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Sample records for 2d double layer

  1. Tunable Electronic Transport Properties of 2D Layered Double Hydroxide Crystalline Microsheets with Varied Chemical Compositions.

    PubMed

    Zhao, Yibing; Hu, Hai; Yang, Xiaoxia; Yan, Dongpeng; Dai, Qing

    2016-09-01

    Transistors based on layered double hydroxides (LDH) single microcrystal are fabricated, whose conductivity of LDH can be tuned by varying metal cations or interlayer anions, but weakly affected by external electric field. The carrier mobility can reach about 1 × 10(-5) cm(2) V(-1) s(-1) , a value comparable to that of organic C60-based transistors. This work paves a way for future electrical applications of LDH. PMID:27416544

  2. 2D double-layer-tube-shaped structure Bi2S3/ZnS heterojunction with enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Wang, Zihang; Fu, Feng; Li, Xiang; Li, Wenhong

    2015-10-01

    Bi2S3/ZnS heterojunction with 2D double-layer-tube-shaped structures was prepared by the facile synthesis method. The corresponding relationship was obtained among loaded content to phase, morphology, and optical absorption property of Bi2S3/ZnS composite. The results shown that Bi2S3 loaded could evidently change the crystallinity of ZnS, enhance the optical absorption ability for visible light of ZnS, and improve the morphologies and microstructure of ZnS. The photocatalytic activities of the Bi2S3/ZnS sample were evaluated for the photodegradation of phenol and desulfurization of thiophene under visible light irradiation. The results showed that Bi2S3 loaded greatly improved the photocatalytic activity of ZnS, and the content of loaded Bi2S3 had an impact on the catalytic activity of ZnS. Moreover, the mechanism of enhanced photocatalytic activity was also investigated by analysis of relative band positions of Bi2S3 and ZnS, and photo-generated hole was main active radicals during photocatalytic oxidation process.

  3. Double Layers in Astrophysics

    NASA Technical Reports Server (NTRS)

    Williams, Alton C. (Editor); Moorehead, Tauna W. (Editor)

    1987-01-01

    Topics addressed include: laboratory double layers; ion-acoustic double layers; pumping potential wells; ion phase-space vortices; weak double layers; electric fields and double layers in plasmas; auroral double layers; double layer formation in a plasma; beamed emission from gamma-ray burst source; double layers and extragalactic jets; and electric potential between plasma sheet clouds.

  4. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. PMID:25169938

  5. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials.

  6. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  7. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  8. Optical modulators with 2D layered materials

    NASA Astrophysics Data System (ADS)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.

  9. On 2D bisection method for double eigenvalue problems

    SciTech Connect

    Ji, X.

    1996-06-01

    The two-dimensional bisection method presented in (SIAM J. Matrix Anal. Appl. 13(4), 1085 (1992)) is efficient for solving a class of double eigenvalue problems. This paper further extends the 2D bisection method of full matrix cases and analyses its stability. As in a single parameter case, the 2D bisection method is very stable for the tridiagonal matrix triples satisfying the symmetric-definite condition. Since the double eigenvalue problems arise from two-parameter boundary value problems, an estimate of the discretization error in eigenpairs is also given. Some numerical examples are included. 42 refs., 1 tab.

  10. Double resonance rotational spectroscopy of CH2D+

    NASA Astrophysics Data System (ADS)

    Töpfer, Matthias; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar

    2016-09-01

    Context. Deuterated forms of CH are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH2D+ in space to date. Aims: Four submillimetre rotational lines of CH2D+ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection. Methods: We used a low-temperature ion trap and applied a novel IR-mm-wave double resonance method to measure the rotational lines of CH2D+. Results: We measured 21 low-lying (J ≤ 4) rotational transitions of CH2D+ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.

  11. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

  12. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  13. Van der Waals stacked 2D layered materials for optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjing; Wang, Qixing; Chen, Yu; Wang, Zhuo; Wee, Andrew T. S.

    2016-06-01

    The band gaps of many atomically thin 2D layered materials such as graphene, black phosphorus, monolayer semiconducting transition metal dichalcogenides and hBN range from 0 to 6 eV. These isolated atomic planes can be reassembled into hybrid heterostructures made layer by layer in a precisely chosen sequence. Thus, the electronic properties of 2D materials can be engineered by van der Waals stacking, and the interlayer coupling can be tuned, which opens up avenues for creating new material systems with rich functionalities and novel physical properties. Early studies suggest that van der Waals stacked 2D materials work exceptionally well, dramatically enriching the optoelectronics applications of 2D materials. Here we review recent progress in van der Waals stacked 2D materials, and discuss their potential applications in optoelectronics.

  14. Tests on Double Layer Metalization

    NASA Technical Reports Server (NTRS)

    Woo, D. S.

    1983-01-01

    28 page report describes experiments in fabrication of integrated circuits with double-layer metalization. Double-layer metalization requires much less silicon "real estate" and allows more flexibility in placement of circuit elements than does single-layer metalization.

  15. Teaching the Double Layer.

    ERIC Educational Resources Information Center

    Bockris, J. O'M.

    1983-01-01

    Suggests various methods for teaching the double layer in electrochemistry courses. Topics addressed include measuring change in absolute potential difference (PD) at interphase, conventional electrode potential scale, analyzing absolute PD, metal-metal and overlap electron PDs, accumulation of material at interphase, thermodynamics of electrified…

  16. Double layer secure sketch

    NASA Astrophysics Data System (ADS)

    Li, Cai

    2012-09-01

    Secure sketch has been applied successfully in a wide variety of applications like cryptography, biometric authentication systems and so on. All of these secure sketches have properties in common namely error-tolerance and small entropy loss. The former ensures an input set w' can unlock the system if w' is substantially overlapped with a template set w while the latter means it is hard for an adversary to get the information of w even with the knowledge of s, which is produced by w and stored in the system publicly. In their constructions, they all consider w as a set of atomic elements. However, in the real word, it is very likely the elements in the template set are sets as well. In this paper, we propose a double layer secure sketch to address this issue.

  17. Interpretive 2-D treatment of scrape-off-layer plasmas

    SciTech Connect

    Umansky, M.; Allen, A.; Daughton, W.

    1996-12-31

    The width of the scrape-off-layer in a tokamak is determined by cross field transport. In Alcator C-mod the plasma parameters in the scrape-off-layer are measured at upstream and divertor plate locations. We solve a 2-D scrape-off-layer heat conduction equation in the flux geometry (as determined by EFIT) of the C-mod experiment. Bolometric measurements are utilized for the radiative loss term. We use the end wall probe measurements of electron temperature as a boundary condition and the fast scanning probe measurements of upstream temperature are treated as constraints to determine the cross field transport and thermal conductivity. Results are compared with 1-D onion-skin-model predictions.

  18. Advanced double layer capacitors

    NASA Technical Reports Server (NTRS)

    Sarangapani, S.; Lessner, P.; Forchione, J.; Laconti, A. B.

    1989-01-01

    There is a need for large amounts of power to be delivered rapidly in a number of airborne and space systems. Conventional, portable power sources, such as batteries, are not suited to delivering high peak power pulses. The charge stored at the electrode-electrolyte double layer is, however, much more assessible on a short time scale. Devices exploiting this concept were fabricated using carbon and metal oxides (Pinnacle Research) as the electrodes and sulfuric acid as the electrolyte. The approach reported, replaces the liquid sulfuric acid electrolyte with a solid ionomer electrolyte. The challenge is to form a solid electrode-solid ionomer electrolyte composite which has a high capacitance per geometric area. The approach to maximize contact between the electrode particles and the ionomer was to impregnate the electrode particles using a liquid ionomer solution and to bond the solvent-free structure to a solid ionomer membrane. Ruthenium dioxide is the electrode material used. Three strategies are being pursued to provide for a high area electrode-ionomer contact: mixing of the RuOx with a small volume of ionomer solution followed by filtration to remove the solvent, and impregnation of the ionomer into an already formed RuOx electrode. RuOx powder and electrodes were examined by non-electrochemical techniques. X-ray diffraction has shown that the material is almost pure RuO2. The electrode structure depends on the processing technique used to introduce the Nafion. Impregnated electrodes have Nafion concentrated near the surface. Electrodes prepared by the evaporation method show large aggregates of crystals surrounded by Nafion.

  19. Spotting 2D atomic layers on aluminum nitride thin films.

    PubMed

    Chandrasekar, Hareesh; Bharadwaj B, Krishna; Vaidyuala, Kranthi Kumar; Suran, Swathi; Bhat, Navakanta; Varma, Manoj; Srinivasan Raghavan

    2015-10-23

    Substrates for 2D materials are important for tailoring their fundamental properties and realizing device applications. Aluminum nitride (AIN) films on silicon are promising large-area substrates for such devices in view of their high surface phonon energies and reasonably large dielectric constants. In this paper epitaxial layers of AlN on 2″ Si wafers have been investigated as a necessary first step to realize devices from exfoliated or transferred atomic layers. Significant thickness dependent contrast enhancements are both predicted and observed for monolayers of graphene and MoS2 on AlN films as compared to the conventional SiO2 films on silicon, with calculated contrast values approaching 100% for graphene on AlN as compared to 8% for SiO2 at normal incidences. Quantitative estimates of experimentally measured contrast using reflectance spectroscopy show very good agreement with calculated values. Transistors of monolayer graphene on AlN films are demonstrated, indicating the feasibility of complete device fabrication on the identified layers.

  20. Ab initio modeling of 2D layered organohalide lead perovskites.

    PubMed

    Fraccarollo, Alberto; Cantatore, Valentina; Boschetto, Gabriele; Marchese, Leonardo; Cossi, Maurizio

    2016-04-28

    A number of 2D layered perovskites A2PbI4 and BPbI4, with A and B mono- and divalent ammonium and imidazolium cations, have been modeled with different theoretical methods. The periodic structures have been optimized (both in monoclinic and in triclinic systems, corresponding to eclipsed and staggered arrangements of the inorganic layers) at the DFT level, with hybrid functionals, Gaussian-type orbitals and dispersion energy corrections. With the same methods, the various contributions to the solid stabilization energy have been discussed, separating electrostatic and dispersion energies, organic-organic intralayer interactions and H-bonding effects, when applicable. Then the electronic band gaps have been computed with plane waves, at the DFT level with scalar and full relativistic potentials, and including the correlation energy through the GW approximation. Spin orbit coupling and GW effects have been combined in an additive scheme, validated by comparing the computed gap with well known experimental and theoretical results for a model system. Finally, various contributions to the computed band gaps have been discussed on some of the studied systems, by varying some geometrical parameters and by substituting one cation in another's place. PMID:27131557

  1. Simulation of auroral double layers

    NASA Technical Reports Server (NTRS)

    Hubbard, R. F.; Joyce, G.

    1979-01-01

    Some basic properties of plasma double layers are deduced from a particle-in-cell computer simulation and related to parallel electric-field structures above the auroral regions. The simulation results on the processes leading to double-layer formation are examined, particularly in relation to the transient stage and double-layer structure and stability. It is concluded that: (1) a large potential difference applied to a finite-length plasma will be concentrated in a shocklike localized region instead of occurring over the entire length of the system; (2) the initial stage in double-layer formation is dominated by a large-potential pulse propagating in the direction of the induced electrostatic drift; (3) the entire potential is dropped over a specific scale length once the double layer has formed; and (4) this scale length is expected to be of the order of 1 km for a double layer above a discrete auroral arc with a potential of 10 kV and the electric-field vector parallel to the magnetic-field vector.

  2. Double layers above the aurora

    NASA Technical Reports Server (NTRS)

    Temerin, M.; Mozer, F. S.

    1987-01-01

    Two different kinds of double layers were found in association with auroral precipitation. One of these is the so-called electrostatic shock, which is oriented at an oblique angle to the magnetic field in such a way that the perpendicular electric field is much larger than the parallel electric field. This type of double layer is often found at the edges of regions of upflowing ion beams and the direction of the electric fields in the shock points toward the ion beam. The potential drop through the shock can be several kV and is comparable to the total potential needed to produce auroral acceleration. Instabilities associated with the shock may generate obliquely propagating Alfven waves, which may accelerate electrons to produce flickering auroras. The flickering aurora provides evidence that the electrostatic shock may have large temporal fluctuations. The other kind of double layer is the small-amplitude double layer found in regions of upward flowing in beams, often in association with electrostatic ion cyclotron waves. The parallel and perpendicular electric fields in these structures are comparable in magnitude. The associated potentials are a few eV. Since many such double layers are found in regions of upward flowing ion beams, the combined potential drop through a set of these double layers can be substantial.

  3. A 2-D semi-analytical model of double-gate tunnel field-effect transistor

    NASA Astrophysics Data System (ADS)

    Huifang, Xu; Yuehua, Dai; Ning, Li; Jianbin, Xu

    2015-05-01

    A 2-D semi-analytical model of double gate (DG) tunneling field-effect transistor (TFET) is proposed. By aid of introducing two rectangular sources located in the gate dielectric layer and the channel, the 2-D Poisson equation is solved by using a semi-analytical method combined with an eigenfunction expansion method. The expression of the surface potential is obtained, which is a special function for the infinite series expressions. The influence of the mobile charges on the potential profile is taken into account in the proposed model. On the basis of the potential profile, the shortest tunneling length and the average electrical field can be derived, and the drain current is then constructed by using Kane's model. In particular, the changes of the tunneling parameters Ak and Bk influenced by the drain—source voltage are also incorporated in the predicted model. The proposed model shows a good agreement with TCAD simulation results under different drain—source voltages, silicon film thicknesses, gate dielectric layer thicknesses, and gate dielectric layer constants. Therefore, it is useful to optimize the DG TFET and this provides a physical insight for circuit level design. Project supported by the National Natural Science Foundation of China (No. 61376106) and the Graduate Innovation Fund of Anhui University.

  4. Probing dipole-dipole interaction in a rubidium gas via double-quantum 2D spectroscopy.

    PubMed

    Gao, Feng; Cundiff, Steven T; Li, Hebin

    2016-07-01

    We have implemented double-quantum 2D spectroscopy on a rubidium vapor and shown that this technique provides sensitive and background-free detection of the dipole-dipole interaction. The 2D spectra include signals from both individual atoms and interatomic interactions, allowing quantitative studies of the interaction. A theoretical model based on the optical Bloch equations is used to reproduce the experimental spectrum and confirm the origin of double-quantum signals. PMID:27367074

  5. A laboratory investigation of potential double layers

    NASA Technical Reports Server (NTRS)

    Leung, Philip

    1987-01-01

    In a triple plasma device, the injection of electron current from the source chamber to the target chamber causes the formation of a potential double layer. At a low current density, the space charge of the injected current produces a virtual cathode-type potential double layer. This double layer is stable, and various wave instabilities are observed to associate with this double layer. As the current density is increased, the double layer becomes unstable, and a moving double layer results. As the current density is increased further, the enhanced ionization causes the neutralization of the space charge of the electron beam, and the beam plasma discharge is ignited.

  6. A laboratory investigation of potential double layers

    NASA Technical Reports Server (NTRS)

    Leung, Philip

    1987-01-01

    In a triple plasma device, the injection of electron current from the source chamber to the target chamber causes the formation of a potential double layer. At a low current density, the space charge of the injected current produces a virtual cathode-type potential double layer. This double layer is stable and various wave instabilities are observed to associate with this double layer. As the current density is increased, the double layer becomes unstable and a moving double layer results. As the current density is increased further, the enhanced ionization causes the neutralization of the space charge of the electron beam and the 'beam plasma discharge' is ignited.

  7. Layer-by-Layer Assembled 2D Montmorillonite Dielectrics for Solution-Processed Electronics.

    PubMed

    Zhu, Jian; Liu, Xiaolong; Geier, Michael L; McMorrow, Julian J; Jariwala, Deep; Beck, Megan E; Huang, Wei; Marks, Tobin J; Hersam, Mark C

    2016-01-01

    Layer-by-layer assembled 2D montmorillonite nanosheets are shown to be high-performance, solution-processed dielectrics. These scalable and spatially uniform sub-10 nm thick dielectrics yield high areal capacitances of ≈600 nF cm(-2) and low leakage currents down to 6 × 10(-9) A cm(-2) that enable low voltage operation of p-type semiconducting single-walled carbon nanotube and n-type indium gallium zinc oxide field-effect transistors. PMID:26514248

  8. Control of electronic properties of 2D carbides (MXenes) by manipulating their transition metal layers

    DOE PAGES

    Anasori, Babak; Shi, Chenyang; Moon, Eun Ju; Xie, Yu; Voigt, Cooper A.; Kent, Paul R. C.; May, Steven J.; Billinge, Simon J. L.; Barsoum, Michel W.; Gogotsi, Yury

    2016-02-24

    In this paper, a transition from metallic to semiconducting-like behavior has been demonstrated in two-dimensional (2D) transition metal carbides by replacing titanium with molybdenum in the outer transition metal (M) layers of M3C2 and M4C3 MXenes. The MXene structure consists of n + 1 layers of near-close packed M layers with C or N occupying the octahedral site between them in an [MX]nM arrangement. Recently, two new families of ordered 2D double transition metal carbides MXenes were discovered, M'2M"C2 and M'2M"2C3 – where M' and M" are two different early transition metals, such as Mo, Cr, Ta, Nb, V, andmore » Ti. The M' atoms only occupy the outer layers and the M" atoms fill the middle layers. In other words, M' atomic layers sandwich the middle M"–C layers. Using X-ray atomic pair distribution function (PDF) analysis on Mo2TiC2 and Mo2Ti2C3 MXenes, we present the first quantitative analysis of structures of these novel materials and experimentally confirm that Mo atoms are in the outer layers of the [MC]nM structures. The electronic properties of these Mo-containing MXenes are compared with their Ti3C2 counterparts, and are found to be no longer metallic-like conductors; instead the resistance increases mildly with decreasing temperatures. Density functional theory (DFT) calculations suggest that OH terminated Mo–Ti MXenes are semiconductors with narrow band gaps. Measurements of the temperature dependencies of conductivities and magnetoresistances have confirmed that Mo2TiC2Tx exhibits semiconductor-like transport behavior, while Ti3C2Tx is a metal. Finally, this finding opens new avenues for the control of the electronic and optical applications of MXenes and for exploring new applications, in which semiconducting properties are required.« less

  9. Dynamical aspects of electrostatic double layers

    NASA Astrophysics Data System (ADS)

    Raadu, Michael A.; Rasmussen, J. Juul

    1988-05-01

    Electrostatic double layers have been proposed as an acceleration mechanism in solar flares and other astrophysical objects. They have been extensively studied in the laboratory and by means of computer simulations. The theory of steady-state double layers implies several existence criteria, in particular the Bohm criteria, restricting the conditions under which double layers may form. In the present paper several already published theoretical models of different types of double layers are discussed. It is shown that the existence conditions often imply current-driven instabilities in the ambient plasma, at least for strong double layers, and it is argued that such conditions must be used with care when applied to real plasmas. Laboratory double layers, and by implication those arising in astrophysical plasmas, often produce instabilities in the surrounding plasma and are generally time-dependent structures. Naturally occurring double layers should therefore, be far more common than the restrictions deduced from idealized time-independent models would imply. In particular it is necessary to understand more fully the time-dependent behavior of double layers. In the present paper the dynamics of weak double layers is discussed. Also a model for moving a strong double layer, where an associated potential minimum plays a significant role, is presented.

  10. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways.

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-01-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout. PMID:27464908

  11. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways.

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-07-28

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.

  12. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

    NASA Astrophysics Data System (ADS)

    Wang, Zenghui; Feng, Philip X.-L.

    2016-07-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.

  13. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

    PubMed Central

    Wang, Zenghui; Feng, Philip X.-L.

    2016-01-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout. PMID:27464908

  14. Double layers and circuits in astrophysics

    NASA Technical Reports Server (NTRS)

    Alfven, Hannes

    1986-01-01

    As the rate of energy release in a double layer with voltage delta V is P approx I delta V, a double layer must be treated as a part of a circuit which delivers the current I. As neither double layer nor circuit can be derived from magnetofluid models of a plasma, such models are useless for treating energy transfer by means of double layers. They must be replaced by particle models and circuit theory. A simple circuit is suggested which is applied to the energizing of auroral particles, to solar flares, and to intergalactic double radio sources. Application to the heliospheric current systems leads to the prediction of two double layers on the Sun's axis which may give radiations detectable from Earth. Double layers in space should be classified as a new type of celestial object (one example is the double radio sources). It is tentatively suggested in X-ray and Gamma-ray bursts may be due to exploding double layers (although annihilation is an alternative energy source). A study of how a number of the most used textbooks in astrophysics treat important concepts like double layers, critical velocity, pinch effects and circuits is made.

  15. Double layers and circuits in astrophysics

    SciTech Connect

    Alfven, H.

    1986-12-01

    As the rate of energy release in a double layer with voltage ..delta..V is P approx. = I..delta..V, a double layer must be treated as a part of a circuit which delivers the current I. As neither double layer nor circuit can be derived from magnetofluid models of a plasma, such models are useless for treating energy transfer by means of double layers. They must be replaced by particle models and circuit theory. A simple circuit is suggested which is applied to the energizing of auroral particles, to solar flares, and to intergalactic double radio sources. Application to the heliospheric current systems leads to the prediction of two double layers on the sun's axis which may give radiations detectable from Earth. Double layers in space should be classified as a new type of celestial object (one example is the double radio sources). It is tentatively suggested that X-ray and ..gamma..-ray bursts may be due to exploding double layers (although annihilation is an alternative energy source). A study of how a number of the most used textbooks in astrophysics treat important concepts such as double layers, critical velocity, pinch effects, and circuits is made.

  16. Electron temperature differences and double layers

    NASA Technical Reports Server (NTRS)

    Chan, C.; Hershkowitz, N.; Lonngren, K. E.

    1983-01-01

    Electron temperature differences across plasma double layers are studied experimentally. It is shown that the temperature differences across a double layer can be varied and are not a result of thermalization of the bump-on-tail distribution. The implications of these results for electron thermal energy transport in laser-pellet and tandem-mirror experiments are also discussed.

  17. Height-dependent transition from 3-D to 2-D turbulence in the hurricane boundary layer

    NASA Astrophysics Data System (ADS)

    Byrne, David; Zhang, Jun A.

    2013-04-01

    Here we show, from in situ aircraft measurements in the hurricane boundary layer, a height-dependent transition of the flow from 3-D to 2-D turbulence. This marks a fundamental change in the energy dynamics of the hurricane boundary layer due to the fact that in 3-D, energy flows downscale from larger to smaller scales, whereas in 2-D, it flows upscale, from smaller to larger scales. These results represent the first measurement of the 2-D upscale energy flux in the atmosphere and also the first to characterize the transition from 3-D to 2-D. It is shown that the large-scale parent vortex may gain energy directly from small scales in tropical cyclones.

  18. Few-layer III-VI and IV-VI 2D semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Sucharitakul, Sukrit; Liu, Mei; Kumar, Rajesh; Sankar, Raman; Chou, Fang C.; Chen, Yit-Tsong; Gao, Xuan

    Since the discovery of atomically thin graphene, a large variety of exfoliable 2D materials have been thoroughly explored for their exotic transport behavior and promises in technological breakthroughs. While most attention on 2D materials beyond graphene is focused on transition metal-dichalcogenides, relatively less attention is paid to layered III-VI and IV-VI semiconductors such as InSe, SnSe etc which bear stronger potential as 2D materials with high electron mobility or thermoelectric figure of merit. We will discuss our recent work on few-layer InSe 2D field effect transistors which exhibit carrier mobility approaching 1000 cm2/Vs and ON-OFF ratio exceeding 107 at room temperature. In addition, the fabrication and device performance of transistors made of mechanically exfoliated multilayer IV-VI semiconductor SnSe and SnSe2 will be discussed.

  19. Instability limits for spontaneous double layer formation

    SciTech Connect

    Carr, J. Jr.; Galante, M. E.; McCarren, D.; Scime, E. E.; Sears, S.; VanDervort, R. W.; Magee, R. M.; Reynolds, E.

    2013-11-15

    We present time-resolved measurements that demonstrate that large amplitude electrostatic instabilities appear in pulsed, expanding helicon plasmas at the same time as particularly strong double layers appear in the expansion region. A significant cross-correlation between the electrostatic fluctuations and fluctuations in the number of ions accelerated by the double layer electric field is observed. No correlation is observed between the electrostatic fluctuations and ions that have not passed through the double layer. These measurements confirm that the simultaneous appearance of the electrostatic fluctuations and the double layer is not simple coincidence. In fact, the accelerated ion population is responsible for the growth of the instability. The double layer strength, and therefore, the velocity of the accelerated ions, is limited by the appearance of the electrostatic instability.

  20. Electric fields and double layers in plasmas

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1987-01-01

    Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamical features of the double layers are discussed. These features, as seen in simulations, laboratory experiments, and theory, indicate that double layers and the currents through them undergo slow oscillations which are determined by the ion transit time across an effective length of the system in which double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations were considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields and double layers in an expanding plasma is discussed.

  1. Double layers and circuits in astrophysics

    NASA Technical Reports Server (NTRS)

    Alfven, H.

    1986-01-01

    A simple circuit is applied to the energizing of auroral particles, to solar flares, and to intergalactic double radio sources. Application to the heliospheric current systems leads to the prediction of two double layers on the Sun's axis which may give radiations detectable from Earth. Double layers in space should be classified as a new type of celestial object. It is suggested that X-ray and gamma-ray bursts may be due to exploding double layers (although annihilation is an alternative energy source). The way the most used textbooks in astrophysics treat concepts like double layers, critical velocity, pinch effects and circuits was studied. It is found that students using these textbooks remain essentially ignorant of even the existence of these, although some of the phenomena were discovered 50 yr ago.

  2. Double layers and circuits in astrophysics

    SciTech Connect

    Alfven, H.

    1986-05-01

    A simple circuit is applied to the energizing of auroral particles, to solar flares, and to intergalactic double radio sources. Application to the heliospheric current systems leads to the prediction of two double layers on the Sun's axis which may give radiations detectable from Earth. Double layers in space should be classified as a new type of celestial object. It is suggested that x-ray and gamma-ray bursts may be due to exploding double layers (although annihilation is an alternative energy source). The way the most used textbooks in astrophysics treat concepts like double layers, critical velocity, pinch effects and circuits was studied. It is found that students using these textbooks remain essentially ignorant of even the existence of these, although some of the phenomena were discovered 50 yr ago.

  3. Part I. Layered Double Hydroxides

    NASA Astrophysics Data System (ADS)

    Dimotakis, Emmanuel Dimitrios

    A new general method for the preparation of well -ordered layered double hydroxides (LDHs), (Mg_ {rm 1-x}Al_{ rm x} (OH)_2) (X^{rm n-}) _{rm n/x}{cdot}yH _2O, interlayered by organic anions has been developed. It is based on the reaction of meixnerite, (Mg_3Al(OH)_8) (OH) cdot2H_2O, with the free acid form of the desired anion--using glycerol as a swelling agent--to yield single crystalline products that are not readily available by conventional synthetic methods. The (Mg_3Al(OH) _8) -adipate and -p-toluenesulfonate derivatives undergo facile ion exchange reactions with Keggin-type (XM_{12}O_ {40}) ^{rm n -} or lacunary (XM_{11 }O_{39}) ^{rm m-} polyoxometalates (POMs) to form well-ordered, microporous pillared derivatives with the highest N_2 BET surface areas reported to date, namely 107 and 155 m^2 /g, respectively. Meixnerite, (Mg_3Al(OH) _8) (OH) cdot2H _2O, has unexpectedly been found to undergo similar ion exchange reactions, in a topotactic way, with retention of the structure of the intercalated POMs. The meixnerite was conveniently prepared for the first time from calcination of (Mg_3Al(OH) _8) (CO_3) _{0.5}{cdot}2H _2O and aqueous hydrolysis of the resulting NaCl-type solid solution. Metal carbonyl clusters have also been examined for ion-exchange (i.e., { (Pt _3(CO)_6) _{rm n}}^ {2-}) in these LDH-precursors. This chemistry is compared with the surface chemistry of (Mg_3 Al(OH)_8) (X^ {rm n-}) _{ rm 1/n}{cdot}2H _2O (X = CO_3^{2 -} or OH^{-}). It has been shown that the surface hydrolysis reaction: CO _3^{2-} + H _2O longrightarrow HCO_3^{-} + OH ^-, causes reductive condensation reactions of neutral carbonyl clusters with the LDH. The reactions were as efficient as with Na metal in solution. In part II of this work, Li-fluorohectorite, has been pillared with titanium polyoxocations derived from the acidic hydrolysis of TiCl_4 or Ti(i-OC_3H_7) _4. Raman spectroscopy of the product indicates that the pillars have a structure analogous to TiO_2(B) phase

  4. Double layers on auroral field lines

    NASA Technical Reports Server (NTRS)

    Hudson, M. K.; Lotko, W.; Witt, E.

    1982-01-01

    Time-stationary solutions to the Vlasov-Poisson equation for ion holes and double layers were examined along with particle simulations which pertain to recent observations of small amplitude (e phi)/t sub e approx. 1 electric field structures on auroral field lines. Both the time-stationary analysis and the simulations suggest that double layers evolve from holes in ion phase space when their amplitude reaches (e phi)/t sub e approx. 1. Multiple small amplitude double layers which are seen in long simulation systems and are seen to propagate past spacecraft may account for the acceleration of plasma sheet electrons to produce the discrete aurora.

  5. Layout decomposition of self-aligned double patterning for 2D random logic patterning

    NASA Astrophysics Data System (ADS)

    Ban, Yongchan; Miloslavsky, Alex; Lucas, Kevin; Choi, Soo-Han; Park, Chul-Hong; Pan, David Z.

    2011-04-01

    Self-aligned double pattering (SADP) has been adapted as a promising solution for sub-30nm technology nodes due to its lower overlay problem and better process tolerance. SADP is in production use for 1D dense patterns with good pitch control such as NAND Flash memory applications, but it is still challenging to apply SADP to 2D random logic patterns. The favored type of SADP for complex logic interconnects is a two mask approach using a core mask and a trim mask. In this paper, we first describe layout decomposition methods of spacer-type double patterning lithography, then report a type of SADP compliant layouts, and finally report SADP applications on Samsung 22nm SRAM layout. For SADP decomposition, we propose several SADP-aware layout coloring algorithms and a method of generating lithography-friendly core mask patterns. Experimental results on 22nm node designs show that our proposed layout decomposition for SADP effectively decomposes any given layouts.

  6. Stitching 2D polymeric layers into flexible interpenetrated metal-organic frameworks within single crystals.

    PubMed

    Zhang, Zi-Xuan; Ding, Ni-Ni; Zhang, Wen-Hua; Chen, Jin-Xiang; Young, David J; Hor, T S Andy

    2014-04-25

    A 2D coordination polymer prepared with bulky diethylformamide solvates exhibits channels which allow dipyridyl bridging ligands to diffuse into the crystal lattice. The absorbed dipyridyls thread through the pores of one layer and substitute the surface diethylformamide molecules on the neighboring layers to stitch alternate layers to form flexible interpenetrated metal-orgaic frameworks. The threading process also results in exchange of the bulky diethylformamide solvates for aqua to minimize congestion and, more strikingly, forces the slippage of two-dimensional layers, while still maintaining crystallinity. PMID:24692130

  7. 2D water layer enclathrated between Mn(II)-Ni(CN){sub 4} coordination frameworks

    SciTech Connect

    Ray, Ambarish; Bhowmick, Indrani; Sheldrick, William S.; Jana, Atish Dipankar; Ali, Mahammed

    2009-10-15

    A [Ni(CN){sub 4}]{sup 2-}based two-dimensional Mn(II) coordination polymer {l_brace}Mn(H{sub 2}O){sub 2}[NiCN]{sub 4}.4H{sub 2}O{r_brace}, in which the coordination layers are stacked on top of each other sandwiching 2D water layer of boat-shaped hexagonal water clusters has been synthesized. The complex exhibits high thermal decomposition temperature and reversible water absorption, which were clearly demonstrated by thermal and PXRD studies on the parent and rehydrated complex after dehydration. - Abstract: A coordination polymer, {l_brace}Mn(H{sub 2}O){sub 2}[NiCN]{sub 4}.4H{sub 2}O{r_brace}{sub n}, showed that the coordination layers are stacked on top of each other sandwiching 2D ice layer of boat-shaped hexagonal water clusters . Display Omitted

  8. Comparison with Analytical Solution: Generation and Radiation of Acoustic Waves from a 2-D Shear Layer

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2000-01-01

    An acoustic source inside of a 2-D jet excites an instability wave in the shear layer resulting in sound radiating away from the shear layer. Solve the linearized Euler equations to predict the sound radiation outside of the jet. The jet static pressure is assumed to be constant. The jet flow is parallel and symmetric about the x-axis. Use a symmetry boundary condition along the x-axis.

  9. A new hydrodynamic analysis of double layers

    NASA Technical Reports Server (NTRS)

    Hora, Heinrich

    1987-01-01

    A genuine two-fluid model of plasmas with collisions permits the calculation of dynamic (not necessarily static) electric fields and double layers inside of plasmas including oscillations and damping. For the first time a macroscopic model for coupling of electromagnetic and Langmuir waves was achieved with realistic damping. Starting points were laser-produced plasmas showing very high dynamic electric fields in nonlinear force-produced cavitous and inverted double layers in agreement with experiments. Applications for any inhomogeneous plasma as in laboratory or in astrophysical plasmas can then be followed up by a transparent hydrodynamic description. Results are the rotation of plasmas in magnetic fields and a new second harmonic resonance, explanation of the measured inverted double layers, explanation of the observed density-independent, second harmonics emission from laser-produced plasmas, and a laser acceleration scheme by the very high fields of the double layers.

  10. Three step double layers in the laboratory. [plasma physics

    NASA Technical Reports Server (NTRS)

    Bailey, Andrew, III; Hershkowitz, Noah

    1988-01-01

    A new class of stationary double layer structure, with three or more distinct steps, is demonstrated in the laboratory. A large monotonic potential increase results from a series of smaller double layers. In many respects, these double layer structures resemble those inferred from satellite measurements of auroral double layers. This new class of double layer appears to depend on turbulence for its existence and to be a hybrid structure, intermediate between anomalous resistivity and BGK double layers.

  11. Nonrigid 2D registration of fluoroscopic coronary artery image sequence with layered motion

    NASA Astrophysics Data System (ADS)

    Park, Taewoo; Jung, Hoyup; Yun, Il Dong

    2016-03-01

    We present a new method for nonrigid registration of coronary artery models with layered motion information. 2D nonrigid registration method is proposed that brings layered motion information into correspondence with fluoroscopic angiograms. The registered model is overlaid on top of interventional angiograms to provide surgical assistance during image-guided chronic total occlusion procedures. The proposed methodology is divided into two parts: layered structures alignments and local nonrigid registration. In the first part, inpainting method is used to estimate a layered rigid transformation that aligns layered motion information. In the second part, a nonrigid registration method is implemented and used to compensate for any local shape discrepancy. Experimental evaluation conducted on a set of 7 fluoroscopic angiograms results in a reduced target registration error, which showed the effectiveness of the proposed method over single layered approach.

  12. Strain-displacement relations for strain engineering in single-layer 2d materials

    NASA Astrophysics Data System (ADS)

    Midtvedt, Daniel; Lewenkopf, Caio H.; Croy, Alexander

    2016-03-01

    We investigate the electromechanical coupling in single-layer 2d materials. For non-Bravais lattices, we find important corrections to the standard macroscopic strain-microscopic atomic-displacement theory. We put forward a general and systematic approach to calculate strain-displacement relations for several classes of 2d materials. We apply our findings to graphene as a study case, by combining a tight binding and a valence force-field model to calculate electronic and mechanical properties of graphene nanoribbons under strain. The results show good agreement with the predictions of the Dirac equation coupled to continuum mechanics. For this long wave-limit effective theory, we find that the strain-displacement relations lead to a renormalization correction to the strain-induced pseudo-magnetic fields. A similar renormalization is found for the strain-induced band-gap of black phosphorous. Implications for nanomechanical properties and electromechanical coupling in 2d materials are discussed.

  13. 2D array of cold-electron nanobolometers with double polarised cross-dipole antennas

    PubMed Central

    2012-01-01

    A novel concept of the two-dimensional (2D) array of cold-electron nanobolometers (CEB) with double polarised cross-dipole antennas is proposed for ultrasensitive multimode measurements. This concept provides a unique opportunity to simultaneously measure both components of an RF signal and to avoid complicated combinations of two schemes for each polarisation. The optimal concept of the CEB includes a superconductor-insulator-normal tunnel junction and an SN Andreev contact, which provides better performance. This concept allows for better matching with the junction gate field-effect transistor (JFET) readout, suppresses charging noise related to the Coulomb blockade due to the small area of tunnel junctions and decreases the volume of a normal absorber for further improvement of the noise performance. The reliability of a 2D array is considerably increased due to the parallel and series connections of many CEBs. Estimations of the CEB noise with JFET readout give an opportunity to realise a noise equivalent power (NEP) that is less than photon noise, specifically, NEP = 4 10−19 W/Hz1/2 at 7 THz for an optical power load of 0.02 fW. PMID:22512950

  14. 2D array of cold-electron nanobolometers with double polarised cross-dipole antennas

    NASA Astrophysics Data System (ADS)

    Kuzmin, Leonid S.

    2012-04-01

    A novel concept of the two-dimensional (2D) array of cold-electron nanobolometers (CEB) with double polarised cross-dipole antennas is proposed for ultrasensitive multimode measurements. This concept provides a unique opportunity to simultaneously measure both components of an RF signal and to avoid complicated combinations of two schemes for each polarisation. The optimal concept of the CEB includes a superconductor-insulator-normal tunnel junction and an SN Andreev contact, which provides better performance. This concept allows for better matching with the junction gate field-effect transistor (JFET) readout, suppresses charging noise related to the Coulomb blockade due to the small area of tunnel junctions and decreases the volume of a normal absorber for further improvement of the noise performance. The reliability of a 2D array is considerably increased due to the parallel and series connections of many CEBs. Estimations of the CEB noise with JFET readout give an opportunity to realise a noise equivalent power (NEP) that is less than photon noise, specifically, NEP = 4 10-19 W/Hz1/2 at 7 THz for an optical power load of 0.02 fW.

  15. Evaporative thinning: a facile synthesis method for high quality ultrathin layers of 2D crystals.

    PubMed

    Huang, Yi-Kai; Cain, Jeffrey D; Peng, Lintao; Hao, Shiqiang; Chasapis, Thomas; Kanatzidis, Mercouri G; Wolverton, Christopher; Grayson, Matthew; Dravid, Vinayak P

    2014-10-28

    The palette of two-dimensional materials has expanded beyond graphene in recent years to include the chalcogenides among other systems. However, there is a considerable paucity of methods for controlled synthesis of mono- and/or few-layer two-dimensional materials with desirable quality, reproducibility, and generality. Here we show a facile top-down synthesis approach for ultrathin layers of 2D materials down to monolayer. Our method is based on controlled evaporative thinning of initially large sheets, as deposited by vapor mass-transport. Rather than optimizing conditions for monolayer deposition, our approach makes use of selective evaporation of thick sheets to control the eventual thickness, down to a monolayer, a process which appears to be self-stopping. As a result, 2D sheets with high yield, high reproducibility, and excellent quality can be generated with large (>10 μm) and thin (∼ 1-2 nm) dimensions. Evaporative thinning promises to greatly reduce the difficulty involved in isolating large, mono- and few-layers of 2D materials for subsequent studies.

  16. Doubled CO2 Effects on NO(y) in a Coupled 2D Model

    NASA Technical Reports Server (NTRS)

    Rosenfield, J. E.; Douglass, A. R.

    1998-01-01

    Changes in temperature and ozone have been the main focus of studies of the stratospheric impact of doubled CO2. Increased CO2 is expected to cool the stratosphere, which will result in increases in stratospheric ozone through temperature dependent loss rates. Less attention has been paid to changes in minor constituents which affect the O3 balance and which may provide additional feedbacks. Stratospheric NO(y) fields calculated using the GSFC 2D interactive chemistry-radiation-dynamics model show significant sensitivity to the model CO2. Modeled upper stratospheric NO(y) decreases by about 15% in response to CO2 doubling, mainly due to the temperature decrease calculated to result from increased cooling. The abundance of atomic nitrogen, N, increases because the rate of the strongly temperature dependent reaction N + O2 yields NO + O decreases at lower temperatures. Increased N leads to an increase in the loss of NO(y) which is controlled by the reaction N + NO yields N2 + O. The NO(y) reduction is shown to be sensitive to the NO photolysis rate. The decrease in the O3 loss rate due to the NO(y) changes is significant when compared to the decrease in the O3 loss rate due to the temperature changes.

  17. Turbulent boundary layer over 2D and 3D large-scale wavy walls

    NASA Astrophysics Data System (ADS)

    Chamorro, Leonardo P.; Hamed, Ali M.; Castillo, Luciano

    2015-11-01

    In this work, an experimental investigation of the developing and developed flow over two- and three-dimensional large-scale wavy walls was performed using high-resolution planar particle image velocimetry in a refractive-index-matching flume. The 2D wall is described by a sinusoidal wave in the streamwise direction with amplitude to wavelength ratio a/ λx = 0.05. The 3D wall is defined with an additional wave superimposed on the 2D wall in the spanwise direction with a/ λy = 0.1. The flow was characterized at Reynolds numbers of 4000 and 40000, based on the bulk velocity and the flume half height. Instantaneous velocity fields and time-averaged turbulence quantities reveal strong coupling between large-scale topography and the turbulence dynamics near the wall. Turbulence statistics show the presence of a well-structured shear layer that enhances the turbulence for the 2D wavy wall, whereas the 3D wall exhibits different flow dynamics and significantly lower turbulence levels, particularly for which shows about 30% reduction. The likelihood of recirculation bubbles, levels and spatial distribution of turbulence, and the rate of the turbulent kinetic energy production are shown to be severely affected when a single spanwise mode is superimposed on the 2D wall. POD analysis was also performed to further understand distinctive features of the flow structures due to surface topography.

  18. Multi-layered coarse grid modelling in 2D urban flood simulations

    NASA Astrophysics Data System (ADS)

    Chen, Albert S.; Evans, Barry; Djordjević, Slobodan; Savić, Dragan A.

    2012-11-01

    SummaryRegular grids are commonly used in 2D flood modelling due to wide availability of terrain models and low pre-processing required for input preparation. Despite advances in both computing software and hardware, high resolution flood modelling remains computationally demanding when applied to a large study area when the available time and resources are limited. Traditional grid coarsening approach may reduce not only the computing demands, but also the accuracy of results due to the loss of detailed information. To keep key features that affect flow propagation within coarse grid, the approach proposed and tested in this paper adopts multiple layers in flood modelling to reflect individual flow paths separated by buildings within a coarse grid cell. The cell in each layer has its own parameters (elevation, roughness, building coverage ratio, and conveyance reduction factors) to describe itself and the conditions at boundaries with neighbourhood cells. Results of tests on the synthetic case study and the real world urban area show that the proposed multi-layered approach greatly improves the accuracy of coarse grid modelling with an insignificant additional computing cost. The proposed approach has been tested in conjunction with the UIM model by taking the high resolution results as the benchmark. The implementation of the proposed multi-layered methodology to any regular grid based 2D model would be straightforward.

  19. Contrast enhancement based on layered difference representation of 2D histograms.

    PubMed

    Lee, Chulwoo; Lee, Chul; Kim, Chang-Su

    2013-12-01

    A novel contrast enhancement algorithm based on the layered difference representation of 2D histograms is proposed in this paper. We attempt to enhance image contrast by amplifying the gray-level differences between adjacent pixels. To this end, we obtain the 2D histogram h(k, k + l ) from an input image, which counts the pairs of adjacent pixels with gray-levels k and k + l , and represent the gray-level differences in a tree-like layered structure. Then, we formulate a constrained optimization problem based on the observation that the gray-level differences, occurring more frequently in the input image, should be more emphasized in the output image. We first solve the optimization problem to derive the transformation function at each layer. We then combine the transformation functions at all layers into the unified transformation function, which is used to map input gray-levels to output gray-levels. Experimental results demonstrate that the proposed algorithm enhances images efficiently in terms of both objective quality and subjective quality.

  20. Highly-resolved 2D HYDRA simulations of Double-Shell Ignition Designs

    SciTech Connect

    Milovich, J L; Amendt, P; Hamza, A; Marinak, M; Robey, H

    2006-06-30

    Double-shell (DS) targets (Amendt, P. A. et al., 2002) offer a complementary approach to the cryogenic baseline design (Lindl, J. et al., 2004) for achieving ignition on the National Ignition Facility (NIF). Among the expected benefits are the ease of room temperature preparation and fielding, the potential for lower laser backscatter and the reduced need for careful shock timing. These benefits are offset, however, by demanding fabrication tolerances, e.g., shell concentricity and shell surface smoothness. In particular, the latter is of paramount importance since DS targets are susceptible to the growth of interface perturbations from impulsive and time-dependent accelerations. Previous work (Milovich, J. L. et al., 2004) has indicated that the growth of perturbations on the outer surface of the inner shell is potentially disruptive. To control this instability new designs have been proposed requiring bimetallic inner shells and material-matching mid-Z nanoporous foam. The challenges in manufacturing such exotic foams have led to a further evaluation of the densities and pore sizes needed to reduce the seeding of perturbations on the outer surface of the inner shell, thereby guiding the ongoing material science research efforts. Highly-resolved 2D simulations of porous foams have been performed to establish an upper limit on the allowable pore sizes for instability growth. Simulations indicate that foams with higher densities than previously thought are now possible. Moreover, while at the present time we are only able to simulate foams with average pore sizes larger than 1 micron (due to computational limitations), we can conclude that these pore sizes are potentially problematic. Furthermore, the effect of low-order hohlraum radiation asymmetries on the growth of intrinsic surface perturbations is also addressed. Highly-resolved 2D simulations indicate that the transverse flows that are set up by these low-order mode features (which can excite Kelvin

  1. Evolution of vortices in 2D boundary layer and in the Couette flow

    NASA Astrophysics Data System (ADS)

    Zametaev, Vladimir B.; Gorbushin, Anton R.

    2016-10-01

    A 2D incompressible laminar boundary layer and the Couette flow having the low velocity fluctuations are considered using asymptotic methods at high Reynolds number. Two classes of solutions for the first order inviscid perturbations have been derived. The integral-differential equation with initial data describing evolution of vortices in time have been solved numerically. It was found that the discontinuities are formed in a smooth solution for a vertical velocity component with the time increase. This first type solution explains instability mechanism in the Couette flow. The second class of solutions contains a singularity at the boundary layer bottom which reminds a source-sink with a variable intensity. The singularity can absorb the fluid from the main part of the boundary layer and eject it back with a possibly "new" vorticity.

  2. The start-to-end chemometric image processing of 2D thin-layer videoscans.

    PubMed

    Komsta, Łukasz; Cieśla, Łukasz; Bogucka-Kocka, Anna; Józefczyk, Aleksandra; Kryszeń, Jakub; Waksmundzka-Hajnos, Monika

    2011-05-13

    The purpose of the research was to recommend a unified procedure of image preprocessing of 2D thin layer videoscans for further supervised or unsupervised chemometric analysis. All work was done with open source software. The videoscans saved as JPG files underwent the following procedures: denoising using a median filter, baseline removal with the rollerball algorithm and nonlinear warping using spline functions. The application of the proposed procedure enabled filtration of random difference between images (background intensity changes and spatial differences of the spots location). After the preprocessing only spot intensities have an influence on the performed PCA or other techniques. The proposed technique was successfully applied to recognize the differences between three Carex species from the 2D videoscans of the extracts. The proposed solution may be of value for the any chemometric task--both unsupervised and supervised.

  3. Propagating double layers in electronegative plasmas

    SciTech Connect

    Meige, A.; Plihon, N.; Hagelaar, G. J. M.; Boeuf, J.-P.; Chabert, P.; Boswell, R. W.

    2007-05-15

    Double layers have been observed to propagate from the source region to the diffusion chamber of a helicon-type reactor filled up with a low-pressure mixture of Ar/SF{sub 6} [N. Plihon et al., J. Appl. Phys. 98, 023306 (2005)]. In the present paper the most significant and new experimental results are reported. A fully self-consistent hybrid model in which the electron energy distribution function, the electron temperature, and the various source terms are calculated is developed to investigate these propagating double layers. The spontaneous formation of propagating double layers is only observed in the simulation for system in which the localized inductive heating is combined with small diameter chambers. The conditions of formation and the properties of the propagating double layers observed in the simulation are in good agreement with that of the experiment. By correlating the results of the experiment and the simulation, a formation mechanism compatible with ion two-stream instability is proposed.

  4. Particle simulation of auroral double layers

    NASA Technical Reports Server (NTRS)

    Smith, Bruce L.; Okuda, Hideo

    1987-01-01

    Work on the simulation of auroral double layers (DLs) with realistic particle-in-cell models is presented. An early model simulated weak DLs formed in a self-consistent circuit but under conditions subject to the ion-acoustic instability. Recent work has focused on strong DLs formed when currentless jets are injected into a dipole magnetic field.

  5. Exciton dynamics in suspended monolayer and few-layer MoS₂ 2D crystals.

    PubMed

    Shi, Hongyan; Yan, Rusen; Bertolazzi, Simone; Brivio, Jacopo; Gao, Bo; Kis, Andras; Jena, Debdeep; Xing, Huili Grace; Huang, Libai

    2013-02-26

    Femtosecond transient absorption spectroscopy and microscopy were employed to study exciton dynamics in suspended and Si₃N₄ substrate-supported monolayer and few-layer MoS₂ 2D crystals. Exciton dynamics for the monolayer and few-layer structures were found to be remarkably different from those of thick crystals when probed at energies near that of the lowest energy direct exciton (A exciton). The intraband relaxation rate was enhanced by more than 40 fold in the monolayer in comparison to that observed in the thick crystals, which we attributed to defect assisted scattering. Faster electron-hole recombination was found in monolayer and few-layer structures due to quantum confinement effects that lead to an indirect-direct band gap crossover. Nonradiative rather than radiative relaxation pathways dominate the dynamics in the monolayer and few-layer MoS₂. Fast trapping of excitons by surface trap states was observed in monolayer and few-layer structures, pointing to the importance of controlling surface properties in atomically thin crystals such as MoS₂ along with controlling their dimensions.

  6. Quasi-simultaneous interaction method for solving 2D boundary layer flows over plates and airfoils

    NASA Astrophysics Data System (ADS)

    Bijleveld, H. A.; Veldman, A. E. P.

    2012-11-01

    This paper studies unsteady 2D boundary layer flows over dented plates and a NACA 0012 airfoil. An inviscid flow is assumed to exist outside the boundary layer and is solved iteratively with the boundary layer flow together with the interaction method until a matching solution is achieved. Hereto a quasi-simultaneous interaction method is applied, in which the integral boundary layer equations are solved together with an interaction-law equation. The interaction-law equation is an approximation of the external flow and based on thin-airfoil theory. It is an algebraic relation between the velocity and displacement thickness. The interaction-law equation ensures that the eigenvalues of the system of equations do not have a sign change and that no singularities occur. Three numerical schemes are used to solve the boundary layer flow with the interaction method. These are: a standard scheme, a splitting method and a characteristics solver. All schemes use a finite difference discretization. The three schemes yield comparable results for the simulations carried out. The standard scheme is deviating most from the splitting and characteristics solvers. The results show that the eigenvalues remain positive, even in separation. As expected, the addition of the interaction-law equation prevents a sign change of the eigenvalues. The quasi-simultaneous interaction scheme is applicable to the three numerical schemes tested.

  7. Oriented 2D covalent organic framework thin films on single-layer graphene.

    PubMed

    Colson, John W; Woll, Arthur R; Mukherjee, Arnab; Levendorf, Mark P; Spitler, Eric L; Shields, Virgil B; Spencer, Michael G; Park, Jiwoong; Dichtel, William R

    2011-04-01

    Covalent organic frameworks (COFs), in which molecular building blocks form robust microporous networks, are usually synthesized as insoluble and unprocessable powders. We have grown two-dimensional (2D) COF films on single-layer graphene (SLG) under operationally simple solvothermal conditions. The layered films stack normal to the SLG surface and show improved crystallinity compared with COF powders. We used SLG surfaces supported on copper, silicon carbide, and transparent fused silica (SiO(2)) substrates, enabling optical spectroscopy of COFs in transmission mode. Three chemically distinct COF films grown on SLG exhibit similar vertical alignment and long-range order, and two of these are of interest for organic electronic devices for which thin-film formation is a prerequisite for characterizing their optoelectronic properties.

  8. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    PubMed Central

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  9. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors.

    PubMed

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III-V, and II-VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain-low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  10. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Zhang, Yong

    2016-04-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side.

  11. Double sodium layers observation over Beijing, China

    NASA Astrophysics Data System (ADS)

    Wang, Jihong; Yang, Yong; Cheng, Xuewu; Yang, Guotao; Song, Shalei; Gong, Shunsheng

    2012-08-01

    The altitude of the sodium layer in the mesosphere and lower thermosphere is usually from 80 km to 105 km. In this paper, we report a set of double sodium layer (DSL) events observed by sodium lidar over Beijing, China. In these DSL events, the normal sodium layer and secondary sodium layer (SeSL) present separately. There were about 17 DSL events occurred in 319 observation nights during 2009˜2011. All DSL events were observed in spring and summer. The SeSL appeared independently within the altitude range from 105 km to 130 km. The density of the SeSL is very high. The maximum ratio of peak density and the ratio of column density for the SeSL to the normal sodium layer are up to ˜60% and ˜47%, respectively. The SeSL lasted several hours, and then merged into the normal sodium layer. After the SeSL, a sporadic sodium layer occurred in the normal sodium layer.

  12. Double layers and double wells in arbitrary degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.

    2016-06-01

    Using the generalized hydrodynamic model, the possibility of variety of large amplitude nonlinear excitations is examined in electron-ion plasma with arbitrary electron degeneracy considering also the ion temperature effect. A new energy-density relation is proposed for plasmas with arbitrary electron degeneracy which reduces to the classical Boltzmann and quantum Thomas-Fermi counterparts in the extreme limits. The pseudopotential method is employed to find the criteria for existence of nonlinear structures such as solitons, periodic nonlinear structures, and double-layers for different cases of adiabatic and isothermal ion fluids for a whole range of normalized electron chemical potential, η0, ranging from dilute classical to completely degenerate electron fluids. It is observed that there is a Mach-speed gap in which no large amplitude localized or periodic nonlinear excitations can propagate in the plasma under consideration. It is further revealed that the plasma under investigation supports propagation of double-wells and double-layers the chemical potential and Mach number ranges of which are studied in terms of other plasma parameters. The Mach number criteria for nonlinear waves are shown to significantly differ for cases of classical with η0 < 0 and quantum with η0 > 0 regimes. It is also shown that the localized structure propagation criteria possess significant dissimilarities for plasmas with adiabatic and isothermal ions. Current research may be generalized to study the nonlinear structures in plasma containing positrons, multiple ions with different charge states, and charged dust grains.

  13. Generation and Radiation of Acoustic Waves from a 2D Shear Layer

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2000-01-01

    A thin free shear layer containing an inflection point in the mean velocity profile is inherently unstable. Disturbances in the flow field can excite the unstable behavior of a shear layer, if the appropriate combination of frequencies and shear layer thicknesses exists, causing instability waves to grow. For other combinations of frequencies and thicknesses, these instability waves remain neutral in amplitude or decay in the downstream direction. A growing instability wave radiates noise when its phase velocity becomes supersonic relative to the ambient speed of sound. This occurs primarily when the mean jet flow velocity is supersonic. Thus, the small disturbances in the flow, which themselves may generate noise, have generated an additional noise source. It is the purpose of this problem to test the ability of CAA to compute this additional source of noise. The problem is idealized such that the exciting disturbance is a fixed known acoustic source pulsating at a single frequency. The source is placed inside of a 2D jet with parallel flow; hence, the shear layer thickness is constant. With the source amplitude small enough, the problem is governed by the following set of linear equations given in dimensional form.

  14. Double layers acting as particles accelerators

    SciTech Connect

    Sanduloviciu, M.; Lozneanu, E.

    1995-12-31

    It is shown that self-consistent stable and unstable double layers generated in plasma after a self-organisation process are able to accelerate charged particles. The implication of cosmic double layers (Dls) in the acceleration of electrical charged particles long been advocated by Alfven and his Stockholm school is today disputed by argument that static electric fields associated with Dls are conservative and consequently the line integral of the electric field outside the DL balances the line integral inside it. Related with this dispute we will evidence some, so far not considered, facts which are in our opinion arguments that aurora Dls are able to energize particles. For justifying this assertion we start from recent experimental results concerning the phenomenology of self-consistent Dls whose generation involve beside ionisations the neutrals excitations which are at tile origin of the light phenomena as those observed in auroras.

  15. Double layer capacitance of carbon foam electrodes

    SciTech Connect

    Delnick, F.M.; Ingersoll, D.; Firsich, D.

    1993-11-01

    We have evaluated a wide variety of microcellular carbon foams prepared by the controlled pyrolysis and carbonization of several polymers including: polyacrylonitrile (PAN), polymethacrylonitrile (PMAN), resorcinol/formaldehyde (RF), divinylbenzene/methacrylonitrile (DVB), phenolics (furfuryl/alcohol), and cellulose polymers such as Rayon. The porosity may be established by several processes including: Gelation (1-5), phase separation (1-3,5-8), emulsion (1,9,10), aerogel/xerogel formation (1,11,12,13), replication (14) and activation. In this report we present the complex impedance analysis and double layer charging characteristics of electrodes prepared from one of these materials for double layer capacitor applications, namely activated cellulose derived microcellular carbon foam.

  16. Photoactive oriented films of layered double hydroxides.

    PubMed

    Lang, Kamil; Kubát, Pavel; Mosinger, Jirí; Bujdák, Juraj; Hof, Martin; Janda, Pavel; Sýkora, Jan; Iyi, Nobuo

    2008-08-14

    The treatment of nano-ordered oriented films of layered double hydroxide (LDH) with dodecyl sulfate increased the interlayer distance from 0.4 to 1.96 nm, which allowed the intercalation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS). The re-stacking of separated layers and the rebuilding of crystals oriented parallel to the surface of quartz slides was confirmed by X-ray diffraction and atomic force microscopy. The hybrid films contained homogeneously distributed porphyrin molecules with preserved photophysical properties such as fluorescence, triplet state formation, and energy transfer, thus forming singlet oxygen.

  17. Double layered tailorable advanced blanket insulation

    NASA Technical Reports Server (NTRS)

    Falstrup, D.

    1983-01-01

    An advanced flexible reusable surface insulation material for future space shuttle flights was investigated. A conventional fly shuttle loom with special modifications to weave an integral double layer triangular core fabric from quartz yarn was used. Two types of insulating material were inserted into the cells of the fabric, and a procedure to accomplish this was developed. The program is follow up of a program in which single layer rectangular cell core fabrics are woven and a single type of insulating material was inserted into the cells.

  18. Vortex lines in layered superconductors. I. From 3D to 2D behaviour

    NASA Astrophysics Data System (ADS)

    Feinberg, D.

