Hyperuniformity and its generalizations.

PubMed

Torquato, Salvatore

2016-08-01

Disordered many-particle hyperuniform systems are exotic amorphous states of matter that lie between crystal and liquid: They are like perfect crystals in the way they suppress large-scale density fluctuations and yet are like liquids or glasses in that they are statistically isotropic with no Bragg peaks. These exotic states of matter play a vital role in a number of problems across the physical, mathematical as well as biological sciences and, because they are endowed with novel physical properties, have technological importance. Given the fundamental as well as practical importance of disordered hyperuniform systems elucidated thus far, it is natural to explore the generalizations of the hyperuniformity notion and its consequences. In this paper, we substantially broaden the hyperuniformity concept along four different directions. This includes generalizations to treat fluctuations in the interfacial area (one of the Minkowski functionals) in heterogeneous media and surface-area driven evolving microstructures, random scalar fields, divergence-free random vector fields, and statistically anisotropic many-particle systems and two-phase media. In all cases, the relevant mathematical underpinnings are formulated and illustrative calculations are provided. Interfacial-area fluctuations play a major role in characterizing the microstructure of two-phase systems (e.g., fluid-saturated porous media), physical properties that intimately depend on the geometry of the interface, and evolving two-phase microstructures that depend on interfacial energies (e.g., spinodal decomposition). In the instances of random vector fields and statistically anisotropic structures, we show that the standard definition of hyperuniformity must be generalized such that it accounts for the dependence of the relevant spectral functions on the direction in which the origin in Fourier space is approached (nonanalyticities at the origin). Using this analysis, we place some well-known energy spectra from the theory of isotropic turbulence in the context of this generalization of hyperuniformity. Among other results, we show that there exist many-particle ground-state configurations in which directional hyperuniformity imparts exotic anisotropic physical properties (e.g., elastic, optical, and acoustic characteristics) to these states of matter. Such tunability could have technological relevance for manipulating light and sound waves in ways heretofore not thought possible. We show that disordered many-particle systems that respond to external fields (e.g., magnetic and electric fields) are a natural class of materials to look for directional hyperuniformity. The generalizations of hyperuniformity introduced here provide theoreticians and experimentalists new avenues to understand a very broad range of phenomena across a variety of fields through the hyperuniformity "lens."

Hyperuniformity and its generalizations

NASA Astrophysics Data System (ADS)

Torquato, Salvatore

2016-08-01

Disordered many-particle hyperuniform systems are exotic amorphous states of matter that lie between crystal and liquid: They are like perfect crystals in the way they suppress large-scale density fluctuations and yet are like liquids or glasses in that they are statistically isotropic with no Bragg peaks. These exotic states of matter play a vital role in a number of problems across the physical, mathematical as well as biological sciences and, because they are endowed with novel physical properties, have technological importance. Given the fundamental as well as practical importance of disordered hyperuniform systems elucidated thus far, it is natural to explore the generalizations of the hyperuniformity notion and its consequences. In this paper, we substantially broaden the hyperuniformity concept along four different directions. This includes generalizations to treat fluctuations in the interfacial area (one of the Minkowski functionals) in heterogeneous media and surface-area driven evolving microstructures, random scalar fields, divergence-free random vector fields, and statistically anisotropic many-particle systems and two-phase media. In all cases, the relevant mathematical underpinnings are formulated and illustrative calculations are provided. Interfacial-area fluctuations play a major role in characterizing the microstructure of two-phase systems (e.g., fluid-saturated porous media), physical properties that intimately depend on the geometry of the interface, and evolving two-phase microstructures that depend on interfacial energies (e.g., spinodal decomposition). In the instances of random vector fields and statistically anisotropic structures, we show that the standard definition of hyperuniformity must be generalized such that it accounts for the dependence of the relevant spectral functions on the direction in which the origin in Fourier space is approached (nonanalyticities at the origin). Using this analysis, we place some well-known energy spectra from the theory of isotropic turbulence in the context of this generalization of hyperuniformity. Among other results, we show that there exist many-particle ground-state configurations in which directional hyperuniformity imparts exotic anisotropic physical properties (e.g., elastic, optical, and acoustic characteristics) to these states of matter. Such tunability could have technological relevance for manipulating light and sound waves in ways heretofore not thought possible. We show that disordered many-particle systems that respond to external fields (e.g., magnetic and electric fields) are a natural class of materials to look for directional hyperuniformity. The generalizations of hyperuniformity introduced here provide theoreticians and experimentalists new avenues to understand a very broad range of phenomena across a variety of fields through the hyperuniformity "lens."

Three-Dimensional Visualization of Interfacial Phenomena Using Confocal Microscopy

NASA Astrophysics Data System (ADS)

Shieh, Ian C.

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

Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains

PubMed Central

Pollard, Benjamin

2016-01-01

Summary Intermolecular interactions and nanoscale phase separation govern the properties of many molecular soft-matter systems. Here, we combine infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM) with force–distance spectroscopy for simultaneous characterization of both nanoscale optical and nanomechanical molecular properties through hybrid imaging. The resulting multichannel images and correlative analysis of chemical composition, spectral IR line shape, modulus, adhesion, deformation, and dissipation acquired for a thin film of a nanophase separated block copolymer (PS-b-PMMA) reveal complex structural variations, in particular at domain interfaces, not resolved in any individual signal channel alone. These variations suggest that regions of multicomponent chemical composition, such as the interfacial mixing regions between microdomains, are correlated with high spatial heterogeneity in nanoscale material properties. PMID:27335750

Single-Molecule Interfacial Electron Transfer

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

Lu, H. Peter

This project is focused on the use of single-molecule high spatial and temporal resolved techniques to study molecular dynamics in condensed phase and at interfaces, especially, the complex reaction dynamics associated with electron and energy transfer rate processes. The complexity and inhomogeneity of the interfacial ET dynamics often present a major challenge for a molecular level comprehension of the intrinsically complex systems, which calls for both higher spatial and temporal resolutions at ultimate single-molecule and single-particle sensitivities. Combined single-molecule spectroscopy and electrochemical atomic force microscopy approaches are unique for heterogeneous and complex interfacial electron transfer systems because the static andmore » dynamic inhomogeneities can be identified and characterized by studying one molecule at a specific nanoscale surface site at a time. The goal of our project is to integrate and apply these spectroscopic imaging and topographic scanning techniques to measure the energy flow and electron flow between molecules and substrate surfaces as a function of surface site geometry and molecular structure. We have been primarily focusing on studying interfacial electron transfer under ambient condition and electrolyte solution involving both single crystal and colloidal TiO 2 and related substrates. The resulting molecular level understanding of the fundamental interfacial electron transfer processes will be important for developing efficient light harvesting systems and broadly applicable to problems in fundamental chemistry and physics. We have made significant advancement on deciphering the underlying mechanism of the complex and inhomogeneous interfacial electron transfer dynamics in dyesensitized TiO 2 nanoparticle systems that strongly involves with and regulated by molecule-surface interactions. We have studied interfacial electron transfer on TiO 2 nanoparticle surfaces by using ultrafast single-molecule spectroscopy and electrochemical AFM metal tip scanning microscopy, focusing on understanding the interfacial electron transfer dynamics at specific nanoscale electron transfer sites with high-spatially and temporally resolved topographic-and-spectroscopic characterization at individual molecule basis, characterizing single-molecule rate processes, reaction driving force, and molecule-substrate electronic coupling. One of the most significant characteristics of our new approach is that we are able to interrogate the complex interfacial electron transfer dynamics by actively pin-point energetic manipulation of the surface interaction and electronic couplings, beyond the conventional excitation and observation.« less

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

PubMed

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

2015-11-02

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

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

PubMed Central

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

2015-01-01

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

Effects of carbon fiber surface characteristics on interfacial bonding of epoxy resin composite subjected to hygrothermal treatments

NASA Astrophysics Data System (ADS)

Li, Min; Liu, Hongxin; Gu, Yizhuo; Li, Yanxia; Zhang, Zuoguang

2014-01-01

The changes of interfacial bonding of three types of carbon fibers/epoxy resin composite as well as their corresponding desized carbon fiber composites subjecting to hygrothermal conditions were investigated by means of single fiber fragmentation test. The interfacial fracture energy was obtained to evaluate the interfacial bonding before and after boiling water aging. The surface characteristics of the studied carbon fiber were characterized using X-ray photoelectron spectroscopy. The effects of activated carbon atoms and silicon element at carbon fiber surface on the interfacial hygrothermal resistance were further discussed. The results show that the three carbon fiber composites with the same resin matrix possess different hygrothermal resistances of interface and the interfacial fracture energy after water aging can not recovery to the level of raw dry sample (irreversible changes) for the carbon fiber composites containing silicon. Furthermore, the activated carbon atoms have little impact on the interfacial hygrothermal resistance. The irreversible variations of interfacial bonding and the differences among different carbon fiber composites are attributed to the silicon element on the carbon fiber bodies, which might result in hydrolyzation in boiling water treatment and degrade interfacial hygrothermal resistance.

Adsorption of 2 Chloroethyl Ethyl Sulfide on Silica: Binding Mechanism and Energy of a Bifunctional Hydrogen-Bond Acceptor at the Gas Surface Interface

DTIC Science & Technology

2014-11-19

C. A. S.; Sumpter, K. B.; Wagner, G. W.; Rice, J. S. Degradation of the Blister Agent Sulfur Mustard, Bis(2-chloroethyl) Sulfide, on Concrete . J...SECURITY CLASSIFICATION OF: This work investigates the fundamental nature of sulfur mustard surface adsorption by characterizing interfacial hydrogen...nature of sulfur mustard surface adsorption by characterizing interfacial hydrogen bonding and other intermolecular forces for the surrogate molecule

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

PubMed

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

2016-11-01

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

Effects of Ag addition on solid–state interfacial reactions between Sn–Ag–Cu solder and Cu substrate

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

Yang, Ming

Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientationmore » evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface. - Highlights: •Role of Ag in IMC formation during Sn–Ag–Cu soldering was investigated. •Ag affects coarsening, crystallographic orientation, and IMC growth. •Diffusion pathways of Sn and Cu are affected differently by Ag. •Ag slows Cu diffusion to inhibit IMC growth at solder/substrate interface.« less

Comparison of Fluid-Fluid Interfacial Areas Measured with X-ray Microtomography and Interfacial Partitioning Tracer Tests for the same Samples.

PubMed

McDonald, Kieran; Carroll, Kenneth C; Brusseau, Mark L

2016-07-01

Two different methods are currently used for measuring interfacial areas between immiscible fluids within 3-D porous media, high-resolution microtomographic imaging and interfacial partitioning tracer tests (IPTT). Both methods were used in this study to measure non-wetting/wetting interfacial areas for a natural sand. The microtomographic imaging was conducted on the same packed columns that were used for the IPTTs. This is in contrast to prior studies comparing the two methods, for which in all cases different samples were used for the two methods. In addition, the columns were imaged before and after the IPTTs to evaluate the potential impacts of the tracer solution on fluid configuration and attendant interfacial area. The interfacial areas measured using IPTT are ~5 times larger than the microtomographic-measured values, which is consistent with previous work. Analysis of the image data revealed no significant impact of the tracer solution on NAPL configuration or interfacial area. Other potential sources of error were evaluated, and all were demonstrated to be insignificant. The disparity in measured interfacial areas between the two methods is attributed to the limitation of the microtomography method to characterize interfacial area associated with microscopic surface roughness due to resolution constraints.

What Can Interfacial Water Molecules Tell Us About Solute Structure?

NASA Astrophysics Data System (ADS)

Willard, Adam

The molecular structure of bulk liquid water reflects a molecular tendency to engage in tetrahedrally coordinated hydrogen bonding. At a solute interface waters preferred three-dimensional hydrogen bonding network must conform to a locally anisotropy interfacial environment. Interfacial water molecules adopt configurations that balance water-solute and water-water interactions. The arrangements of interfacial water molecules, therefore encode information about the effective solute-water interactions. This solute-specific information is difficult to extract, however, because interfacial structure also reflects waters collective response to an anisotropic hydrogen bonding environment. Here I present a methodology for characterizing the molecular-level structure of liquid water interface from simulation data. This method can be used to explore waters static and/or dynamic response to a wide range of chemically and topologically heterogeneous solutes such as proteins.

An improved interfacial bonding model for material interface modeling

PubMed Central

Lin, Liqiang; Wang, Xiaodu; Zeng, Xiaowei

2016-01-01

An improved interfacial bonding model was proposed from potential function point of view to investigate interfacial interactions in polycrystalline materials. It characterizes both attractive and repulsive interfacial interactions and can be applied to model different material interfaces. The path dependence of work-of-separation study indicates that the transformation of separation work is smooth in normal and tangential direction and the proposed model guarantees the consistency of the cohesive constitutive model. The improved interfacial bonding model was verified through a simple compression test in a standard hexagonal structure. The error between analytical solutions and numerical results from the proposed model is reasonable in linear elastic region. Ultimately, we investigated the mechanical behavior of extrafibrillar matrix in bone and the simulation results agreed well with experimental observations of bone fracture. PMID:28584343

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

PubMed

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

2016-01-07

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

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

DOE PAGES

Wang, Ziying; Santhanagopalan, Dhamodaran; Zhang, Wei; ...

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. In this paper, 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 situmore » conditions. Using a LiCoO 2/LiPON/Si thin film battery, an unexpected structurally disordered interfacial layer between LiCoO 2 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 LiCoO 2/LiPON interface is caused by chemical changes rather than space charge effects. Finally, 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

Characterization of interfacial failure in SiC reinforced Si3N4 matrix composite material by both fiber push-out testing and Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Eldridge, J. I.; Honecy, F. S.

1990-01-01

AES depth profiling and a fiber push-out test for interfacial shear-strength determination have been used to ascertain the mechanical/chemical properties of the fiber/matrix interface in SiC-reinforced reaction-bonded Si3N4, with attention to the weak point where interfacial failure occurs. In the cases of both composite fracture and fiber push-outs, the interfacial failure occurred either between the two C-rich coatings that are present on the double-coated SiC fibers, or between the inner C-rich coating and the SiC fiber. Interface failure occurs at points of very abrupt concentration changes.

Materials Science of Electrodes and Interfaces for High-Performance Organic Photovoltaics

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

Marks, Tobin

The science of organic photovoltaic (OPV) cells has made dramatic advances over the past three years with power conversion efficiencies (PCEs) now reaching ~12%. The upper PCE limit of light-to-electrical power conversion for single-junction OPVs as predicted by theory is ~23%. With further basic research, the vision of such devices, composed of non-toxic, earth-abundant, readily easily processed materials replacing/supplementing current-generation inorganic solar cells may become a reality. Organic cells offer potentially low-cost, roll-to-roll manufacturable, and durable solar power for diverse in-door and out-door applications. Importantly, further gains in efficiency and durability, to that competitive with inorganic PVs, will require fundamental,more » understanding-based advances in transparent electrode and interfacial materials science and engineering. This team-science research effort brought together an experienced and highly collaborative interdisciplinary group with expertise in hard and soft matter materials chemistry, materials electronic structure theory, solar cell fabrication and characterization, microstructure characterization, and low temperature materials processing. We addressed in unconventional ways critical electrode-interfacial issues underlying OPV performance -- controlling band offsets between transparent electrodes and organic active-materials, addressing current loss/leakage phenomena at interfaces, and new techniques in cost-effective low temperature and large area cell fabrication. The research foci were: 1) Theory-guided design and synthesis of advanced crystalline and amorphous transparent conducting oxide (TCO) layers which test our basic understanding of TCO structure-transport property relationships, and have high conductivity, transparency, and tunable work functions but without (or minimizing) the dependence on indium. 2) Development of theory-based understanding of optimum configurations for the interfaces between oxide electrodes/interfacial layers and OPV active layer organic molecules/polymers. 3) Exploration and perfection of new processing strategies and cell architectures for the next-generation, large-area flexible OPVs. The goal has been to develop for the solar energy community the fundamental scientific understanding needed to design, fabricate, prototype, and ultimately test high-efficiency cells incorporating these new concepts. We achieved success in all of these directions.« less

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…

The Diverse Structures and Functions of Surfactant Proteins.

PubMed

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

2016-07-01

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

A platelet-to-pyramid shape transition under the influence of the adsorbate substrate interfacial energy

NASA Astrophysics Data System (ADS)

Lin, Cheng-Hsiao; Tsai, Yan-Chr

2002-07-01

Within the Tersoff approximation, we obtain an analytic expression for the elastic self-energy of a truncated hut which is more general than that of a truncated pyramid [C. Duport, C. Priester, J. Villain, in: Morphological Organization in Epitaxial Growth and Removal, World Scientific Series on Directions in Condensed Matter Physics, 1997, p. 73]. A pyramidal cluster studied previously can be treated as a square-based hut within the present formalism. The previous results [C. Duport, C. Priester, J. Villain, in: Morphological Organization in Epitaxial Growth and Removal, World Scientific Series on Directions in Condensed Matter Physics, 1997, p. 73; C. Duport, Université de Grenoble, Juin 1996; Phys. Rep. 324 (2000) 271] were obtained on the assumptions of neglecting the adsorbate-substrate interfacial energy and the equilibrium cluster forming with a square base. They predicted that when the volume of a cluster is above some critical value, it preferably forms as a pyramid rather than a platelet in the absence of other strained clusters. Instead, in this paper, we take the interfacial energy into account, based on the work by Korutcheva et al. [I. Markov, Crystal Growth for Beginners, Fundamentals of Nucleation, Crystal Growth Epitaxy, World Scientific, Singapore, 1995; Phys. Rev. B 61 (2000) 16890]. Besides, we start with the consideration of a hut cluster probably forming with a rectangular base instead of a square one [C. Duport, C. Priester, J. Villain, in: Morphological Organization in Epitaxial Growth and Removal, World Scientific Series on Directions in Condensed Matter Physics, 1997, p. 73; C. Duport, Université de Grenoble, Juin 1996]. By employing the derived analytic expression of the surface and elastic energies, we find that the two- to three- dimensional (2D-3D) transition with the inclusion of the adsorbate-substrate interfacial energy is quantitatively modified. It should provide more accurate predicted values of the critical volume in 2D-3D transitions. Furthermore, in the absence of other clusters on a substrate, a pyramid forms above the critical volume and calculations also show that at equilibrium a single cluster forms with a square base for a given cluster volume, which justifies the previous assumption [C. Duport, C. Priester, J. Villain, in: Morphological Organization in Epitaxial Growth and Removal, World Scientific Series on Directions in Condensed Matter Physics, 1997, p. 73; C. Duport, Université de Grenoble, Juin 1996; Phys. Rep. 324 (2000) 271].

Hofmeister effect on the interfacial free energy of aliphatic and aromatic surfaces studied by chemical force microscopy.

PubMed

Patete, Jonathan; Petrofsky, John M; Stepan, Jeffery; Waheed, Abdul; Serafin, Joseph M

2009-01-15

This work describes chemical force microscopy (CFM) studies of specific-ion effects on the aqueous interfacial free energy of hydrophobic monolayers. CFM measurements allow for the characterization of interfacial properties on length scales below 100 nm. The ions chosen span the range of the Hofmeister series, from the kosmotropic Na(2)SO(4) to the chaotropic NaSCN. The salt concentrations used are typical of many laboratory processes such as protein crystallization, 2-3 M. Both aliphatic (terminal methyl) and aromatic (terminal phenyl) monolayers were examined, and rather pronounced differences were observed between the two cases. The specific-ion dependence of the aliphatic monolayer closely follows the Hofmeister series, namely the chaotropic ions lowered the interfacial free energy and the kosmotropic ions increased the interfacial free energy. However, the aromatic monolayer had significant deviations from the Hofmeister series. Possible origins for this difference are discussed.

Computation of Anisotropic Bi-Material Interfacial Fracture Parameters and Delamination Creteria

NASA Technical Reports Server (NTRS)

Chow, W-T.; Wang, L.; Atluri, S. N.

1998-01-01

This report documents the recent developments in methodologies for the evaluation of the integrity and durability of composite structures, including i) the establishment of a stress-intensity-factor based fracture criterion for bimaterial interfacial cracks in anisotropic materials (see Sec. 2); ii) the development of a virtual crack closure integral method for the evaluation of the mixed-mode stress intensity factors for a bimaterial interfacial crack (see Sec. 3). Analytical and numerical results show that the proposed fracture criterion is a better fracture criterion than the total energy release rate criterion in the characterization of the bimaterial interfacial cracks. The proposed virtual crack closure integral method is an efficient and accurate numerical method for the evaluation of mixed-mode stress intensity factors.

Atomic-scale mapping of electronic structures across heterointerfaces by cross-sectional scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Chiu, Ya-Ping; Huang, Bo-Chao; Shih, Min-Chuan; Huang, Po-Cheng; Chen, Chun-Wei

2015-09-01

Interfacial science has received much attention recently based on the development of state-of-the-art analytical tools that can create and manipulate the charge, spin, orbital, and lattice degrees of freedom at interfaces. Motivated by the importance of nanoscale interfacial science that governs device operation, we present a technique to probe the electronic characteristics of heterointerfaces with atomic resolution. In this work, the interfacial characteristics of heteroepitaxial structures are investigated and the fundamental mechanisms that pertain in these systems are elucidated through cross-sectional scanning tunneling microscopy (XSTM). The XSTM technique is employed here to directly observe epitaxial interfacial structures and probe local electronic properties with atomic-level capability. Scanning tunneling microscopy and spectroscopy experiments with atomic precision provide insight into the origin and spatial distribution of electronic properties across heterointerfaces. The first part of this report provides a brief description of the cleavage technique and spectroscopy analysis in XSTM measurements. The second part addresses interfacial electronic structures of several model heterostructures in current condensed matter research using XSTM. Topics to be discussed include high-κ‘s/III-V’s semiconductors, polymer heterojunctions, and complex oxide heterostructures, which are all material systems whose investigation using this technique is expected to benefit the research community. Finally, practical aspects and perspectives of using XSTM in interface science are presented.

TFB:TPDSi2 interfacial layer usable in organic photovoltaic cells

DOEpatents

Marks, Iobin J [Evanston, IL; Hains, Alexander W [Evanston, IL

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.

On 'large-scale' stable fiber displacement during interfacial failure in metal matrix composites

NASA Technical Reports Server (NTRS)

Petrich, R. R.; Koss, D. A.; Hellmann, J. R.; Kallas, M. N.

1993-01-01

Experimental results are presented to show that interfacial failure in sapphire-reinforced niobium is characterized by 'large-scale' (5-15 microns) plasticity-controlled fiber displacements occurring under increasing loads. The results are based on the responses during thin-slice fiber pushout tests wherein the fiber is supported over a hole twice the fiber diameter. The results describe an interfacial failure process that should also occur near fiber ends during pullout when a fiber is well-bonded to a soft, ductile matrix, such that eventual failure occurs by shear within the matrix near the interface.

Quantitative characterization of the interfacial adhesion of Ni thin film on steel substrate: A compression-induced buckling delamination test

NASA Astrophysics Data System (ADS)

Zhu, W.; Zhou, Y. C.; Guo, J. W.; Yang, L.; Lu, C.

2015-01-01

A compression-induced buckling delamination test is employed to quantitatively characterize the interfacial adhesion of Ni thin film on steel substrate. It is shown that buckles initiate from edge flaws and surface morphologies exhibit symmetric, half-penny shapes. Taking the elastoplasticity of film and substrate into account, a three-dimensional finite element model for an edge flaw with the finite size is established to simulate the evolution of energy release rates and phase angles in the process of interfacial buckling-driven delamination. The results show that delamination propagates along both the straight side and curved front. The mode II delamination plays a dominant role in the process with a straight side whilst the curved front experiences almost the pure mode I. Based on the results of finite element analysis, a numerical model is developed to evaluate the interfacial energy release rate, which is in the range of 250-315 J/m2 with the corresponding phase angle from -41° to -66°. These results are in agreement with the available values determined by other testing methods, which confirms the effectiveness of the numerical model.

Tensorial Minkowski functionals of triply periodic minimal surfaces

PubMed Central

Mickel, Walter; Schröder-Turk, Gerd E.; Mecke, Klaus

2012-01-01

A fundamental understanding of the formation and properties of a complex spatial structure relies on robust quantitative tools to characterize morphology. A systematic approach to the characterization of average properties of anisotropic complex interfacial geometries is provided by integral geometry which furnishes a family of morphological descriptors known as tensorial Minkowski functionals. These functionals are curvature-weighted integrals of tensor products of position vectors and surface normal vectors over the interfacial surface. We here demonstrate their use by application to non-cubic triply periodic minimal surface model geometries, whose Weierstrass parametrizations allow for accurate numerical computation of the Minkowski tensors. PMID:24098847

Graphene Oxide-Polymer Composite Langmuir Films Constructed by Interfacial Thiol-Ene Photopolymerization

NASA Astrophysics Data System (ADS)

Luo, Xiaona; Ma, Kai; Jiao, Tifeng; Xing, Ruirui; Zhang, Lexin; Zhou, Jingxin; Li, Bingbing

2017-02-01

The effective synthesis and self-assembly of graphene oxide (GO) nanocomposites are of key importance for a broad range of nanomaterial applications. In this work, a one-step chemical strategy is presented to synthesize stable GO-polymer Langmuir composite films by interfacial thiol-ene photopolymerization at room temperature, without use of any crosslinking agents and stabilizing agents. It is discovered that photopolymerization reaction between thiol groups modified GO sheets and ene in polymer molecules is critically responsible for the formation of the composite Langmuir films. The film formed by Langmuir assembly of such GO-polymer composite films shows potential to improve the mechanical and chemical properties and promotes the design of various GO-based nanocomposites. Thus, the GO-polymer composite Langmuir films synthesized by interfacial thiol-ene photopolymerization with such a straightforward and clean manner, provide new alternatives for developing chemically modified GO-based hybrid self-assembled films and nanomaterials towards a range of soft matter and graphene applications.

Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes.

PubMed

Wang, Yong-Lei; Golets, Mikhail; Li, Bin; Sarman, Sten; Laaksonen, Aatto

2017-02-08

Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P 6,6,6,14 ][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P 6,6,6,14 ] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P 6,6,6,14 ] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P 6,6,6,14 ][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P 6,6,6,14 ] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm 2 ), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P 6,6,6,14 ] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.

A micromechanical study of the damage mechanics of acrylic particulate composites under thermomechanical loading

NASA Astrophysics Data System (ADS)

Nie, Shihua

The main aim of this dissertation was to characterize the damage mechanism and fatigue behavior of the acrylic particulate composite. This dissertation also investigated how the failure mechanism is influenced by changes in certain parameters including the volume fraction of particle, the interfacial bonding strength, the stiffness and thickness of the interphase, and the CTE mismatch between the particle and the matrix. Monotonic uniaxial tensile and compressive testing under various temperatures and strain rates, isothermal low-cycle mechanical testing and thermal cycling of a plate with a cutout were performed. The influence of the interfacial bonding strength between the particle and the matrix on the failure mechanism of the ATH filled PMMA was investigated using in situ observations under uniaxial loading conditions. For composites with weak interfacial bonding, the debonding is the major damage mode. For composites with strong interfacial bonding, the breakage of the agglomerate of particles is the major damage mode. Experimental studies also demonstrated the significant influence of interfacial bonding strength on the fatigue life of the ATH filled PMMA. The damage was characterized in terms of the elastic modulus degradation, the load-drop parameter, the plastic strain range and the hysteresis dissipation. Identifying the internal state variables that quantify material degradation under thermomechanical loading is an active research field. In this dissertation, the entropy production, which is a measure of the irreversibility of the thermodynamic system, is used as the metric for damage. The close correlation between the damage measured in terms of elastic modulus degradation and that obtained from the finite element simulation results validates the entropy based damage evolution function. A micromechanical model for acrylic particulate composites with imperfect interfacial bonds was proposed. Acrylic particulate composites are treated as three-phase composites consisting of agglomerated particles, bulk matrix and an interfacial transition zone around the agglomerate. The influence of the interfacial bonding and the CTE mismatch between the matrix and the filler on the overall thermomechanical behavior of composites is studied analytically and experimentally. The comparison of analytical simulation with experimental data demonstrated the validity of the proposed micromechanical model for acrylic particulate composites with an imperfect interface. (Abstract shortened by UMI.)

Growth Kinetics of Magnesio-Aluminate Spinel in Al/Mg Lamellar Composite Interface

NASA Astrophysics Data System (ADS)

Fouad, Yasser; Rabeeh, Bakr Mohamed

The synthesis of Mg-Al2O3 double layered interface is introduced via the application of hot isostatic pressing, HIPing, in Al-Mg foils. Polycrystalline spinel layers are grown experimentally at the interfacial contacts between Al-Mg foils. The growth behavior of the spinel layers along with the kinetic parameters characterizing interface motion and long-range diffusion is established. Low melting depressant (LMD), Zn, and alloying element segregation tends to form micro laminated and/or Nano structure interphase in a lamellar composite solid state processing. Nano composite ceramic interphase materials offer interesting mechanical properties not achievable in other materials, such as superplastic flow and metal-like machinability. Microstructural characterization, mechanical characterization is also established via optical microscopy scanning electron microscopy, energy dispersive X-ray spectroscopy and tensile testing. Chemical and mechanical bonding via inter diffusion processing with alloy segregation are dominant for interphase kinetics. Mechanical characterization with interfacial shear strength is also introduced. HIPing processing is successfully applied on 6082 Al-alloy and AZ31 magnesium alloy for either particulate or micro-laminated interfacial composite processing. The interphase kinetic established through localized micro plasticity, metal flow, alloy segregation and delocalized Al oxide and Mg oxide. The kinetic of interface/interphase induce new nontraditional crack mitigation a long with new bridging and toughening mechanisms.

Dentin-cement Interfacial Interaction

PubMed Central

Atmeh, A.R.; Chong, E.Z.; Richard, G.; Festy, F.; Watson, T.F.

2012-01-01

The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca2+, OH-, and CO32- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements. PMID:22436906

Adsorption at the biocompatible α-pinene-water interface and emulsifying properties of two eco-friendly surfactants.

PubMed

Trujillo-Cayado, Luis Alfonso; Ramírez, Pablo; Alfaro, María Carmen; Ruíz, Manuela; Muñoz, José

2014-10-01

In this contribution, we provide an accurate characterization at the α-pinene/water interface of two commercial polyoxytheylene glycerol ester surfactants which differ in the number of ethylene oxide (EO) groups, comprising a systematic analysis of interfacial pressure isotherms, dynamic curves, interfacial rheology and emulsifying properties. Polyoxyethylene glycerol esters derived from cocoa oil are non-ionic surfactants obtained from a renewable source which fulfill the environmental and toxicological requirements to be used as eco-friendly emulsifying agents. α-Pinene is a renewable biosolvent completely insoluble in water, which could find numerous applications. Interfacial rheology and equilibrium interfacial pressure data fitted a rigorous reorientation model that assumes that the surfactant molecules, when adsorbed at the interface, can acquire two orientations. The surfactant with the highest number of EO groups (Levenol C201) turned out to be more surface active at the α-pinene/water interface. In addition, the surfactant with the lowest number of EO groups (Levenol H&B) is solubilized into the adjacent oil phase. Slightly concentrated α-pinene emulsions were obtained using both surfactants. Nevertheless, more stable α-pinene emulsions with smaller droplet sizes and lower polidispersity were obtained when Levenol C201 was used as emulsifier instead of Levenol H&B. The systematic characterization presented in this work provides important new findings on the interfacial and emulsifying properties of polyoxytheylene glycerol ester surfactants, which can be applied in the rational development of new biocompatible products. Copyright © 2014 Elsevier B.V. All rights reserved.

Interfacial recombination at /AlGa/As/GaAs heterojunction structures

NASA Technical Reports Server (NTRS)

Ettenberg, M.; Kressel, H.

1976-01-01

Experiments were conducted to determine the interfacial recombination velocity at Al0.25Ga0.75As/GaAs and Al0.5Ga0.5As/GaAs heterojunctions. The recombination velocity was derived from a study of the injected minority-carrier lifetime as a function of the junction spacing. It is found that for heterojunction spacings in excess of about 1 micron, the interfacial recombination can be characterized by a surface recombination velocity of 4,000 and 8,000 cm/sec for the two types of heterojunctions, respectively. For double-heterojunction spacings below 1 micron, the constancy of the minority-carrier lifetime suggests that the interfacial recombination velocity decreases effectively. This effect is technologically very important since it makes it possible to construct very low-threshold injection lasers. No such effect is observed in single-heterojunction diodes.

Surface force and vibrational spectroscopic analyses of interfacial water molecules in the vicinity of methoxy-tri(ethylene glycol)-terminated monolayers: mechanisms underlying the effect of lateral packing density on bioinertness.

PubMed

Sekine, Taito; Asatyas, Syifa; Sato, Chikako; Morita, Shigeaki; Tanaka, Masaru; Hayashi, Tomohiro

Unequivocal dependence of bioinertness of self-assembled monolayers of methoxy-tri(ethylene glycol)-terminated alkanethiol (EG3-OMe SAMs) on their packing density has been a mystery for more than two decades. We tackled this long-standing question by performing surface force and surface-enhanced infrared absorption (SEIRA) spectroscopic measurements. Our surface force measurements revealed a physical barrier of interfacial water in the vicinity of the Au-supported EG3-OMe SAM (low packing density), whereas the Ag-supported one (high packing density) did not possess such interfacial water. In addition, the results of SEIRA measurements clearly exhibited that hydrogen bonding states of the interfacial water differ depending on the substrates. We also characterized the bioinertness of these SAMs by protein adsorption tests and adhesion assays of platelet and human umbilical vein endothelial cells. The hydrogen bonding states of the interfacial water and water-induced interaction clearly correlated with the bioinertness of the SAMs, suggesting that the interfacial water plays an important role determining the interaction of the SAMs with biomolecules and cells.

Structural phase transitions and time-resolved dynamics of solid-supported interfacial methanol observed by reflection electron diffraction

NASA Astrophysics Data System (ADS)

Yang, Ding-Shyue; He, Xing; Wu, Chengyi

Due to their large scattering cross sections with matter, electrons are suitable for contactless probing of solid-supported surface assemblies, especially in a reflection geometry. Direct visualization of assembly structures through electron diffraction further enables studies of ultrafast structural dynamics through the pump-probe scheme as well as discoveries of hidden phase changes in equilibrium that have been obscure in spectroscopic measurements. In this presentation, we report our first observation of unique two-stage transformations of interfacial methanol on smooth hydrophobic surfaces. The finding may reconcile the inconsistent previous reports of the crystallization temperature using various indirect methods. Dynamically, energy transfer across a solid-molecule interface following photoexcitation of the substrate is found to be highly dependent on the structure of interfacial methanol. If it is only 2-dimensionally ordered, as the film thickness increases, a prolonged time in the decrease of diffraction intensity is seen, signifying an inefficient vibrational coupling in the surface normal direction. Implications of the dynamics results and an outlook of interfacial studies using time-resolved and averaged electron diffraction will be discussed. We gratefully acknowledge the support from the R. A. Welch Foundation (Grant No. E-1860), the Donors of the American Chemical Society Petroleum Research Fund (ACS-PRF), and the University of Houston.

Improving the durability of the optical fiber sensor based on strain transfer analysis

NASA Astrophysics Data System (ADS)

Wang, Huaping; Jiang, Lizhong; Xiang, Ping

2018-05-01

To realize the reliable and long-term strain detection, the durability of optical fiber sensors has attracted more and more attention. The packaging technique has been considered as an effective method, which can enhance the survival ratios of optical fiber sensors to resist the harsh construction and service environment in civil engineering. To monitor the internal strain of structures, the embedded installation is adopted. Due to the different material properties between host material and the protective layer, the monitored structure embedded with sensors can be regarded as a typical model containing inclusions. Interfacial characteristic between the sensor and host material exists obviously, and the contacted interface is prone to debonding failure induced by the large interfacial shear stress. To recognize the local interfacial debonding damage and extend the effective life cycle of the embedded sensor, strain transfer analysis of a general three-layered sensing model is conducted to investigate the failure mechanism. The perturbation of the embedded sensor on the local strain field of host material is discussed. Based on the theoretical analysis, the distribution of the interfacial shear stress along the sensing length is characterized and adopted for the diagnosis of local interfacial debonding, and the sensitive parameters influencing the interfacial shear stress are also investigated. The research in this paper explores the interfacial debonding failure mechanism of embedded sensors based on the strain transfer analysis and provides theoretical basis for enhancing the interfacial bonding properties and improving the durability of embedded optical fiber sensors.

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

PubMed Central

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

2013-01-01

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

Synthesis and characterization of self-assembled monolayers on gold generated from partially fluorinated alkanethiols and aliphatic dithiocarboxylic acids

NASA Astrophysics Data System (ADS)

Colorado, Ramon, Jr.

The formation of novel self-assembled monolayers (SAMs) on gold from the adsorption of four distinct series of partially fluorinated alkanethiols (PFAs) and one series of chelating aliphatic dithiocarboxylic acids (ADTCAs) is reported. The SAMs were characterized by optical ellipsometry, contact angle goniometry, polarization modulation infrared absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). The results for the PFA SAMs provided evidence for both the importance of oriented surface dipoles in influencing interfacial wettabilities and the significance of the degree of fluorination of the PFAs in determining the dispersive interfacial energies of the films. In addition, a series of PFA SAMs was used to demonstrate that the attenuation lengths of photoelectrons in fluorocarbon films are indistinguishable from those in hydrocarbon films. The results for the ADTCA SAMs demonstrated that the use of a chelating headgroup induces structural changes within the monolayers that influence the interfacial properties of the films.

In Situ Visualization of the Growth and Fluctuations of Nanoparticle Superlattice in Liquids

NASA Astrophysics Data System (ADS)

Ou, Zihao; Shen, Bonan; Chen, Qian

We use liquid phase transmission electron microscopy to image and understand the crystal growth front and interfacial fluctuation of a nanoparticle superlattice. With single particle resolution and hundreds of nanoscale building blocks in view, we are able to identify the interface between ordered lattice and disordered structure and visualize the kinetics of single building block attachment at the lattice growth front. The spatial interfacial fluctuation profiles support the capillary wave theory, from which we derive a surface stiffness value consistent with scaling analysis. Our experiments demonstrate the potential of extending model study on collective systems to nanoscale with single particle resolution and testing fundamental theories of condensed matter at a length scale linking atoms and micron-sized colloids.

Autonomic Materials for Smarter, Safer, Longer-Lasting Batteries (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum)

ScienceCinema

Thackeray, Michael (Director, Center for Electrical Energy Storage); CEES Staff

2017-12-09

'Autonomic Materials for Smarter, Safer, Longer-Lasting Batteries' was submitted by the Center for Electrical Energy Storage (CEES) to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. CEES, an EFRC directed by Michael Thackery at Argonne National Laboratory is a partnership of scientists from three institutions: ANL (lead), Northwestern University, and the University of Illinois at Urbana-Champaign. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of the Center for Electrical Energy Storage is 'to acquire a fundamental understanding of interfacial phenomena controlling electrochemical processes that will enable dramatic improvements in the properties and performance of energy storage devices, notable Li ion batteries.' Research topics are: electrical energy storage, batteries, battery electrodes, electrolytes, adaptive materials, interfacial characterization, matter by design; novel materials synthesis, charge transport, and defect tolerant materials.

Influence of Organic Matter - Mineral Interfacial Reactions on Metal(loid) Speciation and Bioaccessibility

NASA Astrophysics Data System (ADS)

Chorover, J.; Kong, S.; Root, R. A.; Thomas, A.

2015-12-01

Bioaccessibility of contaminant metals in geomedia is often measured on the basis of kinetic release to solution during in vitro reaction with biofluid simulants. We postulate that development of a predictive-mechanistic understanding of bioaccessibility requires knowledge of metal(loid) molecular speciation upon sample introduction, as well as its change over the course of the in vitro reaction. Our results - including data from batch, column, mesocosm and field studies pertaining to arsenic, lead, and zinc contaminated materials - indicate the strong influence of organic matter and associated biological activity on metal(loid) speciation in mine tailings and related model systems. Furthermore, presence/absence of organic matter during bioassays affects the kinetics of metal(loid) release into biofluid simulants through multiple mechanisms.

Micromotion-induced strain fields influence early stages of repair at bone-implant interfaces

PubMed Central

Wazen, Rima M.; Currey, Jennifer A.; Guo, Hongqiang; Brunski, John B.; Helms, Jill A.; Nanci, Antonio

2013-01-01

Implant loading can create micromotion at the bone-implant interface. The interfacial strain associated with implant micromotion could contribute to regulating the tissue healing response. Excessive micromotion can lead to fibrous encapsulation and implant loosening. Our objective was to characterize the influence of interfacial strain on bone regeneration around implants in mouse tibiae. A micromotion system was used to create strain under conditions of (1) no initial contact between implant and bone, and (2) a direct bone-implant contact. Pin- and screw-shaped implants were subjected to displacements of 150 μm or 300 μm, 60 cycles/day, for 7 days. Pin-shaped implants placed in 5 animals were subjected to 3 sessions of 150 μm displacement per day, with 60 cycles per session. Control implants in both types of interfaces were stabilized throughout the healing period. Experimental strain analyses, microtomography, image-based displacement mapping, and finite element simulations were used to characterize interfacial strain fields. Calcified tissue sections were prepared and stained with Goldner to evaluate tissue reaction in higher and lower strain regions. In stable implants, bone formation occurred consistently around the implants. In implants subjected to micromotion, bone regeneration was disrupted in areas of high strain concentrations (e.g. > 30%), whereas lower strain values were permissive of bone formation. Increasing implant displacement or number of cycles per day also changed the strain distribution and disturbed bone healing. These results indicate that not only implant micromotion but also the associated interfacial strain field contributes to regulating the interfacial mechanobiology at healing bone-implant interfaces. PMID:23337705

Effect of metal surface topography on mechanical bonding at simulated total hip stem-cement interfaces.

PubMed

Chen, C Q; Scott, W; Barker, T M

1999-01-01

Bonding and loosening mechanisms between bone cement and joint prostheses have not been well identified. In this study, the effects of simulated hip stem surface topography on the interfacial shear strength were examined. Six different surface topographies were used. They were described by several surface characterization parameters that may directly relate to the interfacial bonding strength: average surface roughness R(a), root mean square slope R(Deltaq), correlation length beta, and fluid retention index R(ri). The shear strengths between Palacos E bone cement and stainless steel rods were measured using an Instron materials testing machine. We found that cement can "flow" into the surface microtopography and establish good contact with the metal surface. The results show that the interfacial strength increases monotonically with the increase of R(Deltaq) instead of with R(a). The relationship between interfacial strength and surface parameters shows that a metal stem with an isotropic surface texture, higher R(Deltaq), and greater R(ri) gives a higher interfacial strength. Copyright 1999 John Wiley & Sons, Inc.

Tunable anomalous hall effect induced by interfacial catalyst in perpendicular multilayers

NASA Astrophysics Data System (ADS)

Zhang, J. Y.; Peng, W. L.; Sun, Q. Y.; Liu, Y. W.; Dong, B. W.; Zheng, X. Q.; Yu, G. H.; Wang, C.; Zhao, Y. C.; Wang, S. G.

2018-04-01

The interfacial structures, playing a critical role on the transport properties and the perpendicular magnetic anisotropy in thin films and multilayers, can be modified by inserting an ultrathin functional layer at the various interfaces. The anomalous Hall effect (AHE) in the multilayers with core structure of Ta/CoFeB/X/MgO/Ta (X: Hf or Pt) is tuned by interfacial catalytic engineering. The saturation anomalous Hall resistance (RAH) is increased by 16.5% with 0.1 nm Hf insertion compared with the reference sample without insertion. However, the RAH value is decreased by 9.0% with 0.1 nm Pt insertion. The interfacial states were characterized by the X-ray photoelectron spectroscopy (XPS). The XPS results indicate that a strong bonding between Hf and O for Hf insertion, but no bonding between Pt and O for Pt insertion. The bonding between metal and oxygen leads to various oxygen migration behavior at the interfaces. Therefore, the opposite behavior about the RAH originates from the different oxygen behavior due to various interfacial insertion. This work provides a new approach to manipulate spin transport property for the potential applications.

The evaluation of the interfacial behavior of LaRC-TPI/Graphite Composites

NASA Technical Reports Server (NTRS)

Ogden, A. L.; Wilkes, G. L.; Hyer, M. W.; Loos, A. C.; Muellerleile, J. T.

1992-01-01

Discussed are the results of several approaches recently considered for improving the interfacial adhesion of LaRC-TPI/graphite composites. Two approaches were investigated, namely altering the matrix and altering the fiber. As a result, three types of LaRC-TPI laminates were produced: amorphous/AS-4, amorphous/XAS, and semicrystalline/AS-4. The laminates were characterized using the transverse tensile test, scanning electron microscopy, optical microscopy, and thermal analysis.

Fabrication of High-Performance Polymer Bulk-Heterojunction Solar Cells by the Interfacial Modifications III

DTIC Science & Technology

2011-04-30

University of Tennessee) 3. "An ambipolar to n-type transformation in pentacene -based organic field-effect transistors" Org. Electron. 12, 509 (2011...OFETs). An ambipolar to n-type transformation in pentacene -based organic field-effect transistors (OFETs) of Al source-drain electrodes had been...correlated with the interfacial interactions between Al electrodes and pentacene , as characterized by analyzing Near-edge X-ray absorption fine structure

Interfacial Fracture Toughness of Adhesive Resin Cement-Lithium-Disilicate/Resin-Composite Blocks.

PubMed

Mesmar, Samer; Ruse, N Dorin

2017-09-15

Resin composite blocks (RCB) are advocated as alternative to ceramic blocks (CB). Prior to use, adherence to these materials should characterized. This study aimed to test the null hypothesis (H 0 ) that material and surface treatment combinations do not influence interfacial fracture toughness (K IC ) of a self-cured adhesive resin cement [RelyX Ultimate (RXU)] to RCB or CB, under nonaged and aged conditions. Two RCB, Lava Ultimate (LU) and Enamic (EN), and one CB, IPS e.max Press (EMP) were used. Half-size [(6 × 6 × 6 × 6 mm)] specimens were prepared for EMP (n = 30), EN (n = 30), and LU (n = 60). RCB specimens were prepared by wet cutting/grinding, while CB specimens were pressed. Surfaces of EMP and EN were preconditioned with hydrofluoric acid (5%); surfaces of LU were sandblasted with either 27 μm alumina (LUS) or 30 μm silica-modified alumina Rocatec soft (LUR). All specimens were bonded with Scotchbond Universal adhesive and RXU. Additionally, twenty (4 × 4 × 4 × 8 mm) RXU specimens were prepared. All specimens were stored in water at 37°C and tested after 1 and 60 days. Interfacial K IC was determined with the notchless triangular prism specimen K IC test. Results were analyzed with two-way ANOVA and Scheffé multiple means comparisons (α = 0.05). Preconditioned and selected fractured surfaces were characterized with scanning electron microscopy. At 24 hours, LUS-RXU and LUR-RXU had significantly higher interfacial K IC than EN-RXU and EMP-RXU and were not different from K IC of RXU. Aging lead to a significant decrease in K IC of RXU and interfacial K IC of LUS-RXU, LUR-RXU, and EMP-RXU; interfacial K IC of EN-RXU was not affected. Based on the results, H 0 was rejected. Under the conditions of this study, at 24 hours, interfacial K IC of LUS-RXU and LUR-RXU was superior to EMP-RXU and EN-RXU. Aging in water at 37°C did not affect interfacial K IC of EN-RXU but adversely affected K IC of RXU and the other interfacial K IC . The results suggest that RXU and its adherence to LU and EMP deteriorates upon exposure to water at 37°C. In making clinical decisions related to material selection, practitioners should consider in vitro results. © 2017 by the American College of Prosthodontists.

Characterization of the hydrogen-bond network of water around sucrose and trehalose: H-O-H bending analysis

NASA Astrophysics Data System (ADS)

Shiraga, Keiichiro; Adachi, Aya; Ogawa, Yuichi

2017-06-01

The bioprotective properties of disaccharides have been linked to destructuring effect on the hydrogen-bond structure of the interfacial water around the disaccharide solute, but its detailed mechanisms are yet to be provided. In this study, we characterized the destructuring effect based on the complex dielectric constants of interfacial water around sucrose and trehalose in the H-O-H bending region. Our analysis showed that the destructuring effect around disaccharides involves substantial disordering of the hydrogen-bond structure and formation of strong disaccharide-water hydrogen-bond. Such a destructuring effect caused by disaccharides is totally distinct from what happens with temperature increases of neat water.

Adsorption and Retardation of PFASs in Soil

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Interface Bond Improvement of Sisal Fibre Reinforced Polylactide Composites with Added Epoxy Oligomer

PubMed Central

Hao, Mingyang; Qiu, Feng; Wang, Xiwen

2018-01-01

To improve the interfacial bonding of sisal fiber-reinforced polylactide biocomposites, polylactide (PLA) and sisal fibers (SF) were melt-blended to fabricate bio-based composites via in situ reactive interfacial compatibilization with addition of a commercial grade epoxy-functionalized oligomer Joncryl ADR@-4368 (ADR). The FTIR (Fourier Transform infrared spectroscopy) analysis and SEM (scanning electron microscope) characterization demonstrated that the PLA molecular chain was bonded to the fiber surface and the epoxy-functionalized oligomer played a hinge-like role between the sisal fibers and the PLA matrix, which resulted in improved interfacial adhesion between the fibers and the PLA matrix. The interfacial reaction and microstructures of composites were further investigated by thermal and rheological analyses, which indicated that the mobility of the PLA molecular chain in composites was restricted because of the introduction of the ADR oligomer, which in turn reflected the improved interfacial interaction between SF and the PLA matrix. These results were further justified with the calculation of activation energies of glass transition relaxation (∆Ea) by dynamic mechanical analysis. The mechanical properties of PLA/SF composites were simultaneously reinforced and toughened with the addition of ADR oligomer. The interfacial interaction and structure–properties relationship of the composites are the key points of this study. PMID:29518949

Interface Bond Improvement of Sisal Fibre Reinforced Polylactide Composites with Added Epoxy Oligomer.

PubMed

Hao, Mingyang; Wu, Hongwu; Qiu, Feng; Wang, Xiwen

2018-03-07

To improve the interfacial bonding of sisal fiber-reinforced polylactide biocomposites, polylactide (PLA) and sisal fibers (SF) were melt-blended to fabricate bio-based composites via in situ reactive interfacial compatibilization with addition of a commercial grade epoxy-functionalized oligomer Joncryl ADR @ -4368 (ADR). The FTIR (Fourier Transform infrared spectroscopy) analysis and SEM (scanning electron microscope) characterization demonstrated that the PLA molecular chain was bonded to the fiber surface and the epoxy-functionalized oligomer played a hinge-like role between the sisal fibers and the PLA matrix, which resulted in improved interfacial adhesion between the fibers and the PLA matrix. The interfacial reaction and microstructures of composites were further investigated by thermal and rheological analyses, which indicated that the mobility of the PLA molecular chain in composites was restricted because of the introduction of the ADR oligomer, which in turn reflected the improved interfacial interaction between SF and the PLA matrix. These results were further justified with the calculation of activation energies of glass transition relaxation (∆ E a ) by dynamic mechanical analysis. The mechanical properties of PLA/SF composites were simultaneously reinforced and toughened with the addition of ADR oligomer. The interfacial interaction and structure-properties relationship of the composites are the key points of this study.

Interface control of bulk ferroelectric polarization

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

Yu, P; Luo, Weidong; Yi, D.

2012-01-01

The control of material interfaces at the atomic level has led to no- vel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we em- ploy a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectricmore » hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite un- derlayers extends the generality of this phenomenon.« less

Predicting the mixed-mode I/II spatial damage propagation along 3D-printed soft interfacial layer via a hyperelastic softening model

NASA Astrophysics Data System (ADS)

Liu, Lei; Li, Yaning

2018-07-01

A methodology was developed to use a hyperelastic softening model to predict the constitutive behavior and the spatial damage propagation of nonlinear materials with damage-induced softening under mixed-mode loading. A user subroutine (ABAQUS/VUMAT) was developed for numerical implementation of the model. 3D-printed wavy soft rubbery interfacial layer was used as a material system to verify and validate the methodology. The Arruda - Boyce hyperelastic model is incorporated with the softening model to capture the nonlinear pre-and post- damage behavior of the interfacial layer under mixed Mode I/II loads. To characterize model parameters of the 3D-printed rubbery interfacial layer, a series of scarf-joint specimens were designed, which enabled systematic variation of stress triaxiality via a single geometric parameter, the slant angle. It was found that the important model parameter m is exponentially related to the stress triaxiality. Compact tension specimens of the sinusoidal wavy interfacial layer with different waviness were designed and fabricated via multi-material 3D printing. Finite element (FE) simulations were conducted to predict the spatial damage propagation of the material within the wavy interfacial layer. Compact tension experiments were performed to verify the model prediction. The results show that the model developed is able to accurately predict the damage propagation of the 3D-printed rubbery interfacial layer under complicated stress-state without pre-defined failure criteria.

Synthesis and electrochemical properties of polyaniline nanofibers by interfacial polymerization.

PubMed

Manuel, James; Ahn, Jou-Hyeon; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Kim, Jae-Kwang; Jacobsson, Per

2012-04-01

Polyaniline nanofibers were prepared by interfacial polymerization with different organic solvents such as chloroform and carbon tetrachloride. Field emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties of polyaniline nanofibers. Chemical characterization was carried out using Fourier transform infrared spectroscopy, UV-Vis spectroscopy, and X-ray diffraction spectroscopy and surface area was measured using BET isotherm. Polyaniline nanofibers doped with lithium hexafluorophosphate were prepared and their electrochemical properties were evaluated.

The evaluation of the interfacial behavior of LaRC-TPI/Graphite Composites

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

Ogden, A.L.; Wilkes, G.L.; Hyer, M.W.

1992-07-01

Discussed are the results of several approaches recently considered for improving the interfacial adhesion of LaRC-TPI/graphite composites. Two approaches were investigated, namely altering the matrix and altering the fiber. As a result, three types of LaRC-TPI laminates were produced: amorphous/AS-4, amorphous/XAS, and semicrystalline/AS-4. The laminates were characterized using the transverse tensile test, scanning electron microscopy, optical microscopy, and thermal analysis. 17 refs.

Probing the Origin of Interfacial Carriers in SrTiO 3$-$LaCrO 3 Superlattices

DOE PAGES

Comes, Ryan B.; Spurgeon, Steven R.; Kepaptsoglou, Despoina M.; ...

2017-01-13

Emergent phenomena at complex oxide interfaces could provide the basis for a wide variety of next-generation devices, including photovoltaics and spintronics. To date, detailed characterization and computational modeling of interfacial defects, cation intermixing, and film stoichiometry have helped to explain many of the novel behaviors observed at a single heterojunction. Unfortunately, many of the techniques employed to characterize a single heterojunction are less effective for a superlattice made up of a repeating series of interfaces that induce collective interfacial phenomena throughout a film. These repeating interfaces present an untapped opportunity to introduce an additional degree of complexity, such as confinedmore » electric fields, that cannot be realized in a single heterojunction. In this work, we explore the properties of SrTiO 3–LaCrO 3 superlattices to understand the role of defects, including variations in cation stoichiometry of individual layers of the superlattice, intermixing across interfaces, and interfacial oxygen vacancies. Using X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy electron energy-loss spectroscopy (STEM-EELS), we quantify the stoichiometry of individual layers of the superlattice and determine the degree of intermixing in these materials. By comparing these results to both density functional theory (DFT) models and STEM-EELS measurements of the Ti and Cr valence in each layer of the superlattice, we correlate different types of defects with the associated materials properties of the superlattice. In conclusion, we show that a combination of ab initio modeling and complementary structural characterization methods can offer unique insight into structure–property relationships in many oxide superlattice systems.« less

An Unusual Salt Effect in an Interfacial Nucleophilic Substitution Reaction.

PubMed

Li, Shuheng; Mrksich, Milan

2018-06-12

This paper reports a kinetic characterization of the interfacial reaction of N-methylpyrrolidine with a self-assembled monolayer presenting an iodoalkyl group. SAMDI (self-assembled monolayers for matrix-assisted laser desorption/ionization) mass spectrometry was used to determine the extent of reaction for monolayers that were treated with a range of concentrations of the nucleophile for a range of times. These data revealed a second-order rate constant for the reaction that was approximately 100-fold greater than that for the analogous solution-phase reaction. However, addition of sodium iodide to the reaction mixture resulted in a 7-fold decrease in the reaction rate. Addition of bromide and chloride salts also gave slower rate constants for the reaction, but only at 100- and 1000-fold higher concentrations than was observed with iodide, respectively. The corresponding solution-phase reactions, by contrast, had rate constants that were unaffected by the concentration of halide salts. This work provides a well-characterized example illustrating the extent to which the kinetics and properties of an interfacial reaction can depart substantially from their better-understood solution-phase counterparts.

Buried homojunction in CdS/Sb2Se3 thin film photovoltaics generated by interfacial diffusion

NASA Astrophysics Data System (ADS)

Zhou, Ying; Li, Yang; Luo, Jiajun; Li, Dengbing; Liu, Xinsheng; Chen, Chao; Song, Huaibing; Ma, Jingyuan; Xue, Ding-Jiang; Yang, Bo; Tang, Jiang

2017-07-01

Antimony selenide (Sb2Se3) emerges as a very promising non-toxic absorber material for thin film photovoltaics, and most of the devices, either in the superstrate or substrate configuration, employed CdS as the buffer layer. Due to the peculiar one-dimensional crystal structure of Sb2Se3, severe interfacial diffusion would be expected. In this letter, the interfacial diffusion in CdS/Sb2Se3 photovoltaics was carefully characterized from a combined material and device physics characterization. The results indicated that a buried homojunction located deep inside the Sb2Se3 absorber layer due to Cd diffusion, instead of the apparent CdS/Sb2Se3 heterojunction, dictated charge separation and device performance in Sb2Se3 thin film solar cells. Cd diffusion converted p-type Sb2Se3 into n-type by introducing a donor level with an activation energy of 0.22 eV. Our studies deepen the understanding of Sb2Se3 photovoltaics and shed light on their further performance optimization.

Analysis of Carbon Nanotube Pull-out from a Polymer Matrix

NASA Technical Reports Server (NTRS)

Frankland, S. J. V.; Harik, V. M.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

Molecular dynamics (MD) simulations of carbon nanotube (NT) pull-out from a polymer matrix are carried out. As the NT pull-out develops in the simulation, variations in the displacement and velocities of the NT are monitored. The existence of a carbon-ring-based period in NT sliding during pull-out is identified. Linear trends in the NT velocity-force relation are observed and used to estimate an effective viscosity coefficient for interfacial sliding at the NT/polymer interface. As a result, the entire process of NT pull-out is characterized by an interfacial friction model that is based on a critical pull-out force, and an analog of Newton's friction law used to describe the NT/polymer interfacial sliding.

