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Sample records for static dielectric properties

  1. Static dielectric properties of the Stockmayer fluid from computer simulation

    NASA Astrophysics Data System (ADS)

    Adams, D. J.; Adams, E. M.

    A number of summation methods for simulating polar liquids are compared using the Stockmayer potential fluid. The nearest image convention is found to have thermodynamic properties dependent on the cell shape. Spherical truncation and a summation proposed by Smith and Perram give reasonable agreement with the thermodynamic properties found from other methods but are not suitable for determining dielectric properties. The reaction field and Ewald-Kornfeld summation methods are in close agreement on the thermodynamic properties and have some measure of agreement on dielectric properties. However, the correlation function hΔ(r) clearly shows the effect of the truncation of the direct dipole-dipole interaction. It is concluded that an Ewald summation is the most appropriate method for simulating polar liquids. Thermodynamic and static dielectric properties of the Stockmayer fluid, determined from Monte Carlo and molecular dynamics calculations using the Ewald-Kornfeld summation, are presented. Calculations with large applied fields have been made to study dielectric saturation. The local field is examined in some detail and a distinction is made between Onsager's analysis of the local field into two components, which is supported by the present results, and Onsager's model for polar liquids which provides values for these components that do not agree well with the present results.

  2. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions.

    PubMed

    Kumar, P; Coronel, P; Simunovic, J; Truong, V D; Sandeep, K P

    2007-05-01

    Continuous flow microwave sterilization is an emerging technology that has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temperature range of 20 to 130 degrees C and compared with those measured by the conventional approach (under static conditions). The food products chosen for this study were skim milk, green pea puree, carrot puree, and salsa con queso. Second-order polynomial correlations for the dependence of dielectric properties at 915 MHz of the food products on temperature were developed. Dielectric properties measured under static and continuous flow conditions were similar for homogeneous food products such as skim milk and vegetable puree, but they were significantly different for salsa con queso, which is a multiphase food product. The results from this study suggest that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system.

  3. Static and dynamic dielectric properties of 6-OCB and 8-OCB

    NASA Astrophysics Data System (ADS)

    Czerkas, Susan; Burczyk, A.; Czechowski, Grzegorz; Jadzyn, Jan

    1999-12-01

    Static electric permittivity and dielectric relaxation have been measured in isotropic and nematic phase of 6-OCB and 8- OCB. On the basis of the temperature dependence of the principal static permittivities of nematics, (epsilon) (parallel)(T) and (epsilon) (perpendicular)(T), using the Maier-Meier equations, the following quantities have been obtained: i) the angle between the dipole moment vector and the long axis of mesogenic molecules, ii) the molecule apparent dipole moment square (mu) 2app(T) and iii) the nematic order parameter S(T). From the temperature dependence of the dielectric relaxation time, the activation energy for the molecular rotation around the short axis has been calculated and, taking into account the viscosity data, the effective dimensions of the nematogen molecules have been evaluated.

  4. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous flow microwave sterilization is an emerging technology which has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temp...

  5. Dielectric properties of SPC/E and TIP4P under the static electric field and microwave field

    NASA Astrophysics Data System (ADS)

    Li, Di; Jia, Guo-zhu

    2016-05-01

    Nonequilibrium molecular dynamics simulations of the SPC/E and TIP4P models have been performed both in the absence and presence of the static electric field (0-3×109 V/m) and the microwave field (2.45 G, 0-3×109 V/m). The radial distribution function, dielectric constant, polarizability, dielectric relaxation time, hydrogen bonding and diffusion coefficient were investigated. Significant alteration in the static electric field has effect on the tetrahedral structure of water; the interaction between microwave and water depends on the hydrogen bonding. The 3×107 V/m is threshold intensity, as the intensity of the static electric field increases the decline of the dielectric constant becomes more pronounced, and the polarizability obviously increased with the increase of microwave field. And the life of hydrogen bonding is oscillatory under the high static electric field strength.

  6. Static and dynamic effects of chirality in dielectric media

    NASA Astrophysics Data System (ADS)

    Lakes, R. S.

    2016-09-01

    Chiral dielectrics are considered from the perspective of continuum representations of spatial heterogeneity. Static effects in isotropic chiral dielectrics are predicted, provided the electric field has nonzero third spatial derivatives. The effects are compared with static chiral phenomena in Cosserat elastic materials which obey generalized continuum constitutive equations. Dynamic monopole-like magnetic induction is predicted in chiral dielectric media.

  7. Dielectric properties of aerogels

    SciTech Connect

    Hrubesh, L.W.; Keene, L.E.; Latorre, V.R. )

    1993-07-01

    We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 [degree]K using microwave frequencies (2, 10, and 18--40 GHz), for bulk SiO[sub 2]-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel densities from 10 to 500 kg/m[sup 3]. For the same range of densities, the measured loss tangents vary linearly between values of 2[times]10[sup [minus]4] and 7[times]10[sup [minus]2]. The observed linearity of the dielectric properties with density in aerogels at microwave frequencies shows that their dielectric behavior is more gas-like than solid-like. The dielectric properties of aerogels are shown to be significantly affected by the adsorbed water internal to the bulk material. For example, water accounts for 7% of the dielectric constant and 70% of the loss at microwave frequencies for silica aerogels. Because of their very high porosity, even with the water content, the aerogels are among the few materials exhibiting such low dielectric properties. Our measurements show that aerogels with greater than 99% porosity have dielectric constants less than 1.03; these are the lowest values ever reported for a bulk solid material.

  8. Giant Static Dielectric Constant of Strained PbTiO3

    NASA Astrophysics Data System (ADS)

    Wang, Yuan-Xu

    2009-01-01

    First-principles density functional perturbation calculations are employed to study the dielectric and piezoelectric properties of strained tetragonal PbTiO3. Lattice distortion, static dielectric constant, Born effective charge, zone-centre phonons, and piezoelectric constant are obtained. For the strained tetragonal PbTiO3, we obtain a giant static dielectric constant (3600) under a strain 0.77%. Moreover, the calculated piezoelectric constant e15 of strained PbTiO3 reaches about 203 C/m2 which is about 20 times of that of unstrained system. The giant static dielectric constant is mainly due to the softening of the lowest-frequency phonon mode and the reduce of Ti-O bond length. This work demonstrates a route to a giant static dielectrics for electrically microwave and other devices.

  9. Dielectric Properties Of Nanoferrites

    SciTech Connect

    Jankov, Stevan B.; Cvejic, Zeljka N.; Rakic, Srdjan; Srdic, Vladimir

    2007-04-23

    Dielectric properties: permittivity, loss factor, tan delta and ionic conductivity of nanostructured ferrites have been measured. Samples used were nickel, zinc and yttrium doped ferrites mixed in various ratios. The synthesis has been performed using precipitation method and obtained powders were pressed in pellets under varying pressure. X-ray diffractography approach for the refinement of structure and microstructural analysis has been performed. All parameters have been measured in 1 Hz to 100 kHz frequency range and 30 deg. C to 80 deg. C temperature range. Significant improvements in permittivity, loss factor and ionic conductivity comparing to bulk samples have been observed.

  10. Thermally driven sign switch of static dielectric constant of VO2 thin film

    NASA Astrophysics Data System (ADS)

    Kana Kana, J. B.; Vignaud, G.; Gibaud, A.; Maaza, M.

    2016-04-01

    Smart multifunctional materials exhibiting phase transition and tunable optical and/electrical properties provide a new direction towards engineering switchable devices. Specifically, the reversible, tunable and sign switch dielectric constants via external temperature stimuli observed in vanadium dioxide (VO2) make it a candidate of choice for tunable and switchable technologies devices. Here we report new aspect of the metal-insulator transition (MIT) through the sign switch of the static dielectric constant εS of pure VO2. As it is shown, the static dielectric constant showed an abrupt change from positive at T < 70 °C to negative at T > 70 °C. εS > 0 confirms the insulating phase where charges are localized while εS < 0 confirms the metallic phase of VO2 where charges are delocalized. We report for the first time the tunability of the dielectric constant from a negative sign for the static dielectric constant of VO2 thin film rarely found in real physical systems. We also demonstrate the tunability and switchability of the real and imaginary part of the dielectric constant (ε) via external temperature stimuli. More specifically, the real (ε) and Imaginary (ε) showed an abrupt thermal hysteresis which clearly confirms the phase transition.

  11. Dielectric properties of marsh vegetation

    NASA Astrophysics Data System (ADS)

    Kochetkova, Tatiana D.; Suslyaev, Valentin I.; Shcheglova, Anna S.

    2015-10-01

    The present work is devoted to the measurement of the dielectric properties of mosses and lichens in the frequency range from 500 MHz to 18 GHz. Subjects of this research were three species of march vegetation - moss (Dicranum polysetum Michx), groundcedar (Diphasiastrum complanatum (L.) Holub) and lichen (Cladonia stellaris). Samples of vegetation were collected in Tomsk region, Western Siberia, Russia. Complex dielectric permittivity was measured in coaxial section by Agilent Technologies vector network analyzer E8363B. Green samples was measured for some moisture contents from 100% to 3-5 % during a natural drying. The measurements were performed at room temperature, which remained within 21 ÷ 23 ° C. The frequency dependence of the dielectric constant for the three species of marsh vegetation differ markedly. Different parts of the complex permittivity dependency on moisture were fitted by line for all frequency points. Two break point were observed corresponding to the transition of water in the vegetation in various phase states. The complex permittivity spectra of water in the vegetation allow determining the most likely corresponding dielectric model of water in the vegetation by the method of hypothesis testing. It is the Debye's model. Parameters of Debye's model were obtained by numerical methods for all of three states of water. This enables to calculate the dielectric constant of water at any frequency range from 500 MHz to 18 GHz and to find the parameters of the dielectric model of the vegetation.

  12. Dielectric Properties of Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Simpson, J. O.; Farmer, B. L.

    1997-01-01

    Molecular modeling and dielectric measurements are being used to identify mechanisms governing piezoelectric behavior in polyimides such as dipole orientation during poling, as well as degree of piezoelectricity achievable. Molecular modeling on polyimides containing pendant, polar nitrile (CN) groups has been completed to determine their remanent polarization. Experimental investigation of their dielectric properties evaluated as a function of temperature and frequency has substantiated numerical predictions. With this information in hand, we are then able to suggest changes in the molecular structures, which will then improve upon the piezoelectric response.

  13. Microwave dielectric properties of biopolymers

    NASA Astrophysics Data System (ADS)

    Bartsch, Carrie M.; Subramanyam, Guru; Grote, James G.; Hopkins, F. Kenneth; Brott, Lawrence L.; Naik, Rajesh R.

    2006-09-01

    A new capacitive test structure is used to characterize biopolymers at microwave frequencies. The new test structure is comprised of a parallel plate capacitor, combined with coplanar waveguide-based input and output feed lines. This allows microwave measurements to be taken easily under an applied DC electric field. The microwave dielectric properties are characterized for two biopolymer thin films: a deoxyribonucleic acid (DNA)-based film and a bovine serum albumin (BSA)-based film. These bio-dielectric thin-films are compared with a standard commercial polymer thin film, poly[Bisphenol A carbonate-co-4,4'(3,3,5-trimethyl cyclohexylidene) diphenol], or amorphous polycarbonate (APC).

  14. USDA/ARS and dielectric properties research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An overview of the research is presented, including RF dielectric heating for seed treatment, insect control, product conditioning, and moisture and quality sensing applications, equipment used, dielectric properties measurement techniques, broad- frequency- range data obtained, and research results...

  15. Dielectric properties of gel collected from shark electrosensors

    NASA Astrophysics Data System (ADS)

    Hughes, Mary E.; Brown, Brandon R.; Hutchison, John C.; Murray, Royce W.

    2003-03-01

    To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity and a loss peak corresponding to a long relaxation time (about 1 ms). Impedance measurements of the native (nondialyzed) gel reliable to 0.1 Hz will be presented and compared to the dialyzed gel. Ramifications of the gel's dielectric properties for the electric sense will be explored.

  16. Real space electrostatics for multipoles. III. Dielectric properties

    NASA Astrophysics Data System (ADS)

    Lamichhane, Madan; Parsons, Thomas; Newman, Kathie E.; Gezelter, J. Daniel

    2016-08-01

    In Papers I and II, we developed new shifted potential, gradient shifted force, and Taylor shifted force real-space methods for multipole interactions in condensed phase simulations. Here, we discuss the dielectric properties of fluids that emerge from simulations using these methods. Most electrostatic methods (including the Ewald sum) require correction to the conducting boundary fluctuation formula for the static dielectric constants, and we discuss the derivation of these corrections for the new real space methods. For quadrupolar fluids, the analogous material property is the quadrupolar susceptibility. As in the dipolar case, the fluctuation formula for the quadrupolar susceptibility has corrections that depend on the electrostatic method being utilized. One of the most important effects measured by both the static dielectric and quadrupolar susceptibility is the ability to screen charges embedded in the fluid. We use potentials of mean force between solvated ions to discuss how geometric factors can lead to distance-dependent screening in both quadrupolar and dipolar fluids.

  17. Electronic and dielectric properties of MoS{sub 2}-MoX{sub 2} heterostructures

    SciTech Connect

    Sharma, Munish Jamdagni, Pooja; Ahluwalia, P. K; Kumar, Ashok

    2015-05-15

    We present a comparative study of electronic and dielectric properties of MoS{sub 2}−MoX{sub 2} heteostructures (where X=S, Se, Te) within the framework of density functional theory (DFT). Electronic band structure, real and imaginary part of dielectric function, electron energy loss spectra and static dielectric constant have been calculated for each system and compared with one another. A systematic decrease/increase in band gap/static dielectric constant is observed as the X changes from S to Te. These results provide a physical basis for the potential applications of these heterostructures in optoelectronic devices.

  18. Electronic, mechanical and dielectric properties of silicane under tensile strain

    SciTech Connect

    Jamdagni, Pooja Sharma, Munish; Ahluwalia, P. K.; Kumar, Ashok; Thakur, Anil

    2015-05-15

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  19. Electronic, mechanical and dielectric properties of silicane under tensile strain

    NASA Astrophysics Data System (ADS)

    Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.

    2015-05-01

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  20. Dielectric properties and electronic applications of aerogels

    SciTech Connect

    Hrubesh, L.W.; Pekala, R.W.

    1993-07-01

    Among their other exceptional properties, aerogels also exhibits unusual dielectric properties due to their nano-sized structures and high porosities. For example, our measurements of the dielectric constants and loss tangents for several aerogel varieties at microwave frequencies show that they both vary linearly with the aerogel density, indicating that the dielectric behavior of aerogels is more gas-like than solid-like. We have also measured the dielectric strength of silica aerogels and find that they are better than ceramics for high voltage insulation. The low dielectric constants and loss tangents of aerogels, along with their controllable thermal expansion properties, make them desirable materials for use as thin films in high speed integrated digital and microwave circuitry.

  1. Techniques for Measuring the Dielectric Properties of Agricultural Products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectrics and dielectric properties of materials are defined generally, and methods for measuring dielectric properties of agricultural products are described for several frequency ranges from audio frequencies through microwave frequencies. These include measurement with impedance and admittance...

  2. Microwave dielectric properties of boreal forest trees

    NASA Technical Reports Server (NTRS)

    Xu, G.; Ahern, F.; Brown, J.

    1993-01-01

    The knowledge of vegetation dielectric behavior is important in studying the scattering properties of the vegetation canopy and radar backscatter modelling. Until now, a limited number of studies have been published on the dielectric properties in the boreal forest context. This paper presents the results of the dielectric constant as a function of depth in the trunks of two common boreal forest species: black spruce and trembling aspen, obtained from field measurements. The microwave penetration depth for the two species is estimated at C, L, and P bands and used to derive the equivalent dielectric constant for the trunk as a whole. The backscatter modelling is carried out in the case of black spruce and the results are compared with the JPL AIRSAR data. The sensitivity of the backscatter coefficient to the dielectric constant is also examined.

  3. Dielectric and elastic properties of liquid crystals.

    PubMed

    Zakharov, A V; Dong, R Y

    2001-09-01

    The structural properties, the static and relaxation dielectric coefficients [epsilon(j) and epsilon(j)(omega) (j= ||, perpendicular)], the rotational diffusion constants D( perpendicular) and D( ||), the orientational correlation times tau(1)(i0) (i=0,1), and the bulk elastic constants K(i) (i=1,2,3) are investigated for polar liquid crystals, such as 4-n-pentyl-4(')-cyanobiphenyl (5CB). epsilon(j) are calculated by a combination of the existing molecular theory and statistical-mechanical approach (SMA) that takes into account translational and orientational correlations as well as their coupling, whereas epsilon(j)(omega) are calculated by combining SMA and nuclear magnetic resonance relaxation theory, both based on a rotational diffusion model in which the reorientation of an individual molecule is assumed as stochastic Brownian motion in a potential of mean torque. Reasonable agreement between the calculated and experimental values of epsilon(j) and epsilon(j)(omega) for 5CB is obtained. The bulk Frank elastic constants K(i) (i=1,2,3), for splay, twist, and bend distortion modes, as well as their ratios K(3)/K(1) and K(2)/K(1) are also obtained.

  4. Tailoring dielectric properties of ferroelectric-dielectric multilayers

    SciTech Connect

    Kesim, M. T.; Zhang, J.; Cole, M. W.; Misirlioglu, I. B.

    2014-01-13

    We develop a nonlinear thermodynamic model for multilayer ferroelectric heterostructures that takes into account electrostatic and electromechanical interactions between layers. We concentrate on the effect of relative layer fractions and in-plane thermal stresses on dielectric properties of Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}-, BaTiO{sub 3}-, and PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT)-SrTiO{sub 3} (STO) multilayers on Si and c-sapphire. We show that dielectric properties of such multilayers can be significantly enhanced by tailoring the growth/processing temperature and the STO layer fraction. Our computations show that large tunabilities (∼90% at 400 kV/cm) are possible in carefully designed barium strontium titanate-STO and PZT-STO even on Si for which there exist substantially large in-plane strains.

  5. Calculation of the dielectric properties of semiconductors

    NASA Astrophysics Data System (ADS)

    Engel, G. E.; Farid, Behnam

    1992-12-01

    We report on numerical calculations of the dynamical dielectric function in silicon, using a continued-fraction expansion of the polarizability and a recently proposed representation of the inverse dielectric function in terms of plasmonlike excitations. A number of important technical refinements to further improve the computational efficiency of the method are introduced, making the ab initio calculation of the full energy dependence of the dielectric function comparable in cost to calculation of its static value. Physical results include the observation of previously unresolved features in the random-phase approximated dielectric function and its inverse within the framework of density-functional theory in the local-density approximation, which may be accessible to experiment. We discuss the dispersion of plasmon energies in silicon along the Λ and Δ directions and find improved agreement with experiment compared to earlier calculations. We also present quantitative evidence indicating the degree of violation of the Johnson f-sum rule for the dielectric function due to the nonlocality of the one-electron potential used in the underlying band-structure calculations.

  6. How does static stretching decrease the dielectric constant of VHB 4910 elastomer?

    NASA Astrophysics Data System (ADS)

    Vu-Cong, T.; Nguyen-Thi, N.; Jean-Mistral, C.; Sylvestre, A.

    2014-03-01

    Subject to a voltage, dielectric elastomers deform by the effect of Maxwell stress which is depended directly on the dielectric constant of the material. The combination of large strain, soft elastic response and good dielectric properties has established VHB 4910 elastomer as the most used material for dielectric elastomer actuators. However, the effect of stretch on the dielectric constant for this elastomer is much debated topic while controversy results are demonstrated in the literature. The dielectric constant of this material is studied and demonstrated that it decreases slightly or hugely among the stretch but any pertinent response and any physic explications are validated by the scientific community. In this paper, we presented a detail study about dielectric behavior of VHB 4910 elastomer versus a broadband of stretch and temperature. We found that the dielectric constant of this material depends strongly on the stretch following a polynomial law. Among all the explanations of stretch dependence of the dielectric constant of VHB 4910 in the literature: the crystallization, the change of glass transition temperature, the decrease of dipole orientation, the electrostriction effect under stress; and based on our experimental result, we conclude that the decrease of dipole orientation seems the main reason to the drop of dielectric constant of VHB 4910 elastomer versus the stretch. We proposed also an accurate model describing the dielectric constant of this material for a large range of stretch and temperature.

  7. Electrical properties and dielectric spectroscopy of Ar+ implanted polycarbonate

    NASA Astrophysics Data System (ADS)

    Chawla, Mahak; Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Nair, K. G. M.

    2015-05-01

    The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar+ ions in the fluence ranging from 1×1014 to 1×1016 ions cm-2. The beam current used was ˜0.40 µA cm-2. The electrical conduction behaviour of virgin and Ar+ implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ɛ' vs. imaginary part of complex permittivity, ɛ″). The Cole-Cole plots have also been used to determine static dielectric constant (ɛs), optical dielectric constant (ɛ∞), spreading factor (α), average relaxation time (τ0) and molecular relaxation time (τ). The dielectric behaviour has been found to be significantly affected due to Ar+ implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  8. Influence of hydrogen bonds and temperature on dielectric properties

    NASA Astrophysics Data System (ADS)

    Ortiz de Urbina, Jordi; Sesé, Gemma

    2016-07-01

    Dielectric properties are evaluated by means of molecular dynamics simulations on two model systems made up of dipolar molecules. One of them mimics methanol, whereas the other differs from the former only in the ability to form hydrogen bonds. Static dielectric properties such as the permittivity and the Kirkwood factor are evaluated, and results are analyzed by considering the distribution of relative orientations between molecular dipoles. Dipole moment-time correlation functions are also evaluated. The relevance of contributions associated with autocorrelations of molecular dipoles and with cross-correlations between dipoles belonging to different molecules has been investigated. For methanol, the Debye approximation for the overall dipole moment correlation function is not valid at room temperature. The model applies when hydrogen bonds are suppressed, but it fails upon cooling the nonassociated liquid. Important differences between relaxation times associated with dipole auto- versus cross-correlations as well as their relative relevance are at the root of the Debye model breakdown.

  9. Influence of hydrogen bonds and temperature on dielectric properties.

    PubMed

    Ortiz de Urbina, Jordi; Sesé, Gemma

    2016-07-01

    Dielectric properties are evaluated by means of molecular dynamics simulations on two model systems made up of dipolar molecules. One of them mimics methanol, whereas the other differs from the former only in the ability to form hydrogen bonds. Static dielectric properties such as the permittivity and the Kirkwood factor are evaluated, and results are analyzed by considering the distribution of relative orientations between molecular dipoles. Dipole moment-time correlation functions are also evaluated. The relevance of contributions associated with autocorrelations of molecular dipoles and with cross-correlations between dipoles belonging to different molecules has been investigated. For methanol, the Debye approximation for the overall dipole moment correlation function is not valid at room temperature. The model applies when hydrogen bonds are suppressed, but it fails upon cooling the nonassociated liquid. Important differences between relaxation times associated with dipole auto- versus cross-correlations as well as their relative relevance are at the root of the Debye model breakdown. PMID:27575177

  10. Real space electrostatics for multipoles. III. Dielectric properties.

    PubMed

    Lamichhane, Madan; Parsons, Thomas; Newman, Kathie E; Gezelter, J Daniel

    2016-08-21

    In Papers I and II, we developed new shifted potential, gradient shifted force, and Taylor shifted force real-space methods for multipole interactions in condensed phase simulations. Here, we discuss the dielectric properties of fluids that emerge from simulations using these methods. Most electrostatic methods (including the Ewald sum) require correction to the conducting boundary fluctuation formula for the static dielectric constants, and we discuss the derivation of these corrections for the new real space methods. For quadrupolar fluids, the analogous material property is the quadrupolar susceptibility. As in the dipolar case, the fluctuation formula for the quadrupolar susceptibility has corrections that depend on the electrostatic method being utilized. One of the most important effects measured by both the static dielectric and quadrupolar susceptibility is the ability to screen charges embedded in the fluid. We use potentials of mean force between solvated ions to discuss how geometric factors can lead to distance-dependent screening in both quadrupolar and dipolar fluids. PMID:27544088

  11. Dielectric polarization transients in biological tissue moving in a static magnetic field.

    PubMed

    Jokela, Kari; Laakso, Ilkka

    2016-09-01

    Movement of a body in a static magnetic field gives rise to the Lorentz force that induces in the medium both electric currents and dielectric polarization. It is usually assumed that the conductivity of biological tissues is sufficiently high in order to neglect dielectric phenomenon arising from non-equilibrium of polarization charges. However, the permittivity of biological tissues is extremely high and the relaxation time of free charges is relatively low. In this study, we examined the effect of dielectric polarization on the electric field (EF) induced by human movements in a strong magnetic field (MF). Analytic equations for brain and bone equivalent spheres translating and rotating in a uniform MF were derived from Maxwell equations. Several examples were computed by using Fast Fourier Transform to examine transient dielectric effects in a time domain. The results showed that dielectric polarization transients do arise, but in the case of homogeneous medium, they are vanishingly small. In contrast, the local dielectric transients are not vanishingly small in heterogeneous medium. However, due to limited acceleration and deceleration of normal human movements, the transients are relatively small, at maximum a few dozen percent of the EF induced by the change of the magnetic flux. Taking into account the high uncertainty in numerical simulation, the dielectric transients can be neglected in the case of biological materials but not in the case of many non-biological materials of low conductivity. Bioelectromagnetics. 37:409-422, 2016. © 2016 Wiley Periodicals, Inc.

  12. Dielectric polarization transients in biological tissue moving in a static magnetic field.

    PubMed

    Jokela, Kari; Laakso, Ilkka

    2016-09-01

    Movement of a body in a static magnetic field gives rise to the Lorentz force that induces in the medium both electric currents and dielectric polarization. It is usually assumed that the conductivity of biological tissues is sufficiently high in order to neglect dielectric phenomenon arising from non-equilibrium of polarization charges. However, the permittivity of biological tissues is extremely high and the relaxation time of free charges is relatively low. In this study, we examined the effect of dielectric polarization on the electric field (EF) induced by human movements in a strong magnetic field (MF). Analytic equations for brain and bone equivalent spheres translating and rotating in a uniform MF were derived from Maxwell equations. Several examples were computed by using Fast Fourier Transform to examine transient dielectric effects in a time domain. The results showed that dielectric polarization transients do arise, but in the case of homogeneous medium, they are vanishingly small. In contrast, the local dielectric transients are not vanishingly small in heterogeneous medium. However, due to limited acceleration and deceleration of normal human movements, the transients are relatively small, at maximum a few dozen percent of the EF induced by the change of the magnetic flux. Taking into account the high uncertainty in numerical simulation, the dielectric transients can be neglected in the case of biological materials but not in the case of many non-biological materials of low conductivity. Bioelectromagnetics. 37:409-422, 2016. © 2016 Wiley Periodicals, Inc. PMID:27243146

  13. Magnetic and dielectric properties of lunar samples

    NASA Technical Reports Server (NTRS)

    Strangway, D. W.; Pearce, G. W.; Olhoeft, G. R.

    1977-01-01

    Dielectric properties of lunar soil and rock samples showed a systematic character when careful precautions were taken to ensure there was no moisture present during measurement. The dielectric constant (K) above 100,000 Hz was directly dependent on density according to the formula K = (1.93 + or - 0.17) to the rho power where rho is the density in g/cc. The dielectric loss tangent was only slightly dependent on density and had values less than 0.005 for typical soils and 0.005 to 0.03 for typical rocks. The loss tangent appeared to be directly related to the metallic ilmenite content. It was shown that magnetic properties of lunar samples can be used to study the distribution of metallic and ferrous iron which shows systematic variations from soil type to soil type. Other magnetic characteristics can be used to determine the distribution of grain sizes.

  14. Spacecraft dielectric material properties and spacecraft charging

    SciTech Connect

    Frederickson, A.R.; Cotts, D.B.; Wall, J.A.; Bouquet, F.L.

    1986-01-01

    With an eye towards applications in the space radiation environment and in nuclear instrumentation, the contributors to this volume provide a multi-disciplinary review of theory and experimentation with conductivity in dielectrics, especially insulators, to establish guidelines for design of materials which do not electrically discharge or breakdown. The authors' analysis of polymer literature suggests several candidates for the purpose of proposing anti-static polymers for use in the space radiation environment. Experimental data is systematically referenced and suggestions for improving such data are made. The book also contains an extensive reference list.

  15. Microwave dielectric properties of plant materials

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Jedlicka, R. P.

    1984-01-01

    Three waveguide transmission systems covering the 1-2, 3.5-6.5, and 7.5-8.5 GHZ bands were used to measure the dielectric properties of vegetation material as a function of moisture content and microwave frequency. The materials measured included, primarily, the leaves and stalks of corn and wheat. Dielectric measurements also were made of the liquid included in the vegetation material after it was extracted from the vegetation by mechanical means. The extracted liquids were found to have an equivalent NaCl salinity of about 10 per mil, which can have a significant effect on the dielectric loss at frequencies below 5 GHz. The results of attempts to model the dielectric constant of the vegetatioon-water mixture in terms of the dielectric constants and volume fractions of its constituent parts (i.e., bulk vegetation, air, bound water, and free water) are discussed. Additionally, measurements of the temporal variations in the total attenuation at 10.2 GHz are presented for a corn canopy and a soybean canopy.

  16. Imaging the static dielectric constant in vitro and in living cells by a bioconjugable GFP chromophore analog.

    PubMed

    Signore, Giovanni; Abbandonato, Gerardo; Storti, Barbara; Stöckl, Martin; Subramaniam, Vinod; Bizzarri, Ranieri

    2013-02-28

    A fluorescent probe structurally similar to the GFP chromophore is demonstrated to report the local static dielectric constant. This probe can be chemically functionalized for selective targeting at the intracellular level.

  17. A Study of Dielectric Properties of Proteinuria between 0.2 GHz and 50 GHz

    PubMed Central

    Mun, Peck Shen; Ting, Hua Nong; Ong, Teng Aik; Wong, Chew Ming; Ng, Kwan Hong; Chong, Yip Boon

    2015-01-01

    This paper investigates the dielectric properties of urine in normal subjects and subjects with chronic kidney disease (CKD) at microwave frequency of between 0.2 GHz and 50 GHz. The measurements were conducted using an open-ended coaxial probe at room temperature (25°C), at 30°C and at human body temperature (37°C). There were statistically significant differences in the dielectric properties of the CKD subjects compared to those of the normal subjects. Statistically significant differences in dielectric properties were observed across the temperatures for normal subjects and CKD subjects. Pearson correlation test showed the significant correlation between proteinuria and dielectric properties. The experimental data closely matched the single-pole Debye model. The relaxation dispersion and relaxation time increased with the proteinuria level, while decreasing with the temperature. As for static conductivity, it increased with proteinuria level and temperature. PMID:26066351

  18. Tunable Dielectric Properties of Ferrite-Dielectric Based Metamaterial

    PubMed Central

    Bi, K.; Huang, K.; Zeng, L. Y.; Zhou, M. H.; Wang, Q. M.; Wang, Y. G.; Lei, M.

    2015-01-01

    A ferrite-dielectric metamaterial composed of dielectric and ferrite cuboids has been investigated by experiments and simulations. By interacting with the electromagnetic wave, the Mie resonance can take place in the dielectric cuboids and the ferromagnetic precession will appear in the ferrite cuboids. The magnetic field distributions show the electric Mie resonance of the dielectric cuboids can be influenced by the ferromagnetic precession of ferrite cuboids when a certain magnetic field is applied. The effective permittivity of the metamaterial can be tuned by modifying the applied magnetic field. A good agreement between experimental and simulated results is demonstrated, which confirms that these metamaterials can be used for tunable microwave devices. PMID:25993433

  19. Dielectric and electrical transport properties of biopolymers

    NASA Astrophysics Data System (ADS)

    Bartsch, Carrie M.; Subramanyam, Guru; Grote, James G.; Hopkins, F. Kenneth; Brott, Lawrence L.; Naik, Rajesh R.

    2007-02-01

    A new capacitive test structure is used to characterize biopolymers at microwave frequencies. The new test structure is comprised of a parallel plate capacitor, combined with coplanar waveguide-based input and output feed lines. This allows electrical measurements to be taken easily under an applied DC electric field and at various temperatures. The dielectric properties are characterized for two biopolymer thin films: a deoxyribonucleic acid (DNA)-based film and a bovine serum albumin (BSA)-based film. These bio-dielectric thin films are compared with a standard commercial polymer thin film, poly[Bisphenol A carbonate-co-4,4'(3,3,5-trimethyl cyclohexylidene) diphenol], also known as amorphous polycarbonate (APC).

  20. Spacecraft dielectric material properties and spacecraft charging

    NASA Technical Reports Server (NTRS)

    Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

    1986-01-01

    The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

  1. Use of material dielectric properties for agricultural applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of dielectric properties of materials for applications in agriculture are reviewed, and research findings on use of dielectric heating of materials and on sensing of product moisture content and other quality factors are discussed. Dielectric heating applications, include treatment of seed...

  2. Dielectric, magnetic, and phonon properties of nickel hydroxide

    NASA Astrophysics Data System (ADS)

    Hermet, P.; Gourrier, L.; Bantignies, J.-L.; Ravot, D.; Michel, T.; Deabate, S.; Boulet, P.; Henn, F.

    2011-12-01

    We carried out a complete study (magnetic, electronic, dielectric, dynamic, and elastic properties) of the nickel hydroxide [Ni(OH)2] from first-principles calculations based on density functional theory. No theoretical investigations of these physical properties have been previously reported in literature. Our work supports that Ni(OH)2 is an A-type antiferromagnetic material. In addition, it is negative uniaxial and semiconducting with a direct band gap at the Γ point around 3 eV. By contrast to its electronic dielectric tensor, its static tensor is strongly anisotropic in the plane orthogonal to its optical axis. This anisotropy is mainly governed by a highly polar phonon centered around 510 cm-1 and assigned as a rotational Eu mode. Both Raman and infrared spectra have been computed to clarify the longstanding debate on the assignment of the Ni(OH)2 phonon modes reported in literature. All these theoretical results are fruitfully compared to the experimental ones obtained on large Ni(OH)2 “pseudosingle” crystals when available.

  3. Towards Automated Benchmarking of Atomistic Forcefields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive

    PubMed Central

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

    2015-01-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the forcefield employed. While experimental measurements of fundamental physical properties offer a straightforward approach for evaluating forcefield quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark datasets 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 forcefield accuracy. Here, we examine the feasibility of benchmarking atomistic forcefields 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 forcefield (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 forcefields in the representation low dielectric environments such as those seen in binding cavities or biological membranes. PMID:26339862

  4. Dielectric Properties of PVDF/PZT

    SciTech Connect

    Zak, A. Khorsand; Chen, Gan Wee; Majid, W. H. Abd.

    2011-03-30

    Poly(vinylidene fluoride)/ lead zirconate titanate nanocomposite (PVDF/PZT-NPs) were successfully prepared by mixing fine Pb(Zr{sub 0.52}, Ti{sub 0.48})O{sub 3} nanoparticles (PZT-NPs) into a PVDF solution under ultrasonication. The mixture was spin coated onto glass substrate and then annealed at 80 deg. C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to characterize the structure and properties of the obtained thin-film nanocomposites. The nanocomposites exhibited good dielectric stability over a wide frequency range.

  5. Spacecraft dielectric surface charging property determination

    NASA Technical Reports Server (NTRS)

    Williamson, W. S.

    1987-01-01

    The charging properties of 127 micron thick polyimide, (a commonly used spacecraft dielectric material) was measured under conditions of irradiation by a low-current-density electron beam with energy between 2 and 14 keV. The observed charging characteristics were consistent with predictions of the NASCAP computer model. The use of low electron current density results in a nonlinearity in the sample-potential versus beam-energy characteristic which is attributed to conduction leakage through the sample. Microdischarges were present at relatively low beam energies.

  6. Temperature and Moisture Dependent Dielectric Properties of Legume Flours Associated with Dielectric Heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric property data are important in developing thermal treatments using radio frequency (RF) and microwave (MW) energy and essential to estimate the heating uniformity in electromagnetic fields. Dielectric properties of flour samples from four legumes (chickpea, green pea, lentil, and soybean)...

  7. How polar are ionic liquids? Determination of the static dielectric constant of an imidazolium-based ionic liquid by microwave dielectric spectroscopy.

    PubMed

    Wakai, Chihiro; Oleinikova, Alla; Ott, Magnus; Weingärtner, Hermann

    2005-09-15

    In a pilot study of the dielectric constant of room-temperature ionic liquids, we use dielectric spectroscopy in the megahertz/gigahertz regime to determine the complex dielectric function of five 1-alkyl-3-methylimidazolium salts, from which the static dielectric constant epsilon is obtained by zero-frequency extrapolation. The results classify the salts as moderately polar solvents. The observed epsilon-values at 298.15 K fall between 15.2 and 8.8, and epsilon decreases with increasing chain length of the alkyl residue of the cation. The anion sequence is trifluoromethylsulfonate > tetrafluoroborate approximately tetrafluorophosphate. The results indicate markedly lower polarities than found by spectroscopy with polarity-sensitive solvatochromic dyes.

  8. Microwave dielectric properties of dry rocks

    NASA Technical Reports Server (NTRS)

    Ulaby, Fawwaz T.; Dobson, Myron C.; East, Jack R.; Bengal, Thomas H.; Garvin, James B.; Evans, Diane L.

    1990-01-01

    A combination of techniques was used to measure the dielectric properties of 80 rock samples in the microwave region. The real part (RP) of the relative dielectric constant was measured in 0.1-GHz steps from 0.5 to 18 GHz, and the imaginary part (IP) was measured at five frequencies between 1.6 and 16 GHz. The bulk density rho(b) was also measured for all the samples, and the bulk chemical composition (BCC) was determined for 56 of the samples. RP is found to be frequency-independent at 0.5-18 GHz for all samples, and rho(b) accounts for about 50 percent of the observed variance. For silicate rocks, as much as 78 percent of the variance is explained by the combination of rho(b) and the fractional contents of oxides when the silicates are subgrouped by genesis. In contrast, IP decreases with increasing frequency for most rock samples, and no statistically significant relationships are found between IP and rho(b). For subgrouped silicate rocks, 60 percent of the variance in IP can be explained by BCC.

  9. Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

    NASA Astrophysics Data System (ADS)

    Sonoda, Milton T.; Elola, M. Dolores; Skaf, Munir S.

    2016-10-01

    The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l-1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm-1) components of the dielectric response spectrum. The low-frequency (<0.1 cm-1) components, however, are markedly influenced by sugar concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions.

  10. Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions.

    PubMed

    Sonoda, Milton T; Dolores Elola, M; Skaf, Munir S

    2016-10-19

    The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l(-1) are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm(-1)) components of the dielectric response spectrum. The low-frequency (<0.1 cm(-1)) components, however, are markedly influenced by sugar concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions. PMID:27546528

  11. Dielectric properties of agricultural materials and their application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book is prepared as a comprehensive source of information on dielectric properties of agricultural materials for scientific researchers and engineers involved in practical application of radio-frequency and microwave energy for potential problem solutions. Dielectric properties of materials det...

  12. Dielectric properties for prediction of moisture content in Vidalia onions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microwave Sensing provides a means for nondestructively determining the amount of moisture in materials by sensing the dielectric properties of the material. In this study, dielectric properties of Vidalia onions were analyzed for moisture dependence at 13.36 GHz and 23°C for moisture content betwee...

  13. A modified field model of waveguide reflection dielectric resonator for microwave measurements of dielectric properties

    NASA Astrophysics Data System (ADS)

    Sheen, Jyh

    2008-02-01

    A modified electromagnetic field model of a waveguide reflection dielectric resonator is suggested for measurements of dielectric properties of the homogeneous and isotropic medium in the microwave frequencies. Reflection signal is measured for the calculations of dielectric properties. A dielectric rod sample is put inside of a rectangular cavity made by a microwave waveguide. The sample's dielectric constant and loss tangent are computed from the unloaded quality factor and the resonant frequency of the TE01δ mode as well as the structure dimensions. For first time, this waveguide reflection dielectric resonator is applied on dielectric constant measurement. A modified field model of the waveguide reflection resonator is developed from the Itoh-Rudokas model [IEEE Trans. Microwave Theory Tech. MTT-25, 52 (1977)] of the parallel-plate dielectric resonator. This modification is justified by the dramatic improvement in the accuracy of dielectric constant measurements. The main merit of this field model is that it provides very simple electromagnetic field expressions of this TE01δ field mode. In addition, accuracies of various methods for calculating the power factor and conducting loss, which have never been given before, will be investigated in this article.

  14. 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.

  15. Microwave axial dielectric properties of carbon fiber.

    PubMed

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-01-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity. PMID:26477579

  16. Microwave axial dielectric properties of carbon fiber

    PubMed Central

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-01-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity. PMID:26477579

  17. Microwave axial dielectric properties of carbon fiber

    NASA Astrophysics Data System (ADS)

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-10-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity.

  18. Dielectric properties of liquid phase molecular clusters using the external field method: molecular dynamics study.

    PubMed

    Abeyrathne, Chathurika D; Halgamuge, Malka N; Farrell, Peter M; Skafidas, Efstratios

    2014-07-21

    We analyzed the dielectric properties of molecular liquids using the external field method with reaction field approximations. The applicability of this method to determine the dielectric properties of molecules with zero (1,4-dioxane) and non-zero (water and bio-molecular aqueous solutions) permanent dipole moment was studied. The relative static dielectric constant obtained using the external field method for polar and non-polar molecular liquids, including molecules with zero permanent dipole moment, agreed well with the experimental values presented in the literature. Our results indicate that the Debye relaxation time constants estimated from the non-equilibrium simulations using the external field method were accurate for molecules whose permanent dipole moments were less than 12 D.

  19. Factors influencing the dielectric properties of agricultural and food products.

    PubMed

    Nelson, Stuart O; Trabelsi, Samir

    2012-01-01

    Dielectric properties of materials are defined, and the major factors that influence these properties of agricultural and food materials, namely, frequency of the applied radiofrequency or microwave electric fields, and water content, temperature, and density of the materials, are discussed on the basis of fundamental concepts. The dependence of measured dielectric properties on these factors is illustrated graphically and discussed for a number of agricultural and food products, including examples of grain, peanuts, fruit, eggs, fresh chicken meat, whey protein gel, and a macaroni and cheese preparation. General observations are provided on the nature of the variation of the dielectric properties with the major variables.

  20. Dielectric properties of honeydew melons and correlation with quality.

    PubMed

    Guo, Wen-chuan; Nelson, Stuart O; Trabelsi, Samir; Kays, Stanley J

    2007-01-01

    Dielectric properties of three honeydew melon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and impedance analyzer over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melons and also on tissue samples from the edible internal tissue. Moisture content and soluble solids content (SSC) were measured for internal tissue samples, and SSC (sweetness) was used as the quality factor for correlation with the dielectric properties. Individual dielectric constant and loss factor correlations with SSC were low, but a high correlation was obtained between the SSC and permittivity from a complex-plane plot of dielectric constant and loss factor, each divided by SSC, for both the external surface and internal tissue measurements. However, SSC prediction from the dielectric properties by these relationships was not as high as expected. Permittivity data (dielectric constant and loss factor) for the melons are presented graphically to show their relationships with frequency for external surface and internal tissue measurements. A dielectric relaxation for the external surface measurements, which is attributable to bound water and Maxwell-Wagner relaxations, is also illustrated. Coefficients of determination for complex-plane plots, moisture content and SSC relationship, and penetration depth are also shown graphically. Further studies are needed for determining the practicality of sensing melon quality from the dielectric properties.

  1. Frequency and temperature dependence of dielectric properties of chicken meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of chicken breast meat were measured with an open-ended coaxial-line probe between 200 MHz and 20 GHz at temperatures ranging from -20 degree C to +25 degree C. At a given temperature, the frequency dependence of the dielectric constant reveals two relaxations while those of th...

  2. Automated Monitoring Of Dielectric Properties Of Tree Trunks

    NASA Technical Reports Server (NTRS)

    Mcdonald, Kyle C.; Chun, William

    1996-01-01

    Semiautomated instrumentation system called "dielectric monitoring system" (DMS) developed for measuring microwave permittivities of selected components of plants, in particular, of active xylems in tree trunks. System set up with coaxial probes inserted in tree trunks to measure dielectric properties. Can be left to operate unattended to gather data on permittivities as function of time.

  3. Composition-based prediction of dielectric properties of foods.

    PubMed

    Sun, E; Datta, A; Lobo, S

    1995-01-01

    Prediction of accurate dielectric property data from fundamental principles for systems as complex as foods has not been possible. Simple prediction models based on easily measurable composition data can serve many useful purposes. Literature dielectric data on foods and their composition were statistically correlated. Dielectric data on salt solutions were measured to explain some of the results. When composition data were not available, standard handbook compositions were used. Inclusion of all types of foods (meats, fruits, and vegetables) inhibited any useful correlation with composition. Based on a smaller data set of meats, both dielectric constant and loss increased with water and salt content. Dielectric constant generally decreased with temperature whereas dielectric loss decreased with temperature at lower salt concentrations and increased with temperature at higher salt concentrations.

  4. 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

  5. Dielectric properties of human placenta, umbilical cord and amniotic fluid

    NASA Astrophysics Data System (ADS)

    Peyman, A.; Gabriel, C.; Benedickter, H. R.; Fröhlich, J.

    2011-04-01

    The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 °C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the presence of high water content Wharton's jelly. The results also demonstrate large differences in the dielectric properties of amniotic and cerebrospinal fluids. The data presented can be used in numerical simulations of the exposure of pregnant women to electromagnetic fields.

  6. Collective and static properties of model two-component plasmas

    SciTech Connect

    Arkhipov, Yu. V.; Askaruly, A.; Davletov, A. E.; Meirkanova, G. M.; Ballester, D.; Tkachenko, I. M.

    2007-08-15

    Classical MD data on the charge-charge dynamic structure factor of two-component plasmas (TCP) modeled in Phys. Rev. A 23, 2041 (1981) are analyzed using the sum rules and other exact relations. The convergent power moments of the imaginary part of the model system dielectric function are expressed in terms of its partial static structure factors, which are computed by the method of hypernetted chains using the Deutsch effective potential. High-frequency asymptotic behavior of the dielectric function is specified to include the effects of inverse bremsstrahlung. The agreement with the MD data is improved, and important statistical characteristics of the model TCP, such as the probability to find both electron and ion at one point, are determined.

  7. Collective and static properties of model two-component plasmas.

    PubMed

    Arkhipov, Yu V; Askaruly, A; Ballester, D; Davletov, A E; Meirkanova, G M; Tkachenko, I M

    2007-08-01

    Classical MD data on the charge-charge dynamic structure factor of two-component plasmas (TCP) modeled in Phys. Rev. A 23, 2041 (1981) are analyzed using the sum rules and other exact relations. The convergent power moments of the imaginary part of the model system dielectric function are expressed in terms of its partial static structure factors, which are computed by the method of hypernetted chains using the Deutsch effective potential. High-frequency asymptotic behavior of the dielectric function is specified to include the effects of inverse bremsstrahlung. The agreement with the MD data is improved, and important statistical characteristics of the model TCP, such as the probability to find both electron and ion at one point, are determined. PMID:17930158

  8. Properties of nanoscale dielectrics from first principles computations

    NASA Astrophysics Data System (ADS)

    Shi, Ning

    In recent years, dielectric materials of nanoscale dimensions have aroused considerable interest. We mention two examples. First, in the semiconductor industry, in order to keep pace with Moore's law scaling, the thickness of gate oxide dielectric material is reaching nanoscale dimensions. Second, the high energy density capacitor industry is currently considering dielectric composites with a polymer host matrix filled with inorganic dielectric nanoparticles or polarizable organic molecules. The driving force for the former application is high dielectric constants (or high-k), and those for the latter are high-k and/or high dielectric breakdown strengths. Thus, it is important to characterize the electronic and dielectric properties of materials in the nano-regime, where surface and interface effects naturally play a dominant role. The primary goal of this work is to determine the extent to which such surface/interface effects modify the dielectric constants, band edges, and dielectric breakdown strengths of systems with at least one of their dimensions in the nano-regime. Towards that end, we have developed new computational methodologies at the first principles (density functional) level of theory. These methods have then been applied to several relevant and critical nanoscale systems, including Si:SiO2 and Si:HfO2 heterojunctions, and polymeric composites containing Cu-phthalocyanine and SiO2 nanoparticles.

  9. Dielectric and magnetic properties of some gadolinium silica nanoceramics

    SciTech Connect

    Coroiu, I. Pascuta, P. Bosca, M. Culea, E.

    2013-11-13

    Some nanostructure gadolinium silica glass-ceramics were obtained undergoing a sol gel method and a heat-treatment at 1000°C about two hours. The magnetic and dielectric properties of these samples were studied. The magnetic properties were evidenced performing susceptibility measurements in the 80-300K temperature range. A Curie-Weiss behavior has acquired. The values estimated for paramagnetic Curie temperature being small and positive suggest the presence of weak ferromagnetic interactions between Gd{sup 3+} ions. The dielectric properties were evaluated from dielectric permittivity (ε{sub r}) and dielectric loss (tanδ) measurements at the frequency 1 kHz, 10 kHz and 100 kHz, in the 25-225°C temperature range and dielectric dispersion at room temperature for 79.5 kHz - 1GHz frequency area. The dielectric properties suggest that the main polarization mechanism corresponds to interfacial polarization, characteristic for polycrystalline-structured dielectrics. The polycrystalline structure of the samples is due to the polymorphous transformations of the nanostructure silica crystallites in the presence of gadolinium oxide. They were highlighted by SEM micrographs.

  10. Dielectric properties of human colostrum at microwave frequencies.

    PubMed

    Lonappan, Anil; Rajasekharan, Chadrasekharan; Thomas, Vinu; Bindu, Gopinathan; Mathew, Kattackal Thomas

    2007-01-01

    This article communicates the study of both the dielectric properties of human colostrums and breast milk at microwave frequencies. The colostrum samples were taken immediately after child birth and breast milk samples were collected at weekly intervals following the delivery. Rectangular cavity perturbation technique is used for the measurements of dielectric properties at the S-band of microwave frequency. The dielectric constants of the colostrums samples and breast milk samples are found to increase as weeks elapse, which is attributed to the reduced fat content and increased lactose concentration. The conductivity of these samples is similarly found to increase due to the increased dilution.

  11. Dielectric properties of porcine glands, gonads and body fluids.

    PubMed

    Peyman, A; Gabriel, C

    2012-10-01

    Dielectric properties of porcine glandular tissues and gonads (in vivo) and body fluids (in vitro) have been obtained in the frequency range of 50 MHz to 20 GHz. The experimental data were fitted to a two term Cole-Cole expression. The data presented complement the available dielectric properties of tissues in the literature and can be used in numerical simulations of the exposure of people to electromagnetic fields.

  12. [Dielectric properties of human sweat fluid in the microwave range].

    PubMed

    Romanov, A N

    2010-01-01

    The dielectric properties of sweat fluid gathered from different zones of the human body have been studied in the frequency range from 300 MHz to 3 GHz. It has been shown that the dielectric properties of sweat of different zones differ. The dependence of refraction and absorption indices on the frequency of the signal and the mass concentration of substances dissolved in sweat liquid has been determined.

  13. Optical Transmission Properties of Dielectric Aperture Arrays

    NASA Astrophysics Data System (ADS)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index

  14. 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.

  15. Ab initio investigation of electronic and vibrational contributions to linear and nonlinear dielectric properties of ice

    SciTech Connect

    Casassa, S.; Baima, J.; Mahmoud, A.; Kirtman, B.

    2014-06-14

    Electronic and vibrational contributions to the static and dynamic (hyper)polarizability tensors of ice XI and model structures of ordinary hexagonal ice have been theoretically investigated. Calculations were carried out by the finite field nuclear relaxation method for periodic systems (FF-NR) recently implemented in the CRYSTAL code, using the coupled-perturbed Kohn-Sham approach (CPKS) for evaluating the required electronic properties. The effect of structure on the static electronic polarizabilities (dielectric constants) and second-hyperpolarizabilities is minimal. On the other hand, the vibrational contributions to the polarizabilities were found to be significant. A reliable evaluation of these (ionic) contributions allows one to discriminate amongst ice phases characterized by different degrees of proton-order, primarily through differences caused by librational motions. Transverse static and dynamic vibrational (hyper)polarizabilities were found by extrapolating calculations for slabs of increasing size, in order to eliminate substantial surface contributions.

  16. Dielectric properties and microstructures for various MLCCs coated with additives

    NASA Astrophysics Data System (ADS)

    Oh, Min Wook; Yeo, Dong Hun; Shin, Hyo Soon; Jeong, Dae Yong

    2013-12-01

    As electronic devices become smaller and have higher capacity, dielectric thin films are being used in the development of multilayer ceramic capacitors (MLCCs). Smaller BaTiO3 dielectric particles should be used to obtain the thickness of low dielectric layers. Further, MLCC properties are achieved through the uniform addition of various additives, but the existing method of adding nano additives has limitations. As such, this study evaluated the dielectric properties of BaTiO3 pellets after using the liquid coating method to add additives such as Dy, Mg, Mn, Cr, and Si to 150 nm BaTiO3 dielectric powder. Mn, Cr, and Si ions were each fixed at 0.1, 0.1, and 0.65 mol-%. Sintering was performed in a reducing atmosphere, and the microstructure and the dielectric properties were evaluated while varying Dy from 0.5 to 1.0 mol-% and Mg from 1.0 to 2.0 mol-%. Grain growth was observed for higher amounts of Dy, but were suppressed for higher amounts of Mg. With regards to changes in particle size, both the permittivity and the temperature coefficient of capacitance (TCC) increased with increasing particle size. The permittivity was highest for Si=0.65, Mn=0.1, Cr=0.1 Dy=0.75, and Mg=2.0 mol-%. These levels also satisfied the TCC properties of X7R. In the microstructure, the core-shell was the most developed.

  17. Dielectric properties of certain biological materials at microwave frequencies.

    PubMed

    Kumar, S B; Mathew, K T; Raveendranath, U; Augustine, P

    2001-01-01

    In the medical field, microwaves play a larger role for treatment than diagnosis. For the detection of diseases by microwave methods, it is essential to know the dielectric properties of biological materials. For the present study, a cavity perturbation technique was employed to determine the dielectric properties of these materials. Rectangular cavity resonators were used to measure the complex permittivity of human bile, bile stones, gastric juice and saliva. The measurements were carried out in the S and J bands. It is observed that normal and infected bile have different dielectric constant and loss tangent. Dielectric constant of infected bile and gastric juice varies from patient to patient. Detection and extraction of bile stone with possible method of treatment is also discussed.

  18. Synthesis, microstructure and dielectric properties of zirconium doped barium titanate

    NASA Astrophysics Data System (ADS)

    Kumar, Rohtash; Asokan, K.; Patnaik, S.; Birajdar, Balaji

    2016-05-01

    We report on synthesis, microstructural and relaxor ferroelectric properties of Zirconium(Zr) doped Barium Titanate (BT) samples with general formula Ba(Ti1-xZrx)O3 (x=0.20, 0.35). These lead-free ceramics were prepared by solid state reaction route. The phase transition behavior and temperature dependent dielectric properties and composition dependent ferroelectric properties were investigated. XRD analysis at room temperature confirms phase purity of the samples. SEM observations revealed retarded grain growth with increasing Zr mole fraction. Dielectric properties of BZT ceramics is influenced significantly by small addition of Zr mole fraction. With increasing Zr mole fraction, dielectric constant decreases while FWHM and frequency dispersion increases. Polarization vs electric field hysteresis measurements reveal ferroelectric relaxor phase at room temperature. The advantages of such substitution maneuvering towards optimizing ferroelectric properties of BaTiO3 are discussed.

  19. Electrical properties and dielectric spectroscopy of Ar{sup +} implanted polycarbonate

    SciTech Connect

    Chawla, Mahak Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Nair, K. G. M.

    2015-05-15

    The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar{sup +} ions in the fluence ranging from 1×10{sup 14} to 1×10{sup 16} ions cm{sup −2}. The beam current used was ∼0.40 µA cm{sup −2}. The electrical conduction behaviour of virgin and Ar{sup +} implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ε′ vs. imaginary part of complex permittivity, ε″). The Cole-Cole plots have also been used to determine static dielectric constant (ε{sub s}), optical dielectric constant (ε{sub ∞}), spreading factor (α), average relaxation time (τ{sub 0}) and molecular relaxation time (τ). The dielectric behaviour has been found to be significantly affected due to Ar{sup +} implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  20. Dielectric and other properties of polyimide aerogels containing fluorinated blocks.

