Graphene-enhanced intermolecular interaction at interface between copper- and cobalt-phthalocyanines

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

Dou, Wei-Dong; Center of Super-Diamond and Advanced Films; Huang, Shu-Ping

2015-10-07

Interfacial electronic structures of copper-phthalocyanine (CuPc), cobalt-phthalocyanine (CoPc), and graphene were investigated experimentally by using photoelectron spectroscopy. While the CuPc/graphene interface shows flat band structure and negligible interfacial dipole indicating quite weak molecule-substrate interaction, the CuPc/CoPc/graphene interface shows a large interfacial dipole and obvious energy level bending. Controlled experiments ruled out possible influences from the change in film structure of CuPc and pure π–π interaction between CoPc and CuPc. Analysis based on X-ray photoelectron spectroscopy and density functional theory reveals that the decrease in the work function for the CuPc/CoPc/graphene system is induced by the intermolecular interaction between CuPc andmore » CoPc which is enhanced owning to the peculiar electronic properties at the CoPc-graphene interface.« less

Insights into the structural effects of layered cathode materials for high voltage sodium-ion batteries

DOE PAGES

Xu, Gui -Liang; Amine, Rachid; Xu, Yue -Feng; ...

2017-06-08

Cathode materials are critical to the energy density, power density and safety of sodium-ion batteries (SIBs). Herein, we performed a comprehensive study to elucidate and exemplify the interplay mechanism between phase structures, interfacial microstrain and electrochemical properties of layered-structured Na xNi 1/3Co 1/3Mn 1/3O 2 cathode materials for high voltage SIBs. The electrochemical test results showed that Na xNi 1/3Co 1/3Mn 1/3O 2 with an intergrowth P2/O3/O1 structure demonstrates better electrochemical performance and better thermal stability than Na xNi 1/3Co 1/3Mn 1/3O 2 with P2/O3 binary-phase integration and Na xNi 1/3Co 1/3Mn 1/3O 2 where only the P phase ismore » dominant. This result is caused by the distinct interfacial microstrain development during the synthesis and cycling of the P2/O3/O1 phase. In operando high energy X-ray diffraction further revealed that the intergrowth P2/O1/O3 cathode can inhibit the irreversible P2–O2 phase transformation and simultaneously improve the structure stability of the O3 and O1 phases during cycling. Here, we believe that interfacial microstrain can serve as an indispensable bridge to guide future design and synthesis of high performance SIB cathode materials and other high energy battery materials.« less

Controllable positive exchange bias via redox-driven oxygen migration

DOE PAGES

Gilbert, Dustin A.; Olamit, Justin; Dumas, Randy K.; ...

2016-03-21

We report that ionic transport in metal/oxide heterostructures offers a highly effective means to tailor material properties via modification of the interfacial characteristics. However, direct observation of ionic motion under buried interfaces and demonstration of its correlation with physical properties has been challenging. Using the strong oxygen affinity of gadolinium, we design a model system of Gd xFe 1-x/NiCoO bilayer films, where the oxygen migration is observed and manifested in a controlled positive exchange bias over a relatively small cooling field range. The exchange bias characteristics are shown to be the result of an interfacial layer of elemental nickel andmore » cobalt, a few nanometres in thickness, whose moments are larger than expected from uncompensated NiCoO moments. This interface layer is attributed to a redox-driven oxygen migration from NiCoO to the gadolinium, during growth or soon after. Ultimately, these results demonstrate an effective path to tailoring the interfacial characteristics and interlayer exchange coupling in metal/oxide heterostructures.« less

Controllable Interfacial Coupling Effects on the Magnetic Dynamic Properties of Perpendicular [Co/Ni]5/Cu/TbCo Composite Thin Films.

PubMed

Tang, Minghong; Zhao, Bingcheng; Zhu, Weihua; Zhu, Zhendong; Jin, Q Y; Zhang, Zongzhi

2018-02-07

Dynamic magnetic properties in perpendicularly exchange-coupled [Co/Ni] 5 /Cu (t Cu = 0-2 nm)/TbCo structures show strong dependences on the interfacial antiferromagnetic strength J ex , which is controlled by the Cu interlayer thickness. The precession frequency f and effective damping constant α eff of a [Co/Ni] 5 multilayer differ distinctly for parallel (P) and antiparallel (AP) magnetization orientation states. For samples with a thin t Cu , f of the AP state is apparently higher, whereas α eff is lower than that in the P state, owing to the unidirectional exchange bias effect (H EB ) from the TbCo layer. The differences in f and α eff between the two states gradually decrease with increasing t Cu . By using a uniform precession model including an additional H EB term, the field-dependent frequency curves can be well-fitted, and the fitted H EB value is in good agreement with the experimental data. Moreover, the saturation damping constant α 0 displays a nearly linear correlation with J ex . It decreases significantly with J ex and eventually approaches a constant value of 0.027 at t Cu = 2 nm where J ex vanishes. These results provide a better understanding and effective control of magnetization dynamics in exchange-coupled composite structures for spintronic applications.

Metal-Organic Framework-Stabilized CO2/Water Interfacial Route for Photocatalytic CO2 Conversion.

PubMed

Luo, Tian; Zhang, Jianling; Li, Wei; He, Zhenhong; Sun, Xiaofu; Shi, Jinbiao; Shao, Dan; Zhang, Bingxing; Tan, Xiuniang; Han, Buxing

2017-11-29

Here, we propose a CO 2 /water interfacial route for photocatalytic CO 2 conversion by utilizing a metal-organic framework (MOF) as both an emulsifier and a catalyst. The CO 2 reduction occurring at the CO 2 /water interface produces formate with remarkably enhanced efficiency as compared with that in conventional solvent. The route is efficient, facile, adjustable, and environmentally benign, which is applicable for the CO 2 transformation photocatalyzed by different kinds of MOFs.

Pore-scale modeling of wettability effects on CO2-brine displacement during geological storage

NASA Astrophysics Data System (ADS)

Basirat, Farzad; Yang, Zhibing; Niemi, Auli

2017-11-01

Wetting properties of reservoir rocks and caprocks can vary significantly, and they strongly influence geological storage of carbon dioxide in deep saline aquifers, during which CO2 is supposed to displace the resident brine and to become permanently trapped. Fundamental understanding of the effect of wettability on CO2-brine displacement is thus important for improving storage efficiency and security. In this study, we investigate the influence of wetting properties on two-phase flow of CO2 and brine at the pore scale. A numerical model based on the phase field method is implemented to simulate the two-phase flow of CO2-brine in a realistic pore geometry. Our focus is to study the pore-scale fluid-fluid displacement mechanisms under different wetting conditions and to quantify the effect of wettability on macroscopic parameters such as residual brine saturation, capillary pressure, relative permeability, and specific interfacial area. Our simulation results confirm that both the trapped wetting phase saturation and the normalized interfacial area increase with decreasing contact angle. However, the wetting condition does not appear to influence the CO2 breakthrough time and saturation. We also show that the macroscopic capillary pressures based on the pressure difference between inlet and outlet can differ significantly from the phase averaging capillary pressures for all contact angles when the capillary number is high (log Ca > -5). This indicates that the inlet-outlet pressure difference may not be a good measure of the continuum-scale capillary pressure. In addition, the results show that the relative permeability of CO2 can be significantly lower in strongly water-wet conditions than in the intermediate-wet conditions.

Early stages of epitaxial CoSi 2 formation on Si(111) surface as investigated by ARUPS, XPS, LEED and work function variation

NASA Astrophysics Data System (ADS)

Pirri, C.; Peruchetti, J. C.; Gewinner, G.; Derrien, J.

1985-04-01

We performed the CoSi 2 formation on a clean (7 × 7) Si(111) surface under UHV conditions. The used techniques were angle resolved UV photoemission, X-ray photoemission, work function change and low energy electron diffraction in order to study the electronic and structural properties of the interface during its formation. At room temperature, a small amount of Co reacts strongly with Si to form an interfacial and very thin cobalt suicide. The ultraviolet photoelectron spectrum displays already two features corresponding respectively to the Co 3d and Si 3p electron bonding states and the Co 3d non-bonding states. With increasing coverage ( θ ≳ 4 ML) it seems that the interfacial suicide prevents further Co-Si interdiffusion to achieve the suicide reaction and a metal rich film is found. At high temperature (˜ 600°C) and in the first monolayer range, several superstructures are found (√7 × √7, and 2 × 2). They are induced by a Co-Si bidimensional compound where the Co atoms are not yet completely surrounded by Si atoms as in their bulk CoSi 2 structure. With increasing coverage, a CoSi 2-like photoemission spectrum is observed reflecting the formation of the disilicide. The LEED pattern testifies an epitaxial growth displaying a (1 × 1) CoSi 2 diagram. The work function change technique also reflects faithfully this growth.

Enhancing the microwave absorption properties of amorphous CoO nanosheet-coated Co (hexagonal and cubic phases) through interfacial polarizations.

PubMed

Deng, Jiushuai; Li, Shimei; Zhou, Yuanyuan; Liang, Luyang; Zhao, Biao; Zhang, Xi; Zhang, Rui

2018-01-01

Core-shell flower-like composites were successfully prepared by a simple polyol method. These composites were formed by coating dual-phased (face-centered cubic [fcc] and hexagonal close-packed [hcp]) Co with amorphous CoO nanosheets. The microwave absorption properties of the flower-like Co@CoO paraffin composites with various Co@CoO amounts were then investigated. Results showed that the paraffin-based composite containing 70wt% flower-like Co@CoO displayed excellent microwave absorption properties (R E =24.74dB·GHz/mm). The minimum reflection loss of -30.4dB was obtained at 16.1GHz with a small thickness of 1.5mm, and 1.5mm bandwidth reached 4.6GHz (13.4-18GHz) below -10dB (90% microwave absorption). The excellent microwave absorption properties of flower-like Co@CoO are attributed to the synergetic effect between magnetic loss and dielectric loss, and the magnetic loss makes a main contribution to absorption. The core-shell flower-like structures with dual Co phases also contributed to microwave absorption. The amorphous CoO nanosheets were able to generate multiple reflections and exhibit scattering. In addition, the novel absorption mechanism that enhanced interfacial polarization was proposed. This enhancement resulted from the presence of interfaces between the hcp and fcc phases and between the core-shell Co@CoO composites. Copyright © 2017 Elsevier Inc. All rights reserved.

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

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

Thermal and electrochemical properties of PEO-LiTFSI-Pyr14TFSI-based composite cathodes, incorporating 4 V-class cathode active materials

NASA Astrophysics Data System (ADS)

Wetjen, Morten; Kim, Guk-Tae; Joost, Mario; Appetecchi, Giovanni B.; Winter, Martin; Passerini, Stefano

2014-01-01

Poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PEO-LiTFSI-Pyr14TFSI)-based 4 V-class composite cathodes, incorporating either Li(Ni1/3Co1/3Mn1/3)O2 or Li(Ni0.8Co0.15Al0.05)O2 were prepared by a hot-pressing process and successively investigated in terms of their morphological, thermal, and electrochemical properties. Thereby, excellent mechanical and thermal properties could be demonstrated for all composite cathodes. The electrochemical performance of truly dry all-solid-state Li/P(EO)10LiTFSI-(Pyr14TFSI)2/composite cathode batteries at temperatures as low as 40 °C revealed high delivered capacities. However, in comparison with LiFePO4, the 4 V-class composite cathodes also indicated much lower capacity retention. In-depth investigations on the interfacial properties of Li(Ni0.8Co0.15Al0.05)O2 composite cathodes revealed a strong dependence on the anodic cut-off potential and the presence of current flow through the cell, whereby different degradation mechanisms could be characterized upon cycling, according to which the finite growth of a surface films at both electrode/polymer electrolyte interfaces inhibited continuous decomposition of the polymer electrolyte even at potentials as high as 4.3 V. Moreover, the presence of Pyr14TFSI in the 4 V-class composite cathodes sustainably reduced the cathode interfacial resistance and presumably diminished the corrosion of the aluminum current collector.

Effect of Co doping on the structural and dielectric properties of ZnO nanoparticles

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

Ram, Mast, E-mail: Mastram1999@yahoo.com; Bala, Kanchan; Sharma, Hakikat

This paper reports on the synthesis of Co doped Zn{sub 1-x}Co{sub x}O (x= 0.0, 0.01, 0.02, 0.03 and 0.05) nanoparticles by solution combustion method using urea as a fuel. The Structural and dielectric properties of the samples were studied. Crystallite sizes were obtained from X-ray diffraction (XRD) patterns whose values decreased with increase in Co concentration. The XRD study reveals that Co{sup 2+} ions substitute the Zn{sup 2+} ion without changing the wurtzite structure of pristine ZnO up to Co concentrations of 5%. The dielectric constants, dielectric loss (tanδ) and ac conductivity (σ{sub ac}) were studied as the function ofmore » frequency and composition, which have been explained by Maxwell-Wagner type interfacial polarization and discussed Koops phenomenological theory.« less

Spin State Control using Oxide Interfaces in LaCoO3-based Heterostructures

NASA Astrophysics Data System (ADS)

Lee, Sangjae; Disa, Ankit; Walker, Frederick; Ahn, Charles

The flexibility of the spin degree of freedom of the Co 3d orbitals in LaCoO3 suggests that they can be changed through careful design of oxide heterostructures. Interfacial coupling and dimensional confinement can be used to control the magnetic exchange, crystal fields, and Hund's coupling, through orbital and charge reconstructions. These parameters control the balance between multiple spin configurations, thereby modifying the magnetic ordering of LaCoO3. We study (LaCoO3)m /(LaTiO3)2 heterostructures grown by molecular beam epitaxy, which allow interfacial charge transfer from Ti to Co, in addition to structural and dimensional constraints. The electronic polarization at the interface and consequent structural distortions suppress the ferromagnetism in the LaCoO3 layers. This effect extends well beyond the interface, with ferromagnetic order absent up to LaCoO3 layer thickness of m =10. We compare the properties of the LaCoO3/LaTiO3heterostructureswithLaCoO3/SrTiO3, to untangle how charge transfer and structural modifications control the spin and magnetic configuration in cobaltates.

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

Li, Binzhi; Chopdekar, Rajesh V.; N'Diaye, Alpha T.

The impact of interfacial electronic reconstruction on the magnetic characteristics of La0.7Sr0.3CoO3 (LSCO)/La0.7Sr0.3MnO3 (LSMO) superlattices was investigated as a function of layer thickness using a combination of soft x-ray magnetic spectroscopy and bulk magnetometry. We found that the magnetic properties of the LSCO layers are impacted by two competing electronic interactions occurring at the LSCO/substrate and LSMO/LSCO interfaces. For thin LSCO layers (< 5 nm), the heterostructures exist in a highly coupled state where the chemically distinct layers behave as a single magnetic compound with magnetically active Co2+ ions. As the LSCO thickness increases, a high coercivity LSCO layer developsmore » which biases a low coercivity layer, which is composed not only of the LSMO layer, but also an interfacial LSCO layer. These results suggest a new route to tune the magnetic properties of transition metal oxide heterostructures through careful control of the interface structure.« less

The role of interfacial metal silicates on the magnetism in FeCo/SiO 2 and Fe 49% Co 49% V 2% /SiO 2 core/shell nanoparticles

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

Desautels, R. D.; Freeland, J. W.; Rowe, M. P.

2015-05-07

We have investigated the role of spontaneously formed interfacial metal silicates on the magnetism of FeCo/SiO2 and Fe49%Co49%V2%/SiO2 core/shell nanoparticles. Element specific x-ray absorption and photoelectron spectroscopy experiments have identified the characteristic spectral features of metallic iron and cobalt from within the nanoparticle core. In addition, metal silicates of iron, cobalt, and vanadium were found to have formed spontaneously at the interface between the nanoparticle core and silica shell. X-ray magnetic circular dichroism experiments indicated that the elemental magnetism was a result of metallic iron and cobalt with small components from the iron, cobalt, and vanadium silicates. Magnetometry experiments havemore » shown that there was no exchange bias loop shift in the FeCo nanoparticles; however, exchange bias from antiferromagnetic vanadium oxide was measured in the V-doped nanoparticles. These results showed clearly that the interfacial metal silicates played a significant role in the magnetism of these core/shell nanoparticles, and that the vanadium percolated from the FeCo-cores into the SiO2-based interfacial shell.« less

Anomalous Hall effect assisted by interfacial chemical reaction in perpendicular Co/Pt multilayers

NASA Astrophysics Data System (ADS)

Liu, Qian; Jiang, Shaolong; Teng, Jiao

2018-05-01

To uncover the underlying mechanism of Mg effect on the improved anomalous Hall effect (AHE) of perpendicular [Pt/Co]3/Mg/HfO2 multilayers, the X-ray photoelectron spectroscopy analysis has been carried out. It is found that Mg interlayer at the Co/HfO2 interface could prevent the Co oxidation to some extent via interfacial chemical reaction. As a result, A large anomalous Hall resistivity (ρAH) is obtained in perpendicular [Pt/Co]3/Mg/HfO2 multilayers, with a maximum ρAH of 3.02 μΩ cm, which is 59% larger than that in Co/Pt multilayers without Mg insertion. This effective modification of the AHE based on interfacial chemical reaction provides a promising pathway for spintronic applications.

Fabrication of CA/TPU Helical Nanofibers and its Mechanism Analysis

NASA Astrophysics Data System (ADS)

Wu, Huihui; Zhao, Shihang; Han, Lei

2018-04-01

To explore the mechanism of cellulose acetate (CA)/thermoplastic polyurethane (TPU) on the fabrication of helical nanofibers, a series of experiments were conducted to find the optimum spinning conditions. The experimental results show that the CA (14 wt%, DMAc/acetone, 1/2 volume ratio)/TPU2 (18 wt%, DMAc/acetone, 3/1 volume ratio) system can fabricate helical nanofibers effectively via co-electrospinning. We focus on the interfacial interaction between the polymer components induced by the polymer structure and intrinsic properties, including solution properties, hydrogen bonding, and miscibility behavior of the two solutions. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) are employed to investigate the interfacial interaction between the two phases of the polymer system. The analysis results provide the explanation of the experimental results that the CA/TPU system has the potential for producing helical nanofibers effectively. This study based on the interfacial interaction between polymer components provides an insight into the mechanism of CA/TPU helical fiber formation and introduces a richer choice of materials for the application of helical fibers.

Thickness dependencies of structural and magnetic properties of cubic and tetragonal Heusler alloy bilayer films

NASA Astrophysics Data System (ADS)

Ranjbar, R.; Suzuki, K. Z.; Sugihara, A.; Ando, Y.; Miyazaki, T.; Mizukami, S.

2017-07-01

The thickness dependencies of the structural and magnetic properties for bilayers of cubic Co-based Heusler alloys (CCHAs: Co2FeAl (CFA), Co2FeSi (CFS), Co2MnAl (CMA), and Co2MnSi (CMS)) and D022-MnGa were investigated. Epitaxy of the B2 structure of CCHAs on a MnGa film was achieved; the smallest thickness with the B2 structure was found for 3-nm-thick CMS and CFS. The interfacial exchange coupling (Jex) was antiferromagnetic (AFM) for all of the CCHAs/MnGa bilayers except for unannealed CFA/MnGa samples. A critical thickness (tcrit) at which perpendicular magnetization appears of approximately 4-10 nm for the CMA/MnGa and CMS/MnGa bilayers was observed, whereas this thickness was 1-3 nm for the CFA/MnGa and CFS/MnGa films. The critical thickness for different CCHAs materials is discussed in terms of saturation magnetization (Ms) and the Jex .

Interfacial binding of divalent cations to calixarene-based Langmuir monolayers

DOE PAGES

Tulli, Ludovico G.; Wang, Wenjie; Lindemann, William R.; ...

2015-02-20

The interactions of Langmuir monolayers produced through the self-assembly of an amphiphilic p-carboxycalix[4]arene with a series of divalent, fourth-period transition metals, at the air-water interface, were investigated. Changes in the interfacial behavior of 1 in response to the presence of CuCl 2, CoCl 2, MnCl 2, and NiCl 2 were studied by means of Langmuir compression isotherms and Brewster angle microscopy (BAM). The measurements revealed that the self-assembly properties of 1 are significantly affected by Cu 2+ ions. The interactions of 1-based monolayers with Co 2+ and Cu 2+ ions were further investigated by means of synchrotron radiation-based X-ray reflectivitymore » (XRR), X-ray near-total-reflection fluorescence (XNTRF), and grazing incidence X-ray diffraction (GIXD). XNTRF and XRR analyses revealed that the monolayer of 1 binds more strongly to Cu 2+ than Co 2+ ions. In the presence of relatively high concentrations of Cu 2+ ions in the subphase (1.4 × 10 -3 M), XNTRF exhibited anomalous depth profile behavior and GIXD measurements showed considerably strong diffuse scattering. Furthermore, both measurements suggest the formation of Cu 2+ clusters contiguous to the monolayer of 1.« less

Modeling the Effects of Interfacial Characteristics on Gas Permeation Behavior of Nanotube-Mixed Matrix Membranes.

PubMed

Chehrazi, Ehsan; Sharif, Alireza; Omidkhah, Mohammadreza; Karimi, Mohammad

2017-10-25

Theoretical approaches that accurately predict the gas permeation behavior of nanotube-containing mixed matrix membranes (nanotube-MMMs) are scarce. This is mainly due to ignoring the effects of nanotube/matrix interfacial characteristics in the existing theories. In this paper, based on the analogy of thermal conduction in polymer composites containing nanotubes, we develop a model to describe gas permeation through nanotube-MMMs. Two new parameters, "interfacial thickness" (a int ) and "interfacial permeation resistance" (R int ), are introduced to account for the role of nanotube/matrix interfacial interactions in the proposed model. The obtained values of a int , independent of the nature of the permeate gas, increased by increasing both the nanotubes aspect ratio and polymer-nanotube interfacial strength. An excellent correlation between the values of a int and polymer-nanotube interaction parameters, χ, helped to accurately reproduce the existing experimental data from the literature without the need to resort to any adjustable parameter. The data includes 10 sets of CO 2 /CH 4 permeation, 12 sets of CO 2 /N 2 permeation, 3 sets of CO 2 /O 2 permeation, and 2 sets of CO 2 /H 2 permeation through different nanotube-MMMs. Moreover, the average absolute relative errors between the experimental data and the predicted values of the proposed model are very small (less than 5%) in comparison with those of the existing models in the literature. To the best of our knowledge, this is the first study where such a systematic comparison between model predictions and such extensive experimental data is presented. Finally, the new way of assessing gas permeation data presented in the current work would be a simple alternative to complex approaches that are usually utilized to estimate interfacial thickness in polymer composites.

The role of interfacial metal silicates on the magnetism in FeCo/SiO{sub 2} and Fe{sub 49%}Co{sub 49%}V{sub 2%}/SiO{sub 2} core/shell nanoparticles

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

Desautels, R. D., E-mail: rddesautels@physics.umanitoba.ca; Toyota Research Institute of North America, Ann Arbor, Michigan 48169; Freeland, J. W.

2015-05-07

We have investigated the role of spontaneously formed interfacial metal silicates on the magnetism of FeCo/SiO{sub 2} and Fe{sub 49%}Co{sub 49%}V{sub 2%}/SiO{sub 2} core/shell nanoparticles. Element specific x-ray absorption and photoelectron spectroscopy experiments have identified the characteristic spectral features of metallic iron and cobalt from within the nanoparticle core. In addition, metal silicates of iron, cobalt, and vanadium were found to have formed spontaneously at the interface between the nanoparticle core and silica shell. X-ray magnetic circular dichroism experiments indicated that the elemental magnetism was a result of metallic iron and cobalt with small components from the iron, cobalt, andmore » vanadium silicates. Magnetometry experiments have shown that there was no exchange bias loop shift in the FeCo nanoparticles; however, exchange bias from antiferromagnetic vanadium oxide was measured in the V-doped nanoparticles. These results showed clearly that the interfacial metal silicates played a significant role in the magnetism of these core/shell nanoparticles, and that the vanadium percolated from the FeCo-cores into the SiO{sub 2}-based interfacial shell.« less

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.

Directing Reaction Pathways through Controlled Reactant Binding at Pd-TiO2 Interfaces.

PubMed

Zhang, Jing; Wang, Bingwen; Nikolla, Eranda; Medlin, J Will

2017-06-01

Recent efforts to design selective catalysts for multi-step reactions, such as hydrodeoxygenation (HDO), have emphasized the preparation of active sites at the interface between two materials having different properties. However, achieving precise control over interfacial properties, and thus reaction selectivity, has remained a challenge. Here, we encapsulated Pd nanoparticles (NPs) with TiO 2 films of regulated porosity to gain a new level of control over catalyst performance, resulting in essentially 100 % HDO selectivity for two biomass-derived alcohols. This catalyst also showed exceptional reaction specificity in HDO of furfural and m-cresol. In addition to improving HDO activity by maximizing the interfacial contact between the metal and metal oxide sites, encapsulation by the nanoporous oxide film provided a significant selectivity boost by restricting the accessible conformations of aromatics on the surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2-b][1]benzothiophene.

PubMed

Tsutsui, Yusuke; Schweicher, Guillaume; Chattopadhyay, Basab; Sakurai, Tsuneaki; Arlin, Jean-Baptiste; Ruzié, Christian; Aliev, Almaz; Ciesielski, Artur; Colella, Silvia; Kennedy, Alan R; Lemaur, Vincent; Olivier, Yoann; Hadji, Rachid; Sanguinet, Lionel; Castet, Frédéric; Osella, Silvio; Dudenko, Dmytro; Beljonne, David; Cornil, Jérôme; Samorì, Paolo; Seki, Shu; Geerts, Yves H

2016-09-01

The structural and electronic properties of four isomers of didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12-BTBT) have been investigated. Results show the strong impact of the molecular packing on charge carrier transport and electronic polarization properties. Field-induced time-resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm(2) V(-1) s(-1) for the 2,7-isomer, holding great promise for the field of organic electronics. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacial spin-filter assisted spin transfer torque effect in Co/BeO/Co magnetic tunnel junction

NASA Astrophysics Data System (ADS)

Tang, Y.-H.; Chu, F.-C.

2015-03-01

The first-principles calculation is employed to demonstrate the spin-selective transport properties and the non-collinear spin-transfer torque (STT) effect in the newly proposed Co/BeO/Co magnetic tunnel junction. The subtle spin-polarized charge transfer solely at O/Co interface gives rise to the interfacial spin-filter (ISF) effect, which can be simulated within the tight binding model to verify the general expression of STT. This allows us to predict the asymmetric bias behavior of non-collinear STT directly via the interplay between the first-principles calculated spin current densities in collinear magnetic configurations. We believe that the ISF effect, introduced by the combination between wurtzite-BeO barrier and the fcc-Co electrode, may open a new and promising route in semiconductor-based spintronics applications.

Resolving Discrepancies in the Measurements of the Interfacial Tension for the CO2 + H2O Mixture by Computer Simulation.

PubMed

Müller, Erich A; Mejía, Andrés

2014-04-03

Literature values regarding the pressure dependence of the interfacial tension of the system of carbon dioxide (CO2) + water (H2O) show an unexplained divergence and scatter at the transition between low-pressure gas-liquid equilibrium and the high-pressure liquid-liquid equilibrium. We employ the Statistical Associating Fluid Theory (SAFT) and canonical molecular dynamics simulations based on the corresponding coarse grained force field to map out the phase diagram of the mixture and the interfacial tension for this system. We showcase how at ambient temperatures a triple point (gas-liquid-liquid) is expected and detail the implications that the appearance of the third phase has on the interfacial tensions of the system.

Magnetic properties influenced by interfaces in ultrathin Co/Ge(1 0 0) and Co/Ge(1 1 1) films

NASA Astrophysics Data System (ADS)

Tsay, J. S.; Yao, Y. D.; Cheng, W. C.; Tseng, T. K.; Wang, K. C.; Yang, C. S.

2003-10-01

Magnetic properties influenced by interfaces in ultrathin Co/Ge(1 0 0) and Co/Ge(1 1 1) films with thickness below 28 monolayers (ML) have been studied using the surface magneto-optic Kerr effect (SMOKE) technique. In both systems, the nonferromagnetic layer, as an interface between Co and Ge, plays an important role during annealing. In general, ultrathin Co films with fixed total thickness but fabricated at different temperatures on the same substrate, their Kerr hysteresis loops disappear roughly at the same temperature. This suggests that the thickness of the interfacial layer could inversely prevent the diffusion between Co and Ge substrate. From the annealing studies for both systems with total film thickness of 28 monolayers, we have found that Kerr signal disappears at 375 K for Co/Ge(1 1 1) and 425 K for Co/Ge(1 0 0) films. This suggests that Co/Ge(1 1 1) films possess a lower thermal stability than that of the Co/Ge(1 0 0) films. Our experimental data could be explained by different interfacial condition between Ge(1 0 0) and Ge(1 1 1), the different onset of interdiffusion, and the surface structure condition of Ge(1 0 0) and Ge(1 1 1).

Probing and Manipulating the Interfacial Defects of InGaAs Dual-Layer Metal Oxides at the Atomic Scale.

PubMed

Wu, Xing; Luo, Chen; Hao, Peng; Sun, Tao; Wang, Runsheng; Wang, Chaolun; Hu, Zhigao; Li, Yawei; Zhang, Jian; Bersuker, Gennadi; Sun, Litao; Pey, Kinleong

2018-01-01

The interface between III-V and metal-oxide-semiconductor materials plays a central role in the operation of high-speed electronic devices, such as transistors and light-emitting diodes. The high-speed property gives the light-emitting diodes a high response speed and low dark current, and they are widely used in communications, infrared remote sensing, optical detection, and other fields. The rational design of high-performance devices requires a detailed understanding of the electronic structure at this interface; however, this understanding remains a challenge, given the complex nature of surface interactions and the dynamic relationship between the morphology evolution and electronic structures. Herein, in situ transmission electron microscopy is used to probe and manipulate the structural and electrical properties of ZrO 2 films on Al 2 O 3 and InGaAs substrate at the atomic scale. Interfacial defects resulting from the spillover of the oxygen-atom conduction-band wavefunctions are resolved. This study unearths the fundamental defect-driven interfacial electric structure of III-V semiconductor materials and paves the way to future high-speed and high-reliability devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacial exchange coupling and magnetization reversal in perpendicular [Co/Ni]N/TbCo composite structures.

PubMed

Tang, M H; Zhang, Zongzhi; Tian, S Y; Wang, J; Ma, B; Jin, Q Y

2015-06-15

Interfacial exchange coupling and magnetization reversal characteristics in the perpendicular heterostructures consisting of an amorphous ferrimagnetic (FI) TbxCo(100-x) alloy layer exchange-coupled with a ferromagnetic (FM) [Co/Ni]N multilayer have been investigated. As compared with pure TbxCo(100-x) alloy, the magnetization compensation composition of the heterostructures shift to a higher Tb content, implying Co/Ni also serves to compensate the Tb moment in TbCo layer. The net magnetization switching field Hc⊥ and interlayer interfacial coupling field Hex, are not only sensitive to the magnetization and thickness of the switched TbxCo(100-x) or [Co/Ni]N layer, but also to the perpendicular magnetic anisotropy strength of the pinning layer. By tuning the layer structure we achieve simultaneously both large Hc⊥ = 1.31 T and Hex = 2.19 T. These results, in addition to the fundamental interest, are important to understanding of the interfacial coupling interaction in the FM/FI heterostructures, which could offer the guiding of potential applications in heat-assisted magnetic recording or all-optical switching recording technique.

Aquivion Perfluorosulfonic Superacid as an Efficient Pickering Interfacial Catalyst for the Hydrolysis of Triglycerides.

PubMed

Shi, Hui; Fan, Zhaoyu; Hong, Bing; Pera-Titus, Marc

2017-09-11

Rational design of the surface properties of heterogeneous catalysts can boost the interfacial activity in biphasic reactions through the generation of Pickering emulsions. This concept, termed Pickering interfacial catalysis (PIC), has shown promising credentials in acid-catalyzed transesterification, ester hydrolysis, acetalization, etherification, and alkylation reactions. PIC has now been applied to the efficient, solvent-free hydrolysis of the triglyceride glyceryl trilaurate to lauric acid, catalyzed by Aquivion perfluorosulfonic superacid at mild conditions (100 °C and ambient pressure). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

First-principles study of spin-transfer torque in Co{sub 2}MnSi/Al/Co{sub 2}MnSi spin-valve

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

Tang, Ling, E-mail: lingtang@zjut.edu.cn; Yang, Zejin, E-mail: zejinyang@zjut.edu.cn

The spin-transfer torque (STT) in Co{sub 2}MnSi(CMS)/Al/Co{sub 2}MnSi spin-valve system with and without interfacial disorder is studied by a first-principles noncollinear wave-function-matching method. It is shown that in the case of clean interface the angular dependence of STT for CoCo/Al (the asymmetry parameter Λ≈4.5) is more skewed than that for MnSi/Al (Λ≈2.9), which suggests the clean CoCo/Al architecture is much more efficient for the application on radio frequency oscillation. We also find that even with interfacial disorder the spin-valve of half-metallic CMS still has a relatively large parameter Λ compared to that of conventional ferromagnet. In addition, for clean interfacemore » the in-plane torkance of MnSi/Al is about twice as large as that of CoCo/Al. However, as long as the degree of interfacial disorder is sufficiently large, the CoCo/Al and MnSi/Al will show approximately the same magnitude of in-plane torkance. Furthermore, our results demonstrate that CMS/Al/CMS system has very high efficiency of STT to switch the magnetic layer of spin-valve.« less

Wettability of supercritical carbon dioxide/water/quartz systems: simultaneous measurement of contact angle and interfacial tension at reservoir conditions.

PubMed

Saraji, Soheil; Goual, Lamia; Piri, Mohammad; Plancher, Henry

2013-06-11

Injection of carbon dioxide in deep saline aquifers is considered as a method of carbon sequestration. The efficiency of this process is dependent on the fluid-fluid and rock-fluid interactions inside the porous media. For instance, the final storage capacity and total amount of capillary-trapped CO2 inside an aquifer are affected by the interfacial tension between the fluids and the contact angle between the fluids and the rock mineral surface. A thorough study of these parameters and their variations with temperature and pressure will provide a better understanding of the carbon sequestration process and thus improve predictions of the sequestration efficiency. In this study, the controversial concept of wettability alteration of quartz surfaces in the presence of supercritical carbon dioxide (sc-CO2) was investigated. A novel apparatus for measuring interfacial tension and contact angle at high temperatures and pressures based on Axisymmetric Drop Shape Analysis with no-Apex (ADSA-NA) method was developed and validated with a simple system. Densities, interfacial tensions, and dynamic contact angles of CO2/water/quartz systems were determined for a wide range of pressures and temperatures relevant to geological sequestration of CO2 in the subcritical and supercritical states. Image analysis was performed with ADSA-NA method that allows the determination of both interfacial tensions and contact angles with high accuracy. The results show that supercritical CO2 alters the wettability of quartz surface toward less water-wet conditions compared to subcritical CO2. Also we observed an increase in the water advancing contact angles with increasing temperature indicating less water-wet quartz surfaces at higher temperatures.

Improved electrochemical and thermal properties of nickel rich LiNi0.6Co0.2Mn0.2O2 cathode materials by SiO2 coating

NASA Astrophysics Data System (ADS)

Cho, Woosuk; Kim, Sang-Min; Song, Jun Ho; Yim, Taeeun; Woo, Sang-Gil; Lee, Ko-Woon; Kim, Jeom-Soo; Kim, Young-Jun

2015-05-01

A surface coating of SiO2 is applied to a Ni rich LiNi0.6Co0.2Mn0.2O2 cathode material in a bid to improve its electrochemical and thermal properties. A uniform coating is achieved through a wet process using nano-sized SiO2 powder, and though the coated electrode is found to exhibit a reduced rate capability, its cycle performance at a high temperature of 60 °C is greatly enhanced. The effect of this SiO2 coating is further investigated by electrochemical impedance spectroscopy, which confirms that it suppresses the growth of interfacial impedance during progressive cycles. The SiO2 coating also demonstrates good HF scavenging ability, producing a subsequent reduction in the degradation of the active core material. The thermal properties of LiNi0.6Co0.2Mn0.2O2 are also improved by the SiO2 coating due to a reduction in the direct contact between the electrode and electrolyte. On the basis of these results, SiO2 coating is considered a viable surface modification method for improving the electrochemical and thermal properties of LiNi0.6Co0.2Mn0.2O2.

Phase Equilibria of the Ternary Sn-Pb-Co System at 250°C and Interfacial Reactions of Co with Sn-Pb Alloys

NASA Astrophysics Data System (ADS)

Wang, Chao-hong; Kuo, Chun-yi; Yang, Nian-cih

2015-11-01

The isothermal section of the ternary Sn-Pb-Co system at 250°C was experimentally determined through a series of the equilibrated Sn-Pb-Co alloys of various compositions. The equilibrium phases were identified on the basis of compositional analysis. For the Sn-Co intermetallic compounds (IMCs), CoSn3, CoSn2, CoSn and Co3Sn2, the Pb solubility was very limited. There exist five tie-triangle regions. The Co-Pb system involves one monotectic reaction, so the phase separation of liquid alloys near the Co-Pb side occurred prior to solidification. The immiscibility field was also determined. Additionally, interfacial reactions between Co and Sn-Pb alloys were conducted. The reaction phase for the Sn-48 at.%Pb and Sn-58 at.%Pb at 250°C was CoSn3 and CoSn2, respectively. Both of them were simultaneously formed in the Sn-53 at.%Pb/Co. The formed IMCs were closely associated to the phase equilibria relationship of the liquid-CoSn3-CoSn2 tie-triangle. Furthermore, with increasing temperatures, the phase formed in equilibrium with Sn-37 wt.%Pb was found to transit from CoSn3 to CoSn2 at 275°C. We propose a simple method of examining the phase transition temperature in the interfacial reactions to determine the boundaries of the liquid-CoSn3-CoSn2 tie-triangles at different temperatures.

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

Interfacial reaction and microstructure between the Sn3Ag0.5Cu solder and Cu-Co dual-phase substrate

NASA Astrophysics Data System (ADS)

Li, Chao; Hu, Xiaowu; Jiang, Xiongxin; Li, Yulong

2018-07-01

In this study, interfacial reactions and microstructures of the Sn3Ag0.5Cu (SAC305)/Cu- xCo ( x = 0, 30 and 50 wt%) systems were investigated during reflowing at 290 °C and solid-state aging at 150 °C for various time. The effects of different contents of Co in substrate on interfacial reaction in SAC305/Cu- xCo system were discussed. It was found that the addition of Co into pure copper substrate to achieve alloying would effectively inhibit the growth of IMC layers. Comparison among the thickness of the intermetallic compound (IMC) in three kinds of SAC305/Cu-Co systems indicated that the IMC layer of SAC305/Cu joint was thicker than that of the other two types of solder joints. The composition of the SAC305/Cu IMC layers was Cu6Sn5 and Cu3Sn. Three kinds of reaction phases (Cu,Co)6Sn5, (Cu,Co)Sn2 and (Cu,Co)3Sn were found at the interfaces of the SAC305/Cu-30Co and SAC305/Cu-50Co joints. Remarkably the (Cu,Co)Sn2 phase was found adjacent to the Co-rich phase after soldering and eliminated after the aging treatment. While the (Cu,Co)3Sn phase accumulated increasingly adjacent to the substrate with the increased aging time. The results suggested that the Co content increased from 30 to 50 wt% in substrate lead to significant restraint of the growth of interfacial IMC. In addition, the thickness of the interfacial IMC layer was linear with the square root of the aging time during the aging process. The reaction rate between Sn atoms in solder and Cu, Co atoms in substrate was quite different, which lead to the fact that the interface of SAC305/Cu-Co is uneven on the side of substrate after reflowing and aging.

Pore scale study of multiphase multicomponent reactive transport during CO 2 dissolution trapping

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

Chen, Li; Wang, Mengyi; Kang, Qinjun

Solubility trapping is crucial for permanent CO 2 sequestration in deep saline aquifers. For the first time, a pore-scale numerical method is developed to investigate coupled scCO 2-water two-phase flow, multicomponent (CO 2(aq), H +, HCO 3 –, CO 3 2 – and OH –) mass transport, heterogeneous interfacial dissolution reaction, and homogeneous dissociation reactions. Pore-scale details of evolutions of multiphase distributions and concentration fields are presented and discussed. Time evolutions of several variables including averaged CO 2(aq) concentration, scCO 2 saturation, and pH value are analyzed. Specific interfacial length, an important variable which cannot be determined but is requiredmore » by continuum models, is investigated in detail. Mass transport coefficient or efficient dissolution rate is also evaluated. The pore-scale results show strong non-equilibrium characteristics during solubility trapping due to non-uniform distributions of multiphase as well as slow mass transport process. Complicated coupling mechanisms between multiphase flow, mass transport and chemical reactions are also revealed. Lastly, effects of wettability are also studied. The pore-scale studies provide deep understanding of non-linear non-equilibrium multiple physicochemical processes during CO 2 solubility trapping processes, and also allow to quantitatively predict some important empirical relationships, such as saturation-interfacial surface area, for continuum models.« less

Pore scale study of multiphase multicomponent reactive transport during CO 2 dissolution trapping

DOE PAGES

Chen, Li; Wang, Mengyi; Kang, Qinjun; ...

2018-04-26

Solubility trapping is crucial for permanent CO 2 sequestration in deep saline aquifers. For the first time, a pore-scale numerical method is developed to investigate coupled scCO 2-water two-phase flow, multicomponent (CO 2(aq), H +, HCO 3 –, CO 3 2 – and OH –) mass transport, heterogeneous interfacial dissolution reaction, and homogeneous dissociation reactions. Pore-scale details of evolutions of multiphase distributions and concentration fields are presented and discussed. Time evolutions of several variables including averaged CO 2(aq) concentration, scCO 2 saturation, and pH value are analyzed. Specific interfacial length, an important variable which cannot be determined but is requiredmore » by continuum models, is investigated in detail. Mass transport coefficient or efficient dissolution rate is also evaluated. The pore-scale results show strong non-equilibrium characteristics during solubility trapping due to non-uniform distributions of multiphase as well as slow mass transport process. Complicated coupling mechanisms between multiphase flow, mass transport and chemical reactions are also revealed. Lastly, effects of wettability are also studied. The pore-scale studies provide deep understanding of non-linear non-equilibrium multiple physicochemical processes during CO 2 solubility trapping processes, and also allow to quantitatively predict some important empirical relationships, such as saturation-interfacial surface area, for continuum models.« less

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.

Pore scale study of multiphase multicomponent reactive transport during CO2 dissolution trapping

NASA Astrophysics Data System (ADS)

Chen, Li; Wang, Mengyi; Kang, Qinjun; Tao, Wenquan

2018-06-01

Solubility trapping is crucial for permanent CO2 sequestration in deep saline aquifers. For the first time, a pore-scale numerical method is developed to investigate coupled scCO2-water two-phase flow, multicomponent (CO2(aq), H+, HCO3-, CO32- and OH-) mass transport, heterogeneous interfacial dissolution reaction, and homogeneous dissociation reactions. Pore-scale details of evolutions of multiphase distributions and concentration fields are presented and discussed. Time evolutions of several variables including averaged CO2(aq) concentration, scCO2 saturation, and pH value are analyzed. Specific interfacial length, an important variable which cannot be determined but is required by continuum models, is investigated in detail. Mass transport coefficient or efficient dissolution rate is also evaluated. The pore-scale results show strong non-equilibrium characteristics during solubility trapping due to non-uniform distributions of multiphase as well as slow mass transport process. Complicated coupling mechanisms between multiphase flow, mass transport and chemical reactions are also revealed. Finally, effects of wettability are also studied. The pore-scale studies provide deep understanding of non-linear non-equilibrium multiple physicochemical processes during CO2 solubility trapping processes, and also allow to quantitatively predict some important empirical relationships, such as saturation-interfacial surface area, for continuum models.

Role of the Cu-ZrO 2 Interfacial Sites for Conversion of Ethanol to Ethyl Acetate and Synthesis of Methanol from CO 2 and H 2 [The Role of the Cu-ZrO 2 Interfacial Sites for Ethanol Conversion to Ethyl Acetate and Methanol Synthesis from CO 2 and H 2

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

Ro, Insoo; Liu, Yifei; Ball, Madelyn R.

Well-defined Cu catalysts containing different amounts of zirconia were synthesized by controlled surface reactions (CSRs) and atomic layer deposition methods and studied for the selective conversion of ethanol to ethyl acetate and for methanol synthesis. Selective deposition of ZrO 2 on undercoordinated Cu sites or near Cu nanoparticles via the CSR method was evidenced by UV–vis absorption spectroscopy, scanning transmission electron microscopy, and inductively coupled plasma absorption emission spectroscopy. The concentrations of Cu and Cu-ZrO 2 interfacial sites were quantified using a combination of subambient CO Fourier transform infrared spectroscopy and reactive N 2O chemisorption measurements. The oxidation states ofmore » the Cu and ZrO 2 species for these catalysts were determined using X-ray absorption near edge structure measurements, showing that these species were present primarily as Cu 0 and Zr 4+, respectively. Here, it was found that the formation of Cu-ZrO 2 interfacial sites increased the turnover frequency by an order of magnitude in both the conversion of ethanol to ethyl acetate and the synthesis of methanol from CO 2 and H 2.« less

Role of the Cu-ZrO 2 Interfacial Sites for Conversion of Ethanol to Ethyl Acetate and Synthesis of Methanol from CO 2 and H 2 [The Role of the Cu-ZrO 2 Interfacial Sites for Ethanol Conversion to Ethyl Acetate and Methanol Synthesis from CO 2 and H 2

DOE PAGES

Ro, Insoo; Liu, Yifei; Ball, Madelyn R.; ...

2016-09-06

Well-defined Cu catalysts containing different amounts of zirconia were synthesized by controlled surface reactions (CSRs) and atomic layer deposition methods and studied for the selective conversion of ethanol to ethyl acetate and for methanol synthesis. Selective deposition of ZrO 2 on undercoordinated Cu sites or near Cu nanoparticles via the CSR method was evidenced by UV–vis absorption spectroscopy, scanning transmission electron microscopy, and inductively coupled plasma absorption emission spectroscopy. The concentrations of Cu and Cu-ZrO 2 interfacial sites were quantified using a combination of subambient CO Fourier transform infrared spectroscopy and reactive N 2O chemisorption measurements. The oxidation states ofmore » the Cu and ZrO 2 species for these catalysts were determined using X-ray absorption near edge structure measurements, showing that these species were present primarily as Cu 0 and Zr 4+, respectively. Here, it was found that the formation of Cu-ZrO 2 interfacial sites increased the turnover frequency by an order of magnitude in both the conversion of ethanol to ethyl acetate and the synthesis of methanol from CO 2 and H 2.« less

Modulated exchange bias in NiFe/CoO/α-Fe2O3 trilayers and NiFe/CoO bilayers

NASA Astrophysics Data System (ADS)

Li, X.; Lin, K.-W.; Yeh, W.-C.; Desautels, R. D.; van Lierop, J.; Pong, Philip W. T.

2017-02-01

While the exchange bias in ferromagnetic/antiferromagnetic (FM/AF) bilayer and FM1/AF/FM2 trilayer configurations has been widely investigated, the role of an AF2 layer in FM/AF1/AF2 trilayer configurations is still not well understood. In this work, the magnetic properties of NiFe/CoO, NiFe/α-Fe2O3 bilayers, and NiFe/CoO/α-Fe2O3 trilayer were studied comparatively. The microstructure and chemical composition were characterized. Temperature dependent magnetometry reveals increased irreversibility temperature in NiFe/CoO/α-Fe2O3 trilayer compared with NiFe/CoO bilayer. The magnetic hysteresis loops show that the exchange bias (Hex) and coercivity (Hc) depend strongly on the anisotropy of AF layer (CoO, α-Fe2O3 and CoO/α-Fe2O3). Our work shows that the AF1/AF2 interfacial interactions can be used effectively for tuning the exchange bias in FM/AF1/AF2 trilayers.

A Capillary Flow Dynamics-Based Sensing Modality for Direct Environmental Pathogen Monitoring.

PubMed

Klug, Katherine E; Reynolds, Kelly A; Yoon, Jeong-Yeol

2018-04-20

Toward ultra-simple and field-ready biosensors, we demonstrate a novel assay transducer mechanism based on interfacial property changes and capillary flow dynamics in antibody-conjugated submicron particle suspensions. Differential capillary flow is tunable, allowing pathogen quantification as a function of flow rate through a paper-based microfluidic device. Flow models based on interfacial and rheological properties indicate a significant relationship between the flow rate and the interfacial effects caused by target-particle aggregation. This mechanism is demonstrated for assays of Escherichia coli K12 in water samples and Zika virus (ZIKV) in blood serum. These assays achieved very low limits of detection compared with other demonstrated methods (1 log CFU/mL E. coli and 20 pg/mL ZIKV whole virus) with an operating time of 30 s, showing promise for environmental and health monitoring. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Finite Size Effects in Submonolayer Catalysts Investigated by CO Electrosorption on PtsML/Pd(100).

PubMed

Yuan, Qiuyi; Doan, Hieu A; Grabow, Lars C; Brankovic, Stanko R

2017-10-04

A combination of scanning tunneling microscopy, subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS), and density functional theory (DFT) is used to quantify the local strain in 2D Pt clusters on the 100 facet of Pd and its effect on CO chemisorption. Good agreement between SNIFTIRS experiments and DFT simulations provide strong evidence that, in the absence of coherent strain between Pt and Pd, finite size effects introduce local compressive strain, which alters the chemisorption properties of the surface. Though this effect has been widely neglected in prior studies, our results suggest that accurate control over cluster sizes in submonolayer catalyst systems can be an effective approach to fine-tune their catalytic properties.

Interfacial and transport properties of nanoconstrained inorganic and organic materials

NASA Astrophysics Data System (ADS)

Kocherlakota, Lakshmi Suhasini

Nanoscale constraints impact the material properties of both organic and inorganic systems. The systems specifically studied here are (i) nanoconstrained polymeric systems, poly(l-trimethylsilyl-1-propyne) (PTMSP) and poly(ethylene oxide) (PEO) relevant to gas separation membranes (ii) Zwitterionic polymers poly(sulfobetaine methacrylate)(pSBMA), poly(carboxybetaine acrylamide) (pCBAA), and poly(oligo(ethylene glycol) methyl methacrylate) (PEGMA) brushes critical for reducing bio-fouling (iii) Surface properties of N-layer graphene sheets. Interfacial constraints in ultrathin poly(l-trimethylsilyl-1-propyne) (PTMSP) membranes yielded gas permeabilities and CO2/helium selectivities that exceed bulk PTMSP membrane transport properties by up to three-fold for membranes of submicrometer thickness. Indicative of a free volume increase, a molecular energetic mobility analysis (involving intrinsic friction analysis) revealed enhanced methyl side group mobilities in thin PTMSP membranes with maximum permeation, compared to bulk films. Aging studies conducted over the timescales relevant to the conducted experiments signify that the free volume states in the thin film membranes are highly unstable in the presence of sorbing gases such as CO2. To maintain this high free volume configuration of polymer while improving the temporal stability an "inverse" architecture to conventional polymer nanocomposites was investigated, in which the polymer phase of PTMSP and PEO were interfacially and dimensionally constrained in nanoporous anodic aluminum oxide (AAO) membranes. While with this architecture the benefits of nanocomposite and ultrathin film membranes of PTMSP could be reproduced and improved upon, also the temporal stability could be enhanced substantially. The PEO-AAO nanocomposite membranes also revealed improved gas selectivity properties of CO2 over helium. In the thermal transition studies of zwitterionic pSBMA brushes a reversible critical transition temperature of 60 °C in 27 nm films was evidenced, indicating changes in molecular conformations with respect to the temperature. pCBAA and pEGMA brushes displayed no thermal transitions, suggesting that the molecular conformations of these systems were insensitive to temperature in the investigated regime. The surface energy of a dimensionally constrained inorganic system, graphene is studied via local Hamaker constant determination from a single graphene layer to bulk graphite. Intrinsic friction scattering analysis of dipolar fluctuations of the Van der Waals interactions between an atomic force microscopy tip and graphene layers revealed a four-fold reduction in the surface energy from bulk HOPG to graphene. A numerical analysis based on electron energy loss spectroscopy confirms quantitatively the results.

Spin scattering asymmetric coefficients and enhanced specific interfacial resistance of fully epitaxial current-perpendicular-to-plane giant magnetoresistance spin valves using alternate monatomic layered [Fe/Co]n and a Ag spacer layer

NASA Astrophysics Data System (ADS)

Jung, J. W.; Shiozaki, R.; Doi, M.; Sahashi, M.

2011-04-01

Using current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) measurement, we have evaluated the bulk and interface spin scattering asymmetric coefficients, βF and γF/N and the specific interfacial resistance, AR*F/N, for exchange-biased spin-valves consisting of artificially ordered B2 structure Fe50Co50 and Ag spacer layer. Artificially epitaxial ordered Fe50Co50 superlattices have been successfully fabricated on MgO (001) substrate by alternate monatomic layer (AML) deposition at a substrate temperature of 75 °C. The structural properties of the full epitaxial trilayer, AML[Fe/Co]n/Ag/AML[Fe/Co]n, on the Ag electrode have been confirmed by in situ reflection high-energy electron diffraction and transmission electron diffraction microscopy. A considerably large resistance-area product change and MR ratio (ΔRA > 3 mΩμm2 and MR ratio ˜5%) were confirmed even at thin AML[Fe/Co]n layer at room temperature (RT) in our spin-valve elements. The estimated values of βF and γF/N were 0.80 and 0.84 ± 0.02, respectively, from the Valet-Fert theory analysis of ΔRA as a function of thickness of the ferromagnetic layer (3, 4, and 5 nm) on the basis of the two-current model.

Seal glass compatibility with bare and (Mn,Co) 3O 4 coated Crofer 22 APU alloy in different atmospheres

NASA Astrophysics Data System (ADS)

Mahapatra, M. K.; Lu, K.

To prevent gas mixing and leakage during solid oxide fuel/electrolyzer cell operation, the interconnect/seal glass interface should bond well and remain stable. A SrO-La 2O 3-Al 2O 3-SiO 2 (SABS-0) seal glass has been bonded to bare Crofer 22 APU alloy and (Mn,Co) 3O 4 coated Crofer 22 APU alloy. The stability of the interconnect/SABS-0 interface has been studied in air and H 2/H 2O atmospheres at 800 °C for 1000 h. The interconnect/seal glass interaction involves the oxidation of the bare and (Mn,Co) 3O 4 coated Crofer 22 APU alloy surfaces, inter-diffusion of elements, chemical reaction, and the devitrification of the SABS-0 glass. The study shows that the thermal treatment atmosphere greatly affects the interfacial stability of both bare Crofer 22 APU/SABS-0 and (Mn,Co) 3O 4 coated Crofer 22 APU/SABS-0 samples. The interfacial stability is better in the H 2/H 2O atmosphere for both samples. The instability of the (Mn,Co) 3O 4 coating under the thermal treatment conditions degrades the interfacial compatibility of the (Mn,Co) 3O 4 coated Crofer 22 APU/SABS-0 sample.

Interfacial properties of black phosphorus/transition metal carbide van der Waals heterostructures

NASA Astrophysics Data System (ADS)

Yuan, Hao; Li, Zhenyu

2018-06-01

Owing to its outstanding electronic properties, black phosphorus (BP) is considered as a promising material for next-generation optoelectronic devices. In this work, devices based on BP/MXene (Zr n+1C n T2, T = O, F, OH, n = 1, 2) van der Waals (vdW) heterostructures are designed via first-principles calculations. Zr n+1C n T2 compositions with appropriate work functions lead to the formation of Ohmic contact with BP in the vertical direction. Low Schottky barriers are found along the lateral direction in BP/Zr2CF2, BP/Zr2CO2H2, BP/Zr3C2F2, and BP/Zr3C2O2H2 bilayers, and BP/Zr3C2O2 even exhibits Ohmic contact behavior. BP/Zr2CO2 is a semiconducting heterostructure with type-II band alignment, which facilitates the separation of electron-hole pairs. The band structure of BP/Zr2CO2 can be effectively tuned via a perpendicular electric field, and BP is predicted to undergo a transition from donor to acceptor at a 0.4 V/Å electric field. The versatile electronic properties of the BP/MXene heterostructures examined in this work highlight their promising potential for applications in electronics.

Graphene-ferromagnet interfaces: hybridization, magnetization and charge transfer.

PubMed

Abtew, Tesfaye; Shih, Bi-Ching; Banerjee, Sarbajit; Zhang, Peihong

2013-03-07

Electronic and magnetic properties of graphene-ferromagnet interfaces are investigated using first-principles electronic structure methods in which a single layer graphene is adsorbed on Ni(111) and Co(111) surfaces. Due to the symmetry matching and orbital overlap, the hybridization between graphene pπ and Ni (or Co) d(z(2)) states is very strong. This pd hybridization, which is both spin and k dependent, greatly affects the electronic and magnetic properties of the interface, resulting in a significantly reduced (by about 20% for Ni and 10% for Co) local magnetic moment of the top ferromagnetic layer at the interface and an induced spin polarization on the graphene layer. The calculated induced magnetic moment on the graphene layer agrees well with a recent experiment. In addition, a substantial charge transfer across the graphene-ferromagnet interfaces is observed. We also investigate the effects of thickness of the ferromagnet slab on the calculated electronic and magnetic properties of the interface. The strength of the pd hybridization and the thickness-dependent interfacial properties may be exploited to design structures with desirable magnetic and transport properties for spintronic applications.

Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

NASA Astrophysics Data System (ADS)

Demirezen, S.; Kaya, A.; Yerişkin, S. A.; Balbaşı, M.; Uslu, İ.

In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε‧, ε‧, tanδ, electric modulus (M‧ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε‧, ε‧, tanδ, M‧, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε‧, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε‧ and ε″ values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of ε‧ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M‧ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M‧ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε‧, ε″, tanδ, M‧, M″ and ac electric conductivity (σac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

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

PubMed

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

2016-01-20

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

Rational Construction of Uniform CoNi-Based Core-Shell Microspheres with Tunable Electromagnetic Wave Absorption Properties.

PubMed

Chen, Na; Jiang, Jian-Tang; Xu, Cheng-Yan; Yan, Shao-Jiu; Zhen, Liang

2018-02-16

Core-shell particles with integration of ferromagnetic core and dielectric shell are attracting extensive attention for promising microwave absorption applications. In this work, CoNi microspheres with conical bulges were synthesized by a simple and scalable liquid-phase reduction method. Subsequent coating of dielectric materials was conducted to acquire core-shell structured CoNi@TiO 2 composite particles, in which the thickness of TiO 2 is about 40 nm. The coating of TiO 2 enables the absorption band of CoNi to effectively shift from K u to S band, and endows CoNi@TiO 2 microspheres with outstanding electromagnetic wave absorption performance along with a maximum reflection loss of 76.6 dB at 3.3 GHz, much better than that of bare CoNi microspheres (54.4 dB at 17.8 GHz). The enhanced EMA performance is attributed to the unique core-shell structures, which can induce dipole polarization and interfacial polarization, and tune the dielectric properties to achieve good impedance matching. Impressively, TiO 2 coating endows the composites with better microwave absorption capability than CoNi@SiO 2 microspheres. Compared with SiO 2 , TiO 2 dielectric shells could protect CoNi microspheres from merger and agglomeration during annealed. These results indicate that CoNi@TiO 2 core-shell microspheres can serve as high-performance absorbers for electromagnetic wave absorbing application.

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

Effects of post-deposition magnetic field annealing on magnetic properties of NiO/Co90Fe10 bilayers

NASA Astrophysics Data System (ADS)

Zheng, Chao; Su, Shan; Chiu, Chun-Cheng; Skoropata, Elizabeth; Desautels, Ryan D.; van Lierop, Johan; Lin, Ko-Wei; Pong, Philip W. T.

2018-01-01

The ferromagnetic (FM)/antiferromagnetic (AF) bilayer structures have drawn intensive attention because of their wide applications in modern spintronic devices. While abundant published works have been reported on the interface effects of the FM/AF bilayers caused by the magnetic field annealing (MFA) process, the volume effects caused by the MFA treatment have been rarely considered. In this work, the microstructural and magnetic properties of the NiO/CoFe bilayers with various CoFe thicknesses were investigated under different annealing temperatures. At high annealing temperature, the interlayer mixing and exchange coupling between NiO and CoFe layers were promoted and consequently the interface effects were facilitated. The interfacial oxides acted as pinning centers and randomly pinned the FM domains, leading to an increase of coercivity and a considerable degradation of uniaxial anisotropy. The increase of coercivity was also contributed by the enhancement of the interfacial exchange coupling between the NiO and CoFe layers after MFA. As the CoFe thickness increased, the volume effects tended to dominate over the interface effects, resulting in the preservation the uniaxially anisotropic features of CoFe. These results indicate that both the coercivity and anisotropic features of the NiO/CoFe bilayers can be directly affected by the MFA process, opening up the possibility of modifying the magnetism in the NiO/CoFe bilayers and offering an effective way to improve the performance of modern spintronic devices.

Flexible fiber-reinforced composites with improved interfacial adhesion by mussel-inspired polydopamine and poly(methyl methacrylate) coating.

