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Sample records for double layer charging

  1. 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.

  2. "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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Interplay between Depletion and Double-Layer Forces Acting between Charged Particles in Solutions of Like-Charged Polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Moazzami-Gudarzi, Mohsen; Kremer, Tomislav; Valmacco, Valentina; Maroni, Plinio; Borkovec, Michal; Trefalt, Gregor

    2016-08-01

    Direct force measurements between negatively charged silica particles in the presence of a like-charged strong polyelectrolyte were carried out with an atomic force microscope. The force profiles can be quantitatively interpreted as a superposition of depletion and double-layer forces. The depletion forces are modeled with a damped oscillatory profile, while the double-layer forces with the mean-field Poisson-Boltzmann theory for a strongly asymmetric electrolyte, whereby an effective valence must be assigned to the polyelectrolyte. This effective valence is substantially smaller than the bare valence due to ion condensation effects. The unusual aspect of the electrical double layer in these systems is the exclusion of the like-charged polyelectrolyte from the vicinity of the surface, leading to a strongly nonexponential diffuse ionic layer that is dominated by counterions and has a well-defined thickness. As the oscillatory depletion force sets in right after this layer, this condition can be used to predict the phase of the oscillatory depletion force.

  8. Interplay between Depletion and Double-Layer Forces Acting between Charged Particles in Solutions of Like-Charged Polyelectrolytes.

    PubMed

    Moazzami-Gudarzi, Mohsen; Kremer, Tomislav; Valmacco, Valentina; Maroni, Plinio; Borkovec, Michal; Trefalt, Gregor

    2016-08-19

    Direct force measurements between negatively charged silica particles in the presence of a like-charged strong polyelectrolyte were carried out with an atomic force microscope. The force profiles can be quantitatively interpreted as a superposition of depletion and double-layer forces. The depletion forces are modeled with a damped oscillatory profile, while the double-layer forces with the mean-field Poisson-Boltzmann theory for a strongly asymmetric electrolyte, whereby an effective valence must be assigned to the polyelectrolyte. This effective valence is substantially smaller than the bare valence due to ion condensation effects. The unusual aspect of the electrical double layer in these systems is the exclusion of the like-charged polyelectrolyte from the vicinity of the surface, leading to a strongly nonexponential diffuse ionic layer that is dominated by counterions and has a well-defined thickness. As the oscillatory depletion force sets in right after this layer, this condition can be used to predict the phase of the oscillatory depletion force. PMID:27588884

  9. 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.

  10. 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.

  11. Investigation of surface charge density on solid-liquid interfaces by modulating the electrical double layer.

    PubMed

    Moon, Jong Kyun; Song, Myung Won; Pak, Hyuk Kyu

    2015-05-20

    A solid surface in contact with water or aqueous solution usually carries specific electric charges. These surface charges attract counter ions from the liquid side. Since the geometry of opposite charge distribution parallel to the solid-liquid interface is similar to that of a capacitor, it is called an electrical double layer capacitor (EDLC). Therefore, there is an electrical potential difference across an EDLC in equilibrium. When a liquid bridge is formed between two conducting plates, the system behaves as two serially connected EDLCs. In this work, we propose a new method for investigating the surface charge density on solid-liquid interfaces. By mechanically modulating the electrical double layers and simultaneously applying a dc bias voltage across the plates, an ac electric current can be generated. By measuring the voltage drop across a load resistor as a function of bias voltage, we can study the surface charge density on solid-liquid interfaces. Our experimental results agree very well with the simple equivalent electrical circuit model proposed here. Furthermore, using this method, one can determine the polarity of the adsorbed state on the solid surface depending on the material used. We expect this method to aid in the study of electrical phenomena on solid-liquid interfaces. PMID:25923410

  12. Study of surface charge density on solid/liquid interfaces by modulating the electrical double layer

    NASA Astrophysics Data System (ADS)

    Pak, Hyuk Kyu; Moon, Jong Kyun

    2014-11-01

    A solid surface in contact with water or aqueous solution usually carries specific electric charges. These surface charges attract counter ions from the liquid side. Since the geometry of opposite charge distribution parallel to the solid/liquid interface is similar to that of a capacitor, it is called an electrical double layer capacitor (EDLC). Therefore, there is an electrical potential difference across an EDLC in equilibrium. When a liquid bridge is formed between two conducting plates, the system behaves as two serially connected EDLCs. In this work, we propose a new method for investigating the surface charge density on solid/liquid interfaces. By mechanically modulating the electrical double layers and simultaneously applying a DC bias voltage across the plates, an AC electric current can be generated. By measuring the voltage difference between the plates as a function of bias voltage, we can study the surface charge density on solid/liquid interfaces. Our experimental results agree very well with the simple equivalent circuit model proposed here. Furthermore, using this method, one can determine the polarity of the adsorbed state on the solid surface depending on the material used. This work was supported by Center for Soft and Living Matter through IBS program in Korea.

  13. Investigation of surface charge density on solid-liquid interfaces by modulating the electrical double layer.

    PubMed

    Moon, Jong Kyun; Song, Myung Won; Pak, Hyuk Kyu

    2015-05-20

    A solid surface in contact with water or aqueous solution usually carries specific electric charges. These surface charges attract counter ions from the liquid side. Since the geometry of opposite charge distribution parallel to the solid-liquid interface is similar to that of a capacitor, it is called an electrical double layer capacitor (EDLC). Therefore, there is an electrical potential difference across an EDLC in equilibrium. When a liquid bridge is formed between two conducting plates, the system behaves as two serially connected EDLCs. In this work, we propose a new method for investigating the surface charge density on solid-liquid interfaces. By mechanically modulating the electrical double layers and simultaneously applying a dc bias voltage across the plates, an ac electric current can be generated. By measuring the voltage drop across a load resistor as a function of bias voltage, we can study the surface charge density on solid-liquid interfaces. Our experimental results agree very well with the simple equivalent electrical circuit model proposed here. Furthermore, using this method, one can determine the polarity of the adsorbed state on the solid surface depending on the material used. We expect this method to aid in the study of electrical phenomena on solid-liquid interfaces.

  14. Investigation of surface charge density on solid-liquid interfaces by modulating the electrical double layer

    NASA Astrophysics Data System (ADS)

    Moon, Jong Kyun; Song, Myung Won; Pak, Hyuk Kyu

    2015-05-01

    A solid surface in contact with water or aqueous solution usually carries specific electric charges. These surface charges attract counter ions from the liquid side. Since the geometry of opposite charge distribution parallel to the solid-liquid interface is similar to that of a capacitor, it is called an electrical double layer capacitor (EDLC). Therefore, there is an electrical potential difference across an EDLC in equilibrium. When a liquid bridge is formed between two conducting plates, the system behaves as two serially connected EDLCs. In this work, we propose a new method for investigating the surface charge density on solid-liquid interfaces. By mechanically modulating the electrical double layers and simultaneously applying a dc bias voltage across the plates, an ac electric current can be generated. By measuring the voltage drop across a load resistor as a function of bias voltage, we can study the surface charge density on solid-liquid interfaces. Our experimental results agree very well with the simple equivalent electrical circuit model proposed here. Furthermore, using this method, one can determine the polarity of the adsorbed state on the solid surface depending on the material used. We expect this method to aid in the study of electrical phenomena on solid-liquid interfaces.

  15. 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.

  16. Modulation of Field Electron Emission from Carbon Nanotubes by Double layer Charging

    NASA Astrophysics Data System (ADS)

    Zakhidov, Anvar

    2005-03-01

    Field emission from carbon nanotubes is well known phenomenon. In this work we present a novel method of modulating the current densities and threshold voltages. We studied field emission characteristics of HIPCO Single Walled Nanotube (SWNT) paper charged in NaCl electrolyte. The charge injection was by double layer electro chemical doping and it showed significant change in the threshold electric fields and the current densities. This was attributed mostly to a change in the work function and partially due to the change in the field enhancement factor beta. The turn on field (for 1microA of emission current) was seen to change from 1.04 V/micron to 0.82 V/micron for the negatively charged paper (Na ions) and similarly on the positively charged (Cl ions) it increased from 1.01 V/micron to 2.1 V/micron. Calculated values of the work function were compared with values from Kelvin Probe measurements. The work function values showed a significant decrease in the negatively charged samples and a sharp increase in the positively charged samples as compared to the uncharged ones. Experiments were repeated by varying the charging time from 2000 sec to 3 hrs with the current being kept constant.

  17. 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.

  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. Ionic density distributions near the charged colloids: Spherical electric double layers

    SciTech Connect

    Kim, Eun-Young; Kim, Soon-Chul

    2013-11-21

    We have studied the structure of the spherical electric double layers on charged colloids by a density functional perturbation theory, which is based both on the modified fundamental-measure theory for the hard spheres and on the one-particle direct correlation functional (DCF) for the electronic residual contribution. The contribution of one-particle DCF has been approximated as the functional integration of the second-order correlation function of the ionic fluids in a bulk phase. The calculated result is in very good agreement with the computer simulations for the ionic density distributions and the zeta potentials over a wide range of macroion sizes and electrolyte concentrations, and compares with the results of Yu et al. [J. Chem. Phys. 120, 7223 (2004)] and modified Poisson-Boltzmann approximation [L. B. Bhuiyan and C. W. Outhwaite, Condens. Matter Phys. 8, 287 (2005)]. The present theory is able to provide interesting insights about the charge inversion phenomena occurring at the interface.

  20. 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.

  1. Evidence of double layer/capacitive charging in carbon nanomaterial-based solid contact polymeric ion-selective electrodes.

    PubMed

    Cuartero, Maria; Bishop, Josiah; Walker, Raymart; Acres, Robert G; Bakker, Eric; De Marco, Roland; Crespo, Gaston A

    2016-08-11

    This paper presents the first direct spectroscopic evidence for double layer or capacitive charging of carbon nanomaterial-based solid contacts in all-solid-state polymeric ion-selective electrodes (ISEs). Here, we used synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and SR valence band (VB) spectroscopy in the elucidation of the charging mechanism of the SCs.

  2. Highly conductive nanostructured C-TiO2 electrodes with enhanced electrochemical stability and double layer charge storage capacitance.

    PubMed

    Mole, Fraser; Wang, Jue; Clayton, Daniel A; Xu, Cailing; Pan, Shanlin

    2012-07-17

    The present work reports the structural and electrochemical properties of carbon-modified nanostructured TiO(2) electrodes (C-TiO(2)) prepared by anodizing titanium in a fluoride-based electrolyte followed by thermal annealing in an atmosphere of methane and hydrogen in the presence of Fe precursors. The C-TiO(2) nanostructured electrodes are highly conductive and contain more than 1 × 10(10) /cm(2) of nanowires or nanotubes to enhance their double layer charge capacitance and electrochemical stability. Electrogenerated chemiluminescence (ECL) study shows that a C-TiO(2) electrode can replace noble metal electrodes for ultrasensitive ECL detection. Dynamic potential control experiments of redox reactions show that the C-TiO(2) electrode has a broad potential window for a redox reaction. Double layer charging capacitance of the C-TiO(2) electrode is found to be 3 orders of magnitude higher than an ideal planar electrode because of its high surface area and efficient charge collection capability from the nanowire structured surface. The effect of anodization voltage, surface treatment with Fe precursors for carbon modification, the barrier layer between the Ti substrate, and anodized layer on the double layer charging capacitance is studied. Ferrocene carboxylic acid binds covalently to the anodized Ti surface forming a self-assembled monolayer, serving as an ideal precursor layer to yield C-TiO(2) electrodes with better double layer charging performance than the other precursors.

  3. 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

  4. Bias-free, solar-charged electric double-layer capacitors.

    PubMed

    Wu, Hao; Geng, Jing; Wang, Yuhang; Wang, Yanli; Peng, Zheng; Zheng, Gengfeng

    2014-12-21

    The conversion of solar energy with simultaneous electric energy storage provides a promising means for optimizing energy utilization efficiency and reducing device volume. In this paper, a 3-dimensional mesoporous carbon coated branched TiO2 nanowire composite is rationally designed for direct conversion and storage of solar energy as electric double-layer capacitive energy. The 1-dimensional, crystalline TiO2 trunks serve as long light absorption and continuous charge transport pathways, and the high-density TiO2 branches can efficiently increase the contact area with the surface coated mesoporous carbon layers. In addition, the ordered and uniformed mesopores provide large pore sizes for electrolyte penetration, and a high surface area for charge absorption and storage. Under a 1-sun illumination and no external electric bias, this branched TiO2/mesoporous carbon composite exhibits specific capacitances of over 30 and 23.4 F g(-1), at current densities of 0.1 and 0.5 A g(-1), respectively. An excellent stability of >50 photocharging-electrical discharging cycles has also been demonstrated, suggesting the potential of further developing this hybrid material structure for simultaneous solar conversion and electric energy storage.

  5. Bimodal behaviour of charge carriers in graphene induced by electric double layer

    NASA Astrophysics Data System (ADS)

    Tsai, Sing-Jyun; Yang, Ruey-Jen

    2016-07-01

    A theoretical investigation is performed into the electronic properties of graphene in the presence of liquid as a function of the contact area ratio. It is shown that the electric double layer (EDL) formed at the interface of the graphene and the liquid causes an overlap of the conduction bands and valance bands and increases the density of state (DOS) at the Fermi energy (EF). In other words, a greater number of charge carriers are induced for transport and the graphene changes from a semiconductor to a semimetal. In addition, it is shown that the dependence of the DOS at EF on the contact area ratio has a bimodal distribution which responses to the experimental observation, a pinnacle curve. The maximum number of induced carriers is expected to occur at contact area ratios of 40% and 60%. In general, the present results indicate that modulating the EDL provides an effective means of tuning the electronic properties of graphene in the presence of liquid.

  6. Limitations and strengths of uniformly charged double-layer theory: physical significance of capacitance anomalies.

    PubMed

    Partenskii, Michael B; Jordan, Peter C

    2008-06-01

    Theoretical studies of electrical double layers typically consider the response of ionic conductors to the field of uniform charge-density distributions sigma ("sigma -control"). Many such analyses predict apparent anomalies of differential capacitance, C , including divergences and negative values. To clarify misconceptions regarding these predictions, we critically reexamine some theoretical approaches dealing with the admissible sign of C . We examine the anomalies' origin and stress its relation to the artificiality of sigma-control. We show that calculations based on sigma-control can illuminate the nature of instabilities and phase transitions under the physically attainable conditions of potential control, where applied voltage phi rather than sigma is fixed. For illustration, we discuss the physical nature of the "ultimate anomaly," negative integral capacitance predicted by some recent analyses. We also show that sigma-control anomalies can explain some experimentally observed features of C(phi) . PMID:18643227

  7. Bimodal behaviour of charge carriers in graphene induced by electric double layer

    PubMed Central

    Tsai, Sing-Jyun; Yang, Ruey-Jen

    2016-01-01

    A theoretical investigation is performed into the electronic properties of graphene in the presence of liquid as a function of the contact area ratio. It is shown that the electric double layer (EDL) formed at the interface of the graphene and the liquid causes an overlap of the conduction bands and valance bands and increases the density of state (DOS) at the Fermi energy (EF). In other words, a greater number of charge carriers are induced for transport and the graphene changes from a semiconductor to a semimetal. In addition, it is shown that the dependence of the DOS at EF on the contact area ratio has a bimodal distribution which responses to the experimental observation, a pinnacle curve. The maximum number of induced carriers is expected to occur at contact area ratios of 40% and 60%. In general, the present results indicate that modulating the EDL provides an effective means of tuning the electronic properties of graphene in the presence of liquid. PMID:27464986

  8. Dynamics of electrical double layer formation in room-temperature ionic liquids under constant-current charging conditions.

    PubMed

    Jiang, Xikai; Huang, Jingsong; Zhao, Hui; Sumpter, Bobby G; Qiao, Rui

    2014-07-16

    We report detailed simulation results on the formation dynamics of an electrical double layer (EDL) inside an electrochemical cell featuring room-temperature ionic liquids (RTILs) enclosed between two planar electrodes. Under relatively small charging currents, the evolution of cell potential from molecular dynamics (MD) simulations during charging can be suitably predicted by the Landau-Ginzburg-type continuum model proposed recently (Bazant et al 2011 Phys. Rev. Lett. 106 046102). Under very large charging currents, the cell potential from MD simulations shows pronounced oscillation during the initial stage of charging, a feature not captured by the continuum model. Such oscillation originates from the sequential growth of the ionic space charge layers near the electrode surface. This allows the evolution of EDLs in RTILs with time, an atomistic process difficult to visualize experimentally, to be studied by analyzing the cell potential under constant-current charging conditions. While the continuum model cannot predict the potential oscillation under such far-from-equilibrium charging conditions, it can nevertheless qualitatively capture the growth of cell potential during the later stage of charging. Improving the continuum model by introducing frequency-dependent dielectric constant and density-dependent ion diffusion coefficients may help to further extend the applicability of the model. The evolution of ion density profiles is also compared between the MD and the continuum model, showing good agreement.

  9. Dynamics of electrical double layer formation in room-temperature ionic liquids under constant-current charging conditions

    SciTech Connect

    Jiang, Xikai; Huang, Jingsong; Zhao, Hui; Sumpter, Bobby G; Qiao, Rui

    2014-01-01

    We report detailed simulation results on the formation dynamics of an electrical double layer (EDL) inside an electrochemical cell featuring room-temperature ionic liquids (RTILs) enclosed between two planar electrodes. Under relatively small charging currents, the evolution of cell potential during charging can be suitably predicted by the Landau-Ginzburg-type continuum model proposed recently (M. Z. Bazant, B. D. Storey, and A. A. Kornyshev, Phys. Rev. Lett., 106, 046102, 2011). Under very large charging currents, the cell potential shows pronounced oscillation during the initial stage of charging, a feature not captured by the continuum model. Such oscillation originates from the sequential growth of the ionic space charge layers near the electrode surface, allowing the evolution of EDLs in RTILs with time, an atomistic process difficult to visualize experimentally, to be studied by analyzing the cell potential under constant current charging conditions. While the continuum model cannot predict the potential oscillation under such far-from-equilibrium charging conditions, it can nevertheless qualitatively capture the growth of cell potential during the later stage of charging. Improving the continuum model by introducing frequency-dependent dielectric constant and density-dependent ion diffusion coefficients may help to further extend the applicability of the model. Keywords: ionic

  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. Improved memory characteristics of charge trap memory by employing double layered ZrO2 nanocrystals and inserted Al2O3

    NASA Astrophysics Data System (ADS)

    Tang, Z. J.; Li, R.; Zhang, X. W.; Hu, D.; Zhao, Y. G.

    2016-07-01

    The charge trap memory capacitors incorporating a stacked charge trapping layer consisting of double layered ZrO2 nanocrystals (NCs) and inserted Al2O3 have been fabricated and investigated. It is observed that the memory capacitor with stacked trapping layer exhibits a hysteresis window as large as 14.3 V for ±10 V sweeping gate voltage range, faster program/erase speed, improved endurance performance, and good data retention characteristics with smaller extrapolated ten years charge loss at room temperature and 125 °C compared to single layered NCs. The special energy band alignment and the introduced additional traps of double layered ZrO2 NCs and inserted Al2O3 change the trapping and loss behavior of charges, and jointly contribute to the remarkable memory characteristics. Therefore, the memory capacitor with a stacked charge trapping layer is a promising candidate in future nonvolatile charge trap memory device design and application.

  12. Effects of the internal structure of spheroidal divalent ions on the charge density profiles of the electric double layer.

    PubMed

    Ibarra-Armenta, José Guadalupe; Martín-Molina, Alberto; Bohinc, Klemen; Quesada-Pérez, Manuel

    2012-12-14

    In this work, the effects of the internal structure of charge for ions are analyzed by means of Monte Carlo simulations within a modified primitive model of electric double layer with spheroidal ions. The simulation results are compared to those obtained from a generalized Poisson-Boltzmann theory, where the separation of the charges within the spheroidal ions is considered. The spheroidal divalent ions have finite dimensions and two identical unitary charges separated by a distance of one diameter. Two structurally equivalent but oppositely charged ionic species are considered: coions and counterions. In the simulation, the number of particles is not fixed and the grand canonical ensemble is employed to reach the thermodynamic equilibrium. Meanwhile, the variational theory is applied to the analytical density functional. The fixed separation between charges within the spheroidal ions causes the orientational ordering of the spheroidal ions (with quadrupolar charge distributions) leading to very different charge distributions than those of the regular divalent ions from the primitive model of electrolyte. The internal structure of ions could be dramatically relevant for the modelling of large molecules, which are known to posses complex charge distributions. PMID:23249020

  13. 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.

  14. 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.

  15. Electrical double layer at dielectric liquid/solid interface. Space charge measurements using the thermal step methods

    SciTech Connect

    Toureille, A.; Touchard, G.; Richardson, T.

    1996-12-31

    The experimental evidence of the Electrical Double Layer (EDL) at the Dielectric Liquid-Solid Interface is an important question: first, it is a fundamental problem which has given several physical models and then numerous industrial applications concerns electrical engineering (transformers, wet cables and capacitors). The Thermal Step Technique, recently, has shown its great sensitivity to measure space charge in several geometries in particular in cables. So this method has been tried here to verify the assumptions made in models established few years ago.

  16. Variable charge and electrical double layer of mineral-water interfaces: silver halides versus metal (hydr)oxides.

    PubMed

    Hiemstra, Tjisse

    2012-11-01

    Classically, silver (Ag) halides have been used to understand thermodynamic principles of the charging process and the corresponding development of the electrical double layer (EDL). A mechanistic approach to the processes on the molecular level has not yet been carried out using advanced surface complexation modeling (SCM) as applied to metal (hydr)oxide interfaces. Ag halides and metal (hydr)oxides behave quite differently in some respect. The location of charge in the interface of Ag halides is not a priori obvious. For AgI(s), SCM indicates the separation of interfacial charge in which the smaller silver ions are apparently farther away from the surface than iodide. This charge separation can be understood from the surface structure of the relevant crystal faces. Charge separation with positive charge above the surface is due to monodentate surface complex formation of Ag(+) ions binding to I sites located at the surface. Negative surface charge is due to the desorption of Ag(+) ions out of the lattice. These processes can be described with the charge distribution (CD) model. The MO/DFT optimized geometry of the complex is used to estimate the value of the CD. SCM reveals the EDL structure of AgI(s), having two Stern layers in series. The inner Stern layer has a very low capacitance (C(1) = 0.15 ± 0.01 F/m(2)) in comparison to that of metal (hydr)oxides, and this can be attributed to the strong orientation of the (primary) water molecules on the local electrostatic field of the Ag(+) and I(-) ions of the surface (relative dielectric constant ε(r) ≈ 6). Depending on the extent of water ordering, mineral surfaces may in principle develop a second Stern layer. The corresponding capacitance (C(2)) will depend on the degree of water ordering that may decrease in the series AgI (C(2) = 0.57 F/m(2)), goethite (C(2) = 0.74 F/m(2)), and rutile (C(2) = ∞), as discussed. The charging principles of AgI minerals iodargyrite and miersite may also be applied to minerals

  17. Dust-acoustic solitary waves and double layers in a magnetized dusty plasma with nonthermal ions and dust charge variation

    SciTech Connect

    El-Taibany, W.F.; Sabry, R.

    2005-08-15

    The effect of nonthermal ions and variable dust charge on small-amplitude nonlinear dust-acoustic (DA) waves is investigated. It is found that both compressive and rarefactive solitons exist and depend on the nonthermal parameter a. Using a reductive perturbation theory, a Zakharov-Kuznetsov (ZK) equation is derived. At critical value of a, a{sub c}, a modified ZK equation with third- and fourth-order nonlinearities, is obtained. Depending on a, the solution of the evolution equation reveals whether there is coexistence of both compressive and rarefactive solitary waves or double layers (DLs) with the possibility of their two kinds. In addition, for certain plasma parameters, the solitary wave disappears and a DL is expected. The variation of dust charge number, wave velocity, and soliton amplitude and its width against system parameters is investigated for the DA solitary waves. It is shown that the incorporation of both the adiabatic dust-charge variation and the nonthermal distributed ions modifies significantly the nature of DA solitary waves and DA DLs. The findings of this investigation may be useful in understanding the ion acceleration mechanisms close to the Moon and also enhances our knowledge on pickup ions around unmagnetized bodies, such as comets, Mars, and Venus.

  18. Atomistic and molecular effects in electric double layers at high surface charges

    SciTech Connect

    Templeton, Jeremy Alan; Lee, Jonathan; Mani, Ali

    2015-06-16

    Here, the Poisson–Boltzmann theory for electrolytes near a charged surface is known to be invalid due to unaccounted physics associated with high ion concentration regimes. In order to investigate this regime, fluids density functional theory (f-DFT) and molecular dynamics (MD) simulations were used to determine electric surface potential as a function of surface charge. Based on these detailed computations, for electrolytes with nonpolar solvent, the surface potential is shown to depend quadratically on the surface charge in the high charge limit. We demonstrate that modified Poisson–Boltzmann theories can model this limit if they are augmented with atomic packing densities provided by MD. However, when the solvent is a highly polar molecule water an intermediate regime is identified in which a constant capacitance is realized. Simulation results demonstrate the mechanism underlying this regime, and for the salt water system studied here, it persists throughout the range of physically realistic surface charge densities so the potential’s quadratic surface charge dependence is not obtained.

  19. Understanding the spurious DFT fractional charge in the electrochemical double layer

    NASA Astrophysics Data System (ADS)

    Chen, Leanne; Bajdich, Michal; Luntz, Alan; Chan, Karen; Norskov, Jens

    An ongoing challenge in computational electrochemistry is the accurate determination of electrochemical barriers at constant electrode potential. Recently, our group developed an efficient scheme to determine the barriers using a simple extrapolation based on the interfacial charge. However, semilocal DFT calculations have shown that the magnitude of the charge of solvated species (H3O+, OH-, Li+, Na+) in the outer Helmholtz plane is not 1e, but always near 0.6e, which suggests a charge delocalization error in DFT. Furthermore, we frequently observe inaccurate alignment of the metal Fermi and solvent energy levels. Using an increasing amount of exact exchange, we first analyze the charge delocalization error in the dissociation of NaCl molecule, where a large amount of exchange is need to reproduce the step-like transition of charge from +1 to 0 on the dissociated Na and Cl. Next, we apply the same method to the metal-water interface with solvated ions at varying distances from the surface. The performance of hybrid and other fractional charge-corrected functionals will be discussed together with the possibility of a simple correction scheme.

  20. Atomistic and molecular effects in electric double layers at high surface charges

    DOE PAGESBeta

    Templeton, Jeremy Alan; Lee, Jonathan; Mani, Ali

    2015-06-16

    Here, the Poisson–Boltzmann theory for electrolytes near a charged surface is known to be invalid due to unaccounted physics associated with high ion concentration regimes. In order to investigate this regime, fluids density functional theory (f-DFT) and molecular dynamics (MD) simulations were used to determine electric surface potential as a function of surface charge. Based on these detailed computations, for electrolytes with nonpolar solvent, the surface potential is shown to depend quadratically on the surface charge in the high charge limit. We demonstrate that modified Poisson–Boltzmann theories can model this limit if they are augmented with atomic packing densities providedmore » by MD. However, when the solvent is a highly polar molecule water an intermediate regime is identified in which a constant capacitance is realized. Simulation results demonstrate the mechanism underlying this regime, and for the salt water system studied here, it persists throughout the range of physically realistic surface charge densities so the potential’s quadratic surface charge dependence is not obtained.« less

  1. Simulation of electric double layers around charged colloids in aqueous solution of variable permittivity.

    PubMed

    Fahrenberger, Florian; Xu, Zhenli; Holm, Christian

    2014-08-14

    The ion distribution around charged colloids in solution has been investigated intensely during the last decade. However, few theoretical approaches have included the influence of variation in the dielectric permittivity within the system, let alone in the surrounding solvent. In this article, we introduce two relatively new methods that can solve the Poisson equation for systems with varying permittivity. The harmonic interpolation method approximately solves the Green's function in terms of a spherical harmonics series, and thus provides analytical ion-ion potentials for the Hamiltonian of charged systems. The Maxwell equations molecular dynamics algorithm features a local approach to electrostatics, allowing for arbitrary local changes of the dielectric constant. We show that the results of both methods are in very good agreement. We also found that the renormalized charge of the colloid, and with it the effective far field interaction, significantly changes if the dielectric properties within the vicinity of the colloid are changed. PMID:25134594

  2. 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.

  3. 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.

  4. 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…

  5. 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.

