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Sample records for dielectric liquids icdl

  1. Radiation Resistances of Dielectric Liquids

    NASA Technical Reports Server (NTRS)

    Bouquet, Frank L.; Somoano, Robert B.

    1987-01-01

    Report presents data on effects of ionizing radiation on dielectric liquids for high-energy-density, pulsed-power capacitors. Based on Jet Propulsion Laboratory test results, search of NASA and Department of Energy computer files, survey of open literature, and contacts with manufacturers and suppliers. Covers 22 organic liquids, although detailed data found for only one compound, polydimethyl siloxane. Generic data on effects of radiation on compounds with similar chemical structures provided where data on specific compounds lacking.

  2. Counteracting Gravitation In Dielectric Liquids

    NASA Technical Reports Server (NTRS)

    Israelsson, Ulf E.; Jackson, Henry W.; Strayer, Donald M.

    1993-01-01

    Force of gravity in variety of dielectric liquids counteracted by imposing suitably contoured electric fields. Technique makes possible to perform, on Earth, variety of experiments previously performed only in outer space and at great cost. Also used similarly in outer space to generate sort of artificial gravitation.

  3. Miniaturization of dielectric liquid microlens in package

    PubMed Central

    Yang, Chih-Cheng; Tsai, C. Gary; Yeh, J. Andrew

    2010-01-01

    This study presents packaged microscale liquid lenses actuated with liquid droplets of 300–700 μm in diameter using the dielectric force manipulation. The liquid microlens demonstrated function focal length tunability in a plastic package. The focal length of the liquid lens with a lens droplet of 500 μm in diameter is shortened from 4.4 to 2.2 mm when voltages applied change from 0 to 79 Vrms. Dynamic responses that are analyzed using 2000 frames∕s high speed motion cameras show that the advancing and receding times are measured to be 90 and 60 ms, respectively. The size effect of dielectric liquid microlens is characterized for a lens droplet of 300–700 μm in diameter in an aspect of focal length. PMID:21267438

  4. RF cavity using liquid dielectric for tuning and cooling

    DOEpatents

    Popovic, Milorad; Johnson, Rolland P.

    2012-04-17

    A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

  5. Transparent Conveyor of Dielectric Liquids or Particles

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.; Mantovani, James G.

    2009-01-01

    The concept of a transparent conveyor of small loose dielectric parti cles or small amounts of dielectric liquids has emerged as an outgro wth of an effort to develop efficient, reliable means of automated re moval of dust from solar cells and from windows of optical instrumen ts. This concept is based on the previously reported concept of an e lectrodynamic screen, according to which a grid-like electric field is established on and near a surface and is moved along the surface p erpendicularly to the grid lines. The resulting electrodynamic force s on loose dielectric particles or dielectric liquid drops in the vic inity would move the particles or drops along the surface. In the or iginal dust-removal application, dust particles would thus be swept out of the affected window area. Other potential applications may occ ur in nanotechnology -- for example, involving mixing of two or more fluids and/or nanoscale particles under optical illumination and/or optical observation.

  6. Tunable dielectric liquid lens on flexible substrate

    NASA Astrophysics Data System (ADS)

    Lu, Yen-Sheng; Tu, Hongen; Xu, Yong; Jiang, Hongrui

    2013-12-01

    We demonstrate the fabrication of a tunable-focus dielectric liquid lens (DLL) on a flexible substrate made of polydimethylsiloxane, which was wrapped onto a goggle surface to show its functionality. As a positive meniscus converging lens, the DLL has the focal length variable from 14.2 to 6.3 mm in 1.3 s when the driving voltage increases to 125 Vrms. The resolving power of the DLL is 17.95 line pairs per mm. The DLL on a flexible, curvilinear surface is promising for expanded field of view covered as well as in reconfigurable optical systems.

  7. Simple liquid models with corrected dielectric constants.

    PubMed

    Fennell, Christopher J; Li, Libo; Dill, Ken A

    2012-06-14

    Molecular simulations often use explicit-solvent models. Sometimes explicit-solvent models can give inaccurate values for basic liquid properties, such as the density, heat capacity, and permittivity, as well as inaccurate values for molecular transfer free energies. Such errors have motivated the development of more complex solvents, such as polarizable models. We describe an alternative here. We give new fixed-charge models of solvents for molecular simulations--water, carbon tetrachloride, chloroform, and dichloromethane. Normally, such solvent models are parametrized to agree with experimental values of the neat liquid density and enthalpy of vaporization. Here, in addition to those properties, our parameters are chosen to give the correct dielectric constant. We find that these new parametrizations also happen to give better values for other properties, such as the self-diffusion coefficient. We believe that parametrizing fixed-charge solvent models to fit experimental dielectric constants may provide better and more efficient ways to treat solvents in computer simulations. PMID:22397577

  8. Dynamics of a Liquid Dielectric Attracted by a Cylindrical Capacitor

    ERIC Educational Resources Information Center

    Nardi, Rafael; Lemos, Nivaldo A.

    2007-01-01

    The dynamics of a liquid dielectric attracted by a vertical cylindrical capacitor are studied. Contrary to what might be expected from the standard calculation of the force exerted by the capacitor, the motion of the dielectric is different depending on whether the charge or the voltage of the capacitor is held constant. The problem turns out to…

  9. Ionic structure in liquids confined by dielectric interfaces

    NASA Astrophysics Data System (ADS)

    Jing, Yufei; Jadhao, Vikram; Zwanikken, Jos W.; Olvera de la Cruz, Monica

    2015-11-01

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as in the design of double-layer supercapacitors for energy storage and in the extraction of metal ions from wastewater. In this article, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric interfaces using molecular dynamics simulations and liquid state theory. We explore the effects of high electrolyte concentrations, multivalent ions, dielectric contrasts, and external electric field on the ionic distributions. We observe the presence of non-monotonic ionic density profiles leading to a layered structure in the fluid which is attributed to the competition between electrostatic and steric (entropic) interactions. We find that thermal forces that arise from symmetry breaking at the interfaces can have a profound effect on the ionic structure and can oftentimes overwhelm the influence of the dielectric discontinuity. The combined effect of ionic correlations and inhomogeneous dielectric permittivity significantly changes the character of the effective interaction between the two interfaces.

  10. Ionic structure in liquids confined by dielectric interfaces.

    PubMed

    Jing, Yufei; Jadhao, Vikram; Zwanikken, Jos W; Olvera de la Cruz, Monica

    2015-11-21

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as in the design of double-layer supercapacitors for energy storage and in the extraction of metal ions from wastewater. In this article, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric interfaces using molecular dynamics simulations and liquid state theory. We explore the effects of high electrolyte concentrations, multivalent ions, dielectric contrasts, and external electric field on the ionic distributions. We observe the presence of non-monotonic ionic density profiles leading to a layered structure in the fluid which is attributed to the competition between electrostatic and steric (entropic) interactions. We find that thermal forces that arise from symmetry breaking at the interfaces can have a profound effect on the ionic structure and can oftentimes overwhelm the influence of the dielectric discontinuity. The combined effect of ionic correlations and inhomogeneous dielectric permittivity significantly changes the character of the effective interaction between the two interfaces. PMID:26590543

  11. Dielectric constant of liquid alkanes and hydrocarbon mixtures

    NASA Technical Reports Server (NTRS)

    Sen, A. D.; Anicich, V. G.; Arakelian, T.

    1992-01-01

    The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

  12. Heating liquid dielectrics by time dependent fields

    NASA Astrophysics Data System (ADS)

    Khalife, A.; Pathak, U.; Richert, R.

    2011-10-01

    Steady state and time-resolved dielectric relaxation experiments are performed at high fields on viscous glycerol and the effects of energy absorption from the electric field are studied. Time resolution is obtained by a sinusoidal field whose amplitude is switched from a low to a high level and by recording voltage and current traces with an oscilloscope during this transition. Based on their distinct time and frequency dependences, three sources of modifying the dynamics and dielectric loss via an increase in the effective temperature can be distinguished: electrode temperature, real sample temperature, and configurational temperatures of the modes that absorbed the energy. Isothermal conditions that are desired for focusing on the configurational temperature changes (as in dielectric hole burning and related techniques) are maintained only for very thin samples and for moderate power levels. For high frequencies, say ν > 1 MHz, changes of the real temperature will exceed the effects of configurational temperatures in the case of macroscopic samples. Regarding microwave chemistry, heating via cell phone use, and related situations in which materials are subject to fields involving frequencies beyond the MHz regime, we conclude that changes in the configurational (or fictive) temperatures remain negligible compared with the increase of the real temperature. This simplifies the assessment of how time dependent electric fields modify the properties of materials.

  13. Magnetic field tunable capacitive dielectric:ionic-liquid sandwich composites

    NASA Astrophysics Data System (ADS)

    Wu, Ye; Bhalla, Amar; Guo, Ruyan

    2016-03-01

    We examined the tunability of the capacitance for GaFeO3-ionic liquid-GaFeO3 composite material by external magnetic and electric field. Up to 1.6 folds of capacitance tunability could be achieved at 957 kHz with voltage 4 V and magnetic field 0.02 T applied. We show that the capacitance enhancement is due to the polarization coupling between dielectric layer and ionic liquid layer.

  14. (Tenth international conference on conduction and breakdown in dielectric liquids)

    SciTech Connect

    Christophorou, L.G.

    1990-10-05

    The traveler attended the 10th International Conference on Conduction and Breakdown in dielectric Liquids held in Grenoble, France, September 10--14, 1990. He chaired the opening session of the conference, presented one paper, co-authored a second paper presented at the meeting, participated in the discussions during the formal sessions, and had informal discussions with many of the participants.

  15. Optical control of gas-contained liquid dielectrics

    NASA Astrophysics Data System (ADS)

    Venedictov, S. V.; Mitrofanov, G. A.; Svetlakov, N. E.; Strel'nikov, M. Y.

    1997-09-01

    The comparative analysis of the requirement sensitivity threshold for chromatographic and optical methods of monitoring of gases content of liquid dielectrics was made. There is suggested to use the optical manner for the express- analysis of content of gases in transformer oil. The measurement equipment is mounted immediately on filled by oil electrical apparatus.

  16. Microsparks Generated by Charged Particles in Dielectric Liquids

    NASA Astrophysics Data System (ADS)

    Geiger, Robert

    2012-10-01

    The electrodynamics of charged particles in dielectric liquids have been described by several authors [1,2]. As a charged particle approaches an electrode of opposite charge the local electric field eventually exceeds the dielectric strength of the liquid and a microspark is generated. These plasmas can be very small, about < 5 μm, and may exhibit non-thermal behavior. Such non-thermal behavior can provide interesting and efficient chemical reactions [3]. An understanding of the plasma properties for this type of discharge can provide a simple means of generating non-thermal plasmas in dielectric liquids, such as oils or other hydrocarbons, which can be used to chemically process the liquids. Such a technology may lead to a highly efficient method of heavy oil upgrading which can be easily scaled. In order to understand the plasma properties optical emission spectroscopy is carried out for various hydrocarbons and voltage-current characteristics are used to determine the energy cost for this process. [4pt] [1] Melcher, James R. Continuum Electromechanics. Cambridge, MA: MIT Press, 1981.[0pt] [2] Jones, Thomas B. Electromechanics of Particles. Cambridge University Press 1995.[0pt] [3] Staack, D., Fridman, A., Gutsol, A., Gogotsi, Y. and Friedman, G. 2008, Angew. Chem., Int. Ed. 47, 8020.

  17. Effect of dielectric and liquid on plasma sterilization using dielectric barrier discharge plasma.

    PubMed

    Mastanaiah, Navya; Johnson, Judith A; Roy, Subrata

    2013-01-01

    Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ≥ 6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ≥ 6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30°C-66 °C (for FR4) and 20 °C-49 °C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

  18. Effect of Dielectric and Liquid on Plasma Sterilization Using Dielectric Barrier Discharge Plasma

    PubMed Central

    Mastanaiah, Navya; Johnson, Judith A.; Roy, Subrata

    2013-01-01

    Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ≥6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ≥6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30°C–66°C (for FR4) and 20°C–49°C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

  19. A dielectric liquid contact thermal switch with electrowetting actuation

    NASA Astrophysics Data System (ADS)

    McLanahan, A. R.; Richards, C. D.; Richards, R. F.

    2011-10-01

    We present the design, fabrication and characterization of a new kind of MEMS thermal switch based on electrowetting actuation of a dielectric liquid contact. The thermal switch consists of a thin layer (30-120 µm thick) of a dielectric liquid, such as glycerin or water, squeezed between two silicon dies. The gas pressure in the gap can be varied from ambient down to 0.6 T. The switch operates by changing the conductive path between the two silicon dies by moving the thin layer of dielectric liquid using electrowetting. The result is a bi-stable thermal switch that can change between a low thermal resistance state and a high thermal resistance state. Electrowetting measurements indicate switching time on the order of 2-40 s with switching time increasing as gap width decreases. The power required to switch states is less than 2 mW. Heat transfer measurements indicate thermal resistance ratios of up to ROFF/RON = 14, with the highest thermal resistance ratios found for the smallest gap (30 µm) and the lowest pressure (0.6 T).

  20. Dielectric studies of molecular motions in glassy and liquid nicotine

    NASA Astrophysics Data System (ADS)

    Kaminski, K.; Paluch, M.; Ziolo, J.; Ngai, K. L.

    2006-06-01

    The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10-2-109 Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural α-relaxation and its precursor, the Johari-Goldstein β-relaxation. The α-relaxation is well described by the Fourier transform of the Kohlrausch-Williams-Watts stretched exponential function with an approximately constant stretch exponent that is equal to 0.70 as the glass transition temperature is approached. The dielectric α-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein β-relaxation time determined from the dielectric spectra is in good agreement with the primitive relaxation time of the coupling model calculated from parameters of the structural α-relaxation. The shape of the dielectric spectra of nicotine is compared with that of other glass-formers having about the same stretch exponent, and they are shown to be nearly isomorphic. The results indicate that the molecular dynamics of nicotine conform to the general pattern found in other glass-formers, and the presence of the universal Johari-Goldstein secondary relaxation, which plays a role in the crystallization of amorphous pharmaceuticals.

  1. Local Field Factors and Dielectric Properties of Liquid Benzene.

    PubMed

    Davari, Nazanin; Daub, Christopher D; Åstrand, Per-Olof; Unge, Mikael

    2015-09-01

    Local electric field factors are calculated for liquid benzene by combining molecular dynamic simulations with a subsequent force-field model based on a combined charge-transfer and point-dipole interaction model for the local field factor. The local field factor is obtained as a linear response of the local field to an external electric field, and the response is calculated at frequencies through the first absorption maximum. It is found that the largest static local field factor is around 2.4, while it is around 6.4 at the absorption frequency. The linear susceptibility, the dielectric constant, and the first absorption maximum of liquid benzene are also studied. The electronic contribution to the dielectric constant is around 2.3 at zero frequency, in good agreement with the experimental value around 2.2, while it increases to 6.3 at the absorption frequency. The π → π* excitation energy is around 6.0 eV, as compared to the gas-phase value of around 6.3 eV, while the experimental values are 6.5 and 6.9 eV for the liquid and gas phase, respectively, demonstrating that the gas-to-liquid shift is well-described. PMID:26241379

  2. The effect of side-chain liquid crystalline concentration in liquid crystal on dielectric properties

    NASA Astrophysics Data System (ADS)

    Gökçen, M.; Köysal, O.; Yıldırım, M.; Altındal, Ş.

    2012-08-01

    As liquid crystal (LC), E63 and as doping material, side-chain liquid crystalline polymer (SLCP) were used in this study. In order to observe the effect of SLCP concentration in LC on the dielectric properties in a wide range of frequency and bias voltage, SLCP was doped into E63 with 0 (pure E63), 1 and 10 wt%. The bias voltage and frequency dependence of the dielectric properties of pure E63 and doped mixtures (E63/SCLP) have been investigated using the admittance spectroscopy method (C-V and G/ω-V) in the frequency range of 10 kHz-10 MHz at room temperature. The values of dielectric constant (ɛ‧) and real (M‧) and imaginary (M″) parts of electric modulus of the pure E63 and E63/SLCP (1 and 10%) were calculated using the measured admittance values. Moreover, dielectric anisotropy (Δɛ) was also obtained for each sample as a function of frequency. Results show that the values of dielectric parameters are strong functions of frequency and applied bias voltage depending on the concentration amount. Furthermore, dielectric anisotropy has negative values according to p/n type changing for each sample after a critical frequency value.

  3. The preparation of electrohydrodynamic bridges from polar dielectric liquids.

    PubMed

    Wexler, Adam D; López Sáenz, Mónica; Schreer, Oliver; Woisetschläger, Jakob; Fuchs, Elmar C

    2014-01-01

    Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented. PMID:25350319

  4. The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

    PubMed Central

    Wexler, Adam D.; López Sáenz, Mónica; Schreer, Oliver; Woisetschläger, Jakob; Fuchs, Elmar C.

    2014-01-01

    Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented. PMID:25350319

  5. Synthesis and evaluation of oleic acid esters as dielectric liquids

    SciTech Connect

    Thomas, P.; Sridhar, S.; Krishnaswamy, K.R.

    1996-12-31

    The worldwide depletion of petroleum crude and the search for technologically and ecologically alternative to PCB`s has led to the development of synthetic liquid dielectric which are non-flammable, non-toxic and bio-degradable. Esters like Methyl oleate and Pentaerthritol tetra oleate were synthesized in the laboratory. These esters were evaluated for its Physical, Chemical, Electrical and Aging properties and the values obtained compare well with those of commercially available liquids like Midel 7131 and RTemp fluid. Further accelerated aging studies were performed on these esters and the data obtained reveal that the esters prepared in the laboratory has very good chemical stability towards oxidation without inhibitor when compared to Midel 7131 and RTemp fluid which have phenolic inhibitors.

  6. Dielectric Properties of Low-Level Liquid Waste

    SciTech Connect

    L. E. Lagos; M. A. Ebadian

    1998-10-20

    The purpose of this study was to develop a data collection containing values for the dielectric properties of various low-level liquid waste (LLLW) simulants measured as a function of frequency, temperature, and composition. The investigation was motivated by current interest in the use of microwave processing for the treatment of radioactive waste. A large volume of transuranic liquid and sludge produced by the U.S. Department of Defense (DOD) during the production of nuclear fiel bars is stored at several U.S. Department of Energy (DOE) sites around the United States. Waste storage and disposal space is scarce, expensive, and must be minimized. Thus, several DOE sites are pursuing the use of microwave heating as a means of achieving volume reduction and solidification of low-level liquid wastes. It is important to know which microwave frequencies should be employed tc achieve the most efficient processing at a range of different temperatures. The dielectric properties of the LLLW simulants can be utilized to determine the optimum frequencies for use with a particular LLLW or with other LLLWS of similar composition. Furthermore, nonlinear thermal processes, such as thermal runaway, which occur in the material being treated cannot be modeled without a knowledge of the temperature dependence of the dielectric properties. Often, this data does not exist; however, when it does, only very limited data near room temperature are available. The data collection generated in this study can be used to predict the behavior of a variety of microwave thermal treatment technologies, which have the potential of substantially reducing the volume of the LLLWS that are currently stored at many DOE sites. This information should help the users of the microwave reduction and solidification technology to optimize microwave processes used in the treatment of LLLW. The microwave reduction and solidification technology has clear advantages over other methods of reducing LLLWS. These

  7. Computing the dielectric constant of liquid water at constant dielectric displacement

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Sprik, Michiel

    2016-04-01

    The static dielectric constant of liquid water is computed using classical force field based molecular dynamics simulation at fixed electric displacement D . The method to constrain the electric displacement is the finite-temperature classical variant of the constant D method developed by Stengel, Spaldin, and Vanderbilt [Nat. Phys. 5, 304 (2009), 10.1038/nphys1185]. There is also a modification of this scheme imposing fixed values of the macroscopic field E . The method is applied to the popular SPC/E model of liquid water. We compare four different estimates of the dielectric constant, two obtained from fluctuations of the polarization at D =0 and E =0 and two from the variation of polarization with finite D and E . It is found that all four estimates agree when properly converged. The computational effort to achieve convergence varies, however, with constant D calculations being substantially more efficient. We attribute this difference to the much shorter relaxation time of longitudinal polarization compared to transverse polarization accelerating constant D calculations.

  8. Challenges of using dielectric elastomer actuators to tune liquid lens

    NASA Astrophysics Data System (ADS)

    Keong, Gih-Keong; La, Thanh-Giang; Shiau, Li-Lynn; Tan, Adrian W. Y.

    2014-03-01

    Recently, dielectric elastomer actuators (DEAs) have been adopted to tune liquid membrane lens, just like ciliary muscles do to the lens in human eye. However, it faces some challenges, such as high stress, membrane puncture, high driving voltage requirement, and limited focus distance (not more than 707cm), that limit its practical use. The design problem gets more complex as the liquid lens shares the same elastomeric membrane as the DEA. To address these challenges, we separate DEA from the lens membrane. Instead, a liquid-immersed DEA, which is safe from terminal failure, is used as a diaphragm pump to inflate or deflate the liquid lens by hydraulic pressure. This opens up the possibility that the DEA can be thinned down and stacked up to reduce the driving voltage, independent of the lens membrane thickness. Preliminary study showed that our 8-mm-diameter tunable lens can focus objects in the range of 15cm to 50cm with a small driving voltage of 1.8kV. Further miniaturization of DEA could achieve a driving voltage less than 1kV.

  9. Dielectric barrier discharge ionization for liquid chromatography/mass spectrometry.

    PubMed

    Hayen, Heiko; Michels, Antje; Franzke, Joachim

    2009-12-15

    An atmospheric pressure microplasma ionization source based on a dielectric barrier discharge with a helium plasma cone outside the electrode region has been developed for liquid chromatography/mass spectrometry (LC/MS). For this purpose, the plasma was realized in a commercial atmospheric pressure ionization source. Dielectric barrier discharge ionization (DBDI) was compared to conventional electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) in the positive ionization mode. Therefore, a heterogeneous compound library was investigated that covered polar compounds such as amino acids, water-soluble vitamins, and nonpolar compounds like polycyclic aromatic hydrocarbons and functionalized hydrocarbons. It turned out that DBDI can be regarded as a soft ionization technique characterized by only minor fragmentation similar to APCI. Mainly protonated molecules were detected. Additionally, molecular ions were observed for polycyclic aromatic hydrocarbons and derivatives thereof. During DBDI, adduct formation with acetonitrile occurred. For aromatic compounds, addition of one to four oxygen atoms and to a smaller extend one nitrogen and oxygen was observed which delivered insight into the complexity of the ionization processes. In general, compounds covering a wider range of polarities can be ionized by DBDI than by ESI. Furthermore, limits of detection compared to APCI are in most cases equal or even better. PMID:19911793

  10. Atmospheric pressure dielectric barrier discharges interacting with liquid covered tissue

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Kushner, Mark J.

    2014-04-01

    The interaction of plasmas with liquids is of increasing importance in biomedical applications. Tissues treated by atmospheric pressure dielectric barrier discharges (DBDs) in plasma medicine are often covered by a thin layer of liquid, typically a blood serum like water with dissolved gases and proteins up to hundreds of micrometres thick. The liquid processes the plasma-produced radicals and ions prior to their reaching the tissue. In this paper, we report on a computational investigation of the interaction of DBDs in humid air with a thin water layer covering tissue. The water layer, 50-400 µm thick, contains dissolved O2aq (aq means an aqueous species) and alkane-like hydrocarbons (RHaq). In the model, the DBDs are operated with multiple pulses at 100 Hz followed by a 1 s afterglow. Gas phase reactive oxygen and nitrogen species (RONS) intersect the water-vapour saturated air above the liquid and then solvate when reaching the water. The photolysis of water by plasma-produced UV/VUV plays a significant role in the production of radicals. Without RHaq, O_{2aq}^{-} , ONOO_{aq}^{-} , NO_{3aq}^{-} and hydronium (H_{3} O_{aq}^{+} ) dominate the water ions with H_{3} O_{aq}^{+} determining the pH. The dominant RONS in the liquid are O3aq, H2O2aq, and HNOxaq. Dissolved O2aq assists the production of HNO3aq and HOONOaq during the afterglow. With RHaq, reactive oxygen species are largely consumed, leaving an R·aq (alkyl radical) to reach the tissue. These results are sensitive to the thickness of the water layer.

  11. Dielectric Anisotropy of Gold Nanoparticle Colloids in Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Visco, Angelo; Foust, Jon; Mahmood, Rizwan

    We present electrical and optical studies of hexanethiol-treated gold nanoparticle (GNPs) colloids in 4-cyano-4 '-pentyl-biphenyl (5CB) liquid crystals. Preliminary data analysis suggests an unusual behavior of sudden drop and then rise in the dielectric anisotropy at a critical concentration of 0.0862% by wt. GNPs and a sudden rise and then drop in the nematic to isotropic transition temperature. Above the critical concentration the data level off to within the uncertainty of the experimental errors. This colloidal system will help us to understand the interaction and the effects of nanoparticles on the self-assembly of LC molecules and the manner in which these particles organize in LC. This study is important for further developments in nanotechnology, sharp and fast display panels, and within the medical field.

  12. Mechanisms of dielectric polarization in thermotropic liquid-crystalline complexes based on lanthanides

    NASA Astrophysics Data System (ADS)

    Dobrun, L. A.; Kovshik, A. P.; Ryumtsev, E. I.; Knyazev, A. A.; Galyametdinov, Yu. G.

    2016-06-01

    The components of the dielectric constant of a terbium-based liquid-crystalline complex have been measured in the frequency range of 350-5 × 106 Hz. The magnitude and sign of the dielectric anisotropy of the complex have been determined. Dispersion of the dielectric constants in the liquid-crystalline and isotropic phases has been found. The mechanisms responsible for the relaxation phenomena that appear in the studied sample have been determined. The time of dielectric relaxation, the activation energy, and the dipole moment of the complex have been obtained.

  13. Dielectric Relaxation and Rheological Behavior of Supramolecular Polymeric Liquid

    SciTech Connect

    Lou, Nan; Wang, Yangyang; Li, Xiaopeng; Li, Haixia; Wang, Ping

    2013-01-01

    A model self-complementary supramolecular polymer based on thymine and diamidopyridine triple hydrogen-bonding motifs has been synthesized, and its dielectric and rheological behavior has been investigated. The formation of supramolecular polymers has been unequivocally demonstrated by nuclear magnetic resonance, electrospray ionization mass spectrometry with traveling wave ion mobility separation, dielectric spectroscopy, and rheology. The dynamical behaviors of this associating polymer generally conform to those of type-A polymers, with a low-frequency chain relaxation and a high-frequency relaxation visible in both rheological and dielectric measurements. The dielectric chain relaxation shows the ideal symmetric Debye-like shape, resembling the peculiar features of hydrogen-bonding monoalcohols. Detailed analysis shows that there exists a weak decoupling between the mechanical terminal relaxation and dielectric Debye-like relaxation. The origin of the Debye-like dielectric relaxation is further discussed in the light of monoalcohols.

  14. Direct evidence of the dielectric confinement effect in the infrared spectra of organic liquids

    NASA Astrophysics Data System (ADS)

    Perova, Tatiana S.; Shaganov, Igor I.; Melnikov, Vasily A.; Berwick, Kevin

    2009-09-01

    In this study, the size (dielectric) confinement effect on the peak position of intra-molecular vibrations in the infrared spectra of liquid benzene, carbon disulphide and chloroform is described theoretically, and observed experimentally, for the first time. It is shown that the shift in the peak position due to the dielectric confinement effect can reach a few tenths of a wavenumber for strong vibrational bands. The results obtained confirm the applicability of the dispersive local-field approach for the description of the dielectric confinement effect for liquid media, as well as for crystalline and amorphous solids.

  15. Alignment of cholesteric liquid crystals using the macroscopic flexoelectric polarization contribution to dielectric properties

    NASA Astrophysics Data System (ADS)

    Outram, B. I.; Elston, S. J.

