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1

Static polarizabilities of dielectric nanoclusters  

SciTech Connect

A cluster consisting of many atoms or molecules may be considered, in some circumstances, to be a single large molecule with a well-defined polarizability. Once the polarizability of such a cluster is known, one can evaluate certain properties--e.g. the cluster's van der Waals interactions, using expressions derived for atoms or molecules. In the present work, we evaluate the static polarizability of a cluster using a microscopic method that is exact within the linear and dipolar approximations. Numerical examples are presented for various shapes and sizes of clusters composed of identical atoms, where the term 'atom' actually refers to a generic constituent, which could be any polarizable entity. The results for the clusters' polarizabilities are compared with those obtained by assuming simple additivity of the constituents' atomic polarizabilities; in many cases, the difference is large, demonstrating the inadequacy of the additivity approximation. Comparison is made (for symmetrical geometries) with results obtained from continuum models of the polarizability. Also, the surface effects due to the nonuniform local field near a surface or edge are shown to be significant.

Kim, Hye-Young; Sofo, Jorge O.; Cole, Milton W. [Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Velegol, Darrell [Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Mukhopadhyay, Gautam [Physics Department, Indian Institute of Technology-Bombay, Powai, Mumbai 400076 (India)

2005-11-15

2

A comparative study of the mesomorphic properties of fluoro-isothiocyanated and fluorinated terphenyl liquid crystals from birefringence, static dielectric permittivity, splay elastic constant and rotational viscosity measurements  

NASA Astrophysics Data System (ADS)

A few recently synthesized fluoro-substituted alkyl terphenyl isothiocyanates as well as three analogous fluoro-substituted terphenyl fluorides were investigated by birefringence, static dielectric permittivity, splay elastic constant and rotational viscosity measurements. The influence of the position of fluoro substituent on the physical properties was investigated. In 3,3? and 3,5-difluoro substitution, although the fluorine atoms point in the same direction, 3,5 substitution leads to higher values of ??, ??, ??, ?n, no and ne than 3,3?-difluoro substitution. The figure of merit values, however, indicate that the 3,5-difluoro substituted isothiocyanated compound is a better component for mixture formulation in comparison with both the 3,3'-difluoro substituted or the 3',3,5-trifluoro substituted compound. Terphenyl isothiocyanated compounds are found to exhibit high birefringence and low rotational viscosity, which are suitable candidates for infrared applications while the fluorinated analogues are for visible applications.

Das, M. K.; Pramanik, A.; Das, B.; Szczuciski, ?.; D?browski, R.

2012-10-01

3

Dielectric properties of a disordered Bose condensate  

Microsoft Academic Search

The frequency-dependent and wave-number-dependent dielectric properties of a condensate of a boson gas with static disorder are evaluated. For weak disorder the condensate is superfluid and the disorder induces a mass enchancement. For strong disorder the condensate is insulating and the static dielectric function is finite. Numerical solutions for the frequency dependence of the density relaxation function and the dynamical

A. Gold

1986-01-01

4

Dielectric properties of aerogels  

SciTech Connect

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

Hrubesh, L.W.; Keene, L.E.; Latorre, V.R. (Chemistry and Material Sciences Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1993-07-01

5

Analogue black holes for light rays in static dielectrics  

NASA Astrophysics Data System (ADS)

Propagation of light in nonlinear materials is here studied in the regime of the geometrical optics. It is shown that a spherically symmetric medium at rest with some specific dielectric properties can be used to produce an exact analogue model for a class of space-times which includes spherically symmetric and static black hole solutions. The optical model here presented can be a useful tool to reproduce in laboratory the behavior of optical null geodesics near a compact object with an observable gravitational Schwarzschild radius.

Bittencourt, E.; De Lorenci, V. A.; Klippert, R.; Novello, M.; Salim, J. M.

2014-07-01

6

Dielectric Properties of Foods.  

National Technical Information Service (NTIS)

The dielectric properties of various types of meats have been determined as a function of frequency and temperature. The specific meat products which have been tested include raw beef, pork, chicken breast, chicken thigh, and turkey rolls. The frequencies...

D. I. C. Wang S. A. Goldblith

1975-01-01

7

Pressure dependence of the static dielectric properties of K(H1-xDx)2PO4 and RbH2PO4  

Microsoft Academic Search

The effects of hydrostatic pressure on the static dielectric constant, ?c, Curie-Weiss constant, C, saturation polarization, Ps, and transition temperature, Ts, of the ferroelectrics K(H1-xDx)2PO4, and RbH2PO4 were investigated. The pressure dependence of Tc is known from earlier work and the present work extends the results to other deuterium concentrations, x; however, the results on C and Ps are largely

G. A. Samara

1978-01-01

8

Static dielectric properties of two nematogenic compounds and their binary mixtures showing induced smectic Ad and re-entrant nematic phases  

Microsoft Academic Search

Static dielectric permittivity measurements on a binary system of 4-cyanophenyl [4' (4''-n-heptylphenyl)] benzoate (referred to as 7CPB) + 4-cyanophenyl 4-nonylbenzoate (referred to as 9.CN) showing both induced smectic Ad and re-entrant nematic phases in a certain concentration range (0.4

Akhileshwar Prasad; Malay Kumar Das

2011-01-01

9

Dielectric properties of mirin in the microwave frequency range  

Microsoft Academic Search

Dielectric properties of mirin (sweet rice wine for seasoning) at the microwave frequency range of 3003000MHz and temperature range of 570C were measured. The effects of temperature, frequency and liquid concentration on dielectric properties were investigated. Dielectric constant and loss factor were related to frequency by using the modified ColeCole equation. The important parameters such as relaxation wavelength, static dielectric

Fumihiko Tanaka; Toshitaka Uchino; Daisuke Hamanaka; Griffiths Gregory Atungulu; Yen-Con Hung

2008-01-01

10

Dielectric Properties Of Nanoferrites  

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

11

Dielectric properties of epoxy nanocomposites  

Microsoft Academic Search

The dielectric properties of epoxy nanocomposites with insulating nano-fillers, viz., TiO2, ZnO and AI2O3 were investigated at low filler concentrations by weight. Epoxy nanocomposite samples with a good dispersion of nanoparticles in the epoxy matrix were prepared and experiments were performed to measure the dielectric permittivity and tan delta (400 Hz-1 MHz), dc volume resistivity and ac dielectric strength. At

Santanu Singha; M. Joy Thomas

2008-01-01

12

Dielectric properties of aerogels  

Microsoft Academic Search

We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 [degree]K using microwave frequencies (2, 10, and 18--40 GHz), for bulk SiO[sub 2]-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel

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

1993-01-01

13

Physical and dielectric properties of pharmaceutical powders  

Microsoft Academic Search

The limited availability of published physical and dielectric property data for pharmaceutical powders hinders the design of processing systems, particularly dryers. In this study, the physical properties (solubility and boiling point) and dielectric properties, in terms of temperature rise, dielectric constant, and dielectric loss factor, of selected pharmaceutical powders were measured. The pharmaceutical actives, paracetamol and aspirin, and selected common

C. M McLoughlin; W. A. M McMinn; T. R. A Magee

2003-01-01

14

DIELECTRIC PROPERTIES OF TERPHENYL MIXTURES  

Microsoft Academic Search

The electrical properties of a mixture of terphenyls were measured. The ; data for dielectric constant at 1, 10. and 100 kc are summarized as a function of ; temperature over the range 375 to 675 deg F. The dipole moments of the terphenyl ; isomers are shown to be approximately zero and the induced polarizability is ; shown to

R. J. Sullivan; F. C. Silvey

1960-01-01

15

Dielectric Properties of Piezoelectric Polyimides  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

16

Dielectric properties of several recently synthesized compounds with various LC phases  

Microsoft Academic Search

Results of dielectric studies (static and dynamic) carried out on several new synthesized substances (in most cases the tolane derivatives) are presented. Apart from pure substances the mixtures of two or more components were also studied. The dielectric properties: tensor components of the permittivity, the dielectric anisotropy, low and high frequency relaxation times are analyzed in view of dipole structures

Stanislaw Urban; Joanna Czub; Roman Dabrowski; B. Gestblom; Horst Kresse

2004-01-01

17

Microstructural and dielectric susceptibility effects on predictions of dielectric properties  

Microsoft Academic Search

In modeling the dielectric properties of inhomogeneous materials, the treatment of the electric field interaction s differentiate the usual modeling formalism and their accuracy. In this paper, we show that the performance of effective medium methods is dependent upon a number of variables - defect concentration, alignment, and the dielectric constant of the material itself. Using our previously developed finite

Kim F. Ferris; Gregory J. Exarhos; Steven M. Risser

1997-01-01

18

Dielectric properties of gel collected from shark electrosensors  

NASA Astrophysics Data System (ADS)

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.

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

2003-03-01

19

Dielectric properties of Jordanian oil shales  

Microsoft Academic Search

Microwave heating has been suggested by various authors as a suitable technology for extraction of organic material from oil shales. However, one of the limiting factors in the development of this technology is a lack of accurate dielectric property data for design purposes. In this study the dielectric behaviour of El-lajun oil shale is quantified. The dielectric constant and loss

Mohammad Al-Harahsheh; Sam Kingman; Abdurrahman Saeid; John Robinson; Georgios Dimitrakis; Hani Alnawafleh

2009-01-01

20

Effect of Smectic Ordering on the Dielectric Properties of Reentrant Nematic Mixtures  

Microsoft Academic Search

We have measured the static dielectric constants ?? and ?? as well as the low-frequency dispersion of ?par for mixtures of two eutectic compositions exhibiting a reentrant nematic phase over a range of concentration. The dielectric properties of a nematic mixture, whose concentration is close to the critical concentration ( Ccr) at which the smectic phase appears, are found to

B. R. Ratna; R. Shashidhar; M. Bock; A. Gbl-wunsch; G. Heppke

1983-01-01

21

Dielectric properties and electronic applications of aerogels  

SciTech Connect

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

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

1993-07-01

22

Dielectric properties of rapidly grown KDP crystals  

Microsoft Academic Search

The dielectric properties of rapidly grown potassium dihydrogen phosphate KH2PO4 (KDP) crystals have been studied over a wide temperature range and compared with the properties of traditionally grown KDP\\u000a crystals. It was found that the contribution of domains to permittivity in rapidly grown crystals is considerably less than\\u000a in conventionally grown ones. The dielectric properties in various growth sectors of

S. V. Grabovskii; I. V. Shnaidshtein; B. A. Strukov

2003-01-01

23

Dielectric properties of yeast cells  

Microsoft Academic Search

Summary Dielectric measurements were made on suspensions of intact yeast cells over a frequency range of 10 kHz to 100 MHz. The suspensions showed typical dielectric dispersions, which are considered to be caused by the presence of cytoplasmic membranes with sufficiently low conductivity. Since the conductivity of the cell wall was found to be of nearly the same value as

Koji Asami; Tetsuya Hanai; Naokazu Koizumi

1976-01-01

24

Static Properties of Fibre Metal Laminates  

Microsoft Academic Search

In this article a brief overview of the static properties of Fibre Metal Laminates is given. Starting with the stress-strain relation, an effective calculation tool for uniaxial stress-strain curves is given. The method is valid for all Glare types. The Norris failure model is described in combination with a Metal Volume Fraction approach leading to a useful tool to predict

M. Hagenbeek; C. van Hengel; O. J. Bosker; C. A. J. R. Vermeeren

2003-01-01

25

Microwave dielectric properties of boreal forest trees  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

26

Room Temperature Static Lattice Dielectric Constant of Lead Telluride by a Microwave Cavity-Perturbation Technique.  

National Technical Information Service (NTIS)

The authors have measured the room-temperature static lattice dielectric constant of PbTe using a cavity-perturbation technique. The result, epsilon = 800 + or - 220, implies a transverse optic phonon frequency omega = 23 + or - 4/3/cm in agreement with v...

G. M. T. Foley D. N. Langenberg

1975-01-01

27

Dielectric properties of fiber-filled composites  

NASA Astrophysics Data System (ADS)

Results are presented of the comprehensive experimental investigation of the dielectric properties of composites filled with conducting fibers results. The results apply to the percolation threshold values and microwave dielectric dispersion of these materials. The fiber-filled composites exhibit a great variety of dielectric dispersion behavior, and offer wide possibilities of tailoring their dielectric dispersion. The experimental data are in good agreement with the recent theoretical approach [see A. N. Lagarkov and A. K. Sarychev, Phys. Rev. B 53, 6318 (1996)] as regards the values of percolation threshold and the shape of dielectric dispersion dependences. This agreement is a validation of the original assumption that the permittivity of effective medium is a scale dependent function in fiber-filled composites.

Lagarkov, A. N.; Matytsin, S. M.; Rozanov, K. N.; Sarychev, A. K.

1998-10-01

28

Tailoring dielectric properties of ferroelectric-dielectric multilayers  

NASA Astrophysics Data System (ADS)

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 Ba0.6Sr0.4TiO3-, BaTiO3-, and PbZr0.2Ti0.8O3 (PZT)-SrTiO3 (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.

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

2014-01-01

29

Determining the static dielectric permittivity of ion conducting materials when obscured by electrode polarization  

NASA Astrophysics Data System (ADS)

A method is derived for the determination of the static dielectric permittivity of ion conducting materials when this parameter is obscured by electrode polarization in as-recorded low frequency dielectric spectra. The method requires permittivity measurements at two different electrode separations, and is applicable when the electric fields created by charge separation near the electrode surfaces do not induce nonlinear effects in the frequency region where electrode polarization begins to affect the dielectric response. The performance of the method is illustrated by the analysis of an ion conducting cellulose gel biosynthesized by the Acetobacter. xylinum bacterium. The method opens up possibilities to obtain more detailed information about dynamic processes in ion conducting materials from dielectric spectroscopy.

Gra?Sj, Johan; Welch, Ken; Strmme, Maria

2008-09-01

30

Microwave Dielectric Properties of Plant Materials  

Microsoft Academic Search

Three waveguide transmission systems covering the 1-2, 3.5-6.5, and 7.5-8.5 GHz bands were used to measure the dielectric properties of vegetation material as a function of moisture content and microwave frequency. The materials measured included, primarily, the leaves and stalks of corn and wheat. Dielectric measurements also were made of the liquid included in the vegetation material after it was

Fawwaz T. Ulaby; R. P. Jedlicka

1984-01-01

31

An ab-initio Computational Method to Determine Dielectric Properties of Biological Materials  

PubMed Central

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.

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

2013-01-01

32

Quasi-static and dynamic inflation of a dielectric elastomer membrane actuator  

NASA Astrophysics Data System (ADS)

This paper presents quasi-static and dynamic results for dielectric elastomer actuators subject to a uniform mechanical pressure and an applied voltage. The numerical quasi-static results are compared to experimental data for actuators made from 3M VHB material. It is shown that the theoretical model for the active inflation of hyperelastic membranes is sensitive to the explicit form of the assumed strain energy function. The optimal constants of 2-Term and 3-Term Ogden models are determined from uniaxial and biaxial stress experimental data. Using the best overall values for the material constants, the electro-elastic model is used to predict the voltage-dependent behavior for the inflation of dielectric elastomer actuators. The correlation between the numerical results and the experimental data is good. In previous work, inertial effects have been neglected and a quasi-static approach employed. The method is presently expanded to include the dynamic response of dielectric elastomer actuators. In this case inertial effects become increasingly important as different equilibria modes are obtained during dynamic operation. The results show the potential for voltage-controlled bifurcations during the inflation of spherical dielectric elastomer actuators.

Goulbourne, Nakhiah; Frecker, Mary; Mockensturm, Eric

2005-05-01

33

Dielectric Properties of Cryogenic Liquids  

Microsoft Academic Search

Electric-breakdown measurements at 60 Hz have been made with cryogenic liquids-nitrogen, hydrogen, and helium. All of the cryogenic liquids have higher breakdown voltages than conventional transformer oil, except liquid helium which breaks down at a considerably lower voltage. The measured values of dielectric constant for the cryogenic liquids agree quite well with the published literature. The dissipation factor of the

KCENNETH N. MATHES

1967-01-01

34

Characterization and Metrology of Medium Dielectric Constant Gate Dielectric Films  

Microsoft Academic Search

The characterization and optical metrology of physical properties of thin dielectric films and film stacks composed of metal oxides with static dielectric constants from ? ? 4t o? ? 25 is reviewed. These dielectric films are designed to mimic the behavior of silicon dioxide gate dielectrics of 1 to 2 nm thickness, with the elevated dielectric constant allowing a gate

A. C. Diebold; W. W. Chism

35

Critical Slowing-Down and Static Dielectric Constant of Monoclinic RbD2PO4  

NASA Astrophysics Data System (ADS)

The real and imaginary parts of the complex dielectric constant along the b axis of monoclinic RbD2PO4 were measured in a frequency range between 106 Hz and 109 Hz. It was found that RbD2PO4 shows dielectric critical slowing-down near the ferrielectric phase transition point. In addition, the static dielectric constants (\\varepsilon0) of RbD2PO4 and the partially deuterated crystal Rb(D0.3H0.7)2PO4 were also measured at 104 Hz. A theoretical expression of \\varepsilon0 for a ferrielectric phase transition was obtained on the basis of the quasi-one-dimensional Ising model with assumed two sublattices. The remarkable deviations of \\varepsilon0 from the Curie-Weiss law observed in these crystals were analyzed successfully by the present theoretical result and the experimental results were discussed.

Komukae, Masaru; Makita, Yasuharu

1985-11-01

36

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

PubMed

A fluorescent probe structurally similar to the GFP chromophore is demonstrated to report the local static dielectric constant. This probe can be chemically functionalized for selective targeting at the intracellular level. PMID:23340669

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

2013-02-28

37

Circuit Properties of Microwave Dielectric Resonators  

Microsoft Academic Search

The purpose of this paper is to present experimental data on the circuit properties of dielectric resonators which do not have conducting boundaries. The resonators are constructed of single-crystal rutile and strontium titanate, which, as has been shown by several authors, can form resonators of miniatnre size and high unloaded Q. We consider the lowest-order H mode, give measured values

ARTHUR KARP; HERBERT J. SHAW; DONALD K. WINSLOW

1968-01-01

38

Dielectric Properties of Polymers. A Bibliography.  

National Technical Information Service (NTIS)

A bibliography of 216 items is reported on the dielectric properties of polymers. It is limited to the references in the author's personal file. However, these cover the significant journals in the field, for the years 1955-1966. Complete subject and auth...

D. W. Levi D. A. Teetsel

1966-01-01

39

Dielectric Properties of Ceramics at Microwave Frequencies.  

National Technical Information Service (NTIS)

The dielectric properties of alumina and silicon nitride have been determined using modified rectangular microwave waveguide techniques from 220 to 900 deg C over 8-12 GHz and modified coax techniques from 25 deg to 500 deg C over 2-18 GHz. The coax techn...

B. M. Pierce J. R. Chow N. H. Harris R. L. Eisenhart

1992-01-01

40

Dielectric Properties of a Nematic Binary Mixture  

Microsoft Academic Search

In this paper, a phase diagram is developed for the molar mixtures of nematic liquid crystals of 5CB and MBBA. In order to understand the interaction of the two systems, dielectric permittivities ? and ? were measured for mixtures of various concentrations. The usual assumption is that in the absence of chemical reactions the bulk physical properties add up as

Shila Garg; Tom Spears

2004-01-01

41

Effective dielectric and elastic properties of nanoporous low-k media  

Microsoft Academic Search

This paper presents a mathematically defined characterization of random porous media including random self-similarity and surface fractality. The initial two-phase structure is transformed into a three-phase system by introducing the internal surface layer as the third phase. Effective medium theories are utilized to calculate macroscopic dielectric and elastic properties. The dependence of both the static dielectric constant and Young's modulus

H. Hermann

2010-01-01

42

Dielectric properties of Apollo 14 lunar samples.  

NASA Technical Reports Server (NTRS)

Laboratory characterization of dielectric properties of lunar samples 14301,41, 14310,75, 14318,30 and 14321,163 is made. Our measurements of dielectric constants and losses were made over a range of frequency from 100 Hz to 10 MHz and temperature from 77 to 473 K by two-terminal capacitance substitution methods. The dielectric behavior of these samples is generally similar to other lunar samples from Apollo 11 and Apollo 12 sites when these samples are free from absorbed moisture. As did sample 12002,58, sample 14310,75 showed a distinctive dispersion that may be associated with the presence of water, and different values of the activation energy for conduction as the temperature was varied. The activation energies range from about 0.03 to 0.5 eV.

Chung, D. H.; Westphal, W. B.; Olhoeft, G. R.

1972-01-01

43

Microwave dielectric properties of plant materials  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

44

Dielectric properties of battery electrolytes  

NASA Technical Reports Server (NTRS)

An effort was made to determine the effects of electromagnetic radiation on the terminal properties of electrochemical cells. Various constituents of the battery were measured to determine basic electromagnetic properties. These properties were used to predict how much radiation would be absorbed by a battery in a particular field configuration. The frequency range covered from 0 to 40 GHz with the greatest emphasis on the microwave range from 2.6 to 40 GHz. The measurements were made on NiCd, AgZn, and Pb acid cells. Results from observation show nothing which suggested any interaction between radiation and cells, and no incidence of any peaks of energy absorption was observed.

1971-01-01

45

Spectroscopic evidence for strong oscillating and static dielectric polarizations in malignant cells.  

PubMed

Analysis of splitting and shifting of malignant cell (mammary carcinoma and virally transformed cells) Raman and microwave spectral lines suggests that the Raman line splittings are due to non-linear second-order coupling of a coherently excited optical polarization wave with other polarization modes within these malignant cells. The microwave splittings are believed due to the non-linear second-order coupling effects of a lower frequency acoustic wave. The spectral line shiftings are believed indicative of a strong static dielectric polarization (ferroelectric state) of the cells. PMID:7433537

Cooper, M S; Theimer, O

1980-01-01

46

DIELECTRIC PROPERTIES OF VARIOUS NANOCOMPOSITE MATERIALS  

SciTech Connect

Composite materials based on polymers are used in various engineering applications due to their ability to be tailored for a specific application. As a result a composite could be selected or designed for a high performance part such as field grading applications in high voltage technology. Presently, there exists no commercially available material for electric field control. For this reason in this study we characterize a polymeric system composed of a thermoplast polymer filled with nanometer size ceramic particles. Since it is hard to tailor or to predict properties of composites theoretically, an Edisonian approach is employed. Composites with different filler weight concentrations are prepared and their dielectric performance are characterized. Impedance spectroscopy technique at a constant frequency is used to determine the dielectric properties of the composites at low temperatures. Measurement results and potential applications of the composite systems are presented.

Tuncer, E. [Oak Ridge National Laboratory (ORNL); Polizos, G. [Oak Ridge National Laboratory (ORNL); James, D. R. [Oak Ridge National Laboratory (ORNL); Sauers, I. [Oak Ridge National Laboratory (ORNL); Ellis, A. R. [Oak Ridge National Laboratory (ORNL); More, K. L. [Oak Ridge National Laboratory (ORNL)

2010-01-01

47

Nonlinear dielectric properties of barium strontium titanate ceramics  

Microsoft Academic Search

In barium strontium titanate (BaxSr1?xTiO3) ceramics, obvious tunabilities of both dielectric permittivity and loss tangent under external DC bias field were observed. The temperature and frequency dependences of nonlinear dielectric properties were studied. Polarizing process was carried out to evaluate the influence of domain reorientation on dielectric nonlinearity in the ferroelectric polycrystalline samples. The nonlinear variation of dielectric properties under

Xiaoyong Wei; Xi Yao

2003-01-01

48

Spacecraft dielectric material properties and spacecraft charging  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

49

Dielectric properties for monitoring the quality of heated oils  

Microsoft Academic Search

Dielectric properties (dielectric constant ?? and dielectric loss ??) were compared to conventional methods of analysis (viscosity,\\u000a refractive index, iodine value, peroxide value and free fatty acids) for evaluating the frying quality of a blend of cottonseed\\u000a and sunflower oils. The apparent relaxation time, ?, the activation energy H and the entropy change S for dielectric relaxation\\u000a of the heated

S. M. El-Shami; I. Zaki Selim; I. M. El-Anwar; M. Hassan El-Mallah

1992-01-01

50

Microwave Dielectric Properties of On-Chip Liquid Films  

Microsoft Academic Search

A microwave characterization method for on-chip liquid film dielectric property measurement is developed. Microstrip-line based on-chip test structures are fabricated to characterize the microwave dielectric properties of various on-chip liquid films: DI water and binary mixtures of DI water with glucose and ethanol. The obtained microwave dielectric properties are presented in Cole-Cole diagrams, which show general frequency dependence similar to

Chunrong Song; Syed Azimuudin; Byungje Lee; Frances Harackiewicz; Max Yen; Divan Ralu; Axel Hoffman; Pingshan Wang

2006-01-01

51

Spacecraft dielectric surface charging property determination  

NASA Technical Reports Server (NTRS)

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.

Williamson, W. S.

1987-01-01

52

On the Calculation of the Dielectric Properties of Liquid Ionic Systems  

NASA Astrophysics Data System (ADS)

The calculation of dielectric properties of fluids, which is straightforward for homogeneous dipolar liquids, presents several intricacies when applied to ionic liquids. We investigate, for a model sodium chloride aqueous solution, three different methods which could provide an estimate of the static permittivity, namely (a) the Einstein-Helfand approach, (b) the first moment of the current-current correlation functions, and (c) the analysis of the low frequency limit of the dielectric spectrum. The contribution to the static permittivity of the sodium chloride solution coming from the ion-ion correlations, often neglected in simulation studies but implicitly taken into account in experimental measurements, are shown to be important, although particularly hard to measure. In the case of our model sodium chloride solutions, we find these dynamic contributions to be the main cause of the saturation of the dielectric constant with increasing salt concentration.

Sega, Marcello; Kantorovich, Sofia S.; Arnold, Axel; Holm, Christian

53

Mass Properties Measurement System: Dynamics and Statics Measurements.  

National Technical Information Service (NTIS)

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 ...

K. L. Doty

1993-01-01

54

Millimeter wave and terahertz dielectric properties of biological materials  

Microsoft Academic Search

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

Usman Ansar Khan

2007-01-01

55

Microwave dielectric properties of dry rocks  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

56

Radio-frequency and microwave dielectric properties of insects.  

PubMed

Basic principles and definitions of dielectric properties of materials are presented. Data from the literature on the dielectric properties of insects are briefly reviewed and discussed in relation to insect control by selective dielectric heating. Because early measurements of the dielectric properties of insects were taken on bulk samples of insects (insect and air-space dielectric mixtures), a means for converting the dielectric properties, or permittivities, of bulk samples of particulate materials to those of the solid particles is described. The technique uses the Landau & Lifshitz, Looyenga dielectric mixture equation and information on the bulk densities of air-insect mixtures used for dielectric properties measurements along with the densities of the insects. Such converted data for the dielectric constants and loss factors of the insects are presented and collected for comparison with other measurements of insect tissues and permittivity determinations from more recent microwave measurements of these same parameters. Resulting data are presented for reference, and comparisons are presented and discussed briefly. PMID:15038553

Nelson, S O

2001-01-01

57

Investigation of microwave dielectric properties of biodiesel components.  

PubMed

Advanced microwave technology has the potential to significantly enhance the biodiesel production process. Knowledge of dielectric properties of materials plays a major role in microwave design for any process. Dielectric properties (?' and ?") of biodiesel precursors: soybean oil, alcohols and catalyst and their different mixtures were measured using a vector network analyzer and a slim probe in an open ended coaxial probe method at four different temperatures (30, 45, 60 and 75 C) and in the frequency range of 280 MHz to 4.5 GHz. Results indicate that the microwave dielectric properties depend significantly on both temperature and frequency. Addition of catalyst significantly affected the dielectric properties. Dielectric properties behaved differently when oil, alcohol and catalyst was mixed at room temperature before heating and when the oil and the alcohol catalyst mixture was heated separately to a pre-determined temperature before mixing. These results can be used in designing microwave based transesterification system. PMID:23131637

Muley, Pranjali D; Boldor, Dorin

2013-01-01

58

Collective and static properties of model two-component plasmas  

SciTech Connect

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

Arkhipov, Yu. V.; Askaruly, A.; Davletov, A. E.; Meirkanova, G. M. [Department of Optics and Plasma Physics, al-Farabi Kazakh National University, Tole Bi 96, Almaty 050012 (Kazakhstan); Ballester, D.; Tkachenko, I. M. [Department of Applied Mathematics, Polytechnic University of Valencia, Camino de Vera s/n, 46022 Valencia (Spain)

2007-08-15

59

Dielectric properties of supercooled cryoprotectant agents  

NASA Astrophysics Data System (ADS)

The dielectric properties of glycerol, propylene glycol, ethylene glycol and dimethyl sulphoxide have been measured in various aqueous concentrations generally sufficient to allow supercooling rather than freezing. The temperature range investigated is from to and the frequency range is 100 MHz to 2 GHz. The aim is to find the materials and conditions most favourable for very rapid re-warming of perfused biological tissue by electromagnetic fields, avoiding thermal runaway in the bulk and local non-uniformity of temperature. Frequencies below 500 MHz are generally indicated.

Michelson, S. C.; Evans, S.

1996-10-01

60

Dielectric properties and electrical conduction in yttrium iron garnet (YIG)  

Microsoft Academic Search

The dielectric properties (dielectric constant and loss) of a single crystal of yttrium iron garnet (Y3Fe5O12) were measured in the temperature range 77725 K and in the frequency range 100 Hz-1 MHz. AC conductivity was derived from\\u000a dielectric constant and loss. DC conductivity was measured in the temperature range 30725 K. Thermoelectric power (TEP) was\\u000a measured from 77800 K. On

Lalitha Sirdeshmukh; K Krishna Kumar; S Bal Laxman; A Rama Krishna; G Sathaiah

1998-01-01

61

Dielectric properties of two phases of crystalline lutetium oxide  

Microsoft Academic Search

High-dielectric constant oxides are the focus of intense current research. As a contribution to the rationalization of the search for candidate materials, we compare the dielectric properties obtained from first-principles linear-response calculations for two phasesthe ground state bixbyite and the competing hexagonal structuresof the crystalline oxide Lu2O3. The dielectric constants of bixbyite is about 12 and that of hexagonal is

Pietro Delugas; Vincenzo Fiorentini

2005-01-01

62

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

PubMed

We analyzed the dielectric properties of molecular liquids using the external field method with reaction field approximations. The applicability of this method to determine the dielectric properties of molecules with zero (1,4-dioxane) and non-zero (water and bio-molecular aqueous solutions) permanent dipole moment was studied. The relative static dielectric constant obtained using the external field method for polar and non-polar molecular liquids, including molecules with zero permanent dipole moment, agreed well with the experimental values presented in the literature. Our results indicate that the Debye relaxation time constants estimated from the non-equilibrium simulations using the external field method were accurate for molecules whose permanent dipole moments were less than 12 D. PMID:24899067

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

2014-07-21

63

Microwave dielectric properties of some laser crystals  

Microsoft Academic Search

The relative dielectric permittivity and the dielectric loss tangent of KH2PO4, KD2PO4, PbWO4, PbMoO4, Al2O3, LiF and KCl single crystals used in laser technique are investigated with the help of the waveguide-dielectric resonances at frequencies of 7 - 12 GHz. The effect of gamma-irradiation with doses up to 2middot105 Gy on the characteristics of crystals is determined . It is

A. N. Levchenko; V. B. Tyutyunnik; I. M. Pritula; A. V. Kosinova; A. N. Shekhovtsov; A. L. Babarika; K. O. Govina; L. I. Babarika; V. V. Chizhov; O. T. Nikolov; M. B. Kosmyna

2008-01-01

64

Thermal and compositional properties of cocoa butter during static crystallization  

Microsoft Academic Search

Studies were conducted using differential scanning calorimetry (DSC) and high performance liquid chromatography (HPLC) to\\u000a determine the thermal properties and glyceride composition of cocoa butter crystals formed under static conditions. In addition\\u000a to these studies, visual characterization of the crystallites was obtained with polarized light microscopy (PLM). Crystals\\u000a were formed under controlled static or motionless conditions at formation temperatures of

Paul S. Dimick; Douglas M. Manning

1987-01-01

65

Macroscopic static and dynamic mechanical properties of Yule marble  

Microsoft Academic Search

The static and dynamic tensile and compressive properties of Colorado Yule marble have been obtained from samples all secured from the same parent slab. Specimens were cored in the three principal directions of this transversely isotropic material, the axis of symmetry having been determined petrographically. Standard quasi-static and creep tests were performed, and both Hopkinson-bar and split-Hopkinson-bar tests were conducted

S. P. Howe; W. Goldsmith; J. L. Sackman

1974-01-01

66

Dielectric properties of barium titanate supramolecular nanocomposites  

NASA Astrophysics Data System (ADS)

Nanostructured dielectric composites can be obtained by dispersing high permittivity fillers, barium titanate (BTO) nanocubes, within a supramolecular framework. Thin films of BTO supramolecular nanocomposites exhibit a dielectric permittivity (?r) as high as 15 and a relatively low dielectric loss of ~0.1 at 1 kHz. These results demonstrate a new route to control the dispersion of high permittivity fillers toward high permittivity dielectric nanocomposites with low loss. Furthermore, the present study shows that the size distribution of nanofillers plays a key role in their spatial distribution and local ordering and alignment within supramolecular nanostructures.

Lee, Keun Hyung; Kao, Joseph; Parizi, Saman Salemizadeh; Caruntu, Gabriel; Xu, Ting

2014-03-01

67

Dielectric properties of barium titanate supramolecular nanocomposites.  