  6. Dynamical Generation of Quasi-Stationary Alfvenic Double Layers and Charge Holes and Unified Theory of Quasi-Static and Alfvenic Auroral Arc Formation

    NASA Astrophysics Data System (ADS)

    Song, Y.; Lysak, R. L.

    2015-12-01

    Parallel E-fields play a crucial role for the acceleration of charged particles, creating discrete aurorae. However, once the parallel electric fields are produced, they will disappear right away, unless the electric fields can be continuously generated and sustained for a fairly long time. Thus, the crucial question in auroral physics is how to generate such a powerful and self-sustained parallel electric fields which can effectively accelerate charge particles to high energy during a fairly long time. We propose that nonlinear interaction of incident and reflected Alfven wave packets in inhomogeneous auroral acceleration region can produce quasi-stationary non-propagating electromagnetic plasma structures, such as Alfvenic double layers (DLs) and Charge Holes. Such Alfvenic quasi-static structures often constitute powerful high energy particle accelerators. The Alfvenic DL consists of localized self-sustained powerful electrostatic electric fields nested in a low density cavity and surrounded by enhanced magnetic and mechanical stresses. The enhanced magnetic and velocity fields carrying the free energy serve as a local dynamo, which continuously create the electrostatic parallel electric field for a fairly long time. The generated parallel electric fields will deepen the seed low density cavity, which then further quickly boosts the stronger parallel electric fields creating both Alfvenic and quasi-static discrete aurorae. The parallel electrostatic electric field can also cause ion outflow, perpendicular ion acceleration and heating, and may excite Auroral Kilometric Radiation.

  7. 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.

  8. Solvent Role in the Formation of Electric Double Layers with Surface Charge Regulation: A Bystander or a Key Participant?

    NASA Astrophysics Data System (ADS)

    Fleharty, Mark E.; van Swol, Frank; Petsev, Dimiter N.

    2016-01-01

    The charge formation at interfaces involving electrolyte solutions is due to the chemical equilibrium between the surface reactive groups and the potential determining ions in the solution (i.e., charge regulation). In this Letter we report our findings that this equilibrium is strongly coupled to the precise molecular structure of the solution near the charged interface. The neutral solvent molecules dominate this structure due to their overwhelmingly large number. Treating the solvent as a structureless continuum leads to a fundamentally inadequate physical picture of charged interfaces. We show that a proper account of the solvent effect leads to an unexpected and complex system behavior that is affected by the molecular and ionic excluded volumes and van der Waals interactions.

  9. Solvent Role in the Formation of Electric Double Layers with Surface Charge Regulation: A Bystander or a Key Participant?

    PubMed

    Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

    2016-01-29

    The charge formation at interfaces involving electrolyte solutions is due to the chemical equilibrium between the surface reactive groups and the potential determining ions in the solution (i.e., charge regulation). In this Letter we report our findings that this equilibrium is strongly coupled to the precise molecular structure of the solution near the charged interface. The neutral solvent molecules dominate this structure due to their overwhelmingly large number. Treating the solvent as a structureless continuum leads to a fundamentally inadequate physical picture of charged interfaces. We show that a proper account of the solvent effect leads to an unexpected and complex system behavior that is affected by the molecular and ionic excluded volumes and van der Waals interactions. PMID:26871358

  10. Emitter space charge layer transit time in bipolar junction transistors

    NASA Astrophysics Data System (ADS)

    Rustagi, S. C.; Chattopadhyaya, S. K.

    1981-04-01

    The charge defined emitter space charge layer transit times of double diffused transistors have been calculated using a regional approach, and compared with the corresponding base transit times. The results obtained for emitter space-charge layer transit times have been discussed with reference to the capacitance analysis of Morgan and Smit (1960) for graded p-n junctions.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. Molecular dynamics simulation of the spherical electrical double layer of a soft nanoparticle: effect of the surface charge and counterion valence.

    PubMed

    Nedyalkova, Miroslava; Madurga, Sergio; Pisov, Stoyan; Pastor, Isabel; Vilaseca, Eudald; Mas, Francesc

    2012-11-01

    Molecular dynamics simulations were performed to study the ion and water distribution around a spherical charged nanoparticle. A soft nanoparticle model was designed using a set of hydrophobic interaction sites distributed in six concentric spherical layers. In order to simulate the effect of charged functionalyzed groups on the nanoparticle surface, a set of charged sites were distributed in the outer layer. Four charged nanoparticle models, from a surface charge value of -0.035 C m(-2) to -0.28 C m(-2), were studied in NaCl and CaCl(2) salt solutions at 1 M and 0.1 M concentrations to evaluate the effect of the surface charge, counterion valence, and concentration of added salt. We obtain that Na(+) and Ca(2+) ions enter inside the soft nanoparticle. Monovalent ions are more accumulated inside the nanoparticle surface, whereas divalent ions are more accumulated just in the plane of the nanoparticle surface sites. The increasing of the the salt concentration has little effect on the internalization of counterions, but significantly reduces the number of water molecules that enter inside the nanoparticle. The manner of distributing the surface charge in the nanoparticle (uniformly over all surface sites or discretely over a limited set of randomly selected sites) considerably affects the distribution of counterions in the proximities of the nanoparticle surface.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Pion double charge exchange and hadron dynamics

    SciTech Connect

    Johnson, M.B.

    1991-01-01

    This paper will review theoretical results to show how pion double charge exchange is contributing to our understanding of hadron dynamics in nuclei. The exploitation of the nucleus as a filter is shown to be essential in facilitating the comparison between theory and experiment. 23 refs., 3 figs., 2 tabs.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Systematics of pion double charge exchange

    SciTech Connect

    Gilman, R.A.

    1985-10-01

    Differential cross sections have been measured for pion-induced double-charge-exchange (DCX) reactions leading to double-isobaric-analog states (DIAS) and low-lying nonanalog states in the residual nuclei. A description of the experimental details and data analysis is presented. The experimentally observed systematics of reactions leading to DIAS, to nonanalog ground states, and to low-lying 2 states are described. Lowest-order optical-model calculations of DIAS DCX are compared to the data. Efforts to understand the anomalies by invoking additional reaction-mechanism amplitudes and a higher-order optical potential are described. Calculations of nonanalog DCX reactions leading to J/sup / = 0 states were performed within a distorted-wave impulse-approximation framework. The sensitivities of these calculations to input parameters are discussed. 58 refs., 41 figs., 16 tabs.

  18. Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-} redox in the interlayer determined by the charge density of Zn{sub n}Cr-layered double hydroxides

    SciTech Connect

    Zhang, Jia; Xu, Yunfeng; Liu, Jiangyong; Zhou, Jizhi; Xu, Zhi Ping; Qian, Guangren

    2013-02-15

    Redox of Fe(CN){sub 6}{sup 3-} and Fe(CN){sub 6}{sup 4-} in the ZnCr layered double hydroxide interlayer has been investigated. The conversion from Fe(CN){sub 6}{sup 3-} to Fe(CN){sub 6}{sup 4-} or from Fe(CN){sub 6}{sup 4-} to Fe(CN){sub 6}{sup 3-} in the ZnCr-LDH interlayer has been confirmed, depending on the Zn:Cr molar ratio. Both Fe(CN){sub 6}{sup 3-} and Fe(CN){sub 6}{sup 4-} are observed in all samples no matter whether the initial anion is Fe(CN){sub 6}{sup 3-} or Fe(CN){sub 6}{sup 4-} before precipitation. Deconvolution of the FTIR band around 2100 cm{sup -1} reveals that the relative amount of Fe(CN){sub 6}{sup 4-} and Fe(CN){sub 6}{sup 3-} in the LDH interlayer is considerably dependent on the Zn:Cr molar ratio. In brief, Fe(CN){sub 6}{sup 4-} is preferred at the ratio of 2:1 while there is more Fe(CN){sub 6}{sup 3-} in the ratio of 4:1. Therefore, it is our hypothesis that the charge density of the hydroxide layer is a key factor that directs the redox of Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-}. The possible redox processes have also been proposed. - Graphical abstract: Redox reactions of Fe(CN){sub 6}{sup 3-} and Fe(CN){sub 6}{sup 4-} take place in the ZnCr layered double hydroxide (LDH) interlayer, which are reflected by Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-} FTIR area ratio. Highlights: Black-Right-Pointing-Pointer An interlayer redox phenomena was observed in Fe(CN){sub 6}{sup 3/4-} intercalated ZnCr-LDHs. Black-Right-Pointing-Pointer The ratio of interlayer redox was examined by FTIR fitting analysis. Black-Right-Pointing-Pointer The tendency of redox was influenced by Zn:Cr molar ratio. Black-Right-Pointing-Pointer The mechanism relies on the charge density of metal hydroxyl layer.

  19. 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.

  20. 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

  1. 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.

  2. Double charge exchange at high impact energies

    NASA Astrophysics Data System (ADS)

    Belkić, Dževad

    1994-03-01

    In fast ion-atom collisions, double ionization always dominates the two-electron transfer. For this reason, an adequate description of double charge exchange requires proper inclusion of intermediate ionization channels. This is even more important in two- than in one-electron transitions. First-order Born-type perturbation theories ignore throughout these electronic continuum intermediate states and hence provide utterly unreliable high energy cross sections for two-electron capture processes. Therefore, it is essential to use second- and higher-order theories, which include the intermediate ionization continua of the two electrons in an approximate manner. In the present paper, a new second-order theory called the Born distorted wave (BDW) approximation is introduced and implemented in the case of symmetric resonant double electron capture from the ground state of helium by fast alpha particles. A genuine four-body formalism is adopted, in contrast to the conventional independent particle model of atomic scattering theory. The obtained results for the total cross sections are compared with the available experimental data, and satisfactory agreement is recorded. As the incident energy increases, a dramatic improvement is obtained in going from the CB1 to the BDW approximation, since the latter closely follows the measurement, whereas the former overestimates the observed total cross sections by two orders of magnitude. This strongly indicates that the role of continuum intermediate states is decisive, even at those incident energies for which the Thomas double scattering effects are not important. This is in sharp contrast to the case of one-electron transfer atomic reactions.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  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.

    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.

  10. 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.

  11. 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.

  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. Effect of (HfO2) X (Al2O3)1- X /SiO2 double-layered blocking oxide on program and erase speed in charge trapping memory devices

    NASA Astrophysics Data System (ADS)

    Oh, Jinho; Ko, Eun Jung; Na, Heedo; Ko, Dae-Hong; Sohn, Hyunchul

    2016-03-01

    In this work, the effect of hole injection into the charge trap layers from channel prior to program operation is investigated in charge trapping (CT) memory with stacked blocking oxide (BO). For efficient hole injection, a (HfO2) X (Al2O3)1 - X /SiO2 stacked BO structure is used. The CT memory device with stacked BO shows faster programming and erasing speed compared with single-layered SiO2 BO. The enhanced programming speed is attributed to the enhanced electric field introduced by excess holes injected into SiN charge trap layer. In addition, efficient hole injection from channel produced the widened memory window in CT memory.

  14. Quantum capacitance and charge sensing of a superconducting double dot

    NASA Astrophysics Data System (ADS)

    Lambert, N. J.; Esmail, A. A.; Edwards, M.; Pollock, F. A.; Lovett, B. W.; Ferguson, A. J.

    2016-09-01

    We study the energetics of a superconducting double dot, by measuring both the quantum capacitance of the device and the response of a nearby charge sensor. We observe different behaviour for odd and even charge states and describe this with a model based on the competition between the charging energy and the superconducting gap. We also find that, at finite temperatures, thermodynamic considerations have a significant effect on the charge stability diagram.

  15. Flow through a charged biopolymer layer

    NASA Astrophysics Data System (ADS)

    Mokady, A. J.; Mestel, A. J.; Winlove, C. P.

    1999-03-01

    The polyelectrolyte layer coating mammalian cells, known as the glycocalyx, is important in communicating flow information to the cell. In this paper, the layer is modelled as a semi-infinite, doubly periodic array of parallel charged cylinders. The electric potential and ion distributions surrounding such an array are found using the Poisson Boltzmann equation and an iterative domain decomposition technique. Similar methods are used to calculate Stokes flows, driven either by a shear at infinity or by an electric field, parallel or transverse to the cylinders. The resulting electric streaming currents due to flow over endothelial cells, and the electrophoretic mobilities of red blood cells are deduced as functions of polymer concentration and electrolyte molarity. It is shown that only the top portion of the layer is important in these effects.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Determination of layer-charge characteristics of smectites

    USGS Publications Warehouse

    Christidis, G.E.; Eberl, D.D.

    2003-01-01

    A new method for calculation of layer charge and charge distribution of smectites is proposed. The method is based on comparisons between X-ray diffraction (XRD) patterns of K-saturated, ethylene glycol-solvated, oriented samples and calculated XRD patterns for three-component, mixed-layer systems. For the calculated patterns it is assumed that the measured patterns can be modeled as random interstratifications of fully expanding 17.1 A?? layers, partially expanding 13.5 A?? layers and non-expanding 9.98 A?? layers. The technique was tested using 29 well characterized smectites. According to their XRD patterns, smectites were classified as group 1 (low-charge smectites) and group 2 (high-charge smectites). The boundary between the two groups is at a layer charge of -0.46 equivalents per half unit-cell. Low-charge smectites are dominated by 17.1 A?? layers, whereas high-charge smectites contain only 20% fully expandable layers on average. Smectite properties and industrial applications may be dictated by the proportion of 17.1 A?? layers present. Non-expanding layers may control the behavior of smectites during weathering, facilitating the formation of illite layers after subsequent cycles of wetting and drying. The precision of the method is better than 3.5% at a layer charge of -0.50; therefore the method should be useful for basic research and for industrial purposes.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Intershell interaction in double walled carbon nanotubes: Charge transfer and orbital mixing

    NASA Astrophysics Data System (ADS)

    Zólyomi, V.; Koltai, J.; Rusznyák, Á.; Kürti, J.; Gali, Á.; Simon, F.; Kuzmany, H.; Szabados, Á.; Surján, P. R.

    2008-06-01

    Recent nuclear-magnetic-resonance measurements on isotope engineered double walled carbon nanotubes (DWCNTs) surprisingly suggest a uniformly metallic character of all nanotubes, which can only be explained by the interaction between the layers. Here we study the intershell interaction in DWCNTs by density-functional theory and the intermolecular Hückel model. Both methods find charge transfer between the inner and outer tubes. We find that the charge transfer between the walls is on the order of 0.001e-/atom and that the inner tube is always negatively charged. We also observe orbital mixing between the states of the layers. We find that these two effects combined can in some cases lead to a semiconductor-to-metal transition of the double walled tube, but not necessarily in all cases. We extend our study to multiwalled nanotubes as well, with up to six layers in total. We find similar behavior as in the case of DWCNTs: electrons tend to be transferred from the outermost layer toward the innermost one. We find a notable peculiarity in the charge transfer when the (5,0) tube is present as the innermost tube; we attribute this to the σ-π mixing in such small diameter tubes.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  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. 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.

  7. Layer Charge of Clay Minerals; Selected papers from the Symposium on Current Knowledge on the Layer Charge of Clay Minerals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This Special issue contains papers based on the contributions presented during the workshop “Current Knowledge on the Layer Charge of Clay Minerals”, held on September 18 and 19, 2004, in the Smolenice Castle, Slovakia. Layer charge is one of the most important characteristics of clay minerals as it...

  8. Analysis of carrier transport and carrier trapping in organic diodes with polyimide-6,13-Bis(triisopropylsilylethynyl)pentacene double-layer by charge modulation spectroscopy and optical second harmonic generation measurement

    SciTech Connect

    Lim, Eunju E-mail: taguchi.d.aa@m.titech.ac.jp; Taguchi, Dai E-mail: taguchi.d.aa@m.titech.ac.jp Iwamoto, Mitsumasa E-mail: taguchi.d.aa@m.titech.ac.jp

    2014-08-18

    We studied the carrier transport and carrier trapping in indium tin oxide/polyimide (PI)/6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)/Au diodes by using charge modulation spectroscopy (CMS) and time-resolved electric field induced optical second harmonic generation (TR-EFISHG) measurements. TR-EFISHG directly probes the spatial carrier behaviors in the diodes, and CMS is useful in explaining the carrier motion with respect to energy. The results clearly indicate that the injected carriers move across TIPS-pentacene thorough the molecular energy states of TIPS-pentacene and accumulate at the PI/TIPS-pentacene interface. However, some carriers are trapped in the PI layers. These findings take into account the capacitance-voltage and current-voltage characteristics of the diodes.

  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. 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.

  11. 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.

  12. Ion-acoustic double layers in a five component cometary plasma with kappa described electrons and ions

    NASA Astrophysics Data System (ADS)

    Michael, Manesh; Venugopal, C.; Sreekala, G.; Willington, Neethu Theresa; Sebastian, Sijo

    2016-07-01

    We investigate the propagation characteristics of Ion-acoustic solitons and double layers in a five component cometary plasma consisting of positively and negatively charged oxygen ions, kappa described hydrogen ions, hot solar electrons, and slightly colder cometary electrons. The KdV and modified KdV equations are derived for the system and its solution is plotted for different kappa values and negatively charged oxygen ion densities. It is found that the strength of double layer increases with increasing spectral indices. It, however, decreases with increasing negatively charged oxygen ion densities. The parameter for the transition from compressive to rarefactive soliton is also specified. The presence of negatively charged oxygen ions can significantly affect the nonlinearity coefficients (both quadratic and cubic) of a double layer.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Pion double charge exchange scattering above the delta resonance

    SciTech Connect

    Burleson, G.R.

    1989-01-01

    Data are presented on pion-nucleus double-charge-exchange scattering at energies between 300 and 500 MeV, the highest energies measured so far, together with a review of results at lower energies. The small-angle excitation functions disagree with predictions based on a sex-quark cluster model and on an optical model consistent with single-charge-exchange scattering at these energies, but they are consistent with a distorted-wave calculation. Data on f{sub 7/2}-shell nuclei are in partial agreement with a two-amplitude model which is successful at lower energies. In order to achieve good understanding of this process at these energies, more work; both experimental and theoretical, is needed. 16 refs., 6 figs.

  2. 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.

  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

    2016-01-01

    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

  4. 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.

  5. 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

  6. 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

  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. Ion specific effects on the stability of layered double hydroxide colloids.

    PubMed

    Pavlovic, Marko; Huber, Robin; Adok-Sipiczki, Monika; Nardin, Corinne; Szilagyi, Istvan

    2016-05-01

    Positively charged layered double hydroxide particles composed of Mg(2+) and Al(3+) layer-forming cations and NO3(-) charge compensating anions (MgAl-NO3-LDH) were synthesized and the colloidal stability of their aqueous suspensions was investigated in the presence of inorganic anions of different charges. The formation of the layered structure was confirmed by X-ray diffraction, while the charging and aggregation properties were explored by electrophoresis and light scattering. The monovalent anions adsorb on the oppositely charged surface to a different extent according to their hydration state leading to the Cl(-) > NO3(-) > SCN(-) > HCO3(-) order in surface charge densities. The ions on the right side of the series induce the aggregation of MgAl-NO3-LDH particles at lower concentrations, whereas in the presence of the left ones, the suspensions are stable even at higher salt levels. The adsorption of multivalent anions gave rise to charge neutralization and charge reversal at appropriate concentrations. For some di, tri and tetravalent ions, charge reversal resulted in restabilization of the suspensions in the intermediate salt concentration regime. Stable samples were also observed at low salt levels. Particle aggregation was fast near the charge neutralization point and at high concentrations. These results, which evidence the colloidal stability of MgAl-NO3-LDH in the presence of various anions, are of prime fundamental interest. These are also critical for applications to develop stable suspensions of primary particles for water purification processes, with the aim of the removal of similar anions by ion exchange. PMID:26997621

  9. 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.

  10. 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

  11. 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.

  12. Evaluation of molecular dynamics simulation methods for ionic liquid electric double layers.

    PubMed

    Haskins, Justin B; Lawson, John W

    2016-05-14

    We investigate how systematically increasing the accuracy of various molecular dynamics modeling techniques influences the structure and capacitance of ionic liquid electric double layers (EDLs). The techniques probed concern long-range electrostatic interactions, electrode charging (constant charge versus constant potential conditions), and electrolyte polarizability. Our simulations are performed on a quasi-two-dimensional, or slab-like, model capacitor, which is composed of a polarizable ionic liquid electrolyte, [EMIM][BF4], interfaced between two graphite electrodes. To ensure an accurate representation of EDL differential capacitance, we derive new fluctuation formulas that resolve the differential capacitance as a function of electrode charge or electrode potential. The magnitude of differential capacitance shows sensitivity to different long-range electrostatic summation techniques, while the shape of differential capacitance is affected by charging technique and the polarizability of the electrolyte. For long-range summation techniques, errors in magnitude can be mitigated by employing two-dimensional or corrected three dimensional electrostatic summations, which led to electric fields that conform to those of a classical electrostatic parallel plate capacitor. With respect to charging, the changes in shape are a result of ions in the Stern layer (i.e., ions at the electrode surface) having a higher electrostatic affinity to constant potential electrodes than to constant charge electrodes. For electrolyte polarizability, shape changes originate from induced dipoles that soften the interaction of Stern layer ions with the electrode. The softening is traced to ion correlations vertical to the electrode surface that induce dipoles that oppose double layer formation. In general, our analysis indicates an accuracy dependent differential capacitance profile that transitions from the characteristic camel shape with coarser representations to a more diffuse

  13. Evaluation of molecular dynamics simulation methods for ionic liquid electric double layers

    NASA Astrophysics Data System (ADS)

    Haskins, Justin B.; Lawson, John W.

    2016-05-01

    We investigate how systematically increasing the accuracy of various molecular dynamics modeling techniques influences the structure and capacitance of ionic liquid electric double layers (EDLs). The techniques probed concern long-range electrostatic interactions, electrode charging (constant charge versus constant potential conditions), and electrolyte polarizability. Our simulations are performed on a quasi-two-dimensional, or slab-like, model capacitor, which is composed of a polarizable ionic liquid electrolyte, [EMIM][BF4], interfaced between two graphite electrodes. To ensure an accurate representation of EDL differential capacitance, we derive new fluctuation formulas that resolve the differential capacitance as a function of electrode charge or electrode potential. The magnitude of differential capacitance shows sensitivity to different long-range electrostatic summation techniques, while the shape of differential capacitance is affected by charging technique and the polarizability of the electrolyte. For long-range summation techniques, errors in magnitude can be mitigated by employing two-dimensional or corrected three dimensional electrostatic summations, which led to electric fields that conform to those of a classical electrostatic parallel plate capacitor. With respect to charging, the changes in shape are a result of ions in the Stern layer (i.e., ions at the electrode surface) having a higher electrostatic affinity to constant potential electrodes than to constant charge electrodes. For electrolyte polarizability, shape changes originate from induced dipoles that soften the interaction of Stern layer ions with the electrode. The softening is traced to ion correlations vertical to the electrode surface that induce dipoles that oppose double layer formation. In general, our analysis indicates an accuracy dependent differential capacitance profile that transitions from the characteristic camel shape with coarser representations to a more diffuse

  14. Evaluation of molecular dynamics simulation methods for ionic liquid electric double layers.

    PubMed

    Haskins, Justin B; Lawson, John W

    2016-05-14

    We investigate how systematically increasing the accuracy of various molecular dynamics modeling techniques influences the structure and capacitance of ionic liquid electric double layers (EDLs). The techniques probed concern long-range electrostatic interactions, electrode charging (constant charge versus constant potential conditions), and electrolyte polarizability. Our simulations are performed on a quasi-two-dimensional, or slab-like, model capacitor, which is composed of a polarizable ionic liquid electrolyte, [EMIM][BF4], interfaced between two graphite electrodes. To ensure an accurate representation of EDL differential capacitance, we derive new fluctuation formulas that resolve the differential capacitance as a function of electrode charge or electrode potential. The magnitude of differential capacitance shows sensitivity to different long-range electrostatic summation techniques, while the shape of differential capacitance is affected by charging technique and the polarizability of the electrolyte. For long-range summation techniques, errors in magnitude can be mitigated by employing two-dimensional or corrected three dimensional electrostatic summations, which led to electric fields that conform to those of a classical electrostatic parallel plate capacitor. With respect to charging, the changes in shape are a result of ions in the Stern layer (i.e., ions at the electrode surface) having a higher electrostatic affinity to constant potential electrodes than to constant charge electrodes. For electrolyte polarizability, shape changes originate from induced dipoles that soften the interaction of Stern layer ions with the electrode. The softening is traced to ion correlations vertical to the electrode surface that induce dipoles that oppose double layer formation. In general, our analysis indicates an accuracy dependent differential capacitance profile that transitions from the characteristic camel shape with coarser representations to a more diffuse

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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

  2. Emergence of a Stern Layer from the Incorporation of Hydration Interactions into the Gouy-Chapman Model of the Electrical Double Layer.

    PubMed

    Brown, Matthew A; Bossa, Guilherme Volpe; May, Sylvio

    2015-10-27

    In one of the most commonly used phenomenological descriptions of the electrical double layer, a charged solid surface and a diffuse region of mobile ions are separated from each other by a thin charge-depleted Stern layer. The Stern layer acts as a capacitor that improves the classical Gouy-Chapman model by increasing the magnitude of the surface potential and limiting the maximal counterion concentration. We show that very similar Stern-like properties of the diffuse double layer emerge naturally from adding a nonelectrostatic hydration repulsion to the electrostatic Coulomb potential. The interplay of electrostatic attraction and hydration repulsion of the counterions and the surface leads to the formation of a diffuse counterion layer that remains well separated from the surface. In addition, hydration repulsions between the ions limit and control the maximal ion concentration and widen the width of the diffuse double layer. Our mean-field model, which we express in terms of electrostatic and hydration potentials, is physically consistent and conceptually similar to the classical Gouy-Chapman model. It allows the incorporation of ion specificity, accounts for hydration properties of charged surfaces, and predicts Stern layer properties, which we analyze in terms of the effective size of the hydrated counterions. PMID:26474036

  3. 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.

  4. Double Photoionization of Beryllium atoms using Effective Charge approximation

    NASA Astrophysics Data System (ADS)

    Saha, Haripada

    2016-05-01

    We plan to report the results of our investigation on double photoionization K-shell electrons from Beryllium atoms. We will present the results of triple differential cross sections at excess energy of 20 eV using our recently extended MCHF method. We will use multiconfiguration Hartree Fock method to calculate the wave functions for the initial state. The final state wave functions will be obtained in the angle depended Effective Charge approximation which accounts for electron correlation between the two final state continuum electrons. We will discuss the effect of core correlation and the valence shell electrons in the triple differential cross section. The results will be compared with the available accurate theoretical calculations and experimental findings.

  5. Pion double charge exchange in a composite-meson model

    SciTech Connect

    Kezerashvili, R. Ya.; Boyko, V. S.

    2007-01-15

    The pion double charge exchange amplitude is evaluated in a composite-meson model based on the four-quark interaction. The model assumes that the mesons are two-quark systems and can interact with each other only through quark loops. To evaluate the meson exchange current contribution, the form factors of the two-pion decay modes of the {rho},{sigma}, and f{sub 0} mesons have been used in the calculations. The contribution of the four-quark box diagram has been taken into account as well as a contact diagram. The contributions of the {rho},{sigma}, and f{sub 0} mesons increase the forward scattering cross section, which depends weakly on the energy.

  6. 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-charge

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

    USGS Publications Warehouse

    Christidis, G.E.; Blum, A.E.; Eberl, D.D.

    2006-01-01

    The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644-655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na2CO3, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of - 0.425 to - 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed. ?? 2006 Elsevier B.V. All rights reserved.

  13. 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

  14. 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

  15. Photochemistry in constrained spaces: Zeolites and layered double metal hydroxides. Progress report, September 15, 1993--September 15, 1994

    SciTech Connect

    Dutta, P.K.

    1995-02-01

    The authors have continued their research in the area of assembly and reactivity of photochemical systems in zeolites and double layered metal hydroxides. Over the last year, the authors have focused on two issues, increasing the photochemical efficiency of charge separation in a triad system and the chemistry of Ru(bpy){sup 3+}{sub 3} in zeolites.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. [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

  3. 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.

  4. 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.

  5. Electrical double layers and differential capacitance in molten salts from density functional theory

    DOE PAGESBeta

    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

  6. Electrical double layers and differential capacitance in molten salts from density functional theory

    SciTech Connect

    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. In 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.

