This was supported by laboratory vacuum filtration tests. Using flotation agents as the wetting medium, the heat of immersion was found to vary with kerosene concentration, pH, kaolin addition and oxidation of the solid surface. The results of these ..delta..H/sub imm/ measurements were found to correlate very well with results obtained by independent flotation experiments performed under the same conditions.

  9. Correlating interfacial properties with stress transfer in SMA composites

    SciTech Connect

    Kline, G.E.; Jonnalagadda, K.; Sottos, N.R.

    1995-12-31

    Shape memory alloy (SMA) wires have been proposed as large strain actuators for use in smart structures. SMA wires can be embedded in a host material to alter the stiffness or modal response and provide vibration control. The interaction between the embedded SMA and the host material is critical to applications requiring transfer of loads or strain from the wire to the host. Paine, Jones and Rogers have asserted the importance of interfacial adhesion between embedded SMA wires and the host material. When the SMA wires are actuated, large shear strains are generated at the SMA/host interface. The stronger the interface, the greater the transfer of strain from the actuator to the host material. Although there has been a significant amount of research dedicated to characterizing and modeling the response of SMA alone, little work has been done to understand the behavior of embedded SMA wires. Maximum displacement, load transfer and repeatability of actuation of the embedded wire are particularly critical in assessing the effects of the host material. This work continues to investigate the interaction between SMA wires and a host polymer matrix. High resolution photoelasticity was utilized to study the internal stresses induced during actuation of an embedded shape memory alloy wire in a polymer matrix. The influence of several wire surface treatments on the resulting stresses and load transfer was investigated. Four different surface treatments were considered: untreated, acid etched, hand sanded and sandblasted. Pull-out data indicated that sandblasting of wires increased the SMA/polymer interfacial bond strength while hand sanding and acid cleaning actually decreased the bond strength. Wires with greater adhesion (sandblasted) resulted in higher stresses induced in the polymer while those with lower adhesion transferred less load. Overall, properties of the SMA/polymer interface were shown to significantly affect the performance of the embedded SMA actuator.

  10. Interfacial and transport properties of nanoconstrained inorganic and organic materials

    NASA Astrophysics Data System (ADS)

    Kocherlakota, Lakshmi Suhasini

    Nanoscale constraints impact the material properties of both organic and inorganic systems. The systems specifically studied here are (i) nanoconstrained polymeric systems, poly(l-trimethylsilyl-1-propyne) (PTMSP) and poly(ethylene oxide) (PEO) relevant to gas separation membranes (ii) Zwitterionic polymers poly(sulfobetaine methacrylate)(pSBMA), poly(carboxybetaine acrylamide) (pCBAA), and poly(oligo(ethylene glycol) methyl methacrylate) (PEGMA) brushes critical for reducing bio-fouling (iii) Surface properties of N-layer graphene sheets. Interfacial constraints in ultrathin poly(l-trimethylsilyl-1-propyne) (PTMSP) membranes yielded gas permeabilities and CO2/helium selectivities that exceed bulk PTMSP membrane transport properties by up to three-fold for membranes of submicrometer thickness. Indicative of a free volume increase, a molecular energetic mobility analysis (involving intrinsic friction analysis) revealed enhanced methyl side group mobilities in thin PTMSP membranes with maximum permeation, compared to bulk films. Aging studies conducted over the timescales relevant to the conducted experiments signify that the free volume states in the thin film membranes are highly unstable in the presence of sorbing gases such as CO2. To maintain this high free volume configuration of polymer while improving the temporal stability an "inverse" architecture to conventional polymer nanocomposites was investigated, in which the polymer phase of PTMSP and PEO were interfacially and dimensionally constrained in nanoporous anodic aluminum oxide (AAO) membranes. While with this architecture the benefits of nanocomposite and ultrathin film membranes of PTMSP could be reproduced and improved upon, also the temporal stability could be enhanced substantially. The PEO-AAO nanocomposite membranes also revealed improved gas selectivity properties of CO2 over helium. In the thermal transition studies of zwitterionic pSBMA brushes a reversible critical transition temperature of 60

  11. Interfacial properties of cell culture media with cell-protecting additives.

    PubMed

    Michaels, J D; Nowak, J E; Mallik, A K; Koczo, K; Wasan, D T; Papoutsakis, E T

    1995-08-20

    In an effort to identify key rheological properties that contribute to cell protection against shear damage, we have measured surface shear and dilatationai viscosities, dynamic surface tension, foaminess, and foam stability for media containing cell-protecting additives. In a companion article,(18) we found that cell-to-bubble attachment was decreased in media containing Methocel, Pluronic F68, or polyvinyl alcohol (PVA). In medium containing polyethylene glycol (PEG) or potyvinyl-pyrrolidone (PVP), attachment was increased. PEG, PVP, serum (FBS), and serum albumin (BSA) increased the surface viscosity of the air/medium surface (thus, producing a more rigid interface), whereas F68 and PVA lowered it greatly. Foaming experiments showed that Methocel, PEG, PVA, and F68 decreased the foam half-life while FBS, BSA, and PVP were foam stabilizers. Interestingly, the foam stability of CHO cell suspensions decreased significantly for cell concentrations higher than ca. 2 x 10(6) cells/mL. Nonviable CHO cells reduced foam stability further. Dynamic surface tension values of the media tested were found significantly differentfrom their static surface tension values. The interfacial properties measured and the results presented in the companion study suggest that the additives that lower dynamic surface tension the most (Methocel, F68, and PVA) correlate well with reduced cell-to-bubble attachment, and thus, cell protection. Reduced dynamic surface tension with these additives implies faster surfactant adsorption, mobile interfaces, lower surface viscosity, and foam destabilization. Because PEG and PVP resulted in increased cell-to-bubble attachment and had different interfacial properties, a different mechanism (compared with Methocel, PVP, and F68) is apparently responsible for their protective effect. Finally, cell protection offered by FBS and BSA is attributed to the foam stabilization properties provided by these additives. (c) 1995 John Wiley & Sons Inc.

  12. Interfacial Phenomena and Thermophysical Properties of Molten Steel and Oxides

    NASA Astrophysics Data System (ADS)

    Watanabe, Masahito; Onodera, Kenta; Ueno, Shoya; Tsukada, Takao; Tanaka, Toshihiro; Tamaru, Haruka; Ishikawa, Takehiko

    At present, interfacial phenomena between molten steel and oxides, usually called slag or mold flux, play an important role in steel processing for material design. Therefore, understanding interfacial tension is important for process control. From this, we propose an interfacial tension measurement technique between molten steel and oxides using a modified oscillating drop method with levitation techniques. The interfacial tension data using traditional techniques based on the sessile drop method have been obtained only at temperatures around the melting point of iron due to dissolution of containers and the substrate into molten steel and oxides in higher temperature regions. Our proposed technique to obtain the temperature dependence of interfacial tension between molten iron and oxides is to use a core-shell form droplet including an interface between two liquids using electrostatic levitation, which negates the use for containers. The experiment was performed on the International Space Station using the electrostatic levitation furnace (ELF) in the KIBO module.

  13. 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

  14. Liquid properties of embryonic tissues: Measurement of interfacial tensions

    NASA Astrophysics Data System (ADS)

    Foty, Ramsey A.; Forgacs, Gabor; Pfleger, Cathie M.; Steinberg, Malcolm S.

    1994-04-01

    The flow of embryonic tissues during morphogenesis has been ascribed to tissue interfacial tensions arising from cell adhesion. Testing this explanation requires the demonstration that tissue interfacial tensions are measurable physical quantities. We describe a device that continuously records all parameters necessary to determine the tensions of living tissues at the interface with the surrounding medium. We monitor the relaxation of an imposed stress in two embryonic tissues, measure their interfacial tensions, and demonstrate that these are consistent with these tissues' mutual spreading behavior.

  15. Investigation of the mechanical and interfacial properties of adenovirus

    NASA Astrophysics Data System (ADS)

    Matthews, William Garrett

    The ability to investigate materials at the single molecule and macromolecule level became a reality with the introduction of the atomic force microscope (AFM) by Bennig et al. in 1986. Presented in this dissertation is a modification to the AFM that facilitates imaging of delicate samples under liquids. The instrument was subsequently used to investigate a variety of material and interfacial properties of adenovirus. Firstly, the elasticity of adenovirus particles in air and in water was measured. The virus was found to be some fifty fold more compliant in water than in air, with the measured elastic modulus changing from 15 MPa to 770 MPa. Individual viruses also were translated across a variety of surfaces, and the force required to do these manipulations was recorded. A variety of behaviors were observed, including evidence for rolling of the particles. This measurement constitutes one of the first direct observations of rolling behavior on this length scale. Finally, viruses were observed to shed their capsid proteins when deposited on positively charged magnesium intercalated mica. The resulting core structure was investigated, and the uncoating process was captured in a series of images. These images represent one of the first molecular level processes to be observed at the single molecule level.

  16. Field theoretic simulations of the interfacial properties of complex coacervates

    NASA Astrophysics Data System (ADS)

    Riggleman, Robert; Fredrickson, Glenn

    2011-03-01

    Many biological processes and emerging technologies, such as wet adhesives and biosensors, rely on the association between oppositely charged polyelectrolytes. Such association is driven not only by the electrostatic interactions between the polyelectrolytes, but there is also a substantial entropy gain associated with counterion release upon complexation. In some cases, the association between oppositely charged polymers can lead to a solid precipitate while others can result in a fluid phase rich in polyelectrolytes (coacervate phase) coexisting with a polyelectrolyte-dilute solvent phase. For many of the applications seeking to exploit coacervation, characterization of the interface between the solvent phase and the coacervate is of paramount importance. In this talk, we will present the results of field-theoretic simulations for a coarse-grained polyelectrolyte model that exhibits complex coacervation. Our simulations sample the fully-fluctuating fields in three-dimensions and provide a detailed characterization of the interface between the solvent and the coacervate phase for symmetric polyelectrolytes (where both the polycations and the polyanions carry identical charge densities) as a function of salt concentration and strength of the electrostatic fields. Finally, we characterize the interfacial properties for a select set of asymmetric conditions.

  17. Investigation of Mechanical Properties and Interfacial Mechanics of Crystalline Nanomaterials

    NASA Astrophysics Data System (ADS)

    Qin, Qingquan

    Nanowires (NWs) and nanotubes (NTs) are critical building blocks of nanotechnologies. The operation and reliability of these nanomaterials based devices depend on their mechanical properties of the nanomaterials, which is therefore important to accurately measure the mechanical properties. Besides, the NW--substrate interfaces also play a critical role in both mechanical reliability and electrical performance of these nanodevices, especially when the size of the NW is small. In this thesis, we focus on the mechanical properties and interface mechanics of three important one dimensional (1D) nanomaterials: ZnO NWs, Ag NWs and Si NWs. For the size effect study, this thesis presents a systematic experimental investigation on the elastic and failure properties of ZnO NWs under different loading modes: tension and buckling. Both tensile modulus (from tension) and bending modulus (from buckling) were found to increase as the NW diameter decreased from 80 to 20 nm. The elastic modulus also shows loading mode dependent; the bending modulus increases more rapidly than the tensile modulus. The tension experiments showed that fracture strain and strength of ZnO NWs increase as the NW diameter decrease. A resonance testing setup was developed to measure elastic modulus of ZnO NWs to confirm the loading mode dependent effect. A systematic study was conducted on the effect of clamping on resonance frequency and thus measured Young's modulus of NWs via a combined experiment and simulation approach. A simple scaling law was provided as guidelines for future designs to accurate measure elastic modulus of a cantilevered NW using the resonance method. This thesis reports the first quantitative measurement of a full spectrum of mechanical properties of five-fold twinned Ag NWs including Young's modulus, yield strength and ultimate tensile strength. In situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a SEM. Young's modulus, yield strength and

  18. Rheological and interfacial properties at the equilibrium of almond gum tree exudate (Prunus dulcis) in comparison with gum arabic.

    PubMed

    Mahfoudhi, Nesrine; Sessa, Mariarenata; Ferrari, Giovanna; Hamdi, Salem; Donsi, Francesco

    2016-06-01

    Almond gum contains an arabinogalactan-type polysaccharide, which plays an important role in defining its interfacial and rheological properties. In this study, rheological and interfacial properties of almond gum and gum arabic aqueous dispersions were comparatively investigated. The interfacial tension of almond gum and gum arabic aqueous dispersions was measured using the pendant drop method in hexadecane. The asymptotic interfacial tension values for almond gum were significantly lower than the corresponding values measured for gum arabic, especially at high concentration. Rheological properties were characterized by steady and oscillatory tests using a coaxial geometry. Almond gum flow curves exhibited a shear thinning non-Newtonian behavior with a tendency to a Newtonian plateau at low shear rate, while gum arabic flow curves exhibited such behavior only at high shear rate. The influence of temperature (5-50  ℃) on the flow curves was studied at 4% (m/m) gum concentration and the Newtonian viscosities at infinite and at zero shear rate, for gum arabic and almond gum, respectively, were accurately fitted by an Arrhenius-type equation. The dynamic properties of the two gum dispersions were also studied. Both gum dispersions exhibited viscoelastic properties, with the viscous component being predominant in a wider range of concentrations for almond gum, while for gum arabic the elastic component being higher than the elastic one especially at higher concentrations.The rheological and interfacial tension properties of almond gum suggest that it may represent a possible substitute of gum arabic in different food applications. © The Author(s) 2015.

  19. Interfacial effects on dielectric properties of polymer-particle nanocomposites

    NASA Astrophysics Data System (ADS)

    Siddabattuni, Sasidhar Veeranjaneyulu

    Dielectric materials that are capable of efficiently storing large amounts of electrical energy are desirable for many electronic and power devices. Since the electrical energy density in a dielectric material is limited to epsilonVb2/2, where is the dielectric permittivity of the material and Vb is the breakdown strength, increased permittivity and breakdown strength are required for large energy storage density. Interfacial effects can influence the dielectric properties, especially dielectric breakdown resistance in polymer-particle nanocomposites. Several functional organophosphates were used to modify the surface of titania and barium titanate nanofiller particles in order to achieve covalent interface when interacted with polymer and to study the influence the electronic nature of filler surfaces on dielectric properties, in particular the breakdown resistance. Surface modified powders were analyzed by thermogravimetric analysis (TGA) and by X-ray photoelectron spectroscopy (XPS). The dielectric composite films obtained by incorporating surface modified powders in epoxy thermosetting polymer were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), impedance spectroscopy, and dielectric breakdown strength measurements. At 30 vol-% filler concentration, a calculated energy density of ˜8 J/cm3 was observed for titania based composites and ˜8.3 J/cm3 for barium titanate based composites involving electron scavenging interface with minimal dielectric losses compared to pure polymer. Covalent interface composites yielded energy density of ˜7.5 J/cm3 for barium titanate based composites at 30 vol.-%. The data indicate that improved dispersion, breakdown strengths and energy densities resulted when electron-poor functional groups were located at the particle surfaces even compared to covalent interface.

  20. Interfacial and mechanical properties of self-assembling systems

    NASA Astrophysics Data System (ADS)

    Carvajal, Daniel

    Self-assembly is a fascinating phenomena where interactions between small subunits allow them to aggregate and form complex structures that can span many length scales. These self-assembled structures are especially important in biology where they are necessary for life as we know it. This dissertation is a study of three very different self-assembling systems, all of which have important connections to biology and biological systems. Drop shape analysis was used to study the interfacial assembly of amphiphilic block copolymers at the oil/water interface. When biologically functionalyzed copolymers are used, this system can serve as a model for receptor-ligand interactions that are used by cells to perform many activities, such as interact with their surroundings. The physical properties of a self-assembling membrane system were quantified using membrane inflation and swelling experiments. These types of membranes may have important applications in medicine such as drug eluting (growth factor eluting) scaffolds to aid in wound healing. The factors affecting the properties of bis(leucine) oxalamide gels were also explored. We believe that this particular system will serve as an appropriate model for biological gels that are made up of fiber-like and/or rod-like structures. During the course of the research presented in this dissertation, many new techniques were developed specifically to allow/aid the study of these distinct self-assembling systems. For example, numerical methods were used to predict drop stability for drop shape analysis experiments and the methods used to create reproducibly create self-assembling membranes were developed specifically for this purpose. The development of these new techniques is an integral part of the thesis and should aid future students who work on these projects. A number ongoing projects and interesting research directions for each one of the projects is also presented.

  1. Interfacial and emulsifying properties of soybean peptides with different degrees of hydrolysis.

    PubMed

    Imura, Tomohiro; Nakayama, Mio; Taira, Toshiaki; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2015-01-01

    In this study, the effects of the degree of hydrolysis on the interfacial and emulsifying properties of soybean peptides were evaluated based on surface and interfacial tension, dynamic light scattering (DLS), and freeze-fracture transmission electron microscopy (FF-TEM) analyses. Of the five evaluated soybean peptides (SP95, SP87, SP75, SP49, and SP23), those with higher degrees of hydrolysis (SP95 and SP87) did not exhibit noticeable surface-active properties in water, whereas those with relatively low degrees of hydrolysis (SP75, SP49, and SP23) exhibited remarkable surface tension-lowering activity. The latter set (SP75, SP49, and SP23) also formed giant associates with average sizes ranging from 64.5 nm to 82.6 nm above their critical association concentration (CAC). Moreover, SP23 with the lowest degree of hydrolysis exhibited excellent emulsifying activity for soybean oil, and FF-TEM analysis demonstrated that the emulsions were stabilized by a lamella-like multilayer peptide structure on the oil droplets that prevented coagulation. The peptide with the lowest degree of hydrolysis (SP23) was effective not only for soybean oil emulsification, but also for the emulsification of liquid paraffin and silicon oil that are generally difficult to emulsify.

  2. Interfacial structure and wetting properties of water droplets on graphene under a static electric field.

    PubMed

    Ren, Hongru; Zhang, Leining; Li, Xiongying; Li, Yifan; Wu, Weikang; Li, Hui

    2015-09-28

    The behavior of water droplets located on graphene in the presence of various external electric fields (E-fields) is investigated using classical molecular dynamics (MD) simulations. We explore the effect of E-field on mass density distribution, water polarization as well as hydrogen bonds (H-bonds) to gain insight into the wetting properties of water droplets on graphene and their interfacial structure under uniform E-fields. The MD simulation results reveal that the equilibrium water droplets present a hemispherical, a conical and an ordered cylindrical shape with the increase of external E-field intensity. Accompanied by the shape variation of water droplets, the dipole orientation of water molecules experiences a remarkable change from a disordered state to an ordered state because of the polarization of water molecules induced by static E-field. The distinct two peaks in mass density and H-bond distribution profiles demonstrate that water has a layering structure in the interfacial region, which sensitively depends on the strong E-field (>0.8 V nm(-1)). In addition, when the external E-field is parallel to the substrate, the E-field would make the contact angle of the water droplets become small and increase its wettability. Our findings provide the possibility to control the structure and wetting properties of water on graphene by tuning the direction and intensity of external E-field which is of importance for relevant industrial processes on the solid surface.

  3. Relationship Between Interfacial Strength and Materials Properties in Hybrid Organic/Inorganic Nanomaterials

    NASA Astrophysics Data System (ADS)

    Snyder, Chad; Richardson, Mickey; Zhou, Jing; Holmes, Gale; Karim, Alamgir; D'Souza, Nandika

    2008-03-01

    Thermal interface materials (TIM's) are critical to the semiconductor electronics industry for heat dissipation, a potential show-stopper for future technology nodes. Essentially, an epoxy nanocomposite, TIMs suffer from a series of typical nanocomposite limitations including heat conduction in nanoscale inclusions, nanoparticle dispersion, void formation with thermal cycling, and interfacial resistance between the matrix and filler. It is postulated that the interfacial adhesion between the matrix and nanofiller is at the root cause of many of these difficulties, however, few techniques exist to characterize this critical property. Compounding this are the overall difficulties associated with characterizing these materials in their ultimate applications, i.e., thin films. To this end, a novel series of organic/inorganic hybrid nanostructured materials based on layered double hydroxides in epoxy matrices were designed as a test bed to develop the measurement techniques needed to elucidate the relationship between the material structure and dynamics and the ultimate materials properties. Initial results are presented based on characterization by mechanical, dielectric, and thermal spectroscopies.

  4. Specific effects of monovalent counterions on the structural and interfacial properties of dodecyl sulfate monolayers.

    PubMed

    Allen, Daniel T; Saaka, Yussif; Pardo, Luis Carlos; Lawrence, M Jayne; Lorenz, Christian D

    2016-11-09

    A series of molecular dynamics simulations have been conducted in order to study the specific ion effects of Li(+), Na(+), Cs(+) and NH4(+) cations on dodecyl sulfate (DS(-)) monolayers. Varying the counterion had no appreciable effect on the structure of the surfactant molecules within the different monolayers. However, the different counterions have a significant effect on the interfacial properties of the monolayer. In particular, we have investigated to what extent each of the counterions is dehydrated when interacting with the DS(-) headgroup, the specific interactions between the counterions and the headgroup and the salt bridging of the headgroups caused by each counterion. The NH4(+) ions are found to directly compete with water molecules to form hydrogen bonds with the DS(-) headgroup and as a result the ammonium dodecyl sulfate monolayer is the least hydrated of any of those studied. The Cs(+) ions are strongly bound to the headgroup and weakly hydrated, such that they would prefer to displace water in the DS(-) hydration shell to interact with the headgroups. In the case of the Li(+) ions, they interact almost as strongly with the DS(-) headgroups as the Na(+) ions, but are generally less hydrated than the Na(+) ions and consequently the lithium dodecyl sulfate monolayers are less hydrated than the sodium dodecyl sulfate monolayers. Therefore, by changing the counterion, one can modify the interfacial properties of the surfactant monolayer, and thus affect their ability to encapsulate poorly water soluble drug molecules, which we discuss further in the manuscript.

  5. 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. © 2012 American Chemical Society

  6. Identifying Mechanisms of Interfacial Dynamics Using Single-Molecule Tracking

    PubMed Central

    Kastantin, Mark; Walder, Robert; Schwartz, Daniel K.

    2012-01-01

    The “soft” (i.e. non-covalent) interactions between molecules and surfaces are complex and highly-varied (e.g. hydrophobic, hydrogen bonding, ionic) often leading to heterogeneous interfacial behavior. Heterogeneity can arise either from spatial variation of the surface/interface itself or from molecular configurations (i.e. conformation, orientation, aggregation state, etc.). By observing adsorption, diffusion, and desorption of individual fluorescent molecules, single-molecule tracking can characterize these types of heterogeneous interfacial behavior in ways that are inaccessible to traditional ensemble-averaged methods. Moreover, the fluorescence intensity or emission wavelength (in resonance energy transfer experiments) can be used to simultaneously track molecular configuration and directly relate this to the resulting interfacial mobility or affinity. In this feature article, we review recent advances involving the use of single-molecule tracking to characterize heterogeneous molecule-surface interactions including: multiple modes of diffusion and desorption associated with both internal and external molecular configuration, Arrhenius activated interfacial transport, spatially dependent interactions, and many more. PMID:22716995

  7. Identifying mechanisms of interfacial dynamics using single-molecule tracking.

    PubMed

    Kastantin, Mark; Walder, Robert; Schwartz, Daniel K

    2012-08-28

    The "soft" (i.e., noncovalent) interactions between molecules and surfaces are complex and highly varied (e.g., hydrophobic, hydrogen bonding, and ionic), often leading to heterogeneous interfacial behavior. Heterogeneity can arise either from the spatial variation of the surface/interface itself or from molecular configurations (i.e., conformation, orientation, aggregation state, etc.). By observing the adsorption, diffusion, and desorption of individual fluorescent molecules, single-molecule tracking can characterize these types of heterogeneous interfacial behavior in ways that are inaccessible to traditional ensemble-averaged methods. Moreover, the fluorescence intensity or emission wavelength (in resonance energy transfer experiments) can be used to track the molecular configuration and simultaneously directly relate this to the resulting interfacial mobility or affinity. In this feature article, we review recent advances involving the use of single-molecule tracking to characterize heterogeneous molecule-surface interactions including multiple modes of diffusion and desorption associated with both internal and external molecular configuration, Arrhenius-activated interfacial transport, spatially dependent interactions, and many more.

  8. Interfacial solvation and excited state photophysical properties of 7-aminocoumarins at silica/liquid interfaces

    NASA Astrophysics Data System (ADS)

    Roy, Debjani

    The properties of solutes adsorbed at interfaces can be very different compared to bulk solution limits. This thesis examines how polar, hydrophilic silica surfaces and different solvents systematically change a solute's equilibrium and dynamic solvation environment at solid/liquid interfaces. The primary tools used in these studies are steady state fluorescence spectroscopy and time correlated single photon counting (TCSPC) --a fluorescence method capable resolving fluorescence emission on the picosecond timescale. To sample adsorbed solutes, TCSPC experiments were carried out in total internal reflection (TIR) geometry. These studies used total of six different 7-aminocoumarin dyes to isolate the effects of molecular and electronic structure on solute photophysical behavior. Fluorescence lifetimes measured in the TIR geometry are compared to the lifetimes of coumarins in bulk solution using different solvents to infer interfacial polarity and excited state solute conformation and dynamics. Steady state emission experiments measuring the behavior of the coumarins adsorbed at silica surfaces from bulk methanol solutions show that all coumarins had a similar affinity DeltaG ads ˜ - 25-30 kJ/mole. Despite these similar adsorption energetics solute structure had a very pronounced effect on the tendency of solutes to aggregate and form multilayers. Our finding suggests that hydrogen bonding donating properties of the silica surface plays a dominant role in determining the interfacial behavior of these solutes. The silica surface also had pronounced effects on the time dependent emission of some solutes. In particular, the strong hydrogen bond donating properties of the silica surface inhibit formation of a planar, charge transfer state through hydrogen bond donation to the solute's amine group. A consequence of this interaction is that the time dependent emission from solutes adsorbed at the surface appears to be more similar to emission from solutes in nonpolar

  9. Structural characterization of interfacial n-octanol and 3-octanol using molecular dynamic simulations.

    PubMed

    Napoleon, Raeanne L; Moore, Preston B

    2006-03-02

    Structurally isomeric octanol interfacial systems, water/vapor, 3-octanol/vapor, n-octanol/vapor, 3-octanol/water, and n-octanol/water are investigated at 298 K using molecular dynamics simulation techniques. The present study is intended to investigate strongly associated liquid/liquid interfaces and probe the atomistic structure of these interfaces. The octanol and water molecules were initially placed randomly into a box and were equilibrated using constant pressure techniques to minimize bias within the initial conditions as well as to fully sample the structural conformations of the interface. An interface formed via phase separation during equilibration and resulted in a slab geometry with a molecularly sharp interface. However, some water molecules remained within the octanol phase with a mole fraction of 0.12 after equilibration. The resulting "wet" octanol interfaces were analyzed using density profiles and orientational order parameters. Our results support the hypothesis of an ordered interface only 1 or 2 molecular layers deep before bulk properties are reached for both the 3-octanol and water systems. However, in contrast to most other interfacial systems studied by molecular dynamics simulations, the n-octanol interface extends for several molecular layers. The octanol hydroxyl groups form a hydrogen-bonding network with water which orders the surface molecules toward a preferred direction and produces a hydrophilic/hydrophobic layering. The ordered n-octanol produces an oscillating low-high density of oxygen atoms out of phase with a high-low density of carbon atoms, consistent with an oscillating dielectric. In contrast, the isomeric 3-octanol has only a single carbon-rich layer directly proximal to the interface, which is a result of the different molecular topology. Both 3-octanol and n-octanol roughen the water interface with respect to the water/vapor interface. The "wet" octanol phases, in the octanol/water systems reach bulk properties in a

  10. Insights into the role of protein molecule size and structure on interfacial properties using designed sequences

    PubMed Central

    Dwyer, Mirjana Dimitrijev; He, Lizhong; James, Michael; Nelson, Andrew; Middelberg, Anton P. J.

    2013-01-01

    Mixtures of a large, structured protein with a smaller, unstructured component are inherently complex and hard to characterize at interfaces, leading to difficulties in understanding their interfacial behaviours and, therefore, formulation optimization. Here, we investigated interfacial properties of such a mixed system. Simplicity was achieved using designed sequences in which chemical differences had been eliminated to isolate the effect of molecular size and structure, namely a short unstructured peptide (DAMP1) and its longer structured protein concatamer (DAMP4). Interfacial tension measurements suggested that the size and bulk structuring of the larger molecule led to much slower adsorption kinetics. Neutron reflectometry at equilibrium revealed that both molecules adsorbed as a monolayer to the air–water interface (indicating unfolding of DAMP4 to give a chain of four connected DAMP1 molecules), with a concentration ratio equal to that in the bulk. This suggests the overall free energy of adsorption is equal despite differences in size and bulk structure. At small interfacial extensional strains, only molecule packing influenced the stress response. At larger strains, the effect of size became apparent, with DAMP4 registering a higher stress response and interfacial elasticity. When both components were present at the interface, most stress-dissipating movement was achieved by DAMP1. This work thus provides insights into the role of proteins' molecular size and structure on their interfacial properties, and the designed sequences introduced here can serve as effective tools for interfacial studies of proteins and polymers. PMID:23303222

  11. Structures and ultrafast dynamics of interfacial water assemblies on smooth hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Yang, Ding-Shyue; He, Xing

    2017-09-01

    Using time-averaged and ultrafast electron diffraction, structures and ultrafast dynamics of interfacial water assemblies on smooth hydrophobic surfaces are reported. The lack of hydrophilic interaction and topographical template effect from the support surface leads to the formation of small, mostly randomly-oriented, ice crystallites with the cubic structure. Dynamically, following the substrate photoexcitation, interfacial water assemblies undergo four stages of changes-ultrafast melting, nonequilibrium isotropic phase transformation, annealing, and restructuring-which are closely correlated with the substrate dynamics. The connectivity and cooperative nature of the hydrogen-bonded network is considered crucial for water assemblies to withstand large structural motions without sublimation on ultrashort times.

  12. Intermittent Single-Molecule Interfacial Electron Transfer Dynamics

    SciTech Connect

    Biju, Vasudevan P.; Micic, Miodrag; Hu, Dehong; Lu, H. Peter

    2004-08-04

    We report on single molecule studies of photosensitized interfacial electron transfer (ET) processes in Coumarin 343 (C343)-TiO2 nanoparticle (NP) and Cresyl Violet (CV+)-TiO2 NP systems, using time-correlated single photon counting coupled with scanning confocal fluorescence microscopy. Fluorescence intensity trajectories of individual dye molecules adsorbed on a semiconductor NP surface showed fluorescence fluctuations and blinking, with time constrants distributed from sub-milliseconds to several seconds.

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

    NASA Astrophysics Data System (ADS)

    Mak, Sze Yi; Shum, Ho Cheung

    2014-11-01

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

  14. Rheological interfacial properties of plant protein-arabic gum coacervates at the oil-water interface.

    PubMed

    Ducel, V; Richard, J; Popineau, Y; Boury, F

    2005-01-01

    This study concerns the interfacial properties of the plant proteins-arabic gum coacervates, which are involved in encapsulation processes based on complex coacervation. The results make it possible to deduce the prerequisite characteristics of the protein, which are involved in the coacervate interfacial properties. The influence of pH and concentration on protein interfacial properties was also studied so as to enable us to predict the best conditions to achieve encapsulation. It has been established that, to obtain a good encapsulation yield, the coacervate must show high surface-active properties and its adsorption on the oil droplets must be favored compared to the free protein adsorption. On the other hand, mechanical properties of the interfacial film made of the coacervate, appear to be a key parameter, as reflected by the dilational viscoelasticity measurements. When compared to the properties of the proteins films, an increase of the rigidity of the interfacial film was shown with the coacervates. It was also observed that viscoelastic properties of the coacervate film were strongly reduced, as well as the associated relaxation times. In acidic conditions, the coacervates containing alpha-gliadin are characterized by an interfacial viscoelastic behavior. This behavior reflects the softness of the interfacial film. This viscoelasticity allows also the formation of a continuous layer around the oil droplets to be encapsulated. Drop tensiometry is shown to be a method that could allow the most adapted protein to be selected and the conditions of the coacervation process to be optimized with regard to concentration and pH.

  15. Ligand and interfacial dynamics in a homodimeric hemoglobin

    PubMed Central

    Gupta, Prashant Kumar; Meuwly, Markus

    2016-01-01

    The structural dynamics of dimeric hemoglobin (HbI) from Scapharca inaequivalvis in different ligand-binding states is studied from atomistic simulations on the μs time scale. The intermediates are between the fully ligand-bound (R) and ligand-free (T) states. Tertiary structural changes, such as rotation of the side chain of Phe97, breaking of the Lys96–heme salt bridge, and the Fe–Fe separation, are characterized and the water dynamics along the R-T transition is analyzed. All these properties for the intermediates are bracketed by those determined experimentally for the fully ligand-bound and ligand-free proteins, respectively. The dynamics of the two monomers is asymmetric on the 100 ns timescale. Several spontaneous rotations of the Phe97 side chain are observed which suggest a typical time scale of 50–100 ns for this process. Ligand migration pathways include regions between the B/G and C/G helices and, if observed, take place in the 100 ns time scale. PMID:26958581

  16. Wetting and interfacial properties of water nanodroplets in contact with graphene and monolayer boron-nitride sheets.

    PubMed

    Li, Hui; Zeng, Xiao Cheng

    2012-03-27

    Born-Oppenheim quantum molecular dynamics (QMD) simulations are performed to investigate wetting, diffusive, and interfacial properties of water nanodroplets in contact with a graphene sheet or a monolayer boron-nitride (BN) sheet. Contact angles of the water nanodroplets on the two sheets are computed for the first time using QMD simulations. Structural and dynamic properties of the water droplets near the graphene or BN sheet are also studied to gain insights into the interfacial interaction between the water droplet and the substrate. QMD simulation results are compared with those from previous classic MD simulations and with the experimental measurements. The QMD simulations show that the graphene sheet yields a contact angle of 87°, while the monolayer BN sheet gives rise to a contact angle of 86°. Hence, like graphene, the monolayer BN sheet is also weakly hydrophobic, even though the BN bonds entail a large local dipole moment. QMD simulations also show that the interfacial water can induce net positive charges on the contacting surface of the graphene and monolayer BN sheets, and such charge induction may affect electronic structure of the contacting graphene in view that graphene is a semimetal. Contact angles of nanodroplets of water in a supercooled state on the graphene are also computed. It is found that under the supercooled condition, water nanodroplets exhibit an appreciably larger contact angle than under the ambient condition.

  17. Effect of Neck Formation on the Measurement of Dynamic Interfacial Tension in a Drop Volume Tensiometer

    PubMed

    Campanelli; Wang

    1997-06-15

    Dynamic interfacial tension values obtained by drop volume tensiometry will be affected under certain experimental conditions by the formation of a neck between the drop and the capillary tip. This phenomenon must be accounted for to obtain accurate values of interfacial tension. In this work, neck formation for a water-mineral oil system is studied under conditions where hydrodynamic effects can be neglected. A model originally developed for the determination of the surface tension of a suspended drop is modified for application to dynamic interfacial tensions of surfactant-containing liquids. The model relates apparent values of interfacial tension calculated from drops possessing necks to actual values. Experiments with Span 80 (sorbitan monooleate) and sodium dodecyl sulfate (SDS) surfactants in a mineral oil-water system are used to test the validity of the developed model. For the small tip diameter used, good agreement is obtained for Span 80 up to the critical micelle concentration, and for low concentrations of SDS, when the surfactant adsorption is diffusion-limited. In both cases, the neck diameter of the growing drop can be considered constant over the range of dynamic interfacial tensions tested.

  18. Molecular Dynamics Study of Freezing Point and Solid-Liquid Interfacial Free Energy of Stockmayer Fluids

    SciTech Connect

    Wang, J.; Apte, Pankaj; Morris, James R; Zeng, X.C.

    2013-01-01

    Freezing temperatures of Stockmayer fluids with different dipolar strength at zero pressure are estimated and computed using three independent molecular-dynamics (MD) simulation methods, namely, the superheating-undercooling method, the constant-pressure and constant-temperature (NPT) two phase coexistence method, and the constant-pressure and constant-enthalpy (NPH) coexistence method. The best estimate of the freezing temperature (in reduced unit) for the Stockmayer (SM) fluid with a reduced dipole moment is 0.656 0.001, 0.726 0.002 and 0.835 0.005, respectively. The freezing temperature increases with the dipolar strength. The solid-liquid interfacial free energies of the (111), (110) and (100) interface are calculated for the first time using two independent methods, namely, the cleaving-wall method and the interfacial fluctuation method. Both methods predict that the interfacial free energy increases with the dipole moment. Although the interfacial fluctuation method suggests a weaker interfacial anisotropy, particularly for strongly dipolar SM fluids, both methods predicted the same trend of interfacial anisotropy, that is, .

  19. Tunable Magnetization Dynamics in Interfacially Modified Ni81Fe19/Pt Bilayer Thin Film Microstructures.

    PubMed

    Ganguly, Arnab; Azzawi, Sinan; Saha, Susmita; King, J A; Rowan-Robinson, R M; Hindmarch, A T; Sinha, Jaivardhan; Atkinson, Del; Barman, Anjan

    2015-12-01

    Interface modification for control of ultrafast magnetic properties using low-dose focused ion beam irradiation is demonstrated for bilayers of two technologically important materials: Ni81Fe19 and Pt. Magnetization dynamics were studied using an all-optical time-resolved magneto-optical Kerr microscopy method. Magnetization relaxation, precession, damping and the spatial coherence of magnetization dynamics were studied. Magnetization precession was fitted with a single-mode damped sinusoid to extract the Gilbert damping parameter. A systematic study of the damping parameter and frequency as a function of irradiation dose varying from 0 to 3.3 pC/μm(2) shows a complex dependence upon ion beam dose. This is interpreted in terms of both intrinsic effects and extrinsic two-magnon scattering effects resulting from the expansion of the interfacial region and the creation of a compositionally graded alloy. The results suggest a new direction for the control of precessional magnetization dynamics, and open the opportunity to optimize high-speed magnetic devices.

  20. Tunable Magnetization Dynamics in Interfacially Modified Ni81Fe19/Pt Bilayer Thin Film Microstructures

    PubMed Central

    Ganguly, Arnab; Azzawi, Sinan; Saha, Susmita; King, J. A.; Rowan-Robinson, R. M.; Hindmarch, A. T.; Sinha, Jaivardhan; Atkinson, Del; Barman, Anjan

    2015-01-01

    Interface modification for control of ultrafast magnetic properties using low-dose focused ion beam irradiation is demonstrated for bilayers of two technologically important materials: Ni81Fe19 and Pt. Magnetization dynamics were studied using an all-optical time-resolved magneto-optical Kerr microscopy method. Magnetization relaxation, precession, damping and the spatial coherence of magnetization dynamics were studied. Magnetization precession was fitted with a single-mode damped sinusoid to extract the Gilbert damping parameter. A systematic study of the damping parameter and frequency as a function of irradiation dose varying from 0 to 3.3 pC/μm2 shows a complex dependence upon ion beam dose. This is interpreted in terms of both intrinsic effects and extrinsic two-magnon scattering effects resulting from the expansion of the interfacial region and the creation of a compositionally graded alloy. The results suggest a new direction for the control of precessional magnetization dynamics, and open the opportunity to optimize high-speed magnetic devices. PMID:26621499

  1. Interfacial Polymerization on Dynamic Complex Colloids: Creating Stabilized Janus Droplets.

    PubMed

    He, Yuan; Savagatrup, Suchol; Zarzar, Lauren D; Swager, Timothy M

    2017-03-01

    Complex emulsions, including Janus droplets, are becoming increasingly important in pharmaceuticals and medical diagnostics, the fabrication of microcapsules for drug delivery, chemical sensing, E-paper display technologies, and optics. Because fluid Janus droplets are often sensitive to external perturbation, such as unexpected changes in the concentration of the surfactants or surface-active biomolecules in the environment, stabilizing their morphology is critical for many real-world applications. To endow Janus droplets with resistance to external chemical perturbations, we demonstrate a general and robust method of creating polymeric hemispherical shells via interfacial free-radical polymerization on the Janus droplets. The polymeric hemispherical shells were characterized by optical and fluorescence microscopy, scanning electron microscopy, and confocal laser scanning microscopy. By comparing phase diagrams of a regular Janus droplet and a Janus droplet with the hemispherical shell, we show that the formation of the hemispherical shell nearly doubles the range of the Janus morphology and maintains the Janus morphology upon a certain degree of external perturbation (e.g., adding hydrocarbon-water or fluorocarbon-water surfactants). We attribute the increased stability of the Janus droplets to (1) the surfactant nature of polymeric shell formed and (2) increase in interfacial tension between hydrocarbon and fluorocarbon due to polymer shell formation. This finding opens the door of utilizing these stabilized Janus droplets in a demanding environment.

  2. The Dynamic Interfacial Oxygen Potential Between Iron-Carbon Droplets and Oxidizing Slag

    NASA Astrophysics Data System (ADS)

    Gu, Kezhuan; Dogan, Neslihan; Coley, Kenneth S.

    2017-10-01

    The dynamic nature of the interfacial oxygen potential during dephosphorization was investigated based on the concept that P_{{{O}2 }} at the interface between slag and liquid metal is determined by the balance between oxygen supply from reducible oxides in the slag and oxygen consumption by alloying elements in the metal. Combining this approach with the knowledge that at the phosphorus reversion point the interfacial oxygen potential can be determined from the bulk phosphorus partition ratio, the mass transfer coefficient for FeO, k FeO, was determined for different slags and found to increase with increasing FeO content. In foamy slags, k FeO was found to be a linear function of slag liquid fraction. Equating the mass transfer rate of FeO in the slag with decarburization rate, the dynamic interfacial oxygen potential was calculated over the course of the reaction, and its effect on the rate determining step for dephosphorization was evaluated.

  3. Comparative study on dispersion and interfacial properties of single walled carbon nanotube/polymer composites using Hansen solubility parameters.

    PubMed

    Ma, Jing; Larsen, Raino Mikael

    2013-02-01

    Dispersion and interfacial strain transfer of single walled carbon nanotubes (SWNTs) are two major challenges for the utilization of SWNTs as reinforcements in polymer composites. Surface modifications could help change the dispersion and interfacial properties. In this study, nanocomposites were fabricated by solution blending 1 wt % SWNTs with various modification (nonmodified, nitric acid functionalized, and amine functionalized SWNTs) and three kinds of polymeric materials (polycarbonate, polyvinylidene fluoride, and epoxy). Chemical compatibilities between SWNTs and solvents or polymers are calculated by the Hansen solubility parameters (HSP) method. The dispersion of the SWNTs in solvents is evaluated by dynamic light scattering. The dispersion of SWNTs in polymers evaluated by a light optical microscope (LOM) generally agrees with the HSP prediction. The strain transfer from the matrix to SWNTs is mainly related to the dispersion, the bundle size, the residual thermal stresses on the sample, and, to lesser degree, the HSP.

  4. Effects of Graphene Oxide Modified Sizing Agents on Interfacial Properties of Carbon Fibers/Epoxy Composites.

    PubMed

    Zhang, Qingbo; Jiang, Dawei; Liu, Li; Huang, Yudong; Long, Jun; Wu, Guangshun; Wu, Zijian; Umar, Ahmad; Guo, Jiang; Zhang, Xi; Guo, Zhanhu

    2015-12-01

    A kind of graphene oxide (GO) modified sizing agent was used to improve the interfacial properties of carbon fibers/epoxy composites. The surface topography of carbon fibers was investigated by scanning electron microscopy (SEM). The surface compositions of carbon fibers were determined by X-ray photoelectron spectroscopy (XPS) and the interfacial properties of composites were studied by interlaminar shear strength (ILSS). The results show that the existence of GO increases the content of reactive functional groups on carbon fiber surface. Thus it enhances the interfacial properties of carbon fibers/epoxy composites. When GO loading in sizing agents is 1 wt%, the ILSS value of composite reaches to 96.2 MPa, which is increased by 27.2% while comparing with unsized carbon fiber composites. Furthermore, the ILSS of composites after aging is also increased significantly with GO modified sizing agents.

  5. Effect of interfacial entanglement density on the melt and glassy properties of attractive polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Akcora, Pinar

    2014-03-01

    Individual dispersion of silica nanoparticles of 13 nm and 56 nm sizes in poly(methyl methacrylate) is achieved by the right choice of a solvent.By using this well-defined model attractive system, it was shown in our previous work that the conformation of PMMA on attractive silica surfaces can be dynamically altered by applying large amplitude oscillatory shear (LAOS) well above the Tg of the polymer.Correspondingly, the entanglement density of polymer is increased due to dynamic heterogeneities between the matrix and the adsorbed polymer. Here, we investigate, on the same system, the effect of different interfacial entanglement densities on the melt and glassy properties (Tg, fragility and physical aging).Instead of surface modification of particles, which leads to poor control over the dispersion, we tuned the interfaces by applying LAOS above Tg of the composites and by using binary blends of short (Mw<Me) PMMA chains.With various nanoparticle concentrations and polymer blend ratios, we systematically study the effect of the confinement parameter (ID/2Rg) on the glass transition and dynamic fragility obtained from DSC and rheometry.Our results suggest that unlike Tg, the fragility presents strong dependence on ID/2Rg.

  6. Effect of ZnO nanoparticle and hexadecyltrimethylammonium bromide on the dynamic and equilibrium oil-water interfacial tension.

    PubMed

    Moghadam, Tahereh Fereidooni; Azizian, Saeid

    2014-02-13

    The effect of ZnO nanoparticles on the dynamic and equilibrium interfacial tension in the presence and absence of cationic surfactant CTAB was investigated. The results show that nanoparticles solely have no effect on interfacial tension. However, in the presence of CTAB, both particles and surfactants are adsorbed at the interface, and by a synergistic effect decrease the interfacial tension more. The effect of ZnO nanoparticles on the contact angle and stability of emulsions was studied too. The dynamic interfacial tension data were fitted with two different models. The results show that the adsorption mechanism of surfactant from bulk to interface was controlled by the mixed diffusion-kinetic model.

  7. Influence of organic acid and organic base interactions on interfacial properties in NAPL--water systems.

    PubMed

    Hsu, Hsin-Lan; Demond, Avery H

    2007-02-01

    Interfacial properties play an important role in determining the transport and distribution of waste nonaqueous phase liquids (NAPLs) in groundwater. To develop a better understanding of the solute interactions governing the interfacial properties of waste NAPLs, this study examined the interfacial tension and contact angle of a tetrachloroethylene/water/quartz system containing octanoic acid and dodecylamine as a function of pH. The results showed that interactions between these solutes affected the system's interfacial properties significantly, producing a positive synergism. For example, octanoic acid, which by itself does not affect wettability, could reverse the wettability of quartz in the presence of dodecylamine. The significant reduction in interfacial tension and increase in contact angle around neutral pH was, based on the results of speciation modeling, attributed to the formation of a complex composed of the protonated organic base and deprotonated organic acid, whose formation also peaks around neutral pH. Thus, measures of the content of only one class of compounds, such as the base number, are inadequate descriptors of a NAPL's ability to alter wettability.

  8. 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.

  9. Assessment of interfacial microstructure and bond properties in aged GRC using a novel microindentation method

    SciTech Connect

    Zhu, W.; Bartos, P.J.M.

    1997-11-01

    Changes of microstructure and properties in the interfacial zone of glass fiber reinforced cement (GRC) under the effect of aging were investigated. A novel technique based on a microindentation apparatus was developed and successfully used to carry out microstrength testing in the interfacial area and push-in tests on selected individual fibers within a strand. By continuously monitoring load vs. displacement, the new technique allowed the microstrength to be measured in small, porous areas of the fiber-matrix interfacial zone, and particularly within the glass fiber strand/bundle. The results showed that the embrittlement of aged GRC was closely associated with a substantial increase of the microstrength values within the fiber bundle during the aging process. It was also revealed that a wide range of bond properties existed within the fiber strand. The resistance to fiber sliding was much greater at the outer filaments than at the inner central filaments of the fiber strand/bundle.

  10. Finite-size effects on molecular dynamics interfacial thermal-resistance predictions

    NASA Astrophysics Data System (ADS)

    Liang, Zhi; Keblinski, Pawel

    2014-08-01

    Using molecular dynamics simulations, we study the role of finite size effects on the determination of interfacial thermal resistance between two solids characterized by high phonon mean free paths. In particular, we will show that a direct, heat source-sink method leads to strong size effect, associated with ballistic phonon transport to and from, and specular reflections at the simulation domain boundary. Lack of proper account for these effects can lead to incorrect predictions about the role of interfacial bonding and structure on interfacial thermal resistance. We also show that the finite size effect can be dramatically reduced by introduction of rough external boundaries leading to diffuse phonon scattering, as explicitly demonstrated by phonon wave-packet simulations. Finally, we demonstrate that when careful considerations are given to the effects associated with the finite heat capacity of the simulation domains and phonon scattering from the external surfaces, a size-independent interfacial resistance can be properly extracted from the time integral of the correlation function of heat power across the interface. Our work demonstrates that reliable and consistent values of the interfacial thermal resistance can be obtained by equilibrium and nonequilibrium methods with a relatively small computational cost.

  11. Solid solution directionally solidified eutectics: Model systems for structure-property relationships in interfacial fracture

    NASA Astrophysics Data System (ADS)

    Brewer, Luke Nathaniel

    The next generation of high temperature materials for application in aerospace and power generation systems will be required to withstand temperatures well in excess of 1200°C, often in oxidizing atmospheres. Oxide-oxide directionally solidified eutectics (DSE's) have shown promise as high temperature ceramic materials, only to be limited by their lack of fracture toughness at room temperature. In the case of DSE oxide materials, the interfacial fracture behavior has been blamed for the poor performance in the past and is the subject of interest in this work. In this thesis, the solid solution, directionally solidified quaternary eutectic (SS-DSE), Co1-xNixO/ZrO2(CaO), is developed as a model system for the study of interfacial fracture in oxide-oxide DSE's. A variety of structural and mechanical characterization techniques are applied to investigate structure-property relationships for interfacial fracture behavior. The optical floating zone technique was employed for growing both the eutectic crystals and their single crystal counterparts, Co1-x NixO. Co1-xNixO/ZrO2(CaO) was shown to possess the necessary structural elements to serve as a model system for interfacial fracture. Lamellar microstructures were observed for all compositions. The crystallographic relationships between phases evolved as a model solid solution. Interdiffusion of chemical species was minimal, allowing the layers to treated independently. The core of this thesis is dedicated to studying the nature of interfacial fracture behavior in oxide eutectics. This study is motivated by the novel observation of extensive interfacial delamination for the system CoO/ZrO 2(CaO). A transition from interfacial delamination to interfacial penetration is observed for compositions of Co1-xNixO/ZrO 2(CaO) with x > 0.2. The residual stress state in these materials was investigated using X-ray and neutron diffraction-based techniques. The role of plasticity in interfacial fracture was explored using a

  12. Dynamic interfacial tension in binary systems and spontaneous pulsation of individual drops by their dissolution

    SciTech Connect

    Ostrovsky, M.V.; Ostrovsky, R.M.

    1983-06-01

    This work discusses what influence various factors (dynamic interfacial tension, Marangoni instability, and natural convection) have to produce spontaneous pulsation of liquid drops in binary systems and to influence the kinetics of their dissolution. Measurements were taken of (1) dynamic interfacial tension and phase density in 6 binary systems, (2) the frequency of the spontaneous kicking of dissolving drops, and (3) the mass transfer coefficient in 2 systems with natural convection. The causes of normal deformation of the interface layer by dissolution of liquid in liquid were analyzed. It was shown that local changes of interfacial tension bring forth the appearance of local drop deformation, and the kicking of drops. In nonequilibrium 2-component liquid- liquid systems, the values of interfacial tension, the mass transfer coefficient, and the frequency and intensity of drop pulsation decrease simultaneously with the decrease of the driving force of dissolution. The relationships among these values are shown. This connection indicates that the Marangoni effect and natural convection are responsible for surface spontaneous convection and the increase of the mass transfer coefficient. 17 references.

  13. Fluctuation-induced dynamics of multiphase liquid jets with ultra-low interfacial tension.

    PubMed

    Sauret, Alban; Spandagos, Constantinos; Shum, Ho Cheung

    2012-09-21

    Control of fluid dynamics at the micrometer scale is essential to emulsion science and materials design, which is ubiquitous in everyday life and is frequently encountered in industrial applications. Most studies on multiphase flow focus on oil-water systems with substantial interfacial tension. Advances in microfluidics have enabled the study of multiphase flow with more complex dynamics. Here, we show that the evolution of the interface in a jet surrounded by a co-flowing continuous phase with an ultra-low interfacial tension presents new opportunities to the control of flow morphologies. The introduction of a harmonic perturbation to the dispersed phase leads to the formation of interfaces with unique shapes. The periodic structures can be tuned by controlling the fluid flow rates and the input perturbation; this demonstrates the importance of the inertial effects in flow control at ultra-low interfacial tension. Our work provides new insights into microfluidic flows at ultra-low interfacial tension and their potential applications.

  14. Probing model tumor interfacial properties using piezoelectric cantilevers

    NASA Astrophysics Data System (ADS)

    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.