Preparation of superhydrophobic glass fiber and interfacially reinforced glass fiber/epoxy composites by grafting polysiloxane nanowires

NASA Astrophysics Data System (ADS)

Lv, Junwei; Wang, Bin; Ma, Qi; Li, Mengyao; Wang, Wenjing; Lu, Gaotaihang; Li, Hui; Zhao, Chunxia

2018-04-01

Ethyltrichlorosilane used as precursor reacted with glass fiber (GF) surface. Then polysiloxane was functionalized onto GF surface to improve GF’s hydrophobicity and interfacial properties of GF reinforced composites. Fourier transform infrared spectroscopy (FTIR) confirmed the successful grafting of polysiloxane onto GF’s surface. Energy dispersive spectroscopy (EDS) characterized the variation of chemical composition of GF surface. Scanning electron microscopy (SEM) images showed that the polysiloxane was grafted onto GF’s surface uniformly and the surface roughness of GF was enhanced obviously. Static contact angle analysis (SCA) revealed the significant improvement of surface hydrophobicity. Compared with the original GF composites, the interfacial shear strength (IFSS) increased by 36.52%. Meanwhile, we discovered a facile way to accomplish the experiment.

Interfacial Magnetism in Complex Oxide Heterostructures Probed by Neutrons and X-rays

DOE PAGES

Liu, Yaohua; Ke, Xianglin

2015-09-02

Magnetic complex-oxide heterostructures are of keen interest because a wealth of phenomena at the interface of dissimilar materials can give rise to fundamentally new physics and potentially valuable functionalities. Altered magnetization, novel magnetic coupling and emergent interfacial magnetism at the epitaxial layered-oxide interfaces have all been intensively investigated, which shapes our understanding on how to utilize those materials, particularly for spintronics. Neutron and x-ray based techniques have played a decisive role in characterizing interfacial magnetic structures and clarifying the underlying physics in this rapidly developing field. Here we review some recent experimental results, with an emphasis on those studied viamore » polarized neutron reflectometery and polarized x-ray absorption spectroscopy. We conclude with some perspectives.« less

Interfacial magnetism in complex oxide heterostructures probed by neutrons and x-rays.

PubMed

Liu, Yaohua; Ke, Xianglin

2015-09-23

Magnetic complex-oxide heterostructures are of keen interest because a wealth of phenomena at the interface of dissimilar materials can give rise to fundamentally new physics and potentially valuable functionalities. Altered magnetization, novel magnetic coupling and emergent interfacial magnetism at the epitaxial layered-oxide interfaces are under intensive investigation, which shapes our understanding on how to utilize those materials, particularly for spintronics. Neutron and x-ray based techniques have played a decisive role in characterizing interfacial magnetic structures and clarifying the underlying physics in this rapidly developing field. Here we review some recent experimental results, with an emphasis on those studied via polarized neutron reflectometery and polarized x-ray absorption spectroscopy. We conclude with some perspectives.

Enhanced interfacial properties of carbon fiber composites via aryl diazonium reaction “on water”

NASA Astrophysics Data System (ADS)

Wang, Yuwei; Meng, Linghui; Fan, Liquan; Ma, Lichun; Qi, Meiwei; Yu, Jiali; Huang, Yudong

2014-10-01

Polyacrylonitrile-based carbon fibers were functionalized with phenyl amine group via aryl diazonium reaction "on water" to improve their interfacial bonding with resin matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize ordered degree, functional groups, chemical states and morphology of carbon fiber surface, respectively. The results showed that phenyl amine groups were grafted on the fiber surface successfully. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 73%, while the tensile strength was down very slightly. Hence aryl diazonium reaction "on water" could be a facile green platform to functionalize carbon fibers for many interesting applications.

Dynamics at a Peptide-TiO2 Anatase (101) Interface.

PubMed

Polimeni, Marco; Petridis, Loukas; Smith, Jeremy C; Arcangeli, Caterina

2017-09-28

The interface between biological matter and inorganic materials is a widely investigated research topic due to possible applications in biomedicine and nanotechnology. In this context, the molecular level adsorption mechanism that drives specific recognition between small peptide sequences and inorganic surfaces represents an important topic likely to provide much information useful for designing bioderived materials. Here, we investigate the dynamics at the interface between a Ti-binding peptide sequence (AMRKLPDAPGMHC) and a TiO 2 anatase surface by using molecular dynamics (MD) simulations. In the simulations the adsorption mechanism is characterized by diffusion of the peptide from the bulk water phase toward the TiO 2 surface, followed by the anchoring of the peptide to the surface. The anchoring is mediated by the interfacial water layers by means of the charged groups of the side chains of the peptide. The peptide samples anchored and dissociated states from the surface and its conformation is not affected by the surface when anchored.

Dynamics at a Peptide–TiO 2 Anatase (101) Interface

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

Polimeni, Marco; Petridis, Loukas; Smith, Jeremy C.

The interface between biological matter and inorganic materials is a widely investigated research topic due to possible applications in biomedicine and nanotechnology. In this context, the molecular level adsorption mechanism that drives specific recognition between small peptide sequences and inorganic surfaces represents an important topic likely to provide much information useful for designing bioderived materials. In this paper, we investigate the dynamics at the interface between a Ti-binding peptide sequence (AMRKLPDAPGMHC) and a TiO 2 anatase surface by using molecular dynamics (MD) simulations. In the simulations the adsorption mechanism is characterized by diffusion of the peptide from the bulk watermore » phase toward the TiO 2 surface, followed by the anchoring of the peptide to the surface. The anchoring is mediated by the interfacial water layers by means of the charged groups of the side chains of the peptide. Finally, the peptide samples anchored and dissociated states from the surface and its conformation is not affected by the surface when anchored.« less

Dynamics at a Peptide–TiO 2 Anatase (101) Interface

DOE PAGES

Polimeni, Marco; Petridis, Loukas; Smith, Jeremy C.; ...

2017-08-29

The interface between biological matter and inorganic materials is a widely investigated research topic due to possible applications in biomedicine and nanotechnology. In this context, the molecular level adsorption mechanism that drives specific recognition between small peptide sequences and inorganic surfaces represents an important topic likely to provide much information useful for designing bioderived materials. In this paper, we investigate the dynamics at the interface between a Ti-binding peptide sequence (AMRKLPDAPGMHC) and a TiO 2 anatase surface by using molecular dynamics (MD) simulations. In the simulations the adsorption mechanism is characterized by diffusion of the peptide from the bulk watermore » phase toward the TiO 2 surface, followed by the anchoring of the peptide to the surface. The anchoring is mediated by the interfacial water layers by means of the charged groups of the side chains of the peptide. Finally, the peptide samples anchored and dissociated states from the surface and its conformation is not affected by the surface when anchored.« less

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells.

PubMed

Xiao, Minyu; Joglekar, Suneel; Zhang, Xiaoxian; Jasensky, Joshua; Ma, Jialiu; Cui, Qingyu; Guo, L Jay; Chen, Zhan

2017-03-08

A wide variety of charge carrier dynamics, such as transport, separation, and extraction, occur at the interfaces of planar heterojunction solar cells. Such factors can affect the overall device performance. Therefore, understanding the buried interfacial molecular structure in various devices and the correlation between interfacial structure and function has become increasingly important. Current characterization techniques for thin films such as X-ray diffraction, cross section scanning electronmicroscopy, and UV-visible absorption spectroscopy are unable to provide the needed molecular structural information at buried interfaces. In this study, by controlling the structure of the hole transport layer (HTL) in a perovskite solar cell and applying a surface/interface-sensitive nonlinear vibrational spectroscopic technique (sum frequency generation vibrational spectroscopy (SFG)), we successfully probed the molecular structure at the buried interface and correlated its structural characteristics to solar cell performance. Here, an edge-on (normal to the interface) polythiophene (PT) interfacial molecular orientation at the buried perovskite (photoactive layer)/PT (HTL) interface showed more than two times the power conversion efficiency (PCE) of a lying down (tangential) PT interfacial orientation. The difference in interfacial molecular structure was achieved by altering the alkyl side chain length of the PT derivatives, where PT with a shorter alkyl side chain showed an edge-on interfacial orientation with a higher PCE than that of PT with a longer alkyl side chain. With similar band gap alignment and bulk structure within the PT layer, it is believed that the interfacial molecular structural variation (i.e., the orientation difference) of the various PT derivatives is the underlying cause of the difference in perovskite solar cell PCE.

Metal-dielectric interactions

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1979-01-01

Metal direlectric surface interactions and dielectric films on metal substrates were investigated. Since interfacial interaction depends so heavily on the nature of the surfaces, analytical surface tools such as Auger emission spectroscopy, X-ray photoelectron spectroscopy and field ion microscopy were used to assist in surface and interfacial characterization. The results indicate that with metals contacting certain glasses in the clean state interfacial, bonding produces fractures in the glasses while when a film such as water is present, fractures occur in the metal near the interface. Friction forces were used to measure the interfacial bond strengths. Studies with metals contacting polymers using field ion microscopy revealed that strong bonding forces could develop being between a metal and polymer surface with polymer transferring to the metal surface in various ways depending upon the forces applied to the surface in contact. With the deposition of refractory carbides, silicides and borides onto metal and alloy substrates the presence of oxides at the interface or active gases in the deposition plasma were shown to alter interfacial properties and chemistry. Auger ion depth profile analysis indicated the chemical composition at the interface and this could be related to the mechanical, friction, and wear behavior of the coating.

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

PubMed

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

2015-10-07

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

Interfacial Control of Ferromagnetism in Ultrathin La0.67Ca0.33MnO3 Sandwiched between CaRu1-xTixO3 (x = 0-0.8) Epilayers.

PubMed

Chen, Binbin; Chen, Pingfan; Xu, Haoran; Jin, Feng; Guo, Zhuang; Lan, Da; Wan, Siyuan; Gao, Guanyin; Chen, Feng; Wu, Wenbin

2016-12-21

Controlling functionalities in oxide heterostructures remains challenging for the rather complex interfacial interactions. Here, by modifying the interface properties with chemical doping, we achieve a nontrivial control over the ferromagnetism in ultrathin La 0.67 Ca 0.33 MnO 3 (LCMO) layer sandwiched between CaRu 1-x Ti x O 3 [CRTO(x)] epilayers. The Ti doping suppresses the interfacial electron transfer from CRTO(x) to LCMO side; as a result, a steadily decreased Curie temperature with increasing x, from 262 K at x = 0 to 186 K at x = 0.8, is observed for the structures with LCMO fixed at 3.2 nm. Moreover, for more insulating CRTO(x ≥ 0.5), the electron confinement induces an interfacial Mn-e g (x 2 -y 2 ) orbital order in LCMO which further attenuates the ferromagnetism. Also, in order to characterize the heterointerfaces, for the first time the doping- and thickness-dependent metal-insulator transitions in CRTO(x) films are examined. Our results demonstrate that the LCMO/CRTO(x) heterostructure could be a model system for investigating the interfacial multiple interactions in correlated oxides.

Proceedings of the International Workshop on Condensed Matter Theories (8th) Held in San Juan, Puerto Rico on 1-5 June 1992

DTIC Science & Technology

1993-01-15

Canosa, R. Rossignoli and A. Plastino 10. Time-dependent N-Level Systems J. Aliaga , J.L Gruver and A. N. Proto 7 4 Atoms and Molecules 1. Atoms in...Interfacial Phase Transitions Underlying Amphiphile Micellar Self-Assembly A. Robledo and C. Varea 3. Hot-solid Properties From Liquid Structure Within

Analysis of main parameters affecting substrate/mortar contact area through tridimensional laser scanner.

PubMed

Stolz, Carina M; Masuero, Angela B

2015-10-01

This study assesses the influence of the granulometric composition of sand, application energy and the superficial tension of substrates on the contact area of rendering mortars. Three substrates with distinct wetting behaviors were selected and mortars were prepared with different sand compositions. Characterization tests were performed on fresh and hardened mortars, as well as the rheological characterization. Mortars were applied to substrates with two different energies. The interfacial area was then digitized with 3D scanner. Results show that variables are all of influence on the interfacial contact in the development area. Furthermore, 3D laser scanning proved to be a good method to contact area measurement. Copyright © 2015 Elsevier Inc. All rights reserved.

AC impedance investigations of proton conduction in Nafion(sup TM)

NASA Astrophysics Data System (ADS)

Cahan, B. D.; Wainright, J. S.

1993-12-01

AC impedance spectroscopy has been employed to study the conduction of protons in Nafion 117 polymer electrolyte membrane. Both two- and four-electrode geometries have been used to uniquely distinguish between the membrane impedance and the interfacial impedances. The results show that the impedance of Nafion for frequencies up to 100 kHz is characterized by a pure resistance, similar to conventional liquid electrolytes. The frequency dependent features observed using a two-electrode geometry are shown to be consistent will well-characterized interfacial impedances and do not arise from ionic conduction in the membrane. These results show that previous two-electrode studies reported in the literature have misinterpreted the impedance of the electrode interfaces as belonging to the conduction process in the electrolyte.

Interfacial Chemistry-Induced Modulation of Schottky Barrier Heights: In Situ Measurements of the Pt-Amorphous Indium Gallium Zinc Oxide Interface Using X-ray Photoelectron Spectroscopy.

PubMed

Flynn, Brendan T; Oleksak, Richard P; Thevuthasan, Suntharampillai; Herman, Gregory S

2018-01-31

A method to understand the role of interfacial chemistry on the modulation of Schottky barrier heights for platinum and amorphous indium gallium zinc oxide (a-IGZO) interfaces is demonstrated through thermal processing and background ambient pressure control. In situ X-ray photoelectron spectroscopy was used to characterize the interfacial chemistries that modulate barrier heights in this system. The primary changes were a significant chemical reduction of indium, from In 3+ to In 0 , that occurs during deposition of Pt on to the a-IGZO surface in ultrahigh vacuum. Postannealing and controlling the background ambient O 2 pressure allows further tuning of the reduction of indium and the corresponding Schottky barrier heights from 0.17 to 0.77 eV. Understanding the detailed interfacial chemistries at Pt/a-IGZO interfaces may allow for improved electronic device performance, including Schottky diodes, memristors, and metal-semiconductor field-effect transistors.

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

PubMed

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

2002-08-01

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

Electrodes for Semiconductor Gas Sensors

PubMed Central

Lee, Sung Pil

2017-01-01

The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode–semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode–semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect. PMID:28346349

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

NASA Astrophysics Data System (ADS)

Li, Kun; Gu, Boqin; Zhu, Wanfu

2017-03-01

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

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

NASA Astrophysics Data System (ADS)

Cui, Yi; Chen, Zengtao

2017-02-01

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

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

PubMed

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

2014-11-18

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

Water at surfaces with tunable surface chemistries

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows

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

Xia Wang; Xiaodong Sun; Benjamin Doup

In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present workmore » aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.« less

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

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

Hou, L.R., E-mail: houlr629@163.com; Lian, L.; Zhou, L.

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 photostabilitymore » after four recycles.« less

Characterizing ceramics and the interfacial adhesion to resin: II- the relationship of surface treatment, bond strength, interfacial toughness and fractography.

PubMed

Della-Bona, Alvaro

2005-06-01

The clinical success of resin bonding procedures for indirect ceramic restorations and ceramic repairs depends on the quality and durability of the bond between the ceramic and the resin. The quality of this bond will depend upon the bonding mechanisms that are controlled in part by the surface treatment that promote micromechanical and/or chemical bonding to the substrate. The objective of this review is to correlate interfacial toughness (K A) with fracture surface morphological parameters of the dental ceramic-resin systems as a function of ceramic surface treatment. This analysis is designed to identify mechanisms that promote adhesion of these ceramic-resin systems and an appropriate bond test method to yield relevant adhesion performance data.

On well-posedness of variational models of charged drops.

PubMed

Muratov, Cyrill B; Novaga, Matteo

2016-03-01

Electrified liquids are well known to be prone to a variety of interfacial instabilities that result in the onset of apparent interfacial singularities and liquid fragmentation. In the case of electrically conducting liquids, one of the basic models describing the equilibrium interfacial configurations and the onset of instability assumes the liquid to be equipotential and interprets those configurations as local minimizers of the energy consisting of the sum of the surface energy and the electrostatic energy. Here we show that, surprisingly, this classical geometric variational model is mathematically ill-posed irrespective of the degree to which the liquid is electrified. Specifically, we demonstrate that an isolated spherical droplet is never a local minimizer, no matter how small is the total charge on the droplet, as the energy can always be lowered by a smooth, arbitrarily small distortion of the droplet's surface. This is in sharp contrast to the experimental observations that a critical amount of charge is needed in order to destabilize a spherical droplet. We discuss several possible regularization mechanisms for the considered free boundary problem and argue that well-posedness can be restored by the inclusion of the entropic effects resulting in finite screening of free charges.

On well-posedness of variational models of charged drops

PubMed Central

Novaga, Matteo

2016-01-01

Electrified liquids are well known to be prone to a variety of interfacial instabilities that result in the onset of apparent interfacial singularities and liquid fragmentation. In the case of electrically conducting liquids, one of the basic models describing the equilibrium interfacial configurations and the onset of instability assumes the liquid to be equipotential and interprets those configurations as local minimizers of the energy consisting of the sum of the surface energy and the electrostatic energy. Here we show that, surprisingly, this classical geometric variational model is mathematically ill-posed irrespective of the degree to which the liquid is electrified. Specifically, we demonstrate that an isolated spherical droplet is never a local minimizer, no matter how small is the total charge on the droplet, as the energy can always be lowered by a smooth, arbitrarily small distortion of the droplet's surface. This is in sharp contrast to the experimental observations that a critical amount of charge is needed in order to destabilize a spherical droplet. We discuss several possible regularization mechanisms for the considered free boundary problem and argue that well-posedness can be restored by the inclusion of the entropic effects resulting in finite screening of free charges. PMID:27118921

Albumin-mediated deposition of bone-like apatite onto nano-sized surfaces: Effect of surface reactivity and interfacial hydration.

PubMed

D'Elia, Noelia L; Gravina, Noel; Ruso, Juan M; Marco-Brown, Jose L; Sieben, Juan M; Messina, Paula V

2017-05-15

The bioactivity of an implant is displayed on its ability to induce heterogeneous nucleation of biogenic apatite onto its surface upon immersion in body fluids; forming, through this layer, a stable bond with the host tissue. The present article evaluates the bioactivity of different nanostructured substrates based on synthetic hydroxyapatite (HA) and titania (TiO 2 ) nanoparticles, where we extend the debate regarding the selective roles played by the presence of albumin on the biogenic apatite coating evolution. The substrates bone-bonding potential was evaluated by keeping the materials in contact with Simulated Body Fluid, while the influence of the presence of Bovine Serum Albumin in bioactivity was analyzed by a spectrophotometric technique. Our results show that materials' surface reactivity and their interfacial hydration are responsible for the bonding-site alteration and surface charge density distribution, which in turn, regulate the protein adsorption process. As a matter of fact, variations on the protein adsorbed density have a directly proportional impact on calcium binding sites, which should be responsible for the initiation of the mineralization process, disturbing the deposition of the interfacial calcium phosphate (Ca-P) mineralized coating. Copyright © 2017 Elsevier Inc. All rights reserved.

Novel Colloidal and Dynamic Interfacial Phenomena in Liquid Crystalline Systems

DTIC Science & Technology

2014-09-13

Pablo. Effects of anchoring strength on the diffusivity of nanoparticles in model liquid-crystalline fluids, Soft Matter, (03 2011): 6828. doi...10.1021/la103975s Santanu Kumar Pal, Claribel Acevedo-Ve?lez, Jacob T. Hunter, Nicholas L. Abbott. Effects of Divalent Ligand Interactions on Surface...peer-reviewed journals: (c) Presentations 7 Presentation #1 (a) Electrical double layer and specific ion effects at interfaces between thermotropic

Non-Newtonian fluid flow over a heterogeneously slippery surface

NASA Astrophysics Data System (ADS)

Haase, A. Sander; Wood, Jeffery A.; Sprakel, Lisette M. J.; Lammertink, Rob G. H.

2015-11-01

The no-slip boundary condition does not always hold. In the past, we have investigated the influence of effective wall slip on interfacial transport for a bubble mattress - a superhydrophobic surface consisting of an array of transverse gas-filled grooves. We proved experimentally that the amount of effective wall slip depends on the bubble protrusion angle and the surface porosity (Karatay et al., PNAS 110, 2013), and predicted that mass transport can be enhanced significantly (Haase et al., Soft Matter 9, 2013). Both studies involve the flow of water. In practise, however, many liquids encountered are non-Newtonian, like blood and polymer solutions. This raises some interesting questions. How does interfacial transport depend on the rheological properties of the liquid? Does the time-scale of the experiment matter? A bubble mattress is a suitable platform to investigate this, due to local variations in shear rate. We predict that for shear-thinning liquids, compared to water, the amount of wall slip can be enhanced considerably, although this depends on the applied flow rate. Experiments are performed to proof this behaviour. Simulations are used to assess what will happen when the characteristic time-scale of the system matches the relaxation time of the visco-elastic liquid. R.G.H.L. acknowledges the European Research Council for the ERC starting grant 307342-TRAM.

Characterization of the interfacial heat transfer coefficient for hot stamping processes

NASA Astrophysics Data System (ADS)

Luan, Xi; Liu, Xiaochuan; Fang, Haomiao; Ji, Kang; El Fakir, Omer; Wang, LiLiang

2016-08-01

In hot stamping processes, the interfacial heat transfer coefficient (IHTC) between the forming tools and hot blank is an essential parameter which determines the quenching rate of the process and hence the resulting material microstructure. The present work focuses on the characterization of the IHTC between an aluminium alloy 7075-T6 blank and two different die materials, cast iron (G3500) and H13 die steel, at various contact pressures. It was found that the IHTC between AA7075 and cast iron had values 78.6% higher than that obtained between AA7075 and H13 die steel. Die materials and contact pressures had pronounced effects on the IHTC, suggesting that the IHTC can be used to guide the selection of stamping tool materials and the precise control of processing parameters.

Imaging interfacial electrical transport in graphene–MoS{sub 2} heterostructures with electron-beam-induced-currents

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

White, E. R., E-mail: ewhite@physics.ucla.edu; Kerelsky, Alexander; Hubbard, William A.

2015-11-30

Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS{sub 2} heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrentmore » collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.« less

Theoretical vibrational sum-frequency generation spectroscopy of water near lipid and surfactant monolayer interfaces. II. Two-dimensional spectra.

PubMed

Roy, S; Gruenbaum, S M; Skinner, J L

2014-12-14

The structural stability and function of biomolecules is strongly influenced by the dynamics and hydrogen bonding of interfacial water. Understanding and characterizing the dynamics of these water molecules require a surface-sensitive technique such as two-dimensional vibrational sum-frequency generation (2DSFG) spectroscopy. We have combined theoretical 2DSFG calculations with molecular dynamics simulations in order to investigate the dynamics of water near different lipid and surfactant monolayer surfaces. We show that 2DSFG can distinguish the dynamics of interfacial water as a function of the lipid charge and headgroup chemistry. The dynamics of water is slow compared to the bulk near water-zwitterionic and water-anionic interfaces due to conformational constraints on interfacial water imposed by strong phosphate-water hydrogen bonding. The dynamics of water is somewhat faster near water-cationic lipid interfaces as no such constraint is present. Using hydrogen bonding and rotational correlation functions, we characterize the dynamics of water as a function of the distance from the interface between water and zwitterionic lipids. We find that there is a transition from bulk-like to interface-like dynamics approximately 7 Å away from a zwitterionic phosphatidylcholine monolayer surface.

Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

PubMed

Luo, Nan; Xu, Rongle; Yang, Min; Yuan, Xing; Zhong, Hui; Fan, Yaobo

2015-12-01

A novel inorganic-organic composite membrane, namely poly(vinylidene fluoride) PVDF-glass fiber (PGF) composite membrane, was prepared and reinforced by interfacial ultraviolet (UV)-grafting copolymerization to improve the interfacial bonding strength between the membrane layer and the glass fiber. The interfacial polymerization between inorganic-organic interfaces is a chemical cross-linking reaction that depends on the functionalized glass fiber with silane coupling (KH570) as the initiator and the polymer solution with acrylamide monomer (AM) as the grafting block. The Fourier transform infrared spectrometer-attenuated total reflectance (FTIR-ATR) spectra and the energy dispersive X-ray (EDX) pictures of the interface between the glass fiber and polymer matrix confirmed that the AM was grafted to the surface of the glass fiber fabric and that the grafting polymer was successfully embedded in the membrane matrix. The formation mechanisms, permeation, and anti-fouling performance of the PGF composite membrane were measured with different amounts of AM in the doping solutions. The results showed that the grafting composite membrane improved the interfacial bonding strength and permeability, and the peeling strength was improved by 32.6% for PGF composite membranes with an AM concentration at 2wt.%. Copyright © 2015. Published by Elsevier B.V.

A Synopsis of Interfacial Phenomena in Lithium-Based Polymer Electrolyte Electrochemical Cells

NASA Technical Reports Server (NTRS)

Baldwin, Richard S.; Bennett, William R.

2007-01-01

The interfacial regions between electrode materials, electrolytes and other cell components play key roles in the overall performance of lithium-based batteries. For cell chemistries employing lithium metal, lithium alloy or carbonaceous materials (i.e., lithium-ion cells) as anode materials, a "solid electrolyte interphase" (SEI) layer forms at the anode/electrolyte interface, and the properties of this "passivating" layer significantly affect the practical cell/battery quality and performance. A thin, ionically-conducting SEI on the electrode surface can beneficially reduce or eliminate undesirable side reactions between the electrode and the electrolyte, which can result in a degradation in cell performance. The properties and phenomena attributable to the interfacial regions existing at both anode and cathode surfaces can be characterized to a large extent by electrochemical impedance spectroscopy (EIS) and related techniques. The intention of the review herewith is to support the future development of lithium-based polymer electrolytes by providing a synopsis of interfacial phenomena that is associated with cell chemistries employing either lithium metal or carbonaceous "composite" electrode structures which are interfaced with polymer electrolytes (i.e., "solvent-free" as well as "plasticized" polymer-binary salt complexes and single ion-conducting polyelectrolytes). Potential approaches to overcoming poor cell performance attributable to interfacial effects are discussed.

In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

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

Qu, Lin; Zhao, Ning; Ma, Haitao, E-mail: htma@dlut.edu.cn

2014-05-28

Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu{sub 6}Sn{sub 5} IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end aftermore » solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu{sub 6}Sn{sub 5} IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics.« less

Interfacial oxide re-growth in thin film metal oxide III-V semiconductor systems

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

McDonnell, S.; Dong, H.; Hawkins, J. M.

2012-04-02

The Al{sub 2}O{sub 3}/GaAs and HfO{sub 2}/GaAs interfaces after atomic layer deposition are studied using in situ monochromatic x-ray photoelectron spectroscopy. Samples are deliberately exposed to atmospheric conditions and interfacial oxide re-growth is observed. The extent of this re-growth is found to depend on the dielectric material and the exposure temperature. Comparisons with previous studies show that ex situ characterization can result in misleading conclusions about the interface reactions occurring during the metal oxide deposition process.

Langmuir-Blodgett Films of Supported Polyester Dendrimers

PubMed Central

Redón, Rocío; Carreón-Castro, M. Pilar; Mendoza-Martínez, F. J.

2012-01-01

Amphiphiles with a dendritic structure are attractive materials as they combine the features of dendrimers with the self-assembling properties and interfacial behavior of water-air affinities. We have synthesized three generations of polyester dendrimers and studied their interfacial properties on the Langmuir films. The behavior obtained was, as a rule, the lowest generation dendrimers behaving like traditional amphiphiles and the larger molecules presenting complicated isotherms. The Langmuir films of these compounds have been characterized by their surface pressure versus molecular area (π/A) and Brewster angle microscopy (BAM) observations. PMID:24052855

Dynamic Forces Between Two Deformable Oil Droplets in Water

NASA Astrophysics Data System (ADS)

Dagastine, Raymond R.; Manica, Rogério; Carnie, Steven L.; Chan, D. Y. C.; Stevens, Geoffrey W.; Grieser, Franz

2006-07-01

The understanding of static interactions in colloidal suspensions is well established, whereas dynamic interactions more relevant to biological and other suspended soft-matter systems are less well understood. We present the direct force measurement and quantitative theoretical description for dynamic forces for liquid droplets in another immiscible fluid. Analysis of this system demonstrates the strong link between interfacial deformation, static surface forces, and hydrodynamic drainage, which govern dynamic droplet-droplet interactions over the length scale of nanometers and over the time scales of Brownian collisions. The results and analysis have direct bearing on the control and manipulation of suspended droplets in soft-matter systems ranging from the emulsions in shampoo to cellular interactions.

Experimental soft-matter science

NASA Astrophysics Data System (ADS)

Nagel, Sidney R.

2017-04-01

Soft materials consist of basic units that are significantly larger than an atom but much smaller than the overall dimensions of the sample. The label "soft condensed matter" emphasizes that the large basic building blocks of these materials produce low elastic moduli that govern a material's ability to withstand deformations. Aside from softness, there are many other properties that are also caused by the large size of the constituent building blocks. Soft matter is dissipative, disordered, far from equilibrium, nonlinear, thermal and entropic, slow, observable, gravity affected, patterned, nonlocal, interfacially elastic, memory forming, and active. This is only a partial list of how matter created from large component particles is distinct from "hard matter" composed of constituents at an atomic scale. Issues inherent in soft matter raise problems that are broadly important in diverse areas of science and require multiple modes of attack. For example, far-from-equilibrium behavior is confronted in biology, chemistry, geophysics, astrophysics, and nuclear physics. Similarly, issues dealing with disorder appear broadly throughout many branches of inquiry wherever rugged landscapes are invoked. This article reviews the discussions that occurred during a workshop held on 30-31 January 2016 in which opportunities in soft-matter experiment were surveyed. Soft matter has had an exciting history of discovery and continues to be a fertile ground for future research.

Modeling of second-harmonic generation of circumferential guided wave propagation in a composite circular tube

NASA Astrophysics Data System (ADS)

Li, Mingliang; Deng, Mingxi; Gao, Guangjian; Xiang, Yanxun

2018-05-01

This paper investigated modeling of second-harmonic generation (SHG) of circumferential guided wave (CGW) propagation in a composite circular tube, and then analyzed the influences of interfacial properties on the SHG effect of primary CGW. Here the effect of SHG of primary CGW propagation is treated as a second-order perturbation to its linear wave response. Due to the convective nonlinearity and the inherent elastic nonlinearity of material, there are second-order bulk driving forces and surface/interface driving stresses in the interior and at the surface/interface of a composite circular tube, when a primary CGW mode propagates along its circumference. Based on the approach of modal expansion analysis for waveguide excitation, the said second-order driving forces/stresses are regarded as the excitation sources to generate a series of double-frequency CGW modes that constitute the second-harmonic field of the primary CGW propagation. It is found that the modal expansion coefficient of each double-frequency CGW mode is closely related to the interfacial stiffness constants that are used to describe the interfacial properties between the inner and outer circular parts of the composite tube. Furthermore, changes in the interfacial stiffness constants essentially influence the dispersion relation of CGW propagation. This will remarkably affect the efficiency of cumulative SHG of primary CGW propagation. Some finite element simulations have been implemented of response characteristics of cumulative SHG to the interfacial properties. Both the theoretical analyses and numerical simulations indicate that the effect of cumulative SHG is found to be much more sensitive to changes in the interfacial properties than primary CGW propagation. The potential of using the effect of cumulative SHG by primary CGW propagation to characterize a minor change in the interfacial properties is considered.

Fluid displacement fronts in porous media: pore scale interfacial jumps, pressure bursts and acoustic emissions

NASA Astrophysics Data System (ADS)

Moebius, Franziska; Or, Dani

2014-05-01

The macroscopically smooth and regular motion of fluid fronts in porous media is composed of numerous rapid pore-scale interfacial jumps and pressure bursts that involve intense interfacial energy release in the form of acoustic emissions. The characteristics of these pore scale events affect residual phase entrapment and transport properties behind the front. We present experimental studies using acoustic emission technique (AE), rapid imaging, and liquid pressure measurements to characterize these processes during drainage and imbibition in simple porous media. Imbibition and drainage produce different AE signatures (AE amplitudes obey a power law). For rapid drainage, AE signals persist long after cessation of front motion reflecting fluid redistribution and interfacial relaxation. Imaging revealed that the velocity of interfacial jumps often exceeds front velocity by more than 50 fold and is highly inertial component (Re>1000). Pore invasion volumes reduced deduced from pressure fluctuations waiting times (for constant withdrawal rates) show remarkable agreement with geometrically-deduced pore volumes. Discrepancies between invaded volumes and geometrical pores increase with increasing capillary numbers due to constraints on evacuation opportunity times and simultaneous invasion events. A mechanistic model for interfacial motions in a pore-throat network was developed to investigate interfacial dynamics focusing on the role of inertia. Results suggest that while pore scale dynamics were sensitive to variations in pore geometry and boundary conditions, inertia exerted only a minor effect on phase entrapment. The study on pore scale invasion events paints a complex picture of rapid and inertial motions and provides new insights on mechanisms at displacement fronts that are essential for improved macroscopic description of multiphase flows in porous media.

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.

Humidity-dependent compression-induced glass transition of the air–water interfacial Langmuir films of poly(D,L-lactic acid- ran-glycolic acid) (PLGA)

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

Kim, Hyun Chang; Lee, Hoyoung; Jung, Hyunjung

2015-08-26

Constant rate compression isotherms of the air–water interfacial Langmuir films of poly(D,L-lactic acid- ran-glycolic acid) (PLGA)show a distinct feature of an exponential increase in surface pressure in the high surface polymer concentration regime. We have previously demonstrated that this abrupt increase in surface pressure is linked to the glass transition of the polymer film, but the detailed mechanism of this process is not understood. In order to obtain a molecular-level understanding of this behavior, we performed extensive characterizations of the surface mechanical, structural and rheological properties of Langmuir PLGA films at the air–water interface, using combined experimental techniques including themore » Langmuir film balance, X-ray reflectivity and double-wall-ring interfacial rheometry methods.« less

Probing interfacial energetics and charge transfer kinetics in semiconductor nanocomposites: New insights into heterostructured TiO 2/BiVO 4 photoanodes

DOE PAGES

Hess, Lucas H.; Cooper, Jason K.; Loiudice, Anna; ...

2017-02-28

Heterostructured nanocomposites offer promise for creating systems exhibiting functional properties that exceed those of the isolated components. For solar energy conversion, such combinations of semiconducting nanomaterials can be used to direct charge transfer along pathways that reduce recombination and promote efficient charge extraction. However, interfacial energetics and associated kinetic pathways often differ significantly from predictions derived from the characteristics of pure component materials, particularly at the nanoscale. Here, the emergent properties of TiO 2/BiVO 4 nanocomposite photoanodes are explored using a combination of X-ray and optical spectroscopies, together with photoelectrochemical (PEC) characterization. Application of these methods to both the puremore » components and the fully assembled nanocomposites reveals unpredicted interfacial energetic alignment, which promotes ultrafast injection of electrons from BiVO 4 into TiO 2. Physical charge separation yields extremely long-lived photoexcited states and correspondingly enhanced photoelectrochemical functionality. This work highlights the importance of probing emergent interfacial energetic alignment and kinetic processes for understanding mechanisms of solar energy conversion in complex nanocomposites.« less

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.

Oxygen deficiency induced deterioration in microstructure and magnetic properties at Y{sub 3}Fe{sub 5}O{sub 12}/Pt interface

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

Song, Dongsheng; Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn; Ma, Li

2015-07-27

Transport efficiency of pure spin current across the ferromagnetic films adjacent with a nonmagnetic metal is strongly dependent on the spin mixing conductance, which is very sensitive to atomic-level interface conditions. Here, by the means of advanced electron microscopy techniques, atomic structure, electronic structure, and magnetic properties at Y{sub 3}Fe{sub 5}O{sub 12} (YIG)/Pt interface are detailed characterized to correlate the microstructure and magnetic properties with interfacial transport properties. It is found that the order-disorder structure transformation at the interface is accompanied with oxygen deficiency, thus the reduced iron valence and the break of magnetic atom-O-magnetic atom bridges, which is responsiblemore » for superexchange interaction and magnetic order. It is also found that the magnetic moment of interfacial iron ions is decreased. The disorder interfacial layer with suppressed magnetism finally contributes to the declined spin transport efficiency. Our results provide the knowledge to control and manipulate the interfacial structure and properties in order to obtain higher spin transport efficiency.« less

On the enrichment of hydrophobic organic compounds in fog droplets

NASA Astrophysics Data System (ADS)

Valsaraj, K. T.; Thoma, G. J.; Reible, D. D.; Thibodeaux, L. J.

The unusual degree of enrichment of hydrophobic organics in fogwater droplets reported by several investigators can be interpreted as a result of (a) the effects of temperature correction on the reported enrichment factors, (b) the effects of colloidal organic matter (both filterable and non-filterable) in fog water and (c) the effects of the large air-water interfacial adsorption of neutral hydrophobic organics on the tiny fog droplets. The enrichment factor was directly correlated to the hydrophobicity (or the activity coefficient in water) of the compounds, as indicated by their octanol-water partition constants. Compounds with large octanol-water partition coefficients (high activity coefficients in water) showed the largest enrichment. Available experimental data on the adsorption of hydrophobic compounds at the air-water interface and on colloidal organic carbon were used to show that the large specific air-water interfacial areas of fog droplets contribute significantly to the enrichment factor.

Thermal conductance of interfaces with molecular layers - low temperature transient absorption study on gold nanorods supported on self assembled monolayers

NASA Astrophysics Data System (ADS)

Wang, Wei; Huang, Jingyu; Murphy, Catherine; Cahill, David; University of Illinois At Urbana Champaign, Department of Materials Science; Engineering Team; Department Collaboration

2011-03-01

While heat transfer via phonons across solid-solid boundary has been a core field in condense matter physics for many years, vibrational energy transport across molecular layers has been less well elucidated. We heat rectangular-shaped gold nanocrystals (nanorods) with Ti-sapphire femtosecond pulsed laser at their longitudinal surface plasmon absorption wavelength to watch how their temperature evolves in picoseconds transient. We observed single exponential decay behavior, which suggests that the heat dissipation is only governed by a single interfacial conductance value. The ``RC'' time constant was 300ps, corresponding to a conductance value of 95MW/ m 2 K. This interfacial conductance value is also a function of ambient temperature since at temperatures as low as 80K, which are below the Debye temperature of organic layers, several phonon modes were quenched, which shut down the dominating channels that conduct heat at room temperature.

Surface and interfacial chemistry of high-k dielectric and interconnect materials on silicon

NASA Astrophysics Data System (ADS)

Kirsch, Paul Daniel

Surfaces and interfaces play a critical role in the manufacture and function of silicon based integrated circuits. It is therefore reasonable to study the chemistries at these surfaces and interfaces to improve existing processes and to develop new ones. Model barium strontium titanate high-k dielectric systems have been deposited on ultrathin silicon oxynitride in ultrahigh vacuum. The resulting nanostructures are characterized with secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). An interfacial reaction between Ba and Sr atoms and SiOxNy was found to create silicates, BaSixOy or SrSi xOy. Inclusion of N in the interfacial oxide decreased silicate formation in both Ba and Sr systems. Furthermore, inclusion of N in the interfacial oxide decreased the penetration of Ba and Sr containing species, such as silicides and silicates. Sputter deposited HfO2 was studied on nitrided and unnitrided Si(100) surfaces. XPS and SIMS were used to verify the presence of interfacial HfSixOy and estimate its relative amount on both nitrided and unnitrided samples. More HfSixOy formed without the SiNx interfacial layer. These interfacial chemistry results are then used to explain the electrical measurements obtained from metal oxide semiconductor (MOS) capacitors. MOS capacitors with interfacial SiNx exhibit reduced leakage current and increased capacitance. Lastly, surface science techniques were used to develop a processing technique for reducing thin films of copper (II) and copper (I) oxide to copper. Deuterium atoms (D*) and methyl radicals (CH3*) were shown to reduce Cu 2+ and/or Cu1+ to Cu0 within 30 min at a surface temperature of 400 K under a flux of 1 x 1015 atoms/cm2s. Temperature programmed desorption experiments suggest that oxygen leaves the surface as D2O and CO2 for the D* and CH3* treated surfaces, respectively.

Development of a new test for the easy characterization of the adhesion at the interface of bilayer tablets: proof-of-concept study by experimental design.

PubMed

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

2014-12-30

Although, adhesion at the interface of bilayer tablets is critical for their design it is difficult to characterize this adhesion between layers. In view of this, a new test with an easy implementation was proposed for the characterization of the interface of bilayer tablets. This work is presented as a proof-of-concept study to investigate the reliability of this new test with regard to the effects of some critical process parameters (e.g., compaction pressure applied on each layer) and material attributes (e.g., elasticity of the layered materials) on the interfacial adhesion of bilayer tablets. This was investigated using a design of experiment approach and the results obtained were in good accordance with those obtained with other tests and thus, confirms the potential of such a method for the measurement of the interfacial adhesion of bilayer tablets. Copyright © 2014 Elsevier B.V. All rights reserved.

[Analysis of mechanism of transition zones among β, δ and γ dispersions in brain white matter and grey matter].

PubMed

Tian, Rui; Lu, Mai

2017-08-01

In order to explore the application of the dielectric properties of white matter and grey matter in β, δ and γ dispersion transition zones used in clinical medicine and microwave imaging technology, we calculated the dielectric constant and its increment by using Cole-Cole equation. Based on the mutation of the increment of dielectric constant, the frequency range of three dispersions were evaluated. The dominate dispersion and the corresponding polarization mechanism were analyzed by using Cole-Cole circle. The results showed that there are 3 transition zones in brain white matter, which occur between β and δ dispersion, δ and γ dispersion and β and γ dispersion respectively. In grey matter, there are only 2 transition zones, which are between β and δ dispersion and δ and γ dispersion respectively. By comparing the frequency range of white matter and grey matter, the frequency range in white matter is broader than that in grey matter for the transition zone of β and δ dispersion with the β dispersion occupying dominate position in both tissues, and the corresponding polarization mechanism is interfacial polarization. For the transition zone of δ and γ dispersion, the frequency range in white matter is also broader than that in grey matter with the δ dispersion occupying dominate position in both tissues, and the corresponding polarization mechanism is orientation polarization. This study can provide basic theory and reference for diagnosis of brain diseases and microwave imaging technology.

Structural Characterization of Biocompatible Reverse Micelles Using Small-Angle X-ray Scattering, 31P Nuclear Magnetic Resonance, and Fluorescence Spectroscopy.

PubMed

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

2018-04-19

The most critical problem regarding the use of reverse micelles (RMs) in several fields is the toxicity of their partial components. In this sense, many efforts have been made to characterize nontoxic RM formulations on the basis of biological amphiphiles and/or different oils. In this contribution, the microstructure of biocompatible mixed RMs formulated by sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) and tri- n-octylphosphine oxide (TOPO) surfactants dispersed in the friendly solvent methyl laurate was studied by using SAXS and 31 P NMR and by following the solvatochromic behavior of the molecular probe 4-aminophthalimide (4-AP). The results indicated the presence of RM aggregates upon TOPO incorporation with a droplet size reduction and an increase in the interfacial fluidity in comparison with pure AOT RMs. When confined inside the mixed systems, 4-AP showed a red-edge excitation shift and confirmed the increment of interfacial fluidity upon TOPO addition. Also, the partition between the external nonpolar solvent and the RM interface and an increase in both the local micropolarity and the capability to form a hydrogen bond interaction between 4-AP and a mixed interface were observed. The findings have been explained in terms of the nonionic surfactant structure and its complexing nature expressed at the interfacial level. Notably, we show how two different approaches, i.e., SAXS and the solvatochromism of the probe 4-AP, can be used in a complementary way to enhance our understanding of the interfacial fluidity of RMs, a parameter that is difficult to measure directly.

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

PubMed

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

2015-08-07

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.

RF MEMS microswitches design and characterization

NASA Astrophysics Data System (ADS)

Lafontan, Xavier; Dufaza, Christian; Robert, Michel; Perez, Guy; Pressecq, Francis

2000-08-01

This paper presents the work performed in MUMPs on RF MEMS micro-switch. Concepts, design and characterization of switches are studied. The study particularly focuses on the electrical resistance characterization and modelization. The switches developed uses two different principle: overflowed gold and hinged beam. The realized contacts exhibited high on resistance (~20(Omega) ) due to nanoscopics asperities of contacts and insulating interfacial films. Results of a typical contact cleaning method are also presented.

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

PubMed

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

2016-06-01

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

Interfacial exciplex formation in bilayers of conjugated polymers.

PubMed

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

2013-10-28

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.

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

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

Effect of Substrate Compliance on Measuring Delamination Properties of Elastic Thin Foil

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

Liu, C.

Through the analysis of a model problem, a thin elastic plate bonded to an elastic foundation, we address several issues related to the miniature bulge test for measuring the energy-release rate associated with the interfacial fracture of a bimaterial system, where one of the constituents is a thin foil. These issues include the effect of the substrate compliance on the interpretation of the energy release rate, interfacial strength, and the identification of the boundary of the deforming bulge or the location of the interfacial crack front. The analysis done also suggests a way for measuring the so-called foundation modulus, whichmore » characterizes the property of the substrate. An experimental example, a stainless steel thin foil bonded to an aluminum substrate through hot-isostatic-pressing (HIP), is used to illustrate and highlight some of the conclusions of the model analysis.« less

Effect of Substrate Compliance on Measuring Delamination Properties of Elastic Thin Foil

DOE PAGES

Liu, C.

2018-03-20

Through the analysis of a model problem, a thin elastic plate bonded to an elastic foundation, we address several issues related to the miniature bulge test for measuring the energy-release rate associated with the interfacial fracture of a bimaterial system, where one of the constituents is a thin foil. These issues include the effect of the substrate compliance on the interpretation of the energy release rate, interfacial strength, and the identification of the boundary of the deforming bulge or the location of the interfacial crack front. The analysis done also suggests a way for measuring the so-called foundation modulus, whichmore » characterizes the property of the substrate. An experimental example, a stainless steel thin foil bonded to an aluminum substrate through hot-isostatic-pressing (HIP), is used to illustrate and highlight some of the conclusions of the model analysis.« less

A nano-bio interfacial protein corona on silica nanoparticle.

PubMed

Zhang, Hongyan; Peng, Jiaxi; Li, Xin; Liu, Shengju; Hu, Zhengyan; Xu, Guiju; Wu, Ren'an

2018-07-01

Nano-bio interaction takes the crucial role in bio-application of nanoparticles. The systematic mapping of interfacial proteins remains the big challenge as low level of proteins within interface regions and lack of appropriate technology. Here, a facile proteomic strategy was developed to characterize the interfacial protein corona (noted as IPC) that has strong interactions with silica nanoparticle, via the combination of the vigorous elution with high concentration sodium dodecyl sulfate (SDS) and the pre-isolation of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The trace level IPCs for silica nanoparticle were thus qualitatively and quantitatively identified. Bioinformatics analyses revealed the intrinsic compositions, relevance and potential regularity addressing the strong interactions between IPC and nanoparticle. This strategy in determining IPCs is opening an avenue to give a deep insight to understand the interaction between proteins and not only nanoparticles but also other bulk materials. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of isothermal and cyclic exposures on interface structure and mechanical properties of FPalpha-Al2O3/aluminum composites. [polycrystaline alumina fibers

NASA Technical Reports Server (NTRS)

Kim, W. M.; Koczak, M. J.; Lawley, A.

1979-01-01

The microstructural and interface stability of FPalpha-Al203/Al-Li composites are investigated as a function of isothermal exposure at 500 C or thermal cycling between 140 and 500 C with hold time at Tmax. Interfacial morphology, growth kinetics, crystal structure, and composition of interfacial reaction products are characterized. Strength is monitored in the transverse orientation, and fracture mechanics is analyzed in terms of interface reaction products. The interfacial reaction product in FP/Al is Li2O.5Al2O3. Significant fiber-matrix reaction occurs during fabrication. The number of thermal cycles rather than total time at Tmax is the determining factor in strength degradation, thermal cycling giving rise to voids at the fiber-matrix interface. Extensive interface failures occur at composite fracture stresses below about 128 MPa; above this stress level failure is attributed to ductile matrix fracture.

Exploring the specific features of interfacial enzymology based on lipase studies.

PubMed

Aloulou, Ahmed; Rodriguez, Jorge A; Fernandez, Sylvie; van Oosterhout, Dirk; Puccinelli, Delphine; Carrière, Frédéric

2006-09-01

Many enzymes are active at interfaces in the living world (such as in the signaling processes at the surface of cell membranes, digestion of dietary lipids, starch and cellulose degradation, etc.), but fundamental enzymology remains largely focused on the interactions between enzymes and soluble substrates. The biochemical and kinetic characterization of lipolytic enzymes has opened up new paths of research in the field of interfacial enzymology. Lipases are water-soluble enzymes hydrolyzing insoluble triglyceride substrates, and studies on these enzymes have led to the development of specific interfacial kinetic models. Structure-function studies on lipases have thrown light on the interfacial recognition sites present in the molecular structure of these enzymes, the conformational changes occurring in the presence of lipids and amphiphiles, and the stability of the enzymes present at interfaces. The pH-dependent activity, substrate specificity and inhibition of these enzymes can all result from both "classical" interactions between a substrate or inhibitor and the active site, as well as from the adsorption of the enzymes at the surface of aggregated substrate particles such as oil drops, lipid bilayers or monomolecular lipid films. The adsorption step can provide an alternative target for improving substrate specificity and developing specific enzyme inhibitors. Several data obtained with gastric lipase, classical pancreatic lipase, pancreatic lipase-related protein 2 and phosphatidylserine-specific phospholipase A1 were chosen here to illustrate these specific features of interfacial enzymology.

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

Structure and orientation of interfacial proteins determined by sum frequency generation vibrational spectroscopy: method and application.

PubMed

Ye, Shuji; Wei, Feng; Li, Hongchun; Tian, Kangzhen; Luo, Yi

2013-01-01

In situ and real-time characterization of molecular structures and orientation of proteins at interfaces is essential to understand the nature of interfacial protein interaction. Such work will undoubtedly provide important clues to control biointerface in a desired manner. Sum frequency generation vibrational spectroscopy (SFG-VS) has been demonstrated to be a powerful technique to study the interfacial structures and interactions at the molecular level. This paper first systematically introduced the methods for the calculation of the Raman polarizability tensor, infrared transition dipole moment, and SFG molecular hyperpolarizability tensor elements of proteins/peptides with the secondary structures of α-helix, 310-helix, antiparallel β-sheet, and parallel β-sheet, as well as the methodology to determine the orientation of interfacial protein secondary structures using SFG amide I spectra. After that, recent progresses on the determination of protein structure and orientation at different interfaces by SFG-VS were then reviewed, which provides a molecular-level understanding of the structures and interactions of interfacial proteins, specially understanding the nature of driving force behind such interactions. Although this review has focused on analysis of amide I spectra, it will be expected to offer a basic idea for the spectral analysis of amide III SFG signals and other complicated molecular systems such as RNA and DNA. Copyright © 2013 Elsevier Inc. All rights reserved.

Surface modification and characterization of aramid fibers with hybrid coating

NASA Astrophysics Data System (ADS)

Chen, Jianrui; Zhu, Yaofeng; Ni, Qingqing; Fu, Yaqin; Fu, Xiang

2014-12-01

Aramid fibers were modified through solution dip-coating and interfacial in situ polymerization using a newly synthesized SiO2/shape memory polyurethane (SiO2/SMPU) hybrid. Fourier transform infrared and X-ray photoelectron spectroscopy indicated that the synthesized SiO2/SMPU hybrid successfully coated the fiber surface. The surface morphology of the aramid fibers and the single fiber tensile strength and interfacial shear strength (IFSS) of the composites were determined. The IFSS of the fiber coated with the hybrid improved by 45%, which benefited from a special "pizza-like" structure on the fiber surface.

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.

Electrodeposition of Ni on Bi2Te3 and Interfacial Reaction Between Sn and Ni-Coated Bi2Te3

NASA Astrophysics Data System (ADS)

Tseng, Yu-Chen; Lee, Hsuan; Hau, Nga Yu; Feng, Shien-Ping; Chen, Chih-Ming

2018-01-01

Bismuth-telluride (Bi2Te3)-based compounds are common thermoelectric materials used for low-temperature applications, and nickel (Ni) is usually deposited on the Bi2Te3 substrates as a diffusion barrier. Deposition of Ni on the p-type (Sb-doped) and n-type (Se-doped) Bi2Te3 substrates using electroplating and interfacial reactions between Sn and Ni-coated Bi2Te3 substrates are investigated. Electrodeposition of Ni on different Bi2Te3 substrates is characterized based on cyclic voltammetry and Tafel measurements. Microstructural characterizations of the Ni deposition and the Sn/Ni/Bi2Te3 interfacial reactions are performed using scanning electron microscopy. A faster growth rate is observed for the Ni deposition on the n-type Bi2Te3 substrate which is attributed to a lower activation energy of reduction due to a higher density of free electrons in the n-type Bi2Te3 material. The common Ni3Sn4 phase is formed at the Sn/Ni interfaces on both the p-type and n-type Bi2Te3 substrates, while the NiTe phase is formed at a faster rate at the interface between Ni and n-type Bi2Te3 substrates.

Location-Specific Measurements of The Glass Transition Temperature in Fluorescently Labeled Diblock Copolymers

NASA Astrophysics Data System (ADS)

Christie, Dane; Register, Richard; Priestley, Rodney

Block copolymers can self-assemble into periodic structures containing a high internal surface area, nanoscale domain periods, and periodically varying composition profiles. Depending on their components, block copolymers may also exhibit variations in their dynamic properties e.g., glass transition temperature (Tg) across the domain period. Measuring the variation of Tg across the domain period of block copolymers has remained a significant challenge due to the nanometer length scale of the domain period. Here we use fluorescence spectroscopy and the selective incorporation of a pyrene-containing methacrylate monomer at various positions along the chain to characterize the distribution of glass transition temperatures across the domain period of an amorphous block copolymer. The pyrene-containing monomer location is determined from the monomer segment distribution calculated using self-consistent field theory. Our model system is a lamella-forming diblock copolymer of poly(butyl methacrylate - b- methyl methacrylate). We show that Tg is asymmetrically distributed across the interface; as the interface is approached, larger gradients in Tg exist in the hard PMMA-rich domain than in the soft PBMA-rich domain. By characterizing Tg of PBMA or PMMA interfacial segments, we show that polymer dynamics at the interface are heterogeneous; there is a 15 K difference in Tg measured between PBMA interfacial segments and PMMA interfacial segments.

Exploring Interfacial Events in Gold-Nanocluster-Sensitized Solar Cells: Insights into the Effects of the Cluster Size and Electrolyte on Solar Cell Performance.

PubMed

Abbas, Muhammad A; Kim, Tea-Yon; Lee, Sang Uck; Kang, Yong Soo; Bang, Jin Ho

2016-01-13

Gold nanoclusters (Au NCs) with molecule-like behavior have emerged as a new light harvester in various energy conversion systems. Despite several important strides made recently, efforts toward the utilization of NCs as a light harvester have been primarily restricted to proving their potency and feasibility. In solar cell applications, ground-breaking research with a power conversion efficiency (PCE) of more than 2% has recently been reported. Because of the lack of complete characterization of metal cluster-sensitized solar cells (MCSSCs), however, comprehensive understanding of the interfacial events and limiting factors which dictate their performance remains elusive. In this regard, we provide deep insight into MCSSCs for the first time by performing in-depth electrochemical impedance spectroscopy (EIS) analysis combined with physical characterization and density functional theory (DFT) calculations of Au NCs. In particular, we focused on the effect of the size of the Au NCs and electrolytes on the performance of MCSSCs and reveal that they are significantly influential on important solar cell characteristics such as the light absorption capability, charge injection kinetics, interfacial charge recombination, and charge transport. Besides offering comprehensive insights, this work represents an important stepping stone toward the development of MCSSCs by accomplishing a new PCE record of 3.8%.

Growth and characterization of InSb on (1 0 0) Si for mid-infrared application

NASA Astrophysics Data System (ADS)

Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt

2018-05-01

Monolithic integration of InSb on (1 0 0) Si is a practical approach to realizing on-chip mid-infrared photonic devices. An InSb layer was grown on a (1 0 0) Si substrate using an AlSb/GaSb buffer containing InSb quantum dots (QDs). The growth process for the buffer involved the growth of GaSb on Si using an interfacial misfit array, followed by InSb QDs on AlSb to decrease the density of microtwins. InSb layers were separately grown on AlSb and GaSb surfaces to compare the effect of different interfacial misfit arrays. The samples were characterized using transmission electron microscopy and X-ray diffraction to determine the structural properties of the buffer and InSb layers. The InSb on the AlSb sample exhibited higher crystal quality than the InSb on GaSb sample due to a more favorable arrangement of interfacial misfit dislocations. Hall measurements of unintentionally doped InSb layers demonstrated a higher carrier mobility in the InSb on the AlSb sample than in InSb on GaSb. Growing InSb on AlSb also improved the photoresponsivity of InSb as a photoconductor on Si.

Optically active polyurethane@indium tin oxide nanocomposite: Preparation, characterization and study of infrared emissivity

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

Yang, Yong; Zhou, Yuming, E-mail: ymzhou@seu.edu.cn; Ge, Jianhua

Highlights: ► Silane coupling agent of KH550 was used to connect the ITO and polyurethanes. ► Infrared emissivity values of the hybrids were compared and analyzed. ► Interfacial synergistic action and orderly secondary structure were the key factors. -- Abstract: Optically active polyurethane@indium tin oxide and racemic polyurethane@indium tin oxide nanocomposites (LPU@ITO and RPU@ITO) were prepared by grafting the organics onto the surfaces of modified ITO nanoparticles. LPU@ITO and RPU@ITO composites based on the chiral and racemic tyrosine were characterized by FT-IR, UV–vis spectroscopy, X-ray diffraction (XRD), SEM, TEM, and thermogravimetric analysis (TGA), and the infrared emissivity values (8–14 μm)more » were investigated in addition. The results indicated that the polyurethanes had been successfully grafted onto the surfaces of ITO without destroying the crystalline structure. Both composites possessed the lower infrared emissivity values than the bare ITO nanoparticles, which indicated that the interfacial interaction had great effect on the infrared emissivity. Furthermore, LPU@ITO based on the optically active polyurethane had the virtue of regular secondary structure and more interfacial synergistic actions between organics and inorganics, thus it exhibited lower infrared emissivity value than RPU@ITO based on the racemic polyurethane.« less

A Study of Influencing Factors on the Tensile Response of a Titanium Matrix Composite With Weak Interfacial Bonding

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Arnold, Steven M.

2000-01-01

The generalized method of cells micromechanics model is utilized to analyze the tensile stress-strain response of a representative titanium matrix composite with weak interfacial bonding. The fiber/matrix interface is modeled through application of a displacement discontinuity between the fiber and matrix once a critical debonding stress has been exceeded. Unidirectional composites with loading parallel and perpendicular to the fibers are examined, as well as a cross-ply laminate. For each of the laminates studied, analytically obtained results are compared to experimental data. The application of residual stresses through a cool-down process was found to have a significant effect on the tensile response. For the unidirectional laminate with loading applied perpendicular to the fibers, fiber packing and fiber shape were shown to have a significant effect on the predicted tensile response. Furthermore, the interface was characterized through the use of semi-emperical parameters including an interfacial compliance and a "debond stress;" defined as the stress level across the interface which activates fiber/matrix debonding. The results in this paper demonstrate that if architectural factors are correctly accounted for and the interface is appropriately characterized, the macro-level composite behavior can be correctly predicted without modifying any of the fiber or matrix constituent properties.

Arresting dissolution by interfacial rheology design

PubMed Central

Beltramo, Peter J.; Gupta, Manish; Alicke, Alexandra; Liascukiene, Irma; Gunes, Deniz Z.; Baroud, Charles N.