    2013-09-01

    By considering the contribution of flexoelectricity to a cholesteric liquid crystal's dielectric permittivity, we show that both flexoelectric and dielectric effects allow the alignment of the Uniform Lying Helix (ULH) in devices with in-plane-switching (IPS) electrodes. The non-uniformity of fields produced by IPS electrodes is found to be crucial to allow ULH formation. The ULH is stabilised using homeotropic alignment conditions without polymer networks. Thus, a framework has been developed and tested for aligning and making stable cholesteric liquid crystals that incorporates both flexoelectric and dielectric field effects. Applications include bistable and ultra-fast display technology.

  16. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide.

    PubMed

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25-60 (o)C) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  17. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    PubMed Central

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 oC) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  18. Transient Current of Nematic Liquid Crystals with Negative Dielectric Anisotropy Induced by Step-Voltage Excitation

    NASA Astrophysics Data System (ADS)

    Iwata, Yosuke; Naito, Hiroyoshi; Inoue, Masaru; Ichinose, Hideo; Klasen-Memmer, Melanie; Tarumi, Kazuaki

    2004-12-01

    A simple theory for measuring the rotational viscosity has been proposed from the analysis of transient current, induced by step-voltage excitation, in nematic liquid crystal cells (NLCs) with positive dielectric anisotropy [M. Imai et al.: Jpn. J. Appl. Phys. 33 (1994) L119]. The applicability of the theory to NLCs with negative dielectric anisotropy has been examined. It is found that the transient current shape of NLCs with negative dielectric anisotropy is different from that of NLCs with positive dielectric anisotropy, and hence, the theory cannot directly be applied to the analysis of the transient current of NLCs with negative dielectric anisotropy. Computer simulation shows that the transient current of NLCs with negative dielectric anisotropy is successfully reproduced by taking into account the flow effects with an appropriate boundary condition and that the flow effects play a key role in eliciting a faster electrooptic response in vertically aligned NLC displays.

  19. Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

    NASA Technical Reports Server (NTRS)

    Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

    1994-01-01

    Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

  20. High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Yen, Chih-Feng; Fan, Cho-Han

    2014-09-01

    The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.

  1. Effect of polarization on dielectric behaviour of PET/0.8PHB polymer liquid crystals

    SciTech Connect

    Yarramaneni, Sridharbabu; Sharma, Anu; Quamara, J. K.

    2014-04-24

    Dielectric constant and loss behaviour of pristine and polarized samples of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) polymer liquid crystals were studied at continuous temperatures ranging from 20 °C to 250 °C, polarized at potentials 500V and 2000V with high precision d.c. power supply. Dielectric constant appears to be almost linearly dependent in the lower temperature region and is independent in the higher temperature region. Dielectric loss becomes approximately ten times lower at higher temperatures.

  2. Dielectric relaxation and birefringence study of 7.O5O.7 dimeric liquid crystal compound

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Debanjan; Paul-Choudhury, Sandip; Alapati, Parameswara Rao; Bhattacharjee, Ayon

    2016-05-01

    Measurement of dielectric relaxation and birefringence phenomenon of dimeric liquid crystal compound with the dependence of temperature was reported in this paper. Homogeneous (HG) and homeotropic (HT) alignment of the cell are introduced to investigate the dielectric relaxation, activation energy and birefringence. Cole-Cole plots analyzed the dielectric relaxation of the dimeric compound. The observed Cole-Cole plots were semi-circular, and the relaxation mechanism obeys the non-Debye type of relaxation behaviour. Slater's perturbation equations have been used to analysis the activation energy of the compound. The birefringence of the compound has positively anisotropy and thin prism mechanism was used to study the anisotropy of the compound.

  3. Effect of polarization on dielectric behaviour of PET/0.8PHB polymer liquid crystals

    NASA Astrophysics Data System (ADS)

    Yarramaneni, Sridharbabu; Sharma, Anu; Quamara, J. K.

    2014-04-01

    Dielectric constant and loss behaviour of pristine and polarized samples of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) polymer liquid crystals were studied at continuous temperatures ranging from 20 °C to 250 °C, polarized at potentials 500V and 2000V with high precision d.c. power supply. Dielectric constant appears to be almost linearly dependent in the lower temperature region and is independent in the higher temperature region. Dielectric loss becomes approximately ten times lower at higher temperatures.

  4. Quantitative assessment of radiation force effect at the dielectric air-liquid interface

    PubMed Central

    Capeloto, Otávio Augusto; Zanuto, Vitor Santaella; Malacarne, Luis Carlos; Baesso, Mauro Luciano; Lukasievicz, Gustavo Vinicius Bassi; Bialkowski, Stephen Edward; Astrath, Nelson Guilherme Castelli

    2016-01-01

    We induce nanometer-scale surface deformation by exploiting momentum conservation of the interaction between laser light and dielectric liquids. The effect of radiation force at the air-liquid interface is quantitatively assessed for fluids with different density, viscosity and surface tension. The imparted pressure on the liquids by continuous or pulsed laser light excitation is fully described by the Helmholtz electromagnetic force density. PMID:26856622

  5. Numerical investigation of conduction pumping of dielectric liquid film using flush-mounted electrodes

    NASA Astrophysics Data System (ADS)

    Gharraei, Reza; Esmaeilzadeh, Esmaeil; Heirani Nobari, Mohammad Reza

    2014-02-01

    Electrohydrodynamic conduction pumping of dielectric liquid films using flush-mounted electrodes is investigated numerically. Two major factors consisting of the ion mobility difference and electrodes' configuration can affect the conduction pumps. The relative importance of these factors on the hydrodynamic behavior has been studied at different configurations of flush-mounted electrodes for conduction pumping of various dielectric liquids with different electrical properties. Furthermore, the effect of heterocharge layer structure on the hydrodynamic behavior of conduction pump has been studied. The electrical behavior and flow patterns of dielectric liquids with real measured mobilities are compared with the experimental results, and new features of conduction pumping are found. The numerical results indicate that in the various operating conditions, the flow direction is dictated by the dominant factor.

  6. Pumping of Dielectric Liquids Using Non-Uniform-Field Induced Electrohydrodynamic Flow

    NASA Astrophysics Data System (ADS)

    Ryu, Jae Chun; Kim, Wonkyoung; Kang, Kwan Hyoung

    2010-11-01

    Pumping of dielectric liquids or poorly conducting liquids is necessary in cooling of microelectronic devices, dispensing liquids in miniature systems for chemical and biological analysis, and micropumping of organic solvents for microreactor. Electrical pumping of liquids is more attractive than conventional mechanical pumping methods because of many advantages such as simple design, no mechanical parts, low acoustic noise, and lightweight. We present a new electrohydrodynamic (EHD) pumping method for dielectric liquids. The pumping method relies on the EHD flow generated by electric-field dependent electrical conductivity (Onsager effect). A polar additive plays an important role in enhancing the field-dependency of conductivity. When ac voltage is applied, a fast and regular flow was produced around electrodes. Flow speed is proportional to cube of electric-field strength and inversely to applied frequency. The experimental results showed good agreement with numerical analysis which is based on our model.

  7. Nonlinear waves on the free surface of a dielectric liquid in an oblique electric field

    SciTech Connect

    Gashkov, M. A.; Zubarev, N. M. Kochurin, E. A.

    2015-09-15

    The nonlinear dynamics of the free surface of an ideal dielectric liquid that is exposed to an external oblique electric field has been studied theoretically. In the framework of the Hamiltonian formalism, a system of nonlinear integro-differential equations has been derived that describes the dynamics of nonlinear waves in the small-angle approximation. It is established that for a liquid with high dielectric permittivity, these equations have a solution in the form of plane waves of arbitrary shape that propagate without distortion in the direction of the horizontal component of the external field.

  8. Influence of gold nanorods size on electro-optical and dielectric properties of ferroelectric liquid crystals

    SciTech Connect

    Podgornov, Fedor V.; Ryzhkova, Anna V.; Haase, Wolfgang

    2010-11-22

    The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational viscosity of the FLC/GNRs nanodispersions independently on the GNRs diameter. Oppositely, the relaxation frequency and the dielectric strength of the Goldstone mode strongly depend on the GNRs diameter, which can be explained by the charge transfer between the GNRs and FLC molecules.

  9. Dynamics of glass-forming liquids. XIV. A search for ultraslow dielectric relaxation in glycerol

    NASA Astrophysics Data System (ADS)

    Richert, Ranko

    2010-08-01

    A recent dielectric study of various polyalcohols reported on the general occurrence of an ultraslow process with Debye type character in hydrogen bonded liquids [R. Bergman, H. Jansson, and J. Swenson, J. Chem. Phys. 132, 044504 (2010)], whereas previous work suggested that such behavior is specific to monoalcohols only. Clarifying this issue is highly relevant for assessing models aimed at rationalizing these modes that are slower than the primary structural relaxation and associated with a single time constant. To this end, the dielectric relaxation of glycerol is measured at different electrode distances with high accuracy. In this manner, electrode polarization can be separated from the dielectric signals intrinsic in the supercooled liquid. In the frequency range below the loss peak frequency ωmax of the α-process, only dc-conductivity is required to understand the dielectric properties of supercooled glycerol within a margin of ɛ″≈±0.1 and thus no indication of an ultraslow peak is found. More quantitatively, any dielectric Debye like mode located around 10-5ωmax would need to have an amplitude smaller than 0.4% of that of the primary dielectric process to be consistent with the present findings, in contrast to previous claims of >50%.

  10. Dielectric response of metal/SrTiO{sub 3}/two-dimensional electron liquid heterostructures

    SciTech Connect

    Mikheev, Evgeny; Raghavan, Santosh; Stemmer, Susanne

    2015-08-17

    Maximizing the effective dielectric constant of the gate dielectric stack is important for electrostatically controlling high carrier densities inherent to strongly correlated materials. SrTiO{sub 3} is uniquely suited for this purpose, given its extremely high dielectric constant, which can reach 10{sup 4}. Here, we present a systematic study of the thickness dependence of the dielectric response and leakage of SrTiO{sub 3} that is incorporated into a vertical structure on a high-carrier-density two-dimensional electron liquid (2DEL). A simple model can be used to interpret the data. The results show a need for improved interface control in the design of metal/SrTiO{sub 3}/2DEL devices.

  11. Nano-electromechanical rotation of graphene and giant enhancement in dielectric anisotropy in a liquid crystal

    SciTech Connect

    Basu, Rajratan Kinnamon, Daniel; Garvey, Alfred

    2015-05-18

    A nematic liquid crystal (LC) is doped with dilute concentrations of pristine monolayer graphene (GP) flakes, and the LC + GP hybrids are found to exhibit a dramatic increase in the dielectric anisotropy. Electric field-dependent conductance studies reveal that the graphene flakes follow the nematic director that mechanically rotates on increasing an applied electric field. Further studies show that the π–π electron stacking, between the graphene's honeycomb structure and the LC's benzene rings, stabilizes pseudo-nematic domains that collectively amplify the dielectric anisotropy by improving the orientational order parameter in the nematic phase. These anisotropic domains interact with the external electric field, resulting in a nonzero dielectric anisotropy in the isotropic phase as well. The enhancement in dielectric anisotropy, due to the LC–graphene coupling, is found to have subsequent positive impacts on the LC's orientational threshold field and elasticity that allows the nematic director to respond quicker on switching the electric field off.

  12. Dielectric and electro-optical properties of polymer-stabilized liquid crystal system

    NASA Astrophysics Data System (ADS)

    Pande, Mukti; Tripathi, Pankaj Kumar; Misra, Abhishek Kumar; Manohar, Shashwati; Manohar, Rajiv; Singh, Shri

    2016-03-01

    In this work, we report the results of dielectric and electro-optical properties as a function of temperature for both pure liquid crystal matrix and polymer-stabilized liquid crystal (PSLC). The threshold and saturation voltages have been determined from transmission-voltage curves. We have studied the polymer domains formation in PSLC with variation of concentration of polymer in liquid crystal matrix. It is observed that the dielectric anisotropy of PSLC is significantly influenced by the polar order present in the polymer domains environment. A delicate interplay between the orientational order of liquid crystal and polymeric domains determines the molecular orientations of PSLC with respect to the director of the LC system.

  13. Electrorheological Source of Nonlinear Dielectric Effects in Molecular Glass-Forming Liquids.

    PubMed

    Samanta, Subarna; Richert, Ranko

    2016-08-11

    We have measured the dielectric relaxation spectra of eight glass-forming liquids in the presence of electric direct current (dc)-bias fields ranging from 100 to 500 kV/cm. For every sample, we observe two distinct field-induced effects: a reduction in the relaxation amplitude and an increase in the primary structural relaxation time that is associated with viscous flow. Whereas amplitude change is typical of the well-known dielectric saturation, the field-induced increase in viscosity is a source of nonlinear behavior that has been recognized only recently. We find that this electrorheological behavior occurs in all polar liquids of this study, and its magnitude is correlated with the field-induced change in thermodynamic entropy. It constitutes a significant source of nonlinear dielectric behavior, which occurs for both dc and alternating current fields. PMID:27404019

  14. Dielectric relaxations of small carbohydrate molecules in the liquid and glassy states

    SciTech Connect

    Noel, T.R.; Ring, S.G.; Whittam, M.A.

    1992-06-25

    Dielectric relaxations of several vitreous and liquid monosaccharides were measured at 100 - 10{sup 5} Hz and -100 to 150 {degrees}C. Depending upon the molecule, one or two relaxations were observed. Primary alcohol moieties on the monosaccharide conferred higher activation energies than those without, such as xylitol and glucitol. 19 refs., 7 figs., 2 tabs.

  15. Apparatus for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, J.; Ogletree, D.F.; Salmeron, M.; Xiao, X.

    1998-04-28

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged. 9 figs.

  16. Method for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, Jun; Ogletree, D. Frank; Salmeron, Miguel; Xiao, Xudong

    1999-01-01

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged.

  17. Apparatus for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, Jun; Ogletree, D. Frank; Salmeron, Miguel; Xiao, Xudong

    1998-01-01

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged.

  18. Method for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, J.; Ogletree, D.F.; Salmeron, M.; Xiao, X.

    1999-03-09

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged. 9 figs.

  19. Influence of dielectric properties on van der Waals/Casimir forces in solid-liquid systems

    SciTech Connect

    Zwol, P. J. van; Palasantzas, G.; De Hosson, J. Th. M.

    2009-05-15

    In this paper, we present calculations of van der Waals/Casimir forces, described by Lifshitz theory, for the solid-liquid-solid system using measured dielectric functions of all involved materials for the wavelength range from millimeters down to subnanometers. It is shown that even if the dielectric function is known over all relevant frequency ranges, the scatter in the dielectric data can lead to very large scatter in the calculated van der Waals/Casimir forces. Especially when the liquid dielectric function becomes comparable in magnitude to the dielectric function of one of the interacting solids, the associated variation in the force can be up to a factor of 2 for plate-plate separations 5-500 nm. This corresponds to an uncertainty up to 100% in the theory prediction for a specific system. As a result accuracy testing of the Lifshitz theory under these circumstances is rather questionable. Finally we discuss predictions of Lifshitz theory regarding multiple repulsive-attractive transitions with separation distance, as well as nontrivial scaling of the van der Waals/Casimir force with distance.

  20. Second Law violations in the wake of the Electrocaloric Effect in liquid dielectrics

    NASA Astrophysics Data System (ADS)

    Trupp, Andreas

    2002-11-01

    In any textbook on physics, Coulomb's law of the mutual force between two point charges q0 at a distance r is modified by the appearance of the term K if the point charges are embedded in a dielectric: F = 1/4πɛ0 q0/2K r2 = 4πɛ0 K V2 The dimensionless constant K (⩾ 1) denotes the permittivity of the dielectric. According to this formula, the force is either reduced by the factor 1/K -if the charges q0 are kept invariant in amount-, or is increased by the factor K -if the potential V is kept invariant- as a result of the introduction of the dielectric. V is the potential of the location of one point charge as a result of the field generated by the other point charge. Feynman argues that the formula is correct only if the dielectric is a liquid, and that it does not work properly with solids. His criticism does not go far enough. Two simple experiments with a liquid dielectric (backed by theoretical reflections) reveal that the formula is correct only if the two point charges have opposite signs (negative and positive). If the signs are equal, the formula reads (when applied to point charges in liquid dielectrics): F = 1/4πɛ0 q0/2K2 r2 = 4πɛ0 V2 Hence the force is reduced by the factor 1/K2 if the charges (of equal sign) are kept invariant, and is left unaffected by the introduction of the dielectric if the potential V is kept invariant. With a so revised formula, cyclic processes can be performed in which the electrocaloric effect (that heats up the dielectric when the electric field is being built, and cools down the dielectric when the field is disappearing) is no longer symmetrical, leading to the conversion of ambient heat to electric work as a net result of the work cycle.

  1. Dielectric Properties of Polypropylene-Based Nanocomposites with Ionic Liquid-Functionalized Multiwalled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Xu, Pei; Gui, Haoguan; Hu, Yadong; Bahader, Ali; Ding, Yunsheng

    2014-07-01

    Nanocomposites were prepared from polypropylene (PP) and untreated multiwalled carbon nanotubes (MWCNTs) or MWCNTs surface-functionalized with ionic liquids (MIL), as fillers, and their dielectric properties were compared. The physical (cation-π/π-π) interaction between the ionic liquids and the MWCNTs was apparent from Raman spectroscopy and from thermogravimetric analysis. Morphology characterization revealed that ionic liquids improve the dispersibility of MWCNTs in the PP matrix. It is suggested that the substantial increase in the dielectric permittivity of the nanocomposites compared with that of the PP originates from a remarkable Maxwell-Wagner-Sillars (MWS) effect at percolation threshold where mobile charge carriers are blocked at internal interfaces between the MIL and the PP matrix. The high polarity of ionic liquids may reinforce the MWS effect, and the nonconducting organic groups of the ionic liquids promote the low loss tangent and low conductivity of the MIL/PP nanocomposites. Compared with MWCNTs/PP nanocomposites, lower loss tangent and higher dielectric permittivity were observed for MIL/PP nanocomposites, making the material more attractive for application in electronics.

  2. Nanoliter liquid characterization by open whispering-gallery mode dielectric resonators at millimeter wave frequencies

    NASA Astrophysics Data System (ADS)

    Shaforost, E. N.; Klein, N.; Vitusevich, S. A.; Offenhäusser, A.; Barannik, A. A.

    2008-10-01

    We present an approach for identification and concentration determination of liquids of pico to nanoliter volumes at a frequency of 35 GHz based on a whispering-gallery mode (WGM) dielectric resonator technique. A quasioptical coupling scheme based on dielectric image waveguides was employed to excite high-Q running wave WGMs with uniform azimuthal field distribution in cylindrical sapphire disks with quality factors up to 4×105 at room temperature. Measurement of the liquid induced changes in the resonator quality factor and resonance frequency has been performed for droplets down to 90 pl volume spotted at different positions on the surface of the sapphire disk. We have employed our method for concentration determination of ethanol, glucose, and albumin dissolved in water. Solutions with concentration values well below 10% could be clearly separated from pure water. Our method is promising for the characterization of biological liquids.

  3. Vaporization heat transfer of dielectric liquids on a wick-covered surface

    NASA Technical Reports Server (NTRS)

    Gu, C. B.; Chow, L. C.; Baker, K.

    1993-01-01

    Vaporization heat transfer characteristics were measured for the dielectric liquid FC-72 on a horizontal heated surface covered with wire screen wicks with the mesh number for the screens varying from 24 to 100. In such a situation the liquid level can be either higher or lower than the heated surface. When the liquid level was above the heated surface (shallow pool boiling), the height of the liquid level above the surface, h, was varied from 0 to 10 mm. When the liquid level was below the heated surface (evaporation through capillary pumping), the distance from the liquid level to the edge of the surface, L, was adjusted from 0 to 15 mm. Experimental data revealed that the critical heat flux (CHF) decreases as the mesh number is increased from 24 to 100 for both vaporation and shallow pool boiling, showing that the vapor-escaping limit is more important than the capillary limit in flat plate heat pipe application.

  4. Liquid Metals: Stretchable, High-k Dielectric Elastomers through Liquid-Metal Inclusions (Adv. Mater. 19/2016).

    PubMed

    Bartlett, Michael D; Fassler, Andrew; Kazem, Navid; Markvicka, Eric J; Mandal, Pratiti; Majidi, Carmel

    2016-05-01

    An all-soft-matter composite consisting of liquid metal microdroplets embedded in a soft elastomer matrix is presented by C. Majidi and co-workers on page 3726. This composite exhibits a high dielectric constant while maintaining exceptional elasticity and compliance. The image shows the composite's microstructure captured by 3D X-ray imaging using a nano-computed tomographic scanner. PMID:27167031

  5. The dielectric response of room-temperature ionic liquids: effect of cation variation.

    PubMed

    Weingärtner, Hermann; Sasisanker, Padmanabhan; Daguenet, Corinne; Dyson, Paul J; Krossing, Ingo; Slattery, John M; Schubert, Thomas

    2007-05-10

    In continuation of recent work on the dielectric response of imidazolium-based ionic liquids (ILs) (J. Phys. Chem. B, 2006, 110, 12682), we report on the effect of cation variation on the frequency-dependent dielectric permittivity up to 20 GHz of ionic liquids. The salts are comprised of pyrrolidinium, pyridinium, tetraalkylammonium, and triethylsulfonium cations combined with the bis-((trifluoromethyl)sulfonyl)imide anion. The dielectric spectra resemble those observed for imidazolium salts with the same anion. In all cases, the major contribution results from a diffusive low-frequency response on the time scale of several 100 ps, which shows a broadly distributed kinetics similar to that of spatially heterogeneous states in supercooled and glassy systems rather than that observed in fluid systems. There is evidence for a weak secondary process near 10-20 ps. Perhaps the most interesting difference to imidazolium salts is founded in the missing portions of the spectra due to processes beyond the upper cutoff frequency of 20 GHz. These are lower than that observed for imidazolium-based salts and seem to vanish for tetraalkylammonium and triethylsulfonium salts. As for imidazolium salts, the extrapolated static dielectric constants are on the order of epsilon(S) congruent with 10-13, classifying these ILs as solvents of moderate polarity. PMID:17279790

  6. Dielectric studies of iron nanoparticles-ferroelectric liquid crystal mixture

    NASA Astrophysics Data System (ADS)

    Khushboo, Sharma, Puneet; Jayoti, Divya; Malik, Praveen; Raina, K. K.

    2016-05-01

    Iron nanoparticles doped ferroelectric liquid crystal mixtures have been prepared and studied in thin planar cell. The effect of temperature and frequency on permittivity behavior in SmC* phase has been studied. Permittivity increases with increasing the temperature in SmC* phase and show a reduction near the SmC*-SmA transition temperature. A Goldstone mode is clearly observed at ~100 Hz.

  7. Dielectric spectroscopy: a technique for the determination of water coordination within ionic liquids.

    PubMed

    Dimitrakis, Georgios; Villar-Garcia, Ignacio J; Lester, Edward; Licence, Peter; Kingman, Samuel

    2008-05-28

    The presence of water can have a significant influence upon both the physical and dielectric properties of ionic liquids and consequently their ability to interact with microwaves. Herein we show that complex permittivity initially decreases as low concentrations of water are added to the system, the continued addition of water gives rise to an inversion in this trend. We propose that this minimum point may be used to identify water dimer formation. PMID:18473042

  8. Conductive and dielectric defects, and anisotropic and isotropic turbulence in liquid crystals: Electric power fluctuation measurements

    NASA Astrophysics Data System (ADS)

    Tóth-Katona, Tibor; Gleeson, James T.

    2004-01-01

    Fluctuations of the injected electric power during electroconvection (EHC) of liquid crystals are reported in both the conductive and the dielectric regime of convection. The amplitude and the frequency of the fluctuations, as well as the probability density functions have been compared in these two regimes and substantial differences have been found both in defect turbulence of EHC and at the DSM1→DSM2 transition.

  9. Stretchable, High-k Dielectric Elastomers through Liquid-Metal Inclusions.

    PubMed

    Bartlett, Michael D; Fassler, Andrew; Kazem, Navid; Markvicka, Eric J; Mandal, Pratiti; Majidi, Carmel

    2016-05-01

    An all-soft-matter composite with exceptional electro-elasto properties is demonstrated by embedding liquid-metal inclusions in an elastomer matrix. This material exhibits a unique combination of high dielectric constant, low stiffness, and large strain limit (ca. 600% strain). The elasticity, electrostatics, and electromechanical coupling of the composite are investigated, and strong agreement with predictions from effective medium theory is found. PMID:27007888

  10. Electrorheology of miscible blended liquid crystalline polymer: A dielectric property approach

    NASA Astrophysics Data System (ADS)

    Kawai, A.; Ide, Y.; Inoue, A.; Ikazaki, F.

    1998-09-01

    A miscible blended liquid crystalline polymer prepared by Asahi Chemical Industry Co. Ltd. was used to study the effect of temperature on electrorheology. The electrorheological (ER) effect was measured using a rotational viscometer at temperatures between 20 and 60 °C. The polymer showed no yield shear stress under an external electric field, and its ER effect increased with decreasing temperature. We explain the electrorheology of the miscible blended liquid crystalline polymer using our ER mechanism, based on Block's model. In our mechanism, for an ER fluid to have an appreciable ER effect, its relaxation frequency must be between 100 and 105 Hz and the difference in the dielectric constant must be large below and above the relaxation frequency. The relaxation frequency of the miscible blended liquid crystalline polymer increased with increasing temperature, and the difference in its dielectric constant below and above the relaxation frequency increased with decreasing temperature. These dielectric properties are explained by the Debye theory and account for the electrorheology of the polymer.

  11. Communication: Solvation and dielectric response in ionic liquids--conductivity extension of the continuum model.

    PubMed

    Zhang, X-X; Schröder, C; Ernsting, N P

    2013-03-21

    The solvation response of a polarity probe in a conducting liquid is analyzed based on simple continuum theory. A multi-exponential description of the dynamics is inverted to give an effective dc conductivity and a generalized permittivity spectrum in terms of Debye modes. For Coumarin 153 in ionic liquids the conductivity is found to be reduced systematically from the bulk value, whereas the permittivity from GHz-THz bulk absorption measurements is well reproduced by the solvation experiment. Thus, by using a dye as molecular antenna, the dielectric dispersion of the microscopic environment can be obtained. PMID:23534620

  12. Pumping of dielectric liquids using non-uniform-field induced electrohydrodynamic flow

    NASA Astrophysics Data System (ADS)

    Kim, Wonkyoung; Chun Ryu, Jae; Kweon Suh, Yong; Hyoung Kang, Kwan

    2011-11-01

    We present a method of pumping dielectric (or non-polar) liquids. The pumping method relies on the electrohydrodynamic flow generated by field dependent electrical conductivity (Onsager effect). Adding a small amount of polar liquid increases the field-dependency of conductivity. Applying either dc or ac voltage produces a fast and regular flow around electrodes. Flow speed is proportional to cube of electric-field strength and inversely to applied frequency. The experimental results agreed well with numerical analysis based on our theoretical model.