    PubMed

    Meador, Mary Ann B; McMillon, Emily; Sandberg, Anna; Barrios, Elizabeth; Wilmoth, Nathan G; Mueller, Carl H; Miranda, Félix A

    2014-05-14

    The dielectric and other properties of a series of low-density polyimide block copolymer aerogels have been characterized. Two different anhydride-capped polyimide oligomers were synthesized: one from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4'-oxidianiline (ODA) and the other from biphenyl-3,3',4,4'-tetracarboxylic dianhydride and ODA. The oligomers were combined with 1,3,5-triaminophenoxybenzene to form a block copolymer networked structure that gelled in under 1 h. The polyimide gels were supercritically dried to give aerogels with relative dielectric constants as low as 1.08. Increasing the amount of 6FDA blocks by up to 50% of the total dianhydride decreased the density of the aerogels, presumably by increasing the free volume and also by decreasing the amount of shrinkage seen upon processing, resulting in a concomitant decrease in the dielectric properties. In this study, we have also altered the density independent of fluorine substitution by changing the polymer concentration in the gelation reactions and showed that the change in dielectric due to density is the same with and without fluorine substitution. The aerogels with the lowest dielectric properties and lowest densities still had compressive moduli of 4-8 MPa (40 times higher than silica aerogels at the same density), making them suitable as low dielectric substrates for lightweight antennas for aeronautic and space applications.

  1. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  2. Spatial variability of dielectric properties in field soils

    NASA Astrophysics Data System (ADS)

    Hendrickx, Jan M. H.; Borchers, Brian; Woolslayer, J.; Dekker, Louis W.; Ritsema, Coen; Paton, S.

    2001-10-01

    Most mine detection sensors are affected by soil properties such as water content, temperature, electrical conductivity, and dielectric constant. The most important of these is water content since it directly influences the three other properties. The variability of these properties may be such that either potential landmine signatures are overshadowed or false alarms result. In this paper we present the results of field measurements in the Netherlands, Panama, and New Mexico on spatial variability of soil water content. We also discuss how the variability of soil water content affects the soils electrical conductivity and dielectric constant and the resulting response of a ground penetrating radar system.

  3. Three dimensional reflectance properties of superconductor-dielectric photonic crystal

    NASA Astrophysics Data System (ADS)

    Pandey, G. N.; Pandey, J. P.; Pandey, U. K.; Sancheti, Bhagyashree; Ojha, S. P.

    2016-05-01

    In this present communication, we have studied the optical properties of Photonics Crystals with super conducting constituent using the TMM method for a stratified medium. We also studied the three dimensional reflectance property of superconductor-dielectric photonic crystal at different temperature and thickness. From above study we show that the superconductor-dielectric photonic crystal may be used as broad band reflector and omnidirectional reflector at low temperature below to the critical temperature. Such property may be applied to make of the reflector which can be used in low temperature region.

  4. Dielectric properties of biomass and biochar mixtures for bioenergy applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomass is an abundant and renewable energy resource, which may be converted into energy-dense products through thermochemical processes such as pyrolysis and gasification. Since microwave heating depends on the dielectric properties of the biomass material, these properties were measured at freque...

  5. Factors affecting the dielectric properties of agricultural and food products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of materials are defined, and the major factors that influence these properties of agricultural and food materials, namely, frequency of the applied radio-frequency and microwave electric fields, water content, temperature, and density of the materials are discussed on the bas...

  6. Factors Influencing the Dielectric Properties of Agricultural and Food Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of materials are defined, and the major factors that influence these properties of agricultural and food materials, namely, frequency of the applied radio-frequency or microwave electric fields, and water content, temperature, and density of the materials, are discussed on the ...

  7. Diurnal changes in the dielectric properties and water status of eastern hemlock and red spruce from Howland, ME

    NASA Technical Reports Server (NTRS)

    Salas, W. A.; Ranson, K. J.; Rock, B. N.; Moss, D. M.

    1991-01-01

    The diurnal characteristics of microwave dielectric properties and water potential of two conifer species were investigated in July and September, 1990. P-band and C-band radial dielectric profiles of hemlock and red spruce, as well as hemlock diurnal water potential and dielectric profiles, are presented. The resulting radial dielectric profiles matched the regions of the functional sapwood (water transport component of the active xylem) in both species such that the sapwood was characterized by a higher dielectric than the bark and heartwood tissues. This is probably due to characteristic differences in the water content of each tissue. As the hemlocks progressed through their diurnal water potential pattern, the dielectric profile remained static until mid-afternoon. As the tension in the water column relaxed (2 to 3 bars) the dielectric constant decreased by 30 to 40 percent. There are several possible explanations for this phenomenon, and these may relate to the dependency of the dielectric measurements on temperature, salinity, and volumetric water content.

  8. Dielectric properties of soils as a function of moisture content

    NASA Technical Reports Server (NTRS)

    Cihlar, J.; Ulaby, F. T.

    1974-01-01

    Soil dielectric constant measurements are reviewed and the dependence of the dielectric constant on various soil parameters is determined. Moisture content is given special attention because of its practical significance in remote sensing and because it represents the single most influential parameter as far as soil dielectric properties are concerned. Relative complex dielectric constant curves are derived as a function of volumetric soil water content at three frequencies (1.3 GHz, 4.0 GHz, and 10.0 GHz) for each of three soil textures (sand, loam, and clay). These curves, presented in both tabular and graphical form, were chosen as representative of the reported experimental data. Calculations based on these curves showed that the power reflection coefficient and emissivity, unlike skin depth, vary only slightly as a function of frequency and soil texture.

  9. Dielectric properties of inorganic fillers filled epoxy thin film

    SciTech Connect

    Norshamira, A. Mariatti, M.

    2015-07-22

    The demand on the small size and high performance electronics has driven changes in the electronic packaging requirements from discrete capacitor to embedded capacitor. Embedded capacitor can improve electrical performance compared with discrete capacitor. This study aimed to achieve high dielectric of epoxy thin film composite that were targeted for application as embedded capacitor. In this study, inorganic fillers such as Calcium Copper Titanate (CCTO), Iron(III) Oxide (Fe{sub 2}O{sub 3}) and Titanium Dioxide (TiO{sub 2}) were loaded in epoxy system at 5 and 20vol%. Morphology and dielectric properties were investigated to identify the effect of fillers loading and types of fillers on the properties of epoxy thin film composite. Based on the study, CCTO with 20vol% loading was found to have good dielectric properties compared to other type of fillers.

  10. Pyroelectric and dielectric properties of calcium barium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Malyshkina, O. V.; Lisitsin, V. S.; Dec, J.; Łukasiewicz, T.

    2014-09-01

    The effect of the calcium concentration on the pyroelectric and dielectric properties of Ca x Ba1 - x Nb2O6 (CBN) crystals has been studied over a wide temperature range. It has been shown that the calcium concentration only influences the Curie point of crystals of this class. It insignificantly changes the absolute values of the permittivity, the coercive field, and the remanent polarization and does not influence their temperature dependences and the shape of the dielectric hysteresis loop. The possibility of the existence of relaxor properties in CBN crystals has been discussed.

  11. Method to characterize dielectric properties of powdery substances

    NASA Astrophysics Data System (ADS)

    Tuhkala, M.; Juuti, J.; Jantunen, H.

    2013-07-01

    An open ended coaxial cavity method for dielectric characterization of powdery substance operating at 4.5 GHz in TEM mode is presented. Classical mixing rules and electromagnetic modeling were utilized with measured effective permittivities and Q factors to determine the relative permittivity and dielectric loss tangent of different powders with ɛr up to 30. The modeling enabled determination of the correction factor for the simplified equation for the relative permittivity of an open ended coaxial resonator and mixing rules having the best correlation with experiments. SiO2, Al2O3, LTCC CT 2000, ZrO2, and La2O3 powders were used in the experiments. Based on the measured properties and Bruggeman symmetric and Looyenga mixing rules, the determined dielectric characteristics of the powders exhibited good correlation with values in the literature. The presented characterization method enabled the determination of dielectric properties of powdery substances within the presented range, and therefore could be applied to various research fields and applications where dielectric properties of powders need to be known and controlled.

  12. Dielectric properties of epoxy resin fly ash composite

    NASA Astrophysics Data System (ADS)

    Pattanaik, A.; Bhuyan, S. K.; Samal, S. K.; Behera, A.; Mishra, S. C.

    2016-02-01

    Epoxy resin is widely used as an insulating material in high voltage applications. Ceramic fillers are always added to the polymer matrix to enhance its mechanical properties. But at the same time, filler materials decreases the electrical properties. So while making the fly ash epoxy composite, it is obvious to detect the effect of fly ash reinforcement on the dielectric nature of the material. In the present research work, fly ash is added to four different weight percentages compositions and post-curing has been done in the atmospheric condition, normal oven and micro oven. Tests were carried out on the developed polymer composite to measure its dielectric permittivity and tan delta value in a frequency range of 1 Hz - 1 MHz. The space charge behaviours were also observed by using the pulse electroacoustic (PEA) technique. The dielectric strength and losses are compared for different conditions.

  13. Impedance and dielectric properties of mercury cuprate at nonsuperconducting state

    NASA Astrophysics Data System (ADS)

    Özdemir, Z. Güven; Çataltepe, Ö. Aslan; Onbaşlı, Ü.

    2015-10-01

    In this paper, impedance and dielectric properties of nonsuperconducting state of the mercury-based cuprate have been investigated by impedance measurements within the frequency interval of 10 Hz-10 MHz for the first time. The dielectric loss factor (tgδ) and ac conductivity (σac) parameters have also been calculated for non-superconducting state. According to impedance spectroscopy analysis, the equivalent circuit of the mercury cuprate system manifests itself as a semicircle in the Nyquist plot that corresponds to parallel connected resistance-capacitance circuit. The oscillation frequency of the circuit has been determined as approximately 45 kHz which coincides with the low frequency radio waves. Moreover, it has been revealed that the mercury-based cuprate investigated has high dielectric constants and hence it may be utilized in microelectronic industry such as capacitors, memory devices etc., at room temperature. In addition, negative capacitance (NC) effect has been observed for the mercury cuprate regardless of the operating temperatures at nonsuperconducting state. Referring to dispersions in dielectric properties, the main contribution to dielectric response of the system has been suggested as dipolar and interfacial polarization mechanisms.

  14. Contribution to the modelling of the electromagnetic properties of random dielectric-conductor mixtures

    NASA Astrophysics Data System (ADS)

    Guillot, Thierry

    1992-05-01

    The electromagnetic properties of dielectric-conductor mixtures are investigated and the validity of several 'mixture laws' is discussed. Wideband microwave absorption can not be performed by means of homogeneous materials. Experimentally, it was noticed that some compounds made with small conducting grains dipersed in a dielectric host can be used in radar absorber design. Many 'mixture laws' were derived to model the dielectric permittivity of dielectric conductor mixtures. Though they give good results for mixtures in which grains are separated, they fail in modeling those in which there exist conducting paths between inclusions. If the paths are tunneling junctions, the mixtures are called 'supercolative'. Electron jumping is responsible for special phenomena: an anomalous direct current conduction threshold; and a 'Jonscher effect' caused by short electrostatic interactions. The mixtures for which the quasi static approximation is not matched inside the conducting medium are considered. It yields an artificial lossy diamagnetic behavior for which a model is derived. Experimental results that show very good agreements with this model are presented. This special effect gives rise to a new method for measuring the electrical conductivity of grain in conducting powders.

  15. Dielectric Properties of Epoxy Resin Composites Filled with Nanocarbon Inclusions

    NASA Astrophysics Data System (ADS)

    Macutkevic, J.; Kranauskaite, I.; Banys, J.; Paddubskaya, A.; Stefanutti, E.; Cataldo, A.; Micciulla, F.; Celzard, A.; Fierro, V.

    2013-05-01

    The epoxy resin composites with various carbon additives were investigated in the frequency range of 20 Hz - 3 GHz at temperatures from room to 500 K. The dielectric properties were found to be strongly impacted by percolation threshold. The lowest percolation threshold (< 0.25 wt.%), was observed in composites with single-walled carbon nanotubes.

  16. Temperature-dependent dielectric properties of a thermoplastic gelatin

    NASA Astrophysics Data System (ADS)

    Landi, Giovanni; Neitzert, Heinz C.; Sorrentino, Andrea

    2016-05-01

    The frequency and the temperature dependence of the dielectric properties of a thermoplastic gelatin based bio-material have been investigated. At lower frequencies the dielectric response is strongly affected by charge carrier accumulation at the electrodes which modifies the dominating hopping conduction mechanism. The variation of the ac conductivity with frequency obeys a Jonscher type power law except for a small deviation in the low frequency range due to the electrode polarization effect. The master curve of the ac conductivity data shows that the conductivity relaxation of the gelatin is temperature independent.

  17. Quasi-static electric properties of insulating polymers at a high voltage for electro-bonded laminates

    NASA Astrophysics Data System (ADS)

    Di Lillo, L.; Carnelli, D. A.; Bergamini, A.; Busato, S.; Ermanni, P.

    2011-05-01

    This paper reports on a high voltage measurement set-up for determining the relative permittivity and the volume resistivity of dielectric polymers. These properties were evaluated on thin films at electric fields up to 80 V µm-1 and in the quasi-static regime at frequencies lower than 1 Hz. It is found that the high field properties of FEP, PFA, polyimide and Mylar are comparable to the respective low field values, while for ferroelectric PVDF poling behavior becomes evident at high fields. High field properties of dielectric polymers are of particular importance in the design of devices relying on electrostatic attraction, such as electro-bonded laminates applied in tunable bending stiffness structures.

  18. 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.

  19. Dielectric Properties and Ion Mobility in Erythrocytes

    PubMed Central

    Pauly, H.; Schwan, H. P.

    1966-01-01

    The impedance of erythrocytes of man, cattle, sheep, dog, cat, rabbit, and chicken was measured in the range from 0.5 to 250 Mc. The dielectric constant of the red cell interior is 50 at 250 Mc, varies but little with species, and can readily be accounted for by the cells' hemoglobin content. The electrical conductivity of the red cell interior was determined between 70 and 100 Mc. The values differ from species to species within the rather limited range from 4.4 to 5.3 mmho/cm. Removal of the cell membranes does not affect the conductivity. Hence, the cell interior behaves, from an electrical point of view, like a highly concentrated hemoglobin solution. A theoretical value for the electrical conductivity of erythrocyte interiors, which is calculated on the basis of the salt content of the cell, ion mobility, and the volume concentration of the hemoglobin, is roughly twice as large as the measured value. This discrepancy is typical not only of the red blood cell. Pertinent measurements show that it is probably caused by hydrodynamic and possibly by electrostatic effects also, which lower the mobility of the ions. From the lower electrical mobility it appears that a lowered diffusion constant of the electrolytes and nonelectrolytes within the cell is indicated. PMID:5970566

  20. Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

    NASA Astrophysics Data System (ADS)

    Clifford, Jallisa Janet

    quantitatively using BbDS. These materials are typically used in solid oxide fuel cells (SOFC). Results show significant effect of microstructural design on material properties at multiple temperatures (up to 800 °C). In the later part of the thesis, we will focus on microstructural changes of fiber reinforced composite materials due to impact and static loading. The changes in dielectric response can then be linked to the bulk mechanical properties of the material and various damage modes. Observing trends in dielectric response enables us to further determine local mechanisms and distribution of properties throughout the damaged specimens. A 3D X-ray microscope and a digital microscope have been used to visualize these changes in material microstructure and validate experimental observations. The increase in damage observed in the material microstructure can then also be linked to the changes in dielectric response. Results show that BbDS is an extremely useful tool for identifying microstructural changes within a heterogeneous material and particularly useful in relating remaining properties. Dielectric material variables can be used directly in property degradation laws and help develop a framework for future predictive modeling methodologies.

  1. Microwave Dielectric Properties of Ceramic/Semicrystalline Polymer Composites

    NASA Astrophysics Data System (ADS)

    Im, Dong Hyeok; Ju, Han Sae; Kim, Eung Soo

    2012-09-01

    The effects of various ceramics and semicrystalline polymers on the dielectric properties of MgMoO4/polypropylene (PP), MgWO4/PP, NiNb2O6/poly(tetrafluoroethylene) (PTFE), and MgNb2O6/PTFE composites were investigated at microwave frequencies. In the frequency range from 1 to 9.4 GHz, the dielectric constant (K) of the composites showed good frequency stability, while their dielectric loss (\\tan δ) increased with increasing frequency, due to the dipolar relaxation process associated with the matrices. With increasing ceramic content, the K and \\tan δ values of the composites increased, due to the K values of the individual components and interfacial polarization between the ceramics and polymers. For the composites with the same amounts of ceramics, the K value and temperature coefficient of the resonant frequency (TCF) of the composites were dependent on the type of ceramics. Also, the measured K values of the composites were compared with the effective dielectric properties calculated by different theoretical models.

  2. Dielectric and structural properties of ferroelectric betaine arsenate films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Yurko, E. I.; Svinarev, F. B.

    2014-12-01

    Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = T c is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from T c = 119 K in the films without deuterium to T c = 149 K, which corresponds to the degree of deuteration of approximately 60-70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

  3. Dielectric and electric properties of new chitosan-hydroxyapatite materials for biomedical application: Dielectric spectroscopy and corona treatment.

    PubMed

    Petrov, Ivo; Kalinkevich, Oksana; Pogorielov, Maksym; Kalinkevich, Aleksei; Stanislavov, Aleksandr; Sklyar, Anatoly; Danilchenko, Sergei; Yovcheva, Temenuzhka

    2016-10-20

    Chitosan-hydroxyapatite composite materials were synthesized and the possibility to make their surface charged by corona discharge treatment has been evaluated. Dielectric and electric properties of the materials were studied by dielectric spectroscopy, including application of equivalent circuits method and computer simulations. Dielectric spectroscopy shows behavior of the materials quite different from that of both chitosan and HA alone. The obtained dielectric permittivity data are of particular interest in predicting the materials' behavior in electrostimulation after implantation. The ε values observed at physiological temperature in the frequency ranges applied are similar to ε data available for bone tissues.

  4. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Jackson, Henry W.

    2010-01-01

    A paper discusses the need to perform accurate dielectric property measurements on larger sized samples, particularly liquids at microwave frequencies. These types of measurements cannot be obtained using conventional cavity perturbation methods, particularly for liquids or powdered or granulated solids that require a surrounding container. To solve this problem, a model has been developed for the resonant frequency and quality factor of a cylindrical microwave cavity containing concentric cylindrical samples. This model can then be inverted to obtain the real and imaginary dielectric constants of the material of interest. This approach is based on using exact solutions to Maxwell s equations for the resonant properties of a cylindrical microwave cavity and also using the effective electrical conductivity of the cavity walls that is estimated from the measured empty cavity quality factor. This new approach calculates the complex resonant frequency and associated electromagnetic fields for a cylindrical microwave cavity with lossy walls that is loaded with concentric, axially aligned, lossy dielectric cylindrical samples. In this approach, the calculated complex resonant frequency, consisting of real and imaginary parts, is related to the experimentally measured quantities. Because this approach uses Maxwell's equations to determine the perturbed electromagnetic fields in the cavity with the material(s) inserted, one can calculate the expected wall losses using the fields for the loaded cavity rather than just depending on the value of the fields obtained from the empty cavity quality factor. These additional calculations provide a more accurate determination of the complex dielectric constant of the material being studied. The improved approach will be particularly important when working with larger samples or samples with larger dielectric constants that will further perturb the cavity electromagnetic fields. Also, this approach enables the ability to have a

  5. Dielectric properties of low-water-content tissues.

    PubMed

    Smith, S R; Foster, K R

    1985-09-01

    The dielectric properties of two low-water-content tissues, bone marrow and adipose tissue, were measured from 1 kHz to 1 GHz. From 1 kHz to 13 MHz, the measurements were performed using a parallel-plate capacitor method. From 10 MHz to 1 GHz, a reflection coefficient technique using an open-ended coaxial transmission line was employed. The tissue water contents ranged from 1 to almost 70% by weight. The dielectric properties correlate well with the values predicted by mixture theory. Comparison with previous results from high-water-content tissues suggests that bone marrow and adipose tissues contain less motionally altered water per unit dry volume than do the previously studied tissues with lower lipid fractions. The high degree of structural heterogeneity of these tissues was reflected in the large scatter of the data, a source of uncertainty that should be considered in practical applications of the present data.

  6. A novel Graphene Oxide film: Synthesis and Dielectric properties

    NASA Astrophysics Data System (ADS)

    Canimkurbey, Betul; San, Sait Eren; Yasin, Muhammad; Köse, Muhammet Erkan

    In this work, we used Hummers method to synthesize Graphene Oxide (GO) and its parallel plate impedance spectroscopic technique to investigate dielectric properties. Graphene Oxide films were coated using drop casting method on ITO substrate. To analyze film morphology, atomic force microscopy was used. Dielectrics measurements of the samples were performed using impedance analyzer (HP-4194) in frequency range (100 Hz to 10MHz) at different temperatures. It was observed that the films' AC conductivity σac varied with angular frequency, ω as ωS, with S<1. The electrical properties of GO showed changes depending on both frequency and temperature. We observed GO film contains direct current (DC) and Correlated Barrier Hopping (CBH) conductivity mechanisms at low and high frequency ranges, respectively. Using solution processed Graphene Oxide will provide potential for organic electronic applications through its photon absorption and transmittance capability in the visible range and excellent electrical parameters.

  7. Ultrashort electric pulse induced changes in cellular dielectric properties.

    PubMed

    Garner, Allen L; Chen, George; Chen, Nianyong; Sridhara, Viswanadham; Kolb, Juergen F; Swanson, R James; Beebe, Stephen J; Joshi, Ravindra P; Schoenbach, Karl H

    2007-10-12

    The interaction of nanosecond duration pulsed electric fields (nsPEFs) with biological cells, and the models describing this behavior, depend critically on the electrical properties of the cells being pulsed. Here, we used time domain dielectric spectroscopy to measure the dielectric properties of Jurkat cells, a malignant human T-cell line, before and after exposure to five 10ns, 150kV/cm electrical pulses. The cytoplasm and nucleoplasm conductivities decreased dramatically following pulsing, corresponding to previously observed rises in cell suspension conductivity. This suggests that electropermeabilization occurred, resulting in ion transport from the cell's interior to the exterior. A delayed decrease in cell membrane conductivity after the nsPEFs possibly suggests long-term ion channel damage or use dependence due to repeated membrane charging and discharging. This data could be used in models describing the phenomena at work.

  8. Boron nitride hollow nanospheres: Synthesis, formation mechanism and dielectric property

    SciTech Connect

    Zhong, B.; Tang, X.H.; Huang, X.X.; Xia, L.; Zhang, X.D.; Wang, C.J.; Wen, G.W.

    2015-04-15

    Highlights: • BN hollow nanospheres are fabricated in large scale via a new CVD method. • Morphology and structure are elucidated by complementary analytical techniques. • Formation mechanism is proposed based on experimental observations. • Dielectric properties are investigated in the X-band microwave frequencies. • BN hollow nanospheres show lower dielectric loss than regular BN powders. - Abstract: Boron nitride (BN) hollow nanospheres have been successfully fabricated by pyrolyzing vapors decomposed from ammonia borane (NH{sub 3}BH{sub 3}) at 1300 °C. The final products have been extensively characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BN hollow nanospheres were ranging from 100 to 300 nm in diameter and around 30–100 nm in thickness. The internal structure of the products was found dependent on the reaction temperatures. A possible formation mechanism of the BN hollow nanospheres was proposed on the basis of the experimental observations. Dielectric measurements in the X-band microwave frequencies (8–12 GHz) showed that the dielectric loss of the paraffin filled by the BN hollow nanospheres was lower than that filled by regular BN powders, which indicated that the BN hollow nanospheres could be potentially used as low-density fillers for microwave radomes.

  9. Dielectric properties of semi-insulating silicon at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Krupka, Jerzy; Kamiński, Paweł; Kozłowski, Roman; Surma, Barbara; Dierlamm, Alexander; Kwestarz, Michał

    2015-08-01

    The permittivity and dielectric loss tangent of high-purity silicon with semi-insulating properties achieved by the irradiation with 23-MeV protons have been measured at frequencies from 1 GHz to 15 GHz. The dielectric losses were separated from the conductor losses on the basis of the total loss tangent measurements versus frequency. The resistivity measurements of the material performed at radio frequencies (RF) by means of the capacitance spectroscopy method have shown the non-uniform resistivity distribution in the direction perpendicular to the surface of the semi-insulating wafer. The excellent agreement between the resistivity measurements results at RF and those obtained by using microwave methods have been achieved. It has been confirmed that high-purity, semi-insulating silicon is practically non-dispersive and possesses extremely low dielectric losses that are constant to within experimental errors in the frequency range from 1 GHz to 350 GHz. In this frequency range, the dielectric loss tangent of semi-insulating silicon is equal to 1.2 ×10-5 .

  10. Structure and Electronic Properties of Polycrystalline Dielectrics

    SciTech Connect

    Mckenna, Keith P.; Shluger, AL

    2013-07-07

    We present an overview of the theoretical approaches that can be employed to model polycrystalline oxides along with a discussion of their limitations and associated challenges. We then present results for two metal oxide materials, MgO and HfO2, where theory and experiment have come together to provide insight into the structure and electronic properties of grain boundaries. Finally, we conclude with a discussion and outlook.

  11. Structure-property relationships in polymers for dielectric capacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Sahil

    Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the alpha-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a >model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to

  12. Structural, electrical and dielectric properties of yttrium substituted nickel ferrites

    NASA Astrophysics Data System (ADS)

    Ishaque, M.; Islam, M. U.; Azhar Khan, M.; Rahman, I. Z.; Genson, A.; Hampshire, S.

    2010-03-01

    The influence of Y 3+ substitution on the structural, electrical and dielectric properties of Ni-Y ferrites was studied in the ferrite series NiY 2xFe 2-2xO 4 where x=0-0.12 in steps of 0.02. This series was prepared by conventional double sintering ceramic method. XRD analysis reveals single phase samples up to x=0.06. At x≥0.08, a secondary phase of iron yttrium oxide (YFeO 3) appears along with the spinel phase. The incorporation of Y 3+ for Fe 3+ ions results in a slight increase of lattice constant due to larger ionic radius of the substituted ions. It was inferred that the substitution of yttrium limits the grain growth. The physical densities are about 90% of their X-ray densities. FTIR spectra obtained at room temperature in the wave number range 370-1100 cm -1 show splitting of the two fundamental absorption bands, thereby confirming the completion of solid state reaction. The increase in dc resistivity has been found with the increase in Y 3+ contents. Dielectric constant (ε‧) and loss tangent (tan δ) were measured at room temperature in the frequency range from 10 Hz to10 MHz. A significant reduction in the values of dielectric constant and dielectric loss tangent has been observed with the increase of Y 3+ ions. The high dc resistivity and low dielectric losses are the desired characteristics of Ni-Y ferrites used to prepare microwave devices.

  13. 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.

  14. Static and dynamic properties of supercooled water in small nanotubes.

    PubMed

    Khademi, Mahdi; Sahimi, Muhammad

    2016-07-14

    The static and dynamic properties of water in small silicon-carbide and carbon nanotubes have been studied over the temperature range 100 K-298 K, using extensive molecular dynamics simulations. The computed properties include the radial distribution function, the cage correlation function, the space-time autocorrelation function, the velocity autocorrelation function, and the self-diffusivity. They all indicate that, under the conditions that we study, water does not freeze in small nanotubes; the Stokes-Einstein relation breaks down, and the self-diffusivity exhibits a transition around 230 K, very close to 228 K, the temperature at which a fragile-to-strong dynamic crossover is supposed to happen. The cage correlation function C(t) decays according to a stretched-exponential function, C(t) ∼ exp[ - (t/τ)(β)], where τ is a relaxation time and β is a topological exponent. PMID:27421415

  15. Static and dynamic properties of supercooled water in small nanotubes

    NASA Astrophysics Data System (ADS)

    Khademi, Mahdi; Sahimi, Muhammad

    2016-07-01

    The static and dynamic properties of water in small silicon-carbide and carbon nanotubes have been studied over the temperature range 100 K-298 K, using extensive molecular dynamics simulations. The computed properties include the radial distribution function, the cage correlation function, the space-time autocorrelation function, the velocity autocorrelation function, and the self-diffusivity. They all indicate that, under the conditions that we study, water does not freeze in small nanotubes; the Stokes-Einstein relation breaks down, and the self-diffusivity exhibits a transition around 230 K, very close to 228 K, the temperature at which a fragile-to-strong dynamic crossover is supposed to happen. The cage correlation function C(t) decays according to a stretched-exponential function, C(t) ˜ exp[ - (t/τ)β], where τ is a relaxation time and β is a topological exponent.

  16. Reconstruction of scattering properties of rough air-dielectric boundary

    NASA Astrophysics Data System (ADS)

    Sokolov, V. G.; Zhdanov, D. D.; Potemin, I. S.; Garbul, A. A.; Voloboy, A. G.; Galaktionov, V. A.; Kirilov, N.

    2016-10-01

    The article is devoted to elaboration of the method of reconstruction of rough surface scattering properties. The object with rough surface is made of transparent dielectric material. Typically these properties are described with bi-directional scattering distribution function (BSDF). Direct measurement of such function is either impossible or very expensive. The suggested solution provides physically reasonable method for the rough surface BSDF reconstruction. The method is based on Monte-Carlo ray tracing simulation for BSDF calculation. Optimization technique is further applied to correctly reconstruct the BSDF. The results of the BSDF reconstruction together with measurement results are presented in the article as well.

  17. Reconstruction of scattering properties of rough air-dielectric boundary

    NASA Astrophysics Data System (ADS)

    Sokolov, V. G.; Zhdanov, D. D.; Potemin, I. S.; Garbul, A. A.; Voloboy, A. G.; Galaktionov, V. A.; Kirilov, N.

    2016-08-01

    The article is devoted to elaboration of the method of reconstruction of rough surface scattering properties. The object with rough surface is made of transparent dielectric material. Typically these properties are described with bi-directional scattering distribution function (BSDF). Direct measurement of such function is either impossible or very expensive. The suggested solution provides physically reasonable method for the rough surface BSDF reconstruction. The method is based on Monte-Carlo ray tracing simulation for BSDF calculation. Optimization technique is further applied to correctly reconstruct the BSDF. The results of the BSDF reconstruction together with measurement results are presented in the article as well.

  18. Analysis of Dielectric and Thermal Properties of Polyamide Enamel Filled with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Selvaraj, D. Edison; Sugumaran, C. Pugazhendhi; Ganesan, Lieutenant J.; Ramathilagam, J.

    2013-06-01

    In recent days, there was a significant development in the area of nanoparticles and nanoscale fillers on dielectric, thermal and mechanical properties of polymeric materials. The dielectric and thermal properties of standard polyamide and nanoscale-filled samples were detailed and analyzed. Carbon nanotubes were used as nanofillers. Carbon nanotubes were synthesized by chemical vapor deposition (CVD). The basic properties such as dielectric loss tangent (tan δ), dielectric constant (ɛ), dielectric strength, partial discharge inception voltage, surface resistivity, quality factor, phase angle, dielectric conductivity, dielectric power loss and thermal withstand strength of the polyamide enamel filled with carbon nanotubes were analyzed and compared with the properties of the standard enamel. The experimental results show that carbon nanotubes mixed with polyamide enamel had better thermal properties when compared to that of standard enamel.

  19. Dielectric properties of 'diamondlike' carbon prepared by RF plasma deposition

    NASA Technical Reports Server (NTRS)

    Lamb, J. D.; Woollam, J. A.

    1985-01-01

    Metal-carbon-metal structures were fabricated using either gold or aluminum evaporated electrodes and RF plasma (methane) deposited 'diamondlike' carbon films. Alternating-current conductance and capacitance versus voltage and frequency (10 Hz to 13 MHz) data were taken to determine the dielectric properties of these films. Conductance versus frequency data fit a generalized power law, consistent with both dc and hopping conduction components. The capacitance versus frequency data are well matched to the conductance versus frequency data, as predicted by a Kramers-Kronig analysis. The dielectric loss tangent is nearly constant at 0.5 to 1.0 percent over the frequency range from 1 to 100 kHz. The dc resistivity is above 10 to the 13th ohm cm, and the dc breakdown strength is above 8 x 10 to the 6th V/cm is properly prepared samples.

  20. Dielectric properties of TbMnO3 ceramics

    NASA Astrophysics Data System (ADS)

    Wang, C. C.; Cui, Y. M.; Zhang, L. W.

    2007-01-01

    The complex dielectric properties for ceramic samples of TbMnO3 were investigated as functions of temperature (100K ⩽T⩽360K) and frequency (100Hz⩽f⩽100kHz). Two thermally activated dielectric relaxations were found with the activation energies of 0.30 and 0.22eV for the high- and low-temperature relaxations, respectively. By means of complex impedance analysis the high-temperature relaxation was identified to originate from the internal barrier-layer capacitor effects related to the grain boundaries, and the low-temperature relaxation was ascribed to the dipolar effects induced by charge-carrier-hopping motions inside the grains.

  1. Protein dielectrophoresis and the link to dielectric properties

    PubMed Central

    Camacho-Alanis, Fernanda; Ros, Alexandra

    2015-01-01

    There is a growing interest in protein dielectrophoresis (DEP) for biotechnological and pharmaceutical applications. However, the DEP behavior of proteins is still not well understood which is important for successful protein manipulation. In this paper, we elucidate the information gained in dielectric spectroscopy (DS) and electrochemical impedance spectroscopy (EIS) and how these techniques may be of importance for future protein DEP manipulation. EIS and DS can be used to determine the dielectric properties of proteins predicting their DEP behavior. Basic principles of EIS and DS are discussed and related to protein DEP through examples from previous studies. Challenges of performing DS measurements as well as potential designs to incorporate EIS and DS measurements in DEP experiments are also discussed. PMID:25697193

  2. First-principles study of structural, electronic, vibrational, dielectric and elastic properties of tetragonal Ba₂YTaO₆

    SciTech Connect

    Ganeshraj, C.; Santhosh, P. N.

    2014-10-14

    We report first-principles study of structural, electronic, vibrational, dielectric, and elastic properties of Ba₂YTaO₆, a pinning material in high temperature superconductors (HTS), by using density functional theory. By using different exchange-correlation potentials, the accuracy of the calculated lattice constants of Ba₂YTaO₆ has been achieved with GGA-RPBE, since many important physical quantities crucially depend on change in volume. We have calculated the electronic band structure dispersion, total and partial density of states to study the band gap origin and found that Ba₂YTaO₆ is an insulator with a direct band gap of 3.50 eV. From Mulliken population and charge density studies, we conclude that Ba₂YTaO₆ have a mixed ionic-covalent character. Moreover, the vibrational properties, born effective charges, and the dielectric permittivity tensor have been calculated using linear response method. Vibrational spectrum determined through our calculations agrees well with the observed Raman spectrum, and allows assignment of symmetry labels to modes. We perform a detailed analysis of the contribution of the various infrared-active modes to the static dielectric constant to explain its anisotropy, while electronic dielectric tensor of Ba₂YTaO₆ is nearly isotropic, and found that static dielectric constant is in good agreement with experimental value. The six independent elastic constants were calculated and found that tetragonal Ba₂YTaO₆ is mechanically stable. Other elastic properties, including bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and elastic anisotropy ratios are also investigated and found that Poisson's ratio and Young's modulus of Ba₂YTaO₆ are similar to that of other pinning materials in HTS.

  3. Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si3N4 dielectric layer.

    PubMed

    Shen, Hsien-Hua; Chung, Lung-Yuan; Yao, Da-Jeng

    2015-03-01

    Dielectric breakdown is a common problem in a digital microfluidic system, which limits its application in chemical or biomedical applications. We propose a new fabrication of an electrowetting-on-dielectric (EWOD) device using Si3N4 deposited by low-pressure chemical vapor deposition (LPCVD) as a dielectric layer. This material exhibits a greater relative permittivity, purity, uniformity, and biocompatibility than polymeric films. These properties also increase the breakdown voltage of a dielectric layer and increase the stability of an EWOD system when applied in biomedical research. Medium droplets with mouse embryos were manipulated in this manner. The electrical properties of the Si3N4 dielectric layer-breakdown voltage, refractive index, relative permittivity, and variation of contact angle with input voltage-were investigated and compared with a traditional Si3N4 dielectric layer deposited as a plasma-enhanced chemical vapor deposition to confirm the potential of LPCVD Si3N4 applied as the dielectric layer of an EWOD digital microfluidic system.

  4. Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si3N4 dielectric layer

    PubMed Central

    Shen, Hsien-Hua; Chung, Lung-Yuan

    2015-01-01

    Dielectric breakdown is a common problem in a digital microfluidic system, which limits its application in chemical or biomedical applications. We propose a new fabrication of an electrowetting-on-dielectric (EWOD) device using Si3N4 deposited by low-pressure chemical vapor deposition (LPCVD) as a dielectric layer. This material exhibits a greater relative permittivity, purity, uniformity, and biocompatibility than polymeric films. These properties also increase the breakdown voltage of a dielectric layer and increase the stability of an EWOD system when applied in biomedical research. Medium droplets with mouse embryos were manipulated in this manner. The electrical properties of the Si3N4 dielectric layer—breakdown voltage, refractive index, relative permittivity, and variation of contact angle with input voltage—were investigated and compared with a traditional Si3N4 dielectric layer deposited as a plasma-enhanced chemical vapor deposition to confirm the potential of LPCVD Si3N4 applied as the dielectric layer of an EWOD digital microfluidic system. PMID:25825614

  5. Electrical and dielectric properties of bovine trabecular bone - relationships with mechanical properties and mineral density

    NASA Astrophysics Data System (ADS)

    Sierpowska, J.; Töyräs, J.; Hakulinen, M. A.; Saarakkala, S.; Jurvelin, J. S.; Lappalainen, R.

    2003-03-01

    Interrelationships of trabecular bone electrical and dielectric properties with mechanical characteristics and density are poorly known. While electrical stimulation is used for healing fractures, better understanding of these relations has clinical importance. Furthermore, earlier studies have suggested that bone electrical and dielectric properties depend on the bone density and could, therefore, be used to predict bone strength. To clarify these issues, volumetric bone mineral density (BMDvol), electrical and dielectric as well as mechanical properties were determined from 40 cylindrical plugs of bovine trabecular bone. Phase angle, relative permittivity, loss factor and conductivity of wet bovine trabecular bone were correlated with Young's modulus, yield stress, ultimate strength, resilience and BMDvol. The reproducibility of in vitro electrical and dielectric measurements was excellent (standardized coefficient of variation less than 1%, for all parameters), especially at frequencies higher than 1 kHz. Correlations of electrical and dielectric parameters with the bone mechanical properties or density were frequency-dependent. The relative permittivity showed the strongest linear correlations with mechanical parameters (r > 0.547, p < 0.01, n = 40, at 50 kHz) and with BMDvol (r = 0.866, p < 0.01, n = 40, at 50 kHz). In general, linear correlations between relative permittivity and mechanical properties or BMDvol were highest at frequencies over 6 kHz. In addition, a significant site-dependent variation of electrical and dielectric characteristics, mechanical properties and BMDvol was revealed in bovine femur (p < 0.05, Kruskall-Wallis H-test). Based on the present results, we conclude that the measurement of electrical and dielectric properties provides quantitative information that is related to bone quantity and quality.

  6. Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites

    SciTech Connect

    Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana; Airimioaei, Mirela; Tascu, Sorin; Schileo, Giorgio; Galassi, Carmen

    2013-02-21

    Particulate composites of ferrite and ferroelectric phases with xNiFe{sub 2}O{sub 4} (NF) and (1 - x)Pb{sub 0.988}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.976}Nb{sub 0.024}O{sub 3} (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 Degree-Sign C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

  7. Preparation, Characterization and Dielectric Properties of Epoxy and Polyethylene Nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Mason, Ralf; Stevens, Gary

    Two very different kinds of polymer nanocomposites have been prepared, characterized and investigated by dielectric spectroscopy to investigate the effects of polymer-nanofiller matrix difference on the dielectric response of nanodielectric composites. Linear low density polyethylene (LLDPE) is a non-polar thermoplastic which has a high viscosity even in the melt phase and bisphenol-A epoxy resin with an anhydride hardener is a polar low viscosity thermosetting resin. Nanometric sized aluminium oxide filler was chosen as the common inorganic phase for both nanodielectrics. Generally, nanoparticles aggregate easily and are difficult to separate due to strong surface interactions. In this study various mixing methods were employed from ultrasonic liquid processing to controlled shear flow mixing to investigate the dispersion of the nanofillers. The resultant epoxy and polyethylene nanocomposites were characterized with SEM, TEM, and DSC. The dielectric properties and frequency response of the nanocomposites were measured in the frequency domain from 10-2 Hz to 106 Hz at different temperatures. In polyethylene nanocomposites, significant interfacial polarization is clearly seen. However, in epoxy nanocomposites, no obvious interfacial polarization is found. The results are discussed in terms of the difference in the electrical characteristics of the interfacial region between the polymers and the nano-alumina.

  8. Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites

    NASA Astrophysics Data System (ADS)

    Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Airimioaei, Mirela; Tascu, Sorin; Schileo, Giorgio; Galassi, Carmen; Mitoseriu, Liliana

    2013-02-01

    Particulate composites of ferrite and ferroelectric phases with xNiFe2O4 (NF) and (1 - x)Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3 (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 °C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

  9. The dielectric properties of water within model transbilayer pores.

    PubMed Central

    Sansom, M S; Smith, G R; Adcock, C; Biggin, P C

    1997-01-01

    Ion channels contain extended columns of water molecules within their transbilayer pores. The dynamic properties of such intrapore water have been shown to differ from those of water in its bulk state. In previous molecular dynamics simulations of two classes of model pore (parallel bundles of Ala20 alpha-helices and antiparallel barrels of Ala10 beta-strands), a substantially reduced translational and rotational mobility of waters was observed within the pore relative to bulk water. Molecular dynamics simulations in the presence of a transpore electrostatic field (i.e., a voltage drop along the pore axis) have been used to estimate the resultant polarization (due to reorientation) of the intrapore water, and hence to determine the local dielectric behavior within the pore. It is shown that the local dielectric constant of water within a pore is reduced for models formed by parallel alpha-helix bundles, but not by those formed by beta-barrels. This result is discussed in the context of electrostatics calculations of ion permeation through channels, and the effect of the local dielectric of water within a helix bundle pore is illustrated with a simple Poisson-Boltzmann calculation. Images FIGURE 1 PMID:9370434

  10. Dielectrical properties of PANI/TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Chaturmukha, V. S.; Naveen, C. S.; Rajeeva, M. P.; Avinash, B. S.; Jayanna, H. S.; Lamani, Ashok R.

    2016-05-01

    Conducting polyaniline/titanium dioxide (PANI/TiO2) composites have been succesfully synthesized by insitu polymerization technique. The PANI/TiO2 nanocomposites of different compositions were prepared by varying weight percentage of TiO2 nanoparticles such as 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% into the fixed amount of the aniline monomer. The prepared powder samples were characterized by X-ray diffractometer (XRD) and Scanning electron microscope (SEM). The intensity of diffraction peaks for PANI/TiO2 composites is lower than that for TiO2. SEM pictures show that the nanocomposite were prepared in the form of long PANi chains decorated with TiO2 nanoparticles. The dielectric properties and AC conductivity were studied in the frequency range1K Hz-10M Hz. At higher frequencies, the composites exhibit almost zero dielectric loss and maximum value of σac is found for a concentration of 20 wt% TiO2 in polyaniline. The interface between polyaniline and TiO2 plays an important role in yielding a large dielectric constant in nanocomposites.

  11. Study of dielectric and impedance properties of Mn ferrites

    NASA Astrophysics Data System (ADS)

    Mujasam Batoo, Khalid

    2011-02-01

    The paper reports on the effect of Al substitution on the structural and electrical properties of bulk ferrite series of basic composition MnFe 2-2 xAl 2 xO 4 (0.0≤ x≤0.5) synthesized using solid state reaction method. XRD analysis confirms that all the samples exhibit single phase cubic spinel structure excluding presence of any secondary phase. The dielectric constant shows a normal behaviour with frequency, whereas the loss tangent exhibits an anomalous behaviour with frequency for all compositions. Variation of dielectric properties and ac conductivity with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and hopping of charge between Fe +2 and Fe +3 as well as between Mn +2 and Mn +3 ions at octahedral sites. The complex impedance plane spectra shows the presence of two semicircles up to x=0.2, and only one semicircle for the higher values of x. The analysis of the data shows that the resistive and capacitive properties of the Mn ferrite are mainly due to processes associated with grain and grain boundaries.

  12. Measurement of dielectric and magnetic properties of soil

    SciTech Connect

    Patitz, W.E.; Brock, B.C.; Powell, E.G.

    1995-11-01

    The possibility of subsurface imaging using SAR technology has generated a considerable amount of interest in recent years. One requirement for the successful development of a subsurface imagin system is an understanding of how the soil affects the signal. In response to a need for an electromagnetic characterization of the soil properties, the Radar/Antenna department has developed a measurement system which determines the soils complex electric permittivity and magnetic permeability at UHF frequencies. The one way loss in dB is also calculated using the measured values. There are many reports of measurements of the electric properties of soil in the literature. However, most of these are primarily concerned with measuring only a real dielectric constant. Because some soils have ferromagnetic constituents it is desirable to measure both the electric and magnetic properties of the soil.

  13. Investigation on dielectric properties of atomic layer deposited Al{sub 2}O{sub 3} dielectric films

    SciTech Connect

    Yıldız, Dilber Esra; Yıldırım, Mert; Gökçen, Muharrem

    2014-05-15

    Al/Al{sub 2}O{sub 3}/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer deposition technique in order to investigate dielectric properties of SBDs. For this purpose, admittance measurements were conducted at room temperature between −1 V and 3 V in the frequency range of 10 kHz and 1 MHz. In addition to the investigation of Al{sub 2}O{sub 3} morphology using atomic force microscope, dielectric parameters; such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ), and real and imaginary parts of dielectric modulus (M′ and M″, respectively), were calculated and effect of frequency on these parameters of Al/Al{sub 2}O{sub 3}/p-Si SBDs was discussed. Variations in these parameters at low frequencies were associated with the effect of interface states in low frequency region. Besides dielectric parameters, ac electrical conductivity of these SBDs was also investigated.

  14. Structural and dielectric properties of yttrium substituted nickel ferrites

    SciTech Connect

    Ognjanovic, Stevan M.; Tokic, Ivan; Cvejic, Zeljka; Rakic, Srdjan; Srdic, Vladimir V.

    2014-01-01

    Graphical abstract: - Highlights: • Dense NiFe{sub 2−x}Y{sub x}O{sub 4} ceramics (with 0 ≤ x ≤ 0.3) were prepared. • Pure spinels were obtained for x ≤ 0.07 while for x ≥ 0.15 samples had secondary phases. • With addition of yttrium, ac conductivity slightly increased. • We suggest several effects that can explain the observed changes in ac conduction. • With addition of yttrium, dielectric constant increased while the tg δ decreased. - Abstract: The influence of Y{sup 3+} ions on structural and dielectric properties of nickel ferrites (NiFe{sub 2−x}Y{sub x}O{sub 4}, where 0 ≤ x ≤ 0.3) has been studied. The as-synthesized samples, prepared by the co-precipitation method, were analyzed by XRD and FTIR which suggested that Y{sup 3+} ions were incorporated into the crystal lattice for all the samples. However, the XRD analysis of the sintered samples showed that secondary phases appear in the samples with x > 0.07. The samples have densities greater than 90% TD and the SEM images showed that the grain size decreases with the addition of yttrium. Dielectric properties measured from 150 to 25 °C in the frequency range of 100 Hz–1 MHz showed that the addition of yttrium slightly increases the ac conductivity and decreases the tg δ therefore making the materials better suited for the use in microwave devices.

  15. Measurement of the dielectric properties of sawdust between 0.5 and 15 GHz

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rapid, nondestructive, and subsurface sensing of material properties such as water content can be achieved through dielectric measurements. The interaction between the electromagnetic waves and the material is defined by the dielectric properties, which can be used to determine the physical properti...

  16. Direct measurement of the dielectric polarization properties of DNA

    PubMed Central

    Cuervo, Ana; Dans, Pablo D.; Carrascosa, José L.; Orozco, Modesto; Gomila, Gabriel; Fumagalli, Laura

    2014-01-01

    The electric polarizability of DNA, represented by the dielectric constant, is a key intrinsic property that modulates DNA interaction with effector proteins. Surprisingly, it has so far remained unknown owing to the lack of experimental tools able to access it. Here, we experimentally resolved it by detecting the ultraweak polarization forces of DNA inside single T7 bacteriophages particles using electrostatic force microscopy. In contrast to the common assumption of low-polarizable behavior like proteins (εr ∼ 2–4), we found that the DNA dielectric constant is ∼8, considerably higher than the value of ∼3 found for capsid proteins. State-of-the-art molecular dynamic simulations confirm the experimental findings, which result in sensibly decreased DNA interaction free energy than normally predicted by Poisson–Boltzmann methods. Our findings reveal a property at the basis of DNA structure and functions that is needed for realistic theoretical descriptions, and illustrate the synergetic power of scanning probe microscopy and theoretical computation techniques. PMID:25136104

  17. Microstructure and dielectric properties of biocarbon nanofiber composites

    NASA Astrophysics Data System (ADS)

    Dai, Bo; Ren, Yong; Wang, Gaihua; Ma, Yongjun; Zhu, Pei; Li, Shirong

    2013-06-01

    A kind of web-like carbon with interconnected nanoribbons was fabricated using bacterial cellulose pyrolyzed at various temperatures, and the microwave dielectric properties were investigated. Bacterial cellulose was converted into carbonized bacterial cellulose (CBC) with a novel three-dimensional web built of entangled and interconnected cellulose ribbons when the carbonization temperature was below 1,200°C; the web-like structure was destroyed at a temperature of 1,400°C. Composites of CBC impregnated with paraffin wax exhibited high complex permittivity over a frequency range of 2 to 18 GHz, depending on the carbonization temperature. Both real and imaginary parts were the highest for CBC pyrolyzed at 1,200°C. The complex permittivity also strongly depended on CBC loadings. For 7.5 wt.% loading, the real and imaginary permittivities were about 12 and 4.3, respectively, and the minimum reflection loss was -39 dB at 10.9 GHz. For 30 wt.% loading, the real and imaginary permittivities were about 45 and 80, respectively, and the shielding efficiency was more than 24 dB in the measured frequency range and could be up to 39 dB at 18 GHz. The electromagnetic properties were assumed to correlate with both the dielectric relaxation and the novel web-like structure.

  18. Dielectric Properties of Organic Charge-Transfer Salts

    NASA Astrophysics Data System (ADS)

    Fischer, J. K. H.; Lunkenheimer, P.; Krohns, S.; Manna, R. S.; Hartmann, B.; Schubert, H.; Lang, M.; Müller, J.; Schlueter, J. A.; Mézière, C.; Batail, P.; Loidl, A.

    The BEDT-TTF-based charge-transfer salts have attracted considerable attention due to their often intriguing dielectric properties. An example is κ-(BEDT-TTF)2Cu[N(CN)2]Cl. It was recently found to exhibit multiferroicity, for which a new electric-dipole driven mechanism was proposed. The polar moment in this system was suggested to arise from the dimerization of the BEDT-TTF molecules, combined with charge order. Another interesting recent example is α-(BEDT-TTF)2I3, which shows the signature of relaxor-ferroelectric behavior. Here, we will present an overview of the dielectric properties of the above systems and provide new results on κ-(BEDT-TTF)2Hg(SCN)2Cl, which also seems to show relaxor-ferroelectric behavior in its charge-ordered state. In addition, we present measurements of δ-(EDT-TTF-CONMe2)2Br. This compound lacks dimerization, but exhibits charge order already at room temperature.

  19. Microstructure and dielectric properties of biocarbon nanofiber composites

    PubMed Central

    2013-01-01

    A kind of web-like carbon with interconnected nanoribbons was fabricated using bacterial cellulose pyrolyzed at various temperatures, and the microwave dielectric properties were investigated. Bacterial cellulose was converted into carbonized bacterial cellulose (CBC) with a novel three-dimensional web built of entangled and interconnected cellulose ribbons when the carbonization temperature was below 1,200°C; the web-like structure was destroyed at a temperature of 1,400°C. Composites of CBC impregnated with paraffin wax exhibited high complex permittivity over a frequency range of 2 to 18 GHz, depending on the carbonization temperature. Both real and imaginary parts were the highest for CBC pyrolyzed at 1,200°C. The complex permittivity also strongly depended on CBC loadings. For 7.5 wt.% loading, the real and imaginary permittivities were about 12 and 4.3, respectively, and the minimum reflection loss was -39 dB at 10.9 GHz. For 30 wt.% loading, the real and imaginary permittivities were about 45 and 80, respectively, and the shielding efficiency was more than 24 dB in the measured frequency range and could be up to 39 dB at 18 GHz. The electromagnetic properties were assumed to correlate with both the dielectric relaxation and the novel web-like structure. PMID:23800353

  20. Thermal properties of dielectric solids below 4 K. I - Polycarbonate

    NASA Technical Reports Server (NTRS)

    Cieloszyk, G. S.; Cruz, M. T.; Salinger, G. L.

    1973-01-01

    Polymers and other dielectric materials are frequently used for many purposes in the construction of cryogenic apparatus. Yet very few values of the thermal properties of these materials below 4 K have been reported. It is, however, known that one can not use the Debye theory to extrapolate to lower temperatures the measurements of the specific heat capacity above 1 K. The thermal conductivity also follows no theoretically predictable temperature dependence. As a by-product of our studies of the thermal properties of amorphous and partly crystalline materials below 4 K, we wish to report values for the thermal conductivity, specific heat capacity, and velocity of sound below 4 K in materials useful for the construction of cryogenic apparatus. In this article we will describe our measurement techniques and report values for polycarbonate (Lexan). In subsequent notes we will give values for other materials of interest.

  1. Consequence of cobalt on structural, optical and dielectric properties in ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Zia, Amir; Ahmed, S.; Shah, N. A.; Anis-ur-Rehman, M.; Khan, E. U.; Basit, M.

    2015-09-01

    The critical role of cobalt dopant in ZnO nanostructures with different cobalt concentrations has been explored on the basis of structural, optical and dielectric mechanisms. X-ray diffraction (XRD) analysis shows that the Co+2 ions replace Zn+2 ions in the ZnO matrix, producing lattice strain. Diffused Reflectance Spectroscopy (DRS) shows a red shift in optical energy band gap with increase in cobalt content, along with the presence of transitions in high spin states due to tetrahedrally coordinated cobalt ions. The dielectric characterization explains the disparity in dynamic dielectric parameters like capacitance, dielectric constant, tangent loss, AC conductivity and impedance as a function of frequency. Capacitance and both static and dynamic dielectric constants found to be decreasing with cobalt addition. The anomaly in these pronounced parameters can address the key problems of the material at higher frequencies device operation.

  2. TECHNICAL NOTE: Dielectric and piezoelectric properties of piezoelectric ceramic sulphoaluminate cement composites

    NASA Astrophysics Data System (ADS)

    Cheng, Xin; Huang, Shifeng; Chang, Jun; Lu, Lingchao; Liu, Futian; Ye, Zengmao; Wang, Shoude

    2005-10-01

    Using cement as the matrix of piezoelectric smart composites can solve the problem of mismatch of smart composites and concrete structure in civil engineering. 0 3 cement based piezoelectric composites were fabricated by a compression technique using PMN and sulphoaluminate cement as raw materials. The influence of the PMN content on the dielectric and piezoelectric properties of the composites was investigated. The temperature dependence of the dielectric properties of the composites was discussed in detail. The results indicate that the dielectric constants are almost constant in the temperature range from -30 to 50 °C, which shows excellent dielectric temperature stability. With increasing PMN content, the piezoelectric and dielectric properties of the composites increase. The theoretical values of the dielectric constants show good agreement with the experimental values for the composites.