PubMed

Yi, Mi; Sun, Hongyang; Zhang, Hongcheng; Deng, Xuliang; Cai, Qing; Yang, Xiaoping

2016-01-01

To obtain a kind of light-curable fiber-reinforced composite for dental restoration, an excellent interfacial adhesion between the fiber and the acrylate resin matrix is quite essential. Herein, surface modification on glass fibers were carried out by coating them with poly(methyl methacrylate) (PMMA), polydopamine (PDA), or both. The PMMA or PDA coating was performed by soaking fibers in PMMA/acetone solution or dopamine aqueous solution. PDA/PMMA co-coated glass fibers were obtained by further soaking PDA-coated fibers in PMMA/acetone solution. These modified fibers were impregnated with bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (5:5, w/w) dental resin at a volume fraction of 75%, using unmodified fibers as reference. Light-cured specimens were submitted to evaluations including flexural properties, morphological observation, dynamic mechanical thermal analysis (DMTA) and pull-out test. In comparison with unmodified glass fibers, all the modified glass fibers showed enhancements in flexural strength and modulus of Bis-GMA/TEGDMA resin composites. Results of DMTA and pull-out tests confirmed that surface modification had significantly improved the interfacial adhesion between the glass fiber and the resin matrix. Particularly, the PDA/PMMA co-coated glass fibers displayed the most efficient reinforcement and the strongest interfacial adhesion due to the synergetic effects of PDA and PMMA. It indicated that co-coating method was a promising approach in modifying the interfacial compatibility between inorganic glass fiber and organic resin matrix. Copyright © 2015 Elsevier B.V. All rights reserved.

Engineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior

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

Chopdekar, Rajesh V.; Malik, Vivek K.; Kane, Alexander M.

The extent of interfacial charge transfer and the resulting impact on magnetic interactions were investigated as a function of sublayer thickness in La 0.7Sr 0.3MnO 3/La 0.7Sr 0.3CoO 3 ferromagnetic superlattices. Element-specific soft x-ray magnetic spectroscopy reveals that the electronic structure is altered within 5–6 unit cells of the chemical interface, and can lead to a synthetic ferromagnet with strong magnetic coupling between the sublayers. The saturation magnetization and coercivity depends sensitively on the sublayer thickness due to the length scale of this interfacial effect. For larger sublayer thicknesses, the La 0.7Sr 0.3MnO 3 and La 0.7Sr 0.3CoO 3 sublayersmore » are magnetically decoupled, displaying two independent magnetic transitions with little sublayer thickness dependence. Lastly, these results demonstrate how interfacial phenomena at perovskite oxide interfaces can be used to tailor their functional properties at the atomic scale.« less

Engineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior

DOE PAGES

Chopdekar, Rajesh V.; Malik, Vivek K.; Kane, Alexander M.; ...

2017-12-04

The extent of interfacial charge transfer and the resulting impact on magnetic interactions were investigated as a function of sublayer thickness in La 0.7Sr 0.3MnO 3/La 0.7Sr 0.3CoO 3 ferromagnetic superlattices. Element-specific soft x-ray magnetic spectroscopy reveals that the electronic structure is altered within 5–6 unit cells of the chemical interface, and can lead to a synthetic ferromagnet with strong magnetic coupling between the sublayers. The saturation magnetization and coercivity depends sensitively on the sublayer thickness due to the length scale of this interfacial effect. For larger sublayer thicknesses, the La 0.7Sr 0.3MnO 3 and La 0.7Sr 0.3CoO 3 sublayersmore » are magnetically decoupled, displaying two independent magnetic transitions with little sublayer thickness dependence. Lastly, these results demonstrate how interfacial phenomena at perovskite oxide interfaces can be used to tailor their functional properties at the atomic scale.« less

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.

Structural, electrical and magnetic properties of (Fe, Co) co-doped SnO2 diluted magnetic semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Mehraj, Sumaira; Ansari, M. Shahnawaze; Alimuddin

2015-01-01

Nanostructures (NSs) of basic composition Sn1-xFex/2Cox/2O2 with x=0.00, 0.04, 0.06, 0.08 and 0.1 were synthesized by citrate-gel route and characterized to understand their structural, electrical and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase rutile type tetragonal structure. The crystallite sizes calculated by using Williamson Hall were found to decrease with increasing doping level. In addition to the fundamental Raman peaks of rutile SnO2, the other three weak Raman peaks at about 505, 537 and 688 cm-1 were also observed. Field emission scanning electron microscopy studies showed the emergence of structural transformation. Electric properties such as dc electrical resistivity as a function of temperature and ac conductivity as a function of frequency were also studied. The variation of dielectric properties with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general. Hysteresis loops were clearly observed in M-H curves of Fe and Co co-doped SnO2 NSs. However, pure SnO2 nanoparticles (NPs) showed paramagnetic behaviour which vanished at higher values of magnetic field. The grain and grain boundary contribution in the conduction process is estimated through complex impedance plot fitted with non-linear least square (NLLS) approach which shows that the role of grain boundaries increases rapidly as compared to the grain volume with the increase of Fe and Co ions in to system.

Enhancement of magnetoresistance by inserting thin NiAl layers at the interfaces in Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}/Ag/Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5} current-perpendicular-to-plane pseudo spin valves

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

Jung, J. W.; Sakuraba, Y., E-mail: Sakuraba.Yuya@nims.go.jp; Sasaki, T. T.

2016-03-07

We have investigated the effects of insertion of a thin NiAl layer (≤0.63 nm) into a Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5} (CFGG)/Ag interface on the magnetoresistive properties in CFGG/Ag/CFGG current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo spin valves (PSVs). First-principles calculations of ballistic transmittance clarified that the interfacial band matching at the (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface. The insertion of 0.21-nm-thick NiAl layers at the Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}/Ag interfaces effectively improved the magnetoresistance (MR) output; the observed average and the highest MR ratio (ΔRA) are 62% (25 mΩ μm{sup 2}) and 77% (31 mΩ μm{sup 2}) atmore » room temperature, respectively, which are much higher than those without NiAl insertion. Microstructural analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest interdiffusion even after annealing at 550 °C. The improvement of the interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of the MR output.« less

Defect-driven interfacial electronic structures at an organic/metal-oxide semiconductor heterojunction.

PubMed

Winget, Paul; Schirra, Laura K; Cornil, David; Li, Hong; Coropceanu, Veaceslav; Ndione, Paul F; Sigdel, Ajaya K; Ginley, David S; Berry, Joseph J; Shim, Jaewon; Kim, Hyungchui; Kippelen, Bernard; Brédas, Jean-Luc; Monti, Oliver L A

2014-07-16

The electronic structure of the hybrid interface between ZnO and the prototypical organic semiconductor PTCDI is investigated via a combination of ultraviolet and X-ray photoelectron spectroscopy (UPS/XPS) and density functional theory (DFT) calculations. The interfacial electronic interactions lead to a large interface dipole due to substantial charge transfer from ZnO to 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI), which can be properly described only when accounting for surface defects that confer ZnO its n-type properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancement of electrical and optical performance of N719 by co-sensitization

NASA Astrophysics Data System (ADS)

Shikoh, Ali Sephar; Ahmad, Zubair; Touati, Farid; Al-Muhtaseb, Shaheen A.

2018-04-01

This paper deals with the electrical, optical and electrochemical properties of a metal-free dye C78H74O8 (AS-2), which has been used to improve the photo-detection properties of C58H86N8O8RuS2 (N719) based Dye sensitized photo-sensors (DSPSs). Both dyes were mixed together in various proportions and the most promising ratio N719/AS-2 (1:0.25) was selected for staining photo-anodes for DSPS integration. The fabricated DSPSs were studied in terms of electrical parameters and photodetection properties. The N719/AS-2 (1:0.25) based DSPS were found to have a reduced leakage current, increased breakdown voltage and a closer proximity to an ideal diode, as compared to the N719 based DSPS. Further, the N719/AS-2 (1:0.25) based DSPS was also found to have better linearity at high irradiance levels, thus rendering the co-sensitized device useful as a photosensor in various applications. Electrochemical Impedance Spectroscopy (EIS) analysis was also performed to explain the interfacial charge recombination process.

Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGa xFe 2–xO 4/BaTiO 3 composite

DOE PAGES

Ni, Yan; Zhang, Zhen; Nlebedim, Cajetan I.; ...

2015-03-20

Multiferroic materials exhibit magnetoelectric (ME) coupling and promise new device applications including magnetic sensors, generators, and filters. An effective method for developing ME materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, the electrical and magnetic properties of Ga doped magnetoelectric CoGa xFe 2–xO 4/BaTiO 3 composite are studied systematically. It is found that Ga doping improves the sensitivity of magnetoelastic response and stabilizes the magnetic phase of the composites. More importantly, Ga doping reduces the electrical conductivity of composite, as well as the dielectric loss. Anmore » enhancement of the electrostrain with doping Ga is also observed. Quantitative estimation indicates that magnetoelectric coupling is enhanced for Ga-doped CoGa xFe 2–xO 4/BaTiO 3 composites. As a result, the present work is beneficial to the practical application of composite CoFe 2O 4/BaTiO 3-based multiferroic materials.« less

Calendering effects on the physical and electrochemical properties of Li[Ni1/3Mn1/3Co1/3]O2 cathode

NASA Astrophysics Data System (ADS)

Zheng, Honghe; Tan, Li; Liu, Gao; Song, Xiangyun; Battaglia, Vincent S.

2012-06-01

Li[Ni1/3Mn1/3Co1/3]O2 cathode laminate containing 8% PVDF and 7% acetylene black is fabricated and calendered to different porosities. Calendering effects on the physical and electrochemical properties of the Li[Ni1/3Mn1/3Co1/3]O2 cathode are investigated. It is found that mechanical properties of the composite laminate strongly depend on the electrode porosity whereas the electronic conductivity is not significantly affected by calendering. Electrochemical performances including the specific capacity, the first coulombic efficiency, cycling performance and rate capability for the cathode at different porosities are compared. An optimized porosity of around 30-40% is identified. Electrochemical impedance spectroscopy (EIS) studies illustrate that calendering improves the electronic conductivity between active particles at relatively high porosities, but increases charge transfer resistance at electrode/electrolyte interface at relatively low porosities. An increase of activation energy of Li interfacial transfer for the electrode at 0% porosity indicates a relatively high barrier of activation at the electrode/electrolyte interface, which accounts for the poor rate capability of the electrode at extremely low porosity.

Ionic Effects on Supercritical CO2-Brine Interfacial Tensions: Molecular Dynamics Simulations and a Universal Correlation with Ionic Strength, Temperature, and Pressure.

PubMed

Zhao, Lingling; Ji, Jiayuan; Tao, Lu; Lin, Shangchao

2016-09-13

For geological CO2 storage in deep saline aquifers, the interfacial tension (IFT) between supercritical CO2 and brine is critical for the storage security and design of the storage capacitance. However, currently, no predictive model exists to determine the IFT of supercritical CO2 against complex electrolyte solutions involving various mixed salt species at different concentrations and compositions. In this paper, we use molecular dynamics (MD) simulations to investigate the effect of salt ions on the incremental IFT at the supercritical CO2-brine interface with respect to that at the reference supercritical CO2-water interface. Supercritical CO2-NaCl solution, CO2-CaCl2 solution and CO2-(NaCl+CaCl2) mixed solution systems are simulated at 343 K and 20 MPa under different salinities and salt compositions. We find that the valence of the cations is the primary contributor to the variation in IFT, while the Lennard-Jones potentials for the cations pose a smaller impact on the IFT. Interestingly, the incremental IFT exhibits a general linear correlation with the ionic strength in the above three electrolyte systems, and the slopes are almost identical and independent of the solution types. Based on this finding, a universal predictive formula for IFTs of CO2-complex electrolyte solution systems is established, as a function of ionic strength, temperature, and pressure. The predicted IFTs using the established formula agree perfectly (with a high statistical confidence level of ∼96%) with a wide range of experimental data for CO2 interfacing with different electrolyte solutions, such as those involving MgCl2 and Na2SO4. This work provides an efficient and accurate route to directly predict IFTs in supercritical CO2-complex electrolyte solution systems for practical engineering applications, such as geological CO2 sequestration in deep saline aquifers and other interfacial systems involving complex electrolyte solutions.

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

Polster, C. S.; Zhang, R.; Cyb, M. T.

CO and H{sub 2} oxidation were studied over a series of Pt/CeO{sub 2} catalysts with differing Pt loadings and dispersions. Kinetic rate analysis confirms the presence of dual Langmuir-Hinshelwood (L-H) and Mars and van Krevelen (M-vK) pathways and is used to explain the loss in CO oxidation selectivity at low CO concentrations. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the strong CO coverage dependence on both CO and O{sub 2} concentrations and explains the transition from L-H to M-vK reaction character. Redox site measurements are performed on Pt/CeO{sub 2} catalysts by anaerobic titrations under conditions where themore » M-vK pathway dominates the reaction rate. Similar redox site densities per interfacial Pt atom suggest that interfacial Pt-O-Ce sites are responsible for M-vK redox activity.« less

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.

Interrelationships among Grain Size, Surface Composition, Air Stability, and Interfacial Resistance of Al-Substituted Li7La3Zr2O12 Solid Electrolytes.

PubMed

Cheng, Lei; Wu, Cheng Hao; Jarry, Angelique; Chen, Wei; Ye, Yifan; Zhu, Junfa; Kostecki, Robert; Persson, Kristin; Guo, Jinghua; Salmeron, Miquel; Chen, Guoying; Doeff, Marca

2015-08-19

The interfacial resistances of symmetrical lithium cells containing Al-substituted Li7La3Zr2O12 (LLZO) solid electrolytes are sensitive to their microstructures and histories of exposure to air. Air exposure of LLZO samples with large grain sizes (∼150 μm) results in dramatically increased interfacial impedances in cells containing them, compared to those with pristine large-grained samples. In contrast, a much smaller difference is seen between cells with small-grained (∼20 μm) pristine and air-exposed LLZO samples. A combination of soft X-ray absorption (sXAS) and Raman spectroscopy, with probing depths ranging from nanometer to micrometer scales, revealed that the small-grained LLZO pellets are more air-stable than large-grained ones, forming far less surface Li2CO3 under both short- and long-term exposure conditions. Surface sensitive X-ray photoelectron spectroscopy (XPS) indicates that the better chemical stability of the small-grained LLZO is related to differences in the distribution of Al and Li at sample surfaces. Density functional theory calculations show that LLZO can react via two different pathways to form Li2CO3. The first, more rapid, pathway involves a reaction with moisture in air to form LiOH, which subsequently absorbs CO2 to form Li2CO3. The second, slower, pathway involves direct reaction with CO2 and is favored when surface lithium contents are lower, as with the small-grained samples. These observations have important implications for the operation of solid-state lithium batteries containing LLZO because the results suggest that the interfacial impedances of these devices is critically dependent upon specific characteristics of the solid electrolyte and how it is prepared.

Compatibilization of acrylonitrile-butadiene-styrene terpolymer/poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) blend: effect on morphology, interface, mechanical properties and hydrophilicity

NASA Astrophysics Data System (ADS)

Chen, Tingting; Zhang, Jun

2018-04-01

The compatibilization of acrylonitrile-butadiene-styrene terpolymer (ABS) and poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) blends was first investigated. Styrene-acrylonitrile-glycidyl methacrylate terpolymer (SAG) and ABS grafted with maleic anhydride (ABS-g-MAH) were selected as reactive compatibilizers for the ABS/PETG blends. The compatibilization effect was assessed by scanning electron microscope (SEM), differential scanning calorimetry (DSC) and mechanical properties. And the effect of compatibilizers on the hydrophilicity of the blends was evaluated as well. SEM observation and DSC analysis confirmed that both SAG and ABS-g-MAH compatibilizers could improve the compatibility between ABS and PETG, leading to an improvement in toughness of the blend. The possible cause for the improvement of compatibility was the reaction between compatibilizers and PETG, which could in situ turn out compatibilizers that acted as interfacial agents to enhance the interfacial interaction in the blend. Especially, the addition of SAG significantly decreased the dispersion phase size and the interface voids almost disappeared. Since the in situ reactions between the epoxy groups of SAG and the end groups (sbnd COOH or sbnd OH) of PETG generated PETG-co-SAG copolymer at the blend interface, and the cross-linking reactions proposed to take place between SAG and the PETG-co-SAG copolymer, acting as compatibilizer, could significantly increase the interfacial interaction. The addition of SAG also enhanced the stiffness of the blends. Moreover, the addition of SAG made the blend more hydrophilic, whereas the addition of ABS-g-MAH made the blend more hydrophobic. Therefore, SAG was a good compatibilizer for the ABS/PETG blends and could simultaneously provide the blends with toughening, stiffening and hydrophilic effects.

Synthesis of magnetic Bi2O2CO3/ZnFe2O4 composite with improved photocatalytic activity and easy recyclability

NASA Astrophysics Data System (ADS)

Liu, Yumin; Ren, Hao; Lv, Hua; Guang, Jing; Cao, Yafei

2018-03-01

Magnetic Bi2O2CO3/ZnFe2O4 heterojunction photocatalysts with varying content of ZnFe2O4 were constructed by modifying Bi2O2CO3 nanosheets with mesoporous ZnFe2O4 nanoparticles. The photoactivity of the products was investigated by decomposing RhodamineB (RhB) and it was found that the photoactivity of Bi2O2CO3/ZnFe2O4 composite was closely related to the loading amount of ZnFe2O4. Under simulant sunlight irradiation, the optimum photoactivity of Bi2O2CO3/ZnFe2O4 composite was almost 2.3 and 2.1 times higher than that by bare ZnFe2O4 and Bi2O2CO3, respectively. The improved photoactivity resulted from the synergistic effect of Bi2O2CO3 and ZnFe2O4, which not only extended the photoabsorption region but also significantly facilitated the interfacial charge transfer. Besides the high photocatalytic performance, Bi2O2CO3/ZnFe2O4 composite also exhibited excellent stable and recycling properties, which enabled it have great potential in a long-term practical use.

Transmission electron microscopy and ab initio calculations to relate interfacial intermixing and the magnetism of core/shell nanoparticles

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

Chi, C.-C.; Hsiao, C.-H.; Ouyang, Chuenhou, E-mail: houyang@mx.nthu.edu.tw

2015-05-07

Significant efforts towards understanding bi-magnetic core-shell nanoparticles are underway currently as they provide a pathway towards properties unavailable with single-phased systems. Recently, we have demonstrated that the magnetism of γ-Fe2O3/CoO core-shell nanoparticles, in particular, at high temperatures, originates essentially from an interfacial doped iron-oxide layer that is formed by the migration of Co{sup 2+} from the CoO shell into the surface layers of the γ-Fe2O3 core [Skoropata et al., Phys. Rev. B 89, 024410 (2014)]. To examine directly the nature of the intermixed layer, we have used high-resolution transmission electron microscopy (HRTEM) and first-principles calculations to examine the impact ofmore » the core-shell intermixing at the atomic level. By analyzing the HRTEM images and energy dispersive spectra, the level and nature of intermixing was confirmed, mainly as doping of Co into the octahedral site vacancies of γ-Fe2O3. The average Co doping depths for different processing temperatures (150 °C and 235 °C) were 0.56 nm and 0.78 nm (determined to within 5% through simulation), respectively, establishing that the amount of core-shell intermixing can be altered purposefully with an appropriate change in synthesis conditions. Through first-principles calculations, we find that the intermixing phase of γ-Fe2O3 with Co doping is ferromagnetic, with even higher magnetization as compared to that of pure γ-Fe2O3. In addition, we show that Co doping into different octahedral sites can cause different magnetizations. This was reflected in a change in overall nanoparticle magnetization, where we observed a 25% reduction in magnetization for the 235 °C versus the 150 °C sample, despite a thicker intermixed layer.« less

Light triggered interfacial damage self-healing of poly(p-phenylene benzobisoxazole) fiber composites.

PubMed

Hu, Zhen; Shao, Qing; Huang, Yudong; Yu, Long; Zhang, Dayu; Xu, Xirong; Lin, Jing; Liu, Hu; Guo, Zhanhu

2018-05-04

The interfacial microcracks in the resin matrix composites are difficult to be detected and repaired. However, the self-healing concept provides opportunities to fabricate composites with unusual properties. In the present study, photothermal conversion Ag-Cu 2 S nanoparticles were immobilized onto poly(p-phenylene benzobisoxazole) (PBO) fibers via a polydopamine chemistry. Benefitting from the photothermal effects of Ag-Cu 2 S, the obtained PBO fibers (Ag-Cu 2 S-PBO) efficiently converted the light energy into heat under Xenon lamp irradiation. Then, single PBO fiber composites were prepared using thermoplastic polyurethane as the matrix. It was found that the interfacial damage caused by single fiber pull-out was simply self-healed by Xe light irradiation. This wonderful interfacial damage self-healing property was mainly attributed to the in situ heating generation via photothermal effects of Ag-Cu 2 S in the composite interface. This paper reports a novel strategy to construct advanced composites with light-triggered self-healing properties, which will provide inspiration for preparing high performance composite materials.

Light triggered interfacial damage self-healing of poly(p-phenylene benzobisoxazole) fiber composites

NASA Astrophysics Data System (ADS)

Hu, Zhen; Shao, Qing; Huang, Yudong; Yu, Long; Zhang, Dayu; Xu, Xirong; Lin, Jing; Liu, Hu; Guo, Zhanhu

2018-05-01

The interfacial microcracks in the resin matrix composites are difficult to be detected and repaired. However, the self-healing concept provides opportunities to fabricate composites with unusual properties. In the present study, photothermal conversion Ag-Cu2S nanoparticles were immobilized onto poly(p-phenylene benzobisoxazole) (PBO) fibers via a polydopamine chemistry. Benefitting from the photothermal effects of Ag-Cu2S, the obtained PBO fibers (Ag-Cu2S-PBO) efficiently converted the light energy into heat under Xenon lamp irradiation. Then, single PBO fiber composites were prepared using thermoplastic polyurethane as the matrix. It was found that the interfacial damage caused by single fiber pull-out was simply self-healed by Xe light irradiation. This wonderful interfacial damage self-healing property was mainly attributed to the in situ heating generation via photothermal effects of Ag-Cu2S in the composite interface. This paper reports a novel strategy to construct advanced composites with light-triggered self-healing properties, which will provide inspiration for preparing high performance composite materials.

Supertoughened Biobased Poly(lactic acid)-Epoxidized Natural Rubber Thermoplastic Vulcanizates: Fabrication, Co-continuous Phase Structure, Interfacial in Situ Compatibilization, and Toughening Mechanism.

PubMed

Wang, Youhong; Chen, Kunling; Xu, Chuanhui; Chen, Yukun

2015-09-10

In the presence of dicumyl peroxide (DCP), biobased thermoplastic vulcanizates (TPVs) composed of poly(lactic acid) (PLA) and epoxidized natural rubber (ENR) were prepared through dynamic vulcanization. Interfacial in situ compatibilization between PLA and ENR phases was confirmed by Fourier transform infrared spectroscopy (FT-IR). A novel "sea-sea" co-continuous phase in the PLA/ENR TPVs was observed through scanning electron microscopy (SEM) and differed from the typical "sea-island" morphology that cross-linked rubber particles dispersed in plastic matrix. A sharp, brittle-ductile transition occurred with 40 wt % of ENR, showing a significantly improved impact strength of 47 kJ/m(2), nearly 15 times that of the neat PLA and 2.6 times that of the simple blend with the same PLA/ENR ratio. Gel permeation chromatography (GPC) and dynamic mechanical analysis (DMA) results suggested that a certain amount of DCP was consumed in the PLA phase, causing a slight cross-linking or branching of PLA molecules. the effects of various DCP contents on the impact property were investigated. The toughening mechanism under impact testing was researched, and the influence factors for toughening were discussed.

Suppressed oxygen extraction and degradation of LiNi xMn yCo zO 2 cathodes at high charge cut-off voltages

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

Zheng, Jianming; Yan, Pengfei; Zhang, Jiandong

The capacity degradation mechanism in lithium nickel–manganese–cobalt oxide (NMC) cathodes (LiNi 1/3Mn 1/3Co 1/3O 2 (NMC 333) and LiNi 0.4Mn 0.4Co 0.2O 2 (NMC 442)) during high-voltage (cut-off of 4.8 V) operation has been investigated. In contrast to NMC 442, NMC 333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interfacial stability of NMC 333 was found to be correlatedmore » to its high Co content and the significant overlap between the Co 3+/4+ t 2g and O 2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems.« less

Enhancement of the Device Performance and the Stability with a Homojunction-structured Tungsten Indium Zinc Oxide Thin Film Transistor.

PubMed

Park, Hyun-Woo; Song, Aeran; Choi, Dukhyun; Kim, Hyung-Jun; Kwon, Jang-Yeon; Chung, Kwun-Bum

2017-09-14

Tungsten-indium-zinc-oxide thin-film transistors (WIZO-TFTs) were fabricated using a radio frequency (RF) co-sputtering system with two types of source/drain (S/D)-electrode material of conducting WIZO (homojunction structure) and the indium-tin oxide (ITO) (heterojunction structure) on the same WIZO active-channel layer. The electrical properties of the WIZO layers used in the S/D electrode and the active-channel layer were adjusted through oxygen partial pressure during the deposition process. To explain enhancements of the device performance and stability of the homojunction-structured WIZO-TFT, a systematic investigation of correlation between device performance and physical properties at the interface between the active layer and the S/D electrodes such as the contact resistance, surface/interfacial roughness, interfacial-trap density, and interfacial energy-level alignments was conducted. The homojunction-structured WIZO-TFT exhibited a lower contact resistance, smaller interfacial-trap density, and flatter interfacial roughness than the WIZO-TFT with the heterojunction structure. The 0.09 eV electron barrier of the homojunction-structured WIZO-TFT is lower than the 0.21 eV value that was obtained for the heterojunction-structured WIZO-TFT. This reduced electron barrier may be attributed to enhancements of device performance and stability, that are related to the carrier transport.

Improvement of the interfacial Dzyaloshinskii-Moriya interaction by introducing a Ta buffer layer

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

Kim, Nam-Hui; Jung, Jinyong; Cho, Jaehun

2015-10-05

We report systematic measurements of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) by employing Brillouin light scattering in Pt/Co/AlO{sub x} and Ta/Pt/Co/AlO{sub x} structures. By introducing a tantalum buffer layer, the saturation magnetization and the interfacial perpendicular magnetic anisotropy are significantly improved due to the better interface between heavy metal and ferromagnetic layer. From the frequency shift between Stokes- and anti-Stokes spin-waves, we successively obtain considerably larger iDM energy densities (D{sub max} = 1.65 ± 0.13 mJ/m{sup 2} at t{sub Co} = 1.35 nm) upon adding the Ta buffer layer, despite the nominally identical interface materials. Moreover, the energy density shows an inverse proportionality with the Co layer thickness,more » which is the critical clue that the observed iDMI is indeed originating from the interface between the Pt and Co layers.« less

Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

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

Liang, S. H.; Tao, L. L.; Liu, D. P., E-mail: dpliu@iphy.ac.cn

We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ tomore » 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.« less

Kinetic and structural studies, origins of selectivity, and interfacial charge transfer in the artificial photosynthesis of CO

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

Smieja, Jonathan M.; Benson, Eric E.; Kumar, Bhupendra

The effective design of an artificial photosynthetic system entails the optimization of several important interactions. Herein we report stopped-flow UV-Vis spectroscopy, X-ray crystallography, DFT, and electrochemical kinetic studies of the Re(bipy-tBu)(CO)3(L) catalyst system. A remarkable selectivity for CO2 over H+ was observed by stopped-flow UV-Vis spectroscopy of [Re(bipy-tBu)(CO)3]-. The pseudo-first order rate constant for the reaction with 10 mM CO2 in THF is 35 s-1. This is ca. 15-20 times faster than the reactions with water or methanol at the same concentration in THF. X-ray crystallography and DFT studies of the doubly-reduced anionic species suggest that the HOMO has mixedmore » metal-ligand character rather than being purely dz 2, which is thought to aid catalytic selectivity by favoring binding of CO2 over H+. Electrocatalytic studies performed with the addition of Brönsted acids reveal a primary H/D kinetic isotope effect, indicating that transfer of protons to Re-CO2 is involved in the rate limiting step. Lastly, the effects of electrode surface modification on interfacial electron transfer between a semiconductor and catalyst were investigated and found to affect the observed catalytic rates up to seven-fold, indicating that the properties of the electrode surface should not be overlooked when developing a homogeneous artificial photosynthetic system. This research was supported at the University of Washington, Seattle by the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry (for a fellowship to A. J. M. M.), and, for funds to purchase the stopped-flow instrument, the U.S. National Institutes of Health 13 (Grant GM-50422 to JMM), and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.« less

Hybrid of Co(3)Sn(2)@Co nanoparticles and nitrogen-doped graphene as a lithium ion battery anode.

PubMed

Mahmood, Nasir; Zhang, Chenzhen; Liu, Fei; Zhu, Jinghan; Hou, Yanglong

2013-11-26

A facile strategy was designed for the fabrication of hybrid of Co3Sn2@Co nanoparticles (NPs) and nitrogen-doped graphene (NG) sheets through a hydrothermal synthesis, followed by annealing process. Core-shell architecture of Co3Sn2@Co pin on NG is designed for the dual encapsulation of Co3Sn2 with adaptable ensembles of Co and NG to address the structural and interfacial stability concerns facing tin-based anodes. In the resulted unique architecture of Co3Sn2@Co-NG hybrid, the sealed cobalt cover prevents the direct exposer of Sn with electrolyte because of encapsulated structure and keeps the structural and interfacial integrity of Co3Sn2. However, the elastically strong, flexible and conductive NG overcoat accommodates the volume changes and therefore brings the structural and electrical stabilization of Co3Sn2@Co NPs. As a result, Co3Sn2@Co-NG hybrid exhibits extraordinary reversible capacity of 1615 mAh/g at 250 mA/g after 100 cycles with excellent capacity retention of 102%. The hybrid bears superior rate capability with reversible capacity of 793.9 mAh/g at 2500 mA/g and Coulombic efficiency nearly 100%.

Ultralow 1/f Noise in a Heterostructure of Superconducting Epitaxial Cobalt Disilicide Thin Film on Silicon.

PubMed

Chiu, Shao-Pin; Yeh, Sheng-Shiuan; Chiou, Chien-Jyun; Chou, Yi-Chia; Lin, Juhn-Jong; Tsuei, Chang-Chyi

2017-01-24

High-precision resistance noise measurements indicate that the epitaxial CoSi 2 /Si heterostructures at 150 and 2 K (slightly above its superconducting transition temperature T c of 1.54 K) exhibit an unusually low 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds to an upper limit of Hooge constant γ ≤ 3 × 10 -6 , about 100 times lower than that of single-crystalline aluminum films on SiO 2 capped Si substrates. Supported by high-resolution cross-sectional transmission electron microscopy studies, our analysis reveals that the 1/f noise is dominated by excess interfacial Si atoms and their dimer reconstruction induced fluctuators. Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsically rare at the epitaxial CoSi 2 /Si(100) interface, giving limited trapping-detrapping centers for localized charges. With its excellent normal-state properties, CoSi 2 has been used in silicon-based integrated circuits for decades. The intrinsically low noise properties discovered in this work could be utilized for developing quiet qubits and scalable superconducting circuits for future quantum computing.

Interface roughness induced asymmetric magnetic property in sputter-deposited Co/CoO/Co exchange coupled trilayers

NASA Astrophysics Data System (ADS)

Wang, J.; Sannomiya, T.; Shi, J.; Nakamura, Y.

2012-04-01

The effect of interface roughness on magnetic properties of exchange coupled polycrystalline Co/CoO(tAF)/Co trilayers has been investigated by varying antiferromagnetic layer (CoO) thickness. It has been found that the upper CoO/Co interface becomes rougher with increasing CoO layer thickness, resulting in stronger exchange bias of the upper interface than the lower one. The interfacial exchange coupling is strengthened by the increase of defect-generated uncompensated antiferromagnetic spins; such spins form coupling with spins in the Co layer at the interface. As a result, the CoO layer thickness dependence of exchange bias is much enhanced for the upper Co layer. The transition from anisotropic magnetoresistance to isotropic magnetoresistance for the top Co layer has also been found. This could be attributed to the defects, probably partial thin oxide layers, between Co grains in the top Co layer that leads a switch from spin-orbit scattering related magnetoresistance to spin-dependent electron scattering dominated magnetoresistance.

Interfacial contribution to the dielectric response in semiconducting LaBiMn4/3Co2/3O6

NASA Astrophysics Data System (ADS)

Filippi, M.; Kundys, B.; Ranjith, R.; Kundu, Asish K.; Prellier, W.

2008-05-01

Impedance measurements have been performed on a sintered polycrystalline sample of the perovskite LaBiMn4/3Co2/3O6. Colossal dielectric permittivity is often measured in this class of semiconducting materials as a result of extrinsic factors. Our results show that a large offset in the capacitance, measured on a series of samples with different thickness, is due to the interfacial polarization. This contribution can then be removed from the data, creating a general procedure for dielectric measurements in semiconducting samples.

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

NASA Astrophysics Data System (ADS)

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

2013-08-01

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

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.

Simulating the Effect of Contact Atomic Structure on the Spin-Dependent Transport Properties of Gold Nanowires

NASA Astrophysics Data System (ADS)

Ansarino, Masoud; Ravan, Bahram Abedi

Some experimental research works report on the superb magnetoresistance properties of magnetically contacted gold nanowires. With the intention of trying to understand the spin-dependent transport mechanism of these structures, in this work we have used first-principles density functional theory methods to investigate effects of interface structure on the spintronic characteristics of Au nanowires. Monatomic chains of gold are sandwiched between two ferromagnetic electrodes of Fe and by substituting the interfacial Fe atoms with some other transition metal elements (including Cr, Mn, Co and Ni) the occurrence of possible enhancement in the electronic conductance and magnetoresistance characteristics of the device are investigated. It is observed that replacing the interfacial atoms with Ni raises the junction’s magnetoresistance ratio to as high as 2000%.

pH-responsive ion transport in polyelectrolyte multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA) bearing strong- and weak anionic groups.

PubMed

Maza, Eliana; Tuninetti, Jimena S; Politakos, Nikolaos; Knoll, Wolfgang; Moya, Sergio; Azzaroni, Omar

2015-11-28

The layer-by-layer construction of interfacial architectures displaying stimuli-responsive control of mass transport is attracting increasing interest in materials science. In this work, we describe the creation of interfacial architectures displaying pH-dependent ionic transport properties which until now have not been observed in polyelectrolyte multilayers. We describe a novel approach to create pH-controlled ion-rectifying systems employing polyelectrolyte multilayers assembled from a copolymer containing both weakly and strongly charged pendant groups, poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA), alternately deposited with poly(diallyldimethylammonium chloride) (PDADMAC). The conceptual framework is based on the very contrasting and differential interactions of PSS and MA units with PDADMAC. In our setting, sulfonate groups play a structural role by conferring stability to the multilayer due to the strong electrostatic interactions with the polycations, while the weakly interacting MA groups remain "silent" within the film and then act as on-demand pH-responsive units. When these multilayers are combined with a strong cationic capping layer that repels the passage of cationic probes, a pH-gateable rectified transport of anions is observed. Concomitantly, we also observed that these functional properties are significantly affected when multilayers are subjected to extensive pH cycling as a consequence of irreversible morphological changes taking place in the film. We envision that the synergy derived from combining weak and strong interactions within the same multilayer will play a key role in the construction of new interfacial architectures displaying tailorable ion transport properties.

Integrated CO2 capture-fixation chemistry via interfacial ionic liquid catalyst in laminar gas/liquid flow

NASA Astrophysics Data System (ADS)

Vishwakarma, Niraj K.; Singh, Ajay K.; Hwang, Yoon-Ho; Ko, Dong-Hyeon; Kim, Jin-Oh; Babu, A. Giridhar; Kim, Dong-Pyo

2017-03-01

Simultaneous capture of carbon dioxide (CO2) and its utilization with subsequent work-up would significantly enhance the competitiveness of CO2-based sustainable chemistry over petroleum-based chemistry. Here we report an interfacial catalytic reaction platform for an integrated autonomous process of simultaneously capturing/fixing CO2 in gas-liquid laminar flow with subsequently providing a work-up step. The continuous-flow microreactor has built-in silicon nanowires (SiNWs) with immobilized ionic liquid catalysts on tips of cone-shaped nanowire bundles. Because of the superamphiphobic SiNWs, a stable gas-liquid interface maintains between liquid flow of organoamines in upper part and gas flow of CO2 in bottom part of channel. The intimate and direct contact of the binary reagents leads to enhanced mass transfer and facilitating reactions. The autonomous integrated platform produces and isolates 2-oxazolidinones and quinazolines-2,4(1H,3H)-diones with 81-97% yields under mild conditions. The platform would enable direct CO2 utilization to produce high-valued specialty chemicals from flue gases without pre-separation and work-up steps.

Integrated CO2 capture-fixation chemistry via interfacial ionic liquid catalyst in laminar gas/liquid flow.

PubMed

Vishwakarma, Niraj K; Singh, Ajay K; Hwang, Yoon-Ho; Ko, Dong-Hyeon; Kim, Jin-Oh; Babu, A Giridhar; Kim, Dong-Pyo

2017-03-06

Simultaneous capture of carbon dioxide (CO 2 ) and its utilization with subsequent work-up would significantly enhance the competitiveness of CO 2 -based sustainable chemistry over petroleum-based chemistry. Here we report an interfacial catalytic reaction platform for an integrated autonomous process of simultaneously capturing/fixing CO 2 in gas-liquid laminar flow with subsequently providing a work-up step. The continuous-flow microreactor has built-in silicon nanowires (SiNWs) with immobilized ionic liquid catalysts on tips of cone-shaped nanowire bundles. Because of the superamphiphobic SiNWs, a stable gas-liquid interface maintains between liquid flow of organoamines in upper part and gas flow of CO 2 in bottom part of channel. The intimate and direct contact of the binary reagents leads to enhanced mass transfer and facilitating reactions. The autonomous integrated platform produces and isolates 2-oxazolidinones and quinazolines-2,4(1H,3H)-diones with 81-97% yields under mild conditions. The platform would enable direct CO 2 utilization to produce high-valued specialty chemicals from flue gases without pre-separation and work-up steps.

Integrated CO2 capture-fixation chemistry via interfacial ionic liquid catalyst in laminar gas/liquid flow

PubMed Central

Vishwakarma, Niraj K.; Singh, Ajay K.; Hwang, Yoon-Ho; Ko, Dong-Hyeon; Kim, Jin-Oh; Babu, A. Giridhar; Kim, Dong-Pyo

2017-01-01

Simultaneous capture of carbon dioxide (CO2) and its utilization with subsequent work-up would significantly enhance the competitiveness of CO2-based sustainable chemistry over petroleum-based chemistry. Here we report an interfacial catalytic reaction platform for an integrated autonomous process of simultaneously capturing/fixing CO2 in gas–liquid laminar flow with subsequently providing a work-up step. The continuous-flow microreactor has built-in silicon nanowires (SiNWs) with immobilized ionic liquid catalysts on tips of cone-shaped nanowire bundles. Because of the superamphiphobic SiNWs, a stable gas–liquid interface maintains between liquid flow of organoamines in upper part and gas flow of CO2 in bottom part of channel. The intimate and direct contact of the binary reagents leads to enhanced mass transfer and facilitating reactions. The autonomous integrated platform produces and isolates 2-oxazolidinones and quinazolines-2,4(1H,3H)-diones with 81–97% yields under mild conditions. The platform would enable direct CO2 utilization to produce high-valued specialty chemicals from flue gases without pre-separation and work-up steps. PMID:28262667

Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

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

Streubel, Robert; Lambert, Charles-Henri; Kent, Noah

Inversion symmetry breaking has become a vital research area in modern magnetism with phenomena including the Rashba effect, spin Hall effect, and the Dzyaloshinskii-Moriya interaction (DMI)-a vector spin exchange. The latter one may stabilize chiral spin textures with topologically nontrivial properties, such as Skyrmions. So far, chiral spin textures have mainly been studied in helimagnets and thin ferromagnets with heavy-element capping. Here, the concept of chirality driven by interfacial DMI is generalized to complex multicomponent systems and demonstrated on the example of chiral ferrimagnetism in amorphous GdCo films. Utilizing Lorentz microscopy and X-ray magnetic circular dichroism spectroscopy, and tailoring thickness,more » capping, and rare-earth composition, reveal that 2 nm thick GdCo films preserve ferrimagnetism and stabilize chiral domain walls. Finally, the type of chiral domain walls depends on the rare-earth composition/saturation magnetization, enabling a possible temperature control of the intrinsic properties of ferrimagnetic domain walls.« less

Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

DOE PAGES

Streubel, Robert; Lambert, Charles-Henri; Kent, Noah; ...

2018-05-23

Inversion symmetry breaking has become a vital research area in modern magnetism with phenomena including the Rashba effect, spin Hall effect, and the Dzyaloshinskii-Moriya interaction (DMI)-a vector spin exchange. The latter one may stabilize chiral spin textures with topologically nontrivial properties, such as Skyrmions. So far, chiral spin textures have mainly been studied in helimagnets and thin ferromagnets with heavy-element capping. Here, the concept of chirality driven by interfacial DMI is generalized to complex multicomponent systems and demonstrated on the example of chiral ferrimagnetism in amorphous GdCo films. Utilizing Lorentz microscopy and X-ray magnetic circular dichroism spectroscopy, and tailoring thickness,more » capping, and rare-earth composition, reveal that 2 nm thick GdCo films preserve ferrimagnetism and stabilize chiral domain walls. Finally, the type of chiral domain walls depends on the rare-earth composition/saturation magnetization, enabling a possible temperature control of the intrinsic properties of ferrimagnetic domain walls.« less

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.

Frequency and temperature dependence of dielectric and ac electrical properties of NiFe2O4-ZnO multiferroic nanocomposite

NASA Astrophysics Data System (ADS)

Dutta, Papia; Mandal, S. K.; Dey, P.; Nath, A.

2018-04-01

We have presented the ac electrical properties and dielectric studies of 0.5 NiFe2O4 - 0.5 ZnO multiferroic nanocomposites prepared through low temperature "pyrophoric reaction process". Structural characterization has been carried out through X-ray diffraction technique, which shows the co-existence of both the phases of the nanocomposites. The ac electrical properties of nanocomposites have been studied employing impedance spectroscopy technique. The impedance value is found to increase with increase in magnetic field attributing the magnetostriction property of the composites. Dielectric constant is found to decrease with both the increase in magnetic fields and temperatures. Studies of dielectric constant reveal the Maxwell Wagner interfacial polarization at low frequency regime. Relaxation frequency as a function of magnetic fields and temperatures is found to shift towards the high frequency region.

Insights into electrode/electrolyte interfacial processes and the effect of nanostructured cobalt oxides loading on graphene-based hybrids by scanning electrochemical microscopy

NASA Astrophysics Data System (ADS)

Gupta, Sanju; Carrizosa, Sara B.

2016-12-01

Nanostructured cobalt oxide polymorphs (CoO and Co3O4) deposited via electrodeposition allowed optimal loading on supercapacitive graphene nanosheets producing a set of graphene-based hybrids namely, CoO/GO, CoO/ErGO, Co3O4/GO, Co3O4/rGO, and Co3O4/ErGO, as pseudocapacitive electrochemical electrodes. We gained fundamental insights into the complex physicochemical interfacial processes at electrode surfaces and electrode/electrolyte (or solid/liquid) interfaces by scanning electrochemical microscopy operating in the feedback probe approach and imaging modes while monitoring and mapping the redox probe (re)activity behavior. We determined the various experimental descriptors including diffusion coefficient, electron transfer rate, and electroactive site distribution on electrodes. We emphasize the interplay of (1) heterogeneous basal and edge plane active sites, (2) graphene surface functional moieties (conducting/semiconducting), and (3) crystalline spinel cobalt oxides (semiconducting/insulating) coated graphene, reinforcing the available electron density of states in the vicinity of the Fermi level contributing to higher electroactivity, faster interfacial diffusion, and shorter distances for electron transfer, facilitated through molecular and chemical bridges obtained by electrodeposition as compared with the physical deposition.

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

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.

Suppressed oxygen extraction and degradation of LiNixMnyCozO2 cathodes at high charge cut-off voltages

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

Zheng, Jianming; Yan, Pengfei; Zhang, Jiandong

The capacity degradation mechanism in lithium nickel-manganese-cobalt oxide (NMC) cathodes (LiNi1/3Mn1/3Co1/3O2 (NMC333) and LiNi0.4Mn0.4Co0.2O2 (NMC442)) during high-voltage (cut-off of 4.8 V) operation has been investigated. In contrast to NMC442, NMC333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interfacial stability of NMC333 was found to be correlated to its high Co content and the significant overlap between the Co3+/4+ t(2g)more » and O2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems« less

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.

Combination of first-principles molecular dynamics and XANES simulations for LiCoO2-electrolyte interfacial reactions in a lithium-ion battery

NASA Astrophysics Data System (ADS)

Tamura, Tomoyuki; Kohyama, Masanori; Ogata, Shuji

2017-07-01

We performed a first-principles molecular dynamics (FPMD) simulation of the interfacial reactions between a LiCoO2 electrode and a liquid ethylene carbonate (EC) electrolyte. For configurations during the FPMD simulation, we also performed first-principles Co K-edge x-ray absorption near-edge structure (XANES) simulations, which can properly reproduce the bulk and surface spectra of LiCoO2. We observed strong absorption of an EC molecule on the LiCoO2 {110} surface, involving ring opening of the molecule, bond formation between oxygen atoms in the molecule and surface Co ions, and emission of one surface Li ion, while all the surface Co ions remain Co3 +. The surface Co ions having the bond with an oxygen atom in the molecule showed remarkable changes in simulated K-edge spectra which are similar to those of the in situ observation under electrolyte soaking [D. Takamatsu et al., Angew. Chem., Int. Ed. 51, 11597 (2012), 10.1002/anie.201203910]. Thus, the local environmental changes of surface Co ions due to the reactions with an EC molecule can explain the experimental spectrum changes.

Effect of Mn2+ doping on structural, electrical transport and dielectric properties of CoFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Ansari, Mohd Mohsin Nizam; Khan, Shakeel; Bhargava, Richa; Ahmad, Naseem

2018-05-01

Manganese substituted cobalt ferrites, Co1-xMnxFe2O4 (0.0, 0.1, 0.2, 0.3 and 0.4) were successfully synthesized by sol-gel method. XRD analysis confirmed the formation of a single-phase cubic spinel structures having Fd-3m space group and crystallite size is found to be in the range of 12.9 - 15.5 nm. The lattice parameter increased from 8.4109 Å to 8.4531 Å with increasing Mn2+ ion doping. Dielectric constant (ɛ'), dielectric loss (tanδ) and ac conductivity (σac) were analyzed at room temperature as a function of frequency (42 Hz to 5 MHz) and the behavior is explained on the basis of Maxwell-Wagner interfacial polarization. DC electrical resistivity measurements were carried out by two-probe method. DC electrical resistivity decreases with increase in temperature confirms the semiconducting nature of the samples. Impedance spectroscopy method has been used to understand the conduction mechanism and the effect of grains and grain boundary on the electrical properties of the materials.

A data driven model for the impact of IFT and density variations on CO2 storage capacity in geologic formations

NASA Astrophysics Data System (ADS)

Nomeli, Mohammad A.; Riaz, Amir

2017-09-01

Carbon dioxide (CO2) storage in depleted hydrocarbon reservoirs and deep saline aquifers is one of the most promising solutions for decreasing CO2 concentration in the atmosphere. One of the important issues for CO2 storage in subsurface environments is the sealing efficiency of low-permeable cap-rocks overlying potential CO2 storage reservoirs. Though we focus on the effect of IFT in this study as a factor influencing sealing efficiency or storage capacity, other factors such as interfacial interactions, wettability, pore radius and interfacial mass transfer also affect the mobility and storage capacity of CO2 phase in the pore space. The study of the variation of IFT is however important because the pressure needed to penetrate a pore depends on both the pore size and the interfacial tension. Hence small variations in IFT can affect flow across a large population of pores. A novel model is proposed to find the IFT of the ternary systems (CO2/brine-salt) in a range of temperatures (300-373 K), pressures (50-250 bar), and up to 6 molal salinity applicable to CO2 storage in geological formations through a multi-variant non-linear regression of experimental data. The method uses a general empirical model for the quaternary system CO2/brine-salts that can be made to coincide with experimental data for a variety of solutions. We introduce correction parameters into the model, which compensates for uncertainties, and enforce agreement with experimental data. The results for IFT show a strong dependence on temperature, pressure, and salinity. The model has been found to describe the experimental data in the appropriate parameter space with reasonable precision. Finally, we use the new model to evaluate the effects of formation depth on the actual efficiency of CO2 storage. The results indicate that, in the case of CO2 storage in deep subsurface environments as a global-warming mitigation strategy, CO2 storage capacity increases with reservoir depth.

Influence of CO annealing in metal-oxide-semiconductor capacitors with SiO2 films thermally grown on Si and on SiC

NASA Astrophysics Data System (ADS)

Pitthan, E.; dos Reis, R.; Corrêa, S. A.; Schmeisser, D.; Boudinov, H. I.; Stedile, F. C.

2016-01-01

Understanding the influence of SiC reaction with CO, a by-product of SiC thermal oxidation, is a key point to elucidate the origin of electrical defects in SiC metal-oxide-semiconductor (MOS) devices. In this work, the effects on electrical, structural, and chemical properties of SiO2/Si and SiO2/SiC structures submitted to CO annealing were investigated. It was observed that long annealing times resulted in the incorporation of carbon from CO in the Si substrate, followed by deterioration of the SiO2/Si interface, and its crystallization as SiC. Besides, this incorporated carbon remained in the Si surface (previous SiO2/Si region) after removal of the silicon dioxide film by HF etching. In the SiC case, an even more defective surface region was observed due to the CO interaction. All MOS capacitors formed using both semiconductor materials presented higher leakage current and generation of positive effective charge after CO annealings. Such results suggest that the negative fixed charge, typically observed in SiO2/SiC structures, is not originated from the interaction of the CO by-product, formed during SiC oxidation, with the SiO2/SiC interfacial region.

Interfacial Properties of Germanium Nitride Dielectric Layers on Germanium.

DTIC Science & Technology

1986-09-30

choice or a process for growing Ge N , layers on germa - nium. a number of workers have employed various de. mum. posited layers on germanium. While...N00014-84-K-0459 V6 Office of Naval Research (Mr. Max N . Yoder, Electronic Division) 4: 800 North Quincy Street Arlington, Virginia 22217 Interfacial...z4) 3 Co0 C14 CM- Lfl n X sj E 𔃺 01 N S) Li (m* m n1 Ln m CU OT X)-(, (L 0IX) D/13si E- 1 0n CtZ) 4-4C ~ IN I- I L L0tX Cd) JN N in - Growth of

Microfluidic study for investigating migration and residual phenomena of supercritical CO2 in porous media

NASA Astrophysics Data System (ADS)

Park, Gyuryeong; Wang, Sookyun; Lee, Minhee; Um, Jeong-Gi; Kim, Seon-Ok

2017-04-01

The storage of CO2 in underground geological formation such as deep saline aquifers or depleted oil and gas reservoirs is one of the most promising technologies for reducing the atmospheric CO2 release. The processes in geological CO2 storage involves injection of supercritical CO2 (scCO2) into porous formations saturated with brine and initiates CO2 flooding with immiscible displacement. The CO2 migration and porewater displacement within geological formations, and , consequentially, the storage efficiency are governed by the interaction of fluid and rock properties and are affected by the interfacial tension, capillarity, and wettability in supercritical CO2-brine-mineral systems. This study aims to observe the displacement pattern and estimate storage efficiency by using micromodels. This study aims to conduct scCO2 injection experiments for visualization of distribution of injected scCO2 and residual porewater in transparent pore networks on microfluidic chips under high pressure and high temperature conditions. In order to quantitatively analyze the porewater displacement by scCO2 injection under geological CO2 storage conditions, the images of invasion patterns and distribution of CO2 in the pore network are acquired through a imaging system with a microscope. The results from image analysis were applied in quantitatively investigating the effects of major environmental factors and scCO2 injection methods on porewater displacement process by scCO2 and storage efficiency. The experimental observation results could provide important fundamental information on capillary characteristics of reservoirs and improve our understanding of CO2 sequestration progress.

Heterostructured WS2 /CH3 NH3 PbI3 Photoconductors with Suppressed Dark Current and Enhanced Photodetectivity.

PubMed

Ma, Chun; Shi, Yumeng; Hu, Weijin; Chiu, Ming-Hui; Liu, Zhixiong; Bera, Ashok; Li, Feng; Wang, Hong; Li, Lain-Jong; Wu, Tom

2016-05-01

Heterostructured photoconductors based on hybrid perovskites and 2D transition-metal dichalcogenides are fabricated and characterized. Due to the superior properties of CH3 NH3 PbI3 and WS2 , as well as the efficient interfacial charge transfer, such photoconductors show high performance with on/off ratio of ≈10(5) and responsivity of ≈17 A W(-1) . Furthermore, the response times of the heterostructured photoconductors are four orders of magnitude faster compared to the counterpart of a perovskite single layer. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electroforming free controlled bipolar resistive switching in Al/CoFe2O4/FTO device with self-compliance effect

NASA Astrophysics Data System (ADS)

Munjal, Sandeep; Khare, Neeraj

2018-02-01

Controlled bipolar resistive switching (BRS) has been observed in nanostructured CoFe2O4 (CFO) films using an Al (aluminum)/CoFe2O4/FTO (fluorine-doped tin oxide) device. The fabricated device shows electroforming-free uniform BRS with two clearly distinguished and stable resistance states without any application of compliance current, with a resistance ratio of the high resistance state (HRS) and the low resistance state (LRS) of >102. Small switching voltage (<1 volt) and lower current in both the resistance states confirm the fabrication of a low power consumption device. In the LRS, the conduction mechanism was found to be Ohmic in nature, while the high-resistance state (HRS/OFF state) was governed by the space charge-limited conduction mechanism, which indicates the presence of an interfacial layer with an imperfect microstructure near the top Al/CFO interface. The device shows nonvolatile behavior with good endurance properties, an acceptable resistance ratio, uniform resistive switching due to stable, less random filament formation/rupture, and a control over the resistive switching properties by choosing different stop voltages, which makes the device suitable for its application in future nonvolatile resistive random access memory.

A multifunctional biphasic water splitting catalyst tailored for integration with high-performance semiconductor photoanodes

NASA Astrophysics Data System (ADS)

Yang, Jinhui; Cooper, Jason K.; Toma, Francesca M.; Walczak, Karl A.; Favaro, Marco; Beeman, Jeffrey W.; Hess, Lucas H.; Wang, Cheng; Zhu, Chenhui; Gul, Sheraz; Yano, Junko; Kisielowski, Christian; Schwartzberg, Adam; Sharp, Ian D.

2017-03-01

Artificial photosystems are advanced by the development of conformal catalytic materials that promote desired chemical transformations, while also maintaining stability and minimizing parasitic light absorption for integration on surfaces of semiconductor light absorbers. Here, we demonstrate that multifunctional, nanoscale catalysts that enable high-performance photoelectrochemical energy conversion can be engineered by plasma-enhanced atomic layer deposition. The collective properties of tailored Co3O4/Co(OH)2 thin films simultaneously provide high activity for water splitting, permit efficient interfacial charge transport from semiconductor substrates, and enhance durability of chemically sensitive interfaces. These films comprise compact and continuous nanocrystalline Co3O4 spinel that is impervious to phase transformation and impermeable to ions, thereby providing effective protection of the underlying substrate. Moreover, a secondary phase of structurally disordered and chemically labile Co(OH)2 is introduced to ensure a high concentration of catalytically active sites. Application of this coating to photovoltaic p+n-Si junctions yields best reported performance characteristics for crystalline Si photoanodes.

Nanoscale Insight and Control of Structural and Electronic Properties of Organic Semiconductor / Metal Interfaces

NASA Astrophysics Data System (ADS)

Maughan, Bret

Organic semiconductor interfaces are promising materials for use in next-generation electronic and optoelectronic devices. Current models for metal-organic interfacial electronic structure and dynamics are inadequate for strongly hybridized systems. This work aims to address this issue by identifying the factors most important for understanding chemisorbed interfaces with an eye towards tuning the interfacial properties. Here, I present the results of my research on chemisorbed interfaces formed between thin-films of phthalocyanine molecules grown on monocrystalline Cu(110). Using atomically-resolved nanoscale imaging in combination with surface-sensitive photoemission techniques, I show that single-molecule level interactions control the structural and electronic properties of the interface. I then demonstrate that surface modifications aimed at controlling interfacial interactions are an effective way to tailor the physical and electronic structure of the interface. This dissertation details a systematic investigation of the effect of molecular and surface functionalization on interfacial interactions. To understand the role of molecular structure, two types of phthalocyanine (Pc) molecules are studied: non-planar, dipolar molecules (TiOPc), and planar, non-polar molecules (H2Pc and CuPc). Multiple adsorption configurations for TiOPc lead to configuration-dependent self-assembly, Kondo screening, and electronic energy-level alignment. To understand the role of surface structure, the Cu(110) surface is textured and passivated by oxygen chemisorption prior to molecular deposition, which gives control over thin-film growth and interfacial electronic structure in H2Pc and CuPc films. Overall, the work presented here demonstrates a method for understanding interfacial electronic structure of strongly hybridized interfaces, an important first step towards developing more robust models for metal-organic interfaces, and reliable, predictive tuning of interfacial properties.

Influence of pH and fuels on the combustion synthesis, structural, morphological, electrical and magnetic properties of CoFe{sub 2}O{sub 4} nanoparticles

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

Shanmugavani, A.; Selvan, R.Kalai, E-mail: selvankram@buc.edu.in; Layek, Samar

2015-11-15

Nanocrystalline spinel cobalt ferrite particles are synthesized by simple combustion method using aspartic acid and glycine as fuels. The single phase cubic structure of CoFe{sub 2}O{sub 4} is revealed through X-ray diffraction analysis (XRD). Further the Rietveld refinement confirms the formation of inverse spinel structure of CoFe{sub 2}O{sub 4}. The characteristic functional groups of Co–O and Fe–O are identified from Fourier Transform Infrared (FT-IR) analysis. Uniform distribution of of nearly spherical particles with the size range of 40–80 nm is identified through field emission scanning electron microscope (FESEM) images. The calculated DC conductivity is 1.469 × 10{sup −7} and 2.214more » × 10{sup −8} S cm{sup −1}, for CoFe{sub 2}O{sub 4} synthesized using aspartic acid and glycine, respectively. The dielectric behavior obeys the Maxwell–Wagner interfacial polarization. The ferromagnetic behavior of CoFe{sub 2}O{sub 4} is identified using VSM analysis and the calculated coercivity is 27 Oe and saturation magnetization is 68 emu/g.« less

Interfacial activity of polymeric surfactants at the polystyrene-carbon dioxide interface

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

Harrison, K.L.; Rocha, S.R.P. da; Yates, M.Z.

1998-11-24

The reduction of the interfacial tension at the polystyrene (PS, M{sub n} = 1850)-supercritical CO{sub 2} interface is reported for poly(1,1-dihydroperfluorooctyl acrylate)(PFOA) and the block copolymers PS-b-PFOA(3.7K/27K) and PS-b-poly(dimethylsiloxane) (PDMS) (2K/16K, 500/10K) at 45 C. PS-b-PDMS (2K/16K) lowers the interfacial tension to 0.5 dyn/cm at 45 C and 238 bar, more than that of any of the other copolymers. On the basis of the dynamics of the lowering of the interfacial tension, the apparent diffusion coefficient of PS-b-PDMS (2K/16K) is 8 {times} 10{sup {minus}6} cm{sup 2}/s. The critical micelle concentration of PS-b-PFOA (3.7K/27K) is 9 {times} 10{sup {minus}4} wt %.more » Whereas both the PDMS- and PFOA-based copolymers studied adsorb on the PS surface, PS-b-PFOA is much more effective in stabilizing the PS emulsions. The difference in stabilization is discussed in terms of the surfactant adsorption and the interactions of the anchor and buoy blocks with CO{sub 2} and the PS surface.« less

CL-20/DNB co-crystal based PBX with PEG: molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Zhang, Jiang; Gao, Pei; Xiao, Ji Jun; Zhao, Feng; Xiao, He Ming

2016-12-01

Molecular dynamics simulation was carried out for CL-20/DNB co-crystal based PBX (polymer-bonded explosive) blended with polymer PEG (polyethylene glycol). In this paper, the miscibility of the PBX models is investigated through the calculated binding energy. Pair correlation function (PCF) analysis is applied to study the interaction of the interface structures in the PBX models. The mechanical properties of PBXs are also discussed to understand the change of the mechanical properties after adding the polymer. Moreover, the calculated diffusion coefficients of the interfacial explosive molecules are used to discuss the dispersal ability of CL-20 and DNB molecules in the interface layer.