PubMed

Nanostructured dielectric composites can be obtained by dispersing high permittivity fillers, barium titanate (BTO) nanocubes, within a supramolecular framework. Thin films of BTO supramolecular nanocomposites exhibit a dielectric permittivity (?r) as high as 15 and a relatively low dielectric loss of ?0.1 at 1 kHz. These results demonstrate a new route to control the dispersion of high permittivity fillers toward high permittivity dielectric nanocomposites with low loss. Furthermore, the present study shows that the size distribution of nanofillers plays a key role in their spatial distribution and local ordering and alignment within supramolecular nanostructures. PMID:24584569

Lee, Keun Hyung; Kao, Joseph; Parizi, Saman Salemizadeh; Caruntu, Gabriel; Xu, Ting

2014-04-01

68

Improving the Dielectric Properties of Polymers by Incorporating Nanoparticles  

Microsoft Academic Search

The paper presents a brief review of the promise of nanotechnology applied to polymeric insulation materials and discusses the electrical properties found. For a variety of nanocomposites, the dielectric behaviour has shown that the interface between the embedded particles and host matrix holds the key to the understanding of the bulk phenomena being observed. Dielectric spectroscopy verified the motion of

C Zou; J C Fothergill; M Fu; J K Nelson

69

Dielectric properties of lithium niobate single crystals doped with gadolinium  

NASA Astrophysics Data System (ADS)

In this paper dielectric properties of LiNbO3:Gd single crystals at temperatures ~ 290-490 K at narrow frequency range (0.5-106 Hz) are presented. The influence of growth conditions was also investigated. The anomalies on dielectric plots depend on the development of the micro- and nano-domain structure.

Palatnikov, M. N.; Sidorov, N. V.; Sandler, V. A.; Bormanis, K.; Smeltere, I.

2013-12-01

70

Dielectric Properties of the Charge Ordered Oxyborate Fe OBO  

Microsoft Academic Search

In this work we present a detailed investigation of the dielectric properties of the oxyborate Fe2OBO3 . This compound exhibits a high dielectric constant at room temperature (epsivr' > 103) for frequencies up to 104 Hz. An impedance spectroscopy analysis of the data reveals an important extrinsic contribution to these high epsivr' values. In order to eliminate the extrinsic contribution,

Manuel Snchez-Andjar; Jorge Mira; Beatriz Rivas-Murias; Susana Yez-Vilar; Neven Biskup; Jos Rivas; Mara A. Sears-Rodrguez

2008-01-01

71

Dielectric Properties of Bulk Anisotropic Structures and Multiphase Mixtures  

Microsoft Academic Search

The method of electrodynamic averaging is described, by which one can obtain the effective dielectric permittivity of volume anisotropic structure determined by the shape of particles, their geometrical sizes, electromagnetic parameters and spatial dense media, to consider multiple interactions between scattering elements and dispersion properties of the media. Tensors of the dielectric permittivity of anisotropic structures are given as the

E. A. Skirta; N. A. Khizhnyak

1993-01-01

72

Millimeter wave and terahertz dielectric properties of biological materials  

NASA Astrophysics Data System (ADS)

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.

Khan, Usman Ansar

73

Dielectric properties of FeCl3 doped PVA films  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

74

Dielectric properties of salt-affected soils  

Microsoft Academic Search

A detailed laboratory experiment was conducted on three soils of different textures viz., sand, sandy clay loam and clay to study the influence of soil salinity and sodicity on the complex dielectric behaviour of soils as a function of volumetric soil moisture using an L-band (1 25 GHz) dielectric probe. The results revealed that soil salinity has no influence on

K. Sreenivas; L. Venkataratnam; P. V. Narasimha Rao

1995-01-01

75

Microwave dielectric properties of surface snow  

Microsoft Academic Search

First results from a recently developed surface sensor for measuring the dielectric constant of snow at about 1 GHz are reported together with ground-based measurements of brightness temperatures between 4.9 and 94 GHz. The data are used to derive spectra of complex dielectric constants of wet snow for frequencies between 1 and 100 GHz. The result is simple: Debye relaxation

CHRISTIAN MATZLER; HUBERT AEBISCHER; ERWIN SCHANDA

1984-01-01

76

Effect of Charged Dislocations On Dielectric, Piezoelectric and Elastic Properties.  

National Technical Information Service (NTIS)

A generalized treatment of the effect of charged dislocations on dielectric, piezoelectric and elastic properties is developed by considering the displacement of a charged dislocation segment, bounded by immobile pinning points, under separate or combined...

C. L. Bauer W. A. Brantley

1968-01-01

77

Dielectric and magnetic properties of some gadolinium silica nanoceramics  

NASA Astrophysics Data System (ADS)

Some nanostructure gadolinium silica glass-ceramics were obtained undergoing a sol gel method and a heat-treatment at 1000C 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 ions. The dielectric properties were evaluated from dielectric permittivity (?r) and dielectric loss (tan?) measurements at the frequency 1 kHz, 10 kHz and 100 kHz, in the 25-225C 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.

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

2013-11-01

78

Dielectric Properties of Electrorheological Fluids Containing Zeolite Particles  

Microsoft Academic Search

Relationships between electrorheological (ER) effects and dielectric properties of suspensions are investigated from measurements of ER and dielectric properties of suspensions containing particles of type A zeolite such as 3A, 4A and 5A. In each suspension containing zeolite 3A or 4A particles, the ER effect is recognized, i.e., an increase in the apparent viscosity is observed when an electric field

Keishi Negita; Yasuhiko Ohsawa

1995-01-01

79

The static actuation of dielectric elastomer actuators: how does pre-stretch improve actuation?  

NASA Astrophysics Data System (ADS)

It has previously been shown that providing dielectric elastomer actuators with a level of pre-stretch can improve properties such as breakdown strength, actuation strain and efficiency. The actuation in such actuators depends on an interplay between the highly nonlinear hyperelastic stress-strain behaviour with the electrostatic Maxwell's stress; however, the direct effects of pre-stretch on the electromechanical coupling have still not been investigated in detail. We compare several experimental results found in the literature on the hyperelastic parameters of the Ogden model for the commonly used material VHB 4910, and introduce a more detailed and thus more accurate fit to a previous uniaxial stress-strain experiment. Electrostatic actuation models for a pure shear cuboid dielectric elastomer actuator with pre-stretch are introduced, for both intensive and extensive variables. For both intensive and extensive variables the constant strain (blocked stress or force) as well as the actuation strain is presented. It is shown how in the particular case of isotropic amorphous elastomers the pre-stretch does not affect the electromechanical coupling directly, and that the enhancement in actuation strain due to pre-stretch occurs through the alteration of the geometrical dimensions of the actuator. Also, the presence of the optimum load is explained as being due to the plateau region in the force-stretch curve, and it is shown that pre-stretch is not able to affect its position. Finally, it is shown how the simplified Ogden fit leads to entirely different conclusions for actuation strain in terms of extensive variables as does the detailed fit, emphasizing the importance of employing accurate hyperelastic models for the stress-stretch behaviour of the elastomer.

Kofod, Guggi

2008-11-01

80

Focusing properties of surface plasmon polariton floating dielectric lenses.  

PubMed

We have investigated the focusing properties of surface plasmon polariton floating dielectric lenses. An analysis of the scattering characteristics of surface plasmon polaritons using a floating dielectric block shows that the air-gap thickness between a floating dielectric block and a metal substrate can be an effective dynamic variable for modulating the amplitude and phase of the transmission coefficient of the surface plasmon polaritons. This property can be used to realize a variable-focusing surface plasmon dielectric lens with the air-gap thickness as the dynamic variable. The focusing properties of a Fresnel lens and a parabolic lens with respect to the air-gap thickness are compared and analyzed. PMID:18542391

Kim, Hwi; Hahn, Joonku; Lee, Byoungho

2008-03-01

81

Mass properties measurement system: Dynamics and statics measurements  

NASA Technical Reports Server (NTRS)

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.

Doty, Keith L.

1993-01-01

82

Dielectric properties of electrospun titanium compound/polymer composite nanofibres  

NASA Astrophysics Data System (ADS)

Poly(vinylpyrrolidone)/tetrabutyl titanate (PVP/ [CH3(CH2)3O]4Ti) composite nanofibres are prepared by electrospinning. After calcining parts of composite nanofibres in air at 700 C, petal-like TiO2 nanostructures are obtained. The characterizations of composite nanofibres and TiO2 nanostructures are carried out by a scanning electron microscope, an x-ray diffractometer, and an infrared spectrometer. Electrospun nanofibres are pressed into pellets under different pressures in order to explore their dielectric properties. It is found that the dielectric constants decrease with frequency increasing. The dielectric constant of the composite nanofibre pellet increases whereas its dielectric loss tangent decreases due to the doped titanium ions compared with those of pure PVP nanofibre pellets. In addition, it is observed that the dielectric constant of the composite nanofibre pellet decreases with the increase of the pressure applied in pelletization.

Li, Meng-Meng; Long, Yun-Ze; Tan, Jin-Shan; Yin, Hong-Xing; Sui, Wan-Mei; Zhang, Zhi-Ming

2010-02-01

83

Dielectric properties of KDP filled porous alumina nanocomposite thin films.  

PubMed

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

Boni, O; Berger, S

2001-12-01

84

Sugar and water contents of honey with dielectric property sensing  

Microsoft Academic Search

The dielectric properties of pure yellow locust, jujube and rape flower honey and their water-adulterated products with water content from 18% to 42.6% were measured with open-ended coaxial-line probe technology and a network analyzer from 10 to 4500MHz at 25C. Dielectric constants of pure honeys and water-added honey samples decreased monotonically with increasing frequency, and increased with increasing water content.

Wenchuan Guo; Xinhua Zhu; Yi Liu; Hong Zhuang

2010-01-01

85

Investigation of the dielectric properties of bismuth pyrochlores  

Microsoft Academic Search

The dielectric properties of polycrystalline bismuth-based pyrochlores of the general chemical form Bi2(B232+B435+)O7 and Bi2(B3+B5+)O7 where B2+ = Mg, Cu, Zn and Ni, B3+ = Sc and In, and B5+ = Nb and Ta, were investigated as a function of temperature and frequency. At low temperatures (T ? 100?150 K), a dielectric dispersion was universally observed within these systems. The

David P. Cann; Clive A. Randall; Thomas R. Shrout

1996-01-01

86

Triboelectric charging and dielectric properties of pharmaceutically relevant mixtures  

Microsoft Academic Search

Binary mixtures of pharmaceutically relevant powders were investigated using dielectric spectroscopy over a frequency range of 10?3 to 300kHz. Two different binary mixtures were studied as a function of concentration; pseudoephedrine hydrochloride in dicalcium phosphate dihydrate and acetaminophen in microcrystalline cellulose, respectively. Dielectric properties obtained from measurements of these systems are reported and found to follow a trend similar to

David A. Engers; Molly N. Fricke; Ann W. Newman; Kenneth R. Morris

2007-01-01

87

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

88

Dielectric Properties of Electrorheological Fluids Containing Zeolite Particles  

NASA Astrophysics Data System (ADS)

Relationships between electrorheological (ER) effects and dielectric properties of suspensions are investigated from measurements of ER and dielectric properties of suspensions containing particles of type A zeolite such as 3A, 4A and 5A. In each suspension containing zeolite 3A or 4A particles, the ER effect is recognized, i.e., an increase in the apparent viscosity is observed when an electric field is applied, and the dielectric property is characterized by a dielectric dispersion in audio frequency region. On the other hand, the suspension containing zeolite 5A particles does not show a distinct ER effect and has a low dielectric constant without dielectric dispersion above 1Hz. These results indicate that relaxation time of the induced polarization is associated with the ER effect; for the appearance of the ER effect the relaxation time should be shorter than a characteristic time. It is suggested that the characteristic time is associated with an angular velocity of rotating particles under a steady shear flow and also that the relaxation time of the polarization is mainly determined by the electric conductivity of the particle.

Negita, Keishi; Ohsawa, Yasuhiko

1995-06-01

89

Dielectric and other properties of polyimide aerogels containing fluorinated blocks.  

PubMed

The dielectric and other properties of a series of low-density polyimide block copolymer aerogels have been characterized. Two different anhydride-capped polyimide oligomers were synthesized: one from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4'-oxidianiline (ODA) and the other from biphenyl-3,3',4,4'-tetracarboxylic dianhydride and ODA. The oligomers were combined with 1,3,5-triaminophenoxybenzene to form a block copolymer networked structure that gelled in under 1 h. The polyimide gels were supercritically dried to give aerogels with relative dielectric constants as low as 1.08. Increasing the amount of 6FDA blocks by up to 50% of the total dianhydride decreased the density of the aerogels, presumably by increasing the free volume and also by decreasing the amount of shrinkage seen upon processing, resulting in a concomitant decrease in the dielectric properties. In this study, we have also altered the density independent of fluorine substitution by changing the polymer concentration in the gelation reactions and showed that the change in dielectric due to density is the same with and without fluorine substitution. The aerogels with the lowest dielectric properties and lowest densities still had compressive moduli of 4-8 MPa (40 times higher than silica aerogels at the same density), making them suitable as low dielectric substrates for lightweight antennas for aeronautic and space applications. PMID:24483208

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

2014-05-14

90

Information for coarticulation: Static signal properties or formant dynamics?  

PubMed

Perception of a speech segment changes depending on properties of surrounding segments in a phenomenon called compensation for coarticulation (Mann, 1980). The nature of information that drives these perceptual changes is a matter of debate. One account attributes perceptual shifts to low-level auditory system contrast effects based on static portions of the signal (e.g., third formant [F3] center or average frequency; Lotto & Kluender, 1998). An alternative account is that listeners' perceptual shifts result from listeners attuning to the acoustic effects of gestural overlap and that this information for coarticulation is necessarily dynamic (Fowler, 2006). In a pair of experiments, we used sinewave speech precursors to investigate the nature of information for compensation for coarticulation. In Experiment 1, as expected by both accounts, we found that sinewave speech precursors produce shifts in following segments. In Experiment 2, we investigated whether effects in Experiment 1 were driven by static F3 offsets of sinewave speech precursors, or by dynamic relationships among their formants. We temporally reversed F1 and F2 in sinewave precursors, preserving static F3 offset and average F1, F2 and F3 frequencies, but disrupting dynamic formant relationships. Despite having identical F3s, selectively reversed precursors produced effects that were significantly smaller and restricted to only a small portion of the continuum. We conclude that dynamic formant relations rather than static properties of the precursor provide information for compensation for coarticulation. PMID:24730744

Viswanathan, Navin; Magnuson, James S; Fowler, Carol A

2014-06-01

91

Role of dielectric function in model GW calculations of structural and optical properties in semiconductors  

NASA Astrophysics Data System (ADS)

Recently proposed nonlocal exchange potential methods such as screened exchange (sX-LDA)(Bylander, Kleinman, Phys. Rev. B 41, 7868 (1990)) and model GW(Gygi, Baldereschi, Phys. Rev. Lett. 62, 2160 (1989)) demonstrated successful extensions of LDA energy bands to treat excited states in semiconductors and insulators. While using different static dielectric functions - a Thomas-Fermi or a Hubbard screening function for the sX-LDA and a step function or an RPA for the model GW - those methods gave surprising agreement of the energy gaps with each other and with experiments. We have investigated semiconductor systems such as Si, Ge, and InSb using the full-potential linearized augmented plane wave (FLAPW) method(Wimmer, Krakauer, Weinert, Freeman, Phys. Rev. B 24, 864 (1981)) within the model GW method including the above dielectric functions. Our focus is on understanding the different results obtained for the structural properties (lattice constants and bulk moduli) and optical properties (band gaps and optical spectra). We find that the results can be interpreted by different long-range screening behavior corresponding to the different static dielectric functions employed in the model GW calculations.

Asahi, Ryoji; Freeman, A. J.

1998-03-01

92

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

PubMed Central

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.

Ji, Zhen; Brace, Christopher L

2011-01-01

93

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

NASA Astrophysics Data System (ADS)

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 time-temperature curve for both relative permittivity and effective conductivity. Coupled electromagnetic-thermal 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 temperature-time integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperature-time 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.

Ji, Zhen; Brace, Christopher L.

2011-08-01

94

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

PubMed

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 time-temperature curve for both relative permittivity and effective conductivity. Coupled electromagnetic-thermal 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 temperature-time integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperature-time 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

Ji, Zhen; Brace, Christopher L

2011-08-21

95

Dynamical, scattering and dielectric properties of ferroelectric crystals  

Microsoft Academic Search

A unified treatment is given of various properties of ferroelectric crystals in their non-polar phases, typified by BaTiO3, KH2PO4 and NaNO2. Certain relations are established between measurable dielectric and scattering properties. Critical scattering is discussed in terms of lattice dynamics.

W. Cochran

1969-01-01

96

Effective elastic, piezoelectric and dielectric properties of braided fabric composites  

Microsoft Academic Search

Composites based upon 3D textile preforms have found broad structural application. This paper presents an analytical methodology for functional composites using piezoceramic fibers in a 3D braided preform. The effective elastic, piezoelectric and dielectric properties of 2-step braided composites with a polymeric matrix have been investigated. In the analytical approach, the effective properties of the braider and axial yarns of

X. Ruan; A. Safari; T.-W. Chou

1999-01-01

97

Use of grain and seed dielectric properties for moisture measurement  

Microsoft Academic Search

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 grain and seed showing their variation with frequency, moisture content, temperature, and bulk density, and references are

Stuart O. Nelson; Samir Trabelsi

2011-01-01

98

The dielectric properties of PC-SAN multilayer composites  

Microsoft Academic Search

Immiscible polymer-polymer systems can have a range of morphological features such as occlusions, co-continuous domains or multilayered structures. Since morphology is known to have a major influence on physical properties, there is a need to characterize the solid state structure. The limited studies available for reference describing the dielectric properties of mixed polymer systems generally focus on miscibility aspects [1

J. H. Daly; J. Guest; D. Hayward; R. A. Pethrick

1991-01-01

99

Static, statistical, and dynamical properties of small sodium clusters  

Microsoft Academic Search

This paper reports results obtained in the study of small alkali metal clusters (2=n=34). Properties of interest include static descriptions of the Potential Energy Surfaces (PES) using a Distance-Dependent Tight Binding hamiltonian (DDTB) and new results obtained with the same hamiltonian through a Monte-Carlo Growth Method (MCGM) which is shown to give an efficient way to sample the PES, but

R. Poteau; D. Maynau; J.-P. Daudey; F. Spiegelmann

1993-01-01

100

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

NASA Astrophysics Data System (ADS)

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.

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

2010-02-01

101

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

102

First principles studies of interface dielectric properties of polymer/metal-oxide nanocomposites  

NASA Astrophysics Data System (ADS)

This thesis is devoted to studying interface dielectric properties of polymer nanocomposites from first principles. We aim to understand at atomic scale the role of interface effects and the dielectric finite size effects of nanoparticles in determining the effective dielectric properties of polymer nanocomposites. To study surface effects from first principles, we first investigate the two common methods, namely dipole correction and Coulomb cutoff, used to eliminate the artificial effects introduced by using the supercell approximation. We implement Coulomb cutoff technique in a plane-wave-based density functional theory code and compare it with dipole correction for the same system under the same conditions. By comparison, both methods are shown to be equivalent and able to remove the artificial effects of periodic images very accurately. We also find that a combination of these two methods offers an easy way to distinguish the localized bound states of interest from highly delocalized unoccupied states while using a relatively small supercell, and to ascertain the convergence of the results with respect to supercell size. To understand the dielectric properties at the atomic scale, we develop a new nanoscale averaging model to connect the macroscopic quantities to the corresponding microscopic ones. This model allows us to compute the spatially resolved local dielectric permittivity, including the critically important ionic contributions, for interfaces and other complex structures. In this model, a simple way of evaluating real-space decay length of the nonlocal dielectric functions is also proposed. By using the dipole correction and our averaging model in supercells, we calculate the optical and static local dielectric permittivity profiles for polymer (polypropylene)/metal-oxide (PbTiO3 and alumina) nanocomposites. Our ab-initio results show that metal-oxide/polymer interface effects are very localized and are mostly confined to the metal-oxide surface side, and that nanoscale metal-oxide slabs can on average retain the macroscopic value of bulk dielectric permittivity. These findings suggest that classical mixing laws associated with macroscopic composites can be applied to model the overall dielectric constant of a real polymer/metal-oxide nanocomposite system.

Yu, Liping

103

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

104

Optical properties of crystalline semiconductors and dielectrics  

Microsoft Academic Search

A new formulation for the complex index of refraction, N(E)=n(E)-ik(E), as a function of photon energy E, for crystalline semiconductors and dielectrics is developed based on our previous derivation of N(E) for amorphous materials. The extinction coefficient k(E) is deduced from a one-electron model with finite lifetime for the excited electron state. The refractive index n(E) is then derived from

A. R. Forouhi; I. Bloomer

1988-01-01

105

Low frequency electrical properties of selected dielectrics  

NASA Astrophysics Data System (ADS)

The resistivity, permittivity, and dissipation factor of selected dielectric materials were measured with a Harris bridge to find an electrode material in an electrohydrodynamic pump which could produce a 45(0) phase shift. The tested materials were: conductive rubber LM9194-20, conductive rubber LM9194-7, Delrin, polymethyl methacrylate, chlorinate polyvinyl chloride, Drogamid, GE No. 14020 phenolic, duct tape lamination, and polytetrafluorethylene.

Kelly, D. P.; Chato, J. C.; Crowley, J. M.

106

Improvement in photoconductor film properties by changing dielectric layer structures  

NASA Astrophysics Data System (ADS)

In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI2 and PbI2) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI2, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors.

Kim, S.; Oh, K.; Lee, Y.; Jung, J.; Cho, G.; Jang, G.; Cha, B.; Park, J.; Nam, S.

2011-01-01

107

Method to characterize dielectric properties of powdery substances  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

108

Dielectric and orientational properties of nematogenic 4- n-octyl(4'-cyanophenyl)benzoate  

NASA Astrophysics Data System (ADS)

Experimental studies of the dielectric properties in the nematic and isotropic phases of 4-cyanophenyl-4'-n-octylbenzoate (8CPB) have been performed in the frequency range from 50 kHz to 100 MHz. The relaxation process related to the rotation around the short molecular axis has been analysed. The results obtained have revealed that in the vicinity of the I-N phase transition, the molecular subdiffusional rotation process occurs. It is connected with the pretransitional effects which are observed both in the static and dynamic dielectric measurements. On the basis of the temperature dependence of the relaxation time in the nematic and isotropic phases, the orientational order parameter has been determined. The values of obtained in this way have been compared with those evaluated from the measurements of the polarized electronic absorption of the dichroic dye, dissolved as guest probe in the mesogenic host.

Bauman, D.; Jad?yn, J.; Wolarz, E.; Modli?ska, A.; D?browski, R.

2010-03-01

109

Dielectric Property Measurements to Support Interpretation of Cassini Radar Data  

NASA Astrophysics Data System (ADS)

Radar observations are useful for constraining surface and near-surface compositions and illuminating geologic processes on Solar System bodies. The interpretation of Cassini radiometric and radar data at 13.78 GHz (2.2 cm) of Titan and other Saturnian icy satellites is aided by laboratory measurements of the dielectric properties of relevant materials. However, existing dielectric measurements of candidate surface materials at microwave frequencies and low temperatures is sparse. We have set up a microwave cavity and cryogenic system to measure the complex dielectric properties of liquid hydrocarbons relevant to Titan, specifically methane, ethane and their mixtures to support the interpretation of spacecraft instrument and telescope radar observations. To perform these measurements, we excite and detect the TM020 mode in a custom-built cavity with small metal loop antennas powered by a Vector Network Analyzer. The hydrocarbon samples are condensed into a cylindrical quartz tube that is axially oriented in the cavity. Frequency sweeps through a resonance are performed with an empty cavity, an empty quartz tube inserted into the cavity, and with a sample-filled quartz tube in the cavity. These sweeps are fit by a Lorentzian line shape, from which we obtain the resonant frequency, f, and quality factor, Q, for each experimental arrangement. We then derive dielectric constants and loss tangents for our samples near 13.78 GHz using a new technique ideally suited for measuring liquid samples. We will present temperature-dependent, dielectric property measurements for liquid methane and ethane. The full interpretation of the radar and radiometry observations of Saturns icy satellites depends critically on understanding the dielectric properties of potential surface materials. By investigating relevant liquids and solids we will improve constrains on lake depths, volumes and compositions, which are important to understand Titans carbon/organic cycle and inevitably the evolution of its environment.

Jamieson, Corey; Barmatz, M.

2012-10-01

110

Measurement of Dielectric Properties of Minerals at Microwave Frequencies.  

National Technical Information Service (NTIS)

The report describes a method the Bureau of Mines devised for measuring the dielectric constant and loss tangent of low-loss minerals at microwave frequencies. Determination of these properties makes it possible to predict the effects of using microwave h...

W. E. Webb R. H. Church

1986-01-01

111

Electrical Conduction and Dielectric Properties of Biodegradable Plastics  

Microsoft Academic Search

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 60C and the melting point (Tm) was about 166C. For the temperature dependence of current density (J), J of PLA

Katsuyoshi Shinyama; Shigetaka Fujita

2005-01-01

112

Mechanical and Dielectric Breakdown Properties of Biodegradable Plastics  

Microsoft Academic Search

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 100C, even the value for LDPE decreased. The Young's modulus of PLA at room temperature was about

Katsuyoshi Shinyama; Shigetaka Fujita

2006-01-01

113

Effective dielectric properties of packed mixtures of insulator particles  

Microsoft Academic Search

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

C. Pecharromn; J. E. Iglesias

1994-01-01

114

Static properties of equilibrium polymers confined in ultrathin films  

NASA Astrophysics Data System (ADS)

The static properties of equilibrium polymer melts confined in ultrathin films are studied by means of Monte Carlo simulations of a lattice model: the bond fluctuation model. In this work we focus on the effects of ultrathin film confinement between two parallel and neutral walls on chain size and molecular weight distribution. We compare our numerical results to analytical calculations by Semenov and Johner [Eur. Phy. J. E, 12, 469 (2003)] who predicted for ultrathin films, logarithmic corrections to the leading mean-field behavior. Our simulation data are compatible with the theoretical results.

Cavallo, Anna; Wittmer, Joachim P.; Johner, Albert; Baschnagel, Joerg

2008-03-01

115

First-principles study of dielectric properties of bulk NaCl and ultrathin NaCl films under a finite external electric field  

Microsoft Academic Search

We present a first-principles study of the dielectric properties of a NaCl crystal and ultrathin NaCl films under a finite external electric field. Our results show that the high-frequency dielectric constant of the films is less affected by the finite-size effect from crystal surfaces and is close to that of the crystal, whereas the static one is sensitive to the

Tomoya Ono; Kikuji Hirose

2005-01-01

116

Dielectric properties of reactor irradiated ferroelectric thin films  

Microsoft Academic Search

Radiation effects in highly oriented Pb1Zr0.53Ti0.47O3 (PZT), Pb0.94La0.06Zr0.65Ti0.35O3 (PLZT-6), and PbiZriO3 (PZ) ferroelectric (FE) and antiferroelectric (AF) thin films are investigated in view of their possible application as a temperature sensitive element in a new bolometer system for ITER (International Thermonuclear Experimental Reactor). The dielectric properties (i.e. hysteresis loops, dielectric constants) of the films were investigated in a frequency range

R. Bittner; K. Humer; H. W. Weber; M. Tyunina; L. Cakare; A. Sternberg; D. V. Kulkov; Y. V. Trushin

2001-01-01

117

Method for Determining Dielectric Properties of Solids from Measurements on Pulverized Materials  

Microsoft Academic Search

A procedure is outlined for determining the dielectric properties of solid materials of known densities from the dielectric properties of pulverized samples measured at a few different bulk densities. Properties for the solid are obtained by extrapolation of functions of the dielectric constant and loss factor that are linearly related to the bulk density of the air-particle mixture.

Stuart O. Nelson; Richard B. Russell

1987-01-01

118

Lunar powder simulator under lunarlike conditions - Dielectric properties  

NASA Technical Reports Server (NTRS)

A powered basalt simulating lunar regolith material was subjected to temperature variations similar to those found in the lunar surface during a lunation. To obtain the dielectric response under simulated lunar conditions, all measurements were made in appropriate vacuums which, in addition, allowed for an evaluation of moisture effects in the powdered sample. It is found that during approximately seven tenths of a lunation the dielectric response of a 5- to 10-cm surface layer should be fairly constant. During the remaining three tenths, it should undergo rapid changes. Changes in the dielectric properties of the surface layer should be controlled by temperature. In the subjacent layers such changes are thought to be controlled by the increasing density of the regolith.

Alvarez, R.

1973-01-01

119

Effect of interfacial layers on dielectric properties in very thin SrBi2Ta2O9 capacitors  

Microsoft Academic Search

The effect of interfacial layers on the dielectric properties in very thin SrBi2Ta2O9 (SBT) capacitors has been investigated using static measurements. Total permittivity (?t) decreased as the film thickness was reduced in both Pt\\/SBT\\/Pt and Ir\\/SBT\\/Pt capacitors. The contribution of the interfacial capacitance (Cint) and bulk capacitance to the total capacitance indicates that Cint of the Ir\\/SBT\\/Pt structure was lower

Bum-Ki Moon; Chiharu Isobe; Katsuyuki Hironaka; Shinichi Hishikawa

2001-01-01

120

A density functional study on dielectric properties of acrylic acid grafted polypropylene  

NASA Astrophysics Data System (ADS)

Influence of acrylic acid grafting of isotactic polypropylene on the dielectric properties of the polymer is investigated using density functional theory (DFT) calculations, both in the molecular modeling and three-dimensional (3D) bulk periodic system frameworks. In our molecular modeling calculations, polarizability volume, and polarizability volume per mass which reflects the permittivity of the polymer, as well as the HOMO-LUMO gap, one of the important measures indicating the electrical breakdown voltage strength, were examined for oligomers with various chain lengths and carboxyl mixture ratios. When a polypropylene oligomer is grafted with carboxyl groups (cf. acrylic acid), our calculations show that the increase of the polarizability volume ?' of the oligomer is proportional to the increase of its mass m, while the ratio ?'/ m decreases from the value of a pure polymer when increasing the mixture ratio. The decreasing ratio of ?'/ m under carboxyl grafting indicates that the material permittivity might also decrease if the mass density of the material remains constant. Furthermore, our calculations show that the HOMO-LUMO gap energy decreases by only about 15% in grafting, but this decrease seems to be independent on the mixture ratio of carboxyl. This indicates that by doping polymers with additives better dielectric properties can be tailored. Finally, using the first-principles molecular DFT results for polarizability volume per mass in connection with the classical Clausius-Mossotti relation, we have estimated static permittivity for acrylic acid grafted polypropylene, assuming the structural density keeping constant under grafting. The computed permittivity values are in a qualitative agreement with the recent experiments, showing increasing tendency of the permittivity as a function of the grafting composition. In order to validate our molecular DFT based approach, we have also carried out extensive three-dimensional bulk periodic first-principles total-energy calculations in the frameworks of the density functional theory and density functional perturbation theory (DFPT) for crystalline acrylic acid grafted polypropylene. Interestingly, the computed electronic and dielectric properties behave very similarly between the simplified molecular DFT modeling and the more realistic 3D bulk periodic DFPT method. In particular, the static permittivity values [?r(0)] from the molecular DFT--Clausius-Mossotti modeling are in excellent agreement with the high-frequency dielectric constant values (V?) from the DFPT method. This obviously implies that the chain-to-chain interaction to dielectric and electronic properties of acrylic acid polypropylene, to a first approximation, can be neglected, therefore justifying the usage of molecular DFT modeling in our calculations.

Ruuska, Henna; Arola, Eero; Kortelainen, Tommi; Rantala, Tapio T.; Kannus, Kari; Valkealahti, Seppo

2011-04-01

121

Microwave Dielectric Properties of Ceramic/Semicrystalline Polymer Composites  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

122

Rheological and dielectric properties of different gold nanoparticle sizes  

PubMed Central

Background Gold nanoparticles (GNPs) have found themselves useful for diagnostic, drug delivery and biomedicine applications, but one of the important concerns is about their safety in clinical applications. Nanoparticle size has been shown to be an extremely important parameter affecting the nanoparticle uptake and cellular internalization. The rheological properties assume to be very important as it affects the pressure drop and hence the pumping power when nano-fluids are circulated in a closed loop. The rheological and dielectric properties have not been documented and identified before. The aim of the present study was to investigate the rheology and the dielectric properties of different GNPs sizes in aqueous solution. Methods 10, 20 and 50 nm GNPs (Product MKN-Au, CANADA) was used in this study. The rheological parameters were viscosity, torque, shear stress, shear rate, plastic viscosity, yield stress, consistency index, and activation energy. These rheological parameters were measured using Brookfield LVDV-III Programmable rheometer supplied with temperature bath and controlled by a computer. Results The shear stress and shear rate of GNPs have shown a linear relationship and GNPs exhibited Newtonian behaviour. The GNPs with larger particle size (50 nm) exhibited more viscosity than those with smaller particle sizes (10 and 20 nm). Viscosity decreased with increasing the temperature for all the examined GNP sizes. The flow behaviour index (n) values were nearly ? 1 for all examined GNP sizes. Dielectric data indicated that the GNPs have strong dielectric dispersion in the frequency range of 20-100 kHz. The conductivity and relaxation time decreased with increasing the GNP size. Conclusions This study indicates that the GNP size has considerable influence on the viscosity of GNPs. The strong dielectric dispersion was GNP size dependent. The decrease in relaxation time might be attributed to increase in the localized charges distribution within the medium confirmed by the conductivity data. This study suggests that further experiments are required to be done after the administration of GNPs through different routes in rats in vivo.

2011-01-01

123

Estimation of the dielectric properties of low-k materials using optical spectroscopy  

NASA Astrophysics Data System (ADS)

The dielectric function spectra of low dielectric constant (low-k) materials have been determined using spectroscopic ellipsometry, near-normal incidence spectroscopic reflectometry, and Fourier transform infrared transmission spectrometry over a wide spectral range from 0.03 to 5.4 eV (230 nm to 40.5 ?m wavelength region). The electronic and ionic contributions to the overall static dielectric constant were determined for representative materials used in the semiconductor industry for interlayer dielectrics: (1) FLARE-organic spin-on polymer, (2) HOSP-spin-on hybrid organic-siloxane polymer from the Honeywell Electronic Materials Company, and (3) SiLK-organic dielectric resin from the Dow Chemical Company. The main contributions to the static dielectric constant of the low-k materials studied were found to be the electronic and ionic absorptions.

Postava, K.; Yamaguchi, T.; Horie, M.

