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Sample records for static dielectric properties

  1. Static Dielectric Properties of Carbon Nanotubes from First Principles

    SciTech Connect

    Kozinsky, Boris; Marzari, Nicola N.

    2006-04-24

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We characterize the response of isolated single-wall (SWNT) and multiwall (MWNT) carbon nanotubes and nanotube bundles to static electric fields using first-principles calculations and densityfunctional theory. The longitudinal polarizability of SWNTs scales as the inverse square of the band gap, while in MWNTs and bundles it is given by the sum of the polarizabilities of the constituent tubes. The transverse polarizability of SWNTs is insensitive to band gaps and chiralities and is proportional to the square of the effective radius; in MWNTs, the outer layers dominate the response. The transverse response is intermediate between metallic and insulating, and a simple electrostatic model based on a scale-invariance relation captures accurately the first-principles results. The dielectric response of nonchiral SWNTs in both directions remains linear up to very high values of applied field.

  2. Simulation studies of ionic liquids: orientational correlations and static dielectric properties.

    PubMed

    Schröder, C; Rudas, T; Steinhauser, O

    2006-12-28

    The ionic liquids BMIM+I-, BMIM+BF4-, and BMIM+PF6- were simulated by means of the molecular dynamics method over a time period of more than 100 ns. Besides the common structural analysis, e.g., radial distribution functions and three dimensional occupancy plots, a more sophisticated orientational analysis was performed. The angular correlation functions g(00)110(r) and g(00)101(r) are the first distance dependent coefficients of the pairwise orientational distribution function g(rij,Omega1,Omega2,Omega12). These functions help to interpret the three dimensional plot and reveal interesting insights into the local structure of the analyzed ionic liquids. Furthermore, the collective network of ionic liquids can be characterized by the Kirkwood factor Gkappa(r) [J. Chem. Phys. 7, 911 (1939)]. The short-range behavior (r<10 A) of this factor may be suitable to predict the water miscibility of the ionic liquid. The long-range limit of Gkinfinity is below 1 which demonstrates the strongly coupled nature of the ionic liquid networks. In addition, this factor relates the orientational structure and the dielectric properties of the ionic liquids. The static dielectric constant epsilon(omega=0) for the simulated system is 8.9-9.5. Since in ionic liquids the very same molecule contributes to the total dipole moment as well as carries a net charge, a small, but significant contribution of the cross term between the total dipole moment and the electric current to epsilon(omega=0) is observed. PMID:17199354

  3. 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...

  4. Static dielectric permittivity of ice from first principles.

    PubMed

    Bonnet, Nicéphore; Marzari, Nicola

    2014-12-12

    The static permittivity of ice is computed from first principles as a function of the electric field, together with the generalized Kirkwood factor. The molecular dipole in ice is unambiguously obtained by an original method combining a slab approach and Berry phase calculations, and the fluctuations of the polarization are sampled by Monte Carlo runs using first-principles model Hamiltonians for different proton configurations. Common approximations in the exchange-correlation functionals overestimate the dielectric permittivity and enhance ferroelectric configurations and the Kirkwood factor, whereas dielectric saturation effects compare well with experiment. PMID:25541777

  5. 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.

  6. Theoretical investigation of dielectric properties of rare earth stillwellite compounds

    NASA Astrophysics Data System (ADS)

    Shaltaf, R.; Khalifeh, J.

    2015-07-01

    Ab initio density functional calculations are performed to investigate the dielectric properties of LnBSiO5 (Ln = Ce, Pr, Nd) with the stillwellite structure. The calculated structural parameters are found to agree well with existing experimental results. The three compounds possess insulating electronic structure with nearly isotropic high frequency dielectric permittivity tensors. On the other hand, the static dielectric permittivity tensors are found to be less isotropic. The anisotropy of static dielectric tensors are found to increase as the atomic number of the lanthanide increases.

  7. 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.

  8. 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.

  9. Applications for Dielectric Properties of Agricultural Products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating are discussed briefly. Values for the dielectric properties of a number of products, including grain, fruit, and poultry products...

  10. Dielectric properties of agricultural products and applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating is discussed briefly. Values for the dielectric properties of a number of products, including grain and seed, fruits and vegetab...

  11. CORRELATING HONEYDEW MELON QUALITY WITH DIELECTRIC PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Honeydew melons were grown and harvested with a range of maturities for measurement of tissue permittivities (dielectric constant and loss factor) to study possible correlations between the dielectric properties and soluble solids (sweetness) for nondestructive sensing of maturity. Permittivities of...

  12. 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.

  13. The Dielectric Properties of Semiconductors

    NASA Astrophysics Data System (ADS)

    Harrison, Walter A.

    1999-06-01

    It is indeed remarkable that aspects of solids as diverse as the bonding and the dielectric properties should be described by the same elementary theory. Phillips (1973) noted such a connection and defined an ionicity of the bonds in semiconductors in terms of the dielectric constant, rather than in terms of the bond energy as had been done by Pauling (1960). They gave remarkably similar ionicity scales, but Phillips argued that the dielectric basis was better because of its more direct relation to the electronic structure. We would agree with this, noting that the bond energy (cf. Eq. (2-34)) contains a term Epro and a complicated dependence upon polarity, while we shall find a rather simple dependence ( proportionality to ?c3 = (1- ?P2)3/2) for the susceptibility and approximately the same for the dielectric constant. The defining of an ionicity to be used to scale properties from one system to another is of course a much less ambitious undertaking than a derivation of the properties in terms of the electronic structure. On the other hand, because of its empirical content it can be a more accurate predictor of experimental values. It can be used, for example, to accurately predict the elastic constant of GaAs by interpolating between Ge and ZnSe which are isoelectronic with it. The result will be much more accurate than our prediction of the value from Eq. (3-11). On the other hand, because our value does not depend on empirical values for similar systems we can make predictions for totally different systems and obtain the dependence upon other features, such as the bond length or metallicity. The goals are completely different. The fact that our polarity is a similar concept to ionicity (in fact related more closely to the square root of the ionicity of Pauling and Phillips than to the ionicity itself (Harrison(1980), p. 190, Christensen, Satpathy, and Pawlowska(1987)), should not be allowed to confuse the totally different goals and methods used in the two approaches. Our covalent, polar and metallic energies have been obtained directly from the free-atom term values and the simultaneous validity of free-electron and tight-binding concepts (with a slight tuning of coefficients to fit the germanium energy bands) and we may proceed to direct predictions of the dielectric properties in terms of them without further parameters or approximations.

  14. Tunable optical properties of silver-dielectric-silver nanoshell

    NASA Astrophysics Data System (ADS)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2014-05-01

    Tunable optical properties of silver-dielectric-silver nanoshell including surface plasmon resonance (SPR) and resonance light scattering (RLS) based on quasi-static theory are investigated. When the silver core radius increases, the longer resonance wavelength red shifts and light scattering cross-section decreases whereas the shorter resonance wavelength blue shifts and the light scattering cross-section increases. The effect of middle dielectric thickness on the light scattering cross-section of nanoshell is different from those of the silver core radius changes. As middle dielectric radius increases, the longer resonance wavelength first blue shifts and then red shifts and the light scattering cross-section increases whereas the shorter resonance wavelength always red shifts and the light scattering cross-section decreases. The sensitivity of RLS to the refractive index of embedding medium is also reported. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness leads to increase the sensitivity of silver-dielectric-silver nanoshell. Tunable optical properties of silver-dielectric-silver nanoshell verify the biosensing potential of this nanostructure.

  15. Dielectric Properties of Ice and Liquid Water from First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Lu, Deyu; Gygi, Franois; Galli, Giulia

    2008-04-01

    We present a first-principles study of the static dielectric properties of ice and liquid water. The eigenmodes of the dielectric matrix ? are analyzed in terms of maximally localized dielectric functions similar, in their definition, to maximally localized Wannier orbitals obtained from Bloch eigenstates of the electronic Hamiltonian. We show that the lowest eigenmodes of ?-1 are localized in real space and can be separated into groups related to the screening of lone pairs, intra-, and intermolecular bonds, respectively. The local properties of the dielectric matrix can be conveniently exploited to build approximate dielectric matrices for efficient, yet accurate calculations of quasiparticle energies.

  16. 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.

  17. Microwave Dielectric Properties of Cereal Grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of five cereal grains (wheat, corn, barley, oats, and grain sorghum) were 19 measured at 23 oC over broad microwave frequency range (5 GHz to 15 GHz) with a free-space-transmission 20 technique. Results of dielectric properties measurement are tabulated for each material for mo...

  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. Microwave dielectric properties of cereal grains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of five cereal grains (wheat, corn, barley, oats, and grain sorghum) were measured at 23°C over a range of moisture contents and over microwave frequencies from 5 to 15 GHz with a free-space transmission technique. Resulting dielectric constants and loss factors are tabulated f...

  1. Volume dependence of the dielectric properties of amorphous SiO2.

    PubMed

    Malyi, Oleksandr I; Boström, Mathias; Kulish, Vadym V; Thiyam, Priyadarshini; Parsons, Drew F; Persson, Clas

    2016-03-01

    Using first principles calculations, the analysis of the dielectric properties of amorphous SiO2 (am-SiO2) was performed. We found that the am-SiO2 properties are volume dependent, and the dependence is mainly induced by the variation of nanoporosity at the atomic scale. In particular, both ionic and electronic contributions to the static dielectric constants are functions of volume with clear trends. Moreover, using the unique parameterization of the dielectric function provided in this work, we predict dielectric functions at imaginary frequencies of different SiO2 polymorphs having similar band gap energies. PMID:26902661

  2. 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.

  3. 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.

  4. 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 11014 to 11016 ions cm-2. The beam current used was 0.40 A 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, ?' vs. imaginary part of complex permittivity, ??). The Cole-Cole plots have also been used to determine static dielectric constant (?s), optical dielectric constant (??), spreading factor (?), average relaxation time (?0) and molecular relaxation time (?). 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.

  5. An ab-initio computational method to determine dielectric properties of biological materials.

    PubMed

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

    2013-01-01

    Frequency dependent dielectric properties are important for understanding the structure and dynamics of biological materials. These properties can be used to study underlying biological processes such as changes in the concentration of biological materials, and the formation of chemical species. Computer simulations can be used to determine dielectric properties and atomic details inaccessible via experimental methods. In this paper, a unified theory utilizing molecular dynamics and density functional theory is presented that is able to determine the frequency dependent dielectric properties of biological materials in an aqueous solution from their molecular structure alone. The proposed method, which uses reaction field approximations, does not require a prior knowledge of the static dielectric constant of the material. The dielectric properties obtained from our method agree well with experimental values presented in the literature. PMID:23652459

  6. 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.

  7. Dielectric Properties of Water Under Extreme Conditions

    NASA Astrophysics Data System (ADS)

    Pan, Ding

    2014-03-01

    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 has greatly limited 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. We also computed the electronic dielectric constant of water as a function of pressure and we found that, contrary to expectations based on widely used simple models, both the refractive index and the electronic band gap of water increase under pressure. The work is supported by DOE-CMCSN under Grant DE-SC0005180 and by the Sloan Foundation through the Deep Carbon Observatory.

  8. Dielectric surface properties of Venus

    NASA Technical Reports Server (NTRS)

    Pettengill, G. H.; Wilt, R. J.; Ford, P. G.

    1992-01-01

    It has been known for over a decade that certain high-altitude regions on Venus exhibit bizarre radar-scattering and radiothermal-emission behavior. For example, observed values for normal-incidence power reflection coefficients in these areas can exceed 0.5; enhanced back scatter in some mountainous areas in the Magellan SAR images creates a bright surface with the appearance of snow; and reduced thermal emission in the anomalous areas makes the surface there appear hundreds of degrees cooler than the corresponding physical surface temperatures. The inferred radio emissivity in several of these regions falls to 0.3 for horizontal linear polarization at viewing angles in the range 20 deg - 40 deg. Several explanations have been offered for these linked phenomena. One involves single-surface reflection from a sharp discontinuity separating two media that have extremely disparate values of electromagnetic propagation. The mismatch may occur in either or both the real (associated with propagation velocity) or imaginary (associated with absorption) components of the relevant indices of refraction, and the discontinuity must take place over a distance appreciably shorter than a wavelength. An example of such an interaction of Earth would occur at the surface of a body of water. At radio wavelengths, water has an index of refraction of 9 (dielectric permittivity of about 80), and an associated loss factor that varies strongly with the amount of dissolved salts, but is generally significant. Its single-surface radar reflectivity at normal incidence is about 0.65, and the corresponding emissivity (viewed at the same angle) is therefore 0.35. Both these values are similar to the extremes found on Venus, but in the absence of liquid water, the process on Venus requires a different explanation. Two of the present authors (Pettengill and Ford) have suggested that scattering from a single surface possessing a very high effective dielectric permittivity could explain many of the unusual characteristics displayed by the Venus surface. A second explantion relates to the volume scattering that results from successive interactions with one or more interfaces interior to the planetary surface. If the near-surface material has a moderately low index of refraction (to ensure that a substantial fraction of the radiation incident from outside is not reflected, but rather penetrates into the surface), and a very low internal propagation loss, successive internal reflections can eventually redirect much of the energy back through the surface toward the viewer. The necessary conditions for this process to be effective are a low internal propagation loss coupled with efficient internal reflection. At sufficiently low temperatures, fractured water ice displays both the necessary low loss and near-total internal reflection. The possibility that this mechanism might be acting on Venus has recently been put forward.

  9. 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

  10. Dielectric properties of Ag/PAN nanocomposites

    NASA Astrophysics Data System (ADS)

    Kudryashov, M. A.; Mashin, A. I.; Logunov, A. A.; Chidichimo, G.; De Filpo, G.

    2014-07-01

    The dependence of electric modulus on the frequency of an ac electric field is studied for the silver/polyacrylonitrile nanocomposite films at several measurement temperatures and AgNO3 contents in the original mixture. It is demonstrated that the frequency dispersion of dielectric properties is well described with the aid of the Cole-Davidson model. The relaxation maxima on the curve of the imaginary part of the electric modulus versus frequency are interpreted using the interfacial polarization.

  11. Frequency-wavelength calculator with table of dielectric properties

    NASA Technical Reports Server (NTRS)

    Thompson, L. L.

    1972-01-01

    Frequency-wavelength calculator has been developed which rapidly and accurately calculates wavelength of given frequency in specific dielectric material. Unit fits into shirt pocket and includes table of dielectric properties and one-step calculator.

  12. 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.

  13. 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.

  14. 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.

  15. 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)...

  16. 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. PMID:16853170

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

    NASA Astrophysics Data System (ADS)

    Qian, Zhixin

    2015-11-01

    The exchange contribution, ?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 ?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 ?1(k, 0) at the wavevectors of k = 0, k = 2kF, and at limiting large k are derived. The results all verify those obtained by Engel and Vosko.

  18. A Database for the Static Dielectric Constant of Water and Steam

    NASA Astrophysics Data System (ADS)

    Fernndez, Diego P.; Mulev, Y.; Goodwin, A. R. H.; Levelt Sengers, J. M. H.

    1995-01-01

    All reliable sources of data for the static dielectric constant or relative permittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS-90 temperature scale. The data extend over a temperature range from 238 to 873 K and over a pressure range from 0.1 MPa up to 1189 MPa. The evaluative part of this work includes a review of the different types of measurement techniques, and the corrections for frequency dependence due to the impedance of circuit components, and to electrode polarization. It also includes a detailed assessment of the uncertainty of each particular data source, as compared to other sources in the same range of pressure and temperature. Both the raw and the corrected data have been tabulated, and are also available on diskette. A comprehensive list of references to the literature is included.

  19. Temperature and moisture dependent dielectric properties of legume flours associated with dielectric heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of flour samples from four legumes (chickpea, green pea, lentil, and soybean) at four different moisture contents were measured using an open-ended coaxial probe and impedance analyzer at frequencies of 10 to 1800 MHz and temperatures of 20 to 90°C. The dielectric constant and ...

  20. 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...

  1. 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.

  2. 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

  3. 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

  4. The dielectric properties of polycrystalline C60

    NASA Astrophysics Data System (ADS)

    Yan, Feng; Wang, Ye-Ning

    1998-06-01

    The dielectric properties (1-50 kHz) of polycrystalline C60 have been carefully studied from 70 to 300 K. Below 170 K, the ac conductance ?(T) is proportional to the temperature, which is thought to be due to the phonon-assisted jump of electrons between localized states around the Fermi level. A significant change of the slope of the capacitance versus temperature curve occurs at 85 K, which can be attributed to the glass transition. It is confirmed that electric dipoles may be induced by orientational defects in C60 crystal. The capacitance drop around 256 K is found to originate from the disappearance of the orientational defects above the order-disorder phase-transition temperature.

  5. Dielectric Properties of Onion-Like Carbon Composites

    NASA Astrophysics Data System (ADS)

    Macutkevic, J.; Grigalaitis, R.; Banys, J.; Hens, S.; Borjanovic, V.; Shenderova, O.; Kuznetsov, V.; Moseenkov, S.

    2013-05-01

    Dielectric properties of onion-like carbon and polyurethane composite prepared using different procedures were investigated in the frequency range up to 1 MHz. We show that broadband dielectric spectroscopy is powerful tool to determine technological fingerprints in the studied materials. It is demonstrated that cured samples annealed at temperature close to the melting point (450 K) exhibit substantially higher dielectric permittivity and electrical conductivity in comparison with untreated samples.

  6. 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.

  7. Effect of Dielectric Property of Hydrous Dispersoid on Electrorheology

    NASA Astrophysics Data System (ADS)

    Kawai, Akiko; Uchida, Kunio; Kamiya, Kunio; Gotoh, Akihiro; Yoda, Satoshi; Urabe, Kei; Ikazaki, Fumikazu

    The effect of the dielectric property was investigated of titania and microcrystalline cellulose particles dispersed in a silicon oil on Electrorheology(ER). A commom understanding of the mechanism of ER is the electrical interaction by the interfacial polarization of dispersed particles. Block et al. reported the relaxation frequency of ER fluids, i. e. the rate of polarization, was very important to have an appreciable ER effect. We found that the free water on the cellulose and the titania particles dispersed in the silicon oil, which is respectively dehydrated below the temperature of ca. 110 and 300 degree centigrade, was necessary for an appreciable ER effect. The relation was measured between the water content and the dielectric properties such as dielectric constant ? and dielectric loss factor ? ", as the water adsorbed on the particles was estimated to alter the dielectric properties of the ER fluid. Both the dielectric constant and the relaxation frequency, which is defined by the applied frequency for a peak of the dielectric loss factor, increased with the increase of the water content The relation was discussed between the ER effect and the dielectric properties.

  8. Models for the Microwave Dielectric Properties of Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Based on microwave dielectric properties of wheat, corn, barley, oats, grain sorghum, soybeans, canola, shelled peanuts and pod peanuts measured over ranges of frequency and moisture content, models are developed for predicting the dielectric constant and loss factor of these commodities. Nearly li...

  9. Microwave Dielectric Properties Models for Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Based on microwave dielectric properties of wheat, corn, barley, oats, grain sorghum, soybeans, canola, shelled peanuts and pod peanuts measured over ranges of frequency and moisture content, models are developed for predicting the dielectric constant and loss factor of these commodities. Nearly lin...

  10. 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. PMID:8600277

  11. Dielectric properties of FeCl3 doped PVA films

    NASA Astrophysics Data System (ADS)

    Mahavar, H. K.; Rawat, A.; Singh, P. J.

    2013-06-01

    Polyvinyl alcohol (PVA) and FeCl3 doped films with different concentrations were prepared using solution grown technique, in order to investigate the effect of FeCl3 doping (up to 10%) on dielectric properties of PVA host at microwave frequency and at room temperature. Measurements of the dielectric parameters such as dielectric permittivity, dielectric loss, loss tangent, a. c. conductivity and relaxation time were carried out. The changes in the dielectric parameters have been observed with doping concentration of FeCl3 in PVA matrix. We have used dielectric data at microwave frequencies as a tool to evaluate optical constants, like extinction coefficient `k' and refractive index `n' of the films.

  12. 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 polarization and birefringence effects, it was determined that one can not utilize the dielectric properties of powder-containing packages to differentiate hoax attacks and serious security threats.

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

    NASA Astrophysics Data System (ADS)

    Peyman, A.; Gabriel, C.; Benedickter, H. R.; Frhlich, 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.

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

    PubMed

    Peyman, A; Gabriel, C; Benedickter, H R; Frhlich, 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. PMID:21364261

  15. First-principles calculations of the dielectric and vibrational properties of ferroelectric and paraelectric BaAl2O4

    NASA Astrophysics Data System (ADS)

    Xie, Congwei; Zeng, Qingfeng; Dong, Dong; Gao, Shuang; Cai, Yongqing; Oganov, Artem R.

    2014-05-01

    First-principles calculations have been conducted to study the structural, dielectric, and vibrational properties of ferroelectric and paraelectric BaAl2O4. High-frequency and static dielectric constants, and phonon frequencies at the Brillouin zone center are reported. Both BaAl2O4 polymorphs are promising infrared-transparent materials due to their low electronic dielectric constants. The ferroelectric and paraelectric BaAl2O4 have much smaller permittivity compared to the classical ferroelectric materials. From an atomic nanostructure standpoint, the abnormally low permittivity of BaAl2O4 polymorphs is mainly related to low coordination numbers of Ba (9) and Al (4).

  16. Static dielectric function and scaling of the ac conductivity for universal and nonuniversal percolation systems

    NASA Astrophysics Data System (ADS)

    McLachlan, D. S.; Sauti, G.; Chiteme, C.

    2007-07-01

    Experimental results and simulations of scaled plots of the normalized conductivity [log(?mr(?,?,T)/?mr(?,0,T))] against the scaled frequency [ log(?/?ce) or log(?/?cp) ], for different conductor volume fractions ? , for various percolation systems are examined and analyzed. Here, ?ce is the critical scaling frequency obtained from superimposing experimental results, and ?cp is the ? value at the peak of the imaginary impedance against frequency curve, which is shown to be a valid scaling frequency. The values obtained for the high frequency slopes, as well as ?ce and ?cp , of all experimental scaling curves are not in agreement with the widely accepted predictions of percolation theory, which incorporate universality relations. It is proposed that this is due to the behavior of the zero frequency (static) dielectric constant [?mr(?,0,T)] that appears in the equations for the critical scaling frequencies ( ?ce and ?cp ) for each ? value. Using an original method, ?mr(?,0,T) is calculated for both the simulated and experimental results. The unexpected behavior observed for the nonuniversal experimental [?mr(?,0,T)] results is found to be in qualitative agreement with the simulation results made using the two exponent phenomenological percolation equation when the ratios of the real conductivities of the components are not zero (in practice, ?ir/?cr?10-18 ). Experimental results for universal conductivity systems, with different compositions or at different temperatures, can also be scaled onto master curves using the same procedures, as for percolation systems. The similarities and differences between these experimental results are qualitatively discussed.

  17. Structural and Dielectric Properties of Subnanometric Laminates of Binary Oxides.

    PubMed

    Kahouli, Abdelkader; Lebedev, Oleg; Ben Elbahri, Marwa; Mercey, Bernard; Prellier, Wilfrid; Riedel, Stefan; Czernohorsky, Malte; Lallemand, Florent; Bunel, Catherine; Lüders, Ulrike

    2015-11-25

    Capacitors with a dielectric material consisting of amorphous laminates of Al2O3 and TiO2 with subnanometer individual layer thicknesses can show strongly enhanced capacitance densities compared to the bulk or laminates with nanometer layer thickness. In this study, the structural and dielectric properties of such subnanometer laminates grown on silicon by state-of-the-art atomic layer deposition are investigated with varying electrode materials. The laminates show a dielectric constant reaching 95 combined with a dielectric loss (tan δ) of about 0.2. The differences of the observed dielectric properties in capacitors with varying electrodes indicate that chemical effects at the interface with the TiN electrode play a major role, while the influence of the local roughness of the individual layers is rather limited. PMID:26523935

  18. The evolution of dielectric properties measurement techniques for agricultural products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The important applications for dielectric properties, or electric permittivities, of agricultural products are described and the evolution of techniques used for their measurement over frequencies ranging from audio to microwave ranges are described briefly. References are cited for further informat...

  19. 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.

  20. 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. PMID:18161420

  1. 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 units (RIU) and a dynamic range as large as 0.17 RIU. Subsequently, optical transmission properties through a self-mixing interferometer array are studied and a novel high-resolution cost-effective optical spectrometer is proposed. The miniature interferometer-based spectrometer is made of polymethyl methacrylate (PMMA) with a CCD as the detector. The detected intensity of each CCD pixels contains the spectral information. Since each frequency component in the incoming beam corresponds to a unique phase difference of the two beam portions of each optical interferometer, the total intensity received by each CCD pixel, which is resulted from the addition of the interference signals from all the frequency components in the beam, should also be unique. Therefore, the spectrum calculation is a problem to solve an ill-posed linear system by using Tikhonov regularization method. Simulation results show that the resolution can reach picometer level. Apart from the choice of path difference between the interfering beams, the spectral resolution also depends on the signal-to-noise ratio and analogue-digital conversion resolution (dynamic range) of the CCD chip. In addition, the theory of uniform waveguide scattering is explored to expand the possibility of using such mini-interferometers for performing free-space spectral analysis of waveguide devices. At the same time, the method of least squares is used to correct the pixel non-uniformity of the CCD so as to improve the performance of the spectrometer. The sensor chip and spectrometer chip introduced here are based on the interference of light transmitted through dielectric aperture arrays. Their compact feature renders these devices ideal for miniaturization and integration as the systems in microfluidics architectures and lab-on-chip designs.

  2. 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.

  3. Dielectric properties of proteins from simulations: tools and techniques

    NASA Astrophysics Data System (ADS)

    Simonson, Thomas; Perahia, David

    1995-09-01

    Tools and techniques to analyze the dielectric properties of proteins are described. Microscopic dielectric properties are determined by a susceptibility tensor of order 3 n, where n is the number of protein atoms. For perturbing charges not too close to the protein, the dielectric relaxation free energy is directly related to the dipole-dipole correlation matrix of the unperturbed protein, or equivalently to the covariance matrix of its atomic displacements. These are straightforward to obtain from existing molecular dynamics packages such as CHARMM or X- PLOR. Macroscopic dielectric properties can be derived from the dipolar fluctuations of the protein, by idealizing the protein as one or more spherical media. The dipolar fluctuations are again directly related to the covariance matrix of the atomic displacements. An interesting consequence is that the quasiharmonic approximation, which by definition exactly reproduces this covariance matrix, gives the protein dielectric constant exactly. Finally a technique is reviewed to obtain normal or quasinormal modes of vibration of symmetric protein assemblies. Using elementary group theory, and eliminating the high-frequency modes of vibration of each monomer, the limiting step in terms of memory and computation is finding the normal modes of a single monomer, with the other monomers held fixed. This technique was used to study the dielectric properties of the Tobacco Mosaic Virus protein disk.

  4. 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.

  5. Radiation induced changes in electronic and dielectric properties of polyoxymethylene

    SciTech Connect

    Sreepad, H. R.; Ravi, H. R.; Ahmed, Khaleel; Waghmare, Umesh V.

    2012-06-05

    First-principle calculations have been done for the Orthorhombic helical Polyoxymethylene. Electronic density of states calculation gives a value of 6.6 eV as the band gap. Phonon frequencies have been calculated at the Gamma point. Phonon modes show wave numbers ranging from 55 cm{sup -1} to 3020 cm{sup -1}. The value of Dielectric constant has been experimentally determined. The gamma irradiation of the sample causes variations in the electronic and dielectric properties of the material. Electrical conductivity increases with increase in dosage of irradiation. Percentage of crystallinity increases where as the value of dielectric constant decreases with increase in dosage of irradiation.

  6. Recent progress on dielectric properties of protic ionic liquids

    NASA Astrophysics Data System (ADS)

    Wojnarowska, Zaneta; Paluch, Marian

    2015-02-01

    Protic ionic liquids (PILs) are key materials for a wide range of emerging technologies. In particular, these systems have long been envisioned as promising candidates for fuel cells. Therefore, in recent years special attention has been devoted to thorough studies of these compounds. Amongst others, dielectric properties of PILs at ambient and elevated pressure have become the subject of intense research. The reason for this lies in the role of broadband dielectric spectroscopy in recognizing the conductivity mechanism in protic ionic systems. In this paper, we summarize the dielectric results of various PILs reflecting recent advances in this field.

  7. Recent progress on dielectric properties of protic ionic liquids.

    PubMed

    Wojnarowska, Zaneta; Paluch, Marian

    2015-02-25

    Protic ionic liquids (PILs) are key materials for a wide range of emerging technologies. In particular, these systems have long been envisioned as promising candidates for fuel cells. Therefore, in recent years special attention has been devoted to thorough studies of these compounds. Amongst others, dielectric properties of PILs at ambient and elevated pressure have become the subject of intense research. The reason for this lies in the role of broadband dielectric spectroscopy in recognizing the conductivity mechanism in protic ionic systems. In this paper, we summarize the dielectric results of various PILs reflecting recent advances in this field. PMID:25634823

  8. Effects of dielectric material properties on graphene transistor performance

    NASA Astrophysics Data System (ADS)

    Jang, Sung Kyu; Jeon, Jaeho; Jeon, Su Min; Song, Young Jae; Lee, Sungjoo

    2015-07-01

    Graphene has attracted attention due to its excellent electrical properties; however, the electrical performance of graphene devices, including device hysteresis, mobility, and conductivity, tends to be limited by the supporting dielectric layer properties. In this work, the impact of a dielectric material on a graphene transistor was investigated by fabricating graphene field effect transistors integrated with four different dielectric substrates (SiO2, Al2O3, Si3N4 and hexagonal boron nitride) and by comparing the transistor performances. Results revealed that the carrier transport characteristics of the graphene transistors, including the hysteresis, Dirac point shift, and mobility, were highly correlated with the hydrophobicity-induced charge trapping and surface optical phonon energies of the dielectric materials.

  9. 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.

  10. Interfacial effects on dielectric properties of polymer-particle nanocomposites

    NASA Astrophysics Data System (ADS)

    Siddabattuni, Sasidhar Veeranjaneyulu

    Dielectric materials that are capable of efficiently storing large amounts of electrical energy are desirable for many electronic and power devices. Since the electrical energy density in a dielectric material is limited to epsilonVb2/2, where is the dielectric permittivity of the material and Vb is the breakdown strength, increased permittivity and breakdown strength are required for large energy storage density. Interfacial effects can influence the dielectric properties, especially dielectric breakdown resistance in polymer-particle nanocomposites. Several functional organophosphates were used to modify the surface of titania and barium titanate nanofiller particles in order to achieve covalent interface when interacted with polymer and to study the influence the electronic nature of filler surfaces on dielectric properties, in particular the breakdown resistance. Surface modified powders were analyzed by thermogravimetric analysis (TGA) and by X-ray photoelectron spectroscopy (XPS). The dielectric composite films obtained by incorporating surface modified powders in epoxy thermosetting polymer were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), impedance spectroscopy, and dielectric breakdown strength measurements. At 30 vol-% filler concentration, a calculated energy density of 8 J/cm3 was observed for titania based composites and 8.3 J/cm3 for barium titanate based composites involving electron scavenging interface with minimal dielectric losses compared to pure polymer. Covalent interface composites yielded energy density of 7.5 J/cm3 for barium titanate based composites at 30 vol.-%. The data indicate that improved dispersion, breakdown strengths and energy densities resulted when electron-poor functional groups were located at the particle surfaces even compared to covalent interface.

  11. Mass properties measurement system: Dynamics and statics measurements

    NASA Technical Reports Server (NTRS)

    Doty, Keith L.

    1993-01-01

    This report presents and interprets experimental data obtained from the Mass Properties Measurement System (MPMS). Statics measurements yield the center-of-gravity of an unknown mass and dynamics measurements yield its inertia matrix. Observations of the MPMS performance has lead us to specific design criteria and an understanding of MPMS limitations.

  12. Expanded modeling of temperature-dependent dielectric properties for microwave thermal ablation

    PubMed Central

    Ji, Zhen; Brace, Christopher L

    2011-01-01

    Microwaves are a promising source for thermal tumor ablation due to their ability to rapidly heat dispersive biological tissues, often to temperatures in excess of 100 C. At these high temperatures, tissue dielectric properties change rapidly and, thus, so do the characteristics of energy delivery. Precise knowledge of how tissue dielectric properties change during microwave heating promises to facilitate more accurate simulation of device performance and helps optimize device geometry and energy delivery parameters. In this study, we measured the dielectric properties of liver tissue during high-temperature microwave heating. The resulting data were compiled into either a sigmoidal function of temperature or an integration of the timetemperature curve for both relative permittivity and effective conductivity. Coupled electromagneticthermal simulations of heating produced by a single monopole antenna using the new models were then compared to simulations with existing linear and static models, and experimental temperatures in liver tissue. The new sigmoidal temperature-dependent model more accurately predicted experimental temperatures when compared to temperaturetime integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperaturetime integration, 27.0% for linear and 32.8% for static models at the antenna input power of 50 W. Correcting for tissue contraction improved agreement for powers up to 75 W. The sigmoidal model also predicted substantial changes in heating pattern due to dehydration. We can conclude from these studies that a sigmoidal model of tissue dielectric properties improves prediction of experimental results. More work is needed to refine and generalize this model. PMID:21791728

  13. Dielectric properties of hypothermic rat artery.

    PubMed

    Marzec, E; Sosnowski, P; Olszewski, J; Krauss, H; Pi?tek, J; Samborski, W; Micker, M; Zawadzi?ski, J

    2013-01-01

    The temperature and frequency dependencies of the dielectric parameters for the rat artery are used to analyse effects of hypothermia on this tissue. Measurements were performed over the frequency range 500 Hz to 100 kHz and at temperatures from 19 to 60C. The artery samples contained about 12% water by mass at room temperature at a relative humidity of 70%. The frequency dependencies of the loss tangent for the control, mild hypothermic and moderate hypothermic artery exhibit two peaks at 2 kHz and 35 kHz in the ?-dispersion region. The results were discussed in terms of the distribution of relaxation frequencies and the activation energy for the conduction and polarization mechanisms particularly in the elastin-water and collagen-water systems. The knowledge about dielectric behavior of the hypothermic rat artery in vitro is important due to clinical application of local and systemic hypothermia. PMID:22789782

  14. Optical properties of semiconductors and dielectrics

    NASA Astrophysics Data System (ADS)

    Mushinskii, V. P.

    The volume contains theoretical and experimental papers on nonequilibrium processes in semiconductors and dielectrics. Topics discussed include analysis of exciton and biexciton states in anisotropic multilayer structures, the Cotton-Mouton effect at local centers in ion crystals, and consideration of the polariton effect in the theory of small impurity centers. Papers are also presented on photoconductivity and photoluminescence effects in some binary semiconductors and on optical data recording using a multilayer structure containing bismuth germanate.

  15. 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...

  16. Use of grain and seed dielectric properties for moisture measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The importance of moisture measurement in grain and seed is discussed, and a brief history of the development of moisture sensing instruments, based on sensing electrical properties of these materials, is presented. Data are presented graphically on the permittivities or dielectric properties of gra...

  17. 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.

  18. Dielectric and optical properties of polymer liquid crystal composite

    NASA Astrophysics Data System (ADS)

    Manohar, Rajiv; Tripathi, G.; Singh, A. K.; Srivastava, A. K.; Shukla, J. P.; Prajapati, A. K.

    2006-11-01

    Dielectric properties of polymer liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300 375 K and frequency range of 100 Hz 10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared.

  19. 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.

  20. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effective Anisotropic Dielectric Properties of Crystal Composites

    NASA Astrophysics Data System (ADS)

    Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming; Franklin, G. Shin

    2010-02-01

    Transformation field method (TFM) is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective anisotropic dielectric responses are formulated in terms of the transformation field. Furthermore, the numerical results show that the effective anisotropic dielectric responses of crystal composites periodically vary as a function of the rotating angle between the principal dielectric axes of inclusion and matrix crystal materials. It is found that at larger inclusion volume fraction the inclusion shapes induce profound effect on the effective anisotropic dielectric responses.

  1. Dielectric properties of crystalline organic molecular films in the limit of zero overlap

    NASA Astrophysics Data System (ADS)

    D'Avino, Gabriele; Vanzo, Davide; Soos, Zoltn G.

    2016-01-01

    We present the calculation of the static dielectric susceptibility tensor and dipole field sums in thin molecular films in the well-defined limit of zero intermolecular overlap. Microelectrostatic and charge redistribution approaches are applied to study the evolution of dielectric properties from one to a few molecular layers in films of different conjugated molecules with organic electronics applications. Because of the conditional convergence of dipolar interactions, dipole fields depend on the shape of the sample and different values are found in the middle layer of a thick film and in the bulk. The shape dependence is eliminated when depolarization is taken into account, and the dielectric tensor of molecular films converges to the bulk limit within a few molecular layers. We quantify the magnitude of surface effects and interpret general trends among different systems in terms of molecular properties, such as shape, polarizability anisotropy, and supramolecular organization. A connection between atomistic models for molecular dielectrics and simpler theories for polarizable atomic lattices is also provided.

