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1

Simulation studies of ionic liquids: Orientational correlations and static dielectric properties  

NASA Astrophysics Data System (ADS)

The ionic liquids BMIM+I-, BMIM+BF4-, and BMIM+PF6- were simulated by means of the molecular dynamics method over a time period of more than 100ns. Besides the common structural analysis, e.g., radial distribution functions and three dimensional occupancy plots, a more sophisticated orientational analysis was performed. The angular correlation functions g00110(r) and g00101(r) are the first distance dependent coefficients of the pairwise orientational distribution function g(rij,?1,?2,?12). These functions help to interpret the three dimensional plot and reveal interesting insights into the local structure of the analyzed ionic liquids. Furthermore, the collective network of ionic liquids can be characterized by the Kirkwood factor G?(r ) [J. Chem. Phys. 7, 911 (1939)]. The short-range behavior (r<10Å) of this factor may be suitable to predict the water miscibility of the ionic liquid. The long-range limit of Gk? is below 1 which demonstrates the strongly coupled nature of the ionic liquid networks. In addition, this factor relates the orientational structure and the dielectric properties of the ionic liquids. The static dielectric constant ?(? =0) for the simulated system is 8.9-9.5. Since in ionic liquids the very same molecule contributes to the total dipole moment as well as carries a net charge, a small, but significant contribution of the cross term between the total dipole moment and the electric current to ?(? =0) is observed.

Schröder, C.; Rudas, T.; Steinhauser, O.

2006-12-01

2

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

PubMed

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

Schröder, C; Rudas, T; Steinhauser, O

2006-12-28

3

Dielectric properties of liquid ethanol. A computer simulation study Leonor Saiz  

E-print Network

Dielectric properties of liquid ethanol. A computer simulation study Leonor Saiz Departament de Fi Static and dynamic dielectric properties of liquid ethanol have been studied as a function of the wave have been calculated. The infrared spectra and the dielectric relaxation of the liquid have been also

Saiz, Leonor

4

Dielectric properties of agricultural products and applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

5

Applications for Dielectric Properties of Agricultural Products  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

6

Dielectric properties of PMT-PT crystals  

NASA Astrophysics Data System (ADS)

Results of broadband dielectric investigations of 0.94PbMg1/3Ta2/3O3-0.06PbTiO3 (0.94PMT-0.06PT or PMT-PT) crystals in wide temperature range from 100 K to 950 K are presented. Below 300 K the dielectric properties of crystals are governed by polar nanoregions dynamics. However, at higher temperatures (above 600 K) the electrical conductivity effects also become important. The electrical conductivity occurs presumably due the hopping of oxygen vacancies and demonstrates change in the activation energy close to 750 K. The change in the activation energy can be explained by increase of concentration of single ionized vacancies. No anomaly in the temperature dependence of the static dielectric permittivity was observed in wide temperature range from 213 K to 950 K and the dependence was successfully described by spherical random bonds random fields theory. Moreover, two different contributions were successfully separated in the distributions of relaxation times in PMT-PT crystals. These contributions were attributed to different polar nanoregions dynamics. Moreover, the different freezing temperatures values were obtained for most probable and longest relaxation times, which was explained with an idea of continuous distribution of relaxation times broadening on cooling in relaxors. The critical remarks about the Vogel-Fulcher law application for relaxors are addressed in the paper.

Palaimiene, E.; Macutkevic, J.; Banys, J.; Kania, A.

2014-09-01

7

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

8

Dielectric properties of conductive ionomers  

NASA Astrophysics Data System (ADS)

Ion and polymer dynamics of ion-containing polymers were investigated, with the majority of results obtained from application of a physical model of electrode polarization (EP) to dielectric spectroscopy data. The physical model of MacDonald, further developed by Coelho, was extended for application to tan delta (the ratio of dielectric loss to dielectric constant) as a function of frequency. The validity of this approach was confirmed by plotting the characteristic EP time as a function of thickness and comparing the actual and predicted unrelaxed dielectric constant for a poly(ethylene oxide) (PEO)-based ionomer neutralized by lithium, sodium, and cesium. Results were obtained for ion mobility and mobile ion concentration for a neat PEO-based ionomer, two (methoxyethoxy-ethoxy phosphazene) (MEEP) -based ionomers, two MEEP-based salt-doped polymers, sulfonated polystyrene (SPS) neutralized by sodium with a high sulfonation fraction, and SPS neutralized by zinc with a low sulfonation fraction. Additionally, the conductivity parameters of six plasticized forms of a neat PEO-based ionomer were characterized, but the method apparently failed to correctly evaluate bulk ionic behavior. In all cases except the SPS ionomers ion mobility follows a Vogel-Fulcher-Tammann (VFT) temperature dependence. In all cases, mobile ion concentration follows an Arrhenius temperature dependence. Fitting parameters from these two relationships yielded direct information about the state of ionic diffusion and ion pairing in each system. Combination of these two functionalities predicts a relationship for conductivity that is significantly different than the VFT relation typically used in the literature to fit conductivity. The most outstanding result was the extremely small fraction of ions found to be mobile. For ionomers it can be concluded that the primary reason for low conductivities arises from the low fraction of mobile ions. The local and segmental dynamics of the neat and plasticized PEO-based ionomer were also studied in comparison to conductivity, with the conclusion that the glass transition temperature (a manifestation of the segmental segments) is the primary property governing conduction behavior in single-phase ionomers. Consideration of the solvent quality parameters yielded a similar result, that the plasticization effect on the glass transition is far stronger than the dielectric constant, donor number, or viscosity of the solvents.

Klein, Robert James

9

Microwave Dielectric Properties of Cereal Grains  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

10

Techniques for Measuring the Dielectric Properties of Agricultural Products  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

11

Microwave dielectric properties of cereal grains  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

12

Pyroelectric and dielectric properties of ceramics  

Microsoft Academic Search

Ferroelectric oxide ceramics have been investigated as possible alternatives to highly sensitive triglycine sulfate (TGS) crystals for their use in room temperature infrared detectors. In this paper dielectric and pyroelectric properties of some ceramics based on modified lead titanate and others are presented. The figures-of-merit of these ceramics calculated using the measured dielectric and pyroelectric data are presented. The relative

A. K. Batra; Ryan Moxon; Padmaja Guggilla; M. D. Aggarwal; M. E. Edwards

2010-01-01

13

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

14

Tailoring dielectric properties of ferroelectric-dielectric multilayers  

SciTech Connect

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

Kesim, M. T.; Zhang, J. [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Cole, M. W. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005 (United States); Misirlioglu, I. B. [Faculty of Engineering and Natural Sciences, Sabanc? University, Orhanl?/Tuzla, 34956 Istanbul (Turkey); Alpay, S. P., E-mail: p.alpay@ims.uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

2014-01-13

15

Dielectric nanocomposites with insulating properties  

Microsoft Academic Search

Polymer nanocomposites possess promising high performances as engineering materials, if they are prepared and fabricated properly. Some work has been recently done on such polymer nanocomposites as dielectrics and electrical insulation. This was reviewed in 2004 based on the literatures published up to 2003. New significant findings have been added since then. Furthermore, a multi-core model with the far-distance effect,

Toshikatsu Tanaka

2005-01-01

16

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.

Grâsjö, Johan; Welch, Ken; Strømme, Maria

2008-09-01

17

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

18

Dielectric surface properties of Venus  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

19

Dielectric Properties of Agricultural Products and Some Applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

20

Frequency-wavelength calculator with table of dielectric properties  

NASA Technical Reports Server (NTRS)

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

Thompson, L. L.

1972-01-01

21

Transverse dielectric properties of boron nitride nanotubes by ab initio electric field calculations  

NASA Astrophysics Data System (ADS)

Extensive ab initio finite electric-field calculations are performed to study the static transverse dielectric properties of boron nitride nanotubes via the sawtooth potential approach. It is shown that the transverse polarizability is proportional to the tube radius rather than to the square of it, and that the screening factor is not a constant but decreases monotonically with increasing tube radius. A classical cylindrical dielectric shell model, with a dielectric constant of 5.90 and an effective shell thickness of 2.50 Å, is shown to reproduce very well the ab initio results for both single- and multiwalled boron nitride nanotubes.

Lan, Hai-Ping; Ye, Lin-Hui; Zhang, Shuang; Peng, Lian-Mao

2009-05-01

22

Dielectric properties of Ag/PAN nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

23

Dielectric Properties of Biodegradable Polymers  

Microsoft Academic Search

In order to respond to soaring public concern about environmental protection, various biodegradable polymers have been developed. The present paper reports the electrical conduction and breakdown properties of various biodegradable polymers such as poly-L-lactic acid (PLLA), polyethylene terephthalate succinate (PETS), polycaprolactone butylene succinate (PCL-BS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyhydroxybutyrate\\/valerate (PHB\\/V) in comparison to those of low-density

Y. Ohki; N. Hirai

2006-01-01

24

Fundamentals of dielectric properties measurements and agricultural applications.  

PubMed

Dielectrics and dielectric properties are defined generally and dielectric measurement methods and equipment are described for various frequency ranges from audio frequencies through microwave frequencies. These include impedance and admittance bridges, resonant frequency, transmission-line, and free-space methods in the frequency domain and time-domain and broadband techniques. Many references are cited describing methods in detail and giving sources of dielectric properties data. Finally a few applications for such data are presented and sources of tabulated and dielectric properties data bases are identified. PMID:21721322

Nelson, Stuart O

2010-01-01

25

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

26

The dielectric properties of polymer-water systems  

E-print Network

THE DIELECTRIC PROPERTIES OF POLYMER- WATER SYSTEMS A Thesis by JOE BILL LEWIS Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1976 Major... Subject: Chemistry THE DIELECTRIC PROPERTIES OF POLYMER- WATER SYSTEMS A Thesis by JOE SILL LEWIS Approved as to style and content by: C z Cnairman, o Comni ttee Head of Department 1 I Member Member December 1976 ABSTRACT The Dielectric...

Lewis, Joe Bill

2012-06-07

27

Basics of Measuring the Dielectric Properties of Materials  

E-print Network

Agilent Basics of Measuring the Dielectric Properties of Materials Application Note #12;Contents 2 the dielectric properties of materials. Agilent measure- ment instruments, such as network analyzers, LCR meters......................................................................................32 #12;Introduction Every material has a unique set of electrical characteristics that are dependent

Anlage, Steven

28

Dielectric properties of polyamide-imide  

NASA Astrophysics Data System (ADS)

The dielectric properties of poly(amide imide) (PAI) films are investigated in a large temperature range. A moisture-dependent relaxation (?-relaxation between -100 °C and 20 °C) and a non-cooperative local dipole relaxation (?-relaxation between 40 °C and 200 °C) display an Arrhenius-type behaviour with an activation energy of 0.50 eV and 1.22 eV, respectively. In the near glass transition (Tg) region at 277 °C, a relaxation process (?-relaxation) occurs due to cooperative segmental motions of the chains and follows a non-linear Vogel-Fulcher-Tamman (VFT) temperature dependence with a strong fragility. Simultaneously in the same temperature range, both a conduction process (?-conduction) and an electrode polarization phenomenon (?-relaxation) are also present. The ?-conduction also follows a VFT behaviour but it possesses a lower fragility in the above-Tg region. This discrepancy is assigned to a partial decoupling between ionic transport and segmental chain motions. The dielectric strength of PAI films exhibits a negative temperature dependence. The near-Tg region corresponds to a change from a thermal breakdown mechanism to an electromechanical breakdown due to the glass-liquid phase transition. Above Tg, the formation of a space-charge probably also involves an electro-thermal breakdown mechanism.

Diaham, S.; Locatelli, M.-L.

2013-05-01

29

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

30

High-? gate dielectrics: Current status and materials properties considerations  

Microsoft Academic Search

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 ?m complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film

G. D. Wilk; R. M. Wallace; J. M. Anthony

2001-01-01

31

Dielectric Properties of Onion-Like Carbon Composites  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

32

KTN Dielectric Properties at Microwave Frequencies: Substrate Influence  

Microsoft Academic Search

To determine the dielectric properties of ferroelectric thin-films over a wide range of frequencies we developed a simple and efficient method based on the measurement of coplanar waveguide realized on ferroelectric\\/dielectric heterostructures by using a Spectral Domain Approach. We applied this method to KTa1?xNbxO3 (KTN) thin-films deposited on different substrates. The strong differences observed in the dielectric behavior of KTNs

Vincent Laur; Gérard TannÉ; Paul Laurent; Anthony Rousseau; ValÉrie Bouquet; Maryline Guilloux-Viry; Fabrice Huret

2007-01-01

33

Dielectric properties and structure particularity of silver stearate  

NASA Astrophysics Data System (ADS)

Dielectric properties, parameters and structure particularity of silver stearate are studied. The silver stearate sample in monolithic formation was researched by method of dielectric spectroscopy. Measurements were realized by spectrometer Novocontrol Technologies "Concept 41" in wide range of frequencies and temperatures. Dielectric parameters of silver stearate were measured and calculated. ?-relaxation process in temperature band 80 – 130°C and first phase transition at 126°C. are found.

Goryaev, M. A.; Castro, R. A.; Smirnov, A. P.

2014-12-01

34

Dielectric properties of lead-magnesium niobate ceramics  

Microsoft Academic Search

Dielectric properties are reported for lead magnesium niobate (PbMg ââ Nb ââ Oâ) ceramics which were prepared as single phase (i.e., without pyrochlore) with an improved technique. Dielectric constants of 18,000 for pure PMN and 31,000 for PMN with 10% PbTiOâ were achieved; these values are 50% larger than those reported in the literature. The dielectric constant of PMN ceramics

S. L. Swartz; T. R. SHROUT; W. A. SCHULZE; L. E. CROSS

1984-01-01

35

Models for the Microwave Dielectric Properties of Grain and Seed  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

36

Tunable dielectric properties of transition metal dichalcogenides.  

PubMed

Since discovery of graphene, layered materials have drawn considerable attention because of their possible exfoliation into single and multilayer 2D sheets. Because of strong surface effects, the properties of these materials vary drastically with the number of layers in a sheet. We have performed first-principles density functional based calculations to evaluate the electron energy loss spectrum (EELS) of bulk, monolayer, and bilayer configurations of several transition metal dichalcogenides, which include semiconducting as well as metallic compounds. Our investigation shows that the peaks in the EELS spectra move toward larger wavelengths (red shift) with the decrease in number of layers. The ? plasmon peak shifts slightly by 0.5-1.0 eV, while a significant shift of around 5.5-13.0 eV is obtained for ? + ? plasmon, when exfoliated from bulk to single-layer. This underscores the importance of the interlayer coupling on the loss spectra and the dielectric properties. Our results are found to be in very good agreement with the recent measurements performed by Coleman et al. (Science2011, 331, 568). PMID:21707067

Johari, Priya; Shenoy, Vivek B

2011-07-26

37

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

38

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

39

On thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals  

NASA Astrophysics Data System (ADS)

Thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals are studied using the pseudo-spin model for proton subsystem within a two-particle cluster approximation neglecting the proton tunneling on hydrogen bonds. Temperature dependence of spontaneous polarization, heat capacity, static dielectric permittivity and dielectric dispersion in wide frequency range is calculated for both compounds in two structural phases. At a proper set of model parameters, a good quantitative description of the corresponding experimental data is obtained.

Zachek, I. R.; Shchur, Ya.; Levitskii, R. R.; Bilenka, O. B.

2014-11-01

40

Dielectric properties of porcine glands, gonads and body fluids.  

PubMed

Dielectric properties of porcine glandular tissues and gonads (in vivo) and body fluids (in vitro) have been obtained in the frequency range of 50 MHz to 20 GHz. The experimental data were fitted to a two term Cole-Cole expression. The data presented complement the available dielectric properties of tissues in the literature and can be used in numerical simulations of the exposure of people to electromagnetic fields. PMID:22982710

Peyman, A; Gabriel, C

2012-10-01

41

Dielectric properties of porcine glands, gonads and body fluids  

NASA Astrophysics Data System (ADS)

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

Peyman, A.; Gabriel, C.

2012-10-01

42

Optical Transmission Properties of Dielectric Aperture Arrays  

NASA Astrophysics Data System (ADS)

Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index units (RIU) and a dynamic range as large as 0.17 RIU. Subsequently, optical transmission properties through a self-mixing interferometer array are studied and a novel high-resolution cost-effective optical spectrometer is proposed. The miniature interferometer-based spectrometer is made of polymethyl methacrylate (PMMA) with a CCD as the detector. The detected intensity of each CCD pixels contains the spectral information. Since each frequency component in the incoming beam corresponds to a unique phase difference of the two beam portions of each optical interferometer, the total intensity received by each CCD pixel, which is resulted from the addition of the interference signals from all the frequency components in the beam, should also be unique. Therefore, the spectrum calculation is a problem to solve an ill-posed linear system by using Tikhonov regularization method. Simulation results show that the resolution can reach picometer level. Apart from the choice of path difference between the interfering beams, the spectral resolution also depends on the signal-to-noise ratio and analogue-digital conversion resolution (dynamic range) of the CCD chip. In addition, the theory of uniform waveguide scattering is explored to expand the possibility of using such mini-interferometers for performing free-space spectral analysis of waveguide devices. At the same time, the method of least squares is used to correct the pixel non-uniformity of the CCD so as to improve the performance of the spectrometer. The sensor chip and spectrometer chip introduced here are based on the interference of light transmitted through dielectric aperture arrays. Their compact feature renders these devices ideal for miniaturization and integration as the systems in microfluidics architectures and lab-on-chip designs.

Yang, Tao

43

Dielectric properties and microstructures for various MLCCs coated with additives  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

44

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

45

Microwave Dielectric Properties of a New Series of Phosphates  

NASA Astrophysics Data System (ADS)

The dielectric ceramics in the system Ca2+xLa8-x(SiO4)6-x(PO4)xO2 (x = 0, 2, 4 and 6) were investigated as promising materials for microwave applications. The ceramics were prepared by the conventional solid state ceramic route. The relative permittivity of ceramics was in the range 11.7-14.4 and all the compositions showed low dielectric loss (tan ? < 10-3) at 1 MHz. The composition with x = 2 showed good microwave dielectric properties of ?r = 13.8, Quxf = 27900GHz and ?f = -11 ppm/ °C.

Thomas, Dhanesh; Sebastian, M. T.

2011-11-01

46

Recent progress on dielectric properties of protic ionic liquids.  

PubMed

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

Wojnarowska, Zaneta; Paluch, Marian

2015-02-25

47

Dielectric properties of human fetal organ tissues at radio frequencies.  

PubMed

The in vitro dielectric properties of human fetal organ tissues were measured in the frequency range from 100 kHz to 500 MHz at 24 degrees C. The dielectric measurements were performed by using a network analyzer (HP4195A) and a coaxial line capacitive sensor. The tested samples, including skin, muscle, heart, lung, liver, kidney, spleen, and brain tissues, were obtained from the legal abortion of five women with 14-16 weeks gestation periods. PMID:8915552

Lu, Y; Cui, H; Yu, J; Mashimo, S

1996-01-01

48

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 25°C. 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

49

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

50

Interfacial effects on dielectric properties of polymer-particle nanocomposites  

NASA Astrophysics Data System (ADS)

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

Siddabattuni, Sasidhar Veeranjaneyulu

51

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

52

Modeling of dielectric properties of complex fluids with an equation of state.  

PubMed

The static permittivity is a key property for describing solutions containing polar and hydrogen bonding compounds. However, the precise relationship between the molecular and dielectric properties is not well-established. Here we show that the relative permittivity at zero frequency (static permittivity) can be modeled simultaneously with thermodynamic properties. The static permittivity is calculated from an extension of the framework developed by Onsager, Kirkwood, and Fröhlich to associating mixtures. The thermodynamic properties are calculated from the cubic-plus-association (CPA) equation of state that includes the Wertheim association model as formulated in the statistical associating fluid theory (SAFT) to account for hydrogen bonding molecules. We show that, by using a simple description of the geometry of the association, we may calculate the Kirkwood g-factor as a function of the probability of hydrogen bond formation. The results show that it is possible to predict the static permittivity of complex mixtures over wide temperature and pressure ranges from simple extensions of well-established theories simultaneously with the calculation of thermodynamic properties. PMID:23458349

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

2013-03-28

53

Dielectric properties of grain-grainboundary binary system  

NASA Astrophysics Data System (ADS)

Dielectric properties of grain-grainboundary binary system are analyzed theoretically and compared with unary system and classical Maxwell-Wagner (MW) polarization in binary system. It is found that MW polarization appears at higher frequency compared with intrinsic polarization for grain-grainboundary binary system, which is abnormal compared with classical dielectric theory. This dielectric anomaly is premised on the existence of electronic relaxation at grainboundary. The origin of giant dielectric constant of CaCu3Ti4O12 (CCTO) ceramics is also investigated on the basis of the theoretical results. It is proposed that low frequency relaxation originates from electronic relaxation of oxygen vacancy at depletion layer, while high frequency relaxation comes from MW polarization. The results of this paper offer a quantitative identification of MW polarization from intrinsic polarization at grainboundary and a judgment of the mechanism and location of a certain polarization in grain-grainboundary binary system.

Cheng, Peng-Fei; Li, Sheng-Tao; Wang, Hui

2014-09-01

54

Dielectric and Piezoelectric Properties of Barium Titanate  

Microsoft Academic Search

The dielectric constant and loss of barium titanate and barium-strontium titanate have been measured at biasing field strengths from 0 to 5 megavolts per meter, at temperatures from -50°C to +135°C and at frequencies from 0.1 to 25 megacycles. The measurements versus temperature indicate the expected agreement with the Curie-Weiss law at temperatures above the Curie point. Measurements versus field

Shepard Roberts

1947-01-01

55

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

56

Pyroelectric and dielectric properties of calcium barium niobate single crystals  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

57

High-? gate dielectrics: Current status and materials properties considerations  

NASA Astrophysics Data System (ADS)

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 ?m complementary metal-oxide-semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward successful integration into the expected processing conditions for future CMOS technologies, especially due to their tendency to form at interfaces with Si (e.g. silicates). These pseudobinary systems also thereby enable the use of other high-? materials by serving as an interfacial high-? layer. While work is ongoing, much research is still required, as it is clear that any material which is to replace SiO2 as the gate dielectric faces a formidable challenge. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation.

Wilk, G. D.; Wallace, R. M.; Anthony, J. M.

2001-05-01

58

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

SciTech Connect

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

Y?ld?z, Dilber Esra [Department of Physics, Faculty of Arts and Sciences, Hitit University, Çorum 19030 (Turkey); Y?ld?r?m, Mert; Gökçen, Muharrem [Department of Physics, Faculty of Arts and Sciences, Düzce University, Düzce 81620 (Turkey)

2014-05-15

59

Monitoring Coaxial-Probe Contact Force for Dielectric Properties Measurement  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

60

Studies on the dielectric properties of CdS nanoparticles  

NASA Astrophysics Data System (ADS)

CdS is one of the most important II-VI semiconductors with applications in solar cells, optoelectronics and electronic devices. CdS nanoparticles were synthesized by the wet chemical method. The crystal structure and grain size of the particles were determined by X-ray diffraction. The optical properties were studied by the ultraviolet-visible absorption spectrum. The dielectric properties of CdS nanoparticles were studied in the frequency range of 50 Hz-5 MHz at different temperatures. The frequency dependence of the dielectric constant and dielectric loss is found to decrease with an increase in the frequency at different temperatures. The dielectric properties of CdS nanoparticles are found to be significantly enhanced specially in the low frequency range due to confinement. Further, electronic properties, such as valence electron plasma energy, average energy gap or Penn gap, Fermi energy and electronic polarizability of the CdS nanoparticles were calculated. The AC electrical conductivity measurements reveal that the conduction depends on both the frequency and the temperatures.

Suresh, Sagadevan

2014-03-01

61

Ferroelectric and dielectric properties of strontium bismuth niobate vanadates  

E-print Network

Ferroelectric and dielectric properties of strontium bismuth niobate vanadates Yun Wu and Guozhong 19 November 1999; accepted 20 April 2000) Strontium bismuth niobate vanadates, SrBi2(VxNb1-x)2O9 qualitatively different nondestructive read op- erations.3 Recently, bismuth oxide layered perovskite materials

Cao, Guozhong

62

Dielectric properties of Ba2YMoO6 ceramics  

NASA Astrophysics Data System (ADS)

Double-perovskite Ba2YMoO6 ceramics were prepared via the solid-state reaction route. Their dielectric properties were investigated as a function of temperature (100 °C?T?800 °C) and frequency (300 Hz?f?5 MHz). In the temperature below 600 °C, two thermally activated dielectric relaxations can be well identified. The low-temperature relaxation was ascribed to be a dipolar relaxation caused by oxygen vacancy diffusion, and the high-temperature relaxation is found to be a Maxwell-Wagner relaxation due to surface-layer effect.

Li, Qiuju; Ren, Jun; Cui, Jiangyu; Yu, Yi; Zhang, Jian; Wang, Chunchang

2014-10-01

63

Measurement of the Dielectric Properties of Sawdust Between 0.5 and 15 GHz  

Microsoft Academic Search

The aim of this paper was to measure the broadband dielectric properties of sawdust. Knowledge of dielectric proper- ties is important in improving understanding of a material and can lead to the development of methods for determining physical properties such as moisture and salt content. The broadband di- electric properties of sawdust were measured with an open-ended coaxial-line dielectric probe.

Ana M. Paz; Samir Trabelsi; Stuart O. Nelson; Eva Thorin

2011-01-01

64

Effects of Parallel and Perpendicular Compressive Stresses on the Dielectric and Ferroelectric Properties of Soft PZT Ceramics  

Microsoft Academic Search

Effects of compressive stress on the dielectric and ferroelectric properties of commercial soft PZT ceramics were investigated. The dielectric and ferroelectric properties were measured under compressive stress applied parallel and perpendicular to an electric field direction. The results showed that the dielectric properties; i.e. the dielectric constant (?r) and dielectric loss tangent (tan ?), and the ferroelectric characteristics; i.e. the

Muangjai Unruan; Supon Ananta; Yongyut Laosiritaworn; Athipong Ngamjarurojana; Ruyan Guo; Amar Bhalla; Rattikorn Yimnirun

2010-01-01

65

Liquid crystals Correlation between static and dynamic polarimetric properties and  

E-print Network

-Stabilized Ferroelectric Liquid Crystal cells Snapshot Mueller matrix polarimetry was performed for static and dynamic resolution is often poor. A snapshot Mueller matrix polarimeter [5] was recently developed by our team polarimeters. Moreover, the Mueller matrix gives access independently to each polarimetric property

Boyer, Edmond

66

Electrical conductivity and dielectric property of fly ash geopolymer pastes  

NASA Astrophysics Data System (ADS)

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

Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

2011-02-01

67

Dielectric properties of human glioma and surrounding tissue.  

PubMed

Dielectric properties of human glioma and surrounding tissue from five patients were measured. Experiments were performed at frequencies of 5-500 MHz at 24 +/- 0.5 degrees C using a Network Analyser and a coaxial line capacitive sensor. The permittivity and conductivity of tumours were 30% higher than that of the surrounding tissues due to their higher water content. The characteristic of less differentiation in tumours clearly was reflected in the dielectric properties, namely a smaller parameter for the relaxation time distribution of the tumour's dielectric relaxation. With the dielectric data, the power absorption ratios of tumour to surrounding tissue were calculated for four representative electromagnetic (EM) irradiation cases. The calculation shows that power absorption ratios are strongly dependent on the incident direction of the EM wave and optimum frequency. To improve therapeutic efficiency, it is appropriate to have the electric field vector (E) parallel to the interface of tumour/surrounding tissue at optimum frequencies around 100 MHz, and the case of E perpendicular to the interface must be avoided in applications of EM hyperthermia for brain tumours. PMID:1479201

Lu, Y; Li, B; Xu, J; Yu, J

1992-01-01

68

Dielectric and structural properties of ferroelectric betaine arsenate films  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

69

Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.  

PubMed

Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes. PMID:17995773

Sakiyan, Ozge; Sumnu, Gulum; Sahin, Serpil; Meda, Venkatesh

2007-05-01

70

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

71

Terahertz Dielectric Properties and Low-Frequency Phonon Resonances of ZnO Nanostructures  

E-print Network

Terahertz Dielectric Properties and Low-Frequency Phonon Resonances of ZnO Nanostructures Jiaguang-infrared optical and dielectric properties of nanostructured ZnO of different morphologies are characterized with dielectric theories combined with effective medium models. Different ZnO nanostructure morphologies exhibit

72

Thermal and dielectric properties of sweetpotato puree  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

73

Symmetry properties of anisotropic dielectric gratings  

Microsoft Academic Search

This paper describes a theoretical analysis of liquid crystal grating structures and their properties based on the symmetry of the constitutive equations. Exact equations derived by using Bloch-Floquet theorem for one-dimensional anisotropic gratings are discussed. Scattering efficiency of the gratings is analyzed using the method of coupled plane waves having well defined parallel components of the wave vector to decompose

P. Galatola; C. Oldano; P. B. Sunilkumar

1994-01-01

74

Electrical properties of double layer dielectric structures for space technology  

Microsoft Academic Search

Polymeric films such as polyimide (PI) and polyethylene terephthalate (PET) are used in space technology as thermal blankets. Thin SiO2 and SiN coatings plasma deposited onto PI and PET surfaces were proposed to protect the blanket materials against the space environment. The electrical properties of this kind of dual layer dielectric structure were investigated to understand the mechanisms for suppressing

Anqing Lian

1993-01-01

75

Electrical conductivity and dielectric property of fly ash geopolymer pastes  

Microsoft Academic Search

The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were\\u000a studied. The effects of the liquid alkali solution to ash ratios (L\\/A) were analyzed. The mineralogical compositions and microstructures\\u000a of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM).\\u000a The 10 mol sodium

Sakonwan Hanjitsuwan; Prinya Chindaprasirt; Kedsarin Pimraksa

2011-01-01

76

Analysis of bread dielectric properties using mixture equations  

Microsoft Academic Search

Breads are prone to rapid microbial spoilage, particularly mold growth. In order to develop in-package pasteurization treatments based on radio frequency or microwave energy, a combined open-ended coaxial probe and mixture equation method was used to obtain bread dielectric properties over the frequency range of 1-1800MHz and the temperature range of 25°C–85°C. Influences of frequency, moisture content and temperature on

Yanhong Liu; Juming Tang; Zhihuai Mao

2009-01-01

77

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

78

Quasi-static high-resolution magnetic-field detection based on dielectric optical resonators  

NASA Astrophysics Data System (ADS)

In this paper we present a high resolution magnetic field sensor that is based on the perturbation of the optical modes (whispering gallery mode, WGM) of a spherical dielectric resonator. The optical resonator is side coupled to a tapered single mode optical fiber. One side of the optical fiber is coupled to a distribute feedback diode laser, while the other end is connected to a photodiode. The optical modes of the dielectric cavity are perturbed using a metglas sheet that is in contact with the resonator. When the metglas sheet is exposed to an external magnetic field it elongates perturbing the optical modes of the dielectric cavity. This in turn leads to a shift in the optical resonances. By measuring the induced WGM shift the magnetic field can be measured. Preliminary results show sensor resolution of a few nanoteslas.

