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Sample records for high interfacial adhesionvia

  1. Preparation of pHEMA-CP composites with high interfacial adhesionvia template-driven mineralization

    SciTech Connect

    Song, Jie; Saiz, Eduardo; Bertozzi, Carolyn R.

    2002-12-05

    We report a template-driven nucleation and mineral growth process for the high-affinity integration of calcium phosphate (CP) with a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel scaffold. A mineralization technique was developed that exposes carboxylate groups on the surface of crosslinked pHEMA, promoting high-affinity nucleation and growth of calcium phosphate on the surface along with extensive calcification of the hydrogel interior. External factors such as the heating rate, the agitation of the mineral stock solution and the duration of the process that affect the outcome of the mineralization were investigated. This template-driven mineralization technique provides an efficient approach toward bonelike composites with high mineral-hydrogel interfacial adhesion strength.

  2. 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.

  3. 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.

  4. Interfacial phenomena in high-kappa dielectrics

    NASA Astrophysics Data System (ADS)

    Mathew, Anoop

    The introduction of novel high-kappa dielectric materials to replace the traditional SiO2 insulating layer in CMOS transistors is a watershed event in the history of transistor development. Further, replacement of the traditional highly-doped polycrystalline silicon gate electrode with a new set of materials for metal gates complicates the transition and introduces further integration challenges. A whole variety of new material surfaces and interfaces are thus introduced that merit close investigation to determine parameters for optimal device performance. Nitrogen is a key component that improves the performance of a variety of materials for the next generation of these CMOS transistors. Nitrogen is introduced into new gate dielectric materials such as hafnium silicates as well as in potential metal gate materials such as hafnium nitride. A photoemission study of the binding energies of the various atoms in these systems using photoemission reveals the nature of the atomic bonding. The current study compares hafnium silicates of various compositions which were thermally nitrided at different temperatures in ammonia, hafnium nitrides, and thin HfO2 films using photoelectron spectroscopy. A recurring theme that is explored is the competition between oxygen and nitrogen atoms in bonding with hafnium and other atoms. The N 1s photoemission peak is seen to have contributions from its bonding with hafnium, oxygen, and silicon atoms. The Hf 4f and O 1s spectra similarly exhibit signatures of their bonding environment with their neighboring atoms. Angle resolved photoemission and in-situ annealing/argon sputtering experiments are used to elucidate the nature of the bonding and its evolution with processing. A nondestructive profilitng of nitrogen distribution as a function of composition in nitrided hafnium silicates is also constructed using angle resolved photoemission as a function of the take-off angle. These results are corroborated with depth reconstruction obtained

  5. Comparison of interfacial partitioning tracer test and high-resolution microtomography measurements of fluid-fluid interfacial areas for an ideal porous medium

    NASA Astrophysics Data System (ADS)

    Narter, Matt; Brusseau, Mark L.

    2010-08-01

    Fluid-fluid interfacial area for porous media systems can be measured with the aqueous phase interfacial partitioning tracer test (IPTT) method or with high-resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous medium surface roughness on film-associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (±5 cm-1), while microtomography produced an interfacial area of 2.7 (±2 cm-1). Maximum specific interfacial areas, equivalent to areas normalized by nonwetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth sphere assumption and to the specific solid surface area measured using the N2/Brunauer, Emmett, and Teller (BET) method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid-fluid interfacial area and that they are comparable in the absence of the impact of surface roughness.

  6. COMPARISON OF INTERFACIAL PARTITIONING TRACER TEST AND HIGH-RESOLUTION MICROTOMOGRAPHY MEASUREMENTS OF FLUID-FLUID INTERFACIAL AREAS FOR AN IDEAL POROUS MEDIUM.

    PubMed

    Narter, Matt; Brusseau, Mark L

    2010-08-01

    Fluid-fluid interfacial area for porous-media systems can be measured with the aqueous-phase interfacial partitioning tracer test (IPTT) method or with high-resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous-medium surface roughness on film-associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass-beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (± 5 cm(-1)), while microtomography produced an interfacial area of 2.7 (± 2 cm(-1)). Maximum specific interfacial areas, equivalent to areas normalized by non-wetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth-sphere assumption, and to the specific solid surface area measured using the N2/BET method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid-fluid interfacial area, and that they are comparable absent the impact of surface roughness. PMID:24604925

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

    PubMed

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

    2015-02-11

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

  8. High interfacial activity of polymers "grafted through" functionalized iron oxide nanoparticle clusters.

    PubMed

    Foster, Lynn M; Worthen, Andrew J; Foster, Edward L; Dong, Jiannan; Roach, Clarissa M; Metaxas, Athena E; Hardy, Clifford D; Larsen, Eric S; Bollinger, Jonathan A; Truskett, Thomas M; Bielawski, Christopher W; Johnston, Keith P

    2014-09-01

    The mechanism by which polymers, when grafted to inorganic nanoparticles, lower the interfacial tension at the oil-water interface is not well understood, despite the great interest in particle stabilized emulsions and foams. A simple and highly versatile free radical "grafting through" technique was used to bond high organic fractions (by weight) of poly(oligo(ethylene oxide) monomethyl ether methacrylate) onto iron oxide clusters, without the need for catalysts. In the resulting ∼1 μm hybrid particles, the inorganic cores and grafting architecture contribute to the high local concentration of grafted polymer chains to the dodecane/water interface to produce low interfacial tensions of only 0.003 w/v % (polymer and particle core). This "critical particle concentration" (CPC) for these hybrid inorganic/polymer amphiphilic particles to lower the interfacial tension by 36 mN/m was over 30-fold lower than the critical micelle concentration of the free polymer (without inorganic cores) to produce nearly the same interfacial tension. The low CPC is favored by the high adsorption energy (∼10(6) kBT) for the large ∼1 μm hybrid particles, the high local polymer concentration on the particles surfaces, and the ability of the deformable hybrid nanocluster cores as well as the polymer chains to conform to the interface. The nanocluster cores also increased the entanglement of the polymer chains in bulk DI water or synthetic seawater, producing a viscosity up to 35,000 cP at 0.01 s(-1), in contrast with only 600 cP for the free polymer. As a consequence of these interfacial and rheological properties, the hybrid particles stabilized oil-in-water emulsions at concentrations as low as 0.01 w/v %, with average drop sizes down to 30 μm. In contrast, the bulk viscosity was low for the free polymer, and it did not stabilize the emulsions. The ability to influence the interfacial activity and rheology of polymers upon grafting them to inorganic particles, including clusters

  9. Simulation of interfacial fracture in highly crosslinked adhesives

    SciTech Connect

    STEVENS,MARK J.

    2000-05-22

    The fracture of highly-crosslinked networks is investigated by molecular dynamics simulations. The network is modeled as a bead-spring polymer network between two solid surfaces. The network is dynamically formed by crosslinking an equilibrated liquid mixture. Tensile pull fracture is simulated as a function of the number of interracial bonds. The sequence of molecular structural deformations that lead to failure are determined, and the connectivity is found to strongly control the stress-strain response and failure modes. The failure strain is related to the minimal paths in the network that connect the two solid surfaces. The failure stress is a fraction of the ideal stress required to fracture all the interracial bonds, and is linearly proportional to the number of interracial bonds. By allowing only a single bond between a crosslinker and the surface, interracial failure always occurs. Allowing up to half of the crosslinker's bonds to occur with the surface, cohesive failure can occur.

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

    SciTech Connect

    Hopkins, Patrick E.

    2011-10-01

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

  11. High On/Off Ratio Memristive Switching of Manganite/Cuprate Bilayer by Interfacial Magnetoelectricity

    DOE PAGESBeta

    Shen, Xiao; Pennycook, Timothy J.; Hernandez-Martin, David; Pérez, Ana; Puzyrev, Yevgeniy S.; Liu, Yaohua; te Velthuis, Suzanne G. E.; Freeland, John W.; Shafer, Padraic; Zhu, Chenhui; et al

    2016-05-27

    Memristive switching serves as the basis for a new generation of electronic devices. Conventional memristors are two-terminal devices in which the current is turned on and off by redistributing point defects, e.g., vacancies. Memristors based on alternative mechanisms have been explored, but achieving both high on/off ratio and low switching energy, as needed in applications, remains a challenge. This paper reports memristive switching in La0.7Ca0.3MnO3/PrBa2Cu3O7 bilayers with an on/off ratio greater than 103 and results of density functional theory calculations in terms of which it is concluded that the phenomenon is likely the result of a new type of interfacialmore » magnetoelectricity. More specifically, this study shows that an external electric field induces subtle displacements of the interfacial Mn ions, which switches on/off an interfacial magnetic “dead layer”, resulting in memristive behavior for spin-polarized electron transport across the bilayer. The interfacial nature of the switching entails low energy cost, about of a tenth of atto Joule for writing/erasing a “bit”. To conclude, the results indicate new opportunities for manganite/cuprate systems and other transition metal oxide junctions in memristive applications.« less

  12. Effect of Interfacial characteristics of metal clad polymeric substrates on electrical high frequency interconnection performance

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Romanofsky, R. R.; Ponchak, G. E.; Liu, D. C.

    1984-01-01

    Etched metallic conductor lines on metal clad polymeric substrates are used for electronic component interconnections. Significant signal losses are observed for microstrip conductor lines used for interconnecting high frequency devices. At these frequencies, the electronic signal travels closer to the metal-polymer interface due to the skin effect. Copper-teflon interfaces were characterized by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to determine the interfacial properties. Data relating roughness of the copper film to signal losses was compared to theory. Films used to enhance adhesion are found, to contribute to these losses.

  13. Interfacial Engineering for Highly Efficient-Conjugated Polymer-Based Bulk Heterojunction Photovoltaic Devices

    SciTech Connect

    Alex Jen; David Ginger; Christine Luscombe; Hong Ma

    2012-04-02

    The aim of our proposal is to apply interface engineering approach to improve charge extraction, guide active layer morphology, improve materials compatibility, and ultimately allow the fabrication of high efficiency tandem cells. Specifically, we aim at developing: i. Interfacial engineering using small molecule self-assembled monolayers ii. Nanostructure engineering in OPVs using polymer brushes iii. Development of efficient light harvesting and high mobility materials for OPVs iv. Physical characterization of the nanostructured systems using electrostatic force microscopy, and conducting atomic force microscopy v. All-solution processed organic-based tandem cells using interfacial engineering to optimize the recombination layer currents vi. Theoretical modeling of charge transport in the active semiconducting layer The material development effort is guided by advanced computer modeling and surface/ interface engineering tools to allow us to obtain better understanding of the effect of electrode modifications on OPV performance for the investigation of more elaborate device structures. The materials and devices developed within this program represent a major conceptual advancement using an integrated approach combining rational molecular design, material, interface, process, and device engineering to achieve solar cells with high efficiency, stability, and the potential to be used for large-area roll-to-roll printing. This may create significant impact in lowering manufacturing cost of polymer solar cells for promoting clean renewable energy use and preventing the side effects from using fossil fuels to impact environment.

  14. Bismuth Interfacial Doping of Organic Small Molecules for High Performance n-type Thermoelectric Materials.

    PubMed

    Huang, Dazhen; Wang, Chao; Zou, Ye; Shen, Xingxing; Zang, Yaping; Shen, Hongguang; Gao, Xike; Yi, Yuanping; Xu, Wei; Di, Chong-An; Zhu, Daoben

    2016-08-26

    Development of chemically doped high performance n-type organic thermoelectric (TE) materials is of vital importance for flexible power generating applications. For the first time, bismuth (Bi) n-type chemical doping of organic semiconductors is described, enabling high performance TE materials. The Bi interfacial doping of thiophene-diketopyrrolopyrrole-based quinoidal (TDPPQ) molecules endows the film with a balanced electrical conductivity of 3.3 S cm(-1) and a Seebeck coefficient of 585 μV K(-1) . The newly developed TE material possesses a maximum power factor of 113 μW m(-1)  K(-2) , which is at the forefront for organic small molecule-based n-type TE materials. These studies reveal that fine-tuning of the heavy metal doping of organic semiconductors opens up a new strategy for exploring high performance organic TE materials. PMID:27496293

  15. High-resolution imaging and spectroscopy of interfacial water at single bond limit

    NASA Astrophysics Data System (ADS)

    Jiang, Ying

    Hydrogen bond is one of the most important weak interactions in nature and plays an essential role in a broad spectrum of physics, chemistry, biology, energy and material sciences. The conventional methods for studying hydrogen-bonding interaction are all based on spectroscopic or diffraction techniques. However, those techniques have poor spatial resolution and only measure the average properties of many hydrogen bonds, which are susceptible to the structural inhomogeneity and local environments, especially when interfacial systems are concerned. The spatial variation and inter-bond coupling of the hydrogen bonds leads to significant spectral broadening, which prohibits the accurate understanding of the experimental data. In this talk, I will present our recent progress on the development of new-generation scanning probe microscopy/spectroscopy (SPM/S) with unprecedentedly high sensitivity and resolution, for addressing weak inter- and intra-molecular interactions, such as hydrogen bonds and van der Waals force. Based on a qPlus sensor, we have succeeded to push the real-space study of a prototypical hydrogen-bonded system, i.e. water, down to single bond limit. Combined with state-of-the-arts quantum simulations, we have discovered exotic nuclear quantum effects (NQEs) in interfacial water and revealed the quantum nature of the hydrogen bond from a completely new perspective

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

    SciTech Connect

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

    2008-11-12

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

  17. Interfacial thermal resistance between high-density polyethylene (HDPE) and sapphire

    NASA Astrophysics Data System (ADS)

    Zheng, Kun; Zhu, Jie; Ma, Yong-Mei; Tang, Da-Wei; Wang, Fo-Song

    2014-10-01

    To improve the thermal conductivity of polymeric composites, the numerous interfacial thermal resistance (ITR) inside is usually considered as a bottle neck, but the direct measurement of the ITR is hardly reported. In this paper, a sandwich structure which consists of transducer/high density polyethylene (HDPE)/sapphire is prepared to study the interface characteristics. Then, the ITRs between HDPE and sapphire of two samples with different HDPE thickness values are measured by time-domain thermoreflectance (TDTR) method and the results are ~ 2 × 10-7 m2·K·W-1. Furthermore, a model is used to evaluate the importance of ITR for the thermal conductivity of composites. The model's analysis indicates that reducing the ITR is an effective way of improving the thermal conductivity of composites. These results will provide valuable guidance for the design and manufacture of polymer-based thermally conductive materials.

  18. Hydrophobic and high adhesive polyaniline layer of rectangular microtubes fabricated by a modified interfacial polymerization

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanqiang; Gong, Xiangxiang; Qu, Yun; Han, Jie

    2016-08-01

    A modified interfacial polymerization of aniline is developed to fabricate hydrophobic and adhesive polyaniline (PANI) layer of rectangular microtubes on the glass substrate. The modified method uses pentanol as an organic medium to dissolve aniline monomer, with the water film of oxidant and surfactant on the glass substrate as water phase. The effects of some synthetic parameters (such as monomer concentration, alcohol molecular structure and surfactant type) on the morphology of PANI layer are studied for better understanding the fabrication of PANI nanostructures on the film. The alcohol molecular structure plays key role for the supermolecular assembly of PANI chains into nanostructures, while the surfactant may direct the array and deposition of these nanostructures on the glass substrate. The formation reason of PANI rectangular sub-microtubes is roughly interpreted according to our previous works. Wettability experiment indicates that the as-prepared PANI layer exhibits excellent hydrophobicity and high adhesive properties to water drop.

  19. Soft microcapsules with highly plastic shells formed by interfacial polyelectrolyte-nanoparticle complexation.

    PubMed

    Kaufman, Gilad; Nejati, Siamak; Sarfati, Raphael; Boltyanskiy, Rostislav; Loewenberg, Michael; Dufresne, Eric R; Osuji, Chinedum O

    2015-10-14

    Composite microcapsules have been aggressively pursued as designed chemical entities for biomedical and other applications. Common preparations rely on multi-step, time consuming processes. Here, we present a single-step approach to fabricate such microcapsules with shells composed of nanoparticle-polyelectrolyte and protein-polyelectrolyte complexes, and demonstrate control of the mechanical and release properties of these constructs. Interfacial polyelectrolyte-nanoparticle and polyelectrolyte-protein complexation across a water-oil droplet interface results in the formation of capsules with shell thicknesses of a few μm. Silica shell microcapsules exhibited a significant plastic response at small deformations, whereas lysozyme incorporated shells displayed a more elastic response. We exploit the plasticity of nanoparticle incorporated shells to produce microcapsules with high aspect ratio protrusions by micropipette aspiration. PMID:26169689

  20. Effects of Interfacial Fluorination on Performance Enhancement of High-k-Based Charge Trap Flash Memory

    NASA Astrophysics Data System (ADS)

    Wang, Chenjie; Huo, Zongliang; Liu, Ziyu; Liu, Yu; Cui, Yanxiang; Wang, Yumei; Li, Fanghua; Liu, Ming

    2013-07-01

    The effects of interfacial fluorination on the metal/Al2O3/HfO2/SiO2/Si (MAHOS) memory structure have been investigated. By comparing MAHOS memories with and without interfacial fluorination, it was identified that the deterioration of the performance and reliability of MAHOS memories is mainly due to the formation of an interfacial layer that generates excess oxygen vacancies at the interface. Interfacial fluorination suppresses the growth of the interfacial layer, which is confirmed by X-ray photoelectron spectroscopy depth profile analysis, increases enhanced program/erase efficiency, and improves data retention characteristics. Moreover, it was observed that fluorination at the SiO-HfO interface achieves a more effective performance enhancement than that at the HfO-AlO interface.

  1. Interfacial tension of hydrocarbon + water/brine systems under high pressure

    SciTech Connect

    Cai, B.Y.; Yang, J.T.; Guo, T.M.

    1996-05-01

    The interfacial tension of hydrocarbon + water/brine systems is one of the basic physical properties required for performing process calculations in petroleum, natural gas, and petrochemical industries. Interfacial tensions of 10 normal alkane + water/brine and hydrocarbon mixture + water/brine systems were measured by using a pendent drop instrument. The temperature and pressure ranges of measurements are (25 to 80) C and (1 to 300) bar, respectively. The effects of temperature, pressure, and salt content have been studied. It was found that the interfacial tension is sensitive to temperature and salt concentration but weakly dependent on pressure and salt species.

  2. Surface and interfacial engineering of iron oxide nanoplates for highly efficient magnetic resonance angiography.

    PubMed

    Zhou, Zijian; Wu, Changqiang; Liu, Hanyu; Zhu, Xianglong; Zhao, Zhenghuan; Wang, Lirong; Xu, Ye; Ai, Hua; Gao, Jinhao

    2015-03-24

    Magnetic resonance angiography using gadolinium-based molecular contrast agents suffers from short diagnostic window, relatively low resolution and risk of toxicity. Taking into account the chemical exchange between metal centers and surrounding protons, magnetic nanoparticles with suitable surface and interfacial features may serve as alternative T1 contrast agents. Herein, we report the engineering on surface structure of iron oxide nanoplates to boost T1 contrast ability through synergistic effects between exposed metal-rich Fe3O4(100) facets and embedded Gd2O3 clusters. The nanoplates show prominent T1 contrast in a wide range of magnetic fields with an ultrahigh r1 value up to 61.5 mM(-1) s(-1). Moreover, engineering on nanobio interface through zwitterionic molecules adjusts the in vivo behaviors of nanoplates for highly efficient magnetic resonance angiography with steady-state acquisition window, superhigh resolution in vascular details, and low toxicity. This study provides a powerful tool for sophisticated design of MRI contrast agents for diverse use in bioimaging applications. PMID:25670480

  3. High efficiency of the spin-orbit torques induced domain wall motion in asymmetric interfacial multilayered Tb/Co wires

    SciTech Connect

    Bang, Do; Awano, Hiroyuki

    2015-05-07

    We investigated current-induced DW motion in asymmetric interfacial multilayered Tb/Co wires for various thicknesses of magnetic and Pt-capping layers. It is found that the driving mechanism for the DW motion changes from interfacial to bulk effects at much thick magnetic layer (up to 19.8 nm). In thin wires, linearly depinning field dependence of critical current density and in-plane field dependence of DW velocity suggest that the extrinsic pinning governs field-induced DW motion and injecting current can be regarded as an effective field. It is expected that the high efficiency of spin-orbit torques in thick magnetic multilayers would have important implication for future spintronic devices based on in-plane current induced-DW motion or switching.

  4. Determination of the metal/die interfacial heat transfer coefficient of high pressure die cast B390 alloy

    NASA Astrophysics Data System (ADS)

    Cao, Yongyou; Guo, Zhipeng; Xiong, Shoumei

    2012-07-01

    High-pressure die cast B390 alloy was prepared on a 350 ton cold chamber die casting machine. The metal/die interfacial heat transfer coefficient of the alloy was investigated. Considering the filling process, a "finger"-shaped casting was designed for the experiments. This casting consisted of five plates with different thicknesses (0.05 inch or 1.27 mm to 0.25 inch or 6.35 mm) as well as individual ingates and overflows. Experiments under various operation conditions were conducted, and temperatures were measured at various specific locations inside the die. Based on the results, the interfacial heat transfer coefficient and heat flux were determined by solving the inverse heat transfer problem. The influence of the mold-filling sequence, sensor locations, as well as processing parameters including the casting pressure, die temperature, and fast/slow shot speeds on the heat transfer coefficient were discussed.

  5. Improvement in the breakdown endurance of high-κ dielectric by utilizing stacking technology and adding sufficient interfacial layer

    PubMed Central

    2014-01-01

    Improvement in the time-zero dielectric breakdown (TZDB) endurance of metal-oxide-semiconductor (MOS) capacitor with stacking structure of Al/HfO2/SiO2/Si is demonstrated in this work. The misalignment of the conduction paths between two stacking layers is believed to be effective to increase the breakdown field of the devices. Meanwhile, the resistance of the dielectric after breakdown for device with stacking structure would be less than that of without stacking structure due to a higher breakdown field and larger breakdown power. In addition, the role of interfacial layer (IL) in the control of the interface trap density (Dit) and device reliability is also analyzed. Device with a thicker IL introduces a higher breakdown field and also a lower Dit. High-resolution transmission electron microscopy (HRTEM) of the samples with different IL thicknesses is provided to confirm that IL is needed for good interfacial property. PMID:25246869

  6. Interfacial tension measured at high expansion rates and within milliseconds using microfluidics.

    PubMed

    Muijlwijk, Kelly; Hinderink, Emma; Ershov, Dmitry; Berton-Carabin, Claire; Schroën, Karin

    2016-05-15

    To understand droplet formation and stabilisation, technologies are needed to measure interfacial tension at micrometer range and millisecond scale. In this paper, microtechnology is used, and that allows us to access these ranges and derive a model for surfactant free systems. The predicting power of the model was tested, and we found that it can be used to accurately (validated with >60 experiments) describe droplet size for a wide range of flow rates, interfacial tensions, and continuous phase viscosities. The model was used next to determine interfacial tensions in a system with hexadecane and sodium dodecylsulfate (SDS) solutions, and it was found that the model can be used for droplet formation times ranging from 0.4 to 9.4ms while using a wide range of process conditions. The method described here differs greatly from standard dynamic interfacial tension methods that use quiescent, mostly diffusion-limited situations. The effects that we measured are much faster due to enhanced mass transfer; this allows us to assess the typical time scales used in industrial emulsification devices. PMID:26930542

  7. Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-05-01

    Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  8. The origin of high electrolyte-electrode interfacial resistances in lithium cells containing garnet type solid electrolytes.

    PubMed

    Cheng, Lei; Crumlin, Ethan J; Chen, Wei; Qiao, Ruimin; Hou, Huaming; Franz Lux, Simon; Zorba, Vassilia; Russo, Richard; Kostecki, Robert; Liu, Zhi; Persson, Kristin; Yang, Wanli; Cabana, Jordi; Richardson, Thomas; Chen, Guoying; Doeff, Marca

    2014-09-14

    Dense LLZO (Al-substituted Li7La3Zr2O12) pellets were processed in controlled atmospheres to investigate the relationships between the surface chemistry and interfacial behavior in lithium cells. Laser induced breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, synchrotron X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) studies revealed that Li2CO3 was formed on the surface when LLZO pellets were exposed to air. The distribution and thickness of the Li2CO3 layer were estimated by a combination of bulk and surface sensitive techniques with various probing depths. First-principles thermodynamic calculations confirmed that LLZO has an energetic preference to form Li2CO3 in air. Exposure to air and the subsequent formation of Li2CO3 at the LLZO surface is the source of the high interfacial impedances observed in cells with lithium electrodes. Surface polishing can effectively remove Li2CO3 and dramatically improve the interfacial properties. Polished samples in lithium cells had an area specific resistance (ASR) of only 109 Ω cm(2) for the LLZO/Li interface, the lowest reported value for Al-substituted LLZO. Galvanostatic cycling results obtained from lithium symmetrical cells also suggest that the quality of the LLZO/lithium interface has a significant impact on the device lifetime. PMID:25057850

  9. Studies of the nature of interfacial barriers in high efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Bates, Clayton W., Jr.

    1985-01-01

    The effects of interfacial barriers in crystalline silicon solar cells were studied. The effort was directed toward the investigation and use of such techniques as Angular Resolved Parameter Spectroscopy (ARAPS) and Impedance Spectroscopy in initially characterizing n-type Si doped to levels commonly used for n+p solar cells, and eventually Si solar cells. The objectives of the research are given. Those accomplished are detailed, as are recommendations for future work.

  10. 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

  11. 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.

  12. Interfacial characteristics of diamond/aluminum composites with high thermal conductivity fabricated by squeeze-casting method

    SciTech Connect

    Jiang, Longtao; Wang, Pingping; Xiu, Ziyang; Chen, Guoqin; Lin, Xiu; Dai, Chen; Wu, Gaohui

    2015-08-15

    In this work, aluminum matrix composites reinforced with diamond particles (diamond/aluminum composites) were fabricated by squeeze casting method. The material exhibited a thermal conductivity as high as 613 W / (m · K). The obtained composites were investigated by scanning electron microscope and transmission electron microscope in terms of the (100) and (111) facets of diamond particles. The diamond particles were observed to be homogeneously distributed in the aluminum matrix. The diamond{sub (111)}/Al interface was found to be devoid of reaction products. While at the diamond{sub (100)}/Al interface, large-sized aluminum carbides (Al{sub 4}C{sub 3}) with twin-crystal structure were identified. The interfacial characteristics were believed to be responsible for the excellent thermal conductivity of the material. - Graphical abstract: Display Omitted - Highlights: • Squeeze casting method was introduced to fabricate diamond/Al composite. • Sound interfacial bonding with excellent thermal conductivity was produced. • Diamond{sub (111)}/ aluminum interface was firstly characterized by TEM/HRTEM. • Physical combination was the controlling bonding for diamond{sub (111)}/aluminum. • The growth mechanism of Al{sub 4}C{sub 3} was analyzed by crystallography theory.

  13. High reduction of interfacial charge recombination in colloidal quantum dot solar cells by metal oxide surface passivation

    NASA Astrophysics Data System (ADS)

    Chang, Jin; Kuga, Yuki; Mora-Seró, Iván; Toyoda, Taro; Ogomi, Yuhei; Hayase, Shuzi; Bisquert, Juan; Shen, Qing

    2015-03-01

    Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar cells (CQDSCs). By coating thin TiO2 layers onto ZnO-NW surfaces, the open-circuit voltage and power conversion efficiency have been improved by over 40% in PbS CQDSCs. Characterization by transient photovoltage decay and impedance spectroscopy indicated that the interfacial recombination was significantly reduced by the surface passivation strategy. An efficiency as high as 6.13% was achieved through the passivation approach and optimization for the length of the ZnO-NW arrays (device active area: 16 mm2). All solar cells were tested in air, and exhibited excellent air storage stability (without any performance decline over more than 130 days). This work highlights the significance of metal oxide passivation in achieving high performance BHJ solar cells. The charge recombination mechanism uncovered in this work could shed light on the further improvement of PbS CQDSCs and/or other types of solar cells.Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar

  14. 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

  15. Silicon dioxide with a silicon interfacial layer as an insulating gate for highly stable indium phosphide metal-insulator-semiconductor field effect transistors

    NASA Technical Reports Server (NTRS)

    Kapoor, V. J.; Shokrani, M.

    1991-01-01

    A novel gate insulator consisting of silicon dioxide (SiO2) with a thin silicon (Si) interfacial layer has been investigated for high-power microwave indium phosphide (InP) metal-insulator-semiconductor field effect transistors (MISFETs). The role of the silicon interfacial layer on the chemical nature of the SiO2/Si/InP interface was studied by high-resolution X-ray photoelectron spectroscopy. The results indicated that the silicon interfacial layer reacted with the native oxide at the InP surface, thus producing silicon dioxide, while reducing the native oxide which has been shown to be responsible for the instabilities in InP MISFETs. While a 1.2-V hysteresis was present in the capacitance-voltage (C-V) curve of the MIS capacitors with silicon dioxide, less than 0.1 V hysteresis was observed in the C-V curve of the capacitors with the silicon interfacial layer incorporated in the insulator. InP MISFETs fabricated with the silicon dioxide in combination with the silicon interfacial layer exhibited excellent stability with drain current drift of less than 3 percent in 10,000 sec, as compared to 15-18 percent drift in 10,000 sec for devices without the silicon interfacial layer. High-power microwave InP MISFETs with Si/SiO2 gate insulators resulted in an output power density of 1.75 W/mm gate width at 9.7 GHz, with an associated power gain of 2.5 dB and 24 percent power added efficiency.

  16. MODELING THE EFFECT OF WATER VAPOR ON THE INTERFACIAL BEHAVIOR OF HIGH-TEMPERATURE AIR IN CONTACT WITH Fe20Cr SURFACES

    SciTech Connect

    Chialvo, Ariel A; Brady, Michael P; Keiser, James R; Cole, David R

    2011-01-01

    The purpose of this communication is to provide an atomistic view, via molecular dynamic simulation, of the contrasting interfacial behavior between high temperature dry- and (10-40 vol%) wet-air in contact with stainless steels as represented by Fe20Cr. It was found that H2O preferentially adsorbs and displaces oxygen at the metal/fluid interface. Comparison of these findings with experimental studies reported in the literature is discussed. Keywords: Fe-Cr alloys, metal-fluid interfacial behavior, wet-air, molecular simulation

  17. High efficiency and high photo-stability zinc-phthalocyanine based planar heterojunction solar cells with a double interfacial layer

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Min; Whan Kim, Ji; Shim, Hyun-Sub; Kim, Jang-Joo

    2012-09-01

    The use of CuI and MoO3 as a double interfacial layer between indium tin oxide (ITO) and a zinc phthalocyanine (ZnPc) layer improves the power conversion efficiency (ηp) and the photo-stability at the same time in ZnPc based solar cells. Insertion of CuI without MoO3 increased ηp more than 2 times to 3.3%. However, the photo-stability is lowered even further due to diffusion of Cu. Insertion of the MoO3 layer between the ITO and CuI prevents the diffusion of Cu under UV illumination to achieve the improved photo-stability and ηp.

  18. Formation of carbonaceous nano-layers under high interfacial pressures during lubrication with mineral and bio-based oils

    SciTech Connect

    Baltrus, John P.

    2014-01-01

    In order to better protect steel surfaces against wear under high loads, understanding of chemical reactions between lubricants and metal at high interfacial pressures and elevated temperatures needs to be improved. Solutions at 5 to 20 wt. % of zinc di-2-ethylhexyl dithio phosphate (ZDDP) and chlorinated paraffins (CP) in inhibited paraffinic mineral oil (IPMO) and inhibited soy bean oil (ISBO) were compared on a Twist Compression Tribotester (TCT) at 200 MPa. Microscopy of wear tracks after 10 seconds tribotesting showed much smoother surface profiles than those of unworn areas. X-ray photoelectron spectroscopy (XPS) coupled with Ar-ion sputtering demonstrated that additive solutions in ISBO formed 2–3 times thicker carbon-containing nano-layers compared to IPMO. The amounts of Cl, S or P were unexpectedly low and detectable only on the top surface with less than 5 nm penetration. CP blends in IPMO formed more inorganic chlorides than those in ISBO. It can be concluded that base oils are primarily responsible for the thickness of carbonaceous nano-layers during early stages of severe boundary lubrication, while CP or ZDDP additive contributions are important, but less significant.

  19. 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

  20. Reinforced Epoxy Nanocomposite Sheets Utilizing Large Interfacial Area from a High Surface Area Single-Walled Carbon Nanotube Scaffold

    NASA Astrophysics Data System (ADS)

    Kobashi, Kazufumi; Nishino, Hidekazu; Yamada, Takeo; Futaba, Don; Yumura, Motoo; Hata, Kenji

    2011-03-01

    We employed single-walled carbon nanotubes (SWNTs) with the available highest specific surface area (more than 1000 m2/g) that provided very large interfacial area for the matrix to fabricate epoxy composite sheets. Through mechanical redirection of the SWNT alignment to horizontal to create a laterally aligned scaffold sheet, into which epoxy resin was impregnated. The SWNT scaffold was engineered in structure to meet the these two nearly mutually exclusive demands, i.e. to have nanometer meso-pores (2-50 nm) to facilitate homogeneous impregnation of the epoxy resin and to have mechanical strength to tolerate the compaction forces generated during impregnation. Through this approach, a SWNT/epoxy composite sheet with a nearly ideal morphology was realized where long and aligned SWNTs were loaded at high weight fraction (33 percent) with an intertube distance approaching the radius of gyration for polymers. The resultant composite showed a Young's modulus of 15.0 GPa and a tensile strength of 104 MPa, thus achieving 5.4 and 2.1 times reinforcement as compared to the neat epoxy resin.

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

    PubMed Central

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

    2015-01-01

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

  2. The role of interfacial dislocation networks in high temperature creep of superalloys

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Draper, S. L.; Hull, D. R.; Mackay, R. A.; Nathal, M. V.

    1989-01-01

    The dislocation networks generated during high-temperature creep of several single-crystal nickel-based superalloys are analyzed. The networks continually evolve during creep at relatively low temperatures or eventually reach a more stable configuration at high temperatures. Specifically, the role of these networks in directional coarsening processes are studied, along with their formation kinetics, characteristics, and stability during creep. The results of this study combined with previous findings suggest that the directional coarsening process is strongly influenced by elastic strain energy. The dislocation networks formed during primary creep are found to be stable during all subsequent creep stages. Aspects of these dislocation networks are determined to be a product of both the applied creep stress and coherency strains.

  3. High post-annealing stability for perpendicular [Co/Ni] n multilayers by preventing interfacial diffusion

    NASA Astrophysics Data System (ADS)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Han, Gang; Liu, Qian-Qian; Liu, Yi-Wei; Wang, Dong-Wei; Feng, Chun; Li, Ming-Hua; Yu, Guang-Hua

    2016-05-01

    This paper reports that by introducing an appropriate thickness of Cu spacer at a Co/Ni interface, the perpendicular magnetic anisotropy of [Co/Cu/Ni] n multilayers can be maintained at the annealing temperature as high as 400 °C, implying high post-annealing stability. X-ray reflectivity results demonstrate that the multilayers with Cu spacer exhibit good multilayer structure, indicating the weak intermixing of Co and Ni, which is one important reason for the enhanced post-annealing stability of perpendicular magnetic anisotropy. The result is of great importance for out-of-plane magnetized spintronic devices which need to be combined with complementary metal-oxide semiconductors.

  4. High-Speed AFM Images of Thermal Motion Provide Stiffness Map of Interfacial Membrane Protein Moieties

    PubMed Central

    2014-01-01

    The flexibilities of extracellular loops determine ligand binding and activation of membrane receptors. Arising from fluctuations in inter- and intraproteinaceous interactions, flexibility manifests in thermal motion. Here we demonstrate that quantitative flexibility values can be extracted from directly imaging the thermal motion of membrane protein moieties using high-speed atomic force microscopy (HS-AFM). Stiffness maps of the main periplasmic loops of single reconstituted water channels (AqpZ, GlpF) revealed the spatial and temporal organization of loop-stabilizing intraproteinaceous H-bonds and salt bridges. PMID:25516527

  5. Interfacial Engineering of Semiconductor-Superconductor Junctions for High Performance Micro-Coolers

    NASA Astrophysics Data System (ADS)

    Gunnarsson, D.; Richardson-Bullock, J. S.; Prest, M. J.; Nguyen, H. Q.; Timofeev, A. V.; Shah, V. A.; Whall, T. E.; Parker, E. H. C.; Leadley, D. R.; Myronov, M.; Prunnila, M.

    2015-12-01

    The control of electronic and thermal transport through material interfaces is crucial for numerous micro and nanoelectronics applications and quantum devices. Here we report on the engineering of the electro-thermal properties of semiconductor-superconductor (Sm-S) electronic cooler junctions by a nanoscale insulating tunnel barrier introduced between the Sm and S electrodes. Unexpectedly, such an interface barrier does not increase the junction resistance but strongly reduces the detrimental sub-gap leakage current. These features are key to achieving high cooling power tunnel junction refrigerators, and we demonstrate unparalleled performance in silicon-based Sm-S electron cooler devices with orders of magnitudes improvement in the cooling power in comparison to previous works. By adapting the junctions in strain-engineered silicon coolers we also demonstrate efficient electron temperature reduction from 300 mK to below 100 mK. Investigations on junctions with different interface quality indicate that the previously unexplained sub-gap leakage current is strongly influenced by the Sm-S interface states. These states often dictate the junction electrical resistance through the well-known Fermi level pinning effect and, therefore, superconductivity could be generally used to probe and optimize metal-semiconductor contact behaviour.

  6. Interfacial Engineering of Semiconductor–Superconductor Junctions for High Performance Micro-Coolers

    PubMed Central

    Gunnarsson, D.; Richardson-Bullock, J. S.; Prest, M. J.; Nguyen, H. Q.; Timofeev, A. V.; Shah, V. A.; Whall, T. E.; Parker, E. H. C.; Leadley, D. R.; Myronov, M.; Prunnila, M.

    2015-01-01

    The control of electronic and thermal transport through material interfaces is crucial for numerous micro and nanoelectronics applications and quantum devices. Here we report on the engineering of the electro-thermal properties of semiconductor-superconductor (Sm-S) electronic cooler junctions by a nanoscale insulating tunnel barrier introduced between the Sm and S electrodes. Unexpectedly, such an interface barrier does not increase the junction resistance but strongly reduces the detrimental sub-gap leakage current. These features are key to achieving high cooling power tunnel junction refrigerators, and we demonstrate unparalleled performance in silicon-based Sm-S electron cooler devices with orders of magnitudes improvement in the cooling power in comparison to previous works. By adapting the junctions in strain-engineered silicon coolers we also demonstrate efficient electron temperature reduction from 300 mK to below 100 mK. Investigations on junctions with different interface quality indicate that the previously unexplained sub-gap leakage current is strongly influenced by the Sm-S interface states. These states often dictate the junction electrical resistance through the well-known Fermi level pinning effect and, therefore, superconductivity could be generally used to probe and optimize metal-semiconductor contact behaviour. PMID:26620423

  7. Interfacial Engineering of Semiconductor-Superconductor Junctions for High Performance Micro-Coolers.

    PubMed

    Gunnarsson, D; Richardson-Bullock, J S; Prest, M J; Nguyen, H Q; Timofeev, A V; Shah, V A; Whall, T E; Parker, E H C; Leadley, D R; Myronov, M; Prunnila, M

    2015-01-01

    The control of electronic and thermal transport through material interfaces is crucial for numerous micro and nanoelectronics applications and quantum devices. Here we report on the engineering of the electro-thermal properties of semiconductor-superconductor (Sm-S) electronic cooler junctions by a nanoscale insulating tunnel barrier introduced between the Sm and S electrodes. Unexpectedly, such an interface barrier does not increase the junction resistance but strongly reduces the detrimental sub-gap leakage current. These features are key to achieving high cooling power tunnel junction refrigerators, and we demonstrate unparalleled performance in silicon-based Sm-S electron cooler devices with orders of magnitudes improvement in the cooling power in comparison to previous works. By adapting the junctions in strain-engineered silicon coolers we also demonstrate efficient electron temperature reduction from 300 mK to below 100 mK. Investigations on junctions with different interface quality indicate that the previously unexplained sub-gap leakage current is strongly influenced by the Sm-S interface states. These states often dictate the junction electrical resistance through the well-known Fermi level pinning effect and, therefore, superconductivity could be generally used to probe and optimize metal-semiconductor contact behaviour. PMID:26620423

  8. Achieving a Low Interfacial Density of States with a Flat Distribution in High-κ Ga2O3(Gd2O3) Directly Deposited on Ge

    NASA Astrophysics Data System (ADS)

    Lin, Chunan; Lin, Hanchung; Chiang, Tsunghung; Chu, Reilin; Chu, Lungkun; Lin, Tsungda; Chang, Yaochung; Wang, Wei-E.; Raynien Kwo, J.; Hong, Minghwei

    2011-11-01

    The interfacial density of states (Dit) distribution of high-κ dielectric Ga2O3(Gd2O3) [GGO] directly deposited on n-type Ge(100) without invoking any interfacial passivation layer (IPL) was established using conductance measurements and charge pumping (CP) technique. The conductance measurements yielded Dit values in the range of (1-4)×1011 cm-2 eV-1 from the mid-gap energy to the conduction band edge within the Ge band gap, which are consistent with the mean Dit value of ˜2×1011 cm-2 eV-1 near the mid-gap obtained independently by the CP method. The flat Dit distribution at the conduction band edge compares favorably with those attained using IPLs such as SiO2/Si-cap and GeO2.

  9. Potential Impact of Interfacial Bonding Efficiency on High-Burnup Spent Nuclear Fuel Vibration Integrity during Normal Transportation

    SciTech Connect

    Jiang, Hao; Wang, Jy-An John; Wang, Hong

    2014-01-01

    Finite element analysis (FEA) was used to investigate the impacts of interfacial bonding efficiency at pellet pellet and pellet clad interfaces on spent nuclear fuel (SNF) vibration integrity. The FEA simulation results were also validated and benchmarked with reverse bending fatigue test results on surrogate rods consisting of stainless steel (SS) tubes with alumina-pellet inserts. Bending moments (M) are applied to the FEA models to evaluate the system responses of the surrogate rods. From the induced curvature, , the flexural rigidity EI can be estimated as EI=M/ . The impacts of interfacial bonding efficiency on SNF vibration integrity include the moment carrying capacity distribution between pellets and clad and the impact of cohesion on the flexural rigidity of the surrogate rod system. The result also indicates that the immediate consequences of interfacial de-bonding are a load carrying capacity shift from the fuel pellets to the clad and a reduction of the composite rod flexural rigidity. Therefore, the flexural rigidity of the surrogate rod and the bending moment bearing capacity between the clad and fuel pellets are strongly dependent on the efficiency of interfacial bonding at the pellet pellet and pellet clad interfaces. The above-noted phenomenon was calibrated and validated by reverse bending fatigue testing using a surrogate rod system.

  10. Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-11-01

    Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  11. 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

  12. Interfacial material for solid oxide fuel cell

    DOEpatents

    Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

    1999-01-01

    Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

  13. High sulfur content polymer nanoparticles obtained from interfacial polymerization of sodium polysulfide and 1,2,3-trichloropropane in water.