  3. Microwave Dielectric and Propagation Properties of Vegetation Canopies

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T. (Principal Investigator)

    1985-01-01

    A vegetation canopy is a highly inhomogeneous medium at microwave frequencies, and because the scattering elements (leaves, stalks, fruits, and branches) have a nonuniform distribution in orientation, the canopy is likely to exhibit nonisotropic attenuation properties. In some canopies, the stalk may contain the overwhelming majority of the plant's biomass, which suggests that an incident radar wave would be differentially attenuated by the canopy depending on the direction of the incident electric field relative to the stalks' orientation. The propagation properties of a vegetation canopy play a central role in modeling both the backscattering behavior observed by an imaging radar and the emission observed by a radiometer. These propagation properties are in turn governed by the dielectric properties and the size, shape, and slope distributions of the scatteres. In spite of the critical need for canopy propagation models and experimental data, very few investigations had been conducted (prior to this study) to determine the extinction properties of vegetation canopies, either by constituent type (leaves, stalks, etc.) or as a whole.

  4. 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

  5. The influence of charged-induced variations in the local permittivity on the static and dynamic properties of polyelectrolyte solutions

    NASA Astrophysics Data System (ADS)

    Fahrenberger, Florian; Hickey, Owen A.; Smiatek, Jens; Holm, Christian

    2015-12-01

    There is a large body of literature investigating the static and dynamic properties of polyelectrolytes due both to their widespread application in industrial processes and their ubiquitous presence in biology. Because of their highly charged nature, polyelectrolytes tend to alter the local dielectric permittivity of the solution within a few nanometers of their backbone. This effect has, however, been almost entirely ignored in both simulations and theoretical work. In this article, we apply our recently developed electrostatic solver based on Maxwell's equations to examine the effects of the permittivity reduction in the vicinity of the polyelectrolyte. We first verify our new approach by calculating and comparing ion distributions around a linear fixed polyelectrolyte and find both quantitative and qualitative changes in the ion distribution. Further simulations with an applied electric field show that the reduction in the local dielectric constant increases the mobility of the chains by approximately ten percent. More importantly, variations in the local dielectric constant lead to qualitatively different behavior of the conductivity.

  6. The influence of charged-induced variations in the local permittivity on the static and dynamic properties of polyelectrolyte solutions.

    PubMed

    Fahrenberger, Florian; Hickey, Owen A; Smiatek, Jens; Holm, Christian

    2015-12-28

    There is a large body of literature investigating the static and dynamic properties of polyelectrolytes due both to their widespread application in industrial processes and their ubiquitous presence in biology. Because of their highly charged nature, polyelectrolytes tend to alter the local dielectric permittivity of the solution within a few nanometers of their backbone. This effect has, however, been almost entirely ignored in both simulations and theoretical work. In this article, we apply our recently developed electrostatic solver based on Maxwell's equations to examine the effects of the permittivity reduction in the vicinity of the polyelectrolyte. We first verify our new approach by calculating and comparing ion distributions around a linear fixed polyelectrolyte and find both quantitative and qualitative changes in the ion distribution. Further simulations with an applied electric field show that the reduction in the local dielectric constant increases the mobility of the chains by approximately ten percent. More importantly, variations in the local dielectric constant lead to qualitatively different behavior of the conductivity.

  7. Dielectric properties of betaine phosphite and deuterated betaine phosphite films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Pankova, G. A.; Frederiks, I. D.; Lemanov, V. V.

    2011-01-01

    Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO3, α-SiO2, α-Al2O3, and NdGaO3 substrates. These films consist of large single-crystal blocks in which the polar axis ( b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = T c is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature T c: from T c = 200 K for BPI-based structures to T c = 280 K for structures with a high degree of deuteration ( d ˜ 90%).

  8. A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors

    PubMed Central

    Bibi, Fabien; Villain, Maud; Guillaume, Carole; Sorli, Brice; Gontard, Nathalie

    2016-01-01

    Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced. PMID:27527179

  9. A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors.

    PubMed

    Bibi, Fabien; Villain, Maud; Guillaume, Carole; Sorli, Brice; Gontard, Nathalie

    2016-08-04

    Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced.

  10. A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors.

    PubMed

    Bibi, Fabien; Villain, Maud; Guillaume, Carole; Sorli, Brice; Gontard, Nathalie

    2016-01-01

    Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced. PMID:27527179

  11. Temperature and moisture dependence of the dielectric properties of silica sand.

    PubMed

    Liu, Chenhui; Zhang, Libo; Peng, Jinhui; Srinivasakannan, Chandrasekar; Liu, Bingguo; Xia, Hongying; Zhou, Junwen; Xu, Lei

    2013-01-01

    The major objective of this work was to investigate the effects of temperature and moisture content on the dielectric properties of silica sand. The dielectric properties of moist silica sand at five temperatures between 20 to 100 degrees C, covering different moisture content levels at a frequency of 2.45 GHz, were measured with an open-ended coaxial probe dielectric measurement system. The wave penetration depth was calculated based on the measured dielectric data. The results show moisture content to be the major influencing factor for the variation of dielectric properties. Dielectric constant, loss factor and loss tangent all increase linearly with increasing moisture content. Three predictive empirical models were developed to relate the dielectric constant, loss factor, loss tangent of silica sand as a linear function of moisture content. An increase in temperature between 20 to 100 degrees C was found to increase the dielectric constant and loss factor. The penetration depth decreased with increase in moisture content and temperature. Variation in penetration depth was found to vary linearly with decrease in moisture content. An predictive empirical model was developed to calculate penetration depth for silica sand. This study offers useful information on dielectric properties of silica sand for developing microwave drying applications in mineral processing towards designing better microwave sensors for measuring silica sand moisture content.

  12. Microwave Dielectric Properties of Soil and Vegetation and Their Estimation From Spaceborne Radar

    NASA Technical Reports Server (NTRS)

    Dobson, M. Craig; McDonald, Kyle C.

    1996-01-01

    This paper is largely tutorial in nature and provides an overview of the microwave dielectric properties of certain natural terrestrial media (soils and vegetation) and recent results in estimating these properties remotely from airborne and orbital synthetic aperture radar (SAR).

  13. Quantitative property-structural relation modeling on polymeric dielectric materials

    NASA Astrophysics Data System (ADS)

    Wu, Ke

    Nowadays, polymeric materials have attracted more and more attention in dielectric applications. But searching for a material with desired properties is still largely based on trial and error. To facilitate the development of new polymeric materials, heuristic models built using the Quantitative Structure Property Relationships (QSPR) techniques can provide reliable "working solutions". In this thesis, the application of QSPR on polymeric materials is studied from two angles: descriptors and algorithms. A novel set of descriptors, called infinite chain descriptors (ICD), are developed to encode the chemical features of pure polymers. ICD is designed to eliminate the uncertainty of polymer conformations and inconsistency of molecular representation of polymers. Models for the dielectric constant, band gap, dielectric loss tangent and glass transition temperatures of organic polymers are built with high prediction accuracy. Two new algorithms, the physics-enlightened learning method (PELM) and multi-mechanism detection, are designed to deal with two typical challenges in material QSPR. PELM is a meta-algorithm that utilizes the classic physical theory as guidance to construct the candidate learning function. It shows better out-of-domain prediction accuracy compared to the classic machine learning algorithm (support vector machine). Multi-mechanism detection is built based on a cluster-weighted mixing model similar to a Gaussian mixture model. The idea is to separate the data into subsets where each subset can be modeled by a much simpler model. The case study on glass transition temperature shows that this method can provide better overall prediction accuracy even though less data is available for each subset model. In addition, the techniques developed in this work are also applied to polymer nanocomposites (PNC). PNC are new materials with outstanding dielectric properties. As a key factor in determining the dispersion state of nanoparticles in the polymer matrix

  14. Characterization of dielectric properties of nanocellulose from wood and algae for electrical insulator applications.

    PubMed

    Le Bras, David; Strømme, Maria; Mihranyan, Albert

    2015-05-01

    Cellulose is one of the oldest electrically insulating materials used in oil-filled high-power transformers and cables. However, reports on the dielectric properties of nanocellulose for electrical insulator applications are scarce. The aim of this study was to characterize the dielectric properties of two nanocellulose types from wood, viz., nanofibrillated cellulose (NFC), and algae, viz., Cladophora cellulose, for electrical insulator applications. The cellulose materials were characterized with X-ray diffraction, nitrogen gas and moisture sorption isotherms, helium pycnometry, mechanical testing, and dielectric spectroscopy at various relative humidities. The algae nanocellulose sample was more crystalline and had a lower moisture sorption capacity at low and moderate relative humidities, compared to NFC. On the other hand, it was much more porous, which resulted in lower strength and higher dielectric loss than for NFC. It is concluded that the solid-state properties of nanocellulose may have a substantial impact on the dielectric properties of electrical insulator applications.

  15. Magnetic and dielectric properties of 3Y-TZP/strontium doped barium ferrite composite

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Wang, Shan-Shan; Guo, Rui-Song; Cai, Guang-Lan; Guo, Wei-Na; Wu, Chen

    2015-02-01

    Magnetic and dielectric properties of 3Y-TZP/20 wt.% Ba1-xSrxFe12O19 (x = 0, 0.25, 0.5, 0.75) composites prepared by solid state reaction method are investigated. The magnetic properties are improved in the composites with the strontium doped barium ferrite. When x = 0.25, the saturation magnetization of the ferrite reaches the maximum. This is due to the migration of Fe3+ induced by the Sr2+ doping. The dielectric properties are also improved in the composite with the strontium doped barium ferrite. When x = 0.5, the dielectric constant and dielectric loss possess the maximum. This is caused by the lattice distortion resulting from the Sr2+ doping. The dielectric properties are analyzed by the universal relaxation law.

  16. Dielectric properties of polymer composites with the addition of ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kisiel, A.; Konieczny, M.; Zabska, M.

    2016-02-01

    The aim of the work was examination of the dielectric properties of a new type of polymer nanocomposites based on PVDF (polyvinylidene fluoride), or a copolymer P(VDF-HFP) with addition of ferrite nanoparticles. The addition of nanofillers leads not only to the formation of polar ß-phase of PVDF, which shows unique piro-, piezo- and ferroelectric properties used in many applications, but also affects the dielectric and magnetoelectric properties of these nanocomposites. In the work the dielectric properties of polymer composites, such as volume resistivity, permittivity and dielectric loss were investigated Measurements of dielectric parameters were performed in a climate chamber at temperature range of 25-100°C, at selected frequencies in the range 20-200 kHz. The results obtained are valuable not only for an application of this type of nanocomposites in various types of transducers, but also for analysis of the physical phenomena occurring in the polymer composites doped with nanoparticles.

  17. Dielectric Properties of Lead Monoxide Filled Unsaturated Polyester Based Polymer Composites

    NASA Astrophysics Data System (ADS)

    Harish, V.; Kumar, H. G. Harish; Nagaiah, N.

    2011-07-01

    Lead monoxide filled isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the dielectric properties of the composites. The present study showed that the dielectric constant (ɛ'), dielectric loss (ɛ″) and ac conductivity (σac) of isopthalate based unsaturated polyester resin increases with the increase in wt% PbO filler in polymer matrix.

  18. Numerical studies on the electromagnetic properties of the nonlinear Lorentz Computational model for the dielectric media

    SciTech Connect

    Abe, H.; Okuda, H.

    1994-06-01

    We study linear and nonlinear properties of a new computer simulation model developed to study the propagation of electromagnetic waves in a dielectric medium in the linear and nonlinear regimes. The model is constructed by combining a microscopic model used in the semi-classical approximation for the dielectric media and the particle model developed for the plasma simulations. It is shown that the model may be useful for studying linear and nonlinear wave propagation in the dielectric media.

  19. Dielectric properties at microwave frequencies studied in partially filled cylindrical TE011 cavities.

    PubMed

    Regier, M; Schubert, H

    2000-01-01

    To measure mean complex dielectric constants of heterogeneous materials with high dielectric losses (like emulsions or granular materials), partially filled TE011 cavities with a time consuming calibration procedure have been used [Persch, 1997], [Risman, 1971], since no suitable theory could be found in literature. In this work, an analytical solution is derived and tested by experiments and numerical results, showing a quantitative agreement, thus making calibration procedures for the measurement of dielectric properties in TE011 resonators unnecessary.

  20. Structural and dielectric properties of CTAB modified ZrO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Sidhu, Gaganpreet Kaur; Tripathi, S. K.; Kumar, Rajesh

    2016-05-01

    Zirconia (ZrO2) has been considered as one of the most investigated materials among various metal oxides due its outstanding dielectric properties and ionic conduction properties, which is mainly due to its high oxygen ion conduction. ZrO2 nanoparticles were synthesized using surfactant (CTAB) to study the variation of its dielectric behavior at room temperature. Surfactants form a unique class of chemical compounds, because of their remarkable ability to influence the properties of surfaces and interfaces of nanostructures. The dielectric properties of prepared nanoparticles were studied using LCR meter.

  1. Preparation and unique dielectric properties of nanoporous materials with well-controlled closed-nanopores.

    PubMed

    Zhao, Cuijiao; Wei, Xiaonan; Huang, Yawen; Ma, Jiajun; Cao, Ke; Chang, Guanjun; Yang, Junxiao

    2016-07-28

    Although general porous materials have a low dielectric constant, their uncontrollable opened porous structure results in high dielectric loss and poor barrier properties, thus limiting their application as interconnect dielectrics. In this study, polymeric nanoporous materials with well-controlled closed pores were prepared by incorporating polystyrene (PS) hollow nanoparticles into polyethylene (PE/HoPS). SEM images suggested a closed porous structure for PE/HoPS. In order to show the effect of the porous structure on dielectric properties, nanoporous materials with an opened or uncontrollable porous structure were prepared by etching SiO2/PE or PE/PS@SiO2 composites. PE/HoPSs composites showed an apparently lower dielectric constant and loss compared with the opened porous PE, demonstrating the advantages of a closed porous structure upon enhancing low-dielectric performance. The low dielectric performance of the PE/HoPS composites is linked with high water resistance owing to their closed porous characteristics. When incorporating 15.3 wt% HoPS (porosity: ∼6.9%), the dielectric constant reached 2.08. This value is lower than that calculated from the serial model. Our work revealed that the incorporation of HoPS not only reduces the porosity, but also alters the intrinsic properties of PE, as a result, leading to a greatly reduced dielectric constant. PMID:27363945

  2. Preparation and unique dielectric properties of nanoporous materials with well-controlled closed-nanopores.

    PubMed

    Zhao, Cuijiao; Wei, Xiaonan; Huang, Yawen; Ma, Jiajun; Cao, Ke; Chang, Guanjun; Yang, Junxiao

    2016-07-28

    Although general porous materials have a low dielectric constant, their uncontrollable opened porous structure results in high dielectric loss and poor barrier properties, thus limiting their application as interconnect dielectrics. In this study, polymeric nanoporous materials with well-controlled closed pores were prepared by incorporating polystyrene (PS) hollow nanoparticles into polyethylene (PE/HoPS). SEM images suggested a closed porous structure for PE/HoPS. In order to show the effect of the porous structure on dielectric properties, nanoporous materials with an opened or uncontrollable porous structure were prepared by etching SiO2/PE or PE/PS@SiO2 composites. PE/HoPSs composites showed an apparently lower dielectric constant and loss compared with the opened porous PE, demonstrating the advantages of a closed porous structure upon enhancing low-dielectric performance. The low dielectric performance of the PE/HoPS composites is linked with high water resistance owing to their closed porous characteristics. When incorporating 15.3 wt% HoPS (porosity: ∼6.9%), the dielectric constant reached 2.08. This value is lower than that calculated from the serial model. Our work revealed that the incorporation of HoPS not only reduces the porosity, but also alters the intrinsic properties of PE, as a result, leading to a greatly reduced dielectric constant.

  3. Microstructure and microwave dielectric properties of modified zinc titanates (II)

    SciTech Connect

    Kim, H.T. |; Byun, J.D.; Kim, Y.

    1998-06-01

    Zinc titanates ZnO-TiO{sub 2} (Zn/Ti = 0.67--2.0) and Zn{sub 1{minus}x}Mg{sub x}TiO{sub 3} (x = 0--0.4) were prepared by a conventional mixed-oxide method, and the microstructure and dielectric properties in the microwave range were investigated. In the ZnO-TiO{sub 2} system, zinc orthotitanate, Zn{sub 2}TiO{sub 4}, had rutile solubility up to 0.33 mol followed by a decrease in the cubic lattice parameters as the amount of rutile increased. The zero {tau}{sub f} was obtained near Zn/Ti = 1.15 composition. The {epsilon}{sub r} and Q*f of the composition were 25 and 23,000, respectively. In the Zn{sub 1{minus}x}Mg{sub x}TiO{sub 3} system, the composite structure with zinc orthotitanate and rutile of 1ZnO{center_dot}1TiO{sub 2} transformed into the (Zn, Mg)TiO{sub 3} hexagonal solid solution at x = 0.3--0.4. However, phase decomposition occurred in this range at a temperature above 1160 C, which induced microcracks and resulted in a decrease in Q factors. A range of dielectric resonators with {epsilon}{sub r} = 20--30, Q = 2,500--13,000 at GHz, and {tau}{sub f} = {minus}70 to +50 ppm/C can be obtained in this system at a sintering temperature as low as 1,100 C.

  4. Local Electronic And Dielectric Properties at Nanosized Interfaces

    SciTech Connect

    Bonnell, Dawn A.

    2015-02-23

    Final Report to the Department of Energy for period 6/1/2000 to 11/30/2014 for Grant # DE-FG02-00ER45813-A000 to the University of Pennsylvania Local Electronic And Dielectric Properties at Nanosized Interfaces PI: Dawn Bonnell The behavior of grain boundaries and interfaces has been a focus of fundamental research for decades because variations of structure and composition at interfaces dictate mechanical, electrical, optical and dielectric properties in solids. Similarly, the consequence of atomic and electronic structures of surfaces to chemical and physical interactions are critical due to their implications to catalysis and device fabrication. Increasing fundamental understanding of surfaces and interfaces has materially advanced technologies that directly bear on energy considerations. Currently, exciting developments in materials processing are enabling creative new electrical, optical and chemical device configurations. Controlled synthesis of nanoparticles, semiconducting nanowires and nanorods, optical quantum dots, etc. along with a range of strategies for assembling and patterning nanostructures portend the viability of new devices that have the potential to significantly impact the energy landscape. As devices become smaller the impact of interfaces and surfaces grows geometrically. As with other nanoscale phenomena, small interfaces do not exhibit the same properties as do large interfaces. The size dependence of interface properties had not been explored and understanding at the most fundamental level is necessary to the advancement of nanostructured devices. An equally important factor in the behavior of interfaces in devices is the ability to examine the interfaces under realistic conditions. For example, interfaces and boundaries dictate the behavior of oxide fuel cells which operate at extremely high temperatures in dynamic high pressure chemical environments. These conditions preclude the characterization of local properties during fuel cell

  5. Review on dielectric properties of rare earth doped barium titanate

    NASA Astrophysics Data System (ADS)

    Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

    2016-07-01

    Rare earth doped Barium Titanate (BaTiO3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO3 downshifted the Curie temperature (TC). Transition temperature also known as Curie temperature, TC where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO3, Er-doped BaTiO3, Sm-doped BaTiO3, Nd-doped BaTiO3 and Ce-doped BaTiO3 had been proved to increase and the transition temperature or also known as TC also lowered down to room temperature as for all the RE doped BaTiO3 except for Er-doped BaTiO3.

  6. In-Situ Mechanical Property Evaluation of Dielectric Ceramics in Multilayer Capacitors

    SciTech Connect

    Wereszczak, A.A.; Riester, L.; Breder, K.

    2000-04-03

    The Young's modulus, hardness, and fracture toughness of barium titanate dielectric ceramics in three commercially available multilayer capacitors (MLCs) were measured in-situ using indentation and a mechanical properties microprobe. The three MLCs were equivalent in size (0805), capacitance (0.1 uF) and dielectric type (X7R). The Young's modulus and hardness of the dielectric ceramics in the three MLCs were similar, while there were statistically significant differences in their fracture toughnesses. The results provide insight into the assessment of MLC mechanical reliability, and show that equivalent electrical MLC rating is not necessarily a guarantee that the dielectric ceramics in them will exhibit equivalent mechanical performance.

  7. Dielectric properties of almond shells in the development of radio frequency and microwave pasteurization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To develop pasteurization treatments based on radio frequency (RF) or microwave energy, dielectric properties of almond shells were determined using an open-ended coaxial-probe with an impedance analyzer over a frequency range of 10 to 1800 MHz. Both the dielectric constant and loss factor of almond...

  8. Optical/Dielectric Properties of Inhomogeneous Optical Material: A New Method of Evaluation

    NASA Technical Reports Server (NTRS)

    Nagendra, C. L.; Lamb, J. L.

    1993-01-01

    A new method, based on Effective mean Field Theory, is proposed for the evaluation of the optical/dielectric properties of inhomogeneous materials, in which the real and imaginary parts of the dielectric function are determined by solving a simultaneous non-linear equation.

  9. Measuring and modeling of radiofrequency dielectric properties of chicken breast meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of chicken breast meat are important for both dielectric heating and quality sensing applications. In heating applications they allow optimization of energy transfer and uniformity of heating. In sensing applications, they can be used to predict quality attributes of the chicke...

  10. Assessing Chicken Meat Freshness through Measurement of Radio-Frequency Dielectric Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Change in freshness of chicken meat was assessed through measurement of the dielectric properties with a vector network analyzer and an open-ended coaxial-line probe between 200 MHz and 20 GHz at 23 oC. Chicken meat samples were stored in a refrigerator for 8 days at 4 oC. Changes in dielectric cons...

  11. Dielectric properties and heating rate of broccoli powder as related to radio-frequency heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recently, Salmonella contamination was identified in low-moisture foods including dried vegetable powder. Radio Frequency (RF) dielectric heating is a potential alternative pasteurization method with short heating time. Dielectric properties of broccoli powder with 6.9, 9.1, 12.2, and 14.9%, w. b....

  12. Influence of color on dielectric properties of marinated poultry breast meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric behavior of foods when exposed to radio-frequency and microwave electric fields is highly influenced by moisture content and the degree of water binding with constituents of the food materials. The ability to correlate specific food quality characteristics with the dielectric properti...

  13. Effect of incorporating aromatic and chiral groups on the dielectric properties of poly(dimethyltin esters).

    PubMed

    Baldwin, Aaron F; Ma, Rui; Huan, Tran Doan; Cao, Yang; Ramprasad, Ramamurthy; Sotzing, Gregory A

    2014-12-01

    High-dielectric constant materials are critical for numerous applications such as photovoltaics, photonics, transistors, and capacitors. There are numerous polymers used as dielectric layers in these applications but can suffer from having a low dielectric constant, small band gap, or ferroelectricity. Here, the structure-property relationship of various poly(dimethyltin esters) is described that look to enhance the dipolar and atomic polarization component of the dielectric constant. These polymers are also modeled using first principles calculations based on density functional theory (DFT) to predict such values as the total, electronic, and ionic dielectric constant as well as structure. A strong correlation is achieved between the theoretical and experimental values with the polymers exhibiting dielectric constants >4.5 with dissipation on the order of 10(-3) -10(-2) .

  14. Infrared Dielectric Properties of Low-Stress Silicon Oxide

    NASA Technical Reports Server (NTRS)

    Cataldo, Giuseppe; Wollack, Edward J.; Brown, Ari D.; Miller, Kevin H.

    2016-01-01

    Silicon oxide thin films play an important role in the realization of optical coatings and high-performance electrical circuits. Estimates of the dielectric function in the far- and mid-infrared regime are derived from the observed transmittance spectrum for a commonly employed low-stress silicon oxide formulation. The experimental, modeling, and numerical methods used to extract the dielectric function are presented.

  15. Perturbative no-hair property of form fields for higher dimensional static black holes

    SciTech Connect

    Shiromizu, Tetsuya; Ohashi, Seiju; Tanabe, Kentaro

    2011-04-15

    In this paper we examine the static perturbation of p-form field strengths around higher dimensional Schwarzschild spacetimes. As a result, we can see that the static perturbations do not exist when p{>=}3. This result supports the no-hair properties of p-form fields. However, this does not exclude the presence of the black objects having nonspherical topology.

  16. Measuring the dielectric properties of soil-organic mixtures using coaxial impedance dielectric reflectometry

    NASA Astrophysics Data System (ADS)

    Francisca, Franco M.; Montoro, Marcos A.

    2012-05-01

    Contamination of soils with non-aqueous phase liquids (NAPLs) is frequently produced by accidental spills and storage tanks or pipes leakage. The main goals dealing with soil and groundwater contamination include determining the extension of the affected zone, monitoring the contaminant plume and quantifying the pollution degree. The objective of this work is to evaluate the potential of dielectric permittivity measurements to detect the presence of NAPLs in sands. Tested samples were fine, medium, coarse and silty sand with different volumetric contents of water and paraffin oil. The dielectric permittivity was measured by means of a Coaxial Impedance Dielectric Reflectometry method in specimens with either known fluid content or at different stages during immiscible displacement tests. A simplified method was developed to quantify the amount of oil from dielectric permittivity measurements and effective mixture media models. Obtained results showed that groundwater contamination with NAPL and the monitoring of immiscible fluid displacement in saturated porous media can be clearly identified from dielectric measurements. Finally, very accurate results can be obtained when computing the contamination degree with the proposed method in comparison with the real volumetric content of NAPL (r2 > 90%).

  17. Synthesis, characterization and dielectric properties of SnO2 thin films.

    PubMed

    Yıldırım, M Ali; Yıldırım, Sümeyra Tuna; Sakar, Emine Fedakar; Ateş, Aytunç

    2014-12-10

    SnO2 thin films have been grown on glass substrates using Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature and ambient pressure. The annealing temperature effect on the structural, morphological, optical and electrical properties of SnO2 thin films has been investigated. The X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) studies have showed that all the films have exhibited polycrystalline nature with tetragonal structure and have been covered well on glass substrates. The crystalline and surface properties of the films have improved with increasing annealing temperature. The band gap values have been changed from 3.73 to 3.66eV depending on the annealing temperature. The refractive index (n), optical static and high frequency dielectric constants (εo, ε∞) values have been calculated as a function of the annealing temperature. The resistivity values of the films have changed between 10(-1) - 10(-3)Ωcm with annealing temperature and light at room temperature. PMID:24929316

  18. Synthesis and dielectric properties of the ceramic-metal-polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Qi, Lai

    This dissertation is devoted to the development of new dielectric composite materials for potentially implementing the embedded capacitor technology. In this dissertation, you will be presented with the material development concepts, current status of research and heretofore the latest results that were obtained under the synthesis-structure-property research scheme. Embedded capacitor is an important emerging technology for meeting the performance and functionality requirements of next-generation electronic devices. One major obstacle for implementing this technology is the scarcity of dielectric materials with appropriate dielectric and mechanical properties. Particle-filled polymer-based composite (0-3 connectivity) is widely considered as a promising solution to meet those material development requirements. Currently, the reported 0-3 composites can be categorized into two general types according to the filler materials that they use, i.e., insulating fillers (ceramics) and conductive fillers (metals). The composites that are filled with traditional dielectric ceramics, e.g., barium titanate (BaTiO3) have advantages of predictable dielectric properties, high reliability, low dielectric loss and easy fabrication, etc. However, these composites face a dilemma of low dielectric constants, which are usually below 100. The development of dielectric materials filled with metal particles origins from the studies of the percolation theory, which observed the spike-like divergent behavior of dielectric constant at the percolation threshold. Although high dielectric constants (>1000) of metal-polymer composites have been reported in several works, the practical usefulness of those percolative composites is jeopardized by several serious drawbacks. First, those high dielectric constants were achieved only within a narrow filler concentration range near the threshold, which means higher dielectric constants always come with higher risk of percolation (shorting of the

  19. Influence of color on dielectric properties of marinated poultry breast meat.

    PubMed

    Samuel, D; Trabelsi, S

    2012-08-01

    The dielectric behavior of foods when exposed to radio-frequency and microwave electric fields is highly influenced by moisture content and the degree of water binding with constituents of the food materials. The ability to correlate specific food quality characteristics with the dielectric properties can lead to the development of rapid, nondestructive techniques for such quality measurements. Water-holding capacity is a critical attribute in meat quality. Up to 50% of raw poultry meat in the United States is marinated with mixtures of water, salts, and phosphates. The objective of this study was to determine if variations in breast meat color would affect the dielectric properties of marinated poultry meat over a broad frequency range from 500 MHz to 50 GHz. Poultry meat was obtained from a local commercial plant in Georgia (USA). Color and pH measurements were taken on the breast filets. Groups of breast filets were sorted into classes of pale and normal before adding marination pickup percentages of 0, 5, 10, and 15. Breast filets were vacuum-tumbled and weighed for pickup percentages. Dielectric properties of the filets were measured with a coaxial open-ended probe on samples equilibrated to 25°C. Samples from pale meat exhibited higher dielectric properties than samples from normal meat. No differences could be observed between samples from pale and normal meat after marination of the samples. Overall, dielectric properties increased as the marination pickup increased (α=0.05). Marination pickup strongly influenced the dielectric loss factor. Differences between samples marinated at different pickup levels were more pronounced at lower frequencies for the dielectric loss factor. As frequency increased, the differences between samples decreased. Differences in dielectric constant between samples were not as consistent as those seen with the dielectric loss factor.

  20. Dielectric properties modelling of cellular structures with PDMS for micro-sensor applications

    NASA Astrophysics Data System (ADS)

    Kachroudi, Achraf; Basrour, Skandar; Rufer, Libor; Sylvestre, Alain; Jomni, Fathi

    2015-12-01

    Electro-active polymers are emerging in the fields of actuators and micro-sensors because their good dielectric and mechanical properties makes them suitable for such applications. In this work, we focus on micro-structured (cellular) polymer materials (referred as piezoelectrets or ferroelectrets) that need prior charging to attain piezoelectric behaviour. The development of such applications requires an in-depth knowledge of the intrinsic dielectric properties of such structures and models to enable the accurate prediction of a given micro-structured material’s dielectric properties. Various polymers including polypropylene, polytetrafluoroethylene, fluoroethylenepropylene, cyclo-olefines and poly(ethylene terephthalate) in a cellular form have been studied by researchers over the last fifteen years. However, there is still a lack of information on the intrinsic dielectric properties of the most recently used dielectric polymer (polydimethylsiloxane, PDMS) over wide frequency and temperature ranges. In this work, we shall propose an exhaustive equivalent electrical circuit model and explain how it can be used to predict the micro-structured PDMS complex permittivity versus frequency and temperature. The results obtained from the model were found to be in good agreement with experimental data for various micro-structured PDMS materials. Typically, for micro-sensor applications, the dielectric constant and dielectric losses are key factors which need to be minimized. We have developed a configuration which enables both to be strongly reduced with a reduction of 16% in the dielectric constant of a micro-structured PDMS compared with the bulk material. In addition, the phenomena responsible for dielectric losses variations with frequency and temperature are discussed and correlated with the theoretical model. Our model is thus proved to be a powerful tool for the control of the dielectric properties of micro-structured PDMS material for micro-sensor applications.

  1. The review of various synthesis methods of barium titanate with the enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    More, S. P.; Topare, R. J.

    2016-05-01

    The Barium Titanate is a very well known dielectric ceramic belongs to perovskite structure. It has very wide applications in the field of electronic, electro ceramic, electromechanical and electro-optical applications. Barium Titanate has very high dielectric constant as well as low dielectric loss. Substituted dielectrics are one of the most important technological compounds in modern electro ceramics. Its electrical properties can be tuned flexibly by a simple substitution technique. This has encouraged researchers to select a typical cation to be substituted at cationic sites. In the present paper, the review of various synthesis methods of Barium Titanate compound with the effect of different dopants, the grain size on the dielectric properties at various temperatures is discussed.

  2. Dielectric properties of water inside single-walled carbon nanotubes.

    PubMed

    Mikami, Fuminori; Matsuda, Kazuyuki; Kataura, Hiromichi; Maniwa, Yutaka

    2009-05-26

    In this paper, we report novel ferroelectric properties of a new form of ice inside single-walled carbon nanotubes (SWCNTs). These are called "ice nanotubes" (ice NTs) and they consist of polygonal water rings stacked one-dimensionally along the SWCNT axis. We performed molecular dynamics (MD) calculations for the ice NTs under an external electric field and in a temperature range between 100 and 350 K. It is revealed that ice NTs show stepwise polarization with a significant hysteresis loop as a function of the external field strength. In particular, pentagonal and heptagonal ice NTs are found to be the world's smallest ferroelectrics with spontaneous polarization of around 1 microC/cm(2). The n-gonal ice NT, where n = 5, 6, or 7, has (n + 1)-polarized structures with different polarizations. These findings suggest potential applications of SWCNTs encapsulating dielectric materials for the fabrication of the smallest ferroelectric devices. Experimental evidence for the presence of ice NTs inside SWCNTs is also discussed in great detail.

  3. Dielectric Properties of 4-methoxy-4'-cyanobiphenyl (1 OCB) in the Supercooled Isotropic and Nematic Phases

    NASA Astrophysics Data System (ADS)

    Urban, Stanisław; Gestblom, Bo; Pawlus, Sebastian

    2003-06-01

    Dielectric studies of 4-methoxy-4'-cyanobiphenyl (1 OCB) in the supercooled isotropic and nematic phases were performed with the aid of three set-ups covering the frequency range 10 kHz - 5 GHz. In the static measurements the nematic phase could be supercooled down to 25 K below the clearing point, whereas in the dynamic studies a 12 K range was covered in a single run. The relaxation times and activation enthalpies characterising the molecular rotations around the principal inertia moment axes were determined. The predictions of theories based on the assumption of the rod-like molecules are well applicable to the dielectric data obtained.

  4. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Jackson, Henry W. (Inventor)

    2014-01-01

    A method, system, apparatus, and computer readable medium has been provided with the ability to obtain a complex permittivity dielectric or a complex permeability micron of a sample in a cavity. One or more complex-valued resonance frequencies f(sub m) of the cavity, wherein each f(sub m) is a measurement, are obtained. Maxwell's equations are solved exactly for dielectric, and/or micron, using the f(sub m) as known quantities, thereby obtaining the dielectric and/or micron of the sample.

  5. Dynamic Properties of Dielectric Susceptibility in Ferroelectric Thin Films

    NASA Astrophysics Data System (ADS)

    Cui, Lian; Cui, Haiying; Wu, Chunmei; Yang, Guihua; He, Zelong; Wang, Yuling; Che, Jixin

    2016-02-01

    In this paper, frequency, temperature, film thickness, surface effects, and various parameters dependence of dielectric susceptibility is investigated theoretically for ferroelectric thin films by the modified Landau theory under an AC applied field. The dielectric susceptibility versus AC applied field shows butterfly-shaped behavior, and depends strongly on the frequency and amplitude of the field and temperature. Our study shows that the existence of the surface transition layer can depress the dielectric susceptibility of a ferroelectric thin film. These results are well consistent with the phenomena reported in experiments.

  6. Dielectric properties measurement of substrate and support materials

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao

    1990-01-01

    In this paper a fast and straightforward waveguide measurement technique is described for the determination of the dielectric constant and loss tangent of many commercially available materials. These dielectric materials include Cuflon, Teflon, Arlon's polyimides, Lockheed's ceramic foams, and Rogers Duroid materials. The effective dielectric constant and loss tangent of Hexsel's honeycomb material is also measured by this method and is compared to the predicted data obtained using the volume averaging theory. The accuracy and other features of this measurement technique are also discussed.

  7. Dielectric properties, screening and compressibility for bilayer systems

    NASA Astrophysics Data System (ADS)

    Kyrkos, Stamatios

    We examine the dielectric properties, screening and compressibility for charged particle bilayer systems. In the process, we first review the screening problem of a charged impurity in a one component plasma in 3D, 2D and bilayer systems within the framework of the linear response theory, both for weak and strong coupling. In the weakly coupled domain, the approach is based on the RPA response matrix. The behavior that emerges is marked by an unexpected nonmonotonic dependence of the screened charges and potential on the layer separation. In the strong coupling domain we use the link provided by the classical fluctuation dissipation theorem between the response matrix and the structure function matrix that was independently calculated by W. L. Slattery, et al. and S. Chakravatry et al . What emerges is a screening scenario where one layer exhibits an overscreening and the other an antiscreening behavior. To go beyond the linear response approximation, we also examine, within the RPA approach, higher order (quadratic) contributions to the screening both in 2D and 3D, based on the quadratic density response previously calculated by J. M. Rommel. These contributions are expected to play an important role at higher coupling or higher Z values. Finally, since the response function and the screening behavior are intimately linked to the isothermal compressibility of the system, we examine the inverse compressibility matrix and its properties for a bilayer system, both within the Debye approximation and for strongly coupled systems. The later as based on previously obtained hypernetted chain (HNC) and molecular dynamics results by G. D. Doolen and Z. Donko.

  8. An overview of laminate materials with enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    Mumby, Stephen J.

    1989-03-01

    This report focuses on laminate materials (resins and reinforcements) having potential applications in the manufacture of multi-layer printed wiring boards (PWBs) that are required to efficiently transmit high-speed digital pulses. It is intended to be a primer and a reference for selection of candidate materials for such high-performance PWBs. Included are dielectric and physical properties, and where available chemical composition and/or structure, commercial availability, compatibility with typical PWB processing schemes and approximate relative cost. Recommendations are made as to the most viable candidate materials for this type of PWB application, based on a comparison of electrical and physical properties together with processing and cost considerations. The cyanate ester resin system appears promising. Such a resin may be reinforced with regular E-glass, or the more newly available S-glass, to produce a laminate useful for intermediate performance applications. For more demanding applications the E-glass will have to be replaced by a material of much lower relative permittivity. The expanded-PTFE reinforced laminates from W. L. Gore appear to be a good choice for these applications. The processing of the Gore materials can be expected to deviate from that used with FR-4 type materials, but is likely to be less problematic than laminates comprised of a fluorinated resin. Processing is a key obstacle to the implementation of any of the new materials herein. If implementation is to be successful, programs must be established to develop and optimize processing procedures. Cost will remain an important issue. However, the higher cost of the new materials may be justified in high-end products by the performance they deliver.

  9. Ultrawideband temperature-dependent dielectric properties of animal liver tissue in the microwave frequency range.

    PubMed

    Lazebnik, Mariya; Converse, Mark C; Booske, John H; Hagness, Susan C

    2006-04-01

    The development of ultrawideband (UWB) microwave diagnostic and therapeutic technologies, such as UWB microwave breast cancer detection and hyperthermia treatment, is facilitated by accurate knowledge of the temperature- and frequency-dependent dielectric properties of biological tissues. To this end, we characterize the temperature-dependent dielectric properties of a representative tissue type-animal liver-from 0.5 to 20 GHz. Since discrete-frequency linear temperature coefficients are impractical and inappropriate for applications spanning wide frequency and temperature ranges, we propose a novel and compact data representation technique. A single-pole Cole-Cole model is used to fit the dielectric properties data as a function of frequency, and a second-order polynomial is used to fit the Cole-Cole parameters as a function of temperature. This approach permits rapid estimation of tissue dielectric properties at any temperature and frequency.

  10. Changes in the dielectric properties of rat tissue as a function of age at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Peyman, A.; Rezazadeh, A. A.; Gabriel, C.

    2001-06-01

    The dielectric properties of ten rat tissues at six different ages were measured at 37 °C in the frequency range of 130 MHz to 10 GHz using an open-ended coaxial probe and a computer controlled network analyser. The results show a general decrease of the dielectric properties with age. The trend is more apparent for brain, skull and skin tissues and less noticeable for abdominal tissues. The variation in the dielectric properties with age is due to the changes in the water content and the organic composition of tissues. The percentage decrease in the dielectric properties of certain tissues in the 30 to 70 day old rats at cellular phone frequencies have been tabulated. These data provide an important input in the provision of rigorous dosimetry in lifetime-exposure animal experiments. The results provide some insight into possible differences in the assessment of exposure for children and adults.

  11. Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties.

    PubMed

    Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

    2016-03-14

    Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.

  12. Cobalt iron-oxide nanoparticle modified poly(methyl methacrylate) nanodielectrics. Dielectric and electrical insulation properties

    NASA Astrophysics Data System (ADS)

    Tuncer, Enis; Rondinone, Adam J.; Woodward, Jonathan; Sauers, Isidor; James, D. Randy; Ellis, Alvin R.

    2009-03-01

    In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that the matrix polymeric material is confined in approximately 100 nm size cages between particle clusters. The particle clusters are composed of separated spherical particles which comprise unconnected networks in the matrix. The dielectric relaxation and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide particles. The dielectric breakdown measurements performed at 77 K showed that these nanodielectrics are potentially useful as an electrical insulation material for cryogenic high voltage applications. Finally, structural and dielectric properties of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have low dielectric permittivity regardless of the permittivity of nanoparticles are when the particles are coordinated with a low dielectric permittivity surfactant.

  13. Computational study of filler microstructure and effective property relations in dielectric composites

    NASA Astrophysics Data System (ADS)

    Wang, Yu U.; Tan, Daniel Q.

    2011-05-01

    Phase field modeling and computer simulation is employed to study the relations between filler microstructures and effective properties of dielectric composites. The model solves electrostatic equations in terms of polarization vector field in reciprocal space using a fast Fourier transform technique and parallel computing algorithm. Composites composed of linear constituent phases of different dielectric constants are considered. Interphase boundary conditions are automatically taken into account without explicitly tracking interphase interfaces in the composites. Various factors associated with filler microstructures are systematically investigated, including dielectric constant mismatch between fillers and matrix, particle size, shape, orientation, volume fraction, and spatial arrangement as well as directional alignment. Heterogeneous distributions of polarization, charge density, and local electric field are calculated for each composite microstructure, based on which effective dielectric constant and dielectric anisotropy of the composites are determined. It is found that electrostatic interactions among high-dielectric-constant fillers embedded in low-dielectric-constant matrix play critical roles in determining the composite properties, which sensitively depend on filler arrangement and, especially, directional alignment into fibrous microstructures (chains). Such microstructurally engineered composites, whose fillers are not randomly dispersed, exhibit strong dielectric anisotropy despite all constituent components being isotropic.

  14. (Ba,Sr)TiO{sub 3} dielectrics: Relationship between bulk and thin film properties

    SciTech Connect

    Kingon, A. I.; Streiffer, S. K.; Parker, C. B.; Stemmer, S.

    1999-12-22

    Thin films of complex perovskites have a number of potentially important applications. Of major scientific and practical concern is the scaling of properties as film dimensions are reduced. This paper describes a satisfactory relationship between bulk and thin film dielectric properties of (Ba,Sr)TiO{sub 3}. Relative contributions of strain, A:B cation stoichiometry, and interface are separated to explain temperature dependent dielectric behavior.

  15. Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain

    NASA Astrophysics Data System (ADS)

    Tak, S. K.; Shekhawat, M. S.; Mangal, R.

    2010-06-01

    Five sample mixtures of kaolin, ball clay, feldspar and Quartz were formulated and porcelain samples fabricated. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. A composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded a body with high dielectric strength of 19kV/mm compare to an ISO graded product having dielectric strength 14.6 KV/mm after firing at 1225°C.

  16. Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain

    SciTech Connect

    Tak, S. K.; Shekhawat, M. S.; Mangal, R.

    2010-06-29

    Five sample mixtures of kaolin, ball clay, feldspar and Quartz were formulated and porcelain samples fabricated. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. A composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded a body with high dielectric strength of 19 kV/mm compare to an ISO graded product having dielectric strength 14.6 KV/mm after firing at 1225 deg. C.

  17. Infrared Dielectric Properties of Low-stress Silicon Nitride

    NASA Technical Reports Server (NTRS)

    Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

    2012-01-01

    Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

  18. Properties of fiber reinforced plastics about static and dynamic loadings

    NASA Astrophysics Data System (ADS)

    Kudinov, Vladimir V.; Korneeva, Natalia V.

    2016-05-01

    A method for investigation of impact toughness of anisotropic polymer composite materials (reinforced plastics) with the help of CM model sample in the configuration of microplastic (micro plastic) and impact pendulum-type testing machine under static and dynamic loadings has been developed. The method is called "Break by Impact" (Impact Break IB). The estimation of impact resistance CFRP by this method showed that an increase in loading velocity ~104 times the largest changes occurs in impact toughness and deformation ability of a material.

  19. Static and dynamic properties of large polymer melts in equilibrium

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Ping; Kremer, Kurt

    2016-04-01

    We present a detailed study of the static and dynamic behaviors of long semiflexible polymer chains in a melt. Starting from previously obtained fully equilibrated high molecular weight polymer melts [G. Zhang et al., ACS Macro Lett. 3, 198 (2014)], we investigate their static and dynamic scaling behaviors as predicted by theory. We find that for semiflexible chains in a melt, results of the mean square internal distance, the probability distributions of the end-to-end distance, and the chain structure factor are well described by theoretical predictions for ideal chains. We examine the motion of monomers and chains by molecular dynamics simulations using the ESPResSo++ package. The scaling predictions of the mean squared displacement of inner monomers, center of mass, and relations between them based on the Rouse and the reptation theory are verified, and related characteristic relaxation times are determined. Finally, we give evidence that the entanglement length Ne,PPA as determined by a primitive path analysis (PPA) predicts a plateau modulus, GN 0 = /4 5 ( ρ k B T / N e ) , consistent with stresses obtained from the Green-Kubo relation. These comprehensively characterized equilibrium structures, which offer a good compromise between flexibility, small Ne, computational efficiency, and small deviations from ideality, provide ideal starting states for future non-equilibrium studies.

  20. Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

    SciTech Connect

    Mene, Ravindra U.; Mahabole, Megha P.; Mohite, K.C.; Khairnar, Rajendra S.

    2014-02-01

    Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as a function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.

  1. Dielectric properties of muscle and liver from 500 MHz-40 GHz.

    PubMed

    Abdilla, Lourdes; Sammut, Charles; Mangion, Louis Zammit

    2013-06-01

    Dielectric properties are the most important parameters determining energy deposition when biological tissues are exposed to radio frequency and microwave fields. Energy absorption is determined by the specific absorption rate (SAR). SAR distributions can be computed accurately only if the complex relative permittivity of the target tissue is known to a sufficiently high accuracy, and currently there is a lack of data on the dielectric properties of biological tissues at high frequencies. In this study, tissue dielectric properties are measured using an open-ended coaxial probe technique from 500 MHz up to 40 GHz. We present dielectric data for ex vivo bovine and porcine muscle and liver tissues at 37 °C. One-pole Cole-Cole model is used to fit the measured data as a function of frequency and the dispersion parameters are presented. This data is supported by an accurate study on reference liquids such as methanol and ethanediol.

  2. Effects of acidic functional groups on dielectric properties of sodium alginates and carrageenans in water.

    PubMed

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Okamura, Kei; Ueda, Tadaharu; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2015-01-22

    This study investigated the dielectric properties of sodium alginates and carrageenans in water at frequencies between 100 MHz and 20 GHz in regard to water-hydrocolloid interactions via acidic functional groups. Both sodium alginates and carrageenans showed conduction loss at lower frequencies and dielectric loss at higher frequencies. Reduction and desulfation of sodium alginates and carrageenans, which decreased the numbers of acidic functional groups, decreased their conduction loss. In addition, H(+)-form carrageenans showed the highest ionic conduction. Correlational analysis of dielectric properties and related physical parameters showed that the loss tangent (tanδ) of the hydrocolloid solution was determined by the conductivity of the aqueous solution. Especially at pH below 2, strong H(+) conduction was associated with high tanδ probably due to the Grotthuss mechanism. The molecular dynamics of free water and H(+), viscosity conditions were also suggested to be associated with dielectric property of water-hydrocolloid system. PMID:25439871

  3. Microstructure and microwave dielectric properties of modified zinc titanates (I)

    SciTech Connect

    Kim, H.T. |; Byun, J.D.; Kim, Y.

    1998-06-01

    Zinc metatitanate, ZnTiO{sub 3}, decomposes into zinc orthotitanate and rutile on heating above 945 C. It was found that this material could be a useful candidate for microwave resonator materials. The substitution of Zn by less than 10 mol% of Ba, Ca, or Sr achieves near zero {tau}{sub f} in spite of the fact that BaTiO{sub 3}, CaTiO{sub 3}, and SrTiO{sub 3} themselves have positive {tau}{sub f}. The origin of the temperature-compensating characteristics of the modified system was found to be in the reduction or elimination of rutile by the formation of new phases such as Ba{sub 3}Zn{sub 7}Ti{sub 12}O{sub 34}, Ca{sub 2}Zn{sub 4}Ti{sub 15}O{sub 36}, and Sr{sub 2}Zn{sub 4}Ti{sub 15}O{sub 36} polytitanates, which have much lower positive {tau}{sub f} than the rutile. It was revealed that zinc orthotitanate grains containing around 0.33 mol excess rutile have Zn{sub 2}Ti{sub 3}O{sub 8} nanosize precipitates in the grain. The precipitates had a structural coherency with the Zn{sub 2}TiO{sub 4} cubic matrix phase. The modified system has microwave dielectric properties of {epsilon}{sub r} = 25--32, Q factor at 10 GHz = 2,300--5,400, and {tau}{sub f} = +56 to {minus}22 ppm/C.

  4. Dielectric and Electromechanical Properties of Polyurethane and Polydimethylsiloxane Blends and their Nanocomposites

    NASA Astrophysics Data System (ADS)

    Cakmak, Enes

    Conventional means of converting electrical energy to mechanical work are generally considered too noisy and bulky for many contemporary technologies such as microrobotic, microfluidic, and haptic devices. Dielectric electroactive polymers (D-EAPs) constitude a growing class of electroactive polymers (EAP) that are capable of producing mechanica work induced by an applied electric field. D-EAPs are considered remarkably efficient and well suited for a wide range of applications, including ocean-wave energy harvesters and prosthetic devices. However, the real-world application of D-EAPs is very limited due to a number of factors, one of which is the difficulty of producing high actuation strains at acceptably low electric fields. D-EAPs are elastomeric polymers and produce large strain response induced by external electric field. The electromechanical properties of D-EAPs depend on the dielectric properties and mechanical properties of the D-EAP. In terms of dielectric behavior, these actuators require a high dielectric constant, low dielectric loss, and high dielectric strength to produce an improved actuation response. In addition to their dielectric properties, the mechanical properties of D-EAPs, such as elastic moduli and hysteresis, are also of importance. Therefore, material properties are a key feature of D-EAP technology. DE actuator materials reported in the literature cover many types of elastomers and their composites formed with dielectric fillers. Along with polymeric matrix materials, various ceramic, metal, and organic fillers have been employed in enhancing dielectric behavior of DEs. This work describes an effort to characterize elastomer blends and composites of different matrix and dielectric polymer fillers according to their dielectric, mechanical, and electromechanical responses. This dissertation focuses on the development and characterization of polymer-polymer blends and composites from a high-k polyurethane (PU) and polydimethylsiloxane

  5. Investigating low frequency dielectric properties of a composite using the distribution of relaxation times technique

    SciTech Connect

    Tuncer, Enis

    2006-01-01

    The distribution of relaxation times approach, a less frequently employed dielectric data analysis technique, is utilized to better understand the relaxation characteristics of composites consisting of metal-coated, hollow glass spheres dispersed in a paraffin wax matrix. The dielectric properties of the composite samples are measured by means of impedance spectroscopy in the frequency range 0.1mHz to 10 MHz. The application of a mixture law is not appropriate for the analysis of the frequency-dependent properties of the considered system on this broad frequency range. However, utilization of the distribution of relaxation times procedure to study the dielectric behaviour shows clear trends in the mixtures' relaxation spectra. Relaxation processes of the paraffin wax and those specific to the composites are found from the extracted distribution of relaxation times spectra. The influence of the filler concentration, q, on the dielectric properties is examined; a relaxation with a narrow distribution at intermediate frequencies becomes broad with the addition of the filler. This relaxation, in the form of the low-frequency-dispersions (also known as constant phase angle) phenomenon, dominates the dielectric properties of the composites with high bead concentration, q > 0:15. The variation in dielectric properties of individual samples whose bead concentrations q are nominally the same is discussed in terms of possible microstructural variations.

  6. Investigating low-frequency dielectric properties of a composite using the distribution of relaxation times technique

    SciTech Connect

    Tuncer, Enis; Bowler, Nicola; Youngs, I. J.; Lymer, K. P.

    2006-01-01

    The distribution of relaxation times approach, a less frequently employed dielectric data analysis technique, is utilized to better understand the relaxation characteristics of composites consisting of metal-coated, hollow glass spheres dispersed in a paraffin wax matrix. The dielectric properties of the composite samples are measured by means of impedance spectroscopy in the frequency range 0.1 mHz to 10 MHz. The application of a mixture law is not appropriate for the analysis of the frequency-dependent properties of the considered system on this broad frequency range. However, utilization of the distribution of relaxation times procedure to study the dielectric behaviour shows clear trends in the mixtures' relaxation spectra. Relaxation processes of the paraffin wax and those specific to the composites are found from the extracted distribution of relaxation times spectra. The influence of the filler concentration, q, on the dielectric properties is examined; a relaxation with a narrow distribution at intermediate frequencies becomes broad with the addition of the filler. This relaxation, in the form of the low-frequency-dispersions (also known as constant phase angle) phenomenon, dominates the dielectric properties of the composites with high bead concentration, q>0.15. The variation in dielectric properties of individual samples whose bead concentrations q are nominally the same is discussed in terms of possible microstructural variations.

  7. Nanoscale Mapping of Dielectric Properties of Nanomaterials from Kilohertz to Megahertz Using Ultrasmall Cantilevers.

    PubMed

    Cadena, Maria J; Sung, Seung Hyun; Boudouris, Bryan W; Reifenberger, Ronald; Raman, Arvind

    2016-04-26

    Electrostatic force microscopy (EFM) is often used for nanoscale dielectric spectroscopy, the measurement of local dielectric properties of materials as a function of frequency. However, the frequency range of atomic force microscopy (AFM)-based dielectric spectroscopy has been limited to a few kilohertz by the resonance frequency and noise of soft microcantilevers used for this purpose. Here, we boost the frequency range of local dielectric spectroscopy by 3 orders of magnitude from a few kilohertz to a few megahertz by developing a technique that exploits the high resonance frequency and low thermal noise of ultrasmall cantilevers (USCs). We map the frequency response of the real and imaginary components of the capacitance gradient (∂C(ω)/∂z) by using second-harmonic EFM and a theoretical model, which relates cantilever dynamics to the complex dielectric constant. We demonstrate the method by mapping the nanoscale dielectric spectrum of polymer-based materials for organic electronic devices. Beyond offering a powerful extension to AFM-based dielectric spectroscopy, the approach also allows the identification of electrostatic excitation frequencies which affords high dielectric contrast on nanomaterials.

  8. Dielectric properties of multiatomic alcohols: 1,4-butanediol

    NASA Astrophysics Data System (ADS)

    Zhuravlev, V. I.

    2015-12-01

    The dielectric spectra of 1,4-butanediol in the temperature range of 298-423 K are analyzed using the theoretical approaches of Debye, Davidson-Cole, and Forsman, based on the Dissado-Hill theory. It is shown that the dielectric spectra of 1,4-butanediol are described by the Davidson-Cole equation, and the βDC parameter has a pronounced strong temperature dependence. In the Debye theory, the spectrum of the dielectric relaxation of 1,4-butanediol is presented as the sum of two region of dispersions. Conclusions are reached as to the possible mechanisms of dispersion responsible for the obtained regions. The relaxation times of 1,4-butanediol calculated using different equations describing the nonlinear behavior of the relaxation time are compared. The dipole moments of clusters are obtained for the first time and a preliminary analysis is performed using the Dissado-Hill cluster model.

  9. Structural and dielectric properties of yttrium-substituted hydroxyapatites.

    PubMed

    Kaygili, Omer; Dorozhkin, Sergey V; Ates, Tankut; Gursoy, N Canan; Keser, Serhat; Yakuphanoglu, Fahrettin; Selçuk, A Birkan

    2015-02-01

    Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content.

