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Sample records for dynamic interfacial properties

  1. Green-Kubo relations for dynamic interfacial excess properties

    NASA Astrophysics Data System (ADS)

    Sagis, Leonard M. C.

    2012-08-01

    In this paper we analyze the fluctuations of the in-plane interfacial excess fluxes in multiphase systems, in the context of the extended irreversible thermodynamics formalism. We derive expressions for the time correlation functions of the surface extra stress tensor, the surface mass flux vector, and the surface energy flux vector, and use these expressions to derive Green-Kubo relations for the surface shear viscosity, the surface dilatational viscosity, the surface diffusion coefficient, and the surface thermal conductivity. These Green-Kubo relations can be used to compute these excess transport coefficients using for example molecular dynamics simulations.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  3. Effect of Interfacial Bonding on Interphase Properties in SiO2/Epoxy Nanocomposite: A Molecular Dynamics Simulation Study.

    PubMed

    Wang, Zhikun; Lv, Qiang; Chen, Shenghui; Li, Chunling; Sun, Shuangqing; Hu, Songqing

    2016-03-23

    Atomistic molecular dynamics simulations have been performed to explore the effect of interfacial bonding on the interphase properties of a nanocomposite system that consists of a silica nanoparticle and the highly cross-linked epoxy matrix. For the structural properties, results show that interfacial covalent bonding can broaden the interphase region by increasing the radial effect range of fluctuated mass density and oriented chains, as well as strengthen the interphase region by improving the thermal stability of interfacial van der Waals excluded volume and reducing the proportion of cis conformers of epoxy segments. The improved thermal stability of the interphase region in the covalently bonded model results in an increase of ∼21 K in the glass transition temperature (Tg) compared to that of the pure epoxy. It is also found that interfacial covalent bonding mainly restricts the volume thermal expansion of the model at temperatures near or larger than Tg. Furthermore, investigations from mean-square displacement and fraction of immobile atoms point out that interfacial covalent and noncovalent bonding induces lower and higher mobility of interphase atoms than that of the pure epoxy, respectively. The obtained critical interfacial bonding ratio when the interphase and matrix atoms have the same mobility is 5.8%. These results demonstrate that the glass transitions of the interphase and matrix will be asynchronous when the interfacial bonding ratio is not 5.8%. Specifically, the interphase region will trigger the glass transition of the matrix when the ratio is larger than 5.8%, whereas it restrains the glass transition of the matrix when the ratio is smaller than 5.8%. PMID:26927032

  4. 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

  5. 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

  6. Dynamic interfacial properties of human tear-lipid films and their interactions with model-tear proteins in vitro.

    PubMed

    Svitova, Tatyana F; Lin, Meng C

    2016-07-01

    This review summarizes the current state of knowledge regarding interfacial properties of very complex biological colloids, specifically, human meibum and tear lipids, and their interactions with proteins similar to the proteins found in aqueous part of human tears. Tear lipids spread as thin films over the surface of tear-film aqueous and play crucial roles in tear-film stability and overall ocular-surface health. The vast majority of papers published to date report interfacial properties of meibum-lipid monolayers spread on various aqueous sub-phases, often containing model proteins, in Langmuir trough. However, it is well established that natural human ocular tear lipids exist as multilayered films with a thickness between 30 and 100nm, that is very much disparate from 1 to 2nm thick meibum monolayers. We employed sessile-bubble tensiometry to study the dynamic interfacial and rheological properties of reconstituted multilayered human tear-lipid films. Small amounts (0.5-1μg) of human tear lipids were deposited on an air-bubble surface to produce tear-lipid films in thickness range 30-100nm corresponding to ocular lipid films. Thus, we were able to overcome major Langmuir-trough method limitations because ocular tear lipids can be safely harvested only in minute, sub-milligram quantities, insufficient for Langmuir through studies. Sessile-bubble method is demonstrated to be a versatile tool for assessing conventional synthetic surfactants adsorption/desorption dynamics at an air-aqueous solution interface. (Svitova T., Weatherbee M., Radke C.J. Dynamics of surfactant sorption at the air/water interface: continuous-flow tensiometry. J. Colloid Interf. Sci. 2003;261:1170-179). The augmented flow-sessile-bubble setup, with step-strain relaxation module for dynamic interfacial rheological properties and high-precision syringe pump to generate larger and slow interfacial area expansions-contractions, was developed and employed in our studies. We established that

  7. 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.

  8. 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

  9. 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

  10. Molecular Dynamics Simulations of CO2/Water/Quartz Interfacial Properties: Impact of CO2 Dissolution in Water.

    PubMed

    Javanbakht, Gina; Sedghi, Mohammad; Welch, William; Goual, Lamia

    2015-06-01

    The safe trapping of carbon dioxide (CO2) in deep saline aquifers is one of the major concerns of CO2 sequestration. The amount of capillary trapping is dominated by the capillary pressure of water and CO2 inside the reservoir, which in turn is controlled by the interfacial tension (IFT) and the contact angle (CA) of CO2/water/rock systems. The measurement of IFT and CA could be very challenging at reservoir conditions, especially in the presence of toxic cocontaminants. Thus, the ability to accurately predict these interfacial properties at reservoir conditions is very advantageous. Although the majority of existing molecular dynamics (MD) studies of CO2/water/mineral systems were able to capture the trends in IFT and CA variations with pressure and temperature, their predictions often deviated from experimental data, possibly due to erroneous models and/or overlooked chemical reactions. The objective of this study was to improve the MD predictions of IFT and CA of CO2/water/quartz systems at various pressure and temperature conditions by (i) considering the chemical reactions between CO2 and water and (ii) using a new molecular model for α-quartz surface. The results showed that the presence of carbonic acid at the CO2/water interface improved the predictions of IFT, especially at low temperature and high pressure where more CO2 dissolution occurs. On the other hand, the effect on CA was minor. The slight decrease in CA observed across the pressure range investigated could be attributed to an increase in the total number of H-bonds between fluid molecules and quartz surface. PMID:25965772

  11. Alkane-Metal Interfacial Structure and Elastic Properties by Molecular Dynamics Simulation.

    PubMed

    Sebeck, Katherine; Shao, Chen; Kieffer, John

    2016-07-01

    The structure of amorphous materials near the interface with an ordered substrate can be affected by various characteristics of the adjoining phases, such as the lattice spacing of the adherent surface, polymer chain length, and adhesive strength. To discern the influence of each of these factors, four FCC metal lattices are examined for three chain lengths of n-alkane and van der Waals interfacial interactions are controlled by adjusting the Lennard-Jones 12-6 potential parameters. The role of interaction strength is investigated for a single chain length and substrate combination. Four nanoconfined systems are also analyzed in terms of their mechanical strength. A strong layering effect is observed near the interface for all systems. The distinctiveness of polymer layering, i.e., the maximum density and spatial extent, exhibits a logarithmic dependence on the interaction strength between polymer and substrate. Congruency with the substrate lattice parameter further enhances this effect. Moreover, the elastic modulus of the alkane phase as a function of layer thickness indicates that the effects of ordering within the structure extend beyond the immediately obvious interfacial region. PMID:27282363

  12. 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.

  13. Interfacial welding of dynamic covalent network polymers

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  14. The stability and interfacial properties of functionalized silica nanoparticles dispersed in brine studied by molecular dynamics

    NASA Astrophysics Data System (ADS)

    de Lara, Lucas S.; Rigo, Vagner A.; Miranda, Caetano R.

    2015-10-01

    The charge accumulation and surface tension of overall neutral functionalized silica nanoparticles (NPs) dispersed in brine (NaCl and CaCl2) were studied using large scale fully atomistic molecular dynamics. Sulphonic (SA) and ethylene-glycol (EG) functional groups have been incorporated in the NP surface respectively, covering both the hydrophobic and hydrophilic characters. For the latter, groups with one (EG) and two (PEG2) monomers were considered. The ion distribution in electrolyte aqueous solution and its accumulation around NPs were monitored for different salt concentrations (from 0.05 up to 1 wt%), and temperature (300 and 350 K) at 1 atm. At certain conditions, the ion accumulation surrounding the overall neutral NPs leads to a formation of electrical double layers (EDL). Compared with the monovalent ions (NaCl), the accumulation of divalent ions (CaCl2) was found to be more pronounced and the thickness of the EDL around the NPs is more compact. According to the functional group attached, the EDL width also reduces going from EG, to PEG2, to SA. Our simulations suggest that the EDL formation, its narrowing, the large variation of the interface tension, followed by a steep increase in ion mobility are conditions which may precede instability of functionalized NPs dispersion in brine.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    Bulk and surface properties of the ionic liquids 1-alkyl-3-methyl-imidazolium iodides ([Cnmim]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 [C4mim]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 [C4mim]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 [C8mim]I > [C6mim]I > [C4mim]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 profile and

  16. 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.

  17. Interfacial gauge methods for incompressible fluid dynamics.

    PubMed

    Saye, Robert

    2016-06-01

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

  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. Investigating the interfacial dynamics of thin films

    NASA Astrophysics Data System (ADS)

    Rosenbaum, Aaron W.

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

  20. 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.

  1. 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.

  2. 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

  3. Understanding the interfacial layer dynamics of polymer nanocomposites from broadband dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Carroll, Robert; Cheng, Shiwang; Sokolov, Alexei

    Polymer nanocomposites show many advanced mechanical, thermal, optical, and transport properties mainly due to the vast interfacial area between the polymer matrix and nanoparticles. Recent studies show that there is an interfacial polymer layer with structure and dynamics that are different from the bulk polymer, and that contributes to the advanced macroscopic properties. It has been shown that broadband dielectric spectroscopy provides good method to study the interfacial dynamics in nanocomposites. However, current dielectric spectroscopy studies ignore the heterogeneous nature of polymer nanocomposites. Models based on a simple superposition of bulk polymer and interfacial layer spectra, or those that assume the interfacial layer is dynamically ``dead'' are inaccurate. In this talk, the prevailing methods in the literature will be compared with an accurate method accounting for the heterogeneity of the nanocomposites. Different nanocomposites with well-dispersed nanoparticles will be used as examples. The analysis clearly shows that the width and the amplitude of the relaxation peaks are affected by the data analysis. Thus accurate quantitative conclusions on properties and thickness of the interfacial layer can be achieved only using heterogeneous models.

  4. Mass transfer and interfacial properties in two-phase microchannel flows

    NASA Astrophysics Data System (ADS)

    Martin, Jeffrey D.; Hudson, Steven D.

    2009-11-01

    Drop-based microfluidic devices are becoming more common, and molecular mass transfer and drop circulation are issues that often affect the performance of such devices. Moreover, interfacial properties and surfactant mass transfer rates govern emulsion behavior. Since these phenomena depend strongly on drop size, measurement methods using small drops and flow typical of applications are desired. Using mineral oil as a continuous phase, water droplets and an alcohol surfactant, we demonstrate here a microfluidic approach to measure the interrelated phenomena of dynamic interfacial tension, surfactant mass transfer and interfacial retardation that employs droplet flows in a microchannel with constrictions/expansions. Interfacial flow is influenced markedly by adsorption of surfactant: severe interfacial retardation (by a factor of 30) is observed at low surfactant concentrations and interface remobilization is observed at higher surfactant concentrations. The interfacial tension is described by Langmuir kinetics and the parameters for interfaces with mineral oil (studied here) compare closely with those previously found at air interfaces. For the conditions explored, the surfactant mass transfer is described well by a mixed kinetic-diffusion limited model, and the desorption rate coefficients are measured to be both approximately 70 s-1. The transition from a diffusion-controlled to mixed diffusion-kinetic mass transfer mechanism predicted with reducing drop size is verified. This experimental approach (i.e. adjustable geometry and drop size and height) can therefore probe interfacial dynamics in simple and complex flow.

  5. 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

  6. 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.

  7. 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).

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

    SciTech Connect

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

    2014-03-28

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

  9. An aggregation-induced-emission platform for direct visualization of interfacial dynamic self-assembly.

    PubMed

    Li, Junwei; Li, Yuan; Chan, Carrie Y K; Kwok, Ryan T K; Li, Hongkun; Zrazhevskiy, Pavel; Gao, Xiaohu; Sun, Jing Zhi; Qin, Anjun; Tang, Ben Zhong

    2014-12-01

    An in-depth understanding of dynamic interfacial self-assembly processes is essential for a wide range of topics in theoretical physics, materials design, and biomedical research. However, direct monitoring of such processes is hampered by the poor imaging contrast of a thin interfacial layer. We report in situ imaging technology capable of selectively highlighting self-assembly at the phase boundary in real time by employing the unique photophysical properties of aggregation-induced emission. Its application to the study of breath-figure formation, an immensely useful yet poorly understood phenomenon, provided a mechanistic model supported by direct visualization of all main steps and fully corroborated by simulation and theoretical analysis. This platform is expected to advance the understanding of the dynamic phase-transition phenomena, offer insights into interfacial biological processes, and guide development of novel self-assembly technologies. PMID:25363745

  10. An Aggregation-Induced-Emission Platform for Direct Visualization of Interfacial Dynamic Self-Assembly**

    PubMed Central

    Chan, Carrie Y.K.; Kwok, Ryan T.K.; Li, Hongkun; Zrazhevskiy, Pavel; Gao, Xiaohu; Sun, Jing Zhi; Qin, Anjun; Tang, Ben Zhong

    2015-01-01

    An in-depth understanding of dynamic interfacial self-assembly processes is essential for a wide range of topics in theoretical physics, materials design, and biomedical research. However, direct monitoring of such processes is hampered by the poor imaging contrast of a thin interfacial layer. We report in situ imaging technology capable of selectively highlighting self-assembly at the phase boundary in real time by employing the unique photophysical properties of aggregation-induced emission. Its application to the study of breath-figure formation, an immensely useful yet poorly understood phenomenon, provided a mechanistic model supported by direct visualization of all main steps and fully corroborated by simulation and theoretical analysis. This platform is expected to advance the understanding of the dynamic phase-transition phenomena, offer insights into interfacial biological processes, and guide development of novel self-assembly technologies. PMID:25363745

  11. 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.

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

    DOE PAGESBeta

    Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.

    2014-07-25

    Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface.more » The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical

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

    PubMed

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

    2011-01-17

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

  14. 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).

  15. 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.

  16. 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.

  17. Monitoring interfacial dynamics by pulsed laser techniques

    SciTech Connect

    Richmond, G.L.

    1991-01-01

    Goal is to develop new optical methods for the study of dynamic processes at the electrode/electrolyte interface. In the past year, optical second harmonic generation was used for time resolved measurements of thallium electrodeposition on Cu(111). Other studies included the study of the photochemistry involved in a GaAs surface treatment known as photowashing, and the study of picosecond time resolved luminescence decays from GaAs in electrochemical environments (power dependent effects). 4 figs. (DLC)

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Effects of wettability and interfacial nanobubbles on flow through structured nanochannels: an investigation of molecular dynamics

    NASA Astrophysics Data System (ADS)

    Yen, Tsu-Hsu

    2015-12-01

    Solid-fluid boundary conditions are strongly influenced by a number of factors, including the intrinsic properties of the solid/fluid materials, surface roughness, wettability, and the presence of interfacial nanobubbles (INBs). The interconnected nature of these factors means that they should be considered jointly. This paper employs molecular dynamics (MD) simulation in a series of studies aimed at elucidating the influence of wettability in boundary behaviour and the accumulation of interfacial gas. Specifically, we examined the relationship between effective slip length, the morphology of nanobubbles, and wettability. Two methods were employed for the promotion of hydrophobicity between two structured substrates with similar intrinsic contact angles. We also compared anisotropic and isotropic atomic arrangements in the form of graphite and Si(100), respectively. A physical method was employed to deal with variations in surface roughness, whereas a chemical method was used to adjust the wall-fluid interaction energy (ɛwf). We first compared the characteristic properties of wettability, including contact angle and fluid density within the cavity. We then investigated the means by which variations in solid-fluid interfacial wettability affect interfacial gas molecules. Our results reveal that the morphology of INB on a patterned substrate is determined by wettability as well as the methods employed for the promotion of hydrophobicity. The present study also illustrates the means by which the multiple effects of the atomic arrangement of solids, surface roughness, wettability and INB influence effective slip length.

  3. Interfacial structure and dynamics of fatty alcohols: Effects of chain branching

    NASA Astrophysics Data System (ADS)

    Kurtz, Rachel Elana

    The interfacial and bulk dynamic properties of fatty alcohol materials are of great interest as subjects of research and for a range of practical applications. One example is the use of surfactants to stabilize systems such as emulsions and foams. Interfacial viscoelasticity impacts the transport properties of the system. This thesis describes an investigation into interfacial phenomena: straight- and branched-chain hexadecanol and eicosanol mixtures. In this study, the rheology of Langmuir films of hexadecanol and eicosanol straight and branched mixtures was examined. Surface pressure vs. area isotherms, interfacial rheology, Brewster angle microscopy, and X-ray diffraction and reflectivity were all used to elucidate the behavior and structure of the fatty alcohol systems as a function of branched concentration. It was found that for eicosanol below a surface pressure of 25 mN/m, the branched chains are in the monolayer, yet phase-separated from the straight chains. At higher surface pressures, the branched chains are expelled, and presumably form micelles in the subphase. In contrast, the hexadecanol branched chains are not in the monolayer at any surface pressure. These different behaviors are explained in terms of straight-chain flexibility. The effect of the monolayer structure on the surface shear viscosity will be discussed. These studies provide a deeper understanding of the structure and behavior of amphiphilic mixtures, and will ultimately aid in developing models for lipids, micelle formation, and other important biological functions.

  4. 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

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

    PubMed

    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

    2016-07-26

    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. PMID:27337392

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

    DOE PAGESBeta

    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.; et al

    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

  7. Monitoring interfacial dynamics by pulsed laser techniques: Annual report

    SciTech Connect

    Richmond, G.

    1987-01-01

    Several types of materials have been surveyed including thin film and layered semiconductors as well as a metal and semimetal. Second harmonic (SH) generation measurements on these materials were made using both nanosecond (Q-switched) and picosecond (mode-locked) pulsed Nd:YAG lasers with appropriate gated or photon counting detection. Initial studies were performed under steady state conditions in order to optimize the experiments for time-resolved studies. SHG were also extended to the time domain. A means of monitoring surface structure and reconstruction phenomena in-situ was developed. This discovery now opens a broad new area of dynamic interfacial measurements to be done in-situ.

  8. 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

  9. 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

  10. Mimicking mussel adhesion to improve interfacial properties in composites

    PubMed Central

    Hamming, L. M.; Fan, X. W.; Messersmith, P. B.; Brinson, L. C.

    2009-01-01

    The macroscale properties of polymer-matrix composites depend immensely on the quality of the interaction between the reinforcement phase and the bulk polymer. This work presents a method to improve the interfacial adhesion between metal-oxides and a polymer matrix by performing surface-initiated polymerization (SIP) by way of a biomimetic initiator. The initiator was modeled after 3,4-dihydroxy-L-phenylalanine (dopa), an amino acid that is highly concentrated in mussel foot adhesive proteins. Mechanical pull out tests of NiTi and Ti-6Al-4V wires from poly (methyl methacrylate) (PMMA) were performed to directly test the interfacial adhesion. These tests demonstrated improvements in maximum interfacial shear stress of 116% for SIP-modified NiTi wires and 60% for SIP-modified Ti-6Al-4V wires over unmodified specimens. Polymer chain growth from the metal oxides was validated using x-ray photoemission spectroscopy (XPS), ellipsometry, scanning electron microscopy (SEM), and contact angle analysis. PMID:19578545

  11. 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.

  12. 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.

  13. 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. PMID:24667937

  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. 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.

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

    PubMed

    Zhang, Hao; Douglas, Jack F

    2013-01-28

    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/f (α) 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 analytic

  17. Linear interfacial polymerization: theory and simulations with dissipative particle dynamics.

    PubMed

    Berezkin, Anatoly V; Kudryavtsev, Yaroslav V

    2014-11-21

    Step-growth alternating interfacial polymerization between two miscible or immiscible monomer melts is investigated theoretically and by dissipative particle dynamics simulations. In both cases the kinetics for an initially bilayer system passes from the reaction to diffusion control. The polymer composed of immiscible monomers precipitates at the interface forming a film of nearly uniform density. It is demonstrated that the reaction proceeds in a narrow zone, which expands much slower than the whole film, so that newly formed polymer is extruded from the reaction zone. This concept of "reactive extrusion" is used to analytically predict the degree of polymerization and distribution of all components (monomers, polymer, and end groups) within the film in close agreement with the simulations. Increasing the comonomer incompatibility leads to thinner and more uniform films with the higher average degree of polymerization. The final product is considerably more polydisperse than expected for the homogeneous step-growth polymerization. The results extend the previous theoretical reports on interfacial polymerization and provide new insights into the internal film structure and polymer characteristics, which are important for membrane preparation, microencapsulation, and 3D printing technologies. A systematic way of mapping the simulation data onto laboratory scales is discussed. PMID:25416911

  18. 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.

  19. 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.

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

    PubMed

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

    2015-05-01

    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

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

    DOE PAGESBeta

    Reichert, Matthew D.; Alvarez, Nicolas J.; Brooks, Carlton F.; Grillet, Anne M.; Mondy, Lisa A.; Anna, Shelley L.; Walker, Lynn M.

    2014-09-24

    Pendant bubble and drop devices are invaluable tools in understanding surfactant behavior at fluid–fluid interfaces. The simple instrumentation and analysis are used widely to determine adsorption isotherms, transport parameters, and interfacial rheology. However, much of the analysis performed is developed for planar interfaces. Moreover, the application of a planar analysis to drops and bubbles (curved interfaces) can lead to erroneous and unphysical results. We revisit this analysis for a well-studied surfactant system at air–water interfaces over a wide range of curvatures as applied to both expansion/contraction experiments and interfacial elasticity measurements. The impact of curvature and transport on measured propertiesmore » is quantified and compared to other scaling relationships in the literature. Our results provide tools to design interfacial experiments for accurate determination of isotherm, transport and elastic properties.« less

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Cavanagh, Daniel P.; Eckmann, David M.

    2002-10-01

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

  4. Interfacial electrical properties of ion-beam sputter deposited amorphous carbon on silicon

    NASA Technical Reports Server (NTRS)

    Khan, A. A.; Woollam, J. A.; Chung, Y.; Banks, B.

    1983-01-01

    Amorphous, 'diamond-like' carbon films have been deposited on Si substrates, using ion-beam sputtering. The interfacial properties are studied using capacitance and conductance measurements. Data are analyzed using existing theories for interfacial electrical properties. The density of electronic states at the interface, along with corresponding time constants are determined.

  5. 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; 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. In this study, 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. 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. Finally, the results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (~0.15 eV).

  6. Interfacial ionic ‘liquids’: connecting static and dynamic structures

    DOE PAGESBeta

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

    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. In this study, 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. 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. Finally, the results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (~0.15 eV).« less

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

    PubMed

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

    2011-05-17

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

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

    PubMed Central

    Haghighatpanah, Shayesteh; Bohlén, Martin; Bolton, Kim

    2014-01-01

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

  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. A molecular dynamics study to determine the solid-liquid interfacial tension using test area simulation method (TASM)

    NASA Astrophysics Data System (ADS)

    Nair, Anjan R.; Sathian, Sarith P.

    2012-08-01

    Molecular dynamics (MD) studies on heat transfer from a heated nanoparticle into the surrounding fluid have indicated that the fluid next to a spherical nanoparticle can get heated well above its boiling point without observing a phase change, while a contradicting behavior was observed for a flat surface-fluid interface. Another interesting observation is that the critical heat flux was found to increase with increase in the wetting characteristics of solid. Thus, the interfacial tension or free energy of solid-liquid interface could play a pivotal role in the mechanism of heat transfer. A recent study by Gloor et al. [J. Chem. Phys. 123, 134703 (2005)], 10.1063/1.2038827 has proposed test area simulation method (TASM) for the determination of interfacial tension. The present study involves the determination and the comparison of solid-liquid interfacial tension for planar and spherical interfaces using MD based on TASM and analyze the results. A higher interfacial tension value is observed for spherical nanoparticle fluid interface compared to flat surface fluid interface. The results also indicate that the solid-liquid interfacial tension is a size and temperature dependent property. The results from this study are also expected to give better insights into the possible reasons for the observed differences in the thermal transport for spherical nanoparticle-liquid interface compared to planar-liquid interface.

  11. 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

  12. 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. PMID:26163565

  13. 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.

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

    PubMed

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

    2012-03-01

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

  15. 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

  16. On the influence of interfacial properties to the bending rigidity of layered structures

    NASA Astrophysics Data System (ADS)

    Peng, Shenyou; Wei, Yujie

    2016-07-01

    Layered structures are ubiquitous, from one-atom thick layers in two-dimensional materials, to nanoscale lipid bi-layers, and to micro and millimeter thick layers in composites. The mechanical behavior of layered structures heavily depends on the interfacial properties and is of great interest in engineering practice. In this work, we give an analytical solution of the bending rigidity of bilayered structures as a function of the interfacial shear strength. Our results show that while the critical bending stiffness when the interface starts to slide plastically is proportional to the interfacial shear strength, there is a strong nonlinearity between the rigidity and the applied bending after interfacial plastic shearing. We further give semi-analytical solutions to the bending of bilayers when both interfacial shearing and pre-existing crack are present in the interface of rectangular and circular bilayers. The analytical solutions are validated by using finite element simulations. Our analysis suggests that interfacial shearing resistance, interfacial stiffness and preexisting cracks dramatically influence the bending rigidity of bilayers. The results can be utilized to understand the significant stiffness difference in typical biostructures and novel materials, and may also be used for non-destructive detection of interfacial crack in composites when stiffness can be probed through vibration techniques.

  17. Static interfacial properties of Bose-Einstein-condensate mixtures

    NASA Astrophysics Data System (ADS)

    Indekeu, Joseph O.; Lin, Chang-You; Van Thu, Nguyen; Van Schaeybroeck, Bert; Phat, Tran Huu

    2015-03-01

    The interfacial profiles and interfacial tensions of phase-separated binary mixtures of Bose-Einstein condensates are studied theoretically. The two condensates are characterized by their respective healing lengths ξ1 and ξ2 and by the interspecies repulsive interaction K . An exact solution to the Gross-Pitaevskii (GP) equations is obtained for the special case ξ2/ξ1=1 /2 and K =3 /2 . Furthermore, applying a double-parabola approximation (DPA) to the energy density featured in GP theory allows us to define a DPA model, which is much simpler to handle than GP theory but nevertheless still captures the main physics. In particular, a compact analytic expression for the interfacial tension is derived that is useful for all ξ1,ξ2 , and K . An application to wetting phenomena is presented for condensates adsorbed at an optical wall. The wetting phase boundary obtained within the DPA model nearly coincides with the exact one in GP theory.

  18. Interfacial properties and mechanical behavior of titanium aluminides

    SciTech Connect

    Yoo, M.H.; Fu, C.L.

    1998-01-01

    The role of various interfaces in deformation and fracture behavior of two phase TiAl-Ti{sub 3}Al alloys is analyzed on the basis of the specific interfacial and surface energies determined from ab initio calculations. The propensity of twinning observed in these alloys is consistent with the low true twin boundary energy. The strong plastic anisotropy reported in TiAl polysynthetically twinned (PST) crystals is attributed partly to the localized slip along lamellar interfaces, thus lowering the yield stress for soft orientations. Interfacial fracture energies are estimated to be the highest for the {alpha}{sub 2}/{gamma} lamellar boundary and the lowest for the 120 {degree} rotational {gamma}/{gamma} boundary. The fracture mode mixity plays an important role in the crack-tip plasticity by ordinary slip and true twinning, leading to translamellar and interfacial fracture.

  19. Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation.

    PubMed

    Amat, Miguel A; Rutledge, Gregory C

    2010-03-21

    A molecular dynamics study is presented to assess the performance of a united-atom model in the prediction of liquid-vapor interfacial properties for short-chain perfluoroalkanes and their alkane counterparts. In particular, the ability of this model to discriminate between the surface-energy values of these two types of compounds was investigated over a wide temperature range corresponding to the liquid-vapor region. Comparisons with available experimental data and surface-tension predictions given by other force-field parameterizations, including those based on the more computationally demanding all-atom method, were performed to gauge the viability of this model. It was found that the model used in this study captures qualitatively the expected behavior of surface energy between alkanes and perfluoroalkanes and yields values that are in excellent agreement with experimental data, especially in the high-temperature limit as the critical temperature is approached. PMID:20331313

  20. Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation

    NASA Astrophysics Data System (ADS)

    Amat, Miguel A.; Rutledge, Gregory C.

    2010-03-01

    A molecular dynamics study is presented to assess the performance of a united-atom model in the prediction of liquid-vapor interfacial properties for short-chain perfluoroalkanes and their alkane counterparts. In particular, the ability of this model to discriminate between the surface-energy values of these two types of compounds was investigated over a wide temperature range corresponding to the liquid-vapor region. Comparisons with available experimental data and surface-tension predictions given by other force-field parameterizations, including those based on the more computationally demanding all-atom method, were performed to gauge the viability of this model. It was found that the model used in this study captures qualitatively the expected behavior of surface energy between alkanes and perfluoroalkanes and yields values that are in excellent agreement with experimental data, especially in the high-temperature limit as the critical temperature is approached.

  1. 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.

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

    SciTech Connect

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

    1993-06-01

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

  3. Understanding about How Different Foaming Gases Effect the Interfacial Array Behaviors of Surfactants and the Foam Properties.

    PubMed

    Sun, Yange; Qi, Xiaoqing; Sun, Haoyang; Zhao, Hui; Li, Ying

    2016-08-01

    In this paper, the detailed behaviors of all the molecules, especially the interfacial array behaviors of surfactants and diffusion behaviors of gas molecules, in foam systems with different gases (N2, O2, and CO2) being used as foaming agents were investigated by combining molecular dynamics simulation and experimental approaches for the purpose of interpreting how the molecular behaviors effect the properties of the foam and find out the key factors which fundamentally determine the foam stability. Sodium dodecyl sulfate SDS was used as the foam stabilizer. The foam decay and the drainage process were determined by Foamscan. A texture analyzer (TA) was utilized to measure the stiffness and viscoelasticity of the foam films. The experimental results agreed very well with the simulation results by which how the different gas components affect the interfacial behaviors of surfactant molecules and thereby bring influence on foam properties was described. PMID:27434752

  4. 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

  5. Interfacial Properties of Raw and Roasted Peanut Oils as Related to Emulsification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Roasted peanut oil is a unique product that can impart a desirable roasted peanut flavor in various emulsified formulations. Emulsification properties are a function of the oil physical properties, which include interfacial tension, viscosity, and density among others. These physical properties ha...

  6. 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

    2015-01-01

    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/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. PMID:26621499

  7. 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

  8. 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, .

  9. An ab initio molecular dynamics study of the liquid-vapor interface of an aqueous NaCl solution: inhomogeneous density, polarity, hydrogen bonds, and frequency fluctuations of interfacial molecules.

    PubMed

    Choudhuri, Jyoti Roy; Chandra, Amalendu

    2014-11-21

    We have presented a first principles simulation study of the structural and dynamical properties of a liquid-vapor interfacial system of a concentrated (5.3 M) aqueous NaCl solution. We have used ab initio molecular dynamics to examine the structural and dynamical properties of the bulk and interfacial regions. The structural aspects of the system that have been considered here include the inhomogeneous density profiles of ions and water molecules, hydrogen bond distributions, orientational profiles, and also vibrational frequency distributions in the bulk and interfacial regions. It is found that the sodium ions are mostly located in the interior, while the chloride anions occupy a significant portion of the interface of the slab. The water dipoles at the interface prefer to orient parallel to the surface. The dynamical aspects of the interfaces are investigated in terms of diffusion, orientational relaxation, hydrogen bond dynamics, and vibrational spectral diffusion. The results of the interfacial dynamics are compared with those of the corresponding bulk region. It is observed that the interfacial molecules exhibit faster diffusion and orientational relaxation with respect to the bulk. However, the interfacial molecules are found to have longer hydrogen bond lifetimes than those of the bulk. We have also investigated the correlations of hydrogen bond relaxation with the vibrational frequency fluctuations of interfacial water molecules. PMID:25416903

  10. Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles

    PubMed Central

    Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

    2015-01-01

    Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701

  11. Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles.

    PubMed

    Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

    2015-01-01

    Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701

  12. Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles

    NASA Astrophysics Data System (ADS)

    Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

    2015-11-01

    Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials.

  13. 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. PMID:26682416

  14. Tailoring Interfacial Properties by Controlling Carbon Nanotube Coating Thickness on Glass Fibers Using Electrophoretic Deposition.

    PubMed

    Tamrakar, Sandeep; An, Qi; Thostenson, Erik T; Rider, Andrew N; Haque, Bazle Z Gama; Gillespie, John W

    2016-01-20

    The electrophoretic deposition (EPD) method was used to deposit polyethylenimine (PEI) functionalized multiwall carbon nanotube (CNT) films onto the surface of individual S-2 glass fibers. By varying the processing parameters of EPD following Hamaker's equation, the thickness of the CNT film was controlled over a wide range from 200 nm to 2 μm. The films exhibited low electrical resistance, providing evidence of coating uniformity and consolidation. The effect of the CNT coating on fiber matrix interfacial properties was investigated through microdroplet experiments. Changes in interfacial properties due to application of CNT coatings onto the fiber surface with and without a CNT-modified matrix were studied. A glass fiber with a 2 μm thick CNT coating and the unmodified epoxy matrix showed the highest increase (58%) in interfacial shear strength (IFSS) compared to the baseline. The increase in the IFSS was proportional to CNT film thickness. Failure analysis of the microdroplet specimens indicated higher IFSS was related to fracture morphologies with higher levels of surface roughness. EPD enables the thickness of the CNT coating to be adjusted, facilitating control of fiber/matrix interfacial resistivity. The electrical sensitivity provides the opportunity to fabricate a new class of sizing with tailored interfacial properties and the ability to detect damage initiation. PMID:26699906

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

    SciTech Connect

    Wang, Hsin-Fu

    1994-12-31

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

  16. 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.

  17. Effects of interfacial bonding in the Si-carbon nanotube nanocomposite: A molecular dynamics approach

    NASA Astrophysics Data System (ADS)

    Kim, Byung-Hyun; Lee, Kwang-Ryeol; Chung, Yong-Chae; Gunn Lee, June

    2012-08-01

    We investigated the effects of interfacial bonding on the mechanical properties in the Si-carbon nanotube (CNT) nanocomposite by a molecular dynamics approach. To describe the system appropriately, we used a hybrid potential that includes Tersoff, AIREBO (adaptive intermolecular reactive empirical bond order), and Lennard-Jones potentials. With increasing bonding strength at the interface of Si matrix and CNT, toughness as well as Young's modulus and maximum strength increased steadily. CNT pull-out and load transfer on the strong CNT were identified as the main mechanisms for the enhanced properties. At optimum bonding, crack tip was deflected around CNT and the fracture proceeded in plastic mode through Si matrix owing to the strong reinforcement of CNT, and resulted in a further enhancement of toughness. At maximum bonding, however, only load transfer is operative and the fracture returned to brittle mode. We concluded that a strong interface as long as the CNT maintains its structural integrity is desirable to realize the optimum result.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  19. AFM probing of polymer/nanofiller interfacial adhesion and its correlation with bulk mechanical properties in a poly(ethylene terephthalate) nanocomposite.

    PubMed

    Aoyama, Shigeru; Park, Yong Tae; Macosko, Christopher W; Ougizawa, Toshiaki; Haugstad, Greg

    2014-11-01

    The interfacial adhesion between polymer and nanofiller plays an important role in affecting the properties of nanocomposites. The detailed relationship between interfacial adhesion and bulk properties, however, is unclear. In this work, we developed an atomic force microscopy (AFM)-based abrasive scanning methodology, as applied to model laminate systems, to probe the strength of interfacial adhesion relevant to poly(ethylene terephthalate) (PET)/graphene or clay nanocomposites. Graphite and mica substrates covered with ∼2 nm thick PET films were abrasively sheared by an AFM tip as a model measurement of interfacial strength between matrix PET and dispersed graphene and clay, respectively. During several abrasive raster-scan cycles, PET was shear-displaced from the scanned region. At temperatures below the PET glass transition, PET on graphite exhibited abrupt delamination (i.e., full adhesive failure), whereas PET on mica did not; rather, it exhibited a degree of cohesive failure within the shear-displaced layer. Moreover, 100-fold higher force scanning procedures were required to abrade through an ultimate "precursor" layer of PET only ∼0.2-0.5 nm thick, which must be largely disentangled from the matrix polymer. Thus, the adhesive interface of relevance to the strength of clay-filler nanocomposites is between matrix polymer and strongly bound polymer. At 90 °C, above the bulk PET glass transition temperature, the PET film exhibited cohesive failure on both graphite and mica. Our results suggest that there is little difference in the strength of the relevant interfacial adhesion in the two nanocomposites within the rubbery dynamic regime. Further, the bulk mechanical properties of melt mixed PET/graphene and PET/clay nanocomposites were evaluated by dynamic mechanical analysis. The glassy dynamic storage modulus of the PET/clay nanocomposite was higher than that of PET/graphene, correlating with the differences in interfacial adhesion probed by AFM. PMID

  20. The role of dispersants' dynamic interfacial tension in effective crude oil spill dispersion.

    PubMed

    Riehm, David A; McCormick, Alon V

    2014-07-15

    The dispersion effectiveness of dispersants containing Tween 80, Span 80, and dioctyl sodium sulfosuccinate (DOSS) was characterized using a modified Swirling Flask test, and was correlated with both initial and dynamic interfacial tension produced by those dispersants at an oil-water interface. Compositional trends in effectiveness were shown to be governed by: (1) initial oil-water interfacial tension observed upon dispersant-oil-saltwater contact; (2) rate of increase (or decrease) from the initial interfacial tension as DOSS was rapidly lost to the aqueous phase; and (3) gradually slowing kinetics of dispersant adsorption to the oil-water interface as Span 80 concentration was increased, which ultimately diminished dispersion effectiveness considerably even as dynamic interfacial tension remained <10(-3) mN/m. It is proposed that this third phenomenon results not only from the hydrophobicity of Span 80, but also from the dependence of mixed Tween-Span-DOSS reverse micelles' stability in crude oil on dispersant composition. PMID:24889318

  1. Surface Restricted Grating Studies of Interfacial Charge Transfer Dynamics at N-Gallium ARSENIDE(100) Liquid Junction.