2017-01-01

A strategy to halt dissolution of particle-coated air bubbles in water based on interfacial rheology design is presented. Whereas previously a dense monolayer was believed to be required for such an “armored bubble” to resist dissolution, in fact engineering a 2D yield stress interface suffices to achieve such performance at submonolayer particle coverages. We use a suite of interfacial rheology techniques to characterize spherical and ellipsoidal particles at an air–water interface as a function of surface coverage. Bubbles with varying particle coverages are made and their resistance to dissolution evaluated using a microfluidic technique. Whereas a bare bubble only has a single pressure at which a given radius is stable, we find a range of pressures over which bubble dissolution is arrested for armored bubbles. The link between interfacial rheology and macroscopic dissolution of ∼ 100 μm bubbles coated with ∼ 1 μm particles is presented and discussed. The generic design rationale is confirmed by using nonspherical particles, which develop significant yield stress at even lower surface coverages. Hence, it can be applied to successfully inhibit Ostwald ripening in a multitude of foam and emulsion applications. PMID:28893993

Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites

NASA Technical Reports Server (NTRS)

Asthana, R.; Tiwari, R.; Tewari, S. N.

1995-01-01

Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

An algorithm for simulating fracture of cohesive-frictional materials

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

Nukala, Phani K; Sampath, Rahul S; Barai, Pallab

Fracture of disordered frictional granular materials is dominated by interfacial failure response that is characterized by de-cohesion followed by frictional sliding response. To capture such an interfacial failure response, we introduce a cohesive-friction random fuse model (CFRFM), wherein the cohesive response of the interface is represented by a linear stress-strain response until a failure threshold, which is then followed by a constant response at a threshold lower than the initial failure threshold to represent the interfacial frictional sliding mechanism. This paper presents an efficient algorithm for simulating fracture of such disordered frictional granular materials using the CFRFM. We note that,more » when applied to perfectly plastic disordered materials, our algorithm is both theoretically and numerically equivalent to the traditional tangent algorithm (Roux and Hansen 1992 J. Physique II 2 1007) used for such simulations. However, the algorithm is general and is capable of modeling discontinuous interfacial response. Our numerical simulations using the algorithm indicate that the local and global roughness exponents ({zeta}{sub loc} and {zeta}, respectively) of the fracture surface are equal to each other, and the two-dimensional crack roughness exponent is estimated to be {zeta}{sub loc} = {zeta} = 0.69 {+-} 0.03.« less

Experimental metrology to obtain thermal phonon transmission coefficients at solid interfaces

NASA Astrophysics Data System (ADS)

Hua, Chengyun; Chen, Xiangwen; Ravichandran, Navaneetha K.; Minnich, Austin J.

2017-05-01

Interfaces play an essential role in phonon-mediated heat conduction in solids, impacting applications ranging from thermoelectric waste heat recovery to heat dissipation in electronics. From the microscopic perspective, interfacial phonon transport is described by transmission coefficients that link vibrational modes in the materials composing the interface. However, direct experimental determination of these coefficients is challenging because most experiments provide a mode-averaged interface conductance that obscures the microscopic detail. Here, we report a metrology to extract thermal phonon transmission coefficients at solid interfaces using ab initio phonon transport modeling and a thermal characterization technique, time-domain thermoreflectance. In combination with transmission electron microscopy characterization of the interface, our approach allows us to link the atomic structure of an interface to the spectral content of the heat crossing it. Our work provides a useful perspective on the microscopic processes governing interfacial heat conduction.

Experimental metrology to obtain thermal phonon transmission coefficients at solid interfaces

DOE PAGES

Hua, Chengyun; Chen, Xiangwen; Ravichandran, Navaneetha K.; ...

2017-05-17

Interfaces play an essential role in phonon-mediated heat conduction in solids, impacting applications ranging from thermoelectric waste heat recovery to heat dissipation in electronics. From the microscopic perspective, interfacial phonon transport is described by transmission coefficients that link vibrational modes in the materials composing the interface. But, direct experimental determination of these coefficients is challenging because most experiments provide a mode-averaged interface conductance that obscures the microscopic detail. Here, we report a metrology to extract thermal phonon transmission coefficients at solid interfaces using ab initio phonon transport modeling and a thermal characterization technique, time-domain thermoreflectance. In combination with transmission electronmore » microscopy characterization of the interface, our approach allows us to link the atomic structure of an interface to the spectral content of the heat crossing it. This work provides a useful perspective on the microscopic processes governing interfacial heat conduction.« less

[In Situ Polymerization and Characterization of Hydroxyapatite/polyurethane Implanted Material].

PubMed

Gu, Muqing; Xiao, Fengjuan; Liang, Ye; Yue, Lin; Li, Song; Li, Lanlan; Feng, Feifei

2015-08-01

In order to improve the interfacial bonding strength of hydroxyapatite/polyurethane implanted material and dispersion of hydroxyapatite in the polyurethane matrix, we in the present study synthesized nano-hydroxyapatite/polyurethane composites by in situ polymerization. We then characterized and analyzed the fracture morphology, thermal stability, glass transition temperature and mechanical properties. We seeded MG63 cells on composites to evaluate the cytocompatibility of the composites. In situ polymerization could improve the interfacial bonding strength, ameliorate dispersion of hydroxyapatite in the properties of the composites. After adding 20 wt% hydroxyapatite into the polyurethane, the thermal stability was improved and the glass transition temperatures were increased. The tensile strength and maximum elongation were 6.83 MPa and 861.17%, respectively. Compared with those of pure polyurethane the tensile strength and maximum elongation increased by 236.45% and 143.30%, respectively. The composites were helpful for cell adhesion and proliferation in cultivation.

Shear Strength and Interfacial Toughness Characterization of Sapphire-Epoxy Interfaces for Nacre-Inspired Composites.

PubMed

Behr, Sebastian; Jungblut, Laura; Swain, Michael V; Schneider, Gerold A

2016-10-12

The common tensile lap-shear test for adhesive joints is inappropriate for brittle substrates such as glasses or ceramics where stress intensifications due to clamping and additional bending moments invalidate results. Nevertheless, bonding of glasses and ceramics is still important in display applications for electronics, in safety glass and ballistic armor, for dental braces and restoratives, or in recently developed bioinspired composites. To mechanically characterize adhesive bondings in these fields nonetheless, a novel approach based on the so-called Schwickerath test for dental sintered joints is used. This new method not only matches data from conventional analysis but also uniquely combines the accurate determination of interfacial shear strength and toughness in one simple test. The approach is verified for sapphire-epoxy joints that are of interest for bioinspired composites. For these, the procedure not only provides quantitative interfacial properties for the first time, it also exemplarily suggests annealing of sapphire at 1000 °C for 10 h for mechanically and economically effective improvements of the interfacial bond strength and toughness. With increases of strength and toughness from approximately 8 to 29 MPa and from 2.6 to 35 J/m 2 , respectively, this thermal modification drastically enhances the properties of unmodified sapphire-epoxy interfaces. At the same time, it is much more convenient than wet-chemical approaches such as silanization. Hence, besides the introduction of a new testing procedure for adhesive joints of brittle or expensive substrates, a new and facile annealing process for improvements of the adhesive properties of sapphire is suggested and quantitative data for the mechanical properties of sapphire-epoxy interfaces that are common in synthetic nacre-inspired composites are provided for the first time.

Interfacial Interaction between Transmembrane Ocular Mucins and Adhesive Polymers and Dendrimers Analyzed by Surface Plasmon Resonance

PubMed Central

Noiray, M.; Briand, E.; Woodward, A. M.; Argüeso, P.; Molina Martínez, I. T.; Herrero-Vanrell, R.; Ponchel, G.

2013-01-01

Purpose Development of the first in vitro method based on biosensor chip technology designed for probing the interfacial interaction phenomena between transmembrane ocular mucins and adhesive polymers and dendrimers intended for ophthalmic administration. Methods The surface plasmon resonance (SPR) technique was used. A transmembrane ocular mucin surface was prepared on the chip surface and characterized by QCM-D (Quartz Crystal Microbalance with Dissipation) and XPS (X-ray photoelectron spectroscopy). The mucoadhesive molecules tested were: hyaluronic acid (HA), carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose (HPMC), chitosan (Ch) and polyamidoamine dendrimers (PAMAM). Results While Ch originated interfacial interaction with ocular transmembrane mucins, for HA, CMC and HPMC, chain interdiffusion seemed to be mandatory for bioadherence at the concentrations used in ophthalmic clinical practise. Interestingly, PAMAM dendrimers developed permanent interfacial interactions with transmembrane ocular mucins whatever their surface chemical groups, showing a relevant importance of co-operative effect of these multivalent systems. Polymers developed interfacial interactions with ocular membrane-associated mucins in the following order: Ch(1 %) > G4PAMAM-NH2(2 %) = G4PAMAM-OH(2 %) > G3.5PAMAM-COOH(2 %)≫ CMC(0.5 %) = HA(0.2 %) = HPMC(0.3 %). Conclusions The method proposed is useful to discern between the mucin-polymer chemical interactions at molecular scale. Results reinforce the usefulness of chitosan and den-drimers as polymers able to increase the retention time of drugs on the ocular surface and hence their bioavailability. PMID:22565639

A combined molecular dynamics/micromechanics/finite element approach for multiscale constitutive modeling of nanocomposites with interface effects

NASA Astrophysics Data System (ADS)

Yang, B. J.; Shin, H.; Lee, H. K.; Kim, H.

2013-12-01

We introduce a multiscale framework based on molecular dynamic (MD) simulation, micromechanics, and finite element method (FEM). A micromechanical model, which considers influences of the interface properties, nanoparticle (NP) size, and microcracks, is developed. Then, we perform MD simulations to characterize the mechanical properties of the nanocomposite system (silica/nylon 6) with varying volume fraction and size of NPs. By comparing the MD with micromechanics results, intrinsic physical properties at interfacial region are derived. Finally, we implement the developed model in the FEM code with the derived interfacial parameters, and predict the mechanical behavior of the nanocomposite at the macroscopic scale.

Characterization and measurement of polymer wear

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Aron, P. R.

1984-01-01

Analytical tools which characterize the polymer wear process are discussed. The devices discussed include: visual observation of polymer wear with SEM, the quantification with surface profilometry and ellipsometry, to study the chemistry with AES, XPS and SIMS, to establish interfacial polymer orientation and accordingly bonding with QUARTIR, polymer state with Raman spectroscopy and stresses that develop in polymer films using a X-ray double crystal camera technique.

Influence of the side chain and substrate on polythiophene thin film surface, bulk, and buried interfacial structures.

PubMed

Xiao, Minyu; Jasensky, Joshua; Zhang, Xiaoxian; Li, Yaoxin; Pichan, Cayla; Lu, Xiaolin; Chen, Zhan

2016-08-10

The molecular structures of organic semiconducting thin films mediate the performance of various devices composed of such materials. To fully understand how the structures of organic semiconductors alter on substrates due to different polymer side chains and different interfacial interactions, thin films of two kinds of polythiophene derivatives with different side-chains, poly(3-hexylthiophene) (P3HT) and poly(3-potassium-6-hexanoate thiophene) (P3KHT), were deposited and compared on various surfaces. A combination of analytical tools was applied in this research: contact angle goniometry and X-ray photoelectron spectroscopy (XPS) were used to characterize substrate dielectric surfaces with varied hydrophobicity for polymer film deposition; X-ray diffraction and UV-vis spectroscopy were used to examine the polythiophene film bulk structure; sum frequency generation (SFG) vibrational spectroscopy was utilized to probe the molecular structures of polymer film surfaces in air and buried solid/solid interfaces. Both side-chain hydrophobicity and substrate hydrophobicity were found to mediate the crystallinity of the polythiophene film, as well as the orientation of the thiophene ring within the polymer backbone at the buried polymer/substrate interface and the polymer thin film surface in air. For the same type of polythiophene film deposited on different substrates, a more hydrophobic substrate surface induced thiophene ring alignment with the surface normal at both the buried interface and on the surface in air. For different films (P3HT vs. P3KHT) deposited on the same dielectric substrate, a more hydrophobic polythiophene side chain caused the thiophene ring to align more towards the surface at the buried polymer/substrate interface and on the surface in air. We believe that the polythiophene surface, bulk, and buried interfacial molecular structures all influence the hole mobility within the polythiophene film. Successful characterization of an organic conducting thin film surface, buried interfacial, and bulk structures is a first crucial step in understanding the structure-function relationship of such films in order to optimize device performance. An in-depth understanding on how the side-chain influences the interfacial and surface polymer orientation will guide the future molecular structure design of organic semiconductors.

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

NASA Astrophysics Data System (ADS)

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

2012-06-01

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

Characterization of Surface Modification of Polyethersulfone Membrane

USDA-ARS?s Scientific Manuscript database

Surface modification of polyethersulfone (PES) membrane surface using UV/ozone-treated grafting and interfacial polymerization on membrane surface was investigated in order to improve the resistance of membrane surface to protein adsorption. These methods of surface modification were compared in te...

Characterization of interfacial waves in horizontal core-annular flow

NASA Astrophysics Data System (ADS)

Tripathi, Sumit; Bhattacharya, Amitabh; Singh, Ramesh; Tabor, Rico F.

2016-11-01

In this work, we characterize interfacial waves in horizontal core annular flow (CAF) of fuel-oil and water. Experimental studies on CAF were performed in an acrylic pipe of 15.5mm internal diameter, and the time evolution of the oil-water interface shape was recorded with a high speed camera for a range of different flow-rates of oil (Qo) and water (Qw). The power spectrum of the interface shape shows a range of notable features. First, there is negligible energy in wavenumbers larger than 2 π / a , where a is the thickness of the annulus. Second, for high Qo /Qw , there is no single dominant wavelength, as the flow in the confined annulus does not allow formation of a preferred mode. Third, for lower Qo /Qw , a dominant mode arises at a wavenumber of 2 π / a . We also observe that the power spectrum of the interface shape depends weakly on Qw, and strongly on Qo, perhaps because the net shear rate in the annulus appears to depend weakly on Qw as well. We also attempt to build a general empirical model for CAF by relating the interfacial stress (calculated via the mean pressure gradient) to the flow rate in the annulus, the annular thickness and the core velocity. Authors are thankful to Orica Mining Services (Australia) for the financial support.

Forward-bias diode parameters, electronic noise, and photoresponse of graphene/silicon Schottky junctions with an interfacial native oxide layer

NASA Astrophysics Data System (ADS)

An, Yanbin; Behnam, Ashkan; Pop, Eric; Bosman, Gijs; Ural, Ant

2015-09-01

Metal-semiconductor Schottky junction devices composed of chemical vapor deposition grown monolayer graphene on p-type silicon substrates are fabricated and characterized. Important diode parameters, such as the Schottky barrier height, ideality factor, and series resistance, are extracted from forward bias current-voltage characteristics using a previously established method modified to take into account the interfacial native oxide layer present at the graphene/silicon junction. It is found that the ideality factor can be substantially increased by the presence of the interfacial oxide layer. Furthermore, low frequency noise of graphene/silicon Schottky junctions under both forward and reverse bias is characterized. The noise is found to be 1/f dominated and the shot noise contribution is found to be negligible. The dependence of the 1/f noise on the forward and reverse current is also investigated. Finally, the photoresponse of graphene/silicon Schottky junctions is studied. The devices exhibit a peak responsivity of around 0.13 A/W and an external quantum efficiency higher than 25%. From the photoresponse and noise measurements, the bandwidth is extracted to be ˜1 kHz and the normalized detectivity is calculated to be 1.2 ×109 cm Hz1/2 W-1. These results provide important insights for the future integration of graphene with silicon device technology.

Enhancing Efficiency of Perovskite Solar Cells via Surface Passivation with Graphene Oxide Interlayer.

PubMed

Li, Hao; Tao, Leiming; Huang, Feihong; Sun, Qiang; Zhao, Xiaojuan; Han, Junbo; Shen, Yan; Wang, Mingkui

2017-11-08

Perovskite solar cells have been demonstrated as promising low-cost and highly efficient next-generation solar cells. Enhancing V OC by minimization the interfacial recombination kinetics can further improve device performance. In this work, we for the first time reported on surface passivation of perovskite layers with chemical modified graphene oxides, which act as efficient interlayer to reduce interfacial recombination and enhance hole extraction as well. Our modeling points out that the passivation effect mainly comes from the interaction between functional group (4-fluorophenyl) and under-coordinated Pb ions. The resulting perovskite solar cells achieved high efficient power conversion efficiency of 18.75% with enhanced high open circuit V OC of 1.11 V. Ultrafast spectroscopy, photovoltage/photocurrent transient decay, and electronic impedance spectroscopy characterizations reveal the effective passivation effect and the energy loss mechanism. This work sheds light on the importance of interfacial engineering on the surface of perovskite layers and provides possible ways to improve device efficiency.

Formation of periodic interfacial misfit dislocation array at the InSb/GaAs interface via surface anion exchange

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

Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai

The relationship between growth temperature and the formation of periodic interfacial misfit (IMF) dislocations via the anion exchange process in InSb/GaAs heteroepitaxy was systematically investigated. The microstructural and electrical properties of the epitaxial layer were characterized using atomic force microscope, high-resolution x-ray diffraction, transmission electron microscopy, and Hall resistance measurement. The formation of interfacial misfit (IMF) dislocation arrays depended on growth temperature. A uniformly distributed IMF array was found in a sample grown at 310 °C, which also exhibited the lowest threading dislocation density. The analysis suggested that an incomplete As-for-Sb anion exchange process impeded the formation of IMF on samplemore » grown above 310 °C. At growth temperature below 310 °C, island coalescence led to the formation of 60° dislocations and the disruption of periodic IMF array. All samples showed higher electron mobility at 300 K than at 77 K.« less

Effects of bulk and free surface shear flows on amyloid fibril formation

NASA Astrophysics Data System (ADS)

Posada, David; Sorci, Mirco; Belfort, Georges; Hirsa, Amir

2008-11-01

Amyloid diseases such as Alzheimer's and Huntington's, among others, are characterized by the conversion of monomers to oligomers (precursors) and then to amyloid fibrils. Besides factors such as concentration, pH, and ionic strength, evidence exists that shearing flow strongly influences amyloid formation in vitro. Also, during fibrillation in the presence of either gas or solid surfaces, both the polarity and roughness of the surfaces play a significant role in the kinetics of the fibrillation process. By studying the nucleation and growth of a model system (insulin fibrils) in a well-defined flow field, we can identify the flow and interfacial conditions that impact protein aggregation kinetics. The present flow system consists of an annular region, bounded by stationary inner and outer cylinders and driven by rotation of the floor, with either a hydrophobic (air) or hydrophilic (solid) interface. We show both the combined and separated effects of shear and interfacial hydrophobicity on the fibrillation process, and the use of interfacial shear viscosity as a parameter for quantifying the oligomerization process.

Root Cause Investigation of Lead-Free Solder Joint Interfacial Failures After Multiple Reflows

NASA Astrophysics Data System (ADS)

Li, Yan; Hatch, Olen; Liu, Pilin; Goyal, Deepak

2017-03-01

Solder joint interconnects in three-dimensional (3D) packages with package stacking configurations typically must undergo multiple reflow cycles during the assembly process. In this work, interfacial open joint failures between the bulk solder and the intermetallic compound (IMC) layer were found in Sn-Ag-Cu (SAC) solder joints connecting a small package to a large package after multiple reflow reliability tests. Systematic progressive 3D x-ray computed tomography experiments were performed on both incoming and assembled parts to reveal the initiation and evolution of the open failures in the same solder joints before and after the reliability tests. Characterization studies, including focused ion beam cross-sections, scanning electron microscopy, and energy-dispersive x-ray spectroscopy, were conducted to determine the correlation between IMC phase transformation and failure initiation in the solder joints. A comprehensive failure mechanism, along with solution paths for the solder joint interfacial failures after multiple reflow cycles, is discussed in detail.

Preparation of carbon fiber unsaturated sizing agent for enhancing interfacial strength of carbon fiber/vinyl ester resin composite

NASA Astrophysics Data System (ADS)

Jiao, Weiwei; Cai, Yemeng; Liu, Wenbo; Yang, Fan; Jiang, Long; Jiao, Weicheng; Wang, Rongguo

2018-05-01

The practical application of carbon fiber (CF) reinforced vinyl ester resin (VE) composite was hampered seriously by the poor interfacial adhesion property. In this work, a novel unsaturated sizing agent was designed and prepared to improve the interfacial strength by covalently bonding CF with VE matrix. The main component of the sizing agent, N-(4‧4-diaminodiphenyl methane)-2-hydroxypropyl methacrylate (DMHM), was synthesized and confirmed by FTIR and NMR. XPS results of sized carbon fiber (SCF) showed that DMHM has adhered to desized fiber surface and reacted with some active functional groups on the surface. The SCF was characterized by high surface roughness and surface energy (especially the polar component), which means better wettability by VE. As a result, the interface shear strength and interlaminar shear strength of SCF/VE composite were enhanced by 96.56% and 66.07% respectively compared with CF/VE composite, benefited mainly from the strong and tough interphase.

Electrochemical Grafting of Graphene Nano Platelets with Aryl Diazonium Salts.

PubMed

Qiu, Zhipeng; Yu, Jun; Yan, Peng; Wang, Zhijie; Wan, Qijin; Yang, Nianjun

2016-10-26

To vary interfacial properties, electrochemical grafting of graphene nano platelets (GNP) with 3,5-dichlorophenyl diazonium tetrafluoroborate (aryl-Cl) and 4-nitrobenzene diazonium tetrafluoroborate (aryl-NO 2 ) was realized in a potentiodynamic mode. The covalently bonded aryl layers on GNP were characterized using atomic force microscopy and X-ray photoelectron spectroscopy. Electrochemical conversion of aryl-NO 2 into aryl-NH 2 was conducted. The voltammetric and impedance behavior of negatively and positively charged redox probes (Fe(CN) 6 3-/4- and Ru(NH 3 ) 6 2+/3+ ) on three kinds of aryl layers grafted on GNP reveal that their interfacial properties are determined by the charge states of redox probes and reactive terminal groups (-Cl, -NO 2 , -NH 2 ) in aryl layers. On aryl-Cl and aryl-NH 2 garted GNP, selective and sensitive monitoring of positively charged lead ions as well as negatively charged nitrite and sulfite ions was achieved, respectively. Such a grafting procedure is thus a perfect way to design and control interfacial properties of graphene.

From coherent to incoherent mismatched interfaces: A generalized continuum formulation of surface stresses

NASA Astrophysics Data System (ADS)

Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

2014-12-01

The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. The coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent and incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.

From coherent to incoherent mismatched interfaces. A generalized continuum formulation of surface stresses

DOE PAGES

Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

2014-08-19

The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. Additionally, the coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent andmore » incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu 2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.« less

Interfacial adsorption and surfactant release characteristics of magnetically functionalized halloysite nanotubes for responsive emulsions.

PubMed

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

2016-02-01

Magnetically responsive oil-in-water emulsions are effectively stabilized by a halloysite nanotube supported superparamagnetic iron oxide nanoparticle system. The attachment of the magnetically functionalized halloysite nanotubes at the oil-water interface imparts magnetic responsiveness to the emulsion and provides a steric barrier to droplet coalescence leading to emulsions that are stabilized for extended periods. Interfacial structure characterization by cryogenic scanning electron microscopy reveals that the nanotubes attach at the oil-water interface in a side on-orientation. The tubular structure of the nanotubes is exploited for the encapsulation and release of surfactant species that are typical of oil spill dispersants such as dioctyl sulfosuccinate sodium salt and polyoxyethylene (20) sorbitan monooleate. The magnetically responsive halloysite nanotubes anchor to the oil-water interface stabilizing the interface and releasing the surfactants resulting in reduction in the oil-water interfacial tension. The synergistic adsorption of the nanotubes and the released surfactants at the oil-water interface results in oil emulsification into very small droplets (less than 20μm). The synergy of the unique nanotubular morphology and interfacial activity of halloysite with the magnetic properties of iron oxide nanoparticles has potential applications in oil spill dispersion, magnetic mobilization and detection using magnetic fields. Copyright © 2015 Elsevier Inc. All rights reserved.

Characterization of surface active materials derived from farm products

USDA-ARS?s Scientific Manuscript database

Surface active materials obtained by chemical modification of plant protein isolates (lupin, barley, oat), corn starches (dextrin, normal, high amylose, and waxy) and soybean oil (soybean oil based polysoaps, SOPS) were investigated for their surface and interfacial properties using axisymmetric dro...

Preparation, characterization, and infrared emissivity property of optically active polyurethane/TiO{sub 2}/SiO{sub 2} multilayered microspheres

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

Yang Yong; Zhou Yuming, E-mail: ymzhou@seu.edu.cn; Ge Jianhua

Optically active polyurethane/titania/silica (LPU/TiO{sub 2}/SiO{sub 2}) multilayered core-shell composite microspheres were prepared by the combination of titania deposition on the surface of silica spheres and subsequent polymer grafting. LPU/TiO{sub 2}/SiO{sub 2} was characterized by FT-IR, UV-vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), SEM and TEM, and the infrared emissivity value (8-14 {mu}m) was investigated in addition. The results indicated that titania and polyurethane had been successfully coated onto the surfaces of silica microspheres. LPU/TiO{sub 2}/SiO{sub 2} exhibited clearly multilayered core-shell construction. The infrared emissivity values reduced along with the increase of covering layers thus provedmore » that the interfacial interactions had direct influence on the infrared emissivity. Besides, LPU/TiO{sub 2}/SiO{sub 2} multilayered microspheres based on the optically active polyurethane took advantages of the orderly secondary structure and strengthened interfacial synergistic actions. Consequently, it possessed the lowest infrared emissivity value. - Graphical Abstract: Optically active polyurethane/titania/silica (LPU/TiO{sub 2}/SiO{sub 2}) multilayered core-shell composite microspheres were prepared by the combination of titania deposition on the surface of silica spheres and subsequent polymer grafting. Highlights: > Optically active polyurethane based on tyrosine was used for the modification of nanoparticles. > LPU/TiO{sub 2}/SiO{sub 2} multilayered core-shell microspheres were prepared and characterized. > Interfacial interactions and secondary structure affected the infrared emissivity of composite.« less

The effect of bioadhesive on the interfacial compatibility and pervaporation performance of composite membranes by MD and GCMC simulation.

PubMed

Wang, Baohe; Nie, Yan; Ma, Jing

2018-03-01

Combing molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulation, the effect of bioadhesive transition layer on the interfacial compatibility of the pervaporation composite membranes, and the pervaporation performance toward penetrant molecules were investigated. In our previous experimental study, the structural stability and permeability selectivity of the composite membranes were considerably enhanced by the introduction of bioadhesive carbopol (CP). In the present study, the interfacial compatibility and the interfacial energies between the chitosan (CS) separation layer, CP transition layer and the support layer were investigated, respectively. The mobility of polymer chains, free volume in bulk and interface regions were evaluated by the mean-square displacement (MSD) and free volume voids (FFV) analysis. The diffusion and sorption behavior of water/ethanol molecules in bulk and interface regions were characterized. The simulation results of membrane structure have good consistency, indicating that the introduction of CP transition layer improved the interfacial compatibility and interaction between the separation layer and the support layer. Comparing the bulk region of the separation layer, the mobility and free volume of the polymer chain in the interface region decreased and thus reduced the swelling of CS active layer, revealing the increased diffusion selectivity toward the permeated water and ethanol molecules. The strong hydrogen bonds interaction between the COOH of the CP transition layer and water molecules increased the adsorption of water molecules in the interface region. The simulation results were quite consistent with the experimental results. Copyright © 2018 Elsevier Inc. All rights reserved.

The influence of interfacial slip on two-phase flow in rough pores

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

Kucala, Alec; Martinez, Mario J.; Wang, Yifeng

The migration and trapping of supercritical CO 2 (scCO 2) in geologic carbon storage is strongly dependent on the geometry and wettability of the pore network in the reservoir rock. During displacement, resident fluids may become trapped in the pits of a rough pore surface forming an immiscible two-phase fluid interface with the invading fluid, allowing apparent slip flow at this interface. We present a two-phase fluid dynamics model, including interfacial tension, to characterize the impact of mineral surface roughness on this slip flow. We show that the slip flow can be cast in more familiar terms as a contact-anglemore » (wettability)-dependent effective permeability to the invading fluid, a nondimensional measurement which relates the interfacial slip to the pore geometry. The analysis shows the surface roughness-induced slip flow can effectively increase or decrease this effective permeability, depending on the wettability and roughness of the mineral surfaces. Configurations of the pore geometry where interfacial slip has a tangible influence on permeability have been identified. The results suggest that for large roughness features, permeability to CO 2 may be enhanced by approximately 30% during drainage, while the permeability to brine during reimbibition may be enhanced or diminished by 60%, depending on the contact angle with the mineral surfaces and degrees of roughness. For smaller roughness features, the changes in permeability through interfacial slip are small. As a result, a much larger range of effective permeabilities are suggested for general fluid pairs and contact angles, including occlusion of the pore by the trapped phase.« less

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

PubMed

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

2011-05-17

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

The influence of interfacial slip on two-phase flow in rough pores

DOE PAGES

Kucala, Alec; Martinez, Mario J.; Wang, Yifeng; ...

2017-08-01

The migration and trapping of supercritical CO 2 (scCO 2) in geologic carbon storage is strongly dependent on the geometry and wettability of the pore network in the reservoir rock. During displacement, resident fluids may become trapped in the pits of a rough pore surface forming an immiscible two-phase fluid interface with the invading fluid, allowing apparent slip flow at this interface. We present a two-phase fluid dynamics model, including interfacial tension, to characterize the impact of mineral surface roughness on this slip flow. We show that the slip flow can be cast in more familiar terms as a contact-anglemore » (wettability)-dependent effective permeability to the invading fluid, a nondimensional measurement which relates the interfacial slip to the pore geometry. The analysis shows the surface roughness-induced slip flow can effectively increase or decrease this effective permeability, depending on the wettability and roughness of the mineral surfaces. Configurations of the pore geometry where interfacial slip has a tangible influence on permeability have been identified. The results suggest that for large roughness features, permeability to CO 2 may be enhanced by approximately 30% during drainage, while the permeability to brine during reimbibition may be enhanced or diminished by 60%, depending on the contact angle with the mineral surfaces and degrees of roughness. For smaller roughness features, the changes in permeability through interfacial slip are small. As a result, a much larger range of effective permeabilities are suggested for general fluid pairs and contact angles, including occlusion of the pore by the trapped phase.« less

The influence of interfacial slip on two-phase flow in rough pores

NASA Astrophysics Data System (ADS)

Kucala, Alec; Martinez, Mario J.; Wang, Yifeng; Noble, David R.

2017-08-01

The migration and trapping of supercritical CO2 (scCO2) in geologic carbon storage is strongly dependent on the geometry and wettability of the pore network in the reservoir rock. During displacement, resident fluids may become trapped in the pits of a rough pore surface forming an immiscible two-phase fluid interface with the invading fluid, allowing apparent slip flow at this interface. We present a two-phase fluid dynamics model, including interfacial tension, to characterize the impact of mineral surface roughness on this slip flow. We show that the slip flow can be cast in more familiar terms as a contact-angle (wettability)-dependent effective permeability to the invading fluid, a nondimensional measurement which relates the interfacial slip to the pore geometry. The analysis shows the surface roughness-induced slip flow can effectively increase or decrease this effective permeability, depending on the wettability and roughness of the mineral surfaces. Configurations of the pore geometry where interfacial slip has a tangible influence on permeability have been identified. The results suggest that for large roughness features, permeability to CO2 may be enhanced by approximately 30% during drainage, while the permeability to brine during reimbibition may be enhanced or diminished by 60%, depending on the contact angle with the mineral surfaces and degrees of roughness. For smaller roughness features, the changes in permeability through interfacial slip are small. A much larger range of effective permeabilities are suggested for general fluid pairs and contact angles, including occlusion of the pore by the trapped phase.

Effect of 100 MeV Si7+ ions' irradiation on Pd/n-GaAs Schottky diodes

NASA Astrophysics Data System (ADS)

Sinha, O. P.

2017-12-01

Pd/n-GaAs realized devices (junction made on a virgin substrate prior to irradiation) and Pd/n-GaAs fabricated devices (junction realized after the virgin substrate irradiation) have been irradiated with 100 MeV Si7+ ions for the varying fluence of 1012-1013 ions/cm2. The devices have been characterized by I-V and C-V techniques for an electrical response. The electrical characterization of these devices shows the presence of interfacial layer. Moreover, the C-V characteristics show strong frequency dependence behavior, which indicates the involvement of interfacial charge layer with deep electron states. The hydrogenation of these devices has not caused any significant change in the electrical (I-V and C-V) characteristics. The observed results have been discussed in the realm of radiation-induced defects, which cause the carrier removal and compensation phenomena to cause the observed high resistivity and filling and unfilling of these traps' level to cause strong frequency dependence behavior.

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

NASA Technical Reports Server (NTRS)

Bachmann, Klaus J.

1995-01-01

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

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

McAdams, Brian J.; Pearson, Raymond A.

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 believedmore » 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-critical load levels. The results display an interfacial strength ranking similar to that observed during monotonic testing. The fatigue results indicate that monotonic fracture mechanics testing may be an adequate screening tool to help predict cyclic underfill failure; however lifetime data is required to predict reliability.« less

Inducing Propulsion of Colloidal Dimers by Breaking the Symmetry in Electrohydrodynamic Flow.

PubMed

Ma, Fuduo; Yang, Xingfu; Zhao, Hui; Wu, Ning

2015-11-13

We show that dielectric colloidal dimers with broken symmetry in geometry, composition, or interfacial charges can all propel in directions that are perpendicular to the applied ac electric field. The asymmetry in particle properties ultimately results in an unbalanced electrohydrodynamic flow on two sides of the particles. Consistent with scaling laws, the propulsion direction, speed, and orientation of dimers can be conveniently tuned by frequency. The new propulsion mechanism revealed here is important for building colloidal motors and studying collective behavior of active matter.

Killing mediated spatial structure in V. Cholerae biofilms

NASA Astrophysics Data System (ADS)

Yanni, David

Most bacteria live in biofilms, which are implicated in 60 - 80 % of microbial infections in the body. The spatial structure of a biofilm confers advantages to its member-cells, such as antibiotic resistance, and is strongly affected by competition between strains and taxa. However, A complete picture of how competition affects the self-organized structure of these complex, far-from-equilibrium systems, is yet to emerge. To that end, we investigate phase separation dynamics driven by T6SS-facilitated bacterial warfare in a system composed of two strains of mutually antagonistic V. cholerae. T6SS is a contact mediated killing mechanism present in 25 % of all gram negative bacteria, and has been shown by recent work to play a major role in the spatial assortment of biofilms. T6SS events induce lysis, causing variations in local mechanical pressure, and acting as thermalizing events. We study cells immobilized in biofilms at the air-solid interface, so our experimental system represents a different type active matter, wherein activity is due to cell death and reproduction, not mobility. Here, we show how that activity imposes a constraint of minimal curvature on strain-strain interfaces; an effective Laplace pressure is characterized which governs interfacial dynamics.

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

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

The energetics of adhesion in composite materials

NASA Astrophysics Data System (ADS)

Harding, Philip Hiram

Composite materials are used throughout modern society, and often the most important parameter in determining their properties is the adhesion at material interfaces within the composite. A broad investigation is completed, the global objective of which is to develop understanding of the role of adhesion in composite materials. The scope of this study ranges from macroscopic effects of adhesion on filled polymer composites to microscopic adhesion measurements with engineered interfaces. The surface of a filler material is systematically modified and surface characterization techniques are used to quantify the influence of the surface treatments on surface energetics and wetting properties. Filled polymer composites are prepared and composite mechanical properties determined with beam deflection tests. Filler surface treatments significantly alter the composite yield stress for composites which fail interfacially and are observed to increase or decrease mechanical strength, depending on the chemical nature of the modification. Thermodynamic adhesion mechanisms active at the filler-matrix interfaces are then explored by making direct interfacial strength measurements whereby a single spherical particle is introduced into the polymeric matrix. Interfacial strength is determined by submitting the single-particle composite (SPC) to uni-axial tension and relating the macroscopic stress at interfacial failure to that experienced at the interface. The technique provides a measurement of interfacial strength between two elastic materials, one unaffected by frictional forces, viscoelasticity, and thermal stresses. The SPC measurements are used to verify proposed adhesion mechanisms at the various filler-polymer interfaces and establish the role of adhesion in the filled polymer composites. The SPC technique is then used to investigate the adhesion promotion mechanism of organofunctional silanes, which are shown to be controlled by the compatibility and penetration of the silane organofunctional group. The effects of thermal residual stresses on interfacial strength are also investigated using the SPC technique. Processing conditions, i.e., time-temperature profiles, are used to systematically vary the thermal residual stresses within the polymeric matrix. The interfaces studied are deleteriously affected by increases in thermal residual stresses.

Interface-Assisted Synthesis of 2D Materials: Trend and Challenges.

PubMed

Dong, Renhao; Zhang, Tao; Feng, Xinliang

2018-06-18

The discovery of graphene one decade ago has triggered enormous interest in developing two-dimensional materials (2DMs)-that is 2D allotropes of various elements or compounds (consisting of two or more covalently bonded elements) or molecular frameworks with periodic structures. At present, various synthesis strategies have been exploited to produce 2DMs, such as top-down exfoliation and bottom-up chemical vapor deposition and solution synthesis methods. In this review article, we will highlight the interfacial roles toward the controlled synthesis of inorganic and organic 2DMs with varied structural features. We will summarize the state-of-the-art progress on interfacial synthesis strategies and address their advancements in the structural, morphological, and crystalline control by the direction of the arrangement of the molecules or precursors at a confined 2D space. First, we will provide an overview of the interfaces and introduce their advantages and uniqueness for the synthesis of 2DMs, followed by a brief classification of inorganic and organic 2DMs achieved by interfacial synthesis. Next, the currently developed interfacial synthesis strategies combined with representative inorganic and organic 2DMs are summarized, including the description of method details, the corresponding structural features, and the insights into the advantages and limitations of the synthesis methods, along with some recommendable characterization methods for understanding the interfacial assembly of the precursors and crystal growth of 2DMs. After that, we will discuss several classes of emerging organic 2DMs with particular emphasis on the structural control by the interfacial synthesis strategies. Note that, inorganic 2DMs will not be categorized separately due to the fact that a number of review articles have covered the synthesis, structure, processing, and applications. Finally, the challenges and perspectives are provided regarding the future development of interface-assisted synthesis of 2DMs with diverse structural and functional control.

DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

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

X. Wang; X. Sun; H. Zhao

In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do notmore » exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in which flow regime transition occurs.« less

A novel broadband impedance method for detection of cell-derived microparticles

PubMed Central

Lvovich, Vadim; Srikanthan, Sowmya; Silverstein, Roy L.

2010-01-01

A novel label-free method is presented to detect and quantify cell-derived microparticles (MPs) by the electrochemical potential-modulated electrochemical impedance spectroscopy (EIS). MPs are present in elevated concentrations during pathological conditions and play a major role in the establishment and pathogenesis of many diseases. Considering this, accurate detection and quantification of MPs is very important in clinical diagnostics and therapeutics. A combination of bulk solution electrokinetic sorting and interfacial impedance responses allows achieving detection limits as low as several MPs per µL. By fitting resulting EIS spectra with an equivalent electrical circuit, the bulk solution electrokinetic and interfacial impedance responses were characterized. In the bulk solution two major relaxations were prominent - β-relaxation in low MHz region due to the MP capacitive membrane bridging, and α-relaxation at ∼ 10 kHz due to counter ions diffusion. At low frequencies (10-0.1 Hz) at electrochemical potentials exceeding −100 mV, a facile interfacial Faradaic process of oxidation in MPs coupled with diffusion and non Faradaic double layer charging dominate, probably due to oxidation of phospholipids and/or proteins on the MP surface and MP lysis. Buffer influence on the MP detection demonstrated that that a relatively low conductivity Tyrode’s buffer background solution is preferential for the MP electrokinetic separation and characterization. This study also demonstrated that standard laboratory methods such as flow cytometry underestimate MP concentrations, especially those with smaller average sizes, by as much as a factor of 2 to 40. PMID:20729061

Effects of physical and chemical aspects on membrane fouling and cleaning using interfacial free energy analysis in forward osmosis.

PubMed

Zhang, Wanzhu; Dong, Bingzhi

2018-05-20

Natural organic matter (NOM) in micro-polluted water purification using membranes is a critical issue to handle. Understanding the fouling mechanism in the forward osmosis (FO) process, particularly identifying the predominant factor that controls membrane fouling, could have significant effects on exerting the advantages of FO technique. Cellulose triacetate no-woven (CTA-NW) membrane is applied to experiments with a high removal efficiency (> 99%) for the model foulant. Tannic acid (TA) is used as a surrogate foulant for NOM in the membrane fouling process, thus enabling the analysis of the effects of physical and chemical aspects of water flux, retention, and adsorption. The membrane fouling behavior is affected mainly by the combined effects of the osmotic dragging force and the interaction of the pH in the working solution, foulants, and calcium ions, as demonstrated by the water flux loss and the changes of membrane retention and adsorption. The fouled CTA-NW membrane (in PRO mode) could be flux-recovered by > 85% through physical cleaning methods. The interfacial free energy analysis theory was used to analyze the membrane fouling behavior with calculating the interfacial cohesion and adhesion free energies. The cohesion free energy refers to the deposition of foulants (TA or TA combined with calcium ions) on a fouled membrane. In addition, the adhesion free energy could be used to evaluate the interaction between foulants and a clean membrane.

Impact of air exposure and surface chemistry on Li-Li 7La 3Zr 2O 12 interfacial resistance

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

Sharafi, Asma; Yu, Seungho; Naguib, Michael

Li 7La 3Zr 2O 12 (LLZO) is a promising solid-state electrolyte that could enable solid-state-batteries (SSB) employing metallic Li anodes. For a SSB to be viable, the stability and charge transfer kinetics at the Li–LLZO interface should foster facile plating and stripping of Li. Contrary to these goals, recent studies have reported high Li–LLZO interfacial resistance which was attributed to a contamination layer that forms upon exposure of LLZO to air. This study clarifies the mechanisms and consequences associated with air exposure of LLZO; additionally, strategies to minimize these effects are described. First-principles calculations reveal that LLZO readily reacts withmore » humid air; the most favorable reaction pathway involves protonation of LLZO and formation of Li2CO3. X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy were used to characterize the surface and subsurface chemistry of LLZO as a function of relative humidity and exposure time. Additionally, electrochemical impedance spectroscopy was used to measure the Li–LLZO interfacial resistance as a function of surface contamination. These data indicate that air exposure-induced contamination impacts the interfacial resistance significantly, when exposure time exceeds 24 h. The results of this study provide valuable insight into the sensitivity of LLZO to air and how the effects of air contamination can be reversed.« less

Stiffness, strength and adhesion characterization of electrochemically deposited conjugated polymer films

PubMed Central

Qu, Jing; Ouyang, Liangqi; Kuo, Chin-chen; Martin, David C.

2015-01-01

Conjugated polymers such as poly(3,4-ethylenedioxythiphene) (PEDOT) are of interest for a variety of applications including interfaces between electronic biomedical devices and living tissue. The mechanical properties, strength, and adhesion of these materials to solid substrates are all vital for long-term applications. We have been developing methods to quantify the mechanical properties of conjugated polymer thin films. In this study the stiffness, strength and the interfacial shear strength (adhesion) of electrochemically deposited PEDOT and PEDOT-co-1,3,5-tri[2-(3,4-ethylene dioxythienyl)]-benzene (EPh) were studied. The estimated Young’s modulus of the PEDOT films was 2.6 ± 1.4 GPa, and the strain to failure was around 2%. The tensile strength was measured to be 56 ± 27 MPa. The effective interfacial shear strength was estimated with a shear-lag model by measuring the crack spacing as a function of film thickness. For PEDOT on gold/palladium-coated hydrocarbon film substrates an interfacial shear strength of 0.7 ± 0.3 MPa was determined. The addition of 5 mole% of a tri-functional EDOT crosslinker (EPh) increased the tensile strength of the films to 283 ± 67 MPa, while the strain to failure remained about the same (2%). The effective interfacial shear strength was increased to 2.4 ± 0.6 MPa. PMID:26607768

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.

Interfacial ordering of thermotropic liquid crystals triggered by the secondary structures of oligopeptides.

PubMed

Wang, Xiaoguang; Yang, Pei; Mondiot, Frederic; Li, Yaoxin; Miller, Daniel S; Chen, Zhan; Abbott, Nicholas L

2015-12-07

We report that assemblies formed by eight oligopeptides at phospholipid-decorated interfaces of thermotropic liquid crystals (LCs) trigger changes in ordering of the LCs that are dependent on the secondary structures of the oligopeptides (as characterized in situ using infrared-visible sum-frequency spectroscopy).

SPRUCE Advanced Molecular Techniques Provide a Rigorous Method for Characterizing Organic Matter Quality in Complex Systems: Supporting Data

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

Wilson, Rachel M; Tfaily, Malak M

These data are provided in support of the Commentary, Advanced molecular techniques provide a rigorous method for characterizing organic matter quality in complex systems, Wilson and Tfaily (2018). Measurement results demonstrate that optical characterization of peatland dissolved organic matter (DOM) may not fully capture classically identified chemical characteristics and may, therefore, not be the best measure of organic matter quality.

Characterization of White Matter Injury in a Rat Model of Chronic Cerebral Hypoperfusion.

PubMed

Choi, Bo-Ryoung; Kim, Dong-Hee; Back, Dong Bin; Kang, Chung Hwan; Moon, Won-Jin; Han, Jung-Soo; Choi, Dong-Hee; Kwon, Kyoung Ja; Shin, Chan Young; Kim, Bo-Ram; Lee, Jongmin; Han, Seol-Heui; Kim, Hahn Young

2016-02-01

Chronic cerebral hypoperfusion can lead to ischemic white matter injury resulting in vascular dementia. To characterize white matter injury in vascular dementia, we investigated disintegration of diverse white matter components using a rat model of chronic cerebral hypoperfusion. Chronic cerebral hypoperfusion was modeled in Wistar rats by permanent occlusion of the bilateral common carotid arteries. We performed cognitive behavioral tests, including the water maze task, odor discrimination task, and novel object test; histological investigation of neuroinflammation, oligodendrocytes, myelin basic protein, and nodal or paranodal proteins at the nodes of Ranvier; and serial diffusion tensor imaging. Cilostazol was administered to protect against white matter injury. Diverse cognitive impairments were induced by chronic cerebral hypoperfusion. Disintegration of white matter was characterized by neuroinflammation, loss of oligodendrocytes, attenuation of myelin density, structural derangement at the nodes of Ranvier, and disintegration of white matter tracts. Cilostazol protected against cognitive impairments and white matter disintegration. White matter injury induced by chronic cerebral hypoperfusion can be characterized by disintegration of diverse white matter components. Cilostazol might be a therapeutic strategy against white matter disintegration in patients with vascular dementia. © 2015 American Heart Association, Inc.

Suppressing interfacial water signals to assist the peak assignment of the N⁺-H stretching mode in sum frequency generation vibrational spectroscopy.

PubMed

Nguyen, Khoi Tan; Nguyen, Anh V

2015-11-21

Amines are one of the common functional groups of interest due to their abundant presence in natural proteins, surfactants and other chemicals. However, their accurate spectral assignment of vibrational modes, critical to interpreting SFG signals for characterizing various bio-interfaces such as protein-membrane interaction and surfactant adsorption, still remains elusive. Herein we present a systematic study to identify and justify the correct peak assignment of the N(+)-H stretching mode at the air-water interface. We used three special surfactants: hexadecylamine (a primary amine without counterions), dodecylamine hydrochloride (a primary amine with counterions) and hexadecyltrimethylammonium bromide as a control (the N(+)-H stretching mode is absent in this quarternary amine). We suppressed the SFG interfacial water signals using saturated NaCl solutions. Our designed experiments resolved the current controversy and concluded that the 3080 cm(-1) peak is from the N(+)-H vibrations, while the 3330 cm(-1) peak is not due to ammonium species but rather originates from the interfacial water vibrational modes or the backbone amide modes.

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

NASA Astrophysics Data System (ADS)

Zhu, Shuihan

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

Fabrication of metal nanoelectrodes by interfacial reactions.

PubMed

Zhu, Xinyu; Qiao, Yonghui; Zhang, Xin; Zhang, Sensen; Yin, Xiaohong; Gu, Jing; Chen, Ye; Zhu, Zhiwei; Li, Meixian; Shao, Yuanhua

2014-07-15

Despite great improvements in the past decades, the controllable fabrication of metal nanoelectrodes still remains very challenging. In this work, a simple and general way to fabricate metal nanoelectrodes (Ag, Au, and Pt) is developed. On the basis of interfacial reactions at nano-liquid/liquid interfaces supported at nanopipettes, the nanoparticles can be formed in situ and have been used to block the orifices of pipettes to make nanoelectrodes. The effect of the driving force for interfacial reaction at the liquid/liquid interface, the ratio of redox species in organic and aqueous phases, and the surface charge of the inner wall of a pipette have been studied. The fabricated nanoelectrodes have been characterized by scanning electron microscopy (SEM) and electrochemical techniques. A silver electrode with about 10 nm in radius has been employed as the scanning electrochemical microscopy (SECM) probe to explore the thickness of a water/nitrobenzene (W/NB) interface, and this value is equal to 0.8 ± 0.1 nm (n = 5). This method of fabrication of nanoelectrodes can be extended to other metal or semiconductor electrodes.

Measuring Interlayer Shear Stress in Bilayer Graphene

NASA Astrophysics Data System (ADS)

Wang, Guorui; Dai, Zhaohe; Wang, Yanlei; Tan, PingHeng; Liu, Luqi; Xu, Zhiping; Wei, Yueguang; Huang, Rui; Zhang, Zhong

2017-07-01

Monolayer two-dimensional (2D) crystals exhibit a host of intriguing properties, but the most exciting applications may come from stacking them into multilayer structures. Interlayer and interfacial shear interactions could play a crucial role in the performance and reliability of these applications, but little is known about the key parameters controlling shear deformation across the layers and interfaces between 2D materials. Herein, we report the first measurement of the interlayer shear stress of bilayer graphene based on pressurized microscale bubble loading devices. We demonstrate continuous growth of an interlayer shear zone outside the bubble edge and extract an interlayer shear stress of 40 kPa based on a membrane analysis for bilayer graphene bubbles. Meanwhile, a much higher interfacial shear stress of 1.64 MPa was determined for monolayer graphene on a silicon oxide substrate. Our results not only provide insights into the interfacial shear responses of the thinnest structures possible, but also establish an experimental method for characterizing the fundamental interlayer shear properties of the emerging 2D materials for potential applications in multilayer systems.

Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Yang, H. F.; Liu, Z. T.; Fan, C. C.; Yao, Q.; Xiang, P.; Zhang, K. L.; Li, M. Y.; Liu, J. S.; Shen, D. W.

2016-08-01

By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001)- and (111)-orientated polar LaNiO3 thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO3 and iso-polarity LaAlO3 substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. For largely polar (111)-orientated films, we showed that iso-polarity LaAlO3 (111) substrate was more suitable than Nb-doped SrTiO3. In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO3 based superlattices.

Engineering High-Energy Interfacial Structures for High-Performance Oxygen-Involving Electrocatalysis.

PubMed

Guo, Chunxian; Zheng, Yao; Ran, Jingrun; Xie, Fangxi; Jaroniec, Mietek; Qiao, Shi-Zhang

2017-07-10

Engineering high-energy interfacial structures for high-performance electrocatalysis is achieved by chemical coupling of active CoO nanoclusters and high-index facet Mn 3 O 4 nano-octahedrons (hi-Mn 3 O 4 ). A thorough characterization, including synchrotron-based near edge X-ray absorption fine structure, reveals that strong interactions between both components promote the formation of high-energy interfacial Mn-O-Co species and high oxidation state CoO, from which electrons are drawn by Mn III -O present in hi-Mn 3 O 4 . The CoO/hi-Mn 3 O 4 demonstrates an excellent catalytic performance over the conventional metal oxide-based electrocatalysts, which is reflected by 1.2 times higher oxygen evolution reaction (OER) activity than that of Ru/C and a comparable oxygen reduction reaction (ORR) activity to that of Pt/C as well as a better stability than that of Ru/C (95 % vs. 81 % retained OER activity) and Pt/C (92 % vs. 78 % retained ORR activity after 10 h running) in alkaline electrolyte. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Technical Reports Server (NTRS)

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

1997-01-01

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

Microstructure-dependent fracture toughness (JIC) variations in dissimilar pipe welds for pressure vessel system of nuclear plants

NASA Astrophysics Data System (ADS)

Rathod, Dinesh W.; Pandey, Sunil; Singh, P. K.; Kumar, Suranjit

2017-09-01

In present study, dissimilar metal weld (DMW) joints between SA508Gr.3cl.1 ferritic steel and SS304LN pipes were prepared using Inconel 82/182, and Inconel 52/152 consumables. Metallurgical properties and their influence on fracture toughness of weldment regions and interfacial regions could play a significant role in integrity assessment of these joints. Ni-based consumables exhibit complex metallurgical properties at interfacial regions. The metallurgical characterization and fracture toughness studies of Inconel 82/182 and Inconel 52/152 joints have been carried out for determining the optimum consumable for DMW joint requirements and the effect of microstructure on fracture toughness in weldment regions. The present codes and procedures for integrity assessment of DMW joints have not given due considerations of metallurgical properties. The requirements for metallurgical properties by considering their effect on fracture toughness properties in integrity assessment have been discussed for reliable analysis. Inconel 82/182 is preferred over Inconel 52/152 joints owing to favorable metallurgical and fracture toughness properties across the interfacial and weldment regions.

Structural inhomogeneity of interfacial water at lipid monolayers revealed by surface-specific vibrational pump-probe spectroscopy.

PubMed

Bonn, Mischa; Bakker, Huib J; Ghosh, Avishek; Yamamoto, Susumu; Sovago, Maria; Campen, R Kramer

2010-10-27

We report vibrational lifetime measurements of the OH stretch vibration of interfacial water in contact with lipid monolayers, using time-resolved vibrational sum frequency (VSF) spectroscopy. The dynamics of water in contact with four different lipids are reported and are characterized by vibrational relaxation rates measured at 3200, 3300, 3400, and 3500 cm(-1). We observe that the water molecules with an OH frequency ranging from 3300 to 3500 cm(-1) all show vibrational relaxation with a time constant of T(1) = 180 ± 35 fs, similar to what is found for bulk water. Water molecules with OH groups near 3200 cm(-1) show distinctly faster relaxation dynamics, with T(1) < 80 fs. We successfully model the data by describing the interfacial water containing two distinct subensembles in which spectral diffusion is, respectively, rapid (3300-3500 cm(-1)) and absent (3200 cm(-1)). We discuss the potential biological implications of the presence of the strongly hydrogen-bonded, rapidly relaxing water molecules at 3200 cm(-1) that are decoupled from the bulk water system.

Controlling interfacial properties in supported metal oxide catalysts through metal–organic framework templating

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

Abney, Carter W.; Patterson, Jacob T.; Gilhula, James C.

Precise control over the chemical structure of hard-matter materials is a grand challenge of basic science and a prerequisite for the development of advanced catalyst systems. In this work we report the application of a sacrificial metal-organic framework (MOF) template for the synthesis of a porous supported metal oxide catalyst, demonstrating proof-of-concept for a highly generalizable approach to the preparation new catalyst materials. Application of 2,2’-bipyridine-5,5’-dicarboxylic acid as the organic strut in the Ce MOF precursor results in chelation of Cu 2+ and affords isolation of the metal oxide precursor. Following pyrolysis of the template, homogeneously dispersed CuO nanoparticles aremore » formed in the resulting porous CeO 2 support. By partially substituting non-chelating 1,1’-biphenyl-4,4’-dicarboxylic acid, the Cu 2+ loading and dispersion can be finely tuned, allowing precise control over the CuO/CeO 2 interface in the final catalyst system. Characterization by x-ray diffraction, x-ray absorption fine structure spectroscopy, and in situ IR spectroscopy/mass spectrometry confirm control over interface formation to be a function of template composition, constituting the first report of a MOF template being used to control interfacial properties in a supported metal oxide. Using CO oxidation as a model reaction, the system with the greatest number of interfaces possessed the lowest activation energy and better activity under differential conditions, but required higher temperature for catalytic onset and displayed inferior efficiency at 100 °C than systems with higher Cu-loading. This finding is attributable to greater CO adsorption in the more heavily-loaded systems, and indicates catalyst performance for these supported oxide systems to be a function of at least two parameters: size of adsorption site and extent of interface. In conclusion, optimization of catalyst materials thus requires precise control over synthesis parameters, such as is demonstrated by this MOF-templating method.« less

The electron injection rate in CdSe quantum dot sensitized solar cells: from a bifunctional linker and zinc oxide morphology.

PubMed

Ding, Wei-Lu; Peng, Xing-Liang; Sun, Zhu-Zhu; Li, Ze-Sheng

2017-11-09

Herein, we have investigated the effect of both the bifunctional linker (L1, L2, L3, and L4) and ZnO morphology (porous nanoparticles (NPs), nanowires (NWs), and nanotubes (NTs-A and NTs-Z)) on the electron injection in CdSe QD sensitized solar cells by first-principles simulation. Via calculating the partitioned interfaces formed by different components (linker/QDs and ZnO/linker), we found that the electronic states of QDs and every ZnO substrate are insensitive to any linker, while the frontier orbitals of L1-L4 (with increased delocalization) manifest a systematical negative-shift. Because of the lowest unoccupied molecular orbital (LUMO) of L1 compared to its counterparts aligned in the region of the virtual states of QDs or the substrate with a high density of states, it always yields a stronger electronic coupling with QDs and varied substrates. After characterization of the complete ZnO/linker/QD system, we found that the electron injection time (τ) vastly depends on both the linker and substrate. On the one hand, L1 bridged QDs and every substrate always achieve the shortest τ compared to their counterpart associated cases. On the other hand, NW supported systems always yield the shortest τ no matter what the linker is. Overall, the NW/L1/QD system achieves the fastest injection by ∼160 fs. This essentially stems from the shortest molecular length of L1 decreasing the distance between QDs and the substrate, subsequently improving the interfacial coupling. Meanwhile, the NW supported cases generate the less sensitive virtual states for both the QDs and NWs, ensuring a less variable interfacial coupling. These facts combined can provide understanding of the effects contributed from the linker and the oxide semiconductor morphology on charge transfer with the aim of choosing an appropriate component with fast directional electron injection.

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

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

Jagannadham, K., E-mail: jag-kasichainula@ncsu.edu

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 tungstenmore » 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.« less

Surface adsorption behaviour of milk whey protein and pectin mixtures under conditions of air-water interface saturation.