  2. Microwave measurement and modeling of the dielectric properties of vegetation

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay Lal

    Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties. The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa. Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Therefore, a dielectric measurement system based upon the probe reflection technique has been set up to measure dielectric properties of green plants over a frequency range from 300 MHz to 18 GHz, moisture contents from 12%, wet basis to 79%, wet basis, and temperatures from -15C to 30C. Dielectric properties of chopped alfalfa were measured with this system over frequency range of 300 MHz to 18 GHz, moisture content from 11.5%, wet basis, to 73%, wet basis, and density over the range from 139 kg m-3 to 716 kg m-3 at 23C. The system accuracy was found to be +/-6% and +/-10% in measuring the dielectric constant and loss factor respectively. Empirical, semi empirical and theoretical models that require only moisture content and operating frequency were determined to represent the dielectric properties of both leaves and stems of alfalfa at 22C. The empirical models fitted the measured dielectric data extremely well. The root mean square error (RMSE) and the coefficient of determination (r2) for dielectric constant and loss factor of leaves were 0.89 and 0.99, and 0.52 and 0.99 respectively. The RMSE and r2 values for dielectric constant and loss factor of stems were 0.89 and 0.99, and 0.77 and 0.99 respectively. Among semi empirical or theoretical models, Power law model showed better performance (RMSE = 1.78, r2 = 0.96) in modeling dielectric constant of leaves, and Debye-ColeCole model was more appropriate (RMSE = 1.23, r2 = 0.95) for the loss factor. For stems, the Debye-ColeCole models (developed on an assumption that they do not shrink as they dry) were found to be the best models to calculate the dielectric constant with RMSE 0.53 and r2 = 0.99, and dielectric loss factor with RMSE = 065 and r2 = 0.95. (Abstract shortened by UMI.)

  3. Dielectric properties of inorganic fillers filled epoxy thin film

    NASA Astrophysics Data System (ADS)

    Norshamira, A.; Mariatti, M.

    2015-07-01

    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 (Fe2O3) and Titanium Dioxide (TiO2) 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.

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

    NASA Astrophysics Data System (ADS)

    Malyshkina, O. V.; Lisitsin, V. S.; Dec, J.; ?ukasiewicz, 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.

  5. Tuning the dielectric properties of metallic-nanoparticle/elastomer composites by strain

    NASA Astrophysics Data System (ADS)

    Gaiser, Patrick; Binz, Jonas; Gompf, Bruno; Berrier, Audrey; Dressel, Martin

    2015-02-01

    Tunable metal/dielectric composites are promising candidates for a large number of potential applications in electronics, sensor technologies and optical devices. Here we systematically investigate the dielectric properties of Ag-nanoparticles embedded in the highly flexible elastomer poly-dimethylsiloxane (PDMS). As tuning parameter we use uniaxial and biaxial strain applied to the composite. We demonstrate that both static variations of the filling factor and applied strain lead to the same behavior, i.e., the filling factor of the composite can be tuned by application of strain. In this way the effective static permittivity ?eff of the composite can be varied over a very large range. Once the Poisson's ratio of the composite is known, the strain dependent dielectric constant can be accurately described by effective medium theory without any additional free fit parameter up to metal filling factors close to the percolation threshold. It is demonstrated that, starting above the percolation threshold in the metallic phase, applying strain provides the possibility to cross the percolation threshold into the insulating region. The change of regime from conductive phase down to insulating follows the description given by percolation theory and can be actively controlled.

  6. 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 ?r 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.

  7. Dielectric and Pyroelectric Properties of Epitaxial Multilayer Ferroelectrics with Dielectric Buffer Layers

    NASA Astrophysics Data System (ADS)

    Sun, Fu-Chang; Alpay, S. Pamir

    2015-03-01

    A nonlinear thermodynamic model is employed to compute the dielectric and pyroelectric properties of heteroepitaxial BaTiO3-SrTiO3 multilayers on SrTiO3, LaAlO3, MgO and Si substrates. The methodology takes into account electromechanical and electrostatic coupling and the strain relaxation due to the formation of misfit dislocations. Using different combinations of layer thickness, we show that the dielectric and pyroelectric properties can be enhanced using misfit strain and degree of strain relaxation as design parameters. This methodology can be used to optimize properties of ferroelectric multilayers in functional electronic devices for charge storage, IR sensing, and on-chip heating cooling.

  8. 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.

  9. High field dielectric properties of anisotropic polymer-ceramic composites

    SciTech Connect

    Tomer, V.; Randall, C. A.

    2008-10-01

    Using dielectrophoretic assembly, we create anisotropic composites of BaTiO{sub 3} particles in a silicone elastomer thermoset polymer. We study a variety of electrical properties in these composites, i.e., permittivity, dielectric breakdown, and energy density as function of ceramic volume fraction and connectivity. The recoverable energy density of these electric-field-structured composites is found to be highly dependent on the anisotropy present in the system. Our results indicate that x-y-aligned composites exhibit higher breakdown strengths along with large recoverable energy densities when compared to 0-3 composites. This demonstrates that engineered anisotropy can be employed to control dielectric breakdown strengths and nonlinear conduction at high fields in heterogeneous systems. Consequently, manipulation of anisotropy in high-field dielectric properties can be exploited for the development of high energy density polymer-ceramic systems.

  10. Millimeter-wave dielectric properties of infrared window materials

    NASA Astrophysics Data System (ADS)

    Ho, W. W.

    1987-01-01

    The millimeter-wave dielectric properties of a series of IR window materials were determined over the temperature range 23-1000 C. Materials studied included Al2O3, ZnS, ZnSe, aluminum oxynitride (ALON), and magnesium-spinel (MgAl2O4). These materials all exhibited fairly high millimeter-wave dielectric constants, but with essentially negligible room-temperature losses for most applications. However, both the dielectric constant and loss tangent increase significantly with increasing temperatures. The increases in dielectric constant with temperature can be analyzed in terms of a macroscopic dielectric virial expansion model, and are primarily due to the effective increase in volume for each polarizable unit of the material. Consequently, a strategy to overcome this degradation would be to search for new materials or composite structures with low thermal expansion coefficients. The observed millimeter-wave loss properties are characteristic of contributions from intergranular impurities and show an onset of increased absorption at about 500. However, even at 1000 C, typical loss tangents are still below 0.05, and should be acceptable in most millimeter-wave window applications for reasonable thicknesses.

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

    NASA Astrophysics Data System (ADS)

    zdemir, Z. Gven; ataltepe, . Aslan; Onba?l?, .

    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 10Hz-10MHz for the first time. The dielectric loss factor (tg?) and ac conductivity (?ac) 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 45kHz 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.

  12. 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, Arin S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-10-01

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

  13. Monitoring Coaxial-Probe Contact Force for Dielectric Properties Measurement

    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...

  14. MICROWAVE DIELECTRIC PROPERTIES OF CEREAL GRAIN AND SEED

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of wheat, corn and soybeans were measured with a free-space-transmission technique at room temperature between 2.0 and 18.0 GHz over wide ranges of bulk density and moisture content of practical interest. For better accuracy and optimum use of the vector network analyzer (VNA) ...

  15. Dielectric Properties of Honeydew Melons and Correlation with Quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 melo...

  16. Dielectric Properties of Watermelons and Correlation with Soluble Solids Content

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of four small-sized watermelon 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 t...

  17. Thermodynamic and optical properties of plasma, metals, and dielectrics

    NASA Astrophysics Data System (ADS)

    Boiko, Iu. V.; Grishin, Iu. M.; Kamrukov, A. S.; Kovalenko, L. V.; Chuvashev, S. N.

    The handbook contains analytically derived data on the principal thermodynamic and optical properties of the plasma of a variety of metals and dielectrics. In particular, data are included on the partial composition, degree of ionization, pressure, internal energy, effective adiabatic exponent, absorption coefficients, and Rosseland-averaged radiation mean free path of the plasma of metals and dielectrics at temperatures between 1000 and 10 exp 6 K and plasma densities of 10 exp -4 to 1 kg/cu m. The materials covered include copper, stainless steel, tungsten, molybdenum, tantalum, zirconium, chromium, niobium, nickel, silicon, ZrO2, SiO2, Teflon, Plexiglas, textolite, polyformaldehyde, and caprolactum

  18. Electrical, optical and dielectric properties of HCl doped polyaniline nanorods

    NASA Astrophysics Data System (ADS)

    Chutia, P.; Kumar, A.

    2014-03-01

    In this report we have investigated the optical, electrical and dielectric properties of HCl doped polyaniline nanorods synthesized by the interfacial polymerization technique. High resolution transmission electron microscope (HRTEM) micrographs confirm the formation of nanorods. X-ray diffraction pattern shows the semicrystalline nature of polyaniline nanorods with a diameter distribution in the range of 10-22 nm. The chemical and electronic structures of the polyaniline nanorods are investigated by micro-Raman and UV-vis spectroscopy. Dielectric relaxation spectroscopy has been applied to study the dielectric permittivity, modulus formalism and ac conductivity as a function of frequency and temperature. The ac conductivity follows a power law with frequency. The variation of frequency exponent with temperature suggests that the correlated barrier hopping is the dominant charge transport mechanism. The existence of both polaron and bipolaron in the transport mechanism has been confirmed from the binding energy calculations.

  19. Electrical conductivity and dielectric property of fly ash geopolymer pastes

    NASA Astrophysics Data System (ADS)

    Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

    2011-02-01

    The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied. The effects of the liquid alkali solution to ash ratios (L/A) were analyzed. The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes. The pastes were cured at 40C. It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios. The conductivity increases but the dielectric constant decreases with increasing frequency.

  20. Theoretical estimation of static dielectric constants for high temperature Tl-Ba-Ca-Cu-O

    SciTech Connect

    Boudreaux, E.A. . Dept. of Chemistry)

    1998-12-20

    Bulk dielectric constants, [epsilon][sub c], for the layered BaCaTlCuO high-[Tc] superconductors have been calculated from polarizability calculations. A correlation between [Tc] and [epsilon] has been derived. Estimates of the electrons' contribution, [epsilon][sub e], have also been reported.

  1. 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, ?-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.

  2. Thermal and dielectric properties of sweetpotato puree

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pureeing of sweetpotato (SP) is carried out to enhance the conversion of the roots into value-added products. During processing, production and home utilization, the puree is often heated (conventional cooking or microwaved), hence the need to measure these properties of SP puree. Thermal (specific ...

  3. 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 larger sample of interest, such as a liquid or powdered or granulated solid, inside a cylindrical container.

  4. Measurements of dielectric properties for intense heating applications

    SciTech Connect

    Borrego, J.M.; Connor, K.A.; Braunstein, J.

    1996-12-31

    Dielectric measurements for frequencies in the tens of gigahertz are discussed. Interpretation of measurements obtained for mixtures are presented based on some simple analytical models and finite-element analysis of the wave structure in the measurement apparatus. In the work reported on here, the authors decided to look at measurements in the range of 25--40 GHz and see if they could use finite-element analysis of experimental conditions to identify the model of dielectric mixtures that seems to work the best. A great deal of high power microwave work has involved making ceramics, vitrification of soils, processing of minerals, etc. The authors, therefore, decided to focus on the properties of some common minerals. They chose sand for its obvious abundance and rutile with very different properties.

  5. Mechanically strained tuning of the electronic and dielectric properties of monolayer honeycomb structure of tungsten disulphide(WS2)

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Mohan, Brij; Kumar, Arun; Ahluwalia, P. K.

    2013-02-01

    First principle calculations have been performed to investigate the influence of mechanical strains on the electronic and dielectric properties of monolayer honeycomb structure of WS2. Our results reveal that mechanical strains reduce the band gap causing a direct-indirect band gap and semiconductor-metal transitions. These transitions, however, depends on the types of applied strain. Asymmetrical biaxial strain has been found to retain the identity of WS2 as a direct band gap semiconductor for 13% value of strain. Imaginary part of dielectric function(?2) shows red-shift in the structure peak energy with applied strains. Static dielectric constant(?s) has been found to have significant dependence on the type of applied strain.

  6. 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.

  7. Investigating effects of aging on radio-frequency dielectric properties of chicken meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effects of aging on dielectric properties of chicken meat were tracked through measurement of the dielectric properties with an open-ended coaxial probe between 200 MHz and 20 GHz at 23 oC. The chicken meat was stored in a refrigerator for 13 days at 4 oC. The changes in dielectric constant and loss...

  8. Microwave dielectric properties of wooden cross-arms

    NASA Astrophysics Data System (ADS)

    bin Khalid, Kaida; bin Shari, Mohd H.; Keong, Ng K.; Fuad, Syed A.

    1999-10-01

    When wooden poles and cross-arms are exposed to weather, its surface undergoes changes such warping, loss of some surface fibers and surface roughing. As a result of weathering, its unprotected surface tends to absorb more moisture as compare to the surface of sound wood. After the rain, the moisture will sustain in the weathered wood for some time before it is dried out. There is a possibility to relate the quality of the wooden cross-arms with the amount of its moisture content (MC) at a particular time. This work deals with the effect of weather on the dielectric properties of wooden cross-arms. The samples from sound wood, incipient decay and decay woods were chosen for dielectric study with frequency ranging from 0.2 GHz to 20 GHz. It is found that the decay wood can absorbed more than 70% MC (dry-basis) as compare to sound wood of only about 30% MC. The results of the dielectric measurement are compared with the values predicted by dielectric mixture equations. From the above study, there is a great possibility of using microwave reflection method to determine the moisture content and condition of wooden cross-arms.

  9. Dielectric and structural properties of aqueous nonpolar solute mixtures

    NASA Astrophysics Data System (ADS)

    Shvab, I.; Sadus, Richard J.

    2012-09-01

    The dielectric properties and molecular structure of water mixtures with different nonpolar solutes (methane and noble gases) are studied using molecular dynamics. The water-water, water-solute, and solute-solute interactions are calculated using the combination of a polarizable potential [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007), 10.1063/1.2786449] for water plus the Lennard-Jones potential. The effect of solute size and concentration on the solubility of the system, hydrogen bonding, dielectric constant, and dipole moment are investigated over a temperature range of 278-750 K and solute percentage mole fractions up to 30%. Solute particles affect the structure of water, resulting in the compression of oxygen-oxygen and oxygen-hydrogen radial distribution functions. The influence of the solute extends both to relatively low concentrations and high temperatures. The coordination numbers of aqueous solutions of the nonpolar solutes appear to be proportional to the size of the solute particles. Our study shows the destructive influence of the nonpolar solute on both the tetrahedral water structure and hydrogen bond formation at solute concentrations greater than 30%. The presence of nonpolar particles typically decreases both the dielectric constant and dipole moment. The decrease of dielectric constant and water dipole moment is directly proportional to the solute concentration and temperature.

  10. Dielectric and structural properties of aqueous nonpolar solute mixtures.

    PubMed

    Shvab, I; Sadus, Richard J

    2012-09-28

    The dielectric properties and molecular structure of water mixtures with different nonpolar solutes (methane and noble gases) are studied using molecular dynamics. The water-water, water-solute, and solute-solute interactions are calculated using the combination of a polarizable potential [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007)] for water plus the Lennard-Jones potential. The effect of solute size and concentration on the solubility of the system, hydrogen bonding, dielectric constant, and dipole moment are investigated over a temperature range of 278-750 K and solute percentage mole fractions up to 30%. Solute particles affect the structure of water, resulting in the compression of oxygen-oxygen and oxygen-hydrogen radial distribution functions. The influence of the solute extends both to relatively low concentrations and high temperatures. The coordination numbers of aqueous solutions of the nonpolar solutes appear to be proportional to the size of the solute particles. Our study shows the destructive influence of the nonpolar solute on both the tetrahedral water structure and hydrogen bond formation at solute concentrations greater than 30%. The presence of nonpolar particles typically decreases both the dielectric constant and dipole moment. The decrease of dielectric constant and water dipole moment is directly proportional to the solute concentration and temperature. PMID:23020337

  11. Optical properties of silicon oxynitride dielectric waveguides

    NASA Astrophysics Data System (ADS)

    Bossi, Donald E.; Hammer, Jacob M.; Shaw, Joseph M.

    1987-02-01

    The plasma-enhanced CVD process for the deposition of silicon oxynitride films is used to deposit SiON waveguide films on fused quartz substrates. The dependence of SiON refractive index, wavelength dispersion, and optical attenuation on film composition is examined for the guided modes of a slab waveguide. The optical properties of a SiON film deposited on a crystalline quartz substrate are also examined. Both the film's refractive index and wavelength dispersion characteristics are shown to be functions of the molar composition. The reduction of surface scattering losses at the film-substrate interface is noted to result in significantly improved power attenuation characteristics.

  12. 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 250C 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 180C. 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 200C, high melting point (> 225C) and melting onset at 160 - 190C indicated that P4MP could be used at 180 - 200C. Thin free-standing films (~10 mum) with controlled crystal structure and surface morphology were prepared using blade coating and their drying dynamics were measured using a custom-designed solvent-casting platform. These films were further stretched uniaxially or biaxially, and their effect on the dielectric properties of P4MP was studied.

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

    PubMed

    Davari, Nazanin; Daub, Christopher D; strand, 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 ? ? ?* excitation energy is around 6.0 eV, as compared to the gas-phase value of around 6.3 eV, while the experimental values are 6.5 and 6.9 eV for the liquid and gas phase, respectively, demonstrating that the gas-to-liquid shift is well-described. PMID:26241379

  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 ? 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 Hz1 MHz showed that the addition of yttrium slightly increases the ac conductivity and decreases the tg ? therefore making the materials better suited for the use in microwave devices.

  15. 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

  16. 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.

  17. 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 ?), dielectric constant (?), 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.

  18. Improved instrumentation for monitoring the diurnal and seasonal cycles in the dielectric properties of forest canopies

    NASA Technical Reports Server (NTRS)

    Guerra, Abel G.; Mcdonald, Kyle C.; Way, Jobea

    1992-01-01

    The design and implementation of a dielectric measurement system that facilitates the automated and continuous in situ monitoring of the dielectric properties of several canopy constituents is presented. This system utilizes the same coaxial line reflection coefficient measurement technique as the portable dielectric probe (PDP) while incorporating several features that facilitate the automated monitoring of canopy dielectric properties. The new system is capable of continuously monitoring the dielectric properties of the canopy constituents in a near-simultaneous fashion. The implementation of a data logger as a user interface has increased the number of measurements that the instrument is able to store in memory while significantly improving system reliability.

  19. 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.

  20. Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

    2016-01-01

    Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature (T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

  1. Temperature Dependence of the Radio-Frequency 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 temperature ranging from -20 oC to +25 oC. At a given frequency, the temperature dependence reveals a sharp increase of the dielectric constant and dielectric loss factor a...

  2. Static properties and moisture content properties of polyester fabrics modified by plasma treatment and chemical finishing

    NASA Astrophysics Data System (ADS)

    Kan, C. W.; Yuen, C. W. M.

    2008-01-01

    Low temperature plasma treatment has been conducted in textile industry and has some success in the dyeing and finishing processes. In this paper, an attempt was made to apply low temperature plasma treatment to improve the anti-static property of polyester fabric. The polyester fabrics were treated under different conditions using low temperature plasma. An Orthogonal Array Testing Strategy was employed to determine the optimum treatment condition. After low temperature plasma treatment, the polyester fabrics were evaluated with different characterisation methods. Under the observation of scanning electron microscope, the surface structure of low temperature plasma-treated polyester fabric was seriously altered. This provided more capacity for polyester to capture moisture and hence increase the dissipation of static charges. The relationship between moisture content and half-life decay time for static charges was studied and the results showed that the increment of moisture content would result in shortening the time for the dissipation of static charges. Moreover, there was a great improvement in the anti-static property of the low temperature plasma-treated polyester fabric after comparing with that of the polyester fabric treated with commercial anti-static finishing agent.

  3. Mechanisms of electrorheology: the effect of the dielectric property

    NASA Astrophysics Data System (ADS)

    Ikazaki, F.; Kawai, A.; Uchida, K.; Kawakami, T.; Edamura, K.; Sakurai, K.; Anzai, H.; Asako, Y.

    1998-02-01

    The effect of the dielectric properties of electrorheological fluids on electrorheology was investigated in DC electric fields by using both hydrous and anhydrous electrorheological fluids. The relaxation frequency, which is defined by a local maximum of the dielectric loss factor of an electrorheological fluid, was in the range from 100-0022-3727/31/3/014/img11 whenever the electrorheological fluid had a large electrorheological effect. This effect increased with increasing difference between the dielectric constants 0022-3727/31/3/014/img12 below and above the relaxation frequency both for hydrous and anhydrous electrorheological fluids, when the relaxation frequency was in the range 100-0022-3727/31/3/014/img11. For the electrorheological fluid containing microcrystalline cellulose, the change of the rheology curve, namely the shear rate versus shear stress (0022-3727/31/3/014/img14 versus 0022-3727/31/3/014/img15) curve, with increasing adsorbed water content could be interpreted in terms of the relation between the shear rate and the polarization rate. The mechanism of electrorheology could also explain the effect of the current density on the ER effect.

  4. Testing techniques for determining static mechanical properties of Pneumatic tires

    NASA Technical Reports Server (NTRS)

    Dodge, R. N.; Larson, R. B.; Clark, S. K.; Nybakken, G. H.

    1974-01-01

    Fore-aft, lateral, and vertical spring rates of model and full-scale pneumatic tires were evaluated by testing techniques generally employed by industry and various testing groups. The purpose of this experimental program was to investigate what effects the different testing techniques have on the measured values of these important static tire mechanical properties. The testing techniques included both incremental and continuous loadings applied at various rates over half, full, and repeated cycles. Of the three properties evaluated, the fore-aft stiffness was demonstrated to be the most affected by the different testing techniques used to obtain it. Appreciable differences in the fore-aft spring rates occurred using both the increment- and continuous-loading techniques; however, the most significant effect was attributed to variations in the size of the fore-aft force loop. The dependence of lateral stiffness values on testing techniques followed the same trends as that for fore-aft stiffness, except to a lesser degree. Vertical stiffness values were found to be nearly independent of testing procedures if the nonlinear portion of the vertical force-deflection curves is avoided.

  5. The study of dielectric properties of the endohedral fullerenes

    NASA Astrophysics Data System (ADS)

    Bhusal, Shusil

    Dielectric response of the metal nitride fullerenes is studied using the density functional theory at the all-electron level using generalized gradient approximation. The dielectric response is studied by computing the static dipole polarizabilities using the finite field method, i.e. by numerically differentiating the dipole moments with respect to electric field. The endohedral fullerenes studied in this work are Sc3N C68(6140), Sc3N C68(6146), Sc3N C70(7854), Sc3N C70(7960), Sc3N C76(17490), Sc3N C78(22010), Sc3N C80(31923), Sc3N C80(31924), Sc3N C82(39663), Sc3N C90(43), Sc3N C90(44), Sc3N C92(85), Sc3N C94(121), Sc3N C96(186), Sc3N C98(166). Using the Voronoi and Hirschfield approaches as implemented in our NRLMOL code, we determine the atomic contributions to the total polarizability. The site-specific contributions to the polarizability of endohedral fullerenes allowed us to determine the polarizability of two subsystems: the fullerene shell and the encapsulated Sc3N unit. Our results showed that the contributions to the total polarizability from the encapsulated Sc3N units are vanishingly small. Thus, the total polarizability of the endohedral fullerene is almost entirely due to the outer fullerene shell. These fullerenes are excellent molecular models of a Faraday cage.

  6. 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.

  7. Plasmonic glasses: optical properties of amorphous metal-dielectric composites.

    PubMed

    Antosiewicz, Tomasz J; Apell, S Peter

    2014-01-27

    Plasmonic glasses composed of metallic inclusions in a host dielectric medium are investigated for their optical properties. Such structures characterized by short-range order can be easily fabricated using bottom-up, self-organization methods and may be utilized in a number of applications, thus, quantification of their properties is important. We show, using T-Matrix calculations of 1D, 2D, and 3D plasmonic glasses, that their plasmon resonance position oscillates as a function of the particle spacing yielding blue- and redshifts up to 0.3 eV in the visible range with respect to the single particle surface plasmon. Their properties are discussed in light of an analytical model of an average particle's polarizability that originates from a coupled dipole methodology. PMID:24515212

  8. 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.

  9. 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...

  10. dielectrics

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Yen, Chih-Feng

    2014-09-01

    The (NH4)2S treatment can reduce native oxides and passivate GaAs. Atomic layer-deposited Al2O3 can further remove the residue native oxides by self-cleaning. Stacked with high dielectric constant TiO2 prepared by atomic layer deposition on Al2O3/(NH4)2S-treated GaAs MOS capacitor, the leakage current densities can reach 4.5 10-8 and 3.4 10-6 A/cm2 at 2 MV/cm. The net effective dielectric constant of the entire stack is 18 and the interface state density is about 4.2 1011/cm2/eV. The fabricated enhancement-mode n-channel GaAs MOSFET exhibited good electrical characteristics with a maximum g m of 122 mS/mm and electron mobility of 226 cm2/V s.

  11. Direct measurement of the dielectric polarization properties of DNA

    PubMed Central

    Cuervo, Ana; Dans, Pablo D.; Carrascosa, Jos 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 (?r ? 24), 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 PoissonBoltzmann 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

  12. Structural, dielectric and magnetic properties of Ni substituted zinc ferrite

    NASA Astrophysics Data System (ADS)

    Kumbhar, S. S.; Mahadik, M. A.; Mohite, V. S.; Rajpure, K. Y.; Kim, J. H.; Moholkar, A. V.; Bhosale, C. H.

    2014-08-01

    NixZn1-xFe2O4 ferrite has been synthesized by the ceramic method using Ni CO3, ZnO, Fe2O3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of NixZn1-xFe2O4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of NixZn1-xFe2O4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of NixZn1-xFe2O4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x=0.8, is attributed to magnetic moment of Fe3+ ions.

  13. 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 1,200C; the web-like structure was destroyed at a temperature of 1,400C. 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 1,200C. 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.

  14. Dielectric Properties of Diesel and Gasoline by Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Arik, Enis; Altan, Hakan; Esenturk, Okan

    2014-09-01

    In this study we have investigated the dielectric properties of diesel and gasoline in the Terahertz (THz) spectral region. We present frequency dependent absorption coefficients, refractive indices, and dielectric constants calculated from the transient measurements of the fuel oils between 0.1 and 1.1 THz. Observed weak absorption coefficient of fuel oils is explained by transient dipole moments induced by collisions between individual molecules. Fuel oils were modeled successfully with Debye model to investigate the relaxation dynamics after interaction with the electric field. Significant differences in relaxation times of molecules in diesel and gasoline are attributed to the differences in their intermolecular forces. Dispersion forces are much greater in diesel due to the longer hydrocarbon chains (C8-C40) compared to that (C4-C12) of the gasoline. This leads to a comparably faster relaxation right after THz electric field is applied. Clear differences in optical properties offer a simple yet effective way to discriminate fuel oils from each other by using THz spectroscopy without any danger of combustion or decomposition of the samples. Such an approach may also be used for the quality determination of either fuels. The study presents the great potential of THz spectroscopy to study very complex mixtures like fuel oils by the use of instantaneous THz wave/matter interactions and relaxation dynamics of the constituent molecules.

  15. 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.

  16. 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.

  17. Effective dielectric properties of packed mixtures of insulator particles

    NASA Astrophysics Data System (ADS)

    Pecharromn, C.; Iglesias, J. E.

    1994-03-01

    We present an expression, obtained by following the principles of the effective medium theory (EMT), to compute average dielectric properties of mixtures of random ellipsoids. We show that our formulation is quite general and includes former expressions, valid only for dilute mixtures, as particular cases; moreover it gives accurate predictions when compared with experimental measurements in the whole range of filling factors. The expression can be extended to mixtures of irregularly shaped particles with very little loss of accuracy. Also, our equation is suitable to be used with anisotropic samples. The equation requires an additional parameter, which amounts to a percolation threshold, to the parameters usually employed to describe a binary mixture in EMT, namely, the dielectrical functions of the components and the filling factor. This parameter contains information about the geometry of the particle packing, and approximate values have been found by numerical simulation of different arrangements of spheres in a matrix. Reflectance IR spectra have been measured on pressed pellets of particles of LiF, MgO, ?-Fe2O3, and MgAl2O4 and compared with the spectra predicted by the expression presented in this paper, and other previous formulations.

  18. Mechanical and Dielectric Breakdown Properties of Biodegradable Plastics

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

    The mechanical and dielectric breakdown properties of polylactic acid (PLA), which is a biodegradable plastic, were examined, and a physicochemical analysis was performed. At room temperature, the tensile strength of PLA was about 100 MPa, almost the same as for PP, but at 100°C, even the value for LDPE decreased. The Young's modulus of PLA at room temperature was about 3.6 GPa, about 1.7 times the value for PP, and about 11 times the value for LDPE. The Young's modulus of PLA decreased slowly with a rise in temperature, and at high temperatures, 60°C and above, it decreased rapidly. The dielectric breakdown strength (EB) of PLA at room temperature was about 6.2 MV/cm, about 1.4 times the value for LDPE. The EB of PLA increased with an increase in temperature, and was about 6.9 MV/cm at 60°C (∂EB/∂T≥0). In this region, it is thought that a secondary effect due to space charge occurred, as well as an electron avalanche breakdown. However, the EB of PLA decreased at temperatures higher than 60°C in the high temperature region (∂EB/∂T<0). In this domain, it is thought that thermal breakdown occurred, and that electromechanical breakdown also occurred in the high temperature domain of 80°C and above.

  19. Structural and Dielectric Properties of Quartz-Water Interfaces

    SciTech Connect

    Wander, Matthew C.; Clark, Aurora E.

    2008-11-19

    The structure, orientation, and dielectric of water at the quartz|water interface has been examined under different hydration levels using classical molecular dynamics. The properties of 1H?O/10 Ų, 2H?O/10 Ų, 4H?O/10 Ų, and bulk water on quartz have been benchmarked against experimental data. Structurally, the simulations match existing sum-frequency spectroscopy data, which indicate the existence and orientation of both frozen and loosely bound water on the quartz surface. Good agreement has also been found with existing experimental dielectric data for the 1H?O/10 Ų level of hydration, and a clear difference has been found in the values of ?s = 48, ?| = 48, and ?? = 40 for the first slice of a bulk-water-solid interface and ?s= 30, ?| = 30, and ?? = 10 for that of 1H?O/10 Ų water coverage. Overall there is a fundamental difference in shielding between a single interface and the 1H?O/10 2 level of hydration.

  20. Unraveling dielectric and electrical properties of ultralow-loss lead magnesium niobate titanate pyrochlore dielectric thin films for capacitive applications

    SciTech Connect

    Zhu, X. H.; Defaye, E.; Suhm, A.; Fribourg-Blanc, E.; Aied, M.; Zhu, J. L.; Xiao, D. Q.; Zhu, J. G.

    2010-05-15

    PbO-MgO-Nb{sub 2}O{sub 5}-TiO{sub 2} (PMNT) pyrochlore thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. Very interestingly, these pyrochlore-structured PMNT thin films exhibited ultralow dielectric losses, with a typical loss tangent as low as 0.001, and relatively high dielectric constants, typically {epsilon}{sub r{approx}}170. It was found that the relative permittivity slightly but continuously increased upon cooling without any signature of a structural phase transition, displaying a quantum paraelectriclike behavior; meanwhile, the PMNT pyrochlore thin films did not show any noticeable dielectric dispersion in the real part of permittivity over a wide temperature range (77-400 K). Their dielectric responses could, however, be efficiently tuned by applying a dc electric field. A maximum applied bias field of 1 MV/cm resulted in a {approx}20% tunability of the dielectric permittivity, giving rise to a fairly large coefficient of the dielectric nonlinearity, {approx}2.5x10{sup 9} J C{sup -4} m{sup -5}. Moreover, the PMNT pyrochlore films exhibited superior electrical insulation properties with a relatively high breakdown field (E{sub breakdown{approx}}1.5 MV/cm) and a very low leakage current density of about 8.2x10{sup -7} A/cm{sup 2} obtained at an electric field intensity as high as 500 kV/cm.

  1. 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. PMID:26723625

  2. 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.

  3. 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 include the incineration of combustibles, the evaporation of combustibles, the evaporation of liquids, and the compaction of noncombustibles. The handling of radioactive liquid waste is generally carried out within closed systems consisting of highly corrosion-resistant, welded, leak-tight pipes, tanks, and other apparatus. High power microwave processing is a promising technology for reducing risks to the environment and human health, thereby supporting the DOE's decontamination and decommissioning (D&D) objectives.

  4. 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.

  5. Large dielectric permittivity and possible correlation between magnetic and dielectric properties in bulk BaFeO{sub 3??}

    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??}. A large dielectric permittivity comparable to that of other semiconducting oxides is observed in BaFeO{sub 3??}. 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??} indicating its importance in both fundamental science as well as in applications.

  6. Static properties of polymer chains in porous media

    NASA Astrophysics Data System (ADS)

    Honeycutt, J. D.; Thirumalai, D.

    1989-04-01

    The static properties of a polymer molecule in a porous medium are investigated. The porous medium is simulated using a site percolation model in which the various sites are occupied (or unoccupied) randomly. A freely jointed chain is allowed to move in continuous space between the obstacles. Effects of excluded volume interactions between the links have also been studied. Using a generalized Flory theory, we have shown that, when the strength of disorder is large enough, the mean square end-to-end distance scales as N2?, where N is the number of links in the chain, and ? takes on a value different from that for a free chain. Under these conditions, the polymer assumes a compact, globule-like conformation. For sufficiently large N, the Flory theory gives ?=1/(d+2) for freely jointed chains and ?=1/d for chains with excluded volume. Various correlation functions such as the distribution of the end-to-end distance and density profile of monomers with respect to the center of mass of the chain have been computed using Monte Carlo simulations. These results are interpreted using scaling concepts and an approximate variational theory based on replica methods. The limitations of the replica variational theory are assessed by an application to the directed polymer in a quenched random environment. We have also studied the shape fluctuations that the polymer molecule undergoes in the random environment. It is argued that these shape fluctuations are relevant to the transport mechanism of polymers in random media. The results obtained for the porous media are contrasted with those found for polymers in media where the obstacles are arranged in a regular manner.

  7. Static and dynamic properties of critical fluctuations in lipid bilayers

    NASA Astrophysics Data System (ADS)

    Honerkamp-Smith, Aurelia Rose

    A current popular view in cell biology is that sub-micron, dynamic heterogeneity in lipid and protein composition arises within the plasma membranes of resting cells. Local changes in membrane composition may affect protein activity, which is sensitive to the lipid environment. We have observed dynamic heterogeneity in lipid membranes in the form of composition fluctuations near a miscibility critical point. In this thesis we quantitatively describe the dynamic and static properties of these fluctuations. We evaluate the temperature dependence of line tension between liquid domains and of fluctuation correlation lengths in lipid membranes in order to extract a critical exponent, nu. We obtain nu = 1.2 +/- 0.2, consistent with the Ising model prediction nu = 1. From probability distributions of pixel intensities in fluorescence images of membranes, we also extract an independent critical exponent of beta = 0.124 +/- 0.03, which is consistent with the Ising prediction of beta = 1/8. We have systematically measured the effective dynamic critical exponent z eff in a lipid membrane while cooling the system toward a critical point. We observe that zeff slightly increases from a value of roughly 2.6 as xi → 0, to zeff = 3.0 +/- 0.15 at xi = 13 sm. Our measurements are consistent with the prediction that zeff → 3.00 as T → Tc for a 2-D system with conserved order parameter in contact with a bulk 3-D liquid. To our knowledge, no other systematic measurement of zeff with increasing xi exists for a 2-D system with conserved order parameter. We also report the solubility limit of several biologically relevant sterols in electroformed giant unilamellar vesicle membranes containing phosphatidylcholine (PC) lipids in ratios of 1:1:X DPPC:DOPC:sterol. We find solubility limits of cholesterol, lanosterol, ergosterol, stigmasterol, and beta-sitosterol using nuclear magnetic resonance.

  8. Grain and Seed Moisture and Density Measurement through Sensing of Dielectric Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The importance of moisture measurement in grain and seed is discussed, and a brief history of the development of moisture sensing instruments, based on sensing of dielectric properties of these materials, is presented. Data are presented graphically on the permittivities or dielectric properties of...

  9. 10- to 1800-MHz dielectric properties of fresh apples during storage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric properties of fresh apples of three cultivars were measured at 24 degrees C over 10 weeks in storage at 4 degrees C to determine whether these properties might be used to determine quality factors such as soluble solids content (SSC), firmness, moisture content and pH. The dielectric...