  13. Spreading of Thin Droplets of Perfect and Leaky Dielectric Liquids on Inclined Surfaces.

    PubMed

    Corbett, Andrew; Kumar, Satish

    2016-07-01

    The spreading of droplets may be influenced by electric fields, a situation that is relevant to applications such as coating, printing, and microfluidics. In this work we study the effects of an electric field on the gravity-driven spreading of two-dimensional droplets down an inclined plane. We consider both perfect and leaky dielectric liquids, as well as perfectly and partially wetting systems. In addition to the effects of electric fields, we examine the use of thermocapillary forces to suppress the growth of the capillary ridge near the droplet front. Lubrication theory is applied to generate a set of coupled partial differential equations for interfacial height and charge, which are then solved numerically with a finite-difference method. Electric fields increase the height of the capillary ridge in both perfect and leaky dielectric droplets due to electrostatic pressure gradients that drive liquid into the ridge. In leaky dielectrics, large interfacial charge gradients in the contact-line region create shear stresses that also enhance ridge growth and the formation of trailing minor ridges. The coalescence of these ridges can significantly affect the long-time thinning rate of leaky dielectric droplets. In partially wetting liquids, electric fields promote the splitting of smaller droplets from the primary droplet near the receding contact line due to the interplay between electrostatic forces and disjoining pressure. Cooling from below and heating from above generates thermocapillary forces that counteract the effects of electric fields and suppress the growth of the capillary ridge. The results of this work have important implications for manipulating the spreading of droplets down inclined surfaces. PMID:27247998

  14. Asymptotic and numerical analysis of electrohydrodynamic flows of dielectric liquid.

    PubMed

    Suh, Y K; Baek, K H; Cho, D S

    2013-08-01

    We perform an asymptotic analysis of electrohydrodynamic (EHD) flow of nonpolar liquid subjected to an external, nonuniform electric field. The domain of interest covers the bulk as well as the thin dissociation layers (DSLs) near the electrodes. Outer (i.e., bulk) equations for the ion transport in hierarchical order of perturbation parameters can be expressed in linear form, whereas the inner (i.e., DSL) equations take a nonlinear form. We derive a simple formula in terms of various parameters which can be used to estimate the relative importance of the DSL-driven flow compared with the bulk-driven flow. EHD flow over a pair of cylindrical electrodes is then solved asymptotically and numerically. It is found that in large geometric scale and high ion concentration the EHD flow is dominated by the bulk-charge-induced flow. As the scale and concentration are decreased, the DSL-driven slip velocity increases and the resultant flow tends to dominate the domain and finally leads to flow reversal. We also conduct a flow-visualization experiment to verify the analysis and attain good agreement between the two results with parameter tuning. We finally show, based on the comparison of experimental and numerical solutions, that the rate of free-ion generation (dissociation) should be less than the one predicted from the existing formula. PMID:24032920

  15. Density fluctuations and dielectric constant of water in low and high density liquid states

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik; Zhang, Cui; Galli, Giulia A.; Franzese, Giancarlo; Stanley, H. Eugene

    2012-02-01

    The hypothesis of a liquid-liquid critical point (LLCP) in the phase diagram of water, though first published many years ago, still remains the subject of a heated debate. According to this hypothesis there exists a critical point near T 244 K, and P 215 MPa, located at the end of a coexistence line between a high density liquid (HDL) and a low density liquid state (LDL). The LLCP lies below the homogenous nucleation temperature of water and it has so far remained inaccessible to experiments. We study a model of water exhibiting a liquid-liquid phase transition (that is a liquid interacting through the ST2 potential) and investigate the properties of dipolar fluctuations as a function of density, in the HDL and LDL. We find an interesting correlation between the macroscopic dielectric constants and the densities of the two liquids in the vicinity of the critical point, and we discuss possible implications for measurements close to the region where the LLCP may be located.

  16. Dielectric analysis of micelles and microemulsions formed in a hydrophilic ionic liquid. I. Interaction and percolation.

    PubMed

    Lian, Yiwei; Zhao, Kongshuang

    2011-10-01

    Dielectric measurements were carried out on binary mixtures of Triton X-100 (TX-100, a nonionic surfactant with a polyoxyethylene chain) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)], a hydrophilic ionic liquid), and [bmim][BF(4)]/TX-100/cyclohexane microemulsions in a wide frequency range to study the molecular interaction and percolation in these systems. Striking dielectric relaxations were observed, and the dc conductivity data were obtained from the measured total dielectric loss spectra. The interaction between TX-100 and [bmim][BF(4)] is estimated by analyzing the dc conductivity of TX-100/[bmim][BF(4)] solutions in light of the Bruggeman's effective medium approximation, which indicates that spherical micelles are formed when the TX-100 volume fraction is below 48% and the number of cations associated with every TX-100 molecule is eight. For IL-oil microemulsions, both the dependence of dc conductivity and the permittivity (for fixed frequency) on cyclohexane concentration were used to identify the oil-in-IL, bicontinuous, and IL-in-oil microregions. Both the conduction and dielectric relaxation behavior suggest that a static percolation occurs in this hydrophilic IL microemulsion. PMID:21859133

  17. Highly Efficient Electrohydrodynamic Pumping: Molecular Isomer Effect of Dielectric Liquids, and Surface States of Electrodes.

    PubMed

    Abe, Hiroshi; Imai, Yusuke; Tokunaga, Naoki; Yamashita, Yasuhiro; Sasaki, Yoshiki

    2015-11-11

    Highly efficient electrohydrodynamic (EHD) pumping was obtained by a combination of a dielectric liquid having a molecular isomer and electrodes with a smooth surface. Four kinds of surface states of Cu electrodes were processed by conventional mechanical polishing, fine diamond paste polishing, chemical etching and Au vapor deposition. A series of hydrofluoroether liquids (HFEs) were used as dielectric liquids: C3F7OCH3 (HFE-7000), C4F9OCH3 (HFE-7100), C4F9OC2H5 (HFE-7200), C6F13OCH3 (HFE-7300), and C5H5F6OC3HF6 (HFE-7600). The coexistence of normal (n-) and isomer (i-) HFEs and their molar fractions were examined by NMR spectroscopy. Among the dielectric liquids, the hybrid n- and i-HFE-7600 showed highly efficient EHD pumping, where the electric current, I, was sufficiently suppressed by the smooth surface of the electrodes. The maximum hydrostatic pressure Δpmax was ∼7500 Pa with 12 kV and I = 19 μA. The smooth surface of the electrodes contributes not only to the formation of a stable electric double layer (EDL) but also to the prevention of charge injection from the electrodes. Polarization pumping derived from the stable EDL enables highly efficient energy transfer without discharging, or damage to the sample and electrodes. The dipole moments of the HFEs were estimated by density functional theory calculations. The hydrostatic pressure was found to be proportional to the difference in the calculated dipole moment between n- and i-HFEs. Numerical simulations were carried out to examine the experimentally obtained electrode gap dependence of the hydrostatic pressure. PMID:26465161

  18. Dielectric insulation characteristics of liquid-nitrogen-impregnated laminated paper-insulated cable

    SciTech Connect

    Suzuki, H.; Ishihara, K.; Akita, S. )

    1992-10-01

    This paper reports that the electric characteristics and insulation design strength of a liquid-nitrogen-impregnated synthetic insulation was considered. It found to detect the impregnation of liquid nitrogen by measuring the electrostatic capacitance of the cable [epsilon] [center dot] tan [delta] an index of the dielectric loss, was 0.31% for cellulose paper and 0.18% for semisynthetic paper, PPLP and OPPL. It is found that the decline of the thickness dependence of the breakdown strength of the liquid-nitrogen-impregnated insulating cable is steeper than that of the OF cables. It is possible to design the insulation strength of the 66 kV cable to 10 kV/mm.

  19. Universal scaling of dielectric response of various liquid crystals and glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Gałązka, M.; Juszyńska-Gałązka, E.; Osiecka, N.; Bąk, A.

    2016-04-01

    We present a new generalized scaling relationship accounting both for the real and imaginary parts of the complex permittivity data. The generalized scaling procedure has been successfully used for various relaxation processes in liquid crystals (4-bromobenzylidene-4‧-pentyloxyaniline, 4-bromobenzylidene-4‧-hexyloxyaniline, 4‧-butyl-4-(2-methylbutoxy)-azoxybenzene, 4-ethyl-4‧-octylazoxybenzene), and in glass-forming liquids (glycerol, propylene carbonate, salol, cresolphthalein-dimethylether). As it is shown, one obtains common master-curve for liquid-like phases (isotropic liquid, cholesteric, nematic, smectic A), solid-like phases (smectic B, conformationally disorder crystal) and supercooled liquid phase.

  20. Retreating behavior of a charged ionic liquid droplet in a dielectric liquid under electric field

    NASA Astrophysics Data System (ADS)

    Ahn, Myung Mo; Im, Do Jin; Kang, In Seok

    2013-11-01

    Ionic liquids show great promise as excellent solvents or catalysts in energy and biological fields due to their unique chemical and physical properties. The ionic liquid droplets in microfluidic systems can also be used as a potential platform for chemical biological reactions. In order to control electrically the ionic liquid droplets in a microfluidic device, the charging characteristics of ionic liquid droplets need to be understood. In this work, the charging characteristics of various ionic liquids are investigated by using the parallel plate electrodes system. Under normal situation, a charged droplet shows bouncing motion between electrodes continuously. However, for some special ionic liquids, interesting retreating behavior of charged ionic liquid droplet has been observed. This retreating behavior of ionic liquid droplet has been analyzed experimentally by the image analysis and the electrometer signal analysis. Based on the hypothesis of charge leakage of the retreating ionic liquid droplets, FT-IR spectroscopy analysis has also been performed. The retreating behavior of ionic liquid droplet is discussed from the intermolecular point of view according to the species of ionic liquids. This research was supported by grant No. 2013R1A1A2011956 funded by the Ministry of Science, ICT and Future Planning (MSIP) and by grant No. 2013R1A1A2010483 funded by the Ministry of Education, Science and Technology (MEST) through the NRF.

  1. Electro-Thermal Tuning in a Negative Dielectric Cholesteric Liquid Crystal Material

    SciTech Connect

    Natarajan,L.; Wofford, J.; Tondiglia, V.; Sutherland, R.; Koerner, H.; Vaia, R.; Bunning, T.

    2008-01-01

    The thermal and electrical tunability of a cholesteric liquid crystal containing a negative dielectric anisotropy liquid crystal in a planar alignment was studied. The physical, optical, and electro-optical characteristics of mixtures containing different ratios of chiral dopant S811 and the negative dielectric anisotropy liquid crystal ZLI-2806 were examined. A smectic A phase was seen at room temperature for S811 loadings >20 wt%. Below 20%, a room temperature cholesteric phase was observed. Upon heating mixtures with composition S811 >20%, the selective reflection notch of the cholesteric phase appeared and blueshifted with temperature. Thermal tuning from 2300?to?500?nm was observed over the temperature range of 23-55? C. Polarized optical microscopy, differential scanning calorimetry, and x-ray studies were utilized to confirm the temperature-dependent phase behavior. Tuning of ? 50?nm by the application of a direct current electric field was also observed with no onset of electrohydrodynamic instabilities for voltages up to {approx} 300 V. Bandwidth broadening but not tuning was obtained with the application of alternating current fields. Electrical tuning is likely due to pitch contraction brought about through the annealing of defects.

  2. Enhanced optoelastic interaction range in liquid crystals with negative dielectric anisotropy

    NASA Astrophysics Data System (ADS)

    Simoni, F.; Lalli, S.; Lucchetti, L.; Criante, L.; Brasselet, E.

    2014-01-01

    We demonstrate that the long-range interaction between surface-functionalized microparticles immersed a nematic liquid crystal—a "nematic colloid"—and a laser-induced "ghost colloid" can be enhanced by a low-voltage quasistatic electric field when the nematic mesophase has a negative dielectric anisotropy. The optoelastic trapping distance is shown to be enhanced by a factor up to 2.5 in presence of an electric field. Experimental data are quantitatively described with a theoretical model accounting for the spatial overlap between the orientational distortions around the microparticle and those induced by the trapping light beam itself.

  3. Dielectric Response of Glass-Forming Liquids in the Nonlinear Regime

    NASA Astrophysics Data System (ADS)

    Samanta, Subarna

    Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements. The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be 'slaved' to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein beta-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins. The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the

  4. Highly sensitive terahertz dielectric sensor for small-volume liquid samples

    NASA Astrophysics Data System (ADS)

    Soltani, A.; Neshasteh, H.; Mataji-Kojouri, A.; Born, N.; Castro-Camus, E.; Shahabadi, M.; Koch, M.

    2016-05-01

    We present a resonator-based sensor for the measurement of the refractive index of dielectric liquid samples. The proposed sensor operates on the basis of an electromagnetic resonance between a thin metallic grating and a reflecting ground plane. The fluid whose refractive index is to be measured fills the region between the metallic grating and the ground plane and causes a considerable shift in the resonance frequency (>500 GHz/RIU). The sensor has a relatively simple structure; therefore, it can be manufactured economically on industrial scales.

  5. Lattice Boltzmann model for Coulomb-driven flows in dielectric liquids

    NASA Astrophysics Data System (ADS)

    Luo, Kang; Wu, Jian; Yi, Hong-Liang; Tan, He-Ping

    2016-02-01

    In this paper, we developed a unified lattice Boltzmann model (LBM) to simulate electroconvection in a dielectric liquid induced by unipolar charge injection. Instead of solving the complex set of coupled Navier-Stokes equations, the charge conservation equation, and the Poisson equation of electric potential, three consistent lattice Boltzmann equations are formulated. Numerical results are presented for both strong and weak injection regimes, and different scenarios for the onset and evolution of instability, bifurcation, and chaos are tracked. All LBM results are found to be highly consistent with the analytical solutions and other numerical work.

  6. Lattice Boltzmann model for Coulomb-driven flows in dielectric liquids.

    PubMed

    Luo, Kang; Wu, Jian; Yi, Hong-Liang; Tan, He-Ping

    2016-02-01

    In this paper, we developed a unified lattice Boltzmann model (LBM) to simulate electroconvection in a dielectric liquid induced by unipolar charge injection. Instead of solving the complex set of coupled Navier-Stokes equations, the charge conservation equation, and the Poisson equation of electric potential, three consistent lattice Boltzmann equations are formulated. Numerical results are presented for both strong and weak injection regimes, and different scenarios for the onset and evolution of instability, bifurcation, and chaos are tracked. All LBM results are found to be highly consistent with the analytical solutions and other numerical work. PMID:26986441

  7. Enhanced optoelastic interaction range in liquid crystals with negative dielectric anisotropy

    SciTech Connect

    Simoni, F.; Lalli, S.; Lucchetti, L.; Criante, L.

    2014-01-06

    We demonstrate that the long-range interaction between surface-functionalized microparticles immersed a nematic liquid crystal—a “nematic colloid”—and a laser-induced “ghost colloid” can be enhanced by a low-voltage quasistatic electric field when the nematic mesophase has a negative dielectric anisotropy. The optoelastic trapping distance is shown to be enhanced by a factor up to 2.5 in presence of an electric field. Experimental data are quantitatively described with a theoretical model accounting for the spatial overlap between the orientational distortions around the microparticle and those induced by the trapping light beam itself.

  8. Temperature-tunable lasing in negative dielectric chiral nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Wu, Ri-Na; Wu, Jie; Wu, Xiao-Jiao; Dai, Qin

    2015-05-01

    In this work, negative dielectric nematic liquid crystal SLC12V620-400, chiral dopant S811, and laser dye DCM are used to prepare dye-doped chiral nematic liquid crystal laser sample. In order to investigate temperature-tunable lasing in negative dielectric chiral nematic liquid crystal, we measure the transmission and lasing spectrum of this sample. The photonic band gap (PBG) is observed to red shift with its width reducing from 71.2 nm to 40.2 nm, and its short-wavelength band edge moves 55.3 nm while the long-wavelength band edge only moves 24.9 nm. The wavelength of output laser is found to red shift from 614.4 nm at 20 °C to 662.8 nm at 67 °C, which is very different from the previous experimental phenomena. The refractive indices, parallel and perpendicular to the director in chiral nematic liquid crystal have different dependencies on temperature. The experiment shows that the pitch of this chiral nematic liquid crystal increases with the increase of temperature. The decrease in the PBG width, different shifts of band edges, and the red shift of laser wavelength are the results of refractive indices change and pitch thermal elongation. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Outstanding Young Scholars Growth Plans of Colleges and Universities in Liaoning Province, China (Grant No. LJQ2013022), the Science and Technology Research of Liaoning Province, China (Grant No. L2010465), the Open Funds of Liaoning Province Key Laboratory of Laser and Optical Information of Shenyang Ligong University, China.

  9. Vaporization heat transfer of dielectric liquids on enhanced surfaces covered with screen wicks

    NASA Technical Reports Server (NTRS)

    Gu, C. B.; Chow, L. C.; Pais, M. R.; Baker, K.

    1993-01-01

    Experiments were conducted to investigate the vaporization heat transfer characteristics for the dielectric liquid FC-72 on several wicking surfaces which may be used in flat-plate heat pipes. The wicking materials studied included microstructure enhanced surfaces and coarse surfaces covered with screen meshes. Experimental data for q versus deltaT curves and critical heat fluxes were obtained for the two different operating conditions of a heat pipe, evaporation, and shallow pool boiling. When the liquid level was above the heated surface, the height of the liquid level above the surface was varied from 0 to 10 mm. When the liquid level was below the heated surface, the distance from the liquid level to the edge of the surface was adjusted from 0 to 15 mm. Experimental results revealed that for shallow pool boiling when the heated surface was covered with a wire screen mesh, the heat transfer coefficient increased at lower heat fluxes but the critical heat flux (CHF) decreased for all the surfaces tested. In the case of evaporation, both CHF and the heat transfer coefficient increased as the microstructure surfaces were covered with screen meshes.

  10. A new application of the nonlinear dielectric method for studying relaxation processes in liquids

    NASA Astrophysics Data System (ADS)

    Górny, M.; Ziolo, J.; Rzoska, S. J.

    1996-12-01

    The measurement setup for studying changes of electric permittivity induced in liquids by a strong electric field nonlinear dielectric effect, (NDE) is presented. The construction is based on the idea of frequency modulation of an LC generator (with an inductance L and a capacitance C in resonant circuit), proposed by Malecki [J. Chem. Soc. Faraday Trans. II 72, 104 (1976)]. The strong electric field is applied in the form of rectangular pulses (typically 1-4 ms). The setup enables measurements in a broad range of frequencies (80 kHz-12 MHz) and contains a new calibrating system, minimizing the influence of systematic error on the measured NDE values. We also indicate menthol as a standard, reference liquid in NDE studies. New applications of the NDE technique for studying relaxation processes in critical solution are also presented. They are based on the time resolved analysis of NDE decay after switching off the strong electric field.

  11. Experimental setup for simultaneous measurements of neutron diffraction and dielectric spectroscopy during crystallization of liquids

    NASA Astrophysics Data System (ADS)

    Jiménez-Ruiz, M.; Sanz, A.; Nogales, A.; Ezquerra, T. A.

    2005-04-01

    Here we present an experimental setup to obtain information on structural and dynamical changes in liquids during crystallization. This setup consists in a sample cell that allows performing simultaneous measurements of neutron diffraction and dielectric spectroscopy experiments. The capabilities of the technique have been probed by following in real time the crystallization process of a model liquid: the isopropanol. By performing the simultaneous experiment information can be obtained from both phases, amorphous and crystalline, and therefore it can provide a complete description of the changes occurring during a crystallization process. The use of this setup allowed us to demonstrate that a breakage of the hydrogen-bond network is a precursor step for the crystallization of isopropanol.

  12. On two optomechanical effects of laser-induced electrostriction in dielectric liquids

    NASA Astrophysics Data System (ADS)

    Gojani, Ardian B.; Bejtullahu, Rasim; Obayashi, Shigeru

    2014-09-01

    This paper presents electrostriction from the phenomenological perspective, and gives details on two mechanical effects arising from laser-matter interaction. Electrostriction is the tendency of materials to compress in the presence of a varying electric field. In this paper, the investigated materials are polar and nonpolar dielectric liquids. It is stressed that the dominant factor is the time evolution of the laser pulse, which causes tensile stresses and acoustic waves. The study is supported by experimental realization of electrostriction, which can be detected only at favorable conditions (observed in water, but not in castor oil). This study will shed light in developing measurement techniques (e.g., laser-induced grating spectroscopy) and in explaining the onset of cavities and laser-induced liquid breakdown.

  13. Slow dielectric response of Debye-type in water and other hydrogen bonded liquids

    NASA Astrophysics Data System (ADS)

    Jansson, Helén; Bergman, Rikard; Swenson, Jan

    2010-05-01

    The slow dynamics of some hydrogen bonded glass-forming liquids has been investigated by broadband dielectric spectroscopy. We show that the polyalcohols glycerol, xylitol, and sorbitol, and mixtures of glycerol and water, and in fact, even pure water exhibit a process of Debye character at longer time-scales than the glass transition and viscosity related α-relaxation. Even if it is less pronounced, this process displays many similarities to the well-studied Debye-like process in monoalcohols. It can be observed in both the negative derivative of the real part of the permittivity or in the imaginary part of the permittivity, if the conductivity contribution is reduced. In the present study the conductivity contribution has been suppressed by use of a thin Teflon film placed between the sample and one of the electrodes. The new findings might have important implications for the structure and dynamics of hydrogen bonded liquids in general, and for water in particular.

  14. The inactivation of Chlorella spp. with dielectric barrier discharge in gas-liquid mixture

    NASA Astrophysics Data System (ADS)

    Song, Dan; Sun, Bing; Zhu, Xiaomei; Yan, Zhiyu; Liu, Hui; Liu, Yongjun

    2013-03-01

    The inactivation of Chlorella spp. with high voltage and frequency pulsed dielectric barrier discharge in hybrid gas-liquid reactor with a suspension electrode was studied experimentally. In the hybrid gas-liquid reactor, a steel plate was used as high voltage electrode while a quartz plate as a dielectric layer, another steel plate placing in the aqueous solution worked as a whole ground electrode. A suspension electrode is installed near the surface of solution between high voltage and ground electrode to make the dielectric barrier discharge uniform and stable, the discharge gap was between the quartz plate and the surface of the water. The effect of peak voltage, treatment time, the initial concentration of Chlorella spp. and conductivity of solution on the inactivation rate of Chlorella spp. was investigated, and the inactivation mechanism of Chlorella spp. preliminarily was studied. Utilizing this system inactivation of Chlorella spp., the inactivation rate increased with increasing of peak voltage, treatment time and electric conductivity. It was found that the inactivation rate of Chlorella spp. arrived at 100% when the initial concentration was 4 × 106 cells mL-1, and the optimum operation condition required a peak voltage of 20 kV, a treatment time of 10 min and a frequency of 7 kHz. Though the increasing of initial concentration of the Chlorella spp. contributed to the addition of interaction probability between the Chlorella spp. and O3, H2O2, high-energy electrons, UV radiation and other active substances, the total inactivation number raise, but the inactivation rate of the Chlorella spp. decreased.

  15. Microwave dielectric constant of liquid hydrocarbons: Application to the depth estimation of Titan's lakes

    NASA Astrophysics Data System (ADS)

    Paillou, Philippe; Mitchell, Karl; Wall, Stephen; Ruffié, Gilles; Wood, Charles; Lorenz, Ralph; Stofan, Ellen; Lunine, Jonathan; Lopes, Rosaly; Encrenaz, Pierre

    2008-03-01

    Cassini RADAR reveals the surface of Titan since flyby Ta acquired on October 2004. The RADAR instrument discovered volcanic structures, craters, dunes, channels, lakes and seas. In particular, flyby T16 realized in July 2006 imaged tens of radar-dark features close to Titan's north pole. They are interpreted as lakes filled with liquid hydrocarbons - mainly methane, a key material in the geologic and climatic history of Titan. In order to perform quantitative analysis and modeling of the radar response of Titan's lakes, the dielectric constant of liquid hydrocarbons is a crucial parameter, in particular to estimate the radar wave attenuation. We present here first measurements of the dielectric constant of LNG (Liquefied Natural Gas), mainly composed of methane, at Ku-band (10-13 GHz): we obtained a value $\\varepsilon$ = 1.75 - 0.002j. This value is used to model the radar backscattering of lakes observed during T16 flyby. Using a two-layer scattering model, we derive a relationship that is used to estimate a minimum depth for Titan's lakes. The proposed relationship is also coherent with the observation that the larger and then the deeper lakes are also the darker in radar images.

  16. Liquid 1-propanol studied by neutron scattering, near-infrared, and dielectric spectroscopy

    SciTech Connect

    Sillrén, P.; Matic, A.; Karlsson, M.; Koza, M.; Maccarini, M.; Fouquet, P.; Götz, M.; Bauer, Th.; Gulich, R.; Lunkenheimer, P.; Loidl, A.; Mattsson, J.; Gainaru, C.; Vynokur, E.; Schildmann, S.; Bauer, S.; Böhmer, R.

    2014-03-28

    Liquid monohydroxy alcohols exhibit unusual dynamics related to their hydrogen bonding induced structures. The connection between structure and dynamics is studied for liquid 1-propanol using quasi-elastic neutron scattering, combining time-of-flight and neutron spin-echo techniques, with a focus on the dynamics at length scales corresponding to the main peak and the pre-peak of the structure factor. At the main peak, the structural relaxation times are probed. These correspond well to mechanical relaxation times calculated from literature data. At the pre-peak, corresponding to length scales related to H-bonded structures, the relaxation times are almost an order of magnitude longer. According to previous work [C. Gainaru, R. Meier, S. Schildmann, C. Lederle, W. Hiller, E. Rössler, and R. Böhmer, Phys. Rev. Lett. 105, 258303 (2010)] this time scale difference is connected to the average size of H-bonded clusters. The relation between the relaxation times from neutron scattering and those determined from dielectric spectroscopy is discussed on the basis of broad-band permittivity data of 1-propanol. Moreover, in 1-propanol the dielectric relaxation strength as well as the near-infrared absorbance reveal anomalous behavior below ambient temperature. A corresponding feature could not be found in the polyalcohols propylene glycol and glycerol.

  17. Liquid 1-propanol studied by neutron scattering, near-infrared, and dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Sillrén, P.; Matic, A.; Karlsson, M.; Koza, M.; Maccarini, M.; Fouquet, P.; Götz, M.; Bauer, Th.; Gulich, R.; Lunkenheimer, P.; Loidl, A.; Mattsson, J.; Gainaru, C.; Vynokur, E.; Schildmann, S.; Bauer, S.; Böhmer, R.

    2014-03-01

    Liquid monohydroxy alcohols exhibit unusual dynamics related to their hydrogen bonding induced structures. The connection between structure and dynamics is studied for liquid 1-propanol using quasi-elastic neutron scattering, combining time-of-flight and neutron spin-echo techniques, with a focus on the dynamics at length scales corresponding to the main peak and the pre-peak of the structure factor. At the main peak, the structural relaxation times are probed. These correspond well to mechanical relaxation times calculated from literature data. At the pre-peak, corresponding to length scales related to H-bonded structures, the relaxation times are almost an order of magnitude longer. According to previous work [C. Gainaru, R. Meier, S. Schildmann, C. Lederle, W. Hiller, E. Rössler, and R. Böhmer, Phys. Rev. Lett. 105, 258303 (2010)] this time scale difference is connected to the average size of H-bonded clusters. The relation between the relaxation times from neutron scattering and those determined from dielectric spectroscopy is discussed on the basis of broad-band permittivity data of 1-propanol. Moreover, in 1-propanol the dielectric relaxation strength as well as the near-infrared absorbance reveal anomalous behavior below ambient temperature. A corresponding feature could not be found in the polyalcohols propylene glycol and glycerol.

  18. Electrowetting-on-dielectric assisted bubble detachment in a liquid film

    NASA Astrophysics Data System (ADS)

    Wang, S.; Chen, H. H.; Chen, C. L.

    2016-05-01

    Drawing inspiration from electrowetting-controlled droplets, the potential advantages of electrowetting for bubble dynamics are investigated experimentally. In this study, we present and characterize an open electrowetting-on-dielectric (EWOD) system for studying the bubble behavior. Both detachment and non-detachment processes of a small single bubble in a thick liquid film under EWOD were experimentally observed. The measurement of contact angle changes of the small air bubble shows relatively good agreement with Young-Lippmann's equation within the majority of the test voltage range, except for the saturation region. Meanwhile, we have experimentally demonstrated both the characteristics of single- and double-bubble detachment within a thin liquid film. Direct bubble detachment may occur when it touches the gas-liquid interface during the process of contact angle change, while indirect bubble detachment is highly possible due to the dramatic oscillation resulting from the detachment of adjacent bubbles. The experimental results demonstrate that EWOD can effectively facilitate the detachment of small air bubble in a thin liquid film.