PubMed

Perez, Adrián A; Sánchez, Cecilio Carrera; Patino, Juan M Rodríguez; Rubiolo, Amelia C; Santiago, Liliana G

2011-07-01

Milk whey proteins (MWP) and pectins (Ps) are biopolymer ingredients commonly used in the manufacture of colloidal food products. Therefore, knowledge of the interfacial characteristics of these biopolymers and their mixtures is very important for the design of food dispersion formulations (foams and/or emulsions). In this paper, we examine the adsorption and surface dilatational behaviour of MWP/Ps systems under conditions in which biopolymers can saturate the air-water interface on their own. Experiments were performed at constant temperature (20 °C), pH 7 and ionic strength 0.05 M. Two MWP samples, β-lactoglobulin (β-LG) and whey protein concentrate (WPC), and two Ps samples, low-methoxyl pectin (LMP) and high-methoxyl pectin (HMP) were evaluated. The contribution of biopolymers (MWP and Ps) to the interfacial properties of mixed systems was evaluated on the basis of their individual surface molecular characteristics. Biopolymer bulk concentration capable of saturating the air-water interface was estimated from surface pressure isotherms. Under conditions of interfacial saturation, dynamic adsorption behaviour (surface pressure and dilatational rheological characteristics) of MWP/Ps systems was discussed from a kinetic point of view, in terms of molecular diffusion, penetration and configurational rearrangement at the air-water interface. The main adsorption mechanism in MWP/LMP mixtures might be the MWP interfacial segregation due to the thermodynamic incompatibility between MWP and LMP (synergistic mechanism); while the interfacial adsorption in MWP/HMP mixtures could be characterized by a competitive mechanism between MWP and HMP at the air-water interface (antagonistic mechanism). The magnitude of these phenomena could be closely related to differences in molecular composition and/or aggregation state of MWP (β-LG and WPC). Copyright © 2011 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2017-02-01

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

Effect of processing parameters on the formation of C{sub f}/LAS composites/Ag−Cu−Ti/TC4 brazed joint

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

Liu, Duo; Niu, Hongwei

C{sub f}/LAS composites were successfully jointed to TC4 alloy with Ag−Cu−Ti filler by vacuum brazing. The interfacial microstructure of TC4/C{sub f}/LAS composites joints was characterized by employing scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-diffraction (XRD) and transmission electron microscopy (TEM). The determination of the thin interfacial reaction layer (TiSi{sub 2} + TiC layer) was realized by TEM. The effect of holding time on the interfacial microstructure and shear strength were investigated. With the increasing holding time, the thickness of diffusion layer, Ti{sub 3}Cu{sub 4} layer, and TiSi{sub 2} + TiC layer increased obviously, on the contrary, that ofmore » Ti−Cu intermetallic compound layers decreased gradually. Besides, blocky Ti{sub 3}Cu{sub 4} phase was coarsened when the joint was brazed at 890 °C for 20 min, which deteriorated the mechanical properties of the joint dramatically. The interfacial evolution of TC4/C{sub f}/LAS composites joint and the formation of TiSi{sub 2}, TiC, Ti{sub 3}Cu{sub 4}, TiCu and Ti{sub 2}Cu phases were expounded. The maximum shear strength of 26.4 MPa was obtained when brazed at 890 °C for 10 min. - Highlights: •The thin interface reaction layer was determined to be TiSi{sub 2} + TiC layer by TEM. •Holding time had influence on the interfacial microstructure and joint properties. •Microstructural evolution mechanism and reactions of brazed joints were expounded.« less

Electrical properties and interfacial issues of high-k/Si MIS capacitors characterized by the thickness of Al{sub 2}O{sub 3} interlayer

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

Wang, Xing; Liu, Hongxia, E-mail: hxliu@mail.xidian.edu.cn; Fei, Chenxi

2016-06-15

A thin Al{sub 2}O{sub 3} interlayer deposited between La{sub 2}O{sub 3} 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 Al{sub 2}O{sub 3} interlayer increase. Meanwhile, some disadvantages such as the degradations in interface trap and oxide trapped charge characteristics were also observed.

Interfacial mixing in as-deposited Si/Ni/Si layers analyzed by x-ray and polarized neutron reflectometry

NASA Astrophysics Data System (ADS)

Bhattacharya, Debarati; Basu, Saibal; Singh, Surendra; Roy, Sumalay; Dev, Bhupendra Nath

2012-12-01

Interdiffusion occurring across the interfaces in a Si/Ni/Si layered system during deposition at room temperature was probed using x-ray reflectivity (XRR) and polarized neutron reflectivity (PNR). Exploiting the complementarity of these techniques, both structural and magnetic characterization with nanometer depth resolution could be achieved. Suitable model fitting of the reflectivity profiles identified the formation of Ni-Si mixed alloy layers at the Si/Ni and Ni/Si interfaces. The physical parameters of the layered structure, including quantitative assessment of the stoichiometry of interfacial alloys, were obtained from the analyses of XRR and PNR patterns. In addition, PNR provided magnetic moment density profile as a function of depth in the stratified medium.

Development of large-surface Nafion-metal composite actuator and its electrochemical characterization

NASA Astrophysics Data System (ADS)

Noh, Taegeun; Tak, Yong Suk; Nam, Jaedo; Jeon, Jaewook; Kim, Hunmo; Choi, Hyoukryeol; Bae, Sang Sik

2001-07-01

Behaviors of nafion-based actuators are significantly affected by interfacial area between electrode and polymer electrolyte. Replication method was utilized to manufacture a large surface-area composite actuator. Etched aluminum foil was used as a template for replication using liquid nafion solution. Measurement of double layer charging and scanning electron microscopy indicated that interfacial area was greatly increased by replication method. Higher surface area induced a better bending performance of ionic polymer metal composite (IPMC). In parallel, the effect of cations on IPMC was interpreted with constant current experiment, linear sweep voltammetry and electrochemical impedance spectroscopy. For univalent cations, ion size is the most influencing parameter on ionic mobility inside membrane. However, ion-ion interaction affects an ionic mobility for divalent cations.

Chemistry of the metal-polymer interfacial region.

PubMed

Leidheiser, H; Deck, P D

1988-09-02

In many polymer-metal systems, chemical bonds are formed that involve metal-oxygen-carbon complexes. Infrared and Mössbauer spectroscopic studies indicate that carboxylate groups play an important role in some systems. The oxygen sources may be the polymer, the oxygen present in the oxide on the metal surface, or atmospheric oxygen. Diffusion of metal ions from the substrate into the polymer interphase may occur in some systems that are cured at elevated temperatures. It is unclear whether a similar, less extensive diffusion occurs over long time periods in systems maintained at room temperature. The interfacial region is dynamic, and chemical changes occur with aging at room temperature. Positron annihilation spectroscopy may have application to characterizing the voids at the metal-polymer interface.

Nonlocal thermal transport across embedded few-layer graphene sheets

DOE PAGES

Liu, Ying; Huxtable, Scott T.; Yang, Bao; ...

2014-11-13

Thermal transport across the interfaces between few-layer graphene sheets and soft materials exhibits intriguing anomalies when interpreted using the classical Kapitza model, e.g., the conductance of the same interface differs greatly for different modes of interfacial thermal transport. Using atomistic simulations, we show that such thermal transport follows a nonlocal flux-temperature drop constitutive law and is characterized jointly by a quasi-local conductance and a nonlocal conductance instead of the classical Kapitza conductance. Lastly, the nonlocal model enables rationalization of many anomalies of the thermal transport across embedded few-layer graphene sheets and should be used in studies of interfacial thermal transportmore » involving few-layer graphene sheets or other ultra-thin layered materials.« less

Soft-Matter Printed Circuit Board with UV Laser Micropatterning.

PubMed

Lu, Tong; Markvicka, Eric J; Jin, Yichu; Majidi, Carmel

2017-07-05

When encapsulated in elastomer, micropatterned traces of Ga-based liquid metal (LM) can function as elastically deformable circuit wiring that provides mechanically robust electrical connectivity between solid-state elements (e.g., transistors, processors, and sensor nodes). However, LM-microelectronics integration is currently limited by challenges in rapid fabrication of LM circuits and the creation of vias between circuit terminals and the I/O pins of packaged electronics. In this study, we address both with a unique layup for soft-matter electronics in which traces of liquid-phase Ga-In eutectic (EGaIn) are patterned with UV laser micromachining (UVLM). The terminals of the elastomer-sealed LM circuit connect to the surface mounted chips through vertically aligned columns of EGaIn-coated Ag-Fe 2 O 3 microparticles that are embedded within an interfacial elastomer layer. The processing technique is compatible with conventional UVLM printed circuit board (PCB) prototyping and exploits the photophysical ablation of EGaIn on an elastomer substrate. Potential applications to wearable computing and biosensing are demonstrated with functional implementations in which soft-matter PCBs are populated with surface-mounted microelectronics.

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all-atom molecular dynamics simulations.

PubMed

Ou, Shu-Ching; Cui, Di; Wezowicz, Matthew; Taufer, Michela; Patel, Sandeep

2015-06-15

In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of hydrophobicity in terms of alternative but parallel signatures such as interfacial fluctuations, dewetting transitions, and enhanced fluctuation probabilities at interfaces. © 2015 Wiley Periodicals, Inc.

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

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

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

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

Raman imaging at biological interfaces: applications in breast cancer diagnosis.

PubMed

Surmacki, Jakub; Musial, Jacek; Kordek, Radzislaw; Abramczyk, Halina

2013-05-24

One of the most important areas of Raman medical diagnostics is identification and characterization of cancerous and noncancerous tissues. The methods based on Raman scattering has shown significant potential for probing human breast tissue to provide valuable information for early diagnosis of breast cancer. A vibrational fingerprint from the biological tissue provides information which can be used to identify, characterize and discriminate structures in breast tissue, both in the normal and cancerous environment. The paper reviews recent progress in understanding structure and interactions at biological interfaces of the human tissue by using confocal Raman imaging and IR spectroscopy. The important differences between the noncancerous and cancerous human breast tissues were found in regions characteristic for vibrations of carotenoids, fatty acids, proteins, and interfacial water. Particular attention was paid to the role played by unsaturated fatty acids and their derivatives as well as carotenoids and interfacial water. We demonstrate that Raman imaging has reached a clinically relevant level in regard to breast cancer diagnosis applications. The results presented in the paper may have serious implications on understanding mechanisms of interactions in living cells under realistically crowded conditions of biological tissue.

Multifunctional Poro-Vascular Composites for UAV Performance Enhancement

DTIC Science & Technology

2012-07-31

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

Adhesion Potential of Intestinal Microbes Predicted by Physico-Chemical Characterization Methods

PubMed Central

Niederberger, Tobias; Fischer, Peter; Rühs, Patrick Alberto

2015-01-01

Bacterial adhesion to epithelial surfaces affects retention time in the human gastro-intestinal tract and therefore significantly contributes to interactions between bacteria and their hosts. Bacterial adhesion among other factors is strongly influenced by physico-chemical factors. The accurate quantification of these physico-chemical factors in adhesion is however limited by the available measuring techniques. We evaluated surface charge, interfacial rheology and tensiometry (interfacial tension) as novel approaches to quantify these interactions and evaluated their biological significance via an adhesion assay using intestinal epithelial surface molecules (IESM) for a set of model organisms present in the human gastrointestinal tract. Strain pairs of Lactobacillus plantarum WCFS1 with its sortase knockout mutant Lb. plantarum NZ7114 and Lb. rhamnosus GG with Lb. rhamnosus DSM 20021T were used with Enterococcus faecalis JH2-2 as control organism. Intra-species comparison revealed significantly higher abilities for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T to dynamically increase interfacial elasticity (10−2 vs. 10−3 Pa*m) and reduce interfacial tension (32 vs. 38 mN/m). This further correlated for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T with the decrease of relative hydrophobicity (80–85% vs. 57–63%), Zeta potential (-2.9 to -4.5 mV vs. -8.0 to -13.8 mV) and higher relative adhesion capacity to IESM (3.0–5.0 vs 1.5–2.2). Highest adhesion to the IESM collagen I and fibronectin was found for Lb. plantarum WCFS1 (5.0) and E. faecalis JH2-2 (4.2) whereas Lb. rhamnosus GG showed highest adhesion to type II mucus (3.8). Significantly reduced adhesion (2 fold) to the tested IESM was observed for Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T corresponding with lower relative hydrophobicity, Zeta potential and abilities to modify interfacial elasticity and tension. Conclusively, the use of Zeta potential, interfacial elasticity and interfacial tension are proposed as suitable novel descriptive and predictive parameters to study the interactions of intestinal microbes with their hosts. PMID:26295945

The role of Minkowski functionals in the thermodynamics of two-phase systems

NASA Astrophysics Data System (ADS)

Eder, Gerhard

2018-01-01

Within this work quite old concepts from integral geometry are applied to classical equilibrium thermodynamics of two-phase systems. In addition to the area as basic interfacial quantity the full geometric characterization of the interface is used, which includes the two remaining Minkowski functionals, the mean curvature integral and the Euler Poincaré characteristic. The basic energetic characteristic of the interface (i.e. the interfacial tension) is extended by two additional properties: edge force as (up to a factor 4/π) the work necessary to form a right-angled edge of unit length, and item energy as the work to form an additional item in the phase morphology. Both quantities are of increasing importance, when going to micro- and nano-scales. They are subsequently used for interfaces of arbitrary shape to derive a relationship extending the classical Young-Laplace equation. The supplementary contribution is proportional to the Gaussian curvature, with the edge force as proportionality constant. Furthermore, both edge force and item energy are shown to be applicable to the description of crystal nucleation in liquids (extending the classical Becker Döring theory). It turns out, that even above the thermodynamic melting temperature stable nuclei can be present in the liquid phase. They immediately are able to grow when quenched to a temperature below a characteristic temperature. This temperature of spontaneous homogeneous nucleation is simply connected to the edge force, whereas the number of stable clusters per unit volume is dominated by the item energy. Finally, the additional energetic interfacial properties are used in a similar way to characterize the stability of emulsions.

Determination of interfacial states in solid heterostructures using a variable-energy positron beam

DOEpatents

Asoka kumar, Palakkal P. V.; Lynn, Kelvin G.

1993-01-01

A method and means is provided for characterizing interfacial electron states in solid heterostructures using a variable energy positron beam to probe the solid heterostructure. The method includes the steps of directing a positron beam having a selected energy level at a point on the solid heterostructure so that the positron beam penetrates into the solid heterostructure and causes positrons to collide with the electrons at an interface of the solid heterostructure. The number and energy of gamma rays emitted from the solid heterostructure as a result of the annihilation of positrons with electrons at the interface are detected. The data is quantified as a function of the Doppler broadening of the photopeak about the 511 keV line created by the annihilation of the positrons and electrons at the interface, preferably, as an S-parameter function; and a normalized S-parameter function of the data is obtained. The function of data obtained is compared with a corresponding function of the Doppler broadening of the annihilation photopeak about 511 keV for a positron beam having a second energy level directed at the same material making up a portion of the solid heterostructure. The comparison of these functions facilitates characterization of the interfacial states of electrons in the solid heterostructure at points corresponding to the penetration of positrons having the particular energy levels into the interface of the solid heterostructure. Accordingly, the invention provides a variable-energy non-destructive probe of solid heterostructures, such as SiO.sub.2 /Si, MOS or other semiconductor devices.

Determination of interfacial states in solid heterostructures using a variable-energy positron beam

DOEpatents

Asokakumar, P.P.V.; Lynn, K.G.

1993-04-06

A method and means is provided for characterizing interfacial electron states in solid heterostructures using a variable energy positron beam to probe the solid heterostructure. The method includes the steps of directing a positron beam having a selected energy level at a point on the solid heterostructure so that the positron beam penetrates into the solid heterostructure and causes positrons to collide with the electrons at an interface of the solid heterostructure. The number and energy of gamma rays emitted from the solid heterostructure as a result of the annihilation of positrons with electrons at the interface are detected. The data is quantified as a function of the Doppler broadening of the photopeak about the 511 keV line created by the annihilation of the positrons and electrons at the interface, preferably, as an S-parameter function; and a normalized S-parameter function of the data is obtained. The function of data obtained is compared with a corresponding function of the Doppler broadening of the annihilation photopeak about 511 keV for a positron beam having a second energy level directed at the same material making up a portion of the solid heterostructure. The comparison of these functions facilitates characterization of the interfacial states of electrons in the solid heterostructure at points corresponding to the penetration of positrons having the particular energy levels into the interface of the solid heterostructure. Accordingly, the invention provides a variable-energy non-destructive probe of solid heterostructures, such as SiO[sub 2]/Si, MOS or other semiconductor devices.

A novel broadband impedance method for detection of cell-derived microparticles.

PubMed

Lvovich, Vadim; Srikanthan, Sowmya; Silverstein, Roy L

2010-10-15

A novel label-free method is presented to detect and quantify cell-derived microparticles (MPs) by the electrochemical potential-modulated electrochemical impedance spectroscopy (EIS). MPs are present in elevated concentrations during pathological conditions and play a major role in the establishment and pathogenesis of many diseases. Considering this, accurate detection and quantification of MPs is very important in clinical diagnostics and therapeutics. A combination of bulk solution electrokinetic sorting and interfacial impedance responses allows achieving detection limits as low as several MPs per μL. By fitting resulting EIS spectra with an equivalent electrical circuit, the bulk solution electrokinetic and interfacial impedance responses were characterized. In the bulk solution two major relaxations were prominent-β-relaxation in low MHz region due to the MP capacitive membrane bridging, and α-relaxation at ∼10 kHz due to counter ions diffusion. At low frequencies (10-0.1 Hz) at electrochemical potentials exceeding -100 mV, a facile interfacial Faradaic process of oxidation in MPs coupled with diffusion and non-Faradaic double layer charging dominate, probably due to oxidation of phospholipids and/or proteins on the MP surface and MP lysis. Buffer influence on the MP detection demonstrated that a relatively low conductivity Tyrode's buffer background solution is preferential for the MP electrokinetic separation and characterization. This study also demonstrated that standard laboratory methods such as flow cytometry underestimate MP concentrations, especially those with smaller average sizes, by as much as a factor of 2-40. Copyright © 2010 Elsevier B.V. All rights reserved.

Characterization of the surface and interfacial properties of the lamina splendens

NASA Astrophysics Data System (ADS)

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

2017-06-01

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

Characterization of the reaction products and precipitates at the interface of carbon fiber reinforced magnesium–gadolinium composite

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

Wang, Yaping; Jiang, Longtao, E-mail: longtaojiang@163.com; Chen, Guoqin

2016-03-15

In the present work, carbon fiber reinforced magnesium-gadolinium composite was fabricated by pressure infiltration method. The phase composition, micro-morphology, and crystal structure of reaction products and precipitates at the interface of the composite were investigated. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed the segregation of gadolinium element at the interface between carbon fiber and matrix alloy. It was shown that block-shaped Gd4C5, GdC2 and nano-sized Gd2O3 were formed at the interface during the fabrication process due to the interfacial reaction. Furthermore, magnesium-gadolinium precipitates including needle-like Mg5Gd (or Mg24Gd5) and thin plate-shaped long period stacking-ordered phase, were also observedmore » at the interface and in the matrix near the interface. The interfacial microstructure and bonding mode were influenced by these interfacial products, which were beneficial for the improvement of the interfacial bonding strength. - Highlights: • Gadolinium element segregated on the surface of carbon fibers. • Block-shaped Gd{sub 4}C{sub 5} and GdC{sub 2} were formed at the interface via chemical reaction. • Gadolinium and oxygen reacted at the interface and formed nano-scaled Gd{sub 2}O{sub 3}. • The precipitates formed in the interface were identified to be Mg{sub 5}Gd (or Mg{sub 24}Gd{sub 5}) and plate-shaped long period stacking-ordered phase.« less

Brazing of Carbon Carbon Composites to Cu-clad Molybdenum for Thermal Management Applications

NASA Technical Reports Server (NTRS)

Singh, M.; Asthana, R.; Shpargel, T> P.

2007-01-01

Advanced carbon carbon composites were joined to copper-clad molybdenum (Cu/Mo) using four active metal brazes containing Ti (Cu ABA, Cusin-1 ABA, Ticuni, and Ticusil) for potential use in thermal management applications. The brazed joints were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Knoop microhardness measurements across the joint region. Metallurgically sound C-C/Cu/Mo joints, devoid of interfacial cracks formed in all cases. The joint interfaces were preferentially enriched in Ti, with Cu ABA joints exhibiting the largest interfacial Ti concentrations. The microhardness measurements revealed hardness gradients across the joint region, with a peak hardness of 300-350 KHN in Cusin-1 ABA and Ticusil joints and 200-250 KHN in Cu ABA and Ticuni joints, respectively.

Interfacial bubbles formed by plunging thin liquid films in a pool

NASA Astrophysics Data System (ADS)

Salkin, Louis; Schmit, Alexandre; David, Richard; Delvert, Alexandre; Gicquel, Eric; Panizza, Pascal; Courbin, Laurent

2017-06-01

We show that the immersion of a horizontally suspended thin film of liquid in a pool of the same fluid creates an interfacial bubble, that is, a bubble at the liquid-air interface. Varying the fluid properties, the film's size, and its immersion velocity, our experiments unveil two formation regimes characterized by either a visco-capillary or an inertio-capillary mechanism that controls the size of a produced bubble. To rationalize these results, we compare the pressure exerted by the air flow under a plunging film with the Laplace pressure needed to generate film dimpling, which subsequently yields air entrapment and the production of a bubble. This physical model explains the power-law variations of the bubble size with the governing dimensionless number for each regime.

Micro-wrinkling and delamination-induced buckling of stretchable electronic structures

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

Oyewole, O. K.; Department of Materials Science and Engineering, Kwara State University, Malete, P.M.B 1530, Ilorin, Kwara State; Yu, D.

This paper presents the results of experimental and theoretical/computational micro-wrinkles and buckling on the surfaces of stretchable poly-dimethylsiloxane (PDMS) coated with nano-scale Gold (Au) layers. The wrinkles and buckles are formed by the unloading of pre-stretched PDMS/Au structure after the evaporation of nano-scale Au layers. They are then characterized using atomic force microscopy and scanning electron microscopy. The critical stresses required for wrinkling and buckling are analyzed using analytical models. The possible interfacial cracking that can occur along with film buckling is also studied using finite element simulations of the interfacial crack growth. The implications of the results are discussedmore » for potential applications of micro-wrinkles and micro-buckles in stretchable electronic structures and biomedical devices.« less

Positron Annihilation Spectroscopy as a Novel Interfacial Probe for Thin Polymeric Films and Nano-Composites

NASA Astrophysics Data System (ADS)

Awad, Somia; Chen, Hongmin; Maina, Grace; Lee, L. James; Gu, Xiaohong; Jean, Y. C.

2010-03-01

Positron annihilation spectroscopy (PAS) has been developed as a novel probe to characterize the sub-nanometer defect, free volume, profile from the surface, interfaces, and to the bulk in polymeric materials when a variable mono-energy slow positron beam is used. Free-volume hole sizes, fractions, and distributions are measurable as a function of depth at the high precision. PAS has been successfully used to study the interfacial properties of polymeric nanocomposites at different chemical bonding. In nano-scale thin polymeric films, such as in PS/SiO2, and PU/ZnO, significant variations of Tg as a function of depth and of wt% oxide are observed. Variations of Tg are dependent on strong or weak interactions between polymers and nano-scale oxides surfaces.

Application of ESCA to the determination of stoichiometry in sputtered coatings and interface regions

NASA Technical Reports Server (NTRS)

Wheeler, D. R.

1978-01-01

X-ray photoelectron spectroscopy was used to characterize radiofrequency sputter deposited films of several refractory compounds. Both the bulk film properties such as purity and stoichiometry and the character of the interfacial region between the film and substrate were examined. The materials were CrB2, MoS2, Mo2C, and Mo2B5 deposited on 440C steel. It was found that oxygen from the sputtering target was the primary impurity in all cases. Biasing improves the film purity. The effect of biasing on film stoichiometry is different for each compound. Comparison of the interfacial composition with friction data suggests that adhesion of these films is improved if a region of mixed film and iron oxides can be formed.

Potential Barrier Lowering and Electrical Transport at the LaAlO3/SrTiO3 Interface

NASA Astrophysics Data System (ADS)

Suzuki, Yuri

2009-03-01

Interfacial phenomena form the basis for modern-day devices and continue to be an area of fundamental interest in condensed matter research. Advances in oxide thin film fabrication have enabled the synthesis of atomically precise oxide interfaces and hence have allowed for controlled investigation of interfacial phenomena in these materials. With the rich variety of functionalities exhibited by transition-metal oxides, a wide array of novel properties may be achieved at oxide heterointerfaces. An exemplary study is the discovery of metallicity at the interface of two band insulators, LaAlO3 (LAO) and SrTiO3 (STO), which has stimulated many subsequent experimental as well as theoretical studies. However, there is still intense debate on the origin of metallicity, specifically whether it arises from electronic reconstruction or oxygen vacancies. Using a combination of vertical transport measurements across and lateral transport measurements along the LAO/STO heterointerface, we demonstrate that significant potential barrier lowering and band bending are the cause of interfacial metallicity. Transport measurements across the heterointerface, indicate that barrier lowering and enhanced band bending extends over 2.5 nm into LAO as well as STO. We explain the origins of high-temperature carrier saturation, lower carrier concentration, and higher mobility in the sample with the thinnest LAO film on a STO substrate. Lateral transport results suggest that parasitic interface scattering centers limit the low-temperature lateral electron mobility of the metallic channel. [4pt] *In collaboration with Franklin Wong, Miaofang Chi, Rajesh Chopdekar, Brittany Nelson-Cheeseman and Nigel Browning.

Contributions of residues of pancreatic phospholipase A2 to interfacial binding, catalysis, and activation.

PubMed

Yu, B Z; Rogers, J; Tsai, M D; Pidgeon, C; Jain, M K

1999-04-13

Primary rate and equilibrium parameters for 60 site-directed mutants of bovine pancreatic phospholipase A2 (PLA2) are analyzed so incremental contributions of the substitution of specific residues can be evaluated. The magnitude of the change is evaluated so a functional role in the context of the N- and C-domains of PLA2 can be assigned, and their relationship to the catalytic residues and to the i-face that makes contact with the interface. The effect of substitutions and interfacial charge is characterized by the equilibrium dissociation constant for dissociation of the bound enzyme from the interface (Kd), the dissociation constant for dissociation of a substrate mimic from the active site of the bound enzyme (KL), and the interfacial Michaelis constants, KM and kcat. Activity is lost (>99.9%) on the substitution of H48 and D49, the catalytic residues. A more than 95% decrease in kcat is seen with the substitution of F5, I9, D99, A102, or F106, which form the substrate binding pocket. Certain residues, which are not part of the catalytic site or the substrate binding pocket, also modulate kcat. Interfacial anionic charge lowers Kd, and induces kcat activation through K56, K53, K119, or K120. Significant changes in KL are seen by the substitution of N6, I9, F22, Y52, K53, N71, Y73, A102, or A103. Changes in KM [=(k2+k-1)/k1] are attributed to kcat (=k2) and KL (=k-1/k1). Some substitutions change more than one parameter, implying an allosteric effect of the binding to the interface on KS, and the effect of the interfacial anionic charge on kcat. Interpreted in the context of the overall structure, results provide insights into the role of segments and domains in the microscopic events of catalytic turnover and processivity, and their allosteric regulation. We suggest that the interfacial recognition region (i-face) of PLA2, due to the plasticity of certain segments and domains, exercises an allosteric control on the substrate binding and chemical step.

Phase-Transfer Energetics of Small-Molecule Alcohols Across the Water-Hexane Interface: Molecular Dynamics Simulation Using Charge Equilibration Models

PubMed Central

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

2010-01-01

We study the water-hexane interface using molecular dynamics (MD) and polarizable charge equilibration (CHEQ) force fields. Bulk densities for TIP4P-FQ water and hexane, 1.0086±0.0002 g/cm3 and 0.6378±0.0001 g/cm3, demonstrate excellent agreement with experiment. Interfacial width and interfacial tension are consistent with previously reported values. The in-plane component of the dielectric permittivity (ε∥) for water is shown to decrease from 81.7±0.04 to unity, transitioning longitudinally from bulk water to bulk hexane. ε∥ for hexane reaches a maximum in the interface, but this term represents only a small contribution to the total dielectric constant (as expected for a non-polar species). Structurally, net orientations of the molecules arise in the interfacial region such that hexane lies slightly parallel to the interface and water reorients to maximize hydrogen bonding. Interfacial potentials due to contributions of the water and hexane are calculated to be -567.9±0.13mV and 198.7±0.01mV, respectively, giving rise to a total potential in agreement with the range of values reported from previous simulations of similar systems. Potentials of mean force (PMF) calculated for methanol, ethanol, and 1-propanol for the transfer from water to hexane indicate an interfacial free energy minimum, corresponding to the amphiphilic nature of the molecules. The magnitudes of transfer free energies were further characterized from the solvation free energies of alcohols in water and hexane using thermodynamic integration. This analysis shows that solvation free energies for alcohols in hexane are 0.2-0.3 kcal/mol too unfavorable, whereas solvation of alcohols in water is approximately 1 kcal/mol too favorable. For the pure hexane-water interfacial simulations, we observe a monotonic decrease of the water dipole moment to near-vacuum values. This suggests that the electrostatic component of the desolvation free energy is not as severe for polarizable models than for fixed-charge force fields. The implications of such behavior pertain to the modeling of polar and charged solutes in lipidic environments. PMID:21414823

Adhesion of nitrile rubber to UV-assisted surface chemical modified PET fabric, part II: Interfacial characterization of MDI grafted PET

NASA Astrophysics Data System (ADS)

Razavizadeh, Mahmoud; Jamshidi, Masoud

2016-08-01

Fiber to rubber adhesion is an important subject in rubber industry. It is well known that surface treatment (i.e. physical, mechanical and chemical) is an effective method to improve interfacial bonding of fibers and/or fabrics to rubbers. UV irradiation is an effective method which has been used to increase fabric-rubber interfacial interactions. In this research UV assisted chemical modification of PET fabrics was used to increase PET to nitrile rubber (NBR) adhesion. Nitrile rubber is a perfect selection as fuel and oil resistant rubber. However it has weak bonding to PET fabric. For this purpose PET fabric was carboxylated under UV irradiation and then methylenediphenyl diisocyanate (MDI) was grafted on carboxylated PET. The chemical composition of the fabric before and after surface treatment was investigated by X-ray photoelectron spectroscopy (XPS). The sectional morphology of the experimental PET fibers and the interface between rubber compound and PET fabric was studied using scanning electron microscope (SEM). The morphology and structure of the product were analyzed by an energy dispersive X-ray spectrometer (EDX). FTIR-ATR and H NMR analysis were used to assess surface modifications on the PET irradiated fabrics.

Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

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

Yang, H. F.; Liu, Z. T.; Fan, C. C.

2016-08-15

By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001)- and (111)-orientated polar LaNiO{sub 3} thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO{sub 3} and iso-polarity LaAlO{sub 3} substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. For largely polar (111)-orientated films, we showed that iso-polarity LaAlO{sub 3} (111) substrate was more suitable than Nb-doped SrTiO{sub 3}. In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentionsmore » need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO{sub 3} based superlattices.« less

Delayed Alumina Scale Spallation on Rene'n5+y: Moisture Effects and Acoustic Emission

NASA Technical Reports Server (NTRS)

Smialek, James L.; Morscher, Gregory N.

2001-01-01

The single crystal superalloy Rene'N5 (with or without Y-doping and hydrogen annealing) was cyclically oxidized at 1150 C for 1000 hours. After considerable scale growth (>= 500 hours), even the adherent alumina scales formed on Y-doped samples exhibited delayed interfacial spallation during subsequent water immersion tests, performed up to one year after oxidation. Spallation was characterized by weight loss, the amount of spalled area, and acoustic emission response. Hydrogen annealing (prior to oxidation) reduced spallation both before and after immersion, but without measurably reducing the bulk sulfur content of the Y-doped alloys. The duration and frequency of sequential, co-located acoustic emission events implied an interfacial crack growth rate at least 10(exp -3) m/s, but possibly higher than 10(exp 2) m/s. This is much greater than classic moisture-assisted slow crack growth rates in bulk alumina (10(exp -6) to 10(exp -3) m/s), which may still have occurred undetected by acoustic emission. An alternative failure sequence is proposed: an incubation process for preferential moisture ingress leads to a local decrease in interfacial toughness, thus allowing fast fracture driven by stored strain energy.

Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

DOE PAGES

Bondi, Robert J.; Marinella, Matthew J.

2015-02-28

First-principles density-functional theory (DFT) calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (V O n; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta 2O 5) and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. V O n of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta 2O 5, V O 0 are characterized by structural contractionmore » and electron density localization, while V O 2+ promote structural expansion and are depleted of electron density. In contrast, interfacial V O 0 and V O 2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced V O center. Interfacial V O 2+ extract electron density from metallic Ta indicating V O 2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.« less

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.

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

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

Jiang, Longtao, E-mail: longtaojiang@163.com; Wang, Pingping; Xiu, Ziyang

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. Themore » 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.« less

Insect flight on fluid interfaces: a chaotic interfacial oscillator

NASA Astrophysics Data System (ADS)

Mukundarajan, Haripriya; Prakash, Manu

2013-11-01

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

Flow-induced 2D protein crystallization: characterization of the coupled interfacial and bulk flows.

PubMed

Young, James E; Posada, David; Lopez, Juan M; Hirsa, Amir H

2015-05-14

Two-dimensional crystallization of the protein streptavidin, crystallizing below a biotinylated lipid film spread on a quiescent air-water interface is a well studied phenomenon. More recently, 2D crystallization induced by a shearing interfacial flow has been observed at film surface pressures significantly lower than those required in a quiescent system. Here, we quantify the interfacial and bulk flow associated with 2D protein crystallization through numerical modeling of the flow along with a Newtonian surface model. Experiments were conducted over a wide range of conditions resulting in a state diagram delineating the flow strength required to induce crystals for various surface pressures. Through measurements of the velocity profile at the air-water interface, we found that even in the cases where crystals are formed, the macroscopic flow at the interface is well described by the Newtonian model. However, the results show that even in the absence of any protein in the system, the viscous response of the biotinylated lipid film is complicated and strongly dependent on the strength of the flow. This observation suggests that the insoluble lipid film plays a key role in flow-induced 2D protein crystallization.

Thermal characterization of static and dynamical properties of the confined molecular systems interacting through dispersion force.

PubMed

Ramos, Sergio Luis L M; Ogino, Michihiko; Oguni, Masaharu

2015-01-28

We investigated the thermal properties of liquid methylcyclohexane and racemic sec-butylcyclohexane, as representatives of a molecular system with only dispersion-force intermolecular interactions, confined in the pores (thickness/diameter d = 12, 6, 1.1 nm) of silica gels by adiabatic calorimetry. The results imply a heterogeneous picture for molecular aggregate under confinement consisting of an interfacial region and an inner pore one. In the vicinity of a glass-transition temperature T(g,bulk) of bulk liquid, two distinguishable relaxation phenomena were observed for the confined systems and their origins were attributed to the devitrification, namely glass transition, processes of (1) a layer of interfacial molecules adjacent to the pore walls and (2) the molecules located in the middle of the pore. A third glass-transition phenomenon was observed at lower temperatures and ascribed to a secondary relaxation process. The glass transition of the interfacial-layer molecules was found to proceed at temperatures rather above T(g,bulk), whereas that of the molecules located in the inner pore region occurred at temperatures below T(g,bulk). We discuss the reason why the molecules located in different places in the pores reveal the respectively different dynamical properties.

Characterization of the interface between cellulosic fibers and a thermoplastic matrix

Treesearch

Feipeng P. Liu; Michael P. Wolcott; Douglas J. Gardner; Timothy G. Rials

1994-01-01

The applicability of the microbond test to evaluate the interfacial properties between cellulosic fibers and thermoplastics was studied. Acetylation and beat treatment were applied to modify the surface of cellulosic fibers (rayon, cotton, and wood). The apparent diameters and surface free energies of the fibers were estimated by dynamic contact angle (DCA) analysis....

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

PubMed

Sun, Dachuan; Guo, Hongxia

2012-08-09

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

Molecular characterization of macrophyte-derived dissolved organic matters and their implications for lakes

USDA-ARS?s Scientific Manuscript database

Chemical properties of whole organic matter (OM) and its dissolved organic matter (DOM) fraction from six dominant macrophytes in Lake Dianchi were comparatively characterized, and their environmental implications were discussed. Significant differences in chemical composition of the OM samples were...

Characterization of adhesion at carbon fiber-fluorinated epoxy interface and effect of environmental degradation

NASA Astrophysics Data System (ADS)

Dasgupta, Suman

2011-12-01

Carbon fiber reinforced polymers are excellent candidates for aerospace, automobile and other mobile applications due to their high specific strength and modulus. The most prominent aerospace application of carbon fiber composites in recent times is the Boeing 787 Dreamliner, which is the world's first major commercial airliner to extensively use composite materials. The critical issue, which needs to be addressed hereby, is long-term safety. Hence, long-term durability of composite materials in such applications becomes a point of concern. Conventional polymer matrices, such as thermosetting resins, which are used as matrix material in carbon fiber composites, are susceptible to degradation in the form of chemical corrosion, UV degradation and moisture, in severe environmental conditions. Fluorinated polymers offer a viable alternative as matrix material, due to their reduced susceptibility to environmental degradation. The epoxy system used in this study is fluorinated Tetra-glycidyl methylene di-aniline (6F-TGMDA), which was developed by polymer scientists at NASA Langley Research Center. The hydrophobic nature of this epoxy makes it a potential matrix material in aerospace applications. However, its compatibility in carbon fiber-reinforced composites remains to be investigated. This study aims to characterize the interfacial properties in carbon fiber reinforced fluorinated epoxy composites. Typical interfacial characterization parameters, like interfacial shear strength, estimated from the microbond test, proved to be inadequate in accurately estimating adhesion since it assumes a uniform distribution of stresses along the embedded fiber length. Also, it does not account for any residual stresses present at the interface, which might arise due to thermal expansion differences and Poisson's ratio differences of the fiber and matrix. Hence, an analytical approach, which calculates adhesion pressure at the interface, was adopted. This required determination of the unknown mechanical and physical properties of the resin, the relaxation modulus (determined using nano-indentation) and coefficient of thermal expansion (determined using coherent gradient sensing). The adhesional pressure for 6F TGMDA-carbon fiber interface was found to be 135.48 MPa compared to 138.47 MPa for the Diamino diphenyl sulphone (DDS) cured TGMDA-carbon fiber interface. The fact that the adhesional pressure does not show significant decrease upon fluorination of the epoxy system is an advantage. The hydrophobicity of fluorine can be utilized to manufacture environmentally resistant composites while keeping the level of interfacial adhesion the same as in the case of conventional epoxy system, DDS cured TGMDA.

First-principles study on influence of molybdenum on acicular ferrite formation on TiC particles in microallyed steels

NASA Astrophysics Data System (ADS)

Hua, Guomin; Li, Changsheng; Cheng, Xiaonong; Zhao, Xinluo; Feng, Quan; Li, Zhijie; Li, Dongyang; Szpunar, Jerzy A.

2018-01-01

In this study, influences of molybdenum on acicular ferrite formation on precipitated TiC particles are investigated from thermodynamic and kinetic respects. In thermodynamics, Segregation of Mo towards austenite/TiC interface releases the interfacial energy and induces phase transformation from austenite to acicular ferrite on the precipitated TiC particles. The Phase transformation can be achieved by displacive deformation along uniaxial Bain path. In addition, the segregation of Mo atom will also lead to the enhanced stability of ferrite in comparison with austenite no matter at low temperature or at high temperature. In kinetics, the Mo solute in acicular ferrite can effectively suppress the diffusion of carbon atoms, which ensures that orientation relationship between acicular ferrite and austenitized matrix can be satisfied during the diffusionless phase transformation. In contrast to ineffectiveness of TiC particles, the alloying Mo element can facilitate the formation of acicular ferrite on precipitated TiC particles, which is attributed to the above thermodynamic and kinetic reasons. Furthermore, Interfacial toughness and ductility of as-formed acicular ferrite/TiC interface can be improved simultaneously by segregation of Mo atom.

Study of vertical Si/SiO2 interface using laser-assisted atom probe tomography and transmission electron microscopy.

PubMed

Lee, J H; Lee, B H; Kim, Y T; Kim, J J; Lee, S Y; Lee, K P; Park, C G

2014-03-01

Laser-assisted atom probe tomography has opened the way to three-dimensional visualization of nanostructures. However, many questions related to the laser-matter interaction remain unresolved. We demonstrate that the interface reaction can be activated by laser-assisted field evaporation and affects the quantification of the interfacial composition. At a vertical interface between Si and SiO2, a SiO2 molecule tends to combine with a Si atom and evaporate as a SiO molecule, reducing the evaporation field. The features of the reaction depend on the direction of the laser illumination and the inner structure of tip. A high concentration of SiO is observed at a vertical interface between Si and SiO2 when the Si column is positioned at the center of the tip, whereas no significant SiO is detected when the SiO2 layer is at the center. The difference in the interfacial compositions of two samples was due to preferential evaporation of the Si layer. This was explained using transmission electron microscopy observations before and after atom probe experiments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Interfacial Effects in Solid-Liquid Electrolytes for Improved Stability and Performance of Dye-Sensitized Solar Cells.

PubMed

Bella, Federico; Popovic, Jelena; Lamberti, Andrea; Tresso, Elena; Gerbaldi, Claudio; Maier, Joachim

2017-11-01

With the purpose of achieving stable dye-sensitized solar cells (DSSCs) with high efficiency, a new type of soft matter electrolyte is tested in which specific amounts of nanosized silica particles are finely dispersed in short-chained polyethylene glycol dimethylether encompassing an iodide/triiodide redox mediator. This results in a solid-liquid composite having synergistic electrical and favorable mechanical properties. The combination of interfacial effects and particle network formation promotes enhanced ion transport, which directly impacts the short-circuit photocurrent density. Thorough analysis reveals that this newly elaborated class of electrolytes is able to improve, at the same time, the thermal and long-term stability of DSSCs, as well as power conversion efficiency under standard and lower irradiation intensities. Lab-scale devices with champion efficiency exceeding 11% under attenuated sunlight (20 mW cm -2 , with a compact TiO 2 blocking layer) are obtained, along with impressively stable performance under both thermal stress and light soaking in an indoor environment (>96% performance retention after 2500 h of accelerated aging under full sun alternated with thermal ramps), matching the durability criteria applied to silicon solar cells for outdoor applications. The new findings might foster widespread practical application of DSSCs.

Multiple Concentric Cylinder Model (MCCM) user's guide

NASA Technical Reports Server (NTRS)

Williams, Todd O.; Pindera, Marek-Jerzy

1994-01-01

A user's guide for the computer program mccm.f is presented. The program is based on a recently developed solution methodology for the inelastic response of an arbitrarily layered, concentric cylinder assemblage under thermomechanical loading which is used to model the axisymmetric behavior of unidirectional metal matrix composites in the presence of various microstructural details. These details include the layered morphology of certain types of ceramic fibers, as well as multiple fiber/matrix interfacial layers recently proposed as a means of reducing fabrication-induced, and in-service, residual stress. The computer code allows efficient characterization and evaluation of new fibers and/or new coating systems on existing fibers with a minimum of effort, taking into account inelastic and temperature-dependent properties and different morphologies of the fiber and the interfacial region. It also facilitates efficient design of engineered interfaces for unidirectional metal matrix composites.

Compression failure mechanisms of single-ply, unidirectional, carbon-fiber composites

NASA Technical Reports Server (NTRS)

Ha, Jong-Bae; Nairn, John A.

1992-01-01

A single-ply composite compression test was used to study compression failure mechanisms as a function of fiber type, matrix type, and interfacial strength. Composites made with low- and intermediate-modulus fibers (Hercules AS4 and IM7) in either an epoxy (Hercules 3501-6) or a thermoplastic (ULTEM and LARC-TPI) matrix failed by kink banding and out-of-plane slip. The failures proceeded by rapid and catastrophic damage propagation across the specimen width. Composites made with high-modulus fibers (Hercules HMS4/3501-6) had a much lower compression strength. Their failures were characterized by kink banding and longitudinal splitting. The damage propagated slowly across the specimen width. Composites made with fibers treated to give low interfacial strength had low compression strength. These composites typically failed near the specimen ends and had long kink bands.

Characterization of linear interfacial waves in a turbulent gas-liquid pipe flow

NASA Astrophysics Data System (ADS)

Ayati, A. A.; Farias, P. S. C.; Azevedo, L. F. A.; de Paula, I. B.

2017-06-01

The evolution of interfacial waves on a stratified flow was investigated experimentally for air-water flow in a horizontal pipe. Waves were introduced in the liquid level of stratified flow near the pipe entrance using an oscillating plate. The mean height of liquid layer and the fluctuations superimposed on this mean level were captured using high speed cameras. Digital image processing techniques were used to detect instantaneous interfaces along the pipe. The driving signal of the oscillating plate was controlled by a D/A board that was synchronized with acquisitions. This enabled to perform phase-locked acquisitions and to use ensemble average procedures. Thereby, it was possible to measure the temporal and spatial evolution of the disturbances introduced in the flow. In addition, phase-locked measurements of the velocity field in the liquid layer were performed using standard planar Particle Image Velocimetry (PIV). The velocity fields were extracted at a fixed streamwise location, whereas the measurements of the liquid level were performed at several locations along the pipe. The assessment of the setup was important for validation of the methodology proposed in this work, since it aimed at providing results for further comparisons with theoretical models and numerical simulations. Therefore, the work focuses on validation and characterization of interfacial waves within the linear regime. Results show that under controlled conditions, the wave development can be well captured and reproduced. In addition, linear waves were observed for liquid level oscillations lower than about 1.5% of the pipe diameter. It was not possible to accurately define an amplitude threshold for the appearance of nonlinear effects because it strongly depended on the wave frequency. According to the experimental findings, longer waves display characteristics similar to linear waves, while short ones exhibit a more complex evolution, even for low amplitudes.

On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures.

PubMed

Chai, Herzl; Lee, James J-W; Mieleszko, Adam J; Chu, Stephen J; Zhang, Yu

2014-08-01

Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations. Copyright © 2014 Acta Materialia Inc. All rights reserved.

Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces

PubMed Central

Irokawa, Yoshihiro

2011-01-01

In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C–V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C–V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C–V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I–V) characterization, suggesting that low-frequency C–V method would be effective in detecting very low hydrogen concentrations. PMID:22346597

Impact of pressure and temperature on CO2-brine-mica contact angles and CO2-brine interfacial tension: Implications for carbon geo-sequestration.

PubMed

Arif, Muhammad; Al-Yaseri, Ahmed Z; Barifcani, Ahmed; Lebedev, Maxim; Iglauer, Stefan

2016-01-15

Precise characterization of wettability of CO2-brine-rock system and CO2-brine interfacial tension at reservoir conditions is essential as they influence capillary sealing efficiency of caprocks, which in turn, impacts the structural and residual trapping during CO2 geo-sequestration. In this context, we have experimentally measured advancing and receding contact angles for brine-CO2-mica system (surface roughness ∼12nm) at different pressures (0.1MPa, 5MPa, 7MPa, 10MPa, 15MPa, 20MPa), temperatures (308K, 323K, and 343K), and salinities (0wt%, 5wt%, 10wt%, 20wt% and 30wt% NaCl). For the same experimental matrix, CO2-brine interfacial tensions have also been measured using the pendant drop technique. The results indicate that both advancing and receding contact angles increase with pressure and salinity, but decrease with temperature. On the contrary, CO2-brine interfacial tension decrease with pressure and increase with temperature. At 20MPa and 308K, the advancing angle is measured to be ∼110°, indicating CO2-wetting. The results have been compared with various published literature data and probable factors responsible for deviations have been highlighted. Finally we demonstrate the implications of measured data by evaluating CO2 storage heights under various operating conditions. We conclude that for a given storage depth, reservoirs with lower pressures and high temperatures can store larger volumes and thus exhibit better sealing efficiency. Copyright © 2015 Elsevier Inc. All rights reserved.

Strongly coupled Sm0.2Ce0.8O2-Na2CO3 nanocomposite for low temperature solid oxide fuel cells: One-step synthesis and super interfacial proton conduction

NASA Astrophysics Data System (ADS)

Zhang, Guanghong; Li, Wenjian; Huang, Wen; Cao, Zhiqun; Shao, Kang; Li, Fengjiao; Tang, Chaoyun; Li, Cuihua; He, Chuanxin; Zhang, Qianling; Fan, Liangdong

2018-05-01

Highly conductive ceria-carbonate composite represents one type of most promising electrolyte materials for low temperature solid oxide fuel cells (SOFCs). Composites with large oxide-carbonate interface and homogeneous element/phase distribution are desirable to further enhance electrical properties and to study the ionic conduction mechanism. In this work, we report the successful synthesis of element/phase well-distributed, interfacial strongly coupled Sm0.2Ce0.8O2-Na2CO3 (NSDC) nanocomposite with different residual carbonate contents by an in-situ one-pot one-step citric acid-nitrate combustion method. Interestingly, NSDC shows distinct properties over those prepared by conventional methods and improved ionic conductivity. In particular, NSDC9010 nanocomposite displays a proton conductivity of 0.044 S cm-1 at 650 °C, which is 3-5 times higher than the oxide proton conductors. Electrolyte supported SOFCs based on the resultant nanocomposite electrolyte, NSDC9010, give the best power output of 281.5 mW cm-2 at 600 °C with LiNiO2 symmetric electro-catalysts. The excellent ionic conductivity and fuel cell performance are correlated with the unique core-shell structure, good phase distribution and large interfacial area induced by the one-step fabrication method, the strong coupling between oxide and carbonate as verified by the differential thermal and Raman spectroscopy characterization results and the optimal interfacial carbonate layer thickness by intentionally adjusting of carbonate contents.

Interactions of chitin nanocrystals with β-lactoglobulin at the oil-water interface, studied by drop shape tensiometry.

PubMed

Gülseren, Ibrahim; Corredig, Milena

2013-11-01

Particle stabilized emulsions have been gaining increasing attention in the past few years, because of their unique interfacial properties. However, interactions between food grade particles and other surfactants at the interface still need to be understood. In this research, the interfacial properties of chitin nanocrystals (ChN) were studied in the presence of a surface active milk protein, β-lactoglobulin (β-lg), often used to stabilize oil-in-water emulsions. ChN were prepared by acid hydrolysis of chitin. At low pH (pH 3), ChN and β-lg do not interact, as demonstrated by light scattering measurements, and both components carry positive charge. The properties of the interface were tested using drop shape tensiometry. Addition of ChN or β-lg to the aqueous phase reduced the interfacial tension, and β-lg adsorption was characterized with an increase in the interfacial elasticity. When β-lg was added to a solution containing 0.1% ChN, the film elasticity increased first and then decreased with increasing β-lg concentration. The mixed film elasticity was the highest at a combination of 0.1% ChN+0.01% β-lg, when both molecules were simultaneously added to the aqueous phase. On the other hand, when β-lg was added after ChN, the protein did not affect the properties of the interface, indicating that the ChN (0.1%) equilibrated film was stable and that protein-protein interactions, normally resulting in an increase in the film elasticity, did not occur. Copyright © 2013 Elsevier B.V. All rights reserved.

The Initial Comparison Study of Sodium Lignosulfonate, Sodium Dodecyl Benzene Sulfonate, and Sodium p-Toluene Sulfonate Surfactant for Enhanced Oil Recovery

NASA Astrophysics Data System (ADS)

Khoirul Anas, Argo; Iman Prakoso, Nurcahyo; Sasvita, Dilla

2018-04-01

Surfactant (surface active agent) exhibit numerous interesting properties that enable their use as additional component in mobilising of residual oil from capillary pore after secondary recovery process using gas injection and water flooding. In this study, Sodium Lignosulfonate (SLS) surfactant was successfully synthesized by applying batch method using lignin from oil palm empty fruit bunches as precursor. Furthermore, its performance in reducing interfacial tension of crude oil and formation water colloidal system was compared with commercial available surfactant including Sodium Dodecyl Benzene Sulfonate (SDBS) and Sodium p-Toluene Sulfonate (SpTS). The synthesized SLS surfactant was characterized by using Fourier Transform Infrared (FTIR) spectroscopy. Meanwhile, its performance in reducing interfacial tension of crude oil and formation water colloidal system was analyzed by using compatibility test, phase behaviour analysis, and interfacial tension (IFT) measurement. The compatibility test shows that SLS, SDBS, and SpTS surfactants were compatible with formation water. In addition, the phase behaviour analysis shows that SLS surfactant was better than SpTS surfactant, while SDBS surfactant generates the highest performance proved by the best microemulsion formation resulted by SDBS. Furthermore, the optimum concentration of SLS, SDBS, and SpTS surfactants in reducing the interfacial tension of crude oil and formation water was 1.0%. The IFT measurement indicates that the performance of SLS with the value of 1.67 mN/m was also better than SpTS surfactant with the value of 3.59 mN/m. Meanwhile, SDBS surfactant shows the best performance with the IFT value of 0.47 mN/m.

Application of optical 3D measurement on thin film buckling to estimate interfacial toughness

NASA Astrophysics Data System (ADS)

Jia, H. K.; Wang, S. B.; Li, L. A.; Wang, Z. Y.; Goudeau, P.

2014-03-01

The shape-from-focus (SFF) method has been widely studied as a passive depth recovery and 3D reconstruction method for digital images. An important step in SFF is the calculation of the focus level for different points in an image by using a focus measure. In this work, an image entropy-based focus measure is introduced into the SFF method to measure the 3D buckling morphology of an aluminum film on a polymethylmethacrylate (PMMA) substrate at a micro scale. Spontaneous film wrinkles and telephone-cord wrinkles are investigated after the deposition of a 300 nm thick aluminum film onto the PMMA substrate. Spontaneous buckling is driven by the highly compressive stress generated in the Al film during the deposition process. The interfacial toughness between metal films and substrates is an important parameter for the reliability of the film/substrate system. The height profiles of different sections across the telephone-cord wrinkle can be considered a straight-sided model with uniform width and height or a pinned circular model that has a delamination region characterized by a sequence of connected sectors. Furthermore, the telephone-cord geometry of the thin film can be used to calculate interfacial toughness. The instability of the finite element model is introduced to fit the buckling morphology obtained by SFF. The interfacial toughness is determined to be 0.203 J/m2 at a 70.4° phase angle from the straight-sided model and 0.105 J/m2 at 76.9° from the pinned circular model.

Bonding measurement -Strength and fracture mechanics approaches.

PubMed

Anunmana, Chuchai; Wansom, Wiroj

2017-07-26

This study investigated the effect of cross-sectional areas on interfacial fracture toughness and bond strength of bilayered dental ceramics. Zirconia core ceramics were veneered and cut to produce specimens with three different cross-sectional areas. Additionally, monolithic specimens of glass veneer were also prepared. The specimens were tested in tension until fracture at the interface and reported as bond strength. Fracture surfaces were observed, and the apparent interfacial toughness was determined from critical crack size and failure stress. The results showed that cross-sectional area had no effect on the interfacial toughness whereas such factor had a significant effect on interfacial bond strength. The study revealed that cross-sectional area had no effect on the interfacial toughness, but had a significant effect on interfacial bond strength. The interfacial toughness may be a more reliable indicator for interfacial bond quality than interfacial bond strength.

Interfacial Effects and Organization of Inorganic-Organic Composite Solids.

DTIC Science & Technology

1998-05-20

SITU NMR STUDY OF THE HYDROTHERMAL SYNTHESIS OF TEMPLATE-MEDIATED MICROPOROUS ALUMINOPHOSPHATE MATERIALS, Conne M Gersrdin, Pnnccton Univ, Dept...quantitatively characterize the hydrothermal medium while the synthesis proceeds can yield to a better description of the different steps of the...Inorganic-Organic Composite Solids," focused on recent applications in materials synthesis that use structure-directing agents and self-assembly

Countercurrent distribution of biological cells

NASA Technical Reports Server (NTRS)

Brooks, D. E.

1982-01-01

Detailed physiochemical studies of dextran/poly(ethylene glycol) (PEG) two phase systems were carried out to characterize and provide understanding of the properties of the systems which determine cell partition and the electrophoretic behavior of phase drops responsible for electric field driven phase separation. A detailed study of the electrostatic and electrokinetic potentials developed in these systems was carried out. The salt partition was examined both in phase systems and with pure polymer solutions via equilibrium dialysis and mechanism of sulfate, chloride and phosphate partition shown to be exclusion by PEG rather than binding by dextran. Salt partition was shown to have a strong effect on the polymer compositions of the phases as well, an effect which produces large changes in the interfacial tension between them. These effects were characterized and the interfacial tension shown to obey a power law with respect to its dependence on the length of the tie line describing the system composition on a phase diagram. The electrostatic potential differences measured via salt bridges were shown to obey thermodynamic predictions. The electrophoretic mobilities measured were utilized to provide a partial test of Levine's incomplete theory of phase drop electrophoresis. The data were consistent with Levine's expression over a limited range of the variables tested.

Introduction

NASA Astrophysics Data System (ADS)

2014-12-01

This special issue of Applied Surface Science is a compilation of papers inspired by the symposium on "Surface/Interfaces Characterization and Renewable Energy" held at the 2013 MRS Fall Meeting. Practical uses of renewable energy are one of the greatest technical challenges today. The symposium explored a number of surface and interface-related questions relevant to this overarching theme. Topics from fuel cells to photovoltaics, from water splitting to fundamental and practical issues in charge generation and storage were discussed. The work presented included the use of novel experimental spectroscopic and microscopic analytical techniques, theoretical and computational understanding of interfacial phenomena, characterization of intricate behavior of charged species, as well as molecules and molecular fragments at surfaces and interfaces. It emphasized fundamental understanding of underlying processes, as well as practical devices design and applications of surface and interfacial phenomena related to renewable energy. These subjects are complicated by the transport of photons, electrons, ions, heat, and almost any other form of energy. Given the current concerns of climate change, energy independence and national security, this work is important and of interest to the field of Applied Surface Science. The sixteen papers published in this special issue have all been refereed.

2D-HB-Network at the air-water interface: A structural and dynamical characterization by means of ab initio and classical molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Pezzotti, Simone; Serva, Alessandra; Gaigeot, Marie-Pierre

2018-05-01

Following our previous work where the existence of a special 2-Dimensional H-Bond (2D-HB)-Network was revealed at the air-water interface [S. Pezzotti et al., J. Phys. Chem. Lett. 8, 3133 (2017)], we provide here a full structural and dynamical characterization of this specific arrangement by means of both Density Functional Theory based and Force Field based molecular dynamics simulations. We show in particular that water at the interface with air reconstructs to maximize H-Bonds formed between interfacial molecules, which leads to the formation of an extended and non-interrupted 2-Dimensional H-Bond structure involving on average ˜90% of water molecules at the interface. We also show that the existence of such an extended structure, composed of H-Bonds all oriented parallel to the surface, constrains the reorientional dynamics of water that is hence slower at the interface than in the bulk. The structure and dynamics of the 2D-HB-Network provide new elements to possibly rationalize several specific properties of the air-water interface, such as water surface tension, anisotropic reorientation of interfacial water under an external field, and proton hopping.

High-Potential Porphyrins Supported on SnO 2 and TiO 2 Surfaces for Photoelectrochemical Applications

DOE PAGES

Jiang, Jianbing; Swierk, John R.; Materna, Kelly L.; ...