Ioppolo, Tindaro; Rubino, Edoardo

2013-06-01

79

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

80

Optical properties of metal-dielectric composites  

NASA Astrophysics Data System (ADS)

In Chapter 1, nonlinear optical properties of silver colloidal aggregates are studied. The real and imaginary parts of the cubic susceptibility of silver colloid aggregates are measured. It is found that the coefficient of nonlinear absorption strongly depends on the laser wavelength and intensity. Optical limiting effect in fractal silver colloids is observed. It is shown experimentally that the enhanced optical nonlinearity of aggregated metal colloids is connected with an enhancement of the local field in resonant domains of large clusters. The enhancement factor of the nonlinear absorption in aggregated silver colloids is about 700 as compared with nonaggregated samples. In Chapter 2, nonlinear optical properties of Au nanoparticles created by ion implantation, are under investigation. Nondegenerate forward four-wave mixing technique is used to measure the third order nonlinear susceptibility for composite materials with Au nanocrystals formed inside a SiO2 glass matrix. The Au nanocrystals are formed by the ion implantation and annealing method that produces very high volume fraction of nanoparticles. Large value of |?(3)| has been measured to be ~1.3 × 10 -7 esu. Two characteristic relaxation times, 5.3 ps and 0.66 ps, are estimated from the detuning curve of |?(3)| and discussed using different models. In Chapter 3, localization of optical excitations and selective photomodification are studied experimentally in fractal aggregates of silver colloidal nanoparticles. The localized optical excitations of the fractal colloids cover a broad spectral range, from the visible to the infrared. We show that the absorbed laser energy is localized in an increasingly smaller number of particles with increasing the laser wavelength from 355 nm to 1900 nm. The size of the photomodified regions can be as small as 20 nm. The observed modification is explained by optically induced sintering (coalescence) of colloidal nanoparticles. In Chapter 4, macroscopic natural optical activity observed in a metal cluster medium is reported. Circular dichroism spectroscopy is performed on a number of different colloidal solutions of silver. Circular dichroism is observed in both monomer and aggregated cluster media. A hypothesis explaining optical activity based on the anomalous crystal structure of the clusters is proposed and discussed.

Lepeshkin, Nickolai Nickolaevich

2001-12-01

81

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

82

Structure and dielectric properties of La{sub x}Hf{sub (1?x)}O{sub y} thin films: The dependence of components  

SciTech Connect

Graphical abstract: - Highlights: • La{sub x}Hf{sub (1?x)}O{sub y} thin films were grown by pulse laser deposition method. • The thin film with 10% La/(La + Hf) atom ratio forms a cubic HfO{sub 2} phase. • The amorphous thin films due to more La introduced have almost same local structure. • The main infrared phonon modes move to lower frequency for the amorphous thin films. • The static dielectric constants of the amorphous thin films increase with La content. - Abstract: La{sub x}Hf{sub (1?x)}O{sub y} (x = 0, 0.1, 0.3, 0.5, 0.7, y=2?(1/2)x) thin films were grown by pulsed laser deposition (PLD) method. The component dependence of the structure and vibration properties of these thin films is studied by combining X-ray diffraction, X-ray absorption fine structure (XAFS) and infrared spectroscopy. The thin film with 10% La/(La + Hf) atom ratio forms a cubic HfO{sub 2} phase and it has the largest static dielectric constant. More La atoms introduced cause amorphous phase formed and the static dielectric constants increase with the La content. Although XAFS indicates that these amorphous thin films have almost same local structures, the infrared phonon modes with most contribution to the static dielectric constant move to lower frequency, which results in the component dependence of the dielectric constant.

Qi, Zeming, E-mail: zmqi@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Cheng, Xuerui [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002 (China); Zhang, Guobin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Li, Tingting [Institute of Microelectronics of Chinese Academy of Science, Beijing 100029 (China); Wang, Yuyin; Shao, Tao; Li, Chengxiang; He, Bo [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China)

2013-07-15

83

Temperature Dependence of the Radio-Frequency Dielectric Properties of Chicken Meat  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of chicken breast meat were measured with an open-ended coaxial-line probe between 200 MHz and 20 GHz at temperature ranging from -20 oC to +25 oC. At a given frequency, the temperature dependence reveals a sharp increase of the dielectric constant and dielectric loss factor a...

84

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. PMID:22078458

2011-01-01

85

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

86

Semi-Automatic System for Testing Dielectric Properties of Low-Voltage Busbar  

Microsoft Academic Search

One semi-automatic system is developed for testing the dielectric properties and grounding resistance of low-voltage busbar, one type of large-capacity electric power transmission equipment. The dielectric properties mainly include the insulation resistance and leakage current of busbar under occasional high voltage. The withstanding voltage and insulation resistance tester is used for testing its dielectric properties, and the earth continuity tester

Yang Xuemei; She Jiangfeng

2010-01-01

87

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

88

Ferroelectric and dielectric properties of electroactive oligomers and nanocomposites  

NASA Astrophysics Data System (ADS)

Polyvinylidene fluoride (PVDF) and its copolymers have been well established as ferroelectric polymers. The dielectric and ferroelectric properties for vinylidene fluoride (VDF) oligomer thin films were investigated. By synthesizing oligomers instead of long polymer chains, films with higher crystalinity can be formed and the locations of oligomers can be controlled for applications such as molecular electronics. Evidence of ferroelectricity was observed in oligomer thin films evaporated onto room temperature substrates and by Langmuir-Blodgett (LB) deposition. Voltage and frequency dependence of the capacitance was measured. Oligomers functionalized with phosphonic acid formed self-assembled monolayers (SAM) on aluminum and mica substrates. Film thickness was measured by ellipsometry and atomic force microscopy (AFM). The time dependence on film growth was measured for SAMs on mica substrates by AFM. The islands had already formed by 1 minute, and by 1 hour film was continuous. Additionally, studies were performed on composite dielectric systems with the goal of fabricating high energy density dielectrics containing nanoparticles with an organic shell. The first two types of samples had barium titante nanoparticles coated with functionalized alkanes or VDF oligomers. The first sample type consisted of coated nanoparticles embedded in a PVDF copolymer or terpolymer spin-coated film. At low particle concentrations, the matrix properties dominated the electrical measurements while at high concentrations, the samples were electrically fragile. The second sample type consisted of alternating layers of LB terpolymer and LB nanoparticles. These samples allowed for high particle concentrations while maintaining the high breakdown strength of the polymer layers. The final type of sample was titanium dioxide nanoparticles formed by cluster deposition and coated with an evaporated paraffin or VDF oligomer. These samples tended to have low breakdown strengths and poor repeatability from sample to sample. The final study was on the effect of humidity in poly(vinylidene fluoride- trifluoroethylene) 70:30. Water vapor could enter the film, reside in the lattice, and affect the dielectric measurements. Based on dielectric measurements, the amount of water in the film at 80% relative humidity was 0.046%. With 50 nm aluminum electrodes, the vapor entered the film quickly, although it took five to six hours to leave at room temperature.

Kraemer, Kristin L.

89

Dielectric and piezoelectric properties of perovskite materials at cryogenic temperatures  

Microsoft Academic Search

Dielectric and piezoelectric properties of perovskite materials including La modified Pb(Zr, Ti)O3 (PZT's), (Ba, Sr)TiO3 (BST) polycrystalline ceramics and Pb(Zn1\\/3 Nb2\\/3)O3-PbTiO3 (PZN-PT) single crystals were investigated for capacitor and actuator applications at cryogenic temperatures. PZTs were compositionally engineered to have decreased Curie temperatures (Tc) by La and Sn doping in order to compensate for the loss of extrinsic contributions to

D.-S. Paik; S.-E. Park; T. R. Shrout; W. Hackenberger

1999-01-01

90

Dielectric properties of Rhodamine-B and metal doped hydrogels  

NASA Astrophysics Data System (ADS)

The electric and dielectric properties of Rhodamine-B (RB) and metal ions (Ag+, Co2+, Cr3+, Mn2+ and Ni2+) doped hydrogels have been analyzed in an extended frequency range by impedance spectroscopy. The RB doped hydrogels has been found to be sensitive to ionic conduction and electrode polarization according to the metal doped hydrogels. We have shown that the ionic conductive of RB doped hydrogels is originated from the free ions motion within the doped hydrogels at high frequency. We have also taken into account the Cl- and N+ ions in the structure of RB provide additional ionic contribution to RB doped hydrogels.

Okutan, M.; Co?kun, R.; Öztürk, M.; Yalç?n, O.

2015-01-01

91

Synthesis and Dielectric Properties of Nanocrystalline BASRTIO3  

NASA Astrophysics Data System (ADS)

Ba0.7Sr0.3TiO3 was prepared via simple sol-gel method by using titanium tetrabutoxide, barium and strontium carbonates, citric acid and ethylene glycol as starting materials. Simultaneous Thermal Analysis (STA) was used to examine thermal behavior of xerogel. The crystallite size of BST was about 21nm calculated by X-Ray diffraction (XRD) and confirmed by transition electron microscopy (TEM). Using these nanocrystalline powders, BST pellets were prepared and sintered in various temperatures. The grain size effect on electrical properties was studied and found that as the grain size decreased, the dielectric constant decreased too.

Golmohammad, M.; Nemati, A.; Faghihi Sani, M. A.

92

Studies on the structural dielectric electrical and thermoelectric properties of some complex perovskite oxides; -.  

E-print Network

??The thesis presents an investigation of dielectric electric and newlinethermoelectric properties of some rare earth substituted barium and strontium newlinebased complex perovskites The synthesis of… (more)

Vimala, R

2014-01-01

93

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

94

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

95

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 1,200°C; the web-like structure was destroyed at a temperature of 1,400°C. Composites of CBC impregnated with paraffin wax exhibited high complex permittivity over a frequency range of 2 to 18 GHz, depending on the carbonization temperature. Both real and imaginary parts were the highest for CBC pyrolyzed at 1,200°C. The complex permittivity also strongly depended on CBC loadings. For 7.5 wt.% loading, the real and imaginary permittivities were about 12 and 4.3, respectively, and the minimum reflection loss was -39 dB at 10.9 GHz. For 30 wt.% loading, the real and imaginary permittivities were about 45 and 80, respectively, and the shielding efficiency was more than 24 dB in the measured frequency range and could be up to 39 dB at 18 GHz. The electromagnetic properties were assumed to correlate with both the dielectric relaxation and the novel web-like structure. PMID:23800353

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

2013-01-01

96

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 1,200°C; the web-like structure was destroyed at a temperature of 1,400°C. Composites of CBC impregnated with paraffin wax exhibited high complex permittivity over a frequency range of 2 to 18 GHz, depending on the carbonization temperature. Both real and imaginary parts were the highest for CBC pyrolyzed at 1,200°C. The complex permittivity also strongly depended on CBC loadings. For 7.5 wt.% loading, the real and imaginary permittivities were about 12 and 4.3, respectively, and the minimum reflection loss was -39 dB at 10.9 GHz. For 30 wt.% loading, the real and imaginary permittivities were about 45 and 80, respectively, and the shielding efficiency was more than 24 dB in the measured frequency range and could be up to 39 dB at 18 GHz. The electromagnetic properties were assumed to correlate with both the dielectric relaxation and the novel web-like structure.

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

2013-06-01

97

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

2014-09-01

98

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 1,200°C; the web-like structure was destroyed at a temperature of 1,400°C. Composites of CBC impregnated with paraffin wax exhibited high complex permittivity over a frequency range of 2 to 18 GHz, depending on the carbonization temperature. Both real and imaginary parts were the highest for CBC pyrolyzed at 1,200°C. The complex permittivity also strongly depended on CBC loadings. For 7.5 wt.% loading, the real and imaginary permittivities were about 12 and 4.3, respectively, and the minimum reflection loss was -39 dB at 10.9 GHz. For 30 wt.% loading, the real and imaginary permittivities were about 45 and 80, respectively, and the shielding efficiency was more than 24 dB in the measured frequency range and could be up to 39 dB at 18 GHz. The electromagnetic properties were assumed to correlate with both the dielectric relaxation and the novel web-like structure. PMID:23800353

2013-01-01

99

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

NASA Astrophysics Data System (ADS)

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 21.7 GPa. 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.

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

2013-12-01

100

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

101

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

102

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

103

Highly Accurate Debye Models for Normal and Malignant Breast Tissue Dielectric Properties at Microwave Frequencies  

Microsoft Academic Search

The finite difference time domain (FDTD) method is widely used as a computational tool for development, validation, and optimization of emerging microwave breast cancer detection and treatment techniques. When expressed in terms of Debye parameters, dispersive breast tissue dielectric properties can be efficiently incorporated into FDTD codes. Previously, we experimentally characterized the dielectric properties of a large number of excised

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

2007-01-01

104

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

105

Electro-optic and dielectric properties of Hafnium-doped congruent lithiumniobate crystals  

E-print Network

1 Electro-optic and dielectric properties of Hafnium-doped congruent lithium­niobate crystals report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We affected by the introduction of hafnium ions and therefore Hf-doped LN has the advantage of low

Boyer, Edmond

106

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 120°C 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

107

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

108

Heterogeneous Anthropomorphic Phantoms with Realistic Dielectric Properties for Microwave Breast Imaging Experiments  

PubMed Central

We present a technique for fabricating realistic breast phantoms for microwave imaging experiments. Using oil-in-gelatin dispersions that mimic breast tissue dielectric properties at microwave frequencies, we constructed four heterogeneous phantoms spanning the full range of volumetric breast densities. We performed CT scans and dielectric properties measurements to characterize each phantom. PMID:21866208

Mashal, Alireza; Gao, Fuqiang; Hagness, Susan C.

2011-01-01

109

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 Å2 level of hydration.

Wander, Matthew C.; Clark, Aurora E.

2008-11-19

110

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

NASA Astrophysics Data System (ADS)

PbO-MgO-Nb2O5-TiO2 (PMNT) pyrochlore thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. Very interestingly, these pyrochlore-structured PMNT thin films exhibited ultralow dielectric losses, with a typical loss tangent as low as 0.001, and relatively high dielectric constants, typically ?r˜170. It was found that the relative permittivity slightly but continuously increased upon cooling without any signature of a structural phase transition, displaying a quantum paraelectriclike behavior; meanwhile, the PMNT pyrochlore thin films did not show any noticeable dielectric dispersion in the real part of permittivity over a wide temperature range (77-400 K). Their dielectric responses could, however, be efficiently tuned by applying a dc electric field. A maximum applied bias field of 1 MV/cm resulted in a ˜20% tunability of the dielectric permittivity, giving rise to a fairly large coefficient of the dielectric nonlinearity, ˜2.5×109 J C-4 m-5. Moreover, the PMNT pyrochlore films exhibited superior electrical insulation properties with a relatively high breakdown field (Ebreakdown˜1.5 MV/cm) and a very low leakage current density of about 8.2×10-7 A/cm2 obtained at an electric field intensity as high as 500 kV/cm.

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

2010-05-01

111

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

112

Virtual crystal approximation revisited: Application to dielectric and piezoelectric properties of perovskites  

E-print Network

properties of perovskites L. Bellaiche Physics Department, University of Arkansas, Fayetteville, Arkansas class of materials, the ferroelectric perovskite solid solutions. Their work strongly suggests to predict the anomalous dielectric and piezoelectric properties of perovskite solid solutions. A second

Vanderbilt, David

113

Effect of various ionizing radiations on polymer properties. Dielectric properties of polytetrafluoroethylene  

SciTech Connect

The authors have studied the effect of the kind of ionizing radiation on the radiation-induced changes in the dielectric properties of polytetrafluoroethylene (PTFE). This kind of radiation substantially affects the slope of the dielectric loss (tan {delta}). The largest difference in tan {delta} occurs between n,{gamma} irradiation, on the one hand, and {sup 60}Co {gamma} irradiation and protons, on the other. There is a smaller difference in tan {gamma} between the {sup 60}Co {gamma} irradiation and protons. This difference is due to the dependence of the concentration of stabilized macroradicals on the kind of ionizing radiation. 9 refs., 4 figs., 2 tabs.

Matveev, V.K.; Noifekh, A.I.; Klinshpont, E.R.; Milinchuk, V.K.

1992-09-01

114

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

115

Dielectric Properties of Mashed Potatoes Relevant to Microwave and Radio-frequency Pasteurization and Sterilization Processes  

Microsoft Academic Search

Dielectric properties of mashed potatoes relevant to microwave and radio-frequency (RF) pasteuriza- tion and sterilization processes were measured over 1 to 1800 MHz and 20 °C to 120 °C. Effects of moisture content (81.6% to 87.8%, wb) and salt content (0.8% to 2.8%, wb) were investigated. Dielectric loss factors and constants decreased with frequency. Dielectric loss factors increased with temperature

D. G UAN; M. CHENG; Y. WANG; J. TANG

2004-01-01

116

Dielectric Properties of Lead Monoxide Filled Unsaturated Polyester Based Polymer Composites  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

117

The Evolution of Static and Dynamic Elastic Properties Under Triaxial Conditions  

NASA Astrophysics Data System (ADS)

Elastic properties can be measured statically where strain data are recorded and related to stress during slow unloading of a specimen, or dynamically, where the elasticity can be calculated from the seismic wave velocity. Knowledge of the elastic properties is important in fault zone studies as microcracks change the elastic properties of rock and hence the stress state surrounding faults. In order to understand the elastic properties of the crust at depth using seismology, the relationship between the static and dynamic properties must be known. Previous studies have been performed under uniaxial stress and it has been unclear as to how the results might relate to triaxial stress states. These results have shown that: (1) an increase in the density of microcrack damage causes a decrease in static and dynamic Young's modulus and an increase in static and dynamic Poisson's ratios; (2) stress-dependency of static and dynamic elastic properties exist due to opening of cracks; (3) there is a linear relationship between static and dynamic Young's moduli and a significant discrepancy between the static and dynamic Poisson's ratios; and (4) the static and dynamic properties differ due to the size distribution of the crack population relative to the amplitude and frequency of the applied stress, frictional sliding on closed cracks during loading/unloading, and the assumption of isotropic elasticity in the sample. From these studies, some key questions that need addressing are: Is the evolution of static and dynamic properties the same under triaxial stress? Is the correlation between static and dynamic properties better under triaxial stress? We have developed a high pressure triaxial apparatus that can measure static and dynamic properties simultaneously. Here, results of the evolution and comparison of static and dynamic are represented based a more realistic crustal stress state.

Blake, O. O.; Faulkner, D. R.; Rietbrock, A.

2011-12-01

118

Dielectric Properties of Spherical Dielectric Oxide Powder and Its Ceramic-Polymer Composite  

NASA Astrophysics Data System (ADS)

A spherical filler of Ca0.65Sr0.35TiO3 dielectric oxide was prepared by flame fusion to improve the fluidity of ceramic-polymer compounds. The dielectric permittivity of the powder decreased by about 20% after melting-spheroidization but recovered after being heat-treated above 1150°C for 4 h. Composite dielectrics made from the spherical powder and a thermosetting polymer exhibited lower viscosity before hardening, thus making it possible to increase the filler concentration by over 5 vol %. A dielectric permittivity between 12 and 19 was achieved by adjusting the filler concentration of the spherical powder in the range of 40-70 vol %.

Che, Shenglei; Kanada, Isao; Sakamoto, Norimasa

2005-09-01

119

Effect of cenosphere on dielectric properties of low density polyethylene  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

120

Study of Microwave Dielectric Properties of Perovskite Thin Films by Near-Field Microscopy  

Microsoft Academic Search

Perovskite thin film materials possess good dielectric properties, which vary with applied voltage, and have thus been thoroughly investigated for applications as thin film tunable microwave devices. However, the tunability of the thin film materials derived from the frequency response of the thin film devices suffers from ambiguity in extracting the true dielectric response of the thin film materials in

Yi-Chun Chen; Yun-Shuo Hsieh; Hsiu-Fung Cheng; I-Nan Lin

2004-01-01

121

EFFECT OF NON-EQUILIBRATED MOISTURE ON MICROWAVE DIELECTRIC PROPERTIES OF WHEAT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of wheat samples, in which moisture equilibrium was upset by adding water, were tracked versus time in the frequency range between 5 GHz and 15 GHz at room temperature (23 degrees C). Results show an initial drop in the dielectric constant and loss factor, which reflects the i...

122

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

123

Influence of Nonequilibrated Water on Microwave Dielectric Properties of Wheat and Related Errors In Moisture Sensing  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of wheat samples, in which moisture equilibrium was upset by adding water, were tracked versus time in the frequency range between 5 GHz and 15 GHz at room temperature (23 degrees Celsius). Results show an initial drop in the dielectric constant and loss factor, which reflects...

124

Effect of "Natural" Water and "Added" Water on Dielectric Properties of Shelled Corn at Microwave Frequencies  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of samples of shelled corn of “natural” water content and those prepared by adding water were measured in free space at microwave frequencies and room temperature of 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 6 GHz show...

125

Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite  

E-print Network

Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite J Available online 1 December 2009 Keywords: Onion like carbon PMMA Electromagnetic coating Dielectric permittivity Thermal stability A novel lightweight onion-like carbon (OLC) based Poly(methyl metacrylate) (PMMA

Mayer, Alexandre

126

Dielectric and ferroelectric properties of phosphoric acid doped triglycine sulfate single crystals  

Microsoft Academic Search

Single crystals of triglycine sulfate (TGS) grown with 25–50 mol% phosphoric acid dopant in solution were investigated for their dielectric, ferroelectric and mechanical hardness properties. A 25 mol% of H3PO4 in solution yielded crystals with a large area in the ac plane without any seed crystal. The room temperature (300 K) dielectric constant (??) and tan? in the frequency range

Aparna Saxena; Vinay Gupta; K. Sreenivas

2001-01-01

127

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

128

Non-linear dielectric properties in based-PMN relaxor ferroelectrics  

Microsoft Academic Search

The investigation of the non-linear dielectric response in ferroelectric materials has become one of the most important issues in the field of ferroelectricity due to its technological and scientific interest. Rather, from the practical point of view the understanding of the non-linear dielectric properties is essential to improve the performance of ferroelectric multilayer capacitors and actuators devices, which commonly operate

J. de Los S. Guerra; M. H. Lente; J. A. Eiras

2007-01-01

129

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

Microsoft Academic Search

We have investigated the effects of electrical conductivity of the constituents on the dielectric and piezoelectric properties of ferroelectric 0-3 composites. The time-dependent internal electric fields are first derived, which can be induced by an applied ac field in dielectric measurement or stress in piezoelectric measurement. Our previously developed model [C. K. Wong, Y. M. Poon, and F. G. Shin,

C. K. Wong; F. G. Shin

2005-01-01

130

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

131

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

132

Electrical properties of double layer dielectric structures for space technology  

NASA Astrophysics Data System (ADS)

Polymeric films such as polyimide (PI) and polyethylene terephthalate (PET) are used in space technology as thermal blankets. Thin SiO2 and SiN coatings plasma deposited onto PI and PET surfaces were proposed to protect the blanket materials against the space environment. The electrical properties of this kind of dual layer dielectric structure were investigated to understand the mechanisms for suppressing charge accumulation and flashover. Bulk and surface electrical conductivities of thin single-layer PI and PET samples and of the dual layer SiO2 and SiN combinations with PI and PET were measured in a range of applied electrical fields. The capacitance voltage (CV) technique was used for analyzing charge transport and distribution in the structures. The electric current in the bulk of the SiO2/PI and SiN/PI samples was found to depend on the polarity of the electric field. Other samples did not exhibit any such polarity effect. The polarity dependence is attributed to charge trapping at the PI/plasma deposit interface. The CV characteristics of the Al-PI-SiO2-Si structure confirm that charges which can modify the local electric field can be trapped near the interface. A model is proposed to interpret the properties of the currents in dual layer structures. This model can semi-quantitatively explain all the observed results.

Lian, Anqing

1993-04-01

133

Effect of Incorporating Aromatic and Chiral Groups on the Dielectric Properties of Poly(dimethyltin esters).  

PubMed

High-dielectric constant materials are critical for numerous applications such as photovoltaics, photonics, transistors, and capacitors. There are numerous polymers used as dielectric layers in these applications but can suffer from having a low dielectric constant, small band gap, or ferroelectricity. Here, the structure-property relationship of various poly(dimethyltin esters) is described that look to enhance the dipolar and atomic polarization component of the dielectric constant. These polymers are also modeled using first principles calculations based on density functional theory (DFT) to predict such values as the total, electronic, and ionic dielectric constant as well as structure. A strong correlation is achieved between the theoretical and experimental values with the polymers exhibiting dielectric constants >4.5 with dissipation on the order of 10(-3) -10(-2) . PMID:25381737

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

2014-12-01

134

Dielectric properties of polymer-particle nanocomposites influenced by electronic nature of filler surfaces.  

PubMed

The interface between the polymer and the particle has a critical role in altering the properties of a composite dielectric. Polymer-ceramic nanocomposites are promising dielectric materials for many electronic and power devices, combining the high dielectric constant of ceramic particles with the high dielectric breakdown strength of a polymer. Self-assembled monolayers of electron rich or electron poor organophosphate coupling groups were applied to affect the filler-polymer interface and investigate the role of this interface on composite behavior. The interface has potential to influence dielectric properties, in particular the leakage and breakdown resistance. The composite films synthesized from the modified filler particles dispersed into an epoxy polymer matrix were analyzed by dielectric spectroscopy, breakdown strength, and leakage current measurements. The data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths resulted when electropositive phenyl, electron-withdrawing functional groups were located at the polymer-particle interface. At a 30 vol % particle concentration, dielectric composite films yielded a maximum energy density of ~8 J·cm(-3) for TiO2-epoxy nanocomposites and ~9.5 J·cm(-3) for BaTiO3-epoxy nanocomposites. PMID:23452250

Siddabattuni, Sasidhar; Schuman, Thomas P; Dogan, Fatih

2013-03-01

135

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 25°C. Samples from pale meat exhibited higher dielectric properties than samples from normal meat. No differences could be observed between samples from pale and normal meat after marination of the samples. Overall, dielectric properties increased as the marination pickup increased (?=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

136

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

137

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, Sümeyra Tuna; Sakar, Emine Fedakar; Ate?, Aytunç

2014-12-01

138

Enhanced dielectric properties from barium strontium titanate films with strontium titanate buffer layers  

E-print Network

Enhanced dielectric properties from barium strontium titanate films with strontium titanate buffer in their PE state. One of the leading material candidates for tunable materials is barium strontium titanate- tive amounts of Ba and Sr. TC for pure barium t

Alpay, S. Pamir

139

Dielectric properties of MgO-doped compositionally graded multilayer barium strontium titanate films  

E-print Network

Dielectric properties of MgO-doped compositionally graded multilayer barium strontium titanate shifters and filters operat- ing in the microwave regime.1­4 Ferroelectrics FEs such as barium strontium. Required amounts of barium

Alpay, S. Pamir

140

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

PubMed

The development of ultrawideband (UWB) microwave diagnostic and therapeutic technologies, such as UWB microwave breast cancer detection and hyperthermia treatment, is facilitated by accurate knowledge of the temperature- and frequency-dependent dielectric properties of biological tissues. To this end, we characterize the temperature-dependent dielectric properties of a representative tissue type-animal liver-from 0.5 to 20 GHz. Since discrete-frequency linear temperature coefficients are impractical and inappropriate for applications spanning wide frequency and temperature ranges, we propose a novel and compact data representation technique. A single-pole Cole-Cole model is used to fit the dielectric properties data as a function of frequency, and a second-order polynomial is used to fit the Cole-Cole parameters as a function of temperature. This approach permits rapid estimation of tissue dielectric properties at any temperature and frequency. PMID:16552116

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

2006-04-01

141

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

142

Dielectric and electromechanical properties of barium and zirconium co-doped sodium bismuth titanate  

E-print Network

Compositional exploration was conducted within the alkaline bismuth titanate system by doping on the A- and B- sites with Ba?² and Zr??, respectively. Results on the phase, dielectric and electromechanical properties of ...

Sheets, Sossity A. (Sossity Amber), 1973-

2000-01-01

143

Dielectric properties and magnetoelectric effects in FeCo-MgF insulating nanogranular films  

NASA Astrophysics Data System (ADS)

Multifunctional properties of matter, including dielectric and magnetic properties, are of great interest in physics and applications. Here, we investigate the dielectric properties and magnetoelectric effects in FeCo-MgF insulating nanogranular films. These films have a nanogranular structure in which Fe-Co alloy-based magnetic granules are dispersed in an Mg-F insulator-based matrix. Both a large dielectric constant of about 420 at 100 kHz and a large magnetoelectric effect of about 6.2% are obtained at room temperature. Insulating nanogranular films are a new class of multifunctional materials. The dielectric properties and the magnetoelectric effects originate in the nano-structure which consists of a magnetic metal and an insulator, and are explained by the spin-dependent tunneling charge oscillation between a pair of magnetic granules.

Kobayashi, N.; Iwasa, T.; Ishida, K.; Masumoto, H.

2015-01-01

144

Volume sensing properties of open-ended coaxial probes for dielectric spectroscopy of breast tissue  

Microsoft Academic Search

An ultrawideband microwave imaging approach to early breast cancer detection is based on the hypothesis that there exists a significant dielectric-properties contrast between cancerous and normal breast tissue at microwave frequencies. Definitive knowledge of the dielectric properties of breast tissue in the RF\\/microwave frequency range (0.1-20 GHz) is required for the development of novel technologies related to the detection and

D. Popovic; M. Okoniewski; D. Hagl; J. H. Booske; S. C. Hagness

2001-01-01

145

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

Microsoft Academic Search

The development of ultrawideband (UWB) microwave diagnostic and therapeutic technologies, such as UWB microwave breast cancer detection and hyperthermia treatment, is facilitated by accurate knowledge of the temperature- and frequency-dependent dielectric properties of biological tissues. To this end, we characterize the temperature-dependent dielectric properties of a representative tissue type—animal liver—from 0.5 to 20 GHz. Since discrete-frequency linear temperature coefficients are

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

2006-01-01

146

Preliminary non-destructive assessment of moisture content, hydration and dielectric properties of Portland cement concrete  

E-print Network

PRELIMINARY NON-DESTRUCTIVE ASSESSMENT OF MOISTURE CONTENT, HYDRATION AND DIELECTRIC PROPERTIES OF PORTLAND CEMENT CONCRETE A Thesis by IVAN AVELAR LEZAMA Submitted to the Office of Graduate Studies of Texas A... AND DIELECTRIC PROPERTIES OF PORTLAND CEMENT CONCRETE A Thesis by IVAN AVELAR LEZAMA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE...

Avelar Lezama, Ivan

2007-04-25

147

Dimension effects on the dielectric properties of fine BaTiO3 ceramics  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

148

Effect of sintering on structural and dielectric properties of PLZT ferroelectrics  

SciTech Connect

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

Janrao, Prashant, E-mail: vlmathe@physics.unipune.ac.in; Mathe, V. L., E-mail: vlmathe@physics.unipune.ac.in [Department of Physics, University of Pune, Ganeshkhind, Pune-411007 (India)

2014-04-24

149

Dielectric Properties of Soils at UHF and Microwave Frequencies  

Microsoft Academic Search

The complex dielectric constant of four soils, including a sand, a silt, and two clays, wa* measured over the frequency range from 0.1 x 10 * Hz to 26 X 10 * Hz. The water content of the soils was varied from 0.0 g H20\\/g soil to 0.15 g H20\\/g soil, and the temperature from 24øC to -20øC. The dielectric

P. Hoekstra; A. Delaney

1974-01-01

150

Dielectric property of ferroelectric-insulator-semiconductor junction  

Microsoft Academic Search

The voltage dependence of the high-frequency capacitance of a metal-ferroelectric-insulator-semiconductor (MFIS) structure is analyzed by relating the potential profile to the dielectric hysteresis of the ferroelectric thin film. About one hundredth of the dielectric polarization of ferroelectric ceramic PZT is enough to control the Si surface potential for ferroelectric gate FET memory, and large coercive force is required to obtain

Masanori Okuyama; Wenbiao Wu; Yoshihiro Oishi; Takeshi Kanashima

1997-01-01

151

Infrared Dielectric Properties of Low-stress Silicon Nitride  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

152

Shear-induced particle rotation and its effect on electrorheological and dielectric properties in cellulose suspension  

NASA Astrophysics Data System (ADS)

Electrorheological (ER) and dielectric properties under high electric fields were measured simultaneously on hydroxypropylcellulose suspension. When measuring these properties as a function of frequency of the electric field, we found a positive peak in each spectrum of the ER effect and the first-order dielectric permittivity while a negative one in the spectrum of the third-order dielectric permittivity with these peak frequencies nearly equal to (shearrate)/4? . Referring to the well-known results for the particle rotation in the sheared suspension, it is suggested that the observed peaks are due to shear-induced particle rotation and the rotation occurs even under high electric field. On the basis of these results, effects of the particle rotation on the ER and the dielectric properties are discussed.