  10. Dielectric properties of the multicomponent PZT-type solid solution

    NASA Astrophysics Data System (ADS)

    Bochenek, Dariusz; Niemiec, Przemysław; Adamczyk, Małgorzata; Machnik, Zbigniew; Dercz, Grzegorz

    2015-10-01

    In this paper the multicomponent PZT-type solid solution doped by barium, calcium, strontium, bismuth and germanium with composition: Pb0.975Ba0.01Ca0.01Sr0.005(Zr0.52Ti0.48)O3 + 1.4 wt.% Bi2O3 + 0.3 wt.% GeO obtained by hot uniaxial pressing method is described. The results of structural, dielectric, ferroelectric and electromechanical studies of these ceramics are presented. It has been stated that introduction to the basic composition PZT admixtures of the barium, calcium, strontium, bismuth and germanium has a positive effect on the electro-physic parameters of obtained ceramic samples. This material has good microstructure, with high value of the dielectric permittivity (with the high temperature of phase transition) as well as low dielectric losses. It allows considering this material as elements for low frequency and high temperature electromechanical transducers.

  11. Dielectric properties of polyfunctional alcohols: 2,3-butanediol

    NASA Astrophysics Data System (ADS)

    Zhuravlev, V. I.

    2016-08-01

    Using a variety theoretical approaches within the Debye, Davidson-Cole, and Forsman models, and an approach based on the Dissado-Hill theory, dielectric spectra of 2,3-butanediol in the temperature range of 298 to 423 K are analyzed. It is shown that the dielectric spectra of 2,3-butanediole are described by the Davidson-Cole equation, and the βDC parameter depends strongly on temperature. The spectrum of dielectric relaxation of 2,3-butanediol within the Debye theory is presented as the sum of two areas of dispersion, and conclusions are drawn regarding possible mechanisms of dispersion responsible for the obtained fields. The relaxation times of 2,3-butanediol, calculated using different equations describing the nonlinear behavior of relaxation times, are compared. The dipole moments of clusters are obtained for the first time using the Dissado-Hill cluster model, and a preliminary analysis of them is performed.

  12. Dielectric properties of antiferroelectric liquid-crystalline mixtures

    NASA Astrophysics Data System (ADS)

    Goc, F.; Kuczynski, Wojciech; Malecki, J.; Dabrowski, Roman S.; Hoffmann, Jerzy

    1999-12-01

    Antiferroelectric liquid crystalline mixtures having smectic CA* phase in very broad temperature range have been investigated. Measurements of dielectric relaxation and spontaneous polarization were performed. Two absorption peaks in the existence range of the antiferroelectric CA* phase in the kHz-MHz range of frequency were observed. Both peaks are quite weak and of Debye type. Their characteristic dielectric strengths are almost temperature independent. The peaks are probably related to the motions of molecules on the side of a cone, defined by the molecule tilt angle, the slower process is related to the motions of molecules, tilted in opposite directions in subsequent layers and moving in the same direction. The process with shorter relaxation time is attributed to the movement of molecules in opposite directions. Both modes are active in dielectric measurements due to small residual polarization being a consequence of the helical superstructure.

  13. Dielectric properties of uncooked chicken breast muscles from ten to one thousand eight hundred megahertz.

    PubMed

    Zhuang, H; Nelson, S O; Trabelsi, S; Savage, E M

    2007-11-01

    The dielectric properties, consisting of the dielectric constant (epsilon') and loss factor (epsilon''), were measured with an open-ended coaxial-line probe and impedance analyzer for uncooked broiler breast muscle pectoralis major and pectoralis minor, deboned at 2- and 24-h postmortem, over the frequency range from 10 to 1,800 MHz at temperatures ranging from 5 to 85 degrees C. The dielectric property profiles of chicken breast muscle are dependent upon the radio-wave and microwave frequencies and temperature. Increasing frequency from 10 to 1,800 MHz results in decreasing values of the dielectric constant and loss factor regardless of temperature in this range, chicken breast muscle type, or deboning time. However, the response to temperature varies with the frequency, muscle type, and deboning time. There are no differences in the dielectric constant and loss factor values at frequencies of 26 or 1,800 MHz between samples deboned at 2- and at 24-h postmortem. However, the muscle type significantly affects the average values of the dielectric constant and loss factor, with pectoralis minor having significantly higher average values. Both the deboning time and muscle type significantly affect the average values of the loss tangent (tan delta = dielectric loss factor/dielectric constant) at 26 and 1,800 MHz, with pectoralis minor having higher values than pectoralis major and 2-h samples having higher values than 24-h samples. Our quality measurements also show there are significant differences in chicken meat quality characteristics, including color, pH, drip loss, water holding capacity, and texture (Warner-Bratzler shear force value) between the different muscle types and between different deboning times in the same test. These results suggest that there is a probable potential for using dielectric property measurements to assess the quality of chicken meat.

  14. Correlation of the Dielectric Properties of Dispersed Particles with the Electrorheological Effect

    PubMed

    Hao; Xu; Xu

    1997-06-15

    The dc field rheological properties and frequency dependent dielectric properties of a set of electrorheological (ER) fluids composed of oxidized polyacrylonitrile or aluminosilicate materials dispersed in silicone oil were examined in this paper. Our experimental investigations show that there is a complicated relationship between the dielectric properties of dispersed particles and the ER effect. The dielectric loss of dispersed particles, which has not attracted much attention in previous work, was found to play a considerable role in ER response. The large dielectric loss tangent, experimentally around 0.10 at 1000 Hz, is found to be needed for a strong ER effect. A good ER solid material should first have large dielectric loss, and then the higher the dielectric constant, the stronger the ER effect. The large dielectric loss would facilitate the turning of dispersed particles, and the high dielectric constant would maintain the fibrillation structure stable and strong. Two processes, the particle turning process and the particle polarization process, are thought to be involved in ER activity. Our findings, in connection with the Wagner model, can better explain why the strongest ER effect occurs at particle conductivity of 10(-7) S/m; why the shear stress of some ER fluids decreases with frequency while with others the shear stress increases with frequency; and why trace water can enhance the ER effect considerably, which would help in understanding the mechanism of the ER effect. Too large a dielectric loss is thought to be unfavorable for the ER effect, and its suitable range is worth further study. The results also present a method of designing high performance ER fluids, which would significantly promote development of electrorheology and its application in industrial areas.

  15. Molecular level materials design for improvements of actuation properties of dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Kofod, G.; Stoyanov, H.; Kollosche, M.; Risse, S.; Ragusch, H.; McCarthy, D. N.; Waché, R.; Rychkov, D.; Dansachmüller, M.

    2011-04-01

    Dielectric elastomer actuators are soft electro-mechanical transducers with possible uses in robotic, orthopaedic and automotive applications. The active material must be soft and have a high ability to store electrical energy. Hence, three properties of the elastic medium in a dielectric elastomer actuator affect the actuation properties directly: dielectric constant, electric breakdown strength, and mechanical stiffness. The dielectric constant of a given elastomer can be improved by mixing it with other components with a higher dielectric constant, which can be classified as insulating or conducting. In this paper, an overview of all approaches proposed so far for dielectric constant improvement in these soft materials will be provided. Insulating particles such as TiO2 nanoparticles can raise the dielectric constant, but may also lead to stiffening of the composite, such that the overall actuation is lowered. It is shown here how a chemical coating of the TiO2 nanoparticles leads to verifiable improvements. Conducting material can also lead to improvements, as has been shown in several cases. Simple percolation, relying on the random distribution of conducting nanoparticles, commonly leads to drastic lowering of the breakdown strength. On the other hand, conducting polymer can also be employed, as has been demonstrated. We show here how an approach based on a specific chemical reaction between the conducting polymer and the elastomer network molecules solves the problem of premature breakdown which is otherwise typically found.

  16. Analysis of the dielectric properties of trunk wood in dominant conifer species from New England and Siberia

    NASA Technical Reports Server (NTRS)

    Ranson, K. J.; Rock, B. N.; Salas, W. A.; Smith, K.; Williams, D. L.

    1992-01-01

    Data were collected for dominant conifer species. Dielectric properties of trunk wood were measured using a C-band dielectric probe. For certain specimens, electrical resistance was also measured using a shigometer. The water status of the trees studies was determined either by use of a Scholander pressure chamber on branch samples collected simultaneously with dielectric measurements or by fresh-weight/dry-weight assessment of wood core samples extracted and analyzed with the dielectric probe and shigometer. Diurnal delectric properties and xylem water column tension are inversely correlated such that real and imaginary dielectric values drop as tension increases. The dielectric properties were positively correlated with wood core moisture content while electrical resistance was poorly correlated with wood core moisture content in one species studied. Results support the view that dielectric properties are strongly correlated with moisture status in trunk wood, and possibly ion concentrations associated with decay processes in damaged specimens.

  17. Dielectric properties of multiatomic alcohols: 1,3-butanediol

    NASA Astrophysics Data System (ADS)

    Zhuravlev, V. I.

    2016-10-01

    The dielectric spectra of 1,3-butanediol in the temperature range of 298-423 K are analyzed using a variety of theoretical approaches. It is shown that the dielectric spectra of 1,3-butanediol are described by the Davidson-Cole equation. Conclusions as to possible mechanisms of dispersion are drawn using the Debye theory. The relaxation times of 1,3-butanediol, calculated in different ways, are compared. The dipole moments of clusters are calculated for the first time using the Dissado-Hill cluster model.

  18. Dielectric properties of polyamide 12-chromium(III) oxide nanocomposites

    NASA Astrophysics Data System (ADS)

    Zuev, Vjacheslav V.; Shapoval, Ekaterina S.; Sakhatskii, Aleksandr S.

    2016-08-01

    Broadband dielectric spectroscopy was employed to study polymer nanocomposites based on PA12 filled with of nanosized chromium(III) oxide. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. Three relaxation processes and Maxwell-Wagner-Sillars (MWS) interfacial polarizations were observed. It was found that presence of nanosized amphoteric chromium(III) oxide leads to softening of polyamide matrix that manifested in decrease of the activation energy of the α- and β-relaxation processes and glass transition temperatures. The softening of polymer matrix is the reason of the decrease of mechanical strength of polymer nanocomposites as compared with neat PA12.

  19. Saturation effects on the joint elastic-dielectric properties of carbonates

    NASA Astrophysics Data System (ADS)

    Han, Tongcheng; Clennell, Michael Ben; Pervukhina, Marina; Josh, Matthew

    2016-06-01

    We used a common microstructural model to investigate the cross-property relations between elastic wave velocities and dielectric permittivity in carbonate rocks. A unified model based on validated self-consistent effective medium theory was used to quantify the effects of porosity and water saturation on both elastic properties (compressional and shear wave velocities) and electromagnetic properties (dielectric permittivity). The results of the forward models are presented as a series of cross-plots covering a wide range of porosities and water saturations and for microstructures that correspond to different predominant aspect ratios. It was found that dielectric permittivity correlated approximately linearly with elastic wave velocity at each saturation stage, with slopes varying gradually from positive at low saturation conditions to negative at higher saturations. The differing sensitivities of the elastic and dielectric rock properties to changes in porosity, pore morphology and water saturation can be used to reduce uncertainty in subsurface fluid saturation estimation when co-located sonic and dielectric surveys are available. The joint approach is useful for cross-validation of rock physics models for analysing pore structure and saturation effects on elastic and dielectric responses.

  20. Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement

    PubMed Central

    Yao, Jiafeng; Kodera, Tatsuya; Obara, Hiromichi; Sugawara, Michiko; Takei, Masahiro

    2015-01-01

    The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry. PMID:26392831

  1. Dielectric properties of I-III-VI2-type chalcopyrite semiconductors

    NASA Astrophysics Data System (ADS)

    Xue, D.; Betzler, K.; Hesse, H.

    2000-11-01

    Dielectric properties of I-III-VI2-type ternary chalcopyrite semiconductors, including linear and second order nonlinear optical susceptibilities at 10.6 μm, have been quantitatively studied from the chemical bond viewpoint. Contributions from each type of constituent chemical bond, i.e., I - VI and III - VI bonds, to the total linear and nonlinear optical properties of these compounds at 10.6 μm have been theoretically determined. The chemical bond method quantitatively expresses the trends in the dielectric properties of these compounds, which is helpful for carrying out modeling of their properties.

  2. Structural and dielectric properties of Cu doped CeO2

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Chand, F.; Kumar, Parmod; Meena, R. C.; Kumar, Ashish; Asokan, K.

    2016-05-01

    In the present work, we report the structural and dielectric properties of Cu doped CeO2 compounds synthesized by solid state reaction method. X-ray diffraction study confirms the formation of cubic phase with Fm-3m space group corresponding to fluorite CeO2 structure. The crystallite size was found to decrease with Cu concentration. Furthermore, the dielectric measurements were carried out by varying frequency in the temperature range of 120 to 380 K. It has been found that the increase in Cu concentration in the host lattice leads to an enhancement in dielectric constant.

  3. Optical and dielectric properties of L-methionine L-methioninium hydrogen maleate single crystal

    NASA Astrophysics Data System (ADS)

    Vasudevan, P.; Sankar, S.; Gokulraj, S.

    2013-02-01

    An organic nonlinear optical single crystal L-methionine L-methioninium hydrogen maleate has been grown by solution growth technique. It is confirmed from XRD data that the crystal belongs to monoclinic system with non-centrosymmetric space group P21. Photoluminescence study was carried out for the grown crystal and maximum emission occurs at 395 nm. Dielectric measurements were made for the frequency range from 100 Hz to 5 MHz. The lower value of dielectric constant and dielectric loss at higher frequencies reveal that the material possesses enhanced optical quality with lesser defects. Nonlinear optical property was confirmed by Kurtz and Perry technique.

  4. Dielectric properties of rat embryo and foetus as a function of gestation

    NASA Astrophysics Data System (ADS)

    Peyman, A.; Gabriel, C.

    2012-04-01

    The dielectric properties of rat embryos/foetuses have been acquired at several stages of gestation at 37 °C and in the frequency range of 40 MHz-20 GHz. Measurements were carried out on homogenized tissues, as trial experiments did not show any systematic difference between the dielectric data of intact and homogenized tissues at microwave frequencies. The results showed that dielectric properties of the foetus are generally higher than adult muscle and brain. The measured data also showed some decline for both permittivity and conductivity as the foetus grew from 18 to 20 days old; however, these changes were not statistically significant. Data were also collected for placenta and amniotic fluid which were in good agreement with those recently obtained from human tissues. Finally, tabulated numerical dielectric data for rat foetal tissues are presented for a wide range of medical and telecommunication frequencies.

  5. Grain size effect on magnetic and dielectric properties of hexagonal YbMnO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Han, Tai-Chun; Hsu, Hsin-Kai; Chu, Yih-Tsyr; Hu, Yu-Min

    2015-05-01

    We have synthesized a series of YbMnO3 nanoparticles with different grain sizes (25-450 nm) and study the effect of grain size on their structural, magnetic, and dielectric properties. The YbMnO3 nanoparticles crystallized in hexagonal perovskite-type structure. It shows that magnetic and dielectric properties are strongly dependent on the grain size. The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 70 to 86 K. A corresponding shift in the peak-positions of dielectric anomaly and AFM transition temperature is observed, indicating a strong correlation between the magnetic ordering and the electric polarization. As evidenced by the variation in the ab-plane lattice parameters and Mn-O bond lengths, the AFM interactions and dielectric anomalies of YbMnO3 can be effectively modulated by varying grain size.

  6. First-principles investigation of band offsets and dielectric properties of Silicon-Silicon Nitride interfaces

    NASA Astrophysics Data System (ADS)

    Pham, Tuan Anh; Li, Tianshu; Gygi, Francois; Galli, Giulia

    2011-03-01

    Silicon Nitride (Si3N4) is a possible candidate material to replace or be alloyed with SiO2 to form high-K dielectric films on Si substrates, so as to help prevent leakage currents in modern CMOS transistors. Building on our previous work on dielectric properties of crystalline and amorphous Si3N4 slabs, we present an analysis of the band offsets and dielectric properties of crystalline-Si/amorphous Si3N4 interfaces based on first principles calculations. We discuss shortcomings of the conventional bulk-plus line up approach in band offset calculations for systems with an amorphous component, and we present the results of band offsets obtained from calculations of local density of states. Finally, we describe the role of bonding configurations in determining band edges and dielectric constants at the interface. We acknowledge financial support from Intel Corporation.

  7. Reflectance properties of one-dimensional metal-dielectric ternary photonic crystal

    NASA Astrophysics Data System (ADS)

    Pandey, G. N.; Kumar, Narendra; Thapa, Khem B.; Ojha, S. P.

    2016-05-01

    Metallic photonic crystal has a very important application in absorption enhancement in solar cells. It has been found that an ultra-thin metallic layer becomes transparent due to internal scattering of light through the each interface of the dielectric and metal surfaces. The metal has absorption due to their surface plasmon and the plasmon has important parameters for changing optical properties of the metal. We consider ternary metallic-dielectric photonic crystal (MDPC) for having large probabilities to change the optical properties of the MDPC and the photonic crystals may be changed by changing dimensionality, symmetry, lattice parameters, Filling fraction and effective refractive index refractive index contrast. In this present communication, we try to show that the photonic band gap in ternary metal-dielectric photonic crystal can be significantly enlarged when air dielectric constant is considered. All the theoretical analyses are made based on the transfer matrix method together with the Drude model of metal.

  8. Study Of Structural And Dielectric Properties Of Ni-Mg Ferrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Nongjai, Razia; Batoo, Khalid Mujasam; Khan, Shakeel

    2010-12-01

    Ferrite nanoparticles of basic composition Ni0.7Mg0.3Fe2-xAlxO4 (0.0≤x≤0.5) were prepared through citrate gel method and characterized using XRD, TEM and dielectric spectroscopy techniques. The dielectric properties were studied as a function of frequency (42 Hz-5 MHz) at room temperature. The average particle size has been found between 8-17 nm. The dispersion in dielectric properties and ac conductivity (σac), with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+ as well as between Ni2+ and Ni3+ ions at B-sites. The dielectric loss tangent (tan δ) shows abnormal behavior for the compositions 0.3, 0.4 and 0.5 which has been explained in the light of Rezlescue model.

  9. Millimeter Waveband Dielectric Properties of Nanocomposite Materials Based on Opal Matrices with Particles of Spinels

    NASA Astrophysics Data System (ADS)

    Rinkevich, A. B.; Perov, D. V.; Pakhomov, Ya A.; Samoylovich, M. I.; Kuznetsov, E. A.

    2016-11-01

    The dielectric properties of 3D nanocomposites based on opal matrices containing the particles of compounds with spinel structure have been studied. Microwave measurements have been carried out in the frequency range from 26 to 38 GHz. The frequency dependences of transmission and reflection coefficients are obtained. The values of the real and imaginary parts of complex dielectric permittivity have been retrieved. The X-ray phase analysis of the nanocomposites is performed and their structures are studied.

  10. Millimeter Waveband Dielectric Properties of Nanocomposite Materials Based on Opal Matrices with Particles of Spinels

    NASA Astrophysics Data System (ADS)

    Rinkevich, A. B.; Perov, D. V.; Pakhomov, Ya A.; Samoylovich, M. I.; Kuznetsov, E. A.

    2016-09-01

    The dielectric properties of 3D nanocomposites based on opal matrices containing the particles of compounds with spinel structure have been studied. Microwave measurements have been carried out in the frequency range from 26 to 38 GHz. The frequency dependences of transmission and reflection coefficients are obtained. The values of the real and imaginary parts of complex dielectric permittivity have been retrieved. The X-ray phase analysis of the nanocomposites is performed and their structures are studied.

  11. Microstructures and Dielectric Properties of PZT Coatings Prepared by Supersonic Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Li, Guolu; Gu, Linsong; Wang, Haidou; Xing, Zhiguo; Zhu, Lina

    2014-02-01

    This paper studied the microstructures and dielectric properties of PZT coatings prepared by supersonic plasma spraying. Samples of the PZT coatings were evaluated by various techniques. The phases and microstructures of the coatings were investigated by XRD, SEM, and TEM, respectively. The results showed that the coatings deposited on steel substrate had a dense microstructure, and there was no phase transformation during spraying. Additionally, the Curie temperature of the PZT coatings was about 370 °C by the investigation of dielectric constant.

  12. Size effect on dielectric properties of synthetic diamond

    NASA Astrophysics Data System (ADS)

    Batsanov, Stepan S.; Dan'kin, Dmitry A.

    2016-07-01

    Reducing sizes of diamond crystals in the micrometer range progressively increases their dielectric permittivity. This effect is due to the surface shells of solids where under-coordinated atoms diminish the energy of chemical bonding on a surface that reduces the frequency of atomic vibration but also create a distortion in atomic order causing spontaneous polarization.

  13. Thermal, dielectric and structural properties of Enceladus' leading face

    NASA Astrophysics Data System (ADS)

    Le Gall, Alice; Bonnefoy, Léa; Leyrat, Cedric; Janssen, Michael A.

    2016-10-01

    The Cassini RADAR was initially designed to examine the surface of Titan through the veil of its optically-opaque atmosphere. However, it is occasionally used to observe airless Saturn's moons from long range and, less frequently, during targeted flybys. In particular, the 16th targeted encounter of Enceladus (Nov. 6, 2011, flyby E16) was dedicated to the RADAR instrument which then acquired data for over 4 hours. This paper focuses on the mid-resolution (0.1-0.6REnceladus) and low-resolution polarized data (0.6-1.0REnceladus) collected during the E16 flyby in the radiometry mode of the RADAR, mainly on the leading side of the moon.In its passive mode, the RADAR records the thermal emission at 2-cm wavelength from, likely, the first meters of an icy surface. Ries and Janssen (2015) first analyzed the E16 mid-resolution radiometry observation and reported on a large-scale emissivity anomaly, possibly associated with the seemingly young tectonized Leading Hemisphere Terrain mapped by Crow-Willard and Pappalardo (2015). With the goal of further investigating the extension of the anomaly region and providing constrains on the thermal, dielectric and structural properties of Enceladus' near surface, we have re-examined this dataset as well as observations acquired in two orthogonal polarizations with the help of a thermal model. This thermal model accounts for both diurnal and seasonal variations of the incident flux, including eclipses which is of importance for the E16 observations partially occurred during a solar eclipse by Saturn.Preliminary results suggest that the average thermal inertia of the near surface of Enceladus' leading face is relatively low, as low as 40 Jm-2K-1s-1/2 . This value does not depart much from the one inferred from measurements in the IR suggesting that the surface of Enceladus is covered by a very porous regolith, at least a few meters thick. In agreement, with this interpretation, the degree of volume scattering (i.e., high

  14. Study of low weight percentage filler on dielectric properties of MCWNT-epoxy nanocomposites

    NASA Astrophysics Data System (ADS)

    Trihotri, Manindra; Dwivedi, U. K.; Malik, M. M.; Khan, Fozia Haque; Qureshi, M. S.

    2016-09-01

    An attempt is made to study the effect of low weight percentage multiwall carbon nanotube (MWCNT) powder on dielectric properties of MWCNT reinforced epoxy composites. For that MWCNT (of different low weight percentage) reinforced epoxy composite was prepared by dispersing the MWCNT in resin. Samples were prepared by solution casting process and characterized for their dielectric properties such as dielectric constant (ɛ‧), dielectric dissipation factor (tan δ) and AC conductivity (σac). The main objective is the investigation of the dielectric properties of the prepared samples at the low weight percentage of the filler at different temperatures and frequencies. From the two mechanisms of electrical conduction, first the leakage current obtained by the formation of a percolation network in the matrix and the other by tunneling of electrons formed among conductors nearby (tunneling current); here we are getting conduction by the second mechanism. Generally, leakage current makes more contribution to conductivity than tunneling current. Dielectric dissipation factor at 250Hz frequency is greater than all other frequencies and starts increasing from 60∘C. The peak height of the transition temperature decreases with increasing frequency. This study shows that the addition of a low weight percentage of MWCNT can modify considerably the electrical behavior of epoxy nanocomposites without chemical functionalization of filler.

  15. Measuring Static and Dynamic Properties of Frozen Silty Soils

    SciTech Connect

    Furnish, M.D.

    1998-09-30

    A mechanical characterization of frozen silty soils has been conducted to support computer modeling of penetrators. The soils were obtained from the Eilson AFB (Alaska) vicinity. Quasi-static testing with a multiaxial system in a cold room and intermediate strain rate testing with a split Hopkinson pressure bar were conducted. Maximum stresses achieved were slightly above 1 GPa, apparently limiting the observed behavior primarily to elastic compression and pore crushing phenomena. Lower temperatures seem to increase the strength of the material markedly, although not by a simple factor. Lower temperatures and higher strain rates increase the apparent Young's and bulk moduli as well (an increase of {approximately} a factor of two is observed for strain rate increasing from 0.001 s{sup {minus}1} to 800 s{sup {minus}1}). The strength also depends strongly on strain rate. Increasing the strain rate from 0.001 {sup {minus}1} to 0.07 {sup {minus}1} increases the strength by a factor of five to ten (to values of order 1 GPa). However,only a small increase in strength is seen as strain rate is increased to {approximately} 10{sup 2}--10{sup 3} s{sup {minus}1}. The reliability of the strength measurements at strain rates< 1 s{sup {minus}1} is decreased due to details of the experimental geometry, although general trends are observable. A recipe is provided for a simulant soil based on bentonite, sand, clay-rich soil and water to fit the {approximately} 6% air-filled porosity, density and water content of the Alaska soils, based on benchtop mixing and jacketed compression testing of candidate mixes.

  16. Ab Initio Study of the Dielectric and Electronic Properties of Multilayer GaS Films.

    PubMed

    Li, Yan; Chen, Hui; Huang, Le; Li, Jingbo

    2015-03-19

    The dielectric properties of multilayer GaS films have been investigated using a Berry phase method and a density functional perturbation theory approach. A linear relationship has been observed between the number of GaS layers and slab polarizability, which can be easily converged at a small supercell size and has a weak correlation with different stacking orders. Moreover, the intercoupling effect of the stacking pattern and applied vertical field on the electronic properties of GaS bilayers has been discussed. The band gaps of different stacking orders show various downward trends with the increasing field, which is interpreted as giant Stark effect. Our study demonstrates that the slab polarizability as the substitution of conventional dielectric constant can act as an independent and reliable parameter to elucidate the dielectric properties of low-dimensional systems and that the applied electric field is an effective method to modulate the electric properties of nanostructures.

  17. Static and yawed-rolling mechanical properties of two type 7 aircraft tires

    NASA Technical Reports Server (NTRS)

    Tanner, J. A.; Stubbs, S. M.; Mccarty, J. L.

    1981-01-01

    Selected mechanical properties of 18 x 5.5 and 49 x 17 size, type 7 aircraft tires were evaluated. The tires were subjected to pure vertical loads and to combined vertical and lateral loads under both static and rolling conditions. Parameters for the static tests consisted of tire load in the vertical and lateral directions, and parameters for the rolling tests included tire vertical load, yaw angle, and ground speed. Effects of each of these parameters on the measured tire characteristics are discussed and, where possible, compared with previous work. Results indicate that dynamic tire properties under investigation were generally insensitive to speed variations and therefore tend to support the conclusion that many tire dynamic characteristics can be obtained from static and low speed rolling tests. Furthermore, many of the tire mechanical properties are in good agreement with empirical predictions based on earlier research.

  18. Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials

    SciTech Connect

    McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

    2011-01-03

    Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

  19. Dielectric properties of wheat flour mixed with oat meal

    NASA Astrophysics Data System (ADS)

    Łuczycka, D.; Czubaszek, A.; Fujarczuk, M.; Pruski, K.

    2013-03-01

    Possibilities of using electric methods for determining admixtures of oat meal to wheat flour, type 650 are presented. In wheat flour, oat meal and mixtures containing 10, 20 and 30% of the oat meal, moisture, protein, starch and ash content, sedimentation value, yield and softening of wet gluten were determined. In samples containing 0, 5, 10, 15, 20, 25, 30 and 100% of oat meal, the dielectric loss factor and conductivity were determined using an impedance analyzer for electromagnetic field frequency ranging from 0.1-20 kHz. It was found that the dielectric loss factor varied for tested material. The best distinguishing between tested mixtures was obtained at the measuring electromagnetic field frequency of 20 kHz. The loss factor was significantly correlated with the yield of wet gluten and the sedimentation value, parameters indicating the amount and quality of gluten proteins in flour.

  20. Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium

    NASA Astrophysics Data System (ADS)

    Mir, Showkat H.; Jha, Prakash C.; Islam, M. S.; Banarjee, Amitava; Luo, Wei; Dabhi, Shweta D.; Jha, Prafulla K.; Ahuja, R.

    2016-07-01

    In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young’s modulus E, Poisson’s ratio v, shear modulus G, anisotropy factor A and Pugh’s ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory.

  1. Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium

    PubMed Central

    Mir, Showkat H.; Jha, Prakash C.; Islam, M. S.; Banarjee, Amitava; Luo, Wei; Dabhi, Shweta D.; Jha, Prafulla K.; Ahuja, R.

    2016-01-01

    In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young’s modulus E, Poisson’s ratio v, shear modulus G, anisotropy factor A and Pugh’s ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory. PMID:27384709

  2. Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium.

    PubMed

    Mir, Showkat H; Jha, Prakash C; Islam, M S; Banarjee, Amitava; Luo, Wei; Dabhi, Shweta D; Jha, Prafulla K; Ahuja, R

    2016-01-01

    In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young's modulus E, Poisson's ratio v, shear modulus G, anisotropy factor A and Pugh's ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory. PMID:27384709

  3. Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium.

    PubMed

    Mir, Showkat H; Jha, Prakash C; Islam, M S; Banarjee, Amitava; Luo, Wei; Dabhi, Shweta D; Jha, Prafulla K; Ahuja, R

    2016-07-07

    In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young's modulus E, Poisson's ratio v, shear modulus G, anisotropy factor A and Pugh's ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory.

  4. Factors Influencing the Dielectric Properties of Agricultural Products and Food Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of materials are defined, and the major factors that influence these properties of agricultural and food materials, namely, frequency of the applied radio-frequency and microwave electric fields, water content, temperature, and density of the materials are discussed on the bas...

  5. Improving the Dielectric Properties of Ethylene-Glycol Alkanethiol Self-Assembled Monolayers

    PubMed Central

    2014-01-01

    Self-assembled monolayers (SAMs) can be formed at the interface between solids and fluids, and are often used to modify the surface properties of the solid. One of the most widely employed SAM systems is exploiting thiol-gold chemistry, which, together with alkane-chain-based molecules, provides a reliable way of SAM formation to modify the surface properties of electrodes. Oligo ethylene-glycol (OEG) terminated alkanethiol monolayers have shown excellent antifouling properties and have been used extensively for the coating of biosensor electrodes to minimize nonspecific binding. Here, we report the investigation of the dielectric properties of COOH-capped OEG monolayers and demonstrate a strategy to improve the dielectric properties significantly by mixing the OEG SAM with small concentrations of 11-mercaptoundecanol (MUD). The monolayer properties and composition were characterized by means of impedance spectroscopy, water contact angle, ellipsometry and X-ray photoelectron spectroscopy. An equivalent circuit model is proposed to interpret the EIS data and to determine the conductivity of the monolayer. We find that for increasing MUD concentrations up to about 5% the resistivity of the SAM steadily increases, which together with a considerable decrease of the phase of the impedance, demonstrates significantly improved dielectric properties of the monolayer. Such monolayers will find widespread use in applications which depend critically on good dielectric properties such as capacitive biosensor. PMID:24447311

  6. Superlensing properties of one-dimensional dielectric photonic crystals

    NASA Astrophysics Data System (ADS)

    Savo, Salvatore; di Gennaro, Emiliano; Andreone, Antonello

    2009-10-01

    We present the experimental observation of the superlensing effect in a slab of a one-dimensional photonic crystal made of tilted dielectric elements. We show that this flat lens can achieve subwavelength resolution in different frequency bands. We also demonstrate that the introduction of a proper corrugation on the lens surface can dramatically improve both the transmission and the resolution of the imaged signal.

  7. Dielectric, thermal and mechanical properties of ADP doped PVA composites

    NASA Astrophysics Data System (ADS)

    Naik, Jagadish; Bhajantri, R. F.; Ravindrachary, V.; Rathod, Sunil G.; Sheela, T.; Naik, Ishwar

    2015-06-01

    Polymer composites of poly(vinyl alcohol) (PVA), doped with different concentrations of ammonium dihydrogen phosphate (ADP) has been prepared by solution casting. The formation of complexation between ADP and PVA was confirmed with the help of Fourier transforms infrared (FTIR) spectroscopy. Thermogravimetric analysis (TGA) shows thermal stability of the prepared composites. Impedance analyzer study revealed the increase in dielectric constant and loss with increase the ADP concentration and the strain rate of the prepared composites decreases with ADP concentration.

  8. Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties

    NASA Astrophysics Data System (ADS)

    Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

    2016-03-01

    Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased

  9. Internal and interfacial dielectric properties of cytochrome c from molecular dynamics in aqueous solution.

    PubMed Central

    Simonson, T; Perahia, D

    1995-01-01

    The dielectric properties of proteins are central to their stability and activity. We use the Fröhlich-Kirkwood theory of dielectrics to analyze two 1-ns molecular dynamics simulations of ferro- and ferricytochrome c in spherical droplets of 1400 water molecules. Protein and solvent are idealized as a series of concentric, spherical, dielectric media. Analysis results depend strongly on the treatment of the charged protein side chains at the protein/solvent interface. If charged side chains are viewed as part of the protein medium, then the protein dipole fluctuations are dominated by large, mutually uncorrelated, anisotropic, motions of the charged side chains. It is then incorrect to view the protein region as a single, homogeneous dielectric material. If one does take this view, estimates of the protein "dielectric constant" vary from 16 to 37, depending on the exact choice of model parameters. In contrast, if the charged portions of the charged side chains are viewed as part of the solvent medium, then theory and simulation are consistent: the protein dipole fluctuations excluding charged side chains are roughly those of a homogeneous, isotropic dielectric medium, with a dielectric constant of 4.7 +/- 1.0 (ferro) or 3.4 +/- 1.0 (ferri), in agreement with powder experiments. Statistical uncertainty and sensitivity to model parameters are small. Analysis of the radial dependence of the dipole fluctuations suggests that the inner half of the protein has a somewhat lower dielectric constant of 1.5-2, consistent with its biological function in electron transfer. These results suggest that Poisson-Boltzmann models could treat the protein bulk as a low-dielectric medium and the charged surface groups as part of the solvent region. Images Fig. 1 Fig. 3 PMID:7862638

  10. NIR emission studies and dielectric properties of Er3+-doped multicomponent tellurite glasses

    NASA Astrophysics Data System (ADS)

    Sajna, M. S.; Thomas, Sunil; Jayakrishnan, C.; Joseph, Cyriac; Biju, P. R.; Unnikrishnan, N. V.

    2016-05-01

    Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~ 63 nm), stimulated emission cross-section (9.67 × 10- 21 cm2) and lifetime (2.56 ms) of 4I13/2 level for 0.5 mol% of Er3+ makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er3+ ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er3+ -doped glass was confirmed as the optimum composition.

  11. NIR emission studies and dielectric properties of Er(3+)-doped multicomponent tellurite glasses.

    PubMed

    Sajna, M S; Thomas, Sunil; Jayakrishnan, C; Joseph, Cyriac; Biju, P R; Unnikrishnan, N V

    2016-05-15

    Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~63 nm), stimulated emission cross-section (9.67 × 10(-21) cm(2)) and lifetime (2.56 ms) of (4)I13/2 level for 0.5 mol% of Er(3+) makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er(3+) ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er(3+) -doped glass was confirmed as the optimum composition. PMID:26967514

  12. NIR emission studies and dielectric properties of Er(3+)-doped multicomponent tellurite glasses.

    PubMed

    Sajna, M S; Thomas, Sunil; Jayakrishnan, C; Joseph, Cyriac; Biju, P R; Unnikrishnan, N V

    2016-05-15

    Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~63 nm), stimulated emission cross-section (9.67 × 10(-21) cm(2)) and lifetime (2.56 ms) of (4)I13/2 level for 0.5 mol% of Er(3+) makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er(3+) ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er(3+) -doped glass was confirmed as the optimum composition.

  13. Static and dynamic properties of poly(3-hexylthiophene) films at liquid/vacuum interfaces.

    PubMed

    Yimer, Yeneneh Y; Tsige, Mesfin

    2012-11-28

    All-atom molecular dynamics simulations are used to study static and dynamic properties of poly(3-hexylthiophene) (P3HT) films at liquid/vacuum interfaces with regards to their dependence on both temperature and molecular weight. The static properties of the films are characterized by calculating specific volume, interfacial width, orientational ordering of the hexyl groups, and surface tension. The specific volume found to be a monotonically decreasing function of the molecular weight while its dependence on temperature follows the Simha-Somcynsky's equation of state. The orientational ordering calculations show the hexyl groups protruding from the vacuum side of the interface, where the degree of order at the interface is found to be strongly dependent on both temperature and molecular weight. The surface tension values show a linear dependence on temperature and the molecular weight dependence is equally described by both M(-2∕3) and M(-1) power law models. The dynamic properties are quantified by calculating diffusion coefficients for the chain centers-of-mass and thiophene ring segments as well as first-order and second-order end-to-end vector autocorrelations and chain backbone torsion autocorrelation. All calculated dynamic properties show strong dependence on both temperature and molecular weight. All the autocorrelations are well described by Kohlrausch-Williams-Watts equation. Our detailed analysis of the static and dynamic properties of P3HT films show that the calculated static and dynamic properties data can be fit with well-known polymer models.

  14. Microwave dielectric properties of inorganic fullerene-like tungsten disulfide nanoparticles

    NASA Astrophysics Data System (ADS)

    Chang, Hong; Dimitrakis, Georgios; Xu, Fang; Yi, Chenbo; Kingman, Samuel; Zhu, Yanqiu

    2013-01-01

    The dielectric response of inorganic fullerene-like (IF) tungsten disulfide (WS2) nanoparticles prepared by a sulfidization reaction of WO3 nanoparticles has been investigated, against commercial platelet 2H-WS2 particles, using a cavity perturbation technique at microwave frequencies at temperatures ranging from 20 to 750 °C. The IF-WS2 nanoparticles showed both temperature and frequency dependent dielectric properties. The different dielectric behaviour between the IF-WS2 and 2H-WS2 can be attributed to the different conductivity and structure peculiar to the materials. The microstructure and thermal stability of the IF-WS2 and 2H-WS2 were thoroughly examined, to correlate with the resulting dielectric responses.

  15. Electrical and Dielectric Properties of Exfoliated Graphite/Polyimide Composite Films with Low Percolation Threshold

    NASA Astrophysics Data System (ADS)

    Yu, Li; Zhang, Yi-He; Shang, Jiwu; Ke, Shan-Ming; Tong, Wang-shu; Shen, Bo; Huang, Hai-Tao

    2012-09-01

    Exfoliated graphite/polyimide composite films were synthesized by in situ polymerization. The electrical and dielectric properties of composite films with different volume fraction of exfoliated graphite were investigated over the frequency range from 103 Hz to 3 × 106 Hz. The dielectric behavior of the composite films was investigated by percolation theory and a microcapacitor model. A low percolation threshold f c ≈ 3.1 vol.% was obtained due to the high aspect ratio of the exfoliated graphite. Both the dielectric constant and alternating-current (AC) conductivity showed an abrupt increase in the vicinity of the percolation threshold. The ultralarge enhancement of the dielectric constant near and beyond the percolation threshold was due to Maxwell-Wagner-Sillars (MWS) interfacial polarization between the exfoliated graphite and polyimide and interface polarization between the composite film and electrode.

  16. Synthesis and dielectric properties of Zn doped GdFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Sai Vandana, C.; Guravamma, J.; Hemalatha Rudramadevi, B.

    2016-09-01

    GdFeO3 and GdZn0.3Fe0.7O3 ceramics were prepared by standard Solid State Reaction method at 1200°C. The structural changes and crystallite sizes of the undoped and Zn doped ceramics were studied using the XRD data. Microstructural features and elemental composition of GdFeO3 and GdZn0.3Fe0.7O3 ceramics were determined from SEM and EDS analysis. Room temperature dielectric measurements such as dielectric constant (ɛ´), tangent loss (tan5) and AC conductivity (oac) were carried out in the frequency range (100Hz to 1MHz). Improved dielectric properties of GdZn0.3Fe0.7O3 over GdFeO3 ceramics with low values of dielectric loss render them as potential materials in the areas of microwave communication systems, information storage, spintronics, sensors, etc.

  17. Comparison effects and dielectric properties of different dose methylene-blue-doped hydrogels.

    PubMed

    Yalçın, O; Coşkun, R; Okutan, M; Öztürk, M

    2013-08-01

    The dielectric properties of methylene blue (MB)-doped hydrogels were investigated by impedance spectroscopy. The real part (ε') and the imaginary part (ε") of the complex dielectric constant and the energy loss tangent/dissipation factor (tan δ) were measured in the frequency range of 10 Hz to 100 MHz at room temperature for pH 5.5 value. Frequency variations of the resistance, the reactance, and the impedance of the samples have also been investigated. The dielectric permittivity of the MB-doped hydrogels is sensitive to ionic conduction and electrode polarization in low frequency. Furthermore, the dielectric behavior in high-frequency parts was attributed to the Brownian motion of the hydrogen bonds. The ionic conduction for MB-doped samples was prevented for Cole-Cole plots, while the Cole-Cole plots for pure sample show equivalent electrical circuit. The alternative current (ac) conductivity increases with the increasing MB concentration and the frequency.

  18. Dielectric properties of mammalian breast milk at radiofrequencies.

    PubMed

    Laogun, A A

    1986-05-01

    The relative permittivity and AC conductivity of breast milk have been investigated in four different mammalian species, human, cow, goat and sheep, in the frequency range 0.1-100 MHz and at a room temperature of 26.5 +/- 0.5 degrees C. The results showed that the sheep milk exhibited the largest dielectric dispersion, followed in decreasing order by milks from the goat, cow and human. The dielectric data were fitted to the Debye and Cole-Cole structural equations and the fitted parameters have been presented for the different species. The curve-fitting analysis has shown that for all the milk samples the Cole-Cole model gave a better fit to the dielectric data than the Debye model, thus suggesting heterogeneity of structure in milk. On the basis of the Cole-Cole model, the relaxation times in the mammalian milks were found to be distributed about the mean values of 162 +/- 10, 171 +/- 9, 177 +/- 14 and 192 +/- 12 ns for human, cow, goat and sheep milks, respectively.

  19. Microwave Dielectric and Magnetic Properties of Co-Zn Ferrites

    NASA Astrophysics Data System (ADS)

    Lamani, A. R.; Jayanna, H. S.; Naveen, C. S.; Rajeeva, M. P.; Prasanna, G. D.

    2015-02-01

    The dielectric permittivity, loss tangent, in the frequency range 1MHz to 1.8 GHz and hysteresis loop parameters at room temperature were studied on a series of Zn substituted cobalt ferrites with general formula Co1-xZnx Fe2O4 where (x=0.0, 0.2, 0.4, 0.6, 1.0.). The experimental results indicate that the Zn substitution affects all these parameters. The observed dispersion in dielectric permittivity with frequency is in accordance with Maxwell-Wagner model. The high temperature sintering is used to synthesize these materials via solid state reaction route and these samples were characterized by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM). The saturation magnetizations (MS) Hc and Mr of the Particles were measured at room temperature. Here for the smaller dopent concentration Ms increases with increasing in the Zn content this can explained on the basis of increased number of magnetic ions in the spinel lattice, at some point Ms decrease because of the difference between the magnetic moment of Fe2+ and Zn2+, the magnetic moment of the A sub lattice will increases and the moment of the B sub lattice will decrease. The variation of crystalline shape ellipsoid is correlated with variation of dielectric constant.

  20. Molecular motion, dielectric response, and phase transition of charge-transfer crystals: acquired dynamic and dielectric properties of polar molecules in crystals.

    PubMed

    Harada, Jun; Ohtani, Masaki; Takahashi, Yukihiro; Inabe, Tamotsu

    2015-04-01

    Molecules in crystals often suffer from severe limitations on their dynamic processes, especially on those involving large structural changes. Crystalline compounds, therefore, usually fail to realize their potential as dielectric materials even when they have large dipole moments. To enable polar molecules to undergo dynamic processes and to provide their crystals with dielectric properties, weakly bound charge-transfer (CT) complex crystals have been exploited as a molecular architecture where the constituent polar molecules have some freedom of dynamic processes, which contribute to the dielectric properties of the crystals. Several CT crystals of polar tetrabromophthalic anhydride (TBPA) molecules were prepared using TBPA as an electron acceptor and aromatic hydrocarbons, such as coronene and perylene, as electron donors. The crystal structures and dielectric properties of the CT crystals as well as the single-component crystal of TBPA were investigated at various temperatures. Molecular reorientation of TBPA molecules did not occur in the single-component crystal, and the crystal did not show a dielectric response due to orientational polarization. We have found that the CT crystal formation provides a simple and versatile method to develop molecular dielectrics, revealing that the molecular dynamics of the TBPA molecules and the dielectric property of their crystals were greatly changed in CT crystals. The TBPA molecules underwent rapid in-plane reorientations in their CT crystals, which exhibited marked dielectric responses arising from the molecular motion. An order-disorder phase transition was observed for one of the CT crystals, which resulted in an abrupt change in the dielectric constant at the transition temperature.

  1. Mechanical strain dependent electronic and dielectric properties of two-dimensional honeycomb structures of MoX2 (X=S, Se, Te)

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Ahluwalia, P. K.

    2013-06-01

    Mechanical strain induced tunability in two-dimensional (2D) honeycomb structures of MoX2 (X=S, Se, Te) with a focus on dielectric properties have been investigated in the framework of density functional theory. Mechanical strains reduce the band gap of considered semiconductors by causing a direct-to-indirect band gap transitions and finally rendering them into metal at critical value depending on the types of applied strain. The ultimate tensile strength estimated for MoS2, MoSe2 and MoTe2 monolayers is ∼7 GPa, ∼6 GPa and ∼5 GPa respectively. Band-gap deformation potentials have been found to posses strong dependence on the types of applied strain. Small tensile strains increases the exciton binding energies which can have importance in the applications of optoelectronics. Dielectric properties too get influenced by the type of applied strain as well as the type of material. Imaginary part of dielectric function (ɛ2) shows redshift in the structure peak energy on the application of strains with significant dependence on the types of applied strain. Static dielectric constant (ɛs) has been found to increase with the increase of tensile strains (both uniaxial and biaxial) and asymmetric biaxial strain. On the other hand, ɛs decreases for smaller magnitude of compression strains and show increase at higher magnitude. The change in the magnitude of ɛs particularly for compression strains remain material specific.

  2. Linear and nonlinear optical properties of hybrid metallic–dielectric plasmonic nanoantennas

    PubMed Central

    Hentschel, Mario; Metzger, Bernd; Knabe, Bastian

    2016-01-01

    Summary We study the linear and nonlinear optical properties of hybrid metallic–dielectric plasmonic gap nanoantennas. Using a two-step-aligned electron beam lithography process, we demonstrate the ability to selectively and reproducibly fill the gap region of nanoantennas with dielectric nanoparticles made of lithium niobate (LiNbO3) with high efficiency. The linear optical properties of the antennas are modified due to the large refractive index of the material. This leads to a change in the coupling strength as well as an increase of the effective refractive index of the surrounding. The combination of these two effects causes a red- or blue-shift of the plasmonic modes, respectively. We find that the nonlinear optical properties of the combined system are only modified in the range of one order of magnitude. The observed changes in our experiments in the nonlinear emission can be traced to the changed dielectric environment and thus the modified linear optical properties. The intrinsic nonlinearity of the dielectric used is in fact small when compared to the nonlinearity of the metallic part of the hybrid antennas. Thus, the nonlinear signals generated by the antenna itself are dominant in our experiments. We demonstrate that the well-known nonlinear response of bulk dielectric materials cannot always straightforwardly be used to boost the nonlinear response of nanoscale antenna systems. Our results significantly deepen the understanding of these interesting hybrid systems and offer important guidelines for the design of nanoscale, nonlinear light sources. PMID:26925359

  3. Linear and nonlinear optical properties of hybrid metallic-dielectric plasmonic nanoantennas.

    PubMed

    Hentschel, Mario; Metzger, Bernd; Knabe, Bastian; Buse, Karsten; Giessen, Harald

    2016-01-01

    We study the linear and nonlinear optical properties of hybrid metallic-dielectric plasmonic gap nanoantennas. Using a two-step-aligned electron beam lithography process, we demonstrate the ability to selectively and reproducibly fill the gap region of nanoantennas with dielectric nanoparticles made of lithium niobate (LiNbO3) with high efficiency. The linear optical properties of the antennas are modified due to the large refractive index of the material. This leads to a change in the coupling strength as well as an increase of the effective refractive index of the surrounding. The combination of these two effects causes a red- or blue-shift of the plasmonic modes, respectively. We find that the nonlinear optical properties of the combined system are only modified in the range of one order of magnitude. The observed changes in our experiments in the nonlinear emission can be traced to the changed dielectric environment and thus the modified linear optical properties. The intrinsic nonlinearity of the dielectric used is in fact small when compared to the nonlinearity of the metallic part of the hybrid antennas. Thus, the nonlinear signals generated by the antenna itself are dominant in our experiments. We demonstrate that the well-known nonlinear response of bulk dielectric materials cannot always straightforwardly be used to boost the nonlinear response of nanoscale antenna systems. Our results significantly deepen the understanding of these interesting hybrid systems and offer important guidelines for the design of nanoscale, nonlinear light sources. PMID:26925359

  4. A method for in vivo detection of abnormal subepidermal tissues based on dielectric properties.

    PubMed

    Zhang, Liang; Liu, Peiguo; Dong, Xiuzhen; Zhou, Dongming; Shi, Xuetao

    2014-01-01

    In this paper, a convenient and noninvasive scanning imaging method using microwave frequency band for abnormal subepidermal tissues detection is proposed in the aim to improve diagnosis and prognosis in clinical environments. This method is based on the reflective detection technology with coaxial probe that is used to measure the dielectric properties of tissues. An improved equivalent circuit and simulated annealing algorithm (SA) were used in this work to analyze the dielectric properties of tissues. Computational simulations incorporating a simplified model of subcutaneous hemorrhage described in this work were used to evaluate this method. The dielectric properties data of tissues in the model of simulation is derived from the literature. The simulation results demonstrated the potential of this method to detect abnormal subepidermal tissues conveniently and expose them in the image accurately. PMID:25227057

  5. An electrodeless system for measurement of liquid sample dielectric properties in radio frequency band.

    PubMed

    Hartwig, V; Giovannetti, G; Vanello, N; Costantino, M; Landini, L; Benassi, A

    2006-01-01

    An electrodeless measurement system based on a resonant circuit is proposed for the measurement of dielectric properties of liquid samples at RF (radio frequency). Generally, properties as dielectric constant, loss factor and conductivity are measured by parallel plate capacitor cells: this method has several limitations in the case of particular liquid samples and in the range of radiofrequencies. Our method is based on the measurements of resonance frequency and quality factor of a LC resonant circuit in different measuring conditions, without and with the liquid sample placed inside a test tube around which the home made coil is wrapped. The measurement is performed using a network analyzer and a dual loop probe, inductively coupled with the resonant circuit. One of the advantages of this method is the contactless between the liquid sample and the measurement electrodes. In this paper the measurement system is described and test measurements of conventional liquids dielectric properties are reported.

  6. Mechanical and dielectric properties of carbon nanotubes/poly (vinyl alcohol) nanocomposites

    NASA Astrophysics Data System (ADS)

    Amrin, Sayed; Deshpande, V. D.

    2016-05-01

    In this work, two series of nanocomposites of poly(vinyl alcohol) (PVA) incorporated with multiwalled carbon nanotubes (MWNT) and carboxyl functionalized multiwalled carbon nanotubes (MWNT-COOH) were fabricated using solution-cast method and their tensile and dielectric properties were studied. Tensile tests were carried out on composite films of MWNT/PVA and MWNT-COOH/PVA for different loading levels. Results show that overall mechanical properties of the MWNT-COOH/PVA composite was greatly improved as compared to the MWNT/PVA film. The dielectric properties of nanocomposites were investigated in a frequency range from 0.1Hz to 10MHz at room temperature respectively. Compared to MWNT/PVA composites, higher dielectric constant and ac conductivity was achieved in MWNT-COOH/PVA nanocomposite, which can be well explained by the interfacial polarization effect.

  7. Dielectric properties and electrical conductivity of flat micronic graphite/polyurethane composites

    NASA Astrophysics Data System (ADS)

    Plyushch, Artyom; Macutkevic, Jan; Kuzhir, Polina P.; Banys, Juras; Fierro, Vanessa; Celzard, Alain

    2016-03-01

    Results of broadband dielectric spectroscopy of flat micronic graphite (FMG)/polyurethane (PU) resin composites are presented in a wide temperature range (25-450 K). The electrical percolation threshold was found to lie between 1 and 2 vol. % of FMG. Above the percolation threshold, the composites demonstrated a huge hysteresis of properties on heating and cooling from room temperature up to 450 K, along with extremely high values of dielectric permittivity and electrical conductivity. Annealing proved to be a very simple but powerful tool for significantly improving the electrical properties of FMG-based composites. In order to explain this effect, the distributions of relaxation times were calculated by the complex impedance formalism. Below room temperature, both dielectric permittivity and electrical conductivity exhibited a very low temperature dependence, mainly caused by the different thermal properties of FMG and pure PU matrix.

  8. Measurement of dielectric properties and determination of microwave emissivity of polluted waters

    NASA Technical Reports Server (NTRS)

    Blume, H.-J. C.

    1980-01-01

    The dielectric properties of polluted waters are measured with a reflection-type resonant cavity at 1.43 GHz. Very small water samples in quartz tubes of known volume are placed in the center of the maximum electric field. Measurement of the resonance-frequency variation and a change of the cavity's quality factor are used to determine the dielectric properties. The microwave emissivity of the polluted water is then calculated via the Fresnel equation and applied to data reductions of microwave radiometer measurements.

  9. Dielectric and Ferroelectric Properties of Lead Lanthanum Zirconate Titanate Thin Films for Capacitive Energy Storage

    NASA Astrophysics Data System (ADS)

    Tong, Sheng

    As the increasing requirement of alternative energy with less pollution influence and higher energy efficient, new energy source and related storage methods are hot topic nowadays. Capacitors that supply high instant power are one of the keys in this application for both economic and functional design aspects. To lower the cost and increases the volumetric efficiency and reliability, relaxor thin films are considered as one of the candidates of the next generation capacitors. The research mainly focuses on dielectric and ferroelectric properties of lead lanthanum zirconate titanate or Pb1-xLax(ZryTi1-y)O3 (PLZT, x/y/1-y) relaxor thin films deposited on silicon (Si) and nickel (Ni) substrates in a range of thickness with different bottom electrodes, e.g. Platinum (Pt) and LaNiO3 (LNO). The final fabricated PLZT film capacitors will show strong potential for the energy storage application. The method adopted is the acetic acid assisted sol-gel deposition for the PLZT thin films. The wet chemical process is cost-effective and easily to scale up for plant/industrial products. We investigated the different bottom electrode/substrate influence in structure, microstructure, phases/defects, and heat-treatment conditions to achieve the optimized PLZT thin films. Issues of basic physical size effects in the PLZT thin films were also investigated, including thickness effects in the dielectric and ferroelectric properties of the films in a wide range of temperatures, the phase transition of the thin-film relaxors, lanthanum content effect, electrode-dielectric junction, misfit strain effect, etc. Based on the results and analysis, optimum PLZT film capacitors can be determined of proper substrate/electrode/dielectric that achieves the desired dielectric properties required for different applications, especially a more cost-effective method to develop volumetrically efficient capacitors with high charge density, energy density, dielectric breakdown strength, energy storage

  10. Dielectric properties and emissivity of seawater at C-band microwave frequency.

    PubMed

    Murugkar, A G; Joshi, A S; Kurtadikar, M L

    2012-10-01

    Microwave remote sensing applications over ocean using radar and radiometers, a precise knowledge of emissivity and reflectivity, are required. Emissivity of ocean surface is a function of the surface configuration, frequency of radiation, temperature and its dielectric properties. The emissivity of a smooth ocean surface at a particular wavelength is determined by its complex dielectric properties. In present study, laboratory measurements of complex dielectric properties, real part epsilon', and imaginary part epsilon", of surface seawater samples collected from Bay of Bengal and Arabian Sea are carried out. Measurements of these seawater samples are done at 5 GHz and 30 degrees C using an automated C-band microwave bench set up. The salinity of samples is also measured using autosalinometer. The salinity values are used to determine epsilon' and epsilon" using the Debye equations. The normal incidence emissivity and brightness temperature values for smooth sea surface are reported for surface samples. The dielectric constant epsilon' decreases and dielectric loss increases with increase in salinity at 5 GHz and 30 degrees C. At normal incidence, emissivity is almost constant for varying salinities.