2001-10-01

124

Dielectric Properties of Phospholipids in Chloroform.  

National Technical Information Service (NTIS)

Permittivity was studied as a function of temperature and concentration for selected phospholipids in chloroform. Reduced lecithin, egg lecithin, and plant lecithin were used in this study to provide a range of properties in fatty-acid chain composition. ...

D. L. Jernigan G. M. Adams T. L. Sallee

1971-01-01

125

First principles studies of interface dielectric properties of polymer\\/metal-oxide nanocomposites  

Microsoft Academic Search

This thesis is devoted to studying interface dielectric properties of polymer nanocomposites from first principles. We aim to understand at atomic scale the role of interface effects and the dielectric finite size effects of nanoparticles in determining the effective dielectric properties of polymer nanocomposites. To study surface effects from first principles, we first investigate the two common methods, namely dipole

Liping Yu

2009-01-01

126

Investigation of dielectric and thermal properties of nano-filler (ZrO2) mixed enamel  

Microsoft Academic Search

In recent years, significant developments in nano-particles\\/fillers for electrical, thermal, and mechanical properties have been observed. In the present work, experimentally the dielectric and thermal properties of standard\\/nano-filled sample of enamel with Zirconia as filler have been critically examined. The dielectric loss (tan ?), dielectric constant (?), insulation strength, partial discharge inception voltage and weight loss of the material have

C. Pugazhendhi Sugumaran; M. R. Mohan; K. Udayakumar

2010-01-01

127

Determining bulk density of granular materials from microwave measurements of their dielectric properties  

Microsoft Academic Search

A dielectric method for determining bulk density of granular materials from measurement of their dielectric properties at microwave frequencies is presented. A complex-plane representation of the dielectric properties, normalized to bulk density, is used to generate calibration equations at 7 GHz for cereal grain and seed over wide ranges of moisture content and temperature

Samir Trabelsi; Andrzej W. Kraszewski; S. O. Nelson

2001-01-01

128

Static and Cyclic Creep Properties of Ti-6Al-4V for Several Heat Treatments.  

National Technical Information Service (NTIS)

The room temperature static and 'cyclic' creep properties were determined for Ti-6Al-4V in three anneal conditions (alpha beta) anneal, beta anneal and recrystallized anneal). The static and 'cyclic' creep strains were inversely related to microstructure....

C. M. Gilmore M. A. Imam

1975-01-01

129

Dielectric properties and hydrogen bonding interaction behaviour in binary mixtures of glycerol with amides and amines  

Microsoft Academic Search

The concentration dependent static dielectric constant, high frequency limit dielectric constant, excess dielectric constant and the effective Kirkwood correlation factor of the binary mixtures of glycerol with formamide, N,N-dimethylformamide, N,N-dimethylacetamide, ethanolamine and N,N-dimethylaminoethanol have been determined at 30C. The values of these functions emphasize mainly on the hydrogen bonding interactions between the unlike molecules in glycerol-amides and glycerol-amines mixtures, in

R. J. Sengwa; Vinita Khatri; Sonu Sankhla

2008-01-01

130

Thermal and dielectric properties of KH2PO4 at very low temperatures  

Microsoft Academic Search

Specific heat capacity, thermal conductivity and complex dielectric constant of KH2 PO4 have been measured to temperatures as low as 0.1 K. An increase of glasslike anomalies of the specific heat and the thermal conductivity after neutron irradiation has been found. After removing of an applied static electric field a logarithmic time dependence of the dielectric constant has been observed.

H.-E. Zimmer; J. Engert; E. Hegenbarth

1987-01-01

131

Static, statistical, and dynamical properties of small sodium clusters  

NASA Astrophysics Data System (ADS)

This paper reports results obtained in the study of small alkali metal clusters (2? n?34). Properties of interest include static descriptions of the Potential Energy Surfaces (PES) using a Distance-Dependent Tight Binding hamiltonian (DDTB) and new results obtained with the same hamiltonian through a Monte-Carlo Growth Method (MCGM) which is shown to give an efficient way to sample the PES, but may also be helpful to estimate the statistical occurrences of the various isomers (catching areas). The probability for generating a given configuration is proportional to a Boltzmann distribution factor and hence a temperature dependence is introduced in the study of the PES. In section 2, the temperature dependence of the optical response for small clusters (on the example of Na4) is simulated through ab initio calculations of the electronic structure coupled with Monte-Carlo dynamics on the absorbing system in the ground state.

Poteau, R.; Maynau, D.; Daudey, J.-P.; Spiegelmann, F.

1993-03-01

132

Ultrashort electric pulse induced changes in cellular dielectric properties.  

PubMed

The interaction of nanosecond duration pulsed electric fields (nsPEFs) with biological cells, and the models describing this behavior, depend critically on the electrical properties of the cells being pulsed. Here, we used time domain dielectric spectroscopy to measure the dielectric properties of Jurkat cells, a malignant human T-cell line, before and after exposure to five 10ns, 150kV/cm electrical pulses. The cytoplasm and nucleoplasm conductivities decreased dramatically following pulsing, corresponding to previously observed rises in cell suspension conductivity. This suggests that electropermeabilization occurred, resulting in ion transport from the cell's interior to the exterior. A delayed decrease in cell membrane conductivity after the nsPEFs possibly suggests long-term ion channel damage or use dependence due to repeated membrane charging and discharging. This data could be used in models describing the phenomena at work. PMID:17706595

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

2007-10-12

133

Dielectric properties of iron-bismuthate glass  

Microsoft Academic Search

Oxide glasses containing iron ions are of great interest because of their technological applications such as ferrites [1]. Some studies on the structural and magnetic properties of these glasses have been reported [2 4]. Iron ions in these glasses are considered to assemble together and form clusters which exhibit superparamagnetic behaviour, and below the freezing temperature individual spins are frozen

Aswini Ghosh

1989-01-01

134

Emulsions as materials with adjustable dielectric properties  

Microsoft Academic Search

Emulsions are examined as materials with adjustable electrical properties (relative permittivity and conductivity). The emulsions are simple mixtures of oil, saline solution, and a stabilizing agent (emulsifier). The relative permittivity of oil is around two, while that of water is around 80. Thus, a wide range of relative permittivity can be obtained by mixing these components. The conductivity of the

G. S. Smith

1988-01-01

135

Dielectric Properties Investigation of Polyaniline Prepared by Using Fenton's Reagent  

Microsoft Academic Search

The frequency dependence of the dielectric properties and dc conductivity (?dc) of polyaniline samples that have been prepared in a conducting state by a chemical method using Fenton's reagent were investigated. These samples were prepared at constant molar ratio H2O2\\/aniline (r=1) and at different concentrations of both H2O2 and aniline (0.2M, 0.4M, and 0.5M). The measurements were carried out using

M. M. Ayad; M. K. El-Nimr; E. A. Zaki

2009-01-01

136

Some Dielectric and Optical Properties of KD2PO4  

Microsoft Academic Search

The Curie point of KD2PO4 is found to be 2221K, which is 9K higher than previously reported. It is believed that the higher value is due to more complete deuteration. Other physical properties (at room temperature unless otherwise noted) are as follows: dielectric constant from 208 to 300K; contour shearmode resonance-frequency constant from 270 to 320K; elastic compliance, s66E=165310?12 m2?N;

T. R. Sliker; S. R. Burlage

1963-01-01

137

Dielectric, ferroelectric, magnetic, and magnetoelectric properties of multiferroic laminated composites  

Microsoft Academic Search

Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)\\/polyvinylidene-fluoride (PVDF) particulate composite layers and Tb-Dy-Fe alloy (Terfenol-D)\\/PVDF particulate composite layers, prepared by a simple hot-molding technique, were reported. In the laminated composites, the polymer PVDF is inert and used just as a binder. The measured dielectric, ferroelectric, magnetic, and magnetoelectric properties demonstrate strong dependence on volume fraction f of the PVDF

N. Cai; J. Zhai; C.-W. Nan; Y. Lin; Z. Shi

2003-01-01

138

Dielectric Properties of Binary Mixtures of MBBA and 7CB  

Microsoft Academic Search

The dielectric properties of mixtures of 4-methoxyybenzylidene-4-butylaniline (MBBA) and 4-n-heptyl-4'-cyanobiphenyl (7CB) were investigated at different molar concentrations. The isotropic-nematic phase boundary was determined for various mixtures in order to calculate the nematic range. For some concentrations, there was a second transition to a higher order smectic phase, most likely a Smectic G. Our previous work on MBBA and 5CB indicated

John Gamble; Shila Garg

2006-01-01

139

Manipulation and sensing of microparticles using dielectric properties  

NASA Astrophysics Data System (ADS)

The ability of electrokinetics to manipulate biological microparticles, such as cells and bacteria, has great applications in Lab-on-a-chip devices, and micro-total analysis systems (mTAS). In these methods, non-uniform AC electric fields interact with the dielectric properties of suspended biological microparticles to induce forces and torques on the particles, in order to manipulate them. This is usually done using devices which are planar microelectrode arrays patterned on glass substrates. These devices usually exploit the fact that biological microparticles are dielectrically heterogeneous structures, and that each different type of biological particle has a distinct dielectric frequency response signature. This enables discrimination and selectivity of cells when manipulating electrokinetically. Electrokinetics in the form of Dielectrophoresis (DEP) and Travelling-Wave Dielectrophoresis (TWD) are used to induce rectilinear motion on suspended microparticles, whilst electrorotation is used to induce torques. This paper presents a device for manipulating biological microparticles using electrokinetics. The device consists of planar metal electrode arrays patterned on glass. The device exploits the dielectric frequency response of the microparticles for manipulation as well as sensing.

Higginbotham, Steven N.; Sweatman, Denis R.

2005-02-01

140

Testing techniques for determining static mechanical properties of Pneumatic tires  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

141

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

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

142

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

NASA Astrophysics Data System (ADS)

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.

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

2008-01-01

143

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

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

144

Gallium Phosphate Thin Films: Synthesis and Dielectric Properties  

NASA Astrophysics Data System (ADS)

Deposits of dielectric gallium phosphate thin films on silicon and gallium arsenide semiconductors have been obtained by pyrolysis of an aerosol produced by ultrasonic spraying ("pyrosol" process) and containing the organometallic precursors gallium acetylacetonate and tributyl phosphate. The composition and microstructure of the layers are discussed with respect to the experimental conditions. For this paper, electrical properties were also studied. Using the metal-insulator-semiconductor structure, the behavior of conductivity under direct current, capacitance, and dielectric loss was studied in terms of frequency, temperature, and chemical composition. The sites involved in the conduction process are structural defects directly related to the oxygen excess present in deposits which leads to the formation of M-O dangling bonds ( M=Ga or P).

Tourtin, F.; Armand, P.; Ibanez, A.; Philippot, E.

1997-11-01

145

Sine-Gordon kinks on a discrete lattice. II. Static properties  

Microsoft Academic Search

The differences in the static properties between the discrete and continuum kink solutions of the one-dimensional sine-Gordon equation are found with use of a discretized Hamiltonian formalism which we have developed previously. The difference in the kink profile is treated as a static dressing of the continuum soliton. We point out some of the salient features of the static dressing

P. Stancioff; C. Willis; M. El-Batanouny; S. Burdick

1986-01-01

146

Measurement of breast - tumor phantom dielectric properties for microwave breast cancer treatment evaluation  

Microsoft Academic Search

Most phantom models do not include distinct definitions of tumor and normal tissue. This article proposes a novel solid breast - tumor phantom for microwave hyperthermia in breast cancer treatment. According to tissue dielectric properties reported, we performed phantom. A Network Analyzer and Dielectric Probe Kit measured dielectric constant and electrical conductivity for both breast normal tissue and tumor phantom.

R. Ortega-Palacios; Lorenzo Leija; Arturo Vera; M. F. J. Cepeda

2010-01-01

147

Processing, microstructure, and microwave dielectric properties of tunable (barium,strontium)titanate thin films  

Microsoft Academic Search

Barium strontium titanate (BST) materials have been extensively investigated for their applicationability in microwave varactors of monolithic circuits. Compared to bulk BST, thin films exhibited significant degradations in their dielectric properties, including suppressed dielectric constants and tunabilities, increased losses, and diffuse temperature dependences of dielectric constant. To understand the causes of these degradations, Three research lines were followed to conduct

Hui Du

2009-01-01

148

Effect of clay on dielectric properties of oil-sand media  

Microsoft Academic Search

While the dielectric properties of oil itself are well known, neither the dielectric constant nor the resistivity of a multiphase system consisting of a matrix with clay, containing oil and more or less water, is at all well known. Presented herein are some measured values of the dielectric constant based on a preliminary study of multiphase systems consisting of (1)

R. P. Singh; D. Rankin

1986-01-01

149

A spherical model with directional interactions. I. Static properties  

NASA Astrophysics Data System (ADS)

We introduce a simple spherical model whose structural properties are similar to the ones generated by models with directional interactions, by employing a binary mixture of large and small hard spheres, with a square-well attraction acting only between particles of different sizes. The small particles provide the bonds between the large ones. With a proper choice of the interaction parameters, as well as of the relative concentration of the two species, it is possible to control the effective valence. Here we focus on a specific choice of the parameters which favors tetrahedral ordering and study the equilibrium static properties of the system in a large window of densities and temperatures. Upon lowering the temperature we observe a progressive increase in local order, accompanied by the formation of a four-coordinated network of bonds. Three different density regions are observed: At low density the system phase separates into a gas and a liquid phase; at intermediate densities a network of fully bonded particles develops; at high densities-due to the competition between excluded volume and attractive interactions-the system forms a defective network. The very same behavior has been previously observed in numerical studies of nonspherical models for molecular liquids, such as water, and in models of patchy colloidal particles. Different from these models, theoretical treatments devised for spherical potentials, e.g., integral equations and ideal mode coupling theory for the glass transition, can be applied in the present case, opening the way for a deeper understanding of the thermodynamic and dynamic behavior of low valence molecules and particles.

Zaccarelli, Emanuela; Sciortino, Francesco; Tartaglia, Piero

2007-11-01

150

Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites  

SciTech Connect

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

Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana [Faculty of Physics, 'Al. I. Cuza' University of Iasi 700506, Iasi (Romania); Airimioaei, Mirela [Faculty of Chemistry, 'Al. I. Cuza' University of Iasi 700506, Iasi, Romania and Dept. Chemistry and Process Engineering, University of Genoa, P-le Kennedy no. 1, I-16129, Genoa (Italy); Tascu, Sorin [RAMTECH Faculty of Physics, 'Al. I. Cuza' University of Iasi 700506 (Romania); Schileo, Giorgio [Christian Doppler Laboratory for Advanced Ferroic Oxides, Sheffield Hallam University, Howard Street, Sheffield S1 1WB (United Kingdom); Galassi, Carmen [CNR-ISTEC, Via Granarolo no. 64, I-48018 Faenza (Italy)

2013-02-21

151

Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

152

Dielectric properties of stoichiometric and defect-induced hydroxyapatite  

NASA Astrophysics Data System (ADS)

Dehydrated hydroxyapatite (HAp), OH- ion-defect induced hydroxyapatite, was prepared for dielectric measurements. We evaluated the dielectric properties of HAp in 100-500 C, and found dielectric relaxations of two kinds. At lower temperature, relaxation that was attributed to the reorientations of OH- ions was observed, where the relaxation strengths were influenced strongly by the OH- concentrations. The activation energy of the OH- reorientation, which was unaffected by the OH- concentrations, was ascertained as 0.62-0.63 eV. However, in a higher temperature range, relaxations that had larger relaxation strength were observed and were regarded as originating from the displacement of OH- ions and O2- ions. The activation energies of the larger relaxation, which were affected by the OH- concentrations, were ascertained as 0.73 eV and 0.81 eV. Those values are comparable to the activation energy of proton conduction, implying that the proton conduction in HAp starts at a low temperature.

Horiuchi, N.; Endo, J.; Wada, N.; Nozaki, K.; Nakamura, M.; Nagai, A.; Katayama, K.; Yamashita, K.

2013-04-01

153

Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.  

PubMed

Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan ?) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces. PMID:24145704

Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

2013-12-01

154

Temperature behavior of dielectric and piezoelectric properties of samarium-doped lead titanate ceramics  

Microsoft Academic Search

The dielectric and electromechanical coupling properties of Sm-doped and Mn-doped PbTiO3 ceramics were investigated from 4.2 to 300 K. The upper and lower limits of the ceramic dielectric and piezoelectric properties were calculated by averaging the single-domain constants that were determined from a phenomenological theory. Comparisons of the measured and calculated properties were then made. The measured dielectric permittivity ?T33

J. N. Kim; MICHAEL J. HAUN; SEI JOO JANG; L. E. Cross; X. R. Xue

1989-01-01

155

Dielectric property improvement of polymer-nanosized strontium titanate-composites for applications in microelectronics  

Microsoft Academic Search

With respect to applications in microelectronics the frequency and temperature dependent dielectric properties of a series\\u000a of polymer-based composites, consisting of a thermally curable unsaturated polyester-styrene resin and nanosized strontium\\u000a titanate filler, have been characterized. Following earlier investigations targeting an improvement of dielectric properties\\u000a the impact of a thermal treatment of the dielectric filler on the resulting composite properties was

Thomas Hanemann; Holger Gesswein; Benedikt Schumacher

156

Broadband, high-temperature dielectric properties measurements of thin substrates using open-ended probes  

Microsoft Academic Search

A metallized-ceramic probe has been designed for high-temperature broadband dielectric properties measurements. The probe has been used to make complex dielectric properties measurements over the frequency band from 500 MHz to 3 GHz, and up to temperatures as high as 1000C. We present results illustrating the use of this probe for broadband, high-temperature, dielectric properties measurements of thin samples and

Shane Bringhurst; Magdy F. Iskander; M. J. White

1997-01-01

157

Dielectric properties of doping-free NaMnO: Origin of the observed colossal dielectric constant  

Microsoft Academic Search

The semiconducting NaMnO 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 ε{sub R} value

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

2006-01-01

158

Dielectric properties of doping-free NaMn7O12 : Origin of the observed colossal dielectric constant  

Microsoft Academic Search

The semiconducting NaMn7O12 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 20Hzto1MHz . Standard measurements on metallized samples exhibit an apparent colossal dielectric constant (CDC) with an gammaR value of several thousands at

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

2006-01-01

159

Dielectric properties of liquid crystals in polycapillary matrices  

NASA Astrophysics Data System (ADS)

This paper reports on the results of investigations into the dielectric properties of liquid crystals embedded in polycapillary matrices and describes a technique for their measurement. It has been revealed that the chemical structure of the rigid core and the length of mobile alkyl groups of liquid-crystal molecules of the alkylcyanobiphenyl group substantially affect the equilibrium configuration of the liquid-crystal director in capillaries. The reorientation of liquid-crystal molecules embedded in capillaries in the nematic phase under the influence of an external magnetic field has been investigated.

Belyaev, B. A.; Drokin, N. A.; Kumakhov, M. A.; Shabanov, V. F.

2010-06-01

160

Characterization of concrete properties from dielectric properties using ground penetrating radar  

Microsoft Academic Search

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 (?'

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

2009-01-01

161

Quantum confinement effects on the band structure and dielectric properties of nanostructured GaAs  

Microsoft Academic Search

The electronic band structure and dielectric properties of a GaAs quantum well have been investigated using the pseudopotential approach. The effect of quantum confinement on the electronic and dielectric properties of GaAs has been examined. It is found that significant variations in the studied properties occur at quantum well widths below 5 nm. The information may be useful in obtaining

Najah Hamed M. Al Wadiy; Nadir Bouarissa; M. Ajmal Khan

2011-01-01

162

Measurement of dielectric and magnetic properties of soil  

SciTech Connect

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.

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

1995-11-01

163

Static and dynamic properties of critical fluctuations in lipid bilayers  

NASA Astrophysics Data System (ADS)

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.

Honerkamp-Smith, Aurelia Rose

164

Investigation of lattice dynamical and dielectric properties of MgO under high pressure by means of mid-and far-infrared spectroscopy.  

PubMed

We investigate the lattice dynamical and dielectric properties of MgO single crystals and powders by measurements in the mid-and far-infrared frequency region under high pressures, ranging up to 21.7GPa. The shift of the restrahlen region is used to determine the pressure dependence of the transverse and longitudinal optical modes. The analysis of the refractive index in the mid-and far-infrared region allowed us to obtain the pressure behavior of the static and electronic dielectric constants. The transverse effective charge slowly decreases under high pressure, reflecting the stability of MgO. As a consequence, the pressure dependence of the static and electronic dielectric constants is mainly determined by the pressure dependence of the polar phonon frequency and Penn gap, resulting in a pronounced decrease of the former and a moderate decrease of the latter. PMID:24275846

Pellicer-Porres, J; Segura, A; Ferrer-Roca, Ch; Sans, J A; Dumas, P

2013-12-18

165

Dielectric properties of doping-free NaMn7O12 : Origin of the observed colossal dielectric constant  

NASA Astrophysics Data System (ADS)

The semiconducting NaMn7O12 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 20Hzto1MHz . Standard measurements on metallized samples exhibit an apparent colossal dielectric constant (CDC) with an ?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 TCO=176K and shows a net bulk dielectric constant value ?R?68 at room temperature.

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

2006-07-01

166

Thermodynamic and optical properties of plasma, metals, and dielectrics  

SciTech Connect

This book presents analytically-obtained data on the principal thermodynamic properties (partial composition, degree of ionization, pressure, internal energy, effective adiabatic exponent) of the plasma of metals such as copper, stainless steel (Kh18N10T), tungsten, molybdenum, tantalum, zirconium, chromium, niobium, nickel, and silicon, and of dielectrics-zirconium dioxide (ZrO{sub 2}), silicon dioxide (SiO{sub 2}), polytetrafluorethylene (Teflon), organic glass (Plexiglas), textolite, polyformaldehyde and caprolactum at temperatures T between 10{sup 4} and 10{sup 6} K and plasma densities p = 10{sup {minus}4} TO 1 Kg/m{sup 3}. Since plasma systems employing the products of erosion of dielectrics (16--18) can be efficiently employed as sources of wide-bank radiation and used as such in solving a number of scientific and applied problems, we list her the analytically obtained values of the principal optical properties (continuous-absorption coefficient, group absorption coefficient, Planck-average absorption coefficient and Rosseland-averaged radiation mean free path) of the plasmas of Teflon, Plexiglas, textolite, polyformaldehyde and caprolactum over the previously mentioned ranges of T and p.

Protasov, Y.S.

1991-01-01

167

Structural, dielectric and magnetic properties of Ni substituted zinc ferrite  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

168

Dielectric Properties of Diesel and Gasoline by Terahertz Spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Arik, Enis; Altan, Hakan; Esenturk, Okan

2014-06-01

169

Microstructure and dielectric properties of biocarbon nanofiber composites  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

170

Microstructure and dielectric properties of biocarbon nanofiber composites  

PubMed Central

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.

2013-01-01

171

Microstructure and dielectric properties of biocarbon nanofiber composites.  

PubMed

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. PMID:23800353

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

2013-01-01

172

Dielectric Properties of Close-Packed Disordered Suspensions  

NASA Astrophysics Data System (ADS)

Multiple scattering techniques are used to calculate the dielectric properties of composites, specifically, close-packed disordered suspensions. Composites are usually described using single-site, long-wavelength approximations which are not applicable for either close-packed or disordered systems. In a suspension, the dielectric properties can be described in terms of electromagnetic waves multiply scattered from the inclusions and, therefore, we can use the power of Multiple-Scattering Theory together with Roth's Effective-Medium Approximation (EMA). The EMA goes beyond previous approximations as it includes particle size effects and local field fluctuations. We apply the EMA to two types of suspensions: (1) strong scattering systems of metal spheres embedded in insulating hosts and (2) a weak scattering system of pressed Al(,2)O(,3) particles. The EMA reproduces the basic features of the relevant experimental results better than other approximations. In order to further explore the utility of the EMA, we examine a model system of a Drude metal in an insulating host. The trends observed in the EMA results are those expected for a close -packed composite on the basis of general theoretical arguments.

Davis, Victoria Ann

173

Dielectric Properties of Fruits and Insect Pests as related to Radio Frequency and Microwave Treatments  

Microsoft Academic Search

Information on dielectric properties of commodities and insect pests is needed in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. Dielectric properties of six commodities along with four associated insect pests were measured between 1 and 1800MHz using an open-ended coaxial-line probe technique and at temperatures between 20 and 60C. The dielectric loss

S. Wang; J. Tang; J. A. Johnson; E. Mitcham; J. D. Hansen; G. Hallman; S. R. Drake; Y. Wang

2003-01-01

174

Dielectric and ferroelectric properties of lead indium niobate ceramic prepared by wolframite method  

Microsoft Academic Search

The dielectric and ferroelectric properties of lead indium niobate (Pb(In1\\/2Nb1\\/2)O3, PIN) ceramic prepared by an oxide-mixing method via wolframite route were investigated. The 98.5% perovskite fine-grained PIN ceramics with average grain sizes of 12?m were obtained by sintering at 1050C for 2h. The dielectric properties of the PIN were of relaxor ferroelectric behavior with temperature of dielectric maximum (Tm) ?

S. Wongsaenmai; S. Ananta; X. Tan; R. Yimnirun

2008-01-01

175

Hydration properties of adenosine phosphate series as studied by microwave dielectric spectroscopy  

Microsoft Academic Search

Hydration properties of adenine nucleotides and orthophosphate (Pi) in aqueous solutions adjusted to pH=8 with NaOH were studied by high-resolution microwave dielectric relaxation (DR) spectroscopy at 20C. The dielectric spectra were analyzed using a mixture theory combined with a least-squares Debye decomposition method. Solutions of Pi and adenine nucleotides showed qualitatively similar dielectric properties described by two Debye components. One

George Mogami; Tetsuichi Wazawa; Nobuyuki Morimoto; Takao Kodama; Makoto Suzuki

2011-01-01

176

Determination of dielectric properties of corn seeds from 1 to 100 MHz  

Microsoft Academic Search

The dielectric properties of corn seeds were determined in the ranges of 9.7121.51% wet basis (w.b.) for moisture content, 772.5902.2kg\\/m3 for bulk density and 1100MHz for frequency of applied electric field using a coaxial capacitor sample holder. Effects of the parameters such as moisture content, bulk density and frequency on the dielectric properties were investigated. The dielectric constant, loss factor

Kamil Sacilik; Ahmet Colak

2010-01-01

177

Temperature Dependent Dielectric Properties of Polycrystalline Aluminum Oxide Substrates with Various Impurities  

Microsoft Academic Search

Temperature dependent dielectric properties of 92% and 99.6% polycrystalline aluminum oxide (Al2O3) substrate materials between room temperature and 550degC are reported, and compared with those of 96% Al2O3. Parallel-plate capacitors with aluminum oxide dielectrics and gold electrodes were used for measurement of the dielectric properties of these materials. The capacitance and parallel conductance of these Al2O3 materials were directly measured

Liang-Yu Chen

2007-01-01

178

Disclosed dielectric and electromechanical properties of hydrogenated nitrile-butadiene dielectric elastomer  

NASA Astrophysics Data System (ADS)

This paper presents a comprehensive study of the effects of acrylonitrile content, crosslink density and plasticization on the dielectric and electromechanical performances of hydrogenated nitrile-butadiene dielectric elastomer. It was found that by increasing the acrylonitrile content of hydrogenated nitrile-butadiene dielectric elastomer, the dielectric constant will be improved accompanied with a sharp decrease of electrical breakdown strength leading to a small actuated strain. At a fixed electric field, a high crosslink density increased the elastic modulus of dielectric elastomer, but it also enhanced the electrical breakdown strength leading to a high actuated strain. Adding a plasticizer into the dielectric elastomer decreased the dielectric constant and electrical breakdown strength slightly, but reduced the elastic modulus sharply, which was beneficial for obtaining a large strain at low electric field from the dielectric elastomer. The largest actuated strain of 22% at an electric field of 30 kV mm-1 without any prestrain was obtained. Moreover, the hydrogenated nitrile-butadiene dielectric actuator showed good history dependence. This proposed material has great potential to be an excellent dielectric elastomer.

Yang, Dan; Tian, Ming; Dong, Yingchao; Liu, Haoliang; Yu, Yingchun; Zhang, Liqun

2012-03-01

179

Dielectric Properties of Sweet Potato Purees at 915 MHz as Affected by Temperature and Chemical Composition  

Microsoft Academic Search

A process for rapid sterilization and aseptic packaging of sweet potato puree using a continuous flow microwave system operating at 915 MHz has been successfully developed. In microwave processing, dielectric properties have a major role in determining the interaction between purees and the electromagnetic energy. The objective of this research was to determine how dielectric properties are affected by temperature

T. A. Brinley; V. D. Truong; P. Coronel; J. Simunovic; K. P. Sandeep

2008-01-01

180

Dielectric properties of salmon fillets as a function of temperature and composition  

Microsoft Academic Search

Dielectric properties for anterior, middle, tail, and belly portions of Alaska pink salmon (Oncornynchus gorbuscha) fillets were measured at frequencies between 27 and 1800MHz from 20 to 120C to provide insights for improving the modeling of microwave (MW) and radio frequency (RF) commercial sterilization processes of salmon products. Compositional differences contributed to the observed slight differences in the dielectric properties

Yu Wang; Juming Tang; Barbara Rasco; Fanbin Kong; Shaojin Wang

2008-01-01

181

Modification of dielectric properties of porous glass by adsorption of hydrogen  

Microsoft Academic Search

We have investigated the dielectric properties of a porous glass (Vycor 7930, typical pore radius: ~3 nm) with submonolayer coverages of H2, HD, or D2 on the pore surface by means of a capacitive technique between 5 and 20 K. The adsorption of hydrogen influences, depending on the hydrogen species as well as on the coverage, the dielectric glass properties.

A. Dertinger; M. Schindler; Y. Kondo; F. Pobell

1997-01-01

182

Mechanical and Dielectric Breakdown Properties of Biodegradable Plastics  

NASA Astrophysics Data System (ADS)

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 100C, 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, 60C 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 60C (?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 60C 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 80C and above.

Shinyama, Katsuyoshi; Fujita, Shigetaka

183

Structural and Dielectric Properties of Quartz-Water Interfaces  

SciTech Connect

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.

Wander, Matthew C.; Clark, Aurora E.

2008-11-19

184

Dielectric Properties of Low-Level Liquid Waste  

SciTech Connect

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.

L. E. Lagos; M. A. Ebadian

1998-10-20

185

Dielectric properties of epoxy based nanocomposites for high voltage insulation  

Microsoft Academic Search

Epoxy polymer with micro, nano and micro + nano silica fillers have been evaluated for their electrical performance in high voltage insulation applications. The dielectric strength of these samples was measured in accordance with the ASTM D-149 standard. Dielectric spectroscopy was used to understand the role of space charge and interfaces in these materials. The results of dielectric spectroscopy suggest

G. Iyer; R. S. Gorur; R. Richert; A. Krivda; L. E. Schmidt

2011-01-01

186

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

NASA Technical Reports Server (NTRS)

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).

Dobson, M. Craig; McDonald, Kyle C.

1996-01-01

187

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

SciTech Connect

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.

Shiromizu, Tetsuya; Ohashi, Seiju; Tanabe, Kentaro [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2011-04-15

188

Characterization of concrete properties from dielectric properties using ground penetrating radar  

SciTech Connect

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.

Lai, W.L.; Kou, S.C. [Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Tsang, W.F. [Department of Building and Real Estate, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Poon, C.S. [Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)], E-mail: cecspoon@inet.polyu.edu.hk

2009-08-15

189

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

SciTech Connect

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.

Abe, H.; Okuda, H.

1994-06-01

190

Dielectric properties of liquid-crystalline copolymers with side cyanobiphenyl groups and acrylic acid units  

Microsoft Academic Search

Dielectric properties of a number of liquid-cry stalline comb-shaped copolymers with different ratios of side-chain mesogenic\\u000a cyanobiphenyl groups and acrylic acid units are studied. In the electric-field frequency range 300 Hz-100 MHz, temperature\\u000a dependences of dielectric permittivity are obtained for nematic and isotropic phases. The times of relaxation and the energies\\u000a of activation for processes responsible for dielectric-permittivity dispersion are

A. P. Kovshik; O. V. Magdysyuk; S. G. Polushin; E. B. Barmatov; M. V. Barmatova; E. I. Ryumtsev

2010-01-01

191

Dielectric and dynamic mechanical properties of polyimideclay nanocomposite films  

Microsoft Academic Search

An intercalation process was used to prepare polyimideclay nanocomposite films from the polyimide precursors (PMDA-ODA) and organo-modified clay in N,N-dimethylacetamide. The structure of the films was characterized by X-ray diffraction and transmission electron microscope techniques. The dielectric and dynamic mechanical properties of the films were studied over broad temperature and frequency ranges. The dependences of dielectric constant, dielectric loss, storage

Yi-He Zhang; Zhi-Min Dang; Shao-Yun Fu; John H. Xin; Jian-Guo Deng; Juntao Wu; Shiyong Yang; Lai-Feng Li; Qing Yan

2005-01-01

192

Dielectric properties of Ta2O5-ZrO2 polycrystalline ceramics  

Microsoft Academic Search

The dielectric properties of (Ta2O5)1-x(ZrO2)x polycrystalline ceramics at 1 MHz and temperatures between 0 and 100 C are reported for 0.0dielectric constant is moderately enhanced in the solid solution as a function of Zr content, and there is a significant decrease in the temperature coefficient of the dielectric constant (TCK). The annealing temperature of the ceramics is found

R. J. Cava; J. J. Krajewski

1998-01-01

193

The dielectric properties of nylon 6,6\\/aramid fibre microcomposites in the presence of transcrystallinity  

Microsoft Academic Search

Dielectric spectroscopy was applied in the present work for the first time to polymeric composite materials containing transcrystallinity, wherein the dielectric properties of pure nylon 6,6 and of aramid fibre-reinforced nylon 6,6 microcomposites were examined over wide frequency and temperature ranges. The temperature behaviour of the dielectric losses of the materials indicated three polarization processes, related to either local or

H Nuriel; N Kozlovich; Y Feldman; G Marom

2000-01-01

194

Effects of MnO 2 concentration on dielectric properties of barium strontium titanate glass ceramics  

Microsoft Academic Search

The phase development, microstructural evolution and dielectric properties of manganese-doped barium strontium titanate glass ceramics have been studied. The specimens with (Ba,Sr)TiO3 (BST) as the major crystalline phase were prepared by bulk crystallization process. The results show that the dielectric constant and the dielectric loss measured at room temperature pass through a maximum with increasing MnO2 concentration. This MnO2 concentration

Xiang-Rong Wang; Yong Zhang; Tao Ma; Chang-Sheng Deng; Xia-Ming Dai

195

Dielectric Properties of MoS 2 and Pt Catalysts: Effects of Temperature and Microwave Frequency  

Microsoft Academic Search

The effects of temperature and microwave frequency on the dielectric properties of MoS2 and Pt catalysts together with an aluminum oxide support were investigated. Dielectric constants and dielectric loss factors were measured in a temperature range of 200-800 C by a cavity resonator technique with a cylindrical copper cavity resonating in TM0n0 modes (n = 1, 2, ... ,5), which

Xunli Zhang; David O. Hayward; D. Michael P. Mingos

2002-01-01

196

Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics  

NASA Astrophysics Data System (ADS)

Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics are reviewed with the aim of providing an insight into different processes which may affect the behaviour of ferroelectric devices, such as ferroelectric memories and micro-electro-mechanical systems. Taking into consideration recent advances in this field, topics such as polarization switching, polarization fatigue, effects of defects, depletion layers, and depolarization fields on hysteresis loop behaviour, and contributions of domain-wall displacement to dielectric and piezoelectric properties are discussed. An introduction into dielectric, pyroelectric, piezoelectric and elastic properties of ferroelectric materials, symmetry considerations, coupling of electro-mechanical and thermal properties, and definitions of relevant ferroelectric phenomena are provided.