  15. Signatures of dynamic screening in interfacial thermal transport of graphene

    NASA Astrophysics Data System (ADS)

    Ong, Zhun-Yong; Fischetti, Massimo V.; Serov, Andrey Y.; Pop, Eric

    2013-05-01

    The interaction between graphene and various substrates plays an important and limiting role on the behavior of graphene films and devices. Here we uncover that dynamic screening of so-called remote substrate phonons (RPs) has a significant effect on the thermal coupling at the graphene-substrate interface. We calculate the thermal conductance hRP between graphene electrons and substrate, and its dependence on carrier density and temperature for SiO2, HfO2, h-BN, and Al2O3 substrates. The dynamic screening of RPs leads to one order of magnitude or more decrease in hRP and a change in its dependence on carrier density. Dynamic screening predicts a decrease of ˜1 MW K-1 m-2 while static screening predicts a rise of ˜10 MW K-1 m-2 when the carrier density in Al2O3-supported graphene is increased from 1012 to 1013 cm-2.

  16. Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties.

    PubMed

    Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

    2016-06-01

    In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties.

  17. Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties

    PubMed Central

    Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

    2016-01-01

    In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties. PMID:27245687

  18. Modeling micelle formation and interfacial properties with iSAFT classical density functional theory

    NASA Astrophysics Data System (ADS)

    Wang, Le; Haghmoradi, Amin; Liu, Jinlu; Xi, Shun; Hirasaki, George J.; Miller, Clarence A.; Chapman, Walter G.

    2017-03-01

    Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents). To help obtain a better understanding of the dependence of surfactant properties on molecular structure, a classical density functional theory, also known as interfacial statistical associating fluid theory, has been applied to study the effects of surfactant architecture on micelle formation and interfacial properties for model nonionic surfactant/water/oil systems. In this approach, hydrogen bonding is explicitly included. To minimize the free energy, the system minimizes interactions between hydrophobic components and hydrophilic components with water molecules hydrating the surfactant head group. The theory predicts micellar structure, effects of surfactant architecture on critical micelle concentration, aggregation number, and interfacial tension isotherm of surfactant/water systems in qualitative agreement with experimental data. Furthermore, this model is applied to study swollen micelles and reverse swollen micelles that are necessary to understand the formation of a middle-phase microemulsion.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  20. Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

    2016-06-01

    In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties.

  1. Molecular dynamics simulation aiming at interfacial characteristics of polymer chains on nanotubes with different layers

    NASA Astrophysics Data System (ADS)

    Li, Kun; Gu, Boqin; Zhu, Wanfu

    2017-03-01

    A molecular dynamics (MD) simulations study is performed on multiwalled carbon nanotubes (MWNTs)/acrylonitrile-butadiene rubber (NBR) composites. The physisorption and interfacial characteristics between the various MWNTs and polymer macromolecular chains are identified. The effects of nanotube layers on the nanotubes/polymer interactions are examined. Each of the situation result and surface features is characterized by binding energy (Eb). It is shown that the binding energy (Eb) increase with the number of layers.

  2. Tactical tuning of the surface and interfacial properties of graphene: A Versatile and rational electrochemical approach.

    PubMed

    Vusa, Chiranjeevi Srinivasa Rao; Venkatesan, Manju; K, Aneesh; Berchmans, Sheela; Arumugam, Palaniappan

    2017-08-21

    Designing a versatile and rational method for the tactical tuning of the surface and interfacial properties of graphene is an essential yet challenging task of many scientific areas including health care, sensors, energy, and the environment. A method was designed herein to tackle the challenge and tune the surface and interfacial properties of graphene using a simple electrochemical tethering of arylamines that provides diverse reactive end groups to graphene. This method resulted in the preparation of graphenes with thiol, hydroxy, amine, carboxyl, and sulfonate surface functionalities respectively. X-ray photoelectron spectroscopy, scanning electron microscopy, and cyclic voltammetry were used to study the chemical, morphological, and electrochemical properties of the modified graphenes. The results show the promising scope of the reported method towards the tactical tuning of the surface and interfacial properties of graphene. Also, this method can give fundamental insights of the surface tuning of graphene and its structurally similar materials. Hence, this approach can be used to advantageously tune the surface properties of the other structurally similar nanocarbons and their hybrid materials to make them potential candidates for many applications.

  3. Comparisons of the foaming and interfacial properties of whey protein isolate and egg white proteins.

    PubMed

    Davis, J P; Foegeding, E A

    2007-02-15

    Whipped foams (10%, w/v protein, pH 7.0) were prepared from commercially available samples of whey protein isolate (WPI) and egg white protein (EWP), and subsequently compared based on yield stress (tau(0)), overrun and drainage stability. Adsorption rates and interfacial rheological measurements at a model air/water interface were quantified via pendant drop tensiometry to better understand foaming differences among the ingredients. The highest tau(0) and resistance to drainage were observed for standard EWP, followed by EWP with added 0.1% (w/w) sodium lauryl sulfate, and then WPI. Addition of 25% (w/w) sucrose increased tau(0) and drainage resistance of the EWP-based ingredients, whereas it decreased tau(0) of WPI foams and minimally affected their drainage rates. These differing sugar effects were reflected in the interfacial rheological measurements, as sucrose addition increased the dilatational elasticity for both EWP-based ingredients, while decreasing this parameter for WPI. Previously observed relationships between tau(0) and interfacial rheology did not hold across the protein types; however, these measurements did effectively differentiate foaming behaviors within EWP-based ingredients and within WPI. Interfacial data was also collected for purified beta-lactoglobulin (beta-lg) and ovalbumin, the primary proteins of WPI and EWP, respectively. The addition of 25% (w/w) sucrose increased the dilatational elasticity for adsorbed layers of beta-lg, while minimally affecting the interfacial rheology of adsorbed ovalbumin, in contrast to the response of WPI and EWP ingredients. These experiments underscore the importance of utilizing the same materials for interfacial measurements as used for foaming experiments, if one is to properly infer interfacial information/mechanisms and relate this information to bulk foaming measurements. The effects of protein concentration and measurement time on interfacial rheology were also considered as they relate to bulk

  4. Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics

    NASA Astrophysics Data System (ADS)

    Shavorskiy, Andrey; Cordones, Amy; Vura-Weis, Josh; Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Bluhm, Hendrik; Strader, Matthew; Cho, Hana; Lin, Ming-Fu; Bacellar, Camila; Khurmi, Champak; Hertlein, Marcus; Guo, Jinghua; Tyliszczak, Tolek; Prendergast, David; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A.; Schoenlein, Robert W.; Belkacem, Ali; Weber, Thorsten; Neumark, Daniel M.; Leone, Stephen R.; Nordlund, Dennis; Ogasawara, Hirohito; Nilsson, Anders R.; Krupin, Oleg; Turner, Joshua J.; Schlotter, William F.; Holmes, Michael R.; Heimann, Philip A.; Messerschmidt, Marc; Minitti, Michael P.; Beye, Martin; Gul, Sheraz; Zhang, Jin Z.; Huse, Nils; Gessner, Oliver

    2013-04-01

    X-ray based spectroscopy techniques are particularly well suited to gain access to local oxidation states and electronic dynamics in complex systems with atomic pinpoint accuracy. Traditionally, these techniques are applied in a quasi-static fashion that usually highlights the steady-state properties of a system rather than the fast dynamics that often define the system function on a molecular level. Novel x-ray spectroscopy techniques enabled by free electron lasers (FELs) and synchrotron based pump-probe schemes provide the opportunity to monitor intramolecular and interfacial charge transfer processes in real-time and with element and chemical specificity. Two complementary time-domain xray photoelectron spectroscopy techniques are presented that are applied at the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS) to study charge transfer processes in N3 dye-sensitized ZnO semiconductor nanocrystals, which are at the heart of emerging light-harvesting technologies.

  5. Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics

    SciTech Connect

    Shavorskiy, Andrey; Hertlein, Marcus; Guo Jinghua; Tyliszczak, Tolek; Cordones, Amy; Vura-Weis, Josh; Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Khurmi, Champak; Belkacem, Ali; Weber, Thorsten; Gessner, Oliver; Bluhm, Hendrik; Strader, Matthew; Cho, Hana; Coslovich, Giacomo; Kaindl, Robert A.; Lin, Ming-Fu; and others

    2013-04-19

    X-ray based spectroscopy techniques are particularly well suited to gain access to local oxidation states and electronic dynamics in complex systems with atomic pinpoint accuracy. Traditionally, these techniques are applied in a quasi-static fashion that usually highlights the steady-state properties of a system rather than the fast dynamics that often define the system function on a molecular level. Novel x-ray spectroscopy techniques enabled by free electron lasers (FELs) and synchrotron based pump-probe schemes provide the opportunity to monitor intramolecular and interfacial charge transfer processes in real-time and with element and chemical specificity. Two complementary time-domain xray photoelectron spectroscopy techniques are presented that are applied at the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS) to study charge transfer processes in N3 dye-sensitized ZnO semiconductor nanocrystals, which are at the heart of emerging light-harvesting technologies.

  6. Flax Fiber Quality and Influence on Interfacial Properties of Composites.

    USDA-ARS?s Scientific Manuscript database

    Measured flax physical and chemical properties could potentially impact binding and thus the stress transfer between the matrix and fiber. The study included 14 linseed samples with 12 samples ranging in cleanliness and retting produced using hammer mill technology from 2000, 2006 and 2007 with 2 sa...

  7. Dynamically­ Reconfigurable Complex Emulsions via Tunable Interfacial Tensions

    NASA Astrophysics Data System (ADS)

    Swager, Timothy

    This lecture will focus on the design of systems wherein a reconfiguration of the materials can be triggered chemically of mechanically. The utility of these methods is to generate transduction mechanisms by which chemical and biological sensors can be developed. Three different types of systems will be discussed. (1) Particles wherein a protease enzyme releases strain in the particle by breaking crosslinks. (2) Assemblies of polymers at air water interfaces and the demonstration of a luminescence strain response upon compression. (3) Dynamic colloids produced from immiscible fluorocarbon/hydrocarbon mixtures and ability to convert the core and shell layers of the particles as well as the conversion to Janus particles. The latter system's morphology changes can be triggered chemically or optically.

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

    PubMed

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

    2012-06-15

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

  9. 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.

  10. 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.

  11. Elucidating the role of interfacial materials properties in microfluidic packages.

    SciTech Connect

    Edwards, Thayne L.

    2013-01-01

    The purpose of this work was to discover a method to investigate the properties of interfaces as described by a numerical physical model. The model used was adopted from literature and applied to a commercially available multiphysics software package. By doing this the internal properties of simple structures could be elucidated and then readily applied to more complex structures such as valves and pumps in laminate microfluidic structures. A numerical finite element multi-scale model of a cohesive interface comprised of heterogeneous material properties was used to elucidate irreversible damage from applied strain energy. An unknown internal state variable was applied to characterize the damage process. Using a constrained blister test, this unknown internal state variable could be determined for an adherend/adhesive/adherend body. This is particularly interesting for laminate systems with microfluidic and microstructures contained within the body. A laminate structure was designed and fabricated that could accommodate a variety of binary systems joined using nearly any technique such as adhesive, welding (solvent, laser, ultrasonic, RF, etc.), or thermal. The adhesive method was the most successful and easy to implement but also one of the more difficult to understand, especially over long periods of time. Welding methods are meant to achieve a bond that is similar to bulk properties and so are easier to predict. However, methods of welding often produce defects in the bonds.. Examples of the test structures used to elucidate the internal properties of the model were shown and demonstrated. The real life examples used this research to improve upon current designs and aided in creating complex structures for sensor and other applications.

  12. The role played by modified bioinspired surfaces in interfacial properties of biomaterials.

    PubMed

    Paterlini, Thais T; Nogueira, Lucas F B; Tovani, Camila B; Cruz, Marcos A E; Derradi, Rafael; Ramos, Ana P

    2017-08-22

    The success of a biomaterial relies on an appropriate interaction between the surface of that biomaterial and the surrounding environment; more specifically, the success of a biomaterial depends on how fluids, proteins, and cells interact with the foreign material. For this reason, the surface properties of biomaterial, such as composition, charge, wettability, and roughness, must be optimized for a desired application to be achieved. In this review we highlight different bioinspired approaches that are used to manipulate and fine-tune the interfacial properties of biomaterials. Inspired by noteworthy natural processes, researchers have developed materials with a functional anatomy that range from hierarchical hybrid structures to self-cleaning interfaces. In this review we focus on (1) the creation of particles and modified surfaces inspired by the structure and composition of biogenic mineralized tissues, (2) the development of biofunctional coatings, (3) materials inspired by biomembranes and proteins, and (4) the design of superwettable materials. Our intention is to point out different bioinspired methodologies that have been used to design materials for biomedical applications and to discuss how interfacial properties modified by manipulation of these materials determine their final biological response. Our objective is to present future research directions and to highlight the potential of bioinspired materials. We hope this review will provide an understanding of the interplay between interfacial properties and biological response so that successful biomaterials can be achieved.

  13. Subcritical Water Induced Complexation of Soy Protein and Rutin: Improved Interfacial Properties and Emulsion Stability.

    PubMed

    Chen, Xiao-Wei; Wang, Jin-Mei; Yang, Xiao-Quan; Qi, Jun-Ru; Hou, Jun-Jie

    2016-09-01

    Rutin is a common dietary flavonoid with important antioxidant and pharmacological activities. However, its application in the food industry is limited mainly because of its poor water solubility. The subcritical water (SW) treatment provides an efficient technique to solubilize and achieve the enrichment of rutin in soy protein isolate (SPI) by inducing their complexation. The physicochemical, interfacial, and emulsifying properties of the complex were investigated and compared to the mixtures. SW treatment had much enhanced rutin-combined capacity of SPI than that of conventional method, ascribing to the well-contacted for higher water solubility of rutin with stronger collision-induced hydrophobic interactions. Compared to the mixtures of rutin with proteins, the complex exhibited an excellent surface activity and improved the physical and oxidative stability of its stabilized emulsions. This improving effect could be attributed to the targeted accumulation of rutin at the oil-water interface accompanied by the adsorption of SPI resulting in the thicker interfacial layer, as evidenced by higher interfacial protein and rutin concentrations. This study provides a novel strategy for the design and enrichment of nanovehicle providing water-insoluble hydrophobic polyphenols for interfacial delivery in food emulsified systems. © 2016 Institute of Food Technologists®

  14. Effect of Cu2+ Activation on Interfacial Water Structure at the Sphalerite Surface as Studied by Molecular Dynamics Simulation

    SciTech Connect

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

    2015-12-10

    In the first part of this paper, an experimental contact angle study of the fresh and Cu2+ activated sphalerite-ZnS surface as well as the covellite-CuS (001) surface is reported describing the increased hydrophobic character of the surface during Cu2+ activation. In addition to these experimental results, the fresh sphalerite-ZnS (110), copper-zinc sulfide-CuZnS2 (110), villamaninite- CuS2 (100), and covellite-CuS (001) surfaces were examined using Molecular Dynamics Simulation (MDS). Our MDS results on the behavior of interfacial water at the fresh sphalerite-ZnS (110), copper-zinc sulfide-CuZnS2 (110), villamaninite-CuS2 (100), and covellite-CuS (001) surfaces include simulated contact angles, water number density distribution, water dipole orientation, water residence time, and hydrogen-bonding considerations. The copper content at the Cu2+ activated sphalerite surface seems to account for the increased hydrophobicity as revealed by both experimental and MD simulated contact angle measurements. The relatively greater hydrophobic character developed at the Cu2+ activated sphalerite surface and at the copper-zinc sulfide surface has been described by MDS, based on the structure of interfacial water and its dynamic properties. L.X.D. acknowledges funding from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences.

  15. Dynamic interfacial trapping of flexural waves in structured plates

    PubMed Central

    Craster, R. V.; Movchan, A. B.; Movchan, N. V.; Jones, I. S.

    2016-01-01

    The paper presents new results on the localization and transmission of flexural waves in a structured plate containing a semi-infinite two-dimensional array of rigid pins. In particular, localized waves are identified and studied at the interface boundary between the homogeneous part of the flexural plate and the part occupied by rigid pins. A formal connection has been made with the dispersion properties of flexural Bloch waves in an infinite doubly periodic array of rigid pins. Special attention is given to regimes corresponding to standing waves of different types as well as Dirac-like points that may occur on the dispersion surfaces. A single half-grating problem, hitherto unreported in the literature, is also shown to bring interesting solutions. PMID:27118892

  16. Monitoring interfacial dynamics by pulsed laser techniques. Final report

    SciTech Connect

    Richmond, G.

    1995-12-31

    The research is aimed at understanding the structural, electronic, and reactive properties of semiconductors in solutions. Focus is on Si and GaAs surfaces because they are used in photovoltaic devices, etc. The pulsed laser techniques used included surface second harmonic generation in Si and laser induced photoluminescence in GaAs. SHG can measure space charge effects in the semiconductor under various conditions, ie, immersed in electrolyte, in presence of oxide overlayers, and under UHV conditions. The Si studies demonstrated the sensitivity of the phase of the SH response to space charge effects. With GaAs, time-correlated single photon counting methods were used in the picosecond time regime to examine the recombination luminescence following above band gap excitation (surface trapping velocities).

  17. Determination of the Si-conducting polymer interfacial properties using A-C impedance techniques

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, Salvador; Moacanin, Jovan

    1985-01-01

    A study was made of the interfacial properties of poly(pyrrole) (PP) deposited electrochemically onto single crystal p-Si surfaces. The interfacial properties are dependent upon the counterions. The formation of 'quasi-ohmic' and 'nonohmic' contacts, respectively, of PP(ClO4) and PP films doped with other counterions (BF4 and para-toluene sulfonate) with p-Si, are explained in terms of the conductivity of these films and the flat band potential, V(fb), of PP relative to that of p-Si. The PP film seems to passivate or block intrinsic surface states present on the p-Si surface. The differences in the impedance behavior of para-toluene sulfonate doped and ClO4 doped PP are compared.

  18. Driving magnetization dynamics with interfacial spin-orbit torques (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hoffmann, Axel F.; Zhang, Wei; Sklenar, Joseph; Jungfleisch, Matthias Benjamin; Jiang, Wanjun; Hsu, Bo; Xiao, Jiao; Pearson, John E.; Fradin, Frank Y.; Liu, Yaohua; Ketterson, John B.; Yang, Zheng

    2016-10-01

    Bulk spin Hall effects are well know to provide spin orbit torques, which can be used to drive magnetization dynamics [1]. But one of the reoccurring questions is to what extend spin orbit torques may also originate at the interface between materials with strong spin orbit coupling and the ferromagnets. Using spin torque driven ferromagnetic resonance we show for two systems, where interfacial torques dominate, that they can be large enough to be practically useful. First, we show spin transfer torque driven magnetization dynamics based on Rashba-Edelstein effects at the Bi/Ag interface [2]. Second, we will show that combining permalloy with monolayer MoS2 gives rise to sizable spin-orbit torques. Given the monolayer nature of MoS2 it is clear that bilk spin Hall effects are negligible and therefore the spin transfer torques are completely interfacial in nature. Interestingly the spin orbit torques with MoS2 show a distinct dependence on the orientation of the magnetization in the permalloy, and become strongly enhanced, when the magnetization is pointing perpendicular to the interfacial plane. This work was supported by the U.S. Department of Energy, Office of Science, Materials Science and Engineering Division. [1] A. Hoffmann, IEEE Trans. Mag. 49, 5172 (2013). [2] W. Zhang et al., J. Appl. Phys. 117, 17C727 (2015). [3] M. B. Jungfleisch et al., arXiv:1508.01410.

  19. Single-molecule interfacial electron transfer dynamics manipulated by an external electric current.

    PubMed

    Zhang, Guofeng; Xiao, Liantuan; Chen, Ruiyun; Gao, Yan; Wang, Xiaobo; Jia, Suotang

    2011-08-14

    Interfacial electron transfer (IET) dynamics in a 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine (DiD) dye molecule/indium tin oxide (ITO) film system have been probed at the ensemble and single-molecule levels. By comparing the difference in the external electric current (EEC) dependence of the fluorescence intensities and lifetimes of the ensembles and single molecules, it is shown that the single-molecule probe can effectively demonstrate IET dynamics. The backward electron transfer and electron transfer from the ground state induce single-molecule fluorescence quenching when an EEC is applied to the DiD/ITO film system.

  20. Electrochemical evaluation of the p-Si/conducting polymer interfacial properties

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Distefano, S.; Moacanin, J.

    1988-01-01

    Results are presented from an experimental investigation of the contact resistance and interfacial properties of a p-Si/conducting polymer interface for solar cell applications. The electronic character of the polymer/semiconductor function is determined by studying the electrochemical behavior of both poly(isothianapthene) (PITN) and polypyrrole (PP) in an acetonitrile solution on p-silicon electrodes. The results obtained indicate that while PITN is intrinsically more conductive than PP, neither passivates surface states nor forms ohmic contact.

  1. Electrochemical evaluation of the p-Si/conducting polymer interfacial properties

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Distefano, S.; Moacanin, J.

    1988-01-01

    Results are presented from an experimental investigation of the contact resistance and interfacial properties of a p-Si/conducting polymer interface for solar cell applications. The electronic character of the polymer/semiconductor function is determined by studying the electrochemical behavior of both poly(isothianapthene) (PITN) and polypyrrole (PP) in an acetonitrile solution on p-silicon electrodes. The results obtained indicate that while PITN is intrinsically more conductive than PP, neither passivates surface states nor forms ohmic contact.

  2. Interfacial properties of aluminum/glass-fiberreinforced polypropylene sandwich composites

    NASA Astrophysics Data System (ADS)

    Baştürk, S. B.; Guruşçu, A.; Tanoğlu, M.

    2013-07-01

    Aluminum/glass-fiber-reinforced polypropylene (Al/GFPP) laminates were manufactured by using various surface pretreatment techniques. Adhesion at the composite/metal interface was achieved by a surface pretreatment of Al sheets with amino-based silane coupling agents, incorporation of a polyolefin-based adhesive film and modification with a PP-based film containing 20 wt.% of maleic-anhydride-modified polypropylene (PP-g-MA). In order to increase the effect of bonding between components of the laminates, the combination of silane treatment and the addition of the PP-based film was also investigated. The mechanical properties (shear, peel, and bending strengths) of adhesively bonded Al/GFPP laminates were examined to evaluate the effects of the surface treatments mentioned. It was revealed that the adhesion in the laminated Al/GFPP systems could be improved by the treatment of aluminum surface with an amino-based silane coupling agent. Judging from the results of peel and bending strength, with incorporation of polyolefin-based films, adhesion in the Al/GFPP laminates increased significantly. The modification of Al/GFPP interfaces with a PP-g-MA/PP layer led to the highest improvement in their adhesion properties. The combination of surface modification with silane and addition of PP-based films did not yield the high bending strength desired. This may be due to the insufficient bonding between silane groups and PP-based films.

  3. Effects of dispersion and interfacial modification on the macroscale properties of TiO2 polymer matrix nanocomposites

    PubMed Central

    Hamming, Lesley M.; Qiao, Rui; Messersmith, Phillip B.; Brinson, L. Catherine

    2009-01-01

    This paper quantifies how the quality of dispersion and the quality of the interfacial interaction between TiO2 nanoparticles and host polymer independently affect benchmark properties such as glass transition temperature (Tg), elastic modulus and loss modulus. By examining these composites with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM), we were able to demonstrate changes in properties depending on the adhesive/wetting or repulsive/dewetting interactions the nanoparticles have with the bulk polymer. We further quantified the dispersion of TiO2 nanoparticles in polymethylmethacrylate (PMMA) matrices by a digital-optical method and correlated those values to the degree of Tg depression compared to neat PMMA. Samples with the same weight percent of nanoparticles but better dispersion showed larger shifts in Tg. PMID:20161273

  4. The influence of interfacial properties on two-phase liquid flow of organic contaminants in groundwater

    SciTech Connect

    Hayes, K.F.; Demond, A.H.

    1991-08-01

    An improved understanding of the factors influencing the movement of a separate organic liquid phase in groundwater aquifers is important to the US Department of Energy's efforts to alleviate groundwater contamination by many common solvents. The overall objective of this project is to investigate how changes in interfacial chemical properties affect two-phase flow relationships. Specifically, the objective is to develop a quantitative theory that will enable the prediction of changes in the capillary pressure-saturation relationship, a fundamental constitutive relationship in multiphase flow modeling, from changes in interfacial properties through a knowledge of their effect on wettability. The work over the past eight months of the project summarized here shows the interrelationship between the surface chemical properties of sorption, electrophoretic mobility, contact angle, surface tension and capillary pressure, and how the effects on capillary pressure might be predicted on the basis of surface tension and contact angle. The model system we have been examining consists of o-xylene, water, silica sand, and cetyltrimethylammonium bromide (CTAB), in which all three interfacial tensions of the system change.

  5. Interfacial Ga-As suboxide: Structural and electronic properties

    SciTech Connect

    Colleoni, Davide Pasquarello, Alfredo

    2015-07-20

    The structural and electronic properties of Ga-As suboxide representative of the transition region at the GaAs/oxide interface are studied through density functional calculations. Two amorphous models generated by quenches from the melt are taken under consideration. The absence of As–O bonds indicates that the structure is a mixture of GaAs and Ga-oxide, in accordance with photoemission experiments. The band edges of the models are found to be closely aligned to those of GaAs. The simulation of charging and discharging processes leads to the identification of an As-related defect with an energy level at ∼0.7 eV above the GaAs valence band maximum, in good agreement with the experimental density of interface states.

  6. Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells

    NASA Astrophysics Data System (ADS)

    Edley, Michael

    Photovoltaic energy is a clean and renewable source of electricity; however, it faces resistance to widespread use due to cost. Nanostructuring decouples constraints related to light absorption and charge separation, potentially reducing cost by allowing a wider variety of processing techniques and materials to be used. However, the large interfacial areas also cause an increased dark current which negatively affects cell efficiency. This work focuses on extremely thin absorber (ETA) solar cells that used a ZnO nanowire array as a scaffold for an extremely thin CdSe absorber layer. Photoexcited electrons generated in the CdSe absorber are transferred to the ZnO layer, while photogenerated holes are transferred to the liquid electrolyte. The transfer of photoexcited carriers to their transport layer competes with bulk recombination in the absorber layer. After charge separation, transport of charge carriers to their respective contacts must occur faster than interfacial recombination for efficient collection. Charge separation and collection depend sensitively on the dimensions of the materials as well as their interfaces. We demonstrated that an optimal absorber thickness can balance light absorption and charge separation. By treating the ZnO/CdSe interface with a CdS buffer layer, we were able to improve the Voc and fill factor, increasing the ETA cell's efficiency from 0.53% to 1.34%, which is higher than that achievable using planar films of the same material. We have gained additional insight into designing ETA cells through the use of dynamic measurements. Ultrafast transient absorption spectroscopy revealed that characteristic times for electron injection from CdSe to ZnO are less than 1 ps. Electron injection is rapid compared to the 2 ns bulk lifetime in CdSe. Optoelectronic measurements such as transient photocurrent/photovoltage and electrochemical impedance spectroscopy were applied to study the processes of charge transport and interfacial recombination

  7. Photo-visualization Study Illustrating the Effects of Interfacial Properties on Multiphase Flow in Glass Bead Micromodels

    NASA Astrophysics Data System (ADS)

    Cianci, J. A.; Hwang, S. I.; Powers, S. E.

    2001-05-01

    The mechanics of mobilization and dynamics that affect the path and fate of the DNAPL in the subsurface are not fully understood. Dynamics such as fingering may short-circuit and ultimately lead to trapped pockets of DNAPL in the subsurface. These physical flow phenomena can be changed by adjusting chemical conditions of the NAPL/water interface, wettability properties of the subsurface particles, or by the introduction of biosurfactants to the subsurface system. This research focuses on multiphase flow phenomena in glass bead micromodels as effected by surface tension and wettability changes. Two-dimensional glass bead micromodels are constructed with 0.5-mm glass beads with, water wetting and NAPL wetting capillary barriers. Images are captured on a streaming video feed and analyzed using integrated computer capture and analysis software. Under initially water-saturated conditions, transient conditions are characterized by overall model drainage dynamics, fingering dynamics, and pressure-saturation comparisons. Steady state attributes are qualified by spatial distribution of residual saturation, and quantified by size and shape analysis of the capturing pores, and blob analysis of the residual NAPL. Micro scale analysis is being performed to evaluate changes in curvature of liquid/bead interfaces. The micromodels have been performing according to our expectations. Systems with lower interfacial tensions are characterized by lower capillary entry pressures and wider fingers, which are not easily short-circuited to form residual NAPL pockets. Residual blob sizes are smaller than in the system with a higher interfacial tension. It is anticipated by understanding differences in these pore scale processes, we can produce conditions such that the fingering dynamics of the system can be altered and, ultimately, the trapped pockets of residual NAPL can be minimized.

  8. Interfacial Properties and Design of Functional Energy Materials

    SciTech Connect

    Sumpter, Bobby G; Liang, Liangbo; Nicolai, Adrien; Meunier, V.

    2014-01-01

    The vital importance of energy to society continues to demand a relentless pursuit of energy responsive materials that can bridge fundamental chemical structures at the molecular level and achieve improved functionality, such as efficient energy conversion/storage/transmission, over multiple length scales. This demand can potentially be realized by harnessing the power of self-assembly a spontaneous process where molecules or much larger entities form ordered aggregates as a consequence of predominately non-covalent (weak) interactions. Self-assembly is the key to bottom-up design of molecular devices, because the nearly atomic-level control is very difficult to realize in a top-down, e.g., lithographic approach. However, while function (e.g., charge mobility) in simple systems such as single crystals can often be predicted, predicting the function of the great variety of self-assembled molecular architectures is complicated by the lack of understanding and control over nanoscale interactions, mesoscale architectures, and macroscale (long-range) order. To establish a foundation toward delivering practical solutions, it is critical to develop an understanding of the chemical and physical mechanisms responsible for the self-assembly of molecular and hybrid materials on various substrates. Typically molecular self-assembly involves poorly understood non-covalent intermolecular and substrate-molecule interactions compounded by local and/or collective influences from the substrate atomic lattice (symmetry and/or topological features) and electronic structure. Thus, progress towards unraveling the underlying physicochemical processes that control the structure and macroscopic physical, mechanical, electrical, and transport properties of materials increasingly requires tight integration of theory, modeling and simulation with precision synthesis, advanced experimental characterization, and device measurements. In this mode, theory and simulation can greatly accelerate the

  9. Effect of molecular flexibility of Lennard-Jones chains on vapor-liquid interfacial properties.

    PubMed

    Blas, F J; Moreno-Ventas Bravo, A I; Algaba, J; Martínez-Ruiz, F J; MacDowell, L G

    2014-03-21

    We have determined the interfacial properties of short fully flexible chains formed from tangentially bonded Lennard-Jones monomeric units from direct simulation of the vapor-liquid interface. The results obtained are compared with those corresponding to rigid-linear chains formed from the same chain length, previously determined in the literature [F. J. Blas, A. I. M.-V. Bravo, J. M. Míguez, M. M. Piñeiro, and L. G. MacDowell, J. Chem. Phys. 137, 084706 (2012)]. The full long-range tails of the potential are accounted for by means of an improved version of the inhomogeneous long-range corrections of Janeček [J. Phys. Chem. B 129, 6264 (2006)] proposed recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2008)] valid for spherical as well as for rigid and flexible molecular systems. Three different model systems comprising of 3, 5, and 6 monomers per molecule are considered. The simulations are performed in the canonical ensemble, and the vapor-liquid interfacial tension is evaluated using the test-area method. In addition to the surface tension, we also obtained density profiles, coexistence densities, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the chain length and rigidity on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. Comparison between predictions for fully flexible and rigid-linear chains, formed by the same number of monomeric units, indicates that the main effects of increasing the flexibility, i.e., passing from a rigid-linear to a fully flexible chain, are: (a) to decrease the difference between the liquid and vapor densities; (b) to decrease the critical temperature and

  10. Interfacial properties and design of functional energy materials.

    PubMed

    Sumpter, Bobby G; Liang, Liangbo; Nicolaï, Adrien; Meunier, Vincent

    2014-11-18

    CONSPECTUS: The vital importance of energy to society continues to demand a relentless pursuit of energy responsive materials that can bridge fundamental chemical structures at the molecular level and achieve improved functionality and performance. This demand can potentially be realized by harnessing the power of self-assembly, a spontaneous process where molecules or much larger entities form ordered aggregates as a consequence of predominately noncovalent (weak) interactions. Self-assembly is the key to bottom-up design of molecular devices, because the nearly atomic-level control is very difficult to realize in a top-down, for example, lithographic, approach. However, while function in simple systems such as single crystals can often be evaluated a priori, predicting the function of the great variety of self-assembled molecular architectures is complicated by the lack of understanding and control over nanoscale interactions, mesoscale architectures, and macroscale order. To establish a foundation toward delivering practical solutions, it is critical to develop an understanding of the chemical and physical mechanisms responsible for the self-assembly of molecular and hybrid materials on various support substrates. Typical molecular self-assembly involves noncovalent intermolecular and substrate-molecule interactions. These interactions remain poorly understood, due to the combination of many-body interactions compounded by local or collective influences from the substrate atomic lattice and electronic structure. Progress toward unraveling the underlying physicochemical processes that control the structure and macroscopic physical, chemical, mechanical, electrical, and transport properties of materials increasingly requires tight integration of theory, modeling, and simulation with precision synthesis, advanced experimental characterization, and device measurements. Theory, modeling, and simulation can accelerate the process of materials understanding and design

  11. Probing interfacial electron dynamics with time-resolved X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Neppl, Stefan

    2015-05-01

    Time-resolved core-level spectroscopy techniques using laser pulses to initiate and short X-ray pulses to probe photo-induced processes have the potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics at complex interfaces. We describe the implementation of femto- and picosecond time-resolved photoelectron spectroscopy at the Linac Coherent Light Source (LCLS) and at the Advanced Light Source (ALS) in order to follow light-driven electron dynamics at dye-semiconductor interfaces on femto- to nanosecond timescales, and from the perspective of individual atomic sites. A distinct transient binding-energy shift of the Ru3d photoemission lines originating from the metal centers of N3 dye-molecules adsorbed on nanoporous ZnO is observed 500 fs after resonant HOMO-LUMO excitation with a visible laser pulse. This dynamical chemical shift is accompanied by a characteristic surface photo-voltage response of the semiconductor substrate. The two phenomena and their correlation will be discussed in the context of electronic bottlenecks for efficient interfacial charge-transfer and possible charge recombination and relaxation pathways leading to the neutralization of the transiently oxidized dye following ultrafast electron injection. First steps towards in operando time-resolved X-ray absorption spectroscopy techniques to monitor interfacial chemical dynamics will be presented.

  12. 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.

  13. Liquid-vapor equilibrium and interfacial properties of square wells in two dimensions

    NASA Astrophysics Data System (ADS)

    Armas-Pérez, Julio C.; Quintana-H, Jacqueline; Chapela, Gustavo A.

    2013-01-01

    Liquid-vapor coexistence and interfacial properties of square wells in two dimensions are calculated. Orthobaric densities, vapor pressures, surface tensions, and interfacial thicknesses are reported. Results are presented for a series of potential widths λ* = 1.4, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5, where λ* is given in units of the hard core diameter σ. Critical and triple points are explored. No critical point was found for λ* < 1.4. Corresponding states principle analysis is performed for the whole series. For λ* = 1.4 and 1.5 evidence is presented that at an intermediate temperature between the critical and the triple point temperatures the liquid branch becomes an amorphous solid. This point is recognized in Armas-Pérez et al. [unpublished] as a hexatic phase transition. It is located at reduced temperatures T* = 0.47 and 0.35 for λ* = 1.4 and 1.5, respectively. Properties such as the surface tension, vapor pressure, and interfacial thickness do not present any discontinuity at these points. This amorphous solid branch does not follow the corresponding state principle, which is only applied to liquids and gases.

  14. Understanding the interfacial properties of nanostructured liquid crystalline materials for surface-specific delivery applications.

    PubMed

    Dong, Yao-Da; Larson, Ian; Barnes, Timothy J; Prestidge, Clive A; Allen, Stephanie; Chen, Xinyong; Roberts, Clive J; Boyd, Ben J

    2012-09-18

    Nonlamellar liquid crystalline dispersions such as cubosomes and hexosomes have great potential as novel surface-targeted active delivery systems. In this study, the influence of internal nanostructure, chemical composition, and the presence of Pluronic F127 as a stabilizer, on the surface and interfacial properties of different liquid crystalline particles and surfaces, was investigated. The interfacial properties of the bulk liquid crystalline systems with coexisting excess water were dependent on the internal liquid crystalline nanostructure. In particular, the surfaces of the inverse cubic systems were more hydrophilic than that of the inverse hexagonal phase. The interaction between F127 and the bulk liquid crystalline systems depended on the internal liquid crystalline structure and chemical composition. For example, F127 adsorbed to the surface of the bulk phytantriol cubic phase, while for monoolein cubic phase, F127 was integrated into the liquid crystalline structure. Last, the interfacial adsorption behavior of the dispersed liquid crystalline particles also depended on both the internal nanostructure and the chemical composition, despite the dispersions all being stabilized using F127. The findings highlight the need to understand the specific surface characteristics and the nature of the interaction with colloidal stabilizer for understanding and optimizing the behavior of nonlamellar liquid crystalline systems in surface delivery applications.

  15. The influence of interfacial properties on two-phase liquid flow of organic contaminants in groundwater

    SciTech Connect

    Hayes, K.F.; Demond, A.H.

    1990-09-01

    The purpose of this project is to investigate how changes in interfacial chemical properties affect two-phase transport relationships. Specifically, the objective is to develop a quantitative theory that will enable the prediction of changes in the capillary pressure-saturation relationship, a fundamental constitutive relationship in multiphase flow modeling, from changes in interfacial properties through a knowledge of their effect on wettability. The information presented here summarizes the progress we have made in the first project period. Based on preliminary adsorption, surface charge and surface potential measurements, we have demonstrated that it is possible to change the wettability of silica in a controlled manner by adsorbing varying quantities of a strongly-binding, cationic surfactant like cetyltrimethylammonium bromide (CTAB). Adsorption, surface charge and surface potential measurements have been made on the silica-water-CTAB system to yield a relationship between the amount adsorbed and the interfacial potential. Our work on the ideal soil model has demonstrated that the incorporation of roughness effects in the ideal soil model improves the prediction of the operative contact angles for drainage and imbibition from the intrinsic contact angle. This leads to better estimates of the capillary pressure-saturation relationships. Preliminary capillary pressure experiments on the silica-water-air system have shown that adsorption of a surfactant at the solid surface changes the capillary pressure-saturation relationship significantly.

  16. Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

    NASA Astrophysics Data System (ADS)

    Yang, Chunyan; Persson, Bo

    2008-03-01

    We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load [1-4]. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the interfacial separation approaches to zero. The present results may be very important for soft solids, e.g., rubber, or for very smooth surfaces, where complete contact can be reached at moderate high loads without plastic deformation of the solids. References: [1] C. Yang and B.N.J. Persson, arXiv:0710.0276, (to appear in Phys. Rev. Lett.) [2] B.N.J. Persson, Phys. Rev. Lett. 99, 125502 (2007) [3] L. Pei, S. Hyun, J.F. Molinari and M.O. Robbins, J. Mech. Phys. Sol. 53, 2385 (2005) [4] M. Benz, K.J. Rosenberg, E.J. Kramer and J.N. Israelachvili, J. Phy. Chem. B.110, 11884 (2006)

  17. Evaluation of the interfacial bond properties between carbon phenolic and glass phenolic composites

    NASA Technical Reports Server (NTRS)

    Jordan, K.; Clinton, R.; Jeelani, S.

    1991-01-01

    The effects of moisture and surface finish on the mechanical and physical properties of the interfacial bond between carbon/phenolic (C/P) and glass/phenolic (G/P) composite materials have been studied. Test results indicate that moisture substantially degrades the integrity of the interfacial bond between C/P and G/P materials. The apparent effect of the autoclave curing of the C/P material reduces the ultimate interlaminar shear length of the C/P material by 20 percent compared to the hydroclave curing of the C/P material. The variation in applied surface finishes is found to have no appreciable effect on the ultimate interlaminar shear strength of the interface in the wet laminate.

  18. Interfacial Reaction and Mechanical Properties of Sn-Bi Solder joints

    PubMed Central

    Huang, Ying; Zhang, Zhijie

    2017-01-01

    Sn-Bi solder with different Bi content can realize a low-to-medium-to-high soldering process. To obtain the effect of Bi content in Sn-Bi solder on the microstructure of solder, interfacial behaviors in solder joints with Cu and the joints strength, five Sn-Bi solders including Sn-5Bi and Sn-15Bi solid solution, Sn-30Bi and Sn-45Bi hypoeutectic and Sn-58Bi eutectic were selected in this work. The microstructure, interfacial reaction under soldering and subsequent aging and the shear properties of Sn-Bi solder joints were studied. Bi content in Sn-Bi solder had an obvious effect on the microstructure and the distribution of Bi phases. Solid solution Sn-Bi solder was composed of the β-Sn phases embedded with fine Bi particles, while hypoeutectic Sn-Bi solder was composed of the primary β-Sn phases and Sn-Bi eutectic structure from networked Sn and Bi phases, and eutectic Sn-Bi solder was mainly composed of a eutectic structure from short striped Sn and Bi phases. During soldering with Cu, the increase on Bi content in Sn-Bi solder slightly increased the interfacial Cu6Sn5 intermetallic compound (IMC)thickness, gradually flattened the IMC morphology, and promoted the accumulation of more Bi atoms to interfacial Cu6Sn5 IMC. During the subsequent aging, the growth rate of the IMC layer at the interface of Sn-Bi solder/Cu rapidly increased from solid solution Sn-Bi solder to hypoeutectic Sn-Bi solder, and then slightly decreased for Sn-58Bi solder joints. The accumulation of Bi atoms at the interface promoted the rapid growth of interfacial Cu6Sn5 IMC layer in hypoeutectic or eutectic Sn-Bi solder through blocking the formation of Cu6Sn5 in solder matrix and the transition from Cu6Sn5 to Cu3Sn. Ball shear tests on Sn-Bi as-soldered joints showed that the increase of Bi content in Sn-Bi deteriorated the shear strength of solder joints. The addition of Bi into Sn solder was also inclined to produce brittle morphology with interfacial fracture, which suggests that the

  19. Hydrogen bonding and vibrational energy relaxation of interfacial water: A full DFT molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Jeon, Jonggu; Hsieh, Cho-Shuen; Nagata, Yuki; Bonn, Mischa; Cho, Minhaeng

    2017-07-01

    The air-water interface has been a subject of extensive theoretical and experimental studies due to its ubiquity in nature and its importance as a model system for aqueous hydrophobic interfaces. We report on the structure and vibrational energy transfer dynamics of this interfacial water system studied with equilibrium and non-equilibrium molecular dynamics simulations employing a density functional theory -based description of the system and the kinetic energy spectral density analysis. The interfacial water molecules are found to make fewer and weaker hydrogen (H)-bonds on average compared to those in the bulk. We also find that (i) the H-bonded OH groups conjugate to the free OH exhibit rather low vibrational frequencies (3000-3500 cm-1); (ii) the presence of a significant fraction (>10%) of free and randomly oriented water molecules at the interface ("labile water"), neither of whose OH groups are strong H-bond donors; (iii) the inertial rotation of free OH groups, especially from the labile water, contribute to the population decay of excited free OH groups with comparable rate and magnitude as intramolecular energy transfer between the OH groups. These results suggest that the labile water, which might not be easily detectable by the conventional vibrational sum frequency generation method, plays an important role in the surface water dynamics.

  20. Hydrogen bonding and vibrational energy relaxation of interfacial water: A full DFT molecular dynamics simulation.

    PubMed

    Jeon, Jonggu; Hsieh, Cho-Shuen; Nagata, Yuki; Bonn, Mischa; Cho, Minhaeng

    2017-07-28

    The air-water interface has been a subject of extensive theoretical and experimental studies due to its ubiquity in nature and its importance as a model system for aqueous hydrophobic interfaces. We report on the structure and vibrational energy transfer dynamics of this interfacial water system studied with equilibrium and non-equilibrium molecular dynamics simulations employing a density functional theory -based description of the system and the kinetic energy spectral density analysis. The interfacial water molecules are found to make fewer and weaker hydrogen (H)-bonds on average compared to those in the bulk. We also find that (i) the H-bonded OH groups conjugate to the free OH exhibit rather low vibrational frequencies (3000-3500 cm(-1)); (ii) the presence of a significant fraction (>10%) of free and randomly oriented water molecules at the interface ("labile water"), neither of whose OH groups are strong H-bond donors; (iii) the inertial rotation of free OH groups, especially from the labile water, contribute to the population decay of excited free OH groups with comparable rate and magnitude as intramolecular energy transfer between the OH groups. These results suggest that the labile water, which might not be easily detectable by the conventional vibrational sum frequency generation method, plays an important role in the surface water dynamics.

  1. Wetting and Interfacial Tension Dynamics of Oil-Nanofluids-Surface Minerals System

    NASA Astrophysics Data System (ADS)

    Bai, L.; Li, C.; Darnault, C. J. G.; Korte, C.; Ladner, D.; Daigle, H.

    2015-12-01

    Among the techniques used in enhanced oil recovery (EOR), chemical injection involves the injection of surfactants to increase the oil mobility and decrease the interfacial tension (IFT). With the nanotechnology revolution, the use of nanoparticles has shown unique opportunities in petroleum engineering due to their physico-chemical properties. Our research examines the potential application of nanoparticles as a means of EOR by studying the influence of silicon oxide nanoparticles on the wettability and IFT of oil-nanofluids-surface systems. Batch studies were conducted to assess the stability of the nanoparticle suspensions of different concentrations (0, 0.001, 0.005, 0.01, 0.05 and 0.1 wt. %) in different reservoir conditions with and without the addition of surfactants (i.e. 5% brine, and Tween 20 at 0.5 and 2 cmc). Testing of oil-nanofluids and oil-nanofluids-minerals interactions was performed using crude oils from West Texas (light, API 40), Prudhoe Bay (medium, API 28), and Lloydminster (heavy, API 20). The dynamic behavior of IFT was measured using a pendant drop method. Results for 5% brine-nanoparticle systems indicated that 0.001 and 0.01 wt.% of nanoparticles contributed to a significant decrease of IFT for West Texas and Prudhoe Bay oils, while the highest decrease of IFT for Lloydminster was reported with 0.1 wt.% nanoparticles. IFT decrease was also enhanced by surfactant, and the addition of nanoparticles at 0.001 wt.% to surfactant resulted in significant decrease of IFT in most of the tested oil-nanofluid systems. The sessile drop method was used to measure the dynamic behavior of the contact angle of these oil droplets on minerals surface made of thin sections from Berea and Boise sandstone cores through a wetting test. Different nanofluid and surfactant concentrations were tested for the optimization of changes in wettability, which is a critical phase in assessing the behavior of nanofluids for optimal EOR with the selected crude oils.

  2. Optimization of interfacial properties of carbon fiber/epoxy composites via a modified polyacrylate emulsion sizing

    NASA Astrophysics Data System (ADS)

    Yuan, Xiaomin; Zhu, Bo; Cai, Xun; Liu, Jianjun; Qiao, Kun; Yu, Junwei

    2017-04-01

    The adhesion behavior of epoxy resin to carbon fibers has always been a challenge, on account of the inertness of carbon fibers and the lack of reactive functional groups. In this work, a modified polyacrylate sizing agent was prepared to modify the interface between the carbon fiber and the epoxy matrix. The surface characteristics of carbon fibers were investigated to determine chemical composition, morphology, wettability, interfacial phase analysis and interfacial adhesion. Sized carbon fibers featured improved wettability and a slightly decreased surface roughness due to the coverage of a smooth sizing layer, compared with the unsized ones. Moreover, the content of surface activated carbon atoms increased from 12.65% to 24.70% and the interlaminar shear strength (ILSS) of carbon fiber/epoxy composites raised by 14.2%, indicating a significant improvement of chemical activity and mechanical property. SEM images of the fractured surface of composites further proved that a gradient interfacial structure with increased thicknesses was formed due to the transition role of the sizing. Based on these results, a sizing mechanism consisting of chemical interaction bonding and physical force absorption was proposed, which provides an efficient and feasible method to solve the poor adhesion between carbon fiber and epoxy matrix.

  3. Interfacial properties, thin film stability and foam stability of casein micelle dispersions.

    PubMed

    Chen, Min; Sala, Guido; Meinders, Marcel B J; van Valenberg, Hein J F; van der Linden, Erik; Sagis, Leonard M C

    2017-01-01

    Foam stability of casein micelle dispersions (CMDs) strongly depends on aggregate size. To elucidate the underlying mechanism, the role of interfacial and thin film properties was investigated. CMDs were prepared at 4°C and 20°C, designated as CMD4°C and CMD20°C. At equal protein concentrations, foam stability of CMD4°C (with casein micelle aggregates) was markedly higher than CMD20°C (without aggregates). Although the elastic modulus of CMD4°C was twice as that of CMD20°C at 0.005Hz, the protein adsorbed amount was slightly higher for CMD20°C than for CMD4°C, which indicated a slight difference in interfacial composition of the air/water interface. Non-linear surface dilatational rheology showed minor differences between mechanical properties of air/water interfaces stabilized by two CMDs. These differences in interfacial properties could not explain the large difference in foam stability between two CMDs. Thin film analysis showed that films made with CMD20°C drained to a more homogeneous film compared to films stabilized by CMD4°C. Large casein micelle aggregates trapped in the thin film of CMD4°C made the film more heterogeneous. The rupture time of thin films was significantly longer for CMD4°C (>1h) than for CMD20°C (<600s) at equal protein concentration. After homogenization, which broke down the aggregates, the thin films of CMD4°C became much more homogeneous, and both the rupture time of thin films and foam stability decreased significantly. In conclusion, the increased stability of foam prepared with CMD4°C appears to be the result of entrapment of casein micelle aggregates in the liquid films of the foam.

  4. Interplay of interfacial noise and curvature-driven dynamics in two dimensions

    NASA Astrophysics Data System (ADS)

    Roy, Parna; Sen, Parongama

    2017-02-01

    We explore the effect of interplay of interfacial noise and curvature-driven dynamics in a binary spin system. An appropriate model is the generalized two-dimensional voter model proposed earlier [M. J. de Oliveira, J. F. F. Mendes, and M. A. Santos, J. Phys. A: Math. Gen. 26, 2317 (1993), 10.1088/0305-4470/26/10/006], where the flipping probability of a spin depends on the state of its neighbors and is given in terms of two parameters, x and y . x =0.5 andy =1 correspond to the conventional voter model which is purely interfacial noise driven, while x =1 and y =1 correspond to the Ising model, where coarsening is fully curvature driven. The coarsening phenomena for 0.5 dynamical behavior of the relevant quantities show characteristic differences from both x =0.5 and 1. The most remarkable result is the existence of two time scales for x ≥xc where xc≈0.7 . On the other hand, we have studied the exit probability which shows Ising-like behavior with a universal exponent for any value of x >0.5 ; the effect of x appears in altering the value of the parameter occurring in the scaling function only.

  5. Effects of surface pressure on the properties of Langmuir monolayers and interfacial water at the air-water interface.

    PubMed

    Lin, Wei; Clark, Anthony J; Paesani, Francesco

    2015-02-24

    The effects of surface pressure on the physical properties of Langmuir monolayers of palmitic acid (PA) and dipalmitoylphosphatidic acid (DPPA) at the air/water interface are investigated through molecular dynamics simulations with atomistic force fields. The structure and dynamics of both monolayers and interfacial water are compared across the range of surface pressures at which stable monolayers can form. For PA monolayers at T = 300 K, the untilted condensed phase with a hexagonal lattice structure is found at high surface pressure, while the uniformly tilted condensed phase with a centered rectangular lattice structure is observed at low surface pressure, in agreement with the available experimental data. A state with uniform chain tilt but no periodic spatial ordering is observed for DPPA monolayers on a Na(+)/water subphase at both high and low surface pressures. The hydrophobic acyl chains of both monolayers pack efficiently at all surface pressures, resulting in a very small number of gauche defects. The analysis of the hydrogen-bonding structure/dynamics at the monolayer/water interface indicates that water molecules hydrogen-bonded to the DPPA head groups reorient more slowly than those hydrogen-bonded to the PA head groups, with the orientational dynamics becoming significantly slower at high surface pressure. Possible implications for physicochemical processes taking place on marine aerosols in the atmosphere are discussed.

  6. Relating emulsion stability to interfacial properties for pharmaceutical emulsions stabilized by Pluronic F68 surfactant.

    PubMed

    Powell, Kristin Conrad; Damitz, Robert; Chauhan, Anuj

    2017-04-15

    We explore mechanisms of emulsion stability for several systems using Pluronic F68 and a range of oils commonly used in pharmaceutics and cosmetics. We report measurements of dynamic emulsion drop size, zeta potential, and creaming time, as well as dynamic interfacial tension and interfacial viscoelasticity. Experiments show that with 1wt% Pluronic F68, soybean oil emulsions were the most stable with no creaming over six months, followed by isopropyl myristate, octanoic acid, and then ethyl butyrate. The eventual destabilization occurred due to the rising of large drops which formed through Ostwald ripening and coalescence. While Ostwald ripening is important, it is not the dominant destabilization mechanism for the time scale of interest in pharmaceutical emulsions. The more significant destabilization mechanism, coalescence, is reduced through surfactant adsorption, which decreases surface tension, increases surface elasticity, and adds a stearic hindrance to collisions. Though the measured values of elasticity obtained using a standard oscillatory pendant drop method did not correlate to emulsion stability, this is because the frequencies for the measurements were orders of magnitude below those relevant to coalescence in emulsions. However, we show that the high frequency elasticity obtained by fitting the surface tension data to a Langmuir isotherm has very good correlation with the emulsion stability, indicating that the elasticity of the interface plays a key role in stabilizing these pharmaceutical formulations. Further, this study highlights how these important high frequency elasticity values can be easily estimated from surface isotherms. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Interfacial properties of water/CO2: a comprehensive description through a Gradient Theory-SAFT-VR Mie approach.