  11. Tailoring Dielectric Properties and Energy Density of Ferroelectric Polymer Nanocomposites by High-k Nanowires.

    PubMed

    Wang, Guanyao; Huang, Xingyi; Jiang, Pingkai

    2015-08-19

    High dielectric constant (k) polymer nanocomposites have shown great potential in dielectric and energy storage applications in the past few decades. The introduction of high-k nanomaterials into ferroelectric polymers has proven to be a promising strategy for the fabrication of high-k nanocomposites. One-dimensional large-aspect-ratio nanowires exhibit superiority in enhancing k values and energy density of polymer nanocomposites in comparison to their spherical counterparts. However, the impact of their intrinsic properties on the dielectric properties of polymer nanocomposites has been seldom investigated. Herein, four kinds of nanowires (Na2Ti3O7, TiO2, BaTiO3, and SrTiO3) with different inherent characteristics are elaborately selected to fabricate high-k ferroelectric polymer nanocomposites. Dopamine functionalization facilitates the excellent dispersion of these nanowires in the ferroelectric polymer matrix because of the strong polymer/nanowire interfacial adhesion. A thorough comparative study on the dielectric properties and energy storage capability of the nanowires-based nanocomposites has been presented. The results reveal that, among the four types of nanowires, BaTiO3 NWs show the best potential in improving the energy storage capability of the proposed nanocomposites, resulting from the most signficant increase of k while retaining the rather low dielectric loss and leakage current.

  12. Ferroelectric films of deuterated glycine phosphite: Structure and dielectric properties

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Svinarev, F. B.; Lemanov, V. V.

    2013-05-01

    Polycrystalline textured films of deuterated glycine phosphite consisting of single-crystal blocks with lateral dimensions ˜(50-100) μm and a thickness d ˜ (1-5) μm have been grown by evaporation on NdGaO3(100) and α-Al2O3 substrates with preliminarily deposited interdigitated electrodes, as well as on Al substrates. The c* ( Z) crystallographic axis in the blocks is normal to the film plane, and the a ( X) axis and the polar axis b ( Y) are oriented in the film plane. The temperature dependences of the capacitance of the structures measured with the interdigitated electrode system reveal a strong dielectric anomaly at the film transition to the ferroelectric state. The phase transition temperature T c depends on the degree of deuteration D of the glycine phosphite. The maximum value T c = 275 K obtained in the structures studied corresponds to a degree of deuteration of the glycine phosphite D ˜ 50%. The frequency behavior of the dielectric hysteresis loops in glycine phosphite films differs radically from that of the previously studied films of deuterated betaine phosphite, which evidences that polarization switching in these structures proceeds by different mechanisms. It has been that application of a dc bias to the electrodes changes the shape of the dielectric hysteresis loops and shifts them along the electric field axis. The shift of the loops depends on the sign, magnitude, and time of application of the bias. Possible mechanisms underlying the induced unipolarity are discussed.

  13. Dielectric properties of Asteroid Vesta's surface as constrained by Dawn VIR observations

    NASA Astrophysics Data System (ADS)

    Palmer, Elizabeth M.; Heggy, Essam; Capria, Maria T.; Tosi, Federico

    2015-12-01

    Earth and orbital-based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, one can constrain their surface textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith-employing an analogy to the dielectric properties of lunar soil, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the real part of the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.3 to 2.5 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diurnal temperature, ranging from 6 × 10-3 to 8 × 10-3. We estimate the surface porosity to be ∼55% in the upper meter of the regolith, as derived from VIR observations. This is ∼12% higher than previous estimation of porosity derived from previous Earth-based X- and S-band radar observation. We suggest that the radar backscattering properties of asteroid Vesta will be mainly driven by the changes in surface roughness rather than potential dielectric variations in the upper regolith in the X- and S-band.

  14. Dielectric properties of pharmaceutical materials relevant to microwave processing: effects of field frequency, material density, and moisture content.

    PubMed

    Heng, Paul W S; Loh, Z H; Liew, Celine V; Lee, C C

    2010-02-01

    The rising popularity of microwaves for drying, material processing and quality sensing has fuelled the need for knowledge concerning dielectric properties of common pharmaceutical materials. This article represents one of the few reports on the density and moisture content dependence of the dielectric properties of primary pharmaceutical materials and their relevance to microwave-assisted processing. Dielectric constants (epsilon') and losses (epsilon'') of 13 pharmaceutical materials were measured over a frequency range of 1 MHz-1 GHz at 23 +/- 1 degrees C using a parallel-electrode measurement system. Effects of field frequency, material density and moisture content on dielectric properties were studied. Material dielectric properties varied considerably with frequency. At microwave frequencies, linear relationships were established between cube-root functions of the dielectric parameters [symbols: see text] and density which enabled dielectric properties of materials at various densities to be estimated by regression. Moisture content was the main factor that contributed to the disparities in dielectric properties and heating capabilities of the materials in a laboratory microwave oven. The effectiveness of a single frequency density-independent dielectric function for moisture sensing applications was explored and found to be suitable within low ranges of moisture contents for a model material.

  15. Impact of apoptosis on the on-line measured dielectric properties of CHO cells.

    PubMed

    Zalai, Dénes; Tobak, Teodóra; Putics, Ákos

    2015-12-01

    Apoptosis is a common type of cell death in biopharmaceutical cell culture processes which causes decrease in viable cell density and product yield. The progression of apoptosis has been reported to influence the dielectric properties of mammalian cells; however, the on-line detection of these effects has been rarely described. This study provides a comprehensive analysis of the on-line detectability of dielectric changes upon apoptosis induction in an industrial fed-batch process of CHO cells expressing a recombinant monoclonal antibody. Using capacitance signals, measured at 25 frequencies, the impact of apoptosis on the dielectric spectra was investigated in eight bioreactor cultivations in which various process conditions were combined with two different apoptosis induction strategies (camptothecin treatment and glucose starvation). To differentiate the apoptosis-related information from the cell concentration-associated variance in the multivariate capacitance datasets, principal component analysis (PCA) was used. A second principal component, explaining an explicit proportion (>20%) of the variance, was identified to be related to dielectric changes induced by apoptosis. Furthermore, the analysis of caspase-3 and -7 activation and DNA fragmentation showed that the detected dielectric change occurred in the early phase of apoptosis. The presented results verify that apoptosis has a considerable impact on the dielectric features of CHO cells and it can be monitored on-line with the introduced tool-set combining capacitance measurement with multivariate data analysis. PMID:26440966

  16. Impact of apoptosis on the on-line measured dielectric properties of CHO cells.

    PubMed

    Zalai, Dénes; Tobak, Teodóra; Putics, Ákos

    2015-12-01

    Apoptosis is a common type of cell death in biopharmaceutical cell culture processes which causes decrease in viable cell density and product yield. The progression of apoptosis has been reported to influence the dielectric properties of mammalian cells; however, the on-line detection of these effects has been rarely described. This study provides a comprehensive analysis of the on-line detectability of dielectric changes upon apoptosis induction in an industrial fed-batch process of CHO cells expressing a recombinant monoclonal antibody. Using capacitance signals, measured at 25 frequencies, the impact of apoptosis on the dielectric spectra was investigated in eight bioreactor cultivations in which various process conditions were combined with two different apoptosis induction strategies (camptothecin treatment and glucose starvation). To differentiate the apoptosis-related information from the cell concentration-associated variance in the multivariate capacitance datasets, principal component analysis (PCA) was used. A second principal component, explaining an explicit proportion (>20%) of the variance, was identified to be related to dielectric changes induced by apoptosis. Furthermore, the analysis of caspase-3 and -7 activation and DNA fragmentation showed that the detected dielectric change occurred in the early phase of apoptosis. The presented results verify that apoptosis has a considerable impact on the dielectric features of CHO cells and it can be monitored on-line with the introduced tool-set combining capacitance measurement with multivariate data analysis.

  17. Dielectric spectroscopy at the nanoscale by atomic force microscopy: A simple model linking materials properties and experimental response

    SciTech Connect

    Miccio, Luis A. Colmenero, Juan; Kummali, Mohammed M.; Alegría, Ángel; Schwartz, Gustavo A.

    2014-05-14

    The use of an atomic force microscope for studying molecular dynamics through dielectric spectroscopy with spatial resolution in the nanometer scale is a recently developed approach. However, difficulties in the quantitative connection of the obtained data and the material dielectric properties, namely, frequency dependent dielectric permittivity, have limited its application. In this work, we develop a simple electrical model based on physically meaningful parameters to connect the atomic force microscopy (AFM) based dielectric spectroscopy experimental results with the material dielectric properties. We have tested the accuracy of the model and analyzed the relevance of the forces arising from the electrical interaction with the AFM probe cantilever. In this way, by using this model, it is now possible to obtain quantitative information of the local dielectric material properties in a broad frequency range. Furthermore, it is also possible to determine the experimental setup providing the best sensitivity in the detected signal.

  18. Dielectric properties of glassy disaccharides for electromagnetic interference shielding application

    NASA Astrophysics Data System (ADS)

    Wlodarczyk, P.; Hawelek, L.; Paluch, M.; Wlodarczyk, A.; Wojnarowska, Z.; Kolano-Burian, A.

    2015-11-01

    Three amorphous disaccharides (sucrose, trehalose, and lactulose) and their mixtures were studied in order to evaluate their ability to absorb a high frequency (>1 MHz) electromagnetic wave. The materials were characterized by a dielectric loss tangent. It was found out that the highest tan(δ) value is observed in pure amorphous sucrose (tan(δ) = 0.17 at f = 1 MHz at T = 293 K). Moreover, the best Tg/tan(δ) ratio is observed in binary mixtures of sucrose and trehalose. A high glass transition temperature is advantageous as it increases operational temperatures of the material. The high tangent delta in microwave frequencies of sugars is connected with the mobility of sugar groups (possibly -CH2OH). The energy of the electromagnetic wave is converted into rotational movements of side groups and in consequence it is dissipated in the form of heat. It was proven that the polar low molecular glasses such as sugars may form dielectric components of composite microwave absorbers.

  19. AC Conductivity and Dielectric Properties of Borotellurite Glass

    NASA Astrophysics Data System (ADS)

    Taha, T. A.; Azab, A. A.

    2016-10-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  20. AC Conductivity and Dielectric Properties of Borotellurite Glass

    NASA Astrophysics Data System (ADS)

    Taha, T. A.; Azab, A. A.

    2016-06-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF-xTeO2 (x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density (ρ) was determined by the Archimedes method at room temperature. The density (ρ) and molar volume (V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity (σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  1. Optical properties of silica fibers and layered dielectric mirrors

    SciTech Connect

    Cooke, D.W.; Farnum, E.H.; Clinard, F.W. Jr.; Bennett, B.L.; Portis, A.M.

    1996-04-01

    Radioluminescence (RL) from virgin and neutron-irradiated (10{sup 23} n-m{sup -2}) silica fibers has been measured in the temperature interval 4 to 300 K. Unirradiated specimens exhibit a decrease in RL intensity with increasing temperature such that the intensity is extremely weak at room temperature. The luminescence is well described by a barrier-limited exciton mechanism. in contrast, the heavily-irradiated samples show an increase in RL with elevated temperatures such that the intensity at room temperature is about twice that measured at 4 K. Neutron irradiation presumably produces many luminescence centers that act as radiative sites for exciton decay. Absolute specular reflectance of a series of neutron irradiated, layered dielectric mirrors was also measured. In addition to structural damage that has already been reported, we typically found approximately 10% reduction in the reflectance following irradiation. These results suggest that neither fibers nor dielectric mirrors are well suited for use near the high radiation area of the ITER plasma.

  2. Magnetic, dielectric and sensing properties of manganese substituted copper ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, E. Ranjith; Jayaprakash, R.; Devi, G. Sarala; Reddy, P. Siva Prasada

    2014-04-01

    Manganese substituted copper ferrite nanoparticles were synthesized by an auto-combustion technique using metal nitrates and urea for gas sensor application. The products were characterized by XRD, SEM, EDX, TEM and VSM techniques. The effect of annealing temperature on the particle size, magnetic and dielectric properties of Mn-Cu ferrite nanoparticles was analyzed. The size of the particles are in the range of ~9-45 nm. The effect of annealing on the magnetic properties is discussed with the help of variation in saturation magnetization (Ms) and coercivity (Hc) by vibrating sample magnetometer (VSM). The dielectric loss and dielectric constant have been measured in the frequency range of 100 kHz-5 MHz. Furthermore, Conductance response of Mn-Cu ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG).

  3. Dielectric properties of barium zirconate titanate (BZT) ceramics tailored by different donors for high voltage applications

    NASA Astrophysics Data System (ADS)

    Qi, Jian Quan; Liu, Bai Bo; Tian, Hu Yong; Zou, Han; Yue, Zhen Xing; Li, Long Tu

    2012-10-01

    The dielectric properties of BZT ceramics with different Zr contents and donor types are studied. It is shown that the large enhancement of the dielectric permittivity is achieved accompanying with the remarkable shift of Curie temperature in the samples doped with donors such as La, Nd, Sm, Eu, Dy, and Yb, whereas the results are different in them doped with other type of donors such as Ce and Y. The shift of Curie temperature is related to the ionic radii of the doped donors. A smaller ion results in a greater shift. The dielectric properties of BZT with different doping levels of Yb are also studied and showed that there is a preferable doping content as Yb ˜0.1% to make the material with the highest permittivity, ɛ ˜25,800, withstand voltage >˜3.5 kV/mm.

  4. Dielectric properties of residual water in amorphous lyophilized mixtures of sugar and drug

    NASA Astrophysics Data System (ADS)

    El Moznine, R.; Smith, G.; Polygalov, E.; Suherman, P. M.; Broadhead, J.

    2003-02-01

    Dielectric relaxation spectroscopy was used to investigate the properties of residual water in lyophilized formulations of a proprietary tri-phosphate drug containing a sugar (trehalose, lactose or sucrose) or dextran. The dielectric properties of each formulation were determined in the frequency range (0.1 Hz-0.1 MHz) and temperature range (30°C-Tg). The temperature dependence of the relaxation times for all samples showed Arrhenuis behaviour, from which the activation energy was derived. Proton hopping through the hydrogen-bonded network (clusters) of water molecules was suggested as the principle mode of charge transport. Significant differences in dielectric relaxation kinetics and activation energy were observed for the different formulations, which were found to correlate with the amount of monophosphate degradation product.

  5. Studies of dielectric properties of mammalian tissues after gamma-irradiation

    NASA Astrophysics Data System (ADS)

    Abd El-Salaam, S.; Sallam, S.; Talaat, M. S.

    1996-12-01

    In vitro dielectric measurements (relative permeability and conductivity) of excised liver, kidney, cardiac muscle, spleen and eye of rabbits, were carried out at frequencies of 1-250 kHz and at room temperature. These were done before, immediately and 7 days after gamma irradiation at doses 1-5 Gy. The obtained results indicated significant increase in both relative permitivity and conductivity of tissues at higher doses immediately after irradiation. After 7 days, the changes showed some recovery, more obvious at lower doses. These changes in dielectric properties, after irradiation, may reflect the particular biological organization of each tissue and some mechanisms of radiation damage to these tissues particular to cell membrane, counter-ion polarization associated with intrinsic membrane charges and conductive transport in extracellular medium. This may help to elucidate the mechanisms of variation of dielectric properties of different tissues under the effect of radiation.

  6. Effects of Large Nuclear Quadrupoles on Dielectric Properties of Glasses at Very Low Temperatures

    NASA Astrophysics Data System (ADS)

    Luck, A.; Fleischmann, A.; Reiser, A.; Enss, C.

    2014-12-01

    The universal behaviour of amorphous solids at low temperatures, governed by atomic tunneling systems as described by the standard tunneling model, has long been a generally accepted fact. In the last years, however, measurements of dielectric two-pulse polarization echoes have revealed that nuclear quadrupole moments involved in atomic tunneling systems can cause specific material-dependent effects in magnetic fields. We have performed measurements of the dielectric properties of the two multicomponent glasses N-KZFS11 and HY-1, containing several percent of tantalum oxide and holmium oxide respectively. As 181Ta and 165Ho both carry very large nuclear quadrupole moments, these glasses are ideal candidates to study the influence of nuclear quadrupole moments on the properties of glasses at very low temperatures. Our measurements not only show unique dielectric behaviour in both glasses, but also differ significantly from various predictions of the standard tunneling model.

  7. Morphology, Structural and Dielectric Properties of Vacuum Evaporated V2O5 Thin Films

    NASA Astrophysics Data System (ADS)

    Sengodan, R.; Shekar, B. Chandar; Sathish, S.

    Vanadium pentoxide (V2O5) thin films were deposited on well cleaned glass substrate using evaporation technique under the pressure of 10-5 Torr. The thickness of the films was measured by the multiple beam interferometry technique and cross checked by using capacitance method. Metal-Insulator-Metal (MIM) structure was fabricated by using suitable masks to study dielectric properties. The dielectric properties were studied by employing LCR meter in the frequency range 12 Hz to 100 kHz for various temperatures. The temperature co- efficient of permittivity (TCP), temperature co-efficient of capacitance (TCC) and dielectric constant (ɛ) were calculated. The activation energy was calculated and found to be very low. The activation energy was found to be increasing with increase in frequency. The obtained low value of activation energy suggested that the hopping conduction may be due to electrons rather than ions.

  8. Tailoring Dielectric and Actuated Properties of Elastomer Composites by Bioinspired Poly(dopamine) Encapsulated Graphene Oxide.

    PubMed

    Ning, Nanying; Ma, Qin; Liu, Suting; Tian, Ming; Zhang, Liqun; Nishi, Toshio

    2015-05-27

    In this study, we obtained dielectric elastomer composites with controllable dielectric and actuated properties by using a biomimetic method. We used dopamine (DA) to simultaneously coat the graphene oxide (GO) and partially reduce GO by self-polymerization of DA on GO. The poly(dopamine) (PDA) coated GO (GO-PDA) was assembled around rubber latex particles by hydrogen bonding interaction between carboxyl groups of carboxylated nitrile rubber (XNBR) and imino groups or phenolic hydroxyl groups of GO-PDA during latex compounding, forming a segregated GO-PDA network at a low percolation threshold. The results showed that the introduction of PDA on GO prevented the restack of GO in the matrix. The dielectric and actuated properties of the composites depend on the thickness of PDA shell. The dielectric loss and the elastic modulus decrease, and the breakdown strength increases with increasing the thickness of PDA shell. The maximum actuated strain increases from 1.7% for GO/XNBR composite to 4.4% for GO-PDA/XNBR composites with the PDA thickness of about 5.4 nm. The actuated strain at a low electric field (2 kV/mm) obviously increases from 0.2% for pure XNBR to 2.3% for GO-PDA/XNBR composite with the PDA thickness of 1.1 nm, much higher than that of other DEs reported in previous studies. Thus, we successfully obtained dielectric composites with low dielectric loss and improved breakdown strength and actuated strain at a low electric field, facilitating the wide application of dielectric elastomers. PMID:25938262

  9. Tailoring Dielectric and Actuated Properties of Elastomer Composites by Bioinspired Poly(dopamine) Encapsulated Graphene Oxide.

    PubMed

    Ning, Nanying; Ma, Qin; Liu, Suting; Tian, Ming; Zhang, Liqun; Nishi, Toshio

    2015-05-27

    In this study, we obtained dielectric elastomer composites with controllable dielectric and actuated properties by using a biomimetic method. We used dopamine (DA) to simultaneously coat the graphene oxide (GO) and partially reduce GO by self-polymerization of DA on GO. The poly(dopamine) (PDA) coated GO (GO-PDA) was assembled around rubber latex particles by hydrogen bonding interaction between carboxyl groups of carboxylated nitrile rubber (XNBR) and imino groups or phenolic hydroxyl groups of GO-PDA during latex compounding, forming a segregated GO-PDA network at a low percolation threshold. The results showed that the introduction of PDA on GO prevented the restack of GO in the matrix. The dielectric and actuated properties of the composites depend on the thickness of PDA shell. The dielectric loss and the elastic modulus decrease, and the breakdown strength increases with increasing the thickness of PDA shell. The maximum actuated strain increases from 1.7% for GO/XNBR composite to 4.4% for GO-PDA/XNBR composites with the PDA thickness of about 5.4 nm. The actuated strain at a low electric field (2 kV/mm) obviously increases from 0.2% for pure XNBR to 2.3% for GO-PDA/XNBR composite with the PDA thickness of 1.1 nm, much higher than that of other DEs reported in previous studies. Thus, we successfully obtained dielectric composites with low dielectric loss and improved breakdown strength and actuated strain at a low electric field, facilitating the wide application of dielectric elastomers.

  10. 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.

  11. Static and dynamic elastic properties of rocks from the Canadian Shield

    SciTech Connect

    King, M.S.

    1983-01-01

    As part of a number of research studies in the Canadian Shield associated with the stability of underground mine openings, seismic reflection surveys, and the proposed use of a tunnel-boring machine (TBM) for developing mine headings, a long-term laboratory rock mechanics program has been conducted to determine the static and dynamic elastic properties of samples of igneous and metamorphic rocks from the Canadian Shield. This paper reports the results of 174 measurements of static elastic modulus and 152 measurements of uniaxial compressive strength for these rocks as a function of dynamic elastic modulus. 20 references, 5 figures.

  12. Strain tunable ferroelectric and dielectric properties of BaZrO{sub 3}

    SciTech Connect

    Zhang, Yajun; Liu, Man; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

    2014-06-14

    The crucial role of epitaxial (in-plane) strain on the structural, electronic, energetic, ferroelectric, and dielectric properties of BaZrO{sub 3} (BZO) is investigated using density-functional theory calculations. We demonstrate that the BZO crystal subjected to a critical compressive (or tensile) strain exhibits non-trivial spontaneous polarization that is higher than that of well-known ferroelectrics BaTiO{sub 3}, while the BZO crystal is essentially paraelectric in the absence of strain. The electronic structure and Born-effective-charge analyses elucidate that the strain-induced paraelectric-to-ferroelectric transition is driven by the orbital hybridization of d-p electrons between zirconium and oxygen. Through the strain-induced paraelectric-to-ferroelectric phase transition, the dielectric response of BZO is significantly enhanced by the in-plane strain. The tensile strain increases the in-plane dielectric constant by a factor of seven with respect to that without the strain, while the compression tends to enhance the out-of-plane dielectric response. Therefore, strain engineering makes BZO an important electromechanical material due to the diversity in ferroelectric and dielectric properties.

  13. Effect of argon ion implantation on the electrical and dielectric properties of CR-39

    NASA Astrophysics Data System (ADS)

    Chawla, Mahak; Shekhawat, Nidhi; Goyal, Meetika; Gupta, Divya; Sharma, Annu; Aggarwal, Sanjeev

    2016-05-01

    The objective of the present work is to study the effect of 130 keV Ar+ ions on the electrical and dielectric properties of CR-39 samples at various doses 5×1014, 1×1015 and 1×1016 Ar+ cm-2. Current-Voltage (I-V characteristics) measurements have been used to study the electrical properties of virgin and Ar+ implanted CR-39 specimens. The current has been found to be increased with increasing voltage as well as with increasing ion dose. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. The dielectric constant has been found to be decreasing whereas dielectric loss factor increases with increasing ion fluence. These kind of behavior observed in the implanted specimens indicate towards the formation of carbonaceous clusters due to the cross linking, chemical bond cleavage, formation of free radicals. The changes observed in the dielectric behavior have been further correlated with the structural changes observed through I-V characteristics.

  14. A Comprehensive Study on Dielectric Properties of Volcanic Rock/PANI Composites

    NASA Astrophysics Data System (ADS)

    Kiliç, M.; Karabul, Y.; Okutan, M.; İçelli, O.

    2016-05-01

    Basalt is a very well-known volcanic rock that is dark colored and relatively rich in iron and magnesium, almost located each country in the world. These rocks have been used in the refused rock industry, to produce building tiles, construction industrial, highway engineering. Powders and fibers of basalt rocks are widely used of radiation shielding, thermal stability, heat and sound insulation. This study examined three different basalt samples (coded CM-1, KYZ-13 and KYZ-24) collected from different regions of Van province in Turkey. Polyaniline (PANI) is one of the representative conductive polymers due to its fine environmental stability, huge electrical conductivity, as well as a comparatively low cost. Also, the electrical and thermal properties of polymer composites containing PANI have been widely studied. The dielectric properties of Basalt/Polyaniline composites in different concentrations (10, 25, 50 wt.% PANI) have been investigated by dielectric spectroscopy method at the room temperature. The dielectric parameters (dielectric constants, loss and strength) were measured in the frequency range of 102 Hz-106 Hz at room temperature. The electrical mechanism change with PANI dopant. A detailed dielectrically analysis of these composites will be presented.

  15. Piezoelectric and dielectric properties of nanoporous polyvinylidence fluoride (PVDF) films

    NASA Astrophysics Data System (ADS)

    Zhao, Ping; Wang, Shifa; Kadlec, Alec

    2016-04-01

    A nanoporous polyvinylidene Fluoride (PVDF) thin film was developed for applications in energy harvesting, medical surgeries, and industrial robotics. This sponge-like nanoporous PVDF structure dramatically enhanced the piezoelectric effect because it yielded considerably large deformation under a small force. A casting-etching method was adopted to make films, which is effective to control the porosity, flexibility, and thickness of the film. The films with various Zinc Oxide (ZnO) mass fractions ranging from 10 to 50% were fabricated to investigate the porosity effect. The piezoelectric coefficient d33 as well as dielectric constant and loss of the films were characterized. The results were analyzed and the optimal design of the film with the right amount of ZnO nanoparticles was determined.

  16. Dielectric properties of concrete at S and X bands: a near-field investigation

    NASA Astrophysics Data System (ADS)

    Bois, Karl J.; Benally, Aaron D.; Nowak, Paul S.; Zoughi, Reza

    1999-10-01

    When inspecting concrete structures with microwaves (radars, embedded microwave sensors, modulated scattering techniques, etc.) the dielectric properties of the concrete are considered as a ground truth data and must be known. During the past three years, extensive microwave near-field measurements of the reflection properties of concrete specimens with varying water-to-cement (w/c) ratios, sand-to-cement (s/c) ratios and coarse aggregate-to-cement (ca/c) ratios have been conducted. These experiments were conducted using open-ended rectangular waveguide probes radiating into a half-space of these concrete specimens. These measurements were conducted at S- (2.6 - 3.95 GHz) and X-bands (8.2 - 12.4 GHz). Moreover, an electromagnetic model, which took into account the presence of higher-order modes at the waveguide aperture, was also used to model this process. Finally, a root finding technique was applied to calculate the effective dielectric properties of the concrete specimens. This paper presents the results of these measurements and calculations as they related to determining the dielectric properties of concrete. Since concrete is a heterogeneous material, the results from many locations in a specimen are reported rendering effective dielectric properties showing the mean and standard deviation of the measurements and calculations at these frequency bands. The results of the dielectric constant can also be used to predict the reflection properties of concrete when using a standoff distance (i.e. non-contact measurements) or when using other types of microwave sensors.

  17. Frequency, temperature, density and moisture dependence of dielectric properties of unshelled and shelled peanuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of unshelled and shelled peanuts were measured with a free-space-transmission technique between 2 and 18 GHz over wide ranges of bulk density, moisture content, and temperature. For better accuracy a pair of horn/lens antennas providing a focused beam was used; the sample was p...

  18. Coaxial-probe contact-force monitoring for dielectric properties measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A means is described for measuring and monitoring the contact force applied to a material sample with an open-ended coaxial-line probe for purposes of measuring the dielectric properties of semisolid material samples such as fruit, vegetable and animal tissues. The equipment consists of a stainless...

  19. Study made of dielectric properties of promising materials for cryogenic capacitors

    NASA Technical Reports Server (NTRS)

    Mathes, K. N.; Minnich, S. H.

    1967-01-01

    Experimental investigations were conducted to determine dielectric properties of promising materials for cryogenic capacitors to be used in energy storage and pulse applications. The three classes of materials investigated were inorganic bonded ferroelectric materials, anodic coatings on metal foils, and polar low temperature liquids.

  20. Anisotropic dielectric properties of two-dimensional matrix in pseudo-spin ferroelectric system

    NASA Astrophysics Data System (ADS)

    Kim, Se-Hun

    2016-10-01

    The anisotropic dielectric properties of a two-dimensional (2D) ferroelectric system were studied using the statistical calculation of the pseudo-spin Ising Hamiltonian model. It is necessary to delay the time for measurements of the observable and the independence of the new spin configuration under Monte Carlo sampling, in which the thermal equilibrium state depends on the temperature and size of the system. The autocorrelation time constants of the normalized relaxation function were determined by taking temperature and 2D lattice size into account. We discuss the dielectric constants of a two-dimensional ferroelectric system by using the Metropolis method in view of the Slater-Takagi defect energies.

  1. Investigations of structural, dielectric and optical properties on silicon ion irradiated glycine monophosphate single crystals

    NASA Astrophysics Data System (ADS)

    Kanagasekaran, T.; Mythili, P.; Bhagavannarayana, G.; Kanjilal, D.; Gopalakrishnan, R.

    2009-08-01

    The 50 MeV silicon ion irradiation induced modifications on structural, optical and dielectric properties of solution grown glycine monophosphate (GMP) crystals were studied. The high-resolution X-ray diffraction study shows the unaltered value of integrated intensity on irradiation. The dielectric constant as a function of frequency and temperature was studied. UV-visible studies reveal the decrease in bandgap values on irradiation and presence of F-centers. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The scanning electron micrographs reveal the defects formed on irradiation.

  2. Dielectric properties of doping-free NaMn{sub 7}O{sub 12}: Origin of the observed colossal dielectric constant

    SciTech Connect

    Cabassi, R.; Bolzoni, F.; Gauzzi, A.; Gilioli, E.; Prodi, A.; Licci, F.

    2006-07-15

    The semiconducting NaMn{sub 7}O{sub 12} is a doping-free compound with several coexistent properties such as orbital ordering, charge ordering, and magnetic orderings of different types. We investigated its dielectric response by means of frequency impedance measurements in the range from 20 Hz to 1 MHz. Standard measurements on metallized samples exhibit an apparent colossal dielectric constant (CDC) with an {epsilon}{sub R} value of several thousands at low frequencies, but a careful equivalent circuit analysis allows one to ascribe the observed CDC to the effect of a depletion layer on the metal-semiconductor junctions. We bypass this effect by means of a nonstandard technique employing mica linings: the resulting dielectric behavior exhibits the presence of the charge ordering transition at T{sub CO}=176 K and shows a net bulk dielectric constant value {epsilon}{sub R}{approx_equal}68 at room temperature.

  3. Dielectric, piezoelectric and damping properties of novel 2-2 piezoelectric composites

    NASA Astrophysics Data System (ADS)

    Dongyu, Xu; Xin, Cheng; Banerjee, Sourav; Lei, Wang; Shifeng, Huang

    2015-02-01

    Here, a strip-shaped 2-2 cement/polymer-based piezoelectric composite was designed and fabricated. The dielectric, piezoelectric and electromechanical coupling properties of the composite were investigated as well as the coupling effects between the thickness and lateral modes of the piezoelectric composites. The dielectric and piezoelectric properties of the composites can be greatly influenced by variations of the piezoelectric ceramic volume fraction and the structural dimensions of the composites. Excellent properties have been achieved for ultrasonic transducer applications in civil engineering monitoring fields, such as large piezoelectric voltage constants, high thickness electromechanical coupling coefficients and low acoustic impedance. The damping property of the composites was especially studied. The maximum damping loss factor of the composites is between 0.28-0.32, and the glass transition temperature is between 55°-66 °C.

  4. Structural and dielectric properties of Gd doped bismuth ferrite-lead titanate

    SciTech Connect

    Mohanty, N. K. Behera, A. K. Satpathy, S. K. Behera, B. Nayak, P.

    2014-04-24

    0.5BiGd{sub x}Fe{sub 1−x}O{sub 3}−0.5PbTiO{sub 3} with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and studied that the materials show tetragonal structure at room temperature for all concentration of Gd. Studies of dielectric properties (ε{sub r} and tanδ) of the above compound at different frequencies in a wide range of temperature (25°-500°C) with an impedance analyser revealed that the dielectric constant increases with increase in Gd concentration as well temperature and the compound do not have any dielectric anomaly in the studied frequency and temperature range.

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

    NASA Astrophysics Data System (ADS)

    Ram, Mast; Bala, Kanchan; Sharma, Hakikat; Negi, N. S.

    2016-05-01

    This paper reports on the synthesis of Co doped Zn1-xCoxO (x= 0.0, 0.01, 0.02, 0.03 and 0.05) nanoparticles by solution combustion method using urea as a fuel. The Structural and dielectric properties of the samples were studied. Crystallite sizes were obtained from X-ray diffraction (XRD) patterns whose values decreased with increase in Co concentration. The XRD study reveals that Co2+ ions substitute the Zn2+ ion without changing the wurtzite structure of pristine ZnO up to Co concentrations of 5%. The dielectric constants, dielectric loss (tanδ) and ac conductivity (σac) were studied as the function of frequency and composition, which have been explained by Maxwell-Wagner type interfacial polarization and discussed Koops phenomenological theory.

  6. SHI induced modification in structural, optical, dielectric and thermal properties of poly ethylene oxide films

    NASA Astrophysics Data System (ADS)

    Patel, Gnansagar B.; Bhavsar, Shilpa; Singh, N. L.; Singh, F.; Kulriya, P. K.

    2016-07-01

    Poly ethylene oxide (PEO) films were synthesized by solution cast method. These self-standing films were exposed with 60 MeV C+5 ion and 100 MeV Ni+7 ion at different fluences. SHI induced effect was investigated by employing various techniques. The crystalline size decreased upon irradiation as observed from XRD analysis. FTIR analysis reveals the decrement in the peak intensity upon irradiation. Tauc's method was used to determine the optical band gap (Eg), which shows decreasing trends with increase of fluence. The dielectric properties were investigated in the frequency range 10 Hz to 10 MHz for unirradiated and irradiated films. The dielectric constant remains same for the broad-spectrum of frequency and increases at lower frequency. The dielectric loss also moderately influence as a function of frequency due to irradiation. DSC analysis validated the results of XRD. Scanning electron microscopy (SEM) reveals that there is significant change in the surface morphology due to irradiation.

  7. Influence of molecular adsorption on the dielectric properties of a single wall nanotube: a model sensor.

    PubMed

    Langlet, R; Arab, M; Picaud, F; Devel, M; Girardet, C

    2004-11-15

    Recent measurements of the resonance frequency of a copper disk covered with carbon nanotube bundles have shown characteristic resonance shifts during exposure with various gas molecules. The shifts were interpreted as the change of the dielectric permittivity of the system forming the sensor due to the electric properties of the adsorbed molecules. Starting from a simplified sensor model formed by one single wall nanotube, we develop a self-consistent approach to describe the variation of the linear dielectric susceptibility of the tube at the atomic scale when molecules are adsorbed at its external surface. The sensitivity of this model sensor is tested as a function of the apolar or polar nature of the admolecules, their adsorption geometry, their concentration, and the characteristics of the tube (length, diameter,...). The comparison with data on dielectric constant changes vs adsorption, coming from measurements of the resonance frequency shifts, displays striking agreement for most of the molecular species considered. PMID:15538888

  8. Microwave Dielectric Properties of Polystyrene-Forsterite (Mg2SiO4) Composite

    NASA Astrophysics Data System (ADS)

    Sasikala, T. S.; Sebastian, M. T.

    2016-01-01

    Polystyrene-Mg2SiO4 ceramic composites have been prepared by kneading followed by hot pressing. The dielectric properties of the composites have been investigated at both radio and microwave frequency ranges as a function of filler loading up to 50 vol.%. The dielectric constant and loss tangent increased with the ceramic filler content. The composite with 50 vol.% filler had a dielectric constant of 4.0 and loss tangent of 0.006 at 5 GHz, with Vickers microhardness of 35 HV. The coefficient of thermal expansion of the composite decreased and the thermal conductivity increased with the filler loading. PS-Mg2SiO4 composites are possible candidates for microwave substrate applications.

  9. Structural and dielectric properties of CuO-doped SrTiO{sub 3} ceramics

    SciTech Connect

    Naidu, K. Chandra Babu Sarmash, T. Sofi; Maddaiah, M.; Reddy, V. Narasimha; Subbarao, T.

    2015-06-24

    Copper-doped SrTiO{sub 3} (ST) ceramic powders were processed by solid-state route diffusion (SRD) bulk preparation technique. We reported the effect of Cu{sup +2} ions on the dielectric response of ST and it established the substantial increase in dielectric constant (ε{sub r}) than undoped ST from 303K-673K and low loss (tanδ) for good dielectric applications. In respect of the electrical properties ac- activation energies were computed of range 0.089-0.319eV using lnσ Vs 1/T plots. The microstructure was examined with grain sizes 6-9µm of uniform distribution by field emission scanning electron microscope (FESEM). Some additional phases SrCu{sub 3}Ti{sub 4}O{sub 12} and TiO{sub 2} rutiles were detected by X-ray diffraction technique.

  10. Dielectric properties of ferroelectric betaine phosphite crystals with a high degree of deuteration

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Yurko, E. I.; Svinarev, F. B.; Pankova, G. A.

    2015-12-01

    The dielectric properties of deuterated betaine phosphite crystals with a high degree of deuteration in the region of the antiferrodistorsive (at T = T c1) and ferroelectric (at T = T c2) phase transitions have been investigated. The temperature behavior of the dielectric permittivity of betaine phosphite and deuterated betaine phosphite has been described within the framework of the Landau thermodynamic model taking into account the biquadratic coupling between the polar order parameter of the ferroelectric transition and the nonpolar order parameter of the antiferrodistorsive phase transition. It has been shown that an increase in the degree of deuteration leads to a decrease in the coupling between the order parameters. An increase in the temperature of the ferroelectric phase transition due to the deuteration of betaine phosphite is caused by an increase in the dielectric permittivity in the symmetric phase above the temperature of the antiferrodistorsive phase transition.

  11. Ferrite with extraordinary electric and dielectric properties prepared from self-combustion technique

    SciTech Connect

    Chen Qian; Du Piyi; Huang Wenyan; Jin Lu; Weng Wenjian; Han Gaorong

    2007-03-26

    Nickel-zinc ferrites (Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) with extraordinary electric and dielectric properties were prepared by self-combustion technique. The resistivity of ferrite in the ferric citrate system is on the order of 10{sup 10} {omega} cm, which is about four orders higher than that of ferrite in the ferric nitrate system as well as that of ferrite prepared by the conventional method. The dielectric loss of sample in the ferric citrate system is only 0.008. The amorphous phase and its encapsulation well around the grains have played most important roles in both high resistivity and low dielectric loss of ferrite in the ferric citrate system.

  12. Microwave Dielectric Properties of Ceramic and Nanocomposite Titanates of Transition Metal

    NASA Astrophysics Data System (ADS)

    Rinkevich, Anatoly B.; Kuznetsov, Evgeny A.; Perov, Dmitry V.; Ryabkov, Yury I.; Samoylovich, Mikhail I.; Klescheva, Svetlana M.

    2014-10-01

    Ceramic and nanocomosite samples of the titanates of transition metals have been synthesized and their microwave dielectric properties have been investigated. Frequency and magnetic field dependences of the transmission and reflection coefficients in centimeter and millimeter wavebands were measured. It is established for most of studied ceramic titanates that transmission coefficient increases and reflection coefficient decreases when frequency increases. An absorption maximum has been found for ceramic sample made of Co0.9Fe0.1TiO3. The real and imaginary parts of complex dielectric permittivity were determined from measurements of transmission and reflection coefficients. On the whole, real part of dielectric permittivity of nanocomposite titanates based on an opal matrix is less than for ceramic titanates.

  13. The dielectric properties of granular media saturated with DNAPL/water mixtures

    NASA Astrophysics Data System (ADS)

    Ajo-Franklin, J. B.; Geller, J. T.; Harris, J. M.

    2004-09-01

    We present the results of five experiments investigating the dielectric properties of granular materials partially saturated with trichloroethylene (TCE), a common dense non-aqueous contaminant. Previous research has investigated the radar signatures of similar solvents in controlled field experiments but no core-scale measurements have verified the appropriate petrophysical model. Broadband dielectric measurements were performed using a time domain reflectometry (TDR) system coupled to a solvent-compatible coaxial transmission line. Two synthetic samples and three natural aquifer samples were fully saturated with water and then subjected to an axial TCE injection until breakthrough was observed. The resulting dielectric measurements show good agreement with the empirical complex refractive index model (CRIM) allowing a reasonable prediction of the radar reflectivities and transmission velocities expected in field surveys targeting pools of similar non-aqueous contaminants.

  14. Study to determine dielectric properties of sandstone, shale, coal, and slate

    NASA Technical Reports Server (NTRS)

    Bassett, H. L.; Sheppard, A. P.

    1976-01-01

    Triplicate dielectric constant and loss tangent measurements on samples of sandstone, shale, coal, and slate were performed. Each of the three necessary configurations of the coal material was sampled to obtain measurements, with each sample machined parallel to the coal layering orientation. The coal samples were machined perpendicular to the coal layering and measured. They were conditioned at 100% humidity and at room temperature and remeasured; then conditioned in an elevated environment, and remeasured for dielectric properties. The coal data appear to remain relatively constant over the microwave frequency region. At the Ghz frequencies, the relative dielectric constant of coal is slightly higher for the E-field parallel to the layers than for the perpendicular case.

  15. Dielectric properties of polymer composites with carbon nanotubes of different diameters.

    PubMed

    Macutkevic, Jan; Paddubskaya, Alesia; Kuzhir, Polina; Banys, Juras; Maksimenko, Sergey; Kuznetsov, Vladimir L; Mazov, Ilya N; Krasnikov, Dmitrij V

    2014-07-01

    The dielectric properties of Polymethylmetacrylate (PMMA) composites filled with CVD made multiwalled carbon nanotubes (MWCNT) of different mean outer diameters (d - 9 nm and 12-14 nm) were investigated at temperatures from 300 K to 390 K and in a wide frequency range (20 Hz-1 MHz). The percolation threshold is lower in composites with thick nanotubes. Below percolation threshold the dielectric permittivity was found also to be higher for composites with thicker carbon nanotubes. The temperature dependence of the complex dielectric permittivity of the investigated composites below percolation is mainly caused by beta relaxation in pure PMMA polymer matrix. The potential barrier for PMMA molecules rotation is higher in composites with thicker MWCNT and demonstrates non-monotonous concentration dependence. PMID:24758044

  16. Measuring and Modeling of the Dielectric Properties and Attenuation of Vegetation

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.

    1984-01-01

    The dielectric properties of vegetation material--primarily agricultural plants--as a function of moisture content and microwave frequency was measured and used to develop dielectric mixing models for the vegetation-water mixture. A model for the loss factor of a vegetation canopy was also developed. During the first phase of this investigation, three waveguide transmission systems covering from 1 to 2-GHz, from 3.5 to 6.5-GHz, and from 7.5 to 8.5-GHz bands were constructed and calibrated. By measuring the magnitude and phase of the field transmission coefficient of a given sample, it was possible to calculate the real and imaginary parts of the complex dielectric constant of the sample. Measurements were made for numerous samples of leaves and stalks of wheat and corn, and for wheat heads. Also, dielectric measurements were made of the liquid included in the vegetation material after extraction by mechanical means. The propagation loss is more than an order of magnitude greater than had previously been assumed. Various types of dielectric mixing models were investigated in terms of the available data, and a propagation model was developed and evaluated against direct canopy attenuation measurements. The canopy measurements were made by transmitting a signal from a radar antenna mounted atop a truck-mounted boom, and using a small antenna mounted on a rail beneath the canopy to receive it.

  17. Effect of DC bias on dielectric properties of nanocrystalline CuAlO2

    NASA Astrophysics Data System (ADS)

    Prakash, T.; Ramasamy, S.; Murty, B. S.

    2013-03-01

    Grain boundary effect on the room temperature dielectric behavior in mechanically alloyed nanocrystalline CuAlO2 has been investigated using impedance spectroscopy under the applied DC bias voltages 0 V to 4.8 V in a periodic interval of 0.2 V. Analysis of impedance data confirms the existence of double Schottky potential barrier heights ( Φ b ) between two adjacent grains (left and right side) with grain boundary and its influences in dielectric relaxation time ( τ), dielectric constant ( ɛ') and dielectric loss (tan δ) factor. Also, clear evidence on the suppression of Φ b was demonstrated in the higher applied bias voltages with the parameter τ. At equilibrium state, τ is 0.63 ms and it was reduced to 0.13 ms after the 3.2 V applied DC bias. These observed DC bias voltage effects are obeying `brick layer model' and also elucidates Φ b is playing a crucial role in controlling dielectric properties of nanomaterials.

  18. Dielectric properties of the polar head group region of zwitterionic lipid bilayers.

    PubMed Central

    Raudino, A; Mauzerall, D

    1986-01-01

    A theoretical model describing the dielectric properties of the lipid membrane-water interface region was developed. The rotating polar head groups (e.g. phosphatidylcholine) were simulated as a collection of interacting dipoles imbedded in a nonhomogeneous dielectric. The interactions between the nearest neighborhood were explicitly taken into account, while the other interactions were evaluated by means of the continuum theories. The values of the dielectric constant, its anisotropy and the spontaneous polarization of the interface were evaluated. As an application, we calculated the energy of interaction between an ion and the membrane polar head group region. The results indicate a small spontaneous polarization of the interface (1-1.7 Debyes per lipid molecule) due to the tilting angle of the choline residue with respect to the membrane surface. This dipolar field partially compensates that of opposite orientation originating from the ester group region, giving calculated overall dipolar potentials in better agreement with the experimental data. Our model suggests also a very strong dielectric anisotropy of the interface region, the component of the dielectric constant perpendicular to the membrane plane being much smaller than the parallel component. PMID:3756297

  19. Temperature and frequency dependent dielectric properties of Ni-Mg-Zn-Co ferrites

    NASA Astrophysics Data System (ADS)

    Patil, S. B.; Patil, R. P.; Ghodake, J. S.; Chougule, B. K.

    2014-01-01

    The ferrites having general formula Ni0.5-xMgx-0.01Zn0.5-yCoy+0.01Fe2O4 (x=0.1, 0.2, 0.3, 0.4 and y=0.1, 0.2, 0.3, 0.4) were prepared by ceramic method. The X-ray diffraction studies of compositions reveal formation of single-phase cubic spinal structure. Dielectric properties such as dielectric constant ɛ', dielectric loss tangent (tan δ), and ac resistivity were measured at room temperature as a function of frequency in the range from 1 kHz to 1 MHz. The plots of dielectric constant ɛ' vs frequency show a normal dielectric behavior of spinel ferrites. The variation of loss tangent (tan δ) as a function of frequency shows a decreasing trend for all the samples except for the composition with x=0.3 and y=0.1, and y=0.2. The variation of ac resistivity with frequency of all the samples shows a decreasing trend with increase in frequency, a normal behavior of ferrites. All the variations are explained on the basis of Fe2+/Fe3+ ion concentration on octahedral sites as well as the electronic hopping between Fe2+↔Fe3+ ions.

  20. Dielectric, thermal and mechanical properties of zirconium silicate reinforced high density polyethylene composites for antenna applications.

    PubMed

    Varghese, Jobin; Nair, Dinesh Raghavan; Mohanan, Pezholil; Sebastian, Mailadil Thomas

    2015-06-14

    A low cost and low dielectric loss zirconium silicate (ZrSiO4) reinforced HDPE (high-density polyethylene) composite has been developed for antenna applications. The 0-3 type composite is prepared by dispersing ZrSiO4 fillers for various volume fractions (0.1 to 0.5) in the HDPE matrix by the melt mixing process. The composite shows good microwave dielectric properties with a relative permittivity of 5.6 and a dielectric loss of 0.003 at 5 GHz at the maximum filler loading of 0.5 volume fraction. The composite exhibits low water absorption, excellent thermal and mechanical properties. It shows a water absorption of 0.03 wt%, a coefficient of thermal expansion of 70 ppm per °C and a room temperature thermal conductivity of 2.4 W mK(-1). The composite shows a tensile strength of 22 MPa and a microhardness of 13.9 kg mm(-2) for the filler loading of 0.5 volume fraction. The HDPE-ZrSiO4 composites show good dielectric, thermal and mechanical properties suitable for microwave soft substrate applications. A microstrip patch antenna is designed and fabricated using the HDPE-0.5 volume fraction ZrSiO4 substrate and the antenna parameters are investigated. PMID:25981704

  1. Fabrication and Dielectric Properties of Lead-Free Inorganic Particles-Epoxy Resin Composites

    NASA Astrophysics Data System (ADS)

    Kobune, Masafumi; Takasaki, Keiko; Yazawa, Tetsuo

    2006-09-01

    Inorganic-organic composites with a 0-3 connectivity are fabricated from inorganic particles with a high relative permittivity (\\varepsilonr) and a low dielectric loss (\\tanδ), and epoxy resin. The compacted powder obtained by pulverizing BaZrO3-BaTiO3-Ba(Fe1/2Ta1/2)O3 (BZTFT) ceramics has 1/12th the \\varepsilonr and 72 times the \\tanδ of the ceramics. On the basis of the relationship between \\varepsilonr and BZTFT filler content, the experimental values of the composites are determined to be in good agreement with theoretical values calculated by following Nielsen’s complex rule in the filler content range of 50-80 vol %. The temperature dependence of the dielectric properties of BZTFT powder/epoxy resin (90/10, v/v) composites measured at different frequencies suggests that the temperature characteristics of the present materials correspond to the Z8T characteristics [Z8T; Electronic Industries Association (EIA) standard: Δ C/C25 {\\degC} is expressed as a rate of change within +22 and -33% in the temperature range from 10 to 150 °C] when represented by the temperature characteristics of surface-mounted capacitors. It is shown that the effect of the vacuum drying of the filler on the dielectric properties of the composites is larger than that of the silane coupling treatment and that the dielectric properties can be improved synergistically by performing both treatments.

  2. Effect of high-pressure on calorimetric, rheological and dielectric properties of selected starch dispersions.

    PubMed

    Ahmed, Jasim; Singh, Ajaypal; Ramaswamy, H S; Pandey, Pramod K; Raghavan, G S V

    2014-03-15

    Effects of high-pressure (HP) treatment on the rheological, thermal and dielectric properties of the four selected starch dispersions (two modified starches, one native and one resistant) were evaluated. Differential scanning calorimetry (DSC) and oscillatory rheometry were employed to assess the extent of starch gelatinization and the developed gel rigidity (G') of starch gels after HP treatment. It was observed that starch dispersions gelatinized completely at 500 MPa with a 30-min holding time. The HP-treated starch samples exhibited predominantly solid-like (G'>G") behavior except for the resistant starch. Pressure-induced gel rigidity differed significantly among starch samples. The G' of starch gels increased with the pressure (400-600 MPa) in the studied frequency range (0.1-10 Hz) except for the native starch where a marginal decrease was recorded at similar condition. The holding time (15-30 min) and concentration (20-25% w/w) significantly attributed towards gel rigidity of starch samples. Measurement of dielectric properties of HP-treated samples over the frequency range 450-4450 MHz indicated differences in the dielectric constant (ɛ'), loss factor (ɛ") and penetration depth among starch gels. Pressure did not show any effect on dielectric property of the resistant starch sample. Power penetration depth decreased significantly with frequency and with the pressure.

  3. Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells.

    PubMed

    Wu, Liqun; Lanry Yung, Lin-Yue; Lim, Kian-Meng

    2012-03-01

    In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius-Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis.

  4. Broadband dielectric/electric properties of epoxy thin films filled with multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Macutkevic, Jan; Kuzhir, Polina P.; Paddubskaya, Alesia G.; Banys, Juras; Maksimenko, Sergey A.; Stefanutti, Eleonora; Micciulla, Federico; Bellucci, Stefano

    2013-01-01

    Many attempts have been made to fully explore flexibility, resistance to corrosion, and processing advantage of epoxy resin filled with carbon nanotubes (CNTs) as conductive filler, although sometimes with a certain degradation of polymers' intrinsic properties. It is important to move the percolation threshold into the region of smaller CNTs' concentration. The results of a broadband dielectric investigation of multiwalled CNT (MWCNT)/epoxy resin composites in wide temperature range from room temperature to 450 K were analyzed for percolation. Far below the percolation threshold (0.25 wt. % MWCNT) the dielectric properties of the composite are mostly determined by alpha relaxation in pure polymer matrix and the freezing temperature decreases due to the extra free volume at the polymer-filler interface. Close to the percolation threshold, the composite shows the negative temperature coefficient effect in the temperature region, where the pure polymer matrix becomes conductive. The activation energy of DC conductivity increases with the MWCNT concentration far below the percolation threshold and decreases close to it (1.5 wt. % MWCNT). The dielectric analysis of the MWCNT/epoxy resin reveals a significant influence of the polymer matrix on the temperature dependence of composite dielectric properties.

  5. The study of dielectric, pyroelectric and piezoelectric properties on hot pressed PZT-PMN systems

    SciTech Connect

    Srivastava, Geetika; Umarji, A. M.; Maglione, Mario

    2012-12-15

    Hot uniaxial pressing technique has been adopted for the densification of PZT-PMN system with an aim to yield dense ceramics and to lower the sintering temperature and time for achieving better and reproducible electronic properties. The ceramics having >97% theoretical density and micron size grains are investigated for their dielectric, pyroelectric and piezoelectric properties. The effect of Li and Mn addition has also been studied.

  6. Dielectric and complex impedance properties of tetravalent hafnium (HF 4+) integrated cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Sanchez, Luis

    The work presented in this thesis was carried out to understand the effects of tetravalent hafnium (Hf4+) ion on the crystal structure and phase, surface morphology, electrical, dielectric and complex impedance properties of cobalt ferrite (CoFe2O4; CFO). Hafnium incorporated cobalt ferrite, CoFe2-xHfxO4, with x = 0.00, 0.05, 0.075, 0.10, 0.15 and 0.20 were prepared by the standard solid state ceramic synthesis method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations were performed to determine the structural properties. Most important aspect of this study is to explore the dielectric and complex impedance properties as a function of variable temperature (T=300-1000 K) and frequency (f=20 Hz -1 MHz). Room temperature and the temperature dependence of dielectric constant, loss factor, complex impedance, and the ac resistivity measurements enabled us to understand the effect of temperature and frequency on the electrical and dielectric properties on CoFe2-xHfxO4 and, thus, to derive structure-property relation. X-ray diffraction (XRD) patterns for Hf-incorporated CFO confirm the formation of majority of CFO spinel [with space group Fd3m (227)] phase, in addition to the small amount of HfO2 monoclinic [space group, P1 21/c (14)] phase leading to formation of CFO-Hf composites. The lattice constant values derived from XRD for CFO-Hf were found to increase from 8.374 A (x = 0.000) to 8.391 A (x = 0.200). The lattice expansion is significant at the very first step of Hf-incorporation and then slows down with progressive Hf-incorporation. SEM imaging analysis indicates that Hf resides at the grain boundaries for CFO-Hf. The dielectric constant (epsilon') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for epsilon- T (>450 K) variation. Correspondingly, electrical

  7. Study of dielectric and piezoelectric properties of CNT reinforced PZT-PVA 0-3 composite

    NASA Astrophysics Data System (ADS)

    Vyas, Prince; Prajapat, Rampratap; Manmeeta, Saxena, Dhiraj

    2016-05-01

    Ferroelectric ceramic/polymer composites have the compliance of polymers which overcome the problems of brittleness in ceramics. By imbedding piezoelectric ceramic powder into a polymer matrix, 0-3 composites with good mechanical properties and high dielectric breakdown strength can be developed. The obtained composites of 0-3 connectivity exhibit the piezoelectric properties of ceramics and flexibility, strength and lightness of polymer. These composites can be used in vibration sensing and transducer applications specially as piezoelectric sensors. A potential way to improve piezoelectric& dielectric properties of theses composites is by inclusion of another conductive phase in these composites as reported in the literature. In present work, we prepared PZT-PVA 0-3 composites with 60% ceramic volume fraction reinforced with CNTs with volume ranging from 0 to 1.5 vol%. These CNT reinforced composites were obtained using hot press method with thickness of 200 µm having 0-3 conductivity. These composites were poled applying DC voltage. Dielectric properties of these samples were obtained in a wide frequency range (100 Hz to 1 Mhz) at room temperature. The piezoelectric properties of these composites were analyzed by measuring piezoelectric charge constants (d33). The dielectric and piezoelectric properties of these composites were studied as a function of CNT volume content. In these reinforced composites, CNTs act as a conductive filler dispersed in the matrix which in turn facilitates poling and results in an increase of the piezoelectric properties of the composite due to formation of percolation path through the composites. With a CNT content of 0.3 vol.% in PZT/PVA/CNTs, an increase of 61.3 % was observed in piezoelectric strain factors (d33). In these CNT reinforced composites, a substantial increase (approx. 67%) was also observed in dielectric constant and approximately 89% increase was observed in dielectric loss factor. Results so obtained are in the good

  8. Dielectric and insulating properties of an acrylic DEA material at high near-DC electric fields

    NASA Astrophysics Data System (ADS)

    Di Lillo, L.; Schmidt, A.; Bergamini, A.; Ermanni, P.; Mazza, E.