Facile synthesis of mesoporous spinel NiCo2O4 nanostructures as highly efficient electrocatalysts for urea electro-oxidation

NASA Astrophysics Data System (ADS)

Ding, Rui; Qi, Li; Jia, Mingjun; Wang, Hongyu

2014-01-01

Mesoporous spinel nickel cobaltite (NiCo2O4) nanostructures were synthesized via a facile chemical deposition method coupled with a simple post-annealing process. The physicochemical properties were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. The electrocatalytic performances were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo2O4 materials exhibit typical agglomerate mesoporous nanostructures with a large surface area (190.1 m2 g-1) and high mesopore volume (0.943 cm3 g-1). Remarkably, the NiCo2O4 shows much higher catalytic activity, lower overpotential, better stability and greater tolerance towards urea electro-oxidation compared to those of cobalt oxide (Co3O4) synthesized by the same procedure. The NiCo2O4 electrode delivers a current density of 136 mA cm-2 mg-1 at 0.7 V (vs. Hg/HgO) in 1 M KOH and 0.33 M urea electrolytes accompanied with a desirable stability. The impressive electrocatalytic activity is largely ascribed to the high intrinsic electronic conductivity, superior mesoporous nanostructures and rich surface Ni active species of the NiCo2O4 materials, which can largely boost the interfacial electroactive sites and charge transfer rates for urea electro-oxidation, indicating promising applications in future wastewater remediation, hydrogen production and fuel cells.Mesoporous spinel nickel cobaltite (NiCo2O4) nanostructures were synthesized via a facile chemical deposition method coupled with a simple post-annealing process. The physicochemical properties were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. The electrocatalytic performances were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo2O4 materials exhibit typical agglomerate mesoporous nanostructures with a large surface area (190.1 m2 g-1) and high mesopore volume (0.943 cm3 g-1). Remarkably, the NiCo2O4 shows much higher catalytic activity, lower overpotential, better stability and greater tolerance towards urea electro-oxidation compared to those of cobalt oxide (Co3O4) synthesized by the same procedure. The NiCo2O4 electrode delivers a current density of 136 mA cm-2 mg-1 at 0.7 V (vs. Hg/HgO) in 1 M KOH and 0.33 M urea electrolytes accompanied with a desirable stability. The impressive electrocatalytic activity is largely ascribed to the high intrinsic electronic conductivity, superior mesoporous nanostructures and rich surface Ni active species of the NiCo2O4 materials, which can largely boost the interfacial electroactive sites and charge transfer rates for urea electro-oxidation, indicating promising applications in future wastewater remediation, hydrogen production and fuel cells. Electronic supplementary information (ESI) available: XRD patterns of NO and CO; XRD patterns and XPS profiles of CO; SEM images of CO; BET plots of CO; XPS quantitative analysis of NCO; a comparison of N2 sorption data between NCO and CO; the fitted values of impedimetric parameters of NCO and CO electrodes. See DOI: 10.1039/c3nr05359h

Interfacial crowding of nanoplatelets in co-continuous polymer blends: assembly, elasticity and structure of the interfacial nanoparticle network.

PubMed

Altobelli, R; Salzano de Luna, M; Filippone, G

2017-09-27

The sequence of events which leads to the interfacial crowding of plate-like nanoparticles in co-continuous polymer blends is investigated through a combination of morphological and rheological analyses. Very low amounts (∼0.2 vol%) of organo-modified clay are sufficient to suppress phase coarsening in a co-continuous polystyrene/poly(methyl methacrylate) blend, while lower particle loading allows for a tuning of the characteristic size of the polymer phases at the μm-scale. In any case, an interfacial network of nanoparticles eventually forms, which is driven by the preferred polymer-polymer interface. The elastic features and stress-bearing ability of this peculiar nanoparticle assembly are studied in detail by means of a descriptive two-phase viscoelastic model, which allows isolation of the contribution of the filler network. The role of the co-continuous matrix in driving the space arrangement of the nanoparticles is emphasized by means of comparative analysis with systems based on the same polymers and nanoparticles, but in which the matrix is either a pure polymer or a blend with drop-in-matrix morphology. The relaxation dynamics of the interfacial network was found not to depend on the matrix microstructure, which instead substantially affects the assembly of the nanoplatelets. When the host medium is co-continuous, the particles align along the preferred polymer-polymer interface, percolating at a very low amount (∼0.17 vol%) and prevalently interacting edge-to-edge. The stress bearing ability of such a network is much higher than that in the case of matrix based on a homogeneous polymer or a drop-in-matrix blend, but its elasticity shows low sensitivity to the filler content.

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.

Wettability shifts caused by CO2 aging on mineral surfaces

NASA Astrophysics Data System (ADS)

Liang, B.; Clarens, A. F.

2015-12-01

Interfacial forces at the CO2/brine/mineral ternary interface have a well-established impact on multiphase flow properties through porous media. In the context of geologic carbon sequestration, this wettability will impact capillary pressure, residual trapping, and a variety of other key parameters of interest. While the wettability of CO2 on pure mineral and real rock sample have been studied a great deal over the past few year, very little is known about how the wettability of these rocks could change over long time horizons as CO2 interacts with species in the brine and on the mineral surface. In this work we sought to explore the role that dilute inorganic and organic species that are likely to exist in connate brines might have on a suite of mineral species. High-pressure contact angle experiments were carried out on a suite of polished mineral surfaces. Both static captive bubble and advancing/receding contact angle measurements were carried out. The effect of ionic strength, and in particular the valence of the dominant ions in the brine are found to have an important impact on the wettability which cannot be explained solely based on the shifts in the interfacial tension between the CO2 and brine. More significantly, three organic species, formate, acetate, and oxalate, all three of which are representative species commonly encountered in the saline aquifers that are considered target repositories for carbon sequestration. All three organic species show impacts on wettability, with the organics generally increasing the CO2 wetting of the mineral surface. Not all pure minerals respond the same to the presence of organics, with micas showing a more pronounced influence than quartz. Sandstone and limestone samples aged with different kinds of hydrocarbons, a surrogate for oil-bearing rocks, are generally more CO2-wet, with larger contact angles in the CO2/brine system. Over multiple days, the contact angle decreases, which could be attributed to partitioning of oil films off of the surface and into the CO2 phase, which drives the wettability towards the original water-wet state. This effect could be particularly important for organic rich repositories like depleted oil and gas fields or fractured shale formations where organic species could be presented both on mineral surfaces and in the aqueous phase.

A Review of Major Non-Power-Related Carbon Dioxide Stream Compositions

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

Last, George V.; Schmick, Mary T.

A critical component in the assessment of long-term risk from geologic sequestration of carbon dioxide (CO2) is the ability to predict mineralogical and geochemical changes within storage reservoirs as a result of rock-brine-CO2 reactions. Impurities and/or other constituents in CO2 source streams selected for sequestration can affect both the chemical and physical (e.g., density, viscosity, interfacial tension) properties of CO2 in the deep subsurface. The nature and concentrations of these impurities are a function of both the industrial source(s) of CO2, as well as the carbon capture technology used to extract the CO2 and produce a concentrated stream for subsurfacemore » injection and geologic sequestration. This article reviews the relative concentrations of CO2 and other constituents in exhaust gases from major non-energy-related industrial sources of CO2. Assuming that carbon capture technology would remove most of the incondensable gases N2, O2, and Ar, leaving SO2 and NOx as the main impurities, the authors then summarize the relative proportions of the remaining impurities assumed to be present in CO2 source streams that could be targeted for geologic sequestration. The summary is presented relative to five potential sources of CO2: 1) Flue Gas with Flue Gas Desulfurization, 2) Combustion Stack from Coke Production, 3) Portland Cement Kilns, 4) Natural Gas Combustion, and 5) Lime Production.« 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

g-C3N4/NiAl-LDH 2D/2D Hybrid Heterojunction for High-Performance Photocatalytic Reduction of CO2 into Renewable Fuels.

PubMed

Tonda, Surendar; Kumar, Santosh; Bhardwaj, Monika; Yadav, Poonam; Ogale, Satishchandra

2018-01-24

2D/2D interface heterostructures of g-C 3 N 4 and NiAl-LDH are synthesized utilizing strong electrostatic interactions between positively charged 2D NiAl-LDH sheets and negatively charged 2D g-C 3 N 4 nanosheets. This new 2D/2D interface heterojunction showed remarkable performance for photocatalytic CO 2 reduction to produce renewable fuels such as CO and H 2 under visible-light irradiation, far superior to that of either single phase g-C 3 N 4 or NiAl-LDH nanosheets. The enhancement of photocatalytic activity could be attributed mainly to the excellent interfacial contact at the heterojunction of g-C 3 N 4 /NiAl-LDH, which subsequently results in suppressed recombination, and improved transfer and separation of photogenerated charge carriers. In addition, the optimal g-C 3 N 4 /NiAl-LDH nanocomposite possessed high photostability after successive experimental runs with no obvious change in the production of CO from CO 2 reduction. Our findings regarding the design, fabrication and photophysical properties of 2D/2D heterostructure systems may find use in other photocatalytic applications including H 2 production and water purification.

Interfacial chemical and electronic structure of cobalt deposition on 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT)

NASA Astrophysics Data System (ADS)

Zhu, Menglong; Lyu, Lu; Niu, Dongmei; Zhang, Hong; Zhang, Yuhe; Liu, Peng; Gao, Yongli

2017-04-01

Interfacial chemical and electronic structure of Co deposition on 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene(C8-BTBT) was investigated by ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS). Chemical reaction of cobalt with C8-BTBT at the interface is confirmed by a new component of S 2s peak which is electron-rich compared to the original one of C8-BTBT molecules. Intensity evolution of the core level in XPS indicates that the adsorption of Co atoms is mainly at the surface without deeper diffusion into C8-BTBT layer. Initial deposition of Co atoms downward shifts the core levels of C8-BTBT by electron transfer from isolated Co atoms or clusters to the C8-BTBT. Further deposition of Co upward shifts the core levels of C8-BTBT because of the neutralization of the thicker metal Co film. Our investigation suggests an inert buffer layer inserted to protect organic layer from reaction or decomposition and to lower the carrier barriers for both the electron and hole to improve the performance of Co/C8-BTBT-based OFETs.

Investigation on the electrochemical interfacial properties of 2-aminothiophenol functionalized graphene oxide modified electrode

NASA Astrophysics Data System (ADS)

Immanuel, Susan; Aparna T., K.; Sivasubramanian, R.

2018-04-01

In this paper the interfacial behavior of graphene oxide and 2-aminothiophenol functionalized graphene oxide was investigated by electrochemical method. The GO was prepared by modified Hummers method and the 2-aminothiophenol was covalently attached on the surface of GO sheets. The electrochemical properties were investigated using a redox couple and the electrokinetic parameter was inferred. It was found that the ATP-GO exhibited slow kinetics compared to GO due to the increased deformation of GO sheets after ATP functionalization.

Computational study of interfacial charge transfer complexes of 2-anthroic acid adsorbed on a titania nanocluster for direct injection solar cells

NASA Astrophysics Data System (ADS)

Manzhos, Sergei; Kotsis, Konstantinos

2016-09-01

Adsorption and light absorption properties of interfacial charge transfer complexes of 2-anthroic acid and titania, promising for direct-injection solar cells, are studied ab initio. The formation of interfacial charge transfer bands is observed. The intensity of visible absorption is relatively low, highlighting a key challenge facing direct injection cells. We show that the popular strategy of using a lower level of theory for geometry optimization followed by single point calculations of adsorption or optical properties introduces significant errors which have been underappreciated: by up to 3 eV in adsorption energies, by up to 5 times in light absorption intensity.

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

Improved interfacial and electrical properties of atomic layer deposition HfO2 films on Ge with La2O3 passivation

NASA Astrophysics Data System (ADS)

Li, Xue-Fei; Liu, Xiao-Jie; Cao, Yan-Qiang; Li, Ai-Dong; Li, Hui; Wu, Di

2013-01-01

We report the characteristics of HfO2 films deposited on Ge substrates with and without La2O3 passivation at 250 °C by atomic layer deposition (ALD) using La[N(SiMe3)2]3 and Hf[N(CH3)(C2H5)]4 as the precursors. The HfO2 is observed to form defective HfGeOx at its interface during 500 °C postdeposition annealing. The insertion of an ultrathin La2O3 interfacial passivation layer effectively prevents the Ge outdiffusion and improves interfacial and electrical properties. Capacitance equivalent thickness (CET) of 1.35 nm with leakage current density JA of 8.3 × 10-4 A/cm2 at Vg = 1 V is achieved for the HfO2/La2O3 gate stacks on Ge substrates.

Voltage control of magnetic anisotropy in epitaxial Ru/Co2FeAl/MgO heterostructures

NASA Astrophysics Data System (ADS)

Wen, Zhenchao; Sukegawa, Hiroaki; Seki, Takeshi; Kubota, Takahide; Takanashi, Koki; Mitani, Seiji

2017-03-01

Voltage control of magnetic anisotropy (VCMA) in magnetic heterostructures is a key technology for achieving energy-efficiency electronic devices with ultralow power consumption. Here, we report the first demonstration of the VCMA effect in novel epitaxial Ru/Co2FeAl(CFA)/MgO heterostructures with interfacial perpendicular magnetic anisotropy (PMA). Perpendicularly magnetized tunnel junctions with the structure of Ru/CFA/MgO were fabricated and exhibited an effective voltage control on switching fields for the CFA free layer. Large VCMA coefficients of 108 and 139 fJ/Vm for the CFA film were achieved at room temperature and 4 K, respectively. The interfacial stability in the heterostructure was confirmed by repeating measurements. Temperature dependences of both the interfacial PMA and the VCMA effect were also investigated. It is found that the temperature dependences follow power laws of the saturation magnetization with an exponent of ~2, where the latter is definitely weaker than that of conventional Ta/CoFeB/MgO. The significant VCMA effect observed in this work indicates that the Ru/CFA/MgO heterostructure could be one of the promising candidates for spintronic devices with voltage control.

Interfacial stability of CoSi2/Si structures grown by molecular beam epitaxy

NASA Technical Reports Server (NTRS)

George, T.; Fathauer, R. W.

1992-01-01

The stability of CoSi2/Si interfaces was examined in this study using columnar silicide structures grown on (111) Si substrates. In the first set of experiments, Co and Si were codeposited using MBE at 800 C and the resulting columnar silicide layer was capped by epitaxial Si. Deposition of Co on the surface of the Si capping layer at 800 C results in the growth of the buried silicide columns. The buried columns grow by subsurface diffusion of the deposited Co, suppressing the formation of surface islands of CoSi2. The column sidewalls appear to be less stable than the top and bottom interfaces, resulting in preferential lateral growth and ultimately in the coalescence of the columns to form a continuous buried CoSi2 layer. In the second set of experiments, annealing of a 250 nm-thick buried columnar layer at 1000 C under a 100 nm-thick Si capping layer results in the formation of a surface layer of CoSi2 with a reduction in the sizes of the CoSi2 columns. For a sample having a thicker Si capping layer the annealing leads to Ostwald ripening producing buried equiaxed columns. The high CoSi2/Si interfacial strain could provide the driving force for the observed behavior of the buried columns under high-temperature annealing.

Modeling of Compositional Effects of Foam Assisted CO2 Storage Processes

NASA Astrophysics Data System (ADS)

Naderi Beni, A.; Varavei, A.; Farajzadeh, R.; Delshad, M.

2012-12-01

Foaming of carbon dioxide (CO2, e.g. from fossil-fuel power plants) has been proposed as a possible strategy to resolve the limitations of direct disposal of CO2 into (saline) aquifers. Such limitations include gravity segregation that may damage the caprock and aquifer rock property alteration as a result of geochemical interactions. Foam may also block the CO2 leakage paths, resulting in an overall storage security enhancement. In this regard, specific aspects of composition and type of gas (N2 vs. CO2) may affect the foaming properties of gas-surfactant systems. The aim of this study is to determine these effects on the foaming properties of gas-surfactant solutions. To this end, we study the physics of foam assisted CO2 storage by modeling coreflood experiments. Different options such as simplified population balance foam model and a table-look-up approach were used to couple the fluid flow and mass transport equations in a reservoir simulator. Both laboratory and numerical results show that three regions along the flow direction can be distinguished: (i) an upstream region characterized by low liquid saturation, (ii) a region downstream of the foam front where the liquid saturation is still unchanged with a value of one and (iii) a frontal region characterized by a mixing of flowing foam and liquid, exhibiting fine fingering effects. It is also shown that the extent of the fingering behavior caused by the rock heterogeneity depends on foam strength. Additionally, permeation of gas through foam films is a strong function of water salinity and appears to have significant impact on foam in CO2 storage. It further turns out that the amount of dissolved CO2 in brine can be considerable and, therefore, the effect of water solubility cannot be neglected in simulation studies. In summary, the differences in the foaming behavior of nitrogen and carbon dioxide can be explained by the differences in their physical properties of solubility in water, interfacial tension, pH effect, and wettability. Among which solubility seems to be the most critical one because (1) the amount of available CO2 for foaming will be lower due to its higher dissolution compared to N2 at similar conditions and (2) it significantly affects gas permeability coefficient and thus the foam stability.

Fundamental study of CO2-H2O-mineral interactions for carbon sequestration, with emphasis on the nature of the supercritical fluid-mineral interface.

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

Bryan, Charles R.; Dewers, Thomas A.; Heath, Jason E.

2013-09-01

In the supercritical CO2-water-mineral systems relevant to subsurface CO2 sequestration, interfacial processes at the supercritical fluid-mineral interface will strongly affect core- and reservoir-scale hydrologic properties. Experimental and theoretical studies have shown that water films will form on mineral surfaces in supercritical CO2, but will be thinner than those that form in vadose zone environments at any given matric potential. The theoretical model presented here allows assessment of water saturation as a function of matric potential, a critical step for evaluating relative permeabilities the CO2 sequestration environment. The experimental water adsorption studies, using Quartz Crystal Microbalance and Fourier Transform Infrared Spectroscopymore » methods, confirm the major conclusions of the adsorption/condensation model. Additional data provided by the FTIR study is that CO2 intercalation into clays, if it occurs, does not involve carbonate or bicarbonate formation, or significant restriction of CO2 mobility. We have shown that the water film that forms in supercritical CO2 is reactive with common rock-forming minerals, including albite, orthoclase, labradorite, and muscovite. The experimental data indicate that reactivity is a function of water film thickness; at an activity of water of 0.9, the greatest extent of reaction in scCO2 occurred in areas (step edges, surface pits) where capillary condensation thickened the water films. This suggests that dissolution/precipitation reactions may occur preferentially in small pores and pore throats, where it may have a disproportionately large effect on rock hydrologic properties. Finally, a theoretical model is presented here that describes the formation and movement of CO2 ganglia in porous media, allowing assessment of the effect of pore size and structural heterogeneity on capillary trapping efficiency. The model results also suggest possible engineering approaches for optimizing trapping capacity and for monitoring ganglion formation in the subsurface.« less

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

PubMed Central

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

2016-01-01

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

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

PubMed

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

2016-06-01

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

The Role of Interfaces in Polyethylene/Metal-Oxide Nanocomposites for Ultrahigh-Voltage Insulating Materials.

PubMed

Pourrahimi, Amir Masoud; Olsson, Richard T; Hedenqvist, Mikael S

2018-01-01

Recent progress in the development of polyethylene/metal-oxide nanocomposites for extruded high-voltage direct-current (HVDC) cables with ultrahigh electric insulation properties is presented. This is a promising technology with the potential of raising the upper voltage limit in today's underground/submarine cables, based on pristine polyethylene, to levels where the loss of energy during electric power transmission becomes low enough to ensure intercontinental electric power transmission. The development of HVDC insulating materials together with the impact of the interface between the particles and the polymer on the nanocomposites electric properties are shown. Important parameters from the atomic to the microlevel, such as interfacial chemistry, interfacial area, and degree of particle dispersion/aggregation, are discussed. This work is placed in perspective with important work by others, and suggested mechanisms for improved insulation using nanoparticles, such as increased charge trap density, adsorption of impurities/ions, and induced particle dipole moments are considered. The effects of the nanoparticles and of their interfacial structures on the mechanical properties and the implications of cavitation on the electric properties are also discussed. Although the main interest in improving the properties of insulating polymers has been on the use of nanoparticles, leading to nanodielectrics, it is pointed out here that larger microscopic hierarchical metal-oxide particles with high surface porosity also impart good insulation properties. The impact of the type of particle and its inherent properties (purity and conductivity) on the nanocomposite dielectric and insulating properties are also discussed based on data obtained by a newly developed technique to directly observe the charge distribution on a nanometer scale in the nanocomposite. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three-dimensional Macroscopic Scaffolds With a Gradient in Stiffness for Functional Regeneration of Interfacial Tissues

PubMed Central

Singh, Milind; Dormer, Nathan; Salash, Jean R.; Christian, Jordan M.; Moore, David S.; Berkland, Cory; Detamore, Michael S.

2010-01-01

A novel approach has been demonstrated to construct biocompatible, macroporous 3-D tissue engineering scaffolds containing a continuous macroscopic gradient in composition that yields a stiffness gradient along the axis of the scaffold. Polymeric microspheres, made of poly(d,l-lactic-co-glycolic acid) (PLGA), and composite microspheres encapsulating a higher stiffness nano-phase material (PLGA encapsulating CaCO3 or TiO2 nanoparticles) were used for the construction of microsphere-based scaffolds. Using controlled infusion of polymeric and composite microspheres, gradient scaffolds displaying an anisotropic macroscopic distribution of CaCO3/TiO2 were fabricated via an ethanol sintering technique. The controllable mechanical characteristics and biocompatible nature of these scaffolds warrants further investigation for interfacial tissue engineering applications. PMID:20336753

Interfacial structure of soft matter probed by SFG spectroscopy.

PubMed

Ye, Shen; Tong, Yujin; Ge, Aimin; Qiao, Lin; Davies, Paul B

2014-10-01

Sum frequency generation (SFG) vibrational spectroscopy, an interface-specific technique in contrast to, for example, attenuated total reflectance spectroscopy, which is only interface sensitive, has been employed to investigate the surface and interface structure of soft matter on a molecular scale. The experimental arrangement required to carry out SFG spectroscopy, with particular reference to soft matter, and the analytical methods developed to interpret the spectra are described. The elucidation of the interfacial structure of soft matter systems is an essential prerequisite in order to understand and eventually control the surface properties of these important functional materials. Copyright © 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dopant-Modulating Mechanism of Lithium Adsorption and Diffusion at the Graphene /Li2S Interface

NASA Astrophysics Data System (ADS)

Guo, Lichao; Li, Jiajun; Wang, Huayu; Zhao, Naiqin; Shi, Chunsheng; Ma, Liying; He, Chunnian; He, Fang; Liu, Enzuo

2018-02-01

Graphene modification is one of the most effective routes to enhance the electrochemical properties of the transition-metal sulfide anode for Li-ion batteries and the Li2S cathode for Li-S batteries. Boron, nitrogen, oxygen, phosphorus, and sulfur doping greatly affect the electrochemical properties of Li2S /graphene . Here, we investigate the interfacial binding energy, lithium adsorption energy, interface diffusion barrier, and electronic structure by first-principles calculations to unveil the diverse effects of different dopants during interfacial lithiation reactions. The interfacial lithium storage follows the pseudocapacitylike mechanism with intercalation character. Two different mechanisms are revealed to enhance the interfacial lithium adsorption and diffusion, which are the electron-deficiency host doping and the vacancylike structure evolutions with bond breaking. The synergistic effect between different dopants with diverse doping effects is also proposed. The results give a theoretical basis for the materials design with doped graphene as advanced materials modification for energy storage.

Improvisation of mechanical and electrical properties of Cu by reinforcing MWCNT using modified electro-co-deposition process

NASA Astrophysics Data System (ADS)

Belgamwar, Sachin U.; Sharma, N. N.

2018-04-01

Multi-walled Carbon nanotubes–copper (MWCNT/Cu) composite powders with variable MWCNT content were synthesized by modified electro-co-deposition method. The electro-co-deposited MWCNT/Cu powders were consolidated by conventional compaction and sintering process. The consolidated products were then hot rolled and cold drawn to fine wires. The MWCNT/Cu composite wire samples were characterized for electrical and mechanical properties. We have been able to achieve an increase of around 8% in electrical conductivity of the form wires repeatedly. It has been observed that there was gradual improvement in the properties with reinforcement of MWCNT in the copper matrix. The betterment of electrical property has been achieved with simultaneous improvement in mechanical properties of the wire. The yield strength of MWCNT/Cu composite wire was found to be four times and the tensile strength two times greater than that of pure copper. The improved properties are attributed to the proper distribution of MWCNTs in the copper matrix and excellent interfacial bonding between MWCNT and composite copper fabricated by the modified method.

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.

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.

Effect of TiO 2 particle size and layer thickness on mesoscopic perovskite solar cells

DOE PAGES

Lee, Dong Geon; Kim, Min-cheol; Kim, Byeong Jo; ...

2017-11-16

Mesoporous TiO 2 (mp-TiO 2) layers are commonly used as electron transport layers in perovskite solar cells, which help to extract electrons from the perovskite light-absorbing layer and transport them to the electrodes. We investigated the effects of the layer thickness of mp-TiO 2 and particle size of TiO 2 on photovoltaic properties, in terms of the surface area of the mp-layer and the interfacial areas of the TiO 2 nanoparticles in the mp-layer. Various mp-TiO 2 layers with thicknesses of 150, 250, and 400 nm and particle sizes of 25 nm and 41 nm were prepared to compare themore » photovoltaic properties of such layer-containing perovskite solar cells. Time-resolved photoluminescence decay and impedance studies showed that interfacial resistance as well as perovskite-to-TiO 2 charge injection are important factors affecting photovoltaic performance. The deterioration of the photovoltaic parameters with increasing TiO 2/TiO 2 interfacial area also confirms that the interfacial series resistance that arises from these connections should be reduced to enhance the performance of mesoscopic perovskite solar cells.« less

Effect of TiO 2 particle size and layer thickness on mesoscopic perovskite solar cells

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

Lee, Dong Geon; Kim, Min-cheol; Kim, Byeong Jo

Mesoporous TiO 2 (mp-TiO 2) layers are commonly used as electron transport layers in perovskite solar cells, which help to extract electrons from the perovskite light-absorbing layer and transport them to the electrodes. We investigated the effects of the layer thickness of mp-TiO 2 and particle size of TiO 2 on photovoltaic properties, in terms of the surface area of the mp-layer and the interfacial areas of the TiO 2 nanoparticles in the mp-layer. Various mp-TiO 2 layers with thicknesses of 150, 250, and 400 nm and particle sizes of 25 nm and 41 nm were prepared to compare themore » photovoltaic properties of such layer-containing perovskite solar cells. Time-resolved photoluminescence decay and impedance studies showed that interfacial resistance as well as perovskite-to-TiO 2 charge injection are important factors affecting photovoltaic performance. The deterioration of the photovoltaic parameters with increasing TiO 2/TiO 2 interfacial area also confirms that the interfacial series resistance that arises from these connections should be reduced to enhance the performance of mesoscopic perovskite solar cells.« less

Direct Observation of Interfacial Dzyaloshinskii-Moriya Interaction from Asymmetric Spin-wave Propagation in W/CoFeB/SiO2 Heterostructures Down to Sub-nanometer CoFeB Thickness

PubMed Central

Chaurasiya, Avinash Kumar; Banerjee, Chandrima; Pan, Santanu; Sahoo, Sourav; Choudhury, Samiran; Sinha, Jaivardhan; Barman, Anjan

2016-01-01

Interfacial Dzyaloshinskii-Moriya interaction (IDMI) is important for its roles in stabilizing the skyrmionic lattice as well as soliton-like domain wall motion leading towards new generation spintronic devices. However, achievement and detection of IDMI is often hindered by various spurious effects. Here, we demonstrate the occurrence of IDMI originating primarily from W/CoFeB interface in technologically important W/CoFeB/SiO2 heterostructures using Brillouin light scattering technique. Due to the presence of IDMI, we observe asymmetry in the peak frequency and linewidth of the spin-wave spectra in the Damon-Eshbach (DE) geometry at finite k wave-vectors. The DMI constant is found to scale as the inverse of CoFeB thickness, over the whole studied thickness range, confirming the presence of IDMI in our system without any extrinsic effects. Importantly, the W/CoFeB interface shows no degradation down to sub-nanometer CoFeB thickness, which would be useful for devices that aim to use pronounced interface effects. PMID:27586260

Lattice Boltzmann simulations of supercritical CO2-water drainage displacement in porous media: CO2 saturation and displacement mechanism.

PubMed

Yamabe, Hirotatsu; Tsuji, Takeshi; Liang, Yunfeng; Matsuoka, Toshifumi

2015-01-06

CO2 geosequestration in deep aquifers requires the displacement of water (wetting phase) from the porous media by supercritical CO2 (nonwetting phase). However, the interfacial instabilities, such as viscous and capillary fingerings, develop during the drainage displacement. Moreover, the burstlike Haines jump often occurs under conditions of low capillary number. To study these interfacial instabilities, we performed lattice Boltzmann simulations of CO2-water drainage displacement in a 3D synthetic granular rock model at a fixed viscosity ratio and at various capillary numbers. The capillary numbers are varied by changing injection pressure, which induces changes in flow velocity. It was observed that the viscous fingering was dominant at high injection pressures, whereas the crossover of viscous and capillary fingerings was observed, accompanied by Haines jumps, at low injection pressures. The Haines jumps flowing forward caused a significant drop of CO2 saturation, whereas Haines jumps flowing backward caused an increase of CO2 saturation (per injection depth). We demonstrated that the pore-scale Haines jumps remarkably influenced the flow path and therefore equilibrium CO2 saturation in crossover domain, which is in turn related to the storage efficiency in the field-scale geosequestration. The results can improve our understandings of the storage efficiency by the effects of pore-scale displacement phenomena.

Nanoscale doping heterogeneity in few-layer WSe2 exfoliated onto noble metals revealed by correlated SPM and TERS imaging

NASA Astrophysics Data System (ADS)

Jariwala, Deep; Krayev, Andrey; Wong, Joeson; Robinson, A. Edward; Sherrott, Michelle C.; Wang, Shuo; Liu, Gang-Yu; Terrones, Mauricio; Atwater, Harry A.

2018-07-01

While extensive research effort has been devoted to the study of the 2D semiconductor–insulator interfaces in transition metal dichalcogenides (TMDCs), there is little knowledge about the electronic quality of the semiconductor–metal interface in the atomically thin limit. Here, we present the first correlated nanoscale mapping of the interface of atomically thin WSe2 with noble metals using co-localized scanning probe microscopy and tip-enhanced optical spectroscopy (TEOS), such as tip-enhanced Raman spectroscopy (TERS). Nanoscale maps of the topography, surface potential, Raman spectra, and the photocurrent amplitude of the WSe2/metal interfaces reveal striking results. Specifically, correlations between surface potential, resonant Raman signatures and photocurrents that indicate the presence of inhomogeneities within interfacial electronic properties, which we attribute to variations in the local doping of the WSe2 likely caused by intrinsic compositional fluctuations or defects. Our results suggest that local electrostatic variations at a lateral scale of 10–100 nm are present even in the highest quality of TMDC crystals and must be considered towards understanding of all interfacial phenomena, particularly in device applications that rely on the buried metal–semiconductor junction interface.

ComplexContact: a web server for inter-protein contact prediction using deep learning.

PubMed

Zeng, Hong; Wang, Sheng; Zhou, Tianming; Zhao, Feifeng; Li, Xiufeng; Wu, Qing; Xu, Jinbo

2018-05-22

ComplexContact (http://raptorx2.uchicago.edu/ComplexContact/) is a web server for sequence-based interfacial residue-residue contact prediction of a putative protein complex. Interfacial residue-residue contacts are critical for understanding how proteins form complex and interact at residue level. When receiving a pair of protein sequences, ComplexContact first searches for their sequence homologs and builds two paired multiple sequence alignments (MSA), then it applies co-evolution analysis and a CASP-winning deep learning (DL) method to predict interfacial contacts from paired MSAs and visualizes the prediction as an image. The DL method was originally developed for intra-protein contact prediction and performed the best in CASP12. Our large-scale experimental test further shows that ComplexContact greatly outperforms pure co-evolution methods for inter-protein contact prediction, regardless of the species.

Impact of Interfacial Layers in Perovskite Solar Cells.

PubMed

Cho, An-Na; Park, Nam-Gyu

2017-10-09

Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of surface Fe-S hybrid structure on the activity of the perfect and reduced α-Fe2O3(001) for chemical looping combustion

NASA Astrophysics Data System (ADS)

Xiao, Xianbin; Qin, Wu; Wang, Jianye; Li, Junhao; Dong, Changqing

2018-05-01

Sulfurization of the gradually reduced Fe2O3 surfaces is inevitable while Fe2O3 is used as an oxygen carrier (OC) for coal chemical looping combustion (CLC), which will result in formation of Fe-S hybrid structure on the surfaces. The Fe-S hybrid structure will directly alter the reactivity of the surfaces. Therefore, detailed properties of Fe-S hybrid structure over the perfect and reduced Fe2O3(001) surfaces, and its effect on the interfacial interactions, including CO oxidization and decomposition on the surfaces, were investigated by using density functional theory (DFT) calculations. The S atom prefers to chemically bind to Fe site with electron transfer from the surfaces to the S atom, and a deeper reduction of Fe2O3(001) leads to an increasing interaction between S and Fe. The formation of Fe-S hybrid structure alters the electronic properties of the gradually reduced Fe2O3(001) surfaces, promoting CO oxidation on the surfaces ranging from Fe2O3 to FeO, but depressing carbon deposition on the surfaces ranging from FeO to Fe. The sulfurized FeO acts as a watershed to realize relatively high CO oxidation rate and low carbon deposition. Results provided a fundamental understanding for controlling and optimizing the CLC processes.

Interfacial oxygen migration and its effect on the magnetic anisotropy in Pt/Co/MgO/Pt films

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

Chen, Xi; Feng, Chun, E-mail: fengchun@ustb.edu.cn, E-mail: ghyu@mater.ustb.edu.cn; Liu, Yang

2014-02-03

This paper reports the interfacial oxygen migration effect and its induced magnetic anisotropy evolution in Pt/Co/MgO/Pt films. During depositing the MgO layer, oxygen atoms from the MgO combine with the neighboring Co atoms, leading to the formation of CoO at the Co/MgO interface. Meanwhile, the films show in-plane magnetic anisotropy (IMA). After annealing, most of the oxygen atoms in CoO migrate back to the MgO layer, resulting in obvious improvement of Co/MgO interface and the enhancement of effective Co-O orbital hybridization. These favor the evolution of magnetic anisotropy from IMA to perpendicular magnetic anisotropy (PMA). The oxygen migration effect ismore » achieved by the redox reaction at the Co/MgO interface. On the contrary, the transfer from IMA to PMA cannot be observed in Pt/Co/Pt films due to the lack of interfacial oxygen migration.« less

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.

Effect of Hybrid Talc-Basalt Fillers in the Shell Layer on Thermal and Mechanical Performance of Co-Extruded Wood Plastic Composites

PubMed Central

Huang, Runzhou; Mei, Changtong; Xu, Xinwu; Kärki, Timo; Lee, Sunyoung; Wu, Qinglin

2015-01-01

Hybrid basalt fiber (BF) and Talc filled high density polyethylene (HDPE) and co-extruded wood-plastic composites (WPCs) with different BF/Talc/HDPE composition levels in the shell were prepared and their mechanical, morphological and thermal properties were characterized. Incorporating BFs into the HDPE-Talc composite substantially enhanced the thermal expansion property, flexural, tensile and dynamic modulus without causing a significant decrease in the tensile and impact strength of the composites. Strain energy estimation suggested positive and better interfacial interactions of HDPE with BFs than that with talc. The co-extruded structure design improved the mechanical properties of WPC due to the protective shell layer. The composite flexural and impact strength properties increased, and the thermal expansion decreased as BF content increased in the hybrid BF/Talc filled shells. The cone calorimetry data demonstrated that flame resistance of co-extruded WPCs was improved with the use of combined fillers in the shell layer, especially with increased loading of BFs. The combined shell filler system with BFs and Talc could offer a balance between cost and performance for co-extruded WPCs. PMID:28793726

Effect of Hybrid Talc-Basalt Fillers in the Shell Layer on Thermal and Mechanical Performance of Co-Extruded Wood Plastic Composites.

PubMed

Huang, Runzhou; Mei, Changtong; Xu, Xinwu; Kärki, Timo; Lee, Sunyoung; Wu, Qinglin

2015-12-08

Hybrid basalt fiber (BF) and Talc filled high density polyethylene (HDPE) and co-extruded wood-plastic composites (WPCs) with different BF/Talc/HDPE composition levels in the shell were prepared and their mechanical, morphological and thermal properties were characterized. Incorporating BFs into the HDPE-Talc composite substantially enhanced the thermal expansion property, flexural, tensile and dynamic modulus without causing a significant decrease in the tensile and impact strength of the composites. Strain energy estimation suggested positive and better interfacial interactions of HDPE with BFs than that with talc. The co-extruded structure design improved the mechanical properties of WPC due to the protective shell layer. The composite flexural and impact strength properties increased, and the thermal expansion decreased as BF content increased in the hybrid BF/Talc filled shells. The cone calorimetry data demonstrated that flame resistance of co-extruded WPCs was improved with the use of combined fillers in the shell layer, especially with increased loading of BFs. The combined shell filler system with BFs and Talc could offer a balance between cost and performance for co-extruded WPCs.

Interfacial structure and electrical properties of ultrathin HfO2 dielectric films on Si substrates by surface sol-gel method

NASA Astrophysics Data System (ADS)

Gong, You-Pin; Li, Ai-Dong; Qian, Xu; Zhao, Chao; Wu, Di

2009-01-01

Ultrathin HfO2 films with about ~3 nm thickness were deposited on n-type (1 0 0) silicon substrates using hafnium chloride (HfCl4) source by the surface sol-gel method and post-deposition annealing (PDA). The interfacial structure and electrical properties of ultrathin HfO2 films were investigated. The HfO2 films show amorphous structures and smooth surface morphologies with a very thin interfacial oxide layer of ~0.5 nm and small surface roughness (~0.45 nm). The 500 °C PDA treatment forms stronger Hf-O bonds, leading to passivated traps, and the interfacial layer is mainly Hf silicate (HfxSiyOz). Equivalent oxide thickness of around 0.84 nm of HfO2/Si has been obtained with a leakage current density of 0.7 A cm-2 at Vfb + 1 V after 500 °C PDA. It was found that the current conduction mechanism of HfO2/Si varied from Schottky-Richardson emission to Fowler-Nordheim tunnelling at an applied higher positive voltage due to the activated partial traps remaining in the ultrathin HfO2 films.

Hydrophobic Materials Based on Salts of Di(2-ethylhexyl)phosphoric Acid

NASA Astrophysics Data System (ADS)

Kizim, N. F.; Golubina, E. N.

2018-03-01

Interfacial formations of material based on metals di(2-ethylhexyl)phosphates of various metals exhibit hydrophobic properties. The contact angle of the surface, modified by the interfacial formations materials, could reach up to 140° depending on the nature of the solvent, the metal salt, the number of applications.

Passivation of GaSb using molecular beam epitaxy Y{sub 2}O{sub 3} to achieve low interfacial trap density and high-performance self-aligned inversion-channel p-metal-oxide-semiconductor field-effect-transistors

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

Chu, R. L.; Chiang, T. H.; Hsueh, W. J.

2014-11-03

Molecular beam epitaxy deposited rare-earth oxide of Y{sub 2}O{sub 3} has effectively passivated GaSb, leading to low interfacial trap densities of (1–4) × 10{sup 12 }cm{sup −2} eV{sup −1} across the energy bandgap of GaSb. A high saturation drain current density of 130 μA/μm, a peak transconductance of 90 μS/μm, a low subthreshold slope of 147 mV/decade, and a peak field-effect hole mobility of 200 cm{sup 2}/V-s were obtained in 1 μm-gate-length self-aligned inversion-channel GaSb p-Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs). In this work, high-κ/GaSb interfacial properties were better in samples with a high substrate temperature of 200 °C than in those with high κ's deposited at room temperature, in terms of themore » interfacial electrical properties, particularly, the reduction of interfacial trap densities near the conduction band and the MOSFET device performance.« less

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.

Ionic Liquids as the MOFs/Polymer Interfacial Binder for Efficient Membrane Separation.

PubMed

Lin, Rijia; Ge, Lei; Diao, Hui; Rudolph, Victor; Zhu, Zhonghua

2016-11-23

Obtaining strong interfacial affinity between filler and polymer is critical to the preparation of mixed matrix membranes (MMMs) with high separation efficiency. However, it is still a challenge for micron-sized metal organic frameworks (MOFs) to achieve excellent compatibility and defect-free interface with polymer matrix. Thin layer of ionic liquid (IL) was immobilized on micron-sized HKUST-1 to eliminate the interfacial nonselective voids in MMMs with minimized free ionic liquid (IL) in polymer matrix, and then the obtained IL decorated HKUST-1 was incorporated into 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-2,3,5,6-tetramethyl-1,3-phenyldiamine (6FDA-Durene) to fabricate MMMs. Acting as a filler/polymer interfacial binder, the favorable MOF/IL and IL/polymer interaction can facilitate the enhancement of MOF/polymer affinity. Compared to MMM with only HKUST-1 incorporation, MMM with IL decorated HKUST-1 succeeded in restricting the formation of nonselective interfacial voids, leading to an increment in CO 2 selectivity. The IL decoration method can be an effective approach to eliminate interfacial voids in MMMs, extending the filler selection to a wide range of large-sized fillers.

Atomistic modeling for interfacial properties of Ni-Al-V ternary system

NASA Astrophysics Data System (ADS)

Dong, Wei-ping; Lee, Byeong-Joo; Chen, Zheng

2014-05-01

Interatomic potentials for Ni-Al-V ternary systems have been developed based on the second-nearest-neighbor modified embedded-atom method potential formalism. The potentials can describe various fundamental physical properties of the relevant materials in good agreement with experimental information. The potential is utilized for an atomistic computation of interfacial properties of Ni-Al-V alloys. It is found that vanadium atoms segregate on the γ-fcc/L12 interface and this segregation affects the interfacial properties. The applicability of the atomistic approach to an elaborate alloy design of advanced Ni-based superalloys through the investigation of the effect of alloying elements on interfacial properties is discussed.

Diamond film deposition on WC-Co and steel substrates with a CrN interlayer for tribological applications

NASA Astrophysics Data System (ADS)

Chandran, Maneesh; Hoffman, Alon

2016-06-01

The most renowned property of diamond is its exceptional hardness. By depositing diamond films on tungsten carbide (WC-Co) and steel substrates, the hardness of diamond can be combined with the toughness of these materials, resulting in an excellent wear resistance material for tribological applications. However, poor adhesion of diamond coating on these substrates leads to a lesser lifetime for the diamond coated tools than expected. The prime reasons for the lack of proper adhesion are the preferential formation of graphitic layer at the interface due to the catalytic activities of cobalt/iron and the interfacial residual stresses due to the mismatch in thermal expansion coefficients of diamond (1.5  ×  10-6 K-1) and WC-Co (5.2  ×  10-6 K-1) or steel (12  ×  10-6 K-1). In this review, we discuss the possibility of using a Cr-N interlayer as a diffusion barrier to prevent the catalytic activities of cobalt/iron and also to relax the interfacial residual stresses to some extent to enhance the adhesion of diamond coatings on these substrates. An overview of the most pertinent results of the last two decades, including the recent progress is introduced. We describe in detail how the Cr-N interlayer with the desired properties is fabricated. We give a concise overview of diamond deposition process, including the methods to vary the grain size from microcrystalline to nanocrystalline, which are suitable for some tribological applications. We describe in detail on surface and interface analysis, residual stress measurements, assessment adhesion strength and tribological performance of diamond coated WC-Co and steel substrates using various characterization techniques. We conclude by highlighting the current progress and future perspectives of diamond coatings on these substrates for tribological applications.

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

PubMed

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

2016-01-28

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

Spin and Charge Transport in 2D Materials and Magnetic Insulator/Metal Heterostructures

NASA Astrophysics Data System (ADS)

Amamou, Walid

Spintronic devices are very promising for future information storage, logic operations and computation and have the potential to replace current CMOS technology approaching the scaling limit. In particular, the generation and manipulation of spin current enables the integration of storage and logic within the same circuit for more powerful computing architectures. In this thesis, we examine the manipulation of spins in 2D materials such as graphene and metal/magnetic insulator heterostructures. In particular, we investigate the feasibility for achieving magnetization switching of a nanomagnet using graphene as a nonmagnetic channel material for All Spin Logic Device applications. Using in-situ MBE deposition of nanomagnet on graphene spin valve, we demonstrate the presence of an interfacial spin dephasing at the interface between the graphene and the nanomagnet. By introducing a Cu spacer between the nanomagnet and graphene, we demonstrate that this interfacial effect is related to an exchange interaction between the spin current and the disordered magnetic moment of the nanomagnet in the first monolayer. In addition to the newly discovered interfacial spin relaxation effect, the extracted contact resistance area product of the nanomagnet/graphene interface is relatively high on the order of 1Omicrom2. In practice, reducing the contact resistance will be as important as eliminating the interfacial relaxation in order to achieve magnetization switching. Furthermore, we examine spin manipulation in a nonmagnetic Pt using an internal magnetic exchange field produced by the adjacent magnetic insulator CoFe2O4 grown by MBE. Here, we report the observation of a strong magnetic proximity effect of Pt deposited on top of a perpendicular magnetic anisotropy (PMA) inverse spinel material Cobalt Ferrite (CFO, CoFe 2O4). The CFO was grown by MBE and its magnetization was characterized by Vibrating Sample Magnetometry (VSM) demonstrating the strong out of plane magnetic anisotropy of this material. The anomalous Hall measurement on a Pt/CFO Hall bar exhibits a strong non-linear background around the saturation of the out of plane CFO magnetization. After subtraction of the Ordinary Hall Effect (OHE), we extract a strongly hysteretic anomalous Hall voltage that indicates that Pt acquired the magnetization properties of the CFO and has become ferromagnetic due to the proximity effects.

Effect of structure on the tribology of ultrathin graphene and graphene oxide films.

PubMed

Chen, Hang; Filleter, Tobin

2015-03-27

The friction and wear properties of graphene and graphene oxide (GO) with varying C/O ratio were investigated using friction force microscopy. When applied as solid lubricants between a sliding contact of a silicon (Si) tip and a SiO2/Si substrate, graphene and ultrathin GO films (as thin as 1-2 atomic layers) were found to reduce friction by ∼6 times and ∼2 times respectively as compared to the unlubricated contact. The differences in measured friction were attributed to different interfacial shear strengths. Ultrathin films of GO with a low C/O ratio of ∼2 were found to wear easily under small normal load. The onset of wear, and the location of wear initiation, is attributed to differences in the local shear strength of the sliding interface as a result of the non-homogeneous surface structure of GO. While the exhibited low friction of GO as compared to SiO2 makes it an economically viable coating for micro/nano-electro-mechanical systems with the potential to extend the lifetime of devices, its higher propensity for wear may limit its usefulness. To address this limitation, the wear resistance of GO samples with a higher C/O ratio (∼4) was also studied. The higher C/O ratio GO was found to exhibit much improved wear resistance which approached that of the graphene samples. This demonstrates the potential of tailoring the structure of GO to achieve graphene-like tribological properties.

Enhancement in the interfacial perpendicular magnetic anisotropy and the voltage-controlled magnetic anisotropy by heavy metal doping at the Fe/MgO interface

NASA Astrophysics Data System (ADS)

Nozaki, Takayuki; Yamamoto, Tatsuya; Tamaru, Shingo; Kubota, Hitoshi; Fukushima, Akio; Suzuki, Yoshishige; Yuasa, Shinji

2018-02-01

We investigated the influence of heavy metal doping at the Fe/MgO interface on the interfacial perpendicular magnetic anisotropy (PMA) and the voltage-controlled magnetic anisotropy (VCMA) in magnetic tunnel junctions prepared by sputtering-based deposition. The interfacial PMA was increased by tungsten doping and a maximum intrinsic interfacial PMA energy, Ki,0 of 2.0 mJ/m2 was obtained. Ir doping led to a large increase in the VCMA coefficient by a factor of 4.7 compared with that for the standard Fe/MgO interface. The developed technique provides an effective approach to enhancing the interfacial PMA and VCMA properties in the development of voltage-controlled spintronic devices.

The stability of aluminium oxide monolayer and its interface with two-dimensional materials

NASA Astrophysics Data System (ADS)

Song, Ting Ting; Yang, Ming; Chai, Jian Wei; Callsen, Martin; Zhou, Jun; Yang, Tong; Zhang, Zheng; Pan, Ji Sheng; Chi, Dong Zhi; Feng, Yuan Ping; Wang, Shi Jie

2016-07-01

The miniaturization of future electronic devices requires the knowledge of interfacial properties between two-dimensional channel materials and high-κ dielectrics in the limit of one atomic layer thickness. In this report, by combining particle-swarm optimization method with first-principles calculations, we present a detailed study of structural, electronic, mechanical, and dielectric properties of Al2O3 monolayer. We predict that planar Al2O3 monolayer is globally stable with a direct band gap of 5.99 eV and thermal stability up to 1100 K. The stability of this high-κ oxide monolayer can be enhanced by substrates such as graphene, for which the interfacial interaction is found to be weak. The band offsets between the Al2O3 monolayer and graphene are large enough for electronic applications. Our results not only predict a stable high-κ oxide monolayer, but also improve the understanding of interfacial properties between a high-κ dielectric monolayer and two-dimensional material.

A multifunctional biphasic water splitting catalyst tailored for integration with high-performance semiconductor photoanodes

DOE PAGES

Yang, Jinhui; Cooper, Jason K.; Toma, Francesca M.; ...

2016-11-07

Artificial photosystems are advanced by the development of conformal catalytic materials that promote desired chemical transformations, while also maintaining stability and minimizing parasitic light absorption for integration on surfaces of semiconductor light absorbers. We demonstrate that multifunctional, nanoscale catalysts that enable high-performance photoelectrochemical energy conversion can be engineered by plasma-enhanced atomic layer deposition. The collective properties of tailored Co 3 O 4 /Co(OH) 2 thin films simultaneously provide high activity for water splitting, permit efficient interfacial charge transport from semiconductor substrates, and enhance durability of chemically sensitive interfaces. Furthermore, these films comprise compact and continuous nanocrystalline Co 3 O 4more » spinel that is impervious to phase transformation and impermeable to ions, thereby providing effective protection of the underlying substrate. Moreover, a secondary phase of structurally disordered and chemically labile Co(OH) 2 is introduced to ensure a high concentration of catalytically active sites. Application of this coating to photovoltaic p + n-Si junctions yields best reported performance characteristics for crystalline Si photoanodes.« less

The Role of Water in Mediating Interfacial Adhesion and Shear Strength in Graphene Oxide.

PubMed

Soler-Crespo, Rafael A; Gao, Wei; Mao, Lily; Nguyen, Hoang T; Roenbeck, Michael R; Paci, Jeffrey T; Huang, Jiaxing; Nguyen, SonBinh T; Espinosa, Horacio D

2018-06-12

Graphene oxide (GO), whose highly tunable surface chemistry enables the formation of strong interfacial hydrogen-bond networks, has garnered increasing interest in the design of devices that operate in the presence of water. For instance, previous studies have suggested that controlling GO's surface chemistry leads to enhancements in interfacial shear strength, allowing engineers to manage deformation pathways and control failure mechanisms. However, these previous reports have not explored the role of ambient humidity and only offer extensive chemical modifications to GO's surface as the main pathway to control GO's interfacial properties. Herein, through atomic force microscopy experiments on GO-GO interfaces, the adhesion energy and interfacial shear strength of GO were measured as a function of ambient humidity. Experimental evidence shows that adhesion energy and interfacial shear strength can be improved by a factor of 2-3 when GO is exposed to moderate (∼30% water weight) water content. Furthermore, complementary molecular dynamics simulations uncovered the mechanisms by which these nanomaterial interfaces achieve their properties. They reveal that the strengthening mechanism arises from the formation of strongly interacting hydrogen-bond networks, driven by the chemistry of the GO basal plane and intercalated water molecules between two GO surfaces. In summary, the methodology and findings here reported provide pathways to simultaneously optimize GO's interfacial and in-plane mechanical properties, by tailoring the chemistry of GO and accounting for water content, in engineering applications such as sensors, filtration membranes, wearable electronics, and structural materials.

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

Aerosol Particle Interfacial Thermodynamics and Phase Partitioning Measurements Using Biphasic Microfluidics

NASA Astrophysics Data System (ADS)

Dutcher, Cari; Metcalf, Andrew

2015-03-01

Secondary organic aerosol particles are nearly ubiquitous in the atmosphere and yet there remain large uncertainties in their formation processes and ambient properties. These particles are complex microenvironments, which can contain multiple interfaces due to internal aqueous-organic phase partitioning and to the external liquid-vapor surface. Interfacial properties affect the ambient aerosol morphology, or internal structure of the particle, which in turn can affect the way a particle interacts with an environment of condensable clusters and organic vapors. To improve our ability to accurately predict ambient aerosol morphology, we must improve our knowledge of aerosol interfaces and their interactions with the ambient environment. Unfortunately, many techniques employed to measure interfacial properties do so in bulk solutions or in the presence of a ternary (e.g. solid) phase. In this talk, a novel method using biphasic microscale flows will be introduced for generating, trapping, and perturbing complex interfaces at atmospherically relevant conditions. These microfluidic experiments utilize high-speed imaging to monitor interfacial phenomena at the microscale and are performed with phase contrast and fluorescence microscopy on a temperature-controlled inverted microscope stage. From these experiments, interfacial thermodynamic properties such as surface or interfacial tension, rheological properties such as interfacial moduli, and kinetic properties such as mass transfer coefficients can be measured or inferred.

Interfacial Dzyaloshinskii-Moriya interaction sign in Ir/Co2FeAl systems investigated by Brillouin light scattering

NASA Astrophysics Data System (ADS)

Belmeguenai, M.; Gabor, M. S.; Roussigné, Y.; Petrisor, T.; Mos, R. B.; Stashkevich, A.; Chérif, S. M.; Tiusan, C.

2018-02-01

C o2FeAl (CFA) ultrathin films, of various thicknesses (0.9 nm ≤tCFA≤1.8 nm ), have been grown by sputtering on Si substrates, using Ir as a buffer layer. The magnetic properties of these structures have been studied by vibrating sample magnetometry (VSM), miscrostrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations show that films are mostly in-plane magnetized and the saturating field perpendicular to the film plane increases with decreasing CFA thickness suggesting the existence of a perpendicular interface anisotropy. The presence of a magnetic dead layer of 0.44 nm has been detected by VSM. The MS-FMR with the magnetic field applied perpendicularly to the film plane has been used to determine the gyromagnetic factor. The BLS measurements reveal a pronounced nonreciprocal spin wave propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (DMI) induced by the Ir interface with CFA, which increases with decreasing CFA thickness. The DMI sign has been found to be the same (negative) as that of Pt/Co, in contrast to the ab initio calculation on Ir/Co, where it is found to be positive. The thickness dependence of the effective DMI constant shows the existence of two regimes similarly to that of the perpendicular anisotropy constant. The surface DMI constant Ds was estimated to be -0.37 pJ /m for the thickest samples, where a linear thickness dependence of the effective DMI constant has been observed.

Interfacial enhancement of carbon fiber composites by growing TiO2 nanowires onto amine-based functionalized carbon fiber surface in supercritical water

NASA Astrophysics Data System (ADS)

Ma, Lichun; Li, Nan; Wu, Guangshun; Song, Guojun; Li, Xiaoru; Han, Ping; Wang, Gang; Huang, Yudong

2018-03-01

A novel amine-based functionalization method was developed to improve the interfacial adhesion between TiO2 NWs and CFs in supercritical water. The microstructure, morphology and mechanical properties of CFs were investigated. It was found that introducing hexamethylenetetramine (HMTA) dendrimers and branched polyethyleneimine (PEI) on CF could increase significantly the adhesion strength between CF and TiO2 NWs and their interfacial shear strength with epoxy resin, and the order is CF-PEI-TiO2 NWs > CF-HMTA-TiO2 NWs > CF-COOH-TiO2 NWs > CF-TiO2 NW. Meanwhile, the reinforcing mechanisms and interfacial failure modes have also been discussed. We believe that these effective methods may provide theoretical foundation for the preparation of high performance composite materials.

Effects of Interphase Modification and Biaxial Orientation on Dielectric Properties of Poly(ethylene terephthalate)/Poly(vinylidene fluoride-co-hexafluoropropylene) Multilayer Films.

PubMed

Yin, Kezhen; Zhou, Zheng; Schuele, Donald E; Wolak, Mason; Zhu, Lei; Baer, Eric

2016-06-01

Recently, poly(vinylidene fluoride) (PVDF)-based multilayer films have demonstrated enhanced dielectric properties, combining high energy density and high dielectric breakdown strength from the component polymers. In this work, further enhanced dielectric properties were achieved through interface/interphase modulation and biaxial orientation for the poly(ethylene terephthalate)/poly(methyl methacrylate)/poly(vinylidene fluoride-co-hexafluoropropylene) [PET/PMMA/P(VDF-HFP)] three-component multilayer films. Because PMMA is miscible with P(VDF-HFP) and compatible with PET, the interfacial adhesion between PET and P(VDF-HFP) layers should be improved. Biaxial stretching of the as-extruded multilayer films induced formation of highly oriented fibrillar crystals in both P(VDF-HFP) and PET, resulting in improved dielectric properties with respect to the unstretched films. First, the parallel orientation of PVDF crystals reduced the dielectric loss from the αc relaxation in α crystals. Second, biaxial stretching constrained the amorphous phase in P(VDF-HFP) and thus the migrational loss from impurity ions was reduced. Third, biaxial stretching induced a significant amount of rigid amorphous phase in PET, further enhancing the breakdown strength of multilayer films. Due to the synergistic effects of improved interfacial adhesion and biaxial orientation, the PET/PMMA/P(VDF-HFP) 65-layer films with 8 vol % PMMA exhibited optimal dielectric properties with an energy density of 17.4 J/cm(3) at breakdown and the lowest dielectric loss. These three-component multilayer films are promising for future high-energy-density film capacitor applications.

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

Gas Transport Properties of Polybenzimidazole and Poly(Phenylene Oxide) Mixed Matrix Membranes Incorporated with PDA-Functionalised Titanate Nanotubes

NASA Astrophysics Data System (ADS)

Giel, V.; Perchacz, M.; Kredatusová, J.; Pientka, Z.

2017-01-01

Functionalised titanate nanotubes (TiNTs) were incorporated to poly(5,5-bisbenzimidazole-2,2-diyl-1,3-phenylene) (PBI) or poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) for improving the interfacial compatibility between the polymer matrix and inorganic material and for altering the gas separation performance of the neat polymer membranes. Functionalisation consisted in oxidative polymerisation of dopamine-hydrochloride on the surface of non-functionalised TiNTs. Transmission electron microscopy (TEM) confirmed that a thin polydopamine (PDA) layer was created on the surface of TiNTs. 1.5, 3, 6, and 9 wt.% of PDA-functionalised TiNTs (PDA-TiNTs) were dispersed to each type of polymer matrix to create so-called mixed matrix membranes (MMMs). Infrared spectroscopy confirmed that -OH and -NH groups exist on the surface of PDA-TiNTs and that the nanotubes interact via H-bonding with PBI but not with PPO. The distribution of PDA-TiNTs in the MMMs was to some extent uniform as scanning electron microscope (SEM) studies showed. Beyond, PDA-TiNTs exhibit positive effect on gas transport properties, resulting in increased selectivities of MMMs. The addition of nanotubes caused a decrease in permeabilities but an increase in selectivities. It is shown that 9 wt.% of PDA-TiNTs in PBI gave a rise to CO2/N2 and CO2/CH4 selectivities of 112 and 63 %, respectively. In case of PPO-PDA-TiNT MMMs, CO2/N2 and CO2/CH4 selectivity increased about 25 and 17 %, respectively. Sorption measurement showed that the presence of PDA-TiNTs in PBI caused an increase in CO2 sorption, whereas the influence on other gases is less noticeable.

Pressure-induced reinforcement of interfacial superconductivity in a Bi2Te3/Fe1+yTe heterostructure

NASA Astrophysics Data System (ADS)

Shen, Junying; Heuckeroth, Claire; Deng, Yuhang; He, Qinglin; Liu, Hong Chao; Liang, Jing; Wang, Jiannong; Sou, Iam Keong; Schilling, James S.; Lortz, Rolf

2017-12-01

We investigate the hydrostatic pressure dependence of interfacial superconductivity occurring at the atomically sharp interface between two non-superconducting materials: the topological insulator (TI) Bi2Te3 and the parent compound Fe1+yTe of the chalcogenide iron-based superconductors. Under pressure, a significant increase in the superconducting transition temperature Tc is observed. We interpret our data in the context of a pressure-induced enhanced coupling of the Fe1+yTe interfacial layer with the Bi2Te3 surface state, which modifies the electronic properties of the interface layer in a way that superconductivity emerges and becomes further enhanced under pressure. This demonstrates the important role of the TI in the interfacial superconducting mechanism.

Band Offsets and Interfacial Properties of HfAlO Gate Dielectric Grown on InP by Atomic Layer Deposition.

PubMed

Yang, Lifeng; Wang, Tao; Zou, Ying; Lu, Hong-Liang

2017-12-01

X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy have been used to determine interfacial properties of HfO 2 and HfAlO gate dielectrics grown on InP by atomic layer deposition. An undesirable interfacial InP x O y layer is easily formed at the HfO 2 /InP interface, which can severely degrade the electrical performance. However, an abrupt interface can be achieved when the growth of the HfAlO dielectric on InP starts with an ultrathin Al 2 O 3 layer. The valence and conduction band offsets for HfAlO/InP heterojunctions have been determined to be 1.87 ± 0.1 and 2.83 ± 0.1 eV, respectively. These advantages make HfAlO a potential dielectric for InP MOSFETs.