    1994-02-01

    The fundamental aspects of vortices in layered superconductors (natural or artificial multilayered materials) are reviewed, focusing on the role of anisotropy and very short coherence lengths. These materials divide into three classes, with increasing T_c's : chalcogenides, organic superconductors and high-T_c copper oxides. The first part of the paper summarizes the quantitative features of the vortex lattice, due to the incorporation of anisotropy in the 3D Ginzburg-Landau or London descriptions : anisotropy of critical fields and vortex lattice, elastic coefficients and melting. This kind of model describes most of the properties of moderately anisotropic compounds as Y : 123. The second part concerns the Josephson-coupled layered systems and identifies in which regimes vortices exhibit a quasi-2D character. Qualitatively new features as Josephson vortices, 2D vortices, Kosterlitz-Thouless transition and lock-in of vortices are reviewed. This analysis is adapted to compounds as Bi : 2212 or multilayers, but also to Y : 123 for some aspects. On passe en revue les aspects fondamentaux des vortex dans les supraconducteurs lamellaires (naturels ou superréseaux artificiels), en mettant l'accent sur le rôle de l'anisotropie et des très courtes longueurs de cohérence. Ces composés se divisent en trois classes, de T_c croissants : chalcogénures, supraconducteurs organiques et oxydes de cuivre à haut T_c. La première partie de l'article résume les aspects quantitatifs dus à l'incorporation de l'anisotropie dans les descriptions 3D Ginzburg-Landau ou London du réseau de vortex.: anisotropie des champs critiques et du réseau de vortex, coefficients élastiques et fusion. Ce type de modèle décrit une grande partie des propriétés des composés modérément anisotropes tels que Y : 123. La seconde partie concerne les systèmes lamellaires à couplage Josephson et identifie dans quels régimes les vortex présentent un caractère quasi-2D. Des effets

  19. Turbulent boundary layer over 2D and 3D large-scale wavy walls

    NASA Astrophysics Data System (ADS)

    Hamed, Ali M.; Kamdar, Arpeet; Castillo, Luciano; Chamorro, Leonardo P.

    2015-10-01

    An experimental investigation of the flow over two- and three-dimensional large-scale wavy walls was performed using high-resolution planar particle image velocimetry in a refractive-index-matching (RIM) channel. The 2D wall is described by a sinusoidal wave in the streamwise direction with amplitude to wavelength ratio a/λx = 0.05. The 3D wall is defined with an additional wave superimposed on the 2D wall in the spanwise direction with a/λy = 0.1. The flow over these walls was characterized at Reynolds numbers of 4000 and 40 000, based on the bulk velocity and the channel half height. Flow measurements were performed in a wall-normal plane for the two cases and in wall-parallel planes at three heights for the 3D wavy wall. Instantaneous velocity fields and time-averaged turbulence quantities reveal strong coupling between large-scale topography and the turbulence dynamics near the wall. Turbulence statistics show the presence of a well-structured shear layer that enhances the turbulence for the 2D wavy wall, whereas the 3D wall exhibits different flow dynamics and significantly lower turbulence levels. It is shown that the 3D surface limits the dynamics of the spanwise turbulent vortical structures, leading to reduced turbulence production and turbulent stresses and, consequently, lower average drag (wall shear stress). The likelihood of recirculation bubbles, levels and spatial distribution of turbulence, and rate of the turbulent kinetic energy production are shown to be severely affected when a single spanwise mode is superimposed on the 2D sinusoidal wall. Differences of one and two order of magnitudes are found in the turbulence levels and Reynolds shear stress at the low Reynolds number for the 2D and 3D cases. These results highlight the sensitivity of the flow to large-scale topographic modulations; in particular the levels and production of turbulent kinetic energy as well as the wall shear stress.

  20. Quantum dust-acoustic double layers

    NASA Astrophysics Data System (ADS)

    Moslem, W. M.; Shukla, P. K.; Ali, S.; Schlickeiser, R.

    2007-04-01

    The quantum dust-acoustic double layers (QDADLs) are studied in an unmagnetized, collisionless quantum dusty plasma whose constituents are the electrons, ions, and negatively/positively charged dust particles. By employing the quantum hydrodynamical equations and the reductive perturbation technique, a quantum extended Korteweg-de Vries equation is derived. A steady-state double-layer solution of the latter is presented by taking into account the quantum-mechanical effects. It is numerically found that both compressive and rarefactive QDADLs can exist only for positive charged dust particles under the condition ni0/ne0<1, where ni0(ne0) is the unperturbed number density of the ions (electrons). It is further noted that the formation of the compressive and the rarefactive double layers depends on the quantum plasma parameters. The relevance of the present investigation to the dust charge impurities in laser-solid interactions is discussed. In general, this study should be useful for the diagnostics of charged dust impurities in ultrasmall microelectronic and nanoelectronic components, as well as in astrophysical objects where charged dust particles are inherently present.

  1. Few-layer Phosphorene: An Ideal 2D Material For Tunnel Transistors.

    PubMed

    Ameen, Tarek A; Ilatikhameneh, Hesameddin; Klimeck, Gerhard; Rahman, Rajib

    2016-06-27

    2D transition metal dichalcogenides (TMDs) have attracted a lot of attention recently for energy-efficient tunneling-field-effect transistor (TFET) applications due to their excellent gate control resulting from their atomically thin dimensions. However, most TMDs have bandgaps (Eg) and effective masses (m(*)) outside the optimum range needed for high performance. It is shown here that the newly discovered 2D material, few-layer phosphorene, has several properties ideally suited for TFET applications: 1) direct Eg in the optimum range ~1.0-0.4 eV, 2) light transport m(*) (0.15 m0), 3) anisotropic m(*) which increases the density of states near the band edges, and 4) a high mobility. These properties combine to provide phosphorene TFET outstanding ION ~ 1 mA/um, ON/OFF ratio ~ 10(6) for a 15 nm channel and 0.5 V supply voltage, thereby significantly outperforming the best TMD-TFETs and CMOS in many aspects such as ON/OFF current ratio and energy-delay products. Furthermore, phosphorene TFETS can scale down to 6 nm channel length and 0.2 V supply voltage within acceptable range in deterioration of the performance metrics. Full-band atomistic quantum transport simulations establish phosphorene TFETs as serious candidates for energy-efficient and scalable replacements of MOSFETs.

  2. A cyclo‐P6 Ligand Complex for the Formation of Planar 2D Layers

    PubMed Central

    Heindl, Claudia; Peresypkina, Eugenia V.; Lüdeker, David; Brunklaus, Gunther; Virovets, Alexander V.

    2016-01-01

    Abstract The all‐phosphorus analogue of benzene, stabilized as middle deck in triple‐decker complexes, is a promising building block for the formation of graphene‐like sheet structures. The reaction of [(CpMo)2(μ,η6:η6‐P6)] (1) with CuX (X=Br, I) leads to self‐assembly into unprecedented 2D networks of [{(CpMo)2P6}(CuBr)4]n (2) and [{(CpMo)2P6}(CuI)2]n (3). X‐ray structural analyses show a unique deformation of the previously planar cyclo‐P6 ligand. This includes bending of one P atom in an envelope conformation as well as a bisallylic distortion. Despite this, 2 and 3 form planar layers. Both polymers were furthermore analyzed by 31P{1H} magic angle spinning (MAS) NMR spectroscopy, revealing signals corresponding to six non‐equivalent phosphorus sites. A peak assignment is achieved by 2D correlation spectra as well as by DFT chemical shift computations. PMID:26711699

  3. Few-layer Phosphorene: An Ideal 2D Material For Tunnel Transistors.

    PubMed

    Ameen, Tarek A; Ilatikhameneh, Hesameddin; Klimeck, Gerhard; Rahman, Rajib

    2016-01-01

    2D transition metal dichalcogenides (TMDs) have attracted a lot of attention recently for energy-efficient tunneling-field-effect transistor (TFET) applications due to their excellent gate control resulting from their atomically thin dimensions. However, most TMDs have bandgaps (Eg) and effective masses (m(*)) outside the optimum range needed for high performance. It is shown here that the newly discovered 2D material, few-layer phosphorene, has several properties ideally suited for TFET applications: 1) direct Eg in the optimum range ~1.0-0.4 eV, 2) light transport m(*) (0.15 m0), 3) anisotropic m(*) which increases the density of states near the band edges, and 4) a high mobility. These properties combine to provide phosphorene TFET outstanding ION ~ 1 mA/um, ON/OFF ratio ~ 10(6) for a 15 nm channel and 0.5 V supply voltage, thereby significantly outperforming the best TMD-TFETs and CMOS in many aspects such as ON/OFF current ratio and energy-delay products. Furthermore, phosphorene TFETS can scale down to 6 nm channel length and 0.2 V supply voltage within acceptable range in deterioration of the performance metrics. Full-band atomistic quantum transport simulations establish phosphorene TFETs as serious candidates for energy-efficient and scalable replacements of MOSFETs. PMID:27345020

  4. Few-layer Phosphorene: An Ideal 2D Material For Tunnel Transistors

    PubMed Central

    Ameen, Tarek A.; Ilatikhameneh, Hesameddin; Klimeck, Gerhard; Rahman, Rajib

    2016-01-01

    2D transition metal dichalcogenides (TMDs) have attracted a lot of attention recently for energy-efficient tunneling-field-effect transistor (TFET) applications due to their excellent gate control resulting from their atomically thin dimensions. However, most TMDs have bandgaps (Eg) and effective masses (m*) outside the optimum range needed for high performance. It is shown here that the newly discovered 2D material, few-layer phosphorene, has several properties ideally suited for TFET applications: 1) direct Eg in the optimum range ~1.0–0.4 eV, 2) light transport m* (0.15 m0), 3) anisotropic m* which increases the density of states near the band edges, and 4) a high mobility. These properties combine to provide phosphorene TFET outstanding ION ~ 1 mA/um, ON/OFF ratio ~ 106 for a 15 nm channel and 0.5 V supply voltage, thereby significantly outperforming the best TMD-TFETs and CMOS in many aspects such as ON/OFF current ratio and energy-delay products. Furthermore, phosphorene TFETS can scale down to 6 nm channel length and 0.2 V supply voltage within acceptable range in deterioration of the performance metrics. Full-band atomistic quantum transport simulations establish phosphorene TFETs as serious candidates for energy-efficient and scalable replacements of MOSFETs. PMID:27345020

  5. Few-layer Phosphorene: An Ideal 2D Material For Tunnel Transistors

    NASA Astrophysics Data System (ADS)

    Ameen, Tarek A.; Ilatikhameneh, Hesameddin; Klimeck, Gerhard; Rahman, Rajib

    2016-06-01

    2D transition metal dichalcogenides (TMDs) have attracted a lot of attention recently for energy-efficient tunneling-field-effect transistor (TFET) applications due to their excellent gate control resulting from their atomically thin dimensions. However, most TMDs have bandgaps (Eg) and effective masses (m*) outside the optimum range needed for high performance. It is shown here that the newly discovered 2D material, few-layer phosphorene, has several properties ideally suited for TFET applications: 1) direct Eg in the optimum range ~1.0–0.4 eV, 2) light transport m* (0.15 m0), 3) anisotropic m* which increases the density of states near the band edges, and 4) a high mobility. These properties combine to provide phosphorene TFET outstanding ION ~ 1 mA/um, ON/OFF ratio ~ 106 for a 15 nm channel and 0.5 V supply voltage, thereby significantly outperforming the best TMD-TFETs and CMOS in many aspects such as ON/OFF current ratio and energy-delay products. Furthermore, phosphorene TFETS can scale down to 6 nm channel length and 0.2 V supply voltage within acceptable range in deterioration of the performance metrics. Full-band atomistic quantum transport simulations establish phosphorene TFETs as serious candidates for energy-efficient and scalable replacements of MOSFETs.

  6. Computer program BL2D for solving two-dimensional and axisymmetric boundary layers

    NASA Technical Reports Server (NTRS)

    Iyer, Venkit

    1995-01-01

    This report presents the formulation, validation, and user's manual for the computer program BL2D. The program is a fourth-order-accurate solution scheme for solving two-dimensional or axisymmetric boundary layers in speed regimes that range from low subsonic to hypersonic Mach numbers. A basic implementation of the transition zone and turbulence modeling is also included. The code is a result of many improvements made to the program VGBLP, which is described in NASA TM-83207 (February 1982), and can effectively supersede it. The code BL2D is designed to be modular, user-friendly, and portable to any machine with a standard fortran77 compiler. The report contains the new formulation adopted and the details of its implementation. Five validation cases are presented. A detailed user's manual with the input format description and instructions for running the code is included. Adequate information is presented in the report to enable the user to modify or customize the code for specific applications.

  7. Computer program BL2D for solving two-dimensional and axisymmetric boundary layers

    NASA Astrophysics Data System (ADS)

    Iyer, Venkit

    1995-05-01

    This report presents the formulation, validation, and user's manual for the computer program BL2D. The program is a fourth-order-accurate solution scheme for solving two-dimensional or axisymmetric boundary layers in speed regimes that range from low subsonic to hypersonic Mach numbers. A basic implementation of the transition zone and turbulence modeling is also included. The code is a result of many improvements made to the program VGBLP, which is described in NASA TM-83207 (February 1982), and can effectively supersede it. The code BL2D is designed to be modular, user-friendly, and portable to any machine with a standard fortran77 compiler. The report contains the new formulation adopted and the details of its implementation. Five validation cases are presented. A detailed user's manual with the input format description and instructions for running the code is included. Adequate information is presented in the report to enable the user to modify or customize the code for specific applications.

  8. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    PubMed

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  9. Current-free double layers: A review

    SciTech Connect

    Singh, Nagendra

    2011-12-15

    During the last decade, there has been an upsurge in the research on current-free DLs (CFDLs). Research includes theory, laboratory measurements, and various applications of CFDLs ranging from plasma thrusters to acceleration of charged particles in space and astrophysical plasmas. The purpose of this review is to present a unified understanding of the basic plasma processes, which lead to the formation of CFDLs. The review starts with the discussion on early research on electric fields and double layers (DLs) and ion acceleration in planar plasma expansion. The review continues with the formation of DLs and rarefaction shocks (RFS) in expanding plasma with two electron populations with different temperatures. The basic theory mitigating the formation of a CFDL by two-electron temperature population is reviewed; we refer to such CFDLs as double layers structures formation by two-temperature electron populations (TET-CFDLs). Application of TET-CFDLS to ion acceleration in laboratory and space plasmas was discussed including the formation of stationary steady-state DLs. A quite different type of CFDLs forms in a helicon plasma device (HPD), in which plasma abruptly expands from a narrow plasma source tube into a wide diffusion tube with abruptly diverging magnetic fields. The formation mechanism of the CFDL in HPD, referred here as current free double layer structure in helicon plasma device (HPD-CFDL), and its applications are reviewed. The formation of a TET-CFDL is due to the self-consistent separation of the two electron populations parallel to the ambient magnetic field. In contrast, a HPD-CFDL forms due to self-consistent separation of electrons and ion perpendicular to the abruptly diverging magnetic field in conjunction with the conducting wall of the expansion chamber in the HPD. One-dimensional theoretical models of CFDLs based on steady-state solution of Vlasov-Poisson system of equations are briefly discussed. Applications of CFDLs ranging from helicon

  10. Mixing and reaction in the subsonic 2-D turbulent free shear layer

    NASA Astrophysics Data System (ADS)

    Frieler, Clifford Eugene

    Several aspects of mixing and reaction in a turbulent two-dimensional shear layer have been studied. Experiments have been performed with reacting H2, F2, and NO in inert diluent gases. Sensing the heat release by these reactions, several aspects of the mixing process can be examined without the usual resolution limitations. For example, in contrast with direct measurements of composition, the amount of mixed fluid can be conservatively estimated with the results of the "flip" experiments. These have been performed over a range of density ratios, Reynolds numbers and heat release.The effects of initial conditions are of primary importance when comparisons to other studies are undertaken. Aspects as fundamental as growth rate of the turbulent region, or as obscure as the mixed fluid flux ratio depend strongly on the boundary conditions of this flow. These effects are examined in conjunction with those of Reynolds number and density ratio. For most cases studied here, tripping of the high speed boundary layer led to growth rate decreases. An exception was found for the case of high density ratio where the opposite effect was observed. This anomalous result occurred at conditions under which a new mode of instability has been shown to exist. Parallels exist between this unusual result and those of Batt in the uniform density case.An extensive study of the effects of density ratio on the mixing and reaction in the 2-D shear layer has been performed. Results indicate that several aspects of the mixing process are remarkably similar. Profiles of mixed fluid change little as the density ratio varies by a factor of 30. The integral amount of mixed fluid varies less than 6% for all density ratios examined. This insensitivity contrasts with that of the profiles of mixed fluid composition. While having very similar shapes the profiles are offset by an amount which depends very strongly upon the density ratio. The entrainment into the mixing layer has also been examined. Power

  11. Stanene: Atomically Thick Free-standing Layer of 2D Hexagonal Tin

    NASA Astrophysics Data System (ADS)

    Saxena, Sumit; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-08-01

    Stanene is one of most important of 2D materials due to its potential to demonstrate room temperature topological effects due to opening of spin-orbit gap. In this pursuit we report synthesis and investigation of optical properties of stanene up to few layers, a two-dimensional hexagonal structural analogue of graphene. Atomic scale morphological and elemental characterization using HRTEM equipped with SAED and EDAX detectors confirm the presence of hexagonal lattice of Sn atoms. The position of Raman peak along with the inter-planar ‘d’ spacing obtained from SAED for prepared samples are in good agreement with that obtained from first principles calculations and confirm that the sheets are not (111) α-Sn sheets. Further, the optical signature calculated using density functional theory at ~191 nm and ~233 nm for low buckled stanene are in qualitative agreement with the measured UV-Vis absorption spectrum. AFM measurements suggest interlayer spacing of ~0.33 nm in good agreement with that reported for epitaxial stanene sheets. No traces of oxygen were observed in the EDAX spectrum suggesting the absence of any oxidized phases. This is also confirmed by Raman measurements by comparing with oxidized stanene sheets.

  12. Stanene: Atomically Thick Free-standing Layer of 2D Hexagonal Tin

    PubMed Central

    Saxena, Sumit; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-01-01

    Stanene is one of most important of 2D materials due to its potential to demonstrate room temperature topological effects due to opening of spin-orbit gap. In this pursuit we report synthesis and investigation of optical properties of stanene up to few layers, a two-dimensional hexagonal structural analogue of graphene. Atomic scale morphological and elemental characterization using HRTEM equipped with SAED and EDAX detectors confirm the presence of hexagonal lattice of Sn atoms. The position of Raman peak along with the inter-planar ‘d’ spacing obtained from SAED for prepared samples are in good agreement with that obtained from first principles calculations and confirm that the sheets are not (111) α-Sn sheets. Further, the optical signature calculated using density functional theory at ~191 nm and ~233 nm for low buckled stanene are in qualitative agreement with the measured UV-Vis absorption spectrum. AFM measurements suggest interlayer spacing of ~0.33 nm in good agreement with that reported for epitaxial stanene sheets. No traces of oxygen were observed in the EDAX spectrum suggesting the absence of any oxidized phases. This is also confirmed by Raman measurements by comparing with oxidized stanene sheets. PMID:27492139

  13. Stanene: Atomically Thick Free-standing Layer of 2D Hexagonal Tin.

    PubMed

    Saxena, Sumit; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-08-05

    Stanene is one of most important of 2D materials due to its potential to demonstrate room temperature topological effects due to opening of spin-orbit gap. In this pursuit we report synthesis and investigation of optical properties of stanene up to few layers, a two-dimensional hexagonal structural analogue of graphene. Atomic scale morphological and elemental characterization using HRTEM equipped with SAED and EDAX detectors confirm the presence of hexagonal lattice of Sn atoms. The position of Raman peak along with the inter-planar 'd' spacing obtained from SAED for prepared samples are in good agreement with that obtained from first principles calculations and confirm that the sheets are not (111) α-Sn sheets. Further, the optical signature calculated using density functional theory at ~191 nm and ~233 nm for low buckled stanene are in qualitative agreement with the measured UV-Vis absorption spectrum. AFM measurements suggest interlayer spacing of ~0.33 nm in good agreement with that reported for epitaxial stanene sheets. No traces of oxygen were observed in the EDAX spectrum suggesting the absence of any oxidized phases. This is also confirmed by Raman measurements by comparing with oxidized stanene sheets.

  14. Boundary Layer Control of Rotating Convection Systems: the Transition from 2D to 3D Turbulence

    NASA Astrophysics Data System (ADS)

    King, Eric; Stellmach, S.; Noir, J.; Hansen, U.; Aurnou, J.

    2008-09-01

    Recent studies have reproduced the patterns of zonal flow and thermal emission on the Giant Planets using deep convection models. For example, it has been shown that the fundamental differences between the winds of the Ice Giants, Uranus and Neptune, and the Gas Giants, Jupiter and Saturn, may be explained by the breakdown of the influence of rotation on convection. Here, we present results from a coupled suite of laboratory experiments and numerical simulations of rotating convection which span a broad range of parameter space. We observe distinct transitions from rotationally controlled, quasi-2D dynamics to strongly 3D, non-rotating style convection. We quantify the boundary between these two regimes as a function of the Rayleigh and Ekman numbers. The transition is not determined, as long assumed, by the convective Rossby number, but instead is controlled by boundary layer dynamics. It may then be easier than previously thought for convection systems to break free from the constraints of rotation. We are presently investigating how this transition correlates with zonal flows and magnetic field generation on the Giant Planets. Funding provided by NSF Geophysics Program (EAR/IF) and NASA Planetary Atmospheres Program.

  15. Development of an ab-initio calculation method for 2D layered materials-based optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Kim, Han Seul; Kim, Yong-Hoon

    We report on the development of a novel first-principles method for the calculation of non-equilibrium nanoscale device operation process. Based on region-dependent Δ self-consistent field method beyond the standard density functional theory (DFT), we will introduce a novel method to describe non-equilibrium situations such as external bias and simultaneous optical excitations. In particular, we will discuss the limitation of conventional method and advantage of our scheme in describing 2D layered materials-based devices operations. Then, we investigate atomistic mechanism of optoelectronic effects from 2D layered materials-based devices and suggest the optimal material and architecture for such devices.

  16. Electric fields and double layers in plasmas

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1987-01-01

    Various mechanisms for driving double layers (DLs) in plasmas are described, including applied potential drops, currents, contact potentials, and plasma expansions. Somne dynamic features of the DLs are discussed; and it is demonstrated that DLs and the currents through them undergo slow oscillations, determined by the ion transit time across an effective length of the system in which the DLs form. It is shown that a localized potential dip forms at the low potential end of a DL, which interrupts the electron current through it according to the Langmuir criterion whenever the ion flux into the DL is disrupted. Also considered is the generation of electric fields perpendicular to the ambient magnetic field by contact potentials.

  17. Low temperature double-layer capacitors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik J. (Inventor); Smart, Marshall C. (Inventor); West, William C. (Inventor)

    2011-01-01

    Double-layer capacitors capable of operating at extremely low temperatures (e.g., as low as -75.degree. C.) are disclosed. Electrolyte solutions combining a base solvent (e.g., acetonitrile) and a cosolvent are employed to lower the melting point of the base electrolyte. Example cosolvents include methyl formate, ethyl acetate, methyl acetate, propionitrile, butyronitrile, and 1,3-dioxolane. An optimized concentration (e.g., 0.10 M to 0.75 M) of salt, such as tetraethylammonium tetrafluoroborate, is dissolved into the electrolyte solution. In some cases (e.g., 1,3-dioxolane cosolvent) additives, such as 2% by volume triethylamine, may be included in the solvent mixture to prevent polymerization of the solution. Conventional device form factors and structural elements (e.g., porous carbon electrodes and a polyethylene separator) may be employed.

  18. Thermopower enhancement by fractional layer control in 2D oxide superlattices.

    PubMed

    Choi, Woo Seok; Ohta, Hiromichi; Lee, Ho Nyung

    2014-10-22

    Precise tuning of the 2D carrier density by using fractional δ-doping of d electrons improves the thermoelectric properties of oxide heterostructures. This promising result can be attributed to the anisotropic band structure in the 2D system, indicating that δ-doped oxide superlattices are good candidates for advanced thermoelectrics.

  19. Optical and Electrical Characteristics of Graphene Double Layer Formed by a Double Transfer of Graphene Single Layers.

    PubMed

    Kim, Young Jun; Bae, Gi Yoon; Chun, Sungwoo; Park, Wanjun

    2016-03-01

    We demonstrate formation of double layer graphene by means of a double transfer using two single graphene layers grown by a chemical vapor deposition method. It is observed that shiftiness and broadness in the double-resonance of Raman scattering are much weaker than those of bilayer graphene formed naturally. Transport characteristics examined from transmission line measurements and field effect transistors show the similar behavior with those of single layer graphene. It indicates that interlayer separation, in electrical view, is large enough to avoid correlation between layers for the double layer structure. It is also observed from a transistor with the double layer graphene that molecules adsorpted on two inner graphene surfaces in the double layered structure are isolated and conserved from ambient environment. PMID:27455706

  20. Optical and Electrical Characteristics of Graphene Double Layer Formed by a Double Transfer of Graphene Single Layers.

    PubMed

    Kim, Young Jun; Bae, Gi Yoon; Chun, Sungwoo; Park, Wanjun

    2016-03-01

    We demonstrate formation of double layer graphene by means of a double transfer using two single graphene layers grown by a chemical vapor deposition method. It is observed that shiftiness and broadness in the double-resonance of Raman scattering are much weaker than those of bilayer graphene formed naturally. Transport characteristics examined from transmission line measurements and field effect transistors show the similar behavior with those of single layer graphene. It indicates that interlayer separation, in electrical view, is large enough to avoid correlation between layers for the double layer structure. It is also observed from a transistor with the double layer graphene that molecules adsorpted on two inner graphene surfaces in the double layered structure are isolated and conserved from ambient environment.

  1. Generation and Radiation of Acoustic Waves from a 2-D Shear Layer

    NASA Technical Reports Server (NTRS)

    Agarwal, Anurag; Morris, Philip J.

    2000-01-01

    A parallel numerical simulation of the radiation of sound from an acoustic source inside a 2-D jet is presented in this paper. This basic benchmark problem is used as a test case for scattering problems that are presently being solved by using the Impedance Mismatch Method (IMM). In this technique, a solid body in the domain is represented by setting the acoustic impedance of each medium, encountered by a wave, to a different value. This impedance discrepancy results in reflected and scattered waves with appropriate amplitudes. The great advantage of the use of this method is that no modifications to a simple Cartesian grid need to be made for complicated geometry bodies. Thus, high order finite difference schemes may be applied simply to all parts of the domain. In the IMM, the total perturbation field is split into incident and scattered fields. The incident pressure is assumed to be known and the equivalent sources for the scattered field are associated with the presence of the scattering body (through the impedance mismatch) and the propagation of the incident field through a non-uniform flow. An earlier version of the technique could only handle uniform flow in the vicinity of the source and at the outflow boundary. Scattering problems in non-uniform mean flow are of great practical importance (for example, scattering from a high lift device in a non-uniform mean flow or the effects of a fuselage boundary layer). The solution to this benchmark problem, which has an acoustic wave propagating through a non-uniform mean flow, serves as a test case for the extensions of the IMM technique.

  2. Simulations of double layers in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Fu, X.; Cowee, M.; Gary, S. P.; Winske, D.

    2015-12-01

    A double layer (DL) is a nonlinear electrostatic structure consisting of two layers of opposite charge in the plasma, with a characteristic potential jump and unipolar electric field. Previous observations and simulations of DLs in the auroral region showed that those DLs are closely related to ion acoustic waves and typically propagate at ion sound speed. However, recent observation of DLs in the magnetosphere near the equator shows that some DLs propagate at a speed much greater than ion sound speed, inferring a different type of DL that may be associated with electron acoustic waves. In this study, we investigate the formation of DLs in two scenarios in the magnetosphere using particle-in-cell simulations. First, in a current-carrying uniform plasma, we artificially change the ion to electron mass ratio to study the transition from ion-acoustic DLs to electron-acoustic structures. Second, we study the formation of DLs at the boundary of two electron populations with different temperatures. These results may explain recent observations of different types of nonlinear electrostatic structures by Van Allen Probes.

  3. Pseudocapacitive Electrodes Produced by Oxidant-Free Polymerization of Pyrrole between the Layers of 2D Titanium Carbide (MXene).

    PubMed

    Boota, Muhammad; Anasori, Babak; Voigt, Cooper; Zhao, Meng-Qiang; Barsoum, Michel W; Gogotsi, Yury

    2016-02-17

    Heterocyclic pyrrole molecules are in situ aligned and polymerized in the -absence of an oxidant between layers of the 2D Ti3C2Tx (MXene), resulting in high volumetric and gravimetric capacitances with capacitance retention of 92% after 25,000 cycles at a 100 mV s(-1) scan rate.

  4. Pseudocapacitive Electrodes Produced by Oxidant-Free Polymerization of Pyrrole between the Layers of 2D Titanium Carbide (MXene)

    DOE PAGES

    Boota, M.; Anasori, Babak; Voigt, C.; Zhao, Meng-Qiang; Barsoum, M. W.; Gogotsi, Yury

    2016-02-17

    Heterocyclic pyrrole molecules are in situ aligned and polymerized in the ­absence of an oxidant between layers of the 2D Ti3C2Tx (MXene), resulting in high volumetric and gravimetric capacitances with capacitance retention of 92% after 25 000 cycles at a 100 mV s-1 scan rate.

  5. Layered-double-hydroxide-modified electrodes: electroanalytical applications.

    PubMed

    Tonelli, Domenica; Scavetta, Erika; Giorgetti, Marco

    2013-01-01

    Two-dimensional inorganic solids, such as layered double hydroxides (LDHs), also defined as anionic clays, have open structures and unique anion-exchange properties which make them very appropriate materials for the immobilization of anions and biomolecules that often bear an overall negative charge. This review aims to describe the important aspects and new developments of electrochemical sensors and biosensors based on LDHs, evidencing the research from our own laboratory and other groups. It is intended to provide an overview of the various types of chemically modified electrodes that have been developed with these 2D layered materials, along with the significant advances made over the last several years. In particular, we report the main methods used for the deposition of LDH films on different substrates, the conductive properties of these materials, the possibility to use them in the development of membranes for potentiometric anion analysis, the early analytical applications of chemically modified electrodes based on the ability of LDHs to preconcentrate redox-active anions and finally the most recent applications exploiting their electrocatalytic properties. Another promising application field of LDHs, when they are employed as host structures for enzymes, is biosensing, which is described considering glucose as an example.

  6. Enhanced photon absorption in spiral nanostructured solar cells using layered 2D materials.

    PubMed

    Tahersima, Mohammad H; Sorger, Volker J

    2015-08-28

    Recent investigations of semiconducting two-dimensional (2D) transition metal dichalcogenides have provided evidence for strong light absorption relative to its thickness attributed to high density of states. Stacking a combination of metallic, insulating, and semiconducting 2D materials enables functional devices with atomic thicknesses. While photovoltaic cells based on 2D materials have been demonstrated, the reported absorption is still just a few percent of the incident light due to their sub-wavelength thickness leading to low cell efficiencies. Here we show that taking advantage of the mechanical flexibility of 2D materials by rolling a molybdenum disulfide (MoS(2))/graphene (Gr)/hexagonal boron nitride stack to a spiral solar cell allows for optical absorption up to 90%. The optical absorption of a 1 μm long hetero-material spiral cell consisting of the aforementioned hetero stack is about 50% stronger compared to a planar MoS(2) cell of the same thickness; although the volumetric absorbing material ratio is only 6%. A core-shell structure exhibits enhanced absorption and pronounced absorption peaks with respect to a spiral structure without metallic contacts. We anticipate these results to provide guidance for photonic structures that take advantage of the unique properties of 2D materials in solar energy conversion applications.

  7. Pd/Ni-WO3 anodic double layer gasochromic device

    DOEpatents

    Lee, Se-Hee; Tracy, C. Edwin; Pitts, J. Roland; Liu, Ping

    2004-04-20

    An anodic double layer gasochromic sensor structure for optical detection of hydrogen in improved response time and with improved optical absorption real time constants, comprising: a glass substrate; a tungsten-doped nickel oxide layer coated on the glass substrate; and a palladium layer coated on the tungsten-doped nickel oxide layer.

  8. Coronal electron confinement by double layers

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2013-12-01

    In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.

  9. Coronal Electron Confinement by Double Layers

    NASA Astrophysics Data System (ADS)

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2013-12-01

    In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.

  10. Auroral weak double layers: A critical assessment

    NASA Astrophysics Data System (ADS)

    Koskinen, Hannu E. J.; Mälkki, Anssi M.

    Weak double layers (WDLs) were first observed in the mid-altitude auroral magnetosphere in 1976 by the S3-3 satellite. The observations were confirmed by Viking in 1986, when more detailed information of these small-scale plasma structures became available. WDLs are upward moving rarefactive solitary structures with negative electric potential. The potential drop over a WDL is typically 0-1 V with electric field pointing predominantly upward. The structures are usually found in relatively weak (≤2 kV) auroral acceleration regions where the field-aligned current is upward, but sometimes very small. The observations suggest that WDLs exist in regions of cool electron and ion background. Most likely the potential structures are embedded in the background ion population that may drift slowly upward. There have been several attempts for plasma physical explanation of WDLs but so far the success has not been very good. Computer simulations have been able to produce similar structures, but usually for somewhat unrealistic plasma parameters. A satisfactory understanding of the phenomenon requires consideration of the role of WDLs in the magnetosphere-ionosphere (MI) coupling, including the large-scale electric fields, both parallel and perpendicular to the magnetic field, and the Alfvén waves mediating the coupling. In this report we give a critical review of our present understanding of WDLs. We try to find out what can be safely deduced from the observations, what are just educated guesses, and where we may go wrong.

  11. Physical mechanism of current-free double layers

    SciTech Connect

    Chen, Francis F.

    2006-03-15

    Undriven double layers observed in plasmas expanding along magnetic fields are the result of a sheath instability connected with the Bohm criterion. Diverging magnetic field lines cause the presheath acceleration of ions, causing a potential jump resembling that of a double layer. The process stops when it runs out of energy.

  12. A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent

    SciTech Connect

    Gao, Xue-Miao; Guo, Qian; Zhao, Jiong-Peng; Liu, Fu-Chen

    2012-12-15

    A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D framework with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.

  13. Two-dimensional double layer in plasma in a diverging magnetic field

    SciTech Connect

    Saha, S. K.; Raychaudhuri, S.; Chowdhury, S.; Janaki, M. S.; Hui, A. K.

    2012-09-15

    Plasma created by an inductive RF discharge is allowed to expand along a diverging magnetic field. Measurement of the axial plasma potential profile reveals the formation of an electric double layer near the throat of the expansion chamber. An accelerated ion beam has been detected in the downstream region, confirming the presence of the double layer. The 2-D nature of the ion energy distribution function of the downstream plasma has been studied by a movable ion energy analyser, which shows that the beam radius increases along the axial distance. The 2-D structure of the plasma potential has been studied by a movable emissive probe. The existence of a secondary lobe in the contour plot of plasma equipotential is a new observation. It is also an interesting observation that the most diverging magnetic field line not intercepting the junction of the discharge tube and the expansion chamber has an electric field aligned with it.

  14. 2D Graphene Oxide Nanosheets as an Adhesive Over-Coating Layer for Flexible Transparent Conductive Electrodes

    NASA Astrophysics Data System (ADS)

    Moon, In Kyu; Kim, Jae Il; Lee, Hanleem; Hur, Kangheon; Kim, Woon Chun; Lee, Hyoyoung

    2013-01-01

    In recent, highly transparent and flexible, two-dimensional (2D) graphene oxide (GO) nanosheet has been paid attention for various applications. Due to an existence of a large amount of oxygen functional groups, the single 2D GO nanosheet has an insulating, transparent, highly dispersible in the eco-friendly water, and hydrophilic property that has strong adhesion to the hydrophilic surface, which will be the best candidate for the use of an over-coating layer (OCL) and protecting layer for a conductive nanowire based indium-free transparent conductive film (TCF). The ultrathin 2D adhesive GO OCL nanosheet is expected to tightly hold silver nanowires (AgNWs), reduce sheet resistance and produce uniform TCF, providing complete solution that simultaneously solves a high haze, low transparency with a conventional OCL and mechanical instability in cases without a thick OCL. Our novel 2D insulating and hydrophilic GO OCL successfully provided a large-area, flexible, and highly transparent AgNW TCF.

  15. The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of CO adsorption

    SciTech Connect

    Liu, Li; Zhou, Zihao; Guo, Qinlin; Yan, Zhen; Yao, Yunxi; Goodman, D. Wayne

    2011-09-01

    The growth and morphology of two-dimensional (2-D) gold islands on a single-layer graphene supported on Ru(0001) have been studied by scanning tunneling microscopy (STM). Our findings show that gold exhibits 2-D structures up to a gold dosage of 0.75 equivalent monolayers, and that these 2-D gold islands are thermally stable at room temperature. Parallel polarization modulation infrared reflection absorption spectroscopic (PM-IRAS) and high resolution electron energy loss spectroscopic (HREELS) studies indicate that carbon monoxide (CO) adsorbs on these 2-D gold islands at 85 K, showing a characteristic CO stretching feature at 2095 cm-1 for a saturation coverage of CO. The red shift of the CO stretching frequency compared to that on charge neutral gold is consistent with electron transfer from graphene to gold, i.e., an electron-rich gold overlayer. Preliminary data obtained by dosing molecular oxygen onto this CO pre-covered surface suggest that the 2-D gold islands catalyze the oxidation of CO.

  16. Generation and Radiation of Acoustic Waves from a 2-D Shear Layer using the CE/SE Method

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Wang, Xiao Y.; Chang, Sin-Chung; Jorgenson, Philip C. E.

    2000-01-01

    In the present work, the generation and radiation of acoustic waves from a 2-D shear layer problem is considered. An acoustic source inside of a 2-D jet excites an instability wave in the shear layer, resulting in sound Mach radiation. The numerical solution is obtained by solving the Euler equations using the space time conservation element and solution element (CE/SE) method. Linearization is achieved through choosing a small acoustic source amplitude. The Euler equations are nondimensionalized as instructed in the problem statement. All other conditions are the same except that the Crocco's relation has a slightly different form. In the following, after a brief sketch of the CE/SE method, the numerical results for this problem are presented.

  17. Resolution of anisotropic and shielded highly conductive layers using 2-D electromagnetic modelling in the Rhine Graben and Black Forest

    NASA Astrophysics Data System (ADS)

    Tezkan, Bülent; Červ, Václav; Pek, Josef

    1992-12-01

    Anisotropy in magnetotelluric (MT) data has been found very often and has been explained as the result of local structures of different conductivities. In this paper, an observed anisotropy in MT data is not interpreted qualitatively in terms of local structures but is modelled quantitatively by a quasi-anisotropic layer. Besides the MT transfer functions, measurements of the vertical magnetic component are required. The second goal of this paper is to describe a method which permits the resolution of mid-crustal conductive layers in the presence of an additional high-conductivity layer at the surface. This method is possible in a two-dimensional (2-D) situation that limits the spatial extension of the surface structure. Again, vertical magnetic field recordings are necessary, but the phase of the E-polarization with respect to the 2-D structure is the most sensitive parameter. Using two field sites in Southern Germany, it has been possible to give a quantitative explanation of anisotropy and an improved depth resolution, and to derive an integrated conductivity of the highly conductive mid-crustal layers using MT and geomagnetic depth sounding data. The anisotropic highly conductive layer is located 12 km beneath the poorly conductive Black Forest crystalline rocks, whereas it is at a depth of 6 km beneath the highly conductive Rhine Graben sediments.

  18. Layered double hydroxides toward electrochemical energy storage and conversion: design, synthesis and applications.

    PubMed

    Shao, Mingfei; Zhang, Ruikang; Li, Zhenhua; Wei, Min; Evans, David G; Duan, Xue

    2015-11-14

    Two-dimensional (2D) materials have attracted increasing interest in electrochemical energy storage and conversion. As typical 2D materials, layered double hydroxides (LDHs) display large potential in this area due to the facile tunability of their composition, structure and morphology. Various preparation strategies, including in situ growth, electrodeposition and layer-by-layer (LBL) assembly, have been developed to directly modify electrodes by using LDH materials. Moreover, several composite materials based on LDHs and conductive matrices have also been rationally designed and employed in supercapacitors, batteries and electrocatalysis with largely enhanced performances. This feature article summarizes the latest developments in the design, preparation and evaluation of LDH materials toward electrochemical energy storage and conversion.

  19. Challenges facing lithium batteries and electrical double-layer capacitors.

    PubMed

    Choi, Nam-Soon; Chen, Zonghai; Freunberger, Stefan A; Ji, Xiulei; Sun, Yang-Kook; Amine, Khalil; Yushin, Gleb; Nazar, Linda F; Cho, Jaephil; Bruce, Peter G

    2012-10-01

    Energy-storage technologies, including electrical double-layer capacitors and rechargeable batteries, have attracted significant attention for applications in portable electronic devices, electric vehicles, bulk electricity storage at power stations, and "load leveling" of renewable sources, such as solar energy and wind power. Transforming lithium batteries and electric double-layer capacitors requires a step change in the science underpinning these devices, including the discovery of new materials, new electrochemistry, and an increased understanding of the processes on which the devices depend. The Review will consider some of the current scientific issues underpinning lithium batteries and electric double-layer capacitors.

  20. A Large-Area Transferable Wide Band Gap 2D Silicon Dioxide Layer.

    PubMed

    Büchner, Christin; Wang, Zhu-Jun; Burson, Kristen M; Willinger, Marc-Georg; Heyde, Markus; Schlögl, Robert; Freund, Hans-Joachim

    2016-08-23

    An atomically smooth silica bilayer is transferred from the growth substrate to a new support via mechanical exfoliation at millimeter scale. The atomic structure and morphology are maintained perfectly throughout the process. A simple heating treatment results in complete removal of the transfer medium. Low-energy electron diffraction, Auger electron spectroscopy, scanning tunneling microscopy, and environmental scanning electron microscopy show the success of the transfer steps. Excellent chemical and thermal stability result from the absence of dangling bonds in the film structure. By adding this wide band gap oxide to the toolbox of 2D materials, possibilities for van der Waals heterostructures will be broadened significantly.

  1. A Large-Area Transferable Wide Band Gap 2D Silicon Dioxide Layer.

    PubMed

    Büchner, Christin; Wang, Zhu-Jun; Burson, Kristen M; Willinger, Marc-Georg; Heyde, Markus; Schlögl, Robert; Freund, Hans-Joachim

    2016-08-23

    An atomically smooth silica bilayer is transferred from the growth substrate to a new support via mechanical exfoliation at millimeter scale. The atomic structure and morphology are maintained perfectly throughout the process. A simple heating treatment results in complete removal of the transfer medium. Low-energy electron diffraction, Auger electron spectroscopy, scanning tunneling microscopy, and environmental scanning electron microscopy show the success of the transfer steps. Excellent chemical and thermal stability result from the absence of dangling bonds in the film structure. By adding this wide band gap oxide to the toolbox of 2D materials, possibilities for van der Waals heterostructures will be broadened significantly. PMID:27421042

  2. Double-peaked sodium layers at high latitudes

    NASA Technical Reports Server (NTRS)

    Von Zahn, U.; Goldberg, R. A.; Stegman, J.; Witt, G.

    1989-01-01

    Na lidar observations indicate that at high latitudes in summer the neutral Na layer frequently attains a double-peaked structure. The main layer with a maximum near 90 km altitude is supplemented by a secondary, narrow layer near 95 km altitude. Results are presented concerning secondary sodium layers. It appears likely that the formation of secondary Na layers observed frequently above the lidar site is not solely a 'sodium phenomenon', but part of a more comprehensive layering process for metal atoms and ions. Na(+)/Na density ratios close to 0.5 near the peaks of both the main and secondary layers are derived.

  3. Double sodium layer observation over Beijing, China by lidar

    NASA Astrophysics Data System (ADS)

    Wang, Jihong; Yang, Guotao; Yong, Yang; Song, Shalei; Gong, Shunsheng; Cheng, Xuewu

    2012-07-01

    The sodium layer is usually located between 80-105 km. The double sodium layer (DSL) event observed by sodium lidar (light detection and radar) over Wuhan extend the altitude to about 125km. A secondary sodium layer appeared above the normal sodium layer. However, the exact mechanism responsible for the DSL formation is still unclear, due to lack of DSL events observed. In this paper, we reports a series of double sodium layer events observed by sodium lidar over Beijing, China. About ten DSL events occurred during 2010 and 2011. All DSL events were observed in summer. The SeSL last about several hours and joined the normal sodium layer, which seems its loss mechanism. When the SeSL disappeared, the sporadic sodium layer occurred in the normal sodium layer.

  4. Single-Layered Hittorf's Phosphorus: A Wide-Bandgap High Mobility 2D Material.

    PubMed

    Schusteritsch, Georg; Uhrin, Martin; Pickard, Chris J

    2016-05-11

    We propose here a two-dimensional material based on a single layer of violet or Hittorf's phosphorus. Using first-principles density functional theory, we find it to be energetically very stable, comparable to other previously proposed single-layered phosphorus structures. It requires only a small energetic cost of approximately 0.04 eV/atom to be created from its bulk structure, Hittorf's phosphorus, or a binding energy of 0.3-0.4 J/m(2) per layer, suggesting the possibility of exfoliation in experiments. We find single-layered Hittorf's phosphorus to be a wide band gap semiconductor with a direct band gap of approximately 2.5 eV, and our calculations show it is expected to have a high and highly anisotropic hole mobility with an upper bound lying between 3000-7000 cm(2) V(-1) s(-1). These combined properties make single-layered Hittorf's phosphorus a very good candidate for future applications in a wide variety of technologies, in particular for high frequency electronics, and optoelectronic devices operating in the low wavelength blue color range.

  5. Drag of a turbulent boundary layer with transverse 2D circular rods on the wall

    NASA Astrophysics Data System (ADS)

    Kamruzzaman, Md; Djenidi, L.; Antonia, R. A.; Talluru, K. M.

    2015-06-01

    In this paper, we present the results of a turbulent boundary layer developing over a rod-roughened wall with a spacing of ( is the spacing between two adjacent roughness elements, and is the rod diameter). Static pressure measurements are taken around a single roughness element to accurately determine the friction velocity, and the error in the origin, , which are the two prominent issues that surround rough-wall boundary layers. In addition, velocity measurements are taken at several streamwise locations using hot-wire anemometry to obtain from the momentum integral equation. Results showed that both methods give consistent values for , indicating that the contribution of the viscous drag over this rough wall is negligible. This supports the results of Perry et al. (J Fluid Mech 177:437-466, 1969) and Antonia and Luxton (J Fluid Mech 48(04):721-761, 1971) in a boundary layer and of Leonardi et al. (2003) in a channel flow but does not agree with those of Furuya et al. (J Fluids Eng 98(4):635-643, 1976). The results show that both and can be unambiguously measured on this particular rough wall. This paves the way for a proper comparison between the boundary layer developing over this wall and the smooth-wall turbulent boundary layer.

  6. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-10-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

  7. Single-Layered Hittorf's Phosphorus: A Wide-Bandgap High Mobility 2D Material.

    PubMed

    Schusteritsch, Georg; Uhrin, Martin; Pickard, Chris J

    2016-05-11

    We propose here a two-dimensional material based on a single layer of violet or Hittorf's phosphorus. Using first-principles density functional theory, we find it to be energetically very stable, comparable to other previously proposed single-layered phosphorus structures. It requires only a small energetic cost of approximately 0.04 eV/atom to be created from its bulk structure, Hittorf's phosphorus, or a binding energy of 0.3-0.4 J/m(2) per layer, suggesting the possibility of exfoliation in experiments. We find single-layered Hittorf's phosphorus to be a wide band gap semiconductor with a direct band gap of approximately 2.5 eV, and our calculations show it is expected to have a high and highly anisotropic hole mobility with an upper bound lying between 3000-7000 cm(2) V(-1) s(-1). These combined properties make single-layered Hittorf's phosphorus a very good candidate for future applications in a wide variety of technologies, in particular for high frequency electronics, and optoelectronic devices operating in the low wavelength blue color range. PMID:27110837

  8. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    PubMed Central

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-01-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors. PMID:27713550

  9. Quantum electron-acoustic double layers in a magnetoplasma

    SciTech Connect

    Misra, A. P.; Samanta, S.

    2008-12-15

    Using a quantum magnetohydrodynamic (QMHD) model, the existence of small but finite amplitude quantum electron-acoustic double layers (QEADLs) is reported in a magnetized collisionless dense quantum plasma whose constituents are two distinct groups of cold and hot electrons, and the stationary ions forming only the neutralizing background. It is shown that the existence of steady state solutions of these double layers obtained from an extended Korteweg-de Vries (KdV) equation depends parametrically on the ratio of the cold to hot electron unperturbed number density ({delta}), the quantum diffraction parameter (H), the obliqueness parameter (l{sub z}), and the external magnetic field via the normalized electron-cyclotron frequency ({omega}). It is found that the system supports both compressive and rarefactive double layers depending on the parameters {delta} and l{sub z}. The effects of all these parameters on the profiles of the double layers are also examined numerically.

  10. A fast and accurate method to predict 2D and 3D aerodynamic boundary layer flows

    NASA Astrophysics Data System (ADS)

    Bijleveld, H. A.; Veldman, A. E. P.

    2014-12-01

    A quasi-simultaneous interaction method is applied to predict 2D and 3D aerodynamic flows. This method is suitable for offshore wind turbine design software as it is a very accurate and computationally reasonably cheap method. This study shows the results for a NACA 0012 airfoil. The two applied solvers converge to the experimental values when the grid is refined. We also show that in separation the eigenvalues remain positive thus avoiding the Goldstein singularity at separation. In 3D we show a flow over a dent in which separation occurs. A rotating flat plat is used to show the applicability of the method for rotating flows. The shown capabilities of the method indicate that the quasi-simultaneous interaction method is suitable for design methods for offshore wind turbine blades.

  11. A novel class of strain gauges based on layered percolative films of 2D materials.

    PubMed

    Hempel, Marek; Nezich, Daniel; Kong, Jing; Hofmann, Mario

    2012-11-14

    Here we report on the fabrication and characterization of a novel type of strain gauge based on percolative networks of 2D materials. The high sensitivity of the percolative carrier transport to strain induced morphology changes was exploited in strain sensors that can be produced from a wide variety of materials. Highly reliable and sensitive graphene-based thin film strain gauges were produced from solution processed graphene flakes by spray deposition. Control of the gauge sensitivity could be exerted through deposition-induced changes to the film morphology. This exceptional property was explained through modeling of the strain induced changes to the flake-flake overlap for different percolation networks. The ability to directly deposit strain gauges on complex-shaped and transparent surfaces was presented. The demonstrated scalable fabrication, superior sensitivity over conventional sensors, and unique properties of the described strain gauges have the potential to improve existing technology and open up new fields of applications for strain sensors.

  12. Layered double hydroxide stability. 1. Relative stabilities of layered double hydroxides and their simple counterparts

    NASA Technical Reports Server (NTRS)

    Boclair, J. W.; Braterman, P. S.

    1999-01-01

    Solutions containing di- and trivalent metal chlorides [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+; M(III) = Al3+, Fe3+] were titrated with NaOH to yield hydrotalcite-like layered double hydroxides (LDH), [[M(II)]1-x[M(III)]x(OH)2][Cl]x yH2O, by way of M(III) hydroxide/hydrous oxide intermediates. Analysis of the resultant titration curves yields nominal solubility constants for the LDH. The corresponding LDH stabilities are in the order Mg < Mn < Co approximately Ni < Zn for M(II) and Al < Fe for M(III). The stability of LDH relative to the separate metal hydroxides/hydrous oxides is discussed.

  13. Wind-tunnel experiments of thermally-stratified turbulent boundary layer flow over a wall-mounted 2-D block

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

    2014-05-01

    Turbulent boundary-layer flows over complex topography have been extensively studied in the atmospheric sciences and wind engineering communities. The upwind turbulence level, the atmospheric thermal stability and the shape of the topography as well as surface characteristics play important roles in turbulent transport of momentum and scalar fluxes. However, to the best of our knowledge, atmospheric thermal stability has rarely been taken into account in laboratory simulations, particularly in wind-tunnel experiments. Extension of such studies in thermally-stratified wind tunnels will substantially advance our understanding of thermal stability effects on the physics of flow over complex topography. Additionally, high-resolution experimental data can be used for development of new parameterization of surface fluxes and validation of numerical models such as Large-Eddy Simulation (LES). A series of experiments of neutral and thermally-stratified boundary-layer flows over a wall-mounted 2-D block were conducted at the Saint Anthony Falls Laboratory boundary-layer wind tunnel. The 2-D block, with a width to height ratio of 2:1, occupied the lowest 25% of the turbulent boundary layer. Stable and convective boundary layers were simulated by independently controlling the temperature of air flow, the test section floor, and the wall-mounted block surfaces. Measurements using high-resolution Particle Image Velocimetry (PIV), x-wire/cold-wire anemometry, thermal-couples and surface heat flux sensors were made to quantify the turbulent properties and surface fluxes in distinct macroscopic flow regions, including the separation/recirculation zones, evolving shear layer and the asymptotic far wake. Emphasis will be put on addressing thermal stability effects on the spatial distribution of turbulent kinetic energy (TKE) and turbulent fluxes of momentum and scalar from the near to far wake region. Terms of the TKE budget equation are also inferred from measurements and

  14. Controlling turbulent boundary layer separation using biologically inspired 2D transverse grooves

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Jones, Emily; Afroz, Farhana

    2013-11-01

    It is theorized that the presence of grooves, such as the sinusoidal ones found on dolphin skin or the cavities that form between bristled shark skin scales, can lead to induced boundary layer mixing and result in the control of turbulent boundary layer separation. To test this hypothesis, a series of water tunnel experiments using DPIV studied the characteristics of a flat plate turbulent boundary layer whereby a rotating cylinder was used to induce an adverse pressure gradient and resulting flow separation. The experiments were repeated with the use of a plate covered with two types of grooves, rectangular and sinusoidal, with a spacing of 2 mm in size. Flow similarity of the cavity flow was preserved between the experiments and flow over bristled shark skin scales. Both geometries resulted in a reduction of flow separation as measured by backflow coefficient. In addition, Reynolds stress profiles showed that as the pressure gradient was increased, the sinusoidal geometry outperformed the rectangular grooves in terms of increased mixing close to the wall. The sinusoidal plate also generated a lower momentum deficit within the boundary layer which would indicate a smaller drag penalty. Support from NSF grant CBET 0932352 and a UA Graduate Council Fellowship is gratefully acknowledged.

  15. Acoustic transmission through a 2-D orthotropic multi-layered infinite cylindrical shell

    NASA Astrophysics Data System (ADS)

    Blaise, A.; Lesueur, C.

    1992-05-01

    An investigation is presented of the transmission loss of two-dimensional orthotropic multilayered infinite cylindrical shells. Equations of motion are established by using a variational displacement formulation; these equations remain unchanged in form whatever the number of layers. Numerical results are presented illustrating the influence of acoustic and structural parameters on the transmission loss.

  16. Unipolar Complementary Circuits Using Double Electron Layer Tunneling Tansistors

    SciTech Connect

    Blount, M.A.; Hafich, M.J.; Moon, J.S.; Reno, J.L.; Simmons, J.A.

    1998-10-19

    We demonstrate unipolar complementary circuits consisting of a pair of resonant tunneling transistors based on the gate control of 2D-2D interlayer tunneling, where a single transistor - in addition to exhibiting a welldefined negative-differential-resistance can be operated with either positive or negative transconductance. Details of the device operation are analyzed in terms of the quantum capacitance effect and band-bending in a double quantum well structure, and show good agreement with experiment. Application of resonant tunneling complementary logic is discussed by demonstrating complementary static random access memory using two devices connected in series.

  17. Study of spatial growth of disturbances in an Incompressible Double Shear Layer flow configuration

    NASA Astrophysics Data System (ADS)

    Natarajan, Hareshram; Jacobs, Gustaaf

    2014-11-01

    The spatial growth of disturbance within the linear instability regime in an incompressible 2D double shear layer flow configuration is studied by performing a Direct Numerical Simulation. The motivation of this study is to characterize the effect of the presence of an additional shear layer on the spatial growth of a shear layer instability. Initially, a DNS of an incompressible single shear layer is performed and the spatial growth rate of various disturbance frequency modes are validated with Linear Stability Analysis. The addtional shear layer is found to impact the spatial growth rates of the different disturbances and the frequency of the mode with the maximum growth rate is found to be shifted.

  18. Band engineering in a van der Waals heterostructure using a 2D polar material and a capping layer

    NASA Astrophysics Data System (ADS)

    Cho, Sung Beom; Chung, Yong-Chae

    2016-06-01

    Van der Waals (vdW) heterostructures are expected to play a key role in next-generation electronic and optoelectronic devices. In this study, the band alignment of a vdW heterostructure with 2D polar materials was studied using first-principles calculations. As a model case study, single-sided fluorographene (a 2D polar material) on insulating (h-BN) and metallic (graphite) substrates was investigated to understand the band alignment behavior of polar materials. Single-sided fluorographene was found to have a potential difference along the out-of-plane direction. This potential difference provided as built-in potential at the interface, which shift the band alignment between h-BN and graphite. The interface characteristics were highly dependent on the interface terminations because of this built-in potential. Interestingly, this band alignment can be modified with a capping layer of graphene or BN because the capping layer triggered electronic reconstruction near the interface. This is because the bonding nature is not covalent, but van der Waals, which made it possible to avoid Fermi-level pinning at the interface. The results of this study showed that diverse types of band alignment can be achieved using polar materials and an appropriate capping layer.

  19. Bioelectronic interfaces by spontaneously organized peptides on 2D atomic single layer materials

    PubMed Central

    Hayamizu, Yuhei; So, Christopher R.; Dag, Sefa; Page, Tamon S.; Starkebaum, David; Sarikaya, Mehmet

    2016-01-01

    Self-assembly of biological molecules on solid materials is central to the “bottom-up” approach to directly integrate biology with electronics. Inspired by biology, exquisite biomolecular nanoarchitectures have been formed on solid surfaces. We demonstrate that a combinatorially-selected dodecapeptide and its variants self-assemble into peptide nanowires on two-dimensional nanosheets, single-layer graphene and MoS2. The abrupt boundaries of nanowires create electronic junctions via spatial biomolecular doping of graphene and manifest themselves as a self-assembled electronic network. Furthermore, designed peptides form nanowires on single-layer MoS2 modifying both its electric conductivity and photoluminescence. The biomolecular doping of nanosheets defined by peptide nanostructures may represent the crucial first step in integrating biology with nano-electronics towards realizing fully self-assembled bionanoelectronic devices. PMID:27653460

  20. Bioelectronic interfaces by spontaneously organized peptides on 2D atomic single layer materials

    NASA Astrophysics Data System (ADS)

    Hayamizu, Yuhei; So, Christopher R.; Dag, Sefa; Page, Tamon S.; Starkebaum, David; Sarikaya, Mehmet

    2016-09-01

    Self-assembly of biological molecules on solid materials is central to the “bottom-up” approach to directly integrate biology with electronics. Inspired by biology, exquisite biomolecular nanoarchitectures have been formed on solid surfaces. We demonstrate that a combinatorially-selected dodecapeptide and its variants self-assemble into peptide nanowires on two-dimensional nanosheets, single-layer graphene and MoS2. The abrupt boundaries of nanowires create electronic junctions via spatial biomolecular doping of graphene and manifest themselves as a self-assembled electronic network. Furthermore, designed peptides form nanowires on single-layer MoS2 modifying both its electric conductivity and photoluminescence. The biomolecular doping of nanosheets defined by peptide nanostructures may represent the crucial first step in integrating biology with nano-electronics towards realizing fully self-assembled bionanoelectronic devices.