  19. The dielectric behaviour of snow: A study versus liquid water content

    NASA Technical Reports Server (NTRS)

    Ambach, W.; Denoth, A.

    1980-01-01

    Snow is treated as a heterogeneous dielectric material consisting of ice, air, and water. The greater difference in the high frequency relative permittivity of dry snow and water allows to determine the liquid water content by measurements of the relative permittivity of snow. A plate condenser with a volume of about 1000 cv cm was used to measure the average liquid water content in a snow volume. Calibration was carried out using a freezing calorimeter. In order to measure the liquid water content in thin snow layers, a comb-shaped condenser was developed, which is the two dimensional analogon of the plate condenser. With this moisture meter the liquid water content was measured in layers of a few millimeters in thickness, whereby the effective depth of measurement is given by the penetration depth of electric field lines which is controlled by the spacing of the strip lines. Results of field measurements with both moisture meters, the plate condenser and the comb-shaped condenser, are given.

  20. Liquid Argon Dielectric Breakdown Studies with the MicroBooNE Purification System

    SciTech Connect

    Acciarri, R.; Carls, B.; James, C.; Johnson, B.; Jostlein, H.; Lockwitz, S.; Lundberg, B.; Raaf, J. L.; Rameika, R.; Rebel, B.; Zeller, G. P.; Zuckerbrot, M.

    2014-11-04

    The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-per-trillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.

  1. Investigations into modeling and further estimation of detection limits of the liquid electrode dielectric barrier discharge.

    PubMed

    Krähling, Tobias; Michels, Antje; Geisler, Sebastian; Florek, Stefan; Franzke, Joachim

    2014-06-17

    The liquid electrode dielectric barrier discharge (LE-DBD) is a miniaturized atmospheric pressure plasma as emission excitation source for elemental determination with pulsed behavior. Metals dissolved in liquids are detectable in flow systems with low flow rates of 20 μL min(-1) by means of optical emission spectrometry using a simple portable spectrometer. Time-resolved determination of the hydrogen excitation temperature Tαβ indicates that the LE-DBD does not reach a stable state during a burning phase, whereat the maximum and minimum Tαβ is independent of the flow rate. Adding dissolved metals to the liquid electrode does not influence the minimum Tαβ at the end of a burning phase. With the help of measured doubly charged lanthanum lines and spatially resolved measurements, the mechanism of the liquid transfer into the plasma will be clarified. Emissions from metal oxides indicate a thermal evaporation transfer mechanism, but only an additional electrospray-like transfer mechanism can explain the observed La III emissions and nonhomogeneous spatial distribution of exited species. The reaction pathways for electrosprayed hydrated metal ions are discussed for triply and doubly charged ions. The analytical performance is evaluated for 23 elements from the categories of alkali, alkaline earth, transition, and poor metals. The achieved detection limits are between 0.016 mg L(-1) for Li and 41 mg L(-1) for Bi. PMID:24831065

  2. Molecular dynamics of a binary mixture of twist-bend nematic liquid crystal dimers studied by dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Robles-Hernández, Beatriz; Sebastián, Nerea; Salud, Josep; Diez-Berart, Sergio; Dunmur, David A.; Luckhurst, Geoffrey R.; López, David O.; de la Fuente, M. Rosario

    2016-06-01

    We report a comprehensive dielectric characterization of a liquid crystalline binary mixture composed of the symmetric mesogenic dimer CB7CB and the nonsymmetric mesogenic dimer FFO9OCB. In addition to the high-temperature nematic phase, such a binary mixture shows a twist-bend nematic phase at room temperature which readily vitrifies on slow cooling. Changes in the conformational distribution of the dimers are reflected in the dielectric permittivity and successfully analyzed by means of an appropriate theoretical model. It is shown that the dielectric spectra of the mixture reflect the different molecular dipole properties of the components, resembling in the present case the characteristic dielectric spectra of nonsymmetric dimers. Comparison of the nematic and twist-bend nematic phases reveals that molecular dynamics are similar despite the difference in the molecular environment.

  3. Dielectric relaxations of polyether-based polyurethanes containing ionic liquids as antistatic agents.

    PubMed

    Tsurumaki, Akiko; Bertasi, Federico; Vezzù, Keti; Negro, Enrico; Di Noto, Vito; Ohno, Hiroyuki

    2016-01-28

    Dielectric properties of polyurethanes containing poly(propylene oxide) (PO) and poly(ethylene oxide) (EO) units are discussed, along with the results of direct current (DC) measurements and broadband electrical spectroscopy (BES) studies. The dielectric properties of polyether-containing polyurethanes (PUs) are compared to those of PUs containing 1000 ppm of ionic liquids (ILs) as antistatic agents. The effects of the chemical environment of these ILs, including anion-fixed polymers (PU-AF), cation-fixed polymers (PU-CF), and a simple mixture of IL with the PUs (PU-IL), are compared and discussed on the basis of ion mobility. DC measurements suggest that the charge current is attributed not only to the electrode polarization but also to continuous dielectric relaxation. BES studies elucidate that both fast and slow relaxations are taking place in EO-rich domains in pristine PU and PU-AF. The activation energies of the slow relaxation and of the ionic conductivity are similar, suggesting that the ionic conductivity of these materials is attributed to the ion exchange reaction in EO/ion complexes. In contrast, only fast relaxations are observed in the domains mostly comprised of ion-depleted EO in the PUs containing "free" anions, i.e., PU-CF and PU-IL. This suggests that [Tf2N](-) ligands are weakly interacting with the EO chains and contribute effectively to the ion conduction. Thus, enhanced ionic conductivity is observed in PU-CF and PU-IL, yielding sufficient antistatic effects. Taking into account its long shelf life, arising from the lack of IL bleed-out, PU-CF is concluded to be the most promising candidate. PMID:26700822

  4. Dielectric and electro-optical studies of a nickel-ferrite-nanoparticle- doped ferroelectric liquid crystal mixture

    NASA Astrophysics Data System (ADS)

    Khushboo; Sharma, Puneet; Malik, Praveen; Raina, K. K.

    2016-02-01

    Effect of magnetic nanoparticles (nickel ferrite) doping on the dielectric and electro-optical properties of a ferroelectric liquid crystal mixture has been studied. In a doped ferroelectric liquid crystal mixture, dispersion of a small amount (0.25 wt.%) of nickel ferrite nanoparticles decreases the polarization and improves the response time compared to an undoped mixture. The significant changes in the polarization and response time are explained on the basis of dipole-dipole interaction and anchoring phenomena. Dielectric permittivity also increases with increasing the temperature of the SmC* phase and shows a reduction in dielectric loss in a doped sample. A Goldstone mode is clearly observed at ∼200 and ∼500 Hz in an undoped and a doped sample, respectively.

  5. Effect of boundary surfaces on the effective dielectric susceptibility of the helical structure of a ferroelectric liquid crystal

    SciTech Connect

    Kaznacheev, A. V.; Pozhidaev, E. P.

    2015-08-15

    We present the results of a theoretical investigation of the effect of boundary surfaces of a liquidcrystal cell on the effective dielectric susceptibility of the helical structure of a ferroelectric smectic C* liquid crystal (FLC). We consider for this purpose the deformation and untwisting of the helix by solid surfaces bounding the FLC layer. An analytic expression is obtained for critical thickness d{sub c} of the liquid-crystal layer, for which untwisting of the helix by surfaces takes place. In calculating the effective dielectric susceptibility, it is shown that the deformation of the FLC helix by the boundaries leads to the occurrence of anisotropy in the effective dielectric susceptibility in the plane perpendicular to the helix axis.

  6. Dielectric response of imidazolium-based room-temperature ionic liquids.

    PubMed

    Daguenet, Corinne; Dyson, Paul J; Krossing, Ingo; Oleinikova, Alla; Slattery, John; Wakai, Chihiro; Weingärtner, Hermann

    2006-06-29

    We have used microwave dielectric relaxation spectroscopy to study the picosecond dynamics of five low-viscosity, highly conductive room temperature ionic liquids based on 1-alkyl-3-methylimidazolium cations paired with the bis((trifluoromethyl)sulfonyl)imide anion. Up to 20 GHz the dielectric response is bimodal. The longest relaxation component at the time scale of several 100 ps reveals strongly nonexponential dynamics and correlates with the viscosity in a manner consistent with hydrodynamic predictions for the diffusive reorientation of dipolar ions. Methyl substitution at the C2 position destroys this correlation. The time constants of the weak second process at the 20 ps time scale are practically the same for each salt. This intermediate process seems to correlate with similar modes in optical Kerr effect spectra, but its physical origin is unclear. The missing high-frequency portion of the spectra indicates relaxation beyond the upper cutoff frequency of 20 GHz, presumably due to subpicosecond translational and librational displacements of ions in the cage of their counterions. There is no evidence for orientational relaxation of long-lived ion pairs. PMID:16800602

  7. Dielectric and electro-optic measurements of nematic liquid crystals doped with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Peterson, Matthew; Georgiev, Georgi; Atherton, Timothy; Cebe, Peggy

    We studied the effects of carbon nanotubes (CNTs) on the dielectric and electro-optic properties of nematic 5CB liquid crystals (LCs). Samples containing 0.01%, 0.10% and 1.00% CNTs by weight were prepared. Anti- parallel rubbed cells with a nominal thickness of 10 μm were prepared using indium tin oxide coated glass cells and a polyimide alignment layer. The capacitance and dissipation factor were measured using an Agilent 4284A precision LCR meter. From these measurements, the complex dielectric permittivity was determined as a function of frequency. Analysis of the low frequency regime (f <1000 Hz) indicates that 5CB samples containing CNTs have a higher conductance than neat samples. The Fréedericksz transition critical voltage was noted by a sharp increase in capacitance after an initial plateau. Numerical simulations of CNT-facilitated switching show that polarization induced on the nanotubes from capacitive effects can significantly reduce the critical voltage in DC electric fields, in agreement with experimental results. Measurements of the critical voltage over a range of frequencies will also be presented. Research was supported by the National Science Foundation, DMR1206010.

  8. Unsaturated and Saturated Flow Front Tracking in Liquid Composite Molding Processes using Dielectric Sensors

    NASA Astrophysics Data System (ADS)

    Carlone, P.; Palazzo, G. S.

    2015-10-01

    Liquid composite molding processes are manufacturing techniques involving the impregnation and saturation of dry fibrous preforms by means of injection or infusion of catalyzed resin systems. Complete wetting of the reinforcement and reduction of voids are key issues to enhance mechanical properties of the final product, as a consequence on line monitoring and control of resin flow is highly desirable to detect and avoid potentialbet macro- as well as micro-voids. In this paper, parallel-plate dielectric sensors were investigated to track the position of unsaturated as well as saturated flow fronts through dual scale porous media. Sensors configuration was analyzed and improved via electromagnetic (EM) finite element simulations. The effectiveness of the proposed system was assessed in one-dimensional impregnation tests. Good agreement was found between unsaturated front positions provided by the considered system and acquired through conventional visual techniques. An indirect verification strategy, based on CFD and EM simulations of the process, was applied to investigate the reliability of dielectric sensors with respect to saturation phenomena. Obtained outcomes highlighted the intriguing capabilities of the proposed method.

  9. Anisotropic instability of a dielectric liquid in a strong uniform electric field: Decay into a two-phase system of vapor filaments in a liquid.

    PubMed

    Kupershtokh, Alexander L; Medvedev, Dmitry A

    2006-08-01

    The linear stability analysis of dielectric liquid placed in uniform electric field with respect to perturbations of density of an initially uniform state was carried out. The electric field increases the instability increment for the stratification along the field and decreases it for the transversal stratification. Thus, anisotropic separation into liquid and vapor phases is possible in high electric fields for a liquid that is initially in unstable state, as well as in metastable or stable states. Computer simulations of electrohydrodynamics confirm the theoretical calculations. It is important that new regions of low density phase appear as narrow cylindrical channels oriented along the field. This mechanism of generation of gaseous phase in locally high electric field can play a key role in processes of inception and ultrafast propagation of streamers during breakdown of liquid dielectrics in nanosecond range. PMID:17025435

  10. Effect of cadmium selenide quantum dots on the dielectric and physical parameters of ferroelectric liquid crystal

    SciTech Connect

    Singh, D. P.; Gupta, S. K.; Manohar, R.; Varia, M. C.; Kumar, S.; Kumar, A.

    2014-07-21

    The effect of cadmium selenide quantum dots (CdSe QDs) on the dielectric relaxation and material constants of a ferroelectric liquid crystal (FLC) has been investigated. Along with the characteristic Goldstone mode, a new relaxation mode has been induced in the FLC material due to the presence of CdSe QDs. This new relaxation mode is strongly dependent on the concentration of CdSe QDs but is found to be independent of the external bias voltage and temperature. The material constants have also been modified remarkably due to the presence of CdSe QDs. The appearance of this new relaxation phenomenon has been attributed to the concentration dependent interaction between CdSe QDs and FLC molecules.

  11. Sign reversal of dielectric anisotropy of ferroelectric liquid crystals doped with cadmium telluride quantum dots

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Silotia, P.; Biradar, A. M.

    2011-08-01

    A small amount of cadmium telluride quantum dots (CdTe QDs) has been doped into various ferroelectric liquid crystals (FLCs) to observe the modifications in the alignment and dielectric anisotropy (Δɛ) of the composites. The CdTe QDs have induced a uniform homeotropic (HMT) alignment in most of the FLC mixtures. We observed an unexpected switching (from HMT to homogeneous configuration) of CdTe QDs doped FLC CS1026 (having positive Δɛ) by the application of high dc bias. This reverse switching has been attributed to the interaction between FLC molecules and CdTe QDs which caused the sign reversal of Δɛ of FLC CS1026.

  12. Static dielectric function with exact exchange contribution in the electron liquid

    SciTech Connect

    Qian, Zhixin

    2015-11-15

    The exchange contribution, Π{sub 1}(k, 0), to the static dielectric function in the electron liquid is evaluated exactly. Expression for it is derived analytically in terms of one quadrature. The expression, as presented in Eq. (3) in the Introduction, turns out to be very simple. A fully explicit expression (with no more integral in it) for Π{sub 1}(k, 0) is further developed in terms of series. Equation (3) is proved to be equal to the expression obtained before under some mathematical assumption by Engel and Vosko [Phys. Rev. B 42, 4940 (1990)], thus in the meanwhile putting the latter on a rigorous basis. The expansions of Π{sub 1}(k, 0) at the wavevectors of k = 0, k = 2k{sub F}, and at limiting large k are derived. The results all verify those obtained by Engel and Vosko.

  13. Confined liquid crystaline 5CB in 2D Thermodynamic Space - Preliminary Dielectric Relaxation Study

    NASA Astrophysics Data System (ADS)

    Pawlus, S.; Osinska, J.; Rzoska, S. J.; Kralj, S.; Cordoyiannis, G.

    Results of preliminary broadband dielectric spectroscopy studies in a wide range of temperatures and pressures range for a mixture of rod-like liquid crystalline 4-cyano-4-pentylalkylbiphenyl (5CB) and hydrophilic silica spheres (Aerosil 300) are shown. Pretransitional anomaly, observed previously in the bulk 5CB, has been found. Temperature dynamics of the mixture was investigated with via the DC conductivity σ, coupled to the reorientational relaxation. The derivative based analysis of electric conductivity showed a clear non-Arrhenius dynamics and indicated the anomalous increase of the fragility strength coefficient on approaching the isotropic-nematic transition. Pressure investigations of the solidification from the nematic phase showed the increase of the transition temperature on pressuring but with unusual increasing of dT NS /dP coefficient.

  14. The role of temperature on dielectric relaxation and conductivity mechanism of dark conglomerate liquid crystal phase

    NASA Astrophysics Data System (ADS)

    Yildiz, Alptekin; Canli, Nimet Yilmaz; Özdemir, Zeynep Güven; Ocak, Hale; Eran, Belkız Bilgin; Okutan, Mustafa

    2016-03-01

    In this study, dielectric properties and ac conductivity mechanism of the bent-core liquid crystal 3‧-{4-[4-(3,7-Dimethyloctyloxy)benzoyloxy]benzoyloxy}-4-{4-[4-[6-(1,1,3,3,5,5,5-heptamethyltrisiloxan-1yl)hex-1-yloxy]benzoyloxy]benzoyloxy}biphenyl (DBB) have been analyzed by impedance spectroscopy measurements at different temperatures. According to the polarizing microscopy results, DBB liquid crystal compound exhibits a dark conglomerate mesophase (DC[*] phase) which can be identified by the occurrence of a conglomerate of domains with opposite chirality. The chiral domains of this low-birefringent mesophase become more visible by rotating the polarizer. The variation of the real (ε‧) and imaginary (ε″) parts of dielectric constant with angular frequency and Cole-Cole curves of DBB have been analyzed. The fitting results for dispersion curves at different temperatures revealed that DBB system exhibits nearly Debye-type relaxation except for 125 °C. Moreover, it has been determined that while the relaxation frequencies shift to higher frequencies as the temperature increases from 25 °C to 125 °C, the peak intensities remarkably decrease with increasing temperature. According to Cole-Cole plot and phase angle versus frequency curve, it has been determined that DBB LC may have a possibility of utilizing as a super-capacitor at room temperature. Furthermore, it has been found that the conductivity mechanism of the DBB alters from Correlated Barrier Hoping (CBH) model to Quantum Tunneling Model (QMT) with in increasing temperature at high frequency region. In terms of CBH model, optical band gaps at 25 °C and 75 °C temperatures have also been calculated. Finally, activation energies for some selected angular frequencies have also been calculated.

  15. Nanosecond electro-optics of a nematic liquid crystal with negative dielectric anisotropy.

    PubMed

    Borshch, Volodymyr; Shiyanovskii, Sergij V; Li, Bing-Xiang; Lavrentovich, Oleg D

    2014-12-01

    We study a nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N ̂). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to N ̂. The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (nanosecond) changes in optical characteristics, such as birefringence. PMID:25615116

  16. Linear and non-linear dielectric properties of a short-pitch ferroelectric liquid crystal stabilized by a polymer network.

    PubMed

    Cherfi, Y; Hemine, J; Douali, R; Beldjoudi, N; Ismaili, M; Leblond, J M; Legrand, C; Daoudi, A

    2010-12-01

    Linear and non-linear dielectric measurements were carried out on a ferroelectric liquid crystal stabilized by an anisotropic polymer network. The polymerization process was achieved at room temperature. It was performed from an achiral monomer in the ferroelectric chiral smectic C phase, exhibiting a very short helical pitch and a large polarization. The linear and non-linear dielectric spectroscopy were also completed by textural morphology as well as structural and ferroelectric characterizations. All these measurements were carried out on a pure ferroelectric liquid crystal material and on composite films containing two polymer concentrations. The increase of the polymer network density leads to a decrease of the dielectric strength determined in the linear and non-linear dielectric spectroscopy. The complementarity between the linear and non-linear dielectric measurements and their confrontation with a theoretical model allowed the simultaneous determination of some physical parameters such as macroscopic polarization, rotational viscosity and twist elastic energy. We also discuss the effect of the polymer network density on the obtained physical parameters. PMID:21107879

  17. Dielectric spectroscopy of a polymerizing liquid and the evolution of molecular dynamics with increase in the number of covalent bonds

    NASA Astrophysics Data System (ADS)

    Parthun, M. G.; Johari, G. P.

    1995-07-01

    Dielectric spectroscopy and calorimetry studies of a low viscosity, initially monomeric liquid undergoing spontaneous chemical reaction, to form a linear chain polymer while maintaining isothermal conditions, have been used to determine how the number of covalent bonds formed during the growth of a linear chain affects the dielectric permittivity, relaxation time, and the spectral shape. During this reaction, the static permittivity decreased and the relaxation time increased towards limiting values. As the number of covalent bonds increased towards the Avogadro number, the change in the complex permittivity as measured for a fixed frequency was phenomenologically similar to that observed on varying the frequency, although the exact formalisms in both cases differed. In both cases the relaxation function could be well described by a stretched exponential or sum of exponentials, with a width that decreased as the liquid's state changed from monomeric liquid to a fully reacted chain polymer. The observed increase in the relaxation time with the number of bonds formed seems consistent with the decrease in the configurational entropy or the number of accessible configurations available to the structure, under isothermal conditions. It decreases progressively more slowly as the number of covalent bonds in the structure increases. As this occurs, a second relaxation process at higher frequencies is revealed. The dielectric manifestation of the irreversible process of covalent bond formation is remarkably similar to that observed on supercooling a molecular or polymeric liquid. The study demonstrates how negative feedback between molecular diffusion and chemical reaction vitrifies a liquid isothermally.

  18. Pool boiling of dielectric liquids on porous graphite and extended copper surfaces

    NASA Astrophysics Data System (ADS)

    Parker, Jack L.

    This work investigated pool boiling of the dielectric liquids HFE-7100 and FC-72 on plane copper and porous graphite and on copper surfaces with corner pins. The work investigated the effects of surface orientation and liquid subcooling and, for the copper surfaces with corner pins, the effect of surface roughness. In addition, investigations were made studying the heat transfer by natural convection and nucleate boiling, as well as the effects of liquid subcooling (up to 30 K) and surface inclination (0°--upward facing, to 180°--downward facing) on nucleate boiling heat transfer and Critical Heat Flux (CHF). The results are applicable to direct immersion cooling by nucleate boiling of high power computer chips dissipating 50 - 100 W/cm2 while maintaining the junction temperature for the chips below the recommended values (˜85 °C). Pool boiling experiments are performed with degassed HFE-7100 and FC-72 liquids using uniformly heated 10 x 10 mm porous graphite and copper surfaces with corner pins. The measured footprint temperatures and thermal power removed from the surfaces are used to construct the pool boiling curves and determine the critical heat flux and corresponding surface superheat. Results are compared with those obtained on plane copper of same heated footprint area. The obtained CHF values are also compared with those reported in the open literature for plane, micro-porous, and macro-structured surfaces. Digital photographs and video are obtained to help explain and interpret the results. For the first time, natural convection correlations for dielectric liquids on plane, porous, and copper with corner pins developed. These correlations are important to electronic cooling in the stand-by mode when the heat dissipation by the chips is only a few watts. Results show that the power removed by natural convection from surfaces with corner pins is 67% more than from plane Si and Cu surfaces at the same surface superheat. Using porous graphite and copper

  19. Electro-optical and dielectric properties of CdSe quantum dots and 6CHBT liquid crystals composites

    SciTech Connect

    Singh, U. B.; Pandey, M. B.; Dhar, R; Pandey, A. S.; Kumar, S.; Dabrowski, R.

    2014-11-15

    We have prepared the composites of a room temperature nematic liquid crystal namely 4-(trans-4-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) and Cadmium Selenide Quantum Dots (CdSe-QDs) and investigated their electro-optical and dielectric properties. Effect of dispersion of CdSe-QDs on various electro-optical and display parameters of host liquid crystalline material have been studied. Physical parameters, such as switching threshold voltage and splay elastic constant have been altered drastically for composites. Dispersion of QDs in a liquid crystals medium destabilizes nematic ordering of the host and decreases the nematic-to-isotropic transition temperature.

  20. Charge and energy transferred from a plasma jet to liquid and dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Mussard, M. Dang Van Sung; Foucher, E.; Rousseau, A.

    2015-10-01

    A key parameter in using plasma jets for biomedical applications is the transferred energy to the living tissues. The objective of this paper is to understand which parameters control the energy transfer from the plasma jet to a liquid or a dielectric surface. The plasma jet is flown with helium and ignited by a 600 Hz ac high voltage (up to 15 kV). Capacitors are connected to two measurement electrodes placed in the plasma source region, and under the sample. Charge and energy transferred are estimated by plotting Lissajous cycles; the number of bullets and the charge probability density function are also calculated. It is shown that the applied voltage and the gap (distance between the end of the tube and the sample) have a dramatic influence on the energy deposition on the sample as well as on the charge probability density function. Surprisingly, both gap distance and voltage have very little influence on the number of bullets reaching the sample per cycle. It is also shown that the conductivity of the liquid sample has almost no influence on the energy deposition and charge probability density function.

  1. Dynamics of hydrogen-bonded liquids confined to mesopores: A dielectric and neutron spectroscopy study

    SciTech Connect

    Mel`nichenko, Y.B.; Schueller, J.; Richert, R.; Ewen, B.; Loong, C.

    1995-08-08

    In this paper we present and discuss experimental results on molecular mobility in propylene glycol and its three oligomers confined to the {similar_to}100 A pores of a controlled porous glass. The objective is to elucidate the finite size effects on the dynamics of hydrogen-bonded liquids of different molecular weights but identical chemical composition. The methods of dielectric and neutron spectroscopy have been employed to investigate both the low- and high-frequency features as a function of temperature. We find that all fluids in pores separate into two distinct liquid phases. (i) molecules physisorbed at the surface which exhibit a dramatic frustration of their mobility related to a substantial {ital positive} shift of the glass transition temperature {ital T}{sub {ital g}} by up to {Delta}{ital T}{sub {ital g}}{approx}+47 K; and (ii) relatively ``free`` molecules in the inner pore space subject to only moderate retardation of the {alpha} and normal mode relaxation and substantial broadening of the distribution of relaxation times. The shift in {ital T}{sub {ital g}} for the {alpha} process with {Delta}{ital T}{sub {ital g}}{approx}+5 K is maximal for the monomer liquid and gradually diminishes with increasing molecular weight or decreasing intermolecular hydrogen bonding. The inelastic neutron spectrum of confined propylene glycol shows the boson peak as expected in bulk strong and intermediate glass formers in the vicinity of {ital T}{sub {ital g}}. This effect can be attributed to the finite-size induced crossover from long wave vibrations characteristic of a continuous medium to localized vibrations in a confined geometry. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  2. Dielectric properties of liquid-crystal azomethine polymer with a side alkyl-substituted chain, doped with fullerene C60

    NASA Astrophysics Data System (ADS)

    Kovalev, D. S.; Kostromin, S. V.; Musteaţa, V.; Cozan, V.; Bronnikov, S. V.

    2016-04-01

    We studied the actual and imaginary components of the dielectric constant of liquid-crystal azomethine polymer with a side chain, doped with 0.5 wt % of fullerene C60, over a wide range of temperatures and frequencies; measurements were made by means of dielectric spectroscopy. By analyzing the frequency dependence of the dielectric constant, we detected the relaxation processes (α, β1, and β2) in the nanocomposite, corresponding to certain modes of molecular motion and described them by the Arrhenius equations (β1- and β2-processes) and the Vogel-Fulcher-Tamman equation (α-process). An antiplasticization effect is discovered after doping the polymer with fullerene C60, which manifests itself in increasing the glass transition temperature of the nanocomposite compared to this parameter typical of pure polymer.

  3. Dielectric constant and low-frequency infrared spectra for liquid water and ice Ih within the E3B model

    SciTech Connect

    Shi, L.; Ni, Y.; Drews, S. E. P.; Skinner, J. L.

    2014-08-28

    Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm{sup −1} in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecular interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.

  4. Optically switchable multi-stopband of non-quarter-wavelength dielectric multilayer using azobenzene polymer liquid crystal

    NASA Astrophysics Data System (ADS)

    Ozaki, Ryotaro; Kadowaki, Kazunori; Hagio, Takashi; Yagi, Ryohei; Kuwahara, Yutaka; Kurihara, Seiji

    2015-09-01

    Non-quarter-wave stacked dielectric multilayers including azobenzene polymer liquid crystal layers are investigated in this study. The azobenzene polymer liquid crystal has a photoinduced reversible refractive index based on photoisomerization. By using the reversible refractive-index change, the reflectance of a stopband can be controlled. In this system, the azobenzene molecules change their conformation when they are irradiated with ultraviolet (UV) or visible light. In general, stacking many layers of different thicknesses can produce broadband or multicolor reflections for a dielectric multilayer. However, in a multilayer having thick azobenzene layers, UV or visible light used for controlling photoisomerization hardly reaches the bottom part of the multilayer because the light is mainly absorbed at its top surface. To solve this problem, the dependence on the thickness ratio of the multilayer is investigated and a non-quarter-wave stacked multilayer having RGB reflections is experimentally demonstrated using thin azobenzene layers.