    PubMed

    Lafitte, Thomas; Mendiboure, Bruno; Piñeiro, Manuel M; Bessières, David; Miqueu, Christelle

    2010-09-02

    The Gradient Theory of fluid interfaces is for the first time combined with the SAFT-VR Mie EOS to model the interfacial properties of the water/CO(2) mixture. As a preliminary test of the performance of the coupling between both theories, liquid-vapor interfacial properties of pure water have been determined. The complex temperature dependence of the surface tension of water can be accurately reproduced, and the interfacial thickness is in good agreement with experimental data and simulation results. The water/CO(2) mixture presents several types of interfaces as the liquid water may be in contact with gaseous, liquid, or supercritical CO(2). Here, the interfacial tension of the water/CO(2) mixture is modeled accurately by the gradient theory with a unique value of the crossed influence parameter over a broad range of thermodynamic conditions. The interfacial density profiles show a systematic adsorption of CO(2) in the interface. Moreover, when approaching the saturation pressure of CO(2), a prewetting transition is highlighted. The adsorption isotherm of CO(2) is computed as well in the case of a gas/liquid interface and compared with experimental data. The good agreement obtained is an indirect proof of the consistency of interfacial density profiles computed with the gradient theory for this mixture and confirms that the gradient theory is suitable and reliable to describe the microstructure of complex fluid interfaces.

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

    PubMed

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

    2013-09-21

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

  9. Interfacial Rheological Properties of Contrast Microbubble Targestar P as a Function of Ambient Pressure.

    PubMed

    Kumar, Krishna N; Sarkar, Kausik

    2016-04-01

    In this Technical Note, we determine the interfacial rheological parameters of the encapsulation of the contrast agent Targestar P using ultrasound attenuation. The characteristic parameters are obtained according to two interfacial rheological models. The properties-surface dilatational elasticity (0.09 ± 0.01 N/m) and surface dilatational viscosity (8 ± 0.1E-9 N·s/m)-are found to be of similar magnitude for both models. Contrast microbubbles experience different ambient pressure in different organs. We also measure these parameters as functions of ambient pressure using attenuation measured at different overpressures (0, 100 and 200 mm Hg). For each value of ambient hydrostatic pressure, we determine the rheological properties, accounting for changes in the size distribution caused by the pressure change. We discuss different models of size distribution change under overpressure: pure adiabatic compression or gas exchange with surrounding medium. The dilatational surface elasticity and viscosity are found to increase with increasing ambient pressure.

  10. Interfacial electron transfer dynamics of ru(II)-polypy6ridine sensitized TiO2

    SciTech Connect

    Jakubikova, Elena; Martin, Richard L; Batista, Enrique R; Snoeberger, Robert C; Batista, Victor S

    2009-01-01

    Quantum dynamics simulations combined with density functional theory calculations are applied to study interfacial electron transfer (IET) from pyridine-4-phosphonic acid, [Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 2+} and [Ru(tpy)(bpy)(H{sub 2}O)-Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 4+} into the (101) surface of anatase TiO{sub 2}. IET rate from pyridine-4-phosphonic acid attached to the nanoparticle in bidentate mode ({tau} {approx} 100 fs) is an order of magnitude faster than the IET rate of the adsorbate attached in the monodentate mode ({tau} {approx} 1 ps). Upon excitation with visible light, [Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 2+} attached to TiO{sub 2} in bidentate binding mode will undergo IET with the rate of {approx} 1-10 ps, which is competitive with the excited state decay into the ground state. The probability of electron injection from [Ru(tpy)(bpy)(H{sub 2}O)-Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 4+} is rather low, as the excitation with visible light localizes the excited electron in the tpy-tpy bridge, which does not have favorable coupling with the TiO{sub 2} nanoparticle. The results are relevant to better understanding of the adsorbate features important for promoting efficient interfacial electron transfer into the semiconductor.

  11. Dynamic Ordering Transitions of Liquid Crystals Driven by Interfacial Complexes Formed Between Polyanions and Amphiphilic Polyamines

    PubMed Central

    Kinsinger, Michael I.; Buck, Maren E.; Campos, Fernando

    2011-01-01

    We report the design of an amphiphilic polyamine based on poly(2-alkenyl azlactone) (polymer 1) that strongly couples the formation of polyelectrolyte complexes at aqueous/liquid crystal (LC) interfaces to ordering transitions in the LC. We demonstrate that the addition of a strong anionic polyelectrolyte to aqueous solutions in contact with polymer 1-laden LC interfaces (prepared by Langmuir-Schaefer transfer of monolayers of polymer 1 onto micrometer-thick films of nematic LC) triggers ordering transitions in the LCs. We further demonstrate that changes in the ordering of the LCs (i) are driven by electrostatic interactions between the polyelectrolytes, (ii) involve multivalent interactions between the polyelectrolytes, and (iii) are triggered by reorganization of the hydrophobic side chains of amphiphilic polymer 1 upon formation of the interfacial complexes. The results presented in this paper lead us to conclude that ordering transitions in LCs can be used to provide insights into the structure and dynamics of interfacial complexes formed between polyelectrolytes. PMID:18991416

  12. Physical Explanation of Coupled Cell-Cell Rotational Behavior and Interfacial Morphology: A Particle Dynamics Model

    PubMed Central

    Leong, Fong Yew

    2013-01-01

    Previous studies have reported persistent rotational behavior between adherent cell-cell pairs cultured on micropatterned substrates, and this rotation is often accompanied by a sigmoidal deflection of the cell-cell interface. Interestingly, the cell-cell rotation runs in the opposite reference frame from what could be expected of single cell locomotion. Specifically, the rotation of the cell pair consists of each individual cell protruding from the inwardly regressive arm of the cell-cell interface, and retracting from the other outwardly protrusive arm. To this author’s knowledge, the cause of this elusive behavior has not yet been clarified. Here, we propose a physical model based on particle dynamics, accounting for actomyosin forcing, viscous dissipation, and cortical tension. The results show that a correlation in actomyosin force vectors leads to both persistent rotational behavior and interfacial deflection in a simulated cell cluster. Significantly, the model, without any artificial cues, spontaneously and consistently reproduces the same rotational reference frame as experimentally observed. Further analyses show that the interfacial deflection depends predominantly on cortical tension, whereas the cluster rotation depends predominantly on actomyosin forcing. Together, these results corroborate the hypothesis that both rotational and morphological phenomena are, in fact, physically coupled by an intracellular torque of a common origin. PMID:24268142

  13. Physical explanation of coupled cell-cell rotational behavior and interfacial morphology: a particle dynamics model.

    PubMed

    Leong, Fong Yew

    2013-11-19

    Previous studies have reported persistent rotational behavior between adherent cell-cell pairs cultured on micropatterned substrates, and this rotation is often accompanied by a sigmoidal deflection of the cell-cell interface. Interestingly, the cell-cell rotation runs in the opposite reference frame from what could be expected of single cell locomotion. Specifically, the rotation of the cell pair consists of each individual cell protruding from the inwardly regressive arm of the cell-cell interface, and retracting from the other outwardly protrusive arm. To this author's knowledge, the cause of this elusive behavior has not yet been clarified. Here, we propose a physical model based on particle dynamics, accounting for actomyosin forcing, viscous dissipation, and cortical tension. The results show that a correlation in actomyosin force vectors leads to both persistent rotational behavior and interfacial deflection in a simulated cell cluster. Significantly, the model, without any artificial cues, spontaneously and consistently reproduces the same rotational reference frame as experimentally observed. Further analyses show that the interfacial deflection depends predominantly on cortical tension, whereas the cluster rotation depends predominantly on actomyosin forcing. Together, these results corroborate the hypothesis that both rotational and morphological phenomena are, in fact, physically coupled by an intracellular torque of a common origin.

  14. Liquid-liquid interfacial properties of a symmetrical Lennard-Jones binary mixture

    SciTech Connect

    Martínez-Ruiz, F. J.; Blas, F. J.; Moreno-Ventas Bravo, A. I.

    2015-09-14

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

  15. Liquid-liquid interfacial properties of a symmetrical Lennard-Jones binary mixture

    NASA Astrophysics Data System (ADS)

    Martínez-Ruiz, F. J.; Moreno-Ventas Bravo, A. I.; Blas, F. J.

    2015-09-01

    We determine the interfacial properties of a symmetrical binary mixture of equal-sized spherical Lennard-Jones molecules, σ11 = σ22, with the same dispersive energy between like species, ɛ11 = ɛ22, but different dispersive energies between unlike species low enough to induce phase separation. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janec̆ek [J. Phys. Chem. B 110, 6264 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] and Martínez-Ruiz et al. [J. Chem. Phys. 141, 184701 (2014)], to deal with the interaction energy and microscopic components of the pressure tensor. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of the symmetrical mixture with different cut-off distances rc and in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The liquid-liquid interfacial tension is also evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the test-area methodology. This allows to check the validity of the recent extensions presented to deal with the contributions due to long-range corrections for intermolecular energy and pressure tensor in the case of binary mixtures that exhibit liquid-liquid immiscibility. In addition to the pressure tensor and the surface tension, we also obtain density profiles and coexistence densities and compositions as functions of pressure, at a given temperature. According to our results, the main effect of increasing the cut-off distance rc is to sharpen the liquid-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative minimum in the total density profiles of the symmetrical mixture. This minimum is related with a desorption of the molecules

  16. Liquid-liquid interfacial properties of a symmetrical Lennard-Jones binary mixture.

    PubMed

    Martínez-Ruiz, F J; Moreno-Ventas Bravo, A I; Blas, F J

    2015-09-14

    We determine the interfacial properties of a symmetrical binary mixture of equal-sized spherical Lennard-Jones molecules, σ11 = σ22, with the same dispersive energy between like species, ϵ11 = ϵ22, but different dispersive energies between unlike species low enough to induce phase separation. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janec̆ek [J. Phys. Chem. B 110, 6264 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] and Martínez-Ruiz et al. [J. Chem. Phys. 141, 184701 (2014)], to deal with the interaction energy and microscopic components of the pressure tensor. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of the symmetrical mixture with different cut-off distances rc and in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The liquid-liquid interfacial tension is also evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the test-area methodology. This allows to check the validity of the recent extensions presented to deal with the contributions due to long-range corrections for intermolecular energy and pressure tensor in the case of binary mixtures that exhibit liquid-liquid immiscibility. In addition to the pressure tensor and the surface tension, we also obtain density profiles and coexistence densities and compositions as functions of pressure, at a given temperature. According to our results, the main effect of increasing the cut-off distance rc is to sharpen the liquid-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative minimum in the total density profiles of the symmetrical mixture. This minimum is related with a desorption of the molecules

  17. 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.

  18. Influence of interfacial properties on Ostwald ripening in crosslinked multilayered oil-in-water emulsions.

    PubMed

    Zeeb, Benjamin; Gibis, Monika; Fischer, Lutz; Weiss, Jochen

    2012-12-01

    The influence of interfacial crosslinking, layer thickness and layer density on the kinetics of Ostwald ripening in multilayered emulsions at different temperatures was investigated. Growth rates of droplets were measured by monitoring changes in the droplet size distributions of 0.5% (w/w) n-octane, n-decane, and n-dodecane oil-in-water emulsions using static light scattering. Lifshitz-Slyozov-Wagner theory was used to calculate Ostwald ripening rates. A sequential two step process, based on electrostatic deposition of sugar beet pectin onto fish gelatin or whey protein isolate (WPI) interfacial membranes, was used to manipulate the interfacial properties of the oil droplets. Laccase was added to the fish gelatin-beet pectin emulsions to promote crosslinking of adsorbed pectin molecules via ferulic acid groups, whereas heat was induced to promote crosslinking of WPI and helix coil transitions of fish gelatin. Ripening rates of single-layered, double-layered and crosslinked emulsions increased as the chain length of the n-alkanes decreased. Emulsions containing crosslinked fish gelatin-beet pectin coated droplets had lower droplet growth rates (3.1±0.3×10(-26) m(3)/s) than fish gelatin-stabilized droplets (7.3±0.2×10(-26) m(3)/s), which was attributed to the formation of a protective network. Results suggest that physical or enzymatic biopolymer-crosslinking of interfaces may reduce the molecular transport of alkanes between the droplets in the continuous phase. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. Interfacial Structure, Dynamics, and Transport of Polyelectrolyte Membrane Materials for Fuel Cells

    NASA Astrophysics Data System (ADS)

    Soles, Christopher; Page, K.; Eastman, S.; Kim, S.; Kang, S.; Dura, J.; National Institute of Standards; Technology; Polymers Divison Team; NIST Collaboration

    2011-03-01

    Polymer electrolyte membranes (PEM) fuel cells show promise for a wide range of applications both in the transportation sector and for stationary power production due to their high charge density and low operating temperatures. While the structure and transport of bulk PEMs have been studied extensively, little is known about these materials at interfaces and under confinement, as they exist within the membrane electrode assembly (MEA). Using neutron/ x-ray reflectivity and polarization-modulation infrared reflection-absorption spectroscopy, we have studied the polymer-substrate interfacial structure, swelling, and water transport as function of humidity, surface chemistry, and film thickness. The interfacial structure is highly dependent upon the substrate surface chemistry and the swelling/water diffusivity are suppressed when the PEM is confined to a thin film. This new information will enable researchers to more accurately model the performance of the MEA as current simulations typically rely on bulk property values to predict water and proton transport under these conditions.

  20. Effects of microbial processes on electrolytic and interfacial electrical properties of unconsolidated sediments

    NASA Astrophysics Data System (ADS)

    Abdel Aal, Gamal Z.; Atekwana, Estella A.; Slater, Lee D.; Atekwana, Eliot A.

    2004-06-01

    The effect of microbial processes on electrical properties of unconsolidated sediments was investigated in a laboratory experiment consisting of biotic and abiotic sand columns. The biotic column (nutrient, diesel and bacteria) showed (a) temporal increase in the real, imaginary, and surface conductivity, and (b) temporal decrease in the formation factor. The abiotic columns (nutrient; and nutrient and diesel) showed no significant changes. Increase in microbial population numbers, decrease in organic carbon source, nitrate, and sulfate and increase in dissolved inorganic carbon and fluid conductivity were indicative of microbial activity in the biotic column. We also measure relative increase in the interfacial electrical properties that exceed relative increase in the electrolytic conductivity. Thus changes in the real and imaginary conductivity were induced by microbial processes. These results suggest that interpretation of geoelectrical data from near surface environments should consider effects of microbial processes.

  1. Interfacial properties of a carbyne-rich nanostructured carbon thin film in ionic liquid.

    PubMed

    Bettini, Luca Giacomo; Della Foglia, Flavio; Piseri, Paolo; Milani, Paolo

    2016-03-18

    Nanostructured carbon sp(2) (ns-C) thin films with up to 30% of sp-coordinated atoms (carbynes) were produced in a high vacuum by the low kinetic energy deposition of carbon clusters produced in the gas phase and accelerated by a supersonic expansion. Immediately after deposition the ns-C films were immersed in situ in an ionic liquid electrolyte. The interfacial properties of ns-C films in the ionic liquid electrolyte were characterized by electrochemical impedance spectroscopy and cyclic voltammetry (CV). The so-prepared carbyne-rich electrodes showed superior electric double layer (EDL) capacitance and electric conductivity compared to ns-C electrodes containing only sp(2) carbon, showing the substantial influence of carbynes on the electrochemical properties of nanostructured carbon electrodes.

  2. Interfacial phenomena and dynamic contact angle modulation in microcapillary flows subjected to electroosmotic actuation.

    PubMed

    Chakraborty, Debapriya; Chakraborty, Suman

    2008-09-02

    The dynamic evolution of an incompressible liquid meniscus inside a microcapillary is investigated, under the combined influences of viscous, capillary, intermolecular, pondermotive, and electroosmotic effects. In the limit of small capillary numbers, an advancing meniscus shape is shown to merge smoothly with the precursor film, using matched asymptotic analysis. A scaling relationship is also established for the dynamic contact angle as a nondimensional function of the capillary number and the applied electrical voltage. The analysis is further generalized by invoking a kinetic slip model for overcoming the constraints of meniscus tip singularity. The kinetic slip model is subsequently utilized to analyze the interfacial dynamics from the perspective of the results obtained from the matched asymptotic analysis. A generalization is achieved in this regard, which may provide a sound basis for controlling the topographical features of a dynamically evolving meniscus in a microcapillary subjected to electrokinetic effects. These results are also in excellent agreement with the experimental findings over a wide range of capillary number values.

  3. Improving interfacial, mechanical and tribological properties of alumina coatings on Al alloy by plasma arc heat-treatment of substrate

    NASA Astrophysics Data System (ADS)

    Hou, Guoliang; An, Yulong; Zhao, Xiaoqin; Zhou, Huidi; Chen, Jianmin; Li, Shuangjian; Liu, Xia; Deng, Wen

    2017-07-01

    Plasma sprayed ceramic coatings can be used to improve the mechanical properties and wear resistance of aluminum alloys, but there are still some challenges to effectively increase their interfacial adhesion. Thus we conducted plasma arc-heat treatment (PA-HT) of Al alloy substrate before plasma spraying, hoping to tune the microstructure of Al2O3 coatings and improve their interfacial strength as well as mechanical and tribological properties. The influences of PA-HT on the microstructure of alumina coatings were analyzed by X-ray diffraction, transmission electron microscopy and scanning electron microscopy, while its effect on mechanical and tribological properties were evaluated by a nano-indentation tester and a friction and wear tester. Results demonstrate that a few columnar δ-Al2O3 generated on substrate surface after PA-HT at 200-250 °C can induce the epitaxial growth of γ-Al2O3 grains in Al2O3 coatings, thereby enhancing their interfacial bonding. Besides, elevating substrate temperature can help alumina droplets to melt into the interior of substrate and eliminate holes at the interface, finally increasing the interfacial anchorage force. More importantly, no interfacial holes can allow the heat of droplets to be rapidly transmitted to substrate, which is beneficial to yield smaller crystals in coatings and greatly enhance their strength, hardness and wear resistance.

  4. Density functional theory study of the interfacial properties of Ni/Ni3Si eutectic alloy

    NASA Astrophysics Data System (ADS)

    Zhao, Yuhong; Wen, Zhiqin; Hou, Hua; Guo, Wei; Han, Peide

    2014-06-01

    In order to clarify the heterogeneous nucleation potential of α-Ni grains on Ni3Si particles in Ni-Ni3Si eutectic alloy, the work of adhesion (Wad), fracture toughness (G), interfacial energy (γi), and electronic structure of the index (0 0 1), (1 1 0) and (1 1 1) Ni/Ni3Si interfaces with two different cohesive manners are investigated using first-principles method based on density functional theory. Results indicate that the center site stacking sequence (OM) is preferable to continue the natural stacking sequence of bulk Ni and Ni3Si. Since OM stacking interfaces have larger Wad, G and γi than that of the top site stacking (OT) interfaces. The Ni/Ni3Si (1 1 0) interface with OM stacking has the best mechanical properties. Therefore, the formation of this interface can improve the stability, ductility and fracture toughness of Ni-Ni3Si eutectic alloy. The calculated interfacial energy of Ni/Ni3Si (0 0 1), (1 1 0) and (1 1 1) interfaces with OM stacking proves the excellent nucleation potency of Ni3Si particles for α-Ni phase from thermodynamic considerations. Besides, the electronic structure and chemical bonding of (1 1 0) interface with OM stacking are also discussed.

  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. Magnetic properties and interfacial characteristics of all-epitaxial Heusler-compound stacking structures

    NASA Astrophysics Data System (ADS)

    Yamada, S.; Honda, S.; Hirayama, J.; Kawano, M.; Santo, K.; Tanikawa, K.; Kanashima, T.; Itoh, H.; Hamaya, K.

    2016-09-01

    We study magnetic properties and interfacial characteristics of all-epitaxial D 03-Fe3Si /L 21 - Fe3 -xMnxSi /L 21-Co2FeSi Heusler-compound trilayers grown on Ge(111) by room-temperature molecular beam epitaxy. We find that the magnetization reversal processes can be intentionally designed by changing the chemical composition of the intermediate Fe3 -xMnxSi layers because of their tunable ferromagnetic-paramagnetic phase-transition temperature. From first-principles calculations, interfacial half metallicity in the Co2FeSi layer is nearly expected when the sequence of stacking layers along <111 > of the Fe2MnSi /Co2FeSi interface includes the atomic row of L 21 - or B 2 -ordered structures. We believe that Co2FeSi /Fe2MnSi /Co2FeSi trilayer systems stacked along <111 > will open a new avenue for high-performance current-perpendicular-to-plane giant magnetoresistive devices with Heusler compounds.

  7. Effect of excluded volume interactions on the interfacial properties of colloid-polymer mixtures

    NASA Astrophysics Data System (ADS)

    Fortini, Andrea; Bolhuis, Peter G.; Dijkstra, Marjolein

    2008-01-01

    We report a numerical study of equilibrium phase diagrams and interfacial properties of bulk and confined colloid-polymer mixtures using grand canonical Monte Carlo simulations. Colloidal particles are treated as hard spheres, while the polymer chains are described as soft repulsive spheres. The polymer-polymer, colloid-polymer, and wall-polymer interactions are described by density-dependent potentials derived by Bolhuis and Louis [Macromolecules 35, 1860 (2002)]. We compared our results with those of the Asakura-Oosawa-Vrij model [J. Chem. Phys. 22, 1255 (1954); J. Polym Sci 33, 183 (1958); Pure Appl. Chem. 48, 471 (1976)] that treats the polymers as ideal particles. We find that the number of polymers needed to drive the demixing transition is larger for the interacting polymers, and that the gas-liquid interfacial tension is smaller. When the system is confined between two parallel hard plates, we find capillary condensation. Compared with the Asakura-Oosawa-Vrij model, we find that the excluded volume interactions between the polymers suppress the capillary condensation. In order to induce capillary condensation, smaller undersaturations and smaller plate separations are needed in comparison with ideal polymers.

  8. Effect of the Incorporation of Nanosized Titanium Dioxide on the Interfacial Properties of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine Langmuir Monolayers.

    PubMed

    Guzmán, Eduardo; Santini, Eva; Ferrari, Michele; Liggieri, Libero; Ravera, Francesca

    2017-09-27

    The effect of the incorporation of hydrophilic titanium dioxide (TiO2) nanoparticles on the interfacial properties of Langmuir monolayers of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) has been evaluated combining interfacial thermodynamic studies, dilatational rheology, and Brewster angle microscopy (BAM). The results show that the TiO2 nanoparticles are able to penetrate DPPC layers, modifying the organization of the molecules and, consequently, the phase behavior and viscoelastic properties of the systems. Measurements of dilational viscoelasticity against the frequency have been performed, using the oscillatory barrier method, at different values of the surface pressure corresponding to different degrees of compression of the monolayer. The presence of TiO2 nanoparticles also affects the dynamic response of the monolayer modifying both the quasi-equilibrium dilatational elasticity and the high frequency limit of the viscoelastic modulus. The principal aim of this work is to understand the fundamental physicochemical bases related to the incorporation of specific nanoparticles of technological interest into the interfacial layer with biological relevance such as phospholipid layers. This can provide information on potential adverse effects of nanoparticles for health and the environment.

  9. Determination of interfacial mechanical properties of ceramic composites by the compression of micro-pillar test specimens

    SciTech Connect

    Shih, Chunghao; Katoh, Yutai; Leonard, Keith J.; Bei, Hongbin; Lara-Curzio, Edgar

    2013-03-23

    A novel method to determine the fiber-matrix interfacial properties of ceramic matrix composites is proposed and evaluated; where micro- pillar samples containing inclined fiber/matrix interfaces were prepared from a SiC fiber reinforced SiC matrix composites then compression-tested using the nano-indentation technique. This new test method employs a simple geometry and mitigates the uncertainties associated with complex stress state in the conventional single filament push-out method for the determination of interfacial properties. Based on the test results using samples with different interface orientations , the interfacial debond shear strength and the internal friction coefficient are explicitly determined and compared with values obtained by other test methods.

  10. Interfacial rheology in complex flow

    NASA Astrophysics Data System (ADS)

    Martin, Jeffrey; Hudson, Steven

    2009-03-01

    Multiphase liquid systems are omnipresent in and essential to everyday life, e.g. foods, pharmaceutics, cosmetics, paints, oil recovery, etc. The morphology and stability of such systems depend on dynamic interfacial properties and processes. Typical methods utilized to measure such interfacial properties often employ drops that are much larger and flows that are much simpler than those encountered in typical processing applications. A microfluidic approach is utilized to measure dynamic structure and kinetics in multiphase systems with drop sizes comparable to those encountered in applications and flow complexity that is easily adjustable. The internal circulation and deformation of an aqueous droplet in clear mineral oil is measured using particle tracers and a detailed shape analysis, which is capable of measuring sub-micron deviations in drop shape. Deformation dynamics, detailed drop shape, interfacial tension, and internal circulation patterns and velocities are measured in Poiseuille and transient elongational flows. Flow kinematics are adjusted by varying the microchannel geometry, relative drop size, and drop height. The effects of confinement on interfacial dynamics and circulation patterns and velocities are also explored.

  11. Interfacial dynamics of two immiscible fluids in spatially periodic porous media: The role of substrate wettability

    NASA Astrophysics Data System (ADS)

    Mondal, Pranab Kumar; DasGupta, Debabrata; Chakraborty, Suman

    2014-07-01

    We delineate the contact line dynamics of two immiscible fluids in a medium having spatially periodic porous structures. The flow is driven by an external applied pressure gradient. We bring out the combined consequences of the solid fraction distribution and the substrate wettability on the resulting dynamics of the contact line, by employing phase-field formalism. We capture the sequence of spatiotemporal events leading to formation of liquid bridges by trapping a small amount of displaced phase fluid between two consecutive porous blocks, as dictated by the combinations of substrate wettability and solid fraction. We also demonstrate the existence of a regime of complete interfacial recovery, depending on the parametric space of the governing parameters under concern. Our results essentially demonstrate the intricate mechanisms by virtue of which the wettabilities of the substrates alter the dynamical evolutions of interfaces and the subsequent shapes and sizes of the adsorbed dispersed phases, bearing far-ranging consequences in several practical applications ranging from oil recovery to groundwater flow.

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

    PubMed

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

    2017-05-17

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

  13. Comparing interfacial dynamics in protein-protein complexes: an elastic network approach.

    PubMed

    Zen, Andrea; Micheletti, Cristian; Keskin, Ozlem; Nussinov, Ruth

    2010-08-08

    The transient, or permanent, association of proteins to form organized complexes is one of the most common mechanisms of regulation of biological processes. Systematic physico-chemical studies of the binding interfaces have previously shown that a key mechanism for the formation/stabilization of dimers is the steric and chemical complementarity of the two semi-interfaces. The role of the fluctuation dynamics at the interface of the interacting subunits, although expectedly important, proved more elusive to characterize. The aim of the present computational study is to gain insight into salient dynamics-based aspects of protein-protein interfaces. The interface dynamics was characterized by means of an elastic network model for 22 representative dimers covering three main interface types. The three groups gather dimers sharing the same interface but with good (type I) or poor (type II) similarity of the overall fold, or dimers sharing only one of the semi-interfaces (type III). The set comprises obligate dimers, which are complexes for which no structural representative of the free form(s) is available. Considerations were accordingly limited to bound and unbound forms of the monomeric subunits of the dimers. We proceeded by first computing the mobility of amino acids at the interface of the bound forms and compare it with the mobility of (i) other surface amino acids (ii) interface amino acids in the unbound forms. In both cases different dynamic patterns were observed across interface types and depending on whether the interface belongs to an obligate or non-obligate complex. The comparative investigation indicated that the mobility of amino acids at the dimeric interface is generally lower than for other amino acids at the protein surface. The change in interfacial mobility upon removing "in silico" the partner monomer (unbound form) was next found to be correlated with the interface type, size and obligate nature of the complex. In particular, going from the

  14. Void initiation from interfacial debonding of spherical silicon particles inside a silicon-copper nanocomposite: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Cui, Yi; Chen, Zengtao

    2017-02-01

    Silicon particles with diameters from 1.9 nm to 30 nm are embedded in a face-centered-cubic copper matrix to form nanocomposite specimens for simulation. The interfacial debonding of silicon particles from the copper matrix and the subsequent growth of nucleated voids are studied via molecular dynamics (MD). The MD results are examined from several different perspectives. The overall mechanical performance is monitored by the average stress-strain response and the accumulated porosity. The ‘relatively farthest-traveled’ atoms are identified to characterize the onset of interfacial debonding. The relative displacement field is plotted to illustrate both subsequent interfacial debonding and the growth of a nucleated void facilitated by a dislocation network. Our results indicate that the initiation of interfacial debonding is due to the accumulated surface stress if the matrix is initially dislocation-free. However, pre-existing dislocations can make a considerable difference. In either case, the dislocation emission also contributes to the subsequent debonding process. As for the size effect, the debonding of relatively larger particles causes a drop in the stress-strain curve. The volume fraction of second-phase particles is found to be more influential than the size of the simulation box on the onset of interfacial debonding. The volume fraction of second-phase particles also affects the shape of the nucleated void and, therefore, influences the stress response of the composite.

  15. Interfacial properties of Quillaja saponins and its use for micellisation of lutein esters.

    PubMed

    Tippel, Janine; Lehmann, Maren; von Klitzing, Regine; Drusch, Stephan

    2016-12-01

    Natural food colourants, colouring foods and bioactive food ingredients need to be solubilised for their incorporation in food. Aim of the present study was to investigate the micelle-forming properties of saponins from Quillaja saponaria Mollina (QS) in order to solubilise a lutein ester extract for its incorporation in food matrices. QS showed a high surface activity and functionality with respect to micellisation as derived from interfacial tension measurements and subsequent data fitting to the classical Frumkin model. The composition of the aqueous phase affected the lutein ester incorporation as revealed by particle size, zeta potential and colour measurements. In terms of morphology of lutein ester loaded saponin micelles (LMS), cryo-TEM micrographs showed depending on the composition of the medium both, spherical and elongated branched micelles.

  16. Interfacial properties of hydrosoluble polymers. Final report, June 15, 1993--June 15, 1996

    SciTech Connect

    1996-12-31

    During this period, the authors treated a myriad of problems associated with the interfacial properties of macromolecules. Many of them concerned indirect interactions between surfaces engendered by intervening species. The issues ranged from colloidal forces to membrane induced coupling between embedded macromolecules (membrane-bound proteins). This report presents summaries of the following papers published as a result of this study: membrane interactions with polymers and colloids; escape transitions and force laws for compressed polymer mushrooms; interaction between finite-sized particles and end grafted polymers; one long chain among shorter chains--the Flory approach revisited; conformation of star polymers in high molecular weight solvents; membrane-induced interactions between inclusions; filled polymer brushes--a hydrodynamic analogy; polymer adsorption at liquid/air interfaces under lateral pressure; flow induced instability of the interface between a fluid and a gel at low Reynolds number; and fluctuation-induced forces in stacked fluid membranes.

  17. Optical properties of a conjugated-polymer-sensitised solar cell: the effect of interfacial structure.

    PubMed

    Drumm, Daniel W; Bilic, A; Tachibana, Y; Miller, A; Russo, S P

    2015-06-14

    Dye-sensitised solar cells (DSSCs) have sparked considerable interest over two decades. Recently, a method of polymer-wire sensitisation was demonstrated; the polymer is suggested to form a hole transport pathway (wire) following initial charge separation. We predict the optical properties of this polymer in various interfacial configurations, including the effects of chain length and attachment to {100} or {101} TiO2 facets. Contrary to most DSSCs, the {100} facet model best describes the experimental spectrum, predicting a relative thickness of 5.7 ± 0.2 μm, although {101} attachment, if implemented, may improve collection efficiency. Long chains are optimal, and stable attachment sites show minimal differences to absorbance in the major solar emission (visible) band. Combinations of {100}, {101}, and pseudo-bulk TiO2 models in three-parameter fits to experiment confirm the relative importance of the {100} facet.

  18. Electrical properties of the amorphous interfacial layer between Al electrodes and epitaxial NiO films

    SciTech Connect

    Hyuck Jang, Jae; Kwon, Ji-Hwan; Kim, Miyoung; Ran Lee, Seung; Char, Kookrin

    2012-04-23

    The amorphous interfacial layer (a-IL) between Al electrode and epitaxial NiO films were studied using electron energy-loss spectroscopy (EELS) and energy-dispersive x-ray spectroscopy. Two distinct properties were found in the a-IL, i.e., a lower metallic and an upper insulating layer. EELS results revealed that the metallic Ni atoms were responsible for the conducting nature of the lower oxide amorphous layer. The resistance behavior of Al/a-IL/epi-NiO was changed from a high to a low resistance state after forming process. The resistance change could be explained by the formation of a nanocrystalline metal alloy in the insulating amorphous layer.

  19. Impact of Interfacial Defects on the Properties of Monolayer Transition Metal Dichalcogenide Lateral Heterojunctions.

    PubMed

    Cao, Zhen; Harb, Moussab; Lardhi, Sheikha; Cavallo, Luigi

    2017-03-28

    We explored the impact of interfacial defects on the stability and optoelectronic properties of monolayer transition metal dichalcogenide lateral heterojunctions using a density functional theory approach. As a prototype, we focused on the MoS2-WSe2 system and found that even a random alloy-like interface with a width of less than 1 nm has only a minimal impact on the band gap and alignment compared to the defect-less interface. The largest impact is on the evolution of the electrostatic potential across the monolayer. Similar to defect-less interfaces, a small number of defects results in an electrostatic potential profile with a sharp change at the interface, which facilitates exciton dissociation. Differently, a large number of defects results in an electrostatic potential profile switching smoothly across the interface, which is expected to reduce the capability of the heterojunction to promote exciton dissociation. These results are generalizable to other transition metal dichalcogenide lateral heterojunctions.

  20. The Effect of Interfacial Properties and Liquid Flow on the Stability of Powder Islands

    NASA Astrophysics Data System (ADS)

    Ong, Xin Yi; Taylor, Spencer E.; Ramaioli, Marco

    2017-06-01

    This study aims at understanding the interplay between the interfacial properties of the powder grains and the characteristics of the liquid flow used to disperse them, in order to obtain an effective dispersion of a powder in a liquid, avoiding air entrainment. The dispersion of grain "rafts" and powder islands "stacks" was investigated both on a static and on a moving air-liquid interface. Powder wicking prevents the formation of a powder island when the grain contact angle is below a critical contact angle. Above the critical contact angle, a powder island forms and grows to a critical depth that depends on grain radius and contact angle. Imposing a flow on the air-liquid interface can either promote water impregnation, reducing the depth of the powder island or destabilise the whole island. In the latter case, the island sinks, forming a heterogeneous powder structure that is wet outside and dry inside.

  1. Interfacial structure, thermodynamics, and electrostatics of aqueous methanol solutions via molecular dynamics simulations using charge equilibration models.

    PubMed

    Patel, Sandeep; Zhong, Yang; Bauer, Brad A; Davis, Joseph E

    2009-07-09

    We present results from molecular dynamics simulations of methanol-water solutions using charge equilibration force fields to explicitly account for nonadditive electronic interaction contributions to the potential energy. We study solutions across the concentration range from 0.1 to 0.9 methanol mole fraction. At dilute concentrations, methanol density is enhanced at the liquid-vapor interface, consistent with previous molecular dynamics and experimental studies. Interfacial thickness exhibits a monotonic increase with increasing methanol mole fraction, while surface tensions display monotonic decrease with methanol concentration, in qualitative agreement with experimental data and previous molecular dynamics predictions using polarizable force fields. In terms of interfacial structure, in keeping with predictions of traditional force fields, there is a unique preferential orientation of methanol molecules at the interface. Moreover, there is a free energetic preference for methanol molecules at the interface as evidenced by potential of mean force calculations. The pmf calculations suggest an interfacial state with 0.8 kcal/mol stability relative to the bulk, again in qualitative agreement with previous simulation and experimental studies. Interfacial potentials based on double integration of total charge density range from -610 to -330 mV over the dilute to concentrated regimes, respectively. The preponderance of methanol at the interface at all mole fractions gives rise to a dominant methanol contribution to the total interfacial potential. Interestingly, there is a transition of the water surface potential contribution from negative to positive upon the transition from methanol mole fraction of 0.1 to 0.2. The dipole and quadrupole contributions to the water component of the total interfacial potential are effectively of equal magnitude and opposite sign, thus cancelling one another. We compute the in-plane component of the dielectric permittivity along the

  2. Removing adsorbed heavy metal ions from sand surfaces via applying interfacial properties of rhamnolipid.

    PubMed

    Haryanto, Bode; Chang, Chien-Hsiang

    2015-01-01

    In this study, the interfacial properties of biosurfactant rhamnolipid were investigated and were applied to remove adsorbed heavy metal ions from sand surfaces with flushing operations. The surface tension-lowering activity, micelle charge characteristic, and foaming ability of rhamnolipid were identified first. For rhamnolipid in water, the negatively charged characteristic of micelles or aggregates was confirmed and the foaming ability at concentrations higher than 40 mg/L was evaluated. By using the rhamnolipid solutions in a batch washing approach, the potential of applying the interfacial properties of rhamnolipid to remove adsorbed copper ions from sand surfaces was then demonstrated. In rhamnolipid solution flushing operations for sand-packed medium, higher efficiency was found for the removal of adsorbed copper ions with residual type than with inner-sphere interaction type, implying the important role of interaction type between the copper ion and the sand surface in the removal efficiency. In addition, the channeling effect of rhamnolipid solution flow in the sand-packed medium was clearly observed in the solution flushing operations and was responsible for the low removal efficiency with low contact areas between solution and sand. By using rhamnolipid solution with foam to flush the sand-packed medium, one could find that the channeling effect of the solution flow was reduced and became less pronounced with the increase in the rhamnolipid concentration, or with the enhanced foaming ability. With the reduced channeling effect in the flushing operations, the removal efficiency for adsorbed copper ions was significantly improved. The results suggested that the foam-enhanced rhamnolipid solution flushing operation was efficient in terms of surfactant usage and operation time.

  3. Toward an Understanding of the Microstructure and Interfacial Properties of PIMs/ZIF-8 Mixed Matrix Membranes.

    PubMed

    Benzaqui, Marvin; Semino, Rocio; Menguy, Nicolas; Carn, Florent; Kundu, Tanay; Guigner, Jean-Michel; McKeown, Neil B; Msayib, Kadhum J; Carta, Mariolino; Malpass-Evans, Richard; Le Guillouzer, Clément; Clet, Guillaume; Ramsahye, Naseem A; Serre, Christian; Maurin, Guillaume; Steunou, Nathalie

    2016-10-12

    A study integrating advanced experimental and modeling tools was undertaken to characterize the microstructural and interfacial properties of mixed matrix membranes (MMMs) composed of the zeolitic imidazolate framework ZIF-8 nanoparticles (NPs) and two polymers of intrinsic microporosity (PIM-1 and PIM-EA-TB). Analysis probed both the initial ZIF-8/PIM-1 colloidal suspensions and the final hybrid membranes. By combination of dynamic light scattering (DLS) and transmission electron microscopy (TEM) analytical and imaging techniques with small-angle X-ray scattering (SAXS), the colloidal suspensions were shown to consist mainly of two distinct kinds of particles, namely, polymer aggregates of about 200 nm in diameter and densely packed ZIF-8-NP aggregates of a few 100 nm in diameter with a 3 nm thick polymer top-layer. Such aggregates are likely to impart the granular texture of ZIF-8/PIMs MMMs as shown by SEM-XEDS analysis. At the molecular scale, modeling studies showed that the surface coverage of ZIF-8 NPs by both polymers appears not to be optimal with the presence of microvoids at the interfaces that indicates only a moderate compatibility between the polymer and ZIF-8. This study shows that the microstructure of MMMs results from a complex interplay between the ZIF-8/PIM compatibility, solvent, surface chemistry of the ZIF-8 NPs, and the physicochemical properties of the polymers such as molecular structure and rigidity.

  4. Poly(N-isopropylacrylamide) microgels at the oil-water interface: interfacial properties as a function of temperature.

    PubMed

    Monteux, Cécile; Marlière, Claire; Paris, Pauline; Pantoustier, Nadège; Sanson, Nicolas; Perrin, Patrick

    2010-09-07

    Highly monodisperse poly(N-isopropylacrylamide), PNiPAM, microgels were prepared by the conventional radical polymerization of NiPAM in the presence of dimethylamino ethyl methacrylate (DMAEMA) monomers at various concentrations. The effect of DMAEMA on the polymerization of PNiPAM microgels was examined at constant initiator (V50) and cross-linker (MBA) concentrations. The presence of DMAEMA in the synthesis batch allows for the preparation of PNiPAM microgels with controlled size and a narrow size distribution. The oil(dodecane)/water interfacial properties of the model PNiPAM microgels were then investigated. The pendant drop technique was used to measure the interfacial tensions as a function of temperature. Over the whole range of temperature (20-45 degrees C), the interfacial tension remains low (on the order of 17 mN/m) and goes through a minimum (12 mN/m) at a temperature of about 34 degrees C, which well matches the volume phase transition temperature (VPTT) of PNiPAM microgels. Below the VPTT, the decrease in the interfacial tension with temperature is likely to be due to the adsorption of dense layers because of the decrease of the excluded volume interactions. Above the VPTT, we suggest that the increase in the interfacial tension with temperature comes from the adsorption of loosely packed PNiPAM microgels. We also studied the effect of temperature on the stability of emulsions. Dodecane in water emulsions, which form at ambient temperature, are destabilized as the temperature exceeds the VPTT. In light of the interfacial tension results, we suggest that emulsion destabilization arises from the adsorption of aggregates above the VPTT and not from an important desorption of microgels. Aggregate adsorption would bring a sufficiently high number of dodecane molecules into contact with water to induce coalescence without changing the interfacial tension very much.

  5. Vapor-liquid critical and interfacial properties of square-well fluids in slit pores.

    PubMed

    Jana, Subimal; Singh, Jayant K; Kwak, Sang Kyu

    2009-06-07

    Vapor-liquid phase equilibria of square-well (SW) fluids of variable interaction range: lambdasigma=1.25, 1.75, 2.0, and 3.0 in hard slit pores are studied by means of grand-canonical transition-matrix Monte Carlo (GC-TMMC) simulation. Critical density under confinement shows an oscillatory behavior as slit width, H, reduced from 12sigma to 1sigma. Two linear regimes are found for the shift in the critical temperature with the inverse in the slit width. The first regime is seen for H>2.0sigma with linear increase in the slope of shift in the critical temperature against inverse slit width with increasing interaction range. Subsequent decrease in H has little consequence on the critical temperature and it remains almost constant. Vapor-liquid surface tensions of SW fluids of variable well extent in a planar slit pore of variable slit width are also reported. GC-TMMC results are compared with that from slab based canonical Monte Carlo and molecular dynamics techniques and found to be in good agreement. Although, vapor-liquid surface tension under confinement is found to be lower than the bulk surface tension, the behavior of surface tension as a function of temperature is invariant with the variable pore size. Interfacial width, xi, calculated using a hyperbolic function increases with decreasing slit width at a given temperature, which is contrary to what is being observed recently for cylindrical pores. Inverse scaled interfacial width (xi/H), however, linearly increases with increase in the scaled temperature (T(c,bulk)-T)/T(c,bulk).

  6. Ultrafast interfacial charge transfer dynamics in dye-sensitized and quantum dot solar cell

    NASA Astrophysics Data System (ADS)

    Ghosh, Hirendra N.

    2013-02-01

    Dye sensitized solar cell (DSSC) appeared to be one of the good discovery for the solution of energy problem. We have been involved in studying ultrafast interfacial electron transfer dynamics in DSSC using femtosecond laser spectroscopy. However it has been realized that it is very difficult to design and develop higher efficient one, due to thermodynamic limitation. Again in DSSC most of the absorbed photon energy is lost as heat within the cell, which apart from decreasing the efficiency also destabilizes the device. It has been realized that quantum dot solar cell (QDSC) are the best bet where the sensitizer dye molecules can be replaced by suitable quantum dot (QD) materials in solar cell. The quantum-confinement effect in semiconductors modifies their electronic structure, which is a very important aspect of these materials. For photovoltaic applications, a long-lived charge separation remains one of the most essential criteria. One of the problems in using QDs for photovoltaic applications is their fast charge recombination caused by nonradiative Auger processes, which occur predominantly at lower particle sizes due to an increase in the Coulomb interaction between electrons and holes. Various approaches, such as the use of metal-semiconductor composites, semiconductor-polymer composite, and semiconductor core-shell heterostructures, have been attempted to minimize the fast recombination between electrons and holes. To make higher efficient solar devices it has been realised that it is very important to understand charge carrier and electron transfer dynamics in QD and QD sensitized semiconductor nanostructured materials. In the present talk, we are going to discuss on recent works on ultrafast electron transfer dynamics in dye-sensitized TiO2 nanoparticles/film [1-12] and charge (electron/hole) transfer dynamics in quantum dot core-shell nano-structured materials [13-17].

  7. Improved interfacial properties of GaAs MOS capacitor with NH3-plasma-treated ZnON as interfacial passivation layer

    NASA Astrophysics Data System (ADS)

    Gong, Jingkang; Xu, Jingping; Liu, Lu; Lu, Hanhan; Liu, Xiaoyu; Feng, Yaoyao

    2017-09-01

    The GaAs MOS capacitor was fabricated with HfTiON as high-k gate dielectric and NH3-plasma-treated ZnON as interfacial passivation layer (IPL), and its interfacial and electrical properties are investigated compared to its counterparts with ZnON IPL but no NH3-plasma treatment and without ZnON IPL and no plasma treatment. Experimental results show that low interface-state density near midgap (1.17 × 1012 cm‑2 eV‑1) and small gate leakage current density have been achieved for the GaAs MOS device with the stacked gate dielectric of HfTiON/ZnON plus NH3-plasma treatment. These improvements could be ascribed to the fact that the ZnON IPL can effectively block in-diffusion of oxygen atoms and out-diffusion of Ga and As atoms, and the NH3-plasma treatment can provide not only N atoms but also H atoms and NH radicals, which is greatly beneficial to removal of defective Ga/As oxides and As-As band, giving a high-quality ZnON/GaAs interface. Project supported by the National Natural Science Foundation of China (Nos. 61176100, 61274112, 61404055).

  8. Interfacial and foaming properties of prolylenglycol alginates. Effect of degree of esterification and molecular weight.

    PubMed

    Baeza, Rosa; Sanchez, Cecilio Carrera; Pilosof, Ana M R; Patino, Juan M Rodríguez

    2004-08-01

    In the present work we have studied the characteristics of propylene glycol alginates (PGA) adsorption at the air-water interface and the viscoelastic properties of the films in relation to its foaming properties. To evaluate the effect of the degree of PGA esterification and viscosity, different commercial samples were studied--Kelcoloid O (KO), Kelcoloid LVF (KLVF) and Manucol ester (MAN). The temperature (20 degrees C) and pH (7.0) were maintained constant. For time-dependent surface pressure measurements and surface dilatational properties of adsorbed PGA at the air-water interface an automatic drop tensiometer was used. The foam was generated by whipping and then the foam capacity and stability was determined. The results reveal a significant interfacial activity for PGA due to the hydrophobic character of the propylene glycol groups. The kinetics of adsorption at the air-water interface can be monitored by the diffusion and penetration of PGA at the interface. The adsorbed PGA film showed a high viscoelasticity. The surface dilatational modulus depends on the PGA and its concentration in the aqueous phase. Foam capacity of PGA solutions increased in the order KO > MAN > KLVF, which followed the increase in surface pressure and the decrease in the viscosities of PGA solutions. The stability of PGA foams monitored by the drainage rate and collapse time follows the order MAN > KLVF > KO. The foam stability depends on the combined effect of molecular weight/degree of esterification of PGA, solution viscosity and viscoelasticity of the adsorbed PGA film.

  9. Impact of Interfacial Roughness on the Sorption Properties of Nanocast Polymers

    SciTech Connect

    Sridhar, Manasa; Gunugunuri, Krishna R.; Hu, Naiping; Motahari, Ahmad; Zuo, Xiaobing; Schaefer, Dale W.; Thiel, Stephen W.; Smirniotis, Panagiotis G.

    2016-03-16

    Nanocasting is an emerging method to prepare organic polymers with regular, nanometer pores using inorganic templates. This report assesses the impact of imperfect template replication on the sorption properties of such polymer castings. Existing X-ray diffraction data show that substantial diffuse scattering exists in the small-angle region even though TEM images show near perfect lattices of uniform pores. To assess the origin of the diffuse scattering, the morphology of the phenol - formaldehyde foams (PFF) was investigated by small-angle X-ray scattering (SAXS). The observed diffuse scattering is attributed to interfacial roughness due to fractal structures. Such roughness has a profound impact on the sorption properties. Conventional pore- filling models, for example, overestimate protein sorption capacity. A mathematical framework is presented to calculate sorption properties based on observed morphological parameters. The formalism uses the surface fractal dimension determined by SAXS in conjunction with nitrogen adsorption isotherms to predict lysozyme sorption. The results are consistent with measured lysozyme loading.

  10. Impact of Interfacial Roughness on the Sorption Properties of Nanocast Polymers

    DOE PAGES

    Sridhar, Manasa; Gunugunuri, Krishna R.; Hu, Naiping; ...

    2016-03-16

    Nanocasting is an emerging method to prepare organic polymers with regular, nanometer pores using inorganic templates. This report assesses the impact of imperfect template replication on the sorption properties of such polymer castings. Existing X-ray diffraction data show that substantial diffuse scattering exists in the small-angle region even though TEM images show near perfect lattices of uniform pores. To assess the origin of the diffuse scattering, the morphology of the phenol - formaldehyde foams (PFF) was investigated by small-angle X-ray scattering (SAXS). The observed diffuse scattering is attributed to interfacial roughness due to fractal structures. Such roughness has a profoundmore » impact on the sorption properties. Conventional pore- filling models, for example, overestimate protein sorption capacity. A mathematical framework is presented to calculate sorption properties based on observed morphological parameters. The formalism uses the surface fractal dimension determined by SAXS in conjunction with nitrogen adsorption isotherms to predict lysozyme sorption. The results are consistent with measured lysozyme loading.« less

  11. The Impact of Chemical Substitutions on Interfacial Properties of REE Orthophosphates (Monazite, Xenotime)

    NASA Astrophysics Data System (ADS)

    Gamage McEvoy, J.; Thibault, Y.

    2016-12-01

    Mineral surface properties strongly influence liquid-solid interface behaviour in the presence of various ligands, and can significantly affect processes of natural (ex. fluids, melts) and industrial (ex. oil recovery) relevance. Many Rare Earth Element (REE)-bearing minerals display extensive solid solutions resulting in significant chemical variations which influence their crystal and surface properties and, can consequently impact the interfacial features of their interaction with substances such as organic molecules (i.e. reactivity and sorption). For example, the surface charge properties of some REE orthophosphates show an uncharacteristically wide variation in reported values, where large differences in literature are commonly attributed to compositional differences between samples. However the impact of these chemical substitutions remains largely unknown. As such, the aim of this research was to systematically investigate the influence of mineralogical variation within the compositional space of the REE orthophosphates on their surface chemistry and resulting interaction with organic molecules. To better isolate the chemical, structural, and morphological variables, the synthesis of REE orthophosphate crystals along a number of defined substitutions was conducted, and their surface chemistry characteristics benchmarked against well-characterized natural monazite and xenotime from various localities. The interaction of these crystal surfaces with model organic molecules (long chain carboxylic acids and alkyl hydroxamic acids, respectively) was then studied and characterized via surface (X-ray photoelectron) and near-surface (vibrational) spectroscopic techniques. The implications of crystal surface-organic molecule interactions to mineral processing through flotation were also experimentally investigated.

  12. Effect of the interfacial layer composition on the properties of emulsion creams.

    PubMed

    Mackie, Alan R; Ridout, Michael J; Moates, Graham; Husband, Fiona A; Wilde, Peter J

    2007-07-11

    We have quantified observed differences in the microstructure and rheology of creaming emulsions stabilized by protein and low molecular weight surfactants. In this study, we made two sets of emulsions from a single parent emulsion, which differed only in their interfacial composition (i.e., either protein or surfactant). The protein studied was whey protein isolate. The zeta potential of the surfactant-stabilized emulsion was controlled by mixing anionic (SDS) and nonionic (Brij 35) surfactants to match the zeta potential of the protein-stabilized emulsion. Despite this, ultrasonic creaming measurements and confocal microscopy showed that the structures within the cream layers were different between the two sets of emulsions. The protein-stabilized emulsions appeared to slow or arrest the packing within the cream, leading to a lower density network of emulsion droplets, whereas the surfactant emulsion droplets rearranged more quickly into a well-packed, concentrated cream layer. Rheological analysis of the creams showed that despite the protein-stabilized emulsions having a lower dispersed phase volume fraction, their elastic modulus was approximately 30 times greater than that of a comparable surfactant-stabilized emulsion. These differences were caused by the ability of the protein to form a highly viscoelastic interfacial network around the droplets which may include intermolecular covalent cross-links. At close range the adhesive nature of the interaction between the layers contributes to the microstructure and rheology of concentrated emulsions. This is the first time that such well-defined emulsion systems have been studied in detail both noninvasively to look at the impact on creaming and also invasively to look at the impact on bulk rheological properties.