    PubMed

    Lim, Jeewoo; Jung, Unho; Joe, Won Tae; Kim, Eui Tae; Pyun, Jeffrey; Char, Kookheon

    2015-06-01

    Sulfur-rich materials have recently attracted keen interest for their potentials in optical, electrochemical, and pesticidal applications as well as their utility in dynamic covalent bond chemistry. Many sulfur-rich polymers, however, are insoluble and processing methods are therefore very limited. The synthesis and characterization of water-dispersible polymer nanoparticles (NPs) with the sulfur content exceeding 75% by weight, obtained from the interfacial polymerization between 1,2,3-trichloropropane and sodium polysulfide in water is reported here. The interfacial polymerization yields well-defined sulfur-rich NPs in the presence of surfactants, which are capable of serving a dual role as a phase transfer catalyst on top of emulsifiers. Such dual role allows for the control of the product NP size by varying its concentration. The surfactants can be easily removed by centrifugation and redispersion in water is also reported here. The resulting sulfur-rich NPs are characterized through elemental analysis, dynamic light scattering, ζ-potential measurements, and scanning electron microscopy. PMID:25847485

  14. Exploring the interfacial structure of protein adsorbates and the kinetics of protein adsorption: an in situ high-energy X-ray reflectivity study.

    PubMed

    Evers, Florian; Shokuie, Kaveh; Paulus, Michael; Sternemann, Christian; Czeslik, Claus; Tolan, Metin

    2008-09-16

    The high energy X-ray reflectivity technique has been applied to study the interfacial structure of protein adsorbates and protein adsorption kinetics in situ. For this purpose, the adsorption of lysozyme at the hydrophilic silica-water interface has been chosen as a model system. The structure of adsorbed lysozyme layers was probed for various aqueous solution conditions. The effect of solution pH and lysozyme concentration on the interfacial structure was measured. Monolayer formation was observed for all cases except for the highest concentration. The adsorbed protein layers consist of adsorbed lysozyme molecules with side-on or end-on orientation. By means of time-dependent X-ray reflectivity scans, the time-evolution of adsorbed proteins was monitored as well. The results of this study demonstrate the capabilities of in situ X-ray reflectivity experiments on protein adsorbates. The great advantages of this method are the broad wave vector range available and the high time resolution. PMID:18715021

  15. 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.

  16. 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

  17. 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

  18. Argon Cluster Sputtering Source for ToF-SIMS Depth Profiling of Insulating Materials: High Sputter Rate and Accurate Interfacial Information.

    PubMed

    Wang, Zhaoying; Liu, Bingwen; Zhao, Evan W; Jin, Ke; Du, Yingge; Neeway, James J; Ryan, Joseph V; Hu, Dehong; Zhang, Kelvin H L; Hong, Mina; Le Guernic, Solenne; Thevuthasan, Suntharampilai; Wang, Fuyi; Zhu, Zihua

    2015-08-01

    The use of an argon cluster ion sputtering source has been demonstrated to perform superiorly relative to traditional oxygen and cesium ion sputtering sources for ToF-SIMS depth profiling of insulating materials. The superior performance has been attributed to effective alleviation of surface charging. A simulated nuclear waste glass (SON68) and layered hole-perovskite oxide thin films were selected as model systems because of their fundamental and practical significance. Our results show that high sputter rates and accurate interfacial information can be achieved simultaneously for argon cluster sputtering, whereas this is not the case for cesium and oxygen sputtering. Therefore, the implementation of an argon cluster sputtering source can significantly improve the analysis efficiency of insulating materials and, thus, can expand its applications to the study of glass corrosion, perovskite oxide thin film characterization, and many other systems of interest. PMID:25953490

  19. Design and simulation of high-breakdown-voltage GaN-based vertical field-effect transistor with interfacial charge engineering

    NASA Astrophysics Data System (ADS)

    Du, Jiangfeng; Liu, Dong; Bai, Zhiyuan; Luo, Qian; Yu, Qi

    2016-05-01

    A high-breakdown-voltage GaN-based vertical field-effect transistor with negative fixed interfacial charge engineering (GaN ICE-VHFET) is proposed in this work. The negative charge inverts an n-GaN buffer layer along the oxide/GaN interface, inducing a vertical hole layer. Thus, the entire buffer layer consists of a p+-hole inversion layer and an n-pillar buffer layer, and the p-pillar laterally depletes the n-GaN buffer layer, and the electric field distribution becomes more uniform. Simulation results show that the breakdown voltage of the GaN ICE-VHFET increases by 193% and the on-resistance of such a device is still very low when compared with those of conventional vertical FETs. Its figure of merit even exceeds the GaN one-dimensional limit.

  20. Argon Cluster Sputtering Source for ToF-SIMS Depth Profiling of Insulating Materials: High Sputter Rate and Accurate Interfacial Information

    NASA Astrophysics Data System (ADS)

    Wang, Zhaoying; Liu, Bingwen; Zhao, Evan W.; Jin, Ke; Du, Yingge; Neeway, James J.; Ryan, Joseph V.; Hu, Dehong; Zhang, Kelvin H. L.; Hong, Mina; Le Guernic, Solenne; Thevuthasan, Suntharampilai; Wang, Fuyi; Zhu, Zihua

    2015-08-01

    The use of an argon cluster ion sputtering source has been demonstrated to perform superiorly relative to traditional oxygen and cesium ion sputtering sources for ToF-SIMS depth profiling of insulating materials. The superior performance has been attributed to effective alleviation of surface charging. A simulated nuclear waste glass (SON68) and layered hole-perovskite oxide thin films were selected as model systems because of their fundamental and practical significance. Our results show that high sputter rates and accurate interfacial information can be achieved simultaneously for argon cluster sputtering, whereas this is not the case for cesium and oxygen sputtering. Therefore, the implementation of an argon cluster sputtering source can significantly improve the analysis efficiency of insulating materials and, thus, can expand its applications to the study of glass corrosion, perovskite oxide thin film characterization, and many other systems of interest.

  1. Effective thermal conductivity of metal and non-metal particulate composites with interfacial thermal resistance at high volume fraction of nano to macro-sized spheres

    SciTech Connect

    Faroughi, Salah Aldin; Huber, Christian

    2015-02-07

    In this study, we propose a theoretical model to compute the effective thermal conductivity of metal and dielectric spherical particle reinforced composites with interfacial thermal resistance. We consider a wide range of filler volume fraction with sizes ranging from nano- to macro-scale. The model, based on the differential effective medium theory, accounts for particle interactions through two sets of volume fraction corrections. The first correction accounts for a finite volume of composite and the second correction introduces a self-crowding factor that allows us to develop an accurate model for particle interaction even for high volume fraction of fillers. The model is examined to other published models, experiments, and numerical simulations for different types of composites. We observe an excellent agreement between the model and published datasets over a wide range of particle volume fractions and material properties of the composite constituents.

  2. Understanding the interfacial phenomena of a 4.7 V and 55 °C Li-ion battery with Li-rich layered oxide cathode and grap2hite anode and its correlation to high-energy cycling performance

    NASA Astrophysics Data System (ADS)

    Pham, Hieu Quang; Hwang, Eui-Hyung; Kwon, Young-Gil; Song, Seung-Wan

    2016-08-01

    Research progress of high-energy performance and interfacial phenomena of Li1.13Mn0.463Ni0.203Co0.203O2 cathode and graphite anode in a 55 °C full-cell under an aggressive charge cut-off voltage to 4.7 V (4.75 V vs. Li/Li+) is reported. Although anodic instability of conventional electrolyte is the critical issue on high-voltage and high-temperature cell operation, interfacial phenomena and the solution to performance improvement have not been reported. Surface spectroscopic evidence revealed that structural degradation of both cathode and anode materials, instability of surface film at cathode, and metal-dissolution from cathode and -deposition at anode, and a rise of interfacial resistance with high-voltage cycling in 55 °C conventional electrolyte are resolved by the formation of a stable surface film with organic/inorganic mixtures at cathode and solid electrolyte interphase (SEI) at anode using blended additives of fluorinated linear carbonate and vinylene carbonate. As a result, significantly improved cycling stability of 77% capacity retention delivering 227-174 mAhg-1 after 50 cycles is obtained, corresponding to 819-609 Wh per kg of cathode active material. Interfacial stabilization approach would pave the way of controlling the performance and safety, and widening the practical application of Li-rich layered oxide cathode materials and high-voltage electrolyte materials in various high-energy density Li-ion batteries.

  3. Interfacial thermodynamics and kinetics of sorption of diclofenac on prepared high performance flower-like MoS2.

    PubMed

    Zhang, Yalei; Yin, Zengfu; Dai, Chaomeng; Zhou, Xuefei; Chen, Wen

    2016-11-01

    Flower-like MoS2 with numerous wrinkled nanosheets was prepared via a facile hydrothermal method. The surface morphology and microstructure of the obtained materials were characterized using X-ray diffraction data (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Additionally, the compositions of the flower-like MoS2 were further revealed by an energy dispersion spectrometer (EDX) and X-ray photoelectron spectrometry (XPS). The obtained MoS2 was used as an adsorbent to remove diclofenac (DCF, C14H10Cl2NO2Na) from aqueous solutions and presented excellent performance for removing DCF. The sorption kinetics, isotherms and effect of solution pH on the sorption were evaluated in batch sorption experiments. The sorption characteristics of the interactions between DCF and MoS2 in water were analyzed using a pseudo-second-order model, an intraparticle diffusion model and Boyd model to determine the sorption rate-determining steps. It was concluded that the sorption of DCF on MoS2 was fitted better by the pseudo-second-order model and that external diffusion governed the sorption process of DCF onto the MoS2. The interfacial interaction free energies between DCF and MoS2 in the sorption process can be calculated based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO). The flower-like MoS2 presenting excellent performance for removing DCF, could be a better choice of treating DCF-containing wastewaters. PMID:27475708

  4. A facile and general preparation of high-performance noble-metal-based free-standing nanomembranes by a reagentless interfacial self-assembly strategy

    NASA Astrophysics Data System (ADS)

    Wu, Haoxi; He, Haili; Zhai, Yujuan; Li, Haijuan; Lai, Jianping; Jin, Yongdong

    2012-10-01

    As a simple and flexible 2D platform, the water-air interface is envisioned as an environmentally-friendly approach to prepare ultrathin free-standing nanomembranes (FNMs) of monolayered nanoparticles of interest via interfacial self-assembly. However, attempts so far have been rather rare due to the lack of efficient methods. In this article, we report on a facile and general strategy for fabrication of a family of noble metal-based FNMs by a simple and reagentless interfacial self-assembly tactics to prepare functional (plasmonic or catalytic) FNMs, such as Au, Ag, Pd, Pt-FNMs and their bimetallic hybrids, Ag/Au-FNMs and Pd/Pt-FNMs. The organic solvent-free process, varying somewhat from metal to metal only in precursors, reducing agents and dosage of reagents used, is found to be a general phenomenon and ligand-independent (irrespective of the monolayer quality of the resulting FNMs), allowing the growth of high-quality noble metal-based FNMs with well-defined nanoparticulate and monolayer morphology as large as several square centimeters. Heat treatment (boiling) is performed to accelerate the formation of FNMs within 15 min. More significantly, the as-prepared plasmonic Au-FNMs acting as a SERS substrate show a superior activity; whereas the resulting catalytic Pd-FNMs, except for their excellent ethanol electrooxidation performance, exhibit higher electrocatalytic activity for formic acid oxidation than commercial catalysts.As a simple and flexible 2D platform, the water-air interface is envisioned as an environmentally-friendly approach to prepare ultrathin free-standing nanomembranes (FNMs) of monolayered nanoparticles of interest via interfacial self-assembly. However, attempts so far have been rather rare due to the lack of efficient methods. In this article, we report on a facile and general strategy for fabrication of a family of noble metal-based FNMs by a simple and reagentless interfacial self-assembly tactics to prepare functional (plasmonic or

  5. Greatly improved interfacial passivation of in-situ high κ dielectric deposition on freshly grown molecule beam epitaxy Ge epitaxial layer on Ge(100)

    SciTech Connect

    Chu, R. L.; Liu, Y. C.; Lee, W. C.; Huang, M. L.; Kwo, J. E-mail: mhong@phys.ntu.edu.tw; Lin, T. D.; Hong, M. E-mail: mhong@phys.ntu.edu.tw; Pi, T. W.

    2014-05-19

    A high-quality high-κ/Ge interface has been achieved by combining molecule beam epitaxy grown Ge epitaxial layer and in-situ deposited high κ dielectric. The employment of Ge epitaxial layer has sucessfully buried and/or removed the residue of unfavorable carbon and native oxides on the chemically cleaned and ultra-high vacuum annealed Ge(100) wafer surface, as studied using angle-resolved x-ray photoelectron spectroscopy. Moreover, the scanning tunneling microscopy analyses showed the significant improvements in Ge surface roughness from 3.5 Å to 1 Å with the epi-layer growth. Thus, chemically cleaner, atomically more ordered, and morphologically smoother Ge surfaces were obtained for the subsquent deposition of high κ dielectrics, comparing with those substrates without Ge epi-layer. The capacitance-voltage (C-V) characteristics and low extracted interfacial trap density (D{sub it}) reveal the improved high-κ/Ge interface using the Ge epi-layer approach.

  6. Quasiparticle interfacial level alignment of highly hybridized frontier levels: H2O on TiO2(110).

    PubMed

    Migani, Annapaola; Mowbray, Duncan J; Zhao, Jin; Petek, Hrvoje

    2015-01-13

    Knowledge of the frontier levels' alignment prior to photoirradiation is necessary to achieve a complete quantitative description of H2O photocatalysis on TiO2(110). Although H2O on rutile TiO2(110) has been thoroughly studied both experimentally and theoretically, a quantitative value for the energy of the highest H2O occupied levels is still lacking. For experiment, this is due to the H2O levels being obscured by hybridization with TiO2(110) levels in the difference spectra obtained via ultraviolet photoemission spectroscopy (UPS). For theory, this is due to inherent difficulties in properly describing many-body effects at the H2O-TiO2(110) interface. Using the projected density of states (DOS) from state-of-the-art quasiparticle (QP) G0W0, we disentangle the adsorbate and surface contributions to the complex UPS spectra of H2O on TiO2(110). We perform this separation as a function of H2O coverage and dissociation on stoichiometric and reduced surfaces. Due to hybridization with the TiO2(110) surface, the H2O 3a1 and 1b1 levels are broadened into several peaks between 5 and 1 eV below the TiO2(110) valence band maximum (VBM). These peaks have both intermolecular and interfacial bonding and antibonding character. We find the highest occupied levels of H2O adsorbed intact and dissociated on stoichiometric TiO2(110) are 1.1 and 0.9 eV below the VBM. We also find a similar energy of 1.1 eV for the highest occupied levels of H2O when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than those estimated from UPS difference spectra, which are inconclusive in this energy region. Finally, we apply self-consistent QPGW (scQPGW1) to obtain the ionization potential of the H2O-TiO2(110) interface. PMID:26574222

  7. Quasiparticle Interfacial Level Alignment of Highly Hybridized Frontier Levels: H2O on TiO2(110)

    SciTech Connect

    Migani, Annapaola; Mowbray, Duncan J.; Zhao, Jin; Petek, Hrvoje

    2015-01-13

    Knowledge of the frontier levels’ alignment prior to photoirradiation is necessary to achieve a complete quantitative description of H2O photocatalysis on TiO2(110). Although H2O on rutile TiO2(110) has been thoroughly studied both experimentally and theoretically, a quantitative value for the energy of the highest H2O occupied levels is still lacking. For experiment, this is due to the H2O levels being obscured by hybridization with TiO2(110) levels in the difference spectra obtained via ultraviolet photoemission spectroscopy (UPS). For theory, this is due to inherent difficulties in properly describing many-body effects at the H2O–TiO2(110) interface. Using the projected density of states (DOS) from state-of-the-art quasiparticle (QP) G0W0, we disentangle the adsorbate and surface contributions to the complex UPS spectra of H2O on TiO2(110). We perform this separation as a function of H2O coverage and dissociation on stoichiometric and reduced surfaces. Due to hybridization with the TiO2(110) surface, the H2O 3a1 and 1b1 levels are broadened into several peaks between 5 and 1 eV below the TiO2(110) valence band maximum (VBM). These peaks have both intermolecular and interfacial bonding and antibonding character. We find the highest occupied levels of H2O adsorbed intact and dissociated on stoichiometric TiO2(110) are 1.1 and 0.9 eV below the VBM. We also find a similar energy of 1.1 eV for the highest occupied levels of H2O when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than those estimated from UPS difference spectra, which are inconclusive in this energy region. Finally, we apply self-consistent QPGW (scQPGW1) to obtain the ionization potential of the H2O–TiO2(110) interface.

  8. A polymerized C60 coating enhancing interfacial stability at three-dimensional LiCoO2 in high-potential regime

    NASA Astrophysics Data System (ADS)

    Hudaya, Chairul; Halim, Martin; Pröll, Johannes; Besser, Heino; Choi, Wonchang; Pfleging, Wilhelm; Seifert, Hans Jürgen; Lee, Joong Kee

    2015-12-01

    The interfacial instabilities, including side reactions due to electrolyte decompositions and Cobalt (Co) dissolutions, are the main detrimental processes at LiCoO2 cathode when a high-voltage window (>4.2 V) is applied. Nevertheless, cycling the cathode with a voltage above 4.2 V would deliver an increased gravimetric capacity, which is desired for high power battery operation. To address these drawbacks, we demonstrate a synergistic approach by manufacturing the three-dimensional high-temperature LiCoO2 electrodes (3D HT-LCO) using laser-microstructuring, laser-annealing and subsequent coating with polymerized C60 thin films (C60@3D HT-LCO) by plasma-assisted thermal evaporation. The C60@3D HT-LCO cathode delivers higher initial discharge capacity compared to its theoretical value, i.e. 175 mA h g-1 at 0.1 C with cut-off voltage of 3.0-4.5 V. This cathode combines the advantages of the 3D electrode architecture and an advanced C60 coating/passivation concept leading to an improved electrochemical performance, due to an increased active surface area, a decreased charge transfer resistance, a prevented Co dissolution into the electrolyte and a suppressed side reaction and electrolyte decomposition. This work provides a novel solution for other cathode materials having similar concerns in high potential regimes for application in lithium-ion microbatteries.

  9. High-Performance Si/SiOx Nanosphere Anode Material by Multipurpose Interfacial Engineering with Black TiO2-x.

    PubMed

    Bae, Juhye; Kim, Dae Sik; Yoo, Hyundong; Park, Eunjun; Lim, Young-Geun; Park, Min-Sik; Kim, Young-Jun; Kim, Hansu

    2016-02-24

    Silicon oxides (SiOx) have attracted recent attention for their great potential as promising anode materials for lithium ion batteries as a result of their high energy density and excellent cycle performance. Despite these advantages, the commercial use of these materials is still impeded by low initial Coulombic efficiency and high production cost associated with a complicated synthesis process. Here, we demonstrate that Si/SiOx nanosphere anode materials show much improved performance enabled by electroconductive black TiO2-x coating in terms of reversible capacity, Coulombic efficiency, and thermal reliability. The resulting anode material exhibits a high reversible capacity of 1200 mAh g(-1) with an excellent cycle performance of up to 100 cycles. The introduction of a TiO2-x layer induces further reduction of the Si species in the SiOx matrix phase, thereby increasing the reversible capacity and initial Coulombic efficiency. Besides the improved electrochemical performance, the TiO2-x coating layer plays a key role in improving the thermal reliability of the Si/SiOx nanosphere anode material at the same time. We believe that this multipurpose interfacial engineering approach provides another route toward high-performance Si-based anode materials on a commercial scale. PMID:26820496

  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 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.

  12. Effect of Process Parameters, Casting Thickness, and Alloys on the Interfacial Heat-Transfer Coefficient in the High-Pressure Die-Casting Process

    NASA Astrophysics Data System (ADS)

    Guo, Zhi-Peng; Xiong, Shou-Mei; Liu, Bai-Cheng; Li, Mei; Allison, John

    2008-12-01

    The heat transfer at the metal-die interface is believed to have great influence on the solidification process and cast structure of the high-pressure die-casting (HPDC) process. The present article focused on the effects of process parameters, casting thickness, and alloys on the metal-die interfacial heat-transfer coefficient (IHTC) in the HPDC process. Experiment was carried out on a cold-chamber die-casting machine with two casting alloys AM50 and ADC12. A special casting, namely, “step-shape” casting, was used and cast against a H13 steel die. The IHTC was determined using an inverse approach based on the temperature measurements inside the die. Results show that the IHTC is different at different steps and changes as the solidification of the casting proceeds. Process parameters only influence the IHTC in its peak value, and for both AM50 and ADC12 alloys, a greater fast shot velocity leads to a greater IHTC peak value at steps 1 and 2. The initial die surface temperature has a more prominent influence on the IHTC peak values at the thicker steps, especially step 5. Results also show that a closer contact between the casting and die could be achieved when the casting alloy is ADC12 instead of AM50, which consequently leads to a higher IHTC.

  13. Interfacial electronic structure and charge transfer of hybrid graphene quantum dot and graphitic carbon nitride nanocomposites: insights into high efficiency for photocatalytic solar water splitting.

    PubMed

    Ma, Zuju; Sa, Rongjian; Li, Qiaohong; Wu, Kechen

    2016-01-14

    New metal-free carbon nanodot/carbon nitride (C3N4) nanocomposites have shown to exhibit high efficiency for photocatalytic solar water splitting. (J. Liu, et al., Science, 2015, 347, 970) However, the mechanism underlying the ultrahigh performance of these nanocomposites and consequently the possibilities for further improvements are not at present clear. In this work, we performed hybrid functional calculations and included long-range dispersion corrections to accurately characterize the interfacial electron coupling of the graphene quantum dot-graphitic carbon nitride composites (Gdot/g-C3N4). The results revealed that the band gap of Gdot/g-C3N4 could be engineered by changing the lateral size of Gdots. In particular, the C24H12/g-C3N4 composites present an ideal band gap of 1.92 eV to harvest a large part of solar light. More interestingly, a type-II heterojunction is formed at the interface of the Gdot/g-C3N4 composites, a desirable feature for enhanced photocatalytic activity. The charge redistribution at the interface leads to strong electron depletion above the Gdot sheet and electron accumulation below the g-C3N4 monolayer, potentially facilitating the separation of H2O oxidation and reduction reactions. Furthermore, we suggested that the photocatalytic performance of the Gdot/g-C3N4 nanocomposites can be further improved by decreasing the thickness of Gdots and tuning the size of Gdots. PMID:26659558

  14. Effect of high-pressure H{sub 2}O treatment on elimination of interfacial GeO{sub X} layer between ZrO{sub 2} and Ge stack

    SciTech Connect

    Huang, Chen-Shuo; Liu, Po-Tsun

    2011-08-22

    This investigation demonstrates the effect of high-pressure H{sub 2}O treatment on the elimination of the interfacial germanium suboxide (GeO{sub X}) layer between ZrO{sub 2} and Ge. The formation of GeO{sub X} interlayer increases the gate-leakage current and worsen the controllability of the gate during deposition or thermal cycles. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy reveal that high-pressure H{sub 2}O treatment eliminates the interfacial GeO{sub X} layer. The physical mechanism involves the oxidation of non-oxidized Zr with H{sub 2}O and the reduction of GeO{sub X} by H{sub 2}. Treatment with H{sub 2}O reduces the gate-leakage current of a ZrO{sub 2}/Ge capacitor by a factor of 1000.

  15. Mesoporous titania-vertical nanorod films with interfacial engineering for high performance dye-sensitized solar cells.

    PubMed

    Ahmed, Irfan; Fakharuddin, Azhar; Wali, Qamar; Bin Zainun, Ayib Rosdi; Ismail, Jamil; Jose, Rajan

    2015-03-13

    Working electrode (WE) fabrication offers significant challenges in terms of achieving high-efficiency dye-sensitized solar cells (DSCs). We have combined the beneficial effects of vertical nanorods grown on conducting glass substrate for charge transport and mesoporous particles for dye loading and have achieved a high photoconversion efficiency of (η) > 11% with an internal quantum efficiency of ∼93% in electrode films of thickness ∼7 ± 0.5 μm. Controlling the interface between the vertical nanorods and the mesoporous film is a crucial step in attaining high η. We identify three parameters, viz., large surface area of nanoparticles, increased light scattering of the nanorod-nanoparticle layer, and superior charge transport of nanorods, that simultaneously contribute to the improved photovoltaic performance of the WE developed. PMID:25687409

  16. Probing Interfacial Emulsion Stability Controls using Electrorheology

    NASA Astrophysics Data System (ADS)

    Wang, Xiuyu; Brandvik, Amy; Alvarado, Vladimir

    2010-11-01

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

  17. FinalReport for completed IPP-0110 and 0110A Projects:"High Energy Ion Technology of Interfacial Thin Film Coatings for Electronic, Optical and Industrial Applications"

    SciTech Connect

    Brown, Ian

    2009-09-01

    The DOE-supported IPP (Initiatives for Proliferation Prevention) Project, IPP-0110, and its accompanying 'add-on project' IPP-0110A, entitled 'High Energy Ion Technology of Interfacial Thin Film Coatings for Electronic, Optical and Industrial Applications' was a collaborative project involving the Lawrence Berkeley National Laboratory (LBNL) as the U.S. DOE lab; the US surface modification company, Phygen, Inc., as the US private company involved; and the High Current Electronics Institute (HCEI) of the Russian Academy of Sciences, Tomsk, Siberia, Russia, as the NIS Institute involved. Regular scientific research progress meetings were held to which personnel came from all participating partners. The meetings were held mostly at the Phygen facilities in Minneapolis, Minnesota (with Phygen as host) with meetings also held at Tomsk, Russia (HCEI as host), and at Berkeley, California (LBNL as host) In this way, good exposure of all researchers to the various different laboratories involved was attained. This report contains the Final Reports (final deliverables) from the Russian Institute, HCEI. The first part is that for IPP-0110A (the 'main part' of the overall project) and the second part is that for the add-on project IPP-0110A. These reports are detailed, and contain all aspects of all the research carried out. The project was successful in that all deliverables as specified in the proposals were successfully developed, tested, and delivered to Phygen. All of the plasma hardware was designed, made and tested at HCEI, and the performance was excellent. Some of the machine and performance parameters were certainly of 'world class'. The goals and requirements of the IPP Project were well satisfied. I would like to express my gratitude to the DOE IPP program for support of this project throughout its entire duration, and for the unparalleled opportunity thereby provided for all of the diverse participants in the project to join in this collaborative research. The

  18. The Effect of Interfacial Roughness on the Thin Film Morphology and Charge Transport of High-Performance Polythiophenes

    SciTech Connect

    Youngsuk,J.; Kline, J.; Fischer, D.; Lin, E.; Heeney, M.; McCulloch, I.; DeLongchamp, D.

    2008-01-01

    We control and vary the roughness of a dielectric upon which a high-performance polymer semiconductor, poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT) is cast, to determine the effects of roughness on thin-film microstructure and the performance of organic field-effect transistors (OFETs). pBTTT forms large, well-oriented terraced domains with high carrier mobility after it is cast upon flat, low-surface-energy substrates and heated to a mesophase. Upon dielectrics with root-mean square (RMS) roughness greater than 0.5 nm, we find significant morphological changes in the pBTTT active layer and significant reductions in its charge carrier mobility. The pBTTT films on rough dielectrics exhibit significantly less order than those on smooth dielectrics through characterization with atomic force microscopy and X-ray diffraction. This critical RMS roughness implies that there exists a condition at which the pBTTT domains no longer conform to the local nanometer-scale curvature of the substrate.

  19. High-Magnetization FeCo Nanochains with Ultrathin Interfacial Gaps for Broadband Electromagnetic Wave Absorption at Gigahertz.

    PubMed

    Zhang, Xuefeng; Li, Yixing; Liu, Rongge; Rao, Yi; Rong, Huawei; Qin, Gaowu

    2016-02-10

    Superparamagnetic FeCo nanochains consisting of assembled ∼25 nm nanoparticles and ∼1 nm gaps are synthesized by facial wet-chemical route and exhibit significant electromagnetic absorption at gigahertz. Both the dielectric and magnetic loss factors present dual-resonance behaviors at 2-18 GHz frequencies, originated from the asymmetric architecture of the cubic FeCo particles that assembled in a one-dimensional chain structure. Theoretical analyses uncover that the origins of the enhancement of electromagnetic losses are ascribed to the high magnetization (228 emu/g) and the ultrathin gaps (∼1 nm), which enhances the Snoek limit and induces anisotropic dielectric polarizations, consequently constructing a proper electromagnetic match. PMID:26775668

  20. High-Efficiency Nonfullerene Polymer Solar Cell Enabling by Integration of Film-Morphology Optimization, Donor Selection, and Interfacial Engineering.

    PubMed

    Zhang, Xin; Li, Weiping; Yao, Jiannian; Zhan, Chuanlang

    2016-06-22

    Carrier mobility is a vital factor determining the electrical performance of organic solar cells. In this paper we report that a high-efficiency nonfullerene organic solar cell (NF-OSC) with a power conversion efficiency of 6.94 ± 0.27% was obtained by optimizing the hole and electron transportations via following judicious selection of polymer donor and engineering of film-morphology and cathode interlayers: (1) a combination of solvent annealing and solvent vapor annealing optimizes the film morphology and hence both hole and electron mobilities, leading to a trade-off of fill factor and short-circuit current density (Jsc); (2) the judicious selection of polymer donor affords a higher hole and electron mobility, giving a higher Jsc; and (3) engineering the cathode interlayer affords a higher electron mobility, which leads to a significant increase in electrical current generation and ultimately the power conversion efficiency (PCE). PMID:27246160

  1. 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.

  2. 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

  3. 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.

  4. Single-step formation of ZnO/ZnWO(x) bilayer structure via interfacial engineering for high performance and low energy consumption resistive memory with controllable high resistance states.

    PubMed

    Lin, Shih-Ming; Huang, Jian-Shiou; Chang, Wen-Chih; Hou, Te-Chien; Huang, Hsin-Wei; Huang, Chi-Hsin; Lin, Su-Jien; Chueh, Yu-Lun

    2013-08-28

    A spontaneously formed ZnO/ZnWOx bilayer resistive memory via an interfacial engineering by one-step sputtering process with controllable high resistance states was demonstrated. The detailed formation mechanism and microstructure of the ZnWOx layer was explored by X-ray photoemission spectroscopy (XPS) and transmission electron microscope in detail. The reduced trapping depths from 0.46 to 0.29 eV were found after formation of ZnWOx layer, resulting in an asymmetric I-V behavior. In particular, the reduction of compliance current significantly reduces the switching current to reach the stable operation of device, enabling less energy consumption. Furthermore, we demonstrated an excellent performance of the complementary resistive switching (CRS) based on the ZnO/ZnWOx bilayer structure with DC endurance >200 cycles for a possible application in three-dimensional multilayer stacking. PMID:23876031

  5. 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

  6. Interfacial solvation thermodynamics.

    PubMed

    Ben-Amotz, Dor

    2016-10-19

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

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

    SciTech Connect

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

    2007-09-01

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

  8. Interfacial instabilities and Kapitsa pendula

    NASA Astrophysics Data System (ADS)

    Krieger, Madison

    2015-11-01

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

  9. Interfacial insert for electrical connectors

    NASA Technical Reports Server (NTRS)

    Macavay, D.

    1975-01-01

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

  10. 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

    that leads to splitting (fluid separation). We investigate the interaction of these prominent interfacial instabilities in the absence of gravity, concentrating on harmonically vibrated rectangular containers of fluid. We compare vibroequilibria theory with direct numerical simulations and consider the effect of surfaces waves, which can excite sloshing motion of the vibroequilibria. We systematically investigate the saddle-node bifurcation experienced by a symmetric singly connected vibroequilibria solution, for sufficiently deep containers, as forcing is increased. Beyond this instability, the fluid rapidly separates into (at least) two distinct masses. Pronounced hysteresis is associated with this transition, even in the presence of gravity. The interaction of vibroequilibria and frozen waves is investigated in two-fluid systems. Preparations for a parabolic flight experiment on fluids vibrated at high frequencies are discussed.

  11. More About Measuring Interfacial Tension Between Liquids

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  12. 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.

  13. Interfacial shear stress in stratified flow in a horizontal rectangular duct

    SciTech Connect

    Lorencez, C.; Kawaji, M.; Murao, Y.

    1995-09-01

    Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods.

  14. 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

  15. 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.

  16. 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.

  17. Understanding interfacial chemistry and stability for performance improvement and fade of high-energy Li-ion battery of LiNi0.5Co0.2Mn0.3O2//silicon-graphite

    NASA Astrophysics Data System (ADS)

    Nguyen, Dan-Thien; Kang, Joonsup; Nam, Kyoung-Mo; Paik, Younkee; Song, Seung-Wan

    2016-01-01

    Understanding the chemical processes that occur at the electrode/electrolyte interface in a battery is crucial, as the interactions between anode/cathode and electrolyte and between cathode and anode of a full-cell determine the final battery performance. We have investigated the correlation among cycling performance, interfacial reaction behavior and the solid electrolyte interphase (SEI) stability of a LiNi0.5Co0.2Mn0.3O2//Si-graphite full-cell under an aggressive test condition between 3.0 and 4.55 V using fluoroethylene carbonate (FEC)-based electrolyte, and blended additives of methyl (2,2,2-trifluoroethyl)carbonate (FEMC) and vinylene carbonate (VC). Through the formation of a stable SEI at both high-voltage cathode and anode, metal dissolution from the cathode is inhibited and full-cell achieves enhanced cycling performance. Interfacially stabilized full-cell delivers a high energy of 622 Wh per kg of active material and improved capacity retention, whereas the cell in conventional electrolyte shows a rapid performance fade.

  18. 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

  19. Interfacial gauge methods for incompressible fluid dynamics.

    PubMed

    Saye, Robert

    2016-06-01

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

  20. 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

  1. Interfacial Kinetics of High-Al-Containing Ultra-Lightweight Steels with Calcium Silicate-Based Molten Oxides at High Temperature

    NASA Astrophysics Data System (ADS)

    Kim, Gi Hyun; Sohn, Il

    2016-06-01

    The kinetics of the high-temperature reaction between high-Al- and -Mn-containing steels and synthesized molten calcium silicate-based fluxes from 1623 K to 1643 K (1350 °C to 1370 °C) was studied. Cylindrical steel rods were rotated in the molten fluxes for 300 to 1200 seconds at various temperatures below the melting point of the steels. The rods were connected to a rheometer, and the initial reaction rates were estimated from the torque variations. The dissolution of the steel into the molten slag was correlated to the variation in torque. The kinetics of the reaction between the rods and the slag estimated from the torque and subsequently from the viscosity were confirmed from the mass balance and from the variation in the chemical compositions of the rods and the molten slags, respectively. The liquid-phase mass transfer coefficient of Al2O3 was calculated to be 1.14 × 10-2 cm/s at 1623 K (1350 °C) and 1.52 × 10-2 cm/s at 1633 K (1360 °C). The kinetics calculated assuming liquid-phase mass transfer control was observed to be similar to the aforementioned kinetics determined from the dynamic viscosity variations. On the basis of dimensionless analysis of the Sherwood number (Sh = 0.05·Re0.65Sc0.31), liquid-phase mass transfer from the metal/flux interface was observed to be the rate-controlling step.

  2. Achieving high capacity in bulk-type solid-state lithium ion battery based on Li6.75La3Zr1.75Ta0.25O12 electrolyte: Interfacial resistance

    NASA Astrophysics Data System (ADS)

    Liu, Ting; Ren, Yaoyu; Shen, Yang; Zhao, Shi-Xi; Lin, Yuanhua; Nan, Ce-Wen

    2016-08-01

    A bulk-type all-solid-state lithium ion battery based on Ta-doped Li6.75La3Zr1.75Ta0.25O12 (LLZ-Ta) is prepared by a simple solid state process with high capacity of 279.0 μAh cm-2 at 80 °C. However, severe polarization is discovered during charging/discharging cycles at room temperature (RT) for battery with a higher active cathode loading. Large interfacial resistance due to the poor contact at the interfaces between cathode and LLZ-Ta solid electrolyte and at the interfaces within the composite cathode layer is proven to be the main reason for the poor electrochemical performance of the battery at RT. The polarization could be suppressed at elevated temperature, which is attributed to the decreased interfacial resistance as indicated by the results of impedance measurements and gives rise to much enhanced performance of the all-solid-state battery.

  3. Morphology controlled synthesis of platinum nanoparticles performed on the surface of graphene oxide using a gas-liquid interfacial reaction and its application for high-performance electrochemical sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Zheng, Jianbin

    2016-07-21

    In this paper, we report a novel morphology-controlled synthetic method. Platinum (Pt) nanoparticles with three kinds of morphology (aggregation-like, cube-like and globular) were grown on the surface of graphene oxide (GO) using a simple gas-liquid interfacial reaction and Pt/GO nanocomposites were obtained successfully. According to the experimental results, the morphology of the Pt nanoparticles can be controlled by adjusting the reaction temperature with the protection of chitosan. The obtained Pt/GO nanocomposites were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). Then the Pt/GO nanocomposites with the three kinds of morphology were all used to fabricate electrochemical sensors. The electrochemical experimental results indicated that compared with various reported electrochemical sensors, the Pt/GO modified sensors in this work exhibit a low detection limit, high sensitivity and an extra wide linear range for the detection of nitrite. In addition, the synthesis of Pt particles based on a gas-liquid interfacial reaction provides a new platform for the controllable synthesis of nanomaterials. PMID:27181605

  4. 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.

  5. Rheology and interfacial tension of biopolymers

    NASA Astrophysics Data System (ADS)

    Kandadai, Madhuvanthi A.

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

  6. 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.

  7. Low interfacial trap density and high-temperature thermal stability in atomic layer deposited single crystal Y2O3/n-GaAs(001)

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Hsun; Fu, Chien-Hua; Lin, Keng-Yung; Chen, Kuan-Hsiung; Chang, Tsong-Wen; Raynien Kwo, J.; Hong, Minghwei

    2016-08-01

    A low interfacial trap density (D it) of 2.2 × 1011 eV‑1 cm‑2 has been achieved with an atomic layer deposited (ALD) single crystal Y2O3 epitaxially on n-GaAs(001), along with a small frequency dispersion of 10.3% (2.6%/decade) at the accumulation region in the capacitance–voltage (C–V) curves. The D it and frequency dispersion in the C–V curves in this work are the lowest among all of the reported ALD-oxides on n-type GaAs(001). The D it was measured using the conductance–voltage (G–V) and quasi-static C–V (QSCV) methods. Moreover, the heterostructure was thermally stable with rapid annealing at 900 °C under various durations in He and N2, which has not been achieved in the heterostructures of ALD-Al2O3 or HfO2 on GaAs.

  8. Pre-treatments applied to oxidized aluminum surfaces to modify the interfacial bonding with bis-1,2-(triethoxysilyl)ethane (BTSE). Part I. High-purity Al with native oxide

    NASA Astrophysics Data System (ADS)

    Teo, M.; Kim, J.; Wong, P. C.; Wong, K. C.; Mitchell, K. A. R.

    2005-12-01

    A remote microwave-generated H 2 plasma and heating to 250 °C were separately used to modify high-purity oxidized aluminum surfaces and to assess whether these treatments can help enhance adhesion with bis-1,2-(triethoxysilyl)ethane (BTSE) coatings. Different initial oxide surfaces were considered, corresponding to the native oxide and to surfaces formed by the Forest Products Laboratory (FPL) treatment applied for either 15 or 60 min. BTSE is applied from solution at pH 4, and competing processes of etching, protonation (to form OH groups) and coupling (to form Al sbnd O sbnd Si interfacial bonds) occur at the solid-liquid interface. Scanning electron microscopy (SEM) was used to determine how the topographies of the modified Al surfaces changed with the different pre-treatments and with exposure to a buffer solution of pH 4. Secondary-ion mass spectrometry (SIMS) was used to determine the direct amount of Al sbnd O sbnd Si interfacial bonds by measuring the ratio of peak intensities 71-70 amu, while X-ray photoelectron spectroscopy (XPS) was used to determine the overall strength of the silane coating adhesion by measuring the Si 2p signals before and after application of an ultrasonic rinse to the coated sample. Measured Al 2p and O 1s spectra helped assess how the different pre-treatments modified the various Al oxidized surfaces prior to BTSE coating. Pre-treated samples that showed increased Al sbnd O sbnd Si bonding after BTSE coating corresponded to surfaces, which did not show evidence of significant etching after exposure to a pH 4 environment. This suggests that such surfaces are more receptive to the coupling reaction during exposure to the BTSE coating solution. These surfaces include all H 2 plasma-treated samples, the heated native oxide and the sample that only received the 15 min FPL treatment. In contrast, other surfaces that show evidence of etching in pH 4 environments are samples that received lower amounts of Al sbnd O sbnd Si interfacial

  9. Impact of electrically formed interfacial layer and improved memory characteristics of IrOx/high-κx/W structures containing AlOx, GdOx, HfOx, and TaOx switching materials

    PubMed Central

    2013-01-01

    Improved switching characteristics were obtained from high-κ oxides AlOx, GdOx, HfOx, and TaOx in IrOx/high-κx/W structures because of a layer that formed at the IrOx/high-κx interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled ‘SET/RESET’ current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrOx/high-κx interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrOx/AlOx/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>105 cycles), and data retention of >104 s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications. PMID:24011235

  10. Impact of electrically formed interfacial layer and improved memory characteristics of IrOx/high-κx/W structures containing AlOx, GdOx, HfOx, and TaOx switching materials

    NASA Astrophysics Data System (ADS)

    Prakash, Amit; Maikap, Siddheswar; Banerjee, Writam; Jana, Debanjan; Lai, Chao-Sung

    2013-09-01

    Improved switching characteristics were obtained from high-κ oxides AlOx, GdOx, HfOx, and TaOx in IrOx/high-κx/W structures because of a layer that formed at the IrOx/high-κx interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled `SET/RESET' current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrOx/high-κx interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrOx/AlOx/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>105 cycles), and data retention of >104 s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications.

  11. Interfacial electronic effects control the reaction selectivity of platinum catalysts.

    PubMed

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts. PMID:26808458

  12. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    NASA Astrophysics Data System (ADS)

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  13. Graphene as an efficient interfacial layer for electrochromic devices.

    PubMed

    Lin, Feng; Bult, Justin B; Nanayakkara, Sanjini; Dillon, Anne C; Richards, Ryan M; Blackburn, Jeffrey L; Engtrakul, Chaiwat

    2015-06-01

    This study presents an interfacial modification strategy to improve the performance of electrochromic films that were fabricated by a magnetron sputtering technique. High-quality graphene sheets, synthesized by chemical vapor deposition, were used to modify fluorine-doped tin oxide substrates, followed by the deposition of high-performance nanocomposite nickel oxide electrochromic films. Electrochromic cycling results revealed that a near-complete monolayer graphene interfacial layer improves the electrochromic performance in terms of switching kinetics, activation period, coloration efficiency, and bleached-state transparency, while maintaining ∼100% charge reversibility. The present study offers an alternative route for improving the interfacial properties between electrochromic and transparent conducting oxide films without relying on conventional methods such as nanostructuring or thin film composition control. PMID:25950270

  14. 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

  15. Interfacial activity in alkaline flooding enhanced oil recovery

    SciTech Connect

    Chan, M.K.

    1981-01-01

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

  16. Self-Powered, High-Speed and Visible-Near Infrared Response of MoO(3-x)/n-Si Heterojunction Photodetector with Enhanced Performance by Interfacial Engineering.