    NASA Astrophysics Data System (ADS)

    Wang, Xiangdong

    1995-01-01

    Heterogeneous electron transfer involves the coupling of a dense manifold of highly delocalized electronic levels of the solid state to a discrete molecular state as well as an abrupt change in phase in the reaction coordinate. These features make this problem unique relative to homogeneous solution phase or gas phase reaction mechanisms which involve coupling between discrete states within a uniform medium. In this work, the advances in Surface Restricted Transient Grating Spectroscopy (Surface Restricted Transient Grating) are discussed in the context of studying interfacial charge transfer processes at single crystal semiconductor surfaces as a means to probe the primary processes governing heterogeneous electron transfer. In situ grating studies of n-GaAs/(Se ^{-2/-1}) aqueous liquid junction have observed 1 ~ 2 picosecond decay components in the presence of the selenium redox couple. Bias voltage and injection intensity dependencies have shown that field focusing of the hole carrier distribution to the surface reaction plane was achieved. Based on the bias voltage and injection intensity dependence, and known hole scavenging properties of Se^{ -2}, the fast initial decay is assigned to interfacial hole transfer. This time scale is coincident with the highly damped diffusive relaxation components of water under the high ionic concentrations present in the Helmholtz double layer of the GaAs electrode surface. The similarity in time scales between charge transfer and the rate limiting nuclear motion in the barrier crossing dynamics indicates that the electronic coupling at the interface is in the strong coupling regime. This study was the first direct time-resolved measurement of interfacial electron transfer from a single crystal surface. The observation that the dynamics are essentially in the strong coupling limit is contrary to conventional treatments of interfacial transfer processes, which assume weak coupling conditions. This result is important as it

  2. Probing model tumor interfacial properties using piezoelectric cantilevers.

    PubMed

    Yegingil, Hakki; Shih, Wan Y; Shih, Wei-Heng

    2010-09-01

    Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G/E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The piezoelectric cantilever used had two lead zirconate titanate layers to facilitate all-electrical elastic (shear) modulus measurements using one single device. We constructed model tissues with tumors by embedding one-dimensional (1D) corrugated inclusions and three-dimensional (3D) spiky-ball inclusions made of modeling clay in gelatin. We showed that for smooth inclusions, G/E was 0.3 regardless of the shear direction. In contrast, for a 1D corrugated rough inclusion G/E was 0.3 only when the shear was parallel to corrugation and G/E increased with an increasing angle between the shear direction and the corrugation. When the shear was perpendicular to corrugation, G/E became >0.7. For 3D isotropic spiky-ball inclusions we showed that the G/E depended on the degree of the roughness. Using the ratio s/r of the spike length (s) to the overall inclusion radius (r) as a roughness parameter, we showed that for inclusions with s/r larger than or equal to 0.28, the G/E ratio over the inclusions was larger than 0.7 whereas for inclusions with s/r less than 0.28, the G/E decreased with decreasing s/r to around 0.3 at s/r=0. In addition, we showed that the depth limit of the G/E measurement is twice the width of the probe area of the piezoelectric cantilever. PMID:20887005

  3. Interfacial dynamics and adhesion behaviors of water and oil droplets in confined geometry.

    PubMed

    Liu, Xiang; Guo, Dan; Liu, Shuhai; Xie, Guoxin; Luo, Jianbin

    2014-07-01

    To simulate the interfacial behaviors in real heterogeneous systems, the point contact condition is constructed to study the classical immiscible displacement problem in this work. Specifically, the interfacial dynamics during the water droplet passing through the oil capillary bridge formed under the point contact condition is investigated. Emphasis is put on the influences of the wettabilities and the relative separation motion of the solid surfaces on the dynamic behavior of the droplets. The observations suggested that the capillary pressure had negligible effect on the movement of the water droplet when it was passing though the oil capillary bridge. The wettability and the relative separation of the disk and ball would influence the final adhesion behaviors of the water droplet after the droplet passed through the oil capillary bridge. Surface tension and adhesion energy were used to interpret these observations. PMID:24946005

  4. Molecular dynamics study of interfacial thermal transport between silicene and substrates.

    PubMed

    Zhang, Jingchao; Hong, Yang; Tong, Zhen; Xiao, Zhihuai; Bao, Hua; Yue, Yanan

    2015-10-01

    In this work, the interfacial thermal transport across silicene and various substrates, i.e., crystalline silicon (c-Si), amorphous silicon (a-Si), crystalline silica (c-SiO2) and amorphous silica (a-SiO2) are explored by classical molecular dynamics (MD) simulations. A transient pulsed heating technique is applied in this work to characterize the interfacial thermal resistance in all hybrid systems. It is reported that the interfacial thermal resistances between silicene and all substrates decrease nearly 40% with temperature from 100 K to 400 K, which is due to the enhanced phonon couplings from the anharmonicity effect. Analysis of phonon power spectra of all systems is performed to interpret simulation results. Contradictory to the traditional thought that amorphous structures tend to have poor thermal transport capabilities due to the disordered atomic configurations, it is calculated that amorphous silicon and silica substrates facilitate the interfacial thermal transport compared with their crystalline structures. Besides, the coupling effect from substrates can improve the interface thermal transport up to 43.5% for coupling strengths χ from 1.0 to 2.0. Our results provide fundamental knowledge and rational guidelines for the design and development of the next-generation silicene-based nanoelectronics and thermal interface materials. PMID:26266456

  5. Effect of heat treatment on carbon fiber surface properties and fibers/epoxy interfacial adhesion

    NASA Astrophysics Data System (ADS)

    Dai, Zhishuang; Zhang, Baoyan; Shi, Fenghui; Li, Min; Zhang, Zuoguang; Gu, Yizhuo

    2011-08-01

    Carbon fiber surface properties are likely to change during the molding process of carbon fiber reinforced matrix composite, and these changes could affect the infiltration and adhesion between carbon fiber and resin. T300B fiber was heat treated referring to the curing process of high-performance carbon fiber reinforced epoxy matrix composites. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the content of activated carbon atoms on treated carbon fiber surface, especially those connect with the hydroxyl decreases with the increasing heat treatment temperature. Inverse gas chromatography (IGC) analysis reveals that the dispersive surface energy γSd increases and the polar surface energy γSsp decreases as the heat treatment temperature increases to 200. Contact angle between carbon fiber and epoxy E51 resin, which is studied by dynamic contact angle test (DCAT) increases with the increasing heat treatment temperature, indicating the worse wettability comparing with the untreated fiber. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the treated carbon fiber/epoxy is lower than that of the untreated T300B fiber which is attributed to the decrement of the content of reactive functional groups including hydrogen group and epoxy group.

  6. 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.

  7. 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

  8. 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

    2016-01-01

    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

  9. Fluid displacement under elastic membranes: Dynamics and interfacial instabilities

    NASA Astrophysics Data System (ADS)

    Al-Housseiny, Talal; Christov, Ivan; Juel, Anne; Stone, Howard

    2012-11-01

    The spreading of fluids under a flexible membrane is a feature of many systems such as the lateral intrusion of magma under a terrestrial crust, or when blood spreads underneath the skin giving the signature color of bruises. In this work, we investigate the displacement of a viscous fluid by a gas underneath an elastic membrane. We consider a radial Hele-Shaw cell where the upper plate is an elastic sheet. The dynamics of the interface between the injected gas and the displaced fluid are fundamentally modified by the presence of an elastic boundary, which leads to the suppression of viscous fingering below a critical flow rate. We demonstrate theoretically the mechanism of suppression and find the corresponding critical flow rate. In addition, we study the dynamics of a stable (circular) interface propagating underneath an elastic membrane and derive the scaling laws for both the position of the interface and the shape of the elastic membrane. Our theoretical findings agree very well with the experimental results of D. Pihler-Puzovic et al. (PRL 2012). T. T. Al-Housseiny is supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0646086.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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).

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

    PubMed

    Martínez-Ruiz, F J; Blas, F J

    2016-04-21

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

  16. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  18. 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.

  19. Anodization of carbon fibers on interfacial mechanical properties of epoxy matrix composites.

    PubMed

    Park, Soo-Jin; Chang, Yong-Hwan; Kim, Yeong-Cheol; Rhee, Kyong-Yop

    2010-01-01

    The influence of anodic oxidation on the mechanical interfacial properties of carbon-fiber-reinforced epoxy resin composites was investigated. The surface properties of the anodized carbon fibers were studied through the measurement of contact angles and through SEM, XPS, and FT-IR analyses. The mechanical interfacial properties of the composites were studied through measurements of interlaminar shear strength (ILSS), critical stress intensity factor (K(IC)), and critical strain energy release rate (G(IC)). It was shown that the surface functional groups containing oxygen on the anodized carbon fibers exert great effects on the surface energetics of fibers and the mechanical interfacial properties, e.g., ILSS, of the resulting composites. Contact angle measurements based on the wicking rate of a test liquid showed that anodic oxidation lead to an increase in the surface free energy of the carbon fibers, mainly in its specific (or polar) component. In terms of surface energetics, it was found that wetting played an important role in increasing the degree of adhesion at interfaces between the fibers and the resin matrices of the composites. PMID:20352820

  20. Effects of inclination and vorticity on interfacial flow dynamics in horizontal and inclined pipes

    NASA Astrophysics Data System (ADS)

    Kiara, Areti; Hendrickson, Kelli; Liu, Yuming

    2015-11-01

    The transport of oil and gas in long horizontal pipelines can be significantly affected by the development of violent roll waves and slugs, but the mechanics causing such transitions have not been well understood. To enable the improvement of the prediction of flow transition criteria in long pipelines we perform theoretical analysis and direct numerical simulations of multiphase pipe flows to quantify the roles of inclination and vorticity in the flow dynamics. We find that backflow or flooding may occur even in the absence of disturbances due to inclination effects and obtain criteria on the maximum pipe length for steady flows. We identify and compare the effects of inclination and vorticity on the stability of interfacial wave disturbances. We discuss the mechanisms of non-linear energy transfer between stable and unstable wave disturbances and present results from direct numerical simulations for the predictions of spectrum evolutions for broad-banded interfacial disturbances in inclined pipes.

  1. 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. PMID:27467966

  2. 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.

  3. 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.

  4. Interfacial antiwear and physicochemical properties of alkylborate-dithiophosphates.

    PubMed

    Shah, Faiz Ullah; Glavatskih, Sergei; Höglund, Erik; Lindberg, Mats; Antzutkin, Oleg N

    2011-04-01

    Boron compounds have become of interest in tribology because of their unique tribochemical and tribological properties. At the same time, dialkyldithiophosphates (DTPs) of transition metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Because of the environmental pollution and health hazards of these compounds, ashless compounds with reduced amounts of sulfur and phosphorus are desirable. This work reports on the synthesis, characterization, and tribological properties of a new class of compounds, alkylborate-dithiophosphates. This class combines two high-iron-affinity surface active groups, borate and dialkyldithiophosphate, into a single molecule. The final products, viscous liquids, were characterized by FT-IR, multinuclear (1)H, (13)C, (31)P, and (11)B NMR spectroscopy and thermal analyses. Residues of one representative compound from this class, DPB-EDTP, after thermal analyses were additionally characterized by multinuclear (13)C, (31)P and (11)B MAS and (31)P CP/MAS NMR spectroscopy. Solid-state NMR data suggest that a dominant part of the solid residue of DPB-EDTP consists of borophosphates. Antiwear and friction properties of a mineral oil with these novel additives were evaluated in a four-ball tribometer in comparison with O,O'-di-n-butyl-dithiophosphato-zinc(II), Zn-BuDTP, as a reference lubricant additive. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy-dispersive X-rays spectroscopy (SEM/EDS). The results show that alkylborate-dithiophosphates, with substantially reduced amounts of sulfur and phosphorus compared with Zn-BuDTP, have considerably better antiwear and friction performance. PMID:21381776

  5. 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

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

    PubMed

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

    2005-04-14

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

  7. Interfacial properties of mixed films of long-chain organics at the air-water interface

    NASA Astrophysics Data System (ADS)

    Gilman, Jessica B.; Tervahattu, Heikki; Vaida, Veronica

    Organic molecules residing at the air-water interface of atmospheric aerosols will have a critical and direct effect on the aerosols' chemical, physical, and optical properties. It is important to study the interfacial properties of such compounds in order to accurately assess these effects. In this study, the compositions of two organic binary films at the air-water interface were monitored as a function of exposure time to the ambient atmosphere. One film was composed of tetracosanoic acid (lignoceric acid, CH 3(CH 2) 22COOH) and nonacosane (C 29H 60), and the second film was composed of octadecanoic acid (stearic acid, CH 3(CH 2) 16COOH) and octadecane (C 18H 38). These films were used as simplified proxies for the organic coating on atmospheric aerosols. The effect of lengthening the hydrocarbon chain on the interfacial longevity of the compounds in the mixed organic film at the air-aqueous interface was determined. The results show that octadecane in a mixed film desorbs from the interface after 72 h while octadecanoic acid remains. For nonacosane, further lengthening of the carbon chain greatly increased its interfacial longevity so that it was comparable with the fatty acids, which remained stable at the interface for at least 144 h. These results are used to explain the preponderance of long-chain fatty acids on the surfaces of collected aerosols and give insight into the degree to which the presence of other long-chain organics may affect the aerosol's chemical and physical properties.

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

    PubMed

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

    2012-10-15

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

  9. Interfacial properties in a discrete model for tumor growth

    NASA Astrophysics Data System (ADS)

    Moglia, Belén; Guisoni, Nara; Albano, Ezequiel V.

    2013-03-01

    We propose and study, by means of Monte Carlo numerical simulations, a minimal discrete model for avascular tumor growth, which can also be applied for the description of cell cultures in vitro. The interface of the tumor is self-affine and its width can be characterized by the following exponents: (i) the growth exponent β=0.32(2) that governs the early time regime, (ii) the roughness exponent α=0.49(2) related to the fluctuations in the stationary regime, and (iii) the dynamic exponent z=α/β≃1.49(2), which measures the propagation of correlations in the direction parallel to the interface, e.g., ξ∝t1/z, where ξ is the parallel correlation length. Therefore, the interface belongs to the Kardar-Parisi-Zhang universality class, in agreement with recent experiments of cell cultures in vitro. Furthermore, density profiles of the growing cells are rationalized in terms of traveling waves that are solutions of the Fisher-Kolmogorov equation. In this way, we achieved excellent agreement between the simulation results of the discrete model and the continuous description of the growth front of the culture or tumor.

  10. 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.

  11. Spontaneous formation of intermediate phases and dynamics of interfacial tension in water-nonionic surfactant-octane systems

    SciTech Connect

    Svitova, T.F.; Smirnova, Yu.P.; Pisarev, S.A.

    1994-05-01

    The kinetics of the spontaneous formation of intermediate phases in aqueous solutions of ethoxylated iso-nonylphenols (iso-C{sub 9}PhEO{sub n}, where n = 5-10)-octane systems was studied at 25{degree}C. The maximum rate of the formation of intermediate phases at this temperature was observed when the number of ethoxy-groups n was 6. The dynamic interfacial tension at the boundary between the aqueous solutions of the surfactants and octane were measured using drop volume and spinning drop methods. The rate of the interfacials tension decrease was maximum and the equilibrium interfacial tension was minimum also at n = 6. A correlation between the dynamics of interfacial processes and the equilibrium phase state of the water-nonionic surfactant-hydrocarbon systems was found for the first time.

  12. 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)

  13. 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

  14. Influence of interfacial properties and inhomogeneity on formation of microdamage in bone

    NASA Astrophysics Data System (ADS)

    Nakade, Rugved

    Microdamage accumulation at the nanoscopic level of bone affects the overall mechanical behavior of the bone. This makes it necessary to study the mechanisms through which microdamage accumulation can take place at the nanoscopic level. Experiments on bone's different hierarchy are difficult because of the small sizes of these hierarchical structures. Prevention of bone fractures is greatly enhanced with the help of predictive computational tools and hence used to evaluate the effects of microdamage in bone. There are two main types of microdamage that can form in the bone; linear cracks and diffuse damage. The bone nanostructure consists of mineral platelets embedded in soft protein called collagen and can be treated as a composite material. In this study, a two-dimensional probabilistic finite element model of the bone nanostructure was developed to evaluate the likely formation of the microdamage in the nanostructure due to changes in material properties of the nanostructure. The influence of the microdamage formation due to the collagen-mineral interface strength and also the effects of inhomogeneity were studied. To study interfacial strength effects, cohesive elements using bilinear traction separation laws were used to simulate the behavior of the interface (by way of interfacial debonding) between the collegen-mineral layers. Random field theory was used to assign spatially correlated random variables in order to assign inhomogeneous material properties to the bone. Correlation lengths were used to control the level of inhomogeneity in the model. The analysis showed that the type of microdamage was significantly influenced by the strength of the mineral-collagen interface. Probabilistic failure analyses indicated that strong interfaces resulted in limited interfacial debonding and narrow stress concentrations around an initial defect in the mineral-collagen composite, thereby suggesting that the likely location of failure was in same plane of the initial

  15. 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.

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

    PubMed

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

    2002-08-01

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

  17. 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

  18. 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.

  19. Emulsifying and interfacial properties of vicilins: role of conformational flexibility at quaternary and/or tertiary levels.

    PubMed

    Liang, Han-Ni; Tang, Chuan-He

    2013-11-20

    Although the functionality of plant proteins (and soy proteins in particular) has been widely investigated in the last decades, the importance of conformational characteristics to their functionalities is still far away from being understood. The aim of the present work was to unravel the role of conformational flexibility at the quaternary and/or tertiary levels in the emulsifying and interfacial properties of phaseolin, an ideal vicilin (or 7S globulin) from red kidney bean. The conformational flexibility at quaternary and tertiary levels of phaseolin was modulated by urea with increasing concentrations from 0 to 8 M, as characterized by using dynamic light scattering (DLS), intrinsic fluorescence and derivative UV spectroscopy, and differential scanning calorimetry (DSC). The emulsifying and interfacial properties, including emulsifying ability, flocculated state of oil droplets (in fresh emulsions), emulsion stability against creaming, and adsorption dynamics at the oil-water interface, were characterized at a specific protein concentration of 0.5% (w/v). The results indicated that increasing the urea concentration resulted in a progressive dissociation of trimeric phaseolin molecules into monomeric subunits, and even a structural unfolding of dissociated subunits; the urea-induced conformational changes at quaternary and/or tertiary levels were reversible, and the molecules at high urea concentrations shared similar structural features to the "molten globule state". On the other hand, increasing the urea concentration progressively improved the emulsifying ability of the protein, and flocculated extent of oil droplets in the fresh emulsions, but led to a progressive decrease in interfacial protein concentration. The improvement of the emulsifying ability was not related to diffusion (during initial adsorption) and penetration at the interface, but highly dependent on ease of structural rearrangement of the adsorbed proteins. These observations clearly

  20. 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.

  1. Velocity-strengthening friction significantly affects interfacial dynamics, strength and dissipation

    PubMed Central

    Bar-Sinai, Yohai; Spatschek, Robert; Brener, Efim A.; Bouchbinder, Eran

    2015-01-01

    Frictional interfaces abound in natural and man-made systems, yet their dynamics are not well-understood. Recent extensive experimental data have revealed that velocity-strengthening friction, where the steady-state frictional resistance increases with sliding velocity over some range, is a generic feature of such interfaces. This physical behavior has very recently been linked to slow stick-slip motion. Here we elucidate the importance of velocity-strengthening friction by theoretically studying three variants of a realistic friction model, all featuring identical logarithmic velocity-weakening friction at small sliding velocities, but differ in their higher velocity behaviors. By quantifying energy partition (e.g. radiation and dissipation), the selection of interfacial rupture fronts and rupture arrest, we show that the presence or absence of strengthening significantly affects the global interfacial resistance and the energy release during frictional instabilities. Furthermore, we show that different forms of strengthening may result in events of similar magnitude, yet with dramatically different dissipation and radiation rates. This happens because the events are mediated by rupture fronts with vastly different propagation velocities, where stronger velocity-strengthening friction promotes slower rupture. These theoretical results may have significant implications on our understanding of frictional dynamics. PMID:25598161

  2. Insight into interfacial effect on effective physical properties of fibrous materials. I. The volume fraction of soft interfaces around anisotropic fibers

    NASA Astrophysics Data System (ADS)

    Xu, Wenxiang; Wang, Han; Niu, Yanze; Bai, Jingtao

    2016-01-01

    With advances in interfacial properties characterization technologies, the interfacial volume fraction is a feasible parameter for evaluating effective physical properties of materials. However, there is a need to determine the interfacial volume fraction around anisotropic fibers and a need to assess the influence of such the interfacial property on effective properties of fibrous materials. Either ways, the accurate prediction of interfacial volume fraction is required. Towards this end, we put forward both theoretical and numerical schemes to determine the interfacial volume fraction in fibrous materials, which are considered as a three-phase composite structure consisting of matrix, anisotropic hard spherocylinder fibers, and soft interfacial layers with a constant dimension coated on the surface of each fiber. The interfacial volume fraction actually represents the fraction of space not occupied by all hard fibers and matrix. The theoretical scheme that adopts statistical geometry and stereological theories is essentially an analytic continuation from spherical inclusions. By simulating such three-phase chopped fibrous materials, we numerically derive the interfacial volume fraction. The theoretical and numerical schemes provide a quantitative insight that the interfacial volume fraction depends strongly on the fiber geometries like fiber shape, geometric size factor, and fiber size distribution. As a critical interfacial property, the present contribution can be further drawn into assessing effective physical properties of fibrous materials, which will be demonstrated in another paper (Part II) of this series.

  3. Effects of pure and dyed PCE on physical and interfacial properties of remedial solutions.

    PubMed

    Jeong, Seung-Woo; Wood, A Lynn; Lee, Tony R

    2002-11-11

    Hydrophobic dyes have been used to visually distinguish dense non-aqueous phase liquid (DNAPL) contaminants from background aqueous phases and soils. The objective of this study was to evaluate the effects of a dyed DNAPL, 0.5 g Oil-Red-O/l of PCE, on the physical properties of remedial solutions: water, co-solvents (50, 70, and 90% (v/v) ethanol), and surfactants (4% (w) sodium dihexyl sulfosuccinate). This study compared the densities, viscosities, and interfacial tensions (IFTs) of the remedial solutions in contact with both dyed and undyed PCE. The presence of the dye in PCE substantially alters the IFTs of water and ethanol solutions, while there is no apparent difference in IFTs of surfactant solutions. The remedial solutions saturated with PCE showed higher viscosities and densities than pure remedial solutions. Solutions with high ethanol content exhibited the largest increases in liquid density. Because physical properties affect the flow of the remedial solutions in porous media, experiments using dyed DNAPLs should assess the influence of dyes on fluid and interfacial properties prior to remediation process analysis. PMID:12409243

  4. Comparison of the interfacial properties of Eugenia uniflora and Triticum vulgaris lectins.

    PubMed

    Andrade, Cesar A S; Oliveira, Maria D L; Santos-Magalhães, Nereide S; Correia, Maria T S; de Melo, Celso P

    2009-01-01

    We have investigated the interfacial and dielectric properties of EuniSL, a recently purified lectin obtained from seeds of Eugenia uniflora (EuniSL), through surface pressure (Pi) and surface potential (DeltaV) measurements of its floating monolayers at the 2.0interfacial properties of both lectins are strongly dependent upon the pH of bulk phase, in general terms EuniSL monolayers seem to be more structured than those of WGA. At the pH range investigated, the interfacial electric double layer values (Psi(0)) calculated from the surface potential are negative, both for EuniSL and WGA. While for EuniSL definite breakpoints in an otherwise linear dependence of Psi(0) and zeta-potential as a function of pH were detected at pH 6.5, similar changes were observed for WGA at pH 8.5, a value close to the isoelectric point (pI) of this lectin. We have then used electrical impedance spectroscopy to investigate the dielectric characteristics of aqueous solutions of the two lectins, assuming a simple Debye relaxation model, and determined the pI of EuniSL as 6.5. While it is well known that the pI of a protein dispersed as a Langmuir film can be determined by surface potential measurements, our results confirm the use of impedance spectroscopy as a valuable and convenient technique that allows the identification of the pI of proteins directly dispersed in aqueous solutions. PMID:18996683

  5. 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

  6. 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.

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

    PubMed

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

    2015-03-21

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

  8. A molecular dynamics study of local pressures and interfacial tensions of SDS micelles and dodecane droplets in water.

    PubMed

    Kitabata, Masahiro; Fujimoto, Kazushi; Yoshii, Noriyuki; Okazaki, Susumu

    2016-06-14

    To obtain the radial (normal) and lateral (transverse) components of the local pressure tensor, PN(R) and PT(R), respectively, and the interfacial tension of micelles, molecular dynamics (MD) calculations were performed for spherical sodium dodecyl sulfate (SDS) micelles. The local pressure tensor was calculated as a function of radial distance R using the Irving-Kirkwood formula. Similar MD calculations were also carried out for an n-dodecane droplet in water to compare the differences in the local pressure and interfacial tension values with those of the micelles. The calculated interfacial tensions were 20 ± 5 and 44 ± 10 mN/m for the SDS micelles and dodecane droplets, respectively. The excess free energies due to the interfacial tension were 340 and 1331 kJ/mol for the SDS micelle and dodecane droplet, respectively. The micelles are stabilized by 991 kJ/mol by covering their hydrophobic cores with hydrophilic groups. The dodecane droplet has a large interfacial tension caused by the zero or positive values of PN(R) - PT(R) at all values of R. In contrast, the small interfacial tension in the SDS micelles comes from the negative PN(R) - PT(R) values over a wide range of R. The pressure difference between the inside and outside of the oil droplet and its interfacial tension well satisfies the Laplace equation. However, the hydrophobic core of the SDS micelle is quite different from the liquid alkane, and the SDS micelles do not follow Laplace's picture. Decomposing the interfacial tension into contributions from various interactions, it is found that those between charged and polar groups dominate the interfacial tension of the SDS micelles. The positive electrostatic potential (1.3 V) on the micelle surface and the negative potential (-0.15 V) on the oil droplet contribute to the interfacial tensions by 19 and 0.5 mN/m, respectively. Thus, the interfacial tension of the SDS micelles is produced by electrostatic interactions, in contrast to the dodecane

  9. A molecular dynamics study of local pressures and interfacial tensions of SDS micelles and dodecane droplets in water

    NASA Astrophysics Data System (ADS)

    Kitabata, Masahiro; Fujimoto, Kazushi; Yoshii, Noriyuki; Okazaki, Susumu

    2016-06-01

    To obtain the radial (normal) and lateral (transverse) components of the local pressure tensor, PN(R) and PT(R), respectively, and the interfacial tension of micelles, molecular dynamics (MD) calculations were performed for spherical sodium dodecyl sulfate (SDS) micelles. The local pressure tensor was calculated as a function of radial distance R using the Irving-Kirkwood formula. Similar MD calculations were also carried out for an n-dodecane droplet in water to compare the differences in the local pressure and interfacial tension values with those of the micelles. The calculated interfacial tensions were 20 ± 5 and 44 ± 10 mN/m for the SDS micelles and dodecane droplets, respectively. The excess free energies due to the interfacial tension were 340 and 1331 kJ/mol for the SDS micelle and dodecane droplet, respectively. The micelles are stabilized by 991 kJ/mol by covering their hydrophobic cores with hydrophilic groups. The dodecane droplet has a large interfacial tension caused by the zero or positive values of PN(R) - PT(R) at all values of R. In contrast, the small interfacial tension in the SDS micelles comes from the negative PN(R) - PT(R) values over a wide range of R. The pressure difference between the inside and outside of the oil droplet and its interfacial tension well satisfies the Laplace equation. However, the hydrophobic core of the SDS micelle is quite different from the liquid alkane, and the SDS micelles do not follow Laplace's picture. Decomposing the interfacial tension into contributions from various interactions, it is found that those between charged and polar groups dominate the interfacial tension of the SDS micelles. The positive electrostatic potential (1.3 V) on the micelle surface and the negative potential (-0.15 V) on the oil droplet contribute to the interfacial tensions by 19 and 0.5 mN/m, respectively. Thus, the interfacial tension of the SDS micelles is produced by electrostatic interactions, in contrast to the dodecane

  10. Two-dimensional materials as emulsion stabilizers: interfacial thermodynamics and molecular barrier properties.

    PubMed

    Creighton, Megan A; Ohata, Yuzo; Miyawaki, Jin; Bose, Arijit; Hurt, Robert H

    2014-04-01

    A new application for two-dimensional (2D) materials is emulsification, where they can serve as ultrathin platelike interfacial stabilizers in two-liquid systems. We present a first detailed thermodynamic analysis of atomically thin 2D materials at organic-aqueous liquid-liquid interfaces and derive expressions for the transfer free energies of emulsion stabilization that account for material geometry, van der Waals transparency or opacity, and variable hydrophobicity. High mass potency is shown to be an intrinsic property of the 2D geometry, which at the atomically thin limit places every atom in contact with both liquid phases, resulting in unit atom efficiency. The thermodynamic model successfully predicts that graphene oxide but not pristine graphene has a favorable hydrophobic-hydrophilic balance for oil-water emulsion stabilization. Multilayer tiling is predicted to occur by the passivation of droplet surface patches left uncovered by packing inefficiencies in the first monolayer, and complete multilayer coverage is confirmed by cryogenic scanning electron microscopy. The molecular barrier function of graphene interfacial films causes a significant suppression of dispersed-phase evaporation rates with potential applications in controlled release. Finally, these emulsions can be used as templates for creating solid graphene foams or graphene microsacks filled with lipophilic cargos. Emerging 2D materials are promising as dispersants or emulsifiers where high mass potency and multifunctional properties are desired. PMID:24625132

  11. 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

  12. 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

  13. 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

  14. Interfacial dynamics of a liposome deforming in an axisymmetric extensional flow

    NASA Astrophysics Data System (ADS)

    Gonzalez-Mancera, Andres; Eggleton, Charles D.

    2007-03-01

    Liposomes are self-enclosed structures composed of curved lipid bilayer membranes which entrap part of the solvent in which they freely float. They are predominantly made from amphiphilic molecules, a special class of surface-active molecules. Liposomes have various applications in science and technology including drug delivery systems, medical diagnostics and they can also be used as simple cellular models for basic research. We simulated the deformation of a liposome in an axisymmetric extensional flow using the boundary integral method. The liposome deforms due to hydrodynamic loading on the interface. The dynamics of the system are characterized by the competition between the hydrodynamic and interfacial forces. The lipid bilayer membrane can be modeled as a hyperelastic continuous material or a liquid-liquid interface with a highly packed surfactant layer. We compare the deformation behavior of liposomes with both types of interfaces and identify similarities and differences between the two models.

  15. Structure, viscoelasticity, and interfacial dynamics of a model polymeric bicontinuous microemulsion.

    PubMed

    Hickey, Robert J; Gillard, Timothy M; Irwin, Matthew T; Lodge, Timothy P; Bates, Frank S

    2016-01-01

    We have systematically studied the equilibrium structure and dynamics of a polymeric bicontinuous microemulsion (BμE) composed of poly(cyclohexylethylene) (PCHE), poly(ethylene) (PE), and a volumetrically symmetric PCHE-PE diblock copolymer, using dynamic mechanical spectroscopy, small angle X-ray and neutron scattering, and transmission electron microscopy. The BμE was investigated over an 80 °C temperature range, revealing a structural evolution and a rheological response not previously recognized in such systems. As the temperature is reduced below the point associated with the lamellar-disorder transition at compositions adjacent to the microemulsion channel, the interfacial area per chain of the BμE approaches that of the neat (undiluted) lamellar diblock copolymer. With increasing temperature, the diblock-rich interface swells through homopolymer infiltration. Time-temperature-superposed linear dynamic data obtained as a function of frequency show that the viscoelastic response of the BμE is strikingly similar to that of the fluctuating pure diblock copolymer in the disordered state, which we associate with membrane undulations and the breaking and reforming of interfaces. This work provides new insights into the structure and dynamics that characterize thermodynamically stable BμEs in the limits of relatively weak and strong segregation. PMID:26439750

  16. 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. PMID:22958854

  17. Growth and interfacial properties of epitaxial CaCuO2 thin films

    NASA Astrophysics Data System (ADS)

    Fuchs, D.; Müller, P.; Sleem, A.; Schneider, R.; Gerthsen, D.; Löhneysen, H. v.

    2012-11-01

    Epitaxial growth and interfacial properties of CaCuO2 films deposited on various perovskite related substrates by pulsed laser ablation were investigated. Highly c-axis oriented films can be stabilized on SrTiO3, LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, and NdGaO3 single crystalline substrates. However, the interface region between film and substrate is often found to be strongly defective. CaCuO2 films grown on (001)- and (110)-oriented NdGaO3 show the best crystallinity with lattice parameters nearly the same as for bulk CaCuO2 and a mosaic spread of about 0.1°. Regions where the interfacial growth is nearly perfect, dominantly show an A-site termination of NdGaO3, i.e., a layer stacking sequence of GaO2/NdO/CuO2/Ca. Resistivity measurements on the films show thermally activated behavior between 300 K and 170 K, i.e., ln R ˜ TA/T, where the activation temperature TA amounts to 116 K, and Mott variable range hopping, i.e., ln R ˜ T-1/4, below about 120 K. With decreasing film thickness, the resistivity increases remarkably, indicating that the interfacial conductivity is more insulating than metallic in character as expected from hole-doping of CaCuO2 due to apical oxygen at the NdO/CuO2 interface. Measurements of the magnetization do not show any indications for two-dimensional superconductivity at the interface. The experimental results suggest that the conductivity is rather caused by particulates of cupric oxide found in a distance of about 10 nm from the interface in the upper part of the film.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Nanostructured carbon sp2 (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 sp2 carbon, showing the substantial influence of carbynes on the electrochemical properties of nanostructured carbon electrodes.

  19. 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. PMID:26878188

  20. 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

  1. Mechanical, thermal, and interfacial properties of green composites with ramie fiber and soy resins.

    PubMed

    Kim, Jun Tae; Netravali, Anil N

    2010-05-12

    Fully biodegradable, green composites were fabricated with ramie fibers and modified soy flour (MSF) resin. Defatted soy flour (SF) was modified by a lab-scale filtration system to improve its mechanical, interfacial, and thermal properties through increasing the protein content. The protein content of SF was increased from 53.1 to 67.5% by filtering out soluble sugars using a microfiber-based filter. Tensile stress and Young's modulus of MSF resins were 35.5 and 1411.7 MPa, respectively, which were significantly higher than those (12.7 and 379.3 MPa) of SF resins. Interfacial shear strength of single ramie fibers with MSF resins ranged from 8.8 to 15.2 MPa, which were about 40-50% higher than those obtained with SF resins. Tensile stress and Young's modulus of ramie fiber-reinforced composites were 88.0 MPa and 2.94 GPa with SF resin and 103.8 MPa and 3.15 GPa with MSF resin. PMID:20405944

  2. 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.

  3. 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

  4. Effect of Polymer/Solid and Polymer/Vapor Instantaneous Interfaces on the Interfacial Structure and Dynamics of Polymer Melt Systems.

    PubMed

    Bekele, Selemon; Tsige, Mesfin

    2016-07-19

    Polymers are used in a wide range of applications that involve chemical and physical processes taking place at surfaces or interfaces which influence the interaction between the polymer material and the substance that comes into contact with it. Polymer surfaces are usually modified either chemically or physically for specific applications such as facilitating wetting, reducing friction, and enhancing adhesion. The variety and complexity of surface and interfacial processes requires a molecular-level understanding of the structural and dynamical properties of the surface/interface layer to help in the design of materials with desired functional properties. Using molecular dynamics (MD) simulations, we investigate the structure and dynamics at the surface of polymer films. We find that the density profiles of the films as a function of distance relative to an instantaneous surface have a structure indicative of a layering at the polymer/vapor interface similar to the typical layered structure observed at the polymer/substrate interface. However, the interfacial molecules at the polymer/vapor interface have a higher mobility compared to that in the bulk while the mobility of the molecules is lower at the polymer/substrate interface. Time correlation of the instantaneous polymer/vapor interface shows that surface fluctuations are strongly temperature dependent and are directly related to the mobility of polymer chains near the interface. PMID:27347740

  5. Investigating the interfacial properties of electrochemically roughened platinum electrodes for neural stimulation.

    PubMed

    Weremfo, Alexander; Carter, Paul; Hibbert, D Brynn; Zhao, Chuan

    2015-03-01

    Platinum electrodes have been electrochemically roughened (roughness factors up to 430) and evaluated for use as neural stimulation electrodes. The roughened electrodes show superior interfacial properties with increasing surface roughness. The roughened electrode (fR = 250) has a charge injection limit of 1.0 mC cm(-2) (400 μs pulse width), which is superior to that of titanium nitride (0.87 mC cm(-2)) but comparable to that of carbon nanotubes (1.0-1.6 mC cm(-2)). The surface roughness can also be optimized for different neural stimulation applications based on the available charge density at a particular pulse width of stimulation. The roughened platinum electrodes demonstrated good mechanical stability under harsh ultrasonication and electrochemical stability under continuous biphasic stimulation, indicating the potential of this biological interface to be safe and stable. PMID:25669232

  6. Properties of halloysite nanotube epoxy resin hybrids and the interfacial reactions in the systems

    NASA Astrophysics Data System (ADS)

    Liu, Mingxian; Guo, Baochun; Du, Mingliang; Cai, Xiaojia; Jia, Demin

    2007-11-01

    A naturally occurred microtubullar silicate, halloysite nanotubes (HNTs), was co-cured with epoxy/cyanate ester resin to form organic-inorganic hybrids. The coefficient of thermal expansion (CTE) of the hybrids with low HNT concentration was found to be substantially lower than that of the plain cured resin. The moduli of the hybrids in the glassy state and rubbery state were significantly higher than those for the plain cured resin. The dispersion of HNTs in the resin matrix was very uniform as revealed by the transmission electron microscopy (TEM) results. The interfacial reactions between the HNTs and cyanate ester (CE) were revealed by the results of Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). The substantially increased properties of the hybrids were attributed to the covalent bonding between the nanotubes and the matrix.

  7. 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. PMID:27374503

  8. 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. PMID:25748376

  9. 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].

  10. 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

  11. Improvement of interfacial property between PBO fibers and epoxy resin by surface grafting of polyhedral oligomeric silsesquioxanes (POSS)

    NASA Astrophysics Data System (ADS)

    Song, B.; Meng, L. H.; Huang, Y. D.

    2012-10-01

    PBO fiber as reinforced material has been widely applied in various fields such as aerospace, automobile and sport apparatus due to excellent mechanic property during past two decades. However, poor interfacial adhesion limits the further application of PBO fiber. To solve this problem, plenty of work has been done. In the present study, the surface of PBO fibers was treated through surface grafting of polyhedral oligomeric silsequioxanes (POSS). The effect of POSS grafting on bulk mechanic property and interfacial property of PBO fiber were studied. Surface chemical composition, surface morphologies, surface free energy, single-fiber tensile strength of untreated and treated PBO fiber were characterized. The results show that POSS nanoparticles were grafted on the fiber surface successfully. The surface characteristics of treated PBO fiber were different from that of untreated one. Oxygen-containing polar functional groups, elemental ratio of oxygen to carbon, surface roughness and surface free energy increased significantly. In addition, interfacial shear strength between treated PBO fibers and epoxy resin increased to 54.9 MPa comparative with untreated one. Meanwhile tensile strength of treated PBO fibers only very little decreased. Therefore, POSS surface grafting can be utilized to enhance the interfacial adhesion between PBO fibers and epoxy resin matrix.

  12. Effect of silica nanoparticles on the interfacial properties of a canonical lipid mixture.

    PubMed

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

    2015-12-01

    The incorporation of silica nanoparticles (NPs) from the subphase into Langmuir lipid monolayers formed by three components, 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and Cholesterol (Chol), modifies the thermodynamic and rheological behavior, as well as the structure of the pristine lipid film. Thus, the combination of structural characterization techniques, such as Brewster Angle Microscopy (BAM) and Atomic Force Microscopy (AFM), with interfacial thermodynamic and dilational rheology studies has allowed us to deepen on the physico-chemical bases governing the interaction between lipid molecules and NPs. The penetration of NPs driven by the interaction (electrostatic or hydrogen bonds) with the polar groups of the lipid molecules affects the phase behaviour (surface pressure-area, П-A , isotherm) of the monolayer. This can be easily rationalized considering the modification of the packing and cohesion of the molecules at the interface as revealed BAM and AFM images. Furthermore, oscillatory barrier experiments have allowed obtaining information related to the effect of NPs on the monolayer response under dynamic conditions that presents a critical impact on the characterization of biological relevant systems because most of the processes of interest for these systems present a dynamic character. PMID:26562189

  13. 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.