Misono, Y.; Negita, K.

2004-12-01

153

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

PubMed

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

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

2015-01-22

154

Effect of DC bias on dielectric properties of nanocrystalline CuAlO2  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

155

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

SciTech Connect

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

Tuncer, Enis [ORNL

2006-01-01

156

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

SciTech Connect

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

Tuncer, Enis [ORNL; Bowler, Nicola [Center for Nondestructive Evaluation, Ames, Iowa; Youngs, I. J. [DSTL, Porton Down, Salisbury, Wiltshire, UK; Lymer, K. P. [QinetiQ Ltd, Hampshire, UK

2006-01-01

157

Laboratory measurements of static and dynamic elastic properties in carbonate  

Microsoft Academic Search

The fact that many of the giant hydrocarbon reservoirs, such as the Ghawar field in Saudi Arabia and the Grosmont formation in Alberta, are formed from carbonates make these rocks and the corresponding reservoirs important research topics. Compressional and shear wave velocities (at 1 MHz) and the quasi-static strains of thirty seven carbonate rock samples were measured as functions of

Aiman M. Bakhorji

2010-01-01

158

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

159

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

160

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

NASA Astrophysics Data System (ADS)

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

Peyman, A.; Gabriel, C.

2012-04-01

161

Structural and dielectric properties of yttrium-substituted hydroxyapatites.  

PubMed

Hydroxyapatite (HAp) samples doped with 0, 2 and 4at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content. PMID:25492204

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

2015-02-01

162

First-principles calculations of the dielectric properties of perovskite-type materials  

Microsoft Academic Search

We compare first-principles (FP) calculations of the ionic effective charges, phonon frequencies, and static dielectric permittivities ?s of several perovskite-type materials. Transition metal ions have anomalously large effective charges, though in the double perovskite CaAl1\\/2Nb1\\/2O3 (CAN), the effective charge of Nb is significantly lower than in the simple perovskite KNbO3, showing different Nb–O bonding chemistry. Tolerance factors, cation chemistry, and

2003-01-01

163

Properties and Applications of Silicon Oxynitride Gate Dielectrics.  

NASA Astrophysics Data System (ADS)

Reducing the size of silicon CMOS transistors enables higher speed, lower-power, denser and cheaper circuits, but introduces many challenges in process technology. As the gate oxide thickness is reduced, and as electric fields in the MOSFET increase, there are increased concerns about hot-carrier damage and oxide breakdown. Additionally, thinner SiO2 layers cannot effectively block diffusion of dopants and impurities. Silicon oxynitride dielectrics minimize these difficulties, making them attractive as gate dielectrics for future CMOS processes. Silicon oxynitrides are thermally grown on Si, in N_2O at temperatures ranging from 800-1100^circC, to thicknesses of 3-10 nm. The resulting material is primarily SiO_2, with 10^14-10^15 cm-2 nitrogen atoms incorporated (as measured by nuclear reaction analysis), equivalent to less than a monolayer of pure Si_3N_4. Secondary ion mass spectroscopy profiles indicate that this nitrogen is mainly near the crystalline silicon/dielectric interface, as a result of two competing reactions:(E.C. Carr, K.A. Ellis and R.A. Buhrman, Appl. Phys. Lett., v. 66, n. 12, p. 1492, (1995).) first, a nitrogen-oxygen species diffuses through the film and reacts at the Si interface, growing a silicon oxynitride layer. As the reaction proceeds and the grown layer is pushed up from the interface, a competing reaction removes the nitrogen from the dielectric ``bulk'', leaving behind SiO_2. This small amount of nitrogen incorporated at the dielectric interface has a dramatic effect on electrical reliability. Nitrogen-containing gate dielectrics inhibit generation of electrical defects and charge traps that degrade device performance, and they can more than double the time until breakdown. Such improvements are attributed to reduction of strain at the interface, which allows stronger bonds and fewer defect precursors. Oxynitrides also have the advantage of acting as a diffusion barrier. In MOS structures, boron dopant atoms originating in the polycrystalline silicon gate electrode can easily diffuse through thin gate dielectrics, resulting in threshold voltage shifts and degrading process control. Nitrogen in the dielectric inhibits boron diffusion, although the mechanism is still unclear. By blocking boron, these oxynitrides allow more aggressive scaling of oxide thickness. Collaborators: D. Brasen, L.C. Feldman, M.L. Green, W. Lennard, L. Manchanda, H. Tang, B.E. Weir, H. Tang.

Krisch, K. S.

1996-03-01

164

Static and dynamic properties of pinned flux-line liquids  

NASA Astrophysics Data System (ADS)

We study the equilibrium statics and nonequilibrium driven dynamics of flux line liquids in presence of a random pinning potential. Under the assumption of replica symmetry, we find in the static case using a replica Gaussian variational method that the only effect of disorder is to increase the tilt modulus and the confining ``mass" of the internal modes of the flux lines, thus decreasing their thermal wandering. In the nonequilibrium, driven case, we derive the long scale, coarse-grained equation of motion of the vortices in presence of disorder, which apart from new Kardar-Parisi-Zhang nonlinearities, has the same form as the equation of motion for unpinned vortices, with renormalized coefficients. This implies, in particular, that the structure factor of a disordered vortex liquid has the same functional form as in the absence of pinning. The expression of the static structure factor derived within our approach is consistent both with experimental data and with the standard theory of elasticity of vortex lattices.

Ettouhami, A. M.

2005-03-01

165

Dielectric properties of barium titanate nanocube ordered assembly sintered at various temperatures  

NASA Astrophysics Data System (ADS)

Single-crystalline BaTiO3 nanocubes were synthesized by a hydrothermal method using a water-soluble titanium complex and surfactants. Ordered assemblies of BaTiO3 nanocubes were directly fabricated on substrates by the dip-coating method. To optimize the conjugation of the nanocubes, the sintering temperature was changed in the range of 750 to 900 °C to compare with the dielectric properties. The microstructures and dielectric properties of BaTiO3 nanocube assemblies sintered at various temperatures were characterized. The structure-property relation and the sintering temperature dependence of the dielectric properties are discussed. The assembly sintered at 850 °C showed the most enhanced dielectric properties. The face-to-face conjugation of the nanocubes was completed and there was good adhesion between the electrode and the assembly at 850 °C. The enhanced dielectric properties were considered to be due to the combination of the single-crystalline nanocubes and the interface between them.

Mimura, Ken-ichi; Kato, Kazumi

2014-09-01

166

Study on dielectric properties of PMN-PZN-PT ferroelectric relaxor ceramics  

Microsoft Academic Search

The influence of additions and processing on the microstructure and properties of PMN-PZN-PT ceramics was studied. Experimental results showed that the DC bias character of PMN-based ceramics doped with PZN could be improved; proper excess MgO is advantageous to inhibiting the pyrochlore phase and increasing the dielectric constant. Dielectric loss could be decreased by adding MnO2. It was also found

Zhilun Gui; Longtu Li; Xiaowen Zhang

1991-01-01

167

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

168

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

Microsoft Academic Search

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

Jérôme Pons; Eric Moreau; Gérard Touchard

2005-01-01

169

Thermal and dielectric properties of LiKSO4 and LiCsSO4  

Microsoft Academic Search

Measurements of the thermal and dielectric properties of single crystals of the double sulfates LiKSO4 and LiCsSO4 are reported. Uncertainty in the determination of the space group of LiCsSO4 is resolved on the basis of optical second harmonic generation and pyroelectric measurements; the correct space group is Pcmn. Measurements of the pyroelectric coefficient, dielectric constant, and specific heat of LiKSO4

M. Delfino; G. M. Loiacono; W. A. Smith; A. Shaulov; Y. H. Tsuo; M. I. Bell

1980-01-01

170

Static and dynamic mechanical properties of infiltrated B 4C–Si composites  

Microsoft Academic Search

The present paper is concerned with the static and the dynamic mechanical properties at strain-rates up to 103s?1, of ceramic composites based on porous B4C infiltrated with molten Si. The static mechanical properties of the infiltrated composites depend on the amount of the residual silicon. The Young's modulus and the hardness increase, while the flexural strength and K1C decrease with

S. Hayun; D. Rittel; N. Frage; M. P. Dariel

2008-01-01

171

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 Å; c = 13.578 Å, and average crystallize size (62.40 ± 21.3) nm. FE-SEM image illustrated the mixture of different shapes (disk, particle and rod) of as-grown nanostructures whereas; EDS spectrum confirmed the elemental purity of the material. FTIR spectroscopy, revealed the characteristic peaks of Cr-O bond stretching vibrations. Energy band gap (3.2 eV) of the nanostructures has been determined using the results of UV-VIS-NIR spectrophotometer. The dielectric properties of the material were checked in the wide frequency region (100Hz-30 MHz). In the low frequency region, the matrix of the dielectric behaves like source as well as sink of electrical energy within the relaxation time. Low value of dielectric loss exhibits that the materials posses good optical quality with lesser defects. The ac conductivity of the material in the high frequency region was found according to frequency power law. The physical-mechanism and the theoretical-interpretation of dielectric-properties of 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

172

Acid Rain Affecting the Electrical Properties of Outdoor Composite Dielectric Materials  

NASA Astrophysics Data System (ADS)

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 on the investigation of acid rain, the composition of artificial acid rain is chosen to agree with the actual composition of precipitation. The surface potential, breakdown voltage, tracking resistance, and surface discharge current of dielectric materials are studied. Furthermore, the degradation mechanisms of electrical properties of composite dielectrics are discussed by investigating the degradation of the chemical and physical microstructures of material surface using Fourier transform infrared (FTIR), the X-ray diffraction spectrum (XDS), and the metalloscope. Experimental results show that the outdoor polymeric dielectrics suffer severely and degrade due to acid rain so that their surface electrical properties deteriorate after aging. The erosion, by acid rain, of the energized dielectric materials is larger than that of outdoor materials used for other purposes.

Wang, Xinsheng; Kumagai, Seiji; Yoshimura, Noboru

1998-12-01

173

Dielectric properties of nanostructured polypropylene-polyhedral oligomeric silsesquioxane compounds  

Microsoft Academic Search

This paper presents the results of the dielectric measurements conducted on polymer nanocompounds consisting of polypropylene (PP) and polyhedral oligomeric silsesquioxane (POSS). The material compounds were analyzed with a scanning electron microscope (SEM) and Raman-atomic force microscope (Raman-AFM). Ac and lightning impulse (LI) breakdown strength of the material compounds were measured. Relative permittivity, loss factor and volume resistivity measurements were

M. Takala; M. Karttunen; P. Salovaara; S. Kortet; K. Kannus; T. Kalliohaka

2008-01-01

174

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

Microsoft Academic Search

The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number

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

2007-01-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

176

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; Wälti, Christoph

2014-02-11

177

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. PMID:24447311

2014-01-01

178

Dielectric properties of cluster-deposited TiO2 nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

179

Measurement of dielectric properties of subcutaneous fat with open-ended coaxial sensors  

NASA Astrophysics Data System (ADS)

A three-layer model of stratum corneum, epidermis/dermis and subcutaneous fat has been developed for the capacitance of an open-ended coaxial line in contact with human skin. Applying the model, the electrical properties of subcutaneous fat can be calculated from skin dielectric measurements with three probes of different sizes. The three-layer model is based on a variational formula for the capacitance of the coaxial probe. An accurate approximation for the dielectric constant of the multilayer cutaneous structure is presented for the inverse problem of solving the dielectric constants of various layers. The method was tested at 300 MHz with breast cancer patients who often have radiotherapy-induced late alterations in the structure of subcutaneous fat due to the development of subcutaneous fibrosis. Measurements from 206 sites yielded a good agreement between the dielectric constant of subcutaneous fat and the clinical score for subcutaneous fibrosis.

Alanen, Esko; Lahtinen, Tapani; Nuutinen, Jouni

1998-03-01

180

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

181

Effect of magnetic field on the dielectric properties of multiferroic composites  

NASA Astrophysics Data System (ADS)

Magneto-dielectric materials are a subject of potential interests in terms of basics research and new device applications. In this study, 0.5BaTiO3-0.5MgFe2O4 composites with ferroelectric and soft magnetic properties, synthesized using wet chemical methods, were investigated for the possibility of controlling the dielectric properties by application of a magnetic field. Composite pellets were thermally treated in air at 950 to 1150 °C for 3 h, and their structural, magnetic and magneticdielectric properties were characterized. All the composites showed soft magnetic properties. The magnetic field was applied to composite pellets in the order of 200 to 400 Oe, and a variation in the dielectric constant was observed. Significant findings, such as an increase in the dielectric constant with increasing of magnetic field, were observed in the composite pellets. The increase in the dielectric constant with respect to the applied magnetic field was depicted as being an effect of increased magnetostriction in the magnetic phase.

Tadi, Ravindar; Kim, Yong-Il; Ryu, Kwon-Sang; Kim, CheolGi

2012-11-01

182

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

183

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

184

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

NASA Technical Reports Server (NTRS)

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

Blume, H.-J. C.

1980-01-01

185

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

186

Simulation of the Mechanical Performance of Cast Steel with Porosity: Static Properties  

E-print Network

Simulation of the Mechanical Performance of Cast Steel with Porosity: Static Properties R.A. Hardin, characteristics and effects of porosity on properties is more critical than ever. In the work presented here, a method for incorporating the effect of porosity on steel stiffness (elastic modulus) is presented

Beckermann, Christoph

187

Nano-structured vanadium: processing and mechanical properties under quasi-static and dynamic compression  

E-print Network

Nano-structured vanadium: processing and mechanical properties under quasi-static and dynamic form 16 September 2003; accepted 9 October 2003 Abstract We have processed fully dense, nano that the grain size of the consolidated V is around 100 nm. Mechanical properties of the nano-structured V were

Wei, Qiuming

188

Static and dynamic mechanical properties of boron carbide processed by spark plasma sintering  

Microsoft Academic Search

Spark plasma sintering (SPS) has become a popular technique for the densification of covalent ceramics. The present investigation is focused on the static mechanical properties and dynamic compressive behavior of SPS consolidated boron carbide powder without any sintering additives. Fully dense boron carbide bodies were obtained by a short high temperature SPS treatment. The mechanical properties of the SPS-processed material,

S. Hayun; M. P. Dariel; N. Frage; E. Zaretzky

2009-01-01

189

Spin Waves and Dielectric Softening of Polar Molecule Condensates  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

190

Ferromagnetic Transition of Heisenberg Ferromagnetic Metal of CoS2 Static Critical Properties  

Microsoft Academic Search

The static magnetic properties near the Curie temperature in CoS2 have been thoroughly studied by using various experimental techniques from high quality single crystals, which were grown by the chemical transport technique. A very small anisotropy in magnetization confirms that CoS2 is the best system to apply the Heisenberg Hamiltonian. The critical indices obey the static scaling hypothesis, which indicates

Haruhiro Hiraka; Yasuo Endoh

1994-01-01

191

Dielectric properties of binary and ternary mixtures of alcohols: Analysis of H-bonded interaction in complex systems  

Microsoft Academic Search

The heterogeneous H-bonded interactions in mixtures of glass-former liquids, i.e., binary mixtures of ethyl alcohol (EA) with ethylene glycol (EG) and ternary mixtures of equi-molar EA+EG system with glycerol (Gly) have been investigated at 21 concentrations by using precisely measured values of static and high frequency limiting dielectric constants at 25°C. Concentration dependent observed negative values of excess dielectric constant

R. J. Sengwa; Sonu Sankhla

2007-01-01

192

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

SciTech Connect

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., E-mail: luisalejandro-miccio@ehu.es; Colmenero, Juan [Centro de Física de Materiales (CSIC-UPV/EHU), P. M. de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center, P. M. de Lardizabal 4, 20018 San Sebastián (Spain); Departamento de Física de Materiales (UPV/EHU), 20080 San Sebastián (Spain); Kummali, Mohammed M.; Alegría, Ángel [Centro de Física de Materiales (CSIC-UPV/EHU), P. M. de Lardizabal 5, 20018 San Sebastián (Spain); Departamento de Física de Materiales (UPV/EHU), 20080 San Sebastián (Spain); Schwartz, Gustavo A. [Centro de Física de Materiales (CSIC-UPV/EHU), P. M. de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center, P. M. de Lardizabal 4, 20018 San Sebastián (Spain)

2014-05-14

193

Dielectric properties of I-III-VI2-type chalcopyrite semiconductors D. Xue, K. Betzler,* and H. Hesse  

E-print Network

Dielectric properties of I-III-VI2-type chalcopyrite semiconductors D. Xue, K. Betzler,* and H Dielectric properties of I-III-VI2-type ternary chalcopyrite semiconductors, including linear and second. INTRODUCTION For more than 20 years, chalcopyrite semiconductors with the formula I-III-VI2 where I, III

Osnabrück, Universität

194

Effect of random surface inhomogeneities on spectral properties of dielectric-disk microresonators: Theory and modeling at millimeter wave range  

NASA Astrophysics Data System (ADS)

The influence of random axially homogeneous surface roughness on spectral properties of dielectric resonators of circular disk form is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields, the method of eigenmode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering that is highly responsible for nondissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object, we use a dielectric disk resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigenfrequencies and the Q factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data.

Ganapolskii, E. M.; Eremenko, Z. E.; Tarasov, Yu. V.

2009-04-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

196

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

NASA Astrophysics Data System (ADS)

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

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

197

Structural and dielectric properties of a complex tungsten bronze ferroelectric  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

198

Dielectric properties of glasses at ultra low temperatures  

SciTech Connect

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

Nishiyama, H.; Akimoto, H.; Okuda, Y.; Ishimoto, H. [Univ. of Tokyo (Japan)

1992-11-01

199

Measuring Static and Dynamic Properties of Frozen Silty Soils  

SciTech Connect

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

Furnish, M.D.

1998-09-30

200

The effect of organo-clay on the dielectric properties of silicone rubber  

NASA Astrophysics Data System (ADS)

Dielectric elastomers are highly deformable and fast response smart materials capable of actuation under electric fields. Among commercially available dielectric elastomers, silicone rubber can be compounded with different fillers in order to modify its electrical and mechanical properties. To study the effect of organically modified montmorillonite (OMMT) on the dielectric properties of silicone rubber, OMMT was added to this rubber at two levels, 2% and 5%, using two methods, low-shear and high-shear mixing. Composites were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The XRD patterns showed different crystallite structures for silicate platelets in the rubber matrix as a result of the two different mixing methods. In low-shear mixing, the ordered crystallite structure of the clay remains almost unchanged, whereas in high-shear mixing it loses its ordered structure, leading to the disappearance of the diffraction peaks. SEM and AFM micrographs depicted better dispersion and more uniform distribution of the organo-clay under high-shear mixing compared to those obtained by low-shear mixing. The tensile properties also confirmed the different degree of dispersion of the nano-clay resulting from the two different methods of mixing. The dielectric properties of the composites were measured under AC electric fields, and the results were compared with reference silicone rubbers with no OMMT. It was shown that the order of organo-clay layers in the less dispersed structure of the clay imparts an additional ionic polarization and higher dielectric permittivity compared to the case where the clay layers are more dispersed and lost their order. The storage and loss dielectric constants of base silicone rubber increase when it is compounded with OMMT.

Razzaghi-Kashani, M.; Gharavi, N.; Javadi, S.

2008-12-01

201

Dielectric property of ferroelectric-insulator-semiconductor junction  

NASA Astrophysics Data System (ADS)

The voltage dependence of the high-frequency capacitance of a metal-ferroelectric-insulator-semiconductor (MFIS) structure is analyzed by relating the potential profile to the dielectric hysteresis of the ferroelectric thin film. About one hundredth of the dielectric polarization of ferroelectric ceramic PZT is enough to control the Si surface potential for ferroelectric gate FET memory, and large coercive force is required to obtain enough voltage window. MFIS structures using Bi-layer-structured ferroelectric thin films are also studied from experimental viewpoint. SrBi 2Ta 2O 9 and Bi 4Ti 3O 12 thin films have been prepared by laser ablation method on both Pt sheet and Si wafers at low temperatures of 400-500°C. SrBi 2Ta 2O 9 thin films have a good (105) preferential orientation, and Bi 4Ti 3O 12 thin films have (117) and c-axis orientations on these substrates. D-E hystereses are obtained in SrBi 2Ta 2O 9 and Bi 4Ti 3O 12 thin films prepared on Pt sheet, and are enough to control the Si surface potential. Ferroelectric film-SiO 2?Si structures show good C-V hysteresis curves owing to the Si surface potential controlled by the D-E hysteresis.

Okuyama, Masanori; Wu, Wenbiao; Oishi, Yoshihiro; Kanashima, Takeshi

1997-06-01

202

THz Dielectric Properties of High Explosives Calculated by Density Functional Theory for the Design of Detectors  

NASA Astrophysics Data System (ADS)

The current need for better detection of explosive devices has imposed a new 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 and ability to penetrate materials that are characteristic of clothing. Typically, the dielectric response properties for electromagnetic wave excitation at THz frequencies, as well as at other frequencies, are determined by means of experimental measurements. The present study, however, emphasizes that density functional theory (DFT), and associated software technology, is sufficiently mature for the determination of dielectric response functions, and actually provides complementary information to that obtained from experiment. In particular, these dielectric response functions provide quantitative initial estimates of spectral response features that can be adjusted with respect to additional information such as laboratory measurements and other types of theory-based calculations, as well as providing for the molecular level interpretation of response structure. This point is demonstrated in the present study by calculations of ground-state resonance structure associated with the high explosives RDX, TNT1, and TNT2 using DFT, which is for the construction of parameterized dielectric response functions for excitation by electromagnetic waves at frequencies within the THz range. The DFT software NRLMOL was used for the calculations of ground-state resonance structure presented here.

Shabaev, A.; Lambrakos, S. G.; Bernstein, N.; Jacobs, V.; Finkenstadt, D.

2011-12-01

203

Dielectric properties of continuous composition spreaded MgO-Ta 2O 5 thin films  

NASA Astrophysics Data System (ADS)

The dielectric properties of MgO-Ta2O5 continuous composition spread (CCS) thin films were investigated. The MgO-Ta2O5 CCS thin films were deposited on Pt/Ti/SiO2/Si substrates by off-Axis RF magnetron sputtering system, and then the films were annealed at 350 °C with rapid thermal annealing system in vacuum. The dielectric constant and loss of MgO-Ta2O5 CCS thin films were plotted via 1500 micron-step measuring. The specific point of Ta2O5-MgO CCS thin film (post annealed at 350 °C) showing superior dielectric properties of high dielectric constant (k ? 28) and low dielectric loss (tan ? < 0?004) at 1 MHz were found in the area of 3-5 mm apart from Ta2O5 side on the substrate. The cation's composition of thin film was Mg:Ta = 0.4:2 at%.

Kim, Yun Hoe; Song, Jong-Han; Kim, Jin Sang; Yoon, Seok-Jin; Park, Kyung Bong; Choi, Ji-Won

2011-11-01

204

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

205

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

SciTech Connect

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

Zhang, Yajun [Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027 (China); Liu, Man; Shimada, Takahiro; Kitamura, Takayuki [Department of Mechanical Engineering and Science, Kyoto University, Nishikyo-ku, Kyoto 615-8540 (Japan); Wang, Jie, E-mail: jw@zju.edu.cn [Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027 (China); Department of Mechanical Engineering and Science, Kyoto University, Nishikyo-ku, Kyoto 615-8540 (Japan)

2014-06-14

206

Static and dynamic magnetostrictive properties of polymer-bonded Fe-Co based alloy composites  

Microsoft Academic Search

Polymer-bonded composites of an Fe-Co based alloy were developed and their magnetostrictive and mechanical properties were characterized. In this work, the static and dynamic magnetostrictive properties as a function of volume fraction of Fe36Co62Ge2 alloy and frequency are characterized. WC powders are especially added to the composites in order to provide increased mechanical properties and extend the high frequency application

S. M. Na; S. W. Kim; K. H. Shin; M. Pasquale; C. P. Sasso; S. H. Lim

2004-01-01

207

Effect of microstructure on static and dynamic mechanical properties of high strength steels  

NASA Astrophysics Data System (ADS)

The high speed deformation behavior of a commercially available dual phase (DP) steel was studied by means of split Hopkinson bar apparatus in shear punch (25m/s) and tension (1000s-1) modes with an emphasis on the influence of microstructure. The cold rolled sheet material was subjected to a variety of heat treatment conditions to produce several different microstructures, namely ferrite plus pearlite, ferrite plus bainite and/or acicular ferrite, ferrite plus bainite and martensite, and ferrite plus different fractions of martensite. Static properties (0.01mm/s for shear punch and 0.001s -1 for tension) of all the microstructures were also measured by an MTS hydraulic machine and compared to the dynamic properties. The effects of low temperature tempering and bake hardening were investigated for some ferrite plus martensite microstructures. In addition, two other materials, composition designed as high strength low alloy (HSLA) steel and transformation induced plasticity (TRIP) steel, were heat treated and tested to study the effect of alloy chemistry on the microstructure and property relationship. A strong effect of microstructure on both static and dynamic properties and on the relationship between static and dynamic properties was observed. According to the variation of dynamic factor with static strength, three groups of microstructures with three distinct behaviors were identified, i.e. classic dual phase (ferrite plus less than 50% martensite), martensite-matrix dual phase (ferrite plus more than 50% martensite), and non-dual phase (ferrite plus non-martensite). Under the same static strength level, the dual phase microstructure was found to absorb more dynamic energy than other microstructures. It was also observed that the general dependence of microstructure on static and dynamic property relationship was not strongly influenced by chemical composition, except the ferrite plus martensite microstructures generated by the TRIP chemistry, which exhibited much better dynamic factor values. This may suggest that solid solution strengthening should be more utilized in the design of crashworthy dual phase steels.

Qu, Jinbo

208

The effect of stress on the dielectric properties of barium strontium titanate thin films  

E-print Network

The effect of stress on the dielectric properties of barium strontium titanate thin films T. M Barium strontium titanate thin films are being developed as capacitors in dynamic random access memories to their large permittivities, barium strontium titan- ate BST bulk ceramics have long been used to make high

Suo, Zhigang

209

Microwave dielectric properties of graded barium strontium titanate films M. W. Cole,1,a  

E-print Network

Microwave dielectric properties of graded barium strontium titanate films M. W. Cole,1,a C. V Received 8 April 2008; accepted 13 April 2008; published online 8 May 2008 Compositionally graded barium, delay lines, filters, and phase shifters for steerable antennas.1­3 Barium strontium titanate BaxSr1-x

Alpay, S. Pamir

210

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

211

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

212

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

213

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

E-print Network

concurrently on 100 SrTiO3 and 111 Pt/ 0001 Al2O3 substrates. Films were deposited on platinized sapphire grown concurrently on 100 SrTiO3 , 0001 Al2O3 , and platinized 0001 Al2O3 sub- states. Films wereInfluence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films

York, Robert A.

214

EFFECT OF SALINITY ON THE DIELECTRIC PROPERTIES OF GEOLOGICAL MATERIALS : IMPLICATION FOR SOIL  

E-print Network

EFFECT OF SALINITY ON THE DIELECTRIC PROPERTIES OF GEOLOGICAL MATERIALS : IMPLICATION FOR SOIL of saline deposits for the detection and mapping of moisture in arid regions on both Earth and Mars. We then present a simulation and experimental study in order to assess the effect of salinity on the permittivity

Paris-Sud XI, Université de

215

> TGRS-2008 < 1 Abstract--Field measurements of dielectric properties of  

E-print Network

to model both the amplitude and phase behaviors of the SAR signal, at C-, and L-bands. These analytical variations of the dielectric properties of saline deposits at both L- and C-band frequencies. Because@enscpb.fr; paillou@obs.u-bordeaux1.fr). A. Freeman, T. Farr, K. McDonald, and B. Chapman are with the Jet Propulsion

Boyer, Edmond

216

Generation of Extended Surface Barrier Discharge on Dielectric Surface Electrical Properties  

Microsoft Academic Search

Dielectric barrier discharge (DBD) with a grounded electrode (sliding electrode) on the same surface as the high voltage electrode (three electrode DBD) was experimentally studied to generate homogeneous surface discharge. Application of AC high voltage generated stable and homogeneous surface plasma between high voltage and grounded electrode without arcing. Electrical properties of the three electrode DBD was experimentally studied. With

K. Takashima; N. Zouzou; E. Moreau; A. Mizuno; G. Touchard

217

Reliability of in vivo measurements of the dielectric properties of anisotropic tissue: a simulative study.  

PubMed

A simulative study was performed to measure the dielectric properties of anisotropic tissue using several in vivo and in vitro probes. COMSOL Multiphysics was selected to carry out the simulation. Five traditional probes and a newly designed probe were used in this study. One of these probes was an in vitro measurement probe and the other five were in vivo. The simulations were performed in terms of the minimal tissue volume for in vivo measurements, the calibration of a probe constant, the measurement performed on isotropic tissue and the measurement performed on anisotropic tissue. Results showed that the in vitro probe can be used to measure the in-cell dielectric properties of isotropic and anisotropic tissues. When measured with the five in vivo probes, the dielectric properties of isotropic tissue were all measured accurately. For the measurements performed on anisotropic tissue, large errors were observed when the four traditional in vivo probes were used, but only a small error was observed when the new in vivo probe was used. This newly designed five-electrode in vivo probe may indicate the dielectric properties of anisotropic tissue more accurately than these four traditional in vivo probes. PMID:23603795

Huo, Xuyang; Shi, Xuetao; You, Fusheng; Fu, Feng; Liu, Ruigang; Tang, Chi; Lu, Qiang; Dong, Xiuzhen

2013-05-21

218

Phase transition and dielectric properties of nanograin BaTiO3 ceramic under high pressure  

E-print Network

ceramics, the inter- nal stresses are mainly compressive and isotropic, like an applied hydrostaticPhase transition and dielectric properties of nanograin BaTiO3 ceramic under high pressure Jinlong with 60 nm grains. The variation of intergranular stresses with reducing grain size is considered

Cao, Wenwu

219

Zirconium tin titanate (ZST) for miniaturized high impedance surfaces: Microwave dielectric properties and applications  

Microsoft Academic Search

A new approach for obtaining metasurfaces realized by employing Frequency Selective Surfaces (FSSs) with small periodicity printed on a new class of high dielectric constant materials is presented. The synergic use of ad-hoc engineered materials and innovative electromagnetic design provides an improvement of the overall device in terms of size reduction and radiative properties.

S. Genovesi; F. Costa; B. Cioni; V. Miceli; G. Gallone; G. Levita; A. Lazzeri; G. Annino; A. Monorchio; G. Moruzzi

2009-01-01

220

SYNTHESIS AND DIELECTRIC PROPERTIES OF LIQUID CRYSTALS CONTAINING TWO CYANO GROUPS  

E-print Network

SYNTHESIS AND DIELECTRIC PROPERTIES OF LIQUID CRYSTALS CONTAINING TWO CYANO GROUPS L. A and low frequency permittivities of nematic liquid crystals (NLC's) are due mainly to the dipole-l, U.S.S.R. Abstract. -- A series of liquid crystalline stilbenes, azocompounds and esters containing

Boyer, Edmond

221

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

222

Dielectric properties of cubic bismuth based pyrochlores containing lithium and fluorine  

Microsoft Academic Search

In this work dielectric properties of Bi1.5Zn1?xLixNb1.5O7?xFx with x=0.25 were investigated in a 20Hz–12GHz frequency and 120–500K temperature range and compared to that of regular cubic BZN (when x=0). Measurements showed that both ceramics have dipolar glass type dielectric dispersion with wide relaxation time distributions. Mean relaxation time follows Arrhenius law in the investigated frequency range, although Vogel–Fulcher law was

Juras Banys; Saulius Rudys; Maksim Ivanov; Jing Li; Hong Wang

2010-01-01

223

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

224

Structural and electrical properties of neodymium oxide high-k gate dielectrics  

NASA Astrophysics Data System (ADS)

In this letter, the authors reported a high-k neodymium oxide gate dielectric grown by reactive rf sputtering. It is found that the Nd2O3 gate dielectric after annealing at 700°C exhibits excellent electrical properties such as low equivalent oxide thickness, high electric breakdown field, and almost no hysteresis and frequency dispersion in C-V curves. This indicates that annealing at 700°C treatment can prevent the interfacial layer and silicate formation, reduce a large amount of interface trap, and passivate a large amount of trapped charge at defect sites.