  13. Characterization of the surface and interfacial properties of the lamina splendens

    NASA Astrophysics Data System (ADS)

    Rexwinkle, Joe T.; Hunt, Heather K.; Pfeiffer, Ferris M.

    2017-06-01

    Joint disease affects approximately 52.5 million patients in the United States alone, costing 80.8 billion USD in direct healthcare costs. The development of treatment programs for joint disease and trauma requires accurate assessment of articular cartilage degradation. The articular cartilage is the interfacial tissue between articulating surfaces, such as bones, and acts as low-friction interfaces. Damage to the lamina splendens, which is the articular cartilage's topmost layer, is an early indicator of joint degradation caused by injury or disease. By gaining comprehensive knowledge on the lamina splendens, particularly its structure and interfacial properties, researchers could enhance the accuracy of human and animal biomechanical models, as well as develop appropriate biomimetic materials for replacing damaged articular cartilage, thereby leading to rational treatment programs for joint disease and injury. Previous studies that utilize light, electron, and force microscopy techniques have found that the lamina splendens is composed of collagen fibers oriented parallel to the cartilage surface and encased in a proteoglycan matrix. Such orientation maximizes wear resistance and proteoglycan retention while promoting the passage of nutrients and synovial fluid. Although the structure of the lamina splendens has been explored in the literature, the low-friction interface of this tissue remains only partially characterized. Various functional models are currently available for the interface, such as pure boundary lubrication, thin films exuded under pressure, and sheets of trapped proteins. Recent studies suggest that each of these lubrication models has certain advantages over one another. Further research is needed to fully model the interface of this tissue. In this review, we summarize the methods for characterizing the lamina splendens and the results of each method. This paper aims to serve as a resource for existing studies to date and a roadmap of the

  14. Characterization of the surface and interfacial properties of the lamina splendens

    NASA Astrophysics Data System (ADS)

    Rexwinkle, Joe T.; Hunt, Heather K.; Pfeiffer, Ferris M.

    2017-01-01

    Joint disease affects approximately 52.5 million patients in the United States alone, costing 80.8 billion USD in direct healthcare costs. The development of treatment programs for joint disease and trauma requires accurate assessment of articular cartilage degradation. The articular cartilage is the interfacial tissue between articulating surfaces, such as bones, and acts as low-friction interfaces. Damage to the lamina splendens, which is the articular cartilage's topmost layer, is an early indicator of joint degradation caused by injury or disease. By gaining comprehensive knowledge on the lamina splendens, particularly its structure and interfacial properties, researchers could enhance the accuracy of human and animal biomechanical models, as well as develop appropriate biomimetic materials for replacing damaged articular cartilage, thereby leading to rational treatment programs for joint disease and injury. Previous studies that utilize light, electron, and force microscopy techniques have found that the lamina splendens is composed of collagen fibers oriented parallel to the cartilage surface and encased in a proteoglycan matrix. Such orientation maximizes wear resistance and proteoglycan retention while promoting the passage of nutrients and synovial fluid. Although the structure of the lamina splendens has been explored in the literature, the low-friction interface of this tissue remains only partially characterized. Various functional models are currently available for the interface, such as pure boundary lubrication, thin films exuded under pressure, and sheets of trapped proteins. Recent studies suggest that each of these lubrication models has certain advantages over one another. Further research is needed to fully model the interface of this tissue. In this review, we summarize the methods for characterizing the lamina splendens and the results of each method. This paper aims to serve as a resource for existing studies to date and a roadmap of the

  15. Molecular dynamics investigation of the physisorption and interfacial characteristics of NBR chains on carbon nanotubes with different characteristics

    NASA Astrophysics Data System (ADS)

    Li, Kun; Gu, Boqin

    2017-07-01

    The present study investigates the physisorption and interfacial interactions between multiwalled carbon nanotubes (MWNTs) with different characteristics, including different numbers of walls and different functional groups, and acrylonitrile-butadiene rubber (NBR) polymer chains based on molecular dynamics simulations performed using modeled MWNT/NBR compound systems. The effects of the initial orientation of NBR chains and their relative distances to nanotubes, number of nanotube layers, and the surface functional groups of nanotubes on nanotube/polymer interactions are examined. Analysis is conducted according to the final configuration obtained in conjunction with the binding energy (Eb), radius of gyration (Rg) and end-to-end distance (h). The results show that the final conformations of NBR chains adsorbed on MWNT surfaces is associated with the initial relative angle of the NBR chains and their distance from the nanotubes. For non-functionalized MWNTs, Eb is almost directly proportional to Rg under equivalent parameters. Moreover, it is observed that functional groups hinder the wrapping of NBR chains on the MWNT surfaces. This indicates that functional groups do not always benefit the macro-mechanical properties of the composites. Moreover, the type of the major interaction force has been dramatically changed into electrostatic force from vdW force because of functionalization.

  16. Single-molecule resolution of protein structure and interfacial dynamics on biomaterial surfaces

    PubMed Central

    McLoughlin, Sean Yu; Kastantin, Mark; Schwartz, Daniel K.; Kaar, Joel L.

    2013-01-01

    A method was developed to monitor dynamic changes in protein structure and interfacial behavior on surfaces by single-molecule Förster resonance energy transfer. This method entails the incorporation of unnatural amino acids to site-specifically label proteins with single-molecule Förster resonance energy transfer probes for high-throughput dynamic fluorescence tracking microscopy on surfaces. Structural changes in the enzyme organophosphorus hydrolase (OPH) were monitored upon adsorption to fused silica (FS) surfaces in the presence of BSA on a molecule-by-molecule basis. Analysis of >30,000 individual trajectories enabled the observation of heterogeneities in the kinetics of surface-induced OPH unfolding with unprecedented resolution. In particular, two distinct pathways were observed: a majority population (∼ 85%) unfolded with a characteristic time scale of 0.10 s, and the remainder unfolded more slowly with a time scale of 0.7 s. Importantly, even after unfolding, OPH readily desorbed from FS surfaces, challenging the common notion that surface-induced unfolding leads to irreversible protein binding. This suggests that protein fouling of surfaces is a highly dynamic process because of subtle differences in the adsorption/desorption rates of folded and unfolded species. Moreover, such observations imply that surfaces may act as a source of unfolded (i.e., aggregation-prone) protein back into solution. Continuing study of other proteins and surfaces will examine whether these conclusions are general or specific to OPH in contact with FS. Ultimately, this method, which is widely applicable to virtually any protein, provides the framework to develop surfaces and surface modifications with improved biocompatibility. PMID:24235137

  17. In-phase and out-of-phase tensile properties of polypropylene/mica composites modified by a novel industrial waste based interfacial agent. Responses at the α and β transitions of the polymer phase

    NASA Astrophysics Data System (ADS)

    García-Martínez, Jesús María; Collar, Emilia P.

    2016-05-01

    This work deals with the study of the evolution with temperature of the in-phase and the out-of-phase responses of polypropylene/mica composites with improved interfacial interactions due to the presence of an industrial waste based interfacial modifier. This one is a p-phenylen-bis-maleamic acid grafted atactic polypropylene (aPP-pPBMA) with 15% w/w grafted pPBMA (5.0.10-4 g.mol-1). This work has been two-fold planned. On one hand, we have used dynamic mechanical parameters to evidence the interfacial improve caused by the addition of the interfacial modifier (aPP-pPBMA). The other purpose has been to obtain a mathematical to predict the overall behaviour of the heterogeneous system for whatever temperature considered. In our case we have merely used the dynamic-mechanical analysis (DMA) for just the α and β transition temperatures. Hence, a Box-Wilson experimental design considering the amount of mica particles and of interfacial agent as independent variables was used to obtain the mathematical model. The study has been tackled by considering the different transitions of the polypropylene matrix in the temperature interval scanned and further application of the Statistical Design of Experiments (sDOE) to each transition temperature in order to make forecasts for the property (E', E") as a function of the composite components and of the type of temperature dependent relaxation phenomena taking place.

  18. Dynamic Properties of Polyurea

    NASA Astrophysics Data System (ADS)

    Youssef, George H.

    The aim of this thesis was to understand the dynamic behavior of polyurea at rates of loading that is outside the reach of plate impact and split-Hopkinson bar experiments. This was motivated by the desire to design polyurea-based armors against hypervelocity impacts such as those arising from shaped charges and explosively formed projectiles with speeds in the range of 9,000 to 30,000 ft/s. By employing the laser-induced stress waves, the tensile strength and fracture energy of polyurea were measured at peak strain rate of 10 7s-1. Tensile strength of 93.1 ±5 MPa and fracture energy values of 6.75 (± 0.5) J/m2 were measured. It was also shown that the Time Temperature Superposition Principle holds for polyurea even at strain rates as high as 105s-1. This strain rate is two orders of magnitude higher than those reported recently by the Caltech group (Zhao, et al.). This important finding suggests that blast simulations of large-scale structures and those of armors involving polyurea can be based on constitutive data gathered under quasi-static conditions. This is quite powerful. With a view towards future reach, preliminary experiments were performed to inquire how polyurca behaves in the presence of other armor materials when subjected to impacts in the nanoseconds timeframe. That is, does it synergistically add its intrinsic impact-mitigating properties to other known defeat mechanisms? To this end, sections in which I to 2 mm thick polyurea layers were sandwiched between glass, acrylic, polyurethane, Al, Steel, and PMMA plates were subjected to laser-generated stress waves. The sections were evaluated based on the amplitude and time profile of the stress wave that exited the sections. Both metal plates resulted in a significant reduction in the transmitted stress wave amplitude. This was due to the large impedance mismatch between the polyurea and the metal which essentially resulted in trapping of the stress wave within the incident substrate. An unexpected

  19. Solvent blends can control cationic reversed micellar interdroplet interactions. The effect of n-heptane:benzene mixture on BHDC reversed micellar interfacial properties: droplet sizes and micropolarity.

    PubMed

    Agazzi, Federico M; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2011-10-27

    We have investigated, for the first time, the effect of the composition of the nonpolar organic media on the benzyl-n-hexadecyl-dimethylammonium chloride (BHDC) reversed micelles (RMs) properties at fixed temperature. To achieve this goal we have used the solvatochromic behavior of 1-methyl-8-oxyquinolinium betaine (QB) as absorption probe and dynamic light scattering (DLS), to monitor droplet sizes, interfacial micropolarity, and sequestrated water structure of water/BHDC/n-heptane:benzene RMs. DLS results confirm the formation of the water/BHDC/n-heptane:benzene RMs at every n-heptane mole fraction (X(Hp)) investigated, that is, X(Hp) = 0.00, 0.13, 0.21, 0.30, and 0.38. Also, DLS was used to measure the RMs diffusion coefficient and to calculate the apparent droplet hydrodynamic diameter (d(App)) at different compositions of the nonpolar organic medium. The data suggest that as the n-heptane content increases, the interdroplet attractive interactions also increase with the consequent increment in the droplet size. Moreover, the interdroplet attractive interactions can be "switched on (increased)" or "switched off (decreased)" by formulation of appropriate n-heptane:benzene mixtures. Additionally, QB spectroscopy was used to obtain the "operational" critical micellar concentration (cmc) and to investigate both the RMs interfacial micropolarity and the sequestrated water structure in every RMs studied. The results show that BHDC RMs are formed at lower surfactant concentration when n-heptane or water content increases. When the interdroplet interaction "switches on", the RMs droplet sizes growth expelling benzene molecules from the RMs interface, favoring the water-BHDC interaction at the interface with the consequent increases in the interfacial micropolarity. Therefore, changing the solvent blend is possible to affect dramatically the interfacial micropolarity, the droplet sizes and the structure of the entrapped water.

  20. Synergistic effect of ZnO nanoparticles and triblock copolymer surfactant on the dynamic and equilibrium oil-water interfacial tension.

    PubMed

    Moghadam, Tahereh Fereidooni; Azizian, Saeid

    2014-09-07

    The present study reports the effects of non-ionic surfactant Pluronic F-127 on the equilibrium and dynamic oil-water interfacial tension in the presence of ZnO nanoparticles. The results show that in the presence of nanoparticles, the decrease of interfacial tension is more. The cooperative behavior of F-127 and ZnO nanoparticles especially at low concentrations increases the surfactant efficiency in lowering the interfacial tension. Statistical rate theory (SRT) and mixed diffusion-kinetic controlled model were used for modeling the dynamic interfacial tension data. The modeling results show that the mechanism of surfactant adsorption is controlled with the mixed diffusion-kinetic model. In addition, the influence of the solution pH on the interfacial tension was investigated. Finally, the effects of F-127 on the contact angle in the absence and presence of ZnO was compared.

  1. Ice-nucleating bacteria control the order and dynamics of interfacial water.

    PubMed

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A; Fischer, Sean A; Pfaendtner, Jim; Backus, Ellen H G; Nagata, Yuki; Fröhlich-Nowoisky, Janine; Schmüser, Lars; Mauri, Sergio; Scheel, Jan F; Knopf, Daniel A; Pöschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-04-01

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

  2. Ice-nucleating bacteria control the order and dynamics of interfacial water

    SciTech Connect

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; Fischer, Sean A.; Pfaendtner, Jim; Backus, Ellen H. G.; Nagata, Yuki; Frohlich-Nowoisky, Janine; Schmuser, Lars; Mauri, Sergio; Scheel, Jan F.; Knopf, Daniel A.; Poschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-04-22

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. Finally, the freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

  3. Macroscopic investigation of water volume effects on interfacial dynamic behaviors between clathrate hydrate and water.

    PubMed

    Cha, Minjun; Couzis, Alexander; Lee, Jae W

    2013-05-14

    This study investigated the effects of the water volume on the interfacial dynamics between cyclopentane (CP) hydrate and water droplet in a CP/n-decane oil mixture. The adhesion force between CP hydrate and various water droplets was determined using the z-directional microbalance. Through repetition of precise measurements over several cycles from contact to detachment, we observed abnormal wetting behaviors in the capillary bridge during the retraction process when the water drop volume is larger than 100 μL. With the increase in water droplet volumes, the contact force between CP hydrate and water also increases up to 300 μL. However, there is a dramatic reduction of increasing rate in the contact forces over 300 μL of water droplet. With the addition of the surfactants of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) to the water droplet, the contact force between CP hydrate and solution droplet exhibits a lower value and a transition volume of the contact force comes with a smaller solution volume of 200 μL. The water volume effects on the liquid wetting of the probe and the size of capillary bridges provide important insight into hydrate growth and aggregation/agglomeration in the presence of free water phase inside gas/oil pipelines.

  4. All-Electrical Measurement of Interfacial Dzyaloshinskii-Moriya Interaction Using Collective Spin-Wave Dynamics.

    PubMed

    Lee, Jong Min; Jang, Chaun; Min, Byoung-Chul; Lee, Seo-Won; Lee, Kyung-Jin; Chang, Joonyeon

    2016-01-13

    Dzyaloshinskii-Moriya interaction (DMI), which arises from the broken inversion symmetry and spin-orbit coupling, is of prime interest as it leads to a stabilization of chiral magnetic order and provides an efficient manipulation of magnetic nanostructures. Here, we report all-electrical measurement of DMI using propagating spin wave spectroscopy based on the collective spin wave with a well-defined wave vector. We observe a substantial frequency shift of spin waves depending on the spin chirality in Pt/Co/MgO structures. After subtracting the contribution from other sources to the frequency shift, it is possible to quantify the DMI energy in Pt/Co/MgO systems. The result reveals that the DMI in Pt/Co/MgO originates from the interfaces, and the sign of DMI corresponds to the inversion asymmetry of the film structures. The electrical excitation and detection of spin waves and the influence of interfacial DMI on the collective spin-wave dynamics will pave the way to the emerging field of spin-wave logic devices.

  5. Diffusion behavior in a liquid-liquid interfacial crystallization by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Kitayama, Akira; Yamanaka, Shinya; Kadota, Kazunori; Shimosaka, Atsuko; Shirakawa, Yoshiyuki; Hidaka, Jusuke

    2009-11-01

    Interfacial crystallization, such as surface crystallization in solution (solid-liquid) and liquid-liquid crystallization, gives us an asymmetric reaction field and is a technique for morphology control of crystals. In the liquid-liquid crystallization, the concentration distribution of solute ions and solvent molecules at the liquid-liquid interface directly relates to nucleation, crystal growth, and crystal morphology. Nonequilibrium molecular dynamics (MD) simulations have been performed at interfaces in NaCl solution/1-butanol and KCl solution/1-butanol system in order to clarify diffusion behavior of solute ions and solvent molecules. As simulation results, the hydrated solute ions were dehydrated with the diffusion of water from solution phase into 1-butanol phase. The different dehydration behaviors between NaCl and KCl solution can be also obtained from MD simulation results. Aggregated ions or clusters were formed by the dehydration near the solution/1-butanol interface. By comparison on the normalized number of total solute ions, the size and number of generated cluster in KCl solution/1-butanol interface are larger than those in the NaCl system. This originates in the difference hydration structures in the each solute ion.

  6. Ice-nucleating bacteria control the order and dynamics of interfacial water

    PubMed Central

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; Fischer, Sean A.; Pfaendtner, Jim; Backus, Ellen H. G.; Nagata, Yuki; Fröhlich-Nowoisky, Janine; Schmüser, Lars; Mauri, Sergio; Scheel, Jan F.; Knopf, Daniel A.; Pöschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-01-01

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy. PMID:27152346

  7. Structure and vibrational dynamics of interfacial Sn layers in Sn/Si multilayers

    NASA Astrophysics Data System (ADS)

    Cuenya, B. Roldan; Keune, W.; Sturhahn, W.; Toellner, T. S.; Hu, M. Y.

    2001-12-01

    The structure and vibrational dynamics of room-temperature-grown nanoscale Sn/amorphous (a-)Si multilayers have been studied by x-ray diffraction, Raman scattering, 119Sn Mössbauer spectroscopy, and 119Sn nuclear-resonant inelastic x-ray scattering (NRIXS) of synchrotron radiation. With increasing Sn-layer thickness, the formation of β-Sn was observed, except at the Sn/Si interfaces, where a 10-Å-thick metastable pure amorphous-α-Sn-like layer remains stabilized. By means of NRIXS we have measured the Sn-projected vibrational density of states (VDOS) in these multilayers (in particular, at the interfaces), and in 500-Å-thick epitaxial α-Sn films on InSb(001) as a reference. Further, the Sn-specific Lamb-Mössbauer factor (f factor), mean kinetic energy per atom, mean atomic force constant, and vibrational entropy per atom were obtained. The VDOS of the amorphous-α-Sn-like interface layer is observed to be distinctly different from that of (bulk) α-Sn and β-Sn, and its prominent vibrational energies are found to scale with those of amorphous Ge and Si. The observed small difference in vibrational entropy (ΔS/kB=+0.17+/-0.05 per atom) between α-Sn and interfacial amorphous-α-like Sn does not account for the stability of the latter phase.

  8. Ice-nucleating bacteria control the order and dynamics of interfacial water

    DOE PAGES

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; ...

    2016-04-22

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering onmore » the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. Finally, the freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.« less

  9. Interfacial dynamics in pressure-driven two-layer laminar channel flow with high viscosity ratios.

    PubMed

    Matar, O K; Lawrence, C J; Sisoev, G M

    2007-05-01

    The large-scale dynamics of an interface separating two immiscible fluids in a channel is studied in the case of large viscosity contrasts. A long-wave analysis in conjunction with the Kármán-Polhausen method to approximate the velocity profile in the less viscous fluid is used to derive a single equation for the interface. This equation accounts for the presence of interfacial stress, capillarity, and viscous retardation as well as inertia in the less viscous fluid layer where the flow is considered to be quasistatic; the equation is shown to reduce to a Benney-type equation and the Kuramoto-Sivashinskiy equation in the relevant limits. The solutions of this equation are parametrized by an initial thickness ratio h0 and a dimensionless parameter S , which measures the relative significance of inertial to capillary forces. A parametric continuation technique is employed, which reveals that nonuniqueness of periodic solutions is possible in certain regions of (h0,S) space. Transient numerical simulations are also reported, whose results demonstrate good agreement with the bifurcation structure obtained from the parametric continuation results.

  10. Investigation of the effect of coal particle sizes on the interfacial and rheological properties of coal-water slurry fuels: Final report, July 1, 1994-June 30, 1996

    SciTech Connect

    Kihm, K.D.

    1996-10-01

    The scope of the project is two fold: (1) examining particle size effect on interfacial properties of CWS fuels by measuring static and dynamic surface tension properties of specially prepared CWS samples containing different ranges of coal particle sizes, and (2) studying the effect of particle size on CWS atomization characteristics by measuring mean diameters of several different CWS sprays generated by sonic air blasting. The results show that both static and dynamic surface tensions decrease with increasing coal particle size and mean droplet diameter of CW-S sprays also decreases with increasing coal particle size. Based on the experimental evidence we conjecture that three different energies are competing in slurry atomization: (1) the internal capillary holding between particles and water, (2) the interfacial surface tensile energy at the slurry surface contacting air, and (3) the external air blast shear energy acting against the former two energies. The internal capillary holding force decreases with increasing particle size. This force is believed to play a major role in determining the effect of particle size on CWS atomization.

  11. Diffusion Bonding of TA15 and Ti2AlNb Alloys: Interfacial Microstructure and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Li, Ping; Ji, Xiaohu; Xue, Kemin

    2017-03-01

    TA15 and Ti2AlNb alloys were joined by diffusion welding. The influence of holding time on morphology and mechanical properties of the joint was studied under two conditions of different bonding pressure and temperature. The interface structure was analyzed by BSE and EDS. The mechanical properties of joints were tested. The results show that the typical interfacial microstructure consists of lath α-phase (TA15 alloy)/flake α phase + α-interfacial phase + α2 phase/B2-rich phase/Ti2AlNb alloy. When bonding at 920 °C and 15 MPa with increasing holding time, the interface microstructure evolves into flake α phase and distributes as a basket-weave and the interfacial coarse spherical α phase distributes as a line. α2 phase and O phase disappear gradually while the content of the B2 phase increases. The tensile strength of the joints is 870, 892 and 903 MPa, for 120, 150 and 210 min holding time, respectively, while the elongation rises as well. When bonding at 940 °C and 10 MPa with increasing holding time, the interfacial area includes more Widmanstatten structure and B2 phase. The tensile strength of joints decreases from 921 to 908 MPa, while the elongation increases from 12 to 15.5%, for holding 120 and 210 min, respectively. The tendency of plastic fracture also increases with holding time for both temperature-pressure combinations.

  12. Thermoelectric properties of a ferromagnet-superconductor hybrid junction: Role of interfacial Rashba spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Dutta, Paramita; Saha, Arijit; Jayannavar, A. M.

    2017-09-01

    We investigate thermoelectric properties of a ferromagnet-superconductor hybrid structure with Rashba spin-orbit interaction and delta function potential barrier at the interfacial layer. The exponential rise of thermal conductance with temperature manifests a crossover temperature scale separating two opposite behaviors of it with the change of polarization in the ferromagnet whereas the inclusion of an interfacial Rashba spin-orbit field results in a nonmonotonic behavior of it with the strength of the Rashba field. We employ scattering matrix approach to determine the amplitudes of all the scattering processes possible at the interface to explain the thermoelectric properties of the device. We examine Seebeck effect and show that higher thermopower can be achieved when the polarization of the ferromagnet tends towards the half-metallic limit. It can be enhanced even for lower polarization in the presence of the finite potential barrier. In the presence of interfacial Rashba spin-orbit interaction, the Seebeck coefficient rises with the increase of barrier strength and polarization at weak or moderate interfacial Rashba field. From the application perspective, we compute the figure of merit and show that z T ˜4 -5 with higher polarization of the ferromagnet both in absence and presence of weak or moderate Rashba spin-orbit interaction along with the scalar potential barrier.

  13. A Quantitative Exploration of the Effect of Interfacial Phenomena on the Thermomechanical Properties of Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Natarajan, Bharath

    Polymer nanocomposites (PNC) are complex material systems in which the prevailing length scales, i.e., the particle size, radii of gyration of the polymer and the interparticle spacing, converge. This convergence leads to an increased dominance of the interface polymer over bulk properties, when compared to conventional "microcomposites". The development of fascinating nanoscopic filler materials (C60, nanotubes, graphene, quantum dots) along with this potential gain in interfacial area has fueled the expansion of PNCs. Nanocomposites literature has demonstrated a myriad of potential chemistries and self assembled structures that could significantly impact a diverse range of applications. However, most noteworthy results in this field are serendipitous and/or are outcomes of resource-intensive "trial and error" experiments supplemented by intuition. Intuition suggests, qualitatively, that the properties of PNCs depend on the individual properties of the participating species, the interphase and the spatial distribution of filler particles. However, the individual roles of these parameters are difficult to identify, since they are interrelated due to their co-dependence on the chemical constitution of the filler and matrix. A quantitative unifying picture is yet to emerge and the commercialization of this material class has been severely hampered by the lack of design rules and structure-property constitutive relationships that would aid in the prediction of bulk properties. In this thesis, a quantitative understanding of interfacial phenomena was sought and structure-property relationships between the filler/matrix interface chemistry and the dispersion and thermomechanical properties of PNCs were obtained by systematic experiments on 2 distinct kinds of nanocomposite systems (a) Enthalpic short silane modified fillers and (b) Entropic long polymer chain grafted filler embedded PNCs. In order to quantitatively understand the role of enthalpic compatibility, an

  14. On the ability of molecular dynamics simulation and continuum electrostatics to treat interfacial water molecules in protein-protein complexes

    PubMed Central

    Copie, Guillaume; Cleri, Fabrizio; Blossey, Ralf; Lensink, Marc F.

    2016-01-01

    Interfacial waters are increasingly appreciated as playing a key role in protein-protein interactions. We report on a study of the prediction of interfacial water positions by both Molecular Dynamics and explicit solvent-continuum electrostatics based on the Dipolar Poisson-Boltzmann Langevin (DPBL) model, for three test cases: (i) the barnase/barstar complex (ii) the complex between the DNase domain of colicin E2 and its cognate Im2 immunity protein and (iii) the highly unusual anti-freeze protein Maxi which contains a large number of waters in its interior. We characterize the waters at the interface and in the core of the Maxi protein by the statistics of correctly predicted positions with respect to crystallographic water positions in the PDB files as well as the dynamic measures of diffusion constants and position lifetimes. Our approach provides a methodology for the evaluation of predicted interfacial water positions through an investigation of water-mediated inter-chain contacts. While our results show satisfactory behaviour for molecular dynamics simulation, they also highlight the need for improvement of continuum methods. PMID:27905545

  15. 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.

  16. An evaluation of the interfacial bond properties between carbon phenolic and glass phenolic composites

    NASA Technical Reports Server (NTRS)

    Jordan, Kelvin; Clinton, Raymond; Jeelani, Shaik

    1989-01-01

    The effects of moisture and surface finish on the mechanical and physical properties of the interfacial bond between the carbon/phenolic (C/P) and glass/phenolic (G/P) composite materials are presented. Four flat panel laminates were fabricated using the C/P and G/P materials. Of the four laminates, one panel was fabricated in which the C/P and G/P materials were cured simultaneously. It was identified as the cocure. The remaining laminates were processed with an initial simultaneous cure of the three C/P billets. Two surface finishes, one on each half, were applied to the top surface. Prior to the application and cure of the G/P material to the machined surface of the three C/P panels, each was subjected to the specific environmental conditioning. Types of conditioning included: (1) nominal fabrication environment, (2) a prescribed drying cycle, and (3) a total immersion in water at 160 F. Physical property tests were performed on specimens removed from the C/P materials of each laminate for determination of the specific gravity, residual volatiles and and resin content. Comparisons of results with shuttle solid rocket motor (SRM) nozzle material specifications verified that the materials used in fabricating the laminates met acceptance criteria and were representative of SRM nozzle materials. Mechanical property tests were performed at room temperature on specimens removed from the G/P, the C/P and the interface between the two materials for each laminate. The double-notched shear strength test was used to determine the ultimate interlaminar shear strength. Results indicate no appreciable difference in the C/P material of the four laminates with the exception of the cocure laminate, where 20 percent reduction in the strength was observed. The most significant effect and the ultimate strength was significantly reduced in the wet material. No appreciable variation was noted between the surface finishes in the wet laminate.

  17. Heat-induced aggregation of thylakoid membranes affect their interfacial properties.

    PubMed

    Östbring, Karolina; Rayner, Marilyn; Albertsson, Per-Åke; Erlanson-Albertsson, Charlotte

    2015-04-01

    Many of our most popular lipid containing foods are in emulsion form. These foods are often highly palatable with high caloric density, that subsequently increases the risk of overconsumption and possibly lead to obesity. Regulating the lipid bioavailability of high-fat foods is one approach to prevent overconsumption. Thylakoids, the chloroplast membrane, creates a barrier around lipid droplets, which prolong lipolysis and increase satiety as demonstrated both in animal and human studies. However, a reduced lipase inhibiting capacity has been reported after heat treatment but the mechanism has not yet been fully established. The aim of this study was to investigate thylakoids' emulsifying properties post heat-treatment and possible links to alterations in lipase inhibiting capacity and chlorophyll degradation. Heat-treatment of thylakoids at either 60 °C, 75 °C or 90 °C for time interval ranging from 15 s to 4 min reduced ability to stabilise emulsions, having increased lipid droplets sizes, reduced emulsification capacity, and elevated surface load as consequence. Emulsifying properties were also found to display a linear relationship to both chlorophyll and lipase inhibiting capacity. The correlations support the hypothesis that heat-treatment induce chlorophyll degradation which promote aggregation within proteins inside the thylakoid membrane known to play a decisive role in interfacial processes. Therefore, heat-treatment of thylakoids affects both chlorophyll content, lipase inhibiting capacity and ability to stabilise the oil-water interface. Since the thylakoid's appetite reducing properties are a surface-related phenomenon, the results are useful to optimize the effect of thylakoids as an appetite reducing agent.

  18. Interfacial sliding properties of bone screw materials and their effect on screw fixation strength.

    PubMed

    Koistinen, Arto P; Korhonen, Hannu; Kröger, Heikki; Lappalainen, Reijo

    2014-09-05

    This study examined the effect of interfacial sliding and test material properties on the fixation strength and insertional properties of self-tapping bone screws. Various substitute materials (polyacetal [POM], poly(methyl methacrylate) [PMMA] and E-glass-filled Epoxy [Sawbones®]) for human bone were evaluated, and the results were compared with the findings for cadaver bone.
 Initial coefficient of friction (CoF) of the screw material stainless steel AISI316 was tested using a pin-on-disk apparatus, and the screws were exposed to pullout tests after insertion torque tests. The effect of a smooth diamond-like carbon (DLC) coating was studied by applying the coating on both CoF test balls and bone screws.
 Mechanical properties of test blocks strongly correlated to both pullout strength and insertion torque of the screws: for noncoated 2.7-mm screws, tensile strength correlated to pullout strength and insertion torque, with Pearson correlation coefficients r=0.977 and r=0.738, respectively. In contrast, CoF correlated strongly to screw insertion torque but not to pullout strength in bone substitute materials (for noncoated 2.7-mm screws, r=0.652 and r=0.248, respectively). There were no significant differences in CoF using noncoated and DLC-coated screw materials against bone substitutes.
 Proper materials for in vitro testing help in evaluating the biomechanics of the implants in advance. However, choosing the material needs attention, as their ability to model human bone depends on test type.

  19. Interfacial Reaction and Die Attach Properties of Zn-Sn High-Temperature Solders

    NASA Astrophysics Data System (ADS)

    Kim, Seongjun; Kim, Keun-Soo; Kim, Sun-Sik; Suganuma, Katsuaki

    2009-02-01

    Interfacial reaction and die attach properties of Zn- xSn ( x = 20 wt.%, 30 wt.%, and 40 wt.%) solders on an aluminum nitride-direct bonded copper substrate were investigated. At the interface with Si die coated with Au/TiN thin layers, the TiN layer did not react with the solder and worked as a good protective layer. At the interface with Cu, CuZn5, and Cu5Zn8 IMC layers were formed, the thicknesses of which can be controlled by joining conditions such as peak temperature and holding time. During multiple reflow treatments at 260°C, the die attach structure was quite stable. The shear strength of the Cu/solder/Cu joint with Zn-Sn solder was about 30 MPa to 34 MPa, which was higher than that of Pb-5Sn solder (26 MPa). The thermal conductivity of Zn-Sn alloys of 100 W/m K to 106 W/m K was sufficiently high and superior to those of Au-20Sn (59 W/m K) and Pb-5Sn (35 W/m K).

  20. Interfacial and mechanical property analysis of waste printed circuit boards subject to thermal shock.

    PubMed

    Li, Jinhui; Duan, Huabo; Yu, Keli; Wang, Siting

    2010-02-01

    Waste printed circuit boards (PCBs) are the focal points for handling electric and electronic waste. In this paper, a thermal shock method was used to pretreat waste PCBs for the improvement of crushing performance. The influence of the thermal shock process on interfacial modification and mechanical property attenuation of PCB waste was studied. The appearance and layer spacing of the basal plane began to change slightly when the temperature reached 200 degrees C. By 250 degrees C, apparent bulging, cracking, and delamination were observed. However, pyrolysis of PCBs occurred when the temperature reached 275 degrees C, where PCBs were carbonized. The thermogravimetric analysis of PCB particles under vacuum showed that 270 degrees C was the starting point of pyrolysis. The tensile and impact strength of PCBs were reduced as shock temperature rose gradually, with a reduction by 2.6 and 16.5%, respectively, at 250 degrees C from its unheated strength. The PCBs that were heated to 250 degrees C achieved 100% liberation, increasing linearly from 13.6% for unheated PCBs through a single-level shear-crusher (2-mm mesh) and resulting in an obvious reduction of 9.5% (dB) in dust and noise at 250 degrees C. These parameters could be helpful for establishing the operational setup for industrial-scale facilities with the aim of achieving a compact process and a highly efficient recovery for waste PCBs compared with those of the traditional combination mechanical technologies.

  1. The control of stoichiometry in Epitaxial semiconductor structures. Interfacial Chemistry: Property relations. A workshop review

    NASA Technical Reports Server (NTRS)

    Bachmann, Klaus J.

    1995-01-01

    A workshop on the control of stoichiometry in epitaxial semiconductor structures was held on August 21-26, 1995 in the hotel Stutenhaus at Vesser in Germany. The secluded location of the workshop in the forest of Thuringia and its informal style stimulated extensive private discussions among the participants and promoted new contacts between young scientists from Eastern and Western Europe and the USA. Topics addressed by the presentations were interactions of precursors to heteroepitaxy and doping with the substrate surface, the control of interfacial properties under the conditions of heteroepitaxy for selected materials systems, methods of characterization of interfaces and native point defects in semiconductor heterostructures and an in depth evaluation of the present status of the control and characterization of the point defect chemistry for one specific semiconductor (ZnGeP2), including studies of both heterostructures and bulk single crystals. The selected examples of presentations and comments given here represent individual choices - made by the author to highlight major points of the discussions.

  2. Ripening during magnetite nanoparticle synthesis: Resulting interfacial defects and magnetic properties

    NASA Astrophysics Data System (ADS)

    Barker, Alex J.; Cage, Brant; Russek, Stephen; Stoldt, Conrad R.

    2005-09-01

    The structure and magnetic properties of magnetite (Fe3O4) nanoparticles synthesized by a solvothermal processing route are investigated. The nanoparticles are grown from the single organometallic precursor Fe(III) acetylacetonate in trioctylamine (TOA) solvent at 260 °C, with and without the addition of heptanoic acid (HA) as a stabilizing agent. From the temporal particle size distributions, x-ray-diffraction patterns, high-resolution transmission electron microscope tilt series experiments, and superconducting quantum interference device magnetometry, we demonstrate that HA, a strong Lewis acid stabilizing agent, slows growth processes during ripening thus reducing the formation of interfacial defects, which we observe in the TOA-only synthesis. Nanoparticles grown with HA remain single crystalline for long growth times (up to 24 h), show a focused particle size distribution for intermediate growth times (3 h), and possess a higher magnetic anisotropy (15.8×104 J/m3) than particles grown without the additional stabilizing agent. The reduced magnetic anisotropy value for the magnetite nanoparticles grown in TOA only (1.29×104 J/m3) is attributed to polycrystallinity induced by the uncontrolled ripening process. This work may have significance for contrast enhancement in magnetic resonance imaging.

  3. Ultrasonic Spot and Torsion Welding of Aluminum to Titanium Alloys: Process, Properties and Interfacial Microstructure

    NASA Astrophysics Data System (ADS)

    Balle, Frank; Magin, Jens

    Hybrid lightweight structures shape the development of future vehicles in traffic engineering and the aerospace industry. For multi-material concepts made out of aluminum and titanium alloys, the ultrasonic welding technique is an alternative effective joining technology. The overlapped structures can be welded in the solid state, even without gas shielding. In this paper the conventional ultrasonic spot welding with longitudinal oscillation mode is compared to the recent ultrasonic torsion welding with a torsional mode at 20 kHz working frequency. For each technique the process parameters welding force, welding energy and oscillation amplitude were optimized for the hybrid joints using design of experiments. Relationships between the process parameters, mechanical properties and related welding zone should be understood. Central aspects of the research project are microscopic studies of the joining zone in cross section and extensive fracture surface analysis. Detailed electron microscopy and spectroscopy of the hybrid interface help to understand the interfacial formation during ultrasonic welding as well as to transfer the gained knowledge for further multi-metal joints.

  4. Control of interfacial properties of Pr-oxide/Ge gate stack structure by introduction of nitrogen

    NASA Astrophysics Data System (ADS)

    Kato, Kimihiko; Kondo, Hiroki; Sakashita, Mitsuo; Nakatsuka, Osamu; Zaima, Shigeaki

    2011-06-01

    We have demonstrated the control of interfacial properties of Pr-oxide/Ge gate stack structure by the introduction of nitrogen. From C- V characteristics of Al/Pr-oxide/Ge 3N 4/Ge MOS capacitors, the interface state density decreases without the change of the accumulation capacitance after annealing. The TEM and TED measurements reveal that the crystallization of Pr-oxide is enhanced with annealing and the columnar structure of cubic-Pr 2O 3 is formed after annealing. From the depth profiles measured using XPS with Ar sputtering for the Pr-oxide/Ge 3N 4/Ge stack structure, the increase in the Ge component is not observed in a Pr-oxide film and near the interface between a Pr-oxide film and a Ge substrate. In addition, the N component segregates near the interface region, amorphous Pr-oxynitride (PrON) is formed at the interface. As a result, Pr-oxide/PrON/Ge stacked structure without the Ge-oxynitride interlayer is formed.

  5. 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.

  6. Interfacial Properties and Mechanisms Dominating Gas Hydrate Cohesion and Adhesion in Liquid and Vapor Hydrocarbon Phases.

    PubMed

    Hu, Sijia; Koh, Carolyn A

    2017-10-03

    The interfacial properties and mechanisms of gas hydrate systems play a major role in controlling their interparticle and surface interactions, which is desirable for nearly all energy applications of clathrate hydrates. In particular, preventing gas hydrate interparticle agglomeration and/or particle-surface deposition is critical to the prevention of gas hydrate blockages during the exploration and transportation of oil and gas subsea flow lines. These agglomeration and deposition processes are dominated by particle-particle cohesive forces and particle-surface adhesive force. In this study, we present the first direct measurements on the cohesive and adhesive forces studies of the CH4/C2H6 gas hydrate in a liquid hydrocarbon-dominated system utilizing a high-pressure micromechanical force (HP-MMF) apparatus. A CH4/C2H6 gas mixture was used as the gas hydrate former in the model liquid hydrocarbon phase. For the cohesive force baseline test, it was found that the addition of liquid hydrocarbon changed the interfacial tension and contact angle of water in the liquid hydrocarbon compared to water in the gas phase, resulting in a force of 23.5 ± 2.5 mN m(-1) at 3.45 MPa and 274 K for a 2 h annealing time period in which hydrate shell growth occurs. It was observed that the cohesive force was inversely proportional to the annealing time, whereas the force increased with increasing contact time. For a longer contact time (>12 h), the force could not be measured because the two hydrate particles adhered permanently to form one large particle. The particle-surface adhesive force in the model liquid hydrocarbon was measured to be 5.3 ± 1.1 mN m(-1) under the same experimental condition. Finally, with a 1 h contact time, the hydrate particle and the carbon steel (CS) surface were sintered together and the force was higher than what could be measured by the current apparatus. A possible mechanism is presented in this article to describe the effect of contact time on the

  7. The role of interfacial rheological properties on Ostwald ripening in emulsions.

    PubMed

    Meinders, Marcel B J; van Vliet, Ton

    2004-05-20

    The coarsening of emulsion droplets by Ostwald ripening is studied by means of numerical simulations in which time-dependent (elastic) interfacial behaviour is taken into account. Theoretical calculations on the dissolution of a single emulsion droplet in an infinite medium at saturated conditions show that the dissolution process can be stopped only when the interfacial tension goes to zero. When interfacial stress relaxation is included, which prevents a continuous zero interfacial tension, no stabilisation of the dissolution process is observed and the droplet dissolves completely. In the case of an ensemble of droplets, numerical calculations on the coarsening of emulsion droplets with finite interfacial elasticity show that a stable situation occurs at finite interfacial tensions of the droplets. This applies for a closed system with the same assumptions as those made in the Lifshitz-Slyozov-Wagner (LSW) theory. The coarsening behaviour strongly depends on the saturation of the dispersed phase in the continuous phase. If the system is in contact with atmosphere, saturation will finally go to unity and stabilisation will only occur for zero interfacial tension of the droplets. For an ensemble of droplets in a closed system, the calculations show that stress-relaxation of the interface causes the Ostwald-ripening process to continue, so no stable situation is reached. Stabilisation can only be accomplished by adding insoluble species to the dispersed phase, by using particles as stabilisers or by micro-encapsulation of the emulsion droplets by thick insoluble interfacial layers, which have a thickness that is in the order of the radius of the droplet.

  8. Magneto-ionic control of interfacial magnetism.

    PubMed

    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 O(2-) 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.

  9. 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.

  10. Spatial mosaic and interfacial dynamics in a Müllerian mimicry system.

    PubMed

    Sasaki, Akira; Kawaguchi, Isao; Yoshimori, Akira

    2002-02-01

    Uncovering why spatial mosaics of mimetic morphs are maintained in a Müllerian mimicry system has been a challenging issue in evolutionary biology. In this article, we analyze the reaction diffusion system that describes two-species Müllerian mimicry in one- and two-dimensional habitats. Due to positive frequency-dependent selection, a local population first approaches the state where one of the comimicking patterns predominates, which is followed by slow movement of boundaries where different patterns meet. We then analyze the interfacial dynamics of the boundaries to find whether a stable cline is maintained and to obtain the wave speed if the cline is unstable. The results are: (1) In a spatially uniform habitat the morph with greater base fitness spreads both in one and two species system. (2) The strength of cross-species interaction determines whether the mimetic morph clines of model and mimic species coalesce into the same geographical region or pass through each other. The joint wave speed of clines decreases by increasing the number of comimicking species in the mimicry ring. (3) In spatial heterogeneous habitats, stable clines can be maintained due to the balance between the base fitness gradient and the biased gene flow by negative curvature of boundary. This allows the persistence of a spatial mosaic even if one of the morphs is in every place advantageous over the other. A balanced cline is also maintained if there is a gradient in the population density. (4) A new advantageous morph occurring at a local region is doomed to go to extinction in a finite time if the "radius" of initial distribution is below a threshold. Possible applications to the heliconiine butterfly mimicry ring, heterozygous disadvantage systems of chromosomal rearrangement and hybrid zone, the third phase of Wright's Shifting Balance theory, and cytoplasmic incompatibility are discussed.

  11. Mechanical property investigation of soft materials by cantilever-based optical interfacial force microscopy.

    PubMed

    Kim, Byung I; Boehm, Ryan D

    2013-01-01

    Cantilever-based optical interfacial force microscopy (COIFM) was applied to the investigation of the mechanical properties of soft materials to avoid the double-spring effect and snap-to-contact problem associated with atomic force microscopy (AFM). When a force was measured as a function of distance between an oxidized silicon probe and the surface of a soft hydrocarbon film, it increases nonlinearly in the lower force region below ∼10 nN, following the Herzian model with the elastic modulus of ∼50 MPa. Above ∼10 nN, it increases linearly with a small oscillatory sawtooth pattern with amplitude 1-2 nN. The pattern suggests the possible existence of the layered structure within the film. When its internal part of the film was exposed to the probe, the force depends on the distance linearly with an adhesive force of -20 nN. This linear dependence suggests that the adhesive internal material behaved like a linear spring with a spring constant of ∼1 N/m. Constant-force images taken in the repulsive and attractive contact regimes revealed additional features that were not observed in the images taken in the noncontact regime. At some locations, however, contrast inversions were observed between the two contact regimes while the average roughness remained constant. The result suggests that some embedded materials had spring constants different from those of the surrounding material. This study demonstrated that the COIFM is capable of imaging mechanical properties of local structures such as small impurities and domains at the nanometer scale, which is a formidable challenge with conventional AFM methods.

  12. Sulfonated methyl esters of fatty acids in aqueous solutions: Interfacial and micellar properties.

    PubMed

    Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Basheva, Elka S; Ivanova, Veronika I; Petkov, Jordan T

    2015-11-01

    The interest to sulfonated methyl esters of fatty acids (SME) has been growing during the last decade, because these surfactants are considered as an environmentally friendly and renewable alternative of the linear alkyl-benzene sulfonates (LAS). Here, we present a quantitative study on the properties of aqueous SME solutions, and especially on their surface tension isotherms, critical micelle concentration (CMC) and its dependence on the concentration of added NaCl. It is demonstrated that the CMC of an ionic surfactant determined by electrical conductivity is insensitive to the presence of a small nonionic admixture, so that the CMC values determined by conductivity represent the CMC of the pure surfactant. Using SME as an example, we have demonstrated the application of a new and powerful method for determining the physicochemical parameters of the pure ionic surfactant by theoretical data analysis ("computer purification") if the used surfactant sample contains nonionic admixtures, which are present as a rule. This method involves fits of the experimental data for surface tension and conductivity by a physicochemical model based on a system of mass-balance, chemical-equilibrium and electric-double-layer equations, which allows us to determine the adsorption and micellization parameters of C12-, C14-, C16- and C18-SME, as well the fraction of nonionic admixtures (if any). Having determined these parameters, we can further predict the interfacial and micellization properties of the surfactant solutions, such as surface tension, adsorption, degree of counterion binding, and surface electric potential at every surfactant, salt and co-surfactant concentrations. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Interfacial effects in multilayers

    SciTech Connect

    Barbee, T.W., Jr.

    1998-04-01

    Interfacial structure and the atomic interactions between atoms at interfaces in multilayers or nano-laminates have significant impact on the physical properties of these materials. A technique for the experimental evaluation of interfacial structure and interfacial structure effects is presented and compared to experiment. In this paper the impact of interfacial structure on the performance of x-ray, soft x-ray and extreme ultra-violet multilayer optic structures is emphasized. The paper is concluded with summary of these results and an assessment of their implications relative to multilayer development and the study of buried interfaces in solids in general.

  14. Influence of carbon nanotubes coatings onto carbon fiber by oxidative treatments combined with electrophoretic deposition on interfacial properties of carbon fiber composite

    NASA Astrophysics Data System (ADS)

    Deng, Chao; Jiang, Jianjun; Liu, Fa; Fang, Liangchao; Wang, Junbiao; Li, Dejia; Wu, Jianjun

    2015-12-01

    To improve the interfacial performance of carbon fiber (CF) and epoxy resin, carbon nanotubes (CNTs) coatings were utilized to achieve this purpose through coating onto CF by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition (EPD) process. The influence of electrophoretically deposited CNTs coatings on the surface properties of CFs were investigated by Fourier transform infrared spectrometer, atomic force microscopy, scanning electron microscopy and dynamic contact angle analysis. The results indicated that the deposition of carbon nanotubes introduced some polar groups to carbon fiber surfaces, enhanced surface roughness and changed surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of CNTs. The thickness and density of the coatings increases with the introduction of pretreatment of the CF during the EPD process. Short beam shear test was performed to examine the effect of carbon fiber functionalization on mechanical properties of the carbon fiber/epoxy resin composites. The interfacial adhesion of CNTs/CF reinforced epoxy composites showed obvious enhancement of interlaminar shear strength by 60.2% and scanning electron microscope photographs showed that the failure mode of composites was changed after the carbon fibers were coated with CNTs.

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

    PubMed

    Ghadar, Yasaman; Clark, Aurora E

    2015-07-07

    Correction for 'Intermolecular network analysis of the liquid and vapor interfaces of pentane and water: microsolvation does not trend with interfacial properties' by Yasaman Ghadar et al., Phys. Chem. Chem. Phys., 2014, 16, 12475-12487.

  16. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.; Wise, J.L.

    1993-09-01

    Controlled impact methods have been employed to obtain dynamic response properties of armor materials. Experimental data have been obtained for high-strength ceramics. Continued analysis of time-resolved velocity interferometer measurements has produced systematic material-property data for Hugoniot and release response, initial and post-yield strength, pressure-induced phase transformation, and dynamic fracture strength. A new technique has been developed to measure hydrodynamic properties of ceramic through shock-wave experiments on metal-ceramic composites and data obtained for silicon carbide. Additional data on several titanium diboride ceramics and high-quality aluminum oxide ceramic have been acquired, and issues regarding the influence of microstructure on dynamic properties have emerged. Comparison of dynamic (Hugoniot elastic limit) strength and indentation hardness data has been performed and important correlations revealed. Innovative impact experiments on confined and unconfined alumina rods using axial and transverse VISAR diagnostics have been demonstrated which permit acquisition of multiaxial dynamic response data. Dynamic failure properties of a high-density aluminosilicate glass, similar in composition to the intergranular glassy phase of some aluminas, have been investigated with regard to yield, spall, and failure-wave propagation.

  17. Functionalization enhancement on interfacial shear strength between graphene and polyethylene

    NASA Astrophysics Data System (ADS)

    Jin, Yikuang; Duan, Fangli; Mu, Xiaojing

    2016-11-01

    Pull-out processes were simulated to investigate the interfacial mechanical properties between the functionalized graphene sheet (FGS) and polyethylene (PE) matrix by using molecular dynamics simulation with ReaxFF reactive force field. The interfacial structure of polymer and the interfacial interaction in the equilibrium FGS/PE systems were also analyzed to reveal the enhancement mechanism of interfacial shear strength. We observed the insertion of functional groups into polymer layer in the equilibrium FGS/PE systems. During the pull-out process, some interfacial chains were attached on the FGS and pulled out from the polymer matrix. The behavior of these pulled out chains was further analyzed to clarify the different traction action of functional groups applied on them. The results show that the traction effect of functional groups on the pulled-out chains is agreement with their enhancement influence on the interfacial shear strength of the FGS/PE systems. They both are basically dominated by the size of functional groups, suggesting the enhancement mechanism of mechanical interlocking. However, interfacial binding strength also exhibits an obvious influence on the interfacial shear properties of the hybrid system. Our simulation show that geometric constrains at the interface is the principal contributor to the enhancement of interfacial shear strength in the FGS/PE systems, which could be further strengthened by the wrinkled morphology of graphene in experiments.

  18. Interfacial Structure, Thermodynamics, and Electrostatics of Aqueous Methanol Solutions via Molecular Dynamics Simulations Using Charge Equilibration Models

    PubMed Central

    Patel, Sandeep; Zhong, Yang; Bauer, Brad A.; Davis, Joseph E.