  5. The order parameter model of liquids and glasses with applications to dielectric relaxation

    NASA Astrophysics Data System (ADS)

    Lesikar, Arnold V.; Moynihan, Cornelius T.

    1980-08-01

    The order parameter model is generalized to describe systems whose equilibrium states depend on other intensive variables, e.g., electric field E, in addition to temperature T and pressure P. The set of order parameters required to specify the state of a liquid or glass is shown to form an abstract Euclidean vector space in the vicinity of a particular equilibrium state. The results of relaxational experiments are then connected with geometric relations in this space of order parameters. Thermodynamic stability requires that certain angles in this space have real values. This leads to thermodynamic stability conditions (TSC's), which include the well known Prigogine-Defay condition for systems with intensive variables T and P and analogs of it for systems with other sets of intensive variables. The order parameter model is applied to dielectric relaxation, and its predictions are tested against available data. It is shown that the addition of E as an intensive variable requires at least one more order parameter to specify the state of the system than the number needed when T and P are the only intensive variables.

  6. Tunable and ultra-elongated photonic nanojet generated by a liquid-immersed core-shell dielectric microsphere

    NASA Astrophysics Data System (ADS)

    Wu, Pinghui; Li, Jia; Wei, Kaihua; Yue, Wenjie

    2015-11-01

    A three-dimensional (3D) photonic nanojet (PNJ) emerging from a liquid-immersed core-shell dielectric microsphere is numerically investigated by the finite-difference time-domain (FDTD) method. An ultra-elongated PNJ with an effective length larger than 57 wavelengths while retaining a high intensity and a large working distance is obtained from the simulation. In particular, PNJ properties, including intensity enhancement, working distance, effective length, and full width at half maximum (FWHM), can be well tuned and controlled by varying the refractive index of the immersed liquid. We believe that this design is applicable to many fields, such as material science, nanophotonics, and biomedicine.

  7. Dynamics of glass-forming liquids. XX. Third harmonic experiments of non-linear dielectric effects versus a phenomenological model

    NASA Astrophysics Data System (ADS)

    Kim, Pyeongeun; Young-Gonzales, Amanda R.; Richert, Ranko

    2016-08-01

    We have re-measured the third harmonic non-linear dielectric response of supercooled glycerol using zero-bias sinusoidal electric fields, with the aim of comparing the resulting susceptibilities with a phenomenological model of non-linear dielectric responses. In the absence of known chemical effects in this liquid, the present model accounts for three sources of non-linear behavior: dielectric saturation, field induced entropy reduction, and energy absorption from the time dependent field. Using parameters obtained from static high field results, the present model reproduces the characteristic features observed in the third harmonic susceptibility spectra: a low frequency plateau originating from dielectric saturation and a peak positioned below the loss peak frequency whose amplitude increases with decreasing temperature. Semi-quantitative agreement is achieved between experiment and the present model, which does not involve spatial scales or dynamical correlations explicitly. By calculating the three contributions separately, the model reveals that the entropy effect is the main source of the "hump" feature of this third harmonic response.

  8. Dielectric spectroscopy study on ionic liquid microemulsion composed of water, TX-100, and BmimPF6

    NASA Astrophysics Data System (ADS)

    Chen, Zhen; Nozaki, Ryusuke

    2012-06-01

    We report here a broadband dielectric spectroscopy study on an ionic liquid microemulsion (ILM) composed of water, Triton X-100 (TX-100), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6). It is found that the phase behavior of this ILM can be easily identified by its dielectric response. The dielectric behavior of the ILM in the GHz range is consistent with that of TX-100/water mixtures with comparable water-to-TX-100 weight ratio. It consists of the relaxations due to ethylene oxide (EO) unit relaxation, hydration water dynamics, and/or free water dynamics. The water content dependence of the EO unit relaxation suggests that this relaxation involves dynamics of hydration water molecules. In the IL-in-water microemulsion phase, it is found that bmimPF6 molecules are preferentially dissolved in water when their concentration in water is lower than the solubility. An additional dielectric relaxation that is absent in the TX-100/water mixtures is observed in the frequency range of 107-108 Hz for this ILM. This low-frequency relaxation is found closely related to the bmimPF6 molecule and could be attributed to the hopping of its cations/anions between the anionic/cationic sites.

  9. Dielectric spectroscopy study on ionic liquid microemulsion composed of water, TX-100, and BmimPF6.

    PubMed

    Chen, Zhen; Nozaki, Ryusuke

    2012-06-28

    We report here a broadband dielectric spectroscopy study on an ionic liquid microemulsion (ILM) composed of water, Triton X-100 (TX-100), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)). It is found that the phase behavior of this ILM can be easily identified by its dielectric response. The dielectric behavior of the ILM in the GHz range is consistent with that of TX-100∕water mixtures with comparable water-to-TX-100 weight ratio. It consists of the relaxations due to ethylene oxide (EO) unit relaxation, hydration water dynamics, and∕or free water dynamics. The water content dependence of the EO unit relaxation suggests that this relaxation involves dynamics of hydration water molecules. In the IL-in-water microemulsion phase, it is found that bmimPF(6) molecules are preferentially dissolved in water when their concentration in water is lower than the solubility. An additional dielectric relaxation that is absent in the TX-100∕water mixtures is observed in the frequency range of 10(7)-10(8) Hz for this ILM. This low-frequency relaxation is found closely related to the bmimPF(6) molecule and could be attributed to the hopping of its cations∕anions between the anionic∕cationic sites. PMID:22755585

  10. Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes

    SciTech Connect

    Wissman, J.; Finkenauer, L.; Deseri, L.; Majidi, C.

    2014-10-14

    We introduce a dielectric elastomer actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K<0). Applying voltage Φ to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ϑ. Treating the elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of Φ. Based on this theory, we predict a dependency of ϑ on Φ that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.

  11. Structure of salts solution in polar dielectric liquids and electrically induced separation of solvated ions

    NASA Astrophysics Data System (ADS)

    Shamanin, Igor V.; Kazaryan, Mishik A.; Sachkov, Victor I.

    2015-12-01

    The aim of study is to demonstrate that separation of solvated ions in solution of mix of salts under the action of external periodic electric field happens because of around ions there are formed clusters consisting of molecules of solvent and the sizes of such clusters have dimensions ~ 0.1 μm. In investigations the sizes of clusters theoretically were defined and experimentally value of frequency of external electric field which action excites the effect of separation of the solvated ions was defined. Experiments were done in the Technical Physics Chair of the National Research Tomsk Polytechnic University. At theoretical determination of the dimensions of clusters Poisson's equation was solved and was considered that polar molecules of solvent are oriented under the action of electric field of an ion. The chemical composition of samples of solutions was determined by means of the spectrophotometry and he X-ray excited fluorescent radiation analysis method. Theoretical estimates and results of experiments confirmed the assumption that clusters which are formed around ions in solutions have the dimensions ~ 0.1 μm. Results of investigation testify that placing of volume distributed electric charge of ion in dielectric liquid is accompanied by formation of the supramolecular particles, which we called "clusters", linear sizes of which is significantly more than first and second radiuses of solvation (~ 1 Angstrom) and reach size ~ 0.1 μm. At such sizes inertial properties of clusters and their natural frequencies give the chance to operate their movement by means of action of external electric field on solution.

  12. Photophoretic assembly and migration of dielectric particles and Escherichia coli in liquids using a subwavelength diameter optical fiber.

    PubMed

    Lei, Hongxiang; Zhang, Yao; Li, Xingmin; Li, Baojun

    2011-07-01

    We demonstrate a photophoretic assembly and migration of dielectric (SiO(2) and TiO(2)) particles and bacteria (Escherichia coli) in liquids by using a subwavelength diameter fiber. With a lightwave at 1.55 μm launched into the fiber, the objects are radiated by the leaking light of the fiber to yield negative photophoretic forces which drive the objects to move toward the fiber, with an average assembling/migrating speed of 5-15 individuals per second (ind/s). The influences of laser-on duration, optical power, and size of particles on the photophoretic velocities are also investigated. PMID:21552637

  13. Ultra-compliant liquid metal electrodes with in-plane self-healing capability for dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Gao, Meng; Mei, Shengfu; Han, Yanting; Liu, Jing

    2013-08-01

    The method of directly printing liquid metal films as highly conductive and super compliant electrodes for dielectric elastomer actuator (DEA) was proposed and experimentally demonstrated with working mechanisms interpreted. Such soft electrodes enable DE film to approach its maximum strain and stress at relatively low voltages. Further, its unique capability of achieving two-dimensional in-plane self-healing by merely actuating the DEA was disclosed, which would allow actuators more tolerant to fault and resilient to abusive environments. This high performance actuator has important value in a wide spectrum of situations ranging from artificial muscle, flexible electronics to smart clothing etc.

  14. Dielectric relaxation in ionic liquid/dipolar solvent binary mixtures: A semi-molecular theory

    NASA Astrophysics Data System (ADS)

    Daschakraborty, Snehasis; Biswas, Ranjit

    2016-03-01

    A semi-molecular theory is developed here for studying dielectric relaxation (DR) in binary mixtures of ionic liquids (ILs) with common dipolar solvents. Effects of ion translation on DR time scale, and those of ion rotation on conductivity relaxation time scale are explored. Two different models for the theoretical calculations have been considered: (i) separate medium approach, where molecularities of both the IL and dipolar solvent molecules are retained, and (ii) effective medium approach, where the added dipolar solvent molecules are assumed to combine with the dipolar ions of the IL, producing a fictitious effective medium characterized via effective dipole moment, density, and diameter. Semi-molecular expressions for the diffusive DR times have been derived which incorporates the effects of wavenumber dependent orientational static correlations, ion dynamic structure factors, and ion translation. Subsequently, the theory has been applied to the binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) with water (H2O), and acetonitrile (CH3CN) for which experimental DR data are available. On comparison, predicted DR time scales show close agreement with the measured DR times at low IL mole fractions (xIL). At higher IL concentrations (xIL > 0.05), the theory over-estimates the relaxation times and increasingly deviates from the measurements with xIL, deviation being the maximum for the neat IL by almost two orders of magnitude. The theory predicts negligible contributions to this deviation from the xIL dependent collective orientational static correlations. The drastic difference between DR time scales for IL/solvent mixtures from theory and experiments arises primarily due to the use of the actual molecular volume ( Vmol dip ) for the rotating dipolar moiety in the present theory and suggests that only a fraction of Vmol dip is involved at high xIL. Expectedly, nice agreement between theory and experiments appears when experimental

  15. Coaxial probe and apparatus for measuring the dielectric spectra of high pressure liquids and supercritical fluid mixtures

    NASA Astrophysics Data System (ADS)

    Lee, Sung B.; Smith, Richard L.; Inomata, Hiroshi; Arai, Kunio

    2000-11-01

    A probe and apparatus were developed for measuring the dielectric spectra (complex permittivity) of high pressure liquids and supercritical fluid mixtures. The probe consisted a 2.2 mm semirigid coaxial cable that was cut off flat and mounted into a high pressure tube. The apparatus for measuring complex permittivity consisted of the dielectric probe, cell, densimeter, piston for varying the system density at constant composition, and magnetic pump for agitation and recirculation, all of which were housed in a constant temperature air bath. The probe is simple, robust, inexpensive, and further, its design allows for quick connection to high pressure systems. Probe accuracy is estimated to be ±0.5 in ɛ' and ±0.5 in ɛ″ from 200 MHz to 18 GHz based on replicate measurements of calibration and 2σ deviations over the interval. Dielectric spectra were measured over the 200 MHz-20 GHz range for methanol+carbon dioxide mixture at 323.2 K and a pressures up to 18 MPa.

  16. Dielectric and electro-optic studies of a bimesogenic liquid crystal composed of bent-core and calamitic units.

    PubMed

    Balachandran, R; Panov, V P; Vij, J K; Shanker, G; Tschierske, C; Merkel, K; Kocot, A

    2014-09-01

    A bimesogen, BR1, composed of a bent-core and calamitic unit, linked laterally via a flexible spacer is investigated by dielectric and electro-optic techniques. X-ray results show the presence of clusters in the nematic phase, and the cluster size is of the order of the thickness of a single layer. The splitting of the small-angle scattering Δχ/2 is about 50°, which indicates SmC like clusters with a significant tilt of the molecules in the quasilayers. The sign reversal of the dielectric anisotropy Δε' is observed as a function of frequency; the behavior is rather similar to that exhibited by the conventional dual frequency nematics, composed of a calamitic mesogen, with the exception that it occurs at much lower frequencies in this material. Interestingly, as the bimesogen enters its nematic phase, the average permittivity decreases as the temperature is lowered. This indicates the onset of antiparallel association of some of the dipoles in the system, and this type of association is much more prominent in BR1 in comparison to other bent-core liquid crystalline systems composed of the same bisbenzoate core unit. The analysis of the dielectric spectra using the Maier-Meier model confirms the onset of an antiparallel correlation of dipoles occurring at the isotropic to nematic phase transition temperature. Additionally these results support a model of the cluster where the transverse dipole moments in the neighboring layers are antiparalleled to each other. PMID:25314464

  17. Analysis of a static undulation on the surface of a thin dielectric liquid layer formed by dielectrophoresis forces

    NASA Astrophysics Data System (ADS)

    Brown, Carl V.; McHale, Glen; Mottram, Nigel J.

    2011-07-01

    A layer of insulating liquid of dielectric constant ɛOil and average thickness h- coats a flat surface at y = 0 at which a one-dimensional sinusoidal potential V(x ,0)=VOcos(πx /p) is applied. Dielectrophoresis forces create a static undulation (or "wrinkle") distortion h(x) of period p at the liquid/air interface. Analytical expressions have been derived for the electrostatic energy and the interfacial energy associated with the surface undulation when h(x)=h--(1/2)Acos(2πx /p) yielding a scaling relationship for A as a function of h-, p, VO, ɛOil and the surface tension. The analysis is valid as A/p → 0, and in this limit convergence with numerical simulation of the system is shown.

  18. Dielectric properties measurement method in the microwave frequencies range for non-polar/polar liquid mixtures characterization

    NASA Astrophysics Data System (ADS)

    Surducan, E.; Neamtu, C.; Ienciu, M.; Surducan, V.; Limare, A.; Fourel, L.

    2015-12-01

    We present a method based on dielectric properties measurements over a large spectrum of frequencies, in the microwave (MW) domain, in order to characterize a liquid mixture. The liquid mixtures consist of non-polar fluids (silicone oil, diesel fuel) and polar additives, in order to increase the specific MW absorption of the mixture for further MW power processing. We have measured the MW specific absorptions for mixtures of silicone oil with 20% and 30% (w/w) isopropanol. In both cases, the mixtures are sufficiently stable over time to allow further studies of thermal convection dynamics initiated by MW heating. For a mixture of diesel fuel with 10% (w/w) alkyl polyglycoside, the main observation was that its MW specific absorption varies over time after the mechanical mixing process.

  19. Effect of flip-flop motion on dielectric spectra of highly ordered liquid crystals.

    PubMed

    Osiecka, N; Massalska-Arodź, M; Galewski, Z; Chłędowska, K; Bąk, A

    2015-11-01

    This paper presents studies of dielectric response of chosen Schiff bases, which have similar molecular structures with different isomerizations of an azomethine bridging group, alkyloxy chain length with n=5 or n=6 carbon atoms, and a bromine or chlorine halogen terminal atom. Significant differences in the values of the maximum of dielectric absorption related to flip-flop molecular jumps in hexagonal smectic-B(Cry) phases have been found despite small differences of molecular dipole moments in these substances. This phenomenon is discussed in relation to the possibilities of the creation of dimers and to steric factors favoring motions. PMID:26651713

  20. Effect of flip-flop motion on dielectric spectra of highly ordered liquid crystals

    NASA Astrophysics Data System (ADS)

    Osiecka, N.; Massalska-Arodź, M.; Galewski, Z.; Chłedowska, K.; Bąk, A.

    2015-11-01

    This paper presents studies of dielectric response of chosen Schiff bases, which have similar molecular structures with different isomerizations of an azomethine bridging group, alkyloxy chain length with n =5 or n =6 carbon atoms, and a bromine or chlorine halogen terminal atom. Significant differences in the values of the maximum of dielectric absorption related to flip-flop molecular jumps in hexagonal smectic-BCry phases have been found despite small differences of molecular dipole moments in these substances. This phenomenon is discussed in relation to the possibilities of the creation of dimers and to steric factors favoring motions.

  1. Nonlinear dielectric response at the excess wing of glass-forming liquids.

    PubMed

    Bauer, Th; Lunkenheimer, P; Kastner, S; Loidl, A

    2013-03-01

    We present nonlinear dielectric measurements of glass-forming glycerol and propylene carbonate applying electrical fields up to 671 kV/cm. The measurements extend to sufficiently high frequencies to allow for the investigation of the nonlinear behavior in the regime of the so-far mysterious excess wing, showing up in the loss spectra of many glass formers as a second power law at high frequencies. Surprisingly, we find a complete lack of nonlinear behavior in the excess wing, in marked contrast to the α relaxation where, in agreement with previous reports, a strong increase of dielectric constant and loss is found. PMID:23521298

  2. Dielectric constants of liquid formamide, N-methylformamide and dimethylformamide via molecular Ornstein-Zernike theory

    NASA Astrophysics Data System (ADS)

    Richardi, Johannes; Krienke, Hartmut; Fries, Pascal H.

    1997-07-01

    Kirkwood factors, yielding dielectric constants, are calculated from pair correlation functions, which are numerical solutions of the hypernetted-chain approximation of molecular Ornstein-Zernike (MOZ) theory. The combined influence of the molecular polarizability and the hydrogen bond strength is investigated. Using a reasonable diameter for the hydrogen size in the amide group, the MOZ Kirkwood factors and dielectric constants are in good agreement with the experimental values. This is explained by the statistical correlations between the orientations of two near molecules. This is consistent with hydrogen bonds, forming networks in formamide and chains in N-methylformamide.

  3. Relaxor-like dielectric response of spin liquid CuCrO{sub 2}

    SciTech Connect

    Mazumder, N. Roy, R.; Ghorai, U. K.; Saha, S.; Chattopadhyay, K. K.

    2014-04-24

    Broadband dielectric analysis (10{sup −2}-10{sup 7} Hz) of layered triangular lattice CuCrO{sub 2} is performed (123 K - 473 K) and analyzed in connection with recently observed spin frustration in this multiferroic [M. Poienar et al. Phys. Rev. B 81, 104411, (2010); M. Frontzek et al. Phys. Rev. B 84, 094448, (2011)]. Most unexpectedly, this well known delafossite has found to have nontrivial charge degrees of freedom, being characterized by a relaxor-like dielectric relaxation around 375 K with FWHM of ∼100K. The result strongly suggests the existence of intermolecular Coulomb interaction between charge disproportionation induced electric dipoles.

  4. Study of surface dielectric barrier discharge generated using liquid electrodes in different gases

    NASA Astrophysics Data System (ADS)

    Galmiz, O.; Pavlinak, D.; Zemanek, M.; Brablec, A.; Cernak, M.

    2016-02-01

    Surface dielectric barrier discharges with conductive water-solution electrodes were generated at atmospheric pressure air, nitrogen, oxygen, and argon. The discharges were studied by conventional and high-speed camera photography. Plasma rotational and vibrational temperatures and the electron number density were estimated using optical emission spectroscopy. Surprisingly, especially for oxygen, the discharge was found to generate visually diffuse strongly non-isothermal plasma. This observation indicates the interesting application potential of the discharge for surface plasma treatments of, i.e. the inner and outer surfaces of hollow dielectric bodies.

  5. Fluctuation-induced dielectric permittivity in the isotropic phase of cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Mukherjee, Prabir K.; Das, Asok K.

    2016-03-01

    The temperature and pressure dependence of the static dielectric permittivity in the isotropic phase of the isotropic to cholesteric phase transition is calculated using Landau-de Gennes’s fluctuation theory, allowing spatial variation of the orientational order parameter. A comparison is made with experimental data available in the isotropic phase of the isotropic to cholesteric phase transition.

  6. Medium-Range Ordering in Liquids Appearing in Nonlinear Dielectric Effect Studies

    NASA Astrophysics Data System (ADS)

    Zioło, Jerzy; Rzoska, Sylwester J.; Drozd-Rzoska, Aleksandra

    Results of nonlinear dielectric effect (NDE) studies in supercooling epoxy resin EPON 5, nitrobenzene and menthol are presented. In each case on cooling a non-exponential decay of the NDE response after switching-off the strong electric field was found. The obtained "nonlinear" relaxation time is more than 106 times longer than the structural relaxation time (alpha relaxation) detected from "linear" broad band dielectric spectroscopy. For EPON 5 it is shown that for the whole tested range of temperatures the NDE relaxation time can be well parameterized by the Vogel-Fulcher-Tamman relation. For higher temperatures the NDE decay time can also be portrayed by the critical-like dependence, with the power exponent y=1.

  7. Dielectric Spectroscopy of Binary Liquid Mixtures of Methanol with Morpholine, Pyrrolidine and some of their Derivatives

    NASA Astrophysics Data System (ADS)

    Syal, V. K.; Becker, U.; Elsebrock, R.; Stockhausen, M.

    1997-09-01

    Dielectric spectra (up to 72 GHz) have been measured at 20 °C for mixtures of methanol and one of the following substances: morpholine, N-methyl morpholine, N-cyano morpholine, pyrrolidine and N-cyano pyrrolidine. The composition dependence of the relaxation parameters shows close similarities for the morpholines and, on the other hand, for the pyrrolidines, which indicates that a structure breaking effect on methanol is exerted by the former but not by the latter group of substances.

  8. Breakdown and Partial Discharge Measurements of Some Commonly Used Dielectric Materials in Liquid Nitrogen for HTS Applications

    SciTech Connect

    James, David Randy; Sauers, Isidor; Ellis, Alvin R; Tuncer, Enis; Tekletsadik, Kasegn; Hazelton, Drew

    2007-01-01

    For high temperature superconducting (HTS) power applications it is necessary to improve the understanding of the dielectric properties of materials in a cryogenic environment. It is necessary to know the breakdown strength of materials and systems as a function of gap in order to scale to higher voltages. The partial discharge (PD) onset voltage for materials is also very important since the primary aging mechanism at cryogenic temperature is PD. Another important design characteristic is the surface flashover voltage of a material in liquid nitrogen as a function of gap. With these characteristics in mind, several generic materials were investigated under a variety of electrode and gap configurations. The impulse breakdown voltage and PD onset of three types of commercial polyetherimide, filled and unfilled, were measured at room temperature and 77 K. A modest increase in PD onset voltage was observed at the lower temperature. Breakdown voltages of fiberglass reinforced plastic (FRP) cylinders for two wall thicknesses were measured which showed a decrease in strength at the larger gap. Breakdown voltages for liquid nitrogen using a sphere-plane electrode geometry were measured. Also flashover voltages along a FRP plate immersed in liquid nitrogen were performed for sphere-plane and rod-plane electrodes at 1 bar pressure. It was found that the breakdown voltage increased only slightly with increasing gap lengths.

  9. Competition between the bulk and the dissociation layer in electrohydrodynamic flow of dielectric liquid around coplanar electrodes.

    PubMed

    Suh, Y K; Baek, K H

    2013-02-01

    An experimental and numerical study has been conducted on the electrohydrodynamic flow around coplanar electrodes with a dielectric liquid: dodecane mixed with the surfactant Span 80. It is shown that the flow is asymmetric, although the electrode is symmetrically arranged, and numerically, we have shown that a difference in the ionic size can reproduce such asymmetric patterns. It is also found that the dissociation layer effect becomes more important in determining the flow pattern than is predicted from the conventional theory where the Langevin formula is used for the recombination constant. In numerical simulations, reducing the recombination constant to 0.035-0.055 times the Langevin value turned out to produce good comparisons between the experimental and the numerical results for the electrode pairs with 1 and 0.2 mm gaps. PMID:23496612

  10. Experimental study of coarsening dynamics of the zigzag wall in a nematic liquid crystal with negative dielectric anisotropy.

    PubMed

    Nagaya, Tomoyuki; Gilli, Jean-Marc

    2002-05-01

    When a homeotropically aligned nematic liquid crystal cell is placed above two permanent magnets forming a magnetic quadrupole, a straight splay-bend wall, or a so-called Ising wall, is formed. With a material of positive dielectric anisotropy, it has been shown that the application of an electric field perpendicular to the plates leads to a zigzag instability of the wall, exclusively related to the elastic anisotropy of the liquid crystal. In this case, the coarsening process of the zigzag is very slow, which in turn leads to experimental difficulties concerning its quantitative investigation. If a material of negative dielectric anisotropy is used under an electric field with low voltage and low frequency, two convective rolls appear along the Ising wall due to the charge focusing effect, which is also responsible, at a higher voltage in the homogenous tilted regions, for the appearance of Williams domains electrohydrodynamic instability. If the voltage is higher than a threshold value, the straight Ising wall spontaneously breaks into a zigzag shape and a fast coarsening of the zigzag proceeds, associated with the annihilation of two neighboring vertices. In the present paper, the coarsening dynamics of this system, which can be considered as a one-dimensional Ising situation, are investigated experimentally. At late times, the average width of the zigzag increases logarithmically with time. This finding is consistent with the theory and also with the numerical simulation of a one-dimensional Cahn-Hilliard situation having a conserved order parameter. The scaling analysis of size distribution of the Ising domain, the shape of the power spectrum, and of the correlation function of the Ising order parameter, as well as the number density correlation functions of kinks also confirms that the dynamical scaling law predicted for one-dimensional conservative systems holds for the coarsening process. As supposed from symmetry arguments, it is confirmed that this

  11. Ultra-wideband electronics, design methods, algorithms, and systems for dielectric spectroscopy of isolated B16 tumor cells in liquid medium

    NASA Astrophysics Data System (ADS)

    Maxwell, Erick N.

    Quantifying and characterizing isolated tumor cells (ITCs) is of interest in surgical pathology and cytology for its potential to provide data for cancer staging, classification, and treatment. Although the independent prognostic significance of circulating ITCs has not been proven, their presence is gaining clinical relevance as an indicator. However, researchers have not established an optimal method for detecting ITCs. Consequently, this Ph.D. dissertation is concerned with the development and evaluation of dielectric spectroscopy as a low-cost method for cell characterization and quantification. In support of this goal, ultra-wideband (UWB), microwave pulse generator circuits, coaxial transmission line fixtures, permittivity extraction algorithms, and dielectric spectroscopy measurement systems were developed for evaluating the capacity to quantify B16-F10 tumor cells in suspension. First, this research addressed challenges in developing tunable UWB circuits for pulse generation. In time-domain dielectric spectroscopy, a tunable UWB pulse generator facilitates exploration of microscopic dielectric mechanisms, which contribute to dispersion characteristics. Conventional approaches to tunable pulse generator design have resulted in complex circuit topologies and unsymmetrical waveform morphologies. In this research, a new design approach for low-complexity, tunable, sub-nanosecond and UWB pulse generator was developed. This approach was applied to the development of a novel generator that produces symmetrical waveforms (patent pending 60/597,746). Next, this research addressed problems with transmission-reflection (T/R) measurement of cell suspensions. In T/R measurement, coaxial transmission line fixtures have historically required an elaborate sample holder for containing liquids, resulting in high cost and complexity. Furthermore, the algorithms used to extract T/R dielectric properties have suffered from myriad problems including local minima and

  12. Two-layered disc quasi-optical dielectric resonators: electrodynamics and application perspectives for complex permittivity measurements of lossy liquids

    NASA Astrophysics Data System (ADS)

    Barannik, A. A.; Cherpak, N. T.; Prokopenko, Yu V.; Filipov, Yu F.; Shaforost, E. N.; Shipilova, I. A.