Pan, Tung-Ming; Lee, Jian-Der; Shu, Wei-Hao; Chen, Tsung-Te

2006-12-01

225

Dielectric Properties of the Lamellar Niobates and Titanoniobates AM2Nb3O10 and ATiNbO5 (A ) H, K, M )  

E-print Network

. Revised Manuscript Received March 31, 1999 The dielectric properties of layer perovskites in the Dion the dielectric properties and the condensation reactions of these lamellar materials are of interest, becauseDielectric Properties of the Lamellar Niobates and Titanoniobates AM2Nb3O10 and ATiNbO5 (A ) H, K

226

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

227

Extraordinary refraction and self-collimation properties of multilayer metallic-dielectric stratified structures  

NASA Astrophysics Data System (ADS)

The extraordinary refraction with negative or zero refraction angle of the layered metamaterial consisting of alternating dielectric and plasmonic layers is theoretically studied. It is shown that the electromagnetic properties can be tuned by the filling factor, the permittivity of the dielectric layer and the plasma frequency of the metallic layer. At different frequency, the layered structures possess different refraction properties with positive, zero or negative refraction angle. By choosing appropriate parameters, positive-to-zero-to-negative-to positive refraction at the desired frequency can be realized. At the frequency with flat equal frequency contour, self-collimation and slow light properties are also found. Such properties can be used in the performance of negative refraction, subwavelength imaging and information propagation.

Zhang, Liwei; Chen, Liang; Zhang, Zhengren; Wang, Wusong; Zhao, Yuhuan; Song, Kechao; Kang, Chaoyang

2015-01-01

228

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

229

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

SciTech Connect

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

Srivastava, Geetika; Umarji, A. M. [Materials Research Centre, Indian Institute of Science, Bangalore-560 012 (India); Maglione, Mario [ICMCB, Universite de Bordeaux,-CNRS, 87, Av Dr Schweitzer 33806 Pessac (France)

2012-12-15

230

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

231

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

SciTech Connect

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

Ramesh, G. [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India)] [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Subramanian, V., E-mail: manianvs@iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Sivasubramanian, V. [Condensed Matter Physics Division, Indira Gandhi Center for Atomic Research, Kalpakkam -603 102 (India)] [Condensed Matter Physics Division, Indira Gandhi Center for Atomic Research, Kalpakkam -603 102 (India)

2010-12-15

232

Microwave Dielectric Properties of Ceramic and Nanocomposite Titanates of Transition Metal  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

233

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

234

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°-500°C) with an impedance analyser revealed that the dielectric constant increases with increase in Gd concentration as well temperature and the compound do not have any dielectric anomaly in the studied frequency and temperature range.

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

2014-04-01

235

Studies on the electrical and dielectric properties of chemically synthesized ?-PbO nanoparticles  

NASA Astrophysics Data System (ADS)

Lead(II) oxide nanoparticles have two forms namely the ?-PbO with tetragonal structure and ?-PbO with orthorhombic structure. The ?-PbO nanoparticles were synthesized via simple chemical precipitation method. The morphology of the nanocrystallites was characterized by XRD technique which revealed that the synthesized nanocrystallite belongs to the ?-PbO phase. The impedance spectroscopy was used to study the electrical and dielectric properties such as dielectric constant, dielectric loss, impedance, and AC conductivity as a function of frequency of the applied electric field and temperature. The results indicated the effective contributions of the grain boundaries are predominant due to the fact that smaller nanoparticles have larger specific surface area which means increased fraction of grain boundaries.

Mythili, N.; Arulmozhi, K. T.

2015-01-01

236

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

SciTech Connect

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

Mohanty, N. K., E-mail: Banarjibehera@gmail.com; Behera, A. K., E-mail: Banarjibehera@gmail.com; Satpathy, S. K., E-mail: Banarjibehera@gmail.com; Behera, B., E-mail: Banarjibehera@gmail.com; Nayak, P., E-mail: Banarjibehera@gmail.com [School of Physics, Sambalpur University, Jyoti Vihar, Burla-768019, Odisha (India)

2014-04-24

237

Investigation of the structural and microwave dielectric properties of mechanically alloyed Fe40Co60 powders  

NASA Astrophysics Data System (ADS)

Fe40Co60 powders were produced by mechanical Alloying (MA) route. Structural and microwave dielectric properties were investigated. Discussion of obtained results is conducted according to milling time. X-Ray powder Diffraction (XRD) shows that disordered ? (Fe40Co60) solid solution of substitution with body centered cubic (bcc) lattice is formed after 2h milling. Halder Wagner analysis reveals that least grain size of 15.59 nm and residual strain up to 0.8% are reached after 60h milling. The evolution of the Voigtian mixing factors according to milling progression confirms that structural properties are governed by residual strain accumulated during high- energy mechanical alloying (Gaussian profiles). Scanning Electron Microscopy (SEM) indicates that obtained powders adopt flattened angular shapes with high surface area. Microwave measurements are undertaken on bulk samples. High values of the dielectric permittivity depicting the conductive behavior of Fe-Co powders are measured. Dielectric permittivity spectra according to milling time shift towards higher values. Enhancement of the dielectric properties is related to the developed structure after milling.

Otmane, F.; Bergheul, S.; Triaa, S.; Azzaz, M.

2014-08-01

238

Temperature Dependence of Dielectric and Ferroelectric Properties of BiFeO3 Thin Films  

SciTech Connect

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

Biegalski, Michael D [ORNL; Jang, J H [Univeristy of Wisconsson; Bark, C [University of Wisconsin, Madison; Eom, Professor Chang-Beom [University of Wisconsin, Madison

2009-01-01

239

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

PubMed Central

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

Raudino, A; Mauzerall, D

1986-01-01

240

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

241

IEEE Transactions01 Dielectrics and ElectricalInsulation Vol.5 No. 3,June 1998 StaticElectrificationof Pressboard/Oil  

E-print Network

Electrificationof Pressboard/Oil Interface and TransientPhenomena ABSTRACT The static electrificationphenomenonof and immersed in a metallic tank containing -4 1of oil; and second vice enables us to measure the electrostaticcharge tendency of oils. The electrostaticcharge ndency (ECT) of insulatingoilsand

Paris-Sud XI, Université de

242

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

243

Static and dynamic elastic properties of rocks from the Canadian Shield  

Microsoft Academic Search

As part of a number of research studies in the Canadian Shield associated with the stability of underground mine openings, seismic reflection surveys, and the proposed use of a tunnel-boring machine (TBM) for developing mine headings, a long-term laboratory rock mechanics program has been conducted to determine the static and dynamic elastic properties of samples of igneous and metamorphic rocks

M KING

1983-01-01

244

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

245

Static magnetic and microwave properties of Li-ferrite films prepared by pulsed laser deposition  

E-print Network

Static magnetic and microwave properties of Li-ferrite films prepared by pulsed laser deposition F University, Fort Collins, Colorado 80523 Highly textured Li-ferrite films have been synthesized by pulsed approaching 1000 °C the growth mode was predominantly 333 . A similar growth mode was recently reported for Ni-ferrite

Patton, Carl

246

Static and dynamic properties of hydrogenated amorphous silicon with voids S. Chakraborty  

E-print Network

Static and dynamic properties of hydrogenated amorphous silicon with voids S. Chakraborty 2009 We have employed ab initio techniques to study the structure and dynamics of voids in amorphous Si and hydrogenated amorphous silicon. Reconstruction effects at void surfaces and dynamical effects associated with H

Drabold, David

247

Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data  

E-print Network

Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data Report Type: Annual Technical Report Reporting Period Start Date: October 1, 2002 Reporting Period Liu, Guohua Gao & Ruijian Li Date Report Issued: March 2004 DOE Award Number: DE-FC26-00BC15309

Reynolds, Albert C.

248

Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data  

E-print Network

Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data Report Type: Annual Technical Report Reporting Period Start Date: October 1, 2001 Reporting Period, Yannong Dong, Jan Arild Skjervheim & Ning Liu Date Report Issued: January 2003 DOE Award Number: DE-FC26

Reynolds, Albert C.

249

Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data  

E-print Network

Report Title: Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data Report Type: Annual Technical Report Reporting Period Start Date: October 1, 2000 Reporting Period, Ruijian Li, Yafes Abacioglu & Yannong Dong Date Report Issued: December 2001 DOE Award Number: DE-FC26

Reynolds, Albert C.

250

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

NASA Astrophysics Data System (ADS)

A number of adaptive structure applications call for the generation of intense electric fields (in excess of 70 MV/m). Such intense fields across the thickness of a thin polymer dielectric layer are typically used to exploit the direct electromechanical coupling in the form of a Maxwell stress: (see manuscript) Where V/d is the applied field, ?0 is the permittivity of vacuum and ? is the relative permittivity of the material. The field that can be applied to the dielectric is limited by the dielectric strength of the material. Below the limit set by the breakdown, the material is generally assumed to have a field independent dielectric constant and to be a perfect insulator, i.e. to have an infinite volume resistivity. While extensive investigations about the mechanical properties of the materials used for electronic Dielectric Elastomer Actuators (DEA) are available from literature, the results of the investigation of the insulating and dielectric properties of these materials, especially under conditions (electric field and frequency) similar to the ones encountered during operation are not available. In the present contribution, we present a method and a set-up for the measurement of the electric properties of thin polymer films, such as the ones used for the fabrication of electronic DEAs, under conditions close to operations. The method and setup where developed to investigate the properties of 'stiff' thin polymer films, such as Polyimide or Polyvinylidenefluoride, used for Electro-Bonded Laminates (EBLs). The properties of the well known VHB 4910 acrylic elastomer are presented to illustrate how the permittivity and the leakage current can be measured as a function of the electric field and the deformation state, using the proposed set-up. The material properties were measured on membranes under different fixed pre-stretch conditions (? 1, ?2=3, 4, 5), in order to eliminate effects due to the change in sample geometry, using gold sputtered electrodes, 20nm thick. The values obtained for the permittivity of the material are in good agreement with the work of other authors. The dissipative properties revealed by the measurements performed at high fields, similar to the ones encountered in operation, indicate that this less investigated aspect of VHB needs to be taken in consideration for real world applications.

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

2011-04-01

251

MWCNTs/SiO2 Composite System: Carrier Transmission, Twin-Percolation and Dielectric Properties  

NASA Astrophysics Data System (ADS)

We synthesize composite systems of multi-wall carbon nanotubes (MWCNTs)/SiO2 by using the sol-gel method. The dielectric properties of the systems with different-concentration MWCNTs are studied. In our MWCNTs/SiO2 inorganic systems, the twin-percolation phenomenon exists when the concentrations of MWCNTs are 5-10% and 15-20%. The permittivity and conductivity have jumping changes. The twin-percolation phenomenon is attributed to the special transfer mechanism of MWCNTs in the system, determined by hopping and migrating electrons. Variations of dielectric properties and conductance of the MWCNTs/SiO2 systems are conformed to the percolation theory. The special percolation phenomenon and electric properties of MWCNTs/SiO2 can help us comprehend the conductivity mechanism of the MWCNTs/SiO2 systems effectively, and promote the development of a high performance function composite system.

Cao, Wen-Qiang; Lu, Ming-Ming; Wen, Bo; Chen, Yuan-Lu; Li, Hong-Bo; Yuan, Jie; Cao, Mao-Sheng

2011-10-01

252

Effect of erythrocytes oscillations on dielectric properties of human diabetic-blood  

NASA Astrophysics Data System (ADS)

It has been demonstrated that the erythrocytes (RBCs) oscillate during their tank-treading motion with high-frequency oscillations. This oscillatory motion drastically affects the dielectric and electrical properties of RBCs. Moreover, the glucose level in blood affects the electrical and dielectric properties of blood. It has been, also, shown that the frequency of these oscillations exponentially decrease from 1.2 MHz down to 0.85 MHz with variation of glucose level from 85 mg/dL up to 346.1 mg/dL. It is expected that these oscillations strongly affect the general physiological properties of blood and would stimulate the curiosity of scientists and bioengineers to present new, more efficient, rapid, safe and viable diagnostic and/or therapeutic methods for blood disorders; in particular diabetes.

Abdalla, S.

2011-03-01

253

Short-wavelength static optical recording properties of nickel phthalocynine thin film  

Microsoft Academic Search

Nickel phthalocyanine thin film was prepared by vacuum deposition, the absorption and transmission spectra, the thermal stability of the film were reported. And the static optical recording properties of the thin film were investigated with a self-developed short-wavelength optical tester with high NA objective lens. The results show that this film occupied suitable absorption and transmission properties for short-wavelength (514.5

Yiqun Wu; Yang Wang; Donghong Gu; Fuxi Gan

2003-01-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

255

Effects of "Natural" Water and "Added" Water on Microwave Dielectric Properties of Shelled Corn at Microwave Frequencies  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of samples of shelled corn of “natural” water content and those prepared by adding water were measured in free space at microwave frequencies and 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 6 GHz show no difference betw...

256

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

257

Influence of gate dielectrics on the electrical properties of F8T2 polyfluorene thin-film transistors  

E-print Network

deposited by LPCVD and PECVD techniques, aluminum oxide deposited by sputtering, titanium oxide deposited. The following dielectrics were used as the gate insulator: titanium oxide (TiO2), aluminum oxide (Al2O3), lowInfluence of gate dielectrics on the electrical properties of F8T2 polyfluorene thin

Kanicki, Jerzy

258

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

259

Dielectric properties of lead-free BZT-KNN perovskite ceramics for energy storage.  

PubMed

Lead-free (1-x)Ba(Zr?.??Ti?.??)O?-x(K?.?Na?.?)NbO? ; x=0-0.05) (BZT-KNN) perovskite ceramics, a materials with potential applications for energy storage, are investigated. The samples are prepared by a solid-state reaction method. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to study the microstructure of the samples. Their dielectric properties and impedance spectra are reported as functions of temperature and frequency. The addition of 1?mol?% (K?.?Na?.?)NbO? to Ba(Zr?.??Ti?.??)O? improves the dielectric constant and enhances its diffuseness in a wide temperature range. The small amount of (K?.?Na?.?)NbO? is found to markedly affect the microstructure of the Ba(Zr?.??Ti?.??)O? ceramic (grain size and other characteristics) without changing the phase or crystal symmetry. In addition, we report that fine substructures in the grains, so-called sheet structures, are responsible for the dielectric properties (both diffuseness and dielectric constant) of (1-x)Ba(Zr?.??Ti?.??)O?-x(K?.?Na?.?)NbO? (x=0-0.03; especially x=0.01) ceramics. PMID:21994154

Gui, Dong-Yun; Liu, Han-Xing; Hao, Hua; Sun, Yue; Cao, Ming-He; Yu, Zhi-Yong

2011-10-17

260

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

261

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

262

Static and dynamic elastic properties of rocks from the Canadian Shield  

SciTech Connect

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

King, M.S.

1983-01-01

263

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

264

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

265

Guiding properties of asymmetric hybrid plasmonic waveguides on dielectric substrates  

PubMed Central

We proposed an asymmetric hybrid plasmonic waveguide which is placed on a substrate for practical applications by introducing an asymmetry into a symmetric hybrid plasmonic waveguide. The guiding properties of the asymmetric hybrid plasmonic waveguide are investigated using finite element method. The results show that, with proper waveguide sizes, the proposed waveguide can eliminate the influence of the substrate on its guiding properties and restore its broken symmetric mode. We obtained the maximum propagation length of 2.49?×?103 ?m. It is approximately equal to that of the symmetric hybrid plasmonic waveguide embedded in air cladding with comparable nanoscale confinement. PMID:24406096

2014-01-01

266

Effects of ?-radiation on dielectric properties of LDPE-Al2O3 nanocomposites  

NASA Astrophysics Data System (ADS)

Until now several methods for processing and characterization have been tested, and some theories and models have been proposed for these materials having a huge nanofiller-polymer interface area which seems to be the main responsible for their unique properties. The accelerated testing by irradiation of LDPE has been extensively studied in order to assess optimized formulation. The present paper characterizes LDPE modified with Al2O3 nanoparticles. The dispersed nanofiller was added in various concentrations (2, 5 and 10 wt%). The accelerated aging under ?-irradiation was accomplished for evaluation of material behavior to hard stressing environment. Dielectric properties (real part of the permittivity and tan delta) and oxidation resistance were discussed. An improvement of the dielectric losses is noticed for the tested nanocomposites at a radiation dose up to 20 kGy. The radiochemical stability studied by chemiluminescence provides satisfactory stability in the correlation with slight modification of basis polymer due to the inert feature of filler.

Ciuprina, Florin; Zaharescu, Traian; Ple?a, Ilona

2013-03-01

267

Optical properties of nanowire dimers with a spatially nonlocal dielectric function.  

SciTech Connect

We study the optical spectra and electromagnetic field enhancements around cylindrical and triangular Ag nanowire dimers, allowing for a spatially nonlocal dielectric function that partially accounts for quantum mechanical effects. For the triangular structures, we pay particular attention to how these properties depend on the sharpness of the nanowire's tips. We demonstrate that significant differences exist from classical electrodynamics that employs a more common, spatially local dielectric function. These differences are shown to arise from the optical excitation of volume plasmons inside of the structures, analogous to one-particle quantum mechanical states, which lead to complex and striking patterns of material polarization. These results are important for further understanding the optical properties of structures at the nanoscale and have implications for numerous physical processes, such as surface-enhanced Raman scattering.

McMahon, J. M.; Gray, S. K.; Schatz, G. C. (Center for Nanoscale Materials); ( CSE); (Northwestern Univ.)

2010-09-01

268

Nondestructive approach for measuring temperature-dependent dielectric properties of epoxy resins.  

PubMed

A practical method for measuring the complex relative permittivity of epoxy resins and other viscous liquids over a wide temperature range in S-band is presented. The method involves inserting a hot glass tube, filled with the liquid-under-test (LUT), into a length of WR-340 rectangular waveguide connected between two ports of a Vector Network Analyzer, which measures the reflection and transmission coefficients at 2.45 GHz. The heating arrangement consists of a temperature-controlled glycol bath, where the LUT-filled glass tube is placed. The dielectric properties are determined using an optimization routine, which minimizes the error between the theoretical and measured scattering coefficient data. The theoretical values of the scattering coefficient data are computed with the help of a numerical 3-D electromagnetic field simulator, the CST Microwave Studio. The dielectric properties of the empty glass tube (required by the simulation code) are also measured using the above methodology. PMID:19227067

Akhtar, M Jaleel; Feher, Lambert E; Thumm, Manfred

2008-01-01

269

On the Dielectric Properties of the Martian-like Surface Sediments  

NASA Technical Reports Server (NTRS)

We have undertaken laboratory electromagnetic characterization of the total set of minerals identified by TES on the Martian surface in order to investigate experimentally the dielectric properties of the sediments covering it in the frequency range from 1 to 30 MHz. Volcanic Rocks with a well defined mineralogy and petrology from potential terrestrial analogues sites have also been included in the study. Our primary objective is to evaluate the range of electrical and magnetic losses that may be encountered by the various Radar sounding and imaging experiments dedicated to map the Martian subsurface searching for underground water. The electromagnetic properties of these Mars-like materials will be presented as a function of various geophysical parameters, such as porosity, bulk density and temperature. The secondary objective, is to locate regions were surface dielectric conditions are suitable for subsurface sounding.

Heggy, E.; Clifford, S. M.; Morris, R. V.; Paillou, P.; Ruffie, G.

2004-01-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

271

Structural properties and electrical characteristics of high- k Dy 2O 3 gate dielectrics  

NASA Astrophysics Data System (ADS)

This paper describes the structural properties and electrical characteristics of thin Dy2O3 dielectrics deposited on silicon substrates by means of reactive sputtering. The structural and morphological features of these films after postdeposition annealing were studied by X-ray diffraction and X-ray photoelectron spectroscopy. It is found that Dy2O3 dielectrics annealed at 700 °C exhibit a thinner capacitance equivalent thickness and better electrical properties, including the interface trap density and the hysteresis in the capacitance-voltage curves. Under constant current stress, the Weibull slope of the charge-to-breakdown of the 700 °C-annealed films is about 1.6. These results are attributed to the formation of well-crystallized Dy2O3 structure and the reduction of the interfacial SiO2 layer.

Pan, Tung-Ming; Chang, Wei-Tsung; Chiu, Fu-Chien

2011-02-01

272

MICROWAVE DIELECTRIC METHODS FOR SENSING PHYSICAL PROPERTIES OF GRANULAR MATERIALS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

273

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

NASA Astrophysics Data System (ADS)

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 reflections. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging.

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

2009-03-01

274

Dielectric, electromechanical, optical, and mechanical properties of lanthanum-modified lead titanate ceramics  

Microsoft Academic Search

Dielectric, electromechanical, optical, and mechanical properties of hot-pressed lanthanum-modified PbTiOâ ceramics were measured as a function of crystal tetragonality, c\\/a, in a range of tetragonal-to-cubic phases. The results obtained in this study are summarized as follows: The c\\/a changes linearly as a function of lanthanum content. Similarly, Curie point changed linearly and remanent polarization, coercive field, and coupling factors decreased

T. Yamamoto; HIDEJI IGARASHI; KIYOSHI OKAZAKI

1983-01-01

275

Magnetic and dielectric properties of Ba12Fe28Ti15O84 layered ferrite ceramics  

Microsoft Academic Search

In this study we report for the first time the magnetic and dielectric properties of the quaternary layered ferrite Ba12Fe28Ti15O84. Dense ferrite ceramics were prepared by conventional sintering using powders obtained by solid-state reaction and by coprecipitation. Only the latter powder resulted in nearly single phase ceramics, whereas larger amounts of secondary phases were observed in the material obtained by

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

2011-01-01

276

Crystal structure and dielectric and magnetic properties of BiCrO 3 as a ferroelectromagnet  

Microsoft Academic Search

We have investigated crystal structure, dielectric and magnetic properties of BiCrO3. The structure of BiCrO3 at room temperature is a highly distorted perovskite-type one with monoclinic C2 symmetry which is the same as that of the ferroelectric phase in BiMnO3. BiCrO3 undergoes a structural phase transition from orthorhombic Pnma with centrosymmetry to monoclinic C2 without centrosymmetry at 440 K. It

S. Niitaka; M. Azuma; M. Takano; E. Nishibori; M. Takata; M. Sakata

2004-01-01

277

Effect of presintering on the dielectric and mechanical properties of porous reaction-bonded silicon nitride  

Microsoft Academic Search

This paper presents the influence of presintering on the dielectric and mechanical properties of porous silicon nitride ceramics which were prepared by reaction sintering in flowing nitrogen atmosphere. Si3N4 ceramics containing 0.8mm spherical pores in diameter and with porosity of about 53% were made by adding 30% in mass pore-forming agent grains prepared by spray prilling. Green bodies were subjected

Jie Xu; Fa Luo; Dongmei Zhu; Xiaolei Su; Wancheng Zhou

2008-01-01

278

Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz  

SciTech Connect

Dielectric properties (i.e., permittivity) are essential in designing, simulating, and modeling microwave applications. The permittivity of stacked leaves of alfalfa (Medicago sativa) were measured with a network analyzer and a coaxial probe, and the effect of moisture content (MC: 12% 73% wet basis), frequency (300 MHz to 18 GHz), bound water (Cole Cole dispersion equation), temperature ( 15 C and 30 C), leaf-orientation, and pressure (0 11 kPa) were investigated. The measured permittivity increased with MC. A critical moisture level (CML) of 23% was reported, below which the permittivity decreased with increasing frequency at 22 C. Above CML and up to 5 GHz, the dielectric constants followed the Cole Cole dispersion, and the dielectric loss factors consisted of ionic and bound water losses. Above 5 GHz, the behavior of the dielectric constant was similar to that of free water, and the polar losses became dominant. Above 0 C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0 C, it was dominated by nonfreezing bound and unfrozen supercooled moistures. The relaxation parameters and the optimum pressure (9 kPa) for the leaf measurements were determined. The effects of variations among the samples, and their orientations had negligible effects on the measured permittivity.

Sokhansanj, Shahabaddine [ORNL; Shrestha, Bijay [University of Saskatchewan; Wood, H.C. [University of Saskatchewan

2011-01-01

279

Magnetic and dielectric properties of Ba12Fe28Ti15O84 layered ferrite ceramics  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

280

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; Han, Jung Hoon; Kim, Kee Hoon

2014-01-01

281

Charge trapping properties of alternative high-kappa dielectrics in MOS devices  

NASA Astrophysics Data System (ADS)

High-kappa dielectrics are promising candidates to replace SiO 2 in advanced integrated circuits in future space systems. Studies of the effects of ionizing radiation and bias-temperature stress (BTS) on high-kappa dielectrics were performed. Trapped charge densities are evaluated as functions of temperature and stress time. Prior radiation exposure enhances BTS-induced degradation in these devices. Worst-case responses in combined effects are positive (or zero) bias irradiation followed by NBTS for HfO2-based devices. Degradation due to oxide or interface trap-charge changes in magnitude with the bias polarity during switched-bias annealing either after irradiation or constant voltage stress (CVS). This demonstrates that metastable electron trapping (dominant during post-rad annealing) and hydrogen transport and reactions (dominant during post-CVS annealing) in the near-interfacial dielectric layers play significant roles in the defect formation process. Additional defect growth with time was observed as a result of additional charge injection through the gate stacks during the annealing process. These results provide insights into fundamental trapping properties of high-kappa dielectrics and can be used to help predict long-term reliability of these devices.

Zhou, Xing

282

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

283

Change in the Dielectric Properties of Normal and Relaxor Ferroelectric Ceramic Composites in BT-PZT and PMN-PZT Systems by an Uniaxial Compressive Stress  

Microsoft Academic Search

Effects of an uniaxial compressive pre-stress on the dielectric properties of normal and relaxor ferroelectric ceramic composites in BT-PZT and PMN-PZT systems are investigated. The dielectric properties are observed under the compressive pre-stress levels up to 15 and 5 MPa for BT-PZT and PMN-PZT, respectively, using a uniaxial compressometer. Both the dielectric constant and the dielectric loss tangent of the

Rattikorn Yimnirun

2006-01-01

284

Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth.  

PubMed

Water is a major component of fluids in the Earth's mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water-rock interactions and, in general, our understanding of aqueous fluids below the Earth's crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth's upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)--insoluble in water under ambient conditions--becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The Earth's deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones. PMID:23513225

Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A; Galli, Giulia

2013-04-23

285

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

NASA Astrophysics Data System (ADS)

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

Jotania, Rajshree; Chanmal, Chetan; Jog, Jyoti

286

Multiferroic oxides: Growth of single crystals and investigation of their magnetic, dielectric and ferroelectric properties  

NASA Astrophysics Data System (ADS)

In this talk, special emphasis will be placed on the crystal growth of various oxides by the floating zone technique using optical furnaces. Oxides such as the RMnO3 compounds exhibit a strong coupling between the magnetic and dielectric properties and some of them exhibit multiferroic behavior. LuFe2O4 is another example of a multiferroic crystal, but in this system, the observed ferroelectric polarisation arises due to the charge ordering and electron correlation effects as opposed to the normally observed polarisation due to ionic displacements. In order to understand the emergence of multiferroic behaviour in the RMnO3 compounds, we have produced single crystals of several pure and substituted RMnO3 compounds and investigated the effects of lattice modulations on the magnetic and dielectric properties. The crystal growth of the LuFe2O4 multiferroic compounds and the investigation of the magnetic, dielectric and ferroelectric properties of these crystals will also be presented.

Balakrishnan, Geetha

2013-02-01

287

Dielectric, piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics  

NASA Astrophysics Data System (ADS)

Specimens of Pb1-1.5 x La x (Zr0.53Ti0.47)1- y- z Fe y Nb z O3 ( x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01) (PZTFN) ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal (space group P4 mm) and rhombohedral (space group R3 c) phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hysteresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response at x ? 0.012, which corresponds to the morphotropic phase boundary (MPB).

Kumar, Arvind; Mishra, S. K.

2014-10-01

288

Effect of temperature on the dielectric properties of carbon black-filled polyethylene matrix composites below the percolation threshold  

NASA Astrophysics Data System (ADS)

The temperature dependence of dielectric properties of carbon black-filled polyethylene matrix composites below the percolation threshold was studied based on the effect medium approximation theory (EMA theory). Although the literature on calculation based on the EMA theory by changing the parameters is vast, an overall discussion taking into account the EMA theory is required to explain the dielectric properties of the composites and their temperature dependence. Changes of the dielectric properties of carbon black-filled PMC and their temperature dependence below the percolation threshold for the volume fraction of carbon black have been discussed based on the EMA theory. The composites satisfy the universal law of conductivity above the percolation threshold, whereas it gives the critical exponent of s = 1 for dielectric constant below percolation threshold. The rates of the decrement of both % changes of dielectric constant and dielectric loss factor for temperature become larger with an increase in the volume fraction below percolation threshold. By incorporating the effect of thermal expansion into the EMA theory, the temperature dependence of dielectric properties is successfully explained.

Shin, Soon-Gi; Kwon, In-Kyu

2011-09-01

289

Dielectric properties of halloysite and halloysite-formamide intercalate  

SciTech Connect

Due to a high increase in electromagnetic pollution, the protection from non-ionizing electromagnetic radiation (EMR) represents an important problem of contemporary environmental science. We are searching for natural materials with the potential for EMR screening. We have discovered that hydro-halloysite has interesting properties as an EMR absorber. Unfortunately, it is a very unstable material. Drying it for even a short period of time leads to the loss of desired properties. In the paper, we have demonstrated that the intercalation of halloysite (the process of introducing guest molecules into the mineral structure) makes it possible to recover the ability to absorb an electromagnetic wave and obtain a promising material for electromagnetic field shielding applications.

Adamczyk, M., E-mail: mariusz.adamczyk@chem.uni.wroc.pl; Rok, M.; Wolny, A.; Orzechowski, K. [Faculty of Chemistry, University of Wroclaw, Wroclaw 50-383 (Poland)

2014-01-14

290

Structure and dielectric properties of composite material based on surface-modified BaTiO3 nanoparticles in polystyrene  

NASA Astrophysics Data System (ADS)

This article reports on studies of the structure and dielectric properties of composites materials based on BaTiO3 nanoparticles in the polymer matrix. It is shown that nanoparticles of barium titanate obtained by peroxide method, have surface enriched hydroxyl (-OH) groups, which allow the formation of strong chemical bonds with the molecules of surfactant. This surface modification prevents agglomeration of nanoparticles, which leads to heterogeneity of mechanical and dielectric properties of the composites. It is shown that the effective dielectric constant for the studied composite material agrees well with the modified Kerner equation for the volume content of nanoparticles within the range from 5 to 35%.

Emelianov, Nikita

2015-01-01

291

Computational study of dielectric function and optical properties of a graphane nano structure containing graphene quantum dot  

NASA Astrophysics Data System (ADS)

Ab-Initio computational study of dielectric function and optical properties of a graphane nano structure containing graphene quantum dot has been undertaken within Density Functional Theory using SIESTA code. Band structure, PDOS, real and imaginary parts of dielectric function, reflectance and energy loss have been calculated and frequencies corresponding to peak positions have been tabulated for each case. A comparison has been made with the corresponding properties of pristine graphene.

Dhar Sharma, Jyoti; Sharma, Munish; Kumar, Naveen; Ahluwalia, P. K.