  14. 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. PMID:26653115

  15. 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

  16. Strain-Mediated Interfacial Dynamics during Au-PbS Core-Shell Nanostructure Formation.

    PubMed

    Niu, Kai-Yang; Liu, Miao; Persson, Kristin A; Han, Yu; Zheng, Haimei

    2016-06-28

    An understanding of the hierarchical nanostructure formation is of significant importance for the design of advanced functional materials. Here, we report the in situ study of lead sulfide (PbS) growth on gold (Au) nanorod seeds using liquid cell transmission electron microscopy (TEM). By tracking the formation dynamics of Au-PbS core-shell nanoparticles, we found the preferential heterogeneous nucleation of PbS on the ends of a Au nanorod prior to the development of a complete PdS shell. During PbS shell growth, drastic sulfidation of Au nanorod was observed, leading to large volume shrinkage (up to 50%) of the initial Au nanorod seed. We also captured intriguing wavy interfacial behavior, which can be explained by our DFT calculation results that the local strain gradient at the core-shell interface facilitates the mass transport and mediates reversible phase transitions of Au ↔ Au2S during the PbS shell growth. PMID:27214625

  17. Molecular dynamics simulations of interfacial interactions between small nanoparticles during diffusion-limited aggregation

    NASA Astrophysics Data System (ADS)

    Lu, Jing; Liu, Dongmei; Yang, Xiaonan; Zhao, Ying; Liu, Haixing; Tang, Huan; Cui, Fuyi

    2015-12-01

    Due to the limitations of experimental methods at the atomic level, research on the aggregation of small nanoparticles (D < 5 nm) in aqueous solutions is quite rare. The aggregation of small nanoparticles in aqueous solutions is very different than that of normal sized nanoparticles. The interfacial interactions play a dominant role in the aggregation of small nanoparticles. In this paper, molecular dynamics simulations, which can explore the microscopic behavior of nanoparticles during the diffusion-limited aggregation at an atomic level, were employed to reveal the aggregation mechanism of small nanoparticles in aqueous solutions. First, the aggregation processes and aggregate structure were depicted. Second, the particle-particle interaction and surface diffusion of nanoparticles during aggregation were investigated. Third, the water-mediated interactions during aggregation were ascertained. The results indicate that the aggregation of nanoparticle in aqueous solutions is affected by particle size. The strong particle-particle interaction and high surface diffusion result in the formation of particle-particle bonds of 2 nm TiO2 nanoparticles, and the water-mediated interaction plays an important role in the aggregation process of 3 and 4 nm TiO2 nanoparticles.

  18. 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. PMID:27152346

  19. Dynamics and mechanisms of interfacial photoinduced electron transfer processes of third generation photovoltaics and photocatalysis.

    PubMed

    Bauer, Christophe; Teuscher, Joël; Brauer, Jan C; Punzi, Angela; Marchioro, Arianna; Ghadiri, Elham; De Jonghe, Jelissa; Wielopolski, Mateusz; Banerji, Natalie; Moser, Jacques E

    2011-01-01

    Photoinduced electron transfer (PET) across molecular/bulk interfaces has gained attention only recently and is still poorly understood. These interfaces offer an excellent case study, pertinent to a variety of photovoltaic systems, photo- and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. They play in particular a key role in the emerging fields of third-generation photovoltaic energy converters and artificial photosynthetic systems aimed at the production of solar fuels, creating a need for a better understanding and theoretical treatment of the dynamics and mechanisms of interfacial PET processes. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test and alter modern theory and computational modeling. One example illustrating recent investigations into the details of the ultrafast processes that form the basis for photoinduced charge separation at a molecular/bulk interface relevant to dye-sensitized solar cells is briefly presented here: Kinetics of interfacial PET and charge recombination processes were measured by fs and ns transient spectroscopy in a heterogeneous donor-bridge-acceptor (D-B-A) system, where D is a Ru(II)(terpyridyl-PO3)(NCS)3 complex, B an oligo-p-phenylene bridge, and A nanocrystalline TiO2. The forward ET reaction was found to be faster than vibrational relaxation of the vibronic excited state of the donor. Instead, the back ET occurred on the micros time scale and involved fully thermalized species. The D-A distance dependence of the electron transfer rate was studied by varying the number of p-phenylene units contained in the bridge moiety. The remarkably low damping factor beta = 0.16 angstroms(-1) observed for the ultrafast charge injection from the dye excited state into the conduction band of TiO2 is attributed to the coupling of electron tunneling with nonequilibrium vibrations redistributed on the bridge

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    PubMed

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

    2016-08-10

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

  7. 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.

  8. Control of Interfacial Properties of Al2O3/Ge Gate Stack Structure Using Radical Nitridation Technique

    NASA Astrophysics Data System (ADS)

    Kato, Kimihiko; Kyogoku, Shinya; Sakashita, Mitsuo; Takeuchi, Wakana; Kondo, Hiroki; Takeuchi, Shotaro; Nakatsuka, Osamu; Zaima, Shigeaki

    2011-10-01

    We have investigated the control of the interfacial properties of Al2O3/Ge gate stack structures by the radical nitridation technique. In the Al2O3/Ge structures formed by the atomic layer deposition method, the interface state density increases with the deposition temperature due to the decrease in the thickness of the Ge oxide interlayer. On the other hand, the hysteresis width of the capacitance-voltage (C-V) characteristics decreases with increasing deposition temperature, which indicates a decrease in the oxide trap density near the interface. We also investigated the control of the interfacial structure by the radical nitridation of Al2O3/Ge to form an interfacial structure after the deposition of a high-k dielectric layer. The results of X-ray photoelectron spectroscopy reveal that an Al2O3/Ge3N4/GeO2/Ge stack structure is formed after the radical nitridation owing to the minimal oxygen diffusion into the Al2O3/Ge interface. Furthermore, the interfacial mixing is suppressed after radical nitridation at less than 300 °C. As a result, we can decrease the interface state density of the Al2O3/Ge sample after the radical nitridation by more than one order of magnitude compared with that without radical nitridation.

  9. Wall-liquid and wall-crystal interfacial free energies via thermodynamic integration: a molecular dynamics simulation study.

    PubMed

    Benjamin, Ronald; Horbach, Jürgen

    2012-07-28

    A method is proposed to compute the interfacial free energy of a Lennard-Jones system in contact with a structured wall by molecular dynamics simulation. Both the bulk liquid and bulk face-centered-cubic crystal phase along the (111) orientation are considered. Our approach is based on a thermodynamic integration scheme where first the bulk Lennard-Jones system is reversibly transformed to a state where it interacts with a structureless flat wall. In a second step, the flat structureless wall is reversibly transformed into an atomistic wall with crystalline structure. The dependence of the interfacial free energy on various parameters such as the wall potential, the density and orientation of the wall is investigated. The conditions are indicated under which a Lennard-Jones crystal partially wets a flat wall. PMID:22852644

  10. The interfacial properties of AOF/ZnS and LWIR bulk HgCdTe materials by MIS structures

    NASA Astrophysics Data System (ADS)

    Wang, Nili; Liu, Shijia; Lan, Tianyi; Zhao, Shuiping; Jiang, Peilu; Li, Xiangyang

    2012-10-01

    The semiconductor-passivating layer interface, as well as the dielectric properties of the passivants, plays an important role in HgCdTe based photoelectric detectors. Anodization is a commonly uses surface passivation for HgCdTe. ZnS is deposited on the AOF (anodic-oxide film) as antireflecting layer. The interfacial properties of the metal insulator semiconductor (MIS) structures were determined by capacitance-voltage (C-V) measurements in the frequency range 10 KHz-10 MHz. The results showed that the MIS detector could not reach the high frequency level even at frequencies up to 10 MHz. The interfacial state densities were 3.4×1011 cm-2q-1V-1 and the fixed charges were 1.1×1012 cm-2. The surface recombination velocity was 700 cm/s.

  11. Effect of surface stoichiometry and interfacial interactions on ultrafast carrier dynamics of crystalline CdTe (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    He, Xing; Punpongjareorn, Napat; Wu, Chengyi; Rajagopal, Karjini; Yang, Ding-Shyue

    2015-08-01

    To improve the efficiency of optoelectronic devices, it is critical to understand the carrier dynamics of photoactive materials and the mechanisms involved, including those effects caused by different surface stoichiometry and/or interfacial interactions. A good example is CdTe, which exhibits cost-effective high performance in thin-film photovoltaic cells; it is also known to show surface oxidation, which may affect device efficiency and hence limit the production methods used. In this contribution, we present ultrafast carrier dynamics of crystalline CdTe specimens with different surface conditions using transient reflectivity measurements, following a femtosecond above-gap excitation. The distinct differences observed in the dynamics and the time constants for oxidized and stoichiometrically restored specimens indicate the major role of surface tellurium oxide on the relaxation of photoinduced carriers. The much slower recovery observed on oxidized surfaces is attributed to a transfer (and trapping) of electrons to the tellurium atoms with a high oxidation state, which signifies a charge separation near the surface. To distinguish the effect caused by oxygen adsorption, we also examined the carrier dynamics of CdTe surfaces covered by a thin layer of water molecules for comparison. These results, which show clear interfacial effects, may have broader implications for the understanding of carrier dynamics in nanostructured and polycrystalline specimens under different chemical environments, as such materials exhibit a high surface-to-volume ratio.

  12. 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.

  13. Production of glycolipid biosurfactants, mannosylerythritol lipids, using sucrose by fungal and yeast strains, and their interfacial properties.

    PubMed

    Morita, Tomotake; Ishibashi, Yuko; Fukuoka, Tokuma; Imura, Tomohiro; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2009-10-01

    Glycolipid biosurfactants, mannosylerythritol lipids (MELs), were produced from glucose and sucrose without vegetable oils. Pseudozyma antarctica JCM 10317, Ustilago maydis NBRC 5346, U. scitaminea NBRC 32730, and P. siamensis CBS 9960 produced mainly MEL-A, MEL-A, MEL-B, and MEL-C respectively. The sucrose-derived MELs showed excellent interfacial properties: low critical micelle concentration as well as that of oil-derived MELs. PMID:19809166

  14. Interfacial stress transfer and property mismatch in discontinuous nanofiber/nanotube composite materials.

    PubMed

    Xu, L Roy; Sengupta, Sreeparna

    2005-04-01

    Novel nanotubes/nanofibers with high strength and stiffness did not lead to high failure strengths/strains of nanocomposite materials. Therefore, the interfacial stress transfer and possible stress singularities, arising at the interfacial ends of discontinuous nanofibers embedded in a matrix, subjected to tensile and shear loading, were investigated by finite element analysis. The effects of Young's moduli and volume fractions on interfacial stress distributions were studied. Round-ended nanofibers were proposed to remove the interfacial singular stresses, which were caused by high stiffness mismatch of the nanoscale reinforcement and the matrix. However, the normal stress induced in the nanofiber through interfacial stress transfer was still less than 2 times that in the matrix. This stress value is far below the high strength of the nanofiber. Therefore, the load transfer efficiency of discontinuous nanofibers or nanotube composites is very low. Hence, nanofibers or nanotubes in continuous forms, which also preclude the formation of singular interfacial stress zones, are recommended over discontinuous nanofibers to achieve high strengths in nanocomposite materials. PMID:16004129

  15. Production of a novel glycolipid biosurfactant, mannosylmannitol lipid, by Pseudozyma parantarctica and its interfacial properties.

    PubMed

    Morita, Tomotake; Fukuoka, Tokuma; Konishi, Masaaki; Imura, Tomohiro; Yamamoto, Shuhei; Kitagawa, Masaru; Sogabe, Atsushi; Kitamoto, Dai

    2009-07-01

    The development of a novel glycolipid biosurfactant was undertaken using the high-level producers of mannosylerythritol lipids (MELs) such as Pseudozyma parantarctica, Pseudozyma antarctica, and Pseudozyma rugulosa. Besides the conventional MELs (MEL-A, MEL-B, and MEL-C), these yeasts produced an unknown glycolipid when they were cultivated in a medium containing 4% (w/v) olive oil and 4% (w/w) mannitol as the carbon source. The unknown glycolipid extracted from the culture medium of P. parantarctica JCM 11752(T) displayed the spot with lower mobility than that of known MELs on TLC and provided mainly two peaks identical to mannose and mannitol on high-performance liquid chromatography after acid hydrolysis. Based on structural analysis by (1)H and (13)C nuclear magnetic resonance, the novel glycolipid was composed of mannose and mannitol as the hydrophilic sugar moiety and was identified as mannosylmannitol lipid (MML). Of the strains tested, P. parantarctica JCM 11752(T) gave the best yield of MML (18.2 g/L), which comprised approximately 35% of all glycolipids produced. We further investigated the interfacial properties of the MML, considering the unique hydrophilic structure. The observed critical micelle concentration (CMC) and the surface tension at CMC of the MML were 2.6 x 10(-6) M and 24.2 mN/m, respectively. In addition, on a water-penetration scan, the MML efficiently formed not only the lamella phase (Lalpha) but also the myelins at a wide range of concentrations, indicating its excellent self-assembling properties and high hydrophilicity. The present glycolipid should thus facilitate the application of biosurfactants as new functional materials. PMID:19296097

  16. 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. PMID:25372426

  17. Single-fiber push-in vs. single-fiber push-out: A comparison between two test methods to determine the interfacial properties of brittle matrix composites

    SciTech Connect

    Ferber, M.K.; Lara-Curzio, E.; Russ, S.E.; Chawla, K.K.

    1995-10-01

    Interfacial properties of Nicalon{trademark}-reinforced brittle matrix composites were determined from single-fiber load-controlled push-in tests using a Mechanical Properties Microprobe (Nanoindenter) and single-fiber displacement-controlled push-out tests using the Interfacial Test System (ITS). A comparison between the results from these two tests is presented along with a discussion of data analysis techniques.

  18. 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. PMID:25363684

  19. 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.

  20. Grafting Poly(3-hexylthiophene) from Silicon Nanocrystal Surfaces: Synthesis and Properties of a Functional Hybrid Material with Direct Interfacial Contact.

    PubMed

    Islam, Muhammad Amirul; Purkait, Tapas K; Mobarok, Md Hosnay; Hoehlein, Ignaz M D; Sinelnikov, Regina; Iqbal, Muhammad; Azulay, Doron; Balberg, Isaac; Millo, Oded; Rieger, Bernhard; Veinot, Jonathan G C

    2016-06-20

    Hybrid functional materials (HFMs) comprised of semiconductor nanoparticles and conjugated polymers offer the potential of synergetic photophysical properties. We have developed HFMs based upon silicon nanocrystals (SiNCs) and the conductive polymer poly(3-hexylthiophene) (SiNC@P3HT) by applying surface-initiated Kumada catalyst transfer polycondensation (SI-KCTP). One unique characteristic of the developed SiNC@P3HT is the formation of a direct covalent bonding between SiNCs and P3HT. The presented method for obtaining direct interfacial attachment, which is not accessible using other methods, may allow for the development of materials with efficient electronic communication at the donor-acceptor interfaces. Systematic characterization provides evidence of a core-shell structure, enhanced interfacial electron and/or energy transfer between the P3HT and SiNC components, as well as formation of a type-II heterostructure. PMID:27144670

  1. Interfacial and gravitationally-related properties of liquid crystals and other fluids

    NASA Astrophysics Data System (ADS)

    Mahajan, Milind Prabhakar

    This thesis describes a series of experiments on liquid crystals and other fluids to investigate behavior related to interfacial constraints, surface tension, and gravitational acceleration. The first part of the thesis deals with liquid crystal alignment surfaces. The grooved surface topography created by a buffing cloth on spin-coated polyimide films was characterized using Atomic Force Microscope (AFM). The shape of grooves was correlated to the microstructure on the lateral surface of rubbing fiber. The orientation induced in the rubbed polyimide was probed using optical retardation measurements. The retardation as a function of rubbing strength was shown to exhibit threshold-like behavior that was sensitive to rubbing history. AFM probe was used to "write" alignment pattern on sub-micron length-scale pixel. Two possible device geometries were constructed and analyzed. In the second half, the thesis discusses the static and dynamic behavior of fluid zones. MnCl2·4H2O was dissolved in water and the solution was magnetically levitated to stimulate low gravity. Static stability of a "bridge" (a fluid zone supported by two equal coaxial disks) was studied as a function of effective gravity and volume of the fluid. The ability of the levitation setup to temporally control effective gravity was exploited to investigate the dynamics of bridge collapse. A sudden change of magnetic current, corresponding to a change in gravity, beyond stability limit resulted in deformation and ultimate collapse of a bridge. A scaling relationship was found for collapse time as a function of the step change in gravity. The results were compared to predictions of a 1-D slice model. The levitated bridges were subjected to axial and lateral oscillations of gravity. The first resonance frequency was found to be maximum at zero effective gravity and decreased with increasing gravity. Comparable results were obtained by numerical simulations. Low gravity experiments on liquid crystals are

  2. 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.

  3. Studies of Interfacial Layer and Its Effect on Magnetic Properties of Glass-Coated Microwires

    NASA Astrophysics Data System (ADS)

    Zhukov, Arcady; Shuvaeva, Evgenia; Kaloshkin, Sergei; Churyukanova, Margarita; Kostitsyna, Elena; Zhdanova, Margarita; Talaat, Ahmed; Ipatov, Mihail; Zhukova, Valentina

    2016-05-01

    We present studies of the interfacial layer between the metallic nucleus and glass coating in ferromagnetic Fe- and Co-rich microwires. Using a scanning electron microscope, we obtained the image of the interfacial layer and the elements distribution within the glass coating and metallic nucleus. This allowed us to estimate the thickness of the interfacial layer ( t il). For both Fe- and Co-rich microwires, t il ≈ 0.5 μm. We measured the frequency dependence of the giant magnetoimpedance ratio in Fe and Co-rich microwires, estimated the minimum penetration depth, and discussed the optimum frequency for different microwires considering the difference of the magnetic structure and the magnetic anisotropy inside the microwire and near the surface.

  4. Well-defined oxide core-polymer shell nanoparticles: interfacial interactions, peculiar dynamics, and transitions in polymer nanolayers.

    PubMed

    Bershtein, V A; Gun'ko, V M; Egorova, L M; Guzenko, N V; Pakhlov, E M; Ryzhov, V A; Zarko, V I

    2010-07-01

    Interfacial interactions, chain dynamics, and glass and melting transitions were studied in well-defined core-shell nanoparticles with amorphous silica or crystalline alumina cores and noncrystallizable poly(vinyl pyrrolidone) (PVP) or crystallizable poly(ethylene glycol) (PEG) shells. Varying particle composition caused regular changes in the shell thickness from 1 to 2 nm (monomolecular layer) up to 90 nm. Far- and mid-IR spectroscopy allowed us to register hydrogen bonding and, tentatively, Lewis/Brønsted (LB) interfacial interactions as well as changes in the dynamics and conformational state of the polymer chains as a function of the nanoshell thickness. Their most pronounced peculiarities were found for the monomolecular polymer layers. The LB interactions were stronger with the alumina substrate than silica. DSC analysis was performed, and the data obtained were in agreement with the spectroscopic data. Unlike the bulk polymer, the PVP monolayer was characterized with an extraordinarily large dynamic heterogeneity within the glass transition while broadening the transition range and varying the activation energy by an order of magnitude. The PEG monolayer adsorbed on silica was totally amorphous, whereas a highly crystalline one with the anomalously thin lamellae, down to 3 nm thick, was adsorbed on an alumina surface, presumably as a result of the quasi-heteroepitaxial crystallization process. PMID:20415443

  5. 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.

  6. 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.

  7. Interfacial effects revealed by ultrafast relaxation dynamics in BiFeO3/YBa2Cu3O7 bilayers

    NASA Astrophysics Data System (ADS)

    Springer, D.; Nair, Saritha K.; He, Mi; Lu, C. L.; Cheong, S. A.; Wu, T.; Panagopoulos, C.; Chia, Elbert E. M.; Zhu, Jian-Xin

    2016-02-01

    The temperature dependence of the relaxation dynamics in the bilayer thin film heterostructure composed of multiferroic BiFeO3 (BFO) and superconducting YBa2Cu3O7 (YBCO) grown on a (001) SrTiO3 substrate is studied by a time-resolved pump-probe technique, and compared with that of pure YBCO thin film grown under the same growth conditions. The superconductivity of YBCO is found to be retained in the heterostructure. We observe a speeding up of the YBCO recombination dynamics in the superconducting state of the heterostructure, and attribute it to the presence of weak ferromagnetism at the BFO/YBCO interface as observed in magnetization data. An extension of the Rothwarf-Taylor model is used to fit the ultrafast dynamics of BFO/YBCO, that models an increased quasiparticle occupation of the ferromagnetic interfacial layer in the superconducting state of YBCO.

  8. Production of glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma siamensis CBS 9960 and their interfacial properties.

    PubMed

    Morita, Tomotake; Konishi, Masaaki; Fukuoka, Tokuma; Imura, Tomohiro; Kitamoto, Dai

    2008-05-01

    The search for a novel producer of glycolipid biosurfactants, mannosylerythritol lipids (MELs), was undertaken on the basis of the analysis of ribosomal DNA sequences of yeast strains of the genus Pseudozyma. In the course of the investigation, Pseudozyma siamensis CBS 9960, which is closely related to Pseudozyma shanxiensis, a known MEL-C producer but with a different morphology, was found to accumulate a large amount of glycolipids. On thin layer chromatography, the extracellular glycolipids showed nearly the same spots as those of the MELs produced by P. shanxiensis. However, the result of high-performance liquid chromatography analysis revealed that the present strain has a much higher glycolipid production yield than P. shanxiensis. From the structural characterization by (1)H and (13)C NMR, the major glycolipid (more than 84% of the total) was identified as a mixture of 4-O-[(2',4'-di-O-acetyl-3'-O-alka(e)noyl)-beta-D-mannopyranosyl]-D-erythritol and 4-O-[(4'-O-acetyl-3'-O-alka(e)noyl-2'-O-butanoyl)-beta-D-mannopyranosyl]-D-erythritol, both of which are types of MEL-C. The present MEL-C possessed a short-chain acid (C(2) or C(4)) at the C-2' position and a long-chain acid (C(16)) at the C-3' position of the mannose moiety, and thus, the hydrophobic part was considerably different from that of conventional MELs, which mainly possess two medium-chain acids (C(10)) at the C-2' and C-3' positions. Under optimal growth conditions with safflower oil in a shake culture, the total amount of MELs reached approximately 19 g/l after 9 d at 25 degrees C. We further investigated the interfacial properties of the present MEL-C, considering its unique hydrophobic structure. The observed critical micelle concentration (CMC) and the surface tension at the CMC of the MEL were 4.5 x 10(-6) M and 30.7 mN/m, respectively. In addition, on a water penetration scan, the MEL efficiently formed the liquid crystal phases such as hexagonal (H) and lamella (L(a)) at a wide range of

  9. 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.

  10. 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.

  11. 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.

  12. Rheology and interfacial properties of aqueous solutions of the diblock polyelectrolyte poly(styrene-block-acrylic acid)

    NASA Astrophysics Data System (ADS)

    Kimerling, Abigail

    In aqueous solutions diblock polyelectrolytes with amphiphilic character form aggregate structures, which affect physical properties such as viscosity, elasticity, surface tension, and film hydrophilicity. Potential applications for diblock polyelectrolyte solutions include coatings, inks, oil recovery agents, personal care products, and biomaterials. By varying the diblock polyelectrolyte and solution properties, the solutions can be tuned to meet the needs of particular applications. The research objective was to identify the influences of block length, pH, and ionic strength on the rheological and interfacial properties of poly(styrene- b-acrylic acid) (PS-PAA) solutions. Six polymers with varied PS and PAA block lengths were examined, all at 1.0 wt% in aqueous solutions. The hydrophobicity of the PS block causes the formation of spherical micelles in aqueous solutions. Increasing the solution pH ionizes the PAA block, which leads to an increase in micelle corona thickness due to repulsions between chains. Major trends observed in the rheological and interfacial properties can be understood in terms of expected changes in the micelle size and interfacial self-assembly with pH, ionic strength, and block length. Addition of NaOH was found to increase the solution pH and initially led to increases in solution viscosity, elasticity, surface tension, and film hydrophilicity. This effect was attributed to creation of larger micelles and greater inter-micellar repulsions as the PAA chain became more fully charged. However, when the concentration of NaOH exceeded a critical value, the solution viscosity, elasticity, and film hydrophilicity decreased. It is believed this was due to charge shielding by excess sodium ions, leading to shrinkage of the micelle corona and smaller micelles. Increasing the PS-PAA solution ionic strength by adding NaCl also provided charge shielding, as observed by decreases in solution viscosity and elasticity. Increasing the length of either

  13. 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.

  14. Correlation between interfacial interactions and mechanical properties of PA-6 doped with surface-capped nano-silica

    NASA Astrophysics Data System (ADS)

    Li, Deliang; Liu, Qing; Yu, Laigui; Li, Xiaohong; Zhang, Zhijun

    2009-06-01

    The polyamide-6 pellets were mixed with nano-SiO 2 particles surface-capped by 3-aminopropyltriethoxysilane (APS) via a melt blending route. PA-6 composites doped with surface-capped nano-SiO 2 (designated as PAMNS, where AMNS refers to APS surface-capped nano-SiO 2). AMNS and the silica samples (designated as EAMNS) extracted by acid etching from various PAMNS samples containing different concentration of amino functional groups on surface-capped nano-silica surfaces were characterized by means of Fourier transformation infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). This aims at revealing the interfacial interaction between AMNS and PA-6 matrix and its effect on the mechanical properties of the filled PA-6 composites. The chemical features and microstructures of the PAMNS composites were analyzed by means of FTIR and transmission electron microscopy (TEM), respectively, while their mechanical properties were evaluated using standardized test rigs. Results demonstrate that the surface-modified nano-SiO 2 particles were uniformly dispersed in PA-6 matrix. The residue silica extracted from various PAMNS samples showed characteristic FTIR absorbance peak of PA-6 and had larger weight losses than AMNS, implying that the polymeric matrix was chemically bonded with the nanofiller particles. The interfacial interactions are closely related to the concentration of functional groups in AMNS, and there might exist a critical concentration at which the strongest interfacial interactions could be reached. Beyond the critical concentration of the functional groups in AMNS, the mechanical properties of the filled PA-6 composites tended to decrease to some extent.

  15. 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

  16. 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. PMID:23258033

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 (PSiO2) 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.

  18. 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.

  19. 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.

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

    SciTech Connect

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

    1995-10-01

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

  1. 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. PMID:22341919

  2. 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. PMID:22781920

  3. 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. PMID:24347268

  4. 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.

  5. Estimation of the Thermodynamic Limit of Overheating for Bulk Water from Interfacial Properties

    NASA Astrophysics Data System (ADS)

    Imre, A. R.; Baranyai, A.; Deiters, U. K.; Kiss, P. T.; Kraska, T.; Quiñones Cisneros, S. E.

    2013-11-01

    The limit of overheating or expanding is an important property of liquids, which is relevant for the design and safety assessment of processes involving pressurized liquids. In this work, the thermodynamic stability limit—the so-called spinodal—of water is calculated by molecular dynamics computer simulation, using the molecular potential model of Baranyai and Kiss. The spinodal pressure is obtained from the maximal tangential pressure within a liquid-vapor interface layer. The results are compared to predictions of various equations of state. Based on these comparisons, a set of equations of state is identified which gives reliable results in the metastable (overheated or expanded) liquid region of water down to MPa.

  6. Accelerated and Outdoor Aging Effects on Photovoltaic Module Interfacial Adhesion Properties

    SciTech Connect

    Jorgensen, G. J.; McMahon, T. J.

    2008-01-01

    We have developed an apparatus that allows the measurement of applied torque as a function of angle of twist during shear removal of cored specimens. This allows us to characterize the strength and durability of various interfaces within many types of photovoltaic (PV) modules. We have used this device to evaluate several parameters in terms of their ability to quantify degradation of interfacial adhesion in weathered PV modules. The usefulness of shear modulus in this regard is marginal. However, peak torque, angle at peak torque, and toughness are very sensitive parameters.

  7. 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.

  8. Comparison of the capillary wave method and pressure tensor route for calculation of interfacial tension in molecular dynamics simulations.

    PubMed

    Nickerson, Stella; Frost, Denzil S; Phelan, Harrison; Dai, Lenore L

    2013-12-01

    We have studied the calculation of surface and interfacial tension for a variety of liquid-vapor and liquid-liquid interfaces using molecular dynamics (MD) simulations. Because of the inherently small scale of MD systems, large pressure fluctuations can cause imprecise calculations of surface tension using the pressure tensor route. The capillary wave method exhibited improved precision and stability throughout all of the simulated systems in this study. In order to implement this method, the interface was defined by fitting an error function to the density profile. However, full mapping of the interface from coordinate files produced enhanced accuracy. Upon increasing the system size, both methods exhibited higher precision, although the capillary wave method was still more reliable. PMID:24122780

  9. 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.

  10. Temperature effects on the interfacial properties of semifluorinated diblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Shrestha, Umesh; Clarson, Stephen; Perahia, Dvora

    The interfacial composition and structure of polymer films influence their response to external stimuli and their wetting behavior. Here we probe temperature effects on the interfacial morphology and surface energies of polytrifluoro propyl methyl siloxane- b-polystyrene (SiF-b-PS) films with SiF volume fraction of φ = 0.03 to 0.46 using atomic force microscopy and surface tension measurement. Films were cast from toluene, selective for PS, and annealed at temperatures ranging from 75 to 210°C, below and above Tg of the PS block (~98°C). For φ = 0. 03 a network of small aggregates is formed and hardly changed over the temperature range studied. For φ = 0.16 an asymmetric diblock, spherical aggregates at room temperature transformed to elongated ones at elevated temperatures whereas in the symmetric case, spherical assemblies at room temperature merged into larger structures. Independent of SiF fraction the contact angle increased with temperature which is indicative of migration of fluorine to the interface. Surprisingly, dewetting was not observed even annealing the film at much higher temperature than Tg of PS. NSF DMR 0907390 2009.

  11. 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.

  12. 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

  13. 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.

  14. Interfacial properties of the enhanced visible-light plasmonic Ag/Bi2WO6 (0 0 1) nanocomposite

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Cao, Kun; Wu, Yi; Zhang, Kun-Hao; Zhou, Ying

    2016-01-01

    First principle calculations are performed to study the interfacial photoelectric properties of Agn/Bi2WO6 (0 0 1) (n = 1, 2, 3, 4) hybrid photocatalyst. The parallel adsorption of Ag cluster leads to more energetic favorable structures due to stronger interfacial interactions. The positive charged Ag cluster may act as excited electron traps and facilitate the electron-hole separation. In particular, hybridization between Ag 5s and O 2p leads to the formation of isolated energy levels above the valence bands, and they become more dispersed with broader bandwidth with the increment of silver cluster size, which is responsible for the enhanced absorption in visible-light region. In the deep valence region, Ag 4d orbital turns more delocalized and hybrid with O 2p states as the cluster size increases, which contributes to more covalent bond feature of Ag-O. Moreover, optical spectra demonstrate obvious red-shifts of the absorption edge with the increment of silver content, which enhances efficiently the visible-light photocatalytic activities of Bi2WO6 (0 0 1). The study provides insights into the enhanced photocatalyic mechanism of Ag/Bi2WO6 (0 0 1) and aids in the design of noble metal loaded visible-light plasmonic photocatalyst.

  15. Determining interfacial properties of submicron low-k films on Si substrate by using wedge indentation technique

    NASA Astrophysics Data System (ADS)

    Yeap, Kong Boon; Zeng, Kaiyang; Jiang, Haiyan; Shen, Lu; Chi, Dongzhi

    2007-06-01

    This article presents studies on using a wedge indentation technique to determine interfacial adhesion properties of low-k dielectric films, namely, methyl-silsesquioxane (MSQ) and black diamond (BD™)films, both on a Si substrate. Interfacial crack initiation and propagation processes in the MSQ/Si system are studied by using focused-ion-beam sectioning of the indentation impressions created by wedge tips with 90° and 120° of inclusion angles, respectively. Furthermore, the indentation induced stress is found to be proportional to the ratio of the indentation volume and the interface delamination crack volume for both plane strain and nonplane strain cases. With this analysis, the interface toughness of the MSQ/Si and BD/Si system, in terms of the strain energy release rate, is determined. The interface toughness for the MSQ/Si system is found to be a value of 1.89±0.28J/m2 for the 90° wedge tip indentation and 1.92±0.08J/m2 for the 120° wedge tip indentation. In addition, using the 120° wedge tip, the interface toughnesses of the BD films on the Si substrate with 200 and 500nm thicknesses are found to be the values of 6.62±1.52 and 6.35±2.27J/m2, respectively.

  16. 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. PMID:26328543

  17. 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.

  18. Comparison between two anionic reverse micelle interfaces: the role of water-surfactant interactions in interfacial properties.

    PubMed

    Quintana, Silvina S; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2012-01-16

    The water/sodium bis(2-ethylhexyl) phosphate (NaDEHP) reverse micelle (RM) system is revisited by using, for the first time, molecular probes to investigate interface properties. The solvatochromic behavior of 1-methyl-8-oxyquinolinium betaine (QB) and 6-propionyl-2-(N,N-dimethyl)aminonaphthalene (PRODAN) in the water/NaDEHP/toluene system is studied, and the results are compared with those obtained in water/sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT)/toluene RM media. The results demonstrate that the micropolarity, microviscosity, interfacial water structure, molecular probe partition, and intramolecular electron-transfer processes are dramatically altered for NaDEHP RM interfaces in comparison to the AOT systems. Because of organic nonpolar solvent penetration into the interface, NaDEHP RM media offer an interface with lower micropolarity and microviscosity than AOT media. Also, the interfacial water in the NaDEHP system shows enhanced water-water hydrogen-bond interaction in comparison with bulk water. The AOT RM interface represents a unique environment for PRODAN to undergo dual emission. PMID:22135080

  19. Interfacial properties of two-carbon fiber reinforced polycarbonate composites using two-synthesized graft copolymers as coupling agents

    SciTech Connect

    Park, J.M.

    2000-05-15

    Two model coupling agents, water-dispersible (WDGP) and tetrahydrofuran (THF)-soluble graft copolymers (TSGP), were synthesized for carbon fiber/polycarbonate (PC) composites. WDGP contains a long polyacrylamide (PAAm) chain grafted on a PC backbone, whereas TSGP contains a short grafted PAAm Chain. Measurements of the interfacial shear strength (IFSS) and other interfacial properties were evaluated using a fragmentation test for two-fiber composites (TFC) to provide the same loading state. Optimal conditions for the treatment was established as a function of treatment time, temperature, initial concentration, and melting procedure. The amount adsorbed on the carbon fiber was higher for WDGP and TSGP were 54% and 74%, respectively. Mechanisms of energy adsorption for WDGP and intermolecular interaction for TSGP can be considered to contribute differently to IFSS improvement. The improvement in IFSS for both coupling agents may be due to chemical and hydrogen bonding in the interface between functional groups in the carbon fiber and PAAm in the coupling agents and to interdiffusion in the interface between PC in coupling agents and matrix PC.

  20. 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

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

    PubMed

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

    2009-01-01

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

  2. Dynamical properties of piano soundboards.

    PubMed

    Chaigne, Antoine; Cotté, Benjamin; Viggiano, Roberto

    2013-04-01

    In pianos, the transfer of energy from strings to soundboard and the radiation of sound are highly dependent on the dynamical properties of the soundboard. In this paper, a numerical study is conducted for various rib configurations, showing that even slight irregularities in rib spacing can induce a strong localization of the soundboard velocity pattern. The effective vibrating area can be further reduced due to the spatial filtering effect of the bridge. Numerical predictions of modal shapes and operating deflection shapes are confirmed by series of measurements made on upright piano soundboards. Simulations of radiated pressure based on measured and calculated soundboard velocity fields show that localization tends to broaden the cone of directivity and to reduce the number of lobes. PMID:23556610

  3. Electronic Transport properties of SET and REST states of interfacial phase-change memory

    NASA Astrophysics Data System (ADS)

    Nakamura, Hisao; Tominaga, Junji; Asai, Yoshihiro; Rungger, Ivan; Narayan, Awadhesh; Sanvito, Stefano

    2015-03-01

    The phase change memory (PCM) is one of most promising nonvolatile information storage technologies. Recently, the superlattice structure of GeTe/Sb2Te3 is proposed as PCM to reduce the restive switching energy. This PCM is called interfacial PCM (iPCM) and it is considered that SET and RESET states are realized only by the flip-flop transition of Ge atoms in crystal phase because of small loss of entropy. Furthermore, the GeTe is sandwiched by Sb2Te3 topological insulator. In this study, we performed the first principles electric transport calculations including spin-orbit interactions. We presents the mechanism of resistive switch by the transition of Ge atoms as well as the volume change effect and the role of spin-orbit interaction to resistance ration of SET and RESE states.

  4. 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.

  5. Shape Oscillations of Bubbles in Water Driven by Modulated Ultrasonic Radiation Pressure and Applications to Interfacial Dynamics

    NASA Astrophysics Data System (ADS)

    Asaki, Thomas James

    1995-01-01

    Acoustic levitation techniques were used for static and dynamic studies of single air bubbles in aqueous solutions. Bubble sizes ranged from 0.3 to 6 mm in radius. The static position of a bubble, determined by the balance between the buoyant and acoustic forces, agrees well with existing theory. Measured bubble aspect ratios are a nonmonotonic increasing function of bubble size and agree well with an improved expression based on the radiation stress tensor. Small amplitude normal mode shape oscillations were induced by modulation of the acoustic radiation pressure and were detected by optical pseudo-extinction and optical interferometry techniques. Driven oscillation frequencies for bubbles in clean water agree well with Lamb theory although significant frequency shifts occur for bubbles of large aspect ratio (_sp{~ }{>}1.3). An improved asymptotic expansion, important for bubbles in fluids and for liquid drops in air, was obtained for the complex free decay frequency. The free decay of quadrupole shape oscillations was measured for nearly spherical bubbles (aspect ratio ~ 1.01) in clean water, clean salt water, sea water, and in the presence of surfactants. Bubbles in clean solutions exhibit behavior indicative of an ideal clean interface. Frequency shifts and excess damping were observed for bubbles in sea water, in aqueous solutions of Triton X-100, and for a bubble coated with the insoluble surfactant stearic acid. The damping and frequency exhibit nonmonotonic behavior with respect to interfacial surfactant coverage; maxima occur at coverages which do not significantly affect the surface tension. At large coverages the damping is increased and the frequency is reduced relative to theoretical expectations for a clean ideal interface at constant surface tension. These results are in qualitative agreement with theories incorporating interfacial viscoelastic effects and with planar-surface capillary ripple experiments which also exhibit maxima in the damping as a

  6. 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.

  7. 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. PMID:27173541

  8. The interfacial properties of SrRuO3/MoS2 heterojunction: a first-principles study

    NASA Astrophysics Data System (ADS)

    Liu, Biao; Wu, Li-Juan; Zhao, Yu-Qing; Wang, Ling-Zhi; Cai, Meng-Qiu

    2016-03-01

    First-principles calculation was used to study the interfacial properties of the SrRuO3 (1 1 1)/MoS2(√3 × √3) heterojunction. It is found that the huge magnetic moments in of monolayer MoS2 largely originate from the Ru-S hybridization for the Ru-terminated interface. Moreover, for the SrO-terminated interface, we studied mainly the metal and semiconductor contact characteristic. The calculated results show that the Schottky barrier height can be significantly reduced to zero for the SrO-terminated interface. Schottky barrier heights dominate the transport behavior of the SrRuO3/MoS2 interface. Our results not only have potential applications in spintronics devices, but also are in favour of the scaling of field effect transistors.

  9. 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. PMID:22298029

  10. 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.