  1. Controlled synthesis of layered double hydroxide nanoplates driven by screw dislocations.

    PubMed

    Forticaux, Audrey; Dang, Lianna; Liang, Hanfeng; Jin, Song

    2015-05-13

    Layered double hydroxides (LDHs) are a family of two-dimensional (2D) materials with layered crystal structures that have found many applications. Common strategies to synthesize LDHs lead to a wide variety of morphologies, from discrete 2D nanosheets to nanoflowers. Here, we report a study of carefully controlled LDH nanoplate syntheses using zinc aluminum (ZnAl) and cobalt aluminum (CoAl) LDHs as examples and reveal their crystal growth to be driven by screw dislocations. By controlling and maintaining a low precursor supersaturation using a continuous flow reactor, individual LDH nanoplates with well-defined morphologies were synthesized on alumina-coated substrates, instead of the nanoflowers that result from uncontrolled overgrowth. The dislocation-driven growth was further established for LDH nanoplates directly synthesized using the respective metal salt precursors. Atomic force microscopy revealed screw dislocation growth spirals, and under transmission electron microscopy, thin CoAl LDH nanoplates displayed complex contrast contours indicative of strong lattice strain caused by dislocations. These results suggest the dislocation-driven mechanism is generally responsible for the growth of 2D LDH nanostructures, and likely other materials with layered crystal structures, which could help the rational synthesis of well-defined 2D nanomaterials with improved properties.

  2. Charged layer with undulated surface: configuration of electrical double layer.

    PubMed

    Lin, Sung-Hwa

    2010-06-15

    A charged layer with undulated surface exists commonly in natural entities (for example the biological membrane layer and the surface of charged colloid) and in artificial fabrications (for example the peripheral surface of ion-exchange membrane pores). When the micro- or nano-scale charged layer systems are concerned, the effect of undulation of charged layer surface on the electrical phenomenon may become great significant. In this work, using the perturbation method, the significance of undulated surface on a charged layer in the electrical phenomenon is investigated. Under assumptions that the undulation amplitude is small and that the Debye-Huckel approximation is applicable, the electrical potential field in three regions is solved simultaneously. Based on the analytical results it is found that, if compared with that in condition of flat surface, the undulation of charged layer surface decreases/increases the magnitude of electrical potential field near the wave crest/trough, due to the curvature of undulated surface. In addition, the surface potential on the undulated surface shows a wavelike distribution. The analytical results also show that, the significance of undulated surface is determined by the physical parameters, including the geometry of undulated surface, the amplitude and the period of undulation, and the fixed charge density in charged layer.

  3. Thin bacteria/Layered Double Hydroxide films using a layer-by-layer approach.

    PubMed

    Halma, Matilte; Khenifi, Aicha; Sancelme, Martine; Besse-Hoggan, Pascale; Bussière, Pierre-Olivier; Prévot, Vanessa; Mousty, Christine

    2016-07-15

    This paper reports the design of thin bacteria/Layered Double Hydroxides (LDH) films in which bacterial cells of Pseudomonas sp. strain ADP were assembled alternatively with Mg2Al-NO3 LDH nanosheets by a layer-by-layer deposition method. The UV-Vis spectroscopy was used to monitor the assembly process, showing a progressive increase in immobilized bacteria amount upon deposited cycles. The {ADP/LDH}n film was characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and atomic force microscopy. The metabolic activity of immobilized bacteria was determined using chronoamperometry by measuring the biochemical oxygen demand in presence of glucose using an artificial electron acceptor (Fe(CN)6(3-)) at 0.5V/Ag-AgCl. A steady current of 0.250μAcm(-2) was reached in about 30s after the addition of 5mM glucose. PMID:27124809

  4. Evolution of seismic layer 2B across the Juan de Fuca Ridge from hydrophone streamer 2-D traveltime tomography

    NASA Astrophysics Data System (ADS)

    Newman, Kori R.; Nedimović, Mladen R.; Canales, J. Pablo; Carbotte, Suzanne M.

    2011-05-01

    How oceanic crust evolves has important implications for understanding both subduction earthquake hazards and energy and mass exchange between the Earth's interior and the oceans. Although considerable work has been done characterizing the evolution of seismic layer 2A, there has been little analysis of the processes that affect layer 2B after formation. Here we present high-resolution 2-D tomographic models of seismic layer 2B along ˜300 km long multichannel seismic transects crossing the Endeavour, Northern Symmetric, and Cleft segments of the Juan de Fuca Ridge. These models show that seismic layer 2B evolves rapidly following a different course than layer 2A. The upper layer 2B velocities increase on average by 0.8 km/s and reach a generally constant velocity of 5.2 ± 0.3 km/s within the first 0.5 Myr after crustal formation. This suggests that the strongest impact on layer 2B evolution may be that of mineral precipitation due to "active" hydrothermal circulation centered about the ridge crest and driven by the heat from the axial magma chamber. Variations in upper layer 2B velocity with age at time scales ≥0.5 Ma show correlation about the ridge axis indicating that in the long term, crustal accretion processes affect both sides of the ridge axis in a similar way. Below the 0.5 Ma threshold, differences in 2B velocity are likely imprinted during crustal formation or early crustal evolution. Layer 2B velocities at propagator wakes (5.0 ± 0.2 km/s), where enhanced faulting and cracking are expected, and at areas that coincide with extensional or transtensional faulting are on average slightly slower than in normal mature upper layer 2B. Analysis of the layer 2B velocities from areas where the hydrothermal patterns are known shows that the locations of current and paleohydrothermal discharge and recharge zones are marked by reduced and increased upper layer 2B velocities, respectively. Additionally, the distance between present up-flow and down-flow zones is

  5. Mass transfer through laminar boundary layer in 2-d microchannels with nonuniform cross section: the effect of wall curvature

    NASA Astrophysics Data System (ADS)

    Pedacchia, Augusta; Adrover, Alessandra

    2012-11-01

    We provide an analytical solution for the combined diffusive and convective 2-d mass transport from a surface film (of arbitrary shape at a given uniform concentration) to a pure solvent flowing in creeping flow conditions into a microchannel, delimited by a flat no-slip surface and by the releasing film itself. Such a problem arises in the study of swelling and dissolution of polimeric thin films under the action of a solvent tangential flow simulating the oral thin film dissolution for drug relase towards the buccal mucosa or oral cavity. We present a similarity solution for laminar forced convection mass (or heat) transfer that generalizes the classical boundary layer solution of the Graetz-Nusselt problem (valid for straight channels or pipes) to a solvent flowing in creeping flow conditions into a 2-d channel with cross-section continuously varying along the axial coordinate x. Close to the releasing boundary, parametrized by a curvilinear abscissa s, both tangential and normal velocity components play a role and their scaling behavior, as a function of wall distance r, should be taken into account in order to have an accurate description of the concentration profile in the boundary layer and of the dependence of the Sherwood number on the curvilinear abscissa s.

  6. Multilabel Image Annotation Based on Double-Layer PLSA Model

    PubMed Central

    Zhang, Jing; Li, Da; Hu, Weiwei; Chen, Zhihua; Yuan, Yubo

    2014-01-01

    Due to the semantic gap between visual features and semantic concepts, automatic image annotation has become a difficult issue in computer vision recently. We propose a new image multilabel annotation method based on double-layer probabilistic latent semantic analysis (PLSA) in this paper. The new double-layer PLSA model is constructed to bridge the low-level visual features and high-level semantic concepts of images for effective image understanding. The low-level features of images are represented as visual words by Bag-of-Words model; latent semantic topics are obtained by the first layer PLSA from two aspects of visual and texture, respectively. Furthermore, we adopt the second layer PLSA to fuse the visual and texture latent semantic topics and achieve a top-layer latent semantic topic. By the double-layer PLSA, the relationships between visual features and semantic concepts of images are established, and we can predict the labels of new images by their low-level features. Experimental results demonstrate that our automatic image annotation model based on double-layer PLSA can achieve promising performance for labeling and outperform previous methods on standard Corel dataset. PMID:24999490

  7. Capacitance of carbon-based electrical double-layer capacitors.

    PubMed

    Ji, Hengxing; Zhao, Xin; Qiao, Zhenhua; Jung, Jeil; Zhu, Yanwu; Lu, Yalin; Zhang, Li Li; MacDonald, Allan H; Ruoff, Rodney S

    2014-01-01

    Experimental electrical double-layer capacitances of porous carbon electrodes fall below ideal values, thus limiting the practical energy densities of carbon-based electrical double-layer capacitors. Here we investigate the origin of this behaviour by measuring the electrical double-layer capacitance in one to five-layer graphene. We find that the capacitances are suppressed near neutrality, and are anomalously enhanced for thicknesses below a few layers. We attribute the first effect to quantum capacitance effects near the point of zero charge, and the second to correlations between electrons in the graphene sheet and ions in the electrolyte. The large capacitance values imply gravimetric energy storage densities in the single-layer graphene limit that are comparable to those of batteries. We anticipate that these results shed light on developing new theoretical models in understanding the electrical double-layer capacitance of carbon electrodes, and on opening up new strategies for improving the energy density of carbon-based capacitors.

  8. Electrochemical double-layer capacitors based on functionalized graphene

    NASA Astrophysics Data System (ADS)

    Pope, Michael Allan

    Graphene is a promising electrode material for electrochemical double-layer capacitors (EDLCs) used for energy storage due to its high electrical conductivity and theoretical specific surface area. However, the intrinsic capacitance of graphene is known to be low and governed by the electronic side of the interface. Furthermore, graphene tends to aggregate and stack together when processed into thick electrode films. This significantly lowers the ion-accessible specific surface area (SSA). Maximizing both the SSA and the intrinsic capacitance are the main problems addressed in this thesis in an effort to improve the specific capacitance and energy density of EDLCs. In contrast to pristine graphene, functionalized graphene produced by the thermal exfoliation of graphite oxide contains residual functional groups and lattice defects. To study how these properties affect the double-layer capacitance, a model electrode system capable of measuring the intrinsic electrochemical properties of functionalized graphene was developed. To prevent artifacts and uncertainties related to measurements on porous electrodes, the functionalized graphene sheets (FGSs) were assembled as densely tiled monolayers using a Langmuir-Blodgett technique. In this way, charging can be studied in a well-defined 2D geometry. The possibility of measuring and isolating the intrinsic electrochemical properties of FGS monolayers was first demonstrated by comparing capacitance and redox probe measurements carried out on coatings deposited on passivated gold and single crystal graphite substrates. This monolayer system was then used to follow the double-layer capacitance of the FGS/electrolyte interface as the structure and chemistry of graphene was varied by thermal treatments ranging from 300 °C to 2100 °C. Elemental analysis and Raman spectroscopy were used to determine the resulting chemical and structural transformation upon heat treatment. It was demonstrated that intrinsically defective

  9. Electrical double layers at the oil/water interface

    NASA Technical Reports Server (NTRS)

    Volkov, A. G.; Deamer, D. W.; Tanelian, D. L.; Markin, V. S.

    1996-01-01

    This review presents the historical development and current status of the theory of the electrical double layer at a liquid/liquid interface. It gives rigorous thermodynamic definitions of all basic concepts related to liquid interfaces and to the electrical double layer. The difference between the surface of a solid electrode and the interface of two immiscible electrolyte solutions (ITIES) is analyzed in connection to their electrical properties. The most important classical relationships for the electrical double layer are presented and critically discussed. The generalized adsorption isotherm is derived. After a short review of the classical Gouy-Chapman and Verwey-Niessen models, more recent developments of the double layer theory are presented. These include effects of variable dielectric permittivity, nonlocal electrostatics, hydration forces, the modified Poisson-Boltzmann equation and the ion-dipole plasma. The relative merits of different theories are estimated by comparing them with computer simulation of the ITIES and electrical double layer. Special attention is given to the structure of ITIES and its variation due to adsorption of ions and amphiphilic molecules.

  10. Micrometer-Thick Graphene Oxide-Layered Double Hydroxide Nacre-Inspired Coatings and Their Properties.

    PubMed

    Yan, You-Xian; Yao, Hong-Bin; Mao, Li-Bo; Asiri, Abdullah M; Alamry, Khalid A; Marwani, Hadi M; Yu, Shu-Hong

    2016-02-10

    Robust, functional, and flame retardant coatings are attractive in various fields such as building construction, food packaging, electronics encapsulation, and so on. Here, strong, colorful, and fire-retardant micrometer-thick hybrid coatings are reported, which can be constructed via an enhanced layer-by-layer assembly of graphene oxide (GO) nanosheets and layered double hydroxide (LDH) nanoplatelets. The fabricated GO-LDH hybrid coatings show uniform nacre-like layered structures that endow them good mechanic properties with Young's modulus of ≈ 18 GPa and hardness of ≈ 0.68 GPa. In addition, the GO-LDH hybrid coatings exhibit nacre-like iridescence and attractive flame retardancy as well due to their well-defined 2D microstructures. This kind of nacre-inspired GO-LDH hybrid thick coatings will be applied in various fields in future due to their high strength and multifunctionalities.

  11. Micrometer-Thick Graphene Oxide-Layered Double Hydroxide Nacre-Inspired Coatings and Their Properties.

    PubMed

    Yan, You-Xian; Yao, Hong-Bin; Mao, Li-Bo; Asiri, Abdullah M; Alamry, Khalid A; Marwani, Hadi M; Yu, Shu-Hong

    2016-02-10

    Robust, functional, and flame retardant coatings are attractive in various fields such as building construction, food packaging, electronics encapsulation, and so on. Here, strong, colorful, and fire-retardant micrometer-thick hybrid coatings are reported, which can be constructed via an enhanced layer-by-layer assembly of graphene oxide (GO) nanosheets and layered double hydroxide (LDH) nanoplatelets. The fabricated GO-LDH hybrid coatings show uniform nacre-like layered structures that endow them good mechanic properties with Young's modulus of ≈ 18 GPa and hardness of ≈ 0.68 GPa. In addition, the GO-LDH hybrid coatings exhibit nacre-like iridescence and attractive flame retardancy as well due to their well-defined 2D microstructures. This kind of nacre-inspired GO-LDH hybrid thick coatings will be applied in various fields in future due to their high strength and multifunctionalities. PMID:26682698

  12. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction

    NASA Astrophysics Data System (ADS)

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A.; Casanova, Fèlix; van der Zant, Herre S. J.; Castellanos-Gomez, Andres; Hueso, Luis E.

    2015-09-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials

  13. A Potential Role of Double Layers on Solar Wind Acceleration

    NASA Astrophysics Data System (ADS)

    Parks, G. K.; McCarthy, M.; Lee, E.; Hong, J.

    2012-12-01

    The distribution function of solar wind (SW) is non-Maxwellian and often includes field-aligned beams. Recently, electrostatic solitary waves (ESW) have been observed in the SW and they have been interpreted as double layers. Taking a cue from Earth's auroral observations that large-scale electric field parallel to magnetic field may be due to many double layers distributed along the geomagnetic field, we have looked at the potential role double layers could play in SW acceleration. This picture would suggest that the halo component of the SW represents a beam that has been accelerated by parallel electric field. The core electrons come from secondaries produced by the beam going through the solar coronal atmosphere. The source of the super-halo component is not known and we speculate that it could represent the field-aligned non-thermal high-energy halo electrons that have been accelerated to ``runaway" energies.

  14. A review of molecular modelling of electric double layer capacitors.

    PubMed

    Burt, Ryan; Birkett, Greg; Zhao, X S

    2014-04-14

    Electric double-layer capacitors are a family of electrochemical energy storage devices that offer a number of advantages, such as high power density and long cyclability. In recent years, research and development of electric double-layer capacitor technology has been growing rapidly, in response to the increasing demand for energy storage devices from emerging industries, such as hybrid and electric vehicles, renewable energy, and smart grid management. The past few years have witnessed a number of significant research breakthroughs in terms of novel electrodes, new electrolytes, and fabrication of devices, thanks to the discovery of innovative materials (e.g. graphene, carbide-derived carbon, and templated carbon) and the availability of advanced experimental and computational tools. However, some experimental observations could not be clearly understood and interpreted due to limitations of traditional theories, some of which were developed more than one hundred years ago. This has led to significant research efforts in computational simulation and modelling, aimed at developing new theories, or improving the existing ones to help interpret experimental results. This review article provides a summary of research progress in molecular modelling of the physical phenomena taking place in electric double-layer capacitors. An introduction to electric double-layer capacitors and their applications, alongside a brief description of electric double layer theories, is presented first. Second, molecular modelling of ion behaviours of various electrolytes interacting with electrodes under different conditions is reviewed. Finally, key conclusions and outlooks are given. Simulations on comparing electric double-layer structure at planar and porous electrode surfaces under equilibrium conditions have revealed significant structural differences between the two electrode types, and porous electrodes have been shown to store charge more efficiently. Accurate electrolyte and

  15. Electric double layer of anisotropic dielectric colloids under electric fields

    NASA Astrophysics Data System (ADS)

    Han, M.; Wu, H.; Luijten, E.

    2016-07-01

    Anisotropic colloidal particles constitute an important class of building blocks for self-assembly directed by electrical fields. The aggregation of these building blocks is driven by induced dipole moments, which arise from an interplay between dielectric effects and the electric double layer. For particles that are anisotropic in shape, charge distribution, and dielectric properties, calculation of the electric double layer requires coupling of the ionic dynamics to a Poisson solver. We apply recently proposed methods to solve this problem for experimentally employed colloids in static and time-dependent electric fields. This allows us to predict the effects of field strength and frequency on the colloidal properties.

  16. Double layer -- a particle accelerator in the magnetosphere

    SciTech Connect

    Fu, Xiangrong

    2015-07-16

    Slides present the material under the following topics: Introduction (What is a double layer (DL)? Why is it important? Key unsolved problems); Theory -- time-independent solutions of 1D Vlasov--Poisson system; Particle-in-cell simulations (Current-driven DLs); and Electron acceleration by DL (Betatron acceleration). Key problems include the generation mechanism, stability, and electron acceleration. In summary, recent observations by Van Allen Probes show large number of DLs in the outer radiation belt, associated with enhanced flux of relativistic electrons. Simulations show that ion acoustic double layers can be generated by field-aligned currents. Thermal electrons can gain energy via betatron acceleration in a dipole magnetic field.

  17. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces.

    PubMed

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  18. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.

  19. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications. PMID:26335856

  20. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    PubMed Central

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  1. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    NASA Astrophysics Data System (ADS)

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-12-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems.

  2. Double-layered cell transfer technology for bone regeneration.

    PubMed

    Akazawa, Keiko; Iwasaki, Kengo; Nagata, Mizuki; Yokoyama, Naoki; Ayame, Hirohito; Yamaki, Kazumasa; Tanaka, Yuichi; Honda, Izumi; Morioka, Chikako; Kimura, Tsuyoshi; Komaki, Motohiro; Kishida, Akio; Izumi, Yuichi; Morita, Ikuo

    2016-01-01

    For cell-based medicine, to mimic in vivo cellular localization, various tissue engineering approaches have been studied to obtain a desirable arrangement of cells on scaffold materials. We have developed a novel method of cell manipulation called "cell transfer technology", enabling the transfer of cultured cells onto scaffold materials, and controlling cell topology. Here we show that using this technique, two different cell types can be transferred onto a scaffold surface as stable double layers or in patterned arrangements. Various combinations of adherent cells were transferred to a scaffold, amniotic membrane, in overlapping bilayers (double-layered cell transfer), and transferred cells showed stability upon deformations of the material including folding and trimming. Transplantation of mesenchymal stem cells from periodontal ligaments (PDLSC) and osteoblasts, using double-layered cell transfer significantly enhanced bone formation, when compared to single cell type transplantation. Our findings suggest that this double-layer cell transfer is useful to produce a cell transplantation material that can bear two cell layers. Moreover, the transplantation of an amniotic membrane with PDLSCs/osteoblasts by cell transfer technology has therapeutic potential for bone defects. We conclude that cell transfer technology provides a novel and unique cell transplantation method for bone regeneration. PMID:27624174

  3. Double-layered cell transfer technology for bone regeneration.

    PubMed

    Akazawa, Keiko; Iwasaki, Kengo; Nagata, Mizuki; Yokoyama, Naoki; Ayame, Hirohito; Yamaki, Kazumasa; Tanaka, Yuichi; Honda, Izumi; Morioka, Chikako; Kimura, Tsuyoshi; Komaki, Motohiro; Kishida, Akio; Izumi, Yuichi; Morita, Ikuo

    2016-09-14

    For cell-based medicine, to mimic in vivo cellular localization, various tissue engineering approaches have been studied to obtain a desirable arrangement of cells on scaffold materials. We have developed a novel method of cell manipulation called "cell transfer technology", enabling the transfer of cultured cells onto scaffold materials, and controlling cell topology. Here we show that using this technique, two different cell types can be transferred onto a scaffold surface as stable double layers or in patterned arrangements. Various combinations of adherent cells were transferred to a scaffold, amniotic membrane, in overlapping bilayers (double-layered cell transfer), and transferred cells showed stability upon deformations of the material including folding and trimming. Transplantation of mesenchymal stem cells from periodontal ligaments (PDLSC) and osteoblasts, using double-layered cell transfer significantly enhanced bone formation, when compared to single cell type transplantation. Our findings suggest that this double-layer cell transfer is useful to produce a cell transplantation material that can bear two cell layers. Moreover, the transplantation of an amniotic membrane with PDLSCs/osteoblasts by cell transfer technology has therapeutic potential for bone defects. We conclude that cell transfer technology provides a novel and unique cell transplantation method for bone regeneration.

  4. Double-layered cell transfer technology for bone regeneration

    PubMed Central

    Akazawa, Keiko; Iwasaki, Kengo; Nagata, Mizuki; Yokoyama, Naoki; Ayame, Hirohito; Yamaki, Kazumasa; Tanaka, Yuichi; Honda, Izumi; Morioka, Chikako; Kimura, Tsuyoshi; Komaki, Motohiro; Kishida, Akio; Izumi, Yuichi; Morita, Ikuo

    2016-01-01

    For cell-based medicine, to mimic in vivo cellular localization, various tissue engineering approaches have been studied to obtain a desirable arrangement of cells on scaffold materials. We have developed a novel method of cell manipulation called “cell transfer technology”, enabling the transfer of cultured cells onto scaffold materials, and controlling cell topology. Here we show that using this technique, two different cell types can be transferred onto a scaffold surface as stable double layers or in patterned arrangements. Various combinations of adherent cells were transferred to a scaffold, amniotic membrane, in overlapping bilayers (double-layered cell transfer), and transferred cells showed stability upon deformations of the material including folding and trimming. Transplantation of mesenchymal stem cells from periodontal ligaments (PDLSC) and osteoblasts, using double-layered cell transfer significantly enhanced bone formation, when compared to single cell type transplantation. Our findings suggest that this double-layer cell transfer is useful to produce a cell transplantation material that can bear two cell layers. Moreover, the transplantation of an amniotic membrane with PDLSCs/osteoblasts by cell transfer technology has therapeutic potential for bone defects. We conclude that cell transfer technology provides a novel and unique cell transplantation method for bone regeneration. PMID:27624174

  5. A photochromic thin film based on salicylideneaniline derivatives intercalated layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Wang, Xin Rui; Lu, Jun; Yan, Dongpeng; Wei, Min; Evans, David G.; Duan, Xue

    2010-06-01

    Optically transparent thin films with photochromic properties have been fabricated by means of co-intercalation of azomethine-H anions (AMH) and 1-pentanesulfonate (PS) with different molar ratios into the galleries of a ZnAl layered double hydroxide (LDH). The photochromism of AMH occurred in a 2D confined inorganic matrix has been studied by steady state and transient UV-vis spectroscopy. The AMH anion undergoes an excited-state intramolecular proton transfer from the enol tautomer to trans-keto tautomer after UV excitation, and the relaxed back-isomerization to the ground state of enol tautomer was investigated by transient UV-vis spectroscopy.

  6. Anti-Ambipolar Field-Effect Transistors Based On Few-Layer 2D Transition Metal Dichalcogenides.

    PubMed

    Li, Yongtao; Wang, Yan; Huang, Le; Wang, Xiaoting; Li, Xingyun; Deng, Hui-Xiong; Wei, Zhongming; Li, Jingbo

    2016-06-22

    Two-dimensional (2D) materials and their related van der Waals heterostructures have attracted considerable interest for their fascinating new properties. There are still many challenges in realizing the potential of 2D semiconductors in practical (opto)electronics such as signal transmission and logic circuit, etc. Herein, we report the gate-tunable anti-ambipolar devices on the basis of few-layer transition metal dichalcogenides (TMDs) heterostructures to gain higher information storage density. Our study shows that carrier concentration regulated by the gate voltage plays a major role in the "anti-ambipolar" behavior, where the drain-source current can only pass through in specific range of gate voltage (Vg) and it will be restrained if the Vg goes beyond the range. Several improved strategies were theoretically discussed and experimentally adopted to obtain higher current on/off ratio for the anti-ambipolar devices, such as choosing suitable p-/n-pair, increasing carrier concentration by using thicker-layer TMDs, and so on. The modified SnS2/WSe2 device with the current on/off ratio exceeding 200 and on-state Vg ranging from -20 to 0 V was successfully achieved. On the basis of the anti-ambipolar field-effect transistors (FETs), we also reveal the potential of three-channel device unit for signal processing and information storage. With the equal quantity N of device units, 3(N) digital signals can be obtained from such three-channel devices, which are much larger than 2(N) ones obtained from traditional two-channel complementary metal oxide semiconductors (CMOS). PMID:27258569

  7. Double-diffusive layering and mixing in Patagonian fjords

    NASA Astrophysics Data System (ADS)

    Pérez-Santos, Iván; Garcés-Vargas, José; Schneider, Wolfgang; Ross, Lauren; Parra, Sabrina; Valle-Levinson, Arnoldo

    2014-12-01

    Double-diffusive layering was quantified for the first time in the Chilean Patagonian fjords region (41.5-56°S). Approximately 600 temperature and salinity profiles collected during 1995-2012 were used to study water masses, quantify diffusive layering and compute the vertical diffusivity of heat. Development of 'diffusive-layering' or simply 'layering' was favored by relatively fresh-cold waters overlying salty-warm waters. Fresh waters are frequently derived from glacial melting that influences the fjord either directly or through rivers. Salty waters are associated with Modified Subantarctic (MSAAW) and Subantarctic Water (SAAW). Double-diffusive convection occurred as layering in 40% of the year-round data and as salt fingering in <1% of the time. The most vigorous layering, was found at depths between 20 and 70 m, as quantified by (a) Turner angles, (b) density ratios, and (c) heat diffusivity (with maximum values of 5 × 10-5 m2 s-1). Diffusive-layering events presented a meridional gradient with less layering within the 41-47°S northern region, relative to the southern region between 47° and 56°S. Layering occupied, on average, 27% and 56% of the water column in the northern and southern regions, respectively. Thermohaline staircases were detected with microprofile measurements in Martinez and Baker channels (48°S), showing homogeneous layers (2-4 m thick) below the pycnocline (10-40 m). Also in this area, increased vertical mixing coincided with the increased layering events. High values of Thorpe scale (LT ∼ 7 m), dissipation rate of TKE (ε = 10-5-10-3 W kg-1) and diapycnal eddy diffusivity (Kρ = 10-6-10-3 m-2 s-1) were associated with diffusive layering. Implications of these results are that diffusive layering should be taken into account, together with other mixing processes such as shear instabilities and wind-driven flows, in biological and geochemical studies.

  8. Comparing comfort and wearability between Type III single-layered and double-layered EVA mouthguards.

    PubMed

    Kenyon, Brian J; Loos, Larry G

    2005-01-01

    This study compared two Type III ethylene vinyl acetate (EVA) mouthguards for wearability, comfort, fit, and patient preference. Twenty-two athletes each received two custom-fabricated athletic mouthguards, a single-layered vacuum-formed EVA mouthguard and a double-layered heat- and pressure-laminated EVA type. Athletes wore each type of mouthguard for a two-week period while playing basketball. At the end of each two-week period, the athletes completed questionnaires that evaluated 17 characteristics of each mouthguard type. Data were analyzed using the binomial test for small numbers. The double-layered heat- and pressure-laminated EVA mouthguard performed as well as or better than the single-layered vacuum-formed type in 14 of the 17 categories. There was a statistically significant patient preference for the double-layered heat- and pressure-laminated mouthguard.

  9. Long-range alignments of single fullerenes by site-selective inclusion into a double-cavity 2D open network.

    PubMed

    Piot, Luc; Silly, Fabien; Tortech, Ludovic; Nicolas, Yohann; Blanchard, Philippe; Roncali, Jean; Fichou, Denis

    2009-09-16

    We show by means of STM that C(60) molecules can be trapped into specific sites of a 2D double-cavity open network, thus forming long-range alignments of single molecules. Since only one of the two cavities has the right size to host C(60), the smallest cavity remains empty and is thus available to trap additional species of smaller size. This novel 2D supramolecular network opens new perspectives in the design of multicomponent guest-host architectures with electronic functionalities. PMID:19462948

  10. Double layer formation at the interface of complex plasmas

    SciTech Connect

    Yaroshenko, V. V.; Thoma, M. H.; Thomas, H. M.; Morfill, G. E.

    2008-08-15

    Necessary conditions are formulated for the generation of a double layer at the interface of a complex plasma and a particle-free electron-ion plasma in a weakly collisional discharge. Examples are calculated for realistic observed complex plasmas, and it is shown that situations of both ''smooth'' transitions and 'sharp' transitions can exist. The model can explain the abrupt boundaries observed.

  11. Study of the anode plasma double layer: optogalvanic detectors

    SciTech Connect

    Gurlui, S.; Dimitriu, D.; Strat, M.; Strat, Georgeta

    2006-01-15

    The experimental and theoretical results show that the anode double layer (DL) is a very sensitive plasma formation suitable for fine optogalvanic studies. The obtained results demonstrate that the parameters of the oscillations sustained by a DL (frequency, amplitude) can be used as optogalvanic detectors.

  12. Specific ion effects via ion hydration: II. Double layer interaction.

    PubMed

    Ruckenstein, Eli; Manciu, Marian

    2003-09-18

    A simple modified Poisson-Boltzmann formalism, which accounts also for those interactions between electrolyte ions and colloidal particles not included in the mean potential, is used to calculate the force between two parallel plates. It is shown that the short-range interactions between ions and plates, such as those due to the change in the hydration free energy of a structure-making/breaking ion that approaches the interface, affect the double layer interaction at large separations through the modification of the surface potential and surface charge density. While at short separations (below the range of the short-range ion-hydration forces) the interaction can be attractive, at larger separations the interaction is always repulsive, as in the traditional theory. When the long-range van der Waals interactions between the ions and the system (ion-dispersion interactions) are accounted for in the modified Poisson-Boltzmann approach, an attractive force between plates can be generated. At sufficiently large separations, this attraction can become even stronger than the traditional van der Waals attraction between plates of finite thickness, thus generating a dominant long-range 'double layer attraction'. At small plate separations, the attraction generated by the ion-dispersion forces combined with the electrostatic repulsion due to the double layers overlap can lead to a variety of interactions, from a weak attraction (which is typically by at least one order of magnitude smaller than the traditional van der Waals attraction between plates) to a strong double layer repulsion (for sufficiently large surface charges). Both types of ion interactions (long-range van der Waals or short-range ionic hydration) strongly affect the magnitude of the double layer interaction, and can account for the specific ion effects observed experimentally. However, they do not affect qualitatively the traditional theory of the colloid stability, which predicts that the colloid is stable

  13. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2.

    PubMed

    Jin, Z; Xia, Z-C; Wei, M; Yang, J-H; Chen, B; Huang, S; Shang, C; Wu, H; Zhang, X-X; Huang, J-W; Ouyang, Z-W

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration. PMID:27485370

  14. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2

    NASA Astrophysics Data System (ADS)

    Jin, Z.; Xia, Z.-C.; Wei, M.; Yang, J.-H.; Chen, B.; Huang, S.; Shang, C.; Wu, H.; Zhang, X.-X.; Huang, J.-W.; Ouyang, Z.-W.

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration.

  15. Plasmon modes of circular cylindrical double-layer graphene.

    PubMed

    Zhao, Tao; Hu, Min; Zhong, Renbin; Chen, Xiaoxing; Zhang, Ping; Gong, Sen; Zhang, Chao; Liu, Shenggang

    2016-09-01

    In this paper, a theoretical investigation on plasmon modes in a circular cylindrical double-layer graphene structure is presented. Due to the interlayer electromagnetic interaction, there exist two branches of plasmon modes, the optical plasmon mode and the acoustic plasmon mode. The characteristics of these two modes, such as mode pattern, effective mode index and propagation loss, are analyzed. The modal behaviors can be effectively tuned by changing the distance between two graphene layers, the chemical potential of graphene and the permittivity of interlayer dielectric. Importantly, the breakup of tradeoff between mode confinement and propagation loss is discovered in the distance-dependent modal behavior, which originates from the unique dispersion properties of a double-layer graphene system. As a consequence, both strong mode confinement and longer propagation length can be achieved. Our results may provide good opportunities for developing applications based on graphene plasmonics in circular cylindrical structure. PMID:27607651

  16. Plasmon modes of circular cylindrical double-layer graphene.

    PubMed

    Zhao, Tao; Hu, Min; Zhong, Renbin; Chen, Xiaoxing; Zhang, Ping; Gong, Sen; Zhang, Chao; Liu, Shenggang

    2016-09-01

    In this paper, a theoretical investigation on plasmon modes in a circular cylindrical double-layer graphene structure is presented. Due to the interlayer electromagnetic interaction, there exist two branches of plasmon modes, the optical plasmon mode and the acoustic plasmon mode. The characteristics of these two modes, such as mode pattern, effective mode index and propagation loss, are analyzed. The modal behaviors can be effectively tuned by changing the distance between two graphene layers, the chemical potential of graphene and the permittivity of interlayer dielectric. Importantly, the breakup of tradeoff between mode confinement and propagation loss is discovered in the distance-dependent modal behavior, which originates from the unique dispersion properties of a double-layer graphene system. As a consequence, both strong mode confinement and longer propagation length can be achieved. Our results may provide good opportunities for developing applications based on graphene plasmonics in circular cylindrical structure.

  17. Bound States in the Continuum in double layer structures

    PubMed Central

    Li, LiangSheng; Yin, Hongcheng

    2016-01-01

    We have theoretically investigated the reflectivity spectrums of single- and double-layer photonic crystal slabs and the dielectric multilayer stack. It is shown that light can be perfectly confined in a single-layer photonic crystal slab at a given incident angle by changing the thickness, permittivity or hole radius of the structure. With a tunable double-layer photonic crystal slab, we demonstrate that the occurrence of tunable bound states in the continuum is dependent on the spacing between two slabs. Moreover, by analytically investigating the Drude lossless multilayer stack model, the spacing dependence of bound states in the continuum is characterized as the phase matching condition that illuminates these states can occur at any nonzero incident angles by adjusting the spacing. PMID:27245435

  18. Layered Structures in Magmatic Systems From Double-Diffusive Convection

    NASA Astrophysics Data System (ADS)

    Hansen, U.; Schmalzl, J.

    2004-05-01

    The evolution of magmatic systems is often influenced by the existence of discrete layers. Such layering can not be explained by gravitational settling and other dynamical mechanisms have been proposed. Double-diffusive convection is considered to be such a mechanism. In the diffusive regime, where the slowly diffusing component (e,g composition) acts to stabilize the system and the fast diffusing component /e.g. heat) provides the destabilizing force, the formation of layers has been observed. Most studies. however, concentrated on the properties of layers and not on the actual formation. In a series of two- and three dimensional numerical experiments, we have investigated the evolution of layers from non-layered initial states. Layer formation is found to depend on the ratio of thermal to compositional diffusivities (the Lewis number). The influence of the Lewis number has been systematically investigated by employing a field approach to monitor the evolution of the composition. Magmatic systems have a very high Lewis number which can hardly be realized with such an approach. We have therefore developed a tracer method, allowing to study the system in the limit of an infinite Lewis number. With both methods we obtain qualitative similar layered structures. In order to better understand layer formation in magmatic systems, we have included effects of temperature-and compositionaly dependent viscosity. Our results show that the viscosity has a strong influence on the temporal evolution of the system and on the resulting type of layering

  19. 2D sandbox experiments of surfactant foams for mobility control and enhanced LNAPL recovery in layered soils

    NASA Astrophysics Data System (ADS)

    Longpré-Girard, Mélanie; Martel, Richard; Robert, Thomas; Lefebvre, René; Lauzon, Jean-Marc

    2016-10-01

    The ability of surfactant foam to enhance mobility control and LNAPL recovery in a heterogeneous porous media was investigated through sandbox experiments with p-xylene used as LNAPL. A layered heterogeneous porous media was represented in a 2D sandbox filled with two layers of coarse and medium silica sand. Based on previous tests, the surfactant solution used was Ammonyx Lo at a concentration of 0.1% (w/w). The sandbox experimental program included tracer tests done under both uncontaminated and contaminated conditions, foam injection under uncontaminated conditions and surfactant solution and foam injection under contaminated conditions. Tracer tests indicated that the permeability contrast between sand layers was increased by LNAPL contamination. Foam injection under uncontaminated conditions presented a S-shaped front that indicated a better mobility control than the piston-shaped front obtained during tracer tests. During foam injection, complete sweep of the sandbox was achieved with 1.8 pore volume (PV) compared to 2.8 PV during tracer injection, thus indicating better mobility control with foam. Pre-flush of the contaminated sandbox with surfactant solution initiated p-xylene mobilization but no free phase was recovered at the effluent. A negligible p-xylene residual saturation was reached following foam injection in the contaminated sandbox. However, mass balance indicated a total recovery of only 48% of the initial p-xylene, thus indicating an underestimation of the recovery by volatilization. Recovery by volatilization was corrected, which gave the following proportions of LNAPL recovery mechanisms: 19% by mobilization, 16% by dissolution and 65% by volatilization. Results show the potential efficiency of foam remediation of LNAPL source zones in heterogeneous porous media. Still, further developments are needed prior to field scale application, which could benefit from in situ foam production that would simplify on-site operations.

  20. Ultrasonicated double wall carbon nanotubes for enhanced electric double layer capacitance

    NASA Astrophysics Data System (ADS)

    Pandey, Srikrishna; Maiti, Uday N.; Palanisamy, Kowsalya; Nikolaev, Pavel; Arepalli, Sivaram

    2014-06-01

    An intense ultrasonication of the double wall carbon nanotubes (DWCNTs) causes fractures and splitting of the individual tubes. This not only generates open tips and edges in DWCNTs but also incorporates defects in the tube walls. The electric double layer capacitor (EDLC) electrodes of intensively ultrasonicated DWCNTs (U-DWCNTs) form organized layered-porous structures. The EDLC behavior of U-DWCNTs electrodes shows dramatic improvements (specific capacitance 10 times and 222 times larger than the pristine DWCNTs at scan rates 5 mV s-1 and 500 mV s-1, respectively) due to the increased wettability of electrodes and accessibility of the electrolyte ions.

  1. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure

    NASA Astrophysics Data System (ADS)

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H.; Khondaker, Saiful I.; Choi, Wonbong; Jung, Yeonwoong

    2016-05-01

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm2) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials.

  2. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure.

    PubMed

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H; Khondaker, Saiful I; Choi, Wonbong; Jung, Yeonwoong

    2016-05-05

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm(2)) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials.

  3. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure

    PubMed Central

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H.; Khondaker, Saiful I.; Choi, Wonbong; Jung, Yeonwoong

    2016-01-01

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm2) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials. PMID:27147503

  4. Regional spherical modeling of 2-D functions: The case of the critical frequency of the F2 ionospheric layer

    NASA Astrophysics Data System (ADS)

    De Santis, A.; De Franceschi, G.; Kerridge, D. J.

    1994-06-01

    In this paper it is shown that Adjusted Spherical Harmonic Analysis (ASHA), previously used for modeling the three-dimensional (3-D) geomagnetic field in a restricted area can be adapted to model general bidimensional (2-D) spherical functions, f(γ, θ). As an example of application the case of the critical frequency of the F2 ionospheric layer, f0F2 is described. By assuming that, at a fixed epoch, the monthly median value of f0F2 is a function only of the geographic longitude γ and colatitude θ, that is f0F2 = f( γ, θ), ASHA has been applied to modeling and mapping this ionospheric parameter over Europe. Here, the FORTRAN-77 computer programs and subprograms are presented enabling the practical and easy use of the ASHA technique to obtain, as a final output, either a grid (2 × 2 degrees) of the computed monthly medians of f0F2 in the European area and the calculated value of the parameter at one point, in the region of interest, as a function of time. The same codes can be adapted easily to be used for modeling any bidimensional function defined over a spherical portion of the Earth.

  5. Experimental Database with Baseline CFD Solutions: 2-D and Axisymmetric Hypersonic Shock-Wave/Turbulent-Boundary-Layer Interactions

    NASA Technical Reports Server (NTRS)

    Marvin, Joseph G.; Brown, James L.; Gnoffo, Peter A.

    2013-01-01

    A database compilation of hypersonic shock-wave/turbulent boundary layer experiments is provided. The experiments selected for the database are either 2D or axisymmetric, and include both compression corner and impinging type SWTBL interactions. The strength of the interactions range from attached to incipient separation to fully separated flows. The experiments were chosen based on criterion to ensure quality of the datasets, to be relevant to NASA's missions and to be useful for validation and uncertainty assessment of CFD Navier-Stokes predictive methods, both now and in the future. An emphasis on datasets selected was on surface pressures and surface heating throughout the interaction, but include some wall shear stress distributions and flowfield profiles. Included, for selected cases, are example CFD grids and setup information, along with surface pressure and wall heating results from simulations using current NASA real-gas Navier-Stokes codes by which future CFD investigators can compare and evaluate physics modeling improvements and validation and uncertainty assessments of future CFD code developments. The experimental database is presented tabulated in the Appendices describing each experiment. The database is also provided in computer-readable ASCII files located on a companion DVD.

  6. Spatial instability of viscous double-layer liquid sheets

    NASA Astrophysics Data System (ADS)

    Ye, Han-Yu; Yang, Li-Jun; Fu, Qing-Fei

    2016-10-01

    This paper investigates the spatial instability of a double-layer viscous liquid sheet moving in a stationary gas medium. A linear stability analysis is conducted and two situations are considered, an inviscid-gas situation and a viscous-gas situation. In the inviscid-gas situation, the basic state of the entire gas phase is stationary and the analytical dispersion relation is derived. Similar to single-layer sheets, the instability of double-layer sheets presents two unstable modes, the sinuous and the varicose modes. However, the result of the base-case double-layer sheet indicates that the cutoff wavenumber of the dispersion curve is larger than that of a single-layer sheet. A decomposition of the growth rate is performed and the result shows that for small wavenumbers, the surface tension of all three interfaces and the aerodynamic forces of both the lower and upper gases contribute significantly to the unstable growth rate. In contrast, for large wavenumbers the major contribution to the unstable growth rate is only the surface tension of the upper interface and the aerodynamic force of the upper gas. In the viscous-gas situation, although the majority of the gas phase is stationary, gas boundary layers exist at the vicinity of the moving liquid sheet, and the stability problem is solved by a spectral collocation method. Compared with the inviscid-gas solution, the growth rate at large wavenumber is significantly suppressed. The decomposition of growth rate indicates that all the aerodynamic and surface tension terms behave consistently throughout the entire unstable wavenumber range. The effects of various parameters are discussed. In addition, the effect of gas viscosity and the gas velocity profile is investigated separately, and the results indicate that both factors affect the maximum growth rate and the dominant wavenumber, although the effect of the gas velocity profile is stronger than that of the gas viscosity.

  7. Electrical power generation by mechanically modulating electrical double layers.

    PubMed

    Moon, Jong Kyun; Jeong, Jaeki; Lee, Dongyun; Pak, Hyuk Kyu

    2013-01-01

    Since Michael Faraday and Joseph Henry made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system in the near future. PMID:23403587

  8. Development and current status of electric double-layer capacitors

    SciTech Connect

    Morimoto, Takeshi; Hiratsuka, Kazuya; Sanada, Yasuhiro; Kurihara, Kaname

    1995-12-31

    An electric double layer capacitor (EDLC) based on the charge storage at the interface between a high surface area carbon electrode and an electrolyte solution is widely used as maintenance-free power source for IC memories and microcomputers. New applications for electric double-layer capacitors have been proposed in recent years. The popularity of these devices is derived from their high energy density relative to conventional capacitors and their long cycle life and high power density relative to batteries. In this paper a classification and a characteristics of industrially produced Japanese small EDLCs are reviewed. Structure and performance of power capacitors under development as well as materials and performance of industrially produced small capacitors are discussed.

  9. Electrical Power Generation by Mechanically Modulating Electrical Double Layers

    NASA Astrophysics Data System (ADS)

    Lee, Dongyun; Moon, Jong Kyun; Jeong, Jaeki; Pak, Hyuk Kyu

    2012-11-01

    Many objects in contact with a liquid acquire some electronic charges on their surfaces. These charges on the surface attract counter ions from the liquid phase. This complex system is called electrical double layer (EDL). Since its geometry and structure is similar to an electric capacitor, it is also called an electrical double layer capacitor (EDLC). In this work we studied two EDLCs formed in a liquid droplet bridge between two parallel solid conducting plates. We found that when the bridge height was mechanically modulated, each EDLC was continuously charged and discharged generating an AC electric current across the plates. The results of this experiment can be useful for constructing a micro-fluidic power generation.

  10. Electrical power generation by mechanically modulating electrical double layers.

    PubMed

    Moon, Jong Kyun; Jeong, Jaeki; Lee, Dongyun; Pak, Hyuk Kyu

    2013-01-01

    Since Michael Faraday and Joseph Henry made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system in the near future.

  11. Interlayer tunneling in double-layer quantum hall pseudoferromagnets.

    PubMed

    Balents, L; Radzihovsky, L

    2001-02-26

    We show that the interlayer tunneling I-V in double-layer quantum Hall states displays a rich behavior which depends on the relative magnitude of sample size, voltage length scale, current screening, disorder, and thermal lengths. For weak tunneling, we predict a negative differential conductance of a power-law shape crossing over to a sharp zero-bias peak. An in-plane magnetic field splits this zero-bias peak, leading instead to a "derivative" feature at V(B)(B(parallel)) = 2 pi Planck's over 2 pi upsilon B(parallel)d/e phi(0), which gives a direct measurement of the dispersion of the Goldstone mode corresponding to the spontaneous symmetry breaking of the double-layer Hall state. PMID:11290258

  12. Experimental investigation of current free double layers in helicon plasmas

    SciTech Connect

    Sahu, B. B.; Tarey, R. D.; Ganguli, A.

    2014-02-15

    The paper presents investigations of current free double layer (CFDL) that forms in helicon plasmas. In contrast to the other work reporting on the same subject, in the present investigations the double layer (DL) forms in a mirror-like magnetic field topology. The RF compensated Langmuir probe measurements show multiple DLs, which are in connection with, the abrupt fall of densities along with potential drop of about 24 V and 18 V. The DLs strengths (e ΔV{sub p})/(k T{sub e}) are about 9.5 and 6, and the corresponding widths are about 6 and 5 D lengths. The potential drop is nearly equal to the thermal anisotropies between the two plasma regions forming the DL, which is present in the plateau region of mirror, unlike the earlier studies on the DL formation in the region of strong gradients in the magnetic field. Also, it presents a qualitative discussion on the mechanism of DL formation.

  13. Observations of double layers in earth's plasma sheet.

    PubMed

    Ergun, R E; Andersson, L; Tao, J; Angelopoulos, V; Bonnell, J; McFadden, J P; Larson, D E; Eriksson, S; Johansson, T; Cully, C M; Newman, D N; Goldman, M V; Roux, A; LeContel, O; Glassmeier, K-H; Baumjohann, W

    2009-04-17

    We report the first direct observations of parallel electric fields (E_{ parallel}) carried by double layers (DLs) in the plasma sheet of Earth's magnetosphere. The DL observations, made by the THEMIS spacecraft, have E_{ parallel} signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth's plasma sheet. PMID:19518640

  14. Observations of Double Layers in Earth's Plasma Sheet

    SciTech Connect

    Ergun, R. E.; Tao, J.; Andersson, L.; Eriksson, S.; Johansson, T.; Angelopoulos, V.; Bonnell, J.; McFadden, J. P.; Larson, D. E.; Cully, C. M.; Newman, D. N.; Goldman, M. V.; Roux, A.; LeContel, O.; Glassmeier, K.-H.; Baumjohann, W.

    2009-04-17

    We report the first direct observations of parallel electric fields (E{sub parallel}) carried by double layers (DLs) in the plasma sheet of Earth's magnetosphere. The DL observations, made by the THEMIS spacecraft, have E{sub parallel} signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth's plasma sheet.

  15. [Rat uterus anastomoses in a single and a double layer].

    PubMed

    Gianaroli, L; Bufferli, M; Livani, M F

    1980-11-15

    The Authors display their results on microsurgical operations in rat's uteri. After having described the instruments and methods used, the surgical techniques and the differences between a single and a double layer suture are discussed. However the formation of intraoperative adherences, which can damage the functional results of the intervention, is studied. And what's more the mean number of live born foetuses is seen as an attainable parameter for future validations. PMID:7011341

  16. Carrier relaxation time divergence in single and double layer cuprates

    NASA Astrophysics Data System (ADS)

    Schneider, M. L.; Rast, S.; Onellion, M.; Demsar, J.; Taylor, A. J.; Glinka, Y.; Tolk, N. H.; Ren, Y. H.; Lüpke, G.; Klimov, A.; Xu, Y.; Sobolewski, R.; Si, W.; Zeng, X. H.; Soukiassian, A.; Xi, X. X.; Abrecht, M.; Ariosa, D.; Pavuna, D.; Krapf, A.; Manzke, R.; Printz, J. O.; Williamsen, M. S.; Downum, K. E.; Guptasarma, P.; Bozovic, I.

    2003-12-01

    We report the transient optical pump-probe reflectivity measurements on single and double layer cuprate single crystals and thin films of ten different stoichiometries. We find that with sufficiently low fluence the relaxation time (tauR) of all samples exhibits a power law divergence with temperature (T): tauR ∝ T^{-3 ± 0.5}. Further, the divergence has an onset temperature above the superconducting transition temperature for all superconducting samples. Possible causes of this divergence are discussed.

  17. Electrostatic double layers as auroral particle accelerators - a problem

    NASA Astrophysics Data System (ADS)

    Bryant, D. A.; Courtier, G. M.

    2015-04-01

    A search of the Annales Geophysicae database shows that double layers and other quasi-static electric potential structures have been invoked hundreds of times since the year 2000 as being the agents of auroral electron acceleration. This is despite the fact that energy transfer by conservative fields has been known for some 200 years to be impossible. Attention is drawn to a long-standing interpretation of the acceleration process in terms of the dynamic fields of electrostatic waves.

  18. Two-dimensional potential double layers and discrete auroras

    NASA Technical Reports Server (NTRS)

    Kan, J. R.; Lee, L. C.; Akasofu, S.-I.

    1979-01-01

    This paper is concerned with the formation of the acceleration region for electrons which produce the visible auroral arc and with the formation of the inverted V precipitation region. The former is embedded in the latter, and both are associated with field-aligned current sheets carried by plasma sheet electrons. It is shown that an electron current sheet driven from the plasma sheet into the ionosphere leads to the formation of a two-dimensional potential double layer. For a current sheet of a thickness less than the proton gyrodiameter solutions are obtained in which the field-aligned potential drop is distributed over a length much greater than the Debye length. For a current sheet of a thickness much greater than the proton gyrodiameter solutions are obtained in which the potential drop is confined to a distance on the order of the Debye length. The electric field in the two-dimensional double-layer model is the zeroth-order field inherent to the current sheet configuration, in contrast to those models in which the electric field is attributed to the first-order field due to current instabilities or turbulences. The maximum potential in the two-dimensional double-layer models is on the order of the thermal energy of plasma sheet protons, which ranges from 1 to 10 keV.

  19. Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics

    PubMed Central

    Munje, Rujuta D.; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

    2015-01-01

    An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10–200 ng/mL. PMID:26420511

  20. Electrostatic supersolitons and double layers at the acoustic speed

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.

    2015-01-15

    Supersolitons are characterized by subsidiary extrema on the sides of a typical bipolar electric field signature or by association with a root beyond double layers in the fully nonlinear Sagdeev pseudopotential description. It has been proven that supersolitons may exist in several plasmas having at least three constituent species, but they cannot be found in weakly nonlinear theory. Another recent aspect of pseudopotential theory is that in certain plasma models and parameter regimes solitons and/or double layers can exist at the acoustic speed, having no reductive perturbation counterparts. Importantly, they signal coexistence between solitons having positive and negative polarity, in that one solution can be realized at a time, depending on infinitesimal perturbations from the equilibrium state. Weaving the two strands together, we demonstrate here that one can even find supersolitons and double layers at the acoustic speed, as illustrated using the model of cold positive and negative ions, in the presence of nonthermal electrons following a Cairns distribution. This model has been discussed before, but the existence and properties of supersolitons at the acoustic speed were not established at the time of publication.

  1. Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics.

    PubMed

    Munje, Rujuta D; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

    2015-09-30

    An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

  2. Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics

    NASA Astrophysics Data System (ADS)

    Munje, Rujuta D.; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

    2015-09-01

    An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

  3. Numerical simulations of double layers and auroral electric fields

    NASA Technical Reports Server (NTRS)

    Singh, N.; Schunk, R. W.; Thiemann, H.

    1984-01-01

    Recent one-dimensional and two-dimensional numerical simulations of double layers (DLs) in the electric fields of the auroral plasma are reviewed, with reference to observational data. It is found that two-dimensional DLs driven by current sheets of finite thickness have different characteristics, depending on whether the layer thickness is less than or much greater than the ion gyroradius: When thickness is less than ion gyroradius, V-shaped DLs form with nearly equal parallel and perpendicular potential drops; when layer thickness is much greater than ion gyroradius the major parallel potential drop occurs outside the current sheet and the perpendicular electric fields are localized at the edges of the current sheet. It is shown that some features of the simulated fields, such as the amplitudes and scale lengths, are qualitatively similar to those observed in space.

  4. Layer-by-Layer Polyelectrolyte Assisted Growth of 2D Ultrathin MoS2 Nanosheets on Various 1D Carbons for Superior Li-Storage.

    PubMed

    Qu, Qunting; Qian, Feng; Yang, Siming; Gao, Tian; Liu, Weijie; Shao, Jie; Zheng, Honghe

    2016-01-20

    Transitional metal sulfide/carbon hybrids with well-defined structures could not only maximize the functional properties of each constituent but engender some unique synergistic effects, holding great promise for applications in Li-ion batteries and supercapacitors and for catalysis. Herein, a facile and versatile approach is developed to controllably grow 2D ultrathin MoS2 nanosheets with a large quantity of exposed edges onto various 1D carbons, including carbon nanotubes (CNTs), electrospun carbon nanofibers, and Te-nanowire-templated carbon nanofibers. The typical approach involves the employment of layer-by-layer (LBL) self-assembled polyelectrolyte, which controls spatially the uniform growth and orientation of ultrathin MoS2 nanosheets on these 1D carbons irrespective of their surface properties. Such unique structures of the as-prepared CNTs@MoS2 hybrid are significantly favorable for the fast diffusions of both Li-ions and electrons, satisfying the kinetic requirements of high-power lithium ion batteries. As a result, CNTs@MoS2 hybrids exhibit excellent electrochemical performances for lithium storage, including a high reversible capacity (1027 mAh g(-1)), high-rate capability (610 mAh g(-1) at 5 C), and excellent cycling stability (negligible capacity loss after 200 continuous cycles).

  5. Layer-by-Layer Polyelectrolyte Assisted Growth of 2D Ultrathin MoS2 Nanosheets on Various 1D Carbons for Superior Li-Storage.

    PubMed

    Qu, Qunting; Qian, Feng; Yang, Siming; Gao, Tian; Liu, Weijie; Shao, Jie; Zheng, Honghe

    2016-01-20

    Transitional metal sulfide/carbon hybrids with well-defined structures could not only maximize the functional properties of each constituent but engender some unique synergistic effects, holding great promise for applications in Li-ion batteries and supercapacitors and for catalysis. Herein, a facile and versatile approach is developed to controllably grow 2D ultrathin MoS2 nanosheets with a large quantity of exposed edges onto various 1D carbons, including carbon nanotubes (CNTs), electrospun carbon nanofibers, and Te-nanowire-templated carbon nanofibers. The typical approach involves the employment of layer-by-layer (LBL) self-assembled polyelectrolyte, which controls spatially the uniform growth and orientation of ultrathin MoS2 nanosheets on these 1D carbons irrespective of their surface properties. Such unique structures of the as-prepared CNTs@MoS2 hybrid are significantly favorable for the fast diffusions of both Li-ions and electrons, satisfying the kinetic requirements of high-power lithium ion batteries. As a result, CNTs@MoS2 hybrids exhibit excellent electrochemical performances for lithium storage, including a high reversible capacity (1027 mAh g(-1)), high-rate capability (610 mAh g(-1) at 5 C), and excellent cycling stability (negligible capacity loss after 200 continuous cycles). PMID:26709711

  6. Characterization of a novel NKG2D and NKp46 double-mutant mouse reveals subtle variations in the NK cell repertoire

    PubMed Central

    Sheppard, Sam; Triulzi, Chiara; Ardolino, Michele; Serna, Daniel; Zhang, Lily; Raulet, David H.

    2013-01-01

    The immunoreceptors NKG2D and NKp46 are known for their capacity to activate natural killer (NK) cell cytotoxicity and secretory responses in the contexts of tumors and infections, yet their roles in NK cell education remain unclear. Here, we provide the first characterization of mice deficient for both NKG2D and NKp46 receptors to address the relevance of their concomitant absence during NK cell development and function. Our findings reveal that NK cells develop normally in double-mutant (DKO) mice. Mice lacking NKG2D but not NKp46 showed subtle differences in the percentages of NK cells expressing inhibitory Ly49 receptors and the adhesion molecule DNAM-1. A slightly increased percentage of terminally differentiated NK cells and functional response to in vitro stimuli was observed in some experiments. These alterations were modest and did not affect NK cell function in vivo in response to mouse cytomegalovirus infection. NKp46 deficiency alone, or in combination with NKG2D deficiency, had no effect on frequency or function of NK cells. PMID:23649470

  7. Self assembly of sandwich-layered 2D silver(I) coordination polymers stabilized by argentophilic interactions: Synthesis, crystal structures and ab initio intramolecular energetics

    NASA Astrophysics Data System (ADS)

    Zorlu, Yunus; Can, Hatice

    2014-11-01

    Two different two-dimensional silver(I) coordination polymers, namely {[Ag2(dcpa)}n (1) and {[Ag2(ma)]}n (2), where dcpa = 4,5-dichlorophthalate; ma = maleate, were synthesized and structurally analyzed by single crystal X-ray diffraction technique. Complexes 1 and 2 represent 2D coordination polymer with metal-organic sandwich type. Two independent Ag(I) ions in both complexes are linked to constructed 2D layer by μ8-η3:η2:η2:η1 (for complex 1) and μ8-η3:η3:η2:η2 (for complex 2) carboxylate bridging fashions. The 2D layers of 1 are further extended into a three-dimensional (3D) supramolecular network by weak Cl⋯Cl interactions while 2D layers of 2 are linked by weak CH⋯O interactions into a 3D supramolecular framework. These two complexes exhibit considerable short Ag-Ag argentophilic interactions. The long-range corrected density functional theory (DFT) method was used to investigate intramolecular energetics, which are responsible for these 2D structures. Natural bond orbital (NBO) analysis with long-range corrected DFT method assists to understand these intramolecular interactions.