  10. Structural, vibrational, and dielectric properties of Ruddlesden-Popper Ba2ZrO4 from first principles

    NASA Astrophysics Data System (ADS)

    Louis, Lydie; Nakhmanson, Serge M.

    2015-04-01

    Using first-principles computational techniques, we have investigated the structural, vibrational, and dielectric properties of a Ruddlesden-Popper-type layered oxide Ba2ZrO4 subjected to a wide range of biaxial strains emulating epitaxial thin-film environment. Under compressive strains, this compound experiences an incommensurate distortion characterized by planar displacements of individual perovskite slabs away from their high symmetry positions. On the other hand, under increasing epitaxial tension, the original centrosymmetric structure becomes unstablefirst, with respect to antiferrodistortive oxygen cage rotations and then also with respect to in-plane polar distortions. Both the incommensurate-to-commensurate and the nonpolar-to-polar phase transformations are accompanied by anomalies of the static dielectric response, however, only in the latter case a divergence of the in-plane dielectric constant is observed. Remarkably, even after the transition into the ferroelectric state (with polarization of up to 0.12 C/m 2 at 3.5% tension) dielectric permittivity of Ba2ZrO4 remains unusually high, which is explained by an emergence of a Goldstone-like excitation in the system manifested through an in-plane libration of the polarization vector. Since Ba2ZrO4 displays a yet poorly understood tendency to absorb small molecules, such as water and CO2, acquiring better insights into the physical underpinnings of its behavior can produce more efficient functional materials for applications in advanced technologies for carbon sequestration.

  11. 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, ?-SiO2, ?-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%).

  12. Electrical Conduction and Dielectric Properties of Biodegradable Plastics

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

    We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60°C and the melting point (Tm) was about 166°C. For the temperature dependence of current density (J), J of PLA became smaller than LDPE, PP and Polyester in the temperature from room temperature to 90°C. However, when sample became 90°C or the higher, J of PLA became larger than other plastics. On the other hand, as a result of measuring J of the same sample again, it became small. For the relative permittivity (εr') indicated intermediate values between that of polyester and those of LDPE and PP.

  13. Dielectric structure design for microwave cloaking considering material properties

    NASA Astrophysics Data System (ADS)

    Heo, Namjoon; Yoo, Jeonghoon

    2016-01-01

    To hide a metallic object from outside observers, we designed cloaking structures to manipulate the propagation path of the microwave at a specific frequency. Dielectric materials are used to realize the cloaking effect and their electromagnetic properties are evaluated to reduce the size of the cloaking structure as well as to take the loss effect into account. We used the structural design method based on the phase field method to control the electric field flow around a target object for cloaking. It is aimed to minimize the scattered electric field measured at the region located behind the target object for a normal incident wave in the X-band frequency range. Numerical examples are given to verify the suggested design process and its results.

  14. 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).

  15. Characterization of concrete properties from dielectric properties using ground penetrating radar

    SciTech Connect

    Lai, W.L.; Kou, S.C.; Tsang, W.F.; Poon, C.S.

    2009-08-15

    This paper presents the experimental results of a study of the relationships between light-weight (LWAC) and normal aggregate concrete (NAC) properties, as well as radar wave properties that are derived by using ground penetrating radar (GPR). The former (LWAC) refers to compressive strength, apparent porosity and saturated density, while the latter (NAC) refers to real part of dielectric permittivity ({epsilon}' or real permittivity) and wave energy level (E). Throughout the test period of the newly cast concrete cured for 90 days, the above mentioned material properties gradually changed which can be attributed to the effects of cement hydration, different types of aggregates and initial water to binder ratios. A number of plots describing various properties of concrete such as dielectric, strength and porosity perspectives were established. From these plots, we compare the characteristics of how much and how fast free water was turned to absorbed water in LWAC and NAC. The underlying mechanisms and a mechanistic model are then developed.

  16. Static properties of hydrostatic thrust gas bearings with curved surfaces.

    NASA Technical Reports Server (NTRS)

    Rehsteiner, F. H.; Cannon, R. H., Jr.

    1971-01-01

    The classical treatment of circular, hydrostatic, orifice-regulated thrust gas bearings, in which perfectly plane bearing plates are assumed, is extended to include axisymmetric, but otherwise arbitrary, plate profiles. Plate curvature has a strong influence on bearing load capability, static stiffness, tilting stiffness, and side force per unit misalignment angle. By a suitable combination of gas inlet impedance and concave plate profile, the static stiffness can be made almost constant over a wide load range, and to remain positive at the closure load. Extensive measurements performed with convex and concave plates agree with theory to within the experimental error throughout and demonstrate the practical feasibility of using curved plates.

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

    PubMed

    Le Bras, David; Strmme, 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. PMID:25885570

  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. Synthesis, multi-nonlinear dielectric resonance and electromagnetic absorption properties of hcp-cobalt particles

    NASA Astrophysics Data System (ADS)

    Wen, Shulai; Liu, Ying; Zhao, Xiuchen; Cheng, Jingwei; Li, Hong

    2014-03-01

    Hcp-cobalt particles were successfully prepared by a liquid phase reduction method, and the microstructure, static magnetic properties, electromagnetic and microwave absorption properties of the cobalt particles with irregular shape were investigated in detail. The measured results indicate that the saturation magnetization was less than that of hcp-Co single crystals, and the coercivity was larger than that of bulk cobalt crystal. The permittivity presents multi-nonlinear dielectric resonance, which may result from the irregular shape containing parts of cutting angle of dodecahedron of cobalt particles. The real part of permeability decreases with the frequency, and the imaginary part has a wide resonant peak. The paraffin-based composite containing 70 wt% cobalt particles possessed strong absorption characteristics with a minimum RL of -38.97 dB at 10.81 GHz and an absorption band with RL under -10 dB from 8.72 to 13.26 GHz when the thickness is 1.8 mm, which exhibits excellent microwave absorption in middle and high frequency. The architectural design of material morphologies is important for improving microwave absorption properties toward future application.

  20. Effect of cenosphere on dielectric properties of low density polyethylene

    NASA Astrophysics Data System (ADS)

    Sharma, Janu; Chand, Navin; Bapat, M. N.

    2012-01-01

    Dielectric characterization of cenosphere filled low density polyethylene composites is reported in this paper. Cenosphere filled low density polyethylene (LDPE) composites with inhomogeneous dispersions of cenosphere were prepared and dielectric measurements have been performed on these composites in the temperature range 34-110 C in the frequency range 1-10 kHz. The dielectric constants of the composites with filler concentrations 0%, 10%, 15% and 20 vol.% were measured. Effect of temperature and frequency variations on dielectric constant (??), dissipation factor (tan ?) and a.c. conductivity (?a.c.) was also determined. The frequency dependent dielectric and conductivity behaviour of flyash cenosphere filled low density polyethylene (LDPE) polymer composites have been studied. Appearance of peak in the dielectric loss curves for all the concentrations confirms the presence of relaxing dipoles in the cenosphere/LDPE composites. The effect of filler distribution on the dielectric constant is examined and the observed differences are attributed to the differences in two kinds of interfaces present: one formed between the touching cenosphere particles and the other formed between LDPE and cenosphere. With the increase of cenosphere content dielectric constant decreased gradually. Maxwell-Garnett approximation fairly fits for the dielectric data obtained experimentally for these composites.

  1. 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.

  2. 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 operation. The objective of this research was to determine the size and interface atomic structure dependence of the electronic properties of metal/oxide interfaces using model materials systems of noble metals on SrTiO3 surfaces; and to develop experimental techniques to probe spatially localized properties under extreme conditions. The outcomes of this research summarized in more detail below include; Discovery of the presence of multiple size dependent transport mechanisms at nanoscale interfaces and determination of the critical size parameter associated with a transition from one to another; Determination of the effect of interface atomic structure and electronic structure at nanoscale interfaces on electronic transport across the interfaces, in particular the role of states associated with under coordinated cations enabling resonant tunneling and/or band bending; Discovery and characterization of size dependent resistive switching at nanoscale interfaces; These advances required the development of a process to produce nanosized contacts with controlled interface orientation over sizes (diameters) ranging from 20-500nm and the determination of the mechanical and electrical parameters for robust and accurate measurement of frequency dependent properties of nanoscale interfaces; Invention of a chamber that enables in situ scanning probe microscopy and spectroscopy at high temperature and reactive gas environments; and First measurement of interface properties in an operating solid oxide fuel cell, quantifying the local electrical potentials and energies associated with two reaction mechanisms.

  3. Excellent dielectric properties of polymer composites based on core-shell structured carbon/silica nanohybrid

    NASA Astrophysics Data System (ADS)

    Lei, Tuo; Xue, Qingzhong; Chu, Liangyong; Han, Zhide; Sun, Jin; Xia, Fujun; Zhang, Zhongyang; Guo, Qikai

    2013-07-01

    Polymer based composites with high dielectric constant and low dielectric loss were fabricated by dispersing core-shell structured carbon/silica nanohybrid (CS) into a poly (vinylidene fluoride) (PVDF) matrix. Due to the high conductive carbon core, nonconductive silica shell and the good dispersion of the CS fillers in PVDF, the CS/PVDF composites exhibited better dielectric properties than most nano-carbon materials/polymer composites. These experimental results can be understood by the percolation theory and microcapacitor model. Our strategy provides a pathway to achieve nano-carbon materials/polymer composites with good dielectric performances.

  4. TEMPERATURE-DEPENDENT BEHAVIOR OF MICROWAVE DIELECTRIC PROPERTIES OF BOUND WATER IN GRAIN AND SEED

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric behavior of bound water in grain and seed was investigated through measurement of the dielectric properties at microwave frequencies over a wide temperature range between 70 degrees Celsius and +21 degrees Celsius. Samples of wheat and soybeans were cooled to 70 degrees Celsius and the...

  5. Investigating the influence of aging on radiofrequency dielectric properties of chicken meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in quality attributes of aging chicken meat were tracked through measurement of the dielectric properties with an open-ended coaxial probe between 200 MHz and 20 GHz at 23 degree C. The chicken meat was stored in a refrigerator for 8 days at 4 degree C. Changes in dielectric constant and los...

  6. Investigating the influence of aging on radiofreuqncy dielectric properties of chicken meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in quality attributes of aging chicken meat were tracked through measurement of the dielectric properties with an open-ended coaxial probe between 200 MHz and 20 GHz at 23 C. The chicken meat was stored in a refrigerator for 8 days at 4 C. Changes in dielectric constant and loss factor wer...

  7. Dielectric Properties of Uncooked Chicken Breast Muscles from 10 to 1800 MHz

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric properties, consisting of the dielectric constant and loss factor, were measured (by using an open-ended coaxial-line probe) for uncooked chicken breast muscle Pectoralis major and Pectoralis minor, deboned at 2 and 24 h postmortem, over the frequency range from 10 to 1800 MHz at tem...

  8. 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....

  9. 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...

  10. 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...

  11. The dielectric properties of the diamond-like films grown by ion-plasma method

    NASA Astrophysics Data System (ADS)

    Brozdnichenko, A. N.; Dolgintsev, D. M.; Castro, R. A.

    2014-12-01

    Diamond-like films was deposited by ion-plasma method in impulse mode. The dielectric properties of the diamond-like films in the frequency of 10-1 - 106 Hz at room temperature were studied. The dispersion of the dielectric parameters indicates the existence of non-Debye relaxation mechanism correlates with structural changes. The charge transfer is temperature activated hopping process.

  12. 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) . PMID:25381737

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

    PubMed

    Y?ld?r?m, M Ali; Y?ld?r?m, Smeyra Tuna; Sakar, Emine Fedakar; Ate?, Aytun

    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 (?o, ??) values have been calculated as a function of the annealing temperature. The resistivity values of the films have changed between 10(-1) - 10(-3)?cm with annealing temperature and light at room temperature. PMID:24929316

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

    NASA Astrophysics Data System (ADS)

    Y?ld?r?m, M. Ali; Y?ld?r?m, Smeyra Tuna; Sakar, Emine Fedakar; Ate?, Aytun

    2014-12-01

    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 3.66 eV depending on the annealing temperature. The refractive index (n), optical static and high frequency dielectric constants (?o, ??) values have been calculated as a function of the annealing temperature. The resistivity values of the films have changed between 10-1 - 10-3 ? cm with annealing temperature and light at room temperature.

  15. 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.

  16. Photoinduced Electron Transfer Elicits a Change in the Static Dielectric Constant of a de Novo Designed Protein.

    PubMed

    Polizzi, Nicholas F; Eibling, Matthew J; Perez-Aguilar, Jose Manuel; Rawson, Jeff; Lanci, Christopher J; Fry, H Christopher; Beratan, David N; Saven, Jeffery G; Therien, Michael J

    2016-02-24

    We provide a direct measure of the change in effective dielectric constant (εS) within a protein matrix after a photoinduced electron transfer (ET) reaction. A linked donor-bridge-acceptor molecule, PZn-Ph-NDI, consisting of a (porphinato)Zn donor (PZn), a phenyl bridge (Ph), and a naphthalene diimide acceptor (NDI), is shown to be a "meter" to indicate protein dielectric environment. We calibrated PZn-Ph-NDI ET dynamics as a function of solvent dielectric, and computationally de novo designed a protein SCPZnI3 to bind PZn-Ph-NDI in its interior. Mapping the protein ET dynamics onto the calibrated ET catalogue shows that SCPZnI3 undergoes a switch in the effective dielectric constant following photoinduced ET, from εS ≈ 8 to εS ≈ 3. PMID:26840013

  17. Structural, conductivity and dielectric properties of Li2SO4

    NASA Astrophysics Data System (ADS)

    Rama Rao, Samudrala; Bheema Lingam, Chittari; Rajesh, Desapogu; Pandu Vijayalakshmi, Raguru; Shamanna Sunandana, Channappayya

    2014-06-01

    Li2SO4 have been synthesized from lithium sulphate monohydrate by melting at 880 °C and slow cooling. The XRD results indicates that the melt cooled Li2SO4 is crystallized to monoclinic structure. The AC conductivity (σac) and dielectric relaxation (tan δ) have been measured within the temperature range 170-250 °C and frequency range 100 Hz-120 kHz, respectively. The DC conductivities are conveniently extracted from σac (typical values ˜2 × 10-7 and ˜2 × 10-6 S/cm at 200 and 250 °C, respectively) and are fitted to linear Arrhenius plot. The slope of this linear plot leads to an activation energy of 1.10 eV. It is found that the conduction in Li2SO4 is mainly through Li+. Further, we carried out first principles calculations and obtained the structural and bonding properties of Li2SO4. From band structure, Li2SO4 is found to be a wide band gap insulator with a band gap of 6.1 eV. The partial density of states reveals the finite states of Li+ near to Fermi level, which limits its use of full capacity. This indicates a kinetic barrier for Li ions and electrons ambipolar diffusion.

  18. Role of solvent dielectric properties on charge transfer from PbS nanocrystals to molecules.

    PubMed

    Hyun, Byung-Ryool; Bartnik, A C; Lee, Jin-Kyun; Imoto, Hiroaki; Sun, Liangfeng; Choi, Joshua J; Chujo, Yoshiki; Hanrath, Tobias; Ober, Christopher K; Wise, F W

    2010-01-01

    Transfer of photoexcited charge from PbS nanocrystals to ligand molecules is investigated in different solvents. We find that the charge transfer rate increases dramatically with solvent dielectric constant. This trend is accounted for by a modified Marcus theory that incorporates only static dielectric effects. The choice of solvent allows significant control of the charge transfer process. As an important example, we find that PbS nanocrystals dispersed in water exhibit charge transfer rates 1000 times higher than the same nanocrystals in organic solvent. Rapid charge extraction will be important to efficient nanocrystal-based photovoltaic and photodetector devices. PMID:19968265

  19. Magnetic and dielectric properties of Mn2V2O7

    NASA Astrophysics Data System (ADS)

    Sannigrahi, J.; Giri, S.; Majumdar, S.

    2016-02-01

    The magnetic and dielectric properties of the manganese di-vanadate compound Mn2V2O7 are reported. The sample shows martensitic type structural transition close to room temperature which is evident both in the magnetic and dielectric data. Mn2V2O7 shows signature of antiferromagnetic type ordering around 17 K with concomitant anomaly in the dielectric properties at the same point, although no spontaneous electric polarization was found below 17 K. This clearly signifies a magnetic order driven electric anomaly and possibly it is antiferroelectric type with no net polarization. The dielectric relaxation behaviours show marked difference across the structural transition close to room temperature. Interestingly, the sample shows reversible switching behaviour across the structural transition close to 300 K between high and low dielectric states which can have important practical applications.

  20. Laboratory measurements of static and dynamic elastic properties in carbonate

    NASA Astrophysics Data System (ADS)

    Bakhorji, Aiman M.

    The fact that many of the giant hydrocarbon reservoirs, such as the Ghawar field in Saudi Arabia and the Grosmont formation in Alberta, are formed from carbonates make these rocks and the corresponding reservoirs important research topics. Compressional and shear wave velocities (at 1 MHz) and the quasi-static strains of thirty seven carbonate rock samples were measured as functions of saturating fluid and confining pressure. Furthermore, P- and S-wave velocities of the saturated samples were measured at constant differential pressure of 15 MPa. The quasi-static strains of the samples under jacketed and unjacketed conditions were also simultaneously acquired. The lithology, mineralogy, porosity and pore type and size distribution of each sample were obtained using a combination of thinsection and scanning electron microscopy, helium porosimetry and mercury intrusion porosimetry. Due to the lack of closing microcracks and compliant pores in low porosity samples, the travel times show slight changes with the confining pressure. Whereas the high porosity samples show remarkable reduction of travel time with the increase of confining pressure in both P- and S-wave. The samples show high sensitivity to the applied differential pressure specially the high porosity samples. We found that the sample physically deformed at pressure above 25 MPa. An evidence of inelastic deformation were observed in few samples even at 25 MPa differential pressure. The samples show no changes in travel time with increasing confining pressure under constant differential pressure, and this behavior is taken to be representative of full saturation of the sample and hence used as a measure of quality control. The comparisons of Biot, Gassmann, squirt-Biot and squirt-Gassmann model predictions with the measured water saturated velocities show that the squirt mechanism is not active on all the studied samples. Biot mechanism is likely to be the principle dispersion mechanism in these samples. For S-wave velocities, Gassmann's model consistently over-predict the saturated at low pressure and closely fit the measured velocities at high pressure, whereas, Biot model over-predicts the saturated velocities in most of the studied samples. The strains measured from the vertical and horizontal strain gages are differing by around 27%. The strains over the horizontal axis are higher than the vertical axis suggesting that the majority of the compliant pores and crack-like pores are oriented almost in direction parallel to the length of the sample. The static bulk modulus is always lower than dynamic one for all measured samples. There is no correlation between porosity and static-dynamic ratio. The measured grain bulk modulus obtained from the unjacketed test is reasonably close to the bulk modulus of the constituent mineral phases.

  1. 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.

  2. 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.

  3. 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.

  4. Large dielectric tunability and microwave properties of Mn-doped (Ba,Sr)TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Yuan, Z.; Lin, Y.; Weaver, J.; Chen, X.; Chen, C. L.; Subramanyam, G.; Jiang, J. C.; Meletis, E. I.

    2005-10-01

    Ferroelectric Ba0.6Sr0.4TiO3 thin films with 2% Mn additional doping were grown on (001) MgO by pulsed laser deposition. The microstructural studies from x-ray diffraction and transmission electron microscopy indicate that the films are highly epitaxial with c-axis oriented and atomic sharp interface. Dielectric property measurements at 1 MHz and room temperature reveal that the as-grown films have outstanding dielectric properties with large tunability of 80% at 40KV/cm, very large dielectric constant value of 3800, and extra low dielectric loss of only 0.001. The high frequency (10-30 GHz) dielectric measurements demonstrate that the films are excellent in both dielectric property and very low dielectric insertion loss. Compared with the pure BSTO films or traditional doping, the additional doping of Mn in BSTO thin films can significantly improve the dielectric property of the as-grown films.

  5. MICROWAVE DIELECTRIC PROPERTIES OF GRAIN IN NONEQUILIBRIUM STATE: EFFECT OF MOISTURE AND TEMPERATURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric-based sensors for nondestructive and instantaneous determination of moisture content and bulk density in cereal grains are calibrated to predict these physical properties from measurement of the relative complex permittivity. At microwave frequencies, a temperature correction is needed, ...

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. DIELECTRIC PROPERTIES OF MATERIALS AND RELATED AGRICULTURAL APPLICATIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Potential Agricultural applications for RF and microwave energy include selective dielectric heating of insects in grain, treatment of seed to improve germination, and conditioning of products to improve nutritional value and shelf life. Measurement applications include permittivity-density relatio...

  9. Structural and Dielectric properties of Acid Activated Metakaolinite and Kaolinite

    NASA Astrophysics Data System (ADS)

    Izci, E.

    2014-06-01

    CC31 kaolinite has been metakaolinized and activated with H_2SO_4 of varying concentrations. The samples were characterized using XRD,SEM, and Raman spectroscopy. The dielectric permittivity of these samples were studied.

  10. Dielectric refractive index dependence of the focusing properties of a dielectric-cylinder-type decagonal photonic quasicrystal flat lens and its photon localization

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Liu, Exian; Fan, Zhigang; Zhang, Xiong

    2015-11-01

    The focusing properties of a dielectric-cylinder-type decagonal photonic quasicrystal flat lens observed at different dielectric refractive indexes are numerically analyzed, showing that, within certain index ranges, the lens can generate images with a resolution below the diffraction limit for a point source. The lens exhibits a double focusing effect within a range of refractive indexes and induces ring photon localization near a certain dielectric refractive index for the point source with the TM mode.

  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

    2016-03-01

    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. PMID:26899884

  12. 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.

  13. 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.

  14. 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 1225C.

  15. Effect of sintering on structural and dielectric properties of PLZT ferroelectrics

    SciTech Connect

    Janrao, Prashant Mathe, V. L.

    2014-04-24

    Here we report synthesis of (Pb{sub 0.93}La{sub 0.07}Zr{sub 0.6}Ti{sub 0.4}O{sub 3}) PLZT by chemical co-precipitation route. The precipitate obtained was subjected to different processing methods namely furnace sintering and hot press sintering. The product obtained was characterized using X-ray diffraction and dielectric measurements techniques. The dielectric properties obtained are correlated with the structural properties of PLZT.

  16. Dimension effects on the dielectric properties of fine BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Hou, Zhi-Wen; Kang, Ai-Guo; Ma, Wei-Qing; Zhao, Xiao-Long

    2014-11-01

    It is found that the core-shell structured grains are easy to produce for fine grain doped BaTiO3 ceramics in the sintering process. We study the influence of the core-shell structure on the CurieWeiss temperature and dielectric properties of BaTiO3 ceramics by using effective medium approximation (EMA). Considering the second approximation, the dielectric properties of fine grain doped BaTiO3 ceramics are consistent with experimental data.

  17. Electromechanical and relaxation dielectric properties of RbHSO4 crystal

    NASA Astrophysics Data System (ADS)

    Zachek, I. R.; Shchur, Ya.; Levitskii, R. R.

    2015-12-01

    The temperature dependence of static and dynamic dielectric permittivity, piezoelectric stresses, elastic constants and heat capacity of ferroelectric RbHSO4 are described based on the four-sublattice pseudo-spin model within the mean field approximation. The pseudo-spins are ascribed to SO4(1f) (f = 1, , 4) groups which have the dynamic dipole moment in paraelectric phase and manifest a static distortion in ferroelectric phase. We established a set of adjustable model parameters which made it possible to interpret various experimental data.

  18. Wave properties of surface polaritons in the dielectric-high-temperature superconductor-dielectric structure

    NASA Astrophysics Data System (ADS)

    Abramov, A. S.; Zolotovskii, I. O.; Sannikov, D. G.; Sementsov, D. I.

    2015-04-01

    The specific features of the surface polariton propagation in the dielectric-high-temperature superconductor-dielectric symmetric structure have been investigated in the temperature region T < T c /2, where the structure can be considered as non-absorbing. It has been shown that the dispersion curves contain two polariton branches, i.e., high-frequency and low-frequency ones, which correspond to symmetric and antisymmetric distributions of transverse components of the wave field. For the high-frequency branch, there is a propagation constant range where the group velocity and energy flux directions are opposite to the phase velocity direction. In this range, a significant deceleration of polariton waves is also observed.

  19. 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.

  20. Structural and dielectric properties of monodisperse TiO2-paraffin core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Balamurugan, Balasubramanian; Kraemer, Kristin; Skomski, Ralph; Ducharme, Stephen; Sellmyer, David

    2010-03-01

    Core-shell nanoparticles made of oxides having high dielectric constant and organic materials with large breakdown field are attractive candidates for higher-energy-density capacitors. In the present study, monodispersed TiO2 nanoparticles were produced using a cluster-deposition method and subsequently coated with uniform paraffin nanoshells using an in-situ thermal evaporation to form core-shell structure. The thickness of the paraffin nanoshells was varied by controlling the evaporation temperature of paraffin. The dielectric properties of TiO2-paraffin core-shell nanoparticles show an enhanced effective dielectric constant with a decrease in the thickness of the nanoshells and also, reveal a minimum dielectric dispersion and low dielectric losses in the frequency range of 100 Hz -- 1MHz, which are highly desirable for potential device applications.

  1. 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.

  2. 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.

  3. 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.

  4. 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 ?DC 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.

  5. Dielectric and conductivity properties of composite polyaniline/polyurethane network

    NASA Astrophysics Data System (ADS)

    Liang, C.; Gest, J.; Leroy, G.; Carru, J.-C.

    2013-09-01

    In this work, we present the dielectric characterization of polyaniline/polyurethane composite. The samples consisting of 0.5%, 1%, and 5% of polyaniline were deposited on glass fiber, and the measurements were performed in a frequency range of 20 Hz to 20 GHz. The results showed a dielectric relaxation strongly dependent on the concentration of polyaniline. This phenomenon is explained by a theoretical model. In this model, we assume that the alternative conductivity of the polymer network systems is due to conducting clusters whose lengths followed a Gaussian distribution. Depending on their size and the frequency of the excitation signal, the clusters showed a resistive or capacitive effect.

  6. Dielectric property measurement of zirconia fibers at high temperatures

    SciTech Connect

    Vogt, G.J.; Tinga, W.R.; Plovnick, R.H.

    1995-05-01

    Using a self-heating, electronically tunable microwave dielectrometer, the complex dielectric constant of zirconia-based filaments was measured at 915 MHz from 350{degrees} to 1100{degrees}C. This fibrous material cools rapidly to near room temperature within several seconds due to a large surface area to volume ratio. Such rapid sample cooling necessitates the use of a self-heating technique to measure the complex dielectric constant at temperatures up to 1100{degrees}C. Sample temperature was measured with optical fiber thermometry. The effect of sample temperature measurement on data accuracy is discussed.

  7. 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.

  8. 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.

  9. 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.

  10. Electric and dielectric properties of nanostructured stoichiometric and excess-iron Ni-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Sutka, A.; Mezinskis, G.; Lusis, A.

    2013-02-01

    In this paper, we report a study of the effect of excess iron on structural, microstructural, electric and dielectric properties of the nanostructured Ni-Zn ferrites Ni1-xZnxFe2+zO4-? of different compositions with x = 0, 0.3, 0.5, 0.7, 1 and z = 0, 0.1. The structural and microstructural properties are estimated from x-ray diffraction and atomic force microscopy (AFM) data. The average grain size, evaluated from AFM topographical analysis, is found to be below 70 nm. The samples exhibit low values of dielectric constant and dielectric loss and a high resistivity. Contrary to earlier conclusions regarding microstructured Ni-Zn ferrites, in nanostructured Ni-Zn ferrites sintered at relatively low temperature and duration, the excess of iron in the composition increases the electrical resistivity and reduces the dielectric constant and loss tangent.

  11. 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.

  12. 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.

  13. Dielectric and rheological properties of polyaniline organic dispersions

    NASA Astrophysics Data System (ADS)

    Bohli, N.; Belhadj Mohamed, A.; Vignras-Lefbvre, V.; Miane, J.-L.

    2009-05-01

    This paper reports the examination of the evolution of polyaniline-organic solvent interactions in the temperature range of 294-353 K. For this purpose, rheological and dielectric investigations have been undertaken for dispersions of plast-doped polyaniline in two different solvents (dichloroacetic acid and formic acid/dichloroacetic acid mixture). Dielectric permittivity has been investigated using the open ended coaxial line method in the frequency range of [100 MHz, 10 GHz]. Dielectric loss spectra of both dispersions showed a relaxation peak which was well fitted by Havriliak-Negami function. The relaxation was attributed to a Maxwell Wagner Sillars relaxation within polyaniline clusters. The difference found between relaxation parameters of the pure solvent and polyaniline dispersions was attributed to the solvent/polyaniline interactions. The relaxation time relative to the PANI/DCAA dispersion followed an Arrhenius law. While a Vogel-Fulcher-Tammann law was found for the relaxation time of PANI/DCAA-FA dispersion. Above a certain temperature, 318 K for PANI/DCAA and 313 K for PANI/DCAA-FA, the rheological parameters of the dispersions changed, thus indicating a morphological change of polyaniline in the dispersion. In the same range of temperature, ? and ? relaxation parameters undergo significant changes. Those changes in dielectric and rheological parameters seem to be related to a structural change occurring in the polyaniline organic dispersion systems while increasing temperature. An interesting correlation between permittivity and viscosity was obtained.

  14. 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.

  15. Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.

    PubMed

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

    2011-01-01

    Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been measured in the MMW region using high-power sources for the first time, using a free-space, quasi-optical MMW spectrometer equipped with high-power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 to 120 and 180 to 260 GHz. These results are compared with MMW permittivity of these materials obtained by other methods as well as to RF, microwave, and optical frequency permittivities for all the materials tested. The effects of both crystallographic orientation and quality of the surface polishing of the crystals have been examined. Uncertainties and possible sources of instrumentation and measurement errors related to the freespace MMW technique are discussed. This work demonstrates that precise MMW permittivity data can be obtained even on relatively small and thin crystals of different surface conditions and orientations using the high-power BWO-based quasioptical approach. PMID:21244971

  16. Fluorinated polymides for interlayer dielectric applications: Tailoring of properties via copolymerization

    SciTech Connect

    Auman, B.C.; McKerrow, A.J.; Ho, P.S.

    1996-10-01

    Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for interlayer dielectric (ILD) applications. It has been shown that copolymerization is a versatile method for tailoring properties of these rigid polyimides. Initial product offerings from DuPont showed an excellent balance of properties for ILD applications. These materials, however, due to their highly rod-like structure and very low in-plane coefficient of thermal expansion (CTE), actually yielded negative thermal stresses on silicon at the 1 {mu}m thicknesses typical of interlayer dielectrics. More flexible materials with higher CTE typically yield positive stress values which can be undesirably quite high. The dielectric constant of these highly rod-like fluorinated polyimides was also somewhat anisotropic, again due to the rod-like nature and resulting high in-plane orientation of these polyimides. Since a thermal stress on silicon near zero and a more isotropic dielectric constant are likely the most desirable states for an ILD, the highly rod-like polyimide was further optimized by incorporation of a more flexible fluorinated comonomer, 6FDA, at various levels to increase CTE and balance dielectric constant. The various properties of this series of fluorinated polyimides were investigated. The results have shown that it is indeed possible to obtain near zero stress on silicon while attaining more isotropic dielectric constant via structure optimization.

  17. Photonic properties of two-dimensional photonic crystals based on monolayer of dielectric microspheres

    NASA Astrophysics Data System (ADS)

    Ayenew, Getachew T.; Chakaroun, Mahmoud; Fabre, Nathalie; Solard, Jean; Fischer, Alexis; Chen, Chii-Chang; Boudrioua, Azzedine; Chan, Chia-Hua

    2012-04-01

    The optical properties of two-dimensional (2D) photonic crystal (PhC) slabs based on self-assembled monolayer of dielectric microspheres are studied. The in-plane transmission spectra of 2D array of dielectric spheres with triangular lattice are investigated using the finite-difference-time-domain (FDTD) method. The structures studied are monolayer of dielectric spheres infiltrated with air ('opals') and air spheres infiltrated with dielectric material ('inverse opals'), with glass substrate sustaining the monolayer of spheres. The transmission spectra are calculated for different values of refractive index contrasts between the spheres and the infiltrated material and for different values of filling fractions (compactness of the spheres). As the refractive index is varied, compact spheres are assumed; and as the filling fraction is varied, the refractive index of the dielectric spheres or the dielectric matrix is fixed to be 2.5. For compact opal structure on glass substrate, a narrow photonic band gap (PBG) is observed in the transmission spectra for dielectric spheres with refractive index higher than around 1.9. When the refractive index is fixed at 2.5, the PBG is observed for more compact spherical arrangement and disappears for more separated spheres. While for inverse opal structure on glass substrate, using non-compact spheres enlarges the width of PBG which is not observed for compact spherical arrangement. The application of the study is to realize organic PhC microcavity laser.

  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. Plant Water Stress Detection Using Radar: The Influence Of Water Stress On Leaf Dielectric Properties

    NASA Astrophysics Data System (ADS)

    van Emmerik, Tim; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick

    2015-04-01

    Recent research on an agricultural maize canopy has demonstrated that leaf water content can change considerably during the day and in response to water stress. Model simulations suggest that these changes have a significant impact on radar backscatter, particularly in times of water stress. Radar is already used for several vegetation and soil monitoring applications, and might be used for water stress detection in agricultural canopies. Radar observations of the land surface are sensitive because it results in two-way attenuation of the reflected signal from the soil surface, and vegetation contributes to total backscatter from the canopy itself. An important driver that determines the impact of vegetation on backscatter is the dielectric constant of the leaves, which is primarily a function of their moisture content. Understanding the effects of water stress on the dynamics of leaf dielectric properties might shed light on how radar can be used to detect vegetation water stress. Previous studies have investigated the dielectric properties of vegetation. However, this has mainly been done using destructive sampling or in-vivo measurements of tree trunks. Unfortunately, few in-vivo measurements of leaf dielectric properties exist. This study presents datasets of in-vivo dielectric measurements of maize leaves, taken during two field experiments. One experiment was done using was done during a period of water stress, the other during a period without. Field measurements revealed a different vertical profile in dielectric properties for the period with and without water stress. During a period of increased water stress, the diurnal dynamics of leaves at different heights responded differently to a decrease in bulk moisture content. This study provides insight in the effect of water stress on leaf dielectric properties and water content, and highlights the potential use of radar for water stress detection in agricultural canopies.

  20. Diabetes mellitus effect on rat corneal dielectric properties.

    PubMed

    Olszewski, J; Marzec, E; Florek, E; Kulza, M

    2012-03-01

    In the course of the study, we carried out a dielectric examination to determine the effect of diabetes mellitus on the rat corneal function. Measurements were performed over the frequency range of 500 Hz-100 kHz in air and at the temperatures from 25 to 150C. The frequency dependencies of the loss tangent for the healthy and the diabetic cornea exhibit two peaks at 2 kHz and 16 kHz in the ?-dispersion region. The amplitude of these both peaks is smaller for the diabetic cornea than that for the healthy one. The temperature dependencies of the loss tangent for the healthy and the diabetic cornea reveal ?-relaxation in the range of 30-70C and 50-90C, respectively. The present study exhibits that the dielectric spectroscopy is useful in detection of the effect of diabetes mellitus on the corneal molecular behavior. PMID:22136803

  1. 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.

  2. TECHNICAL NOTE: Dielectric properties of mixed Li Ni Cd ferrites

    NASA Astrophysics Data System (ADS)

    Kharabe, R. G.; Devan, R. S.; Kanamadi, C. M.; Chougule, B. K.

    2006-04-01

    Ferrites with the general formula Li0.5Ni0.75-x/2Cdx/2Fe2O4 (where x = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by the standard double sintering ceramic method. X-ray diffraction analysis confirmed the single phase spinel structure of the samples. The variation of saturation magnetization (Ms) was studied as a function of Cd content. The dielectric constant (?') and dielectric loss tangent (tan?) were measured at room temperature as a function of frequency in the range 100 Hz 1 MHz. These parameters decrease with increasing frequency for all of the samples. The compositional variation of ?' and ?DC show an inverse trend of variation with each other.

  3. 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.

  4. Static and transport properties of alkyltrimethylammonium cation-based room-temperature ionic liquids.

    PubMed

    Seki, Shiro; Tsuzuki, Seiji; Hayamizu, Kikuko; Serizawa, Nobuyuki; Ono, Shimpei; Takei, Katsuhito; Doi, Hiroyuki; Umebayashi, Yasuhiro

    2014-05-01

    We have measured physicochemical properties of five alkyltrimethylammonium cation-based room-temperature ionic liquids and compared them with those obtained from computational methods. We have found that static properties (density and refractive index) and transport properties (ionic conductivity, self-diffusion coefficient, and viscosity) of these ionic liquids show close relations with the length of the alkyl chain. In particular, static properties obtained by experimental methods exhibit a trend complementary to that by computational methods (refractive index ? [polarizability/molar volume]). Moreover, the self-diffusion coefficient obtained by molecular dynamics (MD) simulation was consistent with the data obtained by the pulsed-gradient spin-echo nuclear magnetic resonance technique, which suggests that computational methods can be supplemental tools to predict physicochemical properties of room-temperature ionic liquids. PMID:24702446

  5. 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) ?m and a thickness d (1-5) ?m have been grown by evaporation on NdGaO3(100) and ?-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.