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

NASA Astrophysics Data System (ADS)

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

2013-01-01

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

Surface Treated Natural Fibres as Filler in Biocomposites

NASA Astrophysics Data System (ADS)

Schwarzova, I.; Stevulova, N.; Singovszka, E.; Terpakova, E.

2015-11-01

Biocomposites based on natural fibres as organic filler have been studied for several years because traditional building materials such as concrete are increasingly being replaced by advanced composite materials. Natural fibres are a potential replacement of glass fibres in composite materials. Inherent advantages such as low density, biodegradability and comparable specific mechanical properties make natural fibres an attractive option. However, limitations such as poor thermal stability, moisture absorption and poor compatibility with matrix are challenges that need to be resolved. The primary objective of this research was to study the effect of surface treatment on properties of hemp hurds like a natural lignocellulosic material and composites made thereof. Industrial hemp fibre is the one of the most suitable fibres for use in composite materials because of its good specific properties, as well as it being biologically degradable and CO2 neutral. Improving interfacial bonding between fibres and matrix is an important factor in using hemp fibres as reinforcement in composites. In order to improve interfacial bonding, modifications can be made to the hemp fibres to remove non- cellulosic compounds, separate hemp fibres from their bundles, and modify the fibre surface. This paper contains the comparison of FTIR spectra caused by combination of physical and chemical treatment of hemp material with unmodified sample. Modification of hemp hurds was carried out by NaOH solution and by ultrasonic treatment (deionized water and NaOH solution were used as the cleaning mediums).

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

Hot Hole Collection and Photoelectrochemical CO2 Reduction with Plasmonic Au/p-GaN Photocathodes.

PubMed

DuChene, Joseph S; Tagliabue, Giulia; Welch, Alex J; Cheng, Wen-Hui; Atwater, Harry A

2018-04-11

Harvesting nonequilibrium hot carriers from plasmonic-metal nanostructures offers unique opportunities for driving photochemical reactions at the nanoscale. Despite numerous examples of hot electron-driven processes, the realization of plasmonic systems capable of harvesting hot holes from metal nanostructures has eluded the nascent field of plasmonic photocatalysis. Here, we fabricate gold/p-type gallium nitride (Au/p-GaN) Schottky junctions tailored for photoelectrochemical studies of plasmon-induced hot-hole capture and conversion. Despite the presence of an interfacial Schottky barrier to hot-hole injection of more than 1 eV across the Au/p-GaN heterojunction, plasmonic Au/p-GaN photocathodes exhibit photoelectrochemical properties consistent with the injection of hot holes from Au nanoparticles into p-GaN upon plasmon excitation. The photocurrent action spectrum of the plasmonic photocathodes faithfully follows the surface plasmon resonance absorption spectrum of the Au nanoparticles and open-circuit voltage studies demonstrate a sustained photovoltage during plasmon excitation. Comparison with Ohmic Au/p-NiO heterojunctions confirms that the vast majority of hot holes generated via interband transitions in Au are sufficiently hot to inject above the 1.1 eV interfacial Schottky barrier at the Au/p-GaN heterojunction. We further investigated plasmon-driven photoelectrochemical CO 2 reduction with the Au/p-GaN photocathodes and observed improved selectivity for CO production over H 2 evolution in aqueous electrolytes. Taken together, our results offer experimental validation of photoexcited hot holes more than 1 eV below the Au Fermi level and demonstrate a photoelectrochemical platform for harvesting hot carriers to drive solar-to-fuel energy conversion.

Pore-Lining Composition and Capillary Breakthrough Pressure of Mudstone Caprocks: Sealing Efficiency of Geologic CO2 Storage Sites

NASA Astrophysics Data System (ADS)

Heath, J. E.; Dewers, T. A.; McPherson, B. J.; Kotula, P. G.

2010-12-01

Subsurface containment of CO2 is predicated on effective caprock sealing. Many previous studies have relied on macroscopic measurements of capillary breakthrough pressure and other petrophysical properties without direct examination of solid phases that line pore networks and directly contact fluids. However, pore-lining phases strongly contribute to sealing behavior through interfacial interactions among CO2, brine, and the mineral or non-mineral phases. Our high resolution (i.e., sub-micron) examination of the composition of pore-lining phases of several continental and marine mudstones indicates that sealing efficiency (i.e., breakthrough pressure) is governed by pore shapes and pore-lining phases that are not identifiable except through direct characterization of pores. Bulk X-ray diffraction data does not indicate which phases line the pores and may be especially lacking for mudstones with organic material. Organics can line pores and may represent once-mobile phases that modify the wettability of an originally clay-lined pore network. For shallow formations (i.e., < ~800 m depth), interfacial tension and contact angles result in breakthrough pressures that may be as high as those needed to fracture the rock—thus, in the absence of fractures, capillary sealing efficiency is indicated. Deeper seals have poorer capillary sealing if mica-like wetting dominates the wettability. We thank the U.S. Department of Energy’s National Energy Technology Laboratory and the Office of Basic Energy Sciences, and the Southeast and Southwest Carbon Sequestration Partnerships for supporting this work. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

A Nonlinear Three-Dimensional Micromechanics Model for Fiber-Reinforced Laminated Composites

DTIC Science & Technology

1993-11-01

Interfacial Properties Employed for the SCS6/Ti-15-3 Composite ......................... 150 11. Constants Employed for the LLFM Predictions of Quasi...Region m Matrix Property or Mean of the Interfacial Stress Distribution ml, m2, m3 Signifies Matrix Region n Normal to Interface r Signifies Equation...usage of the new class of titanium based com- posites in advanced aerospace structures and engines such as are targeted for the advanced tactical fighter

Interferometric 2D Sum Frequency Generation Spectroscopy Reveals Structural Heterogeneity of Catalytic Monolayers on Transparent Materials.

PubMed

Vanselous, Heather; Stingel, Ashley M; Petersen, Poul B

2017-02-16

Molecular monolayers exhibit structural and dynamical properties that are different from their bulk counterparts due to their interaction with the substrate. Extracting these distinct properties is crucial for a better understanding of processes such as heterogeneous catalysis and interfacial charge transfer. Ultrafast nonlinear spectroscopic techniques such as 2D infrared (2D IR) spectroscopy are powerful tools for understanding molecular dynamics in complex bulk systems. Here, we build on technical advancements in 2D IR and heterodyne-detected sum frequency generation (SFG) spectroscopy to study a CO 2 reduction catalyst on nanostructured TiO 2 with interferometric 2D SFG spectroscopy. Our method combines phase-stable heterodyne detection employing an external local oscillator with a broad-band pump pulse pair to provide the first high spectral and temporal resolution 2D SFG spectra of a transparent material. We determine the overall molecular orientation of the catalyst and find that there is a static structural heterogeneity reflective of different local environments at the surface.

Toward Perovskite Solar Cell Commercialization: A Perspective and Research Roadmap Based on Interfacial Engineering.

PubMed

Rajagopal, Adharsh; Yao, Kai; Jen, Alex K-Y

2018-06-08

High-efficiency and low-cost perovskite solar cells (PVKSCs) are an ideal candidate for addressing the scalability challenge of solar-based renewable energy. The dynamically evolving research field of PVKSCs has made immense progress in solving inherent challenges and capitalizing on their unique structure-property-processing-performance traits. This review offers a unique outlook on the paths toward commercialization of PVKSCs from the interfacial engineering perspective, relevant to both specialists and nonspecialists in the field through a brief introduction of the background of the field, current state-of-the-art evolution, and future research prospects. The multifaceted role of interfaces in facilitating PVKSC development is explained. Beneficial impacts of diverse charge-transporting materials and interfacial modifications are summarized. In addition, the role of interfaces in improving efficiency and stability for all emerging areas of PVKSC design are also evaluated. The authors' integral contributions in this area are highlighted on all fronts. Finally, future research opportunities for interfacial material development and applications along with scalability-durability-sustainability considerations pivotal for facilitating laboratory to industry translation are presented. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Engineering the surface of LiCoO 2 electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

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

Xie, Jin; Zhao, Jie; Liu, Yayuan

Here, developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO 2 interfacial layers on LiCoO 2 electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO 2 coating not only prevented interfacial reactions between the LiCoO 2 electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoOmore » 2 without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g –1 was achieved for the LiCoO 2 electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li +/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li +/Li.« less

Engineering the surface of LiCoO 2 electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

DOE PAGES

Xie, Jin; Zhao, Jie; Liu, Yayuan; ...

2017-07-25

Here, developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO 2 interfacial layers on LiCoO 2 electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO 2 coating not only prevented interfacial reactions between the LiCoO 2 electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoOmore » 2 without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g –1 was achieved for the LiCoO 2 electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li +/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li +/Li.« less

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

PubMed

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

2016-03-23

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

Improving Multi-Functional Properties in Polymer Based Nano Composites by Interfacial

NASA Astrophysics Data System (ADS)

Tajaddod, Navid

Polymer nanocomposites (PNCs) have become an area of increasing interest for study in the field of polymer science and technology since the rise of nanotechnology research. Despite the significant amount of progress being made towards producing high quality PNC materials, improvement in the mechanical, electrical, thermal and other functional properties still remain a challenge. To date, these properties are only a fraction of the expected theoretical values predicted for these materials. Development of interfacial regions between the filler and matrix within the composite has been found to be an important focus in terms of processing. Proper interfacial control and development may ensure excellent interaction and property transfer between the filler and polymer matrix in addition to improvement of multi-functional properties of PNCs. The property-structure importance for the existence of the interfacial and interphase region within PNCs is discussed in this thesis work. Two specific PNC systems are selected for study as part of this dissertation in order to understand the effect of interfacial region development on influencing multi-functional property trends. Polyethylene (PE)/boron nitride (BN) and polyacrylonitrile (PAN)/carbon nanotube (CNT) composites were selected to investigate their mechanical performance and thermal and electrical conductivity properties, respectively. For these systems it was found that the interfacial region structure is directly related to the enhancement of the subsequent multi-functional properties.

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.

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

NASA Astrophysics Data System (ADS)

Shepley, Philippa M.; Tunnicliffe, Harry; Shahbazi, Kowsar; Burnell, Gavin; Moore, Thomas A.

2018-04-01

We study the magnetic properties of perpendicularly magnetized Pt/Co/Ir thin films and investigate the domain-wall creep method of determining the interfacial Dzyaloshinskii-Moriya (DM) interaction in ultrathin films. Measurements of the Co layer thickness dependence of saturation magnetization, perpendicular magnetic anisotropy, and symmetric and antisymmetric (i.e., DM) exchange energies in Pt/Co/Ir thin films have been made to determine the relationship between these properties. We discuss the measurement of the DM interaction by the expansion of a reverse domain in the domain-wall creep regime. We show how the creep parameters behave as a function of in-plane bias field and discuss the effects of domain-wall roughness on the measurement of the DM interaction by domain expansion. Whereas modifications to the creep law with DM field and in-plane bias fields have taken into account changes in the energy barrier scaling parameter α , we find that both α and the velocity scaling parameter v0 change as a function of in-plane bias field.

Atomic Scale Studies of Magnetic Multilayers

NASA Astrophysics Data System (ADS)

Plisch, M. J.; Muller, D. A.; Katine, J. A.; Silcox, J.; Buhrman, R. A.

1998-03-01

The structure of interfaces in magnetic multilayers plays a crucial role in determining their transport properties(S.S.P. Parkin, Phys. Rev. Lett. 71), 1641 (1993).. A scanning transmission electron microscope (STEM) which can focus a 100 kV electron beam down to 2Åis used to make spatially resolved measurements across magnetic multilayers. Previous x-ray absorption measurements suggest that the Cu d electrons play a large role in coupling the Co layers(M.G. Samant, et. al., Phys. Rev. Lett. 72), 1112 (1994).. With electon energy loss spectroscopy (EELS), information on the spatial variation of Cu d states can be obtained. Interfacial structure and bonding have been examined in multilayers with 80 ÅCu/50 ÅCo periods (with no GMR) and 9 ÅCu/13 ÅCo periods (with greater than 50% GMR). A heteroepitaxial grain structure persisting across many multilayer periods has been seen in the short period structure, but not in the long period structure. There is mixing at the Cu/Co interface and the Cu d states near the interface are significantly modified by the Co. Fe/Cr multilayers have also been examined.

Dimensionality Controlled Octahedral Symmetry-Mismatch and Functionalities in Epitaxial LaCoO₃/SrTiO₃ Heterostructures.

PubMed

Qiao, Liang; Jang, Jae Hyuck; Singh, David J; Gai, Zheng; Xiao, Haiyan; Mehta, Apurva; Vasudevan, Rama K; Tselev, Alexander; Feng, Zhenxing; Zhou, Hua; Li, Sean; Prellier, Wilfrid; Zu, Xiaotao; Liu, Zijiang; Borisevich, Albina; Baddorf, Arthur P; Biegalski, Michael D

2015-07-08

Epitaxial strain provides a powerful approach to manipulate physical properties of materials through rigid compression or extension of their chemical bonds via lattice-mismatch. Although symmetry-mismatch can lead to new physics by stabilizing novel interfacial structures, challenges in obtaining atomic-level structural information as well as lack of a suitable approach to separate it from the parasitical lattice-mismatch have limited the development of this field. Here, we present unambiguous experimental evidence that the symmetry-mismatch can be strongly controlled by dimensionality and significantly impact the collective electronic and magnetic functionalities in ultrathin perovskite LaCoO3/SrTiO3 heterojunctions. State-of-art diffraction and microscopy reveal that symmetry breaking dramatically modifies the interfacial structure of CoO6 octahedral building-blocks, resulting in expanded octahedron volume, reduced covalent screening, and stronger electron correlations. Such phenomena fundamentally alter the electronic and magnetic behaviors of LaCoO3 thin-films. We conclude that for epitaxial systems, correlation strength can be tuned by changing orbital hybridization, thus affecting the Coulomb repulsion, U, instead of by changing the band structure as the common paradigm in bulks. These results clarify the origin of magnetic ordering for epitaxial LaCoO3 and provide a route to manipulate electron correlation and magnetic functionality by orbital engineering at oxide heterojunctions.

Investigating interfacial contact configuration and behavior of single-walled carbon nanotube-based nanodevice with atomistic simulations

NASA Astrophysics Data System (ADS)

Cui, Jianlei; Zhang, Jianwei; He, Xiaoqiao; Mei, Xuesong; Wang, Wenjun; Yang, Xinju; Xie, Hui; Yang, Lijun; Wang, Yang

2017-03-01

Carbon nanotubes (CNTs), including single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), are considered to be the promising candidates for next-generation interconnects with excellent physical and chemical properties ranging from ultrahigh mechanical strength, to electrical properties, to thermal conductivity, to optical properties, etc. To further study the interfacial contact configurations of SWNT-based nanodevice with a 13.56-Å diameter, the corresponding simulations are carried out with the molecular dynamic method. The nanotube collapses dramatically into the surface with the complete collapse on the Au/Ag/graphite electrode surface and slight distortion on the Si/SiO2 substrate surface, respectively. The related dominant mechanism is studied and explained. Meanwhile, the interfacial contact configuration and behavior, depended on other factors, are also analyzed in this article.

Interfacial reactions between DBD and porous catalyst in dry methane reforming

NASA Astrophysics Data System (ADS)

Kameshima, Seigo; Mizukami, Ryo; Yamazaki, Takumi; Prananto, Lukman A.; Nozaki, Tomohiro

2018-03-01

Interaction between dielectric barrier discharge (DBD) and porous catalyst in dry methane reforming (CH4  +  CO2  =  2H2  +  2CO) was studied. Coke formation behavior and coke morphology, as well as material conversion and selectivity, over the cross-section of porous pellets was investigated comprehensively by SEM analysis, Raman spectroscopy and pulsed reforming diagnosis, showing DBD and porous pellet interaction is possible only in the interfacial region (the external surface of the pellet): neither generation of DBD nor the diffusion of plasma generated reactive species in the internal micropores is possible. Coke formation and gasification mechanism in nonthermal plasma catalysis of DMR were discussed based on the catalyst effectiveness factor: low-temperature plasma catalysis is equivalent to the high-temperature thermal catalysis.

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.

Water structure and its influence on the flotation of carbonate and bicarbonate salts.

PubMed

Ozdemir, O; Celik, M S; Nickolov, Z S; Miller, J D

2007-10-15

Interfacial water structure is a most important parameter that influences the collector adsorption by salt minerals such as borax, potash and trona. According to previous studies, salts can be classified as water structure makers and water structure breakers. Water structure making and breaking properties of salt minerals in their saturated brine solutions are essential to explain their flotation behavior. In this work, water structure making-breaking studies in solutions of carbonate and bicarbonate salts (Na(2)CO(3), K(2)CO(3), NaHCO(3) and NH(4)HCO(3)) in 4 wt% D(2)O in H(2)O mixtures have been performed by FTIR analysis of the OD stretching band. This method reveals a microscopic picture of the water structure making/breaking character of the salts in terms of the hydrogen bonding between the water molecules in solution. The results from the vibrational spectroscopic studies demonstrate that carbonate salts (Na(2)CO(3) and K(2)CO(3)) act as strong structure makers, whereas bicarbonate salts (NaHCO(3) and NH(4)HCO(3)) act as weak structure makers. In addition, the changes in the OD band parameters of carbonate and bicarbonate salt solutions are in agreement with the viscosity characteristics of their solutions.

Interfacial assembly structures and nanotribological properties of saccharic acids.

PubMed

Shi, Hongyu; Liu, Yuhong; Zeng, Qingdao; Yang, Yanlian; Wang, Chen; Lu, Xinchun

2017-01-04

Saccharides have been recognized as potential bio-lubricants because of their good hydration ability. However, the interfacial structures of saccharides and their derivatives are rarely studied and the molecular details of interaction mechanisms have not been well understood. In this paper, the supramolecular assembly structures of saccharic acids (including galactaric acid and lactobionic acid), mediated by hydrogen bonds O-HN and O-HO, were successfully constructed on a highly oriented pyrolytic graphite (HOPG) surface by introducing pyridine modulators and were explicitly revealed by using scanning tunneling microscopy (STM). Furthermore, friction forces were measured in the saccharic acid/pyridine co-assembled system by atomic force microscopy (AFM), revealing a larger value than a pristine saccharic acid system, which could be attributed to the stronger tip-assembled molecule interactions that lead to the higher potential energy barrier needed to overcome. The effort on saccharide-related supramolecular self-assembly and nanotribological behavior could provide a novel and promising pathway to explore the interaction mechanisms underlying friction and reveal the structure-property relationship at the molecular level.

Design of exceptionally strong and conductive Cu alloys beyond the conventional speculation via the interfacial energy-controlled dispersion of γ-Al2O3 nanoparticles

PubMed Central

Zeon Han, Seung; Kim, Kwang Ho; Kang, Joonhee; Joh, Hongrae; Kim, Sang Min; Ahn, Jee Hyuk; Lee, Jehyun; Lim, Sung Hwan; Han, Byungchan

2015-01-01

The development of Cu-based alloys with high-mechanical properties (strength, ductility) and electrical conductivity plays a key role over a wide range of industrial applications. Successful design of the materials, however, has been rare due to the improvement of mutually exclusive properties as conventionally speculated. In this paper, we demonstrate that these contradictory material properties can be improved simultaneously if the interfacial energies of heterogeneous interfaces are carefully controlled. We uniformly disperse γ-Al2O3 nanoparticles over Cu matrix, and then we controlled atomic level morphology of the interface γ-Al2O3//Cu by adding Ti solutes. It is shown that the Ti dramatically drives the interfacial phase transformation from very irregular to homogeneous spherical morphologies resulting in substantial enhancement of the mechanical property of Cu matrix. Furthermore, the Ti removes impurities (O and Al) in the Cu matrix by forming oxides leading to recovery of the electrical conductivity of pure Cu. We validate experimental results using TEM and EDX combined with first-principles density functional theory (DFT) calculations, which all consistently poise that our materials are suitable for industrial applications. PMID:26616045

Design of exceptionally strong and conductive Cu alloys beyond the conventional speculation via the interfacial energy-controlled dispersion of γ-Al2O3 nanoparticles.

PubMed

Han, Seung Zeon; Kim, Kwang Ho; Kang, Joonhee; Joh, Hongrae; Kim, Sang Min; Ahn, Jee Hyuk; Lee, Jehyun; Lim, Sung Hwan; Han, Byungchan

2015-11-30

The development of Cu-based alloys with high-mechanical properties (strength, ductility) and electrical conductivity plays a key role over a wide range of industrial applications. Successful design of the materials, however, has been rare due to the improvement of mutually exclusive properties as conventionally speculated. In this paper, we demonstrate that these contradictory material properties can be improved simultaneously if the interfacial energies of heterogeneous interfaces are carefully controlled. We uniformly disperse γ-Al2O3 nanoparticles over Cu matrix, and then we controlled atomic level morphology of the interface γ-Al2O3//Cu by adding Ti solutes. It is shown that the Ti dramatically drives the interfacial phase transformation from very irregular to homogeneous spherical morphologies resulting in substantial enhancement of the mechanical property of Cu matrix. Furthermore, the Ti removes impurities (O and Al) in the Cu matrix by forming oxides leading to recovery of the electrical conductivity of pure Cu. We validate experimental results using TEM and EDX combined with first-principles density functional theory (DFT) calculations, which all consistently poise that our materials are suitable for industrial applications.

Electrical Control of Metallic Heavy-Metal-Ferromagnet Interfacial States

NASA Astrophysics Data System (ADS)

Bi, Chong; Sun, Congli; Xu, Meng; Newhouse-Illige, Ty; Voyles, Paul M.; Wang, Weigang

2017-09-01

Voltage-control effects provide an energy-efficient means of tailoring material properties, especially in highly integrated nanoscale devices. However, only insulating and semiconducting systems can be controlled so far. In metallic systems, there is no electric field due to electron screening effects and thus no such control effect exists. Here, we demonstrate that metallic systems can also be controlled electrically through ionic rather than electronic effects. In a Pt /Co structure, the control of the metallic Pt /Co interface can lead to unprecedented control effects on the magnetic properties of the entire structure. Consequently, the magnetization and perpendicular magnetic anisotropy of the Co layer can be independently manipulated to any desired state, the efficient spin toques can be enhanced about 3.5 times, and the switching current can be reduced about one order of magnitude. This ability to control a metallic system may be extended to control other physical phenomena.

Laboratory and numerical investigations of kinetic interface sensitive tracers transport for immiscible two-phase flow porous media systems

NASA Astrophysics Data System (ADS)

Tatomir, Alexandru Bogdan A. C.; Sauter, Martin

2017-04-01

A number of theoretical approaches estimating the interfacial area between two fluid phases are available (Schaffer et al.,2013). Kinetic interface sensitive (KIS) tracers are used to describe the evolution of fluid-fluid interfaces advancing in two phase porous media systems (Tatomir et al., 2015). Initially developed to offer answers about the supercritical (sc)CO2 plume movement and the efficiency of trapping in geological carbon storage reservoirs, KIS tracers are tested in dynamic controlled laboratory conditions. N-octane and water, analogue to a scCO2 - brine system, are used. The KIS tracer is dissolved in n-octane, which is injected as the non-wetting phase in a fully water saturated porous media column. The porous system is made up of spherical glass beads with sizes of 100-250 μm. Subsequently, the KIS tracer follows a hydrolysis reaction over the n-octane - water interface resulting in an acid and phenol which are both water soluble. The fluid-fluid interfacial area is described numerically with the help of constitutive-relationships derived from the Brooks-Corey model. The specific interfacial area is determined numerically from pore scale calculations, or from different literature sources making use of pore network model calculations (Joekar-Niasar et al., 2008). This research describes the design of the laboratory setup and compares the break-through curves obtained with the forward model and in the laboratory experiment. Furthermore, first results are shown in the attempt to validate the immiscible two phase flow reactive transport numerical model with dynamic laboratory column experiments. Keywords: Fluid-fluid interfacial area, KIS tracers, model validation, CCS, geological storage of CO2

Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

1990-01-01

The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4 percent H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.

A separation of antiferromagnetic spin motion modes in the training effect of exchange biased Co/CoO film with in-plane anisotropy

NASA Astrophysics Data System (ADS)

Wu, R.; Yun, C.; Ding, S. L.; Wen, X.; Liu, S. Q.; Wang, C. S.; Han, J. Z.; Du, H. L.; Yang, J. B.

2016-08-01

The motion of antiferromagnetic interfacial spins is investigated through the temperature evolution of training effect in a Co/CoO film with in-plane biaxial anisotropy. Significant differences in the training effect and its temperature dependence are observed in the magnetic easy axis and hard axis (HA) and ascribed to the different motion modes of antiferromagnetic interfacial spins, the collective spin cluster rotation (CSR) and the single spin reversal (SSR), caused by different magnetization reversal modes of ferromagnetic layer. These motion modes of antiferromagnetic spins are successfully separated using a combination of an exponential function and a classic n-1/2 function. A larger CSR to SSR ratio and a shorter lifetime of CSR found in the HA indicates that the domain rotation in the ferromagnetic layer tends to activate and accelerate a CSR mode in the antiferromagnetic spins.

Mechanism of phosphorus passivation of near-interface oxide traps in 4H–SiC MOS devices investigated by CCDLTS and DFT calculation

NASA Astrophysics Data System (ADS)

Jayawardena, Asanka; Shen, X.; Mooney, P. M.; Dhar, Sarit

2018-06-01

Interfacial charge trapping in 4H–SiC MOS capacitors with P doped SiO2 or phospho-silicate glass (PSG) as a gate dielectric has been investigated with temperature dependent capacitance–voltage measurements and constant capacitance deep level transient spectroscopy (CCDLTS) measurements. The measurements indicate that P doping in the dielectric results in significant reduction of near-interface electron traps that have energy levels within 0.5 eV of the 4H–SiC conduction band edge. Extracted trap densities confirm that the phosphorus induced near-interface trap reduction is significantly more effective than interfacial nitridation, which is typically used for 4H–SiC MOSFET processing. The CCDLTS measurements reveal that the two broad near-interface trap peaks, named ‘O1’ and ‘O2’, with activation energies around 0.15 eV and 0.4 eV below the 4H–SiC conduction band that are typically observed in thermal oxides on 4H–SiC, are also present in PSG devices. Previous atomic scale ab initio calculations suggested these O1 and O2 traps to be carbon dimers substituted for oxygen dimers (CO=CO) and interstitial Si (Sii) in SiO2, respectively. Theoretical considerations in this work suggest that the presence of P in the near-interfacial region reduces the stability of the CO=CO defects and reduces the density of Sii defects through the network restructuring. Qualitative comparison of results in this work and reported work suggest that the O1 and O2 traps in SiO2/4H–SiC MOS system negatively impact channel mobility in 4H–SiC MOSFETs.

Construction of multifunctional MoSe2 hybrid towards the simultaneous improvements in fire safety and mechanical property of polymer.

PubMed

Wang, Junling; Ma, Chao; Mu, Xiaowei; Cai, Wei; Liu, Longxiang; Zhou, Xia; Hu, Weizhao; Hu, Yuan

2018-06-15

Organic modification of MoSe 2 sheets is firstly achieved by Atherton-Todd reaction, aiming at the acquisition of multifunctional MoSe 2 hybrid. Simultaneous enhancements in fire safety and mechanical property of thermalplastic polyurethane (TPU) are obtained with the presence of this hybrid. Strong interfacial interactions between the functionalized MoSe 2 sheets and TPU can be obtained, making more efficient load transfer from the weak polymer chains to the robust sheets. Besides, more coherent barrier network may be formed in polymer matrix, restraining the diffusion of decomposed fragments and reducing the supply for combustion fuel. Consequently, the decreases in heat release are observed for polymer composites. Notably, the releases of toxic gases, such as HCN and CO, are also suppressed by this barrier network, resulting in the reductions in fire toxicity. This work may open a new door for the functionalization of MoSe 2 sheets and evoke significant developments in its promising applications. Copyright © 2018. Published by Elsevier B.V.

Molecular dynamics computations of brine-CO2 interfacial tensions and brine-CO2-quartz contact angles and their effects on structural and residual trapping mechanisms in carbon geo-sequestration.

PubMed

Iglauer, S; Mathew, M S; Bresme, F

2012-11-15

In the context of carbon geo-sequestration projects, brine-CO(2) interfacial tension γ and brine-CO(2)-rock surface water contact angles θ directly impact structural and residual trapping capacities. While γ is fairly well understood there is still large uncertainty associated with θ. We present here an investigation of γ and θ using a molecular approach based on molecular dynamics computer simulations. We consider a system consisting of CO(2)/water/NaCl and an α-quartz surface, covering a brine salinity range between 0 and 4 molal. The simulation models accurately reproduce the dependence of γ on pressure below the CO(2) saturation pressure at 300 K, and over predict γ by ~20% at higher pressures. In addition, in agreement with experimental observations, the simulations predict that γ increases slightly with temperature or salinity. We also demonstrate that for non-hydroxylated quartz surfaces, θ strongly increases with pressure at subcritical and supercritical conditions. An increase in temperature significantly reduces the contact angle, especially at low-intermediate pressures (1-10 MPa), this effect is mitigated at higher pressures, 20 MPa. We also found that θ only weakly depends on salinity for the systems investigated in this work. Copyright © 2012 Elsevier Inc. All rights reserved.

Organic-Inorganic Hybrid Interfacial Layer for High-Performance Planar Perovskite Solar Cells.

PubMed

Yang, Hao; Cong, Shan; Lou, Yanhui; Han, Liang; Zhao, Jie; Sun, Yinghui; Zou, Guifu

2017-09-20

4,7-Diphenyl-1,10-phenanthroline (Bphen) is an efficient electron transport and hole blocking material in organic photoelectric devices. Here, we report cesium carbonate (Cs 2 CO 3 ) doped Bphen as cathode interfacial layer in CH 3 NH 3 PbI 3-x Cl x based planar perovskite solar cells (PSCs). Investigation finds that introducing Cs 2 CO 3 suppresses the crystallization of Bphen and benefits a smooth interface contact between the perovskite and electrode, resulting in the decrease in carrier recombination and the perovskite degradation. In addition, the matching energy level of Bphen film in the PSCs effectively blocks the holes diffusion to cathode. The resultant power conversion efficiency (PCE) achieves as high as 17.03% in comparison with 12.67% of reference device without doping. Besides, experiments also demonstrate the stability of PSCs have large improvement because the suppressed crystallization of Bphen by doping Cs 2 CO 3 as a superior barrier layer blocks the Ag atom and surrounding moisture access to the vulnerable perovskite layer.

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.

Unexpected molecular weight effect in polymer nanocomposites

DOE PAGES

Cheng, Shiwang; Holt, Adam P.; Wang, Huiqun; ...

2016-01-22

Here, the properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp constrast to theoretical predictions. Further analyses reveal amore » reduction in mass density of the interfacial layer with increasing MW, which can explain these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties.« less

Tailoring the Interfacial Chemical Interaction for High-Efficiency Perovskite Solar Cells.

PubMed

Zuo, Lijian; Chen, Qi; De Marco, Nicholas; Hsieh, Yao-Tsung; Chen, Huajun; Sun, Pengyu; Chang, Sheng-Yung; Zhao, Hongxiang; Dong, Shiqi; Yang, Yang

2017-01-11

The ionic nature of perovskite photovoltaic materials makes it easy to form various chemical interactions with different functional groups. Here, we demonstrate that interfacial chemical interactions are a critical factor in determining the optoelectronic properties of perovskite solar cells. By depositing different self-assembled monolayers (SAMs), we introduce different functional groups onto the SnO 2 surface to form various chemical interactions with the perovskite layer. It is observed that the perovskite solar cell device performance shows an opposite trend to that of the energy level alignment theory, which shows that chemical interactions are the predominant factor governing the interfacial optoelectronic properties. Further analysis verifies that proper interfacial interactions can significantly reduce trap state density and facilitate the interfacial charge transfer. Through use of the 4-pyridinecarboxylic acid SAM, the resulting perovskite solar cell exhibits striking improvements to the reach the highest efficiency of 18.8%, which constitutes an ∼10% enhancement compared to those without SAMs. Our work highlights the importance of chemical interactions at perovskite/electrode interfaces and paves the way for further optimizing performances of perovskite solar cells.

Regio-selective lipase catalyzed hydrolysis of oxanorbornane-based sugar-like amphiphiles at air-water interface: A polarized FT-IRRAS study.

PubMed

Sarangi, Nirod Kumar; Ganesan, M; Muraleedharan, K M; Patnaik, Archita

2017-04-01

Interfacial hydrolysis of oxanorbornane-based amphiphile (Triol C16) by Candida rugosa lipase was investigated using real-time polarized Fourier transform-infrared reflection absorption spectroscopy (FT-IRRAS). The kinetics of hydrolysis was studied by analyzing the ester carbonyl ν(CO) stretching vibration band across the two dimensional (2D) array of molecules at the confined interface. In particular, we demonstrate Triol C16 to form Michaelis-Menten type complex, like that of lipid-substrate analogues, where the Triol C16 head group remained accessible to the catalytic triad of the lipase. The enzyme-induced selective cleavage of the ester bond was spectroscopically monitored by the disappearance of the intense ν(CO) resonance at 1736cm -1 . Consequently, the in situ spectroscopic measurements evidenced selective ester hydrolysis of Triol C16 yielding Tetrol C 2 OH and Palmitic acid, which remained predominantly in the undissociated form at the interface. The conformation sensitive amide I (majorly ν(CO)) and the interfacial water reorganization suggested 2D ordering of the enzyme molecules following which interfacial reactions were employed towards probing the enzyme kinetics at the air/water interface. The investigation demonstrated further the potential of IRRAS spectroscopy for real-time monitoring the hydrolytic product formation and selectivity at biomimetic interfaces. Copyright © 2017 Elsevier B.V. All rights reserved.

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5. Interface Effects

DTIC Science & Technology

1994-04-01

Interfacial Mechanical Properties in Fiber Reinforced Ceramic Composites," 1. Am. Ceram. Soc., 70 (1987) 542-48. [25] P.D. Jero, R.J. Kerans and T.A...Mater., 40 [611251-57 (1992). [16] D.B. Marshall and W. Oliver, "Measurement of Interfacial Mechanical Properties in Fiber-Reinforced Ceramic...Charlottesville. VA 22903, U.S.A. (Received 14 July 1993;fl/al version acepted IS AustrW 1993) Abstract-The interfacial structure / property relationships of a

Galvanostatic Intermittent Titration and Performance Based Analysis of LiNi 0.5 Co 0.2 Mn 0.3 O 2 Cathode

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

Verma, Ankit; Smith, Kandler; Santhanagopalan, Shriram

Galvanostatic intermittent titration technique (GITT) - a popular method for characterizing kinetic and transport properties of battery electrodes - is predicated on the proper evaluation of electrode active area. LiNi 0.5044Co 0.1986Mn 0.2970O 2 (NCM523) material exhibits a complex morphology in which sub-micron primary particles aggregate to form secondary particle agglomerates. Our work proposes a new active area formulation for primary/secondary particle agglomerate materials to better mimic the morphology of NCM532 electrodes. Furthermore, this formulation is then coupled with macro-homogeneous models to simulate GITT and half-cell performance of NCM523 electrodes. Subsequently, the model results are compared against the experimental resultsmore » to refine the area formulation. A single parameter, the surface roughness factor, is proposed to mimic the change in interfacial area, diffusivity and exchange current density simultaneously and detailed modeling results are presented to provide valuable insights into the efficacy of the formulation.« less

Galvanostatic Intermittent Titration and Performance Based Analysis of LiNi 0.5Co 0.2 Mn 0.3O 2Cathode

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

Verma, Ankit; Smith, Kandler; Santhanagopalan, Shriram

Galvanostatic intermittent titration technique (GITT) – a popular method for characterizing kinetic and transport properties of battery electrodes – is predicated on the proper evaluation of electrode active area. LiNi0.5044Co0.1986Mn0.2970O2 (NCM523) material exhibits a complex morphology in which sub-micron primary particles aggregate to form secondary particle agglomerates. This work proposes a new active area formulation for primary/secondary particle agglomerate materials to better mimic the morphology of NCM532 electrodes. This formulation is then coupled with macro-homogeneous models to simulate GITT and half-cell performance of NCM523 electrodes. Subsequently, the model results are compared against the experimental results to refine the area formulation.more » A single parameter, the surface roughness factor, is proposed to mimic the change in interfacial area, diffusivity and exchange current density simultaneously and detailed modeling results are presented to provide valuable insights into the efficacy of the formulation.« less

Galvanostatic Intermittent Titration and Performance Based Analysis of LiNi 0.5 Co 0.2 Mn 0.3 O 2 Cathode

DOE PAGES

Verma, Ankit; Smith, Kandler; Santhanagopalan, Shriram; ...

2017-11-03

Galvanostatic intermittent titration technique (GITT) - a popular method for characterizing kinetic and transport properties of battery electrodes - is predicated on the proper evaluation of electrode active area. LiNi 0.5044Co 0.1986Mn 0.2970O 2 (NCM523) material exhibits a complex morphology in which sub-micron primary particles aggregate to form secondary particle agglomerates. Our work proposes a new active area formulation for primary/secondary particle agglomerate materials to better mimic the morphology of NCM532 electrodes. Furthermore, this formulation is then coupled with macro-homogeneous models to simulate GITT and half-cell performance of NCM523 electrodes. Subsequently, the model results are compared against the experimental resultsmore » to refine the area formulation. A single parameter, the surface roughness factor, is proposed to mimic the change in interfacial area, diffusivity and exchange current density simultaneously and detailed modeling results are presented to provide valuable insights into the efficacy of the formulation.« less

Quantifying Interfacial pH Variation at Molecular Length Scales Using a Concurrent Non-Faradaic Reaction.

PubMed

Ryu, Jaeyune; Wuttig, Anna; Surendranath, Yogesh

2018-05-15

We quantify changes in the interfacial pH local to the electrochemical double layer during electrocatalysis, using a concurrent non-faradaic probe reaction. In the absence of electrocatalysis, nanostructured Pt/C surfaces mediate the reaction of H2 with cis-2-butene-1,4-diol to form a mixture of 1,4-butanediol and n-butanol with a selectivity that is linearly dependent on the bulk solution pH. We show that kinetic branching occurs from a common surface-bound intermediate, ensuring that this probe reaction is uniquely sensitive to the interfacial pH within molecular length scales of the surface. We use the pH-dependent selectivity of this reaction to track changes in interfacial pH during concurrent hydrogen oxidation electrocatalysis and find that the local pH can vary dramatically, > 3 units, relative to the bulk value even at modest current densities in well-buffered electrolytes. This work highlights the key role that interfacial pH variation plays in modulating inner-sphere electrocatalysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-Ray Photoelectron Spectroscopy Study of the Heating Effects on Pd/6H-SiC Schottky Structure

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak

1998-01-01

X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 C for 140 h, a very thin surface layer of PdO mixed with SiO(x) formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are Pd(x)Si (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while gr and Pd2Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (Pd(x)Si, x= 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiO, may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd+Pd(x)Si)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled.

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 formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

DOE PAGES

Wang, Yanggang; Mei, Donghai; Glezakou, Vassiliki Alexandra; ...

2015-03-04

Ab initio Molecular Dynamics simulations and static Density Functional Theory calculations have been performed to investigate the reaction mechanism of CO oxidation on Au/CeO 2 catalyst. It is found that under reaction condition CO adsorption significantly labializes the surface atoms of the Au cluster and leads to the formation of isolated Au+-CO species that resides on the support in the vicinity of the Au particle. In this context, we identified a dynamic single-atom catalytic mechanism at the interfacial area for CO oxidation on Au/CeO 2 catalyst, which is a lower energy pathway than that of CO oxidation at the interfacemore » with the metal particle. This results from the ability of the single atom site to strongly couple with the redox properties of the support in a synergistic manner thereby lowering the barrier for redox reactions. We find that the single Au+ ion, which only exists under reaction conditions, breaks away from the Au cluster to catalyze CO oxidation and returns to the Au cluster after the catalytic cycle is completed. Generally, our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in a catalytic process.« less

Microfluidic ultralow interfacial tensiometry with magnetic particles.

PubMed

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

2013-01-07

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

Interface Engineering of Garnet Solid Electrolytes

NASA Astrophysics Data System (ADS)

Cheng, Lei

Solid lithium ion conductors represent a promising class of materials for next generation high energy density batteries, with the potential for enabling use of high capacity Li metal anodes and providing opportunities for novel lithium-free cathode materials. However, highly resistive interfaces stymie their practical use. This urgent scientific challenge requires mechanistic understanding of ion transport at interfaces, as well as development of novel processes to achieve low interfacial resistances. The goal of this PhD dissertation was to generate fundamental understandings of garnet-structured Al substituted Li7La3Zr2O 12 (LLZO) electrolyte surfaces and interfaces with lithium metal electrodes. Specifically in this research, the topmost surface microstructure, local chemical environment, and surface chemistry were carefully studied. The ceramic processing of garnet is discussed and ways to control the sintering behavior and microstructures were explored and successfully demonstrated. Factors contributing to high interfacial resistance were systematically studied. The source of the high interfacial impedance has been traced to the presence of Li2CO 3 on pellet surfaces resulting from air exposure after processing. In addition, it was discovered that surface grain boundaries are surprisingly fast ion transport pathways and surface microstructure is critically important to lithium ion transport at interfaces. Complex homo- and heterostructured LLZO solid electrolytes with controllable surface and bulk microstructures were successfully fabricated, which allowed the comparison and separation of the contribution from the surface and the bulk. Engineered pellet surfaces allowed us to achieve the lowest interfacial resistance ever reported for this composition, resulting in significantly improved cycling behavior. Lastly, it was found that LLZO surfaces can be effectively stabilized under air exposure conditions, preventing Li2CO3 formation and maintaining low interfacial resistances. This opens new opportunities for garnet solid electrolyte in practical applications.

The foaming properties of camel and bovine whey: The impact of pH and heat treatment.

PubMed

Lajnaf, Roua; Picart-Palmade, Laetitia; Cases, Eliane; Attia, Hamadi; Marchesseau, Sylvie; Ayadi, M A

2018-02-01

The effect of heat treatment (70°C or 90°C for 30min) on the foaming and interfacial properties of acid and sweet whey obtained from bovine and camel fresh milk was examined. The maximum foamability and foam stability were observed for acid whey when compared to sweet whey for both milks, with higher values for the camel whey. This behavior for acid whey was explained by the proximity of the pI of whey protein (4.9-5.2), where proteins were found to carry the lowest negative charge as confirmed by the zeta potential measurements. Interfacial properties of acid camel whey and acid bovine whey were preserved at air water interface even after a heat treatment at 90°C. These results confirmed the pronounced foaming and interfacial properties of acid camel whey, even if acid and sweet bovine whey exhibited the highest viscoelastic modulus after heating. Copyright © 2017 Elsevier Ltd. All rights reserved.

Potential-sensing electrochemical atomic force microscopy for in operando analysis of water-splitting catalysts and interfaces

NASA Astrophysics Data System (ADS)

Nellist, Michael R.; Laskowski, Forrest A. L.; Qiu, Jingjing; Hajibabaei, Hamed; Sivula, Kevin; Hamann, Thomas W.; Boettcher, Shannon W.

2018-01-01

Heterogeneous electrochemical phenomena, such as (photo)electrochemical water splitting to generate hydrogen using semiconductors and/or electrocatalysts, are driven by the accumulated charge carriers and thus the interfacial electrochemical potential gradients that promote charge transfer. However, measurements of the "surface" electrochemical potential during operation are not generally possible using conventional electrochemical techniques, which measure/control the potential of a conducting electrode substrate. Here we show that the nanoscale conducting tip of an atomic force microscope cantilever can sense the surface electrochemical potential of electrocatalysts in operando. To demonstrate utility, we measure the potential-dependent and thickness-dependent electronic properties of cobalt (oxy)hydroxide phosphate (CoPi). We then show that CoPi, when deposited on illuminated haematite (α-Fe2O3) photoelectrodes, acts as both a hole collector and an oxygen evolution catalyst. We demonstrate the versatility of the technique by comparing surface potentials of CoPi-decorated planar and mesoporous haematite and discuss viability for broader application in the study of electrochemical phenomena.

Ferromagnetism in spin-coated cobalt-doped TiO2 thin films and the role of crystalline phases

NASA Astrophysics Data System (ADS)

Salazar Cuaila, J. L.; Alayo, W.; Avellaneda, César O.

2017-11-01

Two sets of Cobalt-doped (1-10% at) TiO2 thin films, for different molar concentrations of the Ti precursor (0.3 and 0.5 mol/L), have been deposited onto Si substrates by combining the Sol Gel process and the Spin Coating technique. The structure of the samples was studied by X-ray reflectivity (XRR) and X-ray diffraction (XRD) and their magnetic properties were analyzed by magnetization measurements as a function of the applied magnetic field. The XRR results provided the thickness and interfacial roughness of the films, while XRD patterns revealed the crystalline phases and lattice parameters. Room temperature ferromagnetic behaviour was observed for some of the atomic Co concentrations by the magnetization measurements. This behaviour has been correlated to the crystalline phases, which were found to be modified by both the molar ratio of Ti precursor and the concentration of the Co dopant. A suppression of ferromagnetism is observed for some atomic Co fractions and it was attributed to the presence of secondary crystalline phases.

Improved electrochemical properties of morphology-controlled titania/titanate nanostructures prepared by in-situ hydrothermal surface modification of self-source Ti substrate for high-performance supercapacitors.

PubMed

Banerjee, Arghya Narayan; Anitha, V C; Joo, Sang W

2017-10-16

Ti substrate surface is modified into two-dimensional (2D) TiO 2 nanoplatelet or one-dimensional (1D) nanorod/nanofiber (or a mixture of both) structure in a controlled manner via a simple KOH-based hydrothermal technique. Depending on the KOH concentration, different types of TiO 2 nanostructures (2D platelets, 1D nanorods/nanofibers and a 2D+1D mixed sample) are fabricated directly onto the Ti substrate surface. The novelty of this technique is the in-situ modification of the self-source Ti surface into titania nanostructures, and its direct use as the electrochemical microelectrode without any modifications. This leads to considerable improvement in the interfacial properties between metallic Ti and semiconducting TiO 2 . Since interfacial states/defects have profound effect on charge transport properties of electronic/electrochemical devices, therefore this near-defect-free interfacial property of Ti-TiO 2 microelectrode has shown high supercapacitive performances for superior charge-storage devices. Additionally, by hydrothermally tuning the morphology of titania nanostructures, the electrochemical properties of the electrodes are also tuned. A Ti-TiO 2 electrode comprising of a mixture of 2D-platelet+1D-nanorod structure reveals very high specific capacitance values (~7.4 mF.cm -2 ) due to the unique mixed morphology which manifests higher active sites (hence, higher utilization of the active materials) in terms of greater roughness at the 2D-platelet structures and higher surface-to-volume-ratio in the 1D-nanorod structures.

Mechanism of CO 2 hydrogenation over Cu/ZrO 2(2̅12) interface from first-principles kinetics Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Hong, Qi-Jun; Liu, Zhi-Pan

2010-10-01

It has been a goal consistently pursued by chemists to understand and control the catalytic process over composite materials. In order to provide deeper insight on complex interfacial catalysis at the experimental conditions, we performed an extensive analysis on CO 2 hydrogenation over a Cu/ZrO 2 model catalyst by employing density functional theory (DFT) calculations and kinetic Monte Carlo (kMC) simulations based on the continuous stirred tank model. The free energy profiles are determined for the reaction at the oxygen-rich Cu/m-ZrO 2 (2̅12) interface, where all interfacial Zr are six-coordinated since the interface accumulates oxidative species at the reaction conditions. We show that not only methanol but also CO are produced through the formate pathway dominantly, whilst the reverse-water-gas-shift (RWGS) channel has only a minor contribution. H 2CO is a key intermediate species in the reaction pathway, the hydrogenation of which dictates the high temperature of CO 2 hydrogenation. The kinetics simulation shows that the CO 2 conversion is 1.20%, the selectivity towards methanol is 68% at 500 K and the activation energies for methanol and CO formation are 0.79 and 1.79 eV, respectively. The secondary reactions due to the product readsorption lower the overall turnover frequency (TOF) but increase the selectivity towards methanol by 16%. We also show that kMC is a more reliable tool for simulating heterogeneous catalytic processes compared to the microkinetics approach.

Interactions Between Stratigraphy and Interfacial Properties on Flow and Trapping in Geologic Carbon Storage

NASA Astrophysics Data System (ADS)

Liang, Bo; Clarens, Andres F.

2018-01-01

Gas leakage from geologic carbon storage sites could undermine the long-term goal of reducing emissions to the atmosphere and negatively impact groundwater resources. Despite this, there remain uncertainties associated with the transport processes that would govern this leakage. These stem from the complex interaction between governing forces (e.g., gravitational, viscous, and capillary), the heterogeneous nature of the porous media, and the characteristic length scales of these leakage events, all of which impact the CO2 fluid flow processes. Here we assessed how sub-basin-scale horizons in porous media could impact the migration and trapping of a CO2 plume. A high-pressure column packed with two layers of sand with different properties (e.g., grain size and wettability) was used to create a low-contrast stratigraphic horizon. CO2 in supercritical or liquid phase was injected into the bottom of the column under various conditions (e.g., temperature, pressure, and capillary number) and the transport of the resulting plume was recorded using electrical resistivity. The results show that CO2 trapping was most strongly impacted by shifting the wettability balance to mixed-wet conditions, particularly for residual saturation. A 16% increase in the cosine of the contact angle for a mixed-wet sand resulted in nearly twice as much residual trapping. Permeability contrast, pressure, and temperature also impacted the residual saturation but to a lesser extent. Flow rate affected the dynamics of saturation profile development, but the effect is transient, suggesting that the other effects observed here could apply to a broad range of leakage conditions.

Stimuli-enabled zipper-like graphene interface for auto-switchable bioelectronics.

PubMed

Mishra, Sachin; Ashaduzzaman, Md; Mishra, Prashant; Swart, Hendrik C; Turner, Anthony P F; Tiwari, Ashutosh

2017-03-15

Graphene interfaces with multi-stimuli responsiveness are of particular interest due to their diverse super-thin interfacial behaviour, which could be well suited to operating complex physiological systems in a single miniaturised domain. In general, smart graphene interfaces switch bioelectrodes from the hydrophobic to hydrophilic state, or vice versa, upon triggering. In the present work, a stimuli encoded zipper-like graphene oxide (GrO)/polymer interface was fabricated with in situ poly(N-isopropylacrylamide-co-diethylaminoethylmethylacrylate), i.e., poly(NIPAAm-co-DEAEMA) directed hierarchical self-assembly of GrO and glucose oxidase (GOx). The designed interface exhibited reversible on/off-switching of bio-electrocatalysis on changing the pH between 5 and 8, via phase transition from super hydrophilic to hydrophobic. The study further indicated that the zipper-like interfacial bioelectrochemical properties could be tuned over a modest change of temperature (i.e., 20-40°C). The resulting auto-switchable interface has implications for the design of novel on/off-switchable biodevices with 'in-built' self-control. Copyright © 2016 Elsevier B.V. All rights reserved.

Rapid and Simple Capillary-Rise/Vanishing Interfacial Tension Method To Determine Crude Oil Minimum Miscibility Pressure: Pure and Mixed CO 2, Methane, and Ethane

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

Hawthorne, Steven B.; Miller, David J.; Jin, Lu

Here, we report a simplification of the capillary-rise/vanishing interfacial tension (IFT) method to measure minimum miscibility pressure (MMP) based on only requiring knowledge of when the interfacial tension approaches zero. Simply measuring the height of the crude oil in a capillary at several pressures from ambient to near the MMP pressure and extrapolating the oil height versus pressure plot to zero oil height yields the MMP without the need of the additional instrumentation and labor required to perform actual IFT measurements. A total of 2-4 MMP values can be determined per day with only one experimental apparatus, and the methodmore » greatly reduces the initial cost and complexity of the required instrumentation. The use of three capillaries having different inner diameters allows for triplicate determinations of MMP from each experiment. Because the actual MMP pressure need not be reached during the experiment, MMP values that exceed the pressure ratings of the equipment can be reasonably estimated (e.g., MMPs using pure nitrogen). The method was used to determine the MMP pressure for crude oil samples from a conventional Muddy Formation reservoir in the Powder River Basin [American Petroleum Institute (API) gravity of 35.8°] and an unconventional Bakken Formation reservoir in the Williston Basin (API gravity of 38.7°). The method is reproducible [typically <4% relative standard deviation (RSD)], and the method gave good agreement for a “live” Bakken oil with the results from a slim tube test of a commercial laboratory. Approximately 80 MMP values were measured using pure CO 2, methane, and ethane as well as 0-100% mole ratios of methane/CO 2 and methane/ethane. For both oil samples, ethane MMPs were ca. one-half those with CO 2, while methane MMPs were ca. double or triple those with CO 2. MMPs with mixed methane/CO 2 showed a linear increase with mole percent methane for both crude oils, while both oils showed an exponential increase in MMP with mole percent methane in ethane, with a little increase in MMP until ca. 20 mol % methane in ethane.« less

Rapid and Simple Capillary-Rise/Vanishing Interfacial Tension Method To Determine Crude Oil Minimum Miscibility Pressure: Pure and Mixed CO 2, Methane, and Ethane

DOE PAGES

Hawthorne, Steven B.; Miller, David J.; Jin, Lu; ...

2016-07-10

Here, we report a simplification of the capillary-rise/vanishing interfacial tension (IFT) method to measure minimum miscibility pressure (MMP) based on only requiring knowledge of when the interfacial tension approaches zero. Simply measuring the height of the crude oil in a capillary at several pressures from ambient to near the MMP pressure and extrapolating the oil height versus pressure plot to zero oil height yields the MMP without the need of the additional instrumentation and labor required to perform actual IFT measurements. A total of 2-4 MMP values can be determined per day with only one experimental apparatus, and the methodmore » greatly reduces the initial cost and complexity of the required instrumentation. The use of three capillaries having different inner diameters allows for triplicate determinations of MMP from each experiment. Because the actual MMP pressure need not be reached during the experiment, MMP values that exceed the pressure ratings of the equipment can be reasonably estimated (e.g., MMPs using pure nitrogen). The method was used to determine the MMP pressure for crude oil samples from a conventional Muddy Formation reservoir in the Powder River Basin [American Petroleum Institute (API) gravity of 35.8°] and an unconventional Bakken Formation reservoir in the Williston Basin (API gravity of 38.7°). The method is reproducible [typically <4% relative standard deviation (RSD)], and the method gave good agreement for a “live” Bakken oil with the results from a slim tube test of a commercial laboratory. Approximately 80 MMP values were measured using pure CO 2, methane, and ethane as well as 0-100% mole ratios of methane/CO 2 and methane/ethane. For both oil samples, ethane MMPs were ca. one-half those with CO 2, while methane MMPs were ca. double or triple those with CO 2. MMPs with mixed methane/CO 2 showed a linear increase with mole percent methane for both crude oils, while both oils showed an exponential increase in MMP with mole percent methane in ethane, with a little increase in MMP until ca. 20 mol % methane in ethane.« less

Elucidation of structural, vibrational and dielectric properties of transition metal (Co2+) doped spinel Mg-Zn chromites

NASA Astrophysics Data System (ADS)

Choudhary, Pankaj; Varshney, Dinesh

2018-05-01

Co2+ doped Mg-Zn spinel chromite compositions Mg0.5Zn0.5-xCoxCr2O4 (0.0 ≤ x ≤ 0.5) have been synthesized by the high-temperature solid state method. Synchrotron and X-ray diffraction (XRD) studies show single-phase crystalline nature. The structural analysis is validated by Rietveld refinement confirms the cubic structure with space group Fd3m. Crystallite size is estimated from Synchrotron XRD which was found to be 30-34 nm. Energy dispersive analysis confirms stoichiometric Mg0.5Zn0.5-xCoxCr2O4 composition. Average crystallite size distribution is estimated from imaging software (Image - J) of SEM is in the range of 100-250 nm. Raman spectroscopy reveals four active phonon modes, and a pronounced red shift is due to enhanced Co2+ concentration. Increased Co2+ concentration in Mg-Zn chromites shows a prominent narrowing of band gap from 3.46 to 2.97 eV. The dielectric response is attributed to the interfacial polarization, and the electrical modulus study supports non-Debye type of dielectric relaxation. Ohmic junctions (minimum potential drop) at electrode interface are active at lower levels of doping (x < 0.2) give rise to a low-frequency semicircle as evidenced from the complex impedance analysis. The low dielectric loss and high ac conductivity of Co2+ doped Mg-Zn spinel chromites are suitable for power transformer applications at high frequencies.

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.

Ab-Initio Interfacial Studies of Cobalt/Copper Multilayers

NASA Astrophysics Data System (ADS)

Villagonzalo, Cristine; Setty, Arun K.; Muratov, Leonid; Cooper, Bernard R.

2002-03-01

We present a study of the interface of cobalt/copper (Co/Cu) multilayrs. For its potential in giant magnetoresistance (GMR) device applications,(S.S.Parkin, et al.), Appl. Phys. Lett. 58 (1991) 2710 the Co/Cu system has been studied extensively. The magnitude of GMR is found to depend sensitively on the nature of the interface, however, the underlying mechanism is not well understood. Therefore, we focus on the energy-configuration of Co/Cu multilayers (of 1-4 monolayers for each element) and on the effects of interpenetration. Using an ab-initio full-potential Linear Muffin-Tin Orbital (FP-LMTO) electronic structure method, we seek a stable interfacial structure. Unlike prior studies, our computations are for the experimentally relevant (111) direction. Our preliminary results indicate that Co impurities in bulk Cu are not energetically favorable, in accord with the experimentally observed immiscibility of Co and Cu. Studies in progress of interfacial relaxation in prelude to consideration of interdiffusion and lattice buckling will also be presented.

Three-dimensional simulation of rivulet and film flows over an inclined plate: Effects of solvent properties and contact angle

DOE PAGES

Singh, Rajesh K.; Galvin, Janine E.; Sun, Xin

2015-12-10

We numerically investigated the film flow down an inclined plate using the volume of fluid (VOF) method. The flow simulations have been systematically carried out for a wide range of parameters, such as inlet size, inclination angle, contact angle, flow rates and solvent properties (viscosity and surface tension). Based on the simulation results, scaling theory is proposed for both interfacial area and for film thickness in terms of the Kapitza number (Ka).The Kapitza number is advantageous because it depends only on solvent properties. The Kapitza number decreases with increased solvent viscosity and is fixed for a given fluid. Here, tomore » investigate the effects of solvent properties on interfacial area a small inlet cross-section was used. The interfacial area decreases with increased value of Ka. The time to reach pseudo-steady state of rivulet is also observed to increase with decreasing Ka. For a fixed flow rate, the inlet cross-section has marginal effect on the interfacial area; however, the developed width of the rivulet remains unchanged. In addition to inlet size, flow rate and solvent properties, the impact of contact angle on film thickness and interfacial area was also investigated. The contact angle has negligible effect for a fully wetted plate, but it significantly affects the interfacial area of the rivulet. Finally, a scaling theory for interfacial area in terms of the contact angle and Ka is presented.« less

Liquid Sulfur Impregnation of Microporous Carbon Accelerated by Nanoscale Interfacial Effects

DOE PAGES

Pascal, Tod A.; Villaluenga, Irune; Wujcik, Kevin H.; ...

2017-03-14

Impregnation of porous carbon matrices with liquid sulfur has been exploited to fabricate composite cathodes for lithium-sulfur batteries, aimed at confining soluble sulfur species near conducting carbon to prevent both loss of active material into the electrolyte and parasitic reactions at the lithium metal anode. Here, through extensive computer simulations, we uncover the strongly favorable interfacial free energy between liquid sulfur and graphitic surfaces that underlies this phenomenon. Previously unexplored curvature-dependent enhancements are shown to favor the filling of smaller pores first and effect a quasi-liquid sulfur phase in microporous domains (diameters <2 nm) that persists ~30° below the expectedmore » freezing point. Evidence of interfacial sulfur on carbon is shown to be a 0.3 eV red shift in the simulated and measured interfacial X-ray absorption spectra. Our results elucidate the critical morphology and thermodynamic properties necessary for future cathode design and highlight the importance of molecular-scale details in defining emergent properties of functional nanoscale interfaces.« less

Liquid Sulfur Impregnation of Microporous Carbon Accelerated by Nanoscale Interfacial Effects.

PubMed

Pascal, Tod A; Villaluenga, Irune; Wujcik, Kevin H; Devaux, Didier; Jiang, Xi; Wang, Dunyang Rita; Balsara, Nitash; Prendergast, David

2017-04-12

Impregnation of porous carbon matrices with liquid sulfur has been exploited to fabricate composite cathodes for lithium-sulfur batteries, aimed at confining soluble sulfur species near conducting carbon to prevent both loss of active material into the electrolyte and parasitic reactions at the lithium metal anode. Here, through extensive computer simulations, we uncover the strongly favorable interfacial free energy between liquid sulfur and graphitic surfaces that underlies this phenomenon. Previously unexplored curvature-dependent enhancements are shown to favor the filling of smaller pores first and effect a quasi-liquid sulfur phase in microporous domains (diameters <2 nm) that persists ∼30° below the expected freezing point. Evidence of interfacial sulfur on carbon is shown to be a 0.3 eV red shift in the simulated and measured interfacial X-ray absorption spectra. Our results elucidate the critical morphology and thermodynamic properties necessary for future cathode design and highlight the importance of molecular-scale details in defining emergent properties of functional nanoscale interfaces.