2013-11-01

292

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

PubMed

The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties. PMID:17473342

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

2007-05-21

293

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

294

Static and dynamic properties of the structural phase transitions in NaNbO3  

Microsoft Academic Search

The static and dynamic properties which characterize the structural phase transitions in NaNbO3 have been widely investigated by transient NMR measurements of the Na23 and Nb93 nuclei in a powdered sample (no large-enough single crystal was available). The temperature range investigated (100-1100 °K) includes both the purely structural transitions associated with the tilting of the NbO6 octahedra and the ferroelectric

A. Avogadro; G. Bonera; F. Borsa; A. Rigamonti

1974-01-01

295

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

296

Quasi-static and high strain rate properties of a cross-ply metal matrix composite  

Microsoft Academic Search

A series of compression tests has been carried out at quasi-static and high strain rates on cylindrical samples of an alumina fiber\\/Al-6061 metal matrix composite. The composite plates were prepared with fibers in the 0°, 0\\/90° and ±45° orientations. It was found that the mechanical properties were strongly dependent upon the imposed strain rate, with fracture stress increases of >50%

I. W. Hall; A. Tasdemirci; J. Derrick

2009-01-01

297

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

E-print Network

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

Duojie Jia; Xiao-wei Wang; Feng Liu

2009-12-28

298

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

E-print Network

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

Jia, Duojie; Liu, Feng

2009-01-01

299

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

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Electrorotation offers a non-invasive tool for dielectric analysis of fish embryos. Black-Right-Pointing-Pointer The three-shell dielectric model matches the rotation spectra of medaka eggs. Black-Right-Pointing-Pointer The capacitance value suggests a double-membrane structure of yolk envelope. -- Abstract: The Japanese medaka fish, Oryzias latipes, has become a powerful vertebrate model organism in developmental biology and genetics. The present study explores the dielectric properties of medaka embryos during pre-hatching development by means of the electrorotation (ROT) technique. Due to their layered structure, medaka eggs exhibited up to three ROT peaks in the kHz-MHz frequency range. During development from blastula to early somite stage, ROT spectra varied only slightly. But as the embryo progressed to the late-somite stage, the ROT peaks underwent significant changes in frequency and amplitude. Using morphological data obtained by light and electron microscopy, we analyzed the ROT spectra with a three-shell dielectric model that accounted for the major embryonic compartments. The analysis yielded a very high value for the ionic conductivity of the egg shell (chorion), which was confirmed by independent osmotic experiments. A relatively low capacitance of the yolk envelope was consistent with its double-membrane structure revealed by transmission electron microscopy. Yolk-free dead eggs exhibited only one co-field ROT peak, shifted markedly to lower frequencies with respect to the corresponding peak of live embryos. The dielectric data may be useful for monitoring the development and changes in fish embryos' viability/conditions in basic research and industrial aquaculture.

Shirakashi, Ryo, E-mail: aa21150@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan)] [Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan); Mischke, Miriam [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)] [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Fischer, Peter [Physiologische Chemie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)] [Physiologische Chemie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Memmel, Simon [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)] [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Krohne, Georg [Abteilung fuer Elektronenmikroskopie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)] [Abteilung fuer Elektronenmikroskopie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Fuhr, Guenter R. [Lehrstuhl fuer Biotechnologie und Medizintechnik, Universitaet des Saarlandes, Saarbruecken (Germany)] [Lehrstuhl fuer Biotechnologie und Medizintechnik, Universitaet des Saarlandes, Saarbruecken (Germany); Zimmermann, Heiko [Lehrstuhl fuer Molekulare und Zellulaere Biotechnologie, Universitaet des Saarlandes, Saarbruecken (Germany)] [Lehrstuhl fuer Molekulare und Zellulaere Biotechnologie, Universitaet des Saarlandes, Saarbruecken (Germany); Sukhorukov, Vladimir L., E-mail: sukhorukov@biozentrum.uni-wuerzburg.de [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)

2012-11-09

300

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

301

Dielectric properties of WS2-coated multiwalled carbon nanotubes studied by energy-loss spectroscopic profiling  

NASA Astrophysics Data System (ADS)

We investigate experimentally the electronic properties of the coating for multiwalled carbon nanotubes covered in tungsten disulfide (WS2) of various thicknesses. Coatings of thicknesses between 2 and 8 monolayers (ML) are analyzed using energy-loss spectroscopic profiling (ELSP), by studying the variations in the plasmon excitations across the coated nanotube, as a function of the coating thickness. We find a change in the ELSP for coatings above 5 ML thickness, which we interpret in terms of a change in its dielectric properties.

Stolojan, Vlad; Silva, S. R. P.; Goringe, Michael J.; Whitby, R. L. D.; Hsu, Wang K.; Walton, D. R. M.; Kroto, Harold W.

2005-02-01

302

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

303

Structure, composition and microwave dielectric properties of bismuth zinc niobate pyrochlore thin films  

NASA Astrophysics Data System (ADS)

(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 (BZN) pyrochlore thin films were deposited onto both Pt/TiO2/SiO2/Si and polycrystalline alumina substrates using pulsed laser deposition technique and then post-annealed using rapid thermal processing. The deposition temperature varies from 300 °C to 600 °C, and all the BZN films showed cubic pyrochlore structure after annealing at 650 °C for 30 min in air. The influence of the substrate associated with crystal structure is significant in the as-deposited films and disappears after post-annealing. The dielectric properties as a function of frequency up to the microwave frequency in both films were measured by LCR meter and split-post dielectric resonator technique. It is found that the BZN film deposited at 400 °C and post-annealed at 650 °C shows excellent dielectric properties with low loss in the microwave frequency range. This result indicates that the BZN thin film is a potential microwave material.

Wang, Zhao; Ren, Wei; Zhan, Xuelei; Shi, Peng; Wu, Xiaoqing

2014-11-01

304

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

NASA Astrophysics Data System (ADS)

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

Sagar, Sadia; Iqbal, Nadeem; Maqsood, Asghari

2013-06-01

305

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

306

Structure-dielectric properties relationships in copper-substituted magnesium ferrites  

SciTech Connect

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

Druc, A.C.; Borhan, A.I. [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania); Nedelcu, G.G.; Leontie, L. [Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania); Iordan, A.R. [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania); Palamaru, M.N., E-mail: palamaru@uaic.ro [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania)

2013-11-15

307

Relative influence upon microwave emissivity of fine-scale stratigraphy, internal scattering, and dielectric properties  

USGS Publications Warehouse

The microwave emissivity of relatively low-loss media such as snow, ice, frozen ground, and lunar soil is strongly influenced by fine-scale layering and by internal scattering. Radiometric data, however, are commonly interpreted using a model of emission from a homogeneous, dielectric halfspace whose emissivity derives exclusively from dielectric properties. Conclusions based upon these simple interpretations can be erroneous. Examples are presented showing that the emission from fresh or hardpacked snow over either frozen or moist soil is governed dominantly by the size distribution of ice grains in the snowpack. Similarly, the thickness of seasonally frozen soil and the concentration of rock clasts in lunar soil noticeably affect, respectively, the emissivities of northern latitude soils in winter and of the lunar regolith. Petrophysical data accumulated in support of the geophysical interpretation of microwave data must include measurements of not only dielectric properties, but also of geometric factors such as finescale layering and size distributions of grains, inclusions, and voids. ?? 1976 Birkha??user Verlag.

England, A.W.

1976-01-01

308

Ferroelectric and dielectric properties of nanocrystalline BiFeO3 multiferroic ceramics synthesized by solution combustion method (SCM)  

NASA Astrophysics Data System (ADS)

Nanocrystalline multiferroic BiFeO3 ceramics was prepared by a novel solution combustion method (SCM). The X-ray diffraction (XRD) studies on structural properties of the synthesized ceramics reveal that the BiFeO3 ceramics has rhombhohedral perovskite structure with an average crystallite size of 15 nm. The ferroelectric P-E hysteresis loop measurement at room temperature shows unsaturated behavior with a partial reversal of polarization. Investigations on temperature dependence of dielectric constant in BiFeO3 demonstrate a clear dielectric anomaly at approximately around 380 °C, which corresponds to antiferromagnetic to paramagnetic phase transition (TN) and also evidences a possible coupling among the electric and magnetic dipoles of BiFeO3. A room temperature variation of dielectric constant " ?" and dielectric loss "tan ?" as a function of frequency in the range of 100 Hz — 1 MHz, confirms that both dielectric constant and loss are strong functions of frequency.

Chaudhari, Yogesh A.; Mahajan, Chandrashekhar M.; Abuassaj, Ebrahim M.; Jagtap, Prashant P.; Patil, Pramod B.; Bendre, Subhash T.

2013-04-01

309

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

PubMed

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

Mallick, Biswajit

2014-01-01

310

Laboratory studies of electrical properties of insulating materials. [thermal insulation of spacecraft dielectrics  

NASA Technical Reports Server (NTRS)

The characteristics of satellites are influenced by the electrical properties of the dielectric exterior. It was found in simulated space environment tests that the electrical conductivities of dielectrics are affected as the result of interactions with various components of the environment. The degree to which the conductivity was affected varied with material. In some instances the changes found to occur could be used to advantage, particularly if they could be enhanced. For example, the increased electrical conductivity of Kapton resulting from solar illumination could be used to advantage to eliminate the charge storage leading to electrical breakdown during magnetic substorms. Similarly the relative immunity of FEP Teflon to change from response to the space environment makes it a logical choice as a solar cell cover in a high-voltage solar array.

Nanevicz, J. E.; Adamo, R. C.; Grier, N.

1978-01-01

311

Structural and optical properties of different dielectric thin films for planar waveguiding applications  

NASA Astrophysics Data System (ADS)

Thin films of two different dielectric materials (Yttrium Oxide and Tantalum Pentoxide) were deposited by reactive sputtering and reactive evaporation to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The optical properties, structure and crystalline phase of the films were found to be dependent on the deposition method and process parameters. X-ray diffraction (XRD) analysis on several of the 'as-deposited' thin films revealed that the films vary from amorphous to highly crystalline depending on material and process parameters. SEM imaging of the Yttrium Oxide layers revealed a regular column structure confirming their crystalline nature and SEM imaging of the Tantalum Pentoxide layers revealed a smooth amorphous layer confirming their XRD diffractrograms. The dielectric thin film layers which allowed guiding in both the visible and infra-red regions of the spectrum had a more amorphous structure.

Pearce, S. J.; Charlton, M. D. B.; Parker, G. J.; Wilkinson, J. S.

2011-03-01

312

Frequency dependent dielectric properties in Schottky diodes based on rubrene organic semiconductor  

NASA Astrophysics Data System (ADS)

Al/rubrene/p-Si Schottky diode has been fabricated by forming a rubrene layer on p type Si by using the spin coating method. The frequency and voltage dependent dielectric constant (??), dielectric loss (??), tangent loss (tan?), electrical modulus (M? and M?), and ac electrical conductivity (?) properties of Al/rubrene/p-Si Schottky diodes have been investigated in the frequency range of 1 kHz-1 MHz at room temperature. It is found that the values of the ??, ?? and tan? decrease with increasing frequency while an increase is observed in ? and the real component (M?) of the electrical modulus. The values of ??, ??, and tan? were found as 5.01, 2.55, and 0.51 for 1 kHz and 2.46, 0.069, and 0.028 for 1 MHz at zero bias, respectively. Furthermore, the imaginary component (M?) of the electric modulus showed a peak that shifts to a higher voltage with decreasing frequency.

Bar??, Behzad

2013-12-01

313

Thickness-dependent dielectric and tunable properties of barium stannate titanate thin films  

NASA Astrophysics Data System (ADS)

Barium stannate titanate Ba(Sn0.15Ti0.85)O3 (BTS) thin films with different thicknesses were grown by sol-gel process on single crystal LaAlO3 (LAO) and Pt/Ti/SiO2/Si substrates, respectively. Coplanar capacitance and parallel plate capacitance structure configurations were formed by preparing interdigital electrodes and parallel plate electrodes on BTS thin films. Both of the films exhibited an enhanced dielectric constant and tunability as the film thickness increases but these two cases are actually based on different mechanisms. The thickness dependent dielectric properties of the films deposited on Pt/Ti/SiO2/Si substrates were mainly attributed to the "dead layer" effect while those of the films grown on LAO substrates were due to strain and grain size of the films.

Song, Sannian; Zhai, Jiwei; Gao, Lina; Yao, Xi; Lu, Shengbo; Xu, Zhengkui

2009-07-01

314

Dielectric and pyroelectric properties of lead zirconate titanate/polyurethane composites  

SciTech Connect

0-3 composite ranging between 0 and 3, of ferroelectric ceramic lead zirconate titanate (PZT) and thermoplastic elastomer polyurethane (PU) were fabricated. The pyroelectric and dielectric properties of the hot-pressed thin film samples of various PZT volume fractions were measured. The experimental dielectric permittivities and losses agreed reasonably well with the Bruggeman model. The room temperature pyroelectric coefficients of the composites were found to increase linearly with PZT volume fraction and substantially larger than expected. For example, for a composite with 30% PZT, its pyroelectric coefficient is about 90 {mu}C/m{sup 2}K at room temperature, which is more than tenfold of a PZT/PVDF composite of the same ceramic volume fraction. We propose a model in which the electrical conductivity of the composite system is taken into consideration to explain the linear relationship and the extraordinarily large pyroelectric coefficients obtained.

Lam, K.S.; Wong, Y.W.; Tai, L.S.; Poon, Y.M.; Shin, F.G. [Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong (China)

2004-10-01

315

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

316

Dielectric, magnetic and magnetoelectric properties of La and Nb codoped bismuth ferrite.  

PubMed

Single-phase Bi(0.80)La(0.20)FeO(3) (BLFO) and Bi(0.80)La(0.20)Fe(1-x)Nb(x)O(3) (BLFNO) samples were prepared in order to study the dielectric, magnetic and magnetoelectric properties of La and Nb codoped BiFeO3. Rietveld refinement of x-ray diffraction patterns of La and Nb codoped samples has been performed using the R3c space group. Magnetic hysteresis loops revealed that codoping can effectively increase the spontaneous magnetization due to change in the bond angle of Fe-O-Fe as a result of distortion created by the Nb5+ doping. Magnetic field-induced relative change of the dielectric constant for BLFO and BLFNO samples is a signature of magnetoelectric coupling. PMID:21914927

Singh, Hemant; Yadav, K L

2011-09-28

317

Dielectric Properties of Selected Tungsten Compounds from 60 MHz to 9.44 GHz  

NASA Astrophysics Data System (ADS)

Crystalline powders of tungsten compounds ammonium paratungstate, ammonium metatungstate, tungsten trioxide hydrate (WO 3 · H 2O), and tungsten blue oxide have been studied. The complex permittivity of the pulverized materials has been measured at room temperature from 60 MHz to 9.44 GHz. Intrinsic permittivity values of the crystalline solids have been derived from the apparent dielectric data of the powder material. Heating rate plots of powder samples of about 30 g at 2.45 GHz and 850 W radiation have also been taken. The slopes of the heating rate plots and the estimated dielectric loss factors of the crystalline solids are correlated. The experimentally observed microwave heating behavior and decomposition properties under microwave irradiation have been explained.

Pfeifer, J.; Csaba, I.; Elek, K.

1994-08-01

318

Influence of O2 on the dielectric properties of CO2 at the elevated temperatures  

NASA Astrophysics Data System (ADS)

SF6 gas is widely used in the high voltage circuit breakers but considering its high global warming potential other substitutes are being sought. Among them CO2 was investigated and even has been used in some practical products. However, at room temperature, the dielectric properties of CO2 are relatively lower than SF6 and air. The goal of this work is to investigate a CO2-based gas to improve the performance of the pure CO2. In this paper, the dielectric properties of hot CO2/O2 mixtures related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300 K to 4000 K and in the pressure range from 0.01 MPa to 1.0 MPa. The species compositions of hot CO2/O2 were obtained based on Gibbs free energy minimization under the assumptions of local thermodynamic equilibrium and local chemical equilibrium. The reduced critical electric field strength of CO2/O2 was determined by balancing electron generation and loss. These were calculated using the electron energy distribution function by solving the Boltzmann transport equation. The validity of the calculation method and the cross sections data was confirmed by comparing the measurements and calculations of the electron swarm data in previous work. The results indicate that in pure CO2 the critical electric field strength is higher only in higher temperature range. By adding the O2 into the CO2, the critical electric field strength at lower temperature is effectively enhanced. CO2/O2 mixtures have a much better dielectric strength than both the pure CO2 and air and thus have the potential to improve the CO2-based gas circuit breakers. Similar conclusions can also be found in others' work, which further confirm the validity of these results.

Rong, Mingzhe; Sun, Hao; Yang, Fei; Wu, Yi; Chen, Zhexin; Wang, Xiaohua; Wu, Mingliang

2014-11-01

319

The Viscoelastic Properties of Passive Eye Muscle in Primates. I: Static Forces and Step Responses  

PubMed Central

The viscoelastic properties of passive eye muscles are prime determinants of the deficits observed following eye muscle paralysis, the root cause of several types of strabismus. Our limited knowledge about such properties is hindering the ability of eye plant models to assist in formulating a patient's diagnosis and prognosis. To investigate these properties we conducted an extensive in vivo study of the mechanics of passive eye muscles in deeply anesthetized and paralyzed monkeys. We describe here the static length-tension relationship and the transient forces elicited by small step-like elongations. We found that the static force increases nonlinearly with length, as previously shown. As expected, an elongation step induces a fast rise in force, followed by a prolonged decay. The time course of the decay is however considerably more complex than previously thought, indicating the presence of several relaxation processes, with time constants ranging from 1 ms to at least 40 s. The mechanical properties of passive eye muscles are thus similar to those of many other biological passive tissues. Eye plant models, which for lack of data had to rely on (erroneous) assumptions, will have to be updated to incorporate these properties. PMID:19337381

Quaia, Christian; Ying, Howard S.; Nichols, Altah M.; Optican, Lance M.

2009-01-01

320

Si dielectric function in a local basis representation: Optical properties, local field effects, excitons, and stopping power  

NASA Astrophysics Data System (ADS)

An atomiclike basis representation is used to analyze the dielectric function ? (q ?+G ?,q ?+G?';? ) of Si. First, we show that a s p3d5 local basis set yields good results for the electronic band structure of this crystal and, then, we analyze the Si optical properties including local field and excitonic effects. In our formulation, we follow Hanke and Sham [W. Hanke and L. J. Sham, Phys. Rev. B 12, 4501 (1975), 10.1103/PhysRevB.12.4501; Phys. Rev. B 21, 4656 (1980), 10.1103/PhysRevB.21.4656], and introduce excitonic effects using a many-body formulation that incorporates a static screened electron-hole interaction. Dynamical effects in this interaction are also analyzed and shown to introduce non-negligible corrections in the optical spectrum. Our results are found in reasonable agreement with the experimental evidence and with other theoretical results calculated with the computationally more demanding plane-wave representation. Finally, calculations for the stopping power of Si are also presented.

Gómez, M.; González, P.; Ortega, J.; Flores, F.

2014-11-01

321

Transport and dielectric properties of water and the influence of coarse-graining: Comparing BMW, SPC/E, and TIP3P models  

SciTech Connect

Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough.

Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar [Department of Computational Biological Chemistry, University of Vienna, Währingerstrasse 17, A-1090 Vienna (Austria)] [Department of Computational Biological Chemistry, University of Vienna, Währingerstrasse 17, A-1090 Vienna (Austria)

2014-02-14

322

Transport and dielectric properties of water and the influence of coarse-graining: Comparing BMW, SPC/E, and TIP3P models  

NASA Astrophysics Data System (ADS)

Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough.

Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar

2014-02-01

323

Transport and dielectric properties of water and the influence of coarse-graining: comparing BMW, SPC/E, and TIP3P models.  

PubMed

Long-term molecular dynamics simulations are used to compare the single particle dipole reorientation time, the diffusion constant, the viscosity, and the frequency-dependent dielectric constant of the coarse-grained big multipole water (BMW) model to two common atomistic three-point water models, SPC/E and TIP3P. In particular, the agreement between the calculated viscosity of BMW and the experimental viscosity of water is satisfactory. We also discuss contradictory values for the static dielectric properties reported in the literature. Employing molecular hydrodynamics, we show that the viscosity can be computed from single particle dynamics, circumventing the slow convergence of the standard approaches. Furthermore, our data indicate that the Kivelson relation connecting single particle and collective reorientation time holds true for all systems investigated. Since simulations with coarse-grained force fields often employ extremely large time steps, we also investigate the influence of time step on dynamical properties. We observe a systematic acceleration of system dynamics when increasing the time step. Carefully monitoring energy/temperature conservation is found to be a sufficient criterion for the reliable calculation of dynamical properties. By contrast, recommended criteria based on the ratio of fluctuations of total vs. kinetic energy are not sensitive enough. PMID:24527900

Braun, Daniel; Boresch, Stefan; Steinhauser, Othmar

2014-02-14

324

Stochastic system identification of skin properties: linear and wiener static nonlinear methods.  

PubMed

Wiener static nonlinear system identification was used to study the linear dynamics and static nonlinearities in the response of skin and underlying tissue under indentation in vivo. A device capable of measuring the dynamic mechanical properties of bulk skin tissue was developed and it incorporates a custom-built Lorentz force actuator that measures the dynamic compliance between the input force (<12 N) and the output displacement (<20 mm). A simple linear stochastic system identification technique produced a variance accounted for (VAF) of 75-81% and Wiener static nonlinear techniques increased the VAF by 5%. Localized linear techniques increased the VAF to 85-95% with longer tests. Indentation experiments were conducted on 16 test subjects to determine device sensitivity and repeatability. Using the device, the coefficient of variation of test metrics was found to be as low as 2% for a single test location. The measured tissue stiffness was 300 N/m near the surface and 4.5 kN/m for high compression. The damping ranged from 5 to 23 N s/m. The bulk skin properties were also shown to vary significantly with gender and body mass index. The device and techniques used in this research can be applied to consumer product analysis, medical diagnosis and tissue research. PMID:22539150

Chen, Yi; Hunter, Ian W

2012-10-01

325

Cooperative Investigation of Relationship Between Static and Fatigue Properties of Wrought N-155 Alloy at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

Report presents the correlation of extensive data obtained relating properties of wrought n-155 alloy under static, combined static and dynamic, and complete reversed dynamic stress conditions. Time period for fracture ranged from 50 to 500 hours at room temperature, 1,000 degrees, 1,200 degrees, and 1,500 degrees F.

1956-01-01

326

Effect of Sintering Temperature on Dielectric Properties of Iron Deficient Nickel-Ferrite  

SciTech Connect

Nickel Ferrite among all the magneto ceramic materials have been studied very much due to its large number of applications. But there is a large scope of modification of its properties. Thus people still working on it for improvisation of its properties via compositional and structural modifications. Present paper reporting the preparation and characterization of iron deficient Nickel ferrite for different sintering temperature. Ferrite samples having the general formula NiFe1.98O{sub 4} were prepared using the standard ceramic method. The phase formation was confirmed by X-ray diffraction technique. The effect of sintering temperature on the electrical properties and resistivity was studied. The data shows that dielectric properties are highly dependent on the sintering temperature.

Rani, Renu [Electroceramics Research Lab, GVM Girls College, Sonepat-131001 (India); School of Physics and Material Science, Thapar University, Patiala-147004 (India); Singh, Sangeeta [Department of Physics, GVM Girls College, Sonepat-131001 (India); Juneja, J. K. [Department of Physics, Hindu College, Sonepat-131001 (India); Prakash, Chandra [Directorate of ER and IPR, DRDO, DRDO Bhawan, New Delhi-110105 (India); Raina, K. K. [School of Physics and Material Science, Thapar University, Patiala-147004 (India)

2011-11-22

327

Normal-state dielectric and transport properties of In-doped Bi–Pb–Sr–Ca–Cu–O  

Microsoft Academic Search

The effect of indium doping on the normal-state transport and dielectric properties of the Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06InxOy (0?x?0.15) has been investigated. The dielectric constant, loss tangent, carrier concentration and electrical resistivity were measured at room temperature as a function of indium concentration. The dielectric constant is found to increase with increasing dopant concentration possibly due to increase in polarization. Impurities in any

R. K Nkum; M. O Gyekye; F Boakye

2002-01-01

328

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

329

Dielectric and vibrational properties of crystalline and amorphous high-k lanthanum aluminate  

NASA Astrophysics Data System (ADS)

High-k oxides are the focus of intense research for their applications in MOS and FLASH devices. A material currently in focus is LaAlO3, with a dielectric constant of 23-24 in the crystal phase, and similar values of around 20-22 in the amorphous phase (although values as low as 15 have also been reported). We have studied LaAlO3 in both phases [1] to identify possible reasons for this apparent conservation of the dielectric properties upon amorphization. Amorphous samples were generated by melt-and-quench using a combination of pair potentials and ab initio dynamics. The linear response density-functional perturbation-theory approach was used to study dynamical response and phonons. We indeed find a large dielectric constant ( 24) in the amorphous: the rationale is that the expected reduction of the anomalous effective charges is compensated by the appearance of new low-frequency (weakly) IR-active modes, whose character is a mixture of La translations (IR in the crystal) and Al-O octahedra rotations (Raman in the crystal). A similar behavior is expected in any rare earth aluminate exhibiting a similar perovskite-related structure (e.g. scandates). 1) P. Delugas, V. Fiorentini, and A. Filippetti, Phys. Rev. B 71, 134302 (2005), and to be published.

Delugas, Pietro; Fiorentini, Vincenzo; Filippetti, Alessio

2006-03-01

330

Preparation and Dielectric Properties of SrZrO3/SrTiO3 Superlattices  

NASA Astrophysics Data System (ADS)

SrZrO3/SrTiO3 (SZO/STO) artificial superlattices were fabricated on STO substrates by the molecular beam epitaxy. The structures of the superlattices were analyzed by reflection high-energy electron diffraction, normal ?-2? scan mode X-ray diffraction analyses and reciprocal space mapping measurement. Their lattice parameters showed that the lattice distortion is dependent on stacking periodicity and is maximum in the [(SZO)10/(STO)10]4 superlattice. The dielectric properties were measured using interdigital electrodes at frequencies up to 110 MHz, and dielectric relaxation was observed in the [(SZO)1/(STO)1]40 and [(SZO)10/(STO)10]4 superlattices in the low-frequency domain. The dielectric permittivities of all superlattices with interdigital electrodes were more than 10,000 at 110 MHz. The charge vs voltage (Q-V) measurement revealed that the SZO/STO superlattices show distinct hysteresis curves, which indicated that ferroelectricity is induced by the superlattices. The origin of the ferroelectricity seems to be related to the anisotropic lattice distortion incorporated into the superlattice structure.

Harigai, Takakiyo; Tanaka, Daisuke; Nam, Song-Min; Kakemoto, Hirofumi; Wada, Satoshi; Saito, Keisuke; Tsurumi, Takaaki

2004-09-01

331

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers  

NASA Technical Reports Server (NTRS)

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

1992-01-01

332

Effect of Different Weight Fraction on Dielectric Properties of Barium Ferrite-Barium Titanate Composites  

NASA Astrophysics Data System (ADS)

Barium ferrite-barium titanate composite systems, (1-x)BaFe12O19 - (x)BaTiO3 with different weight fractions of × = 0.0, 0.1, 0.3 and 0.5 were prepared via the conventional solid state reaction method using nano-sized starting materials. The x-ray diffraction peaks of the composite samples show two phases which can be indexed by the hexagonal barium ferrite and tetragonal barium titanate. Field emission scanning electron microscope (FESEM) image of sample with × = 0.1 shows formation of nano-sized BaTiO3 grains spreading evenly among the micron-sized BaFe12O19 grains after sintering at 1000 °C. The dielectric properties studies at room temperature of the composites samples show that sample with BaTiO3 weight fraction of × = 0.1 has the highest dielectric constant, ?' and lowest loss tangent, tan ? in the studied frequency range between 1 Hz and 1 MHz. Its highest dielectric constant value is ~ 1.2 × 103 and its lowest loss tangent is 0.06 at 50 Hz.

Anuar, S. N.; Zalita, Z.; Shamsudin, R.

2013-04-01

333

Anomalies in electrical and dielectric properties of nanocrystalline Ni-Co spinel ferrite  

SciTech Connect

Nanocrystalline Ni-substituted cobalt ferrite sample is prepared by chemical co-precipitation method. X-ray diffraction and scanning electron microscopy techniques are used to obtain structural and morphological characterizations. Nanocrystalline nature is clearly seen in SEM picture. Variation of electrical resistivity as a function of temperature in the range 300-900 K is investigated. ln {rho} versus 1/T plot shows four break resulting into five regions in 300-900 K temperature range of measurements. The magnetic transition temperature of the sample is determined from resistivity behavior with temperature. The activation energy in different regions is calculated and discussed. Variation of dielectric constant ({epsilon}') with increasing temperature show more than one peak; one at around 773 K and other around 833 K, which is unusual behavior of ferrites. The observed peaks in {epsilon}' variation with temperature show frequency dependence. Electrical and dielectric properties of Ni{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4} sample show unusual behavior in the temperature range 723-833 K. To our knowledge, nobody has discussed anomalous behavior in the temperature range 723-833 K for Ni{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4}. The possible mechanism responsible for the unusual electrical and dielectric behavior of the sample is discussed.

Mathe, V.L. [Novel Materials Research Laboratory, Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, MS (India)], E-mail: vlmathe@physics.unipune.ernet.in; Kamble, R.B. [Novel Materials Research Laboratory, Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, MS (India)

2008-08-04

334

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

PubMed

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

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

2014-06-01

335

A Study of the Dielectric Properties of Dry and Saturated Green River Oil Shale  

SciTech Connect

We measured dielectric permittivity of dry and fluid-saturated Green River oil shale samples over a frequency range of 1 MHz to 1.8 GHz. Dry sample measurements were carried out between room temperature and 146 C, saturated sample measurements were carried out at room temperature. Samples obtained from the Green River formation of Wyoming and from the Anvil Points Mine in Colorado were cored both parallel and perpendicular to layering. The samples, which all had organic richness in the range of 10-45 gal/ton, showed small variations between samples and a relatively small level of anisotropy of the dielectric properties when dry. The real and imaginary part of the relative dielectric permittivity of dry rock was nearly constant over the frequency range observed, with low values for the imaginary part (loss factor). Saturation with de-ionized water and brine greatly increased the values of the real and imaginary parts of the relative permittivity, especially at the lower frequencies. Temperature effects were relatively small, with initial increases in permittivity to about 60 C, followed by slight decreases in permittivity that diminished as temperature increased. Implications of these observations for the in situ electromagnetic, or radio frequency (RF) heating of oil shale to produce oil and gas are discussed.

Sweeney, J; Roberts, J; Harben, P

2007-02-07

336

Dielectric properties of epoxy nanocomposites containing TiO2, Al2O3 and ZnO fillers  

Microsoft Academic Search

This work presents results of dielectric spectroscopy and space charge (PEA) measurements on epoxy resin filled with 10% w\\/w micro- and nano- sized particles of TiO2, Al3O2 and ZnO. The results appear to show that the material from which the nano-particle is made is not highly significant in influencing these results. The results support the proposition that the dielectric properties

J. C. Fothergilll; J. K. Nelson; M. Ful

2004-01-01

337

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

PubMed

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

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

2015-04-01

338

Structural and optical characterization of Cr{sub 2}O{sub 3} nanostructures: Evaluation of its dielectric properties  

SciTech Connect

The structural, optical and dielectric properties of as-grown Cr{sub 2}O{sub 3} nanostructures are demonstrated in this paper. Powder X-ray diffractometry analysis confirmed the rhombohedral structure of the material with lattice parameter, a = b = 4.953 Å; c = 13.578 Å, and average crystallize size (62.40 ± 21.3) nm. FE-SEM image illustrated the mixture of different shapes (disk, particle and rod) of as-grown nanostructures whereas; EDS spectrum confirmed the elemental purity of the material. FTIR spectroscopy, revealed the characteristic peaks of Cr–O bond stretching vibrations. Energy band gap (3.2 eV) of the nanostructures has been determined using the results of UV-VIS-NIR spectrophotometer. The dielectric properties of the material were checked in the wide frequency region (100Hz-30 MHz). In the low frequency region, the matrix of the dielectric behaves like source as well as sink of electrical energy within the relaxation time. Low value of dielectric loss exhibits that the materials posses good optical quality with lesser defects. The ac conductivity of the material in the high frequency region was found according to frequency power law. The physical-mechanism and the theoretical-interpretation of dielectric-properties of Cr{sub 2}O{sub 3} nanostructures attest the potential candidature of the material as an efficient dielectric medium.