  11. New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics.

    PubMed

    Drüschler, Marcel; Borisenko, Natalia; Wallauer, Jens; Winter, Christian; Huber, Benedikt; Endres, Frank; Roling, Bernhard

    2012-04-21

    Ionic liquids are of high interest for the development of safe electrolytes in modern electrochemical cells, such as batteries, supercapacitors and dye-sensitised solar cells. However, electrochemical applications of ionic liquids are still hindered by the limited understanding of the interface between electrode materials and ionic liquids. In this article, we first review the state of the art in both experiment and theory. Then we illustrate some general trends by taking the interface between the extremely pure ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and an Au(111) electrode as an example. For the study of this interface, electrochemical impedance spectroscopy was combined with in situ STM and in situ AFM techniques. In addition, we present new results for the temperature dependence of the interfacial capacitance and dynamics. Since the interfacial dynamics are characterised by different processes taking place on different time scales, the temperature dependence of the dynamics can only be reliably studied by recording and carefully analysing broadband capacitance spectra. Single-frequency experiments may lead to artefacts in the temperature dependence of the interfacial capacitance. We demonstrate that the fast capacitive process exhibits a Vogel-Fulcher-Tamman temperature dependence, since its time scale is governed by the ionic conductivity of the ionic liquid. In contrast, the slower capacitive process appears to be Arrhenius activated. This suggests that the time scale of this process is determined by a temperature-independent barrier, which may be related to structural reorganisations of the Au surface and/or to charge redistributions in the strongly bound innermost ion layer. PMID:22402629

  12. 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.

  13. 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. PMID:25287757

  14. Ferroic Properties in Individual and Multi-Component Nanostructures: The Influence of Size, Shape, and Interfacial Coupling

    NASA Astrophysics Data System (ADS)

    Johnson, Stephanie Howell

    Extrinsic magnetoelectric heterostructure materials receive increased interest because of the potential to tune the magnetoelectric properties through material selection and actively, through applied electric and magnetic field. Understanding the strength of the coupling of ferroic properties in composite solids and the roles of size, shape, and arrangement of the constituent phases is central to realizing high-performance magnetoelectrics and their applications. Nanoscale magnetoelectric materials are excellent candidate systems to study the aforementioned effects of shape and finite size, to meet the growing demand for faster, more efficient, low cost, and above all smaller device components for use in advanced magnetic memories, actuators, transducers, and sensors. Nanoscale materials offer increased interfacial surface area compared with bulk, making them appealing in the design of an enhanced magnetoelectric composite because the magnetoelectric effect in a composite system is driven by interfacial coupling mechanisms. However, nanoscale (approximately 100 nm or less) ferroic materials often exhibit a dimensionality-dependent suppression of ferroic and piezoelectric properties below a critical size. By controlling e.g. the surface chemical environment, introducing strain engineering of films through epitaxy or through the shape of a nanostructure, the ferroelectric phase stability can be tuned for a given material and temperature. In this dissertation nanoscale ferroic and multiferroic properties were investigated, highlighting five characteristic systems: ferromagnetic nanoparticles, ferroelectric nanocubes, extrinsic magnetoelectric nanowires, and resonant beams and resonant membranes. An experimental study of ferromagnetic nanoparticles is presented to underscore the importance of understanding the growth and interfacial coupling mechanisms in ferromagnetic nanoparticle systems. To investigate the finite-size driven ferroelectric phase transition at the

  15. Impact of Hydrophilic Surfaces on Interfacial Water Dynamics Probed with NMR Spectroscopy

    PubMed Central

    Yoo, Hyok; Paranji, Rajan

    2011-01-01

    In suspensions of Nafion beads and of cationic gel beads, NMR spectroscopy showed two water–proton resonances, one representing intimate water layers next to the polymer surface, the other corresponding to water lying beyond. Both resonances show notably shorter spin–lattice relaxation times (T1) and smaller self-diffusion coefficients (D) indicating slower dynamics than bulk water. These findings confirm the existence of highly restricted water layers adsorbed onto hydrophilic surfaces and dynamically stable water beyond the first hydration layers. Thus, aqueous regions on the order of micrometers are dynamically different from bulk water. PMID:22003430

  16. Atomic-scale calculations of interfacial structures and their properties in electronic materials

    NASA Astrophysics Data System (ADS)

    Liang, Tao

    With the tremendous increase in computational power over the last two decades as well as the continuous shrinkage of Si-based Metal Oxide Semiconductor Field Effect Transistors (MOSFET), quantum mechanically based ab initio methods become indispensable tools in nano-scale device engineering. In this work, atomistic simulations including ab initio, nudged elastic band (NEB) and kinetic Monte Carlo methods have been used to (1) calculate the dopant segregation energy at silicon/gate oxide interfaces; (2) characterize the Si:Ge/SiO2 interfacial structure; (3) study the effects of impurity atoms on the diffusion process at Al and Al(Cu) grain boundaries. Using VASP, an ab initio simulation package, we calculated B segregation energy at different atomic sites in perfect and defected Si/SiO 2 interfaces and arsenic segregation energy in Si/LaAlO3 structures. With the presence of O vacancies and H in B doped systems, the predicted segregation energy is 0.85 eV for neutral systems and 1.12 eV for negatively charged systems, which is consistent with experimental measurements (0.51 to 1.47 eV). Recent ab initio structure calculations have examined the stability of various Si(001)/LaAlO3 interfaces and find that a LaO terminated interface with La deficiency or perfect stoichiometry depending on oxygen partial pressure has the lowest energy. Focussing on the La deficient Si/LaAlO3 interfacial structure, we find that the arsenic prefers energetically not to segregate into LaAlO3 nor does it pile up in front of the interface. In combation of atomic-resolution Z-contrast imaging and electron energy loss spectroscopy (EELS), we theorectically calculated the band structure and EELS of a Ge/SiO2 interface. We actually found a chemically abrupt Ge/SiO2 interface, which has never been reported before and which is quite desirable for applications. Furthermore, we formulated a kinetic Monte Carlo model to simulate the oxidation process of Ge ion-implanted Si. Our modeling suggests the

  17. Effect of Sophorolipid n-Alkyl Ester Chain Length on Its Interfacial Properties at the Almond Oil-Water Interface.

    PubMed

    Koh, Amanda; Linhardt, Robert J; Gross, Richard

    2016-06-01

    Sophorolipids (SLs), produced by Candida bombicola, are of interest as potential replacements for hazardous commercial surfactants. For the first time, a series of molecularly edited SLs with ethyl (EE), n-hexyl (HE), and n-decyl (DE) esters were evaluated at an oil (almond oil)-water interface for their ability to reduce interfacial tension (IFT) and generate stable emulsions. An increase in the n-alkyl ester chain length from ethyl to hexyl resulted in a maximum % decrease in the IFT from 86.1 to 95.3, respectively. Furthermore, the critical aggregation concentrations (CACs) decreased from 0.035 to 0.011 and 0.006 mg/mL as the ester chain length was increased from ethyl to n-hexyl and n-decyl, respectively. In contrast, the CAC of natural SL, composed of 50/50 acidic and LSL, is 0.142 mg/mL. Dynamic IFT analysis showed significant differences in diffusion coefficients for all SLs studied. Almond oil emulsions with up to 200:1 (by weight) oil/SL-DE were stable against oil separation for up to 1 week with average droplet sizes below 5 μm. Emulsions of almond oil with natural SLs showed consistent oil separation 24 h after emulsification. A unique connection between IFT and emulsification was found as SL-DE has both the lowest CAC and the best emulsification performance of all natural and modified SLs studied herein. This connection between CAC and emulsification may be generally applicable, providing a tool for the prediction of optimal surfactants in other oil-water interfacial applications. PMID:27159768

  18. 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.

  19. "a" interfacial parameter in Nicolais-Narkis model for yield strength of polymer particulate nanocomposites as a function of material and interphase properties.

    PubMed

    Zare, Yasser

    2016-05-15

    In this paper, "a" interfacial parameter in Nicolais-Narkis model is expressed by thickness "ri" and strength "σi" of interphase between polymer and nanoparticles as well as material properties. "a" parameter is connected to "B1" interfacial parameter in modified Pukanszky model and the effects of "ri" and "σi" on "a" are explained. The negligible difference between "a" values calculated by fitting the experimental results to Nicolais-Narkis model and also, by "B1" results confirms the accurateness of the suggested relation between "a" and "B1" parameters. Additionally, an inverse relation is found between "a" and "B1" parameters for nanocomposites containing spherical nanoparticles. The results demonstrate that the slight levels of "ri" and "σi" data give a large value of "a" which indicates the poor interfacial adhesion. PMID:26955000

  20. Separating the effects of repulsive and attractive forces on the phase diagram, interfacial, and critical properties of simple fluids.

    PubMed

    Fuentes-Herrera, M; Moreno-Razo, J A; Guzmán, O; López-Lemus, J; Ibarra-Tandi, B

    2016-06-01

    Molecular simulations in the canonical and isothermal-isobaric ensembles were performed to study the effect of varying the shape of the intermolecular potential on the phase diagram, critical, and interfacial properties of model fluids. The molecular interactions were modeled by the Approximate Non-Conformal (ANC) theory potentials. Unlike the Lennard-Jones or Morse potentials, the ANC interactions incorporate parameters (called softnesses) that modulate the steepness of the potential in their repulsive and attractive parts independently. This feature allowed us to separate unambiguously the role of each region of the potential on setting the thermophysical properties. In particular, we found positive linear correlation between all critical coordinates and the attractive and repulsive softness, except for the critical density and the attractive softness which are negatively correlated. Moreover, we found that the physical properties related to phase coexistence (such as span of the liquid phase between the critical and triple points, variations in the P-T vaporization curve, interface width, and surface tension) are more sensitive to changes in the attractive softness than to the repulsive one. Understanding the different roles of attractive and repulsive forces on phase coexistence may contribute to developing more accurate models of liquids and their mixtures. PMID:27276958

  1. Preparation and interfacial properties of a novel biodegradable polymer surfactant: poly(ethylene oxide monooleate-block-DL-lactide).

    PubMed

    Nishino, Satoru; Kitamura, Yoshiro; Kishida, Akio; Yoshizawa, Hidekazu

    2005-11-01

    In this paper, we report a novel synthesis of poly(ethylene oxide monooleate-block-DL-lactide) (MOPEO-PLA) in the presence of stannous 2-ethylhexanoate catalyst. By utilizing the surfactant property and the reactive double bond of the amphiphilic MOPEO-PLA, various characteristics of PLA microspheres, such as surface and internal structure, surface morphology, release property, and so on, may potentially be controlled. MOPEO-PLA was found to be hydrophobic enough to prevent loss by dissolution into aqueous solution, which is often a problem for MOPEO. Furthermore, the interfacial tension measurements of a MOPEO-PLA/toluene/water system revealed that MOPEO-PLA had a good surface activity almost equal to that of MOPEO. The MOPEO-PLA/PLA blend films were prepared by solvent casting on a water layer. Contact-angle measurements of MOPEO-PLA/PLA blend films confirmed that the hydrophilic PEO segments were selectivity accumulated at the oil/water interface. Moreover, the surface free energy on the 'water side' of the MOPEO-PLA/PLA blend films was increased because of the increase in polar components as a result of the ether bonds of the PEO segments. Schematic illustration of the adsorption property of a) MOPEO-PLA with a high-molecular-weight PLA segment and b) MOPEO-PLA with a low-molecular-weight PLA segment at an ethyl acetate/water interface. PMID:16245272

  2. 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.

  3. 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).

  4. [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.

  5. Monitoring interfacial dynamics by pulsed laser techniques. Third yearly progress report

    SciTech Connect

    Richmond, G.L.

    1991-12-31

    Goal is to develop new optical methods for the study of dynamic processes at the electrode/electrolyte interface. In the past year, optical second harmonic generation was used for time resolved measurements of thallium electrodeposition on Cu(111). Other studies included the study of the photochemistry involved in a GaAs surface treatment known as photowashing, and the study of picosecond time resolved luminescence decays from GaAs in electrochemical environments (power dependent effects). 4 figs. (DLC)

  6. Capturing interfacial photoelectrochemical dynamics with picosecond time-resolved X-ray photoelectron spectroscopy.

    PubMed

    Neppl, Stefan; Shavorskiy, Andrey; Zegkinoglou, Ioannis; Fraund, Matthew; Slaughter, Daniel S; Troy, Tyler; Ziemkiewicz, Michael P; Ahmed, Musahid; Gul, Sheraz; Rude, Bruce; Zhang, Jin Z; Tremsin, Anton S; Glans, Per-Anders; Liu, Yi-Sheng; Wu, Cheng Hao; Guo, Jinghua; Salmeron, Miquel; Bluhm, Hendrik; Gessner, Oliver

    2014-01-01

    Time-resolved core-level spectroscopy using laser pulses to initiate and short X-ray pulses to trace photoinduced processes has the unique potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics in complex systems. Time-domain studies using transient X-ray absorption and emission techniques have proven extremely valuable to investigate electronic and structural dynamics in isolated and solvated molecules. Here, we describe the implementation of a picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS) technique at the Advanced Light Source (ALS) and its application to monitor photoinduced electron dynamics at the technologically pertinent interface formed by N3 dye molecules anchored to nanoporous ZnO. Indications for a dynamical chemical shift of the Ru3d photoemission line originating from the N3 metal centre are observed ∼30 ps after resonant HOMO-LUMO excitation with a visible laser pump pulse. The transient changes in the TRXPS spectra are accompanied by a characteristic surface photovoltage (SPV) response of the ZnO substrate on a pico- to nanosecond time scale. The interplay between the two phenomena is discussed in the context of possible electronic relaxation and recombination pathways that lead to the neutralisation of the transiently oxidised dye after ultrafast electron injection. A detailed account of the experimental technique is given including an analysis of the chemical modification of the nano-structured ZnO substrate during extended periods of solution-based dye sensitisation and its relevance for studies using surface-sensitive spectroscopy techniques. PMID:25415599

  7. 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. PMID:26253205

  8. Adsorption of cationic surfactants and their effects on the interfacial properties of quartz

    NASA Astrophysics Data System (ADS)

    Jia, Renhe

    This dissertation is primarily concerned with an investigation of the interfacial behavior of natural quartz in aqueous solution where the adsorption of various cationic surfactants is involved. The broad objective of this research was to delineate the mechanisms involved in the adsorption of cationic surfactants using experimental determination of adsorption isotherms, zeta potentials, suspension turbidity, contact angles, induction times, as well as Hallimond tube flotation response. With dodecylpyridinium chloride as the model surfactant, four-region adsorption isotherms were observed and found to correlate well with zeta potential, suspension stability and contact angle measurements. Calculations of adsorption energy showed strong specific adsorption in Region I, probably resulting from H-bonding of the pyridinium headgroup to active sites on the silica. As a result of hemimicelle formation at the solid-liquid interface in Region II, pronounced increases in the adsorption density, zeta potential, and surface hydrophobicity were observed. The stability of quartz suspensions showed a significant drop in this region. In Region III, the zeta potential is reversed and the stability of the suspensions begins to increase again. In this region, the surface hydrophobicity of quartz decreases with further surfactant adsorption, suggesting reverse orientation of the adsorbed surfactant ions. In Region IV, the adsorption isotherm and zeta potential reach a plateau when the surfactant concentration reaches the CMC, and the surface becomes completely hydrophilic. The molecular structure of surfactant ions (chain length, number of hydrocarbon chains and number of headgroups) was found to significantly affect their surface activity. Increasing the hydrocarbon chain length of the surfactant lowers the concentration of surfactant required for minimum suspension stability, as well as redispersion. The adsorption is stronger for surfactants whose structure permits hydrogen bonding

  9. 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.

  10. 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.

  11. Clay/Polyaniline Hybrid through Diazonium Chemistry: Conductive Nanofiller with Unusual Effects on Interfacial Properties of Epoxy Nanocomposites.

    PubMed

    Jlassi, Khouloud; Chandran, Sarath; Poothanari, Mohammed A; Benna-Zayani, Mémia; Thomas, Sabu; Chehimi, Mohamed M

    2016-04-12

    The concept of conductive network structure in thermoset matrix without sacrificing the inherent mechanical properties of thermoset polymer (e.g., epoxy) is investigated here using "hairy" bentonite fillers. The latter were prepared through the in situ polymerization of aniline in the presence of 4-diphenylamine diazonium (DPA)-modified bentonite (B-DPA) resulting in a highly exfoliated bentonite-DPA/polyaniline (B-DPA/PANI). The nanocomposite filler was mixed with diglycidyl ether of bisphenol A (DGEBA), and the curing agent (4,4'-diaminodiphenylsulfone) (DDS) at high temperature in order to obtain nanocomposites through the conventional melt mixing technique. The role of B-DPA in the modification of the interface between epoxy and B-DPA/polyaniline (B-DPA/PANI) is investigated and compared with the filler B/PANI prepared without any diazonium modification of the bentonite. Synergistic improvement in dielectric properties and mechanical properties points to the fact that the DPA aryl groups from the diazonium precursor significantly modify the interface by acting as an efficient stress transfer medium. In DPA-containing nanocomposites, unique fibril formation was observed on the fracture surface. Moreover, dramatic improvement (210-220%) in fracture toughness of epoxy composite was obtained with B-DPA/PANI filler as compared to the weak improvement of 20-30% noted in the case of the B/PANI filler. This work shows that the DPA diazonium salt has an important effect on the improvement of the interfacial properties and adhesion of DGEBA and clay/PANI nanofillers. PMID:26963747

  12. Charge Recombination, Transport Dynamics, and Interfacial Effects in Organic Solar Cells

    SciTech Connect

    Heeger, Alan; Bazan, Guillermo; Nguyen, Thuc-Quyen; Wudl, Fred

    2015-02-27

    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

  13. Dissipative particle dynamics (DPD) study of hydrocarbon-water interfacial tension (IFT)

    NASA Astrophysics Data System (ADS)

    Rezaei, Hossein; Modarress, Hamid

    2015-01-01

    DPD mesoscopic molecular simulation method is applied to investigate the IFT of hydrocarbon (linear alkanes, cycloalkane and aromatics)-water systems. The DPD interaction parameters (aij) as a function of temperature (T) dependent solubility parameter (δ) are evaluated, where, δ, preliminary obtained using all-atom molecular dynamics (MD). It is shown that calculated aij based on equality forces among similar beads give more accurate results. The agreements of the results with experimental data confirm the efficiency of the DPD simulation for calculating the IFT of hydrocarbon-water systems with less computational cost in comparison with the conventional MD simulation.

  14. Obtaining railpad properties via dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Oregui, M.; de Man, A.; Woldekidan, M. F.; Li, Z.; Dollevoet, R.

    2016-02-01

    In this paper, we propose combining dynamic mechanical analysis (DMA) and the time-temperature superposition principle to determine various railpad dynamic properties. Having accurate information regarding the dynamic properties of a railpad is a fundamental requirement for designing tracks and understanding track deterioration. By testing three different railpad types, we demonstrate that the dynamic behavior of railpads over a wide frequency range can be successfully obtained under different preloads and temperatures if time-temperature superposition can be applied. To investigate railpad aging, worn railpads taken from a mainline in the Netherlands are tested. In this case, worn railpads are softer and possess a lower damping capacity than new railpads. In addition to performing these measurements, a Prony series material model is proposed to reproduce the dynamic behavior of railpads. The Prony series model is in good agreement with the measurements. Measured railpad dynamic properties and the corresponding Prony series numerical model provide valuable information for track design and modeling.

  15. 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.

  16. 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.

  17. 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. PMID:26291112

  18. Molecular dynamics study of interfacial confinement effects of aqueous NaCl brines in nanoporous carbon

    SciTech Connect

    Wander, M. C. F.; Shuford, K. L.

    2010-12-09

    In this paper, studies of aqueous electrolyte solutions in contact with a family of porous carbon geometries using classical molecular dynamics simulations are presented. These simulations provide an atomic scale depiction of ion transport dynamics in different environments to elucidate power of aqueous electrolyte supercapacitors. The electrolyte contains alkali metal and halide ions, which allow for the examination of size trends within specific geometries as well as trends in concentration. The electrode pores are modeled as planar graphite sheets and carbon nanotubes with interstices ranging from one to four nanometers. Ordered layers form parallel to the carbon surface, which facilitates focused ion motion under slightly confining conditions. As a result, the ion’s diffusivities are enhanced in the direction of the slit or pore. Further confining the system leads to decreased ion diffusivities. The ions are fully hydrated in all but the smallest slits and pores with those sizes showing increased ion pairing. There is strong evidence of charge separation perpendicular to the surface at all size scales, concentrations, and ion types, providing a useful baseline for examining differential capacitance behavior and future studies on energy storage. These systems show promise as high-power electrical energy storage devices.

  19. Wall and interfacial friction terms of a dynamic whole-range two-fluid model

    SciTech Connect

    Narumo, T.; Rajamaeki, M.

    1996-12-31

    The friction terms of a six-equation two-fluid model in which the momentum equations have been derived using the separation of the flow according to velocity (SFAV) approach have been considered primarily for application in boiling water reactor (BWR) vertical flow conditions. In the SFAV model, only the momentum equations differ from the conventional six-equation model for one-dimensional two-phase flow, which enables the authors to use existing correlations for the source terms appearing in the mass and energy equations. The model has been shown to form a hyperbolic partial differential equation system in any flow conditions without using a separate virtual mass term. Also, the dynamics of the model have been shown to behave correctly by calculating the propagation velocities of small disturbances.

  20. 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.

  1. 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.

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

    PubMed

    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. PMID:27497539

  3. 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

  4. 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.

  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. 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

  7. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations

    NASA Astrophysics Data System (ADS)

    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.

  8. 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. PMID:17677073

  9. 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. PMID:26266702

  10. 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

    2016-01-01

    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

  11. 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.

  12. Glassy Interfacial Dynamics of Ni Nanoparticles: Part II Discrete Breathers as an Explanation of Two-Level Energy Fluctuations

    PubMed Central

    Zhang, Hao; Douglas, Jack F.

    2012-01-01

    Recent studies of the dynamics of diverse condensed amorphous materials have indicated significant heterogeneity in the local mobility and a progressive increase in collective particle motion upon cooling that takes the form of string-like particle rearrangements. In a previous paper (Part I), we examined the possibility that fluctuations in potential energy E and particle mobility μ associated with this ‘dynamic heterogeneity’ might offer information about the scale of collective motion in glassy materials based on molecular dynamics simulations of the glassy interfacial region of Ni nanoparticles (NPs) at elevated temperatures. We found that the noise exponent associated with fluctuations in the Debye-Waller factor, a mobility related quantity, was directly proportional to the scale of collective motion L under a broad range of conditions, but the noise exponent associated with E(t) fluctuations was seemingly unrelated to L. In the present work, we focus on this unanticipated difference between potential energy and mobility fluctuations by examining these quantities at an atomic scale. We find that the string atoms exhibit a jump-like motion between two well-separated bands of energy states and the rate at which these jumps occur seems to be consistent with the phenomenology of the ‘slow-beta’ relaxation process of glass-forming liquids. Concurrently with these local E(t) jumps, we also find ‘quake-like’ particle displacements having a power-law distribution in magnitude so that particle displacement fluctuations within the strings are strikingly different from local E(t) fluctuations. An analysis of these E(t) fluctuations suggests that we are dealing with ‘discrete breather’ excitations in which large energy fluctuations develop in arrays of non-linear oscillators by virtue of large anharmonicity in the interparticle interactions and discreteness effects associated with particle packing. We quantify string collective motions on a fast caging

  13. Structural features of interfacial tyrosine residue in ROBO1 fibronectin domain-antibody complex: Crystallographic, thermodynamic, and molecular dynamic analyses

    PubMed Central

    Nakayama, Taisuke; Mizohata, Eiichi; Yamashita, Takefumi; Nagatoishi, Satoru; Nakakido, Makoto; Iwanari, Hiroko; Mochizuki, Yasuhiro; Kado, Yuji; Yokota, Yuki; Satoh, Reiko; Tsumoto, Kouhei; Fujitani, Hideaki; Kodama, Tatsuhiko; Hamakubo, Takao; Inoue, Tsuyoshi

    2015-01-01

    ROBO1, fibronectin Type-III domain (Fn)-containing protein, is a novel immunotherapeutic target for hepatocellular carcinoma in humans. The crystal structure of the antigen-binding fragment (Fab) of B2212A, the monoclonal antibody against the third Fn domain (Fn3) of ROBO1, was determined in pursuit of antibody drug for hepatocellular carcinoma. This effort was conducted in the presence or absence of the antigen, with the chemical features being investigated by determining the affinity of the antibody using molecular dynamics (MD) and thermodynamics. The structural comparison of B2212A Fab between the complex and the free form revealed that the interfacial TyrL50 (superscripts L, H, and F stand for the residues in the light chain, heavy chain, and Fn3, respectively) played important roles in Fn3 recognition. That is, the aromatic ring of TyrL50 pivoted toward PheF68, forming a CH/π interaction and a new hydrogen bond with the carbonyl O atom of PheF68. MD simulations predicted that the TyrL50-PheF68 interaction almost entirely dominated Fab-Fn3 binding, and Ala-substitution of TyrL50 led to a reduced binding of the resultant complex. On the contrary, isothermal titration calorimetry experiments underscored that Ala-substitution of TyrL50 caused an increase of the binding enthalpy between B2212A and Fn3, but importantly, it induced an increase of the binding entropy, resulting in a suppression of loss in the Gibbs free energy in total. These results suggest that mutation analysis considering the binding entropy as well as the binding enthalpy will aid in the development of novel antibody drugs for hepatocellular carcinoma. PMID:25492858

  14. 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.

  15. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    DOE PAGESBeta

    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 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. Interfacial Octahedral Rotation Mismatch Control of the Symmetry and Properties of SrRuO3.

    PubMed

    Gao, Ran; Dong, Yongqi; Xu, Han; Zhou, Hua; Yuan, Yakun; Gopalan, Venkatraman; Gao, Chen; Fong, Dillon D; Chen, Zuhuang; Luo, Zhenlin; Martin, Lane W

    2016-06-15

    Epitaxial strain can be used 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 an effective route to manipulate material properties. Here, we examine the evolution of the structural motif (i.e., lattice parameters, symmetry, and octahedral rotations) of SrRuO3 films grown on substrates engineered to have the same lattice parameters, but 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 that the tetragonal films exhibit higher resistivity, lower magnetic Curie temperatures, and more isotropic magnetism as compared to those with monoclinic structure. Synchrotron-based quantification of the octahedral rotation network reveals that the tilting pattern in both film variants is the same (albeit with slightly different magnitudes of in-plane rotation angles). 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. PMID:27219026

  17. Impact of interfacial magnetism on magnetocaloric properties of thin film heterostructures

    NASA Astrophysics Data System (ADS)

    Kirby, B. J.; Lau, J. W.; Williams, D. V.; Bauer, C. A.; Miller, Casey W.

    2011-03-01

    Polarized neutron reflectometry was used to determine the depth profile of the magnetic moment per Gd atom, mGd, in a Gd(30 nm)/W(5 nm) multilayer. Despite sharp interfaces observed by transmission electron microscopy, mGd is systematically suppressed near the Gd-W interfaces. Because the peak magnetic entropy change is proportional to mGd2/3, this results in a reduction of the maximum achievable magnetocaloric effect in Gd-W heterostructures. By extension, our results suggest that creating materials with Gd-ferromagnet interfaces may increase the mGd relative to the bulk, leading to enhanced magnetocaloric properties.

  18. 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.

  19. On the Interfacial Properties of Polymers/Functionalized Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Rouhi, S.; Ajori, S.

    2016-03-01

    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.

  20. 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

  1. Challenges associated with sampling dynamic soil properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  2. Optical and interfacial electronic properties of diamond-like carbon films

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Natarajan, V.; Lamb, J.; Khan, A. A.; Bu-Abbud, G.; Banks, B.; Pouch, J.; Gulino, D. A.; Domitz, S.; Liu, D. C.

    1984-01-01

    Hard, semitransparent carbon films were prepared on oriented polished crystal wafers of silicon, indium phosphide and gallium arsenide, as well as on KBr and quartz. Properties of the films were determined using IR and visible absorption spectrocopy, ellipsometry, conductance-capacitance spectroscopy and alpha particle-proton recoil spectroscopy. Preparation techniques include RF plasma decomposition of methane (and other hydrocarbons), ion beam sputtering, and dual-ion-beam sputter deposition. Optical energy band gaps as large as 2.7 eV and extinction coefficients lower than 0.1 at long wavelengths are found. Electronic state densities at the interface with silicon as low as 10 to the 10th states/eV sq cm per were found.

  3. 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. PMID:26212096

  4. Ligand Layer Engineering To Control Stability and Interfacial Properties of Nanoparticles.

    PubMed

    Schulz, Florian; Dahl, Gregor T; Besztejan, Stephanie; Schroer, Martin A; Lehmkühler, Felix; Grübel, Gerhard; Vossmeyer, Tobias; Lange, Holger

    2016-08-01

    The use of mixed ligand layers including poly(ethylene glycol)-based ligands for the functionalization of nanoparticles is a very popular strategy in the context of nanomedicine. However, it is challenging to control the composition of the ligand layer and maintain high colloidal and chemical stability of the conjugates. A high level of control and stability are crucial for reproducibility, upscaling, and safe application. In this study, gold nanoparticles with well-defined mixed ligand layers of α-methoxypoly(ethylene glycol)-ω-(11-mercaptoundecanoate) (PEGMUA) and 11-mercaptoundecanoic acid (MUA) were synthesized and characterized by ATR-FTIR spectroscopy and gel electrophoresis. The colloidal and chemical stability of the conjugates was tested by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and UV/vis spectroscopy based experiments, and their interactions with cells were analyzed by elemental analysis. We demonstrate that the alkylene spacer in PEGMUA is the key feature for the controlled synthesis of mixed layer conjugates with very high colloidal and chemical stability and that a controlled synthesis is not possible using regular PEG ligands without the alkylene spacer. With the results of our stability tests, the molecular structure of the ligands can be clearly linked to the colloidal and chemical stabilization. We expect that the underlying design principle can be generalized to improve the level of control in nanoparticle surface chemistry. PMID:27458652

  5. 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

  6. 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.

  7. 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.

  8. 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. PMID:22662875

  9. 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

  10. 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.

  11. 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. PMID:23148691

  12. Strong improvement of interfacial properties can result from slight structural modifications of proteins: the case of native and dry-heated lysozyme.

    PubMed

    Desfougères, Yann; Saint-Jalmes, Arnaud; Salonen, Anniina; Vié, Véronique; Beaufils, Sylvie; Pezennec, Stéphane; Desbat, Bernard; Lechevalier, Valérie; Nau, Françoise

    2011-12-20

    Identification of the key physicochemical parameters of proteins that determine their interfacial properties is still incomplete and represents a real stake challenge, especially for food proteins. Many studies have thus consisted in comparing the interfacial behavior of different proteins, but it is difficult to draw clear conclusions when the molecules are completely different on several levels. Here the adsorption process of a model protein, the hen egg-white lysozyme, and the same protein that underwent a thermal treatment in the dry state, was characterized. The consequences of this treatment have been previously studied: net charge and hydrophobicity increase and lesser protein stability, but no secondary and tertiary structure modification (Desfougères, Y.; Jardin, J.; Lechevalier, V.; Pezennec, S.; Nau, F. Biomacromolecules 2011, 12, 156-166). The present study shows that these slight modifications dramatically increase the interfacial properties of the protein, since the adsorption to the air-water interface is much faster and more efficient (higher surface pressure). Moreover, a thick and strongly viscoelastic multilayer film is created, while native lysozyme adsorbs in a fragile monolayer film. Another striking result is that completely different behaviors were observed between two molecular species, i.e., native and native-like lysozyme, even though these species could not be distinguished by usual spectroscopic methods. This suggests that the air-water interface could be considered as a useful tool to reveal very subtle differences between protein molecules. PMID:22040020

  13. Interfacial properties of asymmetrically functionalized citrate-stabilized gold and silver nanoparticles related to molecular adsorption

    NASA Astrophysics Data System (ADS)

    Park, Jong-Won

    A detailed understanding of the conformation of adsorbed molecules and regional surface functionalization of metal nanoparticles (MNPs) is challenging for nanometer-size (10 -- 100 m) materials and necessary for fundamental studies and applications. The studies are motivated by open questions related to surface chemistry of noble MNPs. Although citrate-stabilized gold NPs (AuNPs) have been widely used, the citrate layer is not well-understood. Thiols have been suggested to displace citrate anions adsorbed on metal surfaces due to strong gold-sulfur interaction, but quantitative experimental evidence of the extent of ligand-exchange has not been reported. Whereas asymmetrically-functionalized AuNPs are utilized for nanoparticle assembly due to the interparticle coupling of localized surface plasmons, the interface between asymmetric nanoparticles in single assemblies has not been studied. Noble MNPs with sizes smaller than citrate-stabilized AuNPs also need to be surface-modified for stability in water for biological applications. The dissertation presents investigations of the chemical and physical properties of gold and silver NPs (AgNPs) related to ligand adsorption at the metal surface. Firstly, self-assembled layers of citrate adsorbed on AuNP (111), (110), and (100) surfaces were proposed, based on geometric considerations and spectroscopic investigations by infrared (IR) and X-ray photoelectron spectroscopy (XPS). Adsorption characteristics of citrate are the unique structure of adsorbed species, intermolecular interactions through hydrogen bonds and van der Waals attractions, bilayer formation, surface coverage, nanoparticle-stabilization role, and chirality. Secondly, IR and XPS studies showed coadsorption of thiolate on the surface of citrate-stabilized AuNPs. Steric, chelating effects and intermolecular interactions are the origins of the strong adsorption of citrate on AuNP surfaces. Surface coverage was determined from XPS analyses. Thirdly, an

  14. 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.

  15. Dynamic properties of interfaces in soft matter: Experiments and theory

    NASA Astrophysics Data System (ADS)

    Sagis, Leonard M. C.

    2011-10-01

    The dynamic properties of interfaces often play a crucial role in the macroscopic dynamics of multiphase soft condensed matter systems. These properties affect the dynamics of emulsions, of dispersions of vesicles, of biological fluids, of coatings, of free surface flows, of immiscible polymer blends, and of many other complex systems. The study of interfacial dynamic properties, surface rheology, is therefore a relevant discipline for many branches of physics, chemistry, engineering, and life sciences. In the past three to four decades a vast amount of literature has been produced dealing with the rheological properties of interfaces stabilized by low molecular weight surfactants, proteins, (bio)polymers, lipids, colloidal particles, and various mixtures of these surface active components. In this paper recent experiments are reviewed in the field of surface rheology, with particular emphasis on the models used to analyze surface rheological data. Most of the models currently used are straightforward generalizations of models developed for the analysis of rheological data of bulk phases. In general the limits on the validity of these generalizations are not discussed. Not much use is being made of recent advances in nonequilibrium thermodynamic formalisms for multiphase systems, to construct admissible models for the stress-deformation behavior of interfaces. These formalisms are ideally suited to construct thermodynamically admissible constitutive equations for rheological behavior that include the often relevant couplings to other fluxes in the interface (heat and mass), and couplings to the transfer of mass from the bulk phase to the interface. In this review recent advances in the application of classical irreversible thermodynamics, extended irreversible thermodynamics, rational thermodynamics, extended rational thermodynamics, and the general equation for the nonequilibrium reversible-irreversible coupling formalism to multiphase systems are also discussed

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

    PubMed

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

    2011-05-19

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

  17. Effects of reaction layer on interfacial shear properties and strength of fiber in silicon-carbide (SiC) fiber-reinforced titanium alloy composite

    SciTech Connect

    Kagawa, Yutaka; Masuda, Chitoshi; Fujiwara, Chikara; Fukushima, Akira

    1996-12-31

    The effect of the interfacial thickness of the reaction layer on the interfacial shear properties and the tensile strength of double carbon-coated SCS-6 SiC fiber in Ti-15Mo-5Zr-3Al alloy matrix composite was examined. The major reaction layer thickness, that is, titanium-carbide (TiC) layer thickness, varied with heat-exposure temperature and time, respectively, and the resultant mean thickness of the reaction layer of the composite ranged from 0.4 to 1.7 {micro}m. The critical interfacial toughness, G{sub i}{sup c}, and the mean shear sliding resistance, {tau}{sub s}, were evaluated by the thin specimen pushout technique. Tensile strength of the silicon-carbide (SiC) fiber extracted from the titanium alloy matrix before and after the heat exposure was determined in relationship to the thickness of the reaction layer. The critical interface toughness, G{sub i}{sup c}, for the failure of the root of the reaction layer was {approx}4 J/m{sup 2}, and the average shear sliding resistance of the interface, {tau}{sub s}, was 102 to 118 MPa. The interfacial shear mechanical properties were adequate to prevent failure of the fiber due to the stress concentration caused by cracks that formed first in the reaction layer. The results showed that when the growth of reaction layer was within 1.7 {micro}m, the mean strength of the extracted fiber was unaffected by the existence of the reaction layer because of weak bonding between it and the fiber. However, with the increase of the reaction layer thickness, the strength distribution of the extracted fiber tended to Weibull bimodal distribution.

  18. 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

  19. Detection of DNA damage: effect of thymidine glycol residues on the thermodynamic, substrate and interfacial acoustic properties of oligonucleotide duplexes.

    PubMed

    Yang, F; Romanova, E; Kubareva, E; Dolinnaya, N; Gajdos, V; Burenina, O; Fedotova, E; Ellis, J S; Oretskaya, T; Hianik, T; Thompson, M

    2009-01-01

    Thymidine glycol residues in DNA are biologically active oxidative molecular damage sites caused by ionizing radiation and other factors. One or two thymidine glycol residues were incorporated in 19- to 31-mer DNA fragments during automatic oligonucleotide synthesis. These oligonucleotide models were used to estimate the effect of oxidized thymidines on the thermodynamic, substrate and interfacial acoustic properties of DNA. UV-monitoring melting data revealed that modified residues in place of thymidines destabilize the DNA double helix by 8-22 degrees C, depending on the number of lesions, the length of oligonucleotide duplexes and their GC-content. The diminished hybridizing capacity of modified oligonucleotides is presumably due to the loss of aromaticity and elevated hydrophilicity of thymine glycol in comparison to the thymine base. According to circular dichroism (CD) data, the modified DNA duplexes retain B-form geometry, and the thymidine glycol residue introduces only local perturbations limited to the lesion site. The rate of DNA hydrolysis by restriction endonucleases R.MvaI, R.Bst2UI, R.MspR9I and R.Bme1390I is significantly decreased as the thymidine glycol is located in the central position of the double-stranded recognition sequences 5'-CC / WGG-3' (W = A, T) or 5'-CC / NGG-3' (N = A, T, G, C) adjacent to the cleavage site. On the other hand, the catalytic properties of enzymes R.Psp6I and R.BstSCI recognizing the similar sequence are not changed dramatically, since their cleavage site is separated from the point of modification by several base-pairs. Data obtained by gel-electrophoretic analysis of radioactive DNA substrates were confirmed by direct spectrophotometric assay developed by the authors. The effect of thymidine glycol was also observed on DNA hybridization at the surface of a thickness-shear mode acoustic wave device. A 1.9-fold decrease in the rate of duplex formation was noted for oligonucleotides carrying one or two thymidine glycol

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. Dynamic property studies of Sterling engines

    NASA Technical Reports Server (NTRS)

    Tani, Y.; Seibara, M.; Takenai, K.; Yamaguchi, W.

    1984-01-01

    A description is given of the results of dynamic property tests that were carried out using a trial produced prototype of a 50 KW Sterling engine. The features of the engine are shown graphically. A high thermal efficiency is found in the low rotation region.