Enhanced interfacial electron transfer of inverted perovskite solar cells by introduction of CoSe into the electron-transporting-layer

NASA Astrophysics Data System (ADS)

Chen, Shanshan; Yang, Songwang; Sun, Hong; Zhang, Lu; Peng, Jiajun; Liang, Ziqi; Wang, Zhong-Sheng

2017-06-01

To improve the electron transfer at the interface between the perovskite film and the electron-transporting-material (ETM) layer, CoSe doped [6,6]-phenyl C61-butyric acid methyl ester (PCBM) is employed as the ETM layer for the inverted planar perovskite solar cell with NiO as the hole-transporting-material layer. Introduction of CoSe (5.8 wt%) into the PCBM layer improves the conductivity of the ETM layer and decreases the photoluminescence intensity, thus enhancing the interfacial electron extraction and reducing the electron transfer resistance at the perovskite/ETM interface. As a consequence, the power conversion efficiency is enhanced from 11.43% to 14.91% by 30% due to the noted increases in short-circuit current density from 17.95 mA cm-2 to 19.85 mA cm-2 and fill factor from 0.60 to 0.70. This work provides a new strategy to improve the performance of inverted perovskite solar cells.

Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique.

PubMed

Barry, J N; Cowley, A; McNally, P J; Dowling, D P

2014-03-01

Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47°C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0 μm. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing. Copyright © 2013 Wiley Periodicals, Inc.

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

Sharma, Richa; Tandon, R. P., E-mail: ram-tandon@hotmail.com

In the present work, (1-x)Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3}-(x)CoFe{sub 1.8}Mn{sub 0.2}O{sub 4} composites are prepared by standard solid state reaction method. The X-ray diffraction measurement of the composites shows that both the phases coexist in the composite, individually. The morphology of the composites were examined by field emission scanning electron microscopy and reveals homogeneous microstructure with two types of grains, smaller grains of the Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3} (BST) and bigger grains of the CoFe{sub 1.8}Mn{sub 0.2}O{sub 4} (CFM). The dielectric studies show that all the composites exhibit dispersion in the lower frequency region attributable to the interfacial polarization. In addition,more » at lower frequencies, the dielectric constant (ε´) is found to increase with increase in CFM content in the composites. The ferromagnetic properties of the composites improve with the increase in the CFM content.« less

Biosurfactant as an Enhancer of Geologic Carbon Storage: Microbial Modification of Interfacial Tension and Contact Angle in Carbon dioxide/Water/Quartz Systems.

PubMed

Park, Taehyung; Joo, Hyun-Woo; Kim, Gyeong-Yeong; Kim, Seunghee; Yoon, Sukhwan; Kwon, Tae-Hyuk

2017-01-01

Injecting and storing of carbon dioxide (CO 2 ) in deep geologic formations is considered as one of the promising approaches for geologic carbon storage. Microbial wettability alteration of injected CO 2 is expected to occur naturally by microorganisms indigenous to the geologic formation or microorganisms intentionally introduced to increase CO 2 storage capacity in the target reservoirs. The question as to the extent of microbial CO 2 wettability alteration under reservoir conditions still warrants further investigation. This study investigated the effect of a lipopeptide biosurfactant-surfactin, on interfacial tension (IFT) reduction and contact angle alteration in CO 2 /water/quartz systems under a laboratory setup simulating in situ reservoir conditions. The temporal shifts in the IFT and the contact angle among CO 2 , brine, and quartz were monitored for different CO 2 phases (3 MPa, 30°C for gaseous CO 2 ; 10 MPa, 28°C for liquid CO 2 ; 10 MPa, 37°C for supercritical CO 2 ) upon cultivation of Bacillus subtilis strain ATCC6633 with induced surfactin secretion activity. Due to the secreted surfactin, the IFT between CO 2 and brine decreased: from 49.5 to 30 mN/m, by ∼39% for gaseous CO 2 ; from 28.5 to 13 mN/m, by 54% for liquid CO 2 ; and from 32.5 to 18.5 mN/m, by ∼43% for supercritical CO 2 , respectively. The contact angle of a CO 2 droplet on a quartz disk in brine increased: from 20.5° to 23.2°, by 1.16 times for gaseous CO 2 ; from 18.4° to 61.8°, by 3.36 times for liquid CO 2 ; and from 35.5° to 47.7°, by 1.34 times for supercritical CO 2 , respectively. With the microbially altered CO 2 wettability, improvement in sweep efficiency of injected and displaced CO 2 was evaluated using 2-D pore network model simulations; again the increment in sweep efficiency was the greatest in liquid CO 2 phase due to the largest reduction in capillary factor. This result provides novel insights as to the role of naturally occurring biosurfactants in CO 2 storage and suggests that biostimulation of biosurfactant production may be a feasible technique for enhancement of CO 2 storage capacity.

Biosurfactant as an Enhancer of Geologic Carbon Storage: Microbial Modification of Interfacial Tension and Contact Angle in Carbon dioxide/Water/Quartz Systems

PubMed Central

Park, Taehyung; Joo, Hyun-Woo; Kim, Gyeong-Yeong; Kim, Seunghee; Yoon, Sukhwan; Kwon, Tae-Hyuk

2017-01-01

Injecting and storing of carbon dioxide (CO2) in deep geologic formations is considered as one of the promising approaches for geologic carbon storage. Microbial wettability alteration of injected CO2 is expected to occur naturally by microorganisms indigenous to the geologic formation or microorganisms intentionally introduced to increase CO2 storage capacity in the target reservoirs. The question as to the extent of microbial CO2 wettability alteration under reservoir conditions still warrants further investigation. This study investigated the effect of a lipopeptide biosurfactant—surfactin, on interfacial tension (IFT) reduction and contact angle alteration in CO2/water/quartz systems under a laboratory setup simulating in situ reservoir conditions. The temporal shifts in the IFT and the contact angle among CO2, brine, and quartz were monitored for different CO2 phases (3 MPa, 30°C for gaseous CO2; 10 MPa, 28°C for liquid CO2; 10 MPa, 37°C for supercritical CO2) upon cultivation of Bacillus subtilis strain ATCC6633 with induced surfactin secretion activity. Due to the secreted surfactin, the IFT between CO2 and brine decreased: from 49.5 to 30 mN/m, by ∼39% for gaseous CO2; from 28.5 to 13 mN/m, by 54% for liquid CO2; and from 32.5 to 18.5 mN/m, by ∼43% for supercritical CO2, respectively. The contact angle of a CO2 droplet on a quartz disk in brine increased: from 20.5° to 23.2°, by 1.16 times for gaseous CO2; from 18.4° to 61.8°, by 3.36 times for liquid CO2; and from 35.5° to 47.7°, by 1.34 times for supercritical CO2, respectively. With the microbially altered CO2 wettability, improvement in sweep efficiency of injected and displaced CO2 was evaluated using 2-D pore network model simulations; again the increment in sweep efficiency was the greatest in liquid CO2 phase due to the largest reduction in capillary factor. This result provides novel insights as to the role of naturally occurring biosurfactants in CO2 storage and suggests that biostimulation of biosurfactant production may be a feasible technique for enhancement of CO2 storage capacity. PMID:28744272

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.

Removing the Active-Site Flap in Lipase A from Candida antarctica Produces a Functional Enzyme without Interfacial Activation.

PubMed

Wikmark, Ylva; Engelmark Cassimjee, Karim; Lihammar, Richard; Bäckvall, Jan-E

2016-01-01

A mobile region is proposed to be a flap that covers the active site of Candida antarctica lipase A. Removal of the mobile region retains the functional properties of the enzyme. Interestingly interfacial activation, required for the wild-type enzyme, was not observed for the truncated variant, although stability, activity, and stereoselectivity were very similar for the wild-type and variant enzymes. The variant followed classical Michaelis-Menten kinetics, unlike the wild type. Both gave the same relative specificity in the transacylation of a primary and a secondary alcohol in organic solvent. Furthermore, both showed the same enantioselectivity in transacylation of alcohols and the hydrolysis of alcohol esters, as well as in the hydrolysis of esters chiral at the acid part. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

MnFe2O4: Synthesis, morphology and electrochemical properties

NASA Astrophysics Data System (ADS)

Kulkarni, Shrikant; Thombare, Balu; Patil, Shankar

2017-05-01

MnFe2O4 has been synthesized by simple ammonia assisted co-precipitation method to obtain nanocrystalline powder. X-ray diffraction studies confirmed its crystallinity and phase purity. The MnFe2O4 calcined at 1000°C for 4 h has spinel crystal structure with Fd3m space group and lattice constant 8.511 Å. The electrode was prepared by dip coating method on stainless steel substrate and fired at 600°C for 2 h. Random shape grains of 0.2 to 1.5 micron with pores of 1-2 micron dimensions were observed in SEM images. The electrochemical studies of MnFe2O4 were carried out with 1 mole Na2SO4 electrolyte. The MnFe2O4 electrode shows highest specific capacitance of 27.53 F.g-1 and interfacial capacitance of 0.83 F.cm-2.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Environmental Effects on Zirconium Hydroxide Nanoparticles and Chemical Warfare Agent Decomposition: Implications of Atmospheric Water and Carbon Dioxide.

PubMed

Balow, Robert B; Lundin, Jeffrey G; Daniels, Grant C; Gordon, Wesley O; McEntee, Monica; Peterson, Gregory W; Wynne, James H; Pehrsson, Pehr E

2017-11-15

Zirconium hydroxide (Zr(OH) 4 ) has excellent sorption properties and wide-ranging reactivity toward numerous types of chemical warfare agents (CWAs) and toxic industrial chemicals. Under pristine laboratory conditions, the effectiveness of Zr(OH) 4 has been attributed to a combination of diverse surface hydroxyl species and defects; however, atmospheric components (e.g., CO 2 , H 2 O, etc.) and trace contaminants can form adsorbates with potentially detrimental impact to the chemical reactivity of Zr(OH) 4 . Here, we report the hydrolysis of a CWA simulant, dimethyl methylphosphonate (DMMP) on Zr(OH) 4 determined by gas chromatography-mass spectrometry and in situ attenuated total reflectance Fourier transform infrared spectroscopy under ambient conditions. DMMP dosing on Zr(OH) 4 formed methyl methylphosphonate and methoxy degradation products on free bridging and terminal hydroxyl sites of Zr(OH) 4 under all evaluated environmental conditions. CO 2 dosing on Zr(OH) 4 formed adsorbed (bi)carbonates and interfacial carbonate complexes with relative stability dependent on CO 2 and H 2 O partial pressures. High concentrations of CO 2 reduced DMMP decomposition kinetics by occupying Zr(OH) 4 active sites with carbonaceous adsorbates. Elevated humidity promoted hydrolysis of adsorbed DMMP on Zr(OH) 4 to produce methanol and regenerated free hydroxyl species. Hydrolysis of DMMP by Zr(OH) 4 occurred under all conditions evaluated, demonstrating promise for chemical decontamination under diverse, real-world conditions.

Interfacial effect on the structural and optical properties of pure SnO2 and dual shells (ZnO; SiO2) coated SnO2 core-shell nanospheres for optoelectronic applications

NASA Astrophysics Data System (ADS)

Selvi, N.; Sankar, S.; Dinakaran, K.

2014-12-01

Nanocrystallites of SnO2 core and dual shells (ZnO, SiO2) coated SnO2 core-shell nanospheres were successfully synthesized by co-precipitation method. The as prepared and annealed samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM) and UV-Vis analysis. XRD pattern confirms the obtained SnO2 core with tetragonal rutile crystalline structure and the shell ZnO with hexagonal structure. FTIR result shows the functional groups present in the samples. The spherical morphology and the formation of the core-shell structures have been confirmed by HRTEM measurements. The UV-Vis showed that band gap is red shifted for as-prepared and the shells coated core-shell samples. From this investigation it can be concluded that the surface modification with different metal and insulating oxides strongly influences the optical properties of the core-shell materials which enhance their potential applications towards optical devices fabrication.

A separation of antiferromagnetic spin motion modes in the training effect of exchange biased Co/CoO film with in-plane anisotropy

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

Wu, R.; Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS; Yun, C.

2016-08-07

The motion of antiferromagnetic interfacial spins is investigated through the temperature evolution of training effect in a Co/CoO film with in-plane biaxial anisotropy. Significant differences in the training effect and its temperature dependence are observed in the magnetic easy axis and hard axis (HA) and ascribed to the different motion modes of antiferromagnetic interfacial spins, the collective spin cluster rotation (CSR) and the single spin reversal (SSR), caused by different magnetization reversal modes of ferromagnetic layer. These motion modes of antiferromagnetic spins are successfully separated using a combination of an exponential function and a classic n{sup −1/2} function. A largermore » CSR to SSR ratio and a shorter lifetime of CSR found in the HA indicates that the domain rotation in the ferromagnetic layer tends to activate and accelerate a CSR mode in the antiferromagnetic spins.« less

Effect of cross-linking of interfacial sodium caseinate by natural processing on the oxidative stability of oil-in-water (o/w) emulsions.

PubMed

Phoon, Pui Yeu; Paul, Lake N; Burgner, John W; San Martin-Gonzalez, M Fernanda; Narsimhan, Ganesan

2014-04-02

This study investigated how enzymatic cross-linking of interfacial sodium caseinate and emulsification, via high-pressure homogenization, influenced the intrinsic oxidative stability of 4% (w/v) menhaden oil-in-water emulsions stabilized by 1% (w/v) caseinate at pH 7. Oil oxidation was monitored by the ferric thiocyanate perioxide value assay. Higher homogenization pressure resulted in improved intrinsic emulsion oxidative stability, which is attributed to increased interfacial cross-linking as indicated by higher weighted average sedimentation coefficients of interfacial protein species (from 11.2 S for 0 kpsi/0.1 MPa to 18 S for 20 kpsi/137.9 MPa). Moderate dosage of transglutaminase at 0.5-1.0 U/mL emulsion enhanced intrinsic emulsion oxidative stability further, despite a contradictory reduction in the antioxidant property of cross-linked caseinate as tested by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. This implied the prominent role of cross-linked interfacial caseinate as a physical barrier for oxygen transfer, hence its efficacy in retarding oil oxidation.

A study on the dynamic interfacial tension of acidic crude oil/alkali (alkali-polymer) systems--

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

Huang, Y.; Yang, P.; Qin, T.

1989-01-01

This paper describes the investigation of dynamic interfacial tension (DIFT) between the acidic Liao-He crude oil and two types of brine: a simple alkali system and a combined alkali-polymer system. It was found that interfacial tension (IFT) changed markedly with time and that the history of DIFT depended upon the concentration of alkali in the brine. The experimental results also showed that the IFT dropped dramatically as soon as the fresh oil contacted brine causing spontaneous emulsification to occur. The steady-state value of DIFT {gamma} st can be lower with the combined alkali-polymer system than with the simple alkali system.more » The results indicate that biopolymer is more effective than partially hydrolyzed polyacrylamide (PHPAM) for lowering {gamma} st and that Na{sub 2}Co{sub 1} causes a lower {gamma} st than NaOH in the combined alkali-polymer system. Optimized formulations containing Na{sub 2}CO{sub 3} added biopolymer can reduce {gamma} st by two orders of magnitude, and PHPAM can reduce {gamma} st by one order of magnitude. The interaction between alkali and polymer in the combined alkali-polymer system is discussed.« less

A surface physicochemical rationale for calculus formation in the oral cavity

NASA Astrophysics Data System (ADS)

Busscher, Henk J.; White, Don J.; Kamminga-Rasker, Hannetta J.; van der Mei, Henny C.

2004-01-01

Surface free energies of dental hard tissues, including salivary conditioning films on enamel, play a crucial role in mineralization, dissolution and adhesion processes at the tooth surface. These mineralization reactions at oral surfaces control the development and progression of various diseases. In this paper, we compare the surface free energies, as derived from measured contact angles with liquids, of salivary conditioning films on enamel after exposure to dentifrices with and without anti-calculus additives, such as hexametaphosphate, pyrophosphate or zinc citrate trihydrate. Measured contact angles were converted to surface free energies using the concept of Lifshitz-Van der Waals and Lewis acid-base components. Nearly all dentifrices yield film properties with a negative interfacial tension against an aqueous phase, which thermodynamically opposes mineralization. Concurrent with negative interfacial tensions, are positive values of the interfacial free energy of adhesion for octacalcium-phosphate (OCP) to the film surfaces, indicating that adhesion of newly mineralized, calcium-phosphate rich phases is thermodynamically unfavorable. Interestingly, two out of the three dentifrices with anti-calculus additives containing hexametaphosphate and pyrophosphate cause most positive interfacial free energies for OCP adhesion of 5.8 and 2.6 mJ/m 2, respectively. In summary, surface thermodynamical analyses indicate that anti-calculus effects of commercial dentifrice formulations are consistent with more negative interfacial tensions of salivary conditioning films on enamel surfaces and thus with more positive values for the interfacial free energy of adhesion toward newly formed mineral phases. A dentifrice containing hexametaphosphate yielded thermodynamic properties of salivary conditioning films most unfavorable for calculus formation.

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.

Interfacial microstructure and mechanical properties of Cf/AZ91D composites with TiO2 and PyC fiber coatings.

PubMed

Li, Shaolin; Qi, Lehua; Zhang, Ting; Ju, Luyan; Li, Hejun

2017-10-01

In spite of the effectiveness of the fiber coatings on interface modification of carbon fiber reinforced magnesium matrix composites, the cost and exclusive equipment for the coatings preparation are usually ignored during research work. In this paper, pyrolytic carbon (PyC) and TiO 2 were coated on carbon fiber surface to study the effects of fiber coatings on interfacial microstructure and mechanical properties of carbon fiber reinforced AZ91D composites (C f /AZ91D composites). It was indicated that both the two coatings could modify the interface and improve the mechanical properties of the composites. The ultimate tensile strength of the TiO 2 -C f /AZ91D and the PyC-C f /AZ91D composite were 333MPa and 400MPa, which were improved by 41.7% and 70.2% respectively, compared with the untreated-C f /AZ91D composite. The microstructure observation revealed that the strengthening of the composites relied on fiber integrity and moderate interfacial bonding. MgO nano-particles were generated at the interface due to the reaction of TiO 2 with Mg in the TiO 2 -C f /AZ91D composite. The volume expansion resulting from the reaction let to disordered intergranular films and crystal defects at the interface. The fibers were protected and the interfacial reaction was restrained by PyC coating in the PyC-C f /AZ91D composite. The principle to select the coating of fiber was proposed by comparing the effectiveness and cost of the coatings. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Adsorption of Dissolved Gases (CH4, CO2, H2, Noble Gases) by Water-Saturated Smectite Clay Minerals

NASA Astrophysics Data System (ADS)

Bourg, I. C.; Gadikota, G.; Dazas, B.

2016-12-01

Adsorption of dissolved gases by water-saturated clay minerals plays important roles in a range of fields. For example, gas adsorption in on clay minerals may significantly impact the formation of CH4 hydrates in fine-grained sediments, the behavior of CH4 in shale, CO2 leakage across caprocks of geologic CO2 sequestration sites, H2 leakage across engineered clay barriers of high-level radioactive waste repositories, and noble gas geochemistry reconstructions of hydrocarbon migration in the subsurface. Despite its importance, the adsorption of gases on clay minerals remains poorly understood. For example, some studies have suggested that clay surfaces promote the formation of CH4 hydrates, whereas others indicate that clay surfaces inhibit the formation of CH4 hydrates. Here, we present molecular dynamics (MD) simulations of the adsorption of a range of gases (CH4, CO2, H2, noble gases) on clay mineral surfaces. Our results indicate that the affinity of dissolved gases for clay mineral surfaces has a non-monotone dependence on the hydrated radius of the gas molecules. This non-monotone dependence arises from a combination of two effects: the polar nature of certain gas molecules (in particular, CO2) and the templating of interfacial water structure by the clay basal surface, which results in the presence of interfacial water "cages" of optimal size for intermediate-size gas molecules (such as Ne or Ar).

Interfacial and emulsifying properties of designed β-strand peptides.

PubMed

Dexter, Annette F

2010-12-07

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

The effect of the morphology of supported subnanometer Pt clusters on the first and key step of CO 2 photoreduction [Morphology effect of supported subnanometer Pt clusters on first and key step of CO 2 photoreduction

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

Yang, Chi -Ta; Wood, Brandon C.; Bhethanabotla, Venkat R.

2015-09-04

In this study, using density functional theory calculations, we investigate the influence of size-dependent cluster morphology on the synergistic catalytic properties of anatase TiO 2(101) surfaces decorated with subnanometer Pt clusters. Focusing on the formation of the key precursor in the CO 2 photoreduction reaction (bent CO 2 –), we find that flatter (2D-like) Pt clusters that “wet” the TiO 2 surface offer significantly less benefit than 3D-like Pt clusters. We attribute the differences to three factors. First, the 3D clusters provide a greater number of accessible Pt–TiO 2 interfacial sites with geometries that can aid CO 2 bond bendingmore » and charge transfer processes. Second, binding competition among each Pt–CO 2 bonding interaction mitigates maximum orbital overlaps, leading to insufficient CO 2 binding. Third and also most interestingly, the 3D clusters tend to possess higher structural fluxionality than the flatter clusters, which is shown to correlate positively with CO2 binding strength. The preferred morphology adopted by the clusters depends on several factors, including the cluster size and the presence of oxygen vacancies on the TiO 2 surface; this suggests a strategy for optimizing the synergistic effect between Pt clusters and TiO 2 surfaces for CO 2 photocatalysis. Clusters of ~6–8 atoms should provide the largest benefit, since they retain the desired 3D morphology, yet are small enough to exhibit high structural fluxionality. Electronic structure analysis provides additional insight into the electronic motivations for the enhanced binding of CO 2 on TiO 2-supported 3D Pt clusters, as well as suppressed binding on flattened, 2D-like clusters.« less

The complex behavior of the Pd 7 cluster supported on TiO 2 (110) during CO oxidation: adsorbate-driven promoting effect

DOE PAGES

An, Wei; Liu, Ping

2016-09-07

When using the TiO 2(110)-supported Pd7 cluster as a model catalyst, we identified the dynamics of supported metal nanoparticles using density functional theory calculations, at the sub-nanometer scale and under reactive environments. Increasing the CO coverage can induce a structural transformation from Pd 7-3D/TiO 2(110) at low coverage to Pd 7-2D/TiO 2(110) at the saturation coverage wherein CO saturation-driven Pd7-2D/TiO 2(110) structure displays superior CO oxidation activity at the interfacial sites, which are highly active for catalyzing O 2 dissociation and CO oxidation via bifunctional synergy.

Direct Numerical Simulation of Surfactant-Stabilized Emulsions Morphology and Shear Viscosity in Starting Shear Flow

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

Roar Skartlien; Espen Sollum; Andreas Akselsen

2012-07-01

A 3D lattice Boltzmann model for two-phase flow with amphiphilic surfactant was used to investigate the evolution of emulsion morphology and shear stress in starting shear flow. The interfacial contributions were analyzed for low and high volume fractions and varying surfactant activity. A transient viscoelastic contribution to the emulsion rheology under constant strain rate conditions was attributed to the interfacial stress. For droplet volume fractions below 0.3 and an average capillary number of about 0.25, highly elliptical droplets formed. Consistent with affine deformation models, gradual elongation of the droplets increased the shear stress at early times and reduced it atmore » later times. Lower interfacial tension with increased surfactant activity counterbalanced the effect of increased interfacial area, and the net shear stress did not change significantly. For higher volume fractions, co-continuous phases with a complex topology were formed. The surfactant decreased the interfacial shear stress due mainly to advection of surfactant to higher curvature areas. Our results are in qualitative agreement with experimental data for polymer blends in terms of transient interfacial stresses and limited enhancement of the emulsion viscosity at larger volume fractions where the phases are co-continuous.« less

Breaking of the Bancroft rule for multiple emulsions stabilized by a single stimulable polymer.

PubMed

Besnard, L; Protat, M; Malloggi, F; Daillant, J; Cousin, F; Pantoustier, N; Guenoun, P; Perrin, P

2014-09-28

We investigated emulsions of water and toluene stabilized by (co)polymers consisting of styrene (S) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) monomer units with different compositions and structures such as a PDMAEMA homopolymer, a P(S-co-DMAEMA) random copolymer and various PS-b-PDMAEMA and PS-b-(S-co-DMAEMA) block copolymers. The model system is used to study the fundamental conditions under which the different kinds of polymer-stabilized emulsions (direct oil in water, inverse water in oil and multiple emulsions) are stabilized or destabilized by pH change (at constant temperature). Polymer properties like chain conformation at the toluene-water interface as probed by SANS and neutron reflectivity at the liquid-liquid interface, the oil-water partitioning of the polymer chains (Bancroft's rule of thumb) as determined by UV spectroscopy and interfacial tensions measured by the rising and spinning drop techniques are determined. Overall, results evidence that the curvature sign, as defined by positive and negative values as the chain segments occupy preferentially the water and toluene sides of the interface respectively, reliably predicts the emulsion kind. In contrast, the Bancroft rule failed at foreseeing the emulsion type. In the region of near zero curvature the crossover from direct to inverse emulsions occurs through the formation of either unstable coexisting direct and inverse emulsions (i) or multiple emulsions (ii). The high compact adsorption of the chains at the interface as shown by low interfacial tension values does not allow to discriminate between both cases. However, the toluene-water partitioning of the polymeric emulsifier is still a key factor driving the formation of (i) or (ii) emulsions. Interestingly, the stabilization of the multiple emulsions can be tuned to a large extent as the toluene-water polymer partitioning can be adjusted using quite a large number of physico-chemical parameters linked to polymer architecture like diblock length ratio or polymer total molar mass, for example. Moreover, we show that monitoring the oil-water partitioning aspect of the emulsion system can also be used to lower the interfacial tension at low pH to values slightly higher than 0.01 mN m(-1), irrespective of the curvature sign.

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).

Structure of block copolymer micelles in the presence of co-solvents

NASA Astrophysics Data System (ADS)

Robertson, Megan; Wang, Shu; Le, Kim Mai; Piemonte, Rachele; Madsen, Louis

2015-03-01

Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using scattering experiments and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

Amine-Modulated/Engineered Interfaces of NiMo Electrocatalysts for Improved Hydrogen Evolution Reaction in Alkaline Solutions.

PubMed

Gao, Wei; Gou, Wangyan; Zhou, Xuemei; Ho, Johnny C; Ma, Yuanyuan; Qu, Yongquan

2018-01-17

The interface between electrolytes and electrocatalysts would largely determine their corresponding activity and stability. Herein, modulating the surface characteristics of NiMo nanoparticles by various adsorbed amines gives the tunability on their interfacial properties and subsequently improves their catalytic performance for hydrogen evolution reaction (HER) in alkaline solutions. Diamines can significantly improve their HER activity by decreasing the charge-transfer resistance and modulating the electronic structures of interfacial active sites. Importantly, among various amines, ethylenediamine facilitates the HER activity of NiMo with a remarkable decrease of 268 mV in the overpotential to reach 10 mA cm -2 as compared with that of the unmodified NiMo in 1.0 M KOH. This method provides a novel strategy of regulating the interfacial properties to strengthen the catalytic performance of electrocatalysts.

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

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

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

PubMed

Svitova, Tatyana F; Lin, Meng C

2016-07-01

This review summarizes the current state of knowledge regarding interfacial properties of very complex biological colloids, specifically, human meibum and tear lipids, and their interactions with proteins similar to the proteins found in aqueous part of human tears. Tear lipids spread as thin films over the surface of tear-film aqueous and play crucial roles in tear-film stability and overall ocular-surface health. The vast majority of papers published to date report interfacial properties of meibum-lipid monolayers spread on various aqueous sub-phases, often containing model proteins, in Langmuir trough. However, it is well established that natural human ocular tear lipids exist as multilayered films with a thickness between 30 and 100nm, that is very much disparate from 1 to 2nm thick meibum monolayers. We employed sessile-bubble tensiometry to study the dynamic interfacial and rheological properties of reconstituted multilayered human tear-lipid films. Small amounts (0.5-1μg) of human tear lipids were deposited on an air-bubble surface to produce tear-lipid films in thickness range 30-100nm corresponding to ocular lipid films. Thus, we were able to overcome major Langmuir-trough method limitations because ocular tear lipids can be safely harvested only in minute, sub-milligram quantities, insufficient for Langmuir through studies. Sessile-bubble method is demonstrated to be a versatile tool for assessing conventional synthetic surfactants adsorption/desorption dynamics at an air-aqueous solution interface. (Svitova T., Weatherbee M., Radke C.J. Dynamics of surfactant sorption at the air/water interface: continuous-flow tensiometry. J. Colloid Interf. Sci. 2003;261:1170-179). The augmented flow-sessile-bubble setup, with step-strain relaxation module for dynamic interfacial rheological properties and high-precision syringe pump to generate larger and slow interfacial area expansions-contractions, was developed and employed in our studies. We established that this method is uniquely suitable for examination of multilayered lipid-film interfacial properties. Recently it was compellingly proven that chemical composition of human tear lipids extracted from whole tears is substantially different from that of meibum lipids. To be exact, healthy human tear lipids contain 8-16% of polar lipids, similar to lung lipids, and they are mostly double-tailed phospholipids, with C16 and longer alkyl chains. Rationally, one would assume that the results obtained for meibum lipids, devoid of surface-active components such as phospholipids, and, above all, in a form of monolayers, are not pertinent or useful for elucidating behavior and stability of an averaged 60-nm thick ocular tear-lipid films in vivo. The advantage of sessile-bubble technique, specifically, using a small amount of lipids required to attain multilayered films, unlocks the prospect of evaluating and comparing the interfacial properties of human tear lipids collected from a single individual, typically 100-150μg. This is in sharp contrast with several milligrams of lipids that would be required to build equally thick films for Langmuir-trough experiments. The results of our studies provided in-depth understanding of the mechanisms responsible for properties and stability of human tear-lipid films in vivo. Here we summarize recent publications and our latest findings regarding human tear-lipid interfacial properties, their chemical composition, and their interaction with model proteins mimicking the proteins found in human tear-aqueous phase. Published by Elsevier B.V.

Strength and durability of concrete: Effects of cement paste-aggregate interfaces. Part 1: Theoretical study on influence of interfacial transition zone on properties of concrete materials; Final report

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

Zhang, Y.; Chen, W.F.

1998-08-01

This research was based on a two-part basic research investigation studying the effects of cement paste-aggregate interfaces (or interfacial transition zones-ITZ) on strength and durability of concrete. Part 1 dealt with the theoretical study and Part 2 dealt with the experimental.

Interfacial perpendicular magnetic anisotropy in CoFeB/MgO structure with various underlayers

NASA Astrophysics Data System (ADS)

Oh, Young-Wan; Lee, Kyeong-Dong; Jeong, Jong-Ryul; Park, Byong-Guk

2014-05-01

Interfacial perpendicular magnetic anisotropy (PMA) in CoFeB/MgO structures was investigated and found to be critically relied on underlayer material and annealing temperature. With Ta or Hf underlayer, clear PMA is observed in as-deposited samples while no PMA was shown in those with Pt or Pd. This may be attributed to smaller saturation magnetization of the films with Ta or Hf underlayer, which makes the PMA of CoFeB/MgO interface dominates over demagnetization field. On the contrary, samples with Pt or Pd demonstrate PMA only after annealing, which might be due to the CoPt (or CoPd) alloy formation that enhances PMA.

Pore-scale Evaluation of Immiscible Fluid Characteristics and Displacements: Comparison Between Ambient- and Supercritical-Condition Experimental Studies

NASA Astrophysics Data System (ADS)

Herring, A. L.; Wildenschild, D.; Andersson, L.; Harper, E.; Sheppard, A.

2015-12-01

The transport of immiscible fluids within porous media is a topic of great importance for a wide range of subsurface processes; e.g. oil recovery, geologic sequestration of CO2, gas-water mass transfer in the vadose zone, and remediation of non-aqueous phase liquids (NAPLs) from groundwater. In particular, the trapping and mobilization of nonwetting phase fluids (e.g. oil, CO2, gas, or NAPL in water-wet media) is of significant concern; and has been well documented to be a function of both wetting and nonwetting fluid properties, morphological characteristics of the porous medium, and system history. However, generalization of empirical trends and results for application between different fluid-fluid-medium systems requires careful consideration and characterization of the relevant system properties. We present a comprehensive and cohesive description of nonwetting phase behaviour as observed via a suite of three dimensional x-ray microtomography imaging experiments investigating immiscible fluid flow, trapping, and interfacial interactions of wetting (brine) and nonwetting (air, oil, and supercritical CO2) phase in sandstones and synthetic media. Microtomographic images, acquired for drainage and imbibition flow processes, allow for precise and extensive characterization of nonwetting phase fluid saturation, topology, and connectivity; imaging results are paired with externally measured capillary pressure data to provide a comprehensive description of fluid states. Fluid flow and nonwetting phase trapping behaviour is investigated as a function of system history, morphological metrics of the geologic media, and nonwetting phase fluid characteristics; and particular emphasis is devoted to the differences between ambient condition (air-brine) and reservoir condition (supercritical CO2-brine) studies. Preliminary results provide insight into the applicability of using ambient condition experiments to explore reservoir condition processes, and also elucidate the underlying physics of trapping and mobilization of nonwetting phase fluids.

Characterization methods for liquid interfacial layers

NASA Astrophysics Data System (ADS)

Javadi, A.; Mucic, N.; Karbaschi, M.; Won, J. Y.; Lotfi, M.; Dan, A.; Ulaganathan, V.; Gochev, G.; Makievski, A. V.; Kovalchuk, V. I.; Kovalchuk, N. M.; Krägel, J.; Miller, R.

2013-05-01

Liquid interfaces are met everywhere in our daily life. The corresponding interfacial properties and their modification play an important role in many modern technologies. Most prominent examples are all processes involved in the formation of foams and emulsions, as they are based on a fast creation of new surfaces, often of an immense extension. During the formation of an emulsion, for example, all freshly created and already existing interfaces are permanently subject to all types of deformation. This clearly entails the need of a quantitative knowledge on relevant dynamic interfacial properties and their changes under conditions pertinent to the technological processes. We report on the state of the art of interfacial layer characterization, including the determination of thermodynamic quantities as base line for a further quantitative analysis of the more important dynamic interfacial characteristics. Main focus of the presented work is on the experimental possibilities available at present to gain dynamic interfacial parameters, such as interfacial tensions, adsorbed amounts, interfacial composition, visco-elastic parameters, at shortest available surface ages and fastest possible interfacial perturbations. The experimental opportunities are presented along with examples for selected systems and theoretical models for a best data analysis. We also report on simulation results and concepts of necessary refinements and developments in this important field of interfacial dynamics.

Interfacial Area Development in Two-Phase Fluid Flow: Transient vs. Quasi-Static Flow Conditions

NASA Astrophysics Data System (ADS)

Meisenheimer, D. E.; Wildenschild, D.

2017-12-01

Fluid-fluid interfaces are important in multiphase flow systems in the environment (e.g. groundwater remediation, geologic CO2 sequestration) and industry (e.g. air stripping, fuel cells). Interfacial area controls mass transfer, and therefore reaction efficiency, between the different phases in these systems but they also influence fluid flow processes. There is a need to better understand this relationship between interfacial area and fluid flow processes so that more robust theories and models can be built for engineers and policy makers to improve the efficacy of many multiphase flow systems important to society. Two-phase flow experiments were performed in glass bead packs under transient and quasi-static flow conditions. Specific interfacial area was calculated from 3D images of the porous media obtained using the fast x-ray microtomography capability at the Advanced Photon Source. We present data suggesting a direct relationship between the transient nature of the fluid-flow experiment (fewer equilibrium points) and increased specific interfacial area. The effect of flow condition on Euler characteristic (a representative measure of fluid topology) will also be presented.

Co-assembly in chitosan-surfactant mixtures: thermodynamics, structures, interfacial properties and applications.

PubMed

Chiappisi, Leonardo; Gradzielski, Michael

2015-06-01

In this review, different aspects characterizing chitosan-surfactant mixtures are summarized and compared. Chitosan is a bioderived cationic polysaccharide that finds wide-ranged applications in various field, e.g., medical or food industry, in which synergistic effects with surfactant can play a fundamental role. In particular, the behavior of chitosan interacting with strong and weak anionic, nonionic as well as cationic surfactants is reviewed. We put a focus on oppositely charged systems, as they exhibit the most interesting features. In that context, we discuss the thermodynamic description of the interaction and in particular the structural changes as they occur as a function of the mixed systems and external parameters. Moreover, peculiar properties of chitosan coated phospholipid vesicles are summarized. Finally, their co-assembly at interfaces is briefly reviewed. Despite the behavior of the mentioned systems might strongly differ, resulting in a high variety of properties, few general rules can be pointed out which improve the understanding of such complex systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Mixed layers of sodium caseinate + dextran sulfate: influence of order of addition to oil-water interface.

PubMed

Jourdain, Laureline S; Schmitt, Christophe; Leser, Martin E; Murray, Brent S; Dickinson, Eric

2009-09-01

We report on the interfacial properties of electrostatic complexes of protein (sodium caseinate) with a highly sulfated polysaccharide (dextran sulfate). Two routes were investigated for preparation of adsorbed layers at the n-tetradecane-water interface at pH = 6. Bilayers were made by the layer-by-layer deposition technique whereby polysaccharide was added to a previously established protein-stabilized interface. Mixed layers were made by the conventional one-step method in which soluble protein-polysaccharide complexes were adsorbed directly at the interface. Protein + polysaccharide systems gave a slower decay of interfacial tension and stronger dilatational viscoelastic properties than the protein alone, but there was no significant difference in dilatational properties between mixed layers and bilayers. Conversely, shear rheology experiments exhibited significant differences between the two kinds of interfacial layers, with the mixed system giving much stronger interfacial films than the bilayer system, i.e., shear viscosities and moduli at least an order of magnitude higher. The film shear viscoelasticity was further enhanced by acidification of the biopolymer mixture to pH = 2 prior to interface formation. Taken together, these measurements provide insight into the origin of previously reported differences in stability properties of oil-in-water emulsions made by the bilayer and mixed layer approaches. Addition of a proteolytic enzyme (trypsin) to both types of interfaces led to a significant increase in the elastic modulus of the film, suggesting that the enzyme was adsorbed at the interface via complexation with dextran sulfate. Overall, this study has confirmed the potential of shear rheology as a highly sensitive probe of associative electrostatic interactions and interfacial structure in mixed biopolymer layers.

Comprehensive studies of interfacial strain and oxygen vacancy on metal-insulator transition of VO2 film

NASA Astrophysics Data System (ADS)

Fan, L. L.; Chen, S.; Liao, G. M.; Chen, Y. L.; Ren, H.; Zou, C. W.

2016-06-01

As a typical strong correlation material, vanadium dioxide (VO2) has attracted wide interest due to its particular metal-insulator transition (MIT) property. However, the relatively high critical temperature (T c) of ~68 °C seriously hinders its practical applications. Thus modulating the phase transition process and decreasing the T c close to room temperature have been hot topics for VO2 study. In the current work, we conducted a multi-approach strategy to control the phase transition of VO2 films, including the interfacial tensile/compressive strain and oxygen vacancies. A synchrotron radiation reciprocal space mapping technique was used to directly record the interfacial strain evolution and variations of lattice parameters. The effects of interfacial strain and oxygen vacancies in the MIT process were systematically investigated based on band structure and d-orbital electron occupation. It was suggested that the MIT behavior can be modulated through the combined effects of the interfacial strain and oxygen vacancies, achieving the distinct phase transition close to room temperature. The current findings not only provide better understanding for strain engineering and oxygen vacancies controlling phase transition behavior, but also supply a combined way to control the phase transition of VO2 film, which is essential for VO2 film based device applications in the future.

Comprehensive studies of interfacial strain and oxygen vacancy on metal-insulator transition of VO2 film.

PubMed

Fan, L L; Chen, S; Liao, G M; Chen, Y L; Ren, H; Zou, C W

2016-06-29

As a typical strong correlation material, vanadium dioxide (VO2) has attracted wide interest due to its particular metal-insulator transition (MIT) property. However, the relatively high critical temperature (T c) of ~68 °C seriously hinders its practical applications. Thus modulating the phase transition process and decreasing the T c close to room temperature have been hot topics for VO2 study. In the current work, we conducted a multi-approach strategy to control the phase transition of VO2 films, including the interfacial tensile/compressive strain and oxygen vacancies. A synchrotron radiation reciprocal space mapping technique was used to directly record the interfacial strain evolution and variations of lattice parameters. The effects of interfacial strain and oxygen vacancies in the MIT process were systematically investigated based on band structure and d-orbital electron occupation. It was suggested that the MIT behavior can be modulated through the combined effects of the interfacial strain and oxygen vacancies, achieving the distinct phase transition close to room temperature. The current findings not only provide better understanding for strain engineering and oxygen vacancies controlling phase transition behavior, but also supply a combined way to control the phase transition of VO2 film, which is essential for VO2 film based device applications in the future.

Interfacial friction and adhesion of cross-linked polymer thin films swollen with linear chains.

PubMed

Zhang, Qing; Archer, Lynden A

2007-07-03

The preparation and interfacial properties of a new type of tethered, thin-film lubricant coating are presented. These coatings are composed of three components: a dense self-assembled monolayer (SAM) underlayer that presents reactive vinyl groups at its surface; a cross-linked polydimethylsiloxane (PDMS) overlayer that is covalently tethered to the SAM; and free, mobile linear PDMS chains dispersed in the network. We investigate the influence of the molecular weight (Ms) and concentration of the free PDMS chains on the structure and equilibrium swelling properties of the cross-linked films. Using a bead-probe lateral force microscopy measurement technique, we also quantify the interfacial friction and adhesion characteristics of surfaces functionalized with these coatings. We find that both the volume fraction and the molecular weight of free PDMS molecules in the coatings influence their interfacial friction and adhesion properties. For example, the addition of short PDMS chains in dry, cross-linked PDMS thin films yields tethered surface coatings with ultralow friction coefficients (mu = 5.2 x 10(-3)). An analysis based on classical lubrication theory suggests that the reduction in friction force produced by free polymer is a consequence of the gradual separation of asperities on opposing surfaces and the consequent substitution of solid-solid friction by viscous drag of the free polymer chains in the network.

Foaming and adsorption behavior of bovine and camel proteins mixed layers at the air/water interface.

PubMed

Lajnaf, Roua; Picart-Palmade, Laetitia; Attia, Hamadi; Marchesseau, Sylvie; Ayadi, M A

2017-03-01

The aim of this work was to examine foaming and interfacial behavior of three milk protein mixtures, bovine α-lactalbumin-β-casein (M1), camel α-lactalbumin-β-casein (M2) and β-lactoglobulin-β-casein (M3), alone and in binary mixtures, at the air/water interface in order to better understand the foaming properties of bovine and camel milks. Different mixture ratios (100:0; 75:25; 50:50; 25:75; 0:100) were used during foaming tests and interfacial protein interactions were studied with a pendant drop tensiometer. Experimental results evidenced that the greatest foam was obtained with a higher β-casein amount in all camel and bovine mixtures. Good correlation was observed with the adsorption and the interfacial rheological properties of camel and bovine protein mixtures. The proteins adsorbed layers are mainly affected by the presence of β-casein molecules, which are probably the most abundant protein at interface and the most efficient in reducing the interfacial properties. In contrast of, the globular proteins, α-lactalbumin and β-lactoglobulin that are involved in the protein layer composition, but could not compact well at the interface to ensure foams creation and stabilization because of their rigid molecular structure. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanoparticle packing within block copolymer micelles prepared by the interfacial instability method.

PubMed

Nabar, Gauri M; Winter, Jessica O; Wyslouzil, Barbara E

2018-05-02

The interfacial instability method has emerged as a viable approach for encapsulating high concentrations of nanoparticles (NPs) within morphologically diverse micelles. In this method, transient interfacial instabilities at the surface of an emulsion droplet guide self-assembly of block co-polymers and NP encapsulants. Although used by many groups, there are no systematic investigations exploring the relationship between NP properties and micelle morphology. Here, the effect of quantum dot (QD) and superparamagnetic iron oxide NP (SPION) concentration on the shape, size, and surface deformation of initially spherical poly(styrene-b-ethylene oxide) (PS-b-PEO) micelles was examined. Multi-NP encapsulation and uniform dispersion within micelles was obtained even at low NP concentrations. Increasing NP concentration initially resulted in larger numbers of elongated micelles and cylinders with tightly-controlled diameters smaller than those of spherical micelles. Beyond a critical NP concentration, micelle formation was suppressed; the dominant morphology became densely-loaded NP structures that were coated with polymer and exhibited increased polydispersity. Transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) revealed that NPs in densely-loaded structures can be well-ordered, with packing volume fractions of up to 24%. These effects were enhanced in magnetic composites, possibly by dipole interactions. Mechanisms governing phase transitions triggered by NP loading in the interfacial instability process were proposed. The current study helps establish and elucidate the active role played by NPs in directing block copolymer assembly in the interfacial instability process, and provides important guiding principles for the use of this approach in generating NP-loaded block copolymer composites.

Interface Schottky barrier engineering via strain in metal-semiconductor composites

NASA Astrophysics Data System (ADS)

Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

2016-01-01

The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures.The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures. Electronic supplementary information (ESI) available: The changes of Au 5d DOS, valence bands of TiO2, the interfacial bond length and interfacial energy with strain, and the local DOS results for the change of SBH with strain. See DOI: 10.1039/c5nr05583k

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.

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

PubMed

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

2017-05-17

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

The "Rust" Challenge: On the Correlations between Electronic Structure, Excited State Dynamics, and Photoelectrochemical Performance of Hematite Photoanodes for Solar Water Splitting.

PubMed

Grave, Daniel A; Yatom, Natav; Ellis, David S; Toroker, Maytal Caspary; Rothschild, Avner

2018-03-05

In recent years, hematite's potential as a photoanode material for solar hydrogen production has ignited a renewed interest in its physical and interfacial properties, which continues to be an active field of research. Research on hematite photoanodes provides new insights on the correlations between electronic structure, transport properties, excited state dynamics, and charge transfer phenomena, and expands our knowledge on solar cell materials into correlated electron systems. This research news article presents a snapshot of selected theoretical and experimental developments linking the electronic structure to the photoelectrochemical performance, with particular focus on optoelectronic properties and charge carrier dynamics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characteristics of the Martian atmosphere surface layer

NASA Technical Reports Server (NTRS)

Clow, G. D.; Haberle, R. M.

1991-01-01

Researchers extend elements of various terrestrial boundary layer models to Mars in order to estimate sensible heat, latent heat, and momentum fluxes within the Martian atmospheric surface layer. To estimate the molecular viscosity and thermal conductivity of a CO2-H2O gas mixture under Martian conditions, parameterizations were developed. Parameterizations for specific heat and and binary diffusivity were also determined. The Prandtl and Schmidt numbers derived from these thermophysical properties were found to range from 0.78 - 1.0 and 0.47 - 0.70, respectively, for Mars. Brutsaert's model for sensible and latent heat transport within the interfacial sublayer for both aerodynamically smooth and rough airflow was experimentally tested under similar conditions, validating its application to Martian conditions. For the surface sublayer, the researchers modified the definition of the Monin-Obukhov length to properly account for the buoyancy forces arising from water vapor gradients in the Martian atmospheric boundary layer. This length scale was then utilized with similarity theory turbulent flux profiles with the same form as those used by Businger et al. and others. It was found that under most Martian conditions, the interfacial and surface sublayers offer roughly comparable resistance to sensible heat and water vapor transport and are thus both important in determining the associated fluxes.

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

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.

Preparation of ultrathin, robust protein microcapsules through template-mediated interfacial reaction between amine and catechol groups.

PubMed

Wang, Xiaoli; Shi, Jiafu; Jiang, Zhongyi; Li, Zheng; Zhang, Wenyan; Song, Xiaokai; Ai, Qinghong; Wu, Hong

2013-11-11

A novel approach to the synthesis of protein microcapsules is developed through template-mediated interfacial reaction. Protein-doped CaCO3 templates are first synthetized via coprecipitation and then coated with a catechol-containing alginate (AlgDA) layer. Afterward, the templates are exposed to ethylenediamine tetraacetic acid disodium (EDTA) solution to dissolve CaCO3. During CaCO3 dissolution, the generated CO2 gas pushes protein molecules moving to the AlgDA layer, and thereby Michael addition and Schiff base reactions proceed, forming the shell of protein microcapsules. Three kinds of proteins, namely, bovine serum albumin, catalase, and protamine sulfate, are utilized. The shell thickness of microcapsule varies from 25 to 82 nm as the doping amount of protein increased from 2 to 6 mg per 66 mg CaCO3. The protein microcapsules have a robust but flexible shell and can be reversibly deformed upon exposure to osmotic pressure. The bioactivity of protein microcapsules is demonstrated through enzymatic catalysis experiments. The protein microcapsules remain about 80% enzymatic activity of the equivalent free protein. Hopefully, our approach could be extended to many other applications such as drug/gene delivery, tissue scaffolds, and catalysis due to the universality of Michael reaction and Schiff base reactions.

Effects of atmospheric air plasma treatment on interfacial properties of PBO fiber reinforced composites

NASA Astrophysics Data System (ADS)

Zhang, Chengshuang; Li, Cuiyun; Wang, Baiya; Wang, Bin; Cui, Hong

2013-07-01

Poly(p-phenylene benzobisoxazole) (PBO) fiber was modified by atmospheric air plasma treatment. The effects of plasma treatment power and speed on both surface properties of PBO fibers and interfacial properties of PBO/epoxy composites were investigated. Surface chemical composition of PBO fibers were analyzed by X-ray photoelectron spectroscopy (XPS). Surface morphologies of the fibers and interface structures of the composites were examined using scanning electron microscopy (SEM). Interfacial adhesion property of the composites was evaluated by interlaminar shear strength (ILSS). Mechanical properties of PBO multifilament were measured by universal testing machine. The results indicate that atmospheric air plasma treatment introduced some polar or oxygen-containing groups to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. The plasma treatment also improved interfacial adhesion of PBO/epoxy composites but has little effect on tensile properties of PBO multifilament. The ILSS of PBO/epoxy composites increased to 40.0 MPa after atmospheric air plasma treatment with plasma treatment power of 300 W and treatment speed of 6 m/min.

Ferromagnetic resonance of NiCoFe2O4 nanoparticles and microwave absorption properties of flexible NiCoFe2O4-carbon black/poly(vinyl alcohol) composites.

PubMed

Datt, Gopal; Kotabage, Chetan; Abhyankar, A C

2017-08-09

The effect of cationic disorder and particle morphology on the ferromagnetic resonance (FMR) of NiCoFe 2 O 4 nanoparticles (NPs) and the electromagnetic shielding effectiveness of flexible composites (wherein the nanoparticles are used as fillers) has been presented. Upon annealing at 1000 °C, spherical, ∼25 nm, single crystalline (as-prepared) NPs are transformed into octahedral, ∼200 nm, polycrystalline (annealed) NPs and change the cationic distribution significantly. The effect of shape, size and cationic distribution on the resonance properties has been discussed using the randomly-oriented anisotropic-axis model. The temperature dependent evolution of FMR spectra has been found to be consistent with a Bloch spin-relaxation model. Analysis of the FMR spectra reveals that NiCoFe 2 O 4 nanoparticles have a large internal magnetic field along with broad FMR linewidths of ∼2-3 kOe, signifying high magnetic losses that are essential for the absorption of electromagnetic (EM) waves. Next, NiCoFe 2 O 4 -carbon black (NCF-CB) hybrids grafted in a PVA matrix, as flexible composite films with a thickness of ∼1.5 mm, are assessed for EM wave absorption properties in the range of 8-18 GHz. As compared to annealed-NCF-CB/PVA (21 dB, ∼99.5%), the as-prepared-NCF-CB/PVA composite film exhibits significantly large SE of 27 dB (∼99.9% attenuation of the EM wave), with a dominant contribution from absorption (SE A ∼ 21 dB). The electrical conductivity, the electric modulus, and Cole-Cole plots reveal that the dielectric losses in the as-prepared-NCF-CB/PVA have significant contributions from cationic disorder and particle size, as compared to the annealed-NCF-CB/PVA composites. Cationic disorder increases the d-d electron transition probability between adjacent ionic pairs such as Co 2+ /Fe 3+ and a reduced particle size creates large interfacial polarization in the as-prepared NCF/CB hybrids. Considerably large values of the Landes g-factor, magnetic anisotropy and better impedance matching indicate a dominant magnetic loss contribution in ap-NCF (g = 4.5) as compared to an-NCF (g = 2.5) at 300 K.

Catalytic, Conductive Bipolar Membrane Interfaces through Layer-by-Layer Deposition for the Design of Membrane-Integrated Artificial Photosynthesis Systems.

PubMed

McDonald, Michael B; Freund, Michael S; Hammond, Paula T

2017-11-23

In the presence of an electric field, bipolar membranes (BPMs) are capable of initiating water disassociation (WD) within the interfacial region, which can make water splitting for renewable energy in the presence of a pH gradient possible. In addition to WD catalytic efficiency, there is also the need for electronic conductivity in this region for membrane-integrated artificial photosynthesis (AP) systems. Graphene oxide (GO) was shown to catalyze WD and to be controllably reduced, which resulted in electronic conductivity. Layer-by-layer (LbL) film deposition was employed to improve GO film uniformity in the interfacial region to enhance WD catalysis and, through the addition of a conducting polymer in the process, add electronic conductivity in a hybrid film. Three different deposition methods were tested to optimize conducting polymer synthesis with the oxidant in a metastable solution and to yield the best film properties. It was found that an approach that included substrate dipping in a solution containing the expected final monomer/oxidant ratio provided the most predictable film growth and smoothest films (by UV/Vis spectroscopy and atomic force microscopy/scanning electron microscopy, respectively), whereas dipping in excess oxidant or co-spraying the oxidant and monomer produced heterogeneous films. Optimized films were found to be electronically conductive and produced a membrane ohmic drop that was acceptable for AP applications. Films were integrated into the interfacial region of BPMs and revealed superior WD efficiency (≥1.4 V at 10 mA cm -2 ) for thinner films (<10 bilayers≈100 nm) than for either the pure GO catalyst or conducting polymer individually, which indicated that there was a synergistic effect between these materials in the structure configured by the LbL method. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Intermixing enables strong exchange coupling in nanocomposites: Magnetism through the interfacial ferrite in γ -Fe2O3/NiO

NASA Astrophysics Data System (ADS)

Skoropata, E.; Su, T. T.; Ouyang, H.; Freeland, J. W.; van Lierop, J.

2017-07-01

γ -Fe2O3 particles, surface modified with NiO crystallites, form a unique nanocomposite that points to how to tune strong interfacial exchange coupling. We find that Ni2 + migrates into the octahedral sites of the γ -Fe2O3 nanoparticle surface, and this NiFe2O4 -like layer permits effective magnetic coupling of Ni and Fe sites that strengthens the interface exchange. A large increase in coercivity coinciding with a loss of exchange bias is achieved by this strong interfacial coupling that results in a Ni2 + moment reversal in the NiO with the γ -Fe2O3 . This work reveals the importance of intermixing in, and possibility to use, such an exchange coupling regime to alter substantially the coercivity and hence control an important property of exchange-coupled nanocomposite magnets.

Rapid and Simple Capillary-Rise/Vanishing Interfacial Tension Method To Determine Crude Oil Minimum Miscibility Pressure: Pure and Mixed CO 2 , Methane, and Ethane

DOE PAGES

Hawthorne, Steven B.; Miller, David J.; Jin, Lu; ...

2016-07-20

We report here a simplification of the capillary-rise/vanishing interfacial tension (IFT) method to measure minimum miscibility pressure (MMP) based on only requiring knowledge of when the interfacial tension approaches zero. Simply measuring the height of the crude oil in a capillary at several pressures from ambient to near the MMP pressure and extrapolating the oil height versus pressure plot to zero oil height yields the MMP without the need of the additional instrumentation and labor required to perform actual IFT measurements. A total of 2−4 MMP values can be determined per day with only one experimental apparatus, and the methodmore » greatly reduces the initial cost and complexity of the required instrumentation. The use of three capillaries having different inner diameters allows for triplicate determinations of MMP from each experiment. Because the actual MMP pressure need not be reached during the experiment, MMP values that exceed the pressure ratings of the equipment can be reasonably estimated (e.g., MMPs using pure nitrogen). The method was used to determine the MMP pressure for crude oil samples from a conventional Muddy Formation reservoir in the Powder River Basin [American Petroleum Institute (API) gravity of 35.8°] and an unconventional Bakken Formation reservoir in the Williston Basin (API gravity of 38.7°). The method is reproducible [typically <4% relative standard deviation (RSD)], and the method gave good agreement for a “live” Bakken oil with the results from a slim tube test of a commercial laboratory. Approximately 80 MMP values were measured using pure CO2, methane, and ethane as well as 0−100% mole ratios of methane/CO2 and methane/ethane. For both oil samples, ethane MMPs were ca. one-half those with CO2, while methane MMPs were ca. double or triple those with CO2. MMPs with mixed methane/CO2 showed a linear increase with mole percent methane for both crude oils, while both oils showed an exponential increase in MMP with mole percent methane in ethane, with a little increase in MMP until ca. 20 mol % methane in ethane.« less

3D-Printing Electrolytes for Solid-State Batteries.

PubMed

McOwen, Dennis W; Xu, Shaomao; Gong, Yunhui; Wen, Yang; Godbey, Griffin L; Gritton, Jack E; Hamann, Tanner R; Dai, Jiaqi; Hitz, Gregory T; Hu, Liangbing; Wachsman, Eric D

2018-05-01

Solid-state batteries have many enticing advantages in terms of safety and stability, but the solid electrolytes upon which these batteries are based typically lead to high cell resistance. Both components of the resistance (interfacial, due to poor contact with electrolytes, and bulk, due to a thick electrolyte) are a result of the rudimentary manufacturing capabilities that exist for solid-state electrolytes. In general, solid electrolytes are studied as flat pellets with planar interfaces, which minimizes interfacial contact area. Here, multiple ink formulations are developed that enable 3D printing of unique solid electrolyte microstructures with varying properties. These inks are used to 3D-print a variety of patterns, which are then sintered to reveal thin, nonplanar, intricate architectures composed only of Li 7 La 3 Zr 2 O 12 solid electrolyte. Using these 3D-printing ink formulations to further study and optimize electrolyte structure could lead to solid-state batteries with dramatically lower full cell resistance and higher energy and power density. In addition, the reported ink compositions could be used as a model recipe for other solid electrolyte or ceramic inks, perhaps enabling 3D printing in related fields. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

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.

Structural, thermal, optical, and photoacoustic study of nanocrystalline Bi{sub 2}Te{sub 3} produced by mechanical alloying

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

Souza, S. M.; Triches, D. M.; Poffo, C. M.

2011-01-01

Nanocrystalline Bi{sub 2}Te{sub 3} was produced by mechanical alloying and its properties were investigated by differential scanning calorimetry (DSC) x-ray diffraction (XRD), Raman spectroscopy (RS), and photoacoustic spectroscopy (PAS). Combining the XRD and RS results, the volume fraction of the interfacial component in as-milled and annealed samples was estimated. The PAS results suggest that the contribution of the interfacial component to the thermal diffusivity of nanostructured Bi{sub 2}Te{sub 3} is very significant.

Magnetic properties of Co/Rh (001) multilayers studied by x-ray magnetic-circular dichroism

NASA Astrophysics Data System (ADS)

Tomaz, M. A.; Mayo, E.; Lederman, D.; Hallin, E.; Sham, T. K.; O'brien, W. L.; Harp, G. R.

1998-11-01

The layer-averaged magnetic moments of Co and Rh have been measured in sputter deposited Co/Rh (001) multilayer thin films using the x-ray magnetic circular dichroism. The Rh moments were measured at both the L and M absorption edges, where we find that the Rh moment decreases as a function of increasing Rh layer thickness (tRh). The decline of the layer-averaged Rh moment is well described in terms of a simple dilution, implying that the Rh moment is confined to the interfacial region. We find that the Co moment remains largely unaffected, maintaining a bulklike value of 1.7μB in the region preceding the first antiferromagnetic coupling peak where tRh ranges from 0 to 4 Å. We also find, via application of the dichroism sum rules, that the ratio / for Co increases ~10% for this same region. Finally, we contrast the magnetic behavior of the Co/Rh (001) and Fe/Rh (001) multilayer systems.

Nanoscale Chemical Processes Affecting Storage Capacities and Seals during Geologic CO2 Sequestration.

PubMed

Jun, Young-Shin; Zhang, Lijie; Min, Yujia; Li, Qingyun

2017-07-18

Geologic CO 2 sequestration (GCS) is a promising strategy to mitigate anthropogenic CO 2 emission to the atmosphere. Suitable geologic storage sites should have a porous reservoir rock zone where injected CO 2 can displace brine and be stored in pores, and an impermeable zone on top of reservoir rocks to hinder upward movement of buoyant CO 2 . The injection wells (steel casings encased in concrete) pass through these geologic zones and lead CO 2 to the desired zones. In subsurface environments, CO 2 is reactive as both a supercritical (sc) phase and aqueous (aq) species. Its nanoscale chemical reactions with geomedia and wellbores are closely related to the safety and efficiency of CO 2 storage. For example, the injection pressure is determined by the wettability and permeability of geomedia, which can be sensitive to nanoscale mineral-fluid interactions; the sealing safety of the injection sites is affected by the opening and closing of fractures in caprocks and the alteration of wellbore integrity caused by nanoscale chemical reactions; and the time scale for CO 2 mineralization is also largely dependent on the chemical reactivities of the reservoir rocks. Therefore, nanoscale chemical processes can influence the hydrogeological and mechanical properties of geomedia, such as their wettability, permeability, mechanical strength, and fracturing. This Account reviews our group's work on nanoscale chemical reactions and their qualitative impacts on seal integrity and storage capacity at GCS sites from four points of view. First, studies on dissolution of feldspar, an important reservoir rock constituent, and subsequent secondary mineral precipitation are discussed, focusing on the effects of feldspar crystallography, cations, and sulfate anions. Second, interfacial reactions between caprock and brine are introduced using model clay minerals, with focuses on the effects of water chemistries (salinity and organic ligands) and water content on mineral dissolution and surface morphology changes. Third, the hydrogeological responses (using wettability alteration as an example) of clay minerals to chemical reactions are discussed, which connects the nanoscale findings to the transport and capillary trapping of CO 2 in the reservoirs. Fourth, the interplay between chemical and mechanical alterations of geomedia, using wellbore cement as a model geomedium, is examined, which provides helpful insights into wellbore and caprock integrities and CO 2 mineralization. Combining these four aspects, our group has answered questions related to nanoscale chemical reactions in subsurface GCS sites regarding the types of reactions and the property alterations of reservoirs and caprocks. Ultimately, the findings can shed light on the influences of nanoscale chemical reactions on storage capacities and seals during geologic CO 2 sequestration.