Abdullah, M. M., E-mail: abdullahphyzia@gmail.com [Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia); Department of Physics, College of Science and Arts, Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia); Rajab, Fahd M. [Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia) [Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia); Department of Chemical Engineering, College of Engineering, Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia); Al-Abbas, Saleh M. [Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia)] [Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran, 11001 (Saudi Arabia)

2014-02-15

339

Structural and Dielectric Properties of LiSr2Nb5O15 Ceramic  

NASA Astrophysics Data System (ADS)

The polycrystalline sample of LiSr2Nb5O15 (LSN) was prepared by a high temperature solid-state reaction technique. Studies of structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. X-ray studies reveal that the material has an orthorhombic structure at room temperature. Dielectric properties were measured over a wide range of temperature (28-500 °C) and frequency (102-106 Hz). Conductivity of the material increases with rise in temperature.

Behera, Banarji; Mohanty, N. K.; Satpathy, S. K.; Nayak, P.; Choudhary, R. N. P.

2011-11-01

340

Systematic methods for calculation of the dielectric properties of arbitrary plasmas  

NASA Technical Reports Server (NTRS)

In the novel approach presented for calculating the dispersion integrals needed for determining plasma dielectric properties, the dispersion integrals for an arbitrary distortion function with a continuous derivative are systematically expanded in terms of a set of orthogonal functions whose corresponding dispersion functions are already known. This general approach is, on the one hand, implemented for unmagnetized plasmas, and on the other generalized to treat relativistic and magnetized plasmas. The method allows the systematic and efficient calculation of dispersion integrals, for the cases of either real or complex arguments.

Robinson, P. A.

1990-01-01

341

Carbon materials with quasi-graphene layers: The dielectric, percolation properties and the electronic transport mechanism  

NASA Astrophysics Data System (ADS)

We investigate the dielectric properties of multi-walled carbon nanotubes (MWCNTs) and graphite filling in SiO2 with the filling concentration of 2-20 wt.% in the frequency range of 102-107 Hz. MWCNTs and graphite have general electrical properties and percolation phenomena owing to their quasi-structure made up of graphene layers. Both permittivity ? and conductivity ? exhibit jumps around the percolation threshold. Variations of dielectric properties of the composites are in agreement with the percolation theory. All the percolation phenomena are determined by hopping and migrating electrons, which are attributed to the special electronic transport mechanism of the fillers in the composites. However, the twin-percolation phenomenon exists when the concentration of MWCNTs is between 5-10 wt.% and 15-20 wt.% in the MWCNTs/SiO2 composites, while in the graphite/SiO2 composites, there is only one percolation phenomenon in the graphite concentration of 10-15 wt.%. The unique twin-percolation phenomenon of MWCNTs/SiO2 is described and attributed to the electronic transfer mechanism, especially the network effect of MWCNTs in the composites. The network formation plays an essential role in determining the second percolation threshold of MWCNTs/SiO2.

Lu, Ming-Ming; Yuan, Jie; Wen, Bo; Liu, Jia; Cao, Wen-Qiang; Cao, Mao-Sheng

2013-03-01

342

Clinically relevant CNT dispersions with exceptionally high dielectric properties for microwave theranostic applications.  

PubMed

We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ? 70% and ? 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy. PMID:24876108

Xie, Shawn X; Gao, Fuqiang; Patel, Sunny C; Booske, John H; Hagness, Susan C; Sitharaman, Balaji

2014-11-01

343

Enhancement of ferromagnetic and dielectric properties of lanthanum doped bismuth ferrite nanostructures  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.

Chaudhuri, A., E-mail: arka@bose.res.in [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Mandal, K. [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)] [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)

2012-04-15

344

High Temperature Microwave Dielectric Properties of JSC-1AC Lunar Simulant  

NASA Technical Reports Server (NTRS)

Microwave heating has many potential lunar applications including sintering regolith for lunar surface stabilization and heating regolith for various oxygen production reactors. The microwave properties of lunar simulants must be understood so this technology can be applied to lunar operations. Dielectric properties at microwave frequencies for a common lunar simulant, JSC-1AC, were measured up to 1100 C, which is approximately the melting point. The experimentally determined dielectric properties included real and imaginary permittivity (epsilon', epsilon"), loss tangent (tan delta), and half-power depth, the di stance at which a material absorbs 50% of incident microwave energy. Measurements at 2.45 GHz revealed tan delta of JSC-1A increases from 0.02 at 25 C to 0.31 at 110 C. The corresponding half-power depth decreases from a peak of 286 mm at 110 C, to 13 mm at 1100 C. These data indicate that JSC-1AC becomes more absorbing, and thus a better microwave heater as temperature increases. A half-power depth maximum at 100-200 C presents a barrier to direct microwave heating at low temperatures. Microwave heating experiments confirm the sluggish heating effect of weak absorption below 200 C, and increasingly strong absorption above 200 C, leading to rapid heating and melting of JSC-1AC.

Allan, Shawn M.; Merritt, Brandon J.; Griffin, Brittany F.; Hintze, Paul E.; Shulman, Holly S.

2011-01-01

345

Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties  

NASA Astrophysics Data System (ADS)

High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (?r~23.6, Qf~64,300 GHz and ?f~-66 ppm/°C and ?r~24, Qf~75,800 GHz and ?f~-64 ppm/°C) was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min, respectively.

Bafrooei, H. Barzegar; Nassaj, E. Taheri; Hu, C. F.; Huang, Q.; Ebadzadeh, T.

2014-12-01

346

Intrinsic dielectric properties and charge transport in oligomers of organic semiconductor copper phthalocyanine  

Microsoft Academic Search

Various contributions are distinguished in the experimentally detected dielectric response of organic semiconductor copper phthalocyanine. While a giant dielectric constant of virgin samples is shown to be due to extrinsic effects, the temperature dependence of the intrinsic dielectric constant, being of the order of 10, indicates two structural phase transitions, as well as a dielectric relaxation reflecting the charge carriers'

V. Bobnar; A. Levstik; C. Huang; Q. M. Zhang

2005-01-01

347

Dielectric properties of Al2O3 coatings deposited via atmospheric plasma spraying and dry-ice blasting correlated with microstructural characteristics  

NASA Astrophysics Data System (ADS)

In this work, atmospheric plasma spraying combined with dry-ice blasting have been used to prepare alumina (Al2O3) coatings designed for insulating applications. The microstructural characteristics and dielectric properties of Al2O3 coatings were presented. The electrical insulating properties, i.e., dielectric strength and breakdown voltage, were investigated by dielectric breakdown test using direct current and alternating current. Relationships between dielectric properties and coating characteristics were discussed. The results showed that dry-ice blasting used during atmospheric plasma spray process allowed the production of coatings with better dielectric properties than those prepared without dry-ice blasting. The dielectric properties were correlated with the microstructural characteristics, not with phase composition.

Dong, Shujuan; Song, Bo; Liao, Hanlin; Coddet, Christian

2014-08-01

348

Dielectric properties of Al2O3 coatings deposited via atmospheric plasma spraying and dry-ice blasting correlated with microstructural characteristics  

NASA Astrophysics Data System (ADS)

In this work, atmospheric plasma spraying combined with dry-ice blasting have been used to prepare alumina (Al2O3) coatings designed for insulating applications. The microstructural characteristics and dielectric properties of Al2O3 coatings were presented. The electrical insulating properties, i.e., dielectric strength and breakdown voltage, were investigated by dielectric breakdown test using direct current and alternating current. Relationships between dielectric properties and coating characteristics were discussed. The results showed that dry-ice blasting used during atmospheric plasma spray process allowed the production of coatings with better dielectric properties than those prepared without dry-ice blasting. The dielectric properties were correlated with the microstructural characteristics, not with phase composition.

Dong, Shujuan; Song, Bo; Liao, Hanlin; Coddet, Christian

2015-01-01

349

The dielectric properties of normal and malignant breast tissue at microwave frequencies: analysis, conclusions, and implications from the wisconsin\\/calgary study  

Microsoft Academic Search

The clinical efficacy of emerging microwave breast cancer detection and hyperthermia treatment techniques (see [X. Li et al., 2005], [M. Converse et al., 2004] and references therein) depend on the microwave dielectric properties of normal, malignant, and benign breast tissues. Knowledge of these properties has been limited by gaps and discrepancies in previously published small-scale studies reporting the dielectric properties

Mariya Lazebnik; Cynthia B. Watkins; Susan C. Hagness; John H. Booske; Dijana Popovic; Leah McCartney; Michal Okoniewski; Mary J. Lindstrom; Tara M. Breslin; J. Harter; S. Sewall; W. Temple; D. Mew; A. Magliocco; T. Ogilvie

2007-01-01

350

Measurement of the dielectric properties of the epidermis and dermis at frequencies from 0.5 GHz to 110 GHz  

NASA Astrophysics Data System (ADS)

Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with Gabriel’s widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20-100 GHz, the experimental results indicated larger values than those extrapolated from Gabriel’s data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency.

Sasaki, K.; Wake, K.; Watanabe, S.

2014-08-01

351

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

SciTech Connect

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., E-mail: asdemiray@mlab.apph.tohoku.ac.jp; Iihama, S.; Naganuma, H.; Oogane, M.; Ando, Y. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aza-aoba 6-6-05, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Kubota, T.; Mizukami, S., E-mail: mizukami@wpi-aimr.tohoku.ac.jp; Miyazaki, T. [WPI Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-8577 (Japan)

2014-05-07

352

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

353

Polyamides nanoparticles containing flexible linkages and their copper complexes with novel dielectric properties: Structure-property relationship  

NASA Astrophysics Data System (ADS)

We report the chemistry of nanometer-sized spherical aramides nanoparticles and their copper complexes as novel types of hybrids nanomaterials. Based on the flexible linkage type, the average diameters of the nanoparticles-containing sulfone or ether linkage were 140 nm and 190 nm, respectively, as judged by the scanning electron microscopy (SEM) photographs. Incorporation of copper (II) ions into these particles furnished polymeric complexes in (1:2) ratios with square planar geometries. The polymeric structures were proved on the basis of their IR, UV, ESR and elemental analysis data. The thermal properties of the polymers were evaluated by various techniques and results revealed the high thermal stabilities of the hybrids. The calculated limiting oxygen index (LOI) indicates that such macromolecules can be classified as self-extinguishing polymers. The dc electrical conductivity of all samples indicates either semi-conducting or metal-like nature in the regime of semiconductor behaviors. Incorporation of copper significantly improved the conductivity of the resulting complexes due to the enhanced mobility of the charge carriers upon doping. Dielectric losses are characterized by sharp peaks appearing at characteristic frequencies suggesting the presence of relaxing dipoles. The peak positions did not change with temperature indicating a non-activated process. The loss tangent increased with frequency and the peaks shifted toward the lower frequency upon doping suggesting the increase in the energy loss ratio compared to the energy storage in the dielectric. The higher value of dielectric loss at low frequency is due to the free charge motion within the materials. The reported dielectric results revealed anomalous behaviors which have not been reported earlier in similar hybrids.

Hassan, Hammed H. A. M.; Elhusseiny, Amel F.; Sweyllam, Amr M.

2011-08-01

354

Dielectric and transport properties of thin films precipitated from sols with silicon nanoparticles  

SciTech Connect

Dielectric properties of thin films precipitated on solid substrates from colloidal solutions containing silicon nanoparticles (average diameter is 10 nm) are studied by optical ellipsometry and impedance-spectroscopy. In the optical region, the values of real {epsilon} Prime and imaginary {epsilon} Double-Prime components of the complex permittivity {epsilon} vary within 2.1-1.1 and 0.25-0.75, respectively. These values are significantly lower than those of crystalline silicon. Using numerical simulation within the Bruggeman effective medium approximation, we show that the experimental {epsilon} Prime and {epsilon} Double-Prime spectra can be explained with good accuracy, assuming that the silicon film is a porous medium consisting of silicon monoxide (SiO) and air voids at a void ratio of 0.5. Such behavior of films is mainly caused by the effect of outer shells of silicon nanoparticles interacting with atmospheric oxygen on their dielectric properties. In the frequency range of 10-10{sup 6} Hz, the experimentally measured {epsilon} Prime and {epsilon} Double-Prime spectra of thin nanoscale silicon films are well approximated by the semi-empirical Cole-Cole dielectric dispersion law with the term related to free electric charges. The experimentally determined power-law frequency dependence of the ac conductivity means that the electrical transport in films is controlled by electric charge hopping through localized states in the unordered medium of outer shells of silicon nanoparticles composing films. It is found that the film conductivity at frequencies of {<=}2 Multiplication-Sign 10{sup 2} Hz is controlled by proton transport through Si-OH groups on the silicon nanoparticle surface.

Kononov, N. N., E-mail: nnk@kapella.gpi.ru [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Dorofeev, S. G. [Moscow State University, Faculty of Chemistry (Russian Federation); Ishchenko, A. A. [Lomonosov State Academy of Fine Chemical Technology (Russian Federation); Mironov, R. A.; Plotnichenko, V. G.; Dianov, E. M. [Russian Academy of Sciences, Fiber-Optics Research Center, Prokhorov General Physics Institute (Russian Federation)

2011-08-15

355

Dispersion Studies of La Substitution on Dielectric Properties of Multiferroic BiFeO{sub 3} Ceramics  

SciTech Connect

Lanthanum (La)-substituted multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} ceramics with x = 0.0, 0.05, 0.10, 0.15, 0.20 and 0.25 have been prepared by solution combustion method. The effect of La substitution for the dispersion studies on dielectric properties of Bi{sub 1-x}La{sub x}FeO{sub 3} samples have been studied by performing x-ray diffraction (XRD) and dielectric measurements. The results of prepared samples are compared with those of bismuth ferrite (BiFeO{sub 3}). In the measuring frequency of 10 KHz-1 MHz, the dielectric constants and dielectric losses for samples x = 0.20, 0.25 are almost stable and exhibited lowest dielectric loss close to 0.1. The results also shows that stabilization of crystal structure and nonuniformity in spincycloid structure by La substitution enhances the dielectric properties.

Sen, K.; Singh, K.; Gautam, Ashish; Singh, M. [Department of Physics, Himachal Pradesh University, Shimla-171005 (India)

2011-12-12

356

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

NASA Astrophysics Data System (ADS)

We report on the frequency (f=20 Hz-1 MHz) and temperature (T=300-973 K) dependent dielectric properties of hafnium (Hf) incorporated cobalt ferrite (CoF2-xHfxO4 (CFO-Hf); x=0.00-0.20). The dielectric constant (?') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for ?-T (>450 K) variation. Correspondingly, electrical responses in impedance formalism are attributed to the grain and grain-boundary effects which also accounts for the observed two dielectric-relaxations. The results demonstrate that the dielectric phenomena in CFO-Hf can be tailored by tuning Hf-concentration.

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

2014-04-01

357

Optical properties of ultrafine line and space polymeric nanogratings coated with metal and metal-dielectric-metal thin films  

NASA Astrophysics Data System (ADS)

Noble metal and metal-dielectric-metal ultrathin films were deposited on the surfaces of ultrafine polymeric nanogratings, which were fabricated using nanoimprint lithography. Experimental results showed dramatic differences of the surface morphologies for single metal and triple metal-dielectric-metal films deposited on flat and corrugated polymeric surfaces. The effect of the surface morphology on the optical properties was hence investigated and analyzed under linearly polarized light. The surface plasmon resonances of single metal and triple metal-dielectric-metal films deposited on polymeric nanograting surfaces were also characterized based on the Kretschmann prism-coupling method. The single metal and triple metal-dielectric-metal films deposited on polymeric nanograting surfaces are important for the study of photon-plasmon interactions (i.e. couplings and conversions) at the interfaces between a nanograting and metal films.

Leong, Eunice Sok Ping; Wu, Siji; Zhang, Nan; Loh, Wei Wei; Huat Khoo, Eng; Si, Guang Yuan; Dai, Hai Tao; Liu, Yan Jun

2014-02-01

358

Optical properties of ultrafine line and space polymeric nanogratings coated with metal and metal-dielectric-metal thin films.  

PubMed

Noble metal and metal-dielectric-metal ultrathin films were deposited on the surfaces of ultrafine polymeric nanogratings, which were fabricated using nanoimprint lithography. Experimental results showed dramatic differences of the surface morphologies for single metal and triple metal-dielectric-metal films deposited on flat and corrugated polymeric surfaces. The effect of the surface morphology on the optical properties was hence investigated and analyzed under linearly polarized light. The surface plasmon resonances of single metal and triple metal-dielectric-metal films deposited on polymeric nanograting surfaces were also characterized based on the Kretschmann prism-coupling method. The single metal and triple metal-dielectric-metal films deposited on polymeric nanograting surfaces are important for the study of photon-plasmon interactions (i.e. couplings and conversions) at the interfaces between a nanograting and metal films. PMID:24406796

Leong, Eunice Sok Ping; Wu, Siji; Zhang, Nan; Loh, Wei Wei; Khoo, Eng Huat; Si, Guang Yuan; Dai, Hai Tao; Liu, Yan Jun

2014-02-01

359

Fumed silica concentration effect on structure and dielectric properties of a styrene-cross-linked unsaturated polyester resin  

NASA Astrophysics Data System (ADS)

Concentration effects of a high-reactive-surface nanosized SiO2 filler on structure and dielectrical properties of a styrene-cross-linked polyester resin have been experimentally studied. Thermal desorption mass-spectroscopy, IR-spectroscopy, dielectric spectroscopy, and positron annihilation lifetime spectroscopy were used to determine an atomic content of thermal destruction products, IR-reflection spectra, complex dielectric permittivity, and a nature of positron traps as function of filler content in the polymer matrix. Interaction between active surface centers of SiO2-nanoparticles and atoms of polyester chains and styrene molecules gives the non-monotonous influence on the structure of polyester chains, macromolecule polarity, dielectric parameters and the number of positronium nanotraps.

Gorelov, B. M.; Polovina, O. I.; Gorb, A. M.; Dacko, S.; Kostrzewa, M.; Ingram, A.

2012-11-01

360

Extraction of Water from Polar Lunar Permafrost with Microwaves - Dielectric Property Measurements  

NASA Technical Reports Server (NTRS)

Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles. The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year. Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap. The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured.

Ethridge, Edwin C.; Kaukler, William

2009-01-01

361

Electrical resistivity and dielectric properties of helical microorganism cells coated with silver by electroless plating  

NASA Astrophysics Data System (ADS)

In this paper, microorganism cells (Spirulina platens) were used as forming templates for the fabrication of the helical functional particles by electroless silver plating process. The morphologies and ingredients of the coated Spirulina cells were analyzed with scanning electron microscopy and energy dispersive spectrometer. The crystal structures were characterized by employing the X-ray diffraction. The electrical resistivity and dielectric properties of samples containing different volume faction of sliver-coated Spirulina cells were measured and investigated by four-probe meter and vector network analyzer. The results showed that the Spirulina cells were successfully coated with a uniform silver coating and their initial helical shapes were perfectly kept. The electrical resistivity and dielectric properties of the samples had a strong dependence on the volume content of sliver-coated Spirulina cells and the samples could achieve a low percolation value owing to high aspect ratio and preferable helical shape of Spirulina cells. Furthermore, the conductive mechanism was analyzed with the classic percolation theory, and the values of ? and t were obtained.

Cai, Jun; Lan, Mingming; Zhang, Deyuan; Zhang, Wenqiang

2012-09-01

362

A genetic algorithm for optimizing multi-pole Debye models of tissue dielectric properties.  

PubMed

Models of tissue dielectric properties (permittivity and conductivity) enable the interactions of tissues and electromagnetic fields to be simulated, which has many useful applications in microwave imaging, radio propagation, and non-ionizing radiation dosimetry. Parametric formulae are available, based on a multi-pole model of tissue dispersions, but although they give the dielectric properties over a wide frequency range, they do not convert easily to the time domain. An alternative is the multi-pole Debye model which works well in both time and frequency domains. Genetic algorithms are an evolutionary approach to optimization, and we found that this technique was effective at finding the best values of the multi-Debye parameters. Our genetic algorithm optimized these parameters to fit to either a Cole-Cole model or to measured data, and worked well over wide or narrow frequency ranges. Over 10 Hz-10 GHz the best fits for muscle, fat or bone were each found for ten dispersions or poles in the multi-Debye model. The genetic algorithm is a fast and effective method of developing tissue models that compares favourably with alternatives such as the rational polynomial fit. PMID:22975629

Clegg, J; Robinson, M P

2012-10-01

363

Effects of complex additives on structure, phase transitions and dielectric properties of BSPT ceramics  

NASA Astrophysics Data System (ADS)

Influence of complex CaCl2/ KCl additive with low melting temperature ˜870 K on structure, dielectric and polar properties of ceramic solid solutions on the base of composition from Morphotropic Phase Boundary in the system (1-x ) BiScO3- xPbTiO3 (x=0.635, 0.64, 0.645) was studied. Using initial compositions prepared from nitrates solutions dense single phase ceramic samples doped by the additives in amounts up to 5 w. % were obtained at 1320 K. Variations in relative content of rhombohedral and tetragonal phases, changes of crystal structure parameters, and polar properties were observed depending on both x value and amount of additive. Temperature of the 1st order ferroelelctric phase transitions decreased from ˜700 K to 630-650 K in the doped samples due to the introduction of Ca2+/ K+ ions into A sites of perovskite lattice.

Politova, E. D.; Golubko, N. V.; Kaleva, G. M.; Mosunov, A. V.; Stefanovich, S. Yu.; Segalla, A. H.

2014-11-01

364

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

365

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

PubMed

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

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

2011-07-20

366

Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field  

NASA Astrophysics Data System (ADS)

The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675°C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to the ?-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.

Su, Xin; Xu, Guang-ming; Jiang, Jiu-wen

2014-07-01

367

The enhanced polarization relaxation and excellent high-temperature dielectric properties of N-doped SiC  

NASA Astrophysics Data System (ADS)

The dielectric properties and microwave attenuation performance of N-doped SiC have been evaluated in 8.2-12.4 GHz in the temperature range of 293-673 K. The N doping dramatically improves the microwave absorption capability of SiC. The minimum reflection loss of N-doped SiC is enhanced to nearly -30 dB with the effective absorption bandwidth [RL(dB) ? -10 dB] up to 3 GHz at 673 K. The excellent high-temperature dielectric properties are attributed to multi-relaxations, originated from the polarization relaxations of dipoles induced by the N doping and vacancy defects.

Dou, Yan-Kun; Li, Jing-Bo; Fang, Xiao-Yong; Jin, Hai-Bo; Cao, Mao-Sheng

2014-02-01

368

The growth of single-crystals of Pb-K-Niobate and temperature dependence of dielectric property  

E-print Network

THE GROWTH OF SINGLE-CRYSTALS OF PB-K-NIOBATE AND TEMPERATURE DEPENDENCE OF DIELECTRIC PROPERTY A Thesis FAIZUL ISLAM Submitted to the Graduate College of Texas AdrM University in partial ful6llment of the requirement for the degree of MASTER... OF SCIENCE August 1986 Major Subject: Electrical Engineering THE GROWTH OF SINGLE-CRYSTALS OF PB-K-NIOBATE AND CHARACTERIZATION OF DIELECTRIC PROPERTY A Thesis by FAIZUL ISLAM Approved as to style and content by: Dr. Raghvendra y (Chairman...

Islam, Faizul

2012-06-07

369

Potassium Niobate Single-Domain Crystals as Piezoelectrics with Low Dielectric and High Electromechanical Coupling Properties  

NASA Astrophysics Data System (ADS)

Piezoelectric properties of KNbO3 crystals were investigated as a function of the crystallographic direction, such as [110]c of polar direction and [001]c of engineered domain direction. It was confirmed that the sample preparation process induced mechanical damage into the crystals. Thus, the optimum conditions for the mechanical processing of KNbO3 crystals were investigated, and the stressed surface layers of KNbO3 crystals were successfully removed by the chemical etching. It was revealed that the removal of the stressed surface layers was very effective to achieve high mechanical quality factor (Qm). After the treatment, KNbO3 crystals were poled by the 2-step poling method. Using a polarizing microscope, the domain configuration of the poled KNbO3 crystals was observed and was confirmed that the crystal was almost in single-domain state. Using this poled KNbO3 single-domain crystals, the piezoelectric properties with k31 modes were measured using a conventional resonance method. As a result, the [110]c poled KNbO3 crystals exhibited an electromechanical coupling factor (k31) of almost 47 %, the piezoelectric constant (d31) of almost 22 pC/N, the dielectric constant (e33) of almost 44 and Qm over 4,000. These values are extremely higher compared to previous reports on KNbO3 crystals, except for e 33. This result revealed that the KNbO3 crystals are piezoelectric with low dielectric and high electromechanical coupling properties, which makes KNbO3 crystal one of the promising materials for sensor application. Moreover, the piezoelectric properties with k32, k33, k15 and k24 modes were also investigated. Finally, the effect of the engineered domain is discussed.

Wada, Satoshi; Muraoka, K.; Kakemoto, H.; Kumagai, H.; Tsurumi, T.; Science, Graduate School Of; Engineering Collaboration

2002-03-01

370

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

371

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

SciTech Connect

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

Lazarevi?, Zorica Ž., E-mail: lzorica@yahoo.com [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, Zemun, Belgrade (Serbia); Jovaleki?, ?edomir [The Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, Belgrade (Serbia); Sekuli?, Dalibor L. [Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovi?a 6, Novi Sad (Serbia); Milutinovi?, Aleksandra [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, Zemun, Belgrade (Serbia); Baloš, Sebastian; Slankamenac, Miloš [Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovi?a 6, Novi Sad (Serbia); Rom?evi?, Nebojša Ž. [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, Zemun, Belgrade (Serbia)

2013-10-15

372

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

373

A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries  

Microsoft Academic Search

The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we

Mariya Lazebnik; Dijana Popovic; Leah McCartney; Cynthia B. Watkins; Mary J. Lindstrom; Josephine Harter; Sarah Sewall; Travis Ogilvie; Anthony Magliocco; Tara M. Breslin; Walley Temple; Daphne Mew; John H. Booske; Michal Okoniewski; Susan C. Hagness

2007-01-01

374

Finite size effects in the static and dynamic magnetic properties of FeNi wire array structures  

E-print Network

Finite size effects in the static and dynamic magnetic properties of FeNi wire array structures A and dynamic properties of FeNi wire arrays on GaAs 001 substrates. The wires were between 0.4 and 10 m wide- polar coupling can be introduced leading to changes in the field dependent magnetoresistance behavior.5

Adeyeye, Adekunle

375

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.

376

Solution-deposited GdCeO{sub x} thin films: Microstructure, band structure, and dielectric property  

SciTech Connect

Highlights: ? Microstructural and electrical properties of sol–gel-deposited GdCeO{sub x} thin films with different mixing ratios. ? Ce incorporation enhanced crystallization and refractive index, reduced hysteresis, and increased dielectric constant. ? Bandgap gradually decreased with increasing Ce, which was primarily affected by VBO reduction. -- Abstract: The microstructural and electrical properties of solution-deposited GdCeO{sub x} dielectric thin films with different mixing ratios were studied. The Ce incorporation enhanced the degree of crystallization and the refractive index of the Gd{sub 2}O{sub 3} film, reduced the hysteresis and increased the dielectric constant. According to reflective electron energy loss spectroscopy and X-ray photoelectron spectroscopy analyses, the bandgap of the GdCeO{sub x} film gradually decreased with increasing Ce/(Gd + Ce) atomic ratio, which was primarily affected by the reduction of the valence band offset.

Lee, Myung Soo [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)] [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Sang Han; Cho, Mann-Ho [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)] [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyoungsub, E-mail: hsubkim@skku.edu [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)] [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2012-06-15

377

Theoretical and experimental study of the structural, dynamical and dielectric properties of perovskite BaSnO3  

NASA Astrophysics Data System (ADS)

The structural, dynamical and dielectric properties of the cubic phase of perovskite barium stannate BaSnO3, a potential candidate as protonic conductor for solid oxide fuel cells, have been investigated by the means of first-principles density functional calculations, and the structural and electrical properties have been explored at low temperature. From density functional perturbative calculations, the phonon modes, the Born effective charges and the dielectric tensor are derived and analyzed, at zero pressure. The phonon band-structure of the cubic phase does not exhibit unstable modes, in good agreement with x-ray diffraction, which shows that BaSnO3 remains perfectly cubic down to 10 K. The dielectric response in BaSnO3 as measured and calculated is lower than in titanate and zirconate perovskites.

Bévillon, Émile; Chesnaud, Anthony; Wang, Yanzhong; Dezanneau, Guilhem; Geneste, Grégory

2008-04-01

378

Superior dielectric properties for template assisted grown (100) oriented Gd2O3 thin films on Si(100)  

NASA Astrophysics Data System (ADS)

We report about the single crystalline growth and dielectric properties of Gd2O3(100) thin films on Si(100) surface. Using a two step molecular beam epitaxy growth process, we demonstrate that controlled engineering of the oxide/Si interface is a key step to achieve the atypical (100) oriented growth of Gd2O3. Unusually, high dielectric constant values (˜23-27) were extracted from capacitance voltage measurements. Such effect can be understood in terms of a two dimensional charge layer at the Gd2O3/Si interface (W. Sitaputra and R. Tsu, Appl. Phys. Lett. 101, 222903 (2012)) which can influence the dielectric properties of the oxide layer by forming an additional negative quantum capacitance.

Roy Chaudhuri, Ayan; Fissel, A.; Osten, H. J.

2014-01-01

379

Dielectric Properties of Liquid Crystals: Polymer Dispersions and Chiral Smectic Phases.  

NASA Astrophysics Data System (ADS)

The polymer dispersions were made by dissolving a monomer 4-4^'-disacryloylbiphenyl, (concentration between 0.5 to 3 wt. %) and a photo initiator benzoinmethyl ether (5 wt %) in a nematogenic material 4-4^'-n-pentylcyanobiphenyl (5CB) and exposing the films to UV radiation. The dielectric response of these films was measured for various polymer concentrations as a function of field strength, frequency and temperature. For concentration above 1 wt.%, the dependence of the dielectric response on the field strength is small which indicates that the average mesh size is smaller than the electric coherence length (1 times 10 ^{-6}m at 1 times 10^4V/cm). At 0.5 wt.% the effect of the polymer network is still small so that a relatively sharp Frederick's transition is observed. The following materials were studied: 9B (provided by L. C. Chien), C* range 90-144^circ C, spontaneous polarization P_{ rm s} = 400 nC/cm^2 at 120^circC and ZLI 4237 -100 (from EM industries), C* range -20 -61^circC, P_ {rm s} = 20 nC/cm^2 at 25^circC. The dielectric properties observed in thin films depend strongly on the texture. The dielectric constants measured on homeotropic textures at low frequencies vary from varepsilon^' = 4.5 to 4.8 for ZLI and varepsilon^ ' = 12.8 to 13 for 9B. Both materials show in these films a relaxation in the frequency range from 30 to 300Hz depending on temperature. The Goldstone mode dominates in the bookshelf texture at low frequencies. varepsilon^' reaches values up to 30 for the ZLI sample and up to 420 for 9B. The relaxation frequencies of Goldstone modes are around 300 Hz and 20KHz respectively. The bias field dependence of varepsilon^' in the Goldstone range showed an unexpected behavior. With ZLI, varepsilon^' first increases and then decreases when the fields get larger than 0.15V/mum. For 9B, varepsilon^' is not effected by the bias fields up to 1.6 V/mu m. It may be possible that this is due to some deterioration of the sample.