    2014-01-01

    We present results from molecular dynamics simulations of methanol-water solutions using charge equilibration force fields to explicitly account for non-additive electronic interaction contributions to the potential energy. We study solutions across the concentration range from 0.1 to 0.9 methanol mole fraction. At dilute concentrations, methanol density is enhanced at the liquid-vapor interface, consistent with previous molecular dynamics and experimental studies. Interfacial thickness exhibits a monotonic increase with increasing methanol mole fraction, while surface tensions display monotonic decrease with methanol concentration, in qualitative agreement with experimental data and previous molecular dynamics predictions using polarizable force fields. In terms of interfacial structure, in keeping with predictions of traditional force fields, there is a unique preferential orientation of methanol molecules at the interface. Moreover, there is a free energetic preference for methanol molecules at the interface as evidenced by potential of mean force calculations. The pmf calculations suggest an interfacial state with 0.8 kcal/mole stability relative to the bulk, again, in qualitative agreement with previous simulation and experimental studies. Interfacial potentials based on double integration of total charge density range from −610 mV to −330 mV over the dilute to concentrated regimes, respectively. The preponderance of methanol at the interface at all mole fractions gives rise to a dominant methanol contribution to the total interfacial potential. Interestingly, there is a transition of the water surface potential contribution from negative to positive upon the transition from methanol mole fraction of 0.1 to 0.2. The dipole and quadrupole contributions to the water component of the total interfacial potential are effectively of equal magnitude and opposite sign, thus canceling one another. We compute the in-plane component of the dielectric permittivity

  19. Assessment of measurement techniques to determine the interfacial properties of bilayer dental ceramics

    NASA Astrophysics Data System (ADS)

    Anunmana, Chuchai

    The clinical success of all-ceramic dental restorations depends on the quality of interfacial bonding between ceramic layers. In addition, the residual stress in the structure that developed during ceramic processing is one of the important factors that contributes to the quality of the bond. Because all-ceramic restorations are usually fabricated as bilayer or trilayer structures and failures of all-ceramic restorations have been frequently reported as chipping or delamination of the veneer layers, the interfacial quality of bilayer dental ceramic restorations was investigated. However, most of the published bond test data reflect strength values that are inversely related to cross-sectional areas and failure locations are frequently disregarded or bond strength values are misinterpreted. In addition, residual tensile stresses that develop in the structures because of thermal expansion/contraction mismatches may also adversely affect interfacial fracture resistance. The first objective of this study was to determine the interfacial toughness of bonded bilayer ceramics using two different approaches. The results indicate that the short-bar chevron-notch test and a controlled-flaw microtensile test can induce interfacial failure that represents true bonding quality. The second objective of this study was to test the hypothesis that residual stresses estimated from an indentation technique are not significantly different from residual stresses that are calculated based on fractography and flexural strength. The indentation technique may be useful as a simplified method to determine residual stresses in bilayer dental ceramics. The results of this study demonstrate that there is no significant difference in mean residual stresses determined from the two techniques. Because of relationship between residual stresses and apparent interfacial toughness, estimates of residual stresses can now be estimated more rapidly by measuring the apparent interfacial toughness of

  20. Relating foam and interfacial rheological properties of β-lactoglobulin solutions.

    PubMed

    Lexis, M; Willenbacher, N

    2014-12-28

    We have determined bulk rheology of β-lactoglobulin (BLG) foams and surface viscoelasticity of corresponding protein solutions by varying pH as well as type, valency and concentration of the added salt in a wide range. Foam rheology was characterized by the storage modulus G0, the apparent yield stress τy, and the critical strain γc,foam defining the cessation of the linear viscoelastic response. These quantities were determined at gas volume fractions ϕ between 82% and 96%. Surface viscoelasticity was characterized in shear and dilation, corresponding shear and dilational moduli G, E' as well as the critical stress τc,surface and strain γc,surface marking the onset of non-linear response in oscillatory surface shear experiments were determined at fixed frequency. Beyond the widely accepted assumption that G0 and τy are solely determined by the Laplace pressure within the droplets and the gas volume fraction we have found that both quantities strongly depend on corresponding interfacial properties. G0 increases linearly with G and even stronger with E', τy varies proportional to τc,surface and γc,foam scales linearly with γc,surface. Furthermore, deviations from these simple scaling laws with significantly higher reduced G0 and τy values are observed only for foams at pH 5 and when a trivalent salt was added. Then also the dependence of these quantities on ϕ is unusually weak and we attribute these findings to protein aggregation and structure formation across the lamellae than the dominating bulk rheology.

  1. Modulation of MscL activity in droplet interface bilayers through tailored interfacial mechanical properties

    NASA Astrophysics Data System (ADS)

    Najem, Joseph; Freeman, Eric; Sukharev, Sergei; Leo, Donald

    2015-03-01

    MscL, a large-conductance mechanosensitive channel, is an osmolyte release valve that aids bacteria in surviving hypo-osmotic shocks. The large scale of its tension-driven opening transition makes it a strong candidate to serve as a transducer in stimuli-responsive biomolecular materials. In the previous work, a V23T mutant of MscL produced a reliable activation in a droplet interface bilayer (DIB) with applied axial droplet compression. Near the maximal compression, the aqueous droplets deform and the resulting increase in surface area leads to an increase in tension in the water-lipid-oil interface. This increase in tension is the product of the relative change in the droplet surface area and the elastic modulus of the DPhPC monolayer (120 mN/m). Here, we study the interfacial properties of the droplets as a way for modulating the activity of the embedded MscL channels. This is accomplished through varying mixtures of diphytanoyl phospholipids. The results show that gating probability of MscL in DIBs increases when lipids with a higher elastic modulus are used or when cholesterol is added to the monolayer. Moreover, an intrinsic electrical bias inside the lipid membrane is created when having DPhPC lipids with higher dipole in one droplet and DOPhPC characterized with lower dipole, in the other. We would like to acknowledge the financial support provided by the Air Force Office of Scientific Research Basic Research Initiative Grant FA9550-12-1-0464.

  2. Effect of interfacial properties on the activation volume of adsorbed enzymes.

    PubMed

    Schuabb, Vitor; Cinar, Süleyman; Czeslik, Claus

    2016-04-01

    We have studied the enzymatic activities of α-chymotrypsin (α-CT) and horseradish peroxidase (HRP) that are adsorbed on various chemically modified planar surfaces under aqueous solution. The enzymes were adsorbed on bare quartz, hydrophobic poly(styrene) (PS), positively charged poly(allylamine hydrochloride) (PAH), and negatively charged poly(styrene sulfonate) (PSS). Activation volumes of the enzymes at the aqueous-solid interfaces were determined by using high-pressure total internal reflection fluorescence (TIRF) spectroscopy. Apparently, the pressure response of the adsorbed enzymes strongly depends on the interfacial properties. α-CT can be activated by pressure (increasing enzymatic rate) on negatively charged surfaces like quartz and PSS, whereas HRP is activated by pressure on hydrophobic PS. Corresponding negative activation volumes of -29 mL mol(-1) for α-CT on quartz, -23 mL mol(-1) for α-CT on PSS, and -35 mL mol(-1) for HRP on PS are found. In addition, the absolute activities of α-CT and HRP on quartz, PS, PAH and PSS were determined by UV absorption at ambient pressure. Remarkably, large activities are found on those surfaces that are associated with negative activation volumes. However, Fourier transform infrared (FTIR) spectra collected in attenuated total reflection (ATR) mode do not indicate major adsorption induced conformational changes of the enzymes at any interface studied. Overall, the results of this study show that the activity of immobilized enzymes can largely be enhanced by the right combination of adsorbent material and applied pressure. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Improved interfacial and electrical properties of Ge MOS capacitor by using TaON/LaON dual passivation interlayer

    NASA Astrophysics Data System (ADS)

    Cheng, Z. X.; Xu, J. P.; Liu, L.; Huang, Y.; Lai, P. T.; Tang, W. M.

    2016-07-01

    The effects of TaON/LaON dual passivation interlayer on the interfacial and electrical properties of Ge metal-oxide-semiconductor (MOS) capacitor with HfO2 gate dielectric are investigated. As compared to its counterpart with only LaON as passivation interlayer, the formation of HfGeOx and LaHfOx, which would degrade the interfacial quality, is effectively suppressed due to the strong blocking role of the TaON barrier layer against Hf diffusion. As a result, excellent interfacial and electrical properties are achieved for the Ge MOS device with the TaON/LaON dual passivation interlayer: high k value (20.9), low interface-state density (5.32 × 1011 cm-2 eV-1) and oxide-charge density (-3.90 × 1012 cm-2), low gate leakage current density (1.77 × 10-4 A/cm2 at Vg = Vfb + 1 V), and high reliability under high-field stress.

  4. Probing the nanostructure, interfacial interaction, and dynamics of chitosan-based nanoparticles by multiscale solid-state NMR.

    PubMed

    Wang, Fenfen; Zhang, Rongchun; Wu, Qiang; Chen, Tiehong; Sun, Pingchuan; Shi, An-Chang

    2014-12-10

    Chitosan-based nanoparticles (NPs) are widely used in drug and gene delivery, therapy, and medical imaging, but a molecular-level understanding of the internal morphology and nanostructure size, interface, and dynamics, which is critical for building fundamental knowledge for the precise design and efficient biological application of the NPs, remains a great challenge. Therefore, the availability of a multiscale (0.1-100 nm) and nondestructive analytical technique for examining such NPs is of great importance for nanotechnology. Herein, we present a new multiscale solid-state NMR approach to achieve this goal for the investigation of chitosan-poly(N-3-acrylamidophenylboronic acid) NPs. First, a recently developed (13)C multiple cross-polarization magic-angle spinning (MAS) method enabled fast quantitative determination of the NPs' composition and detection of conformational changes in chitosan. Then, using an improved (1)H spin-diffusion method with (13)C detection and theoretical simulations, the internal morphology and nanostructure size were quantitatively determined. The interfacial coordinated interaction between chitosan and phenylboronic acid was revealed by one-dimensional MAS and two-dimensional (2D) triple-quantum MAS (11)B NMR. Finally, dynamic-editing (13)C MAS and 2D (13)C-(1)H wide-line separation experiments provided details regarding the componential dynamics of the NPs in the solid and swollen states. On the basis of these NMR results, a model of the unique nanostructure, interfacial interaction, and componential dynamics of the NPs was proposed.

  5. Focusing on charge-surface interfacial effects to enhance the laser properties of dye-doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Cerdán, Luis; Gartzia-Rivero, Leire; Enciso, Eduardo; Bañuelos, Jorge; López Arbeloa, Iñigo; Costela, Angel; García-Moreno, Inmaculada

    2014-01-01

    The synthesis of nanoparticles (NPs) for which only a single property is modified in a controlled manner is a challenge due to the fact that several physicochemical parameters are entangled. This letter assesses, from both experimental and theoretical points of view, the critical dependence on the charged-surface interfacial effect of the laser behavior in photonic nanomaterials based on dye-doped latexes without interference from other physicochemical parameters. When the dye and the NPs have similar charge nature, strong electrostatic repulsion prevents the dye molecules from being directly adsorbed in the surface and maintains the dye homogeneously distributed inside the NP, thus reducing deleterious interfacial effects. The highly homogeneous inner morphology leads to at least two-fold laser behavior enhancement of Rh6G in cationic NPs as compared with their anionic counterparts, and at least three-fold enhancement over Rh6G behavior in water solution.

  6. Surface and interfacial effect of filler particle on electrical properties of polyvinyledene fluoride/nickel composites

    NASA Astrophysics Data System (ADS)

    Panda, Maheswar; Srinivas, V.; Thakur, A. K.

    2008-12-01

    The effect of processing conditions and filler particle size/surface area on the dielectric behavior of polyvinyledene fluoride/nickel composites is reported. Large enhancement of low frequency dielectric constant with reduction in metal particle size in a metal-polymer composite is observed. Enhancement in the dielectric constant has been attributed to increase in interfacial area and consequent interfacial polarization with reduction in metal particle size. The increased interparticle contacts from the nearest neighbors result in enhanced tunneling probability leading to lowering of percolation threshold for nanosized nickel/polyvinyledene fluoride composites as compared to micron nickel/polyvinyledene fluoride composites.

  7. Effects of temperature and alkali concentration on the dynamic interfacial tension between heavy oil and alkaline solutions

    SciTech Connect

    Chiwetelu, C.I.; Neale, G.H.; Hornof, V. ); George, A.E. )

    1992-01-01

    This paper deals with the screening of a number of alkaline reagents for potential application in the waterflooding of heavy oil reservoirs at moderate temperatures. Sodium hydroxide, sodium metasilicate and sodium orthosilicate were all screened in accordance with a novel methodology that is based on physical and interfacial property measurements for selecting the most appropriate alkali for a target crude. The experimental oil was a Saskatchewan crude with an acid number of 1.88 mg KOH/g oil and a viscosity of 475 mPa.s at 25{degrees} C. The interfacial tension between this oil and distilled water was measured at various temperatures ranging from 25{degrees} C to 75{degrees} C. These tension values were relatively unaffected by changes in temperature as well as by the contact time between the two phases. However, the viscosity of the oil decreased by 87% when the temperature was raised from 35{degrees} C to 75{degrees} C. The addition of small quantities of the alkaline reagents (up to a maximum concentration of 500 mM in salt-free water) resulted in significant reductions in the interfacial tension.

  8. Dynamic Interaction of Interfacial Point Source Loading and Cylinder in an Elastic Quarter with Anti-plane Shear

    NASA Astrophysics Data System (ADS)

    Chun, Gao; Hui, Qi; Nan, Pan Xiang; Bo, Zhao Yuan

    2017-07-01

    Theoretical steady state solution of a semi-circular cylinder impacted by an anti-plane point loading in a vertical bound of an elastic quarter is formulated in this paper through using image method and wave function expansion series. The elastic quarter is extended as a half space, and the semi-circular interfacial cylinder is extended as a circular cylinder. Displacement field is constructed as series of Fourier-Hankel and Fourier-Bessel wave functions. At last, circular boundary is expanded as Fourier series to determine coefficients of wave function. Numerical results show that material parameters have two widely divergent effects on the radial and circumferential dynamic stress distribution.

  9. Dynamic properties of force fields

    NASA Astrophysics Data System (ADS)

    Vitalini, F.; Mey, A. S. J. S.; Noé, F.; Keller, B. G.

    2015-02-01

    Molecular-dynamics simulations are increasingly used to study dynamic properties of biological systems. With this development, the ability of force fields to successfully predict relaxation timescales and the associated conformational exchange processes moves into focus. We assess to what extent the dynamic properties of model peptides (Ac-A-NHMe, Ac-V-NHMe, AVAVA, A10) differ when simulated with different force fields (AMBER ff99SB-ILDN, AMBER ff03, OPLS-AA/L, CHARMM27, and GROMOS43a1). The dynamic properties are extracted using Markov state models. For single-residue models (Ac-A-NHMe, Ac-V-NHMe), the slow conformational exchange processes are similar in all force fields, but the associated relaxation timescales differ by up to an order of magnitude. For the peptide systems, not only the relaxation timescales, but also the conformational exchange processes differ considerably across force fields. This finding calls the significance of dynamic interpretations of molecular-dynamics simulations into question.

  10. The influence of surface properties on carbon fiber/epoxy matrix interfacial adhesion

    SciTech Connect

    Zhuang, H.; Wightman, J.P.

    1996-12-31

    In recent years, as composites become increasingly sophisticated to meet ever-increasing performance requirements, it has become more important to control the interaction between the reinforcing fibers and matrix materials. The major challenge here is the lack of fundamental understanding and knowledge about the reinforcement/matrix system which contribute to the establishment of the interphase. It has been recognized that the state of the fiber surface substantially effects the quality of interfacial adhesion. However, basic and specific correlation is still incomplete. The possible mechanisms by which the fiber surface parameters contribute to the constitution of the fiber/matrix interface include the interfacial chemical and physical interactions caused by fiber surface functionality and surface energy, the mechanical interlocking due to fiber surface irregularity, and, the interfacial wetting based on fiber surface energy. It was the objective of this work to explore the effects of physical and chemical aspects of fiber surfaces on the durability of interfacial adhesion in carbon fiber reinforced composites.

  11. Spin dynamics induced by ultrafast heating with ferromagnetic/antiferromagnetic interfacial exchange in perpendicularly magnetized hard/soft bilayers

    NASA Astrophysics Data System (ADS)

    Ma, Q. L.; Iihama, S.; Zhang, X. M.; Miyazaki, T.; Mizukami, S.

    2015-11-01

    The laser-induced spin dynamics of FeCo in perpendicularly magnetized L10-MnGa/FeCo bilayers with ferromagnetic and antiferromagnetic interfacial exchange coupling (IEC) are examined using the time-resolved magneto-optical Kerr effect. We found a precessional phase reversal of the FeCo layer as the IEC changes from ferromagnetic to antiferromagnetic. Moreover, a precession-suspension window was observed when the magnetic field was applied in a certain direction for the bilayer with ferromagnetic IEC. Our observations reveal that the spin dynamics modulation is strongly dependent on the IEC type within the Landau-Lifshitz-Gilbert depiction. The IEC dependence of the precessional phase and amplitude suggests the interesting method for magnetization dynamics modulation.

  12. Spin dynamics induced by ultrafast heating with ferromagnetic/antiferromagnetic interfacial exchange in perpendicularly magnetized hard/soft bilayers

    SciTech Connect

    Ma, Q. L. E-mail: mizukami@wpi-aimr.tohoku.ac.jp; Miyazaki, T.; Mizukami, S. E-mail: mizukami@wpi-aimr.tohoku.ac.jp; Iihama, S.; Zhang, X. M.

    2015-11-30

    The laser-induced spin dynamics of FeCo in perpendicularly magnetized L1{sub 0}-MnGa/FeCo bilayers with ferromagnetic and antiferromagnetic interfacial exchange coupling (IEC) are examined using the time-resolved magneto-optical Kerr effect. We found a precessional phase reversal of the FeCo layer as the IEC changes from ferromagnetic to antiferromagnetic. Moreover, a precession-suspension window was observed when the magnetic field was applied in a certain direction for the bilayer with ferromagnetic IEC. Our observations reveal that the spin dynamics modulation is strongly dependent on the IEC type within the Landau-Lifshitz-Gilbert depiction. The IEC dependence of the precessional phase and amplitude suggests the interesting method for magnetization dynamics modulation.

  13. Effects of surface treating methods of high-strength carbon fibers on interfacial properties of epoxy resin matrix composite

    NASA Astrophysics Data System (ADS)

    Ma, Quansheng; Gu, Yizhuo; Li, Min; Wang, Shaokai; Zhang, Zuoguang

    2016-08-01

    This paper aims to study the effects of surface treating methods, including electrolysis of anodic oxidation, sizing and heat treatment at 200 °C, on physical and chemical properties of T700 grade high-strength carbon fiber GQ4522. The fiber surface roughness, surface energy and chemical properties were analyzed for different treated carbon fibers, using atom force microscopy, contact angle, Fourier transformed infrared and X-ray photoelectron spectroscopy, respectively. The results show that the adopted surface treating methods significantly affect surface roughness, surface energy and active chemical groups of the studied carbon fibers. Electrolysis and sizing can increase the roughness, surface energy and chemical groups on surface, while heat treatment leads to decreases in surface energy and chemical groups due to chemical reaction of sizing. Then, unidirectional epoxy 5228 matrix composite laminates were prepared using different treated GQ4522 fibers, and interlaminar shear strength and flexural property were measured. It is revealed that the composite using electrolysis and sizing-fiber has the strongest interfacial bonding strength, indicating the important roles of the two treating processes on interfacial adhesion. Moreover, the composite using heat-treating fiber has lower mechanical properties, which is attributed to the decrease of chemical bonding between fiber surface and matrix after high temperature treatment of fiber.

  14. Influence of primary crystallisation conditions on the mechanical and interfacial properties of micronised budesonide for dry powder inhalation.

    PubMed

    Kubavat, Harshal A; Shur, Jagdeep; Ruecroft, Graham; Hipkiss, David; Price, Robert

    2012-07-01

    Investigate the influence of primary crystallisation conditions on the mechanical properties and secondary processing behaviour of budesonide for dry powder inhaler (DPI) formulations. Young's modulus of two batches of budesonide crystals (samples A and B) produced using different anti-solvents was determined using nanoindentation. Physicochemical and surface interfacial properties via the cohesive-adhesive balance (CAB) approach to colloid probe atomic force microscopy (AFM) of air-jet micronised budesonide crystals were also investigated. These data were correlated to in vitro aerosolization performance of carrier-based DPI formulations containing either budesonide samples A or B and lactose monohydrate. Young's modulus of budesonide samples A and B crystals was 0.95 and 4.04 GPa, respectively. Sample A crystals with low Young's modulus exhibited poorer micronisation efficiency than sample B. CAB analysis of micronised budesonide samples A and B, suggest that sample B budesonide had a greater adhesion to lactose than sample A. These data correlated with in vitro aerosolisation studies, which showed that the fine particle delivery of budesonide sample A was higher than that of sample B. In conclusion, crystallisation conditions may affect the mechanical properties of budesonide, and therefore secondary processing of the material and their interfacial properties and product performance in carrier based DPI formulations. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Mechanical and interfacial properties of poly(vinyl chloride) based composites reinforced by cassava stillage residue with different surface treatments

    NASA Astrophysics Data System (ADS)

    Zhang, Yanjuan; Gan, Tao; Li, Qian; Su, Jianmei; Lin, Ye; Wei, Yongzuo; Huang, Zuqiang; Yang, Mei

    2014-09-01

    Cassava stillage residue (CSR), a kind of agro-industrial plant fiber, was modified by coupling agent (CA), mechanical activation (MA), and MA-assisted CA (MACA) surface treatments, respectively. The untreated and different surface treated CSRs were used to prepare plant fibers/polymer composites (PFPC) with poly(vinyl chloride) (PVC) as polymer matrix, and the properties of these CSR/PVC composites were compared. Surface treated CSR/PVC composites possessed better mechanical properties, water resistance and dimensional stability compared with the untreated CSR/PVC composite, attributing to the improvement of interfacial properties between CSR and PVC matrix. MACA-treated CSR was the best reinforcement among four types of CSRs (untreated, MA-treated, CA-treated, and MACA-treated CSRs) because MACA treatment led to the significant improvement of dispersion, interfacial adhesion and compatibility between CSR and PVC. MACA treatment could be considered as an effective and green method for enhancing reinforcement efficiency of plant fibers and the properties of PFPC.

  16. Mass properties measurement system dynamics

    NASA Technical Reports Server (NTRS)

    Doty, Keith L.

    1993-01-01

    The MPMS mechanism possess two revolute degrees-of-freedom and allows the user to measure the mass, center of gravity, and the inertia tensor of an unknown mass. The dynamics of the Mass Properties Measurement System (MPMS) from the Lagrangian approach to illustrate the dependency of the motion on the unknown parameters.

  17. Experimental studies on the surface and interfacial properties of polysiloxanes and their interaction with blood proteins

    NASA Astrophysics Data System (ADS)

    Stuart, James Oliver

    1998-12-01

    The research in this thesis is concerned with the surface and interfacial properties of polysiloxanes and their interaction with blood proteins, particularly fibrinogen. Polysiloxane properties at the polymer/air interface were investigated using secondary ion mass spectrometry (SIMS) and contact angle measurements. Polysiloxane properties at the polymer/water interface were studied using a Langmuir film balance. Interaction with blood proteins was investigated by SIMS and by aggregation studies of polysiloxanes emulsified in the presence of various blood components, namely serum, plasma, and fibrinogen solution upon exposure to the enzyme thrombin. Poly(dimethylsiloxane) (PDMS), poly(phenylmethylsiloxane) (PPMS), and poly(trifluoropropylmethylsiloxane) (PTFPMS) homopolymers and diblock copolymers thereof were studied using SIMS and contact angle measurements. Also studied were a newly synthesized series of random copolymers of poly(methyl(methyl undecanoate)siloxane)-co-poly(dimethylsiloxane) (PMMUS). Key findings include the resolution of discrepancies in SIMS mass fragment assignments in PDMS and establishment of mass peak assignments for PPMS, PTFPMS, and PMMUS. Also, it was shown by SIMS that complete surface saturation of the siloxane components of solution casts films of PDMS/PS and PTFPMS/PS diblock copolymers and blends with PS was achieved at siloxane concentrations as low as 2.0 percent by weight. On the other hand, PPMS/PS diblock copolymers show signature peaks of both polymers at siloxane concentrations as high as 51 percent by weight. All results correspond well with contact angle measurements on the same systems. Finally, the detection of trimethylsilyl end-groups was determined through systemic variation of chain termini and polymer molecular weight. The monolayer behavior of the PMMUS copolymer series of the siloxanes containing cholesteryl ester side-groups was examined using a langmuir film balance. The isotherms of the PMMUS polymers showed

  18. Surface and interfacial properties of polymer blends. Progress report, September 25, 1990--December 24, 1991

    SciTech Connect

    Rafailovich, M.; Sokolov, J.

    1991-11-01

    This is a summary of the research we have conducted since receiving our DOE grant and research plans for the coming year. As you will notice most of the research objectives of our original proposal were met, especially in regard to measuring surface segregation and interface formation in polymer blends. Our program has therefore expanded into other directions such as the study of the surface visco-elastic properties of polymer liquids and solutions, the conformations of polymer chains grafted onto silica surfaces, and the dynamics of cross linked polymer networks.

  19. Noncontact single-pulse optical method to measure interfacial properties in intact systems.

    PubMed

    Clark, David C; Kim, Myung K

    2012-12-15

    We introduce a noncontact purely optical approach to measuring the localized surface properties of an interface within a system using a single optical pressure pulse and a time-resolved digital holographic quantitative phase-imaging technique to track the propagating nanometric capillary disturbance. We demonstrate the proposed method's ability to measure the surface energy of deionized water, methanol, and chemical monolayers formed by surfactants with good agreement to published values. The development of this technique boasts immediate application to static and dynamic systems and near-future applications for living biological cell membranes.

  20. Interfacial water on crystalline silica: A comparative molecular dynamics simulation study

    SciTech Connect

    Ho, Tuan A.; Argyris, D.; Cole, David; Striolo, Alberto

    2011-01-01

    All-atom molecular dynamics simulations were conducted to study the dynamics of aqueous electrolyte solutions confined in slit-shaped silica nanopores of various degrees of protonation. Five degrees of protonation were prepared by randomly removing surface hydrogen atoms from fully protonated crystalline silica surfaces. Aqueous electrolyte solutions containing NaCl or CsCl salt were simulated at ambient conditions. In all cases, the ionic concentration was 1 M. The results were quantified in terms of atomic density distributions within the pores, and the self-diffusion coefficient along the direction parallel to the pore surface. We found evidence for ion-specific properties that depend on ion surface, water ion, and only in some cases ion ion correlations. The degree of protonation strongly affects the structure, distribution, and the dynamic behavior of confined water and electrolytes. Cl ions adsorb on the surface at large degrees of protonation, and their behavior does not depend significantly on the cation type (either Na+ or Cs+ ions are present in the systems considered). The cations show significant ion-specific behavior. Na+ ions occupy different positions within the pore as the degree of protonation changes, while Cs+ ions mainly remain near the pore center at all conditions considered. For a given degree of protonation, the planar self-diffusion coefficient of Cs+ is always greater than that of Na+ ions. The results are useful for better understanding transport under confinement, including brine behavior in the subsurface, with important applications such as environmental remediation.

  1. Thermodynamic properties of gold-water nanofluids using molecular dynamics

    NASA Astrophysics Data System (ADS)

    Puliti, Gianluca; Paolucci, Samuel; Sen, Mihir

    2012-12-01

    The physical behavior of a nanofluids is still not fully understood. This work focuses on the study and understanding of equilibrium thermodynamic properties of several gold-water nanofluids using molecular dynamics simulations. Three different systems are considered, where gold nanoparticles with diameters of 2.6, 5.8, and 6.6 nm are suspended in water for effective nanoparticle volume fractions of 1, 10, and 15 %, respectively. Novelties of this study are in the use of accurate force fields for modeling the inter- and intramolecular interactions of the components, and providing comprehensive thermodynamic properties of the nanofluids. The results are validated with the pure fluid and solid properties. Results indicate that the thermodynamics of the system does not behave as an ideal mixture, due to a combination of several factors such as liquid layering, anisotropicity, and other solid-liquid interfacial effects.

  2. Influence of interfacial oxide on the optical properties of single layer CdTe/CdS quantum dots in porous silicon scaffolds

    SciTech Connect

    Gaur, Girija; Fleetwood, Daniel M.; Weller, Robert A.; Reed, Robert A.; Weiss, Sharon M.; Koktysh, Dmitry S.

    2015-08-10

    Using a combination of continuous wave and time-resolved spectroscopy, we study the effects of interfacial conditions on the radiative lifetimes and photoluminescence intensities of sub-monolayer colloidal CdTe/CdS quantum dots (QDs) embedded in a three-dimensional porous silicon (PSi) scaffold. The PSi matrix was thermally oxidized under different conditions to change the interfacial oxide thickness. QDs embedded in a PSi matrix with ∼0.4 nm of interfacial oxide exhibited reduced photoluminescence intensity and nearly five times shorter radiative lifetimes (∼16 ns) compared to QDs immobilized within completely oxidized, porous silica (PSiO{sub 2}) frameworks (∼78 ns). The exponential dependence of QD lifetime on interfacial oxide thickness in the PSi scaffolds suggests charge transfer plays an important role in the exciton dynamics.

  3. Fabrication of interfacial functionalized porous polymer monolith and its adsorption properties of copper ions.

    PubMed

    Han, Jiaxi; Du, Zhongjie; Zou, Wei; Li, Hangquan; Zhang, Chen

    2014-07-15

    The interfacial functionalized poly (glycidyl methacrylate) (PGMA) porous monolith was fabricated and applied as a novel porous adsorbent for copper ions (Cu(2+)). PGMA porous material with highly interconnected pore network was prepared by concentrated emulsion polymerization template. Then polyacrylic acid (PAA) was grafted onto the interface of the porous monolith by the reaction between the epoxy group on PGMA and a carboxyl group on PAA. Finally, the porous monolith was interfacial functionalized by rich amount of carboxyl groups and could adsorb copper ions effectively. The chemical structure and porous morphology of the porous monolith were measured by Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the effects of pore size distribution, pH value, co-existing ions, contacting time, and initial concentrations of copper ions on the adsorption capacity of the porous adsorbents were studied.

  4. Interfacial structure and electrical properties of transparent conducting ZnO thin films on polymer substrates.

    PubMed

    Lim, Young Soo; Kim, Dae Wook; Kang, Jong-Ho; Seo, Seul Gi; Kim, Bo Bae; Choi, Hyoung-Seuk; Seo, Won-Seon; Cho, Yong Soo; Park, Hyung-Ho

    2013-08-01

    The effects of polymer substrates on the interfacial structure and the thermal stability of Ga-doped ZnO (GZO) thin films were investigated. The GZO thin films were deposited on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates by rf-magnetron sputtering at room temperature, and thermal stability tests of the GZO thin films on the polymer substrates were performed at 150°C up to 8 h in air. Electrical and structural characterizations of the GZO thin films on the PET and the PEN substrates were carried out, and the origins of the stable interfacial structure and the improved thermal stability of the GZO thin film on the PEN substrate were discussed.

  5. Unique Interfacial Properties of the Chlorinated Solvent DNAPL at Savannah River National Laboratory

    SciTech Connect

    Powers, S.E.; Omrane, K.; Grimberg, S.J.

    2004-03-31

    Tetrachloroethene and trichloroethene are the primary constituents in a DNAPL found in the unsaturated zone at the Department of Energy's Savannah River Site (SRS). Following equilibration of the SRS DNAPL with deionized water, the measured interfacial tension was less than 2 dynes/cm and the pH of the aqueous phase 3.8, thus indicating the presence of constituents other than chlorinated solvents. Based on contamination history at DOE facilities, we explored the potential for co-contamination by oils, surfactants or organic acids. Non-aqueous potentiometric titration techniques revealed a high acid content (4 mg (as KOH)/g of DNAPL). Surrogate mixtures of TCE with the hydraulic oil, dibutylbutylphosphonate (DBBP) and tributylphosphate (TBP), which were used in the plutonium production process, also had low interfacial tension but not as low as the value measured for the SRS DNAPL. Research to identify the constituents and mechanisms responsible for the low interfacial tension of this DNAPL is on-going.

  6. Interfacial properties of methane/aqueous VC-713 solution under hydrate formation conditions.

    PubMed

    Peng, Bao-Zi; Sun, Chang-Yu; Liu, Peng; Liu, Yan-Tao; Chen, Jun; Chen, Guang-Jin

    2009-08-15

    The interfacial tensions between methane and aqueous solutions of different contents of VC-713 (a terpolymer of N-vinylpyrrolidone, N-vinylcaprolactam, and dimethylamino-ethyl-methacrylate) were measured at different temperatures and pressures in the hydrate formation region. The surface adsorption free energies of methane were calculated accordingly in order to investigate the effect of this kinetic inhibitor on the nucleation of hydrate. The results show that the presence of VC-713 lowers the interfacial tension, increasing the concentration of methane on the surface of the aqueous phase, and thus promotes nucleation of hydrate at the gas/liquid interface. Additionally, the measured interfacial tension data suggest that VC-713 tends not to form micelles in water. Subsequently, the lateral growth rate of hydrate film on the surface of a methane bubble suspended in the aqueous phase was measured at different pressures to investigate the effect of VC-713 on the growth of hydrate. The results show that the lateral growth rate of hydrate film from aqueous VC-713 solution is much lower than that from pure water, demonstrating that VC-713 significantly inhibits the hydrate growth. The mechanism of the inhibition is also discussed.

  7. Properties of dynamical electromagnetic metamaterials

    NASA Astrophysics Data System (ADS)

    Padilla, Willie J.; Averitt, Richard D.

    2017-08-01

    Electromagnetic metamaterials consist of two or three dimensional arrays of tailored metallic and/or dielectric inclusions and provide unprecedented sub-wavelength control over light-matter interactions. Metamaterials are fashioned to yield a specific response to the electric and magnetic components of light and may be treated as effective media, described by effective optical constants {μ }{{eff}} and {{ɛ }}{{eff}}, and have realized a multitude of exotic properties difficult to achieve with natural materials. An inductive-capacitive unit cell geometry provides enhanced values of optical constants, as well as the ability to dynamically control the novel responses exhibited by electromagnetic metamaterials. The ability of metamaterials to achieve real-time dynamic properties has realized novel applications and has made them relevant for the next revolution in advanced materials and related devices.

  8. Dynamic properties of successful smiles

    PubMed Central

    Helwig, Nathaniel E.; Sohre, Nick E.; Ruprecht, Mark R.; Guy, Stephen J.; Lyford-Pike, Sofía

    2017-01-01

    Facial expression of emotion is a foundational aspect of social interaction and nonverbal communication. In this study, we use a computer-animated 3D facial tool to investigate how dynamic properties of a smile are perceived. We created smile animations where we systematically manipulated the smile’s angle, extent, dental show, and dynamic symmetry. Then we asked a diverse sample of 802 participants to rate the smiles in terms of their effectiveness, genuineness, pleasantness, and perceived emotional intent. We define a “successful smile” as one that is rated effective, genuine, and pleasant in the colloquial sense of these words. We found that a successful smile can be expressed via a variety of different spatiotemporal trajectories, involving an intricate balance of mouth angle, smile extent, and dental show combined with dynamic symmetry. These findings have broad applications in a variety of areas, such as facial reanimation surgery, rehabilitation, computer graphics, and psychology. PMID:28658294

  9. The diastereomers of mannosylerythritol lipids have different interfacial properties and aqueous phase behavior, reflecting the erythritol configuration.

    PubMed

    Fukuoka, Tokuma; Yanagihara, Takashi; Imura, Tomohiro; Morita, Tomotake; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2012-04-01

    Mannosylerythritol lipids (MELs) produced by yeasts are one of the most promising glycolipid biosurfactants. There are two MEL diastereomers, in which the configurations of the erythritol moieties are opposite. The 4-O-β-D-mannopyranosyl-(2S,3R)-erythritol (S-form) or 4-O-β-D-mannopyranosyl-(2R,3S)-erythritol (R-form) is the hydrophilic domain. In this study, we prepared S- and R-form MEL homologs with similar fatty acyl groups, and compared their interfacial properties. Among the four diastereomers (S-MEL-B and -D/R-MEL-B and -D), R-form MELs showed a higher critical aggregation concentration and hydrophilicity compared to the corresponding S-form. R-form MELs also efficiently formed relatively large vesicles compared to S-form. Moreover, we estimated the binary phase diagram of the MEL-water system and compared the aqueous phase behavior among the four diastereomers. The present MELs self-assembled into a lamellar (L(α)) structure at all concentration ranges. Meanwhile, the one-phase L(α) region of R-form MELs was wider than those of S-form MELs. R-form MELs may maintain more water between the polar layers in accordance with an extension of the interlayer spacing. These results suggest that the differences in MEL carbohydrate configurations significantly affect interfacial properties, self-assembly, and hydrate ability. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Influence of oxidation temperature on the interfacial properties of n-type 4H-SiC MOS capacitors

    NASA Astrophysics Data System (ADS)

    Jia, Yifan; Lv, Hongliang; Song, Qingwen; Tang, Xiaoyan; Xiao, Li; Wang, Liangyong; Tang, Guangming; Zhang, Yimen; Zhang, Yuming

    2017-03-01

    The effect of oxidation temperature on interfacial properties of n-type 4H-SiC metal-oxide-semiconductor capacitors has been systematically investigated. Thermal dry oxidation process with three different oxidation temperatures 1200 °C, 1300 °C and 1350 °C were employed to grow SiO2 dielectric, following by the standard post-oxidation annealing (POA) in NO ambience at 1175 °C for 2 h. The root mean square (RMS) roughness measured by Atomic Force Microscopy for the thermally grown SiO2 before POA process is reduced with increasing the oxidation temperature, obtaining an atomically flat surface with a RMS of 0.157 nm from the sample oxidized at 1350 °C. Several kinds of electrical measurements were used to evaluate the densities of near interface traps and effective fixed dielectric charge for the samples, exhibiting a trend reduced with increasing the oxidation temperature. The interface state density of 3 × 1011 cm-2eV-1 at 0.2 eV from the conduction band edge was achieved from conductance method measurement for the sample oxidized at 1350 °C. The results from Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy demonstrate that high oxidation temperature can reduce the width of transition layer, the excess Si and silicon suboxide compositions near the interface, leading to effective improvement of the interfacial properties.

  11. Investigating the use of coupling agents to improve the interfacial properties between a resorbable phosphate glass and polylactic acid matrix.

    PubMed

    Hasan, Muhammad Sami; Ahmed, Ifty; Parsons, Andrew J; Rudd, Chris D; Walker, Gavin S; Scotchford, Colin A

    2013-09-01

    Eight different chemicals were investigated as potential candidate coupling agents for phosphate glass fibre reinforced polylactic acid composites. Evidence of reaction of the coupling agents with phosphate glass and their effect on surface wettability and glass degradation were studied along with their principle role of improving the interface between glass reinforcement and polymer matrix. It was found that, with an optimal amount of coupling agent on the surface of the glass/polymer, interfacial shear strength improved by a factor of 5. Evidence of covalent bonding between agent and glass was found for three of the coupling agents investigated, namely: 3-aminopropyltriethoxysilane; etidronic acid and hexamethylene diisocyanate. These three coupling agents also improved the interfacial shear strength and increased the hydrophobicity of the glass surface. It is expected that this would provide an improvement in the macroscopic properties of full-scale composites fabricated from the same materials which may also help to retain these properties for the desired length of time by retarding the breakdown of the fibre/matrix interface within these composites.

  12. Effects of interfacial interaction on the properties of poly(vinyl chloride)/styrene-butadiene rubber blends

    NASA Astrophysics Data System (ADS)

    Zhu, Shuihan

    PVC/SBR blends---new thermoplastic elastomer material---were developed. They have potential applications due to low costs and low-temperature elasticity. A unique compatibilization method was employed to enhance the mechanical properties of the materials a compatibilizer miscible with one of the blend components can react chemically with the other component(s). Improvements in tensile and impact behavior were observed as a result of the compatibilization. A novel characterization technique to study the interface of PVC/SBR blends was developed. This technique involves the observation of the unstained sample under electron beam irradiation by a transmission electron microscope (TEM). An enrichment of rubber at the interface between PVC and SBR was detected in the compatiblized PVC/SBR blends. Magnetic relaxation measurements show that the rubber concentration in the proximity of PVC increases with the degree of covulcanization between NBR and SBR. The interface development and the rheological effect during processing were investigated. The interfacial concentration profile and the interfacial thickness were obtained by grayscale measurements on TEM micrographs, evaluation of SIMS images, and measurements of micromechanical properties.

  13. Modification of soy protein hydrolysates by Maillard reaction: Effects of carbohydrate chain length on structural and interfacial properties.

    PubMed

    Li, Weiwei; Zhao, Haibo; He, Zhiyong; Zeng, Maomao; Qin, Fang; Chen, Jie

    2016-02-01

    This study investigated the effects of carbohydrate chain length on the structural and interfacial properties of the Maillard reaction conjugates of soy protein hydrolysates (Mw>30 kDa). The covalent attachment of sugars to soy peptides was confirmed by amino acid analysis and examination of the Fourier-transform infrared spectra. The results suggested that the emulsion stability of the conjugates increased as the length of the carbohydrate chains increased. The surface activity measurement revealed that the soy peptide-dextran conjugates were closely packed and that each molecule occupied a small area of the interface. It was further confirmed that the soy peptide-dextran conjugates formed a thick adsorbed layer at the oil-water interface, as observed in the confocal laser scanning micrographs. The interfacial layer of soy peptides was rheologically complex with broad linear viscoelastic region and strong elastic modulus, and the soy peptide-dextran conjugates might form multilayer adsorption at the interface. This study suggested that the improved surface properties of the soy peptide-dextran conjugates were a result of the strong membrane formed by the closely packed molecular and multilayer adsorption at the interface, which provided steric hindrance to flocculation.

  14. Further evidence that interfacial water is the main "driving force" of protein dynamics: a neutron scattering study on perdeuterated C-phycocyanin.

    PubMed

    Combet, Sophie; Zanotti, Jean-Marc

    2012-04-14

    The fundamental role of hydration water (also called interfacial water) is widely recognized in protein flexibility, especially in the existence of the so-called protein "dynamical transition" at around 220 K. In the present study, we take advantage of perdeuterated C-phycocyanin (CPC) and elastic incoherent neutron scattering (EINS) to distinguish between protein dynamics and interfacial water dynamics. Powders of hydrogenated (hCPC) and perdeuterated (dCPC) CPC protein have been hydrated, respectively, with D(2)O or H(2)O and measured by EINS to separately probe protein dynamics (hCPC/D(2)O) and water dynamics (dCPC/H(2)O) at different time- and length-scales. We find that "fast" (<20 ps) local mean-square displacements (MSD) of both protein and interfacial water coincide all along the temperature range, with the same dynamical transition temperature at ~220 K. On higher resolution (<400 ps), two different types of motions can be separated: (i) localized motions with the same amplitude for CPC and hydration water and two transitions at ~170 and ~240 K for both; (ii) large scale fluctuations exhibiting for both water molecules and CPC protein a single transition at ~240 K, with a significantly higher amplitude for the interfacial water than for CPC. Moreover, by comparing these motions with bulk water MSD measured under the same conditions, we show no coupling between bulk water dynamics and protein dynamics all along the temperature range. These results show that interfacial water is the main "driving force" governing both local and large scale motions in proteins.

  15. Fluorescence depolarization and contact angle investigation of dynamic and static interfacial tension of liquid crystal display materials.

    PubMed

    Quintella, Cristina M; Lima, Angelo M V; Gonçalves, Cristiane C; Watanabe, Yuji N; Mammana, Alaide P; Schreiner, Marcos A; Pepe, Iuri; Pizzo, Angela A

    2003-06-01

    Interfacial interactions control two processes empirically known to be critical for molecular anchoring in twisted nematic liquid crystal displays technology (TN-LCDs): surface treatment and filling procedure. Static and dynamical interfacial tensions (Gamma(SL)) between liquids and several substrates with similar roughness were observed respectively by contact angle (theta(c)) of sessile drops and by fluorescence depolarization of thin liquid films flowing at high velocity. Gamma(SL) decreased when glass was coated with tin dioxide and increased with polyvinyl alcohol (PVA) deposition. Drops were circular for all substrates except rubbed PVA, where they flowed spontaneously along the rubbing direction, reaching an oblong form that had theta(c) parallel and perpendicular to the rubbing direction respectively greater and smaller than theta(c) for non-rubbed PVA. This is attributed to polar group alignment generating an asymmetric Gamma(SL) distribution with nanometric preferential direction, inducing a capillary-like flow. Polarization and anisotropy maps for high-velocity flow parallel to the PVA rubbing direction showed an increase in the net alignment of molecular domains and a widening of the region where it occurred. This is attributed to preferential anchoring in the downstream direction, instead of in several directions, as for non-rubbed PVA. This explains why filling direction is crucial for TN-LCDs homogeneous behavior.

  16. Non-Darcy interfacial dynamics of air-water two-phase flow in rough fractures under drainage conditions.

    PubMed

    Chang, Chun; Ju, Yang; Xie, Heping; Zhou, Quanlin; Gao, Feng

    2017-07-04

    Two-phase flow interfacial dynamics in rough fractures is fundamental to understanding fluid transport in fractured media. The Haines jump of non-Darcy flow in porous media has been investigated at pore scales, but its fundamental processes in rough fractures remain unclear. In this study, the micron-scale Haines jump of the air-water interface in rough fractures was investigated under drainage conditions, with the air-water interface tracked using dyed water and an imaging system. The results indicate that the interfacial velocities represent significant Haines jumps when the meniscus passes from a narrow "throat" to a wide "body", with jump velocities as high as five times the bulk drainage velocity. Locally, each velocity jump corresponds to a fracture aperture variation; statistically, the velocity variations follow an exponential function of the aperture variations at a length scale of ~100 µm to ~100 mm. This spatial-scale-invariant correlation may indicate that the high-speed local velocities during the Haines jump would not average out spatially for a bulk system. The results may help in understanding the origin of interface instabilities and the resulting non-uniform phase distribution, as well as the micron-scale essence of the spatial and temporal instability of two-phase flow in fractured media at the macroscopic scale.

  17. Interfacial dynamics and rheology of polymer-grafted nanoparticles at air-water and xylene-water interfaces.

    PubMed

    Alvarez, Nicolas J; Anna, Shelley L; Saigal, Trishna; Tilton, Robert D; Walker, Lynn M

    2012-05-29

    Particle-stabilized emulsions and foams offer a number of advantages over traditional surfactant-stabilized systems, most notably a greater stability against coalescence and coarsening. Nanoparticles are often less effective than micrometer-scale colloidal particles as stabilizers, but nanoparticles grafted with polymers can be particularly effective emulsifiers, stabilizing emulsions for long times at very low concentrations. In this work, we characterize the long-time and dynamic interfacial tension reduction by polymer-grafted nanoparticles adsorbing from suspension and the corresponding dilatational moduli for both xylene-water and air-water interfaces. The dilatational moduli at both types of interfaces are measured by a forced sinusoidal oscillation of the interface. Surface tension measurements at the air-water interface are interpreted with the aid of independent ellipsometry measurements of surface excess concentrations. The results suggest that the ability of polymer-grafted nanoparticles to produce significant surface and interfacial tension reductions and dilatational moduli at very low surface coverage is a key factor underlying their ability to stabilize Pickering emulsions at extremely low concentrations.

  18. Probing interfacial dynamics and mechanics using submerged particle microrheology. I. Theory

    NASA Astrophysics Data System (ADS)

    Shlomovitz, Roie; Evans, Arthur A.; Boatwright, Thomas; Dennin, Michael; Levine, Alex J.

    2014-07-01

    Microrheology relies on tracking the thermal or driven motion of microscopic particles in a soft material. It is well suited to the study of materials that have no three-dimensional realization, which makes them difficult to study using a macroscopic rheometer. For this reason, microrheology is becoming an important rheological probe of Langmuir monolayers and membranes. Interfacial microrheology, however, has been difficult to reconcile quantitatively with more traditional macroscopic approaches. We suggest that uncertainties in accounting for the mechanical coupling of the tracer particle to the interface or membrane are responsible for these discrepancies. To resolve them, we propose a new non-contact approach to interfacial microrheology that uses particles submerged in the subphase a known distance below the interface. In this first of two papers, we present calculations of the response function (and thus the equilibrium fluctuation spectrum) of a spherical particle submerged below a viscoelastic surface that has a finite surface tension and/or bending modulus. In the second paper, we compare these results to submerged particle microrheology in a few example systems, showing quantitative agreement.

  19. Interfacial reflection enhanced optical extinction and thermal dynamics in polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Dunklin, Jeremy R.; Forcherio, Gregory T.; Berry, Keith R.; Roper, D. Keith

    2016-09-01

    Polymer films containing plasmonic nanostructures are of increasing interest for development of responsive energy, sensing, and therapeutic systems. A series of novel gold nanoparticle (AuNP)-polydimethylsiloxane (PDMS) films were fabricated to elucidate enhanced optical extinction from diffractive and scattering induced internal reflection. AuNPs with dramatically different scattering-to-absorption ratios were compared at variable interparticle separations to differentiate light trapping from optical diffraction and Mie scattering. Description of interfacial optical and thermal effects due to these interrelated contributions has progressed beyond Mie theory, Beer's law, effective media, and conventional heat transfer descriptions. Thermal dissipation rates in AuNP-PDMS with this interfacial optical reflection was enhanced relative to films containing heterogeneous AuNPs and a developed thermal dissipation description. This heuristic, which accounts for contributions of both internal and external thermal dissipations, has been shown to accurately predict thermal dissipation rates from AuNP-containing insulating and conductive substrates in both two and three-dimensional systems. Enhanced thermal response rates could enable design and adaptive control of thermoplasmonic materials for a variety of implementations.

  20. Interfacial adhesion between functionalized polyethylene surface and graphene via molecular dynamic simulation.

    PubMed

    Nikkhah, S Javan; Moghbeli, M R; Hashemianzadeh, S M

    2015-05-01

    In this study, interfacial adhesion between functionalized polyethylene (PE) surfaces and graphene were examined using molecular simulation. Various functional groups including amino, carboxy, hydroxy, cyano, isocyanato, oxo, and ethylamino were used to cover the PE surface with surface densities of 0.48, 1.30, and 4.84 groups per nm(2). The interfacial adhesion between the modified PE surfaces and the graphene was quantified via calculation of work of separation (Wsep), the amount of the required work to separate two surfaces without occurring any relaxation and diffusion phenomena. Insertion of the functional groups on the PE surface decreased the amount of Wsep, except for the oxo, amino, and higher densities of the carboxy groups. Increasing the surface group density enhanced the adhesion due to decreasing the surface atomic roughness and increasing the atomic density at the interface. In addition, the effect of surface group rearrangement was investigated via calculation of the work of adhesion (Wadh) while sufficient time had been devoted to relax the interface. The surface reorganization during the relaxation process significantly enhanced adhesion due to eliminating the surface roughness and increasing the surface atomic density.

  1. Estimates of Interfacial Properties in Copper/Nickel Multilayer Thin Films using Hardness and Internal Stress Data

    NASA Astrophysics Data System (ADS)

    Carpenter, John Stuart

    Modeling the defect structure and mechanical properties of metallic multilayer thin films requires estimates of dislocation parameters such as interfacial line energy, interfacial barrier strength, and resistance to confined layer slip (CLS). A method is presented to estimate these parameters using experimental measurements of hardness and internal stress vs. individual layer thickness, h. Cu/Ni multilayers of varying bilayer thickness (20 nm ≤ Λ ≤ 60 nm) and volume fraction (25 ≤ %Ni ≤ 60%) were fabricated via sputtering and characterization performed using x-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Internal stresses for the samples were calculated via peak positions from inplane XRD and second order elastic constants. The experimental techniques of nanoindentation and micropillar compression data were used to look at flow stresses, hardness, and strain rate sensitivities for the Cu/Ni multilayers. Internal stress was seen to increase with decreasing bilayer thickness and decreasing layer thickness for both layer types. In addition, hardness was seen to increase with decreasing bilayer thickness and decreasing Cu layer thickness. The data acquired via characterization and experimentation was used as inputs within a CLS model in order to extract quantities for interfacial properties. It was seen that that separate values of line energy operate in the Cu and Ni layers and that a single effective line energy for the multilayer is inappropriate. This indicates that dislocation loops will encounter a different resistance at the shared interface depending on whether the dislocation loop originates in Ni or Cu. Analytical models for line energy overestimated the line energy in Cu and underestimated the line energy in Ni. It was seen that the interfacial barrier to dislocation motion increased with increasing bilayer thickness and misfit strain. A maximum value of 444 MPa was extrapolated for the

  2. Experimental Assessment of Dynamic Structural Parameters for Homogeneous and Interfacial Charge-Transfer Reactions: Case Studies Based on Time-Dependent Raman Scattering Methods

    DTIC Science & Technology

    1991-04-19

    Assessment of Dynamic Structural Para- meters for Homogeneous and Interfacial Charge-.. L Ag OS) S. K. Doorn, R. L. Blackbourn, C. S. Johnson and J. T. Hupp... dynamic structural problems involving charge transfer reactions is described. We show experimentally that a time-dependent analysis of resonance...REPORT (1991) FOR Contract N00014-88K-0369 Technical Report No. 9 Experimental A .- sessment of Dynamic Structural Parameters for Homogeneous and

  3. SiC-Si interfacial thermal and mechanical properties of reaction bonded SiC/Si ceramic composites

    NASA Astrophysics Data System (ADS)

    Hsu, Chun-Yen; Deng, Fei; Karandikar, Prashant; Ni, Chaoying

    Reaction bonded SiC/Si (RBSC) ceramic composites are broadly utilized in military, semiconductor and aerospace industries. RBSC affords advanced specific stiffness, hardness and thermal. Interface is a key region that has to be considered when working with any composites. Both thermal and mechanical behaviors of the RBSC are highly dependent on the SiC-Si interface. The SiC-Si interface had been found to act as a thermal barrier in restricting heat transferring at room temperature and to govern the energy absorption ability of the RBSC. However, up to present, the role of the SiC-Si interface to transport heat at higher temperatures and the interfacial properties in the nanoscale have not been established. This study focuses on these critically important subjects to explore scientific phenomena and underlying mechanisms. The RBSC thermal conductivity with volume percentages of SiC at 80 and 90 vol% was measured up to 1,200 °C, and was found to decrease for both samples with increasing environmental temperature. The RBSC with 90 vol% SiC has a higher thermal conductivity than that of the 80 vol%; however, is still significantly lower than that of the SiC. The interfacial thermal barrier effect was found to decrease at higher temperatures close 1200 °C. A custom-made in-situ tensile testing device which can be accommodated inside a ZEISS Auriga 60 FIB/SEM has been setup successfully. The SiC-Si interfacial bonding strength was measured at 98 MPa. The observation and analysis of crack propagation along the SiC-Si interface was achieved with in-situ TEM.