  7. Electrical double layers and differential capacitance in molten salts from density functional theory.

    PubMed

    Frischknecht, Amalie L; Halligan, Deaglan O; Parks, Michael L

    2014-08-01

    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. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Molecular Simulations of Graphene-Based Electric Double-Layer Capacitors

    NASA Astrophysics Data System (ADS)

    Kalluri, Raja K.; Konatham, Deepthi; Striolo, Alberto

    2011-03-01

    Towards deploying renewable energy sources it is crucial to develop efficient and cost-effective technologies to store electricity. Traditional batteries are plagued by a number of practical problems that at present limit their widespread applicability. One possible solution is represented by electric double-layer capacitors (EDLCs). To deploy EDLCs at the large scale it is necessary to better understand how electrolytes pack and diffuse within narrow charged pores. We present here simulation results for the concentrated aqueous solutions of NaCl, CsCl, and NaI confined within charged graphene-based porous materials. We discuss how the structure of confined water, the salt concentration, the ions size, and the surface charge density determine the accumulation of electrolytes within the porous network. Our results, compared to data available for bulk systems, are critical for relating macroscopic observations to molecular-level properties of the confined working fluids. Research supported by the Department of Energy.

  16. Molecular dynamics studies of aqueous silica nanoparticle dispersions: salt effects on the double layer formation.

    PubMed

    de Lara, Lucas S; Rigo, Vagner A; Michelon, Mateus F; Metin, Cigdem O; Nguyen, Quoc P; Miranda, Caetano R

    2015-08-19

    The ion distribution around hydroxylated silica nanoparticles (NP-H) dispersed in brine was investigated by fully atomistic molecular dynamics. The NP-H dispersions in aqueous electrolyte media are simulated in solutions of varying salinity (NaCl, CaCl2, and MgCl2), salt concentration (0.06  ×  10(-3) to 3.00  ×  10(-3) mole fraction [Formula: see text]), and temperature (300 and 350 K) at 1 atm. The NP-H models reproduce the observed experimental concentration of silanol and geminal surface sites, which are responsible for local charge variations on the nanoparticles' surface. Interestingly, under certain salt concentration conditions, the formation of an electrical double layer (DL) around the overall neutral NP-H occurs. The resulting DLs are attenuated with increasing temperature for all evaluated salts. With increasing salt concentration, a sign inversion of the effective charge at the first ion layer is observed, which modifies the electrostatic environment around the nanoparticle. The minimum salt concentration that leads to a DL formation at 300 K is 1.05  ×  10(-3), 0.37  ×  10(-3), and 0.06  ×  10(-3) χs for NaCl, CaCl2, and MgCl2, respectively. The width of the DL decreases sequentially in ionic strength from NaCl to CaCl2 to MgCl2, which is similar to that found for highly charged surfaces. These results are in line with our previous experimental data for negative charged NP-H. All together, these observations suggest an interplay mechanism between the formation and narrowing of electric double layers on the stability of NP dispersions in both neutral and negatively charged NP-H.

  17. Molecular dynamics studies of aqueous silica nanoparticle dispersions: salt effects on the double layer formation

    NASA Astrophysics Data System (ADS)

    de Lara, Lucas S.; Rigo, Vagner A.; Michelon, Mateus F.; Metin, Cigdem O.; Nguyen, Quoc P.; Miranda, Caetano R.

    2015-08-01

    The ion distribution around hydroxylated silica nanoparticles (NP-H) dispersed in brine was investigated by fully atomistic molecular dynamics. The NP-H dispersions in aqueous electrolyte media are simulated in solutions of varying salinity (NaCl, CaCl2, and MgCl2), salt concentration (0.06  ×  10-3 to 3.00  ×  10-3 mole fraction {χ\\text{s}} ), and temperature (300 and 350 K) at 1 atm. The NP-H models reproduce the observed experimental concentration of silanol and geminal surface sites, which are responsible for local charge variations on the nanoparticles’ surface. Interestingly, under certain salt concentration conditions, the formation of an electrical double layer (DL) around the overall neutral NP-H occurs. The resulting DLs are attenuated with increasing temperature for all evaluated salts. With increasing salt concentration, a sign inversion of the effective charge at the first ion layer is observed, which modifies the electrostatic environment around the nanoparticle. The minimum salt concentration that leads to a DL formation at 300 K is 1.05  ×  10-3, 0.37  ×  10-3, and 0.06  ×  10-3 {χ\\text{s}} for NaCl, CaCl2, and MgCl2, respectively. The width of the DL decreases sequentially in ionic strength from NaCl to CaCl2 to MgCl2, which is similar to that found for highly charged surfaces. These results are in line with our previous experimental data for negative charged NP-H. All together, these observations suggest an interplay mechanism between the formation and narrowing of electric double layers on the stability of NP dispersions in both neutral and negatively charged NP-H.

  18. Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

    PubMed Central

    Trubetskoy, V S; Loomis, A; Hagstrom, J E; Budker, V G; Wolff, J A

    1999-01-01

    DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors. PMID:10454604

  19. Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

    PubMed

    Trubetskoy, V S; Loomis, A; Hagstrom, J E; Budker, V G; Wolff, J A

    1999-08-01

    DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors.

  20. 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.

  1. 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.

  2. Charge profile in thin layers of Al2O3

    NASA Astrophysics Data System (ADS)

    Kliem, H.; Schmidt, R.; Arlt, G.

    1982-03-01

    The distribution of trapped electrons with respect to space and energy in thin layers of aluminum oxide of MAOS (metal-aluminumoxide-siliconoxide-silicon) capacitors was studied by photoionization. The oxide layers were charged from the n-type silicon by high field injection in the dark. Afterwards it was possible to release more than 85% of the trapped carriers using photons with energies up to 4.2 eV. The measurements of both the flatband voltages and the discharge currents of several bands of photon energies yielded two parameters for the determination of the spatial distribution for the trapped electrons in each energy interval.

  3. Investigation of blast wave characteristics for layered thermobaric charges

    NASA Astrophysics Data System (ADS)

    Trzciński, W. A.; Barcz, K.

    2012-03-01

    The explosion of an annular charge composed of a hexogen core and a layer consisting of a mixture of ammonium nitrate and aluminum particles was studied. X-ray photography was used to trace the curvature of the shock wave in the external layer. The pressure blast characteristics and the light output of the explosion cloud were investigated using bunkers of different sizes and varying levels of the opening (the ratio of the hole surface to the total bunker surface). Overpressure peaks, the impulses of incident waves, and the impulses determined for the specified time duration were analyzed.

  4. 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.

  5. 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.

  6. 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.

  7. Important parameters affecting the cell voltage of aqueous electrical double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Wu, Tzu-Ho; Hsu, Chun-Tsung; Hu, Chi-Chang; Hardwick, Laurence J.

    2013-11-01

    This study discusses and demonstrates how the open-circuit potential and charges stored in the working potential window on positive and negative electrodes affect the cell voltage of carbon-based electrical double-layer capacitors (EDLCs) in aqueous electrolytes. An EDLC consisting of two activated carbon electrodes is employed as the model system for identifying these key parameters although the potential window of water decomposition can be simply determined by voltammetric methods. First, the capacitive performances of an EDLC with the same charge on positive and negative electrodes are evaluated by cyclic voltammetric, charge-discharge, electrochemical impedance spectroscopic (EIS) analyses, and inductance-capacitance-resistance meter (LCR meter). The principles for obtaining the highest acceptable cell voltage of such symmetric ECs with excellent reversibility and capacitor-like behaviour are proposed. Aqueous charge-balanced EDLCs can be operated as high as 2.0 V with high energy efficiency (about 90%) and only 4% capacitance loss after the 600-cycle stability checking. The necessity of charge balance (but not capacitance balance) for positive and negative electrodes is substantiated from the lower acceptable cell voltage of charge-unbalanced EDLCs.

  8. 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.

  9. Rate of Bubble Coalescence following Quasi-Static Approach: Screening and Neutralization of the Electric Double Layer

    PubMed Central

    Katsir, Yael; Marmur, Abraham

    2014-01-01

    Air-bubble coalescence in aqueous electrolytic solutions, following quasi-static approach, was studied in order to understand its slow rate in purified water and high rate in electrolytic solutions. The former is found to be due to surface charges, originating from the speciation of dissolved CO2, which sustain the electric double layer repulsion. Rapid coalescence in electrolytic solutions is shown to occur via two different mechanisms: (1) neutralization of the carbonaceous, charged species by acids; or (2) screening of the repulsive charge effects by salts and bases. The results do not indicate any ion specificity. They can be explained within the DLVO theory for the van der Waals and electric double layer interactions between particles, in contrast to observations of coalescence following dynamic approach. The present conclusions should serve as a reference point to understanding the dynamic behavior. PMID:24589528

  10. Rate of bubble coalescence following quasi-static approach: screening and neutralization of the electric double layer.

    PubMed

    Katsir, Yael; Marmur, Abraham

    2014-01-01

    Air-bubble coalescence in aqueous electrolytic solutions, following quasi-static approach, was studied in order to understand its slow rate in purified water and high rate in electrolytic solutions. The former is found to be due to surface charges, originating from the speciation of dissolved CO2, which sustain the electric double layer repulsion. Rapid coalescence in electrolytic solutions is shown to occur via two different mechanisms: (1) neutralization of the carbonaceous, charged species by acids; or (2) screening of the repulsive charge effects by salts and bases. The results do not indicate any ion specificity. They can be explained within the DLVO theory for the van der Waals and electric double layer interactions between particles, in contrast to observations of coalescence following dynamic approach. The present conclusions should serve as a reference point to understanding the dynamic behavior. PMID:24589528

  11. Charge generation layers comprising transition metal-oxide/organic interfaces. Electronic structure and charge generation mechanism

    SciTech Connect

    Meyer, Jens; Kröger, M.; Hamwi, S.; Gnam, F.; Riedl, T.; Kowalsky, W.; Kahn, Antoine

    2010-01-01

    The energetics of an archetype charge generation layer (CGL) architecture comprising of 4,4' ,4 '' -tris(N -carbazolyl)triphenylamine (TCTA), tungsten oxide (WO3 ) , and bathophenanthroline (BPhen) n-doped with cesium carbonate (Cs2 CO3 ) are determined by ultraviolet and inverse photoemissionspectroscopy. We show that the charge generation process occurs at the interface between the hole-transport material (TCTA) and WO3 and not, as commonly assumed, at the interface between WO3 and the n-doped electron-transport material (BPhen:Cs2 CO3 ) . However, the n-doped layer is also essential to the realization of an efficient CGL structure. The charge generation mechanism occurs via electron transfer from the TCTA highest occupied molecular orbital level to the transition metal-oxide conduction band.

  12. Charge trap memory based on few-layer black phosphorus.

    PubMed

    Feng, Qi; Yan, Faguang; Luo, Wengang; Wang, Kaiyou

    2016-02-01

    Atomically thin layered two-dimensional materials, including transition-metal dichalcogenide (TMDC) and black phosphorus (BP), have been receiving much attention, because of their promising physical properties and potential applications in flexible and transparent electronic devices. Here, for the first time we show nonvolatile charge-trap memory devices, based on field-effect transistors with large hysteresis, consisting of a few-layer black phosphorus channel and a three dimensional (3D) Al2O3/HfO2/Al2O3 charge-trap gate stack. An unprecedented memory window exceeding 12 V is observed, due to the extraordinary trapping ability of the high-k HfO2. The device shows a high endurance of over 120 cycles and a stable retention of ∼30% charge loss after 10 years, even lower than the reported MoS2 flash memory. The high program/erase current ratio, large memory window, stable retention and high on/off current ratio, provide a promising route towards flexible and transparent memory devices utilising atomically thin two-dimensional materials. The combination of 2D materials with traditional high-k charge-trap gate stacks opens up an exciting field of nonvolatile memory devices.

  13. Charge trap memory based on few-layer black phosphorus

    NASA Astrophysics Data System (ADS)

    Feng, Qi; Yan, Faguang; Luo, Wengang; Wang, Kaiyou

    2016-01-01

    Atomically thin layered two-dimensional materials, including transition-metal dichalcogenide (TMDC) and black phosphorus (BP), have been receiving much attention, because of their promising physical properties and potential applications in flexible and transparent electronic devices. Here, for the first time we show nonvolatile charge-trap memory devices, based on field-effect transistors with large hysteresis, consisting of a few-layer black phosphorus channel and a three dimensional (3D) Al2O3/HfO2/Al2O3 charge-trap gate stack. An unprecedented memory window exceeding 12 V is observed, due to the extraordinary trapping ability of the high-k HfO2. The device shows a high endurance of over 120 cycles and a stable retention of ~30% charge loss after 10 years, even lower than the reported MoS2 flash memory. The high program/erase current ratio, large memory window, stable retention and high on/off current ratio, provide a promising route towards flexible and transparent memory devices utilising atomically thin two-dimensional materials. The combination of 2D materials with traditional high-k charge-trap gate stacks opens up an exciting field of nonvolatile memory devices.

  14. Effect of double-stranded DNA on electrical double layer structure at oxide/electrolyte interface in classical molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Maekawa, Yuki; Shibuta, Yasushi; Sakata, Toshiya

    2015-01-01

    The elucidation of the electrical double layer (EDL) structure including biomolecules is helpful in controlling biointerfacial functions in biosensing devices. In this study, the effect of double-stranded DNA (ds-DNA) on the EDL structure at the SiO2/NaClaq interface in a concentrated solution was investigated by classical molecular dynamics (MD) simulation. In 1.0 M NaClaq, negatively charged ds-DNA shielded electrically by cations did not affect the potential profile of the EDL structure. This finding indicates that the simulated bio-interfacial structure allows the detection of ionic charges adsorbed directly onto substrates in a concentrated solution regardless of the presence of shielded biomolecular charges.

  15. Spin and charge transport in double-junction Fe/MgO/GaAs/MgO/Fe heterostructures

    SciTech Connect

    Wolski, S. Szczepański, T.; Dugaev, V. K.; Barnaś, J.; Landgraf, B.; Slobodskyy, T.; Hansen, W.

    2015-01-28

    We present theoretical and experimental results on tunneling current in single Fe/MgO/GaAs and double Fe/MgO/GaAs/MgO/Fe tunnel junctions. The charge and spin currents are calculated as a function of external voltage for different sets of parameters characterizing the semiconducting GaAs layer. Transport characteristics of a single Fe/MgO/GaAs junction reveal typical diode as well as spin diode features. The results of numerical calculations are compared with current-voltage characteristics measured experimentally for double tunnel junction structures, and a satisfactory agreement of the theoretical and experimental results has been achieved.

  16. 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).

  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. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Template-synthesized nanotubes through layer-by-layer assembly under charge interaction.

    PubMed

    Li, Junbai; Cui, Yue

    2006-06-01

    Aqueous polymer nanotubes can be assembled by combining the layer-by-layer (LbL) assembly and template technique under charge interaction. This method allows lots of species, especially in an aqueous system to form a tubular structure in the pores of the template. The tubes functions can be readily modified by introducing various functional components. Such assembled nanotubes are often mechanically stable and highly flexible. They have also numerous potential applications in delivering materials.

  4. 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.

  5. Ion Acceleration by Ultra-intense Laser Pulse Interacting with Double-layer Near-critical Density Plasma

    NASA Astrophysics Data System (ADS)

    Gu, Y. J.; Kong, Q.; Kawata, S.; Izumiyama, T.; Nagashima, T.; Takano, M.; Li, X. F.; Yu, Q.; Barada, D.; Ma, Y. Y.; Wang, P. X.

    2016-03-01

    A collimated ion beam is generated through the interaction between ultra-intense laser pulse and a double layer plasma. The maximum energy is above 1GeV and the total charge of high energy protons is about several tens of nC/μm. The double layer plasma is combined with an underdense plasma and a thin overdense one. The wakefield traps and accelerates a bunch of electrons to high energy in the first underdense slab. When the well collimated electron beam accelerated by the wakefield penetrates through the second overdense slab, it enhances target normal sheath acceleration (TNSA) and breakout after-burner (BOA) regimes. The mechanism is simulated and analyzed by 2.5 dimensional Particle-in-cell code. Compared with single target TNSA or BOA, both the acceleration gradient and energy transfer efficiency are higher in the double layer regime.

  6. Free energy of electrical double layers: Entropy of adsorbed ions and the binding polynomial

    SciTech Connect

    Stigter, D.; Dill, K.A. )

    1989-09-07

    The authors adapt the method of binding polynomials to general problems of binding equilibria of ions to polybases, polyacids, and mixed polyelectrolytes, such as proteins and other colloids. For spherical particles with a smeared charge the interaction effects are taken into account using the Poisson-Boltzmann equation, which is shown to differ little from the Debye-Hueckel approximation under conditions met in most protein solutions. Examples are given of the salt dependence of pH titration equilibria. Binding polynomials produce an extra term in the free energy of the electrical double layer, which arises from the entropy of the adsorbed ions. The maximum term method applied to the binding polynominal yields an expression which is similar to that derived by the charging process of Chan and Mitchell. Applications to monolayers and to polyelectrolyte gels are also discussed.

  7. Impedance analysis of porous carbon electrodes to predict rate capability of electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Yoo, Hyun Deog; Jang, Jong Hyun; Ryu, Ji Heon; Park, Yuwon; Oh, Seung M.

    2014-12-01

    Electrochemical impedance analysis is performed to predict the rate capability of two commercial activated carbon electrodes (RP20 and MSP20) for electric double-layer capacitor. To this end, ac impedance data are fitted with an equivalent circuit that comprises ohmic resistance and impedance of intra-particle pores. To characterize the latter, ionic accessibility into intra-particle pores is profiled by using the fitted impedance parameters, and the profiles are transformed into utilizable capacitance plots as a function of charge-discharge rate. The rate capability that is predicted from the impedance analysis is well-matched with that observed from a charge-discharge rate test. It is found that rate capability is determined by ionic accessibility as well as ohmic voltage drop. A lower value in ionic accessibility for MSP20 is attributed to smaller pore diameter, longer length, and higher degree of complexity in pore structure.

  8. Performance of Liquid Phase Exfoliated Graphene As Electrochemical Double Layer Capacitors Electrodes

    NASA Astrophysics Data System (ADS)

    Huffstutler, Jacob; Wasala, Milinda; Richie, Julianna; Winchester, Andrew; Ghosh, Sujoy; Kar, Swastik; Talapatra, Saikat

    2014-03-01

    We will present the results of our investigations of electrochemical double layer capacitors (EDLCs) or supercapacitors (SC) fabricated using liquid-phase exfoliated graphene. Several electrolytes, such as aqueous potassium hydroxide KOH (6M), ionic 1-Butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and ionic 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate[BMP][FAP] were used. These EDLC's show good performance compared to other carbon nanomaterials based EDLC's devices. We found that the liquid phase exfoliated graphene based devices possess specific capacitance values as high as 262 F/g, when used with ionic liquid electrolyte[BMP][FAP], with power densities (~ 454 W/kg) and energy densities (~ 0.38Wh/kg). Further, these devices indicated rapid charge transfer response even without the use of any binders or specially prepared current collectors. A detailed electrochemical impedance spectroscopy analysis in order to understand the phenomenon of charge storage in these materials will be presented.

  9. 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.

  10. 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.

  11. 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.

  12. 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)

  13. 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.

  14. Evaluation of the constant potential method in simulating electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxing; Yang, Yang; Olmsted, David L.; Asta, Mark; Laird, Brian B.

    2014-11-01

    A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO4-acetonitrile/graphite EDLC. At low potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of "inner-sphere adsorbed" Li+ ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li+ ions to the electrode surface.

  15. Evaluation of the constant potential method in simulating electric double-layer capacitors.

    PubMed

    Wang, Zhenxing; Yang, Yang; Olmsted, David L; Asta, Mark; Laird, Brian B

    2014-11-14

    A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO4-acetonitrile/graphite EDLC. At low potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of "inner-sphere adsorbed" Li(+) ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li(+) ions to the electrode surface. PMID:25399127

  16. Evaluation of the constant potential method in simulating electric double-layer capacitors.

    PubMed

    Wang, Zhenxing; Yang, Yang; Olmsted, David L; Asta, Mark; Laird, Brian B

    2014-11-14

    A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO4-acetonitrile/graphite EDLC. At low potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of "inner-sphere adsorbed" Li(+) ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li(+) ions to the electrode surface.

  17. Evaluation of the constant potential method in simulating electric double-layer capacitors

    SciTech Connect

    Wang, Zhenxing; Laird, Brian B.; Yang, Yang; Olmsted, David L.; Asta, Mark

    2014-11-14

    A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO{sub 4}-acetonitrile/graphite EDLC. At low potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of “inner-sphere adsorbed” Li{sup +} ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li{sup +} ions to the electrode surface.

  18. Vertical Bipolar Charge Plasma Transistor with Buried Metal Layer

    PubMed Central

    Nadda, Kanika; Kumar, M. Jagadesh

    2015-01-01

    A self-aligned vertical Bipolar Charge Plasma Transistor (V-BCPT) with a buried metal layer between undoped silicon and buried oxide of the silicon-on-insulator substrate, is reported in this paper. Using two-dimensional device simulation, the electrical performance of the proposed device is evaluated in detail. Our simulation results demonstrate that the V-BCPT not only has very high current gain but also exhibits high BVCEO · fT product making it highly suitable for mixed signal high speed circuits. The proposed device structure is also suitable for realizing doping-less bipolar charge plasma transistor using compound semiconductors such as GaAs, SiC with low thermal budgets. The device is also immune to non-ideal current crowding effects cropping up at high current densities. PMID:25597295

  19. Boundary layer charge dynamics in ionic liquid-ionic polymer transducers

    NASA Astrophysics Data System (ADS)

    Davidson, Jacob D.; Goulbourne, N. C.

    2011-01-01

    Ionic polymer transducers (IPTs), also known as ionic polymer-metal composites, are soft sensors and actuators which operate through a coupling of microscale chemical, electrical, and mechanical interactions. The use of an ionic liquid as solvent for an IPT has been shown to dramatically increase transducer lifetime in free-air use, while also allowing for higher applied voltages without electrolysis. In this work, we apply Nernst-Planck/Poisson theory to model charge transport in an ionic liquid IPT by considering a certain fraction of the ionic liquid ions as mobile charge carriers, a phenomenon which is unique to ionic liquid IPTs compared to their water-based counterparts. Numerical simulations are performed using the finite element method to examine how the introduction of another pair of mobile ions affects boundary layer charge dynamics, concentration, and charge density distributions in the electric double layer, and the overall charge transferred and current response of the IPT. Due to interactions with the Nafion ionomer, not all of the ionic liquid ions will function as mobile charge carriers; only a certain fraction will exist as "free" ions. The presence of mobile ionic liquid ions in the transducer will increase the overall charge transferred when a voltage is applied, and cause the current in the transducer to decay more slowly. The additional mobile ions also cause the ionic concentration profiles to exhibit a nonlinear dynamic response, characterized by nonmonotonic ionic concentration profiles in space and time. Although the presence of mobile ionic liquid ions increases the overall amount of charge transferred, this additional charge transfer occurs in a somewhat symmetric manner. Therefore, the additional charge transferred due to the ionic liquid ions does not greatly increase the net bending moment of the transducer; in fact, it is possible that ionic liquid ion movement actually decreases the observed bending response. This suggests that an

  20. 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

  1. Bending elasticity of charged surfactant layers: the effect of mixing.

    PubMed

    Bergström, L Magnus

    2006-08-01

    Expressions have been derived from which the spontaneous curvature (H(0)), bending rigidity (k(c)), and saddle-splay constant (k(c)) of mixed monolayers and bilayers may be calculated from molecular and solution properties as well as experimentally available quantities such as the macroscopic hydrophobic-hydrophilic interfacial tension. Three different cases of binary surfactant mixtures have been treated in detail: (i) mixtures of an ionic and a nonionic surfactant, (ii) mixtures of two oppositely charged surfactants, and (iii) mixtures of two ionic surfactants with identical headgroups but different tail volumes. It is demonstrated that k(c)H(0), k(c), and k(c) for mixtures of surfactants with flexible tails may be subdivided into one contribution that is due to bending properties of an infinitely thin surface as calculated from the Poisson-Boltzmann mean field theory and one contribution appearing as a result of the surfactant film having a finite thickness with the surface of charge located somewhat outside the hydrophobic-hydrophilic interface. As a matter of fact, the picture becomes completely different as finite layer thickness effects are taken into account, and as a result, the spontaneous curvature is extensively lowered whereas the bending rigidity is raised. Furthermore, an additional contribution to k(c) is present for surfactant mixtures but is absent for k(c)H(0) and k(c). This contribution appears as a consequence of the minimization of the free energy with respect to the composition of a surfactant layer that is open in the thermodynamic sense and must always be negative (i.e., k(c) is generally found to be brought down by the process of mixing two or more surfactants). The magnitude of the reduction of k(c) increases with increasing asymmetry between two surfactants with respect to headgroup charge number and tail volume. As a consequence, the bending rigidity assumes the lowest values for layers formed in mixtures of two oppositely charged

  2. High-resolution electroencephalogram (EEG) mapping: scalp charge layer

    NASA Astrophysics Data System (ADS)

    Yao, Dezhong; Yin, Zhong Ke; Tang, Xiang Hong; Arendt-Nielsen, Lars; Chen, Andrew C. N.

    2004-11-01

    The neural electrical signal related to the human brain function is one of the tracks to understanding ourselves. Various electroencephalogram imaging techniques have been developed to reveal spatial information on neural activities in the brain from scalp recordings, such as Laplacian, equivalent source layer and potential. Physically, these methods may be classified into two categories: scalp surface or cortical surface based techniques. In this work, the focus is on the scalp surface based equivalent charge layer (ECL), with a comparison to the scalp potential with different references and scalp Laplacian (SL). The contents include theoretical analysis and numeric evaluation of simulated data and real alpha (8-12 Hz) data. The results confirm the fact that SL and ECL are of higher spatial resolution than various scalp potential maps, and for SL and ECL, SL is of higher resolution but more sensitive to noise.

  3. Charge density wave transition in single-layer titanium diselenide

    DOE PAGESBeta

    Chen, P.; Chan, Y. -H.; Fang, X. -Y.; Zhang, Y.; Chou, M. Y.; Mo, S. -K.; Hussain, Z.; Fedorov, A. -V.; Chiang, T. -C.

    2015-11-16

    A single molecular layer of titanium diselenide (TiSe2) is a promising material for advanced electronics beyond graphene--a strong focus of current research. Such molecular layers are at the quantum limit of device miniaturization and can show enhanced electronic effects not realizable in thick films. We show that single-layer TiSe2 exhibits a charge density wave (CDW) transition at critical temperature TC=232±5 K, which is higher than the bulk TC=200±5 K. Angle-resolved photoemission spectroscopy measurements reveal a small absolute bandgap at room temperature, which grows wider with decreasing temperature T below TC in conjunction with the emergence of (2 × 2) ordering.more » The results are rationalized in terms of first-principles calculations, symmetry breaking and phonon entropy effects. The behavior of the Bardeen-Cooper-Schrieffer (BCS) gap implies a mean-field CDW order in the single layer and an anisotropic CDW order in the bulk.« less

  4. Charge density wave transition in single-layer titanium diselenide

    SciTech Connect

    Chen, P.; Chan, Y. -H.; Fang, X. -Y.; Zhang, Y.; Chou, M. Y.; Mo, S. -K.; Hussain, Z.; Fedorov, A. -V.; Chiang, T. -C.

    2015-11-16

    A single molecular layer of titanium diselenide (TiSe2) is a promising material for advanced electronics beyond graphene--a strong focus of current research. Such molecular layers are at the quantum limit of device miniaturization and can show enhanced electronic effects not realizable in thick films. We show that single-layer TiSe2 exhibits a charge density wave (CDW) transition at critical temperature TC=232±5 K, which is higher than the bulk TC=200±5 K. Angle-resolved photoemission spectroscopy measurements reveal a small absolute bandgap at room temperature, which grows wider with decreasing temperature T below TC in conjunction with the emergence of (2 × 2) ordering. The results are rationalized in terms of first-principles calculations, symmetry breaking and phonon entropy effects. The behavior of the Bardeen-Cooper-Schrieffer (BCS) gap implies a mean-field CDW order in the single layer and an anisotropic CDW order in the bulk.