Abegunarathna, Sugath

380

Structural, electronic, vibrational, and dielectric properties of LaBGeO5 from first principles  

NASA Astrophysics Data System (ADS)

Structural, electronic, vibrational, and dielectric properties of LaBGeO5 with the stillwellite structure are determined based on ab initio density functional theory. The theoretically relaxed structure is found to agree well with the existing experimental data with a deviation of less than 0.2%. Both the density of states and the electronic band structure are calculated, showing five distinct groups of valence bands. Furthermore, the Born effective charge, the dielectric permittivity tensors, and the vibrational frequencies at the center of the Brillouin zone are all obtained. Compared to existing model calculations, the vibrational frequencies are found in much better agreement with the published experimental infrared and Raman data, with absolute and relative rms values of 6.04 cm-1, and 1.81%, respectively. Consequently, numerical values for both the parallel and perpendicular components of the permittivity tensor are established as 3.55 and 3.71 (10.34 and 12.28), respectively, for the high-(low-)frequency limit.

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

2014-02-01

381

Dielectric properties of human ovary follicular fluid at 9.2 GHz.  

PubMed

The influence of the follicle size, rapid freezing to -196 degrees capital ES, Cyrillic and cryopreservation in liquid nitrogen within a period of one month of the human ovary follicular fluid (FF) on its dielectric properties is studied by the microwave dielectric method. The FF was obtained from dominant follicles of patients who received treatment for infertility by extracorporal fertilization. We have measured the real part (epsilon') of the complex permittivity of the native and frozen follicular fluids at the room temperature. A resonator type ultra high frequency (UHF) dielectrometer at the frequency of 9.2 GHz has been used. We have also obtained the values of the total protein, hormones and glucose concentration in the FF. It was found that rapid freezing reduces epsilon' of the FF. It can result from the bound water increase in the system. It was also found the rise in permittivity and the total protein concentration with the increase of a follicle size, which could be explained by protein dehydration as a result of its clustering and aggregation. PMID:20435524

Gorobchenko, Olga A; Gerodes, Anna G; Nardid, Oleg A; Nikolov, Oleg T

2010-10-01

382

Structural, spectral, thermal, dielectric, mechanical and optical properties of urea L-alanine acetate single crystals  

NASA Astrophysics Data System (ADS)

A new organic nonlinear optical crystal, urea L-alanine acetate (ULAA) has been grown by solution growth using slow cooling technique with the vision to improve the properties of the L-alanine crystals. Urea and L-alanine material were mixed in the molar ratio 1:4. Solubility and metastable zone width were determined. Single crystal XRD analyses revealed that the crystal lattice of ULAA is orthorhombic system, primitive lattice with cell parameters a=5.7971 Å, b=6.0391 Å, c=12.3276 Å with space group P2 12 12 1 (D 24). High-resolution X-ray diffraction (HR-XRD) analysis was carried out to study their crystalline perfection. FTIR spectrum was recorded to identify the presence of functional groups and molecular structure was confirmed by 1H NMR spectrum. From the mass spectrum, the ratio of compound formation of ULAA was analyzed. Thermal strength of the grown crystal has been studied using thermo-gravimetric (TG) and differential thermal analysis (DTA). Dielectric measurements reveal that the grown crystals have very low dielectric loss. The mechanical behavior was studied by Vickers microhardness test. The grown crystals were found to be transparent in the entire visible region. Preliminary measurement using Kurtz powder technique with Nd-YAG laser light of wavelength 1064 nm indicates that their second harmonic generation (SHG) efficiency is roughly equal to that of pure KDP.

Jaikumar, D.; Kalainathan, S.; Bhagavannarayana, G.

2010-05-01

383

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

NASA Astrophysics Data System (ADS)

The single phase hexagonal YMn0.95Ru0.05O3 compound has been synthesized via solid state reaction method at sintering temperature 1280°C with space group P63cm (25-1079). The detailed dielectric properties were evaluated over broad temperature and frequency ranges. An obvious dielectric relaxation was observed near the antiferromagnetic (AFM) transition temperature. The temperature dependence of the ac resistivity at low frequency infers the semiconducting behavior and favored the variable range hopping conduction model. The obtained experimental data in the temperature range of our study can be described by the equation ?(T) = ?0exp[(T*/T)1/4]. The fitting results are used for the calculation of the temperature scale T* ˜ 0.8 × 104 K and finally the density of state at Fermi level N(EF). The activation energy Ea ˜ 0.0314 eV is calculated from the plot, peak temperature of the loss tangent near the magnetic transition region versus frequency using Arrhenius law.

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

2013-02-01

384

CdSe nanocrystals ingrained dielectric nanocomposites: synthesis and photoluminescence properties  

NASA Astrophysics Data System (ADS)

Cadmium selenide (CdSe) nanocrystals ingrained dielectric nanocomposites in a B2O3–SiO2–Al2O3–Na2O–K2O borosilicate glass system were synthesized by a single step in situ melt quenching technique. The sizes of the nanocrystals as well as the band gap of the nanocomposites were controlled by both concentration of CdSe and post thermal treatment duration. The nanocomposites were characterized by different instrumental techniques including detailed photoluminescence studies. The sizes of the CdSe nanocrystals were found to alter in the range 4–16 nm as estimated from the effective mass approximation model and optical absorption spectroscopy. However, the TEM analysis revealed the generation of two different size ranges, 3–4 and 23–45 nm, of the particles within the dielectric matrix. Selected area diffraction (SAED) and x-ray diffraction (XRD) patterns authenticate the formation of hexagonal nanostructures of CdSe. These nanocomposites were found to be capable of exhibiting strong visible red luminescence around 715 nm on excitation at 446 nm. This has originated from the electron–hole recombination of CdSe nanocrystal and defects or traps related transitions. The properties of these nanocomposites advocate their significant applications as semiconductor based luminescent materials.

Dey, Chirantan; Goswami, Madhumita; Karmakar, Basudeb

2015-01-01

385

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

SciTech Connect

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

Shaltaf, R., E-mail: r.shaltaf@ju.edu.jo; Juwhari, H. K.; Hamad, B.; Khalifeh, J. [Department of Physics, The University of Jordan, 11942 Amman (Jordan); Rignanese, G.-M.; Gonze, X. [Institute of Condensed Matter and Nanosciences (IMCN/NAPS), Université Catholique de Louvain (UCL), 8 Chemin des étoiles, B-1348 Louvain-la Neuve (Belgium); European Theoretical Spectroscopy Facility (ETSF) (Belgium)

2014-02-21

386

Microstructural evolution and dielectric properties of 1D AlN powders synthesized by microwave technique  

NASA Astrophysics Data System (ADS)

Low temperature synthesis of Aluminum nitride (AlN) powders through NH4Cl assisted nitridation have been studied by microwave technique. The effect of processing time on the synthesis of AlN powders has been investigated. The optimum processing time was determined to be 120 min at 630 W, 200 °C. The powders were characterized by X-ray diffraction method (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray analyzer (EDS), Fourier transform infrared spectrometer (FTIR) and Impedance analyzer. XRD results revealed that the product has wurtzite phase of AlN. SEM micrographs show a 1D nanorod of AlN with a granular morphology. FTIR spectra exhibit A1 (TO) and E1 (LO) modes of wurtzite AlN. Dielectric properties of the powders were investigated by means of C-V and C-f and ?'-f characteristics. The reported results indicate a reasonable quality of the obtained AlN powders with high dielectric constant, suitable for application in the fabrication of specific electronic devices.

VasanthiPillay, V.; Vijayalakshmi, K.

2012-06-01

387

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

388

Structural, Dielectric and Transport Properties of (PbSm)(ZrTi)O3 Ceramics  

NASA Astrophysics Data System (ADS)

The solid solutions of Pb1-xSmx(Zr0.50Ti0.50)1-x/4O3 (PSZT), x = 0.00, 0.03, 0.06 and 0.09 were prepared by a mixed oxide method at high temperature (sintering temperature 1200°C). Preliminary X-ray structural analysis suggests the formation of single-phase compounds at room temperature in tetragonal crystal system. The microstructural SEM analysis shows that the grains of the materials are almost spherical and also uniformly distributed over the surface. Detailed studies of dielectric properties (?, tan? and ?) of the materials in a wide temperature range (30-500°C) at different frequencies (103-106 Hz) reveal that the compounds have transition temperatures well above the room temperature. The analysis of the diffusivity of the dielectric peaks in these compounds provides values between 1 and 2, where the higher values indicate great disorder in the system. The temperature dependence of ac conductivity and the value of activation energy in different regions suggest that the conduction process is of mixed type (i.e. singly ionized in ferroelectric region and doubly ionized in paraelectric phase).

Ranjan, Rajiv; Kumar, Rajiv; Behera, Banarji; Choudhary, R. N. P.

389

Synthesis and controlling the optical and dielectric properties of CMC/PVA blend via ?-rays irradiation  

NASA Astrophysics Data System (ADS)

Carboxymethyl cellulose (CMC)/Polyvinyl alcohol (PVA) blend films were prepared by solution casting method. Then, these films were irradiated with ?-rays from a Co-60 source at doses over the range 0-70 kGy to investigate the modifications induced in the optical and dielectric properties. The dielectric constant (??) was measured in the temperature range 303-408 K and in the frequency range 10 kHz-1 MHz. The indirect optical band gap was found to increase within the dose range 0-10 kGy, and to decrease at the higher doses. The refractive index values, however, showed a reversed behavior. The highest transmittance percentage was obtained at 10 kGy dose. According to the frequency and temperature dependence of ??, ?- relaxation peaks were observed in all samples and assigned to the micro-Brownian motion of the blend chains. The values of ?? showed a decrease in the dose range 0-10 kGy and an increase in the dose range 10-70 kGy. The ac conductivity ?ac (T) showed an Arrhenius type behavior separated into two distinct regions. The results of the present system are compared with those of similar materials.

El Sayed, A. M.

2014-02-01

390

Synthesis, characterization, UV and dielectric properties of hexagonal disklike ZnO particles embedded in polyimides  

SciTech Connect

Graphical abstract: The hexagonal disklike ZnO particles with a diameter of 300-500 nm were synthesized from zinc acetate and NaOH in water with citric acid. ZnO/polyimide composite films with different ZnO contents was prepared. The prepared zinc oxide-polyimide composites were characterized for their structure, morphology and thermal behavior. Composites with ZnO particle contents from 1 to 5 wt% show good transparency in the visible region and luminescent properties. Highlights: {yields} A series of novel ZnO/polyimide composite films with different ZnO contents was prepared. {yields} The ZnO was homogeneously dispersed in the PI matrix. {yields} The composites showed the low dielectric constant of 50 at 10{sup 6} Hz. {yields} Homogenous dispersion and the amount of ZnO particles contributed to the dielectric properties of composites. -- Abstract: A series of novel ZnO/polyimide composite films with different ZnO contents was prepared through incorporation hexagonal disklike ZnO particles into poly(amic acid) of the pre polymer of the polyimide. The hexagonal disklike ZnO particles with a diameter of 300-500 nm were synthesized from zinc acetate and NaOH in water with citric acid. The prepared zinc oxide-polyimide composites were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy, scanning electron micrograph, X-ray diffraction and thermal analysis techniques. Thermal analyses show that the ZnO particles were successfully incorporated into the polymer matrix and these ZnO/polymer composites have a good thermal stability. Scanning electron microscopy studies indicate the ZnO particles were uniformly dispersed in the polymer and they remained at the original size (300-500 nm) before immobilization. All composite films with ZnO particle contents from 1 to 5 wt% show good transparency in the visible region and luminescent properties.

Vural, Sema; Koeytepe, Sueleyman [Inonu University, Chemistry Department, 44280 Malatya (Turkey)] [Inonu University, Chemistry Department, 44280 Malatya (Turkey); Seckin, Turgay, E-mail: tseckin@inonu.edu.tr [Inonu University, Chemistry Department, 44280 Malatya (Turkey)] [Inonu University, Chemistry Department, 44280 Malatya (Turkey); Adiguezel, Ibrahim [Inonu University, Physics Department, 44280 Malatya (Turkey)] [Inonu University, Physics Department, 44280 Malatya (Turkey)

2011-10-15

391

Dielectric properties of partially disordered lanthanum-modified lead zirconate titanate relaxor ferroelectrics  

Microsoft Academic Search

Linear and third-order nonlinear dielectric susceptibilities and the dielectric polarization were measured in 6.5\\/65\\/35 lanthanum lead zirconate titanate (PLZT) hot-pressed ceramics. On cooling linear dielectric data show a transition from an ergodic to a nonergodic relaxor phase, while, on heating, a ferroelectric to ergodic relaxor phase transition appears. The third-order dielectric response is reminiscent of an ergodic to nonergodic relaxor

Boris Vodopivec; Cene Filipic; Adrijan Levstik; Janez Holc; Zdravko Kutnjak; Horst Beige

2004-01-01

392

The effect of dopants on the microwave dielectric properties of Ba(Mg{sub 0.33}Ta{sub 0.67})O{sub 3} ceramics  

SciTech Connect

The effect of dopants with different valencies and ionic radii on the densification, structural ordering, and microwave dielectric properties of Ba(Mg{sub 1/3}Ta{sub 2/3})O{sub 3} (BMT) is investigated. It is found that dopants such as Sb{sub 2}O{sub 5}, MnO, ZrO{sub 2}, WO{sub 3}, and ZnO improve the microwave dielectric properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic radii of the dopant has been established. The variation of the dielectric properties of pure and doped BMT at cryogenic temperatures is also discussed.

Surendran, Kuzhichalil P.; Sebastian, Mailadil T.; Mohanan, Pezholil; Jacob, Mohan V. [Materials and Minerals Division, Regional Research Laboratory, Trivandrum-695 019 (India); Department of Electronics, Cochin University of Science and Technology, Kochi-686 022 (India); School of Engineering, James Cook University, QLD 4811 (Australia)

2005-11-01

393

The effect of dopants on the microwave dielectric properties of Ba(Mg0.33Ta0.67)O3 ceramics  

NASA Astrophysics Data System (ADS)

The effect of dopants with different valencies and ionic radii on the densification, structural ordering, and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 (BMT) is investigated. It is found that dopants such as Sb2O5, MnO, ZrO2, WO3, and ZnO improve the microwave dielectric properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic radii of the dopant has been established. The variation of the dielectric properties of pure and doped BMT at cryogenic temperatures is also discussed.

Surendran, Kuzhichalil P.; Sebastian, Mailadil T.; Mohanan, Pezholil; Jacob, Mohan V.

2005-11-01

394

Study of Some Dielectric Properties of Suspensions of Magnesium Particles in Mineral Oil  

NASA Technical Reports Server (NTRS)

The variation of dielectric constant has been measured as a function of the concentration of magnesium particles; the shape, size, and degree of oxidation of the particles; the temperature; and the frequency of oscillation. The variation of dielectric constant and settling rate was investigated as a function of time. Also investigated were the effects of particle concentration, shape and time on dielectric losses.

Altshuller, Aubrey P

1954-01-01

395

A study on the composite dielectric properties for an HTS cable  

Microsoft Academic Search

In order to optimize the insulation design of a cold dielectric high temperature superconducting (HTS) cable, the composite insulation system has been investigated according to the arrangement of laminated polypropylene paper (LPP) and kraft paper in liquid nitrogen. LPP is a prominent insulating material with a high dielectric strength and low dielectric loss, which has been used previously as a

D. S. Kwag; V. D. Nguyen; S. M. Baek; H. J. Kim; J. W. Cho; S. H. Kim

2005-01-01

396

Retrieving the electronic properties of silicon nanocrystals embedded in a dielectric matrix by low-loss EELS  

NASA Astrophysics Data System (ADS)

In this work we apply low-loss electron energy loss spectroscopy (EELS) to probe the structural and electronic properties of single silicon nanocrystals (NCs) embedded in three different dielectric matrices (SiO2, SiC and Si3N4). A monochromated and aberration corrected transmission electron microscope has been operated at 80 kV to avoid sample damage and to reduce the impact of radiative losses. We present a novel approach to disentangle the electronic features corresponding to pure Si-NCs from the surrounding dielectric material contribution through an appropriate computational treatment of hyperspectral datasets. First, the different material phases have been identified by measuring the plasmon energy. Due to the overlapping of Si-NCs and dielectric matrix information, the variable shape and position of mixed plasmonic features increases the difficulty of non-linear fitting methods to identify and separate the components in the EELS signal. We have managed to solve this problem for silicon oxide and nitride systems by applying multivariate analysis methods that can factorize the hyperspectral datacubes in selected regions. By doing so, the EELS spectra are re-expressed as a function of abundance of Si-NC-like and dielectric-like factors. EELS contributions from the embedded nanoparticles as well as their dielectric surroundings are thus studied in a new light, and compared with the dielectric material and crystalline silicon from the substrate. Electronic properties such as band gaps and plasmon shifts can be obtained by a straightforward examination. Finally, we have calculated the complex dielectric functions and the related electron effective mass and density of valence electrons.

Eljarrat, Alberto; López-Conesa, Lluís; López-Vidrier, Julian; Hernández, Sergi; Garrido, Blas; Magén, César; Peiró, Francesca; Estradé, Sònia

2014-11-01

397

Retrieving the electronic properties of silicon nanocrystals embedded in a dielectric matrix by low-loss EELS.  

PubMed

In this work we apply low-loss electron energy loss spectroscopy (EELS) to probe the structural and electronic properties of single silicon nanocrystals (NCs) embedded in three different dielectric matrices (SiO2, SiC and Si(3)N(4)). A monochromated and aberration corrected transmission electron microscope has been operated at 80 kV to avoid sample damage and to reduce the impact of radiative losses. We present a novel approach to disentangle the electronic features corresponding to pure Si-NCs from the surrounding dielectric material contribution through an appropriate computational treatment of hyperspectral datasets. First, the different material phases have been identified by measuring the plasmon energy. Due to the overlapping of Si-NCs and dielectric matrix information, the variable shape and position of mixed plasmonic features increases the difficulty of non-linear fitting methods to identify and separate the components in the EELS signal. We have managed to solve this problem for silicon oxide and nitride systems by applying multivariate analysis methods that can factorize the hyperspectral datacubes in selected regions. By doing so, the EELS spectra are re-expressed as a function of abundance of Si-NC-like and dielectric-like factors. EELS contributions from the embedded nanoparticles as well as their dielectric surroundings are thus studied in a new light, and compared with the dielectric material and crystalline silicon from the substrate. Electronic properties such as band gaps and plasmon shifts can be obtained by a straightforward examination. Finally, we have calculated the complex dielectric functions and the related electron effective mass and density of valence electrons. PMID:25363292

Eljarrat, Alberto; López-Conesa, Lluís; López-Vidrier, Julian; Hernández, Sergi; Garrido, Blas; Magén, César; Peiró, Francesca; Estradé, Sònia

2014-12-21

398

Gigantic enhancement in the dielectric properties of polymer-based composites using core/shell MWCNT/amorphous carbon nanohybrids.  

PubMed

Novel core/shell structured multi-walled carbon nanotube/amorphous carbon (MWCNT@AC) nanohybrids were successfully prepared using a simple and novel method. Subsequently, the MWCNT@AC nanohybrids were used as fillers to enhance the dielectric properties of poly(vinylidene fluoride) (PVDF) based composites. It is found that the dielectric constant of the MWCNT@AC/PVDF composites can reach 5910 (the dielectric loss is ?2), which is considerably better than that of MWCNT/PVDF composites. The uniform amorphous carbon shell provides an insulative layer between adjacent MWCNTs in the polymer matrix, which not only prevents the direct contact of MWCNTs but also improves the dispersibility of the MWCNTs. Therefore, a surprising number of microcapacitors could be formed in the composites before the formation of a conductive network, leading to a gigantic enhancement in the dielectric properties. Our strategy provides a new approach to fabricate excellent dielectric materials for energy storage capacitors. In addition, the design concept used in this work can be extended to other carbon materials. PMID:25640081

Guo, Qikai; Xue, Qingzhong; Sun, Jin; Dong, Mingdong; Xia, Fujun; Zhang, Zhongyang

2015-02-12

399

Dielectric properties of human red blood cells in suspension at radio frequencies.  

PubMed

Dielectric properties of human red blood cells (RBCs) in suspension (hematocrit 50%) from 243 healthy persons (120 males, 123 females) were measured at 25 degrees C in a frequency range of 1-500 MHz, with a coaxial transmission line reflection method (one-side measurement). The measuring system, controlled by an IBM-PC computer, was composed of a network analyzer (HP4195A), an impedance test adapter (HP41951-61001), a coaxial line sensor, and a temperature-controlling set. The data measured revealed a statistically significant age dependence, with a critical age of about 49 years, above which permittivity and conductivity of human RBCs in suspension decreased significantly. PMID:7880172

Lu, Y; Yu, J; Ren, Y

1994-01-01

400

A study of the dielectric and magnetic properties of multiferroic materials using the Monte Carlo method  

NASA Astrophysics Data System (ADS)

A study of the dielectric and magnetic properties of multiferroic materials using the Monte Carlo (MC) method is presented. Two different systems are considered: the first, ferroelectric-antiferromagnetic (FE-AFM) recently studied by X. S. Gaoand J. M. Liu and the second antiferroelectric-ferromagnetic (AFE-FM). Based on the DIFFOUR-Ising hybrid microscopic model developed by Janssen, a Hamiltonian that takes into account the magnetoelectric coupling in both ferroic phases is proposed. The obtained results show that the existence of such coupling modifies the ferroelectric and magnetic ordering in both phases. Additionally, it is shown that the presence of a magnetic or an electric field influences the electric polarization and the magnetization, respectively, making evident the magnetoelectric effect.

Sosa, A.; Almodovar, N. S.; Portelles, J.; Heiras, J.; Siqueiros, J. M.

2012-03-01

401

Interactions of light with rough dielectric surfaces - Spectral reflectance and polarimetric properties  

NASA Technical Reports Server (NTRS)

The nature of the interactions of visible and NIR radiation with the surfaces of rock and mineral samples was investigated by measuring the reflectance and the polarization properties of scattered and reflected light for slab samples of obsidian and fine-grained basalt, prepared to controlled surface roughness. It is shown that the degree to which radiation can penetrate a surface and then scatter back out, an essential criterion for mineralogic determinations based on reflectance spectra, depends not only upon the composition of the material, but also on its physical condition such as sample grain size and surface roughness. Comparison of the experimentally measured reflectance and polarization from smooth and rough slab materials with the predicted models indicates that single Fresnel reflections are responsible for the largest part of the reflected intensity resulting from interactions with the surfaces of dielectric materials; multiple Fresnel reflections are much less important for such surfaces.

Yon, S. A.; Pieters, C. M.

1988-01-01

402

Associating behaviour of pure polar liquids: dielectric properties of heptadecanoic and nonadecanoic acids  

NASA Astrophysics Data System (ADS)

The associating behaviour of heptadecanoic (margaric) and nonadecanoic acids has been studied by the determination of their dielectric properties. The correlation factor between molecular pairs was determined with reference to the Kirkwood-Fröhlich theory. An expression for the degree of association was obtained through simple statistical considerations based on the definition of the effective number of molecules carrying a dipole moment, derived from the Kirkwood-Fröhlich equation. The so evaluated degree of association results very high (percentage of dimer molecules of 93 per cent for heptadecanoic and of 94 per cent for nonadecanoic acid, above the respective melting points) decreasing with increasing temperature. A comparison of dimerization data on heptadecanoic and nonadecanoic acids with those of other lower molecular weight fatty acids, at a given temperature, shows a linear increase of dimerization with molecular weight.

Mognaschi, E. R.; Chierico, A.

403

Dielectric and ferroelectric properties of Al2O3 containing lead titanate based glass-ceramics  

NASA Astrophysics Data System (ADS)

Glass Samples were prepared by conventional melt quenching technique. These glass samples were converted to glass-ceramics by following two stage heat treatment schedule. The density, dielectric constant and volume fraction of PbTiO3 in glass-ceramic samples have been observed to increase with Al2O3 addition. The observed increase in the above properties has been attributed to formation of tetragonal PbTiO3 phase in the glass-ceramics. All the glassceramic samples exhibited the ferroelectric hysteresis loop. The value of remnant polarization was observed to increase with Al2O3 addition. The enhancement in the values of remnant polarization may be attributed to increase in the volume fraction of PbTiO3 phase in glass-ceramics.

Rahangdale, V. U.; Gala, D. K.; Acharya, R. M.; Deshpande, V. K.

2014-04-01

404

Dielectric properties of lead lanthanum zirconate stanate titanate antiferroelectric thin films prepared by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Lead lanthanum zirconate stanate titanate (PLZST) thin films of approximately 200 nm in thickness were deposited on Pt-buffered silicon substrates using pulsed laser deposition method. The samples were prepared under different substrate temperatures but with the same oxygen partial pressure of 0.2 mbar and laser fluence of approximately 4 J/cm2. We found that the Pb loss during the deposition process plays an important role in the formation of perovskite phase. Postdeposition annealing under different oxygen pressure, ranging from 0.2 mbar to atmospheric oxygen pressure but for the same annealing duration (15 min), was carried out in order to clarify the effects of the annealing ambient, from the viewpoint of crystallographic structure as well as electrical and dielectric properties. The physical origin is discussed.

Yao, Yingbang; Zhai, Jiwei; Chen, Haydn

2004-06-01

405

Transmission properties near Dirac-like point in two-dimensional dielectric photonic crystals  

NASA Astrophysics Data System (ADS)

We study the wave transport properties near the Dirac-like point at the Brillouin zone center in two-dimensional dielectric photonic crystals with finite thickness. Both simulations and microwave experiments confirm that the transmittance is nearly inversely proportional to the length (L) of the samples in the propagation direction near the Dirac-like point. This 1/L transmittance law comes from the conically shaped dispersion. Since the conical singularity at the Brillouin zone center corresponds to zero refractive index, the field at the Dirac-like point contains a basic component of nearly uniform field. In contrast, the field at the Dirac point in the corner of the hexagonal Brillouin zone contains a basic component of inhomogeneous standing-wave–like field.

Wang, X.; Jiang, H. T.; Yan, C.; Deng, F. S.; Sun, Y.; Li, Y. H.; Shi, Y. L.; Chen, H.

2014-10-01

406

Static and dynamic magnetic property of MBE-grown Co2FeAl films  

NASA Astrophysics Data System (ADS)

In this work, the static and dynamic magnetic properties of Co2FeAl films grown by molecular beam epitaxy (MBE) were studied by employing the magneto-optical Kerr rotation and ferromagnetic resonance (FMR) measurements. The growth temperature dependent magnetocrystalline anisotropy of MBE-grown Co2FeAl films were first investigated by employing the rotating magneto-optical Kerr effect. Then the magnetization dynamics and Gilbert damping property for high quality Co2FeAl films were investigated in detail by combining both the FMR and time-resolved magneto-optical Kerr rotation techniques. The apparent damping parameter was found to show strong dependence on the strength of the applied magnetic field at low-field regime, but decrease drastically with increasing magnetic field and eventually become a constant value of 0.004 at high-field regime. The inhomogeneity of magnetocrystalline anisotropy and two-magnon scattering are suggested to be responsible for the observed abnormal damping properties observed especially at low field regime. The intrinsic damping parameter of 0.004 is deduced for our highly-ordered Co2FeAl film. Our results provide essential information for highly-ordered MBE-grown Co2FeA film and its possible application in spintronic devices.

Qiao, Shuang; Nie, Shuaihua; Huo, Yan; Zhao, Jianhua; Wu, Yizheng; Zhang, Xinhui

2014-08-01

407

Investigating Moisture, Density, and Temperature Dependence of Dielectric Properties of Unshelled and Shelled Peanuts at Microwave Frequencies  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

408

Modification of polyethylene terephthalate by atmospheric pressure dielectric barrier discharge (DBD) in view of improving the polymer wetting properties  

Microsoft Academic Search

Surface treatment of polymers by discharge plasmas has increasingly found industrial applications due to its capability of modifying uniformly the surface without changing the material bulk properties. This work deals with surface modification of polyethylene terephthalate (PET) by a dielectric barrier discharge (DBD) at atmospheric pressure. The treatments were conducted in air, nitrogen or argon plasma. The polymer surface was

K G Kostov; A L R dos Santos; P A P Nascente; M E Kayama; R P Mota

2012-01-01

409

Dielectric and carrier transport properties of vanadium dioxide thin films across the phase transition utilizing gated capacitor devices  

E-print Network

Dielectric and carrier transport properties of vanadium dioxide thin films across the phase; published 1 November 2010 Vanadium dioxide VO2 is a strongly correlated oxide that undergoes a sharp metal.22.Ch I. INTRODUCTION Vanadium dioxide VO2 is a material of great interest in condensed-matter physics

Yang, Zheng

410

Electrical and dielectric properties of polyanilineAl2O3 nanocomposites derived from various Al2O3 nanostructures  

E-print Network

Electrical and dielectric properties of polyaniline­Al2O3 nanocomposites derived from various Al2O303908j Four Al2O3 nanostructures (i.e. nanofiber, nanoplatelet, nanorod and nanoflake) have been, polyaniline (PANI) nanocomposites incorporating these four Al2O3 nanostructures have been fabricated using

Guo, John Zhanhu

411

Dielectric Properties of Porous Si3N4-SiO2-BN Composites  

NASA Astrophysics Data System (ADS)

Porous Si3N4-SiO2-BN composites were prepared by adding starch as both pore former and consolidator. Bruggeman effective-medium model, Maxwell-Garnett model and logarithmic model were used to describe and predict the dielectric constant of porous Si3N4-SiO2-BN ceramics. Relative dielectric constant of porous Si3N4-SiO2-BN composites decreases with the increase of apparent porosity within limits, and these models can forecast the change of the dielectric constant of the porous ceramics quite well. The minimum relative dielectric constant is 2.5 at the apparent porosity of 0.555 at room-temperature. The relationship between dielectric constant and temperature were investigated. It was found dielectric constant varied a lot with the increase of temperature, and Debye relaxation theory was employed to explain the variation of the dielectric constant with temperature increment. But the Debye relaxation theory can not explain the reason of variation of dielectric constant at the temperature range from 300°C to 900°C. To ascertain the cause of changes of dielectric constant at this temperature region, differential scanning calorimentry (DSC) measurement was performed. In this temperature region, phase transition behavior occurs at nearly 300°C in the porous composites. The new phase probably has a tidy large dielectric constant, and the dielectric constant increases sharply.

Sun, Yinbao; Zhang, Yumin; Li, Dihong; Han, Jiecai

412

An analysis of the microwave dielectric properties of solvent-oil feedstock mixtures at 300-3000 MHz.  

PubMed

Microwaves can be a more efficient method than traditional thermal treatment to deliver the energy required for heating in solvent-oil extraction due to its volumetric, direct coupling with the material. An understanding of the behavior of dielectric properties of solvent-feedstock mixtures is important for designing and optimizing any microwave-based extraction process. In this study rice bran and soybean flour were mixed separately with four different solvents (methanol, ethanol, hexane and isopropanol) at different ratios (1:2, 1:1, 2:1 w/w). For the samples mixed with ethanol, the dielectric properties were measured at 23, 30, 40 and 50 degrees C, while for all other sample-solvent mixtures experiments were performed at room temperature. Dielectric properties were determined using a vector network analyzer and dielectric probe kit using the open-ended coaxial probe method in the frequency range of 300 MHz to 3 GHz. Results from the study indicate that dielectric constants were dependent on frequency and were strongly influenced by temperature, mix ratio and solvent type. The dielectric loss of all mixtures except those with hexane (which were virtually zero) varied with frequency and temperature, solvent type, and mix ratio. Most of the results presented are emphasized at 433, 915 and 2450 MHz, frequencies allocated by the Federal Communication Commission (F.C.C.) for microwave applications. The results of the study, presented here for the first time to our knowledge, will help in selection of appropriate solvent, mixing ratio and frequency for designing microwave-assisted oil extraction systems. PMID:20395139

Terigar, Beatrice G; Balasubramanian, Sundar; Boldor, Dorin

2010-08-01

413

Dielectric properties of FR4 laminates as a function of thickness and the electrical frequency of the measurement  

Microsoft Academic Search

The relationship between the dielectric properties (dielectric constant, ?\\u000a lam\\u000a ?\\u000a and loss factor, ?\\u000a lam\\u000a ?\\u000a ) and thickness of FR-4 laminates was investigated. Thickness variations for laminates reinforced by the same style and number\\u000a of plies of glass cloth were predominantly due to differences in the resin content. At each measurement frequency, values\\u000a of both ?\\u000a lam\\u000a ?