    2011-04-01

    A number of adaptive structure applications call for the generation of intense electric fields (in excess of 70 MV/m). Such intense fields across the thickness of a thin polymer dielectric layer are typically used to exploit the direct electromechanical coupling in the form of a Maxwell stress: (see manuscript) Where V/d is the applied field, ɛ0 is the permittivity of vacuum and ɛ is the relative permittivity of the material. The field that can be applied to the dielectric is limited by the dielectric strength of the material. Below the limit set by the breakdown, the material is generally assumed to have a field independent dielectric constant and to be a perfect insulator, i.e. to have an infinite volume resistivity. While extensive investigations about the mechanical properties of the materials used for electronic Dielectric Elastomer Actuators (DEA) are available from literature, the results of the investigation of the insulating and dielectric properties of these materials, especially under conditions (electric field and frequency) similar to the ones encountered during operation are not available. In the present contribution, we present a method and a set-up for the measurement of the electric properties of thin polymer films, such as the ones used for the fabrication of electronic DEAs, under conditions close to operations. The method and setup where developed to investigate the properties of 'stiff' thin polymer films, such as Polyimide or Polyvinylidenefluoride, used for Electro-Bonded Laminates (EBLs). The properties of the well known VHB 4910 acrylic elastomer are presented to illustrate how the permittivity and the leakage current can be measured as a function of the electric field and the deformation state, using the proposed set-up. The material properties were measured on membranes under different fixed pre-stretch conditions (λ 1, λ2=3, 4, 5), in order to eliminate effects due to the change in sample geometry, using gold sputtered electrodes, 20

  9. Dielectric and Thermal Properties of Transformer Oil Modified by Semiconductive CdS Quantum Dots

    NASA Astrophysics Data System (ADS)

    Abd-Elhady, Amr M.; Ibrahim, Mohamed E.; Taha, T. A.; Izzularab, Mohamed A.

    2016-07-01

    In this paper, modified transformer oil semiconductor quantum dots (QDs) are presented. Cadmium sulfide (CdS) quantum dots of radius 4.5 nm with a hexagonal crystal structure are added to transformer oil to improve its dielectric and thermal properties. CdS QDs modified oil is prepared considering different filler loading levels. Alternating current breakdown voltages of the transformer oil samples before and after the modification are measured based on American Society for Testing and Materials D1816 standard. The relative permittivity and dissipation factor are measured for all samples. Also, thermal properties of the oil samples are experimentally evaluated according to the temperature change measurement considering heating and cooling processes. The results show significant improvements in dielectric and thermal properties of the modified transformer oil, as well as an increase in the breakdown strength by about 81% in comparison to the base transformer oil.

  10. Dielectric and Thermal Properties of Transformer Oil Modified by Semiconductive CdS Quantum Dots

    NASA Astrophysics Data System (ADS)

    Abd-Elhady, Amr M.; Ibrahim, Mohamed E.; Taha, T. A.; Izzularab, Mohamed A.

    2016-10-01

    In this paper, modified transformer oil semiconductor quantum dots (QDs) are presented. Cadmium sulfide (CdS) quantum dots of radius 4.5 nm with a hexagonal crystal structure are added to transformer oil to improve its dielectric and thermal properties. CdS QDs modified oil is prepared considering different filler loading levels. Alternating current breakdown voltages of the transformer oil samples before and after the modification are measured based on American Society for Testing and Materials D1816 standard. The relative permittivity and dissipation factor are measured for all samples. Also, thermal properties of the oil samples are experimentally evaluated according to the temperature change measurement considering heating and cooling processes. The results show significant improvements in dielectric and thermal properties of the modified transformer oil, as well as an increase in the breakdown strength by about 81% in comparison to the base transformer oil.

  11. Depolarization field effect on dielectric and piezoelectric properties of particulate ferroelectric ceramic-polymer composites

    NASA Astrophysics Data System (ADS)

    Ma, Fengde D.; Wang, Yu U.

    2015-03-01

    The effects of depolarization field on the dielectric and piezoelectric properties of ferroelectric ceramic particle-filled polymer-matrix composites are investigated at the underlying domain level. Phase field modeling and simulation reveals that the macroscopic properties of the composites are dominated by depolarization field effect, which depends on the arrangement and alignment rather than the size or internal grain structure of the ferroelectric particulates. It is found that 0-3 particulate composites with random dispersion of ferroelectric particles behave essentially like linear dielectric rather than ferroelectric materials, and domain-level analysis reveals the physical mechanism for lack of domain switching or hysteresis as attributed to strong depolarization effect. Thus, without effective reduction or elimination of the depolarization field, the composites cannot benefit from the functional fillers regardless of their superior properties. In order to exhibit the desired ferroelectric behaviors, it necessitates continuous ferroelectric phase connectivity in the composites.

  12. Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates

    NASA Astrophysics Data System (ADS)

    Rodriguez, Luis A.; García, Carla; Fittipaldi, Mauro; Grace, Landon R.

    2016-03-01

    The potential for recovery of dielectric properties of three water-contaminated fiber-reinforced laminates is investigated using a split-post dielectric resonant technique at X-band (10 GHz). The three material systems investigated are bismaleimide (BMI) reinforced with an eight-harness satin weave quartz fabric, an epoxy resin reinforced with an eight- harness satin weave glass fabric (style 7781), and the same epoxy reinforced with a four-harness woven glass fabric (style 4180). A direct correlation between moisture content, dielectric constant, and loss tangent was observed during moisture absorption by immersion in distilled water at 25 °C for five equivalent samples of each material system. This trend is observed through at least 0.72% water content by weight for all three systems. The absorption of water into the BMI, 7781 epoxy, and 4180 epoxy laminates resulted in a 4.66%, 3.35%, and 4.01% increase in dielectric constant for a 0.679%, 0.608%, and 0.719% increase in water content by weight, respectively. Likewise, a significant increase was noticed in loss tangent for each material. The same water content is responsible for a 228%, 71.4%, and 64.1% increase in loss tangent, respectively. Subsequent to full desorption through drying at elevated temperature, the dielectric constant and loss tangent of each laminate exhibited minimal change from the dry, pre-absorption state. The dielectric constant and loss tangent change after the absorption and desorption cycle, relative to the initial state, was 0.144 % and 2.63% in the BMI, 0.084% and 1.71% in the style 7781 epoxy, and 0.003% and 4.51% in the style 4180 epoxy at near-zero moisture content. The similarity of dielectric constant and loss tangent in samples prior to absorption and after desorption suggests that any chemical or morphological changes induced by the presence of water have not caused irreversible changes in the dielectric properties of the laminates.

  13. High dielectric, dynamic mechanical and thermal properties of polyimide composite film filled with carbon-coated silver nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Lisi; Piao, Xiaoyu; Zou, Heng; Wang, Ya; Li, Hengfeng

    2015-01-01

    High dielectric permittivity materials are much desirable in the electric industry. Filling polymer matrix with conductive powders to form percolative composites is one of the most promising methods to achieve high dielectric permittivity. However, they do not always provide high mechanical properties and thermal stability, which seriously limit their applications. In this study, we present the preparation of functional core-shell structured silver nanowires/polyimide (AgNWs/PI) hybrid film with high dielectric permittivity and low loss dielectric. The core-shell structure of AgNWs was characterized by transmission electric microscopy. The dynamical mechanical analysis showed that AgNWs/PI hybrid films had relative high dynamic mechanical properties with storage modules over 1 Gpa. Moreover, the hybrid films exhibited excellent thermal stability with 5 % weight-loss temperature above 500 °C. The dielectric properties of the carbon-coated AgNWs hybrid films were remarkably improved. The maximum dielectric permittivity of hybrid films is 126 at 102 Hz, which was 39 times higher than that of pure PI matrix, while the dielectric loss of that is still remained at a low value. This study showed a new method to improve the dielectric, dynamic mechanical and thermal properties of films.

  14. Dielectric properties of lead-free BZT-KNN perovskite ceramics for energy storage.

    PubMed

    Gui, Dong-Yun; Liu, Han-Xing; Hao, Hua; Sun, Yue; Cao, Ming-He; Yu, Zhi-Yong

    2011-10-17

    Lead-free (1-x)Ba(Zr₀.₁₅Ti₀.₈₅)O₃-x(K₀.₅Na₀.₅)NbO₃ ; x=0-0.05) (BZT-KNN) perovskite ceramics, a materials with potential applications for energy storage, are investigated. The samples are prepared by a solid-state reaction method. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to study the microstructure of the samples. Their dielectric properties and impedance spectra are reported as functions of temperature and frequency. The addition of 1 mol % (K₀.₅Na₀.₅)NbO₃ to Ba(Zr₀.₁₅Ti₀.₈₅)O₃ improves the dielectric constant and enhances its diffuseness in a wide temperature range. The small amount of (K₀.₅Na₀.₅)NbO₃ is found to markedly affect the microstructure of the Ba(Zr₀.₁₅Ti₀.₈₅)O₃ ceramic (grain size and other characteristics) without changing the phase or crystal symmetry. In addition, we report that fine substructures in the grains, so-called sheet structures, are responsible for the dielectric properties (both diffuseness and dielectric constant) of (1-x)Ba(Zr₀.₁₅Ti₀.₈₅)O₃-x(K₀.₅Na₀.₅)NbO₃ (x=0-0.03; especially x=0.01) ceramics.

  15. Electrical Properties of PVP-SiO2-TMSPM Hybrid Thin Films as OFET Gate Dielectric

    NASA Astrophysics Data System (ADS)

    Bahari, A.; Shahbazi, M.

    2016-02-01

    Organic-inorganic polyvinylpyrrolidone-silicon dioxide-3-(trimethoxysilyl)propyl methacrylate (PVP-SiO2-TMSPM) hybrid solutions have been synthesized using the sol-gel process with different amounts of TMSPM as coupling agent and equivalent amounts of PVP and SiO2. Hybrid solutions were deposited on p-type Si(111) substrates using the spin coating technique, as a gate dielectric material for use in thin-film transistors. The structural properties of the samples were investigated using Fourier-transform infrared spectroscopy and x-ray diffraction analysis. Atomic force microscopy and scanning electron microscopy techniques were applied to study the topography and morphology of the hybrid thin-film samples. Current-voltage ( I- V) curves, capacitance-voltage ( C- V) measurements, and the electrical properties of the organic hybrid thin-film gate dielectrics were also studied in a metal-insulator/polymer-semiconductor structure. According to the results, the J GS curves in terms of V GS showed gate leakage current densities small enough for use as gate dielectric material at interface layers. At V DS = 30 V, in the saturation region, I DS curves in terms of V GS presented higher charge carrier mobility ( μ FET,S = 0.0584 cm2 s-1 V-1) due to lower dielectric constant ( k = 11.43) in the sample with 0.05 weight ratio of TMSPM compared with other samples with different weight ratios of TMSPM.

  16. A first-principles study of the dielectric properties of TiO₂ polymorphs.

    PubMed

    Thilagam, A; Simpson, D J; Gerson, A R

    2011-01-19

    We present an analysis of the dielectric properties of the three polymorphs of TiO₂ (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO₂. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO₂ polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes. PMID:21406847

  17. A first-principles study of the dielectric properties of TiO2 polymorphs

    NASA Astrophysics Data System (ADS)

    Thilagam, A.; Simpson, D. J.; Gerson, A. R.

    2011-01-01

    We present an analysis of the dielectric properties of the three polymorphs of TiO2 (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO2. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO2 polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

  18. Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Rathod, Sunil G.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Naik, Jagadish

    2014-04-01

    In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young's modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charge-storage devices.

  19. Dielectric and Piezoelectric Properties of 10% KF-Doped BaTiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Akishige, Yukikuni; Hiraki, Yuuta; Tsukada, Shinya; Xu, Jun; Morito, Shigekazu; Ohba, Takuya; Walker, Ezekiel Lee; Neogi, Arup

    2010-08-01

    10% KF-doped barium titanate powders, Ba0.9K0.1TiO2.9F0.1, were synthesized through a sol-gel process. The powders, calcined at 650 °C, consist of cubic crystalline particles of ˜70 nm in length; the particle size increases to ˜200 nm as the firing temperature increases to ca. 800 °C, above which F2 begins to evaporate. Dense ceramics were fabricated by the spark plasma sintering (SPS) method; the average grain size is ˜2 µm in lengths. The ceramics, well annealed at 1,000 °C in an O2 gas flow, have good dielectric and piezoelectric properties; the piezoelectric d33 value is 230 pC/N at room temperature. At the ferroelectric Curie temperature TC = 47 °C, the dielectric constant and loss tan δ are 10,000 and <5% at 10 kHz, respectively. The Curie-Weiss relation holds in the fully disordered cubic and ordered rhombohedral phases, showing the second order 1:2 relation. Below 10 kHz, large dielectric dispersion caused by a domain-wall motion appears at the temperature range of -50 to 107 °C. Some discussions are made for these dielectric properties of the ceramics.

  20. Study Of Structural And Dielectric Properties Of Ni-Mg Ferrite Nanoparticles

    SciTech Connect

    Nongjai, Razia; Batoo, Khalid Mujasam; Khan, Shakeel

    2010-12-01

    Ferrite nanoparticles of basic composition Ni{sub 0.7}Mg{sub 0.3}Fe{sub 2-x}Al{sub x}O{sub 4}(0.0{<=}x{<=}0.5) were prepared through citrate gel method and characterized using XRD, TEM and dielectric spectroscopy techniques. The dielectric properties were studied as a function of frequency (42 Hz-5 MHz) at room temperature. The average particle size has been found between 8-17 nm. The dispersion in dielectric properties and ac conductivity ({sigma}{sub ac}), with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe{sup 2+} and Fe{sup 3+} as well as between Ni{sup 2+} and Ni{sup 3+} ions at B-sites. The dielectric loss tangent (tan {delta}) shows abnormal behavior for the compositions 0.3, 0.4 and 0.5 which has been explained in the light of Rezlescue model.

  1. Structural and dielectric properties of Cr-doped Ni-Zn nanoferrites

    NASA Astrophysics Data System (ADS)

    Nasir, S.; Anis-ur-Rehman, M.; Malik, Muhammad Ali

    2011-02-01

    Cr-doped Ni-Zn ferrite nanoparticles having the general formula Ni0.5Zn0.5CrxFe2-xO4 (x=0.1, 0.3, 0.5) were prepared by the simplified sol-gel method. The structural and dielectric properties of the samples sintered at 750±5 °C were studied. X-ray diffraction (XRD) patterns confirm the single-phase spinel structure of the prepared samples. The crystallite size calculated from the most intense peak (3 1 1) using the Debye-Scherrer formula was 29-34 nm. Scanning electron microscope images showed that the particle size of the samples lies in the nanometer regime. The dielectric constant (ɛr), dielectric loss tangent (tan δ) and ac electrical conductivity (σac) of nanocrystalline Cr-Ni-Zn ferrites were investigated as a function of frequency and Cr concentration. The dependence of ɛr, tan δ and σac on the frequency of alternating applied electric field is in accordance with the Maxwell-Wagner model. The effect of Cr doping on the dielectric and electric properties was explained on the basis of cations distribution in the crystal structure.

  2. Dynamic performance of a static or throwing droplet impact onto a solid substrate with different properties

    NASA Astrophysics Data System (ADS)

    Wu, Jie; Li, Ya-Dong

    2016-03-01

    The dynamic performance of a static or throwing droplet impact onto a solid substrate with different properties is numerically studied in this work. After being released or horizontally thrown out, a two-dimensional droplet can fall freely under gravity. The substrate, which is below the droplet, is either hydrophilic/hydrophobic or inhomogeneous. To conduct numerical simulations, a hybrid method is adopted, in which the flow field is solved by using the lattice Boltzmann method and the interface is captured by solving the Cahn-Hilliard equation directly. Given a fixed distance between the droplet and the substrate (H∗), the effects of Bond number (Bo), Weber number (We), and surface property on the performance of droplet impingement are investigated in detail. With the increase of Bond number, the surface coverage area of a static droplet also increases. A hydrophilic surface or an inhomogeneous surface with small advancing/receding angle difference can lead to the breakup of droplet rim due to the bubble entrapment. Moreover, dependent on the Weber number and the surface property, the leading edge rim of a throwing droplet developing on an inhomogeneous surface may break up before or after it contacts the substrate. As a result, compared to the case of static droplet, the surface coverage area will be reduced due to the diffusion of small droplet segment.

  3. Optimization of silver-dielectric-silver nanoshell for sensing applications

    SciTech Connect

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-08-15

    In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell.

  4. Optimization of silver-dielectric-silver nanoshell for sensing applications

    NASA Astrophysics Data System (ADS)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-08-01

    In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell.

  5. Influence of static and dynamic internal actions on elastic nonlinear properties of a granulated unconsolidated medium

    NASA Astrophysics Data System (ADS)

    Shirgina, N. V.; Korobov, A. I.; Kokshaiskii, A. I.

    2013-09-01

    We have studied the influence of external static (pressure) and dynamic (caused by an elastic wave with a finite amplitude) actions on the linear and nonlinear elastic properties of a granulated unconsolidated medium, which was simulated by steel spheres with diameters of 2 and 4 mm. We have analyzed the equation of state for such a medium taking into account the presence of weakly and strongly deformed contacts between individual spheres. We have obtained expressions for the elasticity coefficient and second- and third-order nonlinear elastic parameters, and we have experimentally studied the influence of external static pressure on their values. We have measured the dependence of the velocity of elastic waves on external static pressure and the probing signal amplitude. In the studied medium, a number of structural phase transitions were observed, related to rearrangement of the packing of spheres, which were caused by both static and dynamic actions. The structural phase transition was accompanied by an anomalous change in the nonlinear elastic parameters of the medium and the velocity of elastic waves. We have analyzed the results based on the Hertz theory of contact interaction.

  6. Large dielectric permittivity and possible correlation between magnetic and dielectric properties in bulk BaFeO{sub 3−δ}

    SciTech Connect

    Sagdeo, Archna; Gautam, Kamini; Singh, M. N.; Sinha, A. K.; Ghosh, Haranath; Ganguli, Tapas; Chakrabarti, Aparna; Sagdeo, P. R.; Gupta, S. M.; Nigam, A. K.; Rawat, Rajeev

    2014-07-28

    We report structural, magnetic, and dielectric properties of oxygen deficient hexagonal BaFeO{sub 3−δ}. A large dielectric permittivity comparable to that of other semiconducting oxides is observed in BaFeO{sub 3−δ}. Magnetization measurements indicate magnetic inhomogeneity and the system shows a paramagnetic to antiferromagnetic transition at ∼160 K. Remarkably, the temperature, at which paramagnetic to antiferromagnetic transition occurs, around this temperature, a huge drop in the dissipation factor takes place and resistivity shoots up; this indicates the possible correlation among magnetic and dielectric properties. First principle simulations reveal that some of these behaviors may be explained in terms of many body electron correlation effect in the presence of oxygen vacancy present in BaFeO{sub 3−δ} indicating its importance in both fundamental science as well as in applications.

  7. Dielectric property measurement of ocular tissues up to 110 GHz using 1 mm coaxial sensor.

    PubMed

    Sasaki, K; Isimura, Y; Fujii, K; Wake, K; Watanabe, S; Kojima, M; Suga, R; Hashimoto, O

    2015-08-21

    Measurement of the dielectric properties of ocular tissues up to 110 GHz was performed by the coaxial probe method. A coaxial sensor was fabricated to allow the measurement of small amounts of biological tissues. Four-standard calibration was applied in the dielectric property measurement to obtain more accurate data than that obtained with conventional three-standard calibration, especially at high frequencies. Novel data of the dielectric properties of several ocular tissues are presented and compared with data from the de facto database. PMID:26237580

  8. Exploring Soil Properties through Electromagnetic Sensor-based Complex Dielectric Permittivity

    NASA Astrophysics Data System (ADS)

    Jones, S. B.; Wang, C.; Robinson, D. A.; Tuller, M.

    2009-12-01

    Soil physical and chemical properties contain important information influencing soil quality as well as plant growth and yield, all of which ultimately impact hydrologic, ecologic and agricultural interests. Electromagnetic (EM) sensors are widely used for water content determination using a variety of measurement techniques, most of which are based on soil capacitance or travel-time analysis. Most measurements yield a single dielectric permittivity value (usually at an unknown frequency), which must be interpreted to derive the volumetric water content. Recent research associated with permittivity measurements in the frequency domain suggest that important soil features may be extracted there. The objectives of this work were to explore EM sensor-based frequency-domain measurements and their potential to reveal soil physical and chemical properties. Ten different EM sensors were evaluated using reference dielectric liquids and suspensions. Effective measurement frequencies for sensors outputing dielectric permittivity were estimated using spectra from network analyzer measurements. Eight different soils with varying texture were selected and permittivities were measured at different water contents to observe the potential for extracting soil properties from frequency-domain measurements. Measured permittivities using lower ‘fixed’ frequency sensors were larger in proportion to the fineness of the soil texture than higher frequency, time domain reflectometry (TDR) measurements. In spite of the challenges in separating relaxation and polarization processes, permittivities determined using multiple frequencies (e.g., 50 and 500 MHz) show potential for illuminating soil textural and other soil properties.

  9. An analysis of dielectric properties of synthetic ballast water at frequencies ranging from 300 to 3000 MHz.

    PubMed

    Boldor, Dorin; Ortego, Jeffrey; Rusch, Kelly A

    2008-01-01

    Ballast water presents an important vector for introduction of aquatic invasive species in the coastal waters around the world. Currently there are no established technologies proven to completely eliminate this problem due to the particularities of the ballasting and de-ballasting operations (extremely large volumes of water, efficiency at destroying macro and micro organisms, environmental issues associated with chemical treatments). Continuous microwave heating presents a potential solution to this problem, but the design of suitable applicators depends on the dielectric properties of the ballast water to be processed. The study presented in this paper is focused on the dielectric properties (dielectric constant--epsilon'; dielectric loss--epsilon") of synthetic ballast water inoculated with four organisms at seven different temperatures in the frequency range of 300 to 3000 MHz. The dielectric properties of the mixtures were determined using a network analyzer and a dielectric probe kit using the open-ended coaxial probe method. Numerical analysis was performed on data collected across all frequencies involved with an emphasis placed on F.C.C. allotted frequencies of 433, 915 and 2450 MHz. The dielectric constant was relatively independent of frequency and the organism used, but it showed a remarkable decrease with temperature. The dielectric loss showed an extreme decrease with increasing frequency, marked differences between the different organisms and between different growth stages of the same organism, and a large relatively linear increase with increasing temperature.

  10. An analysis of dielectric properties of synthetic ballast water at frequencies ranging from 300 to 3000 MHz.

    PubMed

    Boldor, Dorin; Ortego, Jeffrey; Rusch, Kelly A

    2008-01-01

    Ballast water presents an important vector for introduction of aquatic invasive species in the coastal waters around the world. Currently there are no established technologies proven to completely eliminate this problem due to the particularities of the ballasting and de-ballasting operations (extremely large volumes of water, efficiency at destroying macro and micro organisms, environmental issues associated with chemical treatments). Continuous microwave heating presents a potential solution to this problem, but the design of suitable applicators depends on the dielectric properties of the ballast water to be processed. The study presented in this paper is focused on the dielectric properties (dielectric constant--epsilon'; dielectric loss--epsilon") of synthetic ballast water inoculated with four organisms at seven different temperatures in the frequency range of 300 to 3000 MHz. The dielectric properties of the mixtures were determined using a network analyzer and a dielectric probe kit using the open-ended coaxial probe method. Numerical analysis was performed on data collected across all frequencies involved with an emphasis placed on F.C.C. allotted frequencies of 433, 915 and 2450 MHz. The dielectric constant was relatively independent of frequency and the organism used, but it showed a remarkable decrease with temperature. The dielectric loss showed an extreme decrease with increasing frequency, marked differences between the different organisms and between different growth stages of the same organism, and a large relatively linear increase with increasing temperature. PMID:19227068

  11. Cooperative Investigation of Relationship Between Static and Fatigue Properties of Wrought N-155 Alloy at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    1956-01-01

    Report presents the correlation of extensive data obtained relating properties of wrought n-155 alloy under static, combined static and dynamic, and complete reversed dynamic stress conditions. Time period for fracture ranged from 50 to 500 hours at room temperature, 1,000 degrees, 1,200 degrees, and 1,500 degrees F.

  12. Stochastic system identification of skin properties: linear and wiener static nonlinear methods.

    PubMed

    Chen, Yi; Hunter, Ian W

    2012-10-01

    Wiener static nonlinear system identification was used to study the linear dynamics and static nonlinearities in the response of skin and underlying tissue under indentation in vivo. A device capable of measuring the dynamic mechanical properties of bulk skin tissue was developed and it incorporates a custom-built Lorentz force actuator that measures the dynamic compliance between the input force (<12 N) and the output displacement (<20 mm). A simple linear stochastic system identification technique produced a variance accounted for (VAF) of 75-81% and Wiener static nonlinear techniques increased the VAF by 5%. Localized linear techniques increased the VAF to 85-95% with longer tests. Indentation experiments were conducted on 16 test subjects to determine device sensitivity and repeatability. Using the device, the coefficient of variation of test metrics was found to be as low as 2% for a single test location. The measured tissue stiffness was 300 N/m near the surface and 4.5 kN/m for high compression. The damping ranged from 5 to 23 N s/m. The bulk skin properties were also shown to vary significantly with gender and body mass index. The device and techniques used in this research can be applied to consumer product analysis, medical diagnosis and tissue research.

  13. MAPPING OF RESERVOIR PROPERTIES AND FACIES THROUGH INTEGRATION OF STATIC AND DYNAMIC DATA

    SciTech Connect

    Albert C. Reynolds; Dean S. Oliver; Yannong Dong; Ning Liu; Guohua Gao; Fengjun Zhang; Ruijian Li

    2004-12-01

    Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. The volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade. The techniques developed in this research will make it easier to use all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. In this project, we have developed computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Specifically, we have developed methods for adjusting porosity and permeability fields to match both production and time-lapse seismic data and have also developed a procedure to adjust the locations of boundaries between facies to match production data. In all cases, the history matched rock property fields are consistent with a prior model based on static data and geologic information. Our work also indicates that it is possible to adjust relative permeability curves when history matching production data.

  14. Thickness-dependent dielectric properties of nanoscale Pt/(Pb,Ba)ZrO 3/BaPbO 3 capacitors

    NASA Astrophysics Data System (ADS)

    Wu, Lin-Jung; Wu, Jenn-Ming

    2007-10-01

    Lead barium zirconate (PBZ) thin films on BaPbO 3(BPO)/Pt/Ti/SiO 2/Si substrates have been prepared by rf-magnetron sputtering at 500 °C. The orientation of PBZ film changes from random to (1 1 1)-prefer oriented when the thickness increases. The grain size increases with increasing PBZ thickness. The dielectric properties are greatly suppressed when the thickness of dielectrics decreases. The dielectric constant and tunability decrease from 536% and 49.1% to 205% and 22.7%, respectively, when the thickness of PBZ decreases from 323 to 62 nm. The origins of the collapsed dielectric behavior are discussed. The variation of dielectric properties with film thickness can be interpreted by (a) antiferroelectric layer at PBZ/BPO interface, (b) dead layer at Pt/PBZ interface, and (c) grain boundary dead layers.

  15. Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate

    SciTech Connect

    P, Sharmila P; Tharayil, Nisha J.

    2014-10-15

    Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.

  16. Room temperature optical and dielectric properties of Sr and Ni doped lanthanum ferrite nanoparticles

    SciTech Connect

    Naseem, Swaleha; Khan, Wasi Singh, B. R.; Naqvi, A. H.

    2015-06-24

    Strontium and nickel doped lanthanum ferrite (LaFeO{sub 3}) nanoparticles (NPs) were prepared reverse micelle (RM) and calcinated at 700°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible spectroscopy and band gap energy was estimated 3.89 eV. Room temperature dielectric constant (ε’) decreases abruptly at lower frequencies owing to the charge transport relaxation time. The observed behavior of the dielectric properties can be attributed on the basis of Koop’s theory based on Maxwell-Wagner’s two layer model in studied nanoparticles.

  17. Optical properties of nanowire dimers with a spatially nonlocal dielectric function.

    PubMed

    McMahon, Jeffrey M; Gray, Stephen K; Schatz, George C

    2010-09-01

    We study the optical spectra and electromagnetic field enhancements around cylindrical and triangular Ag nanowire dimers, allowing for a spatially nonlocal dielectric function that partially accounts for quantum mechanical effects. For the triangular structures, we pay particular attention to how these properties depend on the sharpness of the nanowire's tips. We demonstrate that significant differences exist from classical electrodynamics that employs a more common, spatially local dielectric function. These differences are shown to arise from the optical excitation of volume plasmons inside of the structures, analogous to one-particle quantum mechanical states, which lead to complex and striking patterns of material polarization. These results are important for further understanding the optical properties of structures at the nanoscale and have implications for numerous physical processes, such as surface-enhanced Raman scattering.

  18. On the Dielectric Properties of the Martian-like Surface Sediments

    NASA Technical Reports Server (NTRS)

    Heggy, E.; Clifford, S. M.; Morris, R. V.; Paillou, P.; Ruffie, G.

    2004-01-01

    We have undertaken laboratory electromagnetic characterization of the total set of minerals identified by TES on the Martian surface in order to investigate experimentally the dielectric properties of the sediments covering it in the frequency range from 1 to 30 MHz. Volcanic Rocks with a well defined mineralogy and petrology from potential terrestrial analogues sites have also been included in the study. Our primary objective is to evaluate the range of electrical and magnetic losses that may be encountered by the various Radar sounding and imaging experiments dedicated to map the Martian subsurface searching for underground water. The electromagnetic properties of these Mars-like materials will be presented as a function of various geophysical parameters, such as porosity, bulk density and temperature. The secondary objective, is to locate regions were surface dielectric conditions are suitable for subsurface sounding.

  19. Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate

    NASA Astrophysics Data System (ADS)

    P, Sharmila P.; Tharayil, Nisha J.

    2014-10-01

    Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.

  20. Electronic, Mechanical, and Dielectric Properties of Two-Dimensional Atomic Layers of Noble Metals

    NASA Astrophysics Data System (ADS)

    Kapoor, Pooja; Kumar, Jagdish; Kumar, Arun; Kumar, Ashok; Ahluwalia, P. K.

    2016-08-01

    We present density functional theory-based electronic, mechanical, and dielectric properties of monolayers and bilayers of noble metals (Au, Ag, Cu, and Pt) taken with graphene-like hexagonal structure. The Au, Ag, and Pt bilayers stabilize in AA-stacked configuration, while the Cu bilayer favors the AB stacking pattern. The quantum ballistic conductance of the noble-metal mono- and bilayers is remarkably increased compared with their bulk counterparts. Among the studied systems, the tensile strength is found to be highest for the Pt monolayer and bilayer. The noble metals in mono- and bilayer form show distinctly different electron energy loss spectra and reflectance spectra due to the quantum confinement effect on going from bulk to the monolayer limit. Such tunability of the electronic and dielectric properties of noble metals by reducing the degrees of freedom of electrons offers promise for their use in nanoelectronics and optoelectronics applications.

  1. Nondestructive approach for measuring temperature-dependent dielectric properties of epoxy resins.

    PubMed

    Akhtar, M Jaleel; Feher, Lambert E; Thumm, Manfred

    2008-01-01

    A practical method for measuring the complex relative permittivity of epoxy resins and other viscous liquids over a wide temperature range in S-band is presented. The method involves inserting a hot glass tube, filled with the liquid-under-test (LUT), into a length of WR-340 rectangular waveguide connected between two ports of a Vector Network Analyzer, which measures the reflection and transmission coefficients at 2.45 GHz. The heating arrangement consists of a temperature-controlled glycol bath, where the LUT-filled glass tube is placed. The dielectric properties are determined using an optimization routine, which minimizes the error between the theoretical and measured scattering coefficient data. The theoretical values of the scattering coefficient data are computed with the help of a numerical 3-D electromagnetic field simulator, the CST Microwave Studio. The dielectric properties of the empty glass tube (required by the simulation code) are also measured using the above methodology.

  2. Dielectric, ferroelectric and mechanical Properties of Microwave Sintered Bi based High temperature Piezoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Angalakurthi, Rambabu; Raju, K. C. James

    2011-10-01

    The sintering of advanced ceramics requires fast heating in order to avoid both grain growth and inter diffusion. In this context, the microwave sintering is a powerful method since it enables sintering in a short time. This paper reports the synthesis and characterization of Strontium Bismuth Titanate (SBTi) system. The material powder was prepared by solid state route and sintering was carried out by both conventional and microwave furnaces. Morphological, dielectric, ferroelectric and mechanical properties were studied for both samples. The dielectric constant and loss tangent of the conventional and microwave sintered samples have ranged between (185-195) & (0.005-0.007) and (195-220) & (0.004-0.006) respectively when measured at 1MHz frequency. The microwave sintering of the SBTi ceramics leads to higher densification (97% of the theoretical density), fine microstructure, and good mechanical and ferroelectric properties in much shorter duration of time compared to that of the conventional sintering process.

  3. Effects of γ-radiation on dielectric properties of LDPE-Al2O3 nanocomposites

    NASA Astrophysics Data System (ADS)

    Ciuprina, Florin; Zaharescu, Traian; Pleşa, Ilona

    2013-03-01

    Until now several methods for processing and characterization have been tested, and some theories and models have been proposed for these materials having a huge nanofiller-polymer interface area which seems to be the main responsible for their unique properties. The accelerated testing by irradiation of LDPE has been extensively studied in order to assess optimized formulation. The present paper characterizes LDPE modified with Al2O3 nanoparticles. The dispersed nanofiller was added in various concentrations (2, 5 and 10 wt%). The accelerated aging under γ-irradiation was accomplished for evaluation of material behavior to hard stressing environment. Dielectric properties (real part of the permittivity and tan delta) and oxidation resistance were discussed. An improvement of the dielectric losses is noticed for the tested nanocomposites at a radiation dose up to 20 kGy. The radiochemical stability studied by chemiluminescence provides satisfactory stability in the correlation with slight modification of basis polymer due to the inert feature of filler.

  4. Fabrication of Ag-Nanorods/Polyimide Nanocomposites and Their Thermal, Mechanical, Electrical, and Dielectric Properties.

    PubMed

    Weng, Ling; Yan, Li-Wen; Li, Hong-Xia; Liu, Li-Zhu

    2016-02-01

    Silver nanorods/polyimide (Ag-NRs/PI) nanocomposites with high conductivity (An order of magnitude higher than pure PI), frequency-independent dielectric permittivity (3.8-4.2) and low dielectric loss (<0.05) were prepared by an in-situ polymerization process. Ag-nanorods with a mean width of approximately 300 nm and an average length over 8 microm were synthesized in the presence of polyvinylpyrrolidone (PVP) and NaCl by polyol process. SEM images showed that metallic Ag-nanorods were well dispersed in PI matrix. The structure of Ag-NRs was not destroyed or changed in nanocomposite films and the order of PI molecular chains was maintained as well. The orientation of the Ag-NRs in the PI matrix improved the mechanical properties of nanocomposite films. TGA results showed that the thermal property of nanocomposite films was almost as good as pure PI. PMID:27433637

  5. Influence of Cr2O3 ions on dielectric properties of lead gallium phosphate glass system

    NASA Astrophysics Data System (ADS)

    Little Flower, G.; Sahaya Baskaran, G.; Gandhi, Y.; Srinivasa Rao, Ch

    2009-07-01

    PbO-Ga2O3-P2O5 glasses containing different concentrations of Cr2O3 ranging from 0 to 1.0 mol % were prepared. The differential thermal analysis and dielectric properties (viz., constant epsilon', loss tan δ, a.c. conductivity σac over a wide range of frequency and temperature) have been studied as a function of the concentration of chromium ions. An anomaly has been observed in the dielectric properties of these glasses when the concentration of Cr2O3 is about 0.4 mol %. This anomaly has been explained in the light of different oxidation states of chromium ions in these glasses.

  6. Ferroelectric Bi3.3La0.7Ti3O12-poly (vinylidene-fluoride) composites with enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Sumit; Paul, Joginder; Chand, Subhash; Raina, K. K.; Kumar, Ravi

    2015-05-01

    Ferroelectric ceramic polymer composites of Poly (vinylidene-fluoride) and Bi3.3La0.7Ti3O12 (BLT) were prepared by simple solution casting method. The structural, dielectric and morphological properties were studied systemically. The dielectric results showed that the composites have high dielectric constant with very low dielectric loss. At room temperature, a 10 wt% loaded BLT/PVDF composite film showed a dielectric constant of 109.48, which is six times greater in comparison to pure PVDF. Morphological studies reveal the formation of spherulattic structure of PVDF. These lead free composites with enhanced dielectric properties may prove tremendous potential for energy storage devices.

  7. Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Ameli, A.; Nofar, M.; Saniei, M.; Hossieny, N.; Park, C. B.; Pötschke, P.

    2015-05-01

    A combination of high dielectric permittivity (ɛ') and low dielectric loss (tan δ) is required for charge storage applications. In percolative systems such as conductive polymer composites, however, obtaining high ɛ' and low tan δ is very challenging due to the sharp insulation-conduction transition near the threshold region. Due to the particular arrangement of conductive fillers induced by both foaming and injection molding processes, they may address this issue. Therefore, this work evaluates the application of foam injection molding process in fabricating polymer nanocomposites for energy storage. Polypropylene-multiwalled carbon nanotubes (PP-MWCNT) composites were prepared by melt mixing and foamed in an injection molding process. Electrical conductivity (σ), ɛ' and tan δ were then characterized. Also, scanning and transmission electron microscopy (SEM and TEM) was used to investigate the carbon nanotube's arrangement as well as cellular morphology. The results showed that foam injection-molded composites exhibited highly superior dielectric properties to those of solid counterparts. For instance, foamed samples had ɛ'=68.3 and tan δ =0.05 (at 1.25 vol.% MWCNT), as opposed to ɛ'=17.8 and tan δ=0.04 in solid samples (at 2.56 vol.% MWCNT). The results of this work reveal that high performance dielectric nanocomposites can be developed using foam injection molding technologies for charge storage applications.

  8. Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

    SciTech Connect

    Ameli, A.; Nofar, M.; Saniei, M.; Hossieny, N.; Park, C. B.; Pötschke, P.

    2015-05-22

    A combination of high dielectric permittivity (ε′) and low dielectric loss (tan δ) is required for charge storage applications. In percolative systems such as conductive polymer composites, however, obtaining high ε′ and low tan δ is very challenging due to the sharp insulation-conduction transition near the threshold region. Due to the particular arrangement of conductive fillers induced by both foaming and injection molding processes, they may address this issue. Therefore, this work evaluates the application of foam injection molding process in fabricating polymer nanocomposites for energy storage. Polypropylene-multiwalled carbon nanotubes (PP-MWCNT) composites were prepared by melt mixing and foamed in an injection molding process. Electrical conductivity (σ), ε′ and tan δ were then characterized. Also, scanning and transmission electron microscopy (SEM and TEM) was used to investigate the carbon nanotube’s arrangement as well as cellular morphology. The results showed that foam injection-molded composites exhibited highly superior dielectric properties to those of solid counterparts. For instance, foamed samples had ε′=68.3 and tan δ =0.05 (at 1.25 vol.% MWCNT), as opposed to ε′=17.8 and tan δ=0.04 in solid samples (at 2.56 vol.% MWCNT). The results of this work reveal that high performance dielectric nanocomposites can be developed using foam injection molding technologies for charge storage applications.

  9. Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications.

    PubMed

    Kaygili, Omer; Ates, Tankut; Keser, Serhat; Al-Ghamdi, Ahmed A; Yakuphanoglu, Fahrettin

    2014-08-14

    The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA. PMID:24747847

  10. Dielectric, electrical transport and magnetic properties of Er3+substituted nanocrystalline cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.; Ramana, C. V.

    2016-11-01

    Erbium substituted cobalt ferrite (CoFe2-xErxO4; x=0.0-0.2, referred to CFEO) materials were synthesized by sol-gel auto-combustion method. The effect of erbium (Er3+) substitution on the crystal structure, dielectric, electrical transport and magnetic properties of cobalt ferrite is evaluated. CoFe2-xErxO4 ceramics exhibit the spinel cubic structure without any impurity phase for x≤0.10 whereas formation of the ErFeO3 orthoferrite secondary phase was observed for x≥0.15. All the CFEO samples demonstrate the typical hysteresis (M-H) behavior with a decrease in magnetization as a function of Er content due to weak superexchange interaction. The frequency (f) dependent dielectric constant (ε‧) revealed the usual dielectric dispersion. The ε‧-f dispersion (f=20 Hz to 1 MHz) fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived are ∼10-4 s and ∼0.61(±0.04), respectively. Electrical and dielectric studies indicate that ε‧ increases and the dc electrical resistivity decreases as a function of Er content (x≤0.15). Complex impedance analyses confirm only the grain interior contribution to the conduction process. Temperature dependent electrical transport and room temperature ac conductivity (σac) analyses indicate the semiconducting nature and small polaron hopping.

  11. Effects of Nitrogen Doping on X-band Dielectric Properties of Carbon Nanotube/Polymer Nanocomposites.

    PubMed

    Arjmand, Mohammad; Sundararaj, Uttandaraman

    2015-08-19

    Nitrogen-doped and undoped carbon nanotubes (CNTs) were synthesized by selective passing of source and carrier gases (ethane, ammonia, hydrogen, and argon) over an alumina-supported iron catalyst in a quartz tubular reactor at 650 °C. Synthesized CNTs were mixed with polyvinylidene fluoride with an Alberta polymer asymmetric minimixer (APAM) mixer at 240 °C and 235 rpm, and the resulting nanocomposites were compression molded. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and thermogravimetric analysis (TGA) techniques revealed that introducing nitrogen into the crystalline structure of CNTs resulted in higher crystalline defects. Dielectric measurements showed that nitrogen doping significantly increased dielectric permittivity for a known dielectric loss. This was ascribed to the role of the crystalline defects and nitrogen atoms, which acted as polarizing centers, blocked the nomadic charges, polarized them, and prevented them from moving along CNTs. The obtained results introduce nitrogen doping as a regulative tool to control the dielectric properties of CNT/polymer nanocomposites.

  12. Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic

    NASA Astrophysics Data System (ADS)

    Kim, Jae Wook; Khim, Seunghyun; Chun, Sae Hwan; Jo, Y.; Balicas, L.; Yi, H. T.; Cheong, S.-W.; Harrison, N.; Batista, C. D.; Hoon Han, Jung; Hoon Kim, Kee

    2014-07-01

    Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba2CoGe2O7, where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field (H), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field Hc=37.1 T due to enhanced AF quantum fluctuations. When H>Hc, the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter.

  13. Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications.

    PubMed

    Kaygili, Omer; Ates, Tankut; Keser, Serhat; Al-Ghamdi, Ahmed A; Yakuphanoglu, Fahrettin

    2014-08-14

    The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA.

  14. Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz

    SciTech Connect

    Sokhansanj, Shahabaddine; Shrestha, Bijay; Wood, H.C.

    2011-01-01

    Dielectric properties (i.e., permittivity) are essential in designing, simulating, and modeling microwave applications. The permittivity of stacked leaves of alfalfa (Medicago sativa) were measured with a network analyzer and a coaxial probe, and the effect of moisture content (MC: 12% 73% wet basis), frequency (300 MHz to 18 GHz), bound water (Cole Cole dispersion equation), temperature ( 15 C and 30 C), leaf-orientation, and pressure (0 11 kPa) were investigated. The measured permittivity increased with MC. A critical moisture level (CML) of 23% was reported, below which the permittivity decreased with increasing frequency at 22 C. Above CML and up to 5 GHz, the dielectric constants followed the Cole Cole dispersion, and the dielectric loss factors consisted of ionic and bound water losses. Above 5 GHz, the behavior of the dielectric constant was similar to that of free water, and the polar losses became dominant. Above 0 C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0 C, it was dominated by nonfreezing bound and unfrozen supercooled moistures. The relaxation parameters and the optimum pressure (9 kPa) for the leaf measurements were determined. The effects of variations among the samples, and their orientations had negligible effects on the measured permittivity.

  15. Charge trapping properties of alternative high-kappa dielectrics in MOS devices

    NASA Astrophysics Data System (ADS)

    Zhou, Xing

    High-kappa dielectrics are promising candidates to replace SiO 2 in advanced integrated circuits in future space systems. Studies of the effects of ionizing radiation and bias-temperature stress (BTS) on high-kappa dielectrics were performed. Trapped charge densities are evaluated as functions of temperature and stress time. Prior radiation exposure enhances BTS-induced degradation in these devices. Worst-case responses in combined effects are positive (or zero) bias irradiation followed by NBTS for HfO2-based devices. Degradation due to oxide or interface trap-charge changes in magnitude with the bias polarity during switched-bias annealing either after irradiation or constant voltage stress (CVS). This demonstrates that metastable electron trapping (dominant during post-rad annealing) and hydrogen transport and reactions (dominant during post-CVS annealing) in the near-interfacial dielectric layers play significant roles in the defect formation process. Additional defect growth with time was observed as a result of additional charge injection through the gate stacks during the annealing process. These results provide insights into fundamental trapping properties of high-kappa dielectrics and can be used to help predict long-term reliability of these devices.

  16. Dielectric properties of halloysite and halloysite-formamide intercalate

    SciTech Connect

    Adamczyk, M. Rok, M.; Wolny, A.; Orzechowski, K.

    2014-01-14

    Due to a high increase in electromagnetic pollution, the protection from non-ionizing electromagnetic radiation (EMR) represents an important problem of contemporary environmental science. We are searching for natural materials with the potential for EMR screening. We have discovered that hydro-halloysite has interesting properties as an EMR absorber. Unfortunately, it is a very unstable material. Drying it for even a short period of time leads to the loss of desired properties. In the paper, we have demonstrated that the intercalation of halloysite (the process of introducing guest molecules into the mineral structure) makes it possible to recover the ability to absorb an electromagnetic wave and obtain a promising material for electromagnetic field shielding applications.

  17. Dielectric properties of halloysite and halloysite-formamide intercalate

    NASA Astrophysics Data System (ADS)

    Adamczyk, M.; Rok, M.; Wolny, A.; Orzechowski, K.

    2014-01-01

    Due to a high increase in electromagnetic pollution, the protection from non-ionizing electromagnetic radiation (EMR) represents an important problem of contemporary environmental science. We are searching for natural materials with the potential for EMR screening. We have discovered that hydro-halloysite has interesting properties as an EMR absorber. Unfortunately, it is a very unstable material. Drying it for even a short period of time leads to the loss of desired properties. In the paper, we have demonstrated that the intercalation of halloysite (the process of introducing guest molecules into the mineral structure) makes it possible to recover the ability to absorb an electromagnetic wave and obtain a promising material for electromagnetic field shielding applications.

  18. Dielectric properties of vanadium doped barium titanate synthesized via high-energy ball milling

    NASA Astrophysics Data System (ADS)

    Dulian, Piotr; Bąk, Wojciech; Wieczorek-Ciurowa, Krystyna; Kajtoch, Czesław

    2014-06-01

    The study shows the advisability of using a mechanochemical synthesis method, based on a high-energy planetary ball milling, to a modification of barium titanate by a vanadium doping. This method improves useful properties of BaTi0:95V0:05O3 as a capacitor material. It has a high value of electric permittivity ɛ' in the wide range of temperature and low dielectric losses ɛ″ as well as a low electrical conductivity.

  19. Dielectric properties of doped titanates of transition metals in the millimeter-wavelength range

    NASA Astrophysics Data System (ADS)

    Rinkevich, A. B.; Perov, D. V.; Kuznetsov, E. A.; Pakhomov, Ya. A.; Ryabkov, Yu. I.

    2016-06-01

    Dielectric properties of ceramic titanates of nickel, cobalt, and manganese and their isomorphically substituted solid solutions are studied. Iron and magnesium are used as dopants. Original methods for solid-state synthesis of titanates allow variations in the dispersity of products. The structure and phase composition of products are analyzed. Microwave measurements of permittivity are performed in a frequency interval of 12-38 GHz. Real and imaginary parts of the permittivities of titanates are determined.

  20. Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth.

    PubMed

    Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A; Galli, Giulia

    2013-04-23

    Water is a major component of fluids in the Earth's mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water-rock interactions and, in general, our understanding of aqueous fluids below the Earth's crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth's upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)--insoluble in water under ambient conditions--becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The Earth's deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones.

  1. Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

    PubMed

    Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

    2016-04-13

    Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

  2. Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

    PubMed

    Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

    2016-04-13

    Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field. PMID:27040315

  3. Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Yuan, W. X.; Hark, S. K.

    2010-03-01

    CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

  4. Time domain dielectric spectroscopy of nanosecond pulsed electric field induced changes in dielectric properties of pig whole blood.

    PubMed

    Zhuang, Jie; Kolb, Juergen F

    2015-06-01

    The dielectric spectra of fresh pig whole blood in the β-dispersion range after exposure to 300-nanosecond pulsed electric fields (nsPEFs) with amplitude higher than the supra-electroporation threshold for erythrocytes were recorded by time domain reflectometry dielectric spectroscopy. The implications of the dielectric parameters on the dynamics of post-pulse pore development were discussed in light of the Cole-Cole relaxation model. The temporal development of the Cole-Cole parameters indicates that nsPEFs induced significant poration and swelling of erythrocytes within the first 5 min. The results also show that the majority of erythrocytes could not fully recover from supra-electroporation up to 30 min. The findings of this study suggest that time domain dielectric spectroscopy is a promising label-free and real-time physiological measuring technique for nsPEF-blood related biomedical applications, capable of following the conformational and morphological changes of cells.

  5. Tailoring the dipole properties in dielectric polymers to realize high energy density with high breakdown strength and low dielectric loss

    SciTech Connect

    Thakur, Yash; Lin, Minren; Wu, Shan; Zhang, Q. M. E-mail: qxz1@psu.edu; Cheng, Zhaoxi; Jeong, D.-Y. E-mail: qxz1@psu.edu

    2015-03-21

    High energy density polymer materials are desirable for a broad range of modern power electronic systems. Here, we report the development of a new class of polymer dielectrics based on polyurea and polythiourea, which possess high thermal stability. By increasing the dipole density, the dielectric constant of meta-phenylene polyurea and methylene polythiourea can be increased to 5.7, compared with aromatic polyurea and aromatic polythiourea, which have a dielectric constant in the range of 4.1–4.3. The random dipoles with high dipolar moment and amorphous structure of these polyurea and polythiourea based polymers provide strong scattering to the charge carriers, resulting in low losses even at high electric fields. Consequently, this new class of polymers exhibit a linear dielectric response to the highest field measured (>700 MV/m) with a high breakdown strength, achieving high energy density (>13 J/cm{sup 3}) with high efficiency (>90%)

  6. Complex dielectric properties of anhydrous polycrystalline glucose in the terahertz region

    NASA Astrophysics Data System (ADS)

    Sun, P.; Liu, W.; Zou, Y.; Jia, Qiong Z.; Li, Jia Y.

    2015-03-01

    We utilized terahertz time-domain spectroscopy (THz-TDS) to investigate the complex dielectric properties of solid polycrystalline material of anhydrous glucose (D-(+)-glucose with purity >99.9%). THz transmission spectra of samples were measured from 0.2 to 2.2 THz. The samples were prepared into tablets with thicknesses of 0.362, 0.447, 0.504, 0.522 and 0.626 mm, respectively. The imaginary part of the complex dielectric function of polycrystalline glucose showed that there were multiple characteristic absorption peaks at 1.232, 1.445, 1.522, 1.608, 1.811 and 1.987 THz, respectively. Moreover, for a given characteristic absorption peak, the real part of the complex dielectric function showed anomalous dispersion within the full width half maximum (FWHM) of the absorption peak. Both finite difference time-domain (FDTD) numerical simulations and experimental results showed that the complex dielectric function of anhydrous polycrystalline glucose fits well with the Lorentz dielectric mode. The plasma oscillation frequency was below the frequency of the light waves suggesting that the light waves passed through the polycrystalline glucose tablets. Calculations based on density functional theory (DFT) showed that the characteristic absorption peaks of polycrystalline glucose originated mainly from collective intermolecular vibrations such as hydrogen bonds and crystal phonon modes. The THz radiation can excite the vibrational or rotational energy levels of the biological macromolecules. This leads to changes in their spatial configuration or interactions. This study showed that THz-TDS has potential applications in biological and pharmaceutical research and food industry.

  7. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation

    SciTech Connect

    Shirakashi, Ryo; Mischke, Miriam; Fischer, Peter; Memmel, Simon; Krohne, Georg; Fuhr, Guenter R.; Zimmermann, Heiko; Sukhorukov, Vladimir L.

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer Electrorotation offers a non-invasive tool for dielectric analysis of fish embryos. Black-Right-Pointing-Pointer The three-shell dielectric model matches the rotation spectra of medaka eggs. Black-Right-Pointing-Pointer The capacitance value suggests a double-membrane structure of yolk envelope. -- Abstract: The Japanese medaka fish, Oryzias latipes, has become a powerful vertebrate model organism in developmental biology and genetics. The present study explores the dielectric properties of medaka embryos during pre-hatching development by means of the electrorotation (ROT) technique. Due to their layered structure, medaka eggs exhibited up to three ROT peaks in the kHz-MHz frequency range. During development from blastula to early somite stage, ROT spectra varied only slightly. But as the embryo progressed to the late-somite stage, the ROT peaks underwent significant changes in frequency and amplitude. Using morphological data obtained by light and electron microscopy, we analyzed the ROT spectra with a three-shell dielectric model that accounted for the major embryonic compartments. The analysis yielded a very high value for the ionic conductivity of the egg shell (chorion), which was confirmed by independent osmotic experiments. A relatively low capacitance of the yolk envelope was consistent with its double-membrane structure revealed by transmission electron microscopy. Yolk-free dead eggs exhibited only one co-field ROT peak, shifted markedly to lower frequencies with respect to the corresponding peak of live embryos. The dielectric data may be useful for monitoring the development and changes in fish embryos' viability/conditions in basic research and industrial aquaculture.

  8. Structural, dielectric, and optical properties of yttrium calcium borate glasses

    NASA Astrophysics Data System (ADS)

    Santos, Cristiane N.; De Sousa Meneses, Domingos; Echegut, Patrick; Neuville, Daniel R.; Hernandes, Antonio C.; Ibanez, Alain

    2009-04-01

    Structural and optical properties of stable glasses in the Y2O3-CaO-B2O3 system, containing the same Y/Ca ratio as the YCa4O(BO3)3 (YCOB) crystal, were determined from Raman and reflectance infrared spectroscopy. Changes in optical functions with composition are associated with an increase in the number of non-bridging oxygen and to calcium/yttrium oxides content. Refractive indexes values (from 1.597 to 1.627 at λ =2 μm) are in good agreement with those of the YCOB crystal, an indication that these glasses are potential candidates for optical applications due to their ease of shaping as large bulk samples or fibers.