    PubMed

    Zhao, Chuanxi; Liang, Zhimin; Su, Mingze; Liu, Pengyi; Mai, Wenjie; Xie, Weiguang

    2015-11-25

    Photodetectors with a wide spectrum response are important components for sensing, imaging, and other optoelectronic applications. A molybdenum oxide (MoO(3-x))/Si heterojunction has been applied as solar cells with great success, but its potential in photodetectors has not been explored yet. Herein, a self-powered, high-speed heterojunction photodetector fabricated by coating an n-type Si hierarchical structure with an ultrathin hole-selective layer of molybdenum oxide (MoO(3-x)) is first investigated. Excellent and stable photoresponse performance is obtained by using a methyl group passivated interface. The heterojunction photodetector demonstrated high sensitivity to a wide spectrum from 300 to 1100 nm. The self-powered photodetector shows a high detectivity of (∼6.29 × 10(12) cmHz(1/2) W(-1)) and fast response time (1.0 μs). The excellent photodetecting performance is attributed to the enhanced interfacial barrier height and three-dimensional geometry of Si nanostructures, which is beneficial for efficient photocarrier collection and transportation. Finally, our devices show excellent long-term stability in air for 6 months with negligible performance degradation. The thermal evaporation method for large-scale fabrication of MoO(3-x)/n-Si photodetectors makes it suitable for self-powered, multispectral, and high-speed response photodetecting applications. PMID:26544078

  17. 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.

  18. Preliminary exploration of the interfacial structure of nanocrystalline materials

    SciTech Connect

    Guo, W.Q.; Liu, X.D.; Ding, B.Z.

    1995-12-31

    The present intense interest in exploration on nanostructured materials stems from the studies of interfacial structures of nanocrystalline materials. Up to now, there are two different results of the exploration on interfacial structure of nanocrystalline materials. The first one supposed by Gleiter et al. is a so-called {open_quotes}gas-like{close_quotes} structure. They reported that the interfaces of nanocrystalline materials represent a novel type of solid structure without any long or short range order, corresponding structurally to a {open_quotes}gas-like{close_quotes} solid. This structure can be verified with X-ray diffraction, Mossbauer spectroscopy, positron lifetime spectroscopy and extended X-ray absorption fine structure (EXFAS). The second result obtained by Siegel et al. with high resolution electron microscopy, raman scattering and small angle X-ray and neutron diffraction is that the interfacial structures of nanocrystalline materials are rather similar to those in conventional coarse-grained polycrystals.

  19. Environmental Applications of Interfacial Materials with Special Wettability.

    PubMed

    Wang, Zhangxin; Elimelech, Menachem; Lin, Shihong

    2016-03-01

    Interfacial materials with special wettability have become a burgeoning research area in materials science in the past decade. The unique surface properties of materials and interfaces generated by biomimetic approaches can be leveraged to develop effective solutions to challenging environmental problems. This critical review presents the concept, mechanisms, and fabrication techniques of interfacial materials with special wettability, and assesses the environmental applications of these materials for oil-water separation, membrane-based water purification and desalination, biofouling control, high performance vapor condensation, and atmospheric water collection. We also highlight the most promising properties of interfacial materials with special wettability that enable innovative environmental applications and discuss the practical challenges for large-scale implementation of these novel materials. PMID:26829583

  20. Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion

    NASA Astrophysics Data System (ADS)

    Das, Tanmay; Kulkarni, Prabhanjan D.; Purandare, S. C.; Barshilia, Harish C.; Bhattacharyya, Somnath; Chowdhury, Prasanta

    2014-06-01

    We observed interfacial chemical sharpening due to uphill diffusion in post annealed ultrathin multilayer stack of Co and Pt, which leads to enhanced interfacial perpendicular magnetic anisotropy (PMA). This is surprising as these elements are considered as perfectly miscible. This chemical sharpening was confirmed through quantitative energy dispersive x-ray (EDX) spectroscopy and intensity distribution of images taken on high angle annular dark field (HAADF) detector in Scanning Transmission Electron Microscopic (STEM) mode. This observation demonstrates an evidence of miscibility gap in ultrathin coherent Co/Pt multilayer stacks.

  1. Interfacial adsorption and aggregation of amphiphilic proteins

    NASA Astrophysics Data System (ADS)

    Cheung, David

    2012-02-01

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

  2. Meter-long multiblock copolymer microfibers via interfacial bioorthogonal polymerization

    PubMed Central

    Liu, Shuang; Zhang, Han; Remy, Roddel A.; Deng, Fei; Mackay, Michael E.; Fox, Joseph M.; Jia, Xinqiao

    2015-01-01

    High molecular weight multiblock copolymers are synthesized as robust polymer fibers via interfacial bioorthogonal polymerization employing the rapid cycloaddition of s-tetrazines with strained trans-cyclooctenes. When cell-adhesive peptide was incorporated in the tetrazine monomer, the resulting protein-mimetic polymer fibers provide guidance cues for cell attachment and elongation. PMID:25824805

  3. Measuring Interfacial Tension Between Immiscible Liquids

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  4. Interfacial reactions between titanium and borate glass

    SciTech Connect

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

    1992-12-31

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

  5. Hierarchical Sheet-on-Sheet ZnIn2S4/g-C3N4 Heterostructure with Highly Efficient Photocatalytic H2 production Based on Photoinduced Interfacial Charge Transfer

    PubMed Central

    Zhang, Zhenyi; Liu, Kuichao; Feng, Zhiqing; Bao, Yanan; Dong, Bin

    2016-01-01

    We have realized in-situ growth of ultrathin ZnIn2S4 nanosheets on the sheet-like g-C3N4 surfaces to construct a “sheet-on-sheet” hierarchical heterostructure. The as-synthesized ZnIn2S4/g-C3N4 heterojunction nanosheets exhibit remarkably enhancement on the photocatalytic activity for H2 production. This enhanced photoactivity is mainly attributed to the efficient interfacial transfer of photoinduced electrons and holes from g-C3N4 to ZnIn2S4 nanosheets, resulting in the decreased charge recombination on g-C3N4 nanosheets and the increased amount of photoinduced charge carriers in ZnIn2S4 nanosheets. Meanwhile, the increased surface-active-sites and extended light absorption of g-C3N4 nanosheets after the decoration of ZnIn2S4 nanosheets may also play a certain role for the enhancement of photocatalytic activity. Further investigations by the surface photovoltage spectroscopy and transient photoluminescence spectroscopy demonstrate that ZnIn2S4/g-C3N4 heterojunction nanosheets considerable boost the charge transfer efficiency, therefore improve the probability of photoinduced charge carriers to reach the photocatalysts surfaces for highly efficient H2 production. PMID:26753795

  6. Hierarchical Sheet-on-Sheet ZnIn2S4/g-C3N4 Heterostructure with Highly Efficient Photocatalytic H2 production Based on Photoinduced Interfacial Charge Transfer.

    PubMed

    Zhang, Zhenyi; Liu, Kuichao; Feng, Zhiqing; Bao, Yanan; Dong, Bin

    2016-01-01

    We have realized in-situ growth of ultrathin ZnIn2S4 nanosheets on the sheet-like g-C3N4 surfaces to construct a "sheet-on-sheet" hierarchical heterostructure. The as-synthesized ZnIn2S4/g-C3N4 heterojunction nanosheets exhibit remarkably enhancement on the photocatalytic activity for H2 production. This enhanced photoactivity is mainly attributed to the efficient interfacial transfer of photoinduced electrons and holes from g-C3N4 to ZnIn2S4 nanosheets, resulting in the decreased charge recombination on g-C3N4 nanosheets and the increased amount of photoinduced charge carriers in ZnIn2S4 nanosheets. Meanwhile, the increased surface-active-sites and extended light absorption of g-C3N4 nanosheets after the decoration of ZnIn2S4 nanosheets may also play a certain role for the enhancement of photocatalytic activity. Further investigations by the surface photovoltage spectroscopy and transient photoluminescence spectroscopy demonstrate that ZnIn2S4/g-C3N4 heterojunction nanosheets considerable boost the charge transfer efficiency, therefore improve the probability of photoinduced charge carriers to reach the photocatalysts surfaces for highly efficient H2 production. PMID:26753795

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

    PubMed

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

    2015-09-15

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

  8. Science and technology of thin films and interfacial layers in ferroelectric and high-dielectric constant heterostructures and application to devices.

    SciTech Connect

    Auciello, O.; Materials Science Division

    2006-01-01

    The fabrication of the next generation of complex oxide thin film-based micro and nanoscale devices, such as, for example, low and high density nonvolatile ferroelectric random access memories (FeRAMS), high-dielectric constant (K) high-frequency devices, and the next generation of complimentary metal oxide semiconductor (CMOS) nanoscale devices based on high-K dielectrics, require understanding and control of film growth and interface processes as well as development of materials integration strategies with atomic scale control. In recent years, we developed and applied a unique combination of integrated film synthesis/in situ characterization and ex situ analytical techniques capable of providing information about thin film surface and interface processes at the atomic scale as required for the development of the devices mentioned above. These techniques are also useful for establishing composition-microstructure-property relationships critical for the integration of oxide thin films with semiconductor device platforms for the development of a whole new generation of micro and nanodevices based on film technologies beyond semiconductors and specifically silicon. Our recent work has been focused on developing diffusion barrier layers and heterostructured bottom electrodes that play a critical role in high-density FeRAM integration. We demonstrated that TiAl layers can be used as a material with a double diffusion barrier/bottom electrode functionality for integration of ferroelectric capacitors CMOS devices for fabrication of FeRAMs. We also demonstrated that control of interfaces is critical to the integration of high-K dielectric films with appropriate substrates for the fabrication of high-performance high-frequency devices, and here again a diffusion barrier such as the TiAl layer developed by our group is critical for such integration. These studies revealed that when properly oxidized, nanoscale thick amorphous Ti-Al-O layers exhibit properties that make

  9. Evolution of interfacial Fermi level in In0.53Ga0.47As/high-κ/TiN gate stacks

    NASA Astrophysics Data System (ADS)

    Carr, Adra; Rozen, John; Frank, Martin M.; Ando, Takashi; Cartier, Eduard A.; Kerber, Pranita; Narayanan, Vijay; Haight, Richard

    2015-07-01

    The net charge state was probed of metal-oxide-semiconductor gate stacks consisting of In0.53Ga0.47As /high-κ dielectric/5 nm TiN, for both Al2O3 and HfO2 dielectrics, via investigation of band bending at the InGaAs/high-κ interface. Using pump-probe photoelectron spectroscopy, changes to band bending were studied for each sequential layer deposited onto the InGaAs substrate and subsequent annealing up to 600 °C. Two behavioral regions were observed in annealing studies: (1) a lower temperature (<350 °C) region, attributed to changes at the high-κ/TiN interface, and (2) a higher temperature region (> 350 °C), associated with a net positive charge increase within the oxide. These band bending measurements delineate the impact of processing steps inherently inaccessible via capacitance-voltage electrical characterization.

  10. Highly Enhanced Electromechanical Stability of Large-Area Graphene with Increased Interfacial Adhesion Energy by Electrothermal-Direct Transfer for Transparent Electrodes.

    PubMed

    Kim, Jangheon; Kim, Gi Gyu; Kim, Soohyun; Jung, Wonsuk

    2016-09-01

    Graphene, a two-dimensional sheet of carbon atoms in a hexagonal lattice structure, has been extensively investigated for research and industrial applications as a promising material with outstanding electrical, mechanical, and chemical properties. To fabricate graphene-based devices, graphene transfer to the target substrate with a clean and minimally defective surface is the first step. However, graphene transfer technologies require improvement in terms of uniform transfer with a clean, nonfolded and nontorn area, amount of defects, and electromechanical reliability of the transferred graphene. More specifically, uniform transfer of a large area is a key challenge when graphene is repetitively transferred onto pretransferred layers because the adhesion energy between graphene layers is too low to ensure uniform transfer, although uniform multilayers of graphene have exhibited enhanced electrical and optical properties. In this work, we developed a newly suggested electrothermal-direct (ETD) transfer method for large-area high quality monolayer graphene with less defects and an absence of folding or tearing of the area at the surface. This method delivers uniform multilayer transfer of graphene by repetitive monolayer transfer steps based on high adhesion energy between graphene layers and the target substrate. To investigate the highly enhanced electromechanical stability, we conducted mechanical elastic bending experiments and reliability tests in a highly humid environment. This ETD-transferred graphene is expected to replace commercial transparent electrodes with ETD graphene-based transparent electrodes and devices such as a touch panels with outstanding electromechanical stability. PMID:27564120

  11. Protein interfacial structure and nanotoxicology

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  12. Sinusoidal Forcing of Interfacial Films

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  13. Interfacial Widths of Conjugated Polymer Bilayers

    SciTech Connect

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

    2009-08-13

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

  14. Interfacial Characterization of Dissimilar Joints Between Al/Mg/Al-Trilayered Clad Sheet to High-Strength Low-Alloy Steel

    NASA Astrophysics Data System (ADS)

    Macwan, A.; Jiang, X. Q.; Chen, D. L.

    2015-07-01

    Magnesium (Mg) alloys are increasingly used in the automotive and aerospace sectors to reduce vehicle weight. Al/Mg/Al tri-layered clad sheets are deemed as a promising alternative to improve the corrosion resistance and formability of Mg alloys. The structural application of Al/Mg/Al tri-layered clad sheets inevitably involves welding and joining in the multi-material vehicle body manufacturing. This study aimed to characterize the bonding interface microstructure of the Al/Mg/Al-clad sheet to high-strength low-alloy steel with and without Zn coating using ultrasonic spot welding at different levels of welding energy. It was observed that the presence of Zn coating improved the bonding at the interface due to the formation of Al-Zn eutectic structure via enhanced diffusion. At a higher level of welding energy, characteristic flow patterns of Zn into Al-clad layer were observed with an extensive penetration mainly along some high angle grain boundaries. The dissimilar joints without Zn coating made at a high welding energy of 800 J failed partially from the Al/Fe weld interface and partially from the Al/Mg clad interface, while the joints with Zn coating failed from the Al/Mg clad interface due to the presence of brittle Al12Mg17 phase.

  15. Evolution of interfacial Fermi level in In{sub 0.53}Ga{sub 0.47}As/high-κ/TiN gate stacks

    SciTech Connect

    Carr, Adra; Rozen, John; Frank, Martin M.; Ando, Takashi; Cartier, Eduard A.; Kerber, Pranita; Narayanan, Vijay; Haight, Richard

    2015-07-06

    The net charge state was probed of metal-oxide-semiconductor gate stacks consisting of In{sub 0.53}Ga{sub 0.47}As /high-κ dielectric/5 nm TiN, for both Al{sub 2}O{sub 3} and HfO{sub 2} dielectrics, via investigation of band bending at the InGaAs/high-κ interface. Using pump-probe photoelectron spectroscopy, changes to band bending were studied for each sequential layer deposited onto the InGaAs substrate and subsequent annealing up to 600 °C. Two behavioral regions were observed in annealing studies: (1) a lower temperature (<350 °C) region, attributed to changes at the high-κ/TiN interface, and (2) a higher temperature region (> 350 °C), associated with a net positive charge increase within the oxide. These band bending measurements delineate the impact of processing steps inherently inaccessible via capacitance-voltage electrical characterization.

  16. 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.

  17. Interfacial tension measurements using MRI drop shape analysis.

    PubMed

    Hussain, R; Vogt, S J; Honari, A; Hollingsworth, K G; Sederman, A J; Mitchell, J; Johns, M L

    2014-02-18

    Accurate interfacial tension data for fluid systems such as hydrocarbons and water is essential to many applications such as reservoir oil and gas recovery predictions. Conventional interfacial tension measurement techniques typically use optical images to analyze droplet shapes but require that the continuous-phase fluid be optically transparent and that the fluids are not refractive index matched. Magnetic resonance images obtain contrast between fluids using other mechanisms such as magnetic relaxation weighting, so systems that are impossible to measure with optical methods may be analyzed. In this article, we present high-field (9.4 T) MRI images of various droplets analyzed with axisymmetric drop shape analysis. The resultant interfacial tension data show good agreement with literature data. The method is subsequently demonstrated using both opaque continuous phases and refractive-index-matched fluids. We conclude with a brief consideration of the potential to extrapolate the methodology to lower magnetic fields (0.3 T), featuring more accessible hardware; although droplet imaging is possible, resolution and stability do not currently permit accurate interfacial tension measurements. PMID:24471906

  18. 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

  19. Argon Cluster Sputtering Source for ToF-SIMS Depth Profiling of Insulating Materials: High Sputter Rate and Accurate Interfacial Information

    SciTech Connect

    Wang, Zhaoying; Liu, Bingwen; Zhao, Evan; Jin, Ke; Du, Yingge; Neeway, James J.; Ryan, Joseph V.; Hu, Dehong; Zhang, Hongliang; Hong, Mina; Le Guernic, Solenne; Thevuthasan, Suntharampillai; Wang, Fuyi; Zhu, Zihua

    2015-08-01

    For the first time, the use of an argon cluster ion sputtering source has been demonstrated to perform superiorly relative to traditional oxygen and cesium ion sputtering sources for ToF-SIMS depth profiling of insulating materials. The superior performance has been attributed to effective alleviation of surface charging. A simulated nuclear waste glass, SON68, and layered hole-perovskite oxide thin films were selected as model systems due to their fundamental and practical significance. Our study shows that if the size of analysis areas is same, the highest sputter rate of argon cluster sputtering can be 2-3 times faster than the highest sputter rates of oxygen or cesium sputtering. More importantly, high quality data and high sputter rates can be achieved simultaneously for argon cluster sputtering while this is not the case for cesium and oxygen sputtering. Therefore, for deep depth profiling of insulating samples, the measurement efficiency of argon cluster sputtering can be about 6-15 times better than traditional cesium and oxygen sputtering. Moreover, for a SrTiO3/SrCrO3 bi-layer thin film on a SrTiO3 substrate, the true 18O/16O isotopic distribution at the interface is better revealed when using the argon cluster sputtering source. Therefore, the implementation of an argon cluster sputtering source can significantly improve the measurement efficiency of insulating materials, and thus can expand the application of ToF-SIMS to the study of glass corrosion, perovskite oxide thin films, and many other potential systems.

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

    NASA Astrophysics Data System (ADS)

    Jiang, Fei; Tsuji, Takeshi

    2015-03-01

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

  1. 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

  2. Pt- and TCO-Free Flexible Cathode for DSSC from Highly Conducting and Flexible PEDOT Paper Prepared via in Situ Interfacial Polymerization.

    PubMed

    Anothumakkool, Bihag; Agrawal, Ishita; Bhange, Siddheshwar N; Soni, Roby; Game, Onkar; Ogale, Satishchandra B; Kurungot, Sreekumar

    2016-01-13

    Here, we report the preparation of a flexible, free-standing, Pt- and TCO-free counter electrode in dye-sensitized solar cell (DSSC)-derived from polyethylenedioxythiophene (PEDOT)-impregnated cellulose paper. The synthetic strategy of making the thin flexible PEDOT paper is simple and scalable, which can be achieved via in situ polymerization all through a roll coating technique. The very low sheet resistance (4 Ω/□) obtained from a film of 40 μm thick PEDOT paper (PEDOT-p-5) is found to be superior to the conventional fluorine-doped tin oxide (FTO) substrate. The high conductivity (357 S/cm) displayed by PEDOT-p-5 is observed to be stable under ambient conditions as well as flexible and bending conditions. With all of these features in place, we could develop an efficient Pt- and TCO-free flexible counter electrode from PEDOT-p-5 for DSSC applications. The catalytic activity toward the tri-iodide reduction of the flexible electrode is analyzed by adopting various electrochemical methodologies. PEDOT-p-5 is found to display higher exchange current density (7.12 mA/cm(2)) and low charge transfer resistance (4.6 Ω) compared to the benchmark Pt-coated FTO glass (2.40 mA/cm(2) and 9.4 Ω, respectively). Further, a DSSC fabricated using PEDOT-p-5 as the counter electrode displays a comparable efficiency of 6.1% relative to 6.9% delivered by a system based on Pt/FTO as the counter electrode. PMID:26652291

  3. 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

  4. Studies on the disbonding initiation of interfacial cracks.

    SciTech Connect

    McAdams, Brian J.; Pearson, Raymond A.

    2005-08-01

    With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believed to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub

  5. 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.

  6. 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.

  7. Interfacial oxygen stabilizes composite silicon anodes.

    PubMed

    Sun, Chuan-Fu; Zhu, Hongli; Okada, Morihiro; Gaskell, Karen; Inoue, Yoku; Hu, Liangbing; Wang, YuHuang

    2015-01-14

    Silicon can store Li(+) at a capacity 10 times that of graphite anodes. However, to harness this remarkable potential for electrical energy storage, one has to address the multifaceted challenge of volume change inherent to high capacity electrode materials. Here, we show that, solely by chemical tailoring of Si-carbon interface with atomic oxygen, the cycle life of Si/carbon matrix-composite electrodes can be substantially improved, by 300%, even at high mass loadings. The interface tailored electrodes simultaneously attain high areal capacity (3.86 mAh/cm(2)), high specific capacity (922 mAh/g based on the mass of the entire electrode), and excellent cyclability (80% retention of capacity after 160 cycles), which are among the highest reported. Even at a high rate of 1C, the areal capacity approaches 1.61 mAh/cm(2) at the 500th cycle. This remarkable electrochemical performance is directly correlated with significantly improved structural and electrical interconnections throughout the entire electrode due to chemical tailoring of the Si-carbon interface with atomic oxygen. Our results demonstrate that interfacial bonding, a new dimension that has yet to be explored, can play an unexpectedly important role in addressing the multifaceted challenge of Si anodes. PMID:25513731

  8. Comparison of Interfacial Partitioning Tracer Test and X-ray Microtomography Measurements of Immiscible Fluid-Fluid Interfacial Areas within the Identical System

    NASA Astrophysics Data System (ADS)

    Carroll, K. C.; McDonald, K.; Brusseau, M. L. L.

    2015-12-01

    The interfacial area between immiscible fluids in porous media has been demonstrated to be a critical entity for improved understanding, characterization, and simulation of multiphase flow and mass transport in the subsurface. Two general methods are available for measuring interfacial areas for 3-D porous-media systems, high-resolution microtomographic imaging and interfacial partitioning tracer tests (IPTT). Each method has their associated advantages and disadvantages. A few prior research efforts have conducted comparative analyses of the two methods, which have generally indicated disparities in measured values for natural geomedia. For these studies, however, interfacial areas were measured for separate samples with each method due to method restrictions. Thus, to date, there has been no comparative analysis conducted wherein the two measurement methods were applied to the exact same sample. To address this issue, trichloroethene-water interfacial areas were measured for a system comprising a well-sorted, natural sand (median grain diameter of 0.323 mm) using both X-ray microtomography and IPTTs. The microtomographic imaging was conducted on the same packed columns used to conduct the IPTTs. Columns were imaged before and after the IPTTs to evaluate potential impacts of the tracer tests on fluid configuration. The interfacial areas measured using IPTT were 4-6 times larger than the microtomography results, which is consistent with previous work. This disparity was attributed to the inability of the microtomography method to characterize interfacial area associated with microscopic surface roughness. The results indicate that both methods provide useful measures of interfacial area as long as their limitations are recognized.

  9. 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

  10. Incorporating interfacial phenomena in solidification models

    NASA Technical Reports Server (NTRS)

    Beckermann, Christoph; Wang, Chao Yang

    1994-01-01

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

  11. A study of the interfacial resistive switching mechanism by proton exchange reactions on the SiO(x) layer.

    PubMed

    Zhou, Fei; Chang, Yao-Feng; Chen, Ying-Chen; Wu, Xiaohan; Zhang, Ye; Fowler, Burt; Lee, Jack C

    2016-01-14

    In this work, we investigated SiO(x)-based interfacial resistive switching in planar metal-insulator-metal structures using physical/chemical/electrical analyses. This work helps clarify the interfacial reaction process and mechanism in SiO(x), and also shows the potential for high temperature operation in future nonvolatile memory applications. PMID:26659556

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

    PubMed

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

    2014-08-01

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

  13. Interfacial defects in thin refractory metal films imaged by low-energy electron microscopy

    NASA Astrophysics Data System (ADS)

    Świȩch, W.; Mundschau, M.; Flynn, C. P.

    1999-05-01

    Low-energy electron microscopy is employed to image defects at buried interfaces through the strains they cause at the front surface. The interfacial defects studied here occur in high quality films of Mo(110) grown by molecular beam epitaxy on Al2O3(112¯0). The defects include steps and inclusions on the original sapphire surface and interfacial dislocations created where epitaxial strain causes slip.

  14. Covalent bonding modulated graphene-metal interfacial thermal transport

    NASA Astrophysics Data System (ADS)

    Jiang, Tao; Zhang, Xueqiang; Vishwanath, Suresh; Mu, Xin; Kanzyuba, Vasily; Sokolov, Denis A.; Ptasinska, Sylwia; Go, David B.; Xing, Huili Grace; Luo, Tengfei

    2016-05-01

    We report the covalent bonding enabled modulation of the interfacial thermal conductance between graphene and metals Cu, Al, and Pt by controlling the oxidation of graphene. By combining comprehensive X-ray photoelectron spectroscopy (XPS) analysis and time-domain thermoreflectance measurements, we quantify the effect of graphene oxidation on interfacial thermal conductance. It was found that thermal conductance increases with the degree of graphene oxidation until a peak value is obtained at an oxygen/carbon atom percentage of ~7.7%. The maximum enhancement in thermal conductance was measured to be 55%, 38%, and 49% for interfaces between oxidized graphene and Cu, Al, and Pt, respectively. In situ XPS measurements show that oxygen covalently binds to Cu and graphene simultaneously, forming a highly efficient bridge to enhance the thermal transport. Our molecular dynamics simulations verify that strong interfacial covalent bonds are the key to the thermal conductance enhancement. This work provides valuable insights into the mechanism of functionalization-induced thermal conductance enhancement and design guidelines for graphene-based devices.We report the covalent bonding enabled modulation of the interfacial thermal conductance between graphene and metals Cu, Al, and Pt by controlling the oxidation of graphene. By combining comprehensive X-ray photoelectron spectroscopy (XPS) analysis and time-domain thermoreflectance measurements, we quantify the effect of graphene oxidation on interfacial thermal conductance. It was found that thermal conductance increases with the degree of graphene oxidation until a peak value is obtained at an oxygen/carbon atom percentage of ~7.7%. The maximum enhancement in thermal conductance was measured to be 55%, 38%, and 49% for interfaces between oxidized graphene and Cu, Al, and Pt, respectively. In situ XPS measurements show that oxygen covalently binds to Cu and graphene simultaneously, forming a highly efficient bridge to enhance

  15. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

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

    1990-08-14

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

  16. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

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

    1990-01-01

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

  17. Cantilever based optical interfacial force microscope

    NASA Astrophysics Data System (ADS)

    Bonander, Jeremy R.; Kim, Byung I.

    2008-03-01

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

  18. Modeling interfacial fracture in Sierra.

    SciTech Connect

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

    2013-09-01

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

  19. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  20. Interfacial area transport in bubbly flow

    SciTech Connect

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

    1997-12-31

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

  1. Topology-generating interfacial pattern formation during liquid metal dealloying

    PubMed Central

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

    2015-01-01

    Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growth of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Moreover, we deduce scaling laws governing microstructural length scales and dealloying kinetics. PMID:26582248

  2. Topology-generating interfacial pattern formation during liquid metal dealloying.

    PubMed

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

    2015-01-01

    Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growth of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Moreover, we deduce scaling laws governing microstructural length scales and dealloying kinetics. PMID:26582248

  3. Topology-generating interfacial pattern formation during liquid metal dealloying

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  4. Interfacial Engineering for Quantum-Dot-Sensitized Solar Cells.

    PubMed

    Shen, Chao; Fichou, Denis; Wang, Qing

    2016-04-20

    Quantum-dot-sensitized solar cells (QDSCs) are promising solar-energy-conversion devices, as low-cost alternatives to the prevailing photovoltaic technologies. Compared with molecular dyes, nanocrystalline quantum dot (QD) light absorbers exhibit higher molar extinction coefficients and a tunable photoresponse. However, the power-conversion efficiencies (PCEs) of QDSCs are generally below 9.5 %, far behind their molecular sensitizer counterparts (up to 13 %). These low PCEs have been attributed to a large free-energy loss during sensitizer regeneration, energy loss during the charge-carrier transport and transfer processes, and inefficient charge separation at the QD/electrolyte interfaces, and various interfacial engineering strategies for enhancing the PCE and cell stability have been reported. Herein, we review recent progress in the interfacial engineering of QDSCs and discuss future prospects for the development of highly efficient and stable QDSCs. PMID:26879244

  5. Actuation of interfacial waves in oil-water flows

    NASA Astrophysics Data System (ADS)

    Park, Kyeong; Weheliye, Weheliye; Chinaud, Maxime; Angeli, Panagiota; James Percival Collaboration; Omar. K. Matar Collaboration

    2015-11-01

    Droplet detachment from interfacial waves in two-phase flows has pulled in noteworthy exploration interest. In order to examine this phenomenon experimentally and empower quantitative estimation, it is important to spatially confine the drop formation. In the present study, a cylinder, located close to the inlet of the test section and perpendicular to the direction of the flow, is placed in a two-phase stratified oil-water pipe flow. The introduction of this cylinder actuated interfacial waves and move from stratified to dispersed flow pattern. High speed visualisation and Particle Image Velocimetry (PIV) measurement are utilized to investigate the flow pattern maps of the two-phase flow and the velocity fields in the wake of the cylinder, respectively. These results will be compared with previous experimental studies. Department of Chemical Engineering South Kensington Campus Imperial College London SW7 2AZ.

  6. Topology-generating interfacial pattern formation during liquid metal dealloying

    DOE PAGESBeta

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

    2015-11-19

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

  7. Topology-generating interfacial pattern formation during liquid metal dealloying

    SciTech Connect

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

    2015-11-19

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

  8. 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.

  9. Particles with Tunable Porosity and Morphology by Controlling Interfacial Instability in Block Copolymer Emulsions.

    PubMed

    Ku, Kang Hee; Shin, Jae Man; Klinger, Daniel; Jang, Se Gyu; Hayward, Ryan C; Hawker, Craig J; Kim, Bumjoon J

    2016-05-24

    A series of porous block copolymer (BCP) particles with controllable morphology and pore sizes was fabricated by tuning the interfacial behavior of BCP droplets in oil-in-water emulsions. A synergistic adsorption of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) BCPs and sodium dodecyl sulfate (SDS) to the surface of the emulsion droplet induced a dramatic decrease in the interfacial tension and generated interfacial instability at the particle surface. In particular, the SDS concentration and the P4VP volume fraction of PS-b-P4VP were key parameters in determining the degree of interfacial instability, leading to different types of particles including micelles, capsules, closed-porosity particles, and open-porosity particles with tunable pore sizes ranging from 10 to 500 nm. The particles with open-porosity could be used as pH-responsive, high capacity delivery systems where the uptake and release of multiple dyes could be achieved. PMID:27138967

  10. Modeling and characterization of interfacial adhesion and fracture

    NASA Astrophysics Data System (ADS)

    Yao, Qizhou

    2000-09-01

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

  11. Interfacial stress transfer in a graphene nanosheet toughened hydroxyapatite composite

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Zhang, X. G.; Chen, Y.; Su, J. N.; Liu, W. W.; Zhang, T. H.; Qi, F.; Wang, Y. G.

    2014-10-01

    In recent years, graphene has emerged as potential reinforcing nanofiller in the composites for structural engineering due to its extraordinary high elastic modulus and mechanical strength. As recognized, the transfer of stress from a low modulus matrix to a high-modulus reinforcing graphene and the interfacial behavior at a graphene-matrix interface is the fundamental issue in these composites. In the case of graphene nanosheet (GNS) reinforced hydroxyapatite (HA) composite, this research presented analytical models and simulated that the number of graphene layers of GNSs has little effect on the maximum axial stress (˜0.35 GPa) and the maximum shear stress (˜0.14 GPa) at a GNS-HA interface, and the energy dissipation by GNS pull-out decreases with increasing the number of graphene layers due to weak bonding between them. Also, GNS-HA interfacial delamination and/or GNS rupture were also indentified to be the two key failure mechanisms. The computed results are expected to facilitate a better understanding of the interfacial behavior at a GNS-ceramic interface and to achieve tough ceramics reinforced with GNSs.

  12. Interfacial Shear Strength of Oxide Scale and SS 441 Substrate

    SciTech Connect

    Liu, Wenning N.; Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2011-05-01

    Recent developments on decreasing the operating temperature for Solid Oxide Fuel Cells (SOFCs) have enabled the use of high temperature ferritic alloys as interconnect materials. Oxide scale will inevitably grow on the ferritic interconnects in a high temperature oxidation environment of SOFCs. The growth of the oxide scale induces growth stresses in the scale layer and on the scale/substrate interface. These growth stresses combined with the thermal stresses induced upon stacking cooling by the thermal expansion coefficient mismatch between the oxide scale and the substrate may lead to scale delamination/buckling and eventual spallation, which may lead to serious cell performance degradation. Hence the interfacial adhesion strength between the oxide scale and the substrate is crucial to the reliability and durability of the metallic interconnect in SOFC operating environments. In this paper, we applied an integrated experimental/modeling methodology to quantify the interfacial adhesion strength between the oxide scale and the SS 441 metallic interconnect. The predicted interfacial strength is discussed in details.

  13. Interfacial phase-change memory.

    PubMed

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

    2011-08-01

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

  14. Interfacial Engineering of Molecular Photovoltaics

    NASA Astrophysics Data System (ADS)

    Shelton, Steven Wade

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

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

    SciTech Connect

    Kruzic, Jamie Joseph

    2002-03-01

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

  16. Nanotube attachment for prevention of interfacial delamination

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sharmila M.; Karumuri, Anil K.

    2010-09-01

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

  17. Modelling interfacial cracking with non-matching cohesive interface elements

    NASA Astrophysics Data System (ADS)

    Nguyen, Vinh Phu; Nguyen, Chi Thanh; Bordas, Stéphane; Heidarpour, Amin

    2016-07-01

    Interfacial cracking occurs in many engineering problems such as delamination in composite laminates, matrix/interface debonding in fibre reinforced composites etc. Computational modelling of these interfacial cracks usually employs compatible or matching cohesive interface elements. In this paper, incompatible or non-matching cohesive interface elements are proposed for interfacial fracture mechanics problems. They allow non-matching finite element discretisations of the opposite crack faces thus lifting the constraint on the compatible discretisation of the domains sharing the interface. The formulation is based on a discontinuous Galerkin method and works with both initially elastic and rigid cohesive laws. The proposed formulation has the following advantages compared to classical interface elements: (i) non-matching discretisations of the domains and (ii) no high dummy stiffness. Two and three dimensional quasi-static fracture simulations are conducted to demonstrate the method. Our method not only simplifies the meshing process but also it requires less computational demands, compared with standard interface elements, for problems that involve materials/solids having a large mismatch in stiffnesses.

  18. 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

  19. 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).

  20. Relaxations and Interfacial Water Ordering at the Corundum (110) Surface

    SciTech Connect

    Catalano, Jeffrey G.

    2010-09-17

    In situ high resolution specular X-ray reflectivity measurements were used to examine relaxations and interfacial water ordering occurring at the corundum (110)-water interface. Sample preparation affected the resulting surface structure. Annealing in air at 1373 K produced a reconstructed surface formed through an apparently ordered aluminum vacancy. The effect of the reconstruction on in-plane periodicity was not determined. The remaining aluminum sites on the surface maintain full coordination by oxygen and the surface was coated with a layer of physically adsorbed water. Ordering of water further from the surface was not observed. Acid etching of this surface and preparing a surface through annealing at 723 K both produced an unreconstructed surface with identical relaxations and water ordering. Relaxations were confined primarily to the top {approx}4 {angstrom} of the surface and were dominated by an increased distribution width of the fully occupied surface aluminum site and outward relaxation of the oxygen surface functional groups. A layer of adsorbed water fully coated the surface and occurred in two distinct sites. Water above this showed signs of layering and indicated that water ordering extended 7-10 {angstrom} from the surface. Relaxations and the arrangement of interfacial water were nearly identical on both the unreconstructed corundum and isostructural hematite (110) surfaces. Comparison to corundum and hematite (012) suggests that the arrangement of interfacial water is primarily controlled by mineral surface structure.

  1. Covalent bonding modulated graphene-metal interfacial thermal transport.

    PubMed

    Jiang, Tao; Zhang, Xueqiang; Vishwanath, Suresh; Mu, Xin; Kanzyuba, Vasily; Sokolov, Denis A; Ptasinska, Sylwia; Go, David B; Xing, Huili Grace; Luo, Tengfei

    2016-06-01

    We report the covalent bonding enabled modulation of the interfacial thermal conductance between graphene and metals Cu, Al, and Pt by controlling the oxidation of graphene. By combining comprehensive X-ray photoelectron spectroscopy (XPS) analysis and time-domain thermoreflectance measurements, we quantify the effect of graphene oxidation on interfacial thermal conductance. It was found that thermal conductance increases with the degree of graphene oxidation until a peak value is obtained at an oxygen/carbon atom percentage of ∼7.7%. The maximum enhancement in thermal conductance was measured to be 55%, 38%, and 49% for interfaces between oxidized graphene and Cu, Al, and Pt, respectively. In situ XPS measurements show that oxygen covalently binds to Cu and graphene simultaneously, forming a highly efficient bridge to enhance the thermal transport. Our molecular dynamics simulations verify that strong interfacial covalent bonds are the key to the thermal conductance enhancement. This work provides valuable insights into the mechanism of functionalization-induced thermal conductance enhancement and design guidelines for graphene-based devices. PMID:27174416

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

    SciTech Connect

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

    2002-07-01

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

  3. Interfacial structure in Telluride-based thermoelectric materials.

    SciTech Connect

    Medlin, Douglas L.

    2010-06-01

    Chalcogenide compounds based on the rocksalt and tetradymite structures possess good thermoelectric properties and are widely used in a variety of thermoelectric devices. Examples include PbTe and AgSbTe2, which have the rocksalt structure, and Bi2Te3, Bi2Se3, and Sb2Te3, which fall within the broad tetradymite-class of structures. These materials are also of interest for thermoelectric nanocomposites, where the aim is to improve thermoelectric energy conversion efficiency by harnessing interfacial scattering processes (e.g., reducing the thermal conductivity by phonon scattering or enhancing the Seebeck coefficient by energy filtering). Understanding the phase stability and microstructural evolution within such materials is key to designing processing approaches for optimal thermoelectric performance and to predicting the long-term nanostructural stability of the materials. In this presentation, we discuss our work investigating relationships between interfacial structure and formation mechanisms in several telluride-based thermoelectric materials. We begin with a discussion of interfacial coherency and its special aspects at interfaces in telluride compounds based on the rocksalt and tetradymite structures. We compare perfectly coherent interfaces, such as the Bi2Te3 (0001) twin, with semi-coherent, misfitting interfaces. We next discuss the formal crystallographic analysis of interfacial defects in these systems and then apply this methodology to high resolution transmission electron microscopy (HRTEM) observations of interfaces in the AgSbTe2/Sb2Te3 and PbTe/Sb2Te3 systems, focusing on interfaces vicinal to {l_brace}111{r_brace}/{l_brace}0001{r_brace}. Through this analysis, we identify a defect that can accomplish the rocksalt-to-tetradymite phase transformation through diffusive-glide motion along the interface.

  4. Measurement and Estimation of Organic-Liquid/Water Interfacial Areas for Several Natural Porous Media

    SciTech Connect

    Brusseau, M.L.; Narter, M.; Schnaar, G.; Marble, J.

    2009-06-01

    The objective of this study was to quantitatively characterize the impact of porous-medium texture on interfacial area between immiscible organic liquid and water residing within natural porous media. Synchrotron X-ray microtomography was used to obtain high-resolution, three-dimensional images of solid and liquid phases in packed columns. The image data were processed to generate quantitative measurements of organic-liquid/water interfacial area and of organic-liquid blob sizes. Ten porous media, comprising a range of median grain sizes, grain-size distributions, and geochemical properties, were used to evaluate the impact of porous-medium texture on interfacial area. The results show that fluid-normalized specific interfacial area (A{sub f}) and maximum specific interfacial area (A{sub m}) correlate very well to inverse median grain diameter. These functionalities were shown to result from a linear relationship between effective organic-liquid blob diameter and median grain diameter. These results provide the basis for a simple method for estimating specific organic-liquid/water interfacial area as a function of fluid saturation for a given porous medium. The availability of a method for which the only parameter needed is the simple-to-measure median grain diameter should be of great utility for a variety of applications.

  5. 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.

  6. Ordered mesoporous silica prepared by quiescent interfacial growth method - effects of reaction chemistry

    PubMed Central

    2013-01-01

    Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed. PMID:24237719

  7. Interfacial roughness in ceramic matrix composites

    SciTech Connect

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

    1992-08-01

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

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

    PubMed

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

    2016-04-20

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

  9. Effects of sintering temperature on interfacial structure and interfacial resistance for all-solid-state rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Kato, Takehisa; Yoshida, Ryuji; Yamamoto, Kazuo; Hirayama, Tsukasa; Motoyama, Munekazu; West, William C.; Iriyama, Yasutoshi

    2016-09-01

    Sintering processes yield a mutual diffusion region at the electrode/solid electrolyte interface, which is considered as a crucial problem for developing large-sized all-solid-state rechargeable lithium batteries with high power density. This work focuses on the interface between LiNi1/3Co1/3Mn1/3O2 (NMC) and NASICON-structured Li+ conductive glass ceramics solid electrolyte (Li2Osbnd Al2O3sbnd SiO2sbnd P2O5sbnd TiO2sbnd GeO2: LATP sheet (AG-01)), and investigates the effects of sintering temperature on interfacial structure and interfacial resistance at the NMC/LATP sheet. Thin films of NMC were fabricated on the LATP sheets at 700 °C or 900 °C as a model system. We found that the thickness of the mutual diffusion region was almost the same, ca. 30 nm, in these two samples, but the NMC film prepared at 900 °C had three orders of magnitude larger interfacial resistance than the NMC film prepared at 700 °C. Around the interface between the NMC film prepared at 900 °C and the LATP sheet, Co in the NMC accumulates as a reduced valence and lithium-free impurity crystalline phase will be also formed. These two problems must contribute to drastic increasing of interfacial resistance. Formation of de-lithiated NMC around the interface and its thermal instability at higher temperature may be considerable reason to induce these problems.

  10. Interfacial phenomena in hard-rod fluids

    NASA Astrophysics Data System (ADS)

    Shundyak, K. Y.

    2004-05-01

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

  11. Probing interfacial electronic structures in atomic layer LaMnO{sub3} and SrTiO{sub 3} superlattices.

    SciTech Connect

    Shah, A. B.; Ramasse, Q. M.; Zhai, X.; Wen, J. G.; May, S. J.; Petrov, I.; Bhattacharya, A.; Abbamonte, P.; Eckstein, J. N.; Zuo, J.-M.; Univ. of Illinois; LBNL

    2010-01-01

    The interfacial electronic structure characterization of a m x (LaMnO{sub 3})/n x (SrTiO{sub 3}) superlattice based on scanning transmission electron microscopy and electron energy loss spectroscopy. Evidence of interfacial band alignment and electron transfer are presented based on the observation of O K edge of individual transition metal and oxygen atomic columns. Electron probe aberration correction was essential for the high spatial resolution mapping of interfacial electronic states.