  4. Improved interfacial and electrical properties of vanadyl-phthalocyanine metal-insulator-semiconductor devices with silicon nitride as gate insulator

    SciTech Connect

    Wang, Lijuan Song, Xiaofeng; Liu, Xin; Zhang, Long; Li, Yiping; Yan, Donghang

    2013-12-09

    We have investigated the interfacial and electrical properties of vanadyl-phthalocyanine (VOPc) metal-insulator-semiconductor devices by the measurement of capacitance and conductance. The devices have been fabricated on ordered para-sexiphenyl (p-6P) layer with silicon nitride (SiN{sub x}) as gate insulator. The VOPc/p-6P/SiN{sub x} devices have shown a negligible hysteresis, low series resistance, and high operated frequency. Bulk traps have been distinguished from interface traps by two loss peaks in conductance measurement. Trap densities and distribution of trap energy level have been obtained. The improved properties indicate that VOPc/ p-6P devices with SiN{sub x} insulator hold a great promise of application in flexible displays.

  5. Physical properties and interfacial adaptation of three epoxy resin-based sealers.

    PubMed

    Marciano, Marina A; Guimarães, Bruno M; Ordinola-Zapata, Ronald; Bramante, Clovis M; Cavenago, Bruno C; Garcia, Roberto B; Bernardineli, Norberti; Andrade, Flaviana B; Moraes, Ivaldo G; Duarte, Marco A H

    2011-10-01

    The aim of the study was to evaluate the radiopacity, solubility, flow, film thickness, setting time, and adaptation to the root canal walls of 3 epoxy resin-based sealers: AH Plus, Acroseal, and Adseal. Physical tests were performed following American National Standards Institute/American Dental Association's requirements. For interfacial adaptation analysis, 30 maxillary canines were shaped by using ProTaper instruments. The specimens were divided into 3 groups (n = 10): group 1, AH Plus; group 2, Acroseal; and group 3, Adseal. The sealers were mixed with rhodamine B dye, and the canals were filled by using the lateral compaction technique. The percentage of gaps and voids area was calculated at 2, 4, and 6 mm levels from the apex. Statistical evaluation was performed by using analysis of variance for physical analysis and nonparametric Kruskal-Wallis and Dunn tests for interfacial adaptation (P < .05). No statistical differences were found for adaptation, percentage of voids, solubility, flow, and film thickness among the sealers (P > .05). AH Plus was significantly more radiopaque (P < .05). For the setting time, there were statistical differences among all the studied sealers (P < .05). AH Plus, Acroseal, and Adseal presented similar root canal adaptation, solubility, flow, and film thickness. Statistical differences were found for radiopacity and setting time (P < .05). Copyright © 2011 American Association of Endodontists. All rights reserved.

  6. Surface grafting of Kevlar fibers for improved interfacial properties of fiber-reinforced composites

    SciTech Connect

    Ravichandran, Vasudha.

    1991-01-01

    Matrix-specific chemical modification of the Kevlar fiber surfaces was carried out with the aim of enhancing adhesion, through covalent bonding, to selected thermoset matrix resins such as vinyl ester, unsaturated polyester and epoxy. A two-step grafting method, involving initial metalation followed by subsequent substitution, was used to graft vinyl and epoxy terminated groups onto Kevlar fiber surfaces. The physical changes in fiber surface were characterized by scanning-electron microscopy and surface area measurement and the chemical changes due to grafting were measured by contact angle measurement and neutron activation analysis; high concentrations of double bonds and epoxy groups were measured. The change in interfacial sear strength due to the surface grafting was measured by means of a single fiber pull out test. The results show a nearly twofold increase in the interfacial shear strength due to vinyl terminated grafts in the case of Kevlar/vinyl ester and Kevlar/polyester composites. Kevlar fibers containing the epoxy functionality on the surface had enhanced adhesion to epoxy matrix resin.

  7. Interfacial properties of hydrophilized poly(lactic-co-glycolic acid) layers with various thicknesses.

    PubMed

    Gyulai, G; Pénzes, Cs B; Mohai, M; Lohner, T; Petrik, P; Kurunczi, S; Kiss, É

    2011-10-15

    Biodegradable polyesters such as poly(lactic-co-glycolic acid) copolymers (PLGA) are preferred materials for drug carrier systems although their surface hydrophobicity greatly limits their use in controlled drug delivery. PLGA thin films on a solid support blended with PEG-containing compound (Pluronic) were used as model systems to study the interfacial interactions with aqueous media. Degree of surface hydrophilization was assessed by wettability, and X-ray photoelectron spectroscopy (XPS) measurements. Protein adsorption behavior was investigated by in situ spectroscopic ellipsometry. The degree of protein adsorption showed a good correlation with the hydrophilicity, and surface composition. Unexpectedly, the layer thickness was found to have a great impact on the interfacial characteristics of the polymer films in the investigated regime (20-200 nm). Thick layers presented higher hydrophilicity and great resistance to protein adsorption. That special behavior was explained as the result of the swelling of the polymer film combined with the partial dissolution of Pluronic from the layer. This finding might promote the rational design of surface modified biocompatible nanoparticles.

  8. First-principles study of the Al(001)-Al3Nb(001) interfacial properties

    NASA Astrophysics Data System (ADS)

    Ding, Yanhong; Xu, Rui

    2017-03-01

    The adhesion, interfacial energy and bonding on fcc-Al(001)/D022-Al3Nb(001) interface were investigated using density functional calculations. Considering different terminations of Al3Nb(001) (Al+Nb-terminated and Al-terminated) and stacking sites (top-, bridge- and center-sites), six Al(001)/Al3Nb(001) models were calculated. For the models with same stacking site, Al+Nb-terminated model has larger work of adhesion (Wad) than the Al-terminated one. For the models with same termination, the work of adhesion increases, and the interface energy decreases as the order of center-sited, bridge-sited and top-sited. Al+Nb-terminated-center-sited and Al-terminated-center-sited models are more stable among six models. The interfacial bonding was discussed with analysis of valence electron density distribution and partial density of states (PDOS). The bonding is mainly contributed from Al-Nb covalent bonds and Al-Al metallic interactions.

  9. Dynamical properties of superfluid turbulence

    SciTech Connect

    Lorenson, C.P.

    1985-01-01

    Despite all the experimental work done in recent years to study superfluid turbulence, the understanding of the dynamical properties of this system is still poor. The author designed a new cryogenic probe to perform a series of experiments to study the dynamical response of the vortex line density in turbulent thermal counterflow. The apparatus uses a small glass flow tube to probe the fluctuations in the line density around the two turbulent states (TI, TII) present in this system. A chemical potential gradiometer is used that measures the chemical potential across the flow tube. This quantity is directly related to the vortex line density. The gradiometer also enabled both the steady state and the dynamical properties of the turbulence to be studied. These experiments have established the existence of fluctuations in the chemical potential in turbulent counterflow. For the first time fluctuations in the dissipation were observed in the TI/TII transition region. The fluctuations are characteristic of broad-band noise showing no evidence of fluctuations at preferred frequency. The TI/TII transition is characterized by a sharp increase in the noise power amplitude and its variation with heat current reveals a complex structure.

  10. CH3NH3PbI3 grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition.

    PubMed

    Yao, Zhibo; Wang, Wenli; Shen, Heping; Zhang, Ye; Luo, Qiang; Yin, Xuewen; Dai, Xuezeng; Li, Jianbao; Lin, Hong

    2017-01-01

    Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C(PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C(PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

  11. CH3NH3PbI3 grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

    PubMed Central

    Yao, Zhibo; Wang, Wenli; Shen, Heping; Zhang, Ye; Luo, Qiang; Yin, Xuewen; Dai, Xuezeng; Li, Jianbao; Lin, Hong

    2017-01-01

    Abstract Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C (PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C (PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs. PMID:28458747

  12. Interfacial interaction in monolayer transition metal dichalcogenide/metal oxide heterostructures and its effects on electronic and optical properties: The case of MX2/CeO2

    NASA Astrophysics Data System (ADS)

    Yang, Ke; Huang, Wei-Qing; Hu, Wangyu; Huang, Gui-Fang; Wen, Shuangchun

    2017-01-01

    Using the density functional theory (DFT), we systematically study the interfacial interaction in monolayer MX2 (M = Mo, W; X = S, Se)/CeO2 heterostructures and its effects on electronic and optical properties. The interfacial interaction in the MX2/CeO2 heterostructures depends largely on chalcogens, and its strength determines the band gap variation and important electronic states at the band edges of the heterostructures. The MX2/CeO2 heterostructures with the same chalcogen have similar absorption spectra, from ultraviolet to near-infrared regions. These results suggest that chalcogens importantly determine the properties of MX2/metal oxide heterostructures.

  13. Measurements of interfacial dynamics of gas-liquid displacement in a capillary

    NASA Astrophysics Data System (ADS)

    Yan, Changfei; Qiu, Huihe

    2016-06-01

    Measurement of liquid film thickness in gas-liquid plug/slug flows is a challenging task. A novel laser interference method for measuring the interfacial film thickness of gas-liquid displacement in a plug flow has been developed. This novel technique utilizes light scattering from different liquid/gas interfaces in forming interference fringes. The interference fringes are used for calculating the film thickness. A set of simultaneous equations is derived based on geometrical optics. The experiment set up is not complex and is easy to install. The fringes are recorded by a charge-coupled device high speed camera and the image data are calculated using fast Fourier transform (FFT) and a non-linear least squares Levenberg-Marquardt algorithm. The uncertainty of this measurement technique is quite small (0.3 μm) and the entire film thickness profile can be measured at the same time.

  14. Tuning the Surface Morphologies and Properties of ZnO Films by the Design of Interfacial Layer.

    PubMed

    Li, Yaping; Wang, Hui-Qiong; Zhou, Hua; Du, Damin; Geng, Wei; Lin, Dingqu; Chen, Xiaohang; Zhan, Huahan; Zhou, Yinghui; Kang, Junyong

    2017-09-26

    Wurtzite ZnO films were grown on MgO(111) substrates by plasma-assisted molecular beam epitaxy (MBE). Different initial growth conditions were designed to monitor the film quality. All the grown ZnO films show highly (0001)-oriented textures without in-plane rotation, as illustrated by in situ reflection high-energy electron diffraction (RHEED) and ex situ X-ray diffraction (XRD). As demonstrated by atomic force microscopy (AFM) images, "ridge-like" and "particle-like" surface morphologies are observed for the ZnO films grown in a molecular O2 atmosphere with and without an initial deposition of Zn adatoms, respectively, before ZnO growth with oxygen plasma. This artificially designed interfacial layer deeply influences the final surface morphology and optical properties of the ZnO film. From room-temperature photoluminescence (PL) measurements, a strong defect-related green luminescence band appears for the ZnO film with a "particle-like" morphology but was hardly observed in the films with flat "ridge-like" surface morphologies. Our work suggests that the ZnO crystallinity can be improved and defect luminescence can be reduced by designing interfacial layers between substrates and epilayers.

  15. Influence of Zn Coating on Interfacial Reactions and Mechanical Properties During Laser Welding-Brazing of Mg to Steel

    NASA Astrophysics Data System (ADS)

    Li, Liqun; Tan, Caiwang; Chen, Yanbin; Guo, Wei; Hu, Xinbin

    2012-12-01

    To investigate the influence of Zn coating on the joining of magnesium alloy AZ31 to Zn-coated steel, dissimilar metal joining both with and without Zn coating was performed by the laser welding-brazing (LWB) process. Welding characteristics including joint appearance, identification of interfacial reaction layers, and mechanical properties were comparatively studied. The results indicated that the presence of Zn coating promoted the wetting of liquid filler wire on the steel substrate. Heterogeneous interfacial reaction layers formed along the interface between the Mg alloy and Zn-coated steel, whereas no distinct reaction layer and increased concentration of Al were identified at the interface between the Mg alloy and noncoated steel. The maximum tensile-shear strength of Mg/steel lap joint with Zn coating reached 180 N/mm, which was slightly higher than that achieved without Zn coating (160 N/mm). Failure of joint in both cases occurred at the interface; however, the fracture mode was found to differ. For Zn-coated steel, the crack propagated along the Mg-Zn reaction layer and Fe-Al phase, with little Mg-Zn reaction phases remaining on the steel side. As for noncoated steel, some remnants of the seam adhered to the steel substrate.

  16. Dissimilar Laser Welding/Brazing of 5754 Aluminum Alloy to DP 980 Steel: Mechanical Properties and Interfacial Microstructure

    NASA Astrophysics Data System (ADS)

    Yang, Jin; Li, Yulong; Zhang, Hua; Guo, Wei; Weckman, David; Zhou, Norman

    2015-11-01

    A diode laser welding/brazing technique was used for lap joining of 5754 aluminum alloy to DP 980 steel with Al-Si filler metal. The correlation between joint interfacial microstructure, wettability of filler metal, and mechanical properties was systematically investigated. At low laser power (1.4 kW), a layer of intermetallic compounds, composed of θ-Fe(Al,Si)3 and τ 5 -Al7.2Fe1.8Si, was observed at the interface between fusion zone and steel. Because of the poor wettability of filler metal on the steel substrate, the joint strength was very low and the joint failed at the FZ/steel interface. When medium laser power (2.0 kW) was applied, the wettability of filler metal was enhanced, which improved the joint strength and led to FZ failure. With further increase of laser power to 2.6 kW, apart from θ and τ 5, a new hard and brittle η-Fe2(Al,Si)5 IMC with microcracks was generated at the FZ/steel interface. The formation of η significantly degraded the joint strength. The failure mode changed back to interfacial failure.

  17. Interfacial dilational properties of tea polyphenols and milk proteins with gut epithelia and the role of mucus in nutrient adsorption.

    PubMed

    Guri, Anilda; Li, Yang; Corredig, Milena

    2015-12-01

    By interacting with nutrients, the mucus layer covering the intestinal epithelium may mediate absorption. This study aimed to determine possible interactions between epigallocatechin-3-gallate (EGCG), skim milk proteins or their complexes with human intestinal mucin films. The films were extracted from postconfluent monolayers of HT29-MTX, a human intestinal cell line, and a model system was created using drop shape tensiometry. The EGCG uptake tested in vitro on postconfluent Caco-2 cells or co-cultures of Caco-2/HT29-MTX (mucus producing) showed recovery of bioavailable EGCG only for Caco-2 cell monolayers, suggesting an effect of mucus on absorption. Interfacial dilational rheology was employed to characterize the properties of the interface mixed with mucus dispersion. Adsorption of polyphenols greatly enhanced the viscoelastic modulus of the mucus film, showing the presence of interactions between the nutrient molecules and mucus films. On the other hand, in situ digestion of milk proteins using trypsin showed higher surface activities as a result of protein unfolding and competitive adsorption of the hydrolyzed products. There was an increase of viscoelastic modulus over the drop ageing time for the mixed interfaces, indicating the formation of a stiffer interfacial network. These results bring new insights into the role of the mucus layer in nutrient absorption and the interactions of mucus and dairy products.

  18. Interfacial properties and electron structure of Al/B4C interface: A first-principles study

    NASA Astrophysics Data System (ADS)

    Xian, Yajiang; Qiu, Ruizhi; Wang, Xin; Zhang, Pengcheng

    2016-09-01

    This research aims at investigating the structural, mechanical and electronic properties of the Al (111)/B4C (0001) interface by first-principles calculations. This model geometry Al (111)/B4C (0001) is chosen because the close-packed planes of Al and B4C have the (111) and (0001) orientation, respectively, and the lattice mismatch is only ∼2.1%. Among four B4C (0001) surfaces with different terminations, our calculation of surface free energies predicted that C-terminated B4C (0001) surface is the most stable one. Relaxed atomic geometries, the work of adhesion and interfacial free energies were calculated for three C-terminated B4C (0001)/Al (111) interfaces with different stacking sequences (top-site, hollow-site, and bridge-site). Results reveal that the relaxed top-site (hollow-site-like) Al/B4C interface has the best adhesion force and also be the most stable. The interfacial electron structure including charge density difference, Bader charge and density of states (DOS) is analyzed to determine the nature of metal/carbide bonding and we find the formation of Alsbnd C bond and possibly the formation of Al4C3 in the interface.

  19. First principles calculation of interfacial stability, energy and electronic properties of SiC/ZrB2 interface

    NASA Astrophysics Data System (ADS)

    Xiong, Huihui; Liu, Zhao; Zhang, Henghua; Du, Zheng; Chen, Congmei

    2017-08-01

    Interfacial models of SiC/ZrB2 composite coating were studied by first-principles calculations based on density functional theory (DFT). The cubic SiC and hexagonal ZrB2 were selected in our work, and twelve types of SiC (111)/ZrB2 (0001) interface structures were investigated in consideration of four different terminations and three stacking sequences. The cohesive energy (Wad), interfacial energy (γint), and electronic structure of the SiC/ZrB2 interfaces were all calculated. The results show that the ZrB2 (0001) surface with 9 layers exhibits bulk-like interior characteristic. Among the interfaces of C/Zr terminated hcp-stacked (CZH), Si/Zr terminated hcp-stacked (SZH), C/B terminated center-stacked (CBC) and Si/B terminated center-stacked (SBT), the CZH interface has the largest Wad (6.28 J/m2) and thus is of the best stability. Over the range of zirconium chemical potential, the γint of CZH, SZH, CBC and SBT interfaces are -0.31-2.50 J/m2, 1.07-3.88 J/m2, 2.85-5.66 J/m2 and 2.32-5.13 J/m2, respectively. The calculated electronic properties reveal that, the CZH, CBC and SBT interfaces mainly contain covalent bonding, while the SZH one primarily consists of metallic bonding.

  20. Investigation on interfacial and electrical properties of Ge MOS capacitor with different NH3-plasma treatment procedure

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoyu; Xu, Jingping; Liu, Lu; Cheng, Zhixiang; Huang, Yong; Gong, Jingkang

    2017-08-01

    The effects of different NH3-plasma treatment procedures on interfacial and electrical properties of Ge MOS capacitors with stacked gate dielectric of HfTiON/TaON were investigated. The NH3-plasma treatment was performed at different steps during fabrication of the stacked gate dielectric, i.e. before or after interlayer (TaON) deposition, or after deposition of high-k dielectric (HfTiON). It was found that the excellent interface quality with an interface-state density of 4.79 × 1011 eV-1 cm-2 and low gate leakage current (3.43 × 10-5 A/cm2 at {V}{{g}}=1 {{V}}) could be achieved for the sample with NH3-plasma treatment directly on the Ge surface before TaON deposition. The involved mechanisms are attributed to the fact that the NH3-plasma can directly react with the Ge surface to form more Ge-N bonds, i.e. more GeO x Ny, which effectively blocks the inter-diffusion of elements and suppresses the formation of unstable GeO x interfacial layer, and also passivates oxygen vacancies and dangling bonds near/at the interface due to more N incorporation and decomposed H atoms from the NH3-plasma. Project supported by the National Natural Science Foundation of China (Nos. 61176100, 61274112).

  1. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Madathingal, Rajesh Raman

    The research investigated in this dissertation has focused on understanding the structure-property-function relationships of polymer nanocomposites. The properties of composite systems are dictated by the properties of their components, typically fillers in a polymer matrix. In nanocomposites, the polymer near an interface has significantly different properties compared with the bulk polymer, and the contribution of the adsorbed polymer to composite properties becomes increasingly important as the filler size decreases. Despite many reports of highly favorable properties, the behavior of polymer nanocomposites is not generally predictable, and thus requires a better understanding of the interfacial region. The ability to tailor the filler/matrix interaction and an understanding of the impact of the interface on macroscopic properties are keys in the design of nanocomposite properties. In this original work the surface of silica nanoparticles was tailored by: (a) Changing the number of sites for polymer attachment by varying the surface silanols and, (b) By varying the size/curvature of nanoparticles. The effect of surface tailoring on the dynamic properties after the adsorption of two model polymers, amorphous polymethyl methacrylate (PMMA) and semicrystalline polyethylene oxide (PEO) was observed. The interphase layer of polymers adsorbed to silica surfaces is affected by the surface silanol density as well as the relative size of the polymer compared with the size of the adsorbing substrate. The non-equilibrium adsorption of PMMA onto individual colloidal Stober silica (SiO2) particles, where Rparticle (100nm) > RPMMA (˜6.5nm) was compared with the adsorption onto fumed silica, where Rparticle (7nm) ˜ RPMMA (6.5nm) < Raggregate (˜1000nm), both as a function of silanol density [SiOH] and hydrophobility. In the former case, TEM images showed that the PMMA adsorbed onto individual nanoparticles, so that the number of PMMA chains/bead could be calculated, whereas

  2. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.

    1995-02-01

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.

  3. Interfacial properties of hydrides in α-Zr: a theoretical study

    NASA Astrophysics Data System (ADS)

    Louchez, M.-A.; Besson, R.; Thuinet, L.; Legris, A.

    2017-10-01

    In order to better understand hydride formation in zirconium alloys, heterophase interfaces between α-Zr and γ-ZrH are investigated by means of ab initio atomic-scale simulations of multilayers coupled with continuous elasticity. Our approach allows us to separate out the elastic contribution, leading to basal and prismatic α\\vert γ interface energies around 200 mJ \\cdot m-2 and 750 mJ \\cdot m-2 respectively, i.e. values noticeably higher than previously found for coherent particles such as ζ-Zr2H. By considering interfacial changes of H contents, the possibility of competing elasticity and chemistry effects for interface stability is analyzed. The effects of the strong anisotropy evident in α\\vert γ interface energies on the important practical issue of preferential habit planes are discussed, allowing us to propose a plausible explanation for the experimental results.

  4. Interfacial properties of hydrides in α-Zr: a theoretical study.

    PubMed

    Louchez, M-A; Besson, R; Thuinet, L; Legris, A

    2017-10-18

    In order to better understand hydride formation in zirconium alloys, heterophase interfaces between α-Zr and γ-ZrH are investigated by means of ab initio atomic-scale simulations of multilayers coupled with continuous elasticity. Our approach allows us to separate out the elastic contribution, leading to basal and prismatic [Formula: see text] interface energies around 200 [Formula: see text] and 750 [Formula: see text] respectively, i.e. values noticeably higher than previously found for coherent particles such as ζ-Zr2H. By considering interfacial changes of H contents, the possibility of competing elasticity and chemistry effects for interface stability is analyzed. The effects of the strong anisotropy evident in [Formula: see text] interface energies on the important practical issue of preferential habit planes are discussed, allowing us to propose a plausible explanation for the experimental results.

  5. Chemical Imaging and Dynamical Studies of Reactivity and Emergent Behavior in Complex Interfacial Systems. Final Technical Report

    SciTech Connect

    Sibener, Steven J.

    2014-03-11

    This research program explored the efficacy of using molecular-level manipulation, imaging and scanning tunneling spectroscopy in conjunction with supersonic molecular beam gas-surface scattering to significantly enhance our understanding of chemical processes occurring on well-characterized interfaces. One program focus was on the spatially-resolved emergent behavior of complex reaction systems as a function of the local geometry and density of adsorbate-substrate systems under reaction conditions. Another focus was on elucidating the emergent electronic and related reactivity characteristics of intentionally constructed single and multicomponent atom- and nanoparticle-based materials. We also examined emergent chirality and self-organization in adsorbed molecular systems where collective interactions between adsorbates and the supporting interface lead to spatial symmetry breaking. In many of these studies we combined the advantages of scanning tunneling (STM) and atomic force (AFM) imaging, scanning tunneling local electronic spectroscopy (STS), and reactive supersonic molecular beams to elucidate precise details of interfacial reactivity that had not been observed by more traditional surface science methods. Using these methods, it was possible to examine, for example, the differential reactivity of molecules adsorbed at different bonding sites in conjunction with how reactivity is modified by the local configuration of nearby adsorbates. At the core of this effort was the goal of significantly extending our understanding of interfacial atomic-scale interactions to create, with intent, molecular assemblies and materials with advanced chemical and physical properties. This ambitious program addressed several key topics in DOE Grand Challenge Science, including emergent chemical and physical properties in condensed phase systems, novel uses of chemical imaging, and the development of advanced reactivity concepts in combustion and catalysis including carbon

  6. Role of reactant transport in determining the properties of NIF shells made by interfacial polycondensation

    SciTech Connect

    Hamilton, K.E.; Letts, S.A.; Buckley, S.R.; Fearon, E.M.; Wilemski, G.; Cook, R.C.; Schroen-Carey, D.

    1997-03-01

    Polymer shells up to 2 mm in diameter were prepared using an interfacial polycondensation / cross-linking reaction occurring at the surface of an oil drop. The oil phase is comprised of a solution (20 wt% or less) of isophthaloyl dichloride (IPC) dissolved in an organic solvent. An interfacial reaction is initiated when the IPC-loaded oil drop is submerged in an aqueous solution of poly(p-vinylphenol) (PVP), a poly(electrolyte) at elevated pH. Composition, structure, and surface finish for fully-formed dry shells were assessed using a number of techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), fourier-transform infrared spectroscopy (FTIR), pyrolysis-gas chromatography (GC) mass spectroscopy (MS), microhardness measurements, gas permeability, and solvent permeability measurements. From deposition rate data, a reaction mechanism and key reaction parameters were identified. The deposition rate of shell membrane material was found to be a diffusion limited reaction of IPC through the forming membrane to the exterior shell interface (which is believed to be the reaction front). The final thickness of the film deposited at the interface and the rate of deposition were found to be strong functions of the IPC concentration and oil phase solvent. Films made with diethyl phthalate (DEP) were thinner and harder than films made using 1,6-dichlorohexane (DCH) as a solvent. Differences in solubility of the forming membrane in DCH and DEP appear to be able to account for the differences in deposition rate and the hardness (related to cross-linking density). The deposition can be thought of as a phase separation which is affected by both the poly(electrolyte) / ionomer transition and the amount of cross-linking. Finally, it was found that the choice of oil phase solvent profoundly affects the evolution of the outer surface roughness.

  7. Thermal unfolding of barstar and the properties of interfacial water around the unfolded forms

    SciTech Connect

    Pal, Somedatta; Bandyopadhyay, Sanjoy

    2013-12-21

    Identification of the intermediates along the folding-unfolding pathways and probing their interactions with surrounding solvent are two important but relatively unexplored issues in protein folding. In this work, we have carried out atomistic molecular dynamics simulations to study the thermal unfolding of barstar in aqueous solution from its folded native form at two different temperatures (400 K and 450 K). The calculations at 400 K reveal partial unfolding of two α-helices (helix-1 and helix-2) and their interconnecting loop. At 450 K, on the other hand, the entire protein attains an expanded flexible conformation due to disruption of a large fraction of tertiary contacts and breaking of almost all the secondary structures. These two disordered structures obtained at such high temperatures are then studied around room temperature to probe their influence on the properties of surrounding solvent. It is found that though the unfolding of the protein in general leads to increasingly hydrated interface, but new structural motifs with locally dehydrated interface may also form during the structural transition. Additionally, independent of the conformational state of the protein, its influence on surrounding solvent has been found to be restricted to the first hydration layer.

  8. Interfacial Dynamics in Liquid-Solid Mixtures: A Study of Solidification and Coarsening

    NASA Astrophysics Data System (ADS)

    Gibbs, John W.

    The microstructural evolution of liquid-solid mixtures is examined using X-ray computed tomography to make in-situ, 4D (three spatial dimensions and time) measurements of the interfaces between the liquid and solid phases. Samples are a variety of hypo-eutectic Al-Cu alloys and the total characterized volume is approximately 1 mm3. The coarsening datasets span solid volume fractions of 30% to 80% and have durations of up to 15 hours, making them some of the largest, most comprehensive coarsening datasets. This data is used show that the solid fraction does not have a significant effect on the coarsening rate, unlike in a system of spherical particles. The interfacial curvature and velocity data that is made possible by the 4D measurements is used to develop a relationship between interface shape and the average normal velocity for a piece of interface with that shape. This model accounts for both capillarity and shape-related diffusional effects. Neighborhood related diffusional effects lead to a distribution in velocities about the mean; these distributions are examined and shown to follow a Gaussian distribution. A novel new data collection and processing algorithm for X-ray computed tomography, time-interlaced model-based iterative reconstruction, is used to achieve 4D data with micrometer level spatial resolution and 1.8 second temporal resolution. This is approximately an order of magnitude better than what has been achieved before and yields the first data with sufficient spatial and temporal resolutions to characterize the microstructure during solidification. The resulting data of dendritic growth in an Al-24wt%Cu alloy that is being cooled at 2°C/minute shows the formation of split tip secondary dendrite arms that have not been seen before in transparent organic analogues. A single free-growing dendrite is isolated from this data and analyzed as a function of distance from the tip, resulting in relationships for the volume of solid, Vs proportional to

  9. Effect of Zinc Coatings on Joint Properties and Interfacial Reactions in Aluminum to Steel Ultrasonic Spot Welding

    NASA Astrophysics Data System (ADS)

    Haddadi, F.; Strong, D.; Prangnell, P. B.

    2012-03-01

    Dissimilar joining of aluminum to steel sheet in multimaterial automotive structures is an important potential application of ultrasonic spot welding (USW). Here, the weldability of different zinc-coated steels with aluminum is discussed, using a 2.5-kW USW welder. Results show that soft hot-dipped zinc (DX56-Z)-coated steel results in better weld performance than hard (galv-annealed) zinc coatings (DX53-ZF). For Al to hard galv-annealed-coated steel welds, lap shear strengths reached a maximum of ~80% of the strength of an Al-Al joint after a 1.0 s welding time. In comparison, welds between Al6111-T4 and hot dipped soft zinc-coated steel took longer to achieve the same maximum strength, but nearly matched the Al-Al joint properties. The reasons for these different behaviors are discussed in terms of the interfacial reactions between the weld members.

  10. Ultra-High Pressure Homogenization improves oxidative stability and interfacial properties of soy protein isolate-stabilized emulsions.

    PubMed

    Fernandez-Avila, C; Trujillo, A J

    2016-10-15

    Ultra-High Pressure Homogenization (100-300MPa) has great potential for technological, microbiological and nutritional aspects of fluid processing. Its effect on the oxidative stability and interfacial properties of oil-in-water emulsions prepared with 4% (w/v) of soy protein isolate and soybean oil (10 and 20%, v/v) were studied and compared to emulsions treated by conventional homogenization (15MPa). Emulsions were characterized by particle size, emulsifying activity index, surface protein concentration at the interface and by transmission electron microscopy. Primary and secondary lipid oxidation products were evaluated in emulsions upon storage. Emulsions with 20% oil treated at 100 and 200MPa exhibited the most oxidative stability due to higher amount of oil and protein surface load at the interface. This manuscript addresses the improvement in oxidative stability in emulsions treated by UHPH when compared to conventional emulsions.

  11. Synthesis of fullerene nanowhiskers using the liquid–liquid interfacial precipitation method and their mechanical, electrical and superconducting properties

    PubMed Central

    Miyazawa, Kun’ichi

    2015-01-01

    Fullerene nanowhiskers (FNWs) are thin crystalline fibers composed of fullerene molecules, including C60, C70, endohedral, or functionalized fullerenes. FNWs display n-type semiconducting behavior and are used in a diverse range of applications, including field-effect transistors, solar cells, chemical sensors, and photocatalysts. Alkali metal-doped C60 (fullerene) nanowhiskers (C60NWs) exhibit superconducting behavior. Potassium-doped C60NWs have realized the highest superconducting volume fraction of the alkali metal-doped C60 crystals and display a high critical current density (Jc) under a high magnetic field of 50 kOe. The growth control of FNWs is important for their success in practical applications. This paper reviews recent FNWs research focusing on their mechanical, electrical and superconducting properties and growth mechanisms in the liquid–liquid interfacial precipitation method. PMID:27877738

  12. Dielectric studies on the heterogeneity and interfacial property of composites made of polyacene quinone radical polymers and sulfonated polyurethanes.

    PubMed

    Zhu, Dan; Zhang, Juan; Bin, Yuezhen; Xu, Chunye; Shen, Jian; Matsuo, Masaru

    2012-03-08

    Sulfonated polyurethane (PUI, matrix) is synthesized and composited with polyacene quinone radical polymers (PAQRs, filler). The polarization mechanism of these polymers and composites were investigated in terms of their frequency, temperature, and filler-concentration-dependent dielectric properties. We found that PUI/PAQR composites have a high permittivity, which is attributed to the filler-matrix interfacial polarization and the contact effect. The PAQR-concentration-dependent permittivity of different PUI/PAQR composites reveals a percolation threshold at 20-30 wt % with scaling exponents that indicate the intercluster polarization. The frequency dependence of dielectric response is well-fitted by using the Debye and Cole-Cole functions on the basis of the structural diagrams and equivalent circuit, leading to a detailed evaluation on heterogeneous structures of different PUI/PAQR composites.

  13. Synthesis of fullerene nanowhiskers using the liquid-liquid interfacial precipitation method and their mechanical, electrical and superconducting properties

    NASA Astrophysics Data System (ADS)

    Miyazawa, Kun'ichi

    2015-02-01

    Fullerene nanowhiskers (FNWs) are thin crystalline fibers composed of fullerene molecules, including C60, C70, endohedral, or functionalized fullerenes. FNWs display n-type semiconducting behavior and are used in a diverse range of applications, including field-effect transistors, solar cells, chemical sensors, and photocatalysts. Alkali metal-doped C60 (fullerene) nanowhiskers (C60NWs) exhibit superconducting behavior. Potassium-doped C60NWs have realized the highest superconducting volume fraction of the alkali metal-doped C60 crystals and display a high critical current density (Jc) under a high magnetic field of 50 kOe. The growth control of FNWs is important for their success in practical applications. This paper reviews recent FNWs research focusing on their mechanical, electrical and superconducting properties and growth mechanisms in the liquid-liquid interfacial precipitation method.

  14. Desorption and exchange properties of adsorbed albumin on apatite. Influence of long-term interfacial residence times.

    PubMed

    Mura, M J; Behr, S; Voegel, J C

    1989-12-01

    A technique using 125I-labeled proteins was employed to study static adsorption properties and slow exchange and desorption processes of human albumin in contact with synthetic hydroxyapatite beads. With the aid of a thermostated "minicolumn," the adsorption isotherm was obtained during a so-called multiadsorption process, and could be described by a Langmuir adsorption model (K = 1.10 x 10(10) cm3.mol-1). All kinetic desorption and exchange experiments could be fitted by a simple exponential function of time. No influence of long-term interfacial residence times on characteristic relaxation times or percentage of desorbed or exchanged proteins could be detected in the present system. On the other hand, as compared to the low surface coverage domain, the small percentage of desorbable and high percentage of exchangeable molecules in the adsorption plateau domain was attributed to a bimolecular exchange process.

  15. Desorption and exchange properties of adsorbed albumin on apatite. Influence of long-term interfacial residence times

    SciTech Connect

    Mura, M.J.; Behr, S.; Voegel, J.C. )

    1989-12-01

    A technique using {sup 125}I-labeled proteins was employed to study static adsorption properties and slow exchange and desorption processes of human albumin in contact with synthetic hydroxyapatite beads. With the aid of a thermostated minicolumn, the adsorption isotherm was obtained during a so-called multiadsorption process, and could be described by a Langmuir adsorption model (K = 1.10 x 10(10) cm3.mol-1). All kinetic desorption and exchange experiments could be fitted by a simple exponential function of time. No influence of long-term interfacial residence times on characteristic relaxation times or percentage of desorbed or exchanged proteins could be detected in the present system. On the other hand, as compared to the low surface coverage domain, the small percentage of desorbable and high percentage of exchangeable molecules in the adsorption plateau domain was attributed to a bimolecular exchange process.

  16. A comparison of corn fiber gum, hydrophobically modified starch, gum arabic and soybean soluble polysaccharide: interfacial dynamics, viscoelastic response at oil/water interfaces and emulsion stabilization mechanisms

    USDA-ARS?s Scientific Manuscript database

    The interfacial rheology of polysaccharide adsorption layers of corn fiber gum (CFG), octenyl succinate anhydride-modified starch (OSA-s), gum arabic (GA) and soybean soluble polysaccharides (SSPS) at the oil/water interface and their emulsifying properties in oil-in-water (O/W) emulsions were compa...

  17. The Role of Interfacial Electronic Properties on Phonon Transport in Two-Dimensional MoS2 on Metal Substrates.

    PubMed

    Yan, Zhequan; Chen, Liang; Yoon, Mina; Kumar, Satish

    2016-12-07

    We investigate the role of interfacial electronic properties on the phonon transport in two-dimensional MoS2 adsorbed on metal substrates (Au and Sc) using first-principles density functional theory and the atomistic Green's function method. Our study reveals that the different degree of orbital hybridization and electronic charge distribution between MoS2 and metal substrates play a significant role in determining the overall phonon-phonon coupling and phonon transmission. The charge transfer caused by the adsorption of MoS2 on Sc substrate can significantly weaken the Mo-S bond strength and change the phonon properties of MoS2, which result in a significant change in thermal boundary conductance (TBC) from one lattice-stacking configuration to another for same metallic substrate. In a lattice-stacking configuration of MoS2/Sc, weakening of the Mo-S bond strength due to charge redistribution results in decrease in the force constant between Mo and S atoms and substantial redistribution of phonon density of states to low-frequency region which affects overall phonon transmission leading to 60% decrease in TBC compared to another configuration of MoS2/Sc. Strong chemical coupling between MoS2 and the Sc substrate leads to a significantly (∼19 times) higher TBC than that of the weakly bound MoS2/Au system. Our findings demonstrate the inherent connection among the interfacial electronic structure, the phonon distribution, and TBC, which helps us understand the mechanism of phonon transport at the MoS2/metal interfaces. The results provide insights for the future design of MoS2-based electronics and a way of enhancing heat dissipation at the interfaces of MoS2-based nanoelectronic devices.

  18. In vivo bone response and interfacial properties of titanium-alloy implant with different designs in rabbit model with time.

    PubMed

    Chakraborty, Abhijit; Kundu, Biswanath; Basu, Debabrata; Pal, Tamal Kanti; Nandi, Samit Kumar

    2011-01-01

    Using implants for dental applications are well-accepted procedures as one of the solutions for periodontal defect repair. Suitable design and materials, their reaction with the surrounding hard tissues and interfacial biomechanical properties are still considered to be the primary criteria which need to be addressed systematically. In the present study, a thorough and systemic approach was made to identify a suitable implant, considering the above criteria after both in vitro and in vivo animal trials. Titanium alloy (Ti-6Al-4V) implants, with thread and without thread models, were implanted to the mid-metaphysial portion of the tibia of the right hind leg of three white Australian Chinchilla rabbit species and their effects and response to the surrounding bone were investigated. Parameters studied included hematological and biochemical features (serum alkaline phosphatase and calcium), both preoperatively and postoperatively, consecutively for 7 days and after 1-3 months. The interfacial integrity and compositional variation along the interface were studied using scanning electron microscope (SEM) with energy dispersive analysis of X-ray (EDAX) and histopathology from 1 to 3 months consecutively. Finally, biomechanical properties were studied with the help of push-out test. Bone remineralization started through the process of electro-physiological ionic exchanges, which helps in formation of osteoblastic cells in the area of bony injury. The SEM-EDAX results confirmed the initial stability for the Ti (with thread) implant, but the regeneration of new bone formation was faster in the case of Ti (Without thread) implant, and hence could be used for faster healing. These have also been substantiated through push-out and histopathlogical tests. From the physico-chemical and biomechanical observations, it was found that that smooth type implants were well accepted in the physiological condition although chances of elemental leaching from the surface were also observed

  19. Improved mechanical properties of polylactide nanocomposites-reinforced with cellulose nanofibrils through interfacial engineering via amine-functionalization.

    PubMed

    Lu, Yuan; Cueva, Mario Calderón; Lara-Curzio, Edgar; Ozcan, Soydan

    2015-10-20

    One of the main factors responsible for the mechanical and physical properties of nanocomposites is the effectiveness of the interfacial region to transfer loads and mechanical vibrations between the nano-reinforcements and the matrix. Surface functionalization has been the preferred approach to engineer the interfaces in polymer nanocomposites in order to maximize their potential in structural and functional applications. In this study, amine-functionalized cellulose nanofibrils (mCNF-G1) were synthesized via silylation of the hydroxyl groups on the CNF surface using 3-aminopropyltrimethoxysilane (APTMS). To further increase the amine density (mCNF-G2), dendritic polyamidoamine (PAMAM) was grafted onto mCNF-G1 by the Michael addition of methacrylate onto mCNF-G1, followed by the transamidation of the ester groups of methacrylate using ethylenediamine. Compared to native CNF-reinforced, poly(l-lactide) (PLLA) nanocomposites, amine-functionalized CNF exhibited significantly improved dispersion and interfacial properties within the PLLA matrix due to the grafting of PLLA chains via aminolysis. It is also a more effective nucleating agent, with 15% mCNF-G1 leading to a crystallinity of 32.5%, compared to 0.1 and 8.7% for neat PLLA and native CNF-reinforced composites. We have demonstrated that APTMS-functionalized CNF (mCNF-G1) significantly improved the tensile strength compared to native CNF, with 10% mCNF-G1 being the most effective (i.e., >100% increase in tensile strength). However, we also found that excessive amines on the CNF surface (i.e., mCNF-G2) resulted in decreased tensile strength and modulus due to PLLA degradation via aminolysis. These results demonstrate the potential of optimized amine-functionalized CNF for future renewable material applications.

  20. Engineering interfacial properties by anionic surfactant-chitosan complexes to improve stability of oil-in-water emulsions.

    PubMed

    Zinoviadou, Kyriaki G; Scholten, Elke; Moschakis, Thomas; Biliaderis, Costas G

    2012-03-01

    Oil-in-water emulsions (10% w/w n-tetradecane) were prepared at pH = 5.7 by using, as surface active agents, electrostatically formed complexes of sodium stearoyl lactylate (SSL) at a concentration of 0.4% (w/w) and chitosan (CH) in a concentration range between 0 and 0.48% w/w. The use of complexes in emulsions with a low concentration of CH (<0.24% w/w) resulted in highly flocculated systems; instead, with increased level of CH, the emulsions had a smaller average droplet size and exhibited greater stability during storage. Emulsions stabilised by SSL/CH complexes showed non-Newtonian flow behavior with pronounced shear thinning. Among all formulations studied none showed a gel-like behavior since in all cases the G' (storage modulus) was lower that G'' (loss modulus). Adsorption kinetics of pure SSL and SSL/CH complexes to the oil/water interfaces were evaluated using an automated drop tensiometer (ADT). Even though complexation of SSL with CH resulted in a delay of the adsorption of the surface active species at the oil/water interface, the inclusion of the polysaccharide resulted in substantially improved interfacial properties as indicated by a significant increase of the dilatational modulus. Furthermore, the enhanced interfacial properties of the emulsion droplets resulted in improved stability against freeze-thaw cycling. The results of this study may facilitate the development of frozen food products such as desserts with an ameliorated stability and favorable sensorial characteristics.

  1. The Role of Interfacial Electronic Properties on Phonon Transport in Two-Dimensional MoS2 on Metal Substrates

    DOE PAGES

    Yan, Zhequan; Chen, Liang; Yoon, Mina; ...

    2016-11-08

    In this paper, we investigate the role of interfacial electronic properties on the phonon transport in two-dimensional MoS2 adsorbed on metal substrates (Au and Sc) using first-principles density functional theory and the atomistic Green’s function method. Our study reveals that the different degree of orbital hybridization and electronic charge distribution between MoS2 and metal substrates play a significant role in determining the overall phonon–phonon coupling and phonon transmission. The charge transfer caused by the adsorption of MoS2 on Sc substrate can significantly weaken the Mo–S bond strength and change the phonon properties of MoS2, which result in a significant changemore » in thermal boundary conductance (TBC) from one lattice-stacking configuration to another for same metallic substrate. In a lattice-stacking configuration of MoS2/Sc, weakening of the Mo–S bond strength due to charge redistribution results in decrease in the force constant between Mo and S atoms and substantial redistribution of phonon density of states to low-frequency region which affects overall phonon transmission leading to 60% decrease in TBC compared to another configuration of MoS2/Sc. Strong chemical coupling between MoS2 and the Sc substrate leads to a significantly (~19 times) higher TBC than that of the weakly bound MoS2/Au system. Our findings demonstrate the inherent connection among the interfacial electronic structure, the phonon distribution, and TBC, which helps us understand the mechanism of phonon transport at the MoS2/metal interfaces. Finally, the results provide insights for the future design of MoS2-based electronics and a way of enhancing heat dissipation at the interfaces of MoS2-based nanoelectronic devices.« less

  2. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    NASA Astrophysics Data System (ADS)

    Marstell, Roderick J.; Strandwitz, Nicholas C.

    2015-11-01

    We report the differences in the passivation and electronic properties of aluminum oxide (Al2O3) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Qf Traditional = -8.1 × 1011 cm-2 and Qf NHALD = -3.6 × 1012 cm-2), and a larger degree of chemical passivation than NHALD films (density of interface trap states, Dit Traditional = 5.4 × 1011 eV-1 cm-2 and Dit NHALD = 2.9 × 1012 eV-1 cm-2). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased Dit for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τTraditional = 2.2 × 10-9 s and τNHALD = 1.7 × 10-7 s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces.

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

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

  4. Effect of Surface Oxidation on Interfacial Water Structure at a Pyrite (100) Surface as Studied by Molecular Dynamics Simulation

    SciTech Connect

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

    2015-06-01

    In the first part of this paper, a Scanning Electron Microscopy and contact angle study of a pyrite surface (100) is reported describing the relationship between surface oxidation and the hydrophilic surface state. In addition to these experimental results, the following simulated surface states were examined using Molecular Dynamics Simulation (MDS): fresh unoxidized (100) surface; polysulfide at the (100) surface; elemental sulfur at the (100) surface. Crystal structures for the polysulfide and elemental sulfur at the (100) surface were simulated using Density Functional Theory (DFT) quantum chemical calculations. The well known oxidation mechanism which involves formation of a metal deficient layer was also described with DFT. Our MDS results of the behavior of interfacial water at the fresh and oxidized pyrite (100) surfaces without/with the presence of ferric hydroxide include simulated contact angles, number density distribution for water, water dipole orientation, water residence time, and hydrogen-bonding considerations. The significance of the formation of ferric hydroxide islands in accounting for the corresponding hydrophilic surface state is revealed not only from experimental contact angle measurements but also from simulated contact angle measurements using MDS. The hydrophilic surface state developed at oxidized pyrite surfaces has been described by MDS, on which basis the surface state is explained based on interfacial water structure. 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 the Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES.

  5. Interfacial complex formation in uranyl extraction by tributyl phosphate in dodecane diluent: a molecular dynamics study.

    PubMed

    Ye, Xianggui; Cui, Shengting; de Almeida, Valmor; Khomami, Bamin

    2009-07-23

    Atomistic simulations have been carried out in a multicomponent two-phase system (aqueous and organic phases in direct contact) to investigate the interfacial molecular mechanisms leading to uranyl extraction from the aqueous to organic phase. The aqueous phase consists of the dissolved ions UO2(2+) and nitrate NO3-, with or without H3O+, in water to describe acidic or neutral condition; the organic phase consists of tributyl phosphate, the extractant, in dodecane as the diluent. We find that the interface facilitates the formation of various uranyl complexes, with a general formula UO2(2+)(NO3-)n *mTBP*kH2O, with n+m+k=5, suggesting a 5-fold coordination. The coordination for all three molecular entities has the common feature that they all bind to the uranyl at the uranium atom with an oxygen atom in the equatorial plane perpendicular to the molecular axis of the uranyl, forming a 5-fold symmetry plane. Nitric acid has a strong effect in enhancing the formation of extractable species, which is consistent with experimental findings.

  6. Optoelectronic properties and interfacial durability of CNT and ITO on boro-silicate glass and PET substrates with nano- and heterostructural aspects

    NASA Astrophysics Data System (ADS)

    Park, Joung-Man; Wang, Zuo-Jia; Kwon, Dong-Jun; DeVries, Lawrence

    2011-02-01

    Nano- and hetero-structures of carbon nanotube (CNT) and indium tin oxide (ITO) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as sensing and actuator under cyclic loading. Optimized preparing conditions were obtained for multi-functional purpose of the specimen by obtaining the best dispersion and turbidity in the solution. Optical transmittance and electrical properties were investigated for CNT and ITO dipping and spraying coating on boro-silicate glass and polyethylene terephthalate (PET) substrates by electrical resistance measurement under cyclic loading and wettability test. Uniform dip-coating was performed using Wilhelmy plate method due to its simple and convenience. Spraying coating was applied to the specimen additionally. The change in the electrical resistance and optical properties of coated layer were mainly dependent upon the number of dip-coating, the concentration of CNT and ITO solutions, and the surface treatment condition. Electric properties of coating layers were measured using four-point probe method, and surface resistance was calculated using a dual configuration method. Optical transmittance of CNT and ITO coated PET film was also evaluated using UV spectrum. Surface energy and their hydrophilic and hydrophobic properties of CNT and ITO coated substrates were investigated by wettability test via static and dynamic contact angle measurements. As the elapsing time of cyclic loading passed, the stability of surface resistance and thus comparative interfacial adhesion between coated layer and substrates was evaluated to compare the thermodynamic work of adhesion, Wa. As dip-coating number increased, surface resistance of coated CNT decreased, whereas the transmittance decreased step-by-step due to the thicker CNT and ITO networked layer. Nano- and heterostructural effects of CNT and ITO solution on the optical and electrical effects have been studied continuously.

  7. Improving the interfacial and mechanical properties of short glass fiber/epoxy composites by coating the glass fibers with cellulose nanocrystals

    Treesearch

    A. Asadi; M. Miller; Robert Moon; K. Kalaitzidou

    2016-01-01

    In this study, the interfacial and mechanical properties of cellulose nanocrystals (CNC) coated glass fiber/epoxy composites were investigated as a function of the CNC content on the surface of glass fibers (GF). Chopped GF rovings were coated with CNC by immersing the GF in CNC (0–5 wt%) aqueous suspensions. Single fiber fragmentation (SFF) tests showed that the...

  8. Controlled interfacial electron dynamics in highly efficient Zn2 SnO4 -based dye-sensitized solar cells.

    PubMed

    Shin, Seong Sik; Kim, Dong Wook; Hwang, Daesub; Suk, Jae Ho; Oh, Lee Seul; Han, Byung Suh; Kim, Dong Hoe; Kim, Ju Seong; Kim, Dongho; Kim, Jin Young; Hong, Kug Sun

    2014-02-01

    Among ternary oxides, Zn2 SnO4 (ZSO) is considered for dye-sensitized solar cells (DSSCs) because of its wide bandgap, high optical transmittance, and high electrical conductivity. However, ZSO-based DSSCs have a poor performance record owing largely to the absence of systematic efforts to enhance their performance. Herein, general strategies are proposed to improve the performance of ZSO-based DSSCs involving interfacial engineering/modification of the photoanode. A conformal ZSO thin film (blocking layer) deposited at the fluorine-doped tin oxide-electrolyte interface by pulsed laser deposition suppressed the back-electron transfer effectively while maintaining a high optical transmittance, which resulted in a 22 % improvement in the short-circuit photocurrent density. Surface modification of ZSO nanoparticles (NPs) resulted in an ultrathin ZnO shell layer, a 9 % improvement in the open-circuit voltage, and a 4 % improvement in the fill factor because of the reduced electron recombination at the ZSO NPs-electrolyte interface. The ZSO-based DSSCs exhibited a faster charge injection and electron transport than their TiO2 -based counterparts, and their superior properties were not inhibited by the ZnO shell layer, which indicates their feasibility for highly efficient DSSCs. Each interfacial engineering strategy could be applied to the ZSO-based DSSC independently to lead to an improved conversion efficiency of 6 %, a very high conversion efficiency for a non-TiO2 based DSSC. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Interfacial defects induced electronic property transformation at perovskite SrVO3/SrTiO3 and LaCrO3/SrTiO3 heterointerfaces.

    PubMed

    Li, Junjie; Yin, Deqiang; Li, Qiang; Sun, Rong; Huang, Sumei; Meng, Fanzhi

    2017-03-08

    Unravelling the atomic structure and chemical species of interfacial defects is critical to understanding the origin of interfacial properties in many heterojunctions. Here, by combining advanced transmission electron microscopy, spectroscopy and first-principles calculations, we demonstrate interfacial Ti diffusion in SrVO3/SrTiO3 and LaCrO3/SrTiO3 heterointerfaces and uncover that the interfacial defects induce a significant change in electronic properties by showing an electronic transformation from the insulating state to metallic state at SrVO3/SrTiO3 heterointerfaces due to the hybridization of interfacial Ti d, O p and V d, and a metallic to insulating state transformation at LaCrO3/SrTiO3 because of Ti-Cr mixing induced charge redistribution in the interfacial layer.

  10. Fully biobased and supertough polylactide-based thermoplastic vulcanizates fabricated by peroxide-induced dynamic vulcanization and interfacial compatibilization.