2016-12-03

Here, we report CF 3-substituted porphyrins and evaluate their use as photosensitizers in water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) by characterizing interfacial electron transfer on metal oxide surfaces. Furthermore, by using (CF 3) 2C 6H 3 instead of C 6F 5 substituents at the meso positions, we obtain the desired high potentials while avoiding the sensitivity of C 6F 5 substituents to nucleophilic substitution, a process that limits the types of synthetic reactions that can be used. Both the number of CF 3 groups and the central metal tune the ground and excited-state potentials. A pair of porphyrins bearing carboxylic acidsmore » as anchoring groups were deposited on SnO 2 and TiO 2 surfaces and the interfacial charge-injection and charge-recombination kinetics were characterized by using a combination of computational modeling, terahertz measurements, and transient absorption spectroscopy. We also found that both free-base and metallated porphyrins inject into SnO 2, and that recombination is slower for the latter case. Our findings demonstrate that (CF 3) 2C 6H 3-substituted porphyrins are promising photosensitizers for use in WS-DSPECs.« less

Raman imaging at biological interfaces: applications in breast cancer diagnosis

PubMed Central

2013-01-01

Background One of the most important areas of Raman medical diagnostics is identification and characterization of cancerous and noncancerous tissues. The methods based on Raman scattering has shown significant potential for probing human breast tissue to provide valuable information for early diagnosis of breast cancer. A vibrational fingerprint from the biological tissue provides information which can be used to identify, characterize and discriminate structures in breast tissue, both in the normal and cancerous environment. Results The paper reviews recent progress in understanding structure and interactions at biological interfaces of the human tissue by using confocal Raman imaging and IR spectroscopy. The important differences between the noncancerous and cancerous human breast tissues were found in regions characteristic for vibrations of carotenoids, fatty acids, proteins, and interfacial water. Particular attention was paid to the role played by unsaturated fatty acids and their derivatives as well as carotenoids and interfacial water. Conclusions We demonstrate that Raman imaging has reached a clinically relevant level in regard to breast cancer diagnosis applications. The results presented in the paper may have serious implications on understanding mechanisms of interactions in living cells under realistically crowded conditions of biological tissue. PMID:23705882

Material Characterization for the Analysis of Skin/Stiffener Separation

NASA Technical Reports Server (NTRS)

Davila, Carlos G.; Leone, Frank A.; Song, Kyongchan; Ratcliffe, James G.; Rose, Cheryl A.

2017-01-01

Test results show that separation failure in co-cured skin/stiffener interfaces is characterized by dense networks of interacting cracks and crack path migrations that are not present in standard characterization tests for delamination. These crack networks result in measurable large-scale and sub-ply-scale R curve toughening mechanisms, such as fiber bridging, crack migration, and crack delving. Consequently, a number of unknown issues exist regarding the level of analysis detail that is required for sufficient predictive fidelity. The objective of the present paper is to examine some of the difficulties associated with modeling separation failure in stiffened composite structures. A procedure to characterize the interfacial material properties is proposed and the use of simplified models based on empirical interface properties is evaluated.

Interfacial mixing in high energy-density matter with a multiphysics kinetic model

NASA Astrophysics Data System (ADS)

Haack, Jeff; Hauck, Cory; Murillo, Michael

2017-10-01

We have extended a recently-developed multispecies, multitemperature BGK model to include multiphysics capability that allows modeling of a wider range of plasma conditions. In particular, we have extended the model to describe one spatial dimension, and included a multispecies atomic ionization model, accurate collision physics across coupling regimes, self-consistent electric fields, and degeneracy in the electronic screening. We apply the new model to a warm dense matter scenario in which the ablator-fuel interface of an inertial confinement fusion target is heated, similar to a recent molecular dynamics study, but for larger length and time scales and for much higher temperatures. From our numerical results we are able to explore a variety of phenomena, including hydrogen jetting, kinetic effects (non-Maxwellian and anisotropic distributions), plasma physics (size, persistence and role of electric fields) and transport (relative sizes of Fickean diffision, electrodiffusion and barodiffusion). As compared with the recent molecular dynamics work the kinetic model greatly extends the accessible physical domains we are able to model.

Processing and characterization of phase boundaries in ceramic and metallic materials

NASA Astrophysics Data System (ADS)

Zeng, Liang

The goal of this dissertation work was to explore and describe advanced characterization of novel materials processing. These characterizations were carried out using scanning and transmission electron microscopy (SEM and TEM), and X-ray diffraction techniques. The materials studied included ceramics and metallic materials. The first part of this dissertation focuses on the processing, and the resulting interfacial microstructure of ceramics joined using spin-on interlayers. SEM, TEM, and indentation tests were used to investigate the interfacial microstructural and mechanical property evolution of polycrystalline zirconia bonded to glass ceramic MaCor(TM), and polycrystalline alumina to single crystal alumina. Interlayer assisted specimens were joined using a thin amorphous silica interlayer. This interlayer was produced by spin coating an organic based silica bond material precursor and curing at 200°C, followed by joining in a microwave cavity or conventional electric furnace. Experimental results indicate that in the joining of the zirconia and MaCor(TM) no significant interfacial microstructural and mechanical property differences developed between materials joined either with or without interlayers, due to the glassy nature of MaCor(TM). The bond interface was non-planar, as a result of the strong wetting of MaCor(TM) and silica and dissolution of the zirconia. However, without the aid of a silica interlayer, sapphire and 98% polycrystalline alumina failed to join under the experimental conditions under this study. A variety of interfacial morphologies have been observed, including amorphous regions, fine crystalline alumina, and intimate contact between the sapphire and polycrystalline alumina. In addition, the evolution of the joining process from the initial sputter-cure to the final joining state and joining mechanisms were characterized. The second part of this dissertation focused on the effects of working and heat treatment on microstructure, texture, phase boundary movement, and mechanical property evolution in Ti-6Al-4V wire. The as-received wire consisted of equilibrium a and metastable beta phases and had a moderately strong fiber texture with prism plane normals aligned with the wire axis. The wire was worked by extrusion, solution heat-treatment and water quenching, and aging. The extrusion process strengthened the as-received texture. After solutionization and quenching, microstrucual observations showed the presence of many needlelike martensitic platelets in the prior beta phase regions. Texture analysis revealed that a secondary fiber with basal plane normals aligned with the wire axis emerged at the expense of the initial texture, indicating that highly preferred phase boundary motion (variant selection) occurred during the beta → alpha transformation. The strength of the variant selection consistently increased with solutionization temperature and time. In addition, the effects of dislocation type and density on variant selections were further investigated. This implies that strategic prior deformation and heat treatment can be exploited to design the resulting texture and microstructure and consequently optimize the properties of titanium products.

Influence of interfacial viscosity on the dielectrophoresis of drops

NASA Astrophysics Data System (ADS)

Mandal, Shubhadeep; Chakraborty, Suman

2017-05-01

The dielectrophoresis of a Newtonian uncharged drop in the presence of an axisymmetric nonuniform DC electric field is studied analytically. The present study is focused on the effects of interfacial viscosities on the dielectrophoretic motion and shape deformation of an isolated suspended drop. The interfacial viscosities generate surface-excess viscous stress which is modeled as a two-dimensional Newtonian fluid which obeys the Boussinesq-Scriven constitutive law with constant values of interfacial tension, interfacial shear, and dilatational viscosities. In the regime of small drop deformation, we have obtained analytical solution for the drop velocity and deformed shape by neglecting surface charge convection and fluid inertia. Our study demonstrates that the drop velocity is independent of the interfacial shear viscosity, while the interfacial dilatational viscosity strongly affects the drop velocity. The interfacial viscous effects always retard the dielectrophoretic motion of a perfectly conducting/dielectric drop. Notably, the interfacial viscous effects can retard or augment the dielectrophoretic motion of a leaky dielectric drop depending on the electrohydrodynamic properties. The shape deformation of a leaky dielectric drop is found to decrease (or increase) due to interfacial shear (or dilatational) viscosity.

Thermal oxidation induced degradation of carbon fiber reinforced composites and carbon nanotube sheet enhanced fiber/matrix interface for high temperature aerospace structural applications

NASA Astrophysics Data System (ADS)

Haque, Mohammad Hamidul

Recent increase in the use of carbon fiber reinforced polymer matrix composite, especially for high temperature applications in aerospace primary and secondary structures along with wind energy and automotive industries, have generated new challenges to predict its failure mechanisms and service life. This dissertation reports the experimental study of a unidirectional carbon fiber reinforced bismaleimide (BMI) composites (CFRC), an excellent candidate for high temperature aerospace components, undergoing thermal oxidation at 260 °C in air for over 3000 hours. The key focus of the work is to investigate the mechanical properties of the carbon fiber BMI composite subjected to thermal aging in three key aspects - first, studying its bulk flexural properties (in macro scale), second, characterizing the crack propagation along the fiber direction, representing the interfacial bonding strength between fiber and matrix (in micro scale), and third, introducing nano-structured materials to modify the interface (in nano scale) between the carbon fiber and BMI resin and mechanical characterization to study its influence on mitigating the aging effect. Under the first category, weight loss and flexural properties have been monitored as the oxidation propagates through the fiber/matrix interface. Dynamic mechanical analysis and micro-computed tomography analysis have been performed to analyze the aging effects. In the second category, the long-term effects of thermal oxidation on the delamination (between the composite plies) and debonding (between fiber and matrix) type fracture toughness have been characterized by preparing two distinct types of double cantilever beam specimens. Digital image correlation has been used to determine the deformation field and strain distribution around the crack propagation path. Finally the resin system and the fiber/matrix interface have been modified using nanomaterials to mitigate the degradations caused by oxidation. Nanoclay modified epoxy resin has been characterized for hardness and modulus using nanoindentation technique. A significant reduction of oxidation, which is anticipated to eventually translate into improvement in mechanical properties, has been observed as the nanoclay particles have worked as a retarding agent for the oxidation propagation. Carbon nanotube sheet scrolled carbon fiber tows embedded in epoxy matrix have been investigated for interfacial properties using nanoindentation (push-out test), in micro scale, and using tensile testing (pull-out test), in macro scale. A significant increase in interfacial shear strength has been achieved by this unique materials combination.

High Detectivity Graphene-Silicon Heterojunction Photodetector.

PubMed

Li, Xinming; Zhu, Miao; Du, Mingde; Lv, Zheng; Zhang, Li; Li, Yuanchang; Yang, Yao; Yang, Tingting; Li, Xiao; Wang, Kunlin; Zhu, Hongwei; Fang, Ying

2016-02-03

A graphene/n-type silicon (n-Si) heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity, which can be utilized for the development of high-performance photodetectors. However, graphene/n-Si heterojunction photodetectors reported previously suffer from relatively low specific detectivity due to large dark current. Here, by introducing a thin interfacial oxide layer, the dark current of graphene/n-Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n-Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 10(13) cm Hz(1/2) W(-1) at the peak wavelength of 890 nm in vacuum, which is highest reported detectivity at room temperature for planar graphene/Si heterojunction photodetectors. In addition, the improved graphene/n-Si heterojunction photodetectors possess high responsivity of 0.73 A W(-1) and high photo-to-dark current ratio of ≈10(7) . The current noise spectral density of the graphene/n-Si photodetector has been characterized under ambient and vacuum conditions, which shows that the dark current can be further suppressed in vacuum. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of DMSO and glycerol additives on the property of polyamide reverse osmosis membrane.

PubMed

Wu, Fengjing; Liu, Xiaojuan; Au, Chaktong

2016-10-01

The polyamide reverse osmosis (RO) membranes were prepared through interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). The use of dimethyl sulfoxide (DMSO) and glycerol as additives for the formation of thin-film composite (TFC) was investigated. We studied the effect of DMSO and glycerol addition on membrane property and RO performance. Microscopic morphology was examined by atomic force microscopy and scanning electron microscopy. The surface hydrophilicity was characterized on the basis of water contact angle and surface solid-liquid interfacial free energy (-ΔG SL ). Water flux and salt rejection ability of the membranes prepared with or without the additives were evaluated by cross-flow RO tests. The results reveal that the addition of DMSO and glycerol strongly influences the property of the TFC RO membrane. Compared to the MPD/TMC membrane fabricated without DMSO and glycerol, the MPD/TMC/DMSO/glycerol membrane has a rougher surface and is more hydrophilic, showing smaller water contact angle and larger -ΔG SL value. Without decrease in salt rejection ability, the MPD/TMC/DMSO/glycerol membrane shows water flux significantly larger than that of the MPD/TMC membrane. The unique property of the MPD/TMC/DMSO/glycerol membrane is attributed to the cooperative effect of DMSO and glycerol on membrane structure during the interfacial polymerization process.

Changes in conformational dynamics of basic side chains upon protein–DNA association

PubMed Central

Esadze, Alexandre; Chen, Chuanying; Zandarashvili, Levani; Roy, Sourav; Pettitt, B. Montgometry; Iwahara, Junji

2016-01-01

Basic side chains play major roles in recognition of nucleic acids by proteins. However, dynamic properties of these positively charged side chains are not well understood. In this work, we studied changes in conformational dynamics of basic side chains upon protein–DNA association for the zinc-finger protein Egr-1. By nuclear magnetic resonance (NMR) spectroscopy, we characterized the dynamics of all side-chain cationic groups in the free protein and in the complex with target DNA. Our NMR order parameters indicate that the arginine guanidino groups interacting with DNA bases are strongly immobilized, forming rigid interfaces. Despite the strong short-range electrostatic interactions, the majority of the basic side chains interacting with the DNA phosphates exhibited high mobility, forming dynamic interfaces. In particular, the lysine side-chain amino groups exhibited only small changes in the order parameters upon DNA-binding. We found a similar trend in the molecular dynamics (MD) simulations for the free Egr-1 and the Egr-1–DNA complex. Using the MD trajectories, we also analyzed side-chain conformational entropy. The interfacial arginine side chains exhibited substantial entropic loss upon binding to DNA, whereas the interfacial lysine side chains showed relatively small changes in conformational entropy. These data illustrate different dynamic characteristics of the interfacial arginine and lysine side chains. PMID:27288446

Theoretical vibrational sum-frequency generation spectroscopy of water near lipid and surfactant monolayer interfaces.

PubMed

Roy, S; Gruenbaum, S M; Skinner, J L

2014-11-14

Understanding the structure of water near cell membranes is crucial for characterizing water-mediated events such as molecular transport. To obtain structural information of water near a membrane, it is useful to have a surface-selective technique that can probe only interfacial water molecules. One such technique is vibrational sum-frequency generation (VSFG) spectroscopy. As model systems for studying membrane headgroup/water interactions, in this paper we consider lipid and surfactant monolayers on water. We adopt a theoretical approach combining molecular dynamics simulations and phase-sensitive VSFG to investigate water structure near these interfaces. Our simulated spectra are in qualitative agreement with experiments and reveal orientational ordering of interfacial water molecules near cationic, anionic, and zwitterionic interfaces. OH bonds of water molecules point toward an anionic interface leading to a positive VSFG peak, whereas the water hydrogen atoms point away from a cationic interface leading to a negative VSFG peak. Coexistence of these two interfacial water species is observed near interfaces between water and mixtures of cationic and anionic lipids, as indicated by the presence of both negative and positive peaks in their VSFG spectra. In the case of a zwitterionic interface, OH orientation is toward the interface on the average, resulting in a positive VSFG peak.

Interfacial metal and antibody recognition.

PubMed

Zhou, Tongqing; Hamer, Dean H; Hendrickson, Wayne A; Sattentau, Quentin J; Kwong, Peter D

2005-10-11

The unique ligation properties of metal ions are widely exploited by proteins, with approximately one-third of all proteins estimated to be metalloproteins. Although antibodies use various mechanisms for recognition, to our knowledge, none has ever been characterized that uses an interfacial metal. We previously described a family of CD4-reactive antibodies, the archetype being Q425. CD4:Q425 engagement does not interfere with CD4:HIV-1 gp120 envelope glycoprotein binding, but it blocks subsequent steps required for viral entry. Here, we use surface-plasmon resonance to show that Q425 requires calcium for recognition of CD4. Specifically, Q425 binding of calcium resulted in a 55,000-fold enhancement in affinity for CD4. X-ray crystallographic analyses of Q425 in the presence of Ca(2+), Ba(2+), or EDTA revealed an exposed metal-binding site, partially coordinated by five atoms contributed from four antibody complementarity-determining regions. The results suggest that Q425 recognition of CD4 involves direct ligation of antigen by the Q425-held calcium, with calcium binding each ligating atom of CD4 with approximately 1.5 kcal/mol of binding energy. This energetic contribution, which is greater than that from a typical protein atom, demonstrates how interfacial metal ligation can play a unique role in antigen recognition.

Interfacial metal and antibody recognition

PubMed Central

Zhou, Tongqing; Hamer, Dean H.; Hendrickson, Wayne A.; Sattentau, Quentin J.; Kwong, Peter D.

2005-01-01

The unique ligation properties of metal ions are widely exploited by proteins, with approximately one-third of all proteins estimated to be metalloproteins. Although antibodies use various mechanisms for recognition, to our knowledge, none has ever been characterized that uses an interfacial metal. We previously described a family of CD4-reactive antibodies, the archetype being Q425. CD4:Q425 engagement does not interfere with CD4:HIV-1 gp120 envelope glycoprotein binding, but it blocks subsequent steps required for viral entry. Here, we use surface-plasmon resonance to show that Q425 requires calcium for recognition of CD4. Specifically, Q425 binding of calcium resulted in a 55,000-fold enhancement in affinity for CD4. X-ray crystallographic analyses of Q425 in the presence of Ca2+, Ba2+, or EDTA revealed an exposed metal-binding site, partially coordinated by five atoms contributed from four antibody complementarity-determining regions. The results suggest that Q425 recognition of CD4 involves direct ligation of antigen by the Q425-held calcium, with calcium binding each ligating atom of CD4 with ≈1.5 kcal/mol of binding energy. This energetic contribution, which is greater than that from a typical protein atom, demonstrates how interfacial metal ligation can play a unique role in antigen recognition. PMID:16195378

Aquaporin-Based Biomimetic Polymeric Membranes: Approaches and Challenges

PubMed Central

Habel, Joachim; Hansen, Michael; Kynde, Søren; Larsen, Nanna; Midtgaard, Søren Roi; Jensen, Grethe Vestergaard; Bomholt, Julie; Ogbonna, Anayo; Almdal, Kristoffer; Schulz, Alexander; Hélix-Nielsen, Claus

2015-01-01

In recent years, aquaporin biomimetic membranes (ABMs) for water separation have gained considerable interest. Although the first ABMs are commercially available, there are still many challenges associated with further ABM development. Here, we discuss the interplay of the main components of ABMs: aquaporin proteins (AQPs), block copolymers for AQP reconstitution, and polymer-based supporting structures. First, we briefly cover challenges and review recent developments in understanding the interplay between AQP and block copolymers. Second, we review some experimental characterization methods for investigating AQP incorporation including freeze-fracture transmission electron microscopy, fluorescence correlation spectroscopy, stopped-flow light scattering, and small-angle X-ray scattering. Third, we focus on recent efforts in embedding reconstituted AQPs in membrane designs that are based on conventional thin film interfacial polymerization techniques. Finally, we describe some new developments in interfacial polymerization using polyhedral oligomeric silsesquioxane cages for increasing the physical and chemical durability of thin film composite membranes. PMID:26264033

Reactivity of sulfide-containing silane toward boehmite and in situ modified rubber/boehmite composites by the silane

NASA Astrophysics Data System (ADS)

Lin, Tengfei; Zhu, Lixin; Chen, Weiwei; Wu, Siwu; Guo, Baochun; Jia, Demin

2013-09-01

The silanization reaction between boehmite (BM) nanoplatelets and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide (TESPT) was characterized in detail. Via such modification process, the grafted sulfide moieties on the BM endow reactivity toward rubber and substantially improved hydrophobicity for BM. Accordingly, TESPT was employed as in situ modifier for the nitrile rubber (NBR)/BM compounds to improve the mechanical properties of the reinforced vulcanizates. The effects of BM content and in situ modification on the mechanical properties, curing characteristics and morphology were investigated. BM was found to be effective in improving the mechanical performance of NBR vulcanizates. The NBR/BM composites could be further strengthened by the incorporation of TESPT. The interfacial adhesion of NBR/BM composites was obviously improved by the addition of TESPT. The substantially improved mechanical performance was correlated to the interfacial reaction and the improved dispersion of BM in rubber matrix.

An Optical Interferometric Triaxial Displacement Sensor for Structural Health Monitoring: Characterization of Sliding and Debonding for a Delamination Process

PubMed Central

Chen, Yizheng; Zhuang, Yiyang; Du, Yang; Gerald, Rex E.; Tang, Yan

2017-01-01

This paper presents an extrinsic Fabry–Perot interferometer-based optical fiber sensor (EFPI) for measuring three-dimensional (3D) displacements, including interfacial sliding and debonding during delamination. The idea employs three spatially arranged EFPIs as the sensing elements. In our sensor, the three EFPIs are formed by three endfaces of three optical fibers and their corresponding inclined mirrors. Two coincident roof-like metallic structures are used to support the three fibers and the three mirrors, respectively. Our sensor was calibrated and then used to monitor interfacial sliding and debonding between a long square brick of mortar and its support structure (i.e., a steel base plate) during the drying/curing process. This robust and easy-to-manufacture triaxial EFPI-based 3D displacement sensor has great potential in structural health monitoring, the construction industry, oil well monitoring, and geotechnology. PMID:29165351

An Optical Interferometric Triaxial Displacement Sensor for Structural Health Monitoring: Characterization of Sliding and Debonding for a Delamination Process.

PubMed

Zhu, Chen; Chen, Yizheng; Zhuang, Yiyang; Du, Yang; Gerald, Rex E; Tang, Yan; Huang, Jie

2017-11-22

This paper presents an extrinsic Fabry-Perot interferometer-based optical fiber sensor (EFPI) for measuring three-dimensional (3D) displacements, including interfacial sliding and debonding during delamination. The idea employs three spatially arranged EFPIs as the sensing elements. In our sensor, the three EFPIs are formed by three endfaces of three optical fibers and their corresponding inclined mirrors. Two coincident roof-like metallic structures are used to support the three fibers and the three mirrors, respectively. Our sensor was calibrated and then used to monitor interfacial sliding and debonding between a long square brick of mortar and its support structure (i.e., a steel base plate) during the drying/curing process. This robust and easy-to-manufacture triaxial EFPI-based 3D displacement sensor has great potential in structural health monitoring, the construction industry, oil well monitoring, and geotechnology.

Bioactive glass coatings for orthopedic metallic implants

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

Lopez-Esteban, Sonia; Saiz, Eduardo; Fujino, Sigheru

2003-06-30

The objective of this work is to develop bioactive glass coatings for metallic orthopedic implants. A new family of glasses in the SiO2-Na2O-K2O-CaO-MgO-P2O5 system has been synthesized and characterized. The glass properties (thermal expansion, softening and transformation temperatures, density and hardness) are in line with the predictions of established empirical models. The optimized firing conditions to fabricate coatings on Ti-based and Co-Cr alloys have been determined and related to the glass properties and the interfacial reactions. Excellent adhesion to alloys has been achieved through the formation of 100-200 nm thick interfacial layers (Ti5Si3 on Ti-based alloys and CrOx on Co-Cr).more » Finally, glass coatings, approximately 100 mu m thick, have been fabricated onto commercial Ti alloy-based dental implants.« less

Induced Fit in Protein Multimerization: The HFBI Case

PubMed Central

Riccardi, Laura

2016-01-01

Hydrophobins, produced by filamentous fungi, are small amphipathic proteins whose biological functions rely on their unique surface-activity properties. Understanding the mechanistic details of the multimerization process is of primary importance to clarify the interfacial activity of hydrophobins. We used free energy calculations to study the role of a flexible β-hairpin in the multimerization process in hydrophobin II from Trichoderma reesei (HFBI). We characterized how the displacement of this β-hairpin controls the stability of the monomers/dimers/tetramers in solution. The regulation of the oligomerization equilibrium of HFBI will necessarily affect its interfacial properties, fundamental for its biological function and for technological applications. Moreover, we propose possible routes for the multimerization process of HFBI in solution. This is the first case where a mechanism by which a flexible loop flanking a rigid patch controls the protein-protein binding equilibrium, already known for proteins with charged binding hot-spots, is described within a hydrophobic patch. PMID:27832079

Influence of BN fiber coatings on the interfacial structure of sapphire fiber reinforced NiAl composites

NASA Astrophysics Data System (ADS)

Reichert, K.; Wen, K.; Cremer, R.; Hu, W.; Neuschütz, D.; Gottstein, G.

2001-07-01

A new concept for a tailored fiber-matrix interface for sapphire fiber reinforced NiAl matrix composites is proposed, consisting of an initial hexagonal boron nitride (hBN) fiber coating. For this, single crystal Al 2O 3 fibers were coated with hBN by chemical vapor deposition (CVD). Following a comprehensive characterization of the CVD coating as to composition and structure by means of X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD), the fiber reinforced NiAl matrix composites were fabricated by diffusion bonding at 1400°C. The interfaces NiAl/BN and BN/Al 2O 3 were analyzed by scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and selected area diffraction (SAD). An interfacial reaction between NiAl and hBN to form AlN was revealed using these analytical techniques.

First-passage dynamics of linear stochastic interface models: weak-noise theory and influence of boundary conditions

NASA Astrophysics Data System (ADS)

Gross, Markus

2018-03-01

We consider a one-dimensional fluctuating interfacial profile governed by the Edwards–Wilkinson or the stochastic Mullins-Herring equation for periodic, standard Dirichlet and Dirichlet no-flux boundary conditions. The minimum action path of an interfacial fluctuation conditioned to reach a given maximum height M at a finite (first-passage) time T is calculated within the weak-noise approximation. Dynamic and static scaling functions for the profile shape are obtained in the transient and the equilibrium regime, i.e. for first-passage times T smaller or larger than the characteristic relaxation time, respectively. In both regimes, the profile approaches the maximum height M with a universal algebraic time dependence characterized solely by the dynamic exponent of the model. It is shown that, in the equilibrium regime, the spatial shape of the profile depends sensitively on boundary conditions and conservation laws, but it is essentially independent of them in the transient regime.

Domain Growth Kinetics in Stratifying Foam Films

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Sharma, Vivek

2015-03-01

Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Typical foam films consist of two surfactant-laden surfaces that are μ 5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of viscous and interfacial forces, including disjoining pressure. Interestingly, for certain low molecular weight surfactants, a layered ordering of micelles inside the foam films (thickness <100 nm) leads to a stepwise thinning phenomena called stratification. We experimentally elucidate the influence of these different driving forces, and confinement on drainage kinetics of horizontal stratifying foam films. Thinner, darker domains spontaneously grow within foam films. Quantitative characterization of domain growth visualized in a using Scheludko-type thin film cell and a theoretical model based on lubrication analysis, provide critical insights into hydrodynamics of thin foam films, and the strength and nature of surface forces, including supramolecular oscillatory structural forces.

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. Copyright © 2016 Elsevier Ltd. All rights reserved.

Studies on Hot-Melt Prepregging on PRM-II-50 Polyimide Resin with Graphite Fibers

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Juhas, John; Veverka, Adrienne; Klans, Ojars; Inghram, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Zoha, John; Bubnick, Jim

2004-01-01

A second generation PMR (in situ Polymerization of Monomer Reactants) polyimide resin PMR-II-50, has been considered for high temperature and high stiffness space propulsion composites applications for its improved high temperature performance. As part of composite processing optimization, two commercial prepregging methods: solution vs. hot-melt processes were investigated with M40J fabrics from Toray. In a previous study a systematic chemical, physical, thermal and mechanical characterization of these composites indicated the poor resin-fiber interfacial wetting, especially for the hot-melt process, resulted in poor composite quality. In order to improve the interfacial wetting, optimization of the resin viscosity and process variables were attempted in a commercial hot-melt prepregging line. In addition to presenting the results from the prepreg quality optimization trials, the combined effects of the prepregging method and two different composite cure methods, i.e. hot press vs. autoclave on composite quality and properties are discussed.

The Study of Interpenetration Length between dPS Films and PS-grafted Layers

NASA Astrophysics Data System (ADS)

Lee, Hoyeon; Jo, Seongjun; Hirata, Toyoaki; Yamada, Norifumi L.; Tanaka, Keiji; Ryu, Du Yeol

In polymer thin film system, the type of interfacial interaction is a critical parameter to determining the thermal and physical properties of polymer films. Interestingly, the interfacial energy of grafted substrates with polymer chains is remarkably altered by simply controlling grafting density, which has been referred to as autophobicity. In this study, we investigated the interpenetrating interfaces between deuterated polystyrene (dPS) and grafted substrates with the same chemical identity. PS-grafted substrates were prepared using a grafting-to approach with hydroxyl end-functionalized polystyrene (PSOH) in a dry brush regime, where the brush thickness and grafting density were determined based on the chain length (or molecular weight, Mn) of PSOHs. The interpenetration lengths (ξ) at interfaces between dPS and PS-grafted layers were characterized using neutron reflectivity (NR) measurements (performed at the SOFIA beam-line at J-PARC, Japan). Academic adviser.

Schlieren optical visualization for transient EHD induced flow in a stratified dielectric liquid under gas-phase ac corona discharges

NASA Astrophysics Data System (ADS)

Ohyama, R.; Inoue, K.; Chang, J. S.

2007-01-01

A flow pattern characterization of electrohydrodynamically (EHD) induced flow phenomena of a stratified dielectric fluid situated in an ac corona discharge field is conducted by a Schlieren optical system. A high voltage application to a needle-plate electrode arrangement in gas-phase normally initiates a conductive type EHD gas flow. Although the EHD gas flow motion initiated from the corona discharge electrode has been well known as corona wind, no comprehensive study has been conducted for an EHD fluid flow motion of the stratified dielectric liquid that is exposed to the gas-phase ac corona discharge. The experimentally observed result clearly presents the liquid-phase EHD flow phenomenon induced from the gas-phase EHD flow via an interfacial momentum transfer. The flow phenomenon is also discussed in terms of the gas-phase EHD number under the reduced gas pressure (reduced interfacial momentum transfer) conditions.

Studies on Hot-Melt Prepregging of PMR-II-50 Polyimide Resin with Graphite Fibers

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Juhas, John; Veverka, Adrienne; Klans, Ojars; Inghram, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Zoha, John; Bubnick, Jim

2003-01-01

A Second generation PMR (in situ Polymerization of Monomer Reactants) polyimide resin, PMR-II-50, has been considered for high temperature and high stiffness space propulsion composites applications for its improved high temperature performance. As part of composite processing optimization, two commercial prepregging methods: solution vs. hot-melt processes were investigated with M40J fabrics from Toray. In a previous study a systematic chemical, physical, thermal and mechanical characterization of these composites indicated that poor resin-fiber interfacial wetting, especially for the hot-melt process, resulted in poor composite quality. In order to improve the interfacial wetting, optimization of the resin viscosity and process variables were attempted in a commercial hot-melt prepregging line. In addition to presenting the results from the prepreg quality optimization trials, the combined effects of the prepregging method and two different composite cure methods, i.e., hot press vs. autoclave on composite quality and properties are discussed.

Viscoelastic analysis of a dental metal-ceramic system

NASA Astrophysics Data System (ADS)

Özüpek, Şebnem; Ünlü, Utku Cemal

2012-11-01

Porcelain-fused-to-metal (PFM) restorations used in prosthetic dentistry contain thermal stresses which develop during the cooling phase after firing. These thermal stresses coupled with the stresses produced by mechanical loads may be the dominant reasons for failures in clinical situations. For an accurate calculation of these stresses, viscoelastic behavior of ceramics at high temperatures should not be ignored. In this study, the finite element technique is used to evaluate the effect of viscoelasticity on stress distributions of a three-point flexure test specimen, which is the current international standard, ISO 9693, to characterize the interfacial bond strength of metal-ceramic restorative systems. Results indicate that the probability of interfacial debonding due to normal tensile stress is higher than that due to shear stress. This conclusion suggests modification of ISO 9693 bond strength definition from one in terms of the shear stress only to that accounting for both normal and shear stresses.

Structural rearrangement and dispersion of functionalized graphene sheets in aqueous solutions

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

Lee, Yun Jung; Huang, Liwei; Wang, Howard

2015-09-01

Surfactants are widely used for dispersing graphene and functionalized graphene sheets (FGS) in colloidal suspensions, but there have been few studies of the structure of the dispersed graphene-surfactant complexes in suspension and of their time evolution. Here, we combine experimental study of efficiencies of ionic surfactants/polymers in suspending FGS in water with characterization using atomic force microscopy, small angle neutron scattering, and molecular simulations to probe the detailed structures of FGSs. A systematic study of FGS dispersions using ionic surfactants with varying chain lengths revealed that the effective charge density of surfactant layer defines the concentration of dispersed FGS whilemore » the strength of interfacial binding defines the stability of graphene dispersion over long time aging. Ionic surfactants with strong interfacial binding and large molecular weight increase the dispersing power by over an order of magnitude.« less

Interfacial improvements in biocomposites based on poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) bioplastics reinforced and grafted with α-cellulose fibers

Treesearch

Liqing Wei; Nicole M. Stark; Armando G. McDonald

2015-01-01

In this study, α-cellulose fibers reinforced green biocomposites based on polyhydroxybutyrate (PHB) and the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared and characterized. The α-cellulose fibers were isolated from at-risk intermountain lodgepole pine wood by successive removal of extractives, lignin and hemicellulose...

Reaction Dynamics at Liquid Interfaces

NASA Astrophysics Data System (ADS)

Benjamin, Ilan

2015-04-01

The liquid interface is a narrow, highly anisotropic region, characterized by rapidly varying density, polarity, and molecular structure. I review several aspects of interfacial solvation and show how these affect reactivity at liquid/liquid interfaces. I specifically consider ion transfer, electron transfer, and SN2 reactions, showing that solvent effects on these reactions can be understood by examining the unique structure and dynamics of the liquid interface region.

Molecular tailoring of interfaces for thin film on substrate systems

NASA Astrophysics Data System (ADS)

Grady, Martha Elizabeth

Thin film on substrate systems appear most prevalently within the microelectronics industry, which demands that devices operate in smaller and smaller packages with greater reliability. The reliability of these multilayer film systems is strongly influenced by the adhesion of each of the bimaterial interfaces. During use, microelectronic components undergo thermo-mechanical cycling, which induces interfacial delaminations leading to failure of the overall device. The ability to tailor interfacial properties at the molecular level provides a mechanism to improve thin film adhesion, reliability and performance. This dissertation presents the investigation of molecular level control of interface properties in three thin film-substrate systems: photodefinable polyimide films on passivated silicon substrates, self-assembled monolayers at the interface of Au films and dielectric substrates, and mechanochemically active materials on rigid substrates. For all three materials systems, the effect of interfacial modifications on adhesion is assessed using a laser-spallation technique. Laser-induced stress waves are chosen because they dynamically load the thin film interface in a precise, noncontacting manner at high strain rates and are suitable for both weak and strong interfaces. Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. The influence of processing parameters on adhesion is examined for photodefinable polyimide films on silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). Interfacial strength increases when films are processed with an exposure step as well as a longer cure cycle. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The high toughness of this interface (ca. 100 J/m2) makes it difficult to use more conventional interfacial fracture testing techniques. Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface in an on-demand fashion. The SAM end-group functionality is systematically varied and the corresponding effect on interfacial adhesion between a transfer printed gold (Au) film and a fused silica substrate is measured. SAMs with four different end groups are investigated: methyl, amine, bromine and thiol. In addition to these four end groups, mixed monolayers of increasing molar ratio of thiol to methyl SAMs in solution are investigated. There is a strong dependence of interfacial chemistry on the adhesion strength of Au films. In addition to the chemical functionality of the SAM, surface roughness of the underlying substrate also has a significant impact on the interfacial strength. Thin films of mechanochemically active polymer are subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produces large amplitude stresses (>100 MPa) in short time frames (10-20 ns), leading to very high strain-rates (ca. 107-108 s -1). The polymer system, spiropyran (SP)- linked polystyrene (PS), undergoes a force-induced chemical reaction causing fluorescence and color change. Activation of SP is evident via a fluorescence signal in thin films subject to high strain-rates. In contrast, quasi-static loading of bulk SP-linked PS samples failed to result in SP activation. Mechanoresponsive coatings have potential to indicate deformation under shockwave loading conditions. In addition to SP-linked polymer films, the activation of spiropyran interfacial molecules with different side groups is characterized as they adsorb onto a SAM platform with preferential amine terminating chemistry. The reactivity of SP monolayers due to UV irradiation is evaluated by water contact angle goniometry and fluorescence spectroscopy. Side groups on the interfacial spiropyran molecule affect the reactivity and the proximity of neighboring spiropyrans can prevent efficient mobility.

Requirements of frictional debonding at fiber/matrix interfaces for tough ceramic composites

NASA Astrophysics Data System (ADS)

Hsueh, Chun-Hway

1992-11-01

Optimum toughening of fiber-reinforced ceramic composites requires debonding at fiber/matrix interfaces and subsequent frictional sliding between the fibers and the matrix as the main crack extends through the composite. Criteria of both interfacial debonding vs fiber fracture, and frictional debonding vs frictionless debonding, are illustrated. To achieve interfacial debonding, the ratio of the fiber strength to the interfacial shear strength must exceed a critical value; to achieve a frictional interface after interfacial debonding, the ratio of the interfacial residual clamping stress to the interfacial shear strength must also exceed a critical value. While interfacial debonding is not sensitive to Poisson's effect, the frictional interface is sensitive to Poisson's effect.

Optimal contant time injection policy for enhanced oil recovery and characterization of optimal viscous profiles

NASA Astrophysics Data System (ADS)

Daripa, Prabir

2011-11-01

We numerically investigate the optimal viscous profile in constant time injection policy of enhanced oil recovery. In particular, we investigate the effect of a combination of interfacial and layer instabilities in three-layer porous media flow on the overall growth of instabilities and thereby characterize the optimal viscous profile. Results based on monotonic and non-monotonic viscous profiles will be presented. Time permitting. we will also present results on multi-layer porous media flows for Newtonian and non-Newtonian fluids and compare the results. The support of Qatar National Fund under a QNRF Grant is acknowledged.

Microwave Synthesis and Characterization of Waste Soybean Oil-Based Gemini Imidazolinium Surfactants with Carbonate Linkage

NASA Astrophysics Data System (ADS)

Tripathy, Divya Bajpai; Mishra, Anuradha

Gemini surfactants are presently gaining attention due to their unusual self-assembling characteristics and incomparable interfacial activity. Current research work involves the cost-effective microwave (MW) synthesis of waste soybean oil-based gemini imidazolinium surfactants (GIS) having a carbonate linkage in its spacer moiety. Structural characterizations of the materials have been done using FT-IR, 1H-NMR and 13C-NMR. Using indigenous and natural material as base and MW as energy source for synthesizing the GIS with easily degradable chemical moiety make them to be labeled as green surfactants.

Metal/ceramic interface structures and segregation behavior in aluminum-based composites

DOE PAGES

Zhang, Xinming; Hu, Tao; Rufner, Jorgen F.; ...

2015-06-14

Trimodal Al alloy (AA) matrix composites consisting of ultrafine-­grained (UFG) and coarse-­ grained (CG) Al phases and micron-­sized B 4C ceramic reinforcement particles exhibit combinations of strength and ductility that render them useful for potential applications in the aerospace, defense and automotive industries. Tailoring of microstructures with specific mechanical properties requires a detailed understanding of interfacial structures to enable strong interface bonding between ceramic reinforcement and metal matrix, and thereby allow for effective load transfer. Trimodal AA metal matrix composites typically show three characteristics that are noteworthy: nanocrystalline grains in the vicinity of the B4C reinforcement particles; Mg segregation atmore » AA/B 4C interfaces; and the presence of amorphous interfacial layers separating nanocrystalline grains from B 4C particles. Interestingly, however, fundamental information related to the mechanisms responsible for these characteristics as well as information on local compositions and phases are absent in the current literature. Here in this study, we use high-­resolution transmission electron microscopy, energy-­dispersive X-­ray spectroscopy, electron energy-­loss spectroscopy, and precession assisted electron diffraction to gain fundamental insight into the mechanisms that affect the characteristics of AA/B 4C interfaces. Specifically, we determined interfacial structures, local composition and spatial distribution of the interfacial constituents. Near atomic resolution characterization revealed amorphous multilayers and a nanocrystalline region between Al phase and B 4C reinforcement particles. The amorphous multilayers consist of nonstoichiometric Al xO y, while the nanocrystalline region is comprised of MgO nanograins. The experimental results are discussed in terms of the possible underlying mechanisms at AA/B 4C interfaces.« less

Effects of the c-Si/a-SiO2 interfacial atomic structure on its band alignment: an ab initio study.

PubMed

Zheng, Fan; Pham, Hieu H; Wang, Lin-Wang

2017-12-13

The crystalline-Si/amorphous-SiO 2 (c-Si/a-SiO 2 ) interface is an important system used in many applications, ranging from transistors to solar cells. The transition region of the c-Si/a-SiO 2 interface plays a critical role in determining the band alignment between the two regions. However, the question of how this interface band offset is affected by the transition region thickness and its local atomic arrangement is yet to be fully investigated. Here, by controlling the parameters of the classical Monte Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thicknesses, as well as containing Si at different oxidation states. A hybrid functional method, as shown by our calculations to reproduce the GW and experimental results for bulk Si and SiO 2 , was used to calculate the electronic structure of the heterojunction. This allowed us to study the correlation between the interface band characterization and its atomic structures. We found that although the systems with different thicknesses showed quite different atomic structures near the transition region, the calculated band offset tended to be the same, unaffected by the details of the interfacial structure. Our band offset calculation agrees well with the experimental measurements. This robustness of the interfacial electronic structure to its interfacial atomic details could be another reason for the success of the c-Si/a-SiO 2 interface in Si-based electronic applications. Nevertheless, when a reactive force field is used to generate the a-SiO 2 and c-Si/a-SiO 2 interfaces, the band offset significantly deviates from the experimental values by about 1 eV.

Effects of the c-Si/a-SiO 2 interfacial atomic structure on its band alignment: an ab initio study

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

Zheng, Fan; Pham, Hieu H.; Wang, Lin-Wang

The crystalline-Si/amorphous-SiO 2 (c-Si/a-SiO 2) interface is an important system used in many applications, ranging from transistors to solar cells. The transition region of the c-Si/a-SiO 2 interface plays a critical role in determining the band alignment between the two regions. However, the question of how this interface band offset is affected by the transition region thickness and its local atomic arrangement is yet to be fully investigated. Here in this study, by controlling the parameters of the classical Monte Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thicknesses, as well as containingmore » Si at different oxidation states. A hybrid functional method, as shown by our calculations to reproduce the GW and experimental results for bulk Si and SiO 2, was used to calculate the electronic structure of the heterojunction. This allowed us to study the correlation between the interface band characterization and its atomic structures. We found that although the systems with different thicknesses showed quite different atomic structures near the transition region, the calculated band offset tended to be the same, unaffected by the details of the interfacial structure. Our band offset calculation agrees well with the experimental measurements. This robustness of the interfacial electronic structure to its interfacial atomic details could be another reason for the success of the c-Si/a-SiO 2 interface in Si-based electronic applications. Nevertheless, when a reactive force field is used to generate the a-SiO 2 and c-Si/a-SiO 2 interfaces, the band offset significantly deviates from the experimental values by about 1 eV« less

Effects of the c-Si/a-SiO 2 interfacial atomic structure on its band alignment: an ab initio study

DOE PAGES

Zheng, Fan; Pham, Hieu H.; Wang, Lin-Wang

2017-11-13

The crystalline-Si/amorphous-SiO 2 (c-Si/a-SiO 2) interface is an important system used in many applications, ranging from transistors to solar cells. The transition region of the c-Si/a-SiO 2 interface plays a critical role in determining the band alignment between the two regions. However, the question of how this interface band offset is affected by the transition region thickness and its local atomic arrangement is yet to be fully investigated. Here in this study, by controlling the parameters of the classical Monte Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thicknesses, as well as containingmore » Si at different oxidation states. A hybrid functional method, as shown by our calculations to reproduce the GW and experimental results for bulk Si and SiO 2, was used to calculate the electronic structure of the heterojunction. This allowed us to study the correlation between the interface band characterization and its atomic structures. We found that although the systems with different thicknesses showed quite different atomic structures near the transition region, the calculated band offset tended to be the same, unaffected by the details of the interfacial structure. Our band offset calculation agrees well with the experimental measurements. This robustness of the interfacial electronic structure to its interfacial atomic details could be another reason for the success of the c-Si/a-SiO 2 interface in Si-based electronic applications. Nevertheless, when a reactive force field is used to generate the a-SiO 2 and c-Si/a-SiO 2 interfaces, the band offset significantly deviates from the experimental values by about 1 eV« less

Long-wave-instability-induced pattern formation in an evaporating sessile or pendent liquid layer

NASA Astrophysics Data System (ADS)

Wei, Tao; Duan, Fei

2018-03-01

We investigate the nonlinear dynamics and stability of an evaporating liquid layer subject to vapor recoil, capillarity, thermocapillarity, ambient cooling, viscosity, and negative or positive gravity combined with buoyancy effects in the lubrication approximation. Using linear theory, we identify the mechanisms of finite-time rupture, independent of thermocapillarity and direction of gravity, and predict the effective growth rate of an interfacial perturbation which reveals competition among the mechanisms. A stability diagram is predicted for the onset of long-wave (LW) evaporative convection. In the two-dimensional simulation, we observe well-defined capillary ridges on both sides of the valley under positive gravity and main and secondary droplets under negative gravity, while a ridge can be trapped in a large-scale drained region in both cases. Neglecting the other non-Boussinesq effects, buoyancy does not have a significant influence on interfacial evolution and rupture time but makes contributions to the evaporation-driven convection and heat transfer. The average Nusselt number is found to increase with a stronger buoyancy effect. The flow field and interface profile jointly manifest the LW Marangoni-Rayleigh-Bénard convection under positive gravity and the LW Marangoni convection under negative gravity. In the three-dimensional simulation of moderate evaporation with a random perturbation, the rupture patterns are characterized by irregular ridge networks with distinct height scales for positive and negative gravity. A variety of interfacial and internal dynamics are displayed, depending on evaporation conditions, gravity, Marangoni effect, and ambient cooling. Reasonable agreement is found between the present results and the reported experiments and simulations. The concept of dissipative compacton also sheds light on the properties of interfacial fractalization.

Modelling dental implant extraction by pullout and torque procedures.

PubMed

Rittel, D; Dorogoy, A; Shemtov-Yona, K

2017-07-01

Dental implants extraction, achieved either by applying torque or pullout force, is used to estimate the bone-implant interfacial strength. A detailed description of the mechanical and physical aspects of the extraction process in the literature is still missing. This paper presents 3D nonlinear dynamic finite element simulations of a commercial implant extraction process from the mandible bone. Emphasis is put on the typical load-displacement and torque-angle relationships for various types of cortical and trabecular bone strengths. The simulations also study of the influence of the osseointegration level on those relationships. This is done by simulating implant extraction right after insertion when interfacial frictional contact exists between the implant and bone, and long after insertion, assuming that the implant is fully bonded to the bone. The model does not include a separate representation and model of the interfacial layer for which available data is limited. The obtained relationships show that the higher the strength of the trabecular bone the higher the peak extraction force, while for application of torque, it is the cortical bone which might dictate the peak torque value. Information on the relative strength contrast of the cortical and trabecular components, as well as the progressive nature of the damage evolution, can be revealed from the obtained relations. It is shown that full osseointegration might multiply the peak and average load values by a factor 3-12 although the calculated work of extraction varies only by a factor of 1.5. From a quantitative point of view, it is suggested that, as an alternative to reporting peak load or torque values, an average value derived from the extraction work be used to better characterize the bone-implant interfacial strength. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fluid-fluid interfacial mobility from random walks

NASA Astrophysics Data System (ADS)

Barclay, Paul L.; Lukes, Jennifer R.

2017-12-01

Dual control volume grand canonical molecular dynamics is used to perform the first calculation of fluid-fluid interfacial mobilities. The mobility is calculated from one-dimensional random walks of the interface by relating the diffusion coefficient to the interfacial mobility. Three different calculation methods are employed: one using the interfacial position variance as a function of time, one using the mean-squared interfacial displacement, and one using the time-autocorrelation of the interfacial velocity. The mobility is calculated for two liquid-liquid interfaces and one liquid-vapor interface to examine the robustness of the methods. Excellent agreement between the three calculation methods is shown for all the three interfaces, indicating that any of them could be used to calculate the interfacial mobility.

Method for estimating protein binding capacity of polymeric systems.

PubMed

Sharma, Vaibhav; Blackwood, Keith A; Haddow, David; Hook, Lilian; Mason, Chris; Dye, Julian F; García-Gareta, Elena

2015-01-01

Composite biomaterials made from synthetic and protein-based polymers are extensively researched in tissue engineering. To successfully fabricate a protein-polymer composite, it is critical to understand how strongly the protein binds to the synthetic polymer, which occurs through protein adsorption. Currently, there is no cost-effective and simple method for characterizing this interfacial binding. To characterize this interfacial binding, we introduce a simple three-step method that involves: 1) synthetic polymer surface characterisation, 2) a quick, inexpensive and robust novel immuno-based assay that uses protein extraction compounds to characterize protein binding strength followed by 3) an in vitro 2D model of cell culture to confirm the results of the immuno-based assay. Fibrinogen, precursor of fibrin, was adsorbed (test protein) on three different polymeric surfaces: silicone, poly(acrylic acid)-coated silicone and poly(allylamine)-coated silicone. Polystyrene surface was used as a reference. Characterisation of the different surfaces revealed different chemistry and roughness. The novel immuno-based assay showed significantly stronger binding of fibrinogen to both poly(acrylic acid) and poly(allylamine) coated silicone. Finally, cell studies showed that the strength of the interaction between the protein and the polymer had an effect on cell growth. This novel immuno-based assay is a valuable tool in developing composite biomaterials of synthetic and protein-based polymers with the potential to be applied in other fields of research where protein adsorption onto surfaces plays an important role.

Hybrid particle-continuum simulations coupling Brownian dynamics and local dynamic density functional theory.

PubMed

Qi, Shuanhu; Schmid, Friederike

2017-11-08

We present a multiscale hybrid particle-field scheme for the simulation of relaxation and diffusion behavior of soft condensed matter systems. It combines particle-based Brownian dynamics and field-based local dynamics in an adaptive sense such that particles can switch their level of resolution on the fly. The switching of resolution is controlled by a tuning function which can be chosen at will according to the geometry of the system. As an application, the hybrid scheme is used to study the kinetics of interfacial broadening of a polymer blend, and is validated by comparing the results to the predictions from pure Brownian dynamics and pure local dynamics calculations.

Characterizing white matter tissue in large strain via asymmetric indentation and inverse finite element modeling.

PubMed

Feng, Yuan; Lee, Chung-Hao; Sun, Lining; Ji, Songbai; Zhao, Xuefeng

2017-01-01

Characterizing the mechanical properties of white matter is important to understand and model brain development and injury. With embedded aligned axonal fibers, white matter is typically modeled as a transversely isotropic material. However, most studies characterize the white matter tissue using models with a single anisotropic invariant or in a small-strain regime. In this study, we combined a single experimental procedure - asymmetric indentation - with inverse finite element (FE) modeling to estimate the nearly incompressible transversely isotropic material parameters of white matter. A minimal form comprising three parameters was employed to simulate indentation responses in the large-strain regime. The parameters were estimated using a global optimization procedure based on a genetic algorithm (GA). Experimental data from two indentation configurations of porcine white matter, parallel and perpendicular to the axonal fiber direction, were utilized to estimate model parameters. Results in this study confirmed a strong mechanical anisotropy of white matter in large strain. Further, our results suggested that both indentation configurations are needed to estimate the parameters with sufficient accuracy, and that the indenter-sample friction is important. Finally, we also showed that the estimated parameters were consistent with those previously obtained via a trial-and-error forward FE method in the small-strain regime. These findings are useful in modeling and parameterization of white matter, especially under large deformation, and demonstrate the potential of the proposed asymmetric indentation technique to characterize other soft biological tissues with transversely isotropic properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Characterizing Variability In Ohio River Natural Organic Matter

EPA Science Inventory

Surface water contains natural organic matter (NOM) which reacts with disinfectants creating disinfection byproducts (DBPs), some of which are USEPA regulated contaminants. Characterizing NOM can provide important insight on DBP formation and water treatment process adaptation t...

Tuning Magnetic Order in Transition Metal Oxide Thin Films

NASA Astrophysics Data System (ADS)

Grutter, Alexander John

In recent decades, one of the most active and promising areas of condensed matter research has been that of complex oxides. With the advent of new growth techniques such as pulsed laser deposition and molecular beam epitaxy, a wealth of new magnetic and electronic ground states have emerged in complex oxide heterostructures. The wide variety of ground states in complex oxides is well known and generally attributed to the unprecedented variety of valence, structure, and bonding available in these systems. The tunability of this already diverse playground of states and interactions is greatly multiplied in thin films and heterostructures by the addition of parameters such as substrate induced strain and interfacial electronic reconstruction. Thus, recent studies have shown emergent properties such as the stabilization of ferromagnetism in a paramagnetic system, conductivity at the interface of two insulators, and even exchange bias at the interface between a paramagnet and a ferromagnet. Despite these steps forward, there remains remarkable disagreement on the mechanisms by which these emergent phenomena are stabilized. The contributions of strain, stoichiometry, defects, intermixing, and electronic reconstruction are often very difficult to isolate in thin films and superlattices. This thesis will present model systems for isolating the effects of strain and interfacial electronic interactions on the magnetic state of complex oxides from alternative contributions. We will focus first on SrRuO3, an ideal system in which to isolate substrate induced strain effects. We explore the effects of structural distortions in the simplest case of growth on (100) oriented substrates. We find that parameters including saturated magnetic moment and Curie temperature are all highly tunable through substrate induced lattice distortions. We also report the stabilization of a nonmagnetic spin-zero configuration of Ru4+ in tetragonally distorted films under tensile strain. Through growth on (110) and (111) oriented substrates we explore the effects of different distortion symmetries on SrRuO3 and demonstrate the first reported strain induced transition to a high-spin state of Ru 4+. Finally, we examine the effects of strain on SrRuO3 thin films and demonstrate a completely reversible universal out-of-plane magnetic easy axis on films grown on different substrate orientations. Having demonstrated the ability to tune nearly every magnetic parameter of SrRuO 3 through strain, we turn to magnetic properties at interfaces. We study the emergent interfacial ferromagnetism in superlattices of the paramagnetic metal CaRuO3 and the antiferromagnetic insulator CaMnO3 and demonstrate that the interfacial ferromagnetic layer in this system is confined to a single unit cell of CaMnO3 at the interface. We discuss the remarkable oscillatory dependence of the saturated magnetic moment on the thickness of the CaMnO3 layers and explore mechanisms by which this oscillation may be stabilized. We find long range coherence of the antiferromagnetism of the CaMnO3 layers across intervening layers of paramagnetic CaRuO3. Finally, we utilize the system of LaNiO3/CaMnO3 to separate the effects of intermixing and interfacial electronic reconstruction and conclusively demonstrate intrinsic interfacial ferromagnetism at the interface between a paramagnetic metal and an antiferromagnetic insulator. We find that the emergent ferromagnetism is stabilized through interfacial double exchange and that the leakage of conduction electrons from the paramagnetic metal to the antiferromagnetic insulator is critical to establishing the ferromagnetic ground state.

Biogeochemical linkage between atmosphere and ocean in the eastern equatorial Pacific Ocean: Results from the EqPOS research cruise

NASA Astrophysics Data System (ADS)

Furutani, H.; Inai, Y.; Aoki, S.; Honda, H.; Omori, Y.; Tanimoto, H.; Iwata, T.; Ueda, S.; Miura, K.; Uematsu, M.

2012-12-01

Eastern equatorial Pacific Ocean is a unique oceanic region from several biogeochemical points of view. It is a remote open ocean with relatively high marine biological activity, which would result in limited influence of human activity but enhanced effect of marine natural processes on atmospheric composition. It is also characterized as high nutrient low chlorophyll (HNLC) ocean, in which availability of trace metals such as iron and zinc limits marine primary production and thus atmospheric deposition of these trace elements to the ocean surface is expected to play an important role in regulating marine primary production and defining unique microbial community. High sea surface temperature in the region generates strong vertical air convection which efficiently brings tropospheric atmospheric composition into stratosphere. In this unique eastern equatorial Pacific Ocean, EqPOS (Equatorial Pacific Ocean and Stratospheric/Tropospheric Atmospheric Study) research cruise was organized as a part of SOLAS Japan activity to understand biogeochemical ocean-atmospheric interaction in the region. Coordinated atmospheric, oceanic, and marine biological observations including sampling/characterization of thin air-sea interfacial layer (sea surface microlayer: SML) and launching large stratospheric air sampling balloons were carried out on-board R/V Hakuho Maru starting from 29 January for 39 days. Biogeochemically important trace/long-lived gases such as CO2, dimethyl sulfide (DMS), and some volatile organic carbons (VOCs) both in the atmosphere and seawater were continuously monitored and their air-sea fluxes were also observed using gradient and eddy-covariance techniques. Atmospheric gas measurement of CO2, CH4, N2O, SF6, CO, H2, Ar and isotopic composition of selected gases were further extended to stratospheric air by balloon-born sampling in addition to a vertical profiling of O3, CO2, and H2O with sounding sondes. Physical and chemical properties of marine atmospheric aerosols such as size distribution, total and cloud condensation nuclei concentrations, particle morphology, bulk and single particle chemical composition were also continuously determined to find out potential link between biogenic VOCs emitted from the ocean and aerosol composition. Biological and biogeochemical characterizations of marine microorganisms, suspended particulate matter, dissolved nutrients in seawater and SML were also conducted. In the presentation, brief overview of the research activities during the EqPOS cruise and biogeochemical linkage atmosphere and ocean via atmospheric and oceanic gaseous and particulate matter from ocean surface to stratosphere observed during the cruise and unique importance of SML would be presented.

Analysis of the Organic Matter in Interplanetary Dust Particles: Clues to the Organic Matter in Comets, Asteroids, and Interstellar Grains

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Keller, L. P.

2003-01-01

Reflection spectroscopy suggests the C- , P-, and D-types of asteroids contain abundant carbon, but these Vis-nearIR spectra are featureless, providing no information on the type(s) of carbonaceous matter. Infrared spectroscopy demonstrates that organic carbon is a significant component in comets and as grains or grain coatings in the interstellar medium. Most of the interplanetary dust particles (IDPs) recovered from the Earth s stratosphere are believed to be fragments from asteroids or comets, thus characterization of the carbon in IDPs provides the opportunity to determine the type(s) and abundance of organic matter in asteroids and comets. Some IDPs exhibit isotopic excesses of D and N-15, indicating the presence of interstellar material. The characterization of the carbon in these IDPs, and particularly any carbon spatially associated with the isotopic anomalies, provides the opportunity to characterize interstellar organic matter.

Liquid Sunshine to Fuel Your Car (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum)

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

Breunig, Lloyd

"Liquid Sunshine to Fuel Your Car" was submitted by the Center for Lignocellulose Structure and Formation (CLSF) to the "Life at the Frontiers of Energy Research" video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. CLSF is directed by Daniel Cosgrove at Pennsylvania State University and is a partnership of scientists from three institutions: Penn State (lead), North Carolina State University, and Virginia Tech University. The Office of Basic Energy Sciences in the U.S. Department of Energy's Officemore » of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of the Center for Lignocellulose Structure and Formation is 'to dramatically increase our fundamental knowledge of the formation and physical interactions of bio-polymer networks in plant cell walls to provide a basis for improved methods for converting biomass into fuels.' Research topics are: biofuels (biomass), membrane, interfacial characterization, matter by design, and self-assembly.« less

Liquid Sunshine to Fuel Your Car (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum)

ScienceCinema

Cosgrove, Daniel (Director, Center for Lignocellulose Structure and Formation); CLSF Staff

2017-12-09

'Liquid Sunshine to Fuel Your Car' was submitted by the Center for Lignocellulose Structure and Formation (CLSF) to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. CLSF is directed by Daniel Cosgrove at Pennsylvania State University and is a partnership of scientists from three institutions: Penn State (lead), North Caroline State University, and Virginia Tech University. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of the Center for Lignocellulose Structure and Formation is 'to dramatically increase our fundamental knowledge of the formation and physical interactions of bio-polymer networks in plant cell walls to provide a basis for improved methods for converting biomass into fuels.' Research topics are: biofuels (biomass), membrane, interfacial characterization, matter by design, and self-assembly.