  8. Ultrafast switching of an electrochromic device based on layered double hydroxide/Prussian blue multilayered films

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoxi; Zhou, Awu; Dou, Yibo; Pan, Ting; Shao, Mingfei; Han, Jingbin; Wei, Min

    2015-10-01

    Electrochromic materials are the most important and essential components in an electrochromic device. Herein, we fabricated high-performance electrochromic films based on exfoliated layered double hydroxide (LDH) nanosheets and Prussian blue (PB) nanoparticles via the layer-by-layer assembly technique. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of (LDH/PB)n ultrathin films (UTFs). The resulting (LDH/PB)n UTF electrodes exhibit electrochromic behavior arising from the reversible K+ ion migration into/out of the PB lattice, which induces a change in the optical properties of the UTFs. Furthermore, an electrochromic device (ECD) based on the (LDH/PB)n-ITO/0.1 M KCl electrolyte/ITO sandwich structure displays superior response properties (0.91/1.21 s for coloration/bleaching), a comparable coloration efficiency (68 cm2 C-1) and satisfactory optical contrast (45% at 700 nm), in comparison with other inorganic material-based ECDs reported previously. Therefore, this work presents a facile and cost-effective strategy to immobilize electrochemically active nanoparticles in a 2D inorganic matrix for potential application in displays, smart windows and optoelectronic devices.Electrochromic materials are the most important and essential components in an electrochromic device. Herein, we fabricated high-performance electrochromic films based on exfoliated layered double hydroxide (LDH) nanosheets and Prussian blue (PB) nanoparticles via the layer-by-layer assembly technique. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of (LDH/PB)n ultrathin films (UTFs). The resulting (LDH/PB)n UTF electrodes exhibit electrochromic behavior arising from the reversible K+ ion migration into/out of the PB lattice, which induces a change in the optical properties of the UTFs. Furthermore, an electrochromic device (ECD) based on the (LDH

  9. Large-scale synthesis of highly dispersed layered double hydroxide powders containing delaminated single layer nanosheets.

    PubMed

    Wang, Qiang; O'Hare, Dermot

    2013-07-18

    A facile method for the synthesis of Zn2Al-borate and Mg3Al-borate layered double hydroxides (LDHs) with extremely high specific surface areas of 458.6 and 263 m(2) g(-1) and containing delaminated nanosheets is reported. To the best of our knowledge, this is the first report of LDH powders that still remain exfoliated on drying.

  10. Anode Sheath and Double Layer Solutions with Ionization

    NASA Astrophysics Data System (ADS)

    Scheiner, Brett S.; Baalrud, Scott D.

    2014-10-01

    When an electrode in a plasma is biased more positive than the plasma potential it attracts electrons and repels ions forming a region of negative space charge (electron sheath). Ballistic electrons moving towards this anode gain energy equal to the difference in electrostatic potential energy, Δϕ = ϕ (x) -ϕplasma , with a maximum of ϕanode -ϕplasma . When ϕanode is large enough, electrons can gain enough energy to ionize neutral atoms through electron impact ionization. This leads to a layer of increased ion density near the anode, which can exceed the local electron density at large enough anode biases forming a double layer. We model the sheath potential profile using Poisson's equation with a fluid model for the electron density in the case without ionization and formulate an integral equation for the case with ionization where the ion density depends on an integral from ϕ (x) to ϕanode. An analytic form of the sheath electric field is obtained for the case without ionization and we demonstrate that it asymptotically agrees with the Child-Langmuir solution. We numerically obtain double layer solutions when including ionization and show that the potential profile expands beyond that of the Child-Langmuir solution. This work was supported by the Office of Fusion Science at the U.S. Department of Energy under Contract DE-AC04-94SL85000.

  11. Multi-ion Double Layers in a Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Shahmansouri, M.; Alinejad, H.; Tribeche, M.

    2015-11-01

    A theoretical investigation is carried out to study the existence, formation and basic properties of ion acoustic (IA) double layers (DLs) in a magnetized bi-ion plasma consisting of warm/cold ions and Boltzmann distributed electrons. Based on the reductive perturbation technique, an extended Korteweg de-Vries (KdV) equation is derived. The propagation of two possible modes (fast and slow), and their evolution are investigated. The effects of obliqueness, magnitude of the magnetic field, ion concentration, polarity of ions, and ion temperature on the IA DL profile are analyzed, and then the ranges of parameters for which the IA DLs exist are investigated in details.

  12. Solitary waves and double layers in a dusty electronegative plasma

    SciTech Connect

    Mamun, A. A.; Shukla, P. K.; Eliasson, B.

    2009-10-15

    A dusty electronegative plasma containing Boltzmann electrons, Boltzmann negative ions, cold mobile positive ions, and negatively charged stationary dust has been considered. The basic features of arbitrary amplitude solitary waves (SWs) and double layers (DLs), which have been found to exist in such a dusty electronegative plasma, have been investigated by the pseudopotential method. The small amplitude limit has also been considered in order to study the small amplitude SWs and DLs analytically. It has been shown that under certain conditions, DLs do not exist, which is in good agreement with the experimental observations of Ghim and Hershkowitz [Y. Ghim (Kim) and N. Hershkowitz, Appl. Phys. Lett. 94, 151503 (2009)].

  13. Plasma resonant terahertz photomixers based on double graphene layer structures

    NASA Astrophysics Data System (ADS)

    Ryzhii, Maxim; Shur, Michael S.; Mitin, Vladimir; Satou, Akira; Ryzhii, Victor; Otsuji, Taiichi

    2014-03-01

    We propose terahertz (THz) photomixers based on double graphene layer (DGL) structures, utilizing the interband absorption of modulated optical radiation, tunneling or thermionic inter-GL transitions, and resonant excitation of plasma oscillations. Using the developed device model, we substantiate the operation of the photomixers and calculate their characteristics. We demonstrate that the output frequency-dependent power of THz radiation exhibits pronounced resonant peaks at the plasmonic resonant frequencies. The proposed THz photomixer can surpass the pertinent devices based on the standard heterostructures.

  14. Double-Layered Lateral Meniscus Accompanied by Meniscocapsular Separation.

    PubMed

    Fukuda, Aki; Nishimura, Akinobu; Nakazora, Shigeto; Kato, Ko; Sudo, Akihiro

    2015-01-01

    We report an extremely rare case of double-layered lateral meniscus accompanied by meniscocapsular separation. The upper accessory meniscus was connected with the posterior horn and middle segment of the lower normal meniscus and was more mobile than the lower normal meniscus. A meniscocapsular separation was evident at the overlapping middle segment. Clinical symptoms were significantly improved by the resection of the upper accessory meniscus and the repair of the meniscocapsular separation. Careful arthroscopic analysis of other associated pathologies together with this rare abnormality was needed to achieve clinical improvement.

  15. Simulating Electric Double Layer Capacitance by Using Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    Sun, Ning; Gersappe, Dilip

    2015-03-01

    By using the Lattice Boltzmann Method (LBM) we studied diffuse-charge dynamics in electrochemical systems. We use the LBM to solve Poisson-Nernst-Planck equations (PNP) and Modified Poisson-Nernst-Planck equations (MPNP). The isotropic permittivity of electrolyte is modeled using the Booth model. The results show that both steric effect (MPNP) and isotropic permittivity (Booth model) can have large influence on diffuse-charge dynamics, especially when electrolyte concentration or applied potential is high. This model can be applied to simulate electric double layer capacitance of super capacitors with complex geometry and also incorporate other effects such as heat convection in a modular manner.

  16. Langmuir probe measurements of double-layers in a pulsed discharge

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Crawford, F. W.

    1980-01-01

    Langmuir probe measurements were carried out which confirm the occurrence of double-layers in an argon positive column. Pulsing the discharge current permitted probe measurements to be performed in the presence of the double-layer. Supplementary evidence, obtained from DC and pulsed discharges, indicated that the double-layers formed in the two modes of operation were similar. The double-layers observed were weak and stable; their relation to other classes of double-layers are discussed, and directions for future work are suggested.

  17. Parallel electric fields in extragalactic jets - double layers and anomalous resistivity in symbiotic relationships

    SciTech Connect

    Borovsky, J.E.

    1986-07-01

    After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves. 102 references.

  18. Parallel electric fields in extragalactic jets - Double layers and anomalous resistivity in symbiotic relationships

    NASA Technical Reports Server (NTRS)

    Borovsky, J. E.

    1986-01-01

    After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves.

  19. Langmuir probe measurements of double-layers in a pulsed discharge

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Crawford, F. W.

    1980-01-01

    Langmuir probe measurements have been carried out which confirm the occurrence of double-layers in an argon positive column. Pulsing the discharge current permitted probe measurements to be performed in the presence of the double-layer. Supplementary evidence, obtained from dc and pulsed discharges, indicated that the double-layers formed in the two modes of operation were similar. The double-layers observed were weak and stable; their relation to other classes of double-layers is discussed, and directions for future work are suggested.

  20. Heterogeneous Catalysis by Polyoxometalate-Intercalated Layered Double Hydroxides

    NASA Astrophysics Data System (ADS)

    Rives, Vicente; Carriazo, Daniel; Martín, Cristina

    The preparation, characterisation and catalytic performance of layered double hydroxides (LDH) with the hydrotalcite-type structure containing different polyoxometalates (POM) in the interlayer are studied. Special attention is paid to the preparation procedures, as they control the properties of the solids formed and thus their catalytic behaviour. The study is extended to solids prepared upon thermal decomposition of these POM-LDH systems. It is concluded that the LDH does not act as a simple support, but that its specific properties, such as nature of the cations in the brucite-like layers, specific surface area and the method followed for its preparation, have an outstanding effect on the final catalytic properties of the POM-LDH systems.

  1. High-efficiency exfoliation of layered materials into 2D nanosheets in switchable CO2/Surfactant/H2O system

    NASA Astrophysics Data System (ADS)

    Wang, Nan; Xu, Qun; Xu, Shanshan; Qi, Yuhang; Chen, Meng; Li, Hongxiang; Han, Buxing

    2015-11-01

    Layered materials present attractive and important properties due to their two-dimensional (2D) structure, allowing potential applications including electronics, optoelectronics, and catalysis. However, fully exploiting the outstanding properties will require a method for their efficient exfoliation. Here we present that a series of layered materials can be successfully exfoliated into single- and few-layer nanosheets using the driving forces coming from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). The effect of variable experimental parameters including CO2 pressure, ethanol/water ratio, and initial concentration of bulk materials on the exfoliation yield have been investigated. Moreover, we demonstrate that the exfoliated 2D nanosheets have their worthwhile applications, for example, graphene can be used to prepare conductive paper, MoS2 can be used as fluorescent label to perform cellular labelling, and BN can effectively reinforce polymers leading to the promising mechanical properties.

  2. Effects of Precipitation on Ocean Mixed-Layer Temperature and Salinity as Simulated in a 2-D Coupled Ocean-Cloud Resolving Atmosphere Model

    NASA Technical Reports Server (NTRS)

    Li, Xiaofan; Sui, C.-H.; Lau, K-M.; Adamec, D.

    1999-01-01

    A two-dimensional coupled ocean-cloud resolving atmosphere model is used to investigate possible roles of convective scale ocean disturbances induced by atmospheric precipitation on ocean mixed-layer heat and salt budgets. The model couples a cloud resolving model with an embedded mixed layer-ocean circulation model. Five experiment are performed under imposed large-scale atmospheric forcing in terms of vertical velocity derived from the TOGA COARE observations during a selected seven-day period. The dominant variability of mixed-layer temperature and salinity are simulated by the coupled model with imposed large-scale forcing. The mixed-layer temperatures in the coupled experiments with 1-D and 2-D ocean models show similar variations when salinity effects are not included. When salinity effects are included, however, differences in the domain-mean mixed-layer salinity and temperature between coupled experiments with 1-D and 2-D ocean models could be as large as 0.3 PSU and 0.4 C respectively. Without fresh water effects, the nocturnal heat loss over ocean surface causes deep mixed layers and weak cooling rates so that the nocturnal mixed-layer temperatures tend to be horizontally-uniform. The fresh water flux, however, causes shallow mixed layers over convective areas while the nocturnal heat loss causes deep mixed layer over convection-free areas so that the mixed-layer temperatures have large horizontal fluctuations. Furthermore, fresh water flux exhibits larger spatial fluctuations than surface heat flux because heavy rainfall occurs over convective areas embedded in broad non-convective or clear areas, whereas diurnal signals over whole model areas yield high spatial correlation of surface heat flux. As a result, mixed-layer salinities contribute more to the density differences than do mixed-layer temperatures.

  3. Micro-patterning of ionic reservoirs within a double bilayer lipid membrane to fabricate a 2D array of ion-channel switch based electrochemical biosensors

    SciTech Connect

    Sansinena, J. M.; Yee, C. K.; Sapuri, A.; Swanson, Basil I.; Redondo, A.; Parikh, A. N.

    2004-01-01

    We present a simple approach for the design of ionic reservoir arrays within a double phospholipid bilayer to ultimately develop a 2D array of ion-channel switch based electrochemical biosensors. As a first step, a primary bilayer lipid membrane is deposited onto an array of electrodes patterned onto a substrate surface. Subsequently, an array of microvoids is created within the bilayer by a wet photolithographic patterning of phospholipid bilayers using a deep UV light source and a quartz/chrome photomask. To ensure registry, the photomask used to pattern bilayers is designed to match up the microvoids within the primary bilayer with the array of electrodes on the substrate surface. The deposition of a secondary bilayer lipid membrane onto the primary bilayer that spans across the patterned microvoids leads to the formation of the array of ionic reservoirs within the double phospholipid bilayer. This is accomplished using giant unilamellar vesicles and by exploiting membrane electrostatics. The use of ion-channels incorporated into the secondary bilayer that covers the individual ionic reservoirs allows the construction of a 2D array of ion-channel switch based electrochemical biosensors that are able to recognize different target-agents simultaneously.

  4. Ultrafast switching of an electrochromic device based on layered double hydroxide/Prussian blue multilayered films.

    PubMed

    Liu, Xiaoxi; Zhou, Awu; Dou, Yibo; Pan, Ting; Shao, Mingfei; Han, Jingbin; Wei, Min

    2015-10-28

    Electrochromic materials are the most important and essential components in an electrochromic device. Herein, we fabricated high-performance electrochromic films based on exfoliated layered double hydroxide (LDH) nanosheets and Prussian blue (PB) nanoparticles via the layer-by-layer assembly technique. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of (LDH/PB)n ultrathin films (UTFs). The resulting (LDH/PB)n UTF electrodes exhibit electrochromic behavior arising from the reversible K(+) ion migration into/out of the PB lattice, which induces a change in the optical properties of the UTFs. Furthermore, an electrochromic device (ECD) based on the (LDH/PB)n-ITO/0.1 M KCl electrolyte/ITO sandwich structure displays superior response properties (0.91/1.21 s for coloration/bleaching), a comparable coloration efficiency (68 cm(2) C(-1)) and satisfactory optical contrast (45% at 700 nm), in comparison with other inorganic material-based ECDs reported previously. Therefore, this work presents a facile and cost-effective strategy to immobilize electrochemically active nanoparticles in a 2D inorganic matrix for potential application in displays, smart windows and optoelectronic devices. PMID:26420230

  5. Performance of electric double layer capacitors with polymer gel electrolytes

    SciTech Connect

    Ishikawa, Masashi; Kishino, Takahiro; Katada, Naoji; Morita, Masayuki

    2000-07-01

    Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVdF), tetraethylammonium tetrafluoroborate (TEABF{sub 4}), and propylene carbonate (PC) as a plasticizer have been investigated for electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca. 6 mS/cm at 298 K). To assemble model capacitors with the PVdF gel electrolytes and activated carbon fiber cloth electrodes, a pair of the fixed electrodes was soaked in a precursor solution containing PC, PVdF, and TEABF{sub 4}, followed by evaporation of the PC solvent in a vacuum oven. The resulting gel electrolytes were in good contact with the electrodes. The model capacitors with the PVdF gel electrolytes showed a large value of capacitance and high coulombic efficiency in operation voltage ranges of 1--2 and 1--3 V. It is worth noting that the capacitors with the PVdF electrolytes showed long voltage retention in a self-discharge test. These good characteristics of the gel capacitors were comparable to those of typical double layer capacitors with a liquid organic electrolyte containing PC and TEABF{sub 4}; rather, the voltage retentivity of the PVdF gel capacitors was much superior to that of the capacitors with the organic electrolyte.

  6. Biodiesel synthesis using calcined layered double hydroxide catalysts

    SciTech Connect

    Schumaker, J. Link; Crofcheck, Czarena; TAckett, S. Adam; Santillan-Jimenez, Eduardo; Morgan, Tonya; Ji, Yaying; Crocker, Mark; Toops, Todd J

    2008-01-01

    The catalytic properties of calcined Li-Al, Mg-Al and Mg-Fe layered double hydroxides (LDHs) were examined in two transesterification reactions, namely, the reaction of glyceryl tributyrate with methanol, and the reaction of soybean oil with methanol. While the Li-Al catalysts showed high activity in these reactions at the reflux temperature of methanol, the Mg-Fe and Mg-Al catalysts exhibited much lower methyl ester yields. CO2 TPD measurements revealed the presence of sites of weak, medium and strong basicity on both Mg-Al and Li-Al catalysts, the latter showing higher concentrations of medium and strong base sites; by implication, these are the main sites active in transesterification catalyzed by calcined Li-Al LDHs. Maximum activity was observed for the Li-Al catalysts when a calcination temperature of 450-500 aC was applied, corresponding to decomposition of the layered double hydroxide to the mixed oxide without formation of crystalline lithium aluminate phases.

  7. Testing of double-layer capacitors for high reliability applications

    SciTech Connect

    Clark, N.H.

    1991-01-01

    Double-Layer Capacitors (DLCs) have been used mainly for computer memory backup in consumer applications during the last ten years. Their high capacitance density, along with maintenance-free operation, makes them suited for these applications. In recent years users, mostly in military applications, have expressed interest in using DLCs in high reliability applications both for backup power and pulse power applications. To meet this need, developers have pursued technologies that use carbon and mixed metal oxides as the electrode material to produce high reliability double-layer capacitors. In this paper, a carbon-based DLC that was manufactured by Evans Company, and a mixed metal oxide (MMO) DLC by Pinnacle Research Inc. were evaluated. There is little published data on their reliability and aging characteristics. In addition, questions have arisen as to their environmental stability as a function of temperature, shock, vibration, and linear acceleration. The purpose of this paper is to review the available test data for both types of DLCs under these stress conditions. The data for this paper was generated by Sandia National Laboratories, General Electric Neutron Devices Department, Motorola Company, and Evans Company.

  8. Electrical Power Generation by Mechanically Modulating Electrical Double Layers

    NASA Astrophysics Data System (ADS)

    Pak, Hyuk Kyu; Moon, Jong Kyun

    2014-11-01

    Since Michael Faraday and Joseph Henry made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system and for understanding the interfacial charge distribution in solid-liquid interfaces in the near future. This work was supported by Center for Soft and Living Matter through IBS prgram in Korea.

  9. Are there double layers in unmagnetized electronegative plasmas?

    NASA Astrophysics Data System (ADS)

    Yip, Chi-Shung; Hershkowitz, Noah

    2009-10-01

    Bounded electronegative plasmas are predicted to have electropositive halos. A recent experiment [1] showed that for a negative ion to electron concentration ratio of α=0.43 for an Argon-Oxygen plasma a positive halo was a consequence of negative ion satisfying a Boltzmann relation. When Te/T- is greater than 5+24 [2] and that α is greater than Te/T- [3], the negative ions are predicted to be confined by a double layer. Experiments are reported in Ar-SF6 and Ar-Cl2 plasmas aimed at finding the double layer by varying the gas concentrations. Experiments are carried out in a filament discharge in a multi-dipole chamber, with no magnetic field on the end walls. An unmagnetized boundary of the plasma is set by a bias plate along the axial direction of the chamber. Negative ion concentrations are determined from the phrase velocity of C.W. Ion Acoustic Waves. Electron temperature and density are determined using Langmuir probes. Plasma potentials are determined by emissive probes. Argon drift velocities are determined by Laser Induced Florescence. [1] Ghim, YC and Hershkowitz, N, Applied Physics Letters. 94, 15, 151503 (2009) [2] N. Braithwaite and J. E. Allen, J. Phys. D: Appl. Phys. 21, 1733 (1988) [3] R. N. Franklin, Plasma Sources Sci. Technol. 11, A31, (2002)

  10. Double-layer interaction between two plates with hairy surfaces.

    PubMed

    Huang, Haohao; Ruckenstein, Eli

    2004-05-01

    In most theoretical treatments of colloidal particles with hairy surfaces, only the steric effect is taken into account. The steric force is a short-range interaction and acts only when the chains on different particles begin to interpenetrate each other. However, since the hairy chains are extended into the continuous phase, they constrain the orientation of the water molecules near the surface and, as a result, the dielectric constant in that region can become very different from that in the bulk. The low dielectric constant affects the distributions of ion concentrations and the gradient of the electric field. Therefore, the double-layer interactions between two plates with hairy surfaces cannot be calculated on the basis of the classical Gouy-Chapman theory, which involves a uniform dielectric constant in the Poisson-Boltzmann equation. A model which accounts for the difference in dielectric constants in the hairy region and outside that region is therefore proposed. The ion specificity is also taken into account by using Born's expression for the free energy of hydration of ions. The repulsive forces calculated via the Gouy-Chapman theory and via the new model are compared. The hairy region can have a long range effect on the repulsive double-layer interactions.

  11. Microwave absorption properties of double-layer composites using CoZn/NiZn/MnZn-ferrite and titanium dioxide

    NASA Astrophysics Data System (ADS)

    Das, Sukanta; Nayak, G. C.; Sahu, S. K.; Routray, P. C.; Roy, A. K.; Baskey, H.

    2015-03-01

    Zinc substituted ferrite powders Me0.5Zn0.5Fe2O4 (Me=Co, Mn and Ni) were prepared by the sol-gel auto-combustion method. The present study highlights development of Single layer and double layer composite microwave absorbing materials using Ferrites, Titanium dioxide and Epoxy matrix. Moreover microwave absorption property, i.e. reflection loss evaluated at X-band frequency. XRD analysis of the filler particles were carried out to evaluate crystal structure, average crystallite diameter. Morphology of the filler particles were studied with FESEM. Hysteresis behavior of the ferrites samples were studied with Vibrating Sample Magnetometer. The most important parameter governing the absorption properties of microwave absorbers i.e. permittivity and permeability studied in a vector network analyzer. Measured reflection loss value of single-layer NiZn-ferrite based microwave absorber reaches -11.2 dB at 12.05 GHz. Whereas, reflection loss value of double-layer CoZn-ferrite/ TiO2 based microwave absorber reaches -24.3 dB at 12.02 GHz. The result shows that microwave absorption property and bandwidth of absorption of double-layer microwave absorber was found to improve comparison to single layer.

  12. Structure and dynamics of electrical double layers in organic electrolytes

    SciTech Connect

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent; Qiao, Rui; Feng, Guang

    2010-01-01

    The organic electrolyte of tetraethylammonium tetrafluoroborate (TEABF{sub 4}) in the aprotic solvent of acetonitrile (ACN) is widely used in electrochemical systems such as electrochemical capacitors. In this paper, we examine the solvation of TEA{sup +} and BF{sub 4}{sup -} in ACN, and the structure, capacitance, and dynamics of the electrical double layers (EDLs) in the TEABF{sub 4}-ACN electrolyte using molecular dynamics simulations complemented with quantum density functional theory calculations. The solvation of TEA+ and BF4- ions is found to be much weaker than that of small inorganic ions in aqueous solutions, and the ACN molecules in the solvation shell of both types of ions show only weak packing and orientational ordering. These solvation characteristics are caused by the large size, charge delocalization, and irregular shape (in the case of TEA+ cation) of the ions. Near neutral electrodes, the double-layer structure in the organic electrolyte exhibits a rich organization: the solvent shows strong layering and orientational ordering, ions are significantly contact-adsorbed on the electrode, and alternating layers of cations/anions penetrate ca. 1.1 nm into the bulk electrolyte. The significant contact adsorption of ions and the alternating layering of cation/anion are new features found for EDLs in organic electrolytes. These features essentially originate from the fact that van der Waals interactions between organic ions and the electrode are strong and the partial desolvation of these ions occurs easily, as a result of the large size of the organic ions. Near charged electrodes, distinct counter-ion concentration peaks form, and the ion distribution cannot be described by the Helmholtz model or the Helmholtz + Poisson-Boltzmann model. This is because the number of counter-ions adsorbed on the electrode exceeds the number of electrons on the electrode, and the electrode is over-screened in parts of the EDL. The computed capacitances of the EDLs are in

  13. Intercalation of methotrexatum into layered double hydroxides via exfoliation-reassembly process

    NASA Astrophysics Data System (ADS)

    Liu, Su-Qing; Li, Shu-Ping; Li, Xiao-Dong

    2015-03-01

    In this paper, the intercalation of methotrexatum (MTX) into layered double hydroxides (LDHs) via an exfoliation-reassembly process was reported and the resulting hybrids were then characterized by X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) patterns etc. In the synthesis procedure, LDHs particles were firstly delaminated into well-dispersed 2D nanosheets in formamide by ultrasonic treatment at room temperature, and then the resulting LDH nanosheets were reassembled in MTX solution to form MTX intercalated LDH (MTX/LDHs) hybrids. AFM images showed that during the exfoliation process a large part of LDHs particles were delaminated into single and double brucite layers. XRD patterns and FTIR investigations manifested the successful intercalation of MTX anions into LDHs interlayers for the final samples. It was also found out that the drug-loading capacity of the hybrids increased with the concentrations of MTX solutions, while the morphology became even aggregated. At last, the cell cytotoxicity of the hybrids was estimated by MTT assays on the human lung cancer cells (A549), and the results stated that MTX/LDHs hybrids had effective suppress role on the proliferation of cancer cells.

  14. New coordination polymers from 1D chain, 2D layer to 3D framework constructed from 1,2-phenylenediacetic acid and 1,3-bis(4-pyridyl)propane flexible ligands

    SciTech Connect

    Xin Lingyun; Liu Guangzhen; Wang Liya

    2011-06-15

    The hydrothermal reactions of Cd, Zn, or Cu(II) acetate salts with H{sub 2}PHDA and BPP flexible ligands afford three new coordination polymers, including [Cd(PHDA)(BPP)(H{sub 2}O)]{sub n}(1), [Zn(PHDA)(BPP)]{sub n}(2), and [Cu{sub 2}(PHDA){sub 2}(BPP)]{sub n}(3) (H{sub 2}PHDA=1,2-phenylenediacetic acid, BPP=1,3-bis(4-pyridyl)propane). The single-crystal X-ray diffractions reveal that all three complexes feature various metal carboxylate subunits extended further by the BPP ligands to form a diverse range of structures, displaying a remarked structural sensitivity to metal(II) cation. Complex 1 containing PHDA-bridged binuclear cadmium generates 1D double-stranded chain, complex 2 results in 2D{yields}2D interpenetrated (4,4) grids, and complex 3 displays a 3D self-penetrated framework with 4{sup 8}6{sup 6}8 rob topology. In addition, fluorescent analyses show that both 1 and 2 exhibit intense blue-violet photoluminescence in the solid state. - Graphical Abstract: We show diverse supramolecular frameworks based on the same ligands (PHDA and BPP) and different metal acetate salts including 1D double-stranded chain, 2D {yields} 2D twofold interpenetrated layer, and 3D self-penetration networks. Highlights: > Three metal(II = 2 /* ROMAN ) coordination polymers were synthesized using H{sub 2}PHDA and BPP. > The diversity of structures show a remarked sensitivity to metal(II) center. > Complexes show the enhancement of fluorescence compared to that of free ligand.

  15. Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials--A general bond polarizability model.

    PubMed

    Luo, Xin; Lu, Xin; Cong, Chunxiao; Yu, Ting; Xiong, Qihua; Quek, Su Ying

    2015-01-01

    2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences, leading to different physical properties. Here, we show that regardless of the space group of the 2D materials, the Raman frequencies of the interlayer shear modes observed under the typical z(xx)z configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials. PMID:26469313

  16. High-pressure melt growth and transport properties of SiP, SiAs, GeP, and GeAs 2D layered semiconductors

    NASA Astrophysics Data System (ADS)

    Barreteau, C.; Michon, B.; Besnard, C.; Giannini, E.

    2016-06-01

    Silicon and Germanium monopnictides SiP, SiAs, GeP and GeAs form a family of 2D layered semiconductors. We have succeeded in growing bulk single crystals of these compounds by melt-growth under high pressure (0.5-1 GPa) in a cubic anvil hot press. Large (mm-size), shiny, micaceous crystals of GeP, GeAs and SiAs were obtained, and could be exfoliated into 2D flakes. Small and brittle crystals of SiP were yielded by this method. High-pressure sintered polycrystalline SiP and GeAs have also been successfully used as a precursor in the Chemical Vapor Transport growth of these crystals in the presence of I2 as a transport agent. All compounds are found to crystallize in the expected layered structure and do not undergo any structural transition at low temperature, as shown by Raman spectroscopy down to T=5 K. All materials exhibit a semiconducting behavior. The electrical resistivity of GeP, GeAs and SiAs is found to depend on temperature following a 2D-Variable Range Hopping conduction mechanism. The availability of bulk crystals of these compounds opens new perspectives in the field of 2D semiconducting materials for device applications.

  17. Double Diffusive Layering In The Early Earth's Mantle- Consequences For Thermal History And Surface Dynamics

    NASA Astrophysics Data System (ADS)

    Hansen, U.; Dude, S.

    2011-12-01

    The thermal history of the Earth, it's chemical differentiation and also the reaction of the interior with the atmosphere is largely determined by convective processes within the Earth's mantle. A simple physical model, resembling the situation, shortly after core formation, consists of a compositionally stably stratified mantle, due to magma ocean differentiation , which is heated from below and/or cooled from above. Additionally internal heat sources will serve to power the mantle dynamics. Under such circumstances double diffusive convection will eventually lead to self organized layer formation, even without the existence of jumps is material properties. We have conducted 2D and 3D numerical experiments in Cartesian and spherical geometry, taking into account mantle realistic values, especially a strong temperature dependent viscosity. The experiments show that in a wide parameter rage distinct convective layers evolve in this scenario. The layering strongly controls the heat loss from the core. In the most intensely explored scenario, convection starts at the core-mantle boundary and a stack of layers grow from the lower mantle to the top. Mobilization of the surface occurs after a time span of about 2.5 Gyears. We observe several events of intermittent breakdown of individual layers. This can potentially explain periods of strongly increasing heat flow at the Earth's surface. Alternative models of magma ocean differentiation suggest a freezing of the magma ocean from below. Under such conditions an initially unstable situation may emerge. We observe an initial Rayleigh Taylor instability, again followed by a phase of layered convection, as described above.

  18. Layering and Double-Diffusion Style Convection in Europa's Ocean

    NASA Astrophysics Data System (ADS)

    Vance, S.; Brown, J.

    2004-12-01

    We assess the effects of fluid composition and depth-dependent hydrostatic pressure on dynamics in Europa's ocean for aqueous Na2SO4 and MgSO4. We observe a salinity- and pressure-dependent check on buoyancy in putative upwellings, which may act as mechanism for storing heat in the ocean's base. For either sodium or magnesium, a small excess in salinity of an initially buoyant parcel of water, even for low average ambient salinity, causes upwellings to lose buoyancy before reaching the base of the overlying ice. The result is a two-layer convecting system with a characteristic lifetime dependent on the properties of Europa's ocean, including the balance of heat flow through the system and details of pressure effects on thermal expansion and volumes of mixing. When volume of mixing is neglected plume rise remains dependent on temperature and pressure effects alone. Stratification develops as bottom water continually acquires heat and salt. The added mass of the salt dominates over the thermal expansion. As the rise in temperature becomes sufficient to overcome the salinity effect, upwellings rise to a terminal height determined by the pressure dependence of thermal expansion of the fluid, and by differences in the fluid's temperature and salinity. This regime is similar to double-diffusive convecting systems observed in the Red Sea and Lake Vanda over the last forty years. In the Red Sea, boundary layers separating convecting zones have been observed to move upward as the lower layer acquires heat and salt. By analogy using reasonable parameters for Europa's ocean, we estimate a time scale on the order of 10 Myr for the upward progress of a lower convecting layer saturated with MgSO4, which could correlate with recently inferred change in surface alteration style over the last 70-80 Myr.

  19. Carbon additives for electrical double layer capacitor electrodes

    NASA Astrophysics Data System (ADS)

    Weingarth, D.; Cericola, D.; Mornaghini, F. C. F.; Hucke, T.; Kötz, R.

    2014-11-01

    Electrochemical double layer capacitors (EDLCs) are inherently high power devices when compared to rechargeable batteries. While capacitance and energy storage ability are mainly increased by optimizing the electrode active material or the electrolyte, the power capability could be improved by including conductive additives in the electrode formulations. This publication deals with the use of four different carbon additives - two carbon blacks and two graphites - in standard activated carbon based EDLC electrodes. The investigations include: (i) physical characterization of carbon powder mixtures such as surface area, press density, and electrical resistivity measurements, and (ii), electrochemical characterization via impedance spectroscopy and cyclic voltammetry of full cells made with electrodes containing 5 wt.% of carbon additive and compared to cells made with pure activated carbon electrodes in organic electrolyte. Improved cell performance was observed in both impedance and cyclic voltammetry responses. The results are discussed considering the main characteristics of the different carbon additives, and important considerations about electrode structure and processability are drawn.

  20. Structure and Capacitance of Electrical Double Layers inside Micropores

    NASA Astrophysics Data System (ADS)

    Feng, Guang; Qiao, Rui; Huang, Jingsong; Sumpter, Bobby G.; Meunier, Vincent

    2010-03-01

    Recent experiments indicate that the specific capacitance of micropores (diameter less than 2nm) increases anomalously as the pore size decreases^[1]. To understand the physical origin of this discovery, we performed a series of molecular dynamics simulations to study the electrical double layers (EDLs) in micropores with different shapes (tube vs slit) and pore sizes (0.668nm - 3.342nm). Several different aqueous electrolytes (K^+, Na^+, Cl^-, and F^- in water) were used in these micropores. We quantified the structure of EDLs inside the pores, and computed the capacitance of EDLs. The scaling of capacitance shows a qualitative agreement with the experimental observations. We attribute the anomalous enhancement of capacitance in micropores to the short-range ionelectrode and ionsolvent interactions.[1] J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P. Simon, and P.L. Taberna, Science 2006, 313, 1760.

  1. Layered Double Hydroxide-Based Nanocarriers for Drug Delivery

    PubMed Central

    Bi, Xue; Zhang, Hui; Dou, Liguang

    2014-01-01

    Biocompatible clay materials have attracted particular attention as the efficient drug delivery systems (DDS). In this article, we review developments in the use of layered double hydroxides (LDHs) for controlled drug release and delivery. We show how advances in the ability to synthesize intercalated structures have a significant influence on the development of new applications of these materials. We also show how modification and/or functionalization can lead to new biotechnological and biomedical applications. This review highlights the most recent progresses in research on LDH-based controlled drug delivery systems, focusing mainly on: (i) DDS with cardiovascular drugs as guests; (ii) DDS with anti-inflammatory drugs as guests; and (iii) DDS with anti-cancer drugs as guests. Finally, future prospects for LDH-based drug carriers are also discussed. PMID:24940733

  2. Double-layer shocks in a magnetized quantum plasma.

    PubMed

    Misra, A P; Samanta, S

    2010-09-01

    The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio δ . The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.

  3. Double-layer shocks in a magnetized quantum plasma

    NASA Astrophysics Data System (ADS)

    Misra, A. P.; Samanta, S.

    2010-09-01

    The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio δ . The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.

  4. "Thermal Charging" Phenomenon in Electrical Double Layer Capacitors.

    PubMed

    Wang, Jianjian; Feng, Shien-Ping; Yang, Yuan; Hau, Nga Yu; Munro, Mary; Ferreira-Yang, Emerald; Chen, Gang

    2015-09-01

    Electrical double layer capacitors (EDLCs) are usually charged by applying a potential difference across the positive and negative electrodes. In this paper, we demonstrated that EDLCs can be charged by heating. An open circuit voltage of 80-300 mV has been observed by heating the supercapacitor to 65 °C. The charge generated at high temperature can be stored in the device after its returning to the room temperature, thus allowing the lighting up of LEDs by connecting the "thermally charged" supercapacitors in a series. The underlying mechanism is related to a thermo-electrochemical process that enhances the kinetics of Faradaic process at the electrode surface (e.g., surface redox reaction of functional group, or chemical adsorption/desorption of electrolyte ions) at higher temperature. Effects of "thermal charging" times, activation voltage, rate, and times on "thermally charged" voltage are studied and possible mechanisms are discussed.

  5. Limiting factors for carbon based chemical double layer capacitors

    NASA Technical Reports Server (NTRS)

    Rose, M. Frank; Johnson, C.; Owens, T.; Stevens, B.

    1993-01-01

    The Chemical Double Layer (CDL) capacitor improves energy storage density dramatically when compared with conventional electrolytic capacitors. When compared to batteries, the CDL Capacitor is much less energy dense; however, the power density is orders of magnitude better. As a result, CDL-battery combinations present an interesting pulse power system with many potential applications. Due to the nature of the CDL it is inherently a low voltage device. The applications of the CDL can be tailored to auxiliary energy and burst mode storages which require fast charge/discharge cycles. Typical of the applications envisioned are power system backup, directed energy weapons concepts, electric automobiles, and electric actuators. In this paper, we will discuss some of the general characteristics of carbon-based CDL technology describing the structure, performance parameters, and methods of construction. Further, analytical and experimental results which define the state of the art are presented and described in terms of impact on applications.

  6. Laser Acceleration of Monoenergetic Protons Trapped in Moving Double Layer

    SciTech Connect

    Liu, C. S.; Tripathi, V. K.; Shao, X.

    2008-10-15

    We present analytic theory of monoenergetic protons acceleration by short pulse laser irradiation on a thin foil with specific thickness suggested by Yan et al. in simulations. The laser ponderomotive force pushes the electrons forward, leaving ions behind until the space charge field balances the ponderomotive force at distance {delta}. For the optimal target thickness D = {delta}>c/{omega}{sub p}, the electron sheath piled up at the rear surface of width skin depth moves into vacuum, carrying with it the protons contained in the sheath. These protons are trapped by the self field of the electron sheath and are collectively accelerated as a double layer by the laser ponderomotive force. We present here the analytic expression for the energy of the accelerated protons as a function of time, laser intensity, wavelength, and plasma density. For example, proton energy can reach {approx_equal}200 MeV at a = 5, and pulse length 90 fs.

  7. Double-layer shocks in a magnetized quantum plasma

    SciTech Connect

    Misra, A. P.; Samanta, S.

    2010-09-15

    The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio {delta}. The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.

  8. Nanosized Ni–Al layered double hydroxides—Structural characterization

    SciTech Connect

    Jitianu, Mihaela; Gunness, Darren C.; Aboagye, Doreen E.; Zaharescu, Maria; Jitianu, Andrei

    2013-05-15

    Highlights: ► The takovite anionic clays were obtained using the sol–gel method. ► The effect of samples’ composition on the structural and textural characteristics has been investigated. ► X-ray analysis. ► FTIR spectroscopy evidenced a disordered interlayer structure. ► FESEM and TEM analysis showed that the samples have high porosity. - Abstract: Takovite, a natural mineral with the formula Ni{sub 6}Al{sub 2}(OH){sub 6}CO{sub 3}·5H{sub 2}O belongs to the large class of layered double hydroxides (LDHs) and contains positively charged Ni(II) and Al(III) layers alternating with layers containing carbonate ions and water molecules. Mesoporous takovite-type layered double hydroxides (LDH) of the general formula [Ni{sub 1−x}Al{sub x}(OH){sub 2}]{sup x+}(CO{sub 3}{sup 2−}){sub x/2}·nH{sub 2}O with different Ni/Al molar ratios (1.9–2.8) have been successfully synthesized by the sol–gel method, followed by anionic exchange using nickel acetylacetonate and aluminum isopropylate as cation precursors. A single LDH phase and an anisotropic growth of very small crystallites (below 4 nm) have been evidenced by X-ray diffraction. The effect of samples’ composition on their structural and textural characteristics has been investigated. The BET surface area values are in the range of 100–122 m{sup 2}/g. BJH pore radius decreased with increase in the Al(III) content in the LDHs. FESEM micrographs show large aggregates of highly porous LDH particles, while TEM analysis reveals irregular agglomerates of crystallites, among which some of them displayed a developing hexagonal shape. The average particle size variation with the Al(III) content in the samples follows the same trend as the pore radius, the sample with the highest Ni/Al ratio displaying also the smallest particle size. This sample becomes even more interesting, since TEM analysis shows agglomerates with inside circular structures, feature not observed for the other Ni/Al ratios investigated.

  9. Local, global, and nonlinear screening in twisted double-layer graphene

    NASA Astrophysics Data System (ADS)

    Lu, Chih-Pin; Rodriguez-Vega, Martin; Li, Guohong; Luican-Mayer, Adina; Watanabe, Kenji; Taniguchi, Takashi; Rossi, Enrico; Andrei, Eva Y.

    2016-06-01

    One-atom-thick crystalline layers and their vertical heterostructures carry the promise of designer electronic materials that are unattainable by standard growth techniques. To realize their potential it is necessary to isolate them from environmental disturbances, in particular those introduced by the substrate. However, finding and characterizing suitable substrates, and minimizing the random potential fluctuations they introduce, has been a persistent challenge in this emerging field. Here we show that Landau-level (LL) spectroscopy offers the unique capability to quantify both the reduction of the quasiparticles’ lifetime and the long-range inhomogeneity due to random potential fluctuations. Harnessing this technique together with direct scanning tunneling microscopy and numerical simulations we demonstrate that the insertion of a graphene buffer layer with a large twist angle is a very effective method to shield a 2D system from substrate interference that has the additional desirable property of preserving the electronic structure of the system under study. We further show that owing to its remarkable nonlinear screening capability a single graphene buffer layer provides better shielding than either increasing the distance to the substrate or doubling the carrier density and reduces the amplitude of the potential fluctuations in graphene to values even lower than the ones in AB-stacked bilayer graphene.

  10. The Primary Electroviscous Effect: Thin Double Layers (akappa>1) and a Stern Layer.

    PubMed

    Sherwood; Rubio-Hernández; Ruiz-Reina

    2000-08-01

    The primary electroviscous effect due to the charge clouds surrounding spherical charged particles suspended in an electrolyte was studied by Hinch and Sherwood (J. Fluid Mech. 132, 337 (1983)) in the limit of double layers thin compared to the particle radius a. Here we introduce the effect of a dynamic Stern layer into that analysis, in order to explain the numerical results of Rubio-Hernández et al. (J. Colloid Interface Sci. 206, 334 (1998)) in terms of the ratio of the tangential ionic fluxes within the charge cloud to those within the Stern layer. The predictions of the asymptotic analysis are compared with those of numerical computations. The thickness of the charge cloud is characterized by the Debye length kappa(-1). If akappa>10 the predictions of the asymptotic analysis exhibit the same qualitative behavior as the numerical results, but akappa>1000 is required to achieve quantitative agreement to within 2.5%. Copyright 2000 Academic Press.

  11. Some dynamical properties of very strong double layers in a triple plasma device

    NASA Technical Reports Server (NTRS)

    Carpenter, T.; Torven, S.

    1987-01-01

    Dynamical properties of very strong double layers seen in a differentially pumped triple plasma device are reported. These double layers are V-shaped. The following findings are discussed: (1) Disruptions in the double layer potential and in the plasma current occur when an inductance is placed in series with the bias supply between the sources in the external circuit. These disruptions, which can be highly periodic, are the result of a negative resistance region. (2) When reactances in the circuit are minimized, the double layer exhibits a jitter motion in position approximately equal to the double layer thickness. (3) When the bias between the sources is rapidly turned on, the initial phase in the double layer formation is the occurrence of a constant electric field for the first few microseconds. First the apparatus used in all of the work is discussed and then each of the three phenomena are considered.

  12. Double Layers: Potential Formation and Related Nonlinear Phenomena in Plasmas: Proceedings of the 5th Symposium

    NASA Astrophysics Data System (ADS)

    Iizuka, S.

    1998-02-01

    The Table of Contents for the book is as follows: * PREFACE * INTERNATIONAL SCIENTIFIC COMMITTEE * LOCAL ORGANIZING COMMITTEE AT TOHOKU UNIVERSITY * CHAPTER 1: DOUBLE LAYERS, SHEATHS, AND POTENTIAL STRUCTURES * 1.1 Double Layers * On Fluid Models of Stationary, Acoustic Double Layers (Invited) * Particle Simulation of Double Layer (Invited) * Space-Time Dependence of Non-Steady Double Layers * The Role of Low Energy Electrons for the Generation of Anode Double Layers in Glow Discharges * Arbitrary Amplitude Ion-Acoustic Double Layers in a Dusty Plasma * 1.2 Sheaths * Bounded Plasma Edge Physics as Observed from Simulations in 1D and 2D (Invited) * Control of RF Sheath Structure in RF Diode Discharge * Observation of Density Gradients with Fine Structures and Low Frequency Wave Excitation at the Plasma-Sheath Boundary * Double Sheath Associated with an Electron Emission to a Plasma Containing Negative Ions * Sheath Edge and Floating Potential for Multi-Species Plasmas Including Dust Particles * 1.3 Potential Structures and Oscillations * Potential Structure Formed at a Constriction of a DC He Positive Column and its Coupling with Ionization Wave * Potential Structure in a New RF Magnetron Device with a Hollow Electrode * Potential Disruption in a RF Afterglow Electronegative Plasma * Potential Oscillation in a Strongly Asymmetry RF Discharge Containing Negative Ions * Effects of External Potential Control on Coulomb Dust Behavior * Potential Structure of Carbon Arc Discharge for High-Yield Fullerenes Formation * Control of Axial and Radial Potential Profiles in Tandem Mirrors (Invited) * CHAPTER 2: FIELD-ALIGNED ELECTRIC FIELDS AND RELATED PARTICLE ACCELERATIONS * 2.1 Field-Aligned Potential Formation * Formation of Large Potential Difference in a Plasma Flow along Converging Magnetic Field Lines (Invited) * Presheath Formation in front of an Oblique End-Plate in a Magnetized Sheet Plasma * Plasma Potential Formation Due to ECRH in a Magnetic Well * Electrostatic

  13. Plasmons in spatially separated double-layer graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Bagheri, Mehran; Bahrami, Mousa

    2014-05-01

    Motivated by innovative progresses in designing multi-layer graphene nanostructured materials in the laboratory, we theoretically investigate the Dirac plasmon modes of a spatially separated double-layer graphene nanoribbon system, made up of a vertically offset armchair and metallic graphene nanoribbon pair. We find striking features of the collective excitations in this novel Coulomb correlated system, where both nanoribbons are supposed to be either intrinsic (undoped/ungated) or extrinsic (doped/gated). In the former, it is shown the low-energy acoustical and the high-energy optical plasmon modes are tunable only by the inter-ribbon charge separation. In the later, the aforementioned plasmon branches are modified by the added doping factor. As a result, our model could be useful to examine the existence of a linear Landau-undamped low-energy acoustical plasmon mode tuned via the inter-ribbon charge separation as well as doping. This study might also be utilized for devising novel quantum optical waveguides based on the Coulomb coupled graphene nanoribbons.

  14. Plasmons in spatially separated double-layer graphene nanoribbons

    SciTech Connect

    Bagheri, Mehran; Bahrami, Mousa

    2014-05-07

    Motivated by innovative progresses in designing multi-layer graphene nanostructured materials in the laboratory, we theoretically investigate the Dirac plasmon modes of a spatially separated double-layer graphene nanoribbon system, made up of a vertically offset armchair and metallic graphene nanoribbon pair. We find striking features of the collective excitations in this novel Coulomb correlated system, where both nanoribbons are supposed to be either intrinsic (undoped/ungated) or extrinsic (doped/gated). In the former, it is shown the low-energy acoustical and the high-energy optical plasmon modes are tunable only by the inter-ribbon charge separation. In the later, the aforementioned plasmon branches are modified by the added doping factor. As a result, our model could be useful to examine the existence of a linear Landau-undamped low-energy acoustical plasmon mode tuned via the inter-ribbon charge separation as well as doping. This study might also be utilized for devising novel quantum optical waveguides based on the Coulomb coupled graphene nanoribbons.

  15. Highly dispersed TiO6 units in a layered double hydroxide for water splitting.

    PubMed

    Zhao, Yufei; Chen, Pengyun; Zhang, Bingsen; Su, Dang Sheng; Zhang, Shitong; Tian, Lei; Lu, Jun; Li, Zhuoxin; Cao, Xingzhong; Wang, Baoyi; Wei, Min; Evans, David G; Duan, Xue

    2012-09-17

    A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO(6) units in an MTi-layered double hydroxide matrix (M = Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H(2)-production rate of 31.4 μmol  h(-1) as well as excellent recyclable performance. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mapping and XPS measurement reveal that a high dispersion of TiO(6) octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M(2+)-O-Ti network, rather different from the aggregation state of TiO(6) in the inorganic layered material K(2)Ti(4)O(9). Both transient absorption and photoluminescence spectra demonstrate that the electron-hole recombination process was significantly depressed in the Ti-containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X-ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO(6) units was modified by the adjacent MO(6) octahedron by means of covalent interactions, with a much decreased bandgap of 2.1 eV, which accounts for its superior water-splitting behavior. Therefore, the dispersion strategy for TiO(6) units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion.

  16. Solution-processed 2D niobium diselenide nanosheets as efficient hole-transport layers in organic solar cells.

    PubMed

    Gu, Xing; Cui, Wei; Song, Tao; Liu, Changhai; Shi, Xiaoze; Wang, Suidong; Sun, Baoquan

    2014-02-01

    Thin-layer, two-dimensional NbSe2 nanosheets with lower trap density have been obtained and act as an alternative hole-transporting layer to replace MoO3 in organic solar cells. If poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C71-butyric acid methyl ester acts as an active layer, a power conversion efficiency of 8.10 % has been achieved without any further thermal treatment. The properties of this hole-transporting layer were investigated and the improvements in the devices are discussed.

  17. Quantum ion-acoustic double layers in unmagnetized dense electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Mahmood, S.; Ali, S.

    2009-04-01

    The existence of small amplitude quantum ion-acoustic double layers is studied in an unmagnetized dense electron-positron-ion plasma. For this purpose, the quantum hydrodynamic model is employed to derive a deformed Korteweg-de Vries (dKdV) equation. The steady state double layer solution of dKdV equation is obtained and its dependence on various parameters is discussed. It is found that only compressive double layers can exist in such plasmas. The analytical and numerical studies reveal that the quantum ion-acoustic double layer structures strongly depend on quantum diffraction effects and positron number density.

  18. Final report on LDRD Project: The double electron layer tunneling transistor (DELTT)

    SciTech Connect

    Simmons, J.A.; Moon, J.S.; Blount, M.A.

    1998-06-01

    This report describes the research accomplishments achieved under the LDRD Project ``Double Electron Layer Tunneling Transistor.`` The main goal of this project was to investigate whether the recently discovered phenomenon of 2D-2D tunneling in GaAs/AlGaAs double quantum wells (DQWs), investigated in a previous LDRD, could be harnessed and implemented as the operating principle for a new type of tunneling device the authors proposed, the double electron layer tunneling transistor (DELTT). In parallel with this main thrust of the project, they also continued a modest basic research effort on DQW physics issues, with significant theoretical support. The project was a considerable success, with the main goal of demonstrating a working prototype of the DELTT having been achieved. Additional DELTT advances included demonstrating good electrical characteristics at 77 K, demonstrating both NMOS and CMOS-like bi-stable memories at 77 K using the DELTT, demonstrating digital logic gates at 77 K, and demonstrating voltage-controlled oscillators at 77 K. In order to successfully fabricate the DELTT, the authors had to develop a novel flip-chip processing scheme, the epoxy-bond-and-stop-etch (EBASE) technique. This technique was latter improved so as to be amenable to electron-beam lithography, allowing the fabrication of DELTTs with sub-micron features, which are expected to be extremely high speed. In the basic physics area they also made several advances, including a measurement of the effective mass of electrons in the hour-glass orbit of a DQW subject to in-plane magnetic fields, and both measurements and theoretical calculations of the full Landau level spectra of DQWs in both perpendicular and in-plane magnetic fields. This last result included the unambiguous demonstration of magnetic breakdown of the Fermi surface. Finally, they also investigated the concept of a far-infrared photodetector based on photon assisted tunneling in a DQW. Absorption calculations showed a

  19. Different scenarios for inverse estimation of soil hydraulic parameters from double-ring infiltrometer data using HYDRUS-2D/3D

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Parisa; Ghorbani-Dashtaki, Shoja; Mosaddeghi, Mohammad Reza; Shirani, Hossein; Nodoushan, Ali Reza Mohammadi

    2016-04-01

    In this study, HYDRUS-2D/3D was used to simulate ponded infiltration through double-ring infiltrometers into a hypothetical loamy soil profile. Twelve scenarios of inverse modelling (divided into three groups) were considered for estimation of Mualem-van Genuchten hydraulic parameters. In the first group, simulation was carried out solely using cumulative infiltration data. In the second group, cumulative infiltration data plus water content at h = -330 cm (field capacity) were used as inputs. In the third group, cumulative infiltration data plus water contents at h = -330 cm (field capacity) and h = -15 000 cm (permanent wilting point) were used simultaneously as predictors. The results showed that numerical inverse modelling of the double-ring infiltrometer data provided a reliable alternative method for determining soil hydraulic parameters. The results also indicated that by reducing the number of hydraulic parameters involved in the optimization process, the simulation error is reduced. The best one in infiltration simulation which parameters α, n, and Ks were optimized using the infiltration data and field capacity as inputs. Including field capacity as additional data was important for better optimization/definition of soil hydraulic functions, but using field capacity and permanent wilting point simultaneously as additional data increased the simulation error.

  20. Large-scale simulations of layered double hydroxide nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Thyveetil, Mary-Ann

    Layered double hydroxides (LDHs) have the ability to intercalate a multitude of anionic species. Atomistic simulation techniques such as molecular dynamics have provided considerable insight into the behaviour of these materials. We review these techniques and recent algorithmic advances which considerably improve the performance of MD applications. In particular, we discuss how the advent of high performance computing and computational grids has allowed us to explore large scale models with considerable ease. Our simulations have been heavily reliant on computational resources on the UK's NGS (National Grid Service), the US TeraGrid and the Distributed European Infrastructure for Supercomputing Applications (DEISA). In order to utilise computational grids we rely on grid middleware to launch, computationally steer and visualise our simulations. We have integrated the RealityGrid steering library into the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) 1 . which has enabled us to perform re mote computational steering and visualisation of molecular dynamics simulations on grid infrastruc tures. We also use the Application Hosting Environment (AHE) 2 in order to launch simulations on remote supercomputing resources and we show that data transfer rates between local clusters and super- computing resources can be considerably enhanced by using optically switched networks. We perform large scale molecular dynamics simulations of MgiAl-LDHs intercalated with either chloride ions or a mixture of DNA and chloride ions. The systems exhibit undulatory modes, which are suppressed in smaller scale simulations, caused by the collective thermal motion of atoms in the LDH layers. Thermal undulations provide elastic properties of the system including the bending modulus, Young's moduli and Poisson's ratios. To explore the interaction between LDHs and DNA. we use molecular dynamics techniques to per form simulations of double stranded, linear and plasmid DNA up

  1. Controllable strain fields in multimonolayer 2D-layered TiO2 (110) crystals studied by STM

    NASA Astrophysics Data System (ADS)

    Li, Zhisheng; Potapenko, Denis; Osgood, Richard

    2014-03-01

    Strain of crystal lattice can change the electronic property of materials, such as oxides and semiconductors, significantly. However, experimental studies of lattice effects in oxides are limited especially in atomic scale, due to the difficulty of generating strain field experimentally. In this work, we generate a strain field in multiple monolayer sample of at TiO2 (110) by very low energy bombardment of single crystal TiO2 samples with argon ions at 1000oC. The interstitial argon diffuses so as to form nanometer scale regions of local exfoliated TiO2 layers. These layers retain their unstressed surface reconstruction although the top-most surface layers have a convex morphology. We use STM studies along with a continuum model to show the strain field. Our studies also show that the strained surface layers are free of oxygen vacancies and that the adsorption energy of hydrogen is altered by the local strain field. The authors gratefully acknowledge support of this work by the Basic Energy Sciences Division of the U.S. Department of Energy, Contract No. DE-FG02-90ER14104.

  2. Energy distribution of elastically scattered electrons from double layer samples

    NASA Astrophysics Data System (ADS)

    Tőkési, K.; Varga, D.

    2016-02-01

    We present a theoretical description of the spectra of electrons elastically scattered from thin double layered Au-C samples. The analysis is based on the Monte Carlo simulation of the recoil and Doppler effects in reflection and transmission geometries of the scattering at a fixed angle of 44.3 ° and a primary energy of 40 keV. The relativistic correction is taken into account. Besides the experimentally measurable energy distributions the simulations give many partial distributions separately, depending on the number of elastic scatterings (single, and multiple scatterings of different types). Furthermore, we present detailed analytical calculations for the main parameters of the single scattering, taking into account both the ideal scattering geometry, i.e. infinitesimally small angular range, and the effect of the real, finite angular range used in the measurements. We show our results for intensity ratios, peak shifts and broadenings for four cases of measurement geometries and layer thicknesses. While in the peak intensity ratios of gold and carbon for transmission geometries were found to be in good agreement with the results of the single scattering model, especially large deviations were obtained in reflection geometries. The separation of the peaks, depending on the geometry and the thickness, generally smaller, and the peak width generally larger than it can be expected from the nominal values of the primary energy, scattering angle, and mean kinetic energy of the atoms. We also show that the peaks are asymmetric even for the case of the single scattering due to the finite solid angle. Finally, we present a qualitative comparison with the experimental data. We find our resulting energy distribution of elastically scattered electrons to be in good agreement with recent measurements.

  3. Stimuli-responsive hybrid materials: breathing in magnetic layered double hydroxides induced by a thermoresponsive molecule

    DOE PAGES

    Abellán, Gonzalo; Jordá, Jose Luis; Atienzar, Pedro; Varela, María; Jaafar, Miriam; Gómez-Herrero, Julio; Zamora, Félix; Ribera, Antonio; García, Hermenegildo; Coronado, Eugenio

    2014-12-04

    In this study, a hybrid magnetic multilayer material of micrometric size, with highly crystalline hexagonal crystals consisting of CoAl–LDH ferromagnetic layers intercalated with thermoresponsive 4-(4 anilinophenylazo)benzenesulfonate (AO5) molecules diluted (ratio 9 : 1) with a flexible sodium dodecylsulphate (SDS) surfactant has been obtained. The resulting material exhibits thermochromism attributable to the isomerization between the azo (prevalent at room temperature) and the hydrazone (favoured at higher temperatures) tautomers, leading to a thermomechanical response. In fact, these crystals exhibited thermally induced motion triggering remarkable changes in the crystal morphology and volume. In situ variable temperature XRD of these thin hybrids shows thatmore » the reversible change into the two tautomers is reflected in a shift of the position of the diffraction peaks at high temperatures towards lower interlayer spacing for the hydrazone form, as well as a broadening of the peaks reflecting lower crystallinity and ordering due to non-uniform spacing between the layers. These structural variations between room temperature (basal spacing (BS) = 25.91 Å) and 100 °C (BS = 25.05 Å) are also reflected in the magnetic properties of the layered double hydroxide (LDH) due to the variation of the magnetic coupling between the layers. Finally and in conclusion, our study constitutes one of the few examples showing fully reversible thermo-responsive breathing in a 2D hybrid material. In addition, the magnetic response of the hybrid can be modulated due to the thermotropism of the organic component that, by influencing the distance and in-plane correlation of the inorganic LDH, modulates the magnetism of the CoAl–LDH sheets in a certain range.« less

  4. Stimuli-responsive hybrid materials: breathing in magnetic layered double hydroxides induced by a thermoresponsive molecule

    SciTech Connect

    Abellán, Gonzalo; Jordá, Jose Luis; Atienzar, Pedro; Varela, María; Jaafar, Miriam; Gómez-Herrero, Julio; Zamora, Félix; Ribera, Antonio; García, Hermenegildo; Coronado, Eugenio

    2014-12-04

    In this study, a hybrid magnetic multilayer material of micrometric size, with highly crystalline hexagonal crystals consisting of CoAl–LDH ferromagnetic layers intercalated with thermoresponsive 4-(4 anilinophenylazo)benzenesulfonate (AO5) molecules diluted (ratio 9 : 1) with a flexible sodium dodecylsulphate (SDS) surfactant has been obtained. The resulting material exhibits thermochromism attributable to the isomerization between the azo (prevalent at room temperature) and the hydrazone (favoured at higher temperatures) tautomers, leading to a thermomechanical response. In fact, these crystals exhibited thermally induced motion triggering remarkable changes in the crystal morphology and volume. In situ variable temperature XRD of these thin hybrids shows that the reversible change into the two tautomers is reflected in a shift of the position of the diffraction peaks at high temperatures towards lower interlayer spacing for the hydrazone form, as well as a broadening of the peaks reflecting lower crystallinity and ordering due to non-uniform spacing between the layers. These structural variations between room temperature (basal spacing (BS) = 25.91 Å) and 100 °C (BS = 25.05 Å) are also reflected in the magnetic properties of the layered double hydroxide (LDH) due to the variation of the magnetic coupling between the layers. Finally and in conclusion, our study constitutes one of the few examples showing fully reversible thermo-responsive breathing in a 2D hybrid material. In addition, the magnetic response of the hybrid can be modulated due to the thermotropism of the organic component that, by influencing the distance and in-plane correlation of the inorganic LDH, modulates the magnetism of the CoAl–LDH sheets in a certain range.