Damjanovic, Dragan

1998-09-01

197

Dielectric properties of water in butter and water-AOT-heptane systems measured using terahertz time-domain spectroscopy.  

PubMed

We investigate the dielectric properties of water confined in nanometer-sized inverse micelles in mixtures of water, AOT, and heptane. We show that the dielectric properties of the confined water are dependent on the water pool size and different from those of bulk water. We also discuss the dielectric properties of different vegetable oils, lard, and butter, and use these properties to deduce the dielectric properties of water in butter, which are shown to deviate significantly from the dielectric properties of bulk water. PMID:20828440

Mller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

2010-09-01

198

Static electrically charged fluids in terms of pressure: general property  

NASA Astrophysics Data System (ADS)

A most general exact solution to the Einstein-Maxwell equations for static charged perfect fluid is sought in terms of pressure. Subsequently, metrics ( e ? and e ? ), matter density and electric intensity are expressible in terms of pressure. Consequently, Pressure is found to be an invertible arbitrary function of ?(= c 1+ c 2 r 2), where c 1 and c 2(?0) are arbitrary constants, and r is the radius of star, i.e. p= p( ?). We present a general solution for charged pressure fluid in terms for ?. We list and discuss some old and new solutions which fall in this category.

Bijalwan, Naveen

2011-07-01

199

Microwave measurement of dielectric properties using the TM011 and TE011 modes excited by a generalized nonradiative dielectric resonator  

NASA Astrophysics Data System (ADS)

This paper proposes a new method for measurements of dielectric properties at microwave frequency. The measuring structure is a nonradiative dielectric resonator which is made up of a circular-symmetry cross shaped dielectric and two conducting plates each having a center hole. The dielectric is sandwiched between the two metal plates. Both the resonant TM011 and TE011 modes can be applied in this resonator. The radial mode matching method is employed for analyzing the field distributions, while the transmission-mode Q-factor measurement technique is used for precise determination of unloaded Q0-factor. Complex permittivities of several plastics, such as high-density polyethylene, cross-linked polystyrene, polytetrafluoroethylene and polycarbonate, are measured at room temperature. Their accuracies are justified by comparing the results with those obtained by other well-known techniques. An uncertainty analysis is also presented to estimate the errors resulting from the uncertainties in structure dimensions, resonant frequency, unloaded Q0-factor and conductivity of the metal plate. With this resonator, an accuracy of better than 1.5% is attained in real permittivity, while the uncertainty in loss tangent is within 2.5% for dielectric with loss tangent greater than 5.0 10-4. For material with lower loss, e.g. tan??10-4, the measurement uncertainty in loss tangent would not be greater than 10%. This larger uncertainty in loss tangent for materials with lower loss is mainly due to the uncertainty in conductivity of the metal plate.

Cheng, Guoxin; Liu, Lie; Cai, Dan; Yuan, Chengwei

2012-11-01

200

Texture effects on megahertz dielectric properties of calcite rock samples  

Microsoft Academic Search

Dielectric measurements have been made from 0.5 to 1300 MHz on Whitestone, a quarried calcite rock, saturated with salty water. Whitestone shows a large increase in dielectric permittivity (dispersion) at the low end of this frequency range. When the conductivity of the water is varied, the dielectric permittivity of Whitestone is found to scale as water conductivity\\/frequency, i.e., as the

W. E. Kenyon

1984-01-01

201

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

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

202

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

SciTech Connect

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

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

2000-04-03

203

Influence of the microstructure of vulcanized polybutadiene rubber on the dielectric properties  

Microsoft Academic Search

Dielectric relaxation spectra in the frequency range from 10Hz to 1GHz were obtained at room temperature to study the influence of the network structure formed during vulcanization on the dielectric properties of polybutadiene rubber (BR).Two polybutadiene rubbers with different cis, trans and vinyl content in their molecular structure were used to prepare compounds with a cure system based on sulphur

A. L. Rodriguez Garraza; P. Sorichetti; A. J. Marzocca; C. L. Matteo; G. A. Monti

2011-01-01

204

Electrical conductivity and dielectric properties of PMMA\\/expanded graphite composites  

Microsoft Academic Search

PMMA\\/expanded graphite (EG) composites were prepared by direct solution blending of PMMA with the expanded graphite filler. Electrical conductivity and dielectric properties of the composites were measured by a four-point probe resistivity determiner and a dielectric analyzer (DEA). Interestingly, only 1 wt.% filler content was required to reach the percolation threshold (?) of transition in electrical conductivity from an insulator

Wenge Zheng; Shing-Chung Wong

2003-01-01

205

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

Microsoft Academic Search

We present the results of five experiments investigating the dielectric properties of granular materials partially saturated with trichloroethylene (TCE), a common dense non-aqueous contaminant. Previous research has investigated the radar signatures of similar solvents in controlled field experiments but no core-scale measurements have verified the appropriate petrophysical model. Broadband dielectric measurements were performed using a time domain reflectometry (TDR) system

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

2004-01-01

206

Investigation and verification of mixture dielectric properties of polar liquid mixture  

Microsoft Academic Search

It is important to study the mixture dielectric constant for proper design of an insulation system. All electrical equipment depends somehow on an insulation system to maintain current flow in the proper channels. A high percentage of failures in electrical apparatus is caused by electrical insulation failure, so the study of mixture dielectric properties has extreme importance to the electrical

M. Ashraf Hossain

2004-01-01

207

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

PubMed

The dielectric behavior of foods when exposed to radio-frequency and microwave electric fields is highly influenced by moisture content and the degree of water binding with constituents of the food materials. The ability to correlate specific food quality characteristics with the dielectric properties can lead to the development of rapid, nondestructive techniques for such quality measurements. Water-holding capacity is a critical attribute in meat quality. Up to 50% of raw poultry meat in the United States is marinated with mixtures of water, salts, and phosphates. The objective of this study was to determine if variations in breast meat color would affect the dielectric properties of marinated poultry meat over a broad frequency range from 500 MHz to 50 GHz. Poultry meat was obtained from a local commercial plant in Georgia (USA). Color and pH measurements were taken on the breast filets. Groups of breast filets were sorted into classes of pale and normal before adding marination pickup percentages of 0, 5, 10, and 15. Breast filets were vacuum-tumbled and weighed for pickup percentages. Dielectric properties of the filets were measured with a coaxial open-ended probe on samples equilibrated to 25C. Samples from pale meat exhibited higher dielectric properties than samples from normal meat. No differences could be observed between samples from pale and normal meat after marination of the samples. Overall, dielectric properties increased as the marination pickup increased (?=0.05). Marination pickup strongly influenced the dielectric loss factor. Differences between samples marinated at different pickup levels were more pronounced at lower frequencies for the dielectric loss factor. As frequency increased, the differences between samples decreased. Differences in dielectric constant between samples were not as consistent as those seen with the dielectric loss factor. PMID:22802198

Samuel, D; Trabelsi, S

2012-08-01

208

Polarization Effects on the Millimeter Wave Dielectric Properties of Pesticide  

Microsoft Academic Search

This study investigates the effect of polarization on the dielectric measurements of pesticide. Dispersive Fourier Transform Spectroscopy was utilized to measure the absorption coefficient and refractive index from 180 to 420 GHz. Variations in the results due to polarization and birefringence were investigated by calculating the average value, standard deviation and percentage variations in dielectric data. Noticeable variations in the

Baris C. Piyade; U. A. Khan; M. N. Afsar

2008-01-01

209

Dielectric properties of antiferroelectric liquid-crystalline mixtures  

Microsoft Academic Search

Antiferroelectric liquid crystalline mixtures having smectic CA* phase in very broad temperature range have been investigated. Measurements of dielectric relaxation and spontaneous polarization were performed. Two absorption peaks in the existence range of the antiferroelectric CA* phase in the kHz-MHz range of frequency were observed. Both peaks are quite weak and of Debye type. Their characteristic dielectric strengths are almost

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

1999-01-01

210

Dielectric properties of antiferroelectric-ferroelectric liquid crystalline mixture  

Microsoft Academic Search

Dielectric investigations of ferroelectric liquid crystals at low frequency range enabled to detect two kinds of collective molecular motions: the Goldstone mode and the soft mode. The mixture of recently synthesized ferroelectric and antiferroelectric liquid crystals with relatively broad temperature range of SmC* and SmC*A phase was chosen for investigation of dielectric loss processes.

Marek Wojciechowski; Agnieszka L. Gromiec

2002-01-01

211

Dielectric Properties in Ferroelectric Liquid Crystal Mixtures with Ultrashort Pitch  

Microsoft Academic Search

The dielectric propereties of smectic liquid crystal mixtures containing chiral dopants derived from trifluoromethylated pyranose were studied. In every mixture, a large dielectric response due to the Goldstone mode was observed, indicating the smectic C* phase, although two switching current peaks indicative of the smectic CA* phase were observed in the mixtures with high dopant ratios. With increasing the chiral

Masahito Zennyoji; Jun Yokoyama; Yoichi Takanishi; Ken Ishikawa; Hideo Takezoe; Keizo Itoh

1998-01-01

212

Effective dielectric properties of composite materials in the surface layer  

Microsoft Academic Search

In the framework of the mean-field picture, an expression for the effective dielectric permittivity of an inhomogeneous medium near a flat interface with another dielectric is derived as a function of the distance from the boundary. The obtained formula should be considered as a counterpart of the standard Maxwell-Garnett one, but in the vicinity of a flat boundary. Possibilities of

R. Stepanyan

2003-01-01

213

Synthesis, characterization and dielectric properties of SnO2 thin films  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

214

Synthesis, characterization and dielectric properties of SnO2 thin films.  

PubMed

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

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

2014-12-10

215

Temperature dependence dielectric properties of modified barium titanate-PVB composites  

NASA Astrophysics Data System (ADS)

In this work, attempts are made to prepare ceramic polymer-composite followed by characterization of dielectric properties. The Barium Titanate ceramic powders are synthesized using the hydrothermal process. Silane treatment is carried out on Barium Titanate powder to increase its compatibility with polymer, followed with preparation of ceramic-polymer composite. Polyvinyl Butyral (PVB) is used as matrix for preparation of the composites and the concentration of Barium Titanate is increased from 60 to 90 wt%. Dielectric properties such as volume resistivity, dielectric constant, dissipation factor are evaluated. Results indicate that the dielectric constant and dissipation factor vary between 52 to 120 and 0.01 to 0.07; respectively as the relative ratio of polymer and silane modified Barium Titanate is varied. Specifically, at 90 wt% of silane modified Barium Titanate, the highest dielectric constant of 123 along with dissipation factor of 0.07 is obtained.

Joshi, N. J.; Rakshit, P. B.; Grewal, G. S.; Shrinet, V.; Pratap, A.

2013-06-01

216

Growth, XRD and dielectric properties of triglycine sulpho-phosphate (TGSP) crystals added with magnesium sulfate  

NASA Astrophysics Data System (ADS)

Pure and magnesium sulfate-doped triglycine sulpho-phosphate (TGSP) single crystals were grown by solution method with the slow evaporation technique. Solubility of the samples in de-ionized water was found in various temperatures ranging from 30 to 60 C. Single-crystal X-ray diffraction (XRD) studies on the grown crystals reveal the monoclinic crystal structure. Atomic absorption study (AAS) was carried out to confirm the presence of Mg 2+ in the grown doped TGSP crystals. Dielectric constant and dielectric loss of undoped and magnesium sulfate-doped TGSP crystals were measured for various frequencies and temperatures. It is observed from the studies that solubility and dielectric properties like dielectric constant and dielectric loss increase when TGSP crystal is added with magnesium sulfate. Thermogravimetric and differential thermal analyses (TG/DTA) on the grown crystals have been carried out. The effect of impurity (magnesium sulfate) on structural, electrical and thermal properties of TGSP crystals has been investigated.

Selvarajan, P.; Siva dhas, A.; Freeda, T. H.; Mahadevan, C. K.

2008-12-01

217

Structural, conductivity and dielectric properties of Li2SO4  

NASA Astrophysics Data System (ADS)

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 (?ac) and dielectric relaxation (tan ?) 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 ?ac (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.

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

2014-06-01

218

Crystallinity and Dielectric Properties of PEEK, a Thermoplastic Poly(ether ether ketone).  

National Technical Information Service (NTIS)

The overall objective of this study was to investigate the interdependence of specific dielectric properties of polymers on their fundamental molecular parameters in order to optimize the application of these polymeric materials in critical SMC systems. S...

T. W. Giants

1993-01-01

219

Addendum: Improvement in photoconductor film properties by changing dielectric layer structures Addendum: Improvement in photoconductor film properties by changing dielectric layer structures  

NASA Astrophysics Data System (ADS)

In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI2 and PbI2) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI2, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors

Kim, S.; Oh, K.; Lee, Y.; Jung, J.; Cho, G.; Jang, G.; Cha, B.; Park, J.; Nam, S.

2011-02-01

220

Compositional Design and Properties of a Low-k Silica Dielectric for Multilayer Ceramic Substrate  

NASA Astrophysics Data System (ADS)

Compositional design and properties of a low-dielectric-constant silica composite containing borosilicate glass, high-silica glass and gallium oxide are described. A cristobalite-free silica dielectric with a high sintered density, >95%, is obtained at temperatures less than 1000 C. An analytical approach assuming the mixing rule is used to design compositions with desirable properties, and validated by experimental results. Compositions with a thermal expansion coefficient compatible with Si and GaAs, and dielectric constants in the ranges of 4-5 and 5-6, respectively, at 1 MHz, are developed.

Jean, Jau-Ho; Kuan, Tong-Hua

1995-04-01

221

Dielectric Properties of Two-Phase Mixture Ceramics Composed of Rutile and Its Compounds  

Microsoft Academic Search

Dielectric properties of two-phase mixture systems including rutile (TiO2) have been investigated. One of its binary compounds---MnTiO3, ZnTiO3, PbTiO3 and Al2TiO5-was chosen as the second component. Dielectric constants \\\\varepsilonr and their temperature coefficients tau\\\\varepsilon were first examined at 1 MHz. Dielectric properties in the microwave frequency region were measured in the TE011 mode of a cylindrical specimen. The temperature coefficient

Kiyoshi Haga; Tsuyoshi Ishii; Jin-ichi Mashiyama; Takuro Ikeda

1992-01-01

222

Analytical model and experimental characterization of a dielectric elastomer annulus actuator undergoing large quasi-static deformation  

NASA Astrophysics Data System (ADS)

An analytical model of a thin annulus made of a dielectric elastomer was derived in our earlier work. It is the focus of this paper to fabricate and test the electroactive polymer actuators presented in the model. Radial displacement measurements were obtained using a digital image correlation technique that involved cross-correlating images of the actuator before and after a change in the electric field. Results showed that the two-term Ogden material model provided a good agreement with experimental data. Hysteresis of the dielectric actuators was observed. Radial displacements of material points on the actuator varied between two consecutive tests which may indicate that strain has history-dependent characteristics.

Yang, Eunice; Frecker, Mary I.; Mockensturm, Eric M.; Wu, Danielle

2004-07-01

223

Efficient dielectric function for FDTD simulation of the optical properties of silver and gold nanoparticles  

Microsoft Academic Search

We have developed an efficient parameterization of the dielectric properties of Au and Ag in the energy range between 0.6eV and 6.6eV. The resulting time-domain dielectric function can be used for finite-difference time-domain (FDTD) simulations of the optical properties of nanoparticles. We present FDTD calculations of the extinction spectra of various Au and Ag nanoparticles and show that the calculated

F. Hao; P. Nordlander

2007-01-01

224

Effects of annealing process on dielectric properties of sol-gel derived lead titanate thin films  

Microsoft Academic Search

This paper reports on the effects of annealing process on the dielectric properties of lead titanate (PbTiO3) thin films. The thin films have been deposited on silicon substrates using sol- gel spin coating method. The dielectric properties and resistivity of the thin films annealed at different annealing temperatures and times were then investigated using HIOKI 3532-50 LCR meter and four

R. A. Bakar; M. S. A. Bakar; M. Rusop

2011-01-01

225

Effect of organic dyes on the dielectric properties of KH 2 PO 4 crystals  

Microsoft Academic Search

The effect of organic dyes on the dielectric properties of KH2PO4 (KDP) crystals is studied over a wide range of temperatures. The dielectric properties of KDP crystals doped with molecules\\u000a of the Chicago Sky Blue and Amaranth organic dyes are investigated for the first time. The dye molecules can be incorporated\\u000a into the crystal lattice of KDP and selectively paint

S. V. Grabovskii; I. V. Shnaidshtein; B. A. Strukov

2003-01-01

226

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

SciTech Connect

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

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

1999-12-22

227

A Radio Frequency Sensor For Measurement Of Small Dielectric Property Changes  

Microsoft Academic Search

We propose a sensitive radio frequency (RF) sensor for the measurement of small dielectric property changes. Interference is used to cancel parasitic background signals to improve sensitivity. The device consists of two Wilkinson power dividers, a 180 degree reversephase and an in-phase CPW (coplanar waveguide)-slotline back-toback balun. The small dielectric property changes between de-ionize water and two sets of primary

W.-N. Liu; Y. Yang; K.-M. Huang

2012-01-01

228

Numerical simulations of dielectric properties of composite material with periodic structure  

Microsoft Academic Search

Results of computer simulations and measurements of frequency-dependent dielectric properties of a binary composite material are presented. The studied composite had well-defined 3D periodic structure and was made of paraffin and paper laminate. In the considered frequency range (10?3103Hz), both the constituents were characterized by significantly different dispersive properties of complex dielectric permittivities. These frequency-dependent parameters were measured and were

Yuriy V. Serdyuk; Aleksandr D. Podoltsev; Stanislaw M. Gubanski

2005-01-01

229

Sintering behavior and microwave dielectric properties of nano alpha-alumina  

Microsoft Academic Search

The microstructures and the microwave dielectric properties of nano alpha alumina (?-Al2O3) ceramics have been investigated. It is found that the use of nano particle-sized starting material can significantly improve the densification and their microwave dielectric properties of the specimens. The ?-Al2O3 ceramics can be sintered at 1450 C and increased beyond 99% of its theoretical density at 1500 C.

Cheng-Liang Huang; Jun-Jie Wang; Chi-Yuen Huang

2005-01-01

230

Study of intermolecular interaction of allyl chloride with acetone through dielectric and volumetric properties  

NASA Astrophysics Data System (ADS)

The static dielectric constant (?s)and relaxation time (?) are determined from complex permittivity spectra of Allyl Chloride (ALC) with Acetone (ACE), which are obtained using the Time Domain Reflectometry (TDR) technique in microwave frequency range 10 MHz to 10 GHz. Density (?) and refractive index (nD) were also measured. These parameters are used to determine excess dielectric constant, excess molar volume, and excess molar refraction. The excess parameter is fitted to Redlich-Kister(RK) equation. The values of excess parameters are positive in ALC rich region whereas in ACE rich region are negative.

Sudake, Y. S.; Kamble, S. P.; Maharolkar, A. P.; Patil, S. S.; Khirade, P. W.

2012-06-01

231

Effects of Electric Arc on The Dielectric Properties of Liquid Dielectrics  

Microsoft Academic Search

In high voltage equipment, insulation is an important part. There are solid, liquid, gaseous insulations and combination between them used in various equipments in a power system. Liquid dielectric is widely used in transformer, circuit breaker, capacitor and oil-filled cable. During the operation of the equipment, electric arc may take place in the liquid insulation. The arc contains high energy

Suwarno; Fadli Salim

2006-01-01

232

Structural and Dielectric properties of Acid Activated Metakaolinite and Kaolinite  

NASA Astrophysics Data System (ADS)

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.

Izci, E.

2014-06-01

233

Intercellular adhesion: Modification by dielectric properties of the medium  

Microsoft Academic Search

Summary The low radio frequency dielectric constant of aqueous solutions of glycine, diglycine,d-sorbitol, Dextran and Ficoll were determined. These values were used to predict the dielectric constant of Hanks-199 tissue culture medium to which various concentrations of these compounds had been added. Single cell dispersions of two chick embryonic tissues, 7-day neural retina and 5-day limb bub, were prepared in

Gareth E. Jones

1974-01-01

234

Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain  

SciTech Connect

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.

Tak, S. K. [Manda Institute of Technology, Bikaner (India); Shekhawat, M. S. [Engineering College, Bikaner (India); Mangal, R. [Govt Dungar College, Bikaner (India)

2010-06-29

235

Dielectric properties of colossal permittivity materials: An update  

Microsoft Academic Search

During the last ten years, a lot of interest has been devoted to the so-called colossal dielectric constant (CDC) material. The first materials exhibiting this behavior were the perovskyte-based ceramics based on the CaCu3Ti4O12 composition (CCTO). Relative dielectric permittivity can attain values up to (or even larger than) 105. Nevertheless, their losses are still high, the lower values ranging 10%,

Chafe Cheballah; Zarel Valdez-Nava; Lionel Laudebat; Thierry Lebey; Pierre Bidan; Sombel Diaham; Sophie Guillemet-Fritsch

2011-01-01

236

Electrooptic and dielectric properties of new antiferroelectric liquid crystal mixtures  

Microsoft Academic Search

Two new antiferroelectric liquid crystal mixtures based on optically active hydroxyesters have been studied with respect to their electro-optic and dielectric behavior. The mixtures exhibit only a SmA* phase above SmCa* and show a stable antiferroelectric order over a broad temperature range (?100C). Electro-optic as well as dielectric studies suggest that the SmCa*-SmA* transition is second order. In thin cells

G. Andersson; R. Dabrowski; W. Drzewinski; J. P. F. Lagerwall; M. Matuszczyk; T. Matuszczyk; P. Perkowski; Z. Raszewski

2000-01-01

237

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

PubMed

Dielectric properties are the most important parameters determining energy deposition when biological tissues are exposed to radio frequency and microwave fields. Energy absorption is determined by the specific absorption rate (SAR). SAR distributions can be computed accurately only if the complex relative permittivity of the target tissue is known to a sufficiently high accuracy, and currently there is a lack of data on the dielectric properties of biological tissues at high frequencies. In this study, tissue dielectric properties are measured using an open-ended coaxial probe technique from 500MHz up to 40GHz. We present dielectric data for ex vivo bovine and porcine muscle and liver tissues at 37C. One-pole Cole-Cole model is used to fit the measured data as a function of frequency and the dispersion parameters are presented. This data is supported by an accurate study on reference liquids such as methanol and ethanediol. PMID:23675628

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

2013-06-01

238

Effect of infrared pulsated laser on the dielectric properties of polycarbonate  

NASA Astrophysics Data System (ADS)

Makrofol-De polycarbonate is a class of polymeric solid state nuclear track detector which has many applications in various industrial fields. A study of the modification possibility of the dielectric properties of a Makrofol polymer using laser irradiation has been carried out. In the present work, Makrofol samples were irradiated using different fluences between 0.47 and 10.4 J/cm2 of 5 W infrared laser. The modifications in the laser irradiated Makrofol samples have been studied as a function of fluence using dielectric constant ?', dielectric loss ?'', and AC conductivity ?AC measurements. The frequency dependencies (100 Hz-5 MHz) of ?', ?'' and ?AC at 35 C were investigated. The dielectric constant ?', dielectric loss ?'' and AC conductivity ?AC were also found to increase on heating up to 100 C. The results indicate that ?', ?'' and ?AC depend not only on the frequency and temperature but also on the laser fluence.

Nouh, S. A.; Bahammam, S.

239

Dielectric properties and soft modes in semiconducting (Pb, Sn, Ge)Te  

NASA Astrophysics Data System (ADS)

The narrow-gap semiconductors PbTe, SnTe, GeTe and their alloys exhibit a tendency for a ferroelectric displacive phase transition from a high-temperature rocksalt structure to a rhombohedral phase at low temperatures. The critical temperatures vary within an exceedingly wide range: -70 K(PbTe) up to 650 K(GeTe). Owing to the outstanding simplicity of their crystal structure and their well-known electronic properties, the instability and the chemical trends of Tc can be understood in terms of a quantitative pseudopotential model (Sect.5.2). Phenomenological models explain the temperature dependence of the soft mode outside the critical regime fairly well (Sect.5.1). Critical phenomena, however, deserve further attention: the anomalies of the static dielectric constant (Sects.3.1 and 5.3) and the influence of defects are possibly related to a central peak. Additional systematic investigations on the nature and influence of defects are required to obtain more insight into this highly interesting field of general importance.

Jantsch, W.

240

Dielectric and microstructure properties of polymer carbon black composites  

SciTech Connect

Dielectric and physicochemical properties of a composite material prepared by incorporating carbon black particles into a polymer matrix were investigated. Two types of carbon blacks, having very different structures of aggregates, were used. The volume fraction of the carbon blacks ranged from 0.2{percent} to 7{percent}, i.e. below and above the percolation threshold concentration. The composite samples were characterized in terms of: swelling by a compatible solvent, EPR response, and frequency variation of permittivity. First, the article attempts to evaluate the diffusion coefficient of an appropriate solvent in these materials. Sorption kinetics experiments with toluene indicate that the initial uptake of solvent exhibits a square root dependence in time as a consequence of Ficks law and permit to evaluate the effective diffusion coefficient in the range 10{sup {minus}11}{endash}10{sup {minus}12} m{sup 2}s{sup {minus}1} depending on the volume fraction of the carbon black in the sample. Second, the analysis of the carbon black concentration dependence of the intensity and linewidth of the EPR signals indicates that EPR is an important experimental probe of the structure of the elasticity network. We find a correlation of the percolation threshold concentration which is detected from the dc electrical conductivity with moments of the EPR lines. The conclusions on the elasticity networks deduced from swelling measurements are confirmed by EPR data carried out on swollen samples. On qualitative grounds the role of the specific surface of carbon black is further analyzed. It is suggested that the elasticity network is mainly controlled by secondary (primary) aggregates for samples containing low (high) specific surface carbon blacks. Last, the article reports precise experimental data on the permittivity of these composite materials as a function of frequency. (Abstract Truncated)

Brosseau, C.; Boulic, F.; Queffelec, P.; Bourbigot, C.; Le Mest, Y.; Loaec, J. [Universite de Bretagne Occidentale, 6 avenue Le Gorgeu, B.P. 809, 29285 Brest Cedex, (France)] [Universite de Bretagne Occidentale, 6 avenue Le Gorgeu, B.P. 809, 29285 Brest Cedex, (France); Beroual, A. [CEGELY, Ecole Centrale de Lyon, 36 avenue de Collongue, B. P. 163, 69131 Ecully Cedex (France)] [CEGELY, Ecole Centrale de Lyon, 36 avenue de Collongue, B. P. 163, 69131 Ecully Cedex (France)

1997-01-01

241

Dielectric properties and microstructural characterization of cubic pyrochlored bismuth magnesium niobates  

NASA Astrophysics Data System (ADS)

Cubic bismuth pyrochlores in the -MgO- system have been investigated as promising dielectric materials due to their high dielectric constant and low dielectric loss. Here, we report on the dielectric properties and microstructures of cubic pyrochlored (BMN) ceramic samples synthesized via solid-state reactions. The dielectric constant (measured at 1 MHz) was measured to be at room temperature, and the dielectric loss was as low as 0.001. X-ray diffraction patterns demonstrated that the BMN samples had a cubic pyrochlored structure, which was also confirmed by selected area electron diffraction (SAED) patterns. Raman spectrum revealed more than six vibrational models predicted for the ideal pyrochlore structure, indicating additional atomic displacements of the A and sites from the ideal atomic positions in the BMN samples. Structural modulations of the pyrochlore structure along the [110] and [ 121] directions were observed in SAED patterns and high-resolution transmission electron microscopy (HR-TEM) images. In addition, HR-TEM images also revealed that the grain boundaries (GBs) in the BMN samples were much clean, and no segregation or impure phase was observed forming at GBs. The high dielectric constants in the BMN samples were ascribed to the long-range ordered pyrochlore structures since the electric dipoles formed at the superstructural direction could be enhanced. The low dielectric loss was attributed to the existence of noncontaminated GBs in the BMN ceramics.

Zhang, Yuan; Zhang, Zhihao; Zhu, Xinhua; Liu, Zhiguo; Li, Yangyang; Al-Kassab, Talaat

2014-05-01

242

Structural behavior of alcohol-1,4-dioxane mixtures through dielectric properties using TDR.  

PubMed

The values of complex permittivity for alcohol-1,4-dioxane (DX) mixtures with various concentrations have been determined in the frequency range 10 MHz to 20 GHz using the time domain reflectometry (TDR) method. Numbers of hydrogen bonds between alcohol-alcohol and alcohol-dioxane pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory explanation of the experimental results related to the static dielectric constant. The binding energies for alcohol-alcohol (pair 11) and alcohol-DX (pair 12) are estimated to be -13.98 and -16.25 kJ/mol, respectively. The results have also been compared with previous results of the ethyleneglycol-DX system. PMID:19715297

Kumbharkhane, Ashok C; Shinde, M N; Mehrotra, Suresh C; Oshiki, Noriaki; Shinyashiki, Naoki; Yagihara, Shin; Sudo, Seiichi

2009-09-24

243

Structural Behavior of Alcohol-1,4-Dioxane Mixtures through Dielectric Properties Using TDR  

NASA Astrophysics Data System (ADS)

The values of complex permittivity for alcohol-1,4-dioxane (DX) mixtures with various concentrations have been determined in the frequency range 10 MHz to 20 GHz using the time domain reflectometry (TDR) method. Numbers of hydrogen bonds between alcohol-alcohol and alcohol-dioxane pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory explanation of the experimental results related to the static dielectric constant. The binding energies for alcohol-alcohol (pair 11) and alcohol-DX (pair 12) are estimated to be -13.98 and -16.25 kJ/mol, respectively. The results have also been compared with previous results of the ethyleneglycol-DX system.

Kumbharkhane, Ashok C.; Shinde, M. N.; Mehrotra, Suresh C.; Oshiki, Noriaki; Shinyashiki, Naoki; Yagihara, Shin; Sudo, Seiichi

2009-08-01

244

Material compatibility and dielectric properties of co-fired high and low dielectric constant ceramic packages  

Microsoft Academic Search

Recent trend in integrated ceramics is to have a 3-dimensional integration of passive components onto the low permittivity dielectric substrate to achieve a monolithic multilayer ceramic (MMC) substrate. MMC substrates offer significant gain in both circuit density and device hermiticity leading to increased reliability and low cost packages. Low-temperature glass-ceramic based low K tapes have been demonstrated to have good

Raghu Natarajan; J. P. Dougherty

1997-01-01

245

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

246

Some Dielectric Properties of Barium-Strontium Titanate Ceramics at 3000 Megacycles  

Microsoft Academic Search

The dielectric constant &egr;?&egr;0 and loss tangent tan? of barium-strontium titanate ceramics were measured as a function of temperature and static electric field at frequencies of 10 kc, 500 kc, and 3000 Mc. No frequency dependence of &egr;?&egr;0 was apparent at temperatures above the Curie point. An increase in tan? was observed in going from the low frequencies to 3000

Luther Davis Jr.; Lawrence G. Rubin

1953-01-01

247

Effect of silica aerosil dispersions on the dielectric properties of a nematic liquid crystal  

Microsoft Academic Search

The static and dynamic aspects of (4-n-heptyl-4'-cyanobiphenyl) (7CB) perturbed by the dispersion of 70--diameter hydrophilic silica aerosil spheres have been investigated using dielectric spectroscopy. Results on five mixtures of 7CB plus silica aerosil are presented in order to probe systematically the disorder introduced by the silica aerosil network on the 7CB molecules. Measurements on homeotropically aligned samples have been made

A. Hourri; T. K. Bose; J. Thoen

2001-01-01

248

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

PubMed

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

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

2014-05-01

249

Structural, optical and dielectric property of Co doped Bi2Fe4O9  

NASA Astrophysics Data System (ADS)

Multiferroic Bi2Fe4O9 and Co doped Bi2Fe4O9 are prepared by solid state route reaction method using bismuth oxide(Bi2O3), iron oxide(Fe2O3) and cobalt oxide (Co3O4). Their structural optical and dielectric properties are studied and compared. X-ray diffraction (XRD) results confirm that there is no change in crystal structure due to Co doping. From dielectric constant measurement we conclude that dielectric constant increases due to Co doping. UV-Visible plot shows due to Co doping bang gap energy increases.

Swain, Smita; Mohapatra, S. R.; Sahoo, B.; Singh, A. K.