  6. 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.

  7. 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...

  8. 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

  9. Improving the dielectric properties of ethylene-glycol alkanethiol self-assembled monolayers.

    PubMed

    Zaccari, Irene; Catchpole, Benjamin G; Laurenson, Sophie X; Davies, A Giles; Wlti, Christoph

    2014-02-11

    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

  10. ON THE INFLUENCE OF MOISTURE ON DIELECTRIC PROPERTIES OF POLYETHERETHERKETONE (PEEK) CARBON-FIBER COMPOSITES

    EPA Science Inventory

    An analysis of local and global mechanisms of heat generation and distribution in carbon-fiber-based composites subjected to an alternating magnetic field has shown that heating is dependent upon the dielectric properties of the polymer matrix. These properties were investigated ...

  11. 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 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. Electronic supplementary information (ESI) available: Additional information on dispersion, spectroscopy, and sensor fabrication. See DOI: 10.1039/c5nr07958f

  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 1mol%) 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 (~63nm), stimulated emission cross-section (9.67×10(-21)cm(2)) and lifetime (2.56ms) of (4)I13/2 level for 0.5mol% 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 0.5mol% of Er(3+) -doped glass was confirmed as the optimum composition. PMID:26967514

  13. Dielectric and magnetic properties of (Zn, Co) co-doped SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Khan, Rajwali; Fang, Ming-Hu

    2015-12-01

    Polycrystalline samples of (Zn, Co) co-doped SnO2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO2 powder samples have the same tetragonal structure of SnO2. A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics. Project supported by the National Basic Research Program of China (Grant Nos. 2015CB921004, 2012CB821404, and 2011CBA00103) and the National Natural Science Foundation of China (Grant Nos. 11374261 and 11204059).

  14. Sensitivity of Dielectric Properties to Wear Process on Carbon Nanofiber/High-Density Polyethylene Composites

    NASA Astrophysics Data System (ADS)

    Liu, Tian; Wood, Weston; Zhong, Wei-Hong

    2011-12-01

    We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.

  15. Dielectric properties of cluster-deposited TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Balamurugan, B.; Kraemer, Kristin; Wei, X.; Ducharme, Stephen; Sellmyer, D. J.

    2009-03-01

    TiO2-polymer nanocomposites are expected to have a high dielectric permittivity of TiO2 and large breakdown strength of the polymer, resulting in high energy density suitable for energy storage devices. Since chemically prepared nanocomposites tend to have poor film quality and inhomogeneities due to agglomeration, cluster deposition technique was used to prepare monodispersed TiO2--paraffin nanocomposite films. TiO2 clusters were coated in-flight with paraffin wax having comparatively better dielectric strength (7.9 -- 11.8 MV/m) using a thermal evaporation source in prior to deposition. Bare TiO2 clusters with average particle size ranging from 8 to 12 nm having a maximum dielectric permittivity of 54 were obtained. The structural and dielectric properties of these nanocomposites with varying volume fractions will be discussed. This research is supported by ONR and NCMN.

  16. Tuning the dielectric properties of thiourea analog crystals for efficient nonlinear optical applications

    SciTech Connect

    Sabari Girisun, T.C.; School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu ; Dhanuskodi, S.

    2010-01-15

    Materials with low dielectric constant have attracted a great deal of interest in the field of nonlinear applications and microelectronic industry. Metal complexes of thiourea with group II transition metals (Zn, Cd) as central atom and period III elements (S, Cl) were synthesized by chemical reaction method and single crystals were grown from aqueous solution by slow evaporation method. By parallel plate capacitor technique, the dielectric response, dissipation factor, ac conductivity and impedance of virgin and metal complexes have been studied in the frequency (100 Hz to 5 MHz) and temperature (303-423 K) ranges. Metal complexes of thiourea with cadmium substitute have a low dielectric constant less than 10. Also the presence of chlorine in the metal complex induces noncentro symmetric structure. Hence the role of group II transition metals and period III elements in tuning the dielectric properties for efficient nonlinear applications has been studied.

  17. Tunable dielectric properties and excellent microwave absorbing properties of elliptical Fe3O4 nanorings

    NASA Astrophysics Data System (ADS)

    Tong, Guoxiu; Liu, Yun; Cui, Tingting; Li, Yana; Zhao, Yanting; Guan, Jianguo

    2016-02-01

    Elliptical Fe3O4 nanorings (NRs) with continuously tunable axes that range from 40 nm to 145 nm in length were prepared through a precursor-directed synthetic route to determine the electromagnetic responses generated at 2-18 GHz. The tunability of the dielectric properties of Fe3O4 NRs depends on the long axis rather than on the specific surface area, internal stress, and grain size. Elliptical Fe3O4 NRs exhibit the excellent microwave absorbing properties due to the unique ring-like configuration, which significantly enhances permittivity, multiple scattering, oscillation resonance absorption, microantenna radiation, and interference. These findings indicate that ring-like nanostructures are promising for devising effective microwave absorbers.

  18. 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 (?2) shows redshift in the structure peak energy on the application of strains with significant dependence on the types of applied strain. Static dielectric constant (?s) has been found to increase with the increase of tensile strains (both uniaxial and biaxial) and asymmetric biaxial strain. On the other hand, ?s decreases for smaller magnitude of compression strains and show increase at higher magnitude. The change in the magnitude of ?s particularly for compression strains remain material specific.

  19. 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

  20. 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. PMID:17946603

  1. Functional group dependent dielectric properties of sulfated hydrocolloids extracted from green macroalgal biomass.

    PubMed

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2014-07-17

    Dielectric properties of aqueous solutions of sulfated hydrocolloids (ulvan and rhamnan sulfate) extracted from green macroalgal biomass were studied in a frequency range of 100 MHz-10 GHz. Counterion exchange of native hydrocolloids (mixture of Na(+), Mg(2+) and Ca(2+)) to H(+)-form showed significant increase in loss factor due to ionic conduction. On the other hand, desulfations decreased their loss factors. The results suggested that ionic conduction of H(+) has significant contribution to loss factors. Additionally, H(+)-form hydrocolloids showed significant improvement in hydration, which might also affect the dielectric property of the solution by reducing the amount of free water. The viscosity, however, did not show apparent relevance with the dielectric property. PMID:24702935

  2. Microwave Dielectric Properties of (Ca1-xSrx)SiO3 Ring Silicate Solid Solutions

    NASA Astrophysics Data System (ADS)

    Kagomiya, Isao; Suzuki, Itaru; Ohsato, Hitoshi

    2009-09-01

    The microwave dielectric properties of ?-CaSiO3 and SrSiO3 synthesized by a solid-state reaction were ?r = 6.82, Qf = 42,200 GHz, ?f = -18.9 ppm/C and ?r = 6.78, Qf = 13,100 GHz, ?f = -65.9 ppm/C, respectively. (Ca1-xSrx)SiO3 solid-solution series were also synthesized by a solid-state reaction and their microwave dielectric properties were examined. Two structural-type solid solutions were formed in wide range of x = 0 to 0.4 and 0.6 to 1.0. Good microwave dielectric properties with ?r = 6.62, Qf = 66,700 GHz, and ?f = -40 ppm/C were obtained with x = 0.8 of the (Ca1-xSrx)SiO3 series.

  3. Optical phonon modes and infrared dielectric properties of monoclinic CoWO4 microcrystals

    NASA Astrophysics Data System (ADS)

    Moreira, Roberto L.; Almeida, Rafael M.; Siqueira, Kisla P. F.; Abreu, Cintia G.; Dias, Anderson

    2016-02-01

    The phonon characteristics of CoWO4 microcrystals with monoclinic Wolframite structure were investigated by far-infrared (IR) and Raman spectroscopies. Near-normal spectra were taken for IR light polarization along the principal b-axis (A u modes) and along several angles within the ac-plane (B u modes). The IR spectra were analyzed with a generalized DrudeLorentz model, and all predicted polar phonon modes were fully determined, including their symmetries, the dielectric Lorentz parameters and the non-orthogonal phonon polarizations for the B u modes. Anomalous dispersion and negative values for the real and imaginary parts of the off-diagonal components of the dielectric tensor functions were identified and discussed under the light of the varying phonon polarization directions (spread out in the ac-plane). The obtained static and background dielectric tensors gave an average permittivity of 16.1 (at microwave region), refractive indices along the principal dielectric axes of 2.22, 2.33 and 2.44 (at 1 ?m), the optical axes, and an estimated value for the biaxial angle of the crystal. Polarized Raman spectra on appropriate scattering configurations revealed the 18 non-polar gerade phonons of CoWO4 crystals, with their correct symmetries attributed.

  4. 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.

  5. Dielectric properties of rare earth (Sm and La) substituted lead zirconate titanate (PZT) ceramics

    NASA Astrophysics Data System (ADS)

    Dipti, Singh, Sangeeta; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

    2013-06-01

    In the present paper, we are reporting the studies on dielectric properties of Lanthanum (La) and Samarium (Sm) substituted Lead Zirconate Titanate with compositional formula Pb(1.02-x)SmxZr0.55Ti0.45O3 and Pb(1.02-x)LaxZr0.55Ti0.45O3 with x = 0.00, 0.01, 0.02, 0.03. The materials were synthesized by solid state reaction route. XRD analysis shows that all the samples be in single phase with tetragonal structure. Dielectric properties were studied as a function of temperature.

  6. 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 efficiency, and low dielectric loss, leakage current density.

  7. Dielectric properties of glasses at ultra low temperatures

    SciTech Connect

    Nishiyama, H.; Akimoto, H.; Okuda, Y.; Ishimoto, H.

    1992-11-01

    A temperature dependence in the dielectric constant of vitreous silica has been measured down to a few hundred microkelvin at frequencies between 110Hz and 10kHz. Homosil glass shows a logarithmic increase below 10 mK down to the lowest temperature of 0.61 mK. On the other hand, Suprasil glass exhibits a saturation behavior following a logarithmic increase above 3 mK. These phenomena are discussed on the basis of the two level system. 6 refs., 2 figs.

  8. Structural and dielectric properties of a complex tungsten bronze ferroelectric

    NASA Astrophysics Data System (ADS)

    Padhee, R.; Das, P. R.; Parida, B. N.; Choudhary, R. N. P.

    2012-07-01

    The polycrystalline sample of K2Pb2Y2W2Ti4Nb4O30 was synthesized by a mixed-oxide method at high temperature. The compound formation was checked by preliminary X-ray structural analysis. The SEM micrograph exhibits uniform plate and rod-like grain distribution. Detailed studies of variation of dielectric parameters with temperature and frequency, and polarization confirmed the existence of ferroelectricity in the material, with phase transition at 390C. The ac conductivity follows the Arrhenius equation.

  9. 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.

  10. 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. PMID:26225887

  11. 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.

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

    PubMed

    Zalai, Dnes; Tobak, Teodra; Putics, kos

    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

  13. Influence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Taylor, T. R.; Hansen, P. J.; Pervez, N.; Acikel, B.; York, R. A.; Speck, J. S.

    2003-09-01

    The dielectric permittivity, dielectric quality factor (inverse dielectric loss), and lattice parameter of 140 nm sputtered SrTiO3 films were dependent on the oxygen partial pressure and total chamber pressure (O2+Ar) during film growth. Films were grown at 25 and 75 mTorr (mT) in an oxygen rich and oxygen deficient sputtering gas environment concurrently on (100) SrTiO3 and (111) Pt/(0001) Al2O3 substrates. Films were deposited on platinized sapphire for electrical characterization and the homoepitaxial films were used as a structural and chemical standard. High resolution triple axis x-ray diffraction results showed an increase in mismatch between the film and substrate (200) peak in homoepitaxial SrTiO3 films with higher total growth and lower oxygen pressures. Dielectric quality factors of the SrTiO3 films on platinized sapphire at 1 MHz for the 25 mT (50 sccm Ar/50 sccm O2), 25 mT (90 sccm Ar/10 sccm O2), 75 mT (50 sccm Ar/50 sccm O2), and 75 mT (90 sccm Ar/10 sccm O2) film growths were 320, 251, 209, and 102, respectively; likewise, the dielectric constants follow as 241, 230, 220, and 170, respectively. Improved film dielectric properties were observed for films closer to stoichiometric SrTiO3.

  14. Four-dimensional dielectric property image obtained from electron spectroscopic imaging series.

    PubMed

    Lo, S C; Kai, J J; Chen, F R; Chang, L; Chen, L C; Chiang, C C; Ding, P; Chin, B; Zhang, H; Chen, F

    2001-01-01

    We have demonstrated a new quantitative method to characterize two-dimensional distributions of energy-dependent dielectric function of materials from low loss electron spectroscopic image (ESI) series. Two problems associated with extracted image-spectrum from the low-loss image series, under-sampling and loss of energy resolution, were overcome by using fast Fourier transformation (FFT) interpolation and maximum entropy deconvolution method. In this study, Black Diamond/Si3N4/SiO2/Si-substrate dielectric layer designed for copper metallization was used as the sample. We show that the reconstructed (FFT interpolated and maximum entropy deconvoluted) image-spectrum obtained from ESI series images can be quantified with the same accuracy as conventional electron energy-loss spectroscopy spectra. Since the analysis of the dielectric function is sensitive to the local thickness of the specimen using Kramers-Kronig analysis, we also developed a new method to quantitatively determine the dielectric constant for low-k materials. We have determined the thickness of the Black Diamond using the extrapolated thickness method from the materials of known dielectric constants. Using Kramers-Kronig formula, the dielectric function map can be deduced from two-dimensional reconstructed single scattering spectra with providing the information of thickness. We proposed a four-dimensional data presentation for revealing the uniformity of the energy dependent property. The accuracy of our methods depends on the thickness determination and on the quality of the reconstructed spectra from the image series. PMID:11918416

  15. Structural, spectral and dielectric properties of piezoelectric-piezomagnetic composites

    NASA Astrophysics Data System (ADS)

    Hemeda, O. M.; Tawfik, A.; Amer, M. A.; Kamal, B. M.; El Refaay, D. E.

    2012-10-01

    Composite materials of spinel ferrite (SF) NiZnFe2O4 (NZF) and barium titanate (BT) BaTiO3 were prepared by double sintering ceramic technique. X-ray diffraction patterns for the composite system (1-x) NZF+x BT, showed the presence of mainly of 2 phases, hence confirming the successful preparation of the composite. Some structural and microstructural parameters like porosity, X-ray density, particle size and lattice constant were deduced from the analysis of X-ray data for both phases. Scan electron microscope (SEM) analysis shows nearly a homogeneous microstructure with good dispersion of BT grains as well as the presence of some pores. There was also an enlargement of BT grains with increasing its content. Infra red (IR) spectra of the composite system indicate that BT content affects the intermolecular character of the SF phase. A rise in the dielectric constant occurred at high temperature which was attributed to the effect of space change resulting from the increase of the change carriers in the paramagnetic region. The dielectric loss (tan ?) decreased by increasing BT content.

  16. 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.

  17. Microscopic theory of the dielectric properties of proteins.

    PubMed Central

    Simonson, T; Perahia, D; Brnger, A T

    1991-01-01

    This paper investigates the microscopic mechanisms of charge screening in proteins. The screening of an arbitrary perturbing charge density by a protein and its surrounding solution is characterized by a generalized susceptibility, which is approximately given by the mean dipole-dipole correlation matrix of the system. This susceptibility is a microscopic quantity; the sum of its matrix elements gives the macroscopic susceptibility of continuum electrostatics. When screening of a single perturbing point charge is considered, this susceptibility reduces to a scalar quantity, dependent on position within the protein. The contribution of the positional degrees of freedom of the protein atoms can be estimated from molecular dynamics simulations. This contribution gives rise to large spatial variations of the susceptibility, whose significance for protein function is discussed. The model is applied to the small alpha helix deca-alanine, and to the electron-transfer protein cytochrome c. The results agree qualitatively with previous normal mode calculations. The importance, and the large spatial variations, of charge screening by deca-alanine suggest that dielectric screening may play a role in the binding of charged ligands by helices. In cytochrome c, the dielectric susceptibility in response to a point charge is at a minimum in the central heme region, resulting in a lowering of the reorganization free energy for charge transfer to and from the heme. Images FIGURE 15 FIGURE 16 FIGURE 17 PMID:1646659

  18. 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 (?) 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.

  19. Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

    NASA Astrophysics Data System (ADS)

    Liang, Wei-Zheng; Ji, Yan-Da; Nan, Tian-Xiang; Huang, Jiang; Zeng, Hui-Zhong; Du, Hui; Chen, Chong-Lin; Lin, Yuan

    2012-06-01

    Barium titanate (BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition (PAD) technique. The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion. Crystal structures, surface morphologies, and dielectric performance were examined and compared for BTO thin films annealed under different temperatures. Correlations between the fabrication conditions, microstructures, and dielectric properties were discussed. BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with inr ~ 400 and tan ? < 0.025 at 100 kHz. The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

  20. 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.

  1. Effect of crystal structure on strontium titanate thin films and their dielectric properties

    NASA Astrophysics Data System (ADS)

    Kampangkeaw, Satreerat

    Strontium titanate (SrTiO3 or STO) has application in radio and microwave-frequency tunable capacitor devices particularly at low temperatures due to its high dielectric constant, low loss and the electric field tunability of its dielectric constant. The main goal of improving the performance in these devices is to increase the tunability and decrease the dielectric loss at the same time, especially at microwave frequencies. Thin films of STO however, show dramatic differences compared to the bulk. The dielectric constant of bulk STO increases nonlinearly from 300 at room temperature to 30000 at 4 K and the loss range is 10-3--10 -4. On the other hand. STO thin films, while showing a dielectric constant close to 300 at room temperature, typically reach a maximum between 1000 and 10000 in the 30 K to 100 K range before decreasing, and the high-loss range is 10-2--10-3. We have grown strontium titanate thin films using a pulsed laser deposition technique on substrates selected to have a small lattice mismatch between the film and substrate. Neodymium gallate (NdGaO3 or NGO) and lanthanum aluminate (LaAlO3 or LAO) substrates were good candidates due to only 1--2% mismatching. Film capacitor devices were fabricated with 25 micron gap separation. 1.5 mm total gap length and an overall 1 x 2 mm dimension using standard lithography and gold metal evaporative techniques. Their nonlinear dielectric constant and loss tangent were measured at low frequencies and also at 2 GHz, and from room temperature down to 4 K. The resulting films show significant variations of dielectric properties with position on the substrates with respect to the deposition plume axis. In the presence of DC electric fields up to +/-4 V/mum, STO films show improved dielectric tunability and low loss in regions far from the plume axis. We found that the films grown on NCO have lower dielectric loss than those on LAO due to a closer match of the NCO lattice to that of STO. We investigated the possible causes that make dielectric behavior in STO thin films different from the bulk. We characterized such film structures as lattice parameters, out-of-plane grain size, in-plane grain size, thickness, roughness, strains, and defects using ellipsometry, atomic force microscopy, and a high-resolution X-ray diffractometry. In plane grain size and percentage of defects were found to play a major role on the dielectric performance of the films.

  2. Dynamic and Static Shell Properties of White and Brown Shell Eggs Exposed to Modified-pressure Microcrack Detection Technology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dynamic and static shell properties of eggs provide important insight to egg quality. Understanding how processing and handling procedures affect both dynamic and static shell properties can enhance the safety and quality of egg reaching consumers. A study was conducted to determine if dynamic she...

  3. Rapid and Nondestructive Determination of Moisture Content in Peanut Kernels from Microwave Measurement of Dielectric Properties of Pods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method for moisture determination in peanut kernels from measurement of the dielectric properties of peanut pods at microwave frequencies is presented. The dielectric properties of peanut kernels and pods were measured in free space with a vector network analyzer and a pair of focused beam horn-l...

  4. 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

  5. Understanding the Dielectric Properties of Liquid Amides from a Polarizable Force Field

    PubMed Central

    Harder, Edward; Anisimov, Victor M.; Whitfield, Troy; MacKerell, Alexander D.; Roux, Benoît

    2016-01-01

    The role played by electronic polarization in the dielectric properties of liquid N-methyl acetamide (NMA) is examined using molecular dynamics simulations with a polarizable force field based on classical Drude oscillators. The model presented is the first force field shown to reproduce the anomalously large dielectric constant of liquid NMA. Details of the molecular polarizability are found to be important. For instance, all elements of the polarizability tensor, rather then just the trace, impact on the condensed phase properties. Two factors related to electronic polarizability are found to contribute to this large dielectric constant. First is the significant enhancement of the mean amide molecular dipole magnitude, which is 50% larger in the liquid than in the gas phase. Second is the consequent strong hydrogen bonding between molecular neighbors that enhances the orientational alignment of the molecular dipoles. Polarizable models of amide compounds that have two (acetamide) and zero (N,N-dimethyl acetamide) polar hydrogen-bond donor atoms are also investigated. Experimentally, the neat liquid dielectric constants at 373 K are 100 for NMA, 66 for acetamide and 26 for N,N-dimethyl acetamide. The polarizable models replicate this trend, predicting a dielectric constant of 92 ± 5 for NMA, 66 ± 3 for acetamide and 23 ± 1 for N,N-dimethyl acetamide. PMID:18302362

  6. 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.

  7. Dielectric property of MoS(2) crystal in terahertz and visible regions.

    PubMed

    Yan, Xianding; Zhu, Lipeng; Zhou, Yixuan; E, Yiwen; Wang, Li; Xu, Xinlong

    2015-08-01

    Two-dimensional materials such as MoS2 have attracted much attention in recent years due to their fascinating optoelectronic properties. The dielectric response of MoS2 crystal in both the terahertz (THz) and visible regions is studied in this work. Time-domain THz spectroscopy is employed for the THz property investigation. The real and imaginary parts of the complex dielectric constant of MoS2 crystal are found to follow a Drude model, which is due to the intrinsic carrier absorption. In the visible region, ellipsometry is used to investigate the dielectric response. The general trend of the complex dielectric constant is found to be described with a Lorentz model, while two remarkable dielectric response peaks are observed to be located at 1.85 and 2.03eV, which has been attributed to the splitting arising from the combined effect of interlayer coupling and spin-orbit coupling. This work can be the research foundation for future optoelectronic applications with MoS2. PMID:26368087

  8. Dielectric property of MoS_2 crystal in terahertz and visible regions

    NASA Astrophysics Data System (ADS)

    Yan, Xianding; Zhu, Lipeng; Zhou, Yixuan; E, Yiwen; Wang, Li; Xu, Xinlong

    2015-08-01

    Two-dimensional materials such as MoS2 have attracted much attention in recent years due to their fascinating optoelectronic properties. Dielectric property of MoS2 is desired for the optoelectronic application. In this paper, terahertz (THz) time-domain spectroscopy and ellipsometry technology are employed to investigate the dielectric response of MoS2 crystal in THz and visible region. The real and imaginary parts of the complex dielectric constant of MoS2 crystal are found to follow a Drude model in THz region, which is due to the intrinsic carrier absorption. In visible region, the general trend of the complex dielectric constant is found to be described with a Lorentz model, while two remarkable peaks are observed at 1.85 and 2.03 eV, which have been attributed to the splitting arising from the combined effect of interlayer coupling and spin-orbit coupling. This work affords the fundamental dielectric data for the future optoelectronic applications with MoS2.

  9. Dielectric properties of PLZT film-on-foil capacitors.

    SciTech Connect

    Ma, B.; Kwon, D.-K.; Narayanan, M.; Balachandran, U.; Energy Systems

    2008-07-31

    We have deposited Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} (PLZT) films on nickel foils to create film-on-foil capacitor sheets. Measurements with PLZT films on LaNiO{sub 3}-buffered Ni foils yielded the following: relative permittivity {approx} 1300 and dielectric loss (tan {delta}) {approx} 0.05, leakage current density of 6.6 x 10{sup ? }9 A/cm{sup 2} (at 25 C) and 1.4 x 10{sup -8} A/cm{sup 2} (at 150 C), and mean breakdown field strength > 2.4 MV/cm. Based on the hysteresis loop measurement, an energy storage density of {approx} 17 J/cm{sup 3} was obtained for such a capacitor at 50% of the mean breakdown field.

  10. Influence of Water content of RF and Microwave Dielectric Properties of Foods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    ABSTRACT The importance of dielectric properties of food materials is discussed with respect to their influence on the heating of materials by radio-frequency and microwave energy and their use for rapid, nondestructive sensing of quality characteristics of such materials. Data are presented graph...

  11. Variation of the dielectric properties of chicken breast meet with frequency and temperature

    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 oC to +25 oC. To ensure temperature uniformity between the different components of the measurement assembly, the measurements were performed in...

  12. A brief history of grain and seed moisture sensing through dielectric properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The importance of moisture measurement in grain and seed is discussed, and a brief history of the development of electrical moisture sensing instruments, based on sensing electrical properties of these materials, is presented. Data are presented graphically on the permittivities or dielectric prope...

  13. Dielectric Properties of Birch Wood in the High-Frequency Range

    NASA Astrophysics Data System (ADS)

    Goreshnev, M. A.; Litvishko, E. S.; Lopatin, V. V.

    2016-01-01

    Results of measurement of dielectric properties of birch wood in the radio-frequency range depending on its humidity are presented. The dependences obtained indicate strong influence of wood anisotropy especially at low frequencies. It is shown that it is irrational to use the wood for insulation if its humidity exceeds 15-20%.

  14. Properties of humidity sensors with porous Al2O3 as a dielectric layer

    NASA Astrophysics Data System (ADS)

    Chachulski, Bogdan; Jasinski, Grzegorz; Zajt, Teresa; Nowakowski, Antoni; Jasinski, Piotr

    2004-07-01

    The effect of humidity influence on characteristics of a ceramic sensor with a porous dielectric Al2O3 layer is presented. Influence of chosen electrolytic process parameters on electrical properties of the sensor is shown. The experimental data of two groups of sensors are interpreted using two, known from literature, electric equivalent circuits.

  15. 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...

  16. Effects of acid, salt and soaking time on the dielectric properties of acidified vegetables

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to design a continuous microwave process for pasteurization of acidified vegetables, equilibration phenomena in acid and salt solutions must be examined with regards to changes in dielectric properties. The objective of this study was to examine the effects of acid and salt concentration o...

  17. FREE-SPACE MEASUREMENT OF DIELECTRIC PROPERTIES OF CEREAL GRAIN AND OILSEED AT MICROWAVE FREQUENCIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Principles of dielectric properties measurement by microwave free-space transmission measurements are presented, and the important sources of errors in such measurements are discussed. A system, including a vector network analyzer, horn/lens antennas, holder for grain and oilseed samples, and a rad...

  18. 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...

  19. A Study on Subsequent Static Aging and Mechanical Properties of Hot-Rolled AA2017

    NASA Astrophysics Data System (ADS)

    Khalili, L.; Serajzadeh, S.

    2014-08-01

    In this work, the effects of rolling parameters, cooling media, and deformation path on mechanical properties and aging behavior of hot-rolled AA2017 were studied. First, hot-rolling experiments were conducted under different working conditions, and the rolled strips were then aged at room temperature for up to 57 days during which hardness and tensile tests were carried out to record the changes in the mechanical properties of the alloy. Furthermore, due to the importance of static recrystallization on subsequent aging behavior, the rate of recrystallization was also computed. To this end, a mathematical model was developed to predict thermomechanical responses during hot rolling using the finite element software, Abaqus/Explicit. Then, a physically-based model was employed for the determination of the kinetics of static recrystallization using the predicted thermomechanical parameters. Finally, the effects of rolling schedule on the mechanical properties and the aging behavior of rolled alloy were evaluated by means of the experimental results and the predictions. The results indicate that natural aging occurs in the hot-rolled alloy, while its influence on the mechanical properties is highly affected by the static recrystallization occurring in the interpass region and/or after rolling on the run-out table.

  20. Magnetic, structural, and dielectric properties of CuB{sub 2}O{sub 4}

    SciTech Connect

    Nenert, G.; Palstra, T. T. M.; Bezmaternykh, L. N.; Vasiliev, A. N.

    2007-10-01

    We have studied the magnetic, structural, and dielectric properties of a single crystal of CuB{sub 2}O{sub 4}. We show that both reported magnetic transitions are observable in the magnetization, irrespective of the measured direction of the crystal. This is in agreement with recent neutron data. More importantly, our study demonstrates the absence of dielectric anomalies at the various magnetic transitions despite the reported magnetoelectric symmetry. This demonstrates that the polarization remains zero at any temperature. Consequently, we interpret our data as the evidence for a very weak or the absence of linear magnetoelectric coupling in this material.

  1. Dielectric properties of composites based on nanocrystalline cellulose with triglycine sulfate

    NASA Astrophysics Data System (ADS)

    Nguen, Kh. T.; Milovidova, S. D.; Sidorkin, A. S.; Rogazinskaya, O. V.

    2015-03-01

    The dielectric properties and frequency dispersion of the dielectric characteristics of nanocrystalline cellulose-triglycine sulfate composites have been studied in the low- and infralow-frequency ranges (from 10-3 to 103 Hz) in a weak electric field. It has been shown that the phase transition in these composites is diffuse and displaced to the higher temperatures range as compared to the transition in bulk triglycine sulfate. In the composites under study, a significant dispersion of the permittivity, presumably caused by a positive Maxwell-Wagner relaxation, is observed.

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

    SciTech Connect

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

    2010-11-22

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

  3. 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.

  4. A neutral theory with environmental stochasticity explains static and dynamic properties of ecological communities.

    PubMed

    Kalyuzhny, Michael; Kadmon, Ronen; Shnerb, Nadav M

    2015-06-01

    Understanding the forces shaping ecological communities is crucial to basic science and conservation. Neutral theory has made considerable progress in explaining static properties of communities, like species abundance distributions (SADs), with a simple and generic model, but was criticised for making unrealistic predictions of fundamental dynamic patterns and for being sensitive to interspecific differences in fitness. Here, we show that a generalised neutral theory incorporating environmental stochasticity may resolve these limitations. We apply the theory to real data (the tropical forest of Barro Colorado Island) and demonstrate that it much better explains the properties of short-term population fluctuations and the decay of compositional similarity with time, while retaining the ability to explain SADs. Furthermore, the predictions are considerably more robust to interspecific fitness differences. Our results suggest that this integration of niches and stochasticity may serve as a minimalistic framework explaining fundamental static and dynamic characteristics of ecological communities. PMID:25903067

  5. Anti-static properties of some cationic polymers used in hair care products.

    PubMed

    Patel, C U

    1983-10-01

    Synopsis Anti-static properties of cationic polymers on hair have been measured by using an electrostatic voltmeter. Comparisons are made with conventional cationic surfactants. Behaviour of cationic polymers from a cationic base and an anionic base have been explained. Experiments are performed to arrive at the hypothesis that cationic polymers form a complex with anionic detergent and that this cation-anion complex solubilizes in excess of anionic detergent, but on dilution with water it forms a turbid solution. PMID:19469985

  6. Analytical Solution for the SU(2) Hedgehog Skyrmion and Static Properties of Nucleons

    NASA Astrophysics Data System (ADS)

    Jia, Duo-Jie; Wang, Xiao-Wei; Liu, Feng

    2010-12-01

    An analytical solution for symmetric Skyrmion is proposed for the SU(2) Skyrme model, which takes the form of the hybrid form of a kink-like solution, given by the instanton method. The static properties of nucleons is then computed within the framework of collective quantization of the Skyrme model, in a good agreement with that given by the exact numeric solution. The comparisons with the previous results as well as the experimental values are also presented.

  7. High frequency dielectric properties of A5B4O15 microwave ceramics

    NASA Astrophysics Data System (ADS)

    Kamba, S.; Petzelt, J.; Buixaderas, E.; Haubrich, D.; Van?k, P.; Kuel, P.; Jawahar, I. N.; Sebastian, M. T.; Mohanan, P.

    2001-04-01

    High-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca; B=Nb, Ta) dielectric ceramics are studied by means of the microwave cavity technique, a combination of far-infrared reflection and transmission spectroscopy and time-resolved terahertz transmission spectroscopy. Microwave permittivity ?' and Qf factor vary, depending on the chemical composition, between 11 and 51, and 2.4 and 88 THz, respectively. The temperature coefficient ?f varies between -73 and 232 ppm/C, and in two samples |?f| is less than 15 ppm/C. It is shown that the microwave permittivity ?' of the ceramics studied is determined by the polar phonon contributions and that linear extrapolation of the submillimeter dielectric loss ?? down to the microwave region is in agreement with the microwave data of single phase samples. The relationship among phonon spectra, the crystal structure, and the unit cell volume is discussed.

  8. Structural and dielectric properties of sputtered SrxZr(1-x)Oy

    NASA Astrophysics Data System (ADS)

    Grube, Matthias; Martin, Dominik; Weber, Walter M.; Mikolajick, Thomas; Riechert, Henning

    2013-06-01

    Over the past years, high-k dielectrics have been incorporated into modern semiconductor devices. One example is ZrO2, which has been introduced in memory applications. This paper elucidates some difficulties with pure ZrO2 like unintended crystallization during the growth of the dielectric and the evolution of the monoclinic phase, which reduces the k-value. The admixture of Sr is shown as a solution to circumvent those issues. A detailed structural analysis for a varying stoichiometry ranging from pure ZrO2 to the perovskite SrZrO3 is given. The detected crystal structures are correlated to our observations of the dielectric properties obtained by an electrical characterization.

  9. 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.

  10. 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.

  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. Dielectric properties of lead indium niobate ceramics synthesized by conventional solid state reaction method

    SciTech Connect

    Ramesh, G.; Subramanian, V.; Sivasubramanian, V.

    2010-12-15

    Pyrochlore free lead indium niobate ceramics are successfully prepared using wolframite precursor by conventional solid state reaction method in air atmosphere, by adding an excess amount of MgO in PbO-InNbO{sub 4} mixture. The dielectric properties of lead indium niobate ceramic studied as a function of both temperature and frequency indicate relaxor ferroelectric behavior with maximum dielectric constant of 4310 at 40 {sup {omicron}}C for 1 kHz. Lowering of transition temperature and enhancement of dielectric constant at room temperature, compared to earlier reports, may be due to the diffusion of magnesium ion into the lead indium niobate. The saturation polarization P{sub s}, measured at room temperature, is found to be 22.5 {mu}C/cm{sup 2} for 40 kV/cm.

  13. AC conductivity and dielectric properties of bulk tungsten trioxide (WO3)

    NASA Astrophysics Data System (ADS)

    El-Nahass, M. M.; Ali, H. A. M.; Saadeldin, M.; Zaghllol, M.

    2012-11-01

    AC conductivity and dielectric properties of tungsten trioxide (WO3) in a pellet form were studied in the frequency range from 42 Hz to 5 MHz with a variation of temperature in the range from 303 K to 463 K. AC conductivity, ?ac(?) was found to be a function of ?s where ? is the angular frequency and s is the frequency exponent. The values of s were found to be less than unity and decrease with increasing temperature, which supports the correlated barrier hopping mechanism (CBH) as the dominant mechanism for the conduction in WO3. The dielectric constant (??) and dielectric loss (??) were measured. The Cole-Cole diagram determined complex impedance for different temperatures.

  14. Change in dielectric properties of triglycine sulfate in a constant magnetic field

    NASA Astrophysics Data System (ADS)

    Ivanova, E. S.; Rumyantsev, I. D.; Petrzhik, E. A.

    2016-01-01

    The effect of a constant magnetic field on the dielectric properties of triglycine sulfate crystals has been investigated. It has been shown that, after the magnetic treatment of the crystal (2 T, 20 min), the hysteresis loop becomes narrower; i.e., the coercive field decreases, and the dielectric permittivity changes in the region of the phase transition. It has been found that the observed effect is anisotropic with respect to the orientation of the crystal in a magnetic field and occurs when the vector of magnetic induction is perpendicular to the polar axis of the crystal. The relative orientation of the magnetic field and the domain structure determines its sign. The doping of the crystal with chromium makes the effect more pronounced and leads to a change in the kinetics of the magnetically stimulated increase in the dielectric permittivity.

  15. 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.