  5. Dynamical simulation of dipolar Janus colloids: Dynamical properties

    NASA Astrophysics Data System (ADS)

    Hagy, Matthew C.; Hernandez, Rigoberto

    2013-05-01

    The dynamical properties of dipolar Janus particles are studied through simulation using our previously-developed detailed pointwise (PW) model and an isotropically coarse-grained (CG) model [M. C. Hagy and R. Hernandez, J. Chem. Phys. 137, 044505 (2012), 10.1063/1.4737432]. The CG model is found to have accelerated dynamics relative to the PW model over a range of conditions for which both models have near identical static equilibrium properties. Physically, this suggests dipolar Janus particles have slower transport properties (such as diffusion) in comparison to isotropically attractive particles. Time rescaling and damping with Langevin friction are explored to map the dynamics of the CG model to that of the PW model. Both methods map the diffusion constant successfully and improve the velocity autocorrelation function and the mean squared displacement of the CG model. Neither method improves the distribution of reversible bond durations f(tb) observed in the CG model, which is found to lack the longer duration reversible bonds observed in the PW model. We attribute these differences in f(tb) to changes in the energetics of multiple rearrangement mechanisms. This suggests a need for new methods that map the coarse-grained dynamics of such systems to the true time scale.

  6. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction.

    PubMed

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-01-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation. PMID:27452115

  7. Structural and dynamical properties of water on chemically modified surfaces: The role of the instantaneous surface

    NASA Astrophysics Data System (ADS)

    Bekele, Selemon; Tsige, Mesfin

    Surfaces of polymers such as atactic polystyrene (aPS) represent very good model systems for amorphous material surfaces. Such polymer surfaces are usually modified either chemically or physically for a wide range of applications that include friction, lubrication and adhesion. It is thus quite important to understand the structural and dynamical properties of liquids that come in contact with them to achieve the desired functional properties. Using molecular dynamics (MD) simulations, we investigate the structural and dynamical properties of water molecules in a slab of water in contact with atactic polystyrene surfaces of varying polarity. We find that the density of water molecules and the number distribution of hydrogen bonds as a function of distance relative to an instantaneous surface exhibit a structure indicative of a layering of water molecules near the water/PS interface. For the dynamics, we use time correlation functions of hydrogen bonds and the incoherent structure function for the water molecules. Our results indicate that the polarity of the surface dramatically affects the dynamics of the interfacial water molecules with the dynamics slowing down with increasing polarity. This work was supported by NSF Grant DMR1410290.

  8. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction

    PubMed Central

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-01-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation. PMID:27452115

  9. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction

    NASA Astrophysics Data System (ADS)

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-07-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation.

  10. Investigation on the Microstructure, Interfacial IMC Layer, and Mechanical Properties of Cu/Sn-0.7Cu-xNi/Cu Solder Joints

    NASA Astrophysics Data System (ADS)

    Yang, Li; Ge, Jinguo; Zhang, Yaocheng; Dai, Jun; Liu, Haixiang; Xiang, Jicen

    2016-04-01

    Sn-0.7Cu-xNi composite solder has been fabricated via mechanical mixing of different weight percentages of Ni particles with Sn-0.7Cu solder paste, and the effect of the Ni concentration on the microstructure, wettability, and tensile properties of Cu/Sn-0.7Cu-xNi/Cu solder joints investigated. The results show that refined dot-shaped particles of intermetallic compounds (IMCs) are uniformly dispersed in a primary β-Sn matrix in the Cu/Sn-0.7Cu-(0.05-0.1)Ni/Cu solder joints. The interfacial IMC layer thickness increased slightly when adding Ni content to 0.05 wt.%, then rapidly when further increasing the Ni concentration to 0.4 wt.%. Excellent wettability with bright appearance was obtained for the Sn-0.7Cu-0.05Ni solder due to diminished interfacial tension. The tensile properties improved after adding Ni content to 0.05 wt.% due to the presence of the refined dot-like IMC particles, in agreement with theoretical predictions based on the combination of dispersion and grain-refinement strengthening mechanisms. Refined microstructure and enhanced mechanical properties were obtained for the Cu/Sn-0.7Cu-0.05Ni/Cu solder joint.

  11. Investigation on the Microstructure, Interfacial IMC Layer, and Mechanical Properties of Cu/Sn-0.7Cu- xNi/Cu Solder Joints

    NASA Astrophysics Data System (ADS)

    Yang, Li; Ge, Jinguo; Zhang, Yaocheng; Dai, Jun; Liu, Haixiang; Xiang, Jicen

    2016-07-01

    Sn-0.7Cu- xNi composite solder has been fabricated via mechanical mixing of different weight percentages of Ni particles with Sn-0.7Cu solder paste, and the effect of the Ni concentration on the microstructure, wettability, and tensile properties of Cu/Sn-0.7Cu- xNi/Cu solder joints investigated. The results show that refined dot-shaped particles of intermetallic compounds (IMCs) are uniformly dispersed in a primary β-Sn matrix in the Cu/Sn-0.7Cu-(0.05-0.1)Ni/Cu solder joints. The interfacial IMC layer thickness increased slightly when adding Ni content to 0.05 wt.%, then rapidly when further increasing the Ni concentration to 0.4 wt.%. Excellent wettability with bright appearance was obtained for the Sn-0.7Cu-0.05Ni solder due to diminished interfacial tension. The tensile properties improved after adding Ni content to 0.05 wt.% due to the presence of the refined dot-like IMC particles, in agreement with theoretical predictions based on the combination of dispersion and grain-refinement strengthening mechanisms. Refined microstructure and enhanced mechanical properties were obtained for the Cu/Sn-0.7Cu-0.05Ni/Cu solder joint.

  12. 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

  13. Phase behavior and interfacial properties of a switchable ethoxylated amine surfactant at high temperature and effects on CO2-in-water foams.

    PubMed

    Chen, Yunshen; Elhag, Amro S; Reddy, Prathima P; Chen, Hao; Cui, Leyu; Worthen, Andrew J; Ma, Kun; Quintanilla, Heriberto; Noguera, Jose A; Hirasaki, George J; Nguyen, Quoc P; Biswal, Sibani L; Johnston, Keith P

    2016-05-15

    The interfacial properties for surfactants at the supercritical CO2-water (C-W) interface at temperatures above 80°C have very rarely been reported given limitations in surfactant solubility and chemical stability. These limitations, along with the weak solvent strength of CO2, make it challenging to design surfactants that adsorb at the C-W interface, despite the interest in CO2-in-water (C/W) foams (also referred to as macroemulsions). Herein, we examine the thermodynamic, interfacial and rheological properties of the surfactant C12-14N(EO)2 in systems containing brine and/or supercritical CO2 at elevated temperatures and pressures. Because the surfactant is switchable from the nonionic state to the protonated cationic state as the pH is lowered over a wide range in temperature, it is readily soluble in brine in the cationic state below pH 5.5, even up to 120°C, and also in supercritical CO2 in the nonionic state. As a consequence of the affinity for both phases, the surfactant adsorption at the CO2-water interface was high, with an area of 207Å(2)/molecule. Remarkably, the surfactant lowered the interfacial tension (IFT) down to ∼5mN/m at 120°C and 3400 psia (23MPa), despite the low CO2 density of 0.48g/ml, indicating sufficient solvation of the surfactant tails. The phase behavior and interfacial properties of the surfactant in the cationic form were favorable for the formation and stabilization of bulk C/W foam at high temperature and high salinity. Additionally, in a 1.2 Darcy glass bead pack at 120°C, a very high foam apparent viscosity of 146 cP was observed at low interstitial velocities given the low degree of shear thinning. For a calcium carbonate pack, C/W foam was formed upon addition of Ca(2+) and Mg(2+) in the feed brine to keep the pH below 4, by the common ion effect, in order to sufficiently protonate the surfactant. The ability to form C/W foams at high temperatures is of interest for a variety of applications in chemical synthesis

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

    PubMed

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

    2015-02-21

    Coexistence and interfacial properties of a triangle-well (TW) fluid are obtained with the aim of mimicking the Lennard-Jones (LJ) potential and approach the properties of noble gases. For this purpose, the scope of the TW is varied to match vapor-liquid densities and surface tension. Surface tension and coexistence curves of TW systems with different ranges were calculated with replica exchange Monte Carlo and compared to those data previously reported in the literature for truncated and shifted (STS), truncated (ST), and full Lennard-Jones (full-LJ) potentials. We observed that the scope of the TW potential must be increased to approach the STS, ST, and full-LJ properties. In spite of the simplicity of TW expression, a remarkable agreement is found. Furthermore, the variable scope of the TW allows for a good match of the experimental data of argon and xenon. PMID:25702023

  15. Modified embedded-atom method interatomic potential and interfacial thermal conductance of Si-Cu systems: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Abs da Cruz, Carolina; Chantrenne, Patrice; Gomes de Aguiar Veiga, Roberto; Perez, Michel; Kleber, Xavier

    2013-01-01

    Thermal contact conductance of metal-dielectric systems is a key parameter that has to be taken into account for the design and reliability of nanostructured microelectronic systems. This paper aims to predict this value for Si-Cu interfaces using molecular dynamics simulations. To achieve this goal, a modified embedded atom method interatomic potential for Si-Cu system has been set based upon previous MEAM potentials for pure Cu and pure Si. The Si-Cu cross potential is determined by fitting key properties of the alloy to results obtained by ab initio calculations. It has been further evaluated by comparing the structure and energies of Cu dimmers in bulk Si and CumSin clusters to ab initio calculations. The comparison between MD and ab initio calculation also concerns the energy barrier of Cu migration along the (110) channel in bulk Si. Using this interatomic potential, non equilibrium molecular dynamics has been performed to calculate the thermal contact conductance of a Si-Cu interface at different temperature level. The results obtained are in line with previous experimental results for different kind of interfaces. This confirms that the temperature variation of the thermal conductance might not find its origin in the electron-phonon interactions at the interface nor in the quantification of the energy of the vibration modes. The diffuse mismatch model is also used in order to discuss these results.

  16. Interfacial anisotropy in the transport of liquid crystals confined between flat, structureless walls: a molecular dynamics simulation approach.

    PubMed

    Mima, Toshiki; Yasuoka, Kenji

    2008-01-01

    Molecular dynamics simulations of uniaxial Gay-Berne ellipsoids as prolate liquid crystal molecules confined between two flat, structureless walls have been carried out in order to investigate anisotropy in their dynamic properties. Several physical quantities are profiled as a function of distance from a wall. The walls stimulate ellipsoids into different behaviors from those of the bulk system. The profiles of self-diffusion coefficients, which are distinguished in each direction of a director-based coordinate system, show that the ellipsoids are more diffusive parallel to the walls and less diffusive perpendicular to the walls with decreasing distance from the walls. According to the self-rotation coefficient and rotational viscosity profiles, ellipsoids are easy to rotate parallel to the walls and hard to rotate in the plane perpendicular to the walls. The analyses of velocity autocorrelation functions, angular velocity autocorrelation functions, director angular velocity autocorrelation functions, and their spectra are useful for the investigation of anisotropy near the walls. We conclude that the flat, structureless wall not only prevents ellipsoids from diffusing and rotating in the plane perpendicular to the walls, but also stimulates them to diffuse and rotate in the plane parallel to the walls. PMID:18351864

  17. Interfacial anisotropy in the transport of liquid crystals confined between flat, structureless walls: A molecular dynamics simulation approach

    NASA Astrophysics Data System (ADS)

    Mima, Toshiki; Yasuoka, Kenji

    2008-01-01

    Molecular dynamics simulations of uniaxial Gay-Berne ellipsoids as prolate liquid crystal molecules confined between two flat, structureless walls have been carried out in order to investigate anisotropy in their dynamic properties. Several physical quantities are profiled as a function of distance from a wall. The walls stimulate ellipsoids into different behaviors from those of the bulk system. The profiles of self-diffusion coefficients, which are distinguished in each direction of a director-based coordinate system, show that the ellipsoids are more diffusive parallel to the walls and less diffusive perpendicular to the walls with decreasing distance from the walls. According to the self-rotation coefficient and rotational viscosity profiles, ellipsoids are easy to rotate parallel to the walls and hard to rotate in the plane perpendicular to the walls. The analyses of velocity autocorrelation functions, angular velocity autocorrelation functions, director angular velocity autocorrelation functions, and their spectra are useful for the investigation of anisotropy near the walls. We conclude that the flat, structureless wall not only prevents ellipsoids from diffusing and rotating in the plane perpendicular to the walls, but also stimulates them to diffuse and rotate in the plane parallel to the walls.

  18. Multifractal properties of ball milling dynamics

    SciTech Connect

    Budroni, M. A. Pilosu, V.; Rustici, M.; Delogu, F.

    2014-06-15

    This work focuses on the dynamics of a ball inside the reactor of a ball mill. We show that the distribution of collisions at the reactor walls exhibits multifractal properties in a wide region of the parameter space defining the geometrical characteristics of the reactor and the collision elasticity. This feature points to the presence of restricted self-organized zones of the reactor walls where the ball preferentially collides and the mechanical energy is mainly dissipated.

  19. Transport properties of interfacial Si-rich layers formed on silicate minerals during weathering: Implications for environmental concerns

    NASA Astrophysics Data System (ADS)

    Daval, Damien; Rémusat, Laurent; Bernard, Sylvain; Wild, Bastien; Micha, Jean-Sébastien; Rieutord, François; Fernandez-Martinez, Alejandro

    2015-04-01

    The dissolution of silicate minerals is of primary importance for various processes ranging from chemical weathering to CO2 sequestration. Whether it determines the rates of soil formation, CO2 uptake and its impact on climate change, channeling caused by hydrothermal circulation in reservoirs of geothermal power plants, durability of radioactive waste confinement glasses or geological sequestration of CO2, the same strategy is commonly applied for determining the long term evolution of fluid-rock interactions. This strategy relies on a bottom-up approach, where the kinetic rate laws governing silicate mineral dissolution are determined from laboratory experiments. However, a long-standing problem regarding this approach stems from the observation that laboratory-derived dissolution rates overestimate their field counterparts by orders of magnitude, casting doubt on the accuracy and relevance of predictions based on reactive-transport simulations. Recently [1], it has been suggested that taking into account the formation of amorphous Si-rich surface layers (ASSL) as a consequence of mineral dissolution may contribute to decrease the large gap existing between laboratory and natural rates. Our ongoing study is aimed at deciphering the extent to which ASSL may represent a protective entity which affects the dissolution rate of the underlying minerals, both physically (passivation) and chemically (by promoting the formation of a local chemical medium which significantly differs from that of the bulk solution). Our strategy relies on the nm-scale measurement of the physicochemical properties (diffusivity, thickness and density) of ASSL formed on cleavages of a model mineral (wollastonite) and their evolution as a function of reaction progress. Our preliminary results indicate that the diffusivity of nm-thick ASSL formed on wollastonite surface is ~1,000,000 times smaller than that reported for an aqueous medium, as estimated from the monitoring of the progression of a

  20. Impact of Gd2O3 passivation layer on interfacial and electrical properties of atomic-layer-deposited ZrO2 gate dielectric on GaAs

    NASA Astrophysics Data System (ADS)

    Gong, Youpin; Zhai, Haifa; Liu, Xiaojie; Kong, Jizhou; Wu, Di; Li, Aidong

    2014-02-01

    ZrO2 gate dielectric films were fabricated on n-GaAs substrates by atomic layer deposition (ALD), using metal organic chemical vapor deposition (MOCVD)-derived ultrathin Gd2O3 film as interfacial control layer between ZrO2 and n-GaAs. The interfacial structure, capacitance-voltage and current-voltage properties of ZrO2/n-GaAs and ZrO2/Gd2O3/n-GaAs metal-oxide-semiconductor (MOS) capacitors have been investigated. The introduction of an ultrathin Gd2O3 control layer can effectively suppress the formation of As oxides and high valence Ga oxide at the high k/GaAs interface which evidently improved the electrical properties of GaAs-based MOS capacitors, such as higher accumulation capacitance and lower leakage current density. It was found that the current conduction mechanism of MOS capacitors varied from Poole-Frenkel emission to Schottky-Richardson emission after introducing the thin Gd2O3 layer. The band alignments of interfaces for ZrO2/GaAs and ZrO2/Gd2O3/GaAs were established, which indicates that the conduction band offset (CBO) for ZrO2/GaAs and ZrO2/Gd2O3/GaAs stacks are ˜1.45 and ˜1.62 eV, correspondingly.

  1. Enhanced electroactive and mechanical properties of poly(vinylidene fluoride) by controlling crystallization and interfacial interactions with low loading polydopamine coated BaTiO₃.

    PubMed

    Jia, Nan; Xing, Qian; Liu, Xu; Sun, Jing; Xia, Guangmei; Huang, Wei; Song, Rui

    2015-09-01

    Poly(vinylidene fluoride) (PVDF) is a semi-crystalline polymer and the polar β-phase of PVDF shows superb electroactive properties. In order to enhance the β-phase of PVDF, extreme low content of BaTiO3 nanoparticles (BT-NPs) coated with polydopamine (Pdop) were incorporated into PVDF matrix by solution casting. The β-phase of the resulting PVDF nanocomposites film was dramatically increased and the d33 value reached 34.3±0.4 pCN(-1). It is found that the Pdop layer could improve the dispersibility and stability of the BT NPs in solution and endow the BT NPs good dispersity in the PVDF matrix. Moreover, the interfacial interaction between PVDF chains and the surface of BT-Pdop nanoparticles (BT-Pdop NPs) were revealed, in which the CF2 groups on PVDF could interact with the electron-rich plane of aromatic ring of Pdop moiety. This interaction, led to the increase of the crystallization activation energy as derived from the DSC nonisothermal crystallization measurement. The α-β crystal transformation, organization of interfacial interactions as well as the prevention of agglomeration of BT-NPs confer the improvement of mechanical and thermal properties of PVDF, such as toughness, tensile strength, elongation at break, and thermal conductivity. PMID:25985420

  2. Effect of dispersive long-range corrections to the pressure tensor: The vapour-liquid interfacial properties of the Lennard-Jones system revisited

    SciTech Connect

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

    2014-11-14

    We propose an extension of the improved version of the inhomogeneous long-range corrections of Janeček [J. Phys. Chem. B 110, 6264–6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, r{sub c} = 2.5, 3, 4, and 5σ. In addition, we have also considered cutoff distances r{sub c} = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long-range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial

  3. Effect of dispersive long-range corrections to the pressure tensor: The vapour-liquid interfacial properties of the Lennard-Jones system revisited

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    We propose an extension of the improved version of the inhomogeneous long-range corrections of Janeček [J. Phys. Chem. B 110, 6264-6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, rc = 2.5, 3, 4, and 5σ. In addition, we have also considered cutoff distances rc = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long-range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness

  4. Polymer nanocomposites: permeability, chain dynamics, mechanical properties

    NASA Astrophysics Data System (ADS)

    Sahu, Laxmi

    2005-03-01

    Polymer nanocomposites based on dispersion of surfactant treated expandable smectite clays such as montmorillonite layered silicates (MLS) have shown promise as organic-inorganic hybrids with the potential to improve barrier properties. Separately, flexible displays based on plastic substrates have reduced lifetimes tied to the low barrier properties. While there has been a general attribution of improved barrier properties to the tortuous path, this does not consider the influence the introduction of a secondary filler has on the morphology of the host polymer. Here we examine the influence of MLS nanoplatelets on the barrier properties and chain dynamics of polymers. We investigate the potential for host polymer modification by comparing two crystallizable polymers nylon and PET and resulting well dispersed nanocomposites. We study mechanical, cyclic fatigue and permeability of films. Permeability of the biaxially stretched film and when the film undergoes fatigue of 50 and 10000 cycles are also measured. Chain dynamics were modeled based on the Burger model fit to creep-recovery data. A systematic approach to predict the permeability considering amorphous, crystalline and MLS content and comparison with experimental values were done. We also conducted water absorption measurements to highlight the water absorption differences in the two polymers. Dimensional stability of PET was studied by measuring coefficient of thermal expansion of thin film on Si substrate by ellipsometry method.

  5. Coalescence of water films on carbon-based substrates: the role of the interfacial properties and anisotropic surface topography.

    PubMed

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

    2015-05-01

    Molecular dynamics (MD) simulations are carried out to study the coalescence of identical adjacent and nonadjacent water films on graphene (G), vertically or horizontally stacked carbon nanotube arrays (VCNTA and HCNTA respectively). We highlight the key importance of carbon-based substrates in the growth of the liquid bridge connecting the two water films. This simulation provides reliable evidence to confirm a linear increase of the liquid bridge height, which is sensitive to the surface properties and the geometric structure. In the case of nonadjacent water films, the meniscus liquid bridge occurs solely on the VCNTA, which is attributed to the spreading of water films driven by the capillary force. Our results provide an available method to tune the coalescence of adjacent or nonadjacent films with alteration of topographically patterned surfaces, which has important implications in the design of condensation, ink-jet printing and drop manipulation on a substrate. PMID:25839066

  6. Dynamic properties of Drosophila olfactory electroantennograms.

    PubMed

    Schuckel, Julia; Meisner, Shannon; Torkkeli, Päivi H; French, Andrew S

    2008-05-01

    Time-dependent properties of chemical signals are probably crucially important to many animals, but little is known about the dynamics of chemoreceptors. Behavioral evidence of dynamic sensitivity includes the control of moth flight by pheromone plume structure, and the ability of some blood-sucking insects to detect varying concentrations of carbon dioxide, possibly matched to host breathing rates. Measurement of chemoreceptor dynamics has been limited by the technical challenge of producing controlled, accurate modulation of olfactory and gustatory chemical concentrations over suitably wide ranges of amplitude and frequency. We used a new servo-controlled laminar flow system, combined with photoionization detection of surrogate tracer gas, to characterize electroantennograms (EAG) of Drosophila antennae during stimulation with fruit odorants or aggregation pheromone in air. Frequency response functions and coherence functions measured over a bandwidth of 0-100 Hz were well characterized by first-order low-pass linear filter functions. Filter time constant varied over almost a tenfold range, and was characteristic for each odorant, indicating that several dynamically different chemotransduction mechanisms are present. Pheromone response was delayed relative to fruit odors. Amplitude of response, and consequently signal-to-noise ratio, also varied consistently with different compounds. Accurate dynamic characterization promises to provide important new information about chemotransduction and odorant-stimulated behavior. PMID:18320197

  7. Dynamic molecular crystals with switchable physical properties.

    PubMed

    Sato, Osamu

    2016-06-21

    The development of molecular materials whose physical properties can be controlled by external stimuli - such as light, electric field, temperature, and pressure - has recently attracted much attention owing to their potential applications in molecular devices. There are a number of ways to alter the physical properties of crystalline materials. These include the modulation of the spin and redox states of the crystal's components, or the incorporation within the crystalline lattice of tunable molecules that exhibit stimuli-induced changes in their molecular structure. A switching behaviour can also be induced by changing the molecular orientation of the crystal's components, even in cases where the overall molecular structure is not affected. Controlling intermolecular interactions within a molecular material is also an effective tool to modulate its physical properties. This Review discusses recent advances in the development of such stimuli-responsive, switchable crystalline compounds - referred to here as dynamic molecular crystals - and suggests how different approaches can serve to prepare functional materials. PMID:27325090

  8. Dynamic tensile properties of human placenta.

    PubMed

    Manoogian, Sarah J; Bisplinghoff, Jill A; McNally, Craig; Kemper, Andrew R; Santago, Anthony C; Duma, Stefan M

    2008-12-01

    Automobile crashes are the largest cause of injury death for pregnant females and the leading cause of traumatic fetal injury mortality in the United States. Computational models, useful tools to evaluate the risk of fetal loss in motor vehicle crashes, are based on a limited number of quasi-static material tests of the placenta. This study presents a total of 20 dynamic uniaxial tensile tests on the maternal side of the placenta and 10 dynamic uniaxial tensile tests on the chorion layer of the placenta. These tests were completed from 6 human placentas to determine material properties at a strain rate of 7.0 strains/s. The results show that the average peak strain at failure for both the maternal portion and the chorion layer of the placenta are similar with a value of 0.56 and 0.61, respectively. However, the average failure stress for the chorion layer, 167.8 kPa, is much higher than the average failure stress for the placenta with the chorionic plate removed, 18.6 kPa. This is due to differences in the structure and function of these layers in the placenta. In summary, dynamic loading data for the placenta have been determined for use in computational modeling of pregnant occupant kinematics in motor vehicle crashes. Moreover the computational model should utilize the material properties for the placenta without the chorion layer. PMID:18996533

  9. SiC (SCS-6) Fiber Reinforced-Reaction Formed SiC Matrix Composites: Microstructure and Interfacial Properties

    NASA Technical Reports Server (NTRS)

    Singh, M.; Dickerson, R. M.; Olmstead, Forrest A.; Eldridge, J. I.

    1997-01-01

    Microstructural and interfacial characterization of unidirectional SiC (SCS-6) fiber reinforced-reaction formed SiC (RFSC) composites has been carried out. Silicon-1.7 at.% molybdenum alloy was used as the melt infiltrant, instead of pure silicon, to reduce the activity of silicon in the melt as well as to reduce the amount of free silicon in the matrix. Electron microprobe analysis was used to evaluate the microstructure and phase distribution in these composites. The matrix is SiC with a bi-modal grain-size distribution and small amounts of MoSi2, silicon, and carbon. Fiber push-outs tests on these composites showed that a desirably low interfacial shear strength was achieved. The average debond shear stress at room temperature varied with specimen thickness from 29 to 64 MPa, with higher values observed for thinner specimens. Initial frictional sliding stresses showed little thickness dependence with values generally close to 30 MPa. Push-out test results showed very little change when the test temperature was increased to 800 C from room temperature, indicating an absence of significant residual stresses in the composite.

  10. Direct spontaneous growth and interfacial structural properties of inclined GaN nanopillars on r-plane sapphire

    SciTech Connect

    Adikimenakis, A.; Aretouli, K. E.; Tsagaraki, K.; Androulidaki, M.; Georgakilas, A.; Lotsari, A.; Dimitrakopulos, G. P. Kehagias, Th.; Komninou, Ph.

    2015-06-28

    The spontaneous growth of GaN nanopillars (NPs) by direct plasma-assisted molecular beam epitaxy on nitridated r-plane sapphire substrates has been studied. The emanation of metal-polarity NPs from inside an a-plane nonpolar GaN film was found to depend on both the substrate nitridation and the growth conditions. The density of NPs increased with increasing the duration of the nitridation process and the power applied on the radio-frequency plasma source, as well as the III/V flux ratio, while variation of the first two parameters enhanced the roughness of the substrate's surface. Transmission electron microscopy (TEM) techniques were employed to reveal the structural characteristics of the NPs and their nucleation mechanism from steps on the sapphire surface and/or interfacial semipolar GaN nanocrystals. Lattice strain measurements showed a possible Al enrichment of the first 5–6 monolayers of the NPs. By combining cross-sectional and plan-view TEM observations, the three-dimensional model of the NPs was constructed. The orientation relationship and interfacial accommodation between the NPs and the nonpolar a-plane GaN film were also elucidated. The NPs exhibited strong and narrow excitonic emission, suggesting an excellent structural quality.

  11. Brazing ZrO{sub 2} ceramic to Ti–6Al–4V alloy using NiCrSiB amorphous filler foil: Interfacial microstructure and joint properties

    SciTech Connect

    Cao, J.; Song, X.G.; Li, C.; Zhao, L.Y.; Feng, J.C.

    2013-07-15

    Reliable brazing of ZrO{sub 2} ceramic and Ti–6Al–4V alloy was achieved using NiCrSiB amorphous filler foil. The interfacial microstructure of ZrO{sub 2}/Ti–6Al–4V joints was characterized by scanning electron microscope, energy dispersive spectrometer and micro-focused X-ray diffractometer. The effects of brazing temperature on the interfacial microstructure and joining properties of brazed joints were investigated in detail. Active Ti of Ti–6Al–4V alloy dissolved into molten filler metal and reacted with ZrO{sub 2} ceramic to form a continuous TiO reaction layer, which played an important role in brazing. Various reaction phases including Ti{sub 2}Ni, Ti{sub 5}Si{sub 3} and β-Ti were formed in brazed joints. With an increasing of brazing temperature, the TiO layer thickened gradually while the Ti{sub 2}Ni amount reduced. Shear test indicated that brazed joints tend to fracture at the interface between ZrO{sub 2} ceramic and brazing seam or Ti{sub 2}Ni intermetallic layer. The maximum average shear strength reached 284.6 MPa when brazed at 1025 °C for 10 min. - Graphical Abstract: Interfacial microstructure of ZrO{sub 2}/TC4 joint brazed using NiCrSiB amorphous filler foil was: ZrO{sub 2}/TiO/Ti{sub 2}Ni + β-Ti + Ti{sub 5}Si{sub 3}/β-Ti/Widmanstätten structure/TC4. - Highlights: • Brazing of ZrO{sub 2} ceramic and Ti-6Al-4V alloy was achieved. • Interfacial microstructure was TiO/Ti{sub 2}Ni + β + Ti{sub 5}Si{sub 3}/β/Widmanstätten structure. • The formation of TiO produced the darkening effect of ZrO{sub 2} ceramic. • The highest joining strength of 284.6MPa was obtained.

  12. Influence of post-deposition annealing on interfacial properties between GaN and ZrO{sub 2} grown by atomic layer deposition

    SciTech Connect

    Ye, Gang; Wang, Hong Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong; Geok Ng, Serene Lay; Ji, Rong; Liu, Zhi Hong

    2014-10-13

    Influence of post-deposition annealing on interfacial properties related to the formation/annihilation of interfacial GaO{sub x} layer of ZrO{sub 2} grown by atomic layer deposition (ALD) on GaN is studied. ZrO{sub 2} films were annealed in N{sub 2} atmospheres in temperature range of 300 °C to 700 °C and analyzed by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that Ga-O bond to Ga-N bond area ratio decreases in the samples annealed at temperatures lower than 500 °C, which could be attributed to the thinning of GaO{sub x} layer associated with low surface defect states due to “clean up” effect of ALD-ZrO{sub 2} on GaN. However, further increase in annealing temperature results in deterioration of interface quality, which is evidenced by increase in Ga-O bond to Ga-N bond area ratio and the reduction of Ga-N binding energy.

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

    PubMed

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

    2016-08-23

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

  14. Structural and dynamical properties of complex networks

    NASA Astrophysics Data System (ADS)

    Ghoshal, Gourab

    Recent years have witnessed a substantial amount of interest within the physics community in the properties of networks. Techniques from statistical physics coupled with the widespread availability of computing resources have facilitated studies ranging from large scale empirical analysis of the worldwide web, social networks, biological systems, to the development of theoretical models and tools to explore the various properties of these systems. Following these developments, in this dissertation, we present and solve for a diverse set of new problems, investigating the structural and dynamical properties of both model and real world networks. We start by defining a new metric to measure the stability of network structure to disruptions, and then using a combination of theory and simulation study its properties in detail on artificially generated networks; we then compare our results to a selection of networks from the real world and find good agreement in most cases. In the following chapter, we propose a mathematical model that mimics the structure of popular file-sharing websites such as Flickr and CiteULike and demonstrate that many of its properties can solved exactly in the limit of large network size. The remaining part of the dissertation primarily focuses on the dynamical properties of networks. We first formulate a model of a network that evolves under the addition and deletion of vertices and edges, and solve for the equilibrium degree distribution for a variety of cases of interest. We then consider networks whose structure can be manipulated by adjusting the rules by which vertices enter and leave the network. We focus in particular on degree distributions and show that, with some mild constraints, it is possible by a suitable choice of rules to arrange for the network to have any degree distribution we desire. In addition we define a simple local algorithm by which appropriate rules can be implemented in practice. Finally, we conclude our

  15. Influence of string-like cooperative atomic motion on surface diffusion in the (110) interfacial region of crystalline Ni

    SciTech Connect

    Zhang, Hao E-mail: jack.douglas@nist.gov; Yang, Ying; Douglas, Jack F. E-mail: jack.douglas@nist.gov

    2015-02-28

    Although we often think about crystalline materials in terms of highly organized arrays of atoms, molecules, or even colloidal particles, many of the important properties of this diverse class of materials relating to their catalytic behavior, thermodynamic stability, and mechanical properties derive from the dynamics and thermodynamics of their interfacial regions, which we find they have a dynamics more like glass-forming (GF) liquids than crystals at elevated temperatures. This is a general problem arising in any attempt to model the properties of naturally occurring crystalline materials since many aspects of the dynamics of glass-forming liquids remain mysterious. We examine the nature of this phenomenon in the “simple” case of the (110) interface of crystalline Ni, based on a standard embedded-atom model potential, and we then quantify the collective dynamics in this interfacial region using newly developed methods for characterizing the cooperative dynamics of glass-forming liquids. As in our former studies of the interfacial dynamics of grain-boundaries and the interfacial dynamics of crystalline Ni nanoparticles (NPs), we find that the interface of bulk crystalline Ni exhibits all the characteristics of glass-forming materials, even at temperatures well below the equilibrium crystal melting temperature, T{sub m}. This perspective offers a new approach to modeling and engineering the properties of crystalline materials.

  16. Influence of string-like cooperative atomic motion on surface diffusion in the (110) interfacial region of crystalline Ni.

    PubMed

    Zhang, Hao; Yang, Ying; Douglas, Jack F

    2015-02-28

    Although we often think about crystalline materials in terms of highly organized arrays of atoms, molecules, or even colloidal particles, many of the important properties of this diverse class of materials relating to their catalytic behavior, thermodynamic stability, and mechanical properties derive from the dynamics and thermodynamics of their interfacial regions, which we find they have a dynamics more like glass-forming (GF) liquids than crystals at elevated temperatures. This is a general problem arising in any attempt to model the properties of naturally occurring crystalline materials since many aspects of the dynamics of glass-forming liquids remain mysterious. We examine the nature of this phenomenon in the "simple" case of the (110) interface of crystalline Ni, based on a standard embedded-atom model potential, and we then quantify the collective dynamics in this interfacial region using newly developed methods for characterizing the cooperative dynamics of glass-forming liquids. As in our former studies of the interfacial dynamics of grain-boundaries and the interfacial dynamics of crystalline Ni nanoparticles (NPs), we find that the interface of bulk crystalline Ni exhibits all the characteristics of glass-forming materials, even at temperatures well below the equilibrium crystal melting temperature, Tm. This perspective offers a new approach to modeling and engineering the properties of crystalline materials. PMID:25725748

  17. Influence of string-like cooperative atomic motion on surface diffusion in the (110) interfacial region of crystalline Ni

    PubMed Central

    Zhang, Hao; Yang, Ying; Douglas, Jack F.

    2015-01-01

    Although we often think about crystalline materials in terms of highly organized arrays of atoms, molecules, or even colloidal particles, many of the important properties of this diverse class of materials relating to their catalytic behavior, thermodynamic stability, and mechanical properties derive from the dynamics and thermodynamics of their interfacial regions, which we find they have a dynamics more like glass-forming (GF) liquids than crystals at elevated temperatures. This is a general problem arising in any attempt to model the properties of naturally occurring crystalline materials since many aspects of the dynamics of glass-forming liquids remain mysterious. We examine the nature of this phenomenon in the “simple” case of the (110) interface of crystalline Ni, based on a standard embedded-atom model potential, and we then quantify the collective dynamics in this interfacial region using newly developed methods for characterizing the cooperative dynamics of glass-forming liquids. As in our former studies of the interfacial dynamics of grain-boundaries and the interfacial dynamics of crystalline Ni nanoparticles (NPs), we find that the interface of bulk crystalline Ni exhibits all the characteristics of glass-forming materials, even at temperatures well below the equilibrium crystal melting temperature, Tm. This perspective offers a new approach to modeling and engineering the properties of crystalline materials. PMID:25725748

  18. Physical and Dynamical Properties of Asteroid Families

    NASA Astrophysics Data System (ADS)

    Zappalà, V.; Cellino, A.; dell'Oro, A.; Paolicchi, P.

    2002-03-01

    The availability of a number of statistically reliable asteroid families and the independent confirmation of their likely collisional origin from dedicated spectroscopic campaigns has been a major breakthrough, making it possible to develop detailed studies of the physical properties of these groupings. Having been produced in energetic collisional events, families are an invaluable source of information on the physics governing these phenomena. In particular, they provide information about the size distribution of the fragments, and on the overall properties of the original ejection velocity fields. Important results have been obtained during the last 10 years on these subjects, with important implications for the general understanding of the collisional history of the asteroid main belt, and the origin of near-Earth asteroids. Some important problems have been raised from these studies and are currently debated. In particular, it has been difficult so far to reconcile the inferred properties of family-forming events with current understanding of the physics of catastrophic collisional breakup. Moreover, the contribution of families to the overall asteroid inventory, mainly at small sizes, is currently controversial. Recent investigations are also aimed at understanding which kind of dynamical evolution might have affected family members since the time of their formation. In addition to potential consequences on the interpretation of current data, there is some speculative possibility of obtaining some estimate of the ages of these groupings. Physical characterization of families will likely represent a prerequisite for further advancement in understanding the properties and history of the asteroid population.

  19. Effect of interfacial structure on bioinert properties of poly(2-methoxyethyl acrylate)/poly(methyl methacrylate) blend films in water.

    PubMed

    Hirata, T; Matsuno, H; Kawaguchi, D; Yamada, N L; Tanaka, M; Tanaka, K

    2015-07-14

    In this study, we found that the surface made of a mixture of poly(2-methoxyethyl acrylate) (PMEA) and poly(methyl methacrylate) (PMMA) exhibited excellent blood compatibility by inhibiting platelet adhesion. To obtain a better understanding of this bioinertness, the polymer/water interface was characterized by neutron reflectivity measurements and sum frequency generation spectroscopy, in conjunction with bubble contact angle measurements. Based on the results, we can say that the outermost region of the blend film was reorganized in water. When the orientation of PMEA segments at the water interface became random with increasing immersion time, the fractional amount of lower-coordinated water molecules increased at the interface. Such an interfacial structure caused the suppression of platelet adhesion. PMID:26077905

  20. A preliminary study on the dynamic-mechanical behaviour of compression moulded polypropylene/carbon fiber composites interfacially modified by a succinic anhydride grafted atactic polypropylene from polymer wastes

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Present communication is devoted to the study of the effect of a novel interfacial agent in polypropylene/carbon fibre composites. The interfacial agent used is a succinic anhydride grafted atactic polypropylene containing both succinic bridges and side grafts (aPP-SASA) and with 5.6% (5.6.10-4g/mol) of grafting content obtained at the GIP labs. The study considers the study dynamic-mechanical behaviour with temperature at a frequency of 1 hz to ascertain the differences in the interfacial activity. The samples were compression molded in order to isolate as far as possible the effect of the solely aPP-SASA in absence of those synergetic effects due to the preferential orientation of the fibres.

  1. Exact dynamic properties of molecular motors

    NASA Astrophysics Data System (ADS)

    Boon, N. J.; Hoyle, R. B.

    2012-08-01

    Molecular motors play important roles within a biological cell, performing functions such as intracellular transport and gene transcription. Recent experimental work suggests that there are many plausible biochemical mechanisms that molecules such as myosin-V could use to achieve motion. To account for the abundance of possible discrete-stochastic frameworks that can arise when modeling molecular motor walks, a generalized and straightforward graphical method for calculating their dynamic properties is presented. It allows the calculation of the velocity, dispersion, and randomness ratio for any proposed system through analysis of its structure. This article extends work of King and Altman ["A schematic method of deriving the rate laws of enzyme-catalyzed reactions," J. Phys. Chem. 60, 1375-1378 (1956)], 10.1021/j150544a010 on networks of enzymatic reactions by calculating additional dynamic properties for spatially hopping systems. Results for n-state systems are presented: single chain, parallel pathway, divided pathway, and divided pathway with a chain. A novel technique for combining multiple system architectures coupled at a reference state is also demonstrated. Four-state examples illustrate the effectiveness and simplicity of these methods.