  5. Charge density wave transition in single-layer titanium diselenide.

    PubMed

    Chen, P; Chan, Y-H; Fang, X-Y; Zhang, Y; Chou, M Y; Mo, S-K; Hussain, Z; Fedorov, A-V; Chiang, T-C

    2015-01-01

    A single molecular layer of titanium diselenide (TiSe2) is a promising material for advanced electronics beyond graphene-a strong focus of current research. Such molecular layers are at the quantum limit of device miniaturization and can show enhanced electronic effects not realizable in thick films. We show that single-layer TiSe2 exhibits a charge density wave (CDW) transition at critical temperature TC=232±5 K, which is higher than the bulk TC=200±5 K. Angle-resolved photoemission spectroscopy measurements reveal a small absolute bandgap at room temperature, which grows wider with decreasing temperature T below TC in conjunction with the emergence of (2 × 2) ordering. The results are rationalized in terms of first-principles calculations, symmetry breaking and phonon entropy effects. The observed Bardeen-Cooper-Schrieffer (BCS) behaviour of the gap implies a mean-field CDW order in the single layer and an anisotropic CDW order in the bulk. PMID:26568512

  6. Counterion-only electrical double layers: An application of density functional theory

    NASA Astrophysics Data System (ADS)

    Liu, Longcheng

    2015-08-01

    Within the framework of density functional theory, a self-consistent approach of weighted correlation approximation is developed to give an accurate account of the cross correlations between the Coulombic interaction and the hard-sphere exclusion in the counterion-only electrical double layers. Application of the approach to the cases of practical interest, against the Monte Carlo simulations, shows that it is excellent in describing the structural properties and the pressures of the confined solutions involving both mono- and divalent counterions between two planar charged walls. In particular, the study suggests that the relative importance of electrostatic correlations in comparison to the effects of ionic excluded volume and direct Coulomb interactions depends on the valency of the counterions and the surface charge density. In a clay system with mixed counterions, the competition between the mono- and divalent ions results in a large swelling when the fraction of surface charge compensated by monovalent counterions is greater than 30%. In the opposite situation involving mostly divalent counterions, a limited swelling is found and the attraction between the clay particles favors the formation of stacks incorporating a water layer of about 1.0 nm. These findings are consistent with experimental observations, giving insight into some mechanisms governing the stability of colloidal clay in salt-free or dilute solutions.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Double layers and other phenomena in low-pressure plasma columns generated by ultra-violet light

    SciTech Connect

    Valentini, H.-B.; Kaiser, D.

    2015-12-15

    Low-pressure steady-state plasmas are analysed by means of a two-fluid model in both plane and cylindrical geometries. The charged particles are generated by UV illumination. Both a Gaussian and a one-step profile of the ionization are taken into account. Numerical results reveal various types of solutions depending on the ionization profile and the collisionality. The first state arises if the ionization spreads from the centre over a great part of the plasma. It has an almost quasineutral plasma core and a positively charged boundary sheath. The curvature of the number density of the charge particles is negative, except the boundary sheath. The second state occurs if the ionization is mainly localized in the vicinity of the centre and the collisionality is below a threshold. A slightly positive plasma core is surrounded by a double layer there where the ionization falls off steeply. Between the double layer and the boundary sheath a broad zone can exist where the plasma is nearly quasi-neutral and the electric field is small. Within the double layer the ion drift speed attains the Bohm velocity in collisionless plasmas, it is smaller in collisional cases. In a broad domain, the curvature of the number density of the charged particles can be positive. This is a feature of the so-called contracted columns. The transition between both the states occurs abruptly under collisonless conditions and becomes smooth as the collisionality increases. The minimum of the space charge density can become positive in this case. Several layers are possible, as well. Using the Gaussian profile analytical criteria can be given for a few of the mentioned phenomena. Probably, ionization profiles prescribed by photons allow to understand the origin of the contracted column more completely than up to now.

  17. Thermally Induced Charge Reversal of Layer-by-Layer Assembled Single-Component Polymer Films.

    PubMed

    Richardson, Joseph J; Tardy, Blaise L; Ejima, Hirotaka; Guo, Junling; Cui, Jiwei; Liang, Kang; Choi, Gwan H; Yoo, Pil J; De Geest, Bruno G; Caruso, Frank

    2016-03-23

    Temperature can be harnessed to engineer unique properties for materials useful in various contexts and has been shown to affect the layer-by-layer (LbL) assembly of polymer thin films and cause physical changes in preassembled polymer thin films. Herein we demonstrate that exposure to relatively low temperatures (≤ 100 °C) can induce physicochemical changes in cationic polymer thin films. The surface charge of polymer films containing primary and secondary amines reverses after heating (from positive to negative), and different characterization techniques are used to show that the change in surface charge is related to oxidation of the polymer that specifically occurs in the thin film state. This charge reversal allows for single-polymer LbL assembly to be performed with poly(allylamine) hydrochloride (PAH) through alternating heat/deposition steps. Furthermore, the negative charge induced by heating reduces the fouling and cell-association of PAH-coated planar and particulate substrates, respectively. This study highlights a unique property of thin films which is relevant to LbL assembly and biofouling and is of interest for the future development of thin polymer films for biomedical systems. PMID:26953514

  18. 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.

  19. Morphology-dependent stimulated Raman scattering imaging. II. Experimental studies of solvent structure in the diffuse electric double layer

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Xiang; Moortgat, Philip A.; Aker, Pamela M.

    1996-11-01

    Experimental confirmation that morphology-dependent stimulated Raman scattering can be used as an optical imaging technique is given. The water structure variations present at a charged water/air interface have been mapped. The measured structure variations track precisely that given by the Gouy-Chapman theory. We present, to our knowledge, the first experimental investigations of water solvent response in the diffuse part of the electric double layer. Imaging experiments on droplets charged to both positive and negative values have enabled us to determine the neutral water/air interface potential.

  20. Morphology-dependent stimulated Raman scattering imaging. II. Experimental studies of solvent structure in the diffuse electric double layer

    SciTech Connect

    Zhang, J.; Moortgat, P.A.; Aker, P.M.

    1996-11-01

    Experimental confirmation that morphology-dependent stimulated Raman scattering can be used as an optical imaging technique is given. The water structure variations present at a charged water/air interface have been mapped. The measured structure variations track precisely that given by the Gouy{endash}Chapman theory. We present, to our knowledge, the first experimental investigations of water solvent response in the diffuse part of the electric double layer. Imaging experiments on droplets charged to both positive and negative values have enabled us to determine the neutral water/air interface potential. {copyright} {ital 1996 American Institute of Physics.}

  1. Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot.

    PubMed

    Biesinger, D E F; Scheller, C P; Braunecker, B; Zimmerman, J; Gossard, A C; Zumbühl, D M

    2015-09-01

    We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor backaction are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time. PMID:26382695

  2. Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot.

    PubMed

    Biesinger, D E F; Scheller, C P; Braunecker, B; Zimmerman, J; Gossard, A C; Zumbühl, D M

    2015-09-01

    We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor backaction are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time.

  3. Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot

    NASA Astrophysics Data System (ADS)

    Biesinger, D. E. F.; Scheller, C. P.; Braunecker, B.; Zimmerman, J.; Gossard, A. C.; Zumbühl, D. M.

    2015-09-01

    We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor backaction are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time.

  4. DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer.

    PubMed

    Bronder, Thomas S; Poghossian, Arshak; Scheja, Sabrina; Wu, Chunsheng; Keusgen, Michael; Mewes, Dieter; Schöning, Michael J

    2015-09-16

    Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAH layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance-voltage and constant-capacitance measurements. In addition, the surface morphology of the PAH layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event. PMID:26327272

  5. DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer.

    PubMed

    Bronder, Thomas S; Poghossian, Arshak; Scheja, Sabrina; Wu, Chunsheng; Keusgen, Michael; Mewes, Dieter; Schöning, Michael J

    2015-09-16

    Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAH layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance-voltage and constant-capacitance measurements. In addition, the surface morphology of the PAH layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event.

  6. The effects of the electrical double layer on giant ionic currents through single-walled carbon nanotubes.

    PubMed

    Bearden, Samuel; Zhang, Guigen

    2013-03-29

    We developed a computational model for investigating the cause for the high ionic current through a single-walled carbon nanotube nanofluidic device by considering the electrical double layer at a solid-liquid interface. With this model, we were able to examine the influence of the Gouy-Chapman-Stern electrical double layer and the solution concentration on the ionic conductance in the device. Results showed that the conductance-concentration relationship predicted from our model agreed well with experimental observation. Moreover, our model showed that the compact layer thickness increased with the increase of the bulk solution concentration, reducing the internal volume of the nanotube channel available for fluid transport. Fluid within the channel had an enhanced concentration and a net charge which increased the electroosmotic and electrophoretic transport properties of the device, increasing the total ionic conductance of the system.

  7. Local semi-empirical formulae for the contact values of the singlet distribution functions of a double layer.

    PubMed

    Silvestre-Alcantara, Whasington; Bhuiyan, Lutful Bari; Henderson, Douglas

    2010-05-13

    The electrochemical double layer is an important practical and theoretical problem. Generally speaking, experiment gives valuable information about quantities, such as potential differences, that involve integrals of density and charge profiles but does not provide direct information about the profiles themselves. Computer simulations have given numerical information about these profiles. However, explicit expressions are useful in understanding these data. For some years an exact expression has been known for the contact value of total density profile of the ions in the double layer but, until recently, an expression for the contact value of the more important charge profile has been lacking. A few years ago, a semi-empirical local result for the charge profile, valid at low electrode charge, was proposed and, very recently, extended to higher electrode charge. This expression contains a parameter; the effect of variations in this parameter is explored in this paper and the result is compared with a large set of simulation data for the contact values of various profiles that we have accumulated in the past few years. The agreement of the semi-empirical expression with our simulation results is excellent. The best values for this parameter are fairly close to the value suggested by theory.

  8. Local semi-empirical formulae for the contact values of the singlet distribution functions of a double layer

    PubMed Central

    Silvestre-Alcantara, Whasington; Henderson, Douglas

    2010-01-01

    The electrochemical double layer is an important practical and theoretical problem. Generally speaking, experiment gives valuable information about quantities, such as potential differences, that involve integrals of density and charge profiles but does not provide direct information about the profiles themselves. Computer simulations have given numerical information about these profiles. However, explicit expressions are useful in understanding these data. For some years an exact expression has been known for the contact value of total density profile of the ions in the double layer but, until recently, an expression for the contact value of the more important charge profile has been lacking. A few years ago, a semi-empirical local result for the charge profile, valid at low electrode charge, was proposed and, very recently, extended to higher electrode charge. This expression contains a parameter; the effect of variations in this parameter is explored in this paper and the result is compared with a large set of simulation data for the contact values of various profiles that we have accumulated in the past few years. The agreement of the semi-empirical expression with our simulation results is excellent. The best values for this parameter are fairly close to the value suggested by theory. PMID:20543999

  9. Layer-dependent surface potential of phosphorene and anisotropic/layer-dependent charge transfer in phosphorene-gold hybrid systems.

    PubMed

    Xu, Renjing; Yang, Jiong; Zhu, Yi; Yan, Han; Pei, Jiajie; Myint, Ye Win; Zhang, Shuang; Lu, Yuerui

    2016-01-01

    The surface potential and the efficiency of interfacial charge transfer are extremely important for designing future semiconductor devices based on the emerging two-dimensional (2D) phosphorene. Here, we directly measured the strong layer-dependent surface potential of mono- and few-layered phosphorene on gold, which is consistent with the reported theoretical prediction. At the same time, we used an optical way photoluminescence (PL) spectroscopy to probe charge transfer in the phosphorene-gold hybrid system. We firstly observed highly anisotropic and layer-dependent PL quenching in the phosphorene-gold hybrid system, which is attributed to the highly anisotropic/layer-dependent interfacial charge transfer.

  10. Dynamical aspects of various solitary waves and double layers in dusty plasmas

    NASA Astrophysics Data System (ADS)

    Das, G. C.; Sarma, Jnanjyoti; Talukdar, M.

    1998-01-01

    Employing quasipotential analysis, the Sagdeev potential equation has been derived in a multicomponent plasma consisting of free and trapped electrons and contaminated by the dust charged grains forming therein by the attachment of electrons to finite-size dust particles. Because of the free and trapped electrons in the dusty plasma, the plasma-acoustic wave exhibits the different features of various solitary waves. The Sagdeev potential equation, at a small-amplitude approximation, leads to the evaluation, by a proposed new formalism of a simple wave solution technique, of the new scenario of solitary wave propagation in a dusty plasma. It has been shown that the ordering of the nonisothermality in the dusty plasma also plays a unique role. In the case of a plasma with first-order nonisothermality, the Sagdeev potential equation derives the compressive solitary wave propagation, while for plasma with higher-order nonisothermality the method might fail to solve the Sagdeev potential equation and, thus, an alternate method is used to reveal the coexistence of compressive and rarefactive solitary waves. In addition, for certain plasma parameters, the solitary waves disappear and a double layer is expected. Again, with the better approximation in the Sagdeev potential, more features of solitary waves, known as spiky and explosive, along with the double layers, are also highlighted. The observations made of the solitary waves could be of further interest in the understanding of laboratory and space plasmas.

  11. Dynamical aspects of various solitary waves and double layers in dusty plasmas

    SciTech Connect

    Das, G.C.; Sarma, J.; Talukdar, M.

    1998-01-01

    Employing quasipotential analysis, the Sagdeev potential equation has been derived in a multicomponent plasma consisting of free and trapped electrons and contaminated by the dust charged grains forming therein by the attachment of electrons to finite-size dust particles. Because of the free and trapped electrons in the dusty plasma, the plasma-acoustic wave exhibits the different features of various solitary waves. The Sagdeev potential equation, at a small-amplitude approximation, leads to the evaluation, by a proposed new formalism of a simple wave solution technique, of the new scenario of solitary wave propagation in a dusty plasma. It has been shown that the ordering of the nonisothermality in the dusty plasma also plays a unique role. In the case of a plasma with first-order nonisothermality, the Sagdeev potential equation derives the compressive solitary wave propagation, while for plasma with higher-order nonisothermality the method might fail to solve the Sagdeev potential equation and, thus, an alternate method is used to reveal the coexistence of compressive and rarefactive solitary waves. In addition, for certain plasma parameters, the solitary waves disappear and a double layer is expected. Again, with the better approximation in the Sagdeev potential, more features of solitary waves, known as spiky and explosive, along with the double layers, are also highlighted. The observations made of the solitary waves could be of further interest in the understanding of laboratory and space plasmas.{copyright} {ital 1998 American Institute of Physics.}

  12. Double-layer capacitance in a dual lithium ion insertion cell

    SciTech Connect

    Ong, I.J.; Newman, J.

    1999-12-01

    The addition of double-layer capacitance into a mathematical model of a dual lithium ion insertion cell is investigated. Double-layer capacitance is introduced in both the negative electrode and the positive electrode. For the purposes of this paper, a Li{sub x}C{sub 6}{vert{underscore}bar}propylene carbonate + 1 M LiClO{sub 4}{vert{underscore}bar}Li{sub y}Mn{sub 2}O{sub 4} cell is used for the collection of simulation results. Simulation results on the effect of short-time pulses passed through the cell are presented. Differences in the transient potential response in the negative and positive electrodes at short times are made between an electrode with a resistive film and one without and between situations with small and large rates of change of the open-circuit potential with state of charge. A simpler resistive-capacitive model is developed which clarifies many features of the modified behavior due to the capacitance but without simultaneously dealing with the discharge of the active material and concentration gradients.

  13. On the plasma environment of solitary waves and weak double layers

    SciTech Connect

    Koskinen, H.E.J. ); Lundin, R. ); Holback, B. )

    1990-05-01

    Observations of charged particles during events of solitary waves and weak double layer-like structures by the Swedish magnetospheric research satellite Viking are discussed. The observations took place in relatively weak acceleration regions at altitudes between 1 and 2 R{sub E}. The total accelerating potential was typically somewhat less than 1 kV. The characteristics of ion and electron spectra indicate that the main part of the potential was below the satellite but osme field-aligned acceleration of elections had also taken place above it. The composition of the ion beams was domianted by protons with a variable concentration (0-30%) of oxygen ions. While it is difficult to determine the exact parameters of the background plasma, there is clear evidence of the presence of cool background electrons and ions. It is proposed that the weak double layer-like structures are structures in the cool ambient ions and convect slowly upward with the ion population. On the other hand, the structures accelerate auroral electrons toward Earth and beam ions from the ionosphere upward. It is suggested that the structures are likely to contribute to the perpendicular heating of the ion beams.

  14. 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

  15. 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.

  16. Considerations for consistent characterization of electrochemical double-layer capacitor performance

    NASA Astrophysics Data System (ADS)

    Zuliani, Jocelyn E.; Caguiat, Johnathon N.; Kirk, Donald W.; Jia, Charles Q.

    2015-09-01

    Electrochemical double-layer capacitors (EDLCs) are emerging energy storage devices that provide high power density and rapid charging rates, with higher energy density than conventional capacitors. Extensive research efforts have been devoted to develop novel, high performing electrode materials to improve device performance, particularly to increase energy density. A number of methods have been used to characterize and report the performance of EDLCs in literature. The lack of a consistent and representative normalization parameter and the absence of consistent electrochemical testing procedures make the comparison of performance data challenging. In this work, key factors that affect EDLC performance data are discussed. Consideration is given to potential normalization parameters: mass, volume, and specific surface area (SSA). As well, an investigation into the effects of charging rate, maximum operating voltage window, and electrochemical analysis technique is performed. This work demonstrates the dependence of measured capacitance on maximum voltage window and the variation in performance between two different electrode materials. Moreover, an inherent discrepancy between cyclic voltammetry (CV) and galvanostatic cycling (GC) capacitance values at fast charging rates has been observed. We hope this effort will assist in the development of a much needed international protocol for accurate measurement and characterization of EDLC performance.

  17. Edge effects in vertically-oriented graphene based electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Yang, Huachao; Yang, Jinyuan; Bo, Zheng; Zhang, Shuo; Yan, Jianhua; Cen, Kefa

    2016-08-01

    Vertically-oriented graphenes (VGs) have been demonstrated as a promising active material for electric double-layer capacitors (EDLCs), partially due to their edge-enriched structure. In this work, the 'edge effects', i.e., edges as the promoters of high capacitance, in VG based EDLCs are investigated with experimental research and numerical simulations. VGs with diverse heights (i.e., edge-to-basal ratios) and edge densities are prepared with varying the plasma-enabled growth time and employing different plasma sources. Electrochemical measurements show that the edges play a predominant role on the charge storage behavior of VGs. A simulation is further conducted to unveil the roles of the edges on the separation and adsorption of ions within VG channels. The initial charge distribution of a VG plane is obtained with density functional theory (DFT) calculations, which is subsequently applied to a molecular dynamics (MD) simulation system to gain the insights into the microscope EDLC structures. Compared with the basal planes, the edges present higher initial charge density (by 4.2 times), higher ion packing density (by 2.6 times), closer ion packing location (by 0.8 Å), and larger ion separation degree (by 14%). The as-obtained findings will be instructive in designing the morphology and structure of VGs for enhanced capacitive performances.

  18. Electric potential calculation in molecular simulation of electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxing; Olmsted, David L.; Asta, Mark; Laird, Brian B.

    2016-11-01

    For the molecular simulation of electric double layer capacitors (EDLCs), a number of methods have been proposed and implemented to determine the one-dimensional electric potential profile between the two electrodes at a fixed potential difference. In this work, we compare several of these methods for a model LiClO4-acetonitrile/graphite EDLC simulated using both the traditional fixed-charged method (FCM), in which a fixed charge is assigned a priori to the electrode atoms, or the recently developed constant potential method (CPM) (2007 J. Chem. Phys. 126 084704), where the electrode charges are allowed to fluctuate to keep the potential fixed. Based on an analysis of the full three-dimensional electric potential field, we suggest a method for determining the averaged one-dimensional electric potential profile that can be applied to both the FCM and CPM simulations. Compared to traditional methods based on numerically solving the one-dimensional Poisson’s equation, this method yields better accuracy and no supplemental assumptions.

  19. Electric potential calculation in molecular simulation of electric double layer capacitors.

    PubMed

    Wang, Zhenxing; Olmsted, David L; Asta, Mark; Laird, Brian B

    2016-11-23

    For the molecular simulation of electric double layer capacitors (EDLCs), a number of methods have been proposed and implemented to determine the one-dimensional electric potential profile between the two electrodes at a fixed potential difference. In this work, we compare several of these methods for a model LiClO4-acetonitrile/graphite EDLC simulated using both the traditional fixed-charged method (FCM), in which a fixed charge is assigned a priori to the electrode atoms, or the recently developed constant potential method (CPM) (2007 J. Chem. Phys. 126 084704), where the electrode charges are allowed to fluctuate to keep the potential fixed. Based on an analysis of the full three-dimensional electric potential field, we suggest a method for determining the averaged one-dimensional electric potential profile that can be applied to both the FCM and CPM simulations. Compared to traditional methods based on numerically solving the one-dimensional Poisson's equation, this method yields better accuracy and no supplemental assumptions.

  20. Edge effects in vertically-oriented graphene based electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Yang, Huachao; Yang, Jinyuan; Bo, Zheng; Zhang, Shuo; Yan, Jianhua; Cen, Kefa

    2016-08-01

    Vertically-oriented graphenes (VGs) have been demonstrated as a promising active material for electric double-layer capacitors (EDLCs), partially due to their edge-enriched structure. In this work, the 'edge effects', i.e., edges as the promoters of high capacitance, in VG based EDLCs are investigated with experimental research and numerical simulations. VGs with diverse heights (i.e., edge-to-basal ratios) and edge densities are prepared with varying the plasma-enabled growth time and employing different plasma sources. Electrochemical measurements show that the edges play a predominant role on the charge storage behavior of VGs. A simulation is further conducted to unveil the roles of the edges on the separation and adsorption of ions within VG channels. The initial charge distribution of a VG plane is obtained with density functional theory (DFT) calculations, which is subsequently applied to a molecular dynamics (MD) simulation system to gain the insights into the microscope EDLC structures. Compared with the basal planes, the edges present higher initial charge density (by 4.2 times), higher ion packing density (by 2.6 times), closer ion packing location (by 0.8 Å), and larger ion separation degree (by 14%). The as-obtained findings will be instructive in designing the morphology and structure of VGs for enhanced capacitive performances.

  1. Electric potential calculation in molecular simulation of electric double layer capacitors.

    PubMed

    Wang, Zhenxing; Olmsted, David L; Asta, Mark; Laird, Brian B

    2016-11-23

    For the molecular simulation of electric double layer capacitors (EDLCs), a number of methods have been proposed and implemented to determine the one-dimensional electric potential profile between the two electrodes at a fixed potential difference. In this work, we compare several of these methods for a model LiClO4-acetonitrile/graphite EDLC simulated using both the traditional fixed-charged method (FCM), in which a fixed charge is assigned a priori to the electrode atoms, or the recently developed constant potential method (CPM) (2007 J. Chem. Phys. 126 084704), where the electrode charges are allowed to fluctuate to keep the potential fixed. Based on an analysis of the full three-dimensional electric potential field, we suggest a method for determining the averaged one-dimensional electric potential profile that can be applied to both the FCM and CPM simulations. Compared to traditional methods based on numerically solving the one-dimensional Poisson's equation, this method yields better accuracy and no supplemental assumptions. PMID:27624573

  2. Microscopic Insights into the Electrochemical Behavior of Nonaqueous Electrolytes in Electric Double-Layer Capacitors.

    PubMed

    Jiang, De-En; Wu, Jianzhong

    2013-04-18

    Electric double-layer capacitors (EDLCs) are electrical devices that store energy by adsorption of ionic species at the inner surface of porous electrodes. Compared with aqueous electrolytes, ionic liquid and organic electrolytes have the advantage of larger potential windows, making them attractive for the next generation of EDLCs with superior energy and power densities. The performance of both ionic liquid and organic electrolyte EDLCs hinges on the judicious selection of the electrode pore size and the electrolyte composition, which requires a comprehension of the charging behavior from a microscopic view. In this Perspective, we discuss predictions from the classical density functional theory (CDFT) on the dependence of the capacitance on the pore size for ionic liquid and organic electrolyte EDLCs. CDFT is applicable to electrodes with the pore size ranging from that below the ionic dimensionality to mesoscopic scales, thus unique for investigating the electrochemical behavior of the confined electrolytes for EDLC applications. PMID:26282139

  3. Microscopic Insights into the Electrochemical Behavior of Nonaqueous Electrolytes in Electric Double-Layer Capacitors

    SciTech Connect

    Jiang, Deen; Wu, Jianzhong

    2013-01-01

    Electric double-layer capacitors (EDLCs) are electrical devices that store energy by adsorption of ionic species at the inner surface of porous electrodes. Compared with aqueous electrolytes, ionic liquid and organic electrolytes have the advantage of larger potential windows, making them attractive for the next generation of EDLCs with superior energy and power densities. The performance of both ionic liquid and organic electrolyte EDLCs hinges on the judicious selection of the electrode pore size and the electrolyte composition, which requires a comprehension of the charging behavior from a microscopic view. In this Perspective, we discuss predictions from the classical density functional theory (CDFT) on the dependence of the capacitance on the pore size for ionic liquid and organic electrolyte EDLCs. CDFT is applicable to electrodes with the pore size ranging from that below the ionic dimensionality to mesoscopic scales, thus unique for investigating the electrochemical behavior of the confined electrolytes for EDLC applications.

  4. Extending the low temperature operational limit of double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Brandon, Erik J.; West, William C.; Smart, Marshall C.; Whitcanack, Larry D.; Plett, Gary A.

    This work describes the design and testing of organic electrolyte systems that extend the low temperature operational limit of double-layer capacitors (also known as supercapacitors) beyond that of typical commercially available components. Electrolytes were based on a tetraethylammonium tetrafluoroborate/acetonitrile system, modified with low melting co-solvents (such as formates, esters and cyclic ethers) to enable charging and discharging of test cells to as low as -75 °C. Cell capacitance exhibited little dependence on the electrolyte salt concentration or the nature of the co-solvent used, however, both variables strongly influenced the cell equivalent series resistance (ESR). Minimizing the increase in ESR posed the greatest design challenge, which limited realistic operation of these test cells to -55 °C (still improved relative to the typical rated limit of -40 °C for commercially available non-aqueous cells).

  5. APPLICATIONS OF LAYERED DOUBLE HYDROXIDES IN REMOVING OXYANIONS FROM OIL REFINING AND COAL MINING WASTEWATER

    SciTech Connect

    Song Jin; Paul Fallgren

    2006-03-01

    Western Research Institute (WRI), in conjunction with the U.S. Department of Energy (DOE), conducted a study of using the layered double hydroxides (LDH) as filter material to remove microorganisms, large biological molecules, certain anions and toxic oxyanions from various waste streams, including wastewater from refineries. Results demonstrate that LDH has a high adsorbing capability to those compounds with negative surface charge. Constituents studied include model bacteria, viruses, arsenic, selenium, vanadium, diesel range hydrocarbons, methyl tert-butyl ether (MTBE), mixed petroleum constituents, humic materials and anions. This project also attempted to modify the physical structure of LDH for the application as a filtration material. Flow characterizations of the modified LDH materials were also investigated. Results to date indicate that LDH is a cost-effective new material to be used for wastewater treatment, especially for the treatment of anions and oxyanions.

  6. Electric double-layer capacitors based on highly graphitized nanoporous carbons derived from ZIF-67.

    PubMed

    Torad, Nagy L; Salunkhe, Rahul R; Li, Yunqi; Hamoudi, Hicham; Imura, Masataka; Sakka, Yoshio; Hu, Chi-Chang; Yamauchi, Yusuke

    2014-06-23

    Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one-step direct carbonization of cobalt-containing zeolitic imidazolate framework-67 (ZIF-67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp(2) -bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge-discharge measurements. Our NPC is very promising for efficient electrodes for high-performance supercapacitor applications. A maximum specific capacitance of 238 F g(-1) is observed at a scan rate of 20 mV s(-1) . This value is very high compared to previous works on carbon-based electric double layer capacitors.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  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. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Removal of 2,4-dichlorophenoxyacetic acid by calcined Zn-Al-Zr layered double hydroxide.

    PubMed

    Chaparadza, Allen; Hossenlopp, Jeanne M

    2011-11-01

    The adsorption equilibrium, kinetics, and thermodynamics of removal of 2,4-dichlorophenoxy-acetic acid (2,4-D) from aqueous solutions by a calcined Zn-Al layered double hydroxide incorporated with Zr(4+) were studied with respect to time, temperature, pH, and initial 2,4-D concentration. Zr(4+) incorporation into the LDH was used to enhance 2,4-D uptake by creating higher positive charges and surface/layer modification of the adsorbent. The LDH was capable of removing up to 98% of 2,4-D from 5 to 400 ppm aqueous at adsorbent dosages of 500 and 5000 mg L(-1). The adsorption was described by a Langmuir-type isotherm. The percentage 2,4-D removed was directly proportional to the adsorbent dosage and was optimized with 8% Zr(4+) ion content, relative to the total metals (Zr(4+)+Al(3+)+Zn(2+)). Selected mass transfer and kinetic models were applied to the experimental data to examine uptake mechanism. The boundary layer and intra-particle diffusion played important roles in the adsorption mechanisms of 2,4-D, and the kinetics followed a pseudo-second order kinetic model with an enthalpy, ΔH(ads) of -27.7±0.9 kJ mol(-1). Regeneration studies showed a 6% reduction in 2,4-D uptake capacity over six adsorption-desorption cycles when exposed to an analyte concentration of 100 ppm.