    PubMed

    Liu, Guang-Chen; He, Yi-Song; Zeng, Jian-Bing; Li, Qiu-Tong; Wang, Yu-Zhong

    2014-11-10

    A fully biobased and supertough thermoplastic vulcanizate (TPV) consisting of polylactide (PLA) and a biobased vulcanized unsaturated aliphatic polyester elastomer (UPE) was fabricated via peroxide-induced dynamic vulcanization. Interfacial compatibilization between PLA and UPE took place during dynamic vulcanization, which was confirmed by gel measurement and NMR analysis. After vulcanization, the TPV exhibited a quasi cocontinuous morphology with vulcanized UPE compactly dispersed in PLA matrix, which was different from the pristine PLA/UPE blend, exhibiting typically phase-separated morphology with unvulcanized UPE droplets discretely dispersed in matrix. The TPV showed significantly improved tensile and impact toughness with values up to about 99.3 MJ/m(3) and 586.6 J/m, respectively, compared to those of 3.2 MJ/m(3) and 16.8 J/m for neat PLA, respectively. The toughening mechanisms under tensile and impact tests were investigated and deduced as massive shear yielding of the PLA matrix triggered by internal cavitation of VUPE. The fully biobased supertough PLA vulcanizate could serve as a promising alternative to traditional commodity plastics.

  11. Effects of interfacial layer structures on crystal structural properties of ZnO films

    SciTech Connect

    Park, J. S.; Minegishi, T.; Lee, S. H.; Im, I. H.; Park, S. H.; Hanada, T.; Goto, T.; Cho, M. W.; Yao, T.; Hong, S. K.; Chang, J. H.

    2008-01-15

    Single crystalline ZnO films were grown on Cr compound buffer layers on (0001) Al{sub 2}O{sub 3} substrates by plasma assisted molecular beam epitaxy. In terms of lattice misfit reduction between ZnO and substrate, the CrN and Cr{sub 2}O{sub 3}/CrN buffers are investigated. The structural and optical qualities of ZnO films suggest the feasibility of Cr compound buffers for high-quality ZnO films growth on (0001) Al{sub 2}O{sub 3} substrates. Moreover, the effects of interfacial structures on selective growth of different polar ZnO films are investigated. Zn-polar ZnO films are grown on the rocksalt CrN buffer and the formation of rhombohedral Cr{sub 2}O{sub 3} results in the growth of O-polar films. The possible mechanism of polarity conversion is proposed. By employing the simple patterning and regrowth procedures, a periodical polarity converted structure in lateral is fabricated. The periodical change of the polarity is clearly confirmed by the polarity sensitive piezo response microscope images and the opposite hysteretic characteristic of the piezo response curves, which are strict evidences for the validity of the polarity controlling method as well as the successful fabrication of the periodical polarity controlled ZnO structure.

  12. Interfacial investigation and mechanical properties of glass-Al-glass anodic bonding process

    NASA Astrophysics Data System (ADS)

    Hu, Lifang; Xue, Yongzhi; Shi, Fangrong

    2017-10-01

    Glass-Al-glass with Al as common anode was successfully bonded together through the anodic bonding process. SEM and EDS were conducted to investigate the interfacial structure of the glass-Al-glass samples. Special attention was given to the element distribution after the bonding process. The element profile of the transitional layer was investigated by glow discharge optical emission microscopy. The results showed that ion migration played an important role during the anodic bonding process, Na+ would precipitate from the back of the glass, and a Na+ depletion region formed at the bonding interface. At the same time, O2‑ diffused into the bonding interface and reacted with the Al, which resulted in a successful bonding process. Furthermore, Al migrated into the glass, which could enhance the bonding process. The peak current of the glass-Al-glass bonding was two times larger than that of the Al-glass bonding, which meant that the glass-Al-glass bonding process could be considered equivalent to two individual Al-glass bonding processes. Tensile strength tests showed that the glass was fractured, and the fractures propagated into the bonding interface, which indicated a reliable bonding process.

  13. Interpreting attenuation at different excitation amplitudes to estimate strain-dependent interfacial rheological properties of lipid-coated monodisperse microbubbles.

    PubMed

    Xia, Lang; Porter, Tyrone M; Sarkar, Kausik

    2015-12-01

    Broadband attenuation of ultrasound measured at different excitation pressures being different raises a serious theoretical concern, because the underlying assumption of linear and independent propagation of different frequency components nominally requires attenuation to be independent of excitation. Here, this issue is investigated by examining ultrasound attenuation through a monodisperse lipid-coated microbubble suspension measured at four different acoustic excitation amplitudes. The attenuation data are used to determine interfacial rheological properties (surface tension, surface dilatational elasticity, and surface dilatational viscosity) of the encapsulation according to three different models. Although different models result in similar rheological properties, attenuation measured at different excitation levels (4-110 kPa) leads to different values for them; the dilatation elasticity (0.56 to 0.18 N/m) and viscosity (2.4 × 10(-8) to 1.52 × 10(-8) Ns/m) both decrease with increasing pressure. Numerically simulating the scattered response, nonlinear energy transfer between frequencies are shown to be negligible, thereby demonstrating the linearity in propagation and validating the attenuation analysis. There is a second concern to the characterization arising from shell properties being dependent on excitation amplitude, which is not a proper constitutive variable. It is resolved by arriving at a strain-dependent rheology for the encapsulation. The limitations of the underlying analysis are discussed.

  14. Modulation of interfacial electronic properties in PbI2 and BN van der Waals heterobilayer via external electric field

    NASA Astrophysics Data System (ADS)

    Ma, Yaqiang; Zhao, Xu; Niu, Mengmeng; Dai, Xianqi; Li, Wei; Wang, Xiaolong; Zhao, Mingyu; Wang, Tianxing; Tang, Yanan

    2017-07-01

    The interfacial electronic properties of PbI2 and BN van der Waals (vdW) heterobilayer are explored by using density functional theory (DFT) method. An intrinsic type-II heterostructure with a wide bandgap is demonstrated. The spatial separation of the lowest energy electron-hole pairs can be actualised and make PbI2/BN heterostructure as a good candidate for applications in optoelectronics and solar cell. A simulation of Efield is actualized to modify its electronic properties. Band alignment converts from type-II to type-I heterostructure separated by a forward voltage with the value of about 0.07 V/Å. Three regions implying different Efield-sensitive properties are obtained from the variations of bandgap with Efield. The charge redistribution with an Efield is mainly on the surface of PbI2 and BN layers as well as the amount of electrons depends on the strength of Efield. In addition, the PbI2/BN heterobilayer exhibits more outstanding optical conductivity capability. Our results could bring forward a new perspective on sensor and shed light on the design of novel nano- and optoelectronics based on the PbI2/BN vdW heterostructure.

  15. 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.

  16. Separating the effects of repulsive and attractive forces on the phase diagram, interfacial, and critical properties of simple fluids.

    PubMed

    Fuentes-Herrera, M; Moreno-Razo, J A; Guzmán, O; López-Lemus, J; Ibarra-Tandi, B

    2016-06-07

    Molecular simulations in the canonical and isothermal-isobaric ensembles were performed to study the effect of varying the shape of the intermolecular potential on the phase diagram, critical, and interfacial properties of model fluids. The molecular interactions were modeled by the Approximate Non-Conformal (ANC) theory potentials. Unlike the Lennard-Jones or Morse potentials, the ANC interactions incorporate parameters (called softnesses) that modulate the steepness of the potential in their repulsive and attractive parts independently. This feature allowed us to separate unambiguously the role of each region of the potential on setting the thermophysical properties. In particular, we found positive linear correlation between all critical coordinates and the attractive and repulsive softness, except for the critical density and the attractive softness which are negatively correlated. Moreover, we found that the physical properties related to phase coexistence (such as span of the liquid phase between the critical and triple points, variations in the P-T vaporization curve, interface width, and surface tension) are more sensitive to changes in the attractive softness than to the repulsive one. Understanding the different roles of attractive and repulsive forces on phase coexistence may contribute to developing more accurate models of liquids and their mixtures.

  17. Interfacial properties of α / β-Bi2O3 homo-junction from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Li, Qiu-Yi; Zhao, Zong-Yan

    2015-10-01

    To construct hetero-/homo-junction is an effective way to improve the performance of photocatalyst. However, some basic and important issues about the underlying mechanism of this strategy still need to be further confirmed and explained. In the present work, the interfacial properties of α / β-Bi2O3 composite photocatalyst with homo-junction are in-depth investigated by density functional theory calculations. Owing to partially saturated dangling bonds, the electronic structure of interface model exhibits both the features of bulk and surface models. Importantly, the interfacial states are mainly arising from the layer of β-Bi2O3@Interface. At the interface of α / β-Bi2O3 homo-junction, the energy bands of β-Bi2O3 are relatively down-shifting compared with those of α-Bi2O3, resulting in form the staggered gaps (type II), which is very favorable for the improvement of photocatalytic performance. Moreover, the built-in electric field of homo-junction points from β-Bi2O3 layer to α-Bi2O3 layer under equilibrium, so the photon-generated electron-hole pairs can be spatially separated by the α / β-Bi2O3 homo-junction. Furthermore, to construct α / β-Bi2O3 homo-junction not only keep the advantageous of visible-light absorption of β-Bi2O3, but also improve the visible-light absorption of α-Bi2O3.

  18. Improved interfacial and electrical properties of Ge MOS devices with ZrON/GeON dual passivation layer

    NASA Astrophysics Data System (ADS)

    Wenyu, Yuan; Jingping, Xu; Lu, Liu; Yong, Huang; Zhixiang, Cheng

    2016-05-01

    The interfacial and electrical characteristics of Ge metal-oxide-semiconductor (MOS) devices with a dual passivation layer of ZrON/GeON formed by NH3- or N2-plasma treatment are investigated. The experimental results show that the NH3-plasma treated sample exhibits significantly improved interfacial and electrical properties as compared to the samples with N2-plasma treatment and no treatment: a lower interface-state density at the midgap (1.64 × 1011 cm-2 · eV-1) and gate leakage current (9.32 × 10-5 A/cm2 at Vfb + 1 V), a small capacitance equivalent thickness (1.11 nm) and a high k value (32). X-ray photoelectron spectroscopy is used to analyze the involved mechanisms. It is indicated that more GeON and less GeOx (x < 2) are formed on the Ge surface during NH3-plasma treatment than the N2-plasma treatment, resulting in a high-quality high-k/Ge interface, because H atoms and NH radicals in NH3-plasma can enhance volatilization of the unstable low-k GeOx, creating high-quality GeON passivation layer. Moreover, more nitrogen incorporation in ZrON/GeON induced by NH3-plasma treatment can build a stronger N barrier and thus more effectively inhibit in-diffusion of O and Ti from high-k gate dielectric and out-diffusion of Ge. Project supported by the National Natural Science Foundation of China (Nos. 6127411261176100, 61404055).

  19. Charge Transfer as a Probe for the Interfacial Properties of Quantum Dot-Ligand Complexes

    NASA Astrophysics Data System (ADS)

    Weinberg, David Joseph

    This dissertation describes the study of charge transfer interactions between colloidal quantum dots (QDs) and molecular redox partners in the context of both fundamental investigations of charge recombination mechanisms in nanocrystal-molecule systems, and as a technique to probe the properties of the QD ligand shell. Charge separation in a system of CdS nanocrystals and organic hole acceptors results in the formation of a spin-correlated radical ion pair. Interrogating this photogenerated species with EPR and magnetic field effect transient absorption techniques reveals that the charge recombination dynamics of this donor-acceptor system are dictated by the radical pair intersystem crossing mechanism on the nanosecond timescale. These experiments also indicate that the photoinjected electron localizes at a CdS QD surface trap state, and the coupling between the electron and hole in this spin-correlated system is low. Additional studies involving the CdS QDs and organic hole acceptors are proposed which would investigate the exchange of charge and energy within the nanocrystal organic adlayer. Collisional charge transfer interactions between substituted benzoquinone molecules and PbS QDs coated with mixed monolayers of oleic acid and perfluorodecanethiol are monitored via photoluminescence and transient absorption spectroscopies. These experiments reveal that partially fluorinated ligand shells are less permeable to solution phase molecules and offer greater protection of the nanocrystal surface than their aliphatic counterparts. Only a small amount of fluorinated surfactant ( 20% surface coverage) is necessary to profoundly change the permeability of the ligand shell, and the protective nature of these fluorinated molecules is likely a combination of the molecular volume and oleophobicity of these ligands. Follow up work is discussed which would elucidate the influence of solvent and extent of surfactant fluorination on the permeability of these ligand shells, as

  20. [Monitoring interfacial dynamics by pulsed laser techniques]. [Annual report, August 1, 1988--July 31, 1989

    SciTech Connect

    Richmond, G.

    1989-12-31

    Goal is the development and application of new optical methods to the study of dynamic processes at the electrode/electrolyte interface. The technique which was primarily focused on was second harmonic generation (SHG) because of its suitability for probing buried interfaces. A photothermal deflection spectroscopy station was also built for broad band study of the absorptivity of the interface. Dynamic processes initiated by either a fast potential step or a fast photoexcitation pulse was investigated. In the first case, metal/aqueous electrode systems were studied by time-resolved SHG. In the second, several photoactive materials of interest for solar energy devices were studied.

  1. Perfluorocarbon thin films and polymer brushes on stainless steel 316 L for the control of interfacial properties.

    PubMed

    Kruszewski, Kristen M; Gawalt, Ellen S

    2011-07-05

    Perfluorocarbon thin films and polymer brushes were formed on stainless steel 316 L (SS316L) to control the surface properties of the metal oxide. Substrates modified with the films were characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), contact angle analysis, atomic force microscopy (AFM), and cyclic voltammetry (CV). Perfluorooctadecanoic acid (PFOA) was used to form thin films by self-assembly on the surface of SS316L. Polypentafluorostyrene (PFS) polymer brushes were formed by surface-initiated polymerization using SAMs of 16-phosphonohexadecanoic acid (COOH-PA) as the base. PFOA and PFS were effective in significantly reducing the surface energy and thus the interfacial wetting properties of SS316L. The SS316L control exhibited a surface energy of 38 mN/m compared to PFOA and PFS modifications, which had surface energies of 22 and 24 mN/m, respectively. PFOA thin films were more effective in reducing the surface energy of the SS316L compared to PFS polymer brushes. This is attributed to the ordered PFOA film presenting aligned CF(3) terminal groups. However, PFS polymer brushes were more effective in providing corrosion protection. These low-energy surfaces could be used to provide a hydrophobic barrier that inhibits the corrosion of the SS316L metal oxide surface.

  2. Tensile properties and interfacial bonding of multi-layered, high-purity titanium strips fabricated by ARB process.

    PubMed

    Ghafari-Gousheh, Soroush; Nedjad, Syamak Hossein; Khalil-Allafi, Jafar

    2015-11-01

    Severe plastic deformation (SPD) processing has shown very effective in promotion of mechanical properties of metals and alloys. In this study, the results of investigating mechanical properties and also inter-layer bond performance of accumulative roll bonded high purity titanium (HP-Ti) strips are presented. High purity titanium plates were severely deformed by use of a combination of cold rolling (CR) to a thickness reduction of approximately 87% and then accumulative roll bonding (ARB) for three cycles (N=3) at ambient temperature. Optical and scanning electron microscopy, tensile testing, and hardness measurements were conducted. The ARB strips exhibited lower tensile strength and ductility in comparison to cold rolled one which can basically be attributed to the poor function of the latest bonds established in the centerlines of the strips. Fractographic examinations revealed the interfacial de-bonding along the centerline between the layers having undergone roll bonding for just one cycle. It was while the interfaces having experienced roll bonding for more cycles showed much higher resistance against delaminating.

  3. Interfacial and Electrical Properties of Ge MOS Capacitor by ZrLaON Passivation Layer and Fluorine Incorporation

    NASA Astrophysics Data System (ADS)

    Huang, Yong; Xu, Jing-Ping; Liu, Lu; Cheng, Zhi-Xiang; Lai, Pui-To; Tang, Wing-Man

    2017-09-01

    Ge Metal-Oxide-Semiconductor (MOS) capacitor with HfTiON/ZrLaON stacked gate dielectric and fluorine-plasma treatment is fabricated, and its interfacial and electrical properties are compared with its counterparts without the ZrLaON passivation layer or the fluorine-plasma treatment. Experimental results show that the sample exhibits excellent performances: low interface-state density (3.7×1011 cm‑2eV‑1), small flatband voltage (0.21 V), good capacitance-voltage behavior, small frequency dispersion and low gate leakage current (4.41×10‑5 A/cm2 at Vg = Vfb + 1V). These should be attributed to the suppressed growth of unstable Ge oxides on the Ge surface during gate-dielectric annealing by the ZrLaON interlayer and fluorine incorporation, thus greatly reducing the defective states at/near the ZrLaON/Ge interface and improving the electrical properties of the device.

  4. Single fiber push-out characterization of interfacial mechanical properties in unidirectional CVI-C/SiC composites by the nano-indentation technique

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; Ren, Chengzu; Zhou, Changling; Xu, Hongzhao; Jin, Xinmin

    2015-12-01

    The characterization of interfaces in woven ceramic matrix composites is one of the most challenging problems in composite application. In this investigation, a new model material consisting of the chemical vapor infiltration unidirectional C/SiC composites with PyC fiber coating were prepared and evaluated to predict the interfacial mechanic properties of woven composites. Single fiber push-out/push-back tests with the Berkovich indenter were conducted on the thin sliced specimens using nano-indentation technique. To give a detailed illustration of the interfacial crack propagation and failure mechanism, each sector during the push-out process was analyzed at length. The test results show that there is no detectable difference between testing a fiber in a direct vicinity to an already tested fiber and testing a fiber in vicinity to not-pushed fibers. Moreover, the interface debonding and fiber sliding mainly occur at the PyC coating, and both the fiber and surrounding matrix have no plastic deformation throughout the process. Obtained from the load-displacement curve, the interfacial debonding strength (IDS) and friction stress (IFS) amount to, respectively, 35 ± 5 MPa and 10 ± 1 MPa. Based on the findings, the interfacial properties with PyC fiber coating can be predicted. Furthermore, it is expected to provide a useful guideline for the design, evaluation and optimal application of CVI-C/SiC.

  5. Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1990-01-01

    The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4 percent H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.

  6. Effect of interfacial layers on physical and electrical properties of dinaphtho[2,3-b:2‧,3‧-d]thiophene organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Shaari, Safizan; Naka, Shigeki; Okada, Hiroyuki

    2017-03-01

    We fabricated hexyl-substituted dinaphtho[2,3-b:2‧,3‧-d]thiophene (C6-DNT-V) organic thin-film transistors (OTFTs) with different interfacial layers. The interfacial layers comprised various types of polymers, polyimide, self-assembled monolayers, and high-κ materials. We investigated the effect of interfacial layers on the physical and electrical properties of C6-DNT-V OTFTs. The relationships between mobility and contact angle, threshold voltage and contact angle, on/off ratio and contact angle, mobility and X-ray diffraction intensity, and mobility and dielectric constant were investigated. We found that the contact angle strongly affected the threshold voltage, and the correlation coefficient was calculated to be 0.88. This is due to the fact that use of interfacial layers on the dielectric surface changes the contact angle and hence the surface energy. The altered surface energy will contribute to a change in the grain boundary of C6-DNT-V and affect the shift in threshold voltage. The relationships between other properties showed correlation coefficients of lower than 0.51.

  7. Enhanced interfacial strength of carbon nanotube/copper nanocomposites via Ni-coating: Molecular-dynamics insights

    NASA Astrophysics Data System (ADS)

    Duan, Ke; Li, Li; Hu, Yujin; Wang, Xuelin

    2017-04-01

    The molecular bridging between carbon nanotube (CNT) within the meta matrix is hopeful for enhancing nanocomposite's mechanical performance. One of the main problems for nanocomposites is the inadequate bonding between nonstructural reinforcement and meta matrix. Ni-coating on CNT is an effective method to overcome the drawback of the inadequate strength, but the enhancing mechanism has not well interpreted yet. In this paper, the enhancing mechanism will be interpreted from the molecular-dynamics insights. The pullout process of CNT and Ni-coated CNT against copper matrix is investigated. The effects of geometric parameters, including CNT length and diameter, are taken into considerations and discussed. Results show that the interfacial strength is significantly improved after the Ni-coated CNT, which shows a good agreement with the experimental results available in the open literature. Besides, the sliding mechanism of Ni-coated CNTs against copper matrix is much more like a kind of friction sliding and directly related to the embedded zone. However, the pullout force of the CNT without Ni-coating is nearly proportional to its diameter, but independent of embedded length.

  8. Biofuels spills in surface waters - a laboratory investigation of mixing and interfacial dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxiang; Cotel, Aline

    2016-11-01

    There are increasing risks of spills of ethanol-based biofuels in aquatic environments, however the environmental impact of such accidents is poorly understood and no adequate mitigation strategies are in place today. The interaction of water and biofuels is a complex dynamical problem and we aim to quantify the physical processes involved in such dynamics. A solution of ethanol and glycol is used to represent a typical ethanol-based fuel. A small-scale Plexiglas tank has been designed to investigate the effect of natural conditions on the mixing of water and biofuels, e.g. slope angle, flow rate, wave amplitude and frequency in wind driven conditions. Our previous work showed that the existence of two distinct mixing regimes; a first turbulence-driven fast mixing regime and a second regime driven by interface instabilities. We investigate these mixing regimes under an extended range of physical parameters representing more natural configurations. Funded by NSF.

  9. Interfacial wicking dynamics and its impact on critical heat flux of boiling heat transfer

    NASA Astrophysics Data System (ADS)

    Kim, Beom Seok; Lee, Hwanseong; Shin, Sangwoo; Choi, Geehong; Cho, Hyung Hee

    2014-11-01

    Morphologically driven dynamic wickability is essential for determining the hydrodynamic status of solid-liquid interface. We demonstrate that the dynamic wicking can play an integral role in supplying and propagating liquid through the interface, and govern the critical heat flux (CHF) against surface dry-out during boiling heat transfer. For the quantitative control of wicking, we manipulate the characteristic lengths of hexagonally arranged nanopillars within sub-micron range through nanosphere lithography combined with top-down metal-assisted chemical etching. Strong hemi-wicking over the manipulated interface (i.e., wicking coefficients) of 1.28 mm/s0.5 leads to 164% improvement of CHF compared to no wicking. As a theoretical guideline, our wickability-CHF model can make a perfect agreement with improved CHF, which cannot be predicted by the classic models pertaining to just wettability and roughness effects, independently.

  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. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    SciTech Connect

    Marstell, Roderick J.; Strandwitz, Nicholas C.

    2015-11-14

    We report the differences in the passivation and electronic properties of aluminum oxide (Al{sub 2}O{sub 3}) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Q{sub f} {sub Traditional} = −8.1 × 10{sup 11 }cm{sup −2} and Q{sub f} {sub NHALD} = −3.6 × 10{sup 12 }cm{sup −2}), and a larger degree of chemical passivation than NHALD films (density of interface trap states, D{sub it} {sub Traditional} = 5.4 × 10{sup 11 }eV{sup −1 }cm{sup −2} and D{sub it} {sub NHALD} = 2.9 × 10{sup 12 }eV{sup −1 }cm{sup −2}). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased D{sub it} for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τ{sub Traditional} = 2.2 × 10{sup −9} s and τ{sub NHALD} = 1.7 × 10{sup −7} s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces.

  12. Atomic scale characterization of interfacial water near an oxide surface using molecular dynamics simulations.

    PubMed

    Deshmukh, Sanket A; Sankaranarayanan, Subramanian K R S

    2012-11-28

    Atomic scale characterization of the structure and dynamics of confined water molecules located near the metal oxide-aqueous interface is carried out using molecular dynamics simulations. Proximity effects on water molecules (H(2)O) near a magnesium oxide surface (MgO(100)) at room temperature are evaluated based on various structural and dynamical correlation functions. Translational and orientational order parameters are used to quantify the extent of ordering of water molecules near the oxide surface. There is significant ordering of water molecules in the two layers close to the oxide interface and the extent of ordering decreases with increasing distance from the oxide-water interface. The characteristic structural features of proximal water molecules near oxide-aqueous interfaces are strongly correlated to their vibrational densities of states. Systematic trends in libration, bending, and stretching bands are correlated with local ordering of water molecules and the hydrogen-bonding network. We find that restricted transverse oscillations result in larger blue shifts in O-O-O bending and O-O stretching bands for water molecules having increased proximity to the interface. The O-H stretching band is red-shifted whereas the libration bands for proximal water are blue shifted with respect to bulk water; the extent of shifts are sensitive to the interface proximity, their local confinement and their hydrogen bonding status.

  13. Charge Recombination, Transport Dynamics, and Interfacial Effects in Organic Solar Cells

    SciTech Connect

    Heeger, Alan; Bazan, Guillermo; Nguyen, Thuc-Quyen; Wudl, Fred

    2015-02-12

    The need for renewable sources of energy is well known. Conversion of sunlight to electricity using solar cells is one of the most important opportunities for creating renewable energy sources. The research carried out under DE-FG02-08ER46535 focused on the science and technology of “Plastic” solar cells comprised of organic (i.e. carbon based) semiconductors. The Bulk Heterojunction concept involves a phase separated blend of two organic semiconductors each with dimensions in the nano-meter length scale --- one a material that functions as a donor for electrons and the other a material that functions as an acceptor for electrons. The nano-scale inter-penetrating network concept for “Plastic” solar cells was created at UC Santa Barbara. A simple measure of the impact of this concept can be obtained from a Google search which gives 244,000 “hits” for the Bulk Heterojunction solar cell. Research funded through this program focused on four major areas: 1. Interfacial effects in organic photovoltaics, 2. Charge transfer and photogeneration of mobile charge carriers in organic photovoltaics, 3. Transport and recombination of the photogenerated charge carriers in organic photovoltaics, 4. Synthesis of novel organic semiconducting polymers and semiconducting small molecules, including conjugated polyelectrolytes. Following the discovery of ultrafast charge transfer at UC Santa Barbara in 1992, the nano-organic (Bulk Heterojunction) concept was formulated. The need for a morphology comprising two interpenetrating bicontinuous networks was clear: one network to carry the photogenerated electrons (negative charge) to the cathode and one network to carry the photo-generated holes (positive charge) to the anode. This remarkable self-assembled network morphology has now been established using Transmission electron Microscopy (TEM) either in the Phase Contrast mode or via TEM-Tomography. The steps involved in delivering power from a solar cell to an external circuit

  14. Interfacial effects on the behavior of partially bonded metal matrix composite properties

    NASA Technical Reports Server (NTRS)

    Caruso, J. J.; Chamis, C. C.

    1990-01-01

    A novel computational method developed at NASA-Lewis in order to predict the behavior of unidirectional composites has been used to explore the effects of partial debonding and fiber fracture on the behavior of room temperature and high temperature metal-matrix composites. Attention is presently given to the influence of disbonding, which occurs with fractured fibers, on the ply properties of metal-matrix composites with orthotropic fibers, in the case of a graphite fiber-reinforced copper-matrix composite. It is shown that, for small amounts of partial bonding on fractured fibers, composite material properties are not significantly affected.

  15. Photoinduced Interfacial Electron Injection Dynamics in Dye-Sensitized Solar Cells under Photovoltaic Operating Conditions.

    PubMed

    Teuscher, Joël; Décoppet, Jean-David; Punzi, Angela; Zakeeruddin, Shaik M; Moser, Jacques-E; Grätzel, Michael

    2012-12-20

    We report a pump-probe spectroscopy study of electron injection rates in dye-sensitized solar cell (DSSC) devices. We examine the case of working devices employing an N719 ruthenium sensitizer and an iodide electrolyte. Electron injection is found to occur mainly on a sub-100 fs time scale, followed by a slower component with a lifetime of 26.9 ps, in accordance with previous reports on model samples. The amplitude of this latter component varies with electrolyte composition from 25 to 9%. The appearance of slower components in the electron injection dynamics may be attributed to an aggregated or weakly bound state of the surface-adsorbed N719 sensitizer. Further measurements are reported varying the cell light bias and load conditions, revealing no influence on electron injection dynamics. No other electron injection event is found to occur up to 1 ns. These results show no evidence for a slowdown of electron injection under working conditions compared to model systems for the electrolytes examined in this study.

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

    PubMed

    Solano Canchaya, José G; Dequidt, Alain; Goujon, Florent; Malfreyt, Patrice

    2016-08-07

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

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

    NASA Astrophysics Data System (ADS)

    Solano Canchaya, José G.; Dequidt, Alain; Goujon, Florent; Malfreyt, Patrice

    2016-08-01

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

  18. Dynamic Deformation Properties of Energetic Composite Materials

    DTIC Science & Technology

    2002-12-01

    the dynamic mechanical properties and detonation of energetic materials. It also included some preliminary data on the effect of particle size on the...study of the dynamic mechanical properties and detonation of energetic materials. It also included some preliminary data on the effect of particle size...qualitative only. 33 5. DEFLAGRATION-TO- DETONATION (DDT) STUDIES As part of an on-going programme to investigate the properties of ultrafine energetic

  19. The changes in electrical and interfacial properties of polyimide exposed to dielectric barrier discharge in SF₆ medium.

    PubMed

    Alisoy, Hafiz Z; Koseoglu, Murat

    2013-01-01

    The formation mechanism of space charges in polyimide (PI) which was exposed to dielectric barrier discharge (DBD) in SF6 medium and the effects of the space charges on interfacial and electrical properties of PI were investigated. The variation of normalized surface charge density on PI sample was calculated and illustrated for different DBD exposure times. The surface potential was measured to determine the effect of the space charges on the sample. Then, the contact angle values were measured to obtain the relation between the surface energy and the surface charge density. The expressions for the total charge and the concentration of trapped electrons were derived by using Poisson and continuity equations at stationary state. The space charges were determined experimentally by using thermally stimulated depolarization current (TSDC) method. Also, SEM image and FTIR spectrum of virgin and treated samples were presented to observe the structural variations. It was seen that the approach for the formation mechanism of the space charges agreed with the experimental data. However, it was concluded particularly for the short-time DBD treatments that the space charges accumulated in the sample should be considered besides the effects of surface functionalization in the determination of the surface energy.

  20. Molecular simulations of the n -alkane liquid-vapor interface: interfacial properties and their long range corrections.

    PubMed

    Ibergay, C; Ghoufi, A; Goujon, F; Ungerer, P; Boutin, A; Rousseau, B; Malfreyt, P

    2007-05-01

    Monte Carlo simulations have been performed to study the interfacial properties of the liquid-vapor interface of alkanes. We highlight the chemical equilibrium of the liquid-vapor interface by calculating a local chemical potential including the appropriate long-range corrections profiles. We extend the "test-area" (TA) technique developed by Gloor [J. Chem. Phys. 123, 134703 (2005)] on Lennard-Jones and square-well fluids to molecular systems. We establish both operational expressions of the TA approach for the calculation of the surface tension profile and the corresponding long-range corrections by underlining the approximations used. We compare the results between the different operational expressions of the surface tension and focus on the truncation procedures to explain the difference between the different techniques using either the potential or force equations. We make the results of surface tension identical between the different methods by using consistent potential and force equations. In the case of a relatively small cutoff, we propose to show that the Irving-Kirkwood definition and TA methods lead to the same value of the surface tension under condition that appropriate long-range corrections be included in the calculation. We end this paper by calculation of the entropy change profile and a comparison with experiments.

  1. Graphene scavenges free radicals to synergistically enhance structural properties in a gamma-irradiated polyethylene composite through enhanced interfacial interactions.

    PubMed

    Kolanthai, Elayaraja; Bose, Suryasarathi; Bhagyashree, K S; Bhat, S V; Asokan, K; Kanjilal, D; Chatterjee, Kaushik

    2015-09-21

    A unique strategy for scavenging free radicals in situ on exposure to gamma irradiation in polyethylene (PE) nanocomposites is presented. Blends of ultra-high molecular weight PE and linear low-density PE (PEB) and their nanocomposites with graphene (GPEB) were prepared by melt mixing to develop materials for biomedical implants. The effect of gamma irradiation on the microstructure and mechanical properties was systematically investigated. The neat blend and the nanocomposite were subjected to gamma-ray irradiation in order to improve the interfacial adhesion between PE and graphene sheets. Structural and thermal characterization revealed that irradiation induced crosslinking and increased the crystallinity of the polymer blend. The presence of graphene further enhanced the crystallinity via crosslinks between the polymer matrix and the filler on irradiation. Graphene was found to scavenge free radicals as confirmed by electron paramagnetic resonance spectroscopy. Irradiation of graphene-containing polymer composites resulted in the largest increase in modulus and hardness compared to either irradiation or addition of graphene to PEB alone. This study provides new insight into the role of graphene in polymer matrices during irradiation and suggests that irradiated graphene-polymer composites could emerge as promising materials for use as articulating surfaces in biomedical implants.

  2. A second order virtual node algorithm for Navier-Stokes flow problems with interfacial forces and discontinuous material properties

    NASA Astrophysics Data System (ADS)

    Schroeder, Craig; Stomakhin, Alexey; Howes, Russell; Teran, Joseph M.

    2014-05-01

    We present a numerical method for the solution of the Navier-Stokes equations in three dimensions that handles interfacial discontinuities due to singular forces and discontinuous fluid properties such as viscosity and density. We show that this also allows for the enforcement of normal stress and velocity boundary conditions on irregular domains. The method improves on results in [1] (which solved the Stokes equations in two dimensions) by providing treatment of fluid inertia as well as a new discretization of jump and boundary conditions that accurately resolves null modes in both two and three dimensions. We discretize the equations using an embedded approach on a uniform MAC grid to yield discretely divergence-free velocities that are second order accurate. We maintain our interface using the level set method or, when more appropriate, the particle level set method. We show how to implement Dirichlet (known velocity), Neumann (known normal stress), and slip velocity boundary conditions as special cases of our interface representation. The method leads to a discrete, symmetric KKT system for velocities, pressures, and Lagrange multipliers. We also present a novel simplification to the standard combination of the second order semi-Lagrangian and BDF schemes for discretizing the inertial terms. Numerical results indicate second order spatial accuracy for the velocities (L∞ and L2) and first order for the pressure (in L∞, second order in L2). Our temporal discretization is also second order accurate.

  3. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations.

    PubMed

    Zhong, Hongxia; Quhe, Ruge; Wang, Yangyang; Ni, Zeyuan; Ye, Meng; Song, Zhigang; Pan, Yuanyuan; Yang, Jinbo; Yang, Li; Lei, Ming; Shi, Junjie; Lu, Jing

    2016-03-01

    Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in 2D MoS2-Sc interface and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts generally have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency.

  4. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations

    PubMed Central

    Zhong, Hongxia; Quhe, Ruge; Wang, Yangyang; Ni, Zeyuan; Ye, Meng; Song, Zhigang; Pan, Yuanyuan; Yang, Jinbo; Yang, Li; Lei, Ming; Shi, Junjie; Lu, Jing

    2016-01-01

    Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in 2D MoS2-Sc interface and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts generally have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency. PMID:26928583

  5. The Changes in Electrical and Interfacial Properties of Polyimide Exposed to Dielectric Barrier Discharge in SF6 Medium

    PubMed Central

    Alisoy, Hafiz Z.; Koseoglu, Murat

    2013-01-01

    The formation mechanism of space charges in polyimide (PI) which was exposed to dielectric barrier discharge (DBD) in SF6 medium and the effects of the space charges on interfacial and electrical properties of PI were investigated. The variation of normalized surface charge density on PI sample was calculated and illustrated for different DBD exposure times. The surface potential was measured to determine the effect of the space charges on the sample. Then, the contact angle values were measured to obtain the relation between the surface energy and the surface charge density. The expressions for the total charge and the concentration of trapped electrons were derived by using Poisson and continuity equations at stationary state. The space charges were determined experimentally by using thermally stimulated depolarization current (TSDC) method. Also, SEM image and FTIR spectrum of virgin and treated samples were presented to observe the structural variations. It was seen that the approach for the formation mechanism of the space charges agreed with the experimental data. However, it was concluded particularly for the short-time DBD treatments that the space charges accumulated in the sample should be considered besides the effects of surface functionalization in the determination of the surface energy. PMID:23844414

  6. Study on the interfacial adhesion property of low-k thin film by the surface acoustic waves with cohesive zone model

    NASA Astrophysics Data System (ADS)

    Xiao, Xia; Qi, Haiyang; Tao, Ye; Kikkawa, Takamaro

    2016-12-01

    The cohesive zone model being increasingly used in discrete fracture processes simulation is adopted to study the interfacial adhesion property of low dielectric constant film deposited on the silicon substrate in this work. The two parameters, maximum normal traction and normal interface characteristic length in cohesive zone model, are taken into account to calculate the theoretical surface acoustic wave dispersion curves. Broadband surface acoustic wave signals with effective frequency up to 200 MHz are generated by short pulse ultraviolet laser source and detected by a piezoelectric transducer. The interfacial adhesion properties of dense and porous films determined accurately by matching the experimental dispersion curves with the calculated theoretical dispersion curves are 10.7 PPa/m and 2.8 PPa/m, respectively. The results show that the adhesion quality of dense low dielectric constant film is better than that of the porous. The study exhibits that the adhesion properties determined by improved laser-generated surface acoustic wave technique have the same trends with the test results of the nanoscratch technique, which indicates that the surface acoustic wave technique with cohesive zone model is a promising and nondestructive method for determining interfacial adhesion properties between low dielectric constant film and substrate.

  7. Mixing antiferromagnets to tune NiFe-[IrMn/FeMn] interfacial spin-glasses, grains thermal stability, and related exchange bias properties

    SciTech Connect

    Akmaldinov, K.; Ducruet, C.; Portemont, C.; Joumard, I.; Prejbeanu, I. L.; Dieny, B.; Baltz, V.

    2014-05-07

    Spintronics devices and in particular thermally assisted magnetic random access memories require a wide range of ferromagnetic/antiferromagnetic (F/AF) exchange bias (EB) properties and subsequently of AF materials to fulfil diverse functionality requirements for the reference and storage. For the reference layer, large EB energies and high blocking temperature (T{sub B}) are required. In contrast, for the storage layer, mostly moderate T{sub B} are needed. One of the present issues is to find a storage layer with properties intermediate between those of IrMn and FeMn and in particular: (i) with a T{sub B} larger than FeMn for better stability at rest-T but lower than IrMn to reduce power consumption at write-T and (ii) with improved magnetic interfacial quality, i.e., with reduced interfacial glassy character for lower properties dispersions. To address this issue, the EB properties of F/AF based stacks were studied for various mixed [IrMn/FeMn] AFs. In addition to EB loop shifts, the F/AF magnetic interfacial qualities and the AF grains thermal stability are probed via measurements of the low- and high-temperature contributions to the T{sub B} distributions, respectively. A tuning of the above three parameters is observed when evolving from IrMn to FeMn via [IrMn/FeMn] repetitions.

  8. Crossing Interfacial Frontiers: Surface Chemical Dynamics at the Temporal and Spatial Limit (435th Brookhaven Lecture)

    SciTech Connect

    Camillone III, Nicholas

    2008-04-16

    Surface chemical reactions are ubiquitous in nature and industry: they have been used successfully to remove environmental pollutants, fabricate microelectronics, and produce vital chemicals such as fertilizer, fuel and food. But understanding the chemical dynamics of these reactions is limited, and the ability to study real-time surface chemistry is just being developed. The lecturer will discuss recent results of studies of the oxidation of carbon monoxide on the surface of palladium, which have resulted in new insights into molecule-molecule and molecule-surface interactions. In addition, he will describe a new project at the Center for Functional Nanomaterials that combines ultra-fast laser excitation with a new, state-of-the-art scanning tunneling microscope to probe electronic excitation and photo-induced chemistry at surfaces. It will have a resolution in both space and time that will allow the speaker and his colleagues to watch fast chemical processes at a molecule's eye-view.

  9. New insights into the Mo/Cu(In,Ga)Se2 interface in thin film solar cells: Formation and properties of the MoSe2 interfacial layer

    NASA Astrophysics Data System (ADS)

    Klinkert, T.; Theys, B.; Patriarche, G.; Jubault, M.; Donsanti, F.; Guillemoles, J.-F.; Lincot, D.

    2016-10-01

    Being at the origin of an ohmic contact, the MoSe2 interfacial layer at the Mo/Cu(In,Ga)Se2 interface in CIGS (Cu(In,Ga)Se2 and related compounds) based solar cells has allowed for very high light-to-electricity conversion efficiencies up to 22.3%. This article gives new insights into the formation and the structural properties of this interfacial layer. Different selenization-steps of a Mo covered glass substrate prior to the CIGS deposition by co-evaporation led to MoSe2 interfacial layers with varying thickness and orientation, as observed by x-ray diffraction and atomic resolution transmission electron microscopy. A novel model based on the anisotropy of the Se diffusion coefficient in MoSe2 is proposed to explain the results. While the series resistance of finished CIGS solar cells is found to correlate with the MoSe2 orientation, the adhesion forces between the CIGS absorber layer and the Mo substrate stay constant. Their counter-intuitive non-correlation with the configuration of the MoSe2 interfacial layer is discussed and related to work from the literature.

  10. Effects of ultrathin AlAs interfacial layer on the structure and optical properties of GaInP epilayer grown on germanium

    NASA Astrophysics Data System (ADS)

    Jia, S. P.; Chen, G. F.; He, W.; Dai, P.; Chen, J. X.; Lu, S. L.; Yang, H.

    2014-10-01

    Structure and optical properties of GaInP epilayer with the ultrathin interfacial layers grown on germanium by metal-organic vapor-phase epitaxy (MOVPE) were characterized by high resolution transmission electron microscopy (HRTEM), photoluminescence (PL), Raman as well as surface morphology measurement. A five angstroms (5 Å) AlAs interfacial layer results in the decrease of PL intensity arising from the emission of [Ge(Ga,In) - V(Ga,In)] complex. With the incorporation of AlAs interfacial layer, an increased ordered degree of GaInP epilayer is observed. On the basis of the combination of step-terrace-reconstruction (STR) mode with the dimer-induced-stress model, a CuPt-B type ordering of GaInP which is related to AlAs reconstruction with 2× periodicity process is proposed to explain this effect. Long range order occurs as a consequence of the minimization of the strain energy with increased interfacial layer thickness from 5 Å to 5 nm.

  11. New insights into the Mo/Cu(In,Ga)Se2 interface in thin film solar cells: Formation and properties of the MoSe2 interfacial layer.

    PubMed

    Klinkert, T; Theys, B; Patriarche, G; Jubault, M; Donsanti, F; Guillemoles, J-F; Lincot, D

    2016-10-21

    Being at the origin of an ohmic contact, the MoSe2 interfacial layer at the Mo/Cu(In,Ga)Se2 interface in CIGS (Cu(In,Ga)Se2 and related compounds) based solar cells has allowed for very high light-to-electricity conversion efficiencies up to 22.3%. This article gives new insights into the formation and the structural properties of this interfacial layer. Different selenization-steps of a Mo covered glass substrate prior to the CIGS deposition by co-evaporation led to MoSe2 interfacial layers with varying thickness and orientation, as observed by x-ray diffraction and atomic resolution transmission electron microscopy. A novel model based on the anisotropy of the Se diffusion coefficient in MoSe2 is proposed to explain the results. While the series resistance of finished CIGS solar cells is found to correlate with the MoSe2 orientation, the adhesion forces between the CIGS absorber layer and the Mo substrate stay constant. Their counter-intuitive non-correlation with the configuration of the MoSe2 interfacial layer is discussed and related to work from the literature.

  12. Carvacrol affects interfacial, structural and transfer properties of chitosan coatings applied onto polyethylene.

    PubMed

    Kurek, Mia; Brachais, Claire-Hélène; Sčetar, Mario; Voilley, Andrée; Galić, Kata; Couvercelle, Jean-Pierre; Debeaufort, Frédéric

    2013-08-14

    Different chitosan coating solutions were tested with the aim of investigating their adhesion and wettability onto polyethylene film to improve packaging performance and provide antimicrobial properties. Surface wetting kinetics was monitored by contact angle measurements. Addition of ethanol and carvacrol improved wettability and adhesion of the thin chitosan layer. Structure, water vapour, O2, CO2 and air permeabilities of self supported chitosan films and coated polyethylene were determined. The formation of a thin chitosan layer on polyethylene improved gas barrier properties decreasing the Permeability Coefficient for oxygen and carbon dioxide ( [Formula: see text] , [Formula: see text] ) from 100 to 10,000 times. Presence of carvacrol in the chitosan coating layer increased [Formula: see text] , [Formula: see text] and Pair by a factor of ten. Moreover, it influenced film microstructure. However chitosan was shown to be good gas barrier film in the dry state.

  13. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    SciTech Connect

    Baggetto, Loic; Charvillat, Cedric; Thebault, Yannick; Esvan, Jerome; Lafont, Marie-Christine; Scheid, Emmanuel; Veith, Gabriel M.; Vahlas, Constantin

    2015-12-02

    Ti/Al2O3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties but an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.

  14. Interfacial Octahedral Rotation Mismatch Control of the Symmetry and Properties of SrRuO 3

    DOE PAGES

    Gao, Ran; Dong, Yongqi; Xu, Han; ...

    2016-05-24

    We can use epitaxial strain to tune the properties of complex oxides with perovskite structure. Beyond just lattice mismatch, the use of octahedral rotation mismatch at heterointerfaces could also provide a route to manipulate material properties. We examine the evolution of the lattice (i.e., parameters, symmetry, and octahedral rotations) of SrRuO3 films grown on substrates engineered to have the same lattice parameters, but 2 different octahedral rotations. SrRuO3 films grown on SrTiO3 (001) (no octahedral rotations) and GdScO3-buffered SrTiO3 (001) (with octahedral rotations) substrates are found to exhibit monoclinic and tetragonal symmetry, respectively. Electrical transport and magnetic measurements reveal thatmore » the tetragonal films exhibit higher resistivity, lower magnetic Curie temperatures, and more isotropic magnetism as compared to those with monoclinic structure. Synchrotron-based half-order Bragg peak analysis reveals that the octahedral rotation pattern in both film variants is the same (albeit with slightly different magnitudes of in-plane rotation angles). Furthermore, the abnormal rotation pattern observed in tetragonal SrRuO3 indicates a possible decoupling between the internal octahedral rotation and lattice symmetry, which could provide new opportunities to engineer thin-film structure and properties.« less

  15. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    DOE PAGES

    Baggetto, Loic; Charvillat, Cedric; Thebault, Yannick; ...

    2015-12-02

    Ti/Al2O3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties butmore » an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.« less

  16. Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell

    SciTech Connect

    Pan, Shanlin

    2014-11-16

    Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest that the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an

  17. Maximizing integrated optical and electrical properties of a single ZnO nanowire through native interfacial doping.

    PubMed

    Ding, Huaiyi; Pan, Nan; Ma, Chao; Wu, Yukun; Li, Junwen; Cai, Hongbing; Zhang, Kun; Zhang, Guanghui; Ren, Wenzhen; Li, Jianqi; Luo, Yi; Wang, Xiaoping; Hou, J G

    2014-05-21

    A native interfacial doping layer introduced in core-shell type ZnO nano-wires by a simple vapor phase re-growth procedure endows the produced nano-wires with both excellent electrical and optical performances compared to conventional homogeneous ZnO nanowires. The unique Zn-rich interfacial structure in the core-shell nanowires plays a crucial role in the outstanding performances.

  18. Aqua Ions-Graphene Interfacial and Confinement Behavior: Insights from isobaric-isothermal molecular dynamics

    SciTech Connect

    Chialvo, Ariel A; Cummings, Peter T

    2011-01-01

    We carry out a systematic micro-structural characterization of the solidfluid interface (SFI) of water and simple metal chloride aqueous solutions in contact with a free standing plate or with two such plates separated by an inter-plate distance 0 ! h( ) ! 30 at ambient conditions via isothermalisobaric molecular dynamics. With this characterization we target the interrogation of the system in search for answers to fundamental questions regarding the structure of the external and internal (confined) SFI s, the effect of the differential hydration behavior among species and its link to species expulsion from confinement. For water at ambient conditions we found that the structure of the external SFI s is independent of the interplate distance h in the range 0 ! h( ) ! 30 , i.e., the absence of wallmediated correlation effects between external and internal SFI s, and that for h < 9 the slit-pores de-wet. Moreover, we observed a selective expulsion of ions caused by the differential hydration between the anion and the cations with a consequent charging of the slit-pore. All these observations were interpreted in terms of the axial profiles for precisely defined order parameters including tetrahedral configuration, hydrogen bonding, and species coordination numbers.

  19. PRODAN dual emission feature to monitor BHDC interfacial properties changes with the external organic solvent composition.

    PubMed

    Agazzi, Federico M; Rodriguez, Javier; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2013-03-19

    We have investigated the water/benzyl-n-hexadecyldimethylammonium chloride (BHDC)/n-heptane:benzene reverse micelles (RMs) interfaces properties using 6-propionyl-2-(N,N-dimethyl)aminonaphthalene, PRODAN, as molecular probe. We have used absorption and emission (steady-state and time-resolved) spectroscopy of PRODAN to monitor the changes in the RMs interface functionalities upon changing the external organic solvent blend. We demonstrate that PRODAN is a useful probe to investigate how the external solvent composition affects the micelle interface properties. Our results show that changes in the organic solvent composition in water/BHDC/n-heptane:benzene RMs have a dramatic effect on the photophysics of PRODAN. Thus, increasing the aliphatic solvent content over the aromatic one produces PRODAN partition and PRODAN intramolecular electron transfer (ICT) processes. Additionally, the water presence in these RMs makes the PRODAN ICT process favored with the consequent decreases in the LE emission intensity and a better definition of the charge transfer (CT) band. All this evidence suggests that the benzene molecules are expelled out of the interface, and the water-BHDC interactions are stronger with more presence of water molecules in the polar part of the interface. Thus, we demonstrate that a simple change in the composition of the external phase promotes remarkable changes in the RMs interface. Finally, the results obtained with PRODAN together with those reported in a previous work in our lab reveal that the external phase is important when trying to control the properties of RMs interface. It should be noted that the external phase itself, besides the surfactant and the polar solvent sequestrated, is a very important control variable that can play a key role if we consider smart application of these RMs systems.

  20. Interfacial properties of avian stratum corneum monolayers investigated by Brewster angle microscopy and vibrational sum frequency generation.

    PubMed

    Adams, Ellen M; Champagne, Alex M; Williams, Joseph B; Allen, Heather C

    2017-08-12

    The outermost layer of skin, the stratum corneum (SC), contains a complex mixture of lipids, which controls the rate of cutaneous water loss (CWL) in reptiles, mammals, and birds. However, the molecular structure of SC lipids and how molecular configurations influence CWL is poorly understood. Here, the organization and structure of SC lipids extracted from birds were investigated by means of Langmuir films. Properties of lipids from the SC of arid and semi-arid adapted larks, known to have a low CWL, were compared with lipids extracted from the SC of mesic lark species with higher CWL to gain insight into how structure impacts CWL. Film properties were probed with surface pressure-area isotherms, Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG). Results indicate organization and ordering of SC lipids in the arid-adapted hoopoe lark was vastly different from all other species, forming a miscible, rigid monolayer, whereas monolayers from semi-arid and mesic species were immiscible and disordered. Probing of interfacial water structure reveals that film morphology determines organization of water molecules near the monolayer; monolayers with a porous morphology had an increased population of water molecules that are weakly hydrogen-bonded. In general, CWL appears related to the miscibility and ordering of lipid components within the SC, as well as the ability of these lipids to interact with water molecules. From a broader perspective, CWL in larks appears linked to both the SC lipid composition and the aridity of the species' environment. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. On the Interfacial Properties of Polymers/Functionalized Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Rouhi, S.; Ajori, S.

    2016-06-01

    Molecular dynamics (MD) simulations is used to study the adsorption of polyethylene (PE) and poly(ethylene oxide) (PEO) on the functionalized single-walled carbon nanotubes (SWCNTs). The effects of functionalization factor weight percent on the interaction energies of polymer chains with nanotubes are studied. Besides, the influences of different functionalization factors on the SWCNT/polymer interactions are investigated. It is shown that for both types of polymer chains, the largest interaction energies associates with the random O functionalized nanotubes. Besides, increasing temperature results in increasing the nanotube/polymer interaction energy. Considering the final shapes of adsorbed polymer chains on the SWCNTs, it is observed that the adsorbed conformations of PE chains are more contracted than those of PEO chains.

  2. The Property Suffix Tree with Dynamic Properties

    NASA Astrophysics Data System (ADS)

    Kopelowitz, Tsvi

    Recently there has been much interest in the Property Indexing Problem ([1],[7],[8]), where one is interested to preprocess a text T of size n over alphabet Σ (which we assume is of constant size), and a set of intervals π over the text positions, such that give a query pattern P of size m we can report all of the occurrences of P in T which are completely contained within some interval from π. This type of matching is extremely helpful in scenarios in molecular biology where it has long been a practice to consider special areas in the genome by their structure.

  3. The effect of interfacial octahedral behavior on magnetic properties in ultrathin manganite films

    NASA Astrophysics Data System (ADS)

    Moon, Eun Ju; Cheng, X. M.; Keavney, D. J.; May, S. J.