  5. High-efficiency exfoliation of layered materials into 2D nanosheets in switchable CO2/Surfactant/H2O system

    PubMed Central

    Wang, Nan; Xu, Qun; Xu, Shanshan; Qi, Yuhang; Chen, Meng; Li, Hongxiang; Han, Buxing

    2015-01-01

    Layered materials present attractive and important properties due to their two-dimensional (2D) structure, allowing potential applications including electronics, optoelectronics, and catalysis. However, fully exploiting the outstanding properties will require a method for their efficient exfoliation. Here we present that a series of layered materials can be successfully exfoliated into single- and few-layer nanosheets using the driving forces coming from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). The effect of variable experimental parameters including CO2 pressure, ethanol/water ratio, and initial concentration of bulk materials on the exfoliation yield have been investigated. Moreover, we demonstrate that the exfoliated 2D nanosheets have their worthwhile applications, for example, graphene can be used to prepare conductive paper, MoS2 can be used as fluorescent label to perform cellular labelling, and BN can effectively reinforce polymers leading to the promising mechanical properties. PMID:26568039

  6. Thermal effects of asymmetric electrolytes in electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    d'Entremont, Anna L.; Pilon, Laurent

    2015-01-01

    This study presents a thermal model, derived from first principles, for electric double layer capacitors (EDLCs) with multiple ion species and/or asymmetric electrolytes. It accounts for both irreversible and reversible heat generation rates resulting from the transient electrodiffusion of ions within the electrolyte. Detailed numerical simulations of EDLCs with planar electrodes and binary and asymmetric electrolytes were performed under galvanostatic cycling. The irreversible Joule heating decreased with increasing valency and/or diffusion coefficient of either ion. The local reversible heat generation rate near a given electrode was determined by the properties of the counterion. It increased with increasing counterion valency and/or decreasing counterion diameter. As a result, the electrode with the counterion of smaller diameter and/or larger valency experienced significantly larger temperature oscillations during galvanostatic cycling than the opposite electrode. In general, EDLC electrolytes featuring ions with large valency and/or small diameter produce large capacitance but also large reversible heating. The present study suggests that EDLC electrolytes should feature large bulk ion concentrations and at least one ion with a large diffusion coefficient to minimize both irreversible and reversible heating.

  7. Removal of boron species by layered double hydroxides: a review.

    PubMed

    Theiss, Frederick L; Ayoko, Godwin A; Frost, Ray L

    2013-07-15

    Boron, which is an essential element for plants, is toxic to humans and animals at high concentrations. Layered double hydroxides (LDHs) and thermally activated LDHs have shown good uptake of a range of boron species in laboratory scale experiments when compared to current available methods, which are for the most part ineffective or prohibitively expensive. LDHs were able to remove anions from water by anion exchange, the reformation (or memory) effect and direct precipitation. The main mechanism of boron uptake appeared to be anion exchange, which was confirmed by powder X-ray diffraction (XRD) measurements. Solution pH appeared to have little effect on boron sorption while thermal activation did not always significantly improve boron uptake. In addition, perpetration of numerous LDHs with varying boron anions in the interlayer region by direct co-precipitation and anion exchange have been reported by a number of groups. The composition and orientation of the interlayer boron ions could be identified with reasonable certainty by applying a number of characterisation techniques including: powder XRD, nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy. There is still considerable scope for future research on the application of LDHs for the removal of boron contaminants.

  8. Ambipolar Electric Double Layer Transistors Using Organic Single Crystals

    NASA Astrophysics Data System (ADS)

    Takenobu, Taishi; Wen, Di; Shimotani, Hidekazu; Ono, Shimpei; Iwasa, Yoshihiro

    2011-03-01

    Among organic devices, ambipolar transistors are very unique device, in which both electrons and holes are equally mobile and we are able to observe light emission through the recombination of them. Progress in the applications of such light-emitting transistors (LETs) based on organic single crystals has provided possibilities in developing organic laser. However, in these LETs, the current density is still low for lasing, and, therefore, a different device structure is necessary to overcome this issue. Here we show the first demonstration of organic ambipolar electric double layer transistors (EDLTs), in which the gate dielectric is not a conventional insulator but an electrolyte. The peculiar merit of EDLT is extremely high conductivity due to the huge capacitance of the EDL formed at the organic/electrolyte interfaces. Consequently, we can increase current density. In this study, we used rubrene single crystal and ion-gel as the active material and electrolyte, respectively. These present results will provide a prospect for further development in LET operation.

  9. Experimental investigation of double layers in expanding plasmas

    SciTech Connect

    Plihon, N.; Chabert, P.; Corr, C. S.

    2007-01-15

    Double layers (DLs) have been observed in a plasma reactor composed of a source chamber attached to a larger expanding chamber. Positive ion beams generated across the DL were characterized in the low plasma potential region using retarding field energy analyzers. In electropositive gases, DLs were formed at very low pressures (between 0.1 and 1 mTorr) with the plasma expansion forced by a strongly diverging magnetic field. The DL remains static, robust to changes in boundary conditions, and its position is related to the magnetic field lines. The voltage drop across the DL increases with decreasing pressure; i.e., with increasing electron temperature (around 20 V at 0.17 mTorr). DLs were also observed in electronegative gases without a magnetic field over a greater range of pressure (0.5 to 10 mTorr). The actual profile of the electronegative DL is very sensitive to external parameters and intrusive elements, and they propagate at high negative ion fraction. Electrostatic probes measurements and laser-induced photodetachment show discontinuities in all plasma parameters (electron density, electron temperature, negative ion fraction) at the DL position. The voltage drop across the electronegative DL is about 8 V, is independent of the gas pressure and therefore of the electron temperature.

  10. Lubrication approximation in completed double layer boundary element method

    NASA Astrophysics Data System (ADS)

    Nasseri, S.; Phan-Thien, N.; Fan, X.-J.

    This paper reports on the results of the numerical simulation of the motion of solid spherical particles in shear Stokes flows. Using the completed double layer boundary element method (CDLBEM) via distributed computing under Parallel Virtual Machine (PVM), the effective viscosity of suspension has been calculated for a finite number of spheres in a cubic array, or in a random configuration. In the simulation presented here, the short range interactions via lubrication forces are also taken into account, via the range completer in the formulation, whenever the gap between two neighbouring particles is closer than a critical gap. The results for particles in a simple cubic array agree with the results of Nunan and Keller (1984) and Stoksian Dynamics of Brady etal. (1988). To evaluate the lubrication forces between particles in a random configuration, a critical gap of 0.2 of particle's radius is suggested and the results are tested against the experimental data of Thomas (1965) and empirical equation of Krieger-Dougherty (Krieger, 1972). Finally, the quasi-steady trajectories are obtained for time-varying configuration of 125 particles.

  11. Bionanocomposites based on layered double hydroxides as drug delivery systems

    NASA Astrophysics Data System (ADS)

    Aranda, Pilar; Alcântara, Ana C. S.; Ribeiro, Ligia N. M.; Darder, Margarita; Ruiz-Hitzky, Eduardo

    2012-10-01

    The present work introduces new biohybrid materials involving layered double hydroxides (LDH) and biopolymers to produce bionanocomposites, able to act as effective drug delivery systems (DDS). Ibuprofen (IBU) and 5-aminosalicylic acid (5-ASA) have been chosen as model drugs, being intercalated in a Mg-Al LDH matrix. On the one side, the LDHIBU intercalation compound prepared by ion-exchange reaction was blended with the biopolymers zein, a highly hydrophobic protein, and alginate, a polysaccharide widely applied for encapsulating drugs. On the other side, the LDH- 5-ASA intercalation compound prepared by co-precipitation was assembled to the polysaccharides chitosan and pectin, which show mucoadhesive properties and resistance to acid pH values, respectively. Characterization of the intercalation compounds and the resulting bionanocomposites was carried out by means of different experimental techniques: X-ray diffraction, infrared spectroscopy, chemical and thermal analysis, as well as optical and scanning electron microscopies. Data on the swelling behavior and drug release under different pH conditions are also reported.

  12. Removal of boron species by layered double hydroxides: a review.

    PubMed

    Theiss, Frederick L; Ayoko, Godwin A; Frost, Ray L

    2013-07-15

    Boron, which is an essential element for plants, is toxic to humans and animals at high concentrations. Layered double hydroxides (LDHs) and thermally activated LDHs have shown good uptake of a range of boron species in laboratory scale experiments when compared to current available methods, which are for the most part ineffective or prohibitively expensive. LDHs were able to remove anions from water by anion exchange, the reformation (or memory) effect and direct precipitation. The main mechanism of boron uptake appeared to be anion exchange, which was confirmed by powder X-ray diffraction (XRD) measurements. Solution pH appeared to have little effect on boron sorption while thermal activation did not always significantly improve boron uptake. In addition, perpetration of numerous LDHs with varying boron anions in the interlayer region by direct co-precipitation and anion exchange have been reported by a number of groups. The composition and orientation of the interlayer boron ions could be identified with reasonable certainty by applying a number of characterisation techniques including: powder XRD, nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy. There is still considerable scope for future research on the application of LDHs for the removal of boron contaminants. PMID:23635479

  13. Junction conditions in quadratic gravity: thin shells and double layers

    NASA Astrophysics Data System (ADS)

    Reina, Borja; Senovilla, José M. M.; Vera, Raül

    2016-05-01

    The junction conditions for the most general gravitational theory with a Lagrangian containing terms quadratic in the curvature are derived. We include the cases with a possible concentration of matter on the joining hypersurface—termed as thin shells, domain walls or braneworlds in the literature—as well as the proper matching conditions where only finite jumps of the energy-momentum tensor are allowed. In the latter case we prove that the matching conditions are more demanding than in general relativity. In the former case, we show that generically the shells/domain walls are of a new kind because they possess, in addition to the standard energy-momentum tensor, a double layer energy-momentum contribution which actually induces an external energy flux vector and an external scalar pressure/tension on the shell. We prove that all these contributions are necessary to make the entire energy-momentum tensor divergence-free, and we present the field equations satisfied by these energy-momentum quantities. The consequences of all these results are briefly analyzed.

  14. A two-step etching route to ultrathin carbon nanosheets for high performance electrical double layer capacitors

    NASA Astrophysics Data System (ADS)

    Ding, Bing; Wang, Jie; Wang, Ya; Chang, Zhi; Pang, Gang; Dou, Hui; Zhang, Xiaogang

    2016-05-01

    Two-dimensional (2D) carbon materials have attracted intense research interest for electrical double layer capacitors (EDLCs) due to their high aspect ratio and large surface area. Herein, we propose an exfoliation-chlorination route for preparing ultrathin carbon nanosheets by using ternary layered carbide Ti3AlC2 as the precursor. Due to the large intersheet space of exfoliated layered carbide (MXene), the as-prepared carbon nanosheets exhibit a thickness of 3-4 nm and a large specific surface area of 1766 m2 g-1 with hierarchical porosity. These features significantly improve the ion-accessible surface area for charge storage and shorten the ion transport length in the thin dimension. As a result, the carbon nanosheets show a high specific capacitance (220 F g-1 at 0.5 A g-1), remarkable high power capability (79% capacitance retention at 20 A g-1) when measured in a symmetrical two-electrode configuration in an aqueous electrolyte. The method described in this work provides a new route to prepare 2D electrode materials from a bulk precursor, thus exploiting their full potential for EDLCs.Two-dimensional (2D) carbon materials have attracted intense research interest for electrical double layer capacitors (EDLCs) due to their high aspect ratio and large surface area. Herein, we propose an exfoliation-chlorination route for preparing ultrathin carbon nanosheets by using ternary layered carbide Ti3AlC2 as the precursor. Due to the large intersheet space of exfoliated layered carbide (MXene), the as-prepared carbon nanosheets exhibit a thickness of 3-4 nm and a large specific surface area of 1766 m2 g-1 with hierarchical porosity. These features significantly improve the ion-accessible surface area for charge storage and shorten the ion transport length in the thin dimension. As a result, the carbon nanosheets show a high specific capacitance (220 F g-1 at 0.5 A g-1), remarkable high power capability (79% capacitance retention at 20 A g-1) when measured in a

  15. Asymmetric Wicking and Reduced Evaporation Time of Droplets Penetrating a Thin Double-Layered Porous Material

    NASA Astrophysics Data System (ADS)

    Vahdani, Aria; Gat, Amir; Nowakowski, Albert; Navaz, Homayun; Gharib, Morteza

    2013-11-01

    We study numerically and experimentally the penetration and evaporation dynamics of droplets wicking into a thin double-layered porous material with order-of-magnitude difference in the physical properties (such as capillary pressure drop, porosity or permeability) between the layers. We show that such double-layered porous materials can be used to create highly asymmetrical wicking properties, preventing liquid droplets wicking from one surface to the other, while allowing for wicking in the reverse direction. In addition, these double-layered porous materials are shown to reduce the evaporation time of droplets penetrating into the porous surface, compared with a single-layered material of equal thickness and physical properties similar to either of the layers. The asymmetric wicking and reduced evaporation time demonstrated in such double-layered porous materials may be of interest to applications such as medical bandages and wearable fabrics.

  16. Synthesis, characterization and structure determination of two isotypes of a layered aluminophosphate with a new 2D network topology

    SciTech Connect

    Tuel, A. . E-mail: tuel@catalyse.cnrs.fr; Lorentz, Ch.; Gramlich, V.; Baerlocher, Ch.

    2005-07-15

    Two isotypes of a new layered aluminophosphate, further denoted MDAP-3 and MDAE-1, have been synthesized under hydrothermal conditions using N-methyl-1,3-propanediamine and N-methyl-ethylenediamine, respectively. MDAP-3, with the empirical formula [Al{sub 2}(HPO{sub 4})(PO{sub 4}){sub 2}](C{sub 4}N{sub 2}H{sub 14})(H{sub 2}O), crystallizes in the orthorhombic space group Pna2(1) (No. 33) with a=9.602(16)A, b=9.26(2)A, c=16.03(3)A, Z=4, R{sub 1}=0.0498 and wR{sub 2}=0.1217. The second solid, MDAE-1, with the empirical formula [Al{sub 2}(HPO{sub 4})(PO{sub 4}){sub 2}](C{sub 3}N{sub 2}H{sub 12})(H{sub 2}O), crystallizes in the same space group with a=9.4250(19)A, b=9.3170(19)A, c=15.907(3)A, Z=4, R{sub 1}=0.0407 and wR{sub 2}=0.0954. The two compounds possess the same layer topology. Inorganic layers contain PO{sub 3}=O, PO{sub 3}OH, AlO{sub 4} and AlO{sub 6} polyhedra, linked together to generate a new 4x8 net. MDAP-3 and MDAE-1 represent the first examples of two-dimensional layered aluminophosphates with the Al{sub 2}P{sub 3}O{sub 12} stoichiometry, and containing AlO{sub 6} octahedra.

  17. In situ optical measurement of the rapid Li intercalation and deintercalation dynamics in colloidal 2D layered TiS2 nanodiscs

    NASA Astrophysics Data System (ADS)

    Ren, Jiageng; Camacho-Forero, Luis E.; Rossi, Daniel; Park, Yerok; Balbuena, Perla B.; Son, Dong Hee

    2016-05-01

    We report the in situ optical measurements of the rapid Li intercalation and deintercalation dynamics in 2-dimensional (2D) layered transition metal dichalcogenide (TMD) with a nanoscale lateral dimension using thin films fabricated with size-controlled colloidal TiS2 nanodiscs. The films exhibiting high optical homogeneity, where the interband absorption changes near-linearly to the amount of intercalated Li, enabled facile optical probing of the intercalation dynamics overcoming the shortcomings of amperometry susceptible to complications from non-Faradaic processes. The time scale of Li intercalation and deintercalation was on the order of seconds in the nanodiscs of ~100 nm lateral dimension, indicating sufficiently rapid dynamic control of the intercalation-induced material properties with a reduced lateral dimension. The change in the rate and reversibility of the dynamics during the multiple intercalation/deintercalation cycles was also measured, providing a unique window to observe the effect of potential structural changes on the intercalation and deintercalation dynamics in 2D layered TMD structures with a nanoscale lateral dimension.We report the in situ optical measurements of the rapid Li intercalation and deintercalation dynamics in 2-dimensional (2D) layered transition metal dichalcogenide (TMD) with a nanoscale lateral dimension using thin films fabricated with size-controlled colloidal TiS2 nanodiscs. The films exhibiting high optical homogeneity, where the interband absorption changes near-linearly to the amount of intercalated Li, enabled facile optical probing of the intercalation dynamics overcoming the shortcomings of amperometry susceptible to complications from non-Faradaic processes. The time scale of Li intercalation and deintercalation was on the order of seconds in the nanodiscs of ~100 nm lateral dimension, indicating sufficiently rapid dynamic control of the intercalation-induced material properties with a reduced lateral dimension

  18. Demonstration of synchronised scanning Lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

    NASA Astrophysics Data System (ADS)

    van Dooren, M. F.; Kühn, M.; PetroviĆ, V.; Bottasso, C. L.; Campagnolo, F.; Sjöholm, M.; Angelou, N.; Mikkelsen, T.; Croce, A.; Zasso, A.

    2016-09-01

    This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dual- Lidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of Lidar scanning to measuring small scale wind flow effects. The downsides of Lidar with respect to the hot wire probes are the larger measurement probe volume and the loss of some measurements due to moving blades. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning, and the fact that remote sensing techniques do not disturb the flow while measuring. The research campaign revealed a high potential for using short-range WindScanner Lidar for accurately measuring small scale flow structures in a wind tunnel.

  19. Dynamical features and electric field strengths of double layers driven by currents. [in auroras

    NASA Technical Reports Server (NTRS)

    Singh, N.; Thiemann, H.; Schunk, R. W.

    1985-01-01

    In recent years, a number of papers have been concerned with 'ion-acoustic' double layers. In the present investigation, results from numerical simulations are presented to show that the shapes and forms of current-driven double layers evolve dynamically with the fluctuations in the current through the plasma. It is shown that double layers with a potential dip can form even without the excitation of ion-acoustic modes. Double layers in two-and one-half-dimensional simulations are discussed, taking into account the simulation technique, the spatial and temporal features of plasma, and the dynamical behavior of the parallel potential distribution. Attention is also given to double layers in one-dimensional simulations, and electrical field strengths predicted by two-and one-half-dimensional simulations.

  20. Dimensional Reduction From 2D Layer to 1D Band for Germanophosphates Induced by the "Tailor Effect" of Fluoride.

    PubMed

    Huang, Chun-Zuo; Liu, Biao; Wen, Lei; Zhuang, Rong-Chuan; Zhao, Jing-Tai; Pan, Yuanming; Mi, Jin-Xiao; Huang, Ya-Xi

    2015-07-20

    The "tailor effect" of fluoride, exclusively as a terminal rather than a bridge, was applied successfully to design low-dimensional structures in the system of transition metal germanophosphates for the first time. Two series of new compounds with low-dimensional structures are reported herein. K[M(II)Ge(OH)2(H0.5PO4)2] (M = Fe, Co) possess flat layered structures built from single chains of edge-sharing M(II)O6 and GeO6 octahedra interconnected by HPO4 tetrahedra. Their fluorinated derivatives, K4[M(II)Ge2F2(OH)2(PO4)2(HPO4)2]·2H2O (M = Fe, Co), exhibit band structures of two four-membered ring germanium phosphate single chains sandwiched by M(II)O6 octahedra via corner-sharing. Both of these structures contain anionic chains of the condensation of four-membered rings built from alternating GeO4Φ2 (Φ = F, OH) octahedra and PO4 tetrahedra via sharing common GeO4Φ2 (Φ = F, OH) octahedra, the topology of which is the same as that of the mineral kröhnkite [Na2Cu(SO4)2·2H2O]. Note that the switch from the two-dimensional layered structure to the one-dimensional band structure was performed simply by the addition of a small amount of KF·2H2O to the reaction mixture. This structural alteration arises from the incorporation of one terminal F atom to the coordination sphere of Ge, which breaks the linkage between the transition metal and germanium octahedra in the layer to form the band structure.

  1. Uncertainty Assessments of 2D and Axisymmetric Hypersonic Shock Wave - Turbulent Boundary Layer Interaction Simulations at Compression Corners

    NASA Technical Reports Server (NTRS)

    Gnoffo, Peter A.; Berry, Scott A.; VanNorman, John W.

    2011-01-01

    This paper is one of a series of five papers in a special session organized by the NASA Fundamental Aeronautics Program that addresses uncertainty assessments for CFD simulations in hypersonic flow. Simulations of a shock emanating from a compression corner and interacting with a fully developed turbulent boundary layer are evaluated herein. Mission relevant conditions at Mach 7 and Mach 14 are defined for a pre-compression ramp of a scramjet powered vehicle. Three compression angles are defined, the smallest to avoid separation losses and the largest to force a separated flow engaging more complicated flow physics. The Baldwin-Lomax and the Cebeci-Smith algebraic models, the one-equation Spalart-Allmaras model with the Catrix-Aupoix compressibility modification and two-equation models including Menter SST, Wilcox k-omega 98, and Wilcox k-omega 06 turbulence models are evaluated. Each model is fully defined herein to preclude any ambiguity regarding model implementation. Comparisons are made to existing experimental data and Van Driest theory to provide preliminary assessment of model form uncertainty. A set of coarse grained uncertainty metrics are defined to capture essential differences among turbulence models. Except for the inability of algebraic models to converge for some separated flows there is no clearly superior model as judged by these metrics. A preliminary metric for the numerical component of uncertainty in shock-turbulent-boundary-layer interactions at compression corners sufficiently steep to cause separation is defined as 55%. This value is a median of differences with experimental data averaged for peak pressure and heating and for extent of separation captured in new, grid-converged solutions presented here. This value is consistent with existing results in a literature review of hypersonic shock-turbulent-boundary-layer interactions by Roy and Blottner and with more recent computations of MacLean.

  2. 2D layered transport properties from topological insulator Bi2Se3 single crystals and micro flakes

    PubMed Central

    Chiatti, Olivio; Riha, Christian; Lawrenz, Dominic; Busch, Marco; Dusari, Srujana; Sánchez-Barriga, Jaime; Mogilatenko, Anna; Yashina, Lada V.; Valencia, Sergio; Ünal, Akin A.; Rader, Oliver; Fischer, Saskia F.

    2016-01-01

    Low-field magnetotransport measurements of topological insulators such as Bi2Se3 are important for revealing the nature of topological surface states by quantum corrections to the conductivity, such as weak-antilocalization. Recently, a rich variety of high-field magnetotransport properties in the regime of high electron densities (∼1019 cm−3) were reported, which can be related to additional two-dimensional layered conductivity, hampering the identification of the topological surface states. Here, we report that quantum corrections to the electronic conduction are dominated by the surface states for a semiconducting case, which can be analyzed by the Hikami-Larkin-Nagaoka model for two coupled surfaces in the case of strong spin-orbit interaction. However, in the metallic-like case this analysis fails and additional two-dimensional contributions need to be accounted for. Shubnikov-de Haas oscillations and quantized Hall resistance prove as strong indications for the two-dimensional layered metallic behavior. Temperature-dependent magnetotransport properties of high-quality Bi2Se3 single crystalline exfoliated macro and micro flakes are combined with high resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy, confirming the structure and stoichiometry. Angle-resolved photoemission spectroscopy proves a single-Dirac-cone surface state and a well-defined bulk band gap in topological insulating state. Spatially resolved core-level photoelectron microscopy demonstrates the surface stability. PMID:27270569

  3. 2D layered transport properties from topological insulator Bi2Se3 single crystals and micro flakes

    NASA Astrophysics Data System (ADS)

    Chiatti, Olivio; Riha, Christian; Lawrenz, Dominic; Busch, Marco; Dusari, Srujana; Sánchez-Barriga, Jaime; Mogilatenko, Anna; Yashina, Lada V.; Valencia, Sergio; Ünal, Akin A.; Rader, Oliver; Fischer, Saskia F.

    2016-06-01

    Low-field magnetotransport measurements of topological insulators such as Bi2Se3 are important for revealing the nature of topological surface states by quantum corrections to the conductivity, such as weak-antilocalization. Recently, a rich variety of high-field magnetotransport properties in the regime of high electron densities (˜1019 cm-3) were reported, which can be related to additional two-dimensional layered conductivity, hampering the identification of the topological surface states. Here, we report that quantum corrections to the electronic conduction are dominated by the surface states for a semiconducting case, which can be analyzed by the Hikami-Larkin-Nagaoka model for two coupled surfaces in the case of strong spin-orbit interaction. However, in the metallic-like case this analysis fails and additional two-dimensional contributions need to be accounted for. Shubnikov-de Haas oscillations and quantized Hall resistance prove as strong indications for the two-dimensional layered metallic behavior. Temperature-dependent magnetotransport properties of high-quality Bi2Se3 single crystalline exfoliated macro and micro flakes are combined with high resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy, confirming the structure and stoichiometry. Angle-resolved photoemission spectroscopy proves a single-Dirac-cone surface state and a well-defined bulk band gap in topological insulating state. Spatially resolved core-level photoelectron microscopy demonstrates the surface stability.

  4. 2D layered transport properties from topological insulator Bi2Se3 single crystals and micro flakes.

    PubMed

    Chiatti, Olivio; Riha, Christian; Lawrenz, Dominic; Busch, Marco; Dusari, Srujana; Sánchez-Barriga, Jaime; Mogilatenko, Anna; Yashina, Lada V; Valencia, Sergio; Ünal, Akin A; Rader, Oliver; Fischer, Saskia F

    2016-06-07

    Low-field magnetotransport measurements of topological insulators such as Bi2Se3 are important for revealing the nature of topological surface states by quantum corrections to the conductivity, such as weak-antilocalization. Recently, a rich variety of high-field magnetotransport properties in the regime of high electron densities (∼10(19) cm(-3)) were reported, which can be related to additional two-dimensional layered conductivity, hampering the identification of the topological surface states. Here, we report that quantum corrections to the electronic conduction are dominated by the surface states for a semiconducting case, which can be analyzed by the Hikami-Larkin-Nagaoka model for two coupled surfaces in the case of strong spin-orbit interaction. However, in the metallic-like case this analysis fails and additional two-dimensional contributions need to be accounted for. Shubnikov-de Haas oscillations and quantized Hall resistance prove as strong indications for the two-dimensional layered metallic behavior. Temperature-dependent magnetotransport properties of high-quality Bi2Se3 single crystalline exfoliated macro and micro flakes are combined with high resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy, confirming the structure and stoichiometry. Angle-resolved photoemission spectroscopy proves a single-Dirac-cone surface state and a well-defined bulk band gap in topological insulating state. Spatially resolved core-level photoelectron microscopy demonstrates the surface stability.

  5. Acoustic double layer structures in dense magnetized electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Akhtar, N.; Mahmood, S.

    2011-11-01

    The acoustic double layer structures are studied using quantum hydrodynamic model in dense magnetized electron-positron-ion plasmas. The extended Korteweg-de Vries is derived using reductive perturbation method. It is found that increase in the ion concentration in dense magnetized electron-positron plasmas increases the amplitude as well as the steepness of the double layer structure. However, increase in the magnetic field strength and decrease in the obliqueness of the nonlinear acoustic wave enhances only the steepness of the double layer structures. The numerical results have also been shown by using the data of the outer layer regions of white dwarfs given in the literature.

  6. Acoustic double layer structures in dense magnetized electron-positron-ion plasmas

    SciTech Connect

    Akhtar, N.; Mahmood, S.

    2011-11-15

    The acoustic double layer structures are studied using quantum hydrodynamic model in dense magnetized electron-positron-ion plasmas. The extended Korteweg-de Vries is derived using reductive perturbation method. It is found that increase in the ion concentration in dense magnetized electron-positron plasmas increases the amplitude as well as the steepness of the double layer structure. However, increase in the magnetic field strength and decrease in the obliqueness of the nonlinear acoustic wave enhances only the steepness of the double layer structures. The numerical results have also been shown by using the data of the outer layer regions of white dwarfs given in the literature.

  7. Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

    NASA Technical Reports Server (NTRS)

    Boclair, J. W.; Braterman, P. S.; Jiang, J.; Lou, S.; Yarberry, F.

    1999-01-01

    Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

  8. Does the plasma radiate near a Double Layer?

    NASA Astrophysics Data System (ADS)

    Pottelette, Raymond; Berthomier, Matthieu; Pickett, Jolene

    2016-04-01

    Earth is an intense radio source in the kilometer wavelength range. Being a direct consequence of the parallel acceleration processes taking place in the Earth's auroral region, the radiation contains fundamental information on the characteristic spatial and temporal scales of the turbulent accelerating layer. It is now widely assumed that the cyclotron maser instability leads to Auroral Kilometric Radiation (AKR) generation. It has been suggested from the FAST measurements that the AKR results from a so-called horseshoe electron distribution. This distribution is generated when a localized parallel electric field - called Double Layer (DL) - accelerates earthward the electrons that propagate into an increasing magnetic field. The magnetic moment of the electrons is conserved so that their pitch angle is increased. This results in the creation of a horseshoe-like shape for the electron distribution exhibiting large positive velocity gradients in the direction perpendicular to B, thereby providing free energy for the AKR generation which takes place at the local electron gyrofrequency. In these circumstances, the radiation is generated far away (several thousand kilometers) from a DL, because the parallel accelerated electrons need to travel a long distance before forming a horseshoe distribution. From an experimental point of view, it is not an easy task to highlight the presence of DLs, because they are moving transient structures so that high time resolution measurements are needed. A detailed analysis suggests that these large-amplitude parallel electric fields are located inside sharp density gradients at the interface separating the cold, dense ionospheric plasma from the hot, tenuous magnetospheric plasma. We present some FAST observations which illustrate the generation of elementary radiation events in the neighborhood of a DL. The events occur 10 to 20% above the local electron gyrofrequency in association with the presence of nonlinear coherent structures

  9. Novel vertical hetero- and homo-junction tunnel field-effect transistors based on multi-layer 2D crystals

    NASA Astrophysics Data System (ADS)

    Lu, Shang-Chun; Mohamed, Mohamed; Zhu, Wenjuan

    2016-03-01

    Vertical hetero- and homo-junction tunnel FET (TFET) based on multi-layer black phosphorus (BP) and transition metal dichalcogenides are proposed and studied by numerical simulations employing the semi-classical density gradient quantum correction model. It is found that the vertical TFET based on BP can achieve high on-current (>200 μA μm-1) and steep subthreshold swing (average value = 24.6 mV/dec) simultaneously, due to its high mobility, direct narrow bandgap, and low dielectric constant. We also found that the on-current in vertical TFETs based on MoS2/MoSe2 hetero-junction is two orders of magnitudes higher than the one in MoS2 homo-junction TFET, due to the reduced effective bandgap in heterostructure with staggered band alignment. In addition, we present various design considerations and recommendations as well as provide a qualitative comparison with published data.

  10. On Parametric Sensitivity of Reynolds-Averaged Navier-Stokes SST Turbulence Model: 2D Hypersonic Shock-Wave Boundary Layer Interactions

    NASA Technical Reports Server (NTRS)

    Brown, James L.

    2014-01-01

    Examined is sensitivity of separation extent, wall pressure and heating to variation of primary input flow parameters, such as Mach and Reynolds numbers and shock strength, for 2D and Axisymmetric Hypersonic Shock Wave Turbulent Boundary Layer interactions obtained by Navier-Stokes methods using the SST turbulence model. Baseline parametric sensitivity response is provided in part by comparison with vetted experiments, and in part through updated correlations based on free interaction theory concepts. A recent database compilation of hypersonic 2D shock-wave/turbulent boundary layer experiments extensively used in a prior related uncertainty analysis provides the foundation for this updated correlation approach, as well as for more conventional validation. The primary CFD method for this work is DPLR, one of NASA's real-gas aerothermodynamic production RANS codes. Comparisons are also made with CFL3D, one of NASA's mature perfect-gas RANS codes. Deficiencies in predicted separation response of RANS/SST solutions to parametric variations of test conditions are summarized, along with recommendations as to future turbulence approach.

  11. Double layer field shaping systems for toroidal plasmas

    DOEpatents

    Ohyabu, Nobuyoshi

    1982-01-01

    Methods and apparatus for plasma generation, confinement and control such as Tokamak plasma systems are described having a two layer field shaping coil system comprising an inner coil layer close to the plasma and an outer coil layer to minimize the current in the inner coil layer.

  12. An iterated three-layer model of the double layer with permanent dipoles

    NASA Astrophysics Data System (ADS)

    Macdonald, J. Ross; Liu, S. H.

    1983-03-01

    There does not exist a theory of the ionic double layer at a completely blocking metal electrode in liquid electrolytes which is adequate in the charge/potential region where ions and solvent molecules begin to approach saturated conditions. Under these conditions, a continuum theory, such as that of Gouy and Chapman (GC), becomes entirely inadequate. Here the problem is attacked in a semi-discrete way by first partitioning the space charge region into layers parallel to the planar blocking electrode. Each layer is part of a cubic lattice with lattice-site spacing determined by the pure solvent concentration. Lattice sites may be occupied by ions of either sign or by solvent molecules, taken as spheres having a permanent dipole moment. The solvent molecule finite-length dipoles are then approximated by slabs of constant point-dipole polarization. Thus each of the planes parallel to the electrode is a locus of ion centers, and the polarization is accounted for by equal and opposite charge layers equidistant on either side of an ionic charge layer. The mean polarization and ionic concentration in each three-layer region are determined self-consistently by free energy minimization, and electrostatic equations are employed to couple the electrical conditions in one layer to those adjacent. This ion-dipole model (IDM) is solved self-consistently for arbitrary molarity in two regimes: the weak-field situation where the electrode charge approaches zero, and the arbitrary field-strength regime. In the first case, an, exact, closed-form solution is obtained which reduces to that of GC in the appropriate limit, but numerical analysis is required in the second situation. The present treatment provides a more realistic account of the electrical effects of discrete solvent dipoles than do those treatments, such as the GC model, which represent them entirely by a background, non-saturable, or even saturable, bulk dielectric constant. Here polarization saturation enters naturally

  13. Streamline and vorticity topology of eruption from a boundary layer induced by a 2D vortex patch

    NASA Astrophysics Data System (ADS)

    Andersen, Morten; Brons, Morten; Thompson, Mark

    2012-11-01

    We investigate the flow field generated by a vortex patch near a wall. Secondary vortices are created and boundary layer eruption may occur for increasing time or Reynolds number. The stream line topology and the vorticity topology are investigated and compared motivated by the work of Kudela & Malecha, Fluid Dyn. Res. 2009. Keeping track of vortices is a widely used procedure to explain ``what is going on'' in a fluid. However, different measures may be used for identifying a vortex. We will compare two of them under simplified conditions namely in the case of two dimensional incompressible flow with constant third component of the velocity vector. In the vorticity formulation a vortex is identified as an extremum of the vorticity. In the stream function formulation, if an elliptic fixed point exists then a vortex exists. The coordinate system is moving with constant speed equal to the generating vortex speed in inviscid flow. We find that vortex creation occur by saddle - node bifurcations in the streamlines, not by pinching off as suggested by Kudela & Malecha. Close to the creation of vortices, good agreement between the vorticity structure and the streamline topology is observed. At later stages, this may break down and streamline centers may disappear even though a vor.

  14. Wind-tunnel experiments of turbulent flow over a surface-mounted 2-D block in a thermally-stratified boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

    2014-11-01

    Turbulent flows over complex surface topography have been of great interest in the atmospheric science and wind engineering communities. The geometry of the topography, surface roughness and temperature characteristics as well as the atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography models, under neutrally stratified boundary-layer conditions, have provided insights into fluid dynamics. However, atmospheric thermal stability has rarely been considered in laboratory experiments, e.g., wind-tunnel experiments. Series of wind-tunnel experiments of thermally-stratified boundary-layer flow over a surface-mounted 2-D block, in a well-controlled boundary-layer wind tunnel, will be presented. Measurements using high-resolution PIV, x-wire/cold-wire anemometry and surface heat flux sensors were conducted to quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Results will be shown to address thermal stability effects on momentum and scalar flux distribution in the wake, as well as dominant mechanism of turbulent kinetic energy generation and consumption. The authors gratefully acknowledge funding from the Swiss National Foundation (Grant 200021-132122), the National Science Foundation (Grant ATM-0854766) and NASA (Grant NNG06GE256).

  15. A theory study of the multiplication characteristics of InP/InGaAs avalanche photodiodes with double multiplication layers and double charge layers

    NASA Astrophysics Data System (ADS)

    Liu, Guipeng; Chen, Wenjie; Liu, Linsheng; Jin, Peng; Tian, Yonghui; Yang, Jianhong

    2016-09-01

    An In0.53Ga0.47As/InP avalanche photodiodes (APD) structure with double multiplication layers and double charge layers has been proposed. The calculated results with considering the dead space effect show that a thin 2nd multiplication layer will reduce the excess noise factor F in this structure for a fixed mean gain . And its performances will reach the best when the 2nd multiplication layer is 0.01 μm, which will reduce the excess noise factor 7% compared to a conventional APD for =10. The effects of 1st and 2nd charge layers on the APD have also been studied in this paper.

  16. Tunability of double layer coupled plasmonic system and its application in displacement sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Wanwan; Feng, Yuanming; Zhang, Yanxiao; Lin, Wang

    2016-04-01

    We illustrate the mechanism of multispectral Fano-like phenomenon in a double layer coupled plasmonic system and investigate its tunability by changing the geometrical parameters. By tuning the parameters in the double layer system, we show that the height of the dielectric layer between two layers plays an important role in the transmission spectrum for the studied range. The application of the double layer coupled plasmonic system in displacement sensing is also demonstrated by moving the bottom layer leftward and forward with respect to the top layer. The frequency of the spectrum peak is shown to be a linear function of forward displacement up to 2 nm. The simulations demonstrate that the small displacement can lead to frequency shift and amplitude change of the transmission peak.

  17. A two-step etching route to ultrathin carbon nanosheets for high performance electrical double layer capacitors.

    PubMed

    Ding, Bing; Wang, Jie; Wang, Ya; Chang, Zhi; Pang, Gang; Dou, Hui; Zhang, Xiaogang

    2016-06-01

    Two-dimensional (2D) carbon materials have attracted intense research interest for electrical double layer capacitors (EDLCs) due to their high aspect ratio and large surface area. Herein, we propose an exfoliation-chlorination route for preparing ultrathin carbon nanosheets by using ternary layered carbide Ti3AlC2 as the precursor. Due to the large intersheet space of exfoliated layered carbide (MXene), the as-prepared carbon nanosheets exhibit a thickness of 3-4 nm and a large specific surface area of 1766 m(2) g(-1) with hierarchical porosity. These features significantly improve the ion-accessible surface area for charge storage and shorten the ion transport length in the thin dimension. As a result, the carbon nanosheets show a high specific capacitance (220 F g(-1) at 0.5 A g(-1)), remarkable high power capability (79% capacitance retention at 20 A g(-1)) when measured in a symmetrical two-electrode configuration in an aqueous electrolyte. The method described in this work provides a new route to prepare 2D electrode materials from a bulk precursor, thus exploiting their full potential for EDLCs.

  18. A two-step etching route to ultrathin carbon nanosheets for high performance electrical double layer capacitors.

    PubMed

    Ding, Bing; Wang, Jie; Wang, Ya; Chang, Zhi; Pang, Gang; Dou, Hui; Zhang, Xiaogang

    2016-06-01

    Two-dimensional (2D) carbon materials have attracted intense research interest for electrical double layer capacitors (EDLCs) due to their high aspect ratio and large surface area. Herein, we propose an exfoliation-chlorination route for preparing ultrathin carbon nanosheets by using ternary layered carbide Ti3AlC2 as the precursor. Due to the large intersheet space of exfoliated layered carbide (MXene), the as-prepared carbon nanosheets exhibit a thickness of 3-4 nm and a large specific surface area of 1766 m(2) g(-1) with hierarchical porosity. These features significantly improve the ion-accessible surface area for charge storage and shorten the ion transport length in the thin dimension. As a result, the carbon nanosheets show a high specific capacitance (220 F g(-1) at 0.5 A g(-1)), remarkable high power capability (79% capacitance retention at 20 A g(-1)) when measured in a symmetrical two-electrode configuration in an aqueous electrolyte. The method described in this work provides a new route to prepare 2D electrode materials from a bulk precursor, thus exploiting their full potential for EDLCs. PMID:27181616

  19. 2D Space-Confined Synthesis of Few-Layer MoS2 Anchored on Carbon Nanosheet for Lithium-Ion Battery Anode.

    PubMed

    Zhou, Jingwen; Qin, Jian; Zhang, Xiang; Shi, Chunsheng; Liu, Enzuo; Li, Jiajun; Zhao, Naiqin; He, Chunnian

    2015-04-28

    A facile and scalable 2D spatial confinement strategy is developed for in situ synthesizing highly crystalline MoS2 nanosheets with few layers (≤5 layers) anchored on 3D porous carbon nanosheet networks (3D FL-MoS2@PCNNs) as lithium-ion battery anode. During the synthesis, 3D self-assembly of cubic NaCl particles is adopted to not only serve as a template to direct the growth of 3D porous carbon nanosheet networks, but also create a 2D-confined space to achieve the construction of few-layer MoS2 nanosheets robustly lain on the surface of carbon nanosheet walls. In the resulting 3D architecture, the intimate contact between the surfaces of MoS2 and carbon nanosheets can effectively avoid the aggregation and restacking of MoS2 as well as remarkably enhance the structural integrity of the electrode, while the conductive matrix of 3D porous carbon nanosheet networks can ensure fast transport of both electrons and ions in the whole electrode. As a result, this unique 3D architecture manifests an outstanding long-life cycling capability at high rates, namely, a specific capacity as large as 709 mAh g(-1) is delivered at 2 A g(-1) and maintains ∼95.2% even after 520 deep charge/discharge cycles. Apart from promising lithium-ion battery anode, this 3D FL-MoS2@PCNN composite also has immense potential for applications in other areas such as supercapacitor, catalysis, and sensors.

  20. Design of double layer printed spiral coils for wirelessly-powered biomedical implants.

    PubMed

    Ashoori, Ehsan; Asgarian, Farzad; Sodagar, Amir M; Yoon, Euisik

    2011-01-01

    In this paper employing double layer printed spiral coils (PSCs) is proposed for wireless power transmission in implantable biomedical applications. Detailed modeling of this type of PSCs is presented. Both calculations and measurements of fabricated double layer PSCs indicate that this structure can decrease the size of typical single layer PSCs without any change in the most important parameters of the coils, such as quality factor. Also, it is shown that with equal PSC dimensions and design parameters, double layer PSCs achieve significantly higher inductances and quality factors. Ultimately, a pair of double layer PSCs with a distance of 5 mm in air is used in an inductive link. The power transfer efficiency of this link is about 79.8% with a carrier frequency of 5 MHz and coupling coefficient of 0.189. PMID:22254943

  1. Design of double layer printed spiral coils for wirelessly-powered biomedical implants.

    PubMed

    Ashoori, Ehsan; Asgarian, Farzad; Sodagar, Amir M; Yoon, Euisik

    2011-01-01

    In this paper employing double layer printed spiral coils (PSCs) is proposed for wireless power transmission in implantable biomedical applications. Detailed modeling of this type of PSCs is presented. Both calculations and measurements of fabricated double layer PSCs indicate that this structure can decrease the size of typical single layer PSCs without any change in the most important parameters of the coils, such as quality factor. Also, it is shown that with equal PSC dimensions and design parameters, double layer PSCs achieve significantly higher inductances and quality factors. Ultimately, a pair of double layer PSCs with a distance of 5 mm in air is used in an inductive link. The power transfer efficiency of this link is about 79.8% with a carrier frequency of 5 MHz and coupling coefficient of 0.189.

  2. Improving Breakdown Behavior by Substrate Bias in a Novel Double Epi-layer Lateral Double Diffused MOS Transistor

    NASA Astrophysics Data System (ADS)

    Li, Qi; Wang, Wei-Dong; Liu, Yun; Wei, Xue-Ming

    2012-02-01

    A new lateral double diffused MOS (LDMOS) transistor with a double epitaxial layer formed by an n-type substrate and a p-type epitaxial layer is reported (DEL LDMOS). The mechanism of the improved breakdown characteristic is that the high electric field around the drain is reduced by substrate reverse bias, which causes the redistribution of the bulk electric field in the drift region, and the vertical blocking voltage is shared by the drain side and the source side. The numerical results indicate that the trade-off between breakdown voltage and on-resistance of the proposed device is improved greatly in comparison to that of the conventional LDMOS.

  3. Electrochemical Double Layered Capacitor Development and Implementation System

    NASA Astrophysics Data System (ADS)

    Strunk, Gavin P.

    Electrochemical Double Layered Capacitors (EDLC's) are becoming a more popular topic of research for hybrid power systems, especially vehicles. They are known for their high power density, high cycle life, low internal resistance, and wider operating temperature compared to batteries. They are rarely used as a standalone power source; however, because of their lack of energy density compared to batteries and fuel cells. Researchers are now discovering the benefits of using them in hybrid systems. The increased complexity of a hybrid power source presents many challenges. A major drawback of this complexity is the lack of design tools to assist a designer in translating a simulation all the way to a full scale implementation. A full spectrum of tools was designed to assist designers at all stages of implementation including: single cell testing, a multi-cell management system, and a full scale vehicle data acquisition system to monitor performance. First, the full scale vehicle data acquisition is described. The system is isolated from the electric shuttle bus it was tested on to allow the system to be ported to other vehicles and applications. This was done to modularize the system to characterize a wide variety of full scale applications. Next, a single cell test system was designed that allows the designer to characterize cell specifications, as well as, test control and safety systems in a controlled environment. The goal is to ensure safety systems can be thoroughly tested to ensure robustness as the bank is scaled up. This system also includes simulation models that provide examples of using the simulation to predict the behavior of a cell and the test system to validate the results of the simulation. This information is then used by the designer to more effectively design sensor ranges for the bank. Finally, a multi-cell EDLC management system was designed to implement a bank. It incorporates 12 series EDLC cells per control module, and the modular design

  4. Efficient uranium capture by polysulfide/layered double hydroxide composites.

    PubMed

    Ma, Shulan; Huang, Lu; Ma, Lijiao; Shim, Yurina; Islam, Saiful M; Wang, Pengli; Zhao, Li-Dong; Wang, Shichao; Sun, Genban; Yang, Xiaojing; Kanatzidis, Mercouri G

    2015-03-18

    There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO2(2+)) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of S(x)-LDH composites (LDH is Mg/Al layered double hydroxide, [S(x)](2-) is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (q(m) = 330 mg/g), large K(d)(U) values (10(4)-10(6) mL/g at 1-300 ppm U concentration), and high % removals (>95% at 1-100 ppm, or ∼80% for ppb level seawater) for UO2(2+) species. The S(x)-LDHs are exceptionally efficient for selectively and rapidly capturing UO2(2+) both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value K(d)(U) of 3.4 × 10(6) mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca(2+)/Na(+), S(x)-LDH exhibits superior selectivity for UO2(2+), over previously reported sorbents. Under low U concentrations, (S4)(2-) coordinates to UO2(2+) forming anionic complexes retaining in the LDH gallery. At high U concentrations, (S4)(2-) binds to UO2(2+) to generate neutral UO2S4 salts outside the gallery, with NO3(-) entering the interlayer to form NO3-LDH. In the presence of high Cl(-) concentration, Cl(-) preferentially replaces [S4](2-) and intercalates into LDH. Detailed comparison of U removal efficiency of S(x)-LDH with various known sorbents is reported. The excellent uranium adsorption ability along with the environmentally safe, low-cost constituents points to the high potential of S(x)-LDH materials for selective uranium capture.

  5. Theory of a Stationary Current-Free Double Layer in a Collisionless Plasma

    SciTech Connect

    Ahedo, Eduardo; Martinez Sanchez, Manuel

    2009-09-25

    Current-free double layers can develop in a collisionless, inertia-controlled plasma with two electron populations, expanding in a convergent-divergent nozzle. The double layer characteristics depend on whether they develop at the nozzle divergent side, convergent side, or throat. The divergent-geometry double layer describes faithfully the Hairapetian-Stenzel experiment [Phys. Rev. Lett. 65, 175 (1990)], whereas the two other types correspond with those studied in self-similar expansions and wall-collection models of similar plasmas.

  6. Accretion onto neutron stars with the presence of a double layer

    NASA Technical Reports Server (NTRS)

    Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

    1987-01-01

    It is known, from laboratory experiments, that double layers will form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

  7. Accretion onto neutron stars with the presence of a double layer

    NASA Technical Reports Server (NTRS)

    Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

    1986-01-01

    It is known from laboratory experiments that double layers can form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

  8. Metallicity of Ca2Cu6P5 with single and double copper-pnictide layers

    DOE PAGES

    Li, Li; Parker, David; Chi, Miaofang; Tsoi, Georgiy M.; Vohra, Yogesh K.; Sefat, Athena S.

    2016-02-16

    Here, we report thermodynamic and transport properties, and also theoretical calculations, for Cu-based compound Ca2Cu6P5 and compare with CaCu2-dP2. Both materials have layers of edge-sharing copper pnictide tetrahedral CuP4, similar to Fe–As and Fe–Se layers (with FeAs4, FeSe4) in the iron-based superconductors. Despite the presence of this similar transition-metal pnictide layer, we find that both Ca2Cu6P5 and CaCu2-δP2 have temperature-independent magnetic susceptibility and show metallic behavior with no evidence of either magnetic ordering or superconductivity down to 1.8 K CaCu2-δP2 is slightly off-stoichiometric, with δ = 0.14. Theoretical calculations suggest that unlike Fe 3d-based magnetic materials with a large densitymore » of states (DOS) at the Fermi surface, Cu have comparatively low DOS, with the majority of the 3d spectral weight located well below Fermi level. The room-temperature resistivity value of Ca2Cu6P5 is only 9 μΩ-cm, due to a substantial plasma frequency and an inferred electron-phonon coupling λ of 0.073 (significantly smaller than that of metallic Cu). Also, microscopy result shows that Cu–Cu distance along the c-axis within the double layers can be very short (2.5 Å), even shorter than metallic elemental copper bond (2.56 Å). The value of dρ/dT for CaCu2-δP2 at 300 K is approximately three times larger than in Ca2Cu6P5, which suggests the likelihood of stronger electron-phonon coupling. This study shows that the details of Cu-P layers and bonding are important for their transport characteristics. In addition, it emphasizes the remarkable character of the DOS of ‘122’ iron-based materials, despite much structural similarities.« less

  9. Unravelling the electrochemical double layer by direct probing of the solid/liquid interface.

    PubMed

    Favaro, Marco; Jeong, Beomgyun; Ross, Philip N; Yano, Junko; Hussain, Zahid; Liu, Zhi; Crumlin, Ethan J

    2016-01-01

    The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzing the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential. PMID:27576762

  10. Unravelling the electrochemical double layer by direct probing of the solid/liquid interface

    NASA Astrophysics Data System (ADS)

    Favaro, Marco; Jeong, Beomgyun; Ross, Philip N.; Yano, Junko; Hussain, Zahid; Liu, Zhi; Crumlin, Ethan J.

    2016-08-01

    The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzing the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential.

  11. Unravelling the electrochemical double layer by direct probing of the solid/liquid interface

    PubMed Central

    Favaro, Marco; Jeong, Beomgyun; Ross, Philip N.; Yano, Junko; Hussain, Zahid; Liu, Zhi; Crumlin, Ethan J.

    2016-01-01

    The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzing the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential. PMID:27576762

  12. Dynamics of multiple double layers in high pressure glow discharge in a simple torus

    SciTech Connect

    Kumar Paul, Manash; Sharma, P. K.; Thakur, A.; Kulkarni, S. V.; Bora, D.

    2014-06-15

    Parametric characterization of multiple double layers is done during high pressure glow discharge in a toroidal vessel of small aspect ratio. Although glow discharge (without magnetic field) is known to be independent of device geometry, but the toroidal boundary conditions are conducive to plasma growth and eventually the plasma occupy the toroidal volume partially. At higher anode potential, the visibly glowing spots on the body of spatially extended anode transform into multiple intensely luminous spherical plasma blob structures attached to the tip of the positive electrode. Dynamics of multiple double layers are observed in argon glow discharge plasma in presence of toroidal magnetic field. The radial profiles of plasma parameters measured at various toroidal locations show signatures of double layer formation in our system. Parametric dependence of double layer dynamics in presence of toroidal magnetic field is presented here.

  13. Sagdeev potential approach for large amplitude compressional Alfvenic double layers in viscous plasmas

    SciTech Connect

    Panwar, Anuraj; Rizvi, H.; Ryu, C. M.

    2013-11-15

    Sagdeev’s technique is used to study the large amplitude compressional Alfvenic double layers in a magnetohydrodynamic plasma taking into account the small plasma β and small values of kinematic viscosity. Dispersive effect raised by non-ideal electron inertia currents perpendicular to the ambient magnetic field. The range of allowed values of the soliton speed, M (Mach number), plasma β (ratio of the plasma thermal pressure to the pressure in the confining magnetic field), and viscosity coefficient, wherein double layer may exist, are determined. In the absence of collisions, viscous dissipation modifies the Sagdeev potential and results in large amplitude compressional Alfvenic double layers. The depth of Sagdeev potential increases with the increasing Mach number and plasma β, however, decreases with the increasing viscosity. The double layer structure increases with the increasing plasma β, but decreases with increasing viscous dissipation μ(tilde sign)

  14. Dynamics of ion acoustic double layers in a magnetized two-population electrons plasma

    SciTech Connect

    Shahmansouri, M.

    2013-10-15

    The obliquely propagating ion acoustic (IA) double-layers are investigated in a magnetized two population electron plasmas. The extended Korteweg–de Vries equation is derived by using the reductive perturbation technique. The effect of obliqueness (l{sub z}) and magnitude of the external magnetic field (ω{sub ci}), as well as the electron number density (β) on the double-layer profile, is studied, and then the ranges of parameters for which the double-layers exist are investigated in detail. We found that the combined effects of l{sub z}, ω{sub ci}, and β significantly modify the basic properties (viz. amplitude and width) of the IA double-layers.

  15. Conditions for double layers in the Earth's magnetosphere and perhaps in other astrophysical objects

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1987-01-01

    Double layers form along auroral field lines in the Earth's magnetosphere. They form in order to maintain current continuity in the ionosphere in the presence of a magnetospheric electric field E with nabla x E is not equal to 0. Features which govern the formation of the double layers are: (1) the divergence of E, (2) the conductivity of the ionosphere, and (3) the current-voltage characteristics of auroral magnetic field lines. Astrophysical situations where nabla x E is not equal to 0 is applied to a conducting plasma similar to the Earth's ionosphere are potential candidates for the formation of double layers. The region with nabla x E is not equal to 0 can be generated within, or along field lines connected to, the conducting plasma. In addition to nabla x E, shear neutral flow in the conducting plasma can also form double layers.

  16. Unravelling the electrochemical double layer by direct probing of the solid/liquid interface.

    PubMed

    Favaro, Marco; Jeong, Beomgyun; Ross, Philip N; Yano, Junko; Hussain, Zahid; Liu, Zhi; Crumlin, Ethan J

    2016-08-31

    The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzing the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential.

  17. Simulation of double-layer capacitor performance in two PMAD applications

    SciTech Connect

    Bone, N.K.; Moss, B.S.; White, C.S.; Nelms, R.M.; Spyker, R.L.

    1998-07-01

    Recent developments in double-layer capacitor technology have yielded devices with increased capacitance and energy storage capability. As a result, these capacitors can now be considered for higher power and energy applications such as electric vehicle acceleration and electromechanical actuation. Presented in this paper are the results from an examination into using double-layer capacitors in two high power applications. The first is the starting transient of a large DC motor from a battery with and without a double-layer capacitor bank. In the second, a double-layer capacitor bank is used with an inverter to provide ride-through capability to a load during a fault on an AC power system. Both applications are simulated using SABER, a commercial software package.

  18. Shock waves and double layers in electron degenerate dense plasma with viscous ion fluids

    SciTech Connect

    Mamun, A. A.; Zobaer, M. S.

    2014-02-15

    The properties of ion-acoustic shock waves and double layers propagating in a viscous degenerate dense plasma (containing inertial viscous ion fluid, non-relativistic and ultra-relativistic degenerate electron fluid, and negatively charged stationary heavy element) is investigated. A new nonlinear equation (viz. Gardner equation with additional dissipative term) is derived by the reductive perturbation method. The properties of the ion-acoustic shock waves and double layers are examined by the analysis of the shock and double layer solutions of this new equation (we would like to call it “M-Z equation”). It is found that the properties of these shock and double layer structures obtained from this analysis are significantly different from those obtained from the analysis of standard Gardner or Burgers’ equation. The implications of our results to dense plasmas in astrophysical objects (e.g., non-rotating white dwarf stars) are briefly discussed.

  19. Double-layer-gate architecture for few-hole GaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Wang, D. Q.; Hamilton, A. R.; Farrer, I.; Ritchie, D. A.; Klochan, O.

    2016-08-01

    We report the fabrication of single and double hole quantum dots using a double-layer-gate design on an undoped accumulation mode {{Al}}x{{Ga}}1-x{As}/GaAs heterostructure. Electrical transport measurements of a single quantum dot show varying addition energies and clear excited states. In addition, the two-level-gate architecture can also be configured into a double quantum dot with tunable inter-dot coupling.

  20. Time evolution of ion-acoustic double layers in an unmagnetized plasma

    SciTech Connect

    Bharuthram, R.; Momoniat, E.; Mahomed, F.; Singh, S. V.; Islam, M. K.

    2008-08-15

    Ion-acoustic double layers are examined in an unmagnetized, three-component plasma consisting of cold ions and two temperature electrons. Both of the electrons are considered to be Boltzmann distributed and the ions follow the usual fluid dynamical equations. Using the method of characteristics, a time-dependent solution for ion-acoustic double layers is obtained. Results of the findings may have important consequences for the real time satellite observations in the space environment.