  9. Dynamical- and static-disorder effects on charge transport property of organic semiconductors

    NASA Astrophysics Data System (ADS)

    Ishii, Hiroyuki; Kobayashi, Nobuhiko; Hirose, Kenji

    2014-03-01

    In comparison with inorganic materials, electron transfer energy of typical organic semiconductors is small in the range of 10 - 100meV, which is comparable to the magnitude of dynamical disorder of transfer energy originating from the thermal fluctuations of molecular motions. Furthermore, the static disorder inevitably exists in realistic organic devices and disturbs the transport of charge carrier. To clarify the influence of the dynamical and static disorders on the mobility, we employ a realistic static-disorder potential, which is deduced from the data obtained by electron-spin-resonance spectroscopy. We evaluate the carrier mobilities of pentacene and rubrene semiconductors under the realistic situation, using our time-dependent wave-packet diffusion method. In this methodology, we carry out the quantum-mechanical time-evolution calculations of wave packets and the classical molecular dynamics simulations simultaneously. We clarify the relation between the charge transport property and these disorders. We will talk about these results in my presentation. This work was supported by JST, PRESTO, and a Grant-in-Aid for Scientific Research from the JSPS.

  10. Si dielectric function in a local basis representation: Optical properties, local field effects, excitons, and stopping power

    NASA Astrophysics Data System (ADS)

    Gómez, M.; González, P.; Ortega, J.; Flores, F.

    2014-11-01

    An atomiclike basis representation is used to analyze the dielectric function ɛ (q ⃗+G ⃗,q ⃗+G⃗';ω ) of Si. First, we show that a s p3d5 local basis set yields good results for the electronic band structure of this crystal and, then, we analyze the Si optical properties including local field and excitonic effects. In our formulation, we follow Hanke and Sham [W. Hanke and L. J. Sham, Phys. Rev. B 12, 4501 (1975), 10.1103/PhysRevB.12.4501; Phys. Rev. B 21, 4656 (1980), 10.1103/PhysRevB.21.4656], and introduce excitonic effects using a many-body formulation that incorporates a static screened electron-hole interaction. Dynamical effects in this interaction are also analyzed and shown to introduce non-negligible corrections in the optical spectrum. Our results are found in reasonable agreement with the experimental evidence and with other theoretical results calculated with the computationally more demanding plane-wave representation. Finally, calculations for the stopping power of Si are also presented.

  11. Dielectric properties of novel polyurethane-PZT-graphite foam composites

    NASA Astrophysics Data System (ADS)

    Tolvanen, Jarkko; Hannu, Jari; Nelo, Mikko; Juuti, Jari; Jantunen, Heli

    2016-09-01

    Flexible foam composite materials offer multiple benefits to future electronic applications as the rapid development of the electronics industry requires smaller, more efficient, and lighter materials to further develop foldable and wearable applications. The aims of this work were to examine the electrical properties of three- and four-phase novel foam composites in different conditions, find the optimal mixture for four-phase foam composites, and study the combined effects of lead zirconate titanate (PZT) and graphite fillers. The flexible and highly compressible foams were prepared in a room-temperature mixing process using polyurethane, PZT, and graphite components as well as their combinations, in which air acted as one phase. In three-phase foams the amount of PZT varied between 20 and 80 wt% and the amount of graphite, between 1 and 15 wt%. The four-phase foams were formed by adding 40 wt% of PZT while the amount of graphite ranged between 1 and 15 wt%. The presented results and materials could be utilized to develop new flexible and soft sensor applications by means of material technology.

  12. Dielectric properties of novel polyurethane–PZT–graphite foam composites

    NASA Astrophysics Data System (ADS)

    Tolvanen, Jarkko; Hannu, Jari; Nelo, Mikko; Juuti, Jari; Jantunen, Heli

    2016-09-01

    Flexible foam composite materials offer multiple benefits to future electronic applications as the rapid development of the electronics industry requires smaller, more efficient, and lighter materials to further develop foldable and wearable applications. The aims of this work were to examine the electrical properties of three- and four-phase novel foam composites in different conditions, find the optimal mixture for four-phase foam composites, and study the combined effects of lead zirconate titanate (PZT) and graphite fillers. The flexible and highly compressible foams were prepared in a room-temperature mixing process using polyurethane, PZT, and graphite components as well as their combinations, in which air acted as one phase. In three-phase foams the amount of PZT varied between 20 and 80 wt% and the amount of graphite, between 1 and 15 wt%. The four-phase foams were formed by adding 40 wt% of PZT while the amount of graphite ranged between 1 and 15 wt%. The presented results and materials could be utilized to develop new flexible and soft sensor applications by means of material technology.

  13. Dielectric properties of lava flows west of Ascraeus Mons, Mars

    USGS Publications Warehouse

    Carter, L.M.; Campbell, B.A.; Holt, J.W.; Phillips, R.J.; Putzig, N.E.; Mattei, S.; Seu, R.; Okubo, C.H.; Egan, A.F.

    2009-01-01

    The SHARAD instrument on the Mars Reconnaissance Orbiter detects subsurface interfaces beneath lava flow fields northwest of Ascraeus Mons. The interfaces occur in two locations; a northern flow that originates south of Alba Patera, and a southern flow that originates at the rift zone between Ascraeus and Pavonis Montes. The northern flow has permittivity values, estimated from the time delay of echoes from the basal interface, between 6.2 and 17.3, with an average of 12.2. The southern flow has permittivity values of 7.0 to 14.0, with an average of 9.8. The average permittivity values for the northern and southern flows imply densities of 3.7 and 3.4 g cm-3, respectively. Loss tangent values for both flows range from 0.01 to 0.03. The measured bulk permittivity and loss tangent values are consistent with those of terrestrial and lunar basalts, and represent the first measurement of these properties for dense rock on Mars. Copyright 2009 by the American Geophysical Union.

  14. Static and dynamic magnetic properties of cubic Mn-Co-Ga Heusler films

    SciTech Connect

    Demiray, A. S. Iihama, S.; Naganuma, H.; Oogane, M.; Ando, Y.; Kubota, T.; Mizukami, S. Miyazaki, T.

    2014-05-07

    We investigated the static and dynamic magnetic properties of thin films of Mn-Co-Ga Heusler compound. Gilbert damping and exchange stiffness constants of the films were evaluated by using the ferromagnetic resonance technique in the X-band regime (f = 9.4 GHz). By analyzing the experimental spectra, magnetic parameters of the films such as the line width and the Gilbert damping were deduced, and the exchange stiffness constant was estimated from the perpendicular standing spin-wave resonance. The Gilbert damping constant was estimated to be 0.017 in a specific film composition. The exchange stiffness constant showed a linear dependence on the film composition.

  15. Investigation of structural, optical, electrical and dielectric properties of catalytic sprayed hausmannite thin film

    SciTech Connect

    Larbi, T.; Ouni, B.; Boukhachem, A.; Boubaker, K. Amlouk, M.

    2014-12-15

    Hausmannite Mn{sub 3}O{sub 4} thin film have been synthesized using spray pyrolysis method. These films are characterized using X-ray diffraction (XRD), atomic force microscope AFM, UV–vis–NIR spectroscopy and impedance spectroscopy. XRD study confirms the tetragonal structure of the as-deposited films with lattice parameters, a = 5.1822 Å and c = 9.4563 Å and a grain size of about 56 nm. UV–vis–NIR spectroscopy was further used to estimate optical constants such as extinction coefficient, refractive index, band gap and Urbach energy. Moreover, impedance spectroscopy analysis was employed to estimate electrical and dielectrical properties of the sprayed thin films. The activation energy values deduced from DC conductivity and relaxation frequency were almost the same, revealing that the transport phenomena is thermally activated by hopping between localized states. The AC conductivity is found to be proportional to ω{sup s}. The temperature dependence of the AC conductivity and the frequency exponent, s was reasonably well interpreted in terms of the correlated barrier-hopping CBH model. The dielectric properties were sensitive to temperature and frequency. The study of the electrical modulus indicated that the charge carrier was localized. Experimental results concerning optical constants as Urbach energy, dielectric constant, electric modulus and AC and DC conductivity were discussed in terms of the hopping model as suggested by Elliott.

  16. Molecular dynamics simulation of liquid water confined inside graphite channels: dielectric and dynamical properties.

    PubMed

    Martí, J; Nagy, G; Guàrdia, E; Gordillo, M C

    2006-11-30

    Electric and dielectric properties and microscopic dynamics of liquid water confined between graphite slabs are analyzed by means of molecular dynamics simulations for several graphite-graphite separations at ambient conditions. The electric potential across the interface shows oscillations due to water layering, and the overall potential drop is about -0.28 V. The total dielectric constant is larger than the corresponding value for the bulklike internal region of the system. This is mainly due to the preferential orientations of water nearest the graphite walls. Estimation of the capacitance of the system is reported, indicating large variations for the different adsorption layers. The main trend observed concerning water diffusion is 2-fold: on one hand, the overall diffusion of water is markedly smaller for the closest graphite-graphite separations, and on the other hand, water molecules diffuse in interfaces slightly slower than those in the bulklike internal areas. Molecular reorientational times are generally larger than those corresponding to those of unconstrained bulk water. The analysis of spectral densities revealed significant spectral shifts, compared to the bands in unconstrained water, in different frequency regions, and associated to confinement effects. These findings are important because of the scarce information available from experimental, theoretical, and computer simulation research into the dielectric and dynamical properties of confined water.

  17. Relative influence upon microwave emissivity of fine-scale stratigraphy, internal scattering, and dielectric properties

    USGS Publications Warehouse

    England, A.W.

    1976-01-01

    The microwave emissivity of relatively low-loss media such as snow, ice, frozen ground, and lunar soil is strongly influenced by fine-scale layering and by internal scattering. Radiometric data, however, are commonly interpreted using a model of emission from a homogeneous, dielectric halfspace whose emissivity derives exclusively from dielectric properties. Conclusions based upon these simple interpretations can be erroneous. Examples are presented showing that the emission from fresh or hardpacked snow over either frozen or moist soil is governed dominantly by the size distribution of ice grains in the snowpack. Similarly, the thickness of seasonally frozen soil and the concentration of rock clasts in lunar soil noticeably affect, respectively, the emissivities of northern latitude soils in winter and of the lunar regolith. Petrophysical data accumulated in support of the geophysical interpretation of microwave data must include measurements of not only dielectric properties, but also of geometric factors such as finescale layering and size distributions of grains, inclusions, and voids. ?? 1976 Birkha??user Verlag.

  18. Dielectric and Piezoelectric Properties of PZT Composite Thick Films with Variable Solution to Powder Ratios

    PubMed Central

    Wu, Dawei; Zhou, Qifa; Shung, Koping Kirk.; Bharadwaja, Srowthi N.; Zhang, Dongshe; Zheng, Haixing

    2010-01-01

    The use of PZT films in sliver-mode high-frequency ultrasonic transducers applications requires thick, dense, and crack-free films with excellent piezoelectric and dielectric properties. In this work, PZT composite solutions were used to deposit PZT films >10 μm in thickness. It was found that the functional properties depend strongly on the mass ratio of PZT sol–gel solution to PZT powder in the composite solution. Both the remanent polarization, Pr, and transverse piezoelectric coefficient, e31,f, increase with increasing proportion of the sol–gel solution in the precursor. Films prepared using a solution-to-powder mass ratio of 0.5 have a remanent polarization of 8 μC/cm2, a dielectric constant of 450 (at 1 kHz), and e31,f = −2.8 C/m2. Increasing the solution-to-powder mass ratio to 6, the films were found to have remanent polarizations as large as 37 μC/cm2, a dielectric constant of 1250 (at 1 kHz) and e31,f = −5.8 C/m2. PMID:20376196

  19. Mechanical and dielectric properties of SEBS modified by graphite inclusion and composite interface

    NASA Astrophysics Data System (ADS)

    Grigorescu, Ramona Marina; Ciuprina, Florin; Ghioca, Paul; Ghiurea, Marius; Iancu, Lorena; Spurcaciu, Bogdan; Panaitescu, Denis Mihaela

    2016-02-01

    Tough and flexible dielectrics were prepared using graphite (G), a natural and low-cost resource, as filler in polystyrene-b-(ethylene-co-butylene)-b-polystyrene (SEBS) and maleinized SEBS (SEBS-MA) matrices. The disintegration of graphite in submicron particles was accomplished by the shear forces during the melt processing step and it was highlighted by atomic force microscopy. Simultaneous increase of tensile strain, strength and Young's modulus was noticed for SEBS/G and SEBS-MA/G composites compared to unfilled matrices, this remarkable feature being previously reported only for some nanocomposites. Moreover, an exponential variation of the dielectric permittivity with the volume fraction of G was obtained. Higher reinforcing efficiency and better dielectric properties were observed in SEBS-MA/G composites, compared to the corresponding SEBS/G composites, due to the stronger polymer-filler interface and better dispersion of graphite. This study brings new insights into nanolevel properties of SEBS composites and it opens new perspectives on high performance composites by using graphite instead of expensive graphene and efficient melt mixing process.

  20. Investigation of dielectric properties of La0.33NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Mondal, Tanusree; Sarun, P. M.; Das, Sayantani; Sinha, T. P.

    2015-06-01

    La0.33NbO3 ceramics was prepared via conventional solid-state reaction method. Structural analysis show the existence of single phase of La0.33NbO3 has been synthesized with an average particle size of 2 µm - 4 µm estimated from FESEM image. Detailed investigation on the dielectric properties and AC conductivity of the La0.33NbO3 ceramics in a wide range of frequency (800 Hz - 5 MHz) and temperatures (30 °C - 300 °C) revealed that these properties are strongly temperature and frequency dependent.

  1. Microstructures and dielectric properties of CaCu3Ti4O12 ceramics via combustion method

    NASA Astrophysics Data System (ADS)

    Yuan, W. X.; Li, Z. J.

    2012-01-01

    CaCu3Ti4O12 (CCTO) powder was synthesized by the combustion method. The effect of sintering temperature was studied on dielectric properties of the prepared ceramic samples. They have the dielectric constant of ~31 000 and 80 000 for the grain size of 0.3 and 30-100 μm. It is unusual for CCTO with a grain size of 0.3 μm to have a dielectric constant of ~31 000. Their giant dielectric constant could be explained by a two-step internal-barrier-layer-capacitor model, associated with grain boundaries and domain boundaries. The existence of domain boundaries helped to explain the contradiction of the dielectric mechanisms between polycrystalline and single-crystal CCTO.

  2. Dielectric and electro-optical properties of polymer-stabilized liquid crystal. II. Polymer PiBMA dispersed in MBBA

    NASA Astrophysics Data System (ADS)

    Tripathi, Pankaj Kumar; Pande, Mukti; Singh, Shri

    2016-09-01

    In continuation of our earlier work (Pande et al. in Appl Phys A 122:217-226, 2016), we report the results of dielectric and electro-optical properties of pure MBBA and PSLC (polymer PiBMA dispersed in MBBA) systems. The polymer networks domains formed are found to be anisotropic and are oriented in the direction of electric field for both the planar and homeotropic alignment cells. The dielectric anisotropy, optical anisotropy, response time, threshold voltage, splay elastic constant and rotational viscosity were observed for both the LC and PSLC systems with electric field. The liquid crystal properties are affected significantly with increasing concentration of polymer in pure LC material. It has been observed that the polymer networks interaction plays a major role in changing the properties of PSLC system. The effect of dielectric loss and dielectric permittivity on both pure LC and PSLC systems is also discussed.

  3. MAPPING OF RESERVOIR PROPERTIES AND FACIES THROUGH INTEGRATION OF STATIC AND DYNAMIC DATA

    SciTech Connect

    Albert C. Reynolds; Dean S. Oliver; Fengjun Zhang; Yannong Dong; Jan Arild Skjervheim; Ning Liu

    2003-01-01

    Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. But while the volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade, it is not yet possible to make use of all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. The goal of this project is to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem is necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management. Facies (defined here as regions of relatively uniform petrophysical properties) are common features of all reservoirs. Because the flow properties of the various facies can vary greatly, knowledge of the location of facies boundaries is of utmost importance for the prediction of reservoir performance and for the optimization of reservoir management. When the boundaries between facies are fairly well known, but flow properties are poorly known, the average properties for all facies can be determined using traditional techniques. Traditional history matching honors dynamic data by adjusting petrophysical properties in large areas, but in the process of adjusting the reservoir model ignores the static data and often results in implausible reservoir

  4. Dielectric and Thermal Properties of Polyimide-Poly(ethylene oxide) Nanofoamed Films

    NASA Astrophysics Data System (ADS)

    Zhang, Yi-He; Yu, Li; Zhao, Li-Hang; Tong, Wang-Shu; Huang, Hai-Tao; Ke, Shan-Ming; Chan, H. L. W.

    2012-08-01

    Polyimide nanofoamed films have been prepared by incorporating poly(ethylene oxide) (PEO) into poly(amide acid) (PAA) precursors with subsequent imidization of PAA precursors at high temperature. The porous structure, thermal decomposition temperature, and dielectric property of nanofoamed films were investigated by scanning electron microscopy, thermogravimetric analysis, and impedance spectroscopy. Nanopores with sizes around 40 nm to 200 nm were formed in nanofoamed films by pyrolysis of PEO during the imidization progress. The decomposition temperature of nanofoamed films decreased slightly with increasing volume fraction of nanopores and maintained the high decomposition temperature of 499.7 °C when the volume fraction of nanopores was 10.9 %. The dielectric constant of nanofoamed films decreased from 3.4 for pure PI to 2.4 at 103 Hz through the introduction of nanopores with volume fraction of 10.9 %.

  5. Improved nonlinear slot waveguides using dielectric buffer layers: properties of TM waves.

    PubMed

    Elsawy, Mahmoud M R; Renversez, Gilles

    2016-04-01

    We propose an improved version of the symmetric metal slot waveguides with a Kerr-type nonlinear dielectric core adding linear dielectric buffer layers between the metal regions and the core. Using a finite element method to compute the stationary nonlinear modes, we provide the full phase diagrams of its main transverse magnetic modes as a function of the total power, buffer layer, and core thicknesses that are more complex than the ones of the simple nonlinear metal slot. We show that these modes can exhibit spatial transitions toward specific modes of the new structure as a function of power. We also demonstrate that, for the main modes, the losses are reduced compared to the previous structures, and that they can now decrease with power. Finally, we describe the stability properties of the main stationary solutions using nonlinear FDTD simulations. PMID:27192282

  6. Dielectric properties of Gd3Ba2Mn2Cu2O12 manganocuprate

    NASA Astrophysics Data System (ADS)

    Rayaprol, S.; Kaushik, S. D.; Kumar, N.; Gaur, N. K.; Saha, J.; Patnaik, S.

    2011-04-01

    The magnetocapacitance and magnetoresistance of Gd3Ba2Mn2Cu2O12 (Gd-3222) has been measured in the temperature range of 2-300 K. The capacitance increases with increasing temperature from 2-300 K, and exhibits a steplike feature at ˜95 K (for 1 kHz). On increasing the probe frequency this step gets broaden and shifts to higher temperature ˜150 K (for 75 kHz). The observation of frequency dependence in capacitance and dielectric loss (tan δ) exhibits Maxwell-Wagner type relaxor behavior in this compound. Magnetocapacitance was observed on the application of magnetic field. No observable magnetoresistance could be observed in this compound, indicating that the magnetoelectric coupling observed from the dielectric constant measurement with and without magnetic field, is of capacitive origin. The results of magnetocapacitance and magnetoresistance of the Gd-3222 compound are presented in the light of current interest in exploring manganite systems for multiferroic properties.

  7. Sensing Properties of a Fabry-Perot Dielectric Structure and Dimer Nanoparticles

    DOE PAGES

    Polemi, A.; Shuford, K. L.

    2012-01-01

    We investigate the use of a Fabry-Perot dielectric structure combined with differently shaped nanoparticles for Surface Enhanced Raman Scattering. In particular, we show how an ideal two-layer Fabry-Perot configuration enhances the local surface field of silver nanoparticles positioned on the surface of the structure. We develop the concept using disc dimers and then extend the discussion to bowtie nanoparticles. The structure is excited by a single emitter, which couples to the nanoparticles through the dielectric layers, producing a wide aperture field that can be used to excite multiple dimers. We show how an array of nanoparticles can be properly arrangedmore » in order to increase the total scattering signal generated from the structure. The layered geometry produces robust field properties in between nanoparticles, making the overall sensing characteristics less sensitive to the interparticle seperation distance and incident polarization.« less

  8. Electrical and Mechanical Properties of the Dielectric Capacitor Film Based on Polyvinylidene Fluoride and Aromatic Polythiourea

    NASA Astrophysics Data System (ADS)

    Li, Ya; Fu, Qiong; Li, Lili; Li, Weiping

    2016-10-01

    To obtain the flexible dielectric material suitable for mass produced supercapacitor, blend films based on polyvinylidene fluoride (PVDF) and aromatic polythiourea (ArPTU) were prepared by solution casting. We found that the PVDF/ArPTU blend film is a good energy storage material for capacitors with high breakdown strength and low loss at high filed. The breakdown field of PVDF/ArPTU (90/10) film is more than 700 MV/m, and the maximum released energy density is up to 11 J/cm3 with discharging efficiency above 80%. We also proved that the mechanical property of blend films is much better than that of pure ArPTU film, and the toughness and softness are close to the level of PVDF film. The blend film based on PVDF and ArPTU is a flexible dielectric material in the manufacture of supercapacitor.

  9. Dielectric and pyroelectric properties of lead zirconate titanate/polyurethane composites

    NASA Astrophysics Data System (ADS)

    Lam, K. S.; Wong, Y. W.; Tai, L. S.; Poon, Y. M.; Shin, F. G.

    2004-10-01

    0-3 composite ranging between 0 and 3, of ferroelectric ceramic lead zirconate titanate (PZT) and thermoplastic elastomer polyurethane (PU) were fabricated. The pyroelectric and dielectric properties of the hot-pressed thin film samples of various PZT volume fractions were measured. The experimental dielectric permittivities and losses agreed reasonably well with the Bruggeman model. The room temperature pyroelectric coefficients of the composites were found to increase linearly with PZT volume fraction and substantially larger than expected. For example, for a composite with 30% PZT, its pyroelectric coefficient is about 90μC/m2K at room temperature, which is more than tenfold of a PZT/PVDF composite of the same ceramic volume fraction. We propose a model in which the electrical conductivity of the composite system is taken into consideration to explain the linear relationship and the extraordinarily large pyroelectric coefficients obtained.

  10. Dielectric and pyroelectric properties of lead zirconate titanate/polyurethane composites

    SciTech Connect

    Lam, K.S.; Wong, Y.W.; Tai, L.S.; Poon, Y.M.; Shin, F.G.

    2004-10-01

    0-3 composite ranging between 0 and 3, of ferroelectric ceramic lead zirconate titanate (PZT) and thermoplastic elastomer polyurethane (PU) were fabricated. The pyroelectric and dielectric properties of the hot-pressed thin film samples of various PZT volume fractions were measured. The experimental dielectric permittivities and losses agreed reasonably well with the Bruggeman model. The room temperature pyroelectric coefficients of the composites were found to increase linearly with PZT volume fraction and substantially larger than expected. For example, for a composite with 30% PZT, its pyroelectric coefficient is about 90 {mu}C/m{sup 2}K at room temperature, which is more than tenfold of a PZT/PVDF composite of the same ceramic volume fraction. We propose a model in which the electrical conductivity of the composite system is taken into consideration to explain the linear relationship and the extraordinarily large pyroelectric coefficients obtained.

  11. Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

    2016-05-01

    Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

  12. Dielectric and relaxation properties of poly(o-anisidine)/graphene nanocomposite

    NASA Astrophysics Data System (ADS)

    Sangamithirai, D.; Narayanan, V.; Stephen, A.

    2016-05-01

    Poly(o-anisidine)/graphene (POA/GR) nanocomposite was synthesized via chemical oxidative polymerization of o-anisidine in the presence of graphene sheets in acidic medium. The electrical properties of the nanocomposite are studied using AC impedance spectroscopic technique. It has been found that the room temperature electrical conductivity value enhanced from 1.28 × 10-6 S cm-1 to 4.47 × 10-4 S cm-1 on addition of 10 wt % of graphene into the polymer. An analysis of real and imaginary parts of dielectric permittivity reveals that both ɛ` and ɛ״ increases with the decrease of frequency at all temperature levels. Frequency dependence of dielectric loss (tan δ) spectrum indicates that hopping frequency increases with temperature and the relaxation time decreases from 2.67 × 10-5 to 7.28 × 10-6 sec.

  13. Laboratory studies of electrical properties of insulating materials. [thermal insulation of spacecraft dielectrics

    NASA Technical Reports Server (NTRS)

    Nanevicz, J. E.; Adamo, R. C.; Grier, N.

    1978-01-01

    The characteristics of satellites are influenced by the electrical properties of the dielectric exterior. It was found in simulated space environment tests that the electrical conductivities of dielectrics are affected as the result of interactions with various components of the environment. The degree to which the conductivity was affected varied with material. In some instances the changes found to occur could be used to advantage, particularly if they could be enhanced. For example, the increased electrical conductivity of Kapton resulting from solar illumination could be used to advantage to eliminate the charge storage leading to electrical breakdown during magnetic substorms. Similarly the relative immunity of FEP Teflon to change from response to the space environment makes it a logical choice as a solar cell cover in a high-voltage solar array.

  14. Transport and dielectric properties of water and the influence of coarse-graining: Comparing BMW, SPC/E, and TIP3P models

    SciTech Connect

    Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar

    2014-02-14

    Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough.

  15. Transport and dielectric properties of water and the influence of coarse-graining: Comparing BMW, SPC/E, and TIP3P models

    NASA Astrophysics Data System (ADS)

    Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar

    2014-02-01

    Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough.

  16. Transport and dielectric properties of water and the influence of coarse-graining: comparing BMW, SPC/E, and TIP3P models.

    PubMed

    Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar

    2014-02-14

    Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough. PMID:24527900

  17. Influence of O2 on the dielectric properties of CO2 at the elevated temperatures

    NASA Astrophysics Data System (ADS)

    Rong, Mingzhe; Sun, Hao; Yang, Fei; Wu, Yi; Chen, Zhexin; Wang, Xiaohua; Wu, Mingliang

    2014-11-01

    SF6 gas is widely used in the high voltage circuit breakers but considering its high global warming potential other substitutes are being sought. Among them CO2 was investigated and even has been used in some practical products. However, at room temperature, the dielectric properties of CO2 are relatively lower than SF6 and air. The goal of this work is to investigate a CO2-based gas to improve the performance of the pure CO2. In this paper, the dielectric properties of hot CO2/O2 mixtures related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300 K to 4000 K and in the pressure range from 0.01 MPa to 1.0 MPa. The species compositions of hot CO2/O2 were obtained based on Gibbs free energy minimization under the assumptions of local thermodynamic equilibrium and local chemical equilibrium. The reduced critical electric field strength of CO2/O2 was determined by balancing electron generation and loss. These were calculated using the electron energy distribution function by solving the Boltzmann transport equation. The validity of the calculation method and the cross sections data was confirmed by comparing the measurements and calculations of the electron swarm data in previous work. The results indicate that in pure CO2 the critical electric field strength is higher only in higher temperature range. By adding the O2 into the CO2, the critical electric field strength at lower temperature is effectively enhanced. CO2/O2 mixtures have a much better dielectric strength than both the pure CO2 and air and thus have the potential to improve the CO2-based gas circuit breakers. Similar conclusions can also be found in others' work, which further confirm the validity of these results.

  18. The effect of dielectric properties of sintering additives on microwave sintered silicon nitride ceramics.

    PubMed

    Chockalingam, Sreekumar; George, Jacob; Earl, David; Amarakoon, Vasantha R W

    2008-01-01

    Silicon nitride requires the use of susceptive additives for microwave liquid phase sintering due to the material's low dielectric loss. In this article, we report the effect of complex dielectric properties of two compositions of sintering aids on 2.45 GHz microwave sintered Si3N4 with respect to power absorption, temperature distribution and densification behavior. The temperature dependent dielectric properties were measured from 25 degrees C to 1400 degrees C using a conventional cavity perturbation technique. Finite Difference Time Domain (FDTD) electromagnetic simulations coupled with a thermal solver was used to predict the microwave power absorption and the corresponding temperature evolution inside the samples. The additive with higher dielectric loss (4 wt% MgO, 6 wt% Y2O3 and 2.5 wt% ZrO2) produces a greater sintered density than the lower loss additive (4 wt% MgO and 6 wt% Y2O3) or pure Si3N4. Although microwave loss at temperatures below 600 degrees C is insignificant with or without the additives, the loss begins to increase at higher temperatures when the additives are present and has a strong upward trend above 1000 degrees C. Above 1200 degrees C the sample containing ZrO2 exhibited the greatest loss. Numerical simulations at the peak sintering temperature show greater microwave power absorption and higher temperature in the sample with the highest loss additive. The simulation results correlate to the difference in densification behavior observed. The simulation was also useful because the material temperature was not accurately provided by optical pyrometer measurements of the crucible sample holder.

  19. The effect of dielectric properties of sintering additives on microwave sintered silicon nitride ceramics.

    PubMed

    Chockalingam, Sreekumar; George, Jacob; Earl, David; Amarakoon, Vasantha R W

    2008-01-01

    Silicon nitride requires the use of susceptive additives for microwave liquid phase sintering due to the material's low dielectric loss. In this article, we report the effect of complex dielectric properties of two compositions of sintering aids on 2.45 GHz microwave sintered Si3N4 with respect to power absorption, temperature distribution and densification behavior. The temperature dependent dielectric properties were measured from 25 degrees C to 1400 degrees C using a conventional cavity perturbation technique. Finite Difference Time Domain (FDTD) electromagnetic simulations coupled with a thermal solver was used to predict the microwave power absorption and the corresponding temperature evolution inside the samples. The additive with higher dielectric loss (4 wt% MgO, 6 wt% Y2O3 and 2.5 wt% ZrO2) produces a greater sintered density than the lower loss additive (4 wt% MgO and 6 wt% Y2O3) or pure Si3N4. Although microwave loss at temperatures below 600 degrees C is insignificant with or without the additives, the loss begins to increase at higher temperatures when the additives are present and has a strong upward trend above 1000 degrees C. Above 1200 degrees C the sample containing ZrO2 exhibited the greatest loss. Numerical simulations at the peak sintering temperature show greater microwave power absorption and higher temperature in the sample with the highest loss additive. The simulation results correlate to the difference in densification behavior observed. The simulation was also useful because the material temperature was not accurately provided by optical pyrometer measurements of the crucible sample holder. PMID:19227072

  20. Static friction properties between human palmar skin and five grabrail materials.

    PubMed

    O'Meara, D M; Smith, R M

    2001-09-15

    The purpose of this study was to investigate the static friction properties between human palmar skin and five grabrail materials (chrome, stainless steel, power-coated steel, textured aluminium and knurled steel) for dry, wet and soapy hands. Thirty subjects (15 female, 15 male) participated in this study, their ages ranging from 19 to 45 years with a mean age of 28 years. The normal force, friction force, and coefficient of static friction were determined by measuring three-dimensional forces while slipping the palm of the hand over the surface of a grabrail. A repeated measures ANOVA indicated that gender, age, hand size and trial effect had no significant influence (p>0.05) on these results. The coefficient of friction (p<0.001) and friction force (p<0.001) were significantly lower when the hand was soapy than when it was dry or wet. The normal force applied when the hand was soapy was significantly greater (p<0.001) than when it was dry or wet. No significant difference was found between dry and wet hands. The two textured materials displayed superior friction properties when the hand was soapy, while the smooth materials performed best when the hand was dry.

  1. Correlations in the properties of static and rapidly rotating compact stars

    SciTech Connect

    Agrawal, B. K.; Kumar, Raj; Dhiman, Shashi K.

    2008-04-15

    Correlations in the properties of the static compact stars (CSs) and the ones rotating with the highest observed frequency of 1122 Hz are studied using a large set of equations of state (EOSs). These EOSs span various approaches and their chemical composition varies from the nucleons to hyperons and quarks in {beta}-equilibrium. It is found that the properties of static CS, like the maximum gravitational mass M{sub max}{sup stat} and radius R{sub 1.4}{sup stat} corresponding to the canonical mass and supramassive or nonsupramassive nature of the CS rotating at 1122 Hz are strongly correlated. In particular, only those EOSs yield the CS rotating at 1122 Hz to be nonsupramassive for which ((M{sub max}{sup stat}/M{sub {center_dot}})){sup 1/2}((10 km/R{sub 1.4}{sup stat})){sup 3/2} is greater than unity. A suitable parametric form which can be used to split the M{sub max}{sup stat}-R{sub 1.4}{sup stat} plane into the regions of different supramassive nature of the CS rotating at 1122 Hz is presented. Currently measured maximum gravitational mass 1.76M{sub {center_dot}} of PSR J0437-4715 suggests that the CS rotating at 1122 Hz can be nonsupramassive provided R{sub 1.4}{sup stat}{<=}12.4 km.

  2. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Wang, Ziyu; Ding, Yi; Lu, Zhihong; Sun, Haoliang; Li, Ya; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

    2013-11-01

    This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  3. Improved dielectric and mechanical properties of polystyrene-hybrid silica sphere composite induced through bifunctionalization at the interface.

    PubMed

    Sasikala, Thottunkal S; Nair, Bindu P; Pavithran, Chorappan; Sebastian, Mailadil T

    2012-06-26

    Hybrid silica spheres (HS) of size 270-350 nm with vinyl and aminopropyl surface groups were incorporated in polystyrene (PS), and its effect on dielectric properties, coefficient of thermal expansion (CTE), and strength of PS-HS composite was studied. Incorporation of HS in PS followed a decrease in the dielectric constant from 3.2 for PS to 2.6 for composite with 7.5 vol % HS. The decrease in the dielectric constant was attributed to (i) increased interfacial porosity, (ii) formation of anhydrous HS having low dielectric constant, during hot processing of the composites, and (iii) dispersion and preservation of the anhydrous HS in the hydrophobic matrix. The dielectric constant of the composites with HS content up to 7.5 vol % does not vary much with temperature in the range from -20 to 65 °C. These composites also exhibited reduced CTE and improved flexural strength/stiffness due to good interfacial bonding through HS vinyl groups and dispersion of the filler in the matrix. The dielectric loss increased with HS content, and the loss measured for 7.5 vol % PS-HS composite was 6 × 10(-3), as compared to 10(-4) for PS. At HS loading above 7.5 vol %, the tendency of HS to agglomerate and form percolated structure lead to an increase in the dielectric constant and decrease in the mechanical properties of the composites. PMID:22616660

  4. Effects of annealing conditions on the dielectric properties of solution-processed Al2O3 layers for indium-zinc-tin-oxide thin-film transistors.

    PubMed

    Kim, Yong-Hoon; Kim, Kwang-Ho; Park, Sung Kyu

    2013-11-01

    In this paper, the effects of annealing conditions on the dielectric properties of solution-processed aluminum oxide (Al2O3) layers for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) have been investigated. The dielectric properties of Al2O3 layers such as leakage current density and dielectric strength were largely affected by their annealing conditions. In particular, oxygen partial pressure in rapid thermal annealing, and the temperature profile of hot plate annealing had profound effects on the dielectric properties. From a refractive index analysis, the enhanced dielectric properties of Al2O3 gate dielectrics can be attributed to higher film density depending on the annealing conditions. With the low-temperature-annealed Al2O3 gate dielectric at 350 degrees C, solution-processed IZTO TFTs with a field-effect mobility of approximately 2.2 cm2/Vs were successfully fabricated. PMID:24245333

  5. An automatic approach for calibrating dielectric bone properties by combining finite-element and optimization software tools.

    PubMed

    Su, Yukun; Kluess, Daniel; Mittelmeier, Wolfram; van Rienen, Ursula; Bader, Rainer

    2016-09-01

    The dielectric properties of human bone are one of the most essential inputs required by electromagnetic stimulation for improved bone regeneration. Measuring the electric properties of bone is a difficult task because of the complexity of the bone structure. Therefore, an automatic approach is presented to calibrate the electric properties of bone. The numerical method consists of three steps: generating input from experimental data, performing the numerical simulation, and calibrating the bone dielectric properties. As an example, the dielectric properties at 20 Hz of a rabbit distal femur were calibrated. The calibration process was considered as an optimization process with the aim of finding the optimum dielectric bone properties that match most of the numerically calculated simulation and experimentally measured data sets. The optimization was carried out automatically by the optimization software tool iSIGHT in combination with the finite-element solver COMSOL Multiphysics. As a result, the optimum conductivity and relative permittivity of the rabbit distal femur at 20 Hz were found to be 0.09615 S/m and 19522 for cortical bone and 0.14913 S/m and 1561507 for cancellous bone, respectively. The proposed method is a potential tool for the identification of realistic dielectric properties of the entire bone volume. The presented approach combining iSIGHT with COMSOL is applicable to, amongst others, designing implantable electro-stimulative devices or the optimization of electrical stimulation parameters for improved bone regeneration. PMID:26777343

  6. An automatic approach for calibrating dielectric bone properties by combining finite-element and optimization software tools.

    PubMed

    Su, Yukun; Kluess, Daniel; Mittelmeier, Wolfram; van Rienen, Ursula; Bader, Rainer

    2016-09-01

    The dielectric properties of human bone are one of the most essential inputs required by electromagnetic stimulation for improved bone regeneration. Measuring the electric properties of bone is a difficult task because of the complexity of the bone structure. Therefore, an automatic approach is presented to calibrate the electric properties of bone. The numerical method consists of three steps: generating input from experimental data, performing the numerical simulation, and calibrating the bone dielectric properties. As an example, the dielectric properties at 20 Hz of a rabbit distal femur were calibrated. The calibration process was considered as an optimization process with the aim of finding the optimum dielectric bone properties that match most of the numerically calculated simulation and experimentally measured data sets. The optimization was carried out automatically by the optimization software tool iSIGHT in combination with the finite-element solver COMSOL Multiphysics. As a result, the optimum conductivity and relative permittivity of the rabbit distal femur at 20 Hz were found to be 0.09615 S/m and 19522 for cortical bone and 0.14913 S/m and 1561507 for cancellous bone, respectively. The proposed method is a potential tool for the identification of realistic dielectric properties of the entire bone volume. The presented approach combining iSIGHT with COMSOL is applicable to, amongst others, designing implantable electro-stimulative devices or the optimization of electrical stimulation parameters for improved bone regeneration.

  7. Investigation of optical and interfacial properties of Ag/Ta{sub 2}O{sub 5} metal dielectric multilayer structure

    SciTech Connect

    Sarkar, P. Jena, S.; Tokas, R. B.; Thakur, S.; Sahoo, N. K.; Rao, K. D.; Misal, J. S.; Prathap, C.

    2015-06-24

    One-dimensional periodic metal-dielectric multilayer thin film structures consisting of Ag and Ta{sub 2}O{sub 5} alternating layers are deposited on glass substrate using RF magnetron sputtering technique. The spectral property of the multilayers has been investigated using spectrophotometry technique. The optical parameters such as refractive index, extinction coefficient, band gap etc., along with film thickness as well as the interfacial layer properties which influence these properties have been probed with spectroscopic ellipsometry technique. Atomic force microscopy has been employed to characterize morphological properties of this metal-dielectric multilayer.

  8. Static transport properties of random alloys: Vertex corrections in conserving approximations

    NASA Astrophysics Data System (ADS)

    Turek, I.

    2016-06-01

    The theoretical formulation and numerical evaluation of the vertex corrections in multiorbital techniques of theories of electronic properties of random alloys are analyzed. It is shown that current approaches to static transport properties within the so-called conserving approximations lead to the inversion of a singular matrix as a direct consequence of the Ward identity relating the vertex corrections to one-particle self-energies. We propose a simple removal of the singularity for quantities (operators) with vanishing average values for electron states at the Fermi energy, such as the velocity or the spin torque; the proposed scheme is worked out in detail in the self-consistent Born approximation and the coherent-potential approximation. Applications involve calculations of the residual resistivity for various random alloys, including spin-polarized and relativistic systems, treated on an ab initio level, with particular attention paid to the role of different symmetries (inversion of space and time).

  9. Evolving Density and Static Mechanical Properties in Plutonium from Self-Irradiation

    SciTech Connect

    Chung, B W; Thompson, S R; Lema, K E; Hiromoto, D S; Ebbinghaus, B B

    2008-07-31

    Plutonium, because of its self-irradiation by alpha decay, ages by means of lattice damage and helium in-growth. These integrated aging effects result in microstructural and physical property changes. Because these effects would normally require decades to measure, studies are underway to assess the effects of extended aging on the physical properties of plutonium alloys by incorporating roughly 7.5 weight % of highly specific activity isotope {sup 238}Pu into the {sup 239}Pu metal to accelerate the aging process. This paper presents updated results of self-irradiation effects on {sup 238}Pu-enriched alloys measured by immersion density, dilatometry, and tensile tests. After nearly 90 equivalent years of aging, both the immersion density and dilatometry show that the enriched alloys continue to decreased in density by {approx}0.002% per year, without void swelling. Quasi-static tensile measurements show that the aging process increases the strength of plutonium alloys.

  10. Effect of Sintering Temperature on Dielectric Properties of Iron Deficient Nickel-Ferrite

    SciTech Connect

    Rani, Renu; Singh, Sangeeta; Juneja, J. K.; Prakash, Chandra; Raina, K. K.

    2011-11-22

    Nickel Ferrite among all the magneto ceramic materials have been studied very much due to its large number of applications. But there is a large scope of modification of its properties. Thus people still working on it for improvisation of its properties via compositional and structural modifications. Present paper reporting the preparation and characterization of iron deficient Nickel ferrite for different sintering temperature. Ferrite samples having the general formula NiFe1.98O{sub 4} were prepared using the standard ceramic method. The phase formation was confirmed by X-ray diffraction technique. The effect of sintering temperature on the electrical properties and resistivity was studied. The data shows that dielectric properties are highly dependent on the sintering temperature.

  11. Vanadium oxide nanotubes VOx-NTs: Hydrothermal synthesis, characterization, electrical study and dielectric properties

    SciTech Connect

    Nefzi, H.; Sediri, F.

    2013-05-01

    Vanadium oxide nanotubes (VOx-NTs) have been synthesized via one-step hydrothermal treatment. The compounds were analyzed through X-ray powder diffraction; scanning electron microscope, UV–Visible spectroscopy, X-ray photoelectron spectroscopy (XPS) and complex impedance spectroscopy. The electrical and dielectric properties dependence on temperature (302–523 K) and on frequency (5 Hz to 13 MHz) of VOx-NTs have been reported. The complex impedance plots exhibits the presence of grain and grain boundaries. Dielectric data were analyzed using complex permittivity and complex electrical modulus for the sample at various temperatures. The presence of non-Debye type of relaxation has been confirmed by the complex modulus analysis. AC conductivity exhibits two conduction mechanisms: at high temperature, a translational motion with a sudden hopping and at low temperature, a localized hopping with a small hopping or reorientational motion. DC conductivity indicated, negative temperature coefficient of resistance (NTCR) type behavior. - Graphical abstract: The imaginary part of dielectric constant decreases with the increase in frequency at all temperatures and the values of ε´´ exhibit considerable frequency dispersion in the lower frequency range . Highlights: •Vanadium oxide nanotubes (VOx-NTs) were synthesized. •Non-debye type of relaxation has been confirmed. •AC conductivity exhibits two conduction mechanisms. •DC conductivity indicated negative temperature coefficient of resistance type behavior.

  12. Improved dielectric and magnetic properties of Ti modified BiCaFeO3 multiferroic ceramics

    NASA Astrophysics Data System (ADS)

    Reetu; Agarwal, Ashish; Sanghi, Sujata; Ashima; Ahlawat, Neetu

    2013-01-01

    Ti substituted BiCaFeO3 ceramics having compositions Bi0.8Ca0.2Fe1-xTixO3 (x = 0.0, 0.1, 0.2) were synthesized by the conventional solid state reaction method. Powder X-ray diffraction investigations performed at room temperature show that all samples possess a rhombohedrally distorted perovskite structure described by the space group R3c. Rietveld refinement presented a good agreement between the observed and calculated patterns. Dielectric response of these samples was analyzed in the frequency range 1 kHz-5 MHz at different temperatures. Dispersion in dielectric constant (έ) and dielectric loss factor (tanδ) values decreases with Ti substitution. έ increases and tanδ decreases significantly by Ti substitution. Magnetic measurements were carried out at room temperature up to a field of 20 kOe. Magnetic properties of Bi0.8Ca0.2FeO3 ceramic are greatly improved on Ti substitution along with a significant opening in the room temperature M-H hysteresis loop. The values of remnant magnetization (Mr) 0.08 and 0.13 emu/g; coercivity (Hc) 4.25 and 5.50 kOe are observed for samples with x = 0.1 and 0.2, respectively.

  13. Apparatus and method to measure dielectric properties (ɛ' and ɛ″) of ionic liquids

    NASA Astrophysics Data System (ADS)

    Göllei, Attila; Vass, András; Pallai, Elisabeth; Gerzson, Miklós; Ludányi, Lajos; Mink, János

    2009-04-01

    Conventional techniques for measurement of dielectric properties of ionic liquids or electrolyte solutions fail because the samples are largely short circuited by the high electrical conductance. The object of the author's research activity was to elaborate an apparatus (microwave dielectrometer) and method suitable to measure the dielectric constant (ɛ') and loss factor (ɛ″) of well conducting ionic liquids and other solvents. This process is based on a revised waveguide method completed with an automatic calibration possibility. Contrary to conventional measuring methods this technique uses about 20 W/g power density. The measurements were carried out at 2.45 GHz frequency in the temperature range from 10 up to 100 °C. The obtained (ɛ') and (ɛ″) values of different solvents were compared with several published (calculated and measured) data. Statistical analysis was used to determine the error of measurements and distilled water was chosen as a standard for study of data dispersion. To accomplish statistical analysis, namely, the dielectric characteristics have to be determined at the same temperature. The values of variances were less or equal 1 in case of ɛ' and decrease with increasing temperature. In case of ɛ″ the variance data were much smaller.

  14. Apparatus and method to measure dielectric properties (epsilon(') and epsilon(")) of ionic liquids.

    PubMed

    Göllei, Attila; Vass, András; Pallai, Elisabeth; Gerzson, Miklós; Ludányi, Lajos; Mink, János

    2009-04-01

    Conventional techniques for measurement of dielectric properties of ionic liquids or electrolyte solutions fail because the samples are largely short circuited by the high electrical conductance. The object of the author's research activity was to elaborate an apparatus (microwave dielectrometer) and method suitable to measure the dielectric constant (epsilon(')) and loss factor (epsilon(")) of well conducting ionic liquids and other solvents. This process is based on a revised waveguide method completed with an automatic calibration possibility. Contrary to conventional measuring methods this technique uses about 20 W/g power density. The measurements were carried out at 2.45 GHz frequency in the temperature range from 10 up to 100 degrees C. The obtained (epsilon(')) and (epsilon(")) values of different solvents were compared with several published (calculated and measured) data. Statistical analysis was used to determine the error of measurements and distilled water was chosen as a standard for study of data dispersion. To accomplish statistical analysis, namely, the dielectric characteristics have to be determined at the same temperature. The values of variances were less or equal 1 in case of epsilon(') and decrease with increasing temperature. In case of epsilon(") the variance data were much smaller. PMID:19405682

  15. Dielectric Properties of Layered ZnTa2O6/Poly(tetrafluoroethylene) Composites

    NASA Astrophysics Data System (ADS)

    Jeon, Chang Jun; Kim, Eung Soo

    2012-11-01

    The effects of ZnTa2O6 content and layered structure on the dielectric properties of ZnTa2O6/poly(tetrafluoroethylene) (PTFE) composites were investigated at microwave frequency. With increasing ZnTa2O6 content, the dielectric constant (K) and dielectric loss (tan δ) of the composites increased due to the K values of the individual components and the microstructure. For the composites with layered structures, tan δ was dependent on the internal strain of the composites. Several types of theoretical models were employed to predict the effective K of the composites and the predicted values were compared with experimental data. The temperature coefficient of resonant frequency (TCF) was also discussed as it characterises the thermal stability of the composites. Typically, K of 4.24, tan δ of 1.36 ×10-3 and, TCF of 4.75 ppm/°C were obtained for the single layered PTFE composites with 0.2 volume fraction (Vf) of ZnTa2O6.

  16. Optical and dielectric properties of nanocomposites systems based on epoxy resins and reactive polyhedral oligosilsquioxanes

    NASA Astrophysics Data System (ADS)

    Eed, H.; Hassouneh, O.; Ramadin, Y.; Zihlif, A.; Ragosta, G.; Elimat, Z. M.

    2013-01-01

    An epoxy network structure made of diglycidylether of bisphenol-A and diamino diphenylsulfone was modified by adding various amounts of an epoxy functionalized polyhedral oligomeric silsesquioxane. The obtained nanocomposites were characterized in terms of optical and dielectric properties. The UV-absorption spectra were collected in the wavelength range of 400-800 nm. The optical data were analyzed in terms of absorption formula for non-crystalline materials. The optical energy gap and other basic constants, such as energy tails, dielectric constants, refractive index and optical conductivity, were determined and showed a clear dependence on the POSS concentration. It was found that the optical energy gap for the neat epoxy resin is less than for nanocomposites, and it decreases with increase in the POSS content. The refractive index of nanocomposites was determined from the calculated values of absorption and reflectance. It was found that the refractive index and the dielectric constants increased with increase in the POSS concentration. The optical conductivity, which is a measure of the optical absorption, increased with the POSS content. Furthermore, it was found that the glass transition temperature and the optical energy gap correlate well with the POSS filler concentration.

  17. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics.

    PubMed

    Pirc, R; Rožič, B; Koruza, J; Cordoyiannis, G; Malič, B; Kutnjak, Z

    2015-11-18

    The dielectric and thermal properties of an antiferroelectric (AFE) material characterised by an intermediate ferroelectric (FE) phase between the AFE and paraelectric phase in zero field are studied by means of a generalised Landau-Kittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the Rae-Dove (RD) model of re-entrant phase transitions. The sublattice polarisation components are calculated as functions of temperature and the applied electric field by minimising numerically the free energy. The calculated dielectric susceptibility shows anomalies at the boundaries of the intermediate FE phase, characteristic for first-order phase transitions. It is shown that this behaviour is in qualitative agreement with the measured dielectric constant in Ba-doped PbZrO3 ceramics. The model also predicts a negative adiabatic electrocaloric temperature change ΔT in a broad temperature range in the AFE phase, in qualitative agreement with experiments. The dipolar heat capacity is also predicted to be negative in the intermediate phase in zero field, in analogy with the results of the RD model. PMID:26490797

  18. A Study of the Dielectric Properties of Dry and Saturated Green River Oil Shale

    SciTech Connect

    Sweeney, J; Roberts, J; Harben, P

    2007-02-07

    We measured dielectric permittivity of dry and fluid-saturated Green River oil shale samples over a frequency range of 1 MHz to 1.8 GHz. Dry sample measurements were carried out between room temperature and 146 C, saturated sample measurements were carried out at room temperature. Samples obtained from the Green River formation of Wyoming and from the Anvil Points Mine in Colorado were cored both parallel and perpendicular to layering. The samples, which all had organic richness in the range of 10-45 gal/ton, showed small variations between samples and a relatively small level of anisotropy of the dielectric properties when dry. The real and imaginary part of the relative dielectric permittivity of dry rock was nearly constant over the frequency range observed, with low values for the imaginary part (loss factor). Saturation with de-ionized water and brine greatly increased the values of the real and imaginary parts of the relative permittivity, especially at the lower frequencies. Temperature effects were relatively small, with initial increases in permittivity to about 60 C, followed by slight decreases in permittivity that diminished as temperature increased. Implications of these observations for the in situ electromagnetic, or radio frequency (RF) heating of oil shale to produce oil and gas are discussed.

  19. Thickness dependence of the dielectric properties of thermally evaporated Sb2Te3 thin films

    NASA Astrophysics Data System (ADS)

    Ulutas, K.; Deger, D.; Yakut, S.

    2013-03-01

    Sb2Te3 thin films of different thickness (23 - 350 nm) were prepared by thermal evaporation technique. The thickness dependence of the ac conductivity and dielectric properties of the Sb2Te3 films have been investigated in the frequency range 10 Hz- 100 kHz and within the temperature range 293-373K. Both the dielectric constant epsilon1 and dielectric loss factor epsilon2 were found to depend on frequency, temperature and film thickness. The frequency and temperature dependence of ac conductivity (σac(ω)) has also been determined. The ac conductivity of our samples satisfies the well known ac power law; i.e., σac(ω) propto ωs where s<1 and independent of the film thickness. The temperature dependence of ac conductivity and parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energies were evaluated for various thicknesses. The temperature coefficient of the capacitance (TCC) and permitivity (TCP) were determined as a function of the film thickness. The microstructure of the samples were analyzed using X-ray diffraction (XRD). This results are discussed on the base of the differences in their morphologies and thicknesses. The tendency for amorphization of the crystalline phases becomes evident as the film thickness increases.

  20. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Rožič, B.; Koruza, J.; Cordoyiannis, G.; Malič, B.; Kutnjak, Z.

    2015-11-01

    The dielectric and thermal properties of an antiferroelectric (AFE) material characterised by an intermediate ferroelectric (FE) phase between the AFE and paraelectric phase in zero field are studied by means of a generalised Landau-Kittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the Rae-Dove (RD) model of re-entrant phase transitions. The sublattice polarisation components are calculated as functions of temperature and the applied electric field by minimising numerically the free energy. The calculated dielectric susceptibility shows anomalies at the boundaries of the intermediate FE phase, characteristic for first-order phase transitions. It is shown that this behaviour is in qualitative agreement with the measured dielectric constant in Ba-doped PbZrO3 ceramics. The model also predicts a negative adiabatic electrocaloric temperature change Δ T in a broad temperature range in the AFE phase, in qualitative agreement with experiments. The dipolar heat capacity is also predicted to be negative in the intermediate phase in zero field, in analogy with the results of the RD model.

  1. Dielectric elastomer for stretchable sensors: influence of the design and material properties

    NASA Astrophysics Data System (ADS)

    Jean-Mistral, C.; Iglesias, S.; Pruvost, S.; Duchet-Rumeau, J.; Chesné, S.

    2016-04-01

    Dielectric elastomers exhibit extended capabilities as flexible sensors for the detection of load distributions, pressure or huge deformations. Tracking the human movements of the fingers or the arms could be useful for the reconstruction of sporting gesture, or to control a human-like robot. Proposing new measurements methods are addressed in a number of publications leading to improving the sensitivity and accuracy of the sensing method. Generally, the associated modelling remains simple (RC or RC transmission line). The material parameters are considered constant or having a negligible effect which can lead to serious reduction of accuracy. Comparisons between measurements and modelling require care and skill, and could be tricky. Thus, we propose here a comprehensive modelling, taking into account the influence of the material properties on the performances of the dielectric elastomer sensor (DES). Various parameters influencing the characteristics of the sensors have been identified: dielectric constant, hyper-elasticity. The variations of these parameters as a function of the strain impact the linearity and sensitivity of the sensor of few percent. The sensitivity of the DES is also evaluated changing geometrical parameters (initial thickness) and its design (rectangular and dog-bone shapes). We discuss the impact of the shape regarding stress. Finally, DES including a silicone elastomer sandwiched between two high conductive stretchable electrodes, were manufactured and investigated. Classic and reliable LCR measurements are detailed. Experimental results validate our numerical model of large strain sensor (>50%).

  2. High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

    NASA Technical Reports Server (NTRS)

    Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

    1992-01-01

    Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

  3. Studies of ferroelectric and dielectric properties of pure and doped barium titanate prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Bisen, Supriya; Mishra, Ashutosh; Jarabana, Kanaka M.