Chemical demulsification of petroleum emulsions using oil-soluable demulsifiers

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

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

1991-02-01

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

Smart Materials, Structures, and Mathematical Issues for Active Damage Control

DTIC Science & Technology

1997-10-01

composites at both low and high velocities. The effect of low volume fractions (3% and 6%) of embedded Nitinol fibers on the impact-absorbing ability...ICI Wilton Materials Research Center General Dynamics Lockheed-Martin Hercules Aerospace Company U.S. Nitinol Owens-Corning DSB Associates...Reduction in a Plate," submitted to AIAA Journal. Paine, J. S. N., Rogers, C. A. 1993. "Characterization of Interfacial Adhesion of Nitinol Fibers

Synthesis of Long-Chain-Branched (LCB) Polysulfones for Multifunctional Transport Membranes

DTIC Science & Technology

2010-09-01

R.; Dutta, N. K. Interfacial Interactions in Aprotic Ionic Liquid Based Protonic Membrane and Its Correlation with High Temperature Conductivity...rigidity. The series of novel polymers was characterized for chemical structure, thermal transitions, and molecular weight. Ionic conductivity was tested...Although much progress exists based on perfluorosulfonated platforms ( Nafion , σ ≈ 10-1 – 10-2 S/cm) new and more complicated parameters arise as

Characterization of molybdenum particles reinforced Al6082 aluminum matrix composites with improved ductility produced using friction stir processing

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

Selvakumar, S., E-mail: lathaselvam1963@gmail.com

Aluminum matrix composites (AMCs) reinforced with various ceramic particles suffer a loss in ductility. Hard metallic particles can be used as reinforcement to improve ductility. The present investigation focuses on using molybdenum (Mo) as potential reinforcement for Mo(0,6,12 and 18 vol.%)/6082Al AMCs produced using friction stir processing (FSP). Mo particles were successfully retained in the aluminum matrix in its elemental form without any interfacial reaction. A homogenous distribution of Mo particles in the composite was achieved. The distribution was independent upon the region within the stir zone. The grains in the composites were refined considerably due to dynamic recrystallization andmore » pinning effect. The tensile test results showed that Mo particles improved the strength of the composite without compromising on ductility. The fracture surfaces of the composites were characterized with deeply developed dimples confirming appreciable ductility. - Highlights: •Molybdenum particles used as reinforcement for aluminum composites to improve ductility. •Molybdenum particles were retained in elemental form without interfacial reaction. •Homogeneous dispersion of molybdenum particles were observed in the composite. •Molybdenum particles improved tensile strength without major loss in ductility. •Deeply developed dimples on the fracture surfaces confirmed improved ductility.« less

Characterization of Interfacial Chemistry of Adhesive/Dentin Bond Using FTIR Chemical Imaging With Univariate and Multivariate Data Processing

PubMed Central

Wang, Yong; Yao, Xiaomei; Parthasarathy, Ranganathan

2008-01-01

Fourier transform infrared (FTIR) chemical imaging can be used to investigate molecular chemical features of the adhesive/dentin interfaces. However, the information is not straightforward, and is not easily extracted. The objective of this study was to use multivariate analysis methods, principal component analysis and fuzzy c-means clustering, to analyze spectral data in comparison with univariate analysis. The spectral imaging data collected from both the adhesive/healthy dentin and adhesive/caries-affected dentin specimens were used and compared. The univariate statistical methods such as mapping of intensities of specific functional group do not always accurately identify functional group locations and concentrations due to more or less band overlapping in adhesive and dentin. Apart from the ease with which information can be extracted, multivariate methods highlight subtle and often important changes in the spectra that are difficult to observe using univariate methods. The results showed that the multivariate methods gave more satisfactory, interpretable results than univariate methods and were conclusive in showing that they can discriminate and classify differences between healthy dentin and caries-affected dentin within the interfacial regions. It is demonstrated that the multivariate FTIR imaging approaches can be used in the rapid characterization of heterogeneous, complex structure. PMID:18980198

"Supersaturated" self-assembled charge-selective interfacial layers for organic solar cells.

PubMed

Song, Charles Kiseok; Luck, Kyle A; Zhou, Nanjia; Zeng, Li; Heitzer, Henry M; Manley, Eric F; Goldman, Samuel; Chen, Lin X; Ratner, Mark A; Bedzyk, Michael J; Chang, Robert P H; Hersam, Mark C; Marks, Tobin J

2014-12-24

To achieve densely packed charge-selective organosilane-based interfacial layers (IFLs) on the tin-doped indium oxide (ITO) anodes of organic photovoltaic (OPV) cells, a series of Ar2N-(CH2)n-SiCl3 precursors with Ar = 3,4-difluorophenyl, n = 3, 6, 10, and 18, was synthesized, characterized, and chemisorbed on OPV anodes to serve as IFLs. To minimize lateral nonbonded -NAr2···Ar2N- repulsions which likely limit IFL packing densities in the resulting self-assembled monolayers (SAMs), precursor mixtures having both small and large n values are simultaneously deposited. These "heterogeneous" SAMs are characterized by a battery of techniques: contact angle measurements, X-ray reflectivity, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), cyclic voltammetry, and DFT computation. It is found that the headgroup densities of these "supersaturated" heterogeneous SAMs (SHSAMs) are enhanced by as much as 17% versus their homogeneous counterparts. Supersaturation significantly modifies the IFL properties including the work function (as much as 16%) and areal dipole moment (as much as 49%). Bulk-heterojunction OPV devices are fabricated with these SHSAMs: ITO/IFL/poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][2-[[(2-ethylhexyl)oxy]carbonyl]-3-fluorothieno[3,4-b]thiophenediyl

“Supersaturated” Self-Assembled Charge-Selective Interfacial Layers for Organic Solar Cells

DOE PAGES

Song, Charles Kiseok; Luck, Kyle A.; Zhou, Nanjia; ...

2014-11-24

Here, to achieve densely packed charge-selective organosilane-based interfacial layers (IFLs) on the tin-doped indium oxide (ITO) anodes of organic photovoltaic (OPV) cells, a series of Ar 2N-(CH 2) n-SiCl3 precursors with Ar = 3,4-difluorophenyl, n = 3, 6, 10, and 18, was synthesized, characterized, and chemisorbed on OPV anodes to serve as IFLs. To minimize lateral nonbonded -NAr 2···Ar 2N- repulsions which likely limit IFL packing densities in the resulting self-assembled monolayers (SAMs), precursor mixtures having both small and large n values are simultaneously deposited. These “heterogeneous” SAMs are characterized by a battery of techniques: contact angle measurements, X-ray reflectivity,more » X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), cyclic voltammetry, and DFT computation. It is found that the headgroup densities of these “supersaturated” heterogeneous SAMs (SHSAMs) are enhanced by as much as 17% versus their homogeneous counterparts. Supersaturation significantly modifies the IFL properties including the work function (as much as 16%) and areal dipole moment (as much as 49%). Bulk-heterojunction OPV devices are fabricated with these SHSAMs: ITO/IFL/poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2- b:4,5- b']dithiophene-2,6-diyl][2-[[(2-ethylhexyl)oxy]carbonyl]-3-fluorothieno[3,4-b]thiophenediyl

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

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

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

2015-03-21

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

In Situ Apparatus to Study Gas-Metal Reactions and Wettability at High Temperatures for Hot-Dip Galvanizing Applications

NASA Astrophysics Data System (ADS)

Koltsov, A.; Cornu, M.-J.; Scheid, J.

2018-02-01

The understanding of gas-metal reactions and related surface wettability at high temperatures is often limited due to the lack of in situ surface characterization. Ex situ transfers at low temperature between annealing furnace, wettability device, and analytical tools induce noticeable changes of surface composition distinct from the reality of the phenomena.Therefore, a high temperature wettability device was designed in order to allow in situ sample surface characterization by x-rays photoelectron spectroscopy after gas/metal and liquid metal/solid metal surface reactions. Such airless characterization rules out any contamination and oxidation of surfaces and reveals their real composition after heat treatment and chemical reaction. The device consists of two connected reactors, respectively, dedicated to annealing treatments and wettability measurements. Heat treatments are performed in an infrared lamp furnace in a well-controlled atmosphere conditions designed to reproduce gas-metal reactions occurring during the industrial recrystallization annealing of steels. Wetting experiments are carried out in dispensed drop configuration with the precise control of the deposited droplets kinetic energies. The spreading of drops is followed by a high-speed CCD video camera at 500-2000 frames/s in order to reach information at very low contact time. First trials have started to simulate phenomena occurring during recrystallization annealing and hot-dip galvanizing on polished pure Fe and FeAl8 wt.% samples. The results demonstrate real surface chemistry of steel samples after annealing when they are put in contact with liquid zinc alloy bath during hot-dip galvanizing. The wetting results are compared to literature data and coupled with the characterization of interfacial layers by FEG-Auger. It is fair to conclude that the results show the real interest of such in situ experimental setup for interfacial chemistry studies.

The use of on-line characterization technologies during the manufacture of nanostructured materials

NASA Astrophysics Data System (ADS)

Barbas, Joana Margarida de Oliveira

Since their potential has become widely recognized, one of the major research lines on polymer-clay nanocomposites has focused on the preparation of well dispersed systems, which involves investigating their compounding (including their structural and morphological characterization) and the determination of their physical and mechanical performances. Currently, there is an understanding that a high degree of dispersion, particularly exfoliation, of the nanoclay is required to improve the overall performance. Although the influencing parameters are known - interfacial adhesion, chemical affinity and operating conditions - the effect of each on the onset and extent of the organoclay dispersion are still subject of debate. Twin screw extrusion allows for control of the main variables (shear, stress and time), but also, due to the typical modular construction, offers a high degree of freedom in creating the adequate screw design and enables knowledgeable alteration of the barrel. These features offer a solid basis for the development and implementation of apt on-line/in-line monitoring techniques, able to follow up the evolution of dispersion of polymer-clay nanocomposites during processing. This research included the validation, implementation and application of a methodology based on inline Near-Infrared (NIR) Spectroscopy for the characterization of the dispersion along the extruder axis. The results showed that the operating conditions have great impact on the dispersion level, but also that degradation may affect the interfacial chemistry of the system, altering the dispersion pathways. Overall the results obtained confirm that NIR is a valid tool for the on-line characterization of these materials, offering the possibility of assessing in real time the clay dispersion, enabling proper corrective and optimization actions over the material characteristics in a timely manner.

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

PubMed

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

1999-02-01

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

Feasibility of using sodium chloride as a tracer for the characterization of the distribution of matter in complex multi-compartment 3D bioreactors for stem cell culture.

PubMed

Gerlach, Jörg C; Witaschek, Tom; Strobel, Catrin; Brayfield, Candace A; Bornemann, Reinhard; Catapano, Gerardo; Zeilinger, Katrin

2010-06-01

The experimental characterization of the distribution of matter in complex multi-compartment three-dimensional membrane bioreactors for human cell culture is complicated by tracer interactions with the membranes and other bioreactor constituents. This is due to the fact that membranes with a high specific surface area often feature a hydrophobic chemical backbone that may adsorb tracers often used to this purpose, such as proteins and dyes. Membrane selectivity, and its worsening caused by protein adsorption, may also hinder tracer transfer across neighboring compartments, thus preventing effective characterization of the distribution of matter in the whole bioreactor. Tracer experiments with sodium chloride (NaCl) may overcome some of these limitations and be effectively used to characterize the distribution of matter in complex 3D multi-compartments membrane bioreactors for stem cell culture. NaCl freely permeates most used membranes, it does not adsorb on uncharged membranes, and its concentration may be accurately measured in terms of solution conductivity. In this preliminary study, the feasibility of complex multi-compartment membrane bioreactors was investigated with a NaCl concentration pulse challenge to characterize how their distribution of matter changes when they are operated under different conditions. In particular, bioreactors consisting of three different membrane types stacked on top of one another to form a 3D network were characterized under different feed conditions.

CHARACTERIZATION OF EMISSIONS FROM BURNING INCENSE

EPA Science Inventory

The primary objective of this study was to improve the characterization of particulate matter emissions from burning incense. Emissions of particulate matter were measured for 23 different types of incense using a cyclone/filter method. Emission rates for PM2.5 (particulate matte...

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

PubMed

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

2015-03-12

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.

Effects of Different Barium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

NASA Astrophysics Data System (ADS)

Adabifiroozjaei, Esmaeil; Koshy, Pramod; Rastkerdar, Ebad

2011-08-01

An experimental study was conducted to investigate the interfacial phenomena between an Al alloy and andalusite low-cement castables (LCCs) containing fixed contents of barium compounds (BaO, BaSO4, and BaCO3) at 1123 K and 1433 K (850 °C and 1160 °C) using the Alcoa cup test. Interfacial reaction products and phases formed during heat treatment of the refractory samples were characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) and X-ray diffraction analysis (XRD). The addition of both BaO and BaSO4 led to a significant reduction of alloy penetration into the refractory. Hexa-celsian formation was observed in both these refractories, which drastically increased their corrosion resistance. Barite decomposition was observed at 1373 K (1100 °C) in the presence of alumina and silica, which was the precursor for hexa-celsian formation. Barium silicates were formed in all samples containing additives; however, this did not have any major influence on the corrosion resistance. Solidified eutectics of BaSi2 and α-BaAl2Si2 formed in all these samples, which acted as an interfacial barrier that prevented additional molten aluminum penetration; however, the positive effect of intermetallic formation was offset by glassy phase formation in samples containing BaCO3 as the additive.

Membrane Perturbation Induced by Interfacially Adsorbed Peptides

PubMed Central

Zemel, Assaf; Ben-Shaul, Avinoam; May, Sylvio

2004-01-01

The structural and energetic characteristics of the interaction between interfacially adsorbed (partially inserted) α-helical, amphipathic peptides and the lipid bilayer substrate are studied using a molecular level theory of lipid chain packing in membranes. The peptides are modeled as “amphipathic cylinders” characterized by a well-defined polar angle. Assuming two-dimensional nematic order of the adsorbed peptides, the membrane perturbation free energy is evaluated using a cell-like model; the peptide axes are parallel to the membrane plane. The elastic and interfacial contributions to the perturbation free energy of the “peptide-dressed” membrane are evaluated as a function of: the peptide penetration depth into the bilayer's hydrophobic core, the membrane thickness, the polar angle, and the lipid/peptide ratio. The structural properties calculated include the shape and extent of the distorted (stretched and bent) lipid chains surrounding the adsorbed peptide, and their orientational (C-H) bond order parameter profiles. The changes in bond order parameters attendant upon peptide adsorption are in good agreement with magnetic resonance measurements. Also consistent with experiment, our model predicts that peptide adsorption results in membrane thinning. Our calculations reveal pronounced, membrane-mediated, attractive interactions between the adsorbed peptides, suggesting a possible mechanism for lateral aggregation of membrane-bound peptides. As a special case of interest, we have also investigated completely hydrophobic peptides, for which we find a strong energetic preference for the transmembrane (inserted) orientation over the horizontal (adsorbed) orientation. PMID:15189858

Interfacial Reaction During High Energy Ball Milling Dispersion of Carbon Nanotubes into Ti6Al4V

NASA Astrophysics Data System (ADS)

Adegbenjo, A. O.; Olubambi, P. A.; Potgieter, J. H.; Nsiah-Baafi, E.; Shongwe, M. B.

2017-12-01

The unique thermal and mechanical properties of carbon nanotubes (CNTs) have made them choice reinforcements for metal matrix composites (MMCs). However, there still remains a critical challenge in achieving homogeneous dispersion of CNTs in metallic matrices. Although high energy ball milling (HEBM) has been reported as an effective method of dispersing CNTs into metal matrices, a careful selection of the milling parameters is important not to compromise the structural integrity of CNTs which may cause interfacial reactions with the matrix. In this study, multi-walled carbon nanotubes (MWCNTs) were purified by annealing in argon and vacuum atmospheres at 1000 and 1800 °C, respectively, for 5 h to remove possible metallic catalyst impurities. Subsequently, 1, 2 and 3 wt.% MWCNTs were dispersed by adapted HEBM into Ti6Al4V alloy metal matrix. Raman spectroscopy (RS), x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectrometry and transmission electron microscopy techniques were used to characterize the as-received and annealed MWCNTs, as well as the admixed MWCNT/Ti6Al4V nanocomposite powders. The experimental results showed that vacuum annealing successfully eliminated retained nickel (Ni) catalysts from MWCNTs, while the adapted HEBM method achieved a relative homogeneous dispersion of MWCNTs into the Ti6Al4V matrix and helped to control interfacial reactions between defective MWCNTs and the metal matrix.

Sensitivity improvement of a sandwich-type ELISA immunosensor for the detection of different prostate-specific antigen isoforms in human serum using electrochemical impedance spectroscopy and an ordered and hierarchically organized interfacial supramolecular architecture.

PubMed

Gutiérrez-Zúñiga, Gabriela Guadalupe; Hernández-López, José Luis

2016-01-01

A gold millielectrode (GME) functionalized with a mixed (16-MHA + EG3SH) self-assembled monolayer (SAM) was used to fabricate an indirect enzyme-linked immunosorbent assay (ELISA) immunosensor for the sensitive detection of prostate-specific antigen (PSA), a prostate cancer (PCa) biomarker, in human serum samples. To address and minimize the issue of non-specific protein adsorption, an organic matrix (amine-PEG3-biotin/avidin) was assembled on the previously functionalized electrode surface to build up an ordered and hierarchically organized interfacial supramolecular architecture: Au/16-MHA/EG3SH/amine-PEG3-biotin/avidin. The electrode was then exposed to serum samples at different concentrations of a sandwich-type immunocomplex molecule ((Btn)Ab-AgPSA-(HRP)Ab), and its interfacial properties were characterized using electrochemical impedance spectroscopy (EIS). Calibration curves for polarization resistance (RP) and capacitance (1/C) vs. total and free PSA concentrations were obtained and their analytical quality parameters were determined. This approach was compared with results obtained from a commercially available ELISA immunosensor. The results obtained in this work showed that the proposed immunosensor can be successfully applied to analyze serum samples of patients representative of the Mexican population. Copyright © 2015 Elsevier B.V. All rights reserved.

Impact of carbon nanotubes based nanofluid on oil recovery efficiency using core flooding

NASA Astrophysics Data System (ADS)

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

2018-06-01

This study aims to investigate the influence of carbon nanotubes based nanofluid on interfacial tension and oil recovery efficiency. Practically multi-walled carbon nanotubes were successfully synthesized using chemical vapour deposition technique and characterized using X-ray diffraction and Field Emission Scanning Electron microscope in order to understand its structure, shape, and morphology. Nanofluids are one of the interesting new agents for enhanced oil recovery (EOR) that can change the reservoir rock-fluid properties in terms of interfacial tension and wettability. In this work, different concentration of carbon nanotubes based fluids were prepared and the effect of each concentration on surface tension was determined using pendant drop method. After specifying the optimum concentration of carbon nanotubes based nanofluid, core flooding experiment was conducted by two pore volume of brine and two pore volume of nanofluid and then oil recovery factor was calculated. The results show that carbon nanotubes can bring in additional recovery factor of 18.57% in the glass bead sample. It has been observed that nanofluid with high surface tension value gives higher recovery. It was found that the optimum value of concentration is 0.3 wt% at which maximum surface tension of 33.46 mN/m and oil recovery factor of 18.57% was observed. This improvement in recovery factor can be recognized due to interfacial tension reduction and wettability alteration.

Polyaniline decorated Bi2MoO6 nanosheets with effective interfacial charge transfer as photocatalysts and optical limiters.

PubMed

Zhao, Wei; Li, Cheng; Wang, Aijian; Lv, Cuncai; Zhu, Weihua; Dou, Shengping; Wang, Qian; Zhong, Qin

2017-11-01

Polyaniline (PANI)-decorated Bi 2 MoO 6 nanosheets (BMO/PANI) were prepared by a facile solvothermal method. Different characterization techniques, including X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance ultraviolet-visible spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy, photocurrent spectroscopy, and nanosecond time-resolved emission studies, have been employed to investigate the structure, optical and electrical properties of the BMO/PANI composites. The wide absorption of the samples in the visible light region makes them suitable for nonlinear transmission and photocatalytic activity studies. The associated photocatalytic activity and optical nonlinearities for the BMO/PANI composites are shown to be dependent on the PANI loadings. The rational mechanisms responsible for deteriorating pollutants and improving optical nonlinearities were also proposed, which could be mainly attributed to the efficient interfacial charge transfer and the interfacial electronic interactions between PANI and Bi 2 MoO 6 . The photoluminescence spectroscopy, electrochemical impedance spectroscopy, and photocurrent spectroscopy studies confirmed that the interface charge separation efficiency was greatly improved by coupling Bi 2 MoO 6 with PANI. The tuning of photocatalysis and nonlinear optical behaviors with variation in the content of PANI provides an easy way to attain tunable properties, which are exceedingly required in optoelectronics applications.

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

PubMed

Guri, Anilda; Li, Yang; Corredig, Milena

2015-12-01

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

Improvement of interfacial interactions using natural polyphenol-inspired tannic acid-coated nanoclay enhancement of soy protein isolate biofilms

NASA Astrophysics Data System (ADS)

Wang, Zhong; Kang, Haijiao; Zhang, Wei; Zhang, Shifeng; Li, Jianzhang

2017-04-01

In this study, a novel and economic surface modification technique for montmorillonite (MMT) nanosheets, a biocompatible coupling cross-linking agent, was developed on an attempt at improving the interfacial adhesion with soy protein isolate (SPI) matrix. Inspired by natural polyphenol, the "green dip-coating" method using tannic acid (TA) to surface-modify MMT (TA@MMT). SPI nanocomposite films modified with MMT or TA@MMT, as well as the control ones, were prepared via the casting method. The TA layer was successfully coated on the MMT surface through the (FeIII) ions coordination chemistry and the synthetic samples were characterized by the Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The compatibility and interfacial interactions between modified MMT and SPI matrix were greatly enhanced by the TA-FeIII coating on the MMT surface. The mechanical properties, water resistance, and thermal stability of the resultant biofilm were increased accordingly. Compared with that of the unmodified SPI film, the tensile strength of the nanocomposite films modified by the green dip-coating was increased by 113.3%. These SPI-based nanocomposite films showed the favorable potential in terms of food packing applications due to their efficient barriers to water vapor and UV and/or visible light.

Changes in conformational dynamics of basic side chains upon protein-DNA association.

PubMed

Esadze, Alexandre; Chen, Chuanying; Zandarashvili, Levani; Roy, Sourav; Pettitt, B Montgometry; Iwahara, Junji

2016-08-19

Basic side chains play major roles in recognition of nucleic acids by proteins. However, dynamic properties of these positively charged side chains are not well understood. In this work, we studied changes in conformational dynamics of basic side chains upon protein-DNA association for the zinc-finger protein Egr-1. By nuclear magnetic resonance (NMR) spectroscopy, we characterized the dynamics of all side-chain cationic groups in the free protein and in the complex with target DNA. Our NMR order parameters indicate that the arginine guanidino groups interacting with DNA bases are strongly immobilized, forming rigid interfaces. Despite the strong short-range electrostatic interactions, the majority of the basic side chains interacting with the DNA phosphates exhibited high mobility, forming dynamic interfaces. In particular, the lysine side-chain amino groups exhibited only small changes in the order parameters upon DNA-binding. We found a similar trend in the molecular dynamics (MD) simulations for the free Egr-1 and the Egr-1-DNA complex. Using the MD trajectories, we also analyzed side-chain conformational entropy. The interfacial arginine side chains exhibited substantial entropic loss upon binding to DNA, whereas the interfacial lysine side chains showed relatively small changes in conformational entropy. These data illustrate different dynamic characteristics of the interfacial arginine and lysine side chains. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Enhancing interfacial magnetization with a ferroelectric

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

Meyer, Tricia L.; Herklotz, Andreas; Lauter, Valeria

Ferroelectric control of interfacial magnetism has attracted much attention. However, the coupling of these two functionalities has not been understood well at the atomic scale. The lack of scientific progress is mainly due to the limited characterization methods by which the interface’s magnetic properties can be probed at an atomic level. In this paper, we use polarized neutron reflectometry to probe the evolution of the magnetic moment at interfaces in ferroelectric/strongly correlated oxide [PbZr 0.2Ti 0.8O 3/La 0.8Sr 0.2MnO 3(PZT/LSMO)] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deterioratedmore » and such magnetic deterioration can be greatly improved by interfacing with a strongly polar PZT film. Magnetoelectric coupling of magnetism and ferroelectric polarization was observed within a couple of nanometers of the interface via an increase in the LSMO surface magnetization to 4.0μ B/f.u., a value nearly 70% higher than the surface magnetization of our LSMO film without interfacing with a ferroelectric layer. We attribute this behavior to hole depletion driven by the ferroelectric polarization. Finally, these compelling results not only probe the presence of nanoscale magnetic suppression and its control by ferroelectrics, but also emphasize the importance of utilizing probing techniques that can distinguish between bulk and interfacial phenomena.« less

Enhancing interfacial magnetization with a ferroelectric

DOE PAGES

Meyer, Tricia L.; Herklotz, Andreas; Lauter, Valeria; ...

2016-11-21

Ferroelectric control of interfacial magnetism has attracted much attention. However, the coupling of these two functionalities has not been understood well at the atomic scale. The lack of scientific progress is mainly due to the limited characterization methods by which the interface’s magnetic properties can be probed at an atomic level. In this paper, we use polarized neutron reflectometry to probe the evolution of the magnetic moment at interfaces in ferroelectric/strongly correlated oxide [PbZr 0.2Ti 0.8O 3/La 0.8Sr 0.2MnO 3(PZT/LSMO)] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deterioratedmore » and such magnetic deterioration can be greatly improved by interfacing with a strongly polar PZT film. Magnetoelectric coupling of magnetism and ferroelectric polarization was observed within a couple of nanometers of the interface via an increase in the LSMO surface magnetization to 4.0μ B/f.u., a value nearly 70% higher than the surface magnetization of our LSMO film without interfacing with a ferroelectric layer. We attribute this behavior to hole depletion driven by the ferroelectric polarization. Finally, these compelling results not only probe the presence of nanoscale magnetic suppression and its control by ferroelectrics, but also emphasize the importance of utilizing probing techniques that can distinguish between bulk and interfacial phenomena.« less

Direct handling of sharp interfacial energy for microstructural evolution

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

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

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.

Direct handling of sharp interfacial energy for microstructural evolution

DOE PAGES

Hernández–Rivera, Efraín; Tikare, Veena; Noirot, Laurence; ...

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.

Microscale characterization of metallic coatings for a high strength high conductivity copper alloy

NASA Astrophysics Data System (ADS)

Jain, Piyush

NiCrAlY overlay coatings are being considered by NASA's Glenn Research Center to prevent blanching and reduce thermo-mechanical fatigue of rocket engine combustion chamber liners made of GRCop-84 (Cu-8%Cr-4%Nb) for reusable launch vehicles (RLVs). However, their successful application depends upon their integrity to the GRCop-84 during multiple firings of rocket engines. This study focuses on determining the adhesion of NiCrAlY coatings and their microstructural stability on GRCop-84 as a function of thermal cycling. Specimens were prepared by depositing NiCrAlY top coat on GRCop-84 by vacuum plasma spaying with a thin layer of Cu-26Cr as a bond coat. A thermal cycling rig was built to thermally cycle the NiCrAlY/Cu-26Cr/GRCop-84 specimens from RT to 600°C in an argon environment, with 10 minutes hold at 600°C, and 4 minutes hold at RT. Samples were cut from the coupons in as-received condition (AR), after 100 thermal cycles (TC-100), and after 300 thermal cycles (TC-300) for characterization. A newly developed interfacial microsample testing technique was employed to determine the adhesion of the coatings on GRCop-84, where bowtie shaped microsamples having interfaces normal to the tensile axis were tested. Interfacial microsamples of NiCrAlY/Cu-26Cr/GRCop-84 in all the conditions (AR, TC-100, and TC-300) failed cohesively in the substrate at a UTS of 380+/-5 MPa and their interfaces remained intact. The microstructural characterization revealed that microstructure of the NiCrAlY/Cu-26Cr/GRCop-84 specimens does not degrade as a function of thermal cycling. Constitutive properties of NiCrAlY, Cu-26Cr, and GRCop-84 were measured by testing monolithic samples and were used to build the finite element model (FEM) of the interfacial microsamples. The FE model analyzed the local stress-strain in the interfacial microsamples during the testing and confirmed the strength of the interfaces to be higher than 380+/-5 MPa. Depleted zones, devoid of Cr2Nb particles, were observed in the substrate near the interface, which has been attributed to uncontrolled processing parameters during the coating deposition. The interfacial microsamples containing depleted zones, failed at 335+/-25 MPa in AR condition exhibiting cohesive-adhesive failure, and at 360+/-15 MPa in TC-300 condition exhibiting adhesive failure. All these results suggested that the presence of depleted zone decreases the adhesion of the coating and should be avoided in future coatings deposition. Adhesion of two top coats, NiCrAlY (with the Cu-26Cr bond coat) and the Cu-26Cr (without any bond coat), were found to be lower on the grit blasted GRCop-84 than on the polished GRCop-84. The adhesion of both the top coats on polished GRCop-84 was measured to be 380+/-5 MPa with cohesive failure in the substrate, while the adhesion of NiCrAlY top coat on the grit blasted GRCop-84 was measured to be 142+/-35 MPa with cohesive failure in the Cu-26Cr bond coat, and the adhesion of Cu-26Cr top coat on the grit blasted GRCop-84 was measured to be 360+/-25 MPa with cohesive failure in the Cu-26Cr top coat. The microstructural characterization revealed that the reason of lower strength of top coats on the grit blasted GRCop-84 was the porosity present in the coatings on the grit blasted GRCop-84, while the coatings on the polished GRCop-84 did not have any measurable porosity.

Advanced solid-state NMR spectroscopy of natural organic matter

USDA-ARS?s Scientific Manuscript database

Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially the systematic approach to NOM characterization, and their ...

Phase separation in thermal systems: A lattice Boltzmann study and morphological characterization

NASA Astrophysics Data System (ADS)

Gan, Yanbiao; Xu, Aiguo; Zhang, Guangcai; Li, Yingjun; Li, Hua

2011-10-01

We investigate thermal and isothermal symmetric liquid-vapor separations via a fast Fourier transform thermal lattice Boltzmann (FFT-TLB) model. Structure factor, domain size, and Minkowski functionals are employed to characterize the density and velocity fields, as well as to understand the configurations and the kinetic processes. Compared with the isothermal phase separation, the freedom in temperature prolongs the spinodal decomposition (SD) stage and induces different rheological and morphological behaviors in the thermal system. After the transient procedure, both the thermal and isothermal separations show power-law scalings in domain growth, while the exponent for thermal system is lower than that for isothermal system. With respect to the density field, the isothermal system presents more likely bicontinuous configurations with narrower interfaces, while the thermal system presents more likely configurations with scattered bubbles. Heat creation, conduction, and lower interfacial stresses are the main reasons for the differences in thermal system. Different from the isothermal case, the release of latent heat causes the changing of local temperature, which results in new local mechanical balance. When the Prandtl number becomes smaller, the system approaches thermodynamical equilibrium much more quickly. The increasing of mean temperature makes the interfacial stress lower in the following way: σ=σ0[(Tc-T)/(Tc-T0)]3/2, where Tc is the critical temperature and σ0 is the interfacial stress at a reference temperature T0, which is the main reason for the prolonged SD stage and the lower growth exponent in the thermal case. Besides thermodynamics, we probe how the local viscosities influence the morphology of the phase separating system. We find that, for both the isothermal and thermal cases, the growth exponents and local flow velocities are inversely proportional to the corresponding viscosities. Compared with the isothermal case, the local flow velocity depends not only on viscosity but also on temperature.

Bonding to CAD-CAM Composites: An Interfacial Fracture Toughness Approach.

PubMed

Eldafrawy, M; Ebroin, M G; Gailly, P A; Nguyen, J-F; Sadoun, M J; Mainjot, A K

2018-01-01

The objective of this study was to evaluate the interfacial fracture toughness (IFT) of composite cement with dispersed filler (DF) versus polymer-infiltrated ceramic network (PICN) computer-aided design and computer-aided manufacturing (CAD-CAM) composite blocks after 2 different surface pretreatments using the notchless triangular prism (NTP) test. Two DFs (Cerasmart [CRT] and Lava Ultimate [LVA]), 2 PICNs (Enamic [ENA] and experimental PICN [EXP]), and e.max CAD lithium disilicate glass-ceramic (EMX, control) prism samples were bonded to their counterparts with Variolink Esthetic DC composite cement after either hydrofluoric acid etching (HF) or gritblasting (GR). Both procedures were followed by silanization. All samples ( n = 30 per group) were thermocycled (10,000 cycles) and tested for their IFT in a water bath at 36°C. Moreover, representative samples from each group were subjected to a developed interfacial area ratio (Sdr) measurement by profilometry and scanning electron microscopy (SEM) characterization. EXP-HF gave the highest IFT (1.85 ± 0.39 MPa·m 1/2 ), followed by EMX-HF and ENA-HF, while CRT-HF gave the lowest (0.15 ± 0.22 MPa·m 1/2 ). PICNs gave significantly better results with HF, and DF showed better results with GR. A 2-way analysis of variance indicated that there were significantly higher IFT and Sdr for PICNs than for DF. A positive correlation ( r² = 0.872) was found between IFT and Sdr. SEM characterization showed the specific microstructure of the surface of etched PICNs, indicating the presence of a retentive polymer-based honeycomb structure. Etching of the typical double-network microstructure of PICNs causes an important increase in the Sdr and IFT, while DF should be gritblasted. DF exhibited significantly lower Sdr and IFT values than PICNs. The present results show the important influence of the material class and surface texture, and consequently the micromechanical bond, on the adhesive interface performance of CAD-CAM composites.

Extracting elastic properties of an atomically thin interfacial layer by time-domain analysis of femtosecond acoustics

NASA Astrophysics Data System (ADS)

Chen, H.-Y.; Huang, Y.-R.; Shih, H.-Y.; Chen, M.-J.; Sheu, J.-K.; Sun, C.-K.

2017-11-01

Modern devices adopting denser designs and complex 3D structures have created much more interfaces than before, where atomically thin interfacial layers could form. However, fundamental information such as the elastic property of the interfacial layers is hard to measure. The elastic property of the interfacial layer is of great importance in both thermal management and nano-engineering of modern devices. Appropriate techniques to probe the elastic properties of interfacial layers as thin as only several atoms are thus critically needed. In this work, we demonstrated the feasibility of utilizing the time-resolved femtosecond acoustics technique to extract the elastic properties and mass density of a 1.85-nm-thick interfacial layer, with the aid of transmission electron microscopy. We believe that this femtosecond acoustics approach will provide a strategy to measure the absolute elastic properties of atomically thin interfacial layers.

A Theoretical Review on Interfacial Thermal Transport at the Nanoscale.

PubMed

Zhang, Ping; Yuan, Peng; Jiang, Xiong; Zhai, Siping; Zeng, Jianhua; Xian, Yaoqi; Qin, Hongbo; Yang, Daoguo

2018-01-01

With the development of energy science and electronic technology, interfacial thermal transport has become a key issue for nanoelectronics, nanocomposites, energy transmission, and conservation, etc. The application of thermal interfacial materials and other physical methods can reliably improve the contact between joined surfaces and enhance interfacial thermal transport at the macroscale. With the growing importance of thermal management in micro/nanoscale devices, controlling and tuning the interfacial thermal resistance (ITR) at the nanoscale is an urgent task. This Review examines nanoscale interfacial thermal transport mainly from a theoretical perspective. Traditional theoretical models, multiscale models, and atomistic methodologies for predicting ITR are introduced. Based on the analysis and summary of the factors that influence ITR, new methods to control and reduce ITR at the nanoscale are described in detail. Furthermore, the challenges facing interfacial thermal management and the further progress required in this field are discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Interfacial crystalline structures in injection over-molded polypropylene and bond strength.

PubMed

Yan, Bowen; Wu, Hong; Jiang, Genjie; Guo, Shaoyun; Huang, Jian

2010-11-01

This paper describes interfacial crystalline structures found in injection overmolded polypropylene components and the relationship of these structures to bond strength between the components. The combined effects of the development of hierarchical gradient structures and the particular thermomechanical environment near the interface on the interfacial crystalline structures were investigated in detail by PLM, SEM, DSC, WAXD, and infrared dichroism spectroscopy. The experimental results showed that during molding there was competitive formation of interfacial crystalline structures consisted of "shish-kebab" layer (SKL) and a transcrystalline layers (TCL). Variation in shear stress (controlled by injection pressure and injection speed) plays an important role in the formation of the SKL. The formation of TCL is influenced by the thermal environment, namely melt temperature and mold temperature. Increasing within certain limits, interfacial temperature and the thermal gradient near the interface promotes β-iPP growth. The relationship between interfacial crystalline structures and interfacial bond strength was established by lap shear measurement. The interfacial bond strength is improved by enhancing the formation of TCL, but reduced if SKL predominates.

Second Harmonic Generation characterization of SOI wafers: Impact of layer thickness and interface electric field

NASA Astrophysics Data System (ADS)

Damianos, D.; Vitrant, G.; Lei, M.; Changala, J.; Kaminski-Cachopo, A.; Blanc-Pelissier, D.; Cristoloveanu, S.; Ionica, I.

2018-05-01

In this work, we investigate Second Harmonic Generation (SHG) as a non-destructive characterization method for Silicon-On-Insulator (SOI) materials. For thick SOI stacks, the SHG signal is related to the thickness variations of the different layers. However, in thin SOI films, the comparison between measurements and optical modeling suggests a supplementary SHG contribution attributed to the electric fields at the SiO2/Si interfaces. The impact of the electric field at each interface of the SOI on the SHG is assessed. The SHG technique can be used to evaluate interfacial electric fields and consequently interface charge density in SOI materials.

Synthesis of hybrid interfacial silica-based nanospheres composite as a support for ultra-small palladium nanoparticle and application of PdNPs/HSN in Mizoroki-Heck reaction

NASA Astrophysics Data System (ADS)

Rostamnia, Sadegh; Kholdi, Saba

2017-12-01

The silica based hollow nanosphere (silica-HNS) containing polymer of polyaniline was synthesized and chosen as a promising support for PdNPs. Then it was applied as a green catalyst in the reaction of Heck coupling with high yield. TEM and SEM-EDX/mapping images were used to study the structure and morphology. FT-IR spectroscopy, Thermal gravimetry analysis (TGA), and BET were used to characterize and investigate the catalyst. Also, the amounts of Pd loading were characterized by ICP-AES technique. Catalyst recyclability showed 5 successful runs for the reaction.

Isolation and Characterization of Biosurfactant Producing Bacteria for the Application in Enhanced Oil Recovery

NASA Astrophysics Data System (ADS)

Prasad, Niraj; Dasgupta, Sumita; Chakraborty, Mousumi; Gupta, Smita

2017-07-01

In the present study, a biosurfactant producing bacterial strain was isolated, screened and identified. Further, various fermentation conditions (such as pH (5-10), incubation period (24-96h) and incubation temperature (20-60 °C) were optimized for maximum production of biosurfactant. The produced biosurfactant was characterized by measuring emulsification index, foaming characteristics, rhamnolipid detection, interfacial tension between water and oil and stability against pH and temperature for its potential application in oil recovery process. The additional oil recovery for two different sand, sand1 and sand2, was found to be 49% and 38%, respectively.

Positronics of subnanometer atomistic imperfections in solids as a high-informative structure characterization tool.

PubMed

Shpotyuk, Oleh; Filipecki, Jacek; Ingram, Adam; Golovchak, Roman; Vakiv, Mykola; Klym, Halyna; Balitska, Valentyna; Shpotyuk, Mykhaylo; Kozdras, Andrzej

2015-01-01

Methodological possibilities of positron annihilation lifetime (PAL) spectroscopy applied to characterize different types of nanomaterials treated within three-term fitting procedure are critically reconsidered. In contrast to conventional three-term analysis based on admixed positron- and positronium-trapping modes, the process of nanostructurization is considered as substitutional positron-positronium trapping within the same host matrix. Developed formalism allows estimate interfacial void volumes responsible for positron trapping and characteristic bulk positron lifetimes in nanoparticle-affected inhomogeneous media. This algorithm was well justified at the example of thermally induced nanostructurization occurring in 80GeSe2-20Ga2Se3 glass.

Preparation, characterization and conductivity study of nitro-mercurated styrene butadiene rubber/silver doped zinc oxide nanocomposites

NASA Astrophysics Data System (ADS)

Anilkumar, T.; Naik, Adarsh Ajith; Ramesan, M. T.

2017-06-01

Here we report the preparation of nitromercurated styrene butadiene rubber (NMSBR)/silver doped zinc oxide nanocomposite by inexpensive and ecofriendly two roll mill mixing. The composites were characterized by UV, FTIR, XRD, SEM, TGA and conductivity measurements. UV and FTIR spectrum indicated the interfacial interaction between the polymer and nanoparticles.XRD and SEM images showed the uniform arrangement of nanoparticles within the macromolecular chain. TGA study indicated the better thermal resistance of the composite. The dielectric properties and AC conductivity ofnanocomposites were much greater than nitromercurated SBR and they may be used as multifunctional materials for nanoelectronic devices.

Positronics of subnanometer atomistic imperfections in solids as a high-informative structure characterization tool

NASA Astrophysics Data System (ADS)

Shpotyuk, Oleh; Filipecki, Jacek; Ingram, Adam; Golovchak, Roman; Vakiv, Mykola; Klym, Halyna; Balitska, Valentyna; Shpotyuk, Mykhaylo; Kozdras, Andrzej

2015-02-01

Methodological possibilities of positron annihilation lifetime (PAL) spectroscopy applied to characterize different types of nanomaterials treated within three-term fitting procedure are critically reconsidered. In contrast to conventional three-term analysis based on admixed positron- and positronium-trapping modes, the process of nanostructurization is considered as substitutional positron-positronium trapping within the same host matrix. Developed formalism allows estimate interfacial void volumes responsible for positron trapping and characteristic bulk positron lifetimes in nanoparticle-affected inhomogeneous media. This algorithm was well justified at the example of thermally induced nanostructurization occurring in 80GeSe2-20Ga2Se3 glass.

Characterization of Nanoencapsulated Centella asiatica and Zingiber officinale Extract Using Combination of Malto Dextrin and Gum Arabic as Matrix

NASA Astrophysics Data System (ADS)

Meliana, Y.; Harmami, S. B.; Restu, W. K.

2017-02-01

This research investigated nanoencapsulation of Centella asiatica and Zingiber officinale extract. The encapsulated extract was used as a complex matrix of multi-layered interfacial membranes between malto dextrin and gum Arabic. Characterization of nanoencapsulation using Transmission Electron Microscope (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and BET surface area (SA) showed the morphology, functional group and cumulative adsorption in the surface area of pores. The TEM image of the nanoencapsulated powders of Centella asiatica and Zingiber officinale extract showed a nearly spherical shape with the particle size of 664 nm from its average radius.

Effect of demulsifiers on interfacial properties governing crude oil demulsification

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

Mukherjee, S.; Kushnick, A.P.

1987-01-01

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

Nanoparticles in natural systems II: The natural oxide fraction at interaction with natural organic matter and phosphate

NASA Astrophysics Data System (ADS)

Hiemstra, Tjisse; Antelo, Juan; van Rotterdam, A. M. D.(Debby); van Riemsdijk, Willem H.

2010-01-01

Information on the particle size and reactive surface area of natural samples and its interaction with natural organic matter (NOM) is essential for the understanding bioavailability, toxicity, and transport of elements in the natural environment. In part I of this series ( Hiemstra et al., 2010), a method is presented that allows the determination of the effective reactive surface area ( A, m 2/g soil) of the oxide particles of natural samples which uses a native probe ion (phosphate) and a model oxide (goethite) as proxy. In soils, the natural oxide particles are generally embedded in a matrix of natural organic matter (NOM) and this will affect the ion binding properties of the oxide fraction. A remarkably high variation in the natural phosphate loading of the oxide surfaces ( Γ, μmol/m 2) is observed in our soils and the present paper shows that it is due to surface complexation of NOM, acting as a competitor via site competition and electrostatic interaction. The competitive interaction of NOM can be described with the charge distribution (CD) model by defining a ≡NOM surface species. The interfacial charge distribution of this ≡NOM surface species can be rationalized based on calculations done with an evolved surface complexation model, known as the ligand and charge distribution (LCD) model. An adequate choice is the presence of a charge of -1 v.u. at the 1-plane and -0.5 v.u. at the 2-plane of the electrical double layer used (Extended Stern layer model). The effective interfacial NOM adsorption can be quantified by comparing the experimental phosphate concentration, measured under standardized field conditions (e.g. 0.01 M CaCl 2), with a prediction that uses the experimentally derived surface area ( A) and the reversibly bound phosphate loading ( Γ, μmol/m 2) of the sample (part I) as input in the CD model. Ignoring the competitive action of adsorbed NOM leads to a severe under-prediction of the phosphate concentration by a factor ˜10 to 1000. The calculated effective loading of NOM is low at a high phosphate loading ( Γ) and vice versa, showing the mutual competition of both constituents. Both constituents in combination usually dominate the surface loading of natural oxide fraction of samples and form the backbone in modeling the fate of other (minor) ions in the natural environment. Empirically, the effective NOM adsorption is found to correlate well to the organic carbon content (OC) of the samples. The effective NOM adsorption can also be linked to DOC. For this, a Non-Ideal Competitive adsorption (NICA) model is used. DOC is found to be a major explaining factor for the interfacial loading of NOM as well as phosphate. The empirical NOM-OC relation or the parameterized NICA model can be used as an alternative for estimating the effective NOM adsorption to be implemented in the CD model for calculation of the surface complexation of field samples. The biogeochemical impact of the NOM-PO 4 interaction is discussed.

Experimental study on interfacial area transport in downward two-phase flow

NASA Astrophysics Data System (ADS)

Wang, Guanyi

In view of the importance of two group interfacial area transport equations and lack of corresponding accurate downward flow database that can reveal two group interfacial area transport, a systematic database for adiabatic, air-water, vertically downward two-phase flow in a round pipe with inner diameter of 25.4 mm was collected to gain an insight of interfacial structure and provide benchmarking data for two-group interfacial area transport models. A four-sensor conductivity probe was used to measure the local two phase flow parameters and data was collected with data sampling frequency much higher than conventional data sampling frequency to ensure the accuracy. Axial development of local flow parameter profiles including void fraction, interfacial area concentration, and Sauter mean diameter were presented. Drastic inter-group transfer of void fraction and interfacial area was observed at bubbly to slug transition flow. And the wall peaked interfacial area concentration profiles were observed in churn-turbulent flow. The importance of local data about these phenomenon on flow structure prediction and interfacial area transport equation benchmark was analyzed. Bedsides, in order to investigate the effect of inlet conditions, all experiments were repeated after installing the flow straightening facility, and the results were briefly analyzed. In order to check the accuracy of current data, the experiment results were cross-checked with rotameter measurement as well as drift-flux model prediction, the averaged error is less than 15%. Current models for two-group interfacial area transport equation were evaluated using these data. The results show that two-group interfacial area transport equations with current models can predict most flow conditions with error less than 20%, except some bubbly to slug transition flow conditions and some churn-turbulent flow conditions. The disagreement between models and experiments could result from underestimate of inter-group void transfer.

Hafnium oxide films for application as gate dielectrics

NASA Astrophysics Data System (ADS)

Hsu, Shuo-Lin

The deposition and characterization of HfO2 films for potential application as a high-kappa gate dielectric in MOS devices has been investigated. DC magnetron reactive sputtering was utilized to prepare the HfO2 films. Structural, chemical, and electrical analyses were performed to characterize the various physical, chemical and electrical properties of the sputtered HfO2 films. The sputtered HfO2 films were annealed to simulate the dopant activation process used in semiconductor processing, and to study the thermal stability of the high-kappa, films. The changes in the film properties due to the annealing are also discussed in this work. Glancing angle XRD was used to analyse the atomic scale structure of the films. The as deposited films exhibit an amorphous, regardless of the film thickness. During post-deposition annealing, the thicker films crystallized at lower temperature (< 600°C), and ultra-thin (5.8 nm) film crystallized at higher temperature (600--720°C). The crystalline phase which formed depended on the thickness of the films. The low temperature phase (monoclinic) formed in the 10--20 nm annealed films, and high temperature phase (tetragonal) formed in the ultra-thin annealed HfO2 film. TEM cross-section studies of as deposited samples show that an interfacial layer (< 1nm) exists between HfO2/Si for all film thicknesses. The interfacial layer grows thicker during heat treatment, and grows more rapidly when grain boundaries are present. XPS surface analysis shows the as deposited films are fully oxidized with an excess of oxygen. Interfacial chemistry analysis indicated that the interfacial layer is a silicon-rich silicate layer, which tends to transform to silica-like layer during heat treatment. I-V measurements show the leakage current density of the Al/as deposited-HfO 2/Si MOS diode is of the order of 10-3 A/cm 2, two orders of magnitude lower than that of a ZrO2 film with similar physical thickness. Carrier transport is dominated by Schottky emission at lower electric fields, and by Frenkel-Poole emission in the higher electric field region. After annealing, the leakage current density decreases significantly as the structure remains amorphous structure. It is suggested that this decrease is assorted with the densification and defect healing which accures when the porous as-deposited amorphous structure is annealed. The leakage current density increases of the HfO2 layer crystallizes on annealing, which is attributed to the presence of grain boundaries. C-V measurements of the as deposited film shows typical C-V characteristics, with negligible hystersis, a small flat band voltage shift, but great frequency dispersion. The relative permittivity of HfO2/interfacial layer stack obtained from the capacitance at accumulation is 15, which corresponds to an EOT (equivalent oxide thickness) = 1.66 nm. After annealing, the frequency dispersion is greatly enhanced, and the C-V curve is shifted toward the negative voltage. Reliability tests show that the HfO2 films which remain amorphous after annealing possess superior resistance to constant voltage stress and ambient aging. This study concluded that the sputtered HfO 2 films exhibit an amorphous as deposited. Postdeposition annealing alters the crystallinity, interfacial properties, and electrical characteristics. The HfO2 films which remain amorphous structure after annealing possess the best electrical properties.

Author Correction: Decoupling electron and ion storage and the path from interfacial storage to artificial electrodes

NASA Astrophysics Data System (ADS)

Chen, Chia-Chin; Maier, Joachim

2018-05-01

In the version of this Perspective originally published, in the sentence "It is worthy of note that the final LiF-free situation characterized by MnO taking up the holes and the (F- containing) MnO surface taking up the lithium ions is also a subcase of the job-sharing concept23.", the word `holes' should have been `electrons'. This has now been corrected.

Neutron Reflectivity and Grazing Angle Diffraction

PubMed Central

Ankner, J. F.; Majkrzak, C. F.; Satija, S. K.

1993-01-01

Over the last 10 years, neutron reflectivity has emerged as a powerful technique for the investigation of surface and interfacial phenomena in many different fields. In this paper, a short review of some of the work on neutron reflectivity and grazing-angle diffraction as well as a description of the current and planned neutron rcflectometers at NIST is presented. Specific examples of the characterization of magnetic, superconducting, and polymeric surfaces and interfaces are included. PMID:28053457

ENVIRONMENTAL RESEARCH BRIEF: CHARACTERIZATION OF ORGANIC MATTER IN SOIL AND AQUIFER SOLIDS

EPA Science Inventory

The focus of this work was the evaluation of analytical methods to determine and characterize fractions of subsurface organic matter. Major fractions of total organic carbon (TOC) include: particulate organic carbon (POC) in aquifer material, dissolved organic carbon (DOC) and ...

Comprehensive characterization of atmospheric organic matter in Fresno, California fog water

USGS Publications Warehouse

Herckes, P.; Leenheer, J.A.; Collett, J.L.

2007-01-01

Fogwater collected during winter in Fresno (CA) was characterized by isolating several distinct fractions and characterizing them by infrared and nuclear magnetic resonance (NMR) spectroscopy. More than 80% of the organic matter in the fogwater was recovered and characterized. The most abundant isolated fractions were those comprised of volatile acids (24% of isolated carbon) and hydrophilic acids plus neutrals (28%). Volatile acids, including formic and acetic acid, have been previously identified as among the most abundant individual species in fogwater. Recovered hydrophobic acids exhibited some properties similar to aquatic fulvic acids. An insoluble particulate organic matter fraction contained a substantial amount of biological material, while hydrophilic and transphilic fractions also contained material suggestive of biotic origin. Together, these fractions illustrate the important contribution biological sources make to organic matter in atmospheric fog droplets. The fogwater also was notable for containing a large amount of organic nitrogen present in a variety of species, including amines, nitrate esters, peptides, and nitroso compounds. ?? 2007 American Chemical Society.

Comprehensive characterization of atmospheric organic matter in Fresno, California fog water.

PubMed

Herckes, Pierre; Leenheer, Jerry A; Collett, Jeffrey L

2007-01-15

Fogwater collected during winter in Fresno (CA) was characterized by isolating several distinct fractions and characterizing them by infrared and nuclear magnetic resonance (NMR) spectroscopy. More than 80% of the organic matter in the fogwater was recovered and characterized. The most abundant isolated fractions were those comprised of volatile acids (24% of isolated carbon) and hydrophilic acids plus neutrals (28%). Volatile acids, including formic and acetic acid, have been previously identified as among the most abundant individual species in fogwater. Recovered hydrophobic acids exhibited some properties similar to aquatic fulvic acids. An insoluble particulate organic matter fraction contained a substantial amount of biological material, while hydrophilic and transphilic fractions also contained material suggestive of biotic origin. Together, these fractions illustrate the important contribution biological sources make to organic matter in atmospheric fog droplets. The fogwater also was notable for containing a large amount of organic nitrogen present in a variety of species, including amines, nitrate esters, peptides, and nitroso compounds.

Variable charge transfer state energies at nanostructured pentacene/C60 interfaces

NASA Astrophysics Data System (ADS)

Lin, YunHui L.; Zhang, Fengyu; Kerner, Ross A.; Yang, Terry Chien-Jen; Kahn, Antoine; Rand, Barry P.

2018-05-01

While it has recently been recognized that organic donor-acceptor charge transfer (CT) state energies can vary substantially under different interfacial morphologies, this behavior is under-appreciated in the context of organic singlet fission solar cells where a specific alignment between the triplet state of the fission material and the CT state of the donor-acceptor interface is necessary to the function of the device. In this work, we demonstrate that the CT state energy of a prototypical pentacene-C60 singlet fission system is around 1 eV in most systems, but can vary over 300 meV depending on the composition and morphology of the interface. Moreover, we show that the inclusion of a poly(3-hexylthiophene-2,5-diyl) underlayer, which commonly serves as a triplet blocker and hole collector in pentacene/C60 solar cells, helps promote active layer morphologies with stabilized, low energy CT states. These trends in the interfacial energetics are correlated with structural characterization of the films by atomic force microscopy and x-ray diffraction.

Sugary interfaces mitigate contact damage where stiff meets soft

PubMed Central

Yoo, Hee Young; Iordachescu, Mihaela; Huang, Jun; Hennebert, Elise; Kim, Sangsik; Rho, Sangchul; Foo, Mathias; Flammang, Patrick; Zeng, Hongbo; Hwang, Daehee; Waite, J. Herbert; Hwang, Dong Soo

2016-01-01

The byssal threads of the fan shell Atrina pectinata are non-living functional materials intimately associated with living tissue, which provide an intriguing paradigm of bionic interface for robust load-bearing device. An interfacial load-bearing protein (A. pectinata foot protein-1, apfp-1) with L-3,4-dihydroxyphenylalanine (DOPA)-containing and mannose-binding domains has been characterized from Atrina's foot. apfp-1 was localized at the interface between stiff byssus and the soft tissue by immunochemical staining and confocal Raman imaging, implying that apfp-1 is an interfacial linker between the byssus and soft tissue, that is, the DOPA-containing domain interacts with itself and other byssal proteins via Fe3+–DOPA complexes, and the mannose-binding domain interacts with the soft tissue and cell membranes. Both DOPA- and sugar-mediated bindings are reversible and robust under wet conditions. This work shows the combination of DOPA and sugar chemistry at asymmetric interfaces is unprecedented and highly relevant to bionic interface design for tissue engineering and bionic devices. PMID:27305949

Alternating current response studies on nickel ferrite-niobium composite at room temperature

NASA Astrophysics Data System (ADS)

Reddy, L. P. Babu; Rajprakash, H. G.; Chethan, B.; Vijayakumari, S. C.; Ravikiran, Y. T.

2018-05-01

In the present research NDNF -Niobium Pentaxide doped Nickel Ferrite [NiFe2O4-Nb2O5-50%] composite was prepared by Mechano-Chemical mixing of NiFe2O4 [NF] with Nb2O5. NF and the NDNF were structurally characterized by four transform infrared spectroscopy [FTIR] and X-ray diffraction [XRD] techniques. The presence of characteristic absorption bands of NF and Nb2O5 in the FTIR spectrum of NDNF with small shift confirmed interfacial interaction of NF with Nb2O5. XRD studies also confirm interfacial interaction between NF and Nb2O5 in the composite and crystalline nature with an average crystallite size of 30nm. The Alternating Current (AC) response parameters of NF and the NDNF were comparatively studied in the frequency range 100Hz-1MHz at room temperature. Increase in AC conductivity of the NDNF has compared to NF was observed and discussed based on the electron hole exchange mechanism.

Investigation on Bond-Slip Behavior of Z-Pin Interfaces in X-Cor® Sandwich Structures Using Z-Pin Pull-Out Test

NASA Astrophysics Data System (ADS)

Shan, Hangying; Xiao, Jun; Chu, Qiyi

2018-05-01

The Z-Pin interfacial bond properties play an important role in the structural performance of X-Cor® sandwich structures. This paper presents an experimental investigation on bond-slip behavior of Z-Pin interfaces using Z-Pin pull-out test. Based on the experimental data the whole Z-Pin pull-out process consists of three stages: initial bonding, debonding and frictional sliding. Comparative experimental study on the influence of design parameters on bond-slip behavior of Z-Pin interfaces has also been performed. Numerical analyses were conducted with the ABAQUS finite element (FE) program to simulate the Z-Pins bond-slip response of the pull-out test. The Z-Pins interfacial bond-slip behavior was implemented using nonlinear spring elements characterized with the constitutive relation from experimental results. Numerical results were validated by comparison with experimental data, and reasonably good agreement was achieved between experimental and analytical pull-out force-slip curves.

Understanding the Interface Dipole of Copper Phthalocyanine (CuPc)/C60: Theory and Experiment.