  1. Synthesis and properties of a cuprate superconductor containing double mercury-oxygen layers.

    PubMed

    Radaelli, P G; Perroux, M; Marezio, M; de Brion, S; Tholence, J L; Huang, Q; Santoro, A

    1994-07-15

    A cuprate superconductor containing double mercury layers was synthesized with a high-pressure, high-temperature technique. The compound, with chemical formula Hg(2)Ba(2)-Y1-xCaxCu(2)O(8-delta), contains a double HgO layer with structure similar to that of rock salt. The prototype compound Hg(2)Ba(2)YCu(2)O(8-delta) is an insulator. Superconductivity is induced in the system by partially replacing yttrium with calcium.

  2. Transition from moving to stationary double layers in a single-ended Q machine

    NASA Technical Reports Server (NTRS)

    Song, Bin; Merlino, R. L.; D'Angelo, N.

    1990-01-01

    Large-amplitude (less than about 100 percent) relaxation oscillations in the plasma potential are known to be generated when the cold endplate of a single-ended Q machine is biased positively. These oscillations are associated with double layers that form near the hot plate (plasma source) and travel toward the endplate at about the ion-acoustic velocity. At the endplate they dissolve and then form again near the hot plate, the entire process repeating itself in a regular manner. By admitting a sufficient amount of neutral gas into the system, the moving double layers were slowed down and eventually stopped. The production of stationary double layers requires an ion source on the high-potential side of the double layers. These ions are provided by ionization of the neutral gas by electrons that are accelerated through the double layer. The dependence of the critical neutral gas pressure required for stationary double-layer formation on endplate voltage, magnetic field strength, and neutral atom mass has been examined. These results are discussed in terms of a simple model of ion production and loss, including ion losses across the magnetic field.

  3. Overview of the Use of Graphene in Electric Double Layer Capacitors

    NASA Astrophysics Data System (ADS)

    Coleman, Arthur

    2012-10-01

    Advances in the manufacture and optimization of Electric Double Layer Capacitors or ultra-capacitors may make them a good alternative to batteries. Using graphene in the EDLC layers seems to limit the high self-discharge and voltage loss on discharge that plagues ultra-capacitors.

  4. Wrinkle Behavior of Hydroforming of Aluminum Alloy Double-Layer Sheets

    NASA Astrophysics Data System (ADS)

    Zhou, Bin-Jun; Xu, Yong-Chao

    2016-07-01

    In this article, the wrinkling behavior and thickness distribution of 5A06 aluminum alloy sheets in an annealed state with thickness of 1.0 mm and 2.5 mm was numerically and experimentally investigated under different hydraulic pressures in the hydroforming of single-layer and double-layer sheets. Note that, in double-layer sheets hydroforming, an upper-aided sheet is needed. The upper, thicker sheet synchronously deforms with the lower, thinner sheet during hydroforming. When the double-layer sheets are separated, a thinner curved sheet part will be manufactured. As can be seen from the simulation and experimental results, the upper, thicker sheet could effectively suppress the wrinkles of the lower, thinner sheet and improve the thickness distribution due to the increasing anti-wrinkle ability of the formed sheet and the interfacial friction between the double-layer sheets. In addition, the maximum hydraulic pressure can be decreased via hydroforming of double-layer sheets; this approach reduces the drawing force for large sheet parts and meets the requirement of energy conservation.

  5. Topological defects in electric double layers of ionic liquids at carbon interfaces

    DOE PAGES

    Black, Jennifer M.; Okatan, Mahmut Baris; Feng, Guang; Cummings, Peter T.; Kalinin, Sergei V.; Balke, Nina

    2015-06-07

    The structure and properties of the electrical double layer in ionic liquids is of interest in a wide range of areas including energy storage, catalysis, lubrication, and many more. Theories describing the electrical double layer for ionic liquids have been proposed, however a full molecular level description of the double layer is lacking. To date, studies have been predominantly focused on ion distributions normal to the surface, however the 3D nature of the electrical double layer in ionic liquids requires a full picture of the double layer structure not only normal to the surface, but also in plane. Here wemore » utilize 3D force mapping to probe the in plane structure of an ionic liquid at a graphite interface and report the direct observation of the structure and properties of topological defects. The observation of ion layering at structural defects such as step-edges, reinforced by molecular dynamics simulations, defines the spatial resolution of the method. Observation of defects allows for the establishment of the universality of ionic liquid behavior vs. separation from the carbon surface and to map internal defect structure. In conclusion, these studies offer a universal pathway for probing the internal structure of topological defects in soft condensed matter on the nanometer level in three dimensions.« less

  6. Topological defects in electric double layers of ionic liquids at carbon interfaces

    SciTech Connect

    Black, Jennifer M.; Okatan, Mahmut Baris; Feng, Guang; Cummings, Peter T.; Kalinin, Sergei V.; Balke, Nina

    2015-06-07

    The structure and properties of the electrical double layer in ionic liquids is of interest in a wide range of areas including energy storage, catalysis, lubrication, and many more. Theories describing the electrical double layer for ionic liquids have been proposed, however a full molecular level description of the double layer is lacking. To date, studies have been predominantly focused on ion distributions normal to the surface, however the 3D nature of the electrical double layer in ionic liquids requires a full picture of the double layer structure not only normal to the surface, but also in plane. Here we utilize 3D force mapping to probe the in plane structure of an ionic liquid at a graphite interface and report the direct observation of the structure and properties of topological defects. The observation of ion layering at structural defects such as step-edges, reinforced by molecular dynamics simulations, defines the spatial resolution of the method. Observation of defects allows for the establishment of the universality of ionic liquid behavior vs. separation from the carbon surface and to map internal defect structure. In conclusion, these studies offer a universal pathway for probing the internal structure of topological defects in soft condensed matter on the nanometer level in three dimensions.

  7. Double-layered target and identification method of individual target correlated with evaporation residues

    NASA Astrophysics Data System (ADS)

    Kaji, D.; Morimoto, K.

    2015-08-01

    A double-layered target system and an identification method (target ID) for individual targets mounted on a rotating wheel using correlation with evaporation residues were newly developed for the study of superheavy elements (SHE). The target system can be used in three modes: conventional single-layered mode, double-layered mode, and energy-degrader mode. The target ID method can be utilized for masking a target, measuring an excitation function without changing the beam energy from the accelerator, and searching for SHE nuclides using multiple targets during a single irradiation.

  8. Radial Strains of Double-layer Cylinders in Hydraulic Props of Powered Supports

    NASA Astrophysics Data System (ADS)

    Buyalich, G. D.; Buyalich, К G.; Voevodin, V. V.

    2016-04-01

    At present a lot of efforts are made to use double-layer power cylinders in hydraulic props of powered supports. To study the response of these cylinders to loads a special finite-element model has been developed and used for investigations into tension effect and double-layer cylinder thickness - radial strain relation under pressure of hydraulic liquid 50 MPa. It has been revealed that double-layer cylinders are distinguished by much lower radial strains in the zone of cup-like sealing elements as if compared with one-layer cylinders, as well as equivalent stresses are lower, and safety factor is higher. The data of the study can be recommended to calculate appropriate geometrical parameters of hydraulic props with respect to lower radial strains of a hydraulic cylinder, which improve its leak-tightness and functioning of cup-like sealing elements. The obtained results can be useful for design and construction of powered supports.

  9. Radial Strains of Double-layer Cylinders in Hydraulic Props of Powered Supports

    NASA Astrophysics Data System (ADS)

    Buyalich, G. D.; Buyalich, К G.; Voevodin, V. V.

    2016-04-01

    At present a lot of efforts are made to use double-layer power cylinders in hydraulic props of powered supports. To study the response of these cylinders to loads a special finite-element model has been developed and used for investigations into tension effect and double-layer cylinder thickness – radial strain relation under pressure of hydraulic liquid 50 МPа. It has been revealed that double-layer cylinders are distinguished by much lower radial strains in the zone of cup-like sealing elements as if compared with one-layer cylinders, as well as equivalent stresses are lower, and safety factor is higher. The data of the study can be recommended to calculate appropriate geometrical parameters of hydraulic props with respect to lower radial strains of a hydraulic cylinder, which improve its leak-tightness and functioning of cup-like sealing elements. The obtained results can be useful for design and construction of powered supports.

  10. Unipolar complementary circuits using double electron layer tunneling transistors

    SciTech Connect

    Moon, J.S.; Simmons, J.A.; Blount, M.A.; Reno, J.L.; Hafich, M.J.

    1999-01-01

    We demonstrate unipolar complementary circuits consisting of a pair of resonant tunneling transistors based on the gate control of two-dimensional{endash}two-dimensional interlayer tunneling, where a single transistor{emdash}in addition to exhibiting a well-defined negative-differential resistance{emdash}can be operated with either positive or negative transconductance. Details of the device operation are analyzed in terms of the quantum capacitance effect and bandbending in a double quantum well structure, and show good agreement with experiment. Application of resonant tunneling complementary logic is discussed by demonstrating complementary static random access memory using two devices connected in series. {copyright} {ital 1999 American Institute of Physics.}

  11. Layered double hydroxide formation in Bayer liquor and its promotional effect on oxalate precipitation

    SciTech Connect

    Perrotta, A.J.; Williams, F.

    1996-10-01

    Enhancing the precipitation of sodium oxalate from Bayer process liquor to improve the quality of alumina product remains an important objective for Bayer refining. The formation of layered double hydroxides by the reaction of alkaline earth oxides, such as lime and magnesia, with Bayer liquor gives a crystal structure which is capable of intercalating anions, both inorganic and organic, within its structure. Both lime and magnesia, with long contact times in Bayer liquor, show layered double hydroxide formation. This layered double hydroxide formation is accompanied with a decrease in the sodium oxalate content in the liquor from about 3 g/L to below 1 g/L. Short contact times lead to a destabilization of the liquor which facilitates sodium oxalate precipitation. Additional work on magnesium hydroxide shows, in comparison to lime and magnesia, much less layered double hydroxide formation with equivalent residence time in the liquor. Destabilization of the liquor also occurs, giving enhanced oxalate precipitation with less alumina being consumed in agreement with lower layered double hydroxide formation. Thermal regeneration of these structures, followed by in-situ recrystallization in Bayer liquor, also gives enhanced oxalate precipitation, suggesting that there is an opportunity for a regenerable oxalate reduction system. The implementation of these experiments and other related technology into the plant has resulted in the Purox Process for enhancing the precipitation of sodium oxalate from Bayer liquor.

  12. Mixing Acid Salts and Layered Double Hydroxides in Nanoscale under Solid Condition.

    PubMed

    Nakayama, Hirokazu; Hayashi, Aki

    2014-01-01

    The immobilization of potassium sorbate, potassium aspartate and sorbic acid in layered double hydroxide under solid condition was examined. By simply mixing two solids, immobilization of sorbate and aspartate in the interlayer space of nitrate-type layered double hydroxide, so called intercalation reaction, was achieved, and the uptakes, that is, the amount of immobilized salts and the interlayer distances of intercalation compounds were almost the same as those obtained in aqueous solution. However, no intercalation was achieved for sorbic acid. Although intercalation of sorbate and aspartate into chloride-type layered double hydroxide was possible, the uptakes for these intercalation compounds were lower than those obtained using nitrate-type layered double hydroxide. The intercalation under solid condition could be achieved to the same extent as for ion-exchange reaction in aqueous solution, and the reactivity was similar to that observed in aqueous solution. This method will enable the encapsulation of acidic drug in layered double hydroxide as nano level simply by mixing both solids. PMID:25080007

  13. Conditions for establishing quasistable double layers in the Earth's auroral upward current region

    SciTech Connect

    Main, D. S.; Newman, D. L.; Ergun, R. E.

    2010-12-15

    The strength and stability of simulated double layers at the ionosphere-auroral cavity boundary have been studied as a function of cold ionospheric electron temperature and density. The simulations are performed with an open boundary one-dimensional particle-in- cell (PIC) simulation and are initialized by imposing a density cavity within the simulation domain. The PIC simulation includes H{sup +} and O{sup +} ion beams, a hot H{sup +} background population, cold ionospheric electrons, and a hot electron population. It is shown that a double layer remains quasistable for a variety of initial conditions and plasma parameters. The average potential drop of the double layer is found to increase as the cold electron temperature decreases. However, in terms of cold electron density, the average potential drop of the double layer is found to increase up to some critical cold electron density and decreases above this value. Comparisons with FAST observations are made and agreement is found between simulation results and observations in the shape and width of the double layer. This study helps put a constraint on the plasma conditions in which a DL can be expected to form and remain quasistable.

  14. Sedimentation Velocity and Potential in Concentrated Suspensions of Charged Spheres with Arbitrary Double-Layer Thickness.

    PubMed

    Keh; Ding

    2000-07-15

    The sedimentation in a homogeneous suspension of charged spherical particles with an arbitrary thickness of the electric double layers is analytically studied. The effects of particle interactions are taken into account by employing a unit cell model. Overlap of the double layers of adjacent particles is allowed, and the polarization effect in the double layer surrounding each particle is considered. The electrokinetic equations that govern the ionic concentration distributions, the electric potential profile, and the fluid flow field in the electrolyte solution in a unit cell are linearized assuming that the system is only slightly distorted from equilibrium. Using a perturbation method, these linearized equations are solved for a symmetrically charged electrolyte with the surface charge density (or zeta potential) of the particle as the small perturbation parameter. An analytical expression for the settling velocity of the charged sphere in closed form is obtained from a balance among its gravitational, electrostatic, and hydrodynamic forces. A closed-form formula for the sedimentation potential in a suspension of identical charged spheres is also derived by using the requirement of zero net electric current. Our results demonstrate that the effects of overlapping double layers are quite significant, even for the case of thin double layers. Copyright 2000 Academic Press.

  15. Dislocated double-layered lateral meniscus mimicking the bucket-handle tear.

    PubMed

    Lee, Kwang Won; Yang, Dae Suk; Choy, Won Sik

    2013-10-01

    Various shapes of congenital abnormalities of the meniscus have been reported. Among them, the double-layered meniscus is rare. This article describes a 22-year-old man with a double-layered lateral meniscus who reported right knee pain with no history of trauma. The double-layered lateral meniscus included both the upper and lower meniscus. The anterior and posterior edge of the upper meniscus was attached to the lower lateral meniscus, and its periphery was not connected to the capsule and the lower meniscus. In addition, the upper meniscus was dislocated into the intercondylar notch, mimicking a bucket-handle tear. However, the lower meniscus was normal in appearance, so a bucket-handle or horizontal tear of the meniscus was ruled out of the differential diagnosis. Although this is a rare case, clinicians should be aware of this anomaly due to the potential for a double-layered meniscus to contribute to a bucket-handle or horizontal tear of the lower meniscus. Therefore, early diagnosis and proper treatment of a double-layered meniscus are needed before an additional injury occurs to a normal meniscus.

  16. Umbilical Cord Mesenchymal Stem Cells Combined With a Collagenfibrin Double-layered Membrane Accelerates Wound Healing.

    PubMed

    Nan, Wenbin; Liu, Rui; Chen, Hongli; Xu, Zhihao; Chen, Jiannan; Wang, Manman; Yuan, Zhiqing

    2015-05-01

    The aim of this study was to examine the effects of human umbilical cord mesenchymal stem cells (hUCMSCs) in combination with a collagen-fibrin double-layered membrane on wound healing in mice. A collagen-fibrin double-layered membrane was prepared, and the surface properties of the support material were investigated using a scanning electron microscope. Twenty-four mice were prepared for use as full-thickness skin wound models and randomly divided into 3 groups: group A, a control group in which the wounds were bound using a conventional method; group B, a group treated with hUCMSCs combined with a collagen membrane; and group C, a group treated with hUCMSCs combined with a collagen-fibrin double-layered membrane. The postoperative concrescence of the wounds was observed daily to evaluate the effects of the different treatments. Scanning electron microscope observation showed the collagen-fibrin scaffolds exhibited a highly porous and interconnected structure, and wound healing in the double-layered membrane group was better than in groups A or B. Treatment with hUCMSCs combined with a collagen-fibrin double-layered membrane accelerated wound healing.

  17. Double Layer of a Gold Electrode Probed by AFM Force Measurements.

    PubMed

    Barten, D; Kleijn, J M; Duval, J; Leeuwen, H P V; Lyklema, J; Cohen Stuart, M A

    2003-02-18

    Colloidal probe atomic force microscopy was used to determine the electric double layer interactions between a gold electrode and a spherical silica probe. The double layer properties of the gold/solution interface were varied through the pH and salt concentration of the electrolyte, as well as by externally applying an electric potential. The double layer potentials ψ(d) of the gold surface were obtained by fitting the force-distance curves according to the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory, using earlier obtained values for the double layer potential of the silica probe as input parameter. It was found that the gold electrode combines the features of reversible and polarizable interfaces; i.e., its charge and potential are determined by both the solution pH and the external potential. The pH dependence is attributed to proton adsorption and desorption from oxidic groups on the gold surface. In the potential range studied, ψ(d) varies linearly with the applied potential; the variation in ψ(d) is roughly 10% of that in the applied potential. The potential of zero force (the external potential at which ψ(d) = 0) varies with pH. The various features of the gold/electrolyte interface are described well by an amphifunctional double layer model. The results of this study form the basis of the interpretation of adsorption studies on gold as a function of pH and externally applied potential.

  18. Numerical simulation on the thermal radiative properties of a 2D SiO2/W/SiO2/W layered grating for thermophotovoltaic applications

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Fu, Ceji

    2016-10-01

    Tailoring the spectrum of thermal emission from the emitter is important for improving the performance of a thermophotovoltaic (TPV) system. In this work, a two-dimensional (2D) layered grating structure made of SiO2 and tungsten (W), which can realize wavelength-selective control of thermal emission, was proposed for a potential emitter in TPV applications. Numerical simulations of the spectral emissivity of the structure from the ultraviolet (UV) to the mid-infrared region reveals that the spectral-normal emissivity of the structure is enhanced to above 0.95 in the wavelength region from 0.55 μm to 1.9 μm for both TE and TM waves, but drops sharply at wavelength larger than 2 μm. Physical mechanisms responsible for the wavelength-selective emissivity were elucidated as due to resonance of magnetic polaritons (MPs) in the SiO2 spacer and in the grooves of the tungsten grating, Wood's anomaly (WA), excitation of surface plasmon polaritons (SPPs) and wave interference. Furthermore, the structure was found to exhibit quasi-diffuse and polarization-insensitive features of thermal emission, suggesting that the proposed structure can serve as the emitter in the design of high performance TPV systems.

  19. Double-gate SnO{sub 2} nanowire electric-double-layer transistors with tunable threshold voltage

    SciTech Connect

    Liu, Huixuan

    2015-06-08

    Double-gate Sb-SnO{sub 2} nanowire electric-double-layer (EDL) transistors with in-plane gates were fabricated using only one shadow mask. The threshold voltage of such devices can be tuned in a wide range from −0.13 V to 0.72 V by the in-plane gate, which allows the device to switch from depletion-mode to enhancement-mode operation. The operation voltage of the double-gate device is 1 V because the EDL gate dielectric can lead to a high gate capacitance (>3.5 μF/cm{sup 2}). Moreover, all double-gate devices show good electrical characteristics with high field-effect mobility (>200 cm{sup 2}/V·s), high drain-current I{sub on/off} ratio (>7 × 10{sup 4}), and small subthreshold slope (<100 mV/dec). These double-gate nanowire EDL transistors can pave the way for an electrically working low-voltage nano-electronic process.

  20. Coulomb drag in anisotropic systems: a theoretical study on a double-layer phosphorene

    NASA Astrophysics Data System (ADS)

    Saberi-Pouya, S.; Vazifehshenas, T.; Farmanbar, M.; Salavati-fard, T.

    2016-07-01

    We theoretically study the Coulomb drag resistivity in a double-layer electron system with highly anisotropic parabolic band structure using Boltzmann transport theory. As an example, we consider a double-layer phosphorene on which we apply our formalism. This approach, in principle, can be tuned for other double-layered systems with paraboloidal band structures. Our calculations show the rotation of one layer with respect to another layer can be considered a way of controlling the drag resistivity in such systems. As a result of rotation, the off-diagonal elements of the drag resistivity tensor have non-zero values at any temperature. In addition, we show that the anisotropic drag resistivity is very sensitive to the direction of momentum transfer between two layers due to highly anisotropic inter-layer electron-electron interaction and also the plasmon modes. In particular, the drag anisotropy ratio, {ρyy}/{ρxx} , can reach up to ˜ 3 by changing the temperature. Furthermore, our calculations suggest that including the local field correction in the dielectric function changes the results significantly. Finally, We examine the dependence of drag resistivity and its anisotropy ratio on various parameters like inter-layer separation, electron density, short-range interaction and insulating substrate/spacer.

  1. Coulomb drag in anisotropic systems: a theoretical study on a double-layer phosphorene.

    PubMed

    Saberi-Pouya, S; Vazifehshenas, T; Farmanbar, M; Salavati-Fard, T

    2016-07-20

    We theoretically study the Coulomb drag resistivity in a double-layer electron system with highly anisotropic parabolic band structure using Boltzmann transport theory. As an example, we consider a double-layer phosphorene on which we apply our formalism. This approach, in principle, can be tuned for other double-layered systems with paraboloidal band structures. Our calculations show the rotation of one layer with respect to another layer can be considered a way of controlling the drag resistivity in such systems. As a result of rotation, the off-diagonal elements of the drag resistivity tensor have non-zero values at any temperature. In addition, we show that the anisotropic drag resistivity is very sensitive to the direction of momentum transfer between two layers due to highly anisotropic inter-layer electron-electron interaction and also the plasmon modes. In particular, the drag anisotropy ratio, [Formula: see text], can reach up to [Formula: see text]3 by changing the temperature. Furthermore, our calculations suggest that including the local field correction in the dielectric function changes the results significantly. Finally, We examine the dependence of drag resistivity and its anisotropy ratio on various parameters like inter-layer separation, electron density, short-range interaction and insulating substrate/spacer.

  2. Role of metallic substrate on the plasmon modes in double-layer graphene structures

    NASA Astrophysics Data System (ADS)

    Cruz, G. Gonzalez de la

    2015-07-01

    Novel heterostructures combining different layered materials offer new opportunities for applications and fundamental studies of collective excitations driven by interlayer Coulomb interactions. In this work, we have investigated the influence of the metallic-like substrate on the plasmon spectrum of a double layer graphene system and a structure consisting of conventional two-dimensional electron gas (2DEG) immersed in a semiconductor quantum well and a graphene sheet with an interlayer separation of d. Long-range Coulomb interactions between substrate and graphene layered systems lead a new set of spectrum plasmons. At long wavelengths (q→0) the acoustic modes (ω~q) depend, besides on the carrier density in each layer, on the distance between the first carrier layer and the substrate in both structures. Furthermore, in the relativistic/nonrelativistic layered structure an undamped acoustic mode emerges for a certain interlayer critical distance dc. On the other hand, the optical plasmon modes emerging from the coupling of the double-layer systems and the substrate, both start at finite frequency at q=0 in contrast to the collective excitation spectrum ω~q1/2 reported in the literature for double-layer graphene structures.

  3. Coulomb drag in anisotropic systems: a theoretical study on a double-layer phosphorene

    NASA Astrophysics Data System (ADS)

    Saberi-Pouya, S.; Vazifehshenas, T.; Farmanbar, M.; Salavati-fard, T.

    2016-07-01

    We theoretically study the Coulomb drag resistivity in a double-layer electron system with highly anisotropic parabolic band structure using Boltzmann transport theory. As an example, we consider a double-layer phosphorene on which we apply our formalism. This approach, in principle, can be tuned for other double-layered systems with paraboloidal band structures. Our calculations show the rotation of one layer with respect to another layer can be considered a way of controlling the drag resistivity in such systems. As a result of rotation, the off-diagonal elements of the drag resistivity tensor have non-zero values at any temperature. In addition, we show that the anisotropic drag resistivity is very sensitive to the direction of momentum transfer between two layers due to highly anisotropic inter-layer electron–electron interaction and also the plasmon modes. In particular, the drag anisotropy ratio, {ρyy}/{ρxx} , can reach up to ∼ 3 by changing the temperature. Furthermore, our calculations suggest that including the local field correction in the dielectric function changes the results significantly. Finally, We examine the dependence of drag resistivity and its anisotropy ratio on various parameters like inter-layer separation, electron density, short-range interaction and insulating substrate/spacer.

  4. Coulomb drag in anisotropic systems: a theoretical study on a double-layer phosphorene.

    PubMed

    Saberi-Pouya, S; Vazifehshenas, T; Farmanbar, M; Salavati-Fard, T

    2016-07-20

    We theoretically study the Coulomb drag resistivity in a double-layer electron system with highly anisotropic parabolic band structure using Boltzmann transport theory. As an example, we consider a double-layer phosphorene on which we apply our formalism. This approach, in principle, can be tuned for other double-layered systems with paraboloidal band structures. Our calculations show the rotation of one layer with respect to another layer can be considered a way of controlling the drag resistivity in such systems. As a result of rotation, the off-diagonal elements of the drag resistivity tensor have non-zero values at any temperature. In addition, we show that the anisotropic drag resistivity is very sensitive to the direction of momentum transfer between two layers due to highly anisotropic inter-layer electron-electron interaction and also the plasmon modes. In particular, the drag anisotropy ratio, [Formula: see text], can reach up to [Formula: see text]3 by changing the temperature. Furthermore, our calculations suggest that including the local field correction in the dielectric function changes the results significantly. Finally, We examine the dependence of drag resistivity and its anisotropy ratio on various parameters like inter-layer separation, electron density, short-range interaction and insulating substrate/spacer. PMID:27221580

  5. Double-layer anti-reflection coating containing a nanoporous anodic aluminum oxide layer for GaAs solar cells.

    PubMed

    Yang, Tianshu; Wang, Xiaodong; Liu, Wen; Shi, Yanpeng; Yang, Fuhua

    2013-07-29

    Multilayer anti-reflection (AR) coatings can be used to improve the efficiency of Gallium Arsenide (GaAs) solar cells. We propose an alternate method to obtain optical thin films with specified refractive indices, which is using a self-assembled nanoporous anodic aluminum oxide (AAO) template as an optical thin film whose effective refractive index can be tuned by pore-widening. Different kinds of double-layer AR coatings each containing an AAO layer were designed and investigated by finite difference time domain (FDTD) method. We demonstrate that a λ /4n - λ /4n AR coating consisting of a TiO(2) layer and an AAO layer whose effective refractive index is 1.32 realizes a 96.8% light absorption efficiency of the GaAs solar cell under AM1.5 solar spectrum (400 nm-860 nm). We also have concluded some design principles of the double-layer AR coating containing an AAO layer for GaAs solar cells.

  6. Application of double-layered skin phantoms for optical flow imaging during laser tattoo treatments

    NASA Astrophysics Data System (ADS)

    Lee, Byeong-il; Song, Woosub; Kim, Hyejin; Kang, Hyun Wook

    2016-05-01

    The feasible application of double-layered skin phantoms was evaluated to identify artificial blood flow with a Doppler optical coherence tomography (DOCT) system for laser tattoo treatments. Polydimethylsiloxane (PDMS) was used to fabricate the artificial phantoms with flow channels embedded. A double-integrating sphere system with an inverse adding-doubling method quantified both the absorption and the reduced scattering coefficients for epidermis and dermis phantoms. Both OCT and caliper measurements confirmed the double-layered phantom structure (epidermis = 136 ± 17 µm vs. dermis = 3.0 ± 0.1 mm). The DOCT method demonstrated that high flow rates were associated with high image contrast, visualizing the position and the shape of the flow channel. Application of the channel-embedded skin phantoms in conjunction with DOCT can be a reliable technique to assess dynamic variations in the blood flow during and after laser tattoo treatments.

  7. Observation of warm, higher energy electrons transiting a double layer in a helicon plasma

    SciTech Connect

    Sung, Yung-Ta Li, Yan; Scharer, John E.

    2015-03-15

    Measurements of an inductive RF helicon argon plasma double layer with two temperature electron distributions including a fast (>80 eV) tail are observed at 0.17 mTorr Ar pressure. The fast, untrapped electrons observed downstream of the double layer have a higher temperature (13 eV) than the trapped (T{sub e} = 4 eV) electrons. The reduction of plasma potential and density observed in the double layer region would require an upstream temperature ten times the measured 4 eV if occurring via Boltzmann ambipolar expansion. The experimental observation in Madison helicon experiment indicates that fast electrons with substantial density fractions can be created at low helicon operating pressures.

  8. Low frequency solitons and double layers in a magnetized plasma with two temperature electrons

    SciTech Connect

    Rufai, O. R.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2012-12-15

    Finite amplitude non-linear ion-acoustic solitary waves and double layers are studied in a magnetized plasma with cold ions fluid and two distinct groups of Boltzmann electrons, using the Sagdeev pseudo-potential technique. The conditions under which the solitary waves and double layers can exist are found both analytically and numerically. We have shown the existence of negative potential solitary waves and double layers for subsonic Mach numbers, whereas in the unmagnetized plasma they can only in the supersonic Mach number regime. For the plasma parameters in the auroral region, the electric field amplitude of the solitary structures comes out to be 49 mV/m which is in agreement of the Viking observations in this region.

  9. Polymer/graphite oxide composites as high-performance materials for electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Tien, Chien-Pin; Teng, Hsisheng

    A single graphene sheet represents a carbon material with the highest surface area available to accommodating molecules or ions for physical and chemical interactions. Here we demonstrate in an electric double layer capacitor the outstanding performance of graphite oxide for providing a platform for double layer formation. Graphite oxide is generally the intermediate compound for obtaining separated graphene sheets. Instead of reduction with hydrazine, we incorporate graphite oxide with a poly(ethylene oxide)-based polymer and anchor the graphene oxide sheets with poly(propylene oxide) diamines. This polymer/graphite oxide composite shows in a "dry" gel-electrolyte system a double layer capacitance as high as 130 F g -1. The polymer incorporation developed here can significantly diversify the application of graphene-based materials in energy storage devices.

  10. Influence of suprathermal background electrons on strong auroral double layers: Laminar and turbulent regimes

    SciTech Connect

    Newman, D. L.; Goldman, M. V.; Sen, N.; Andersson, L.; Ergun, R. E.

    2008-07-15

    A series of one-dimensional Vlasov simulations [Newman et al., Phys. Plasmas 15, 072902 (2008), this issue] show that a sufficiently dense and hot suprathermal electron population can stabilize strong laminar double layers over long periods while regulating their strength and velocity. When suprathermals are less dense or absent, the double layers tend to be sporadic and turbulent. A detailed comparison of the laminar and turbulent regimes reveals that the disruption of the laminar state can be triggered by kinetically modified Buneman instabilities on the low-potential side of the double layer, and by density perturbations that develop into nonlinear coherent shocklike structures on the high-potential side. These findings suggest that the suprathermal electrons may be responsible for suppressing both of these routes to disruption of the laminar state.

  11. Conditions for double layers in the earth's magnetosphere and perhaps in other astrophysical objects

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1987-01-01

    It is suggested that the features which govern the formation of the double layers are: (1) the divergence of the magnetospheric electric field, (2) the ionospheric conductivity, and (3) the current-voltage characteristics of auroral magnetic field lines. Also considered are conditions in other astrophysical objects that could lead to the formation of DLs in a manner analogous to what occurs in the earth's auroral zones. It is noted that two processes can drive divergent Pedersen currents within a collisional conducting layer: (1) sheared plasma flow applied anywhere along the magnetic field lines connected to the conducting layer and (2) a neutral flow with shear within the conducting layer.

  12. Megavolt parallel potentials arising from double-layer streams in the Earth's outer radiation belt.

    PubMed

    Mozer, F S; Bale, S D; Bonnell, J W; Chaston, C C; Roth, I; Wygant, J

    2013-12-01

    Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth's outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230,000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1,000,000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100  km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects. PMID:24476280

  13. Megavolt parallel potentials arising from double-layer streams in the Earth's outer radiation belt.

    PubMed

    Mozer, F S; Bale, S D; Bonnell, J W; Chaston, C C; Roth, I; Wygant, J

    2013-12-01

    Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth's outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230,000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1,000,000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100  km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects.

  14. Organic electrical double layer transistors gated with ionic liquids

    NASA Astrophysics Data System (ADS)

    Xie, Wei; Frisbie, C. Daniel

    2011-03-01

    Transport in organic semiconductors gated with several types of ionic liquids has been systematically studied at charge densities larger than 1013 cm-2 . We observe a pronounced maximum in channel conductance for both p-type and n-type organic single crystals which is attributed to carrier localization at the semiconductor-electrolyte interface. Carrier mobility, as well as charge density and dielectric capacitance are determined through displacement current measurement and capacitance-voltage measurement. By using a larger-sized and spherical anion, tris(pentafluoroethyl)trifluorophosphate (FAP), effective carrier mobility in rubrene can be enhanced substantially up to 3.2 cm2 V-1 s -1 . Efforts have been made to maximize the charge density in rubrene single crystals, and at low temperature when higher gate bias can be applied, charge density can more than double the amount of that at room temperature, reaching 8*1013 cm-2 holes (0.4 holes per rubrene molecule). NSF MRSEC program at the University of Minnesota.

  15. Open-path TDL-Spectrometry for a Tomographic Reconstruction of 2D H2O-Concentration Fields in the Soil-Air-Boundary-Layer of Permafrost

    NASA Astrophysics Data System (ADS)

    Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

    2013-04-01

    The melting of permafrost soils in arctic regions is one of the effects of climate change. It is recognized that climatically relevant gases are emitted during the thawing process, and that they may lead to a positive atmospheric feedback [1]. For a better understanding of these developments, a quantification of the gases emitted from the soil would be required. Extractive sensors with local point-wise gas sampling are currently used for this task, but are hampered due to the complex spatial structure of the soil surface, which complicates the situation due to the essential need for finding a representative gas sampling point. For this situation it would be much preferred if a sensor for detecting 2D-concentration fields of e.g. water vapor, (and in the mid-term also for methane or carbon dioxide) directly in the soil-atmosphere-boundary layer of permafrost soils would be available. However, it also has to be kept in mind that field measurements over long time periods in such a harsh environment require very sturdy instrumentation preferably without the need for sensor calibration. Therefore we are currently developing a new, robust TDLAS (tuneable diode laser absorption spectroscopy)-spectrometer based on cheap reflective foils [2]. The spectrometer is easily transportable, requires hardly any alignment and consists of industrially available, very stable components (e.g. diode lasers and glass fibers). Our measurement technique, open path TDLAS, allows for calibration-free measurements of absolute H2O concentrations. The static instrument for sampling open-path H2O concentrations consists of a joint sending and receiving optics at one side of the measurement path and a reflective element at the other side. The latter is very easy to align, since it is a foil usually applied for traffic purposes that retro-reflects the light to its origin even for large angles of misalignment (up to 60°). With this instrument, we achieved normalized detection limits of up to 0

  16. Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

    SciTech Connect

    Wang, Sujing; Li, Jing

    2015-04-15

    As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn{sub 2}S{sub 2}(bza) (1), Zn{sub 2}S{sub 2}(mbza) (2), Zn{sub 2}S{sub 2}(fbza) (3), Zn{sub 2}S{sub 2}(pca) (4), and Zn{sub 2}S{sub 2}(thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn{sub 2}S{sub 2}(L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy.

  17. Contact condition for the density profiles in spherical and cylindrical double layers

    NASA Astrophysics Data System (ADS)

    Silvestre-Alcantara, Whasington; Henderson, Douglas; Bari Bhuiyan, Lutful

    2015-11-01

    Exact sum rules involving the contact values of the density profiles and bulk osmotic pressure in spherical and cylindrical electric double layers are formulated. When the radius of curvature in these systems tends to infinity, the contact conditions reduce to the well-known contact condition in planar double layer due to Henderson, Blum, and Lebowitz (1979). However, unlike the latter relation, the contact conditions in the non-planar geometries are non-local, and require for their implementation full knowledge of the electrode-ion singlet distribution functions.

  18. Ion phase-space vortices and their relation to small amplitude double layers

    NASA Technical Reports Server (NTRS)

    Pecseli, Hans L.

    1987-01-01

    The properties of ion phase-space vortices are reviewed with particular attention to their role in the formation of small amplitude double layers in current-carrying plasmas. In a one-dimensional analysis, many such double layers simply add up to produce a large voltage drop. A laboratory experiment is carried out in order to investigate the properties of ion phase-space vortices in three dimensions. Their lifetime is significantly reduced as compared with similar results from one-dimensional numerical simulations of the problem.

  19. Ion-acoustic double-layers in a magnetized plasma with nonthermal electrons

    SciTech Connect

    Rios, L. A.; Galvão, R. M. O.

    2013-11-15

    In the present work we investigate the existence of obliquely propagating ion-acoustic double layers in magnetized two-electron plasmas. The fluid model is used to describe the ion dynamics, and the hot electron population is modeled via a κ distribution function, which has been proved to be appropriate for modeling non-Maxwellian plasmas. A quasineutral condition is assumed to investigate these nonlinear structures, which leads to the formation of double-layers propagating with slow ion-acoustic velocity. The problem is investigated numerically, and the influence of parameters such as nonthermality is discussed.

  20. Arbitrary amplitude double layers in warm dust kinetic Alfven wave plasmas

    SciTech Connect

    Gogoi, Runmoni; Devi, Nirupama

    2008-07-15

    Large amplitude electrostatic structures associated with low-frequency dust kinetic Alfvenic waves are investigated under the pressure (temperature) gradient indicative of dust dynamics. The set of equations governing the dust dynamics, Boltzmann electrons, ions and Maxwell's equation have been reduced to a single equation known as the Sagdeev potential equation. Parameter ranges for the existence of arbitrary amplitude double layers are observed. Exact analytical expressions for the energy integral is obtained and computed numerically through which sub-Alfvenic arbitrary amplitude rarefactive double layers are found to exist.

  1. Tooth preparation and fabrication of porcelain veneers using a double-layer technique.

    PubMed

    Chpindel, P; Cristou, M

    1994-09-01

    This article discusses proper tooth preparation when using the double-layered porcelain technique for constructing porcelain veneers designed to produce strength and translucency. Indications for this technique include color correction, restoration of lost tooth structure or improper tooth size, and overall smile design. A new indication--misalignment--has been added. The objective of this article is to review tooth preparation and double-layered laboratory techniques using hydrothermal ceramics in combination. Four cases are used to illustrate the procedure, concentrating on the correction of misaligned teeth.

  2. Large amplitude double layers in a positively charged dusty plasma with nonthermal electrons

    SciTech Connect

    Djebli, M.; Marif, H.

    2009-06-15

    A pseudopotential approach is used to investigate large amplitude dust-acoustic solitary structures for a plasma composed of positively charged dust, cold electrons, and nonthermal hot electrons. Numerical investigation for an adiabatic situation is conducted to examine the existence region of the wave. The negative potential of the double layers is found to be dependent on nonthermal parameters, Mach number, and electrons temperature. A range of the nonthermal parameters values exists for which two possible double layers for the same plasma mix at different Mach numbers and with significant different amplitudes. The present model is used to investigate localized structures in the lower-altitude Earth's ionosphere.

  3. General Bohm and Langmuir conditions for a strong double layer in space plasmas

    NASA Technical Reports Server (NTRS)

    Williams, A. C.

    1986-01-01

    The appropriate Bohm and Langmuir conditions when there are three beam-type particles passing through the double layer in addition to the usual two species of trapped particles are derived. It is shown that the Langmuir conditions, which normally imply a net current through the double layer, are consistent with zero net current when the class of accreting ions is included. It is also found that the Bohm criterion is quite different from its usual form, and that it has nothing to do with instabilities of the plasma at some critical level, as is believed to be true.

  4. Electrostatic soliton and double layer structures in unmagnetized degenerate pair plasmas

    NASA Astrophysics Data System (ADS)

    Mahmood, S.; Khan, S. A.; Ur-Rehman, H.

    2010-11-01

    The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron plasmas in the presence of stationary ions. The quantum hydrodynamic model is employed and reductive perturbation method is used to derive the Korteweg-de Vries (KdV) and extended KdV equations for solitons and double layers, respectively. It is found that in the linear limit both slow acoustic and fast Langmuir waves can propagate in such type of quantum plasmas like in classical pair-ion or pair plasmas. The amplitude and width of the electrostatic solitons are found to be decreasing with the increase in concentration of positrons (or decrease in the concentration of ions) in degenerate electron-positron-ion plasmas. It is found that only rarefactive double layer can exist in such plasmas which depend on various parameters. The dependence of double layer structure on ion concentration and quantum diffraction effects of electrons and positrons are also discussed. The results are also elaborated graphically by considering dense plasma parameters in the outer layers of astrophysical objects such as white dwarfs and neutron stars.

  5. Electrostatic soliton and double layer structures in unmagnetized degenerate pair plasmas

    SciTech Connect

    Mahmood, S.; Khan, S. A.; Ur-Rehman, H.

    2010-11-15

    The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron plasmas in the presence of stationary ions. The quantum hydrodynamic model is employed and reductive perturbation method is used to derive the Korteweg-de Vries (KdV) and extended KdV equations for solitons and double layers, respectively. It is found that in the linear limit both slow acoustic and fast Langmuir waves can propagate in such type of quantum plasmas like in classical pair-ion or pair plasmas. The amplitude and width of the electrostatic solitons are found to be decreasing with the increase in concentration of positrons (or decrease in the concentration of ions) in degenerate electron-positron-ion plasmas. It is found that only rarefactive double layer can exist in such plasmas which depend on various parameters. The dependence of double layer structure on ion concentration and quantum diffraction effects of electrons and positrons are also discussed. The results are also elaborated graphically by considering dense plasma parameters in the outer layers of astrophysical objects such as white dwarfs and neutron stars.

  6. Expanded graphite—Phenolic resin composites based double layer microwave absorber for X-band applications

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti Prasad; Bhattacharyya, Nidhi Saxena

    2014-11-01

    In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt. %, 7 wt. %, 8 wt. %, and 10 wt. % expanded graphite-novolac phenolic resin (EG-NPR) composites, in the frequency range of 8.2-12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing -25 dB absorption bandwidth >2 GHz and -30 dB absorption bandwidth >1 GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3 mm to 3.4 mm. Absorption bandwidths at -10 dB, -20 dB, -25 dB and -30 dB are determined for the fabricated structure. The maximum -25 dB and -30 dB absorption bandwidth of 2.47 GHz and 1.77 GHz, respectively, are observed for the double layer structure with (5 wt. %-8 wt. %) EG-NPR composites with total thickness of 3.2 mm, while -10 dB bandwidth covers the entire X-band range.

  7. Fabrication of fiber-optic EFPI with double-layer SU-8 diaphragm

    NASA Astrophysics Data System (ADS)

    Ding, Ding; Chen, Na; Guo, Qiang; Chen, Zhenyi; Liu, Shupeng; Pang, Fufei; Wang, Tingyun

    2011-12-01

    In this paper, we fabricated fiber-optic extrinsic Fabry-Perot interferometric (EFPI) sensors with photolithography . The sensor has double-layer SU-8 diaphragm: one is the pressure transduction layer; the other is cavity control layer. Since SU-8 material has a low Young's modulus, high pressure sensitivity can be achieved with SU-8 diaphragm. The EFPI were formed by a single mode fiber and a double-layer SU-8 diaphragm. To improve the fringe contrast, gold mirrors with a reflectivity of 50% were evaporated onto the end face of the single mode fiber and the inner face of the SU-8 diaphragm respectively. Experiments were done to estimate the performance of the sensor for static pressure measurement. The results show that an expected cavity length of the sensor was obtained and the EFPI sensor has a good linearity from 100 to 2500 Pa with 100 Pa resolution and a sensitivity of 154.8 nm/kPa.

  8. Surface double-layer structure in (110) oriented BiFeO{sub 3} thin film

    SciTech Connect

    Yang, Tieying; Zhang, Xingmin; Gao, Xingyu; Li, Zhong; Li, Xiaolong; Wang, Can; Feng, Yu; Guo, Haizhong; Jin, Kuijuan

    2014-11-17

    Surface double-layer structure different from the interior was found in BiFeO{sub 3} thin film grown on SrRuO{sub 3} covered SrTiO{sub 3} (110) substrate by pulsed laser deposition. It was shown that BiFeO{sub 3} film exhibits epitaxial phase with single domain. X-ray reflectivity and X-ray photoelectron spectroscopy results revealed a skin layer of less than 1 nm with a reduced electron density and different surface state. Grazing incidence x-ray diffraction convinced a surface multi-domain structure of several nm beneath the surface skin layer. The double-layer near surface structure would be originated from the large depolarization field produced by the single-domain structure with strain.

  9. Bias-dependent molecular-level structure of electrical double layer in ionic liquid on graphite

    SciTech Connect

    Black, Jennifer M; Walters, Deron; Labuda, Aleksander; Feng, Guang; Hillesheim, Patrick C; Dai, Sheng; Cummings, Peter T; Kalinin, Sergei V; Proksch, Roger; Balke, Nina

    2013-01-01

    Bias-dependent structure of electrochemical double layers at liquid-solid interfaces underpin a multitude of phenomena in virtually all areas of scientific enquiry ranging from energy storage and conversion systems, biology, to geophysics and geochemistry. Here we report the bias-evolution of the electric double layer structure of an ionic liquid on highly ordered pyrolytic graphite as a model system for carbon-based electrodes for electrochemical supercapacitors measured by atomic force microscopy. Matching the observed structures to molecular dynamics simulations allows us to resolve steric effects due to cation and anion layers. We observe reconfiguration under applied bias and the orientational transitions in the Stern layer. The synergy between molecular dynamics simulation and experiment provides a comprehensive picture of structural phenomena and long- and short range interactions. This insight will improve understanding of the mechanism of charge storage in electrochemical capacitors on a molecular level which can be used to enhance their electrochemical performance.

  10. Double layers and plasma-wave resistivity in extragalactic jets - Cavity formation and radio-wave emission

    NASA Technical Reports Server (NTRS)

    Borovsky, Joseph E.

    1987-01-01

    Current driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur in extragalactic jets for estimated values of the carried currents. Strong plasma double layers, however, may exist within self-maintained density cavities. The relativistic double-layer-emitted electron and ion beams drive plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layer-emitted electron beams may also emit polarized radio waves via a collective bremsstrahlung process mediated by electrostatic two-stream instabilities.

  11. Double layers and plasma-wave resistivity in extragalactic jets: Cavity formation and radio-wave emission

    NASA Technical Reports Server (NTRS)

    Borovsky, Joseph E.

    1987-01-01

    For estimated values of the currents carried by extragalactic jets, current-driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur. Strong plasma double layers, however, may exist within self-maintained density cavities, the relativistic double-layer-emitted electron, and ion beams driving plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layer-emitted electron beams may also emit polarized radio waves via a collective bremsstrahlung process mediated by electrostatic two-stream instabilities.

  12. Large amplitude dust-acoustic double layers in non-thermal plasmas with positive and negative dust

    SciTech Connect

    Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.; Pillay, S. R.

    2011-11-29

    The existence of large amplitude double layers in a plasma composed of cold negative dust, adiabatic positive dust, non-thermal ions and Boltzmann electrons is investigated using the Sagdeev pseudopotential technique. Both positive potential and negative potential double layers are found to be supported by the model. The variation of the maximum amplitudes of the double layers and corresponding Mach numbers are examined as a function of various plasma parameters. In particular, we investigate to what extent ion non-thermal effects are required for positive potential double layers to occur.

  13. Bias-dependent molecular-level structure of electrical double layer in ionic liquid on graphite.

    PubMed

    Black, Jennifer M; Walters, Deron; Labuda, Aleksander; Feng, Guang; Hillesheim, Patrick C; Dai, Sheng; Cummings, Peter T; Kalinin, Sergei V; Proksch, Roger; Balke, Nina

    2013-01-01

    Here we report the bias-evolution of the electrical double layer structure of an ionic liquid on highly ordered pyrolytic graphite measured by atomic force microscopy. We observe reconfiguration under applied bias and the orientational transitions in the Stern layer. The synergy between molecular dynamics simulation and experiment provides a comprehensive picture of structural phenomena and long and short-range interactions, which improves our understanding of the mechanism of charge storage on a molecular level.

  14. Micromagnetic analysis of Heusler alloy-based perpendicular double barrier synthetic antiferromagnetic free layer MTJs

    NASA Astrophysics Data System (ADS)

    Ghosh, Bahniman; Dwivedi, Kshitij

    2015-07-01

    We investigate spin transfer torque switching in a perpendicular double barrier synthetic antiferromagnetic free layer MTJ stack using micromagnetic simulations. For the material used in free layers, we use two different Cobalt-based Heusler alloys and compare their performance on the basis of switching speed, thermal stability and Tunnel magnetoresistance. We show that for Heusler alloys switching from one state to other is significantly faster but they suffer from the drawback of low thermal stability.

  15. Perpendicular magnetic tunnel junctions with double barrier and single or synthetic antiferromagnetic storage layer

    SciTech Connect

    Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Prejbeanu, Ioan L.; Dieny, Bernard

    2015-06-21

    The magnetic properties of double tunnel junctions with perpendicular anisotropy were investigated. Two synthetic antiferromagnetic references are used, while the middle storage magnetic layer can be either a single ferromagnetic or a synthetic antiferromagnetic FeCoB-based layer, with a critical thickness as large as 3.0 nm. Among the different achievable magnetic configurations in zero field, those with either antiparallel references, and single ferromagnetic storage layer, or parallel references, and synthetic antiferromagnetic storage layer, are of particular interest since they allow increasing the efficiency of spin transfer torque writing and the thermal stability of the stored information as compared to single tunnel junctions. The latter configuration can be preferred when stray fields would favour a parallel orientation of the reference layers. In this case, the synthetic antiferromagnetic storage layer is also less sensitive to residual stray fields.

  16. Double-HE-Layer Detonation-Confinement Sandwich Tests: The Effect of Slow-Layer Density

    NASA Astrophysics Data System (ADS)

    Hill, Larry

    2013-06-01

    Over a period of several years, we have explored the phenomenon in which slabs of high explosives (HEs) with differing detonation speeds are joined along one of their faces. Both are initiated (usually by a line-wave generator) at one edge. If there were no coupling between the layers, the detonation in the fast HE would outrun that in the slow HE. In reality, the detonation in the fast HE transmits an oblique shock into the slow HE, the phase speed of which is equal to the speed of the fast HE. This has one of two effects depending on the particulars. First, the oblique shock transmitted to the slow HE can pre-shock and deaden it, extinguishing the detonation in the slow HE. Second, the oblique shock can transversely initiate the slow layer, pulling its detonation along at the fast HE speed. When the second occurs, it does so at the ``penalty'' of a nominally dead layer, which forms in the slow HE adjacent to the material interface. We present the results of tests in which the fast layer was 3-mm-thick PBX 9501 (95 wt% HMX), and the slow layer was 8-mm-thick PBX 9502 (95 wt% TATB). The purpose was to observe the effect of slow layer density on the ``dead'' layer thickness. Very little effect was observed across the nominal PBX 9502 density range, 1.885-1.895 g/cc.

  17. Design of an Advanced Membrane Electrode Assembly Employing a Double-Layered Cathode for a PEM Fuel Cell.

    PubMed

    Kim, GyeongHee; Eom, KwangSup; Kim, MinJoong; Yoo, Sung Jong; Jang, Jong Hyun; Kim, Hyoung-Juhn; Cho, EunAe

    2015-12-23

    The membrane electrolyte assembly (MEA) designed in this study utilizes a double-layered cathode: an inner catalyst layer prepared by a conventional decal transfer method and an outer catalyst layer directly coated on a gas diffusion layer. The double-layered structure was used to improve the interfacial contact between the catalyst layer and membrane, to increase catalyst utilization and to modify the removal of product water from the cathode. Based on a series of MEAs with double-layered cathodes with an overall Pt loading fixed at 0.4 mg cm(-2) and different ratios of inner-to-outer Pt loading, the MEA with an inner layer of 0.3 mg Pt cm(-2) and an outer layer of 0.1 mg Pt cm(-2) exhibited the best performance. This performance was better than that of the conventional single-layered electrode by 13.5% at a current density of 1.4 A cm(-2).

  18. The tail effect on the shape of an electrical double layer differential capacitance curve

    NASA Astrophysics Data System (ADS)

    Henderson, Douglas; Lamperski, Stanisław; Bari Bhuiyan, Lutful; Wu, Jianzhong

    2013-04-01

    The differential capacitance curve for the double layer formed by an electrolyte dissolved in a solvent is commonly believed to be parabolic-like with a minimum at low electrolyte charge concentration and low electrode surface charge density, and independent of electrolyte concentration at high electrolyte concentrations and high electrode charge and would be, in the absence of solvent effects, featureless at these latter conditions. This is the prediction of the popular Gouy-Chapman-Stern theory. In contrast, for an ionic liquid this curve can have a single or a double hump (or a bell or camel shape). Fedorov et al. [Electrochem. Commun. 12, 296 (2010)], 10.1016/j.elecom.2009.12.019 have related these humps, particularly the double hump, to the neutral tails of ions in many ionic liquids. Evidence presented here shows, however, that such humps are general features of the differential capacitance of a double layer, whether it be formed by ions with or without a neutral tail. The presence of a double or single hump results from the magnitude of the electrolyte charge concentration. For both spherical ions or non-spherical ions consisting of charged heads and neutral tails, the shape of the differential capacitance transforms continuously from a double hump to a single hump as the electrolyte concentration is increased.

  19. Double Layer Charging for Conductivity Enhancement of Pure Metallic and Semiconducting Single Wall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mayo, Nathanael; Kuznetsov, Alexander; Zakhidov, Anvar

    2011-03-01

    Injecting high electronic charge densities can profoundly change the optical, electrical, and magnetic properties of materials. Evidence suggests a possibility of significantly improving conductivity of carbon nanotubes through double layer charge injection. Double layer charge injection can prove to be a powerful method when applied to carbon nanotubes because of theirs high surface area and chemical stability. Investigation has commenced on the effect of charging on various types of carbon nanotubes, specifically 99% purified single wall semiconducting and single wall metallic tubes. An electrical double layer is electrochemically introduced upon a sheet of carbon nanotubes via application of potential (up to +/- 5 volts) to a sample immersed in ionic-liquid-based electrolyte. Resistance of carbon nanotube as a function of applied charging voltage is recorded to determine the effects of charge injection. Results show that the electrical double layer considerably reduces the resistance across both samples. ESR/LFMA studies combined with low temperature magnetic and transport measurements are conducted to search for charge injection induced superconductivity in carbon nanotubes. Supported by AFOSR grant FA 9550-09-1-0384.

  20. Effects of hot electron inertia on electron-acoustic solitons and double layers

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.

    2015-07-15

    The propagation of arbitrary amplitude electron-acoustic solitons and double layers is investigated in a plasma containing cold positive ions, cool adiabatic and hot isothermal electrons, with the retention of full inertial effects for all species. For analytical tractability, the resulting Sagdeev pseudopotential is expressed in terms of the hot electron density, rather than the electrostatic potential. The existence domains for Mach numbers and hot electron densities clearly show that both rarefactive and compressive solitons can exist. Soliton limitations come from the cool electron sonic point, followed by the hot electron sonic point, until a range of rarefactive double layers occurs. Increasing the relative cool electron density further yields a switch to compressive double layers, which ends when the model assumptions break down. These qualitative results are but little influenced by variations in compositional parameters. A comparison with a Boltzmann distribution for the hot electrons shows that only the cool electron sonic point limit remains, giving higher maximum Mach numbers but similar densities, and a restricted range in relative hot electron density before the model assumptions are exceeded. The Boltzmann distribution can reproduce neither the double layer solutions nor the switch in rarefactive/compressive character or negative/positive polarity.

  1. A variational solution to the hypernetted chain equations applied to the electrical double layer

    SciTech Connect

    Feller, S.E.; McQuarrie, D.A.

    1992-04-16

    A variational method for the solution to the hypernetted chain/mean spherical approximation equations applied to the electrical double layer is presented and demonstrated with calculations in the restricted primitive model for electrolytes near a charged planar surface. This variational method is also compared with the modified Gouy-Chapman theory. 20 refs., 7 figs.

  2. Laser cutting silicon-glass double layer wafer with laser induced thermal-crack propagation

    NASA Astrophysics Data System (ADS)

    Cai, Yecheng; Yang, Lijun; Zhang, Hongzhi; Wang, Yang

    2016-07-01

    This study was aimed at introducing the laser induced thermal-crack propagation (LITP) technology to solve the silicon-glass double layer wafer dicing problems in the packaging procedure of silicon-glass device packaged by WLCSP technology, investigating the feasibility of this idea, and studying the crack propagation process of LITP cutting double layer wafer. In this paper, the physical process of the 1064 nm laser beam interact with the double layer wafer during the cutting process was studied theoretically. A mathematical model consists the volumetric heating source and the surface heating source has been established. The temperature and stress distribution was simulated by using finite element method (FEM) analysis software ABAQUS. The extended finite element method (XFEM) was added to the simulation as the supplementary features to simulate the crack propagation process and the crack propagation profile. The silicon-glass double layer wafer cutting verification experiment under typical parameters was conducted by using the 1064 nm semiconductor laser. The crack propagation profile on the fracture surface was examined by optical microscope and explained from the stress distribution and XFEM status. It was concluded that the quality of the finished fracture surface has been greatly improved, and the experiment results were well supported by the numerical simulation results.

  3. Highly oriented nanoplates of layered double hydroxides as an ultra slow release system.

    PubMed

    Lee, Jong Hyeon; Jung, Duk-Young

    2012-06-01

    A novel controlled molecular release based on highly oriented nanoplates of layered double hydroxide was fabricated on indium tin oxide substrates by electrophoretic deposition of exfoliated LDH nanosheets. The LDH particle coating exhibited a superior release performance of the order of hours. PMID:22531710

  4. Significantly Enhanced Separation using ZIF-8 Membranes by Partial Conversion of Calcined Layered Double Hydroxide Precursors.

    PubMed

    Liu, Yi; Peng, Yuan; Wang, Nanyi; Li, Yanshuo; Pan, Jia Hong; Yang, Weishen; Caro, Jürgen

    2015-11-01

    Significantly enhanced H2 /CH4 (ca. 80) selectivity was realized by effective suppression of the framework flexibility of a prepared ZIF-8 membrane. Initially a ZnO buffer layer consisting of 20 nm-sized ZnO-nanoparticle aggregates was fabricated by controlled calcination of a ZnAl-NO3 layered double hydroxide membrane. Owing to its high chemical reactivity, the ZnO buffer layer was partially converted into a well-intergrown ZIF-8 membrane with a certain penetration depth upon solvothermal treatment with ligands. Our method may represent a new concept for the design of advanced MOF membranes with high selectivity. PMID:26427908

  5. Strong interfacial attrition developed by oleate/layered double hydroxide nanoplatelets dispersed into poly(butylene succinate).

    PubMed

    Zhou, Qian; Verney, Vincent; Commereuc, Sophie; Chin, In-Joo; Leroux, Fabrice

    2010-09-01

    Poly(butylene succinate) (PBS) nanocomposite structure was studied as a function of the filler percentage loading. The resulting state of dispersion was evaluated by XRD and TEM, and the interfacial attrition between PBS chain and lamellar platelets by the melt rheological properties. Hybrid organic inorganic (O/I) layered double hydroxide (LDH) organo-modified by oleate anions was used as filler. It was found that the confinement supplied by the LDH framework forces the interleaved organic molecule to be more distant from each other than in the case of oleate salt, this having as an effect to decrease strongly the homonuclear intermolecular (1)H(1)H dipolar interaction. An additional consequence of this relatively free molecular rotation, affecting the (13)C CPMAS response as well, is to facilitate the delamination of the 2D-stacked layers during extrusion since an quasi-exfoliated PBS:Mg(2)Al/oleate structure is observed for filler loading lower than 5% w/w. This is in association to a non-linear viscoelasticity in the low-omega region and the observed shear-thinning tendency compares better than other PBS:silicate nanocomposite derivatives and is here explained by the presence of a percolated LDH nanoparticle network. Indeed the plastic deformation in the low-omega region is found to be restricted by well-dispersed LDH tactoids in association with a rather strong attrition phenomenon between tethered oleate anions and PBS chains.