  1. DNA Damage by Ionizing Radiation: Tandem Double Lesions by Charged Particles

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Chaban, Galina M.; Wang, Dunyou; Dateo, Christopher E.

    2005-01-01

    Oxidative damages by ionizing radiation are the source of radiation-induced carcinogenesis, damage to the central nervous system, lowering of the immune response, as well as other radiation-induced damages to human health. Monte Carlo track simulations and kinetic modeling of radiation damages to the DNA employ available molecular and cellular data to simulate the biological effect of high and low LET radiation io the DNA. While the simulations predict single and double strand breaks and base damages, so far all complex lesions are the result of stochastic coincidence from independent processes. Tandem double lesions have not yet been taken into account. Unlike the standard double lesions that are produced by two separate attacks by charged particles or radicals, tandem double lesions are produced by one single attack. The standard double lesions dominate at the high dosage regime. On the other hand, tandem double lesions do not depend on stochastic coincidences and become important at the low dosage regime of particular interest to NASA. Tandem double lesions by hydroxyl radical attack of guanine in isolated DNA have been reported at a dosage of radiation as low as 10 Gy. The formation of two tandem base lesions was found to be linear with the applied doses, a characteristic of tandem lesions. However, tandem double lesions from attack by a charged particle have not been reported.

  2. 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

  3. The expansion of polarization charge layers into magnetized vacuum - Theory and computer simulations

    NASA Technical Reports Server (NTRS)

    Galvez, Miguel; Borovsky, Joseph E.

    1991-01-01

    The formation and evolution of polarization charge layers on cylindrical plasma streams moving in vacuum are investigated using analytic theory and 2D electrostatic particle-in-cell computer simulations. It is shown that the behavior of the electron charge layer goes through three stages. An early time expansion is driven by electrostatic repulsion of electrons in the charge layer. At the intermediate stage, the simulations show that the electron-charge-layer expansion is halted by the positively charged plasma stream. Electrons close to the stream are pulled back to the stream and a second electron expansion follows in time. At the late stage, the expansion of the ion charge layer along the magnetic field lines accompanies the electron expansion to form an ambipolar expansion. It is found that the velocities of these electron-ion expansions greatly exceed the velocities of ambipolar expansions which are driven by plasma temperatures.

  4. Comparison of Molecular Dynamics with Classical Density Functional and Poisson–Boltzmann Theories of the Electric Double Layer in Nanochannels

    PubMed Central

    2012-01-01

    Comparisons are made among Molecular Dynamics (MD), Classical Density Functional Theory (c-DFT), and Poisson–Boltzmann (PB) modeling of the electric double layer (EDL) for the nonprimitive three component model (3CM) in which the two ion species and solvent molecules are all of finite size. Unlike previous comparisons between c-DFT and Monte Carlo (MC), the present 3CM incorporates Lennard-Jones interactions rather than hard-sphere and hard-wall repulsions. c-DFT and MD results are compared over normalized surface charges ranging from 0.2 to 1.75 and bulk ion concentrations from 10 mM to 1 M. Agreement between the two, assessed by electric surface potential and ion density profiles, is found to be quite good. Wall potentials predicted by PB begin to depart significantly from c-DFT and MD for charge densities exceeding 0.3. Successive layers are observed to charge in a sequential manner such that the solvent becomes fully excluded from each layer before the onset of the next layer. Ultimately, this layer filling phenomenon results in fluid structures, Debye lengths, and electric surface potentials vastly different from the classical PB predictions. PMID:23316120

  5. ({sup 18}O,{sup 18}Ne) double charge-exchange with MAGNEX

    SciTech Connect

    Bondí, M.; Cappuzzello, F.; Nicolosi, D.; Tropea, S.; Agodi, C.; Carbone, D.; Cavallaro, M.; Cunsolo, A.; De Napoli, M.; Foti, A.

    2014-05-09

    An experimental study concerning Double Gamow-Teller (DGT) modes in ({sup 18}O,{sup 18}Ne) Double Charge-Exchange reactions has been very recently performed at INFN-LNS laboratory in Catania. The experiment was performed using a {sup 40}Ca solid target and a {sup 18}O Cyclotron beam at 270 MeV incident energy. Charged ejectiles produced in the reaction were momentum analyzed and identified by MAGNEX spectrometer at very forward angles. Preliminary results are presented in the present paper.

  6. Charge-noise tolerant exchange gates of singlet-triplet qubits in asymmetric double quantum dots

    NASA Astrophysics Data System (ADS)

    Hiltunen, Tuukka; Bluhm, Hendrik; Mehl, Sebastian; Harju, Ari

    2015-02-01

    In the semiconductor double quantum dot singlet-triplet qubit architecture, the decoherence caused by the qubit's charge environment poses a serious obstacle towards large scale quantum computing. The effects of the charge decoherence can be mitigated by operating the qubit in the so-called sweet spot regions where it is insensitive to electrical noise. In this paper, we propose singlet-triplet qubits based on two quantum dots of different sizes. Such asymmetric double quantum dot systems allow the implementation of exchange gates with controllable exchange splitting J operated in the doubly occupied charge region of the larger dot, where the qubit has high resilience to charge noise. In the larger dot, J can be quenched to a value smaller than the intradot tunneling using magnetic fields, while the smaller dot and its larger splitting can be used in the projective readout of the qubit.

  7. Influence of layer charge and charge location on the swelling pressure of dioctahedral smectites

    NASA Astrophysics Data System (ADS)

    Sun, Linlin; Ling, Chian Ye; Lavikainen, Lasse P.; Hirvi, Janne T.; Kasa, Seppo; Pakkanen, Tapani A.

    2016-07-01

    Swelling pressure of dioctahedral smectites in the montmorillonite - beidellite series was investigated by molecular dynamics simulations. The pressure was found to correlate inversely with the magnitude of the layer charge in the range of -0.5 to -1.0 per unit cell. The beidellite type smectites were found to have lower swelling pressure than the montmorillonite type smectites. A clear effect of the type of interlayer cations on the swelling pressure was found. The sodium smectites sustained significant pressure even at longer interlayer distances, while in calcium smectites the pressure decreased soon after the initial swelling. The simulation results are in good agreement with experimental observations and provide a tool for predicting macroscopic swelling behavior in smectites.

  8. The importance of ion size and electrode curvature on electrical double layers in ionic liquids

    SciTech Connect

    Feng, G.; Qiao, R.; Huang, J; Dai, S.; Sumpter, B. G.; Meunier, V.

    2011-01-01

    Room-temperature ionic liquids (ILs) are an emerging class of electrolytes for supercapacitors. We investigate the effects of ion size and electrode curvature on the electrical double layers (EDLs) in two ILs 1-butyl-3-methylimidazolium chloride [BMIM][Cl] and 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF{sub 6}], using a combination of molecular dynamics (MD) and quantum density functional theory (DFT) simulations. The sizes of the counter-ion and co-ion affect the ion distribution and orientational structure of EDLs. The EDL capacitances near both planar and cylindrical electrodes were found to follow the order: [BMIM][Cl] (near the positive electrode) > [BMIM][PF{sub 6}] (near the positive electrode) ≈ [BMIM][Cl] (near the negative electrode) ≈ [BMIM][PF{sub 6}] (near the negative electrode). The EDL capacitance was also found to increase as the electrode curvature increases. These capacitance data can be fit to the Helmholtz model and the recently proposed exohedral electrical double-cylinder capacitor (xEDCC) model when the EDL thickness is properly parameterized, even though key features of the EDLs in ILs are not accounted for in these models. To remedy the shortcomings of existing models, we propose a “Multiple Ion Layers with Overscreening” (MILO) model for the EDLs in ILs that takes into account two critical features of such EDLs, i.e., alternating layering of counter-ions and co-ions and charge overscreening. The capacitance computed from the MILO model agrees well with the MD prediction. Although some input parameters of the MILO model must be obtained from MD simulations, the MILO model may provide a new framework for understanding many important aspects of EDLs in ILs (e.g., the variation of EDL capacitance with the electrode potential) that are difficult to interpret using classical EDL models and experiments.

  9. The Importance of Ion Size and Electrode Curvature on Electrical Double Layers in Ionic Liquids

    SciTech Connect

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

    2010-01-01

    Room-temperature ionic liquids (ILs) are an emerging class of electrolytes for supercapacitors. We investigate the effects of ion size and electrode curvature on the electrical double layers (EDLs) in two ILs 1-butyl-3-methylimidazolium chloride [BMIM][Cl] and 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF(6)], using a combination of molecular dynamics (MD) and quantum density functional theory (DFT) simulations. The sizes of the counter-ion and co-ion affect the ion distribution and orientational structure of EDLs. The EDL capacitances near both planar and cylindrical electrodes were found to follow the order: [BMIM][Cl] (near the positive electrode) > [BMIM][PF(6)] (near the positive electrode) {approx} [BMIM][Cl] (near the negative electrode) {approx} [BMIM][PF(6)] (near the negative electrode). The EDL capacitance was also found to increase as the electrode curvature increases. These capacitance data can be fit to the Helmholtz model and the recently proposed exohedral electrical double-cylinder capacitor (xEDCC) model when the EDL thickness is properly parameterized, even though key features of the EDLs in ILs are not accounted for in these models. To remedy the shortcomings of existing models, we propose a 'Multiple Ion Layers with Overscreening' (MILO) model for the EDLs in ILs that takes into account two critical features of such EDLs, i.e., alternating layering of counter-ions and co-ions and charge overscreening. The capacitance computed from the MILO model agrees well with the MD prediction. Although some input parameters of the MILO model must be obtained from MD simulations, the MILO model may provide a new framework for understanding many important aspects of EDLs in ILs (e.g., the variation of EDL capacitance with the electrode potential) that are difficult to interpret using classical EDL models and experiments.

  10. Intrinsic Charge Carrier Mobility in Single-Layer Black Phosphorus.

    PubMed

    Rudenko, A N; Brener, S; Katsnelson, M I

    2016-06-17

    We present a theory for single- and two-phonon charge carrier scattering in anisotropic two-dimensional semiconductors applied to single-layer black phosphorus (BP). We show that in contrast to graphene, where two-phonon processes due to the scattering by flexural phonons dominate at any practically relevant temperatures and are independent of the carrier concentration n, two-phonon scattering in BP is less important and can be considered negligible at n≳10^{13}  cm^{-2}. At smaller n, however, phonons enter in the essentially anharmonic regime. Compared to the hole mobility, which does not exhibit strong anisotropy between the principal directions of BP (μ_{xx}/μ_{yy}∼1.4 at n=10^{13} cm^{-2} and T=300  K), the electron mobility is found to be significantly more anisotropic (μ_{xx}/μ_{yy}∼6.2). Absolute values of μ_{xx} do not exceed 250 (700)  cm^{2} V^{-1} s^{-1} for holes (electrons), which can be considered as an upper limit for the mobility in BP at room temperature. PMID:27367397

  11. Intrinsic Charge Carrier Mobility in Single-Layer Black Phosphorus

    NASA Astrophysics Data System (ADS)

    Rudenko, A. N.; Brener, S.; Katsnelson, M. I.

    2016-06-01

    We present a theory for single- and two-phonon charge carrier scattering in anisotropic two-dimensional semiconductors applied to single-layer black phosphorus (BP). We show that in contrast to graphene, where two-phonon processes due to the scattering by flexural phonons dominate at any practically relevant temperatures and are independent of the carrier concentration n , two-phonon scattering in BP is less important and can be considered negligible at n ≳1013 cm-2 . At smaller n , however, phonons enter in the essentially anharmonic regime. Compared to the hole mobility, which does not exhibit strong anisotropy between the principal directions of BP (μx x/μy y˜1.4 at n =1013 cm-2 and T =300 K ), the electron mobility is found to be significantly more anisotropic (μx x/μy y˜6.2 ). Absolute values of μx x do not exceed 250 (700 ) cm2 V-1 s-1 for holes (electrons), which can be considered as an upper limit for the mobility in BP at room temperature.

  12. 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.

  13. Surface-barrier photoconverters with graded-gap layers in the space-charge region

    SciTech Connect

    Bobrenko, Yu. N.; Pavelets, S. Yu. Pavelets, A. M.; Semikina, T. V.; Yaroshenko, N. V.

    2015-04-15

    A novel possibility of controlling the parameters of p-Cu{sub 1.8}S-n-II-VI surface-barrier structures by embedding a thin graded-gap layer into a photoconverter space-charge region (SCR) is implemented. The feature of quasi-electric fields built in the SCR, i.e., the fact that an increase in the drift field for minority carriers can be accompanied by a decrease in the potential barrier for majority carriers, is considered. The proper choice of the parameters of the Cd{sub x}Zn{sub 1−x}S graded-gap layer embedded in the Cu{sub 1.8}S-ZnS structure SCR made it possible to double the quantum efficiency in the ultraviolet spectral region. For Cu{sub 1.8}S-CdS photoconverters with a (CdS){sub x}(ZnSe){sub 1−x} intermediate layer, dark diode currents are decreased by three orders of magnitude while retaining a high quantum efficiency.

  14. 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

  15. Curvature Effect on the Capacitance of Electric Double Layers at Ionic Liquid/Onion-Like Carbon Interfaces

    SciTech Connect

    Feng, Guang; Jiang, Deen; Cummings, Peter T

    2012-01-01

    Recent experiments have revealed that onion-like carbons (OLCs) offer high energy density and charging/discharging rates when used as the electrodes in supercapacitors. To understand the physical origin of this phenomenon, molecular dynamics simulations were performed for a room-temperature ionic liquid near idealized spherical OLCs with radii ranging from 0.356 to 1.223 nm. We find that the surface charge density increases almost linearly with the potential applied on electric double layers (EDLs) near OLCs. This leads to a nearly flat shape of the differential capacitance versus the potential, unlike the bell or camel shape observed on planar electrodes. Moreover, our simulations reveal that the capacitance of EDLs on OLCs increases with the curvature or as the OLC size decreases, in agreement with experimental observations. The curvature effect is explained by dominance of charge overscreening over a wide potential range and increased ion density per unit area of electrode surface as the OLC becomes smaller.

  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. Electrical degradation mechanisms of nanoscale charge trap flash memories due to trapped charge in the oxide layer

    NASA Astrophysics Data System (ADS)

    Koh, Kyoung Wook; Kim, Dong Hun; Ryu, Ju Tae; Kim, Tae Whan; Yoo, Keon-Ho

    2015-08-01

    The deterioration of the electrical characteristics of charge trap flash (CTF) memories with a silicon-oxide-nitride-oxide-silicon (SONOS) structure due to the charge traps in the oxide layers attributed to the random trapping and detrapping processes was investigated. Simulation results for the CTF memories showed that the threshold voltage shift was decreased by the charge trapped in the oxide layers in the SONOS structure and that the charge trapped in the blocking oxide had more significant effects than that trapped in the tunneling oxide. The degradation effects of the charge trapped in the blocking oxide on the electrical characteristics of the CTF memories were clarified by examining the vertical electric field in the device.

  18. 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

  19. 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.

  20. 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.

  1. Properties of electric double-layer capacitors with various polymer gel electrolytes

    SciTech Connect

    Liu, X.; Osaka, Tetsuya

    1997-09-01

    Polyethylene oxide (PEO), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN) based gel electrolytes with a mixture of ethylene carbonate and propylene carbonate as plasticizer and lithium perchlorate were used to fabricate an electric double-layer capacitor (EDLC). The performance of EDLCs with these gel electrolytes was investigated by using isotropic high-density graphite electrodes. The ion conductivities of various gel electrolytes were of the order of 10{sup {minus}4} to 10{sup {minus}3} S/cm, and they decreased in the order PAN > PEO > PMMA at ambient temperature. Capacitances approaching the value of EDLCs using organic liquid electrolyte, 20 mF/cm{sup 2}, with an isotropic high-density graphite electrode were obtained in PAN and PMMA gel electrolytes. The EDLC with PMMA-based gel electrolyte showed good charge-discharge behavior over 10{sup 4} cycles at a charge potential of 3.0 V. The rapid progress in the development of electric vehicles and electronic devices has placed increased demand on high-power capacitors. The EDLC is attractive as a rechargeable pulse power source or backup power supply for such applications.

  2. Layered Double Hydroxide Nanotransporter for Molecule Delivery to Intact Plant Cells

    PubMed Central

    Bao, Wenlong; Wang, Junya; Wang, Qiang; O’Hare, Dermot; Wan, Yinglang

    2016-01-01

    Here we report a powerful method that facilitates the transport of biologically active materials across the cell wall barrier in plant cells. Positively charged delaminated layered double hydroxide lactate nanosheets (LDH-lactate-NS) with a 0.5‒2 nm thickness and 30‒60 nm diameter exhibit a high adsorptive capacity for negatively charged biomolecules, including fluorescent dyes such as tetramethyl rhodamine isothiocyanate (TRITC), fluorescein isothiocyanate isomer I(FITC) and DNA molecules, forming neutral LDH-nanosheet conjugates. These neutral conjugates can shuttle the bound fluorescent dye into the cytosol of intact plant cell very efficiently. Furthermore, typical inhibitors of endocytosis and low temperature incubation did not prevent LDH-lactate-NS internalization, suggesting that LDH-lactate-NS penetrated the plasma membrane via non-endocytic pathways, which will widen the applicability to a variety of plant cells. Moreover, the absence of unwanted side effects in our cytological studies, and the nuclear localization of ssDNA-FITC suggest that nano-LDHs have potential application as a novel gene carrier to plants. PMID:27221055

  3. On the generation of double layers from ion- and electron-acoustic instabilities

    NASA Astrophysics Data System (ADS)

    Fu, Xiangrong; Cowee, Misa M.; Gary, S. Peter; Winske, Dan

    2016-03-01

    A plasma double layer (DL) is a nonlinear electrostatic structure that carries a uni-polar electric field parallel to the background magnetic field due to local charge separation. Past studies showed that DLs observed in space plasmas are mostly associated with the ion acoustic instability. Recent Van Allen Probes observations of parallel electric field structures traveling much faster than the ion acoustic speed have motivated a computational study to test the hypothesis that a new type of DLs—electron acoustic DLs—generated from the electron acoustic instability are responsible for these electric fields. Nonlinear particle-in-cell simulations yield negative results, i.e., the hypothetical electron acoustic DLs cannot be formed in a way similar to ion acoustic DLs. Linear theory analysis and the simulations show that the frequencies of electron acoustic waves are too high for ions to respond and maintain charge separation required by DLs. However, our results do show that local density perturbations in a two-electron-component plasma can result in unipolar-like electric field structures that propagate at the electron thermal speed, suggesting another potential explanation for the observations.

  4. Outstanding features of alginate-based gel electrolyte with ionic liquid for electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Soeda, Kazunari; Yamagata, Masaki; Ishikawa, Masashi

    2015-04-01

    An alginate-based gel electrolyte with an ionic liquid (Alg/IL) is investigated for electric double-layer capacitors (EDLCs) by using physicochemical and electrochemical measurements. The Alg/EMImBF4 (EMImBF4 = 1-ethyl-3-methylimidazolium tetrafluoroborate) gel electrolyte is thermally stable up to 280 °C, where EMImBF4 decomposes. Furthermore, the EDLC with the gel electrolyte can be operated even at high temperature. The cell containing Alg/EMImBF4 is also electrochemically stable even under high voltage (∼3.5 V) operation. Thus, the alginate is a suitable host polymer for the gel electrolyte for EDLCs. According to the result of charge-discharge characteristics, the voltage drop in the charge-discharge curve for the cell with Alg/EMImBF4 gel electrolyte is considerably smaller than that with liquid-phase EMImBF4 electrolyte. To clarify the effect of Alg in contact with the activated carbon electrode, we also prepared an Alg-containing ACFC electrode (Alg + ACFC), and evaluated its EDLC characteristics in liquid EMImBF4. The results prove that the presence of Alg close to the active materials significantly reduces the internal resistance of the EDLC cell, which may be attributed to the high affinity of Alg to activated carbon.

  5. Dust-ion-acoustic double layers in multi-ion dusty plasma

    SciTech Connect

    Mamun, A. A.; Deeba, F.

    2015-08-15

    A theoretical investigation has been made on nonplanar (cylindrical and spherical) dust-ionacoustic (DIA) double layers (DLs) in a multi-ion dusty plasma system containing inertial positive and negative ions and arbitrarily charged stationary dust. The dust particles have been considered as arbitrarily (either positively or negatively) charged in order to observe the effects of the dust polarity on the DIA DLs. The ion species were considered to be at different temperatures to observe the effects of the temperatures on that waves. The modified Gardner equation, which has been derived by employing the reductive perturbation method, has been used to analyze time-dependent nonplanar and planar DIA DLs. It has been found that the time evolution of DIA DLs is significantly modified not only by the nonplanar geometry, but also by the polarity, temperature, and mass ratio of the constituent particles. It has been also found that the amplitude of cylindrical DIA DL structures is larger than that of 1D planar ones, but smaller than that of the spherical ones.

  6. 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

  7. 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.

  8. Charge carrier transport properties in layer structured hexagonal boron nitride

    SciTech Connect

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2014-10-15

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (~ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T{sub 0}){sup −α} with α = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm{sup -1}), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  9. Short-range NN and N. Delta. correlations in pion double charge exchange (DCX)

    SciTech Connect

    Johnson, M.B.

    1990-01-01

    I will review several important results related to the short-range nucleon-nucleon and delta-nucleon interaction that have been obtained from recent studies of pion double charge exchange in selected nuclei. 32 refs., 5 figs., 3 tabs.

  10. A tetrastable naphthalenediimide: anion induced charge transfer, single and double electron transfer for combinational logic gates.

    PubMed

    Ajayakumar, M R; Hundal, Geeta; Mukhopadhyay, Pritam

    2013-09-11

    Herein we demonstrate the formation of the first tetrastable naphthalenediimide (NDI, 1a) molecule having multiple distinctly readable outputs. Differential response of 1a to fluoride anions induces intramolecular charge transfer (ICT), single/double electron transfer (SET/DET) leading to a set of combinational logic gates for the first time with a NDI moiety. PMID:23752683

  11. 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.

  12. 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.

  13. 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.

  14. Molecular Dynamics Study of the Electrical Double Layer at Silver Chloride Electrolyte Interfaces

    SciTech Connect

    Zarzycki, Piotr P.; Kerisit, Sebastien N.; Rosso, Kevin M.

    2010-05-20

    Molecular dynamics simulations of the electrical double layer at AgCl/aqueous electrolyte (KCl) interfaces are presented, accompanied by a new force field and properties of bulk AgCl computed using planewave density functional theory. Long dynamics simulations were performed to estimate ion adsorption free energies at the AgCl surface. The simulations demonstrate formation of a bilayer hydration sheet composed of two sublayers of water molecules interconnected by hydrogen bonds. Potassium ions prefer to form an inner-sphere complex, whereas chloride ions prefer outer-sphere complexes. The adsorbed ions/water layers form a relatively rigid structure within the range of ionic strength considered, which confirms the applicability of the Helmholtz model in a high concentration regime. Profiles of the charge density, electric field and electrostatic potential across the simulation cell revealed that oscillations of water molecules govern these quantities. The electrostatic potential generated only by the electrolyte ions was used to study the quasi-Nernstian response of the silver chloride surface to the variation in the ionic strength.

  15. Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Khazanov, George

    2003-01-01

    When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms [Bezzerides et al., 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [Barakat and Schunk, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region [Ergun et al., 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold electron populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an ,extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two

  16. Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: IV. Diffuse Layer Charge/Potential Relationships

    EPA Science Inventory

    Most current electrostatic surface complexation models describing ionic binding at the particle/water interface rely on the use of Poisson - Boltzmann (PB) theory for relating diffuse layer charge densities to diffuse layer electrostatic potentials. PB theory is known to contain ...

  17. Highly efficient, deep-blue phosphorescent organic light emitting diodes with a double-emitting layer structure

    NASA Astrophysics Data System (ADS)

    Fukagawa, H.; Watanabe, K.; Tsuzuki, T.; Tokito, S.

    2008-09-01

    We have demonstrated a highly efficient, deep-blue organic light-emitting diode (OLED) using a host material with a high triplet energy. The OLED device that we have prepared utilizes a phosphorescent guest material, iridium(III)bis(4',6',-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate, exhibits a peak quantum efficiency of about 15.7%. We employed a double-emitting layer (DEL) structure that distributes the carrier recombination region within the device. In this DEL structure, the emission mechanism is such that the energy transfers from the host material in one emitting layer, and the other emitting layer provides for direct charge trapping in the guest material. This DEL structure proved to be quite useful in achieving the reported device characteristics.

  18. A systematic study of ideal and double layer reconstructions of ABO3(001) surfaces (A = Sr, Ba; B = Ti, Zr) from first principles.

    PubMed

    Iles, N; Finocchi, F; Khodja, K Driss

    2010-08-01

    We conducted a comparative study of various reconstructions for the (001) surfaces of SrTiO(3), BaTiO(3), SrZrO(3) and BaZrO(3) perovskites through calculations within the density functional theory. The atomic structure, the thermodynamic stability and the charge distribution of ideal AO or BO(2) terminations, as well as the so-called AO or BO(2) double layer reconstructions were analysed, and it was found that of all the BO(2) double layer reconstructions the most stable are the (2 × 2) and the (√2 × √2) ones. This is mainly due to stress release through the formation of long B-chains. On Ti-based perovskites, these double layer reconstructions were found to be thermodynamically stable, which was not the case for Zr-based perovskites, for which AO terminations dominated most of the stability domain. We also found that the BO(2) double layer reconstructions are accompanied by a substantial charge redistribution, with an almost neutral surface plane. This charge redistribution has important consequences for the reactivity and the behaviour of the electric field close to the surface.

  19. Ionic Asymmetry and Solvent Excluded Volume Effects on Spherical Electric Double Layers: A Density Functional Approach

    SciTech Connect

    Medasani, Bharat; Ovanesyan, Zaven; Thomas, Dennis G.; Sushko, Maria L.; Marucho, Marcelo

    2014-05-29

    In this article we present a classical density functional theory for electrical double layers of spherical macroions that extends the capabilities of conventional approaches by accounting for electrostatic ion correlations, size asymmetry and excluded volume effects. The approach is based on a recent approximation introduced by Hansen-Goos and Roth for the hard sphere excess free energy of inhomogeneous fluids (J. Chem. Phys. 124, 154506). It accounts for the proper and efficient description of the effects of ionic asymmetry and solvent excluded volume, especially at high ion concentrations and size asymmetry ratios including those observed in experimental studies. Additionally, we utilize a leading functional Taylor expansion approximation of the ion density profiles. In addition, we use the Mean Spherical Approximation for multi-component charged hard sphere fluids to account for the electrostatic ion correlation effects. These approximations are implemented in our theoretical formulation into a suitable decomposition of the excess free energy which plays a key role in capturing the complex interplay between charge correlations and excluded volume effects. We perform Monte Carlo simulations in various scenarios to validate the proposed approach, obtaining a good compromise between accuracy and computational cost. We use the proposed computational approach to study the effects of ion size, ion size asymmetry and solvent excluded volume on the ion profiles, integrated charge, mean electrostatic potential, and ionic coordination number around spherical macroions in various electrolyte mixtures. Our results show that both solvent hard sphere diameter and density play a dominant role in the distribution of ions around spherical macroions, mainly for experimental water molarity and size values where the counterion distribution is characterized by a tight binding to the macroion, similar to that predicted by the Stern model.