The enhancement of anomalous Hall effect by inserting MgO layer in perpendicular anisotropic Pd/Co2MnSi/MgO/Pd films

NASA Astrophysics Data System (ADS)

Fu, H. R.; Ma, L.; Tian, N.; You, C. Y.; Wang, K.

2018-05-01

A systematic study of anomalous Hall effect (AHE) was performed in perpendicular magnetic anisotropic Pd/Co2MnSi(tCMS)/MgO/Pd films. The AHE was significantly intensified by inserting MgO layer, which can be ascribed to the enhancement of spin-orbit coupling and interfacial scattering contribution. Moreover, it was found that the Co and Mn ions were reduced at the interface of Co2MnSi/MgO with annealing process. The stable amount of Mn-O bonding was observed at the Co2MnSi/MgO interface after annealing, implying that the proper Mn-O bonding could be favorable for achieving large AHE.

Migration of interfacial oxygen ions modulated resistive switching in oxide-based memory devices

NASA Astrophysics Data System (ADS)

Chen, C.; Gao, S.; Zeng, F.; Tang, G. S.; Li, S. Z.; Song, C.; Fu, H. D.; Pan, F.

2013-07-01

Oxides-based resistive switching memory induced by oxygen ions migration is attractive for future nonvolatile memories. Numerous works had focused their attentions on the sandwiched oxide materials for depressing the characteristic variations, but the comprehensive studies of the dependence of electrodes on the migration behavior of oxygen ions are overshadowed. Here, we investigated the interaction of various metals (Ni, Co, Al, Ti, Zr, and Hf) with oxygen atoms at the metal/Ta2O5 interface under electric stress and explored the effect of top electrode on the characteristic variations of Ta2O5-based memory device. It is demonstrated that chemically inert electrodes (Ni and Co) lead to the scattering switching characteristics and destructive gas bubbles, while the highly chemically active metals (Hf and Zr) formed a thick and dense interfacial intermediate oxide layer at the metal/Ta2O5 interface, which also degraded the resistive switching behavior. The relatively chemically active metals (Al and Ti) can absorb oxygen ions from the Ta2O5 film and avoid forming the problematic interfacial layer, which is benefit to the formation of oxygen vacancies composed conduction filaments in Ta2O5 film thus exhibit the minimum variations of switching characteristics. The clarification of oxygen ions migration behavior at the interface can lead further optimization of resistive switching performance in Ta2O5-based memory device and guide the rule of electrode selection for other oxide-based resistive switching memories.

Interfaces of high-efficiency kesterite Cu2ZnSnS(e)4 thin film solar cells

NASA Astrophysics Data System (ADS)

Gao, Shoushuai; Jiang, Zhenwu; Wu, Li; Ao, Jianping; Zeng, Yu; Sun, Yun; Zhang, Yi

2018-01-01

Cu2ZnSnS(e)4 (CZTS(e)) solar cells have attracted much attention due to the elemental abundance and the non-toxicity. However, the record efficiency of 12.6% for Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is much lower than that of Cu(In,Ga)Se2 (CIGS) solar cells. One crucial reason is the recombination at interfaces. In recent years, large amount investigations have been done to analyze the interfacial problems and improve the interfacial properties via a variety of methods. This paper gives a review of progresses on interfaces of CZTS(e) solar cells, including: (1) the band alignment optimization at buffer/CZTS(e) interface, (2) tailoring the thickness of MoS(e)2 interfacial layers between CZTS(e) absorber and Mo back contact, (3) the passivation of rear interface, (4) the passivation of front interface, and (5) the etching of secondary phases.

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.

Studies of giant magnetoresistance and interfacial structure in Cu/Co and Co/Re multilayers

NASA Astrophysics Data System (ADS)

Setty, Arun; Fernando, G.; Cooper, B. R.

2003-03-01

A study of giant magnetoresistance (GMR) in the Cu/Co [1]and Co/Re multilayer [2,3] systems is presented. The role of interface structure in such systems is significant, and is being investigated using an ab-initio based approach [4]. The role of intermixing [5], impurities and growth textures have been considered. Structural relaxation is taken into account using Hellman-Feynman and symmetry-based approaches. We find lattice spacings in agreement with experiment, energetically establish the favored growth textures and find results motivating the existence of the observed wavy interface in the Cu/Co system [6]. The transport properties of these multilayer systems will be studied using a theoretical model [7] incorporating material parameters obtained from the multiscale modeling approach we envisage. [1] S.S.P. Parkin, Z.G. Li, and D. J. Smith, Appl. Phys. Lett., 58, 2710-2712 (1991). [2] T. Charlton et al, Phys. Rev. B 63, 094404 (2001) [3] T. Charlton et al, Phys. Rev. B 59, 11897-11908 (1999) [4] C. Villagonzalo, A.K. Setty and B.R. Cooper, submitted to Phys. Rev. [5] J. Fassbender, R. Allenspach, and U. Durig. Surf. Sci., 383, L742-L748, (1997). [6] D.J. Larson et al, Appl. Phys. Lett., 73:1125-1127, (1998). [7] J. C. Slonczewski, Phys. Rev. B 39, 6995 (1989).

Improved dielectric properties, mechanical properties, and thermal conductivity properties of polymer composites via controlling interfacial compatibility with bio-inspired method

NASA Astrophysics Data System (ADS)

Ruan, Mengnan; Yang, Dan; Guo, Wenli; Zhang, Liqun; Li, Shuxin; Shang, Yuwei; Wu, Yibo; Zhang, Min; Wang, Hao

2018-05-01

Surface functionalization of Al2O3 nano-particles by mussel-inspired poly(dopamine) (PDA) was developed to improve the dielectric properties, mechanical properties, and thermal conductivity properties of nitrile rubber (NBR) matrix. As strong adhesion of PDA to Al2O3 nano-particles and hydrogen bonds formed by the catechol groups of PDA and the polar acrylonitrile groups of NBR, the dispersion of Al2O3-PDA/NBR composites was improved and the interfacial force between Al2O3-PDA and NBR matrix was enhanced. Thus, the Al2O3-PDA/NBR composites exhibited higher dielectric constant, better mechanical properties, and larger thermal conductivity comparing with Al2O3/NBR composites at the same filler content. The largest thermal conductivity of Al2O3-PDA/NBR composite filled with 30 phr Al2O3-PDA was 0.21 W/m K, which was 122% times of pure NBR. In addition, the Al2O3-PDA/NBR composite filled with 30 phr Al2O3-PDA displayed a high tensile strength about 2.61 MPa, which was about 255% of pure NBR. This procedure is eco-friendly and easy handling, which provides a promising route to polymer composites in application of thermal conductivity field.

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

DOE PAGES

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

2017-08-21

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

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

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

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

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

Gassing in Li4Ti5O12-based batteries and its remedy

PubMed Central

He, Yan-Bing; Li, Baohua; Liu, Ming; Zhang, Chen; Lv, Wei; Yang, Cheng; Li, Jia; Du, Hongda; Zhang, Biao; Yang, Quan-Hong; Kim, Jang-Kyo; Kang, Feiyu

2012-01-01

Destructive gas generation with associated swelling has been a major challenge to the large-scale application of lithium ion batteries (LIBs) made from Li4Ti5O12 (LTO) anodes. Here we report root causes of the gassing behavior, and suggest remedy to suppress it. The generated gases mainly contain H2, CO2 and CO, which originate from interfacial reactions between LTO and surrounding alkyl carbonate solvents. The reactions occur at the very thin outermost surface of LTO (111) plane, which result in transformation from (111) to (222) plane and formation of (101) plane of anatase TiO2. A nanoscale carbon coating along with a stable solid electrolyte interface (SEI) film around LTO is seen most effective as a barrier layer in suppressing the interfacial reaction and resulting gassing from the LTO surface. Such an ability to tune the interface nanostructure of electrodes has practical implications in the design of next-generation high power LIBs. PMID:23209873

Structural and dielectric properties of thin ZrO2 films on silicon grown by atomic layer deposition from cyclopentadienyl precursor

NASA Astrophysics Data System (ADS)

Niinistö, J.; Putkonen, M.; Niinistö, L.; Kukli, K.; Ritala, M.; Leskelä, M.

2004-01-01

ZrO2 thin films with thicknesses below 20 nm were deposited by the atomic layer deposition process on Si(100) substrates at 350 °C. An organometallic precursor, Cp2Zr(CH3)2 (Cp=cyclopentadienyl, C5H5) was used as the zirconium source and water or ozone as oxygen source. The influence of oxygen source and substrate pretreatment on the dielectric properties of ZrO2 films was investigated. Structural characterization with high-resolution transmission electron microscopy was performed to films grown onto HF-etched or native oxide covered silicon. Strong inhibition of ZrO2 film growth was observed with the water process on HF-etched Si. Ozone process on HF-etched Si resulted in interfacial SiO2 formation between the dense and uniform film and the substrate while water process produced interfacial layer with intermixing of SiO2 and ZrO2. The effective permittivity of ZrO2 in Al/ZrO2/Si/Al capacitor structures was dependent on the ZrO2 layer thickness and oxygen source used. The interfacial layer formation increased the capacitance equivalent oxide thickness (CET). CET of 2.0 nm was achieved with 5.9 nm ZrO2 film deposited with the H2O process on HF-stripped Si. The ozone-processed films showed good dielectric properties such as low hysteresis and nearly ideal flatband voltage. The leakage current density was lower and breakdown field higher for the ozone-processed ZrO2 films.

Mixed ion/electron-conductive protective soft nanomatter-based conformal surface modification of lithium-ion battery cathode materials

NASA Astrophysics Data System (ADS)

Park, Jang-Hoon; Kim, Ju-Myung; Lee, Chang Kee; Lee, Sang-Young

2014-10-01

Understanding and control of interfacial phenomena between electrode material and liquid electrolytes are of major scientific importance for boosting development of high-performance lithium ion batteries with reliable electrochemical/safety attributes. Here, as an innovative surface engineering approach to address the interfacial issues, a new concept of mixed ion/electron-conductive soft nanomatter-based conformal surface modification of the cathode material is presented. The soft nanomatter is comprised of an electron conductive carbonaceous (C) substance embedded in an ion conductive polyimide (PI) nanothin compliant film. In addition to its structural uniqueness, the newly proposed surface modification benefits from a simple fabrication process. The PI/carbon soft nanomatter is directly synthesized on LiCoO2 surface via one-pot thermal treatment of polyamic acid (=PI precursor) and sucrose (=carbon source) mixture, where the LiCoO2 powders are chosen as a model system to explore the feasibility of this surface engineering strategy. The resulting PI/carbon coating layer facilitates electronic conduction and also suppresses unwanted side reactions arising from the cathode material-liquid electrolyte interface. These synergistic coating effects of the multifunctional PI/carbon soft nanomatter significantly improve high-voltage cell performance and also mitigate interfacial exothermic reaction between cathode material and liquid electrolyte.

Alkali Salt-Doped Highly Transparent and Thickness-Insensitive Electron-Transport Layer for High-Performance Polymer Solar Cell.

PubMed

Xu, Rongguo; Zhang, Kai; Liu, Xi; Jin, Yaocheng; Jiang, Xiao-Fang; Xu, Qing-Hua; Huang, Fei; Cao, Yong

2018-01-17

Solution-processable highly transparent and thickness-insensitive hybrid electron-transport layer (ETL) with enhanced electron-extraction and electron-transport properties for high-performance polymer solar cell was reported. With the incorporation of Cs 2 CO 3 into the poly[(9,9-bis(6'-((N,N-diethyl)-N-ethylammonium)-hexyl)-2,7-fluorene)-alt-1,4-diphenylsulfide]dibromide (PF6NPSBr) ETL, the power conversion efficiency (PCE) of resulted polymer solar cells (PSCs) was significantly enhanced due to the favorable interfacial contact, energy-level alignment, and thus facile electron transport in the PSC device. These organic-inorganic hybrid ETLs also exhibited high transparency and high electron mobility. All of these combined properties ensured us to design novel thickness-insensitive ETLs that avoid the parasitic absorption of ETL itself simultaneously. With the conventional device structure with poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl} (PTB7-Th) as a donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) as an acceptor, devices with hybrid ETLs exhibited PCE of 8.30-9.45% within a wide range of ETL thickness. A notable PCE of 10.78% was achieved with the thick active layer poly(2,5-thiophene-alt-5,5'-(5,10-bis(4-(2-octyldodecyl)thiophen-2-yl)naphtho[1,2-c:5,6-c']bis([1,2,5]thiadiazole)) (PTNT812):PC 71 BM. These findings indicated that doping alkali salt into the organic interfacial materials can be a promising strategy to design highly efficient and thickness-insensitive ETL, which may be suitable for large-area PSC modules device fabrication with roll-to-roll printing technique.

Phosphine oxide surfactants revisited.

PubMed

Stubenrauch, Cosima; Preisig, Natalie; Laughlin, Robert G

2016-04-01

This review summarizes everything we currently know about the nonionic surfactants alkyl dimethyl (C(n)DMPO) and alkyl diethyl (C(n)DEPO) phosphine oxide (PO surfactants). The review starts with the synthesis and the general properties (Section 2) of these compounds and continues with their interfacial properties (Section 3) such as surface tension, surface rheology, interfacial tension and adsorption at solid surfaces. We discuss studies on thin liquid films and foams stabilized by PO surfactants (Section 4) as well as studies on their self-assembly into lyotropic liquid crystals and microemulsions, respectively (Section 5). We aim at encouraging colleagues from both academia and industry to take on board PO surfactants whenever possible and feasible because of their broad variety of excellent properties. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

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 Cu + promoted surface reactivity: Carbon monoxide oxidation reaction over polycrystalline copper-titania catalysts

DOE PAGES

Senanayake, S. D.; Pappoe, N. A.; Nguyen-Phan, T. -D.; ...

2016-10-01

We have studied the catalytic carbon monoxide (CO) oxidation (CO+0.5O2 → CO2) reaction using a powder catalyst composed of both copper (5wt% loading) and titania (CuOx-TiO2). Our study was focused on revealing the role of Cu, and the interaction between Cu and TiO2, by systematic comparison between two nanocatalysts, CuOx-TiO2 and pure CuOx. We interrogated these catalysts under in situ conditions using X-ray Diffraction (XRD), X-ray Absorption Fine Structure (XAFS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) to probe the structure and electronic properties of the catalyst at all stages of the reaction and simultaneously probe the surface statesmore » or intermediates of this reaction. With the aid of several ex situ characterization techniques including Transmission Electron Microscopy (TEM), the local catalyst morphology and structure was also studied. Our results show that a CuOx-TiO2 system is more active than bulk CuOx for the CO oxidation reaction due to its lower onset temperature and better stability at higher temperatures. Our results also suggests that a surface Cu+ species observed in the CuOx-TiO2 interface are likely to be a key player in the CO oxidation mechanism, while implicating that the stabilization of this species is probably associated with the oxide-oxide interface. Both in situ DRIFTS and XAFS measurements reveal that there is likely to be a Cu(Ti)-O mixed oxide at this interface. We discuss the nature of this Cu(Ti)-O interface and interpret its role on the CO oxidation reaction.« less

Evaluation of Electroplated Co-P Film as Diffusion Barrier Between In-48Sn Solder and SiC-Dispersed Bi2Te3 Thermoelectric Material

NASA Astrophysics Data System (ADS)

Li, Siyang; Yang, Donghua; Tan, Qing; Li, Liangliang

2015-06-01

The diffusion barrier property of Co-P film as a buffer layer between SiC-dispersed Bi2Te3 bulk material and In-48Sn solder was investigated. A Co-P film with thickness of ~6 µm was electroplated on SiC-dispersed Bi2Te3 substrate, joined with In-48Sn solder by a reflow process, and annealed at 100°C for up to 625 h. The formation and growth kinetics of intermetallic compounds (IMCs) at the interface between the In-48Sn and substrate were studied using transmission electron microscopy and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The results showed that crystalline Co(In,Sn)3 formed as an irregular layer adjacent to the solder side at the solder/Co-P interface due to diffusion of Co towards the solder, and a small amount of amorphous Co45P13In12Sn30 appeared at the Co-P side because of diffusion of In and Sn into Co-P. The growth of Co(In,Sn)3 and Co45P13In12Sn30 during solid-state aging was slow, being controlled by interfacial reaction and diffusion, respectively. For comparison, In-48Sn/Bi2Te3-SiC joints were prepared and the IMCs in the joints analyzed. Without a diffusion barrier, In penetrated rapidly into the substrate, which led to the formation of amorphous In x Bi y phase in crystalline In4Te3 matrix. These IMCs grew quickly with prolongation of the annealing time, and their growth was governed by volume diffusion of elements. The experimental data demonstrate that electroplated Co-P film is an effective diffusion barrier for use in Bi2Te3-based thermoelectric modules.

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.

Investigation of thermal energy transport interface of hybrid graphene-carbon nanotube/polyethylene nanocomposites.

PubMed

Liu, Feng; Liu, Xuyang; Hu, Ning; Ning, Huiming; Atobe, Satoshi; Yan, Cheng; Mo, Fuhao; Fu, Shaoyun; Zhang, Jianyu; Wang, Yu; Mu, Xiaojing

2017-10-31

It is well known the thermal properties of three-dimensional (3-D) hybrid graphene (GR)-carbon nanotube (CNT) structures are not superior to that of the individual GR and CNT, however, the 3-D hybrid GR-CNT structures can effectively improve the thermal properties of polymer matrix. Therefore, understanding the thermal energy transport in the interface between polymer matrix and 3-D hybrid GR-CNT structure is essential. Here, the enhancement mechanism of interfacial thermal transport of hybrid GR-CNT structure was explored by applying non-equilibrium molecular dynamics (NEMD) simulations. Three different types of hybrid GR-CNT structures were built. The influences of CNT radius and CNT type for the hybrid GR-CNT on the interfacial thermal properties were also analyzed. Computational results show that among the three different types of hybrid GR-CNT structures, the Model-I, i.e., the covalent bond hybrid GR-CNT structures are of the best interfacial thermal properties. Meanwhile, the CNT radius of hybrid GR-CNT structure has a great influence on the interfacial thermal properties.

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

Composites of ionic liquid and amine-modified SAPO 34 improve CO2 separation of CO2-selective polymer membranes

NASA Astrophysics Data System (ADS)

Hu, Leiqing; Cheng, Jun; Li, Yannan; Liu, Jianzhong; Zhang, Li; Zhou, Junhu; Cen, Kefa

2017-07-01

Mixed matrix membranes with ionic liquids and molecular sieve particles had high CO2 permeabilities, but CO2 separation from small gas molecules such as H2 was dissatisfied because of bad interfacial interaction between ionic liquid and molecular sieve particles. To solve that, amine groups were introduced to modify surface of molecular sieve particles before loading with ionic liquid. SAPO 34 was adopted as the original filler, and four mixed matrix membranes with different fillers were prepared on the outer surface of ceramic hollow fibers. Both surface voids and hard agglomerations disappeared, and the surface became smooth after SAPO 34 was modified by amine groups and ionic liquid [P66614][2-Op]. Mixed matrix membranes with composites of amine-modified SAPO 34 and ionic liquid exhibited excellent CO2 permeability (408.9 Barrers) and CO2/H2 selectivity (22.1).

Direct laser sintered WC-10Co/Cu nanocomposites

NASA Astrophysics Data System (ADS)

Gu, Dongdong; Shen, Yifu

2008-04-01

In the present work, the direct metal laser sintering (DMLS) process was used to prepare the WC-Co/Cu nanocomposites in bulk form. The WC reinforcing nanoparticles were added in the form of WC-10 wt.% Co composite powder. The microstructural features and mechanical properties of the laser-sintered sample were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), and nanoindentation tester. It showed that the original nanometric nature of the WC reinforcing particulates was well retained without appreciable grain growth after laser processing. A homogeneous distribution of the WC reinforcing nanoparticles with a coherent particulate/matrix interfacial bonding was obtained in the laser-sintered structure. The 94.3% dense nanocomposites have a dynamic nanohardness of 3.47 GPa and a reduced elastic modulus of 613.42 GPa.

Magnetisation reversal in anisotropy graded Co/Pd multilayers

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

Barton, C. W., E-mail: craig.barton-2@postgrad.manchester.ac.uk; Thomson, T.

2015-08-14

We demonstrate high precision controllability of the magnetization reversal nucleation process in [Co/Pd]{sub 8} multilayer films consisting of two sets of bilayers with high and low perpendicular anisotropy, respectively. The anisotropy of the entire film is set by the degree of Co/Pd interfacial mixing during deposition which provides fine control of the anisotropy of an individual bilayer in the multilayer stack. The relative number of each type of bilayer is used to select the magnetisation reversal behavior such that changing one bilayer changes the properties of the entire multilayer through anisotropy averaging. A simple extension to the sputtering protocol wouldmore » provide multilayer films with fully graded anisotropy, while maintaining a constant saturation magnetization opening new possibilities for the creation of highly engineered multilayer structures for spin torque devices and future magnetic recording media.« less

Probing properties of the interfacial perimeter sites in TiO x /Au/SiO 2 with 2-propanol decomposition

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

Wu, Yi Y.; Kung, Harold H.

The decomposition of 2-propanol was studied over SiO2, SiO2 with an overlayer of TiO2 (Ti/SiO2), Au/SiO2, and Au/SiO2 with an overlayer of TiO2 (Ti/[Au/SiO2]) at 170–190 °C. There was no reaction on SiO2. Propene was the only product on Ti/SiO2, and its rate of formation increased proportionally with the Ti content. Acetone was the major product (selectivity 65–99%) on all Au-containing catalysts. Its rate of formation also increased with Ti loading. In addition, small amounts of propene were also formed on Ti/[Au/SiO2] the rate of which increased with Ti loading. Characterization of the catalysts with N2 adsorption, STEM, DR-UV-vis spectroscopy,more » XPS, XANES and EXAFS suggested that the Ti formed an amorphous TiO2 overlayer on the catalyst. At high Ti loadings (4–5 wt.%), there were patches of thick porous TiO2 layer, and some microdomains of crystalline TiO2 could be detected. Au was present as 1–3 nm nanoparticles on all catalysts, before and after used in reaction. Only Lewis acid sites were detected based on results from pyridine adsorption, and their quantities increased with Ti loading. Based on the comparison of reaction rates, the dependence of the kinetics on 2-propanol partial pressure, the apparent activation energies, and the effect of co-feeding O2 among different catalysts, it was concluded that propene was formed on the TiO2 overlayer, acetone was formed primarily at the Au-TiO2 interfacial perimeter sites, and α-C-H bond breaking preceding acetone formation was more facile on Au at the interfacial site than other surface Au atoms. Implication of these results to the selective acetone formation in the oxidation of propane in the presence of a O2/H2 mixture was discussed.« less

Current-perpendicular-to-the-plane magnetoresistance from large interfacial spin-dependent scattering between Co{sub 50}Fe{sub 50} magnetic layer and In-Zn-O conductive oxide spacer layer

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

Nakatani, T. M., E-mail: Tomoya.Nakatani@hgst.com; Childress, J. R.

2015-06-28

We have investigated electrically conductive indium-zinc-oxide (IZO) deposited by magnetron sputtering as spacer layer for current-perpendicular-to-the-plane giant magnetoresistance sensor devices. Spin-valves with a Co{sub 50}Fe{sub 50}/IZO/Co{sub 50}Fe{sub 50} trilayer showed resistance-area product (RA) ranging from 110 to 250 mΩ μm{sup 2}, significantly larger than all-metal structures with Ag or Cu spacers (∼40 mΩ μm{sup 2}). Magnetoresistance ratios (ΔR/R) of 2.5% to 5.5% depending on the IZO spacer thickness (1.5–6.0 nm), corresponding to ΔRA values from 3 to 13 mΩ μm{sup 2}, were obtained. The values of ΔRA with the IZO spacers and Co{sub 50}Fe{sub 50} magnetic layers were significantly larger than thosemore » with conventional metal spacers and Co{sub 50}Fe{sub 50} magnetic layers (∼1–2 mΩ μm{sup 2}). The dependence of ΔRA on the magnetic layer thickness suggests that the larger ΔRA obtained with IZO spacer is due to a large interfacial spin-dependent scattering caused by the large specific resistance at the Co{sub 50}Fe{sub 50}/IZO interface. From structural characterization by TEM and the observed dependence of the RA dispersion on device size, the electric current flowing through the IZO spacer is thought to be laterally uniform, similar to normal metal spacers.« less

Capillary pressure-saturation relations in quartz and carbonate sands: Limitations for correlating capillary and wettability influences on air, oil, and supercritical CO2 trapping

NASA Astrophysics Data System (ADS)

Wang, Shibo; Tokunaga, Tetsu K.; Wan, Jiamin; Dong, Wenming; Kim, Yongman

2016-08-01

Capillary pressure (Pc)-saturation (Sw) relations are essential for predicting equilibrium and flow of immiscible fluid pairs in soils and deeper geologic formations. In systems that are difficult to measure, behavior is often estimated based on capillary scaling of easily measured Pc-Sw relations (e.g., air-water, and oil-water), yet the reliability of such approximations needs to be examined. In this study, 17 sets of brine drainage and imbibition curves were measured with air-brine, decane-brine, and supercritical (sc) CO2-brine in homogeneous quartz and carbonate sands, using porous plate systems under ambient (0.1 MPa, 23°C) and reservoir (12.0 MPa, 45°C) conditions. Comparisons between these measurements showed significant differences in residual nonwetting phase saturation, Snw,r. Through applying capillary scaling, changes in interfacial properties were indicated, particularly wettability. With respect to the residual trapping of the nonwetting phases, Snwr, CO2 > Snwr, decane > Snwr, air. Decane-brine and scCO2-brine Pc-Sw curves deviated significantly from predictions assuming hydrophilic interactions. Moreover, neither the scaled capillary behavior nor Snw,r for scCO2-brine were well represented by decane-brine, apparently because of differences in wettability and viscosities, indicating limitations for using decane (and other organic liquids) as a surrogate fluid in studies intended to apply to geological carbon sequestration. Thus, challenges remain in applying scaling for predicting capillary trapping and multiphase displacement processes across such diverse fields as vadose zone hydrology, enhanced oil recovery, and geologic carbon sequestration.

Capillary pressure - saturation relations in quartz and carbonate sands: Limitations for correlating capillary and wettability influences on air, oil, and supercritical CO2 trapping

NASA Astrophysics Data System (ADS)

Tokunaga, T. K.; Wang, S.; Wan, J.; Dong, W.; Kim, Y.

2016-12-01

Capillary pressure (Pc) - saturation (Sw) relations are essential for predicting equilibrium and flow of immiscible fluid pairs in soils and deeper geologic formations. In systems that are difficult to measure, behavior is often estimated based on capillary scaling of easily measured Pc-Sw relations (e.g., air-water, and oil-water), yet the reliability of such approximations needs to be examined. In this study, seventeen sets of brine drainage and imbibition curves were measured with air-brine, decane-brine, and supercritical (sc) CO2-brine in homogeneous quartz and carbonate sands, using porous plate systems under ambient (0.1 MPa, 23 °C) and reservoir (12.0 MPa, 45 °C) conditions. Comparisons between these measurements showed significant differences in residual nonwetting phase saturation, Snw,r. Through applying capillary scaling, changes in interfacial properties were indicated, particularly wettability. With respect to the residual trapping of the nonwetting phases, Snwr, CO2 > Snwr, decane > Snwr, air. Decane-brine and scCO2-brine Pc-Sw curves deviated significantly from predictions assuming hydrophilic interactions. Moreover, neither the scaled capillary behavior nor Snw,r for scCO2-brine were well represented by decane-brine, apparently because of differences in wettability and viscosities, indicating limitations for using decane (and other organic liquids) as a surrogate fluid in studies intended to apply to geological carbon sequestration. Thus, challenges remain in applying scaling for predicting capillary trapping and multiphase displacement processes across such diverse fields as vadose zone hydrology, enhanced oil recovery, and geologic carbon sequestration.

Interfacial states and far-from-equilibrium transitions in the epitaxial growth and erosion on (110) crystal surfaces

NASA Astrophysics Data System (ADS)

Levandovsky, Artem; Golubović, Leonardo; Moldovan, Dorel

2006-12-01

We discuss the far-from-equilibrium interfacial phenomena occurring in the multilayer homoepitaxial growth and erosion on (110) crystal surfaces. Experimentally, these rectangular symmetry surfaces exhibit a multitude of interesting nonequilibrium interfacial structures, such as the rippled one-dimensional periodic states that are not present in the homoepitaxial growth and erosion on the high symmetry (100) and (111) crystal surfaces. Within a unified phenomenological model, we reveal and elucidate this multitude of states on (110) surfaces as well as the transitions between them. By analytic arguments and numerical simulations, we address experimentally observed transitions between two types of rippled states on (110) surfaces. We discuss several intermediary interface states intervening, via consecutive transitions, between the two rippled states. One of them is the rhomboidal pyramid state, theoretically predicted by Golubovic [Phys. Rev. Lett. 89, 266104 (2002)] and subsequently seen, by de Mongeot and co-workers, in the epitaxial erosion of Cu(110) and Rh(110) surfaces [A. Molle , Phys. Rev. Lett. 93, 256103 (2004), and A. Molle , Phys. Rev. B 73, 155418 (2006)]. In addition, we find a number of interesting intermediary states having structural properties somewhere between those of rippled and pyramidal states. Prominent among them are the rectangular rippled states of long rooflike objects (huts) recently seen on Ag(110) surface. We also predict the existence of a striking interfacial structure that carries nonzero, persistent surface currents. Periodic surface currents vortex lattice formed in this so-called buckled rippled interface state is a far-from-equilibrium relative of the self-organized convective flow patterns in hydrodynamic systems. We discuss the coarsening growth of the multitude of the interfacial states on (110) crystal surfaces.

Epitaxial ferromagnetic oxide thin films on silicon with atomically sharp interfaces

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

Coux, P. de; CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, Toulouse Cedex 4; Bachelet, R.

A bottleneck in the integration of functional oxides with silicon, either directly grown or using a buffer, is the usual formation of an amorphous interfacial layer. Here, we demonstrate that ferromagnetic CoFe{sub 2}O{sub 4} films can be grown epitaxially on Si(111) using a Y{sub 2}O{sub 3} buffer layer, and remarkably the Y{sub 2}O{sub 3}/Si(111) interface is stable and remains atomically sharp. CoFe{sub 2}O{sub 4} films present high crystal quality and high saturation magnetization.

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

Microscopic image processing systems for measuring nonuniform film thickness profiles

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

Liu, A.H.; Plawsky, J.L.; DasGupta, S.

1994-01-01

In very thin liquid films. transport processes are controlled by the temperature and the interfacial intermolecular force field which is a function of the film thickness profile and interfacial properties. The film thickness profile and interfacial properties can be measured most efficiently using a microscopic image processing system. IPS, to record the intensity pattern of the reflected light from the film. There are two types of IPS: an image analyzing interferometer (IAI) and/or an image scanning ellipsometer (ISE). The ISE is a novel technique to measure the two dimensional thickness profile of a nonuniform, thin film, from 1 nm upmore » to several {mu}m, in a steady state as well as in a transient state. It is a full field imaging technique which can study every point on the surface simultaneously with high spatial resolution and thickness sensitivity, i.e., it can measure and map the 2-D film thickness profile. Using the ISE, the transient thickness profile of a draining thin liquid film was measured and modeled. The interfacial conditions were determined in situ by measuring the Hamaker constant. The ISE and IAI systems are compared.« less

Free volume dependence on electrical properties of Poly (styrene co-acrylonitrile)/Nickel oxide polymer nanocomposites

NASA Astrophysics Data System (ADS)

Ningaraju, S.; Hegde, Vinayakaprasanna N.; Prakash, A. P. Gnana; Ravikumar, H. B.

2018-04-01

Polymer nanocomposites of Poly (styrene co-acrylonitrile)/Nickel Oxide (PSAN/NiO) have been prepared. The increased free volume sizes up to 0.4 wt% of NiO loading indicates overall reduction in packing density of polymer network. The decreased o-Ps lifetime (τ3) at higher concentration of NiO indicates improved interfacial interaction between the surface of NiO nanoparticles and side chain of PSAN polymer matrix. The increased AC/DC conductivity at lower wt% of NiO loading demonstrates increased number of electric charge carriers/mobile ions and their mobility. The increased dielectric constant and dielectric loss up to 0.4 wt% of NiO loading suggests the increased dipoles polarization.

Influencing the structure of block copolymer micelles with small molecule additives

NASA Astrophysics Data System (ADS)

Robertson, Megan; Singh, Avantika; Cooksey, Tyler; Kidd, Bryce; Piemonte, Rachele; Wang, Shu; Mai Le, Kim; Madsen, Louis

Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using small-angle scattering and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

Mechanical properties of protein adsorption layers at the air/water and oil/water interface: a comparison in light of the thermodynamical stability of proteins.

PubMed

Mitropoulos, Varvara; Mütze, Annekathrin; Fischer, Peter

2014-04-01

Over the last decades numerous studies on the interfacial rheological response of protein adsorption layers have been published. The comparison of these studies and the retrieval of a common parameter to compare protein interfacial activity are hampered by the fact that different boundary conditions (e.g. physico-chemical, instrumental, interfacial) were used. In the present work we review previous studies and attempt a unifying approach for the comparison between bulk protein properties and their adsorption films. Among many common food grade proteins we chose bovine serum albumin, β-lactoglobulin and lysozyme for their difference in thermodynamic stability and studied their adsorption at the air/water and limonene/water interface. In order to achieve this we have i) systematically analyzed protein adsorption kinetics in terms of surface pressure rise using a drop profile analysis tensiometer and ii) we addressed the interfacial layer properties under shear stress using an interfacial shear rheometer under the same experimental conditions. We could show that thermodynamically less stable proteins adsorb generally faster and yield films with higher shear rheological properties at air/water interface. The same proteins showed an analog behavior when adsorbing at the limonene/water interface but at slower rates. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of high pressure homogenization on the structure and the interfacial and emulsifying properties of β-lactoglobulin.

PubMed

Ali, Ali; Le Potier, Isabelle; Huang, Nicolas; Rosilio, Véronique; Cheron, Monique; Faivre, Vincent; Turbica, Isabelle; Agnely, Florence; Mekhloufi, Ghozlene

2018-02-15

The effect of high pressure homogenization (HPH) on the structure of β-lactoglobulin (β-lg) was studied by combining spectroscopic, chromatographic, and electrophoretic methods. The consequences of the resulting structure modifications on oil/water (O/W) interfacial properties were also assessed. Moderated HPH treatment (100 MPa/4 cycles) showed no significant modification of protein structure and interfacial properties. However, a harsher HPH treatment (300 MPa/5 cycles) induced structural transformation, mainly from β-sheets to random coils, wide loss in lipocalin core, and protein aggregation via intermolecular disulfide bridges. HPH-modified β-lg displayed higher surface hydrophobicity leading to a faster adsorption rate at the interface and an earlier formation of an elastic interfacial film at C β-lg  = 0.1 wt%. However, no modification of the interfacial properties was observed at C β-lg  = 1 wt%. At this protein concentration, the prior denaturation of β-lg by HPH did not modify the droplet size of nanoemulsions prepared with these β-lg solutions as the aqueous phases. A slightly increased creaming rate was however observed. The effects of HPH and heat denaturations appeared qualitatively similar, but with differences in their extent. Copyright © 2017 Elsevier B.V. All rights reserved.

Computational Modeling of Interfacial Behaviors in Nanocomposite Materials

PubMed Central

Lin, Liqiang; Wang, Xiaodu; Zeng, Xiaowei

2017-01-01

Towards understanding the bulk material response in nanocomposites, an interfacial zone model was proposed to define a variety of material interface behaviors (e.g. brittle, ductile, rubber-like, elastic-perfectly plastic behavior etc.). It also has the capability to predict bulk material response though independently control of the interface properties (e.g. stiffness, strength, toughness). The mechanical response of granular nanocomposite (i.e. nacre) was investigated through modeling the “relatively soft” organic interface as an interfacial zone among “hard” mineral tablets and simulation results were compared with experimental measurements of stress-strain curves in tension and compression tests. Through modeling varies material interfaces, we found out that the bulk material response of granular nanocomposite was regulated by the interfacial behaviors. This interfacial zone model provides a possible numerical tool for qualitatively understanding of structure-property relationships through material interface design. PMID:28983123

Polymer Mixtures and Films: Free Volume as a Driving Force for Miscibility and Glassiness

NASA Astrophysics Data System (ADS)

DeFelice, Jeffrey

The microscopic characteristics of polymer molecules are connected with many macro- scopic and mechanical properties of their liquid (pure or mixed) and solid states. How these properties are affected by the different molecular attributes of polymers is of particular interest for practical applications of polymer materials. In Part I of this thesis, the thermodynamics of polymer/supercritical CO2 mixtures and blends of linear and branched polymers are modeled using a lattice based equation of state approach. Analyses of trends in the pure component physical properties lead to insight regarding how changes in molecular architecture and/or isotopic labeling affect the relative compatibilities of the mixtures. This approach is also applied to the mixed state to predict the enthalpic and entropic changes of mixing, from which, information is provided about the role of pure component properties in controlling the underlying thermodynamics of the mixtures. In Part II, the focus of this thesis turns to how interfacial effects can shift a number of physical properties in glass forming fluids relative to those of the pure bulk material. One of the most notable deviations from bulk behavior that has been reported for these systems is a change in the glass transition temperature (Tg). In this work, interfacial effects on Tg are probed in film and polymer/additive systems using a simple kinetic lattice model that simulates free volume and mobility in glass forming fluids. For films, the thickness-dependent behavior of Tg is characterized for different types of interfaces, including films that are substrate supported, free- standing, and 'stacked'. Connections are drawn between the size of the region of enhanced mobility near a free surface and the distribution of local Tg values across a film. For polymer/additive systems, where the "interface" is dispersed throughout the material, trends in additive induced Tg changes are analyzed with respect to additive concentration and the strength of the additive's influence on the local mobility of the polymer matrix.

A model of air-sea gas exchange incorporating the physics of the turbulent boundary layer and the properties of the sea surface

NASA Astrophysics Data System (ADS)

Soloviev, Alexander; Schluessel, Peter

The model presented contains interfacial, bubble-mediated, ocean mixed layer, and remote sensing components. The interfacial (direct) gas transfer dominates under conditions of low and—for quite soluble gases like CO2—moderate wind speeds. Due to the similarity between the gas and heat transfer, the temperature difference, ΔT, across the thermal molecular boundary layer (cool skin of the ocean) and the interfacial gas transfer coefficient, Kint are presumably interrelated. A coupled parameterization for ΔT and Kint has been derived in the context of a surface renewal model [Soloviev and Schluessel, 1994]. In addition to the Schmidt, Sc, and Prandtl, Pr, numbers, the important parameters are the surface Richardson number, Rƒ0, and the Keulegan number, Ke. The more readily available cool skin data are used to determine the coefficients that enter into both parameterizations. At high wind speeds, the Ke-number dependence is further verified with the formula for transformation of the surface wind stress to form drag and white capping, which follows from the renewal model. A further extension of the renewal model includes effects of solar radiation and rainfall. The bubble-mediated component incorporates the Merlivat et al. [1993] parameterization with the empirical coefficients estimated by Asher and Wanninkhof [1998]. The oceanic mixed layer component accounts for stratification effects on the air-sea gas exchange. Based on the example of GasEx-98, we demonstrate how the results of parameterization and modeling of the air-sea gas exchange can be extended to the global scale, using remote sensing techniques.

Thermo-Physical Properties of B2O3-Containing Mold Flux for High Carbon Steels in Thin Slab Continuous Casters: Structure, Viscosity, Crystallization, and Wettability

NASA Astrophysics Data System (ADS)

Park, Jun-Yong; Kim, Gi Hyun; Kim, Jong Bae; Park, Sewoong; Sohn, Il

2016-08-01

The effect of B2O3 on the thermo-physical properties of commercial mold fluxes, including the viscosity, crystallization behavior, and wettability, was investigated. Viscosity was measured using the rotating spindle method, and CCT (continuous cooling transformation) diagrams were obtained to investigate the crystallization behavior at various cooling rates using CLSM (confocal laser scanning microscope). The wettability of the fluxes was determined by measuring the contact angles at 1573 K (1300 °C) using the digital images generated by the sessile drop method and were used to calculate the surface tension, interfacial tension, and work of adhesion for Flux A (existing flux) and B (modified flux). These thermo-physical properties were correlated with the structural analysis obtained using FT-IR (Fourier transform-infrared), Raman and MAS-NMR (magic angle spin-nuclear magnetic resonance) spectroscopy. In addition, DTA (differential thermal analysis) was performed on the samples to measure the liquidus temperatures. Higher B2O3 concentrations resulted in lower liquidus temperatures, consequently decreasing the viscosity, the break temperature, and the crystallization temperature. However, B2O3 addition accelerated crystal growth owing to the higher diffusion kinetics of the cations, which also reduced the size of the liquid/solid co-existing region.

Soldering Characteristics and Mechanical Properties of Sn-1.0Ag-0.5Cu Solder with Minor Aluminum Addition

PubMed Central

Leong, Yee Mei; Haseeb, A.S.M.A.

2016-01-01

Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1–0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu3Al2. Cu3Al2 resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu6Sn5 intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu6Sn5 IMC but has no significant effect on the thickness of Cu3Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface. PMID:28773645

Mechanical, structural and dissolution properties of heat treated thin-film phosphate based glasses

NASA Astrophysics Data System (ADS)

Stuart, Bryan W.; Gimeno-Fabra, Miquel; Segal, Joel; Ahmed, Ifty; Grant, David M.

2017-09-01

Here we show the deposition of 2.7 μm thick phosphate based glass films produced by magnetron sputtering, followed by post heat treatments at 500 °C. Variations in degradation properties pre and post heat treatment were attributed to the formation of Hematite crystals within a glass matrix, iron oxidation and the depletion of hydrophilic P-O-P bonds within the surface layer. As deposited and heat treated coatings showed interfacial tensile adhesion in excess of 73.6 MPa; which surpassed ISO and FDA requirements for HA coatings. Scratch testing of coatings on polished substrates revealed brittle failure mechanisms, amplified due to heat treatment and interfacial failure occurring from 2.3 to 5.0 N. Coatings that were deposited onto sandblasted substrates to mimic commercial implant surfaces, did not suffer from tensile cracking or trackside delamination showing substantial interfacial improvements to between 8.6 and 11.3 N. An exponential dissolution rate was observed from 0 to 2 h for as deposited coatings, which was eliminated via heat treatment. From 2 to 24 h ion release rates ordered P > Na > Mg > Ca > Fe whilst all coatings exhibited linear degradation rates, which reduced by factors of 2.4-3.0 following heat treatments.

Structural phases, magnetic properties and Maxwell-Wagner type relaxation of CoFe2O4/Sr2Co2Fe12O22 ferrite composites

NASA Astrophysics Data System (ADS)

Patel, Chirag K.; Solanki, Neha P.; Singh, Charanjeet; Jotania, Rajshree B.; Chauhan, Chetna C.; Kulkarni, Shailja D.; Shirsath, Sagar E.

2017-07-01

CoFe2O4 (S:Y-1:0) and Sr2Co2Fe12O22 (S:Y-0:1) ferrites were synthesized separately by using chemical coprecipitation technique and calcined at 1000 °C for 5 h. The mixed ferrite composites (S:Y-3:7, 4:6, 5:5, 6:4 and 7:3) were prepared by physical mixing of individual ferrite powders in required weight proportions. The prepared composites were heated at 1150 °C for 5 h in a muffle furnace and then slowly cooled to room temperature. The prepared ferrites were characterized using various instrumental techniques like FTIR, XRD, SEM, VSM and dielectric measurements. The x-ray diffraction studies of pure Sr2Co2Fe12O22 ferrite sample show the presence of M and Y-type hexagonal phases, while the composites consist of spinel and Y-type phases. FTIR spectra of all samples show two bands of Fe-O stretching vibrations. VSM results of composites reveal that the values of the saturation magnetization (M s) vary from 50.44 emu g-1 to 31.21 emu g-1, while remanent magnetization values found from 11.18 emu g-1 to 3.70 emu g-1. A higher value of coercivity (H c  =  562 emu g-1) is observed in the composite S:Y-3:7 but M r/M s ratio of pure and composites is found to be less than 0.5. The dielectric behavior is explained using Maxwell-Wegner type interfacial polarization and N. Rezlescu’s model.

Dependence of interfacial Dzyaloshinskii-Moriya interaction and perpendicular magnetic anisotropy on the thickness of the heavy-metal layer

NASA Astrophysics Data System (ADS)

Kim, Nam-Hui; Han, Dong-Soo; Jung, Jinyong; Park, Kwonjin; Swagten, Henk J. M.; Kim, June-Seo; You, Chun-Yeol

2017-10-01

The interfacial Dzyaloshinskii-Moriya interaction (iDMI) and the interfacial perpendicular magnetic anisotropy (iPMA) between a heavy metal and ferromagnet are investigated by employing Brillouin light scattering. With increasing thickness of the heavy-metal (Pt) layer, the iDMI and iPMA energy densities are rapidly enhanced and they saturate for a Pt thickness of 2.4 nm. Since these two individual magnetic properties show the same Pt thickness dependence, this is evidence that the iDMI and iPMA at the interface between the heavy metal and ferromagnet, the physical origin of these phenomena, are effectively enhanced upon increasing the thickness of the heavy-metal layer.

Tunable Manipulation of Mineral Carbonation Kinetics in Nanoscale Water Films via Citrate Additives.

PubMed

Miller, Quin R S; Schaef, Herbert T; Kaszuba, John P; Qiu, Lin; Bowden, Mark E; McGrail, Bernard P

2018-06-06

We explored the influence of a model organic ligand on mineral carbonation in nanoscale interfacial water films by conducting five time-resolved in situ X-ray diffraction (XRD) experiments at 50 °C. Forsterite was exposed to water-saturated supercritical carbon dioxide (90 bar) that had been equilibrated with 0-0.5 m citrate (C 6 H 5 O 7 -3 ) solutions. The experimental results demonstrated that greater concentrations of citrate in the nanoscale interfacial water film promoted the precipitation of magnesite (MgCO 3 ) relative to nesquehonite (MgCO 3 ·3H 2 O). At the highest concentrations tested, magnesite nucleation and growth were inhibited, lowering the carbonation rate constant from 9.1 × 10 -6 to 3.6 × 10 -6 s -1 . These impacts of citrate were due to partial dehydration of Mg 2+ (aq) and the adsorption of citrate onto nuclei and magnesite surfaces. This type of information may be used to predict and tailor subsurface mineralization rates and pathways.

Environmental Applications of Interfacial Materials with Special Wettability

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

Wang, Zhangxin; Elimelech, Menachem; Lin, Shihong

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

Environmental Applications of Interfacial Materials with Special Wettability

DOE PAGES

Wang, Zhangxin; Elimelech, Menachem; Lin, Shihong

2016-02-01

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

Study on Brewster angle thin film polarizer using hafnia-silica mixture as high-refractive-index material

NASA Astrophysics Data System (ADS)

Xu, Nuo; Zhu, Meiping; Sun, Jian; Chai, Yingjie; Kui, Yi; Zhao, Yuanan; Shao, Jianda

2018-02-01

Two kinds of polarizer coatings were prepared by electron beam evaporation, using HfO2-SiO2 mixture and HfO2 as the high-refractive-index materials, respectively. The HfO2-SiO2 mixture layer was implemented by coevaporating SiO2 and metal Hf, the materials were deposited at an oxygen atmosphere to achieve stoichiometric coatings. The certain HfO2 and SiO2 content ratio is controlled by adjusting the deposition rate of HfO2 and SiO2 using individual quartz crystal monitor. The spectral performance, surface and interfacial properties, as well as the laser-induced damage performance were studied and compared. Comparing with polarizer coating using HfO2 as high-refractive-index material, the polarizer coating using HfO2-SiO2 mixture as high-refractive-index material shows better performance with broader polarizing bandwidth, lower surface roughness, better interfacial property while maintaining high laser-induced damage threshold.

Quantum Monte Carlo simulation of the ferroelectric or ferrielectric nanowire with core shell morphology

NASA Astrophysics Data System (ADS)

Feraoun, A.; Zaim, A.; Kerouad, M.

2016-09-01

By using the Quantum Monte Carlo simulation; the electric properties of a nanowire, consisting of a ferroelectric core of spin-1/2 surrounded by a ferroelectric shell of spin-1/2 with ferro- or anti-ferroelectric interfacial coupling have been studied within the framework of the Transverse Ising Model (TIM). We have examined the effects of the shell coupling Js, the interfacial coupling JInt, the transverse field Ω, and the temperature T on the hysteresis behavior and on the electric properties of the system. The remanent polarization and the coercive field as a function of the transverse field and the temperature are examined. A number of characteristic behavior have been found such as the appearance of triple hysteresis loops for appropriate values of the system parameters.

Role of the Heavy Metal's Crystal Phase in Oscillations of Perpendicular Magnetic Anisotropy and the Interfacial Dzyaloshinskii-Moriya Interaction in W /Co -Fe -B /MgO Films

NASA Astrophysics Data System (ADS)

Kim, Gyu Won; Samardak, Alexander S.; Kim, Yong Jin; Cha, In Ho; Ognev, Alexey V.; Sadovnikov, Alexandr V.; Nikitov, Sergey A.; Kim, Young Keun

2018-06-01

The interfacial Dzyaloshinskii-Moriya interaction (IDMI) generally arises in "heavy-metal-ferromagnet" (HM-FM) heterostructures due the strong spin-orbit coupling in HMs and plays a crucial role in the nucleation of Dzyaloshinskii domain walls and Skyrmions that can be efficiently moved by spin-orbit torques. We study the IDMI in W /Co -Fe -B /MgO /Ta films with perpendicular magnetic anisotropy for different crystal structures and thicknesses of W layers treated by postsputtering annealing at 300 °C and 400 °C . We employ Brillouin light scattering spectroscopy to precisely measure the energy density and sign of the IDMI. We reveal two peaks associated with the IDMI: one for the amorphouslike phase of W, and another for α -W . The samples with pure β -W underlayers show the smallest values of IDMI. The sign of the IDMI is positive for all samples with the observed maximum effective and surface values of Deff=0.88 erg /cm2 and Ds=0.51 ×10-7 erg /cm , respectively. We report on the oscillating behavior of the IDMI as a function of thickness, which correlates with the surface anisotropy energy demonstrating common spin-orbit coupling and a robust dependence on the structural properties of the materials used. We ascribe the oscillations of the surface anisotropy and the IDMI mainly to the near inversely proportional dependence on the squared interatomic distance between the HM and FM atoms promoted by the thickness-driven crystal phase formation of W.

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.

Interfacial Healing and Transport Phenomena Modeling ff Biopolymers

NASA Astrophysics Data System (ADS)

Lebron, Karla

This research focuses on the characterization of bioplastics joined using ultrasonic welding and modeling of temperature distributions and interfacial healing. Polylactic acid (PLA), which is typically derived from starch-rich crops such as corn, was studied. While the measurement of activation energy for interfacial healing at weld interfaces of PLA films has been reported, here, this information is used to predict the weld strength of rigid PLA samples welded by ultrasonics. A characterization of the mechanical properties was completed with a tensile test to determine the effects of amplitude, melt velocity and collapse distance on weld strength. From previous interfacial healing activation energy measurements based on an impulse welding method, it was also possible to predict weld strength. It was found that the most influential parameters were weld time, collapse distance and weld velocity. In general, the model predicted weld strength reasonably well with r2 values between 0.77 and 0.78.

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

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

Qu, Ge; Zhao, Xikang; Newbloom, Gregory M.

Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor–acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiopheneco- thieno[3,2- b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π–π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coatingmore » direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. As a result, we further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.« less

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

DOE PAGES

Qu, Ge; Zhao, Xikang; Newbloom, Gregory M.; ...

2017-08-01

Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor–acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiopheneco- thieno[3,2- b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π–π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coatingmore » direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. As a result, we further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.« less

Photoemission Spectroscopy Studies of Methylammonium Lead Iodide Perovskite Thin Films and Interfaces

NASA Astrophysics Data System (ADS)

Thibau, Emmanuel S.

Organometal halide perovskites have recently emerged as promising materials for fundamentally low-cost, high-performance optoelectronics. In this thesis, we utilize thermal co-evaporation of PbI2 and CH3NH 3 I to fabricate thin films of CH3NH3PbI 3. We first investigate the effect of stoichiometry on some of its structural, optical and electronic properties. Then, we study the energy level alignment of CH3NH3PbI3 with 6 organic semiconductors, revealing good agreement between the data and the theory of vacuum level alignment. Finally, the interface formed between CH3NH 3PbI3 and MoO3 is examined. The findings suggest migration of iodide species into the oxide layer, resulting in deterioration of its chemical and electronic properties. Insertion of an organic interlayer is shown to mitigate these undesirable effects. The results of this work could be of use in device engineering, where knowledge of such interfacial phenomena is of utmost importance in achieving optimized device structures.

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

Pascal, Tod A.; Villaluenga, Irune; Wujcik, Kevin H.

Impregnation of porous carbon matrices with liquid sulfur has been exploited to fabricate composite cathodes for lithium-sulfur batteries, aimed at confining soluble sulfur species near conducting carbon to prevent both loss of active material into the electrolyte and parasitic reactions at the lithium metal anode. Here, through extensive computer simulations, we uncover the strongly favorable interfacial free energy between liquid sulfur and graphitic surfaces that underlies this phenomenon. Previously unexplored curvature-dependent enhancements are shown to favor the filling of smaller pores first and effect a quasi-liquid sulfur phase in microporous domains (diameters <2 nm) that persists ~30° below the expectedmore » freezing point. Evidence of interfacial sulfur on carbon is shown to be a 0.3 eV red shift in the simulated and measured interfacial X-ray absorption spectra. Our results elucidate the critical morphology and thermodynamic properties necessary for future cathode design and highlight the importance of molecular-scale details in defining emergent properties of functional nanoscale interfaces.« less

Giant and switchable surface activity of liquid metal via surface oxidation

PubMed Central

Khan, Mohammad Rashed; Eaker, Collin B.; Bowden, Edmond F.; Dickey, Michael D.

2014-01-01

We present a method to control the interfacial tension of a liquid alloy of gallium via electrochemical deposition (or removal) of the oxide layer on its surface. In sharp contrast with conventional surfactants, this method provides unprecedented lowering of surface tension (∼500 mJ/m2 to near zero) using very low voltage, and the change is completely reversible. This dramatic change in the interfacial tension enables a variety of electrohydrodynamic phenomena. The ability to manipulate the interfacial properties of the metal promises rich opportunities in shape-reconfigurable metallic components in electronic, electromagnetic, and microfluidic devices without the use of toxic mercury. This work suggests that the wetting properties of surface oxides—which are ubiquitous on most metals and semiconductors—are intrinsic “surfactants.” The inherent asymmetric nature of the surface coupled with the ability to actively manipulate its energetics is expected to have important applications in electrohydrodynamics, composites, and melt processing of oxide-forming materials. PMID:25228767

What Can We Learn from Solid State NMR on the Electrode-Electrolyte Interface?

PubMed

Haber, Shira; Leskes, Michal

2018-06-11

Rechargeable battery cells are composed of two electrodes separated by an ion-conducting electrolyte. While the energy density of the cell is mostly determined by the redox potential of the electrodes and amount of charge they can store, the processes at the electrode-electrolyte interface govern the battery's lifetime and performance. Viable battery cells rely on unimpeded ion transport across this interface, which depends on its composition and structure. These properties are challenging to determine as interfacial phases are thin, disordered, heterogeneous, and can be very reactive. The recent developments and applications of solid state NMR spectroscopy in the study of interfacial phenomena in rechargeable batteries based on lithium and sodium chemistries are reviewed. The different NMR interactions are surveyed and how these are used to shed light on the chemical composition and architecture of interfacial phases as well as directly probe ion transport across them is described. By combining new methods in solid state NMR spectroscopy with other analytical tools, a holistic description of the electrode-electrolyte interface can be obtained. This will enable the design of improved interfaces for developing battery cells with high energy, high power, and longer lifetime. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonlinear Analytical Modeling of Interfacial Phenomenon and Nano-Size Microstructural Features to Better Correlate Nde Electronic Property Measurements to Material State

NASA Astrophysics Data System (ADS)

Roubidoux, J. A.; Jackson, J. E.; Lasseigne, A. N.; Mishra, B.; Olson, D. L.

2010-02-01

This paper correlates nonlinear material properties to nondestructive electronic measurements by using wave analysis techniques (e.g. Perturbation Methods) and incorporating higher-order phenomena. The correlations suggest that nondestructive electronic property measurements and practices can be used to assess thin films, surface layers, and other advanced materials that exhibit modified behaviors based on their space-charged interfacial behavior.

The Role of Interfacial Electronic Properties on Phonon Transport in Two-Dimensional MoS 2 on Metal Substrates

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

Yan, Zhequan; Chen, Liang; Yoon, Mina

2016-11-08

In this paper, we investigate the role of interfacial electronic properties on the phonon transport in two-dimensional MoS 2 adsorbed on metal substrates (Au and Sc) using first-principles density functional theory and the atomistic Green’s function method. Our study reveals that the different degree of orbital hybridization and electronic charge distribution between MoS 2 and metal substrates play a significant role in determining the overall phonon–phonon coupling and phonon transmission. The charge transfer caused by the adsorption of MoS 2 on Sc substrate can significantly weaken the Mo–S bond strength and change the phonon properties of MoS 2, which resultmore » in a significant change in thermal boundary conductance (TBC) from one lattice-stacking configuration to another for same metallic substrate. In a lattice-stacking configuration of MoS 2/Sc, weakening of the Mo–S bond strength due to charge redistribution results in decrease in the force constant between Mo and S atoms and substantial redistribution of phonon density of states to low-frequency region which affects overall phonon transmission leading to 60% decrease in TBC compared to another configuration of MoS 2/Sc. Strong chemical coupling between MoS 2 and the Sc substrate leads to a significantly (~19 times) higher TBC than that of the weakly bound MoS 2/Au system. Our findings demonstrate the inherent connection among the interfacial electronic structure, the phonon distribution, and TBC, which helps us understand the mechanism of phonon transport at the MoS 2/metal interfaces. Finally, the results provide insights for the future design of MoS 2-based electronics and a way of enhancing heat dissipation at the interfaces of MoS 2-based nanoelectronic devices.« less

Evidence for Interfacial Halogen Bonding.

PubMed

Swords, Wesley B; Simon, Sarah J C; Parlane, Fraser G L; Dean, Rebecca K; Kellett, Cameron W; Hu, Ke; Meyer, Gerald J; Berlinguette, Curtis P

2016-05-10

A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2 (e(-) )/Dye-X(+) , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bactericidal action mechanism of negatively charged food grade clove oil nanoemulsions.

PubMed

Majeed, Hamid; Liu, Fei; Hategekimana, Joseph; Sharif, Hafiz Rizwan; Qi, Jing; Ali, Barkat; Bian, Yuan-Yuan; Ma, Jianguo; Yokoyama, Wallace; Zhong, Fang

2016-04-15

Clove oil (CO) anionic nanoemulsions were prepared with varying ratios of CO to canola oil (CA), emulsified and stabilized with purity gum ultra (PGU), a newly developed succinylated waxy maize starch. Interfacial tension measurements showed that CO acted as a co-surfactant and there was a gradual decrease in interfacial tension which favored the formation of small droplet sizes on homogenization until a critical limit (5:5% v/v CO:CA) was reached. Antimicrobial activity of the negatively charged CO nanoemulsion was determined against Gram positive GPB (Listeria monocytogenes and Staphylococcus aureus) and Gram negative GNB (Escherichia coli) bacterial strains using minimum inhibitory concentration (MIC) and a time kill dynamic method. Negatively charged PGU emulsified CO nanoemulsion showed prolonged antibacterial activities against Gram positive bacterial strains. We concluded that negatively charged CO nanoemulsion droplets self-assemble with GPB cell membrane, and facilitated interaction with cellular components of bacteria. Moreover, no electrostatic interaction existed between negatively charged droplets and the GPB membrane. Copyright © 2015 Elsevier Ltd. All rights reserved.