  6. Ion acoustic solitons/double layers in two-ion plasma revisited

    SciTech Connect

    Lakhina, G. S. Singh, S. V. Kakad, A. P.

    2014-06-15

    Ion acoustic solitons and double layers are studied in a collisionless plasma consisting of cold heavier ion species, a warm lighter ion species, and hot electrons having Boltzmann distributions by Sagdeev pseudo-potential technique. In contrast to the previous results, no double layers and super-solitons are found when both the heavy and lighter ion species are treated as cold. Only the positive potential solitons are found in this case. When the thermal effects of the lighter ion species are included, in addition to the usual ion-acoustic solitons occurring at M > 1 (where the Mach number, M, is defined as the ratio of the speed of the solitary wave and the ion-acoustic speed considering temperature of hot electrons and mass of the heavier ion species), slow ion-acoustic solitons/double layers are found to occur at low Mach number (M < 1). The slow ion-acoustic mode is actually a new ion-ion hybrid acoustic mode which disappears when the normalized number density of lighter ion species tends to 1 (i.e., no heavier species). An interesting property of the new slow ion-acoustic mode is that at low number density of the lighter ion species, only negative potential solitons/double layers are found whereas for increasing densities there is a transition first to positive solitons/double layers, and then only positive solitons. The model can be easily applicable to the dusty plasmas having positively charged dust grains by replacing the heavier ion species by the dust mass and doing a simple normalization to take account of the dust charge.

  7. Dust acoustic double layers in a magnetized dusty self-gravitating plasma with superthermal particles

    NASA Astrophysics Data System (ADS)

    Sabetkar, Akbar; Dorranian, Davoud

    2016-08-01

    Our prime objective of this paper is to examine the parametric regimes for the existence and polarity of dust acoustic double layers (DADLs) and its solitary structures arising from a magnetized self-gravitating opposite polarity dust-plasma (OPDP) model. The constituents of the OPDP model are two species of positively and negatively charged dust grains, Maxwellian electrons and kappa distributed ions. Contributions of gravitational force only on dust grains are taken into account. For weakly nonlinear analysis, the multiple time scale technique has been used to construct the extended Korteweg-de Vries (E-KdV) and modified Korteweg-de Vries (M-KdV) equations. They pinpoint the evolution of DADLs and solitary structures associated with dust acoustic (DA) mode, respectively. The relevant configurational parameters in our study include the superthermality of ions (κ), obliqueness of propagation (θ), ion concentration (δi), static magnetic field B0 (via ω c p , ω c n ), and self-gravitational field (via γ), as well as the density (μ0), charge (α), and mass (β) ratio of positive to negative dust species. The proposed OPDP model permits positive and negative double layer polarities, while higher order nonlinear equation dictates us only positive polarity solitary structures. The main modification due to an increase in self-gravitational field (via γ) is an enhancement in the spatial width of double layers, yet leaving their amplitude, phase speed, and polarity practically unaffected. With enhanced superthermality and other intrinsic parameters in OPDP model, there is an opposite trend in both amplitude and width of double layers, while the amplitude and the width of solitary waves (via M-KdV equation) undergo the identical behaviors. In particular, the amplitude of solitary waves manifests monotonic behavior for permissible range of obliqueness θ, whereas this scenario is acceptable to only width of double layers. The results are discussed in the context of

  8. Bio-Inspired Aquaporinz Containing Double-Skinned Forward Osmosis Membrane Synthesized through Layer-by-Layer Assembly

    PubMed Central

    Wang, Shuzheng; Cai, Jin; Ding, Wande; Xu, Zhinan; Wang, Zhining

    2015-01-01

    We demonstrated a novel AquaporinZ (AqpZ)-incorporated double-skinned forward osmosis (FO) membrane by layer-by-layer (LbL) assembly strategy. Positively charged poly(ethyleneimine) (PEI) and negatively charged poly(sodium 4-styrenesulfonate) (PSS) were alternately deposited on both the top and bottom surfaces of a hydrolyzed polyacrylonitrile (H-PAN) substrate. Subsequently, an AqpZ-embedded 1,2-dioleloyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dioleoyl-3-trimethylammonium- propane (chloride salt) (DOTAP) supported lipid bilayer (SLB) was formed on PSS-terminated (T-PSS) membrane via vesicle rupture method. The morphology and structure of the biomimetic membranes were characterized by in situ atomic force microscopy (AFM), scanning electron microscope (SEM), Fourier transform infrared spectrometer using the attenuated total reflection technique (ATR-FTIR), and contact angle. Moreover, the FO performance of the resultant membrane was measured by using 2 M MgCl2 solution as draw solution and deionized (DI) water as feed solution, respectively. The membrane with a protein-to-lipid weight ratio (P/L) of 1/50 exhibits 13.2 L/m2h water flux and 3.2 g/m2h reversed flux by using FO mode, as well as 15.6 L/m2h water flux and 3.4 L/m2h reversed flux for PRO mode (the draw solution is placed against the active layer). It was also shown that the SLB layer of the double-skinned FO membrane can increase the surface hydrophilicity and reduce the surface roughness, which leads to an improved anti-fouling performance against humic acid foulant. The current work introduced a new method of fabricating high performance biomimetic FO membrane by combining AqpZ and a double-skinned structure based on LbL assembly. PMID:26266426

  9. Using martian single and double layered ejecta craters to probe subsurface stratigraphy

    NASA Astrophysics Data System (ADS)

    Jones, Eriita; Osinski, Gordon R.

    2015-02-01

    Martian craters with fluidized ejecta - including single-layered, double-layered and multiple-layered craters - have been studied extensively, with their formation generally suggested to require some presence of volatiles in the subsurface. However, experimental reproduction of these morphologies, impact modelling, and the occurrence of layered ejecta in putative volatile poor regions suggests that other factors may also play important roles. A recent extensive catalogue of martian impact craters (Robbins, S.J., Hynek, B.M. [2012a]. J. Geophys. Res. 117, E05004) classifies crater ejecta along with their location, diameters and ejecta extents, potentially providing new information on the links between these morphologies and the subsurface. We utilise this catalogue to examine the regional variation in ejecta mobility, onset diameter and the correlation between ejecta mobility and diameter for single- and double-layered ejecta craters on Mars. A simple regional stratigraphic model is developed to explain the observed trends through the viscosity of the layers within the target. Using this model, the potential relative thickness and burial depths of low viscosity layers in the martian subsurface are hypothesised, and compared to other observations and models of subsurface volatiles and how they have varied throughout time.

  10. Si/Ge double-layered nanotube array as a lithium ion battery anode.

    PubMed

    Song, Taeseup; Cheng, Huanyu; Choi, Heechae; Lee, Jin-Hyon; Han, Hyungkyu; Lee, Dong Hyun; Yoo, Dong Su; Kwon, Moon-Seok; Choi, Jae-Man; Doo, Seok Gwang; Chang, Hyuk; Xiao, Jianliang; Huang, Yonggang; Park, Won Il; Chung, Yong-Chae; Kim, Hansu; Rogers, John A; Paik, Ungyu

    2012-01-24

    Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3C rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries.

  11. Acoustic radiation force on a double-layer microsphere by a Gaussian focused beam

    NASA Astrophysics Data System (ADS)

    Wu, Rongrong; Cheng, Kaixuan; Liu, Xiaozhou; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen

    2014-10-01

    A new model for calculating the radiation force on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic radiation force resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic radiation force.

  12. Larger bandgap of elliptical cylinders in two-dimensional double-layer photonic crystals

    NASA Astrophysics Data System (ADS)

    Niu, Jin; Xiang, Yang

    2013-08-01

    We investigate the bandgap properties of two-dimensional double-layer photonic crystals composed of elliptical cylinders in square and triangular lattices, considering cylinders formed of dielectric cores surrounded by interfacial layers of air in magnesium fluoride background. Using the plane-wave numerical expansion method, the bandgap spectrum for the cylinders covered by air rings is obtained for different structural parameters, such as the radius, orientation angle, and lattice constant. The results show that the bandgap of the two-dimensional double-layer photonic crystal is greatly improved compared with traditional two-dimensional photonic crystal and the triangular lattice presents a larger bandgap than the square lattice. The optimal structure parameters to broaden the bandgap are presented.

  13. Acoustic radiation force on a double-layer microsphere by a Gaussian focused beam

    SciTech Connect

    Wu, Rongrong; Cheng, Kaixuan; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen; Liu, Xiaozhou

    2014-10-14

    A new model for calculating the radiation force on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic radiation force resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic radiation force.

  14. Hybrid Materials Based on Magnetic Layered Double Hydroxides: A Molecular Perspective.

    PubMed

    Abellán, Gonzalo; Martí-Gastaldo, Carlos; Ribera, Antonio; Coronado, Eugenio

    2015-06-16

    dielectric strength, to produce two-dimensional nanosheets with atomic thickness that can be used as macromolecular building blocks in the assembly of nanocomposites. We describe how these advantageous properties turn LDHs into excellent vehicles for the preparation of multifunctional materials with increasing levels of complexity. For clarity, the reader will first find a succinct description of the most relevant aspects controlling the magnetism of LDHs followed by their use in the preparation of magnetic hybrids from a molecular perspective. This includes the intercalation anionic species of increasing nuclearity like paramagnetic mononuclear complexes, stimulus-responsive molecular guests, one- and two-dimensional coordination polymers, or even preassembled 2D networks. This approach allows us to evolve from "dual-function" materials with coexistence, for example, of magnetism and superconductivity, to smart materials in which the magnetic or structural properties of the LDH layers can be tuned by applying an external stimulus like light or temperature. We will conclude with a brief look into the promising features offered by magnetic nanocomposites based on LDHs and our views on the most promising directions to be pursued in this context. PMID:25989182

  15. Design, fabrication and characterization of a double layer solid oxide fuel cell (DLFC)

    NASA Astrophysics Data System (ADS)

    Wang, Guangjun; Wu, Xiangying; Cai, Yixiao; Ji, Yuan; Yaqub, Azra; Zhu, Bin

    2016-11-01

    A double layer solid oxide fuel cell (DLSOFC) without using the electrolyte (layer) has been designed by integrating advantages of positive electrode material of lithium ion battery(LiNi0.8Co0.15Al0.05O2) and oxygen-permeable membranes material (trace amount cobalt incorporated terbium doped ceria, TDC + Co) based on the semiconductor physics principle. Instead of using an electrolyte layer, the depletion layer between the anode and cathode served as an electronic insulator to block the electrons but to maintain the electrolyte function for ionic transport. Thus the device with two layers can realize the function of SOFC and at the same time avoids the electronic short circuiting problem. Such novel DLFC showed good performance at low temperatures, for instance, a maximum power density of 230 mWcm-2 was achieved at 500 °C. The working principle of the new device is presented.

  16. Experimental investigation of the Marangoni effect on the stability of a double-diffusive layer

    NASA Technical Reports Server (NTRS)

    Tanny, Josef; Chen, Chuan F.

    1994-01-01

    Stability experiments were carried out in 4-cm-thick, salt-stratified fluid layer by heating from below and cooling from above. The bottom boundary was rigid while the top was either free or rigid. The initial solute Rayleigh number varied from 2.5 x 10(exp 6) to 4.6 x 10(exp 7). For the rigid-free case, at initial solute Rayleigh numbers R(sub s) greater than 5.4 x 10(exp 6), thermal Marangoni instabilities were observed to onset along the free surface at a relatively low thermal Rayleigh number, R(sub t). The convection was very weak, and it had almost no effect on the concentration and temperature distributions. Double-diffusive instabilities along the top free surface were observed to onset at a higher R(sub t), with much stronger convection causing changes in the concentration and temperature distributions near the top. At a yet higher R(sub t), double-diffusive convection was observed to onset along the bottom boundary. Fluid motion in the layer then evolved into fully developed thermal convection of a homogeneous fluid without any further increase in the imposed Delta T. For layers with R(sub s) less than 5.4 x 10(exp 6), Marangoni and double-diffusive instabilities onset simultaneously along the free surface first, while double-diffusive instabilities along the bottom wall onset at a higher R(sub t).

  17. Synthesis of Zn–Fe layered double hydroxides via an oxidation process and structural analysis of products

    SciTech Connect

    Morimoto, Kazuya; Tamura, Kenji; Anraku, Sohtaro; Sato, Tsutomu; Suzuki, Masaya; Yamada, Hirohisa

    2015-08-15

    The synthesis of Zn–Fe(III) layered double hydroxides was attempted, employing different pathways using either Fe(II) or Fe(III) species together with Zn as the initial reagents. The product derived from the synthesis employing Fe(II) was found to transition to a Zn–Fe(III) layered double hydroxides phase following oxidation process. In contrast, the product obtained with Fe(III) did not contain a layered double hydroxides phase, but rather consisted of simonkolleite and hydrous ferric oxide. It was determined that the valency of the Fe reagent used in the initial synthesis affected the generation of the layered double hydroxides phase. Fe(II) species have ionic radii and electronegativities similar to those of Zn, and therefore are more likely to form trioctahedral hydroxide layers with Zn species. - Graphical abstract: The synthesis of Zn–Fe(III) layered double hydroxides was attempted, employing different pathways using either Fe(II) or Fe(III) species together with Zn as the initial reagents. - Highlights: • Iron valency affected the generation of Zn–Fe layered double hydroxides. • Zn–Fe layered double hydroxides were successfully synthesized using Fe(II). • Fe(II) species were likely to form trioctahedral hydroxide layers with Zn species.

  18. DX center analysis in Sn-doped AlGaAs layer of double heterostructures

    NASA Astrophysics Data System (ADS)

    Kaniewski, J.; Kaniewska, M.; Ždánský, K.

    1987-12-01

    Capacitance as well as photovoltage methods have been used to analyze deep centers in an n-type AlGaAs:Sn layer of double heterostructures. It is suggested that the trap with thermal activation energy equal to ΔE2=0.33±0.02 eV is associated with the L minimum of AlGaAs and could be interpreted as a DX center related to Sn. The observed changes of deep center concentration in double heterostructures are due to different Al contents within the depletion region.

  19. Prospective comparative study of single-layer versus double-layer closure of leg wounds after long saphenous vein harvest in coronary artery bypass graft operations

    PubMed Central

    Siddiqi, Mohammad Salman; Al Sabti, Hilal; Mukaddirov, Mirdavron; Sharma, Ashok Kumar

    2011-01-01

    Introduction Wound infection is one of the major complication post CABG that leads to prolonged length of stay and cost post surgery. Coronary artery bypass grafting is one of the most commonly performed operations in the world. The long saphenous vein harvested by traditional techniques is still widely used and caries a risk of wound infection. Objective The purpose of this study is to ascertain if a single-layer closure result in better wound healing and functional outcome as compared with the traditional two-layer closure after harvest of saphenous vein. Methods Sixty-seven consecutive patients undergoing CABG were prospectively randomized to have their leg wound closed by either a single-layer technique with a suction drain or double layers without suction drain. All wounds were assessed for the presence of serous discharge, inflammation, edema, purulent exudates, infection of the deep tissues, and pain postoperatively and two weeks after discharge. Results There were trends towards increased rates of wound related outcomes in patients in double layer group when compared with single layer group. Out of 77 patients in our study, 52 patients underwent single layer closure (males, n = 37; females, n= 15) and 25 patients underwent double layer closure (males, n = 21; females, n = 04). There was significant statistical difference between the treatment groups with single layer group having lower average scores (4.038) compared to double layer group (9.467), P- value 0.001. Patients whose legs were closed with the single layer technique had less post operative edema (23.07% vs 53.30) and pain (44.2 vs 73.33) compared with the double layer group. Conclusions Single-layer leg wound closure over a suction drain has shown a better wound outcome compared to traditional double-layer closure. A possible mechanism of better wound healing in the former technique might be through decreased tissue handling and a reduction in leg edema. PMID:22263084

  20. Skin explosion of double-layer conductors in fast-rising high magnetic fields

    SciTech Connect

    Chaikovsky, S. A. Datsko, I. M.; Labetskaya, N. A.; Ratakhin, N. A.

    2014-04-15

    An experiment has been performed to study the electrical explosion of thick cylindrical conductors using the MIG pulsed power generator capable of producing a peak current of 2.5 MA within 100 ns rise time. The experimental goal was to compare the skin explosion of a solid conductor with that of a double-layer conductor whose outer layer had a lower conductivity than the inner one. It has been shown that in magnetic fields of peak induction up to 300 T and average induction rise rate 3 × 10{sup 9} T/s, the double-layer structure of a conductor makes it possible to achieve higher magnetic induction at the conductor surface before it explodes. This can be accounted for, in particular, by the reduction of the ratio of the Joule heat density to the energy density of the magnetic field at the surface of a double-layer conductor due to redistribution of the current density over the conductor cross section.

  1. Catalyzed double layer cathodes for high performance and long life molten carbonate fuel cells

    SciTech Connect

    Bischoff, M.; Jantsch, U.; Rohland, B.

    1996-12-31

    NiO/LiCoO{sub 2} double layer cathodes (DLCs) were prepared with a thin highly active LiCoO{sub 2}-layer by a new double layer tape casting/sintering procedure. The resulting metallic porous precursor plates were mounted into the MCFC and heated up by a special procedure to form LiCoO{sub 2} from air, Co and Li{sub 2}CO{sub 3} in a solid/gas reaction. MCFCs with highly active NiO/LiCoO{sub 2}-DLCs can operate over prolonged periods of time with a Ni-precipitation which is 10% lower than one finds with state of the art NiO cathodes. According to LiCoO{sub 2}-cathodes have theoretical life times of more than 100 000 hours at nonpressurized conditions. MCFCs with new NiO/LiCoO{sub 2} double layer cathodes (DLC) were investigated with regard to variable parameters of their microstructure. From the agglomerate model of the porous MCFC cathode, the dependence of the polarization resistance from the radius of the agglomerates and the inner agglomerate surface area was calculated.

  2. Influence of nonelectrostatic ion-ion interactions on double-layer capacitance

    NASA Astrophysics Data System (ADS)

    Zhao, Hui

    2012-11-01

    Recently a Poisson-Helmholtz-Boltzmann (PHB) model [Bohinc , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031130 85, 031130 (2012)] was developed by accounting for solvent-mediated nonelectrostatic ion-ion interactions. Nonelectrostatic interactions are described by a Yukawa-like pair potential. In the present work, we modify the PHB model by adding steric effects (finite ion size) into the free energy to derive governing equations. The modified PHB model is capable of capturing both ion specificity and ion crowding. This modified model is then employed to study the capacitance of the double layer. More specifically, we focus on the influence of nonelectrostatic ion-ion interactions on charging a double layer near a flat surface in the presence of steric effects. We numerically compute the differential capacitance as a function of the voltage under various conditions. At small voltages and low salt concentrations (dilute solution), we find out that the predictions from the modified PHB model are the same as those from the classical Poisson-Boltzmann theory, indicating that nonelectrostatic ion-ion interactions and steric effects are negligible. At moderate voltages, nonelectrostatic ion-ion interactions play an important role in determining the differential capacitance. Generally speaking, nonelectrostatic interactions decrease the capacitance because of additional nonelectrostatic repulsion among excess counterions inside the double layer. However, increasing the voltage gradually favors steric effects, which induce a condensed layer with crowding of counterions near the electrode. Accordingly, the predictions from the modified PHB model collapse onto those computed by the modified Poisson-Boltzmann theory considering steric effects alone. Finally, theoretical predictions are compared and favorably agree with experimental data, in particular, in concentrated solutions, leading one to conclude that the modified PHB model adequately predicts the diffuse

  3. Solvent-free synthesis of new metal phosphites with double-layered, pillared-layered, and framework structures

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Zhang, Wei; Shi, Zhonghua; Chen, Yaoqiang; Lin, Zhien

    2014-12-01

    Three new metal phosphites, formulated as (H3O)2·Mn2(HPO3)3 (1), Co(bpy) (H2O) (HPO3) (2), and H2tmpda·Zn3(HPO3)4 (3), have been synthesized under solvent-free conditions, where bpy = 4,4‧-bipyridine, and tmpda = N,N,N‧,N‧-tetramethyl-1,3-propanediamine. Compound 1 has a double-layered structure with a thickness of 5.68 Å. Compound 2 has an inorganic-organic hybrid framework with cobalt phosphite layers pillared by bpy ligands. Compound 3 has a three-dimensional open-framework structure containing 8-ring channels. The temperature dependence of the magnetic susceptibility of compounds 1 and 2 were also investigated.

  4. AA stacking, tribological and electronic properties of double-layer graphene with krypton spacer.

    PubMed

    Popov, Andrey M; Lebedeva, Irina V; Knizhnik, Andrey A; Lozovik, Yurii E; Potapkin, Boris V; Poklonski, Nikolai A; Siahlo, Andrei I; Vyrko, Sergey A

    2013-10-21

    Structural, energetic, and tribological characteristics of double-layer graphene with commensurate and incommensurate krypton spacers of nearly monolayer coverage are studied within the van der Waals-corrected density functional theory. It is shown that when the spacer is in the commensurate phase, the graphene layers have the AA stacking. For this phase, the barriers to relative in-plane translational and rotational motion and the shear mode frequency of the graphene layers are calculated. For the incommensurate phase, both of the barriers are found to be negligibly small. A considerable change of tunneling conductance between the graphene layers separated by the commensurate krypton spacer at their relative subangstrom displacement is revealed by the use of the Bardeen method. The possibility of nanoelectromechanical systems based on the studied tribological and electronic properties of the considered heterostructures is discussed.

  5. Electrical Double Layer Capacitance in a Graphene-embedded Al2O3 Gate Dielectric

    PubMed Central

    Ki Min, Bok; Kim, Seong K.; Jun Kim, Seong; Ho Kim, Sung; Kang, Min-A; Park, Chong-Yun; Song, Wooseok; Myung, Sung; Lim, Jongsun; An, Ki-Seok

    2015-01-01

    Graphene heterostructures are of considerable interest as a new class of electronic devices with exceptional performance in a broad range of applications has been realized. Here, we propose a graphene-embedded Al2O3 gate dielectric with a relatively high dielectric constant of 15.5, which is about 2 times that of Al2O3, having a low leakage current with insertion of tri-layer graphene. In this system, the enhanced capacitance of the hybrid structure can be understood by the formation of a space charge layer at the graphene/Al2O3 interface. The electrical properties of the interface can be further explained by the electrical double layer (EDL) model dominated by the diffuse layer. PMID:26530817

  6. Mechanisms governing the interfacial delamination of thermal barrier coating system with double ceramic layers

    NASA Astrophysics Data System (ADS)

    Xu, Rong; Fan, Xueling; Wang, T. J.

    2016-05-01

    A systematic study of factors affecting the interfacial delamination of thermal barrier coating system (TBCs) with double ceramic layers (DCL) is presented. Crack driving forces for delaminations at two weak interfaces are examined. The results show that a thicker outermost ceramic layer can induce dramatic increase in crack driving force and make the interface between two ceramic coatings become more prone to delamination. The behavior is shown to be more prominent in TBCs with stiffer outmost coating. The thickness ratio of two ceramic layers is an important parameter for controlling the failure mechanisms and determining the lifetime of DCL TBCs under inservice condition. By accounting for the influences of thickness ratio of two ceramic layers and interfacial fracture toughnesses of two involved interfaces, the fracture mechanism map of DCL TBCs has been constructed, in which different failure mechanisms are identified. The results quanlitatively agree with the aviliable experimental data.

  7. High Altitude Double Sodium Layer Observed at Low Latitude and Possible Formation: A Case Study

    NASA Astrophysics Data System (ADS)

    Xue, X.

    2012-12-01

    We report the lidar observations of a double sodium layer (DSL) at Lijiang, China, in March 2012, in which, a high-altitude secondary sodium layer (SeSL) and a sporadic sodium layer (SSL) are co-existed. The SeSL has a maximum density 120 cm-3, 6.7% of that of main layer, and starts at 122 km with full width at half maximum (FWHM) ~ 4-8 km. It does not merge into the main layer for whole observational period. The SSL with a peak density 5500 cm-3, 3 times larger than that of the main layer, appears at 105 km and accompanies with SeSL all the time. Further observations illustrate that multi-layer sporadic E (Es) layers are related to the formation of SeSL and SSL through meridional and zonal diurnal tidal (DT) wind shear mechanisms, respectively, whose efficiency differ at a given altitude according to the ratio of ion-neutral collision frequency to ion gyrofrequency.

  8. Spatial anisotropy and character of the exchange interaction in single and double layer manganites^*.

    NASA Astrophysics Data System (ADS)

    Mryasov, O. N.; Sabiryanov, R. F.; Jaswal, S. S.; Freeman, A. J.

    1998-03-01

    The influence of the doping and number of layers (double vs. single layer) on spatial anisotropy (in-plane J_in vs. inter-plane J_out) in single LaMnO3 and double layer LaSr_2Mn_2O7 manganites studied on the basis of the ab-initio calculations using the linear muffin-tin orbital method generalized to treat non-collinear magnetic configurations^1. We find that contribution of the DE is not effected significantly by the doping (Ca,Sr,Ba) and is substantially smaller than predicted by the Anderson-Hasegawa model. On the other hand, both global and internal lattice distortions dramatically influence the character and strength of the exchange interactions. Spatial anisotropy of the exchange interaction in pure LaMnO3 is found to be slightly underestimated (J_in = 2.0 mRy but J_out = -1.2 mRy) if compared with extracted from newtron scattering experiments (J_in = 1.6 mRy but J_out = -0.8 mRy). We find that exchange interactions in double layer manganites have pronounced two dimensional character with layers effectivaly decoupled (J=0.05 mRy) due to the effect of buffer Sr/La atoms, however within layers J_in = 1 mRy but J_out = 0.3 mRy. ^* Work at NU supported by U.S. DOE (Grant No. DE-FG02-ER45372) and at UNL by NSF [Grant No. OSR9255225], DOE [Grant No. DE-FG2-86ER45262]. ^1 O.N.Mryasov et al., J. of Phys: Condensed Matter 3, 7683 (1991).

  9. Graphene based 2D-materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Palaniselvam, Thangavelu; Baek, Jong-Beom

    2015-09-01

    Ever-increasing energy demands and the depletion of fossil fuels are compelling humanity toward the development of suitable electrochemical energy conversion and storage devices to attain a more sustainable society with adequate renewable energy and zero environmental pollution. In this regard, supercapacitors are being contemplated as potential energy storage devices to afford cleaner, environmentally friendly energy. Recently, a great deal of attention has been paid to two-dimensional (2D) nanomaterials, including 2D graphene and its inorganic analogues (transition metal double layer hydroxides, chalcogenides, etc), as potential electrodes for the development of supercapacitors with high electrochemical performance. This review provides an overview of the recent progress in using these graphene-based 2D materials as potential electrodes for supercapacitors. In addition, future research trends including notable challenges and opportunities are also discussed.

  10. Numerical Well Testing Interpretation Model and Applications in Crossflow Double-Layer Reservoirs by Polymer Flooding

    PubMed Central

    Guo, Hui; He, Youwei; Li, Lei; Du, Song; Cheng, Shiqing

    2014-01-01

    This work presents numerical well testing interpretation model and analysis techniques to evaluate formation by using pressure transient data acquired with logging tools in crossflow double-layer reservoirs by polymer flooding. A well testing model is established based on rheology experiments and by considering shear, diffusion, convection, inaccessible pore volume (IPV), permeability reduction, wellbore storage effect, and skin factors. The type curves were then developed based on this model, and parameter sensitivity is analyzed. Our research shows that the type curves have five segments with different flow status: (I) wellbore storage section, (II) intermediate flow section (transient section), (III) mid-radial flow section, (IV) crossflow section (from low permeability layer to high permeability layer), and (V) systematic radial flow section. The polymer flooding field tests prove that our model can accurately determine formation parameters in crossflow double-layer reservoirs by polymer flooding. Moreover, formation damage caused by polymer flooding can also be evaluated by comparison of the interpreted permeability with initial layered permeability before polymer flooding. Comparison of the analysis of numerical solution based on flow mechanism with observed polymer flooding field test data highlights the potential for the application of this interpretation method in formation evaluation and enhanced oil recovery (EOR). PMID:25302335

  11. A double layer model for solar X-ray and microwave pulsations

    NASA Technical Reports Server (NTRS)

    Tapping, K. F.

    1986-01-01

    The wide range of wavelengths over which quasi-periodic pulsations have been observed suggests that the mechanism causing them acts upon the supply of high energy electrons driving the emission processes. A model is described which is based upon the radial shrinkage of a magnetic flux tube. The concentration of the current, along with the reduction in the number of available charge carriers, can rise to a condition where the current demand exceeds the capacity of the thermal electrons. Driven by the large inductance of the external current circuit, an instability takes place in the tube throat, resulting in the formation of a potential double layer, which then accelerates electrons and ions to MeV energies. The double layer can be unstable, collapsing and reforming repeatedly. The resulting pulsed particle beams give rise to pulsating emission which are observed at radio and X-ray wavelengths.

  12. Simulation of double layers in a model auroral circuit with nonlinear impedance

    NASA Technical Reports Server (NTRS)

    Smith, R. A.

    1986-01-01

    A reduced circuit description of the U-shaped potential structure of a discrete auroral arc, consisting of the flank transmission line plus parallel-electric-field region, is used to provide the boundary condition for one-dimensional simulations of the double-layer evolution. The model yields asymptotic scalings of the double-layer potential, as a function of an anomalous transport coefficient alpha and of the perpendicular length scale l(a) of the arc. The arc potential phi(DL) scales approximately linearly with alpha, and for alpha fixed phi (DL) about l(a) to the z power. Using parameters appropriate to the auroral zone acceleration region, potentials of phi (DPL) 10 kV scale to projected ionospheric dimensions of about 1 km, with power flows of the order of magnitude of substorm dissipation rates.

  13. Controlling spin–orbit interaction in a ferromagnetic Fe/Au double layer

    SciTech Connect

    Samarin, Sergey N.; Kostylev, Mikhail; Williams, James F.; Artamonov, Oleg M.; Baraban, Alexander P.; Guagliardo, Paul

    2015-01-26

    Using spin-polarized single- and two-electron spectroscopy, we probe exchange and spin–orbit interaction in a double layer of Fe and Au on W(110) and measure the spin asymmetry of the Bloch spectral density function of the sample. In a 5 ML iron film, the spin-orbit contribution to the measured asymmetry of the (e,2e) spectra was not detectable, whereas a deposition of about 1 ML of gold introduced a substantial spin-orbit component in the measured asymmetry. At the same time, this double layer still exhibits ferromagnetic properties: (i) the spectral density function asymmetry demonstrate imbalance of spin-up and spin-down electron densities in the valence band and (ii) the Stoner excitation asymmetry has almost the same value as in a pure Fe film.

  14. Nonlinear ion-acoustic double-layers in electronegative plasmas with electrons featuring Tsallis distribution

    NASA Astrophysics Data System (ADS)

    Ghebache, Siham; Tribeche, Mouloud

    2016-04-01

    Weakly nonlinear ion-acoustic (IA) double-layers (DLs), which accompany electronegative plasmas composed of positive ions, negative ions, and nonextensive electrons are investigated. A generalized Korteweg-de Vries equation with a cubic nonlinearity is derived using a reductive perturbation method. Different types of electronegative plasmas inspired from the experimental studies of Ichiki et al. (2001) are discussed. It is shown that the IA wave phase velocity, in different mixtures of negative and positive ions, decreases as the nonextensive parameter q increases, before levelling-off at a constant value for larger q. Moreover, a relative increase of Q involves an enhancement of the IA phase velocity. Existence domains of either solitary waves or double-layers are then presented and their parametric dependence is determined. Owing to the electron nonextensivity, our present plasma model can admit compressive as well as rarefactive IA-DLs.

  15. Detection of copper ions from aqueous solutions using layered double hydroxides thin films deposited by PLD

    NASA Astrophysics Data System (ADS)

    Vlad, A.; Birjega, R.; Matei, A.; Luculescu, C.; Nedelcea, A.; Dinescu, M.; Zavoianu, R.; Pavel, O. D.

    2015-10-01

    Layered double hydroxides (LDHs) thin films with Mg-Al were deposited using pulsed laser deposition (PLD) technique. We studied the ability of our films to detect copper ions in aqueous solutions. Copper is known to be a common pollutant in water, originating from urban and industrial waste. Clay minerals, including layered double hydroxides (LDHs), can reduce the toxicity of such wastes by adsorbing copper. We report on the uptake of copper ions from aqueous solution on LDH thin films obtained via PLD. The obtained thin films were characterized using X-ray Diffraction, Atomic Force Microscopy, and Scanning Electron Microscopy with Energy Dispersive X-ray analysis. The results in this study indicate that LDHs thin films obtained by PLD have potential as an efficient adsorbent for removing copper from aqueous solution.

  16. Multinuclear in situ magnetic resonance imaging of electrochemical double-layer capacitors.

    PubMed

    Ilott, Andrew J; Trease, Nicole M; Grey, Clare P; Jerschow, Alexej

    2014-08-01

    The last decade has seen an intensified interest in the development and use of electrochemical double-layer capacitors, fuelled by the availability of new electrode materials. The use of nanoporous carbons, in particular, with extremely high surface areas for ion adsorption has enabled the development of working devices with significantly increased capacitances that have become viable alternatives to lithium-ion batteries in certain applications. An understanding of the charge storage mechanism and the ion dynamics inside the nanopores is only just emerging, with the most compelling evidence coming from simulation. Here we present the first in situ magnetic resonance imaging experiments of electrochemical double-layer capacitors. These experiments overcome the limitations of other techniques and give spatially resolved chemical information about the electrolyte ions in real time for a working capacitor of standard geometry. The results provide insight into the predominant capacitive processes occurring at different states of charge and discharge.

  17. Topology optimization of double- and triple-layer grids using a hybrid methodology

    NASA Astrophysics Data System (ADS)

    Dehghani, M.; Mashayekhi, M.; Salajegheh, E.

    2016-08-01

    In this article, a hybrid methodology combining evolutionary structural optimization (ESO) and gravitational particle swarm (GPS) methods is proposed for topology optimization of double- and triple-layer grids. In the present methodology, which is called the ESO-GPS method, the size optimization of double- and triple-layer grids is first performed by ESO. Then, the outcomes of the ESO are used to improve the GPS through four modifications. Structural weight is minimized against constraints on the displacements of nodes, internal stresses and element slenderness ratio. The GPS is used to investigate the optimum topology of large-scale skeletal structures with discrete variables whose agents update their respective positions by the particle swarm optimization velocity and the acceleration of the gravitational search algorithm. The numerical results show that the proposed algorithm, the ESO-GPS, performs better than the GPS and the other methods presented in the literature.

  18. Removal of perchlorate in water by calcined MgAl-CO3 layered double hydroxides.

    PubMed

    Yang, Yiqiong; Gao, Naiyun; Deng, Yang; Yu, Guoping

    2013-04-01

    Perchlorate is widely known as an inorganic endocrine disruptor. In this study, MgAl-CO3 layered double hydroxides with different Mg/Al molar ratios were prepared using a coprecipitation method and followed by a calcination process at a temperature range of 300 to 700 degrees C. Results showed that the best synthesis conditions were a calcination temperature of 550 degrees C and Mg/Al molar ratio of 3. Further, the adsorbent and its adsorption product were characterized by x-ray diffraction, Fourier transform-infrared spectroscopy, and thermogravimetric-differential thermal analysis. The layered double hydroxides structures in the adsorbent were lost during calcination at 550 degrees C but were reconstructed subsequent to adsorption of perchlorate, indicating that the "memory effect" appeared to play an important role in perchlorate adsorption. The perchlorate adsorption pattern was best described by the pseudo-second-order kinetics model, while the Freundlich isotherms appropriately explained perchlorate adsorption data.

  19. Kinetic model for an auroral double layer that spans many gravitational scale heights

    SciTech Connect

    Robertson, Scott

    2014-12-15

    The electrostatic potential profile and the particle densities of a simplified auroral double layer are found using a relaxation method to solve Poisson's equation in one dimension. The electron and ion distribution functions for the ionosphere and magnetosphere are specified at the boundaries, and the particle densities are found from a collisionless kinetic model. The ion distribution function includes the gravitational potential energy; hence, the unperturbed ionospheric plasma has a density gradient. The plasma potential at the upper boundary is given a large negative value to accelerate electrons downward. The solutions for a wide range of dimensionless parameters show that the double layer forms just above a critical altitude that occurs approximately where the ionospheric density has fallen to the magnetospheric density. Below this altitude, the ionospheric ions are gravitationally confined and have the expected scale height for quasineutral plasma in gravity.

  20. Measurement of the magnetic induction vector in superconductors using a double-layer Hall sensor array

    NASA Astrophysics Data System (ADS)

    Abulafia, Y.; McElfresh, M.; Shaulov, A.; Yeshurun, Y.; Paltiel, Y.; Majer, D.; Shtrikman, H.; Zeldov, E.

    1998-06-01

    We describe an experimental technique for simultaneous measurement of both the normal (Bz) and the in-plane (Bx) components of the magnetic induction field near the surface of a superconducting sample. This technique utilizes a novel design of a double-layered Hall sensor array fabricated from a GaAs/AlGaAs heterostructure containing two parallel layers of a two-dimensional electron gas. The effectiveness of this technique is demonstrated in measurements of Bx and Bz and the current distribution at the surface of a thin YBa2Cu3O7 crystal.

  1. Nonlinear resonant magnetoelectric interactions and efficient frequency doubling in a ferromagnetic-ferroelectric layered structure

    NASA Astrophysics Data System (ADS)

    Fetisov, L. Y.; Fetisov, Y. K.; Sreenivasulu, G.; Srinivasan, G.

    2013-03-01

    Mechanical strain mediated non-linear magnetoelectric (NLME) coupling is studied in layered composites of ferromagnetic FeBSiC and piezoelectric lead zirconate titanate (PZT) bimorph. The NLME manifests as frequency doubling in the voltage response of the sample to an applied ac magnetic field. It is shown that NLME is strong (i) in the absence of DC magnetic bias, (ii) when the frequency of h is tuned to half the frequency for bending oscillations, and (iii) a PZT bimorph (instead of a single layer of PZT) is used. A model is discussed for the non-linear magnetoelectric coupling that is of interest for RF frequency doublers.

  2. Amniotic membrane extract-loaded double-layered wound dressing: evaluation of gel properties and wound healing.

    PubMed

    Choi, Yeung Keun; Din, Fakhar Ud; Kim, Dong Wuk; Kim, Yong-Il; Kim, Jong Oh; Ku, Sae Kwang; Ra, Jeong-Chan; Huh, Jae-Wook; Lee, Jangik I; Sohn, Dong Hwan; Yong, Chul Soon; Choi, Han-Gon

    2014-07-01

    The conservative single-layered wound dressing system is decomposed when mixed in polyvinyl alcohol (PVA) solution, which means it cannot be used with a temperature-sensitive drug. The goal of this investigation was to make an amniotic membrane extract (AME)-loaded double-layered wound dressing with an improved healing result compared to the conservative single-layered wound dressing systems. The double-layered wound dressing was developed with PVA/sodium alginate using a freeze-melting technique; one layer was PVA layer and the other was the drug-loaded sodium alginate layer. Its gel properties were assessed compared to single-layered wound dressings. Moreover, in vivo wound-healing effects and histopathology were calculated compared to commercial products. The double-layered wound dressing gave a similar gel fraction and Young's module as single-layered wound bandages developed with only PVA, and a similar inflammation ability and WVTR as single-layered wound dressings developed with PVA and sodium alginate. Our data indicate that these double-layered wound bandages were just as swellable, but more elastic and stronger than single-layered wound dressings comprised of the same polymers and quantities, possibly giving an acceptable level of moisture and accumulation of exudates in the wound zone. Compared to the commercial product, the double-layered wound dressing comprising 6.7% PVA, 0.5% sodium alginate and 0.01% AME significantly enhanced the wound-healing effect in the wound-healing test. Histological investigations showed that superior full-thickness wound-healing effects compared to the commercial product. Therefore, the double-layered wound dressing would be an outstanding wound-dressing system with improved wound healing and good gel property.

  3. High power, solvent-free electrochemical double layer capacitors based on pyrrolidinium dicyanamide ionic liquids

    NASA Astrophysics Data System (ADS)

    Wolff, Christian; Jeong, Sangsik; Paillard, Elie; Balducci, Andrea; Passerini, Stefano

    2015-10-01

    In this manuscript are reported the synthesis and physicochemical characterization of low viscosity pyrrolidinium dicyanamide (DCA-) ionic liquids (ILs). Due to their high ionic conductivity, these fluorine-free, molecular solvent-free ILs are excellent candidates to be employed as electrolytes in electrochemical double layer capacitors (EDLCs). Tests of lab-scale prototypes reported herein show that DCA--based EDLCs display high power at room temperature as well as high cycling stability.

  4. Synthesis of ACECLOFENAC/HYDROXYPROPYL-β-CYCLODEXTRIN Intercalated Layered Double Hydroxides and Controlled Release Properties

    NASA Astrophysics Data System (ADS)

    Li, Shifeng; Shen, Yanming; Liu, Dongbin; Fan, Lihui; Wu, Keke; Xiao, Min

    2013-06-01

    Aceclofenac (AC)/hydroxypropyl-β-cyclodextrin (HP-β-CD) complex intercalated layered double hydroxides (LDHs) have been synthesized by reconstruction method. X-ray diffraction, Fourier transform infrared and thermal gravimetric analyses indicated a successful intercalation of AC/HP-β-CD complex into the LDHs gallery. The AC release properties were also studied in different pH values buffer solution. The results indicate that the AC/HP-β-CD intercalated LDH has a potential application in drug delivery agent.

  5. Non-mean-field theory of anomalously large double layer capacitance

    NASA Astrophysics Data System (ADS)

    Loth, M. S.; Skinner, Brian; Shklovskii, B. I.

    2010-07-01

    Mean-field theories claim that the capacitance of the double layer formed at a metal/ionic conductor interface cannot be larger than that of the Helmholtz capacitor, whose width is equal to the radius of an ion. However, in some experiments the apparent width of the double layer capacitor is substantially smaller. We propose an alternate non-mean-field theory of the ionic double layer to explain such large capacitance values. Our theory allows for the binding of discrete ions to their image charges in the metal, which results in the formation of interface dipoles. We focus primarily on the case where only small cations are mobile and other ions form an oppositely charged background. In this case, at small temperature and zero applied voltage dipoles form a correlated liquid on both contacts. We show that at small voltages the capacitance of the double layer is determined by the transfer of dipoles from one electrode to the other and is therefore limited only by the weak dipole-dipole repulsion between bound ions so that the capacitance is very large. At large voltages the depletion of bound ions from one of the capacitor electrodes triggers a collapse of the capacitance to the much smaller mean-field value, as seen in experimental data. We test our analytical predictions with a Monte Carlo simulation and find good agreement. We further argue that our “one-component plasma” model should work well for strongly asymmetric ion liquids. We believe that this work also suggests an improved theory of pseudocapacitance.

  6. Ion-acoustic solitons, double layers and rogue waves in plasma having superthermal electrons

    NASA Astrophysics Data System (ADS)

    Singh Saini, Nareshpal

    2016-07-01

    Most of the space and astrophysical plasmas contain different type of charged particles with non-Maxwellian velocity distributions (e.g., nonthermal, superthermal, Tsallis ). These distributions are commonly found in the auroral region of the Earth's magnetosphere, planetary magnetosphere, solar and stellar coronas, solar wind, etc. The observations from various satellite missions have confirmed the presence of superthermal particles in space and astrophysical environments. Over the last many years, there have been a much interest in studying the different kind of properties of the electrostatic nonlinear excitations (solitons, double layers, rogue waves etc.) in a multi-component plasmas in the presence of superthermal particles. It has been analyzed that superthermal distributions are more appropriate than Maxwellian distribution for the modeling of space data. It is interesting to study the dynamics of various kinds of solitary waves, Double layers, Shocks etc. in varieties of plasma systems containing different kind of species obeying Lorentzian (kappa-type)/Tsallis distribution. In this talk, I have focused on the study of large amplitude IA solitary structures (bipolar solitary structures, double layers etc.), modulational instability and rogue waves in multicomponent plasmas. The Sagdeev potential method has been employed to setup an energy balance equation, from which we have studied the characteristics of large amplitude solitary waves under the influence of superthermality of charged particles and other plasma parameters. The critical Mach number has been determined, above which solitary structures are observed and its variation with superthermality of electrons and other parameters has also been discussed. Double layers have also been discussed. Multiple scale reductive perturbation method has been employed to derive NLS equation. From the different kind of solutions of this equation, amplitude modulation of envelope solitons and rogue waves have been

  7. Ionic Liquids as Electrolytes for Electrochemical Double-Layer Capacitors: Structures that Optimize Specific Energy.

    PubMed

    Mousavi, Maral P S; Wilson, Benjamin E; Kashefolgheta, Sadra; Anderson, Evan L; He, Siyao; Bühlmann, Philippe; Stein, Andreas

    2016-02-10

    Key parameters that influence the specific energy of electrochemical double-layer capacitors (EDLCs) are the double-layer capacitance and the operating potential of the cell. The operating potential of the cell is generally limited by the electrochemical window of the electrolyte solution, that is, the range of applied voltages within which the electrolyte or solvent is not reduced or oxidized. Ionic liquids are of interest as electrolytes for EDLCs because they offer relatively wide potential windows. Here, we provide a systematic study of the influence of the physical properties of ionic liquid electrolytes on the electrochemical stability and electrochemical performance (double-layer capacitance, specific energy) of EDLCs that employ a mesoporous carbon model electrode with uniform, highly interconnected mesopores (3DOm carbon). Several ionic liquids with structurally diverse anions (tetrafluoroborate, trifluoromethanesulfonate, trifluoromethanesulfonimide) and cations (imidazolium, ammonium, pyridinium, piperidinium, and pyrrolidinium) were investigated. We show that the cation size has a significant effect on the electrolyte viscosity and conductivity, as well as the capacitance of EDLCs. Imidazolium- and pyridinium-based ionic liquids provide the highest cell capacitance, and ammonium-based ionic liquids offer potential windows much larger than imidazolium and pyridinium ionic liquids. Increasing the chain length of the alkyl substituents in 1-alkyl-3-methylimidazolium trifluoromethanesulfonimide does not widen the potential window of the ionic liquid. We identified the ionic liquids that maximize the specific energies of EDLCs through the combined effects of their potential windows and the double-layer capacitance. The highest specific energies are obtained with ionic liquid electrolytes that possess moderate electrochemical stability, small ionic volumes, low viscosity, and hence high conductivity, the best performing ionic liquid tested being 1-ethyl-3

  8. Observation of warm, higher energy electrons transiting a double layer in a helicon plasma

    NASA Astrophysics Data System (ADS)

    Sung, Yung-Ta; Li, Yan; Scharer, John

    2015-11-01

    Experimental observations in MadiHeX indicate that fast electrons with substantial density fractions can be created at low helicon operating pressure. Two-temperature electron distributions including a fast (>80 eV) tail are observed in an inductive RF helicon argon plasma double layer at 0.17 mTorr Ar pressure. The fast, untrapped electrons measured downstream of the double layer have a higher temperature of 13 eV than the trapped, upstream electrons with a temperature of 4 eV. The reduction of plasma potential and density observed in the double layer region would require an upstream temperature ten times the measured 4 eV if occurring via Boltzmann ambipolar expansion. Upstream fluctuations of +/- 30% are also observed in the emissive probe measured plasma potential. Sideband frequencies have been observed at +/- 2 kHz of the driven RF frequency of 13.56 MHz, implying a beam instability effect dominantly upstream of the double layer. This can affect ion acceleration and electron temperature distribution in the region. The mechanism behind this has been explored via several plasma diagnostics tools. An RF-compensated Langmuir probe has been used to measure the electron temperatures and densities, which are cross-checked with ADAS, OES and millimeter wave IF. The EEDF in the plasma has also been profiled to understand the acceleration mechanism. A four-grid RPA and an emissive probe have been used to measure the IEDF and plasma potential. The measured IEDF has also been checked with LIF techniques.

  9. Double-Layered PTFE-Covered Nitinol Stents: Experience in 32 Patients with Malignant Esophageal Strictures

    SciTech Connect

    Park, Jung Gu; Jung, Gyoo-Sik Oh, Kyung Seung; Park, Seon-Ja

    2010-08-15

    We evaluated the effectiveness of a double-layered polytetrafluoroethylene (PTFE)-covered nitinol stent in the palliative treatment of malignant esophageal strictures. A double-layered PTFE-covered nitinol stent was designed to reduce the propensity to migration of conventional covered stent. The stent consists of an inner PTFE-covered stent and an outer uncovered nitinol stent tube. With fluoroscopic guidance, the stent was placed in 32 consecutive patients with malignant esophageal strictures. During the follow-up period, the technical and clinical success rates, complications, and cumulative patient survival and stent patency were evaluated. Stent placement was technically successful in all patients, and no procedural complications occurred. After stent placement, the symptoms of 30 patients (94%) showed improvement. During the mean follow-up of 103 days (range, 9-348 days), 11 (34%) of 32 patients developed recurrent symptoms due to tumor overgrowth in five patients (16%), tumor ingrowth owing to detachment of the covering material (PTFE) apart from the stent wire in 3 (9%), mucosal hyperplasia in 2 (6%), and stent migration in 1 (3%). Ten of these 11 patients were treated by means of placing a second covered stent. Thirty patients died, 29 as a result of disease progression and 1 from aspiration pneumonia. The median survival period was 92 days. The median period of primary stent patency was 190 days. The double-layered PTFE-covered nitinol stent seems to be effective for the palliative treatment of malignant esophageal strictures. We believe that the double-layer configuration of this stent can contribute to decreasing the stent's migration rate.

  10. Charge density dependent two-channel conduction in organic electric double layer transistors (EDLTs).

    PubMed

    Xie, Wei; Liu, Feilong; Shi, Sha; Ruden, P Paul; Frisbie, C Daniel

    2014-04-23

    A transport model based on hole-density-dependent trapping is proposed to explain the two unusual conductivity peaks at surface hole densities above 10(13) cm(-2) in rubrene electric double layer transistors (EDLTs). Hole transport in rubrene is described to occur via multiple percolation pathways, where conduction is dominated by transport in the free-site channel at low hole density, and in the trap-site channel at larger hole density. PMID:24496822

  11. Substituted Quaternary Ammonium Salts Improve Low-Temperature Performance of Double-Layer Capacitors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik J.; Smart, Marshall C.; West, William C.

    2011-01-01

    Double-layer capacitors are unique energy storage devices, capable of supporting large current pulses as well as a very high number of charging and discharging cycles. The performance of doublelayer capacitors is highly dependent on the nature of the electrolyte system used. Many applications, including for electric and fuel cell vehicles, back-up diesel generators, wind generator pitch control back-up power systems, environmental and structural distributed sensors, and spacecraft avionics, can potentially benefit from the use of double-layer capacitors with lower equivalent series resistances (ESRs) over wider temperature limits. Higher ESRs result in decreased power output, which is a particular problem at lower temperatures. Commercially available cells are typically rated for operation down to only 40 C. Previous briefs [for example, Low Temperature Supercapacitors (NPO-44386), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), p. 32, and Supercapacitor Electrolyte Solvents With Liquid Range Below 80 C (NPO-44855), NASA Tech Briefs, Vol. 34, No. 1 (January 2010), p. 44] discussed the use of electrolytes that employed low-melting-point co-solvents to depress the freezing point of traditional acetonitrile-based electrolytes. Using these modified electrolyte formulations can extend the low-temperature operational limit of double-layer capacitors beyond that of commercially available cells. This previous work has shown that although the measured capacitance is relatively insensitive to temperature, the ESR can rise rapidly at low temperatures, due to decreased electrolyte conductance within the pores of the high surface- area carbon electrodes. Most of these advanced electrolyte systems featured tetraethylammonium tetrafluoroborate (TEATFB) as the salt. More recent work at JPL indicates the use of the asymmetric quaternary ammonium salt triethylmethylammonium tetrafluoroborate (TEMATFB) or spiro-(l,l')-bipyrrolidium tetrafluoroborate (SBPBF4) in a 1:1 by volume solvent

  12. Synthesis, characterization, and efficacy of antituberculosis isoniazid zinc aluminum-layered double hydroxide based nanocomposites.

    PubMed

    Saifullah, Bullo; El Zowalaty, Mohamed Ezzat; Arulselvan, Palanisamy; Fakurazi, Sharida; Webster, Thomas J; Geilich, Benjamin Mahler; Hussein, Mohd Zobir

    2016-01-01

    The chemotherapy for tuberculosis (TB) is complicated by its long-term treatment, its frequent drug dosing, and the adverse effects of anti-TB drugs. In this study, we have developed two nanocomposites (A and B) by intercalating the anti-TB drug isoniazid (INH) into Zn/Al-layered double hydroxides. The average size of the nanocomposites was found to bê164 nm. The efficacy of the Zn/Al-layered double hydroxides intercalated INH against Mycobacterium tuberculosis was increased by approximately three times more than free INH. The nanocomposites were also found to be active against Gram-positive and -negative bacteria. Compared to the free INH, the nanodelivery formulation was determined to be three times more biocompatible with human normal lung fibroblast MRC-5 cells and 3T3 fibroblast cells at a very high concentration of 50 µg/mL for up to 72 hours. The in vitro release of INH from the Zn/Al-layered double hydroxides was found to be sustained in human body-simulated buffer solutions of pH 4.8 and 7.4. This research is a step forward in making the TB chemotherapy patient friendly. PMID:27486322

  13. The capacitance of ionic liquid electric double layer near nanostructured electrodes

    NASA Astrophysics Data System (ADS)

    Park, Yun Sung; Ahn, Myung Mo; Kang, In Seok

    2015-11-01

    The electric double layer capacitors (EDLC) with nanostructured electrodes have attracted much attention of researchers due to their high power density and long life time. Recently, the ionic liquids are used as an electrolyte of EDLC owing to their electrochemical stability. When ionic liquids are used as an electrolyte, the interrelations between the electric double layer of ionic liquids and the nanostructured electrode must be studied. In this study, the EDLC systems with nanostructured electrodes and ionic liquids are simulated by solving the modified Poisson-Boltzmann equation proposed by Bazant, Storey, and Kornyshev with COMSOL Multiphysics. Several electrode geometries including exohedral, endohedral and arrayed shapes with different length scales are simulated. The potential and charge distributions in the normal direction to the electrode surface are analyzed. The capacitance per unit area is obtained and compared to that of flat electrode. The structure determines the space for counter-ion packing and co-ion gathering, thus has crucial effects on electric double layer capacitance. The critical increase of capacitance with nanoscale confined space is observed with low electrode potential. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (Grant Number: 2013R1A1A2011956).

  14. Repair of Inaccessible Ventral Dural Defect in Thoracic Spine: Double Layered Duraplasty

    PubMed Central

    Lee, Dong-Hyun; Park, Jeong-Ill; Park, Ki-Su; Cho, Dae-Chul; Sung, Joo-Kyung

    2016-01-01

    We propose a double layered (intradural and epidural patch) duraplasty that utilizes Lyoplant and Duraseal. We examined a 47-year-old woman after decompression for thoracic ossification of posterior longitudinal ligament was performed in another hospital. On postoperative day 7, she complained of weakness in both legs. Postoperative magnetic resonance imaging (MRI) showed cerebrospinal fluid (CSF) collection with cord compression. In the operative field, we found 2 large dural defects on the ventral dura mater. We performed a conventional fat graft with fibrin glue. However, the patient exhibited neurologic deterioration, and a postoperative MRI again showed CSF collection. We performed dorsal midline durotomy and inserted a intradural and epidural Lyoplant patch. She immediately experienced diminishing back pain postoperatively. Her visual analog scale and motor power improved markedly. Postoperative MRIs performed at 2 and 16 months showed no spinal cord compression or CSF leakage to the epidural space. We describe a new technique for double layered duraplasty. Although we do not recommend this technique for all dural repairs, double-layered duraplasty may be useful for repairing large inaccessible dural tears in cases of persistent CSF leakage refractory to conventional management. PMID:27437022

  15. Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

    NASA Technical Reports Server (NTRS)

    Smith, Robert A.

    1987-01-01

    The evolution and long-time stability of a double layer (DL) in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double layer potential structure. A simple model is presented in which this current redistribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double layer potential. The flank charging may be represented as that of a nonlinear transmission line. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a one-dimensional simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.

  16. Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

    NASA Technical Reports Server (NTRS)

    Smith, Robert A.

    1987-01-01

    The evolution and long-time stability of a double layer in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double-layer potential structure. A simple model is presented in which this current re-distribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double-layer potential. The flank charging may be represented as that of a nonlinear transmission. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a 1-d simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.

  17. Low Temperature Double-layer Capacitors with Improved Energy Density: An Overview of Recent Development Efforts

    NASA Technical Reports Server (NTRS)

    Brandon, Erik J.; West, William C.; Smart, Marshall C.; Yushin, Gleb; Korenblit, Yair; Kajdos, Adam; Kvit, Alexander; Jagiello, Jacek

    2012-01-01

    Electrochemical double-layer capacitors are finding increased use in a wide range of energy storage applications, particularly where high pulse power capabilities are required. Double-layer capacitors store charge at a liquid/solid interface, making them ideal for low temperature power applications, due to the facile kinetic processes associated with the rearrangement of the electrochemical double-layer at these temperatures. Potential low temperature applications include hybrid and electric vehicles, operations in polar regions, high altitude aircraft and aerospace avionics, and distributed environmental and structural health monitoring. State-of-the-art capacitors can typically operate to -40 C, with a subsequent degradation in power performance below room temperature. However, recent efforts focused on advanced electrolyte and electrode systems can enable operation to temperatures as low as -70 C, with capacities similar to room temperature values accompanied by reasonably low equivalent series resistances. This presentation will provide an overview of recent development efforts to extend and improve the wide temperature performance of these devices.

  18. Magnetohydrodynamic effects on a charged colloidal sphere with arbitrary double-layer thickness.

    PubMed

    Hsieh, Tzu H; Keh, Huan J

    2010-10-01

    An analytical study is presented for the magnetohydrodynamic (MHD) effects on a translating and rotating colloidal sphere in an arbitrary electrolyte solution prescribed with a general flow field and a uniform magnetic field at a steady state. The electric double layer surrounding the charged particle may have an arbitrary thickness relative to the particle radius. Through the use of a simple perturbation method, the Stokes equations modified with an electric force term, including the Lorentz force contribution, are dealt by using a generalized reciprocal theorem. Using the equilibrium double-layer potential distribution from solving the linearized Poisson-Boltzmann equation, we obtain closed-form formulas for the translational and angular velocities of the spherical particle induced by the MHD effects to the leading order. It is found that the MHD effects on the particle movement associated with the translation and rotation of the particle and the ambient fluid are monotonically increasing functions of κa, where κ is the Debye screening parameter and a is the particle radius. Any pure rotational Stokes flow of the electrolyte solution in the presence of the magnetic field exerts no MHD effect on the particle directly in the case of a very thick double layer (κa→0). The MHD effect caused by the pure straining flow of the electrolyte solution can drive the particle to rotate, but it makes no contribution to the translation of the particle.