  16. Temperature Dependence of Dielectric and Ferroelectric Properties of BiFeO3 Thin Films

    SciTech Connect

    Biegalski, Michael D; Jang, J H; Bark, C; Eom, Professor Chang-Beom

    2009-01-01

    Multiferroic materials, with their potential for novel devices and sensors, have spurred an immense amount of research. The most concentrated effort has been on BiFeO3 thin films due to their high N el temperature and high ferroelectric transition temperature. Most studies on BiFeO3 films suffer from electrical leakage, requiring the measurement of dielectric or ferroelectric properties to be conducted at low temperatures. In this work we show that room-temperature leakage is not intrinsic to BiFeO3. Results are shown for highly insulating films, including the temperature dependence (10K to 300K) of the dielectric properties, ferroelectric P-E loops, and leakage current. This data shows very little temperature change in the dielectric constant with a TCC of 0.38 K-1, and dielectric losses below 0.005. The remanent polarization similarly showed no temperature dependence within the error of the measurement with a Pr of 67 1 C/cm2. The leakage current remains below 3x10-4(A/cm2) at 100 kV/cm. This work proves that BiFeO3 does not intrinsically have high leakage, and validates the extrapolation of the properties of BiFeO3 films measured at low temperatures to room temperatures.

  17. Improved dielectric properties of lead lanthanum zirconate titanate thin films on copper substrates.

    SciTech Connect

    Narayanan, M.; Ma, B.; Balachandran, U.; Energy Systems

    2010-01-01

    Thin films of lead lanthanum zirconate titanate (PLZT) were directly deposited on copper substrates by chemical solution deposition and crystallized at temperatures of {approx} 650 C under low oxygen partial pressure (pO{sub 2}) to create film-on-foil capacitor sheets. The dielectric properties of the capacitors formed have much improved dielectric properties compared to those reported previously. The key to the enhanced properties is a reduction in the time that the film is exposed to lower pO{sub 2} by employing a direct insertion strategy to crystallize the films together with the solution chemistry employed. Films exhibited well-saturated hysteresis loops with remanent polarization of {approx} 20 {micro}C/cm{sup 2}, dielectric constant of > 1100, and dielectric loss of < 0.07. Energy densities of {approx} 32 J/cm{sup 3} were obtained at a field of {approx} 1.9 MV/cm on a {approx} 1 {micro}m thick film with 250 {micro}m Pt electrodes.

  18. FDTD simulations and analysis of thin sample dielectric properties measurements using coaxial probes

    SciTech Connect

    Bringhurst, S.; Iskander, M.F.; White, M.J.

    1996-12-31

    A metallized ceramic probe has been designed for high temperature broadband dielectric properties measurements. The probe was fabricated out of an alumina tube and rod as the outer and inner conductors respectively. The alumina was metallized with a 3 mil layer of moly-manganese and then covered with a 0.5 mil protective layer of nickel plating. The probe has been used to make complex dielectric properties measurements over the complete frequency band from 500 MHz to 3 GHz, and for temperatures as high as 1,000 C. A 3D Finite-Difference Time-Domain (FDTD) code was used to help investigate the feasibility of this probe to measure the complex permittivity of thin samples. It is shown that by backing the material under test with a standard material of known dielectric constant, the complex permittivity of thin samples can be measured accurately using the developed FDTD algorithm. This FDTD procedure for making thin sample dielectric properties measurements will be described.

  19. Performance improvements of the hydrophobic and the dielectric properties of parylene C

    NASA Astrophysics Data System (ADS)

    Kahouli, A.; Sylvestre, A.; Laithier, J.-F.

    2013-10-01

    The increase in the hydrophobicity at the same time as the reduction in the dielectric properties of an insulating material are the main factors necessary to improve the signal response of the electrowetting-on-dielectric and the organic field effect transistor electronic devices. Oxygen (O2) and fluorine (CF4) plasma treatments on 3.7 ?m thicknesses-parylene C were carried out to understand the surface hydrophobicity character and their effect on the dielectric properties of the material. Fast hydrophobic recovery was observable during the first day after the O2 treatment due to the reorientation of the polar polymer end chains to the bulk of parylene C. CF4 plasma treatments reveal a noticeably increase of the hydrophobicity as the treatment time increases. Energy dispersive X-ray and Fourier transform infrared analyses have confirmed an increase in the number of fluorine containing CFx bonds where 1 ? x ? 3 after fluorine plasma treatments and after aging. The PPX C film treated with CF4 plasma at 500 W for 30 min indicated the best hydrophobic character and the best dielectric properties due to the highest loading fluorine content in our experimental conditions.

  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. Piezoelectric, dielectric, and ferroelectric properties of 0-3 ceramic/cement composites

    NASA Astrophysics Data System (ADS)

    Xin, Cheng; Shifeng, Huang; Jun, Chang; Zongjin, Li

    2007-05-01

    The sulphoaluminate cement and a piezoelectric ceramic, 0.08Pb(Li1/4Nb3/4)O3.0.47PbTiO3.0.45PbZrO3[P(LN)ZT], were used to fabricate 0-3 cement based piezoelectric composites. The piezoelectric, dielectric, and ferroelectric properties of the composites were mainly investigated. The results indicate that the piezoelectric strain factor d33 increases as the P(LN)ZT volume fraction increases, which follows the cube model well. The dielectric constant ?x and dielectric loss tan ? show similar trends with the d33. In the frequency range of 40-100 kHz, the dielectric constants of the composites decrease sharply, which is mainly attributed to interfacial polarization in the composite. Above 200 kHz, the cement-based piezoelectric composites exhibit good dielectric-frequency stability. Hysteresis measurements indicate that the composites exhibit typical ferroelectric hysteresis loops at room temperature. The remanent polarization Pr and the coercive field Ec of the composites increase as the P(LN)ZT volume fraction increases. Meanwhile, the remnant polarizations Pr shows little asymmetric characterization.

  2. 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.

  3. 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

  4. Effect of shape on the dielectric properties of biological cell suspensions.

    PubMed

    Di Biasio, A; Cametti, C

    2007-11-01

    In this note, we analyze the effect of cell shape on the dielectric and conductometric behavior of biological cell suspension, in a frequency range where the interfacial polarization characteristic of highly heterogeneous systems occurs. We consider two different families of curves, both of them capable of generating a variety of symmetric or asymmetric shapes, ranging from oval, to dog-bone like, to lemniscate curves. These curves, which differ from those generally employed in dielectric models of biological cell suspensions, describe in principle different cells including discocytes, cup-shaped cells, pear-shaped cells, dumbbells and cells with spherical protrusions or invaginations. Our analysis, based on a numerical solution of the Laplace equation by means of boundary element methods, is carried out in the attempt of separating the contributions associated with the different electrical properties of the dielectric media involved from the ones mainly associated with the shape of the cell. We determine the dielectric strength of the dielectric dispersion for a variety of cell shapes and the phenomenological correlation between this parameter of the relaxation and the cell geometry is briefly discussed and commented. PMID:17428746

  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. 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.

  7. 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 responses in impedance formalism are attributed to the grain and grain-boundary effects, respectively, which also accounts for the observed two dielectric-relaxations. The results demonstrate that the dielectric phenomena in CFO-Hf can be tailored by tuning Hf-concentration.

  8. A molecular dynamics study of the dielectric properties of aqueous solutions of alanine and alanine dipeptide

    NASA Astrophysics Data System (ADS)

    Boresch, Stefan; Willensdorfer, Martin; Steinhauser, Othmar

    2004-02-01

    Molecular dynamics simulations were used to compute the frequency-dependent dielectric susceptibility of aqueous solutions of alanine and alanine dipeptide. We studied four alanine solutions, ranging in concentration from 0.13-0.55 mol/liter, and two solutions of alanine dipeptide (0.13 and 0.27 mol/liter). In accord with experiment we find a strong dielectric increment for both solutes, whose molecular origin is shown to be the zwitterionic nature of the solutes. The dynamic properties were analyzed based on a dielectric component analysis into solute, a first hydration shell, and all remaining (bulk) waters. The results of this three component decomposition were interpreted directly, as well as by uniting the solute and hydration shell component to a "suprasolute" component. In both approaches three contributions to the frequency-dependent dielectric properties can be discerned. The quantitatively largest and fastest component arises from bulk water [i.e., water not influenced by the solute(s)]. The interaction between waters surrounding the solute(s) (the hydration shell) and bulk water molecules leads to a relaxation process occurring on an intermediate time scale. The slowest relaxation process originates from the solute(s) and the interaction of the solute(s) with the first hydration shell and bulk water. The primary importance of the hydration shell is the exchange of shell and bulk waters; the self-contribution from bound water molecules is comparatively small. While in the alanine solutions the solute-water cross-terms are more important than the solute self-term, the solute contribution is larger in the dipeptide solutions. In the latter systems a much clearer separation of time scales between water and alanine dipeptide related properties is observed. The similarities and differences of the dielectric properties of the amino acid/peptide solutions studied in this work and of solutions of mono- and disaccharides and of the protein ubiquitin are discussed.

  9. Modeling of dielectric properties of aqueous salt solutions with an equation of state.

    PubMed

    Maribo-Mogensen, Bjørn; Kontogeorgis, Georgios M; Thomsen, Kaj

    2013-09-12

    The static permittivity is the most important physical property for thermodynamic models that account for the electrostatic interactions between ions. The measured static permittivity in mixtures containing electrolytes is reduced due to kinetic depolarization and reorientation of the dipoles in the electrical field surrounding ions. Kinetic depolarization may explain 25-75% of the observed decrease in the permittivity of solutions containing salts, but since this is a dynamic property, this effect should not be included in the thermodynamic modeling of electrolytes. Kinetic depolarization has, however, been ignored in relation to thermodynamic modeling, and authors have either neglected the effect of salts on permittivity or used empirical correlations fitted to the measured static permittivity, leading to an overestimation of the reduction in the thermodynamic static permittivity. We present a new methodology for obtaining the static permittivity over wide ranges of temperatures, pressures, and compositions for use within an equation of state for mixed solvents containing salts. The static permittivity is calculated from a new extension of the framework developed by Onsager, Kirkwood, and Fröhlich to associating mixtures. Wertheim's association model as formulated in the statistical associating fluid theory is used to account for hydrogen-bonding molecules and ion-solvent association. Finally, we compare the Debye-Hückel Helmholtz energy obtained using an empirical model with the new physical model and show that the empirical models may introduce unphysical behavior in the equation of state. PMID:23924202

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

    SciTech Connect

    Ferradini, C.; Jay-Gerin, J.

    1988-12-01

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

  11. 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, ?0 is the permittivity of vacuum and ? 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 (? 1, ?2=3, 4, 5), in order to eliminate effects due to the change in sample geometry, using gold sputtered electrodes, 20nm thick. The values obtained for the permittivity of the material are in good agreement with the work of other authors. The dissipative properties revealed by the measurements performed at high fields, similar to the ones encountered in operation, indicate that this less investigated aspect of VHB needs to be taken in consideration for real world applications.

  12. RAPID COMMUNICATION: On some dielectric properties of PEN

    NASA Astrophysics Data System (ADS)

    Bellomo, J. P.; Lebey, T.

    1996-07-01

    Since poly (ethylene naphtalene-2,6- dicarboxylate) (PEN) gives high performance films with key properties superior to those of PET polyester films, it has been argued that it could be used as a substitute for the latter in a large number of applications. In this paper more information on the electrical properties of this material are given and compared to those of PET. These properties, i.e. complex permittivity and breakdown voltage, are investigated under controlled and uncontrolled environments and before and after thermal ageing at a temperature 0022-3727/29/7/045/img1 higher than the thermal rating of each material.

  13. 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.

  14. Dielectric and piezoelectric properties of BiFeO3 from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Graf, M.; Sepliarsky, M.; Machado, R.; Stachiotti, M. G.

    2015-09-01

    A first-principles based atomistic scheme is used to investigate the dielectric and piezoelectric properties of BiFeO3. The atomistic model fitted from first-principles calculations reproduces very well the structural and polar properties of the material at finite temperature, predicting a direct transition from a low-temperature R3c ferroelectric phase to a Pbnm orthorhombic phase in agreement with experiments. We use this theoretical approach to calculate intrinsic single crystal properties, which are difficult to obtain from experiments due to decomposition and leakage problems. The whole set of dielectric and piezoelectric coefficients for BiFeO3 is computed as a function of temperature, together with the orientation dependence of the longitudinal coefficient d33*.

  15. Effect of Sm on dielectric, ferroelectric and piezoelectric properties of BPTNZ system

    NASA Astrophysics Data System (ADS)

    Kumar, Parveen; Juneja, J. K.; Prakash, Chandra; Raina, K. K.; Singh, Sangeeta

    2013-10-01

    Study on structural, dielectric and ferroelectric properties of Sm substituted BPTNZ system with compositional formula Ba0.80-xSmxPb0.20Zr0.10Ti0.90O3+0.5% Nb2O5 by weight, (x=0 to 0.01 in the steps of 0.0025) was done. Conventional solid state method was adopted for the synthesis of the samples. The single phase was confirmed by X-ray diffraction (XRD) analysis. Scanning electron microscopy was done for microstructural analysis. The dielectric properties were measured as a function of temperature and frequency. Ferroelectric P-E loops were recorded for all the samples at room temperature. Piezoelectric parameters such as ‘d33’ and electromechanical coupling coefficient ‘kp’ were also measured at room temperature for all the samples. The relationship between properties and structure of the prepared ceramics was established and results are discussed here.

  16. 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.

  17. 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 7505 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 (?r), dielectric loss tangent (tan ?) and ac electrical conductivity (?ac) of nanocrystalline Cr-Ni-Zn ferrites were investigated as a function of frequency and Cr concentration. The dependence of ?r, tan ? and ?ac 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.

  18. Electrical Properties of PVP-SiO2-TMSPM Hybrid Thin Films as OFET Gate Dielectric

    NASA Astrophysics Data System (ADS)

    Bahari, A.; Shahbazi, M.

    2015-12-01

    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 (? 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.

  19. Effect of dielectric/organic interface properties on charge transport in organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Kuchibhatla, S.; Korakakis, D.

    2013-04-01

    Charge carrier transport within the organic thin films as well as charge carrier injection between organic layers and organic/inorganic materials such as metal or dielectric layers are crucial factors in determining the efficiency of organic electronic devices. These parameters rely largely on the molecular structure, morphology, and ordering of the organic thin films. Therefore, a profound understanding of the structure of organic materials as well as the properties of the interfacial layers is crucial to enhance the performance of the device. To achieve this fact, structure and morphology of PTCDI-C8 and pentacene thin films on Lithium Fluoride (LiF) have been studied using X-ray reflectivity technique. These films have been integrated into organic thin film transistors (OTFTs) to investigate their transport properties. The structural characterization revealed that the PTCDI-C8 films form an ordered structure on the LiF dielectric layer. Devices with LiF/PTCDI-C8 bilayer exhibit about one order of magnitude higher output current (Ids) at a constant drain-source voltage (Vds) compared to the devices with LiF/pentacene bilayer. The observed differences in the electrical characteristics of these devices can be attributed to the effects of the dielectric/organic interface and the molecular structure of the organic layers. The results of this study present the importance of the dielectric/organic interfaces in the performance of OTFTs.

  20. Dielectric, ferroelectric and piezoelectric properties of La-modified PCT ceramics

    NASA Astrophysics Data System (ADS)

    Singh, Sarabjit; Thakur, O. P.; Prakash, Chandra; Raina, K. K.

    2005-12-01

    Polycrystalline samples of lanthanum-modified PCT ceramics with composition Pb 0.76-3x/2La xCa 0.24Mn 0.02Ti 0.98O 3 (PLCT); x=0-0.08 (in steps of 0.02) were prepared by using conventional dry ceramic technique. Samples were sintered at 1150 C. X-ray analysis confirmed the formation of single-phase compound with tetragonal crystal structure. Dielectric properties were studied in detail as a function of frequency and temperature. From temperature variation of dielectric constant, Curie temperature ( Tc) was determined. Discussion on hysteresis behaviour for all the samples at room temperature is presented. Dielectric constant at room temperature shows an increasing trend and Curie temperature shows decreasing trend with the increase in lanthanum in PCT ceramics. Curie temperature determined from thermal expansion behaviour of sintered samples was found to be in good agreement with that determined from dielectric studies. Piezoelectric properties show a significant improvement with lanthanum substitution.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Disorder driven structural and dielectric properties of silicon substituted strontium titanate

    NASA Astrophysics Data System (ADS)

    Dugu, Sita; Pavunny, Shojan P.; Sharma, Yogesh; Scott, James F.; Katiyar, Ram S.

    2015-07-01

    A systematic study on structural, microstructural, optical, dielectric, and electrical properties of phase-pure silicon-modified SrTiO3 polycrystalline electroceramics synthesized using high energy solid state reaction techniques is presented. The asymmetry and splitting in the x-ray diffractometer spectra and the observation of first order transverse optical TO2 and longitudinal optical LO4 modes in Raman spectra (nominally forbidden) revealed the distortion in the cubic lattice as a result of breaking of inversion symmetry due to doping. A bandgap Eg of 3.27 eV was determined for the sample by diffuse reflectance spectroscopy. A high dielectric constant of ˜400 and very low dielectric loss of ˜0.03 were obtained at 100 kHz near ambient conditions. The temperature dependence of the dielectric data displayed features of high temperature relaxor ferroelectric behavior as evidence of existence of polar nano-regions. The ac conductivity as a function of frequency showed features typical of universal dynamic response and obeyed a power law σ a c = σ d c + A ω n . The temperature dependent dc conductivity followed an Arrhenius relation with activation energy of 123 meV in the 200-500 K temperature range. The linear dielectric response of Pt/SrSi0.03Ti0.97O3/Pt dielectric capacitors was well characterized. The measured leakage current was exceptionally low, 13 nA/cm2 at 8.7 kV/cm, revealing an interface blocked bulk conduction mechanism.

  7. Dielectric property measurement of ocular tissues up to 110 GHz using 1 mm coaxial sensor

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Isimura, Y.; Fujii, K.; Wake, K.; Watanabe, S.; Kojima, M.; Suga, R.; Hashimoto, O.

    2015-08-01

    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.

  8. 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

  9. MICROWAVE DIELECTRIC METHODS FOR SENSING PHYSICAL PROPERTIES OF GRANULAR MATERIALS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the physical properties of granular materials is important in many industries including food and agriculture, pharmaceutical, chemical, and mining. They are often used in quality control as well as process monitoring and control. Therefore, they need to be determined reliably and in rea...

  10. DIELECTRIC PROPERTIES OF POLYVINYL ALCOHOL, POLY(METHYL METHACRYLATE), POLYVINYL BUTYRAL RESIN AND POLYIMIDE AT LOW TEMPERATURES

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R

    2008-01-01

    Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI--Kapton\\textregistered). The dielectric measurements are performed with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 45K to 350K. The dielectric breakdown characteristics of the polymers are measured in a liquid nitrogen bath at atmospheric pressure. It is observed that PI and \\pmma\\ dissolved in toluene have the lowest dielectric losses for temperatures lower than $100\\ \\kelvin$. \\Blx\\ and PI have the smallest spread in their breakdown strength data.

  11. Effect of hafnium-incorporation on the microstructure and dielectric properties of cobalt ferrite ceramics

    NASA Astrophysics Data System (ADS)

    Wells, Stephen Josiah

    The effect of hafnium ion (Hf4+) incorporation in cobalt ferrite (CFO) was studied. Samples of Hf substituted CFO ceramic (CoFe 2-xHfxO4), were synthesized in the laboratory with hafnium concentrations ranging from x=0.000 to x=0.200. X-ray diffraction scans show that the Hafnium CFO crystalizes in the inverse spinel phase. Inclusion of hafnium causes lattice expansion, increasing the lattice parameter from 8.374 A for pure CoFe2O4 to 8.391 A for the highest concentration of hafnium tested (x=0.020). The dielectric properties of CFO are greatly enhanced by inclusion of hafnium. The enhancement is due to the distortion on the lattice from the larger Hf-ions substituting the smaller Fe-ions. Frequency variation of the dielectric properties is well modeled by the modified Debye function, which takes into account multiple ions contributing to relaxation.

  12. Structural, electronic, vibrational and dielectric properties of selected high-shape K semiconductor oxides

    NASA Astrophysics Data System (ADS)

    Scolfaro, L. M. R.; Leite Alves, H. W.; Borges, P. D.; Garcia, J. C.; da Silva, E. F., Jr.

    2014-10-01

    The semiconductor oxides SnO2, HfO2, ZrO2, TiO2 and SrTiO3 are interesting materials for applications as high-K dielectric gate materials in silicon-based devices and spintronics, among others. Here we review our theoretical work about the structural, electronic and vibrational properties of these oxides in their most stable structural phases, including dielectric properties as derived from the electronic structure taking into account the lattice contribution. Finally, we address the recent role played by the presence of transition metal atoms in semiconductor oxides, considering in particular SnO2 as an example in forming diluted magnetic alloys.

  13. Dielectric Properties and Applications of CVD Diamonds in the Millimeter and Terahertz Ranges

    NASA Astrophysics Data System (ADS)

    Garin, B. M.; Parshin, V. V.; Polyakov, V. I.; Rukovishnikov, A. I.; Serov, E. A.; Mocheneva, O. S.; Jia, Ch. Ch.; Tang, W. Z.; Lu, F. X.

    The results of investigation of the dielectric properties in the millimeter and terahertz ranges of diamond samples prepared by using the direct current arc plasma jet (APJ) and the microwave plasma chemical vapour deposition (MPCVD) techniques are presented. Various methods for the measurements of the dielectric properties using high-Q open resonators and cylindrical cavity resonators are discussed while the activation energy of the conductivity and point defect parameters (such as concentration and activation energy of the defect induced levels) in both kinds of diamonds are studied via Conductivity and Charge-based Deep Level Transient Spectroscopy (Q-DLTS) measurements (for the first time in APJ diamond) and compared. The absorption mechanisms in these diamonds grown by different methods are discussed.

  14. 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.

  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. A systematic study on magnetic, dielectric and magnetocapacitance properties of Ni doped bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Yadav, K. L.

    2011-11-01

    In this paper we report the structural, magnetic, magnetocapacitance and dielectric properties of BiFe1-xNixO3 nanoceramics (with x=0, 0.1) prepared by the sol-gel method. XRD analysis showed formation of single phase nanoceramics (particle size 50 nm by TEM). Samples of BiFe1-xNixO3 were divided into two partsone of them quenched in liquid nitrogen and another sintered in the normal way. We observed the enhancement in magnetic and dielectric properties of quenched sample. The splitting of zero field cool (ZFC) and field cool (FC) magnetization curves at low temperature reveals spin- glass behavior. Quenched sample showed the enhancement of blocking temperature.

  17. 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.

  18. 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.

  19. Effect of magnesium substitution on dielectric and magnetic properties of Ni-Zn ferrite

    NASA Astrophysics Data System (ADS)

    Singh, Navneet; Agarwal, Ashish; Sanghi, Sujata; Singh, Paramjeet

    2011-02-01

    The dielectric and magnetic properties of Mg incorporated Ni-Zn spinel ferrites have been investigated. Ni 0.5- xZn 0.5Mg xFe 2O 4 ferrites have been prepared by sol-gel auto-combustion technique. The as prepared ferrites were annealed at 673, 873 and 1073 K. The X-ray diffraction studies reveal the spinel structure of annealed ferrites. The TEM results are in agreement with XRD results. FTIR study has also been carried out to get insight into the structure of these ferrites. The dielectric measurements show that the dielectric constant ( ??), dielectric loss (tan ?) and conductivity ( ?ac) increase on incorporation of Mg in the Ni-Zn ferrite. ??, tan ? and ?ac also show dependence on temperature, frequency of external applied electric field and microstructure of the samples. The magnetic moment measurements reveal that the saturation magnetization ( Ms) increases and coercivity ( Hc) decreases with the increase in concentration of Mg 2+ ions. Ms and Hc also show dependence on the annealing temperature.

  20. Magnetic and dielectric properties of Ba12Fe28Ti15O84 layered ferrite ceramics

    NASA Astrophysics Data System (ADS)

    Curecheriu, L. P.; Buscaglia, M. T.; Ianculescu, A. C.; Frunza, R. C.; Ciuchi, I. V.; Neagu, A.; Apachitei, G.; Bassano, A.; Canu, G.; Postolache, P.; Mitoseriu, L.; Buscaglia, V.

    2011-11-01

    In this study we report for the first time the magnetic and dielectric properties of the quaternary layered ferrite Ba12Fe28Ti15O84. Dense ferrite ceramics were prepared by conventional sintering using powders obtained by solid-state reaction and by coprecipitation. Only the latter powder resulted in nearly single phase ceramics, whereas larger amounts of secondary phases were observed in the material obtained by the solid-state route. According to the HRTEM investigation, the ferrite lattice is originated by the intergrowth of perovskite-like and spinel-like slabs and can be considered as a natural magnetic superlattice. A ferrimagnetic order with saturation magnetization of ?12.5 A m2 kg-1 and coercivity of ~1590 A m-1 (~20 Oe) is proposed at room temperature. The thermomagnetic data indicate a Curie temperature of ~420 K for the quaternary ferrite. An additional magnetic transition was detected at ~700 K and ascribed to a secondary magnetic phase, probably the solid solution of TiO2 in BaFe12O19. An intrinsic relative dielectric constant of the order of 23-50 at room temperature was measured at 109 Hz. At lower frequency the dielectric behaviour is dominated by extrinsic effects related to the heterogeneous electrical nature of the ceramics corresponding to semiconducting grains separated by more insulating grain boundary regions. The dielectric losses are rather high, often >1, indicating an overall semiconducting character of the material.

  1. 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.

  2. 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.

  3. A percolation cluster model of the temperature dependent dielectric properties of hydrated proteins

    NASA Astrophysics Data System (ADS)

    Suherman, Phe Man; Smith, Geoff

    2003-02-01

    This study investigates the temperature dependence of the low frequency dielectric properties (0.1 Hz-1 MHz) of hydrated globular proteins (namely, ovalbumin, lysozyme and pepsin). The study aims to reveal the mechanisms of water-protein interaction from the dielectric response of these model proteins. Two principle dielectric responses were observed for each hydrated protein, namely, an anomalous low frequency dispersion and a dielectric loss peak at higher frequency (called the varepsilon3 dispersion). The low frequency response conformed to a fractional power low of frequency, while the higher frequency response conformed to a Davidson-Cole model. The strength of both processes reached a maximum at a certain temperature within the experimental temperature range. This temperature is referred to as the percolation threshold (PT) and is thought to be associated with the percolation of protons between hydrogen-bonded water molecules. The relaxation times of the varepsilon3 dispersion conformed to Arrhenius behaviour at temperatures below the PT, from which an activation energy (DeltaH) could be calculated. This activation energy is thought to be a measure of the concentration of available charged sites through which proton transport is facilitated. The structural fractal dimension in the hydrated protein system was also calculated, and enabled the approximation of the pathway for charge percolation in the protein matrix.

  4. Dielectric properties of polyhedral oligomeric silsesquioxane (POSS)-based nanocomposites at 77k

    NASA Astrophysics Data System (ADS)

    Pan, Ming-Jen; Gorzkowski, Edward; McAllister, Kelly

    2011-10-01

    The goal of this study is to develop dielectric nanocomposites for high energy density applications at liquid nitrogen temperature by utilizing a unique nano-material polyhedral oligomeric silsesquioxanes (POSS). A POSS molecule is consisted of a silica cage core with 8 silicon and 12 oxygen atoms and organic functional groups attached to the corners of the cage. In this study, we utilize POSS for the fabrication of nanocomposites both as a silica nanoparticle filler to enhance the breakdown strength and as a surfactant for effective dispersion of high permittivity ceramic nanoparticles in a polymer matrix. The matrix materials selected for the study are polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA). The ceramic nanoparticles are barium strontium titanate (BST 50/50) and strontium titanate. The dielectric properties of the solution-cast nanocomposites films were correlated to the composition and processing conditions. We determined that the addition of POSS did not provide enhanced dielectric performance in PVDF- and PMMA-based materials at either room temperature or 77K. In addition, we found that the dielectric breakdown strength of PMMA is lower at 77K than at room temperature, contradicting literature data.

  5. Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications

    NASA Astrophysics Data System (ADS)

    Kaygili, Omer; Ates, Tankut; Keser, Serhat; Al-Ghamdi, Ahmed A.; Yakuphanoglu, Fahrettin

    2014-08-01

    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.

  6. 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. PMID:26218098

  7. 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.

  8. Can diurnal variation in radar backscatter in vegetated areas be explained by changes in dielectric properties?

    NASA Astrophysics Data System (ADS)

    Steele-Dunne, S. C.; Friesen, J.; Van De Giesen, N.

    2012-12-01

    Two recent studies have identified a systematic difference in backscatter between the morning and evening passes of the Wind Scatterometer on the ERS 1/2 satellite in vegetated areas. In some areas, e.g. the West African savanna, these differences appear to correspond to the onset of vegetation water stress. The goal of this study is to test the hypothesis that changes in the dielectric properties of the canopy constituents due to changes in water status could explain the difference. Results will be presented from a numerical study in which the Michigan Microwave Canopy Scattering (MIMICS) model was used to examine the impact of leaf, branch, trunk and soil dielectric properties on C-band and L-band backscatter. For C-band vertically copolarized backscatter, the greatest sensitivity is to leaf moisture (and, hence, dielectric constant), but trunk moisture is significant at low values of leaf moisture content. This suggests that the difference observed in the ERS wind scatterometer observations may be due to changes in leaf moisture content (and hence dielectric constant). We also examined the impact on co- and cross-polarized L-band backscatter to explore the implications for NASA's upcoming SMAP mission. The cross-polarized backscatter was mainly sensitive to leaf properties, while the co-polarized backscatter was mainly sensitive to changes in trunk properties. These results suggest that the difference between morning and evening SMAP radar observations might contain useful information on the canopy water status, an indicator of the availability of water in the root zone.

  9. Effective electromagnetic properties of honeycomb substrate coated with dielectric or magnetic layer

    NASA Astrophysics Data System (ADS)

    Liu, L.; Fan, C. Z.; Zhu, N. B.; Zhao, Z. Y.; Liu, R. P.

    2014-09-01

    Effective electromagnetic properties of aramid honeycomb board coated with a layer of multi-wall carbon nanotube or iron flakes composites were measured with waveguide method from 4 to 12 GHz. It was proved that homogenization theory could predict the effective permittivity or permeability of the honeycomb composites with good accuracy. The coated honeycomb composites of relatively high permittivity and permeability could potentially be used to develop dielectric or magnetic substrate for shielding layer or absorbing structures working at microwave frequencies.

  10. Effect of manganese oxide additive on the dielectric properties of mixed-sintering ceramics

    SciTech Connect

    Takahara, H. )

    1989-08-01

    The influence of internal electrode material on the sintering of mixed-sintering ceramics and the effect of MnO/sub 2/ additive on improving their di-electric properties are investigated for their application as multilayer ceramic capacitors. The resistivities of mixed-sintering ceramic pellets sintered with Ag-Pd electrode material decreased remarkably because of the expulsion of component elements during sintering.

  11. 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.

  12. Magnetic and Dielectric Properties of Polymer-Ceramic Composites Synthesized Using a Melt Compound Technique

    NASA Astrophysics Data System (ADS)

    Jotania, Rajshree; Chanmal, Chetan; Jog, Jyoti

    Polymer composites have emerged as a new class of materials, which have attracted technologist as they display novel properties compared to traditional materials and dramatically improves the performance properties of polymer system. We have synthesized hexaferrite-polymer composites of Polyvinylidene Fluride (PVDF) with BaCa2Fe16O27 (2.0, 5.0 % wt/vol.) using a melt compounding technique. BaCa2Fe16O27 hexaferrite powder was prepared using a microemulsion technique and directly mixed in melted PVDF, following by a low temperature hot pressing. The composites of PVDF with various weight percent of BaCa2Fe16O27 (2.0 & 5.0% wt/vol.) were processed via melt mixing at 200C, with 60 rpm for 5 minutes. The films of uniform thickness are about 0.5 mm is obtained by a compression molded instrument at 200C under 5-ton pressure. The influence of BaCa2Fe16O27 hexaferrite contents on magnetic and dielectric properties of composite was investigated. The prepared PVDF- BaCa2Fe16O27 composite thick films were characterized for their magnetic; dielectric and thermal behavior employing magnetic, dielectric and thermal analysis (TGA/DTA). Maximum saturation magnetization was obtained for 5 % wt/vol. of barium calcium hexaferrite composite.

  13. Magnetic and Dielectric Property Studies in Fe- and NiFe-Based Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Sharma, Himani; Jain, Shubham; Raj, Pulugurtha Markondeya; Murali, K. P.; Tummala, Rao

    2015-10-01

    Metal-polymer composites were investigated for their microwave properties in the frequency range of 30-1000 MHz to assess their application as inductor cores and electromagnetic isolation shield structures. NiFe and Fe nanoparticles were dispersed in epoxy as nanocomposites, in different volume fractions. The permittivity, permeability, and loss tangents of the composites were measured with an impedance analyzer and correlated with the magnetic properties of the particle such as saturation magnetization and field anisotropy. Fe-epoxy showed lower magnetic permeability but improved frequency stability, compared to the NiFe-epoxy composites of the same volume loading. This is attributed to the differences in nanoparticle's structure such as effective metal core size and particle-porosity distribution in the polymer matrix. The dielectric properties of the nanocomposites were also characterized from 30 MHz to 1000 MHz. The instabilities in the dielectric constant and loss tangent were related to the interfacial polarization relaxation of the particles and the dielectric relaxation of the surface oxides.

  14. 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. PMID:23513225

  15. Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates.

    PubMed

    Wang, Yipei; Ma, Yaoguang; Guo, Xin; Tong, Limin

    2012-08-13

    Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates are investigated using a finite-element method. Au and Ag are selected as plasmonic materials for nanowire waveguides with diameters down to 5-nm-level. Typical dielectric materials with relatively low to high refractive indices, including magnesium fluoride (MgF2), silica (SiO2), indium tin oxide (ITO) and titanium dioxide (TiO2), are used as supporting substrates. Basic waveguiding properties, including propagation constants, power distributions, effective mode areas, propagation distances and losses are obtained at the typical plasmonic resonance wavelength of 660 nm. Compared to that of a freestanding nanowire, the mode area of a substrate-supported nanowire could be much smaller while maintaining an acceptable propagation length. For example, the mode area and propagation length of a 100-nm-diameter Ag nanowire with a MgF2 substrate are about 0.004 ?m2 and 3.4 ?m, respectively. The dependences of waveguiding properties on geometric and material parameters of the nanowire-substrate system are also provided. Our results may provide valuable references for waveguiding dielectric-supported metal nanowires for practical applications. PMID:23038541

  16. Optical, dielectric and electrical properties of PVA doped with Sn nanoparticles

    NASA Astrophysics Data System (ADS)

    Amin, G. A. M.; Abd-El Salam, M. H.

    2014-04-01

    Films of pure and doped polyvinyl alcohol (PVA) with different concentrations of Sn nanoparticles (≦̸100 nm) were prepared using casting technique. The effect of Sn addition on micro-structural, optical, electrical and dielectric properties of PVA was investigated. Microstructure of Sn/PVA nanocomposite films was characterized by scanning electron microscopy (SEM). Dielectric properties and ac conductivity measurements were carried out at room temperature over a wide range of frequencies ranging from 50 Hz to 5 MHz. AC conductivity was found to increase with frequency. Besides, addition of Sn nanoparticles to PVA leads to a change in conductivities of the films. Coulomb blockade effect was found to dominate at certain concentrations of Sn which may be used to explain the obtained results. The dielectric properties of the Sn/PVA films were also investigated and results were discussed in correlation with the relevant models. The frequency dependence of the imaginary part of complex electric modulus for the Sn/PVA composites shows a loss peak attributed to interfacial polarization at a certain frequency. Optical energy gap of Sn/PVA films was determined and found to decrease for Sn concentrations up to 20% due to the interaction between the Sn nanoparticles and the host polymeric network leading to the creation of new molecular dipoles. For higher Sn concentrations, the optical energy gap starts to increase which may be resulting from structural changes leading to passivation of localized states near the band edges and hence widening of the energy gap.

  17. Static properties of 2D spin-ice as a sixteen-vertex model

    NASA Astrophysics Data System (ADS)

    Foini, Laura; Levis, Demian; Tarzia, Marco; Cugliandolo, Leticia F.

    2013-02-01

    We present a thorough study of the static properties of 2D models of spin-ice type on the square lattice or, in other words, the sixteen-vertex model. We use extensive Monte Carlo simulations to determine the phase diagram and critical properties of the finite-dimensional system. We put forward a suitable mean-field approximation, by defining the model on carefully chosen trees. We employ the cavity (Bethe-Peierls) method to derive self-consistent equations, the fixed points of which yield the equilibrium properties of the model on the tree-like graph. We compare mean-field and finite-dimensional results. We discuss our findings in the context of experiments in artificial two-dimensional spin-ice.