Interfacial Dzyaloshinskii-Moriya interaction, surface anisotropy energy, and spin pumping at spin orbit coupled Ir/Co interface

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

Kim, Nam-Hui; Jung, Jinyong; Cho, Jaehun

2016-04-04

The interfacial Dzyaloshinskii-Moriya interaction (iDMI), surface anisotropy energy, and spin pumping at the Ir/Co interface are experimentally investigated by performing Brillouin light scattering. Contrary to previous reports, we suggest that the sign of the iDMI at the Ir/Co interface is the same as in the case of the Pt/Co interface. We also find that the magnitude of the iDMI energy density is relatively smaller than in the case of the Pt/Co interface, despite the large strong spin-orbit coupling (SOC) of Ir. The saturation magnetization and the perpendicular magnetic anisotropy (PMA) energy are significantly improved due to a strong SOC. Ourmore » findings suggest that an SOC in an Ir/Co system behaves in different ways for iDMI and PMA. Finally, we determine the spin pumping effect at the Ir/Co interface, and it increases the Gilbert damping constant from 0.012 to 0.024 for 1.5 nm-thick Co.« less

The electrical and interfacial properties of metal-high-k oxide-semiconductor field effect transistors with CeO2/HfO2 laminated gate dielectrics

NASA Astrophysics Data System (ADS)

Chang, Ingram Yin-ku; Chen, Chun-Heng; Chiu, Fu-Chien; Lee, Joseph Ya-min

2007-11-01

Metal-oxide-semiconductor field-effect transistors with CeO2/HfO2 laminated gate dielectrics were fabricated. The transistors have a subthreshold slope of 74.9mV/decade. The interfacial properties were measured using gated diodes. The surface state density Dit was 9.78×1011cm-2eV-1. The surface-recombination velocity (s0) and the minority carrier lifetime in the field-induced depletion region (τ0,FIJ) measured from the gated diode were about 6.11×103cm /s and 1.8×10-8s, respectively. The effective capture cross section of surface state (σs) extracted using the subthreshold-swing measurement and the gated diode was about 7.69×10-15cm2. The effective electron mobility of CeO2/HfO2 laminated gated transistors was determined to be 212cm2/Vs.

Thermal transport in bismuth telluride quintuple layer: mode-resolved phonon properties and substrate effects

PubMed Central

Shao, Cheng; Bao, Hua

2016-01-01

The successful exfoliation of atomically-thin bismuth telluride (Bi2Te3) quintuple layer (QL) attracts tremendous research interest in this strongly anharmonic quasi-two-dimensional material. The thermal transport properties of this material are not well understood, especially the mode-wise properties and when it is coupled with a substrate. In this work, we have performed molecular dynamics simulations and normal mode analysis to study the mode-resolved thermal transport in freestanding and supported Bi2Te3 QL. The detailed mode-wise phonon properties are calculated and the accumulated thermal conductivities with respect to phonon mean free path (MFP) are constructed. It is shown that 60% of the thermal transport is contributed by phonons with MFP longer than 20 nm. Coupling with a-SiO2 substrate leads to about 60% reduction of thermal conductivity. Through varying the interfacial coupling strength and the atomic mass of substrate, we also find that phonon in Bi2Te3 QL is more strongly scattered by interfacial potential and its transport process is less affected by the dynamics of substrate. Our study provides an in-depth understanding of heat transport in Bi2Te3 QL and is helpful in further tailoring its thermal property through nanostructuring. PMID:27263656

The effect of CNTs on structures and catalytic properties of AuPd clusters for H2O2 synthesis.

PubMed

Yang, Hua-feng; Xie, Peng-yang; Yu, Hui-you; Li, Xiao-nian; Wang, Jian-guo

2012-12-28

The structures and catalytic properties of AuPd clusters supported on carbon nanotubes (CNTs) for H(2)O(2) synthesis have been investigated by means of density functional theory calculations. Firstly, the structures of AuPd clusters are strongly influenced by CNTs, in which the bottom layers are mainly composed of Pd and the top layers are a mix of Au and Pd due to the stronger binding of Pd than Au on CNTs. Especially, it is found that O(2) adsorption on the Pd/CNTs interfacial sites is much weaker than that on the only Pd sites, which is in contrast to transition metal oxide (for example TiO(2), Al(2)O(3), CeO(2)) supported metal clusters. Furthermore, Pd ensembles on the interfacial sites have far superior catalytic properties for H(2)O(2) formation than those away from CNT supports due to the changes in electronic structures caused by the CNTs. Therefore, our study provides a physical insight into the enhanced role of carbon supports in H(2)O(2) synthesis over supported AuPd catalysts.

Molecular dynamics simulation of water at mineral surfaces: Structure, dynamics, energetics and hydrogen bonding

NASA Astrophysics Data System (ADS)

Kalinichev, A. G.; Wang, J.; Kirkpatrick, R.

2006-05-01

Fundamental molecular-level understanding of the properties of aqueous mineral interfaces is of great importance for many geochemical and environmental systems. Interaction between water and mineral surfaces substantially affects the properties of both phases, including the reactivity and functionality of the substrate surface, and the structure, dynamics, and energetics of the near surface aqueous phase. Experimental studies of interfacial water structure and dynamics using surface-sensitive techniques such as sum-frequency vibrational spectroscopy or X-ray and neutron reflectivity are not always possible for many practically important substrates, and their results often require interpretation concerning the atomistic mechanisms responsible for the observed behavior. Molecular computer simulations can provide new insight into the underlying molecular- level relationships between the inorganic substrate structure and composition and the structure, ordering, and dynamics of interfacial water. We have performed a series of molecular dynamics (MD) computer simulations of aqueous interfaces with several silicates (quartz, muscovite, and talc) and hydroxides (brucite, portlandite, gibbsite, Ca/Al and Mg/Al double hydroxides) to quantify the effects of the substrate mineral structure and composition on the structural, transport, and thermodynamic properties of water on these mineral surfaces. Due to the prevalent effects of the development of well-interconnected H-bonding networks across the mineral- water interfaces, all the hydroxide surfaces (including a fully hydroxylated quartz surface) show very similar H2O density profiles perpendicular to the interface. However, the predominant orientations of the interfacial H2O molecules and their detailed 2-dimensional near-surface structure and dynamics parallel to the interface are quite different reflecting the differences in the substrate structural charge distribution and the density and orientations of the surface OH groups. The H2O density profiles and other structural and dynamic characteristics of water at the two siloxane surfaces are very different from each other and from the hydroxide surfaces, since the muscovite surface is negatively charged and hydrophilic, while the talc surface is electrostatically neutral and hydrophobic. In general, at hydrophilic neutral surfaces both donating and accepting H-bonds from the H2O molecules are contributing to the development of the interfacial H-bond network, whereas at hydrophilic but charged surfaces only accepting or donating H-bonds with H2O molecules are possible. At the hydrophobic talc surface H-bonds among H2O molecules dominate the interfacial H-bond network and the water-surface interactions are very weak. The first water layer at all substrates is well ordered parallel to the surface, reflecting substrate crystal structures and indicating the reduced translational and orientational mobility of interfacial H2O molecules. At longer time scale (~100ps) their dynamics can be decomposed into a slow, virtually frozen, regime due to the substrate- bound H2O and a faster regime of almost free water reflecting the dynamics far from the surface. At shorter times (>10ps) the two dynamical regimes are superimposed. The much higher ordering of interfacial water (compared to bulk liquid) can not be adequately described as simply "ice-like". To some extent, it rather resembles the behavior of supercooled water.

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.

Surface chemistry of carbon dioxide revisited

NASA Astrophysics Data System (ADS)

Taifan, William; Boily, Jean-François; Baltrusaitis, Jonas

2016-12-01

This review discusses modern developments in CO2 surface chemistry by focusing on the work published since the original review by H.J. Freund and M.W. Roberts two decades ago (Surface Science Reports 25 (1996) 225-273). It includes relevant fundamentals pertaining to the topics covered in that earlier review, such as conventional metal and metal oxide surfaces and CO2 interactions thereon. While UHV spectroscopy has routinely been applied for CO2 gas-solid interface analysis, the present work goes further by describing surface-CO2 interactions under elevated CO2 pressure on non-oxide surfaces, such as zeolites, sulfides, carbides and nitrides. Furthermore, it describes additional salient in situ techniques relevant to the resolution of the interfacial chemistry of CO2, notably infrared spectroscopy and state-of-the-art theoretical methods, currently used in the resolution of solid and soluble carbonate species in liquid-water vapor, liquid-solid and liquid-liquid interfaces. These techniques are directly relevant to fundamental, natural and technological settings, such as heterogeneous and environmental catalysis and CO2 sequestration.

Linking interfacial chemistry of CO2 to surface structures of hydrated metal oxide nanoparticles: hematite.

PubMed

Chernyshova, Irina V; Ponnurangam, Sathish; Somasundaran, Ponisseril

2013-05-14

A better understanding of interaction with dissolved CO2 is required to rationally design and model the (photo)catalytic and sorption processes on metal (hydr)oxide nanoparticles (NPs) in aqueous media. Using in situ FTIR spectroscopy, we address this problem for rhombohedral 38 nm hematite (α-Fe2O3) nanoparticles as a model. We not only resolve the structures of the adsorbed carbonate species, but also specify their adsorption sites and their location on the nanoparticle surface. The spectral relationships obtained present a basis for a new method of characterizing the microscopic structural and acid-base properties (related to individual adsorption sites) of hydrated metal (hydr)oxide NPs using atmospherically derived CO2 as a probe. Specifically, we distinguish two carbonate species suggesting two principally different adsorption mechanisms. One species, which is more weakly adsorbed, has an inner-sphere mononuclear monodentate structure which is formed by a conventional ligand-exchange mechanism. At natural levels of dissolved carbonate and pH from 3 to 11, this species is attached to the most acidic/reactive surface cations (surface states) associated with ferrihydrite-like surface defects. The second species, which is more strongly adsorbed, presents a mixed C and O coordination of bent CO2. This species uniquely recognizes the stoichiometric rhombohedral {104} facets in the NP texture. Like in gas phase, it is formed through the surface coordination of molecular CO2. We address how the adsorption sites hosting these two carbonate species are affected by the annealing and acid etching of the NPs. These results support the nanosize-induced phase transformation of hematite towards ferrihydrite under hydrous conditions, and additionally show that the process starts from the roughened areas of the facet intersections.

Influence of Interfacial Carbide Layer Characteristics on Thermal Properties of Copper-Diamond Composites (Postprint)

DTIC Science & Technology

2014-04-01

wettability of diamond is not an issue. Moreover, the solid-state processing can, in principle , be carried out at relatively low temperatures even for non...capacity. q was mea- sured using Archimedes ’ method, and D was measured with laser flash technique per ASTM E1461. The speci- mens for D measurement... principle , attainable by changing the interfacial Cr3C2 layer characteristics. In an earlier study [3], for a given diamond particle size and volume

An insight into intrinsic interfacial properties between Li metals and Li10GeP2S12 solid electrolytes.

PubMed

Chen, Bingbing; Ju, Jiangwei; Ma, Jun; Zhang, Jianjun; Xiao, Ruijuan; Cui, Guanglei; Chen, Liquan

2017-11-29

Density functional theory simulations and experimental studies were performed to investigate the interfacial properties, including lithium ion migration kinetics, between lithium metal anode and solid electrolyte Li 10 GeP 2 S 12 (LGPS). The LGPS[001] plane was chosen as the studied surface because the easiest Li + migration pathway is along this direction. The electronic structure of the surface states indicated that the electrochemical stability was reduced at both the PS 4 - and GeS 4 -teminated surfaces. For the interface cases, the equilibrium interfacial structures of lithium metal against the PS 4 -terminated LGPS[001] surface (Li/PS 4 -LGPS) and the GeS 4 -terminated LGPS[001] surface (Li/GeS 4 -LGPS) were revealed based on the structural relaxation and adhesion energy analysis. Solid electrolyte interphases were expected to be formed at both Li/PS 4 -LGPS and Li/GeS 4 -LGPS interfaces, resulting in an unstable state of interface and large interfacial resistance, which was verified by the EIS results of the Li/LGPS/Li cell. In addition, the simulations of the migration kinetics show that the energy barriers for Li + crossing the Li/GeS 4 -LGPS interface were relatively low compared with the Li/PS 4 -LGPS interface. This may contribute to the formation of Ge-rich phases at the Li/LGPS interface, which can tune the interfacial structures to improve the ionic conductivity for future all-solid-state batteries. This work will offer a thorough understanding of the Li/LGPS interface, including local structures, electronic states and Li + diffusion behaviors in all-solid-state batteries.

A review on mechanical properties of magnesium based nano composites

NASA Astrophysics Data System (ADS)

Tarafder, Nilanjan; Prasad, M. Lakshmi Vara

2018-04-01

A review was done on Magnesium (Mg) based composite materials reinforced with different nano particles such as TiO2, Cu, Y2O3, SiC, ZrO2 and Al2O3. TiO2 and Al2O3 nanoparticles were synthesised by melt deposition process. Cu, Y2O3, SiC and ZrO2 nanoparticles were synthesised by powder metallurgy process. Composite microstructural characteristics shows that the nano-size reinforcements are uniformly distributed in the composite matrix and also minimum porosity with solid interfacial integrity. The mechanical properties showed yield strength improvement by 0.2 percentage and Ultimate tensile strength (UTS) was also improved for all the nano-particles. But UTS was adversely affected with TiO2 reinforcement while ductility was increased. With Cu reinforcement elastic modulus, hardness and fracture resistance increased and improved the co-efficient of thermal expansion (CTE) of Mg based matrix. By Y2O3 reinforcement hardness, fracture resistance was improved and ductility reached maximum by 0.22 volume percentage of Y2O3 and decreased with succeeding increase in Y2O3 reinforcement. The readings exposed that mechanical properties were gathered from the composite comprising 2.0 weight percentage of Y2O3. Ductility and fracture resistance increased with ZrO2 reinforcement in Mg matrix. Using Al2O3 as reinforcement in Mg composite matrix hardness, elastic modulus and ductility was increased but porosity reduced with well interfacial integrity. Dissipation of energy in the form of damping capacity was resolved by classical vibration theory. The result showed that an increasing up to 0.4 volume percentage alumina content increases the damping capacity up to 34 percent. In another sample, addition of 2 weight percentage nano-Al2O3 particles showed big possibility in reducing CTE from 27.9-25.9×10-6 K-1 in Magnesium, tensile and yield strength amplified by 40MPa. In another test, Mg/1.1Al2O3 nanocomposite was manufactured by solidification process followed by hot extrusion. Results showed that strengthening effect was maintained up to 150°C and fracture characteristics of Mg composite transformed from brittle to mixed ductile mode and fully ductile in attendance of nano-Al2O3 particulates.

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.

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.

Final Report: Molecular Mechanisms of Interfacial Reactivity in Near Surface and Extreme Geochemical Environments (DE-SC0009362)

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

Dixon, David A

2016-03-27

The prediction of the long-term stability and safety of geologic sequestration of greenhouse gases requires a detailed understanding of subsurface transport and chemical interactions between the disposed greenhouse gases and the geologic media. In this regard, mineral-fluid interactions are of prime importance since reactions that occur on or near the interface can assist in the long term sequestration of CO2 by trapping in mineral phases such as carbonates, as well as influencing the subsurface migration of the disposed fluids via creation or plugging of pores or fractures in the host rock strata. Previous research on mineral-fluid interaction for subsurface CO2more » storage has focused almost entirely on the aqueous phase, i.e., reactivity with aqueous solutions or brines containing dissolved CO2. However, interactions with neat to water-saturated non-aqueous fluids are of equal if not greater importance since supercritical CO2 (scCO2) is less dense than the aqueous phase or oil which will create a buoyant scCO2 plume that ultimately will dominate the pore volume within the caprock, and the injected scCO2 will contain water soon after injection and this water can be highly reactive. Collectively, therefore, mineral interactions with water-saturated scCO2-dominated fluids are pivotal and could result in the stable sequestration of CO2 by trapping in mineral phases such as metal carbonates within otherwise permeable zones in the caprock. The primary objective is to unravel the molecular mechanisms governing the reactivity of mineral phases important in the geologic sequestration of CO2 with variably wet supercritical carbon dioxide as a function of T, P, and mineral structure using computational chemistry. This work is in close collaboration with the PNNL Geosciences effort. The focus of the work at The University of Alabama is computational studies of the formation of magnesium and calcium carbonates and oxides and their reactivity and providing computational support of the experimental efforts at PNNL, especially for energetics, structural properties, and interpretation of spectra.« less

Study on interfacial and mechanical improvement of carbon fiber/epoxy composites by depositing multi-walled carbon nanotubes on fibers

NASA Astrophysics Data System (ADS)

Xiao, Chufan; Tan, Yefa; Wang, Xiaolong; Gao, Li; Wang, Lulu; Qi, Zehao

2018-07-01

To improve the interfacial properties between carbon fiber (CF) and epoxy resin (EP), T300 carbon fibers were coated with multi-walled carbon nanotubes (MWCNTs) using aqueous suspension deposition method. The carbon fiber/epoxy laminated composites were prepared by molding process. The wettability and interfacial properties between MWCNTs deposited carbon fibers (MWCNTs-T300) and EP were studied. The mechanical properties of carbon fiber/epoxy laminated composites were tested, and the mechanism of the interface strengthening was discussed. The results show that the surface energy of T300 carbon fiber is obviously increased after MWCNT deposition. The contact angle between MWCNTs-T300 and EP is reduced, and the interfacial energy and adhesion work are greatly improved. The MWCNTs-T300/EP laminated composites have excellent mechanical properties, the flexural strength is 822 MPa, the tensile strength is 841 MPa, and the interlaminar shear strength (ILSS) is 25.68 MPa, which are increased by 15.1%, 17.6% and 12.6% compared with those of the original carbon fiber/EP laminated composites (original T300/EP) respectively. The MWCNTs-T300/EP composites have good interface bonding performance, low porosity and uniform fiber distribution. Interfacial friction and resin toughening are the main mechanisms for the interface enhancement of MWCNTs-T300/EP composites.

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

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.

Effect of Composite Fabrication on the Strength of Single Crystal Al2O3 Fibers in Two Fe-Base Alloy Composites

NASA Technical Reports Server (NTRS)

Draper, Susan L.; Aiken, Beverly J. M.

1998-01-01

Continuous single-crystal Al2O3 fibers have been incorporated into a variety of metal and intermetallic matrices and the results have consistently indicated that the fiber strength had been reduced by 32 to 50% during processing. Two iron-based alloys, FeNiCoCrAl and FeAlVCMn, were chosen as matrices for Al2O3 fiber reinforced metal matrix composites (MMC) with the goal of maintaining Al2O3 fiber strength after composite processing. The feasibility of Al2O3/FeNiCoCrAl and Al2O3/FeAlVCMn composite systems for high temperature applications were assessed in terms of fiber-matrix chemical compatibility, interfacial bond strength, and composite tensile properties. The strength of etched-out fibers was significantly improved by choosing matrices containing less reactive elements. The ultimate tensile strength (UTS) values of the composites could generally be predicted with existing models using the strength of etched-out fibers. However, the UTS of the composites were less than desired due to a low fiber Weibull modulus. Acoustic emission analysis during tensile testing was a useful tool for determining the efficiency of the fibers in the composite and for determining the failure mechanism of the composites.

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

NASA Technical Reports Server (NTRS)

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

1985-01-01

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

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

Effects of oxygen plasma treatment on domestic aramid fiber III reinforced bismaleimide composite interfacial properties

NASA Astrophysics Data System (ADS)

Shi, Chen; Wang, Jing; Chen, Ping; Feng, Jiayue; Cui, Jinyuan; Yang, Faze

2017-12-01

Domestic Aramid Fiber III (DAF III) was modified by oxygen plasma treatment. The fiber surface characteristics was observed by Scanning Electron Microscopy. The results showed that oxygen plasma treatment changed surface morphologies. The effects of oxygen plasma treatment on DAF III reinforced bismaleimides (BMI) composite bending and interfacial properties were investigated, respectively. The ILSS value increased from 49.3 MPa to 56.0 MPa (by 13.5%) after oxygen plasma treatment. The bending strength changed a little. Furthermore, the composite rupture mode changed from interfacial rupture to fiber or resin bulk rupture.

Tuning Interfacial Properties and Processes by Controlling the Rheology and Structure of Poly( N-isopropylacrylamide) Particles at Air/Water Interfaces.

PubMed

Maestro, Armando; Jones, Daniel; Sánchez de Rojas Candela, Carmen; Guzman, Eduardo; Duits, Michel H G; Cicuta, Pietro

2018-06-05

By combining controlled experiments on single interfaces with measurements on solitary bubbles and liquid foams, we show that poly( N-isopropylacrylamide) (PNIPAM) microgels assembled at air/water interfaces exhibit a solid to liquid transition changing the temperature, and that this is associated with the change in the interfacial microstructure of the PNIPAM particles around their volume phase transition temperature. We show that the solid behaves as a soft 2D colloidal glass, and that the existence of this solid/liquid transition offers an ideal platform to tune the permeability of air bubbles covered by PNIPAM and to control macroscopic foam properties such as drainage, stability, and foamability. PNIPAM particles on fluid interfaces allow new tunable materials, for example foam structures with variable mechanical properties upon small temperature changes.

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.

Enhancement of interfacial adhesion between starch and grafted poly(ε-caprolactone).

PubMed

Ortega-Toro, Rodrigo; Santagata, Gabriella; Gomez d'Ayala, Giovanna; Cerruti, Pierfrancesco; Talens Oliag, Pau; Chiralt Boix, M Amparo; Malinconico, Mario

2016-08-20

The use of a modified poly(ε-caprolactone) (gPCL) to enhance polymer miscibility in films based on thermoplastic starch (S) and poly(ε-caprolactone) is reported. PCL was functionalized by grafting with maleic anyhdride (MA) and/or glycidyl methacrylate (GMA) by reactive blending in a batch mixer. gPCL based materials were analysed in terms of their grafting degree, structural and thermal properties. Blends based on starch and PCL (wt. ratio 80:20) with including gPCL (0, 2.5 and 5wt.%), as a compatibilizer, were obtained by extrusion and compression moulding, and their structural, thermal, mechanical and barrier properties were investigated. Blends containing gPCL evidenced better interfacial adhesion between starch and PCL domains, as deduced from both structural (XRD, FTIR, SEM) and bulk properties (DSC, TGA). Moreover, grafted PCL-based compatibilizers greatly improved functional properties of S-PCL blend films, as pointed out from mechanical performance and higher barrier properties, valuable to meet the food packaging requirements. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ferroelectric/ferrimagnetic composite ceramics with depressed interfacial reaction and low dielectric loss

NASA Astrophysics Data System (ADS)

Zheng, Hui; Weng, Wenjian; Han, Gaorong; Du, Piyi

2014-10-01

(1-x)BaTiO3/xNi0.5Zn0.5Fe2O4 (NZFO) ferroelectric/ferrimagnetic composite ceramics with restricted interfacial reaction were prepared by adopting fine NZFO precursors synthesized by combustion method. The dielectric dispersion, loss, and conductivity are significantly reduced at most compositions, particularly at concentrations below the percolation threshold. At x = 0.3, a frequency-stable permittivity of 2300 and a low loss of 0.04 at 1 kHz is realized. The recovery of the dielectric/electric properties is attributed to the interfacial amorphous phase introduced by the fine NZFO precursors, which can act as barrier for ionic inter-diffusion between the two phases and hopping conduction among ferrites.

The interfacial strength of carbon nanofiber epoxy composite using single fiber pullout experiments.

PubMed

Manoharan, M P; Sharma, A; Desai, A V; Haque, M A; Bakis, C E; Wang, K W

2009-07-22

Carbon nanotubes and nanofibers are extensively researched as reinforcing agents in nanocomposites for their multifunctionality, light weight and high strength. However, it is the interface between the nanofiber and the matrix that dictates the overall properties of the nanocomposite. The current trend is to measure elastic properties of the bulk nanocomposite and then compare them with theoretical models to extract the information on the interfacial strength. The ideal experiment is single fiber pullout from the matrix because it directly measures the interfacial strength. However, the technique is difficult to apply to nanocomposites because of the small size of the fibers and the requirement for high resolution force and displacement sensing. We present an experimental technique for measuring the interfacial strength of nanofiber-reinforced composites using the single fiber pullout technique and demonstrate the technique for a carbon nanofiber-reinforced epoxy composite. The experiment is performed in situ in a scanning electron microscope and the interfacial strength for the epoxy composite was measured to be 170 MPa.

Governing Influence of Thermodynamic and Chemical Equilibria on the Interfacial Properties in Complex Fluids.

PubMed

Harikrishnan, A R; Dhar, Purbarun; Gedupudi, Sateesh; Das, Sarit K

2018-04-12

We propose a comprehensive analysis and a quasi-analytical mathematical formalism to predict the surface tension and contact angles of complex surfactant-infused nanocolloids. The model rests on the foundations of the interaction potentials for the interfacial adsorption-desorption dynamics in complex multicomponent colloids. Surfactant-infused nanoparticle-laden interface problems are difficult to deal with because of the many-body interactions and interfaces involved at the meso-nanoscales. The model is based on the governing role of thermodynamic and chemical equilibrium parameters in modulating the interfacial energies. The influence of parameters such as the presence of surfactants, nanoparticles, and surfactant-capped nanoparticles on interfacial dynamics is revealed by the analysis. Solely based on the knowledge of interfacial properties of independent surfactant solutions and nanocolloids, the same can be deduced for complex surfactant-based nanocolloids through the proposed approach. The model accurately predicts the equilibrium surface tension and contact angle of complex nanocolloids available in the existing literature and present experimental findings.

Pseudopotential Computations for Metal/Alumina Interfaces

NASA Astrophysics Data System (ADS)

Zhang, Wenqing

2003-03-01

Metal/alumina interfaces are found, for example, in electronic devices, as thermal barrier coatings in gas turbines, and in coatings to inhibit corrosion and wear. Of particular importance to their performance is their adhesion. Ultrasoft pseudopotentials combined with plane wave methods and density-functional theory have been employed to compute the properties of these relatively complex interfaces, including effects of impurity segregation. Interfacial stoichiometry and impurity content affect interfacial properties importantly. Thermodynamic links between our first principles results and metallurgical variables such as oxygen activity and oxygen partial pressure are established. This allows for a comparison between theoretical predictions and experimental measurements. Good agreement is obtained for predicted interfacial variables such as atomic structure and adhesive bond strengths on comparison with results of sessile drop, fracture, and other experiments on interfaces of Ni, Cu, Al, and Ag with alumina [1-3], including effects of water and sulfur interfacial impurities. Understanding of the nature of the adhesive bonding at the atomic level is obtained by the pseudopotential first principles approach. [1] W.Zhang, and J.R.Smith, and A.G.Evans, Acta Mater., 50,3803(2002). [2] W.Zhang, and J.R.Smith, Phys. Rev. Lett. 85, 3225(2000). [3] W.Zhang, and J.R.Smith, Phys. Rev. B61, 16883(2000).

Gradiently Polymerized Solid Electrolyte Meets with Micro/Nano-Structured Cathode Array.

PubMed

Dong, Wei; Zeng, Xian-Xiang; Zhang, Xu-Dong; Li, Jin-Yi; Shi, Ji-Lei; Xiao, Yao; Shi, Yang; Wen, Rui; Yin, Ya-Xia; Wang, Tai-Shan; Wang, Chun-Ru; Guo, Yu-Guo

2018-05-02

The poor contact between the solid-state electrolyte and cathode materials leads to high interfacial resistance, severely limiting the rate capability of solid Li metal batteries. Herein, an integrative battery design is introduced with a gradiently polymerized solid electrolyte (GPSE), a micro-channel current collector array and nano-sized cathode particles. In-situ formed GPSE encapsulates cathode nanoparticles in the micro-channel with ductile inclusions to lower interfacial impedance, and the stiff surface layer of GPSE toward anode suppresses Li dendrites growth. Li metal batteries based on GPSE and Li-free hydrogenated V2O5 (V2O5-H) cathode exhibit an outstanding high-rate response of up to 5 C (the capacity ratio of 5 C / 1 C is 90.3%) and an ultralow capacity fade rate of 0.07% per cycle over 300 cycles. Other Li-containing cathodes as LiFePO4 and LiNi0.5Mn0.3Co0.2O2 can also operate effectively at 5 C and 2 C rate, respectively. Such an ingenious design may provide new insights into other solid metal batteries through interfacial engineering manipulation at micro and nano level.

Improving the photovoltaic performance of the all-solid-state TiO2 NR/CuInS2 solar cell by hydrogen plasma treatment.

PubMed

Chen, Bingfeng; Niu, Wenzhe; Lou, Zirui; Ye, Zhizhen; Zhu, Liping

2018-07-06

The interfacial properties of the heterojunction between p-type and n-type materials play an important role in the performance of the solar cell. In this paper, a p-type CuInS 2 film was deposited on TiO 2 nanorod arrays by spin coating to fabricate an all-solid-state solar cell and the TiO 2 nanorod arrays were treated with hydrogen plasma(H:TiO 2 ) to ameliorate the interfacial properties. The influence of the hydrogen plasma treatment on the performance of the solar cell was investigated. The short-circuit current density was obviously raised and the power conversion efficiency of the solar cell improved to 0.30%, which is three times that of solar cells without hydrogen plasma treatment. The enhancement of the performance is attributed to not only the enhancement of carrier separation and transport, but the reduction of the recombination of electrons and holes, which is caused by hydrogen plasma treatment.

Improving the photovoltaic performance of the all-solid-state TiO2 NR/CuInS2 solar cell by hydrogen plasma treatment

NASA Astrophysics Data System (ADS)

Chen, Bingfeng; Niu, Wenzhe; Lou, Zirui; Ye, Zhizhen; Zhu, Liping

2018-07-01

The interfacial properties of the heterojunction between p-type and n-type materials play an important role in the performance of the solar cell. In this paper, a p-type CuInS2 film was deposited on TiO2 nanorod arrays by spin coating to fabricate an all-solid-state solar cell and the TiO2 nanorod arrays were treated with hydrogen plasma(H:TiO2) to ameliorate the interfacial properties. The influence of the hydrogen plasma treatment on the performance of the solar cell was investigated. The short-circuit current density was obviously raised and the power conversion efficiency of the solar cell improved to 0.30%, which is three times that of solar cells without hydrogen plasma treatment. The enhancement of the performance is attributed to not only the enhancement of carrier separation and transport, but the reduction of the recombination of electrons and holes, which is caused by hydrogen plasma treatment.

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

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

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

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

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

DOE PAGES

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

2016-06-23

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

Engineering bioactive polymers for the next generation of bone repair

NASA Astrophysics Data System (ADS)

Ho, Emily Y.

Bone disease is a serious health condition among the aged population. In some cases of bone damage it becomes necessary to replace, recontour, and assist in the healing of the bone. Many materials have been proposed as useful replacements but none have been proven to be ideal. In this thesis, two bioactive composites were investigated for bone replacements. First reported material is a hydroxyapatite (HA) particle reinforced polymethylmethacrylate (PMMA) composite treated with a co-polymer coupling agent for mandible augmentations. The influence of the coupling agent on the local mechanical properties of the system before and after simulated biological conditions was determined by applying nano-indentation at the cross-sectional HA/PMMA interface. The local interfacial results were indicative of the global quasi static compression test results. While the coupling agent improved the interfacial and global mechanical properties before and after 24 hours in vitro immersion, it did not affect the surface bioactivity of the system. However, the addition of coupling agent did not provide long term in vitro improvement of both local and global mechanical properties of the composite. An alternative approach of combining a bioactive phase into polymer matrix was developed. The second analyzed material is an injectable composite with osteoconductivity and ideal mechanical biocompatibility for vertebral fracture fixations which we formulated and fabricated. A bioactive component was engineered into the macromolecular structure to facilitate the formation of apatite nucleation sites on a thermo-sensitive polymer, poly(N-isopropylacryamide)-co-poly(ethyleneglycol) dimethacrylate (PNIPAAm-PEGDM), through incorporation of tri-methacryloxypropyltrimethoxysilane (MPS). PNIPAAm-PEGDM is capable of liquid to solid phase transformation at 32°C. In this study, the phase transformation temperature (LCSTs), the in vitro mechanical properties, swelling characteristics and bioactivity of the polymers were evaluated. The addition of NIPS to the polymer encouraged apatite formation and increased its compressive modulus while its LCST remained unchanged. The challenge of this material system is to balance the network-forming and bioactivity inducing MPS with the gain in elastic recovery induced by PEGDM addition to the PNIPAAm base, all while maintaining an injectable material system. This material platform offers a family of polymers that have a range of mechanical properties for various tissue replacements.

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

NASA Technical Reports Server (NTRS)

Pindera, Marek-Jerzy; Salzar, Robert S.

1996-01-01

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

A detailed study of CO 2-brine capillary trapping mechanisms as applied to geologic carbon storage. Final Report

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

Wildenschild, Dorthe

2017-04-06

The proposed research focuses on improved fundamental understanding of the efficiency of physical trapping mechanisms, and as such will provide the basis for subsequent upscaling efforts. The overarching hypothesis of the proposed research is that capillary pressure plays a significant role in capillary trapping of CO 2, especially during the water imbibition stage of the sequestration process. We posit that the relevant physics of the sequestration process is more complex than is currently captured in relative permeability models, which are often based on so-called trapping models to represent relative permeability hysteresis. Our 4 main questions, guiding the 4 main tasksmore » of the proposed research, are as follows: (1) What is the morphology of capillary trapped CO 2 at the pore scale as a function of temperature, pressure, brine concentration, interfacial tension, and pore-space morphology under injection and subsequent imbibition? (2) Is it possible to describe the capillary trapping process using formation-dependent, but otherwise unique continuum-scale functions in permeability-capillary pressure, interfacial area and saturation space, rather than hysteretic functions in permeability-saturation or capillary pressure-saturation space? (3) How do continuum-scale relationships between kr-Pc-S-Anw developed based on pore-scale observations compare with traditional models incorporating relative permeability hysteresis (such as Land’s and other models,) and with observations at the core (5-10cm) scale? (4) How can trapped CO 2 volume be optimized via engineered injection and sweep strategies, and as a function of formation type (incl. heterogeneity)?« less

Influences of surface modification of nano-silica by silane coupling agents on the thermal and frictional properties of cyanate ester resin

NASA Astrophysics Data System (ADS)

Chuang, Wang; Geng-sheng, Jiao; Lei, Peng; Bao-lin, Zhu; Ke-zhi, Li; Jun-long, Wang

2018-06-01

The surface of nano-silicon dioxide (nano-SiO2) particles was modified by small molecular coupling agent KH-560 and macromolecular coupling agent SEA-171, respectively, to change the surface activity and structure. The modified nano-SiO2 was then used for reinforcing cyanate ester resin (CE). Influences of the content of nano-SiO2 and the interfacial structure over the thermal and frictional properties of nano-SiO2/CE composites were investigated. The mechanism of the surface modification of silicon dioxide by KH-560 and SEA-171 was discussed. The experimental results show that the addition of coupling agents increased the interfacial bonding between nano-SiO2 particles and the CE resin so that the heat resistance and friction properties of the composites were improved. After surface treatment of nano-SiO2 by SEA-171, the thermal decomposition temperature of the 3.0 wt% nano-SiO2/CE composites increased nearly by 75 °C and the frictional coefficient was reduced by 25% compared with that of the pure CE, and the wear resistance increased by 77%.

Thin Co/Ni-based bottom pinned spin-transfer torque magnetic random access memory stacks with high annealing tolerance

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

Tomczak, Y., E-mail: Yoann.Tomczak@imec.be; Department of Chemistry, KU Leuven; Swerts, J.

2016-01-25

Spin-transfer torque magnetic random access memory (STT-MRAM) is considered as a replacement for next generation embedded and stand-alone memory applications. One of the main challenges in the STT-MRAM stack development is the compatibility of the stack with CMOS process flows in which thermal budgets up to 400 °C are applied. In this letter, we report on a perpendicularly magnetized MgO-based tunnel junction (p-MTJ) on a thin Co/Ni perpendicular synthetic antiferromagnetic layer with high annealing tolerance. Tunnel magneto resistance (TMR) loss after annealing occurs when the reference layer loses its perpendicular magnetic anisotropy due to reduction of the CoFeB/MgO interfacial anisotropy. Amore » stable Co/Ni based p-MTJ stack with TMR values of 130% at resistance-area products of 9 Ω μm{sup 2} after 400 °C anneal is achieved via moment control of the Co/Ta/CoFeB reference layer. Thinning of the CoFeB polarizing layer down to 0.8 nm is the key enabler to achieve 400 °C compatibility with limited TMR loss. Thinning the Co below 0.6 nm leads to a loss of the antiferromagnetic interlayer exchange coupling strength through Ru. Insight into the thickness and moment engineering of the reference layer is displayed to obtain the best magnetic properties and high thermal stability for thin Co/Ni SAF-based STT-MRAM stacks.« less

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.

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

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.

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.

Hydrogen bonded structure, polarity, molecular motion and frequency fluctuations at liquid-vapor interface of a water-methanol mixture: an ab initio molecular dynamics study.

PubMed

Choudhuri, Jyoti Roy; Chandra, Amalendu

2014-10-07

We have performed ab initio molecular dynamics simulations of a liquid-vapor interfacial system consisting of a mixture of water and methanol molecules. Detailed results are obtained for the structural and dynamical properties of the bulk and interfacial regions of the mixture. Among structural properties, we have looked at the inhomogeneous density profiles of water and methanol molecules, hydrogen bond distributions and also the orientational profiles of bulk and interfacial molecules. The methanol molecules are found to have a higher propensity to be at the interface than water molecules. It is found that the interfacial molecules show preference for specific orientations so as to form water-methanol hydrogen bonds at the interface with the hydrophobic methyl group pointing towards the vapor side. It is also found that for both types of molecules, the dipole moment decreases at the interface. It is also found that the local electric field of water influences the dipole moment of methanol molecules. Among the dynamical properties, we have calculated the diffusion, orientational relaxation, hydrogen bond dynamics, and vibrational frequency fluctuations in bulk and interfacial regions. It is found that the diffusion and orientation relaxation of the interfacial molecules are faster than those of the bulk. However, the hydrogen bond lifetimes are longer at the interface which can be correlated with the time scales found from the decay of frequency time correlations. The slower hydrogen bond dynamics for the interfacial molecules with respect to bulk can be attributed to diminished cooperative effects at the interface due to reduced density and number of hydrogen bonds.

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

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.

Kinetics of the Absorption of CO{sub 2} in Aqueous Solutions of N-Methyldiethanolamine plus Triethylene Tetramine

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

Amann, J.M.G.; Bouallou, C.

2009-04-15

This work focuses on the development of a new solvent for CO{sub 2} capture. This new solvent is an aqueous solution with a blend of N-methyldiethanolamine (MDEA) and triethylene tetramine (TETA), an amine with four amino groups. CO{sub 2} absorption was investigated between 298 and 333 K using a Lewis cell with a constant interfacial area. Several concentrations of MDEA (17.5 and 40 wt %) and TETA (3 and 6 wt %) were assessed. The influence of the CO{sub 2} partial pressure on the absorption rate was pointed out. The addition of small amount of TETA leads to a highmore » increase in the CO{sub 2} absorption rates. A numerical model based on the film theory was used to determine the rate coefficients between CO{sub 2} and TETA for the different solvents. The physicochemical parameters have a huge influence on the determination of the rate coefficients.« less

Li-ion transport in all-solid-state lithium batteries with LiCoO 2 using NASICON-type glass ceramic electrolytes

NASA Astrophysics Data System (ADS)

Xie, J.; Imanishi, N.; Zhang, T.; Hirano, A.; Takeda, Y.; Yamamoto, O.

LiCoO 2 thin films were deposited on the NASICON-type glass ceramics, Li 1+ x+ yAl xTi 2- xSi yP 3- yO 12, by radio frequency (RF) magnetron sputtering and were annealed at different temperatures. The as-deposited and the annealed LiCoO 2 thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). It was found that the films exhibited a (1 0 4) preferred orientation after annealing and Co 3O 4 was observed by annealing over 500 °C due to the reaction between the LiCoO 2 and the glass ceramics. The effect of annealing temperature on the interfacial resistance of glass ceramics/LiCoO 2 and Li-ion transport in the bulk LiCoO 2 thin film was investigated by galvanostatic cycling, cyclic voltammetry (CV), potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) with the Li/PEO/glass ceramics/LiCoO 2 cell. The cell performance was limited by the Li-ion diffusion resistance in Ohara/LiCoO 2 interface as well as in bulk LiCoO 2.

The effect of oxygen-plasma treatment on Kevlar fibers and the properties of Kevlar fibers/bismaleimide composites

NASA Astrophysics Data System (ADS)

Su, Min; Gu, Aijuan; Liang, Guozheng; Yuan, Li

2011-02-01

The effect of oxygen-plasma treatment for Kevlar fibers on the interfacial adhesion and typical macro-properties of Kevlar fiber/bismaleimide composites was intensively studied. It is found that oxygen-plasma treatment significantly affects the interfacial adhesion by changing the chemistry and morphology of the surfaces of the fibers, and thus leading to improved interlaminar shear strength, water resistance and dielectric properties of the composites. However, the improvement is closely related to the treatment power and time. The best condition for treating Kevlar fiber is 70 W for 5 min. Oxygen-plasma treatment provides an effective technique for overcoming the poor interfacial adhesion of Kevlar fiber based composites, and thus showing great potential in fabricating high performance copper clad laminates.

Electrostatic Properties of Aqueous Salt Solution Interfaces: A Comparison of Polarizable and Non-Polarizable Ion Models

PubMed Central

Warren, G. Lee; Patel, Sandeep

2014-01-01

The effects of ion force field polarizability on the interfacial electrostatic properties of ~1 M aqueous solutions of NaCl, CsCl and NaI are investigated using molecular dynamics simulations employing both non-polarizable and Drude-polarizable ion sets. Differences in computed depth-dependent orientational distributions, “permanent” and induced dipole and quadrupole moment profiles, and interfacial potentials are obtained for both ion sets to further elucidate how ion polarizability affects interfacial electrostatic properties among the various salts relative to pure water. We observe that the orientations and induced dipoles of water molecules are more strongly perturbed in the presence of polarizable ions via a stronger ionic double layer effect arising from greater charge separation. Both anions and cations exhibit enhanced induced dipole moments and strong z alignment in the vicinity of the Gibbs dividing surface (GDS) with the magnitude of the anion induced dipoles being nearly an order of magnitude larger than those of the cations and directed into the vapor phase. Depth-dependent profiles for the trace and zz components of the water molecular quadrupole moment tensors reveal 40% larger quadrupole moments in the bulk phase relative to the vapor mimicking a similar observed 40% increase in the average water dipole moment. Across the GDS, the water molecular quadrupole moments increase non-monotonically (in contrast to the water dipoles) and exhibit a locally reduced contribution just below the surface due to both orientational and polarization effects. Computed interfacial potentials for the non-polarizable salts yield values 20 to 60 mV more positive than pure water and increase by an additional 30 to 100 mV when ion polarizability is included. A rigorous decomposition of the total interfacial potential into ion monopole, water and ion dipole, and water quadrupole components reveals that a very strong, positive ion monopole contribution is offset by negative contributions from all other potential sources. Water quadrupole components modulated by the water density contribute significantly to the observed interfacial potential increments and almost entirely explain observed differences in the interfacial potentials for the two chloride salts. By lumping all remaining non-quadrupole interfacial potential contributions into a single “effective” dipole potential, we observe that the ratio of quadrupole to “effective” dipole contributions range from 2:1 in CsCl to 1:1.5 in NaI suggesting that both contributions are comparably important in determining the interfacial potential increments. We also find that oscillations in the quadrupole potential in the double layer region are opposite in sign and partially cancel those of the “effective” dipole potential. PMID:18712908

Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

NASA Astrophysics Data System (ADS)

Lin, Luchan; Zou, Guisheng; Liu, Lei; Duley, Walt W.; Zhou, Y. Norman

2016-05-01

We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO2 structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO2 resulting in the modification of both surfaces and an increase in wettability of TiO2, facilitating the interconnection of Ag and TiO2 nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO2 in the contact region between the Ag and TiO2 nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO2 nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

Solar H2 evolution in water with modified diketopyrrolopyrrole dyes immobilised on molecular Co and Ni catalyst-TiO2 hybrids.

PubMed

Warnan, Julien; Willkomm, Janina; Ng, Jamues N; Godin, Robert; Prantl, Sebastian; Durrant, James R; Reisner, Erwin

2017-04-01

A series of diketopyrrolopyrrole (DPP) dyes with a terminal phosphonic acid group for attachment to metal oxide surfaces were synthesised and the effect of side chain modification on their properties investigated. The organic photosensitisers feature strong visible light absorption ( λ = 400 to 575 nm) and electrochemical and fluorescence studies revealed that the excited state of all dyes provides sufficient driving force for electron injection into the TiO 2 conduction band. The performance of the DPP chromophores attached to TiO 2 nanoparticles for photocatalytic H 2 evolution with co-immobilised molecular Co and Ni catalysts was subsequently studied, resulting in solar fuel generation with a dye-sensitised semiconductor nanoparticle system suspended in water without precious metal components. The performance of the DPP dyes in photocatalysis did not only depend on electronic parameters, but also on properties of the side chain such as polarity, steric hinderance and hydrophobicity as well as the specific experimental conditions and the nature of the sacrificial electron donor. In an aqueous pH 4.5 ascorbic acid solution with a phosphonated DuBois-type Ni catalyst, a DPP-based turnover number (TON DPP ) of up to 205 was obtained during UV-free simulated solar light irradiation (100 mW cm -2 , AM 1.5G, λ > 420 nm) after 1 day. DPP-sensitised TiO 2 nanoparticles were also successfully used in combination with a hydrogenase or platinum instead of the synthetic H 2 evolution catalysts and the platinum-based system achieved a TON DPP of up to 2660, which significantly outperforms an analogous system using a phosphonated Ru tris(bipyridine) dye (TON Ru = 431). Finally, transient absorption spectroscopy was performed to study interfacial recombination and dye regeneration kinetics revealing that the different performances of the DPP dyes are most likely dictated by the different regeneration efficiencies of the oxidised chromophores.

A numeric investigation of co-flowing liquid streams using the Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Somogyi, Andy; Tagg, Randall

2007-11-01

We present a numerical investigation of co-flowing immiscible liquid streams using the Lattice Boltzmann Method (LBM) for multi component, dissimilar viscosity, immiscible fluid flow. When a liquid is injected into another immiscible liquid, the flow will eventually transition from jetting to dripping due to interfacial tension. Our implementation of LBM models the interfacial tension through a variety of techniques. Parallelization is also straightforward for both single and multi component models as only near local interaction is required. We compare the results of our numerical investigation using LBM to several recent physical experiments.

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

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

Effect of the interfacial O and Mg vacancies on electronic structure and transport properties of the FeRh/MgO/FeRh (0 0 1) magnetic tunnel junction: DFT calculations

NASA Astrophysics Data System (ADS)

Sakhraoui, T.; Said, M.

2017-12-01

The electronic, magnetic and transport properties of oxygen or magnesium vacancies at the FeRh/MgO/FeRh (0 0 1) magnetic tunnel junction are studied within first principles. Configurations with one O or Mg vacancy per C(2 × 2) surface unit cell, which is located in the MgO interfacial layers, are investigated. We observed that the O and Mg vacancies defect have a very little influence on the magnetic state of the spacer. Very interestingly, the Fe atoms exhibit an enhanced magnetic moment in the case of Mg-vacancy, this latter was found to decrease in the case of O-vacancy. The variations in the spin polarization and magnetic moment values for Fe and Rh atoms at the interface were found to be larger in presence of Mg vacancy. An analysis of the charge densities of our systems was also performed; large variations in the Mg-vacancy system were observed. This affects more the t2g states of the interfacial Fe atom. Moreover, we present an ab initio calculated transmission and I-V characteristics for FeRh/MgO/FeRh (0 0 1) magnetic tunnel junction and we compare results to those of O and Mg-vacancy at the interface using the TRANSIESTA code, which combines the DFT electronic structure calculations with the non-equilibrium Green function formalism (NEGF) for transport properties. The results show that the zero-bias minority spin transmission is much larger than the majority spin transmission for all structures. In all systems and for all magnetic configurations, minority spin currents are higher than majority spin ones, this means that transport properties are, mainly, determined by minority spin channel.

Interfacial and electrical properties of InGaAs metal-oxide-semiconductor capacitor with TiON/TaON multilayer composite gate dielectric

NASA Astrophysics Data System (ADS)

Wang, L. S.; Xu, J. P.; Liu, L.; Lu, H. H.; Lai, P. T.; Tang, W. M.

2015-03-01

InGaAs metal-oxide-semiconductor (MOS) capacitors with composite gate dielectric consisting of Ti-based oxynitride (TiON)/Ta-based oxynitride (TaON) multilayer are fabricated by RF sputtering. The interfacial and electrical properties of the TiON/TaON/InGaAs and TaON/TiON/InGaAs MOS structures are investigated and compared. Experimental results show that the former exhibits lower interface-state density (1.0 × 1012 cm-2 eV-1 at midgap), smaller gate leakage current (9.5 × 10-5 A/cm2 at a gate voltage of 2 V), larger equivalent dielectric constant (19.8), and higher reliability under electrical stress than the latter. The involved mechanism lies in the fact that the ultrathin TaON interlayer deposited on the sulfur-passivated InGaAs surface can effectively reduce the defective states and thus unpin the Femi level at the TaON/InGaAs interface, improving the electrical properties of the device.

Electronic band structures and optical properties of type-II superlattice photodetectors with interfacial effect.

PubMed

Qiao, Peng-Fei; Mou, Shin; Chuang, Shun Lien

2012-01-30

The electronic band structures and optical properties of type-II superlattice (T2SL) photodetectors in the mid-infrared (IR) range are investigated. We formulate a rigorous band structure model using the 8-band k · p method to include the conduction and valence band mixing. After solving the 8 × 8 Hamiltonian and deriving explicitly the new momentum matrix elements in terms of envelope functions, optical transition rates are obtained through the Fermi's golden rule under various doping and injection conditions. Optical measurements on T2SL photodetectors are compared with our model and show good agreement. Our modeling results of quantum structures connect directly to the device-level design and simulation. The predicted doping effect is readily applicable to the optimization of photodetectors. We further include interfacial (IF) layers to study the significance of their effect. Optical properties of T2SLs are expected to have a large tunable range by controlling the thickness and material composition of the IF layers. Our model provides an efficient tool for the designs of novel photodetectors.

Effect of heat treatment on interfacial and mechanical properties of A6022/A7075/A6022 roll-bonded multi-layer Al alloy sheets

NASA Astrophysics Data System (ADS)

Cha, Joon-Hyeon; Kim, Su-Hyeon; Lee, Yun-Soo; Kim, Hyoung-Wook; Choi, Yoon Suk

2016-09-01

Multi-layered Al alloy sheets can exhibit unique properties by the combination of properties of component materials. A poor corrosion resistance of high strength Al alloys can be complemented by having a protective surface with corrosion resistant Al alloys. Here, a special care should be taken regarding the heat treatment of multi-layered Al alloy sheets because dissimilar Al alloys may exhibit unexpected interfacial reactions upon heat treatment. In the present study, A6022/A7075/A6022 sheets were fabricated by a cold roll-bonding process, and the effect of the heat treatment on the microstructure and mechanical properties was examined. The solution treatment gave rise to the diffusion of Zn, Mg, Cu and Si elements across the core/clad interface. In particular, the pronounced diffusion of Zn, which is a major alloying element (for solid-solution strengthening) of the A7075 core, resulted in a gradual hardness change across the core/clad interface. Mg2Si precipitates and the precipitate free zone were also formed near the interface after the heat treatment. The heat-treated sheet showed high strengths and reasonable elongation without apparent deformation misfit or interfacial delamination during the tensile deformation. The high strength of the sheet was mainly due to the T4 and T6 heat treatment of the A7075 core.

New insights on the complex dynamics of two-phase flow in porous media under intermediate-wet conditions.

PubMed

Rabbani, Harris Sajjad; Joekar-Niasar, Vahid; Pak, Tannaz; Shokri, Nima

2017-07-04

Multiphase flow in porous media is important in a number of environmental and industrial applications such as soil remediation, CO 2 sequestration, and enhanced oil recovery. Wetting properties control flow of immiscible fluids in porous media and fluids distribution in the pore space. In contrast to the strong and weak wet conditions, pore-scale physics of immiscible displacement under intermediate-wet conditions is less understood. This study reports the results of a series of two-dimensional high-resolution direct numerical simulations with the aim of understanding the pore-scale dynamics of two-phase immiscible fluid flow under intermediate-wet conditions. Our results show that for intermediate-wet porous media, pore geometry has a strong influence on interface dynamics, leading to co-existence of concave and convex interfaces. Intermediate wettability leads to various interfacial movements which are not identified under imbibition or drainage conditions. These pore-scale events significantly influence macro-scale flow behaviour causing the counter-intuitive decline in recovery of the defending fluid from weak imbibition to intermediate-wet conditions.

Co-recycling of acrylonitrile-butadiene-styrene waste plastic and nonmetal particles from waste printed circuit boards to manufacture reproduction composites.

PubMed

Sun, Zhixing; Shen, Zhigang; Zhang, Xiaojing; Ma, Shulin

2015-01-01

This study investigated the feasibility of using acrylonitrile-butadiene-styrene (ABS) waste plastic and nonmetal particles from waste printed circuit boards (WPCB) to manufacture reproduction composites (RC), with the aim of co-recycling these two waste resources. The composites were prepared in a twin-crew extruder and investigated by means of mechanical testing, in situ flexural observation, thermogravimatric analysis, and dimensional stability evaluation. The results showed that the presence of nonmetal particles significantly improved the mechanical properties and the physical performance of the RC. A loading of 30 wt% nonmetal particles could achieve a flexural strength of 72.6 MPa, a flexural modulus of 3.57 GPa, and an impact strength of 15.5 kJ/m2. Moreover, it was found that the application of maleic anhydride-grafted ABS as compatilizer could effectively promote the interfacial adhesion between the ABS plastic and the nonmetal particles. This research provides a novel method to reuse waste ABS and WPCB nonmetals for manufacturing high value-added product, which represents a promising way for waste recycling and resolving the environmental problem.

Fabrication of 6FDA-durene membrane incorporated with zeolite T and aminosilane grafted zeolite T for CO2/CH4 separation

NASA Astrophysics Data System (ADS)

Jusoh, Norwahyu; Fong Yeong, Yin; Keong Lau, Kok; Shariff, Azmi Mohd

2017-08-01

In the present work, zeolite T and aminosilane grafted zeolite T are embedded into 6FDA-durene polyimide phase for the fabrication of mixed matrix membranes (MMMs). FESEM images demonstrated that the improvement of interfacial adhesion between zeolite and polymer phases in MMM loaded with aminosilane grafted zeolite T was not significant as compared to zeolite T/6FDA-durene MMM. From the gas permeation test, CO2/CH4 selectivity up to 26.4 was achieved using MMM containing aminosilane grafted zeolite T, while MMM loaded with ungrafted zeolite T showed CO2/CH4 selectivity of 19.1. In addition, MMM incorporated with aminosilane grafted zeolite T particles successfully lies on Robeson upper bound 2008, which makes it an attractive candidate for CO2/CH4 separation.

Role of scaffold network in controlling strain and functionalities of nanocomposite films

DOE PAGES

Chen, Aiping; Hu, Jia -Mian; Lu, Ping; ...

2016-06-10

One novel approach to manipulating functionalities in correlated complex oxides is strain. However, significant epitaxial strain can only be achieved in ultrathin layers. We show that, under direct lattice matching framework, large and uniform vertical strain up to 2% can be achieved to significantly modify the magnetic anisotropy, magnetism, and magnetotransport properties in heteroepitaxial nanoscaffold films, over a few hundred nanometers in thickness. Comprehensive designing principles of large vertical strain have been proposed. Phase-field simulations not only reveal the strain distribution but also suggest that the ultimate strain is related to the vertical interfacial area and interfacial dislocation density. Moreover,more » by changing the nanoscaffold density and dimension, the strain and the magnetic properties can be tuned. The established correlation among the vertical interface—strain—properties in nanoscaffold films can consequently be used to tune other functionalities in a broad range of complex oxide films far beyond critical thickness.« less

Role of scaffold network in controlling strain and functionalities of nanocomposite films

PubMed Central

Chen, Aiping; Hu, Jia-Mian; Lu, Ping; Yang, Tiannan; Zhang, Wenrui; Li, Leigang; Ahmed, Towfiq; Enriquez, Erik; Weigand, Marcus; Su, Qing; Wang, Haiyan; Zhu, Jian-Xin; MacManus-Driscoll, Judith L.; Chen, Long-Qing; Yarotski, Dmitry; Jia, Quanxi

2016-01-01

Strain is a novel approach to manipulating functionalities in correlated complex oxides. However, significant epitaxial strain can only be achieved in ultrathin layers. We show that, under direct lattice matching framework, large and uniform vertical strain up to 2% can be achieved to significantly modify the magnetic anisotropy, magnetism, and magnetotransport properties in heteroepitaxial nanoscaffold films, over a few hundred nanometers in thickness. Comprehensive designing principles of large vertical strain have been proposed. Phase-field simulations not only reveal the strain distribution but also suggest that the ultimate strain is related to the vertical interfacial area and interfacial dislocation density. By changing the nanoscaffold density and dimension, the strain and the magnetic properties can be tuned. The established correlation among the vertical interface—strain—properties in nanoscaffold films can consequently be used to tune other functionalities in a broad range of complex oxide films far beyond critical thickness. PMID:27386578

Non-Faradaic Li + Migration and Chemical Coordination across Solid-State Battery Interfaces

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

Gittleson, Forrest S.; El Gabaly, Farid

Efficient and reversible charge transfer is essential to realizing high-performance solid-state batteries. Efforts to enhance charge transfer at critical electrode–electrolyte interfaces have proven successful, yet interfacial chemistry and its impact on cell function remains poorly understood. Using X-ray photoelectron spectroscopy combined with electrochemical techniques, we elucidate chemical coordination near the LiCoO 2–LIPON interface, providing experimental validation of space-charge separation. Space-charge layers, defined by local enrichment and depletion of charges, have previously been theorized and modeled, but the unique chemistry of solid-state battery interfaces is now revealed. Here we highlight the non-Faradaic migration of Li+ ions from the electrode to themore » electrolyte, which reduces reversible cathodic capacity by ~15%. Inserting a thin, ion-conducting LiNbO 3 interlayer between the electrode and electrolyte, however, can reduce space-charge separation, mitigate the loss of Li+ from LiCoO 2, and return cathodic capacity to its theoretical value. This work illustrates the importance of interfacial chemistry in understanding and improving solid-state batteries.« less

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.

Interface effects on mechanical properties of particle-reinforced composites.

PubMed

Debnath, S; Ranade, R; Wunder, S L; McCool, J; Boberick, K; Baran, G

2004-09-01

Effective bonding between the filler and matrix components typically improves the mechanical properties of polymer composites containing inorganic fillers. The aim of this study was to test the hypothesis that composite flexural modulus, flexure strength, and toughness are directly proportional to filler-matrix interfacial shear strength. The resin matrix component of the experimental composite consisted of a 60:40 blend of BisGMA:TEGDMA. Two levels of photoinitiator components were used: 0.15, and 0.5%. Raman spectroscopy was used to determine degree of cure, and thermogravimetry (TGA) was used to quantify the degree of silane, rubber, or polymer attachment to silica and glass particles. Filler-matrix interfacial shear strengths were measured using a microbond test. Composites containing glass particles with various surface treatments were prepared and the modulus, flexure strength, and fracture toughness of these materials obtained using standard methods. Mechanical properties were measured on dry and soaked specimens. The interfacial strength was greatest for the 5% MPS treated silica, and it increased for polymers prepared with 0.5% initiator compared with 0.15% initiator concentrations. For the mechanical properties measured, the authors found that: (1) the flexural modulus was independent of the type of filler surface treatment, though flexural strength and toughness were highest for the silanated glass; (2) rubber at the interface, whether bonded to the filler and matrix or not, did not improve toughness; (3) less grafting of resin to silanated filler particles was observed when the initiator concentration decreased. These findings suggest that increasing the strength of the bond between filler and matrix will not result in improvements in the mechanical properties of particulate-reinforced composites in contrast to fiber-reinforced composites. Also, contraction stresses in the 0.5 vs 0.15% initiator concentration composites may be responsible for increases in interfacial shear strengths, moduli, and flexural strengths.

The Influence of Fracturing Fluids on Fracturing Processes: A Comparison Between Water, Oil and SC-CO2

NASA Astrophysics Data System (ADS)

Wang, Jiehao; Elsworth, Derek; Wu, Yu; Liu, Jishan; Zhu, Wancheng; Liu, Yu

2018-01-01

Conventional water-based fracturing treatments may not work well for many shale gas reservoirs. This is due to the fact that shale gas formations are much more sensitive to water because of the significant capillary effects and the potentially high contents of swelling clay, each of which may result in the impairment of productivity. As an alternative to water-based fluids, gaseous stimulants not only avoid this potential impairment in productivity, but also conserve water as a resource and may sequester greenhouse gases underground. However, experimental observations have shown that different fracturing fluids yield variations in the induced fracture. During the hydraulic fracturing process, fracturing fluids will penetrate into the borehole wall, and the evolution of the fracture(s) then results from the coupled phenomena of fluid flow, solid deformation and damage. To represent this, coupled models of rock damage mechanics and fluid flow for both slightly compressible fluids and CO2 are presented. We investigate the fracturing processes driven by pressurization of three kinds of fluids: water, viscous oil and supercritical CO2. Simulation results indicate that SC-CO2-based fracturing indeed has a lower breakdown pressure, as observed in experiments, and may develop fractures with greater complexity than those developed with water-based and oil-based fracturing. We explore the relation between the breakdown pressure to both the dynamic viscosity and the interfacial tension of the fracturing fluids. Modeling demonstrates an increase in the breakdown pressure with an increase both in the dynamic viscosity and in the interfacial tension, consistent with experimental observations.