    2007-07-01

    Electromagnetic properties of novel quasi-optical resonators are studied theoretically and experimentally. The resonators are a radially two-layered dielectric disc sandwiched between conducting endplates. The internal layer can be filled with air or lossy liquid. Whispering gallery modes are excited in such a resonator and the mode energy is concentrated near the inner side of the cylindrical surface of an external layer. The measurement data obtained in the Ka-band are compared with theoretical calculations of eigenfrequencies and quality factors of the Teflon resonator filled with water, ethyl alcohol, benzene and aqueous solutions of ethyl alcohol. A number of 'anomalous' properties of the resonator can be described using Maxwell equations. The experimental data on the complex permittivity of a binary mixture water-ethyl alcohol are compared with the values calculated in terms of Debye's function. An important feature of the proposed technique is that it holds promise for making first principle microwave measurements of the permittivity of lossy liquids.

  13. Hyperparametric effects in a whispering-gallery mode rutile dielectric resonator at liquid helium temperatures

    SciTech Connect

    Nand, Nitin R.; Goryachev, Maxim; Floch, Jean-Michel le; Creedon, Daniel L.; Tobar, Michael E.

    2014-10-07

    We report the first observation of low power drive level sensitivity, hyperparametric amplification, and single-mode hyperparametric oscillations in a dielectric rutile whispering-gallery mode resonator at 4.2 K. The latter gives rise to a comb of sidebands at 19.756 GHz. Whereas, most frequency combs in the literature have been observed in optical systems using an ensemble of equally spaced modes in microresonators or fibers, the present work represents generation of a frequency comb using only a single-mode. The experimental observations are explained by an additional 1/2 degree-of-freedom originating from an intrinsic material nonlinearity at optical frequencies, which affects the microwave properties due to the extremely low loss of rutile. Using a model based on lumped circuits, we demonstrate that the resonance between the photonic and material 1/2 degree-of-freedom, is responsible for the hyperparametric energy transfer in the system.

  14. Critical modes due to Archimedean buoyancy and dielectrophoretic force in a dielectric liquid in cylindrical annulus

    NASA Astrophysics Data System (ADS)

    Meyer, Antoine; Yoshikawa, Harunori; Crumeyrolle, Olivier; Mutabazi, Innocent

    2015-11-01

    An incompressible dielectric fluid is confined in a cylindrical annulus maintained at two different temperatures and an electric tension in Earth gravity. The coupling between the electric field and the thermal variation of the permittivity leads to a dilectrophoretic force that acts as a buoyancy force to induce convective flows. We have performed the linear stability analysis to determine the critical parameters and the nature of critical modes for different values of the control parameters. Four types of modes were found: For weak values of the electric tension, the critical modes are either hydrodynamic or thermal modes depending on the Prandtl number and for large values of electric tension lead to electric modes. For its intermediate values, critical modes are columnal vortices, similar to those observed in simulations of the convection in a cylindrical annulus with a radial gravity. Work supported by the CNES-France

  15. Intermolecular and intramolecular reorientations in nonchiral smectic liquid-crystalline phases studied by broadband dielectric spectroscopy

    PubMed

    Schacht; Zugenmaier; Buivydas; Komitov; Stebler; Lagerwall; Gouda; Horii

    2000-04-01

    Molecular dynamics has been studied by broadband dielectric relaxation spectroscopy in the Sm-A, Sm-B, and Sm-E phases (Sm denotes smectic) of a homologous series of nonchiral stilbenes. An assignment of modes is presented based on their dependence on temperature and molecular length, and, as far as they obey the Arrhenius law, their activation energy has been determined. In general, reorientations of entire molecules around their short axis are active, whereas reorientations of entire molecules around their long axis are locked out in the Sm-E phase of shorter homologs, yet intramolecular reorientations of polar sites have been established. Strong evidence is presented for an interdependence of reorientations of entire molecules around the short and long axes within the biaxial Sm-E phase of longer homologs. PMID:11088173

  16. Associating behaviour of pure polar liquids: dielectric properties of lauric acid

    NASA Astrophysics Data System (ADS)

    Mognaschi, E. R.; Laboranti, L. M.

    1994-09-01

    In this paper measurements of the static dielectric permittivity of lauric acid at different temperatures from about 10 K above the MP to 352 K are reported. These data, together with the dependence of the refractive index and density on temperature, are used in order to investigate the associative behaviour of lauric acid. The Kirkwood correlation factor calculated both with the classical Kirkwood-Frddotohlich equation and with that corrected for eflipsoidal shaped molecules are reported and discussed. Both correlation factors obtained indicate the existence of a prevailing antiparallel order of dipole moments. The static permittivity and the correlation factors increase with increasing temperature and this suggests that the number of apolar dimers decreases on going from low to high temperature.

  17. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Hanham, S. M.; Watts, C.; Otter, W. J.; Lucyszyn, S.; Klein, N.

    2015-07-01

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ˜4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ˜5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  18. A study of dielectric breakdown along insulators surrounding conductors in liquid argon

    SciTech Connect

    Lockwitz, Sarah; Jostlein, Hans

    2015-06-12

    High voltage breakdown in liquid argon is an important concern in the design of liquid argon time projection chambers, which are often used as neutrino and dark matter detectors. We have made systematic measurements of breakdown voltages in liquid argon along insulators surrounding negative rod electrodes where the breakdown is initiated at the anode. The measurements were performed in an open cryostat filled with commercial grade liquid argon exposed to air, and not the ultra-pure argon required for electron drift. While not addressing all high voltage concerns in liquid argon, these measurements have direct relevance to the design of high voltage feedthroughs especially for averting the common problem of flash-over breakdown. The purpose of these tests is to understand the effects of materials, of breakdown path length, and of surface topology for this geometry and setup. We have found that the only material-specific effects are those due to their permittivity. We have found that the breakdown voltage has no dependence on the length of the exposed insulator. Lastly, a model for the breakdown mechanism is presented that can help inform future designs.

  19. A study of dielectric breakdown along insulators surrounding conductors in liquid argon

    DOE PAGESBeta

    Lockwitz, Sarah; Jostlein, Hans

    2016-03-22

    High voltage breakdown in liquid argon is an important concern in the design of liquid argon time projection chambers, which are often used as neutrino and dark matter detectors. We have made systematic measurements of breakdown voltages in liquid argon along insulators surrounding negative rod electrodes where the breakdown is initiated at the anode. The measurements were performed in an open cryostat filled with commercial grade liquid argon exposed to air, and not the ultra-pure argon required for electron drift. While not addressing all high voltage concerns in liquid argon, these measurements have direct relevance to the design of highmore » voltage feedthroughs especially for averting the common problem of flash-over breakdown. The purpose of these tests is to understand the effects of materials, of breakdown path length, and of surface topology for this geometry and setup. We have found that the only material-specific effects are those due to their permittivity. We have found that the breakdown voltage has no dependence on the length of the exposed insulator. Lastly, a model for the breakdown mechanism is presented that can help inform future designs.« less

  20. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    SciTech Connect

    Hanham, S. M. Watts, C.; Klein, N.; Otter, W. J.; Lucyszyn, S.

    2015-07-20

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ∼4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ∼5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  1. Influence of moieties for the phase stability, spontaneous polarization and dielectric relaxations in an achiral ferroelectric bent liquid crystal, PBUOB

    NASA Astrophysics Data System (ADS)

    Chalapathi, P. V.; Srinivasulu, M.; Pisipati, V. G. K. M.; Satyanarayana, Ch.; Potukuchi, D. M.

    2011-05-01

    The occurrence of ferroelelectric phases and influence of chemical moieties in the area of supra-molecular achiral Bent core Liquid Crystals (BLCs) are reviewed. Synthesis of an intermediate/higher homolog of PBnOB series (for n=11), PBUOB, viz. 1,3-Phenyline-Bis(4-UndecylOxy Benzoate), is presented. Smectic LC phases exhibited by PBUOB are characterized by Polarized Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and Spontaneous Polarization ( PS) techniques. Observations infer a bi-variant FE LC smectic phase occurrence, viz., isotropic→B 2(FE)→B 5(FE)→solid phases in cooling and solid→B 5→isotropic phases in heating scans. Occurrence of B 2 phase is monotropic (in cooling), while B 5 phase is enantiotropic. I-B 2 and B 2-B 5 phase transitions are found to be of first order nature. The FE phases possess a moderate PS value of ∼40 nC cm -2. Transition temperatures from dielectric studies agree with those from TM and DSC. Two modes of relaxations are observed, viz., a slow scissor mode at ∼1 kHz and a fast mode at ∼1 MHz. Anisotropic Dipolar Model is proposed to explain the reorientation mechanism. Arrhenius shifts of Relaxation Frequency ( fR) show differing activation energies for two modes, i.e., 0.11 and 0.98 eV; 0.25 and 1.18 eV in B 2 and B 5 phases, respectively. Temperature variation of dielectric increment Δ ε and α-parameter LC phases reveals the relative fixture of dipole moment in polar smectic layers. An analytical study for the thermal stability, PS and fR in the FE phases is presented with respect to the constitution and configuration of moieties in BLCs.

  2. Studies of nanosecond pulse surface ionization wave discharges over solid and liquid dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Petrishchev, Vitaly; Leonov, Sergey; Adamovich, Igor V.

    2014-12-01

    Surface ionization wave discharges generated by high-voltage nanosecond pulses, propagating over a planar quartz surface and over liquid surfaces (distilled water and 1-butanol) have been studied in a rectangular cross section test cell. The discharge was initiated using a custom-made, alternating polarity, high-voltage nanosecond pulse plasma generator, operated at a pulse repetition rate of 100-500 Hz, with a pulse peak voltage and current of 10-15 kV and 7-20 A, respectively, a pulse FWHM of ˜100 ns, and a coupled pulse energy of 2-9 mJ/pulse. Wave speed was measured using a capacitive probe. ICCD camera images demonstrated that the ionization wave propagated predominantly over the quartz wall or over the liquid surface adjacent to the grounded waveguide placed along the bottom wall of the test cell. Under all experimental conditions tested, the surface plasma ‘sheet’ was diffuse and fairly uniform, both for positive and negative polarities. The parameters of ionization wave discharge propagating over distilled water and 1-butanol surfaces were close to those of the discharge over a quartz wall. No perturbation of the liquid surface by the discharge was detected. In most cases, the positive polarity surface ionization wave propagated at a higher speed and over a longer distance compared to the negative polarity wave. For all three sets of experiments (surface ionization wave discharge over quartz, water and 1-butanol), wave speed and travel distance decreased with pressure. Diffuse, highly reproducible surface ionization wave discharge was also observed over the liquid butanol-saturated butanol vapor interface, as well as over the distilled water-saturated water vapor interface, without buffer gas flow. No significant difference was detected between surface ionization discharges sustained using single-polarity (positive or negative), or alternating polarity high-voltage pulses. Plasma emission images yielded preliminary evidence of charge removal from the

  3. The dielectric study of insulin-loaded reverse hexagonal (H(II)) liquid crystals.

    PubMed

    Mishraki-Berkowitz, T; Ben Ishai, P; Aserin, A; Feldman, Yu; Garti, N

    2015-04-14

    The dielectric behavior of the insulin-loaded HII mesophase (containing GMO-TAG-water-glycerol-insulin) was studied using two empty reference systems (GMO-TAG-water and GMO-TAG-water-glycerol) at a frequency range of 10(-2)-10(6) Hz, and a temperature range of 290-333 K. Three clearly defined relaxation processes were observed and assigned to the reorientation of GMO polar heads, the tangential movement of counterions at the interface, and the movements of TAGs through the lipid tail. Upon addition of glycerol, a heterogeneous inner structure was formed within the HII cylinders: the water-glycerol core surrounded by a water rigid layer. Upon heating, two critical points were detected referring to the dehydration of the GMO heads (at 304 K, similar to the water-filled HII system) and to energetic modifications (at 316 K), resulting in breaking of the water layer allowing on-demand controlled release. Insulin incorporation combined the features of both reference HII systems. Yet, unlike the empty HII systems, insulin perturbed the GMO-water interface while decreasing the movement of the GMO headgroup, and reducing T0 (296 K). No interactions were formed between the dipole of each counterion at the interface region and the matrix (the GMO), fitting the Debye process. Dynamic behavior was observed, pointing to mobility between the hexagonal rods themselves, enabling controlled release from the HII carrier. PMID:25767829

  4. Environmentally friendly power generator based on moving liquid dielectric and double layer effect

    NASA Astrophysics Data System (ADS)

    Huynh, D. H.; Nguyen, T. C.; Nguyen, P. D.; Abeyrathne, C. D.; Hossain, Md. S.; Evans, R.; Skafidas, E.

    2016-06-01

    An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(108μW)/(mm2HzV2) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting.

  5. Environmentally friendly power generator based on moving liquid dielectric and double layer effect

    PubMed Central

    Huynh, D. H.; Nguyen, T. C.; Nguyen, P. D.; Abeyrathne, C. D.; Hossain, Md. S.; Evans, R.; Skafidas, E.

    2016-01-01

    An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(108μW)/(mm2HzV2) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting. PMID:27255577

  6. Silicon Dioxide Film with Low Dielectric Constants using Liquid-Phase Deposition

    NASA Astrophysics Data System (ADS)

    Chanthamaly, Phonekeo; Arakawa, Taro; Haneji, Nobuo

    1999-10-01

    We propose a method which is advantageous for forming F bonds in the Si O network without any external energy assistance. This method can be used to grow SiO2 films in supersaturated fluorosilicic acid (H2SiF6) at room temperature. The dissociation reaction between H2SiF6 and H2O leads to the formation of silica and the deposition of SiO2 films on the surface of substrates. Because the reaction involves an aqueous acid which contains fluorine, F bonds are formed in the films naturally. The percentage of F atoms increased from 3.5 to 4.75% according to X-ray photoelectron sectroscopy (XPS) survey, and the F1S peak changed from 687.72 to 687.18 eV with an increase in concentration from 2.25 to 3.25 mol/l, respectively. In addition, due to the effect of F bonds inside the film, the dielectric constant also decreased from 3.7 to about 3. Atomic force microscopy (AFM) images showed that the surface roughness increased with increasing H2SiF6 concentration due to the attack of F; however, the maximum surface roghness was less than 0.5 nm.

  7. Non-linear dielectric signatures of entropy changes in liquids subject to time dependent electric fields

    NASA Astrophysics Data System (ADS)

    Richert, Ranko

    2016-03-01

    A model of non-linear dielectric polarization is studied in which the field induced entropy change is the source of polarization dependent retardation time constants. Numerical solutions for the susceptibilities of the system are obtained for parameters that represent the dynamic and thermodynamic behavior of glycerol. The calculations for high amplitude sinusoidal fields show a significant enhancement of the steady state loss for frequencies below that of the low field loss peak. Also at relatively low frequencies, the third harmonic susceptibility spectrum shows a "hump," i.e., a maximum, with an amplitude that increases with decreasing temperature. Both of these non-linear effects are consistent with experimental evidence. While such features have been used to conclude on a temperature dependent number of dynamically correlated particles, Ncorr, the present result demonstrates that the third harmonic susceptibility display a peak with an amplitude that tracks the variation of the activation energy in a model that does not involve dynamical correlations or spatial scales.

  8. Dielectric matrix and plasmon dispersion in strongly coupled electronic bilayer liquids

    SciTech Connect

    Golden, Kenneth I.; Mahassen, Hania; Kalman, Gabor J.; Senatore, Gaetano; Rapisarda, F.

    2005-03-01

    We develop a dielectric matrix and analyze plasmon dispersion in strongly coupled charged-particle bilayers in the T=0 quantum domain. The formulation is based on the classical quasilocalized charge approximation (QLCA) and extends the QLCA formalism into the quantum domain. Its development, which parallels that of the two-dimensional companion paper [Phys. Rev. E 70, 026406 (2004)] by three of the authors, generalizes the single-layer scalar formalism therein to a bilayer matrix formalism. Using pair correlation function data generated from diffusion Monte Carlo simulations, we calculate the dispersion of the in-phase and out-of-phase plasmon modes over a wide range of high-r{sub s} values and layer separations. The out-of-phase spectrum exhibits an exchange-correlation induced long-wavelength energy gap in contrast to earlier predictions of acoustic dispersion softened by exchange and correlations. The energy gap is similar to what has been previously predicted for classical charged-particle bilayers and subsequently confirmed by recent molecular dynamics computer simulations.

  9. Environmentally friendly power generator based on moving liquid dielectric and double layer effect.

    PubMed

    Huynh, D H; Nguyen, T C; Nguyen, P D; Abeyrathne, C D; Hossain, Md S; Evans, R; Skafidas, E

    2016-01-01

    An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(10(8)μW)/(mm(2)HzV(2)) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting. PMID:27255577

  10. Liquid self-diffusion of H2O and DMF molecules in Co-MOF-74: molecular dynamics simulations and dielectric spectroscopy studies.

    PubMed

    Bermúdez-García, J M; Vicent-Luna, J M; Yáñez-Vilar, S; Hamad, S; Sánchez-Andújar, M; Castro-García, S; Calero, S; Señarís-Rodríguez, M A

    2016-07-20

    In this work we use molecular dynamics simulations to study the diffusion of N,N-dimethylformamide (DMF) and H2O as a function of temperature within the well-known metal-organic framework Co2(dobdc)·[G] (G = 2DMF·1H2O), also known as Co-MOF-74. The molecular dynamics simulations show that the diffusivity of guest molecules, which is almost negligible at low temperatures (T < 200 K), increases in the range of 200 < T (K) < 400 up to 3 and 4 orders of magnitude for DMF and H2O, respectively. This molecular diffusion can be easily detected by dielectric spectroscopy as it gives rise to extrinsic interfacial polarization effects that result in an apparent "colossal" dielectric constant at room temperature, εr' ∼ 42 000 (T = 300 K, ν = 10 Hz). Furthermore, the measured dielectric constant exhibits a thermal dependence similar to that of the diffusion coefficient, revealing the parallelism of the dielectric response and the molecular diffusion as a function of temperature. These results highlight: (a) the great utility of the fast and non-destructive dielectric and impedance spectroscopy techniques for the study and detection of the molecular transport of small polar molecules within porous metal-organic frameworks and related materials; (b) the peculiarity and uniqueness of MOF materials with "medium" size nanopores containing guest molecules as they are solid materials in which the guest molecules display a liquid state-like behaviour close to room temperature; and PMID:27353249

  11. FT-IR and dielectric study of water/AOT liquid crystals

    NASA Astrophysics Data System (ADS)

    Calandra, P.; Caponetti, E.; Chillura Martino, D.; D'Angelo, P.; Minore, A.; Turco Liveri, V.

    2000-04-01

    In order to explore the influence of microwave radiation on highly viscous microheterogeneous systems, the evolution of structural and dynamical properties of the water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) liquid crystals as a function of the molar ratio R ( R=[water]/[AOT]) has been investigated by FT-IR spectroscopy and time domain reflectometry. The study emphasises how the progressive hydration of the surfactant head groups is mainly responsible for the structural and dynamical evolution of water/AOT liquid crystals. In particular, it has been found that the state of water at lower R values is strongly perturbed, bulk-like water appears only at R>23 and the water/AOT interface polarisation is controlled by the fast translational dynamics of sodium counterions and the slow orientational dynamics of the AOT ionic head groups.

  12. Computing the Kirkwood g-Factor by Combining Constant Maxwell Electric Field and Electric Displacement Simulations: Application to the Dielectric Constant of Liquid Water.

    PubMed

    Zhang, Chao; Hutter, Jürg; Sprik, Michiel

    2016-07-21

    In his classic 1939 paper, Kirkwood linked the macroscopic dielectric constant of polar liquids to the local orientational order as measured by the g-factor (later named after him) and suggested that the corresponding dielectric constant at short-range is effectively equal to the macroscopic value just after "a distance of molecular magnitude" [ Kirkwood, J. Chem. Phys., 1939, 7, 911 ]. Here, we show a simple approach to extract the short-ranged Kirkwood g-factor from molecular dynamics (MD) simulation by superposing the outcomes of constant electric field E and constant electric displacement D simulations [ Zhang and Sprik, Phys. Rev. B: Condens. Matter Mater. Phys., 2016, 93, 144201 ]. Rather than from the notoriously slow fluctuations of the dipole moment of the full MD cell, the dielectric constant can now be estimated from dipole fluctuations at short-range, accelerating the convergence. Exploiting this feature, we computed the bulk dielectric constant of liquid water modeled in the generalized gradient approximation (PBE) to density functional theory and found it to be at least 40% larger than the experimental value. PMID:27352038

  13. Dielectric investigations of induced memory in chiral doped nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Middha, Manju; Kumar, Rishi; Raina, K. K.

    2015-08-01

    When an electric field is applied to thin film of a chiral doped nematic liquid crystal, unwinding of the helix takes place. Due to the competition of elastic forces of the material with the electrical and surface anchoring forces, defect lines are created. Sometimes after the removal of electric field, the system does not relax back to the original state and shows optical and electro-optical hysteresis. The induction of memory as a result of manipulation of the helix director remains an active field of study and can be useful for the development of memory based bistable low power devices.

  14. Transient, polarity-dependent dielectric response in a twisted nematic liquid crystal under very low frequency excitation.

    PubMed

    Krishnamurthy, K S

    2015-09-01

    The electric Freedericksz transition is a second-order quadratic effect, which, in a planarly aligned nematic liquid crystal layer, manifests above a threshold field as a homogeneous symmetric distortion with maximum director-tilt in the midplane. We find that, upon excitation by a low frequency (<0.2Hz) square-wave field, the instability becomes spatially and temporally varying. This is demonstrated using calamitic liquid crystals, initially in the 90°-twisted planar configuration. The distortion occurs close to the negative electrode following each polarity switch and, for low-voltage amplitudes, decays completely in time. We use the elastically favorable geometry of Brochard-Leger walls to establish the location of maximum distortion. Thus, at successive polarity changes, the direction of extension of both annular and open walls switches between the alignment directions at the two substrates. For high voltages, this direction is largely along the midplane director, while remaining marginally oscillatory. These results are broadly understood by taking into account the time-varying and inhomogeneous field conditions that prevail soon after the polarity reverses. Polarity dependence of the instability is traced to the formation of intrinsic double layers that lead to an asymmetry in field distribution in the presence of an external bias. Momentary field elevation near the negative electrode following a voltage sign reversal leads to locally enhanced dielectric and gradient flexoelectric torques, which accounts for the surface-like phenomenon observed at low voltages. These spatiotemporal effects, also found earlier for other instabilities, are generic in nature. PMID:26465487

  15. Influence of ionic liquid and ionic salt on protein against the reactive species generated using dielectric barrier discharge plasma

    PubMed Central

    Attri, Pankaj; Sarinont, Thapanut; Kim, Minsup; Amano, Takaaki; Koga, Kazunori; Cho, Art E.; Ha Choi, Eun; Shiratani, Masaharu

    2015-01-01

    The presence of salts in biological solution can affect the activity of the reactive species (RS) generated by plasma, and so they can also have an influence on the plasma-induced sterilization. In this work, we assess the influence that diethylammonium dihydrogen phosphate (DEAP), an ionic liquid (IL), and sodium chloride (NaCl), an ionic salt (IS), have on the structural changes in hemoglobin (Hb) in the presence of RS generated using dielectric barrier discharge (DBD) plasma in the presence of various gases [O2, N2, Ar, He, NO (10%) + N2 and Air]. We carry out fluorescence spectroscopy to verify the generation of •OH with or without the presence of DEAP IL and IS, and we use electron spin resonance (ESR) to check the generation of H• and •OH. In addition, we verified the structural changes in the Hb structure after treatment with DBD in presence and absence of IL and IS. We then assessed the structural stability of the Hb in the presence of IL and IS by using molecular dynamic (MD) simulations. Our results indicate that the IL has a strong effect on the conservation of the Hb structure relative to that of IS against RS generated by plasma. PMID:26656857

  16. Dependence of image flickering of negative dielectric anisotropy liquid crystal on the flexoelectric coefficient ratio and the interdigitated electrode structure

    NASA Astrophysics Data System (ADS)

    Lee, Hyojin; Kim, Hyungmin; Kim, Jongyoon; Lee, Ji-Hoon

    2016-02-01

    We experimentally measured the splay (e s) and the bend flexoelectric coefficients (e b) of liquid crystal (LC) mixtures with negative dielectric anisotropy and investigated their effect on the image flicker of the LC mixtures driven with a low frequency electric field. Using the experimentally measured e s and e b, we simulated the transmittance (TR) response with the continuum model. First, we confirmed that the TR simulation results were approximated to the experimental data with only small variation. Second, we varied the simulation parameters of e s , e b, the separation (S), and the width (W) of the interdigitated electrodes and tried to find the optimum condition showing the least image flicker. Given W  =  3.0 μm and e b  =  5.7 pC m-1, it was found that the image flicker could be minimized when the e s /e b value was about 2.4 and the S/W ratio was about 1.5. Because the e s /e b value of the rod-like LC material is generally less than 1, it is desirable to design an interdigitated electrode structure to minimize the image flicker effect.

  17. Influence of ionic liquid and ionic salt on protein against the reactive species generated using dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Attri, Pankaj; Sarinont, Thapanut; Kim, Minsup; Amano, Takaaki; Koga, Kazunori; Cho, Art E.; Ha Choi, Eun; Shiratani, Masaharu

    2015-12-01

    The presence of salts in biological solution can affect the activity of the reactive species (RS) generated by plasma, and so they can also have an influence on the plasma-induced sterilization. In this work, we assess the influence that diethylammonium dihydrogen phosphate (DEAP), an ionic liquid (IL), and sodium chloride (NaCl), an ionic salt (IS), have on the structural changes in hemoglobin (Hb) in the presence of RS generated using dielectric barrier discharge (DBD) plasma in the presence of various gases [O2, N2, Ar, He, NO (10%) + N2 and Air]. We carry out fluorescence spectroscopy to verify the generation of •OH with or without the presence of DEAP IL and IS, and we use electron spin resonance (ESR) to check the generation of H• and •OH. In addition, we verified the structural changes in the Hb structure after treatment with DBD in presence and absence of IL and IS. We then assessed the structural stability of the Hb in the presence of IL and IS by using molecular dynamic (MD) simulations. Our results indicate that the IL has a strong effect on the conservation of the Hb structure relative to that of IS against RS generated by plasma.

  18. Ultra-Broadband Dielectric and Optical Kerr-Effect Study of the Ionic Liquids Ethyl and Propylammonium Nitrate.

    PubMed

    Sonnleitner, Thomas; Turton, David A; Hefter, Glenn; Ortner, Alexander; Waselikowski, Stefan; Walther, Markus; Wynne, Klaas; Buchner, Richard

    2015-07-23

    Dielectric relaxation (DR) and optical Kerr-effect (OKE) spectra of the archetypal protic ionic liquids ethyl- and propylammonium nitrate (EAN and PAN) have been measured over an unusually large frequency range from 200 MHz to 10 THz at temperatures (mostly) between 5 and 65 °C. Analysis of the low-frequency α-relaxation, associated with the cooperative relaxations of the cations (DR) and anions (OKE) and any clusters present, indicated that ion reorientation in EAN is decoupled from viscosity and occurs via cooperative relaxation involving large-angle jumps rather than rotational diffusion. Detailed consideration of the high-frequency parts of the DR and OKE spectra showed that the observed intensities were a complex combination of overlapping and possibly coupled modes. In addition to previously identified intermolecular H-bond vibrations, there are significant contributions from the librations of the cations and anions. The present assignments were shown to be consistent with the isotopic shifts observed for deuterated EAN. PMID:24945675

  19. Pesticide analysis at ppt concentration levels: coupling nano-liquid chromatography with dielectric barrier discharge ionization-mass spectrometry.