  18. Correlation of electrical conductivity, dielectric properties, microwave absorption, and matrix properties of composites filled with graphene nanoplatelets and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Khurram, A. A.; Rakha, Sobia A.; Zhou, Peiheng; Shafi, M.; Munir, Arshad

    2015-07-01

    The DC electrical conductivity, percolation threshold, and dielectric properties of Graphene Nanoplatelets (GNPs) filled epoxy composites are studied and correlated with microwave absorption. The properties of GNPs filled composites are also compared with multiwalled carbon nanotubes (MWCNTs) composites, and GNPs are observed to have superior conductivity than MWCNTs. In all batches, the nanofillers have 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 wt. %. All composites irrespective of the type of nanofiller and viscosity of the matrix have shown electrical percolation threshold at 3.0 wt. %. The dielectric properties, i.e., complex permittivity, tan loss, and AC conductivity, are studied in 100 Hz-5.5 MHz. The DC and AC electrical conductivities (at and below the percolation) measured in 100 Hz-5.5 MHz are correlated to the GNPs and MWCNTs epoxy composites in the microwave frequency range (11-17 GHz). The maximum return loss of -12 dB and -6 dB was determined for MWCNTs and GNPs, respectively. The effects of nanofiller shape and the viscosity of the matrix on the dispersion and interparticle spacing of the conductive fillers within the polymer matrix have been discussed based on the results of conductivity, dielectric, and absorption properties.

  19. 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.

  20. Static and dynamic properties of three-dimensional dot-type magnonic crystals

    NASA Astrophysics Data System (ADS)

    Maksymov, Artur; Spinu, Leonard

    2016-04-01

    The static and dynamic magnetization of three-dimensional magnonic metamaterials has been investigated. By numerical means it was analyzed the impact of space dimensionality on the properties of magnonic crystal with unit cell consisting of four dots. It is find out the possibility of multi-vortex core formation which is related to the increasing of the crystal height by three-dimensional periodicity of single crystal layer. Additionally is provided the analysis of ferromagnetic resonance phenomenon for two-dimensional and three-dimensional structures. For the unsaturated magnetization of three-dimensional crystal the several pronounced resonance frequencies were detected.

  1. Longitudinal static optical properties of hydrogen chains: finite field extrapolations of matrix product state calculations.

    PubMed

    Wouters, Sebastian; Limacher, Peter A; Van Neck, Dimitri; Ayers, Paul W

    2012-04-01

    We have implemented the sweep algorithm for the variational optimization of SU(2) U(1) (spin and particle number) invariant matrix product states (MPS) for general spin and particle number invariant fermionic Hamiltonians. This class includes non-relativistic quantum chemical systems within the Born-Oppenheimer approximation. High-accuracy ab initio finite field results of the longitudinal static polarizabilities and second hyperpolarizabilities of one-dimensional hydrogen chains are presented. This allows to assess the performance of other quantum chemical methods. For small basis sets, MPS calculations in the saturation regime of the optical response properties can be performed. These results are extrapolated to the thermodynamic limit. PMID:22482543

  2. Influence of the Static Dynamic Ergodic Divertor on Edge Turbulence Properties in TEXTOR

    SciTech Connect

    Xu, Y.; Weynants, R. R.; Jachmich, S.; Van Schoor, M.; Vergote, M.; Peleman, P.; Jakubowski, M. W.; Mitri, M.; Reiser, D.; Unterberg, B.; Finken, K. H.

    2006-10-20

    Systematic measurements on the edge turbulence and turbulent transport have been made by Langmuir probe arrays on TEXTOR under various static Dynamic Ergodic Divertor (DED) configurations. Common features are observed. With the DED, in the ergodic zone the local turbulent flux reverses sign from radially outwards to inwards. The turbulence properties are profoundly modified by energy redistribution in frequency spectra and suppression of large scale eddies. The fluctuation poloidal phase velocity changes direction from electron to ion diamagnetic drift, consistent with the observed reversal of the E{sub r}xB flow. In the laminar region, the turbulence is found to react to an observed reduced flow shear.

  3. Influence of the static Dynamic Ergodic Divertor on edge turbulence properties in TEXTOR.

    PubMed

    Xu, Y; Weynants, R R; Jachmich, S; Van Schoor, M; Vergote, M; Peleman, P; Jakubowski, M W; Mitri, M; Reiser, D; Unterberg, B; Finken, K H

    2006-10-20

    Systematic measurements on the edge turbulence and turbulent transport have been made by Langmuir probe arrays on TEXTOR under various static Dynamic Ergodic Divertor (DED) configurations. Common features are observed. With the DED, in the ergodic zone the local turbulent flux reverses sign from radially outwards to inwards. The turbulence properties are profoundly modified by energy redistribution in frequency spectra and suppression of large scale eddies. The fluctuation poloidal phase velocity changes direction from electron to ion diamagnetic drift, consistent with the observed reversal of the Er x B flow. In the laminar region, the turbulence is found to react to an observed reduced flow shear. PMID:17155405

  4. 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 models. In general, boundary locations, average permeability and porosity, relative permeability curves, and local flow properties may all need to be adjusted to achieve a plausible reservoir model that honors all data. In this project, we will characterize the distribution of geologic facies as an indicator random field, making use of the tools of geostatistics as well as the tools of inverse and probability theory for data integration.

  5. Magnetic, dielectric, and magneto-dielectric properties of rare-earth-substituted Aurivillius phase Bi6Fe1.4Co0.6Ti3O18

    NASA Astrophysics Data System (ADS)

    Zuo, X. Z.; Yang, J.; Song, D. P.; Yuan, B.; Tang, X. W.; Zhang, K. J.; Zhu, X. B.; Song, W. H.; Dai, J. M.; Sun, Y. P.

    2014-10-01

    We investigate the magnetic, dielectric, and magnetodielectric properties of rare-earth-substituted Aurivillius phase Bi6Fe1.4Co0.6Ti3O18. The room-temperature ferromagnetic behavior is observed in all samples, and the rare-earth-substituted samples exhibit an enhanced magnetization. The weak ferromagnetism can be ascribed to the spin canting of the antiferromagnetic coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. The dielectric loss of all samples exhibits two dielectric relaxation peaks corresponding to two different relaxation mechanisms. One relaxation process with Ea = 0.5 eV is related to the hoping process of oxygen vacancies and the other one with Ea = 1.6 eV can be ascribed to the intrinsic conduction. The Gd-doped sample exhibits a remarkable magnetodielectric effect (9.4%) at RT implying this Aurivillius phase may be the potential candidate for magnetodielectric applications.

  6. 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%)

  7. 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.

  8. Controllable low dielectric porous polyimide films templated by silica microspheres: microstructure, formation mechanism, and properties.

    PubMed

    Wang, Qihua; Wang, Chao; Wang, Tingmei

    2013-01-01

    In the paper, controllable low dielectric macroporous polyimide (PI) films were prepared using silica microspheres as template, based on the solvent-evaporation-assisted in situ self-assembly of polyamic acid (PAA, precursor of PI) and silica microspheres in N,N-Dimethylformamide (DMF) solution. The interior microstructure of the macroporous PI films and its relationship with mechanical and dielectric properties were investigated. It was found that the macroporous PI films had triple-layer porous structures: ordered porous surface, dense layer in the middle, and interconnected porous structure at the bottom. The thickness of the dense layer in the middle changed with increasing weight content of silica. When SiO(2) wt% was above 40%, the dense layer nearly disappeared. The interconnected porous structure at the bottom was quite homogenous, and the pore size could be controlled by the diameter of silica microspheres. Based on the experimental results, possible formation mechanism of the macroporous PI films was addressed. The mechanical properties of the macroporous PI films were degraded due to the introduction of air void. It was found that the degradation of mechanical properties of macroporous PI films with porosity of 37% is more obvious than that of PI films with porosity below 31%, which could be attributed to the triple-layer microstructure of the films. The air void introduction could effectively reduce the dielectric constant from 4.11 of PI dense films to 2.57 of porous PI films with porosity of 37%. The dielectric constant was only closely related to porosity and had no obvious connection with pore size. PMID:23058979

  9. Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

    SciTech Connect

    Li, X.T.; Du, P.Y.; Zhao, Y.L.; Tu, Y.; Dai, J.L.; Weng, W.J.; Han, G.R.; Song, C.L.

    2010-11-15

    Pb{sub 0.4}Sr{sub 0.6}TiO{sub 3} (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x<0.15, only pure PST perovskite phase were in the thin films. For 0.2dielectric capacitance and dielectric loss. Display Omitted

  10. 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.

  11. 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.

  12. A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries

    NASA Astrophysics Data System (ADS)

    Lazebnik, Mariya; McCartney, Leah; Popovic, Dijana; Watkins, Cynthia B.; Lindstrom, Mary J.; Harter, Josephine; Sewall, Sarah; Magliocco, Anthony; Booske, John H.; Okoniewski, Michal; Hagness, Susan C.

    2007-05-01

    The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties.

  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. Theoretical study of the structural, vibrational and dielectric properties of PbSnTe alloys

    NASA Astrophysics Data System (ADS)

    Leite Alves, Horacio W.; Neto, Antonio R. R.; Petersen, John E.; Borges, Pablo D.; Scolfaro, Luisa M. R.

    2015-03-01

    Thermoelectric devices have promise in dealing with the challenges of the growing demand for alternative clean energy and Te-based materials well-known candidates for them. Recently, we have shown that the high values for the dielectric constant, together with anharmonic LA-TO coupling, reduces the lattice thermal conductivity and enhances the electronic conductivity in PbTe. Also, it was shown that by alloying this material with Se, the electronic conductivity of the alloys is also enhanced. But, it is not clear if the same occurs when alloying with Sn. We show, in this work, our ab initio results for the structural, vibrational and dielectric properties of Pb1-xSnxTe alloys. The calculations were carried out by using the Density Functional Theory, and the alloys were described by the Virtual Crystal Approximation. Our results show that their structural properties do not obey the Vegard rule. However, we have detected that the anharmonic LA-TO coupling still exists and the obtained values for the dielectric constant show higher values than that obtained for PbTe.

  15. Structure-dielectric properties relationships in copper-substituted magnesium ferrites

    SciTech Connect

    Druc, A.C.; Borhan, A.I.; Nedelcu, G.G.; Leontie, L.; Iordan, A.R.; Palamaru, M.N.

    2013-11-15

    Graphical abstract: - Highlights: • Synthesis of copper substituted magnesium ferrites materials is reported. • A shift from cubic to tetragonal structure starting with x = 0.84 was observed. • The dielectric properties are influenced by Cu-substitution. - Abstract: Nanocrystalline powders of copper-substituted magnesium ferrites with general formula Mg{sub 1−x}Cu{sub x}Fe{sub 2}O{sub 4} (x = 0.00, 0.17, 0.34, 0.50, 0.67, 0.84, 1.00) were prepared for the first time by sol–gel auto-combustion method, using glycine as fuel agent. Solid phase chemical reactions and the occurrence of spinel structure were monitored by using infrared spectroscopy. X-ray diffraction analysis confirmed the spinel single-phase formation. A shift from cubic structure to tetragonal structure starting with x = 0.84 was also observed. Microstructure of the samples was analyzed by scanning electron microscopy and particle size was estimated from the micrographs. Analysis of dielectric properties revealed very low values of dielectric loss at frequencies over 10 MHz.

  16. Dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes impregnated polydimethylsiloxane nanocomposite

    NASA Astrophysics Data System (ADS)

    Sagar, Sadia; Iqbal, Nadeem; Maqsood, Asghari

    2013-06-01

    The dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes (F-MWCNT) incorporated into the polydimethylsiloxane (PDMS) were evaluated to determine their potential in the field of electronic materials. Carboxylic functionalization of the pristine multi walled carbon tubes (Ps-MWCNT) was confirmed through Fourier transform infrared spectroscopy, X-ray diffraction patterns for both Ps-MWCNTs and F-MWCNTs elaborated that crystalline behavior did not change with carboxylic moieties. Thermogravimetric and differential thermal analyses were performed to elucidate the thermal stability with increasing weight % addition of F-MWCNTs in the polymer matrix. Crystallization/glass transition / melting temperatures were evaluated using differential scanning calorimeter and it was observed that glass transition and crystallization temperatures were diminished while temperatures of first and second melting transitions were progressed with increasing F-MWCNT concentration in the PDMS matrix. Scanning electron microscopy and energy dispersive x-ray spectroscopy were carried out to confirm the morphology, functionalization, and uniform dispersion of F-MWCNTs in the polymer matrix. Electrical resistivity at temperature range (100-300C), dielectric loss (tan?) and dielectric parameters (epsilon/ epsilon//) were measured in the frequency range (1MHz-3GHz). The measured data simulate that the aforementioned properties were influenced by increasing filler contents in the polymer matrix because of the high polarization of conductive F-MWCNTs at the reinforcement/polymer interface.

  17. 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, UVvisNIR spectroscopy and impedance spectroscopy. XRD study confirms the tetragonal structure of the as-deposited films with lattice parameters, a = 5.1822 and c = 9.4563 and a grain size of about 56 nm. UVvisNIR 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 ?{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.

  18. 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.

  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. Dielectric properties of dates at 2.45 GHz determined with a tunable single-mode resonant cavity.

    PubMed

    Ali, I A; al-Amri, A M; Dawoud, M M

    2000-01-01

    A tunable TM012-mode resonant cavity with an additional tuning mechanism and working at 2.45 GHz has been designed, fabricated and tested for determination of dielectric properties of dates. The cavity has a Q-factor > 5000, and a tuning mechanism which gives it more flexibility and controllability. The cavity has been used for determining the dielectric properties of Rezaiz, the most common type of dates used in the production of data juice in the Eastern Province of the Kingdom of Saudi Arabia. The dielectric constant for this type of dates was 4.6 +/- 0.16, and the loss factor was 0.21 +/- 0.03, at 8.75% moisture. These results are comparable with the dielectric properties of some other fruits, of similar composition, at the same moisture level. PMID:11257826

  1. Unusual dielectric loss properties of carbon nanotube - polyvinylidene fluoride composites in low frequency region (100 Hz

    NASA Astrophysics Data System (ADS)

    Zhao, Guang-Lin; Zhen, Yi; Arredondo, Juan

    2015-03-01

    Systematic investigations on the dielectric properties of multi-walled carbon nanotubes (MWCNTs)-polyvinylidene fluoride (PVDF) composites with a wide MWCNT concentration range (2-9wt%) have been carried out. It was revealed that the dielectric constant are increased by the addition of an appropriate amount of MWCNTs at room temperature. However, when the concentration of MWCNTs in the composites reaches above 5wt%, negative dielectric constants and large dielectric loss in the composites are observed in the low frequency range. The ferroelectric CNT-PVDF polymer composites containing more than 5 wt% MWCNTs have a strong dielectric absorption, which has the potential for acoustic applications. The work was funded in part by AFOSR (Award No. FA9550-09-1-0367) and by NSF LASIGMA Project (Award No. EPS-1003897, NSF92010-15-RII-SUBR).

  2. Dielectric and Magnetic Properties in Relaxor Magnet LuFeCoO4

    NASA Astrophysics Data System (ADS)

    Soda, Minoru; Masuda, Takatsugu

    2016-03-01

    Dielectric and magnetic properties in the relaxor magnet LuFeCoO4 having a triangular lattice are studied by permittivity, magnetization, and neutron diffraction measurements. We found that LuFeCoO4 has the nuclear diffuse scattering induced by Polar Nanoregions (PNRs) where local polarizations in nanoregions are randomly oriented. Synchronized changes in PNRs and magnetic short-range order with decreasing temperature are observed, which reveal the existence of the strong coupling between dielectricity and magnetism. The coincidence of the correlation lengths of the nuclear atoms and spins in the crystallographic a–b plane at the onset temperature of two-dimensional magnetic order is confirmed, suggesting that the magnetic order develops inside the PNRs. With further decreasing temperature, the magnetic correlation extends beyond the domain wall of the crystal cluster in contrast with another relaxor magnet BiFeO3–1/3BaTiO3.

  3. Electrical, Magnetic and Dielectric Properties of Zn1-xCdxO System

    NASA Astrophysics Data System (ADS)

    Kamruzzaman, M.; Khan, M. K. R.; Rahman, M. M.; Karal, M. A. S.; Shahjahan, M.; Ahsan, M. Rafiqul

    The ternary system Zn1-xCdxO (x = 0.00, 0.01, 0.05, 0.10 and 0.15) samples have been synthesized by the solid solution route. The synthesized samples were characterized by their electrical, magnetic and dielectric properties. The resistivity of the samples decreases with increase of Cd concentration and temperature, respectively. The activation energy at 339 K varies from 0.426 to 0.146 eV. The ternary system possesses a negative mass susceptibility having pair of electrons confirmed by the magnetic mass susceptibility measurement. The dielectric constant of the samples increases with increase of Cd and decreases with frequency initially and then remains constant.

  4. Electrical conductivity enhanced dielectric and piezoelectric properties of ferroelectric 0-3 composites

    NASA Astrophysics Data System (ADS)

    Wong, C. K.; Shin, F. G.

    2005-03-01

    We have investigated the effects of electrical conductivity of the constituents on the dielectric and piezoelectric properties of ferroelectric 0-3 composites. The time-dependent internal electric fields are first derived, which can be induced by an applied ac field in dielectric measurement or stress in piezoelectric measurement. Our previously developed model [C. K. Wong, Y. M. Poon, and F. G. Shin, J. Appl. Phys. 90, 4690 (2001)] has been extended to include the additional contribution from the electrical conductivities and the frequency of measurement, which can be significant for ceramic/polymer composites possessing high conductivity in the matrix phase. The model provides an explanation to the surprisingly high piezoelectric d33 values reported by, e.g., Chen et al. [Sens. Actuators, A 65, 194 (1998)]. Explicit expressions for the transient and steady-state responses are given and the effective permittivity, d33, d31, and dh coefficients have been derived.

  5. An Investigation on the Dielectric Properties of Polyaniline-Based Nanocomposite

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Ai, L. H.

    Polyaniline/LiNi0.5Gd0.08Fe1.92O4 nanocomposite was synthesized by an in-situ polymerization of aniline in the presence of LiNi0.5Gd0.08Fe1.92O4 particles. The dielectric properties of the as-prepared polyaniline-based nanocomposite were investigated using an Agilent E4991A RF Impedance/Material Analyzer at room temperature in the frequency range from 1 MHz to 1 GHz. The real (?') and imaginary part (??) of complex permittivity, and dissipation factor (tan ?) were found to be frequency-dependent, which decreased with increasing of frequency. It was shown that ?', ?? and tan ? of the nanocomposite were lower than those of pristine polyaniline. In order to investigate the dielectric process in detail, the complex electric modulii derived from the complex permittivity were analyzed as a function of the frequency.

  6. Tweaking Electrical and Dielectric Properties of Nickel Oxide Nanocrystals by Varying the Surfactant.

    PubMed

    Maheswari, A Uma; Mohan, Sreedevi R; Sivakumar, M; Kumar, S Saravana

    2015-12-01

    The influence of cationic cetyltrimethylammonium bromide (CTAB) and neutral polymeric polyvinylpyrrolidone (PVP) surfactants on electrical and dielectric properties of NiO nanocrystals is investigated. It is demonstrated that, compressive strain of nanocrystals is higher with PVP than that of CTAB. Consequently surfactant type has significant influence on intrinsic defects of nanocrystals. This is attributed to the difference in stabilization of metallic ions against agglomeration that leads to variation in rate of hydrolysis. Particularly, in the case of PVP assisted synthesis, higher stabilization leads to slow nucleation rate with lower defect density. As a result the hopping time of charge carriers decreases which in turn enhances the conductivity of nanocrystals as evidenced from the shifting of dielectric loss peak to higher frequency. PMID:26682362

  7. 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.

  8. Nondestructive analysis of dielectric properties: application to ion beam irradiated tissue response microfibre.

    PubMed

    Mallick, Biswajit

    2014-01-01

    The aim of this work was to investigate the effect of 2.4 MeV proton irradiation on the dielectric property of polyethylene terephthalate (PET) microfibre nondestructively. The dielectric constant ?d of single-microfibre has been measured as-such applying laser diffraction technique. Applying this methodology ?d is found out to be slightly increases with proton fluence except at the fluence 1013 p/cm2 where material shows maximum crosslinking. The variations of the biological interaction with ?d of PET material are correlated. Proton beam modified PET microfibre is therefore accepted to have further potential applications in radiation processing tissue response microfibre, fabrication of medical devices etc. PMID:24642970

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  10. Dielectric properties induced by hindered molecular motion in crystals and liquids

    NASA Astrophysics Data System (ADS)

    Bashirov, F. I.

    1999-09-01

    A united theoretical description of dielectric properties of molecular solids and liquids is developed. The numbering data are tabulated and some results are pictured. The theory expands the fundamental dispersion expressions of complex dielectric permeability, initiated by Debye for molecular liquids, to any condensed molecular medium. Une approche théorique unifiant les propriétés diélectriques des cristaux moléculaires et celles des liquides est développée. Les données numériques sont disposées et les résultats principaux sont imaginés. La théorie élargie les expressions fondamentales de dispersion de la permittivité complexe du diélectrique liquide moléculaire, initié par Debye, à tout milieu condensé moléculaire.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. Mechanical properties of anhydrite and polyhalite in quasi-static triaxial compression

    SciTech Connect

    Teufel, L.W.

    1981-10-01

    Bedded salt of the Salado Formation at the WIPP site in southeastern New Mexico is being considered as a nuclear waste containment media. The Salado Formation is composed of 85 to 90 percent rock salt and the remaining 10 to 15 percent of the formation consists primarily of polycrystalline anhydrite, smaller amounts of polycrystalline polyhalite, and minor amounts of clay. In order to provide a more complete evaluation of the thermomechanical behavior of rock in the Salado Formation adjacent to the proposed repository, a rock mechanics testing program has been initiated to determine the mechanical properties of the two most abundant nonsalt rock, anhydrite and polyhalite. This report summarizes the mechanical properties of these two rock types in dry, room temperature, quasi-static triaxial compression experiments to 20 MPa confining pressure. In addition, Coulomb-Mohr and Mises-Drucker criteria have been fit successfully to both yield and failure stress data.

  17. The influence of fracture density and burial depth on the static and dynamic elastic properties of crystalline rocks

    NASA Astrophysics Data System (ADS)

    Blake, O. O.; Faulkner, D. R.; Tatham, D.

    2013-12-01

    Fracture in rock is a major factor that affects the rock's elastic properties. Elastic properties can be measured statically where stress and strain data are recorded during slow loading of a specimen, or dynamically, where the elasticity can be calculated from P- and S- wave velocity. During crustal deformation, rocks deform nearly statically, hence the relationship between the static and dynamic elastic properties must be known so that the dynamic elastic properties can be converted to static elastic properties to allow geomechanical and geodynamic modelling. In this study, the dynamic and static elastic properties were measured for dry crystalline rocks (Westerly granite) that were thermally treated to 250, 450, 650 and 850C. Increasing the temperature produces an increased fracture density that is isotropically distributed. Experiments were carried out under confining pressure up to crack-closure pressure, 130MPa (~8km burial depth under hydrostatic pore pressure conditions). Increased fracture density within the rock results in a reduction in Young modulus and an increase in the Poisson's ratio, in both the static and dynamic case which is very significant above 573C. The reduction and increase are retarded with increasing confining pressure. At crack-closure pressure the fracture density, in terms of effective medium models, is zero even though the rock still contains cracks. The crack-closure pressure is independent of fracture damage incurred in the rock. We compared the static and dynamic measurements and found a linear relationship between the static and dynamic Young's modulus with very high correlation and a gradient of one which is independent of confining pressure and the amount of fracturing incurred in the samples from thermal treatment. We also found that the static and dynamic Poisson's ratio are in agreement for values less than 0.34. Above this value, the static Poisson's ratio is much higher than the dynamic Poisson's ratio. Voigt-Reuss-Hill averaging technique, which inherently assumes zero crack density, was used to calculate the elastic properties so that a comparison could be made with what we assumed are zero crack density at 130MPa. The results from the Voigt-Reuss-Hill averaging technique are similar to the dynamic elastic properties at crack-closure pressure. Hence the dynamic elastic properties at this pressure could be incorporated into an effective medium model to predict the crack densities at pressure below the crack closure pressure. Changes in crack density are interpreted as creation or opening of cracks. We found that the crack density increased from ~0.2 to 1.8 at 10MPa confining pressure. The increase in the crack density is also retarded with increasing confining pressure.

  18. 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.

  19. Measurements along the growth direction of PMN-PT crystals: dielectric, piezoelectric, and elastic properties.

    PubMed

    Tian, Jian; Han, Pengdi; Payne, David A

    2007-09-01

    Property measurements are reported for Pb(Mg1/3Nb2/3)03-PbTiO3 (PMN-PT) single crystals grown along (001) by a seeded-melt method. Chemical segregation occurs during crystal growth, leading to property changes along the growth direction. Variations in dielectric, piezoelectric, and elastic properties were evaluated for specimens selected from the crystals. Room-temperature data are correlated with Tc and composition that ranged from 27 to 32% PT, i.e., in the vicinity of the morphotropic phase boundary (MPB). While there was little change in the high electromechanical coupling factor k33 (0.87-0.92), both the piezoelectric charge coefficient d33 (1100-1800 pC/N) and the free dielectric constant K3 (4400-7000) were found to vary significantly with position. Increases in d33 and KT33 were relatively offsetting in that the ratio yielded a relatively stable piezoelectric voltage coefficient g33 (27-31 x 10(-3) Vm/N). Values are also reported for the elastic compliance (3.3-6.3 x 10(-11) m2/N) determined from resonance measurements. Enhancements in d33 and K(T)33 were associated with lattice softening (increasing sE33) as the composition approached the MPB. Details are reported for the piezoelectric, dielectric, and elastic properties as a function of growth direction, Tc, and composition. The results are useful for an understanding of properties in PMN-PT crystals and for the design of piezoelectric devices. PMID:17941396

  20. 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.

  1. Nanoscale EELS analysis of dielectric function and bandgap properties in gaN and related materials

    PubMed

    Brockt; Lakner

    2000-08-01

    The low loss region of an EEL spectrum (<50 eV) contains information about excitations of outer shell electrons and thus the electronic structure of a specimen which determines its optical properties. In this work, dedicated electron energy loss spectroscopy (EELS) methods for the experimental acquisition and analysis of spectra are described, which give improved information about the electronic structure near the bandgap region at a spatial resolution in the range of nanometers. For this purpose, we made use of a cold field emission scanning transmission electron microscope (STEM) equipped with a dedicated EELS system. This device provides a subnanometer electron probe and offers an energy resolution of 0.35 eV. Application of suitable deconvolution routines for removal of the zero loss peak extracts information on the bandgap region while the Kramers-Kronig transformation deduces the dielectric properties from the measured energy loss function. These methods have been applied to characterize the optical properties of wide-bandgap materials for the case of III-nitride compounds, which are currently the most promising material for applications on optoelectronic devices working in the blue and ultraviolet spectral range. The obtained results are in excellent agreement with experimental measurements by synchrotron ellipsometry and theoretical studies. The potential of the superior spatial resolution of EELS in a STEM is demonstrated by the analysis of dielectric properties of individual layers of heterostructures and individual defects within wurtzite GaN. PMID:10741613

  2. 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.

  3. 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, UVVisible spectroscopy, X-ray photoelectron spectroscopy (XPS) and complex impedance spectroscopy. The electrical and dielectric properties dependence on temperature (302523 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 ? 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.

  4. Influence of isolated and clustered defects on electronic and dielectric properties of wstite

    NASA Astrophysics Data System (ADS)

    Wdowik, Urszula D.; Piekarz, Przemys?aw; Jochym, Pawe? T.; Parlinski, Krzysztof; Ole?, Andrzej M.

    2015-05-01

    The influence of intrinsic Fe defects in FeO (either single cation vacancies or prototypical 4:1 vacancy clusters) on electronic and dielectric properties is studied within density-functional theory. The importance of local Coulomb interactions at Fe atoms is highlighted and shown to be responsible for the observed insulating Mott gap in FeO, which is reduced by the presence of defects. We investigate nonstoichiometric configurations of Fe1 -xO with x ranging from 3% to 9%, and we find the aliovalent Fe cations in both the regular and interstitial lattice sites of the considered configurations. Furthermore, we show that the trivalent Fe ions, induced by both isolated and clustered Fe vacancies, introduce the empty band states inside the insulating gap, which decreases monotonically with increasing cation vacancy concentration. The Fe1 -xO systems with high defect content become metallic for small values of the Coulomb interaction U , yielding an increase in the dielectric functions and optical reflectivity at low energies, in agreement with the experimental data. Due to the crystal defects, the infrared-active transverse optic phonons split and distribute over a wide range of frequencies, clarifying the origin of the exceptionally large spectral linewidths of the dielectric loss functions observed for wstite in recent experiments.

  5. Dielectric and Electrical Properties of BiFeO3-PbZrO3 Composites

    NASA Astrophysics Data System (ADS)

    Satpathy, S. K.; Mohanty, N. K.; Behera, A. K.; Sen, S.; Behera, Banarji; Nayak, P.

    2015-11-01

    The dielectric and electrical properties of composites prepared by addition of two different amounts of PbZrO3 (PZO) to BiFeO3 (BFO) are discussed. The composites (1 - x)(BiFeO3)- x(PbZrO3) ( x = 0.5, 0.7; i.e., 0.5BF-0.5PZ and 0.3BF-0.7PZ) were synthesized by solid-state reaction. X-ray diffraction analysis confirmed formation of composites with a rhombohedral structure at room temperature. Scanning electron microscopy revealed homogeneously distributed grains. Dielectric constants and dielectric loss increased with decreasing PZO content whereas the transition temperature shifted to higher temperature with decreasing PZO content. Hysteresis loops confirmed the ferroelectric nature of the materials. The Nyquist plot was indicative of the contribution of the bulk effect and a small contribution from the grain boundary effect. Temperature-dependent relaxation occurred for both materials. Non-Debye type electrical impedance was confirmed by asymmetric peak broadening and a spread of relaxation times. Activation energies were calculated from plots of ac conductivity as a function of temperature by linear fitting. Dc and ac conductivity increased with increasing temperature. Activation energies calculated from the complex impedance plot and from the fitted Jonscher power law were very similar, implying conduction by a similar type of charge carrier in both composites.

  6. Magnetic, dielectric, and microwave absorbing properties of iron particles dispersed in rubber matrix in gigahertz frequencies

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Soo; Kim, Sun-Tae; Yoon, Yeo-Choon; Lee, Kyung-Sub

    2005-05-01

    This study investigates high-frequency magnetic, dielectric, and microwave absorbing properties of iron particles dispersed in rubber matrix for the aim of thin microwave absorbers in gigahertz frequencies. High value of magnetic permeability and dielectric constant can be obtained in the composites containing thin flake iron particles which were prepared by mechanical forging of spherical iron powders using an attrition mill. The results are attributed to the reduction of eddy current loss (increase of permeability) and enhancement of space-charge polarization (increase of permittivity). However, if the initial particle size is too small (approaching to skin depth), milling effect for the increase of permeability is not observed and a low dielectric constant is predicted. If the particle size is too large, the permeability value is too small due to strong eddy current loss. With the iron particles controlled in size and shape (flakes) as the absorbent fillers, the thickness can be reduced as low as 1mm with respect to -5dB reflection loss in 1-2GHz.

  7. Electrical and dielectric properties of silver iodide doped selenium molybdate glassy conductors

    NASA Astrophysics Data System (ADS)

    Palui, A.; Deb, B.; Ghosh, A.

    2013-08-01

    Electrical conductivity and dielectric properties of silver iodide doped silver ion mixed-former conducting glasses have been studied in this paper. The frequency dependence of conductivity has been analyzed following the random free-energy barrier model. The charge carrier relaxation time and the activation energy for relaxation have been determined for the present glasses. The applicability of Barton-Nakajima-Namikawa relation has been tested for the present glasses using the results obtained from random free-energy barrier model. The scaling of the conductivity spectra has been performed to understand the effect of temperature as well as composition on the relaxation dynamics. The dielectric data have been analyzed employing the Cole-Cole function, and parameters such as dielectric strength and Cole-Cole exponent have been obtained. The electrode polarization phenomenon for the present glass samples has been studied depending on temperature as well as composition. The different characteristic transitions concerning electrode polarization related to the charge transport at the interface have been obtained and are correlated to the bulk behavior. An estimation of the dc conductivity has been obtained using the result obtained from electrode polarization study and is observed to be very close to the experimental values.

  8. Dielectric Properties of (PbCa)(MeNb)O3 at Microwave Frequencies

    NASA Astrophysics Data System (ADS)

    Kato, Junichi; Kagata, Hiroshi; Nishimoto, Keiji

    1992-09-01

    We have investigated the dielectric properties up to microwave frequencies of ceramics represented as (Pb1-xCax)-(MemNb1-m)O3 where Me is selected from Li, Na, Mg, Zn, Ni, Co, Fe, Y, Yb, Al and Cr. High Q values and small temperature coefficients of resonant frequency were obtained in (PbCa)(Mg1/3Nb2/3)O3, (PbCa)(Ni1/3Nb2/3)O3 and (PbCa)-(Fe1/2Nb1/2)O3 with perovskite structure. These dielectric constants and the Q values for a near-zero temperature coefficient are \\varepsilonr{=}73 with Q{=}1330, \\varepsilonr{=}59 with Q{=}1700 and \\varepsilonr{=}91 with Q{=}1650, respectively. The other ceramics with smaller amounts of perovskite phase had degraded characteristics, i.e., low Q values or large temperature coefficients. In lead- and calcium-based perovskite, it seems that the high dielectric constant occurs due to Pb content in A-sites and smaller average ion radius in B-sites.

  9. Dielectric Properties of Ca-Based Complex Perovskite at Microwave Frequencies

    NASA Astrophysics Data System (ADS)

    Kagata, Hiroshi; Kato, Junichi

    1994-09-01

    We have investigated microwave dielectric properties and crystal structures of Ca(B3+1/2B1/2‧5+)O3 (B: Al, Cr, Mn, Fe; B‧: Nb, Ta) and Ca(B2+1/3B2/3‧5+)O3 (B: Mg, Ca, Co, Ni, Cu, Zn; B‧: Nb, Ta) perovskite ceramics. Compared with well-known Ba-based perovskite dielectrics, the Ca-based complex perovskite dielectrics had lower relative permittivities (ɛr), lower Q values, and larger negative temperature coefficients of resonant frequencies (τf). Ca(Mg1/3Ta2/3)O3 had the highest Q value (Qf=78000 GHz) in this investigation. All Ca(B1/2B1/2‧)O3 had perovskite structures similar to CaTiO3 with a unit cell including four simple perovskite cells. Ca(B1/3B2/3‧)O3 with a small B ion such as Ni had the same structure Ca(B1/2B1/2‧)O3. Ca(B1/3B2/3‧)O3, however, had perovskite structures with larger unit cells than CaTiO3 when B ions had larger ionic radii.

  10. 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.

  11. Structural, dielectric and magnetic properties of Cd/Pb doped W-type hexaferrites

    NASA Astrophysics Data System (ADS)

    Hooda, Ashima; Sanghi, Sujata; Agarwal, Ashish; Dahiya, Reetu

    2014-01-01

    W-type hexaferrites having compositions Ba(Zn0.5Cd0.5)2Fe16O27 (BZCFO) and Ba(Zn0.5Pb0.5)2Fe16O27 (BZPFO) were synthesized by solid state reaction method at high annealing temperature. Their dielectric and magnetic properties as a function of temperature and frequency have been studied. X-ray analysis confirms the presence of W-type hexaferrite phase structure. SEM analysis presented heterogeneous hexagonal shape and sizes of grains. Analysis of Nyquist plots of prepared samples revealed the contribution of electrically active regions corresponding to grains and grain boundaries. The reciprocal temperature dependence of dc electrical resistivity (?) satisfies the Arrhenius relation which depicted the semi-conducting behavior of the samples. The variation of dielectric constant (?') and dielectric loss (tan ?) with temperature (323 K-573 K) and frequency (1 kHz-5 MHz) are studied. Analysis of the experimental conductivity data and 's' parameter shows that correlated barrier hopping (CBH) mechanism is the most probable mechanism of conduction for BZCFO sample; whereas for BZPFO hexaferrite, both correlated barrier hopping (CBH) and quantum mechanical tunneling (QMT) model are applicable for conduction. The BZCFO sample has higher value of saturation magnetization and lower coercivity than BZPFO sample due to the preference of Cd2+ for tetrahedral sites and decrease in number of spin-down magnetic ions.

  12. 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 (?ac(?)) has also been determined. The ac conductivity of our samples satisfies the well known ac power law; i.e., ?ac(?) propto ?s 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.

  13. Dielectric and Pyroelectric Properties of La- and Pr-Modified Tungsten-Bronze Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Parida, B. N.; Das, Piyush R.; Padhee, R.; Choudhary, R. N. P.