2014-04-01

250

Dielectric and Optical Properties of Nematic ODBP-Ph-C7  

NASA Astrophysics Data System (ADS)

Thermotropic biaxial nematic liquid crystals are promising for application in fast switching electro-optical devices.^1 In the present work, we study the optical and dielectric properties of the nematic phase of thermotropic LC material 4,4'(1,3,4-oxadiazole-2,5-diyl) di-p-heptylbenzoate (ODBP-Ph-C7) with boomerang-like molecules, reported to exhibit the biaxial nematic phase^2. We study ODBP-Ph C7 in well-aligned ``monocrystalline'' states. The experiments show unusual optical and dielectric properties of the material, such as high dielectric permittivity and dielectric relaxation time that increases with temperature. We also analyze defect structures formed by ODBP-Ph- C7 in different geometries of confinement and boundary conditions. ^1 G. R. Luckhurst, Thin Solid Films 393, 40 (2001); ^2 B. R. Acharya, A. Primak, T.J. Dingemans, E.T. Samulski and S. Kumar, Pramana J.Phys. 61, 231 (2003).

Senyuk, Bohdan; Wonderly, Hugh; Shiyanovskii, Sergii; Lavrentovich, Oleg; Pergamenshchik, Victor

2009-03-01

251

Dielectric Properties of Two-Phase Mixture Ceramics Composed of Rutile and Its Compounds  

NASA Astrophysics Data System (ADS)

Dielectric properties of two-phase mixture systems including rutile (TiO2) have been investigated. One of its binary compoundsMnTiO3, ZnTiO3, PbTiO3 and Al2TiO5-was chosen as the second component. Dielectric constants \\varepsilonr and their temperature coefficients ?\\varepsilon were first examined at 1 MHz. Dielectric properties in the microwave frequency region were measured in the TE011 mode of a cylindrical specimen. The temperature coefficient of resonant frequency, ?f, of MnTiO3 was negative, and a zero coefficient was found at an intermediate composition x{=}0.13 in the (1-x) MnTiO3-xTiO2 system. In the PbTiO3-TiO2 system, zero ?\\varepsilon composition was confirmed at low frequencies, but composition modification trials aiming to make microwave dielectric measurements possible were unsuccessful throughout the entire system.

Haga, Kiyoshi; Ishii, Tsuyoshi; Mashiyama, Jin-ichi; Ikeda, Takuro

1992-09-01

252

Dielectric and conductivity properties of composite polyaniline/polyurethane network  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

253

Effect of Uniaxial Stress on Dielectric Properties of 03 PZT-Portland Cement Composite  

Microsoft Academic Search

The effects of uniaxial stress on the 03 lead zirconate titanate (PZT)-portland cement (PC) composite were investigated. PZT and PC composites were fabricated using 50% of PZT by volume. At room temperature, the dielectric properties were measured under stress free and stress level up to 57 MPa at the frequency of 1100 kHz. The results showed that the dielectric constant

N. Jaitanong; R. Yimnirun; A. Chaipanich

2009-01-01

254

SrTiO3 Thin Film Preparation by Ion Beam Sputtering and Its Dielectric Properties  

Microsoft Academic Search

SrTiO3 thin films have been prepared on Pd-coated sapphire substrates by ion beam sputtering of a SrTiO3 target, and their dielectric properties have been studied. Oxygen flow introduction was necessary to obtain good insulating films. Dielectric constant \\\\varepsilonr values were 190 and 240 for 430C and 540C substrate temperatures, respectively. These \\\\varepsilonr values were not dependent on film thickness in

Shintaro Yamamichi; Toshiyuki Sakuma; Koichi Takemura; Yoichi Miyasaka

1991-01-01

255

Dielectric Properties of Yeast Cells Expressed With the Motor Protein Prestin  

Microsoft Academic Search

We report on the linear and nonlinear dielectric properties of budding yeast (S. cerevisiae) cells, one strain of which has been genetically modified to express prestin. This motor protein plays a crucial role in\\u000a the large electromotility exhibited by the outer hair cells of mammalian inner ears. Live cell suspensions exhibit enormous\\u000a dielectric responses, which can be used to probe

JOHN H. MILLER JR; Dharmakeerthi Nawarathna; David Warmflash; Fred A. Pereira; William E. Brownell

2005-01-01

256

Low-frequency dielectric properties of DMAAS crystals in the vicinity of 110 K  

Microsoft Academic Search

Dielectric properties in pure and partly deuterated DMAAS crystals have been studied within the frequency range 40?2107 Hz in the vicinity of 110 K. It is established that the crystals possess relatively high conductivity, 10?410?7 ??1 m?1, which is explained by their crystal structure. The frequency dependence of the complex dielectric constant has two linear\\u000a segments, which indicate the change

A. M. Lotonov; L. F. Kirpichnikova; N. D. Gavrilova

2001-01-01

257

On the magnetic and dielectric properties of nickel-neoprene nanoconaposites  

Microsoft Academic Search

Nickel nanocomposites were prepared by incorporating nickel\\u000a nanoparticles in a neoprene matrix according to a specific recipe for\\u000a various loadings of nickel particles. The dielectric properties of these\\u000a composites were evaluated for different frequencies ranging from 100 kHz\\u000a to 8 MHz at different temperatures from 30 degrees C to 120 degrees C.\\u000a The dielectric permittivity increases with increase of nickel

E. Muhammad Abdul Jamal; P. A. Joy; Philip Kurian; M. R. Anantharaman

2010-01-01

258

A study on the optical absorption properties of dielectric-mediated gold nanoshells  

Microsoft Academic Search

Optical absorption properties of dielectric-mediated gold nanoshells were studied experimentally and theoretically. Sodium dodecylbenzenesulfonate (ABS) mediated colloidal gold nanoshells have been prepared via reduction of chlorauric acid (HAuCl4) by sodium citrate in the presence of ABS as a capping agent. Compared with pure gold nanospheres, the plasmon resonance absorption peak of the golddielectric coreshell structure nanospheres red shift and get

Shinong Yan; Yongchang Wang; Tingdun Wen; Jian Zhu

2006-01-01

259

Dielectric and microwave properties of barium strontium titanate (BST) thick films on alumina substrates  

Microsoft Academic Search

The dielectric and microwave properties of barium strontium titanate (BST) thick films on alumina substrates have been investigated. The BST films were screen printed and sintered at temperatures below 1300C. At temperatures below the Curie point the BST films exhibit tunability in the range 1535% under a DC bias field of 2 kV\\/mm. The dielectric loss is critically dependent on

B Su; J. E Holmes; C Meggs; T. W Button

2003-01-01

260

Acid Rain Affecting the Electrical Properties of Outdoor Composite Dielectric Materials  

Microsoft Academic Search

Acid rain is precipitation with acidity, i.e., pH, below 5.6. There is an increasing interest in the degradation of the electrical properties of outdoor composite dielectric materials under severe contaminant conditions such as acid rain. In this study, the degradation effects of acid rain on the outdoor composite dielectrics are investigated by accelerated aging due to artificial acid rain. Based

Xinsheng Wang; Seiji Kumagai; Noboru Yoshimura

1998-01-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

262

Study of Dielectric and Pyroelectric Properties of Sol-Gel Derived BST Thin Films  

Microsoft Academic Search

(Ba,Sr)TiO3 (BST) thin films have received considerable interest in recent years due to their many attractive properties like high dielectric constant, high dielectric breakdown strength and high pyroelectric coefficent. These films have been identified as promising material for several applications such as ferroelectric non-volatile memories and uncooled infrared focal plane arrays [UFPAs]. Barium strontium titanate (Ba0.75Sr0.25TiO3) thin films of thickness

Manoj Kumar; Somnath C. Roy; M. C. Bhatnagar; Seema Agarwal; G. L. Sharma

2005-01-01

263

Influence of heat treatment on the properties of MgO thin films as dielectric layer  

Microsoft Academic Search

Physical properties such as high melting point, low heat capacity and high bonding strength of magnesium oxide, MgO could be get give an advantage to MgO to be used as the dielectric layer. Besides that, MgO also has large band gap (7.8 eV) and high dielectric constant (9.8) could be potentially used as a buffer layer for ferroelectric material. In

Z. Habibah; L. N. Ismail; R. A. Bakar; M. Rusop

2011-01-01

264

Dielectric properties of foods relevant to RF and microwave pasteurization and sterilization  

Microsoft Academic Search

A custom-built temperature-controlled test cell and an Agilent 4291B impedance analyzer were used to determine the dielectric properties of a whey protein gel, a liquid whey protein mixture, and a macaroni and cheese product and their constituents. Dielectric constants, loss factors, and penetration depths for each sample over a temperature range from 20 to 121.1 C, at frequencies of 27,

Yifen Wang; Timothy D. Wig; Juming Tang; Linnea M. Hallberg

2003-01-01

265

Dielectric property of polyimide\\/barium titanate composites and its influence factors (II)  

Microsoft Academic Search

Using poly(amic acid) (PAA) as a precursor followed by thermal imidization, the polyimide\\/barium titanate composite films\\u000a were successfully prepared by a direct mixing method and in situ process. The influence of processing factors, such as particle\\u000a size, distribution mode and polymerization method on dielectric properties was studied. Results revealed that the dielectric\\u000a constant (?) of the composite film increased by

Weidong Liu; Baoku Zhu; Shuhui Xie; Zhikang Xu

2008-01-01

266

Grain size effects on the dielectric properties of ferroelectric Bi2VO5.5 ceramics  

Microsoft Academic Search

Dielectric properties and microstructural characteristics of ferroelectric bismuth vanadate (Bi2VO5.5) ceramics exhibiting grain sizes of 7, 10, 20 and 25 m have been studied. Microstructural studies indicate the presence of ferroelectric 90 domain patterns on the surface as well as in the bulk of the coarse-grained ceramics. The dielectric constant and the loss tangent both at room temperature and in

K. V. R. Prasad; A. R. Raju; K. B. R. Varma

1994-01-01

267

Dielectric-Properties Contrast Enhancement for Microwave Breast Cancer Detection: Numerical Investigations of Microbubble Contrast Agents  

Microsoft Academic Search

The physical basis for microwave breast cancer detection is the dielectric-properties contrast between malignant and normal breast tissue. The Wisconsin-Calgary study showed that this contrast is as high as 10:1 in fatty breast tissue but no more than 10% in fibroglandular tissue. We are investigating the feasibility of air-filled microbubbles as contrast agents for enhancing the malignant-to-normal dielectric contrast. Our

Mariya Lazebnik; Susan C. Hagness; John H. Booske

268

Voltage and frequency dependent dielectric properties of BST-0.5 thin films on alumina substrates  

Microsoft Academic Search

Dielectric properties of Ba0.5Sr0.5TiO3 (BST-0.5) polycrystalline thin films, deposited on alumina substrates by means of reactive pulsed laser deposition (PLD), were measured at GHz frequencies using an interdigital capacitor (IDC). By applying a voltage up to 40 V between the two groups of fingers at room temperature, a high tunability of ?27% was achieved at 5 GHz. A relative dielectric

Sbastien Delprat; Mossaab Ouaddari; Franois Vidal; Mohamed Chaker; Ke Wu

2003-01-01

269

A Static and Dynamic Study of the Mechanical Properties of Electron Beam Cured PDLC Films  

Microsoft Academic Search

This paper reports a study of static and dynamic mechanical properties of electron beam (EB) cured polymer dispersed liquid crystals. These systems consist of micron-sized droplets dispersed in a solid polymer matrix. They are prepared according to the polymerization induced phase separation process initiated by exposure to electron radiation. A difunctional monomer Tripropylene Glycol Diacrylate in short TPGDA is used

A. Olivier; T. Pakula; A. Best; M. Benmouna; X. Coqueret; U. Maschke

2004-01-01

270

Structural and optical characterization of Cr2O3 nanostructures: Evaluation of its dielectric properties  

NASA Astrophysics Data System (ADS)

The structural, optical and dielectric properties of as-grown Cr2O3 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 ; c = 13.578 , 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 Cr2O3 nanostructures attest the potential candidature of the material as an efficient dielectric medium.

Abdullah, M. M.; Rajab, Fahd M.; Al-Abbas, Saleh M.

2014-02-01

271

Measurement of dielectric properties in gigahertz to terahertz frequency range  

Microsoft Academic Search

Measurement of the dielectric constant of thin film in the frequency range of gigahertz (GHz) to terahertz (THz) is crucial for future integrated circuit (IC) interconnect technology. This research focuses on the use of time domain terahertz pulse technology for such characterization. In particular, the goniometric phase shift of a reflected electro magnetic pulse as a function of incident angle

Ming Li

2000-01-01

272

Dielectric properties and structure of aqueous solutions of boric acid  

Microsoft Academic Search

A model of the,structure of aqueous boric acid solution has been constructed, based on the view that the acid molecules are inserted into the ice-like lattice of water. The model predicts the rupture of a certain number of hydrogen bonds in the water structure. Themodel agrees withdata on the density and the dielectric constant of the solution at superhigh frequencies.

A. K. Lyashchenko; V. S. Goncharov; P. S. Yastremskii

1977-01-01

273

The Dielectric Properties of Water and Heavy Water  

Microsoft Academic Search

Measurements by a number of different methods of the dielectric constant and loss angle of water and heavy water at three widely separated wavelengths in the region of anomalous dispersion, ?=10 cm., 3 cm., 1.25 cm., are described. Results show that the Debye equations are exactly obeyed, there being a single time of relaxation varying with the temperature; the ratios

C. H. Collie; J. B. Hasted; D. M. Ritson

1948-01-01

274

Dielectric Properties and Side-Chain Crystallinity of Polyvinyl Stearate  

Microsoft Academic Search

Measurements of the real (&egr;?) and imaginary (&egr;?) parts of the dielectric constant have been made on polyvinyl stearate at temperatures from ?50 to +80C and over a frequency range from 100 to 50 000 cps. Although no full relaxation dispersion region has been found in this frequency range, there are indications of the beginnings of a high-frequency dispersion region

Martin G. Broadhurst; Edwin R. Fitzgerald; Anthony J. Bur

1961-01-01

275

Crystal Structure and Dielectric Properties of PZT Ferroelectric Ceramic Fibers  

Microsoft Academic Search

The crystal structures of PZT ceramic fibers with continuum spinning process were identified, showing a pure tetragonal phase of perovskite for the samples treated at around 900C. The microstructures of the PZT fibers were observed, displaying relatively complex evolution with the increasing of temperature during heat treatment. With the increasing of frequency, the dielectric constants and loss tangents became smaller

Z. X. Xiong; J. Pan; H. Xue; M. F. Mai; H. Qiu; L. F. Chen

2010-01-01

276

Dielectric and rheological properties of polyaniline organic dispersions  

NASA Astrophysics Data System (ADS)

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.

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

2009-05-01

277

The transverse dielectric properties of KH2PO4  

Microsoft Academic Search

We have measured the transverse dielectric constant of KH2PO4 crystal from liquid N2 to room temperatures. Extending the Blinc-de Gennes' model in conjunction with a cluster approximation leads to a new independent determination of the Slater-Takagi parameters and improves significantly the fit of the model to the data.

S. Havlin; E. Litov; H. Sompolinsky

1975-01-01

278

Dielectric Properties of Mixture of Lauryl-Laurate and Hexacosane  

Microsoft Academic Search

Dependence of dielectric loss on the concentration of polar molecules is investigated for the mixtures of long chain compounds (lauryl lauratehexacosane). The experimental results are well explained by the two site model taking account of interaction of ester molecules and this interaction energy quite reasonably determines the critical concentration of the separation of two phases (an ester poor solid solution

Hideki Miyaji; Yoshihito Ohde; Kenjiro Asai

1972-01-01

279

Dielectric properties of a mixture of dipolar hard spheres  

Microsoft Academic Search

A theory for the dielectric constant, ?, of a fluid mixture of dipolar hard spheres is formulated by generalizing the methods developed by Ramshaw and Wertheim for the pure fluid case. The resulting expression for ? depends on the pair distribution functions, g??(r1, ?1, r2, ?2) for a dipolar mixture. Due to the unavailability of exact representations for these dipolar

Ben Freasier; Norman Hamer; Dennis Isbister

1979-01-01

280

Dielectric Properties of Titan's Surface using the Cassini RADAR Radiometer  

Microsoft Academic Search

The Cassini Radar instrument includes a passive microwave radiometer that operates at 13.78 GHz ( 2.2 cm wavelength). The radiometer has been used to image the calibrated thermal emission from a significant portion of Titan's surface, at resolutions ranging from 5 - 500 km and at a variety of emission angles and polarizations. Interpretation in terms of surface dielectric models

Michael A. Janssen; F. Paganelli; R. D. Lorenz

2006-01-01

281

Microstructural Effects on Dielectric Constants of Two-Phase System  

Microsoft Academic Search

The dielectric properties of the binary phase mixture have been investigated theoretically in the effective medium approximation with applications to porous glasses and Mg-PSZ. It is shown that the static dielectric constant of porous glass depends very little upon the pore geometry and size, but can be used for estimating the porosity of the material. In the far-infrared absorption of

Michiko Inoue

1989-01-01

282

Thickness dependent dielectric tunable properties of barium strontium titanate thin films  

NASA Astrophysics Data System (ADS)

Thickness is a very important parameter to control the microstructures, as well as dielectric properties in the Ba0.5Sr0.5TiO3 thin films. Ba0.5Sr0.5TiO3 films with various thicknesses were deposited on Si substrate by chemical solution method. An increase in the grain size as the film thickness increased was observed. The improvement dielectric tunable properties with film thickness were observed and were correlated to the structural properties.

Yadava, Anil K.; Reddy, V. Annapu; Sharma, Vivek; Pathak, N. P.; Nath, R.

2013-06-01

283

Derivation of the cell dielectric properties based on Clausius-Mossotti factor  

NASA Astrophysics Data System (ADS)

The dielectric properties of membrane and cytoplasm of cells were commonly derived using the experimental electrorotation spectra, which are proportional to the spectra of the imaginary part of the Clausius-Mossotti factor (Ki). However, it was found in this study that the cell properties thus derived do not agree with those derived using the experimental spectra of the real part of the Clausius-Mossotti factor (Kr). Both the Kr and Ki spectra are required simultaneously for deriving appropriate cell dielectric properties. Also the membrane and cytoplasm conductivities decrease, while the membrane and cytoplasm permittivities remain relatively unchanged, as the medium conductivity decreases.

Lo, Y. J.; Lei, U.; Chen, K. Y.; Lin, Y. Y.; Huang, C. C.; Wu, M. S.; Yang, P. C.

2014-03-01

284

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

PubMed

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

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

2011-01-01

285

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

PubMed Central

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.

2014-01-01

286

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

PubMed

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

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

2014-02-11

287

Measurements of the Dielectric Properties of Wet Snow Using a Microwave Technique.  

National Technical Information Service (NTIS)

An accurate method of measuring liquid water in snow covers is required to determine the properties of wet snow. The dielectric properties of wet snow must be utilized to adequately measure its liquid water content. In this study the effect of liquid wate...

B. D. Sweeny S. C. Colbeck

1974-01-01

288

Study on the dielectric property of the impure silicon dioxide based on FEM  

Microsoft Academic Search

Researchers have been interested in the study of composite materials' dielectric property for a long time. Composite materials can also be adjusted by selecting the matrix and inclusion, controlling their volume ratio, component geometry, distribution types and so on, to improve properties of the mixture materials. In this paper, for different impurities in silicon dioxide, Finite Element Method (FEM) is

Yonghong Cheng; Lili Jiang; Xiaojun Xie; Naidong Luo; Mang Li; Shengnan Wu

2009-01-01

289

Dielectric properties of a hydrated sulfonated poly(styrene ethylene/butylenes styrene) triblock copolymer  

NASA Astrophysics Data System (ADS)

The present study showed that sulfonated poly(styrene-ethylene/butylenes-styrene) (S-SEBS) triblock copolymer ionomers can be made to exhibit dielectric constants on the order of a hundreds thousand. Although they are too lossy at this point to use as dielectric materials in capacitors or as electrostrictive Maxwell effect transducer materials because of their high hydrogen ion conductivity, the results of these initial dielectric studies as a function of ion content were used to try to understand the effects of a polar plasticizer, water, on dielectric properties of the acid form of this ionomer. This was done before moving on to more tightly bound ions (rather than the hydrogen ions of the sulfonic acid groups used here) and to other polar, less mobile plasticizers (which also interact strongly with the ionic dipoles). The discovery of such high dielectric constants suggested the possibility that low dielectric loss versions of this type of polymer, as well as other members of the class known as ionomers, might find future applications as extremely high dielectric constant materials in capacitors or transducers. Experimental results for films with degrees of sulfonation on the order of 10% or more showed dielectric constants on the order of ?' 100,000 but dielectric loss tangents near D = tan ? 0.3, when the materials were exposed to high humidity conditions. Experiments to determine the effects of water content on the material's dielectric response showed that water can easily move into and out of the films studied and that this transport behavior is strongly correlated to the relative humidity of the environment and to the degree of sulfonation. Water content, in this case, was thus the primary consideration when attempting to understand the observed high dielectric constants in films with degree of sulfonation greater than 5.5%. However, vacuum-dried films were, also, examined and observed to exhibit a dielectric constant on the order of 2 until the degree of sulfonation was greater than 11%. Above this value, the dielectric constant increased by approximately 100% to a value on the order of 4.

Butkewitsch, Stephen; Scheinbeim, Jerry

2006-09-01

290

Dielectric properties of phase-size-control CdS nanoparticles and conventional powders  

NASA Astrophysics Data System (ADS)

Four kinds of CdS samples (cubic and hexagonal nanoparticles as well as cubic and hexagonal conventional powders) were synthesized by sonochemistry and ion exchange, respectively, under controlled conditions. The four kinds of CdS samples were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The two kinds of CdS nanoparticles possess cubic structures with diameters of about 8 nm and hexagonal phases with diameters of about 10 nm while the conventional cubic powders and the conventional hexagonal powders have the same diameters (about 5 m). In particular, the relative dielectric constant and the dielectric loss of these samples were measured in the frequency range 102-108 Hz at room temperature. Compared with the conventional powders, the dielectric properties of nanostructured CdS are significantly enhanced, especially in the low-frequency range, and the different symmetry does not influence the dielectric behavior. A possible explanation for the dielectric behavior of nano-CdS is suggested, where the enhanced dielectric properties result from the nanoscale sizes. (

Zhou, Shao-Min

2003-12-01

291

Dielectric properties of a mixed-valence Pb3Mn7O15 manganese oxide.  

PubMed

We investigated the low-frequency dielectric properties of a Pb(3)Mn(7)O(15) single crystal with manganese ions in the mixed-valence state (Mn(3+)/Mn(4+)). Dielectric relaxation was found in the frequency window from 20 to 100 kHz in the temperature range 110-180 K. The dielectric spectra of the crystal were analyzed using a Debye model. Estimations made within the model and analysis of resistivity data suggest that the relaxation behavior of the dielectric constant is related to polaronic charge carrier hopping. Around 250 K, charge ordering occurs in the crystal when the Mn(3+) and Mn(4+) ions are arranged in a specific order among the crystal sites. With a decrease in temperature, an ac electric field can induce a charge hop between the equivalent lattice sites available, related to crystal symmetry. This hopping is equivalent to the reorientation of an electric dipole that yields Debye-type behavior of the complex dielectric constant. The observed anisotropy in the behavior of the dielectric properties and resistivity can be attributed to a pronounced two-dimensional character of the crystal structure. PMID:21403208

Volkov, N V; Eremin, E V; Sablina, K A; Sapronova, N V

2010-09-22

292

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

NASA Astrophysics Data System (ADS)

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

Gken, M.; Kysal, O.; Y?ld?r?m, M.; Alt?ndal, ?.

2012-08-01

293

Epitaxial growth and in-plane dielectric properties of orthorhombic HoMnO3 films  

NASA Astrophysics Data System (ADS)

Orthorhombic HoMnO3 (HMO) thin films were grown epitaxially on LaAlO3 (001) substrates by using pulsed laser deposition technique. The films showed perfect orthorhombic crystallization and were well-aligned with the substrates. The in-plane dielectric constant and loss of HMO films were measured as functions of temperature (80-300 K) and frequency (120 Hz-100 kHz) by using coplanar interdigital electrodes. Two thermally activated dielectric relaxations were found, and the respective peaks shifted to higher temperatures as the measuring frequency increased. The in-plane dielectric properties of epitaxial orthorhombic HMO films were considered as universal dielectric response behavior, and the dipolar effects and the hopping conductivity induced by the charge carriers were used to explain the results.

Gao, Ping; Wang, WeiTian; Zhang, Wei; Sun, YuMing

2014-04-01

294

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

PubMed Central

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.

2011-01-01

295

Dielectric properties of thin insulating layers measured by Electrostatic Force Microscopy  

NASA Astrophysics Data System (ADS)

In order to measure the dielectric permittivity of thin insulting layers, we developed a method based on electrostatic force microscopy (EFM) experiments coupled with numerical simulations. This method allows to characterize the dielectric properties of materials without any restrictions of film thickness, tip radius and tip-sample distance. The EFM experiments consist in the detection of the electric force gradient by means of a double pass method. The numerical simulations, based on the equivalent charge method (ECM), model the electric force gradient between an EFM tip and a sample, and thus, determine from the EFM experiments the relative dielectric permittivity by an inverse approach. This method was validated on a thin SiO2 sample and was used to characterize the dielectric permittivity of ultrathin poly(vinyl acetate) and polystyrene films at two temperatures.

Riedel, C.; Arinero, R.; Tordjeman, Ph.; Ramonda, M.; Lvque, G.; Schwartz, G. A.; de Oteyza, D. G.; Alegra, A.; Colmenero, J.

2010-04-01

296

Microwave dielectric properties of inorganic fullerene-like tungsten disulfide nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

297

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

SciTech Connect

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.

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

2011-01-03

298

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

PubMed

Dielectric properties of aqueous solutions of sulfated hydrocolloids (ulvan and rhamnan sulfate) extracted from green macroalgal biomass were studied in a frequency range of 100MHz-10GHz. 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

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

2014-07-17

299

Dielectric properties and structural defects in BaTi1-xSnxO3 ceramics  

NASA Astrophysics Data System (ADS)

As a function of Sn doping concentration x, dielectric properties and X-ray diffraction measurements were carried out on BaTi1-xSnxO3 (BTSx) ceramics fabricated by the solid-state reaction route. Positron annihilation lifetime spectroscopy and coincident Doppler-broadening spectroscopy were also measured for the evaluation of defects in the BTSx ceramics. Dielectric properties measurement reveals that the permittivity of BTSx ceramic gradually increases with increasing Sn dopant content for x<=3%, and then decreases. This change of permittivity is found to agree well with the relative defect concentration estimated using two positron annihilation techniques. The S-W plot indicates that the defect species do not change with Sn doping. The variation correlations between defects and dielectric properties further proves that BTSx ceramics with the higher relative defect concentration present a lower permittivity.

Lijuan, Zhang; Lihai, Wang; Jiandang, Liu; Bin, Cheng; Minglei, Zhao; Bangjiao, Ye

2013-06-01

300

Tailoring the Microwave Dielectric Properties of Alkaline Earth Gehlenite Type Ceramic  

NASA Astrophysics Data System (ADS)

The effect of glass fluxing and isovalent substitution on the microwave dielectric properties of low permittivity Sr2Al2SiO7 (SAS) ceramic has been investigated. X - ray diffraction pattern of all the compositions indicate the formation of tetragonal Gehlenite type ceramics with space group P/line{4}21m (no. 113). The addition of small amounts of lithium magnesium zinc borosilicate (LMZBS) glass to Sr2Al2SiO7 ceramic enhanced the densification. Glass fluxing also improved the quality factor and relative permittivity. A small partial substitution of Al3+ and Si4+ by Ga3+ and Ge4+ was found to degrade the dielectric properties of SAS ceramic. The composition Sr2Al2SiO7 + 1 wt. % LMZBS glass showed the best dielectric properties with ?r = 7.3, Quf = 36000 GHz and ?f = -23.0 ppm/C.

Arun, B.; Manu, K. M.; Sebastian, M. T.

301

Densification and Dielectric Properties of Cordierite-Lead Borosilicate Glasses  

NASA Astrophysics Data System (ADS)

To improve the sinterability of P2O5-added cordierite glass, lead borosilicate glass was adopted as a sintering aid. Various sintering temperatures and times were used to observe the effects of heat treatments on the sintering behavior of the cordierite-lead borosilicate glass. The flux effect of lead borosilicate glass aids the coalescence of cordierite glass particles, which promotes the densification. Phase transformation from cordierite glass to the high-temperature ?-cordierite form is the major reaction during the sintering of cordierite-lead borosilicate glass. The dielectric constant of the sintered composites is determined by both the existing crystalline structure and the completeness of densification. The relationship between the volume fraction of lead borosilicate glass and the dielectric constant can be approximated by a linear equation.

Chen, Lih-Shan; Fu, Shen-Li

1992-12-01

302

Dielectric property and conduction mechanism of ultrathin zirconium oxide films  

NASA Astrophysics Data System (ADS)

Stoichiometric, uniform, amorphous ZrO2 films with an equivalent oxide thickness of ~1.5 nm and a dielectric constant of ~18 were deposited by an atomic layer controlled deposition process on silicon for potential applications in metal-oxide-semiconductor (MOS) devices. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole-Frenkel emission at high electric fields. The MOS devices showed low leakage current, small hysteresis (<50 mV), and low interface state density (~21011 cm-2 eV-1). Microdiffraction and high-resolution transmission electron microscopy showed a localized monoclinic phase of ?-ZrO2 and an amorphous interfacial ZrSixOy layer which has a corresponding dielectric constant of 11.

Chang, J. P.; Lin, Y.-S.

2001-11-01

303

Dielectric properties of wheat flour mixed with oat meal  

NASA Astrophysics Data System (ADS)

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.

?uczycka, D.; Czubaszek, A.; Fujarczuk, M.; Pruski, K.

2013-03-01

304

Spin waves and dielectric softening of polar molecule condensates.  

PubMed

We consider an oblate Bose-Einstein condensate of heteronuclear polar molecules in a weak applied electric field. This system supports a rich quasiparticle spectrum that plays a critical role in determining its bulk dielectric properties. In particular, in sufficiently weak fields the system undergoes a polarization wave rotonization, leading to the development of textured electronic structure and a dielectric instability that is characteristic of the onset of a negative static dielectric function. PMID:24745433

Wilson, Ryan M; Peden, Brandon M; Clark, Charles W; Rittenhouse, Seth T

2014-04-01

305

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

NASA Astrophysics Data System (ADS)

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.

Kumar, Ashok; Ahluwalia, P. K.

2013-06-01

306

Dielectric properties of a DMAGaS\\/DMAAS mixed crystal  

Microsoft Academic Search

Dimethylammonium gallium sulphate hexahydrate (DMAGaS) and dimethylammonium aluminum sulphate hexahydrate (DMAAS) are isomorphous and ferroelastic at room temperature. They both show an orderdisorder type transition into a ferroelectric phase, but only DMAGaS exhibits a further first-order transition into a low-temperature nonferroelectric phase. In this article, the results of dielectric measurements of the mixed crystal (DMAGaS)0.9(DMAAS)0.1 are presented. It has been

J. Banys; G. Vlkel; R. Bttcher; D. Michel; Z. Czapla

2005-01-01

307

Dielectric properties of glasses at ultra low temperatures  

Microsoft Academic Search

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 exibits a saturation behavior following a logarithmic increase above 3 mK. These

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

1992-01-01

308

Microwave Measurements of the Dielectric Properties of Gases  

Microsoft Academic Search

An accurate and sensitive method for measuring the complex dielectric constant (&egr;?-i&egr;?) of gases in the microwave region is described and critically investigated for sources of error. A resonant-cavity method is used in which the cavity response curve is displayed on a cathode-ray tube. The variation of resonance frequency and Q of the cavity when filled with gas are determined

George Birnbaum; S. J. Kryder; Harold Lyons

1951-01-01

309

Dielectric properties of LC mixture with induced antiferroelectric phase  

Microsoft Academic Search

Mixture of two liquid crystalline components exhibits the antiferroelectric phase in a broad temperature range at room temperatures,\\u000a though the two components separately do not show an antiferroelectric phase in a temperature range applied. The dielectric\\u000a spectroscopy technique combined with measurements of the selective light reflection was used for identification and characterization\\u000a of the phases and subphases existing in the

M. Wojciechowski; G. W. B?k; M. Tykarska

2008-01-01

310

Size Effects on Dielectric Properties of Nanograin PSN Ceramics  

Microsoft Academic Search

A fundamental interest as well as need for high level of integration of ferroelectric and related materials stimulates research of nanoscale effects. In this contribution we present a study of perovskite PbSc1\\/2Nb1\\/2O3 (PSN) nanograin ceramics performed by means of dielectric spectroscopy. Experimental results clearly show, that small grain sizes limit contribution of polar nanoregions. However, contribution from phonon modes (including

Maksim Ivanov; Juras Banys; C. Bogicevic; Jean-Michel Kiat

2012-01-01

311

The use of static and dynamic physical property measurements to infer structural properties of associated liquids: Acetic acidwater  

Microsoft Academic Search

The anomalies which occur in most static and dynamic physical property measurements on solutions of water in acetic acid can be used with critical analysis to infer associative molecular structures. The anomalies indicate significant structural changes. Proton magnetic resonance chemical shifts for acetic acidwater solutions show a significant structural change occurring in the region of equal molar concentration. Literature values

Robert W. Sims; M. Robert Willicott III; R. R. Inners

1979-01-01

312

The use of static and dynamic physical property measurements to infer structural properties of associated liquids: Acetic acid-water  

Microsoft Academic Search

The anomalies which occur in most static and dynamic physical property measurements on solutions of water in acetic acid can be used with critical analysis to infer associative molecular structures. The anomalies indicate significant structural changes. Proton magnetic resonance chemical shifts for acetic acid-water solutions show a significant structural change occurring in the region of equal molar concentration. Literature values

Robert W. Sims; M. Robert Willicott III; R. R. Inners

1979-01-01

313

Dielectric electrorheological fluids: theory and experiment  

NASA Astrophysics Data System (ADS)

Electrorheological (ER) fluids are a class of materials whose rheological properties are controllable by the application of an electric field. A dielectric electrorheological (DER) fluid is the simplest type of ER fluid, in which the material components follow a linear electrostatic response. We review and discuss the progress of the studies on physics of this type of material. A first-principles theory of DER fluids, along with relevant experimental verifications, are presented in some detail. In particular, the properties presented include static equilibrium structure, shear modulus, static yield stress and its variation with applied electric field frequency, and structure-induced dielectric nonlinearity.