    PubMed

    Mirabelli, Mario F; Wolf, Jan-Christoph; Zenobi, Renato

    2016-05-01

    We report the coupling of nano-liquid chromatography (nano-LC) with an ambient dielectric barrier discharge ionization (DBDI)-based source. Detection and quantification were carried out by high-resolution mass spectrometry (MS), using an LTQ-Orbitrap in full scan mode. Despite the fact that nano-LC systems are rarely used in food analysis, this coupling was demonstrated to deliver extremely high sensitivity in pesticide analysis, with limits of detection (LODs) as low as 10 pg/mL. In all cases, the limits of quantification (LOQs) were compliant with the current EU regulation. An excellent signal linearity over up to four orders of magnitude was also observed. Therefore, this method can easily compete with conventional GC-(EI)-MS or LC-ESI-MS/MS methods and in some cases outperform them. The method was successfully tested for food sample analysis, with apples and baby food, extracted using the QuEChERS approach. Our results demonstrate an outstanding sensitivity (at femtogram level) and reproducibility of the nano-LC-DBDI coupling, capable of improving routine pesticide analysis. To the best of our knowledge, this is the most sensitive and reproducible plasma-MS-based method for pesticide analysis reported to date. PMID:26898206

  20. Selective conversion of methane to synthetic fuels using dielectric barrier discharge contacting liquid film

    NASA Astrophysics Data System (ADS)

    Nozaki, Tomohiro; Goujard, Valentin; Yuzawa, Shuhei; Moriyama, Shota; Ağıral, Anıl; Okazaki, Ken

    2011-07-01

    This paper presents the reaction mechanism of single-step methane partial oxidation to methanol at room temperature using non-thermal plasma microreactor. Macroscopic quantities of hydrogen peroxide (H2O2) and methyl hydroperoxide (CH3OOH) are produced when methane is partially oxidized at room temperature (about 5 °C). CH3OOH is known to be the principle intermediate of incomplete methane oxidation product such as CH3OH and HCHO, but has not been demonstrated experimentally so far. H2O2 promotes post-plasma oxidation of oxygenates in the condensed plasma-synthesized liquid. At an early stage of in-liquid oxidation, H2O2 oxidizes HCHO into HCOOH preferentially; subsequently, HCOOH is fully oxidized to CO2 and H2O. Depending upon the concentration of oxygenates and H2O2, electrical conductivity of the plasma solution dramatically increased, which detrimentally influences plasma properties. Methane partial oxidation with air was also investigated from a practical viewpoint. Generation of active nitrogen species (ANS) is the key to promoting overall methane conversion in the presence of oxygen; however, fragile oxygenates were also decomposed by ANS, thus selectivity for useful oxygenates was degraded in the presence of nitrogen. When oxygen is fully consumed, CH4 conversion is also terminated and water gas shift reaction (CO + H2O = CO2 + H2) becomes predominant.

  1. The interaction between plasma filaments in dielectric barrier discharges and liquid covered wounds: electric fields delivered to model platelets and cells

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu; Tian, Wei; Kushner, Mark J.

    2014-06-01

    The treatment of wounds by atmospheric pressure plasmas in the context of plasma medicine typically proceeds through a liquid layer covering exposed cells. The wounds and their liquid covering often have irregular shapes with electrical properties (i.e. conductivity and permittivities) that may differ not only from wound-to-wound but also for a single wound as healing proceeds. The differing shapes and electrical properties extend into the liquid within the wound that typically contains cellular materials such as blood platelets. The plasma, wound, liquid and intra-liquid cellular components represent an interacting system of mutual dependence. In this paper, we discuss the results from a computational investigation of the treatment of small, liquid-covered wounds by filamentary dielectric barrier discharges. The sizes of the wounds are of the order of the plasma filaments and the liquid within the wound, an approximation of blood serum, contains idealized blood platelets. We find that the electrical properties of a wound can have significant effects on the spreading of the plasma on its surface by virtue of the deformation of the vacuum electric fields due to the shape, the effective capacitance of the wound and the discontinuities in electrical permittivity. This in turn effects the penetration of the electric field to cells under the liquid. The orientation and permittivity of the platelets relative to the liquid determines the electric fields that may stimulate the platelets.

  2. Note: Tesla based pulse generator for electrical breakdown study of liquid dielectrics

    NASA Astrophysics Data System (ADS)

    Veda Prakash, G.; Kumar, R.; Patel, J.; Saurabh, K.; Shyam, A.

    2013-12-01

    In the process of studying charge holding capability and delay time for breakdown in liquids under nanosecond (ns) time scales, a Tesla based pulse generator has been developed. Pulse generator is a combination of Tesla transformer, pulse forming line, a fast closing switch, and test chamber. Use of Tesla transformer over conventional Marx generators makes the pulse generator very compact, cost effective, and requires less maintenance. The system has been designed and developed to deliver maximum output voltage of 300 kV and rise time of the order of tens of nanoseconds. The paper deals with the system design parameters, breakdown test procedure, and various experimental results. To validate the pulse generator performance, experimental results have been compared with PSPICE simulation software and are in good agreement with simulation results.

  3. Note: Tesla based pulse generator for electrical breakdown study of liquid dielectrics.

    PubMed

    Veda Prakash, G; Kumar, R; Patel, J; Saurabh, K; Shyam, A

    2013-12-01

    In the process of studying charge holding capability and delay time for breakdown in liquids under nanosecond (ns) time scales, a Tesla based pulse generator has been developed. Pulse generator is a combination of Tesla transformer, pulse forming line, a fast closing switch, and test chamber. Use of Tesla transformer over conventional Marx generators makes the pulse generator very compact, cost effective, and requires less maintenance. The system has been designed and developed to deliver maximum output voltage of 300 kV and rise time of the order of tens of nanoseconds. The paper deals with the system design parameters, breakdown test procedure, and various experimental results. To validate the pulse generator performance, experimental results have been compared with PSPICE simulation software and are in good agreement with simulation results. PMID:24387484

  4. A dielectric response study of the electronic stopping power of liquid water for energetic protons and a new I-value for water

    NASA Astrophysics Data System (ADS)

    Emfietzoglou, D.; Garcia-Molina, R.; Kyriakou, I.; Abril, I.; Nikjoo, H.

    2009-06-01

    The electronic stopping power of liquid water for protons over the 50 keV to 10 MeV energy range is studied using an improved dielectric response model which is in good agreement with the best available experimental data. The mean excitation energy (I) of stopping power theory is calculated to be 77.8 eV. Shell corrections are accounted for in a self-consistent manner through analytic dispersion relations for the momentum dependence of the dielectric function. It is shown that widely used dispersion schemes based on the random-phase approximation (RPA) can result in sizeable errors due to the neglect of damping and local field effects that lead to a momentum broadening and shifting of the energy-loss function. Low-energy Born corrections for the Barkas, Bloch and charge-state effects practically cancel out down to 100 keV proton energies. Differences with ICRU Report 49 stopping power values and earlier calculations are found to be at the ~20% level in the region of the stopping maximum. The present work overcomes the limitations of the Bethe formula below 1 MeV and improves the accuracy of previous calculations through a more consistent account of the dielectric response properties of liquid water.

  5. A dielectric response study of the electronic stopping power of liquid water for energetic protons and a new I-value for water.

    PubMed

    Emfietzoglou, D; Garcia-Molina, R; Kyriakou, I; Abril, I; Nikjoo, H

    2009-06-01

    The electronic stopping power of liquid water for protons over the 50 keV to 10 MeV energy range is studied using an improved dielectric response model which is in good agreement with the best available experimental data. The mean excitation energy (I) of stopping power theory is calculated to be 77.8 eV. Shell corrections are accounted for in a self-consistent manner through analytic dispersion relations for the momentum dependence of the dielectric function. It is shown that widely used dispersion schemes based on the random-phase approximation (RPA) can result in sizeable errors due to the neglect of damping and local field effects that lead to a momentum broadening and shifting of the energy-loss function. Low-energy Born corrections for the Barkas, Bloch and charge-state effects practically cancel out down to 100 keV proton energies. Differences with ICRU Report 49 stopping power values and earlier calculations are found to be at the approximately 20% level in the region of the stopping maximum. The present work overcomes the limitations of the Bethe formula below 1 MeV and improves the accuracy of previous calculations through a more consistent account of the dielectric response properties of liquid water. PMID:19436107

  6. Thermal, vibrational, and dielectric studies on PVP/LiBF4+ionic liquid [EMIM][BF4]-based polymer electrolyte films

    NASA Astrophysics Data System (ADS)

    Saroj, A. L.; Singh, R. K.; Chandra, S.

    2014-07-01

    Free-standing polymer electrolyte membranes based on poly(vinyl) pyrrolidone (PVP)/salt(LiBF4) having different amounts of ionic liquid (IL) [EMIM][BF4] were prepared and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and alternating current (AC) impedance spectroscopic techniques. The DSC results show a shift in Tm of PVP with salt/or IL content. TGA and DTGA (first derivative of TGA) results give evidence of the presence of uncomplexed PVP, PVP/salt, and PVP/IL complexes. Signatures of these entities are also present in the dielectric spectra. Complexation of PVP with salt and IL has been confirmed by FT-IR analysis. Electrical conductivity as a function of temperature has been studied for PVP/LiBF4/IL [EMIM][BF4]. Role of IL in changing phase transition, conductivity, and dielectric relaxation frequency has been discussed.

  7. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores.

    PubMed

    Całus, Sylwia; Kityk, Andriy V; Borowik, Lech; Lefort, Ronan; Morineau, Denis; Krause, Christina; Schönhals, Andreas; Busch, Mark; Huber, Patrick

    2015-07-01

    We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PMID:26274191

  8. Spontaneous polarization and dielectric relaxation dynamics of ferroelectric liquid crystals derived from 2(S)-[2(S)-ethylhexyolxy] propionic acid and its (S, R)-diastereomer

    NASA Astrophysics Data System (ADS)

    Huang, Lei-Ching; Fu, Chao-Ming

    2015-09-01

    The spontaneous polarization and molecular dynamics of four ferroelectric liquid crystals (FLCs) with two different kinds of core rings and two types of diastereomeric structures were investigated in this study. The FLCs with a biphenyl ring core structure showed higher spontaneous polarization than the FLCs with a naphthalene ring core structure. The complex dielectric spectra exhibited the Goldstone mode in the ferroelectric (SmC*) phase for all FLCs. The complex dielectric spectra of the four FLCs can be optimally fitted by the Debye model and the Cole-Cole model. Moreover, the Goldstone mode was enhanced under low DC bias fields for the FLCs with the (S, R)- diastereomeric structure, whereas the mode was suppressed for the FLCs with the (S, S)- diastereomeric structure. A microscopic molecular dynamic model is proposed to describe the underlying mechanism of the particular enhancement of the Goldstone mode. The experimental results of dielectric spectra and spontaneous polarization are explained in the discussion of the mesomorphic properties related to the FLC molecular structure.

  9. Capacitive Cells for Dielectric Constant Measurement

    ERIC Educational Resources Information Center

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  10. Comparative study of urea and betaine solutions by dielectric spectroscopy: liquid structures of a protein denaturant and stabilizer.

    PubMed

    Hayashi, Yoshihito; Katsumoto, Yoichi; Oshige, Ikuya; Omori, Shinji; Yasuda, Akio

    2007-10-11

    We performed dielectric spectroscopy measurements on aqueous solutions of glycine betaine (N,N,N-trimethylglycine), which is known to be a strong stabilizer of globular proteins, over a wide concentration range (3-62 wt %) and compared the results with our previously published data for aqueous solutions of urea, a representative protein denaturant. The hydration number of betaine (9), calculated on the basis of the reduction in the dielectric relaxation strength of bulk water with addition of betaine, is significantly larger than that of urea (2). Furthermore, the dielectric relaxation time increased with betaine concentration, while that remained nearly constant for the urea-water system over a wide concentration range. This difference between urea and betaine is probably related to their opposite effects on the protein stabilization. PMID:17877386

  11. Spectroscopic measurements of the electron number density, electron temperature and OH(A) rotational distribution in a liquid electrode dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Krähling, Tobias; Geisler, Sebastian; Okruss, Michael; Florek, Stefan; Franzke, Joachim

    2015-12-01

    The electron temperature and number density as well as the OH(A) rotational distribution of a discharge with flowing liquid electrode and dielectric barrier coupling (a liquid electrode dielectric barrier discharge, LE-DBD) were investigated by means of optical emission spectroscopy. By using the Stark broadening of three Strontium lines, the electron number density Ne and the lower bound of the electron temperature Te can be simultaneously measured. The values obtained were Ne = (0.8 - 1.6) × 1016 cm- 3 and Te > 1.1 eV, respectively. The OH(A) rotational distribution deviates from equilibrium and can be described by a superposition of two Boltzmann distributions with T1 = (3230 ± 90) K for K ' ≤ 15 and T2 = (7300 ± 300) K for K ' ≥ 16. Consideration of the formation mechanisms of OH(A) and reaction rates suggests that the dissociative recombination of H2O+ and H3O+ is responsible for the higher rotational state distribution, where these ions can only be produced in the LE-DBD through an electrospray-like process.

  12. Precision liquid level sensor

    DOEpatents

    Field, M.E.; Sullivan, W.H.

    A precision liquid level sensor utilizes a balanced bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge.

  13. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant

    PubMed Central

    2011-01-01

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  14. Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength

    DOEpatents

    Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary

    2014-06-10

    A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.

  15. Toward Automated Benchmarking of Atomistic Force Fields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive.

    PubMed

    Beauchamp, Kyle A; Behr, Julie M; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-10-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the force field employed. Although experimental measurements of fundamental physical properties offer a straightforward approach for evaluating force field quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark data sets of physical properties from non-machine-readable sources requires substantial human effort and is prone to the accumulation of human errors, hindering the development of reproducible benchmarks of force-field accuracy. Here, we examine the feasibility of benchmarking atomistic force fields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating IUPAC-standard format. As a proof of concept, we present a detailed benchmark of the generalized Amber small-molecule force field (GAFF) using the AM1-BCC charge model against experimental measurements (specifically, bulk liquid densities and static dielectric constants at ambient pressure) automatically extracted from the archive and discuss the extent of data available for use in larger scale (or continuously performed) benchmarks. The results of even this limited initial benchmark highlight a general problem with fixed-charge force fields in the representation low-dielectric environments, such as those seen in binding cavities or biological membranes. PMID:26339862

  16. Radiolysis of liquids with high static dielectric constant: An estimate of the total ionization yield, electron thermalization distance, and contribution of heterogeneous reactions

    SciTech Connect

    Ferradini, C.; Jay-Gerin, J.

    1988-12-01

    In a previous study, we found an exponential dependence of the free-ion yield (G/sub fi/) on the static dielectric constant (epsilon/sub s/) for a number of irradiated liquids with epsilon/sub s/>10. On the basis of this study, we develop here a simple model by which we quantitatively estimate the total ionization yield (G/sub tot/), the most probable electron thermalization distance (b), and the yield of solvated electrons that are removed by diffusion-controlled reactions during spur expansion (G/sub dif/). Using solvated electron yields available in the literature, we get G/sub tot/approx. =6.6 mol/100 eV (value nearly independent of the nature of the liquid) and bapprox. =29 A at 298 K. b is found not to depend appreciably on epsilon/sub s/ which indicates that the Coulomb attractive force between the ion and secondary electron is practically inefficient before electron thermalization occurs. The evaluation of G/sub dif/ teaches us that spur reactions have a profound influence in the fate of ion pairs formed during radiolysis of liquids of high epsilon/sub s/ values.

  17. Liquid phase sintering of 20Bi(Zn0.5Ti0.5)O 3-80BaTiO3 dielectrics with bismuth-zinc-borate and bismuth borosilicate glasses

    NASA Astrophysics Data System (ADS)

    Shahin, David I.

    Dielectrics in the Bi(Zn0.5Ti0.5)O3-BaTiO 3 system (specifically 20BZT-80BT, in mol%) are promising candidates for high energy density capacitor applications due to broad temperature-dependent dielectric constant maxima and a relatively field-independent permittivity. Bulk samples require sintering temperatures of greater than 1180°C to reach useful densities. Due to incompatibility of Bi with low-pO2 processing, BZT-BT-based multilayer capacitors must utilize noble metal electrodes that resist oxidation during sintering. Sintering temperatures must be reduced to allow use of less expensive electrode materials (Cu, etc.). This work studies the reduced temperature sintering behavior and dielectric properties of BZT-BT sintered with 30Bi2O3-30ZnO-40B 2O3 and 50Bi2O3-25B2O 3-25SiO2 (mol%) liquid phase formers. Dielectrics sintered with 1v% borate additions and 5v% additions of either the borate or borosilicate achieved relative densities greater than 95% after sintering at 1000°C for four hours. All compositions retained the relaxor behavior exhibited by pure 20BZT-80BT. Increased borate additions led to greater dielectric constant reductions, while increased borosilicate additions yielded no clear trend in the dielectric constant reduction. Energy densities were estimated between 0.3-0.5 J/cm3; smaller glass additions typically led to larger energy densities. Dielectrics sintered with 1v% borate additions are of interest due to their high relative densities (approx. 96%) and energy densities of approximately 0.5 J/cm3 under 100kV/cm electric fields. Studies of BZT-BT/glass interfaces revealed the formation of crystalline interfacial layers less than 10 microns thick. The borate formed a bismuth titanate phase (likely Bi4Ti3O12) during heating to 700°C, whereas the borosilicate formed a barium silicate phase (likely BaSiO3) during processing to 800°C. Similar phases are expected to be present in the liquid phase sintered dielectrics and likely affect the BZT

  18. Molecular Relaxations in Supercooled Liquid and Glassy States of Amorphous Quinidine: Dielectric Spectroscopy and Density Functional Theory Approaches.

    PubMed

    Schammé, Benjamin; Mignot, Mélanie; Couvrat, Nicolas; Tognetti, Vincent; Joubert, Laurent; Dupray, Valérie; Delbreilh, Laurent; Dargent, Eric; Coquerel, Gérard

    2016-08-01

    In this article, we conduct a comprehensive molecular relaxation study of amorphous Quinidine above and below the glass-transition temperature (Tg) through broadband dielectric relaxation spectroscopy (BDS) experiments and theoretical density functional theory (DFT) calculations, as one major issue with the amorphous state of pharmaceuticals is life expectancy. These techniques enabled us to determine what kind of molecular motions are responsible, or not, for the devitrification of Quinidine. Parameters describing the complex molecular dynamics of amorphous Quinidine, such as Tg, the width of the α relaxation (βKWW), the temperature dependence of α-relaxation times (τα), the fragility index (m), and the apparent activation energy of secondary γ relaxation (Ea-γ), were characterized. Above Tg (> 60 °C), a medium degree of nonexponentiality (βKWW = 0.5) was evidenced. An intermediate value of the fragility index (m = 86) enabled us to consider Quinidine as a glass former of medium fragility. Below Tg (< 60 °C), one well-defined secondary γ relaxation, with an apparent activation energy of Ea-γ = 53.8 kJ/mol, was reported. From theoretical DFT calculations, we identified the most reactive part of Quinidine moieties through exploration of the potential energy surface. We evidenced that the clearly visible γ process has an intramolecular origin coming from the rotation of the CH(OH)C9H14N end group. An excess wing observed in amorphous Quinidine was found to be an unresolved Johari-Goldstein relaxation. These studies were supplemented by sub-Tg experimental evaluations of the life expectancy of amorphous Quinidine by X-ray powder diffraction and differential scanning calorimetry. We show that the difference between Tg and the onset temperature for crystallization, Tc, which is 30 K, is sufficiently large to avoid recrystallization of amorphous Quinidine during 16 months of storage under ambient conditions. PMID:27391029

  19. Dielectric, electro-optical, and photoluminescence characteristics of ferroelectric liquid crystals on a graphene-coated indium tin oxide substrate.

    PubMed

    Singh, Dharmendra Pratap; Gupta, Swadesh Kumar; Vimal, Tripti; Manohar, Rajiv

    2014-08-01

    Multilayer graphene was deposited on indium tin oxide (ITO) -coated glass plates and characterized by suitable techniques. A liquid crystal sample cell was designed using graphene deposited ITO glass plates without any additional treatment for alignment. Ferroelectric liquid crystal (FLC) material was filled in the sample cell. The effect of multilayer graphene on the characteristics of FLC material was investigated. The extremely high relative permittivity of pristine graphene and charge transfer between graphene and FLC material were consequences of the enormous increase in relative permittivity for the graphene-FLC (GFLC) system as compared to pure FLC. The presence of multilayer graphene suppresses the ionic impurities, comprised in the FLC material at lower frequencies. The ionic charge annihilation mechanism might be responsible for the reduction of ionic impurities. The presence of graphene reduces the net ferroelectricity and results in a change in the spontaneous polarization of pure FLC. Rotational viscosity of the GFLC system also decreases due to the strong π-π interaction between the FLC molecule and multilayer graphene. The photoluminescence of the GFLC system is blueshifted as compared to pure FLC, which is due to the coupling of energy released in the process of charge annihilation and photon emission. PMID:25215743

  20. Identification of Structural Relaxation in the Dielectric Response of Water

    NASA Astrophysics Data System (ADS)

    Hansen, Jesper S.; Kisliuk, Alexander; Sokolov, Alexei P.; Gainaru, Catalin

    2016-06-01

    One century ago pioneering dielectric results obtained for water and n -alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results, we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols.

  1. The critical behavior of the dielectric constant in the polar + polar binary liquid mixture nitromethane + 3-pentanol: an unusual sign of its critical amplitude in the one-phase region.

    PubMed

    Leys, Jan; Losada-Pérez, Patricia; Troncoso, Jacobo; Glorieux, Christ; Thoen, Jan

    2011-07-14

    Dielectric constant measurements have been carried out in the one- and two-phase regions near the critical point of the polar + polar binary liquid mixture nitromethane + 3-pentanol. In the two-phase region, evidence for the |t|(2β) singularity in the coexistence-curve diameter has been detected, thus confirming the novel predictions of complete scaling theory for liquid-liquid criticality. In the one-phase region, an "unusual" negative sign for the amplitude of the |t|(1-α) singularity has been encountered for the first time in an upper critical solution temperature type of binary liquid mixture at atmospheric pressure. Mass density measurements have also been carried out to provide additional information related to such experimental finding, which entails an increase of the critical temperature T(c) under an electric field. PMID:21766958

  2. Effect of high hydrostatic pressure on the dielectric relaxation in a non-crystallizable monohydroxy alcohol in its supercooled liquid and glassy states

    NASA Astrophysics Data System (ADS)

    Pawlus, S.; Paluch, M.; Nagaraj, M.; Vij, J. K.

    2011-08-01

    The complex relative permittivity of a non-crystallizable secondary alcohol, 5-methyl-2-hexanol, is measured over a wide range of temperatures and pressures up to 1750 MPa (17.5 kbar). The data at atmospheric pressure (P = 0.101 MPa) are analyzed in terms of three processes, and the results are in complete agreement with that of O. E. Kalinovskaya and J. K. Vij [J. Chem. Phys. 112, 3262 (2000)]. Process I is of the Debye type and process II is of the Davidson-Cole type, whereas process III is identified as the Johari-Goldstein relaxation process. For pressures of ˜500 MPa and higher, processes I and II are seen to merge into each other to form a single dominant process which unambiguously cannot be resolved into more than one process. The dielectric relaxation strength of process I decreases slightly initially with pressure and when the two processes have merged at elevated pressures, the total relaxation strength increases with increase in pressure. Process III is better resolvable at higher pressures especially above Tg in the supercooled liquid state for the reason that the separation in the time scales between the dominant and the JG relaxation process increases at elevated pressures. Surprisingly we find a change in the slope in the plot of log τJG vs. 1/T for P = 1750 MPa. The results for the relaxation time of alcohols are compared with the Kirkwood correlation factor, g, and it is found that higher is the g, lower is the relaxation time for process I, and it is more of the Debye type. On a reduction in g brought about by an increase in pressure at lower temperatures, the dominant process becomes non-Debye though extensive hydrogen bonding is still present. The dielectric strength of the merged processes increases with increase in pressure. The values of the steepness index, m = |d log τ/d(Tg/T)|T = Tg for processes I and II are different for P = 0.1 MPa. However the value of m, for the composite process, which is a merger of processes I and II, for P

  3. Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

    SciTech Connect

    Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof

    2015-12-31

    A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities.

  4. Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof

    2015-12-01

    A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities.

  5. Electrode/Dielectric Strip For High-Energy-Density Capacitor

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S.

    1994-01-01

    Improved unitary electrode/dielectric strip serves as winding in high-energy-density capacitor in pulsed power supply. Offers combination of qualities essential for high energy density: high permittivity of dielectric layers, thinness, and high resistance to breakdown of dielectric at high electric fields. Capacitors with strip material not impregnated with liquid.

  6. Simultaneous testing of multiclass organic contaminants in food and environment by liquid chromatography/dielectric barrier discharge ionization-mass spectrometry.

    PubMed

    Gilbert-López, Bienvenida; García-Reyes, Juan F; Meyer, Cordula; Michels, Antje; Franzke, Joachim; Molina-Díaz, Antonio; Hayen, Heiko

    2012-11-21

    A Dielectric Barrier Discharge Ionization (DBDI) LC/MS interface is based on the use of a low-temperature helium plasma, which features the possibility of simultaneous ionization of species with a wide variety of physicochemical properties. In this work, the performance of LC/DBDI-MS for trace analysis of highly relevant species in food and environment has been examined. Over 75 relevant species including multiclass priority organic contaminants and residues such as pesticides, polycyclic aromatic hydrocarbons, organochlorine species, pharmaceuticals, personal care products, and drugs of abuse were tested. LC/DBDI-MS performance for this application was assessed and compared with standard LC/MS sources (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)). The used benchtop Orbitrap mass spectrometer features a 10 Hz polarity switching mode, so that both positive and negative ion mode acquisitions are possible with acquisition cycles matching the requirements of fast liquid chromatography. Both polar and nonpolar species (including those typically analyzed by GC/electron ionization-MS) can be tested in a single run using polarity switching mode. The methodology was found to be effective in detecting a wide array of organic compounds at concentration levels in the low ng L(-1) to μg kg(-1) range in wastewater and food matrices, respectively. The linearity was evaluated in an olive oil extract, obtaining good correlation coefficients in the studied range. Additionally, minor matrix effects (≤15% of signal suppression or enhancement) were observed for most of the studied analytes in this complex fatty matrix. The results obtained were compared with data from both ESI and APCI sources, obtaining a merged coverage between ESI and APCI in terms of analyte ionization and higher overall sensitivity for the proposed ion source based on the DBD principle. The use of this approach further extends the coverage of current LC/MS methods towards

  7. Renewable liquid reflecting zone plate

    DOEpatents

    Toor, Arthur; Ryutov, Dmitri D.

    2003-12-09

    A renewable liquid reflecting zone plate. Electrodes are operatively connected to a dielectric liquid in a circular or other arrangement to produce a reflecting zone plate. A system for renewing the liquid uses a penetrable substrate.

  8. Precision liquid level sensor

    DOEpatents

    Field, M.E.; Sullivan, W.H.

    1985-01-29

    A precision liquid level sensor utilizes a balanced R. F. bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge. 2 figs.

  9. Precision liquid level sensor

    DOEpatents

    Field, Michael E.; Sullivan, William H.

    1985-01-01

    A precision liquid level sensor utilizes a balanced R. F. bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge.

  10. Natural convection immersion cooling of an array of vertically oriented heated protrusions in an enclosure filled with a dielectric liquid: Effects of enclosure width, Prandtl number and component orientation

    NASA Astrophysics Data System (ADS)

    Matthews, Scott T.