    2013-08-01

    The polycrystalline materials Li2Pb2R2W2Ti4Nb4O30 (R = La, Pr) of the tungsten-bronze structural family have been synthesized using a high- temperature mixed-oxide method. Room-temperature x-ray diffraction (XRD) analysis confirms the formation of single-phase compounds. Room-temperature scanning electron micrography of the pellet samples shows a uniform distribution of well-defined different sizes of grains on the surface of the samples, confirming the formation of single-phase compounds. Study of the frequency and temperature dependence of the dielectric constant and loss tangent suggests the existence of dielectric dispersion in the materials. The ferroelectric phase transition in the samples has been studied based on the variation of fitting parameters (calculated from a theoretical model) with temperature. Studies of pyroelectric properties [figure of merit (FOM) and coefficient] show that the materials have reasonably high FOM useful for pyroelectric detectors. The variation of alternating-current (AC) and direct-current (DC) conductivity with inverse absolute temperature (obtained from dielectric data) follows a typical Arrhenius relation. The low leakage current and negative temperature coefficient of resistance behavior of the samples have been verified from J- E plots.

  14. The effect of dielectric properties on the electrorheology of suspensions of silica particles coated with polyaniline

    NASA Astrophysics Data System (ADS)

    Lenglov, Aneka; Pavlnek, Vladimr.; Sha, Petr; Stejskal, Jaroslav; Kitano, Takeshi; Quadrat, Otakar

    2003-04-01

    The flow behaviour of silicone-oil suspensions of five types of silica particles coated with a polyaniline base in a DC electric field has been linked to their dielectric properties. The relaxation frequencies corresponding to the position of the dielectric-loss maxima in the frequency spectra identify the interfacial polarization of suspension particles as a controlling factor for a strong electrorheological effect. The yield stresses of suspensions under the influence of electric field and critical shear rates, at which the chains of polarized particles were broken by shear forces, is correlated with the difference between the limit values of dielectric constants above and below the relaxation frequency. The analysis of particle dipole coefficient ? showed that particle polarizability is the main factor affecting rigidity of the electrorheological structure. In contrast with this, particle shape and size, controlling the field-off suspension viscosity, become unimportant after the electric field has been applied. The plots of the relative viscosity of studied suspensions vs. Mason number characterizing the relation between shear and polarization forces have been discussed. While the results obtained at different shear rates and field strengths were reduced to a single dependence, for various particle suspensions these dependences differed.

  15. 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.

  16. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation.

    PubMed

    Shirakashi, Ryo; Mischke, Miriam; Fischer, Peter; Memmel, Simon; Krohne, Georg; Fuhr, Günter R; Zimmermann, Heiko; Sukhorukov, Vladimir L

    2012-11-01

    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. PMID:23063978

  17. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics.

    PubMed

    Pirc, R; Roi?, B; Koruza, J; Cordoyiannis, G; Mali?, 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 ?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. PMID:26490797

  18. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Roi?, B.; Koruza, J.; Cordoyiannis, G.; Mali?, 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 LandauKittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the RaeDove (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 ? 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.

  19. Dielectric Properties of Cryogenic Gas Mixtures Containing Helium, Neon, and Hydrogen

    NASA Astrophysics Data System (ADS)

    Graber, L.; Kim, W. J.; Cheetham, P.; Kim, C. H.; Rodrigo, H.; Pamidi, S. V.

    2015-12-01

    Past efforts of cooling high temperature superconducting (HTS) power cables by gaseous cryogens focused exclusively on helium. The limited dielectric strength of helium gas necessitated alternatives that could be used in the temperature range suitable for HTS power applications. This paper presents the benefits of gas mixtures containing helium with small concentrations of hydrogen or neon to mitigate the limited dielectric strength of pure helium gas. The expectation was that such gas mixtures could improve dielectric characteristics while maintaining the thermal, non-flammable and non-corrosive properties of pure helium gas. The AC breakdown voltage of helium gas mixtures containing 4 mol% neon or 4 mol% hydrogen respectively have been measured and compared to those of pure helium and pure neon. All measurements were performed at 77 K at gas pressure levels between 0.5 and 2.0 MPa. While the 4 mol% neon mixture did not result in any improvement over pure helium, the 4 mol% hydrogen mixture resulted in 80% higher breakdown strength. This is expected to enable higher operating voltages for gas cooled HTS power devices.

  20. The correlation between dielectric properties and microstructure of femoral bone in rats with different bone qualities.

    PubMed

    Tao, Feng; Fu, Feng; You, Fusheng; Ji, Zhenyu; Wen, Jun; Shi, Xuetao; Dong, Xiuzhen; Yang, Min

    2014-06-01

    Bone dielectric properties (DP) have been extensively studied. However, little literature has reported DP of bone from identical anatomical site under different status and its correlation with microstructure. Therefore, interrelationship between DP and microstructure of rat femurs with varying bone qualities (normal, osteoporotic and partially osteoporotic) was investigated. Diabetic osteoporosis was induced by streptozotocin (STZ) injection. 8 normal rats as control group together with 16 diabetic rats equally assigned to diabetes mellitus (DM) and DM treated by pulsed electromagnetic fields (PEMF) (DM + PEMF) group were used. DM + PEMF group was daily exposed to PEMF of 15 Hz, 1 mT for 8 weeks. After sacrifice, the femurs were harvested for microCT analysis and dielectric measurements (from 10 Hz to 1 MHz). It was found that DP (conductivity and permittivity) altered after PEMF stimulation improved femoral microstructures (p < 0.01). Significant correlations were found between microstructure indices (MI) and conductivity in the full frequency range (|r| ≥ 0.64, n = 24) as well as permittivity in middle and low frequencies (|r| ≥ 0.52, n = 24, from 1 Hz to 1 kHz). The findings demonstrated the good correlation between DP and MI of femoral bone in rats, which makes it possible to distinguish bone under different status and predict MI variation through dielectric measurements. PMID:24710797

  1. 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.

  2. 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.

  3. 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 (>40C) 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 90C, 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 46C 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

  4. Investigation into the electromechanical properties of dielectric elastomers subjected to pre-stressing.

    PubMed

    Jiang, Liang; Betts, Anthony; Kennedy, David; Jerrams, Stephen

    2015-04-01

    Dielectric elastomers (DEs) are being exploited for biological applications such as artificial blood pumps, biomimetic grippers and biomimetic robots. Generally, polyacrylate and silicone rubber (SR) are the most widely used materials for fabricating DEs in terms of mixing with other polymers or compounding them with highly dielectric particles. Furthermore, pre-stretch offers an effective approach to increasing actuated strain and dielectric strength and eliminating 'pull-in' instability. In the work described here, a comparison in electromechanical properties was made between SR/10% barium titanate (BaTiO3) and commercial VHB 4910. Trends in these dielectric parameters are shown graphically for variation in pre-stretch ratio (?pre). It was found that permittivity of SR/10% BaTiO3 was independent of frequency, whereas permittivity was frequency-independent due to the polarization of polymer chains. The maximum deformation and the coupling efficiency for SR/10% BaTiO3 can be achieved at a pre-stretch ratio between 1.6 and 1.9. For VHB 4910, they can be obtained in the pre-stretch ratio range from 2.6 to 3.0. A maximum energy density of 0.05MJ/m(3) was achieved by SR/10% BaTiO3 (?pre=1.6) and VHB 4910 (?pre=3.4). The findings provide an insight into critical pre-stretch ratios required for a range of applications of DEs based on silicone and the commercially available polyacrylate VHB 4910. PMID:25687005

  5. Correlation between dynamic nonlinearity and static mechanical properties of corroded E-glass reinforced polyester composites

    NASA Astrophysics Data System (ADS)

    Van Den Abeele, K.; Van de Velde, K.

    2000-05-01

    Glass-fiber reinforced plastics degrade in different manners when exposed to chemical environments. Migration of chemicals into the matrix results in absorption, chemical reaction, plastization, and dissolution of the matrix. Furthermore, the chemicals cause degradation of the glass fiber itself and debonding between the glass fibers and the matrix material takes place. In this work, we investigate the chemical resistance of pultruded polyester composites as a function of exposure time, and compare the observations from static mechanical tests with the results from nonlinear dynamic vibration experiments for various exposure fluids. The mechanical properties were measured according to ASTM standards, both in flexural and tensile tests. The nonlinear properties were measured using a new nondestructive testing technique called Single Mode Nonlinear Resonance Acoustic Spectroscopy (SIMONRAS). This method focuses on the strain dependence of the resonance frequency while driving a sample at relatively low amplitudes. The obtained relative frequency shift is a measure of the internal microstructural properties of the material. The correlation between this nonlinearity parameter and the mechanical properties as a function of exposure time is extremely good, which implies that the SIMONRAS technique can be used to predict the mechanical degradation of composites due to corrosion in a nondestructive manner.

  6. Modeling of material properties of piezoelectric ceramics taking into account damage development under static compression

    NASA Astrophysics Data System (ADS)

    Mizuno, M.; Nishikata, T.; Okayasu, M.

    2013-10-01

    We have carried out static compression tests in the poling direction for PZT ceramics and evaluated the material properties by measuring the resonance and anti-resonance frequencies and electrostatic capacity at regular intervals. Then the variation in the material properties up to fracture was clarified. Also, the development of internal damage was also clarified quantitatively by evaluating a damage variable on the basis of the continuum damage mechanics. The damage variable was calculated from the ratio of the elastic coefficient to its initial value. In the present paper, the development of internal damage was formulated as an evolution equation of the damage variable. In the formulation, a threshold stress leading to the onset of damage was considered. Moreover, the variation in material properties was related to the damage variable and formulated as material functions of the damage variable. The development of internal damage and the variation in material properties were simulated by the equations proposed in the present paper and the validity of the equations was verified by comparing the predictions with experimental results.

  7. Semiconducting and dielectric properties of barium titanates, tantalates and niobates with perovskite structure

    NASA Astrophysics Data System (ADS)

    Kolodiazhnyi, Taras

    The dielectric and semiconducting properties of two types of ceramics (n-type BaTiO3 and dielectric Ba(B'1/3 B?2/3)O3 where B' = Mg, Zn, Ni, and B? = Nb, Ta) were characterized. Complex impedance analysis and dc conductivity measurements of samples prepared at various PO2 have ruled out oxygen chemisorption in favor of interfacial segregation of cation vacancies as the cause of the positive temperature coefficient of resistivity (PTCR) effect in n-type BaTiO3. The effect of preparation conditions, sintering atmosphere, stoichiometry, and post-sinter anneal on the defect chemistry of BaTiO3 was studied using the electron paramagnetic resonance (EPR) technique. Several paramagnetic defects such as, Ti3+, VBa, and VTi were detected and identified by EPR. Current-voltage characteristics (I-V) of PTCR BaTiO 3 were analyzed in light of space-charge-limited-current, trap-filled-limited-current, Frenkel-Poole, small polaron, and double-Schottky barrier models. It was shown that for the double-Schottky barrier model, a partial stabilisation of the potential barrier is expected when the Fermi level is pinned at grain boundaries by a high density of the interface states. The deviation of I-V characteristics of BaTiO3 in the region of the PTCR effect can be explained by dependence of the population of the interface electron states on applied voltage. Based on the Seebeck and Hall effect measurements, it was found that in the range of 100--300 K, the drift mobility of electrons in BaTiO 3 is not thermally activated, which supports the concept of conduction band electron transport rather than small radii polaron hopping. However, further study over a wider temperature range and on better quality crystals is required to unequivocally clarify the electron transport mechanism in BaTiO 3. Phase composition, degree of cation ordering, and dielectric properties of complex perovskites with general formula Ba(B' 1/3B?2/3)O3 where B' = Mg, Zn, Ni, and B? = Nb, Ta were analyzed. It was shown that in Ba(Mg1/3Ta2/3)O 3 both intrinsic and extrinsic dielectric loss affect the Q-factor, whereas in Ba(Mg1/3Nb2/3)O3 and Ba(Ni 1/3Nb2/3)O3 extrinsic factors such as the second phase and point defects dominate the dielectric loss at microwave frequencies.

  8. Geometrical-optics code for computing the optical properties of large dielectric spheres.

    PubMed

    Zhou, Xiaobing; Li, Shusun; Stamnes, Knut

    2003-07-20

    Absorption of electromagnetic radiation by absorptive dielectric spheres such as snow grains in the near-infrared part of the solar spectrum cannot be neglected when radiative properties of snow are computed. Thus a new, to our knowledge, geometrical-optics code is developed to compute scattering and absorption cross sections of large dielectric particles of arbitrary complex refractive index. The number of internal reflections and transmissions are truncated on the basis of the ratio of the irradiance incident at the nth interface to the irradiance incident at the first interface for a specific optical ray. Thus the truncation number is a function of the angle of incidence. Phase functions for both near- and far-field absorption and scattering of electromagnetic radiation are calculated directly at any desired scattering angle by using a hybrid algorithm based on the bisection and Newton-Raphson methods. With these methods a large sphere's absorption and scattering properties of light can be calculated for any wavelength from the ultraviolet to the microwave regions. Assuming that large snow meltclusters (1-cm order), observed ubiquitously in the snow cover during summer, can be characterized as spheres, one may compute absorption and scattering efficiencies and the scattering phase function on the basis of this geometrical-optics method. A geometrical-optics method for sphere (GOMsphere) code is developed and tested against Wiscombe's Mie scattering code (MIE0) and a Monte Carlo code for a range of size parameters. GOMsphere can be combined with MIE0 to calculate the single-scattering properties of dielectric spheres of any size. PMID:12921277

  9. Static and Field-Oriented Properties of Bowl-Shaped Polynuclear Aromatic Hydrocarbon Fragments.

    PubMed

    Zoppi, Laura; Ferretti, Andrea; Baldridge, Kim K

    2013-11-12

    First principles techniques are used to investigate the structure, linear polarizability, and field-oriented property trends of the series of bowl shaped polynuclear aromatic hydrocarbon fragments, C20H10, C30H10, C40H10, and C50H10. Such structures represent a sequence of minimalistic, capped bucky tube units based on the corannulene molecule, with interesting technological promise imparted by their curvature. Specific issues associated with how the intrinsic dipole and static linear polarizability influences the orientation of these structures in the presence of an external electric field are addressed and shown to correlate well with a simple analytical model. At moderate electric fields, the induced dipoles become comparable and even larger than the intrinsic dipoles due to the large in-plane polarizabilities in these systems. This generates a nontrivial and field dependent orientation of the molecule that can be exploited, for example, to induce switching behavior within molecular nanojunctions. PMID:26583398

  10. Influence of the bias current distribution on the static and dynamic properties of long Josephson junctions

    NASA Astrophysics Data System (ADS)

    Samuelsen, M. R.; Vasenko, S. A.

    1985-01-01

    The maximum supercurrent through a long and narrow Josephson junction has been calculated numerically as a function of an applied magnetic field for various feed current distributions. The results have been shown to depend drastically on the mode of the current feed. In particular, the real nonuniform distribution ηov (x) of the current corresponding to the overlap geometry of the junction is nearly equivalent to the mixture yηun+(1-y)ηin with the factor y approaching unity as the junction length increases: (1-y)=Cy(L/λj)-0.5, Cy≂1.7. In contrast with the static properties, the shape of the zero-field step in the long junction I-V curve appears to be almost independent of the mode of the current feed, because of averaging of the Lorentz force by the travelling Josephson vortices.

  11. Static and dynamic properties of inhomogeneous elastic media on disordered substrate

    NASA Astrophysics Data System (ADS)

    Cule, Dinko; Hwa, Terence

    1998-04-01

    The pinning of an inhomogeneous elastic medium by a disordered substrate is studied analytically and numerically. The static and dynamic properties of a D-dimensional system are shown to be equivalent to those of the well-known problem of a D-dimensional random manifold embedded in (D+D) dimensions. The analogy is found to be very robust, applicable to a wide range of elastic media, including those which are amorphous or nearly periodic, with local or nonlocal elasticity. Also demonstrated explicitly is the equivalence between the dynamic depinning transition obtained at a constant driving force, and the self-organized, near-critical behavior obtained by a (small) constant velocity drive.

  12. Investigation of the dielectric properties of composites based on silicon dioxide with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Goshev, A. A.; Eseev, M. K.; Kapustin, S. N.; Malkov, A. V.; Osokin, C. S.

    2015-11-01

    The aim of this work is an experimental study of the dielectric properties of nanocomposites with a matrix of silica reinforced with multi-walled CNTs at different concentrations and to determine the role of the CNT in the scattering and absorption of electromagnetic radiation in the range of extra-long and medium radio waves (25 Hz-1 MHz). The study found that in addition to the standard behavior of the electrical characteristics of nanocomposites with increasing concentration there was an optimum concentration of carbon nanotubes at which conductivity and absorption of electromagnetic radiation in the material greatly increased. This can be used to enhance the functionality of nanocomposites.

  13. 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.

  14. 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.

  15. Modification Properties of the Dielectric Membrane Films using High Temperature Annealing

    NASA Astrophysics Data System (ADS)

    Veselov, D. S.; Voronov, Yu. A.

    This paper is aimed at studying the influence of high temperature annealing on the films of silicon oxynitride, obtained by reactive magnetron sputtering of silicon in the environment of argon, nitrogen and oxygen. Annealing of the films was performed in nitrogen atmosphere within temperature range of 800 - 1200 C. The chemical composition of obtained films and their properties were studied and their dependence on annealing temperature was shown. The recommendations on application of high temperature annealing in formation process of dielectric membrane structures for sensitive elements of semiconductor gas sensors were developed.

  16. 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.

  17. 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.

  18. 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.; Department of Chemical Engineering, College of Engineering, Najran University, P.O. Box 1988, Najran, 11001 ; 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Static and dynamical properties of heavy water at ambient conditions from first-principles molecular dynamics.

    PubMed

    Sit, P H-L; Marzari, Nicola

    2005-05-22

    The static and dynamical properties of heavy water have been studied at ambient conditions with extensive Car-Parrinello molecular-dynamics simulations in the canonical ensemble, with temperatures ranging between 325 and 400 K. Density-functional theory, paired with a modern exchange-correlation functional (Perdew-Burke-Ernzerhof), provides an excellent agreement for the structural properties and binding energy of the water monomer and dimer. On the other hand, the structural and dynamical properties of the bulk liquid show a clear enhancement of the local structure compared to experimental results; a distinctive transition to liquidlike diffusion occurs in the simulations only at the elevated temperature of 400 K. Extensive runs of up to 50 ps are needed to obtain well-converged thermal averages; the use of ultrasoft or norm-conserving pseudopotentials and the larger plane-wave sets associated with the latter choice had, as expected, only negligible effects on the final result. Finite-size effects in the liquid state are found to be mostly negligible for systems as small as 32 molecules per unit cell. PMID:15945755

  5. Effect of various glass and aramid reinforcements on static and fatigue properties of composites

    SciTech Connect

    Echtermeyer, A.T.; McGeorge, D.; Buene, L.

    1993-12-31

    Composites are widely used as structural materials today. Their full potential can only be achieved by optimizing material selections and laminate layups to the specific application. Such optimizations do not only require a good understanding of the material properties and behavior, but also require a careful assessment of the safety of such an optimized structure. Basic static properties of laminates reinforced by glass and aramid-glass hybrid fabrics were measured. These properties can be used as input to FE-analysis or optimization procedures to find the best laminate for an application. However, marine applications have to withstand slamming from waves and also accidental local impact from various objects floating in the water. These events can cause damage in the structure and have to be considered in order to assess the safety of a structure. Simple tests to evaluate the effects of slamming and impact are required in the marine industry. Fatigue and impact tests were performed and methods were developed to relate test results to slamming and impact on marine structures. All of these factors have to be considered simultaneously to ensure the safety of a marine structure made from composite materials.

  6. Gaussian basis sets for use in correlated molecular calculations. IV. Calculation of static electrical response properties

    SciTech Connect

    Woon, D.E.; Dunning, T.H. Jr. )

    1994-02-15

    An accurate description of the electrical properties of atoms and molecules is critical for quantitative predictions of the nonlinear properties of molecules and of long-range atomic and molecular interactions between both neutral and charged species. We report a systematic study of the basis sets required to obtain accurate correlated values for the static dipole ([alpha][sub 1]), quadrupole ([alpha][sub 2]), and octopole ([alpha][sub 3]) polarizabilities and the hyperpolarizability ([gamma]) of the rare gas atoms He, Ne, and Ar. Several methods of correlation treatment were examined, including various orders of Moller--Plesset perturbation theory (MP2, MP3, MP4), coupled-cluster theory with and without perturbative treatment of triple excitations [CCSD, CCSD(T)], and singles and doubles configuration interaction (CISD). All of the basis sets considered here were constructed by adding even-tempered sets of diffuse functions to the correlation consistent basis sets of Dunning and co-workers. With multiply-augmented sets we find that the electrical properties of the rare gas atoms converge smoothly to values that are in excellent agreement with the available experimental data and/or previously computed results. As a further test of the basis sets presented here, the dipole polarizabilities of the F[sup [minus

  7. 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 Gabriels 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 Gabriels 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.

  8. Effects of crystallization conditions on dielectric and ferroelectric properties of PZT thin films

    NASA Astrophysics Data System (ADS)

    Arajo, E. B.; Eiras, J. A.

    2003-08-01

    This paper reports studies on dielectric and ferroelectric properties of lead zirconate titanate (PZT) thin films crystallized by conventional thermal annealing (CTA) and rapid thermal annealing (RTA) in air, oxygen and nitrogen atmospheres to better understand, control and optimize these properties. The dielectric constant (varepsilon) and dissipation factor (tan delta) values, at a frequency of 100 kHz, for film crystallized in air by CTA process, were 358 and 0.039, respectively. Considering the same frequency for film crystallized in air by RTA, these values were 611 and 0.026, respectively. The different dielectric values were justified by a space-charge or interfacial polarization in films, often characterized as Maxwell-Wagner type. This effect was also responsible to dispersion at frequencies above 1 MHz in film crystallized in air by CTA process and film crystallized by RTA in oxygen atmosphere. The film crystallized by RTA under nitrogen atmosphere presented an evident dispersion at frequencies around 100 Hz, characterized by an increase in both varepsilon and tan delta. This dispersion was attributed to conductivity effects. The remanent polarization (Pr) and coercive field (Ec) were also obtained for all films. Films obtained from RTA in air presented higher Pr (17.8 muC cm-2) than film crystallized from CTA (7.8 muC cm-2). As a function of the crystallization atmospheres, films crystallized by RTA in air and nitrogen presented essentially the same Pr values (around 18 muC cm-2) but the Pr (3.9 muC cm-2) obtained from film crystallized under oxygen atmosphere was profoundly influenced.

  9. 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.

  10. Local Viscoelastic Properties of Live Cells Investigated Using Dynamic and Quasi-Static Atomic Force Microscopy Methods

    PubMed Central

    Cartagena, Alexander; Raman, Arvind

    2014-01-01

    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 invitro 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. PMID:24606928

  11. 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. PMID:24606928

  12. Grain and grain boundary effects on the frequency and temperature dependent dielectric properties of cobalt ferrite-hafnium composites

    NASA Astrophysics Data System (ADS)

    Kolekar, Y. D.; Sanchez, L.; Rubio, E. J.; Ramana, C. V.

    2014-04-01

    We report on the frequency (f=20 Hz-1 MHz) and temperature (T=300-973 K) dependent dielectric properties of hafnium (Hf) incorporated cobalt ferrite (CoF2-xHfxO4 (CFO-Hf); x=0.00-0.20). The dielectric constant (?') 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 ?-T (>450 K) variation. Correspondingly, electrical responses in impedance formalism are attributed to the grain and grain-boundary effects which also accounts for the observed two dielectric-relaxations. The results demonstrate that the dielectric phenomena in CFO-Hf can be tailored by tuning Hf-concentration.

  13. Effect of cation disorder on structural, magnetic and dielectric properties of La2MnCoO6 double perovskite.

    PubMed

    Barn-Gonzlez, A J; Frontera, C; Garca-Muoz, J L; Rivas-Murias, B; Blasco, J

    2011-12-14

    The origin of dielectric anomalies and magnetodielectric response of La(2)MnCoO(6) has been investigated by means of ultra-high resolution synchrotron x-ray powder diffraction, neutron powder diffraction, resistivity, magnetization and dielectric measurements. The study has been performed on two different bulk samples presenting different degrees of Mn/Co order: 95 and 74%. Beside the well-known influence on magnetic properties, our results show that the main effect of disorder lies on the electrical resistivity. Bond distances clearly show Mn(4+)/Co(2+) valence states in the well-ordered sample, while for the disordered one this picture still holds. AC resistivity data show dielectric anomalies and a small magnetodielectric effect, but impedance complex plane analyses prove that these phenomena appear at the frequency-temperature region where extrinsic effects dominate the dielectric response. PMID:22107735

  14. 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. PMID:17677991

  15. Dipolar Correlations and the Dielectric Permittivity of Water

    NASA Astrophysics Data System (ADS)

    Sharma, Manu; Resta, Raffaele; Car, Roberto

    2007-06-01

    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 Kirkwoods 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.

  16. Bone Dielectric Property Variation as a Function of Mineralization at Microwave Frequencies

    PubMed Central

    Meaney, Paul M.; Zhou, Tian; Goodwin, Douglas; Golnabi, Amir; Attardo, Elia A.; Paulsen, Keith D.

    2012-01-01

    A critical need exists for new imaging tools to more accurately characterize bone quality beyond the conventional modalities of dual energy X-ray absorptiometry (DXA), ultrasound speed of sound, and broadband attenuation measurements. In this paper we investigate the microwave dielectric properties of ex vivo trabecular bone with respect to bulk density measures. We exploit a variation in our tomographic imaging system in conjunction with a new soft prior regularization scheme that allows us to accurately recover the dielectric properties of small, regularly shaped and previously spatially defined volumes. We studied six excised porcine bone samples from which we extracted cylindrically shaped trabecular specimens from the femoral heads and carefully demarrowed each preparation. The samples were subsequently treated in an acid bath to incrementally remove volumes of hydroxyapatite, and we tested them with both the microwave measurement system and a micro-CT scanner. The measurements were performed at five density levels for each sample. The results show a strong correlation between both the permittivity and conductivity and bone volume fraction and suggest that microwave imaging may be a good candidate for evaluating overall bone health. PMID:22577365

  17. 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.

  18. 160 MeV Ni12+ ion irradiation effects on the dielectric properties of polyaniline nanotubes

    NASA Astrophysics Data System (ADS)

    Hazarika, J.; Nath, Chandrani; Kumar, A.

    2012-10-01

    We report on the dielectric properties and a.c. conductivity studies of CSA doped polyaniline nanotubes. Nanotubes of 47-100 nm diameter, were synthesized by the self-assembly method and irradiated using Ni12+ ions of 160 MeV energy with fluences of 1 1010, 5 1010, 1 1011 and 3 1011 ions/cm2. X-ray diffraction studies reveal an increase in the degree of crystallinity and consequently, the extent of order of the nanotubes with increasing fluence, but show a lower degree of crystallinity at higher fluence. The decrease in d-spacing for the (100) reflections with fluence is ascribed to the decrease in the tilt angle of the aligned polymer chains. A significant change was seen after irradiation in dielectric and electrical properties which may be correlated with the increased carrier concentration and structural modifications in the polymer films. The surface conductivity of films increases with increasing fluence, which also decreases at higher fluence. The a.c. conduction mechanism for the nanotubes could be explained in terms of correlated barrier hopping model. The existence of polarons as the major charge carriers in the present nanotube system was confirmed by the low values of polaron binding energy, found to decrease with fluence. The hopping distance increases with fluence indicating that the hopping probability increases with fluence.

  19. 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.

  20. Structural and Interfacial Effects on the Dielectric Properties of PVDF and its Composites for Energy Storage

    NASA Astrophysics Data System (ADS)

    Jones, Jennifer; Mayo, Anthony; Zhu, Lei; Tolk, Norman; Mu, Richard

    2014-03-01

    High energy density capacitors based on dielectric polymers are a focus of increasing research effort motivated by the possibility to realize compact and flexible energy storage devices. Multilayered ferroelectric polyvinylidene fluoride (PVDF) systems are fabricated using enabling technology in co-extrusion for increased energy storage efficiency. These micro- and nano-layered polymeric systems result in much improved device performance and a three-time enhancement of capacitive electrical energy density has been demonstrated. PVDF thin film nanocomposites with ZnO nanofillers have also been fabricated and evaluated for further enhancement of energy density storage. To understand the physics of why these multilayered and nanocomposite systems perform better than single layer PVDF we are developing characterization techniques using confocal second harmonic generation (SHG), electric field induced second harmonic (EFISH) and Raman laser spectroscopy. Our results have shown that the combination of Raman and SHG is a very sensitive, non-destructive and versatile technique that can be used to study the ferroelectric and structural properties of these systems. The addition of the EFISH technique allows the interrogation of structural and dielectric properties within individual layers and at the interfaces.

  1. Structural, Dielectric, FT-IR and Complex Impedance Properties of Cobalt Ferrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hashim, Mohd.; Alimuddin, Alimuddin; Ali, Sikander; Kumar, Shalendra; Kumar, Ravi

    2011-11-01

    Cobalt ferrite nanoparticles having the general formula CoFe2-xCuxO4 (0.0 ? x ? 0.5) were prepared by sol-gel method and characterized by using X-Ray diffraction (XRD), scanning electron microscopy (SEM ), Fourier transform infrared spectroscopy (FTIR), dielectric and impedance spectroscopy measurements. Confirmation of the single phase cubic spinel structure was made by using X-ray diffractometer. Lattice parameter `a' is found to decrease with increasing the doping contents. Debye- Scherer formula was used for finding the particle size and found in the range 30-45 nm. Morphological analysis was made by scanning electron microscopy which shows agglomerated flakes of particles having large pores on the surface. FT-IR spectra show two absorption bands assigned to the tetrahedral and octahedral complexes in the frequency range 400-600 cm-1. The variation of dielectric properties ?', ?, tan? with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization. Impedance spectroscopy technique has been used to understand the conduction mechanism and to study the effect of grain and grain boundary on the electrical properties of the Cu doped CoFe2O4 ferrites.

  2. Optical properties of dielectric films dispersed with metal nanoparticles and applications to optically functional materials

    NASA Astrophysics Data System (ADS)

    Wakaki, Moriaki; Yokoyama, Eisuke

    2010-12-01

    Nanoparticles of noble metals exhibit variety of colors in the visible light region due to a surface plasmon resonance. The size-induced properties of nanoparticles enable addition of flexibility to existing systems in many areas. To design a material with desired electrical and optical properties is the aim in many composite materials. In this paper, we report the preparation and characterization of silver nanoparticles in SiO2, TiO2 and ZrO2 films and gold nanoparticles in TiO2 and ZrO2 films. To analyze the dielectric characteristic of the metal-dielectric nanocomposite film, three kinds of matrices with a different refractive index were compared. Titanium dioxide (TiO2) is one of the most promising photocatalysts and actively used in various practical applications. However, only a narrow band in the ultraviolet region of solar light, about 3-4%, is available for photocatalytic reaction. Therefore, the development of TiO2 photocatalysts with higher photoelectric conversion efficiency for visible light is required. Plasmon-induced photocatalytic activity in the ultraviolet and visible light region was studied for the TiO2 thin film dispersed with gold nanoparticles. Photocatalytic activity of Au/TiO2 film was analyzed by degradation of stearic acid, and compared with non-doped TiO2film.

  3. 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.

  4. 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.

  5. Static axial stretching enhances the mechanical properties and cellular responses of fibrin microthreads.

    PubMed

    Grasman, Jonathan M; Pumphrey, Laura M; Dunphy, Melissa; Perez-Rogers, James; Pins, George D

    2014-10-01

    Fibrin microthreads are a platform technology that can be used for a variety of applications, and therefore the mechanical requirements of these microthreads differ for each tissue or device application. To develop biopolymer microthreads with tunable mechanical properties, we analyzed fibrin microthread processing conditions to strengthen the scaffold materials without the use of exogenous crosslinking agents. Fibrin microthreads were extruded, dried, rehydrated and static axially stretched 0-200% of their original lengths; then the mechanical and structural properties of the microthreads were assessed. Stretching significantly increased the tensile strength of microthreads 3-fold, yielding scaffolds with tensile strengths and stiffnesses that equaled or exceeded values reported previously for carbodiimide crosslinked threads without affecting intrinsic material properties such as strain hardening or Poisson's ratio. Interestingly, these stretching conditions did not affect the rate of proteolytic degradation of the threads. The swelling ratios of stretched microthreads decreased, and scanning electron micrographs showed increases in grooved topography with increased stretch, suggesting that stretching may increase the fibrillar alignment of fibrin fibrils. The average cell alignment with respect to the longitudinal axis of the microthreads increased 2-fold with increased stretch, further supporting the hypothesis that stretching microthreads increases the alignment of fibrin fibrils on the surfaces of the scaffolds. Together, these data suggest that stretching fibrin microthreads generates stronger materials without affecting their proteolytic stability, making stretched microthreads ideal for implantable scaffolds that require short degradation times and large initial loading properties. Further modifications to stretched microthreads, such as carbodiimide crosslinking, could generate microthreads to direct cell orientation and align tissue deposition, with additional resistance to degradation for use as a long-term scaffold for tissue regeneration. PMID:24954911

  6. Dynamic and quasi-static mechanical properties of iron-nickel alloy honeycomb

    NASA Astrophysics Data System (ADS)

    Clark, Justin L.

    Several metal honeycombs, termed Linear Cellular Alloys (LCAs), were fabricated via a paste extrusion process and thermal treatment. Two Fe-Ni based alloy compositions were evaluated. Maraging steel and Super Invar were chosen for their compatibility with the process and the wide range of properties they afforded. Cell wall material was characterized and compared to wrought alloy specifications. The bulk alloy was found to compare well with the more conventionally produced wrought product when porosity was taken into account. The presence of extrusion defects and raw material impurities were shown to degrade properties with respect to wrought alloys. The performance of LCAs was investigated for several alloys and cell morphologies. The results showed that out-of-plane properties exceeded model predictions and in-plane properties fell short due to missing cell walls and similar defects. Strength was shown to outperform several existing cellular metals by as much as an order of magnitude in some instances. Energy absorption of these materials was shown to exceed 150 J/cc at strains of 50% for high strength alloys. Finally, the suitability of LCAs as an energetic capsule was investigated. The investigation found that the LCAs added significant static strength and as much as three to five times improvement in the dynamic strength of the system. More importantly, it was shown that the pressures achieved with the LCA capsule were significantly higher than the energetic material could achieve alone. High pressures, approaching 3 GPa, coupled with the fragmentation of the capsule during impact increased the likelihood of initiation and propagation of the energetic reaction. This multi-functional aspect of the LCA makes it a suitable capsule material.

  7. Static Axial Stretching Enhances the Mechanical Properties and Cellular Responses of Fibrin Microthreads

    PubMed Central

    Grasman, Jonathan M.; Pumphrey, Laura; Dunphy, Melissa; Perez-Rogers, James; Pins, George D.

    2014-01-01

    Fibrin microthreads are a platform technology that can be used for a variety of applications, and therefore the mechanical requirements of these microthreads differ for each tissue or device application. To develop biopolymer microthreads with tunable mechanical properties, we analyzed fibrin microthread processing conditions to strengthen the scaffold materials without the use of exogenous crosslinking agents. Fibrin microthreads were extruded, dried, rehydrated, and static axially stretched 0-200% of their original lengths; then the mechanical and structural properties of the microthreads were assessed. Stretching significantly increased the tensile strength of microthreads threefold, yielding scaffolds with tensile strengths and stiffnesses that equaled or exceeded values reported previously for carbodiimide crosslinked threads without affecting intrinsic material properties such as strain hardening or Poisson's ratio. Interestingly, these stretching conditions did not affect the rate of proteolytic degradation of the threads. The swelling ratios of stretched microthreads decreased, and scanning electron micrographs showed increases in grooved topography with increased stretch, suggesting that stretching may increase the fibrillar alignment of fibrin fibrils. The average cell alignment with respect to the longitudinal axis of the microthreads increased twofold with increased stretch, further supporting the hypothesis that stretching microthreads increases the alignment of fibrin fibrils on the surfaces of the scaffolds. Together, these data suggest that stretching fibrin microthreads generates stronger materials without affecting their proteolytic stability, making stretched microthreads ideal for implantable scaffolds that require short degradation times and large initial loading properties. Further modifications to stretched microthreads, such as carbodiimide crosslinking, could generate microthreads to direct cell orientation and align tissue deposition, with additional resistance to degradation for use as a long-term scaffold for tissue regeneration. PMID:24954911

  8. Preparation and electrical properties of (Zr,Sn)TiO{sub 4} dielectric thin films by laser ablation

    SciTech Connect

    Nakagawara, Osamu; Toyota, Yuji; Kobayashi, Masato; Yoshino, Yukio; Katayama, Yuzo; Tabata, Hitoshi; Kawai, Tomoji

    1996-11-01

    (Zr,Sn)TiO{sub 4} is considered as a promising dielectric material for microwave devices owing to the temperature stability of capacitance and excellent microwave properties. Preferential (111)-oriented (Zr,Sn)TiO{sub 4} thin film was obtained by an ArF laser ablation. Properties of the crystallized film were as follows; the temperature coefficient of capacitance TCC was 17.6 ppm/C at 3 MHz and the dielectric constant {var_epsilon}{sub r}, 38 in the microwave range of 1GHZ--10GHz. It has turned out that the crystallization of this material is quite effective for improving dielectrical properties. Surface morphologies were observed by atomic force microscope (AFM). Grains grew on the crystallized film at 1 {micro}m x 1 {micro}m size.