Ma, Hongru; Wen, Weijia; Tam, Wing Yim; Sheng, Ping

2003-06-01

314

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

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

315

AC conductivity and dielectric properties of thermally evaporated PbTe thin films  

NASA Astrophysics Data System (ADS)

AC conductivity and dielectric properties of thermally evaporated lead telluride (PbTe) films have been investigated in the frequency range 30 Hz-100 kHz at various temperatures (303-483 K). The annealing process caused a stabilization of the dielectric properties due to the relief of stress and local structural rearrangement of atoms. The temperature coefficient of capacitance (TCC) and temperature coefficient of permittivity (TCP) have been estimated. The dominant conduction mechanism in the films is attributed to the hopping of thermally activated electrons under ac field. The results of variation of activation energy with frequency and thickness are discussed.

Kungumadevi, L.; Sathyamoorthy, R.; Subbarayan, A.

2010-01-01

316

Dielectric properties of EVA rubber composites at microwave frequencies theory, instrumentation and measurements.  

PubMed

This work describes and evaluates a technique for determining the dielectric properties of carbon-black filled Ethylene Vinyl Acetate (EVA) rubber and presents results on the studies of the effect of frequency on the permittivity and microwave conductivity using resonant cavity perturbation method. The measurements are performed with the aid of a Network Analyzer in X-band. The simplicity of this method lies in the fact that the dielectric properties can be obtained directly from the analytical formula without taking recourse to calibration. PMID:24427870

Banerjee, Prasun; Biswas, Salil Kumar; Ghosh, Gautam

2011-01-01

317

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

NASA Astrophysics Data System (ADS)

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.

Tong, Sheng

318

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

NASA Astrophysics Data System (ADS)

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.

Khalili, L.; Serajzadeh, S.

2014-05-01

319

THz Dielectric Properties of Molecular Clusters of PETN and TNT Calculated by Density Functional Theory  

NASA Astrophysics Data System (ADS)

The need for better detection of explosive devices has imposed a necessity for determining the dielectric response properties of energetic materials with respect to electromagnetic wave excitation. Among the range of different frequencies for electromagnetic excitation, the THz frequency range is of particular interest because of its nondestructive nature. The present study is based on significant progress in density functional theory (DFT), and associated software technology, which is sufficiently mature for the determination of dielectric response functions, and actually provides complementary information to that obtained from experiment. This point is further demonstrated in this study by calculations of ground state resonance structure associated with molecular clusters of the high explosives PETN and TNT using DFT, which is for the construction of parameterized dielectric response functions for excitation by electromagnetic waves at frequencies within the THz range. These dielectric functions provide for different types of analyses concerning the dielectric response of explosives. In particular, these dielectric response functions provide quantitative initial estimates of spectral response features for subsequent adjustment with respect to additional information such as laboratory measurements and other types of theory-based calculations. With respect to qualitative analysis, these spectra provide for the molecular level interpretation of response structure. The DFT software GAUSSIAN was used for the calculations of ground state resonance structure presented here.

Huang, L.; Shabaev, A.; Lambrakos, S. G.; Massa, L.

2012-08-01

320

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

NASA Astrophysics Data System (ADS)

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.

Miccio, Luis A.; Kummali, Mohammed M.; Schwartz, Gustavo A.; Alegra, ngel; Colmenero, Juan

2014-05-01

321

Dielectric properties and temperature profile of fly ash-based geopolymer mortar  

Microsoft Academic Search

In this paper, the fresh properties, dielectric properties and temperature profile of fly ash-based geopolymer mortars are investigated to observe the effect of mixture proportions and time after mixing. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as the activators. The results of fresh properties revealed that the added water could improve the workability of geopolymer mortar. It is

Saysunee Jumrat; Burachat Chatveera; Phadungsak Rattanadecho

2011-01-01

322

Static and dynamic properties of PbTiO3 at finite temperatures  

NASA Astrophysics Data System (ADS)

The ABO3-type perovskite crystals are key to several important technological applications. To mention a few, electro-optics, waveguides, laser frequency doubling and high capacity computer memory cells. In this work, we develop a route to first-principles parametrization of effective Hamiltonian for ferroelectric ferovskites [1] which allows an accurate description of both static and dynamic properties of such materials. We use this method to examine softening of the transverse optical mode in both paraelectric and ferroelectric phases of PbTiO3. The computed static and dynamic properties are in good agreement with the available theoretical and experimental data. Our study also predicts a crossover between a displacive to an order-disorder transition near the Curie point.[4pt] [1] W. Zhong, D. Vanderbilt, and K. M. Rabe, Phys. Rev. B 52, 6301 (1995).

Mani, Brajesh; Ponomareva, Inna

2013-03-01

323

Temperature-dependent dielectric properties of slightly hydrated horn keratin.  

PubMed

With an aim to reveal the mechanism of protein-water interaction in a predominantly two phase model protein system this study investigates the frequency and temperature dependence of dielectric constant epsilon' and loss factor epsilon'' in cow horn keratin in the frequency range 30 Hz to 3 MHz and temperature range 30-200 degrees C at two levels of hydration. These two levels of hydration were achieved by exposing the sample to air at 50% relative humidity (RH) at ambient temperature and by evacuating the sample for 72 h at 105 degrees C. A low frequency dispersion (LFD) and an intermediate frequency alpha-dispersion were the two main dielectric responses observed in the air-dried sample. The LFD and the high frequency arm of the alpha-dispersion followed the same fractional power law of frequency. Within the framework of percolation cluster model these dispersions, respectively have been attributed to percolation of protons between and within the clusters of hydrogen-bonded water molecules bound to polar or ionizable protein components. The alpha-dispersion peak, which results from intra-cluster charge percolation conformed to Cole-Cole modified Debye equation. Temperature dependence of the dielectric constant in the air-dried sample exhibited peaks at 120 and 155 degrees C which have been identified as temperatures of onset of release of water bound to polar protein components in the amorphous and crystalline regions, respectively. An overall rise in the permittivity was observed above 175 degrees C, which has been identified as the onset of chain melting in the crystalline region of the protein. PMID:18275998

Rizvi, Tasneem Zahra; Khan, Muhammad Abdullah

2008-04-01

324

Size-dependent optical and dielectric properties of BiVO4 nanocrystals  

NASA Astrophysics Data System (ADS)

Optical and dielectric properties of BiVO4 nanocrystals with different particle sizes have been investigated. BiVO4 nanocrystals with different particle sizes were synthesized through a solid-state reaction method followed by mechanical ball milling for different time durations. The samples were characterized by X-ray diffraction, UV-Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. Direct and indirect band gap energies were found to vary in the range 4.04-4.16 eV and 3.51-3.67 eV respectively, for different particle sizes. The band gap energies are higher with respect to their values in the bulk BiVO4 due to quantum confinement effects. Dielectric properties of the BiVO4 nanocrystals were investigated and it was found that the dielectric constant increased from 32 to 41 for the reduction of particle size from 29 to 7 nm.

Sarkar, S.; Chattopadhyay, K. K.

2012-04-01

325

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

326

Kink static properties in a discrete Phi4 chain with long-range interactions  

Microsoft Academic Search

We study the discreteness effects on kink static properties in a one-dimensional anharmonic Phi4 chain with a long-range interaction potential of Kac-Baker type. Using the Dirac's second class constraints, we show that the discrete kink experiences the periodic Peierls-Nabarro (PN) potential whose barrier depends strongly on the range of interaction. Numerical calculations reveal that the dressing of the kink profile

P. Woafo; T. C. Kofane; A. S. Bokosah

1993-01-01

327

Static properties of two-component kink in a non-linear discrete polarizability model  

Microsoft Academic Search

We study analytically, in the low-velocity regime, the static properties of two-component kink in a discrete polarizability model with a quartic electronion interaction in one ionic species. Using a discretized Hamiltonian formalism, we derive the exact equations of motion for the two-component kink centre of the mass X(t) and coupled field variables. Numerical analysis is performed to estimate the amplitude

C. M. Ngabireng; P. Woafo; T. C. Kofane

2003-01-01

328

Processing, microstructure, and microwave dielectric properties of tunable (barium,strontium)titanate thin films  

NASA Astrophysics Data System (ADS)

Barium strontium titanate (BST) materials have been extensively investigated for their applicationability in microwave varactors of monolithic circuits. Compared to bulk BST, thin films exhibited significant degradations in their dielectric properties, including suppressed dielectric constants and tunabilities, increased losses, and diffuse temperature dependences of dielectric constant. To understand the causes of these degradations, Three research lines were followed to conduct systematic experiments to test the hypotheses that dislocation-associated inhomogeneous strains and lattice-mismatch-associated homogeneous strains are the principle causes. Over the issue of whether the principle slip-system was <100>{010} or <110>{110} in relaxation process of BST epitaxial films, dislocation characteristics determined using electron microscopy in (001)-, (110)-, and (111)-oriented BST films support a two-stage relaxation mechanism for BST films on SrTiO3. A bowing out of inherited <110> type of dislocations act as minor strain relaxation mechanism followed by film top surface nucleation of <100> type for major strain relaxation. Results supported that <100>{010} slip-system is easier-to-activate in BST. To understand the dislocation-associated inhomogeneous strain effects, (001)-oriented Ba0.6Sr0.4TiO3 films were grown on GdScO3(110), La0.3Sr0.7Al0.65 Tao.35O3(100), NdGaO3(110), LaAlO 3(100), and MgO(100) using pulsed laser deposition under identical conditions. The temperature dependences of in-plane dielectric properties measured using interdigitated capacitors at 5 GHz were compared. Bulk-like dielectric properties were observed in low-dislocation-density Ba0.6Sr0.4TiO 3 films coherently-tensile-strained on GdScO3. Degraded dielectric properties were observed in Ba0.6Sr0.4TiO3 films with high dislocation densities on the other substrates. This supported that the dislocation-associated inhomogeneous strains caused the dielectric property degradation. The homogeneous strain effects were investigated by comparing the in-plane dielectric properties of coherently-strained Ba0.6Sr0.4 TiO3(001) films grown on GdScO3(110) and DyScO 3(110) under identical conditions. The compressively strained Ba 0.6Sr0.4TiO3 films on DyScO3 demonstrated dramatically degraded dielectric properties compared to the bulk-like properties in Ba0.6Sr0.4TiO3 films on GdScO3 while their dislocation densities are similarly low. Landau-Devonshire theory based simulations interpreted the compressive strain effects from DyScO 3. The results support that compressive strain is a principle factor for dielectric property degradations. From the above-described experimental and theoretical investigations, to achieve bulk-like dielectric properties, it is necessary to minimize compressive strains in the direction of measurement and the dislocation-associated inhomogeneous strains in BST thin films.

Du, Hui

329

Strain tunable ferroelectric and dielectric properties of BaZrO3  

NASA Astrophysics Data System (ADS)

The crucial role of epitaxial (in-plane) strain on the structural, electronic, energetic, ferroelectric, and dielectric properties of BaZrO3 (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 BaTiO3, 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.

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

2014-06-01

330

Dielectric properties of carbon-, silicon-, and germanium-based polymers: A first-principles study  

NASA Astrophysics Data System (ADS)

A knowledge of factors that control the electronic structure and dielectric constant of materials would be valuable in the design of new insulators with attractive dielectric properties. In an attempt to systematically and directly understand the role of chemical composition and atomic configuration in determining such properties, we have studied (using first-principles computations) nine homopolymer systems based on XY2 building blocks, where X=C, Si, or Ge and Y=H, F, or Cl. Two possible generic configurations were explored, and our computations utilized dispersion-corrected semilocal exchange-correlation functionals as well as hybrid functionals. Correlations between stability, electronic structure features, infrared intensities, and the dielectric response are established across the chemical and configurational space considered. Homopolymers containing GeF2 or GeCl2 building blocks are identified as particularly promising. These systems display large dielectric constant values (regardless of the underlying crystal structure) and may display a large band gap for particular configurations. The design of a polymer insulator with optimal dielectric constant and band gap may require consideration of heteropolymers (e.g., involving CH2 and GeF2 building blocks). We provide a convenient strategy for the rapid exploration of that extended chemical and configurational space.

Wang, C. C.; Pilania, G.; Ramprasad, R.

2013-01-01

331

Static and dynamic properties of highly turbid media determined by spatially resolved diffusive-wave spectroscopy.  

PubMed

We show that spatially resolved backscattering can be used for simultaneous measurements of static and dynamic properties of highly turbid media. The spatial variation of the backscattered intensity gives access to the transport men free path. The decay of the temporal intensity-intensity correlation function depends on the point of observation. This property can be used to probe complex dynamics with several time scales. The implementation of the method and the data analysis are tested on concentrated suspensions of polystyrene spheres. PMID:12477121

Morin, Fabienne; Borrega, Rgis; Cloitre, Michel; Durian, Douglas

2002-12-01

332

Dielectric confinement and the linear and nonlinear optical properties of semiconductor-doped glasses  

Microsoft Academic Search

The implications of dielectric confinement on the linear and nonlinear optical properties of semiconductor-doped glasses in the resonant regime are considered. First the case of a single resonance is considered and using the nonlocal approach to the local field effect, it is shown that the problem of self-reaction must be properly taken into account. This modifies the predictions regarding intrinsic

D. Ricard; M. Ghanassi; M. C. Schanne-Klein

1994-01-01

333

THz near-invisible materials: the dielectric properties of polystyrene foam  

Microsoft Academic Search

Summary form only given. We show results on THz-TDS measurements on polystyrene foam which demonstrate that this material has dielectric properties that make it very suitable for many THz applications. We have measured the frequency-dependent extinction and refractive index of three kinds of polystyrene foam.

G. Zhao; M. ter Mors; W. T. Wenckebach; P. C. M. Planken

2002-01-01

334

Prediction of physical properties of yeast cell suspensions using dielectric spectroscopy  

Microsoft Academic Search

This work concerns the modelling of the dielectric properties of biological cell suspensions. The relative permittivity of a suspension is proportional to the volume fraction of suspended cells but it would be more useful to know the average cell radius and number density separately. A non-linear least squares algorithm, based on the Levenberg-Marquardt technique, has been developed to predict these

D. J. Currie; M. H. Lee; R. W. Todd

2006-01-01

335

Effect of side chains on the dielectric properties of alkyl esters derived from palm kernel oil  

Microsoft Academic Search

Alkyl ester derivatives were synthesized from laboratory purified palm kernel oil. The steps in the synthesis involved transesterification of palm kernel oil to produce a methyl ester, followed by epoxidation and then the grafting of side chains by esterification with propionic and butyric anhydride. The dielectric and thermal properties of the ester derivatives were analyzed and compared with the methyl

A. A. Abdelmalik; J. C. Fothergill; S. J. Dodd; A. P. Abbott; R. C. Harris

2011-01-01

336

Approximation of aging effect on dielectric tissue properties for SAR assessment of mobile telephones  

Microsoft Academic Search

In electromagnetic dosimetry of children heads for mobile telephones, the dielectric properties of biological tissues for adults are so far being used due to the lack of the ones of children. In this paper, we derived an empirical formula according to Lichtenecker's exponential law for the complex permittivity of various tissues as a function of the hydrated rate or the

Jianqing Wang; Osamu Fujiwara; Soichi Watanabe

2006-01-01

337

The effect of water absorption on the dielectric properties of epoxy nanocomposites  

Microsoft Academic Search

In this research, the influence of water absorption on the dielectric properties of epoxy resin and epoxy micro-composites and nano-composites filled with silica has been studied. Nanocomposites were found to absorb significantly more water than unfilled epoxy. However, the microcomposite absorbed less water than unfilled epoxy: corresponding to the reduced proportion of the epoxy in this composite. The glass transition

Chen Zou; J. C. Fothergill; S. W. Rowe

2008-01-01

338

Effects of uniaxial stress on the piezoelectric, dielectric, and mechanical properties of lead zirconate titanate piezoceramics  

Microsoft Academic Search

Piezoelectric ceramics are often used under compressive stress. It is therefore important to know the properties of these materials as a function of applied stress. We have developed an experiment that allows us to find the piezoelectric charge coefficient d33, elastic compliance S 33, and dielectric constant ? 33 as a function of uniaxial stress in the poled direction. Both

G. Yang; S. F. Liu; W. Ren; B. K. Mukherjee

2001-01-01

339

Aqueous-Develop, Photosensitive Polynorbornene Dielectric: Optimization of Mechanical and Electrical Properties  

NASA Astrophysics Data System (ADS)

The impact of thermal cure conditions on the mechanical and electrical properties of an epoxy cross-linked network incorporating a polynorbornene (PNB) dielectric polymer was studied. The cross-linking of the dielectric composition was achieved by an acid-catalyzed cationic cure reaction initiated by either thermal or photolytic activation of a photoacid generator. It is proposed that the observed mechanical and electrical properties of the fully cured polymer composition are the result of the development of a three-dimensional cross-linked network tying together the PNB polymer and multifunctional epoxy additives. The epoxy ring-opening reaction was measured using Fourier-transform infrared spectroscopy. The reduced modulus, internal film stress, dielectric constant, and swelling behavior of cross-linked films were studied as a function of curing temperature. Trends in the observed properties are explained by formation of a three-dimensional cross-linked network and degradation of the cross-links between the multifunctional epoxy additives at high temperature. It was also found that exposure of the film to aqueous base plays a role in the cure process and has a positive effect on the final properties. The optimum values of modulus, dielectric constant, residual stress, and moisture content were found for films cured at 160C for 1 h. This relatively low cure temperature is potentially advantageous in device assembly and processing.

Raeis-Zadeh, Mehrsa; Melendez, Noraica Davila; Chen, Yu-Chun; Kohl, Paul A.

2011-10-01

340

Preparation, vibrational structure and dielectric properties studies of cotton linter and its derivatives  

Microsoft Academic Search

Preparation of unhydrolyzed and hydrolyzed cotton linters as well as their derivatives (carboxylate, phosphate and phosphosulphonate), vibrational structure and dielectric properties were studied in this work. The vibrational modes were analyzed by FTIR spectroscopy and the band at 1730cm?1 in the carboxylation of unhydrolyzed and hydrolyzed was appeared due to introduce of carboxylic group. The new bands appeared at 1208

A. M. A. Nada; S. H. Mohamed; S. Abd El Mongy; R. Seoudi

2009-01-01

341

Comparison of dielectric properties determined from a computational approach and experiment for anisotropic and periodic heterostructures  

Microsoft Academic Search

The physics of heterostructures is among the forefront problems in materials science. Composite materials also are attractive from the point of view of technological applications such as current-limiting thermistors, radar absorbers, and electromagnetic shields, because they exhibit a variety of interesting mechanical, electric and magnetic properties with the advantage of much reduced cost and weight. To quantify the dielectric response

A. Beroual; C. Brosseau

2001-01-01

342

Effects of Mechanical Pressures on the Dielectric Properties of Polycrystalline Barium-Strontium Titanate  

Microsoft Academic Search

The effects of the following three kinds of mechanical pressures upon the dielectric properties of barium-strontium titanate ceramics have been investigated: (1) hydrostatic pressure, (2) compression parallel to the electrode surface and (3) compression normal to the electrode surface (as shown in Fig. 1). Especially the influences of these pressures on the Curie point and on the permittivity in the

Gen Shirane; Katsuo Sato

1951-01-01

343

Characterization of radio frequency heating of fresh fruits influenced by dielectric properties  

Microsoft Academic Search

Because of its fast and volumetric nature, radio frequency (RF) heating has been looked upon as a way to overcome the problems associated with conventional heating methods used for disinfestation of fruits. But non-uniform heating within fruits is a major obstacle in adaptation of this technology. In this study, RF heating patterns influenced by dielectric properties (DPs) of fruits were

S. L. Birla; S. Wang; J. Tang; G. Tiwari

2008-01-01

344

INFLUENCE OF MASHED POTATO DIELECTRIC PROPERTIES AND CIRCULATING WATER ELECTRIC CONDUCTIVITY ON RADIO FREQUENCY HEATING  

Microsoft Academic Search

Experiments and computer simulations were conducted to systematically investigate the influence of mashed potato dielectric properties and circulating water electric conductivity on electromagnetic field distribution, heating rate, and heating pattern in packaged food during radio frequency (RF) heating processes in a 6 kW, 27 MHz laboratory scale RF heating system. Both experimental and simulation results indicated that for the selected

Jian Wang; Robert G. Olsen; Juming Tang; Zhongwei Tang

345

Effect of temperature variations on the dielectric properties of a radiofrequency, gelatin water phantom  

Microsoft Academic Search

Hyperthermia preliminarly tests are always done on phantom models simulating human tissues. A simple RF phantom (10150 MHz), made with gelatin water mixture was developped by our group for muscle simulation. We discuss the influence of the temperature variations on the dielectric properties. Effect of increasing the concentration of the gelatin powder is also presented.

M. Nadi; C. Marchal; A. Rouane; A. Hedjiedj; D. Kourtiche; G. Prieur

1992-01-01

346

Nondestructive Evaluation of Aircraft Composites Using Dielectric Properties and Imaging in the Terahertz Spectrum  

Microsoft Academic Search

Terahertz imaging and dielectric property measurements were assessed as nondestructive evaluation techniques for damage to aircraft glass fiber composites. Samples with localized heat damage showed a minimal change in refractive index or absorption coefficient; however, material blistering was detected. Voids were located by terahertz imaging using amplitude and phase techniques. Delamination depths were approximated by measuring the timing of Fabry-Perot

C. D. Stoik; M. J. Bohn; J. L. Blackshire

2009-01-01

347

NONDESTRUCTIVE EVALUATION OF AIRCRAFT COMPOSITES USING DIELECTRIC PROPERTIES AND IMAGING IN THE TERAHERTZ SPECTRUM  

Microsoft Academic Search

Terahertz imaging and dielectric property measurements were assessed as nondestructive evaluation techniques for damage to aircraft glass fiber composites. Samples with localized heat damage showed a minimal change in refractive index or absorption coefficient; however, material blistering was detected. Voids were located by terahertz imaging using amplitude and phase techniques. Delamination depths were approximated by measuring the timing of Fabry-Perot

C. D. Stoik; M. J. Bohn; J. L. Blackshire

2009-01-01

348

High-temperature dielectric properties of ruby mica perpendicular to the cleavage planes  

Microsoft Academic Search

Measurements of the dielectric properties of mica normal to the cleavage planes with platinum, silver and graphite electrodes are reported, we believe for the first time in the frequency range 0.01 to 10 000 Hz at fixed temperatures in the range up to 956 K. At high temperatures and low frequencies volume transport is observed giving rise to electrode-independent low

M. A. Chaudhry; A. K. Jonscher

1988-01-01

349

Dielectric properties of anodic films on sputter-deposited TiSi porous columnar films  

Microsoft Academic Search

For electrolytic capacitor application of the single-phase Ti alloys containing supersaturated silicon, which form anodic oxide films with superior dielectric properties, porous Ti7at% Si columnar films, as well as Ti columnar films, have been prepared by oblique angle magnetron sputtering on to aluminum substrate with a concave cell structure to enhance the surface area and hence capacitance. The deposited films

M. Tauseef Tanvir; T. Fujii; Y. Aoki; K. Fushimi; H. Habazaki

2011-01-01

350

Study made of dielectric properties of promising materials for cryogenic capacitors  

NASA Technical Reports Server (NTRS)

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

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

1967-01-01

351

Dielectric properties of hydrogen-incorporated chemical vapor deposited diamond thin films  

Microsoft Academic Search

Diamond thin films with a broad range of microstructures from a ultrananocrystalline diamond (UNCD) form developed at Argonne National Laboratory to a microcrystalline diamond (MCD) form have been grown with different hydrogen percentages in the Ar\\/CH4 gas mixture used in the microwave plasma enhanced chemical vapor deposition (CVD) process. The dielectric properties of the CVD diamond thin films have been

Chao Liu; Xingcheng Xiao; Jian Wang; Bing Shi; Vivekananda P. Adiga; Robert W. Carpick; John A. Carlisle; Orlando Auciello

2007-01-01

352

Average dielectric properties of discrete random media using multiple scattering theory  

Microsoft Academic Search

The average or bulk dielectric properties of discrete random media are investigated using rigorous multiple scattering theory. A model of the random medium is developed as the random distribution of identical, spherical scatterers imbedded in a homogeneous unbounded background medium. Two forms of the radial distribution function are considered, the virial series and the self-consistent form. The average loss tangent

V. N. Bringi; V. K. Varadan; V. V. Varadan

1983-01-01

353

Dielectric properties of film materials based on polyethylene terephthalate and polycarbonate with ferroelectric inclusions  

NASA Astrophysics Data System (ADS)

The dielectric properties of film materials based on polyethylene terephthalate and polycarbonate with inclusions of triglycine sulfate (TGS) and TGS with admixture of L, ?-alanine (ATGS) have been studied. An increase in the temperature of the phase transition in these materials as compared to in bulk TGS and ATGS has been revealed.

Golitsyna, O. M.; Drozhdin, S. N.

2012-08-01

354

Free-space measurement of dielectric properties of cereal grain and oilseed at microwave frequencies  

Microsoft Academic Search

Principles of dielectric property 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 analyser, horn\\/lens antennas, holder for grain and oilseed samples and a radiation absorbing enclosure that was used for such measurements is described, and the techniques and procedures followed to obtain reliable

Samir Trabelsi; Stuart O. Nelson

2003-01-01

355

Dielectric Properties of Mafic Dust-Ice Mixtures: Case Study of the Martian Polar Layered Deposits  

Microsoft Academic Search

The dielectric properties of the dust-ice mixtures (also referred as dirty ice) are key parameters in understanding the suitability of the layered deposits in the Martian poles for radar deep subsurface sounding and hence the investigation of the poles' stratigraphy and the potential presence of subglacier melting at the base of the structure. In a first step toward experimentally investigating

E. Heggy; S. M. Clifford

2005-01-01

356

Correlation of Microwave Dielectric Properties and Microstructure of Unpatterned Ferroelectric Thin Films.  

National Technical Information Service (NTIS)

The influence of low concentration (1 mol%) Mg doping on the structural, microstructural, surface morphological and dielectric properties of Ba(1-x)Sr(x)TiO3 thin films has been measured and analyzed. The films were fabricated on MgO and Pt-Si substrates ...

C. Hubbard E. Ngo M. W. Cole P. C. Joshi R. G. Geyer

2003-01-01

357

Dielectric properties of PLZT film-on-foil capacitors.  

SciTech Connect

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.

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

2008-07-31

358

Dielectric properties of fluxed barium titanate ceramics with zirconia additions  

SciTech Connect

BaTiO{sub 3} compacts, when fluxed with {lt} 2 vol% of a complex borate glass phase, were sintered to near theoretical density at temperatures {lt} 1175{degrees}C in 2 h. Microstructural analysis showed a uniform grain size {lt} 1.0 {mu}m with 0.75 wt% ZrO{sub 2} added to the flux phase as a grain growth inhibitor. TEM analysis revealed a microcrystalline grain-boundary phase with the ZrO{sub 2} resident along the grain boundaries. These samples displayed an essentially flat dielectric profile, low dissipation factors ({lt} 2%) over the range 25{degrees} to 125{degrees}C, a near linear dependence ({approx} {+-} 15%) between 25{degrees} and {minus} 55{degrees}C, and significantly increased voltage stability. X-ray diffraction analysis of these small-grained materials indicates a suppression of the tetragonal structure toward a more cubic modification.

Armstrong, T.R.; Young, K.A.; Buchanan, R.C. (Illinois Univ., Urbana, IL (USA). Dept. of Materials Science and Engineering)

1990-03-01

359

Influence of La2O3 Additions on Chemical Durability and Dielectric Properties of Boroaluminosilicate Glasses  

NASA Astrophysics Data System (ADS)

Boroaluminosilicate glasses containing La2O3 were prepared by the normal quenching method. The glass transition temperatures (Tg) were measured by differential scanning calorimetry (DSC). The structural role of RO was investigated by nuclear magnetic resonance (NMR). Chemical durability was evaluated by weight losses of glass samples after immersion in HC1 solution. High resolution scanning electron microscopy (HR-SEM) was used to examine the surface micrographs of corroded glass samples. The dielectric constant and tangent loss were measured in the frequency range 10-106 Hz. The results revealed that chemical durability and dielectric properties increased with increasing La2O3 content.

Zhang, X. H.; Yue, Y. L.; Wu, H. T.

2012-12-01

360

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

361

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

SciTech Connect

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.

Podgornov, Fedor V.; Ryzhkova, Anna V. [Eduard-Zintl-Institute for Inorganic and Physical Chemistry, Darmstadt University of Technology, Petersenstr. 20, Darmstadt D-64287 (Germany); Department of Physics, Electrical Engineering Technologies Laboratory, South Ural State University, Lenin Ave. 76, Chelyabinsk 454080 (Russian Federation); Haase, Wolfgang [Eduard-Zintl-Institute for Inorganic and Physical Chemistry, Darmstadt University of Technology, Petersenstr. 20, Darmstadt D-64287 (Germany)

2010-11-22

362

Temperature dependence of dielectric properties of (BaSrMg)TiO3 ceramics  

Microsoft Academic Search

The dielectric properties of several high dielectric-based ceramics (BaTiO3) were measured at different temperatures and frequencies. The preternary compound ceramics, (1-y-x)BaTiO3-ySrTiO3-xMgTiO3, were fabricated as ceramic capacitors by using the mixed oxide method. As the results of the electrical measurement of the specimens, the temperature coefficients of the capacitance were decreased and the curie temperature (Tc) were shifted downward in accordance

Beom-Jin Kim; Tae-Gone Park; Myoung-Ho Kim

1997-01-01

363

Microwave Dielectric Properties of Dy2O3 Substituted BiNbO4 Ceramics  

Microsoft Academic Search

The microwave dielectric properties of Bi1-xDyxNbO4 ceramics were investigated as a function of Dy3+ substitution (0<= x<= 0.1). Bi1-xDyxNbO4 compositions prepared at low temperatures (900-960 C). A single orthorhombic (alpha-BiNbO4) phase in all Bi1-xDyxNbO4 compositions was obtained for the whole sintering temperature range. The decrease in the dielectric constant of the Bi1-xDyxNbO4 ceramics with increasing Dy content is attributed to

Hyuk Lim; Young-Jei Oh

2006-01-01

364

Effect of Vanadium Substitution on the Dielectric Properties of Glass Ceramic Bi2212 Superconductor  

Microsoft Academic Search

Glass ceramic superconductors were prepared by the melt-quenching method. The frequency and temperature dependence of dielectric\\u000a constant (??), dielectric loss (??) and loss tangent (tan??) of these superconductors were investigated in the frequency range of 10kHz10MHz and temperature range of 80300K using\\u000a the capacitancevoltage (CV) and conductance-voltage (G\\/w-V) measurements. Effect of vanadium on bulk properties, dc electrical\\u000a resistivity (?) and

?. avdar; H. Koralay; ?. Alt?ndal

2011-01-01

365

Microwave dielectric properties of Zn(Nb 1? x Ta x ) 2O 6 ceramics  

Microsoft Academic Search

Microwave dielectric ceramics Zn(Nb1?xTax)2O6 were prepared by conventional mixed oxide route. The crystal structure and microwave dielectric properties of Zn(Nb1?xTax)2O6 ceramics were investigated systematically using X-ray powder diffraction (XRPD) and a network analyzer. Two kinds of solid solutions based on the ZnNb2O6 and ZnTa2O6 structure, respectively, were observed in this binary system. The sintering temperature of ceramics increased from 1150

YingChun Zhang; ZhenXing Yue; Xiwei Qi; Baorang Li; ZhiLun Gui; LongTu Li

2004-01-01

366

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

SciTech Connect

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.

Cabassi, R.; Bolzoni, F.; Gauzzi, A.; Gilioli, E.; Prodi, A.; Licci, F. [Istituto IMEM-CNR, Area delle Scienze, 43100 Parma (Italy)

2006-07-15

367

Complex permittivity and microwave absorption properties of a composite dielectric absorber  

Microsoft Academic Search

Two types of composite samples were prepared using dielectric particulates such as BaTiO3, polyaniline and conducting carbon in polyurethane matrix. One of the composite samples contains synthesized BaTiO3 and polyaniline, while the other sample using, the commercial ingredients. Structural properties of both synthesized and commercial BaTiO3 and polyaniline have been investigated. Complex permittivity (?r?-j?r?) and microwave absorption properties of the

S. M. Abbas; Mahesh Chandra; A. Verma; R. Chatterjee; T. C. Goel

2006-01-01

368

Dielectric properties of oxidized porous silicon in a low resistivity substrate  

Microsoft Academic Search

Oxidized porous silicon (OPS) is characterized for its high frequency electrical properties up to 50 GHz. Transmission line properties are determined from measurement data and are compared with high and low resistivity silicon benchmark designs. Best OPS performance of 50 Ohm lines is observed on oxide-capped OPS, having attenuation of approximately 2.93 dB\\/cm at 4 GHz with an effective dielectric

Rebecca L. Peterson; Rhonda F. Drayton

2001-01-01

369

The low-frequency dielectric properties of octopus arm muscle measured in vivo  

NASA Astrophysics Data System (ADS)

The conductance and capacitance of octopus arm are measured in vivo over the frequency range 5 Hz to 1 MHz. Measurement of these parameters for a number of electrode separations permits the determination of the variations in tissue conductivity and dielectric constant with frequency. In the range 1 - 100 kHz the conductivity is independent of the frequency f and the dielectric constant varies as . These results, in conjunction with those reported previously for frog skeletal muscle, are consistent with the fractal model for the dielectric properties of animal tissue proposed by Dissado. Transformation of the results to complex impedance spectra indicates the presence of a dispersion above 100 kHz.