  20. Ionic asymmetry and solvent excluded volume effects on spherical electric double layers: A density functional approach

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Ovanesyan, Zaven; Thomas, Dennis G.; Sushko, Maria L.; Marucho, Marcelo

    2014-05-01

    In this article, we present a classical density functional theory for electrical double layers of spherical macroions that extends the capabilities of conventional approaches by accounting for electrostatic ion correlations, size asymmetry, and excluded volume effects. The approach is based on a recent approximation introduced by Hansen-Goos and Roth for the hard sphere excess free energy of inhomogeneous fluids [J. Chem. Phys. 124, 154506 (2006); Hansen-Goos and Roth, J. Phys.: Condens. Matter 18, 8413 (2006)]. It accounts for the proper and efficient description of the effects of ionic asymmetry and solvent excluded volume, especially at high ion concentrations and size asymmetry ratios including those observed in experimental studies. Additionally, we utilize a leading functional Taylor expansion approximation of the ion density profiles. In addition, we use the mean spherical approximation for multi-component charged hard sphere fluids to account for the electrostatic ion correlation effects. These approximations are implemented in our theoretical formulation into a suitable decomposition of the excess free energy which plays a key role in capturing the complex interplay between charge correlations and excluded volume effects. We perform Monte Carlo simulations in various scenarios to validate the proposed approach, obtaining a good compromise between accuracy and computational cost. We use the proposed computational approach to study the effects of ion size, ion size asymmetry, and solvent excluded volume on the ion profiles, integrated charge, mean electrostatic potential, and ionic coordination number around spherical macroions in various electrolyte mixtures. Our results show that both solvent hard sphere diameter and density play a dominant role in the distribution of ions around spherical macroions, mainly for experimental water molarity and size values where the counterion distribution is characterized by a tight binding to the macroion, similar to that

  1. Ionic asymmetry and solvent excluded volume effects on spherical electric double layers: a density functional approach.

    PubMed

    Medasani, Bharat; Ovanesyan, Zaven; Thomas, Dennis G; Sushko, Maria L; Marucho, Marcelo

    2014-05-28

    In this article, we present a classical density functional theory for electrical double layers of spherical macroions that extends the capabilities of conventional approaches by accounting for electrostatic ion correlations, size asymmetry, and excluded volume effects. The approach is based on a recent approximation introduced by Hansen-Goos and Roth for the hard sphere excess free energy of inhomogeneous fluids [J. Chem. Phys. 124, 154506 (2006); Hansen-Goos and Roth, J. Phys.: Condens. Matter 18, 8413 (2006)]. It accounts for the proper and efficient description of the effects of ionic asymmetry and solvent excluded volume, especially at high ion concentrations and size asymmetry ratios including those observed in experimental studies. Additionally, we utilize a leading functional Taylor expansion approximation of the ion density profiles. In addition, we use the mean spherical approximation for multi-component charged hard sphere fluids to account for the electrostatic ion correlation effects. These approximations are implemented in our theoretical formulation into a suitable decomposition of the excess free energy which plays a key role in capturing the complex interplay between charge correlations and excluded volume effects. We perform Monte Carlo simulations in various scenarios to validate the proposed approach, obtaining a good compromise between accuracy and computational cost. We use the proposed computational approach to study the effects of ion size, ion size asymmetry, and solvent excluded volume on the ion profiles, integrated charge, mean electrostatic potential, and ionic coordination number around spherical macroions in various electrolyte mixtures. Our results show that both solvent hard sphere diameter and density play a dominant role in the distribution of ions around spherical macroions, mainly for experimental water molarity and size values where the counterion distribution is characterized by a tight binding to the macroion, similar to that

  2. Ionic asymmetry and solvent excluded volume effects on spherical electric double layers: a density functional approach.

    PubMed

    Medasani, Bharat; Ovanesyan, Zaven; Thomas, Dennis G; Sushko, Maria L; Marucho, Marcelo

    2014-05-28

    In this article, we present a classical density functional theory for electrical double layers of spherical macroions that extends the capabilities of conventional approaches by accounting for electrostatic ion correlations, size asymmetry, and excluded volume effects. The approach is based on a recent approximation introduced by Hansen-Goos and Roth for the hard sphere excess free energy of inhomogeneous fluids [J. Chem. Phys. 124, 154506 (2006); Hansen-Goos and Roth, J. Phys.: Condens. Matter 18, 8413 (2006)]. It accounts for the proper and efficient description of the effects of ionic asymmetry and solvent excluded volume, especially at high ion concentrations and size asymmetry ratios including those observed in experimental studies. Additionally, we utilize a leading functional Taylor expansion approximation of the ion density profiles. In addition, we use the mean spherical approximation for multi-component charged hard sphere fluids to account for the electrostatic ion correlation effects. These approximations are implemented in our theoretical formulation into a suitable decomposition of the excess free energy which plays a key role in capturing the complex interplay between charge correlations and excluded volume effects. We perform Monte Carlo simulations in various scenarios to validate the proposed approach, obtaining a good compromise between accuracy and computational cost. We use the proposed computational approach to study the effects of ion size, ion size asymmetry, and solvent excluded volume on the ion profiles, integrated charge, mean electrostatic potential, and ionic coordination number around spherical macroions in various electrolyte mixtures. Our results show that both solvent hard sphere diameter and density play a dominant role in the distribution of ions around spherical macroions, mainly for experimental water molarity and size values where the counterion distribution is characterized by a tight binding to the macroion, similar to that

  3. Spatiotemporal electrochemical measurements across an electric double layer capacitor electrode with application to aqueous sodium hybrid batteries

    NASA Astrophysics Data System (ADS)

    Tully, Katherine C.; Whitacre, Jay F.; Litster, Shawn

    2014-02-01

    This paper presents in-situ spatiotemporal measurements of the electrolyte phase potential within an electric double layer capacitor (EDLC) negative electrode as envisaged for use in an aqueous hybrid battery for grid-scale energy storage. The ultra-thick electrodes used in these batteries to reduce non-functional material costs require sufficiently fast through-plane mass and charge transport to attain suitable charging and discharging rates. To better evaluate the through-plane transport, we have developed an electrode scaffold (ES) for making in situ electrolyte potential distribution measurements at discrete known distances across the thickness of an uninterrupted EDLC negative electrode. Using finite difference methods, we calculate local current, volumetric charging current and charge storage distributions from the spatiotemporal electrolyte potential measurements. These potential distributions provide insight into complex phenomena that cannot be directly observed using other existing methods. Herein, we use the distributions to identify areas of the electrode that are underutilized, assess the effects of various parameters on the cumulative charge storage distribution, and evaluate an effectiveness factor for charge storage in EDLC electrodes.

  4. Thin double layer approximation to describe streaming current fields in complex geometries: analytical framework and applications to microfluidics.

    PubMed

    Brunet, Edouard; Ajdari, Armand

    2006-05-01

    We set up an analytical framework that allows one to describe and compute streaming effects and electro-osmosis on an equal footing. This framework relies on the thin double layer approximation commonly used for description of electroosmotic flows, but rarely used for streaming problems. Using this framework we quantitatively assess the induction of bulk streaming current patterns by topographic or charge heterogeneities on surfaces. This too also permits analytical computation of all linear electrokinetic effects in complex microfluidic geometries, and we discuss a few immediate applications. PMID:16803036

  5. 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.

  6. 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)

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Organic double layer element driven by triboelectric nanogenerator: Study of carrier behavior by non-contact optical method

    NASA Astrophysics Data System (ADS)

    Chen, Xiangyu; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-02-01

    By using optical electric-field-induced second-harmonic generation (EFISHG) technique, we studied carrier behavior caused by contact electrification (CE) in an organic double-layer element. This double-layer sample was half suspended in the open air, where one electrode (anode or cathode) was connected with a Cu foil for electrification while the other electrode was floated. Results showed two distinct carrier behaviors, depending on the (anode or cathode) connections to the Cu foil, and these carrier behaviors were analyzed based on the Maxwell-Wagner model. The double-layer sample works as a simple solar cell device. The photovoltaic effect and CE process have been proved to be two paralleled effects without strong interaction with each other, while photoconductivity changing in the sample can enhance the relaxation of CE induced charges. By probing the carrier behavior in this half-suspended device, the EFISHG technique has been demonstrated to be an effective non-contact method for clarifying the CE effect on related energy harvesting devices and electronics devices. Meanwhile, the related physical analysis in this letter is also useful for elucidating the fundamental characteristic of hybrid energy system based on solar cell and triboelectric nanogenerator.

  14. 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.

  15. Impact of stray charge on interconnect wire via probability model of double-dot system

    NASA Astrophysics Data System (ADS)

    Xiangye, Chen; Li, Cai; Qiang, Zeng; Xinqiao, Wang

    2016-02-01

    The behavior of quantum cellular automata (QCA) under the influence of a stray charge is quantified. A new time-independent switching paradigm, a probability model of the double-dot system, is developed. Superiority in releasing the calculation operation is presented by the probability model compared to previous stray charge analysis utilizing ICHA or full-basis calculation. Simulation results illustrate that there is a 186-nm-wide region surrounding a QCA wire where a stray charge will cause the target cell to switch unsuccessfully. The failure is exhibited by two new states' dominating the target cell. Therefore, a bistable saturation model is no longer applicable for stray charge analysis. Project supported by the National Natural Science Foundation of China (No. 61172043) and the Key Program of Shaanxi Provincial Natural Science for Basic Research (No. 2011JZ015).

  16. Self-discharge of electrochemical double layer capacitors.

    PubMed

    Lewandowski, Andrzej; Jakobczyk, Pawel; Galinski, Maciej; Biegun, Marcin

    2013-06-14

    Spontaneous voltage drop between EDLC electrodes, when it is kept under the open-circuit condition, is commonly called 'self-discharge' and is interpreted as a result of energy loss by the device. Three mechanisms of self-discharge were proposed: due to a leakage-current, faradaic reactions and charge redistribution. According to the law of energy preservation, if the voltage drop is associated with the energy loss, the energy would more likely be exchanged with the environment. While heat generation was measured during EDLC charging and discharging, the corresponding effect during storage under open-circuit conditions has not been reported. This may support the conclusion that voltage changes during 'self-discharge' are not related to a considerable energy loss. Moreover, it has been shown that a two-stage charging process, i.e. first galvanostatic charging followed by a potentiostatic charge redistribution, resulted in considerably slower potential changes when the device was switched to the open circuit. All discussed models were based on the assumption that the energy accumulated by EDLCs is proportional to the voltage in the second power, with capacitance (C/2) as the proportionality constant. However, it has been shown that during EDLC charging or discharging through a resistance R, equations valid for 'dielectric' and electrolytic capacitors, do not hold in the case of EDLCs. Consequently, the assumption that the energetic state of the EDLC is proportional at any time to the voltage in the second power may not be valid due to considerable variability of the 'constant' C. Therefore, voltage changes may not reflect the energetic state of the device. PMID:23640679

  17. Study of Electrical Conduction Mechanism of Organic Double-Layer Diode Using Electric Field Induced Optical Second Harmonic Generation Measurement.

    PubMed

    Nishi, Shohei; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-04-01

    By using electric field induced optical second harmonic generation (EFISHG) and current voltage (I-V) measurements, we studied the electrical transport mechanism of organic double-layer diodes with a structure of Au/N, N'-di-[(1-naphthyl)-N, N'-diphenyl]-(1,1'-biphenyl)-4,4'-diamine (a-NPD)/poly(methyl methacrylate) (PMMA)/indium zinc oxide (IZO). Here the α-NPD is a carrier transport layer and the PMMA is an electrical insulating layer. The current level was very low, but the I-V characteristics showed a rectifying behavior. The EFISHG measurement selectively and directly probed the electric field across the α-NPD layer, and showed that the electric field across the a-NPD layer is completely relaxed owing to the charge accumulation at the a-NPD/PMMA interface in the region V > 0, whereas the carrier accumulation was not significant in the region V < 0. On the basis of these experimental results, we proposed a model of the rectification. Further, by coupling the I-V characteristics with the EFISHG measurement, the I-V characteristics of the diodes were well converted into the current-electric field (I-E) characteristics of the α-NPD layer and the PMMA layer. The I-E characteristics suggested the Schottky-type conduction governs the carrier transport. We conclude that the I-V measurement coupled with the EFISHG measurement is very useful to study carrier transport mechanism of the organic double-layer diodes. PMID:27451633

  18. Low energy charged particles interacting with amorphous solid water layers.

    PubMed

    Horowitz, Yonatan; Asscher, Micha

    2012-04-01

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 μA) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 ± 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  19. Low energy charged particles interacting with amorphous solid water layers

    NASA Astrophysics Data System (ADS)

    Horowitz, Yonatan; Asscher, Micha

    2012-04-01

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 μA) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 ± 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  20. Low energy charged particles interacting with amorphous solid water layers

    SciTech Connect

    Horowitz, Yonatan; Asscher, Micha

    2012-04-07

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 {mu}A) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 {+-} 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  1. 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.

  2. The sup 11 Li neutron halo radius from pion double charge exchange

    SciTech Connect

    Hayes, A.C.

    1991-01-01

    We have analzed the pion double charge exchange data for the direct population of the ground state of {sup 11}Li by the {sup 11}B({pi}{sup {minus}}, {pi}{sup +}){sup 11}Li reaction and find that the measured cross section determines the rms radius of the last two neutrons in {sup 11}Li to be 5.1{sub {minus} 0.8}{sup +0.6} fm. It is shown that the pion cross-section falls off as the sixth power of the assumed neutron halo radius, so that a radius greater than about 6 fm is ruled out. Indeed, pion double charge is found to act as an unusually sensitive probe of the properties of this exotic neutron rich nucleus. 9 refs., 2 figs.

  3. The role of interfacial water layer in atmospherically relevant charge separation

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Indrani

    Charge separation at interfaces is important in various atmospheric processes, such as thunderstorms, lightning, and sand storms. It also plays a key role in several industrial processes, including ink-jet printing and electrostatic separation. Surprisingly, little is known about the underlying physics of these charging phenomena. Since thin films of water are ubiquitous, they may play a role in these charge separation processes. This talk will focus on the experimental investigation of the role of a water adlayer in interfacial charging, with relevance to meteorologically important phenomena, such as atmospheric charging due to wave actions on oceans and sand storms. An ocean wave generates thousands of bubbles, which upon bursting produce numerous large jet droplets and small film droplets that are charged. In the 1960s, Blanchard showed that the jet droplets are positively charged. However, the charge on the film droplets was not known. We designed an experiment to exclusively measure the charge on film droplets generated by bubble bursting on pure water and aqueous salt solution surfaces. We measured their charge to be negative and proposed a model where a slight excess of hydroxide ions in the interfacial water layer is responsible for generating these negatively charged droplets. The findings from this research led to a better understanding of the ionic disposition at the air-water interface. Sand particles in a wind-blown sand layer, or 'saltation' layer, become charged due to collisions, so much so, that it can cause lightning. Silica, being hydrophilic, is coated with a water layer even under low-humidity conditions. To investigate the importance of this water adlayer in charging the silica surfaces, we performed experiments to measure the charge on silica surfaces due to contact and collision processes. In case of contact charging, the maximum charge separation occurred at an optimum relative humidity. On the contrary, in collisional charging process, no

  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 PAGESBeta

    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. Charge sensing of a few-donor double quantum dot in silicon

    SciTech Connect

    Watson, T. F. Weber, B.; Büch, H.; Fuechsle, M.; Simmons, M. Y.

    2015-12-07

    We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ∼4 orders of magnitude by detuning its energy with respect to the first dot.

  9. Measurement of pion double charge exchange on carbon-13, carbon-14, magnesium-26, and iron-56

    SciTech Connect

    Seidl, P.A.

    1985-02-01

    Cross sections for the /sup 13,14/C,/sup 26/Mg,/sup 56/Fe(..pi../sup +/,..pi../sup -/)/sup 13,14/O,/sup 26/Si,/sup 56/Ni reactions were measured with the Energetic Pion Channel and Spectrometer at the Clinton P. Anderson Meson Physics Facility for 120 less than or equal to T/sub ..pi../ less than or equal to 292 MeV and 0 less than or equal to theta less than or equal to 50. The double isobaric analog states (DIAS) are of primary interest. In addition, cross sections for transitions to /sup 14/O(0/sup +/, 5.92 MeV), /sup 14/O(2/sup +/, 7.77 MeV), /sup 56/Ni(gs), /sup 13/O(gs), and /sup 13/O(4.21 MeV) are presented. The /sup 13/O(4.21 MeV) state is postulated to have J/sup ..pi../ = 1/2/sup -/. The data are compared to previously measured double-charge-exchange cross sections on other nuclei, and the systematics of double charge exchange on T greater than or equal to 1 target nuclei leading to the DIAS are studied. Near the ..delta../sub 33/ resonance, cross sections for the DIAS transitions are in disagreement with calculations in which the reaction is treated as sequential charge exchange through the free pion-nucleon amplitude, while for T/sub ..pi../ > 200 MeV the anomalous features of the 164 MeV data are not apparent. This is evidence for significant higher order contributions to the double-charge-exchange amplitude near the reasonable energy. Two theoretical approaches that include two nucleon processes are applied to the DIAS data. 64 references.

  10. Charge sensing of a few-donor double quantum dot in silicon

    NASA Astrophysics Data System (ADS)

    Watson, T. F.; Weber, B.; Büch, H.; Fuechsle, M.; Simmons, M. Y.

    2015-12-01

    We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ˜4 orders of magnitude by detuning its energy with respect to the first dot.

  11. Particle simulation of auroral double layers. Doctoral thesis

    SciTech Connect

    Smith, B.L.

    1992-06-01

    Externally driven magnetic reconnection has been proposed as a possible mechanism for production of auroral electrons during magnetic substorms. Fluid simulations of magnetic reconnection lead to strong plasma flows towards the increasing magnetic field of the earth. These plasma flows must generate large scale potential drops to preserve global charge neutrality. We have examined currentless injection of plasma along a dipole magnetic field into a bounded region using both analytic techniques and particle simulation.

  12. Capacitively coupled singlet-triplet qubits in the double charge resonant regime

    NASA Astrophysics Data System (ADS)

    Srinivasa, V.; Taylor, J. M.

    2015-12-01

    We investigate a method for entangling two singlet-triplet qubits in adjacent double quantum dots via capacitive interactions. In contrast to prior work, here we focus on a regime with strong interactions between the qubits. The interplay of the interaction energy and simultaneous large detunings for both double dots gives rise to the "double charge resonant" regime, in which the unpolarized (1111) and fully polarized (0202) four-electron states in the absence of interqubit tunneling are near degeneracy, while being energetically well separated from the partially polarized (0211 and 1102) states. A rapid controlled-phase gate may be realized by combining time evolution in this regime in the presence of intraqubit tunneling and the interqubit Coulomb interaction with refocusing π pulses that swap the singly occupied singlet and triplet states of the two qubits via, e.g., magnetic gradients. We calculate the fidelity of this entangling gate, incorporating models for two types of noise—charge fluctuations in the single-qubit detunings and charge relaxation within the low-energy subspace via electron-phonon interaction—and identify parameter regimes that optimize the fidelity. The rates of phonon-induced decay for pairs of GaAs or Si double quantum dots vary with the sizes of the dipolar and quadrupolar contributions and are several orders of magnitude smaller for Si, leading to high theoretical gate fidelities for coupled singlet-triplet qubits in Si dots. We also consider the dependence of the capacitive coupling on the relative orientation of the double dots and find that a linear geometry provides the fastest potential gate.

  13. Highly stable layered double hydroxide colloids: a direct aqueous synthesis route from hybrid polyion complex micelles.

    PubMed

    Layrac, Géraldine; Destarac, Mathias; Gérardin, Corine; Tichit, Didier

    2014-08-19

    Aqueous suspensions of highly stable Mg/Al layered double hydroxide (LDH) nanoparticles were obtained via a direct and fully colloidal route using asymmetric poly(acrylic acid)-b-poly(acrylamide) (PAA-b-PAM) double hydrophilic block copolymers (DHBCs) as growth and stabilizing agents. We showed that hybrid polyion complex (HPIC) micelles constituted of almost only Al(3+) were first formed when mixing solutions of Mg(2+) and Al(3+) cations and PAA3000-b-PAM10000 due to the preferential complexation of the trivalent cations. Then mineralization performed by progressive hydroxylation with NaOH transformed the simple DHBC/Al(3+) HPIC micelles into DHBC/aluminum hydroxide colloids, in which Mg(2+) ions were progressively introduced upon further hydroxylation leading to the Mg-Al LDH phase. The whole process of LDH formation occurred then within the confined environment of the aqueous complex colloids. The hydrodynamic diameter of the DHBC/LDH colloids could be controlled: it decreased from 530 nm down to 60 nm when the metal complexing ratio R (R = AA/(Mg + Al)) increased from 0.27 to 1. This was accompanied by a decrease of the average size of individual LDH particles as R increased (for example from 35 nm at R = 0.27 down to 17 nm at R = 0.33), together with a progressive favored intercalation of polyacrylate rather than chloride ions in the interlayer space of the LDH phase. The DHBC/LDH colloids have interesting properties for biomedical applications, that is, high colloidal stability as a function of time, stability in phosphate buffered saline solution, as well as the required size distribution for sterilization by filtration. Therefore, they could be used as colloidal drug delivery systems, especially for hydrosoluble negatively charged drugs.

  14. 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.

  15. 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.

  16. Electric double-layer capacitor based on an ionic clathrate hydrate.

    PubMed

    Lee, Wonhee; Kwon, Minchul; Park, Seongmin; Lim, Dongwook; Cha, Jong-Ho; Lee, Huen

    2013-07-01

    Herein, we suggest a new approach to an electric double-layer capacitor (EDLC) that is based on a proton-conducting ionic clathrate hydrate (ICH). The ice-like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me4NOH⋅5 H2O show a high specific capacitance, reversible charge-discharge behavior, and a long cycle life. The ionic-hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre-treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more-favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems. PMID:23671039

  17. An electrochemical double layer capacitor using an activated carbon electrode with gel electrolyte binder

    SciTech Connect

    Osaka, Tetsuya, Liu, X.; Nojima, Masashi; Momma, Toshiyuki

    1999-05-01

    An electric double layer capacitor (EDLC) was prepared with an activated carbon powder electrode with poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based gel electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were used as plasticizer and tetraethylammonium tetrafluoroborate (TEABF{sub 4}) was used as the supporting electrolyte. An optimized gel electrolyte of PVdF-HFP/PC/EC/TEABF{sub 4} - 23/31/35/11 mass ratio exhibited high ionic conductivity of 5 {times} 10{sup {minus}3} S/cm, high electrode capacitance, and good mechanical strength. An electrode consisting of activated carbon (AC) with the gel electrolyte as the binder (AC/PVdF-HFP based gel, 7/3 mass ratio) showed a higher specific capacitance and a lower ion diffusion resistance within the electrode than a carbon electrode, prepared with PVdF-HFP binder without plasticizer. This suggests that an electrode mixed with the gel electrolyte has a lower ion diffusion resistance inside the electrode. The highest specific capacitance of 123 F/g was achieved with an electrode containing AC with a specific surface area of 2500 m{sup 2}/g. A coin-type EDLC cell with optimized components showed excellent cycleability exceeding 10{sup 4} cycles with ca. 100% coulombic efficiency achieved when charging and discharging was repeated between 1.0 and 2.5 V at 1.66 mA/cm{sup 2}.

  18. High voltage electric double layer capacitor using a novel solid-state polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Sato, Takaya; Marukane, Shoko; Morinaga, Takashi; Kamijo, Toshio; Arafune, Hiroyuki; Tsujii, Yoshinobu

    2015-11-01

    We designed and fabricated a bipolar-type electric double layer capacitor (EDLC) with a maximum 7.5 V operating voltage using a new concept in solid electrolytes. A cell having a high operating voltage, that is free from liquid leakage and is non-flammable is achieved by a bipolar design utilizing a solid polymer electrolyte made up of particles in a three-dimensional array, such as crystals composed of 75 wt% of hybrid particles decorated with a concentrated ionic liquid polymer brush (PSiP) and 25wt% of an ionic liquid (IL). The resulting solid film had sufficient physical strength and a high enough ionic conductivity to function as an electrolyte. Solidification as well as ionic conduction is due to the regular array of PSiPs, thereby producing a high ion-conductivity from a networked path between cores containing an appropriate amount of IL as a plasticizer. The demonstration cell shows a relatively good cycle durability and rate properties up to a 10C discharge process. It also has a very small leakage current in continuous charging and better self-discharge properties, even at 60 °C, compared with conventional cells. This paper demonstrates the first successful fabrication of a bipolar EDLC in a simple structure using this novel polymer solid electrolyte.

  19. Three-dimensional porous MXene/layered double hydroxide composite for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Wang, Ya; Dou, Hui; Wang, Jie; Ding, Bing; Xu, Yunling; Chang, Zhi; Hao, Xiaodong

    2016-09-01

    In this work, an exfoliated MXene (e-MXene) nanosheets/nickel-aluminum layered double hydroxide (MXene/LDH) composite as supercapacitor electrode material is fabricated by in situ growth of LDH on e-MXene substrate. The LDH platelets homogeneously grown on the surface of the e-MXene sheets construct a three-dimensional (3D) porous structure, which not only leads to high active sites exposure of LDH and facile liquid electrolyte penetration, but also alleviates the volume change of LDH during the charge/discharge process. Meanwhile, the e -MXene substrate forms a conductive network to facilitate the electron transport of active material. The optimized MXene/LDH composite exhibits a high specific capacitance of 1061 F g-1 at a current density of 1 A g-1, excellent capacitance retention of 70% after 4000 cycle tests at a current density of 4 A g-1 and a good rate capability with 556 F g-1 retention at 10 A g-1.

  20. Sound field measurement in a double layer cavitation cluster by rugged miniature needle hydrophones.

    PubMed

    Koch, Christian

    2016-03-01

    During multi-bubble cavitation the bubbles tend to organize themselves into clusters and thus the understanding of properties and dynamics of clustering is essential for controlling technical applications of cavitation. Sound field measurements are a potential technique to provide valuable experimental information about the status of cavitation clouds. Using purpose-made, rugged, wide band, and small-sized needle hydrophones, sound field measurements in bubble clusters were performed and time-dependent sound pressure waveforms were acquired and analyzed in the frequency domain up to 20 MHz. The cavitation clusters were synchronously observed by an electron multiplying charge-coupled device (EMCCD) camera and the relation between the sound field measurements and cluster behaviour was investigated. Depending on the driving power, three ranges could be identified and characteristic properties were assigned. At low power settings no transient and no or very low stable cavitation activity can be observed. The medium range is characterized by strong pressure peaks and various bubble cluster forms. At high power a stable double layer was observed which grew with further increasing power and became quite dynamic. The sound field was irregular and the fundamental at driving frequency decreased. Between the bubble clouds completely different sound field properties were found in comparison to those in the cloud where the cavitation activity is high. In between the sound field pressure amplitude was quite small and no collapses were detected.

  1. Fire and thermal properties of layered double hydroxides and polyurea nanocomposites

    NASA Astrophysics Data System (ADS)

    Nyambo, Calistor

    Layered double hydroxide (LDH) intercalated with linear alkyl carboxylates (CH3(CH2)n COO-, n = 8, 10, 12, 14, 16, 20), borate and benzyl anions were prepared. The effect on fire and thermal properties of the mode of preparation for LDHs (i.e. ion exchange, coprecipitation and rehydration of the calcined LDH methods) has been studied. After characterization, the LDHs were used to prepare nanocomposites with a range of polar and non-polar polymers. Characterization of the LDHs and the nanocomposites was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry analysis (TGA), transmission electron microscopy (TEM) and cone calorimetry. FTIR and XRD analyses confirmed the presence of the charge balancing anions in the galleries of the LDHs. Improvements in fire and thermal properties of the nanocomposites were observed. The cone calorimeter revealed that the addition of LDHs reduces the peak heat release rate significantly. LDHs were combined with commercial fire retardants. Synergistic effects were observed in both TGA and cone calorimetry for formulations containing both LDH and ammonium polyphosphate (APP). Physical and chemical interactions between LDH and APP are responsible for the observed synergy in thermal stability and fire performance.

  2. Enhancing atrazine biodegradation by Pseudomonas sp. strain ADP adsorption to Layered Double Hydroxide bionanocomposites.

    PubMed

    Alekseeva, Tatiana; Prevot, Vanessa; Sancelme, Martine; Forano, Claude; Besse-Hoggan, Pascale

    2011-07-15

    To mimic the role of hydroxide minerals and their humic complex derivatives on the biodegradability of pesticides in soils, synthetic Mg(R)Al Layered Double Hydroxides (LDH) and Mg(R)Al modified by Humic substances (LDH-HA) were prepared for various R values (2, 3 and 4) and fully characterized. Adsorption properties of LDH and LDH-HA toward Pseudomonas sp. strain ADP were evaluated. The adsorption kinetics were very fast (<5 min to reach equilibrium). The adsorption capacities were greater than previously reported (13.5×10(11), 41×10(11) and 45.5×10(11) cells/gLDH for Mg(2)Al, Mg(3)Al and Mg(4)Al, respectively) and varied with both surface charge and textural properties. Surface modification by HA reduced the adsorption capacities of cells by 2-6-fold. Biodegradation kinetics of atrazine by Pseudomonas sp. adsorbed on both LDHs and LDH-HA complexes were measured for various solid/liquid ratios and adsorbed cell amounts. Biodegradation activity of bacterial cells was strongly boosted after adsorption on LDHs, the effect depending on the quantity and properties of the LDH matrix. The maximum biodegradation rate was obtained in the case of a 100 mg/mL Mg(2)Al LDH suspension (26 times higher than that obtained with cells alone). PMID:21596476

  3. In situ small angle neutron scattering revealing ion sorption in microporous carbon electrical double layer capacitors.