Stephen J. Mumby; Jih Yuan

1989-01-01

414

Polymethyl methacrylate (PMMA)-bismuth ferrite (BFO) nanocomposite: low loss and high dielectric constant materials with perceptible magnetic properties.  

PubMed

Herein, poly(methyl methacrylate)-bismuth ferrite (PMMA-BFO) nanocomposites were successfully prepared by an in situ polymerization method for the first time. Initially, the as prepared bismuth ferrite (BFO) nanoparticles were dispersed in the monomer, (methyl methacrylate) by sonication. Benzoyl peroxide was used to initiate the polymerization reaction in ethyl acetate medium. The nanocomposite films were subjected to X-ray diffraction analysis (XRD), (1)H NMR, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), infrared spectroscopy (IR), dielectric and magnetic characterizations. The dielectric measurement of the nanocomposites was investigated at a frequency range of 10 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased value of the dielectric constant with an increase in the loading percentage of BFO as compared to pure PMMA, but also exhibited low dielectric loss values over a wide range of frequencies. The values of the dielectric constant and dielectric loss of the PMMA-BFO5 (5% BFO loading) sample at 1 kHz frequency was found be ~14 and 0.037. The variation of the ferromagnetic response of the nanocomposite was consistent with the varying volume percentage of the nanoparticles. The remnant magnetization (Mr) and saturation magnetization (Ms) values of the composites were found to be enhanced by increasing the loading percentage of BFO. The value of Ms for PMMA-BFO5 was found to be ~6 emu g(-1). The prima facie observations suggest that the nanocomposite is a potential candidate for application in high dielectric constant capacitors. Significantly, based on its magnetic properties the composite will also be useful for use in hard disk components. PMID:25050918

Tamboli, Mohaseen S; Palei, Prakash K; Patil, Santosh S; Kulkarni, Milind V; Maldar, Noormahmad N; Kale, Bharat B

2014-09-21

415

Influence of the Viscoelastic Properties of the Polyimide Dielectric Coating on the Wafer Warpage  

NASA Astrophysics Data System (ADS)

Polyimide is widely used as the dielectric material in wafer level packaging. One potential problem with its application is the warpage and stress generated in the curing process. This paper investigated the material properties of polyimide and its influence on the wafer warpage. The viscoelastic properties of polyimide film were measured and a mathematical model of the properties was developed. Finite element analysis of the wafer warpage was performed and this indicates that the viscoelastic material model gave the best prediction. To better understand the causation of the warpage, curvature evolution of the polyimide-coated silicon wafer during its curing process was measured by a multi-beam optical sensor system. It was found that the warpage was mainly induced by the coefficient of thermal expansion mismatch and that the cure shrinkage of polyimide had little effect. Additionally, the effect of the cooling rate on the wafer warpage was also studied. Both simulation and experiment results showed that a slower cooling rate in the temperature range around the glass transition temperature ( T g) of polyimide will help to reduce the final wafer warpage.

Zhu, Chunsheng; Ning, Wenguo; Xu, Gaowei; Luo, Le

2014-09-01

416

Average dielectric property analysis of complex breast tissue with microwave transmission measurements.  

PubMed

Prior information about the average dielectric properties of breast tissue can be implemented in microwave breast imaging techniques to improve the results. Rapidly providing this information relies on acquiring a limited number of measurements and processing these measurement with efficient algorithms. Previously, systems were developed to measure the transmission of microwave signals through breast tissue, and simplifications were applied to estimate the average properties. These methods provided reasonable estimates, but they were sensitive to multipath. In this paper, a new technique to analyze the average properties of breast tissues while addressing multipath is presented. Three steps are used to process transmission measurements. First, the effects of multipath were removed. In cases where multipath is present, multiple peaks were observed in the time domain. A Tukey window was used to time-gate a single peak and, therefore, select a single path through the breast. Second, the antenna response was deconvolved from the transmission coefficient to isolate the response from the tissue in the breast interior. The antenna response was determined through simulations. Finally, the complex permittivity was estimated using an iterative approach. This technique was validated using simulated and physical homogeneous breast models and tested with results taken from a recent patient study. PMID:25585106

Garrett, John D; Fear, Elise C

2015-01-01

417

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

NASA Astrophysics Data System (ADS)

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

Clark, Justin L.

418

Microwave dielectric properties of BaO-2CeO{sub 2}-nTiO{sub 2} ceramics  

SciTech Connect

The BaO-2CeO{sub 2}-nTiO{sub 2} ceramics with n=3, 4 and 5 have been prepared with CeO{sub 2} as starting material. The ceramics have been characterized using scanning electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques. BaO-2CeO{sub 2}-3TiO{sub 2} (123), BaO-2CeO{sub 2}-4TiO{sub 2} (124) and BaO-2CeO{sub 2}-5TiO{sub 2} (125) ceramics showed dielectric constants of 38, 27 and 32, respectively. All the ceramics showed fairly good unloaded Q-factors. 124 and 125 compounds exhibited low {tau}f values, while 123 showed a high {tau}f value.

Sreemoolanadhan, H. [Regional Research Laboratory, Ceramic Technology Division, Industrial Estate P.O., Papanamcode, Trivandrum, Kerala 695019 (India); Sebastian, M.T. [Regional Research Laboratory, Ceramic Technology Division, Industrial Estate P.O., Papanamcode, Trivandrum, Kerala 695019 (India)]. E-mail: mailadils@yahoo.com; Ratheesh, R. [Anorganische Chemie, Universitat Osnabrueck, D-49069 Osnabrueck (Germany); Blachnik, R. [Anorganische Chemie, Universitat Osnabrueck, D-49069 Osnabrueck (Germany); Woehlecke, M. [Fachbereich Physik, Universitat Osnabrueck, D-49069 Osnabrueck (Germany); Schneider, B. [Fachbereich Physik, Universitat Osnabrueck, D-49069 Osnabrueck (Germany); Neumann, M. [Fachbereich Physik, Universitat Osnabrueck, D-49069 Osnabrueck (Germany); Mohanan, P. [Department of Electronics, Cochin University of Science and Technology, Kochi 682022 (India)

2004-11-01

419

Dielectric Properties of Ca2CuO3-CaCu2O3-CuO Composite Ceramics  

NASA Astrophysics Data System (ADS)

The Ca2CuO3-CaCu2O3-CuO ceramics were synthesized by traditional solid-state sintering method. The complex dielectric response of the samples measured from 102-106 Hz and from 300-500 K reveals very high real part of ? > 104. The activation energy (being about 0.63 eV) calculated by the Arrhenius equation indicates that the oxygen vacancies may contribute to the high dielectric response. And the fitting to a Schottky barrier model of capacitance versus applied voltage suggests that the existence of Schottky barrier at the grain boundaries may be another important reason for the origination of good dielectric properties.

Li, Qing-Shou; Zhang, Yun-Qiang; Li, Li-Ben; Zang, Guo-Zhong

2013-03-01

420

Dielectric and elastic properties of mixed ferroelectric material KTa sub 1 minus x Nb sub x O sub 3  

SciTech Connect

This study describes dielectric and elastic properties of the ferroelectric system KTa{sub 1{minus}x}Nb{sub x}O{sub 3} (KTN) with niobium in the concentration range 1.2% {approximately} 16%. Experimental work on the dielectric and elastic behaviors of the KTN system is discussed. Results on the linear and the nonlinear dielectric constants and on the electric polarization of KTN reveal (a) the occurrence of a structural transition with the appearance of ferroelectric macroregions at {Tc}, even for relatively low impurity concentrations (b) the presence of polar microregions significantly above {Tc}. The phase transition in KTN is driven by the interaction between effective dipolar moments d* rather than a soft mode. Elastic results obtained on KTN provide direct evidence of the two distinct stages through which the transition goes when approaching the critical temperature {Tc}.

Wang Xiaomei.

1991-01-01

421

The effect of nitric acid (HNO3) on growth, spectral, thermal and dielectric properties of triglycine sulphate (TGS) crystal.  

PubMed

The effect of nitric acid (HNO(3)) addition on the growth of triglycine sulphate (TGS) crystal has been studied from the aqueous solution for various concentrations of nitric acid. Significant changes in the crystal size and morphology have been observed in all the grown samples. Single crystal and powder X-ray diffraction analyses confirm the structure and cell parameter values of pure and HNO(3) doped TGS crystals. FT-Raman and FTIR spectra confirm the characteristics absorption bands of pure and HNO(3) doped TGS crystals. The composition of TGS crystals have been confirmed by CHNS analysis. Physical properties such as thermal, dielectric and mechanical studies have been performed for the pure and HNO(3) doped TGS crystals. The dielectric constants of the crystals have been studied as a function of frequency. The results suggest that the HNO(3) is doped into TGS crystal and that the doping increases its dielectric constant. PMID:20004141

Parimaladevi, R; Sekar, C; Krishnakumar, V

2010-02-01

422

Optical and dielectric properties of ZrO2-V2O5 nanocomposites by co-precipitation calcination method  

NASA Astrophysics Data System (ADS)

Nanocrystalline ZrO2-V2O5 composites were synthesized by co-precipitation method and calcined at 500 and 700 °C. The formation of the composite material has been confirmed by X-ray diffraction analysis. The surface morphology was determined by scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis. EDAX analysis confirms equal composition of zirconium and vanadium in the lattice. Optical absorption studies reveal a very low absorption in the entire visible region for the two samples calcined at different temperatures. The dielectric constant and loss of the pelletized samples have been examined at different temperatures as functions of frequency. The higher dielectric constant and phase change at room temperature of the sample calcined at 700 °C showed that higher calcination temperatures enhanced dielectric properties.

Padmamalini, N.; Ambujam, K.

2014-12-01

423

Dielectric property determination of hybrid Al2O3-filled MWCNT buckypaper by the rectangular cavity perturbation technique  

NASA Astrophysics Data System (ADS)

This study investigated the complex dielectric permittivity of freestanding multiwalled carbon nanotube buckypaper (MWCNT-BP) and a synthesized hybrid alumina-filled buckypaper (Al2O3-BP) composite with different alumina loadings (5-30 wt%). The non-destructive microwave transmission technique for complex permittivity determination involving cavity perturbation was employed to characterize a set of Al2O3-BP sheets. This was done by filling a rectangular cavity resonator with a standard dielectric Teflon sample and then performing permittivity measurements for the buckypaper (BP) samples in the X-band frequency range (7-12 GHz). Field-emission scanning electron microscopy (FESEM) was used to analyze the morphology of the MWCNT-BP and the alumina-loaded BP composites. DC electrical resistivity measurements clearly demonstrated conductor-insulator transition. The effect of alumina loadings on the dielectric properties of the synthesized hybrid Al2O3-BP sheet is discussed.

Miao, Hsin-Yuan; Liu, Jih-Hsin; Saravanan, L.; Tsao, Che-Wei; Pan, Jui-Wen

2014-12-01

424

Structural, optical and dielectric property of Co doped Bi{sub 2}Fe{sub 4}O{sub 9}  

SciTech Connect

Multiferroic Bi{sub 2}Fe{sub 4}O{sub 9} and Co doped Bi{sub 2}Fe{sub 4}O{sub 9} are prepared by solid state route reaction method using bismuth oxide(Bi{sub 2}O{sub 3}), iron oxide(Fe{sub 2}O{sub 3}) and cobalt oxide (Co{sub 3}O{sub 4}). 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, E-mail: singhanil@nitrkl.ac.in; Mohapatra, S. R., E-mail: singhanil@nitrkl.ac.in; Sahoo, B., E-mail: singhanil@nitrkl.ac.in; Singh, A. K., E-mail: singhanil@nitrkl.ac.in [Department of Physics, National Institute of Technology, Rourkela -769008, Odisha (India)

2014-04-24

425

The influence of iron- and copper- doped of PANi thin film on their structure and dielectric properties  

NASA Astrophysics Data System (ADS)

Polyaniline (PANi) is one of conductive polymers which are widely studied. PANi has unique in the structure and physical properties that can be controlled by doping. In this work we report the role of CuCl2 and FeCl3 in the crystalline and dielectric properties of PANi/Ag films which was performed by means spin coating method. We employed sonochemical technic to form solutions of PANi ES II prior to spin coating method. The variation of FeCl3 and CuCl2 doped were used in the range of 0 M - 0.5 M. FTIR spectra of PANi EB and PANi ES clarified that the PANis were successfully synthesized. The crystallinity of the films were examined by menas of X-ray diffraction (XRD). While the polymeric grains were evaluated using SEM which is confirmed with the grain size analyses from X-RD data. Dielectric properties shows that introducing Fe and Cu doped could decrease their dielectric constant. The decreasing of dielectric constant was also achieved by increasing frequency.

Diantoro, Markus; Purwaningtyas, Devy; Muthoharoh, Nazilah; Hidayat, Arif; Taufiq, Ahmad; Fuad, Abdulloh

2012-06-01

426

Structural and dielectric properties of La0.8Te0.2MnO3  

NASA Astrophysics Data System (ADS)

We have studied the structural and dielectric properties of La0.8Te0.2MnO3 pervoskite compound, has a rhombohedral structure with space group R-3c, at room temperature. Infrared spectrum shows two active bands located at 611 and 410 cm-1, which can be ascribed to the internal stretching and bending phonon modes. The additional bands observed at 925, 969 and 1383 cm-1 are attributed to the multiphonon scattering. The dielectric constant ?' shows a step like relaxation behaviour and has been discussed with in the frame work of the Kramers-Kronig transformation model. The ac conductivity follows a universal dielectric response (UDR), and the results were discussed and fitted with the Jump relaxation model (JRM). The occurrence of giant or colossal dielectric constant is most likely due to electrode polarization or interface polarization effect. The depletion layers are arising due to the formation of Schottky barriers at the metallic contacts of semiconducting samples, which may be formed by grain boundaries, can give rise to Maxwell-Wagner type relaxation and apparently very high dielectric constants.

Husain, Shahid; Bhat, Irshad; Khan, Wasi; Al-Khataby, Lila

2013-03-01

427

Effects of static magnetic field on cell biomechanical property and membrane ultrastructure.  

PubMed

The bioeffects of magnetic fields on organism have become an attractive area of study in recent decades, but the influence of static magnetic fields (SMFs) on biomechanical property, is rarely reported. This work investigated the effect of SMF (magnetic flux density ranging from 0.26 to 0.33?T, with a gradient of 2.09?T/m) on biomechanical property and ultrastructure of the membrane, and their relationship with F-actin distribution and cell adhesion of human breast adenocarcinoma cells (MCF-7) and human cervical carcinoma cells (HeLa). The two kinds of cells showed different responses to SMF exposure. For MCF-7 cells exposed to SMF for 72?h, the Young's modulus calculated from atomic force microscopy (AFM) indentation curve decreased significantly compared to that in the control group. This reduction was also associated with different actin distribution, revealed by phalloidin fluorescence analysis. Moreover, exposed MCF-7 cells had a smaller adhesion capacity to substrate with a rougher surface as observed by AFM scanning, which was also confirmed by quantitative analysis of the scanning pictures. Nevertheless, no significant changes were observed in the HeLa cell. These findings, from a biomechanical point of view, provide new insights for the mechanism of bioeffects of SMF on cell behaviors. PMID:24619812

Wang, Zhe; Hao, Fengtao; Ding, Chong; Yang, Zhouqi; Shang, Peng

2014-05-01

428

Dielectric properties of polluted soils as a potential tool to detect low level organic pollution in unsaturated soils  

SciTech Connect

The detection of organic pollution in soils is usually made by chemical analysis. Some geophysical methods are available to detect massive and transient pollution. But the standards used in Europe to define a non polluted soil are very strict : some organic compounds (as Polycyclic Aromatic Hydrocarbons) have to be less than 10 ppm. Hence, a geophysical tool allowing to prospect large areas with low rate organic pollution has to be developed. In this aim, our work is the first step of the evaluation of a geophysical method based on the dielectric characteristics of soils, our final goal being in situ measurements of those parameters. Several geophysical methods are already used to monitor organic pollution of groundwater. Both electric and dielectric properties of these pollutants can be used. Conventional DC resistivity measurements and EM methods can provide good results when polluted groundwater is linked with high salinity, while GPR and radiowave EM can be used to detect hydrocarbons by measuring soil dielectric properties. The problem of detecting organic compounds is different for saturated and unsaturated media because the dielectric constant {epsilon}{sub w} of water ({approx} 80, depending on temperature and frequency) is higher than that of dry soils (2<{epsilon}{sub s}<6) and organic liquids ({epsilon}{sub ol} < 6 if the compound is not polar). For saturated soils or rocks, the presence of organic liquid reduces the water saturation component and, consequently, the global dielectric constant of the soil in comparison with non-polluted soil or rock. GPR method can detect contrasting dielectric permittivities due to such phenomena. This method is efficient for high levels of pollution ( > 30% by weight) in a saturated zone and for transient flow because it is easier to compare several GPR sections versus time than to interpret one section without references.

Porokhovoie, S.; Mouza, J. du [Centre de Geologie de l`Ingenieur, Paris (France); Reiter, M. [Houilleres de Bassin Centre-Midi, Saint-Etienne (France)

1996-11-01

429

Dielectric and Elastic Properties of Mixed Ferroelectric Material Potassium TANTALUM(1-X) Niobium(x) Oxide  

NASA Astrophysics Data System (ADS)

Ferroelectricity is one of the important fields in solid state physics because of its scientific and technological significance. This dissertation describes dielectric and elastic properties of the ferroelectric system KTa_{1-x}Nb_{x}O _3 (KTN) with niobium in the concentration range 1.2% ~ 16%. The occurrence and the nature of the phase transition in mixed ferroelectric systems is an intriguing topic due to the introduction of configurational disorder. Experimental results have shown that the critical temperature T _{c} in the KTN system strongly depends on the concentration of Nb and that the transverse optic soft mode frequency decreases as the concentration of Nb increases. However, the origin of the phase transition in this system is not clearly known. In particular, it is not yet clear whether or not the transition is driven by a soft mode and how the nature of the transition evolves as the Nb concentration is changed. This dissertation describes experimental work on the dielectric and elastic behaviors of the KTN system. The results on the linear and the nonlinear dielectric constants and on the electric polarization of KTN reveal (a) the occurrence of a structural transition with the appearance of ferroelectric macroregions at T_{c }, even for relatively low impurity concentrations (b) the presence of polar microregions significantly above T_{c}. The phase transition in KTN is driven by the interaction between effective dipolar moments d* rather than a soft mode. Our experimental results also reveal the coexistence of both dipolar glass like and ferroelectric behaviors in KTN with low Nb concentrations. Elastic results obtained on KTN provide direct evidence of the two distinct stages which the transition go through when approaching the critical temperature T _{c}. The ultrasonic measurements of the longitudinal elastic constant C_ {11} shows the softening of C _{11} with a (T-T_ {c})^{-mu} dependence at intermediate temperature in the first stage. In the sample with high niobium concentrations, the exponent value is found to be about 0.5 and can be explained by the interaction of the sound waves with small fluctuations of the polarization. For low Nb concentration samples, however, mu increases to 2.5. At lower temperature, i.e. closer to T_{c}, C_ {11} appears to deviate from the above divergence, indicating a change in the elastic behavior. This change is accompanied by a steep rise in ultrasonic attenuation, suggesting the presence of polar clusters. It is the interaction between these clusters that eventually leads to the transition.

Wang, Xiaomei

430

Dielectric properties of two diastereoisomers of the arabinose and their equimolar mixture.  

PubMed

Dielectric relaxation measurements were performed on two enantiomers, D- and L-arabinose and their equimolar mixture, and compared to dielectric data obtained for D-ribose. D-Arabinose differs from d-ribose by having the opposite configuration at C2. This study reveals that both D- and L- of arabinose exhibit alpha-relaxation peaks with the same shape for the same alpha-relaxation time tau(alpha), and the same steepness index for the T(g)-scale T-dependence of tau(alpha). However, the two isomers have slightly different glass transition temperatures T(g)'s, and their secondary gamma-relaxation times also differ slightly from the previously observed gamma-relaxation in D-ribose at the same temperature. However, when samples of both investigated monosaccharides are annealed at higher temperatures, their glass transition temperatures become nearly identical. This is an effect of the mutarotation process, which leads to the formation of pairs of the enantiomers and accordingly they should have the same physical properties. The width of the alpha-relaxation of D- and L-arabinose is broader than that of D-ribose, as reflected by the smaller stretch exponent in the Kohlrausch-Williams-Watts function used to fit the data of the former (beta(KWW)=0.46+/-0.01) than the latter (beta(KWW)=0.55+/-0.01). The width of the alpha-relaxation of racemic mixture of the D- and L-arabinose is slightly broader than that of the pure isomers. While the dielectric loss data of D-ribose in the glassy state at ambient and elevated pressures show an inflexion indicating the presence of the JG beta-relaxation, the data of D- and L-arabinose show no such feature for identification of the supposedly universal JG beta-relaxation. Nevertheless, on comparing the loss spectra of D-arabinose with that of D-ribose, the presence of the JG beta-relaxation in D-arabinose has been rationalized. PMID:19857861

Kaminski, Kamil; Kaminska, Ewa; Pawlus, Sebastian; Wlodarczyk, Patryk; Paluch, Marian; Ziolo, Jerzy; Kasprzycka, Anna; Szeja, Wies?aw; Ngai, K L; Pilch, Jerzy

2009-12-14

431

Effects of pyrolysis conditions on dielectric properties of PLZT films derived from a polyvinylpyrrolidone-modified sol-gel process  

SciTech Connect

Graphical abstract: SEM images showing the surface morphology of PLZT films derived from solutions with various PVP content and treated with either RTA (rapid thermal annealing) or SPT (step-wise preheat treatment) process. Highlights: Black-Right-Pointing-Pointer High-quality PLZT films were fabricated by using a polyvinylpyrrolidone-modified sol-gel method. Black-Right-Pointing-Pointer Improved film density and integrity was achieved by employing a novel step-wise preheat treatment (SPT) process. Black-Right-Pointing-Pointer Enhanced dielectric properties were correlated to the improved microstructures as a result of the SPT process. -- Abstract: Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} (PLZT) films were deposited on platinized silicon substrates (Pt/Si) using a polyvinylpyrrolidone (PVP) modified sol-gel method. Pyrolysis of the green films was conducted via two methods: rapid thermal annealing (RTA) and a step-wise preheat treatment (SPT). Microstructure analysis and dielectric property characterization were performed on samples treated by these two methods. Results showed that the SPT-pyrolyzed films exhibited much better dielectric properties when compared with the RTA-pyrolyzed films. The differences in dielectric properties were correlated to microstructural features caused by the different pyrolysis conditions. High-quality PLZT films with high dielectric constant ( Almost-Equal-To 860 at zero bias) and high breakdown strength ( Almost-Equal-To 2.1 MV/cm) were fabricated under controlled pyrolysis conditions. This work demonstrated the potential application of this material for power electronics in electric drive vehicles.

Chao, Sheng, E-mail: Sheng.Chao@kennametal.com [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States)] [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Ma, Beihai; Liu, Shanshan; Narayanan, Manoj; Balachandran, Uthamalingam [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States)] [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

2012-03-15

432

Dielectric function and optical properties of quaternary AlInGaN alloys  

SciTech Connect

The optical properties of quaternary Al{sub x}In{sub y}Ga{sub 1-x-y}N alloy films with 0.16dielectric function (DF) of the AlInGaN samples was determined in the range of 1-10 eV by spectroscopic ellipsometry (SE) at room temperature (synchrotron radiation: BESSY II). The sharp onset of the imaginary part of the DF defines the direct absorption edge of the alloys. At higher photon energies, pronounced peaks are observed in the DF indicating a promising optical quality of the material. These features are correlated to the critical points of the band structure (van Hove singularities). An analytical model, which permits us to accurately describe the dielectric function (or optical constants) in the range of 1-10 eV, is also presented. The band-gap and high-energy interband transition values are obtained by fitting the experimental DF with the analytical model. The strain influence on the bandgap is evaluated by using the kxp formalism. Furthermore, an empirical expression is proposed which allows us to calculate the AlInGaN band-gap and high-energy inter-band transitions in the whole compositional range (x, y). The band-gap values obtained from the empirical expression are in good agreement with both the calculated ab initio and the experimental values determined by SE.

Sakalauskas, E.; Gobsch, G. [Institut fuer Physik, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Reuters, B.; Khoshroo, L. Rahimzadeh; Kalisch, H.; Vescan, A. [GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); Heuken, M. [GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath (Germany); Roeppischer, M.; Cobet, C. [Leibniz-Institut fuer Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Str. 9, 12489 Berlin (Germany); Goldhahn, R. [Institut fuer Physik, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Institut fuer Experimentelle Physik, Otto-von-Guericke-Universitaet Magdeburg, PF 4120, 39016 Magdeburg (Germany)

2011-07-01

433

A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries.  

PubMed

The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we conducted a large-scale study to experimentally determine the ultrawideband microwave dielectric properties of a variety of normal, malignant and benign breast tissues, measured from 0.5 to 20 GHz using a precision open-ended coaxial probe. Previously, we reported the dielectric properties of normal breast tissue samples obtained from reduction surgeries. Here, we report the dielectric properties of normal (adipose, glandular and fibroconnective), malignant (invasive and non-invasive ductal and lobular carcinomas) and benign (fibroadenomas and cysts) breast tissue samples obtained from cancer surgeries. We fit a one-pole Cole-Cole model to the complex permittivity data set of each characterized sample. Our analyses show that the contrast in the microwave-frequency dielectric properties between malignant and normal adipose-dominated tissues in the breast is considerable, as large as 10:1, while the contrast in the microwave-frequency dielectric properties between malignant and normal glandular/fibroconnective tissues in the breast is no more than about 10%. PMID:17921574

Lazebnik, Mariya; Popovic, Dijana; McCartney, Leah; Watkins, Cynthia B; Lindstrom, Mary J; Harter, Josephine; Sewall, Sarah; Ogilvie, Travis; Magliocco, Anthony; Breslin, Tara M; Temple, Walley; Mew, Daphne; Booske, John H; Okoniewski, Michal; Hagness, Susan C

2007-10-21

434

Dielectric Properties of Relaxor-Like P(VDF-TrFE-CFE) Terpolymer  

Microsoft Academic Search

The dynamic processes in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer with a content of 68\\/32\\/9 mol% have been studied by measurements of the temperature and frequency-dependent linear and third-order nonlinear dielectric constants. Analysis of the dielectric response has revealed that dielectric dynamics in this organic system is very similar to behavior observed in various dipolar glasses and relaxors.

B. VODOPIVEC; V. BOBNAR; A. LEVSTIK; Q. M. ZHANG

2004-01-01

435

Spiral configuration of electrodes and dielectric material for sensing an environmental property  

NASA Technical Reports Server (NTRS)

A reliable moisture-indicating capactive sensor is provided with wire electrodes at least one of which includes a coating of moisture-absorbing dielectric material by spirally twisting the wire electrodes about each other, thereby establishing a pair of electrodes in contact with opposite surfaces of a layer of dielectric material, and assuring consistent contact of each electrode with the dielectric material despite changes in environmental conditions.

Laue, Eric G. (Inventor); Stephens, James B. (Inventor)

1989-01-01

436

The dielectric properties on Pb-complex perovskite with low firing temperature  

Microsoft Academic Search

The authors propose new dielectric compositions and their preparation method. The dielectric compositions comprise lead magnesium niobate, lead zinc niobate, and lead lithium tungstate (PMN-PZN-PLW). They can be fired at a temperature between 1000 and 1050°C, and can thus be used with high-silver-content electrodes in manufacturing MLCCs (multilayer ceramic capacitors). The dielectric constant peak is shifted near room temperature with

Hong-In Chae; Kee-Joe Lim; Jeong-Goo Lee; Sang-Seok Lee; Tai-Goo Choy

1991-01-01

437

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

Microsoft Academic Search

The dielectric permittivity, dielectric quality factor (inverse dielectric loss), and lattice parameter of 140 nm sputtered SrTiO3 films were dependent on the oxygen partial pressure and total chamber pressure (O2+Ar) during film growth. Films were grown at 25 and 75 mTorr (mT) in an oxygen rich and oxygen deficient sputtering gas environment concurrently on (100) SrTiO3 and (111) Pt\\/(0001) Al2O3

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

2003-01-01

438

Electrostatic properties of two finite width charged dielectric slabs in water  

NASA Astrophysics Data System (ADS)

We study the electrostatic interaction between two like-charged membranes of finite thickness embedded (composed of five parallel dielectric interfaces) in a medium of higher dielectric constant. A generalized SC theory is applied along with extensive Monte-Carlo simulations which applied numerical algorithm based on the image charge method to calculate accurate electrostatic potential or forces. We found the dielectric discontinuity is important in a SC regime. They drive strong counterion crowding in the central region of the inter-surface space upon increasing the solvent/membrane dielectric mismatch and change the membrane interactions from attractive to repulsive at small separations.

Jho, Y. S.; Kanduc, M.; Naji, A.; Kim, M. W.; Podgornik, R.; Brown, F. L. H.; Pincus, P. A.

2009-03-01

439

Investigation of structure-dielectric property relationships in zirconium oxide, tantalum pentoxide, and oxide-polymer laminate films for high energy density capacitor applications  

Microsoft Academic Search

Pulsed power applications involve transformation of electrical energy into high-peak power pulses through capacitors. There is an immediate need for fast-response capacitors with decreased volume, weight, and cost for pulsed power applications and power distribution systems. This research challenge is dominated by energy density. Energy density is directly related to dielectric properties such as dielectric polarization, conductivity and breakdown strength

Guneet Sethi

2010-01-01

440

Influence of thermal annealing on the dielectric properties and electrical relaxation behaviour in nanostructured CoFe2O4 ferrite  

Microsoft Academic Search

Nanocrystalline cobalt ferrite particles with the grain size of 8 nm were synthesized by using the co-precipitation technique and subsequently heat treated to obtain larger grain sizes. The effect of grain size, cation distribution, frequency and temperature on their dielectric properties has been studied. The dielectric constant (?') of 8 nm grains is found to be an order of magnitude

N. Sivakumar; A. Narayanasamy; C. N. Chinnasamy; B. Jeyadevan

2007-01-01

441

Effect of temperature (-5 to 130 degrees C) and fiber direction on the dielectric properties of beef Semitendinosus at radio frequency and microwave frequencies.  

PubMed

The dielectric properties must be defined to design efficient radio frequency (RF) and microwave (MW) processes by the food manufacturers. The objective of this study was to understand how frequency, temperature, and muscle fiber orientation influence the dielectric properties. The eye of round (Semitendinosus) muscle was selected because it contains large, relatively uniform muscle cells with similar muscle fiber orientation and relatively uniform chemical composition throughout the tissue. Dielectric properties were measured using an open-ended coaxial probe technique at 27, 915, and 1800 MHz and temperatures between -5 and 130 degrees C. Power penetration depth was calculated. Since many commercially prepared, thermally processed, ready-to-eat entrees are made with frozen meat, dielectric property measurements were started from -5 degrees C. The dielectric constant and dielectric loss factors were often higher for muscle with the muscle fiber measured in a parallel orientation to the probe compared to samples of the same treatment (for example, fresh or frozen) in a perpendicular tissue orientation at the same frequency and temperature. Dielectric constant and loss values for frozen beef tended to be higher than fresh beef at the same temperature and frequency. Tissue orientation appeared to have a greater effect on dielectric loss values at lower frequencies. Penetration depth tended to be greater when the direction of propagation was perpendicular to the muscle fiber. PMID:19241544

Basaran-Akgul, N; Basaran, P; Rasco, B A

2008-08-01

442

Dielectric properties of human skin at an acupuncture point in the 50 - 75 GHz frequency range. A pilot study  

PubMed Central

The reason for using acupuncture points as exposure sites in some applications of millimeter wave therapy has been unclear. Acupuncture points have been suspected to exhibit particular direct current (DC), low-frequency electrical and optical properties compared to surrounding skin. To assess if such a biophysical correlation could exist at millimeter wave frequencies used in the therapy, we investigated the dielectric