  12. Microfluidic ultralow interfacial tensiometry with magnetic particles.

    PubMed

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

    2013-01-01

    We describe a technique that measures ultralow interfacial tensions using paramagnetic spheres in a co-flow microfluidic device designed with a magnetic section. Our method involves tuning the distance between the co-flowing interface and the magnet's center, and observing the behavior of the spheres as they approach the liquid-liquid interface-the particles either pass through or are trapped by the interface. Using threshold values of the magnet-to-interface distance, we make estimates of the two-fluid interfacial tension. We demonstrate the effectiveness of this technique for measuring very low interfacial tensions, O(10(-6)-10(-5)) N m(-1), by testing solutions of different surfactant concentrations, and we show that our results are comparable with measurements made using a spinning drop tensiometer. PMID:23154819

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Fiber reinforced solids possessing great fracture toughness: The role of interfacial strength

    NASA Technical Reports Server (NTRS)

    Atkins, A. G.

    1974-01-01

    The high tensile strength characteristic of strong interfacial filament/matrix bonding can be combined with the high fracture toughness of weak interfacial bonding, when the filaments are arranged to have alternate sections of high and low shear stress (and low and high toughness). Such weak and strong areas can be achieved by appropriate intermittent coating of the fibers. An analysis is presented for toughness and strength which demonstrates, in broad terms, the effects of varying the coating parameters of concern. Results show that the toughness of interfaces is an important parameter, differences in which may not be shown up in terms of interfacial strength. Some observations are made upon methods of measuring the components of toughness in composites.

  18. Interfacial friction in cocurrent upward annular flow

    NASA Astrophysics Data System (ADS)

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

    1982-03-01

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

  19. Interfacial Behavior of Polymer Coated Nanoparticle

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  20. INTERFACIAL AREA TRANSPORT AND REGIME TRANSITION IN COMBINATORIAL CHANNELS

    SciTech Connect

    Seugjin Kim

    2011-01-28

    . This study investigates the geometric effects of 90-degree vertical elbows and flow configurations in two-phase flow. The study shows that the elbows make a significant effect on the transport characteristics of two-phase flow, which includes the changes in interfacial structures, bubble interaction mechanisms and flow regime transition. The effect of the elbows is characterized for global and local two-phase flow parameters. The global two-phase flow parameters include two-phase pressure, interfacial structures and flow regime transition. In order to characterize the frictional pressure drop and minor loss across the vertical elbows, pressure measurements are obtained across the test section over a wide range of flow conditions in both single-phase and two-phase flow conditions. A two-phase pressure drop correlation analogous to Lockhart-Martinelli correlation is proposed to predict the minor loss across the elbows. A high speed camera is employed to perform extensive flow visualization studies across the elbows in vertical upward, horizontal and vertical downward sections and modified flow regime maps are proposed. It is found that modified flow regime maps immediately downstream of the vertical upward elbow deviate significantly from the conventional flow regime map. A qualitative assessment of the counter-current flow limitation characteristics specific to the current experimental facility is performed. A multi-sensor conductivity probe is used to measure local two-phase flow parameters such as: void fraction, bubble velocity, interfacial area concentration and bubble frequency. The local measurements are obtained for six different flow conditions at ten measurement locations along axial direction of the test section. Both the vertical-upward and vertical-downward elbows have a significant impact on bubble distribution, resulting in, a bimodal distribution along the horizontal radius of the tube cross-section and migration of bubbles towards the inside of the

  1. The Constrained Vapor Bubble Experiment - Interfacial Flow Region

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  2. Pressure-induced conformational switch of an interfacial protein.

    PubMed

    Johnson, Quentin R; Lindsay, Richard J; Nellas, Ricky B; Shen, Tongye

    2016-06-01

    A special class of proteins adopts an inactive conformation in aqueous solution and activates at an interface (such as the surface of lipid droplet) by switching their conformations. Lipase, an essential enzyme for breaking down lipids, serves as a model system for studying such interfacial proteins. The underlying conformational switch of lipase induced by solvent condition is achieved through changing the status of the gated substrate-access channel. Interestingly, a lipase was also reported to exhibit pressure activation, which indicates it is drastically active at high hydrostatic pressure. To unravel the molecular mechanism of this unusual phenomenon, we examined the structural changes induced by high hydrostatic pressures (up to 1500 MPa) using molecular dynamics simulations. By monitoring the width of the access channel, we found that the protein undergoes a conformational transition and opens the access channel at high pressures (>100 MPa). Particularly, a disordered amphiphilic α5 region of the protein becomes ordered at high pressure. This positive correlation between the channel opening and α5 ordering is consistent with the early findings of the gating motion in the presence of a water-oil interface. Statistical analysis of the ensemble of conformations also reveals the essential collective motions of the protein and how these motions contribute to gating. Arguments are presented as to why heightened sensitivity to high-pressure perturbation can be a general feature of switchable interfacial proteins. Further mutations are also suggested to validate our observations. Proteins 2016; 84:820-827. © 2016 Wiley Periodicals, Inc. PMID:26967808

  3. 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.

  4. Interfacial chemistry at p-GaP photoelectrodes

    SciTech Connect

    Ginley, D.S.; Chamberlain, M.B.

    1982-09-01

    P-GaP photoelectrodes are of interest as cathodes in photosynthetic photoelectrochemical devices. The nature of the surface appears crucial to the efficient utilization of this material. In this study we show how an oxide surface layer is present even in the reductive environment at the surface; that this layer appears to be necessary for efficient interfacial charge transport; and that high solution oxygen concentrations increase the stability of this layer and consequently the electrode. Aging experiments with chemical and surface analyses are included that support these surprising results.

  5. Detrimental effect of interfacial Dzyaloshinskii-Moriya interaction on perpendicular spin-transfer-torque magnetic random access memory

    SciTech Connect

    Jang, Peong-Hwa; Lee, Seo-Won E-mail: kj-lee@korea.ac.kr; Song, Kyungmi; Lee, Seung-Jae; Lee, Kyung-Jin E-mail: kj-lee@korea.ac.kr

    2015-11-16

    Interfacial Dzyaloshinskii-Moriya interaction in ferromagnet/heavy metal bilayers is recently of considerable interest as it offers an efficient control of domain walls and the stabilization of magnetic skyrmions. However, its effect on the performance of perpendicular spin transfer torque memory has not been explored yet. We show based on numerical studies that the interfacial Dzyaloshinskii-Moriya interaction decreases the thermal energy barrier while increases the switching current. As high thermal energy barrier as well as low switching current is required for the commercialization of spin torque memory, our results suggest that the interfacial Dzyaloshinskii-Moriya interaction should be minimized for spin torque memory applications.

  6. Comment on "Effective thermal conductivity of metal and non-metal particulate composites with interfacial thermal resistance at high volume fraction of nano to macro-sized spheres" [J. Appl. Phys. 117, 055104 (2015)

    NASA Astrophysics Data System (ADS)

    Pal, Rajinder

    2015-06-01

    In a recent article, Faroughi and Huber [J. Appl. Phys. 117, 055104 (2015)] propose two theoretical models to compute the effective thermal conductivity of metal and dielectric spherical particle reinforced composites with interfacial thermal resistance. The models are based on the differential effective medium (DEM) theory. The authors have failed to cite and discuss the paper of Pal [Mater. Sci. Eng., A 498, 135-141 (2008)] where similar models have been derived using the same approach (DEM theory). Furthermore, the models proposed by Faroughi and Huber are seriously flawed in that the "excluded volume effect" is taken into account two times, instead of once, in their derivations. Last but not least, there are typos in their models.

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

    PubMed

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

    2015-05-13

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

  8. An excellent candidate for largely reducing interfacial thermal resistance: a nano-confined mass graded interface

    NASA Astrophysics Data System (ADS)

    Zhou, Yanguang; Zhang, Xiaoliang; Hu, Ming

    2016-01-01

    Pursuing extremely low interfacial thermal resistance has long been the task of many researchers in the area of nano-scale heat transfer, in particular pertaining to improve heat dissipation performance in electronic cooling. While it is well known and documented that confining a macroscopic third layer between two dissimilar materials usually increases the overall interfacial thermal resistance, no research has realized the fundamental decrease in resistance so far. By performing nonequilibrium molecular dynamics simulations, we report that the overall interfacial thermal resistance can be reduced by 6 fold by confining mass graded materials with thickness of the order of nanometers. As comparison we also studied the thermal transport across the perfectly abrupt interface and the widely used alloyed (rough) interface, which shows an opposing and significantly large increase in the overall thermal resistance. With the help of frequency dependent interfacial thermal conductance and wave packet dynamics simulation, different mechanisms governing the heat transfer across these three types of interfaces are identified. It is found that for the rough interface there are two different regimes of interfacial heat transfer, which originates from the competition between phonon scattering and the thickness of the interface. The mechanism of dramatically improved interfacial heat transfer across the nano-confined mass graded interface resides in the minor phonon reflection when the phonons first reach the mass graded area and the rare occurrence of phonon scattering in the subsequent interior region. The phonons are found to be gradually truncated by the geometric interfaces and can travel through the mass graded layer with a high transmission coefficient, benefited from the small mass mismatch between two neighboring layers in the interfacial region. Our findings provide deep insight into the phonon transport across nano-confined mass graded layers and also offer significant

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Various Cu-Pb-Al alloys were directionally solidified under 1-g conditions and alternating high-g/low-g conditions (achieved using NSAS's KC-135 aircraft) as a means of studying the influence of interfacial energies and gravitational levels on the resulting microstructures. Directional solidification of low Al content alloys was found to result in samples with coarser more irregular microstructures than in alloys with high Al contents under all the gravity conditions considered. Structures are correlated with interfacial energies, growth rates, and gravitational levels.

  10. An extremely sensitive aptasensor based on interfacial energy transfer between QDS SAMs and GO

    NASA Astrophysics Data System (ADS)

    Sun, Xiangying; Liu, Bin; Yang, Chuanxiao; Li, Congcong

    2014-10-01

    In this work we designed a fluorescent self-assemblied multilayers, with thrombin aptamers and ssDNA as aptamer fixed onto the outermost layer, respectively. This multilayers can effectively sense biomolecules by interfacial florescence resonance energy transfer from multilayers to graphene oxide. High fluorescence quenching efficiency of graphene oxide and self-assemblied membrane' concentration results in good sensitivity for biosensing. A new interfacial sensing method with extremely high sensitivity for thrombin and DNA sequence was established, and the detection limit for thrombin and DNA was 16.2 pM and 72.6 fM, respectively.

  11. An extremely sensitive aptasensor based on interfacial energy transfer between QDS SAMs and GO.

    PubMed

    Sun, Xiangying; Liu, Bin; Yang, Chuanxiao; Li, Congcong

    2014-10-15

    In this work we designed a fluorescent self-assemblied multilayers, with thrombin aptamers and ssDNA as aptamer fixed onto the outermost layer, respectively. This multilayers can effectively sense biomolecules by interfacial florescence resonance energy transfer from multilayers to graphene oxide. High fluorescence quenching efficiency of graphene oxide and self-assemblied membrane' concentration results in good sensitivity for biosensing. A new interfacial sensing method with extremely high sensitivity for thrombin and DNA sequence was established, and the detection limit for thrombin and DNA was 16.2pM and 72.6 fM, respectively. PMID:24835931

  12. Forming compliance dominated memristive switching through interfacial reaction in Ti/TiO2/Au structure

    NASA Astrophysics Data System (ADS)

    Tang, Zhensen; Fang, Liang; Xu, Nuo; Liu, Rulin

    2015-11-01

    The effects of the forming compliance current (CC) on bipolar resistive switching (BRS) characteristics in Au/Ti/TiO2/Au memristive switches were investigated. After forming with a low CC, a typical BRS with an abrupt SET and negative differential resistance RESET behaviors were observed. In comparison, the sample formed with a high CC exhibited an abnormal BRS with stepwise SET and abrupt RESET transitions. The conduction mechanisms at a high resistance state and a low resistance state were analyzed, respectively. The impact of the forming compliance on the interfacial reaction between Ti and TiO2 was discussed. The Ti-induced interfacial layer played an important role of manipulating the oxygen vacancies, thus providing the possibility of affecting the switching behavior. A physical model based on a combination of the bulk and interfacial effects was proposed to explain our observations.

  13. Solid-liquid interfaces of ionic liquid solutions—Interfacial layering and bulk correlations

    NASA Astrophysics Data System (ADS)

    Mezger, Markus; Roth, Roland; Schröder, Heiko; Reichert, Peter; Pontoni, Diego; Reichert, Harald

    2015-04-01

    The influence of the polar, aprotic solvent propylene carbonate on the interfacial structure of the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate on sapphire was investigated by high-energy x-ray reflectivity. Experiments at solvent concentrations between 17 mol. % and 83 mol. % bridge the gap between diluted electrolytes described by the classical Gouy-Chapman theory and pure ionic liquids. Analysis of our experimental data revealed interfacial profiles comprised of alternating anion and cation enriched regions decaying gradually into the bulk liquid. With increasing solvent concentration, we observed a decrease in correlation length of the interfacial layering structure. At high ion concentrations, solvent molecules were found to accumulate laterally within the layers. By separating like-charged ions, they reduce their Coulomb repulsion. The results are compared with the bulk structure of IL/solvent blends probed by x-ray scattering and predictions from fundamental fluid theory.

  14. Monte Carlo simulations of the pressure dependence of the water-acid gas interfacial tensions.

    PubMed

    Biscay, F; Ghoufi, A; Lachet, V; Malfreyt, P

    2009-10-29

    We report two-phase Monte Carlo (MC) simulations of the binary water-acid gas mixtures at high temperature and high pressure. Simulations are performed in the Np(N)AT ensemble in order to reproduce the pressure dependence of the interfacial tensions of the water-CO(2) and water-H(2)S mixtures. The interfacial tension of the binary water-CO(2) mixture is determined from 5 to 45 MPa along the isotherm T = 383 K. Water-H(2)S interfacial tensions are computed along one supercritical isotherm (T = 393 K) in a pressure range of 1-15 MPa. The temperature and pressure conditions investigated here by the MC simulations are typical of the geological storage conditions of these acid gases. The coexisting densities and the compositions of the water-rich and acid-gas-rich phases are compared with experiments and with data calculated from Gibbs ensemble Monte Carlo (GEMC) simulations. PMID:19803493

  15. A new method for modeling rough membrane surface and calculation of interfacial interactions.

    PubMed

    Zhao, Leihong; Zhang, Meijia; He, Yiming; Chen, Jianrong; Hong, Huachang; Liao, Bao-Qiang; Lin, Hongjun

    2016-01-01

    Membrane fouling control necessitates the establishment of an effective method to assess interfacial interactions between foulants and rough surface membrane. This study proposed a new method which includes a rigorous mathematical equation for modeling membrane surface morphology, and combination of surface element integration (SEI) method and the composite Simpson's approach for assessment of interfacial interactions. The new method provides a complete solution to quantitatively calculate interfacial interactions between foulants and rough surface membrane. Application of this method in a membrane bioreactor (MBR) showed that, high calculation accuracy could be achieved by setting high segment number, and moreover, the strength of three energy components and energy barrier was remarkably impaired by the existence of roughness on the membrane surface, indicating that membrane surface morphology exerted profound effects on membrane fouling in the MBR. Good agreement between calculation prediction and fouling phenomena was found, suggesting the feasibility of this method. PMID:26519696

  16. GaN as an interfacial passivation layer: tuning band offset and removing fermi level pinning for III-V MOS devices.

    PubMed

    Zhang, Zhaofu; Cao, Ruyue; Wang, Changhong; Li, Hao-Bo; Dong, Hong; Wang, Wei-Hua; Lu, Feng; Cheng, Yahui; Xie, Xinjian; Liu, Hui; Cho, Kyeongjae; Wallace, Robert; Wang, Weichao

    2015-03-11

    The use of an interfacial passivation layer is one important strategy for achieving a high quality interface between high-k and III-V materials integrated into high-mobility metal-oxide-semiconductor field-effect transistor (MOSFET) devices. Here, we propose gallium nitride (GaN) as the interfacial layer between III-V materials and hafnium oxide (HfO2). Utilizing first-principles calculations, we explore the structural and electronic properties of the GaN/HfO2 interface with respect to the interfacial oxygen contents. In the O-rich condition, an O8 interface (eight oxygen atoms at the interface, corresponding to 100% oxygen concentration) displays the most stability. By reducing the interfacial O concentration from 100 to 25%, we find that the interface formation energy increases; when sublayer oxygen vacancies exist, the interface becomes even less stable compared with O8. The band offset is also observed to be highly dependent on the interfacial oxygen concentration. Further analysis of the electronic structure shows that no interface states are present at the O8 interface. These findings indicate that the O8 interface serves as a promising candidate for high quality III-V MOS devices. Moreover, interfacial states are present when such interfacial oxygen is partially removed. The interface states, leading to Fermi level pinning, originate from unsaturated interfacial Ga atoms. PMID:25639492

  17. Iridium Interfacial Stack - IrIS

    NASA Technical Reports Server (NTRS)

    Spry, David

    2012-01-01

    Iridium Interfacial Stack (IrIS) is the sputter deposition of high-purity tantalum silicide (TaSi2-400 nm)/platinum (Pt-200 nm)/iridium (Ir-200 nm)/platinum (Pt-200 nm) in an ultra-high vacuum system followed by a 600 C anneal in nitrogen for 30 minutes. IrIS simultaneously acts as both a bond metal and a diffusion barrier. This bondable metallization that also acts as a diffusion barrier can prevent oxygen from air and gold from the wire-bond from infiltrating silicon carbide (SiC) monolithically integrated circuits (ICs) operating above 500 C in air for over 1,000 hours. This TaSi2/Pt/Ir/Pt metallization is easily bonded for electrical connection to off-chip circuitry and does not require extra anneals or masking steps. There are two ways that IrIS can be used in SiC ICs for applications above 500 C: it can be put directly on a SiC ohmic contact metal, such as Ti, or be used as a bond metal residing on top of an interconnect metal. For simplicity, only the use as a bond metal is discussed. The layer thickness ratio of TaSi2 to the first Pt layer deposited thereon should be 2:1. This will allow Si from the TaSi2 to react with the Pt to form Pt2Si during the 600 C anneal carried out after all layers have been deposited. The Ir layer does not readily form a silicide at 600 C, and thereby prevents the Si from migrating into the top-most Pt layer during future anneals and high-temperature IC operation. The second (i.e., top-most) deposited Pt layer needs to be about 200 nm to enable easy wire bonding. The thickness of 200 nm for Ir was chosen for initial experiments; further optimization of the Ir layer thickness may be possible via further experimentation. Ir itself is not easily wire-bonded because of its hardness and much higher melting point than Pt. Below the iridium layer, the TaSi2 and Pt react and form desired Pt2Si during the post-deposition anneal while above the iridium layer remains pure Pt as desired to facilitate easy and strong wire-bonding to the Si

  18. Branched artificial nanofinger arrays by mesoporous interfacial atomic rearrangement.

    PubMed

    Kong, Biao; Tang, Jing; Zhang, Yueyu; Selomulya, Cordelia; Gong, Xingao; Liu, Yang; Zhang, Wei; Yang, Jianping; Wang, Wenshuo; Sun, Xiaotian; Wang, Yufei; Zheng, Gengfeng; Zhao, Dongyuan

    2015-04-01

    The direct production of branched semiconductor arrays with highly ordered orientation has proven to be a considerable challenge over the last two decades. Here we report a mesoporous interfacial atomic rearrangement (MIAR) method to directly produce highly crystalline, finger-like branched iron oxide nanoarrays from the mesoporous nanopyramids. This method has excellent versatility and flexibility for heteroatom doping of metallic elements, including Sn, Bi, Mn, Fe, Co, Ni, Cu, Zn, and W, in which the mesoporous nanopyramids first absorb guest-doping molecules into the mesoporous channels and then convert the mesoporous pyramids into branching artificial nanofingers. The crystalline structure can provide more optoelectronic active sites of the nanofingers by interfacial atomic rearrangements of doping molecules and mesopore channels at the porous solid-solid interface. As a proof-of-concept, the Sn-doped Fe2O3 artificial nanofingers (ANFs) exhibit a high photocurrent density of ∼1.26 mA/cm(2), ∼5.25-fold of the pristine mesoporous Fe2O3 nanopyramid arrays. Furthermore, with surface chemical functionalization, the Sn-doped ANF biointerfaces allow nanomolar level recognition of metabolism-related biomolecules (∼5 nm for glutathione). This MIAR method suggests a new growth means of branched mesostructures, with enhanced optoelectronic applications. PMID:25764364

  19. In Situ STEM-EELS observation of nanoscale interfacial phenomena in all-solid-state batteries

    DOE PAGESBeta

    Wang, Ziying; Xin, Huolin L.; Santhanagopalan, Dhamodaran; Zhang, Wei; Wang, Feng; He, Kai; Li, Juchuan; Dudney, Nancy; Meng, Ying Shirley

    2016-05-03

    Behaviors of functional interfaces are crucial factors in the performance and safety of energy storage and conversion devices. Indeed, solid electrode–solid electrolyte interfacial impedance is now considered the main limiting factor in all-solid-state batteries rather than low ionic conductivity of the solid electrolyte. Here, we present a new approach to conducting in situ scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) in order to uncover the unique interfacial phenomena related to lithium ion transport and its corresponding charge transfer. Our approach allowed quantitative spectroscopic characterization of a galvanostatically biased electrochemical system under in situ conditions. Usingmore » a LiCoO2/LiPON/Si thin film battery, an unexpected structurally disordered interfacial layer between LiCoO2 cathode and LiPON electrolyte was discovered to be inherent to this interface without cycling. During in situ charging, spectroscopic characterization revealed that this interfacial layer evolved to form highly oxidized Co ions species along with lithium oxide and lithium peroxide species. Here, these findings suggest that the mechanism of interfacial impedance at the LiCoO2/LiPON interface is caused by chemical changes rather than space charge effects. Insights gained from this technique will shed light on important challenges of interfaces in all-solid-state energy storage and conversion systems and facilitate improved engineering of devices operated far from equilibrium.« less

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

    SciTech Connect

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

    2009-08-15

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

  1. In Situ STEM-EELS Observation of Nanoscale Interfacial Phenomena in All-Solid-State Batteries.

    PubMed

    Wang, Ziying; Santhanagopalan, Dhamodaran; Zhang, Wei; Wang, Feng; Xin, Huolin L; He, Kai; Li, Juchuan; Dudney, Nancy; Meng, Ying Shirley

    2016-06-01

    Behaviors of functional interfaces are crucial factors in the performance and safety of energy storage and conversion devices. Indeed, solid electrode-solid electrolyte interfacial impedance is now considered the main limiting factor in all-solid-state batteries rather than low ionic conductivity of the solid electrolyte. Here, we present a new approach to conducting in situ scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) in order to uncover the unique interfacial phenomena related to lithium ion transport and its corresponding charge transfer. Our approach allowed quantitative spectroscopic characterization of a galvanostatically biased electrochemical system under in situ conditions. Using a LiCoO2/LiPON/Si thin film battery, an unexpected structurally disordered interfacial layer between LiCoO2 cathode and LiPON electrolyte was discovered to be inherent to this interface without cycling. During in situ charging, spectroscopic characterization revealed that this interfacial layer evolved to form highly oxidized Co ions species along with lithium oxide and lithium peroxide species. These findings suggest that the mechanism of interfacial impedance at the LiCoO2/LiPON interface is caused by chemical changes rather than space charge effects. Insights gained from this technique will shed light on important challenges of interfaces in all-solid-state energy storage and conversion systems and facilitate improved engineering of devices operated far from equilibrium. PMID:27140196

  2. 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.

  3. Interfacial sciences in unconventional petroleum production: from fundamentals to applications.

    PubMed

    He, Lin; Lin, Feng; Li, Xingang; Sui, Hong; Xu, Zhenghe

    2015-08-01

    With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply. Compared with the conventional reserves unconventional oil reserves are characterized by extremely high viscosity and density, combined with complex chemistry. As a result, petroleum production from unconventional oil reserves is much more difficult and costly with more serious environmental impacts. As a key underpinning science, understanding the interfacial phenomena involved in unconventional petroleum production, such as oil liberation from host rocks, oil-water emulsions and demulsification, is critical for developing novel processes to improve oil production while reducing GHG emission and other environmental impacts at a lower operating cost. In the past decade, significant efforts and advances have been made in applying the principles of interfacial sciences to better understand complex unconventional oil-systems, while many environmental and production challenges remain. In this critical review, the recent research findings and progress in the interfacial sciences related to unconventional petroleum production are critically reviewed. In particular, the chemistry of unconventional oils, liberation mechanisms of oil from host rocks and mechanisms of emulsion stability and destabilization in unconventional oil production systems are discussed in detail. This review also seeks to summarize the current state-of-the-art characterization techniques and brings forward the challenges and opportunities for future research in this important field of physical chemistry and petroleum. PMID:25986005

  4. Interfacial shear rheology of DPPC under physiologically relevant conditions.

    PubMed

    Hermans, Eline; Vermant, Jan

    2014-01-01

    Lipids, and phosphatidylcholines in particular, are major components in cell membranes and in human lung surfactant. Their ability to encapsulate or form stable layers suggests a significant role of the interfacial rheological properties. In the present work we focus on the surface rheological properties of dipalmitoylphosphatidylcholine (DPPC). Literature results are confusing and even contradictory; viscosity values have been reported differ by several orders of magnitude. Moreover, even both purely viscous and gel-like behaviours have been described. Assessing the literature critically, a limited experimental window has been explored correctly, which however does not yet include conditions relevant for the physiological state of DPPC in vivo. A complete temperature and surface pressure analysis of the interfacial shear rheology of DPPC is performed, showing that the monolayer behaves as a viscoelastic liquid with a domain structure. At low frequencies and for a thermally structured monolayer, the interaction of the molecules within the domains can be probed. The low frequency limit of the complex viscosity is measured over a wide range of temperatures and surface pressures. The effects of temperature and surface pressure on the low frequency viscosity can be analysed in terms of the effects of free molecular area. However, at higher frequencies or following a preshear at high shear rates, elasticity becomes important; most probably elasticity due to defects at the edge of the domains in the layer is probed. Preshearing refines the structure and induces more defects. As a result, disagreeing interfacial rheology results in various publications might be due to different pre-treatments of the interface. The obtained dataset and scaling laws enable us to describe the surface viscosity, and its dependence under physiological conditions of DPPC. The implications on functioning of lung surfactants and lung surfactant replacements will be discussed. PMID:24651838

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

    PubMed Central

    Bai, Yiqun; Abbott, Nicholas L.

    2011-01-01

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

  6. Polymer nanofilms with enhanced microporosity by interfacial polymerization.

    PubMed

    Jimenez-Solomon, Maria F; Song, Qilei; Jelfs, Kim E; Munoz-Ibanez, Marta; Livingston, Andrew G

    2016-07-01

    Highly permeable and selective membranes are desirable for energy-efficient gas and liquid separations. Microporous organic polymers have attracted significant attention in this respect owing to their high porosity, permeability and molecular selectivity. However, it remains challenging to fabricate selective polymer membranes with controlled microporosity that are stable in solvents. Here we report a new approach to designing crosslinked, rigid polymer nanofilms with enhanced microporosity by manipulating the molecular structure. Ultrathin polyarylate nanofilms with thickness down to 20 nm are formed in situ by interfacial polymerization. Enhanced microporosity and higher interconnectivity of intermolecular network voids, as rationalized by molecular simulations, are achieved by using contorted monomers for the interfacial polymerization. Composite membranes comprising polyarylate nanofilms with enhanced microporosity fabricated in situ on crosslinked polyimide ultrafiltration membranes show outstanding separation performance in organic solvents, with up to two orders of magnitude higher solvent permeance than membranes fabricated with nanofilms made from non-contorted planar monomers. PMID:27135857

  7. Effects of Impurities on Alumina-Niobium InterfacialMicrostructures

    SciTech Connect

    McKeown, Joseph T.; Sugar, Joshua D.; Gronsky, Ronald; Glaeser,Andreas M.

    2005-06-20

    Optical microscopy, scanning electron microscopy, and transmission electron microscopy were employed to examine the interfacial microstructural effects of impurities in alumina substrates used to fabricate alumina-niobium interfaces via liquid-film-assisted joining. Three types of alumina were used: undoped high-purity single-crystal sapphire; a high-purity, high-strength polycrystalline alumina; and a lower-purity, lower-strength polycrystalline alumina. Interfaces formed between niobium and both the sapphire and high-purity polycrystalline alumina were free of detectable levels of impurities. In the lower-purity alumina, niobium silicides were observed at the alumina-niobium interface and on alumina grain boundaries near the interface. These silicides formed in small-grained regions of the alumina and were found to grow from the interface into the alumina along grain boundaries. Smaller silicide precipitates found on grain boundaries are believed to form upon cooling from the bonding temperature.

  8. Interfacial geometry dictates cancer cell tumorigenicity

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  9. Interfacial geometry dictates cancer cell tumorigenicity.

    PubMed

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

    2016-08-01

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

  10. The contact area dependent interfacial thermal conductance

    SciTech Connect

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

    2015-12-15

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

  11. Interfacial thermodynamics of micro heat pipes

    SciTech Connect

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

    1995-02-01

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

  12. Hydrophilicity and the viscosity of interfacial water.

    PubMed

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

    2007-05-01

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

  13. Frontiers of interfacial water research :workshop report.

    SciTech Connect

    Cygan, Randall Timothy; Greathouse, Jeffery A.

    2005-10-01

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

  14. Interfacial transport in lithium-ion conductors

    NASA Astrophysics Data System (ADS)

    Shaofei, Wang; Liquan, Chen

    2016-01-01

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

  15. Transient optical diffraction of GaN/aqueous interfaces: Interfacial carrier mobility dependence on surface reactivity

    NASA Astrophysics Data System (ADS)

    Doan, Hoang Q.; Pollock, Kevin L.; Cuk, Tanja

    2016-04-01

    While charge transport and surface reactivity have thus far been treated as independent phenomena, the interfacial carrier mobility could be highly dependent on reaction intermediates that carry localized charge and can hop from site to site along the surface. Here, we demonstrate the use of surface sensitive transient optical grating spectroscopy to measure this lateral, interfacial carrier diffusivity at surfaces with different reactivity. We find that for n-GaN, for which substantial charge transfer occurs during equilibration with the water oxidation reaction, the interfacial hole diffusivity increases from air by a factor greater than two under 0.1 M HBr and 0.1 M Na2SO4 aqueous electrolytes.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. TFB:TPDSi2 interfacial layer usable in organic photovoltaic cells

    DOEpatents

    Marks, Iobin J.; Hains, Alexander W.

    2011-02-15

    The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode; an active organic layer comprising an electron-donating organic material and an electron-accepting organic material; and an interfacial layer formed between the anode and active organic layer, where the interfacial layer comprises a hole-transporting polymer characterized with a hole-mobility higher than that of the electron-donating organic material in the active organic layer, and a small molecule that has a high hole-mobility and is capable of crosslinking on contact with air.

  2. 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.

  3. 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.

  4. Effect of interfacial interactions on the thermal conductivity and interfacial thermal conductance in tungsten–graphene layered structure

    SciTech Connect

    Jagannadham, K.

    2014-09-01

    Graphene film was deposited by microwave plasma assisted deposition on polished oxygen free high conductivity copper foils. Tungsten–graphene layered film was formed by deposition of tungsten film by magnetron sputtering on the graphene covered copper foils. Tungsten film was also deposited directly on copper foil without graphene as the intermediate film. The tungsten–graphene–copper samples were heated at different temperatures up to 900 °C in argon atmosphere to form an interfacial tungsten carbide film. Tungsten film deposited on thicker graphene platelets dispersed on silicon wafer was also heated at 900 °C to identify the formation of tungsten carbide film by reaction of tungsten with graphene platelets. The films were characterized by scanning electron microscopy, Raman spectroscopy, and x-ray diffraction. It was found that tungsten carbide film formed at the interface upon heating only above 650 °C. Transient thermoreflectance signal from the tungsten film surface on the samples was collected and modeled using one-dimensional heat equation. The experimental and modeled results showed that the presence of graphene at the interface reduced the cross-plane effective thermal conductivity and the interfacial thermal conductance of the layer structure. Heating at 650 and 900 °C in argon further reduced the cross-plane thermal conductivity and interface thermal conductance as a result of formation nanocrystalline tungsten carbide at the interface leading to separation and formation of voids. The present results emphasize that interfacial interactions between graphene and carbide forming bcc and hcp elements will reduce the cross-plane effective thermal conductivity in composites.

  5. Formation of Lenses by Liquid Interfacial Surfaces

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  6. Interfacial Protein-Protein Associations

    PubMed Central

    Langdon, Blake B.; Kastantin, Mark; Walder, Robert; Schwartz, Daniel K.

    2014-01-01

    While traditional models of protein adsorption focus primarily on direct protein-surface interactions, recent findings suggest that protein-protein interactions may play a central role. Using high-throughput intermolecular resonance energy transfer (RET) tracking, we directly observed dynamic, protein-protein associations of bovine serum albumin on poly(ethylene glycol) modified surfaces. The associations were heterogeneous and reversible, and associating molecules resided on the surface for longer times. The appearance of three distinct RET states suggested a spatially heterogeneous surface – with areas of high protein density (i.e. strongly-interacting clusters) coexisting with mobile monomers. Distinct association states exhibited characteristic behavior, i.e. partial-RET (monomer-monomer) associations were shorter-lived than complete-RET (protein-cluster) associations. While the fractional surface area covered by regions with high protein density (i.e. clusters) increased with increasing concentration, the distribution of contact times between monomers and clusters was independent of solution concentration, suggesting that associations were a local phenomenon, and independent of the global surface coverage. PMID:24274729

  7. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The study of the interface in a charge-free, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In this paper, the flat interface of a marginally polar binary fluid mixture is stressed by a perpendicular alternating electric field and the resulting instability is characterized by the critical electric field E(sub c) and the pattern observed. The character of the surface dynamics at the onset of instability is found to be strongly dependent on the frequency f of the field applied. The plot of E(sub c) vs. f for a fixed temperature shows a sigmoidal shape, whose low and high frequency limits are well described by a power-law relationship, E(sub c) = epsilon(exp zeta) with zeta = 0.35 and zeta = 0.08, respectively. The low-limit exponent compares well with the value zeta = 4 for a system of conducting and non-conducting fluids. On the other hand, the high-limit exponent coincides with what was first predicted by Onuki. The instability manifests itself as the conducting phase penetrates the non-conducting phase. As the frequency increases, the shape of the pattern changes from an array of bifurcating strings to an array of column-like (or rod-like) protrusions, each of which spans the space between the plane interface and one of the electrodes. For an extremely high frequency, the disturbance quickly grows into a parabolic cone pointing toward the upper plate. As a result, the interface itself changes its shape from that of a plane to that of a high sloping pyramid.

  8. The Interfacial Transition Zone in Alkali-Activated Slag Mortars

    NASA Astrophysics Data System (ADS)

    San Nicolas, Rackel; Provis, John

    2015-12-01

    The interfacial transition zone (ITZ) is known to strongly influence the mechanical and transport properties of mortars and concretes. This paper studies the ITZ between siliceous (quartz) aggregates and alkali activated slag binders in the context of mortar specimens. Backscattered electron images (BSE) generated in an environmental scanning electron microscope (ESEM) are used to identify unreacted binder components, reaction products and porosity in the zone surrounding aggregate particles, by composition and density contrast. X-ray mapping is used to exclude the regions corresponding to the aggregates from the BSE image of the ITZ, thus enabling analysis of only the binder phases, which are segmented into binary images by grey level discrimination. A distinct yet dense ITZ region is present in the alkali-activated slag mortars, containing a reduced content of unreacted slag particles compared to the bulk binder. The elemental analysis of this region shows that it contains a (C,N)-A-S-H gel which seems to have a higher content of Na (potentially deposited through desiccation of the pore solution) and a lower content of Ca than the bulk inner and outer products forming in the main binding region. These differences are potentially important in terms of long-term concrete performance, as the absence of a highly porous interfacial transition zone region is expected to provide a positive influence on the mechanical and transport properties of alkali-activated slag concretes.

  9. Molecular and Interfacial Calculations of Iron(II) Light Harvesters.

    PubMed

    Fredin, Lisa A; Wärnmark, Kenneth; Sundström, Villy; Persson, Petter

    2016-04-01

    Iron-carbene complexes show considerable promise as earth-abundant light-harvesters, and adsorption onto nanostructured TiO2 is a crucial step for developing solar energy applications. Intrinsic electron injection capabilities of such promising Fe(II) N-heterocyclic complexes (Fe-NHC) to TiO2 are calculated here, and found to correlate well with recent experimental findings of highly efficient interfacial injection. First, we examine the special bonding characteristics of Fe-NHC light harvesters. The excited-state surfaces are examined using density functional theory (DFT) and time-dependent DFT (TD-DFT) to explore relaxed excited-state properties. Finally, by relaxing an Fe-NHC adsorbed on a TiO2 nanocluster, we show favorable injection properties in terms of interfacial energy level alignment and electronic coupling suitable for efficient electron injection of excited electrons from the Fe complex into the TiO2 conduction band on ∼100 fs time scales. PMID:27010851

  10. Influence of interfacial rheology on stabilization of the tear film

    NASA Astrophysics Data System (ADS)

    Bhamla, M. Saad; Fuller, Gerald G.

    2014-11-01

    The tear film that protecting the ocular surface is a complex, thin film comprised of a collection of proteins and lipids that come together to provide a number of important functions. Of particular interest in this presentation is meibum, an insoluble layer that is spread from glands lining our eyelids. Past work has focussed on the role of this layer in reducing evaporation, although conflicting evidence on its ability to reduce evaporative loss has been published. We present here the beneficial effects that are derived through the interfacial viscoelasticity of the meibomian lipid film. This is a duplex film is comprised of a rich mixture of phospholipids, long chain fatty esters, and cholesterol esters. Using interfacial rheology measurements, meibum has been shown to be highly viscoelastic. By measuring the drainage and dewetting dynamics of thin aqueous films from hemispherical surfaces where those films are laden with insoluble layers of lipids at controlled surface pressure, we offer evidence that these layers strongly stabilize the films because of their ability to support surface shearing stresses. This alternative view of the role of meibum can help explain the origin of meibomian gland dysfunction, or dry eye disease, where improper compositions of this lipid mixture do not offer the proper mechanical resistance to breakage and dewetting of the tear film.

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

    NASA Astrophysics Data System (ADS)

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

    1988-11-01

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

  12. Application of controlled interfacial pore structures to kinetic studies in alumina

    SciTech Connect

    Roedel, J.; Glaeser, A.M.

    1988-04-01

    The application of controlled-geometry interfacial pore structures to fundamental kinetic studies in alumina is described. Results from studies of the morphological stability of high aspect ratio pore channels, crack healing, pore coarsening and pore elimination in sapphire are presented.

  13. Visible light-initiated interfacial thiol-norbornene photopolymerization for forming islet surface conformal coating

    PubMed Central

    Shih, Han; Mirmira, Raghavendra G.; Lin, Chien-Chi

    2015-01-01

    A cytocompatible visible light-mediated interfacial thiol-norbornene photopolymerization scheme was developed for creating hydrogel conformal coating on pancreatic islets. The step-growth thiol-norbornene reaction affords high consistency and tunability in gel coating thickness. Furthermore, isolated islets coated with thiol-norbornene gel maintained their viability and function in vitro. PMID:26509035

  14. In vacuo interfacial tetrapyrrole metallation.

    PubMed

    Diller, Katharina; Papageorgiou, Anthoula C; Klappenberger, Florian; Allegretti, Francesco; Barth, Johannes V; Auwärter, Willi

    2016-03-21

    The metallation of tetrapyrroles at well-defined surfaces under ultra-high vacuum conditions represents an unconventional synthesis approach to achieve tetrapyrrole-based metal-organic complexes and architectures. Different protocols, pioneered over the last decade, and now widely applied in several fields, provide an elegant route to metallo-tetrapyrrole systems often elusive to conventional procedures and give access and exquisite insight into on-surface tetrapyrrole chemistry. As highlighted by the functionality of metallo-porphyrins in biological or other environments and by the eminent role of metallo-phthalocyanines in synthetic materials, the control on the metal centres incorporated into the macrocycle is of utmost importance to achieve tailored properties in tetrapyrrole-based nanosystems. In the on-surface scenario, precise metallation pathways were developed, including reactions of tetrapyrroles with metals supplied by physical vapour deposition, chemical vapour deposition or the tip of a scanning tunnelling microscope, and self-metallation by atoms of an underlying support. Herein, we provide a comprehensive overview of in vacuo tetrapyrrole metallation, addressing two-dimensional as well as three-dimensional systems. Furthermore, we comparatively assess the available library of on-surface metallation protocols and elaborate on the state-of-the-art methodology. PMID:26781034

  15. Interfacial electrofluidics in confined systems

    PubMed Central

    Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A.; Zhou, Guofu (G.F.)

    2016-01-01

    Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films. PMID:27221211

  16. Interfacial electrofluidics in confined systems

    NASA Astrophysics Data System (ADS)

    Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A.; Zhou, Guofu (G. F.)

    2016-05-01

    Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films.

  17. Interfacial electrofluidics in confined systems.

    PubMed

    Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A; Zhou, Guofu G F

    2016-01-01

    Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it's potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films. PMID:27221211

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

    NASA Astrophysics Data System (ADS)

    Kobayashi, Satoshi; Yamamoto, Tatsuro; Nakai, Asami

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

  19. Effect of coating thickness on interfacial shear behavior of zirconia-coated sapphire fibers in a polycrystalline alumina matrix

    SciTech Connect

    Hellmann, J.R.; Chou, Y.S.

    1995-10-01

    The effect of zirconia (ZrO{sub 2}) interfacial coatings on the interfacial shear behavior in sapphire reinforced alumina was examined in this study. Zirconia coatings of thicknesses ranging from 0.15 to 1.45 {mu}m were applied to single crystal sapphire (Saphikon) fibers using a particulate loaded sol dipping technique. After calcining at 1,100 C in air, the coated fibers were incorporated into a polycrystalline alumina matrix via hot pressing. Interfacial shear strength and sliding behavior of the coated fibers was examined using thin-slice indentation fiber pushout and pushback techniques. In all cases, debonding and sliding occurred at the interface between the fibers and the coating. The coatings exhibited a dense microstructure and led to a higher interfacial shear strength (> 240 MPa) and interfacial sliding stress (> 75 MPa) relative to previous studies on the effect of a porous interphase on interfacial properties. The interfacial shear strength decreased with increasing fiber coating thickness (from 389 {+-} 59 to 241 {+-} 43 MPa for 0.15 to 1.45 {micro}m thick coatings, respectively). Sliding behavior exhibited load modulation with increasing displacement during fiber sliding which is characteristic of fiber roughness-induced stick-slip. The high interfacial shear strengths and sliding stresses measured in this study, as well as the potentially strength degrading surface reconstruction observed on the coated fibers after hot pressing and heat treatment, indicate that dense zirconia coatings are not suitable candidates for optimizing composite toughness and strength in the sapphire fiber reinforced alumina system.

  20. Direct handling of sharp interfacial energy for microstructural evolution

    DOE PAGESBeta

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

    2014-08-24

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

  1. An Air-water Interfacial Area Based Variable Tortuosity Model for Unsaturated Sands

    NASA Astrophysics Data System (ADS)

    Khaleel, R.; Saripalli, P.