PubMed

Sai, Na; Gearba, Raluca; Dolocan, Andrei; Tritsch, John R; Chan, Wai-Lun; Chelikowsky, James R; Leung, Kevin; Zhu, Xiaoyang

2012-08-16

Interface dipole determines the electronic energy alignment in donor/acceptor interfaces and plays an important role in organic photovoltaics. Here we present a study combining first principles density functional theory (DFT) with ultraviolet photoemission spectroscopy (UPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate the interface dipole, energy level alignment, and structural properties at the interface between CuPc and C60. DFT finds a sizable interface dipole for the face-on orientation, in quantitative agreement with the UPS measurement, and rules out charge transfer as the origin of the interface dipole. Using TOF-SIMS, we show that the interfacial morphology for the bilayer CuPc/C60 film is characterized by molecular intermixing, containing both the face-on and the edge-on orientation. The complementary experimental and theoretical results provide both insight into the origin of the interface dipole and direct evidence for the effect of interfacial morphology on the interface dipole.

Development of graphite/copper composites utilizing engineered interfaces. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Devincent, Sandra M.

1991-01-01

In situ measurements of graphite/copper alloy contact angles were made using the sessile drop method. The interfacial energy values obtained from these measurements were then applied to a model for the fiber matrix interfacial debonding phenomenon found in graphite/copper composites. The formation obtained from the sessile drop tests led to the development of a copper alloy that suitably wets graphite. Characterization of graphite/copper alloy interfaces subjected to elevated temperatures was conducted using Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Auger Electron Spectroscopy, and X Ray Diffraction analyses. These analyses indicated that during sessile drop tests conducted at 1130 C for 1 hour, copper alloys containing greater than 0.98 at pct chromium form continuous reaction layers of approx. 10 microns in thickness. The reaction layers are adherent to the graphite surface. The copper wets the reaction layer to form a contact angle of 60 deg or less. X ray diffraction results indicate that the reaction layer is Cr3C2.

Failure Resistance of Fiber-Reinforced Ultra-High Performance Concrete (FRUHPC) Subjected to Blast Loading

NASA Astrophysics Data System (ADS)

Ellis, Brett; Zhou, Min; McDowell, David

2011-06-01

As part of a hierarchy-based computational materials design program, a fully dynamic 3D mesoscale model is developed to quantify the effects of energy storage and dissipation mechanisms in Fiber-Reinforced Ultra-High Performance Concretes (FRUHPCs) subjected to blast loading. This model accounts for three constituent components: reinforcement fibers, cementitious matrix, and fiber-matrix interfaces. Microstructure instantiations encompass a range of fiber volume fraction (0-2%), fiber length (10-15 mm), and interfacial bonding strength (1-100 MPa). Blast loading with scaled distances between 5 and 10 m/kg1/3 are considered. Calculations have allowed the delineation and characterization of the evolutions of kinetic energy, strain energy, work expended on interfacial damage and failure, frictional dissipation along interfaces, and bulk dissipation through granular flow as functions of microstructure, loading and constituent attributes. The relations obtained point out avenues for designing FRUHPCs with properties tailored for specific load environments and reveal trade-offs between various design scenarios.

Study on the Effect of Surface Energy of Polypropylene/Polyamide12 polymer Hybrid Matrix Reinforced with Virgin and Recycled Carbon Fiber

NASA Astrophysics Data System (ADS)

Sena Maia, Bruno

The presented work is focused on characterization of thermal treated recycled and virgin carbon fibers. Their thermal performances, chemical surface composition and its influence on interfacial adhesion phenomena on PP/PA12 hybrid matrix were compared using TGA, FTIR and XPS analysis. Additionally, differences between hybrid matrix structural performances of PP/PA12 using both surface modifiers PMPPIC and MAPP were investigated. Final mechanical properties improvements between 8% up to 17% were reached by addition of PMPPIC in PP/PA12 hybrid matrix. For PP/PA12 matrix reinforcement using virgin and recycled carbon fibers, impact energy was improved up to 98% compared with MAPP modified matrix leading to a novel composite with good energy absorption. Finally, wettability studies and surface free energy analysis of all materials studied support the effect of the addition of PMPPIC, MAPP and carbon fibers in final composite surface thermodynamics bringing important data correlation between interfacial adhesion mechanisms and final composite performance.

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

NASA Technical Reports Server (NTRS)

Moldover, Michael R.; Rainwater, James C.

1988-01-01

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

Interlaminar and ductile characteristics of carbon fibers-reinforced plastics produced by nanoscaled electroless nickel plating on carbon fiber surfaces.

PubMed

Park, Soo-Jin; Jang, Yu-Sin; Rhee, Kyong-Yop

2002-01-15

In this work, a new method based on nanoscaled Ni-P alloy coating on carbon fiber surfaces is proposed for the improvement of interfacial properties between fibers and epoxy matrix in a composite system. Fiber surfaces and the mechanical interfacial properties of composites were characterized by atomic absorption spectrophotometer (AAS), scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), interlaminar shear strength (ILSS), and impact strength. Experimental results showed that the O(1s)/C(1s) ratio or Ni and P amounts had been increased as the electroless nickel plating proceeded; the ILSS had also been slightly improved. The impact properties were significantly improved in the presence of Ni-P alloy on carbon fiber surfaces, increasing the ductility of the composites. This was probably due to the effect of substituted Ni-P alloy, leading to an increase of the resistance to the deformation and the crack initiation of the epoxy system.

Interface enhancement of glass fiber reinforced vinyl ester composites with flame-synthesized carbon nanotubes and its enhancing mechanism.

PubMed

Liao, Lingmin; Wang, Xiao; Fang, Pengfei; Liew, Kim Meow; Pan, Chunxu

2011-02-01

Interface enhancement with carbon nanotubes (CNTs) provides a promising approach for improving shock strength and toughness of glass fiber reinforced plastic (GFRP) composites. The effects of incorporating flame-synthesized CNTs (F-CNTs) into GFRP were studied, including on hand lay-up preparation, microstructural characterization, mechanical properties, fracture morphologies, and theoretical calculation. The experimental results showed that: (1) the impact strength of the GFRP modified by F-CNTs increased by more than 15% over that of the GFRP modified by CNTs from chemical vapor deposition; and (2) with the F-CNT enhancement, no interfacial debonding was observed at the interface between the fiber and resin matrix on the GFRP fracture surface, which indicated strong adhesive strength between them. The theoretical calculation revealed that the intrinsic characteristics of the F-CNTs, including lower crystallinity with a large number of defects and chemical functional groups on the surface, promoted their surface activity and dispersibility at the interface, which improved the interfacial bond strength of GFRP.

Sugary interfaces mitigate contact damage where stiff meets soft

NASA Astrophysics Data System (ADS)

Yoo, Hee Young; Iordachescu, Mihaela; Huang, Jun; Hennebert, Elise; Kim, Sangsik; Rho, Sangchul; Foo, Mathias; Flammang, Patrick; Zeng, Hongbo; Hwang, Daehee; Waite, J. Herbert; Hwang, Dong Soo

2016-06-01

The byssal threads of the fan shell Atrina pectinata are non-living functional materials intimately associated with living tissue, which provide an intriguing paradigm of bionic interface for robust load-bearing device. An interfacial load-bearing protein (A. pectinata foot protein-1, apfp-1) with L-3,4-dihydroxyphenylalanine (DOPA)-containing and mannose-binding domains has been characterized from Atrina's foot. apfp-1 was localized at the interface between stiff byssus and the soft tissue by immunochemical staining and confocal Raman imaging, implying that apfp-1 is an interfacial linker between the byssus and soft tissue, that is, the DOPA-containing domain interacts with itself and other byssal proteins via Fe3+-DOPA complexes, and the mannose-binding domain interacts with the soft tissue and cell membranes. Both DOPA- and sugar-mediated bindings are reversible and robust under wet conditions. This work shows the combination of DOPA and sugar chemistry at asymmetric interfaces is unprecedented and highly relevant to bionic interface design for tissue engineering and bionic devices.

Two-phase Hele-Shaw flow with a moving contact line

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

Weinstein, S.J.; Ungar, L.H.; Dussan, E.B.

1988-01-01

An asymptotic analysis is presented for Hele-Shaw viscous fingering with a moving contact line at flow rates. As in problems where a thin film is present instead of a contact line, the narrow gap limit is nonuniform, and interfacial boundary conditions valid for the Hele-Shaw equations must be determined in order to predict the flow field and interface shape. Many well-posed boundary-value problems can be identified, each corresponding to a different flow regime characterized by the relative sizes of the capillary number (dimensionless velocity) and the dimensionless gap width. These problems incorporate terms corresponding to the gapwise component of themore » interfacial curvature (the curvature in the cross-sectional view of the Hele-Shaw cell) and spanwise curvature (seen in the top view of the cell) in different ways. Nonunique interface solutions typically arise as in the analogous thin film problems. The relationships between the curvature terms, the spectra of allowable solutions, and the implications for stability are discussed.« less

Free Volume Structure of Acrylic-Type Dental Nanocomposites Tested with Annihilating Positrons.

PubMed

Shpotyuk, Olha; Ingram, Adam; Shpotyuk, Oleh

2016-12-01

Positron annihilation spectroscopy in lifetime measuring mode exploring conventional fast-fast coincidence ORTEC system is employed to characterize free volume structure of commercially available acrylic-type dental restorative composite Charisma® (Heraeus Kulzer GmbH, Germany). The measured lifetime spectra for uncured and light-cured composites are reconstructed from unconstrained x3-term fitting and semi-empirical model exploring x3-x2-coupling decomposition algorithm. The governing channel of positron annihilation in the composites studied is ascribed to mixed positron-Ps trapping, where Ps decaying in the third component is caused entirely by input from free-volume holes in polymer matrix, while the second component is defined by free positron trapping in interfacial free-volume holes between filler nanoparticles and surrounded polymer matrix. Microstructure scenario of the photopolymerization shrinkage includes cross-linking of structural chains in polymer matrix followed by conversion of bound positron-electron (positronium) traps in positron-trapping interfacial free-volume voids in a vicinity of agglomerated filler nanoparticles.

Microfluidic Dynamic Interfacial Tensiometry (μDIT).

PubMed

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

2014-05-07

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

Interactions of hydroxyapatite surfaces: conditioning films of human whole saliva.

PubMed

Cárdenas, Marité; Valle-Delgado, Juan José; Hamit, Jildiz; Rutland, Mark W; Arnebrant, Thomas

2008-07-15

Hydroxyapatite is a very interesting material given that it is the main component in tooth enamel and because of its uses in bone implant applications. Therefore, not only the characterization of its surface is of high relevance but also designing reliable methods to study the interfacial properties of films adsorbed onto it. In this paper we apply the colloidal probe atomic force microscopy method to investigate the surface properties of commercially available hydroxyapatite surfaces (both microscopic particles and macroscopic discs) in terms of interfacial and frictional forces. In this way, we find that hydroxyapatite surfaces at physiological relevant conditions are slightly negatively charged. The surfaces were then exposed to human whole saliva, and the surface properties were re-evaluated. A thick film was formed that was very resistant to mechanical stress. The frictional measurements demonstrated that the film was indeed highly lubricating, supporting the argument that this system may prove to be a relevant model for evaluating dental and implant systems.

Atomic and vibrational origins of mechanical toughness in bioactive cement during setting

PubMed Central

Tian, Kun V.; Yang, Bin; Yue, Yuanzheng; Bowron, Daniel T.; Mayers, Jerry; Donnan, Robert S.; Dobó-Nagy, Csaba; Nicholson, John W.; Fang, De-Cai; Greer, A. Lindsay; Chass, Gregory A.; Greaves, G. Neville

2015-01-01

Bioactive glass ionomer cements (GICs) have been in widespread use for ∼40 years in dentistry and medicine. However, these composites fall short of the toughness needed for permanent implants. Significant impediment to improvement has been the requisite use of conventional destructive mechanical testing, which is necessarily retrospective. Here we show quantitatively, through the novel use of calorimetry, terahertz (THz) spectroscopy and neutron scattering, how GIC's developing fracture toughness during setting is related to interfacial THz dynamics, changing atomic cohesion and fluctuating interfacial configurations. Contrary to convention, we find setting is non-monotonic, characterized by abrupt features not previously detected, including a glass–polymer coupling point, an early setting point, where decreasing toughness unexpectedly recovers, followed by stress-induced weakening of interfaces. Subsequently, toughness declines asymptotically to long-term fracture test values. We expect the insight afforded by these in situ non-destructive techniques will assist in raising understanding of the setting mechanisms and associated dynamics of cementitious materials. PMID:26548704

Supercritical angle fluorescence as a tool to study the interaction between lipid bilayer and peptides

NASA Astrophysics Data System (ADS)

Dubois, Valentin; Serrano, Diana; Seeger, Stefan

2017-06-01

The understanding of processes occurring at the interface between two media are of prior importance in various fields of research, from material sciences to biology. A custom-made microscope objective based on the supercritical angle technique was developed in our group, allowing to probe these interfacial events by carrying out surface-sensitive and low invasive spectroscopy of aqueous samples. A biological example of particular interest is the comprehension of neurodegenerative diseases which seem caused by the interaction of specific peptides with the membrane of the neurons. Taking advantage of our optical setup, we used supercritical angle fluorescence spectroscopy to specifically monitor the interaction between a supported lipid bilayer (SLB) and the Amyloid β peptide, notably responsible of the Alzheimer disease. Different forms of the peptide (40 and 42 amino acids composition) were tested and the interfacial fluorescence measured to get information about the lipid integrity and mobility. The adsorption of the peptide was also characterized in terms of kinetic and affinity.

Microstructural characterization of AA5183 aluminum clad AISI 1018 steel prepared by electro spark deposition

NASA Astrophysics Data System (ADS)

Rastkerdar, E.; Aghajani, H.; Kianvash, A.; Sorrell, C. C.

2018-04-01

The application of a simple and effective technique, electro spark deposition (ESD), to create aluminum clad steel plate has been studied. AA5183 aluminum rods were used as the rotating electrode for cladding of the AISI 1018 steel. The microstructure of the interfacial zone including the intermetallic compounds (IMC) layer and the clad metal have been investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM and STEM). According to the results sound aluminum clad with thickness up to 25–30 μm can be achieved. Very thin (<4 μm) IMC layer was formed at the Al/Fe interface and the structural (electron diffraction pattern) and chemical analysis (STEM) conducted by TEM confirmed that the layer is constituted of Fe rich phases, both implying a much improved mechanical properties. Investigation of the orientations of phases at the interfacial zone confirmed absence of any preferred orientation.

Improving the chemical compatibility of sealing glass for solid oxide fuel cells: Blocking the reactive species by controlled crystallization

NASA Astrophysics Data System (ADS)

Zhang, Teng; Zou, Qi; Zeng, Fanrong; Wang, Shaorong; Tang, Dian; Yang, Hiswen

2012-10-01

The chemical compatibility of sealing glass is of great importance for Solid oxide fuel cell (SOFC). In this work, the interfacial reaction between sealing glass and Cr-containing interconnect alloy is characterized by reacting Cr2O3 powders with a representative SrO-containing glass crystallized by different heat-treatment schedules. The crystalline structure and crystalline content of sealing glass are determined by X-ray diffraction. The results show that the fraction of Cr6+ decreases from 39.8 ± 1.9% for quenched glass to 8.2 ± 0.4% for glass crystallized at 900 °C for 2 h. In addition, the interfacial reaction can be further reduced with increasing crystallization temperature and time as well as the addition of nucleation agent (TiO2). The formation of some Sr-containing crystalline phases, Sr2SiO4 and Sr(TiO3), contributes to the improvement of chemical compatibility of sealing glass, in agreement with the results of thermodynamic calculations.

Interaction of a Model Peptide with a Water--Bilayer System

NASA Technical Reports Server (NTRS)

Pohorille, A.; Wilson, M. A.

1994-01-01

We discuss a molecular dynamics study of the alanine dipeptide at the interface between water and a glycerol-1-monooleate (GMO) bilayer. The dipeptide is interfacially active and incorporates into the bilayer without disrupting its structure. The interfacial region that is readily penetrated by the dipeptide spans the entire head group portion of the bilayer. The polar groups of the alanine dipeptide mostly remain well solvated by water and the oxygen atoms of GMO, and conformations of the dipeptide are characterized by (phi, psi) angles typical of alpha-helix and beta-sheet structures. When the molecule is deeper in the bilayer, the C(sub 7eq) state also becomes stable. The barrier to the isomerization reaction at the interface is lower than in bulk phases. After 7 ns of trajectories, the system is not fully equilibrated, due to slow collective motions involving GMO head groups. These result in decreased mobility and lower rates of isomerization of the dipeptide at the interface.

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

Donald, Scott B.; Siekhaus, Wigbert J.; Nelson, Art J.

X-ray photoelectron spectroscopy in combination with secondary ion mass spectrometry depth profiling were used to investigate the surface and interfacial chemistry of C + ion implanted polycrystalline uranium subsequently oxidized in air for over 10 years at ambient temperature. The original implantation of 33 keV C + ions into U 238 with a dose of 4.3 × 10 17 cm –3 produced a physically and chemically modified surface layer that was characterized and shown to initially prevent air oxidation and corrosion of the uranium after 1 year in air at ambient temperature. The aging of the surface and interfacial layersmore » were examined by using the chemical shift of the U 4f, C 1s, and O 1s photoelectron lines. In addition, valence band spectra were used to explore the electronic structure of the aged carbide surface and interface layer. Moreover, the time-of-flight secondary ion mass spectrometry depth profiling results for the aged sample confirmed an oxidized uranium carbide layer over the carbide layer/U metal interface.« less

GaSb and GaSb/AlSb Superlattice Buffer Layers for High-Quality Photodiodes Grown on Commercial GaAs and Si Substrates

NASA Astrophysics Data System (ADS)

Gutiérrez, M.; Lloret, F.; Jurczak, P.; Wu, J.; Liu, H. Y.; Araújo, D.

2018-05-01

The objective of this work is the integration of InGaAs/GaSb/GaAs heterostructures, with high indium content, on GaAs and Si commercial wafers. The design of an interfacial misfit dislocation array, either on GaAs or Si substrates, allowed growth of strain-free devices. The growth of purposely designed superlattices with their active region free of extended defects on both GaAs and Si substrates is demonstrated. Transmission electron microscopy technique is used for the structural characterization and plastic relaxation study. In the first case, on GaAs substrates, the presence of dopants was demonstrated to reduce several times the threading dislocation density through a strain-hardening mechanism avoiding dislocation interactions, while in the second case, on Si substrates, similar reduction of dislocation interactions is obtained using an AlSb/GaSb superlattice. The latter is shown to redistribute spatially the interfacial misfit dislocation array to reduce dislocation interactions.

Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets

NASA Astrophysics Data System (ADS)

Lin, I.-Hsin; Miller, Daniel S.; Bertics, Paul J.; Murphy, Christopher J.; de Pablo, Juan J.; Abbott, Nicholas L.

2011-06-01

The ordering of liquid crystals (LCs) is known to be influenced by surfaces and contaminants. Here, we report that picogram per milliliter concentrations of endotoxin in water trigger ordering transitions in micrometer-size LC droplets. The ordering transitions, which occur at surface concentrations of endotoxin that are less than 10-5 Langmuir, are not due to adsorbate-induced changes in the interfacial energy of the LC. The sensitivity of the LC to endotoxin was measured to change by six orders of magnitude with the geometry of the LC (droplet versus slab), supporting the hypothesis that interactions of endotoxin with topological defects in the LC mediate the response of the droplets. The LC ordering transitions depend strongly on glycophospholipid structure and provide new designs for responsive soft matter.

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.

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

DOE PAGES

Cheng, Shiwang; Carroll, Bobby; Bocharova, Vera; ...

2017-03-30

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

Discovering the Role of Grain Boundary Complexions in Materials

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

Harmer, Martin P.

Grain boundaries are inherently an area of disorder in polycrystalline materials which define the transport and various other material properties. The relationship between the interfacial chemistry, structure and the material properties is not well understood. Among the various taxonomies for grain boundaries, Grain Boundary Complexion is a relatively new conceptual scheme that relates the structure and kinetic properties of grain boundaries. In this classification scheme, grain boundaries are considered to be distinct three dimensional (the thickness being considerably smaller as compared to the other two dimensions but nonetheless discernible) equilibrium thermodynamic phases abutted between two crystalline phases. The stability andmore » structure of these interfacial phases are dictated by various thermodynamic variables such as temperature, stress (pressure), interfacial chemistry (chemical potential) and most importantly by the energies of the adjoining crystal surfaces. These phases are only stable within the constraint of the adjoining grains. Although these interfacial phases are not stable in bulk form, they can transform from one complexion to another as a function of various thermodynamic variables analogous to the behavior of bulk phases. Examples of different complexions have been reported in various publications. However, a systematic investigation exploring the existence of grain boundary complexions in material systems other than alumina remains to be done. Although the role of interfacial chemistry on grain boundary complexions in alumina has been addressed, a clear understanding of the underlying thermodynamics governing complexion formation is lacking. Finally, the effects of grain boundary complexions in bulk material properties are widely unknown. Factors above urge a thorough exploration of grain boundary complexions in a range of different materials systems The purpose of the current program is to verify the existence of grain boundary complexion in a range of materials systems, and to characterize their structures, range of stability and selected physical properties. First, an Au-based bilayer interfacial phase was discovered at a bicrystal boundary in the Si-Au system. This bilayer transitioned abruptly to an intrinsic (“clean”) grain boundary phase, suggesting first-order phase behavior. This study represents the discovery of grain boundary complexions in a completely new system, i.e., a semiconductor-metal system, giving further support to the expectation that grain boundary complexions are a general phenomenon not limited to any particular class of materials. The TiO 2-CuO system exhibited four grain boundary interfacial phases: a monolayer, disordered bilayer, disordered trilayer, and non-wetting nanoscale amorphous drop (which likely resulted from dewetting of a nanoscale IGF). SiO 2 contamination was discovered in the TiO 2-CuO samples, and we hypothesize that this impurity may have caused an “order-disorder” transition to occur. In other words, we expect that pure TiO 2-CuO may have a higher tendency to exhibit ordered bilayer and trilayer complexions, which may also exhibit a well-defined order-disorder transition temperature. In this effort we have also identified unique complexion transitions in yttria and strontium titanate.« less

Evaluation of Changes in Iron Interfacial Composition Using Surface Spectroscopy

NASA Astrophysics Data System (ADS)

Vikesland, P. J.; Kohn, T.; Ball, W. P.; Fairbrother, D.; Roberts, A.

2001-12-01

Although the ability of granular cast iron permeable reactive barriers to attenuate many persistent groundwater contaminants is well established, many uncertainties remain about the interactions that occur between cast iron and contaminant species. To better understand these interactions we set out to evaluate how various inorganic species and organic contaminants affect the interfacial composition of the iron over time. Column studies using granular iron enable us to observe changes in iron interfacial composition as a function of distance along the column as well as of column "age". The spectroscopic evaluations reported here are for ten columns that were fed continuously with simulated anoxic groundwaters of different chemistries. Nine of these columns were packed with untreated sieved cast iron and one was packed with a mixture of cast iron and the aluminosilicate mineral albite. Of the ten columns, seven have been continually fed chlorinated hydrocarbons (CHCs), one has been continually fed nitroaromatic compounds (NACs), and two have only periodically been fed CHCs in their influent. Six of these ten columns were operated for 1100 days and the remaining four were operated for 475 days. In an anaerobic glovebox, sample grains were extracted for surface spectroscopic characterization using solid sampling ports drilled into the columns. At each port, several iron grains were removed and immediately put into headspace free vials containing porewater obtained from the nearest aqueous sampling port. Samples were then analyzed using in-situ Raman analysis, Auger electron spectroscopy (AES), and transmission electron microscopy (TEM). Raman spectra indicate that the interfacial composition of the iron grains changes substantially between the inlet and the outlet of a given column. Near the inlet, Raman bands corresponding to the iron oxides goethite and magnetite are prevalent, whereas grains from a port near the column outlet exhibit bands at 425 and 504 cm-1, corresponding to the Fe2+-OH stretch and the Fe3+-OH stretch, respectively, of the redox-active mineral green rust. Comparisons at two different times (308 and 921 days) suggest that the interfacial composition of the iron grains also changed as the columns aged, with the longer-term downgradient compositions becoming more like those observed upgradient at earlier times. These in-situ Raman observations were supported by both AES and TEM. The observed spatial and temporal changes in the interfacial composition of the iron indicate that the iron grains become more passivated as the columns age. Initially, this passivation is most notable near the influent end of the columns, since that region receives the largest influx of reducible material. As the columns age, the passivated region slowly expands into the distal regions of the columns. This presentation will address the use of surface spectroscopy to analyze these changes in interfacial composition and will relate the observations to feed solution properties and to concurrent observations of reactivity changes. The implications of these results on the design and longevity of cast iron barriers will also be discussed.

Effects of Alternating Hydrogenated and Protonated Segments in polymers on their Wettability.

NASA Astrophysics Data System (ADS)

Smith, Dennis; Traiphol, Rakchart; Cheng, Gang; Perahia, Dvora

2003-03-01

Polymers consisting of alternating hydrogenated and fluorinated segments exhibit unique interfacial characteristics governed by the components that dominate the interface. Presence of fluorine reduces the interfacial energy and is expected to decrease the adhesion to the polymer surface. Thin liquid crystalline (LC) layers of 4,4?-octyl-cyanobiphenyl, cast on top of a polymeric layer consisting of alternating methylstylbine protonated segments bridged by a fluorinated group was used as a mechanistic tool to study of interfacial effects on three parameters: wetting, interfacial alignment and surface induces structures. The liquid crystal cast on a low interfacial energy fluorinated polymeric film exhibits bulk homeotropic alignment as expected. However it fully wetted the polymer surface despite the incompatibility of the protonated LC and mainly fluorinated polymer interface. Further more, it was found to stabilize the interfacial Semitic layers to a higher temperature and induce different surface ordering that was not observed at the same temperature neither in the bulk nor at the interfaces with silicon or glass surface. These results indicate that the interfacial interactions of polymers with liquid crystals are a complex function of both surface energies and the interfacial structure of the polymer.

Experimental observation of standing interfacial waves induced by surface waves in muddy water

NASA Astrophysics Data System (ADS)

Maxeiner, Eric; Dalrymple, Robert A.

2011-09-01

A striking feature has been observed in a laboratory wave tank with a thin layer of clear water overlying a layer of mud. A piston-type wave maker is used to generate long monochromatic surface waves in a tank with a layer of kaolinite clay at the bottom. The wave action on the mud causes the clay particles to rise from the bottom into the water column, forming a lutocline. As the lutocline approaches the water surface, a set of standing interfacial waves form on the lutocline. The interfacial wave directions are oriented nearly orthogonal to the surface wave direction. The interfacial waves, which sometimes cover the entire length and width of the tank, are also temporally subharmonic as the phase of the interfacial wave alternates with each passing surface wave crest. These interfacial waves are the result of a resonant three-wave interaction involving the surface wave train and the two interfacial wave trains. The interfacial waves are only present when the lutocline is about 3 cm of the water surface and they can be sufficiently nonlinear as to exhibit superharmonics and a breaking-type of instability.

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

NASA Astrophysics Data System (ADS)

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

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

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.

TEST METHODS TO CHARACTERIZE PARTICULATE MATTER EMISSIONS AND DEPOSITION RATES IN A RESEARCH HOUSE

EPA Science Inventory

The paper discusses test methods to characterize particulate matter (PM) emissions and deposition rates in a research house. In a room in the research house, specially configured for PM source testing, a high-efficiency particulate air (HEPA)-filtered air supply system, used for...

INTERLABORATORY COMPARISON STUDIES FOR CHARACTERIZATION OF ORGANIC COMPOUNDS IN PARTICULATE MATTER

EPA Science Inventory

A working group of investigators, who are characterizing and quantifying the organic compounds in particulate matter (PM) as part of the US EPA's PM 2.5 research program and related studies, was established three years ago to advance the quality and comparability of data on the...

Analysis and characterization of graphene-on-substrate devices

NASA Astrophysics Data System (ADS)

Berdebes, Dionisis

The purpose of this MS Thesis is the analysis and characterization of graphene on substrate structures prepared at the Birck Nanotechnology Center-Purdue University/IBM Watson Research Center-N.Y., and characterized under low-field transport conditions. First, a literature survey is conducted, both in theoretical and experimental work on graphene transport phenomena, and the open issues are reported. Next, the theory of low-field transport in graphene is reviewed within a Landauer framework. Experimental results of back-gated graphene-on-substrate devices, prepared by the Appenzeller group, are then presented, followed by an extraction of an energy/temperature dependent backscattering mean free path as the main characterization parameter. A key conclusion is the critical role of contacts in two-probe measurements. In this framework, a non-self-consistent Non Equilibrium Green's Function method is employed for the calculation of the odd and even metal-graphene ballistic interfacial resistance. A good agreement with the relevant experimental work is observed.

Preparation and Characterization of New Geopolymer-Epoxy Resin Hybrid Mortars

PubMed Central

Colangelo, Francesco; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Cioffi, Raffaele

2013-01-01

The preparation and characterization of metakaolin-based geopolymer mortars containing an organic epoxy resin are presented here for the first time. The specimens have been prepared by means of an innovative in situ co-reticulation process, in mild conditions, of commercial epoxy based organic resins and geopolymeric slurry. In this way, geopolymer based hybrid mortars characterized by a different content of normalized sand (up to 66% in weight) and by a homogeneous dispersion of the organic resin have been obtained. Once hardened, these new materials show improved compressive strength and toughness in respect to both the neat geopolymer and the hybrid pastes since the organic polymer provides a more cohesive microstructure, with a reduced amount of microcracks. The microstructural characterization allows to point out the presence of an Interfacial Transition Zone similar to that observed in cement based mortars and concretes. A correlation between microstructural features and mechanical properties has been studied too. PMID:28811418

Interfacial Thermal Conductance Limit and Thermal Rectification Across Vertical Carbon Nanotube/Graphene Nanoribbon-Silicon Interfaces

DTIC Science & Technology

2013-01-01

Interfacial thermal conductance limit and thermal rectification across vertical carbon nanotube/graphene nanoribbon-silicon interfaces Ajit K...054308 (2013) Investigation on interfacial thermal resistance and phonon scattering at twist boundary of silicon J. Appl. Phys. 113, 053513 (2013...2013 to 00-00-2013 4. TITLE AND SUBTITLE Interfacial thermal conductance limit and thermal rectification across vertical carbon nanotube/graphene

Open and Filled Hole Static Tensile Strength Characterization of Metal Matrix Composite SCS-9/Beta21s.

DTIC Science & Technology

1992-12-01

Augmentation Program (28) state that for filled hole tensile testing of MMCs the tolerance between the pin diameter and hole diameter must not exceed .0254...Acetate replication, metallography, and fractography will be used in conjunction with analytical methods to define the aforementioned material... fractography that this bi-linear response is due to the release of residual stresses and interfacial failures of the off-axis plies and not micro

Characterization and Development of Advanced Materials: Role & Understanding of Interfacial Phenomena (Congressional)

DTIC Science & Technology

2007-12-01

therefore the resistance to thermal shock of this material. Thus, dopants such as La20 3 are to be avoided and alternative means to decrease the grain...of the furnace. Ceramic laser materials also have other potential advantages. The dopant concentration of the starting material can be adjusted so that...measurements on the polaron conductor (nickel cobalt spinel oxide) indicated that this material can support high current flows in oxygen environments at a few

Reliability Characterization of Digital Microcircuits - Investigation of an In-Process Oxide Reliability Screening Method

DTIC Science & Technology

1993-04-01

CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURIlY CLASSIFICATION 20. UMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT UNCLASSIFIED UNCLASSIFIED...with the silicon underneath, growing a thin nitride layer. This layer of Si 3 N 4 , if not completely removed, will retard oxidation in the area...C. Shatas, K. C. Saraswat and J. D. Meindl, "Interfacial and Breakdown Characteristics of MOS Devices with Rapidly Grown Ultrathin SiO Gate

Evaluation of a single cell and candidate materials with high water content hydrogen in a generic solid oxide fuel cell stack test fixture, Part II: materials and interface characterization

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

Chou, Y. S.; Stevenson, Jeffry W.; Choi, Jung-Pyung

2013-01-01

A generic solid oxide fuel cell (SOFC) test fixture was developed to evaluate candidate materials under realistic conditions. A commerical 50 mm x 50 mm NiO-YSZ anode supported thin YSZ electrolyte cell with lanthanum strontium manganite (LSM) cathode was tested to evaluate the stability of candidate materials. The cell was tested in two stages at 800oC: stage I of low (~3% H2O) humidity and stage II of high (~30% H2O) humidity hydrogen fuel at constant voltage or constant current mode. Part I of the work was published earlier with information of the generic test fixture design, materials, cell performance, andmore » optical post-mortem analysis. In part II, detailed microstructure and interfacial characterizations are reported regarding the SOFC candidate materials: (Mn,Co)-spinel conductive coating, alumina coating for sealing area, ferritic stainless steel interconnect, refractory sealing glass, and their interactions with each other. Overall, the (Mn,Co)-spinel coating was very effective in minimizing Cr migration. No Cr was identified in the cathode after 1720h at 800oC. Aluminization of metallic interconnect also proved to be chemically compatible with alkaline-earth silicate sealing glass. The details of interfacial reaction and microstructure development are discussed.« less

Properties of M40J Carbon/PMR-II-50 Composites Fabricated with Desized and Surface Treated Fibers. Characterization of M40J Desized and Finished Fibers

NASA Technical Reports Server (NTRS)

Allred, Ronald E.; Gosau, Jan M.; Shin, E. Eugene; McCorkle, Linda S.; Sutter, James K.; OMalley, Michelle; Gray, Hugh R. (Technical Monitor)

2002-01-01

To increase performance and durability of high temperature composites for potential rocket engine components, it is necessary to optimize wetting and interfacial bonding between high modulus carbon fibers and high temperature polyimide resins. It has been previously demonstrated that the electro-oxidative shear treatments used by fiber manufacturers are not effective on higher modulus fibers that have fewer edge and defect sites in the surface crystallites. In addition, sizings commercially supplied on most carbon fibers are not compatible with polyimides. This study was an extension of prior work characterizing the surface chemistry and energy of high modulus carbon fibers (M40J and M60J, Torray) with typical fluorinated polyimide resins, such as PMR-II-50. A continuous desizing system which utilizes environmentally friendly chemical- mechanical processes was developed for tow level fiber and the processes were optimized based on weight loss behavior, surface elemental composition (XPS) and morphology (FE-SEM) analyses, and residual tow strength of the fiber, and the similar approaches have been applied on carbon fabrics. Both desized and further treated with a reactive finish were investigated for the composite reinforcement. The effects of desizing and/or subsequent surface retreatment on carbon fiber on composite properties and performance including fiber-matrix interfacial mechanical properties, thermal properties and blistering onset behavior will be discussed in this presentation.

Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures.

PubMed

Wang, Wenliang; Yang, Weijia; Lin, Yunhao; Zhou, Shizhong; Li, Guoqiang

2015-11-13

2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices.

Carbothermic Reduction Reactions at the Metal-Slag Interface in Ti-Bearing Slag from a Blast Furnace

NASA Astrophysics Data System (ADS)

Wang, Yao-Zu; Zhang, Jian-Liang; Liu, Zheng-Jian; Du, Cheng-Bo

2017-11-01

Carbothermic reduction reactions at the metal-slag interface and the mechanisms of iron loss during the smelting of vanadium-bearing titanomagnetite in a blast furnace are still not clear as a result of the limited ability to observe the high-temperature zone of a blast furnace. The chemical composition of a Ti-bearing slag was determined by x-ray fluorescence and x-ray diffraction. The interfaces were characterized by scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy. The interfacial chemical reactions were deduced based on the characterization results and on the thermodynamic calculations performed using Factsage 6.4. The results indicated that the forms of iron in the slag were iron droplets wetted by Ti(C x , N1- x ), mechanically separated by iron and iron oxide. The different forms possessed unique characteristics and were formed by different mechanisms. Iron droplets wetted by Ti(C x , N1- x ) were generated through a series of interfacial reactions between TiO2 in the slag and [C] and [N] in the metal. Iron droplets without attached Ti(C x , N1- x ) were mainly located on the edges of pores and were attributed to the reduction of Fe x O in the slag. Insufficient reduction of iron-bearing minerals made it difficult for iron droplets to aggregate and separate from the slag, which created an Fe x O-enriched zone.

Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

NASA Astrophysics Data System (ADS)

Pal, Hemant; Sharma, Vimal

2014-11-01

The mechanical, electrical, and thermal expansion properties of carbon nanotube (CNT)-based silver and silver-palladium (10:1, w/w) alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver-palladium nanocomposite with CNT resulted in increases in the hardness and Young's modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion (CTE). The hardness and Young's modulus of the nanocomposites were increased by 30%-40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver-palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.

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.

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

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

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

1996-04-01

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

Deformation twinning in a creep-deformed nanolaminate structure

NASA Astrophysics Data System (ADS)

Hsiung, Luke L.

2010-10-01

The underlying mechanism of deformation twinning occurring in a TiAl-(γ)/Ti3Al-(α2) nanolaminate creep deformed at elevated temperatures has been studied. Since the multiplication and propagation of lattice dislocations in both γ and α2 thin lamellae are very limited, the total flow of lattice dislocations becomes insufficient to accommodate the accumulated creep strains. Consequently, the movement of interfacial dislocations along the laminate interfaces, i.e., interface sliding, becomes an alternative deformation mode of the nanolaminate structure. Pile-ups of interfacial dislocations occur when interfacial ledges and impinged lattice dislocations act as obstacles to impede the movement of interfacial dislocations. Deformation twinning can accordingly take place to relieve a stress concentration resulting from the pile-up of interfacial dislocations. An interface-controlled twinning mechanism driven by the pile-up and dissociation of interfacial dislocations is accordingly proposed.

Interfacial adsorption in two-dimensional pure and random-bond Potts models.

PubMed

Fytas, Nikolaos G; Theodorakis, Panagiotis E; Malakis, Anastasios

2017-03-01

We use Monte Carlo simulations to study the finite-size scaling behavior of the interfacial adsorption of the two-dimensional square-lattice q-states Potts model. We consider the pure and random-bond versions of the Potts model for q=3,4,5,8, and 10, thus probing the interfacial properties at the originally continuous, weak, and strong first-order phase transitions. For the pure systems our results support the early scaling predictions for the size dependence of the interfacial adsorption at both first- and second-order phase transitions. For the disordered systems, the interfacial adsorption at the (disordered induced) continuous transitions is discussed, applying standard scaling arguments and invoking findings for bulk critical properties. The self-averaging properties of the interfacial adsorption are also analyzed by studying the infinite limit-size extrapolation of properly defined signal-to-noise ratios.

Effects of image charges, interfacial charge discreteness, and surface roughness on the zeta potential of spherical electric double layers.

PubMed

Gan, Zecheng; Xing, Xiangjun; Xu, Zhenli

2012-07-21

We investigate the effects of image charges, interfacial charge discreteness, and surface roughness on spherical electric double layer structures in electrolyte solutions with divalent counterions in the setting of the primitive model. By using Monte Carlo simulations and the image charge method, the zeta potential profile and the integrated charge distribution function are computed for varying surface charge strengths and salt concentrations. Systematic comparisons were carried out between three distinct models for interfacial charges: (1) SURF1 with uniform surface charges, (2) SURF2 with discrete point charges on the interface, and (3) SURF3 with discrete interfacial charges and finite excluded volume. By comparing the integrated charge distribution function and the zeta potential profile, we argue that the potential at the distance of one ion diameter from the macroion surface is a suitable location to define the zeta potential. In SURF2 model, we find that image charge effects strongly enhance charge inversion for monovalent interfacial charges, and strongly suppress charge inversion for multivalent interfacial charges. For SURF3, the image charge effect becomes much smaller. Finally, with image charges in action, we find that excluded volumes (in SURF3) suppress charge inversion for monovalent interfacial charges and enhance charge inversion for multivalent interfacial charges. Overall, our results demonstrate that all these aspects, i.e., image charges, interfacial charge discreteness, their excluding volumes, have significant impacts on zeta potentials of electric double layers.

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

PubMed

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

2017-05-01

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

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

Cao, J., E-mail: cao_jian@hit.edu.cn; State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001; Song, X.G., E-mail: song_xiaoguohit@yahoo.com.cn

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

A Real Time Investigation of Morphological Evolution During Solidification of Different Alloy Systems

NASA Technical Reports Server (NTRS)

Sen, S.; Kaukler, W. F.; Curreri, P. A.

1999-01-01

Solidification phenomenon which occur at the solid/liquid (s/I) interface play a major role in the determination of structure and hence the technologically important properties of a casting. However, metals being opaque, conclusions related to several important phenomenon such as boundary layer thickness, morphological evolution, and eutectic and cell spacing are deduced from quenching experiments and subsequent post solidification metallographic analysis. Consequently, limited information is obtained about the dynamics of the process. This paper will discuss the recent efforts at the Space Science Laboratory, NASA Marshall Space Flight Center, to view and quantify in-situ and in real time the dynamics of the solidification process and to measure interfacial undercooling. First, a high resolution x-ray transmission microscope (XTM) has been developed to monitor fundamental interfacial phenomena during directional solidification of metals and alloys. The XTM operates in the range of 10-100 KeV and through projection is capable of achieving magnification of up to 16OX. Secondly, an innovative collapsible furnace has been designed to quantify interfacial undercooling by measuring the temperature of a moving s/I interface in reference to a fixed s/l interface. This measurement technique is non-intrusive in nature and is based on the Seebeck principle. In this paper real time results obtained to characterize the dynamics of irregular eutectic spacing will be presented. As an example fiber to lamella or plate transition in the Al-Al2Au eutectic system will be discussed. Further, a resolution limit of 25 micron has permitted viewing in real time morphological instability and cellular growth in Al-Au and Al-Ag systems. Simultaneously, a systematic investigation has been carried out to measure interfacial undercooling for Pb-1 wt.% Sn at and near the marginal stability regime. In conjunction with the XTM observations this study attempts to validate existing relationships between undercooling and growth velocity during plane front growth, marginal stability regime, and stable cellular growth.

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]. To elucidate this behavior we studied a simplified model comprised of an interface between two stacks of graphene ribbons to mimic the contact between multiwalled nanotubes. Our results, in agreement with experiment, show that the interfacial thermal conductance indeed increases with the number of graphene layers, corresponding to larger diameter and larger number of walls in MWCNT. The role of interfacial layer thickness is investigated by modeling a system of a few layers of graphene sandwiched between two silicon slabs. We show, by wave packet simulation and by theoretical calculation of a spring-mass model, that the transmission coefficient of individual vibrational modes is strongly dependent on the frequency and the number of graphene layers due to coherent interference effects; by contrast, the interfacial thermal conductance obtained in NEMD simulation, which represents an integral over all phonons, is essentially independent of the number of graphene layers, in agreement with recent experiments. Furthermore, when we heat one atomic layer of graphene directly, the effective interfacial conductance associated with heat dissipation to the silicon substrate is very small. We attribute this to the resistance associated with heat transfer between high and low frequency phonon modes within graphene. Finally, we also replaced graphene layers by a few WSe2 sheets and observed that interfacial thermal resistance of a Si/n-WSe2/Si structure increases linearly with interface thickness at least for 1 < n <= 20, indicating diffusive heat transfer mechanism, in contrast to ballistic behavior of a few graphene layers. The corresponding thermal conductivity (0.048 W m-1 K-1) of a few WSe2 layers is rather small. By comparing phonon dispersion of graphene layers and WSe2 sheets, we attribute the diffusive behavior of a few WSe2 sheets to abundant optical phonons at low and medium frequencies leading to very short mean free path. Our computational studies of effects of pressure and structural properties on interfacial thermal conductance provide fundamental insights for tunable heat transfer in nanostructures. [1] Professor D. Y. Li from University of Vanderbilt, private communication (Nov. 14, 2011).

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.

Protein Adsorption and Layer Formation at the Stainless Steel-Solution Interface Mediates Shear-Induced Particle Formation for an IgG1 Monoclonal Antibody.

PubMed

Kalonia, Cavan K; Heinrich, Frank; Curtis, Joseph E; Raman, Sid; Miller, Maria A; Hudson, Steven D

2018-03-05

Passage of specific protein solutions through certain pumps, tubing, and/or filling nozzles can result in the production of unwanted subvisible protein particles (SVPs). In this work, surface-mediated SVP formation was investigated. Specifically, the effects of different solid interface materials, interfacial shear rates, and protein concentrations on SVP formation were measured for the National Institute of Standards and Technology monoclonal antibody (NISTmAb), a reference IgG1 monoclonal antibody (mAb). A stainless steel rotary piston pump was used to identify formulation and process parameters that affect aggregation, and a flow cell (alumina or stainless steel interface) was used to further investigate the effect of different interface materials and/or interfacial shear rates. SVP particles produced were monitored using flow microscopy or flow cytometry. Neutron reflectometry and a quartz crystal microbalance with dissipation monitoring were used to characterize adsorption and properties of NISTmAb at the stainless steel interface. Pump/shear cell experiments showed that the NISTmAb concentration and interface material had a significant effect on SVP formation, while the effects of interfacial shear rate and passage number were less important. At the higher NISTmAb concentrations, the adsorbed protein became structurally altered at the stainless steel interface. The primary adsorbed layer remained largely undisturbed during flow, suggesting that SVP formation at high NISTmAb concentration was caused by the disruption of patches and/or secondary interactions.

In situ synthesis of Bi2S3 sensitized WO3 nanoplate arrays with less interfacial defects and enhanced photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Liu, Canjun; Yang, Yahui; Li, Wenzhang; Li, Jie; Li, Yaomin; Chen, Qiyuan

2016-03-01

In this study, Bi2S3 sensitive layer has been grown on the surface of WO3 nanoplate arrays via an in situ approach. The characterization of samples were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet-visible absorption spectroscopy (UV-vis). The results show that the Bi2S3 layer is uniformly formed on the surface of WO3 nanoplates and less interfacial defects were observed in the interface between the Bi2S3 and WO3. More importantly, the Bi2S3/WO3 films as photoanodes for photoelectrochemical (PEC) cells display the enhanced PEC performance compared with the Bi2S3/WO3 films prepared by a sequential ionic layer adsorption reaction (SILAR) method. In order to understand the reason for the enhanced PEC properties, the electron transport properties of the photoelectrodes were studied by using the transient photocurrent spectroscopy and intensity modulated photocurrent spectroscopy (IMPS). The Bi2S3/WO3 films prepared via an in situ approach have a greater transient time constant and higher electron transit rate. This is most likely due to less interfacial defects for the Bi2S3/WO3 films prepared via an in situ approach, resulting in a lower resistance and faster carrier transport in the interface between WO3 and Bi2S3.

Multifunctional organized mesoporous tin oxide films templated by graft copolymers for dye-sensitized solar cells.

PubMed

Park, Jung Tae; Ahn, Sung Hoon; Roh, Dong Kyu; Lee, Chang Soo; Kim, Jong Hak

2014-07-01

The synthesis of organized mesoporous SnO2 films with high porosity, larger pores, and good interconnectivity, obtained by sol-gel templating with an amphiphilic graft copolymer, poly(vinyl chloride)-graft-poly(oxyethylene methacrylate), is reported. An improved performance of dye-sensitized solar cells (DSSCs) is demonstrated by the introduction of a 400 nm thick organized mesoporous SnO2 interfacial (om-SnO2 IF) layer between nanocrystalline TiO2 (nc-TiO2 ) and a fluorine-doped tin oxide substrate. To elucidate the improved efficiency, the structural, optical, and electrochemical properties of the devices were characterized by SEM, UV/Vis spectroscopy, noncontact 3D surface profilometry, intensity-modulated photocurrent/voltage spectroscopy, incident photon-to-electron conversion efficiency, and electrochemical impedance spectroscopy measurements. The energy-conversion efficiency of the solid polymerized ionic liquid based DSSC fabricated with the om-SnO2 IF/nc-TiO2 photoanode reached 5.9% at 100 mW cm(-2) ; this is higher than those of neat nc-TiO2 (3.5%) and organized mesoporous TiO2 interfacial/nc-TiO2 layer (5.4%) photoanodes. The improved efficiency is attributed to the antireflective property, cascadal energy band gap, good interconnectivity, and high electrical conductivity of the om-SnO2 IF layer, which results in enhanced light harvesting, increased electron transport, reduced charge recombination, and decreased interfacial/internal resistance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure of a Premicellar Complex of Alkyl Sulfates with the Interfacial Binding Surfaces of 4 Subunits of Phospholipase A2✰

PubMed Central

Pan, Ying H.; Bahnson, Brian J.

2010-01-01

The properties of three discrete premicellar complexes (E1#, E2#, E3#) of pig pancreatic group-IB secreted phospholipase A2 (sPLA2) with monodisperse alkyl sulfates has been characterized [Berg, O. G., et al., Biochemistry 43, 7999–8013, 2004]. Here we have solved the 2.7 Å crystal structure of group-IB sPLA2 complexed with 12 molecules of octyl sulfate (C8S) in a form consistent with a tetrameric oligomeric that exists during the E1# phase of premicellar complexes. The alkyl tails of the C8S molecules are centered in the middle of the tetrameric cluster of sPLA2 subunits. Three of the four sPLA2 subunits also contain a C8S molecule in the active site pocket. The sulfate oxygen of a C8S ligand is complexed to the active site calcium in 3 of the 4 protein active sites. The interactions of the alkyl sulfate head group with Arg-6 and Lys-10, as well as the backbone amide of Met-20, are analogous to those observed in the previously solved sPLA2 crystal structures with bound phosphate and sulfate anions. The cluster of three anions found in the present structure is postulated to be the site for nucleating the binding of anionic amphiphiles to the interfacial surface of the protein, and therefore this binding interaction has implications for interfacial activation of the enzyme. PMID:20302975

The effect of physiological conditions on the surface structure of proteins: Setting the scene for human digestion of emulsions

NASA Astrophysics Data System (ADS)

Maldonado-Valderrama, J.; Gunning, A. P.; Ridout, M. J.; Wilde, P. J.; Morris, V. J.

2009-10-01

Understanding and manipulating the interfacial mechanisms that control human digestion of food emulsions is a crucial step towards improved control of dietary intake. This article reports initial studies on the effects of the physiological conditions within the stomach on the properties of the film formed by the milk protein ( β -lactoglobulin) at the air-water interface. Atomic force microscopy (AFM), surface tension and surface rheology techniques were used to visualize and examine the effect of gastric conditions on the network structure. The effects of changes in temperature, pH and ionic strength on a pre-formed interfacial structure were characterized in order to simulate the actual digestion process. Changes in ionic strength had little effect on the surface properties. In isolation, acidification reduced both the dilatational and the surface shear modulus, mainly due to strong repulsive electrostatic interactions within the surface layer and raising the temperature to body temperature accelerated the rearrangements within the surface layer, resulting in a decrease of the dilatational response and an increase of surface pressure. Together pH and temperature display an unexpected synergism, independent of the ionic strength. Thus, exposure of a pre-formed interfacial β -lactoglobulin film to simulated gastric conditions reduced the surface dilatational modulus and surface shear moduli. This is attributed to a weakening of the surface network in which the surface rearrangements of the protein prior to exposure to gastric conditions might play a crucial role.

Constructing Solid-Gas-Interfacial Fenton Reaction over Alkalinized-C3N4 Photocatalyst To Achieve Apparent Quantum Yield of 49% at 420 nm.

PubMed

Li, Yunxiang; Ouyang, Shuxin; Xu, Hua; Wang, Xin; Bi, Yingpu; Zhang, Yuanfang; Ye, Jinhua

2016-10-03

Efficient generation of active oxygen-related radicals plays an essential role in boosting advanced oxidation process. To promote photocatalytic oxidation for gaseous pollutant over g-C 3 N 4 , a solid-gas interfacial Fenton reaction is coupled into alkalinized g-C 3 N 4 -based photocatalyst to effectively convert photocatalytic generation of H 2 O 2 into oxygen-related radicals. This system includes light energy as power, alkalinized g-C 3 N 4 -based photocatalyst as an in situ and robust H 2 O 2 generator, and surface-decorated Fe 3+ as a trigger of H 2 O 2 conversion, which attains highly efficient and universal activity for photodegradation of volatile organic compounds (VOCs). Taking the photooxidation of isopropanol as model reaction, this system achieves a photoactivity of 2-3 orders of magnitude higher than that of pristine g-C 3 N 4 , which corresponds to a high apparent quantum yield of 49% at around 420 nm. In-situ electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicate that the notable photoactivity promotion could be ascribed to the collaboration between photocarriers (electrons and holes) and Fenton process to produce abundant and reactive oxygen-related radicals. The strategy of coupling solid-gas interfacial Fenton process into semiconductor-based photocatalysis provides a facile and promising solution to the remediation of air pollution via solar energy.

MBE Growth of Ferromagnetic Metal/Compound Semiconductor Heterostructures for Spintronics

ScienceCinema

Palmstrom, Chris [University of California, Santa Barbara, California, United States

2017-12-09

Electrical transport and spin-dependent transport across ferromagnet/semiconductor contacts is crucial in the realization of spintronic devices. Interfacial reactions, the formation of non-magnetic interlayers, and conductivity mismatch have been attributed to low spin injection efficiency. MBE has been used to grow epitaxial ferromagnetic metal/GA(1-x)AL(x)As heterostructures with the aim of controlling the interfacial structural, electronic, and magnetic properties. In situ, STM, XPS, RHEED and LEED, and ex situ XRD, RBS, TEM, magnetotransport, and magnetic characterization have been used to develop ferromagnetic elemental and metallic compound/compound semiconductor tunneling contacts for spin injection. The efficiency of the spin polarized current injected from the ferromagnetic contact has been determined by measuring the electroluminescence polarization of the light emitted from/GA(1-x)AL(x)As light-emitting diodes as a function of applied magnetic field and temperature. Interfacial reactions during MBE growth and post-growth anneal, as well as the semiconductor device band structure, were found to have a dramatic influence on the measured spin injection, including sign reversal. Lateral spin-transport devices with epitaxial ferromagnetic metal source and drain tunnel barrier contacts have been fabricated with the demonstration of electrical detection and the bias dependence of spin-polarized electron injection and accumulation at the contacts. This talk emphasizes the progress and achievements in the epitaxial growth of a number of ferromagnetic compounds/III-V semiconductor heterostructures and the progress towards spintronic devices.

Mechanical loading regulates human MSC differentiation in a multi-layer hydrogel for osteochondral tissue engineering.

PubMed

Steinmetz, Neven J; Aisenbrey, Elizabeth A; Westbrook, Kristofer K; Qi, H Jerry; Bryant, Stephanie J

2015-07-01

A bioinspired multi-layer hydrogel was developed for the encapsulation of human mesenchymal stem cells (hMSCs) as a platform for osteochondral tissue engineering. The spatial presentation of biochemical cues, via incorporation of extracellular matrix analogs, and mechanical cues, via both hydrogel crosslink density and externally applied mechanical loads, were characterized in each layer. A simple sequential photopolymerization method was employed to form stable poly(ethylene glycol)-based hydrogels with a soft cartilage-like layer of chondroitin sulfate and low RGD concentrations, a stiff bone-like layer with high RGD concentrations, and an intermediate interfacial layer. Under a compressive load, the variation in hydrogel stiffness within each layer produced high strains in the soft cartilage-like layer, low strains in the stiff bone-like layer, and moderate strains in the interfacial layer. When hMSC-laden hydrogels were cultured statically in osteochondral differentiation media, the local biochemical and matrix stiffness cues were not sufficient to spatially guide hMSC differentiation after 21 days. However dynamic mechanical stimulation led to differentially high expression of collagens with collagen II in the cartilage-like layer, collagen X in the interfacial layer and collagen I in the bone-like layer and mineral deposits localized to the bone layer. Overall, these findings point to external mechanical stimulation as a potent regulator of hMSC differentiation toward osteochondral cellular phenotypes. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Evaluating the Role of the Air-Solution Interface on the Mechanism of Subvisible Particle Formation Caused by Mechanical Agitation for an IgG1 mAb.

PubMed

Ghazvini, Saba; Kalonia, Cavan; Volkin, David B; Dhar, Prajnaparamita

2016-05-01

Mechanical agitation of monoclonal antibody (mAb) solutions often leads to protein particle formation. In this study, various formulations of an immunoglobulin G (IgG) 1 mAb were subjected to different controlled interfacial stresses using a Langmuir trough, and protein particles formed at the interface and measured in bulk solution were characterized using atomic force microscopy and flow digital imaging. Results were compared to mAb solutions agitated in glass vials and unstressed controls. At lower pH, mAb solutions exhibited larger hysteresis in their surface pressure versus area isotherms and increased number of particles in bulk solution, when subjected to interfacial stresses. mAb samples subjected to 750-1000 interfacial compression-expansion cycles in 6 h contained high particle numbers in bulk solution, and displayed similar particulation trends when agitated in vials. At compression rates of 50 cycles in 6 h, however, particle levels in mAb solutions were comparable to unstressed controls, despite protein aggregates being present at the air-solution interface. These results suggest that while the air-solution interface serves as a nucleation site for initiating protein aggregation, the number of protein particles measured in bulk mAb solutions depends on the total number of compression cycles that proteins at the air-solution interface are subjected to within a fixed time. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Piezotronic effect in 1D van der Waals solid of elemental tellurium nanobelt for smart adaptive electronics

NASA Astrophysics Data System (ADS)

Gao, Shengjie; Wang, Yixiu; Wang, Ruoxing; Wu, Wenzhuo

2017-10-01

Emerging technologies in wearable systems demand that functional devices can adaptively interact with the human body, where mechanical stimuli are ubiquitous and abundant. However, the electrical manipulation of charge carriers underpins the operations of state-of-the-art devices, and the effective control of interfacial energetics for charge carriers by the dynamic mechanical stimuli is still a relatively unexplored degree of freedom for semiconductor nanodevices. Piezotronic effect in nanostructured piezoelectric semiconductors offers exciting opportunities in addressing the above challenges. Here we report the first experimental exploration of piezotronic effect in 1D van der Waals solid of p-type tellurium nanobelt and systematically investigate the strain-gated charge carriers transport properties. The strain-induced polarization charges at the [10\\bar{1}0] surfaces of Te nanobelt can modulate the electronic transport through the interfacial effect on the Schottky contacts and the volumetric effect on the conducting channel. The competing phenomenon between interfacial and volumetric effects has been studied for the first time in piezotronics. Our research allows the access to a broad range of characterization and application of Te nanomaterials for piezotronics and could guide the future study of piezotronic effect in other materials. This progress in piezotronics, together with emerging methods for deterministic production and assembly of nanomaterials, leads to compelling opportunities for research from basic studies of piezoelectricity and semiconductor properties in functional nanomaterials to the development of ‘smarter’ electronics and optoelectronics.

Wetting of TiC by Al-Cu alloys and interfacial characterization.