  9. Electronic Properties and Persistent Spin Currents of Nanospring under Static Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kosugi, Taichi

    2013-03-01

    Relativistic electronic properties of a nanospring under a static magnetic field are theoretically investigated in the present study. The wave equation accounting for the spin--orbit interaction is derived for the nanospring as a special case of the Pauli equation for a spin-1/2 particle confined to a curved surface under an electromagnetic field. We define the helical momentum operator and show that it commutes with the Hamiltonian owing to the helical geometry of the nanospring. The energy eigenstates are hence also the eigenstates of the helical momentum. We solve the equation numerically to obtain the surface wave functions and the energy spectra. The electronic properties are systematically examined by varying the parameters that characterize the system. It is demonstrated that either the nonzero spin--orbit interaction or the nonzero external magnetic field suffices for the occurrence of the persistent spin current on the nanospring. Two different mechanisms are shown to generate the persistent spin current. One employs the spin--orbit interaction coming from the local inversion asymmetry on the surface, while the other employs the curvature coupling with the external magnetic field.

  10. Theoretical study of static magnetic properties for the chiral and reconstructed graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Park, Suk-Young; Rhim, Jun-Won; Moon, Kyungsun

    2013-03-01

    Recent theoretical study of the chiral graphene nanoribbons(CGNR) has demonstrated the magnetic ordering of the edge states below a certain chiral angle1. Based on the Hubbard model for the CGNR, we study the static properties of the magnetic edge states such as the intra-edge and inter-edge spin stiffness, which are the two crucial parameters to control the thermodynamics of the effective magnetic hamiltonian. For the systematic study of the anti-ferromagnetic inter-edge spin correlations, we calculate the inter-edge spin stiffness as a function of ribbon width and transverse electric field. We also attempt to calculate the electronic and magnetic properties for the other edge geometries such as a reconstructed edge geometry, which has been experimentally confirmed as an edge shape other than zigzag or armchair nanoribbon2 1. Oleg V. Yazyev, Rodrigo B. Capaz, and Steven G. Louie, Phys. Rev. B 84, 115406 (2011). 2. Pekka Koskinen, Sami Malola, and Hannu Hakkinen, Phys. Rev. B 80, 073401 (2009). This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2012R1A1A2006927).

  11. Synthesis and dielectric properties of modified potassium sodium niobate solid solutions

    NASA Astrophysics Data System (ADS)

    Smeltere, I.; Antonova, M.; Kalvane, A.; Bormanis, K.; Livinsh, M.

    2012-05-01

    In the present work processing microstructure and dielectric properties of lead free KNN based ceramics have been studied. Compositions with a stoichiometric formula (1 - x)(K0.5Na0.5)Nb1 - y Sb y O3- xBaTiO3 ( x = 0.01, 0.02, 0.04; y = 0.04, 0.07) were produced by solid state sintering method. The addition of manganese oxide MnO2 after synthesis promoted the sintering and densification of ceramic samples. The influence of BaTiO3 on the microstructure, density and electrical properties was investigated. X-ray diffraction analysis confirmed that obtained samples had a pure perovskite structure with no traces of secondary phase. Phase transition peak at T c is broad indicating the diffuse phase transition.

  12. Tunable dielectric properties of KTaO3 single crystals in the terahertz range

    NASA Astrophysics Data System (ADS)

    Skoromets, V.; Kadlec, C.; N?mec, H.; Fattakhova-Rohlfing, D.; Kuel, P.

    2016-02-01

    Electric-field tunability of the dielectric properties of potassium tantalate single crystal was studied by terahertz spectroscopy in a broad temperature range (40250?K). Complex-valued terahertz transmission spectra of samples were measured with an external electric field perpendicular to the sample surface and parallel to the terahertz wave-vector. We found that the ferroelectric soft mode hardening is fully responsible for the observed electric-field-induced changes in the spectra and no signature of a central mode was detected. We determined the anharmonic properties of the soft-mode potential in the mean field approximation. The observed behavior was compared with that previously reported for SrTiO3 single crystals.

  13. 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. PMID:26604422

  14. Tunable optical properties of a two-dimensional square-lattice superconductor-dielectric Bragg reflector.

    PubMed

    Lee, Huang-Ming; Shyu, Jia-Hong; Horng, Lance; Wu, Jong-Ching

    2011-07-20

    We numerically analyze the optical properties of a two-dimensional (2D) superconducting Bragg reflector (SBR) using the finite element method in conjunction with a two-fluid model. It is found that the wavelength-dependent reflectance spectra of the proposed 2D SBR are strongly dependent on the polarizations of incident light and can be parametrically tuned by the system temperature and the geometric parameters of embedded dielectric rods. Taking advantage of the dispersive superconductor with its zero-refractive index characteristic and the structural periodicity of the proposed superconducting structure, narrow passband filters can be generated near the threshold wavelength. Furthermore, the narrow passband features of the 2D SBR are found to be sustained up to a very large angle of incidence. The extraordinary optical properties imply that the proposed 2D SBR may be applied to the design of an omnidirectional narrowband transmission filter. PMID:21772367

  15. 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 not yet achievable, we expect that the electron and hole will separate in different layers, with potentially measurable effects. Comparisons are made to optical and electrical measurements on these structures, showing good agreement. Next, we explore how shape can impact nanocrystal properties, on top of their intrinsic size or material dependence. By looking at cylindrically shaped nanocrystals, called "nanorods," with aspect ratios ? 10, we explore how having a slightly extended dimension can impact nanocrystal properties. A model is developed to explain their electronic structure, with surprising results. Foremost is that along the extended dimension, electrons and holes are strongly electrically bound, not with each other directly, but with their image charges in the outer host dielectric material. Nevertheless, the energy spectra of the excitons remains nearly host-independent, with the effects of this strong binding instead seen in a redistribution of transition oscillator strength. To test the model, we develop a novel synthesis of high quality PbSe nanorods, and find good agreement with measured absorption spectra. Finally, we present a study on the transfer of charge into and out of a nanocrystal. By modeling the charge transfer process within a modified Marcus Theory, we isolate the relevant parameters that can be used to control the rate of transfer. Primary among these are the values of the quantum dot energy levels, and the electrostatic charging energy of the acceptor. We vary the former by changing the quantum dot size, and the latter by varying the host dielectric constant. To test the model, we chemically bind a small molecular acceptor molecule to the surface of PbS nanocrystals and use transient fluorescence to measure the rate of charge transfer. Both the dependence of the rate on quantum dot size and host dielectric constant show good agreement with the model.

  16. Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

    NASA Astrophysics Data System (ADS)

    Li, Jinglei; Li, Fei; Zhuang, Yongyong; Jin, Li; Wang, Linghang; Wei, Xiaoyong; Xu, Zhuo; Zhang, Shujun

    2014-08-01

    The (Nb + In) co-doped TiO2 ceramics recently attracted considerable attention due to their colossal dielectric permittivity (CP) (˜100,000) and low dielectric loss (˜0.05). In this research, the 0.5 mol. % In-only, 0.5 mol. % Nb-only, and 0.5-7 mol. % (Nb + In) co-doped TiO2 ceramics were synthesized by standard conventional solid-state reaction method. Microstructure studies showed that all samples were in pure rutile phase. The Nb and In ions were homogeneously distributed in the grain and grain boundary. Impedance spectroscopy and I-V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The high conductivity of grain was associated with the reduction of Ti4+ ions to Ti3+ ions, while the migration of oxygen vacancy may account for the conductivity of grain boundary. The effects of annealing treatment and bias filed on electrical properties were investigated for co-doped TiO2 ceramics, where the electric behaviors of samples were found to be susceptible to the annealing treatment and bias field. The internal-barrier-layer-capacitance mechanism was used to explain the CP phenomenon, the effect of annealing treatment and nonlinear I-V behavior for co-doped rutile TiO2 ceramics. Compared with CaCu3Ti4O12 ceramics, the high activation energy of co-doped rutile TiO2 (3.05 eV for grain boundary) was thought to be responsible for the low dielectric loss.

  17. Optical and electrical properties of plasma-oxidation derived HfO 2 gate dielectric films

    NASA Astrophysics Data System (ADS)

    He, G.; Zhu, L. Q.; Liu, M.; Fang, Q.; Zhang, L. D.

    2007-01-01

    High- k gate dielectric HfO 2 thin films have been deposited on Si(1 0 0) by using plasma oxidation of sputtered metallic Hf thin films. The optical and electrical properties in relation to postdeposition annealing temperatures are investigated by spectroscopic ellipsometry (SE) and capacitance-voltage ( C- V) characteristics in detail. X-ray diffraction (XRD) measurement shows that the as-deposited HfO 2 films are basically amorphous. Based on a parameterized Tauc-Lorentz dispersion mode, excellent agreement has been found between the experimental and the simulated spectra, and the optical constants of the as-deposited and annealed films related to the annealing temperature are systematically extracted. Increases in the refractive index n and extinction coefficient k, with increasing annealing temperature are observed due to the formation of more closely packed thin films and the enhancement of scattering effect in the targeted HfO 2 film. Change of the complex dielectric function and reduction of optical band gap with an increase in annealing temperature are discussed. The extracted direct band gap related to the structure varies from 5.77, 5.65, and 5.56 eV for the as-deposited and annealed thin films at 700 and 800 C, respectively. It has been found from the C- V measurement the decrease of accumulation capacitance values upon annealing, which can be contributed to the growth of the interfacial layer with lower dielectric constant upon postannealing. The flat-band voltage shifts negatively due to positive charge generated during postannealing.

  18. 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.

  19. Structural, electrical and dielectric properties of spinel nickel ferrite prepared by soft mechanochemical synthesis

    SciTech Connect

    Lazarevi?, Zorica .; Jovaleki?, ?edomir; Sekuli?, Dalibor L.; Milutinovi?, Aleksandra; Balo, Sebastian; Slankamenac, Milo; Rom?evi?, Neboja .

    2013-10-15

    Graphical abstract: - Highlights: Sintered NiFe{sub 2}O{sub 4} was prepared by a soft mechanochemical route from mixture powders. XRD and Raman measurements indicate that the prepared samples have spinel structure. The activation energy ?E are 0.653 and 0.452 eV for NiFe{sub 2}O{sub 4} samples. Ferrite from Ni(OH){sub 2}/Fe{sub 2}O{sub 3} has lower DC conductivity than from Ni(OH){sub 2}/Fe(OH){sub 3} powders. The values of dielectric constant of samples NiFe{sub 2}O{sub 4} are 70 and 200, respectively. - Abstract: Nickel ferrite, NiFe{sub 2}O{sub 4} was prepared by a soft mechanochemical route from a mixture of (1) Ni(OH){sub 2} and ?-Fe{sub 2}O{sub 3} and (2) Ni(OH){sub 2} and Fe(OH){sub 3} powders in a planetary ball mill for 25 h. The powder samples were sintered at 1100 C for 2 h and were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Impedance spectroscopy techniques were used to study the effect of grain and grain boundary on the electrical properties of the prepared samples. A difference in dielectric constant (?) and dielectric loss tangent (tan ?) of NiFe{sub 2}O{sub 4} samples obtained by the same methods but starting from different initial components was observed.

  20. Room temperature structure vibrational and dielectric properties of Ho modified YMnO3

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Sharma, Poorva; Kumar, Ashwini

    2015-07-01

    The structural, vibrational, and dielectric properties of bulk Ho-doped Y1-xHoxMnO3 (x = 0, 0.03, 0.05) solids prepared by standard solid-state reaction route were investigated. X-ray diffraction (XRD) patterns confirmed the hexagonal P63cm structure of Y1-xHoxMnO3 (x = 0.0, 0.03, 0.05) ceramics. Rietveld refinements of XRD data revealed that the doping ions led to unit cell contraction in three directions due to nearly equal ionic radii of Ho3+ ion (0.901 Å) substituted at the Y-site ion. The grain size of Ho-doped solids varied from 5 to 10 μm. For pristine h-YMnO3, the experimentally observed Raman scattering lines at around 151, 305, 460, and 682 cm-1 are of A1 symmetry, those at 410 cm-1 are of E1 symmetry, and the lines at 139 and 219 cm-1 are of E2 symmetry. Another interesting observation is the existence of an A1 line at 682 cm-1 and an E1 line at about 410 cm-1 which are much stronger than the remaining lines of A1 and E1 symmetries, respectively. The high value of dielectric constant and dielectric loss tangent at low frequency is explained by space charge polarization and the saturation in the high-frequency region is due to the electric dipoles not being in pace with the frequency of the applied electric field.

  1. Structural, dielectric and magnetic properties of Gd substituted manganese ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Murugesan, C.; Sathyamoorthy, B.; Chandrasekaran, G.

    2015-08-01

    Gd3+ ion-substituted manganese ferrite nanoparticles with the chemical formula MnGdxFe2-xO4 (x = 0.0, 0.05, and 0.1) were synthesized by sol-gel auto combustion method. Thermal stability of the as-prepared sample was analyzed using thermo gravimetric and differential thermal analysis (TG-DTA) and the result reveals that the prepared sample is thermally stable above 300 °C. Structural and morphology studies were performed using powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Indexed PXRD patterns confirm the formation of pure cubic spinel structure. The average crystallite sizes calculated using Sherrer’s formula decreased from 47 nm to 32 nm and lattice constant was enhanced from 8.407 Å to 8.432 Å. The FTIR spectrum of manganese ferrite shows a high frequency vibrational band at 564 cm-1 assigned to tetrahedral site and a low frequency vibrational band at 450 cm-1 assigned to octahedral site which are shifted to 556 cm-1 and 439 cm-1 for Gd3+ substitution and confirm the incorporation of Gd3+ into manganese ferrite. SEM analysis shows the presence of agglomerated spherical shaped particles at the surface. Room temperature dielectric and magnetic properties were studied using broadband dielectric spectroscopy (BDS) and vibrating sample magnetometry (VSM). Frequency dependent dielectric constant, ac conductivity and tan delta were found to increase with Gd3+ ion substitution. The measured values of saturation magnetization decrease from 46.6 emu g-1 to 41 emu g-1 with increase in Gd3+ concentration and coercivity decreases from 179.5 Oe to 143 Oe.

  2. Dielectric properties of (CuO, CaO2, and BaO)y/CuTl-1223 composites

    NASA Astrophysics Data System (ADS)

    Mumtaz, M.; Kamran, M.; Nadeem, K.; Jabbar, Abdul; Khan, Nawazish A.; Saleem, Abida; Tajammul Hussain, S.; Kamran, M.

    2013-07-01

    We synthesized (CuO, CaO2, and BaO)y/Cu0.5Tl0.5Ba2Ca2Cu3O10-? (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized them by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties, such as real and imaginary parts of the dielectric constant, dielectric loss, and ac-conductivity of these composites were studied by capacitance and conductance measurements as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). X-ray diffraction analysis reveals that the characteristic behavior of the superconductor phase and the structure of Cu0.5Tl0.5Ba2Ca2Cu3O10-? are nearly undisturbed by doping with nanoparticles. Scanning electron microscopy images show the improvement in the intergranular linking between the superconducting grains occurring with increasing nanoparticle concentration. Microcracks are healed up with these nanoparticles, and superconducting volume fraction is also increased. Dielectric properties of these composites strongly depend on the frequency and temperature. Zero resistivity critical temperature and dielectric properties show opposite trends with the addition of nanoparticles to the Cu0.5Tl0.5Ba2Ca2Cu3O10-? superconductor matrix.

  3. Changes in the dielectric properties of ex vivo bovine liver during microwave thermal ablation at 2.45 GHz

    NASA Astrophysics Data System (ADS)

    Lopresto, Vanni; Pinto, Rosanna; Lovisolo, Giorgio A.; Cavagnaro, Marta

    2012-04-01

    In microwave thermal ablation (MTA) therapy, the dielectric properties of the target tissue play an important role in determining the radiation properties of the microwave ablation antenna. In this work, the ex vivo dielectric properties of bovine liver were experimentally characterized as a function of the temperature during MTA at the frequency of 2.45 GHz. The obtained data were compared with measurements performed at the end of the MTA treatment, and considering the heating achieved with a temperature-controlled water bath. Finally, measured data were used to perform a numerical study evaluating the effects of changes in tissue's dielectric properties during the MTA treatment on the radiation properties of a microwave interstitial ablation antenna, as well as on the obtained thermal lesion. Results evidenced a significant decrease of both relative permittivity (about 38%) and electric conductivity (about 33%) in the tissue during treatment as the temperature increased to over 60 °C, with a dramatic drop when the temperature approached 100 °C. Moreover, the numerical study evidenced that changes in tissue's dielectric properties during the MTA treatment affect the distribution of the power absorbed by the tissue (specific absorption rate—SAR, W kg-1) surrounding the microwave interstitial ablation antenna, leading to a peak SAR up to 20% lower, as well as to a thermal lesion up to 8% longer. This work may represent a preliminary step towards the future development of a procedure for MTA treatment planning.

  4. Magnetic, dielectric, and magneto-dielectric properties of rare-earth-substituted Aurivillius phase Bi₆Fe₁.₄Co₀.₆Ti₃O₁₈

    SciTech Connect

    Zuo, X. Z.; Yang, J. Yuan, B.; Tang, X. W.; Zhang, K. J.; Zhu, X. B.; Song, W. H.; Dai, J. M.; Song, D. P.; Sun, Y. P.

    2014-10-21

    We investigate the magnetic, dielectric, and magnetodielectric properties of rare-earth-substituted Aurivillius phase Bi₆Fe₁.₄Co₀.₆Ti₃O₁₈. The room-temperature ferromagnetic behavior is observed in all samples, and the rare-earth-substituted samples exhibit an enhanced magnetization. The weak ferromagnetism can be ascribed to the spin canting of the antiferromagnetic coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. The dielectric loss of all samples exhibits two dielectric relaxation peaks corresponding to two different relaxation mechanisms. One relaxation process with E{sub a}=0.5 eV is related to the hoping process of oxygen vacancies and the other one with E{sub a}=1.6 eV can be ascribed to the intrinsic conduction. The Gd-doped sample exhibits a remarkable magnetodielectric effect (9.4%) at RT implying this Aurivillius phase may be the potential candidate for magnetodielectric applications.

  5. A Time-Domain Reflectometry Method with Variable Needle Pulse Width for Measuring the Dielectric Properties of Materials.

    PubMed

    Wilczek, Andrzej; Szypłowska, Agnieszka; Kafarski, Marcin; Skierucha, Wojciech

    2016-01-01

    Time-domain reflectometry (TDR) methods used for measuring the dielectric properties of materials mostly utilize step or needle electrical pulses of constant amplitudes and shapes. Our novel approach enables determining the dielectric relaxation time of a sample using the analysis of the amplitudes of reflected pulses of two widths, in addition to bulk dielectric permittivity and electrical conductivity commonly obtained by the TDR technique. The method was developed for various values of electrical conductivity and relaxation time using numerical simulations of a five-rod probe placed in a material with complex dielectric permittivity described by the Debye model with an added electrical conductivity term. The characterization of amplitudes of two pulses of selected widths was done with regard to the dielectric parameters of simulated materials. The required probe parameters were obtained solely from numerical simulations. Verification was performed for the probe placed in aqueous KCl solutions with 14 different electrical conductivity values. The determined relaxation time remained roughly constant and independent of electrical conductivity. The obtained electrical conductivity agreed with the reference values. Our results indicate that the relaxation time, dielectric permittivity and electrical conductivity of the tested solutions can be simultaneously determined using a simple analysis of the amplitude and reflection time of two needle pulses of different widths. PMID:26861318

  6. Electroactive Phase Induced Bi4Ti3O12-Poly(Vinylidene Difluoride) Composites with Improved Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Sumit; Paul, Joginder; Chand, Subhash; Raina, K. K.; Kumar, Ravi

    2015-10-01

    Lead-free ceramic-polymer composite films containing Bi4Ti3O12 (BIT) nanocrystals as the active phase and poly(vinylidene difluoride) as the passive matrix were synthesized by spin coating. The films' structural, morphological, and dielectric properties were systemically investigated by varying the weight fraction of BIT. Formation of electroactive ? and ? phases were strongly affected by the presence of BIT nanocrystals. Analysis was performed by Fourier-transform infrared and Raman spectroscopy. Morphological studies confirmed the homogeneous dispersion of BIT particles within the polymer matrix. The composite films had dielectric constants as high as 52.8 and low dielectric loss of 0.1 at 100 Hz when the BIT content was 10 wt.%. We suggest that the enhanced electroactive phase content of the polymer matrix and interfacial polarization may contribute to the improved dielectric performance of these composite films. Dielectric modulus analysis was performed to enable understanding of the dielectric relaxation process. Non-Debye-type relaxation behavior was observed for the composite films at high temperature.

  7. A Time-Domain Reflectometry Method with Variable Needle Pulse Width for Measuring the Dielectric Properties of Materials

    PubMed Central

    Wilczek, Andrzej; Szypłowska, Agnieszka; Kafarski, Marcin; Skierucha, Wojciech

    2016-01-01

    Time-domain reflectometry (TDR) methods used for measuring the dielectric properties of materials mostly utilize step or needle electrical pulses of constant amplitudes and shapes. Our novel approach enables determining the dielectric relaxation time of a sample using the analysis of the amplitudes of reflected pulses of two widths, in addition to bulk dielectric permittivity and electrical conductivity commonly obtained by the TDR technique. The method was developed for various values of electrical conductivity and relaxation time using numerical simulations of a five-rod probe placed in a material with complex dielectric permittivity described by the Debye model with an added electrical conductivity term. The characterization of amplitudes of two pulses of selected widths was done with regard to the dielectric parameters of simulated materials. The required probe parameters were obtained solely from numerical simulations. Verification was performed for the probe placed in aqueous KCl solutions with 14 different electrical conductivity values. The determined relaxation time remained roughly constant and independent of electrical conductivity. The obtained electrical conductivity agreed with the reference values. Our results indicate that the relaxation time, dielectric permittivity and electrical conductivity of the tested solutions can be simultaneously determined using a simple analysis of the amplitude and reflection time of two needle pulses of different widths. PMID:26861318

  8. Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

    NASA Astrophysics Data System (ADS)

    Pettinelli, Elena; Cosciotti, Barbara; Di Paolo, Federico; Lauro, Sebastian Emanuel; Mattei, Elisabetta; Orosei, Roberto; Vannaroni, Giuliano

    2015-09-01

    The first European mission dedicated to the exploration of Jupiter and its icy moons (JUpiter ICy moons Explorer—JUICE) will be launched in 2022 and will reach its final destination in 2030. The main goals of this mission are to understand the internal structure of the icy crusts of three Galilean satellites (Europa, Ganymede, and Callisto) and, ultimately, to detect Europa's subsurface ocean, which is believed to be the closest to the surface among those hypothesized to exist on these moons. JUICE will be equipped with the 9 MHz subsurface-penetrating radar RIME (Radar for Icy Moon Exploration), which is designed to image the ice down to a depth of 9 km. Moreover, a parallel mission to Europa, which will host onboard REASON (Radar for Europa Assessment and Sounding: Ocean to Near-surface) equipped with 9MHz and 60MHz antennas, has been recently approved by NASA. The success of these experiments strongly relies on the accurate prediction of the radar performance and on the optimal processing and interpretation of radar echoes that, in turn, depend on the dielectric properties of the materials composing the icy satellite crusts. In the present review we report a complete range of potential ice types that may occur on these icy satellites to understand how they may affect the results of the proposed missions. First, we discuss the experimental results on pure and doped water ice in the framework of the Jaccard theory, highlighting the critical aspects in terms of a lack of standard laboratory procedures and inconsistency in data interpretation. We then describe the dielectric behavior of extraterrestrial ice analogs like hydrates and icy mixtures, carbon dioxide ice and ammonia ice. Building on this review, we have selected the most suitable data to compute dielectric attenuation, velocity, vertical resolution, and reflection coefficients for such icy moon environments, with the final goal being to estimate the potential capabilities of the radar missions as a function of the frequency and temperature ranges of interest for the subsurface sounders. We present the different subsurface scenarios and associated radar signal attenuation models that have been proposed so far to simulate the structure of the crust of Europa and discuss the physical and geological nature of various dielectric targets potentially detectable with RIME. Finally, we briefly highlight several unresolved issues that should be addressed, in near future, to improve our capability to produce realistic electromagnetic models of icy moon crusts. The present review is of interest for the geophysical exploration of all solar system bodies, including the Earth, where ice can be present at the surface or at relatively shallow depths.

  9. Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites

    SciTech Connect

    Lakshmi, Mohana; Faisal, Muhammad; Roy, Aashish S.; Khasim, Syed; Department of Physics, University of Tabuk-71491 ; Sajjan, K. C.; Revanasiddappa, M.

    2013-11-15

    Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz – 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

  10. Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites

    SciTech Connect

    Lakshmi, Mohana; Faisal, Muhammad; Roy, Aashish S.; Khasim, Syed; Department of Physics, University of Tabuk-71491 ; Sajjan, K. C.; Revanasiddappa, M.

    2013-11-15

    Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

  11. Influence of SBN70 concentration in PVDF on dielectric and pyroelectric properties of nanocomposites

    NASA Astrophysics Data System (ADS)

    Olszowy, M.; Nogas-?wikiel, E.; ?wikiel, K.

    2011-04-01

    Strontium barium niobate Sr0.7Ba0.3Nb2O6 (SBN70) ceramic nanopowder was dispersed in a poly(vinylidene fluoride) (PVDF) matrix providing a composite with 0-3 connectivity. The SBN70-PVDF composites samples were obtained from ceramic and polymer powders by hot-pressing method. The SBN70 ceramic was prepared by a sol-gel method. The composite surface images were obtained by AFM tapping mode (NT-NDT Solver P47). The dielectric response of the composites was studied in the frequency range 100 Hz - 1 MHz and the temperature range 100 - 430 K. The dielectric properties of the composites display features originated from the PVDF polymer modified by those of SBN70 ceramics. The resulting pyroelectric currents were measured using a Keithley 6517 A electrometer and were used to calculate the pyroelectric coefficient p. The p of poled composites increases from ~24 ?C/m2K in pure PVDF to ~40 ?C/m2K in the composites of ? = 0.2 at room temperature.

  12. Dielectric Properties in Polyamides of m-Xylylenediamine and Dicarboxylic Acids

    NASA Astrophysics Data System (ADS)

    Murata, Yukinobu; Tsunashima, Kenji; Koizumi, Naokazu

    1999-09-01

    Dielectric properties were investigated for polyamides consisting of m-xylylenediamine and aliphatic dicarboxylic acids with the number of carbon atoms from 6 to 11, over a frequency range of 25 Hz to 1 MHz, at temperatures from 200 to 400 K. The α relaxation with a relaxation strength of 60 to 80 was observed at temperatures above the glass transition temperature Tg in quenched amorphous samples and was related to the micro-Brownian motion of the molecular chains of these aromatic polyamides. The dipole moment per repeating unit was 9 to 11 D for the α relaxation. The β relaxation observed at temperatures below room temperature exhibited a small relaxation strength, which was attributed to the motion of carbonyl groups with water molecules bound by a hydrogen bond. The space-charge polarization effects took place at high temperatures and low frequencies. The crystallization occurring during the heating process decreased the dielectric constant and loss in the α relaxation and the space-charge polarization.

  13. Structural, magnetic and dielectric properties of polyaniline/MnCoFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Chitra, Palanisamy; Muthusamy, Athianna; Jayaprakash, Rajan

    2015-12-01

    Ferromagnetic PANI containing MnCoFe2O4 nanocomposites were synthesized by in-situ chemical polymerization of aniline incorporated MnCoFe2O4 nanoparticles (20%, 10% w/w of fine powders) with and without ultrasonic treatment. The MnCoFe2O4 nanoparticles were synthesized by auto combustion method. The PANI/MnCoFe2O4 nanocomposites were characterized with Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the resulting PANI/MnCoFe2O4 nanocomposites was confirmed from the TEM and XRD analysis. The structure and morphology of the composites were confirmed by FT-IR spectroscopy, XRD and SEM. In addition, the electrical and magnetic properties of the nanocomposites were investigated. The PANI/MnCoFe2O4 nanocomposites under applied magnetic field exhibited the hysteresis loops of ferromagnetic nature at room temperature. The variation of Dielectric constant, Dielectric loss, and AC conductivity of PANI/MnCoFe2O4 nanocomposites at room temperature as a function of frequency in the range 50 Hz-5 MHz has been studied. Effect of ultrasonication on the PANI/MnCoFe2O4 nanocomposites was also investigated.

  14. Dielectric Property of Silicate-Doped CaBi4Ti4O15 Thin Films

    NASA Astrophysics Data System (ADS)

    Ogawa, Shota; Kondoh, Yohta; Kimura, Junichi; Funakubo, Hiroshi; Uchida, Hiroshi

    2012-09-01

    Thin films of silicate-doped CaBi4Ti4O15 were fabricated to enhance the insulating property of one-axis-oriented CaBi4Ti4O15 films under an applied electric field. The crystalline phase of CaBi4Ti4O15, a type of bismuth layer-structured dielectric (BLSD) compound, was successfully grown on (100)LaNiO3/(111)Pt/TiO2/(100)Si with the preferential orientation of the (001) plane by the addition of bismuth silicate with a nominal composition of Bi12SiO20 up to 1.00%. The crystallographic orientation of the (001)BLSD plane normal to the substrate surface was degraded by excessive bismuth silicate addition above 1.50%. The breakdown electric field was increased by bismuth silicate addition up to 2.00% without the degraded relative dielectric permittivity (?r) of approximately 230. The bismuth silicate could precipitate between the grain boundaries in the CaBi4Ti4O15 films without an interface reaction or a solid solution that enhances the insulating behavior of the BLSD films.

  15. Dielectric property of NiTiO3 doped substituted ortho-chloropolyaniline composites

    NASA Astrophysics Data System (ADS)

    Lakshmi, Mohana; Roy, Aashish S.; Khasim, Syed; Faisal, Muhammad; Sajjan, K. C.; Revanasiddappa, M.

    2013-11-01

    Ortho-chloropolyaniline (OCP)-NiTiO3 composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO3. Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO3 particles. Surface morphology of OCP and OCP-NiTiO3 composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO3 composites have been investigated in the frequency range of 50 Hz - 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO3 particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

  16. Polyethylene nanocomposite dielectrics: Implications of nanofiller orientation on high field properties and energy storage

    NASA Astrophysics Data System (ADS)

    Tomer, V.; Polizos, G.; Randall, C. A.; Manias, E.

    2011-04-01

    Nanocomposite formation, through the incorporation of high aspect ratio nanoparticles, has been proven to enhance the dielectric properties of thermoplastic polymers, when the mitigation of internal charges and the nature of the interfacial regions are properly adjusted. Here, we explore polyethylene/montmorillonite nanocomposites, and we specifically investigate how to impart desirable dielectric behavior through controlled nanoscale texturing, i.e., through control of the spatial arrangement of the high aspect ratio nanofiller platelets. In particular, it is shown that filler alignment can be used to improve the high electric-field breakdown strength and the recoverable energy density. The origins of the improved high field performance were traced to improved charge-trapping by a synergy of nanofillers and polar maleic anhydride (MAH) groupsintroduced via polyethylene-MAH copolymersas templated by the inorganic nanofillers. Further, it is conclusively demonstrated that the alignment of the two-dimensional nanoparticles has a measurable positive effect on the breakdown strength of the materials and, consequently, on the maximum recoverable energy density.

  17. Low temperature dielectric properties of YMn0.95Ru0.05O3

    NASA Astrophysics Data System (ADS)

    Thakur, Rajesh K.; Thakur, Rasna; Okram, G. S.; Kaurav, N.; Gaur, N. K.

    2013-02-01

    The single phase hexagonal YMn0.95Ru0.05O3 compound has been synthesized via solid state reaction method at sintering temperature 1280°C with space group P63cm (25-1079). The detailed dielectric properties were evaluated over broad temperature and frequency ranges. An obvious dielectric relaxation was observed near the antiferromagnetic (AFM) transition temperature. The temperature dependence of the ac resistivity at low frequency infers the semiconducting behavior and favored the variable range hopping conduction model. The obtained experimental data in the temperature range of our study can be described by the equation ρ(T) = ρ0exp[(T*/T)1/4]. The fitting results are used for the calculation of the temperature scale T* ˜ 0.8 × 104 K and finally the density of state at Fermi level N(EF). The activation energy Ea ˜ 0.0314 eV is calculated from the plot, peak temperature of the loss tangent near the magnetic transition region versus frequency using Arrhenius law.

  18. Dielectric and Electrical Properties of BiFeO3-LiTaO3 Systems

    NASA Astrophysics Data System (ADS)

    Mohanty, Suchismita; Choudhary, R. N. P.

    2015-07-01

    Materials of general formula (Bi1- x Li x )(Fe1- x Ta x )O3 ( x = 0.0, 0.5) were prepared from polycrystalline BiFeO3 and LiTaO3 by solid-state reaction. Analysis of the basic structural properties of the materials by room-temperature x-ray diffraction revealed the formation of single-phase tetragonal crystals for (Bi0.5Li0.5)(Fe0.5Ta0.5)O3. Scanning electron micrographs confirmed the polycrystalline nature of the materials. The microstructure of the materials comprised uniformly distributed grains of unequal size. Studies of the temperature-frequency dependence of dielectric did not reveal any dielectric anomaly or phase transition in the temperature range studied. The presence of hysteresis loops at room temperature confirmed the known ferroelectricity of BiFeO3 and (Bi0.5Li0.5)(Fe0.5Ta0.5)O3. Complex impedance spectroscopic analysis revealed the materials had negative temperature coefficient of resistance (NTCR)-type behavior. The electrical conductivity and relaxation characteristics of the materials suggested the presence of a thermally activated process, and their values suggested the materials had similar types of conductivity and relaxation species. The frequency dependence of the ac conductivity obeyed Jonscher's universal power law.

  19. AC-electronic and dielectric properties of semiconducting phthalocyanine compounds: a comparative study

    NASA Astrophysics Data System (ADS)

    Hraibat, Safa'a. M.; M-L. Kitaneh, Rushdi; Abu-Samreh, Mohammad M.; Saleh, Abdelkarim M.

    2013-11-01

    The AC-electronic and dielectric properties of different phthalocyanine films (ZnPc, CuPc, FePc, and H2Pc) were investigated over a wide range of temperature. Both real and imaginary parts of the dielectric constant (ɛ = ɛ1 - iɛ2) were found to be influenced by temperature and frequency. Qualitatively the behavior was the same for those compounds; however, the central atom, film thickness, and the electrode type play an important role in the variation of their values. The relaxation time, τ, was strongly frequency-dependent at all temperatures and low frequencies, while a weak dependency is observed at higher frequencies. The relaxation activation energy was derived from the slopes of the fitted lines of ln τ and the reciprocal of the temperature (1/T). The values of the activation energy were accounted for the hopping process at low temperatures, while a thermally activated conduction process was dominant at higher temperatures. The maximum barrier height, Wm, was found to be temperature and frequency dependent for all phthalocyanine compounds. The value Wm depends greatly on the nature of the central atom and electrode material type. The correlated barrier hopping model was found to be the appropriate mechanism to describe the charge carrier's transport in phthalocyanine films.

  20. Structural, electronic, vibrational, and dielectric properties of LaBGeO{sub 5} from first principles

    SciTech Connect

    Shaltaf, R. Juwhari, H. K.; Hamad, B.; Khalifeh, J.; Rignanese, G.-M.; Gonze, X.

    2014-02-21

    Structural, electronic, vibrational, and dielectric properties of LaBGeO{sub 5} with the stillwellite structure are determined based on ab initio density functional theory. The theoretically relaxed structure is found to agree well with the existing experimental data with a deviation of less than 0.2%. Both the density of states and the electronic band structure are calculated, showing five distinct groups of valence bands. Furthermore, the Born effective charge, the dielectric permittivity tensors, and the vibrational frequencies at the center of the Brillouin zone are all obtained. Compared to existing model calculations, the vibrational frequencies are found in much better agreement with the published experimental infrared and Raman data, with absolute and relative rms values of 6.04 cm{sup −1}, and 1.81%, respectively. Consequently, numerical values for both the parallel and perpendicular components of the permittivity tensor are established as 3.55 and 3.71 (10.34 and 12.28), respectively, for the high-(low-)frequency limit.