    2005-12-01

    A new variable tortuosity definition is introduced that is based on the immiscible fluid (air-water) interfacial area. Unsaturated media tortuosity (τa) is defined as the ratio of aaw to aaw,o where aaw is the estimated air-water interfacial area in a real unsaturated medium (i.e., a soil sample), and aaw,o is the same variable for the corresponding, idealized capillary bundle. We establish equivalence between the real and the idealized media by letting the laboratory-measured retention curve calculate the distribution of capillary tubes, thereby resulting in an identical pore-size distribution but a new retention curve for the idealized medium. The air-water interfacial area for both real and idealized media is directly proportional to the area under their respective retention curves. With τ being the saturated tortuosity, we relate the variable tortuosity ratio (ττa) to the Seɛ term in Mualem's (ɛ=0.5) and Burdine's (ɛ=2) pore-size distribution models. Thus, instead of using tortuosity and/or pore connectivity formulations that have empirical exponents of either 0.5 or 2, the new model depends on variable interfacial area for varying saturation and soil texture, as reflected in the measured retention data. We tested the new definition of tortuosity for 22 repacked Hanford sediments that are comprised of mostly coarse and fine sands but some also contain a sizeable fraction (as high as 27%) of fines (silt and clay). Replacing the Se2 term in van Genuchten-Mualem (VGM) model by the new interfacial area based variable tortuosity ratio, and still using saturated conductivity and retention parameters, as used in the conventional approach, we obtain interfacial area based K(θ) predictions that are nearly identical to the conventional VGM model predictions. We also compare the interfacial area based K(θ) predictions with the standard Brooks-Corey-Burdine (BCB) model predictions. Compared to the VGM model predictions, interfacial area based BCB K(θ) predictions

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

    NASA Astrophysics Data System (ADS)

    Anastasiadis, Spiros H.

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

  3. Influence of Interfacial Energy on Electric-Field-Induced Sphere-to-Cylinder Transition in Block Copolymer Thin Films

    SciTech Connect

    Wang, J.; Chen, W; Russell, T

    2008-01-01

    The effect of the interfacial energy on the electric-field-induced sphere-to-cylinder (S-to-C) transition in polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) copolymer thin films was studied as a function of the difference in the interfacial interactions of the PS and PMMA blocks with the substrate, d. It was found that the interfacial energies altered both the critical electric field strength and the time scales of kinetics. A very strong preferential interfacial interaction suppressed the electric-field-induced S-to-C transition even though such a transition occurred on a neutralized surface where the interfacial interactions were balanced. For a moderate interfacial interaction, the S-to-C transition can be induced by an applied electric field, but the time scale of the morphology change is much longer. Furthermore, the formation of ionic complexes in the BCP was found to enhance the electric-field-induced S-to-C transition even on a native Si substrate without any surface modification, providing a simple route to generate ordered arrays of high-aspect-ratio cylinders oriented normal to a film surface.

  4. Thermodynamic Model for Fluid-Fluid Interfacial Areas in Porous Media for Arbitrary Drainage-Imbibition Sequences

    SciTech Connect

    Schroth, Martin H.; Oostrom, Mart; Dobson, Richard; Zeyer, Josef

    2008-08-01

    Fluid/fluid interfacial areas are important in controlling the rate of mass and energy transfer between fluid phases in porous media. We present a modified thermodynamically based model (TBM) to predict fluid/fluid interfacial areas in porous media for arbitrary drainage/imbibition sequences. The TBM explicitly distinguishes between interfacial areas associated with continuous (free) and isolated (entrapped) nonwetting fluids. The model is restricted to two-fluid systems in which (1) no significant conversion of mechanical work into heat occurs, (2) the wetting fluid completely wets the porous medium’s solid surfaces, and (3) no changes in interfacial area due to mass transfer between phases occur. We show example calculations for two different drainage/imbibition sequences in two porous media: a highly uniform silica sand and a well-graded silt. The TBM’s predictions for interfacial area associated with free nonwetting-fluid are identical to those of a previously published geometry-based model (GBM). However, predictions for interfacial area associated with entrapped nonwetting-fluid are consistently larger in the TBM than in the GBM. Although a comparison of model predictions with experimental data is currently only possible to a limited extent, good general agreement was found for the TBM. As required model parameters are commonly used as inputs for or tracked during multifluid-flow simulations, the modified TBM may be easily incorporated in numerical codes.

  5. Interfacial fracture resistance of the joint of a solid oxide fuel cell glass-ceramic sealant with metallic interconnect

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Kuang; Shiu, Wei-Hong; Wu, Si-Han; Liu, Chien-Kuo; Lee, Ruey-Yi

    2014-09-01

    Interfacial cracking resistance of a joint between a glass-ceramic sealant (GC-9) and interconnect stainless steel (Crofer 22 H) for planar solid oxide fuel cells is investigated. Interfacial fracture energy is measured at room temperature to 800 °C using a four-point bending test technique. A heat treatment of 100 h or 1000 h at 800 °C is applied for studying the thermal aging effect. Results show the variation trend of interfacial fracture energy with temperature is similar for all given material conditions. Interfacial fracture energy increases with temperature to reach a peak value at 700 °C and then drops at temperature above 700 °C. A 100-h aging treatment does not change the interfacial fracture energy significantly, compared to the non-aged condition. The 1000 h-aged joint, however, has greater interfacial fracture energy than the non-aged and 100 h-aged joints at 700 °C-800 °C. Two types of cracking path in the interior of fracture surface are identified. Firstly, delamination takes place at the interface between the glass-ceramic substrate and chromate layer. Secondly, cracking occurs within the chromate layer. However, for the 1000 h-aged joints tested at 700 °C-800 °C, fracture at the highly oxidized, peripheral regions takes place within the glass-ceramic layer.

  6. 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.

  7. Interfacial Characterization of Rigid Polymer Coatings

    NASA Astrophysics Data System (ADS)

    DeNolf, Garret C.

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

  8. 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.

  9. Weak links and interfacial chemistry in coal

    SciTech Connect

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

    1989-12-31

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

  10. Weak links and interfacial chemistry in coal

    SciTech Connect

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

    1989-01-01

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

  11. Rheology of interfacial protein-polysaccharide composites

    NASA Astrophysics Data System (ADS)

    Fischer, P.

    2013-05-01

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

  12. Viscosity of interfacial water regulates ice nucleation

    SciTech Connect

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

    2014-03-10

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

  13. Interfacial models of nerve fiber cytoskeleton.

    PubMed Central

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

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

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

    SciTech Connect

    Rustwick, Bryce A.

    2005-08-01

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

  16. Interfacial structure in epitaxial perovskite oxides on (001) Ge crystal

    SciTech Connect

    Shen, Xuan; Ahmadi-Majlan, K.; Ngai, Joseph H.; Wu, Di; Su, Dong

    2015-01-19

    We investigated the interfacial structure of hetero-epitaxial SrZr{sub 0.68}Ti{sub 0.32}O{sub 3} thin film deposited on (001) Ge single crystal via transmission electron microscopy (TEM). The results from high-resolution scanning TEM and electron energy-loss spectroscopy show an atomically abrupt interface without secondary phase. We found misfit dislocations with Burgers vector of 1/2a 〈111〉 and threading dislocations with Burgers vector of a 〈100〉. Furthermore, we observed the coupling between dislocation half-loop and anti-phase boundary induced by the lattice terrace of Ge along 〈100〉 direction and their decoupling after annealing. We proposed models based on half-loop theory to interpret the coupling and the dislocation reactions.

  17. Interfacial Charge Transfer States in Condensed Phase Systems

    NASA Astrophysics Data System (ADS)

    Vandewal, Koen

    2016-05-01

    Intermolecular charge transfer (CT) states at the interface between electron-donating (D) and electron-accepting (A) materials in organic thin films are characterized by absorption and emission bands within the optical gap of the interfacing materials. CT states efficiently generate charge carriers for some D-A combinations, and others show high fluorescence quantum efficiencies. These properties are exploited in organic solar cells, photodetectors, and light-emitting diodes. This review summarizes experimental and theoretical work on the electronic structure and interfacial energy landscape at condensed matter D-A interfaces. Recent findings on photogeneration and recombination of free charge carriers via CT states are discussed, and relations between CT state properties and optoelectronic device parameters are clarified.

  18. A study on characteristics of interfacial transition zone in concrete

    SciTech Connect

    Liao, K.-Y.; Chang, P.-K.; Peng, Y.-N.; Yang, C.-C

    2004-06-01

    The aim of this study was to observe the behavior of the interfacial transition zone (ITZ) of high-performance concrete that was under curing in saturated lime water. From the Scanning Electron Microscope (SEM), it was found that the pores and hydration products at the ITZ, within 100 {mu}m between the paste and aggregate, permuted each other during the early hydration stage, and then appeared as a large lump or strip. They gradually became irregular and small lumps for the further curing age. At the curing age of 56 days, the pores almost concentrated within an area of 0-15 {mu}m from the aggregate edge. The hydration products were much denser with the increase in its distance from the aggregate edge.

  19. Interfacial Charge Transfer States in Condensed Phase Systems.

    PubMed

    Vandewal, Koen

    2016-05-27

    Intermolecular charge transfer (CT) states at the interface between electron-donating (D) and electron-accepting (A) materials in organic thin films are characterized by absorption and emission bands within the optical gap of the interfacing materials. CT states efficiently generate charge carriers for some D-A combinations, and others show high fluorescence quantum efficiencies. These properties are exploited in organic solar cells, photodetectors, and light-emitting diodes. This review summarizes experimental and theoretical work on the electronic structure and interfacial energy landscape at condensed matter D-A interfaces. Recent findings on photogeneration and recombination of free charge carriers via CT states are discussed, and relations between CT state properties and optoelectronic device parameters are clarified. PMID:26980308

  20. Weighing graphene with QCM to monitor interfacial mass changes

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  1. Interfacial reaction dependent performance of hollow carbon nanosphere - sulfur composite as a cathode for Li-S battery

    DOE PAGESBeta

    Zheng, Jianming; Yan, Pengfei; Gu, Meng; Wagner, Michael J.; Hays, Kevin A.; Chen, Junzheng; Li, Xiaohong S.; Wang, Chong M.; Zhang, Ji -Guang; Liu, Jun; et al

    2015-05-26

    Lithium-sulfur (Li-S) battery is a promising energy storage system due to its high energy density, cost effectiveness and environmental friendliness of sulfur. However, there are still a number of challenges, such as low Coulombic efficiency and poor long-term cycling stability, impeding the commercialization of Li-S battery. The electrochemical performance of Li-S battery is closely related with the interfacial reactions occurring between hosting substrate and active sulfur species which are poorly conducting at fully oxidized and reduced states. Here, we correlate the relationship between the performance and interfacial reactions in the Li-S battery system, using a hollow carbon nanosphere (HCNS) withmore » highly graphitic character as hosting substrate for sulfur. With an appropriate amount of sulfur loading, HCNS/S composite exhibits excellent electrochemical performance because of the fast interfacial reactions between HCNS and the polysulfides. However, further increase of sulfur loading leads to increased formation of highly resistive insoluble reaction products (Li2S2/Li2S) which limits the reversibility of the interfacial reactions and results in poor electrochemical performance. In conclusion, these findings demonstrate the importance of the interfacial reaction reversibility in the whole electrode system on achieving high capacity and long cycle life of sulfur cathode for Li-S batteries.« less

  2. Interfacial reaction dependent performance of hollow carbon nanosphere - sulfur composite as a cathode for Li-S battery

    SciTech Connect

    Zheng, Jianming; Yan, Pengfei; Gu, Meng; Wagner, Michael J.; Hays, Kevin A.; Chen, Junzheng; Li, Xiaohong S.; Wang, Chong M.; Zhang, Ji -Guang; Liu, Jun; Xiao, Jie

    2015-05-26

    Lithium-sulfur (Li-S) battery is a promising energy storage system due to its high energy density, cost effectiveness and environmental friendliness of sulfur. However, there are still a number of challenges, such as low Coulombic efficiency and poor long-term cycling stability, impeding the commercialization of Li-S battery. The electrochemical performance of Li-S battery is closely related with the interfacial reactions occurring between hosting substrate and active sulfur species which are poorly conducting at fully oxidized and reduced states. Here, we correlate the relationship between the performance and interfacial reactions in the Li-S battery system, using a hollow carbon nanosphere (HCNS) with highly graphitic character as hosting substrate for sulfur. With an appropriate amount of sulfur loading, HCNS/S composite exhibits excellent electrochemical performance because of the fast interfacial reactions between HCNS and the polysulfides. However, further increase of sulfur loading leads to increased formation of highly resistive insoluble reaction products (Li2S2/Li2S) which limits the reversibility of the interfacial reactions and results in poor electrochemical performance. In conclusion, these findings demonstrate the importance of the interfacial reaction reversibility in the whole electrode system on achieving high capacity and long cycle life of sulfur cathode for Li-S batteries.

  3. Preface: Special Topic on Interfacial and Confined Water

    NASA Astrophysics Data System (ADS)

    Molinero, Valeria; Kay, Bruce D.

    2014-11-01

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

  4. Preface: Special Topic on Interfacial and Confined Water

    SciTech Connect

    Molinero, Valeria; Kay, Bruce D.

    2014-11-14

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

  5. Role of interfacial dislocations on creep of a fully lamellar tial

    SciTech Connect

    Hsiung, L M; Nieh, T G

    1999-08-16

    Deformation mechanisms of a fully lamellar TiAl ({gamma} lamellae: 100 {approximately} 300 nm thick, {alpha}{sub 2} lamellae: 10 {approximately} 50 nm thick) crept at 760 C have been investigated. It was found that, as a result of a fine structure, the motion and multiplication of dislocations within both {gamma} and {alpha}{sub 2} lamellae are limited at low creep stresses (< 400 MPa). Thus, the glide and climb of lattice dislocations have insignificant contribution to creep deformation. In contrast, the motion of interfacial dislocations on {gamma}{alpha}{sub 2} and {gamma}{gamma} interfaces (i.e. interface sliding) dominates the deformation at low stresses. The major obstacles impeding the motion of interfacial dislocations was found to be lattice dislocations impinging on lamellar interfaces. The number of impinging lattice dislocations increases as the applied stress increases and, subsequently, causes the pileup of interfacial dislocations on the interfaces. The pileup further leads to the formation of deformation twins. Deformation twinning activated by the pileup of interfacial dislocations is suggested to be the dominant deformation mechanism at high stresses (> 400 MPa).

  6. Carbon Fiber—Vinyl Ester Interfacial Adhesion Improvement by the Use of an Epoxy Coating

    NASA Astrophysics Data System (ADS)

    Vautard, Frederic; Xu, Lanhong; Drzal, Lawrence T.

    With the use of composites expanding into larger structural applications, vinyl ester matrices which are not dependent on an autoclave cure and are more environmentally resistant to water absorption are being investigated. The degree of adhesion between the fiber and matrix has been recognized to be a critical factor in determining the performance of fiber-reinforced composites. The mechanical properties of carbon fiber-vinyl ester composites are low compared to carbon fiber-epoxy composites, partly because of lower interfacial adhesion. The origins of this limitation were investigated. The influence of preferential adsorption of the matrix constituents on the interfacial adhesion was not significant. However, the high cure volume shrinkage was found to be an important factor. An engineered interphase consisting of a partially cross-linked epoxy sizing that could chemically bond to the carbon fiber and form an interpenetrating network with the vinyl ester matrix was found to sharply improve the interfacial adhesion. The mechanisms involved in that improvement were investigated. The diffusion of styrene in the epoxy coating decreased the residual stress induced by the volume shrinkage of the vinyl ester matrix. The optimal value of the thickness was found to be a dominant factor in increasing the value of the interfacial shear strength according to a 2D non-linear finite element model.

  7. Time-dependent behavior of RC beams strengthened with externally bonded FRP plates: interfacial stresses analysis

    NASA Astrophysics Data System (ADS)

    Benyoucef, S.; Tounsi, A.; Benrahou, K. H.; Adda Bedia, E. A.

    2007-12-01

    External bonding of fibre reinforced polymer (FRP) composites has becomes a popular technique for strengthening concrete structures all over the world. An important failure mode of such strengthened members is the debonding of the FRP plate from the concrete due to high interfacial stresses near the plate ends. For correctly installed FRP plate, failure will occur within the concrete. Accurate predictions of the interfacial stresses are prerequisite for designing against debonding failures. In particular, the interfacial stresses between a beam and soffit plate within the linear elastic range have been addressed by numerous analytical investigations. In this study, the time-dependent behavior of RC beams bonded with thin composite plate was investigated theoretically by including the effect of the adherend shear deformations. The time effects considered here are those that arise from shrinkage and creep deformations of the concrete. This paper presents an analytical model for the interfacial stresses between RC beam and a thin FRP plate bonded to its soffit. The influence of creep and shrinkage effect relative to the time of the casting and the time of the loading of the beams is taken into account. Numerical results from the present analysis are presented to illustrate the significance of time-dependent of adhesive stresses.

  8. Improved Interfacial Bonding in Magnesium/Aluminum Overcasting Systems by Aluminum Surface Treatments

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Chen, Yiqing; Luo, Alan A.

    2014-12-01

    "Overcasting" technique is used to produce bimetallic magnesium/aluminum (Mg/Al) structures where lightweight Mg can be cast onto solid Al substrates. An inherent difficulty in creating strong Mg/Al interfacial bonding is the natural oxide film on the solid Al surfaces, which reduces the wettability between molten Mg and Al substrates during the casting process. In the paper, an "electropolishing + anodizing" surface treatment has been developed to disrupt the oxide film on a dilute Al-0.08 wt pct Ga alloy, improving the metallurgical bonding between molten Mg and Al substrates in the bimetallic experiments carried out in a high-vacuum test apparatus. The test results provided valuable information of the interfacial phenomena of the Mg/Al bimetallic samples. The results show significantly improved metallurgical bonding in the bimetallic samples with "electropolishing + anodizing" surface treatment and Ga alloying. It is recommended to adjust the pre-heating temperature and time of the Al substrates and the Mg melt temperature to control the interfacial reactions for optimum interfacial properties in the actual overcasting processes.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  10. Vibrational characteristics of FRP-bonded concrete interfacial defects in a low frequency regime

    NASA Astrophysics Data System (ADS)

    Cheng, Tin Kei; Lau, Denvid

    2014-04-01

    As externally bonded fiber-reinforced polymer (FRP) is a critical load-bearing component of strengthened or retrofitted civil infrastructures, the betterment of structural health monitoring (SHM) methodology for such composites is imperative. Henceforth the vibrational characteristics of near surface interfacial defects involving delamination and trapped air pockets at the FRP-concrete interface are investigated in this study using a finite element approach. Intuitively, due to its lower interfacial stiffness compared with an intact interface, a damaged region is expected to have a set of resonance frequencies different from an intact region when excited by acoustic waves. It has been observed that, when excited acoustically, both the vibrational amplitudes and frequency peaks in the response spectrum of the defects demonstrate a significant deviation from an intact FRP-bonded region. For a thin sheet of FRP bonded to concrete with sizable interfacial defects, the fundamental mode under free vibration is shown to be relatively low, in the order of kHz. Due to the low resonance frequencies of the defects, the use of low-cost equipment for interfacial defect detection via response spectrum analysis is highly feasible.

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

    NASA Astrophysics Data System (ADS)

    Panchamgam, Sashidhar S.

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

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

    PubMed

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

    2016-07-01

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

  13. Thermodynamics, interfacial pressure isotherms and dilational rheology of mixed protein-surfactant adsorption layers.

    PubMed

    Fainerman, V B; Aksenenko, E V; Krägel, J; Miller, R

    2016-07-01

    Proteins and their mixtures with surfactants are widely used in many applications. The knowledge of their solution bulk behavior and its impact on the properties of interfacial layers made great progress in the recent years. Different mechanisms apply to the formation process of protein/surfactant complexes for ionic and non-ionic surfactants, which are governed mainly by electrostatic and hydrophobic interactions. The surface activity of these complexes is often remarkably different from that of the individual protein and has to be considered in respective theoretical models. At very low protein concentration, small amounts of added surfactants can change the surface activity of proteins remarkably, even though no strongly interfacial active complexes are observed. Also small added amounts of non-ionic surfactants change the surface activity of proteins in the range of small bulk concentrations or surface coverages. The modeling of the equilibrium adsorption behavior of proteins and their mixtures with surfactants has reached a rather high level. These models are suitable also to describe the high frequency limits of the dilational viscoelasticity of the interfacial layers. Depending on the nature of the protein/surfactant interactions and the changes in the interfacial layer composition rather complex dilational viscoelasticities can be observed and described by the available models. The differences in the interfacial behavior, often observed in literature for studies using different experimental methods, are at least partially explained by a depletion of proteins, surfactants and their complexes in the range of low concentrations. A correction of these depletion effects typically provides good agreement between the data obtained with different methods, such as drop and bubble profile tensiometry. PMID:26198014

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    PubMed

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

    2008-10-01

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

  16. 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.

  17. Field evidence for a hybrid interfacial-coseismic seismoelectric effect

    NASA Astrophysics Data System (ADS)

    Butler, K. E.; Kulessa, B.; Pugin, A.

    2014-12-01

    In May, 2011, we carried out a field experiment in Leda Clay sediments near Ottawa, Canada to investigate whether seismoelectric conversions might be observed along with the clear P, S and PS converted waves regularly observed during near-surface seismic reflection surveys in that environment. Although high electrical conductivities (~10 Ωm below 6 m depth) were expected to result in weak electrical fields, we were encouraged by the availability of an IVI Minivib 1 vibroseis source, and by the presence of interfacial targets including the top of bedrock at ~23 m depth as well as porosity and textural changes within the overburden revealed by geotechnical logs. Seismic and seismoelectric shot records were acquired separately using both the MiniVib and an in-hole shotgun source. The recording system included 26 grounded dipoles, 4.5 m in length, all equipped with custom-made differential amplifiers. Harmonic subtraction, remote reference subtraction, and stacking of shot records were used to combat electrical noise levels associated with unstable powerline harmonics and apparent AM radio demodulation. Seismic and seismoelectric shot records bear a striking resemblance to each other; direct and refracted P-waves as well as P, S, and PS wave reflections all appear clearly in the seismoelectric records. At first glance, these would appear to be simply co-seismic seismoelectric effects. However, closer inspection reveals that some precede their corresponding seismic arrivals by several milliseconds, and exhibit broader bandwidths (up to 600 Hz) and better coherency. They are inferred to have been generated beneath each dipole receiver by upward travelling P and S-waves arriving at an interface, defined by contrasts in porosity and clay content, 7 m below the surface. These arrivals do not conform to either true co-seismic or true interfacial effects and therefore present a new challenge to our understanding of seismoelectric phenomena.

  18. Interfacial self-assembly of a bacterial hydrophobin

    PubMed Central

    Bromley, Keith M.; Morris, Ryan J.; Hobley, Laura; Brandani, Giovanni; Gillespie, Rachel M. C.; McCluskey, Matthew; Zachariae, Ulrich; Marenduzzo, Davide; Stanley-Wall, Nicola R.; MacPhee, Cait. E.

    2015-01-01

    The majority of bacteria in the natural environment live within the confines of a biofilm. The Gram-positive bacterium Bacillus subtilis forms biofilms that exhibit a characteristic wrinkled morphology and a highly hydrophobic surface. A critical component in generating these properties is the protein BslA, which forms a coat across the surface of the sessile community. We recently reported the structure of BslA, and noted the presence of a large surface-exposed hydrophobic patch. Such surface patches are also observed in the class of surface-active proteins known as hydrophobins, and are thought to mediate their interfacial activity. However, although functionally related to the hydrophobins, BslA shares no sequence nor structural similarity, and here we show that the mechanism of action is also distinct. Specifically, our results suggest that the amino acids making up the large, surface-exposed hydrophobic cap in the crystal structure are shielded in aqueous solution by adopting a random coil conformation, enabling the protein to be soluble and monomeric. At an interface, these cap residues refold, inserting the hydrophobic side chains into the air or oil phase and forming a three-stranded β-sheet. This form then self-assembles into a well-ordered 2D rectangular lattice that stabilizes the interface. By replacing a hydrophobic leucine in the center of the cap with a positively charged lysine, we changed the energetics of adsorption and disrupted the formation of the 2D lattice. This limited structural metamorphosis represents a previously unidentified environmentally responsive mechanism for interfacial stabilization by proteins. PMID:25870300

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  20. Attempt to control the interfacial strength

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.

    1997-11-01

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

  1. Oscillatory interfacial instability between miscible fluids

    NASA Astrophysics Data System (ADS)

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

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

  2. Orientational anisotropy and interfacial transport in polycrystals

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  3. Mapping interfacial excess in atom probe data.

    PubMed

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

    2015-12-01

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

  4. Control of interfacial instabilities using flow geometry

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  5. Surfactants and interfacial phenomena, 2nd Ed

    SciTech Connect

    Rosen

    1989-01-01

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

  6. Nucleation and interfacial adsorption in ternary systems.

    PubMed

    Philippe, T

    2015-03-01

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

  7. Wear and interfacial transport of material

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1975-01-01

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

  8. Interfacial functionalization and engineering of nanoparticles

    NASA Astrophysics Data System (ADS)

    Song, Yang

    The intense research interest in nanoscience and nanotechnology is largely fueled by the unique properties of nanoscale materials. In this dissertation, the research efforts are focused on surface functionalization and interfacial engineering of functional nanoparticles in the preparation of patchy nanoparticles (e.g., Janus nanoparticles and Neapolitan nanoparticles) such that the nanoparticle structures and properties may be manipulated to an unprecedented level of sophistication. Experimentally, Janus nanoparticles were prepared by an interfacial engineering method where one hemisphere of the originally hydrophobic nanoparticles was replaced with hydrophilic ligands at the air|liquid or solid|liquid interface. The amphiphilic surface characters of the Janus nanoparticles were verified by contact angle measurements, as compared to those of the bulk-exchange counterparts where the two types of ligands were distributed rather homogeneously on the nanoparticle surface. In a further study, a mercapto derivative of diacetylene was used as the hydrophilic ligands to prepare Janus nanoparticles by using hydrophobic hexanethiolate-protected gold nanoparticles as the starting materials. Exposure to UV irradiation led to effective covalent cross-linking between the diacetylene moieties of neighboring ligands and hence marked enhancement of the structural integrity of the Janus nanoparticles, which was attributable to the impeded surface diffusion of the thiol ligands on the nanoparticle surface, as manifested in fluorescence measurements of aged nanoparticles. More complicated bimetallic AgAu Janus nanoparticles were prepared by interfacial galvanic exchange reactions of a Langmuir-Blodgett monolayer of 1-hexanethiolate-passivated silver nanoparticles on a glass slide with gold(I)-mercaptopropanediol complex in a water/ethanol solution. The resulting nanoparticles exhibited an asymmetrical distribution not only of the organic capping ligands on the nanoparticle surface but

  9. Liquid-liquid interfacial nanoparticle assemblies

    DOEpatents

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

    2008-12-30

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

  10. Interfacial bonding and electronic structure of GaN/GaAs interface: A first-principles study

    SciTech Connect

    Cao, Ruyue; Zhang, Zhaofu; Wang, Changhong; Li, Haobo; Dong, Hong; Liu, Hui; Wang, Weichao; Xie, Xinjian

    2015-04-07

    Understanding of GaN interfacing with GaAs is crucial for GaN to be an effective interfacial layer between high-k oxides and III-V materials with the application in high-mobility metal-oxide-semiconductor field effect transistor (MOSFET) devices. Utilizing first principles calculations, here, we investigate the structural and electronic properties of the GaN/GaAs interface with respect to the interfacial nitrogen contents. The decrease of interfacial N contents leads to more Ga dangling bonds and As-As dimers. At the N-rich limit, the interface with N concentration of 87.5% shows the most stability. Furthermore, a strong band offsets dependence on the interfacial N concentration is also observed. The valance band offset of N7 with hybrid functional calculation is 0.51 eV. The electronic structure analysis shows that significant interface states exist in all the GaN/GaAs models with various N contents, which originate from the interfacial dangling bonds and some unsaturated Ga and N atoms. These large amounts of gap states result in Fermi level pinning and essentially degrade the device performance.

  11. Interfacial bonding and electronic structure of GaN/GaAs interface: A first-principles study

    NASA Astrophysics Data System (ADS)

    Cao, Ruyue; Zhang, Zhaofu; Wang, Changhong; Li, Haobo; Xie, Xinjian; Dong, Hong; Liu, Hui; Wang, Weichao

    2015-04-01

    Understanding of GaN interfacing with GaAs is crucial for GaN to be an effective interfacial layer between high-k oxides and III-V materials with the application in high-mobility metal-oxide-semiconductor field effect transistor (MOSFET) devices. Utilizing first principles calculations, here, we investigate the structural and electronic properties of the GaN/GaAs interface with respect to the interfacial nitrogen contents. The decrease of interfacial N contents leads to more Ga dangling bonds and As-As dimers. At the N-rich limit, the interface with N concentration of 87.5% shows the most stability. Furthermore, a strong band offsets dependence on the interfacial N concentration is also observed. The valance band offset of N7 with hybrid functional calculation is 0.51 eV. The electronic structure analysis shows that significant interface states exist in all the GaN/GaAs models with various N contents, which originate from the interfacial dangling bonds and some unsaturated Ga and N atoms. These large amounts of gap states result in Fermi level pinning and essentially degrade the device performance.

  12. 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

  13. Interfacial tension in immiscible mixtures of alkali halides.

    PubMed

    Lockett, Vera; Rukavishnikova, Irina V; Stepanov, Victor P; Tkachev, Nikolai K

    2010-02-01

    The interfacial tension of the liquid-phase interface in seven immiscible reciprocal ternary mixtures of lithium fluoride with the following alkali halides: CsCl, KBr, RbBr, CsBr, KI, RbI, and CsI was measured using the cylinder weighing method over a wide temperature range. It was shown that for all mixtures the interfacial tension gradually decreases with growing temperature. The interfacial tension of the reciprocal ternary mixtures at a given temperature increases both with the alkali cation radius (K(+) < Rb(+) < Cs(+)) and with the radius of the halogen anion (Cl(-) < Br(-) < I(-)). PMID:20094678

  14. Probing Interfacial Water on Nanodiamonds in Colloidal Dispersion.

    PubMed

    Petit, Tristan; Yuzawa, Hayato; Nagasaka, Masanari; Yamanoi, Ryoko; Osawa, Eiji; Kosugi, Nobuhiro; Aziz, Emad F

    2015-08-01

    The structure of interfacial water layers around nanoparticles dispersed in an aqueous environment may have a significant impact on their reactivity and on their interaction with biological species. Using transmission soft X-ray absorption spectroscopy in liquid, we demonstrate that the unoccupied electronic states of oxygen atoms from water molecules in aqueous colloidal dispersions of nanodiamonds have a different signature than bulk water. X-ray absorption spectroscopy can thus probe interfacial water molecules in colloidal dispersions. The impacts of nanodiamond surface chemistry and concentration on interfacial water electronic signature are discussed. PMID:26267179

  15. Interfacial Micromechanics in Fibrous Composites: Design, Evaluation, and Models

    PubMed Central

    Lei, Zhenkun; Li, Xuan; Qin, Fuyong; Qiu, Wei

    2014-01-01

    Recent advances of interfacial micromechanics in fiber reinforced composites using micro-Raman spectroscopy are given. The faced mechanical problems for interface design in fibrous composites are elaborated from three optimization ways: material, interface, and computation. Some reasons are depicted that the interfacial evaluation methods are difficult to guarantee the integrity, repeatability, and consistency. Micro-Raman study on the fiber interface failure behavior and the main interface mechanical problems in fibrous composites are summarized, including interfacial stress transfer, strength criterion of interface debonding and failure, fiber bridging, frictional slip, slip transition, and friction reloading. The theoretical models of above interface mechanical problems are given. PMID:24977189

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

    SciTech Connect

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

    1995-08-01

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

  17. The interfacial polycondensation of tetrabromobisphenol-a polycarbonate. 2--Reactivities and phase distribution of catalysts

    SciTech Connect

    Jentau Gu . Catalyst Research Center); Chunshan Wang . Dept. of Chemical Engineering)

    1993-10-05

    Tetrabromobisphenol-A (TBBPA), a sterically hindered bisphenol, is known to give only low molecular weight polymers using the interfacial process. The low reactivity is attributed to the bulkiness and electron-withdrawing bromine substituents at the ortho positions. The optimum reaction conditions for the interfacial polymerization of TBBPA using pyridine derivatives as a catalyst have been developed. From the two-phase concentration distribution constant (K[sub e]) and p K's values of triethylamine, 4-dimethylaminopyridine (DMAP), and TBBPA, the critical process parameters were obtained. Because of its high nucleophilicity and facile leaving character, the DMAP catalyst system produces a high molecular weight TBBPA-polycarbonate (PC) successfully. The profile of the process was followed to obtain a better understanding of the reaction mechanism.

  18. Interfacial Surfactant Ordering in Thin Films of SDS-Encapsulated Single-Walled Carbon Nanotubes.

    PubMed

    Das, Sushanta K; Sengupta, Sanghamitra; Velarde, Luis

    2016-01-21

    The molecular self-assembly of surfactants on the surface of single-walled carbon nanotubes (SWCNT) is currently a common strategy for the tuning of nanotube properties and the stabilization of carbon nanotube dispersions. Here, we report direct measurements of the degree of interfacial ordering for sodium dodecyl sulfate (SDS) surfactants adsorbed on colloidal, single-chirality enriched, SWCNTs within a solid film and investigate the dependence of surface alkyl chain order on the surfactant concentration in the precursor solution. The degree of order for the SWCNT-bound SDS molecules, is probed by vibrational sum frequency generation (VSFG) spectroscopy. We find concrete evidence for the presence of highly ordered surface structures at sufficiently high SDS concentrations, attributed here to cylindrical-like micelle assemblies with the SWCNT at the core. As the SDS concentration decreases, the interfacial order is found to decrease as well, generating a more disordered or random adsorption of surfactants on the nanotube surfaces. PMID:26730991

  19. 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).

  20. Interfacial reaction control and its mechanism of AlN epitaxial films grown on Si(111) substrates by pulsed laser deposition

    PubMed Central

    Wang, Wenliang; Yang, Weijia; Liu, Zuolian; Wang, Haiyan; Wen, Lei; Li, Guoqiang

    2015-01-01

    High-quality AlN epitaxial films have been grown on Si substrates by pulsed laser deposition (PLD) by effective control of the interfacial reactions between AlN films and Si substrates. The surface morphology, crystalline quality and interfacial property of as-grown AlN/Si hetero-interfaces obtained by PLD have been systemically studied. It is found that the amorphous SiAlN interfacial layer is formed during high temperature growth, which is ascribed to the serious interfacial reactions between Si atoms diffused from the substrates and the AlN plasmas produced by the pulsed laser when ablating the AlN target during the high temperature growth. On the contrary, abrupt and sharp AlN/Si hetero-interfaces can be achieved by effectively controlling the interfacial reactions at suitable growth temperature. The mechanisms for the evolution of interfacial layer from the amorphous SiAlN layer to the abrupt and sharp AlN/Si hetero-interfaces by PLD are hence proposed. This work of obtaining the abrupt interfaces and the flat surfaces for AlN films grown by PLD is of paramount importance for the application of high-quality AlN-based devices on Si substrates. PMID:26089026

  1. Interfacial activation of Candida antarctica lipase B: combined evidence from experiment and simulation

    PubMed Central

    Zisis, Themistoklis; Freddolino, Peter L.; Turunen, Petri; van Teeseling, Muriel C. F.

    2015-01-01

    Lipase immobilization is frequently used for altering the catalytic properties of these industrially used enzymes. Many lipases bind strongly to hydrophobic surfaces where they undergo interfacial activation. Candida antarctica lipase B (CalB), one of the most commonly used biocatalysts, is frequently discussed as an atypical lipase lacking interfacial activation. Here we show that CalB displays an enhanced catalytic rate for large, bulky substrates when adsorbed to a hydrophobic interface composed of densely packed alkyl chains. We attribute this increased activity of more than 7-fold to a conformational change that yields a more open active site. This hypothesis is supported by molecular dynamics simulations that show a high mobility for a small ‘lid’ (helix α5) close to the active site. Molecular docking calculations confirm that a highly open conformation of this helix is required for binding large, bulky substrates and that this conformation is favored in a hydrophobic environment. Taken together, our combined approach provides clear evidence for the interfacial activation of CalB on highly hydrophobic surfaces. In contrast to other lipases, however, the conformational change only affects large, bulky substrates, leading to the conclusion that CalB acts like an esterase for small substrates and as a lipase for substrates with large alcohol substituents. PMID:26346632

  2. 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)

  3. Interfacial patterns in magnetorheological fluids: Azimuthal field-induced structures

    NASA Astrophysics Data System (ADS)

    Dias, Eduardo O.; Lira, Sérgio A.; Miranda, José A.

    2015-08-01

    Despite their practical and academic relevance, studies of interfacial pattern formation in confined magnetorheological (MR) fluids have been largely overlooked in the literature. In this work, we present a contribution to this soft matter research topic and investigate the emergence of interfacial instabilities when an inviscid, initially circular bubble of a Newtonian fluid is surrounded by a MR fluid in a Hele-Shaw cell apparatus. An externally applied, in-plane azimuthal magnetic field produced by a current-carrying wire induces interfacial disturbances at the two-fluid interface, and pattern-forming structures arise. Linear stability analysis, weakly nonlinear theory, and a vortex sheet approach are used to access early linear and intermediate nonlinear time regimes, as well as to determine stationary interfacial shapes at fully nonlinear stages.

  4. Interfacial patterns in magnetorheological fluids: Azimuthal field-induced structures.

    PubMed

    Dias, Eduardo O; Lira, Sérgio A; Miranda, José A

    2015-08-01

    Despite their practical and academic relevance, studies of interfacial pattern formation in confined magnetorheological (MR) fluids have been largely overlooked in the literature. In this work, we present a contribution to this soft matter research topic and investigate the emergence of interfacial instabilities when an inviscid, initially circular bubble of a Newtonian fluid is surrounded by a MR fluid in a Hele-Shaw cell apparatus. An externally applied, in-plane azimuthal magnetic field produced by a current-carrying wire induces interfacial disturbances at the two-fluid interface, and pattern-forming structures arise. Linear stability analysis, weakly nonlinear theory, and a vortex sheet approach are used to access early linear and intermediate nonlinear time regimes, as well as to determine stationary interfacial shapes at fully nonlinear stages. PMID:26382499

  5. Effect of self-assembled InAs islands on the interfacial roughness of optical-switched resonant tunneling diode.

    PubMed

    Tian, Haitao; Wang, Lu; Shi, Zhenwu; Gao, Huaiju; Zhang, Shuhui; Wang, Wenxin; Chen, Hong

    2012-01-01

    Embedding a quantum dot [QD] layer between the double barriers of resonant tunneling diode [RTD] is proved to be an effective method to increase the sensitivity of QD-RTD single-photon detector. However, the interfacial flatness of this device would be worsened due to the introduction of quantum dots. In this paper, we demonstrate that the interfacial quality of this device can be optimized through increasing the growth temperature of AlAs up barrier. The glancing incidence X-ray reflectivity and the high-resolution transmission electron microscopy measurements show that the interfacial smoothness has been greatly improved, and the photo-luminescence test indicated that the InAs QDs were maintained at the same time. The smoother interface was attributed to the evaporation of segregated indium atoms at InGaAs surface layer. PACS: 73.40.GK, 73.23._b, 73.21.La, 74.62.Dh. PMID:22333518

  6. Effect of self-assembled InAs islands on the interfacial roughness of optical-switched resonant tunneling diode

    PubMed Central

    2012-01-01

    Embedding a quantum dot [QD] layer between the double barriers of resonant tunneling diode [RTD] is proved to be an effective method to increase the sensitivity of QD-RTD single-photon detector. However, the interfacial flatness of this device would be worsened due to the introduction of quantum dots. In this paper, we demonstrate that the interfacial quality of this device can be optimized through increasing the growth temperature of AlAs up barrier. The glancing incidence X-ray reflectivity and the high-resolution transmission electron microscopy measurements show that the interfacial smoothness has been greatly improved, and the photo-luminescence test indicated that the InAs QDs were maintained at the same time. The smoother interface was attributed to the evaporation of segregated indium atoms at InGaAs surface layer. PACS 73.40.GK, 73.23._b, 73.21.La, 74.62.Dh PMID:22333518

  7. Oxidation and temperature effects on the interfacial shear strength in SCS-6 fiber-reinforced reaction-bonded silicon nitride

    SciTech Connect

    Guermazi, M.

    1995-01-01

    The fiber/matrix interfacial shear strength of Textron SCS-6 SiC-fiber-reinforced reaction-bonded Si{sub 3}N{sub 4} (RBSN) was studied as a function of temperature after oxidation for 24 h at 600 C. Fiber push-out experiments were conducted using a diamond indenter in a high-temperature microhardness tester under vacuum. The interfacial shear strength increased with temperature because of the relief of residual tensile stresses arising from the difference in thermal expansion coefficients between the fiber and the matrix. Most of sublayer 2 of the fiber outer coating, which mainly consisted of carbon in the form of BSU (basic structure unit) aggregates, had disappeared after the heat treatment of the composite. Oxidation resulted in severe changes in the fiber outer coating and caused a lower interfacial shear strength with respect to that of the unoxidized composite.

  8. Interfacial Behavior of Polymers: Using Interfaces to Manipulate Polymers

    SciTech Connect

    Russell, Thomas P.

    2015-02-26

    The self-assembly of block copolymers into arrays of nanoscopic domains with areal densities approaching 10 terbit/in2 offer tremendous promise for the fabrication of ultrahigh density storage devices, batteries and other energy relevant devices. Interfacial interactions play a key role in dictating the orientation and ordering of these self-assembling materials. We have investigated the use of preferential and neutral solvents to overcome interfacial interactions and to rapid accelerate the dynamics of these materials, since the high molecular weight of the polymers significantly slows diffusion processes. Using a tailor-made chamber, we have introduced solvent vapor annealing (SVA) where solvent with a well-defined vapor pressures sells the copolymer film, enabling control over the solvent content in the film and, therefore, the thermodynamics governing the microphase separation of the copolymer, the interactions with the substrate and air interfaces and the dynamics. This tailor-made chamber also allows us to perform in situ grazing incidence x-ray scattering studies where the copolymer films can be characterized on the nanoscopic level over macroscopic distances. The methodologies developed in our laboratories are now used in numerous laboratories world-wide. We have found that arrays of block copolymer microdomains with perfect orientational order can be achieved over macroscopic areas using the SVA processes but the translational order is perturbed during the film drying process. As the copolymer film is swollen, the confinement of the film to the substrate introduces a frustration to the ordering of the microdomains. After equilibrium is achieved, when the swollen films are brought very close to the ordering transition, near perfect ordering is achieved. However, upon removal of the solvent, the confinement of the film to the substrate introduces translational disorder. We have investigated the influence of the rate of solvent removal and have found that

  9. Bulk and interfacial glass transitions of water.

    PubMed

    Bhattacharya, Deepanjan; Payne, Candace N; Sadtchenko, Vlad

    2011-06-16

    Fast scanning calorimetry (FSC) was employed to investigate glass softening dynamics in bulk-like and ultrathin glassy water films. Bulk-like water samples were prepared by vapor-deposition on the surface of a tungsten filament near 140 K where vapor-deposition results in low enthalpy glassy water films. The vapor-deposition approach was also used to grow multiple nanoscale (approximately 50 nm thick) water films alternated with benzene and methanoic films of similar dimensions. When heated from cryogenic temperatures, the ultrathin water films underwent a well manifested glass softening transition at temperatures 20 K below the onset of crystallization. However, no such transition was observed in bulk-like samples prior to their crystallization. These results indicate that thin-film water demonstrates glass softening dynamics that are dramatically distinct from those of the bulk phase. We attribute these differences to water's interfacial glass transition, which occurs at temperatures tens of degrees lower than that in the bulk. Implications of these findings for past studies of glass softening dynamics in various glassy water samples are discussed. PMID:21401034

  10. Nanofiber Scaffold Gradients for Interfacial Tissue Engineering

    PubMed Central

    Ramalingam, Murugan; Young, Marian F.; Thomas, Vinoy; Sun, Limin; Chow, Laurence C.; Tison, Christopher K.; Chatterjee, Kaushik; Miles, William C.; Simon, Carl G.