    2013-03-01

    In ABO3 perovskites, the rotation and distortions of BO6 octahedra lead to crystal symmetric variants of the basic perovskite structure. The rotation angles play a role in magnetic exchange with previous work demonstrating a clear relationship between bond angles and ordering temperatures. Recent work has shown that heteroepitaxial oxide films can be stabilized with non-equilibrium crystal structures due to structural coupling of octahedral behavior across the substrate/film interface. However, it is not yet apparent how the crystal symmetry across a heteroepitaxial oxide interface contributes to magnetic properties. Here, we report on the effect of crystal symmetry in La0.67Sr0.33MnO3 (LSMO), a canonical magnetic oxide, grown using molecular beam epitaxy on different symmetric substrates with similar lattice parameters. For this study, we have used x-ray magnetic circular dichroism, transport, and magnetoresistance measurements to explore the magnetic properties of ultrathin LSMO films for a direct comparison of magnetic behavior in isocompositional perovskites with different octahedral behavior. Work at Drexel Univ. supported by the U.S. ARO (W911NF-12-1-0132). Work at the Advanced Photon Source supported by the U.S. DOE, Office of Basic Energy Sciences (DE-AC02-06CH11357). Work at Bryn Mawr College supported by NSF DMR-1053854.

  4. Synthesis and interfacial properties of monoacyl glyceric acids as a new class of green surfactants.

    PubMed

    Fukuoka, Tokuma; Ikeda, Shintaro; Habe, Hiroshi; Sato, Shun; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai; Sakaki, Keiji

    2012-01-01

    Glyceric acid (GA) is one of the most promising functional hydroxyl acids, and it is abundantly obtained from glycerol by a bioprocess using acetic acid bacteria. In this study, several monoacyl GAs were synthesized by esterification of GA and saturated fatty acyl chlorides (C12, C14, C16, and C18), forming a new class of bio-based surfactants. By the present method, a mixture of two isomers, namely 2-O-acyl and 3-O-acyl GAs, was produced, in which the 2-O-acyl derivatives were obtained as a major product. These isomers were isolated, and their surface-active properties were investigated for the first time. The surface tensions of 2-O-acyl GAs with different chain lengths were determined by the Wilhelmy method. At concentrations below 10(-4) M, the 2-O-acyl GAs exhibited higher surface-active properties compared to commercially available synthetic surfactants. For example, 2-O-lauroyl GA reduced the surface tension of water to around 25 mN/m above the critical micelle concentration (3.0×10(-4) M). In addition, 2-O-acyl derivatives showed higher surface-tension-lowering activity than 3-O-acyl GAs. The monoacyl GAs synthesized herein can potentially be used as "green surfactants."

  5. Molecular assembly, interfacial rheology and foaming properties of oligofructose fatty acid esters.

    PubMed

    van Kempen, Silvia E H J; Schols, Henk A; van der Linden, Erik; Sagis, Leonard M C

    2014-01-01

    Two major types of food-grade surfactants used to stabilize foams are proteins and low molecular weight (LMW) surfactants. Proteins lower the surface tension of interfaces and tend to unfold and stabilize the interface by the formation of a visco-elastic network, which leads to high surface moduli. In contrast, LMW surfactants lower the surface tension more than proteins, but do not form interfaces with a high modulus. Instead, they stabilize the interface through the Gibbs-Marangoni mechanism that relies on rapid diffusion of surfactants, when surface tension gradients develop as a result of deformations of the interface. A molecule than can lower the surface tension considerably, like a LMW surfactant, but also provide the interface with a high modulus, like a protein, would be an excellent foam stabilizer. In this article we will discuss molecules with those properties: oligofructose fatty acid esters, both in pure and mixed systems. First, we will address the synthesis and structural characterization of the esters. Next, we will address self-assembly and rheological properties of air/water interfaces stabilized by the esters. Subsequently, this paper will deal with mixed systems of mono-esters with either di-esters and lauric acid, or proteins. Then, the foaming functionality of the esters is discussed.

  6. Antibiofilm Properties of Interfacially Active Lipase Immobilized Porous Polycaprolactam Prepared by LB Technique

    PubMed Central

    Prabhawathi, Veluchamy; Boobalan, Thulasinathan; Sivakumar, Ponnurengam Malliappan; Doble, Mukesh

    2014-01-01

    Porous biomaterial is the preferred implant due to the interconnectivity of the pores. Chances of infection due to biofilm are also high in these biomaterials because of the presence of pores. Although biofilm in implants contributes to 80% of human infections [1], there are no commercially available natural therapeutics against it. In the current study, glutaraldehyde cross linked lipase was transferred onto a activated porous polycaprolactam surface using Langmuir-Blodgett deposition technique, and its thermostability, slimicidal, antibacterial, biocompatibility and surface properties were studied. There was a 20% increase in the activity of the covalently crosslinked lipase when compared to its free form. This immobilized surface was thermostable and retained activity and stability until 100°C. There was a 2 and 7 times reduction in carbohydrate and 9 and 5 times reduction in biofilm protein of Staphylococcus aureus and Escherichia coli respectively on lipase immobilized polycaprolactam (LIP) when compared to uncoated polycaprolactam (UP). The number of live bacterial colonies on LIP was four times less than on UP. Lipase acted on the cell wall of the bacteria leading to its death, which was confirmed from AFM, fluorescence microscopic images and amount of lactate dehydrogenase released. LIP allowed proliferation of more than 90% of 3T3 cells indicating that it was biocompatible. The fact that LIP exhibits antimicrobial property at the air-water interface to hydrophobic as well as hydrophilic bacteria along with lack of cytotoxicity makes it an ideal biomaterial for biofilm prevention in implants. PMID:24798482

  7. The influence of interfacial properties on two-phase liquid flow of organic contaminants in groundwater. Progress report, January 1, 1991--August 31, 1991

    SciTech Connect

    Hayes, K.F.; Demond, A.H.

    1991-08-01

    An improved understanding of the factors influencing the movement of a separate organic liquid phase in groundwater aquifers is important to the US Department of Energy`s efforts to alleviate groundwater contamination by many common solvents. The overall objective of this project is to investigate how changes in interfacial chemical properties affect two-phase flow relationships. Specifically, the objective is to develop a quantitative theory that will enable the prediction of changes in the capillary pressure-saturation relationship, a fundamental constitutive relationship in multiphase flow modeling, from changes in interfacial properties through a knowledge of their effect on wettability. The work over the past eight months of the project summarized here shows the interrelationship between the surface chemical properties of sorption, electrophoretic mobility, contact angle, surface tension and capillary pressure, and how the effects on capillary pressure might be predicted on the basis of surface tension and contact angle. The model system we have been examining consists of o-xylene, water, silica sand, and cetyltrimethylammonium bromide (CTAB), in which all three interfacial tensions of the system change.

  8. Interfacial microstructure and mechanical properties of brazed aluminum / stainless steel - joints

    NASA Astrophysics Data System (ADS)

    Fedorov, V.; Elßner, M.; Uhlig, T.; Wagner, G.

    2017-03-01

    Due to the demand of mass and cost reduction, joints based on dissimilar metals become more and more interesting. Especially there is a high interest for joints between stainless steel and aluminum, often necessary for example for automotive heat exchangers. Brazing offers the possibilities to manufacture several joints in one step at, in comparison to fusion welding, lower temperatures. In the recent work, aluminum / stainless steel - joints are produced by induction brazing using an AlSi10 filler and a non-corrosive flux. The mechanical properties are determined by tensile shear tests as well as fatigue tests at ambient and elevated temperatures. The microstructure of the brazed joints and the fracture surfaces of the tested samples are investigated by SEM.

  9. Nanostructural Characteristics and Interfacial Properties of Polymer Fibers in Cement Matrix.

    PubMed

    Shalchy, Faezeh; Rahbar, Nima

    2015-08-12

    Concrete is the most used material in the world. It is also one of the most versatile yet complex materials that humans have used for construction. However, an important weakness of concrete (cement-based composites) is its low tensile properties. Therefore, over the past 30 years many studies were focused on improving its tensile properties using a variety of physical and chemical methods. One of the most successful attempts is to use polymer fibers in the structure of concrete to obtain a composite with high tensile strength and ductility. The advantages of polymer fiber as reinforcing material in concrete, both with regard to reducing environmental pollution and the positive effects on a country's economy, are beyond dispute. However, a thorough understanding of the mechanical behavior of fiber-reinforced concrete requires a knowledge of fiber/matrix interfaces at the nanoscale. In this study, a combination of atomistic simulations and experimental techniques has been used to study the nanostructure of fiber/matrix interfaces. A new model for calcium-silicate-hydrate (C-S-H)/fiber interfaces is also proposed on the basis of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. Finally, the adhesion energy between the C-S-H gel and three different polymeric fibers (poly(vinyl alcohol), nylon-6, and polypropylene) were numerically studied at the atomistic level because adhesion plays a key role in the design of ductile fiber-reinforced composites. The mechanisms of adhesion as a function of the nanostructure of fiber/matrix interfaces are further studied and discussed. It is observed that the functional group in the structure of polymer macromolecule affects the adhesion energy primarily by changing the C/S ratio of the C-S-H at the interface and by absorbing additional positive ions in the C-S-H structure.

  10. The effective mechanical properties and the interfacial characterization of CNT reinforced nanocomposites

    NASA Astrophysics Data System (ADS)

    Sadeghi, H.; Naghdabadi, R.

    2009-03-01

    A small volume fraction of Carbon Nanotubes (CNTs) added in a polymeric matrix increases significantly the mechanical properties of the polymers. It is experimentally determined from the TEM images of CNT-based nanocomposites that nanotubes don't stand straight in their embedded matrix and they have some curvature in their shape. The load transfer mechanism between CNT and polymer matrix is also one of the most important issues which is not understood explicitly, yet. In this paper a wavy Single Walled Carbon Nanotube (SWCNT) is modeled as inclusion in a polymer matrix and its effective mechanical properties is studied. This model is based on using 3-D Representive Volume Element (RVE) with long wavy CNT inclusions. The CNT is modeled as a continuum hollow cylindrical shape elastic material with some curvature in its shape. The effect of the waviness of the CNT inclusions and its parameters is studied. We used a new approach in the modeling of interaction between the CNT/matrix at the interface. This approach consists of modeling the physical interaction between CNT and polymeric matrix from point of view of the classical contact phenomenon between two flexible bodies. The results of this new approach are compared with perfectly bonded interface and also those obtained from the rule of mixtures. Results show that the Effective Young Modulus (EYM) of the CNT-based nanocomposites for modeling the interaction of CNT/polymer from the point of view of classical contact approach is slightly smaller than the perfectly bonded condition and is more near to experimental reports. It is also showed that increasing the amplitude of wavy CNT or decreasing its wavelength decreases the EYM of the CNT-based nanocomposites s which is in good agreement with the literature. There were also, a linear relation between the EYM of the CNT-based nanocomposites and the volume fraction of CNT inclusions which was observed by the other authors.

  11. Engineering interfacial properties of organic semiconductors through soft-contact lamination and surface functionalization

    NASA Astrophysics Data System (ADS)

    Shu, Andrew Leo

    Organic electronics is a topic of interest due to its potential for low temperature and solution processing for large area and flexible applications. Examples of organic electronic devices are already available on the market; however these are, in general, still rather expensive. In order to fully realize inexpensive and efficient organic electronics, the properties of organic films need to be understood and strategies developed to take advantage of these properties to improve device performance. This work focuses on two strategies that can be used to control charge transport at interfaces with active organic semiconducting thin films. These strategies are studied and verified with a range of photoemission spectroscopy, surface probe microscopy, and electrical measurements. Vacuum evaporated molecular organic devices have long used layer stacking of different materials as a method of dividing roles in a device and modifying energy level alignment to improve device performance and efficiency. Applying this type of architecture for solution-processed devices, on the other hand, is nontrivial, as an issue of removal of or mixing with underlying layers arises. We present and examine here soft-contact lamination as a viable technique for depositing solution-processed multilayer structures. The energetics at homojunctions of a couple of air-stable polymers is investigated. Charge transport is then compared between a two-layer film and a single-layer film of equivalent thicknesses. The interface formed by soft-contact lamination is found to be transparent with respect to electronic charge carriers. We also propose a technique for modifying electronic level alignment at active organic-organic heterojunctions using dipolar self-assembled monolayers (SAM). An ultra-thin metal oxide is first deposited via a gentle low temperature chemical vapor deposition as an adhesion layer for the SAM. The deposition is shown to be successful for a variety of organic films. A series of

  12. Challenges in Modelling of Lightning-Induced Delamination; Effect of Temperature-Dependent Interfacial Properties

    NASA Technical Reports Server (NTRS)

    Naghipour, P.; Pineda, E. J.; Arnold, S.

    2014-01-01

    Lightning is a major cause of damage in laminated composite aerospace structures during flight. Due to the dielectric nature of Carbon fiber reinforced polymers (CFRPs), the high energy induced by lightning strike transforms into extreme, localized surface temperature accompanied with a high-pressure shockwave resulting in extensive damage. It is crucial to develop a numerical tool capable of predicting the damage induced from a lightning strike to supplement extremely expensive lightning experiments. Delamination is one of the most significant failure modes resulting from a lightning strike. It can be extended well beyond the visible damage zone, and requires sophisticated techniques and equipment to detect. A popular technique used to model delamination is the cohesive zone approach. Since the loading induced from a lightning strike event is assumed to consist of extreme localized heating, the cohesive zone formulation should additionally account for temperature effects. However, the sensitivity to this dependency remains unknown. Therefore, the major focus point of this work is to investigate the importance of this dependency via defining various temperature dependency profiles for the cohesive zone properties, and analyzing the corresponding delamination area. Thus, a detailed numerical model consisting of multidirectional composite plies with temperature-dependent cohesive elements in between is subjected to lightning (excessive amount of heat and pressure) and delamination/damage expansion is studied under specified conditions.

  13. CVD graphene as interfacial layer to engineer the organic donor-acceptor heterojunction interface properties.

    PubMed

    Zhong, Shu; Zhong, Jian Qiang; Mao, Hong Ying; Wang, Rui; Wang, Yu; Qi, Dong Chen; Loh, Kian Ping; Wee, Andrew Thye Shen; Chen, Zhi Kuan; Chen, Wei

    2012-06-27

    We demonstrate the use of chemical-vapor-deposited (CVD) graphene as an effective indium-tin-oxide (ITO) electrode surface modifier to engineer the organic donor-acceptor heterojunction interface properties in an inverted organic solar cell device configuration. As revealed by in situ near-edge X-ray adsorption fine structure measurement, the organic donor-acceptor heterojunction, comprising copper-hexadecafluoro-phthalocyanine (F16CuPc) and copper phthalocyanine (CuPc), undergoes an obvious orientation transition from a standing configuration (molecular π-plane nearly perpendicular to the substrate surface) on the bare ITO electrode to a less standing configuration with the molecular π-plane stacking adopting a large projection along the direction perpendicular to the electrode surface on the CVD graphene-modified ITO electrode. Such templated less-standing configuration of the organic heterojunction could significantly enhance the efficiency of charge transport along the direction perpendicular to the electrode surface in the planar heterojunction-based devices. Compared with the typical standing organic-organic heterojunction on the bare ITO electrode, our in situ ultraviolet photoelectron spectroscopy experiments reveal that the heterojunction on the CVD graphene modified ITO electrode possesses better aligned energy levels with respective electrodes, hence facilitating effective charge collection.

  14. Electronic and Interfacial Properties of PD/6H-SiC Schottky Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Bansal, Gaurav; Petit, Jeremy B.; Knight, Dak; Liu, Chung-Chiun; Wu, Qinghai

    1996-01-01

    Pd/SiC Schottky diodes detect hydrogen and hydrocarbons with high sensitivity. Variation of the diode temperature from 100 C to 200 C shows that the diode sensitivity to propylene is temperature dependent. Long-term heat treating at 425 C up to 140 hours is carried out to determine the effect of extended heat treating on the diode properties and gas sensitivity. The heat treating significantly affects the diode's capacitive characteristics, but the diode's current carrying characteristics are much more stable with a large response to hydrogen. Scanning Electron Microscopy and X-ray Spectrometry studies of the Pd surface after the heating show cluster formation and background regions with grain structure observed in both regions. The Pd and Si concentrations vary between grains. Auger Electron Spectroscopy depth profiles revealed that the heat treating promoted interdiffusion and reaction between the Pd and SiC dw broadened the interface region. This work shows that Pd/SiC Schottky diodes have significant potential as high temperature gas sensors, but stabilization of the structure is necessary to insure their repeatability in long-term, high temperature applications.

  15. Interfacial properties of lignin-based electrospun nanofibers and films reinforced with cellulose nanocrystals.

    PubMed

    Ago, Mariko; Jakes, Joseph E; Johansson, Leena-Sisko; Park, Sunkyu; Rojas, Orlando J

    2012-12-01

    Sub-100 nm resolution local thermal analysis, X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA) measurements were used to relate surface polymer distribution with the composition of electrospun fiber mats and spin coated films obtained from aqueous dispersions of lignin, polyvinyl alcohol (PVA), and cellulose nanocrystal (CNC). Defect-free lignin/PVA fibers were produced with radii which were observed to increase with lignin concentration and with the addition of CNCs. XPS and WCA results indicate a nonlinear relationship between the surface and the bulk compositions. A threshold around 50 wt % bulk composition was identified in which extensive partitioning of PVA and lignin components occurred on the surface below and above this value. In 75:25 wt % lignin/PVA solvent cast films, phase separated domains were observed. Using nanoscale thermal analyses, the continuous phase was determined to be lignin-rich and the discontinuous phase had a lignin/PVA dispersion. Importantly, the size of the phase separated domains was reduced by the addition of CNCs. When electrospun fiber surfaces were lignin-rich, the addition of CNCs affected their surfaces. In contrast, no surface effects were observed with the addition of CNCs in PVA-rich fibers. Overall, we highlight the importance of molecular interactions and phase separation on the surface properties of fibers from lignin as an abundant raw material for the fabrication of new functional materials.

  16. RNA-Based Coacervates as a Model for Membraneless Organelles: Formation, Properties, and Interfacial Liposome Assembly.

    PubMed

    Aumiller, William M; Pir Cakmak, Fatma; Davis, Bradley W; Keating, Christine D

    2016-10-04

    Liquid-liquid phase separation is responsible for formation of P granules, nucleoli, and other membraneless subcellular organelles composed of RNA and proteins. Efforts to understand the physical basis of liquid organelle formation have thus far focused on intrinsically disordered proteins (IDPs) as major components that dictate occurrence and properties. Here, we show that complex coacervates composed of low complexity RNA (polyuridylic acid, polyU) and short polyamines (spermine and spermidine) share many features of IDP-based coacervates. PolyU/polyamine coacervates compartmentalize biomolecules (peptides, oligonucleotides) in a sequence- and length-dependent manner. These solutes retain mobility within the coacervate droplets, as demonstrated by rapid recovery from photobleaching. Coacervation is reversible with changes in solution temperature due to changes in the polyU structure that impact its interactions with polyamines. We further demonstrate that lipid vesicles assemble at the droplet interface without impeding RNA entry/egress. These vesicles remain intact at the interface and can be released upon temperature-induced droplet dissolution.

  17. Interfacial properties of POPC/GDO liquid crystalline nanoparticles deposited on anionic and cationic silica surfaces.

    PubMed

    Chang, Debby P; Dabkowska, Aleksandra P; Campbell, Richard A; Wadsäter, Maria; Barauskas, Justas; Tiberg, Fredrik; Nylander, Tommy

    2016-09-29

    Reversed lipid liquid crystalline nanoparticles (LCNPs) of the cubic micellar (I2) phase have high potential in drug delivery applications due to their ability to encapsulate both hydrophobic and hydrophilic drug molecules. Their interactions with various interfaces, and the consequences for the particle structure and integrity, are essential considerations in their effectiveness as drug delivery vehicles. Here, we have studied LCNPs formed of equal fractions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and glycerol dioleate in the presence of different fractions of the stabilizer Polysorbate 80. We have used a combination of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectometry to reveal the structure and composition of the adsorbed layer on both anionic silica and cationic (aminopropyltriethoxysilane) silanized surfaces. For both types of surfaces, there is a spread near-surface layer comprising lipid and polymer as well as a sparse coverage of intact particles. The composition of the near-surface layer is very close to that of the particles, in contrast to the lipid bilayer observed with related systems. The interaction is stronger for cationic than anionic surfaces, which is rationalized in terms of the negative zeta potential of the LCNPs. The work shows that the attachment of and spreading from LCNPs is influenced by the properties of the surface, the internal structure, composition and stability of the particles as well as the nature of the stabilizer.

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

    PubMed

    Müller, Erich A; Mejía, Andrés

    2011-11-10

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

  19. Understanding the interfacial properties of graphene-based materials/BiOI heterostructures by DFT calculations

    NASA Astrophysics Data System (ADS)

    Dai, Wen-Wu; Zhao, Zong-Yan

    2017-06-01

    Heterostructure constructing is a feasible and powerful strategy to enhance the performance of photocatalysts, because they can be tailored to have desirable photo-electronics properties and couple distinct advantageous of components. As a novel layered photocatalyst, the main drawback of BiOI is the low edge position of the conduction band. To address this problem, it is meaningful to find materials that possess suitable band gap, proper band edge position, and high mobility of carrier to combine with BiOI to form hetertrostructure. In this study, graphene-based materials (including: graphene, graphene oxide, and g-C3N4) were chosen as candidates to achieve this purpose. The charge transfer, interface interaction, and band offsets are focused on and analyzed in detail by DFT calculations. Results indicated that graphene-based materials and BiOI were in contact and formed van der Waals heterostructures. The valence and conduction band edge positions of graphene oxide, g-C3N4 and BiOI changed with the Fermi level and formed the standard type-II heterojunction. In addition, the overall analysis of charge density difference, Mulliken population, and band offsets indicated that the internal electric field is facilitate for the separation of photo-generated electron-hole pairs, which means these heterostructures can enhance the photocatalytic efficiency of BiOI. Thus, BiOI combines with 2D materials to construct heterostructure not only make use of the unique high electron mobility, but also can adjust the position of energy bands and promote the separation of photo-generated carriers, which provide useful hints for the applications in photocatalysis.

  20. Static and dynamic properties of poly(3-hexylthiophene) films at liquid/vacuum interfaces.

    PubMed

    Yimer, Yeneneh Y; Tsige, Mesfin

    2012-11-28

    All-atom molecular dynamics simulations are used to study static and dynamic properties of poly(3-hexylthiophene) (P3HT) films at liquid/vacuum interfaces with regards to their dependence on both temperature and molecular weight. The static properties of the films are characterized by calculating specific volume, interfacial width, orientational ordering of the hexyl groups, and surface tension. The specific volume found to be a monotonically decreasing function of the molecular weight while its dependence on temperature follows the Simha-Somcynsky's equation of state. The orientational ordering calculations show the hexyl groups protruding from the vacuum side of the interface, where the degree of order at the interface is found to be strongly dependent on both temperature and molecular weight. The surface tension values show a linear dependence on temperature and the molecular weight dependence is equally described by both M(-2∕3) and M(-1) power law models. The dynamic properties are quantified by calculating diffusion coefficients for the chain centers-of-mass and thiophene ring segments as well as first-order and second-order end-to-end vector autocorrelations and chain backbone torsion autocorrelation. All calculated dynamic properties show strong dependence on both temperature and molecular weight. All the autocorrelations are well described by Kohlrausch-Williams-Watts equation. Our detailed analysis of the static and dynamic properties of P3HT films show that the calculated static and dynamic properties data can be fit with well-known polymer models.

  1. Effect of interfacial viscoelasticity on the bulk linear viscoelastic moduli of globular protein solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenhuan; Barman, Sourav; Christopher, Gordon F.

    2014-05-01

    The role of interfacial rheology on the bulk linear viscoelastic moduli of low concentration bovine albumin solutions is probed. Previously reported soft gel properties of these systems were attributed to either protein aggregation or organization within the bulk. Instead, these behaviors are shown to be attributable to the measurement error caused by interfacial rheology due to adsorption of bovine serum albumin to the air and water interface. Even at low bulk concentrations, fast interfacial adsorption results in erroneous measurements. When these effects are removed, the solutions are viscous dominated with a dynamic viscosity slightly larger than water.

  2. CRADA Final Report for CRADA No. ORNL99-0544, Interfacial Properties of Electron Beam Cured Composites

    SciTech Connect

    Janke, C.J.

    2005-10-17

    Electron beam (EB) curing is a technology that promises, in certain applications, to deliver lower cost and higher performance polymer matrix composite (PMC) structures compared to conventional thermal curing processes. PMCs enhance performance by making products lighter, stronger, more durable, and less energy demanding. They are essential in weight- and performance-dominated applications. Affordable PMCs can enhance US economic prosperity and national security. US industry expects rapid implementation of electron beam cured composites in aircraft and aerospace applications as satisfactory properties are demonstrated, and implementation in lower performance applications will likely follow thereafter. In fact, at this time and partly because of discoveries made in this project, field demonstrations are underway that may result in the first fielded applications of electron beam cured composites. Serious obstacles preventing the widespread use of electron beam cured PMCs in many applications are their relatively poor interfacial properties and resin toughness. The composite shear strength and resin toughness of electron beam cured carbon fiber reinforced epoxy composites were about 25% and 50% lower, respectively, than those of thermally cured composites of similar formulations. The essential purpose of this project was to improve the mechanical properties of electron beam cured, carbon fiber reinforced epoxy composites, with a specific focus on composite shear properties for high performance aerospace applications. Many partners, sponsors, and subcontractors participated in this project. There were four government sponsors from three federal agencies, with the US Department of Energy (DOE) being the principal sponsor. The project was executed by Oak Ridge National Laboratory (ORNL), NASA and Department of Defense (DOD) participants, eleven private CRADA partners, and two subcontractors. A list of key project contacts is provided in Appendix A. In order to properly

  3. Role of specific interfacial area in controlling properties of immiscible blends of biodegradable polylactide and poly[(butylene succinate)-co-adipate].

    PubMed

    Ojijo, Vincent; Sinha Ray, Suprakas; Sadiku, Rotimi

    2012-12-01

    Binary blends of two biodegradable polymers: polylactide (PLA), which has high modulus and strength but is brittle, and poly[(butylene succinate)-co-adipate] (PBSA), which is flexible and tough, were prepared through batch melt mixing. The PLA/PBSA compositions were 100/0, 90/10, 70/30, 60/40, 50/50, 40/60, 30/70, 10/90, and 0/100. Fourier-transform infrared measurements revealed the absence of any chemical interaction between the two polymers, resulting in a phase-separated morphology as shown by scanning electron microscopy (SEM). SEM micrographs showed that PLA-rich blends had smaller droplet sizes when compared to the PBSA-rich blends, which got smaller with the reduction in PBSA content due to the differences in their melt viscosities. The interfacial area of PBSA droplets per unit volume of the blend reached a maximum in the 70PLA/30PBSA blend. Thermal stability and mechanical properties were not only affected by the composition of the blend, but also by the interfacial area between the two polymers. Through differential scanning calorimetry, it was shown that molten PBSA enhanced crystallization of PLA while the stiff PLA hindered cold crystallization of PBSA. Optimal synergies of properties between the two polymers were found in the 70PLA/30PBSA blend because of the maximum specific interfacial area of the PBSA droplets.

  4. Improved interfacial and electrical properties of Ge MOS capacitor with ZrON/TaON multilayer composite gate dielectric by using fluorinated Si passivation layer

    NASA Astrophysics Data System (ADS)

    Huang, Yong; Xu, Jing-Ping; Liu, Lu; Cheng, Zhi-Xiang; Lai, Pui-To; Tang, Wing-Man

    2017-07-01

    A Ge metal-oxide-semiconductor capacitor with a composite gate dielectric composed of a ZrON/TaON multilayer and a Si passivation layer treated with fluorine plasma is fabricated. Its interfacial and electrical properties are compared with those of its counterparts without the Si passivation layer or the fluorine-plasma treatment. Experimental results show that the device with the fluorinated Si passivation layer exhibits excellent interfacial and electrical performances: low interface-state density (2.0 × 1011 cm2 eV-1 at midgap), small flatband voltage (0.17 V), low gate leakage current (2.04 × 10-6 A/cm2 at Vg = Vfb + 1 V), and high equivalent dielectric constant (22.6). The involved mechanism lies in the fact that the TaSiON interlayer formed by mixing of TaON and Si passivation layers can effectively suppress the growth of unstable Ge oxides to reduce the defective states at/near the TaSiON/Ge interface. Moreover, the fluorine-plasma treatment can passivate the oxygen vacancies and conduce to the blocking of elemental inter-diffusions, thus largely improving the interfacial quality to achieve excellent electrical properties for the device.

  5. Comparison of sizing effect of T700 grade carbon fiber on interfacial properties of fiber/BMI and fiber/epoxy

    NASA Astrophysics Data System (ADS)

    Yao, Lirui; Li, Min; Wu, Qing; Dai, Zhishuang; Gu, Yizhuo; Li, Yanxia; Zhang, Zuoguang

    2012-12-01

    This paper aims to study impact of sizing agents on interfacial properties of two T700 grade high strength carbon fibers with bismaleimide (BMI) and epoxy (EP) resin matrix. The fiber surface roughness and chemical properties are analyzed for sized, desized, and partially desized carbon fibers, using atom force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. FTIR analysis indicates that the sizing agents are chemically reactive, and they can react with BMI and EP at high temperatures. The micro-droplet tests exhibit that the desized carbon fibers have lower interfacial strengths with EP than the sized fibers, however, for BMI matrix, opposite trend is revealed. This is consistent with the chemical reactions of the sizing agents with the EP and BMI resins, in which sufficient reactions are observed for the sizing/EP mixture, while only partial reactions are probed for the sizing/BMI mixture. Interestingly, un-extracted epoxy type sizing particles are observed on partially desized carbon fiber surface, which significantly improves the interfacial adhesion with EP matrix.

  6. Studies on frequency and gate voltage effects on the dielectric properties of Au/n-Si (110) structure with PVA-nickel acetate composite film interfacial layer

    NASA Astrophysics Data System (ADS)

    Tunç, T.; Gökçen, M.; Uslu, İ.

    2012-11-01

    The admittance technique was used in order to investigate the frequency dependence of dielectric constant ( ɛ'), dielectric loss ( ɛ″), dielectric loss tangent (tan δ), the ac electrical conductivity ( σ ac), and the electric modulus of PVA (Ni-doped) structure. Experimental results revealed that the values of ɛ' , ɛ″, (tan δ), σ ac and the electric modulus show fairly large frequency and gate bias dispersion due to the interface charges and polarization. The σ ac is found to increase with both increasing frequency and voltage. It can be concluded that the interface charges and interfacial polarization have strong influence on the dielectric properties of metal-polymer-semiconductor (MIS) structures especially at low frequencies and in depletion and accumulation regions. The results of this study indicate that the ɛ' values of Au/PVA/n-Si with Nickel-doped PVA interfacial layer are quite higher compared to those with pure and other dopant/mixture's of PVA.

  7. 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.

  8. Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes.

    PubMed

    Zhang, Da; Solomon, Paul; Zhang, Shi-Li; Zhang, Zhen

    2017-08-25

    Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/debinding dynamic properties. Here, we employ impedance spectroscopy to systematically characterize this specific noise component for its correlation to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen debinding) processes. This correlation is facilitated by applying our recently developed interfacial impedance model to ultrathin TiO2 layers grown by means of atomic layer deposition (ALD) on a TiN metallic electrode. With an excellent fitting of the measured noise power density spectra by the model for the studied TiO2 layers, we are able to extract several characteristic dynamic parameters for the TiO2 sensing surface. The observed increase of noise with TiO2 ALD cycles can be well accounted for with an increased average binding site density. This study provides insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.

  9. Interfacial Instabilities in Evaporating Drops

    NASA Astrophysics Data System (ADS)

    Moffat, Ross; Sefiane, Khellil; Matar, Omar

    2007-11-01

    We study the effect of substrate thermal properties on the evaporation of sessile drops of various liquids. An infra-red imaging technique was used to record the interfacial temperature. This technique illustrates the non-uniformity in interfacial temperature distribution that characterises the evaporation process. Our results also demonstrate that the evaporation of methanol droplets is accompanied by the formation of wave-trains in the interfacial temperature field; similar patterns, however, were not observed in the case of water droplets. More complex patterns are observed for FC-72 refrigerant drops. The effect of substrate thermal conductivity on the structure of the complex pattern formation is also elucidated.

  10. Challenges associated with sampling dynamic soil properties

    USDA-ARS?s Scientific Manuscript database

    The determination of dynamic soil properties (DSPs) for agricultural practices poses significant challenges, particularly in the context of values derived as part of the National Soil Survey. Although DSPs have been defined as those properties that change over human time scales, limits on the time ...

  11. Static and dynamic properties of Fibonacci multilayers

    NASA Astrophysics Data System (ADS)

    Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A.

    2013-05-01

    We theoretically investigate static and dynamic properties of quasiperiodic magnetic multilayers. We considered identical ferromagnetic layers separated by non-magnetic spacers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr, the minimum energy was determined and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. Regarding dynamic behavior, ferromagnetic resonance (FMR) curves were calculated using an approximation known from the literature. Our numerical results illustrate the effects of quasiperiodicity on the static and dynamic properties of these structures.

  12. Thermal characterization of static and dynamical properties of the confined molecular systems interacting through dispersion force.

    PubMed

    Ramos, Sergio Luis L M; Ogino, Michihiko; Oguni, Masaharu

    2015-01-28

    We investigated the thermal properties of liquid methylcyclohexane and racemic sec-butylcyclohexane, as representatives of a molecular system with only dispersion-force intermolecular interactions, confined in the pores (thickness/diameter d = 12, 6, 1.1 nm) of silica gels by adiabatic calorimetry. The results imply a heterogeneous picture for molecular aggregate under confinement consisting of an interfacial region and an inner pore one. In the vicinity of a glass-transition temperature T(g,bulk) of bulk liquid, two distinguishable relaxation phenomena were observed for the confined systems and their origins were attributed to the devitrification, namely glass transition, processes of (1) a layer of interfacial molecules adjacent to the pore walls and (2) the molecules located in the middle of the pore. A third glass-transition phenomenon was observed at lower temperatures and ascribed to a secondary relaxation process. The glass transition of the interfacial-layer molecules was found to proceed at temperatures rather above T(g,bulk), whereas that of the molecules located in the inner pore region occurred at temperatures below T(g,bulk). We discuss the reason why the molecules located in different places in the pores reveal the respectively different dynamical properties.

  13. Metal/dielectric thermal interfacial transport considering cross-interface electron-phonon coupling: Theory, two-temperature molecular dynamics, and thermal circuit

    NASA Astrophysics Data System (ADS)

    Lu, Zexi; Wang, Yan; Ruan, Xiulin

    2016-02-01

    The standard two-temperature equations for electron-phonon coupled thermal transport across metal/nonmetal interfaces are modified to include the possible coupling between metal electrons with substrate phonons. The previous two-temperature molecular dynamics (TT-MD) approach is then extended to solve these equations numerically at the atomic scale, and the method is demonstrated using Cu/Si interface as an example. A key parameter in TT-MD is the nonlocal coupling distance of metal electrons and nonmetal phonons, and here we use two different approximations. The first is based on Overhauser's "joint-modes" concept, while we use an interfacial reconstruction region as the length scale of joint region rather than the phonon mean-free path as in Overhauser's original model. In this region, the metal electrons can couple to the joint phonon modes. The second approximation is the "phonon wavelength" concept where electrons couple to phonons nonlocally within the range of one phonon wavelength. Compared with the original TT-MD, including the cross-interface electron-phonon coupling can slightly reduce the total thermal boundary resistance. Whether the electron-phonon coupling within the metal block is nonlocal or not does not make an obvious difference in the heat transfer process. Based on the temperature profiles from TT-MD, we construct a new mixed series-parallel thermal circuit. We show that such a thermal circuit is essential for understanding metal/nonmetal interfacial transport, while calculating a single resistance without solving temperature profiles as done in most previous studies is generally incomplete. As a comparison, the simple series circuit that neglects the cross-interface electron-phonon coupling could overestimate the interfacial resistance, while the simple parallel circuit in the original Overhauser's model underestimates the total interfacial resistance.

  14. Sulfur hexafluoride's liquid-vapor coexistence curve, interfacial properties, and diffusion coefficients as predicted by a simple rigid model.

    PubMed

    Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F

    2005-11-15

    We present here molecular-dynamics simulation results of the vapor-liquid coexistence curve, surface tension, and self-diffusion coefficients of sulfur hexafluoride. Sulfur hexafluoride is modeled as a rigid molecule, following the model proposed by Pawley [Mol. Phys. 43, 1321 (1981)]. Vapor-liquid coexistence curve and surface tension are obtained through direct molecular-dynamic simulations in the NVT ensemble. Simulation results are able to reproduce the qualitative shape of the vapor-liquid envelope. However, lower densities, a higher critical temperature, and an overestimated surface tension are obtained here. Those deviations are explained on the basis of the rigidity of the molecular model used. Self-diffusion coefficients are calculated from simulations in the NVE ensemble for different gas states at atmospheric pressure. The rigid model performs better for dynamical properties since simulation results provide very good agreement with available experimental data in this case.

  15. Atomistic Molecular Dynamics Simulation of the Surface Properties of P3HT Films

    NASA Astrophysics Data System (ADS)

    Yimer, Yeneneh; Mofakham, Sima; Dhinojwala, Ali; Tsige, Mesfin

    2011-03-01

    In recent years P3HT has attracted much interest mainly because of its potential applications in solar cells, light emitting diodes and field effect transistors. The performance of these devices is strongly dependent on the structural packing, morphology and interfacial properties of the P3HT. In order to improve the devices efficiency, understanding the structural and dynamical properties of P3HT at the atomic level is important. Most studies on P3HT have mainly focused on understanding its bulk properties. However, the orientation of P3HT chains at the polymer/air interface has not been well investigated. Using molecular dynamics simulations we have studied the interfacial properties of free-standing P3HT films. The simulation results show that at the air/polymer interface the alkane side groups of the P3HT chains orient mainly to the interface in qualitatively good agreement with SFG experimental results. The surface tension of P3HT in its melt state shows strong dependence on temperature and chain length and is directly related to the roughness of the P3HT surface. This work is supported by the NSF (DMR0847580).

  16. Liquid-Vapor Interfacial Properties of Aqueous Solutions of Guanidinium and Methyl Guanidinium Chloride: Influence of Molecular Orientation on Interface Fluctuations

    PubMed Central

    Ou, Shuching; Cui, Di; Patel, Sandeep

    2014-01-01

    The guanidinium cation (C(NH2)3+) is a highly stable cation in aqueous solution due to its efficient solvation by water molecules and resonance stabilization of the charge. Its salts increase the solubility of nonpolar molecules (”salting-in”) and decrease the ordering of water. It is one of the strongest denaturants used in biophysical studies of protein folding. We investigate the behavior of guanidinium and its derivative, methyl guanidinium (an amino acid analogue) at the air-water surface, using atomistic molecular dynamics (MD) simulations and calculation of potentials of mean force. Methyl guanidinium cation is less excluded from the air-water surface than guanidinium cation, but both cations show orientational dependence of surface affinity. Parallel orientations of the guanidinium ring (relative to the Gibbs dividing surface) show pronounced free energy minima in the interfacial region, while ring orientations perpendicular to the GDS exhibit no discernible surface stability. Calculations of surface fluctuations demonstrate that near the air-water surface, the parallel-oriented cations generate significantly greater interfacial fluctuations compared to other orientations, which induces more long-ranged perturbations and solvent density redistribution. Our results suggest a strong correlation with induced interfacial fluctuations and ion surface stability. These results have implications for interpreting molecular-level, mechanistic action of this osmolyte’s interaction with hydrophobic interfaces as they impact protein denaturation (solubilization). PMID:23937431

  17. Optoelectronic and acoustic properties and their interfacial durability of GnP/PVDF/GnP composite actuators with nano-structural control

    NASA Astrophysics Data System (ADS)

    Park, Joung-Man; Kwon, Dong-Jun; Wang, Zuo-Jia; Gu, Ga-Young; DeVries, Lawrence

    2013-03-01

    Nano- and hetero-structures of carbon nanotube (CNT), indium tin oxide (ITO), and Graphene nano Platelet (GnP) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as acoustic actuators. Interfacial durability and electrical properties of CNT, ITO or GnP coated poly(vinylidene fluoride) (PVDF) nanocomposites were investigated for use in acoustic actuator applications. The GnP coated PVDF nanocomposite exhibited better electrical conductivity than either CNT or ITO, due to the unique electrical properties of GnP. GnP nanocomposite coatings also exhibited good acoustical properties. Contact angle, surface energy, work of adhesion, and spreading coefficient measurements were used to explore the interfacial adhesion durability between neat CNT (or plasma treated CNT) and plasma treated PVDF. The acoustic actuation performance of GnP coated PVDF nanocomposites were investigated for different radii of curvature and different coating conditions, using a sound level meter. GnP is considered to be a more appropriate acoustic actuator than either CNT or ITO because of its characteristic electrical properties. A radius of curvature of about 15 degrees was established as being most appropriate. Sound characteristics differed with varying coating thicknesses. The results of this study suggest that it should be possible to manufacture transparent actuators with good sound quality.

  18. Simulation of phase equilibria and interfacial properties of binary mixtures on the liquid-vapour interface using lattice sums

    NASA Astrophysics Data System (ADS)

    López-Lemus, Jorge; Alejandre, José

    Molecular dynamics simulations of Lennard-Jones binary mixtures were performed to obtain phase equilibria and thermodynamic properties for the liquid-vapour interface. The dispersion interactions were handled using the lattice sum method where the full interaction is obtained and there is no requirement for any long range correction to the properties. The application of the method using the Lorentz-Berthelot combining rule for unlike interactions is discussed. The coexisting densities, adsorption of molecules at the interface and surface tension are the main results of this work. Coexisting properties were compared with Gibbs ensemble Monte Carlo results and with those of the grand canonical Monte Carlo method combined with the histogram reweighting technique, and good agreement was found. The lattice sum method results were compared with those of the spherically truncated and shifted potential to analyse the truncation effect. The adsorption of molecules at the interface and surface tension increase with interaction.

  19. Interfacial and electrical properties of SrBi2Ta2O9/ZrO2/Si heterostructures for ferroelectric memory devices

    NASA Astrophysics Data System (ADS)

    Roy, A.; Dhar, A.; Ray, S. K.

    2008-09-01

    We have investigated the interfacial and frequency dependent electrical properties of metal-ferroelectric-insulator-semiconductor capacitors with SrBi2Ta2O9 (SBT) ferroelectric films grown on ZrO2 buffer layer coated Si. Heterostructure SBT and ZrO2 thin films were deposited using rf magnetron sputtering. Interfacial and surface roughness parameters of heterostructures were extracted from the simulation of specular x-ray reflectivity data. The structure exhibited clockwise capacitance-voltage hysteresis with a maximum memory window of 2.0 V at a bias voltage of ±7 V. Frequency dependent (5 kHz-1 MHz) measurements at room temperature indicated that the clockwise hysteresis originates from the ferroelectric domain reversal. A minimum leakage current density of 4×10-8 A/cm2 of fabricated capacitors at an applied voltage of ±5 V revealed that the ZrO2 buffer layer prevents the interfacial diffusion between SBT thin film and the substrate, resulting in an improvement of interface quality. The charge retention time of the ferroelectric capacitor was studied as a function of buffer layer thickness.

  20. The influence of interfacial properties on the two-phase liquid flow of organic contaminants in groundwater. Final report, July 1, 1989--June 30, 1992

    SciTech Connect

    Demond, A.H.; Desai, F.N.; Hayes, K.F.

    1992-12-31

    DOE`s waste sites are contaminated with a variety of organic liquids. Because of their low solubility in water, organic liquids such as these will persist as separate liquid phases and be transported as such in the subsurface. Thus, an improved understanding of the factors influencing the movement of a separate organic liquid phase in the subsurface is important to DOE`s efforts to control groundwater contamination. Wettability is sometimes cited as the most important factor influencing two-phase flow in porous media. The wetting phase migrates preferentially through the smaller pores, whereas the nonwetting phase is concentrated in the larger pores. Typically, aquifers are thought of as strongly water-wet, implying that the organic liquid preferentially occupies the larger pores. But in fact, that state depends on the properties of the three interfaces of the system: between the organic liquid and water, water and the solid, and the organic liquid and the solid. Characteristics of the system which affect the interfacial properties also impact the wettability, such as the nature of the aquifer solids` surfaces, the composition of the goundwater and the properties of the organic contaminant. The alteration of wettability at DOE waste sites may be dominated by the presence of co-contaminants such as organic acids and bases which behave as surface-active agents or surfactants. Because of their physicochemical nature, surfactants will sorb preferentially at the interfaces of the system, thereby impacting the wettability and the distribution of the liquids in the porous medium. The over-all objective of this research was to determine how changes in interfacial properties affect two-phase flow. Specifically, the objective was to examine the effect of surfactant sorption on capillary pressure relationships by correlating measurements of sorption, zeta potential, interfacial tension and contact angle, with changes in the capillary pressure-saturation relationships.

  1. The Influence of Short-Chain Alcohols on Interfacial Tension, Mechanical Properties, Area/Molecule, and Permeability of Fluid Lipid Bilayers

    PubMed Central

    Ly, Hung V.; Longo, Marjorie L.

    2004-01-01

    We used micropipette aspiration to directly measure the area compressibility modulus, bending modulus, lysis tension, lysis strain, and area expansion of fluid phase 1-stearoyl, 2-oleoyl phosphatidylcholine (SOPC) lipid bilayers exposed to aqueous solutions of short-chain alcohols at alcohol concentrations ranging from 0.1 to 9.8 M. The order of effectiveness in decreasing mechanical properties and increasing area per molecule was butanol>propanol>ethanol>methanol, although the lysis strain was invariant to alcohol chain-length. Quantitatively, the trend in area compressibility modulus follows Traube's rule of interfacial tension reduction, i.e., for each additional alcohol CH2 group, the concentration required to reach the same area compressibility modulus was reduced roughly by a factor of 3. We convert our area compressibility data into interfacial tension values to: confirm that Traube's rule is followed for bilayers; show that alcohols decrease the interfacial tension of bilayer-water interfaces less effectively than oil-water interfaces; determine the partition coefficients and standard Gibbs adsorption energy per CH2 group for adsorption of alcohol into the lipid headgroup region; and predict the increase in area per headgroup as well as the critical radius and line tension of a membrane pore for each concentration and chain-length of alcohol. The area expansion predictions were confirmed by direct measurements of the area expansion of vesicles exposed to flowing alcohol solutions. These measurements were fitted to a membrane kinetic model to find membrane permeability coefficients of short-chain alcohols. Taken together, the evidence presented here supports a view that alcohol partitioning into the bilayer headgroup region, with enhanced partitioning as the chain-length of the alcohol increases, results in chain-length-dependent interfacial tension reduction with concomitant chain-length-dependent reduction in mechanical moduli and membrane thickness. PMID

  2. 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

  3. Molecular dynamics (MD) study on the electrochemical properties of electrolytes in lithium-ion battery (LIB) applications

    NASA Astrophysics Data System (ADS)

    Salami, Negin

    While the high energy density and the power along with longer cycle life and less requirements of maintenance distinguish the rechargeable lithium-ion batteries (LIBs) from other energy storage devices, development of an electrolyte of LIBs with optimized properties still constitutes a challenge towards next-generation LIB systems with robust electrochemical performance. The electrolytes serve as the medium to provide ionic conduction path between the electrodes as their basic function. Conductivity of the solutions are mainly affected by their transport properties and the electrolyte electrode/separator interfacial phenomena. Although many contributions on thermodynamic properties of the electrolytes consist of alkyl carbonates mixed with salts have been previously studied, relatively little information is known regarding the correlation between interfacial properties of the electrolyte -electrode/separator with electrochemical properties of the cell. In this study, therefore, we present the impacts of salt concentration and temperature-dependent properties of LIBs on wetting behavior of various electrolytes, i.e., ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and propylene carbonate (PC), in contact with the graphite anode and polyethylene (PE)/polypropylene (PP) separator using molecular dynamics (MD) computational technique. The results based on MD computations affirm the general consistent dependency of interfacial tension energies to polarity of the solvents in DEC, EMC, and PC electrolytes contained 1 M LiPF6 salt. The PC systems interestingly showed inverse trend due to the special stacking motifs of PC layers that may increase the interfacial electrostatic interactions. Temperature did not show significant effect on the interfacial energies of linear solvents whereas PC exhibited more tendency to interact with the graphite anode at T = 25 C compared to the similar solution at 0 C. Moreover, the electrolytes that incorporated same solvents had

  4. Dynamical Properties of Discrete Reaction Networks

    PubMed Central

    Paulevé, Loïc; Craciun, Gheorghe; Koeppl, Heinz

    2013-01-01

    Reaction networks are commonly used to model the dynamics of populations subject to transformations that follow an imposed stoichiometry. This paper focuses on the efficient characterisation of dynamical properties of Discrete Reaction Networks (DRNs). DRNs can be seen as modeling the underlying discrete nondeterministic transitions of stochastic models of reaction networks. In that sense, a proof of non-reachability in a given DRN has immediate implications for any concrete stochastic model based on that DRN, independent of the choice of kinetic laws and constants. Moreover, if we assume that stochastic kinetic rates are given by the mass-action law (or any other kinetic law that gives non-vanishing probability to each reaction if the required number of interacting substrates is present), then reachability properties are equivalent in the two settings. The analysis of two types of global dynamical properties of DRNs is addressed: irreducibility, i.e., the ability to reach any discrete state from any other state; and recurrence, i.e., the ability to return to any initial state. Our results consider both the verification of such properties when species are present in a large copy number, and in the general case. The necessary and sufficient conditions obtained involve algebraic conditions on the network reactions which in most cases can be verified using linear programming. Finally, the relationship of DRN irreducibility and recurrence with dynamical properties of stochastic and continuous models of reaction networks is discussed. PMID:23722628

  5. Physical properties and mantle dynamics

    SciTech Connect

    Shankland, T.J.; Johnson, P.A.; McCall, K.R.

    1997-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Because planetary interiors are remote, laboratory methods and associated theory are an essential step for interpreting geophysical measurements in terms of quantities that are needed for understanding Earth--temperature, composition, stress state, history, and hazards. One objective is the study of minerals and rocks as materials using experimental methods; another is to develop new methods, as in high pressure research, codes for computation in rock/soil physics, or nuclear-based analysis. Accomplishments include developing a single-crystal x-ray diffraction apparatus with application to materials at extremely high pressure and temperature; P-V-T equations of state and seismic velocity measurements for understanding the composition of Earth`s outer 1,000 km; creating computational tools to explain complex stress-strain histories of rocks; and measuring tungsten/thorium ratios W/Th that agree with the hypothesis that Earth accreted heterogeneously. Work performed in this project applies to geosciences, geothermal energy, mineral and rock properties, seismic detection, and isotope dating.

  6. 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

  7. Taming interfacial electronic properties of platinum nanoparticles on vacancy-abundant boron nitride nanosheets for enhanced catalysis

    PubMed Central

    Zhu, Wenshuai; Wu, Zili; Foo, Guo Shiou; Gao, Xiang; Zhou, Mingxia; Liu, Bin; Veith, Gabriel M.; Wu, Peiwen; Browning, Katie L.; Lee, Ho Nyung; Li, Huaming; Dai, Sheng; Zhu, Huiyuan

    2017-01-01

    Taming interfacial electronic effects on Pt nanoparticles modulated by their concomitants has emerged as an intriguing approach to optimize Pt catalytic performance. Here, we report Pt nanoparticles assembled on vacancy-abundant hexagonal boron nitride nanosheets and their use as a model catalyst to embrace an interfacial electronic effect on Pt induced by the nanosheets with N-vacancies and B-vacancies for superior CO oxidation catalysis. Experimental results indicate that strong interaction exists between Pt and the vacancies. Bader charge analysis shows that with Pt on B-vacancies, the nanosheets serve as a Lewis acid to accept electrons from Pt, and on the contrary, when Pt sits on N-vacancies, the nanosheets act as a Lewis base for donating electrons to Pt. The overall-electronic effect demonstrates an electron-rich feature of Pt after assembling on hexagonal boron nitride nanosheets. Such an interfacial electronic effect makes Pt favour the adsorption of O2, alleviating CO poisoning and promoting the catalysis. PMID:28598418

  8. Taming interfacial electronic properties of platinum nanoparticles on vacancy-abundant boron nitride nanosheets for enhanced catalysis

    NASA Astrophysics Data System (ADS)

    Zhu, Wenshuai; Wu, Zili; Foo, Guo Shiou; Gao, Xiang; Zhou, Mingxia; Liu, Bin; Veith, Gabriel M.; Wu, Peiwen; Browning, Katie L.; Lee, Ho Nyung; Li, Huaming; Dai, Sheng; Zhu, Huiyuan

    2017-06-01

    Taming interfacial electronic effects on Pt nanoparticles modulated by their concomitants has emerged as an intriguing approach to optimize Pt catalytic performance. Here, we report Pt nanoparticles assembled on vacancy-abundant hexagonal boron nitride nanosheets and their use as a model catalyst to embrace an interfacial electronic effect on Pt induced by the nanosheets with N-vacancies and B-vacancies for superior CO oxidation catalysis. Experimental results indicate that strong interaction exists between Pt and the vacancies. Bader charge analysis shows that with Pt on B-vacancies, the nanosheets serve as a Lewis acid to accept electrons from Pt, and on the contrary, when Pt sits on N-vacancies, the nanosheets act as a Lewis base for donating electrons to Pt. The overall-electronic effect demonstrates an electron-rich feature of Pt after assembling on hexagonal boron nitride nanosheets. Such an interfacial electronic effect makes Pt favour the adsorption of O2, alleviating CO poisoning and promoting the catalysis.