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties.

PubMed

Burn, D M; Hase, T P A; Atkinson, D

2014-06-11

Modification of the magnetic properties in a thin-film ferromagnetic/non-magnetic bilayer system by low-dose focused ion-beam (FIB) induced intermixing is demonstrated. The highly localized capability of FIB may be used to locally control magnetic behaviour at the nanoscale. The magnetic, electronic and structural properties of NiFe/Au bilayers were investigated as a function of the interfacial structure that was actively modified using focused Ga(+) ion irradiation. Experimental work used MOKE, SQUID, XMCD as well as magnetoresistance measurements to determine the magnetic behavior and grazing incidence x-ray reflectivity to elucidate the interfacial structure. Interfacial intermixing, induced by low-dose irradiation, is shown to lead to complex changes in the magnetic behavior that are associated with monotonic structural evolution of the interface. This behavior may be explained by changes in the local atomic environment within the interface region resulting in a combination of processes including the loss of moment on Ni and Fe, an induced moment on Au and modifications to the spin-orbit coupling between Au and NiFe.

Microstructures and Properties of 40Cu/Ag(Invar) Composites Fabricated by Powder Metallurgy and Subsequent Thermo-Mechanical Treatment

NASA Astrophysics Data System (ADS)

Zhang, Xin; Huang, Yingqiu; Liu, Xiangyu; Yang, Lei; Shi, Changdong; Wu, Yucheng; Tang, Wenming

2018-03-01

Composites of 40Cu/Ag(Invar) were prepared via pressureless sintering and subsequent thermo-mechanical treatment from raw materials of electroless Ag-plated Invar alloy powder and electrolytic Cu powder. Microstructures and properties of the prepared composites were studied to evaluate the effect of the Ag layer on blocking Cu/Invar interfacial diffusion in the composites. The electroless-plated Ag layer was dense, uniform, continuous, and bonded tightly with the Invar alloy substrate. During sintering of the composites, the Ag layer effectively prevented Cu/Invar interfacial diffusion. During cold-rolling, the Ag layer was deformed uniformly with the Invar alloy particles. The composites exhibited bi-continuous network structure and considerably improved properties. After sintering at 775 °C and subsequent thermo-mechanical treatment, the 40Cu/Ag(Invar) composites showed satisfactory comprehensive properties: relative density of 99.0 pct, hardness of HV 253, thermal conductivity of 55.7 W/(m K), and coefficient of thermal expansion of 11.2 × 10-6/K.

Lattice strain induced multiferroicity in PZT-CFO particulate composite

NASA Astrophysics Data System (ADS)

Pradhan, Lagen Kumar; Pandey, Rabichandra; Kumar, Rajnish; Kar, Manoranjan

2018-02-01

Lead Zirconate Titanate [Pb(Zr0.52Ti0.48)O3/PZT] and Cobalt Ferrite [CoFe2O4/CFO] based multiferroic composites [(1-x)PZT-(x)CFO] with (x = 0.10-0.40) have been prepared to study its magnetoelectric (ME) and multiferroic properties. X-ray diffraction method along with the Rietveld refinement technique reveals that the crystal symmetries corresponding to PZT and CFO exist independently in the composites. The effect of interfacial strain on lattice distortion in PZT has been observed. It is well correlated with the magnetoelectric coupling of the composites. Dispersion behavior of dielectric constant with frequency can be explained by the modified Debye model. Different relaxation phenomena have been observed in PZT-CFO particulate composites. The ferroelectric properties of composites decrease with the increase in percentage of CFO in the composite. Both saturation (Ms) and remanent (Mr) magnetization increase with the increase in CFO content in the composite. The maximum ME coupling was found to be 1.339 pC/cm2 Oe for the composition (0.80) PZT-(0.20) CFO at the application of maximum magnetic field of 50 Oe. The multiferroic properties in CFO-PZT can be explained by the lattice strain at the CFO-PZT interfaces.

Influences of modified bacterial cellulose nanofibers (BCNs) on structural, thermophysical, optical, and barrier properties of poly ethylene-co-vinyl acetate (EVA) nanocomposite.

PubMed

Ghadikolaei, Shila Shirdel; Omrani, Abdollah; Ehsani, Morteza

2018-04-14

The BCNs were chemically modified using acetic anhydride with the aim of improving its dispersion and interfacial adhesion. Acetylation of BCNs was confirmed by FT-IR spectroscopy. Morphology studies using TEM and SEM revealed that a reasonable dispersion of the modified BCNs in the EVA matrix was accomplished. The DSC data displayed a little shift in the T g to higher temperatures with the incorporation of both modified and unmodified BCNs. Increased thermal stability of the nanocomposites consisting acetylated BCNs was confirmed by TGA technique. DMA measurements highlighted that the storage modulus increased and the damping properties decreased for the nanocomposites with regard to the neat EVA. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

Molecular dynamics studies of interfacial water at the alumina surface.

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

Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

2011-01-01

Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior atmore » distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.« less

Ordered water structure at hydrophobic graphite interfaces observed by 4D, ultrafast electron crystallography

PubMed Central

Yang, Ding-Shyue; Zewail, Ahmed H.

2009-01-01

Interfacial water has unique properties in various functions. Here, using 4-dimensional (4D), ultrafast electron crystallography with atomic-scale spatial and temporal resolution, we report study of structure and dynamics of interfacial water assembly on a hydrophobic surface. Structurally, vertically stacked bilayers on highly oriented pyrolytic graphite surface were determined to be ordered, contrary to the expectation that the strong hydrogen bonding of water on hydrophobic surfaces would dominate with suppressed interfacial order. Because of its terrace morphology, graphite plays the role of a template. The dynamics is also surprising. After the excitation of graphite by an ultrafast infrared pulse, the interfacial ice structure undergoes nonequilibrium “phase transformation” identified in the hydrogen-bond network through the observation of structural isosbestic point. We provide the time scales involved, the nature of ice-graphite structural dynamics, and relevance to properties related to confined water. PMID:19246378

Interfacial adhesion improvement in carbon fiber/carbon nanotube reinforced hybrid composites by the application of a reactive hybrid resin initiated by gamma irradiation

NASA Astrophysics Data System (ADS)

Szebényi, G.; Faragó, D.; Lámfalusi, Cs.; Göbl, R.

2018-04-01

Interfacial adhesion is a key factor in composite materials. The effective co-working of the reinforcing materials and matrix is essential for the proper load transfer between them, and to achieve the desired reinforcing effect. In case of nanocomposites, especially carbon nanotube (CNT) reinforced nanocomposites the adhesion between the CNTs and the polymer matrix is poor. To improve the interfacial adhesion and exploit the reinforcing effect of these nanoparticles a two step curable epoxy (EP)/vinylester (VE) hybrid resin system was developed where the EP is cured using hardener in the first step, during the composite production, and in the second step the curing of the VE is initiated by gamma irradiation, which also activates the reinforcing materials and the cured matrix component. A total of six carbon fiber reinforced composite systems were compared with neat epoxy and EP/VE hybrid matrices with and without chemical initiator and MWCNT nano-reinforcement. The effect of gamma irradiation was investigated at four absorbed dose levels. According to our three point bending and interlaminar shear test results the adhesion has improved between all constituents of the composite system. It was demonstrated that gamma irradiation has beneficial effect on the static mechanical, especially interlaminar properties of both micro- and nanocomposites in terms of modulus, strength and interlaminar shear strength.

A study of the effect of polystyrene sulfonation on the performance of terephthaloyl chloride-dihydroxydiphenyl sulfone copolymer/polystyrene system

NASA Astrophysics Data System (ADS)

Kahraman, R.; Kahn, K. A.; Ali, S. A.; Hamid, S. H.; Sahin, A. Z.

1998-12-01

Thermal, morphological, and mechanical properties of composites of a liquid crystalline copolymer (LCP) poly(terephthaloyl chloride)-co-(p,p’-dihydroxydiphenyl sulfone) with polystyrene (PS) and sulfonated polystyrene (SPS) are presented and discussed. Sulfonation of polystyrene was expected to improve the interfacial adhesion by introducing hydrogen bonding in the LCP/PS system. The degree of sulfonation was 11 %. The incompatibility (lack of proper interfacial adhesion) of the LCP/PS system resulted in sharp decrease in the composite tensile strength with LCP addition. The performance of the system did not change when processed at a higher temperature (270 °C instead of 225 °C). While a composite plate of 25% LCP/PS could not be fabricated, it was possible for LCP/SPS (processed at 215 °C), indicating some improvement in interfacial bonding by sulfonation. Sulfonation of PS resulted in fracture with some degree of plastic deformation for pure SPS matrix and also the LCP/SPS system with the lowest LCP content (1 wt%), whereas plastic deformation was not observed for PS used as received. The strength of the LCP/SPS system also decreased with increase in LCP content, indicating that 11% sulfonation is not sufficient to introduce significant compatibility, but it was not as dramatic as that for LCP/PS. The performance of the LCP/SPS system was not affected significantly by heat treatment at the process temperature.

On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films.

PubMed

Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E; Alford, Neil McN

2015-01-07

The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.

Interfacial Properties of EXXPRO(TM) and General Purpose Elastomers

NASA Astrophysics Data System (ADS)

Zhang, Y.; Rafailovich, M.; Sokolov, Jon; Qu, S.; Ge, S.; Ngyuen, D.; Li, Z.; Peiffer, D.; Song, L.; Dias, J. A.; McElrath, K. O.

1998-03-01

EXXPRO(Trademark) elastomers are used for tires and many other applications. This elastomer (denoted as BIMS) is a random copolymer of p-methylstyrene (MS) and polyisobutylene (I) with varying degrees of PMS content and bromination (B) on the p-methyl group. BIMS is impermeable to gases, and has good heat, ozone and flex resistance. Very often general purpose elastomers are blended with BIMS. The interfacial width between polybutadiene and BIMS is a sensitive function of the Br level and PMS content. By neutron reflectivity (NR), we studied the dynamics of interface formation as a function of time and temperature for BIMS with varying degrees of PMS and Br. We found that in addition to the bulk parameters, the total film thickness and the proximity of an interactive surface can affect the interfacial interaction rates. The interfacial properties can also be modified by inclusion of particles, such as carbon black (a filler component in tire rubbers). Results will be presented on the relation between the interfacial width as measured by NR and compatibilization studies via AFM and LFM.

Role of polar compensation in interfacial ferromagnetism of LaNiO3/CaMnO3 superlattices

NASA Astrophysics Data System (ADS)

Flint, C. L.; Jang, H.; Lee, J.-S.; N'Diaye, A. T.; Shafer, P.; Arenholz, E.; Suzuki, Y.

2017-07-01

Polar compensation can play an important role in the determination of interfacial electronic and magnetic properties in oxide heterostructures. Using x-ray absorption spectroscopy, x-ray magnetic circular dichroism, bulk magnetometry, and transport measurements, we find that interfacial charge redistribution via polar compensation is essential for explaining the evolution of interfacial ferromagnetism in LaNiO3/CaMnO3 superlattices as a function of LaNiO3 layer thickness. In insulating superlattices (four unit cells or less of LaNiO3), magnetism is dominated by Ni-Mn superexchange, while itinerant electron-based Mn-Mn double exchange plays a role in thicker metallic superlattices. X-ray magnetic circular dichroism and resonant x-ray scattering show that Ni-Mn superexchange contributes to the magnetization even in metallic superlattices. This Ni-Mn superexchange interaction can be explained in terms of polar compensation at the LaNiO3-CaMnO3 interface. These results highlight the different mechanisms responsible for interfacial ferromagnetism and the importance of understanding compensation due to polar mismatch at oxide-based interfaces when engineering magnetic properties.

Tuning the Schottky rectification in graphene-hexagonal boron nitride-molybdenum disulfide heterostructure.

PubMed

Liu, Biao; Zhao, Yu-Qing; Yu, Zhuo-Liang; Wang, Lin-Zhi; Cai, Meng-Qiu

2018-03-01

It was still a great challenge to design high performance of rectification characteristic for the rectifier diode. Lately, a new approach was proposed experimentally to tune the Schottky barrier height (SBH) by inserting an ultrathin insulated tunneling layer to form metal-insulator-semiconductor (MIS) heterostructures. However, the electronic properties touching off the high performance of these heterostructures and the possibility of designing more efficient applications for the rectifier diode were not presently clear. In this paper, the structural, electronic and interfacial properties of the novel MIS diode with the graphene/hexagonal boron nitride/monolayer molybdenum disulfide (GBM) heterostructure had been investigated by first-principle calculations. The calculated results showed that the intrinsic properties of graphene and MoS 2 were preserved due to the weak van der Waals contact. The height of interfacial Schottky barrier can be tuned by the different thickness of hBN layers. In addition, the GBM Schottky diode showed more excellent rectification characteristic than that of GM Schottky diode due to the interfacial band bending caused by the epitaxial electric field. Based on the electronic band structure, we analyzed the relationship between the electronic structure and the nature of the Schottky rectifier, and revealed the potential of utilizing GBM Schottky diode for the higher rectification characteristic devices. Copyright © 2017 Elsevier Inc. All rights reserved.

Molecular Modeling of Thermodynamic and Transport Properties for CO 2 and Aqueous Brines

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

Jiang, Hao; Economou, Ioannis G.; Panagiotopoulos, Athanassios Z.

Molecular simulation techniques using classical force-fields occupy the space between ab initio quantum mechanical methods and phenomenological correlations. In particular, Monte Carlo and molecular dynamics algorithms can be used to provide quantitative predictions of thermodynamic and transport properties of fluids relevant for geologic carbon sequestration at conditions for which experimental data are uncertain or not available. These methods can cover time and length scales far exceeding those of quantum chemical methods, while maintaining transferability and predictive power lacking from phenomenological correlations. The accuracy of predictions depends sensitively on the quality of the molecular models used. Many existing fixed-point-charge models formore » water and aqueous mixtures fail to represent accurately these fluid properties, especially when descriptions covering broad ranges of thermodynamic conditions are needed. Recent work on development of accurate models for water, CO 2, and dissolved salts, as well as their mixtures, is summarized in this Account. Polarizable models that can respond to the different dielectric environments in aqueous versus nonaqueous phases are necessary for predictions of properties over extended ranges of temperatures and pressures. Phase compositions and densities, activity coefficients of the dissolved salts, interfacial tensions, viscosities and diffusivities can be obtained in near-quantitative agreement to available experimental data, using relatively modest computational resources. In some cases, for example, for the composition of the CO 2-rich phase in coexistence with an aqueous phase, recent results from molecular simulations have helped discriminate among conflicting experimental data sets. The sensitivity of properties on the quality of the intermolecular interaction model varies significantly. Properties such as the phase compositions or electrolyte activity coefficients are much more sensitive than phase densities, viscosities, or component diffusivities. Strong confinement effects on physical properties in nanoscale media can also be directly obtained from molecular simulations. Future work on molecular modeling for CO 2 and aqueous brines is likely to be focused on more systematic generation of interaction models by utilizing quantum chemical as well as direct experimental measurements. New ion models need to be developed for use with the current generation of polarizable water models, including ion–ion interactions that will allow for accurate description of dense, mixed brines. Methods will need to be devised that go beyond the use of effective potentials for incorporation of quantum effects known to be important for water, and reactive force fields developed that can handle bond creation and breaking in systems with carbonate and silicate minerals. Lastly, another area of potential future work is the integration of molecular simulation methods in multiscale models for the chemical reactions leading to mineral dissolution and flow within the porous media in underground formations.« less

Molecular Modeling of Thermodynamic and Transport Properties for CO2 and Aqueous Brines.

PubMed

Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

2017-04-18

Molecular simulation techniques using classical force-fields occupy the space between ab initio quantum mechanical methods and phenomenological correlations. In particular, Monte Carlo and molecular dynamics algorithms can be used to provide quantitative predictions of thermodynamic and transport properties of fluids relevant for geologic carbon sequestration at conditions for which experimental data are uncertain or not available. These methods can cover time and length scales far exceeding those of quantum chemical methods, while maintaining transferability and predictive power lacking from phenomenological correlations. The accuracy of predictions depends sensitively on the quality of the molecular models used. Many existing fixed-point-charge models for water and aqueous mixtures fail to represent accurately these fluid properties, especially when descriptions covering broad ranges of thermodynamic conditions are needed. Recent work on development of accurate models for water, CO 2 , and dissolved salts, as well as their mixtures, is summarized in this Account. Polarizable models that can respond to the different dielectric environments in aqueous versus nonaqueous phases are necessary for predictions of properties over extended ranges of temperatures and pressures. Phase compositions and densities, activity coefficients of the dissolved salts, interfacial tensions, viscosities and diffusivities can be obtained in near-quantitative agreement to available experimental data, using relatively modest computational resources. In some cases, for example, for the composition of the CO 2 -rich phase in coexistence with an aqueous phase, recent results from molecular simulations have helped discriminate among conflicting experimental data sets. The sensitivity of properties on the quality of the intermolecular interaction model varies significantly. Properties such as the phase compositions or electrolyte activity coefficients are much more sensitive than phase densities, viscosities, or component diffusivities. Strong confinement effects on physical properties in nanoscale media can also be directly obtained from molecular simulations. Future work on molecular modeling for CO 2 and aqueous brines is likely to be focused on more systematic generation of interaction models by utilizing quantum chemical as well as direct experimental measurements. New ion models need to be developed for use with the current generation of polarizable water models, including ion-ion interactions that will allow for accurate description of dense, mixed brines. Methods will need to be devised that go beyond the use of effective potentials for incorporation of quantum effects known to be important for water, and reactive force fields developed that can handle bond creation and breaking in systems with carbonate and silicate minerals. Another area of potential future work is the integration of molecular simulation methods in multiscale models for the chemical reactions leading to mineral dissolution and flow within the porous media in underground formations.

Molecular Modeling of Thermodynamic and Transport Properties for CO 2 and Aqueous Brines

DOE PAGES

Jiang, Hao; Economou, Ioannis G.; Panagiotopoulos, Athanassios Z.

2017-02-24

Molecular simulation techniques using classical force-fields occupy the space between ab initio quantum mechanical methods and phenomenological correlations. In particular, Monte Carlo and molecular dynamics algorithms can be used to provide quantitative predictions of thermodynamic and transport properties of fluids relevant for geologic carbon sequestration at conditions for which experimental data are uncertain or not available. These methods can cover time and length scales far exceeding those of quantum chemical methods, while maintaining transferability and predictive power lacking from phenomenological correlations. The accuracy of predictions depends sensitively on the quality of the molecular models used. Many existing fixed-point-charge models formore » water and aqueous mixtures fail to represent accurately these fluid properties, especially when descriptions covering broad ranges of thermodynamic conditions are needed. Recent work on development of accurate models for water, CO 2, and dissolved salts, as well as their mixtures, is summarized in this Account. Polarizable models that can respond to the different dielectric environments in aqueous versus nonaqueous phases are necessary for predictions of properties over extended ranges of temperatures and pressures. Phase compositions and densities, activity coefficients of the dissolved salts, interfacial tensions, viscosities and diffusivities can be obtained in near-quantitative agreement to available experimental data, using relatively modest computational resources. In some cases, for example, for the composition of the CO 2-rich phase in coexistence with an aqueous phase, recent results from molecular simulations have helped discriminate among conflicting experimental data sets. The sensitivity of properties on the quality of the intermolecular interaction model varies significantly. Properties such as the phase compositions or electrolyte activity coefficients are much more sensitive than phase densities, viscosities, or component diffusivities. Strong confinement effects on physical properties in nanoscale media can also be directly obtained from molecular simulations. Future work on molecular modeling for CO 2 and aqueous brines is likely to be focused on more systematic generation of interaction models by utilizing quantum chemical as well as direct experimental measurements. New ion models need to be developed for use with the current generation of polarizable water models, including ion–ion interactions that will allow for accurate description of dense, mixed brines. Methods will need to be devised that go beyond the use of effective potentials for incorporation of quantum effects known to be important for water, and reactive force fields developed that can handle bond creation and breaking in systems with carbonate and silicate minerals. Lastly, another area of potential future work is the integration of molecular simulation methods in multiscale models for the chemical reactions leading to mineral dissolution and flow within the porous media in underground formations.« less

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

NASA Astrophysics Data System (ADS)

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

2013-05-01

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

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

NASA Astrophysics Data System (ADS)

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

2013-11-01

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

Chalcogenide and pnictide nanocrystals from the silylative deoxygenation of metal oxides

DOE PAGES

Lin, Chia-Cheng; Tan, Shannon J.; Vela, Javier

2017-09-11

Transition metal chalcogenide and pnictide nanocrystals are of interest for optoelectronic and catalytic applications. In this paper, we present a generalized route to the synthesis of these materials from the silylative deoxygenation of metal oxides with trimethylsilyl reagents. Specific nanophases produced in this way include Ni 3S 2, Ni 5Se 5, Ni 2P, Co 9S 8, Co 3Se 4, CoP, Co 2P, and heterobimetallic (Ni/Co) 9S 8. The resulting chalcogenide nanocrystals are hollow, likely due to differential rates of ion diffusion during the interfacial phase transformation reaction (Kirkendall-type effect). In contrast, the phosphide nanocrystals are solid, likely because they formmore » at higher reaction temperatures. Finally, in all cases, simultaneous partial decomposition of the deoxygenating silyl reagent produces a coating of amorphous silica around the newly formed nanocrystals, which could impact their stability and recyclability.« less

Atomic-layer-deposited Al2O3 and HfO2 on InAlAs: A comparative study of interfacial and electrical characteristics

NASA Astrophysics Data System (ADS)

Wu, Li-Fan; Zhang, Yu-Ming; Lv, Hong-Liang; Zhang, Yi-Men

2016-10-01

Al2O3 and HfO2 thin films are separately deposited on n-type InAlAs epitaxial layers by using atomic layer deposition (ALD). The interfacial properties are revealed by angle-resolved x-ray photoelectron spectroscopy (AR-XPS). It is demonstrated that the Al2O3 layer can reduce interfacial oxidation and trap charge formation. The gate leakage current densities are 1.37 × 10-6 A/cm2 and 3.22 × 10-6 A/cm2 at +1 V for the Al2O3/InAlAs and HfO2/InAlAs MOS capacitors respectively. Compared with the HfO2/InAlAs metal-oxide-semiconductor (MOS) capacitor, the Al2O3/InAlAs MOS capacitor exhibits good electrical properties in reducing gate leakage current, narrowing down the hysteresis loop, shrinking stretch-out of the C-V characteristics, and significantly reducing the oxide trapped charge (Q ot) value and the interface state density (D it). Project supported by the National Basic Research Program of China (Grant No. 2010CB327505), the Advanced Research Foundation of China (Grant No. 914xxx803-051xxx111), the National Defense Advance Research Project, China (Grant No. 513xxxxx306), the National Natural Science Foundation of China (Grant No. 51302215), the Scientific Research Program Funded by Shaanxi Provincial Education Department, China (Grant No. 14JK1656), and the Science and Technology Project of Shaanxi Province, China (Grant No. 2016KRM029).

Implications of interfacial characteristics of food foaming agents in foam formulations.

PubMed

Rodríguez Patino, Juan M; Carrera Sánchez, Cecilio; Rodríguez Niño, Ma Rosario

2008-08-05

The manufacture of food dispersions (emulsions and foams) with specific quality attributes depends on the selection of the most appropriate raw materials and processing conditions. These dispersions being thermodynamically unstable require the use of emulsifiers (proteins, lipids, phospholipids, surfactants etc.). Emulsifiers typically coexist in the interfacial layer with specific functions in the processing and properties of the final product. The optimum use of emulsifiers depends on our knowledge of their interfacial physico-chemical characteristics - such as surface activity, amount adsorbed, structure, thickness, topography, ability to desorb (stability), lateral mobility, interactions between adsorbed molecules, ability to change conformation, interfacial rheological properties, etc. -, the kinetics of film formation and other associated physico-chemical properties at fluid interfaces. These monolayers constitute well defined systems for the analysis of food colloids at the micro- and nano-scale level, with several advantages for fundamental studies. In the present review we are concerned with the analysis of physico-chemical properties of emulsifier films at fluid interfaces in relation to foaming. Information about the above properties would be very helpful in the prediction of optimised formulations for food foams. We concluded that at surface pressures lower than that of monolayer saturation the foaming capacity is low, or even zero. A close relationship was observed between foaming capacity and the rate of diffusion of the foaming agent to the air-water interface. However, the foam stability correlates with the properties of the film at long-term adsorption.

Insilico study of the A(2A)R-D (2)R kinetics and interfacial contact surface for heteromerization.

PubMed

Prakash, Amresh; Luthra, Pratibha Mehta

2012-10-01

G-protein-coupled receptors (GPCRs) are cell surface receptors. The dynamic property of receptor-receptor interactions in GPCRs modulates the kinetics of G-protein signaling and stability. In the present work, the structural and dynamic study of A(2A)R-D(2)R interactions was carried to acquire the understanding of the A(2A)R-D(2)R receptor activation and deactivation process, facilitating the design of novel drugs and therapeutic target for Parkinson's disease. The structure-based features (Alpha, Beta, SurfAlpha, and SurfBeta; GapIndex, Leakiness and Gap Volume) and slow mode model (ENM) facilitated the prediction of kinetics (K (off), K (on), and K (d)) of A(2A)R-D(2)R interactions. The results demonstrated the correlation coefficient 0.294 for K (d) and K (on) and the correlation coefficient 0.635 for K (d) and K (off), and indicated stable interfacial contacts in the formation of heterodimer. The coulombic interaction involving the C-terminal tails of the A(2A)R and intracellular loops (ICLs) of D(2)R led to the formation of interfacial contacts between A(2A)R-D(2)R. The properties of structural dynamics, ENM and KFC server-based hot-spot analysis illustrated the stoichiometry of A(2A)R-D(2)R contact interfaces as dimer. The propensity of amino acid residues involved in A(2A)R-D(2)R interaction revealed the presence of positively (R, H and K) and negatively (E and D) charged structural motif of TMs and ICL3 of A(2A)R and D(2)R at interface of dimer contact. Essentially, in silico structural and dynamic study of A(2A)R-D(2)R interactions will provide the basic understanding of the A(2A)R-D(2)R interfacial contact surface for activation and deactivation processes, and could be used as constructive model to recognize the protein-protein interactions in receptor assimilations.

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.

Effect of Fluorocarbon and Hydrocarbon Chain Lengths in Hybrid Surfactants for Supercritical CO2.

PubMed

Sagisaka, Masanobu; Ono, Shinji; James, Craig; Yoshizawa, Atsushi; Mohamed, Azmi; Guittard, Frédéric; Rogers, Sarah E; Heenan, Richard K; Yan, Ci; Eastoe, Julian

2015-07-14

Hybrid surfactants containing both fluorocarbon (FC) and hydrocarbon (HC) chains have recently been shown to solubilize water and form elongated reversed micelles in supercritical CO2. To clarify the most effective FC and HC chain lengths, the aggregation behavior and interfacial properties of hybrid surfactants FCm-HCn (FC length m/HC length n = 4/2, 4/4, 6/2, 6/4, 6/5, 6/6, and 6/8) were examined in W/CO2 mixtures as functions of pressure, temperature, and water-to-surfactant molar ratio (W0). The solubilizing power of hybrid surfactants for W/CO2 microemulsions was strongly affected by not only the FC length but also by that of the HC. Although the surfactants having short FC and/or HC tails (namely, m/n = 4/2, 4/4, and 6/2) did not dissolve in supercritical CO2 (even at ∼17 mM, ≤400 bar, temperature ≤ 75 °C, and W0 = 0-40), the other hybrid surfactants were able to yield transparent single-phase W/CO2 mixtures identified as microemulsions. The solubilizing power of FC6-HCm surfactants reached a maximum (W0 ∼ 80 at 45 °C and 350 bar) with a hydrocarbon length, m, of 4. The W0 value of 80 is the highest for a HC-FC hybrid surfactant, matching the highest value reported for a FC surfactant which contained more FC groups. High-pressure small-angle neutron scattering measurements from FCm-HCn/D2O/CO2 microemulsions were consistent with growth of the microemulsion droplets with increasing W0. In addition, not only spherical reversed micelles but also nonspherical assemblies (rodlike or ellipsoidal) were found for the systems with FC6-HCn (n = 4-6). At fixed surfactant concentration and W0 (17 mM and W0 = 20), the longest reversed micelles were obtained for FC6-HC6 where a mean aspect ratio of 6.3 was calculated for the aqueous cores.

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.

Ion adsorption at the rutile-water interface: linking molecular and macroscopic properties.

PubMed

Zhang, Z; Fenter, P; Cheng, L; Sturchio, N C; Bedzyk, M J; Predota, M; Bandura, A; Kubicki, J D; Lvov, S N; Cummings, P T; Chialvo, A A; Ridley, M K; Bénézeth, P; Anovitz, L; Palmer, D A; Machesky, M L; Wesolowski, D J

2004-06-08

A comprehensive picture of the interface between aqueous solutions and the (110) surface of rutile (alpha-TiO2) is being developed by combining molecular-scale and macroscopic approaches, including experimental measurements, quantum calculations, molecular simulations, and Gouy-Chapman-Stern models. In situ X-ray reflectivity and X-ray standing-wave measurements are used to define the atomic arrangement of adsorbed ions, the coordination of interfacial water molecules, and substrate surface termination and structure. Ab initio calculations and molecular dynamics simulations, validated through direct comparison with the X-ray results, are used to predict ion distributions not measured experimentally. Potentiometric titration and ion adsorption results for rutile powders having predominant (110) surface expression provide macroscopic constraints of electrical double layer (EDL) properties (e.g., proton release) which are evaluated by comparison with a three-layer EDL model including surface oxygen proton affinities calculated using ab initio bond lengths and partial charges. These results allow a direct correlation of the three-dimensional, crystallographically controlled arrangements of various species (H2O, Na+, Rb+, Ca2+, Sr2+, Zn2+, Y3+, Nd3+) with macroscopic observables (H+ release, metal uptake, zeta potential) and thermodynamic/electrostatic constraints. All cations are found to be adsorbed as "inner sphere" species bonded directly to surface oxygen atoms, while the specific binding geometries and reaction stoichiometries are dependent on ionic radius. Ternary surface complexes of sorbed cations with electrolyte anions are not observed. Finally, surface oxygen proton affinities computed using the MUSIC model are improved by incorporation of ab initio bond lengths and hydrogen bonding information derived from MD simulations. This multitechnique and multiscale approach demonstrates the compatibility of bond-valence models of surface oxygen proton affinities and Stern-based models of the EDL structure, with the actual molecular interfacial distributions observed experimentally, revealing new insight into EDL properties including specific binding sites and hydration states of sorbed ions, interfacial solvent properties (structure, diffusivity, dielectric constant), surface protonation and hydrolysis, and the effect of solution ionic strength.

Interfacial properties at the organic-metal interface probed using quantum well states

NASA Astrophysics Data System (ADS)

Lin, Meng-Kai; Nakayama, Yasuo; Wang, Chin-Yung; Hsu, Jer-Chia; Pan, Chih-Hao; Machida, Shin-ichi; Pi, Tun-Wen; Ishii, Hisao; Tang, S.-J.

2012-10-01

Using angle-resolved photoemission spectroscopy, we investigated the interfacial properties between the long-chain normal-alkane molecule n-CH3(CH2)42CH3 [tetratetracontane (TTC)] and uniform Ag films using the Ag quantum well states. The entire quantum well state energy band dispersions were observed to shift toward the Fermi level with increasing adsorption coverage of TTC up to 1 monolayer (ML). However, the energy shifts upon deposition of 1 ML of TTC are approximately inversely dependent on the Ag film thickness, indicating a quantum-size effect. In the framework of the pushback and image-force models, we applied the Bohr-Sommerfeld quantization rule with the modified Coulomb image potential for the phase shift at the TTC/Ag interface to extract the dielectric constant for 1 ML of TTC.

Fracture Micromechanics of Intermetallic and Ceramic Matrix Continuous Fiber Composites

DTIC Science & Technology

1991-05-01

mechanical properties of titanium matrix composites, but much less information has been published. Only data in the published literature is referenced in...1984, pp. 1931-1940. 18. C.J. Yang, S.M. Jeng and J.-M. Yang " Interfacial properties measurements for SiC fiber-reinforced titanium alloy composites...Analyses of these parameters allowed a determination of interfacial shear strength. Fracture mechanics was used to correlate the micromechanical

Dependency of tunneling magneto-resistance on Fe insertion-layer thickness in Co{sub 2}Fe{sub 6}B{sub 2}/MgO-based magnetic tunneling junctions

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

Chae, Kyo-Suk; Samsung Electronics Co., Ltd., San #16 Banwol-dong, Hwasung-City, Gyeonggi-Do 445-701; Park, Jea-Gun, E-mail: parkjgL@hanyang.ac.kr

For Co{sub 2}Fe{sub 6}B{sub 2}/MgO-based perpendicular magnetic tunneling junctions spin valves with [Co/Pd]{sub n}-synthetic-antiferromagnetic (SyAF) layers, the tunneling-magneto-resistance (TMR) ratio strongly depends on the nanoscale Fe insertion-layer thickness (t{sub Fe}) between the Co{sub 2}Fe{sub 6}B{sub 2} pinned layer and MgO tunneling barrier. The TMR ratio rapidly increased as t{sub Fe} increased up to 0.4 nm by improving the crystalline linearity of a MgO tunneling barrier and by suppressing the diffusion of Pd atoms from a [Co/Pd]{sub n}-SyAF. However, it abruptly decreased by further increasing t{sub Fe} in transferring interfacial-perpendicular magnetic anisotropy into the IMA characteristic of the Co{sub 2}Fe{sub 6}B{sub 2}more » pinned layer. Thus, the TMR ratio peaked at t{sub Fe} = 0.4 nm: i.e., 120% at 29 Ωμm{sup 2}.« less

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

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Preparation of robust braid-reinforced poly(vinyl chloride) ultrafiltration hollow fiber membrane with antifouling surface and application to filtration of activated sludge solution.

PubMed

Zhou, Zhuang; Rajabzadeh, Saeid; Fang, Lifeng; Miyoshi, Taro; Kakihana, Yuriko; Matsuyama, Hideto

2017-08-01

Braid-reinforced hollow fiber membranes with high mechanical properties and considerable antifouling surface were prepared by blending poly(vinyl chloride) (PVC) with poly(vinyl chloride-co-poly(ethylene glycol) methyl ether methacrylate) (poly(VC-co-PEGMA)) copolymer via non-solvent induced phase separation (NIPS). The tensile strength of the braid-reinforced PVC hollow fiber membranes were significantly larger than those of previously reported various types of PVC hollow fiber membranes. The high interfacial bonding strength indicated the good compatibility between the coating materials and the surface of polyethylene terephthalate (PET)-braid. Owing to the surface segregation phenomena, the membrane surface PEGMA coverage increased upon increasing the poly(VC-co-PEGMA)/PVC blending ratio, resulting in higher hydrophilicities and bovine serum albumin (BSA) repulsion. To compare the fouling properties, membranes with similar PWPs were prepared by adjusting the dope solution composition to eliminate the effect of hydrodynamic conditions on the membrane fouling performance. The blend membranes surface exhibited considerable fouling resistance to the molecular adsorption from both BSA solution and activated sludge solution. In both cases, the flux recovered to almost 80% of the initial flux using only water backflush. Considering their great mechanical properties and antifouling resistance to activated sludge solution, these novel membranes show good potential for application in wastewater treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Collaborative Research: Nanopore Confinement of C-H-O Mixed Volatile Fluids Relevant to Subsurface Energy Systems

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

Grady, Brian P.

2015-03-11

The scientific objective of this proposal was to obtain a fundamental atomic- to macro-scale understanding of the sorptivity, structure and dynamics of simple and complex hydrocarbon (HC) fluids at mineral surfaces or within nanoporous matrices over temperatures, pressures and compositions encountered in near-surface and shallow crustal environments. The research supported by this award was complementary to that conducted by the group of Prof. David cole at Ohio State University. The scope of the present award was to utilize molecular-level modeling to provide critically important insights into the interfacial properties of mineral-volatile systems, assist in the interpretation of experimental data andmore » predict fluid behavior beyond the limits of current experimental capability. During the past three years the effort has focused primarily on the behavior of C-H volatiles including methane (CH 4) and propane (C 3H 8), mixed-volatile systems including hydrocarbon - CO 2 with and without H 2O present. The long-range goal is to quantitatively link structure, dynamics and reactivity in complex mineral-/C-H-O systems from the atomic to the molecular to the macroscopic levels. The results are relevant to areas of growing importance such as gas shale, HC-bearing hydrothermal systems, and CO 2 storage.« less

BiVO4/WO3/SnO2 Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell.

PubMed

Baek, Ji Hyun; Kim, Byeong Jo; Han, Gill Sang; Hwang, Sung Won; Kim, Dong Rip; Cho, In Sun; Jung, Hyun Suk

2017-01-18

Coupling dissimilar oxides in heterostructures allows the engineering of interfacial, optical, charge separation/transport and transfer properties of photoanodes for photoelectrochemical (PEC) water splitting. Here, we demonstrate a double-heterojunction concept based on a BiVO 4 /WO 3 /SnO 2 triple-layer planar heterojunction (TPH) photoanode, which shows simultaneous improvements in the charge transport (∼93% at 1.23 V vs RHE) and transmittance at longer wavelengths (>500 nm). The TPH photoanode was prepared by a facile solution method: a porous SnO 2 film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO 3 deposition, leading to the formation of a double layer of dense WO 3 and a WO 3 /SnO 2 mixture at the bottom. Subsequently, a BiVO 4 nanoparticle film was deposited by spin coating. Importantly, the WO 3 /(WO 3 +SnO 2 ) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO 4 /WO 3 heterojunction layer improves light absorption and charge separation. The resultant TPH photoanode shows greatly improved internal quantum efficiency (∼80%) and PEC water oxidation performance (∼3.1 mA/cm 2 at 1.23 V vs RHE) compared to the previously reported BiVO 4 /WO 3 photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoO x electrocatalyst deposition. Finally, we demonstrated a bias-free and stable solar water-splitting by constructing a tandem PEC device with a perovskite solar cell (STH ∼3.5%).

Some device implications of voltage controlled magnetic anisotropy in Co/Gd2O3 thin films through REDOX chemistry

NASA Astrophysics Data System (ADS)

Hao, Guanhua; Noviasky, Nicholas; Cao, Shi; Sabirianov, Ildar; Yin, Yuewei; Ilie, Carolina C.; Kirianov, Eugene; Sharma, Nishtha; Sokolov, Andrei; Marshall, Andrew; Xu, Xiaoshan; Dowben, Peter A.

2018-04-01

The effect of intermediate interfacial oxidation on the in-plane magnetization of multilayer stack Pt/Co/Gd2O3, on a p-type silicon substrate, has been investigated by magneto-optical Kerr effect (MOKE) measurements, the anomalous Hall effect, and magnetoresistance measurements. While voltage controlled perpendicular magnetic anisotropy of a metal/oxide heterostructure is known, this heterostructure displays an inverse relationship between voltage and coercivity. The anomalous Hall effect demonstrates a significant change in hysteresis, with the applied bias sign. There is a higher perpendicular magnetic anisotropy with positive bias exposure.

Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen.

PubMed

Mahne, Nika; Renfrew, Sara E; McCloskey, Bryan D; Freunberger, Stefan A

2018-05-04

Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal-O 2 batteries, and are believed to form and decompose reversibly in metal-O 2 /CO 2 cells. In these cathodes, Li 2 CO 3 decomposes to CO 2 when exposed to potentials above 3.8 V vs. Li/Li + . However, O 2 evolution, as would be expected according to the decomposition reaction 2 Li 2 CO 3 →4 Li + +4 e - +2 CO 2 +O 2 , is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen ( 1 O 2 ) forms upon oxidizing Li 2 CO 3 in an aprotic electrolyte and therefore does not evolve as O 2 . These results have substantial implications for the long-term cyclability of batteries: they underpin the importance of avoiding 1 O 2 in metal-O 2 batteries, question the possibility of a reversible metal-O 2 /CO 2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition-metal cathodes with residual Li 2 CO 3 . © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

DEVELOPMENT AND OPTIMIZATION OF GAS-ASSISTED GRAVITY DRAINAGE (GAGD) PROCESS FOR IMPROVED LIGHT OIL RECOVERY

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

Dandina N. Rao; Subhash C. Ayirala; Madhav M. Kulkarni

This report describes the progress of the project ''Development And Optimization of Gas-Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery'' for the duration of the thirteenth project quarter (Oct 1, 2005 to Dec 30, 2005). There are three main tasks in this research project. Task 1 is a scaled physical model study of the GAGD process. Task 2 is further development of a vanishing interfacial tension (VIT) technique for miscibility determination. Task 3 is determination of multiphase displacement characteristics in reservoir rocks. Section I reports experimental work designed to investigate wettability effects of porous medium, on secondary andmore » tertiary mode GAGD performance. The experiments showed a significant improvement of oil recovery in the oil-wet experiments versus the water-wet runs, both in secondary as well as tertiary mode. When comparing experiments conducted in secondary mode to those run in tertiary mode an improvement in oil recovery was also evident. Additionally, this section summarizes progress made with regard to the scaled physical model construction and experimentation. The purpose of building a scaled physical model, which attempts to include various multiphase mechanics and fluid dynamic parameters operational in the field scale, was to incorporate visual verification of the gas front for viscous instabilities, capillary fingering, and stable displacement. Preliminary experimentation suggested that construction of the 2-D model from sintered glass beads was a feasible alternative. During this reporting quarter, several sintered glass mini-models were prepared and some preliminary experiments designed to visualize gas bubble development were completed. In Section II, the gas-oil interfacial tensions measured in decane-CO{sub 2} system at 100 F and live decane consisting of 25 mole% methane, 30 mole% n-butane and 45 mole% n-decane against CO{sub 2} gas at 160 F have been modeled using the Parachor and newly proposed mechanistic Parachor models. In the decane-CO{sub 2} binary system, Parachor model was found to be sufficient for interfacial tension calculations. The predicted miscibility from the Parachor model deviated only by about 2.5% from the measured VIT miscibility. However, in multicomponent live decane-CO{sub 2} system, the performance of the Parachor model was poor, while good match of interfacial tension predictions has been obtained experimentally using the proposed mechanistic Parachor model. The predicted miscibility from the mechanistic Parachor model accurately matched with the measured VIT miscibility in live decane-CO2 system, which indicates the suitability of this model to predict miscibility in complex multicomponent hydrocarbon systems. In the previous reports to the DOE (15323R07, Oct 2004; 15323R08, Jan 2005; 15323R09, Apr 2005; 15323R10, July 2005 and 154323, Oct 2005), the 1-D experimental results from dimensionally scaled GAGD and WAG corefloods were reported for Section III. Additionally, since Section I reports the experimental results from 2-D physical model experiments; this section attempts to extend this 2-D GAGD study to 3-D (4-phase) flow through porous media and evaluate the performance of these processes using reservoir simulation. Section IV includes the technology transfer efforts undertaken during the quarter. This research work resulted in one international paper presentation in Tulsa, OK; one journal publication; three pending abstracts for SCA 2006 Annual Conference and an invitation to present at the Independents Day session at the IOR Symposium 2006.« less

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

Density, refractive index, interfacial tension, and viscosity of ionic liquids [EMIM][EtSO4], [EMIM][NTf2], [EMIM][N(CN)2], and [OMA][NTf2] in dependence on temperature at atmospheric pressure.

PubMed

Fröba, Andreas P; Kremer, Heiko; Leipertz, Alfred

2008-10-02

The density, refractive index, interfacial tension, and viscosity of ionic liquids (ILs) [EMIM][EtSO 4] (1-ethyl-3-methylimidazolium ethylsulfate), [EMIM][NTf 2] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), [EMIM][N(CN) 2] (1-ethyl-3-methylimidazolium dicyanimide), and [OMA][NTf 2] (trioctylmethylammonium bis(trifluoromethylsulfonyl)imide) were studied in dependence on temperature at atmospheric pressure both by conventional techniques and by surface light scattering (SLS). A vibrating tube densimeter was used for the measurement of density at temperatures from (273.15 to 363.15) K and the results have an expanded uncertainty ( k = 2) of +/-0.02%. Using an Abbe refractometer, the refractive index was measured for temperatures between (283.15 and 313.15) K with an expanded uncertainty ( k = 2) of about +/-0.0005. The interfacial tension was obtained from the pendant drop technique at a temperature of 293.15 K with an expanded uncertainty ( k = 2) of +/-1%. For higher and lower temperatures, the interfacial tension was estimated by an adequate prediction scheme based on the datum at 293.15 K and the temperature dependence of density. For the ILs studied within this work, at a first order approximation, the quantity directly accessible by the SLS technique was the ratio of surface tension to dynamic viscosity. By combining the experimental results of the SLS technique with density and interfacial tension from conventional techniques, the dynamic viscosity could be obtained for temperatures between (273.15 and 333.15) K with an estimated expanded uncertainty ( k = 2) of less than +/-3%. The measured density, refractive index, and viscosity are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with but always smaller than the expanded uncertainties ( k = 2). Besides a comparison with the literature, the influence of structural variations on the thermophysical properties of the ILs is discussed in detail. The viscosities mostly agree with values reported in the literature within the combined estimated expanded uncertainties ( k = 2) of the measurements while our density and interfacial tension data differ by more than +/-1% and +/-5%.

Heteromorphic NiCo2S4/Ni3S2/Ni Foam as a Self-Standing Electrode for Hydrogen Evolution Reaction in Alkaline Solution.

PubMed

Liu, Hui; Ma, Xiao; Rao, Yuan; Liu, Yang; Liu, Jialiang; Wang, Luyang; Wu, Mingbo

2018-04-04

Considerable works have been devoted on developing high-efficiency nonplatinum electrocatalysts for hydrogen evolution reaction (HER). Herein, 3D heteromorphic NiCo 2 S 4 /Ni 3 S 2 nanosheets network has been constructed on Ni foam (denoted as NiCo 2 S 4 /Ni 3 S 2 /NF) serving as a self-standing electrocatalyst through directly thermal sulfurization of a single-source NiCo-layered double hydroxide precursor. The resultant NiCo 2 S 4 /Ni 3 S 2 /NF electrode exhibits outstanding electrocatalytic HER performance with an extremely low onset overpotential of 15 mV and long-term durability in alkaline solution. Such enhanced HER performance can be credited to (1) the massive exposed active sites provided by mixed transition metal chalcogenides (NiCo 2 S 4 and Ni 3 S 2 ), (2) the strong interfacial interaction at NiCo 2 S 4 /Ni 3 S 2 heterojunction interfaces with the strengthened H binding, and (3) the porous highly conductive Ni foam substrate with accelerated electron transfer. This work opens up a new direction to fabricate effective and non-noble-metal electrodes for water splitting and hydrogen generation.

Effect of Carbon Black on Elastomer Blends

NASA Astrophysics Data System (ADS)

Si, Mayu; Koga, Tadanori; Ji, Yuan; Seo, Young-Soo; Rafailovich, Miriam; Sokolov, Jonathan; Gerspacher, M.; Dias, A. J.; Karp, Kriss R.; Satija, Sushil; Lin, Min Y.

2003-03-01

The effects of untreated and heat-treated carbon black N299 on the interfacial properties of PB (Polybutadiene) and terpolymer BIMS [brominated Poly(isobutylene-co-methyl styrene)] were investigated by neutron reflectivity (NR) and lateral force microscopy (LFM). The NR results show that the addition of carbon black significantly slows down the interfacial broadening while heat-treated carbon black has less effect on slowing down the diffusion compared with untreated carbon black. These results were confirmed by the LFM data, which shows the magnitude of lateral force loop of heat-treated carbon black is bigger than that of untreated one. Ultra small and small angle neutron scattering (USANS and SANS) were used to probe the morphology and surface lateral force. Increasing volume concentration of carbon black to 5glass transition temperature of BIMS is also decreased, which was measured by Differential scanning Calorimeter (DSC). XRD analysis indicates that the heat treatment crystallizes the carbon black and strong graphitic peaks are observed. The large degree of crystallization decreases the interaction with the polymer matrix and hence minimizes the effect on the internal dynamics

In-situ polymerized cellulose nanocrystals (CNC)-poly(l-lactide) (PLLA) nanomaterials and applications in nanocomposite processing.

PubMed

Miao, Chuanwei; Hamad, Wadood Y

2016-11-20

CNC-PLLA nanomaterials were synthesized via in-situ ring-opening polymerization of l-lactide in the presence of CNC, resulting in hydrophobic, homogeneous mixture of PLLA-grafted-CNC and free PLLA homopolymer. The free PLLA serves two useful functions: as barrier to further prevent PLLA-g-CNC from forming aggregates, and in creating improved interfacial properties when these nanomaterials are blended with other polymers, hence enhancing their performance. CNC-PLLA nanomaterials can be used for medical or engineering applications as-they-are or by compounding with suitable biopolymers using versatile techniques, such as solution casting, co-extrusion or injection molding, to form hybrid nanocomposites of tunable mechanical properties. When compounded with commercial-grade PLA, the resulting CNC-PLA nanocomposites appear transparent and have tailored (dynamic and static) mechanical and barrier properties, approaching those of poly(ethylene terephthalate), PET. The effect of reaction conditions on the properties of CNC-PLLA nanomaterials have been carefully studied and detailed throughout the paper. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fullerene C60: Surface Energy and Interfacial Interactions in Aqueous Systems

EPA Science Inventory

The underlying mechanisms of fullerene−fullerene, fullerene−water, and fullerene−soil surface interactions in aqueous systems are not well understood. To advance our understanding of these interfacial interactions, the surface properties of Buckminsterfullerene (C60) and quartz s...

Evolution of the interfacial perpendicular magnetic anisotropy constant of the Co2FeAl/MgO interface upon annealing

NASA Astrophysics Data System (ADS)

Conca, A.; Niesen, A.; Reiss, G.; Hillebrands, B.

2018-04-01

We investigate a series of films with different thickness of the Heusler alloy Co2FeAl in order to study the effect of annealing on the interface with a MgO layer and on the bulk magnetic properties. Our results reveal that while the perpendicular interface anisotropy constant K\\perpS is zero for the as-deposited samples, its value increases with annealing up to a value of 1.14 +/- 0.07 mJ m‑2 for the series annealed at 320 °C and of 2.01 +/- 0.7 mJ m‑2 for the 450 °C annealed series owing to a strong modification of the interface during the thermal treatment. This large value ensures a stabilization of a perpendicular magnetization orientation for an extrapolated thickness below 1.7 nm. The data additionally shows that the in-plane biaxial anisotropy constant has a different evolution with thickness in as-deposited and annealed systems. The Gilbert damping parameter α shows minima for all series for a thickness of 40 nm and an absolute minimum value of 2.8+/-0.1×10-3 . The thickness dependence is explained in terms of an inhomogeneous magnetization state generated by the interplay between the different anisotropies of the system and by the crystalline disorder.

Roll-to-Roll Nanoforming of Metals Using Laser-Induced Superplasticity.

PubMed

Goswami, Debkalpa; Munera, Juan C; Pal, Aniket; Sadri, Behnam; Scarpetti, Caio Lui P G; Martinez, Ramses V

2018-05-24

This Letter describes a low-cost, scalable nanomanufacturing process that enables the continuous forming of thin metallic layers with nanoscale accuracy using roll-to-roll, laser-induced superplasticity (R2RLIS). R2RLIS uses a laser shock to induce the ultrahigh-strain-rate deformation of metallic films at room temperature into low-cost polymeric nanomolds, independently of the original grain size of the metal. This simple and inexpensive nanoforming method does not require access to cleanrooms and associated facilities, and can be easily implemented on conventional CO 2 lasers, enabling laser systems commonly used for rapid prototyping or industrial cutting and engraving to fabricate uniform and three-dimensional crystalline metallic nanostructures over large areas. Tuning the laser power during the R2RLIS process enables the control of the aspect ratio and the mechanical and optical properties of the fabricated nanostructures. This roll-to-roll technique successfully fabricates mechanically strengthened gold plasmonic nanostructures with aspect ratios as high as 5 that exhibit high oxidation resistance and strong optical field enhancements. The CO 2 laser used in R2RLIS can also integrate the fabricated nanostructures on transparent flexible substrates with robust interfacial contact. The ability to fabricate ultrasmooth metallic nanostructures using roll-to-roll manufacturing enables the large scale production, at a relatively low-cost, of flexible plasmonic devices toward emerging applications.

Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.

PubMed

Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando

2015-10-21

The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties.

Engineering the Interfaces of Superadsorbing Graphene-Based Electrodes with Gas and Electrolyte to Boost Gas Evolution and Activation Reactions.

PubMed

Zhang, Jun-Jun; Lv, Li-Bing; Zhao, Tian-Jian; Lin, Yun-Xiao; Yu, Qiu-Ying; Su, Juan; Hirano, Shin-Ichi; Li, Xin-Hao; Chen, Jie-Sheng

2018-05-30

Electrochemical gas evolution and activation reactions are complicated processes, involving not only active electrocatalysts but also the interaction among solid electrodes, electrolyte, and gas-phase products and reactants. In this study, multiphase interfaces of superadsorbing graphene-based electrodes were controlled without changing the active centers to significantly facilitate mass diffusion kinetics for superior performance. The achieved in-depth understanding of how to regulate the interfacial properties to promote the electrochemical performance could provide valuable clues for electrode manufacture and for the design of more active electrocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano Titanium Monoxide Crystals and Unusual Superconductivity at 11 K.

PubMed

Xu, Jijian; Wang, Dong; Yao, Heliang; Bu, Kejun; Pan, Jie; He, Jianqiao; Xu, Fangfang; Hong, Zhanglian; Chen, Xiaobo; Huang, Fuqiang

2018-03-01

Nano TiO 2 is investigated intensely due to extraordinary photoelectric performances in photocatalysis, new-type solar cells, etc., but only very few synthesis and physical properties have been reported on nanostructured TiO or other low valent titanium-containing oxides. Here, a core-shell nanoparticle made of TiO core covered with a ≈5 nm shell of amorphous TiO 1+ x is newly constructed via a controllable reduction method to synthesize nano TiO core and subsequent soft oxidation to form the shell (TiO 1+ x ). The physical properties measurements of electrical transport and magnetism indicate these TiO@TiO 1+ x nanocrystals are a type-ІІ superconductor of a recorded T c onset = 11 K in the binary Ti-O system. This unusual superconductivity could be attributed to the interfacial effect due to the nearly linear gradient of O/Ti ratio across the outer amorphous layer. This novel synthetic method and enhanced superconductivity could open up possibilities in interface superconductivity of nanostructured composites with well-controlled interfaces. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Isonitrile-functionalized ruthenium nanoparticles: intraparticle charge delocalization through Ru=C=N interfacial bonds

NASA Astrophysics Data System (ADS)

Zhang, Fengqi; Huang, Lin; Zou, Jiasui; Yang, Jun; Kang, Xiongwu; Chen, Shaowei

2017-09-01

Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) stabilized by 1-hexyl-4-isocyanobenzene (CNBH), denoted as RuCNBH, were prepared by the self-assembly of isonitrile molecules onto the surface of "bare" Ru colloids by virtue of the formation of Ru=C=N- interfacial bonds. FTIR measurements showed that the stretching vibration of the terminal -N≡C bonds at 2119 cm-1 for the monomeric ligands disappeared and concurrently three new bands at 2115, 2043, and 1944 cm-1 emerged with RuCNBH nanoparticles, which was ascribed to the transformation of -N≡C to Ru=C=N- by back donation of Ru-d electrons to the π* orbital of the organic ligands. Metathesis reaction of RuCNBH with vinyl derivatives further corroborated the nature of the Ru=C interfacial bonds. When 1-isocyanopyrene (CNPy) was bounded onto the Ru nanoparticles surface through Ru=C=N interfacial bond (denoted as RuCNPy), the emission maximum was found to red-shift by 27 nm, as compared to that of the CNPy monomers, along with a reduced fluorescence lifetime, due to intraparticle charge delocalization that arose from the conjugated Ru=C=N- interfacial bonds. The results of this study further underline the significance of metal-organic interfacial bonds in the control of intraparticle charge-transfer dynamics and the optical and electronic properties of metal nanoparticles. [Figure not available: see fulltext.

Avalanche atomic switching in strain engineered Sb2Te3-GeTe interfacial phase-change memory cells

NASA Astrophysics Data System (ADS)

Zhou, Xilin; Behera, Jitendra K.; Lv, Shilong; Wu, Liangcai; Song, Zhitang; Simpson, Robert E.

2017-09-01

By confining phase transitions to the nanoscale interface between two different crystals, interfacial phase change memory heterostructures represent the state of the art for energy efficient data storage. We present the effect of strain engineering on the electrical switching performance of the {{Sb}}2{{Te}}3-GeTe superlattice van der Waals devices. Multiple Ge atoms switching through a two-dimensional Te layer reduces the activation barrier for further atoms to switch; an effect that can be enhanced by biaxial strain. The out-of-plane phonon mode of the GeTe crystal remains active in the superlattice heterostructures. The large in-plane biaxial strain imposed by the {{Sb}}2{{Te}}3 layers on the GeTe layers substantially improves the switching speed, reset energy, and cyclability of the superlattice memory devices. Moreover, carefully controlling residual stress in the layers of {{Sb}}2{{Te}}3-GeTe interfacial phase change memories provides a new degree of freedom to design the properties of functional superlattice structures for memory and photonics applications.

Analysis of Genes for Succinoyl Trehalose Lipid Production and Increasing Production in Rhodococcus sp. Strain SD-74

PubMed Central

Inaba, Tomohiro; Tokumoto, Yuta; Miyazaki, Yusuke; Inoue, Naoyuki; Maseda, Hideaki; Nakajima-Kambe, Toshiaki; Uchiyama, Hiroo

2013-01-01

Succinoyl trehalose lipids (STLs) are promising glycolipid biosurfactants produced from n-alkanes that are secreted by Rhodococcus species bacteria. These compounds not only exhibit unique interfacial properties but also demonstrate versatile biochemical actions. In this study, three novel types of genes involved in the biosynthesis of STLs, including a putative acyl coenzyme A (acyl-CoA) transferase (tlsA), fructose-bisphosphate aldolase (fda), and alkane monooxygenase (alkB), were identified. The predicted functions of these genes indicate that alkane metabolism, sugar synthesis, and the addition of acyl groups are important for the biosynthesis of STLs. Based on these results, we propose a biosynthesis pathway for STLs from alkanes in Rhodococcus sp. strain SD-74. By overexpressing tlsA, we achieved a 2-fold increase in the production of STLs. This study advances our understanding of bacterial glycolipid production in Rhodococcus species. PMID:24038682

Activated desorption at heterogeneous interfaces and long-time kinetics of hydrocarbon recovery from nanoporous media.

PubMed

Lee, Thomas; Bocquet, Lydéric; Coasne, Benoit

2016-06-21

Hydrocarbon recovery from unconventional reservoirs (shale gas) is debated due to its environmental impact and uncertainties on its predictability. But a lack of scientific knowledge impedes the proposal of reliable alternatives. The requirement of hydrofracking, fast recovery decay and ultra-low permeability-inherent to their nanoporosity-are specificities of these reservoirs, which challenge existing frameworks. Here we use molecular simulation and statistical models to show that recovery is hampered by interfacial effects at the wet kerogen surface. Recovery is shown to be thermally activated with an energy barrier modelled from the interface wetting properties. We build a statistical model of the recovery kinetics with a two-regime decline that is consistent with published data: a short time decay, consistent with Darcy description, followed by a fast algebraic decay resulting from increasingly unreachable energy barriers. Replacing water by CO2 or propane eliminates the barriers, therefore raising hopes for clean/efficient recovery.

Electrocatalytic performance of Pt nanoparticles sputter-deposited on indium tin oxide toward methanol oxidation reaction: The particle size effect

NASA Astrophysics Data System (ADS)

Ting, Chao-Cheng; Chao, Chih-Hsuan; Tsai, Cheng Yu; Cheng, I.-Kai; Pan, Fu-Ming

2017-09-01

We sputter-deposited Pt nanoparticles with an average size ranging from 2.0 nm to 8.5 nm on the indium-tin oxide (ITO) glass substrate, and studied the effect of the size of Pt nanoparticles on electrocatalytic activity of the Pt/ITO electrode toward methanol oxidation reaction (MOR) in acidic solution. X-ray photoelectron spectroscopy (XPS) reveals an interfacial oxidized Pt layer present between Pt nanoparticles and the ITO substrate, which may modify the surface electronic structure of Pt nanoparticles and thus influences the electrocatalytic properties of the Pt catalyst toward MOR. According to electrochemical analyses, smaller Pt nanoparticles exhibit slower kinetics for CO electrooxidation and MOR. However, a smaller particle size enables better CO tolerance because the bifunctional mechanism is more effective on smaller Pt nanoparticles. The electrocatalytic activity decays rapidly for Pt nanoparticles with a size smaller than 3 nm and larger than 8 nm. The rapid activity decay is attributed to Pt dissolution for smaller nanoparticles and to CO poisoning for larger ones. Pt nanoparticles of 5-6 nm in size loaded on ITO demonstrate a greatly improved electrocatalytic activity and stability compared with those deposited on different substrates in our previous studies.