    PubMed

    Boukhalfa, Sofiane; Gordon, Daniel; He, Lilin; Melnichenko, Yuri B; Nitta, Naoki; Magasinski, Alexandre; Yushin, Gleb

    2014-03-25

    Experimental studies showed the impact of the electrolyte solvents on both the ion transport and the specific capacitance of microporous carbons. However, the related structure-property relationships remain largely unclear and the reported results are inconsistent. The details of the interactions of the charged carbon pore walls with electrolyte ions and solvent molecules at a subnanometer scale are still largely unknown. Here for the first time we utilize in situ small angle neutron scattering (SANS) to reveal the electroadsorption of organic electrolyte ions in carbon pores of different sizes. A 1 M solution of tetraethylammonium tetrafluoroborate (TEATFB) salt in deuterated acetonitrile (d-AN) was used in an activated carbon with the pore size distribution similar to that of the carbons used in commercial double layer capacitors. In spite of the incomplete wetting of the smallest carbon pores by the d-AN, we observed enhanced ion sorption in subnanometer pores under the applied potential. Such results suggest the visible impact of electrowetting phenomena counterbalancing the high energy of the carbon/electrolyte interface in small pores. This behavior may explain the characteristic butterfly wing shape of the cyclic voltammetry curve that demonstrates higher specific capacitance at higher applied potentials, when the smallest pores become more accessible to electrolyte. Our study outlines a general methodology for studying various organic salts-solvent-carbon combinations.

  4. Synthesis and characterization of layered double hydroxides and their potential as nonviral gene delivery vehicles.

    PubMed

    Balcomb, Blake; Singh, Moganavelli; Singh, Sooboo

    2015-04-01

    Layered double hydroxides (LDHs) exhibit characteristic anion-exchange chemistry making them ideal carriers of negatively charged molecules like deoxyribonucleic acid (DNA). In this study, hydrotalcite (Mg-Al) and hydrotalcite-like compounds (Mg-Fe, Zn-Al, and Zn-Fe), also known as LDHs, were evaluated for their potential application as a carrier of DNA. LDHs were prepared by coprecipitation at low supersaturation and characterized by Powder X-ray diffraction (XRD), infrared (IR), Raman, and inductively coupled plasma-optical emission spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD patterns showed strong and sharp diffraction peaks for the (003) and (006) planes indicating well-ordered crystalline materials. TEM images yielded irregular circular to hexagonal-shaped particles of 50-250 nm in size. Varying degrees of DNA binding was observed for all the compounds, and nuclease digestion studies revealed that the LDHs afford some degree of protection to the bound DNA. Minimal toxicity was observed in human embryonic kidney (HEK293), cervical cancer (HeLa) and hepatocellular carcinoma (HepG2) cell lines with most showing a cell viability in excess of 80 %. All LDH complexes promoted significant levels of luciferase gene expression, with the DNA:Mg-Al LDHs proving to be the most efficient in all cell lines. PMID:25969811

  5. Concentration of simple aldehydes by sulfite-containing double-layer hydroxide minerals: implications for biopoesis

    NASA Technical Reports Server (NTRS)

    Pitsch, S.; Krishnamurthy, R.; Arrhenius, G.; Bada, J. L. (Principal Investigator)

    2000-01-01

    Environmental conditions play an important role in conceptual studies of prebiotically relevant chemical reactions that could have led to functional biomolecules. The necessary source compounds are likely to have been present in dilute solution, raising the question of how to achieve selective concentration and to reach activation. With the assumption of an initial 'RNA World', the questions of production, concentration, and interaction of aldehydes and aldehyde phosphates, potential precursors of sugar phosphates, come into the foreground. As a possible concentration process for simple, uncharged aldehydes, we investigated their adduct formation with sulfite ion bound in the interlayer of positively charged expanding-sheet-structure double-layer hydroxide minerals. Minerals of this type, initially with chloride as interlayer counter anion, have previously been shown to induce concentration and subsequent aldolization of aldehyde phosphates to form tetrose, pentose, and hexose phosphates. The reversible uptake of the simple aldehydes formaldehyde, glycolaldehyde, and glyceraldehyde by adduct formation with the immobilized sulfite ions is characterized by equilibrium constants of K=1.5, 9, and 11, respectively. This translates into an observable uptake at concentrations exceeding 50 mM.

  6. 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.}

  7. 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.

  8. Energy transfer through a multi-layer liner for shaped charges

    DOEpatents

    Skolnick, Saul; Goodman, Albert

    1985-01-01

    This invention relates to the determination of parameters for selecting materials for use as liners in shaped charges to transfer the greatest amount of energy to the explosive jet. Multi-layer liners constructed of metal in shaped charges for oil well perforators or other applications are selected in accordance with the invention to maximize the penetrating effect of the explosive jet by reference to four parameters: (1) Adjusting the explosive charge to liner mass ratio to achieve a balance between the amount of explosive used in a shaped charge and the areal density of the liner material; (2) Adjusting the ductility of each layer of a multi-layer liner to enhance the formation of a longer energy jet; (3) Buffering the intermediate layers of a multi-layer liner by varying the properties of each layer, e.g., composition, thickness, ductility, acoustic impedance and areal density, to protect the final inside layer of high density material from shattering upon impact of the explosive force and, instead, flow smoothly into a jet; and (4) Adjusting the impedance of the layers in a liner to enhance the transmission and reduce the reflection of explosive energy across the interface between layers.

  9. Photon-assisted tunneling and charge dephasing in a carbon nanotube double quantum dot

    NASA Astrophysics Data System (ADS)

    Mavalankar, A.; Pei, T.; Gauger, E. M.; Warner, J. H.; Briggs, G. A. D.; Laird, E. A.

    2016-06-01

    We report microwave-driven photon-assisted tunneling in a suspended carbon nanotube double quantum dot. From the resonant linewidth at a temperature of 13 mK, the charge-dephasing time is determined to be 280 ±30 ps. The linewidth is independent of driving frequency, but increases with increasing temperature. The moderate temperature dependence is inconsistent with expectations from electron-phonon coupling alone, but consistent with charge noise arising in the device. The extracted level of charge noise is comparable with that expected from previous measurements of a valley-spin qubit, where it was hypothesized to be the main cause of qubit decoherence. Our results suggest a possible route towards improved valley-spin qubits.

  10. Controlled high-fidelity navigation in the charge stability diagram of a double quantum dot.

    PubMed

    Coden, Diego S Acosta; Romero, Rodolfo H; Räsänen, Esa

    2015-03-25

    We propose an efficient control protocol for charge transfer in a double quantum dot. We consider numerically a two-dimensional model system, where the quantum dots are subjected to time-dependent electric fields corresponding to experimental gate voltages. Our protocol enables navigation in the charge stability diagram from a state to another through controllable variation of the fields. We show that the well-known adiabatic Landau-Zener transition-when supplemented with a time-dependent field tailored with optimal control theory-can remarkably improve the transition speed. The results also lead to a simple control scheme obtained from the experimental charge stability diagram that requires only a single parameter. Eventually, we can achieve the ultrafast performance of the composite pulse protocol that allows the system to be driven at the quantum speed limit.

  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. 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.

  15. 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.

  16. Direct evidence for charge stripes in a layered cobalt oxide

    PubMed Central

    Babkevich, P.; Freeman, P. G.; Enderle, M.; Prabhakaran, D.; Boothroyd, A. T.

    2016-01-01

    Recent experiments indicate that static stripe-like charge order is generic to the hole-doped copper oxide superconductors and competes with superconductivity. Here we show that a similar type of charge order is present in La5/3Sr1/3CoO4, an insulating analogue of the copper oxide superconductors containing cobalt in place of copper. The stripe phase we have detected is accompanied by short-range, quasi-one-dimensional, antiferromagnetic order, and provides a natural explanation for the distinctive hourglass shape of the magnetic spectrum previously observed in neutron-scattering measurements of La2−xSrxCoO4 and many hole-doped copper oxide superconductors. The results establish a solid empirical basis for theories of the hourglass spectrum built on short-range, quasi-static, stripe correlations. PMID:27212023

  17. Charged particle detectors made from thin layers of amorphous silicon

    SciTech Connect

    Morel, J.R.

    1986-05-01

    A series of experiments was conducted to determine the feasibility of using hydrogenated amorphous silicon (..cap alpha..-Si:H) as solid state thin film charged particle detectors. /sup 241/Am alphas were successfully detected with ..cap alpha..-Si:H devices. The measurements and results of these experiments are presented. The problems encountered and changes in the fabrication of the detectors that may improve the performance are discussed.

  18. Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

    NASA Astrophysics Data System (ADS)

    Manohara, G. V.; Vishnu Kamath, P.; Milius, Wolfgang

    2012-12-01

    Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2-5 nm-thick tactoids with a radial dimension of 0.2-0.5 μm.

  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. Discrete element simulation of charging and mixed layer formation in the ironmaking blast furnace

    NASA Astrophysics Data System (ADS)

    Mitra, Tamoghna; Saxén, Henrik

    2015-11-01

    The burden distribution in the ironmaking blast furnace plays an important role for the operation as it affects the gas flow distribution, heat and mass transfer, and chemical reactions in the shaft. This work studies certain aspects of burden distribution by small-scale experiments and numerical simulation by the discrete element method (DEM). Particular attention is focused on the complex layer-formation process and the problems associated with estimating the burden layer distribution by burden profile measurements. The formation of mixed layers is studied, and a computational method for estimating the extent of the mixed layer, as well as its voidage, is proposed and applied on the results of the DEM simulations. In studying a charging program and its resulting burden distribution, the mixed layers of coke and pellets were found to show lower voidage than the individual burden layers. The dynamic evolution of the mixed layer during the charging process is also analyzed. The results of the study can be used to gain deeper insight into the complex charging process of the blast furnace, which is useful in the design of new charging programs and for mathematical models that do not consider the full behavior of the particles in the burden layers.

  6. Discrete element simulation of charging and mixed layer formation in the ironmaking blast furnace

    NASA Astrophysics Data System (ADS)

    Mitra, Tamoghna; Saxén, Henrik

    2016-11-01

    The burden distribution in the ironmaking blast furnace plays an important role for the operation as it affects the gas flow distribution, heat and mass transfer, and chemical reactions in the shaft. This work studies certain aspects of burden distribution by small-scale experiments and numerical simulation by the discrete element method (DEM). Particular attention is focused on the complex layer-formation process and the problems associated with estimating the burden layer distribution by burden profile measurements. The formation of mixed layers is studied, and a computational method for estimating the extent of the mixed layer, as well as its voidage, is proposed and applied on the results of the DEM simulations. In studying a charging program and its resulting burden distribution, the mixed layers of coke and pellets were found to show lower voidage than the individual burden layers. The dynamic evolution of the mixed layer during the charging process is also analyzed. The results of the study can be used to gain deeper insight into the complex charging process of the blast furnace, which is useful in the design of new charging programs and for mathematical models that do not consider the full behavior of the particles in the burden layers.

  7. 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.

  8. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tsukanov, A. A.; Psakhie, S. G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered.

  9. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    PubMed Central

    Tsukanov, A.A.; Psakhie, S.G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered. PMID:26817816

  10. Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes: A Generalized Modified Poisson-Nernst-Planck Model

    SciTech Connect

    Wang, Hainan; Thiele, Alexander; Pilon, Laurent

    2013-11-15

    This paper presents a generalized modified Poisson–Nernst–Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |zi| of either ion species. By contrast, the ion diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τCV and the “RC time scale” τRC corresponding to the characteristic time of ions’ electrodiffusion. For τRC ← τCV, quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τRC → τCV, the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.

  11. 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.

  12. On the theory of electric double layer with explicit account of a polarizable co-solvent.

    PubMed

    Budkov, Yu A; Kolesnikov, A L; Kiselev, M G

    2016-05-14

    We present a continuation of our theoretical research into the influence of co-solvent polarizability on a differential capacitance of the electric double layer. We formulate a modified Poisson-Boltzmann theory, using the formalism of density functional approach on the level of local density approximation taking into account the electrostatic interactions of ions and co-solvent molecules as well as their excluded volume. We derive the modified Poisson-Boltzmann equation, considering the three-component symmetric lattice gas model as a reference system and minimizing the grand thermodynamic potential with respect to the electrostatic potential. We apply present modified Poisson-Boltzmann equation to the electric double layer theory, showing that accounting for the excluded volume of co-solvent molecules and ions slightly changes the main result of our previous simplified theory. Namely, in the case of small co-solvent polarizability with its increase under the enough small surface potentials of electrode, the differential capacitance undergoes the significant growth. Oppositely, when the surface potential exceeds some threshold value (which is slightly smaller than the saturation potential), the increase in the co-solvent polarizability results in a differential capacitance decrease. However, when the co-solvent polarizability exceeds some threshold value, its increase generates a considerable enhancement of the differential capacitance in a wide range of surface potentials. We demonstrate that two qualitatively different behaviors of the differential capacitance are related to the depletion and adsorption of co-solvent molecules at the charged electrode. We show that an additive of the strongly polarizable co-solvent to an electrolyte solution can shift significantly the saturation potential in two qualitatively different manners. Namely, a small additive of strongly polarizable co-solvent results in a shift of saturation potential to higher surface potentials. On

  13. Photocatalytic property and structural stability of CuAl-based layered double hydroxides

    SciTech Connect

    Lv, Ming; Liu, Haiqiang

    2015-07-15

    Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO{sub 2} reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M{sup 2+} on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAl

  14. On the theory of electric double layer with explicit account of a polarizable co-solvent.

    PubMed

    Budkov, Yu A; Kolesnikov, A L; Kiselev, M G

    2016-05-14

    We present a continuation of our theoretical research into the influence of co-solvent polarizability on a differential capacitance of the electric double layer. We formulate a modified Poisson-Boltzmann theory, using the formalism of density functional approach on the level of local density approximation taking into account the electrostatic interactions of ions and co-solvent molecules as well as their excluded volume. We derive the modified Poisson-Boltzmann equation, considering the three-component symmetric lattice gas model as a reference system and minimizing the grand thermodynamic potential with respect to the electrostatic potential. We apply present modified Poisson-Boltzmann equation to the electric double layer theory, showing that accounting for the excluded volume of co-solvent molecules and ions slightly changes the main result of our previous simplified theory. Namely, in the case of small co-solvent polarizability with its increase under the enough small surface potentials of electrode, the differential capacitance undergoes the significant growth. Oppositely, when the surface potential exceeds some threshold value (which is slightly smaller than the saturation potential), the increase in the co-solvent polarizability results in a differential capacitance decrease. However, when the co-solvent polarizability exceeds some threshold value, its increase generates a considerable enhancement of the differential capacitance in a wide range of surface potentials. We demonstrate that two qualitatively different behaviors of the differential capacitance are related to the depletion and adsorption of co-solvent molecules at the charged electrode. We show that an additive of the strongly polarizable co-solvent to an electrolyte solution can shift significantly the saturation potential in two qualitatively different manners. Namely, a small additive of strongly polarizable co-solvent results in a shift of saturation potential to higher surface potentials. On

  15. On the theory of electric double layer with explicit account of a polarizable co-solvent

    NASA Astrophysics Data System (ADS)

    Budkov, Yu. A.; Kolesnikov, A. L.; Kiselev, M. G.

    2016-05-01

    We present a continuation of our theoretical research into the influence of co-solvent polarizability on a differential capacitance of the electric double layer. We formulate a modified Poisson-Boltzmann theory, using the formalism of density functional approach on the level of local density approximation taking into account the electrostatic interactions of ions and co-solvent molecules as well as their excluded volume. We derive the modified Poisson-Boltzmann equation, considering the three-component symmetric lattice gas model as a reference system and minimizing the grand thermodynamic potential with respect to the electrostatic potential. We apply present modified Poisson-Boltzmann equation to the electric double layer theory, showing that accounting for the excluded volume of co-solvent molecules and ions slightly changes the main result of our previous simplified theory. Namely, in the case of small co-solvent polarizability with its increase under the enough small surface potentials of electrode, the differential capacitance undergoes the significant growth. Oppositely, when the surface potential exceeds some threshold value (which is slightly smaller than the saturation potential), the increase in the co-solvent polarizability results in a differential capacitance decrease. However, when the co-solvent polarizability exceeds some threshold value, its increase generates a considerable enhancement of the differential capacitance in a wide range of surface potentials. We demonstrate that two qualitatively different behaviors of the differential capacitance are related to the depletion and adsorption of co-solvent molecules at the charged electrode. We show that an additive of the strongly polarizable co-solvent to an electrolyte solution can shift significantly the saturation potential in two qualitatively different manners. Namely, a small additive of strongly polarizable co-solvent results in a shift of saturation potential to higher surface potentials. On

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. In situ NMR and electrochemical quartz crystal microbalance techniques reveal the structure of the electrical double layer in supercapacitors.

    PubMed

    Griffin, John M; Forse, Alexander C; Tsai, Wan-Yu; Taberna, Pierre-Louis; Simon, Patrice; Grey, Clare P

    2015-08-01

    Supercapacitors store charge through the electrosorption of ions on microporous electrodes. Despite major efforts to understand this phenomenon, a molecular-level picture of the electrical double layer in working devices is still lacking as few techniques can selectively observe the ionic species at the electrode/electrolyte interface. Here, we use in situ NMR to directly quantify the populations of anionic and cationic species within a working microporous carbon supercapacitor electrode. Our results show that charge storage mechanisms are different for positively and negatively polarized electrodes for the electrolyte tetraethylphosphonium tetrafluoroborate in acetonitrile; for positive polarization charging proceeds by exchange of the cations for anions, whereas for negative polarization, cation adsorption dominates. In situ electrochemical quartz crystal microbalance measurements support the NMR results and indicate that adsorbed ions are only partially solvated. These results provide new molecular-level insight, with the methodology offering exciting possibilities for the study of pore/ion size, desolvation and other effects on charge storage in supercapacitors.

  1. 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.

  2. 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

  3. 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.

  4. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    SciTech Connect

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; Chen, Long-Qing; Kalinin, Sergei V.; Maksymovych, Petro

    2015-07-13

    The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up to 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.

  5. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    SciTech Connect

    Cao, Ye; Ievlev, Anton V.; Kalinin, Sergei V.; Maksymovych, Petro; Morozovska, Anna N.; Chen, Long-Qing

    2015-07-13

    Conducting characteristics of topological defects in ferroelectric materials, such as charged domain walls, engendered a broad interest on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics still remains full of unanswered questions and becomes yet more relevant over the growing interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}) junction in applied electric field. We revealed an up to 10-fold local enhancement of electric field realized by large polarization gradient and over-polarization effects due to inherent non-linear dielectric properties of Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The observed field enhancement can be considered on similar grounds as increased doping level, giving rise to reduced switching bias and threshold voltages for charge injection, electrochemical and photoelectrochemical processes.

  6. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    DOE PAGESBeta

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; Chen, Long-Qing; Kalinin, Sergei V.; Maksymovych, Petro

    2015-07-13

    The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up tomore » 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.« less

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Chemical Interaction, Space-charge Layer and Molecule Charging Energy for a TiO2/TCNQ Interface

    PubMed Central

    Martínez, José I.; Flores, Fernando; Ortega, José; Rangan, Sylvie; Ruggieri, Charles; Bartynski, Robert

    2015-01-01

    Three driving forces control the energy level alignment between transition-metal oxides and organic materials: the chemical interaction between the two materials, the organic electronegativity and the possible space charge layer formed in the oxide. This is illustrated in this study by analyzing experimentally and theoretically a paradigmatic case, the TiO2(110) / TCNQ interface: due to the chemical interaction between the two materials, the organic electron affinity level is located below the Fermi energy of the n-doped TiO2. Then, one electron is transferred from the oxide to this level and a space charge layer is developed in the oxide inducing an important increase in the interface dipole and in the oxide work-function. PMID:26877826

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. O(D, D) covariant Noether currents and global charges in double field theory

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Hyuck; Rey, Soo-Jong; Rim, Woohyun; Sakatani, Yuho

    2015-11-01

    Double field theory is an approach for massless modes of string theory, unifying and geometrizing all gauge invariance in manifest O( D, D) covariant manner. In this approach, we derive off-shell conserved Noether current and corresponding Noether potential associated with unified gauge invariance. We add Wald-type counter two-form to the Noether potential and define conserved global charges as surface integral. We check our O( D, D) covariant formula against various string backgrounds, both geometric and non-geometric. In all cases we examined, we find perfect agreements with previous results. Our formula facilitates to evaluate momenta along not only ordinary spacetime directions but also dual spacetime directions on equal footing. From this, we confirm recent assertion that null wave in doubled spacetime is the same as macroscopic fundamental string in ordinary spacetime.

  20. 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.

  1. 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.

  2. 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.

  3. Squeezout phenomena and boundary layer formation of a model ionic liquid under confinement and charging

    NASA Astrophysics Data System (ADS)

    Capozza, R.; Vanossi, A.; Benassi, A.; Tosatti, E.

    2015-02-01

    Electrical charging of parallel plates confining a model ionic liquid down to nanoscale distances yields a variety of charge-induced changes in the structural features of the confined film. That includes even-odd switching of the structural layering and charging-induced solidification and melting, with important changes of local ordering between and within layers, and of squeezout behavior. By means of molecular dynamics simulations, we explore this variety of phenomena in the simplest charged Lennard-Jones coarse-grained model including or excluding the effect a neutral tail giving an anisotropic shape to one of the model ions. Using these models and open conditions permitting the flow of ions in and out of the interplate gap, we simulate the liquid squeezout to obtain the distance dependent structure and forces between the plates during their adiabatic approach under load. Simulations at fixed applied force illustrate an effective electrical pumping of the ionic liquid, from a thick nearly solid film that withstands the interplate pressure for high plate charge to complete squeezout following melting near zero charge. Effective enthalpy curves obtained by integration of interplate forces versus distance show the local minima that correspond to layering and predict the switching between one minimum and another under squeezing and charging.

  4. 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.

  5. First Measurement of the Muon Neutrino Charged Current Quasielastic Double Differential Cross Section

    SciTech Connect

    Aguilar-Arevalo, A.A.; Anderson, C.E.; Bazarko, A.O.; Brice, S.J.; Brown, B.C.; Bugel, L.; Cao, J.; Coney, L.; Conrad, J.M.; Cox, D.C.; Curioni, A.; /Yale U. /Columbia U.

    2010-02-01

    A high-statistics sample of charged-current muon neutrino scattering events collected with the MiniBooNE experiment is analyzed to extract the first measurement of the double differential cross section (d{sup 2}{sigma}/dT{sub {mu}}d cos {theta}{sub {mu}}) for charged-current quasielastic (CCQE) scattering on carbon. This result features minimal model dependence and provides the most complete information on this process to date. With the assumption of CCQE scattering, the absolute cross section as a function of neutrino energy ({sigma}[E{sub {nu}}]) and the single differential cross section (d{sigma}/dQ{sup 2}) are extracted to facilitate comparison with previous measurements. These quantities may be used to characterize an effective axial-vector form factor of the nucleon and to improve the modeling of low-energy neutrino interactions on nuclear targets. The results are relevant for experiments searching for neutrino oscillations.

  6. Neutrino nuclear responses for double beta decays and astro neutrinos by charge exchange reactions

    NASA Astrophysics Data System (ADS)

    Ejiri, Hiroyasu

    2014-09-01

    Neutrino nuclear responses are crucial for neutrino studies in nuclei. Charge exchange reactions (CER) are shown to be used to study charged current neutrino nuclear responses associated with double beta decays(DBD)and astro neutrino interactions. CERs to be used are high energy-resolution (He3 ,t) reactions at RCNP, photonuclear reactions via IAR at NewSUBARU and muon capture reactions at MUSIC RCNP and MLF J-PARC. The Gamow Teller (GT) strengths studied by CERs reproduce the observed 2 neutrino DBD matrix elements. The GT and spin dipole (SD) matrix elements are found to be reduced much due to the nucleon spin isospin correlations and the non-nucleonic (delta isobar) nuclear medium effects. Impacts of the reductions on the DBD matrix elements and astro neutrino interactions are discussed.

  7. First measurement of the muon neutrino charged current quasielastic double differential cross section

    SciTech Connect

    Aguilar-Arevalo, A. A.; Anderson, C. E.; Curioni, A.; Fleming, B. T.; Linden, S. K.; Soderberg, M.; Spitz, J.; Bazarko, A. O.; Laird, E. M.; Meyers, P. D.; Patterson, R. B.; Shoemaker, F. C.; Tanaka, H. A.; Brice, S. J.; Brown, B. C.; Finley, D. A.; Ford, R.; Garcia, F. G.; Kasper, P.; Kobilarcik, T.

    2010-05-01

    A high-statistics sample of charged-current muon neutrino scattering events collected with the MiniBooNE experiment is analyzed to extract the first measurement of the double differential cross section ((d{sup 2{sigma}}/dT{sub {mu}d}cos{theta}{sub {mu}})) for charged-current quasielastic (CCQE) scattering on carbon. This result features minimal model dependence and provides the most complete information on this process to date. With the assumption of CCQE scattering, the absolute cross section as a function of neutrino energy ({sigma}[E{sub {nu}}]) and the single differential cross section ((d{sigma}/dQ{sup 2})) are extracted to facilitate comparison with previous measurements. These quantities may be used to characterize an effective axial-vector form factor of the nucleon and to improve the modeling of low-energy neutrino interactions on nuclear targets. The results are relevant for experiments searching for neutrino oscillations.

  8. 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.

  9. 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.

  10. 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).

  11. 'Bucky gel' of multiwalled carbon nanotubes as electrodes for high performance, flexible electric double layer capacitors.

    PubMed

    Singh, Manoj K; Kumar, Yogesh; Hashmi, S A

    2013-11-22

    We report the preparation of a gelled form of multiwalled carbon nanotubes (MWCNTs) with an ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethane sulfonyl)imide (BMPTFSI)), referred to as 'bucky gel', to be used as binderless electrodes in electrical double layer capacitors (EDLCs). The characteristics of gelled MWCNTs are compared with pristine MWCNTs using transmission electron microscopy, x-ray diffraction and Raman studies. A gel polymer electrolyte film consisting of a blend of poly(vinylidene fluoride-co-hexafluoropropylene) and BMPTFSI, exhibiting a room temperature ionic conductivity of 1.5 × 10(-3) S cm(-1), shows its suitability as an electrolyte/separator in flexible EDLCs. The performance of EDLCs, assembled with bucky gel electrodes, using impedance spectroscopy, cyclic voltammetry and charge-discharge analyses, are compared with those fabricated with pristine MWCNT-electrodes. An improvement in specific capacitance (from 19.6 to 51.3 F g(-1)) is noted when pristine MWCNTs are replaced by gelled MWCNT-binderless electrodes. Although the rate performance of the EDLCs with gelled MWCNT-electrodes is reduced, the pulse power of the device is sufficiently high (~10.5 kW kg(-1)). The gelled electrodes offer improvements in energy and power densities from 2.8 to 8.0 Wh kg(-1) and 2.0 to 4.7 kW kg(-1), respectively. Studies indicate that the gel formation of MWCNTs with ionic liquid is an excellent route to obtain high-performance EDLCs.

  12. The polarization model for hydration/double layer interactions: the role of the electrolyte ions.

    PubMed

    Manciu, Marian; Ruckenstein, Eli

    2004-12-31

    The interactions between hydrophilic surfaces in water cannot be always explained on the basis of the traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and an additional repulsion, the "hydration force" is required to accommodate the experimental data. While this force is in general associated with the organization of water in the vicinity of the surface, different models for the hydration were typically required to explain different experiments. In this article, it is shown that the polarization-model for the double layer/hydration proposed by the authors can explain both (i) the repulsion between neutral lipid bilayers, with a short decay length ( approximately 2 A), which is almost independent of the electrolyte concentration, and, at the same time, (ii) the repulsion between weakly charged mica surfaces, with a longer decay length ( approximately 10 A), exhibiting not only a dependence on the ionic strength, but also strong ion-specific effects. The model, which was previously employed to explain the restabilization of protein-covered latex particles at high ionic strengths and the existence of a long-range repulsion between the apoferritin molecules at moderate ionic strengths, is extended to account for the additional interactions between ions and surfaces, not included in the mean field electrical potential. The effect of the disorder in the water structure on the dipole correlation length is examined and the conditions under which the results of the polarization model are qualitatively similar to those obtained by the traditional theory via parameter fitting are emphasized. However, there are conditions under which the polarization model predicts results that cannot be recovered by the traditional theory via parameter fitting.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. Hybridization Between Natural Extract of Angelica gigas Nakai and Inorganic Nanomaterial of Layered Double Hydroxide via Reconstruction Reaction.