  2. Exact dynamic properties of molecular motors.

    PubMed

    Boon, N J; Hoyle, R B

    2012-08-28

    Molecular motors play important roles within a biological cell, performing functions such as intracellular transport and gene transcription. Recent experimental work suggests that there are many plausible biochemical mechanisms that molecules such as myosin-V could use to achieve motion. To account for the abundance of possible discrete-stochastic frameworks that can arise when modeling molecular motor walks, a generalized and straightforward graphical method for calculating their dynamic properties is presented. It allows the calculation of the velocity, dispersion, and randomness ratio for any proposed system through analysis of its structure. This article extends work of King and Altman ["A schematic method of deriving the rate laws of enzyme-catalyzed reactions," J. Phys. Chem. 60, 1375-1378 (1956)] on networks of enzymatic reactions by calculating additional dynamic properties for spatially hopping systems. Results for n-state systems are presented: single chain, parallel pathway, divided pathway, and divided pathway with a chain. A novel technique for combining multiple system architectures coupled at a reference state is also demonstrated. Four-state examples illustrate the effectiveness and simplicity of these methods. PMID:22938213

  3. The effects of Bi4Ti3O12 interfacial ferroelectric layer on the dielectric properties of Au/n-Si structures

    NASA Astrophysics Data System (ADS)

    Gökçen, Muharrem; Yıldırım, Mert

    2015-06-01

    Au/n-Si metal-semiconductor (MS) and Au/Bi4Ti3O12/n-Si metal-ferroelectric-semiconductor (MFS) structures were fabricated and admittance measurements were held between 5 kHz and 1 MHz at room temperature so that dielectric properties of these structures could be investigated. The ferroelectric interfacial layer Bi4Ti3O12 decreased the polarization voltage by providing permanent dipoles at metal/semiconductor interface. Depending on different mechanisms, dispersion behavior was observed in dielectric constant, dielectric loss and loss tangent versus bias voltage plots of both MS and MFS structures. The real and imaginary parts of complex modulus of MFS structure take smaller values than those of MS structure, because permanent dipoles in ferroelectric layer cause a large spontaneous polarization mechanism. While the dispersion in AC conductivity versus frequency plots of MS structure was observed at high frequencies, for MFS structure it was observed at lower frequencies.

  4. Influences of acid-base property of membrane on interfacial interactions related with membrane fouling in a membrane bioreactor based on thermodynamic assessment.

    PubMed

    Zhao, Leihong; Qu, Xiaolu; Zhang, Meijia; Lin, Hongjun; Zhou, Xiaoling; Liao, Bao-Qiang; Mei, Rongwu; Hong, Huachang

    2016-08-01

    Failure of membrane hydrophobicity in predicting membrane fouling requires a more reliable indicator. In this study, influences of membrane acid base (AB) property on interfacial interactions in two different interaction scenarios in a submerged membrane bioreactor (MBR) were studied according to thermodynamic approaches. It was found that both the polyvinylidene fluoride (PVDF) membrane and foulant samples in the MBR had relatively high electron donor (γ(-)) component and low electron acceptor (γ(+)) component. For both of interaction scenarios, AB interaction was the major component of the total interaction. The results showed that, the total interaction monotonically decreased with membrane γ(-), while was marginally affected by membrane γ(+), suggesting that γ(-) could act as a reliable indicator for membrane fouling prediction. This study suggested that membrane modification for fouling mitigation should orient to improving membrane surface γ(-) component rather than hydrophilicity. PMID:27155263

  5. Droplets in microchannels: dynamical properties of the lubrication film

    NASA Astrophysics Data System (ADS)

    Huerre, Axel; Theodoly, Olivier; Leshansky, Alexander; Valignat, Marie-Pierre; Cantat, Isabelle; Jullien, Marie-Caroline

    2015-11-01

    The motion of droplets or bubbles in confined geometries has been extensively studied; showing an intrinsic relationship between the lubrication film thickness and the droplet velocity. When capillary forces dominate, the lubrication film thickness evolves non linearly with the capillary number due to viscous dissipation both in the droplet and between meniscus and wall. However, this film may become thin enough (tens of nanometers) that intermolecular forces come into play and affect classical scalings. Our experiments yield highly resolved topographies of the shape of the interface and allow us to bring new insights into droplet dynamics in microfluidics. We find and characterize two distinct dynamical regimes, dominated respectively by capillary and intermolecular forces. In the first regime, we also identified a model with interfacial boundary condition considering only viscous stress continuity that agrees well with film thickness dynamics and interface velocity measurement.

  6. Interfacial nanorheology: Probing molecular mobility in mesoscopic polymeric systems

    NASA Astrophysics Data System (ADS)

    Sills, Scott E.

    Investigating the finite size limited structural relaxations in mesoscopic polymer systems is central to nanotechnological applications involving thin films, complex structures, and nanoscale phase-separated systems; for example, polymer electrolyte membranes, optoelectronic devices, and ultrahigh-density thermomechanical data storage (terabit recording). In such systems, bulk statistical averaging and continuum models are jeopardized. Interfacial constraints lead to bulk-deviating molecular dynamics and dictate material and transport properties. The objective of this dissertation is to provide insight to the exotic mesoscopic behaviors in thin films by developing novel rheological and tribological analytical methods based on scanning probe microscopy (SPM). Activation energies are deduced for the molecular motions associated with internal friction dissipation, and the temperature resolved length scale for cooperative motion during the glass transition is directly obtained for polystyrene. These results confirm the dynamical heterogeneity of the glass transition and reveal a crossover from intra- to inter-molecular relaxation in the transition regime. The impact of dimensional constraints on molecular mobility in ultrathin polymer films is explored through interfacial glass-transition profiles. With these profiles, a structural model of the rheological changes near interfacial boundaries is constructed as function of molecular weight and crosslinking density. The manifestation of interfacial constraints in nanotechnological applications is illustrated for thermomechanical recording, where rheological gradients near the substrate dictate the contact pressure and strain shielding at the substrate compromises film stability. A foundation for the critical aspects of interfacial stability is developed, and mechanically graded interfaces and modulus-matching techniques are explored as a means of improving the stability, durability, and stress transmission characteristics

  7. Influence of interfacial and bulk properties of cellulose ethers on lipolysis of oil-in-water emulsions.

    PubMed

    Torcello-Gómez, Amelia; Foster, Timothy J

    2016-06-25

    Cellulose ethers are usually used as secondary emulsifiers. Different types of commercial hydroxypropylmethylcellulose (HPMC) have been used here as the main emulsifier of oil-in-water emulsions to probe their impact on the lipid digestibility under simulated intestinal conditions. The droplet size distribution and ζ-potential of the emulsions subjected to in-vitro lipolysis have been compared with that of control samples (non-digested). The lipolysis has been quantified over time by means of the pH-stat method. The displacement of HPMC from the oil-water interface by bile salts has been assessed by interfacial tension technique. Results show that HPMC delays the lipid digestion of emulsions regardless of the Mw and methoxyl content. The destabilisation of emulsions under intestinal conditions as well as the resistance of HPMC to be displaced from the emulsion interface by bile salts may contribute to this feature. This provides new insights into the mechanisms whereby dietary fibre reduces fat absorption. PMID:27083841

  8. Composition dependent interfacial thermal stability, band alignment and electrical properties of Hf1-xTixO2/Si gate stacks

    NASA Astrophysics Data System (ADS)

    Zhang, J. W.; He, G.; Liu, M.; Chen, H. S.; Liu, Y. M.; Sun, Z. Q.; Chen, X. S.

    2015-08-01

    The optical properties, interface chemistry and band alignment of Hf1-xTixO2 (x = 0.03, 0.08, 0.12 and 0.20) high-k gate dielectric thin films, deposited by RF sputtering on Si substrate, have been systematically investigated. The effect of TiO2 incorporation on the interfacial chemical structure and energy-band discontinuities has been investigated by using X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV-vis). It has been found that the band gap and band offsets of the Hf1-xTixO2 thin film decrease with the increase of TiO2 concentration. Meanwhile, the obtained band offsets are all over 1 eV. Thin film capacitors fabricated with the MOS configuration of Al/Hf1-xTixO2/n-Si/Al exhibits excellent electrical properties with low interface state density, hysteresis voltage and low leakage current density. The suitable band gap, symmetrical band offsets relative to Si and prominent electrical properties render sputtering-derived Hf1-xTixO2 with 9% TiO2 films as promising candidates for high-k gate dielectrics.

  9. Nanoscale Control Over Interfacial Properties in Mixed Reverse Micelles Formulated by Using Sodium 1,4-bis-2-ethylhexylsulfosuccinate and Tri-n-octyl Phosphine Oxide Surfactants.

    PubMed

    Odella, Emmanuel; Falcone, R Darío; Silber, Juana J; Correa, N Mariano

    2016-08-01

    The interfacial properties of pure reverse micelles (RMs) are a consequence of the magnitude and nature of noncovalent interactions between confined water and the surfactant polar head. Addition of a second surfactant to form mixed RMs is expected to influence these interactions and thus affect these properties at the nanoscale level. Herein, pure and mixed RMs stabilized by sodium 1,4-bis-2-ethylhexylsulfosuccinate and tri-n-octyl phosphine oxide (TOPO) surfactants in n-heptane were formulated and studied by varying both the water content and the TOPO mole fraction. The microenvironment generated was sensed by following the solvatochromic behavior of the 1-methyl-8-oxyquinolinium betaine probe and (31) P NMR spectroscopy. The results reveal unique properties of mixed RMs and we give experimental evidence that free water can be detected in the polar core of the mixed RMs at very low water content. We anticipate that these findings will have an impact on the use of such media as nanoreactors for many types of chemical reactions, such as enzymatic reactions and nanoparticle synthesis. PMID:27128745

  10. The influence of interfacial properties on two-phase liquid flow of organic contaminants in groundwater. Progress report, September 1, 1993--August 31, 1994

    SciTech Connect

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

    1994-04-01

    Wettability is sometimes described as the most important factor influencing two-phase flow in porous media. A groundwater aquifer is often thought of as water-wet. But that state, in reality, depends on the nature of the aquifer solids, the composition of the groundwater and the properties of the organic liquid contaminant. The primary purpose of the research conducted here is to examine quantitatively the impact on wettability of a range of factors which may be critical at actual DOE waste sites. The goal is to understand how sorption at the various interfaces of the system modifies interfacial properties, primarily wettability, and then how, in turn, wettability determines the soil transport property of capillary pressure as a function of saturation. Specifically, this research seeks to (1) determine the range of wettability changes that may occur for DOE waste sites using wettability measures suitable for complex systems, (2) establish a correlation between these alternate measures of wettability and the contact angle, (3) establish the mechanism by which metals, organic solutes and soil particle coatings impact wettability, (4) evaluate whether the methodology developed in previous project periods among sorption, contact angle, and capillary pressure can be extended to more complex systems.

  11. Understanding the interfacial behavior in isopycnic Lennard-Jones mixtures by computer simulations.

    PubMed

    Garrido, José Matías; Piñeiro, Manuel M; Mejía, Andrés; Blas, Felipe J

    2016-01-14

    The physical characterization of the singular interfacial behavior of heterogeneous fluid systems is a very important step in preliminary stages of the design process, and also in the subsequent procedures for the determination of the optimal operating conditions. Molar isopycnicity or molar density inversion is a special case of phase equilibrium behavior that directly affects the relative position of phases in heterogeneous mixtures, without being affected by gravitational fields. This work is dedicated to characterize the impact of molar density inversion on the interfacial properties of Lennard-Jones binary mixtures. The results and specific trends of the molar density inversion phenomena on the peculiar calculated composition profiles across the interface and interfacial tensions are explored by using canonical molecular dynamics simulations of the Lennard-Jones binary mixtures. Our results show that the density inversion causes drastic changes in the density profiles of the mixtures. In particular, symmetrical and equal-sized Lennard-Jones mixtures always exhibit desorption along the interfacial zone, i.e. the interfacial concentration profiles show a relative minimum at the interface of the total density profiles that increases when the dispersive energy parameter (ε(ij)) between unlike species decreases. However, as the asymmetry of the Lennard-Jones mixtures increases (σ(i) ≠ σ(j)), the concentration profiles display a relative maximum at the interface, which implies the adsorption of the total density profiles along the interfacial zone. PMID:26660062

  12. Interfacial Tension Effects on Two-phase Flow Properties in Berea Sandstone by a GPU based Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    Jiang, F.; Tsuji, T.

    2013-12-01

    A highly efficient GPU (Graphics Processing Unit) based multi-phase LB (Lattice Boltzmann) method has been developed to investigate the Interfacial Tension (IFT) effect on the fluid flow characteristics inside the micro-scale porous media. Rock pores of Berea sandstone are reconstructed from the high-resolution micro-CT scanned images. Based on the reconstructed digital rock sample, the multi-phase flows are simulated with full resolution at 3.2μm. Under different IFT conditions, numerical analyses are carried out first on steady state two-phase flow to investigate the relative permeability change, and then on the unsteady drainage process to clarify evolution of injected fluid saturation distribution. It is found that when IFT is larger than 0.09, the relative permeability values are almost constants, while as the IFT decreases the relative permeabilities to both phases increase nonlinearly. It is also observed that two certain crucial IFT values σ1 and σ2 exist such that IFT has little impact on the evolution of injected fluid saturation for σ<σ1 and σ>σ2, while if σ1<σ<σ2, saturation will increase with decreasing IFT. For the geological CO2 storage application, our developed simulation method provides the most important parameter (i.e. relative permeability in many conditions) in reservoir simulation. Our method further contributes to improve the CO2 injection efficiency and increase the storage capability of the reservoir. Fig.1 Snapshots of the fluid configurations for primary drainage process

  13. Effect of Interfacial Microstructure Evolution on Mechanical Properties and Fracture Behavior of Friction Stir-Welded Al-Cu Joints

    NASA Astrophysics Data System (ADS)

    Xue, P.; Xiao, B. L.; Ma, Z. Y.

    2015-07-01

    The interfacial microstructure evolution of Al-Cu joints during friction stir welding and post-welding annealing and its influence on the tensile strength and the fracture behavior were investigated in detail. An obvious interface including three sub-layers of α-Al, Al2Cu, and Al4Cu9 intermetallic compound (IMC) layers is generated in the as-FSW joint. With the development of annealing process, the α-Al layer disappeared and a new IMC layer of AlCu formed between initial two IMC layers of Al2Cu and Al4Cu9. The growth rate of IMC layers was diffusion controlled before the formation of Kirkendall voids, with activation energy of 117 kJ/mol. When the total thickness of IMC layers was less than the critical value of 2.5 μm, the FSW joints fractured at the heat-affected zone of Al side with a high ultimate tensile strength (UTS) of ~100 MPa. When the thickness of IMC layers exceeded 2.5 μm, the joints fractured at the interface. For relatively thin IMC layer, the joints exhibited a slightly decreased UTS of ~90 MPa and an inter-granular fracture mode with crack propagating mainly between the Al2Cu and AlCu IMC layers. However, when the IMC layer was very thick, crack propagated in the whole IMC layers and the fracture exhibited trans-granular mode with a greatly decreased UTS of 50-60 MPa.

  14. Dynamic Properties of Langmuir Films by Laser Light Scattering

    NASA Astrophysics Data System (ADS)

    Sanders, John Newell

    A technique and instrumentation for measuring visco-elastic properties of Langmuir film organic monolayers has been developed. This technique is used to characterize certain films used in the manufacture of Langmuir-Blodgett solid films. Furthermore a comparison of the dynamic viscous and elastic moduli determined by this technique is made with static values determined from the Pressure versus Area Isotherm. Briefly, a Langmuir film consists of amphiphilic organic molecules spread in a trough filled with pure water. The hydrophobic ends of the molecules trap them on the water surface. When spread at a dilute concentration the molecules exhibit two dimensional ideal gas behavior. By increasing the surface concentration one obtains two dimensional liquid and finally two dimensional solid behavior. The measurement is performed by electrodynamically driving the liquid surface with the electric field from a razor blade brought to within less than 1 mm of the surface. A sinusoidally varying electric field induces dipoles in the water subphase and generates waves at twice the driving frequency (Attractive dipoles are generated whether the field is positive or negative). The space propagation and damping of these waves is measured by laser light scattering. A focused laser beam incident on the surface is reflected at an angle due to the slope of the waves on the surface. By observing the movement of the beam the amplitude and phase of the oscillation with respect to the driving function may be determined (via a Lock-In amplifier) at various distances from the razor blade. One may directly profile the waves by translating the profiler, or one may observe the variation in amplitude and phase while scanning the frequency or surface pressure. In the latter cases one uses a known reference state to determine the wavelength and damping from the amplitude and phase change. This data is fit by a non-linear least squares curve fitting program to determine the wavelength and space

  15. Nb and Ta layer doping effects on the interfacial energetics and electronic properties of LaAlO3/SrTiO3 heterostructure: first-principles analysis.

    PubMed

    Nazir, Safdar; Behtash, Maziar; Cheng, Jianli; Luo, Jian; Yang, Kesong

    2016-01-28

    The two-dimensional electron gas (2DEG) formed at the n-type (LaO)(+1)/(TiO2)(0) interface in the polar/nonpolar LaAlO3/SrTiO3 (LAO/STO) heterostructure (HS) has emerged as a prominent research area because of its great potential for nanoelectronic applications. Due to its practical implementation in devices, desired physical properties such as high charge carrier density and mobility are vital. In this respect, 4d and 5d transition metal doping near the interfacial region is expected to tailor electronic properties of the LAO/STO HS system effectively. Herein, we studied Nb and Ta-doping effects on the energetics, electronic structure, interfacial charge carrier density, magnetic moment, and the charge confinements of the 2DEG at the n-type (LaO)(+1)/(TiO2)(0) interface of LAO/STO HS using first-principles density functional theory calculations. We found that the substitutional doping of Nb(Ta) at Ti [Nb(Ta)@Ti] and Al [Nb(Ta)@Al] sites is energetically more favorable than that at La [Nb(Ta)@La] and Sr [Nb(Ta)@Sr] sites, and under appropriate thermodynamic conditions, the changes in the interfacial energy of HS systems upon Nb(Ta)@Ti and Nb(Ta)@Al doping are negative, implying that the formation of these structures is energetically favored. Our calculations also showed that Nb(Ta)@Ti and Nb(Ta)@Al doping significantly improve the interfacial charge carrier density with respect to that of the undoped system, which is because the Nb(Ta) dopant introduces excess free electrons into the system, and these free electrons reside mainly on the Nb(Ta) ions and interfacial Ti ions. Hence, along with the Ti 3d orbitals, the Nb 4d and Ta 5d orbitals also contribute to the interfacial metallic states; accordingly, the magnetic moments on the interfacial Ti ions increase significantly. As expected, the Nb@Al and Ta@Al doped LAO/STO HS systems show higher interfacial charge carrier density than the undoped and other doped systems. In contrast, Nb@Ti and Ta@Ti doped systems may

  16. Dynamical properties of the Watsonia asteroid family

    NASA Astrophysics Data System (ADS)

    Tsirvoulis, G.; Novakovic, B.; Knezevic, Z.; Cellino, A.

    2014-07-01

    Introduction: In recent years, a rare class of asteroids has been discovered [1], with its distinguishing characteristic being the anomalous polarimetric properties of its members. Named Barbarians, after (234) Barbara, the prototype of the class, these asteroids show negative polarization at unusually high phase-angles compared to normal asteroids. Motivated by the fact that some of the few discovered Barbarians seemed to be related to the Watsonia asteroid family, Cellino et al. [2] performed a search for more Barbarians among its members. A positive result of this search led to the conclusion that Watsonia is indeed an important repository of Barbarian asteroids. Based on these findings, we decided to analyze this family in detail. Basic information: According to available data, Watsonia is an L-type asteroid family, located in the middle of the main asteroid belt (2.68 < a_{p} < 2.82 au), with low to moderate orbital eccentricities (0.1 < e_{p} < 0.15) and relatively high inclinations (16.5^{o} < i_{p} < 18^{o}). Methodology: The first step in our study is to derive a reliable list of Watsonia family members. To that purpose, we first calculate the synthetic proper elements [3] of an extended catalogue including numbered, as well as multi and single opposition asteroids, in a wide region around the family. To this catalogue we apply the Hierarchical Clustering Method (HCM)[4] to determine the membership of the family, coinciding with the requirement that all confirmed neighboring Barbarians are included (see figure). To detect potential interlopers and refine the membership list, additional data such as the SDSS colors and WISE albedos are used. Moreover, we identify all relevant resonances and analyze the dynamical characteristics of the region occupied by the family. Then we estimate the age of the family, and finally, we perform numerical integrations of test particles to investigate possible dynamical links to other known Barbarians and to the near

  17. The influence of starch oxidization and aluminate coupling agent on interfacial interaction, rheological behavior, mechanical and thermal properties of poly(propylene carbonate)/starch blends

    NASA Astrophysics Data System (ADS)

    Jiang, Guo; Zhang, Shui-Dong; Huang, Han-Xiong; The Key Laboratory of Polymer Processing Engineering of the Ministry of Education Team

    Poly(propylene carbonate) (PPC) is a kind of new biodegradable polymer that is synthesized by copolymerization of propylene oxide and carbon dioxide. In this work, PPC end-capped with maleic anhydride (PPCMA)/thermoplastic starch (TPS), PPCMA/thermoplastic oxidized starch (TPOS) and PPCMA/AL-TPOS (TPOS modified by aluminate coupling agent) blends were prepared by melt blending to improve its thermal and mechanical properties. FTIR results showed that there existed hydrogen-bonding interaction between PPCMA and starch. SEM observation revealed that the compatibility between PPCMA and TPOS was improved by the oxidation of starch. The enhanced interfacial interactions between PPCMA and TPOS led to a better performance of PPC blends such as storage modulus (G'), loss modulus (G''), complex viscosity (η*), tensile strength and thermal properties. Furthermore, the modification of TPOS by aluminate coupling agent (AL) facilitated the dispersion of oxidized starch in PPC matrix, and resulted in increasing the tensile strength and thermal stability. National Natural Science Foundation of China, National Science Fund of Guangdong Province.

  18. Amino-Functionalized Multiwalled Carbon Nanotubes Lead to Successful Ring-Opening Polymerization of Poly(ε-caprolactone): Enhanced Interfacial Bonding and Optimized Mechanical Properties.

    PubMed

    Roumeli, Eleftheria; Papageorgiou, Dimitrios G; Tsanaktsis, Vasilios; Terzopoulou, Zoe; Chrissafis, Konstantinos; Avgeropoulos, Apostolos; Bikiaris, Dimitrios N

    2015-06-01

    In this work, the synthesis, structural characteristics, interfacial bonding, and mechanical properties of poly(ε-caprolactone) (PCL) nanocomposites with small amounts (0.5, 1.0, and 2.5 wt %) of amino-functionalized multiwalled carbon nanotubes (f-MWCNTs) prepared by ring-opening polymerization (ROP) are reported. This method allows the creation of a covalent-bonding zone on the surface of nanotubes, which leads to efficient debundling and therefore satisfactory dispersion and effective load transfer in the nanocomposites. The high covalent grafting extent combined with the higher crystallinity provide the basis for a significant enhancement of the mechanical properties, which was detected in the composites with up to 1 wt % f-MWCNTs. Increasing filler concentration encourages intrinsic aggregation forces, which allow only minor grafting efficiency and poorer dispersion and hence inferior mechanical performance. f-MWCNTs also cause a significant improvement on the polymerization reaction of PCL. Indeed, the in situ polymerization kinetics studies reveal a significant decrease in the reaction temperature, by a factor of 30-40 °C, combined with accelerated the reaction kinetics during initiation and propagation and a drastically reduced effective activation energy. PMID:25950403

  19. Effect of time on the interfacial and foaming properties of beta-lactoglobulin/acacia gum electrostatic complexes and coacervates at pH 4.2.

    PubMed

    Schmitt, Christophe; da Silva, Tânia Palma; Bovay, Claudine; Rami-Shojaei, Sabrina; Frossard, Philippe; Kolodziejczyk, Eric; Leser, Martin E

    2005-08-16

    The electrostatic complexation between beta-lactoglobulin and acacia gum was investigated at pH 4.2 and 25 degrees C. The binding isotherm revealed a spontaneous exothermic reaction, leading to a DeltaHobs = -2108 kJ mol(-1) and a saturation protein to polysaccharide weight mixing ratio of 2:1. Soluble electrostatic complexes formed in these conditions were characterized by a hydrodynamic diameter of 119 +/- 0.6 nm and a polydispersity index of 0.097. The effect of time on the interfacial and foaming properties of these soluble complexes was investigated at a concentration of 0.1 wt % at two different times after mixing (4 min, referred as t approximately 0 h and t = 24 h). At t approximately 0 h, the mixture is mainly made of aggregating soluble electrostatic complexes, whereas after 24 h these complexes have already insolubilize to form liquid coacervates. The surface elasticity, viscosity and phase angle obtained at low frequency (0.01 Hz) using oscillating bubble tensiometry revealed higher fluidity and less rigidity in the film formed at t approximately 0 h. This observation was confirmed by diminishing bubble experiments coupled with microscopy of the thin film. It was thicker, more homogeneous and contained more water at t approximately 0 h as compared to t = 24 h (thinner film, less water). This led to very different gas permeability's of Kt approximately 0 h = 0.021 cm s(-1) and Kt=24 h) = 0.449 cm s(-1), respectively. Aqueous foams produced with the beta-lactoglobulin/acacia gum electrostatic complexes or coacervates exhibited very different stability. The former (t approximately 0 h) had a stable volume, combining low drainage rate and mainly air bubble disproportionation as the destabilization mechanism. By contrast, using coacervates aged for 24 h, the foam was significantly less stable, combining fast liquid drainage and air bubble destabilization though fast gas diffusion followed by film rupture and bubble coalescence. The strong effect of time on

  20. An Investigation into the Effects of Interface Stress and Interfacial Arrangement on Temperature Dependent Thermal Properties of a Biological and a Biomimetic Material

    SciTech Connect

    Tomar, Vikas

    2015-01-13

    A significant effort in the biomimetic materials research is on developing materials that can mimic and function in the same way as biological tissues, on bio-inspired electronic circuits, on bio-inspired flight structures, on bio-mimetic materials processing, and on structural biomimetic materials, etc. Most structural biological and biomimetic material properties are affected by two primary factors: (1) interfacial interactions between an organic and an inorganic phase usually in the form of interactions between an inorganic mineral phase and organic protein network; and (2) structural arrangement of the constituents. Examples are exoskeleton structures such as spicule, nacre, and crustacean exoskeletons. A significant effort is being directed towards making synthetic biomimetic materials based on a manipulation of the above two primary factors. The proposed research is based on a hypothesis that in synthetic materials with biomimetic morphology thermal conductivity, k, (how fast heat is carried away) and thermal diffusivity, D, (how fast a material’s temperature rises: proportional to the ratio of k and heat capacity) can be engineered to be either significantly low or significantly high based on a combination of chosen interface orientation and interfacial arrangement in comparison to conventional material microstructures with the same phases and phase volume fractions. METHOD DEVELOPMENT 1. We have established a combined Raman spectroscopy and nanomechanical loading based experimental framework to perform environment (liquid vs. air vs. vacuum) dependent and temperature dependent (~1000 degree-C) in-situ thermal diffusivity measurements in biomaterials at nanoscale to micron scale along with the corresponding analytical theoretic calculations. (Zhang and Tomar, 2013) 2. We have also established a new classical molecular simulation based framework to measure thermal diffusivity in biomolecular interfaces. We are writing a publication currently (Qu and Tomar

  1. Dielectric properties of the interfacial layer on n-CuInSe/sub 2/ in photoelectrochemical solar cells

    SciTech Connect

    Shen, W.; Aurian-Blajeni, B.; Tomkiewicz, M.

    1986-05-01

    The authors report on the properties of n-CuInSe/sub 2/ single crystals, whose surface has been modified by thermal treatment. Frequency dispersion and electron beam induced current (EBIC) measurements show that the oxidic phase formed at the surface has a porous structure. Comparisons between thermally treated CuInSe/sub 2/ in liquid and solid junction devices confirm that the superficial layer alone is a rather poor conductor and that its electric properties change upon immersion in the electrolyte. The implications of this on the photovoltaic performance of thermally oxidized CuInSe/sub 2/ are discussed.

  2. Effect of plasma surface treatment of recycled carbon fiber on carbon fiber-reinforced plastics (CFRP) interfacial properties

    NASA Astrophysics Data System (ADS)

    Lee, Hooseok; Ohsawa, Isamu; Takahashi, Jun

    2015-02-01

    We studied the effects of plasma surface treatment of recycled carbon fiber on adhesion of the fiber to polymers after various treatment times. Conventional surface treatment methods have been attempted for recycled carbon fiber, but most require very long processing times, which may increase cost. Hence, in this study, plasma processing was performed for 0.5 s or less. Surface functionalization was quantified by X-ray photoelectron spectroscopy. O/C increased from approximately 11% to 25%. The micro-droplet test of adhesion properties and the mechanical properties of CFRP were also investigated.

  3. Microrheology and Particle Dynamics at Liquid-Liquid Interfaces

    NASA Astrophysics Data System (ADS)

    Song, Yanmei

    The rheological properties at liquid-liquid interfaces are important in many industrial processes such as manufacturing foods, pharmaceuticals, cosmetics, and petroleum products. This dissertation focuses on the study of linear viscoelastic properties at liquid-liquid interfaces by tracking the thermal motion of particles confined at the interfaces. The technique of interfacial microrheology is first developed using one- and two-particle tracking, respectively. In one-particle interfacial microrheology, the rheological response at the interface is measured from the motion of individual particles. One-particle interfacial microrheology at polydimethylsiloxane (PDMS) oil-water interfaces depends strongly on the surface chemistry of different tracer particles. In contrast, by tracking the correlated motion of particle pairs, two-particle interfacial microrheology significantly minimizes the effects from tracer particle surface chemistry and particle size. Two-particle interfacial microrheology is further applied to study the linear viscoelastic properties of immiscible polymer-polymer interfaces. The interfacial loss and storage moduli at PDMS-polyethylene glycol (PEG) interfaces are measured over a wide frequency range. The zero-shear interfacial viscosity, estimated from the Cross model, falls between the bulk viscosities of two individual polymers. Surprisingly, the interfacial relaxation time is observed to be an order of magnitude larger than that of the PDMS bulk polymers. To explore the fundamental basis of interfacial nanorheology, molecular dynamics (MD) simulations are employed to investigate the nanoparticle dynamics. The diffusion of single nanoparticles in pure water and low-viscosity PDMS oils is reasonably consistent with the prediction by the Stokes-Einstein equation. To demonstrate the potential of nanorheology based on the motion of nanoparticles, the shear moduli and viscosities of the bulk phases and interfaces are calculated from single

  4. Mechanobiology of interfacial growth

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  5. Influence of the micro- and nanoscale local mechanical properties of the interfacial transition zone on impact behavior of concrete made with different aggregates

    SciTech Connect

    Erdem, Savas Dawson, Andrew Robert; Thom, Nicholas Howard

    2012-02-15

    The influence of the microscale local mechanical properties of the interfacial transition zone (ITZ) on macro-level mechanical response and impact behavior is studied for concretes made with copper slag and gravel aggregates. 3D nanotech vertical scanning interferometry, scanning electron microscopy coupled with energy dispersive X-ray micro-analysis, digital image analysis, and 3D X-ray computed tomography were used to characterize the microstructures and the ITZs. It was deduced that a stronger and denser ITZ in the copper slag specimen would reduce its vulnerability to stiffness loss and contribute to its elastic and more ductile response under impact loading. The analysis also indicated that a significant degeneration in the pore structure of the gravel specimen associated with a relatively weaker and non-homogeneous ITZ occurred under impact. Finally, it was also concluded that increased roughness of ITZ may contribute to the load-carrying capacity of concrete under impact by improving contact point interactions and energy dissipation.

  6. Interfacial effect on the electrochemical properties of the layered graphene/metal sulfide composites as anode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Lv, Yagang; Chen, Biao; Zhao, Naiqin; Shi, Chunsheng; He, Chunnian; Li, Jiajun; Liu, Enzuo

    2016-09-01

    The layered graphene/metal sulfide composites exhibit excellent electrochemical properties as anode materials for lithium ion battery, due to the synergistic effect between metal sulfide and graphene which still needs to be further understood. In this study, Li adsorption and diffusion on MoS2 and SnS2 monolayers and Li2S surface, as well as at their interfaces with graphene, are systematically investigated through first-principles calculations. The analysis of charge density difference, Bader charge, and density of states indicates that the adsorbed Li atoms interact with both the S atoms at metal sulfide surfaces and C atoms in graphene, resulting in larger Li adsorption energies at the interfaces compared with that on the corresponding surfaces, but with almost no enhancement of the energy barriers for Li atom diffusion. The enhanced Li adsorption capability at Li2S/G interface contributes to the extra storage capacity of graphene/metal sulfide composites. Furthermore, the synergistic mechanism between metal sulfide and graphene is revealed. Moreover, band structure analysis shows the electronic conductivity is enhanced with the incorporation of graphene. The results corroborate the interfacial pseudocapacity-like Li atom storage mechanism, and are helpful for the design of layered graphene/metal sulfide composites as anode materials for lithium ion batteries.

  7. Magnetic-field-induced synthesis of Fe{sub 3}O{sub 4} nanorods by a gas–liquid interfacial process: Microstructure control, magnetic and photocatalytic properties

    SciTech Connect

    Zhang, Chun; Mo, Zunli Guo, Ruibin; Teng, Guixiang; Zhao, Guoping

    2014-05-01

    Highlights: • Fe{sub 3}O{sub 4} nanorods were synthesized via a MFI gas–liquid interfacial route. • The morphology of the Fe{sub 3}O{sub 4} nanoparticle can be changed during its growth process. • MF render Fe{sub 3}O{sub 4} nanorods higher degree of crystallinity and better magnetic property. - Abstract: In this paper, we designed a magnetic field (MF) induced gas–liquid interface route to synthesize magnetic Fe{sub 3}O{sub 4} nanorods (NRs). The results showed that the MF can significantly affect the morphology of the particles. In this original method, only relatively inexpensive and environmental chemicals were used. The structure and morphology of the Fe{sub 3}O{sub 4} NRs were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometry technique. The crystal growth mechanisms in the magnetic field induced process were expounded in detail. The as-synthesized Fe{sub 3}O{sub 4} NRs were successfully used as a catalytic carrier for the photo degradation of phenol.

  8. Dynamics at the Polymer/Nanoparticle Interface in Poly(2-vinylpyridine) Nanocomposites

    NASA Astrophysics Data System (ADS)

    Holt, Adam; Bocharova, Vera; Griffin, Philip; Agaprov, Alexander; Imel, Adam; Dadmun, Mark; Sangoro, Joshua; Sokolov, Alexei

    2014-03-01

    The intriguing thermodynamic properties of polymer nanocomposites (PNCs) have often been attributed to the formation of an interfacial polymer region at the nanoparticle surface and a better understanding of how the interfacial region affects the PNC dynamics is desired. The static and dynamic properties of poly(2-vinylpyridine)/silica nanocomposites are investigated by temperature modulated differential scanning calorimetry, broadband dielectric spectroscopy (BDS), and small angle x-ray scattering (SAXS). The SAXS data revealed a core-shell structure formed in interfacial region and BDS data detected the slower relaxation process associated with the interfacial polymer layer. Both static and dynamic measurements estimated the layer thickness to be 4-6 nm. We also demonstrated that the presence of interfacial polymer layer has negligible influence on the glass transition temperature and segmental dynamics of the remaining polymer. These results potentially offer an explanation to recent controversies in studies of polymer nanocomposites due to different experimental techniques.

  9. Analysis and control of nonlinear dynamical behavior with applications to selected interfacial and volumetric materials-related phenomena

    NASA Astrophysics Data System (ADS)

    Gupta, Arnab

    2000-10-01

    The objective of this study was to apply recently developed concepts in the area of nonlinear dynamics to a spectrum of materials-related problems. New models were developed to describe the Portevin---Le Chatelier (PLC) effect and the growth of thin films by ballistic deposition. In addition, a variety of control strategies were developed, intended to favorably alter the dynamical behavior of nonlinear systems. A generalized mathematical description of the PLC effect was presented in the form of delay differential equations. Existing dislocation evolution equations from literature were modified by including a time-delay effect and shown to reproduce experimentally measured characteristics. A new model, based on evolution of the fraction of mobile dislocations due to pinning and depinning by solute atoms, was developed is. The temperature and strain-rate conditions for the PLC effect were mathematically established based on this model. The existence of critical strains and negative strain-rate sensitivity was also explained. A cellular automata-based simple model was developed separately to study slip behavior during inhomogeneous deformation. The change in reloading time and serration amplitude of stress with applied strain-rate from simulations showed good agreement with experimental results. Existing models of chemisorption, thin film growth, plastic instabilities, and voltage collapse in electrical power systems were studied using established techniques for characterizing nonlinear processes. Simple feedback methods including derivative control were used to stabilize certain instabilities in these model systems. The robustness of the control methods was evaluated. Three new feedback methods for control were developed and successfully applied to stabilize an unstable fixed point in a model for dissociative chemisorption of a diatomic gas. A discrete model was developed to simulate the phenomena of surface growth by ballistic deposition. Three parameters were

  10. Interfacial behavior of polymer electrolytes

    SciTech Connect

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

    2003-06-03

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

  11. Three-Dimensional Visualization of Interfacial Phenomena Using Confocal Microscopy

    NASA Astrophysics Data System (ADS)

    Shieh, Ian C.

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

  12. Understanding controls on interfacial wetting at epitaxial graphene: Experiment and Theory

    SciTech Connect

    Zhou, Hua; Ganesh, Panchapakesan; Presser, Volker; Wander, Matthew C; Fenter, Paul; Kent, Paul R; Jiang, Deen; Chialvo, Ariel A; Mcdonough, John; Shuford, Kevin L; Gogotsi, Yury G.

    2012-01-01

    The interaction of interfacial water with graphitic carbon at the atomic scale is studied as a function of the hydrophobicity of epitaxial graphene. High resolution x-ray reflectivity shows that the graphene-water contact angle is controlled by the average graphene thickness, due to the fraction of the film surface expressed as the epitaxial buffer layer whose contact angle (contact angle c = 73 ) is substantially smaller than that of multilayer graphene ( c = 93 ). Classical and ab initio molecular dynamics simulations show that the reduced contact angle of the buffer layer is due to both its epitaxy with the SiC substrate and the presence of interfacial defects. This insight clarifies the relationship between interfacial water structure and hydrophobicity, in general, and suggests new routes to control interface properties of epitaxial graphene.

  13. Understanding controls on interfacial wetting at epitaxial graphene: Experiment and Theory

    SciTech Connect

    Kent, Paul R

    2011-01-01

    The interaction of interfacial water with graphitic carbon at the atomic scale is studied as a function of the hydrophobicity of epitaxial graphene. High resolution x-ray reflectivity shows that the graphene-water contact angle is controlled by the average graphene thickness, due to the fraction of the film surface expressed as the epitaxial buffer layer whose contact angle (contact angle {Theta}{sub c} = 73{sup o}) is substantially smaller than that of multilayer graphene ({Theta}{sub c} = 93{sup o}). Classical and ab initio molecular dynamics simulations show that the reduced contact angle of the buffer layer is due to both its epitaxy with the SiC substrate and the presence of interfacial defects. This insight clarifies the relationship between interfacial water structure and hydrophobicity, in general, and suggests new routes to control interface properties of epitaxial graphene.