    2012-01-01

    We have designed a 2-spinnerette device that can directly electrospin nanofiber scaffolds containing a gradient in composition that can be used to engineer interfacial tissues such as ligament and tendon. Two types of nanofibers are simultaneously electrospun in an overlapping pattern to create a nonwoven mat of nanofibers containing a composition gradient. The approach is an advance over previous methods due to its versatility - gradients can be formed from any materials that can be electrospun. A dye was used to characterize the 2-spinnerette approach and applicability to tissue engineering was demonstrated by fabricating nanofibers with gradients in amorphous calcium phosphate nanoparticles (nACP). Adhesion and proliferation of osteogenic cells (MC3T3-E1 murine pre-osteoblasts) on gradients was enhanced on the regions of the gradients that contained higher nACP content yielding a graded osteoblast response. Since increases in soluble calcium and phosphate ions stimulate osteoblast function, we measured their release and observed significant release from nanofibers containing nACP. The nanofiber-nACP gradients fabricated herein can be applied to generate tissues with osteoblast gradients such as ligaments or tendons. In conclusion, these results introduce a versatile approach for fabricating nanofiber gradients that can have application for engineering graded tissues. PMID:22286209

  11. Interfacial phenomena in gas hydrate systems.

    PubMed

    Aman, Zachary M; Koh, Carolyn A

    2016-03-21

    Gas hydrates are crystalline inclusion compounds, where molecular cages of water trap lighter species under specific thermodynamic conditions. Hydrates play an essential role in global energy systems, as both a hinderance when formed in traditional fuel production and a substantial resource when formed by nature. In both traditional and unconventional fuel production, hydrates share interfaces with a tremendous diversity of materials, including hydrocarbons, aqueous solutions, and inorganic solids. This article presents a state-of-the-art understanding of hydrate interfacial thermodynamics and growth kinetics, and the physiochemical controls that may be exerted on both. Specific attention is paid to the molecular structure and interactions of water, guest molecules, and hetero-molecules (e.g., surfactants) near the interface. Gas hydrate nucleation and growth mechanics are also presented, based on studies using a combination of molecular modeling, vibrational spectroscopy, and X-ray and neutron diffraction. The fundamental physical and chemical knowledge and methods presented in this review may be of value in probing parallel systems of crystal growth in solid inclusion compounds, crystal growth modifiers, emulsion stabilization, and reactive particle flow in solid slurries. PMID:26781172

  12. Nucleation of interfacial nanobubbles via solventless exchange

    NASA Astrophysics Data System (ADS)

    Tan, Beng Hau; Arora, Manish; Ohl, Claus-Dieter

    2014-11-01

    Interfacial nanobubbles are flat spherical caps of gas that attach on wetted hydrophobic surfaces. Nanobubbles are typically nucleated by wetting an atomically smooth surface with a water-solvent exchange. The bubbles appear when water is flushed into the system, but dissolve in ethanol. Although there is abundant evidence to suggest the bubbles are gaseous (for instance with infrared spectroscopy, water-solvent exchanges by themselves cannot rule out the possibility that the structures are organic contaminants rather than gaseous bubbles, e.g.. We report an AFM study of nanobubbles on HOPG using an exchange of saturated water and degassed water. Nanobubbles nucleated by our solventless technique are smaller in radius and height than with the standard solvent exchange technique. The nanobubbles disappear on a second exchange with degassed water. Since the exchange is free of organic solvent, we rule out organic contamination. Moreover, since the exchange affects only the dissolved gas in the liquid, the appearance and disappearance of the bubbles by successive exchange can be conclusively linked to the gas.

  13. Design principles of interfacial thermal conductance

    NASA Astrophysics Data System (ADS)

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

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

  14. Manipulating interfacial hydrogens at palladium via STM.

    PubMed

    Tremblay, Jean Christophe; Blanco-Rey, María

    2015-06-01

    In this contribution, we provide a detailed dynamical analysis of the interfacial hydrogen migration mediated by scanning tunneling microscopy (STM). Contributions from the STM-current and from the non-adiabatic couplings are taken into account using only first principle models. The slight asymmetry of the tunnelling rates with respect to the potential bias sign inferred from experimental observations is reproduced by weighting the contributions of the metal acceptor-donor states for the propagation of the impinging electrons. The quasi-thermal inelastic collision mechanism is treated perturbatively. The influence of hydrogen pre-coverage is also investigated using new potential energy surfaces obtained from periodic density functional theory calculations. Fully quantum dynamical simulations of the system evolution are performed by solving the Pauli master equation, providing insight into the reaction mechanism of STM manipulation of subsurface hydrogens. It is observed that the hydrogen impurity favors resurfacing over occupation of the bulk and subsurface sites whenever possible. The present simulations give strong indication that the experimentally observed protuberances after STM-excitation are due to hydrogen accumulating in the vicinity of the surface. PMID:25948419

  15. Surface and interfacial creases in a bilayer tubular soft tissue

    NASA Astrophysics Data System (ADS)

    Razavi, Mir Jalil; Pidaparti, Ramana; Wang, Xianqiao

    2016-08-01

    Surface and interfacial creases induced by biological growth are common types of instability in soft biological tissues. This study focuses on the criteria for the onset of surface and interfacial creases as well as their morphological evolution in a growing bilayer soft tube within a confined environment. Critical growth ratios for triggering surface and interfacial creases are investigated both analytically and numerically. Analytical interpretations provide preliminary insights into critical stretches and growth ratios for the onset of instability and formation of both surface and interfacial creases. However, the analytical approach cannot predict the evolution pattern of the model after instability; therefore nonlinear finite element simulations are carried out to replicate the poststability morphological patterns of the structure. Analytical and computational simulation results demonstrate that the initial geometry, growth ratio, and shear modulus ratio of the layers are the most influential factors to control surface and interfacial crease formation in this soft tubular bilayer. The competition between the stretch ratios in the free and interfacial surfaces is one of the key driving factors to determine the location of the first crease initiation. These findings may provide some fundamental understanding in the growth modeling of tubular biological tissues such as esophagi and airways as well as offering useful clues into normal and pathological functions of these tissues.

  16. Interfacial Water-Transport Effects in Proton-Exchange Membranes

    SciTech Connect

    Kienitz, Brian; Yamada, Haruhiko; Nonoyama, Nobuaki; Weber, Adam

    2009-11-19

    It is well known that the proton-exchange membrane is perhaps the most critical component of a polymer-electrolyte fuel cell. Typical membranes, such as Nafion(R), require hydration to conduct efficiently and are instrumental in cell water management. Recently, evidence has been shown that these membranes might have different interfacial morphology and transport properties than in the bulk. In this paper, experimental data combined with theoretical simulations will be presented that explore the existence and impact of interfacial resistance on water transport for Nafion(R) 21x membranes. A mass-transfer coefficient for the interfacial resistance is calculated from experimental data using different permeation cells. This coefficient is shown to depend exponentially on relative humidity or water activity. The interfacial resistance does not seem to exist for liquid/membrane or membrane/membrane interfaces. The effect of the interfacial resistance is to flatten the water-content profiles within the membrane during operation. Under typical operating conditions, the resistance is on par with the water-transport resistance of the bulk membrane. Thus, the interfacial resistance can be dominant especially in thin, dry membranes and can affect overall fuel-cell performance.

  17. Interfacial strain effect on gas transport in nanostructured electrodes of solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wen, Kechun; Han, Yupei; Zou, Minda; Lv, Weiqiang; He, Weidong

    2015-09-01

    Most efforts regarding strain effect at the interfaces between electrolytes and electrodes are mainly focused on enhancing the ionic conductivity in electrolytes. However, fundamental insights into the strain effect on gas transport properties in electrodes of fuel cells are still lacking. In this report, quantitative analysis is performed to evaluate the correlation between interfacial strain and the important fuel cells parameters, including limiting current density and concentration polarization. We demonstrate that the strain effect plays an important role in the performance of solid oxide fuel cells with nanostructured electrodes. Our studies provide a powerful platform for reducing concentration polarization by engineering quantitatively the interfacial strain, and facilitating the development of high-efficiency nanostructured fuel cells.

  18. Interfacial stress state present in a 'thin-slice' fibre push-out test

    NASA Technical Reports Server (NTRS)

    Kallas, M. N.; Koss, D. A.; Hahn, H. T.; Hellmann, J. R.

    1992-01-01

    An analysis of the stress distributions along the fiber-matrix interface in a 'thin-slice' fiber push-out test is presented for selected test geometries. For the small specimen thicknesses often required to displace large-diameter fibers with high interfacial shear strengths, finite element analysis indicates that large bending stresses may be present. The magnitude of these stresses and their spatial distribution can be very sensitive to the test configuration. For certain test geometries, the specimen configuration itself may alter the interfacial failure process from one which initiates due to a maximum in shear stress near the top surface adjacent to the indentor, to one which involves mixed mode crack growth up from the bottom surface and/or yielding within the matrix near the interface.

  19. Interfacial hydrothermal synthesis of SnO{sub 2} nanorods towards photocatalytic degradation of methyl orange

    SciTech Connect

    Hou, L.R. Lian, L.; Zhou, L.; Zhang, L.H.; Yuan, C.Z.

    2014-12-15

    Highlights: • Efficient interfacial hydrothermal strategy was developed. • 1D SnO{sub 2} nanorods as an advanced photocatalyst. • SnO{sub 2} nanorods exhibit photocatalytic degradation of the MO. - Abstract: One-dimensional (1D) SnO{sub 2} nanorods (NRs) have been successfully synthesized by means of an efficient interfacial hydrothermal strategy. The resulting product was physically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscope, etc. The as-fabricated SnO{sub 2} NRs exhibited excellent photocatalytic degradation of the methyl orange with high degradation efficiency of 99.3% with only 60 min ultra violet light irradiation. Meanwhile, the 1D SnO{sub 2} NRs exhibited intriguing photostability after four recycles.

  20. Interfacial Shear Strength of Cast and Directionally Solidified Nial-Sapphire Fiber Composites

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Asthana, R.; Noebe, R. D.

    1993-01-01

    The feasibility of fabricating intermetallic NiAl-sapphire fiber composites by casting and zone directional solidification has been examined. The fiber-matrix interfacial shear strengths measured using a fiber push-out technique in both cast and directionally solidified composites are greater than the strengths reported for composites fabricated by powder cloth process using organic binders. Microscopic examination of fibers extracted from cast, directionally solidified (DS), and thermally cycled composites, and the high values of interfacial shear strengths suggest that the fiber-matrix interface does not degrade due to casting and directional solidification. Sapphire fibers do not pin grain boundaries during directional solidification, suggesting that this technique can be used to fabricate sapphire fiber reinforced NiAl composites with single crystal matrices.

  1. A Deterministic Interfacial Cyclic Oxidation Spalling Model. Part 1; Model Development and Parametric Response

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2002-01-01

    An equation has been developed to model the iterative scale growth and spalling process that occurs during cyclic oxidation of high temperature materials. Parabolic scale growth and spalling of a constant surface area fraction have been assumed. Interfacial spallation of the only the thickest segments was also postulated. This simplicity allowed for representation by a simple deterministic summation series. Inputs are the parabolic growth rate constant, the spall area fraction, oxide stoichiometry, and cycle duration. Outputs include the net weight change behavior, as well as the total amount of oxygen and metal consumed, the total amount of oxide spalled, and the mass fraction of oxide spalled. The outputs all follow typical well-behaved trends with the inputs and are in good agreement with previous interfacial models.

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

    NASA Astrophysics Data System (ADS)

    Ristic, R. I.

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

  3. Interfacial magnetic anisotropy of Co90Zr10 on Pt layer.

    PubMed

    Kil, Joon Pyo; Bae, Gi Yeol; Suh, Dong Ik; Choi, Won Joon; Noh, Jae Sung; Park, Wanjun

    2014-11-01

    Spin Transfer Torque (STT) is of great interest in data writing scheme for the Magneto-resistive Random Access Memory (MRAM) using Magnetic Tunnel Junction (MTJ). Scalability for high density memory requires ferromagnetic electrodes having the perpendicular magnetic easy axis. We investigated CoZr as the ferromagnetic electrode. It is observed that interfacial magnetic anisotropy is preferred perpendicular to the plane with thickness dependence on the interfaces with Pt layer. The anisotropy energy (K(u)) with thickness dependence shows a change of magnetic-easy-axis direction from perpendicular to in-plane around 1.2 nm of CoZr. The interfacial anisotropy (K(i)) as the directly related parameters to switching and thermal stability, are estimated as 1.64 erg/cm2 from CoZr/Pt multilayered system. PMID:25958513

  4. X-Ray Diffraction Studies of Interfacial Roughness in Multilayer Thin Films.

    NASA Astrophysics Data System (ADS)

    Phang, Yew Hoong

    1995-01-01

    Multilayer thin films have many interesting and potentially useful properties. Defects can affect the performance of multilayers. Interfacial roughness is an imperfection that is always present in multilayers. The work investigates multilayer interfacial roughness quantitatively using x-ray diffraction (XRD). Specifically, it focuses on (1) developing new ways of using diffuse-intensity XRD to measure quantitatively interfacial roughness in multilayers and (2) correlating roughness information obtained from XRD with the possible origins of roughness. Interfacial roughness in amorphous W/C multilayers and crystalline Si_{1-x}Ge_{x }/Si multilayers on vicinal Si(001) substrates grown by sputter deposition and molecular beam epitaxy respectively is explored using x-ray scattering. By performing appropriate measurements of scattered x-ray intensity, it is possible to measure, in addition to values of magnitudes of interfacial roughness, magnitude of correlated roughness and its lateral correlation length, the degree of correlation between roughness in different interfaces, and the symmetry of correlated roughness with respect to substrate orientation and substrate miscut. In the W/C multilayers prepared under standard conditions, the correlation of roughness in different interfaces is isotropic but incomplete, and can be described by a simple phenomenological model. Using a cumulative roughness function, we identify the wavelength range in which the roughness predominates in these layers and we show that the long-wavelength roughness replicates better than the short-wavelength roughness. In the Si _{1-x}Ge_{x }/Si multilayers, correlated interfacial roughness is highly anisotropic and is aligned with respect to the substrate miscut direction. The lateral length scale of the anisotropic correlated roughness is many times greater than the average separation of the substrate steps. The existence of the anisotropic correlated roughness depends on the Ge concentration in

  5. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume I. Chapters 1-5)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  6. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume II. Chapters 6-10)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  7. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume III. Chapters 11-14)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  8. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume IV. Chapters 15-19)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  9. Interfacial Transport Phenomena Stability in Liquid-Metal/Water Systems

    SciTech Connect

    Michael Corradini; Anderson, Mark; Bonazza, Riccardo; Cho, D. H.

    2002-12-19

    One concept being considered for steam generation in innovative nuclear reactor applications, involves water coming into direct contact with a circulating molten metal. The vigorous agitation of the two fluids, the direct liquid-liquid contact and the consequent large interfacial area can give rise to large heat transfer coefficients and rapid steam generation. For an optimum design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability.In order to investigate the characteristics of such a molten metal/water direct contact heat exchanger, a series of experiments were performed in both a 1-D and 2-d experimental facility. The facilities primarily consist of a liquid-metal melt chamber, heated test section, water pumping/injection system, and steam suppression tank (condenser). A real-time high energy X-ray imaging system along with several temperature measurements and flow measurements were developed and utilized to measure the multiphase flow and obtain an empirical database of local as well as overall system parameters. Results have found volumetric void fraction between 0.05-0.2, overall volumetric heat transfer coefficient ranging from 4-20 kW/m3K, evaporation zone lengths on the order of 10cm and local heat transfer coefficients varying between 500-5000 W/m2K depending on the inlet water injection conditions and system pressure. Time-dependent void fraction distribution and generated water-vapor bubble characteristics (i.e. bubble formation rate, bubble rise velocity, and bubble surface area) were measured using an X-ray image analysis technique. These measurements aided in the determination of the volumetric thermal performance as well as well as the first detailed information on local interfacial phenomenon. This information in turn resulted in the first experimental measurements of the local heat transfer coefficient

  10. Plasticity and interfacial dislocation structures in Ti-Al

    SciTech Connect

    Parrini, L.; Heinrich, H.; Kostorz, G.

    1997-12-31

    The alloy Ti-48.6Al-1.9Cr-1.9Nb-1B with an equiaxed {gamma} microstructure, obtained by heat treatment at 1,200 C for 4 h, and with a lamellar microstructure, obtained by heat treatment at 1,380 C for 1 h, is characterized by compression tests and transmission electron microscopy. A lower activity of superdislocations and a more frequent pinning of ordinary dislocations are detected in the lamellar Ti-Al specimens in comparison with the non-lamellar ones during deformation at room temperature. The activity of superdislocations and the pinning of ordinary dislocations are responsible for the differences in yield stress and brittleness between lamellar and non-lamellar Ti-Al. A very high density of ordinary interfacial dislocations is found in the lamellar structure. These influence the activity of superdislocations and the pinning of ordinary dislocations. At high temperature a change in the deformation mechanism occurs. Above the brittle-to-ductile transition, the material is remarkably softer and the mechanical properties are insensitive to the presence of the lamellar interfaces.

  11. Bulk flow coupled to a viscous interfacial film sheared by a rotating knife edge

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    The measurement of the interfacial properties of highly viscous biofilms, such as DPPC (the primary component of lung surfactant), present on the surface of liquids (bulk phase) continues to attract significant attention. Most measurement techniques rely on shearing the interfacial film and quantifying its viscous response in terms of a surface (excess) viscosity at the air-liquid interface. The knife edge viscometer offers a significant advantage over other approaches used to study highly viscous films as the film is directly sheared by a rotating knife edge in direct contact with the film. However, accurately quantifying the viscous response is non-trivial and involves accounting for the coupled interfacial and bulk phase flows. Here, we examine the nature of the viscous response of water insoluble DPPC films sheared in a knife edge viscometer over a range of surface packing, and its influence on the strength of the coupled bulk flow. Experimental results, obtained via Particle Image Velocimetry in the bulk and at the surface (via Brewster Angle Microscopy), are compared with numerical flow predictions to quantify the coupling across hydrodynamic flow regimes, from the Stokes flow limit to regimes where flow inertia is significant. Supported by NNX13AQ22G, National Aeronautics and Space Administration.

  12. Numerical simulations of the role of a ferroelectric polymer interfacial layer in organic solar cells.

    PubMed

    Liu, Bo; Xu, Feng; Zhang, Xinghua; Yan, Dadong; Lu, Dan

    2016-02-21

    A Pauli master equation method is adopted for the simulation of polymer bulk heterojunction (BHJ) solar cells with vinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) films as interfacial layers. According to previous reports, using highly crystalline P(VDF-TrFE) films as interfacial layers can highly enhance the efficiency of polymer BHJ solar cells, and possible mechanisms for the enhancement by two different groups were given as the dipole induced permanent internal electric field or simply the electrode improvement which implied that the origin is the barrier lowering effect. The correlation between the appearance of S-shaped current density-voltage (J-V) characteristics and the energy barrier is studied first, and then further results indicate that the previous electrode improvement model provides a consistent explanation for the origin of performance enhancement due to the insertion of polarized P(VDF-TrFE) interfacial layers. Moreover, the phenomenon of an increase of the internal electric field observed before can be attributed to better contact conditions which help reduce the bimolecular recombination rate. Comparatively speaking, the electrode improvement model can give a more rational explanation for the origin of performance enhancement experimentally found. In contrast, the dipole induced permanent internal electric field model was not complete enough. PMID:26822850

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  14. A Novel Charged Medium Consisting of Gas-Liquid Interfacial Plasmas

    NASA Astrophysics Data System (ADS)

    Kaneko, Toshiro; Hatakeyama, Rikizo

    2009-11-01

    Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we succeed in creating the reactive gas (plasmas)—liquid (ionic liquids) interfacial field under a low gas pressure condition, where the plasma ion behavior can be controlled. The effects of the plasma ion irradiation on the liquid medium are quantitatively revealed for the first time. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the gas-liquid interfacial plasma are investigated by changing a polarity of the electrode in the liquid to evaluate the plasma-liquid interactions. These results would contribute to synthesizing the metal nanoparticles with carbon nanotubes as a template in the ionic liquid. It is found that the high density, mono-dispersed, and isolated metal nanoparticles are synthesized between or inside the carbon nanotubes by controlling the gas-liquid interfacial plasmas. Furthermore, we can form novel nano-bio composite materials, such as DNA encapsulated carbon nanotubes using the plasma ion irradiation method in an electrolyte plasma with DNA, and demonstrate modifications of the electrical properties of the carbon nanotubes depending on the kinds of encapsulated DNA for the first time.

  15. A Novel Charged Medium Consisting of Gas-Liquid Interfacial Plasmas

    SciTech Connect

    Kaneko, Toshiro; Hatakeyama, Rikizo

    2009-11-10

    Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we succeed in creating the reactive gas (plasmas)--liquid (ionic liquids) interfacial field under a low gas pressure condition, where the plasma ion behavior can be controlled. The effects of the plasma ion irradiation on the liquid medium are quantitatively revealed for the first time. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the gas-liquid interfacial plasma are investigated by changing a polarity of the electrode in the liquid to evaluate the plasma-liquid interactions. These results would contribute to synthesizing the metal nanoparticles with carbon nanotubes as a template in the ionic liquid. It is found that the high density, mono-dispersed, and isolated metal nanoparticles are synthesized between or inside the carbon nanotubes by controlling the gas-liquid interfacial plasmas. Furthermore, we can form novel nano-bio composite materials, such as DNA encapsulated carbon nanotubes using the plasma ion irradiation method in an electrolyte plasma with DNA, and demonstrate modifications of the electrical properties of the carbon nanotubes depending on the kinds of encapsulated DNA for the first time.

  16. Engineering interfacial photo-induced charge transfer based on nanobamboo array architecture for efficient solar-to-chemical energy conversion.

    PubMed

    Wang, Xiaotian; Liow, Chihao; Bisht, Ankit; Liu, Xinfeng; Sum, Tze Chien; Chen, Xiaodong; Li, Shuzhou

    2015-04-01

    Engineering interfacial photo-induced charge transfer for highly synergistic photocatalysis is successfully realized based on nanobamboo array architecture. Programmable assemblies of various components and heterogeneous interfaces, and, in turn, engineering of the energy band structure along the charge transport pathways, play a critical role in generating excellent synergistic effects of multiple components for promoting photocatalytic efficiency. PMID:25704499

  17. Measuring Non-Wetting/Wetting Interfacial Area: Comparing Synchrotron X-ray Microtomography and Interfacial Partitioning Tracer Methods

    NASA Astrophysics Data System (ADS)

    Narter, M. E.; Brusseau, M. L.

    2008-12-01

    Previous studies have shown that non-wetting/wetting interfacial areas measured with synchrotron X-ray microtomography are significantly smaller than those measured using the interfacial tracer test method for natural porous media. Research was conducted to evaluate the source of the disparity between these methods. It has been hypothesized that the disparity is due primarily to resolution constraints associated with microtomography, wherein the interfacial area associated with microscopic surface roughness is not measured. To test this hypothesis, experiments were conducted with glass beads that were shown to have no measureable surface roughness. Tetrachloroethene (PCE) was used as the model non-wetting fluid and sodium dodecylbenzene sulfonate was used as the interfacial tracer. Tracer tests yielded an average interfacial area of 2.8 +/- 5 1/cm while microtomography results produced an interfacial area of 3.4 +/- 2 1/cm. The values are similar for the two methods, indicating that the disparity observed for natural media is likely due to resolution limitations of microtomography.

  18. Influence of the interfacial phase on the structural integrity and oxygen permeability of a dual-phase membrane.

    PubMed

    Sun, Ming; Chen, Xinwei; Hong, Liang

    2013-09-25

    Compositing fluorite Ce0.8Gd0.2O2-δ (CGO) oxide with perovskite La0.4Ba0.6Fe0.8Zn0.2O3-δ (LBFZ) oxide leads to the formation of a minor interfacial BaCeO3 phase upon sintering at 1400 °C. This interfacial composition assures a gastight ceramic membrane with fine grain-boundary structure, in which the LBFZ phase exhibits an improved oxygen permeability over the pristine LBFZ membrane on the same volumetric basis. The presence of the BaCeO3 phase effectively preserves the structural integrity of the composition by limiting the interfacial diffusion of barium ions between LBFZ and CGO. In comparison, replacing CGO with Y0.08Zr0.92O2-δ in the system results in a substantially low oxygen flux due to an overwhelming interfacial diffusion and, consequently, a heavy degradation of LBFZ. Besides structural reinforcement, the high interface between LBFZ and CGO benefits oxygen transport, as is proven through variation of the oxygen partial pressure on the feed side of the membrane and operation temperature. Furthermore, the trade-off between LBFZ loading and interfacial diffusion yields an optimal CGO loading at 40 wt %, which exhibits an oxygen flux of 0.84 cm(3)/cm(2)·min at 950 °C. In summary, the minor interfacial binding between CGO and LBFZ grains is constructive in easing oxygen crossover in the phase boundary with the exception of maintaining membrane structural stability under oxygen permeation conditions. PMID:23977996

  19. Theory of plasmon enhanced interfacial electron transfer

    NASA Astrophysics Data System (ADS)

    Wang, Luxia; May, Volkhard

    2015-04-01

    A particular attempt to improve the efficiency of a dye sensitized solar cell is it's decoration with metal nano-particles (MNP). The MNP-plasmon induced enhancement of the local field enlarges the photoexcitation of the dyes and a subsequent improvement of the charge separation efficiency may result. In a recent work (2014 J. Phys. Chem. C 118 2812) we presented a theory of plasmon enhanced interfacial electron transfer for perylene attached to a TiO2 surface and placed in the proximity of a spherical MNP. These earlier studies are generalized here to the coupling of to up to four MNPs and to the use of somewhat altered molecular parameters. If the MNPs are placed close to each other strong hybridization of plasmon excitations appears and a broad resonance to which molecular excitations are coupled is formed. To investigate this situation the whole charge injection dynamics is described in the framework of the density matrix theory. The approach accounts for optical excitation of the dye coupled to the MNPs and considers subsequent electron injection into the rutile TiO2-cluster. Using a tight-binding model for the TiO2-system with about 105 atoms the electron motion in the cluster is described. We again consider short optical excitation which causes an intermediate steady state with a time-independent overall probability to have the electron injected into the cluster. This probability is used to introduce an enhancement factor which rates the influence of the MNP. Values larger than 500 are obtained.

  20. Liquid-Solid Nanofriction and Interfacial Wetting.

    PubMed

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

    2016-01-26

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

  1. Theory of plasmon enhanced interfacial electron transfer.

    PubMed

    Wang, Luxia; May, Volkhard

    2015-04-10

    A particular attempt to improve the efficiency of a dye sensitized solar cell is it's decoration with metal nano-particles (MNP). The MNP-plasmon induced enhancement of the local field enlarges the photoexcitation of the dyes and a subsequent improvement of the charge separation efficiency may result. In a recent work (2014 J. Phys. Chem. C 118 2812) we presented a theory of plasmon enhanced interfacial electron transfer for perylene attached to a TiO2 surface and placed in the proximity of a spherical MNP. These earlier studies are generalized here to the coupling of to up to four MNPs and to the use of somewhat altered molecular parameters. If the MNPs are placed close to each other strong hybridization of plasmon excitations appears and a broad resonance to which molecular excitations are coupled is formed. To investigate this situation the whole charge injection dynamics is described in the framework of the density matrix theory. The approach accounts for optical excitation of the dye coupled to the MNPs and considers subsequent electron injection into the rutile TiO2-cluster. Using a tight-binding model for the TiO2-system with about 10(5) atoms the electron motion in the cluster is described. We again consider short optical excitation which causes an intermediate steady state with a time-independent overall probability to have the electron injected into the cluster. This probability is used to introduce an enhancement factor which rates the influence of the MNP. Values larger than 500 are obtained. PMID:25764984

  2. Extraction of net interfacial polarization charge from Al{sub 0.54}In{sub 0.12}Ga{sub 0.34}N/GaN high electron mobility transistors grown by metalorganic chemical vapor deposition

    SciTech Connect

    Laurent, Matthew A.; Gupta, Geetak; Wienecke, Steven; Muqtadir, Azim A.; Keller, Stacia; Mishra, Umesh K.; DenBaars, Steven P.

    2014-11-14

    Al{sub x}In{sub y}Ga{sub (1-x-y)}N materials show promise for use in GaN-based heterojunction devices. The growth of these materials has developed to the point where they are beginning to see implementation in high electron mobility transistors (HEMTs) and light emitting diodes. However, the electrical properties of these materials are still poorly understood, especially as related to the net polarization charge at the AlInGaN/GaN interface (Q{sub π}(net)). All theoretical calculations of Q{sub π}(net) share the same weakness: dependence upon polarization bowing parameters, which describe the deviation in Q{sub π}(net) from Vegard's law. In this study, direct analysis of Q{sub π}(net) for Al{sub 0.54}In{sub 0.12}Ga{sub 0.34}N/GaN HEMTs is reported as extracted from C-V, I-V, and Hall measurements performed on samples grown by metalorganic chemical vapor deposition. An average value for Q{sub π}(net) is calculated to be 2.015 × 10{sup −6} C/cm{sup 2}, with just 6.5% variation between measurement techniques.

  3. Interfacial studies in fiber-reinforced thermoplastic-matrix composites

    SciTech Connect

    Brady, R.L.

    1989-01-01

    The major theme of this dissertation is structure/property relationships in fiber-reinforced thermoplastic-matrix composites. Effort has been focused on the interface: interfacial crystallization and fiber/matrix adhesion. Included are investigations on interfacial nucleation and morphology, measurement of fiber/matrix adhesion, effects of interfacial adsorption and crystallization on fiber/matrix adhesion, and composites reinforced with thermotropic liquid crystal copolyester fibers. Crystallization of a copolyester and polybutylene terephthalate with glass, carbon, or aramid fibers has been studied with regard to interfacial morphology. Techniques employed included hot-stage optical microscopy and differential scanning calorimetry. Nucleation by the fibers was found to be a general phenomenon. Morphology could be varied by changing the cooling rate. In order to better monitor fiber /matrix adhesion, a buckled plate test has been developed. The test measures transverse toughness as the parameter characterizing interfacial adhesion in unidirectional, continuous-fiber composites. The test is simple to perform yet has advantages over other interfacial evaluation techniques. The buckled plate test was found to be a sensitive measure of fiber/matrix adhesion. The buckled plate test has been used along with the transverse tensile test to examine how interfacial adsorption and crystallization affect fiber/matrix adhesion in polycarbonate/carbon fiber composites. Adsorption was found to be of primary importance in developing adhesion, while crystallization is a secondary effect. The toughness data have been fit successfully for annealing time and temperature dependence. The dependence of adsorption and transverse toughness on matrix molecular weight was found to be large, with higher molecular weights adsorbing more effectively.

  4. Experimentally Determined Interfacial Area Between Immiscible Fluids in Porous Media

    SciTech Connect

    Crandall, Dustin; Niessner, J; Hassanizadeh, S.M; Smith, Duane

    2008-01-01

    When multiple fluids flow through a porous medium, the interaction between the fluid interfaces can be of great importance. While this is widely recognized in practical applications, numerical models often disregard interactios between discrete fluid phases due to the computational complexity. And rightly so, for this level of detail is well beyond most extended Darcy Law relationships. A new model of two-phase flow including the interfacial area has been proposed by Hassarizadeh and Gray based upon thermodynamic principles. A version of this general equation set has been implemented by Nessner and Hassarizadeh. Many of the interfacial parameters required by this equation set have never been determined from experiments. The work presented here is a description of how the interfacial area, capillary pressure, interfacial velocity and interfacial permeability from two-phase flow experiments in porous media experiments can be used to determine the required parameters. This work, while on-going, has shown the possibility of digitizing images within translucent porous media and identifying the location and behavior of interfaces under dynamic conditions. Using the described methods experimentally derived interfacial functions to be used in larger scale simulations are currently being developed. In summary, the following conclusions can be drawn: (1) by mapping a pore-throat geometry onto an image of immiscible fluid flow, the saturation of fluids and the individual interfaces between the fluids can be identified; (2) the resulting saturation profiles of the low velocity drainage flows used in this study are well described by an invasion percolation fractal scaling; (3) the interfacial area between fluids has been observed to increase in a linear fashion during the initial invasion of the non-wetting fluid; and (4) the average capillary pressure within the entire cell and representative elemental volumes were observed to plateau after a small portion of the volume was

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

    SciTech Connect

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

    2014-07-25

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

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

    DOE PAGESBeta

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

    2014-07-25

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

  7. Interfacial sliding in fibrous brittle-matrix composites

    NASA Astrophysics Data System (ADS)

    Miles, Herbert Frederick, II

    Ceramic materials have desirable characteristics for use in high temperature applications, but due to their brittle nature they were avoided until the recent advent of ceramic matrix composites (CMCs) in which ceramic fibers are inserted into a ceramic matrix to toughen the material by retarding crack growth. This work investigates the role of sliding at interfaces in making brittle matrix composites (BMCs) more crack resistant. A two-dimensional study investigates the effects of roughness, toughness, and friction on the fracture behavior of BMCs. This study was then expanded to an axisymmetric study of a fiber engulfed by a crack. The results indicate that there are significant interaction effects between friction and the other parameters. To achieve 'long' sliding lengths, the magnitude of the interfacial critical energy release rate must be significantly less than the magnitude required to ensure crack deflection. The study then investigates the three-dimensional nature of a crack as it flows past a fiber. A computational analysis is performed to determine the crack propagation angle at a frictional interface. The computational results show good agreement with a novel experimental analysis using modified DCDC specimens. The experiments show, in real time, the propagation of a crack which is perpendicular to and intersects a frictional interface.

  8. Interfacial reactivity of ruthenium nanoparticles protected by ferrocenecarboxylates.

    PubMed

    Chen, Limei; Song, Yang; Hu, Peiguang; Deming, Christopher P; Guo, Yan; Chen, Shaowei

    2014-09-21

    Stable ruthenium nanoparticles protected by ferrocenecarboxylates (RuFCA) were synthesized by thermolytic reduction of RuCl3 in 1,2-propanediol. The resulting particles exhibited an average core diameter of 1.22 ± 0.23 nm, as determined by TEM measurements. FTIR and (1)H NMR spectroscopic measurements showed that the ligands were bound onto the nanoparticle surface via Ru-O bonds in a bidentate configuration. XPS measurements exhibited a rather apparent positive shift of the Fe2p binding energy when the ligands were bound on the nanoparticle surface, which was ascribed to the formation of highly polarized Ru-O interfacial bonds that diminished the electron density of the iron centers. Consistent results were obtained in electrochemical measurements where the formal potential of the nanoparticle-bound ferrocenyl moieties was found to increase by ca. 120 mV. Interestingly, galvanic exchange reactions of the RuFCA nanoparticles with Pd(ii) followed by hydrothermal treatment at 200 °C led to (partial) decarboxylation of the ligands such that the ferrocenyl moieties were now directly bonded to the metal surface, as manifested in voltammetric measurements that suggested intervalence charge transfer between the nanoparticle-bound ferrocene groups. PMID:25075931

  9. Interfacial bond strength of electrophoretically deposited hydroxyapatite coatings on metals.

    PubMed

    Wei, M; Ruys, A J; Swain, M V; Kim, S H; Milthorpe, B K; Sorrell, C C

    1999-07-01

    Hydroxyapatite (HAp) coatings were deposited onto substrates of metal biomaterials (Ti, Ti6Al4V, and 316L stainless steel) by electrophoretic deposition (EPD). Only ultra-high surface area HAp powder, prepared by the metathesis method 10Ca(NO3)2 + 6(NH4)2HPO4 + 8NH4OH), could produce dense coatings when sintered at 875-1000degreesC. Single EPD coatings cracked during sintering owing to the 15-18% sintering shrinkage, but the HAp did not decompose. The use of dual coatings (coat, sinter, coat, sinter) resolved the cracking problem. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) inspection revealed that the second coating filled in the "valleys" in the cracks of the first coating. The interfacial shear strength of the dual coatings was found, by ASTM F1044-87, to be approximately 12 MPa on a titanium substrate and approximately 22 MPa on 316L stainless steel, comparing quite favorably with the 34 MPa benchmark (the shear strength of bovine cortical bone was found to be 34 MPa). Stainless steel gave the better result since -316L (20.5 microm mK(-1)) > alpha-HAp (approximately 14 microm mK(-1)), resulting in residual compressive stresses in the coating, whereas alpha-titanium (approximately 10.3 microm mK(-1)) < alpha-HAp, resulting in residual tensile stresses in the coating. PMID:15348125

  10. Interfacial charging phenomena of aluminum (hydr)oxides

    SciTech Connect

    Hiemstra, T.; Yong, H.; Van Riemsdijk, W.H.

    1999-08-31

    The interfacial charging of Al(OH){sub 3} (gibbsite and bayerite) and Al{sub 2}O{sub 3} has been studied. For Al(OH){sub 3} it can be shown that the very strong variation in charging behavior for different preparations is related to the relative presence of differently reacting crystal planes. The edge faces of the hexagonal gibbsite crystals are proton reactive over the whole pH range, in contrast to the 001 plane, which is mainly uncharged below pH = 10. On this 001 face only doubly coordinated surface groups are found, in contrast to the edges which also have singly coordinated surface groups. The results are fully in agreement with the predictions of the Multi site complexation (MUSIC) model. The proton adsorption, electrolyte ion adsorption, and shift of the IEP of gibbsite and aluminum oxide have been modeled simultaneously. For gibbsite, the ion pair formation of Na is larger than that of Cl, as is evidenced by modeling the experimentally observed upward shift on the IEP and charge reversal at high electrolyte concentrations. All these experimental results can be satisfactorily modeled with the MUSIC model, including the experimental surface potential of aluminum oxide (ISFET).

  11. Fluid interfacial nanoroughness measurement through the morphological characteristics of graphene

    PubMed Central

    Yoon, Hong Min; Lee, Jung Shin; Yeo, Jong-Souk; Lee, Joon Sang

    2014-01-01

    The interfacial nanoroughness of liquid plays an important role in the reliability of liquid lenses, capillary waves, and mass transfer in biological cells [Grilli et al., Opt. Express 16, 8084 (2008), Wang et al., IEEE Photon. Technol. Lett. 18, 2650 (2006), and T. Fukuma et al., 92, 3603 (2007)]. However, the nanoroughness of liquid is hard to visualize or measure due to the instability and dynamics of the liquid-gas interface. In this study, we blanket a liquid water surface with monolayer graphene to project the nanoroughness of the liquid surface. Monolayer graphene can project the surface roughness because of the extremely high flexibility attributed to its one atomic thickness. The interface of graphene and water is successfully mimicked by the molecular dynamics method. The nanoroughness of graphene and water is defined based on density distribution. The correlation among the roughness of graphene and water is developed within a certain temperature range (298–390 K). The results show that the roughness of water surface is successfully transferred to graphene surface. Surface tension is also calculated with a simple water slab. The rise of temperature increased the roughness and decreased the surface tension. Finally, the relationship between graphene roughness and surface tension is fitted with a second-order polynomial equation. PMID:25584110

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

    PubMed

    Armstrong, Ryan T; Berg, Steffen

    2013-10-01

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

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

    PubMed

    Rojas-Chapana, José A; Tributsch, Helmut

    2004-01-01

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

  14. Interfacial thermal degradation in inverted organic solar cells

    SciTech Connect

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

    2015-12-28

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

  15. The effects of interfacial potential on antimicrobial propensity of ZnO nanoparticle.

    PubMed

    Arakha, Manoranjan; Saleem, Mohammed; Mallick, Bairagi C; Jha, Suman

    2015-01-01

    The work investigates the role of interfacial potential in defining antimicrobial propensity of ZnO nanoparticle (ZnONP) against different Gram positive and Gram negative bacteria. ZnONPs with positive and negative surface potential are tested against different bacteria with varying surface potentials, ranging -14.7 to -23.6 mV. Chemically synthesized ZnONPs with positive surface potential show very high antimicrobial propensity with minimum inhibitory concentration of 50 and 100 μg/mL for Gram negative and positive bacterium, respectively. On other hand, ZnONPs of the same size but with negative surface potential show insignificant antimicrobial propensity against the studied bacteria. Unlike the positively charged nanoparticles, neither Zn(2+) ion nor negatively charged ZnONP shows any significant inhibition in growth or morphology of the bacterium. Potential neutralization and colony forming unit studies together proved adverse effect of the resultant nano-bacterial interfacial potential on bacterial viability. Thus, ZnONP with positive surface potential upon interaction with negative surface potential of bacterial membrane enhances production of the reactive oxygen species and exerts mechanical stress on the membrane, resulting in the membrane depolarization. Our results show that the antimicrobial propensity of metal oxide nanoparticle mainly depends upon the interfacial potential, the potential resulting upon interaction of nanoparticle surface with bacterial membrane. PMID:25873247

  16. Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures

    NASA Astrophysics Data System (ADS)

    Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

    2016-03-01

    Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices.

  17. The effects of interfacial potential on antimicrobial propensity of ZnO nanoparticle

    NASA Astrophysics Data System (ADS)

    Arakha, Manoranjan; Saleem, Mohammed; Mallick, Bairagi C.; Jha, Suman

    2015-04-01

    The work investigates the role of interfacial potential in defining antimicrobial propensity of ZnO nanoparticle (ZnONP) against different Gram positive and Gram negative bacteria. ZnONPs with positive and negative surface potential are tested against different bacteria with varying surface potentials, ranging -14.7 to -23.6 mV. Chemically synthesized ZnONPs with positive surface potential show very high antimicrobial propensity with minimum inhibitory concentration of 50 and 100 μg/mL for Gram negative and positive bacterium, respectively. On other hand, ZnONPs of the same size but with negative surface potential show insignificant antimicrobial propensity against the studied bacteria. Unlike the positively charged nanoparticles, neither Zn2+ ion nor negatively charged ZnONP shows any significant inhibition in growth or morphology of the bacterium. Potential neutralization and colony forming unit studies together proved adverse effect of the resultant nano-bacterial interfacial potential on bacterial viability. Thus, ZnONP with positive surface potential upon interaction with negative surface potential of bacterial membrane enhances production of the reactive oxygen species and exerts mechanical stress on the membrane, resulting in the membrane depolarization. Our results show that the antimicrobial propensity of metal oxide nanoparticle mainly depends upon the interfacial potential, the potential resulting upon interaction of nanoparticle surface with bacterial membrane.