Hart, F. X.; Toll, R. B.; Berner, N. J.; Bennett, N. H.

1996-10-01

370

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

NASA Astrophysics Data System (ADS)

0.5BiGdxFe1-xO3-0.5PbTiO3 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 (?r and tan?) of the above compound at different frequencies in a wide range of temperature (25-500C) 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.

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

2014-04-01

371

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

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

372

Fabrication and Properties of Novel Polyetheretherketone/Barium Titanate Composites with Low Dielectric Loss  

NASA Astrophysics Data System (ADS)

Dielectric, thermal, and microhardness properties of high-performance barium titanate (BaTiO3)-filled polyetheretherketone (PEEK) composites were studied. BaTiO3 was varied from 0 vol.% to 67 vol.% in the PEEK matrix. The dielectric constant of the composites measured at 1 MHz increased approximately 14-fold. There was no dispersion in the dielectric constant with frequency between 10 kHz and 15 MHz. The Lichtenecker equation and modified Lichtenecker equation agreed well with the experimental data. The dissipation factor of the composites varied from 0.0056 to 0.0096. Scanning electron microscopy showed uniform dispersion of BaTiO3 in the matrix. The microhardness of the composites increased by more than 2.5-fold compared with pure PEEK. The coefficient of thermal expansion measured below and above the glass-transition temperature was reduced by up to 56%. These results make these composites promising candidate high-temperature organic substrates.

Goyal, R. K.; Madav, V. V.; Pakankar, P. R.; Butee, S. P.

2011-11-01

373

Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics  

NASA Astrophysics Data System (ADS)

The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s-1 at heights of 1-2 mm are reached when filamentary discharges with current peaks up to 20 mA are produced along the surface. In terms of powers, mechanical powers (output) of a few milliwatts are obtained for electrical powers (input) up to 10 W. Variation laws or behaviour with several discharge parameters (applied voltage waveform, distance between electrodes, dielectric thickness and permittivity) have been experimentally determined.

Pons, Jrme; Moreau, Eric; Touchard, Grard

2005-10-01

374

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

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

375

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

PubMed

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

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

2014-07-01

376

Nanoscale dielectric properties of insulating thin films: from single point measurements to quantitative images.  

PubMed

Dielectric relaxation (DR) has shown to be a very useful technique to study dielectric materials like polymers and other glass formers, giving valuable information about the molecular dynamics of the system at different length and time scales. However, the standard DR techniques have a fundamental limitation: they have no spatial resolution. This is of course not a problem when homogeneous and non-structured systems are analyzed but it becomes an important limitation for studying the local properties of heterogeneous and/or nano-structured materials. To overcome this constrain we have developed a novel approach that allows quantitatively measuring the local dielectric permittivity of thin films at the nanoscale by means of Electrostatic Force Microscopy. The proposed experimental method is based on the detection of the local electric force gradient at different values of the tip-sample distance. The value of the dielectric permittivity is then calculated by fitting the experimental points using the Equivalent Charge Method. Even more interesting, we show how this approach can be extended in order to obtain quantitative dielectric images of insulating thin films with an excellent lateral resolution. PMID:20206448

Riedel, C; Schwartz, G A; Arinero, R; Tordjeman, P; Lvque, G; Alegra, A; Colmenero, J

2010-05-01

377

Measuring and modeling of the dielectric properties and attenuation of vegetation  

NASA Technical Reports Server (NTRS)

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

Ulaby, F. T.

1984-01-01

378

Effect of dispersion degree of orientation on dielectric properties of (100)-oriented PST thin film  

NASA Astrophysics Data System (ADS)

(100) Oriented (PbxSr1-x)TiO3 (PST) thin films were prepared on indium tin oxide coated glass substrates by sol-gel technique with rapid thermal processing. The dielectric permittivity and tunability of the thin films with different dispersion degrees of orientation were investigated in detail by characterizing the full width at half maximum of their (100) peak based on rocking curves at different annealing temperatures. Influence of orientation dispersion on dielectric properties was exhibited in the tunable dielectric thin films. It shows that the dielectric constant and hence the tunability of the sol-gel derived PST thin films are improved with the decrease in the dispersion degree of orientation of the perovskite phase other than the increase in the content of crystalline phase in the thin films. The dielectric constant (capacitance) and figure of merit of the oriented thin films are 3-6 times and 1 times higher than that of randomly oriented thin film respectively.

Li, Xiaoting; Hu, Tao; Wang, Biao; Weng, Wenjian; Han, Gaorong; Song, Chenglu; Ma, Ning; Du, Piyi

2013-12-01

379

Structure and Properties of Epitaxial Dielectrics on gallium nitride  

NASA Astrophysics Data System (ADS)

GaN is recognized as a possible material for metal oxide semiconductor field effect transistors (MOSFETs) used in high temperature, high power and high speed electronic applications. However, high gate leakage and low device breakdown voltages limit their use in these applications. The use of high-kappa dielectrics, which have both a high permittivity (?) and high band gap energy (Eg), can reduce the leakage current density that adversely affects MOS devices. La2O3 and Sc2O 3 are rare earth oxides with a large Eg (6.18 eV and 6.3 eV respectively) and a relatively high ? (27 and 14.1 respectively), which make them good candidates for enhancing MOSFET performance. Epitaxial growth of oxides is a possible approach to reducing leakage current and Fermi level pinning related to a high density of interface states for dielectrics on compound semiconductors. In this work, La2O3 and Sc2O 3 were characterized structurally and electronically as potential epitaxial gate dielectrics for use in GaN based MOSFETs. GaN surface treatments were examined as a means for additional interface passivation and influencing subsequent oxide formation. Potassium persulfate (K2(SO4)2) and potassium hydroxide (KOH) were explored as a way to achieve improved passivation and desired surface termination for GaN films deposited on sapphire substrates by metal organic chemical vapor deposition (MOCVD). X-ray photoelectron spectroscopy (XPS) showed that KOH left a nitrogen-rich interface, while K2(SO 4)2 left a gallium-rich interface, which provides a way to control surface oxide formation. K2(SO4)2 exhibited a shift in the O1s peak indicating the formation of a gallium-rich GaOx at the surface with decreased carbon contaminants. GaO x acts as a passivating layer prior to dielectric deposition, which resulted in an order of magnitude reduction in leakage current, a reduced hysteresis window, and an overall improvement in device performance. Furthermore, K2(SO4)2 resulted in an additional 0.4 eV of upward band bending at the surface, which should be considered when determining heterojunction band offsets with GaN. Epitaxial La2O3 and Sc2O3 were successfully deposited on GaN by molecular beam epitaxy (MBE). Sc 2O3 exhibited a cubic bixbyite crystal structure, while La 2O3 had a mix of both cubic and hexagonal crystal structures. A highly defective structure was observed for La2O3, compared to Sc2O3, which results from its larger mismatch with GaN (14.5% and 8.9%, respectively). TEM images indicated an abrupt atomic interface for Sc2O3 films, but an interfacial layer was observed for La2O3 on GaN. Additionally, La 2O3 was shown to be extremely reactive with water and carbon dioxide in air, forming both hydroxides and carbonates within 15 minutes of exposure. Therefore, tantalum and silicon were investigated as in-situ capping metals to prevent these deleterious effects. XPS was utilized to determine a valence band offset (VBO) and conduction band offset of 1.9 +/- 0.1 eV and 0.9 +/- 0.1 eV for La2O 3 on GaN. Similarly, Sc2O3 had a VBO and CBO of 0.8 +/- 0.1 eV and 2.1 +/- 0.1 eV, respectively. Both oxides exhibited sufficient band offsets to prevent thermionic emission of carriers, even at high operation temperatures, making them good candidates for insulator layers in high temperature, high power applications. Preliminary C-V curves, for La2O3 and Sc2 O3 MOS capacitors, showed large charge accumulation layers, extremely high permittivity values, and low hysteresis windows indicative of low density of interface traps and fixed oxide charges. I-V curves showed a reduction in leakage current density for both oxides compared to Si 3N4, a readily used gate dielectric for GaN devices. The larger reduction achieved with La2O3 films is attributed to a passivating interfacial layer that minimizes the amount of dislocations propagating into the oxide. These preliminary results point to the viability of these gate oxides in GaN MOSFET devices.

Wheeler, Virginia Danielle

380

Static dielectric constants and molecular dipole distributions of liquid water and ice-Ih investigated by the PAW-PBE exchange-correlation functional  

NASA Astrophysics Data System (ADS)

The static dielectric constants, ?s, of ice-Ih and liquid water were calculated using density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the projector-augmented-wave (PAW) approach. Proton disordered ice configurations and uncorrelated liquid configurations were sampled with the electrostatic switching method using force fields specially designed to facilitate the ab initio free energy perturbation calculations. Our results indicate that PAW-PBE underestimates the ?s of both ice-Ih and liquid water but predicts the ratio of ice and water ?s in good agreement with experimental measurements. PAW-PBE gives average water dipole moments of 2.50 D in ice-Ih and 2.48 D in the liquid. Our results show that the fixed-charge water models developed by adaptive force matching can reproduce the PAW-PBE dipole moments with an error of approximately 5%. The ice and liquid models created in this work have polarizabilities of 1.32 A?3 and 1.30 A?3, respectively, along the HOH bisector direction.

Rusnak, Andrew J.; Pinnick, Eric R.; Calderon, Camilo E.; Wang, Feng

2012-07-01

381

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

NASA Astrophysics Data System (ADS)

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.

Sanchez, Luis

382

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

NASA Astrophysics Data System (ADS)

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.

Boresch, Stefan; Willensdorfer, Martin; Steinhauser, Othmar

2004-02-01

383

Dielectric properties of polyaniline-montmorillonite clay hybrids.  

PubMed

Polyaniline (PANI)-montmorillonite clay (MMT) hybrid (PANI-MMT) was prepared by mechanical grinding of ANI and MMT in the presence of potassium perdisulphate (KPS) followed by soaking the mass in 0.1 (M) HCI for 24 h. The formation of PANI-MMT hybrid was confirmed by Fourier transform infrared spectroscopic analyses. XRD studies revealed the intercalation of PANI into two-dimensional silicate galleries of MMT HRTEM analyses indicated particle size distribution to be in the range of 40-55 nm. The real part of the dielectric constant reached values as high as 4500 at frequency - 10(2) Hz for a MMT:PANI = 1:1 weight ratio, the value decreasing with increasing frequency up to 25 kHz, and also with increasing MMT loading in the hybrids. This dispersion was indicative of the interfacial space charge polarization (Maxwell Wagner type). Grain boundary resistance and capacitance of the hybrid along with the conductivity-relaxation time for the hybrid at several PANI:MMT weight ratios were evaluated from the complex impedance plot considering the Maxwell-Wagner Two-Layered Model AC conductivity was independent of frequency in the range 0.1-1 kHz and thereafter found to rise in the range 1-25 kHz due to trapped charges. DC conductivity values of the hybrids were lower than the PANI homopolymer. PMID:23755599

Haldar, Ipsita; Biswas, Mukul; Nayak, Arabinda; Ray, Suprakas Sinha

2013-03-01

384

RAPID COMMUNICATION: On some dielectric properties of PEN  

Microsoft Academic Search

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

J. P. Bellomo; T. Lebey

1996-01-01

385

The effect of geometry and surface morphology on the optical properties of metal-dielectric systems  

NASA Astrophysics Data System (ADS)

We analyze the effect of geometry and surface morphology on the optical properties of metal-dielectric systems. Using both analytical and numerical modeling, we study how surface curvature affects the propagation of surface plasmon polaritons (SPPs) along a metal-dielectric interface. We provide an intuitive explanation for how the curvature causes the phase front to distort, causing the SPPs to radiate their energy away from the metal-dielectric interface. We quantify the propagation efficiency as functions of the radius of curvature, and show that it depends nonmonotonically on the bend radius. We also show how the surface morphology influences the transmittance and the reflectance of light from disordered metal-dielectric nanocomposite films. The films consist of semicontinuous silver films of various surface coverage that are chemically deposited onto glass substrates. They exhibit a large and broadband reflection asymmetry in the visible spectral range. In order to investigate how the surface morphology affects the asymmetry, we anneal the samples at various temperatures to induce changes in the morphology, and observe changes in the reflection spectra. Our study indicates that the surface roughness and the metal surface coverage are the key geometric parameters affecting the reflection spectra, and reveals that the large asymmetry is due to the different surface roughness light encounters when incident from different side of the film. Additionally, we analyze how thin metal and dielectric layers affect the optical properties of metal-dielectric systems. Using the concept of dispersion engineering, we show that a metal-dielectric-metal microsphere---a metal sphere coated with a thin dielectric shell, followed by a metal shell---support a band of surface plasmon resonances (SPRs) with nearly identical frequencies. A large number of modes belonging to this band can be excited simultaneously by a plane wave, and hence enhancing the absorption cross-section. We also find that the enhanced absorption is accompanied by a plasmon assisted transparency due to an avoided crossing of dominant SPR bands. We demonstrate numerically that both the enhanced absorption and the plasmon assisted transparency are tunable over the entire visible range. We also present an experimental study of light scattering from silica spheres coated with thin semicontinuous silver shells, and attempt to describe their optical response using a modified scaling theory. This dissertation includes previously published co-authored materials.

Hasegawa, Keisuke

386

Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites  

NASA Astrophysics Data System (ADS)

In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young's modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charge-storage devices.

Rathod, Sunil G.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Naik, Jagadish

2014-04-01

387

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

SciTech Connect

Ferrite nanoparticles of basic composition Ni{sub 0.7}Mg{sub 0.3}Fe{sub 2-x}Al{sub x}O{sub 4}(0.0{<=}x{<=}0.5) were prepared through citrate gel method and characterized using XRD, TEM and dielectric spectroscopy techniques. The dielectric properties were studied as a function of frequency (42 Hz-5 MHz) at room temperature. The average particle size has been found between 8-17 nm. The dispersion in dielectric properties and ac conductivity ({sigma}{sub ac}), with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe{sup 2+} and Fe{sup 3+} as well as between Ni{sup 2+} and Ni{sup 3+} ions at B-sites. The dielectric loss tangent (tan {delta}) shows abnormal behavior for the compositions 0.3, 0.4 and 0.5 which has been explained in the light of Rezlescue model.

Nongjai, Razia; Batoo, Khalid Mujasam; Khan, Shakeel [Dept. of Applied Physics, Aligarh Muslim University, Aligarh, 202002 (India) and King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, 11451 (Saudi Arabia)

2010-12-01

388

Static and dynamic magnetic properties of cubic Mn-Co-Ga Heusler films  

NASA Astrophysics Data System (ADS)

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.

Demiray, A. S.; Kubota, T.; Iihama, S.; Mizukami, S.; Miyazaki, T.; Naganuma, H.; Oogane, M.; Ando, Y.

2014-05-01

389

Static and dynamic properties of trapped fermionic Tonks-Girardeau gases.  

PubMed

We investigate some static and dynamic properties of harmonically trapped fermionic Tonks-Girardeau gases in tight de Broglie waveguides with attractive p-wave interactions induced by a Feshbach resonance. An exact solution for the one-body density matrix is analyzed in terms of its natural orbitals, with the surprising result that for odd, but not for even, numbers of fermions the maximally occupied orbital coincides with the ground harmonic oscillator orbital. A dynamical consequence of this is that when the interactions are turned off the on-axis density remains a maximum for an odd number of fermions, whereas a minimum develops for an even number. PMID:16090592

Girardeau, M D; Wright, E M

2005-07-01

390

Dielectric properties of Mn0.5Zn0.5Fe2O4 ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Mn0.5Zn0.5Fe2O4 ferrite nanoparticles have been prepared by sol-gel auto-combustion method with a view to understand the role of oxidizer to fuel ratio (OFR) on the dielectric properties. XRD study shows the formation of cubic ferrite with spinel structure and particle size increases with the increase in concentration of fuel. Dielectric properties and AC conductivity of the sample measured at room temperature are reported. OFR plays a vital role in determining the dielectric properties and AC conductivity of the prepared samples.

Murugesan, C.; Md Gazzali, P. M.; Sathyamoorthy, B.; Chandrasekaran, G.

2013-02-01

391

Optimization of silver-dielectric-silver nanoshell for sensing applications  

NASA Astrophysics Data System (ADS)

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.

Shirzaditabar, Farzad; Saliminasab, Maryam

2013-08-01

392

Optimization of silver-dielectric-silver nanoshell for sensing applications  

SciTech Connect

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.

Shirzaditabar, Farzad; Saliminasab, Maryam [Department of Physics, Razi University, Kermanshah 67144-15111 (Iran, Islamic Republic of)] [Department of Physics, Razi University, Kermanshah 67144-15111 (Iran, Islamic Republic of)

2013-08-15

393

RAPID COMMUNICATION: On some dielectric properties of PEN  

NASA Astrophysics Data System (ADS)

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.

Bellomo, J. P.; Lebey, T.

1996-07-01

394

Fundamental Properties of Organic Low-k Dielectrics Usable in the Cu Damascene Process  

NASA Astrophysics Data System (ADS)

The material parameters for organic low-k dielectrics usable in the damascene process were studied using two different types of polymers with similar low dielectric constants, namely, the PQ-600 thermoplastic polymer and the SiLK thermosetting polymer. The resistibility of these polymers in the damascene process was investigated through hard-mask (SiO2) deposition, etching and chemical mechanical polishing (CMP) processes using scanning probe microscopy (SPM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and a modified edge liftoff test (m-ELT). For the PQ-600 film, damage was observed in the deposition process and dissolution of the film occurred during chemical cleaning in the etching process. On the other hand, the SiLK film was combinable with the Cu damascene process and usable as an interlayer dielectric (ILD) in one-level Cu wiring. A high glass transition temperature (Tg) and chemical resistance resulting from the thermosetting structure are considered to be the essential properties required for the desired organic low-k dielectrics. In eddition, the electrical properies of the SiLK film were investigated using a one-level test element group (TEG) formed through a single Cu damascene process. The dielectric constant of the SiLK film extracted from the Cu damascene TEG compared with that of bulk SiO2 was reduced by 24%. The leakage current measured at 1 MV/cm between the adjoining Cu lines at the TEG pattern with a hard mask was 9.7 10-10 A/cm2, and dielectric breakdown occurred at 5.5 MV/cm.

Nomura, Yutaka; Ota, Fumihiko; Kurino, Hiroyuki; Koyanagi, Mitsumasa

2005-11-01

395

Dielectric properties of isotactic polypropylene and montmorillonite nanocomposites  

Microsoft Academic Search

Polymer nanocomposites typically consist of inorganic particles dispersed in a polymer matrix. Layered-silicate-based polymer nanocomposites have great potential as low-cost, high-performance materials with various engineering applications. They exhibit enhanced mechanical, thermal, and electrical properties compared with their macro- and micro- counterparts. Polypropylene (PP) exhibits good hardness, thermal, and electrical properties and provides outstanding resistance to moisture and chemicals such as

E. Izci; N. Bowler

2010-01-01

396

Modelling and validation of dielectric properties of human skin in the MHz region focusing on skin layer morphology and material composition  

Microsoft Academic Search

Human skin consists of several layers with distinct dielectric properties. Physiological processes leading to changes in dielectric properties of the specific layers can potentially be non-invasively monitored employing dielectric spectroscopy. So far no comprehensive skin and underlying tissue model is available for this purpose in the frequency range between 1 and 100 MHz. Focusing on this dispersion-dominated frequency region, different

Sonja Huclova; Daniel Erni; Jrg Frhlich

2012-01-01

397

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

SciTech Connect

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.

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

2008-01-01

398

Dielectric Properties of Polyvinyl Alcohol, Poly(methyl Methacrylate), Polyvinyl Butyral Resin and Polyimide at Low Temperatures  

NASA Astrophysics Data System (ADS)

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). 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 45 K to 350 K. 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 K. PVB and PI have the smallest spread in their breakdown strength data.

Tuncer, Enis; Sauers, Isidor; James, D. Randy; Ellis, Alvin R.

2008-03-01

399

Static friction properties between human palmar skin and five grabrail materials.  

PubMed

The purpose of this study was to investigate the static friction properties between human palmar skin and five grabrail materials (chrome, stainless steel, power-coated steel, textured aluminium and knurled steel) for dry, wet and soapy hands. Thirty subjects (15 female, 15 male) participated in this study, their ages ranging from 19 to 45 years with a mean age of 28 years. The normal force, friction force, and coefficient of static friction were determined by measuring three-dimensional forces while slipping the palm of the hand over the surface of a grabrail. A repeated measures ANOVA indicated that gender, age, hand size and trial effect had no significant influence (p>0.05) on these results. The coefficient of friction (p<0.001) and friction force (p<0.001) were significantly lower when the hand was soapy than when it was dry or wet. The normal force applied when the hand was soapy was significantly greater (p<0.001) than when it was dry or wet. No significant difference was found between dry and wet hands. The two textured materials displayed superior friction properties when the hand was soapy, while the smooth materials performed best when the hand was dry. PMID:11693248

O'Meara, D M; Smith, R M

2001-09-15

400

Structural and Microwave Properties of (Mg,Zn/Co)TiO3 Dielectric Ceramics  

NASA Astrophysics Data System (ADS)

The structural and microwave properties of (Mg,Zn/Co)TiO3 dielectric ceramics have been investigated. The grown samples have been characterized by means of x-ray diffraction, Rietveld refinement, scanning electron microscopy, and energy dispersive x-ray spectroscopy analysis. The microwave dielectric properties of grown samples have been measured using the Hakki-Coleman resonator method and found to depend on the ionic polarizability, electronic polarizability, and Mg-site substitutions. The Mg0.95Zn0.05TiO3 compound shows a maximum Q f value of 210,000 GHz (at 10 GHz), ?r of 16.31, and ?f value of -62.43.

Rajput, Shailendra Singh; Keshri, Sunita

2014-04-01

401

Structural, dielectric and AC conductivity properties of Co2+ doped mixed alkali zinc borate glasses  

NASA Astrophysics Data System (ADS)

The Co2+ doped 19.9ZnO+5Li2CO3+25Na2CO3+50B2O3 (ZLNB) mixed alkali zinc borate glasses have been prepared by a conventional melt quenching method. The structural (XRD & FT-IR), dielectric and a.c. conductivity (?ac) properties have been investigated. Amorphous nature of these glasses has been confirmed from their XRD pattern. The dielectric properties and electrical conductivity (?ac) of these glasses have been studied from 100Hz to 5MHz at the room temperature. Based on the observed trends in the a.c. conductivities, the present glass samples are found to exhibit a non-Debye behavior.

Madhu, B. J.; Banu, Syed Asma; Harshitha, G. A.; Shilpa, T. M.; Shruthi, B.

2013-02-01

402

Optical properties of multilayered Period-Doubling and Rudin-Shapiro porous silicon dielectric heterostructures  

NASA Astrophysics Data System (ADS)

To investigate the optical properties in quasi-regular porous-silicon-based dielectric Period-Doubling and Rudin-Shapiro multilayer systems, we study here the reflection of light from these structures. The Period-Doubling and Rudin-Shapiro structures are fabricated in such a way that the optical thickness of each layer is one quarter of 600 and 640 nm respectively. We find that porous silicon Period-Doubling dielectric multilayers could demonstrate the optical properties similar to the classical periodic Febry-Perot interference filters with one or multiple resonant peaks, but with an advantage of having total optical thickness much lesser than the periodic structures. Additionally, light propagation in porous silicon Rudin-Shapiro structures is investigated for the first time, both theoretically and experimentally. The reflectance spectra of the structures exhibit photonic band gaps centered at predetermined wavelengths. In both cases, numerical simulation of light transmission is performed using transfer matrix method.

Agarwal, V.; Mora-Ramos, Miguel E.; Alvarado-Tenorio, B.

2009-05-01

403

Structural, Dielectric, and Electrical Properties of BiFeWO6 Ceramic  

NASA Astrophysics Data System (ADS)

A polycrystalline sample of BiFeWO6 was synthesized using a high-temperature solid-state reaction method. The formation of the single-phase compound was checked using an x-ray diffraction technique. The surface morphology recorded by scanning electron microscopy exhibited a uniform distribution of grains of different sizes on the surface of the sample. The existence of ferroelectric properties in the material was confirmed by temperature-dependent dielectric and polarization studies. The temperature and frequency dependence of the electrical properties (impedance, modulus, and conductivity) of the compound were studied using a complex-impedance spectroscopy technique. The frequency dependence of the modulus and impedance plots confirmed the presence of dielectric and conductivity relaxation processes of non-Debye type. The frequency dependence of the alternating-current (ac) conductivity obeys Jonscher's universal power law.

Rout, Jyoshna; Parida, B. N.; Das, Piyush R.; Choudhary, R. N. P.

2013-12-01

404

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

NASA Astrophysics Data System (ADS)

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.

Kumar, Amit; Yadav, K. L.

2011-11-01

405

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

NASA Astrophysics Data System (ADS)

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.

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.

406

Evolving Density and Static Mechanical Properties in Plutonium from Self-Irradiation  

SciTech Connect

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.

Chung, B W; Thompson, S R; Lema, K E; Hiromoto, D S; Ebbinghaus, B B

2008-07-31

407

Conductive property of metal nano-particle\\/polymer composite dielectrics  

Microsoft Academic Search

In this essay the DC resistivity and high field conductive properties of nano metal\\/polymer composite are studied. It shows that if adding little small-sized Ag particles, the resistivity of composite increased obviously in comparison with pure epoxy resin, and the increasing of resistivity is related to the size and content of Ag particles, and the performance of polymer. High field

Xu Man; Feng Jun-qiang; Cao Xiao-long

2008-01-01

408

First-principles study of structural, electronic, dynamical, and dielectric properties of zirconium silicates  

Microsoft Academic Search

We investigate structural, electronic, dynamical, and dielectric properties of zirconium silicates (ZrSi_xO_y) within density-functional theory. As a first step, we consider crystalline ZrSiO_4, which presents all the principal bonding features occuring in ZrSi_xO_y. For this crystal, the atomic structure is fully relaxed and the structural parameters are found to differ by less than 1.5% from the experimental data. The associated

Gian-Marco Rignanese; Xavier Gonze; Alfredo Pasquarello

2001-01-01

409

Dielectric and spectral properties of DMAAS ferroelectric crystals doped with chromium  

Microsoft Academic Search

This paper presents the results of investigations of the dielectric and spectral properties of NH2(CH3)2Al(SO4)2 6 H2O crystals doped with chromium. In particular, it is shown that the dopant noticeably changes the temperature of ferroelectric phase transition and corresponding thermal dipole relaxation with a critical slowing-down at Tc1. The Cr3+ ions were used as a convenient probe for investigations

V. Kapustianik; Z. Czapla; R. Tchukvinskyi; A. Batiuk; Yu. Eliyachevskyy; Yu. Korchak; V. Rudyk

2004-01-01

410

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

411

Adhesive and Mechanical Properties of NanoParticle Filled Thermoplastic Polyimide Dielectric Films for Microelectronics Packaging  

Microsoft Academic Search

In this study the mechanical and adhesive properties of aluminum nitride (AlN) nano powder filled polyimide composite films (AlN-PI) are investigated to determine their usefulness as dielectric materials in microelectronic packaging. AlN nano powder was mixed in low wt% during synthesis at poly(amic acid) (PAA) stage. AlN-PI films were characterized using DMTA and tensile testing to determine viscoelastic behavior and

M. B. Saeed; M. S. Zhan

2006-01-01

412

Dielectric and transport properties of carbon nanotube-CdS nanostructures embedded in polyvinyl alcohol matrix  

Microsoft Academic Search

Multiwalled carbon nanotube-CdS\\/polyvinyl alcohol (MWCNT-CdS\\/PVA) composites have been grown by a simple chemical process on one-dimensional templates. The plane-view transmission electron micrographs clearly indicate the formation of nanocrystalline CdS on the nanotube surfaces. The superior dielectric behavior of the MWCNT-CdS nanostructures over MWCNT and PVA host matrices has been demonstrated. The dc and ac transport properties of CdS carbon nanotube-insulating

S. P. Mondal; R. Aluguri; S. K. Ray

2009-01-01

413

Dielectric properties of vanadium doped barium titanate synthesized via high-energy ball milling  

NASA Astrophysics Data System (ADS)

The study shows the advisability of using a mechanochemical synthesis method, based on a high-energy planetary ball milling, to a modification of barium titanate by a vanadium doping. This method improves useful properties of BaTi0:95V0:05O3 as a capacitor material. It has a high value of electric permittivity ?' in the wide range of temperature and low dielectric losses ?? as well as a low electrical conductivity.

Dulian, Piotr; B?k, Wojciech; Wieczorek-Ciurowa, Krystyna; Kajtoch, Czes?aw

2014-04-01

414

Comparison of the effects of nanofiller materials on the dielectric properties of epoxy nanocomposites  

Microsoft Academic Search

Composites of organic polymers and well-dispersed nm-sized inorganic fillers, called polymer nanocomposites (NCs), have been attracting much attention as new electrical insulating materials. In this paper, experimental results on the typical dielectric properties, namely, complex permittivity (?r? and ?r?), conductivity, and thermally stimulated depolarization current (TSDC) are evaluated for bisphenol-A epoxy resin and its NCs with boehmite alumina, titania, and

J. Katayama; N. Fuse; M. Kozako; T. Tanaka; Y. Ohki

2011-01-01

415

Superiority of dielectric properties of LDPE\\/MgO nanocomposites over microcomposites  

Microsoft Academic Search

Dielectric properties were compared between two kinds of low-density polyethylene (LDPE) composites prepared by adding near spherical MgO fillers with different diameters of around several ten nm and several \\\\~{A}'\\\\^{A}m. In the whole range of temperature from 0\\\\~{A}'\\\\^{A}C to 90\\\\~{A}'\\\\^{A}C, the conductivity is decreased and the permittivity is increased by the addition of fillers, irrespective of their sizes. However, the

Kazuyuki Ishimoto; Etsu Kanegae; Yoshimichi Ohki; Toshikatsu Tanaka; Yoitsu Sekiguchi; Yoshinao Murata; C. C. Reddy

2009-01-01

416

Investigation on the dielectric properties of nano-titanium dioxide low density polyethylene composites  

Microsoft Academic Search

Dielectric properties of nano-titanium dioxide (TiO2) with diameter about 25 nm - low density polyethylene (LDPE) composites were investigated at the temperature ranging from 293 K to 343 K with the frequency ranging from 0.1 Hz to 100 kHz in the present paper. Experimentally, we observed two peaks in the spectrums; one appears in both pure and incorporated LDPE (abbreviated

Li Shengtao; Yin Guilai; Ni Fengyan; Bai Suna; Li Jianying; Zhang Tuo

2010-01-01

417

Cryogenic Dielectric and Mechanical Properties of Nanowire-A1203 Filled PBT\\/GF Composites  

Microsoft Academic Search

The cryogenic dielectric and mechanical properties of nanowire-Al 2O3 filled PBT\\/GF (glass fiber) composites are investigated by combing macro-performances testing and microstructures analysis. Compared with PBT\\/GF composites, the PBT\\/GF\\/Al2O 3 ternary systems present improved tensile strength as well as impact strength. The fracture surface shows a typical toughened characteristic under SEM observation, which may be explained by the \\

Demei Yu; Yunchuan Xie; Weitao Wan; Xiusheng Guo; Yingxin Xi; Zhantong Mao; Longbiao Huang

2006-01-01

418

A density functional study on dielectric properties of acrylic acid grafted polypropylene  

Microsoft Academic Search

Influence of acrylic acid grafting of isotactic polypropylene on the dielectric properties of the polymer is investigated using density functional theory (DFT) calculations, both in the molecular modeling and three-dimensional (3D) bulk periodic system frameworks. In our molecular modeling calculations, polarizability volume, and polarizability volume per mass which reflects the permittivity of the polymer, as well as the HOMO-LUMO gap,

Henna Ruuska; Eero Arola; Tommi Kortelainen; Tapio T. Rantala; Kari Kannus; Seppo Valkealahti

2011-01-01

419

Free-space measurement of dielectric properties of moist granular materials at microwave frequencies  

Microsoft Academic Search

A-I: Calibration of dielectric-based sensors for reliable online moniforing and confrol of physical properties of moist granular materials requires accurate permittivity measuremenf. For this purpose, a free-space Iransmission fechnique, in which the main sources of errors were minimized, was used lo defermine the dielecfric properfies of three major commodities wheat, shelled corn and soybeans. Data collected at room temperature for

Samir Trabelsi; S. O. Nelson

2003-01-01

420

Preparation of barium titanate nanoparticle sphere arrays and their dielectric properties  

Microsoft Academic Search

Barium titanate (BaTiO3) nanoparticles from 27 to 192 nm were prepared by the 2-step thermal decomposition method from barium titanyl oxalate nanoparticles. These particles were dispersed well into 1-propanol, and dense BaTiO3 nanoparticle sphere arrays without stress-field were prepared by the meniscus method. Temperature dependence of dielectric properties was successfully measured using these dense nanoparticle sphere arrays, and size effect

Satoshi Wada; Aki Yazawa; Takuya Hoshina; Yoshikazu Kameshima; Hirofumi Kakemoto; Takaaki Tsurumi; Yoshihiro Kuroiwa

2008-01-01

421

Mechanical and dielectric properties of Ni\\/Al2O3 composites  

Microsoft Academic Search

Ni\\/Al2O3 composites were prepared by hot pressing approach. The relationship between their microstructure, mechanical, dielectric and magnetic properties with Ni particle content was studied. By increasing the amount of metal in the composite, the relative density and the bending strength decrease gradually. The possible reason is that non-wetting between Ni and alumina in the preparation results in weak adhesion of

LUO Fa; XUE Hui; ZHU Dong-mei; ZHOU Wan-cheng

422

Strukturnye perestrojki i degradatsiya svojstv diehlektricheskikh materialov pod oblucheniem. (Structure rearrangement and degradation of properties in dielectric materials under irradiation).  

National Technical Information Service (NTIS)

Results of optical, electrical and structural investigation of BN and Al(sub 2)O(sub 3) materials which allow one to determine the peculiarities of radiation induced degradation (RID) concerning electrical and optical properties of dielectric materials wi...