  14. Understanding controls on interfacial wetting at epitaxial graphene: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Zhou, Hua; Ganesh, P.; Presser, Volker; Wander, Matthew C. F.; Fenter, Paul; Kent, Paul R. C.; Jiang, De-En; Chialvo, Ariel A.; McDonough, John; Shuford, Kevin L.; Gogotsi, Yury

    2012-01-01

    The interaction of interfacial water with graphitic carbon at the atomic scale is studied as a function of the hydrophobicity of epitaxial graphene. High resolution x-ray reflectivity shows that the graphene-water contact angle is controlled by the average graphene thickness, due to the fraction of the film surface expressed as the epitaxial buffer layer whose contact angle (contact angle θc = 73°) is substantially smaller than that of multilayer graphene (θc = 93°). Classical and ab initio molecular dynamics simulations show that the reduced contact angle of the buffer layer is due to both its epitaxy with the SiC substrate and the presence of interfacial defects. This insight clarifies the relationship between interfacial water structure and hydrophobicity, in general, and suggests new routes to control interface properties of epitaxial graphene.

  15. Interfacial Control of Magnetic Properties at LaMnO3/LaNiO3 Interfaces.

    PubMed

    Gibert, M; Viret, M; Torres-Pardo, A; Piamonteze, C; Zubko, P; Jaouen, N; Tonnerre, J-M; Mougin, A; Fowlie, J; Catalano, S; Gloter, A; Stéphan, O; Triscone, J-M

    2015-11-11

    The functional properties of oxide heterostructures ultimately rely on how the electronic and structural mismatches occurring at interfaces are accommodated by the chosen materials combination. We discuss here LaMnO3/LaNiO3 heterostructures, which display an intrinsic interface structural asymmetry depending on the growth sequence. Using a variety of synchrotron-based techniques, we show that the degree of intermixing at the monolayer scale allows interface-driven properties such as charge transfer and the induced magnetic moment in the nickelate layer to be controlled. Further, our results demonstrate that the magnetic state of strained LaMnO3 thin films dramatically depends on interface reconstructions. PMID:26484628

  16. Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

    NASA Astrophysics Data System (ADS)

    Gao, Qiong; Wang, Kehong

    2016-03-01

    This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

  17. Enhanced Bulk and Interfacial Charge Transfer Dynamics for Efficient Photoelectrochemical Water Splitting: The Case of Hematite Nanorod Arrays.

    PubMed

    Wang, Jian; Feng, Bo; Su, Jinzhan; Guo, Liejin

    2016-09-01

    Charge transport in the bulk and across the semiconductor/electrolyte interface is one of the major issues that limits photoelectrochemical (PEC) performance in hematite photoelectrodes. Efficient charge transport in the entire hematite is of great importance to obtaining high photoelectrochemical properties. Herein, to reach this goal, we employed both TiO2 underlayer and overlayer deposition on hematite nanorod films, followed by a fast annealing treatment. The TiO2 underlayer and overlayer not only serve as dopant sources for carrier density increase but also reduce charge recombination at the fluorine-doped tin oxide (FTO)/hematite interface and accelerate charge transfer across the hematite/electrolyte interface. This synergistic doping and interface modifying effects give rise to an enhanced photoelectrochemical water oxidation performance of hematite nanorod arrays, generating an impressive photocurrent density of 1.49 mA cm(-2) at 1.23 V vs RHE. This is the first report on using both underlayer and overlayer modification with the same material to improve charge transport through the entire electron transport path in hematite, which provides a novel way to manipulate charge transfer across the semiconductor interface for a high-performance photoelectrode. PMID:27508404

  18. Interfacial Properties of Organic Semiconductor-Inorganic Magnetic Oxide Hybrid Spintronic Systems Fabricated Using Pulsed Laser Deposition.

    PubMed

    Majumdar, Sayani; Grochowska, Katarzyna; Sawczak, Miroslaw; Śliwiński, Gerard; Huhtinen, Hannu; Dahl, Johnny; Tuominen, Marjukka; Laukkanen, Pekka; Majumdar, Himadri S

    2015-10-14

    We report fabrication of a hybrid organic semiconductor-inorganic complex oxide interface of rubrene and La0.67Sr0.33MnO3 (LSMO) for spintronic devices using pulsed laser deposition (PLD) and investigate the interface structure and chemical bonding-dependent magnetic properties. Our results demonstrate that with proper control of growth parameters, thin films of organic semiconductor rubrene can be deposited without any damage to the molecular structure. Rubrene, a widely used organic semiconductor with high charge-carrier mobility and spin diffusion length, when grown as thin films on amorphous and crystalline substrates such as SiO2-glass, indium-tin oxide (ITO), and LSMO by PLD at room temperature and a laser fluence of 0.19 J/cm2, reveals amorphous structure. The Raman spectra verify the signatures of both Ag and Bg Raman active modes of rubrene molecules. X-ray reflectivity measurements indicate a well-defined interface formation between surface-treated LSMO and rubrene, whereas X-ray photoelectron spectra indicate the signature of hybridization of the electronic states at this interface. Magnetic measurements show that the ferromagnetic property of the rubrene-LSMO interface improves by >230% compared to the pristine LSMO surface due to this proposed hybridization. Intentional disruption of the direct contact between LSMO and rubrene by insertion of a dielectric AlOx layer results in an observably decreased ferromagnetism. These experimental results demonstrate that by controlling the interface formation between organic semiconductor and half-metallic oxide thin films, it is possible to engineer the interface spin polarization properties. Results also confirm that by using PLD for consecutive growth of different layers, contamination-free interfaces can be obtained, and this finding is significant for the well-controlled and reproducible design of spin-polarized interfaces for future hybrid spintronics devices. PMID:26402298

  19. Impact of Copper-Doped Titanium Dioxide Interfacial Layers on the Interface-State and Electrical Properties of Si-based MOS Devices

    NASA Astrophysics Data System (ADS)

    Akin, Seçkİn; Sönmezoğlu, Savaş

    2015-09-01

    The current study presents the interface-state and electrical properties of silicon (Si)-based metal-oxide-semiconductor (MOS) devices using copper-doped titanium dioxide (Cu:TiO2) nanoparticles for possible applications as an interfacial layer in scaled high-k/metal gate MOSFET technology. The structural properties of the Cu:TiO2 nanoparticles have been obtained by means of X-ray diffraction (XRD), UV-Vis-NIR spectrometry, atomic force microscopy, and scanning electron microscopy measurements; they were compared with pure TiO2 thin film. With the incorporation of Cu, rutile-dominated anatase/rutile multiphase crystalline was revealed by XRD analysis. To understand the nature of this structure, the electronic parameters controlling the device performance were calculated using current-voltage ( I- V), capacitance-voltage ( C- V), and conductance-voltage ( G- V) measurements. The ideality factor ( n) was 1.21 for the Al/Cu:TiO2/ p-Si MOS device, while the barrier height ϕ b was 0.75 eV with semi-log I- V characteristics. This is in good agreement with 0.78 eV measured by the Norde model. Possible reasons for the deviation of the ideality factor from unity have been addressed. From the C- V measurements, the values of diffusion potential, barrier height, and carrier concentration were extracted as 0.67, 0.98 eV, and 8.73 × 1013 cm-3, respectively. Our results encourage further work to develop process steps that would allow the Cu-doped TiO2 film/Si interface to play a major role in microelectronic applications.

  20. Elastocapillary-mediated interfacial assembly

    NASA Astrophysics Data System (ADS)

    Evans, Arthur

    2015-11-01

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

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

    PubMed

    Valero, Margarita; Velázquez, M Mercedes

    2004-10-15

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

  2. Microstructure and interfacial properties of laterally oxidized Al{sub x}Ga{sub 1{minus}x}As

    SciTech Connect

    Twesten, R.D.; Follstaedt, D.M.; Choquette, K.D.

    1996-12-31

    Oxidation of high Al content Al{sub x}Ga{sub 1-x}As has received much attention due to its use in oxide-aperture, vertical-cavity surface emitting lasers (VCSELs) and for passivating AlAs against environmental degradation. We have recently identified the spinel, gamma phase of Al{sub 2}O{sub 3} in layers laterally oxidized in steam at 450 C for x=0.98 & 0.92 and have seen evidence for an amorphous precursor to the gamma phase. At the interface with the unoxidized Al{sub x}Ga{sub 1-x}As, an {approximately}17nm amorphous phase remains which could account for the excellent electrical properties of oxide-confined VCSELs and help reduce stress concentrations at the oxide terminus.

  3. Interfacial Effects on the Thermal and Mechanical Properties of Graphite/Copper Composites. Final Contractor Report Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Devincent, Sandra Marie

    1995-01-01

    Graphite surfaces are not wet by pure copper. This lack of wetting has been responsible for a debonding phenomenon that has been found in continuous graphite fiber reinforced copper matrix composites subjected to elevated temperatures. By suitably alloying copper, its ability to wet graphite surfaces can be enhanced. Information obtained during sessile drop testing has led to the development of a copper-chromium alloy that suitably wets graphite. Unidirectionally reinforced graphite/copper composites have been fabricated using a pressure infiltration casting procedure. P100 pitch-based fibers have been used to reinforce copper and copper-chromium alloys. X-ray radiography and optical microscopy have been used to assess the fiber distribution in the cast composites. Scanning electron microscopy and Auger electron spectroscopy analyses were conducted to study the distribution and continuity of the chromium carbide reaction phase that forms at the fiber/matrix interface in the alloyed matrix composites. The effects of the chromium in the copper matrix on the mechanical and thermal properties of P100Gr/Cu composites have been evaluated through tensile testing, three-point bend testing, thermal cycling and thermal conductivity calculations. The addition of chromium has resulted in an increased shear modulus and essentially zero thermal expansion in the P100Gr/Cu-xCr composites through enhanced fiber/matrix bonding. The composites have longitudinal tensile strengths in excess of 700 MPa with elastic moduli of 393 GPa. After 100 hr at 760 deg C 84 percent of the as-cast strength is retained in the alloyed matrix composites. The elastic moduli are unchanged by the thermal exposure. It has been found that problems with spreading of the fiber tows strongly affect the long transverse tensile properties and the short transverse thermal conductivity of the P100Gr/Cu-xCr composites. The long transverse tensile strength is limited by rows of touching fibers which are paths of

  4. Pickering emulsions stabilized by soft microgels: influence of the emulsification process on particle interfacial organization and emulsion properties.

    PubMed

    Destribats, Mathieu; Wolfs, Mélanie; Pinaud, Florent; Lapeyre, Véronique; Sellier, Elisabeth; Schmitt, Véronique; Ravaine, Valérie

    2013-10-01

    This work reports a new evidence of the versatility of soft responsive microgels as stabilizers for Pickering emulsions. The organization of microgels at the oil-water interface is a function of the preparation pathway. The present results show that emulsification energy can be used as a trigger to modify microgel deformation at the oil-water interface and their packing density: high shear rates bring strong flattening of the microgels, whereas low shear rates lead to dense monolayers, where the microgels are laterally compressed. As a consequence, the resulting emulsions have opposite behavior in terms of flocculation, which arises from bridging between neighboring drops and is strongly dependent on their surface coverage. This strategy can be applied to any microgel which can sufficiently adsorb at low shear rates, i.e. small microgels or lightly cross-linked ones. The control of the organization of microgels at the interface does not only modify emulsion end-use properties but also constitutes a new tool for the development of Janus-type microgels, obtained by chemical modification of the adsorbed microgels. PMID:24050149

  5. Enhanced dielectric properties of electrically poled poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) multilayer films via interfacial polarization

    NASA Astrophysics Data System (ADS)

    Tseng, Jung-Kai; Mackey, Matthew; Zhou, Zheng; Carr, Joel; Schuele, Donald E.; Baer, Eric; Zhu, Lei

    2014-03-01

    Electrically poled poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) multilayer films can be considered as a polymer electret, which stores quasi-permanent charges (i.e., ions) at PVDF/PC interfaces. In this study, the corresponding dielectric properties of electrically poled PVDF/PC multilayer films are investigated experimentally. First, the bipolar hysteresis loop becomes narrower for the poled PVDF/PC multilayer films upon increasing the poling time, because the impurity ions in PVDF are locked at the PVDF/PC interfaces. Second, asymmetric DC conductivity in poled PVDF/PC multilayer films is observed because of the pre-existing electric field in the electret layers. When the pre-existing field is in the same direction of the applied external field, enhanced DC conductivity is observed in the leakage current measurement. In contrast, if the pre-existing field is opposite to the applied external field, decreased DC conductivity is seen. More experimental evidence of polarized charge at the PVDF/PC interfaces in poled PVDF/PC multilayer films is also manifested by thermally stimulated depolarization current (TSDC) experiments.

  6. Mixed-mode interfacial adhesive strength of a thin film on an anisotropic substrate

    NASA Astrophysics Data System (ADS)

    Kitey, Rajesh; Geubelle, Philippe H.; Sottos, Nancy R.

    2009-01-01

    The mixed-mode interfacial adhesion strength between a gold (Au) thin film and an anisotropic passivated silicon (Si) substrate is measured using laser-induced stress wave loading. Test specimens are prepared by bonding a fused silica (FS) prism to the back side of a <1 0 0> Si substrate with a thin silicon nitride (Si xN y) passivation layer deposited on the top surface. A high-amplitude stress wave is developed by pulsed laser ablation of a sacrificial absorbing layer on one of the lateral surfaces of the FS prism. Due to the negative non-linear elastic properties of the FS, the compressive stress wave evolves into a decompression shock with fast fall time. Careful selection of the incident angle between the pulse and the FS/Si interface generates a mode-converted shear wave in refraction, subjecting the Si xN y/Au thin film interface to dynamic mixed-mode loading, sufficient to cause interfacial fracture. A detailed analysis of the anisotropic wave propagation combined with interferometric measurements of surface displacements enables calculation of the interfacial stresses developed under mixed-mode loading. The mixed-mode interfacial strength is compared to the interfacial strength measured under purely tensile loading.

  7. Reaction ensemble molecular dynamics: Direct simulation of the dynamic equilibrium properties of chemically reacting mixtures

    NASA Astrophysics Data System (ADS)

    Brennan, John K.; Lísal, Martin; Gubbins, Keith E.; Rice, Betsy M.

    2004-12-01

    A molecular simulation method to study the dynamics of chemically reacting mixtures is presented. The method uses a combination of stochastic and dynamic simulation steps, allowing for the simulation of both thermodynamic and transport properties. The method couples a molecular dynamics simulation cell (termed dynamic cell) to a reaction mixture simulation cell (termed control cell) that is formulated upon the reaction ensemble Monte Carlo (RxMC) method, hence the term reaction ensemble molecular dynamics. Thermodynamic and transport properties are calculated in the dynamic cell by using a constant-temperature molecular dynamics simulation method. RxMC forward and reverse reaction steps are performed in the control cell only, while molecular dynamics steps are performed in both the dynamic cell and the control cell. The control cell, which acts as a sink and source reservoir, is maintained at reaction equilibrium conditions via the RxMC algorithm. The reaction ensemble molecular dynamics method is analogous to the grand canonical ensemble molecular dynamics technique, while using some elements of the osmotic molecular dynamics method, and so simulates conditions that directly relate to real, open systems. The accuracy and stability of the method is assessed by considering the ammonia synthesis reaction N2+3H2⇔2NH3 . It is shown to be a viable method for predicting the effects of nonideal environments on the dynamic properties (particularly diffusion) as well as reaction equilibria for chemically reacting mixtures.

  8. Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

    NASA Astrophysics Data System (ADS)

    Jain, N.; Zhu, Y.; Maurya, D.; Varghese, R.; Priya, S.; Hudait, M. K.

    2014-01-01

    We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO2) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO2 thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO2 thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO2/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 ± 0.02 eV was determined for the amorphous TiO2 thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO2/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO2/Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ΔEV(100) > ΔEV(111) > ΔEV(110) and a conduction band-offset relation of ΔEC(110) > ΔEC(111) > ΔEC(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO2 for potential high-κ dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.

  9. Improved interfacial and electrical properties of GaAs metal-oxide-semiconductor capacitors with HfTiON as gate dielectric and TaON as passivation interlayer

    NASA Astrophysics Data System (ADS)

    Wang, L. S.; Xu, J. P.; Zhu, S. Y.; Huang, Y.; Lai, P. T.

    2013-08-01

    The interfacial and electrical properties of sputtered HfTiON on sulfur-passivated GaAs with or without TaON as interfacial passivation layer (IPL) are investigated. Experimental results show that the GaAs metal-oxide-semiconductor capacitor with HfTiON/TaON stacked gate dielectric annealed at 600 °C exhibits low interface-state density (1.0 × 1012 cm-2 eV-1), small gate leakage current (7.3 × 10-5 A cm-2 at Vg = Vfb + 1 V), small capacitance equivalent thickness (1.65 nm), and large equivalent dielectric constant (26.2). The involved mechanisms lie in the fact that the TaON IPL can effectively block the diffusions of Hf, Ti, and O towards GaAs surface and suppress the formation of interfacial As-As bonds, Ga-/As-oxides, thus unpinning the Femi level at the TaON/GaAs interface and improving the interface quality and electrical properties of the device.

  10. Properties of earthquakes generated by fault dynamics

    NASA Technical Reports Server (NTRS)

    Carlson, J. M.; Langer, J. S.

    1989-01-01

    A model for fault dynamics consisting of a uniform chain of blocks and springs pulled slowly across a rough surface is presented. The only nonlinear element of the model is a slip-stick friction force between the blocks and the surface. It is found that this model gives rise to events of all sizes. The numerical evaluation of the distribution of earthquake magnitudes results in a power-law spectrum similar to what is observed in nature. Like certain other dissipative dynamical systems, the observed large fluctuations in earthquake magnitude persist because the system is in a state of marginal stability.

  11. High temperature interfacial superconductivity

    SciTech Connect

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

    2012-06-19

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

  12. Investigation of the efect of the coal particle sizes on the interfacial and rheological properties of coal-water slurry fuels

    SciTech Connect

    Kihm, K.D.; Deignan, P.

    1995-11-01

    Experiments were conducted to investigate the effect of particle size on coal-water slurry (CWS) surface tension properties. Two different coal powder samples of different size ranges were obtained through sieving of coal from the Upper Elkhorn Seam. The surfactant (anionic DDBS-soft, dodecylbenzene sulfonic acid) concentration varied from 0 to 1.0% in weight while the coal loading remained at 40% in weight for all the cases. A du Nouy ring tensiometer and a maximum bubble pressure tensiometer measured the static and dynamic surface tensions, respectively, The results show that both static and dynamic surface tensions tend to increase with decreasing coal particle sizes suspended in CWS fuels. Examination of the peak pressure, minimum pressure, surfactant diffusion time, and dead time were also made to correlate these microscopic pressure behavior with the macroscopic dynamic surface tension and to examine the accuracy of the experiment.

  13. STARCH FILLED TERNARY POLYMER COMPOSITES I: DYNAMIC MECHANICAL PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been shown that the dynamic mechanical properties of starch filled blends of polyethylene (PE) and poly (hydroxy ester ether) (PHEE) are strongly dependent on the properties and distribution of the minor component of the blend (PHEE). The effect of this minor component on the viscoelastic pr...

  14. Wavebreaking of Interfacial Stokes Flows

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  15. In Vitro Tissue Differentiation using Dynamics of Tissue Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Chiang; Phillips, Paul J.

    2002-03-01

    Dynamics of tissue mechanical properties of various human tissue types were studied at macroscopic as well as microscopic level in vitro. This study was conducted to enable the development of a feedback system based on dynamics of tissue mechanical properties for intraoperative guidance for tumor treatment (e.g., RF ablation of liver tumor) and noninvasive tumor localization. Human liver tissues, including normal, cancerous, and cirrhotic tissues, were obtained from patients receiving liver transplant or tumor resection at Vanderbilt University Medical Center with the approval of the Vanderbilt Institutional Review Board. Tissue samples, once resected from the patients, were snap-frozen using liquid nitrogen and stored at -70 oC. Measurements of the mechanical properties of these tissue samples were conducted at the University of Tennessee at Knoxville. Dynamics of tissue mechanical properties were measured from both native and thermally coagulated tissue samples at macroscopic and microscopic level. Preliminary results suggest the dynamics of mechanical properties of normal liver tissues are very different from those of cancerous liver tissues. The correlation between the dynamics of mechanical properties at macroscopic level and those at microscopic level is currently under investigation.

  16. Smart interfacial bonding alloys

    SciTech Connect

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

    1999-04-01

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

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

    SciTech Connect

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

    2014-10-01

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

  18. Optical techniques for determining dynamic material properties

    SciTech Connect

    Paisley, D.L.; Stahl, D.B.

    1996-12-31

    Miniature plates are laser-launched with a 10-Joule Nd:YAG for one-dimensional (1-D) impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter x 50 micron thick) and targets (10 mm diameter x 200 micron thick), 1-D impact experiments can be performed in a standard laser-optical laboratory with minimum confinement and collateral damage. The laser-launched plates do not require the traditional sabot on gas guns nor the explosives needed for explosive planewave lenses, and as a result are much more amenable to a wide variety of materials and applications. Because of the small size very high pressure gradients can be generated with relative ease. The high pressure gradients result in very high strains and strain rates that are not easily generated by other experimental methods. The small size and short shock duration (1 - 20 ns) are ideal for dynamically measuring bond strengths of micron-thick coatings. Experimental techniques, equipment, and dynamic material results are reported.

  19. Interfacial band configuration and electrical properties of LaAlO3/Al2O3/hydrogenated-diamond metal-oxide-semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Liu, J. W.; Liao, M. Y.; Imura, M.; Oosato, H.; Watanabe, E.; Tanaka, A.; Iwai, H.; Koide, Y.

    2013-08-01

    In order to search a gate dielectric with high permittivity on hydrogenated-diamond (H-diamond), LaAlO3 films with thin Al2O3 buffer layers are fabricated on the H-diamond epilayers by sputtering-deposition (SD) and atomic layer deposition (ALD) techniques, respectively. Interfacial band configuration and electrical properties of the SD-LaAlO3/ALD-Al2O3/H-diamond metal-oxide-semiconductor field effect transistors (MOSFETs) with gate lengths of 10, 20, and 30 μm have been investigated. The valence and conduction band offsets of the SD-LaAlO3/ALD-Al2O3 structure are measured by X-ray photoelectron spectroscopy to be 1.1 ± 0.2 and 1.6 ± 0.2 eV, respectively. The valence band discontinuity between H-diamond and LaAlO3 is evaluated to be 4.0 ± 0.2 eV, showing that the MOS structure acts as the gate which controls a hole carrier density. The leakage current density of the SD-LaAlO3/ALD-Al2O3/H-diamond MOS diode is smaller than 10-8 A cm-2 at gate bias from -4 to 2 V. The capacitance-voltage curve in the depletion mode shows sharp dependence, small flat band voltage, and small hysteresis shift, which implies low positive and trapped charge densities. The MOSFETs show p-type channel and complete normally off characteristics with threshold voltages changing from -3.6 ± 0.1 to -5.0 ± 0.1 V dependent on the gate length. The drain current maximum and the extrinsic transconductance of the MOSFET with gate length of 10 μm are -7.5 mA mm-1 and 2.3 ± 0.1 mS mm-1, respectively. The enhancement mode SD-LaAlO3/ALD-Al2O3/H-diamond MOSFET is concluded to be suitable for the applications of high power and high frequency electrical devices.

  20. Interfacial band alignment and structural properties of nanoscale TiO{sub 2} thin films for integration with epitaxial crystallographic oriented germanium

    SciTech Connect

    Jain, N.; Zhu, Y.; Hudait, M. K.; Maurya, D.; Varghese, R.; Priya, S.

    2014-01-14

    We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO{sub 2}) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO{sub 2} thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO{sub 2} thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO{sub 2}/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 ± 0.02 eV was determined for the amorphous TiO{sub 2} thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO{sub 2}/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO{sub 2}/Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ΔE{sub V}(100) > ΔE{sub V}(111) > ΔE{sub V}(110) and a conduction band-offset relation of ΔE{sub C}(110) > ΔE{sub C}(111) > ΔE{sub C}(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO{sub 2} for potential high-κ dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.

  1. Clustering properties of dynamical dark energy models

    SciTech Connect

    Avelino, P. P.; Beca, L. M. G.; Martins, C. J. A. P.

    2008-05-15

    We provide a generic but physically clear discussion of the clustering properties of dark energy models. We explicitly show that in quintessence-type models the dark energy fluctuations, on scales smaller than the Hubble radius, are of the order of the perturbations to the Newtonian gravitational potential, hence necessarily small on cosmological scales. Moreover, comparable fluctuations are associated with different gauge choices. We also demonstrate that the often used homogeneous approximation is unrealistic, and that the so-called dark energy mutation is a trivial artifact of an effective, single fluid description. Finally, we discuss the particular case where the dark energy fluid is nonminimally coupled to dark matter.

  2. [Viscoelastic behaviour of inlay waxes. (Part 2) Physical and dynamic viscoelastic properties for binary mixtures of waxes (author's transl)].

    PubMed

    Katakura, N

    1981-01-01

    Binary mixtures of waxes added carnauba wax, beeswax or dammar to paraffin were investigated by measurements of X-ray diffraction, dilatometry, differential thermal analysis and dynamic viscoelasticity. The relationships between the viscoelastic behaviour and the physical properties of these waxes were discussed. Additions of carnauba wax to paraffin changed drastically viscoelastic properties of paraffin, that is, increased the dynamic modulus, G', and decreased the loss tangent, tan delta, in the region of higher temperatures including the crystal transition temperature region of paraffin. The possible explanation for this change of viscoelastic properties is that the presence of crystals of carnauba wax composed of longer chain molecules than that of paraffin rises interfacial interaction. The temperature dependence of viscoelastic properties for binary mixtures of paraffin and beeswax was approximately the same as that of paraffin. This is because paraffin and beeswax may form a sort of homogeneous phases. Additions of dammar to paraffin increased the elasticity of paraffin in the region of lower temperatures, but did not effected to change of G' and tan delta in the region of higher temperatures. Another effect of additions of dammar was to lower the thermal expansion of binary mixtures. PMID:6943233

  3. Dynamic and rheological properties of soft biological cell suspensions

    PubMed Central

    Yazdani, Alireza; Li, Xuejin

    2016-01-01

    Quantifying dynamic and rheological properties of suspensions of soft biological particles such as vesicles, capsules, and red blood cells (RBCs) is fundamentally important in computational biology and biomedical engineering. In this review, recent studies on dynamic and rheological behavior of soft biological cell suspensions by computer simulations are presented, considering both unbounded and confined shear flow. Furthermore, the hemodynamic and hemorheological characteristics of RBCs in diseases such as malaria and sickle cell anemia are highlighted. PMID:27540271

  4. Interfacial Slip in Polymer Blends with Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Jaber, Eihab; Gersappe, Dilip

    2010-03-01

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

  5. Interfacial Slip in Polymer Blends with Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Jaber, Eihab; Gersappe, Dilip

    2009-03-01

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

  6. Interfacial slip in polymer blends with nanoparticles

    NASA Astrophysics Data System (ADS)

    Ortiz, Joseph; Jaber, Eihab; Gersappe, Dilip

    2008-03-01

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

  7. Dynamical Properties of Collisionless Star Streams

    NASA Astrophysics Data System (ADS)

    Carlberg, R. G.

    2015-02-01

    A sufficiently extended satellite in the tidal field of a host galaxy loses mass to create nearly symmetric leading and trailing tidal streams. We study the case in which tidal heating drives mass loss from a low mass satellite. The stream effectively has two dynamical components, a common angular momentum core superposed with episodic pulses with a broader angular momentum distribution. The pulses appear as spurs on the stream, oscillating above and below the stream centerline, stretching and blurring in configuration space as they move away from the cluster. Low orbital eccentricity streams are smoother and have less differential motion than high eccentricity streams. The tail of a high eccentricity stream can develop a fan of particles that wraps around at apocenter in a shell feature. We show that scaling the essentially stationary action-angle variables with the cube root of the satellite mass allows a low mass satellite stream to accurately predict the features in the stream from a satellite a thousand times more massive. As a practical astrophysical application, we demonstrate that narrow gaps in a moderate eccentricity stream, such as GD-1, blur out to 50% contrast over approximately six radial periods. A high eccentricity stream, such as Pal 5, will blur small gaps in only two radial orbits as can be understood from the much larger dispersion of angular momentum in the stream.

  8. OPTICAL AND DYNAMIC PROPERTIES OF UNDOPED AND DOPED SEMICONDUCTOR NANOSTRUCTURES

    SciTech Connect

    Grant, C D; Zhang, J Z

    2007-09-28

    This chapter provides an overview of some recent research activities on the study of optical and dynamic properties of semiconductor nanomaterials. The emphasis is on unique aspects of these properties in nanostructures as compared to bulk materials. Linear, including absorption and luminescence, and nonlinear optical as well as dynamic properties of semiconductor nanoparticles are discussed with focus on their dependence on particle size, shape, and surface characteristics. Both doped and undoped semiconductor nanomaterials are highlighted and contrasted to illustrate the use of doping to effectively alter and probe nanomaterial properties. Some emerging applications of optical nanomaterials are discussed towards the end of the chapter, including solar energy conversion, optical sensing of chemicals and biochemicals, solid state lighting, photocatalysis, and photoelectrochemistry.

  9. Exchange bias mediated by interfacial nanoparticles (invited)

    SciTech Connect

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

    2015-05-07

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

  10. Emulsions for interfacial filtration.

    SciTech Connect

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

    2006-11-01

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

  11. Interfacial engineering of microstructured materials

    NASA Astrophysics Data System (ADS)

    Poda, Aimee

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

  12. Mass properties measurement system: Dynamics and statics measurements

    NASA Technical Reports Server (NTRS)

    Doty, Keith L.

    1993-01-01

    This report presents and interprets experimental data obtained from the Mass Properties Measurement System (MPMS). Statics measurements yield the center-of-gravity of an unknown mass and dynamics measurements yield its inertia matrix. Observations of the MPMS performance has lead us to specific design criteria and an understanding of MPMS limitations.

  13. Static and dynamic properties of supercooled water in small nanotubes.

    PubMed

    Khademi, Mahdi; Sahimi, Muhammad

    2016-07-14

    The static and dynamic properties of water in small silicon-carbide and carbon nanotubes have been studied over the temperature range 100 K-298 K, using extensive molecular dynamics simulations. The computed properties include the radial distribution function, the cage correlation function, the space-time autocorrelation function, the velocity autocorrelation function, and the self-diffusivity. They all indicate that, under the conditions that we study, water does not freeze in small nanotubes; the Stokes-Einstein relation breaks down, and the self-diffusivity exhibits a transition around 230 K, very close to 228 K, the temperature at which a fragile-to-strong dynamic crossover is supposed to happen. The cage correlation function C(t) decays according to a stretched-exponential function, C(t) ∼ exp[ - (t/τ)(β)], where τ is a relaxation time and β is a topological exponent. PMID:27421415

  14. Static and dynamic properties of supercooled water in small nanotubes

    NASA Astrophysics Data System (ADS)

    Khademi, Mahdi; Sahimi, Muhammad

    2016-07-01

    The static and dynamic properties of water in small silicon-carbide and carbon nanotubes have been studied over the temperature range 100 K-298 K, using extensive molecular dynamics simulations. The computed properties include the radial distribution function, the cage correlation function, the space-time autocorrelation function, the velocity autocorrelation function, and the self-diffusivity. They all indicate that, under the conditions that we study, water does not freeze in small nanotubes; the Stokes-Einstein relation breaks down, and the self-diffusivity exhibits a transition around 230 K, very close to 228 K, the temperature at which a fragile-to-strong dynamic crossover is supposed to happen. The cage correlation function C(t) decays according to a stretched-exponential function, C(t) ˜ exp[ - (t/τ)β], where τ is a relaxation time and β is a topological exponent.

  15. Evaluation of biological cell properties using dynamic indentation measurement.

    PubMed

    Cao, Guoxin; Chandra, Namas

    2010-02-01

    Viscoelastic mechanical properties of biological cells are commonly measured using atomic force microscope (AFM) dynamic indentation with spherical tips. A semiempirical analysis based on numerical simulation is built to determine the cell mechanical properties. It is shown that the existing analysis cannot reflect the accurate values of cell elastic/dynamic modulus due to the effects of substrate, indenter tip size, and cell size. Among these factors, substrate not only increases the true contact radius but also interferes the indentation stress field, which can cause the overestimation of cell moduli. Typically, the substrate effect is much stronger than the other two influences in cell indentation; and, thus, the cell modulii are usually overestimated. It is estimated that the moduli can be overestimated by as high as over 200% using the existing analysis. In order to obtain the accurate properties of cells, correction factors that account for these effects are required in the existing analysis. PMID:20365612

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

    PubMed

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

    2015-04-01

    In this work we study, by means of molecular dynamics simulations, the solid-liquid interface of NaCl under coexistence conditions. By analysing capillary waves, we obtain the stiffness for different orientations of the solid and calculate the interfacial free energy by expanding the dependency of the interfacial free energy with the solid orientation in terms of cubic harmonics. We obtain an average value for the solid-fluid interfacial free energy of 89 ± 6 mN m(-1) that is consistent with previous results based on the measure of nucleation free energy barriers [Valeriani et al., J. Chem. Phys. 122, 194501 (2005)]. We analyse the influence of the simulation setup on interfacial properties and find that facets prepared as an elongated rectangular stripe give the same results as those prepared as squares for all cases but the 111 face. For some crystal orientations, we observe at small wave-vectors a behaviour not consistent with capillary wave theory and show that this behavior does not depend on the simulation setup. PMID:25854257

  17. Particle-laden interfaces: direct calculation of interfacial stress from a discrete particle simulation of a pendant drop

    NASA Astrophysics Data System (ADS)

    Gu, Chuan; Botto, Lorenzo

    2015-11-01

    The adsorption of solid particles to fluid interfaces is exploited in several multiphase flow technologies, and plays a fundamental role in the dynamics of particle-laden drops. A fundamental question is how the particles modify the effective mechanical properties of the interface. Using a fast Eulerian-Lagrangian model for interfacial colloids, we have simulated a pendant drop whose surface is covered with spherical particles having short-range repulsion. The interface curvature induces non-uniform and anisotropic interfacial stresses, which we calculate by an interfacial extension of the Irving-Kirkwood formula. The isotropic component of this stress, related to the effective surface tension, is in good agreement with that calculated by fitting the drop shape to the Young-Laplace equation. The anisotropic component, related to the interfacial shear elasticity, is highly non uniform: small at the drop apex, significant along the drop sides. The reduction in surface tension can be substantial even below maximum surface packing. We illustrate this point by simulating phase-coarsening of a two-phase mixture in which the presence of interfacial particles ``freezes'' the coarsening process, for surface coverage well below maximum packing This work is supported by the EU through the Marie Curie Grant FLOWMAT (618335).

  18. Dynamic modulation of the transport properties of the LaAl O3/SrTi O3 interface using uniaxial strain

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Fang, Yue-Wen; Chan, Ngai Yui; Lo, Wing Chong; Li, Dan Feng; Duan, Chun-Gang; Ding, Feng; Dai, Ji Yan

    2016-06-01

    Among the interfacial transport modulations to the LaAl O3/SrTi O3 (LAO/STO) heterostructure, mechanical strain has been proven to be an effective approach by growing the LAO/STO films on different substrates with varying lattice mismatches to STO. However, this lattice-mismatch-induced strain effect is static and biaxial, hindering the study of the strain effect in a dynamic way. In this work we realize dynamic and uniaxial strain to the LAO/STO oxide heterostructure at low temperature, through mechanical coupling from a magnetostrictive template. This anisotropic strain results in symmetry breaking at the interface and induces further splitting of the electronic band structure and therefore produces different conductivities along the x and y in-plane directions. In particular, we observe that along the strained direction the interface conductivity decreases by up to 70 % under a tensile strain, while it increases by 6.8 % under a compressive strain at 2 K. Also, it is revealed that the modulation on the interfacial transport property can be anisotropic, i.e., the resistance changes differently when an excitation current is parallel or perpendicular to the strain direction. This approach of strain engineering provides another degree of freedom for control of transport properties of oxide heterostructures and opens an additional way to investigate strain effects in materials science.

  19. Effect of Pr Valence State on Interfacial Structure and Electrical Properties of Pr Oxide/PrON/Ge Gate Stack Structure

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    In this study, we investigated the valence state and chemical bonding state of Pr in a Pr oxide/PrON/Ge structure. We clarified the relationship between the valence state of Pr and the Pr oxide/Ge interfacial reaction using Pr oxide/Ge and Pr oxide/PrON/Ge samples. We found the formation of three Pr oxide phases in Pr oxide films; hexagonal Pr2O3 (h-Pr2O3) (Pr3+), cubic Pr2O3 (c-Pr2O3) (Pr3+), and c-PrO2 (Pr4+). We also investigated the effect of a nitride interlayer on the interfacial reaction in Pr oxide/Ge gate stacks. In a sample with a nitride interlayer (Pr oxide/PrON/Ge), metallic Pr-Pr bonds are also formed in the c-Pr2O3 film. After annealing in H2 ambient, the diffusion of Ge into Pr oxide is not observed in this sample. Pr-Pr bonds probably prevent the interfacial reaction and Ge oxide formation, considering that the oxygen chemical potential of this film is lower than that of a GeO2/Ge system. On the other hand, the rapid thermal oxidation (RTO) treatment terminates the O vacancies and defects in c-Pr2O3. As a result, c-PrO2 with tetravalent Pr is formed in the Pr oxide/PrON/Ge sample with RTO. In this sample, the leakage current density is effectively decreased in comparison with the sample without RTO. Hydrogen termination works effectively in Pr oxide/PrON/Ge samples with and without RTO, and we can achieve an interface state density of as low as 4 ×1011 eV-1·cm-2.

  20. Electrical properties and interfacial issues of high-k/Si MIS capacitors characterized by the thickness of Al2O3 interlayer

    NASA Astrophysics Data System (ADS)

    Wang, Xing; Liu, Hongxia; Fei, Chenxi; Zhao, Lu; Chen, Shupeng; Wang, Shulong

    2016-06-01

    A thin Al2O3 interlayer deposited between La2O3 layer and Si substrate was used to scavenge the interfacial layer (IL) by blocking the out-diffusion of substrate Si. Some advantages and disadvantages of this method were discussed in detail. Evident IL reduction corroborated by the transmission electron microscopy results suggested the feasibility of this method in IL scavenging. Significant improvements in oxygen vacancy and leakage current characteristics were achieved as the thickness of Al2O3 interlayer increase. Meanwhile, some disadvantages such as the degradations in interface trap and oxide trapped charge characteristics were also observed.

  1. Dynamic properties of elastomer cartridge specimens under a rotating load

    NASA Technical Reports Server (NTRS)

    Darlow, M. S.; Smalley, A. J.; Cunningham, R. E.

    1979-01-01

    This paper presents the results of a program of analysis and test to determine the dynamic properties of elastomer cartridges operating under a rotating load. These measured properties were compared to predictions based on results of unidirectional tests with the same elastomer material. The test method for the dynamic stiffness and damping measurements was essentially the same as the Base Excitation Resonant Mass Method. The primary difference is that the exciting force used for these most recent tests was exerted by rotating unbalance in a rotational test rig rather than a shake table. The specimens tested were: two rectangular cross-section, continuous ring cartridges of different cross-section and three cylindrical button cartridges of different button thickness. Tests were performed for strains from about 0.0001 to about 0.01 (double amplitude). Material properties and prediction equations determined from reciprocating tests were used to make numerical predictions of stiffness, damping, and loss coefficient for the test elements, with encouraging results. Strain was shown to be an important parameter in determining these dynamic properties, particularly damping and loss coefficient.