  18. Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures

    PubMed Central

    Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

    2016-01-01

    Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices. PMID:26954833

  19. Direct numerical simulation of interfacial wave generation in turbulent gas-liquid flows in horizontal channels

    NASA Astrophysics Data System (ADS)

    Campbell, Bryce; Hendrickson, Kelli; Liu, Yuming; Subramani, Hariprasad

    2014-11-01

    For gas-liquid flows through pipes and channels, a flow regime (referred to as slug flow) may occur when waves form at the interface of a stratified flow and grow until they bridge the pipe diameter trapping large elongated gas bubbles within the liquid. Slug formation is often accompanied by strong nonlinear wave-wave interactions, wave breaking, and gas entrainment. This work numerically investigates the fully nonlinear interfacial evolution of a two-phase density/viscosity stratified flow through a horizontal channel. A Navier-Stokes flow solver coupled with a conservative volume-of-fluid algorithm is use to carry out high resolution three-dimensional simulations of a turbulent gas flowing over laminar (or turbulent) liquid layers. The analysis of such flows over a range of gas and liquid Reynolds numbers permits the characterization of the interfacial stresses and turbulent flow statistics allowing for the development of physics-based models that approximate the coupled interfacial-turbulent interactions and supplement the heuristic models built into existing industrial slug simulators.

  20. Interfacial Effects on Lithium Superoxide Disproportionation in Li-O₂ Batteries

    SciTech Connect

    Zhai, Dengyun; Lau, Kah Chun; Wang, Hsien-Hau; Wen, Jianguo; Miller, Dean; Lu, Jun; Kang, Feiyu; Li, Baohua; Yang, Wenge; Gao, Jing; Indacochea, Ernesto; Curtiss, Larry A.; Amine, Khalil

    2015-02-11

    During the cycling of Li-O₂ batteries the discharge process gives rise to dynamically evolving agglomerates composed of lithium-oxygen nanostructures; however, little is known about their composition. In this paper, we present results for a Li-O₂ battery based on an activated carbon cathode that indicate interfacial effects can suppress disproportionation of a LiO₂ component in the discharge product. High-intensity X-ray diffraction and transmission electron microscopy measurements are first used to show that there is a LiO₂ component along with Li₂O₂ in the discharge product. The stability of the discharge product was then probed by investigating the dependence of the charge potential and Raman intensity of the superoxide peak with time. The results indicate that the LiO₂ component can be stable for possibly up to days when an electrolyte is left on the surface of the discharged cathode. Density functional calculations on amorphous LiO₂ reveal that the disproportionation process will be slower at an electrolyte/LiO₂ interface compared to a vacuum/LiO₂ interface. The combined experimental and theoretical results provide new insight into how interfacial effects can stabilize LiO₂ and suggest that these interfacial effects may play an important role in the charge and discharge chemistries of a Li-O₂ battery.

  1. Spatio-temporal evolution of interfacial instabilities in vertical gas-liquid flows

    NASA Astrophysics Data System (ADS)

    Schmidt, Patrick; Valluri, Prashant; Ó Náraigh, Lennon; Lucquiaud, Mathieu

    2014-11-01

    Vertical gas-liquid flows are characteristic for process engineering and widely employed in various technical applications. However, the dynamic behaviour of the liquid interface in such flows is still not fully understood. We focus in our work on characterising the interfacial instability as well as associated interfacial waves in vertical laminar-laminar gas-liquid flows over a wide range of parameters covering different flow regimes, i.e. counter-current, zero-interface velocity (loading) and partial-to-full liquid flow reversal (flooding). High-resolution direct numerical simulations using the TPLS flow solver (http://sourceforge.net/projects/tpls/) reveal the existence of weakly nonlinear interfacial waves, which are in good agreement with Stuart-Landau theory. These waves travel down- or upstream, depending on the flow regime. Furthermore, spatio-temporal linear stability analysis indicates the occurrence of absolute instability within the investigated parameter range. DNS is used to analyse this feature in more detail whereby agreement with linear theory has been established.

  2. 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.

  3. The role of water and mineral-collagen interfacial bonding on microdamage progression in bone.

    PubMed

    Luo, Qing; Leng, Huijie; Wang, Xiaodu; Zhou, Yanheng; Rong, Qiguo

    2014-02-01

    Microdamage would be accumulated in bone due to high-intensity training or even normal daily activity, which may consequently cause fragility fracture or stress fracture. On the other hand, microdamage formation serves as a toughening mechanism in bone. However, the mechanisms that control microdamage initiation and accumulation in bone are still poorly understood. Our previous finite element model indicated that different interfacial properties between mineral and collagen in bone may lead to distinct patterns of microdamage accumulation. Therefore, the current study was designed to examine such prediction and to investigate the role of water and mineral-collagen interactions on microdamage accumulation in bone. To address these issues, 48 mice femurs were divided randomly into four groups. These groups were dehydrated or treated with perfluorotripropylamine (PFTA) or NaF solution to change water distribution and mineral-collagen interfacial bonding in bone. After three-point bending fatigue tests, the types of microdamage (i.e., linear microcracks or diffuse damage) formed in bone were compared between different groups. The results suggested that (1) bone tissues with strong mineral-collagen interfacial bonding facilitate the formation of linear microcraks, and (2) water has little contribution to the growth of microcracks. PMID:24122969

  4. Differences in interfacial bond strengths of graphite fiber-epoxy resin composites

    NASA Technical Reports Server (NTRS)

    Needles, H. L.

    1985-01-01

    The effect of epoxy-size and degree of cure on the interfacial bonding of an epoxy-amine-graphite fiber composite system is examined. The role of the fiber-resin interface in determining the overall mechanical properties of composites is poorly understood. A good interfacial adhesive bond is required to achieve maximum stress transfer to the fibers in composites, but at the same time some form of energy absorbing interfacial interaction is needed to achieve high fracture toughening. The incompatibility of these two processes makes it important to understand the nature and basic factors involved at the fiber-resin interface as stress is applied. The mechanical properties including interlaminar shear values for graphite fiber-resin composites are low compared to glass and boron-resin composites. These differences have been attributed to poor fiber-matrix adhesion. Graphite fibers are commonly subjected to post-treatments including application of organic sizing in order to improve their compatibility with the resin matrix and to protect the fiber tow from damage during processing and lay-up. In such processes, sized graphite fiber tow is impregnated with epoxy resin and then layed-up i nto the appropriate configuration. Following an extended ambient temperature cure, the graphite-resin composite structure is cured at elevated temperature using a programmed temperature sequence to cure and then cool the product.

  5. Distinctive structure and interfacial activity of the human apolipoprotein A-IV 347S isoprotein

    PubMed Central

    Weinberg, Richard B.; Cook, Victoria R.

    2010-01-01

    The T347S polymorphism in the human apolipoprotein (apo) A-IV gene is present at high frequencies among all the world's populations. Carriers of a 347S allele exhibit faster clearance of triglyceride-rich lipoproteins, greater adiposity, and increased risk for developing atherosclerosis, which suggests that this conservative amino acid substitution alters the structure of apo A-IV. Herein we have used spectroscopic and surface chemistry techniques to examine the structure, stability, and interfacial properties of the apo A-IV 347S isoprotein. Circular dichroism spectroscopy revealed that the 347S isoprotein has similar α-helical structure but lower thermodynamic stability than the 347T isoprotein. Fluorescence spectroscopy found that the 347S isoprotein exhibits an enhanced tyrosine emission and reduced tyrosine→tryptophan energy transfer, and second derivative UV absorption spectra noted increased tyrosine exposure, suggesting that the 347S isoprotein adopts a looser tertiary conformation. Surface chemistry studies found that although the 347S isoprotein bound rapidly to the lipid interface, it has a lower interfacial exclusion pressure and lower elastic modulus than the 347T isoprotein. Together, these observations establish that the T347S substitution alters the conformation of apo A-IV and lowers its interfacial activity—changes that could account for the effect of this polymorphism on postprandial lipid metabolism. PMID:20554794

  6. The effects of interfacial potential on antimicrobial propensity of ZnO nanoparticle

    PubMed Central

    Arakha, Manoranjan; Saleem, Mohammed; Mallick, Bairagi C.; Jha, Suman

    2015-01-01

    The work investigates the role of interfacial potential in defining antimicrobial propensity of ZnO nanoparticle (ZnONP) against different Gram positive and Gram negative bacteria. ZnONPs with positive and negative surface potential are tested against different bacteria with varying surface potentials, ranging −14.7 to −23.6 mV. Chemically synthesized ZnONPs with positive surface potential show very high antimicrobial propensity with minimum inhibitory concentration of 50 and 100 μg/mL for Gram negative and positive bacterium, respectively. On other hand, ZnONPs of the same size but with negative surface potential show insignificant antimicrobial propensity against the studied bacteria. Unlike the positively charged nanoparticles, neither Zn2+ ion nor negatively charged ZnONP shows any significant inhibition in growth or morphology of the bacterium. Potential neutralization and colony forming unit studies together proved adverse effect of the resultant nano-bacterial interfacial potential on bacterial viability. Thus, ZnONP with positive surface potential upon interaction with negative surface potential of bacterial membrane enhances production of the reactive oxygen species and exerts mechanical stress on the membrane, resulting in the membrane depolarization. Our results show that the antimicrobial propensity of metal oxide nanoparticle mainly depends upon the interfacial potential, the potential resulting upon interaction of nanoparticle surface with bacterial membrane. PMID:25873247

  7. Elucidating the influence of polymorph-dependent interfacial solvent structuring at chitin surfaces.

    PubMed

    Brown, Aaron H; Walsh, Tiffany R

    2016-10-20

    Interfacial solvent structuring is thought to be influential in mediating the adsorption of biomolecules at aqueous materials interfaces. However, despite the enormous potential for exploitation of aqueous chitin interfaces in industrial, medical and drug-delivery applications, little is known at the molecular-level about such interfacial solvent structuring for chitin. Here we use molecular simulation to predict the structure of the [100] and [010] interfaces of α-chitin and β-chitin dihydrate in contact with liquid water and saline solution. We find the α-chitin [100] interface supports lateral high-density regions in the first water layer at the interface, which are also present, but not as pronounced, for β-chitin. The lateral structuring of interfacial ions at the saline/chitin interface is also more pronounced for α-chitin compared with β-chitin. Our findings provide a foundation for the systematic design of biomolecules with selective binding affinity for different chitin polymorphs. PMID:27474640

  8. Formation of interfacial layer and long-term cyclability of Li-O₂ batteries.

    PubMed

    Nasybulin, Eduard N; Xu, Wu; Mehdi, B Layla; Thomsen, Edwin; Engelhard, Mark H; Massé, Robert C; Bhattacharya, Priyanka; Gu, Meng; Bennett, Wendy; Nie, Zimin; Wang, Chongmin; Browning, Nigel D; Zhang, Ji-Guang

    2014-08-27

    The long-term operation of Li-O2 batteries under full discharge/charge conditions is investigated in a glyme-based electrolyte. The formation of stable interfacial layer on the electrode surface during the initial cycling stabilizes reaction products at subsequent cycling stages as demonstrated by quantitative analyses of the discharge products and the gases released during charging. There is a quick switch from the predominant formation of Li2O2 to the predominant formation of side products during the first few cycles. However, after the formation of the stable interfacial layer, the yield of Li2O2 in the reaction products is stabilized at about 33-40%. Extended cycling under full discharge/charge conditions is achievable upon selection of appropriate electrode materials (carbon source and catalyst) and cycling protocol. Further investigation on the interfacial layer, which in situ forms on air electrode, may increase the long-term yield of Li2O2 during the cycling and enable highly reversible Li-O2 batteries required for practical applications. PMID:25068384

  9. Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures.

    PubMed

    Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

    2016-01-01

    Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices. PMID:26954833

  10. Interfacial Effect on Confined Crystallization of Poly(ethylene oxide)/Silica Composites

    NASA Astrophysics Data System (ADS)

    Su, Yunlan; Zhao, Weiwei; Gao, Xia; Xu, Jianjun; Wang, Dujin

    The impact of nanoconfinement introduced by nanoparticles on polymer crystallization has attracted extensive attention because it plays the decisive role in the ultimate properties of polymer nanocomposites. In this study, interfacial and spatial confinement effects of silica (SiO2) nanoparticles on the crystallization behaviors of poly(ethylene oxide) (PEO)/SiO2 composites were systematically investigated by changing the size and concentration of SiO2 in PEO matrix. The composites with high silica loadings exhibit two crystallization peaks of PEO as determined by differential scanning calorimetry (DSC). The first peak at 7-43 °C is related to the bulk PEO, while the second peak at -20 to -30 °C is attributed to the restricted PEO segments. Three-layer (amorphous, interfacial and bulk) model is proposed to interpret the confined crystallization of PEO/SiO2 composites, which is supported by the results of thermogravimetric analysis (TGA) and solid-state 1H nuclear magnetic resonance (NMR). In amorphous layer, most PEO segments are directly adsorbed on SiO2 surface via hydrogen bonding. The interfacial PEO layer, which is nonuniform, is composed of crystallizable loops and tails extending from amorphous layer. National Natural Science Foundation of China (NSFC) under Contract 21274156.

  11. Interfacial load transfer in polymer/carbon nanotube nanocomposites with a nanohybrid shish kebab modification.

    PubMed

    Nie, Min; Kalyon, Dilhan M; Fisher, Frank T

    2014-09-10

    Interfacial properties are known to have a critical effect on the mechanical properties of a nanocomposite material system. Here, the interfacial load transfer in a carbon nanotube (CNT)/nylon-11 composite was studied with a CNT/nylon-11 nanohybrid shish kebab (NHSK) structure modification using Raman spectroscopy. Characterization of the polymer crystal in the NHSK using differential scanning calorimetry (DSC) for the first time indicates that the NHSK structure formed a more perfect crystal structure than the bulk polymer. On the basis of transmission electron microscopy and DSC results, a new growth model for the NHSK crystal is hypothesized, indicating the formation of an initial uniform crystal layer on the CNT prior to the crystallization of the kebabs. Characterization of the nanocomposites using Raman spectroscopy, with the samples heated to introduce interfacial shear stress caused by thermal expansion mismatch, found that the D* band of the CNT in the NHSK/nylon-11 composite displayed a more pronounced shift with an increase in temperature, which is attributed to the NHSK structure being more effective at transferring load from the nylon matrix to the nanotube inclusions. The NHSK structure was also used to fabricate composites with two amorphous polymers, polycarbonate and poly(methyl methacrylate), to investigate the load transfer mechanism. It was found that when the compatibility between the polymer in the NHSK structure and the bulk polymer matrix at the molecular level is sufficiently high, the ensuing mechanical interlocking effect further enhances the interfacial load transfer for polymer nanocomposites. Additional mechanical characterization of polymer nanocomposites with 0.1 wt % NHSK reinforcement demonstrates how the moduli and ultimate tensile strength of the nanocomposites can be improved via this NHSK structure. PMID:25134606

  12. 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.

  13. Effects of coating thickness and interfacial roughness on cracking and delamination strength of WC-Co coating measured by ring compression test

    NASA Astrophysics Data System (ADS)

    Kato, Masahiko; Nazul, Mahmoud; Itti, Takeshi; Akebono, Hiroyuki; Sugeta, Atsushi; Mitani, Eiji

    2014-08-01

    The effects of coating thickness and interfacial roughness on the interfacial fracture toughness of tungsten carbide-cobalt (WC-Co) coatings were evaluated using a ring compression test. WC-Co powder was sprayed on steel (JIS:SS400) rings by a high-velocity air- fuel method in coatings with various thicknesses and values of interfacial roughness. The ring compression test was carried out, and the cracking and delamination behavior of the coatings was observed using charge-coupled-device cameras. The results showed that cracking perpendicular to the loading direction occurred in the coatings during the ring compression test, and the cracking strength obtained from the ring compression test decreased slightly with increasing coating thickness, but was independent of the interfacial roughness. Upon further increase of the compression load, the coatings delaminated from the substrate. The interfacial fracture toughness calculated from the delamination of the coatings during the ring compression test decreased with increasing coating thickness and increased with increasing interfacial roughness.

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

    PubMed

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

    2015-02-01

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

  15. Modeling interfacial area transport in multi-fluid systems

    SciTech Connect

    Yarbro, S.L.

    1996-11-01

    Many typical chemical engineering operations are multi-fluid systems. They are carried out in distillation columns (vapor/liquid), liquid-liquid contactors (liquid/liquid) and other similar devices. An important parameter is interfacial area concentration, which determines the rate of interfluid heat, mass and momentum transfer and ultimately, the overall performance of the equipment. In many cases, the models for determining interfacial area concentration are empirical and can only describe the cases for which there is experimental data. In an effort to understand multiphase reactors and the mixing process better, a multi-fluid model has been developed as part of a research effort to calculate interfacial area transport in several different types of in-line static mixers. For this work, the ensemble-averaged property conservation equations have been derived for each fluid and for the mixture. These equations were then combined to derive a transport equation for the interfacial area concentration. The final, one-dimensional model was compared to interfacial area concentration data from two sizes of Kenics in-line mixer, two sizes of concurrent jet and a Tee mixer. In all cases, the calculated and experimental data compared well with the highest scatter being with the Tee mixer comparison.

  16. Protein adsorption and interfacial rheology interfering in dilatational experiment

    NASA Astrophysics Data System (ADS)

    Rühs, P. A.; Scheuble, N.; Windhab, E. J.; Fischer, P.

    2013-05-01

    The static and dilatational response of β-lactoglobulin fibrils and native β-lactoglobulin (monomers) at water-air and water-oil interfaces (pH 2) was measured using the pendant drop method. The resulting adsorption behavior and viscoelasticity is dependent of concentration and adsorption time. The interfacial pressure of the β-lactoglobulin fibrils obtained in static measurements was 16-18 mN/m (against air) and 7 mN/m (against oil) for all concentrations. With higher concentrations, faster adsorption kinetics and slightly higher interfacial and surface pressure is achieved but did not lead to higher viscoelastic moduli. The transient saturation of the interface is similar for both the fibril solution and the monomers, however the fibril solution forms a strong viscoelastic network. To evaluate the superimposed adsorption behavior and rheological properties, the formed interfacial layer was subjected to dilatational experiments, which were performed by oscillating the surface area of the drop in sinusoidal and sawtooth (diagonal) deformation manner. The sinusoidal oscillations (time depended area deformation rate) result in a complex interfacial tension behavior against air and oil interfaces and show remarkable differences during compression and expansion as emphasized by Lissajous figures. For diagonal (constant area deformation rate) experiments, a slight bending of the interfacial tension response was observed at low frequencies emphasizing the influence of protein adsorption during rheological measurements.

  17. Effect of interfacial coupling on rectification in organic spin rectifiers

    NASA Astrophysics Data System (ADS)

    Hu, Gui-Chao; Zuo, Meng-Ying; Li, Ying; Zhang, Zhao; Ren, Jun-Feng; Wang, Chuan-Kui

    2015-07-01

    The effect of interfacial coupling on rectification in an organic co-oligomer spin diode is investigated theoretically by considering spin-independent and spin-resolved couplings respectively. In the case of spin-independent coupling, an optimal interfacial coupling strength with a significant enhanced rectification ratio is found, whose value depends on the structural asymmetry of the molecule. In the case of spin-resolved coupling, we found that only the variation of the interfacial coupling with specific spin is effective to modulate the rectification, which is due to the spin-filtering property of the central asymmetric magnetic molecule. A transition of the spin-current rectification between parallel spin-current rectification and antiparallel spin-current rectification may be observed with the variation of the spin-resolved interfacial coupling. The interfacial effect on rectification is further analyzed from the spin-dependent transmission spectrum at different biases. Project supported by the National Natural Science Foundation of China (Grant No. 1374195), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AM017), and the Excellent Young Scholars Research Fund of Shandong Normal University, China.

  18. Some Aspects of Interfacial Phenomena in Steelmaking and Refining

    NASA Astrophysics Data System (ADS)

    Wang, L. J.; Viswanathan, N. N.; Muhmood, L.; Kapilashrami, E.; Seetharaman, S.

    2016-03-01

    Unique experiments were designed to study the surface phenomena in steelmaking reactions. The concept of surface sulfide capacities and an understanding of the surface accumulation of surface-active species, based on experimental results, are presented. In order to understand the flow phenomenon at slag/metal interface, experiments were designed to measure the interfacial velocity of S on the surface of an iron drop immersed in an aluminosilicate slag using the X-ray sessile drop method. The oscillation of the iron drop in the slag due to the change in the surface concentration of sulfur at the slag-metal interface was monitored by X-ray imaging. From the observations, the interfacial velocity of sulfur was evaluated. Similar experiments were performed to measure the interfacial velocity of oxygen at the interface as well as the impact of oxygen potential on the interfacial velocity of sulfur. The interfacial shear viscosity and the dilatational modulus were also evaluated. In a study of the wetting of alumina base by iron drop at constant oxygen pressure under isothermal condition, the contact angle was found to be decreased with the progress of the reaction leading to the formation of hercynite as an intermediate layer creating non-wetting conditions. In the case of silica substrate, an intermediate liquid fayalite layer was formed.

  19. Some Aspects of Interfacial Phenomena in Steelmaking and Refining

    NASA Astrophysics Data System (ADS)

    Wang, L. J.; Viswanathan, N. N.; Muhmood, L.; Kapilashrami, E.; Seetharaman, S.

    2016-08-01

    Unique experiments were designed to study the surface phenomena in steelmaking reactions. The concept of surface sulfide capacities and an understanding of the surface accumulation of surface-active species, based on experimental results, are presented. In order to understand the flow phenomenon at slag/metal interface, experiments were designed to measure the interfacial velocity of S on the surface of an iron drop immersed in an aluminosilicate slag using the X-ray sessile drop method. The oscillation of the iron drop in the slag due to the change in the surface concentration of sulfur at the slag-metal interface was monitored by X-ray imaging. From the observations, the interfacial velocity of sulfur was evaluated. Similar experiments were performed to measure the interfacial velocity of oxygen at the interface as well as the impact of oxygen potential on the interfacial velocity of sulfur. The interfacial shear viscosity and the dilatational modulus were also evaluated. In a study of the wetting of alumina base by iron drop at constant oxygen pressure under isothermal condition, the contact angle was found to be decreased with the progress of the reaction leading to the formation of hercynite as an intermediate layer creating non-wetting conditions. In the case of silica substrate, an intermediate liquid fayalite layer was formed.

  20. 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

  1. 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.

  2. Interfacial force sensor with force-feedback control

    SciTech Connect

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

    1990-01-01

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

  3. Solid/liquid interfacial free energies in binary systems

    NASA Technical Reports Server (NTRS)

    Nason, D.; Tiller, W. A.

    1973-01-01

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

  4. 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.

  5. 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.

  6. Effect of Fiber Surface Structure on Interfacial Reaction between Carbon Fiber and Aluminium

    NASA Astrophysics Data System (ADS)

    Chang, Kuang-Chih; Matsugi, Kazuhiro; Sasaki, Gen; Yanagisawa, Osamu

    Surface structure of carbon fiber and interfacial reaction between fiber and aluminium in carbon fiber reinforced aluminium composites were investigated by high-resolution transmission electron microscopy. Low and high graphitized carbon fiber reinforced pure aluminium composites were prepared by ultrasonic liquid infiltration. Vapor grown carbon nano fiber (VGCF) reinforced pure aluminium composites were prepared by hot-pressing. Heteroatoms, which existed abundantly in the surface of low graphitized carbon fiber, caused carbon lamellar structure in the fiber surface pronounced curvature. VGCF surface structure appeared regular and linear graphitic lamellae. Low graphitized fiber reinforced pure aluminium composites revealed serious interfacial reaction produced crystalline aluminium carbides (Al4C3), compared to composites reinforced by high graphitized fiber. On the other hand, Al4C3 crystalline reactants were not found at the interface of VGCF reinforced pure aluminium composites, but formation of interlayer was observed. In order to promote Al4C3 growth, carbon fiber reinforced composites were heat-treated at 573K and 873K for 1.8ks. Al4C3 interfacial phases in low and high graphitized fiber reinforced aluminium composites grew with the rise in the temperature. The heat-treatment resulted in the formation of non-crystalline Al4C3 interlayer by energy dispersive X-ray spectroscopy analysis of electron microscopy. At high temperature, Al4C3 was not grew and increased merely at the interface between carbon fiber and pure aluminium matrix, and moreover, the formation of new Al4C3 crystal occurred in this interlayer.

  7. Analysis of DNA equilibrium configuration under interfacial traction.

    PubMed

    Wang, Y Z; Zhang, Q C; Wang, W; Yang, Y W

    2016-01-01

    Kirchhoff thin elastic rod models are important in the study of the mechanism determining the configurations of flexible structures not only at the macroscopic but also at the microscopic scale. In this study, the energy balance method has been well applied to analyze the configuration of a DNA elastic rod in the presence of interfacial traction. An approximate solution for the shape equations has been obtained, and the relationship between the interfacial factor and the configuration of the DNA segment is derived. The results may provide an explanation for the onset of the formation of kinks in DNA when immersed in a solution. PMID:27323042

  8. Adhesion and interfacial fracture toughness between hard and soft materials

    NASA Astrophysics Data System (ADS)

    Rahbar, Nima; Wolf, Kurt; Orana, Argjenta; Fennimore, Roy; Zong, Zong; Meng, Juan; Papandreou, George; Maryanoff, Cynthia; Soboyejo, Wole

    2008-11-01

    This paper presents the results of a combined experimental and theoretical study of adhesion between hard and soft layers that are relevant to medical devices such as drug-eluting stents and semiconductor applications. Brazil disk specimens were used to measure the interfacial fracture energies between model parylene C and 316L stainless steel over a wide range of mode mixities. The trends in the overall fracture energies are predicted using a combination of adhesion theories and fracture mechanics concepts. The measured interfacial fracture energies are shown to be in good agreement with the predictions.

  9. The ensemble switch method for computing interfacial tensions.

    PubMed

    Schmitz, Fabian; Virnau, Peter

    2015-04-14

    We present a systematic thermodynamic integration approach to compute interfacial tensions for solid-liquid interfaces, which is based on the ensemble switch method. Applying Monte Carlo simulations and finite-size scaling techniques, we obtain results for hard spheres, which are in agreement with previous computations. The case of solid-liquid interfaces in a variant of the effective Asakura-Oosawa model and of liquid-vapor interfaces in the Lennard-Jones model are discussed as well. We demonstrate that a thorough finite-size analysis of the simulation data is required to obtain precise results for the interfacial tension. PMID:25877563

  10. 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

  11. Modelling temperature and concentration dependent solid/liquid interfacial energies

    NASA Astrophysics Data System (ADS)

    Lippmann, Stephanie; Jung, In-Ho; Paliwal, Manas; Rettenmayr, Markus

    2016-01-01

    Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al-FCC with their respective liquids and compared with experimental data.

  12. Estimating interfacial thermal conductivity in metamaterials through heat flux mapping

    SciTech Connect

    Canbazoglu, Fatih M.; Vemuri, Krishna P.; Bandaru, Prabhakar R.

    2015-04-06

    The variability of the thickness as well as the thermal conductivity of interfaces in composites may significantly influence thermal transport characteristics and the notion of a metamaterial as an effective medium. The consequent modulations of the heat flux passage are analytically and experimentally examined through a non-contact methodology using radiative imaging, on a model anisotropic thermal metamaterial. It was indicated that a lower Al layer/silver interfacial epoxy ratio of ∼25 compared to that of a Al layer/alumina interfacial epoxy (of ∼39) contributes to a smaller deviation of the heat flux bending angle.

  13. The ensemble switch method for computing interfacial tensions

    SciTech Connect

    Schmitz, Fabian; Virnau, Peter

    2015-04-14

    We present a systematic thermodynamic integration approach to compute interfacial tensions for solid-liquid interfaces, which is based on the ensemble switch method. Applying Monte Carlo simulations and finite-size scaling techniques, we obtain results for hard spheres, which are in agreement with previous computations. The case of solid-liquid interfaces in a variant of the effective Asakura-Oosawa model and of liquid-vapor interfaces in the Lennard-Jones model are discussed as well. We demonstrate that a thorough finite-size analysis of the simulation data is required to obtain precise results for the interfacial tension.

  14. 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

  15. 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

  16. 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.

  17. Comprehensive studies of interfacial strain and oxygen vacancy on metal-insulator transition of VO2 film.

    PubMed

    Fan, L L; Chen, S; Liao, G M; Chen, Y L; Ren, H; Zou, C W

    2016-06-29

    As a typical strong correlation material, vanadium dioxide (VO2) has attracted wide interest due to its particular metal-insulator transition (MIT) property. However, the relatively high critical temperature (T c) of ~68 °C seriously hinders its practical applications. Thus modulating the phase transition process and decreasing the T c close to room temperature have been hot topics for VO2 study. In the current work, we conducted a multi-approach strategy to control the phase transition of VO2 films, including the interfacial tensile/compressive strain and oxygen vacancies. A synchrotron radiation reciprocal space mapping technique was used to directly record the interfacial strain evolution and variations of lattice parameters. The effects of interfacial strain and oxygen vacancies in the MIT process were systematically investigated based on band structure and d-orbital electron occupation. It was suggested that the MIT behavior can be modulated through the combined effects of the interfacial strain and oxygen vacancies, achieving the distinct phase transition close to room temperature. The current findings not only provide better understanding for strain engineering and oxygen vacancies controlling phase transition behavior, but also supply a combined way to control the phase transition of VO2 film, which is essential for VO2 film based device applications in the future. PMID:27168422

  18. 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.

  19. 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

  20. Specific effects of Ca(2+) ions and molecular structure of β-lactoglobulin interfacial layers that drive macroscopic foam stability.

    PubMed

    Braunschweig, Björn; Schulze-Zachau, Felix; Nagel, Eva; Engelhardt, Kathrin; Stoyanov, Stefan; Gochev, Georgi; Khristov, Khr; Mileva, Elena; Exerowa, Dotchi; Miller, Reinhard; Peukert, Wolfgang

    2016-07-01

    β-Lactoglobulin (BLG) adsorption layers at air-water interfaces were studied in situ with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry as a function of bulk Ca(2+) concentration. The relation between the interfacial molecular structure of adsorbed BLG and the interactions with the supporting electrolyte is additionally addressed on higher length scales along the foam hierarchy - from the ubiquitous air-water interface through thin foam films to macroscopic foam. For concentrations <1 mM, a strong decrease in SFG intensity from O-H stretching bands and a slight increase in layer thickness and surface pressure are observed. A further increase in Ca(2+) concentrations above 1 mM causes an apparent change in the polarity of aromatic C-H stretching vibrations from interfacial BLG which we associate to a charge reversal at the interface. Foam film measurements show formation of common black films at Ca(2+) concentrations above 1 mM due to considerable decrease of the stabilizing electrostatic disjoining pressure. These observations also correlate with a minimum in macroscopic foam stability. For concentrations >30 mM Ca(2+), micrographs of foam films show clear signatures of aggregates which tend to increase the stability of foam films. Here, the interfacial layers have a higher surface dilatational elasticity. In fact, macroscopic foams formed from BLG dilutions with high Ca(2+) concentrations where aggregates and interfacial layers with higher elasticity are found, showed the highest stability with much smaller bubble sizes. PMID:27337699

  1. Probing the Interfacial Interaction in Layered-Carbon-Stabilized Iron Oxide Nanostructures: A Soft X-ray Spectroscopic Study.

    PubMed

    Zhang, Hui; Liu, Jinyin; Zhao, Guanqi; Gao, Yongjun; Tyliszczak, Tolek; Glans, Per-Anders; Guo, Jinghua; Ma, Ding; Sun, Xu-Hui; Zhong, Jun

    2015-04-22

    We have stabilized the iron oxide nanoparticles (NPs) of various sizes on layered carbon materials (Fe-oxide/C) that show excellent catalytic performance. From the characterization of X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), scanning transmission X-ray microscopy (STXM) and X-ray magnetic circular dichroism spectroscopy (XMCD), a strong interfacial interaction in the Fe-oxide/C hybrids has been observed between the small iron oxide NPs and layered carbon in contrast to the weak interaction in the large iron oxide NPs. The interfacial interaction between the NPs and layered carbon is found to link with the improved catalytic performance. In addition, the Fe L-edge XMCD spectra show that the large iron oxide NPs are mainly γ-Fe2O3 with a strong ferromagnetic property, whereas the small iron oxide NPs with strong interfacial interaction are mainly α-Fe2O3 or amorphous Fe2O3 with a nonmagnetic property. The results strongly suggest that the interfacial interaction plays a key role for the catalytic performance, and the experimental findings may provide guidance toward rational design of high-performance catalysts. PMID:25839786

  2. 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

  3. Comprehensive studies of interfacial strain and oxygen vacancy on metal–insulator transition of VO2 film

    NASA Astrophysics Data System (ADS)

    Fan, L. L.; Chen, S.; Liao, G. M.; Chen, Y. L.; Ren, H.; Zou, C. W.

    2016-06-01

    As a typical strong correlation material, vanadium dioxide (VO2) has attracted wide interest due to its particular metal–insulator transition (MIT) property. However, the relatively high critical temperature (T c) of ~68 °C seriously hinders its practical applications. Thus modulating the phase transition process and decreasing the T c close to room temperature have been hot topics for VO2 study. In the current work, we conducted a multi-approach strategy to control the phase transition of VO2 films, including the interfacial tensile/compressive strain and oxygen vacancies. A synchrotron radiation reciprocal space mapping technique was used to directly record the interfacial strain evolution and variations of lattice parameters. The effects of interfacial strain and oxygen vacancies in the MIT process were systematically investigated based on band structure and d-orbital electron occupation. It was suggested that the MIT behavior can be modulated through the combined effects of the interfacial strain and oxygen vacancies, achieving the distinct phase transition close to room temperature. The current findings not only provide better understanding for strain engineering and oxygen vacancies controlling phase transition behavior, but also supply a combined way to control the phase transition of VO2 film, which is essential for VO2 film based device applications in the future.

  4. 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

  5. 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.

  6. Interfacial Partitioning Tracer Test Measurement of NAPL-Water Interfacial Areas in Porous Media under Two-Phase Flow Condition

    NASA Astrophysics Data System (ADS)

    Zhong, H.; El Ouni, A.; Lin, D.; Wang, B.; Brusseau, M. L.

    2013-12-01

    The NAPL-water interface is of critical importance for the transport, fate, and remediation of organic contaminants in the subsurface due to its influence on contaminant mass transfer, transport, and biotransformation. In this work, the interfacial areas between tetrachloroethene (PCE) liquid (non-wetting phase) and water (wetting phase) in porous media were measured under two-phase flow conditions using the interfacial partitioning tracer test (IPTT) method. Three wetting scenarios of primary drainage, secondary imbibition, and secondary drainage were investigated. Two porous media were used, a well-sorted 45/50 mesh quartz sand and a sandy soil. The theoretical maximum interfacial areas determined from the measured data are compared to the specific solid surface area determined in two ways, based on geometrical calculations for smooth spheres and as measured with the N2/BET method. The results obtained for the NAPL-water system are compared to measurements conducted for comparable air-water systems.

  7. A dual-surfactant approach for the interfacial partitioning tracer test measurement of air-water interfacial area

    NASA Astrophysics Data System (ADS)

    El Ouni, A.; Brusseau, M. L.

    2013-12-01

    Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (A_ia). The method has been shown to provide uncertain measurements that are influenced by surfactant-enhanced drainage. The purpose of this work is to test a revised method that minimizes formation of interfacial-tension gradients in order to prevent surfactant-induced drainage. The method employs a dual-surfactant injection under steady unsaturated-flow conditions. Sodium dodecylbezene sulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning and nonreactive tracers, respectively. Sodium dodecyl sulfate (SDS) was used as the surfactant in the background solution. Three types of porous media were used for the study: a sandy soil, a well-sorted sand, and glass beads. Water saturation was monitored gravimetrically during the experiments. The results obtained with the revised method are compared to those obtained with the standard IPTT method.

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

    PubMed

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

    2016-02-01

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

  9. 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

  10. Radical Polymer Utilization for Interfacial Improvement of Organic Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Sung, Seung Hyun; Bajaj, Nikhil; Rhoads, Jeffrey; Chiu, George; Boudouris, Bryan

    Metal-semiconductor interfacial contact is one of the crucial factors for high-performance organic electronic device applications. In particular, the performance of organic field-effect transistors (OFETs) is critically dependent on the engineering of the interface between the organic semiconductor and the source/drain electrodes. Here, we modulate the performance of pentacene-based OFETs through the inclusion of a specific radical polymer, poly(2,2,6,6-tetramethylpiperidine-1-oxyl methacrylate) (PTMA), at the pentacene-gold electrode interface. Using a simple and fast inkjet printing method, the OFET performance is highly enhanced by the systematic deposition of a thin PTMA layer. The insertion of the radical polymer has an impact on the highly-improved OFET performance due to its redox charge transport ability and the amorphous nature allowing the stable growth of the pentacene. The synergistic effect facilitates the charge injection at the interface of the metal and organic semiconductor, resulting in the highly improved OFET performance. As such, the fundamental insights associated with radical polymers can be widened and their utilization as a highly-improved, low-cost interfacial modifier in myriad organic electronic devices is of great promise.

  11. Measurement of interfacial tension of immiscible liquid pairs in microgravity

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  12. Summer Research Institute Interfacial and Condensed Phase Chemical Physics

    SciTech Connect

    Barlow, Stephan E.

    2004-10-01

    Pacific Northwest National Laboratory (PNNL) hosted its first annual Summer Research Institute in Interfacial and Condensed Phase Chemical Physics from May through September 2004. During this period, fourteen PNNL scientists hosted sixteen young scientists from eleven different universities. Of the sixteen participants, fourteen were graduate students; one was transitioning to graduate school; and one was a university faculty member.

  13. Photon Upconversion Through Tb(3+) -Mediated Interfacial Energy Transfer.

    PubMed

    Zhou, Bo; Yang, Weifeng; Han, Sanyang; Sun, Qiang; Liu, Xiaogang

    2015-10-28

    A strategy of interfacial energy transfer upconversion is demonstrated through the use of a terbium (Tb(3+) ) dopant as energy donor or energy migrator in core-shell-structured nanocrystals. This mechanistic investigation presents a new pathway for photon upconversion, and, more importantly, contributes to the better control of energy transfer at the nanometer length scale. PMID:26378771

  14. Liquid metal actuation by electrical control of interfacial tension

    NASA Astrophysics Data System (ADS)

    Eaker, Collin B.; Dickey, Michael D.

    2016-09-01

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

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

    SciTech Connect

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

    2010-01-01

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

  16. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension

    PubMed Central

    Jackson, Meyer B.

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 oC. PMID:26813712

  17. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension.

    PubMed

    Jackson, Meyer B

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 (o)C. PMID:26813712

  18. Undergraduate Laboratory Experiment Modules for Probing Gold Nanoparticle Interfacial Phenomena

    ERIC Educational Resources Information Center

    Karunanayake, Akila G.; Gunatilake, Sameera R.; Ameer, Fathima S.; Gadogbe, Manuel; Smith, Laura; Mlsna, Deb; Zhang, Dongmao

    2015-01-01

    Three gold-nanoparticle (AuNP) undergraduate experiment modules that are focused on nanoparticles interfacial phenomena have been developed. Modules 1 and 2 explore the synthesis and characterization of AuNPs of different sizes but with the same total gold mass. These experiments enable students to determine how particle size affects the AuNP…

  19. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension

    NASA Astrophysics Data System (ADS)

    Jackson, Meyer B.

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 oC.

  20. Recent progress in interfacial tissue engineering approaches for osteochondral defects.

    PubMed

    Castro, Nathan J; Hacking, S Adam; Zhang, Lijie Grace

    2012-08-01

    This review provides a brief synopsis of the anatomy and physiology of the osteochondral interface, scaffold-based and non-scaffold based approaches for engineering both tissues independently as well as recent developments in the manufacture of gradient constructs. Novel manufacturing techniques and nanotechnology will be discussed with potential application in osteochondral interfacial tissue engineering. PMID:22677924

  1. Biomineralization mechanisms: a kinetics and interfacial energy approach

    NASA Astrophysics Data System (ADS)

    Nancollas, George H.; Wu, Wenju

    2000-04-01

    The calcium phosphates and oxalates are among the most frequently encountered biomineral phases and numerous kinetics studies have been made of their crystallization and dissolution in supersaturated and undersaturated solutions, respectively. These have focused mainly on parameters such as solution composition, ionic strength, pH, temperature, and solid surface characteristics. There is considerable interest in extending such studies to solutions more closely simulating the biological milieu. The constant composition method is especially useful for investigating the mechanisms of these reactions, and in the present work, the interfacial tensions between water and each of these surfaces have been calculated from measured contact angles using surface tension component theory. Values for the calcium phosphate phases such as dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP), hydroxyapatite (HAP), and fluorapatite (FAP) may be compared with data calculated from dissolution kinetics experiments invoking different reaction mechanisms. Agreement between the directly measured interfacial energies and those calculated from the kinetics experiments provides valuable corroborative information about individual growth and dissolution mechanisms. For the calcium phosphates, the much smaller interfacial tensions of OCP and DCPD in contact with water as compared with those of HAP and FAP support the suggestion that the former phases are precursors in HAP and FAP biomineralization. The ability of a surface to nucleate mineral phases is closely related to the magnitude of the interfacial energies. Constant composition studies have also shown that HAP is an effective nucleator of calcium oxalate monohydrate, both of which are frequently observed in renal stones.

  2. Manipulating Ordering Transitions in Interfacially Modified Block Copolymers

    SciTech Connect

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

    2009-01-01

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

  3. Scratching the surface of ice: Interfacial phase transitions and their kinetic implications

    NASA Astrophysics Data System (ADS)

    Limmer, David

    The surface structure of ice maintains a high degree of disorder down to surprisingly low temperatures. This is due to a number of underlying interfacial phase transitions that are associated with incremental changes in broken symmetry relative to the bulk crystal. In this talk I summarize recent work attempting to establish the nature and locations of these different phase transitions as well as how they depend on external conditions and nonequilibrium driving. The implications of this surface disorder is discussed in the context of simple kinetic processes that occur at these interfaces. Recent experimental work on the roughening transition is highlighted.

  4. Diphenylbutylbenzyl- and diphenyldibenzylphosphonium chlorides are interfacial catalysts in cross-linking of fluorine-containing copolymers

    SciTech Connect

    Lavrova, L.N.; Bondarenko, N.A.; Tsvetkov, E.N.; Nudel'man, Z.N.

    1988-09-10

    Vulcanization in a two-phase system with an interfacial transfer catalyst (ITC) is widely used for obtaining highly thermostable rubbers from fluorine-containing rubbers, copolymers of vinylidene fluoride with hexafluoropropylene. A simple method of synthesis of tertiary diphenylalkylphosphines by alkylation of diphenylphosphine with alkyl halides in the presence of an aqueous alkali and aprotic bipolar solvents (dimethyl sulfide, dimethylformamide, and hexamethanol) has now been developed. They synthesized diphenylbutyl- and diphenylbenzylphosphines by this method, and they were subsequently transformed into the corresponding phosphonium salts by treatment with an excess of benzyl chloride. The prepared diphenylbutylbenzyl- and diphenyldibenzyl- phosphonium chlorides were tested as ITC in vulcanization of SKF-26 fluorine-containing rubber.