PubMed

Contreras, A

2007-07-01

The wetting behavior and the interfacial reactions that occurred between molten Al-Cu alloys (1, 4, 8, 20, 33, and 100 wt% Cu) and solid TiC substrates were studied by the sessile drop technique in the temperature range of 800-1130 degrees C. The effect of wetting behavior on the interfacial reaction layer was studied. All the Al-Cu alloys react with TiC at the interface forming an extensive reaction layer. The interface thickness varied with the samples, and depends on the temperature, chemical composition of the alloy and the time of the test. Wetting increases with increasing concentration of copper in the Al-Cu alloy at 800 and 900 degrees C. In contrast, at higher temperature such as 1000 degrees C wetting decreases with increasing copper content. The spreading kinetics and the work of adhesion were evaluated. The high values of activation energies indicated that spreading is not a simple viscosity controlled phenomenon but is a chemical reaction process. The spreading of the aluminum drop is observed to occur according to the formation of Al4C3, CuAl2O4, CuAl2, TiCux mainly, leading to a decreases in the contact angle. As the contact angle decreases the work of adhesion increases with increasing temperature. Al-Cu/TiC assemblies showed cohesive fracture corresponding to a strong interface. However, using pure Cu the adhesion work is poor, and the percentage of cohesion work is also too low (27-34%).

Dry-Surface Simulation Method for the Determination of the Work of Adhesion of Solid-Liquid Interfaces.

PubMed

Leroy, Frédéric; Müller-Plathe, Florian

2015-08-04

We introduce a methodology, referred to as the dry-surface method, to calculate the work of adhesion of heterogeneous solid-liquid interfaces by molecular simulation. This method employs a straightforward thermodynamic integration approach to calculate the work of adhesion as the reversible work to turn off the attractive part of the actual solid-liquid interaction potential. It is formulated in such a way that it may be used either to evaluate the ability of force fields to reproduce reference values of the work of adhesion or to optimize force-field parameters with reference values of the work of adhesion as target quantities. The methodology is tested in the case of water on a generic model of nonpolar substrates with the structure of gold. It is validated through a quantitative comparison to phantom-wall calculations and against a previous characterization of the thermodynamics of the gold-water interface. It is found that the work of adhesion of water on nonpolar substrates is a nonlinear function of the microscopic solid-liquid interaction energy parameter. We also comment on the ability of mean-field approaches to predict the work of adhesion of water on nonpolar substrates. In addition, we discuss in detail the information on the solid-liquid interfacial thermodynamics delivered by the phantom-wall approach. We show that phantom-wall calculations yield the solid-liquid interfacial tension relative to the solid surface tension rather than the absolute solid-liquid interfacial tension as previously believed.

Characterization and source identification of organic matter in view of land uses and heavy rainfall in the Lake Shihwa, Korea.

PubMed

Lee, Yeonjung; Hur, Jin; Shin, Kyung-Hoon

2014-07-15

The characteristics and sources of organic matter in water of the Lake Shihwa, which receives inputs from rural, urban, and industrial areas, were evaluated by examining the biodegradable organic carbon concentration, fluorescence spectra, and carbon and nitrogen isotope ratios, especially during rainy season and dry season. The organic matter transported from rural areas was of refractory nature, while that of industrial origin decomposed rapidly. As compared to the dry season, the organic matter in the rainy season was characterized by a reduced labile fraction. During the dry season, the autochthonous organic matter dominated in the lake, however, the contributions of allochthonous organic sources by industrial and rural areas significantly increased at rainy season. This investigation revealed that the transport of organic matter of anthropogenic origin to the Lake Shihwa was mainly influenced by heavy rainfall. Moreover, each anthropogenic source could differently influence the occurrence of organic matter in water of the Lake Shihwa. Copyright © 2014 Elsevier Ltd. All rights reserved.

Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys.

PubMed

Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

2018-04-20

Al₃TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al₃Zr and Al₃Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al₃TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al₃Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al₃(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al₃(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al₃Zr-core or Al₃Zr(Sc1-1)-core encircled with an Sc-rich shell forms.

Spectroscopic and electrochemical characterization of interfacial biomimetic assemblies on electrochemically generated gold oxide surfaces.

PubMed

Krysiński, Paweł; Blanchard, G J

2005-04-01

We report on the formation of a gold oxide layer and the reaction of this oxide with an acid chloride to form a stable, relatively complete monolayer bound through an ester-like bond to the gold oxide surface. We have used cyclic voltammetry, FTIR and optical ellipsometry to characterize this novel monolayer structure. The exposed functional groups of this monolayer can participate in subsequent surface reactions, opening the door to the use of oxide-based surface attachment chemistry on metallic substrates. This chemistry will allow for the formation of films tailored to contain both hydrophobic and hydrophilic regions, stacked at predetermined distances from the substrate that may serve as biomembrane mimetic assemblies.

CHEMICAL CHARACTERIZATION OF AMBIENT PARTICULATE MATTER NEAR THE WORLD TRADE CENTER: ELEMENTAL CARBON, ORGANIC CARBON, AND MASS RECONSTRUCTION

EPA Science Inventory

Concentrations of elemental carbon (EC), organic carbon matter (OM), particulate matter less than 2.5 um (PM2.5), and reconstructed soil, trace element oxides, and sulfate are reported from four locations near the World Trade Center (WTC) complex for airborne particulate matter (...

Contributions and mechanisms of action of graphite nanomaterials in ultra high performance concrete

NASA Astrophysics Data System (ADS)

Sbia, Libya Ahmed

Ultra-high performance concrete (UHPC) reaches high strength and impermeability levels by using a relatively large volume fraction of a dense binder with fine microstructure in combination with high-quality aggregates of relatively small particle size, and reinforcing fibers. The dense microstructure of the cementitions binder is achieved by raising the packing density of the particulate matter, which covers sizes ranging from few hundred nanometers to few millimeters. The fine microstructure of binder in UHPC is realized by effective use of pozzolans to largely eliminate the coarse crystalline particles which exist among cement hydrates. UHPC incorporates (steel) fibers to overcome the brittleness of its dense, finely structured cementitious binder. The main thrust of this research is to evaluate the benefits of nanmaterials in UHPC. The dense, finely structure cementitious binder as well as the large volume fraction of the binder in UHPC benefit the dispersion of nanomaterials, and their interfacial interactions. The relatively close spacing of nanomaterials within the cementitious binder of UHPC enables them to render local reinforcement effects in critically stressed regions such as those in the vicinity of steel reinforcement and prestressing strands as well as fibers. Nanomaterials can also raise the density of the binder in UHPC by extending the particle size distribution down to the few nanometers range. Comprehensive experimental studies supported by theoretical investigations were undertake in order to optimize the use of nanomaterials in UHPC, identity the UHPC (mechanical) properties which benefit from the introduction of nanomaterials, and define the mechanisms of action of nanomaterials in UHPC. Carbon nanofiber was the primary nanomaterial used in this investigation. Some work was also conducted with graphite nanoplates. The key hypotheses of the project were as follows: (i) nanomaterials can make important contributions to the packing density of the particulate matter in UHPC by extending the particle size distribution down to the few nanometers range; (ii) there are synergistic reinforcing actions of steel fibers and graphite nanomaterials in UHPC, which can be explained by their complementary spacing and also the benefit of nanomaterials to the interfacial bonding and pullout behavior of steel fibers; and (iii) nanomaterials make important contributions to the bonding and pullout behavior of prestressing strands and deformed bars in concrete, which can be attributed to the close spacing of nanomaterials within the highly stressed interfacial regions occurring in the vicinity of strands and reinforcing bars; steel fibers are loss effective in this regard due to the disturbance of their distribution and orientation in the vicinity of strands and bars. These hypotheses were successfully verified through the experimental and theoretical investigations conducted in this research.

Development of One-Group and Two-Group Interfacial Area Transport Equation

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

Ishii, M.; Kim, S.

A dynamic approach employing the interfacial area transport equation is presented to replace the static flow regime dependent correlations for the interfacial area concentration. The current study derives the transport equations for the bubble number, volume, and interfacial area concentration. Accounting for the substantial differences in the transport phenomena of various sizes of bubbles, both one-group and two-group interfacial area transport equations are developed along with the necessary constitutive relations. The framework for the complicated source and sink terms in the two-group transport equation is also presented by identifying the major intragroup and intergroup bubble interaction mechanisms. In view ofmore » evaluating the theoretical model, the one-group interfacial area transport equation is benchmarked based on the available data obtained in a wide range of air-water bubbly flow in round tubes of various diameters. In general, the results show good agreement within the measurement error of {+-}10%.« less

Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

DOE PAGES

Juan, Pierre -Alexandre; Dingreville, Remi

2016-10-31

Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive “interferences” aremore » directly affected by the interface structure and its elastic response. Furthermore, this general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.« less

Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

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

Juan, Pierre -Alexandre; Dingreville, Remi

Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive “interferences” aremore » directly affected by the interface structure and its elastic response. Furthermore, this general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.« less

Search for the ANSER (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum

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

Wasielewski, Michael R.; ANSER Staff

2011-05-01

'Search for the ANSER' was submitted by the Argonne-Northwestern Solar Energy Research Center (ANSER) to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. ANSER, an EFRC directed by Michael Wasielewski at Argonne National Laboratory is a partnership of scientists from five institutions: Argonne National Laboratory, Northwestern University, University of Chicago, University of Illinois at Urbana-Champaign, and Yale. The Office of Basic Energy Sciences in the U.S. Department of Energy'smore » Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. At ANSER, the mission is 'to revolutionize our understanding of molecules, materials and methods necessary to create dramatically more efficient technologies for solar fuels and electricity production.' Research topics are: catalysis (water), electrocatalysis, photocatalysis, photoelectrocatalysis, solar photovoltaic, solar fuels, solar electrodes, photosynthesis, transportation fuels, bio-inspired, spin dynamics, hydrogen (fuel), ultrafast physics, interfacial characterization, matter by design, novel materials synthesis, charge transport, and self-assembly.« less

Autonomic Materials for Smarter, Safer, Longer-Lasting Batteries (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum)

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

Thackeray, Michael M.

"Autonomic Materials for Smarter, Safer, Longer-Lasting Batteries" was submitted by the Center for Electrochemical Energy Science (CEES) to the "Life at the Frontiers of Energy Research" video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. CEES, an EFRC directed by Michael Thackery at Argonne National Laboratory is a partnership of scientists from four institutions: ANL (lead), Northwestern University, Purdue University, and the University of Illinois at Urbana-Champaign. The Office of Basic Energy Sciences in the U.S. Department ofmore » Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of the Center for Electrochemical Energy Science (CEES) is "to create a robust fundamental understanding of the phenomena that control the reactivity of electrified oxide interfaces, films and materials relevant to lithium-ion battery chemistries". Research topics are: electrical energy storage, batteries, battery electrodes, electrolytes, adaptive materials, interfacial characterization, matter by design; novel materials synthesis, charge transport, and defect tolerant materials.« less

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

Chen, Gang

"Battle against Phonons" was submitted by the Solid State Solar Thermal Energy Conversion (S3TEC) EFRC to the "Life at the Frontiers of Energy Research" video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. This video was selected as one of five winners by a distinguished panel of judges for the special award, "Best with Popcorn". S3TEC, an EFRC directed by Gang Chen at the Massachusetts Institute of Technology is a partnership of scientists from four research institutions: MITmore » (lead), Oak Ridge National Laboratory, Boston College, and Rensselaer Polytechnic Institute. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of the Solid-State Solar Thermal Energy Conversion Center is 'to create novel, solid-state materials for the conversion of sunlight into electricity using thermal and photovoltaic processes.' Research topics are: solar photovoltaic, photonic, metamaterial, optics, solar thermal, thermoelectric, phonons, thermal conductivity, defects, ultrafast physics, interfacial characterization, matter by design, novel materials synthesis, charge transport, defect tolerant materials, and scalable processing.« less

Integrating seawater desalination and wastewater reclamation forward osmosis process using thin-film composite mixed matrix membrane with functionalized carbon nanotube blended polyethersulfone support layer.

PubMed

Choi, Hyeon-Gyu; Son, Moon; Choi, Heechul

2017-10-01

Thin-film composite mixed matrix membrane (TFC MMM) with functionalized carbon nanotube (fCNT) blended in polyethersulfone (PES) support layer was synthesized via interfacial polymerization and phase inversion. This membrane was firstly tested in lab-scale integrating seawater desalination and wastewater reclamation forward osmosis (FO) process. Water flux of TFC MMM was increased by 72% compared to that of TFC membrane due to enhanced hydrophilicity. Although TFC MMM showed lower water flux than TFC commercial membrane, enhanced reverse salt flux selectivity (RSFS) of TFC MMM was observed compared to TFC membrane (15% higher) and TFC commercial membrane (4% higher), representing membrane permselectivity. Under effluent organic matter (EfOM) fouling test, 16% less normalized flux decline of TFC MMM was observed compared to TFC membrane. There was 8% less decline of TFC MMM compared to TFC commercial membrane due to fCNT effect on repulsive foulant-membrane interaction enhancement, caused by negatively charged membrane surface. After 10 min physical cleaning, TFC MMM displayed higher recovered normalized flux than TFC membrane (6%) and TFC commercial membrane (4%); this was also supported by visualized characterization of fouling layer. This study presents application of TFC MMM to integrated seawater desalination and wastewater reclamation FO process for the first time. It can be concluded that EfOM fouling of TFC MMM was suppressed due to repulsive foulant-membrane interaction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Search for the ANSER (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum

ScienceCinema

Wasielewski, Michael R. (Director, Argonne-Northwestern Solar Energy Research Center); ANSER Staff

2017-12-09

'Search for the ANSER' was submitted by the Argonne-Northwestern Solar Energy Research Center (ANSER) to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. ANSER, an EFRC directed by Michael Wasielewski at Argonne National Laboratory is a partnership of scientists from five institutions: Argonne National Laboratory, Northwestern University, University of Chicago, University of Illinois at Urbana-Champaign, and Yale. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. At ANSER, the mission is 'to revolutionize our understanding of molecules, materials and methods necessary to create dramatically more efficient technologies for solar fuels and electricity production.' Research topics are: catalysis (water), electrocatalysis, photocatalysis, photoelectrocatalysis, solar photovoltaic, solar fuels, solar electrodes, photosynthesis, transportation fuels, bio-inspired, spin dynamics, hydrogen (fuel), ultrafast physics, interfacial characterization, matter by design, novel materials synthesis, charge transport, and self-assembly.

Advanced solid-state NMR spectroscopy of natural organic matter.

PubMed

Mao, Jingdong; Cao, Xiaoyan; Olk, Dan C; Chu, Wenying; Schmidt-Rohr, Klaus

2017-05-01

Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially a systematic approach to NOM characterization, and their applications to the study of NOM. We discuss some basics of how to acquire high-quality and quantitative solid-state 13 C NMR spectra, and address some common technical mistakes that lead to unreliable spectra of NOM. The identification of specific functional groups in NOM, primarily based on 13 C spectral-editing techniques, is described and the theoretical background of some recently-developed spectral-editing techniques is provided. Applications of solid-state NMR to investigating nitrogen (N) in NOM are described, focusing on limitations of the widely used 15 N CP/MAS experiment and the potential of improved advanced NMR techniques for characterizing N forms in NOM. Then techniques used for identifying proximities, heterogeneities and domains are reviewed, and some examples provided. In addition, NMR techniques for studying segmental dynamics in NOM are reviewed. We also briefly discuss applications of solid-state NMR to NOM from various sources, including soil organic matter, aquatic organic matter, organic matter in atmospheric particulate matter, carbonaceous meteoritic organic matter, and fossil fuels. Finally, examples of NMR-based structural models and an outlook are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

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

PubMed

Ghadar, Yasaman; Clark, Aurora E

2014-06-28

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

Exchange field and Hc dependence on the ferromagnetic material in exchange couples with CoO (abstract)

NASA Astrophysics Data System (ADS)

Takano, Kentaro; Berkowitz, A. E.

1997-04-01

As recording density increases, magnetoresistive (MR) sensors are becoming increasingly important in read heads. NixCo(1-x)O is receiving technological attention for biasing magnetoresistive sensors as a robust alternative to FeMn. The interfacial exchange coupling between a ferromagnetic (FM) layer and an antiferromagnetic (AFM) is observed as an exchange field and an enhanced coercive field of the FM layer. The AFM/FM coupling is sensitive to the interfacial structure and the AFM and FM magnetic parameters. In this work, we deposited various FM layers on similar 300 Å CoO base layers to study the dependence of the FM exchange integral parameter J on the exchange HE and coercive HC fields. CoO was selected as the AFM material because (i) its simple spin and crystal structures facilitate the structural characterization and modeling of its magnetic properties, and (ii) it's modest Néel temperature of 300 K facilitates the use of a superconducting quantum interference device for the magnetic measurements at temperatures ranging from 5 to 400 K. The 300 Å CoO films were reactively sputtered on silicon substrates and capped with various 300 Å FM films, Ni, Co, Fe, and permalloy (Ni81Fe19). The 300 Å CoO base layer films were polycrystalline with columnar grains. The CoO deposition conditions were reproduced to ensure similar structural and magnetic interfacial AF environments. The observed HE temperature dependence cannot be explained by current theoretical models. The temperature dependence of the exchange fields have the common features (i) a blocking temperature Tb=300 K, which corresponds to the bulk Néel temperature of CoO, (ii) a rise in the exchange field with decreasing temperature, (iii) an intermediate temperature region of constant HE (plateau value), and (iv) a second region of linearly increasing HE with decreasing temperatures down to 0 K. The plateau value of the HE decreased inversely with increasing FM magnetization as predicted by theory. The low-temperature increase of HE is more significant in the FM with higher exchange integral J values. The crossover temperature from the plateau to the low-temperature rise in HE appears to be dependent on FM's J value. The increase in the interfacial coupling strength could suggest the magnetic ordering of a secondary phase localized at the interfacial atoms. The temperature dependence of HC enhancement does not share the nonlinear temperature behavior of HE. For T<300 K, HC increases linearly with decreasing temperatures down to 10 K. Although the HC enhancement may have magnetoelastic contributions, the disappearance of the linear enhancement at 300 K, the Néel temperature of CoO, indicates that the dominant mechanism is the interfacial magnetic coupling.

Roles of interfacial reaction on mechanical properties of solder interfaces

NASA Astrophysics Data System (ADS)

Liu, Pilin

This study investigated roles of interfacial reaction in fracture and fatigue of solder interconnects. The interfacial reaction phases in the as-reflowed and after aging were examined by cross-sectional transmission electron microscopy (TEM) while interfacial mechanical properties were determined from a flexural peel fracture mechanics technique. Because of their widespread uses in microelectronic packaging, SnPb solder interfaces, and Bi-containing Pb-free solder interfaces were chosen as the subjects of this study. In the interfacial reaction study, we observed a complicated micro structural evolution during solid-state aging of electroless-Ni(P)/SnPb solder interconnects. In as-reflowed condition, the interfacial reaction produced Ni3Sn 4 and P-rich layers. Following overaging, the interfacial microstructure degenerated into a complex multilayer structure consisting of multiple layers of Ni-Sn compounds and transformed Ni-P phases. In SnPb solder interfacial system, fatigue study showed that the overaging of the high P electroless Ni-P/SnPb interconnects resulted in a sharp reduction in the fatigue resistance of the interface in the high crack growth rate regime. Fracture mechanism analysis indicated that the sharp drop in fatigue resistance was triggered by the brittle fracture of the Ni3Sn2 intermetallic phase developed at the overaged interface. The fatigue behavior was strongly dependent on P concentration in electroless Ni. Kirkendall voids were found in the interfacial region after aging, but they did not cause premature fracture of the solder interfaces. In Bi-containing solder interfacial system, we found that Bi segregated to the Cu-intermetallic interface during aging in SnBi/Cu interconnect. This caused serious embrittlement of Sn-Bi/Cu interface. Further aging induced numerous voids along the Cu3Sn/Cu interface. These interfacial voids were different from Kirkendall voids. Their formation was explained on basis of vacancy condensation at the interface as the Bi segregants reduced the number of effective Cu vacancy sink sites and enhanced void nucleation at the interface. The Bi segregation was avoided by replacing the Cu metallization with Ni. It was found that Bi developed a concentration gradient in the Ni 3Sn4 during interfacial reaction, with the Bi concentration falling off to zero as the Ni/IMC interface was approached. Therefore, the inhibition of Bi segregation by Ni was due to the inability of Bi to reach Ni/IMC interface.

Nanoscale interfacial defect shedding in a growing nematic droplet.

PubMed

Gurevich, Sebastian; Provatas, Nikolas; Rey, Alejandro

2017-08-01

Interfacial defect shedding is the most recent known mechanism for defect formation in a thermally driven isotropic-to-nematic phase transition. It manifests in nematic-isotropic interfaces going through an anchoring switch. Numerical computations in planar geometry established that a growing nematic droplet can undergo interfacial defect shedding, nucleating interfacial defect structures that shed into the bulk as +1/2 point defects. By extending the study of interfacial defect shedding in a growing nematic droplet to larger length and time scales, and to three dimensions, we unveil an oscillatory growth mode involving shape and anchoring transitions that results in a controllable regular distributions of point defects in planar geometry, and complex structures of disclination lines in three dimensions.

Long life hydrocarbon conversion catalyst and method of making

DOEpatents

Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Gao, Yufei [Kennewick, WA

2002-11-12

The present invention includes a catalyst that has at least four layers, (1) porous support, (2) buffer layer, (3) interfacial layer, and optionally (4) catalyst layer. The buffer layer provides a transition of thermal expansion coefficient from the porous support to the interfacial layer thereby reducing thermal expansion stress as the catalyst is heated to high operating temperatures. The method of the present invention for making the at least three layer catalyst has the steps of (1) selecting a porous support, (2) solution depositing an interfacial layer thereon, and optionally (3) depositing a catalyst material onto the interfacial layer; wherein the improvement comprises (4) depositing a buffer layer between the porous support and the interfacial layer.

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

PubMed

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

2017-02-21

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

Catalyst Architecture for Stable Single Atom Dispersion Enables Site-Specific Spectroscopic and Reactivity Measurements of CO Adsorbed to Pt Atoms, Oxidized Pt Clusters, and Metallic Pt Clusters on TiO2.

PubMed

DeRita, Leo; Dai, Sheng; Lopez-Zepeda, Kimberly; Pham, Nicholas; Graham, George W; Pan, Xiaoqing; Christopher, Phillip

2017-10-11

Oxide-supported precious metal nanoparticles are widely used industrial catalysts. Due to expense and rarity, developing synthetic protocols that reduce precious metal nanoparticle size and stabilize dispersed species is essential. Supported atomically dispersed, single precious metal atoms represent the most efficient metal utilization geometry, although debate regarding the catalytic activity of supported single precious atom species has arisen from difficulty in synthesizing homogeneous and stable single atom dispersions, and a lack of site-specific characterization approaches. We propose a catalyst architecture and characterization approach to overcome these limitations, by depositing ∼1 precious metal atom per support particle and characterizing structures by correlating scanning transmission electron microscopy imaging and CO probe molecule infrared spectroscopy. This is demonstrated for Pt supported on anatase TiO 2 . In these structures, isolated Pt atoms, Pt iso , remain stable through various conditions, and spectroscopic evidence suggests Pt iso species exist in homogeneous local environments. Comparing Pt iso to ∼1 nm preoxidized (Pt ox ) and prereduced (Pt metal ) Pt clusters on TiO 2 , we identify unique spectroscopic signatures of CO bound to each site and find CO adsorption energy is ordered: Pt iso ≪ Pt metal < Pt ox . Pt iso species exhibited a 2-fold greater turnover frequency for CO oxidation than 1 nm Pt metal clusters but share an identical reaction mechanism. We propose the active catalytic sites are cationic interfacial Pt atoms bonded to TiO 2 and that Pt iso exhibits optimal reactivity because every atom is exposed for catalysis and forms an interfacial site with TiO 2 . This approach should be generally useful for studying the behavior of supported precious metal atoms.

Dynamic delamination of patterned thin films

NASA Astrophysics Data System (ADS)

Kandula, Soma S. V.; Tran, Phuong; Geubelle, Philippe H.; Sottos, Nancy R.

2008-12-01

We investigate laser-induced dynamic delamination of a patterned thin film on a substrate. Controlled delamination results from our insertion of a weak adhesion region beneath the film. The inertial forces acting on the weakly bonded portion of the film lead to stable propagation of a crack along the film/substrate interface. Through a simple energy balance, we extract the critical energy for interfacial failure, a quantity that is difficult and sometimes impossible to characterize by more conventional methods for many thin film/substrate combinations.

High-discharge-rate lithium ion battery

DOEpatents

Liu, Gao; Battaglia, Vincent S; Zheng, Honghe

2014-04-22

The present invention provides for a lithium ion battery and process for creating such, comprising higher binder to carbon conductor ratios than presently used in the industry. The battery is characterized by much lower interfacial resistances at the anode and cathode as a result of initially mixing a carbon conductor with a binder, then with the active material. Further improvements in cycleability can also be realized by first mixing the carbon conductor with the active material first and then adding the binder.

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

PubMed Central

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

2017-01-01

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

Numerical study on the mechanism of active interfacial debonding detection for rectangular CFSTs based on wavelet packet analysis with piezoceramics

NASA Astrophysics Data System (ADS)

Xu, Bin; Chen, Hongbing; Xia, Song

2017-03-01

In recent years, Piezoelectric Lead Zirconate Titanate (PZT) based active interfacial debonding defect detection approach for concrete-filled steel tubular (CFST) columns has been proposed and validated experimentally. In order to investigate the mechanism of the PZT based interfacial debonding detection approach, a multi-physics coupling finite element model (FEM) composed of surface-mounted PZT actuator, embedded PZT sensor and a rectangular CFST column is constructed to numerically simulate the stress wave propagation induced by the surface-mounted PZT actuator under different excitation signals with different frequency and amplitude. The measurements of the embedded PZT sensor in concrete core of the CFST columns with different interfacial debonding defect lengths and depths are determined numerically with transient dynamic analysis. The linearity between the PZT response and the input amplitude, the effect of different frequency and measurement distance are discussed and the stress wave fields of CFST members without and with interface debonding defects are compared. Then, the response of the embedded PZT in concrete core is analyzed with wavelet packet analysis. The root mean square deviation (RMSD) of wavelet packet energy spectrum of the PZT measurement is employed as an evaluation index for the interfacial debonding detection. The results showed that the defined index under continuous sinusoidal and sweep frequency signals changes with the interfacial defects length and depth and is capable of effectively identifying the interfacial debonding defect between the concrete core and the steel tubular. Moreover, the index under sweep frequency signal is more sensitive to the interfacial debonding. The simulation results indicate that the interfacial debonding defect leads to the changes in the propagation path, travel time and the magnitude of stress waves. The simulation results meet the findings from the previous experimental study by the authors and help understand the mechanism of interfacial debonding defect detection for CFSTs using PZT technology.

Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams.

PubMed

Coutinho, E; Jarmar, T; Svahn, F; Neves, A A; Verlinden, B; Van Meerbeek, B; Engqvist, H

2009-11-01

Current available techniques for transmission electron microscopy (TEM) of tooth-biomaterial interfaces are mostly ineffective for brittle phases and impair integrated chemical and morphological characterization. The aims of this study were (1) to determine the applicability of new focused ion beam (FIB) and broad ion beam (BIB) techniques for TEM preparation of tooth-biomaterial interfaces; (2) to characterize the interfacial interaction with enamel and dentin of a conventional glass-ionomer (Chemfil Superior, DeTrey Dentsply, Germany), a 2-step self-etch (Clearfil SE, Kuraray, Japan) and a 3-step etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to characterize clinically relevant interfaces obtained from actual Class-I cavities. After bonding to freshly extracted human third molars, non-demineralized and non-stained sections were obtained using the FIB/BIB techniques and examined under TEM. The main structures generally disclosed in conventional ultramicrotomy samples were recognized in FIB/BIB-based ones. There were not any major differences between FIB and BIB concerning the resulting ultrastructural morphology. FIB/BIB-sections enabled to clearly resolve sub-micron hydroxyapatite crystals on top of hard tissues and the interface between matrix and filler in all materials, even at nano-scale. Some investigated interfaces disclosed areas with a distinct "fog" or "melted look", which is probably an artifact due to surface damage caused by the high-energy beam. Interfaces with enamel clearly disclosed the distinct "keyhole" shape of enamel rods sectioned at 90 degrees , delimited by a thin electron-lucent layer of inter-rod enamel. At regions where enamel crystals ran parallel with the interface, we observed a lack of interaction and some de-bonding along with interfacial void formation. The FIB/BIB methods are viable and reliable alternatives to conventional ultramicrotomy for preparation of thin sections of brittle and thus difficult to cut biomaterial-hard tissue interfaces. They disclose additional ultrastructural information about both substrates and are more suitable for advanced analytic procedures.

Interfacial Water-Transport Effects in Proton-Exchange Membranes

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

Kienitz, Brian; Yamada, Haruhiko; Nonoyama, Nobuaki

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.more » 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.« less

Controlling Interfacial Separation in Porous Structures by Void Patterning

NASA Astrophysics Data System (ADS)

Ghareeb, Ahmed; Elbanna, Ahmed

Manipulating interfacial response for enhanced adhesion or fracture resistance is a problem of great interest to scientists and engineers. In many natural materials and engineering applications, an interface exists between a porous structure and a substrate. A question that arises is how the void distribution in the bulk may affect the interfacial response and whether it is possible to alter the interfacial toughness without changing the surface physical chemistry. In this paper, we address this question by studying the effect of patterning voids on the interfacial-to-the overall response of an elastic plate glued to a rigid substrate by bilinear cohesive material. Different patterning categories are investigated; uniform, graded, and binary voids. Each case is subjected to upward displacement at the upper edge of the plate. We show that the peak force and maximum elongation at failure depend on the voids design and by changing the void size, alignment or gradation we may control these performance measures. We relate these changes in the measured force displacement response to energy release rate as a measure of interfacial toughness. We discuss the implications of our results on design of bulk heterogeneities for enhanced interfacial behavior.

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

PubMed

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

2013-09-21

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

Interfacial Bonding Energy on the Interface between ZChSnSb/Sn Alloy Layer and Steel Body at Microscale.

PubMed

Wang, Jianmei; Xia, Quanzhi; Ma, Yang; Meng, Fanning; Liang, Yinan; Li, Zhixiong

2017-09-25

To investigate the performance of bonding on the interface between ZChSnSb/Sn and steel body, the interfacial bonding energy on the interface of a ZChSnSb/Sn alloy layer and the steel body with or without Sn as an intermediate layer was calculated under the same loadcase using the molecular dynamics simulation software Materials Studio by ACCELRYS, and the interfacial bonding energy under different Babbitt thicknesses was compared. The results show that the bonding energy of the interface with Sn as an intermediate layer is 10% larger than that of the interface without a Sn layer. The interfacial bonding performances of Babbitt and the steel body with Sn as an intermediate layer are better than those of an interface without a Sn layer. When the thickness of the Babbitt layer of bushing is 17.143 Å, the interfacial bonding energy reaches the maximum, and the interfacial bonding performance is optimum. These findings illustrate the bonding mechanism of the interfacial structure from the molecular level so as to ensure the good bonding properties of the interface, which provides a reference for the improvement of the bush manufacturing process from the microscopic point of view.

Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys

PubMed Central

Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

2018-01-01

Al3TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al3Zr and Al3Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al3TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al3Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al3(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al3(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al3Zr-core or Al3Zr(Sc1-1)-core encircled with an Sc-rich shell forms. PMID:29677155

Interfacial energetics of two-dimensional colloidal clusters generated with a tunable anharmonic interaction potential

NASA Astrophysics Data System (ADS)

Hilou, Elaa; Du, Di; Kuei, Steve; Biswal, Sibani Lisa

2018-02-01

Interfacial characteristics are critical to various properties of two-dimensional (2D) materials such as band alignment at a heterojunction and nucleation kinetics in a 2D crystal. Despite the desire to harness these enhanced interfacial properties for engineering new materials, unexpected phase transitions and defects, unique to the 2D morphology, have left a number of open questions. In particular, the effects of configurational anisotropy, which are difficult to isolate experimentally, and their influence on interfacial properties are not well understood. In this work, we begin to probe this structure-thermodynamic relationship, using a rotating magnetic field to generate an anharmonic interaction potential in a 2D system of paramagnetic particles. At low magnetic field strengths, weakly interacting colloidal particles form non-close-packed, fluidlike droplets, whereas, at higher field strengths, crystallites with hexagonal ordering are observed. We examine spatial and interfacial properties of these 2D colloidal clusters by measuring the local bond orientation order parameter and interfacial stiffness as a function of the interaction strength. To our knowledge, this is the first study to measure the tunable interfacial stiffness of a 2D colloidal cluster by controlling particle interactions using external fields.

Giant interfacial perpendicular magnetic anisotropy in Fe/CuIn 1 -xGaxSe2 beyond Fe/MgO

NASA Astrophysics Data System (ADS)

Masuda, Keisuke; Kasai, Shinya; Miura, Yoshio; Hono, Kazuhiro

2017-11-01

We study interfacial magnetocrystalline anisotropies in various Fe/semiconductor heterostructures by means of first-principles calculations. We find that many of those systems show perpendicular magnetic anisotropy (PMA) with a positive value of the interfacial anisotropy constant Ki. In particular, the Fe/CuInSe 2 interface has a large Ki of ˜2.3 mJ /m2 , which is about 1.6 times larger than that of Fe/MgO known as a typical system with relatively large PMA. We also find that the values of Ki in almost all the systems studied in this work follow the well-known Bruno's relation, which indicates that minority-spin states around the Fermi level provide dominant contributions to the interfacial magnetocrystalline anisotropies. Detailed analyses of the local density of states and wave-vector-resolved anisotropy energy clarify that the large Ki in Fe/CuInSe 2 is attributed to the preferable 3 d -orbital configurations around the Fermi level in the minority-spin states of the interfacial Fe atoms. Moreover, we have shown that the locations of interfacial Se atoms are the key for such orbital configurations of the interfacial Fe atoms.

CHARACTERIZATION OF PARTICULATE MATTER FROM PHOENIX, ARIZONA, USING RAY FLUORESCENCE AND COMPUTER-CONTROLLED SCANNING ELECTRON MICROSCOPY

EPA Science Inventory

Numerous epidemiological studies have found associations between airborne particulate matter measured at community monitors and increased mortality and morbidity. Chemical and physical characteristics of particulate matter (e.g., elemental composition, size) and source identifi...

USING MOLECULAR PROBES TO STUDY INTERFACIAL REDOX REACTION AT FE-BEARING SMECTITES

EPA Science Inventory

The interfacial electron transfer of clay-water systems has a wide range of significance in geochemical and biogeochernical environments. However the mechanism of interfacial electron transport is poorly understood. The electron transfer mechanism at the solid-water interfaces of...

An Effective Reservoir Parameter for Seismic Characterization of Organic Shale Reservoir

NASA Astrophysics Data System (ADS)

Zhao, Luanxiao; Qin, Xuan; Zhang, Jinqiang; Liu, Xiwu; Han, De-hua; Geng, Jianhua; Xiong, Yineng

2017-12-01

Sweet spots identification for unconventional shale reservoirs involves detection of organic-rich zones with abundant porosity. However, commonly used elastic attributes, such as P- and S-impedances, often show poor correlations with porosity and organic matter content separately and thus make the seismic characterization of sweet spots challenging. Based on an extensive analysis of worldwide laboratory database of core measurements, we find that P- and S-impedances exhibit much improved linear correlations with the sum of volume fraction of organic matter and porosity than the single parameter of organic matter volume fraction or porosity. Importantly, from the geological perspective, porosity in conjunction with organic matter content is also directly indicative of the total hydrocarbon content of shale resources plays. Consequently, we propose an effective reservoir parameter (ERP), the sum of volume fraction of organic matter and porosity, to bridge the gap between hydrocarbon accumulation and seismic measurements in organic shale reservoirs. ERP acts as the first-order factor in controlling the elastic properties as well as characterizing the hydrocarbon storage capacity of organic shale reservoirs. We also use rock physics modeling to demonstrate why there exists an improved linear correlation between elastic impedances and ERP. A case study in a shale gas reservoir illustrates that seismic-derived ERP can be effectively used to characterize the total gas content in place, which is also confirmed by the production well.

The Gas-Absorption/Chemical-Reaction Method for Measuring Air-Water Interfacial Area in Natural Porous Media

NASA Astrophysics Data System (ADS)

Lyu, Ying; Brusseau, Mark L.; El Ouni, Asma; Araujo, Juliana B.; Su, Xiaosi

2017-11-01

The gas-absorption/chemical-reaction (GACR) method used in chemical engineering to quantify gas-liquid interfacial area in reactor systems is adapted for the first time to measure the effective air-water interfacial area of natural porous media. Experiments were conducted with the GACR method, and two standard methods (X-ray microtomographic imaging and interfacial partitioning tracer tests) for comparison, using model glass beads and a natural sand. The results of a series of experiments conducted under identical conditions demonstrated that the GACR method exhibited excellent repeatability for measurement of interfacial area (Aia). Coefficients of variation for Aia were 3.5% for the glass beads and 11% for the sand. Extrapolated maximum interfacial areas (Am) obtained with the GACR method were statistically identical to independent measures of the specific solid surface areas of the media. For example, the Am for the glass beads is 29 (±1) cm-1, compared to 32 (±3), 30 (±2), and 31 (±2) cm-1 determined from geometric calculation, N2/BET measurement, and microtomographic measurement, respectively. This indicates that the method produced accurate measures of interfacial area. Interfacial areas determined with the GACR method were similar to those obtained with the standard methods. For example, Aias of 47 and 44 cm-1 were measured with the GACR and XMT methods, respectively, for the sand at a water saturation of 0.57. The results of the study indicate that the GACR method is a viable alternative for measuring air-water interfacial areas. The method is relatively quick, inexpensive, and requires no specialized instrumentation compared to the standard methods.

Mechanistic study of the rubber-brass adhesion interphase

NASA Astrophysics Data System (ADS)

Ashirgade, Akshay

Brass-plated steel tire cords form an essential strengthening component of a radial automobile tire. Adhesion between rubber compound and brass-plated steel tire cord is crucial in governing the overall performance of tires. The rubber-brass interfacial adhesion is influenced by the chemical composition and thickness of the interfacial layer. It has been shown that the interfacial layer consists mainly of sulfides and oxides of copper and zinc. This thesis discusses the effect of changes in the chemical composition and the structure of the interfacial layers due to addition of adhesion promoter resins. Grazing incidence X-Ray Diffraction (GIXRD) experiments were run on sulfidized polished brass coupons previously bonded to six experimental rubber compounds. It was confirmed that heat and humidity conditions lead to physical and chemical changes of the rubber-steel tire cord interfacial layer, closely related to the degree of rubber-brass adhesion. Morphological transformation of the interfacial layer led to loss of adhesion after aging. The adhesion promoter resins inhibit unfavorable morphological changes in the interfacial layer thus stabilizing it during aging and prolonging failure. Tire cord adhesion tests illustrated that the one-component resins improved adhesion after aging using a rubber compound with lower cobalt loading. Based on the acquired diffraction profiles, these resins were also found to impede crystallization of the sulfide layer after aging leading to improved adhesion. Secondary Ion Mass Spectrometry (SIMS) depth profiles, SEM micrographs and AFM images strongly corroborated the findings from GIXRD. FTIR was utilized in a novel way to understand the degradation mechanism due to aging. A model for rubber and interfacial layer degradation is proposed to illustrate the effect of aging and the one-component resins. This interfacial analysis adds valuable new information to our understanding of the complex nature of the rubber-brass bonding mechanism.

Atomic Force Microscopy Nanomechanical Mapping Visualizes Interfacial Broadening between Networks Due to Chemical Exchange Reactions.

PubMed

He, Changfei; Shi, Shaowei; Wu, Xuefei; Russell, Thomas P; Wang, Dong

2018-06-06

The interfacial broadening between two different epoxy networks having different moduli was nanomechanically mapped. The interfacial broadening of the two networks produced an interfacial zone having a gradient in the concentration and, hence, properties of the original two networks. This interfacial broadening of the networks leads to the generation of a new network with a segmental composition corresponding to a mixture of the original two network segments. The intermixing of the two, by nature of the exchange reactions, was on the segmental level. By mapping the time dependence of the variation in the modulus at different temperatures, the kinetics of the exchange reaction was measured and, by varying the temperature, the activation energy of the exchange reaction was determined.

A biomimetic approach to enhancing interfacial interactions: polydopamine-coated clay as reinforcement for epoxy resin.

PubMed

Yang, Liping; Phua, Si Lei; Teo, Jun Kai Herman; Toh, Cher Ling; Lau, Soo Khim; Ma, Jan; Lu, Xuehong

2011-08-01

A facile biomimetic method was developed to enhance the interfacial interaction in polymer-layered silicate nanocomposites. By mimicking mussel adhesive proteins, a monolayer of polydopamine was constructed on clay surface by a controllable coating method. The modified clay (D-clay) was incorporated into an epoxy resin, it is found that the strong interfacial interactions brought by the polydopamine benefits not only the dispersion of the D-clay in the epoxy but also the effective interfacial stress transfer, leading to greatly improved thermomechanical properties at very low inorganic loadings. Rheological and infrared spectroscopic studies show that the interfacial interactions between the D-clay and epoxy are dominated by the hydrogen bonds between the catechol-enriched polydopamine and the epoxy.

Direct observation of interfacial Au atoms on TiO₂ in three dimensions.

PubMed

Gao, Wenpei; Sivaramakrishnan, Shankar; Wen, Jianguo; Zuo, Jian-Min

2015-04-08

Interfacial atoms, which result from interactions between the metal nanoparticles and support, have a large impact on the physical and chemical properties of nanoparticles. However, they are difficult to observe; the lack of knowledge has been a major obstacle toward unraveling their role in chemical transformations. Here we report conclusive evidence of interfacial Au atoms formed on the rutile (TiO2) (110) surfaces by activation using high-temperature (∼500 °C) annealing in air. Three-dimensional imaging was performed using depth-sectioning enabled by aberration-corrected scanning transmission electron microscopy. Results show that the interface between Au nanocrystals and TiO2 (110) surfaces consists of a single atomic layer with Au atoms embedded inside Ti-O. The number of interfacial Au atoms is estimated from ∼1-8 in an interfacial atomic column. Direct impact of interfacial Au atoms is observed on an enhanced Au-TiO2 interaction and the reduction of surface TiO2; both are critical to Au catalysis.

Research on the interfacial behaviors of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Wang, Qiming; Yan, Xiaoqing; Ding, Shurong; Huo, Yongzhong

2010-04-01

The three-dimensional constitutive relations are constructed, respectively, for the fuel particles, the metal matrix and the cladding of dispersion nuclear fuel elements, allowing for the effects of large deformation and thermal-elastoplasticity. According to the constitutive relations, the method of modeling their irradiation behaviors in ABAQUS is developed and validated. Numerical simulations of the interfacial performances between the fuel meat and the cladding are implemented with the developed finite element models for different micro-structures of the fuel meat. The research results indicate that: (1) the interfacial tensile stresses and shear stresses for some cases will increase with burnup, but the relative stresses will decrease with burnup for some micro-structures; (2) at the lower burnups, the interfacial stresses increase with the particle sizes and the particle volume fractions; however, it is not the case at the higher burnups; (3) the particle distribution characteristics distinctly affect the interfacial stresses, and the face-centered cubic case has the best interfacial performance of the three considered cases.

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

PubMed

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

2011-06-01

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

Two-Fluid Models and Interfacial Area Transport in Microgravity Condition

NASA Technical Reports Server (NTRS)

Ishii, Mamoru; Sun, Xiao-Dong; Vasavada, Shilp

2004-01-01

The objective of the present study is to develop a two-fluid model formulation with interfacial area transport equation applicable for microgravity conditions. The new model is expected to make a leapfrog improvement by furnishing the constitutive relations for the interfacial interaction terms with the interfacial area transport equation, which can dynamically model the changes of the interfacial structures. In the first year of this three-year project supported by the U.S. NASA, Office of Biological and Physics Research, the primary focus is to design and construct a ground-based, microgravity two-phase flow simulation facility, in which two immiscible fluids with close density will be used. In predicting the two-phase flow behaviors in any two-phase flow system, the interfacial transfer terms are among the most essential factors in the modeling. These interfacial transfer terms in a two-fluid model specify the rate of phase change, momentum exchange, and energy transfer at the interface between the two phases. For the two-phase flow under the microgravity condition, the stability of the fluid particle interface and the interfacial structures are quite different from those under normal gravity condition. The flow structure may not reach an equilibrium condition and the two fluids may be loosely coupled such that the inertia terms of each fluid should be considered separately by use of the two-fluid model. Previous studies indicated that, unless phase-interaction terms are accurately modeled in the two-fluid model, the complex modeling does not necessarily warrant an accurate solution.

Deposition and characterization of silicon thin-films by aluminum-induced crystallization

NASA Astrophysics Data System (ADS)

Ebil, Ozgenc

Polycrystalline silicon (poly-Si) as a thin-film solar cell material could have major advantages compared to non-silicon thin-film technologies. In theory, thin-film poly-Si may retain the performance and stability of c-Si while taking advantage of established manufacturing techniques. However, poly-Si films deposited onto foreign substrates at low temperatures typically have an average grain size of 10--50 nm. Such a grain structure presents a potential problem for device performance since it introduces an excessive number of grain boundaries which, if left unpassivated, lead to poor solar cell properties. Therefore, for optimum device performance, the grain size of the poly-Si film should be at least comparable to the thickness of the films. For this project, the objectives were the deposition of poly-Si thin-films with 2--5 mum grain size on glass substrates using in-situ and conventional aluminum-induced crystallization (AIC) and the development of a model for AIC process. In-situ AIC experiments were performed using Hot-Wire Chemical Vapor Deposition (HWCVD) both above and below the eutectic temperature (577°C) of Si-Al binary system. Conventional AIC experiments were performed using a-Si layers deposited on aluminum coated glass substrates by Electron-beam deposition, Plasma Enhanced Chemical Vapor Deposition (PECVD) and HWCVD. Continuous poly-Si films with an average grain size of 10 mum on glass substrates were achieved by both in-situ and conventional aluminum-induced crystallization of Si below eutectic temperature. The grain size was determined by three factors; the grain structure of Al layer, the nature of the interfacial oxide, and crystallization temperature. The interface oxide was found to be crucial for AIC process but not necessary for crystallization itself. The characterization of interfacial oxide layer formed on Al films revealed a bilayer structure containing Al2O3 and Al(OH)3 . The effective activation energy for AIC process was determined to be 0.9 eV and depended on the nature of the interfacial oxide layer. Poly-Si layers prepared by AIC technique can be used as seed layers for epitaxial growth of bulk Si layer or as back contacts in c-Si based solar cells.

Microsample Characterization of Coatings for GRCop-84 for High Temperature High Heat Flux Application

NASA Technical Reports Server (NTRS)

Jain, Piyush; Hemker, Kevin J.; Raj, Sai V.

2004-01-01

NASA's Glenn Research Center has developed GRCop-84 (Cu-8at.%Cr-4% Nb), a high conductivity, high strength copper alloy for use as liners in rocket engine combustion chambers, nozzle ramps and other actively-cooled components subject to high heat fluxes. Two metallic coatings, NiCrAlY and Cu-26%Cr, are being considered for preventing blanching, reducing 'dog- house' failures and providing better environmental resistance to the GRCop-84 liners. This presentation will outline a study of coating-substrate interactions that occur as a result of thermal cycling and coating specific properties at different temperatures. A furnace has been built to thermally cycle the samples under argon. The microsample testing approach is being used to measure the coating-substrate interfacial strength. Cu-26Cr/GRCop-84 samples did not show any obvious interdiffusion after 300 thermal cycles. Interfacial strength tests of these samples were affected by porosity present in the samples. A complete set of observations and results for Cu-26Cr and NiCrAlY coatings will be presented.

Structural and elemental characterization of high efficiency Cu2ZnSnS4 solar cells

NASA Astrophysics Data System (ADS)

Wang, Kejia; Shin, Byungha; Reuter, Kathleen B.; Todorov, Teodor; Mitzi, David B.; Guha, Supratik

2011-01-01

We have carried out detailed microstructural studies of phase separation and grain boundary composition in Cu2ZnSnS4 based solar cells. The absorber layer was fabricated by thermal evaporation followed by post high temperature annealing on hot plate. We show that inter-reactions between the bottom molybdenum and the Cu2ZnSnS4, besides triggering the formation of interfacial MoSx, results in the out-diffusion of Cu from the Cu2ZnSnS4 layer. Phase separation of Cu2ZnSnS4 into ZnS and a Cu-Sn-S compound is observed at the molybdenum-Cu2ZnSnS4 interface, perhaps as a result of the compositional out-diffusion. Additionally, grain boundaries within the thermally evaporated absorber layer are found to be either Cu-rich or at the expected bulk composition. Such interfacial compound formation and grain boundary chemistry likely contributes to the lower than expected open circuit voltages observed for the Cu2ZnSnS4 devices.

Interfacial Microstructure and Mechanical Properties of Friction Stir Welded Joints of Commercially Pure Aluminum and 304 Stainless Steel

NASA Astrophysics Data System (ADS)

Murugan, Balamagendiravarman; Thirunavukarasu, Gopinath; Kundu, Sukumar; Kailas, Satish V.; Chatterjee, Subrata

2018-05-01

In the present investigation, friction stir welding of commercially pure aluminum and 304 stainless steel was carried out at varying tool rotational speeds from 200 to 1000 rpm in steps of 200 rpm using 60 mm/min traverse speed at 2 (degree) tool tilt angle. Microstructural characterization of the interfacial zone was carried out using optical microscope and scanning electron microscope. Energy-dispersive spectroscopy indicated the presence of FeAl3 intermetallic phase. Thickness of the intermetallic layer increased with the increase in tool rotational speed. X-ray diffraction studies indicated the formation of intermetallic phases like FeAl2, Fe4Al13, Fe2Al5, and FeAl3. A maximum tensile strength of 90% that of aluminum along with 4.5% elongation was achieved with the welded sample at tool rotational speed of 400 rpm. The stir zone showed higher hardness as compared to base metals, heat affected zone, and thermo-mechanically affected zone due to the presence of intermetallics. The maximum hardness value at the stir zone was achieved at 1000 rpm tool rotational speed.

Highly Efficient Flexible Quantum Dot Solar Cells with Improved Electron Extraction Using MgZnO Nanocrystals.

PubMed

Zhang, Xiaoliang; Santra, Pralay Kanti; Tian, Lei; Johansson, Malin B; Rensmo, Håkan; Johansson, Erik M J

2017-08-22

Colloidal quantum dot (CQD) solar cells have high potential for realizing an efficient and lightweight energy supply for flexible or wearable electronic devices. To achieve highly efficient and flexible CQD solar cells, the electron transport layer (ETL), extracting electrons from the CQD solid layer, needs to be processed at a low-temperature and should also suppress interfacial recombination. Herein, a highly stable MgZnO nanocrystal (MZO-NC) layer is reported for efficient flexible PbS CQD solar cells. Solar cells fabricated with MZO-NC ETL give a high power conversion efficiency (PCE) of 10.4% and 9.4%, on glass and flexible plastic substrates, respectively. The reported flexible CQD solar cell has the record efficiency to date of flexible CQD solar cells. Detailed theoretical simulations and extensive characterizations reveal that the MZO-NCs significantly enhance charge extraction from CQD solids and diminish the charge accumulation at the ETL/CQD interface, suppressing charge interfacial recombination. These important results suggest that the low-temperature processed MZO-NCs are very promising for use in efficient flexible solar cells or other flexible optoelectronic devices.

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

NASA Astrophysics Data System (ADS)

Calvimontes, Alfredo

2018-05-01

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

Atomic layer deposition of ZrO2 on W for metal-insulator-metal capacitor application

NASA Astrophysics Data System (ADS)

Lee, Sang-Yun; Kim, Hyoungsub; McIntyre, Paul C.; Saraswat, Krishna C.; Byun, Jeong-Soo

2003-04-01

A metal-insulator-metal (MIM) capacitor using ZrO2 on tungsten (W) metal bottom electrode was demonstrated and characterized in this letter. Both ZrO2 and W metal were synthesized by an atomic layer deposition (ALD) method. High-quality 110˜115 Å ZrO2 films were grown uniformly on ALD W using ZrCl4 and H2O precursors at 300 °C, and polycrystalline ZrO2 in the ALD regime could be obtained. A 13˜14-Å-thick interfacial layer between ZrO2 and W was observed after fabrication, and it was identified as WOx through angle-resolved x-ray photoelectron spectroscopy analysis with wet chemical etching. The apparent equivalent oxide thickness was 20˜21 Å. An effective dielectric constant of 22˜25 including an interfacial WOx layer was obtained by measuring capacitance and thickness of MIM capacitors with Pt top electrodes. High capacitance per area (16˜17 fF/μm2) and low leakage current (10-7 A/cm2 at ±1 V) were achieved.

Chemistry of MOS-LSI radiation hardening

NASA Technical Reports Server (NTRS)

Grunthaner, P.

1985-01-01

The objective of this task was to obtain chemical information on MOS test samples. Toward this end, high resolution X-ray photoemission spectroscopy (XPS) has been the primary techniques used to characterize the chemistry and structure of the SiO2/Si interface for a variety of MOS structures with differing degrees of susceptibility to damage by ionizing radiation. The major accomplishments of this program are: (1) the identification of a structurally distinct region of SiO2 in the near-interfacial region of thermal SiO2 on Si; (2) the identification in the near-interfacial region of SiO2 structural differences between radiation hard and soft gate oxides; (3) the direct observation of radiation-induced damage sites in thermal SiO2 with XPS using in situ electron stress; (4) the correlation of suboxide state distributions at the SiO2/Si interface with processing parameters and radiation susceptibility; (5) the development of a chemical mechanism for radiation-induced interface state generation in SiO2/Si structures; and (6) the development benign chemical profiling techniques which permit the investigation of oxide/semiconductor structures using surface sensitive electron spectroscopic techniques.

Structural and magnetic characterization of Mn/NiFe bilayers with ion-beam-assisted deposition

NASA Astrophysics Data System (ADS)

Wu, Chun-Hsien; Zheng, Chao; Chiu, Chun-Cheng; Manna, Palash Kumar; van Lierop, Johan; Lin, Ko-Wei; Pong, Philip W. T.

2018-01-01

The exchange bias effect in ferromagnetic (FM)/antiferromagnetic (AF) bilayer structures has been widely investigated because its underlying principle is critical for spintronic applications. In this work, the effect of Ar+ beam bombardment on the microstructural and magnetic properties of the Mn/NiFe thin films was investigated. The in-situ Ar+ bombardment nontrivially promoted the Mn/NiFe intermixing and facilitated the formation of the FeMn phase, accompanied by a remarkable reduction of Mn and NiFe layer thickness. The enhanced Mn/NiFe intermixing greatly disordered the interfacial spins, inhibiting the interfacial exchange coupling and giving rise to a significant decrease of the exchange bias field (H ex). The facilitated Mn/NiFe intermixing effect also dramatically degraded the magnetocrystalline anisotropy of the NiFe crystallites, leading to a notable suppression of the coercivity (H c). These results indicate that both the exchange bias and coercivity of the Mn/NiFe bilayers can be directly affected by the in-situ Ar+ bombardment, offering an effective way to modify the magnetism of the exchange-bias systems.

Redox processes at a nanostructured interface under strong electric fields.

PubMed

Steurer, Wolfram; Surnev, Svetlozar; Netzer, Falko P; Sementa, Luca; Negreiros, Fabio R; Barcaro, Giovanni; Durante, Nicola; Fortunelli, Alessandro

2014-09-21

Manipulation of chemistry and film growth via external electric fields is a longstanding goal in surface science. Numerous systems have been predicted to show such effects but experimental evidence is sparse. Here we demonstrate in a custom-designed UHV apparatus that the application of spatially extended, homogeneous, very high (>1 V nm(-1)) DC-fields not only changes the system energetics but triggers dynamic processes which become important much before static contributions appreciably modify the potential energy landscape. We take a well characterized ultrathin NiO film on a Ag(100) support as a proof-of-principle test case, and show how it gets reduced to supported Ni clusters under fields exceeding the threshold of +0.9 V nm(-1). Using an effective model, we trace the observed interfacial redox process down to a dissociative electron attachment resonant mechanism. The proposed approach can be easily implemented and generally applied to a wide range of interfacial systems, thus opening new opportunities for the manipulation of film growth and reaction processes at solid surfaces under strong external fields.

Ostwald ripening of faceted Si particles in an Al-Si-Cu melt

DOE PAGES

Shahani, A. J.; Xiao, X.; Skinner, K.; ...

2016-07-04

The microstructural evolution of an Al-Si-Cu alloy during Ostwald ripening is imaged via synchrotron-based, four-dimensional (i.e., space and time resolved) X-ray tomography. Samples of composition Al-32 wt%Si-15 wt%Cu were annealed isothermally at 650 °C, in the two-phase solid-liquid regime, while tomographic projections were collected in situ over the course of five hours. Advances in experimental methods and computational approaches enable us to characterize the local interfacial curvatures and velocities during ripening. The sequence of three-dimensional reconstructions and interfacial shape distributions shows highly faceted Si particles in a copper-enriched liquid, that become increasingly isotropic or rounded over time. In addition, wemore » find that the coarsening rate constant is approximately the same in the binary and ternary systems. By coupling these experimental measurements with CALPHAD modeling and ab initio molecular dynamics simulation, we assess the influence of Cu on the coarsening process. Lastly, we find the unusual “pinning” of microstructure at the junction between rough and smooth interfaces and suggest a mechanism for this behavior.« less

Study of Synthesis Polyethylene glycol oleate Sulfonated as an Anionic Surfactant for Enhanced Oil Recovery (EOR)

NASA Astrophysics Data System (ADS)

Sampora, Yulianti; Juwono, Ariadne L.; Haryono, Agus; Irawan, Yan

2017-11-01

Mechanical Enhanced Oil Recovery (EOR) through chemical injection is using an anionic surfactant to improve the recovery of oil residues, particularly in a reservoir area that has certain characteristics. This case led the authors to conduct research on the synthesis of an anionic surfactant based on oleic acid and polyethylene glycol 400 that could be applied as a chemical injection. In this work, we investigate the sulfonation of Polyethylene glycol oleate (PDO) in a sulfuric acid agent. PDO in this experiment was derived from Indonesian palm oil. Variation of mole reactant and reaction time have been studied. The surfactant has been characterized by measuring the interfacial tension, acid value, ester value, saponification value, iodine value, Fourier Transform Infrared (FTIR), and particle size analyzer. There is a new peak at 1170-1178 cm-1 indicating that S=O bond has formed. PDO sulfonate exhibits good surface activity due to interfacial tension of 0,003 mN/m. Thus, polyethylene glycol oleate sulfonate was successfully synthesized and it could be useful as a novel an anionic surfactant.

XPS and SIMS study of the surface and interface of aged C + implanted uranium

DOE PAGES

Donald, Scott B.; Siekhaus, Wigbert J.; Nelson, Art J.

2016-09-08

X-ray photoelectron spectroscopy in combination with secondary ion mass spectrometry depth profiling were used to investigate the surface and interfacial chemistry of C + ion implanted polycrystalline uranium subsequently oxidized in air for over 10 years at ambient temperature. The original implantation of 33 keV C + ions into U 238 with a dose of 4.3 × 10 17 cm –3 produced a physically and chemically modified surface layer that was characterized and shown to initially prevent air oxidation and corrosion of the uranium after 1 year in air at ambient temperature. The aging of the surface and interfacial layersmore » were examined by using the chemical shift of the U 4f, C 1s, and O 1s photoelectron lines. In addition, valence band spectra were used to explore the electronic structure of the aged carbide surface and interface layer. Moreover, the time-of-flight secondary ion mass spectrometry depth profiling results for the aged sample confirmed an oxidized uranium carbide layer over the carbide layer/U metal interface.« less