  2. Properties of Au-H2O nanofluids using molecular dynamics

    NASA Astrophysics Data System (ADS)

    Puliti, Gianluca

    Nanofluids belong to a new class of fluids with supposedly enhanced heat transfer performance. A broad spectrum of applications in science and engineering can potentially benefit from their use. However, the physical explanation for this enhancement, if it exists, is still lacking. The novelty of this work is in a fundamental, realistic, and comprehensive approach to the problem of understanding nanofluids through the use of molecular dynamics simulations with accurate potentials to effectively model realistic materials. Specifically, this study treats the case of a gold--water nanofluid at different particle volume fractions between 1% and 15% by volume. In order to understand more fundamental physical phenomena at the gold-water interface, water confined between gold nanolayers is also studied at different plate separations. Simulations make use of the Quantum Sutton--Chen (QSC) potential for Au--Au interactions, the Extended Simple Point-Charge (SPC/E) forcefield for H 2O--H2O interactions, and a modified Spohr potential for Au--H2O interactions. These potentials ensure that most of the physics is captured properly. For completeness, thermodynamics and transport properties will be discussed for all systems. It is interesting to note that while the thermodynamic properties of the mixture have been commonly used in the literature by assuming that the nanofluid is an ideal mixture, such assumption is found to be generally not correct. Our results of computed thermodymamic properties indicate that values are between 10% and 400% different than ideal mixture predictions. Nevertheless, several works in the nanofluids literature make extensive use of such relations in engineering analyses. The anisotropy induced by the gold-water interface, and its effects appear to be responsible for the disagreement. Transport properties, in particular shear viscosity, and thermal conductivity, are computed using novel equilibrium methods. Specifically, the present work adopts hybrid

  3. Structural and dynamical properties of hot dense matter by a Thomas-Fermi-Dirac molecular dynamics

    NASA Astrophysics Data System (ADS)

    Lambert, F.; Clérouin, J.; Mazevet, S.

    2006-09-01

    We use a model combining, in a consistent way, orbital-free density functional theory (OF-DFT) and molecular dynamics (MD), to compute the thermodynamical, structural and dynamical properties of Fe and Au plasmas at conditions relevant to astrophysics and inertial confinement fusion (ICF). The newly developed parallel numerical scheme presented here allows to propagate hundreds of particles and to obtain accurate transport properties. This allows us to investigate the validity of the commonly used one-component plasma (OCP) model in predicting the pair correlation, the diffusion and viscosity coefficients for these two high-temperature high-density plasmas.

  4. Interfacial instabilities in vibrated fluids

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  5. Relating Dynamic Properties to Atomic Structure in Metallic Glasses

    SciTech Connect

    Sheng, H.W.; Ma, E.; Kramer, Matthew J.

    2012-07-18

    Atomic packing in metallic glasses is not completely random but displays various degrees of structural ordering. While it is believed that local structures profoundly affect the properties of glasses, a fundamental understanding of the structure–property relationship has been lacking. In this article, we provide a microscopic picture to uncover the intricate interplay between structural defects and dynamic properties of metallic glasses, from the perspective of computational modeling. Computational methodologies for such realistic modeling are introduced. Exploiting the concept of quasi-equivalent cluster packing, we quantify the structural ordering of a prototype metallic glass during its formation process, with a new focus on geometric measures of subatomic “voids.” Atomic sites connected with the voids are found to be crucial in terms of understanding the dynamic, including vibrational and atomic transport, properties. Normal mode analysis is performed to reveal the structural origin of the anomalous boson peak (BP) in the vibration spectrum of the glass, and its correlation with atomic packing cavities. Through transition-state search on the energy landscape of the system, such structural disorder is found to be a facilitating factor for atomic diffusion, with diffusion energy barriers and diffusion pathways significantly varying with the degree of structural relaxation/ordering. The implications of structural defects for the mechanical properties of metallic glasses are also discussed.

  6. Photoluminescence properties and exciton dynamics in monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Yan, Tengfei; Qiao, Xiaofen; Liu, Xiaona; Tan, Pingheng; Zhang, Xinhui

    2014-09-01

    In this work, comprehensive temperature and excitation power dependent photoluminescence and time-resolved photoluminescence studies are carried out on monolayer WSe2 to reveal its properties of exciton emissions and related excitonic dynamics. Competitions between the localized and delocalized exciton emissions, as well as the exciton and trion emissions are observed, respectively. These competitions are suggested to be responsible for the abnormal temperature and excitation intensity dependent photoluminescence properties. The radiative lifetimes of both excitons and trions exhibit linear dependence on temperature within the temperature regime below 260 K, providing further evidence for two-dimensional nature of monolayer material.

  7. On the fundamental properties of dynamically hot galaxies

    NASA Astrophysics Data System (ADS)

    Kritsuk, Alexei G.

    1997-01-01

    A two-component isothermal equilibrium model is applied to reproduce basic structural properties of dynamically hot stellar systems immersed in their massive dark haloes. The origin of the fundamental plane relation for giant ellipticals is naturally explained as a consequence of dynamical equilibrium in the context of the model. The existence of two galactic families displaying different behaviour in the luminosity-surface-brightness diagram is shown to be a result of a smooth transition from dwarfs, dominated by dark matter near the centre, to giants dominated by the luminous stellar component. The comparison of empirical scaling relations with model predictions suggests that probably a unique dissipative process was operating during the violent stage of development of stellar systems in the dark haloes, and the depth of the potential well controlled the observed luminosity of the resulting galaxies. The interpretation also provides some restrictions on the properties of dark haloes implied by the fundamental scaling laws.

  8. Use of Mixed CH3-/HC(O)CH2CH2-Si(111) Functionality to Control Interfacial Chemical and Electronic Properties During the Atomic-Layer Deposition of Ultrathin Oxides on Si(111).

    PubMed

    O'Leary, Leslie E; Strandwitz, Nicholas C; Roske, Christopher W; Pyo, Suyeon; Brunschwig, Bruce S; Lewis, Nathan S

    2015-02-19

    Silicon surfaces terminated with a mixed monolayer containing both a propyl aldehyde functionality and methyl groups were prepared and used to control the interfacial chemical and electronic properties of Si(111) surfaces during atomic-layer deposition (ALD) of Al2O3 or MnO. Si(111) surfaces functionalized only with the aldehyde moiety exhibited surface recombination velocities, S, of 2500 ± 600 cm s(-1) whereas the mixed CH3-/HC(O)CH2CH2-Si(111) surfaces displayed S = 25 ± 7 cm s(-1). During the ALD growth of either Al2O3 or MnO, both the HC(O)CH2CH2-Si(111) and CH3-/HC(O)CH2CH2-Si(111) surfaces produced increased metal oxide deposition at low cycle number, relative to H-Si(111) or CH3-Si(111) surfaces. As detected by X-ray photoelectron spectroscopy after the ALD process, the CH3- and mixed CH3-/HC(O)CH2CH2- functionalized Si(111) surfaces exhibited less interfacial SiOx than was observed for ALD of metal oxides on H-Si(111) substrates. PMID:26262493

  9. Iridium Interfacial Stack (IRIS)

    NASA Technical Reports Server (NTRS)

    Spry, David James (Inventor)

    2015-01-01

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

  10. Interfacial behavior of asphaltenes.

    PubMed

    Langevin, Dominique; Argillier, Jean-François

    2016-07-01

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

  11. Information for Coarticulation: Static Signal Properties or Formant Dynamics?

    PubMed Central

    Viswanathan, Navin; Magnuson, James S.; Fowler, Carol A.

    2014-01-01

    Perception of a speech segment changes depending on properties of surrounding segments in a phenomenon called compensation for coarticulation (Mann, 1980). The nature of information that drives these perceptual changes is a matter of debate. One account attributes perceptual shifts to low-level auditory system contrast effects based on static portions of the signal (e.g., third formant [F3] center or average frequency; Lotto & Kluender, 1998). An alternative account is that listeners' perceptual shifts result from listeners attuning to the acoustic effects of gestural overlap and that this information for coarticulation is necessarily dynamic (Fowler, 2006). In a pair of experiments, we used sinewave speech precursors to investigate the nature of information for compensation for coarticulation. In Experiment 1, as expected by both accounts, we found that sinewave speech precursors produce shifts in following segments. In Experiment 2, we investigated whether effects in Experiment 1 were driven by static F3 offsets of sinewave speech precursors, or by dynamic relationships among their formants. We temporally reversed F1 and F2 in sinewave precursors, preserving static F3 offset and average F1, F2, and F3 frequencies, but disrupting dynamic formant relationships. Despite having identical F3s, selectively-reversed precursors produced effects that were significantly smaller and restricted to only a small portion of the continuum. We conclude that dynamic formant relations rather than static properties of the precursor provide information for compensation for coarticulation. PMID:24730744

  12. Information for coarticulation: Static signal properties or formant dynamics?

    PubMed

    Viswanathan, Navin; Magnuson, James S; Fowler, Carol A

    2014-06-01

    Perception of a speech segment changes depending on properties of surrounding segments in a phenomenon called compensation for coarticulation (Mann, 1980). The nature of information that drives these perceptual changes is a matter of debate. One account attributes perceptual shifts to low-level auditory system contrast effects based on static portions of the signal (e.g., third formant [F3] center or average frequency; Lotto & Kluender, 1998). An alternative account is that listeners' perceptual shifts result from listeners attuning to the acoustic effects of gestural overlap and that this information for coarticulation is necessarily dynamic (Fowler, 2006). In a pair of experiments, we used sinewave speech precursors to investigate the nature of information for compensation for coarticulation. In Experiment 1, as expected by both accounts, we found that sinewave speech precursors produce shifts in following segments. In Experiment 2, we investigated whether effects in Experiment 1 were driven by static F3 offsets of sinewave speech precursors, or by dynamic relationships among their formants. We temporally reversed F1 and F2 in sinewave precursors, preserving static F3 offset and average F1, F2 and F3 frequencies, but disrupting dynamic formant relationships. Despite having identical F3s, selectively reversed precursors produced effects that were significantly smaller and restricted to only a small portion of the continuum. We conclude that dynamic formant relations rather than static properties of the precursor provide information for compensation for coarticulation. PMID:24730744

  13. Dynamic and mechanical properties of supported lipid bilayers.

    PubMed

    Wu, Hsing-Lun; Tsao, Heng-Kwong; Sheng, Yu-Jane

    2016-04-21

    Supported lipid bilayers (SLBs) offer an excellent model system for investigating the physico-chemical properties of the cell membrane. In this work, dynamic and mechanical properties of SLBs are explored by dissipative particle dynamics simulations for lipids with different architectures (chain length, kink, and asymmetry associated with lipid tails). It is found that the lateral diffusivity (Dx) and flip-flop rate (FF) grow with increasing temperature in both gel and liquid phases and can be described by an Arrhenius-like expression. Three regimes can be clearly identified for symmetric and asymmetric saturated lipids but only two regimes are observed for kinked lipids. Both Dx and FF grow with decreasing tail length and increasing number of kinks. The stretching (KA) and apparent bending (KB) moduli exhibit concave upward curves with temperature and the minima are attained at Tm. In general, the minima of KA and KB decrease with the chain length and increase with number of kinks. The typical relation among the bending modulus, area stretching modulus, and bilayer thickness is still followed, KB = βKAh(2) and β is much smaller in the gel phase. The dynamic and mechanical properties of lipids with asymmetric tails are found to situate between their symmetric counterparts. PMID:27389237

  14. Dynamic and mechanical properties of supported lipid bilayers

    NASA Astrophysics Data System (ADS)

    Wu, Hsing-Lun; Tsao, Heng-Kwong; Sheng, Yu-Jane

    2016-04-01

    Supported lipid bilayers (SLBs) offer an excellent model system for investigating the physico-chemical properties of the cell membrane. In this work, dynamic and mechanical properties of SLBs are explored by dissipative particle dynamics simulations for lipids with different architectures (chain length, kink, and asymmetry associated with lipid tails). It is found that the lateral diffusivity (Dx) and flip-flop rate (FF) grow with increasing temperature in both gel and liquid phases and can be described by an Arrhenius-like expression. Three regimes can be clearly identified for symmetric and asymmetric saturated lipids but only two regimes are observed for kinked lipids. Both Dx and FF grow with decreasing tail length and increasing number of kinks. The stretching (KA) and apparent bending (KB) moduli exhibit concave upward curves with temperature and the minima are attained at Tm. In general, the minima of KA and KB decrease with the chain length and increase with number of kinks. The typical relation among the bending modulus, area stretching modulus, and bilayer thickness is still followed, KB = βKAh2 and β is much smaller in the gel phase. The dynamic and mechanical properties of lipids with asymmetric tails are found to situate between their symmetric counterparts.

  15. Interfacial adhesion - Theory and experiment

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  16. Interfacial adhesion: Theory and experiment

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    SciTech Connect

    STEVENS,MARK J.

    2000-03-23

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

  18. Graph Theoretic Foundations of Multibody Dynamics Part I: Structural Properties.

    PubMed

    Jain, Abhinandan

    2011-06-21

    This is the first part of two papers that use concepts from graph theory to obtain a deeper understanding of the mathematical foundations of multibody dynamics. The key contribution is the development of a unifying framework that shows that key analytical results and computational algorithms in multibody dynamics are a direct consequence of structural properties and require minimal assumptions about the specific nature of the underlying multibody system. This first part focuses on identifying the abstract graph theoretic structural properties of spatial operator techniques in multibody dynamics. The second part paper exploits these structural properties to develop a broad spectrum of analytical results and computational algorithms.Towards this, we begin with the notion of graph adjacency matrices and generalize it to define block-weighted adjacency (BWA) matrices and their 1-resolvents. Previously developed spatial operators are shown to be special cases of such BWA matrices and their 1-resolvents. These properties are shown to hold broadly for serial and tree topology multibody systems. Specializations of the BWA and 1-resolvent matrices are referred to as spatial kernel operators (SKO) and spatial propagation operators (SPO). These operators and their special properties provide the foundation for the analytical and algorithmic techniques developed in the companion paper.We also use the graph theory concepts to study the topology induced sparsity structure of these operators and the system mass matrix. Similarity transformations of these operators are also studied. While the detailed development is done for the case of rigid-link multibody systems, the extension of these techniques to a broader class of systems (e.g. deformable links) are illustrated. PMID:22102790

  19. Viscoelastic properties of a spinal posterior dynamic stabilisation device.

    PubMed

    Lawless, Bernard M; Barnes, Spencer C; Espino, Daniel M; Shepherd, Duncan E T

    2016-06-01

    The purpose of this study was to quantify the frequency dependent viscoelastic properties of two types of spinal posterior dynamic stabilisation devices. In air at 37°C, the viscoelastic properties of six BDyn 1 level, six BDyn 2 level posterior dynamic stabilisation devices (S14 Implants, Pessac, France) and its elastomeric components (polycarbonate urethane and silicone) were measured using Dynamic Mechanical Analysis. The viscoelastic properties were measured over the frequency range 0.01-30Hz. The BDyn devices and its components were viscoelastic throughout the frequency range tested. The mean storage stiffness and mean loss stiffness of the BDyn 1 level device, BDyn 2 level device, silicone component and polycarbonate urethane component all presented a logarithmic relationship with respect to frequency. The storage stiffness of the BDyn 1 level device ranged from 95.56N/mm to 119.29N/mm, while the BDyn 2 level storage stiffness ranged from 39.41N/mm to 42.82N/mm. BDyn 1 level device and BDyn 2 level device loss stiffness ranged from 10.72N/mm to 23.42N/mm and 4.26N/mm to 9.57N/mm, respectively. No resonant frequencies were recorded for the devices or its components. The elastic property of BDyn 1 level device is influenced by the PCU and silicone components, in the physiological frequency range. The viscoelastic properties calculated in this study may be compared to spinal devices and spinal structures. PMID:27018832

  20. Effect of temperature on structural and dynamic properties of liquid silver - A study in molecular dynamics

    NASA Astrophysics Data System (ADS)

    Banuelos, E. U.; Amarillas, A. P.

    2004-02-01

    In this work we studied the temperature-induced changes in the structural and dynamical properties of liquid Ag using molecular dynamics (DM) computer simulation. The atomic interactions are modeled through a semiempirical potential function which incorporates n-body effects and is based on the second moments approximation of the density of states of a tight-binding Hamiltonian. The caloric curve was used to calculate the latent heat of fusion and the pair distribution function, g(r), was calculated from a set of atomic configurations collected at several time-steps. The dynamical properties are studied through the velocity autocorrelation function and the mean-square displacement. The self-diffusion coefficient and its behavior with the temperature, obtained from our simulations, shows the typical behavior of the simple liquids. Our results are compared to available experimental data.

  1. Investigation of the interfacial condition between bioceramic coatings and metallic substrates using guided waves

    NASA Astrophysics Data System (ADS)

    Saffari, Nader; Ong, Chuon-Szen

    2001-04-01

    The work reported here is on the characterization of the interfacial properties between plasma-sprayed Hydroxyapatite coatings on titanium substrates as used in cement-less hip orthopaedic implants. The phase velocity dispersion for the first Rayleigh-type mode for the coating-substrate system has been shown to be sensitive to the interfacial stiffness. Different interfacial conditions between the coating and substrate have been obtained by cyclic loading of the specimens in a four-point bend fatigue machine. The measured interfacial stiffness is then correlated with the interfacial fracture strength obtained by standard destructive shear tests.

  2. Estimating the biophysical properties of neurons with intracellular calcium dynamics

    NASA Astrophysics Data System (ADS)

    Ye, Jingxin; Rozdeba, Paul J.; Morone, Uriel I.; Daou, Arij; Abarbanel, Henry D. I.

    2014-06-01

    We investigate the dynamics of a conductance-based neuron model coupled to a model of intracellular calcium uptake and release by the endoplasmic reticulum. The intracellular calcium dynamics occur on a time scale that is orders of magnitude slower than voltage spiking behavior. Coupling these mechanisms sets the stage for the appearance of chaotic dynamics, which we observe within certain ranges of model parameter values. We then explore the question of whether one can, using observed voltage data alone, estimate the states and parameters of the voltage plus calcium (V+Ca) dynamics model. We find the answer is negative. Indeed, we show that voltage plus another observed quantity must be known to allow the estimation to be accurate. We show that observing both the voltage time course V (t) and the intracellular Ca time course will permit accurate estimation, and from the estimated model state, accurate prediction after observations are completed. This sets the stage for how one will be able to use a more detailed model of V+Ca dynamics in neuron activity in the analysis of experimental data on individual neurons as well as functional networks in which the nodes (neurons) have these biophysical properties.

  3. Dynamic properties influence the perception of facial expressions.

    PubMed

    Kamachi, Miyuki; Bruce, Vicki; Mukaida, Shigeru; Gyoba, Jiro; Yoshikawa, Sakiko; Akamatsu, Shigeru

    2013-01-01

    Two experiments were conducted to investigate the role played by dynamic information in identifying facial expressions of emotion. Dynamic expression sequences were created by generating and displaying morph sequences which changed the face from neutral to a peak expression in different numbers of intervening intermediate stages, to create fast (6 frames), medium (26 frames), and slow (101 frames) sequences. In experiment 1, participants were asked to describe what the person shown in each sequence was feeling. Sadness was more accurately identified when slow sequences were shown. Happiness, and to some extent surprise, was better from faster sequences, while anger was most accurately detected from the sequences of medium pace. In experiment 2 we used an intensity-rating task and static images as well as dynamic ones to examine whether effects were due to total time of the displays or to the speed of sequence. Accuracies of expression judgments were derived from the rated intensities and the results were similar to those of experiment 1 for angry and sad expressions (surprised and happy were close to ceiling). Moreover, the effect of display time was found only for dynamic expressions and not for static ones, suggesting that it was speed, not time, which was responsible for these effects. These results suggest that representations of basic expressions of emotion encode information about dynamic as well as static properties. PMID:24601038

  4. Anisotropy of the solid–liquid interface properties of the Ni–Zr B33 phase from molecular dynamics simulation

    SciTech Connect

    Wilson, S. R.; Mendelev, M. I.

    2015-01-08

    Solid–liquid interface (SLI) properties of the Ni–Zr B33 phase were determined from molecular dynamics simulations. In order to perform these measurements, a new semi-empirical potential for Ni–Zr alloy was developed that well reproduces the material properties required to model SLIs in the Ni50.0Zr50.0 alloy. In particular, the developed potential is shown to provide that the solid phase emerging from the liquid Ni50.0Zr50.0alloy is B33 (apart from a small fraction of point defects), in agreement with the experimental phase diagram. The SLI properties obtained using the developed potential exhibit an extraordinary degree of anisotropy. It is observed that anisotropies in both the interfacial free energy and mobility are an order of magnitude larger than those measured to date in any other metallic compound. Moreover, the [0 1 0] interface is shown to play a significant role in the observed anisotropy. Our data suggest that the [0 1 0] interface simultaneously corresponds to the lowest mobility, the lowest free energy and the highest stiffness of all inclinations in B33 Ni–Zr. This finding can be understood by taking into account a rather complicated crystal structure in this crystallographic direction.

  5. Anisotropy of the solid–liquid interface properties of the Ni–Zr B33 phase from molecular dynamics simulation

    DOE PAGESBeta

    Wilson, S. R.; Mendelev, M. I.

    2015-01-08

    Solid–liquid interface (SLI) properties of the Ni–Zr B33 phase were determined from molecular dynamics simulations. In order to perform these measurements, a new semi-empirical potential for Ni–Zr alloy was developed that well reproduces the material properties required to model SLIs in the Ni50.0Zr50.0 alloy. In particular, the developed potential is shown to provide that the solid phase emerging from the liquid Ni50.0Zr50.0alloy is B33 (apart from a small fraction of point defects), in agreement with the experimental phase diagram. The SLI properties obtained using the developed potential exhibit an extraordinary degree of anisotropy. It is observed that anisotropies in bothmore » the interfacial free energy and mobility are an order of magnitude larger than those measured to date in any other metallic compound. Moreover, the [0 1 0] interface is shown to play a significant role in the observed anisotropy. Our data suggest that the [0 1 0] interface simultaneously corresponds to the lowest mobility, the lowest free energy and the highest stiffness of all inclinations in B33 Ni–Zr. This finding can be understood by taking into account a rather complicated crystal structure in this crystallographic direction.« less

  6. Reservoir Computing Properties of Neural Dynamics in Prefrontal Cortex

    PubMed Central

    Procyk, Emmanuel; Dominey, Peter Ford

    2016-01-01

    Primates display a remarkable ability to adapt to novel situations. Determining what is most pertinent in these situations is not always possible based only on the current sensory inputs, and often also depends on recent inputs and behavioral outputs that contribute to internal states. Thus, one can ask how cortical dynamics generate representations of these complex situations. It has been observed that mixed selectivity in cortical neurons contributes to represent diverse situations defined by a combination of the current stimuli, and that mixed selectivity is readily obtained in randomly connected recurrent networks. In this context, these reservoir networks reproduce the highly recurrent nature of local cortical connectivity. Recombining present and past inputs, random recurrent networks from the reservoir computing framework generate mixed selectivity which provides pre-coded representations of an essentially universal set of contexts. These representations can then be selectively amplified through learning to solve the task at hand. We thus explored their representational power and dynamical properties after training a reservoir to perform a complex cognitive task initially developed for monkeys. The reservoir model inherently displayed a dynamic form of mixed selectivity, key to the representation of the behavioral context over time. The pre-coded representation of context was amplified by training a feedback neuron to explicitly represent this context, thereby reproducing the effect of learning and allowing the model to perform more robustly. This second version of the model demonstrates how a hybrid dynamical regime combining spatio-temporal processing of reservoirs, and input driven attracting dynamics generated by the feedback neuron, can be used to solve a complex cognitive task. We compared reservoir activity to neural activity of dorsal anterior cingulate cortex of monkeys which revealed similar network dynamics. We argue that reservoir computing is a

  7. Electrical and physicochemical properties of atomic-layer-deposited HfO2 film on Si substrate with interfacial layer grown by nitric acid oxidation

    NASA Astrophysics Data System (ADS)

    Kim, Seung Hyun; Seok, Tae Jun; Jin, Hyun Soo; Kim, Woo-Byoung; Park, Tae Joo

    2016-03-01

    The ultrathin SiO2 interfacial layer (IL) was adopted at the interface between atomic-layer-deposited HfO2 gate dielectric film and a Si substrate, which was grown using nitric acid oxidation (NAO) and O3 oxidation (OZO) prior to HfO2 film deposition. X-ray photoelectron spectroscopy result revealed that Si diffusion from the substrate into the film was suppressed for the film with NAO compared to that with OZO, which was attributed to the higher physical density of IL. The electrical measurement using metal-insulator-semiconductor devices showed that the film with NAO exhibited higher effective permittivity and lower densities of fixed charge and slow state at the interface. Furthermore, the leakage current density at an equivalent electrical thickness was lower for the film with NAO than OZO.

  8. Effects of plasma surface modification on interfacial behaviors and mechanical properties of carbon nanotube-Al{sub 2}O{sub 3} nanocomposites

    SciTech Connect

    Guo Yan; Cho, Hoonsung; Shi Donglu; Lian Jie; Song Yi; Abot, Jandro; Poudel, Bed; Ren Zhifeng; Wang Lumin; Ewing, Rodney C.

    2007-12-24

    The effects of plasma surface modification on interfacial behaviors in carbon nanotube (CNT) reinforced alumina (Al{sub 2}O{sub 3}) nanocomposites were studied. A unique plasma polymerization method was used to modify the surfaces of CNTs and Al{sub 2}O{sub 3} nanoparticles. The CNT-Al{sub 2}O{sub 3} nanocomposites were processed by both ambient pressure and hot-press sintering. The electron microscopy results showed ultrathin polymer coating on the surfaces of CNTs and Al{sub 2}O{sub 3} nanoparticles. A distinctive stress-strain curve difference related to the structural interfaces and plasma coating was observed from the nanocomposites. The mechanical performance and thermal stability of CNT-Al{sub 2}O{sub 3} nanocomposites were found to be significantly enhanced by the plasma-polymerized coating.

  9. The Evolving Properties of Water in a Dynamic Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Ciesla, Fred

    2015-08-01

    Protoplanetary disks are dynamic objects, through which mass and angular momentum are transported as part of the final stages of pre-main sequence evolution of their central stars. These disks are also rich chemical factories, in which materials inherited from the interstellar medium are transformed through a series of reactions (involving, gases, solids, ions, and photons) to the eventual building blocks of the planets.The chemical and physical evolution of a protoplanetary disk are intimately connected. Both solids and gases are subjected to large-scale motions associated with disk evolution and diffusion within the gas. Solids also settle toward the disk midplane and migrate inwards due to gravity and gas drag. This dynamical evolution exposes primitive materials to a range of physical conditions (pressure, temperature, radiation environment) within the disk. It is the integrated effects of these environments that define the physical and chemical properties of a solid grain prior to its incorporation into a planetesimal or planet.Water serves as an interesting tracer of this evolution, as it would be processed in a variety of ways within a protoplanetary disk. I will discuss new methods that allow us to trace the dynamical movement of water vapor and ice throughout the lifetime of a protoplanetary disk and to determine the physical environments to which the water would be exposed. In particular, I will show how the early evolution of a protoplanetary disk impacts the D/H ratio of the water inherited by planetary materials. I will also explore how photodesorption of water by UV photons can lead to the formation of amorphous ice and thus the trapping of noble gases and other volatiles at levels that are much greater than predicted by equilibrium chemistry models. These effects combine to lead to constantly evolving properties of water during the early stages of planet formation. I will also discuss how the observed properties of Solar System bodies constrain these

  10. Inferring Network Dynamics and Neuron Properties from Population Recordings

    PubMed Central

    Linaro, Daniele; Storace, Marco; Mattia, Maurizio

    2011-01-01

    Understanding the computational capabilities of the nervous system means to “identify” its emergent multiscale dynamics. For this purpose, we propose a novel model-driven identification procedure and apply it to sparsely connected populations of excitatory integrate-and-fire neurons with spike frequency adaptation (SFA). Our method does not characterize the system from its microscopic elements in a bottom-up fashion, and does not resort to any linearization. We investigate networks as a whole, inferring their properties from the response dynamics of the instantaneous discharge rate to brief and aspecific supra-threshold stimulations. While several available methods assume generic expressions for the system as a black box, we adopt a mean-field theory for the evolution of the network transparently parameterized by identified elements (such as dynamic timescales), which are in turn non-trivially related to single-neuron properties. In particular, from the elicited transient responses, the input–output gain function of the neurons in the network is extracted and direct links to the microscopic level are made available: indeed, we show how to extract the decay time constant of the SFA, the absolute refractory period and the average synaptic efficacy. In addition and contrary to previous attempts, our method captures the system dynamics across bifurcations separating qualitatively different dynamical regimes. The robustness and the generality of the methodology is tested on controlled simulations, reporting a good agreement between theoretically expected and identified values. The assumptions behind the underlying theoretical framework make the method readily applicable to biological preparations like cultured neuron networks and in vitro brain slices. PMID:22016731

  11. Comparison of interfacial and electrical properties between Al2O3 and ZnO as interface passivation layer of GaAs MOS device with HfTiO gate dielectric

    NASA Astrophysics Data System (ADS)

    Shuyan, Zhu; Jingping, Xu; Lisheng, Wang; Yuan, Huang; Wing Man, Tang

    2015-03-01

    GaAs metal-oxide-semiconductor (MOS) capacitors with HfTiO as the gate dielectric and Al2O3 or ZnO as the interface passivation layer (IPL) are fabricated. X-ray photoelectron spectroscopy reveals that the Al2O3 IPL is more effective in suppressing the formation of native oxides and As diffusion than the ZnO IPL. Consequently, experimental results show that the device with Al2O3 IPL exhibits better interfacial and electrical properties than the device with ZnO IPL: lower interface-state density (7.2 × 1012 eV-1 cm-2), lower leakage current density (3.60 × 10-7 A/cm2 at Vg = 1 V) and good C-V behavior. Project supported by the National Natural Science Foundation of China (Nos. 61176100, 61274112).

  12. Stochastic dynamics of penetrable rods in one dimension: Entangled dynamics and transport properties.

    PubMed

    Craven, Galen T; Popov, Alexander V; Hernandez, Rigoberto

    2015-04-21

    The dynamical properties of a system of soft rods governed by stochastic hard collisions (SHCs) have been determined over a varying range of softness using molecular dynamics simulations in one dimension and analytic theory. The SHC model allows for interpenetration of the system's constituent particles in the simulations, generating overlapping clustering behavior analogous to the spatial structures observed in systems governed by deterministic bounded potentials. Through variation of an assigned softness parameter δ, the limiting ranges of intermolecular softness are bridged, connecting the limiting ensemble behavior from hard to ideal (completely soft). Various dynamical and structural observables are measured from simulation and compared to developed theoretical values. The spatial properties are found to be well predicted by theories developed for the deterministic penetrable-sphere model with a transformation from energetic to probabilistic arguments. While the overlapping spatial structures are complex, the dynamical properties can be adequately approximated through a theory built on impulsive interactions with Enskog corrections. Our theory suggests that as the softness of interaction is varied toward the ideal limit, correlated collision processes are less important to the energy transfer mechanism, and Markovian processes dominate the evolution of the configuration space ensemble. For interaction softness close to hard limit, collision processes are highly correlated and overlapping spatial configurations give rise to entanglement of single-particle trajectories. PMID:25903909

  13. Stochastic dynamics of penetrable rods in one dimension: Entangled dynamics and transport properties

    SciTech Connect

    Craven, Galen T.; Popov, Alexander V.; Hernandez, Rigoberto

    2015-04-21

    The dynamical properties of a system of soft rods governed by stochastic hard collisions (SHCs) have been determined over a varying range of softness using molecular dynamics simulations in one dimension and analytic theory. The SHC model allows for interpenetration of the system’s constituent particles in the simulations, generating overlapping clustering behavior analogous to the spatial structures observed in systems governed by deterministic bounded potentials. Through variation of an assigned softness parameter δ, the limiting ranges of intermolecular softness are bridged, connecting the limiting ensemble behavior from hard to ideal (completely soft). Various dynamical and structural observables are measured from simulation and compared to developed theoretical values. The spatial properties are found to be well predicted by theories developed for the deterministic penetrable-sphere model with a transformation from energetic to probabilistic arguments. While the overlapping spatial structures are complex, the dynamical properties can be adequately approximated through a theory built on impulsive interactions with Enskog corrections. Our theory suggests that as the softness of interaction is varied toward the ideal limit, correlated collision processes are less important to the energy transfer mechanism, and Markovian processes dominate the evolution of the configuration space ensemble. For interaction softness close to hard limit, collision processes are highly correlated and overlapping spatial configurations give rise to entanglement of single-particle trajectories.

  14. The number comb for a soil physical properties dynamic measurement

    NASA Astrophysics Data System (ADS)

    Olechko, K.; Patiño, P.; Tarquis, A. M.

    2012-04-01

    We propose the prime numbers distribution extracted from the soil digital multiscale images and some physical properties time series as the precise indicator of the spatial and temporal dynamics under soil management changes. With this new indicator the soil dynamics can be studied as a critical phenomenon where each phase transition is estimated and modeled by the graph partitioning induced phase transition. The critical point of prime numbers distribution was correlated with the beginning of Andosols, Vertisols and saline soils physical degradation under the unsustainable soil management in Michoacan, Guanajuato and Veracruz States of Mexico. The data banks corresponding to the long time periods (between 10 and 28 years) were statistically compared by RISK 5.0 software and our own algorithms. Our approach makes us able to distill free-form natural laws of soils physical properties dynamics directly from the experimental data. The Richter (1987) and Schmidt and Lipson (2009) original approaches were very useful to design the algorithms to identify Hamiltonians, Lagrangians and other laws of geometric and momentum conservation especially for erosion case.

  15. Optical properties of X-rays--dynamical diffraction.

    PubMed

    Authier, André

    2012-01-01

    The first attempts at measuring the optical properties of X-rays such as refraction, reflection and diffraction are described. The main ideas forming the basis of Ewald's thesis in 1912 are then summarized. The first extension of Ewald's thesis to the X-ray case is the introduction of the reciprocal lattice. In the next step, the principles of the three versions of the dynamical theory of diffraction, by Darwin, Ewald and Laue, are given. It is shown how the comparison of the dynamical and geometrical theories of diffraction led Darwin to propose his extinction theory. The main optical properties of X-ray wavefields at the Bragg incidence are then reviewed: Pendellösung, shift of the Bragg peak, fine structure of Kossel lines, standing waves, anomalous absorption, paths of wavefields inside the crystal, Borrmann fan and double refraction. Lastly, some of the modern applications of the dynamical theory are briefly outlined: X-ray topography, location of adsorbed atoms at crystal surfaces, optical devices for synchrotron radiation and X-ray interferometry. PMID:22186282

  16. Interfacial behaviours of smart composites

    NASA Astrophysics Data System (ADS)

    Poon, Chi-Kin

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

  17. Interfacial chemistry and structure in ceramic composites

    SciTech Connect

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

    1990-09-01

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

  18. Intrinsic interfacial phenomena in manganite heterostructures

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  19. Dynamics of hydraulic properties due to biological clogging

    NASA Astrophysics Data System (ADS)

    Rosenzweig, R.; Shavit, U.; Furman, A.

    2012-04-01

    Classic treatment of soil-water flow is described by the unsaturated version of Darcy's law and Richards' equation, assuming time invariant hydraulic properties, e.g. the saturated hydraulic conductivity, Ks, and van Genuchten-Mualem's α and n. However, when bacteria is present the soil is quite far from being time invariant and biological activity constantly alters the pore-scale structure, leading to macro-scale alteration of the hydraulic properties. This may be of high relevance to processes such as subsurface bioremediation, soil aquifer treatment, wastewater irrigation, and more. In this work we explore the dynamic alteration of soil hydraulic properties by a combination of column experiments and pore-network modeling. We experimentally demonstrate how biological activity clogs an unsaturated soil column and reduces its hydraulic conductivity, while a similar column where biological activity is limited does not clog. Further, we demonstrate that the clogging is preferential to the nutrient input. Next, we develop a pore-network model that uses triangular shape channels. This allows a dual occupancy (water-air) of each channel and high connectivity. The model solves the flow of water, nutrient transport, and biological dynamics. It includes biofilm growth and decay, attachment and detachment, and nutrient exchange between the water and biofilm phases. We perform a sensitivity analysis of the model and qualitatively show through the loss of connectivity how the clogging that was observed in our experiment can be explained.

  20. Locomotion as an emergent property of muscle contractile dynamics.

    PubMed

    Biewener, Andrew A

    2016-01-01

    Skeletal muscles share many common, highly conserved features of organization at the molecular and myofilament levels, giving skeletal muscle fibers generally similar and characteristic mechanical and energetic properties; properties well described by classical studies of muscle mechanics and energetics. However, skeletal muscles can differ considerably in architectural design (fiber length, pinnation, and connective tissue organization), as well as fiber type, and how they contract in relation to the timing of neuromotor activation and in vivo length change. The in vivo dynamics of muscle contraction is, therefore, crucial to assessing muscle design and the roles that muscles play in animal movement. Architectural differences in muscle-tendon organization combined with differences in the phase of activation and resulting fiber length changes greatly affect the time-varying force and work that muscles produce, as well as the energetic cost of force generation. Intrinsic force-length and force-velocity properties of muscles, together with their architecture, also play important roles in the control of movement, facilitating rapid adjustments to changing motor demands. Such adjustments complement slower, reflex-mediated neural feedback control of motor recruitment. Understanding how individual fiber forces are integrated to whole-muscle forces, which are transmitted to the skeleton for producing and controlling locomotor movement, is therefore essential for assessing muscle design in relation to the dynamics of movement. PMID:26792341

  1. Multiscale Modeling of the Effect of Pressure on the Interfacial Tension and Other Cohesion Parameters in Binary Mixtures.

    PubMed

    Mayoral, E; Nahmad-Achar, E

    2016-03-10

    We study and predict the interfacial tension, solubility parameters, and Flory-Huggins parameters of binary mixtures as functions of pressure and temperature, using multiscale numerical simulation. A mesoscopic approach is proposed for simulating the pressure dependence of the interfacial tension for binary mixtures, at different temperatures, using classical dissipative particle dynamics (DPD). The thermodynamic properties of real systems are reproduced via the parametrization of the repulsive interaction parameters as functions of pressure and temperature via molecular dynamics simulations. Using this methodology, we calculate and analyze the cohesive energy density and the solubility parameters of different species obtaining excellent agreement with reported experimental behavior. The pressure- and temperature-dependent Flory-Huggins and repulsive DPD interaction parameters for binary mixtures are also obtained and validated against experimental data. This multiscale methodology offers the benefit of being applicable for any species and under difficult or nonfeasible experimental conditions, at a relatively low computational cost. PMID:26840645

  2. Dynamic properties of high structural integrity auxetic open cell foam

    NASA Astrophysics Data System (ADS)

    Scarpa, F.; Ciffo, L. G.; Yates, J. R.

    2004-02-01

    This paper illustrates various dynamic characteristics of open cell compliant polyurethane foam with auxetic (negative Poisson's ratio) behaviour. The foam is obtained from off-the-shelf open cell polyurethane grey foam with a manufacturing process based on mechanical deformation on a mould in a temperature-controlled oven. The Poisson's ratio is measured with an image processing technique based on edge detection with wavelet methods. Foam samples have been tested in a viscoelastic analyser tensile test machine to determine the Young's modulus and loss factor for small dynamic strains. The same samples have also been tested in an acoustic impedance tube to measure acoustic absorption and specific acoustic resistance and reactance with a transmissibility technique. Another set of tests has been set up on a cam plastometer machine for constant strain rate dynamic crushing analysis. All the tests have been carried out on auxetic and normal foam samples to provide a comparison be