    1991-12-01

    The natural convection heat transfer characteristics of a 3 x 3 array of vertically oriented heated protrusions, immersed in a dielectric liquid, were investigated. Aluminum blocks, 24 x 8 x 6 mm, were used to simulate 20 pin dual in-line packages. Surface temperature measurements of the components were made by imbedding copper-constantan thermocouples below the surface of each component face. A constant heat flux was provided to each component using an Inconel foil heating element. Power supplied to each component varied from 0.115 to 2.90 W. The aluminum blocks were mounted on a plexiglass substrate to form a 3 x 3 array of simulated electronic components. The circuit board containing the components was placed in a rectangular, plexiglass enclosure with inner dimensions: L = 203.2 mm H = 152.0 mm W = 82.6 mm, and a wall thickness of 25.4 mm. The upper boundary was maintained at 10 C, while all other exterior surfaces were insulated. The chamber width, measured from the surface of the circuit board to the opposite, inner wall of the enclosure, was varied from 42 to 7 mm by inserting plexiglass spacers into the enclosure. Two dielectric liquids, FC-75 and FC-43, were used as working fluids. Nondimensional data from this study was combined with the data obtained for a horizontal component orientation, to develop an empirical correlation which predicts the Nusselt number as a function of Rayleigh number, Prandtl number, component orientation, and chamber width.

  11. High voltage research (breakdown strengths of gaseous and liquid insulators) and environmental effects of dielectric gases. Semiannual report, October 1, 1979-March 31, 1980

    SciTech Connect

    Christophorou, L.G.; James, D.R.; Pai, R.Y.

    1980-08-01

    Topics covered include basic studies of gaseous dielectrics, direct current breakdown strengths of gases/mixtures, environmental effects studies and decomposition analyses, impulse studies, breakdown strengths of binary mixtures with concentric cylinder geometry, and a discussion of the experimental apparatus. (GHT)

  12. A simple method for reducing inevitable dielectric loss in high-permittivity dielectric elastomers

    NASA Astrophysics Data System (ADS)

    Madsen, F. B.; Yu, L.; Mazurek, P.; Skov, A. L.

    2016-07-01

    Commercial viability of dielectric elastomers (DEs) is currently limited by a few obstacles, including high driving voltages (in the kV range). Driving voltage can be lowered by either decreasing the Young’s modulus or increasing the dielectric permittivity of silicone elastomers, or a combination thereof. A decrease in the Young’s modulus, however, is often accompanied by a loss in mechanical stability, whereas increases in dielectric permittivity are usually followed by a large increase in dielectric loss followed by a decrease in breakdown strength and thereby the lifetime of the DE. A new soft elastomer matrix, with high dielectric permittivity and a low Young’s modulus, aligned with no loss of mechanical stability, was prepared through the use of commercially available chloropropyl-functional silicone oil mixed into a tough commercial liquid silicone rubber silicone elastomer. The addition of chloropropyl-functional silicone oil in concentrations up to 30 phr was found to improve the properties of the silicone elastomer significantly, as dielectric permittivity increased to 4.4, dielectric breakdown increased up to 25% and dielectric losses were reduced. The chloropropyl-functional silicone oil also decreased the dielectric losses of an elastomer containing dielectric permittivity-enhancing TiO2 fillers. Commercially available chloropropyl-functional silicone oil thus constitutes a facile method for improved silicone DEs, with very low dielectric losses.

  13. Identification of Structural Relaxation in the Dielectric Response of Water.

    PubMed

    Hansen, Jesper S; Kisliuk, Alexander; Sokolov, Alexei P; Gainaru, Catalin

    2016-06-10

    One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results, we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols. PMID:27341258

  14. Asymmetric Dielectric Elastomer Composite Material

    NASA Technical Reports Server (NTRS)

    Stewart, Brian K. (Inventor)

    2014-01-01

    Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

  15. Dielectric Relaxation of Hexadeutero Dimethylsulfoxide

    NASA Astrophysics Data System (ADS)

    Betting, H.; Stockhausen, M.

    1999-11-01

    The dielectric relaxation parameters of the title substance (DMSO-d6) in its pure liquid state are determined from meas-urements up to 72 GHz at 20°C in comparison to protonated DMSO. While the relaxation strengths do not differ, the relax-ation time of DMSO-d 6 is significantly longer (21.3 ps) than that of DMSO (19.5 ps).

  16. Renewable liquid reflection grating

    DOEpatents

    Ryutov, Dmitri D.; Toor, Arthur

    2003-10-07

    A renewable liquid reflection grating. Electrodes are operatively connected to a conducting liquid in an arrangement that produces a reflection grating and driven by a current with a resonance frequency. In another embodiment, the electrodes create the grating by a resonant electrostatic force acting on a dielectric liquid.

  17. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    NASA Astrophysics Data System (ADS)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  18. Dielectric anisotropy in polar solvents under external fields

    NASA Astrophysics Data System (ADS)

    Buyukdagli, Sahin

    2015-08-01

    We investigate dielectric saturation and increment in polar liquids under external fields. We couple a previously introduced dipolar solvent model to a uniform electric field and derive the electrostatic kernel of interacting dipoles. This procedure allows an unambiguous definition of the liquid dielectric permittivity embodying non-linear dielectric response and correlation effects. We find that the presence of the external field results in a dielectric anisotropy characterized by a two-component dielectric permittivity tensor. The increase of the electric field amplifies the permittivity component parallel to the field direction, i.e. dielectric increment is observed along the field. However, the perpendicular component is lowered below the physiological permittivity {{\\varepsilon}w}≈ 77 , indicating dielectric saturation perpendicular to the field. By comparison with Molecular Dynamics simulations from the literature, we show that the mean-field level dielectric response theory underestimates dielectric saturation. The inclusion of dipolar correlations at the weak-coupling level intensify the mean-field level dielectric saturation and improves the agreement with simulation data at weak electric fields. The correlation-corrected theory predicts as well the presence of a metastable configuration corresponding to the antiparallel alignment of dipoles with the field. This prediction can be verified by solvent-explicit simulations where solvent molecules are expected to be trapped transiently in this metastable state.

  19. Dielectric constant, dielectric virial coefficients, and dipole moments of 1,1,1,2-tetrafluoroethane

    SciTech Connect

    Barao, T.; Castro, C.A.N. de; Mardolcar, U.V.; Okambawa, R.; St-Arnaud, J.M.

    1995-11-01

    In this paper the authors report measurements of the dielectric constant of 1,1,1,2-tetrafluoroethane, HFC-134a, an environmentally acceptable refrigerant, under consideration as an alternative replacement of the chlorofluorocarbons, CFCs. The dipole moment in the gaseous phase was found to be (1.91 {+-} 0.19) D, and in the liquid phase (3.54 {+-} 0.01) D. The authors present values of the first three dielectric virial coefficients in the gaseous phase.

  20. Rheo-Dielectric Behavior of Soft Matters

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroshi; Matsumiya, Yumi; Horio, Kazushi; Masubuchi, Yuichi; Uneyama, Takashi

    2012-02-01

    Soft matters are highly susceptible to fast flow without exhibiting macroscopic rupture, and the constituent elements therein can be readily brought into a non-equilibrium state. The dynamics of these elements in this state can be detected with the dielectric method rather easily if the elements have electrical dipoles (and/or net charge). Thus, the rheo-dielectric behavior of the soft matters, detected with a weak electric field superimposed on the flow field, provides us with interesting information for the non-equilibrium dynamics of the constituent elements. This chapter presents a brief summary of the rheo-dielectric behavior of polymers, liquid crystals, and composites to demonstrate the similarities/differences of these materials as well as the usefulness of the rheo-dielectric method

  1. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    NASA Astrophysics Data System (ADS)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  2. Dielectric and phase behavior of dipolar spheroids.

    PubMed

    Johnson, Lewis E; Benight, Stephanie J; Barnes, Robin; Robinson, Bruce H

    2015-04-23

    The Stockmayer fluid, composed of dipolar spheres, has a well-known isotropic-ferroelectric phase transition at high dipole densities. However, there has been little investigation of the ferroelectric transition in nearly spherical fluids at dipole densities corresponding to those found in many polar solvents and in guest-host organic electro-optic materials. In this work, we examine the transition to ordered phases of low-aspect-ratio spheroids under both unperturbed and poled conditions, characterizing both the static dielectric response and thermodynamic properties of spheroidal systems. Spontaneous ferroelectric ordering was confined to a small region of aspect ratios about unity, indicating that subtle changes in sterics can have substantial influence on the behavior of coarse-grained liquid models. Our results demonstrate the importance of molecular shape in obtaining even qualitatively correct dielectric responses and provide an explanation for the success of the Onsager model as a phenomenological representation for the dielectric behavior of polar organic liquids. PMID:25821921

  3. Dielectric strength of sulfur hexafluoride upon condensation

    SciTech Connect

    Antonov, A.V.; Lyapin, A.G.; Popkov, V.I.

    1983-01-01

    The behavior of sulfur hexafluoride in a sealed high-voltage device has been modeled for cooling to the condensation point of the insulating medium. The temperature dependences of the breakdown voltages of sulfur hexafluoride have been investigated for several interelectrode separations. The dielectric strength has been shown to decrease upon condensation with formation of a bridge of boiling liquid phase between the electrodes.

  4. Polyimide thin-film dielectrics on ferroelectrics

    NASA Technical Reports Server (NTRS)

    Galiardi, R. V.

    1977-01-01

    Conducting layers of multi-layered thin-film ferroelectric device, such as is used in liquid crystal/ferroelectric display, can be electrically isolated using thin-film layer of polyimide. Ease of application and high electrical-breakdown strength allow dependable and economical means of providing dielectric for other thin-film microelectronic devices.

  5. Detection of Hazardous Liquids Using Microwaves

    PubMed Central

    Janezic, Michael D; Splett, Jolene D; Coakley, Kevin J

    2014-01-01

    We investigate the feasibility of using dielectric spectra to classify hazardous and nonhazardous liquids. The dielectric spectra of several liquids was obtained with a shielded-open coaxial fixture, and we present a new full-wave model for calculating the complex permittivity of liquids using this fixture. Using the measured complex permittivity for each liquid, we examine several classification methods for distinguishing between the hazardous and nonhazardous liquids and report on the error rates of each method. PMID:26601031

  6. Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

    NASA Astrophysics Data System (ADS)

    Semaltianos, N. G.; Friedt, J.-M.; Chassagnon, R.; Moutarlier, V.; Blondeau-Patissier, V.; Combe, G.; Assoul, M.; Monteil, G.

    2016-05-01

    Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO2) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3-5.3 nm. Nanoparticles synthesized in DI water have band gaps of 5.6 and 5.4 eV, in ethanol 5.72 and 5.65 eV (using low and high pulse energy), and in toluene 3 eV. The values for the relative permittivity in the range of 7.74-8.90 were measured for hafnia nanoparticles' thin films deposited on substrates by drop-casting (self-assembled layers) in parallel plate capacitor structures.

  7. Ion distributions in electrolyte confined by multiple dielectric interfaces

    NASA Astrophysics Data System (ADS)

    Jing, Yufei; Zwanikken, Jos W.; Jadhao, Vikram; de La Cruz, Monica

    2014-03-01

    The distribution of ions at dielectric interfaces between liquids characterized by different dielectric permittivities is crucial to nanoscale assembly processes in many biological and synthetic materials such as cell membranes, colloids and oil-water emulsions. The knowledge of ionic structure of these systems is also exploited in energy storage devices such as double-layer super-capacitors. The presence of multiple dielectric interfaces often complicates computing the desired ionic distributions via simulations or theory. Here, we use coarse-grained models to compute the ionic distributions in a system of electrolyte confined by two planar dielectric interfaces using Car-Parrinello molecular dynamics simulations and liquid state theory. We compute the density profiles for various electrolyte concentrations, stoichiometric ratios and dielectric contrasts. The explanations for the trends in these profiles and discuss their effects on the behavior of the confined charged fluid are also presented.

  8. Dielectric Barrier Discharge Methane Conversion

    NASA Astrophysics Data System (ADS)

    Liu, Chong; Fridman, Alexander; Rabinovich, Alexander; Dobrynin, Danil

    2015-09-01

    With the large amount of nature gas discovery every year, there is an increasing interest on modification of methane. The fact that methane is gaseous makes it less economic and efficient than liquid fuel. Here we propose a new way of converting methane from gas phase to liquid phase. Dielectric barrier discharge is used to treat methane and nitrogen mixture bubbles inside of liquid fuel. Nitrogen is here to help activate methane into an excited state, then it is possible for the excited molecules to react with other liquid hydrocarbon. Gaseous methane is converted in to liquid phase when excited methane replace a hydrogen and add onto the carbon chain. In this study some preliminary experiments is done to verify this hypothesis. There is equivalent weight increases with methane and nitrogen mixture discharging in diesel when compare to only nitrogen discharging in diesel. The same experiment have also been done with gas mixture discharged in 1-methylnaphthalene. And FTIR analysis of the after treatment hydrocarbon liquid all indicates that there is an increasing in C-H bond concentration and a decreasing in phenyl ring structure.

  9. Determination of two-liquid mixture composition by assessing its dielectric parameters 2. modified measuring system for monitoring the dehydration process of bioethanol production

    NASA Astrophysics Data System (ADS)

    Vilitis, O.; Shipkovs, P.; Merkulovs, D.; Rucins, A.; Zihmane-Ritina, K.; Bremers, G.

    2014-02-01

    In Part 2 of the work we describe a modified measuring system for precise monitoring of the dehydration process of bioethanol production. This is based on the earlier proposed system for measuring the concentration of solutions and two-liquid mixtures using devices with capacitive sensors (1-300pF), which provides a stable measuring resolution of ± 0.005 pF at measuring the capacitance of a sensor. In this part of our work we determine additional requirements that are to be imposed on the measuring system at monitoring the ethanol dehydration process and control of bioethanol production. The most important parameters of the developed measuring system are identified. An exemplary calculation is given for the thermocompensated calibration of measuring devices. The results of tests have shown a good performance of the developed measuring system.

  10. Method for producing high dielectric strength microvalves

    SciTech Connect

    Kirby, Brian J.; Reichmuth, David S.; Shepodd, Timothy J.

    2006-04-04

    A microvalve having a cast-in-place and lithographically shaped mobile, polymer monolith for fluid flow control in microfluidic devices and method of manufacture. The microvalve contains a porous fluorinated polymer monolithic element whose pores are filled with an electrically insulating, high dielectric strength fluid, typically a perfluorinated liquid. This combination provides a microvalve that combines high dielectric strength with extremely low electrical conductivity. These microvalves have been shown to have resistivities of at least 100 G.OMEGA. and are compatible with solvents such as water at a pH between 2.7 and 9.0, 1-1 propanol, acetonitrile, and acetone.

  11. Resonant dielectric metamaterials

    SciTech Connect

    Loui, Hung; Carroll, James; Clem, Paul G; Sinclair, Michael B

    2014-12-02

    A resonant dielectric metamaterial comprises a first and a second set of dielectric scattering particles (e.g., spheres) having different permittivities arranged in a cubic array. The array can be an ordered or randomized array of particles. The resonant dielectric metamaterials are low-loss 3D isotropic materials with negative permittivity and permeability. Such isotropic double negative materials offer polarization and direction independent electromagnetic wave propagation.

  12. Dielectrically loaded horns

    NASA Astrophysics Data System (ADS)

    Tun, S. M.; Bustamante, R.; Williams, N.

    Dielectrically loaded horns have been proposed as alternatives to conical corrugated horns in high-performance primary feeds in virtue both of their lower cost and theoretical indications of superior operational bandwidth performance, while retaining circularly symmetric radiation, low sidelobes, and low cross-polarization. A prototype dielectric core-loaded horn, and a dual-band transmit/receive horn antenna incorporating a dielectric rod inside a small corrugated horn, have been developed and tested; the dielectric used for the rod is Rexolite. The high performance obtainable by this inexpensive technology has been experimentally demonstrated.

  13. Millimeter wave and terahertz dielectric properties of biological materials

    NASA Astrophysics Data System (ADS)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  14. A spherical cavity model for quadrupolar dielectrics.

    PubMed

    Dimitrova, Iglika M; Slavchov, Radomir I; Ivanov, Tzanko; Mosbach, Sebastian

    2016-03-21

    The dielectric properties of a fluid composed of molecules possessing both dipole and quadrupole moments are studied based on a model of the Onsager type (molecule in the centre of a spherical cavity). The dielectric permittivity ε and the macroscopic quadrupole polarizability αQ of the fluid are related to the basic molecular characteristics (molecular dipole, polarizability, quadrupole, quadrupolarizability). The effect of αQ is to increase the reaction field, to bring forth reaction field gradient, to decrease the cavity field, and to bring forth cavity field gradient. The effects from the quadrupole terms are significant in the case of small cavity size in a non-polar liquid. The quadrupoles in the medium are shown to have a small but measurable effect on the dielectric permittivity of several liquids (Ar, Kr, Xe, CH4, N2, CO2, CS2, C6H6, H2O, CH3OH). The theory is used to calculate the macroscopic quadrupolarizabilities of these fluids as functions of pressure and temperature. The cavity radii are also determined for these liquids, and it is shown that they are functions of density only. This extension of Onsager's theory will be important for non-polar solutions (fuel, crude oil, liquid CO2), especially at increased pressures. PMID:27004882

  15. A spherical cavity model for quadrupolar dielectrics

    NASA Astrophysics Data System (ADS)

    Dimitrova, Iglika M.; Slavchov, Radomir I.; Ivanov, Tzanko; Mosbach, Sebastian

    2016-03-01

    The dielectric properties of a fluid composed of molecules possessing both dipole and quadrupole moments are studied based on a model of the Onsager type (molecule in the centre of a spherical cavity). The dielectric permittivity ɛ and the macroscopic quadrupole polarizability αQ of the fluid are related to the basic molecular characteristics (molecular dipole, polarizability, quadrupole, quadrupolarizability). The effect of αQ is to increase the reaction field, to bring forth reaction field gradient, to decrease the cavity field, and to bring forth cavity field gradient. The effects from the quadrupole terms are significant in the case of small cavity size in a non-polar liquid. The quadrupoles in the medium are shown to have a small but measurable effect on the dielectric permittivity of several liquids (Ar, Kr, Xe, CH4, N2, CO2, CS2, C6H6, H2O, CH3OH). The theory is used to calculate the macroscopic quadrupolarizabilities of these fluids as functions of pressure and temperature. The cavity radii are also determined for these liquids, and it is shown that they are functions of density only. This extension of Onsager's theory will be important for non-polar solutions (fuel, crude oil, liquid CO2), especially at increased pressures.

  16. Gaseous dielectrics V

    SciTech Connect

    Christophorou, L.G.; Bouldin, D.W.

    1987-01-01

    This symposium represents a transdisciplinary and comprehensive approach to the study of gaseous dielectrics. The goal of the symposium was to demonstrate the effective coupling between basic and applied research and modern technology achieved in this area, and to guide future research and development and industrial use of gaseous dielectrics. Separate abstracts were prepared for 85 papers in these proceedings. (DWL)

  17. Terahertz Artificial Dielectric Lens

    NASA Astrophysics Data System (ADS)

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M.

    2016-03-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices.

  18. Terahertz Artificial Dielectric Lens.

    PubMed

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M

    2016-01-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices. PMID:26973294

  19. Composite dielectric waveguides

    NASA Astrophysics Data System (ADS)

    Yamashita, E.; Atsuki, K.; Kuzuya, R.

    1980-09-01

    The modal analysis of a composite circular dielectric waveguide (CCDW) is presented. Computed values of the propagation constant of a CCDW are compared with those of the homogeneous circular dielectric waveguides (HCDW). Microwave experiments concerning the propagation constant of a CCDW of Teflon and Rexolite are described.

  20. Terahertz Artificial Dielectric Lens

    PubMed Central

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M.

    2016-01-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices. PMID:26973294

  1. A microfabricated sensor for thin dielectric layers.

    PubMed

    Fierlinger, P; DeVoe, R; Flatt, B; Gratta, G; Green, M; Kolkowitz, S; Leport, F; Montero Diez, M; Neilson, R; O'Sullivan, K; Pocar, A; Wodin, J

    2008-04-01

    We describe a sensor for the measurement of thin dielectric layers capable of operation in a variety of environments. The sensor is obtained by microfabricating a capacitor with interleaved aluminum fingers, exposed to the dielectric to be measured. In particular, the device can measure thin layers of solid frozen from a liquid or gaseous medium. Sensitivity to single atomic layers is achievable in many configurations and, by utilizing fast, high sensitivity capacitance readout in a feedback system onto environmental parameters; coatings of few layers can be dynamically maintained. We discuss the design, readout, and calibration of several versions of the device optimized in different ways. We specifically dwell on the case in which atomically thin solid xenon layers are grown and stabilized, in cryogenic conditions, from a liquid xenon bath. PMID:18447546

  2. Nonlinear dielectric effect in supercritical diethyl ether

    NASA Astrophysics Data System (ADS)

    Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J.; Martinez-Garcia, Julio Cesar

    2014-09-01

    Nonlinear dielectric effect (NDE) describes changes of dielectric permittivity induced by a strong electric field in a liquid dielectric. The most classical finding related to this magnitude is the negative sign of NDE in liquid diethyl ether (DEE), recalled by Peter Debye in his Nobel Prize lecture. This article shows that the positive sign of NDE in DEE is also possible, in the supercritical domain. Moreover, NDE on approaching the gas-liquid critical point exhibits a unique critical effect described by the critical exponent ψ ≈ 0.4 close to critical temperature (TC) and ψ ≈ 0.6 remote from TC. This can be linked to the emergence of the mean-field behavior in the immediate vicinity of TC, contrary to the typical pattern observed for critical phenomena. The multi-frequency mode of NDE measurements made it possible to estimate the evolution of lifetime of critical fluctuations. The new way of data analysis made it possible to describe the critical effect without a knowledge of the non-critical background contribution in prior.

  3. Dielectric properties of KDP filled porous alumina nanocomposite thin films.

    PubMed

    Boni, O; Berger, S

    2001-12-01

    A new concept of a composite dielectric thin film fabrication is presented. The fabrication process consists of two stages. The first stage is anodizing a thin aluminum film to produce a porous alumina film that contains an array of nanometer sized parallel pores. The second stage is filling the pores with a saturated KDP (KH2PO4) liquid solution due to capillary forces. After drying KDP nanocrystals are formed inside the pores. This process results in a formation of a composite dielectric thin film composed of the alumina pores walls as one dielectric material and the KDP nanocrystals inside the pores as another dielectric material. The dielectric permittivity of this composite film is higher than that of the porous alumina film at all applied frequencies. The dielectric enhancement is more pronounced at low frequencies due to an interface polarization mechanism. This fabrication process enables controlling the size, composition, and microstructure of the composite dielectric film constituents and thus changing its dielectric properties over a wide range of values. PMID:12914085

  4. Cast dielectric composite linear accelerator

    DOEpatents

    Sanders, David M.; Sampayan, Stephen; Slenes, Kirk; Stoller, H. M.

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  5. Metal-dielectric interactions

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1979-01-01

    There is a wide variety of situations wherein metals are in solid state contact with dielectric materials. The paper reviews some of the factors that influence solid state interactions for metals in contact with dielectric surfaces. Since surfaces play an important part in these reactions, the use of analytical tools in characterizing surfaces is discussed. Adhesion, friction, and wear are utilized as indicators of the nature of interfacial bonding between metals and dielectrics can be effectively determined with adhesion and friction force measurements. Films present on the surface, such as oxygen or water vapor, markedly alter adhesive bond strength which in turn affects friction force and interfacial fracture when attempts are made to separate the contact regions. Analytical surface tools such as the field ion microscope, Auger emission spectroscopy, and X-ray photoelectron spectroscopy are very effective in providing insight into the effect of contact on the surfaces of metals and dielectrics.

  6. Ionic structure in electrolyte confined by dielectric interfaces

    NASA Astrophysics Data System (ADS)

    Jing, Yufei; Jadhao, Vikram; Zwanikken, Jos W.; Olvera de La Cruz, Monica

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials. To model these systems, both the macromolecules and the surrounding solvent are treated as continuous media characterized with different dielectric permittivities. As the macromolecule-liquid boundary is modeled as a dielectric interface, an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. We compute the ionic structure in a model system of electrolyte confined by two planar dielectric interfaces using molecular dynamics simulations and liquid state theory. We give a comprehensive description of the effects of high electrolyte concentrations, multivalent ions, dielectric contrasts, and external electric field on the ionic distributions. We observe novel features in ionic structure near polarizable/unpolarizable macromolecules which is attributed to the competition between electrostatic and steric (entropic) interactions. We argue that the combined effect of ionic correlations and inhomogeneous dielectric permittivity significantly changes the character of the effective interaction between the two macromolecules.

  7. Aperture excited dielectric antennas

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

    1974-01-01

    The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

  8. Dielectric spectroscopy in agrophysics

    NASA Astrophysics Data System (ADS)

    Skierucha, W.; Wilczek, A.; Szypłowska, A.

    2012-04-01

    The paper presents scientific foundation and some examples of agrophysical applications of dielectric spectroscopy techniques. The aim of agrophysics is to apply physical methods and techniques for studies of materials and processes which occur in agriculture. Dielectric spectroscopy, which describes the dielectric properties of a sample as a function of frequency, may be successfully used for examinations of properties of various materials. Possible test materials may include agrophysical objects such as soil, fruit, vegetables, intermediate and final products of the food industry, grain, oils, etc. Dielectric spectroscopy techniques enable non-destructive and non-invasive measurements of the agricultural materials, therefore providing tools for rapid evaluation of their water content and quality. There is a limited number of research in the field of dielectric spectroscopy of agricultural objects, which is caused by the relatively high cost of the respective measurement equipment. With the fast development of modern technology, especially in high frequency applications, dielectric spectroscopy has great potential of expansion in agrophysics, both in cognitive and utilitarian aspects.

  9. Novel Materials with Effective Super Dielectric Constants for Energy Storage

    NASA Astrophysics Data System (ADS)

    Cortes, Francisco Javier Quintero; Phillips, Jonathan

    2015-05-01

    To test a theory of the recently discovered phenomenon of super dielectric behavior at very low frequency, the dielectric constants of several `pastes', composed of porous alumina powders filled to the point of incipient wetness with water containing dissolved sodium chloride, were measured. The effective dielectric low frequency constants of some of the pastes were greater than 1010, dramatically higher than that of any material ever reported. Moreover, the total energy density reported for one capacitor generated with NaCl-based super dielectric material is marginally higher than found in any prior report. These results are consistent with this recently postulated model of low frequency super dielectric behavior in porous, non-conductive materials saturated with ion-containing liquids: upon the application of an electric field, ions dissolved in the saturating liquid contained in the pores will travel to the ends of pore-filling liquid droplets creating giant dipoles. The fields of these giant dipoles oppose the applied field, reducing the net field created per unit of charge on the capacitor plates, effectively increasing charge/voltage ratio, hence capacitance. This is simply a version of the theory of `polarizable media' found in most classic texts on electromagnetism. Other observations reported here include (1) the impact of ion concentration on dielectric values, (2) a maximum voltage similar to that associated with the electrical breakdown of water, (3) the loss of capacitance upon drying, (4) the recovery of capacitance upon the addition of water to a dry super dielectric material, and (5) the linear relationship between capacitance and inverse thickness. All observations are consistent with the earlier proposed model of the super dielectric phenomenon. An extrapolation of results suggests this technology can lead to energy density greater than the best lithium-ion battery.

  10. Conference on electrical insulation and dielectric phenomena (Annual Report)

    SciTech Connect

    Not Available

    1985-01-01

    This book presents the papers discussed at the Annual Report, 1985 Conference on Dielectric Phenomena and Electrical Insulation. The topics covered at the conference were: a study of streamer initiation in liquid hydrocarbons; simulation and verification of transient EHD motion, effects of hydrostatic pressure on the prebreakdown phenomena in dielectric liquids; measurements of surface changes on the barrier and their effects on the oil gap breakdown; space change and ionic conduction in transformer oil; high voltage engineering in space; design of solid insulation systems; and future of high voltage transmission. This description provides only a partial list of the contents.