    PubMed

    Kim, Tae-Hyun; Kim, Hyoung-Jun; Choi, Ae-Jin; Choi, Hyun-Jin; Oh, Jae-Min

    2016-01-01

    We have hybridized layered double hydroxide (LDH) with Angelica gigas Nakai root extract (AGNR) through reversible dehydration-rehydration reaction which is known as reconstruction. LDHs having well-ordered hydrotalcite-like crystal structure and average size 250 ± 20 nm were prepared by hydrothermal method. The root of Angelica gigas Nakai, which has been utilized in the treatment of female disorders as herbal medicine, was treated with methanol to obtain extract. Pristine LDHs were calcined at 400 °C for 8 hours to obtain layered double oxide (LDO), which was further dispersed into extract solution with various AGNR/LDO weight ratios, 0.11, 0.21 and 0.43. The extract content in each hybrid increased in proportion to initial AGNR/LDO ratio, showing the highest content of ~12%. The zeta potential of LDH shifted from +44 mV to +20 mV upon hybridization with extract, which was attributed to the adsorption of negatively charged organic moieties in AGNR on LDH surface. The scanning electron microscopic (SEM) results exhibited that the random stacking of LDH nanolayers resulted in LDH-AGNR hybrid with house-of-cards structure, of which inter-particle cavity serves nano-reservoir for natural extract. According to quantitative analyses, it was revealed that the content of active components in AGNR increased when they were hybridized with LDHs compared with those in AGNR alone.

  18. Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

    NASA Astrophysics Data System (ADS)

    Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

    2015-12-01

    Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

  19. Hybridization Between Natural Extract of Angelica gigas Nakai and Inorganic Nanomaterial of Layered Double Hydroxide via Reconstruction Reaction.

    PubMed

    Kim, Tae-Hyun; Kim, Hyoung-Jun; Choi, Ae-Jin; Choi, Hyun-Jin; Oh, Jae-Min

    2016-01-01

    We have hybridized layered double hydroxide (LDH) with Angelica gigas Nakai root extract (AGNR) through reversible dehydration-rehydration reaction which is known as reconstruction. LDHs having well-ordered hydrotalcite-like crystal structure and average size 250 ± 20 nm were prepared by hydrothermal method. The root of Angelica gigas Nakai, which has been utilized in the treatment of female disorders as herbal medicine, was treated with methanol to obtain extract. Pristine LDHs were calcined at 400 °C for 8 hours to obtain layered double oxide (LDO), which was further dispersed into extract solution with various AGNR/LDO weight ratios, 0.11, 0.21 and 0.43. The extract content in each hybrid increased in proportion to initial AGNR/LDO ratio, showing the highest content of ~12%. The zeta potential of LDH shifted from +44 mV to +20 mV upon hybridization with extract, which was attributed to the adsorption of negatively charged organic moieties in AGNR on LDH surface. The scanning electron microscopic (SEM) results exhibited that the random stacking of LDH nanolayers resulted in LDH-AGNR hybrid with house-of-cards structure, of which inter-particle cavity serves nano-reservoir for natural extract. According to quantitative analyses, it was revealed that the content of active components in AGNR increased when they were hybridized with LDHs compared with those in AGNR alone. PMID:27398576

  20. 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

  1. DNA-base guanine as hydrogen getter and charge-trapping layer embedded in oxide dielectrics for inorganic and organic field-effect transistors.

    PubMed

    Lee, Junyeong; Park, Ji Hoon; Lee, Young Tack; Jeon, Pyo Jin; Lee, Hee Sung; Nam, Seung Hee; Yi, Yeonjin; Lee, Younjoo; Im, Seongil

    2014-04-01

    DNA-base small molecules of guanine, cytosine, adenine, and thymine construct the DNA double helix structure with hydrogen bonding, and they possess such a variety of intrinsic benefits as natural plentitude, biodegradability, biofunctionality, low cost, and low toxicity. On the basis of these advantages, here, we report on unprecedented useful applications of guanine layer as hydrogen getter and charge trapping layer when it is embedded into a dielectric oxide of n-channel inorganic InGaZnO and p-channel organic heptazole field effect transistors (FETs). The embedded guanine layer much improved the gate stability of inorganic FETs gettering many hydrogen atoms in the gate dielectric layer of FET, and it also played as charge trapping layer to which the voltage pulse-driven charges might be injected from channel, resulting in a threshold voltage (Vth) shift of FETs. Such shift state is very ambient-stable and almost irrevocable even under a high electric-field at room temperature. So, Boolean logics are nicely demonstrated by using our FETs with the guanine-embedded dielectric. The original Vth is recovered only under high energy blue photons by opposite voltage pulse (charge-ejection), which indicates that our device is also applicable to nonvolatile photo memory.

  2. 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.

  3. Charge generation layers for all-solution processed organic tandem light emitting diodes with regular device architecture

    NASA Astrophysics Data System (ADS)

    Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Colsmann, Alexander

    2015-10-01

    We present multi-photon OLEDs where enhanced light emission was achieved by stacking two OLEDs utilizing a regular device architecture (top cathode) and an intermediate charge carrier generation layer (CGL) for monolithic device interconnection. With respect to future printing processes for organic optoelectronic devices, all functional layers were deposited from solution. The CGL comprises a low-work function zinc oxide layer that was applied from solution under ambient conditions and at moderate processing temperatures and a high-work function interlayer that was realized from various solution processable precursor-based metal oxides, like molybdenum-, vanadium- and tungsten-oxide. Since every injected electron-hole pair generates two photons, the luminance and the current efficiency of the tandem OLED at a given device current are doubled while the power efficiency remains constant. At a given luminance, the lower operating current in the tandem device reduces electrical stress and improves the device life-time. ToF-SIMS, TEM/FIB and EDX analyses provided evidence of a distinct layer sequence without intermixing upon solution deposition.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Hierarchical Co-based Porous Layered Double Hydroxide Arrays Derived via Alkali Etching for High-performance Supercapacitors

    PubMed Central

    Abushrenta, Nasser; Wu, Xiaochao; Wang, Junnan; Liu, Junfeng; Sun, Xiaoming

    2015-01-01

    Hierarchical nanoarchitecture and porous structure can both provide advantages for improving the electrochemical performance in energy storage electrodes. Here we report a novel strategy to synthesize new electrode materials, hierarchical Co-based porous layered double hydroxide (PLDH) arrays derived via alkali etching from Co(OH)2@CoAl LDH nanoarrays. This structure not only has the benefits of hierarchical nanoarrays including short ion diffusion path and good charge transport, but also possesses a large contact surface area owing to its porous structure which lead to a high specific capacitance (23.75 F cm−2 or 1734 F g−1 at 5 mA cm−2) and excellent cycling performance (over 85% after 5000 cycles). The enhanced electrode material is a promising candidate for supercapacitors in future application. PMID:26278334

  9. Hierarchical Co-based Porous Layered Double Hydroxide Arrays Derived via Alkali Etching for High-performance Supercapacitors

    NASA Astrophysics Data System (ADS)

    Abushrenta, Nasser; Wu, Xiaochao; Wang, Junnan; Liu, Junfeng; Sun, Xiaoming

    2015-08-01

    Hierarchical nanoarchitecture and porous structure can both provide advantages for improving the electrochemical performance in energy storage electrodes. Here we report a novel strategy to synthesize new electrode materials, hierarchical Co-based porous layered double hydroxide (PLDH) arrays derived via alkali etching from Co(OH)2@CoAl LDH nanoarrays. This structure not only has the benefits of hierarchical nanoarrays including short ion diffusion path and good charge transport, but also possesses a large contact surface area owing to its porous structure which lead to a high specific capacitance (23.75 F cm-2 or 1734 F g-1 at 5 mA cm-2) and excellent cycling performance (over 85% after 5000 cycles). The enhanced electrode material is a promising candidate for supercapacitors in future application.

  10. Superparamagnetic magnetite nanocrystals-graphene oxide nanocomposites: facile synthesis and their enhanced electric double-layer capacitor performance.

    PubMed

    Wang, Qihua; Wang, Dewei; Li, Yuqi; Wang, Tingmei

    2012-06-01

    Superparamagnetic magnetite nanocrystals-graphene oxide (FGO) nanocomposites were successfully synthesized through a simple yet versatile one-step solution-processed approach at ambient conditions. Magnetite (Fe3O4) nanocrystals (NCs) with a size of 10-50 nm were uniformly deposited on the surfaces of graphene oxide (GO) sheets, which were confirmed by transmission electron microscopy (TEM) and high-angle annular dark field scanning transmission election microscopy (HAADF-STEM) studies. FGO with different Fe3O4 loadings could be controlled by simply manipulating the initial weight ratio of the precursors. The M-H measurements suggested that the as-prepared FGO nanocomposites have a large saturation magnetizations that made them can move regularly under an external magnetic field. Significantly, FGO nanocomposites also exhibit enhanced electric double-layer capacitor (EDLC) activity compared with pure Fe3O4 NCs and GO in terms of specific capacitance and high-rate charge-discharge. PMID:22905504

  11. Performance of electrical double layer capacitors fabricated with gel polymer electrolytes containing Li+ and K+-salts: A comparison

    NASA Astrophysics Data System (ADS)

    Singh, Manoj K.; Hashmi, S. A.

    2015-06-01

    The comparative performance of the solid-state electrical double layer capacitors (EDLCs) based on the multiwalled carbon nanotube (MWCNT) electrodes and poly (vinaylidinefluoride-co-hexafluoropropyline) (PVdF-HFP) based gel polymer electrolytes (GPEs) containing potassium and lithium salts have been studied. The room temperature ionic conductivity of the GPEs have been found to be ˜3.8×10-3 and 5.9×10-3 S cm-1 for lithium and potassium based systems. The performance of EDLC cells studied by impedance spectroscopy, cyclic voltammetry and constant current charge-discharge techniques, indicate that the EDLC with potassium salt containing GPE shows excellent performance almost equivalent to the EDLC with Li-salt-based GPE.

  12. Fuel Cell/Electric Double Layer Capacitor Hybrid Power Source Using a Multi-port Bidirectional DC-DC Converter

    NASA Astrophysics Data System (ADS)

    Katayama, Noboru; Kogoshi, Sumio

    A fuel cell/electric double layer capacitor hybrid power source using a multi-port bidirectional DC-DC converter has been developed to reduce load variations for the purpose of extending fuel cell life. The proposed converter operates to maintain the fuel cell current, load voltage and bus voltage at constant values with a digital signal processor. The effect of the proposed converter is evaluated. The charging or discharging current of the EDLC rapidly changes along with step loading, and the voltage and current of the fuel cell are maintained at the constant values. Short-time transient responses show that the fuel cell current ripples 0.35 A at 1 A load change in 6 ms.

  13. Role of the electric double layer in the ice nucleation of water droplets under an electric field

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang-Xiong; Li, Xin-Hao; Chen, Min

    2016-09-01

    Figuring out the mechanism of ice nucleation on charged aerosols or in thunderstorms is of fundamental importance in atmospheric science. However, findings on whether the electric field promotes or suppresses heterogeneous ice nucleation are conflicting. In this work, we design an apparatus and test the influence of the electric field on ice nucleation by freezing a series of deionized water droplets resting on solid surfaces with an electric field perpendicular to the substrates. Results show that ice nucleation is obviously promoted under the electric field and is independent of the field direction. Theoretic analyses show that the promotion is due to the reduction of Gibbs free energy which can be partially rationalized by the electric field sustained in the electric double layer at the solid-water interface, with strength about two orders higher than that of the external electric field. Moreover, water-droplet deformation under the electric field is not expected to be the cause of the ice-nucleation promotion.

  14. Contribution of material's surface layer on charge state distribution in laser ablation plasma.

    PubMed

    Kumaki, Masafumi; Steski, Dannie; Ikeda, Shunsuke; Kanesue, Takeshi; Okamura, Masahiro; Washio, Masakazu

    2016-02-01

    To generate laser ablation plasma, a pulse laser is focused onto a solid target making a crater on the surface. However, not all the evaporated material is efficiently converted to hot plasma. Some portion of the evaporated material could be turned to low temperature plasma or just vapor. To investigate the mechanism, we prepared an aluminum target coated by thin carbon layers. Then, we measured the ablation plasma properties with different carbon thicknesses on the aluminum plate. The results showed that C(6+) ions were generated only from the surface layer. The deep layers (over 250 nm from the surface) did not provide high charge state ions. On the other hand, low charge state ions were mainly produced by the deeper layers of the target. Atoms deeper than 1000 nm did not contribute to the ablation plasma formation. PMID:26931982

  15. Contribution of material's surface layer on charge state distribution in laser ablation plasma

    NASA Astrophysics Data System (ADS)

    Kumaki, Masafumi; Steski, Dannie; Ikeda, Shunsuke; Kanesue, Takeshi; Okamura, Masahiro; Washio, Masakazu

    2016-02-01

    To generate laser ablation plasma, a pulse laser is focused onto a solid target making a crater on the surface. However, not all the evaporated material is efficiently converted to hot plasma. Some portion of the evaporated material could be turned to low temperature plasma or just vapor. To investigate the mechanism, we prepared an aluminum target coated by thin carbon layers. Then, we measured the ablation plasma properties with different carbon thicknesses on the aluminum plate. The results showed that C6+ ions were generated only from the surface layer. The deep layers (over 250 nm from the surface) did not provide high charge state ions. On the other hand, low charge state ions were mainly produced by the deeper layers of the target. Atoms deeper than 1000 nm did not contribute to the ablation plasma formation.

  16. 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.

  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. Electronic structure of a dual-layered organic charge transfer salt

    NASA Astrophysics Data System (ADS)

    Jeschke, Harald; Altmeyer, Michaela; Valenti, Roser

    2015-03-01

    We examine the electronic properties of polymorphs of (BEDT-TTF)2Ag(CF3)4(TCE) (1,1,2-trichloroethane) within density functional theory (DFT). While a phase with low superconducting transition temperature Tc = 2 . 6 K exhibits a κ packing motif, two high Tc phases are layered structures consisting of α' and κ packed layers. We determine the electronic structures and discuss the influence of the insulating α' layer on the conducting κ layer. We find that the stripes of high and low charge in the α' layer correspond to a stripe pattern of hopping parameters in the κ layer. This finding is the basis for studying the effect of the different underlying Hamiltonians on the superconducting properties. Research funded within DFG Transregio 49.

  19. 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).

  20. 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.

  1. Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture.

    PubMed

    Deng, Guang-Wei; Wei, Da; Johansson, J R; Zhang, Miao-Lei; Li, Shu-Xiao; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Tu, Tao; Guo, Guang-Can; Jiang, Hong-Wen; Nori, Franco; Guo, Guo-Ping

    2015-09-18

    We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom. PMID:26431005

  2. Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture.

    PubMed

    Deng, Guang-Wei; Wei, Da; Johansson, J R; Zhang, Miao-Lei; Li, Shu-Xiao; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Tu, Tao; Guo, Guang-Can; Jiang, Hong-Wen; Nori, Franco; Guo, Guo-Ping

    2015-09-18

    We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom.

  3. 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.

  4. 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

  5. Positively charged and bipolar layered poly(ether imide) nanofiltration membranes for water softening applications

    NASA Astrophysics Data System (ADS)

    Gassara, S.; Abdelkafi, A.; Quémener, D.; Amar, R. Ben; Deratani, A.

    2015-07-01

    Poly(ether imide) (PEI) ultrafiltration membranes were chemically modified with branched poly(ethyleneimine) to obtain nanofiltration (NF) membrane Cat PEI with a positive charge in the pH range below 9. An oppositely charged polyelectrolyte layer was deposited on the resulting membrane surface by using sodium polystyrene sulfonate (PSSNa) and sodium polyvinyl sulfonate (PVSNa) to prepare a bipolar layered membrane NF Cat PEI_PSS and Cat PEI_PVS having a negatively charged surface and positively charged pores. Cat PEI exhibited good performance to remove multivalent cations (more than 90% of Ca2+) from single salt solutions except in presence of sulfate ions. Adding an anionic polyelectrolyte layer onto the positively charged surface resulted in a significant enhancement of rejection performance even in presence of sulfate anions. Application of the prepared membranes in water softening of natural complex mixtures was successful for the different studied membranes and a large decrease of hardness was obtained. Moreover, Cat PEI_PSS showed a good selectivity for nitrate removal. Fouling experiments were carried out with bovine serum albumin, as model protein foulant. Cat PEI_PSS showed much better fouling resistance than Cat PEI with a quantitative flux recovery ratio.

  6. Debye-Hückel theory of mixed charged-zwitterionic lipid layers

    NASA Astrophysics Data System (ADS)

    Mengistu, D. H.; May, S.

    2008-07-01

    Modeling electrostatic properties of macroions such as charged lipid membranes is especially simple within linear Debye-Hückel theory where analytical solutions are often available. Charged lipid layers typically also contain zwitterionic lipids that possess a large headgroup dipole. We incorporate the presence of zwitterionic lipids into the Debye-Hückel description and derive analytical expressions for the free energies of isolated and interacting lipid layers. Our approach accounts for two major characteristic features of zwitterionic lipids, the firm linkage of the dipole's negatively charged phosphate end to the lipid chain and the comparatively large conformational freedom of the opposite, positively charged, dipole end. This leads to differences in structural properties of mixed anionic and cationic lipid layers that are known from experiment and that the Debye-Hückel description qualitatively recovers. Most notably, this includes the different dependencies of the average cross-sectional area per lipid on the composition of mixed anionic and cationic membranes. In addition, we study the predictions of Debye-Hückel theory regarding the electrostatic influence of zwitterionic lipids on the stability of non-ideally mixed membranes as well as on the adsorption energy of oppositely charged macroions.

  7. 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.

  8. 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.

  9. Charge Transport in Field-Effect Transistors based on Layered Materials and their Heterostructures

    NASA Astrophysics Data System (ADS)

    Kumar, Jatinder

    In the quest for energy efficiency and device miniaturization, the research in using atomically thin materials for device applications is gaining momentum. The electronic network in layered materials is different from 3D counterparts. It is due to the interlayer couplings and density of states because of their 2D nature. Therefore, understanding the charge transport in layered materials is fundamental to explore the vast opportunities these ultra-thin materials offer. Hence, the challenges targeted in the thesis are: (1) understanding the charge transport in layered materials based on electronic network of quantum and oxide capacitances, (2) studying thickness dependence, ranging from monolayer to bulk, of full range-characteristics of field-effect transistor (FET) based on layered materials, (3) investigating the total interface trap charges to achieve the ultimate subthreshold slope (SS) theoretically possible in FETs, (4) understanding the effect of the channel length on the performance of layered materials, (5) understanding the effect of substrate on performance of the TMDC FETs and studying if the interface of transition metal dichalcogenides (TMDCs)/hexagonalboron nitride (h-BN) can have less enough trap charges to observe ambipolar behavior, (6) Exploring optoelectronic properties in 2D heterostructures that includes understanding graphene/WS2 heterostructure and its optoelectronic applications by creating a p-n junction at the interface. The quality of materials and the interface are the issues for observing and extracting clean physics out of these layered materials and heterostructures. In this dissertation, we realized the use of quantum capacitance in layered materials, substrate effects and carrier transport in heterostructure.

  10. Characterization and film properties of electrophoretically deposited nanosheets of anionic titanate and cationic MgAl-layered double hydroxide.

    PubMed

    Matsuda, Atsunori; Sakamoto, Hisatoshi; Mohd Nor, Mohd Arif Bin; Kawamura, Go; Muto, Hiroyuki

    2013-02-14

    Anionic hydrated titanate (H(n)TiO(m): HTO) nanosheets and cationic magnesium-aluminum layered double hydroxide (Mg-Al LDH) nanosheets were electrophoretically deposited on positively and negatively charged indium tin oxide (ITO)-coated glass substrates, respectively. The HTO nanosheets and Mg-Al LDH nanosheets obtained were identified in neutral water as H(2)Ti(4)O(9)·nH(2)O with a ζ-potential of -23 mV and Mg(6)Al(2)(OH)(18)·4.5H(2)O with a ζ-potential of +41 mV, respectively. Dense and smooth HTO and Mg-Al LDH films with layered structures with thicknesses of about 10-15 μm were prepared in 300 s at 7.5 V by electrophoretic deposition (EPD) from the nanosheet suspensions. Both EPD HTO and LDH films showed elasticity because of their layered laminate structures. The HTO thick films demonstrated large adsorption properties and high photocatalytic activity, while the Mg-Al LDH thick films showed relatively high ionic conductivity of 10(-5) S cm(-1) at 80 °C and 80% relative humidity.

  11. A combined FTIR and infrared emission spectroscopy investigation of layered double hydroxide as an effective electron donor.

    PubMed

    Zhang, Jia; Wei, Feng; Liang, Ying; Zhou, Jizhi; Xi, Yunfei; Qian, Guangren; Frost, Ray

    2016-02-01

    A novel method has been presented to characterize electron transfer in layered double hydroxides (LDHs) utilizing an investigation combing FTIR and infrared emission spectroscopy. At room temperature, electron could transfer to interlayer Fe(3+) through monodentate ligand cyanide, and resulted in a reduction of 40% Fe(3+) to Fe(2+). When the environmental temperature increased from 25 to 300°C, reduction of Fe(3+) and Ni(2+) increased to 94% and 42%. Furthermore, electron also transferred to interlayer cation through multidentate ligand EDTA. As a result, LDHs has been proven to be an effective electron donor, and FTIR was a feasible tool in characterizing this property by monitoring the valence state of cations. It was also concluded that octahedral units with OH(-) groups in LDH layer functioned as electron donor centers. Driving force for electron transfer is attributed to the charge density difference between cation layer and probe anion. These results could help to explain the mechanism of various applications of LDHs in catalysis and photocatalysis.

  12. 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.

  13. A combined FTIR and infrared emission spectroscopy investigation of layered double hydroxide as an effective electron donor

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Wei, Feng; Liang, Ying; Zhou, Jizhi; Xi, Yunfei; Qian, Guangren; Frost, Ray

    2016-02-01

    A novel method has been presented to characterize electron transfer in layered double hydroxides (LDHs) utilizing an investigation combing FTIR and infrared emission spectroscopy. At room temperature, electron could transfer to interlayer Fe3 + through monodentate ligand cyanide, and resulted in a reduction of 40% Fe3 + to Fe2 +. When the environmental temperature increased from 25 to 300 °C, reduction of Fe3 + and Ni2 + increased to 94% and 42%. Furthermore, electron also transferred to interlayer cation through multidentate ligand EDTA. As a result, LDHs has been proven to be an effective electron donor, and FTIR was a feasible tool in characterizing this property by monitoring the valence state of cations. It was also concluded that octahedral units with OH- groups in LDH layer functioned as electron donor centers. Driving force for electron transfer is attributed to the charge density difference between cation layer and probe anion. These results could help to explain the mechanism of various applications of LDHs in catalysis and photocatalysis.

  14. 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

  15. Exciton and charge carrier dynamics in few-layer WS2

    NASA Astrophysics Data System (ADS)

    Vega-Mayoral, Victor; Vella, Daniele; Borzda, Tetiana; Prijatelj, Matej; Tempra, Iacopo; Pogna, Eva A. A.; Dal Conte, Stefano; Topolovsek, Peter; Vujicic, Natasa; Cerullo, Giulio; Mihailovic, Dragan; Gadermaier, Christoph

    2016-03-01

    Semiconducting transition metal dichalcogenides (TMDs) have been applied as the active layer in photodetectors and solar cells, displaying substantial charge photogeneration yields. However, their large exciton binding energy, which increases with decreasing thickness (number of layers), as well as the strong resonance peaks in the absorption spectra suggest that excitons are the primary photoexcited states. Detailed time-domain studies of the photoexcitation dynamics in TMDs exist mostly for MoS2. Here, we use femtosecond optical spectroscopy to study the exciton and charge dynamics following impulsive photoexcitation in few-layer WS2. We confirm excitons as the primary photoexcitation species and find that they dissociate into charge pairs with a time constant of about 1.3 ps. The better separation of the spectral features compared to MoS2 allows us to resolve a previously undetected process: these charges diffuse through the samples and get trapped at defects, such as flake edges or grain boundaries, causing an appreciable change of their transient absorption spectra. This finding opens the way to further studies of traps in TMD samples with different defect contents.Semiconducting transition metal dichalcogenides (TMDs) have been applied as the active layer in photodetectors and solar cells, displaying substantial charge photogeneration yields. However, their large exciton binding energy, which increases with decreasing thickness (number of layers), as well as the strong resonance peaks in the absorption spectra suggest that excitons are the primary photoexcited states. Detailed time-domain studies of the photoexcitation dynamics in TMDs exist mostly for MoS2. Here, we use femtosecond optical spectroscopy to study the exciton and charge dynamics following impulsive photoexcitation in few-layer WS2. We confirm excitons as the primary photoexcitation species and find that they dissociate into charge pairs with a time constant of about 1.3 ps. The better

  16. The effect of interfacial layers on charge transport in organic solar cell

    NASA Astrophysics Data System (ADS)

    Mbuyise, Xolani G.; Tonui, Patrick; Mola, Genene Tessema

    2016-09-01

    The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.

  17. Dark matter with invisible light from heavy double charged leptons of almost-commutative geometry?

    NASA Astrophysics Data System (ADS)

    Khlopov, M. Yu; Stephan, C. A.; Fargion, D.

    2006-12-01

    A new candidate for cold dark matter arises from a novel elementary particle model: the almost-commutative AC-geometrical framework. Two heavy leptons are added to the standard model, each one sharing a double opposite electric charge and an own lepton flavour number. The novel mathematical theory of almost-commutative geometry (Connes 1994 Noncommutative Geometry (London: Academic)) wishes to unify gauge models with gravity. In this scenario two new heavy (mL >= 100 GeV), oppositely double charged leptons (A,C), (A with charge -2 and C with charge +2), are born with no twin quark companions. The model naturally involves a new U(1) gauge interaction, possessed only by the AC-leptons and providing a Coulomb-like attraction between them. AC-leptons posses electro-magnetic as well as Z-boson interaction and, according to the charge chosen for the new U(1) gauge interaction, a new 'invisible light' interaction. Their final cosmic relics are bounded into 'neutral' stable atoms (AC) forming the mysterious cold dark matter, in the spirit of the Glashow's Sinister model. An (AC) state is reached in the early Universe along a tail of a few secondary frozen exotic components. They should be here now somehow hidden in the surrounding matter. The two main secondary manifest relics are C2+ (mostly hidden in a neutral (C2+e-e-) 'anomalous helium' atom, at a 10-8 ratio) and a corresponding 'ion' A2- bounded with an ordinary helium ion (4He)2+; indeed the positive helium ions are able to attract and capture the free A2- fixing them into a neutral relic cage that has nuclear interaction (4He2+A2-). The cage preserves the leptons to later recombine with neutral (C2+e-e-) into (AC) evanescent states. In early and late cosmic stages (AC) gas is leading to cold dark matter gravity seeds. It can form dense cores inside dense matter bodies (stars and planets). Binding (C2+e-e-) + (4He2+A2-) into (AC) atoms results in a steady decrease of the anomalous isotopes and a growing concentration

  18. Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

    NASA Astrophysics Data System (ADS)

    Carrillo, J.-M. Y.; Brown, W. M.; Dobrynin, A. V.

    2013-03-01

    We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbone deformation. This deformation mode manifests itself in the backbone deformation ratio, α, and shear viscosity, η, to be universal functions of the Weissenberg number W. The value of the friction coefficient, μ, and viscosity, η, are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, η, and friction coefficient, μ, approaching corresponding values obtained for neutral brush systems. NSF DMR-1004576

  19. Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

    SciTech Connect

    Carrillo, Jan-Michael; Brown, W Michael; Dobrynin, Andrey

    2012-01-01

    We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. In our simulations the solvent molecules were treated explicitly. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbone deformation. This deformation mode manifests itself in the backbone deformation ratio, , and shear viscosity, , to be universal functions of the Weissenberg number W. The value of the friction coefficient, , and viscosity, , are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, , and friction coefficient, , approaching corresponding values obtained for neutral brush systems.

  20. 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.