  5. Exploring interfacial ferromagnetism in manganite-based superlattices

    NASA Astrophysics Data System (ADS)

    Yi, Di; Flint, Charles; Suzuki, Yuri

    Heterointerface of complex oxides provides a rich playground to explore the emergent phenomena that are not found in bulk. In particular, emergent interfacial ferromagnetism has been successfully demonstrated in heterostructures composed of materials which are paramagnetic and antiferromagnetic in bulk. In our previous work, leakage of itinerant electrons from a paramagnetic metal to an antiferromagnetic insulator has been shown to give rise to interfacial ferromagnetism in CaMnO3 based superlattices. However interfacial ferromagnetism in insulating superlattices suggests a more complicated scenario. Therefore a thorough investigation of coupling between charge, lattice and spin degrees of freedom is necessary. In this talk, we focus on the NdNiO3 /CaMnO3 system. By choosing a paramagnetic layer that undergoes a metal-insulator transition, we can explore the role of electron itinerancy in interfacial ferromagnetism in the same sample to eliminate the inconsistencies that may originate from the deposition of multiple samples. We demonstrate that NdNiO3 exhibits a metal-insulator transition as a function of temperature, which can be tuned as a function of film thickness. We have also grown NdNiO3 /CaMnO3 heterostructures with excellent crystallinity. Preliminary transport measurements indicate that the presence of an adjacent CaMnO3 layer also affects the transport in NdNiO3 so that charge transfer from the itinerant layer into the adjacent antiferromagnetic insulating CaMnO3 is likely not the only contribution to interfacial ferromagnetism.

  6. Interfacial characteristic measurements in horizontal bubbly two-phase flow

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Huang, W. D.; Srinivasmurthy, S.; Kocamustafaogullari, G.

    1990-10-01

    Advances in the study of two-phase flow increasingly require detailed internal structure information upon which theoretical models can be formulated. The void fraction and interfacial area are two fundamental parameters characterizing the internal structure of two-phase flow. However, little information is currently available on these parameters, and it is mostly limited to vertical flow configurations. In view of the above, the internal phase distribution of concurrent, air-water bubbly flow in a 50.3 mm diameter transparent pipeline has been experimentally investigated by using a double-sensor resistivity probe. Liquid and gas volumetric superficial velocities ranged from 3.74 to 5.60 m/s and 0.25 to 1.59 m/s, respectively, and average void fractions ranged from 2.12 to 22.5 percent. The local values of void fractions, interfacial area concentration, mean bubble diameter, bubble interface velocity, bubble chord-length and bubble frequency distributions were measured. The experimental results indicate that the void fraction interfacial area concentration and bubble frequency have local maxima near the upper pipe wall, and the profiles tend to flatten with increasing void fraction. The observed peak void fraction can reach 0.65, the peak interfacial area can go up to 900 approximately 1000 sq m/cu m, and the bubble frequency can reach a value of 2200 per s. These ranges of values have never been reported for vertical bubbly flow. It is found that either decreasing the liquid flow rate or increasing the gas flow would increase the local void fraction, the interfacial area concentration and the bubble frequency.

  7. 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

  8. A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection.

    PubMed

    Eita, Mohamed; Usman, Anwar; El-Ballouli, Ala'a O; Alarousu, Erkki; Bakr, Osman M; Mohammed, Omar F

    2015-01-01

    Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. PMID:25163799

  9. Anisotropic nanocolloids: self-assembly, interfacial adsorption, and electrostatic screening

    NASA Astrophysics Data System (ADS)

    de Graaf, J.

    2012-06-01

    In this thesis we consider the influence of anisotropy on the behaviour of colloids using theory and simulations. The recent increase in the ability to synthesize anisotropic particles (cubes, caps, octapods, etc.) has led to samples of sufficient quality to perform self-assembly experiments. Our investigation is therefore particularly relevant to current and future experimental studies of colloids. We examine several topics for which shape anisotropy plays an important role: (1.) - Interfacial adsorption. We introduced the triangular-tessellation technique to approximate the surface areas and line length which are associated with a plane-particle intersection. Our method allowed us to determine the free energy of adsorption for a single irregular colloid with heterogeneous surface properties adsorbed at a flat liquid-liquid interface in the Pieranski approximation. Ellipsoids only adsorbed at the interface perpendicular to the interfacial normal. However, for cylinders we could find a metastable adsorption minimum corresponding to parallel adsorption. We also considered the possible time dependence of the adsorption process using simple dynamics. Finally, we studied the adsorption of truncated nanocubes with a contact-angle surface pattern and we observed that there are three prototypical equilibrium adsorption configurations for these particles. (2.) - Crystal-structure prediction. We extended an existing crystal-structure-prediction algorithm to predict structures for systems comprised of irregular hard particles. Using this technique we examined the high-density crystal structures for 17 irregular nonconvex shapes and we confirmed several mathematical conjectures for the packings of a large set of 142 convex polyhedra. We also proved that we have obtained the densest configurations for rhombicuboctahedra and rhombic enneacontrahedra, respectively. Moreover, we considered a family of truncated cubes, which interpolates between a cube and an octahedron, for which

  10. Interfacially polymerized layers for oxygen enrichment: a method to overcome Robeson's upper-bound limit.

    PubMed

    Tsai, Ching-Wei; Tsai, Chieh; Ruaan, Ruoh-Chyu; Hu, Chien-Chieh; Lee, Kueir-Rarn

    2013-06-26

    Interfacial polymerization of four aqueous phase monomers, diethylenetriamine (DETA), m-phenylenediamine (mPD), melamine (Mela), and piperazine (PIP), and two organic phase monomers, trimethyl chloride (TMC) and cyanuric chloride (CC), produce a thin-film composite membrane of polymerized polyamide layer capable of O2/N2 separation. To achieve maximum efficiency in gas permeance and O2/N2 permselectivity, the concentrations of monomers, time of interfacial polymerization, number of reactive groups in monomers, and the structure of monomers need to be optimized. By controlling the aqueous/organic monomer ratio between 1.9 and 2.7, we were able to obtain a uniformly interfacial polymerized layer. To achieve a highly cross-linked layer, three reactive groups in both the aqueous and organic phase monomers are required; however, if the monomers were arranged in a planar structure, the likelihood of structural defects also increased. On the contrary, linear polymers are less likely to result in structural defects, and can also produce polymer layers with moderate O2/N2 selectivity. To minimize structural defects while maximizing O2/N2 selectivity, the planar monomer, TMC, containing 3 reactive groups, was reacted with the semirigid monomer, PIP, containing 2 reactive groups to produce a membrane with an adequate gas permeance of 7.72 × 10(-6) cm(3) (STP) s(-1) cm(-2) cm Hg(-1) and a high O2/N2 selectivity of 10.43, allowing us to exceed the upper-bound limit of conventional thin-film composite membranes. PMID:23731366

  11. 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.

  12. Interfacial growth of controllable morphology of silver patterns on plastic substrates.

    PubMed

    Cui, Guanghui; Qi, Shengli; Wang, Xiaodong; Tian, Guofeng; Sun, Guang; Liu, Wei; Yan, Xiaona; Wu, Dezhen; Wu, Zhanpeng; Zhang, Li

    2012-10-11

    Controllable growth of newly born silver nanoparticles to fractal, cauliflower-like, microscale disks and continuous silver layers with high conductivity and reflectivity on plastic substrates has been developed via solid-liquid interfacial reduction and growing of ion-doped polymeric films. Such approaches involve polyimide (PI) films as substrates, its corresponding silver-ion-doped precursors as solid oxidants, and facile immersion of ion-doped polymeric films in aqueous reducing solution. The solution reducing process belongs to liquid-solid interfacial reduction processes, during which silver ions doped in polymeric matrix transformed to newly born silver nanoparticles which further aggregated and migrated along the liquid-solid interface to form dendrite, cauliflower-like and lamella disk-like architecture and/or severely compact continuous silver nanolayers with highly reflective and conductive properties. Time-dependent morphology evolutions of silver particles were traced by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). This strategy can also extend to synthesis of many other metals on polymeric films while maintaining outstanding metal-polymer adhesion based on incorporation of various metal ions, and may offer an opportunity to fabricate large scale, high-output, cost-effective processes for metal patterns on flexible polymeric substrates. PMID:23016702

  13. Generic Role of Polymer Supports in the Fine Adjustment of Interfacial Interactions between Solid Substrates and Model Cell Membranes.

    PubMed

    Rossetti, Fernanda F; Schneck, Emanuel; Fragneto, Giovanna; Konovalov, Oleg V; Tanaka, Motomu

    2015-04-21

    To understand the generic role of soft, hydrated biopolymers in adjusting interfacial interactions at biological interfaces, we designed a defined model of the cell-extracellular matrix contacts based on planar lipid membranes deposited on polymer supports (polymer-supported membranes). Highly uniform polymer supports made out of regenerated cellulose allow for the control of film thickness without changing the surface roughness and without osmotic dehydration. The complementary combination of specular neutron reflectivity and high-energy specular X-ray reflectivity yields the equilibrium membrane-substrate distances, which can quantitatively be modeled by computing the interplay of van der Waals interaction, hydration repulsion, and repulsion caused by the thermal undulation of membranes. The obtained results help to understand the role of a biopolymer in the interfacial interactions of cell membranes from a physical point of view and also open a large potential to generally bridge soft, biological matter and hard inorganic materials. PMID:25794040

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

    NASA Astrophysics Data System (ADS)

    Ashby, Paul David

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

  15. 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

  16. 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

  17. 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

  18. Interfacial toughness of bilayer dental ceramics based on a short-bar, chevron-notch test

    PubMed Central

    Anunmana, Chuchai; Anusavice, Kenneth J.; Mecholsky, John J.

    2009-01-01

    Objective The objective of this study was to test the null hypothesis that the interfacial toughness of each of two types of bonded core-veneer bilayer ceramics is not significantly different from the apparent fracture toughness of the control monolithic glass veneer. Methods T-shaped short bars of a lithia-disilicate glass-ceramic core (LC) and yttria-stabilized polycrystalline zirconia core ceramic (ZC) were prepared according to the manufacturer's recommendations. V-shaped notches were prepared by using 25-μm-thick palladium foil, leaving the chevron notch area exposed, and the bars were veneered with a thermally compatible glass veneer (LC/GV and ZC/GV). Additionally, we also bonded the glass veneer to itself as a control group (GV/GV). Specimens were kept in distilled water for 30 days before testing in tension. Eight glass veneer bars were prepared for the analysis of fracture toughness test using the indentation-strength technique. Results The mean interfacial toughness of the LC/GV group was 0.69 [0.11] MPa·m1/2, and did not significantly differ from that of the GV/GV control group, 0.74 (0.17) MPa·m1/2 (p > 0.05). However, the difference between the mean interfacial toughness of the ZC/GV group, 0.13 (0.07) MPa·m1/2, and the LC/GV and the GV/GV groups was statistically significant (p<0.05). Significance For bilayer all-ceramic restorations with high-strength core materials, the veneering ceramics are the weakest link in the design of the structure. Since all-ceramic restorations often fail from chipping of veneer layers or crack initiation at the interface, the protective effects of thermal mismatch stresses oral prosthesis design should be investigated. PMID:19818486

  19. 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.

  20. Interfacial and Mechanical Characterization of Soft Materials Using Polymer Membranes Geometries

    NASA Astrophysics Data System (ADS)

    Laprade, Evan J.

    Polymer membranes have found their way in to a wide range of applications including selective barriers, protective coatings, packaging, sensors, and medical implants, becom- ing more pervasive in our lives every day. Their importance is derived not only from their unique mechanical and interfacial properties, but also from the versatility of their geometry. In this thesis, several polymer membrane geometries are employed to interfacially and mechanically characterize the properties of soft materials and polymer thin films. This thesis is organized in to two sections, the first deals with interfacial characterization using a membrane contact geometry. The centerpiece of this section, and this thesis, was the development of a sensitive membrane peel test to measure adhesion. A model membrane-contact system was used to evaluate an analytical model of large deformation contact and ultimately develop a simple protocol for measuring an adhesion energy using a membrane peel geometry. A second investigation in the section looked at the multiple harmonic behavior of quartz crystal resonators during contact mechanics experiments. An analytical solution to the radial mass sensitivity function was calculated and compared to experimentally measured sensitivity profiles from growing water drop and membrane contact experiments. The second half of this thesis deals with non-contact membrane geometries for mechanically characterizing two novel polymer membranes. The first is a highly water permeable sulfonated pentablock copolymer, designed for water purification applications. In this work these membranes were mechanically characterized with a biaxial creep test to investigate the affect of sulfonation level and processing conditions on their deformation behavior. Lastly pendant drop membranes were fabricated by ionically crosslinking amphiphilic gradient copolymers at an oil/water interface. These robust, self healing membranes were modeled with both an elastic and liquid

  1. Effect of solute transfer and interfacial instabilities on scalar and velocity field around a drop rising in quiescent liquid channel

    NASA Astrophysics Data System (ADS)

    Khanwale, Makrand A.; Khadamkar, Hrushikesh P.; Mathpati, Channamallikarjun S.

    2015-11-01

    Physics of development of flow structures around the drop rising with solute transfer is highly influenced by the interfacial behaviour and is remarkably different than a particle rising under the same conditions. We report on the use of simultaneous particle image velocimetry-planar laser induced fluorescence technique to measure scalar and velocity fields around a drop rising in a quiescent liquid channel. The selected continuous phase is glycerol, and the drop consists of a mixture of toluene, acetone, and a dye rhodamine-6G, with acetone working as a interfacial tension depressant. The drop lies in the spherical region with Eötvös number, Eo = 1.95, Morton number, M = 78.20 and the particle Reynolds number being, Rep = 0.053. With Rep approaching that of creeping flow, we analyse the effect of interfacial instabilities solely, contrary to other investigations [M. Wegener et al., "Impact of Marangoni instabilities on the fluid dynamic behaviour of organic droplets," Int. J. Heat Mass Transfer 52, 2543-2551 (2009); S. Burghoff and E. Y. Kenig, "A CFD model for mass transfer and interfacial phenomena on single droplets," AIChE J. 52, 4071-4078 (2006); J. Wang et al., "Numerical simulation of the Marangoni effect on transient mass transfer from single moving deformable drops," AIChE J. 57, 2670-2683 (2011); R. F. Engberg, M. Wegener, and E. Y. Kenig, "The impact of Marangoni convection on fluid dynamics and mass transfer at deformable single rising droplets—A numerical study," Chem. Eng. Sci. 116, 208-222 (2014)] which account for turbulence as well as interfacial instabilities with Rep in the turbulent range. The velocity and concentration fields obtained are subjected to scale-wise energy decomposition using continuous wavelet transform. Scale-wise probability distribution functions of wavelet coefficients are calculated to check intermittent non-Gaussian behaviour for simultaneous velocity and scalar statistics. Multi-fractal singularity spectra for scalar

  2. 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

  3. Computational implementation of interfacial kinetic transport theory for water vapour transport in porous media

    PubMed Central

    Albaalbaki, Bashar; Hill, Reghan J.

    2014-01-01

    A computational framework is developed for applying interfacial kinetic transport theory to predict water vapour permeability of porous media. Modified conservation equations furnish spatially periodic disturbances from which the average flux and, thus, the effective diffusivity is obtained. The equations are solved exactly for a model porous medium comprising parallel layers of gas and solid with arbitrary solid volume fraction. From the microscale effective diffusivity, a two-point boundary-value problem is solved at the macroscale to furnish the water vapour transport rate in membranes subjected to a finite RH differential. Then, the microscale model is implemented using a computational framework (extended finite-element method) to examine the role of particle size, aspect ratio and positioning for periodic arrays of aligned super-ellipses (model particles that pack with high density). We show that the transverse water vapour permeability can be reduced by an order of magnitude only when fibres with a high-aspect ratio cross section are packed in a periodic staggered configuration. Maximum permeability is achieved at intermediate micro-structural length scales, where gas-phase diffusion is enhanced by surface diffusion, but not limited by interfacial-exchange kinetics. The two-dimensional computations demonstrated here are intended to motivate further efforts to develop efficient computational solutions for realistic three-dimensional microstructures. PMID:24399918

  4. Interfacial characterization of a SiC fiber-reinforced AlN composite

    SciTech Connect

    Park, K.; Vasilos, T.; Sung, C. . Dept. of Chemical and Nuclear Engineering)

    1995-01-01

    In this study, an attempt was made to improve the mechanical properties of AlN by the incorporation of SiC (SCS-6) fibers (TEXTRON Specialty Materials, Lowell, MA) in a unidirectional array. The SiC fibers are one of the most important reinforcements for ceramic- and metal-matrix composites due to high tensile strength (3,450 MPs), high tensile modulus (400 GPa), and low density (3.0 g/cc). The SiC fiber (15 vol %)-reinforced AlN composite was fabricated by hot-pressing in vacuum. The microstructure and chemistry of interfacial regions in as-fabricated and crept composite were characterized using analytical transmission electron microscopy, in order to investigate the nature of the reaction between the fiber and matrix during both composite fabrication and creep tests and to understand the reinforcing effects of SiC fiber in the AlN matrix. Interfacial characteristics of the composite play an important role in influencing the mechanical properties of the composite.

  5. Formation of alternating interfacial layers in Au-12Ge/Ni joints

    PubMed Central

    Lin, Shih-kang; Tsai, Ming-yueh; Tsai, Ping-chun; Hsu, Bo-hsun

    2014-01-01

    Au-Ge alloys are promising materials for high-power and high-frequency packaging, and Ni is frequently used as diffusion barriers. This study investigates interfacial reactions in Au-12Ge/Ni joints at 300°C and 400°C. For the reactions at 300°C, typical interfacial morphology was observed and the diffusion path was (Au) + (Ge)/NiGe/Ni5Ge3/Ni. However, an interesting phenomenon – the formation of (Au,Ni,Ge)/NiGe alternating layers – was observed for the reactions at 400°C. The diffusion path across the interface was liquid/(Au,Ni,Ge)/NiGe/···/(Au,Ni,Ge)/NiGe/Ni2Ge/Ni. The periodic thermodynamic instability at the NiGe/Ni2Ge interface caused the subsequent nucleation of new (Au,Ni,Ge)/NiGe pairs. The thermodynamic foundation and mechanism of formation of the alternating layers are elaborated in this paper. PMID:24690992

  6. Interfacial polymerization of conductive polymers: Generation of polymeric nanostructures in a 2-D space.

    PubMed

    Dallas, Panagiotis; Georgakilas, Vasilios

    2015-10-01

    In the recent advances in the field of conductive polymers, the fibrillar or needle shaped nanostructures of polyaniline and polypyrrole have attracted significant attention due to the potential advantages of organic conductors that exhibit low-dimensionality, uniform size distribution, high crystallinity and improved physical properties compared to their bulk or spherically shaped counterparts. Carrying the polymerization reaction in a restricted two dimensional space, instead of the three dimensional space of the one phase solution is an efficient method for the synthesis of polymeric nanostructures with narrow size distribution and small diameter. Ultra-thin nanowires and nanofibers, single crystal nanoneedles, nanocomposites with noble metals or carbon nanotubes and layered materials can be efficiently synthesized with high yield and display superior performance in sensors and energy storage applications. In this critical review we will focus not only on the interfacial polymerization methods that leads to polymeric nanostructures and composites and their properties, but also on the mechanism and the physico-chemical processes that govern the diffusion and reactivity of molecules and nanomaterials at an interface. Recent advances for the synthesis of conductive polymer composites with an interfacial method for energy storage applications and future perspectives are presented. PMID:26272721

  7. Interface feature characterization and Schottky interfacial layer confirmation of TiO2 nanotube array film

    NASA Astrophysics Data System (ADS)

    Li, Hongchao; Tang, Ningxin; Yang, Hongzhi; Leng, Xian; Zou, Jianpeng

    2015-11-01

    We report here characterization of the interfacial microstructure and properties of titanium dioxide (TiO2) nanotube array films fabricated by anodization. Field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), nanoindentation, atomic force microscopy (AFM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the interface of the film. With increasing annealing temperature from 200 °C to 800 °C, the interfacial fusion between the film and the Ti substrate increased. The phase transformation of the TiO2 nanotube film from amorphous to anatase to rutile took place gradually; as the phase transformation progressed, the force needed to break the film increased. The growth of TiO2 nanotube arrays occurs in four stages: barrier layer formation, penetrating micropore formation, regular nanotube formation, and nanofiber formation. The TiO2 nanotubes grow from the Schottky interface layer rather than from the Ti substrate. The Schottky interface layer's thickness of 35-45 nm was identified as half the diameter of the corresponding nanotube, which shows good agreement to the Schottky interface layer growth model. The TiO2 nanotube film was amorphous and the Ti substrate was highly crystallized with many dislocation walls.

  8. 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.

  9. Stationary patterns in centrifugally driven interfacial elastic fingering.

    PubMed

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

    2014-12-01

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

  10. Stationary patterns in centrifugally driven interfacial elastic fingering

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

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

    1983-08-01

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

  12. Interfacial failure under thermal fatigue loading in multilayered MEMS structures

    NASA Astrophysics Data System (ADS)

    Maligno, A. R.; Whalley, D.; Silberschmidt, V. V.

    2010-06-01

    The reliability of MEMS, and in particular of RF MEMS switches, might be increased by the use of a Physics of Failure (PoF) methodology. A numerical study, based on the finite element method (FEM) and on the representative volume element (RVE) approach was performed to examine the effects of temperature dependent materials properties, temperature variations on failure (e.g. yielding of metals) and to predict interfacial damage in multilayered MEMS structures. The effect of residual stresses, due to electroplating processes of the metal layers was considered in these studies to investigate their effects on MEMS reliability. Numerical results have shown that interfacial damage is mainly concentrated at the plating-base/substrate interface and it is strongly influenced by the temperature dependent material properties and by the presence of residual stresses.

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

    SciTech Connect

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

    2011-08-15

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

  14. Interfacial exciplex formation in bilayers of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Nobuyasu, R. S.; Araujo, K. A. S.; Cury, L. A.; Jarrosson, T.; Serein-Spirau, F.; Lère-Porte, J.-P.; Dias, F. B.; Monkman, A. P.

    2013-10-01

    The donor-acceptor interactions in sequential bilayer and blend films are investigated. Steady-state and time-resolved photoluminescence (PL) were measured to characterize the samples at different geometries of photoluminescence collection. At standard excitation, with the laser incidence at 45° of the normal direction of the sample surface, a band related to the aggregate states of donor molecules appears for both blend and bilayer at around 540 nm. For the PL spectra acquired from the edge of the bilayer, with the laser incidence made at normal direction of the sample surface (90° geometry), a new featureless band emission, red-shifted from donor and acceptor emission regions was observed and assigned as the emission from interfacial exciplex states. The conformational complexity coming from donor/acceptor interactions at the heterojunction interface of the bilayer is at the origin of this interfacial exciplex emission.

  15. Enzymatically activated emulsions stabilised by interfacial nanofibre networks.

    PubMed

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

    2016-03-01

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

  16. Effect of interfacial octahedral behavior in ultrathin manganite films.

    PubMed

    Moon, E J; Balachandran, P V; Kirby, B J; Keavney, D J; Sichel-Tissot, R J; Schlepütz, C M; Karapetrova, E; Cheng, X M; Rondinelli, J M; May, S J

    2014-05-14

    We investigate structural coupling of the MnO6 octahedra across a film/substrate interface and the resultant changes of the physical properties of ultrathin La2/3Sr1/3MnO3 (LSMO) films. In order to isolate the effect of interfacial MnO6 octahedral behavior from that of epitaxial strain, LSMO films are grown on substrates with different symmetry and similar lattice parameters. Ultrathin LSMO films show an increased magnetization and electrical conductivity on cubic (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) compared to those grown on orthorhombic NdGaO3 (NGO) substrates, an effect that subsides as the thickness of the films is increased. This study demonstrates that interfacial structural coupling can play a critical role in the functional properties of oxide heterostructures. PMID:24697503

  17. Interfacial trapping in an aged discotic liquid crystal semiconductor

    NASA Astrophysics Data System (ADS)

    Dawson, Nathan J.; Patrick, Michael S.; Paul, Sanjoy; Ellman, Brett; Semyonov, Alexander; Twieg, Robert J.; Matthews, Rachael; Pentzer, Emily; Singer, Kenneth D.

    2015-08-01

    This study reports on time-of-flight (TOF) hole mobility measurements in aged 2,3,6,7,10,11-Hexakis(pentyloxy)triphenylene columnar liquid crystals. In contrast to the original samples reported in 2006, homeotropically aligned samples yielded TOF transients with an extended non-exponential rise. The experimental data were fit to a simple model that accurately reproduces the TOF transients assuming delayed charge release from traps near the optically excited electrode. While interfacial trapping appears only in the aged materials, the bulk mobility is similar to the pristine material. The model addresses dispersive transport in quasi-one-dimensional materials, determines the charge carrier mobility in systems with interfacial traps, and provides a method for characterizing the traps.

  18. Effects of post-annealing and temperature/humidity treatments on the interfacial adhesion energy of the Cu/SiN x interface for Cu interconnects

    NASA Astrophysics Data System (ADS)

    Jeong, Minsu; Bae, Byung-Hyun; Lee, Hyeonchul; Kang, Hee-Oh; Hwang, Wook-Jung; Yang, Jun-Mo; Park, Young-Bae

    2016-06-01

    The effects of 200 °C post-annealing and 85 °C and 85% relative humidity temperature and humidity (T/H) treatments on the interfacial adhesion energy of a Cu/SiN x interface were systematically investigated. The results of a four-point bending test, X-ray photoemission spectroscopy, and high-resolution transmission electron microscopy revealed that the interfacial adhesion energy during T/H treatment decreased with time faster than during annealing treatment, which is closely related to the faster Cu oxidation of SiN x /Cu interfaces.

  19. 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.

  20. Avalanche in adhesion. [interfacial separation between two Ni crystals

    NASA Technical Reports Server (NTRS)

    Smith, John R.; Bozzolo, Guillermo; Banerjea, Amitava; Ferrante, John

    1989-01-01

    Consider surfaces being brought into contact. It is proposed that atomic layers can collapse or avalanche together when the interfacial spacing falls below a critical distance. This causes a discontinuous drop in the adhesive binding energy. Avalanche can occur regardless of the stiffness of external supports. A simple understanding of the origin of this phenomenon is provided. A numerical calculation has been carried out for adhesion in Ni. A new wear mechanism due to avalanche is suggested.

  1. Influence of interfacial dislocations on hysteresis loops of ferroelectric films

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Hu, S. Y.; Choudhury, S.; Baskes, M. I.; Saxena, A.; Lookman, T.; Jia, Q. X.; Schlom, D. G.; Chen, L. Q.

    2008-11-01

    We investigated the influence of dislocations, located at the interface of a ferroelectric film and its underlying substrate, on the ferroelectric hysteresis loop including the remanent polarization and coercive field using phase-field simulations. We considered epitaxial ferroelectric BaTiO3 films and found that the hysteresis loop is strongly dependent on the type and density of interfacial dislocations. The dislocations that stabilize multiple ferroelectric variants and domains reduce the coercive field, and consequently, the corresponding remanent polarization also decreases.

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

    NASA Astrophysics Data System (ADS)

    Takahashi, Yasuo

    2014-08-01

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

  3. Interfacial thermodynamics of confined water near molecularly rough surfaces

    PubMed Central

    Mittal, Jeetain; Hummer, Gerhard

    2012-01-01

    We study the effects of nanoscopic roughness on the interfacial free energy of water confined between solid surfaces. SPC/E water is simulated in confinement between two infinite planar surfaces that differ in their physical topology: one is smooth and the other one is physically rough on a nanometer length scale. The two thermodynamic ensembles considered, with constant pressure either normal or parallel to the walls, correspond to different experimental conditions. We find that molecular-scale surface roughness significantly increases the solid-liquid interfacial free energy compared to the smooth surface. For our surfaces with a water-wall interaction energy minimum of −1.2 kcal/mol, we observe a transition from a hydrophilic surface to a hydrophobic surface at a roughness amplitude of about 3 Å and a wave length of 11.6 Å, with the interfacial free energy changing sign from negative to positive. In agreement with previous studies of water near hydrophobic surfaces, we find an increase in the isothermal compressibility of water with increasing surface roughness. Interestingly, average measures of the water density and hydrogen-bond number do not contain distinct signatures of increased hydrophobicity. In contrast, a local analysis indicates transient dewetting of water in the valleys of the rough surface, together with a significant loss of hydrogen bonds, and a change in the dipole orientation toward the surface. These microscopic changes in the density, hydrogen bonding, and water orientation contribute to the large increase in the interfacial free energy, and the change from a hydrophilic to a hydrophobic character of the surface. PMID:21043431

  4. Interfacial dilatational deformation accelerates particle formation in monoclonal antibody solutions.

    PubMed

    Lin, Gigi L; Pathak, Jai A; Kim, Dong Hyun; Carlson, Marcia; Riguero, Valeria; Kim, Yoen Joo; Buff, Jean S; Fuller, Gerald G

    2016-04-14

    Protein molecules are amphiphilic moieties that spontaneously adsorb at the air/solution (A/S) interface to lower the surface energy. Previous studies have shown that hydrodynamic disruptions to these A/S interfaces can result in the formation of protein aggregates that are of concern to the pharmaceutical industry. Interfacial hydrodynamic stresses encountered by protein therapeutic solutions under typical manufacturing, filling, and shipping conditions will impact protein stability, prompting a need to characterize the contribution of basic fluid kinematics to monoclonal antibody (mAb) destabilization. We demonstrate that dilatational surface deformations are more important to antibody stability when compared to constant-area shear of the A/S interface. We have constructed a dilatational interfacial rheometer that utilizes simultaneous pressure and bubble shape measurements to study the mechanical stability of mAbs under interfacial aging. It has a distinct advantage over methods utilizing the Young-Laplace equation, which incorrectly describes viscoelastic interfaces. We provide visual evidence of particle ejection from dilatated A/S interfaces and spectroscopic data of ejected mAb particles. These rheological studies frame a molecular understanding of the protein-protein interactions at the complex-fluid interface. PMID:26891116

  5. Interfacial thermal conductance of thiolate-protected gold nanospheres

    NASA Astrophysics Data System (ADS)

    Stocker, Kelsey M.; Neidhart, Suzanne M.; Gezelter, J. Daniel

    2016-01-01

    Molecular dynamics simulations of thiolate-protected and solvated gold nanoparticles were carried out in the presence of a non-equilibrium heat flux between the solvent and the core of the particle. The interfacial thermal conductance (G) was computed for these interfaces, and the behavior of the thermal conductance was studied as a function of particle size, ligand flexibility, and ligand chain length. In all cases, thermal conductance of the ligand-protected particles was higher than the bare metal-solvent interface. A number of mechanisms for the enhanced conductance were investigated, including thiolate-driven corrugation of the metal surface, solvent ordering at the interface, solvent-ligand interpenetration, and ligand ordering relative to the particle surface. Only the smallest particles exhibited significant corrugation. All ligands permitted substantial solvent-ligand interpenetration, and ligand chain length has a significant influence on the orientational ordering of interfacial solvent. Solvent-ligand vibrational overlap, particularly in the low frequency range (<80 cm-1), was significantly altered by ligand rigidity, and had direct influence on the interfacial thermal conductance.

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

    PubMed

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

    2016-05-14

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

  7. Non-contact atomic-level interfacial force microscopy

    SciTech Connect

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

    1997-02-01

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

  8. Interfacial thiol-ene photoclick reactions for forming multilayer hydrogels.

    PubMed

    Shih, Han; Fraser, Andrew K; Lin, Chien-Chi

    2013-03-13

    Interfacial visible light-mediated thiol-ene photoclick reactions were developed for preparing step-growth hydrogels with multilayer structures. The effect of a noncleavage type photoinitiator eosin-Y on visible-light-mediated thiol-ene photopolymerization was first characterized using in situ photorheometry, gel fraction, and equilibrium swelling ratio. Next, spectrophotometric properties of eosin-Y in the presence of various relevant macromer species were evaluated using ultraviolet-visible light (UV-vis) spectrometry. It was determined that eosin-Y was able to reinitiate the thiol-ene photoclick reaction, even after light exposure. Because of its small molecular weight, most eosin-Y molecules readily leached out from the hydrogels. The diffusion of residual eosin-Y from preformed hydrogels was exploited for fabricating multilayer step-growth hydrogels. Interfacial hydrogel coating was formed via the same visible-light-mediated gelation mechanism without adding fresh initiator. The thickness of the thiol-ene gel coating could be easily controlled by adjusting visible light exposure time, eosin-Y concentration initially loaded in the core gel, or macromer concentration in the coating solution. The major benefits of this interfacial thiol-ene coating system include its simplicity and cytocompatibility. The formation of thiol-ene hydrogels and coatings neither requires nor generates any cytotoxic components. This new gelation chemistry may have great utilities in controlled release of multiple sensitive growth factors and encapsulation of multiple cell types for tissue regeneration. PMID:23384151

  9. Growth Kinetics and Mechanics of Hydrate Films by Interfacial Rheology.

    PubMed

    Leopércio, Bruna C; de Souza Mendes, Paulo R; Fuller, Gerald G

    2016-05-01

    A new approach to study and understand the kinetics and mechanical properties of hydrates by interfacial rheology is presented. This is made possible using a "double wall ring" interfacial rheology cell that has been designed to provide the necessary temperature control. Cyclopentane and water are used to form hydrates, and this model system forms these structures at ambient pressures. Different temperature and water/hydrocarbon contact protocols are explored. Of particular interest is the importance of first contacting the hydrocarbon against ice crystals in order to initiate hydrate formation. Indeed, this is found to be the case, even though the hydrates may be created at temperatures above the melting point of ice. Once hydrates completely populate the hydrocarbon/water interface, strain sweeps of the interfacial elastic and viscous moduli are conducted to interrogate the mechanical response and fragility of the hydrate films. The dependence on temperature, Tf, by the kinetics of formation and the mechanical properties is reported, and the cyclopentane hydrate dissociation temperature was found to be between 6 and 7 °C. The formation time (measured from the moment when cyclopentane first contacts ice crystals) as well as the elastic modulus and the yield strain increase as Tf increases. PMID:27076092

  10. Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites

    PubMed Central

    2015-01-01

    The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable. PMID:26523245

  11. Probing Interfacial Processes on Graphene Surface by Mass Detection

    NASA Astrophysics Data System (ADS)

    Kakenov, Nurbek; Kocabas, Coskun

    2013-03-01

    In this work we studied the mass density of graphene, probed interfacial processes on graphene surface and examined the formation of graphene oxide by mass detection. The graphene layers were synthesized by chemical vapor deposition method on copper foils and transfer-printed on a quartz crystal microbalance (QCM). The mass density of single layer graphene was measured by investigating the mechanical resonance of the QCM. Moreover, we extended the developed technique to probe the binding dynamics of proteins on the surface of graphene, were able to obtain nonspecific binding constant of BSA protein of graphene surface in aqueous solution. The time trace of resonance signal showed that the BSA molecules rapidly saturated by filling the available binding sites on graphene surface. Furthermore, we monitored oxidation of graphene surface under oxygen plasma by tracing the changes of interfacial mass of the graphene controlled by the shifts in Raman spectra. Three regimes were observed the formation of graphene oxide which increases the interfacial mass, the release of carbon dioxide and the removal of small graphene/graphene oxide flakes. Scientific and Technological Research Council of Turkey (TUBITAK) grant no. 110T304, 109T209, Marie Curie International Reintegration Grant (IRG) grant no 256458, Turkish Academy of Science (TUBA-Gebip).

  12. Etherification of Wood-Based Hemicelluloses for Interfacial Activity.

    PubMed

    Nypelö, Tiina; Laine, Christiane; Aoki, Masaaki; Tammelin, Tekla; Henniges, Ute

    2016-05-01

    We present wetting, hygroscopicity, and interfacial activity of hemicellulose with respect to etherification and contrast it to their potential as interfacial modifiers, which is demonstrated by oil-in-water emulsification containing up to 60 vol% of the oil phase. Tunable amphiphilicity of hardwood and softwood hemicelluloses, xylans, and galactoglucomannans, respectively, was accomplished via controlled etherification. A series of degree of substitution (DS) of hydroxypropylated and 3-butoxy-2-hydroxypropylated ("butylated") grades was synthesized. The hemicellulose ethers were characterized by gel permeation chromatography, spectroscopic techniques, such as NMR, and contact angle measurements. An attenuated total reflectance infrared method was developed for fast identification of the DS. Near infrared analysis was utilized to explore the hygroscopicity of the material and to perform principle component analysis. The modification to butylated grades decreased the hygroscopicity, whereas the hydroxypropylated grades bound moisture. All of the hemicellulose ethers were water-soluble. The interfacial tension of the aqueous hemicellulose solutions was determined by pendant-drop tensiometer, and it was demonstrated to be dependent on the degree of modification. PMID:27086947

  13. 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.

  14. Interfacial pattern formation in confined power-law fluids

    NASA Astrophysics Data System (ADS)

    Brandão, Rodolfo; Fontana, João V.; Miranda, José A.

    2014-07-01

    The interfacial pattern formation problem in an injection-driven radial Hele-Shaw flow is studied for the situation in which a Newtonian fluid of negligible viscosity displaces a viscous non-Newtonian power-law fluid. By utilizing a Darcy-law-like formulation, we tackle the fluid-fluid interface evolution problem perturbatively, and we derive second-order mode-coupling equations that describe the time evolution of the perturbation amplitudes. This allows us to investigate analytically how the non-Newtonian nature of the dislocated fluid determines the morphology of the emerging interfacial patterns. If the pushed fluid is shear-thinning, our results indicate the development of side-branching structures. On the other hand, if the displaced fluid is shear-thickening, one detects the formation of petal-like shapes, markedly characterized by strong tip-splitting events. Finally, a time-dependent injection protocol is presented that is able to restrain finger proliferation via side-branching and tip-splitting. This permits the emergence of symmetric n-fold interfacial shapes for which the number of fingers remains fixed as time progresses. This procedure generalizes existing controlling strategies for purely Newtonian flow circumstances to the case of a non-Newtonian, displaced power-law fluid.

  15. Tailored interfacial rheology for gastric stable adsorption layers.

    PubMed

    Scheuble, N; Geue, T; Windhab, E J; Fischer, P

    2014-08-11

    Human lipid digestion begins at the interface of oil and water by interfacial adsorption of lipases. Tailoring the available surface area for lipase activity can lead to specific lipid sensing in the body, thus, tailored satiety hormone release. In this study we present biopolymer layers at the MCT-oil/water interface with different stabilities under human gastric environment (37 °C, pH 2, pepsin). Physicochemical changes and enzymatic degradation of interfacial layers were monitored online by interfacial shear rheology. We show the weakening of β-lactoglobulin (β-lg) layers at body temperature and acidification and their hydrolysis by pepsin. If sufficient concentrations of nanocrystalline cellulose (NCC) are given to an existing β-lg layer, this weakening is buffered and the proteolysis delayed. A synergistic, composite layer is formed by adding methylated NCC to the β-lg layer. This layer thermogels at body temperature and resists hydrolysis by pepsin. Coexistence of these two emulsifiers at the air/water interface is evidenced by neutron reflectometry measurements, where morphological information are extracted. The utilized layers and their analysis provide knowledge of physicochemical changes during in vitro digestion of interfaces, which promote functional food formulations. PMID:25029559

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  17. The Interfacial Interaction Problem in Complex Multiple Porosity Fractured Reservoirs

    NASA Astrophysics Data System (ADS)

    Suarez-Arriaga, Mario-Cesar

    2003-04-01

    Many productive reservoirs (oil, gas, water, geothermal) are associated to natural fracturing. Fault zones and fractures act as open networks for fluid and energy flow from depth. Their petrophysical parameters are heterogeneous and randomly distributed, conforming extremely complex natural systems. Here, the simultaneous heat and mass flows are coupled to the deformation of thermoporoelastic rocks. The system's volume is divided into N interacting continua, each one occupying a region of space Vn wrapped by a surface Sn (n=1,N). The mass flow is represented by: ∂/∂t ∫ Vn ρf φdV + ∫ Sn F⃗M ṡ n⃗dS = ∫ Vn qMdV (3) Taking into account a non-isothermal process the coupled equation of energy is: ∂/∂t ∫ Vn [φρf hf + (1 - φ)ρrhr]dV + ∫ Sn F⃗E ṡ n⃗dS = ∫ Vn qEdV (4) Where t means time, φ is porosity, ρf, ρr are fluid and rock densities, F⃗M and F⃗E are total mass and energy flows, qM and qE are volumetric mass and energy extracted or injected into Vn, hf and hr are specific enthalpies for fluid and rock respectively. Rock deformation is coupled through the equation: ∇⃗ ṡ (ρf/μK ṡ ∇⃗pφ)Vn = φ (Dtρf + ρf/VφdVφ/dt)Vn (5) K is the absolute permeability tensor, μ means dynamic fluid viscosity, Dt is a total derivative, pφ is pore pressure and Vφ is the volume of pores in Vn. The N media interact with each other, every one has its own parameters and its own interporosity flow. Modelling these coupled phenomena requires to average highly contrasting physical properties, independently of the method used in the solution of equations. A lot of attention has been devoted to develop realistic numerical models to describe flows in reservoirs under exploitation. But to the best of our knowledge very little attention has been focused on the problem of interfacial interaction and averaging petrophysical parameters in multiple porosity reservoirs.

  18. Individual surface-engineered microorganisms as robust Pickering interfacial biocatalysts for resistance-minimized phase-transfer bioconversion.

    PubMed

    Chen, Zhaowei; Ji, Haiwei; Zhao, Chuanqi; Ju, Enguo; Ren, Jinsong; Qu, Xiaogang

    2015-04-13

    A powerful strategy for long-term and diffusional-resistance-minimized whole-cell biocatalysis in biphasic systems is reported where individually encapsulated bacteria are employed as robust and recyclable Pickering interfacial biocatalysts. By individually immobilizing bacterial cells and optimizing the hydrophobic/hydrophilic balance of the encapsulating magnetic mineral shells, the encased bacteria became interfacially active and locate at the Pickering emulsion interfaces, leading to dramatically enhanced bioconversion performances by minimizing internal and external diffusional resistances. Moreover, in situ product separation and biocatalyst recovery was readily achieved using a remote magnetic field. Importantly, the mineral shell effectively protected the entire cell from long-term organic-solvent stress, as shown by the reusability of the biocatalysts for up to 30 cycles, while retaining high stereoselective catalytic activities, cell viabilities, and proliferative abilities. PMID:25706244

  19. Interfacial study and band alignment of ultrathin La2Hf2O7 films on GaAs substrates

    NASA Astrophysics Data System (ADS)

    Wei, F.; Xiong, Y.-H.; Zhang, X.-Q.; Du, J.; Tu, H.-L.

    2013-09-01

    We report ultrathin amorphous La2Hf2O7 (LHO) films grown on p-GaAs (0 0 1) substrates as high-k gate dielectric using the pulsed laser deposition method. Interfacial characterization of the LHO/GaAs has been carried out. It shows that the interfacial layer with a thickness of less than 0.5 nm is composed of Ga2O3. Experimental results show that the 5.7 ± 0.1 eV bandgap of LHO is aligned to the bandgap of GaAs with a valence band offset of 3.15 ± 0.05 eV and a conduction band offset of 1.1 ± 0.1 eV. Capacitance-voltage and current-voltage measurements indicate that LHO could be a promising gate dielectric for GaAs metal-oxide-semiconductor devices.

  20. The interfacial amorphous double layer and the homogeneous nucleation in reflow of a Sn-Zn solder on Cu substrate

    SciTech Connect

    Pan, Chien-Cheng; Lin, Kwang-Lung

    2011-05-15

    To illustrate the interfacial reaction mechanism, the Sn-Zn[Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga (wt%)] solder was reflowed on Cu substrate at 250 deg. C for 15 s followed by immediate quench in liquid nitrogen. The frozen interfacial microstructure was investigated with high resolution transmission electron microscope. An amorphous double layer was formed at the interface which consists of a 5 nm pure Cu region and a Cu-Zn diffusion region. Nanocrystalline intermetallic compound (IMC) Cu{sub 5}Zn{sub 8} were observed in the Cu-Zn diffusion region. These nanocrystalline IMCs are suggested to form via a homogeneous nucleation process.