  19. Swelling pressure of a divalent-rich bentonite: Diffuse double-layer theory revisited

    NASA Astrophysics Data System (ADS)

    Schanz, Tom; Tripathy, Snehasis

    2009-05-01

    Physicochemical forces are responsible for the swelling pressure development in saturated bentonites. In this paper, the swelling pressures of several compacted bentonite specimens for a range of dry density of 1.10-1.73 Mg/m3 were measured experimentally. The clay used was a divalent-rich Ca-Mg-bentonite with 12% exchangeable Na+ ions. The theoretical swelling pressure-dry density relationship for the bentonite was determined from the Gouy-Chapman diffuse double-layer theory. A comparison of experimental and theoretical results showed that the experimental swelling pressures are either smaller or greater than their theoretical counterparts within different dry density ranges. It is shown that for dry density of the clay less than about 1.55 Mg/m3, a possible dissociation of ions from the surface of the clay platelets contributed to the diffuse double-layer repulsion. At higher dry densities, the adsorptive forces due to surface and ion hydration dominated the swelling pressures of the clay. A comparison of the modified diffuse double-layer theory equations proposed in the literature to determine the swelling pressures of compacted bentonites and the experimental results for the clay in this study showed that the agreement between the calculated and experimental swelling pressure results is very good for dry densities less than 1.55 Mg/m3, whereas at higher dry densities the use of the equations was found to be limited.

  20. Ion Acoustic Solitons and Double Layers in the Solar Wind Having Kappa Distributed Electrons

    NASA Astrophysics Data System (ADS)

    Lakhina, G. S.; Singh, S. V.

    2015-12-01

    It is shown that two types of, slow and fast, ion-acoustic solitary waves can occur in a solar wind plasma consisting of fluid hot protons, hot alpha particles streaming with respect to protons, and suprathermal electrons having k- distribution. The fast ion-acoustic mode is similar to the ion-acoustic mode of proton-electron plasma, and can support only positive potential solitons. The slow ion-acoustic mode is a new mode that occurs due to the presence of alpha particles. This mode can support both positive and negative solitons and double layers. The slow ion-acoustic mode can exist even when the relative streaming, U0, between alphas and protons is zero, provided alpha temperature, Ti, is not exactly equal to 4 times the proton temperature, Tp. An increase of the k- index leads to an increase in the critical Mach number, maximum Mach number and the maximum amplitude of both slow and fast ion-acoustic solitons. The model can explain the amplitudes and widths, but not shapes, of the weak double layers (WDLs) observed in the solar wind at 1 AU by Wind spacecraft in terms of slow ion-acoustic double layers. It is proposed that both slow and fast ion-acoustic solitons may be responsible for the ion- acoustic like wave activity in the solar wind.

  1. Synthesis, characterization, and efficacy of antituberculosis isoniazid zinc aluminum-layered double hydroxide based nanocomposites

    PubMed Central

    Saifullah, Bullo; El Zowalaty, Mohamed Ezzat; Arulselvan, Palanisamy; Fakurazi, Sharida; Webster, Thomas J; Geilich, Benjamin Mahler; Hussein, Mohd Zobir

    2016-01-01

    The chemotherapy for tuberculosis (TB) is complicated by its long-term treatment, its frequent drug dosing, and the adverse effects of anti-TB drugs. In this study, we have developed two nanocomposites (A and B) by intercalating the anti-TB drug isoniazid (INH) into Zn/Al-layered double hydroxides. The average size of the nanocomposites was found to bê164 nm. The efficacy of the Zn/Al-layered double hydroxides intercalated INH against Mycobacterium tuberculosis was increased by approximately three times more than free INH. The nanocomposites were also found to be active against Gram-positive and -negative bacteria. Compared to the free INH, the nanodelivery formulation was determined to be three times more biocompatible with human normal lung fibroblast MRC-5 cells and 3T3 fibroblast cells at a very high concentration of 50 µg/mL for up to 72 hours. The in vitro release of INH from the Zn/Al-layered double hydroxides was found to be sustained in human body-simulated buffer solutions of pH 4.8 and 7.4. This research is a step forward in making the TB chemotherapy patient friendly. PMID:27486322

  2. Predictive double-layer modeling of metal sorption in mine-drainage systems

    SciTech Connect

    Smith, K.S.; Plumlee, G.S.; Ranville, J.F.; Macalady, D.L.

    1996-10-01

    Previous comparison of predictive double-layer modeling and empirically derived metal-partitioning data has validated the use of the double-layer model to predict metal sorption reactions in iron-rich mine-drainage systems. The double-layer model subsequently has been used to model data collected from several mine-drainage sites in Colorado with diverse geochemistry and geology. This work demonstrates that metal partitioning between dissolved and sediment phases can be predictively modeled simply by knowing the water chemistry and the amount of suspended iron-rich particulates present in the system. Sorption on such iron-rich suspended sediments appears to control metal and arsenic partitioning between dissolved and sediment phases, with sorption on bed sediment playing a limited role. At pH > 5, Pb and As are largely sorbed by iron-rich suspended sediments and Cu is partially sorbed; Zn, Cd, and Ni usually remain dissolved throughout the pH range of 3 to 8.

  3. Repair of Inaccessible Ventral Dural Defect in Thoracic Spine: Double Layered Duraplasty.

    PubMed

    Lee, Dong-Hyun; Kim, Kyoung-Tae; Park, Jeong-Ill; Park, Ki-Su; Cho, Dae-Chul; Sung, Joo-Kyung

    2016-06-01

    We propose a double layered (intradural and epidural patch) duraplasty that utilizes Lyoplant and Duraseal. We examined a 47-year-old woman after decompression for thoracic ossification of posterior longitudinal ligament was performed in another hospital. On postoperative day 7, she complained of weakness in both legs. Postoperative magnetic resonance imaging (MRI) showed cerebrospinal fluid (CSF) collection with cord compression. In the operative field, we found 2 large dural defects on the ventral dura mater. We performed a conventional fat graft with fibrin glue. However, the patient exhibited neurologic deterioration, and a postoperative MRI again showed CSF collection. We performed dorsal midline durotomy and inserted a intradural and epidural Lyoplant patch. She immediately experienced diminishing back pain postoperatively. Her visual analog scale and motor power improved markedly. Postoperative MRIs performed at 2 and 16 months showed no spinal cord compression or CSF leakage to the epidural space. We describe a new technique for double layered duraplasty. Although we do not recommend this technique for all dural repairs, double-layered duraplasty may be useful for repairing large inaccessible dural tears in cases of persistent CSF leakage refractory to conventional management. PMID:27437022

  4. Dichotomy of the electronic structure and superconductivity between single-layer and double-layer FeSe/SrTiO3 films.

    PubMed

    Liu, Xu; Liu, Defa; Zhang, Wenhao; He, Junfeng; Zhao, Lin; He, Shaolong; Mou, Daixiang; Li, Fangsen; Tang, Chenjia; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2014-09-23

    The latest discovery of possible high-temperature superconductivity in the single-layer FeSe film grown on a SrTiO3 substrate has generated much attention. Initial work found that, while the single-layer FeSe/SrTiO3 film exhibits a clear signature of superconductivity, the double-layer film shows an insulating behaviour. Such a marked layer-dependent difference is surprising and the underlying origin remains unclear. Here we report a comparative angle-resolved photoemission study between the single-layer and double-layer FeSe/SrTiO3 films annealed in vacuum. We find that, different from the single-layer FeSe/SrTiO3 film, the double-layer FeSe/SrTiO3 film is hard to get doped and remains in the semiconducting/insulating state under an extensive annealing condition. Such a behaviour originates from the much reduced doping efficiency in the bottom FeSe layer of the double-layer FeSe/SrTiO3 film from the FeSe-SrTiO3 interface. These observations provide key insights in understanding the doping mechanism and the origin of superconductivity in the FeSe/SrTiO3 films.

  5. Highly transparent low resistance Ga doped ZnO/Cu grid double layers prepared at room temperature

    NASA Astrophysics Data System (ADS)

    Jang, Cholho; Zhizhen, Ye; Jianguo, Lü

    2015-12-01

    Ga doped ZnO (GZO)/Cu grid double layer structures were prepared at room temperature (RT). We have studied the electrical and optical characteristics of the GZO/Cu grid double layer as a function of the Cu grid spacing distance. The optical transmittance and sheet resistance of the GZO/Cu grid double layer are higher than that of the GZO/Cu film double layer regardless of the Cu grid spacing distance and increase as the Cu grid spacing distance increases. The calculated values for the transmittance and sheet resistance of the GZO/Cu grid double layer well follow the trend of the experimentally observed transmittance and sheet resistance ones. For the GZO/Cu grid double layer with a Cu grid spacing distance of 1 mm, the highest figure of merit (ΦTC = 6.19 × 10-3 Ω-1) was obtained. In this case, the transmittance, resistivity and filling factor (FF) of the GZO/Cu grid double layer are 83.74%, 1.10 × 10-4 Ω·cm and 0.173, respectively. Project supported by the Key Project of the National Natural Science Foundation of China (No. 91333203), the Program for Innovative Research Team in University of Ministry of Education of China (No. IRT13037), the National Natural Science Foundation of China (No. 51172204), and the Zhejiang Provincial Department of Science and Technology of China (No. 2010R50020).

  6. Boosted output performance of triboelectric nanogenerator via electric double layer effect

    PubMed Central

    Chun, Jinsung; Ye, Byeong Uk; Lee, Jae Won; Choi, Dukhyun; Kang, Chong-Yun; Kim, Sang-Woo; Wang, Zhong Lin; Baik, Jeong Min

    2016-01-01

    For existing triboelectric nanogenerators (TENGs), it is important to explore unique methods to further enhance the output power under realistic environments to speed up their commercialization. We report here a practical TENG composed of three layers, in which the key layer, an electric double layer, is inserted between a top layer, made of Al/polydimethylsiloxane, and a bottom layer, made of Al. The efficient charge separation in the middle layer, based on Volta's electrophorus, results from sequential contact configuration of the TENG and direct electrical connection of the middle layer to the earth. A sustainable and enhanced output performance of 1.22 mA and 46.8 mW cm−2 under low frequency of 3 Hz is produced, giving over 16-fold enhancement in output power and corresponding to energy conversion efficiency of 22.4%. Finally, a portable power-supplying system, which provides enough d.c. power for charging a smart watch or phone battery, is also successfully developed. PMID:27703165

  7. Electronic absorption band broadening and surface roughening of phthalocyanine double layers by saturated solvent vapor treatment

    SciTech Connect

    Kim, Jinhyun; Yim, Sanggyu

    2012-10-15

    Variations in the electronic absorption (EA) and surface morphology of three types of phthalocyanine (Pc) thin film systems, i.e. copper phthalocyanine (CuPc) single layer, zinc phthalocyanine (ZnPc) single layer, and ZnPc on CuPc (CuPc/ZnPc) double layer film, treated with saturated acetone vapor were investigated. For the treated CuPc single layer film, the surface roughness slightly increased and bundles of nanorods were formed, while the EA varied little. In contrast, for the ZnPc single layer film, the relatively high solubility of ZnPc led to a considerable shift in the absorption bands as well as a large increase in the surface roughness and formation of long and wide nano-beams, indicating a part of the ZnPc molecules dissolved in acetone, which altered their molecular stacking. For the CuPc/ZnPc film, the saturated acetone vapor treatment resulted in morphological changes in mainly the upper ZnPc layer due to the significantly low solubility of the underlying CuPc layer. The treatment also broadened the EA band, which involved a combination of unchanged CuPc and changed ZnPc absorption.

  8. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-09-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  9. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-07-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  10. Boosted output performance of triboelectric nanogenerator via electric double layer effect

    NASA Astrophysics Data System (ADS)

    Chun, Jinsung; Ye, Byeong Uk; Lee, Jae Won; Choi, Dukhyun; Kang, Chong-Yun; Kim, Sang-Woo; Wang, Zhong Lin; Baik, Jeong Min

    2016-10-01

    For existing triboelectric nanogenerators (TENGs), it is important to explore unique methods to further enhance the output power under realistic environments to speed up their commercialization. We report here a practical TENG composed of three layers, in which the key layer, an electric double layer, is inserted between a top layer, made of Al/polydimethylsiloxane, and a bottom layer, made of Al. The efficient charge separation in the middle layer, based on Volta's electrophorus, results from sequential contact configuration of the TENG and direct electrical connection of the middle layer to the earth. A sustainable and enhanced output performance of 1.22 mA and 46.8 mW cm-2 under low frequency of 3 Hz is produced, giving over 16-fold enhancement in output power and corresponding to energy conversion efficiency of 22.4%. Finally, a portable power-supplying system, which provides enough d.c. power for charging a smart watch or phone battery, is also successfully developed.

  11. The role of buffer layers and double windows layers in a solar cell CZTS performances

    NASA Astrophysics Data System (ADS)

    Mebarkia, C.; Dib, D.; Zerfaoui, H.; Belghit, R.

    2016-07-01

    In the overall context of the diversification of the use of natural resources, the use of renewable energy including solar photovoltaic has become increasingly indispensable. As such, the development of a new generation of photovoltaic cells based on CuZnSnS4 (CZTS) looks promising. Cu2ZnSnS4 (CZTS) is a new film absorber, with good physical properties (band gap energy 1.4-1.6 eV with a large absorption coefficient over 104 cm-1). Indeed, the performance of these cells exceeded 30% in recent years. In the present paper, our work based on modeling and numerical simulation, we used SCAPS to study the performance of solar cells based on Cu2ZnSnS4 (CZTS) and thus evaluate the electrical efficiency η for typical structures of n-ZnO:Al / i-ZnO / n-CdS / p-CZTS and n-ITO / n-ZnO:Al / n-CdS /p-CZTS. Furthermore, the influence of the change of CdS by ZnSeand In2S3buffer layer was treated in this paper.

  12. Enhancement of proton acceleration field in laser double-layer target interaction

    NASA Astrophysics Data System (ADS)

    Gu, Y. J.; Kong, Q.; Kawata, S.; Izumiyama, T.; Li, X. F.; Yu, Q.; Wang, P. X.; Ma, Y. Y.

    2013-07-01

    A mechanism is proposed to enhance a proton acceleration field in laser plasma interaction. A double-layer plasma with different densities is illuminated by an intense short pulse. Electrons are accelerated to a high energy in the first layer by the wakefield. The electrons accelerated by the laser wakefield induce the enhanced target normal sheath (TNSA) and breakout afterburner (BOA) accelerations through the second layer. The maximum proton energy reaches about 1 GeV, and the total charge with an energy higher than 100 MeV is about several tens of μC/μm. Both the acceleration gradient and laser energy transfer efficiency are higher than those in single-target-based TNSA or BOA. The model has been verified by 2.5D-PIC simulations.

  13. Enhancement of proton acceleration field in laser double-layer target interaction

    SciTech Connect

    Gu, Y. J.; Kong, Q.; Li, X. F.; Yu, Q.; Wang, P. X.; Kawata, S.; Izumiyama, T.; Ma, Y. Y.

    2013-07-15

    A mechanism is proposed to enhance a proton acceleration field in laser plasma interaction. A double-layer plasma with different densities is illuminated by an intense short pulse. Electrons are accelerated to a high energy in the first layer by the wakefield. The electrons accelerated by the laser wakefield induce the enhanced target normal sheath (TNSA) and breakout afterburner (BOA) accelerations through the second layer. The maximum proton energy reaches about 1 GeV, and the total charge with an energy higher than 100 MeV is about several tens of μC/μm. Both the acceleration gradient and laser energy transfer efficiency are higher than those in single-target-based TNSA or BOA. The model has been verified by 2.5D-PIC simulations.

  14. Double-Layer Magnetic Nanoparticle-Embedded Silica Particles for Efficient Bio-Separation

    PubMed Central

    Kang, Homan; Cho, Hong-Jun; Park, Sung-Jun; Yang, Jin-Kyoung; Kim, Sehoon; Kim, Hyung-Mo; Jun, Bong-Hyun; Lee, Yoon-Sik

    2015-01-01

    Superparamagnetic Fe3O4 nanoparticles (NPs) based nanomaterials have been exploited in various biotechnology fields including biomolecule separation. However, slow accumulation of Fe3O4 NPs by magnets may limit broad applications of Fe3O4 NP-based nanomaterials. In this study, we report fabrication of Fe3O4 NPs double-layered silica nanoparticles (DL MNPs) with a silica core and highly packed Fe3O4 NPs layers. The DL MNPs had a superparamagnetic property and efficient accumulation kinetics under an external magnetic field. Moreover, the magnetic field-exposed DL MNPs show quantitative accumulation, whereas Fe3O4 NPs single-layered silica nanoparticles (SL MNPs) and silica-coated Fe3O4 NPs produced a saturated plateau under full recovery of the NPs. DL MNPs are promising nanomaterials with great potential to separate and analyze biomolecules. PMID:26599084

  15. Double-Layer Magnetic Nanoparticle-Embedded Silica Particles for Efficient Bio-Separation.

    PubMed

    Kyeong, San; Jeong, Cheolhwan; Kang, Homan; Cho, Hong-Jun; Park, Sung-Jun; Yang, Jin-Kyoung; Kim, Sehoon; Kim, Hyung-Mo; Jun, Bong-Hyun; Lee, Yoon-Sik

    2015-01-01

    Superparamagnetic Fe3O4 nanoparticles (NPs) based nanomaterials have been exploited in various biotechnology fields including biomolecule separation. However, slow accumulation of Fe3O4 NPs by magnets may limit broad applications of Fe3O4 NP-based nanomaterials. In this study, we report fabrication of Fe3O4 NPs double-layered silica nanoparticles (DL MNPs) with a silica core and highly packed Fe3O4 NPs layers. The DL MNPs had a superparamagnetic property and efficient accumulation kinetics under an external magnetic field. Moreover, the magnetic field-exposed DL MNPs show quantitative accumulation, whereas Fe3O4 NPs single-layered silica nanoparticles (SL MNPs) and silica-coated Fe3O4 NPs produced a saturated plateau under full recovery of the NPs. DL MNPs are promising nanomaterials with great potential to separate and analyze biomolecules. PMID:26599084

  16. Electromagnetic properties of a double-layer graphene system with electron-hole pairing

    NASA Astrophysics Data System (ADS)

    Germash, K. V.; Fil, D. V.

    2016-05-01

    We study electromagnetic properties of a double-layer graphene system in which electrons from one layer are coupled with holes from the other layer. The gauge invariant linear response functions are obtained. The frequency dependences of the transmission, reflection, and absorption coefficients are computed. We predict a peak in the reflection and absorption at the frequency equal to the gap in the quasiparticle spectrum. It is shown that the electron-hole pairing results in an essential modification of the spectrum of surface TM plasmons. We find that the optical TM mode splits into a low frequency undamped branch and a high frequency damped branch. At zero temperature the lower branch disappears. It is established that the pairing does not influence the acoustic TM mode. It is also shown that the pairing opens the frequency window in the subgap range for the surface TE wave.

  17. Double-layer anisotropic light diffusion films fabricated using a two-step UV curing technique

    NASA Astrophysics Data System (ADS)

    Kusama, Kentaro; Ishinabe, Takahiro; Katagiri, Baku; Orui, Tomoo; Shoshi, Satoru; Fujikake, Hideo

    2016-04-01

    We developed a novel light diffusion film with a double diffusion layer structure for high reflectivity and a wide diffusion angle range. We demonstrated that the internal layer structure of the light diffusion film is controlled by the diffusion angle of the ultraviolet (UV) light used for photopolymerization. We successfully fabricated two different diffusion layers in a single polymer film using a two-step UV curing process and achieved a wide diffusion angle range and high reflectivity normal to the film surface. Our light diffusion film can control the distribution of diffused light, and should contribute to the development of future low-power reflective displays with high reflectivity similar to the white paper.

  18. A double-layer based model of ion confinement in electron cyclotron resonance ion source

    SciTech Connect

    Mascali, D. Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G.; Torrisi, G.; Sorbello, G.

    2014-02-15

    The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.

  19. Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

    DOEpatents

    Tansu, Nelson; Zhao, Hongping; Zhang, Jing; Liu, Guangyu

    2014-04-01

    A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

  20. Synthesis and characterization of sulfate and dodecylbenzenesulfonate intercalated zinc-iron layered double hydroxides by one-step coprecipitation route

    SciTech Connect

    Zhang Hui Wen Xing; Wang Yingxia

    2007-05-15

    Inorganic sulfate- and organic dodecylbenzenesulfonate (DBS)-intercalated zinc-iron layered double hydroxides (LDHs) materials were prepared by one-step coprecipitation method from a mixed salt solutions containing Zn(II), Fe(II) and Fe(III) salts. The as-prepared samples have been characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption, scanning electron microscopy (SEM), inductively coupled plasma emission spectroscopy (ICP), and Moessbauer spectroscopy (MS). The XRD analyses demonstrate the typical LDH-like layered structural characteristics of both products. The room temperature MS results reveal the characteristics of both the Fe(II) and Fe(III) species for SO{sub 4} {sup 2-}-containing product, while only the Fe(III) characteristic for DBS-containing one. The combination characterization results and Rietveld analysis illustrate that the SO{sub 4} {sup 2-}-containing product possesses the Green Rust two (GR2)-like crystal structure with an approximate chemical composition of [Zn{sub 0.435}.Fe{sup II} {sub 0.094}.Fe{sup III} {sub 0.470}.(OH){sub 2}].(SO{sub 4} {sup 2-}){sub 0.235}.1.0H{sub 2}O, while the DBS-containing one exhibits the common LDH compound-like structure. The contact angle measurement indicates the evident hydrophobic properties of DBS-containing nanocomposite, compared with SO{sub 4} {sup 2-}-containing product, due to the modification of the internal and external surface of LDHs by the organic hydrophobic chain of DBS. - Graphical abstract: For Zn{sup 2+}-Fe{sup 2+}-Fe{sup 3+} GR2(SO{sub 4} {sup 2-}), according to the derived chemical formula, Fe{sup 3+} was arranged at 1a (0, 0, 0) position, while all Zn{sup 2+} were in 2d position with the occupancy 0.645, and the left part of 2d positions were taken by Fe{sup 2+}/Fe{sup 3+}.

  1. Synthesis of layered double hydroxide nanosheets by coprecipitation using a T-type microchannel reactor

    SciTech Connect

    Pang, Xiujiang; Sun, Meiyu; Ma, Xiuming; Hou, Wanguo

    2014-02-15

    The synthesis of Mg{sub 2}Al–NO{sub 3} layered double hydroxide (LDH) nanosheets by coprecipitation using a T-type microchannel reactor is reported. Aqueous LDH nanosheet dispersions were obtained. The LDH nanosheets were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy and particle size analysis, and the transmittance and viscosity of LDH nanosheet dispersions were examined. The two-dimensional LDH nanosheets consisted of 1–2 brucite-like layers and were stable for ca. 16 h at room temperature. In addition, the co-assembly between LDH nanosheets and dodecyl sulfate (DS) anions was carried out, and a DS intercalated LDH nanohybrid was obtained. To the best of our knowledge, this is the first report of LDH nanosheets being directly prepared in bulk aqueous solution. This simple, cheap method can provide naked LDH nanosheets in high quantities, which can be used as building blocks for functional materials. - Graphical abstract: Layered double hydroxide (LDH) nanosheets were synthesized by coprecipitation using a T-type microchannel reactor, and could be used as basic building blocks for LDH-based functional materials. Display Omitted - Highlights: • LDH nanosheets were synthesized by coprecipitation using a T-type microchannel reactor. • Naked LDH nanosheets were dispersed in aqueous media. • LDH nanosheets can be used as building blocks for functional materials.

  2. Analytical model of LDMOS with a double step buried oxide layer

    NASA Astrophysics Data System (ADS)

    Yuan, Song; Duan, Baoxing; Cao, Zhen; Guo, Haijun; Yang, Yintang

    2016-09-01

    In this paper, a two-dimensional analytical model is established for the Buried Oxide Double Step Silicon On Insulator structure proposed by the authors. Based on the two-dimensional Poisson equation, the analytic expressions of the surface electric field and potential distributions for the device are achieved. In the BODS (Buried Oxide Double Step Silicon On Insulator) structure, the buried oxide layer thickness changes stepwise along the drift region, and the positive charge in the drift region can be accumulated at the corner of the step. These accumulated charge function as the space charge in the depleted drift region. At the same time, the electric field in the oxide layer also varies with the different drift region thickness. These variations especially the accumulated charge will modulate the surface electric field distribution through the electric field modulation effects, which makes the surface electric field distribution more uniform. As a result, the breakdown voltage of the device is improved by 30% compared with the conventional SOI structure. To verify the accuracy of the analytical model, the device simulation software ISE TCAD is utilized, the analytical values are in good agreement with the simulation results by the simulation software. That means the established two-dimensional analytical model for BODS structure is valid, and it also illustrates the breakdown voltage enhancement by the electric field modulation effect sufficiently. The established analytical models will provide the physical and mathematical basis for further analysis of the new power devices with the patterned buried oxide layer.

  3. Heat transfer performance of a novel double-layer mini-channel heat sink

    NASA Astrophysics Data System (ADS)

    Tang, Biao; Zhou, Rui; Bai, Pengfei; Fu, Ting; Lu, Longsheng; Zhou, Guofu

    2016-07-01

    High pressure drop and significant non-uniformity in temperature distribution along the streamwise direction are still challenges to the design of mini-channel heat sink. High density mini-channel arrays with high liquid-wall contact area are usually pursued in a conventional single-layer design of heat sink, which also inevitably brings high pressure drop. A novel double-layer structured heat sink is proposed in this paper. Four heat sinks with various designs in mini-channel density and flow direction were fabricated and studied experimentally on the heat transfer performance. The single factor of heat load does not show obvious effect on the overall thermal resistance of the heat sinks. On the other hand, slight decrease in thermal resistance was found with the increase in heat load at high flow rates. Moreover, a computational fluid dynamics modeling work was conducted. The results indicate that the parallel cross-flow field regulated by the double-layer structure enhances the heat exchange in both horizontal and vertical directions and consequently gives an uniform temperature distribution and high heat transfer efficiency.

  4. Spin transport in tantalum studied using magnetic single and double layers

    NASA Astrophysics Data System (ADS)

    Montoya, Eric; Omelchenko, Pavlo; Coutts, Chris; Lee-Hone, Nicholas R.; Hübner, René; Broun, David; Heinrich, Bret; Girt, Erol

    2016-08-01

    We report on spin transport in sputter-grown Ta films measured by ferromagnetic resonance. Spin diffusion length and spin mixing conductance are determined from magnetic damping measurements for a varying thickness of Ta layer 0 ≤dTa≤10 nm. The different boundary conditions of single- and double-magnetic-layer heterostructures Py |Ta and Py |Ta | [Py |Fe ] allow us to significantly narrow down the parameter space and test various models. We show that a common approach of using bulk resistivity value in the analysis yields inconsistent spin diffusion length and spin mixing conductance values for magnetic single- and double-layer structures. X-ray diffraction shows that bulk Ta is a combination of β -Ta and bcc-Ta . However, in the region of significant spin transport, ≲2 nm, there is an intermediate region of growth where the Ta lacks long-range structural order, as observed by transmission electron microscopy. Thickness-dependent resistivity measurements confirm that the bulk and intermediate regions have significantly different resistivity values. We find that the data can be well represented if the intermediate region resistivity value is used in the analysis. Additionally, the data can be fit if resistivity has the measured thickness dependence and spin diffusion length is restricted to be inversely proportional to resistivity. Finally, we rule out a model in which spin diffusion length is a constant, while the resistivity has the measured thickness dependence.

  5. Intercalation of amino acids and peptides into Mg-Al layered double hydroxide by reconstruction method.

    PubMed

    Nakayama, Hirokazu; Wada, Natsuko; Tsuhako, Mitsutomo

    2004-01-28

    The intercalation of amino acids and some peptides into Mg-Al layered double hydroxide known as hydrotalcite was examined. Although the intercalation by ion-exchange method was unsuccessful, all the amino acids except for Lys and Arg, and peptides examined could be intercalated into the layered double hydroxide by reconstruction method using Mg-Al oxide precursor. The uptake amounts of amino acids and peptides were 0.9-2.7 mmol per 1 g of LDH. Intercalation compounds were examined by using XRD and solid-state NMR. For Gly, Ala, Ser, Thr, Pro, Asn, Gln, Asp, Glu, and aspartame the intercalation accompanied the expansion of interlayer distance of the solid products, whereas the other amino acids and oligoglycine showed no expansion. The intercalation mechanism and release profile in K(2)CO(3) aqueous solution were also investigated. And the cointercalation of amino acids and peptides into Mg-Al LDH and easy release of amino acids from the LDH layer were found.

  6. A counter-charge layer in generalized solvents framework for electrical double layers in neat and hybrid ionic liquid electrolytes

    SciTech Connect

    Huang, Jingsong; Feng, Guang; Sumpter, Bobby G; Qiao, Rui; Meunier, Vincent

    2011-01-01

    Room-temperature ionic liquids (RTILs) have received significant attention as electrolytes due to a number of attractive properties such as their wide electrochemical windows. Since electrical double layers (EDLs) are the cornerstone for the applications of RTILs in electrochemical systems such as supercapacitors, it is important to develop an understanding of the structure capacitance relationships for these systems. Here we present a theoretical framework termed counter-charge layer in generalized solvents (CGS) for describing the structure and capacitance of the EDLs in neat RTILs and in RTILs mixed with different mass fractions of organic solvents. Within this framework, an EDL is made up of a counter-charge layer exactly balancing the electrode charge, and of polarized generalized solvents (in the form of layers of ion pairs, each of which has a zero net charge but has a dipole moment the ion pairs thus can be considered as a generalized solvent) consisting of all RTILs inside the system except the counter-ions in the counter-charge layer, together with solvent molecules if present. Several key features of the EDLs that originate from the strong ion ion correlation in RTILs, e.g., overscreening of electrode charge and alternating layering of counter-ions and co-ions, are explicitly incorporated into this framework. We show that the dielectric screening in EDLs is governed predominately by the polarization of generalized solvents (or ion pairs) in the EDL, and the capacitance of an EDL can be related to its microstructure with few a priori assumptions or simplifications. We use this framework to understand two interesting phenomena observed in molecular dynamics simulations of EDLs in a neat IL of 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIM][BF4]) and in a mixture of [BMIM][BF4] and acetonitrile (ACN): (1) the capacitance of the EDLs in the [BMIM][BF4]/ACN mixture increases only slightly when the mass fraction of ACN in the mixture increases from zero

  7. Confined acoustic and optical plasmons in double-layered quantum-wire arrays with strong tunneling

    NASA Astrophysics Data System (ADS)

    Dethlefsen, A. F.; Heyn, Ch.; Heitmann, D.; Schüller, C.

    2006-05-01

    We investigate electronic excitations in GaAs-AlxGa1-xAs double-layered quantum wire arrays with strong tunneling coupling by resonant inelastic light scattering. By applying an external electric field, we can change the one-dimensional (1D) electron density and the symmetry of the double quantum-well (DQW) structure at the same time. We identify confined optical 1D intersubband plasmons (COP) and confined acoustic 1D intersubband plasmons (CAP). Due to the tunneling coupling, the energies of the CAP exhibit a minimum for a symmetric DQW potential, whereas the energies of the COP are dominated by the total carrier density, and are nearly insensitive to the symmetry of the potential.

  8. Design study of double-layer beam trajectory accelerator based on the Rhodotron structure

    NASA Astrophysics Data System (ADS)

    Jabbari, Iraj; Poursaleh, Ali Mohammad; Khalafi, Hossein

    2016-08-01

    In this paper, the conceptual design of a new structure of industrial electron accelerator based on the Rhodotron accelerator is presented and its properties are compared with those of Rhodotron-TT200 accelerator. The main goal of this study was to reduce the power of RF system of accelerator at the same output electron beam energy. The main difference between the new accelerator structure with the Rhodotron accelerator is the length of the coaxial cavity that is equal to the wavelength at the resonant frequency. Also two sets of bending magnets were used around the acceleration cavity in two layers. In the new structure, the beam crosses several times in the coaxial cavity by the bending magnets around the cavity at the first layer and then is transferred to the second layer using the central bending magnet. The acceleration process in the second layer is similar to the first layer. Hence, the energy of the electron beam will be doubled. The electrical power consumption of the RF system and magnet system were calculated and simulated for the new accelerator structure and TT200. Comparing the calculated and simulated results of the TT200 with those of experimental results revealed good agreement. The results showed that the overall electrical power consumption of the new accelerator structure was less than that of the TT200 at the same energy and power of the electron beam. As such, the electrical efficiency of the new structure was improved.

  9. Numerical simulation of current-free double layers created in a helicon plasma device

    SciTech Connect

    Rao, Sathyanarayan; Singh, Nagendra

    2012-09-15

    Two-dimensional simulations reveal that when radially confined source plasma with magnetized electrons and unmagnetized ions expands into diverging magnetic field B, a current-free double layer (CFDL) embedded in a conical density structure forms, as experimentally measured in the Australian helicon plasma device (HPD). The magnetized electrons follow the diverging B while the unmagnetized ions tend to flow directly downstream of the source, resulting in a radial electric field (E{sub Up-Tack }) structure, which couples the ion and electron flows. Ions are transversely (radially) accelerated by E{sub Up-Tack} on the high potential side of the double layer in the CFDL. The accelerated ions are trapped near the conical surface, where E{sub Up-Tack} reverses direction. The potential structure of the CFDL is U-shaped and the plasma density is enhanced on the conical surface. The plasma density is severely depleted downstream of the parallel potential drop ({phi}{sub Double-Vertical-Line Double-Vertical-Line o}) in the CFDL; the density depletion and the potential drop are related by quasi-neutrality condition, including the divergence in the magnetic field and in the plasma flow in the conical structure. The potential and density structures, the CFDL spatial size, its electric field strengths and the electron and ion velocities and energy distributions in the CFDL are found to be in good agreements with those measured in the Australian experiment. The applicability of our results to measured axial potential profiles in magnetic nozzle experiments in HPDs is discussed.

  10. Assessment of the effects of scrape-off layer fluctuations on first wall sputtering with the TOKAM-2D turbulence code

    NASA Astrophysics Data System (ADS)

    Marandet, Y.; Nace, N.; Valentinuzzi, M.; Tamain, P.; Bufferand, H.; Ciraolo, G.; Genesio, P.; Mellet, N.

    2016-11-01

    Plasma material interactions on the first wall of future tokamaks such as ITER and DEMO are likely to play an important role, because of turbulent radial transport. The latter results to a large extent from the radial propagation of plasma filaments through a tenuous background. In such a situation, mean field descriptions (on which transport codes rely) become questionable. First wall sputtering is of particular interest, especially in a full W machine, since it has been shown experimentally that first wall sources control core contamination. In ITER, beryllium sources will be one of the important actors in determining the fuel retention level through codeposition. In this work, we study the effect of turbulent fluctuations on mean sputtering yields and fluxes, relying on a new version of the TOKAM-2D code which includes ion temperature fluctuations. We show that fluctuations enhance sputtering at sub-threshold impact energies, by more than an order of magnitude when fluctuation levels are of order unity.

  11. New layered double hydroxides by prepared by the intercalation of gibbsite

    SciTech Connect

    Rees, Jennifer R.; Burden, Chloe S.; Fogg, Andrew M.

    2015-04-15

    New layered double hydroxides (LDHs) with the composition [MAl{sub 4}(OH){sub 12}]Cl{sub 2}·1.5H{sub 2}O (M=Co, Ni) have been prepared by reacting gibbsite, γ-Al(OH){sub 3}, with the appropriate chloride salt in a synthesis in which the water of crystallization is the only solvent present and fully characterized. These LDHs have been shown to undergo facile anion exchange reactions with both organic and inorganic anions at room temperature making them comparable to other LDHs in this respect. Reactions under the same conditions with CuCl{sub 2}·2H{sub 2}O and ZnCl{sub 2} failed to form the desired LDHs but those with nitrate salts did lead to the formation of the previously reported [MAl{sub 4}(OH){sub 12}](NO{sub 3}){sub 2}·1.5H{sub 2}O (M=Co, Ni) compounds. - Graphical abstract: New layered double hydroxides (LDHs) with the composition [MAl{sub 4}(OH){sub 12}]Cl{sub 2}·1.5H{sub 2}O (M=Co, Ni) have been prepared by reacting gibbsite, γ-Al(OH){sub 3}, with the appropriate chloride salt in a synthesis in which no additional solvent is used and fully characterized. These LDHs have been shown to undergo facile anion exchange reactions with both organic and inorganic anions at room temperature. - Highlights: • Synthesis of new layered double hydroxides, [MAl{sub 4}(OH){sub 12}]Cl{sub 2}·1.5H{sub 2}O (M=Co, Ni). • Demonstration of the anion exchange capacity with both organic and inorganic anions. • Demonstration of the generality of the synthesis for LDHs.

  12. Electrokinetics in nanochannels: part I. Electric double layer overlap and channel-to-well equilibrium.

    PubMed

    Baldessari, Fabio; Santiago, Juan G

    2008-09-15

    In this paper a new model is described for calculating the electric potential field in a long, thin nanochannel with overlapped electric double layers. Electrolyte concentration in the nanochannel is predicted self-consistently via equilibrium between ionic solution in the wells and within the nanochannel. Differently than published models that require detailed iterative numerical solutions of coupled differential equations, the framework presented here is self-consistent and predictions are obtained solving a simple one-dimensional integral. The derivation clearly shows that the electric potential field depends on three new parameters: the ratio of ion density in the channel to ion density in the wells; the ratio of free-charge density to bulk ion density within the channel; and a modified Debye-Hückel thickness, which is the relevant scale for shielding of surface net charge. For completeness, three wall-surface boundary conditions are analyzed: specified zeta-potential; specified surface net charge density; and charge regulation. Predictions of experimentally observable quantities based on the model proposed here, such as depth-averaged electroosmotic flow and net ionic current, are significantly different than results from previous overlapped electric double layer models. In this first paper of a series of two, predictions are presented where channel depth is varied at constant well concentration. Results show that under conditions of electric double layer overlap, electroosmosis contributes only a small fraction of the net ionic current, and that most of the measurable current is due to ionic conduction in conditions of increased counterion density in the nanochannel. In the second of this two-paper series, predictions are presented where well-concentration is varied and the channel depth is held constant, and the model described here is employed to study the dependence of ion mobility on ionic strength, and compare predictions to measurements of ionic

  13. Intercalation and controlled release properties of vitamin C intercalated layered double hydroxide

    SciTech Connect

    Gao, Xiaorui; Lei, Lixu; O'Hare, Dermot; Xie, Juan; Gao, Pengran; Chang, Tao

    2013-07-15

    Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg–Al and Mg–Fe layered double hydroxides (LDHs) have been synthesized by the calcination–rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV–vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO{sub 3}{sup 2−} solutions imply that Mg{sub 3}Al–VC LDH is a better controlled release system than Mg{sub 3}Fe–VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO{sub 3}{sup 2−} solution. - Graphical abstract: Vitamin C anions have been intercalated in the interlayer space of layered double hydroxide and released in CO{sub 3}{sup 2−} solution and deionised water. - Highlights: • Vitamin C intercalated Mg–Al and Mg–Fe layered double hydroxides were prepared. • Release property of vitamin C in aqueous CO{sub 3}{sup 2−} solution is better. • Avrami-Erofe’ev and first-order models provide better fit for release results. • Diffusion-controlled and ion exchange processes occur in deionised water. • An ion exchange process occurs in CO{sub 3}{sup 2−} solution.

  14. Electric double-layer transistor using layered iron selenide Mott insulator TlFe1.6Se2.

    PubMed

    Katase, Takayoshi; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2014-03-18

    A(1-x)Fe(2-y)Se2 (A = K, Cs, Rb, Tl) are recently discovered iron-based superconductors with critical temperatures (Tc) ranging up to 32 K. Their parent phases have unique properties compared with other iron-based superconductors; e.g., their crystal structures include ordered Fe vacancies, their normal states are antiferromagnetic (AFM) insulating phases, and they have extremely high Néel transition temperatures. However, control of carrier doping into the parent AFM insulators has been difficult due to their intrinsic phase separation. Here, we fabricated an Fe-vacancy-ordered TlFe1.6Se2 insulating epitaxial film with an atomically flat surface and examined its electrostatic carrier doping using an electric double-layer transistor (EDLT) structure with an ionic liquid gate. The positive gate voltage gave a conductance modulation of three orders of magnitude at 25 K, and further induced and manipulated a phase transition; i.e., delocalized carrier generation by electrostatic doping is the origin of the phase transition. This is the first demonstration, to the authors' knowledge, of an EDLT using a Mott insulator iron selenide channel and opens a way to explore high Tc superconductivity in iron-based layered materials, where carrier doping by conventional chemical means is difficult.

  15. Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail

    NASA Astrophysics Data System (ADS)

    Sun, R. X.; Zheng, J.; Liao, X. L.; Che, T.; Gou, Y. F.; He, D. B.; Deng, Z. G.

    2014-10-01

    A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

  16. Mössbauer and XRD study of intercalated CaFe-layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Sipiczki, Mónika; Kuzmann, Ernő; Pálinkó, István; Homonnay, Zoltán; Sipos, Pál; Kukovecz, Ákos; Kónya, Zoltán

    2014-04-01

    N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and 57Fe Mössbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.

  17. Film of lignocellulosic carbon material for self-supporting electrodes in electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Funabashi, Tsubasa; Mizuno, Jun; Sato, Masamichi; Kitajima, Masao; Matsuura, Makoto; Shoji, Shuichi

    2013-09-01

    A novel thin, wood-based carbon material with heterogeneous pores, film of lignocellulosic carbon material (FLCM), was successfully fabricated by carbonizing softwood samples of Picea jezoensis (Jezo spruce). Simultaneous increase in the specific surface area of FLCM and its affinity for electrolyte solvents in an electric double-layer capacitor (EDLC) were achieved by the vacuum ultraviolet/ozone (VUV/O3) treatment. This treatment increased the specific surface area of FLCM by 50% over that of original FLCM. The results obtained in this study confirmed that FLCM is an appropriate self-supporting EDLC electrode material without any warps and cracks.

  18. Temperature aspect of degradation of electrochemical double-layer capacitors (EDLC)

    NASA Astrophysics Data System (ADS)

    Baek, Dong-Cheon; Kim, Hyun-Ho; Lee, Soon-Bok

    2015-03-01

    Electric double layer capacitors (EDLC) cells have a process variation and temperature dependency in capacitance so that balancing is required when they are connected in series, which includes electronic voltage management based on capacitance monitoring. This paper measured temperature aspect of capacitance periodically to monitor health and degradation behavior of EDLC stressed under high temperatures and zero below temperatures respectively, which enables estimation of the state of health (SOH) regardless of temperature. At high temperature, capacitance saturation and delayed expression of degradation was observed. After cyclic stress at zero below temperature, less effective degradation and time recovery phenomenon were occurred.

  19. Numerical study of Electrical double layer development: Analysis of the charge genesis

    NASA Astrophysics Data System (ADS)

    Leblanc, P.; Cabaleiro, J. M.; Paillat, T.

    2015-10-01

    This work presents a numerical simulation of the Electric Double Layer (EDL) development process at a solid/liquid interface for adsorption and corrosion models. First, the study is conducted for static EDL development (without liquid flow) until it reaches a static equilibrium. Afterwards, the EDL is perturbed by a laminar liquid flow leading to flow electrification phenomena (dynamic study). The charge conservation equations of the liquid species have been implemented in an industrial code. A parametric study was performed to consider different chemical reaction scenarios and different models.

  20. Superconductivity. Light-induced superconductivity using a photoactive electric double layer.

    PubMed

    Suda, Masayuki; Kato, Reizo; Yamamoto, Hiroshi M

    2015-02-13

    Electric double layers (EDLs) of ionic liquids have been used in superconducting field-effect transistors as nanogap capacitors. Because of the freezing of the ionic motion below ~200 kelvin, modulations of the carrier density have been limited to the high-temperature regime. Here we observe carrier-doping-induced superconductivity in an organic Mott insulator with a photoinduced EDL based on a photochromic spiropyran monolayer. Because the spiropyran can isomerize reversibly between nonionic and zwitterionic isomers through photochemical processes, two distinct built-in electric fields can modulate the carrier density even at cryogenic conditions. PMID:25678657

  1. Thin-shell wormholes with a double layer in quadratic F (R ) gravity

    NASA Astrophysics Data System (ADS)

    Eiroa, Ernesto F.; Figueroa Aguirre, Griselda

    2016-08-01

    We present a family of spherically symmetric Lorentzian wormholes in quadratic F (R ) gravity, with a thin shell of matter corresponding to the throat. At each side of the shell, the geometry has a different constant value of the curvature scalar R . The junction conditions determine the equation of state between the pressure and energy density at the throat, where a double layer is also located. We analyze the stability of the configurations under perturbations preserving the spherical symmetry. In particular, we study thin-shell wormholes with mass and charge. We find that there exist values of the parameters for which stable static solutions are possible.

  2. Synthesis and carbon dioxide sorption of layered double hydroxide/silica foam nanocomposites with hierarchical mesostructure.

    PubMed

    Fu, Liling; Qi, Genggeng; Shekhah, Osama; Belmabkhout, Youssef; Estevez, Luis; Eddaoudi, Mohamed; Giannelis, Emmanuel P

    2014-04-01

    Layered double hydroxides (LDHs) with a hierarchical mesostructure are successfully synthesized on mesoporous silica foams by simple impregnation and hydrothermal treatment. The as-synthesized LDH/silica foam nanocomposites show well-defined mesostructures with high surface areas, large pore volumes, and mesopores of 6-7 nm. The nanocomposites act as carbon dioxide (CO2 ) sorbents under simulated flue gas conditions. They also exhibit significantly enhanced CO2 capacities under high-pressure conditions and high CO2 /N2 and CO2 /CH4 selectivities.

  3. Post heat treatment effects on double layer metal structures for VLSI applications

    NASA Technical Reports Server (NTRS)

    Wade, T. E.; Trotter, J. D.

    1978-01-01

    The realization of high yield double layer metal systems using wet chemistry processes and the ability to extend yields beyond that attainable with wet chemistry by means of post sintering processes at temperatures below 500 C for potential applications in very large scale integration structures were studied. Yields in excess of 98% and average total contact resistance of less than 150 ohms and 200 ohms were realized for a series of 560 vias of 0.5 X 0.5 mils and 0.2 X 0.2 mils in size, respectively.

  4. Electrostatic solitary wave and double layer in a plasma with heavy ions and nonthermally distributed electrons

    SciTech Connect

    Choi, C.-R.; Min, K.-W.; Woo, M.-H.; Ryu, C.-M.

    2010-09-15

    The existence condition for bump and dip type, as well as double layer (DL), solutions of electrostatic solitary waves (ESWs) in a nonthermal electron plasma with heavy ions is investigated by a pseudopotential method. It is found that the nonthermality of electrons determines the existence of the DL solution and that the amplitude of ESWs is enhanced by the density of heavy ions. When the heavy ion density is beyond a certain critical value, ESWs and DLs cannot exist. It is also found that both the lower and upper critical Mach numbers are reduced by the presence of heavy ions.

  5. Double layers in plasmas; Proceedings of the Conference, Huntsville, AL, Mar. 1986

    NASA Technical Reports Server (NTRS)

    Williams, Alton C. (Editor)

    1987-01-01

    Papers are presented on such topics as double layers (DLs) and plasma-wave resistivity in extragalactic jets; the formation of a DL leading to the critical velocity phenomenon; formation mechanisms of laboratory DLs in triple plasma devices; and linear Vlasov stability in one-dimensional DLs. Consideration is also given to weak DLs in the auroral ionosphere; the dynamical properties of very strong DLs in a triple plasma device; particle simulation of auroral DLs; a muonic X-ray laser assisted by the catalyzed fusion of deuterium and tritium; and the feasbility of measuring the nuclear reaction cross sections at energies of several keV in a target under laser compression.

  6. Structure and charging kinetics of electrical double layers at large electrode voltage

    SciTech Connect

    Cagle, Clint; Feng, Guang; Qiao, Rui; Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent

    2009-01-01

    The structure and charging kinetics of electrical double layers (EDLs) at interfaces of NaCl solutions and planar electrodes are studied by molecular dynamics (MD) and Poisson Nernst Planck (PNP) simulations. Based on the MD results and prior experimental data, we show that counterion packing in planar EDLs does not reach the steric limit at electrode voltages below 1 V. In addition, we demonstrate that a PNP model, when complemented with a Stern model, can be effectively used to capture the overall charging kinetics. However, the PNP/Stern model can only give a qualitative description of the fine features of the EDL.

  7. DOUBLE-DIFFUSIVE INSTABILITIES OF A SHEAR-GENERATED MAGNETIC LAYER

    SciTech Connect

    Silvers, Lara J.; Proctor, Michael R. E.; Vasil, Geoffrey M.; Brummell, Nicholas H.

    2009-09-01

    Previous theoretical work has speculated about the existence of double-diffusive magnetic buoyancy instabilities of a dynamically evolving horizontal magnetic layer generated by the interaction of forced vertically sheared velocity and a background vertical magnetic field. Here, we confirm numerically that if the ratio of the magnetic to thermal diffusivities is sufficiently low then such instabilities can indeed exist, even for high Richardson number shear flows. Magnetic buoyancy may therefore occur via this mechanism for parameters that are likely to be relevant to the solar tachocline, where regular magnetic buoyancy instabilities are unlikely.

  8. Direct thrust measurement of a permanent magnet helicon double layer thruster

    SciTech Connect

    Takahashi, K.; Lafleur, T.; Charles, C.; Alexander, P.; Boswell, R. W.; Perren, M.; Laine, R.; Pottinger, S.; Lappas, V.; Harle, T.; Lamprou, D.

    2011-04-04

    Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.

  9. Direct thrust measurement of a permanent magnet helicon double layer thruster

    NASA Astrophysics Data System (ADS)

    Takahashi, K.; Lafleur, T.; Charles, C.; Alexander, P.; Boswell, R. W.; Perren, M.; Laine, R.; Pottinger, S.; Lappas, V.; Harle, T.; Lamprou, D.

    2011-04-01

    Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.

  10. The similarity of electric double-layer interaction from the general Poisson-Boltzmann theory.

    PubMed

    Zhang, Junfeng; Drechsler, Astrid; Grundke, Karina; Kwok, Daniel Y

    2006-08-01

    We studied electric double-layer (EDL) interactions in electrolytes with different valence combinations. Our results show that the interactions are similar for electrolytes with the same co-ion valences and concentrations and such similarity increases with the co-ion valence and surface potential. A scaled surface potential was defined and found to be useful in characterizing the difference in EDL interaction. These results show that co-ions play a more important role than counterions in determining EDL potential and interaction in an electrolyte solution, especially for systems with high co-ion valence and/or high surface potentials.

  11. Effects of mixed discrete surface charges on the electrical double layer.

    PubMed

    Jiménez-Ángeles, Felipe

    2012-08-01

    Adsorption of surface coions and charge reversal are induced at the electrical double layer of a wall charged with positive and negative surface sites next to an electrolyte solution. While for the considered surface charge density these effects are found over a wide range of conditions, they are not observed for the typically employed surface models in equivalent conditions. Important consequences in electrophoresis experiments for different colloids with equal effective surface charge density are foreseen. This study is carried out by means of molecular dynamics simulations.

  12. Laser Induced Fluorescence Studies of Electrostatic Double Layers in an Expanding Helicon Plasma

    NASA Astrophysics Data System (ADS)

    Carr, Jerry, Jr.

    We report the first evidence of a laboratory double layer (DL) collapsing in the presence of an instability studied by Chakraborty Thakur et al. 1 with the use of time resolved laser induced fluorescence (LIF) studies. Higher time resolution studies then provided the first statistically validated proof of the correlation between the ion acoustic instability and a DL. Time-frequency analysis in the form of time resolved cross power spectra and continuous wavelet transforms were used to provide insight into beam formation. The implications of this work is that in the creation of strong DLs in expanding plasmas for plasma propulsion or other applications may be self-limited through instability growth. Over the past decade, experimental and theoretical studies have demonstrated the formation of stable, electrostatic, current-free double layers (CFDLs) in plasmas with a strong density gradient; typically a result of a divergent magnetic field. In this work, we present evidence for the formation of multiple double layers within a single divergent magnetic field structure. Downstream of the divergent magnetic field, multiple accelerated ion populations are observed through laser induced fluorescence measurements of the ion velocity distribution function. The formation of the multiple double layer structure is a strong function of the neutral gas pressure in the experiment. The similarity of the accelerated ion populations observed in these laboratory experiments to ion populations observed in reconnection outflow regions in the magnetosphere and in numerical simulations is also described. If ion energization during magnetic reconnection also results solely from acceleration in electric fields, these observations imply a prediction that the ion heating, i.e., the broadening of ion velocity distribution functions, reported in magnetic reconnection experiments is more accurately described by a superposition of differently accelerated ion populations. Therefore, the ion

  13. The Skylab barium plasma injection experiments. II - Evidence for a double layer

    NASA Technical Reports Server (NTRS)

    Wescott, E. M.; Stenbaek-Nielsen, H. C.; Hallinan, T. J.; Davis, T. N.; Peek, H. M.

    1976-01-01

    Television observations of a barium-plasma flux tube extending from near 4500 km to near 10,000 km during a magnetic substorm and dawn-sector auroral display indicated several interesting anomalous events. Beyond 5500 km, there was a rapid increase in brightness accompanied by flux-tube splitting and diffusion, leaving behind a truncated single flux tube. From the orientation of the flux tube compared with theoretical field models, the presence of a substantial field-aligned current sheet is deduced. A suggested explanation of these phenomena is given in terms of a plasma potential double layer.

  14. Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

    2015-08-01

    Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

  15. Nonpolarizing single layer inorganic and double layer organic-inorganic one-dimensional guided mode resonance filters

    NASA Astrophysics Data System (ADS)

    Saleem, Muhammad Rizwan; Honkanen, Seppo; Turunen, Jari

    2013-03-01

    Guided mode resonance (GMRF) phenomena occurs when the evanescent orders of a diffraction grating are coupled to the waveguide modes and propagate out at given optical parameters such as wavelength, angle, and state of polarization of incident light. The outcoupling field from a waveguide is, in general, polarization sensitive. Polarization insensitive 1D subwavelength grating structures with high diffraction efficiency at normal and oblique incidence are required, for example, in optical communications where output light may possess any polarization state. This means that an s- or p-polarized input optical field, which generally couples TE- or TM-modes in the waveguide under different resonance conditions, can be tuned at one resonance by selecting suitable grating parameters, regardless of the input polarization state. All of the polarization insensitive devices fabricated to date either employing a method which is not cost-effective or simple enough to some extent. In this work, we report the design and fabrication of two types of non-polarizing binary-structured onedimensional (1D) GMRF at normal incidence. A single layer binary-profile TiO2 resonant grating (grating-I) is fabricated by Atomic layer deposition (ALD), electron beam lithography (EBL) and reactive ion etching (RIE), which demonstrates almost perfect non-polarizing filtering effect with 1D grating under normal incidence. A double layer rectangular-profile polycarbonate-TiO2 1D GMR grating (grating-II) is fabricated by nanoimprint lithography (NIL) and ALD which also shows good non-polarizing property and the potential of cost-effective mass fabrication of such functional devices.

  16. Electric Double Layer electrostatics of spherical polyelectrolyte brushes with pH-dependent charge density

    NASA Astrophysics Data System (ADS)

    Li, Hao; Chen, Guang; Sinha, Shayandev; Das, Siddhartha; Soft Matter, Interfaces,; Energy Laboratory (Smiel) Team

    Understanding the electric double layer (EDL) electrostatics of spherical polyelectrolyte (PE) brushes, which are spherical particles grafted with PE layers, is essential for appropriate use of PE-grfated micro-nanoparticles for targeted drug delivery, oil recovery, water harvesting, emulsion stabilization, emulsion breaking, etc. Here we elucidate the EDL electrostatics of spherical PE brushes for the case where the PE exhibits pH-dependent charge density. This pH-dependence necessitates the consideration of explicit hydrogen ion concentration, which in turn dictates the distribution of monomers along the length of the grafted PE. This monomer distribution is shown to be a function of the nature of the sphere (metallic or a charged or uncharged dielectric or a liquid-filled sphere). All the calculations are performed for the case where the PE electrostatics can be decoupled from the PE elastic and excluded volume effects. Initial predictions are also provided for the case where such decoupling is not possible.

  17. Zn-Co layered double hydroxide modified hematite photoanode for enhanced photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Xu, Dongyu; Rui, Yichuan; Li, Yaogang; Zhang, Qinghong; Wang, Hongzhi

    2015-12-01

    Zinc-cobalt layered double hydroxide (LDH) was electrodeposited on Ti-doped hematite photoanodes for the first time, and a significant enhanced performance for photoelectrochemical water splitting was demonstrated over the composite photoanodes. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS) were characterized with the resulted photoanodes. With the electrodepositing treatment, the photocurrent density increased from 1.27 mA/cm2 for pristine hematite to 1.73 mA/cm2 for modified materials at 1.23 V vs. RHE (i.e. 36% improvement). The photocurrent improvement is mainly attributed to a suppression of electron-hole recombination and reduced overpotential for water oxidation at the hematite-electrolyte interface due to the formation of Zn-Co LDH layer on hematite.

  18. Hybrid magnetic materials formed by ferritin intercalated into a layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Clemente-León, Miguel; Coronado, Eugenio; Primo, Vicent; Ribera, Antonio; Soriano-Portillo, Alejandra

    2008-12-01

    A hybrid magnetic material formed by ferritin intercalated into a layered double hydroxide (LDH) of Mg and Al (Mg/Al molar ratio 2) is prepared and characterized through powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, electron probe microanalysis (EPMA) and high resolution transmission electron microscopy (HRTEM). One observes an enhancement in the thermal stability of the ferritin molecules when they are inserted in the layered material. Magnetic measurements of the hybrid material exhibit the typical superparamagnetic behaviour of the ferritin molecule. On the other hand, the intercalation of ferritin into the LDH guarantees a homogeneous dispersion of the ferritin molecules, which do not aggregate even after calcination of the sample. This feature allows obtaining well-dispersed magnetic metal oxide nanoparticles upon calcination of the hybrid material.

  19. Reciprocity in spatial evolutionary public goods game on double-layered network.

    PubMed

    Kim, Jinho; Yook, Soon-Hyung; Kim, Yup

    2016-08-09

    Spatial evolutionary games have mainly been studied on a single, isolated network. However, in real world systems, many interaction topologies are not isolated but many different types of networks are inter-connected to each other. In this study, we investigate the spatial evolutionary public goods game (SEPGG) on double-layered random networks (DRN). Based on the mean-field type arguments and numerical simulations, we find that SEPGG on DRN shows very rich interesting phenomena, especially, depending on the size of each layer, intra-connectivity, and inter-connected couplings, the network reciprocity of SEPGG on DRN can be drastically enhanced through the inter-connected coupling. Furthermore, SEPGG on DRN can provide a more general framework which includes the evolutionary dynamics on multiplex networks and inter-connected networks at the same time.

  20. Electrical double layers and differential capacitance in molten salts from density functional theory

    DOE PAGES

    Frischknecht, Amalie L.; Halligan, Deaglan O.; Parks, Michael L.

    2014-08-05

    Classical density functional theory (DFT) is used to calculate the structure of the electrical double layer and the differential capacitance of model molten salts. The DFT is shown to give good qualitative agreement with Monte Carlo simulations in the molten salt regime. The DFT is then applied to three common molten salts, KCl, LiCl, and LiKCl, modeled as charged hard spheres near a planar charged surface. The DFT predicts strong layering of the ions near the surface, with the oscillatory density profiles extending to larger distances for larger electrostatic interactions resulting from either lower temperature or lower dielectric constant. Inmore » conclusion, overall the differential capacitance is found to be bell-shaped, in agreement with recent theories and simulations for ionic liquids and molten salts, but contrary to the results of the classical Gouy-Chapman theory.« less