O. A. Plaksin V. A. Stepanov P. A. Stepanov L. M. Kryukova A. M. Polyakov

1994-01-01

423

Influence of post deposition annealing on crystallinity and dielectric properties of bismuth magnesium niobate thin films  

NASA Astrophysics Data System (ADS)

The Bi1.5MgNb1.5O7 (BMN) thin films were prepared on Pt-coated sapphire substrates by rf magnetron sputter deposition. The as-deposited amorphous films were thermally treated for crystallization and formation of cubic pyrochlore structure. The effects of annealing treatment on microstructures and dielectric properties of BMN thin films have been investigated. X-ray diffraction detected cubic pyrochlore phases in the films annealed at 650 C and above. The grain size and surface roughness of the films increased with annealing temperature. The as-deposited films and the films annealed up to 600 C showed a low value of dielectric permittivity and high value of loss tangent. An abrupt increase in dielectric permittivity and a decrease in loss tangent appeared at 650 C. The thin films annealed above 650 C showed bias voltage dependence of the dielectric permittivity, and the tunability increased with annealing temperature. However, the leakage current density also increased at high annealing temperatures.

Gao, Libin; Jiang, Shuwen; Li, Ruguan; Li, Bin; Li, Yanrong

2013-11-01

424

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

PubMed

The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA. PMID:24747847

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

2014-08-14

425

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

NASA Astrophysics Data System (ADS)

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.

Suherman, Phe Man; Smith, Geoff

2003-02-01

426

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

427

Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic.  

PubMed

Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba2CoGe2O7, where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field (H), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field Hc=37.1?T due to enhanced AF quantum fluctuations. When H>Hc, the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter. PMID:25072808

Kim, Jae Wook; Khim, Seunghyun; Chun, Sae Hwan; Jo, Y; Balicas, L; Yi, H T; Cheong, S-W; Harrison, N; Batista, C D; Hoon Han, Jung; Hoon Kim, Kee

2014-01-01

428

Fabrication and Dielectric Properties of AlN Filled Epoxy Nano-composites  

NASA Astrophysics Data System (ADS)

Epoxy resins were materials with excellent mechanical, electrical properties and good chemical stability. Thus, they had been used in various fields, especially in electrical and electronic application. However, because they were brittle material, the fields of application were limited. Adding nano-Aluminum Nitride (AlN) into Epoxy resins could improve the toughness of the composites, the thermal behaviors of composites could also be improved, but the influence on dielectric properties was not very clear. In this research, epoxy resin based composites were fabricated. The relationships between the dielectric properties and the nano-AlN particle content were investigated. The results showed that, both relative permittivity (epsilonr) and dielectric loss tangent (tan?) decreased to be less than that of monolithic epoxy when nano-AlN particle content was no more than certain amount, the DC volume resistivity (?v) and low frequency resistivity decreased with increasing nano-AlN content (in certain range of content). AC breakdown strength (EB) did not have an obvious tendency with nano-AlN content.

Gao, Nai-kui; Yu, Xin; Jin, Hai-yun; He, Bo; Dong, Pu; Gao, Chao

2011-10-01

429

Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth  

PubMed Central

Water is a major component of fluids in the Earths 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 waterrock interactions and, in general, our understanding of aqueous fluids below the Earths crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earths upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)insoluble in water under ambient conditionsbecomes 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 Earths deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones.

Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A.; Galli, Giulia

2013-01-01

430

Dielectric-loaded plasmonic nanoantenna arrays: A metamaterial with tuneable optical properties  

NASA Astrophysics Data System (ADS)

The optical properties of metallic nanorod arrays acting as plasmonic nanoantennas have been studied. Large area arrays consisting of bare Au nanorods of diameter and length tuneable in the range of 20-40 and 200-400nm , respectively, and spacing of about 40-100nm have been electrochemically fabricated using templates of anodized nanoporous aluminium oxide. We demonstrate a very strong sensitivity of their resonant optical properties to both the presence of a dielectric load (which is much smaller than the wavelength of the resonant electromagnetic radiation) and modification of the refractive index of this load. This allows us to finely tune the spectral position of the plasmonic resonance of the nanoantenna arrays throughout the visible spectral range from about 550to800nm with a sensitivity better than 3 per 1nm thickness of the dielectric load. Such dielectric-loaded plasmonic nanoantenna arrays represent a type of anisotropic metallodielectric metamaterials with fully adjustable optical properties for imaging, sensing, and nonlinear optical applications.

Dickson, W.; Wurtz, G. A.; Evans, P.; O'Connor, D.; Atkinson, R.; Pollard, R.; Zayats, A. V.

2007-09-01

431

Dielectric and optical properties of nanometric nickel silicides from valence electrons energy-loss spectroscopy experiments.  

PubMed

Valence and Core Electron Energy Loss Spectroscopy (VEELS and CEELS) experiments are performed from nanocrystallized nickel silicide thin films. Three different silicide compounds are identified in the films. Their chemical compositions are determined from Ni-L(2,3) to Si-K core edges quantification. The results obtained are coherent within less than 2% error with the pure Ni2Si, NiSi and NiSi2 phases. The analysis of the shape and energy position of Ni-L(2,3) near edge structures and volume plasmon peaks indicates that both are reliable signatures to identify unambiguously each compound. Nickel silicides low-loss spectra have been submitted as references to the EELS database (www.cemes.fr~eelsdb). Low-loss spectra are processed to extract single scattering spectra and determine the dielectric function. The results show that nickel silicides dielectric functions deduced from VEELS are in quite good agreement with epsilon1 and epsilon2 deduced from ellipsometry experiments. The optical properties (refractive index (n), absorption coefficient (k), reflectivity (R%) and resistivity (rho(opt))), calculated from VEELS dielectric function are then compared in details with the data resulting from others techniques available in the literature. We show that, except some minor divergences, the nickel silicides optical properties are generally well reproduced. This indicates that VEELS is a relevant technique for accessing reliably to physical properties and can be a successful alternative to conventional techniques when high spatial resolution is needed. PMID:16564176

Cheynet, M C; Pantel, R

2006-01-01

432

Microwave dielectric properties of LTCC materials consisting of glassBa 2Ti 9O 20 composites  

Microsoft Academic Search

Interaction between Ba2Ti9O20 microwave dielectric ceramics and BaBSiO glass materials was systematically investigated. BaTi(BO3)2 intermediate phase was induced and its proportion increased with firing temperature. Fortunately, the formed BaTi(BO3)2 phase does not result in marked degradation on the microwave dielectric properties of the Ba2Ti9O20BaBSiO composite materials. Good microwave dielectric properties (K=13.2, QF=1150) were obtained by firing the Ba2Ti9O20BaBSiO (50:50 vol.%)

Weiter Huang; Kuo-Shung Liu; Li-Wen Chu; Ging-Ho Hsiue; I-Nan Lin

2003-01-01

433

Densification and dielectric properties of SrOAl 2 O 3 B 2 O 3 ceramic bodies  

Microsoft Academic Search

.The influence of SrO (0050 wt%) on partial substitution of alpha alumina (corundum) in ceramic composition (95 Al2O35B2O3) have been studied by co-precipitated process and their phase composition, microstructure, microchemistry and microwave dielectric\\u000a properties were studied. Phase composition was revealed by XRD, while microstructure and microchemistry were investigated\\u000a by electron-probe microanalysis (EPMA). The dielectric properties by means of dielectric constant

DOAA A ABDEL AZIZ; SHAMA E AHMED

434

Dielectric properties of SrTiO3 and BST thin films fabricated using ECR-PEMOCVD  

Microsoft Academic Search

The SrTiO3 Thin films were deposited on Pt\\/SiO2\\/Si by ECR-PEMOCVD and their dielectric properties were investigated as a function of composition. The chemical bonding states of elements consisting these films were investigated using X-ray photoelectron spectroscopy (XPS) and Discrete Variational (DV)X? simulation. The asymmetry of composition dependence on dielectric properties was explained by the XPS data. Further, effectiveness of NH3

Joon Sung Lee; Key Soo Kim; Eunah Kim; Kwangsoo No

1998-01-01

435

The Effects of the pH-influenced Structure on the Dielectric Properties of KaoliniteWater Mixtures  

Microsoft Academic Search

The properties of clay-water mixtures are refl ected in their wide-frequency dielectric responses that result from different polarization mechanisms. This feature is useful in various soil science applications but has not been systematically investigated. The objective of this study was to characterize the broadband dielectric spectrum of kaolinite sediments with different charge properties and structures using a slim-form open-ended coaxial

Xiaobo Dong; Yu-Hsing Wang

2008-01-01

436

Moisture content and bulk density dependence of dielectric properties of safflower seed in the radio frequency range  

Microsoft Academic Search

The dielectric properties of safflower seeds were measured over a frequency range of 50kHz to 10MHz at moisture content in a range of 5.3316.48% dry basis (d.b.) with bulk density which changed between 553.6 and 638.8kg\\/m3 using parallel-plate capacitor sample holder. Effects of the parameters such as moisture content, bulk density and frequency on the dielectric properties were studied. The

Kamil Sacilik; Celik Tarimci; Ahmet Colak

2007-01-01

437

Properties of high-dielectric constant complex materials based on transition and rare-earth metal oxides  

Microsoft Academic Search

It was found in elemental transition or rare earth metal (TM\\/RE) oxides that the electrical and material properties are much poor than those of the conventional gate dielectric materials such as silicon oxide or oxynitride. It was also found that the electrical and material properties of the high-dielectric constant (high-k) films can be improved or compromised by using complex structures

Hei Wong

2008-01-01

438

A Investigation of the Dielectric and Hysteresis Properties of Plzt Ferroelectric and Multilayer Composite Thin Films.  

NASA Astrophysics Data System (ADS)

The dielectric and hysteresis properties of ferroelectric and multilayer composite thin films were investigated. PLZT ferroelectrics were produced in bulk ceramic and thin film form from the same acetate precursor solutions in order to compare their electrical and physical properties. Bulk ceramics were hot pressed from chemically coprecipitated powders, and thin films were fabricated by spin and dip coating on Ag and Pt-coated Si substrates. Internal film stress from thermal expansion mismatch between films and substrates was found to contribute to differences in electrical properties and Curie temperatures between the thin film and bulk materials as were interface layer effects, grain size and mechanical clamping from the substrates. Rapid thermal processing (RTP) of PLZT thin films using an automated spin coat reactor was found to improve thin film dielectric and hysteresis properties as well as enhance perovskite phase formation, induce preferred (110) and (111) orientations, decrease grain size and increase microstructural uniformity. RTP films were compared with manually spin coated thin films with conventional furnace pyrolysis (CFP) in order to isolate the effects of heating rate from deposition technique. Heating rates of at least 70^circC per second were obtained by RTP versus 35^circC per second for CFP. The development of composite thin films further optimized PLZT thin film properties. Improved antiferroelectric -to-ferroelectric domain switching with decreased ferroelectric coercive field, increased induced polarization with decreased coercivity and polarization remanence for relaxor-type composites and increased hysteresis loop squareness for ferroelectric memory materials were among the advances compared with films of homogeneous PLZT composition. Experimental dielectric and hysteresis properties were described by a series capacitor model consisting of the linear and nonlinear properties of the individual composite components.

Dausch, David Edward

1995-01-01

439

Relation between static and dynamic rock properties in welded and nonwelded tuff  

SciTech Connect

An integral part of the licensing procedure for the potential nuclear waste repository at Yucca Mountain, Nevada involves accurate prediction of the in situ rheology for design and construction of the facility and emplacement of the canisters containing radioactive waste. The data required as input to successful thermal and mechanical models of the behavior of the repository and surrounding lithologies include bulk density, grain density, porosity, compressional and shear wave velocities, elastic moduli, and compressional and tensile strengths. In this study a suite of experiments was performed on cores recovered from the USW-NRG-6 borehole drilled to support the Exploratory Studies Facility (ESF) at Yucca Mountain. USW-NRG-6 was drilled to a depth of 1100 feet through four thermal/mechanical units of Paintbrush tuff. A large data set has been collected on specimens recovered from borehole USW-NRG-6. Analysis of the results of these experiments showed that there is a correlation between fracture strength, Young`s modulus, compressional wave velocity and porosity. Additional scaling laws relating; static Young`s modulus and compressional wave velocity; and fracture strength and compressional wave velocity are promising. Since there are no other distinct differences in material properties, the scatter that is present at each fixed porosity suggests that the differences in the observed property can be related to the pore structure of the specimen. Image analysis of CT scans performed on each test specimen are currently underway to seek additional empirical relations to aid in refining the correlations between static and dynamic properties of tuff.

Price, R.H. [Sandia National Labs., Albuquerque, NM (United States); Boyd, P.J.; Noel, J.S.; Martin, R.J. III [New England Research, Inc., White River Junction, VT (United States)

1994-07-01

440

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

SciTech Connect

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

Li, X.T. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Du, P.Y., E-mail: dupy@zju.edu.c [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zhao, Y.L.; Tu, Y.; Dai, J.L.; Weng, W.J.; Han, G.R.; Song, C.L. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

2010-11-15

441

Simulated Hail Ice Mechanical Properties and Failure Mechanism at Quasi-Static Strain Rates  

NASA Astrophysics Data System (ADS)

Hail is a significant threat to aircraft both on the ground and in the air. Aeronautical engineers are interested in better understanding the properties of hail to improve the safety of new aircraft. However, the failure mechanism and mechanical properties of hail, as opposed to clear ice, are not well understood. A literature review identifies basic mechanical properties of ice and a failure mechanism based upon the state of stress within an ice sphere is proposed. To better understand the properties of Simulated Hail Ice (SHI), several tests were conducted using both clear and cotton fiber reinforced ice. Pictures were taken to show the internal crystal structure of SHI. SHI crush tests were conducted to identify the overall force-displacement trends at various quasi-static strain rates. High speed photography was also used to visually track the failure mechanism of spherical SHI. Compression tests were done to measure the compression strength of SHI and results were compared to literature data. Fracture toughness tests were conducted to identify the crack resistance of SHI. Results from testing clear ice samples were successfully compared to previously published literature data to instill confidence in the testing methods. The methods were subsequently used to test and characterize the cotton fiber reinforced ice.

Swift, Jonathan M.

442

Dielectric and electrooptic properties of PMN-PT single crystals and thin films  

NASA Astrophysics Data System (ADS)

Dielectric and electro-optical properties of ferroelectric lead magnesium niobate-lead titanate Pb(Mg1/3Nb2/3)O3-PbTiO 3 (or PMN-PT) single crystals and thin films were investigated to assess their potential for optical waveguide applications. Waveguide properties and optical loss of PMN-PT thin films on MgO substrates were examined at a wavelength of 1550 nm. Highly epitaxial PMN-PT thin films were deposited on MgO substrates using pulsed laser deposition. With the structural characterization of the films studied by X-ray diffraction, optimized deposition conditions to obtain high quality thin films in terms of substrate temperature, oxygen pressure, and film thickness were obtained. The surface roughnesses of the PMN-PT thin films relating to the microstructural contributions to optical loss by scattering were examined with atomic force microscopy. Refractive indices, thickness, anisotropy and in-depth index profile of the PMN-PT thin films on MgO substrates were analyzed using the prism coupling method. Dielectric properties of the PMN-PT films with co-planar electrodes were investigated as a function of frequency. Dielectric tunability of the film was determined as a function of frequency. Electro-optical properties of PMN-PT single crystals and thin films on MgO substrate were determined. Thermo-optical properties of the film with and without corona poling were investigated. PMN-PT ridge waveguide devices were fabricated using a process of photolithography. Geometries for the waveguide in single mode propagation at a wavelength of 1550 nm were optimized with effective index method. By using an end-firing method, the waveguide properties of the films were characterized and the propagation loss was determined to be 3.01 dB/cm which lies within the acceptable attenuation range (<5dB/cm) suitable for optical guided wave applications.

Cheng, Kei Chun

443

Electrical properties of dielectric foil for embedded PCB capacitors  

NASA Astrophysics Data System (ADS)

One of the methods of achieving high packaging density of passive elements on the PCB is using the capacitors embedded in multilayer PCB. Test structures consisting of embedded capacitors were fabricated using the FaradFlex capacitive internal layers. Impedance spectroscopy and equivalent circuit modelling was used to determine their electrical properties such as the capacitance, parasitic resistance and inductance. The use of several stages of accelerated ageing allowed us to test the durability of the structures. The results showed good quality stability of the embedded elements. The spatial distribution of the capacitance of the test structures on the surface of the PCB form was tested. The influence of the process parameters during lamination on the values of embedded capacitors was revealed.

Piasecki, T.; Nitsch, K.; Dziedzic, A.; Chabowski, K.; St?plewski, W.; Kozio?, G.

2012-12-01

444

Dielectric Properties of BaTiO3Modified BiFeO3 Ceramics  

Microsoft Academic Search

Multiferroic BiFeO3 has attracted extensive interest due to its potential in several applications. However, pure-phase BiFeO3 is very difficult to obtain. Hence, mixing BiFeO3 with other ferroelectrics, such as BaTiO3, is another approach to obtain materials with possible multiferroic properties. In this study, the BiFeO3 was modified with addition of BaTiO3 via a simple solid state reaction method. Dielectric properties

Sujittra Chandarak; Athipong Ngamjarurojana; Suthum Srilomsak; Pitak Laoratanakul; Saroj Rujirawat; Rattikorn Yimnirun

2010-01-01

445

Approximation of the dielectric properties of Maxwellian plasmas - Dispersion functions and physical constraints  

NASA Technical Reports Server (NTRS)

The dielectric properties of Maxwellian plasmas are approximated using high Pade approximants to the dispersion function and direct approximation of the distribution. Physical constraints on permissible approximations are discussed, and it is found that some previously published results can lead to predictions of qualitatively incorrect wave properties, including unphysical negative damping. Approximate dispersion functions for Maxwellian distributions are given explicitly, and some of the effects of these approximations on the resulting dispersion are discussed. The approximations discussed here are of use both in analytical work and in accelerating large-scale numerical computations.

Robinson, P. A.; Newman, D. L.

1988-01-01

446

Microwave dielectric properties and sintering behaviors of scheelite compound CaMoO 4  

Microsoft Academic Search

The microwave dielectric properties, sintering behaviors of scheelite compound CaMoO4 were investigated using dilatometry, X-ray diffraction, scanning electron microscopy and network analyzer. To improve the sintering property of CaMoO4, samples with different Ca\\/Mo ratio were prepared. The bulk densities of CaMo(x)O4 (for x=1.02, 1.05, 1.08) samples were higher than those of pure CaMoO4 over all temperature range. The well-sintered CaMo(x)O4

Geun-Kyu Choi; Seo-Yong Cho; Jae-Sul An; Kug Sun Hong

2006-01-01

447

Influence of reverted austenite on static and dynamic mechanical properties of a PH 13-8 Mo maraging steel  

Microsoft Academic Search

Maraging steels are martensitic hardenable steels exhibiting an excellent combination of high strength and adequate toughness. Beside the intermetallic precipitates, reverted austenite, formed during aging, is a decisive microstructural constituent. Static tensile tests showed a pronounced influence of its phase fraction on mechanical properties. Reverted austenite also exhibits a distinctive effect on dynamic properties which were investigated on a split-Hopkinson-pressure-bar.

Ronald Schnitzer; Gerald A. Zickler; Erhardt Lach; Helmut Clemens; Silvia Zinner; Thomas Lippmann; Harald Leitner

2010-01-01

448

Acceptor dependent structural, microstructural and dielectric properties of PbTiO3 nano-particles  

NASA Astrophysics Data System (ADS)

Substituted lead titanate PbTi1-xNixO3 nano-particles (1 and 4 mol% Ni content) were synthesized by simple metallo-organic decomposition (MOD) method annealed at 700 C for 3 h. Such type of doping will generally generate oxygen vacancies in the ceramic material and have application in microwave and solar cell devices. Structural properties were studied from XRD pattern and it confirms the formation of single tetragonal phase. Increased tetragonal distortion in crystal structure with the doping of Ni ions is depicted from XRD pattern and was the consequence of ionic radii mismatching between substituting atoms. Calculated average crystallite size values were 28 nm and 37 nm for PNT1 and PNT4 respectively. This pattern was supported by TEM images having a particle size 33 nm and 42 nm for PNT1 and PNT4 respectively. Absence of organic functional groups and formation of M-O bonds was illustrated from FTIR spectrum. Frequency dependent dielectric properties were studied in the range?0.075-10 MHz at 300 K. Its results revealed the improvement in dispersion less behavior up to high frequency range?6 MHz. The slight increase in dielectric loss value (tan ??0.0011) for PNT4 attributed to occurrence of oxygen vacancies in ceramic material due to Ni doping. The temperature dependent dielectric response was measured maximum at 100 KHz. Values of DC resistivity (?) for PNT1 and PNT4 were measured 258.5 and 181.6 ?-cm109 respectively.

Katna, A. K.; Kotnala, R. K.; Negi, N. S.

2013-09-01

449

Effect of Vanadium Substitution on the Dielectric Properties of Glass Ceramic Bi-2212 Superconductor  

NASA Astrophysics Data System (ADS)

Glass ceramic superconductors were prepared by the melt-quenching method. The frequency and temperature dependence of dielectric constant ( ?'), dielectric loss ( ??) and loss tangent (tan ?) of these superconductors were investigated in the frequency range of 10 kHz-10 MHz and temperature range of 80-300 K using the capacitance-voltage (C-V) and conductance-voltage (G/w-V) measurements. Effect of vanadium on bulk properties, dc electrical resistivity ( ?) and ac electrical conductivity ( ? ac) of these superconductors were also investigated. The experimental results showed that ?', ?? and ? ac were strongly temperature and frequency dependent. Negative capacitance (NC) phenomenon has been observed and it is believed that the negative capacitance effect is due to polarization effect. The results can be concluded to imply that the interfacial polarization can occur more easily at low frequencies consequently contributing to the deviation of the dielectric properties and ac electrical conductivity of Bi2Sr2Ca1Cu2O ? and Bi1.9V0.1Sr2Ca1Cu2O ? superconductors.

avdar, ?.; Koralay, H.; Alt?ndal, ?.

2011-07-01

450

Dielectric and Piezoelectric Properties of PZT Composite Thick Films with Variable Solution to Powder Ratios  

PubMed Central

The use of PZT films in sliver-mode high-frequency ultrasonic transducers applications requires thick, dense, and crack-free films with excellent piezoelectric and dielectric properties. In this work, PZT composite solutions were used to deposit PZT films >10 ?m in thickness. It was found that the functional properties depend strongly on the mass ratio of PZT solgel solution to PZT powder in the composite solution. Both the remanent polarization, Pr, and transverse piezoelectric coefficient, e31,f, increase with increasing proportion of the solgel solution in the precursor. Films prepared using a solution-to-powder mass ratio of 0.5 have a remanent polarization of 8 ?C/cm2, a dielectric constant of 450 (at 1 kHz), and e31,f = ?2.8 C/m2. Increasing the solution-to-powder mass ratio to 6, the films were found to have remanent polarizations as large as 37 ?C/cm2, a dielectric constant of 1250 (at 1 kHz) and e31,f = ?5.8 C/m2.

Wu, Dawei; Zhou, Qifa; Shung, Koping Kirk.; Bharadwaja, Srowthi N.; Zhang, Dongshe; Zheng, Haixing

2010-01-01

451

Dielectric and Piezoelectric Properties of PZT Composite Thick Films with Variable Solution to Powder Ratios.  

PubMed

The use of PZT films in sliver-mode high-frequency ultrasonic transducers applications requires thick, dense, and crack-free films with excellent piezoelectric and dielectric properties. In this work, PZT composite solutions were used to deposit PZT films >10 ?m in thickness. It was found that the functional properties depend strongly on the mass ratio of PZT sol-gel solution to PZT powder in the composite solution. Both the remanent polarization, P(r), and transverse piezoelectric coefficient, e(31,) (f), increase with increasing proportion of the sol-gel solution in the precursor. Films prepared using a solution-to-powder mass ratio of 0.5 have a remanent polarization of 8 ?C/cm(2), a dielectric constant of 450 (at 1 kHz), and e(31,) (f) = -2.8 C/m(2). Increasing the solution-to-powder mass ratio to 6, the films were found to have remanent polarizations as large as 37 ?C/cm(2), a dielectric constant of 1250 (at 1 kHz) and e(31,) (f) = -5.8 C/m(2). PMID:20376196

Wu, Dawei; Zhou, Qifa; Shung, Koping Kirk; Bharadwaja, Srowthi N; Zhang, Dongshe; Zheng, Haixing

2009-05-01

452

Influence of the dielectric property on microwave oven heating patterns: application to food materials.  

PubMed

Patterns of power absorption in a microwave oven for a range of dielectric properties of relevance to food processing were investigated. The governing Maxwell's equations with boundary conditions and a TE10 excitation were solved using a finite element method. Food properties were varied from values at their frozen state to values at high temperatures, as would be typical in a thawing process. For low-loss materials such as frozen foods, the high quality factor makes the heating significantly higher only when the size and shape of the load permit a dielectric cavity resonance in the load. Otherwise, the heating pattern will follow the modal electric field pattern of the oven. For moderate loss materials, the patterns will come from the modes of the dielectric cavity. The bandwidths of these modes are larger than the low-loss situation and their overlap results in a heating pattern that is somewhat more uniform. For high-loss materials, the concept of modes is no longer useful as the very large number of modes strongly overlap. The rapidly decaying field and power loss in the high-loss material can probably be characterized as an exponential decay. PMID:9177015

Peyre, F; Datta, A; Seyler, C

1997-01-01

453

Millimeter-Wave Dielectric Properties of Cordierite/Indialite Glass Ceramics  

NASA Astrophysics Data System (ADS)

Millimeter-wave wireless communications with high data transfer and radar system for Pre-Crash Safety System have been developed recently. Cordierite (Mg2Al4Si5O18) is one of the silicates with good millimeter-wave dielectric properties. Cordierite has two polymorphs: cordierite and indialite. Cordierite is of low symmetry form with ordered structure, and indialite is of high symmetry form with disordered structure. In this study, indialite/cordierite glass ceramics are fabricated with good millimeter-wave properties. The \\mathit{Qf} values are dependent on the amount of indialite phase and crystallization conditions. Indialite with high symmetry showed higher \\mathit{Qf} values than cordierite with low symmetry. This result clearly shows that high symmetry results in high \\mathit{Qf} when the samples are prepared under the same crystallization conditions. However, these glass ceramics are very difficult to make under the same conditions because of non-uniform crystallization. These dielectric glass ceramics show high \\mathit{Qf} values of >200{,}000 GHz, low dielectric constant \\varepsilonr = 4.7, and \\mathit{TCf}= -27 ppm/C.

Ohsato, Hitoshi; Kim, Jeong-Seog; Kim, A-Young; Cheon, Chae-Il; Chae, Ki-Woong

2011-09-01

454

Hydration properties of adenosine phosphate series as studied by microwave dielectric spectroscopy.  

PubMed

Hydration properties of adenine nucleotides and orthophosphate (Pi) in aqueous solutions adjusted to pH=8 with NaOH were studied by high-resolution microwave dielectric relaxation (DR) spectroscopy at 20 C. The dielectric spectra were analyzed using a mixture theory combined with a least-squares Debye decomposition method. Solutions of Pi and adenine nucleotides showed qualitatively similar dielectric properties described by two Debye components. One component was characterized by a relaxation frequency (f(c)=18.8-19.7 GHz) significantly higher than that of bulk water (17 GHz) and the other by a much lower f(c) (6.4-7.6 GHz), which are referred to here as hyper-mobile water and constrained water, respectively. By contrast, a hydration shell of only the latter type was found for adenosine (f(c)~6.7 GHz). The present results indicate that phosphoryl groups are mostly responsible for affecting the structure of the water surrounding the adenine nucleotides by forming one constrained water layer and an additional three or four layers of hyper-mobile water. PMID:21167630

Mogami, George; Wazawa, Tetsuichi; Morimoto, Nobuyuki; Kodama, Takao; Suzuki, Makoto

2011-02-01

455

Collective modes and dielectric and superconducting properties of electronic systems in confined geometries  

SciTech Connect

The dielectric response function of electronic systems in restricted geometries is studied as well as some of the consequences, using the self-consistent field method. These consequences include: 1) existence of multiple branches of longitudinal slender acoustic plasma oscillations (SAP) in thin wires; 2) a new superconductivity mechanism in thin wires via the exchange of SAPs by the electrons forming the Cooper pairs, and 3) reduction of the static screening offered by the valence electrons in a thin semiconductor film with respect to the bulk case. The SAP modes are collective modes shown to exist only in thin wires and neither in a bulk system nor in a thin film. They have linear dispersion relations with phase velocities smaller than the Fermi velocity of the system and are not Landau-damped. Numerical examples of these SAP modes in metallic and semiconductor wires are presented, showing that they sould be more easily observable in semiconductor structures. The SAP-induced mechanism of superconductivity is shown to possibly give higher critical temperature T/sub c/ than the phonon mechanism in thin wires. The author presents a semi-rigorous calculation of T/sub c/ and shows that by increasing the frequency of the SAP modes and having a small effective electron mass one would be able to increase T/sub c/. He also shows that the dielectric function of a thin semiconductor slab is wavenumber dependent even at long wavelengths and is not a constant as in the bulk case.

Ulloa, S.E.

1984-01-01

456

Effect of silica aerosil dispersions on the dielectric properties of a nematic liquid crystal.  

PubMed

The static and dynamic aspects of (4-n-heptyl-4'-cyanobiphenyl) (7CB) perturbed by the dispersion of 70-A-diameter hydrophilic silica aerosil spheres have been investigated using dielectric spectroscopy. Results on five mixtures of 7CB plus silica aerosil are presented in order to probe systematically the disorder introduced by the silica aerosil network on the 7CB molecules. Measurements on homeotropically aligned samples have been made from 75 kHz to 30 MHz in the temperature range 30-60 degrees C. It was found for the mixtures that the nematic-isotropic transition temperature is lower than that of the bulk 7CB. Bulklike relaxation processes due to the rotation of the molecules around the short axis have been analyzed, and were found to follow Arrhenius-type behavior in the nematic phase except in the vicinity of the nematic-isotropic transition temperature. These processes are slightly faster in the mixture than in the free phase. A dielectric process in the low frequency range, absent in the bulk, has been observed in samples with higher silica concentration. All the observed relaxation processes in the mixtures are of non-Debye type. PMID:11414916

Hourri, A; Bose, T K; Thoen, J

2001-05-01

457

Observation of modified radiative properties of cold atoms in vacuum near a dielectric surface  

NASA Astrophysics Data System (ADS)

We have observed a distance-dependent absorption linewidth of cold 87Rb atoms close to a dielectric-vacuum interface. This is the first observation of modified radiative properties in vacuum near a dielectric surface. A cloud of cold atoms was created using a magneto-optical trap (MOT) and optical molasses cooling. Evanescent waves (EW) were used to observe the behaviour of the atoms near the surface. We observed an increase of the absorption linewidth by up to 25% with respect to the free-space value. Approximately half the broadening can be explained by cavity quantum electrodynamics (CQED) as an increase of the natural linewidth and inhomogeneous broadening. The remainder we attribute to local Stark shifts near the surface. By varying the characteristic EW length we have observed a distance dependence characteristic for CQED.

Ivanov, V. V.; Cornelussen, R. A.; van Linden van den Heuvell, H. B.; Spreeuw, R. J. C.

2004-11-01

458

Effect of Ni doping on ferroelectric and dielectric properties of strontium barium niobate crystals  

NASA Astrophysics Data System (ADS)

The influence of Ni doping on the ferroelectric and dielectric properties have been examined in Sr0.61Ba0.39Nb2O6 (SBN:61) relaxor crystals. The dopants introduced into SBN:61 crystals promote the switching process by reducing the value of threshold nucleation field, and thus coercive field. We present real-time studies of domain nucleation and growth processes in doped SBN:61 by the nematic liquid crystal (NLC) decoration technique. The broad phase transition and low-frequency dielectric dispersion that are exhibited by doped SBN:61 samples have a strong link to the configuration of the ferroelectrics microdomains, which in turn is strongly determined by Ni ions concentration.

Matyjasek, K.; Wolska, K.; Kaczmarek, S. M.; Subocz, J.; Ivleva, L.

2012-01-01

459

Nonlinear dielectric properties and temperature stabilization effect near the ferroelectric phase transition in sodium trihydrogen selenite.  

PubMed

The ferroelectric phase transition of crystalline sodium trihydrogen selenite has been characterized by domain observations and measurements of electric permittivity, pyroeffect and spontaneous polarization. The first-order character of the phase transition is clearly demonstrated by the phase coexistence and temperature autostabilization. The considerable heating effect at 50Hz ac field is described. The electric field effect on the temperature variation of the electric permittivity, in the phase transition region, shows a considerable domain structure contribution to the permittivity value. It is demonstrated that the dielectric properties of x-and y-samples can be described by classical dielectric state equations: the set of coefficients has been determined. It is concluded that the x-component of spontaneous polarization plays a predominant role in the phase transition. PMID:21690753

Stankiewicz, A; Cach, R; Dacko, S

2006-04-26

460

Vanadium oxide nanotubes VOx-NTs: Hydrothermal synthesis, characterization, electrical study and dielectric properties  

NASA Astrophysics Data System (ADS)

Vanadium oxide nanotubes (VOx-NTs) have been synthesized via one-step hydrothermal treatment. The compounds were analyzed through X-ray powder diffraction; scanning electron microscope, UV-Visible spectroscopy, X-ray photoelectron spectroscopy (XPS) and complex impedance spectroscopy. The electrical and dielectric properties dependence on temperature (302-523 K) and on frequency (5 Hz to 13 MHz) of VOx-NTs have been reported. The complex impedance plots exhibits the presence of grain and grain boundaries. Dielectric data were analyzed using complex permittivity and complex electrical modulus for the sample at various temperatures. The presence of non-Debye type of relaxation has been confirmed by the complex modulus analysis. AC conductivity exhibits two conduction mechanisms: at high temperature, a translational motion with a sudden hopping and at low temperature, a localized hopping with a small hopping or reorientational motion. DC conductivity indicated, negative temperature coefficient of resistance (NTCR) type behavior.

Nefzi, H.; Sediri, F.

2013-05-01