    2016-05-01

    In this work, Barium Titanate (BaTiO3) powders were synthesized via Sol-Gel auto combustion method using citric acid as a chelating agent. We study the behavior of ferroelectric and dielectric properties of pure and doped BaTiO3 on different concentration. To understand the phase and structure of the powder calcined at 900°C were characterized by X-ray Diffraction shows that tetragonal phase is dominant for pure and doped BTO and data fitted by Rietveld Refinement. Electric and Dielectric properties were characterized by P-E Hysteresis and Dielectric measurement. In P-E measurement ferroelectric loop tracer applied for different voltage. The temperature dependant dielectric constant behavior was observed as a function of frequency recorded on hp-Hewlett Packard 4192A, LF impedance, 5Hz-13Hz analyzer.

  4. A method to characterize the dielectric and interfacial properties of metal-insulator-semiconductor structures by microwave measurement

    NASA Astrophysics Data System (ADS)

    Lue, Hang-Ting; Tseng, Tseung-Yuen; Huang, Guo-Wei

    2002-04-01

    We have developed a method to investigate the dielectric and interfacial properties of gate dielectric thin films by microwave measurement. Ba0.5Sr0.5TiO3 (BST) thin films were deposited on 10 Ω cm (normal) and 10 k Ω cm [high-resistivity, (HR)] silicon substrates at the same time by rf magnetron sputtering. For the BST/HR-silicon, coplanar waveguides (CPW) were fabricated and measured at microwave frequencies with thru-reflect-line calibration while capacitance (C-V) measurements were carried out for BST/normal silicon. From the phase change of CPW transmission line and the maximum capacitance in C-V measurement, the dielectric constants of both the BST thin film and interface layer can be determined. Furthermore, the behaviors of insertion loss versus bias voltage were investigated. The results indicate that our method can provide useful information to study the dielectric and interfacial properties of metal-insulator-semiconductor structures.

  5. Influence of nanogold additives on phase formation, microstructure and dielectric properties of perovskite BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Nonkumwong, Jeeranan; Ananta, Supon; Srisombat, Laongnuan

    2015-06-01

    The formation of perovskite phase, microstructure and dielectric properties of nanogold-modified barium titanate (BaTiO3) ceramics was examined as a function of gold nanoparticle contents by employing a combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Archimedes principle and dielectric measurement techniques. These ceramics were fabricated from a simple mixed-oxide method. The amount of gold nanoparticles was found to be one of the key factors controlling densification, grain growth and dielectric response in BaTiO3 ceramics. It was found that under suitable amount of nanogold addition (4 mol%), highly dense perovskite BaTiO3 ceramics with homogeneous microstructures of refined grains (~0.5-3.1 μm) and excellence dielectric properties can be produced.

  6. Measurement of the dielectric properties of high-purity sapphire at 1.865 GHZ from 2-10 Kelvin

    SciTech Connect

    N. Pogue, P. McIntyre, Akhdiyor Sattarov, Charles Reece

    2012-06-01

    A dielectric test cavity was designed and tested to measure the microwave dielectric properties of ultrapure sapphire at cryogenic temperatures. Measurements were performed by placing a large cylindrical crystal of sapphire in a Nb superconducting cavity operating in the TE01 mode at 1.865 GHz. The dielectric constant, heat capacity, and loss tangent were all calculated using experimental data and RF modeling software. The motivation for these measurements was to determine if such a sapphire could be used as a dielectric lens to focus the magnetic field onto a sample wafer in a high field wafer test cavity. The measured properties have been used to finalize the design of the wafer test cavity.

  7. Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures.

    PubMed

    Rossmanna, Christian; Haemmerich, Dieter

    2014-01-01

    The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes. PMID:25955712

  8. Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures

    PubMed Central

    Rossmann, Christian; Haemmerich, Dieter

    2016-01-01

    The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes. PMID:25955712

  9. Effect of tetra ionic substitution on the dielectric properties of Cu-ferrite

    NASA Astrophysics Data System (ADS)

    Mazen, S. A.; Zaki, H. M.

    2003-09-01

    X-ray diffraction (XRD), of the two systems of mixed ferrites Cu1+xTixFe2-2xO4 (where x = 0.0, 0.1, 0.2, 0.3, and 0.4); indicates that the samples of x = 0 (CuFe2O4) and x = 0.1 of the Cu-Ti system were formed in tetragonal structure and all other samples of the two system were formed in the cubic system.The ac conductivity , dielectric constant , dielectric loss and the loss tangent tan δ were determined against frequency at room temperature for Cu-Ge and Cu-Ti ferrites. The measurements of and tan δ were performed over a wide range of frequency and temperature.The Maxwell-Wagner model was applied to analyze the dielectric properties of the investigated systems, according to which the dielectric parameters such as the relaxation time . A value of 1 = 5 × 10-7 s was found for Cu-Ge ferrite and 2 = 1.85 × 10-6 s for Cu-Ti ferrites. The hopping rate (g) was found to be 2 × 106 s-1 and 5.4 × 105 s-1 for the two systems Cu-Ge and Cu-Ti ferrites, respectively.The conduction of the two-ferrite systems was discussed on the basis of the hopping mechanism. The activation energy for conduction was calculated and found in the range of 0.27-0.39 eV for Cu-Ge ferrite and 0.21-0.30 eV for Cu-Ti ferrite. (

  10. Correction of electrode polarization contributions to the dielectric properties of normal and cancerous breast tissues at audio/radiofrequencies

    NASA Astrophysics Data System (ADS)

    Stoneman, M. R.; Kosempa, M.; Gregory, W. D.; Gregory, C. W.; Marx, J. J.; Mikkelson, W.; Tjoe, J.; Raicu, V.

    2007-11-01

    Spurious contributions from electrode polarization (EP) are a major nuisance in dielectric measurements of biological tissues and hamper accurate determination of tissue properties in the audio/radiofrequencies. Various electrode geometries and/or treatments have been employed traditionally to reduce EP contributions, although none succeeded to completely remove EP from measurements on tissues for all practical frequency ranges. A method of correction for contributions of EP to the dielectric properties of tissues is proposed. The method is based on modeling the electrode impedance with suitable functions and on the observation that certain parameters are only dependent on electrodes properties and can thus be determined separately. The method is tested on various samples with known properties, and its usefulness is demonstrated with samples of normal and cancerous human female breast tissue. It is observed that the dielectric properties of the tissues over the frequency range 40 Hz-100 MHz are significantly different among different types of breast tissue. This observation is used further to demonstrate that, by scanning the tip of the measuring dielectric probe (with modest spatial resolution) across a sample of excised breast tissue, significant variations in the electrical properties are detected at a position where a tumor is located. This study shows that dielectric spectroscopy has the potential to offer a viable alternative to the current methods for detection of breast cancer in vivo.

  11. Structural and optical characterization of Cr{sub 2}O{sub 3} nanostructures: Evaluation of its dielectric properties

    SciTech Connect

    Abdullah, M. M.; Rajab, Fahd M.; Al-Abbas, Saleh M.

    2014-02-15

    The structural, optical and dielectric properties of as-grown Cr{sub 2}O{sub 3} nanostructures are demonstrated in this paper. Powder X-ray diffractometry analysis confirmed the rhombohedral structure of the material with lattice parameter, a = b = 4.953 Å; c = 13.578 Å, and average crystallize size (62.40 ± 21.3) nm. FE-SEM image illustrated the mixture of different shapes (disk, particle and rod) of as-grown nanostructures whereas; EDS spectrum confirmed the elemental purity of the material. FTIR spectroscopy, revealed the characteristic peaks of Cr–O bond stretching vibrations. Energy band gap (3.2 eV) of the nanostructures has been determined using the results of UV-VIS-NIR spectrophotometer. The dielectric properties of the material were checked in the wide frequency region (100Hz-30 MHz). In the low frequency region, the matrix of the dielectric behaves like source as well as sink of electrical energy within the relaxation time. Low value of dielectric loss exhibits that the materials posses good optical quality with lesser defects. The ac conductivity of the material in the high frequency region was found according to frequency power law. The physical-mechanism and the theoretical-interpretation of dielectric-properties of Cr{sub 2}O{sub 3} nanostructures attest the potential candidature of the material as an efficient dielectric medium.

  12. A radio frequency device for measurement of minute dielectric property changes in microfluidic channels

    NASA Astrophysics Data System (ADS)

    Song, Chunrong; Wang, Pingshan

    2009-01-01

    We demonstrate a sensitive radio frequency (rf) device to detect small dielectric property changes in microfluidic channel. The device consists of an on-chip Wilkinson power divider and a rat-race hybrid, which are built with planar microstrip lines and thin film chip resistors. Interference is used to cancel parasitic background signals. As a result, the measurement sensitivity is improved by more than 20 dB compared with conventional transmission lines. Compared with an ultrasensitive slot antenna/cuvette assembly [K. M. Taylor and D. W. van der Weide, IEEE Trans. Microwave Theory Tech. 53, 1576 (2005)], the proposed rf device is two times more sensitive.

  13. Electronic and dielectric properties of vacancy clusters as quantum dot in silicane

    SciTech Connect

    Mohan, Brij Sharma, Munish; Ahluwalia, P. K.; Kumar, Ashok

    2015-06-24

    First principal study of electronic and dielectric properties of a silicane nanostructure containing cluster of vacancies as quantum dot (QD) has been investigated within density functional theory (DFT). Electronic band structure and corresponding density of states show the decrease in band gap with increasing size of quantum dot. A band gap of 0.38 eV has been achieved for silicane containing 3QD. Electron energy loss spectra (EEL) function shows additional plasmonic features for QD containing silicane in visible region, which may have potential applications in optoelectronic devices.

  14. Electronic and dielectric properties of vacancy clusters as quantum dot in silicane

    NASA Astrophysics Data System (ADS)

    Mohan, Brij; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.

    2015-06-01

    First principal study of electronic and dielectric properties of a silicane nanostructure containing cluster of vacancies as quantum dot (QD) has been investigated within density functional theory (DFT). Electronic band structure and corresponding density of states show the decrease in band gap with increasing size of quantum dot. A band gap of 0.38 eV has been achieved for silicane containing 3QD. Electron energy loss spectra (EEL) function shows additional plasmonic features for QD containing silicane in visible region, which may have potential applications in optoelectronic devices.

  15. Properties of dielectric-barrier-free atmospheric pressure microplasma driven by submicrosecond dc pulse voltage

    SciTech Connect

    Ha, Chang-Seung; Choi, Joon-Young; Kim, Dong-Hyun; Park, Chung-Hoo; Lee, Hae June; Lee, Ho-Jun

    2009-08-10

    Atmospheric pressure microplasma driven by dc pulse is developed. This device has a simple structure comprised of a flowing helium (He) feed gas and dielectric-free metal electrodes without an external current limiting resistor. It is shown that a stable glow mode plasma can be sustained without arc runaway by limiting the voltage pulse width to shorter than 300 ns. The properties of the device are reported in terms of discharge current waveforms, rotational temperature of N{sub 2}{sup +}, and spatiotemporally resolved optical emission characteristics.

  16. Dielectric Properties of KNO3-NH4NO3 Crystalline Binary Mixtures

    NASA Astrophysics Data System (ADS)

    Milinskii, A. Yu.

    2016-01-01

    The temperature dependences of linear and nonlinear dielectric properties of potassium nitrate (KNO3) and crystalline binary mixtures (KNO3)1-x(NH4NO3)x (x = 0.025, 0.035, 0.05, 0.1) in the temperature interval 300-460 K have been investigated. An influence of the NH4NO3 impurity on the existence interval of the ferroelectric phase with increase of the impurity content has been detected. For x = 0.05 the ferroelectric phase is maintained down to room temperature.

  17. Systematic methods for calculation of the dielectric properties of arbitrary plasmas

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.

    1990-01-01

    In the novel approach presented for calculating the dispersion integrals needed for determining plasma dielectric properties, the dispersion integrals for an arbitrary distortion function with a continuous derivative are systematically expanded in terms of a set of orthogonal functions whose corresponding dispersion functions are already known. This general approach is, on the one hand, implemented for unmagnetized plasmas, and on the other generalized to treat relativistic and magnetized plasmas. The method allows the systematic and efficient calculation of dispersion integrals, for the cases of either real or complex arguments.

  18. Relation between static and dynamic rock properties in welded and nonwelded tuff

    SciTech Connect

    Price, R.H.; Boyd, P.J.; Noel, J.S.; Martin, R.J. III

    1994-07-01

    An integral part of the licensing procedure for the potential nuclear waste repository at Yucca Mountain, Nevada involves accurate prediction of the in situ rheology for design and construction of the facility and emplacement of the canisters containing radioactive waste. The data required as input to successful thermal and mechanical models of the behavior of the repository and surrounding lithologies include bulk density, grain density, porosity, compressional and shear wave velocities, elastic moduli, and compressional and tensile strengths. In this study a suite of experiments was performed on cores recovered from the USW-NRG-6 borehole drilled to support the Exploratory Studies Facility (ESF) at Yucca Mountain. USW-NRG-6 was drilled to a depth of 1100 feet through four thermal/mechanical units of Paintbrush tuff. A large data set has been collected on specimens recovered from borehole USW-NRG-6. Analysis of the results of these experiments showed that there is a correlation between fracture strength, Young`s modulus, compressional wave velocity and porosity. Additional scaling laws relating; static Young`s modulus and compressional wave velocity; and fracture strength and compressional wave velocity are promising. Since there are no other distinct differences in material properties, the scatter that is present at each fixed porosity suggests that the differences in the observed property can be related to the pore structure of the specimen. Image analysis of CT scans performed on each test specimen are currently underway to seek additional empirical relations to aid in refining the correlations between static and dynamic properties of tuff.

  19. Dielectric and electromechanical properties of rare earth calcium oxyborate piezoelectric crystals at high temperatures.

    PubMed

    Yu, Fapeng; Zhang, Shujun; Zhao, Xian; Yuan, Duorong; Qin, Lifeng; Wang, Qing-Ming; Shrout, Thomas R

    2011-04-01

    The electrical resistivity, dielectric, and electromechanical properties of ReCa(4)O(BO(3))(3) (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000 °C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p > 3 × 10(7) ω.cm at 1000 °C. The property variation in ReCOB crystals is discussed with respect to their disordered structure. The highest electromechanical coupling factor κ(26) and piezoelectric coefficient d(26) at 1000°C, were achieved in PrCOB crystals, with values being on the order of 24.7% and 13.1 pC/N, respectively. The high thermal stability of the electromechanical properties, with variation less than 25%, together with the low dielectric loss (<46%) and high mechanical quality factor (>1500) at elevated temperatures of 1000 °C, make ErCOB, YCOB, and GdCOB crystals promising for ultrahigh temperature electromechanical applications.

  20. Clinically relevant CNT dispersions with exceptionally high dielectric properties for microwave theranostic applications.

    PubMed

    Xie, Shawn X; Gao, Fuqiang; Patel, Sunny C; Booske, John H; Hagness, Susan C; Sitharaman, Balaji

    2014-11-01

    We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ∼ 70% and ∼ 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy.

  1. Structural transition, dielectric and bonding properties of BeCN2

    NASA Astrophysics Data System (ADS)

    Gou, Hui-Yang; Gao, Fa-Ming; Zhang, Jing-Wu; Li, Zhi-Ping

    2011-01-01

    By means of first principle total energy calculations, this paper studies the structural transition, elastic, mechanical, dielectric and electronic properties of BeCN2. The calculations in total energy indicate that under ambient condition, the orthorhombic BeSiN2-type BeCN2 (space group Pna21) is a more favoured structure than the tetragonal chalcopyritetype one (space group I-42d). The results of elastic properties reveal that BeCN2 in both orthorhombic and tetragonal structure has higher bulk and shear moduli and smaller Poisson's ratio. The calculated Vicker hardness of tetragonal phase is 36.8 GPa, indicating a hard material. The analyses of electronic structure and electron density difference demonstrate that these excellent mechanical properties are attributed to the stronger covalent-bonding of CN4 and BeN4 subunits in BeCN2 crystal. Also, the orthorhombic BeCN2 phase is found to be a transparent semiconductor material with the calculated direct band gap of about 5.56 eV, superior to the indirect band gap of diamond and c-BN. Moreover, it also calculates Born effective charges and dielectric constants of BeCN2. These results suggest that BeCN2 may have some useful applications as optoelectronic, optical window and wear resistant materials.

  2. High Temperature Microwave Dielectric Properties of JSC-1AC Lunar Simulant

    NASA Technical Reports Server (NTRS)

    Allan, Shawn M.; Merritt, Brandon J.; Griffin, Brittany F.; Hintze, Paul E.; Shulman, Holly S.

    2011-01-01

    Microwave heating has many potential lunar applications including sintering regolith for lunar surface stabilization and heating regolith for various oxygen production reactors. The microwave properties of lunar simulants must be understood so this technology can be applied to lunar operations. Dielectric properties at microwave frequencies for a common lunar simulant, JSC-1AC, were measured up to 1100 C, which is approximately the melting point. The experimentally determined dielectric properties included real and imaginary permittivity (epsilon', epsilon"), loss tangent (tan delta), and half-power depth, the di stance at which a material absorbs 50% of incident microwave energy. Measurements at 2.45 GHz revealed tan delta of JSC-1A increases from 0.02 at 25 C to 0.31 at 110 C. The corresponding half-power depth decreases from a peak of 286 mm at 110 C, to 13 mm at 1100 C. These data indicate that JSC-1AC becomes more absorbing, and thus a better microwave heater as temperature increases. A half-power depth maximum at 100-200 C presents a barrier to direct microwave heating at low temperatures. Microwave heating experiments confirm the sluggish heating effect of weak absorption below 200 C, and increasingly strong absorption above 200 C, leading to rapid heating and melting of JSC-1AC.

  3. Measurement of insulating and dielectric properties of acrylic elastomer membranes at high electric fields

    NASA Astrophysics Data System (ADS)

    Di Lillo, L.; Schmidt, A.; Carnelli, D. A.; Ermanni, P.; Kovacs, G.; Mazza, E.; Bergamini, A.

    2012-01-01

    This work reports on the investigation of VHB 4910 acrylic elastomer insulating and dielectric properties. This material is widely exploited for the realization of actuators with large deformations, dielectric elastomer actuators (DEA), and belongs to the group of so-called electroactive polymers (EAP). Extensive investigations concerning its mechanical properties are available in literature while its electric behavior at working conditions has not received the same level of attention. In this work, the relative permittivity and the volume resistivity have been measured on VHB 4910 membranes under different fixed stretch conditions (λ1, λ2 = 3, 3.6, 4, 5) using circular gold electrodes sputtered onto both sides of the specimens. The measured values of relative permittivity are in fairly good agreement with the results previously published by other groups. The volume resistivity, at field values close to the operational ones, has shown a field-dependent behavior revealing dissipative properties that should be considered in real applications. Further, measurements on circular actuators verify these findings. Consequences for modeling of VHB 4910 are drawn and new material model parameters proposed to account for the value of relative permittivity at high electric fields.

  4. Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties

    NASA Astrophysics Data System (ADS)

    Bafrooei, H. Barzegar; Nassaj, E. Taheri; Hu, C. F.; Huang, Q.; Ebadzadeh, T.

    2014-12-01

    High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (εr~23.6, Qf~64,300 GHz and τf~-66 ppm/°C and εr~24, Qf~75,800 GHz and τf~-64 ppm/°C) was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min, respectively.

  5. Clinically relevant CNT dispersions with exceptionally high dielectric properties for microwave theranostic applications.

    PubMed

    Xie, Shawn X; Gao, Fuqiang; Patel, Sunny C; Booske, John H; Hagness, Susan C; Sitharaman, Balaji

    2014-11-01

    We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ∼ 70% and ∼ 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy. PMID:24876108

  6. Understanding Nonlinear Dielectric Properties in a Biaxially Oriented Poly(vinylidene fluoride) Film at Both Low and High Electric Fields.

    PubMed

    Li, Yue; Ho, Janet; Wang, Jianchuan; Li, Zhong-Ming; Zhong, Gan-Ji; Zhu, Lei

    2016-01-13

    Understanding nonlinear dielectric behavior in polar polymers is crucial to their potential application as next generation high energy density and low loss dielectrics. In this work, we studied nonlinear dielectric properties of a biaxially oriented poly(vinylidene fluoride) (BOPVDF) film under both low and high electric fields. For fundamental nonlinear dielectric constants at low fields (<30 MV/m), Novocontrol high-voltage broadband dielectric spectroscopy (HVBDS) was accurate enough to measure up to the third harmonics. It was observed that the low-field dielectric nonlinearity for the BOPVDF disappeared above 10 Hz at room temperature, suggesting that the low-field dielectric nonlinearity originated from ionic migration of impurity ions rather than dipolar relaxation of the amorphous segments. Above the coercive field (EC ≈ 70 MV/m), bipolar electric displacement-electric field (D-E) loop tests were used to extract the nonlinear behavior for pure PVDF crystals, which had a clear origin of ferroelectric switching of polar crystalline dipoles and domains and nonpolar-to-polar (α → δ → β) phase transformations. By using HVBDS, it was observed that the ferroelectric switching of polar crystalline dipoles and domains in BOPVDF above the EC always took place between 20 and 500 Hz regardless of a broad range of temperature from -30 to 100 °C. This behavior was drastically different from that of the amorphous PVDF dipoles, which had a strong dependence on frequency over orders of magnitude.

  7. Changing the optical and electrical properties of a crown dielectric surface using a 532 nm diode laser

    NASA Astrophysics Data System (ADS)

    Khairuzzaman, Md

    The optical response of a dielectric surface to a given laser radiation can be modified when this surface receives a supplemental uniform energy from an external source such as from the uniform electric field set up by a capacitor voltage. A low capacitor voltage across the dielectric can shift the wavelength of the probe laser as perceived by the dielectric surface toward smaller values. This shift is due to an increase of the vibrational frequency of the electric dipoles located on the dielectric surface. The change in the polarization properties of the dielectric surface suggests the usage of this configuration as an optoelectronic switch driven by a relatively small capacitor voltage. Another goal of this work is to observe the coupling between two lasers through a simultaneous interaction on the surface of a crown dielectric material. We analyze the destructive interference pattern between a weak probe laser and a stronger coupling laser in an electromagnetic induced transparency (EIT)-type configuration. We compare our destructive interference pattern obtained with crown glass illuminated with a diode laser of 532 nm, with previous results where a flint dielectric material was illuminated with the same radiation in similar experimental conditions.

  8. Understanding Nonlinear Dielectric Properties in a Biaxially Oriented Poly(vinylidene fluoride) Film at Both Low and High Electric Fields.

    PubMed

    Li, Yue; Ho, Janet; Wang, Jianchuan; Li, Zhong-Ming; Zhong, Gan-Ji; Zhu, Lei

    2016-01-13

    Understanding nonlinear dielectric behavior in polar polymers is crucial to their potential application as next generation high energy density and low loss dielectrics. In this work, we studied nonlinear dielectric properties of a biaxially oriented poly(vinylidene fluoride) (BOPVDF) film under both low and high electric fields. For fundamental nonlinear dielectric constants at low fields (<30 MV/m), Novocontrol high-voltage broadband dielectric spectroscopy (HVBDS) was accurate enough to measure up to the third harmonics. It was observed that the low-field dielectric nonlinearity for the BOPVDF disappeared above 10 Hz at room temperature, suggesting that the low-field dielectric nonlinearity originated from ionic migration of impurity ions rather than dipolar relaxation of the amorphous segments. Above the coercive field (EC ≈ 70 MV/m), bipolar electric displacement-electric field (D-E) loop tests were used to extract the nonlinear behavior for pure PVDF crystals, which had a clear origin of ferroelectric switching of polar crystalline dipoles and domains and nonpolar-to-polar (α → δ → β) phase transformations. By using HVBDS, it was observed that the ferroelectric switching of polar crystalline dipoles and domains in BOPVDF above the EC always took place between 20 and 500 Hz regardless of a broad range of temperature from -30 to 100 °C. This behavior was drastically different from that of the amorphous PVDF dipoles, which had a strong dependence on frequency over orders of magnitude. PMID:26698912

  9. Dielectric properties of skeletal muscle during ischemia in the frequency range from 50 Hz to 200 MHz.

    PubMed

    Schäfer, M; Kirlum, H J; Schlegel, C; Gebhard, M M

    1999-04-20

    The complex dielectric properties of canine skeletal muscles were measured at 25 degrees C during ischemia in the frequency range from 50 Hz to 200 MHz. The dielectric spectrum of skeletal muscle shows an alpha-dispersion below 1 kHz and a beta-dispersion with a relaxation frequency of about 100 kHz. The alpha-dispersion disappears between 450 and 500 min of ischemia time, the same time during which mechanical contraction was observed, and was restored later. During ischemia, the beta-dispersion is shifted continuously to higher frequencies; and at frequencies above 50 MHz, a decrease of the real part of the dielectric permittivity was measured. The dielectric loss factor decreases during ischemia at frequencies below 500 kHz, only interrupted by a short increase, coinciding with the disappearance of the alpha-dispersion. The principal processes that happen during ischemia inside the skeletal muscle tissues were studied with the help of a model especially designed to simulate membrane effects on the dielectric spectrum. The disappearance of the alpha-dispersion is explained by an increase of conductivity in the membrane of the sarcoplasmic reticulum. Shifting beta-dispersion to higher frequencies is a result of metabolically produced ions and therefore increasing conductivity of the intracellular medium. Decreasing dielectric permittivity at frequencies above 50 MHz and decreasing dielectric loss factor at low frequencies are caused by the cell edema.

  10. Nonlinear Dielectric Properties of Yeast Cells Cultured in Different Environmental Conditions

    NASA Astrophysics Data System (ADS)

    Kawanishi, Gomon; Fukuda, Naoki; Muraji, Masafumi

    The harmonics of the electric current through yeast suspensions, the nonlinear dielectric properties of yeast cells, have particular patterns according to the biological activity of the cells and the measurement of these patterns is a technique for determining the activity of living cells. The concentration of glucose and oxygen in yeast culture medium influences the manifestation of fermentation or respiration of yeast cells. Measurements were made with yeast cells (Saccharomyces cerevisiae) cultured aerobically and anaerobically in sufficient glucose concentration, aerobic fermentation and anaerobic fermentation, and aerobically in limited glucose concentration, respiration. The results showed that the harmonics were barely apparent for yeast cells in aerobic fermentation and respiratory; however, cells in the anaerobic fermentation displayed substantial third and fifth harmonics. We can say that environmental condition affects the yeast cells' nonlinear properties, from another viewpoint, the measurements of the nonlinear properties are available to determine the activity of yeast cells adjusted to the conditions of their cultivation.

  11. Measurements of the thermal, dielectric, piezoelectric, pyroelectric and elastic properties of porous PZT samples

    NASA Astrophysics Data System (ADS)

    Lang, Sidney B.; Ringgaard, Erling

    2012-06-01

    The introduction of porosity into ferroelectric ceramics has been of great interest in recent years. In particular, studies of porous lead-zirconate-titanate ceramic (PZT) have been made. In the research reported, samples of Ferroperm Pz27 with porosities of 20, 25 and 30% were studied. Very complete measurements were made of all of the physical properties relevant for ferroelectric applications including thermal conductivity and diffusivity, heat capacity, dielectric, pyroelectric, piezoelectric and elastic properties. Scanning electron micrographs indicated a change from 3-0 to 3-3 connectivity with increasing porosity. Although most of the physical properties are degraded by the presence of porosity, both piezoelectric and pyroelectric figures-of-merit are improved because of the markedly reduced relative permittivity. Porous ferroelectric ceramics are very promising materials for a number of applications.

  12. The Static and Dynamic Properties of Magnetic Particles in Quasi-Two Dimensional Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Hwang, Yoon-Hwae

    1995-11-01

    The static and dynamic properties of magnetic particles confined in quasi-two dimensional aqueaous solution under magnetic field H are studied using static light scattering and real space video image analysis techniques. In the static study, it is found that the system undergoes a structural transition: single particles to elongated disordered columns to array of correlated columns, as H increases. Different structure regions are separated by two critical field lines H_{C1}(phi) and H_{C2}(phi), where phi is the concentration of the particles. Due to disorders inherited in the self-assembling process the magnetic columns remain short-range ordered even in the high field limit, H >> H_{C2}. The translational and bond-orientational correlation lengths are also measured when H>= H_ {C1}. These appear to be of the order of lattice space both in low and high fields. The system also shows a hysteretic effect and nonergodicity. These observations strongly suggest that the system undergoes a glass transition as H increases. Along with the static measurements, the dynamics of the system is also studied. By tracing the magnetic columns with a video imaging technique, the position of magnetic columns at time t, r_{i} (t), is measured. Using r_{i }(t), the self and the relative motions of magnetic columns are studied. It is found that the self mean-square displacement, < Delta r^2 >, depends on the aligning field H and displays two different behaviors. In short times < Delta r^2 > is subdiffusive whereas in long times exhibits normal diffusion. The characteristic time, separating the two time regimes diverges exponentially with H, indicating fast frozen-in density fluctuations in the system. Our experimental results deviate significantly from the predictions of mode-coupling theory. The relative motion of magnetic column pairs is dominated by the transverse component in all scales. At small scales, the correlated domains (or clusters), consisting of a few columns

  13. Polyamides nanoparticles containing flexible linkages and their copper complexes with novel dielectric properties: Structure-property relationship

    NASA Astrophysics Data System (ADS)

    Hassan, Hammed H. A. M.; Elhusseiny, Amel F.; Sweyllam, Amr M.

    2011-08-01

    We report the chemistry of nanometer-sized spherical aramides nanoparticles and their copper complexes as novel types of hybrids nanomaterials. Based on the flexible linkage type, the average diameters of the nanoparticles-containing sulfone or ether linkage were 140 nm and 190 nm, respectively, as judged by the scanning electron microscopy (SEM) photographs. Incorporation of copper (II) ions into these particles furnished polymeric complexes in (1:2) ratios with square planar geometries. The polymeric structures were proved on the basis of their IR, UV, ESR and elemental analysis data. The thermal properties of the polymers were evaluated by various techniques and results revealed the high thermal stabilities of the hybrids. The calculated limiting oxygen index (LOI) indicates that such macromolecules can be classified as self-extinguishing polymers. The dc electrical conductivity of all samples indicates either semi-conducting or metal-like nature in the regime of semiconductor behaviors. Incorporation of copper significantly improved the conductivity of the resulting complexes due to the enhanced mobility of the charge carriers upon doping. Dielectric losses are characterized by sharp peaks appearing at characteristic frequencies suggesting the presence of relaxing dipoles. The peak positions did not change with temperature indicating a non-activated process. The loss tangent increased with frequency and the peaks shifted toward the lower frequency upon doping suggesting the increase in the energy loss ratio compared to the energy storage in the dielectric. The higher value of dielectric loss at low frequency is due to the free charge motion within the materials. The reported dielectric results revealed anomalous behaviors which have not been reported earlier in similar hybrids.

  14. Measurement of the dielectric properties of the epidermis and dermis at frequencies from 0.5 GHz to 110 GHz

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Wake, K.; Watanabe, S.

    2014-08-01

    Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with Gabriel’s widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20-100 GHz, the experimental results indicated larger values than those extrapolated from Gabriel’s data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency.

  15. Dielectric properties of Al2O3 coatings deposited via atmospheric plasma spraying and dry-ice blasting correlated with microstructural characteristics

    NASA Astrophysics Data System (ADS)

    Dong, Shujuan; Song, Bo; Liao, Hanlin; Coddet, Christian

    2015-01-01

    In this work, atmospheric plasma spraying combined with dry-ice blasting have been used to prepare alumina (Al2O3) coatings designed for insulating applications. The microstructural characteristics and dielectric properties of Al2O3 coatings were presented. The electrical insulating properties, i.e., dielectric strength and breakdown voltage, were investigated by dielectric breakdown test using direct current and alternating current. Relationships between dielectric properties and coating characteristics were discussed. The results showed that dry-ice blasting used during atmospheric plasma spray process allowed the production of coatings with better dielectric properties than those prepared without dry-ice blasting. The dielectric properties were correlated with the microstructural characteristics, not with phase composition.

  16. Dielectric, ferroelectric and piezoelectric properties of Nb{sup 5+} doped BCZT ceramics

    SciTech Connect

    Parjansri, Piewpan; Intatha, Uraiwan; Eitssayeam, Sukum

    2015-05-15

    Highlights: • Average grain size of BCZT ceramic decreased with the increasing Nb{sup 5+} doping. • Dielectric constant value is enhanced with Nb{sup 5+} doping. • Dielectric loss of BCZT − x Nb{sup 5+} ceramics was less than 0.03 at room temperature (1 kHz). • Piezoelectric coefficient decreased with the increasing Nb{sup 5+} doping. • The relaxation behavior is enhanced with the doping of Nb{sup 5+}. - Abstract: This work investigated the electrical properties of Nb{sup 5+} (0.0–1.0 mol%) doped with Ba{sub 0.90}Ca{sub 0.10}Zr{sub 0.10}Ti{sub 0.90}O{sub 3} while adding 1 mol% of Ba{sub 0.90}Ca{sub 0.10}Zr{sub 0.10}Ti{sub 0.90}O{sub 3} seeds. The mixed powder was ball milled for 24 h, calcined and sintered at 1200 °C for 2 h and 1450 °C for 4 h, respectively. The XRD patterns of the ceramic samples were investigated by X-ray diffraction. The electrical properties of ceramics were measured and the results indicated that all samples show a pure perovskite phase with no secondary phase. Density and average grain size values were in the range of 5.60–5.71 g/cm{sup 3} and 12.62–1.86 μm, respectively. The highest dielectric constant, ϵ{sub r} at room temperature (1 kHz) was 4636 found at 1.0 mol% Nb. The dielectric loss, tan δ was less than 0.03 for all samples at room temperature (1 kHz). Other electrical properties, P{sub r}, d{sub 33} and k{sub p} values were decreased with Nb doped relates to the decreasing grain size in BCZT ceramics. Moreover, the degrees of phase transition diffuseness and relaxation behavior were observed in the higher Nb doping.

  17. Dielectric properties of CaNdAlO sub 4 at microwave frequencies

    SciTech Connect

    Konopka, J.; Wolff, I. ); Lewandowski, S.J. )

    1992-07-01

    Dielectric properties of CaNdAlO{sub 4} monocrystals, a prospective substrate material for the deposition of high-{ital T}{sub {ital c}} superconductors, were measured with high accuracy at microwave frequencies from 8 to 40 GHz in the temperature range from 10 to 300 K by measuring the resonant frequencies of a completely filled resonant cavity. The material was found to be highly anisotropic. At 300 K it exhibits the dielectric constant along {ital c} axis {epsilon}{sup {prime}}{sub {ital c}} = 17.68, while the dielectric constant in the {ital a}-{ital b} plane is {epsilon}{prime}=19.62, and loss tangent tan {delta}{sub {ital c}} {congruent} tan {delta} {congruent} 5.1{times} 10{sup {minus}4}. Both {epsilon}{sup {prime}}{sub {ital c}} and {epsilon}{prime} depend strongly on temperature and their thermal coefficients have opposite signs, apparently a unique property of CaNdAlO{sub 4}. Below 160 K microwave losses caused by electric field perpendicular to the optical {ital c} axis increase with decreasing temperature, exhibiting a maximum near 65 K followed by a minimum at 30 K. It is suggested that neodymium ions in CaNdAlO{sub 4} at lower temperatures become magnetically ordered, causing an increase of magnetic permeability {mu}{sup {prime}}{sub {ital c}} {gt} 1 and a significant increase of magnetic losses at microwave frequencies. A crystallographic phase transition below 60 K cannot also be excluded.

  18. Flux Trapping Properties of Bulk HIGH-TC Superconductors in Static Field-Cooling Magnetization

    NASA Astrophysics Data System (ADS)

    Deng, Z.; Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M.

    2013-06-01

    The trapping process and saturation effect of trapped magnetic flux of bulk high-temperature superconductors by static field-cooling magnetization (FCM) are reported in the paper. With a cryogenic Bell Hall sensor attached on the center of the bulk surface, the synchronous magnetic signals were recorded during the whole magnetization process. It enables us to know the flux trapping behavior since the removal of the excitation field, as well as the subsequent flux relaxation phenomenon and the flux dissipation in the quench process of the bulk sample. With the help of flux mapping techniques, the relationship between the trapped flux and the applied field was further investigated; the saturation effect of trapped flux was discussed by comparing the peak trapped field and total magnetic flux of the bulk sample. These studies are useful to understand the basic flux trapping properties of bulk superconductors.

  19. The static and hyper-frequency magnetic properties of a ferromagnetic ferroelectric composite

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Xu, Fang; Qiao, Lijie; Zhou, Ji; Li, Longtu

    2009-02-01

    This paper reports the static and hyper-frequency magnetic properties, as well as their relationship with microstructure, of the ferromagnetic-ferroelectric co-fired composite ceramic, (1- x)Ba 2Zn 1.2Cu 0.8Fe 12O 22- xPb(Ni 1/3Nb 2/3) 0.8Ti 0.2O 3. The X-ray diffraction results did not detect any other phase in the co-fired ceramics, but found a crystal structural distortion of ferrite phase. Scanning electron microscopy photos showed that two phases' grains matched well and stacked compactly and the hexagonal ferrite changed its grain morphology. The saturation magnetization increased with the reduction of magnetic phase in the range of 0< x<0.65 because of the stress-induced structural distortion. The permeability decreases monotonically with the reduction of magnetic phase in the whole composition range.

  20. Static properties of small Josephson tunnel junctions in an oblique magnetic field

    NASA Astrophysics Data System (ADS)

    Monaco, R.; Aaroe, M.; Mygind, J.; Koshelets, V. P.

    2009-04-01

    We have carried out a detailed experimental investigation of the static properties of planar Josephson tunnel junctions in presence of a uniform external magnetic field applied in an arbitrary orientation with respect to the barrier plane. We considered annular junctions, as well as rectangular junctions (having both overlap and cross-type geometries) with different barrier aspect ratios. It is shown how most of the experimental findings in an oblique field can be reproduced invoking the superposition principle to combine the classical behavior of electrically small junctions in an in-plane field together with the small junction behavior in a transverse field that we recently published [R. Monaco , J. Appl. Phys. 104, 023906 (2008)]. We show that the presence of a transverse field may have important consequences, which could be either voluntarily exploited in applications or present an unwanted perturbation.

  1. Study of the vibrational, dielectric and infrared properties of CdSiP2 via first principles

    NASA Astrophysics Data System (ADS)

    Lv, Zhen-Long; Cui, Hong-Ling; Wang, Hui; Li, Xiao-Hong; Ji, Guang-Fu

    2016-11-01

    CdSiP2is a promising nonlinear optical crystal for frequency conversion in the mid-IR spectral range. In this work, the vibrational, dielectric and infrared properties of CdSiP2 are studied by using density functional perturbation calculation. The Born effective charges of the constituent ions, the vibrational modes and the splitting of the longitudinal and transverse optical (LO-TO) frequencies at the Brillouin zone center are calculated and discussed. Its dielectric constant and dielectric spectra are also calculated, which reveals that electrons in CdSiP2 have a larger contribution to the dielectric constant than the lattice. The theoretically obtained birefringence Δn and the simulated infrared reflectance spectra agree well with the available experimental results.

  2. Fumed silica concentration effect on structure and dielectric properties of a styrene-cross-linked unsaturated polyester resin

    NASA Astrophysics Data System (ADS)

    Gorelov, B. M.; Polovina, O. I.; Gorb, A. M.; Dacko, S.; Kostrzewa, M.; Ingram, A.

    2012-11-01

    Concentration effects of a high-reactive-surface nanosized SiO2 filler on structure and dielectrical properties of a styrene-cross-linked polyester resin have been experimentally studied. Thermal desorption mass-spectroscopy, IR-spectroscopy, dielectric spectroscopy, and positron annihilation lifetime spectroscopy were used to determine an atomic content of thermal destruction products, IR-reflection spectra, complex dielectric permittivity, and a nature of positron traps as function of filler content in the polymer matrix. Interaction between active surface centers of SiO2-nanoparticles and atoms of polyester chains and styrene molecules gives the non-monotonous influence on the structure of polyester chains, macromolecule polarity, dielectric parameters and the number of positronium nanotraps.

  3. Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

    NASA Astrophysics Data System (ADS)

    Yuan, Xuepei; Chung, T. C. Mike

    2011-02-01

    A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (ɛ) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a ɛ ˜3, which is independent of a wide range of temperatures and frequencies, slim D-E hysteresis loops, high breakdown strength (E=650 MV/m), narrow breakdown distribution, and reliable energy storage capacity >5 J/cm3 (double that of state-of-the-art biaxially oriented polypropylene capacitors), without showing any increase in energy loss.

  4. A genetic algorithm for optimizing multi-pole Debye models of tissue dielectric properties.

    PubMed

    Clegg, J; Robinson, M P

    2012-10-01

    Models of tissue dielectric properties (permittivity and conductivity) enable the interactions of tissues and electromagnetic fields to be simulated, which has many useful applications in microwave imaging, radio propagation, and non-ionizing radiation dosimetry. Parametric formulae are available, based on a multi-pole model of tissue dispersions, but although they give the dielectric properties over a wide frequency range, they do not convert easily to the time domain. An alternative is the multi-pole Debye model which works well in both time and frequency domains. Genetic algorithms are an evolutionary approach to optimization, and we found that this technique was effective at finding the best values of the multi-Debye parameters. Our genetic algorithm optimized these parameters to fit to either a Cole-Cole model or to measured data, and worked well over wide or narrow frequency ranges. Over 10 Hz-10 GHz the best fits for muscle, fat or bone were each found for ten dispersions or poles in the multi-Debye model. The genetic algorithm is a fast and effective method of developing tissue models that compares favourably with alternatives such as the rational polynomial fit.

  5. Trapping-charging ability and electrical properties study of amorphous insulator by dielectric spectroscopy

    SciTech Connect

    Mekni, Omar Arifa, Hakim; Askri, Besma; Yangui, Béchir; Raouadi, Khaled; Damamme, Gilles

    2014-09-14

    Usually, the trapping phenomenon in insulating materials is studied by injecting charges using a Scanning Electron Microscope. In this work, we use the dielectric spectroscopy technique for showing a correlation between the dielectric properties and the trapping-charging ability of insulating materials. The evolution of the complex permittivity (real and imaginary parts) as a function of frequency and temperature reveals different types of relaxation according to the trapping ability of the material. We found that the space charge relaxation at low frequencies affects the real part of the complex permittivity ε{sup ´} and the dissipation factor Tan(δ). We prove that the evolution of the imaginary part of the complex permittivity against temperature ε{sup ′′}=f(T) reflects the phenomenon of charge trapping and detrapping as well as trapped charge evolution Q{sub p}(T). We also use the electric modulus formalism to better identify the space charge relaxation. The investigation of trapping or conductive nature of insulating materials was mainly made by studying the activation energy and conductivity. The conduction and trapping parameters are determined using the Correlated Barrier Hopping (CBH) model in order to confirm the relation between electrical properties and charge trapping ability.

  6. Microwave-assisted sintering of non-stoichiometric strontium bismuth niobate ceramic: Structural and dielectric properties

    NASA Astrophysics Data System (ADS)

    Singh, Rajveer; Luthra, Vandna; Tandon, R. P.

    2016-11-01

    In recent years the microwave sintering has been utilized for the synthesis of materials in enhancement of the properties. In this paper strontium bismuth niobate (Sr0.8Bi2.2Nb2O9:SBN) bulk ceramic has been synthesized by microwave reactive sintering and conventional heating techniques. A relative density of 99.6% has been achieved for microwave sintered SBN, which is higher than that of (98.81%) conventionally sintered SBN. The phase formation of SBN synthesized by both processes has been confirmed by X-ray diffraction (XRD). The surface morphology of SBN was observed by scanning electron microscopy (SEM). The microstructure was found to be more uniform in case of SBN sintered by microwave sintering. The dielectric properties of SBN were studied as a function of frequency in the temperature range of 30-500 °C. Both the samples synthesized by two different processes were found to follow Curie-Weiss law above the transition temperature. The Curie temperature was found to be higher for microwave sintered SBN. The dielectric constant and the transition temperature were observed to be higher for SBN ceramic synthesized by microwave sintering technique. The ac and dc activation energy values were also found to be higher for microwave sintered SBN as compared to conventional sintering technique.

  7. Extraction of Water from Polar Lunar Permafrost with Microwaves - Dielectric Property Measurements

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Kaukler, William

    2009-01-01

    Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles. The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year. Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap. The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured.

  8. Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

    NASA Astrophysics Data System (ADS)

    Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

    2016-10-01

    This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' } ) and imaginary (ɛ ^' ' } ) parts of the complex permittivity (ɛ ^* ) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

  9. Dipolar correlations and the dielectric permittivity of water.

    PubMed

    Sharma, Manu; Resta, Raffaele; Car, Roberto

    2007-06-15

    The static dielectric properties of liquid and solid water are investigated within linear response theory in the context of ab initio molecular dynamics. Using maximally localized Wannier functions to treat the macroscopic polarization we formulate a first-principles, parameter-free, generalization of Kirkwood's phenomenological theory. Our calculated static permittivity is in good agreement with experiment. Two effects of the hydrogen bonds, i.e., a significant increase of the average local moment and a local alignment of the molecular dipoles, contribute in almost equal measure to the unusually large dielectric constant of water.

  10. Investigation of low field dielectric properties of anisotropic porous Pb(Zr,Ti)O3 ceramics: Experiment and modeling

    NASA Astrophysics Data System (ADS)

    Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.

    2013-12-01

    Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.

  11. Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

    SciTech Connect

    Hakala, J. Alexandra; Stanchina, William; Soong, Yee; Hedges, Sheila

    2011-01-01

    Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (<200° C) and constant oil shale grade, both the relative dielectric constant (ε') and imaginary permittivity (ε'') decrease with increased frequency and remain constant at higher frequencies. At low temperature and constant frequency, ε' decreases or remains constant with oil shale grade, while ε'' increases or shows no trend with oil shale grade. At higher temperatures (>200º C) and constant frequency, epsilon' generally increases with temperature regardless of grade while ε'' fluctuates. At these temperatures, maximum values for both ε' and ε'' differ based upon oil shale grade. Formation fluids, mineral-bound water, and oil shale varve geometry also affect measured dielectric properties. This review presents and synthesizes prior work on the influence of applied frequency, oil shale grade, water, and temperature on the dielectric properties of oil shales that can aid in the future development of frequency- and temperature-specific in situ retorting technologies and oil shale grade assay tools.

  12. Property and Lighting Manipulations for Static Volume Stylization Using a Painting Metaphor.

    PubMed

    Klehm, Oliver; Ihrke, Ivo; Seidel, Hans-Peter; Eisemann, Elmar

    2014-07-01

    Although volumetric phenomena are important for realistic rendering and can even be a crucial component in the image, the artistic control of the volume's appearance is challenging. Appropriate tools to edit volume properties are missing, which can make it necessary to use simulation results directly. Alternatively, high-level modifications that are rarely intuitive, e.g., the tweaking of noise function parameters, can be utilized. Our work introduces a solution to stylize single-scattering volumetric effects in static volumes. Hereby, an artistic and intuitive control of emission, scattering and extinction becomes possible, while ensuring a smooth and coherent appearance when changing the viewpoint. Our method is based on tomographic reconstruction, which we link to the volumetric rendering equation. It analyzes a number of target views provided by the artist and adapts the volume properties to match the appearance for the given perspectives. Additionally, we describe how we can optimize for the environmental lighting to match a desired scene appearance, while keeping volume properties constant. Finally, both techniques can be combined. We demonstrate several use cases of our approach and illustrate its effectiveness.

  13. Static and dynamic magnetic property of MBE-grown Co2FeAl films

    NASA Astrophysics Data System (ADS)

    Qiao, Shuang; Nie, Shuaihua; Huo, Yan; Zhao, Jianhua; Wu, Yizheng; Zhang, Xinhui

    2014-08-01

    In this work, the static and dynamic magnetic properties of Co2FeAl films grown by molecular beam epitaxy (MBE) were studied by employing the magneto-optical Kerr rotation and ferromagnetic resonance (FMR) measurements. The growth temperature dependent magnetocrystalline anisotropy of MBE-grown Co2FeAl films were first investigated by employing the rotating magneto-optical Kerr effect. Then the magnetization dynamics and Gilbert damping property for high quality Co2FeAl films were investigated in detail by combining both the FMR and time-resolved magneto-optical Kerr rotation techniques. The apparent damping parameter was found to show strong dependence on the strength of the applied magnetic field at low-field regime, but decrease drastically with increasing magnetic field and eventually become a constant value of 0.004 at high-field regime. The inhomogeneity of magnetocrystalline anisotropy and two-magnon scattering are suggested to be responsible for the observed abnormal damping properties observed especially at low field regime. The intrinsic damping parameter of 0.004 is deduced for our highly-ordered Co2FeAl film. Our results provide essential information for highly-ordered MBE-grown Co2FeA film and its possible application in spintronic devices.

  14. Electro-optic, thermo-optic, and dielectric properties of YCOB and Nd:YCOB crystals: comparative study

    NASA Astrophysics Data System (ADS)

    Abarkan, Mustapha; Salvestrini, Jean Paul; Pelenc, Denis; Fontana, Marc D.

    2005-02-01

    The electro-optic (EO), thermo-optic, and dielectric coefficients of pure as well as Nd-doped YCa4O(BO3)3 crystals are determined. The frequency and wavelength dependence of the EO coefficients were determined in the 0-150 MHz and 0.5-1.3 μm ranges, respectively. The analysis of the frequency dependences of both EO and dielectric properties provides the unclamped and clamped values of the whole set of coefficients. It appears that the acoustic contributions to the EO and dielectric properties are very low. Small differences in the properties found for the two crystals are attributed to the Nd doping ions. It is to be noticed that, surprisingly, the birefringence (nX-nY) was found to be independent of the temperature in the range 20-40 °C.

  15. Local viscoelastic properties of live cells investigated using dynamic and quasi-static atomic force microscopy methods.

    PubMed

    Cartagena, Alexander; Raman, Arvind

    2014-03-01

    The measurement of viscoelasticity of cells in physiological environments with high spatio-temporal resolution is a key goal in cell mechanobiology. Traditionally only the elastic properties have been measured from quasi-static force-distance curves using the atomic force microscope (AFM). Recently, dynamic AFM-based methods have been proposed to map the local in vitro viscoelastic properties of living cells with nanoscale resolution. However, the differences in viscoelastic properties estimated from such dynamic and traditional quasi-static techniques are poorly understood. In this work we quantitatively reconstruct the local force and dissipation gradients (viscoelasticity) on live fibroblast cells in buffer solutions using Lorentz force excited cantilevers and present a careful comparison between mechanical properties (local stiffness and damping) extracted using dynamic and quasi-static force spectroscopy methods. The results highlight the dependence of measured viscoelastic properties on both the frequency at which the chosen technique operates as well as the interactions with subcellular components beyond certain indentation depth, both of which are responsible for differences between the viscoelasticity property maps acquired using the dynamic AFM method against the quasi-static measurements.

  16. Dielectric properties of cereals at frequencies useful for processes with microwave heating.

    PubMed

    Torrealba-Meléndez, Richard; Sosa-Morales, María Elena; Olvera-Cervantes, José Luis; Corona-Chávez, Alonso

    2015-12-01

    Dielectric properties of barley, corn (white and yellow), sorghum, and wheat at microwave frequencies for heating purpose were analyzed. Properties were determined at 915, 2450 and 5800 MHz with the free space transmission method in the cereals at 20, 30, 40, 50 and 60 °C. ε´ and ε"of all the cereals decreased with increasing frequency. ε´ slightly increased with temperature, while ε "remained practically constant for all the cereals in the temperature range from 20 to 60 °C. Penetration depth decreased with increasing frequency for all the samples, and increased with increasing temperature at 915 MHz, except for barley. These results are useful for further microwave heating applications for the studies on cereals.

  17. Transport and dielectric properties of dense ionized matter from the average-atom RESEOS model

    NASA Astrophysics Data System (ADS)

    Ovechkin, A. A.; Loboda, P. A.; Falkov, A. L.

    2016-09-01

    Electron transport properties of warm and hot dense matter are calculated using two versions of the average-atom approach: Liberman's model and the neutral Wigner-Seitz-sphere model. Electrical conductivity calculations employed the extended Ziman formula, the relaxation-time approximation, the Zubarev method, and the Kubo-Greenwood formula. Thermal conductivities were evaluated in the relaxation-time approximation. The results obtained are in good agreement with experimental data and ab initio calculations. The origin of nonphysical features appearing in the DC electrical and thermal conductivities calculated with the relaxation-time approximation and the Zubarev method is analyzed. AC conductivity and dielectric properties of dense ionized matter are obtained from the radiative opacity data calculated using the RESEOS model.

  18. Synthesis, Characterization and Properties of Ca5A2TiO12 (A=Nb, Ta) Ceramic Dielectric Materials for Applications in Microwave Telecommunication Systems

    NASA Astrophysics Data System (ADS)

    Bijumon, Pazhoor Varghese; Mohanan, Pezholil; Sebastian, Mailadil Thomas

    2002-06-01

    Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Qu× f> 30000 GHz) and small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator applications in microwave integrated circuits.

  19. The dependence of lead-salt nanocrystal properties on morphology and dielectric environment

    NASA Astrophysics Data System (ADS)

    Bartnik, Adam Christopher

    The IV-VI semiconductors, and specifically the lead-salts (PbS, PbSe, and PbTe), are a natural choice for nanocrystal science. In nanocrystals, because of their narrow band gap, small effective masses, and large dielectric constants, they offer a unique combination of both strong confinement and strong dielectric contrast with their environment. Studying how these two effects modify optical and electrical properties of nanocrystals will be the topic of this dissertation. We begin with a summary of the synthesis of high-quality PbS and PbSe nanocrystals. Special care is taken to explain the chemical procedures in detail to an audience not expected to have significant prior chemistry knowledge. The synthesized nanocrystals have bright and tunable emission that spans the edge of the visible to the near-IR spectrum (700--1800 nm), and they are capped with organic ligands making them easily adaptable to different substrates or hosts. This combination of high optical quality and flexible device engineering make them extremely desirable for application. Moving beyond single-material nanocrystals, we next explore nanocrystal heterostructures, specifically materials with a spherical core of one semiconductor and a shell of another. Core-shell structures are commonly used in nanocrystals as a method to separate the core material, where the electrons and holes are expected to stay, from interfering effects at the surface. This typically results in improvements in stability and fluorescence quantum efficiency. To that end, we develop a model to explain how confinement plays out across abrupt changes in material, focusing on the optical and electrical properties of recently synthesized PbSe/PbS core-shell quantum dots. We show that for typical sizes of these nanocrystals, a novel type of nanocrystal heterostructure is created, where electrons and holes extend uniformly across the abrupt material boundary, and the shell does not act as a protecting layer. For very large sizes

  20. Measurements of the dielectric properties of simulated comet material as part of the KOSI 10 experiment

    NASA Technical Reports Server (NTRS)

    Ulamec, S.; Svedhem, H.; Kochan, H.

    1993-01-01

    The dielectric constant epsilon of the snow-mineral used for the comet simulation in the German KOSI 10 experiment was measured in the radio frequency range from 2 to 4 GHz. The traditional microwave bridge method was used, but instead of using a waveguide that contains the sample material small lambda/4 antennas were used as sensors. A change in the dielectric properties indicates a change in density and/or composition, respectively. The method is presented as an analytical tool for measuring such density or composition changes during alteration snow-dust materials. The KOSI (determined from the German: Kometen Simulation) experiments, performed in the Space simulator of the DLR/Institut for Raumsimulation, during the last years revealed many processes that presumably take place on comets. So far, modifications of the internal structure could be identified only during the post-experiment inspection via hardness tests. It was the aim of the KOSI 10 and KOSI 10a experiments to emphasize on a synoptic detection of events like particle emission or crust formation. The composition of the KOSI 10 sample material was an ice-mineral mixture with about 10 percent mineral (olivine) content. An excellent method to investigate the change of the density of the probe material during its exposure to the artificial sun in situ is to do it via the measurement of the dielectric constant. The traditional method to determine epsilon, by using a microwave-bridge to measure the transmission and the reflection factor of the sample material for electromagnetic waves in the radio frequency range, was modified, since the commonly used practice to fill the sample material into a waveguide was not compatible with the need for in situ measurements during the simulation experiment.